The invention provides methods of preventing or treating insulin resistance in a mammalian subject. The methods comprise administering to the subject an effective amount of an aromatic-cationic peptide having at least one net positive charge; a minimum of four amino acids; a maximum of about twenty amino acids; a relationship between the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) wherein 3p.sub.m is the largest number that is less than or equal to r+1; and a relationship between the minimum number of aromatic groups (a) and the total number of net positive charges (p.sub.t) wherein 2a is the largest number that is less than or equal to p.sub.t+1, except that when a is 1, p.sub.t may also be 1.

Description of the Invention

TECHNICAL FIELD

The present invention relates generally to the methods of preventing or treating insulin resistance. In particular, the present invention relates to administering aromatic-cationic peptides in effective amounts to prevent or treat insulin resistance in mammalian skeletal muscle tissues.

BACKGROUND

The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present invention.

Obesity has become a worldwide epidemic, the consequences of which represent a major challenge facing human health in the 21st century. A decrease in the sensitivity of skeletal muscle to insulin is one of the earliest maladies associated with obesity, and its persistence is a prominent risk factor for type II diabetes and cardiovascular disease. The accumulation of lipid in skeletal muscle has long been associated with the development of insulin resistance, a maladaptive response that is currently attributed to the generation and intracellular accumulation of proinflammatory lipid metabolites (e.g., fatty acyl-CoAs, diacylglycerols and/or ceramides) and associated activation of stress-sensitive serine/threonine kinases that antagonize insulin signaling. Skeletal muscle from obese individuals is also characterized by profound reductions in mitochondrial function as evidenced by decreased expression of metabolic genes, reduced respiratory capacity, and mitochondria that are smaller and less abundant, leading to speculation that a decrease in the capacity to oxidize fat due to acquired or inherited mitochondrial insufficiency may be an underlying cause of the lipid accumulation and insulin resistance that develops in various metabolic states.

SUMMARY

The present invention relates generally to the treatment or prevention of insulin resistance in skeletal muscle tissues through administration of therapeutically effective amounts of aromatic-cationic peptides to subjects in need thereof. In particular embodiments, the aromatic-cationic peptides treat or prevent diet-induced insulin resistance by reducing the occurrence of skeletal muscle mitochondrial dysfunction and over-production of reactive oxygen species.

In one aspect, the invention provides a method of treating or preventing insulin resistance and related complications in a mammalian subject, comprising administering to said mammalian subject a therapeutically effective amount of an aromatic-cationic peptide. In some embodiments, the aromatic-cationic peptide is a peptide having:

at least one net positive charge;

a minimum of four amino acids;

a maximum of about twenty amino acids;

a relationship between the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) wherein 3p.sub.m is the largest number that is less than or equal to r+1; and a relationship between the minimum number of aromatic groups (a) and the total number of net positive charges (p.sub.t) wherein 2a is the largest number that is less than or equal to p.sub.t+1, except that when a is 1, p.sub.t may also be 1. In particular embodiments, the mammalian subject is a human.

In one embodiment, 2p.sub.m is the largest number that is less than or equal to r+1, and a may be equal to p.sub.t. The aromatic-cationic peptide may be a water-soluble peptide having a minimum of two or a minimum of three positive charges.

In one embodiment, the peptide comprises one or more non-naturally occurring amino acids, for example, one or more D-amino acids. In some embodiments, the C-terminal carboxyl group of the amino acid at the C-terminus is amidated. In certain embodiments, the peptide has a minimum of four amino acids. The peptide may have a maximum of about 6, a maximum of about 9, or a maximum of about 12 amino acids.

In some embodiments, the peptide has opioid receptor agonist activity. In other embodiments, the peptide does not have opioid receptor agonist activity.

In one embodiment, the peptide comprises a tyrosine or a 2',6'-dimethyltyrosine (Dmt) residue at the N-terminus. For example, the peptide may have the formula Tyr-D-Arg-Phe-Lys-NH.sub.2 (SS-01) or 2',6'-Dmt-D-Arg-Phe-Lys-NH.sub.2 (SS-02). In another embodiment, the peptide comprises a phenylalanine or a 2',6'-dimethylphenylalanine residue at the N-terminus. For example, the peptide may have the formula Phe-D-Arg-Phe-Lys-NH.sub.2 (SS-20) or 2',6'-Dmp-D-Arg-Phe-Lys-NH.sub.2. In a particular embodiment, the aromatic-cationic peptide has the formula D-Arg-2'6'Dmt-Lys-Phe-NH.sub.2 (SS-31).

In one embodiment, the peptide is defined by formula I -- see Original Patent.

In some embodiments, the aromatic-cationic peptides of the invention are used to treat or prevent complications related to insulin resistance in mammalian subjects, which include, but are not limited to, hyperinsulinemia, type II diabetes, abnormal lipid metabolism, abnormal vascular endothelial function, retinopathy, coronary artery disease, cardiovascular disease, renal dysfunction, hypertension, fatty liver, neuropathy, and hyperuricemia. Specific examples of cardiovascular disease potentially caused by long-term insulin resistance include myocardial infarction, hemorrhagic or ischemic stroke (cerebral infarction).

The aromatic-cationic peptides of the invention may be administered in a variety of ways. In some embodiments, the peptides may be administered orally, topically, intranasally, intravenously, subcutaneously, or transdermally (e.g., by iontophoresis).

In another aspect, the invention provides a method of preventing and/or treating diabetes, obesity, hyperlipemia, arteriosclerosis, cerebrovascular disease, hypertension or heart disease comprising administering a therapeutically effective amount of aromatic-cationic peptides to subjects in need thereof. In a particular embodiment, the aromatic-cationic peptide comprises D-Arg-2'6'Dmt-Lys-Phe-NH.sub.2 (SS-31).

DETAILED DESCRIPTION

It is to be appreciated that certain aspects, modes, embodiments, variations and features of the invention are described below in various levels of detail in order to provide a substantial understanding of the present invention.

In practicing the present invention, many conventional techniques in molecular biology, protein biochemistry, cell biology, immunology, microbiology and recombinant DNA are used. These techniques are well-known and are explained in, e.g., Current Protocols in Molecular Biology, Vols. I-III, Ausubel, Ed. (1997); Sambrook et al., Molecular Cloning: A Laboratory Manual, Second Ed. (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989); DNA Cloning: A Practical Approach, Vols. I and II, Glover, Ed. (1985); Oligonucleotide Synthesis, Gait, Ed. (1984); Nucleic Acid Hybridization, Hames & Higgins, Eds. (1985); Transcription and Translation, Hames & Higgins, Eds. (1984); Animal Cell Culture, Freshney, Ed. (1986); Immobilized Cells and Enzymes (IRL Press, 1986); Perbal, A Practical Guide to Molecular Cloning; the series, Meth. Enzymol., (Academic Press, Inc., 1984); Gene Transfer Vectors for Mammalian Cells, Miller & Calos, Eds. (Cold Spring Harbor Laboratory, NY, 1987); and Meth. Enzymol., Vols. 154 and 155, Wu & Grossman, and Wu, Eds., respectively. Methods to detect and measure levels of polypeptide gene expression products (i.e., gene translation level) are well-known in the art and include the use polypeptide detection methods such as antibody detection and quantification techniques. (See also, Strachan & Read, Human Molecular Genetics, Second Edition. (John Wiley and Sons, Inc., NY, 1999)).

The present inventors have discovered that, surprisingly, aromatic-cationic peptides can prevent or treat insulin resistance in mammalian tissues; in particular, insulin resistance in skeletal muscle tissues. In some cases, the insulin resistance may be due to a high fat diet or, more generally, over-nutrition. The peptides of the invention are beneficial in treating diabetic, pre-diabetic or obese insulin resistant, non-diabetic patients. Without intending to limit the invention to a particular mechanism of action, it is believed that loss of mitochondrial integrity and insulin sensitivity stem from a common metabolic disturbance, i.e., oxidative stress. Over-nutrition, particularly from high fat diets may increase mitochondrial reactive oxygen species (ROS) emission and overall oxidative stress in skeletal muscle, leading to both acute and chronic mitochondrial dysfunction and the development of insulin resistance. The aromatic-cationic peptides of the present invention mitigate these effects, thereby improving mitochondrial function in skeletal muscle tissues, thus improving insulin sensitivity. The invention also provides methods of using peptides of the invention to prevent or treat diabetes, pre-diabetes, related metabolic diseases, and complications arising therefrom.

The present inventors found that high fat diet/obesity-induced insulin resistance is related to mitochondrial bioenergetics. The implication is that the oversupply of metabolic substrates causes the mitochondrial respiratory system to become more reduced, generating an increase in ROS emission and shift in the overall redox environment to a more oxidized state that, if persistent, leads to development of insulin resistance. Linking mitochondrial bioenergetics to the etiology of insulin resistance has a number of clinical implications. It is known that standard care of insulin resistance (NIDDM) in humans often results in weight gain and, in selected individuals, increased variability of blood sugar with resulting metabolic and clinical consequences. The examples shown herein demonstrate that treatment of mitochondrial defect with mitochondrial-targeted antioxidant (e.g. an aromatic cationic peptide) provides a new and surprising approach to metabolic correction of insulin resistance without the growth and metabolic effects of increased insulin.

The present invention relates to the reduction of insulin resistance by certain aromatic-cationic peptides. The aromatic-cationic peptides are water-soluble and highly polar. Despite these properties, the peptides can readily penetrate cell membranes. The aromatic-cationic peptides useful in the present invention include a minimum of three amino acids, and preferably include a minimum of four amino acids, covalently joined by peptide bonds. The maximum number of amino acids present in the aromatic-cationic peptides of the present invention is about twenty amino acids covalently joined by peptide bonds. Preferably, the maximum number of amino acids is about twelve, more preferably about nine, and most preferably about six. Optimally, the number of amino acids present in the peptides is four.

The amino acids of the aromatic-cationic peptides useful in the present invention can be any amino acid. As used herein, the term "amino acid" is used to refer to any organic molecule that contains at least one amino group and at least one carboxyl group. Preferably, at least one amino group is at the .alpha. position relative to a carboxyl group. The amino acids may be naturally occurring. Naturally occurring amino acids include, for example, the twenty most common levorotatory (L) amino acids normally found in mammalian proteins, i.e., alanine (Ala), arginine (Arg), asparagine (Asn), aspartic acid (Asp), cysteine (Cys), glutamine (Gln), glutamic acid (Glu), glycine (Gly), histidine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), tryptophan, (Trp), tyrosine (Tyr), and valine (Val). Other naturally occurring amino acids include, for example, amino acids that are synthesized in metabolic processes not associated with protein synthesis. For example, the amino acids ornithine and citrulline are synthesized in mammalian metabolism during the production of urea. Another example of a naturally occurring amino acid include hydroxyproline (Hyp).

The peptides useful in the present invention optionally contain one or more non-naturally occurring amino acids. Optimally, the peptide has no amino acids that are naturally occurring. The non-naturally occurring amino acids may be levorotary (L-), dextrorotatory (D-), or mixtures thereof. Non-naturally occurring amino acids are those amino acids that typically are not synthesized in normal metabolic processes in living organisms, and do not naturally occur in proteins. In addition, the non-naturally occurring amino acids useful in the present invention preferably are also not recognized by common proteases. The non-naturally occurring amino acid can be present at any position in the peptide. For example, the non-naturally occurring amino acid can be at the N-terminus, the C-terminus, or at any position between the N-terminus and the C-terminus.

The non-natural amino acids may, for example, comprise alkyl, aryl, or alkylaryl groups not found in natural amino acids. Some examples of non-natural alkyl amino acids include .alpha.-aminobutyric acid, .beta.-aminobutyric acid, .gamma.-aminobutyric acid, .delta.-aminovaleric acid, and .epsilon.-aminocaproic acid. Some examples of non-natural aryl amino acids include ortho-, meta, and para-aminobenzoic acid. Some examples of non-natural alkylaryl amino acids include ortho-, meta-, and para-aminophenylacetic acid, and .gamma.-phenyl-.beta.-aminobutyric acid. Non-naturally occurring amino acids include derivatives of naturally occurring amino acids. The derivatives of naturally occurring amino acids may, for example, include the addition of one or more chemical groups to the naturally occurring amino acid.

For example, one or more chemical groups can be added to one or more of the 2', 3', 4', 5', or 6' position of the aromatic ring of a phenylalanine or tyrosine residue, or the 4', 5', 6', or 7' position of the benzo ring of a tryptophan residue. The group can be any chemical group that can be added to an aromatic ring. Some examples of such groups include branched or unbranched C.sub.1-C.sub.4 alkyl, such as methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, or t-butyl, C.sub.1-C.sub.4 alkyloxy (i.e., alkoxy), amino, C.sub.1-C.sub.4 alkylamino and C.sub.1-C.sub.4 dialkylamino (e.g., methylamino, dimethylamino), nitro, hydroxyl, halo (i.e., fluoro, chloro, bromo, or iodo). Some specific examples of non-naturally occurring derivatives of naturally occurring amino acids include norvaline (Nva) and norleucine (Nle).

Another example of a modification of an amino acid in a peptide useful in the methods of the present invention is the derivatization of a carboxyl group of an aspartic acid or a glutamic acid residue of the peptide. One example of derivatization is amidation with ammonia or with a primary or secondary amine, e.g. methylamine, ethylamine, dimethylamine or diethylamine. Another example of derivatization includes esterification with, for example, methyl or ethyl alcohol. Another such modification includes derivatization of an amino group of a lysine, arginine, or histidine residue. For example, such amino groups can be acylated. Some suitable acyl groups include, for example, a benzoyl group or an alkanoyl group comprising any of the C.sub.1-C.sub.4 alkyl groups mentioned above, such as an acetyl or propionyl group.

The non-naturally occurring amino acids are preferably resistant, and more preferably insensitive, to common proteases. Examples of non-naturally occurring amino acids that are resistant or insensitive to proteases include the dextrorotatory (D-) form of any of the above-mentioned naturally occurring L-amino acids, as well as L-and/or D-non-naturally occurring amino acids. The D-amino acids do not normally occur in proteins, although they are found in certain peptide antibiotics that are synthesized by means other than the normal ribosomal protein synthetic machinery of the cell. As used herein, the D-amino acids are considered to be non-naturally occurring amino acids.

In order to minimize protease sensitivity, the peptides useful in the methods of the invention should have less than five, preferably less than four, more preferably less than three, and most preferably, less than two contiguous L-amino acids recognized by common proteases, irrespective of whether the amino acids are naturally or non-naturally occurring. Optimally, the peptide has only D-amino acids, and no L-amino acids. If the peptide contains protease sensitive sequences of amino acids, at least one of the amino acids is preferably a non-naturally-occurring D-amino acid, thereby conferring protease resistance. An example of a protease sensitive sequence includes two or more contiguous basic amino acids that are readily cleaved by common proteases, such as endopeptidases and trypsin. Examples of basic amino acids include arginine, lysine and histidine.

The aromatic-cationic peptides should have a minimum number of net positive charges at physiological pH in comparison to the total number of amino acid residues in the peptide. The minimum number of net positive charges at physiological pH will be referred to below as (p.sub.m). The total number of amino acid residues in the peptide will be referred to below as (r). The minimum number of net positive charges discussed below are all at physiological pH. The term "physiological pH" as used herein refers to the normal pH in the cells of the tissues and organs of the mammalian body. For instance, the physiological pH of a human is normally approximately 7.4, but normal physiological pH in mammals may be any pH from about 7.0 to about 7.8.

"Net charge" as used herein refers to the balance of the number of positive charges and the number of negative charges carried by the amino acids present in the peptide. In this specification, it is understood that net charges are measured at physiological pH. The naturally occurring amino acids that are positively charged at physiological pH include L-lysine, L-arginine, and L-histidine. The naturally occurring amino acids that are negatively charged at physiological pH include L-aspartic acid and L-glutamic acid.

Typically, a peptide has a positively charged N-terminal amino group and a negatively charged C-terminal carboxyl group. The charges cancel each other out at physiological pH. As an example of calculating net charge, the peptide Tyr-Arg-Phe-Lys-Glu-His-Trp-D-Arg has one negatively charged amino acid (i.e., Glu) and four positively charged amino acids (i.e., two Arg residues, one Lys, and one His). Therefore, the above peptide has a net positive charge of three.

In one embodiment of the present invention, the aromatic-cationic peptides have a relationship between the minimum number of net positive charges at physiological pH (p.sub.m) and the total number of amino acid residues (r) wherein 3p.sub.m is the largest number that is less than or equal to r+1. In this embodiment, the relationship between the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) is as follows -- see Original Patent.

In another embodiment, the aromatic-cationic peptides have a relationship between the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) wherein 2p.sub.m is the largest number that is less than or equal to r+1. In this embodiment, the relationship between the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) is as follows -- see Original Patent.

In one embodiment, the minimum number of net positive charges (p.sub.m) and the total number of amino acid residues (r) are equal. In another embodiment, the peptides have three or four amino acid residues and a minimum of one net positive charge, preferably, a minimum of two net positive charges and more preferably a minimum of three net positive charges.

It is also important that the aromatic-cationic peptides have a minimum number of aromatic groups in comparison to the total number of net positive charges (p.sub.t). The minimum number of aromatic groups will be referred to below as (a). Naturally occurring amino acids that have an aromatic group include the amino acids histidine, tryptophan, tyrosine, and phenylalanine. For example, the hexapeptide Lys-Gln-Tyr-D-Arg-Phe-Trp has a net positive charge of two (contributed by the lysine and arginine residues) and three aromatic groups (contributed by tyrosine, phenylalanine and tryptophan residues).

The aromatic-cationic peptides useful in the methods of the present invention should also have a relationship between the minimum number of aromatic groups (a) and the total number of net positive charges at physiological pH (p.sub.t) wherein 3a is the largest number that is less than or equal to p.sub.t+1, except that when p.sub.t is 1, a may also be 1. In this embodiment, the relationship between the minimum number of aromatic groups (a) and the total number of net positive charges (p.sub.t) is as follows -- see Original Patent.

In another embodiment, the aromatic-cationic peptides have a relationship between the minimum number of aromatic groups (a) and the total number of net positive charges (p.sub.t) wherein 2a is the largest number that is less than or equal to p.sub.t+1. In this embodiment, the relationship between the minimum number of aromatic amino acid residues (a) and the total number of net positive charges (p.sub.t) is as follows -- see Original Patent.

In another embodiment, the number of aromatic groups (a) and the total number of net positive charges (p.sub.t) are equal.

Carboxyl groups, especially the terminal carboxyl group of a C-terminal amino acid, are preferably amidated with, for example, ammonia to form the C-terminal amide. Alternatively, the terminal carboxyl group of the C-terminal amino acid may be amidated with any primary or secondary amine. The primary or secondary amine may, for example, be an alkyl, especially a branched or unbranched C.sub.1-C.sub.4 alkyl, or an aryl amine. Accordingly, the amino acid at the C-terminus of the peptide may be converted to an amido, N-methylamido, N-ethylamido, N,N-dimethylamido, N,N-diethylamido, N-methyl-N-ethylamido, N-phenylamido or N-phenyl-N-ethylamido group. The free carboxylate groups of the asparagine, glutamine, aspartic acid, and glutamic acid residues not occurring at the C-terminus of the aromatic-cationic peptides of the present invention may also be amidated wherever they occur within the peptide. The amidation at these internal positions may be with ammonia or any of the primary or secondary amines described above.

In one embodiment, the aromatic-cationic peptide useful in the methods of the present invention is a tripeptide having two net positive charges and at least one aromatic amino acid. In a particular embodiment, the aromatic-cationic peptide useful in the methods of the present invention is a tripeptide having two net positive charges and two aromatic amino acids.

Aromatic-cationic peptides useful in the methods of the present invention include, but are not limited to, the following peptide examples -- see Original Patent.

In one embodiment, the peptides useful in the methods of the present invention have mu-opioid receptor agonist activity (i.e., they activate the mu-opioid receptor). Mu-opioid activity can be assessed by radioligand binding assay to cloned mu-opioid receptors or by bioassays suing the guinea pig ileum (Schiller et al., Eur J Med Chem, 35:895-901, 2000; Zhao et al., J Pharmacol Exp Ther 307:947-954, 2003). Activation of the mu-opioid receptor typically elicits an analgesic effect. In certain instances, an aromatic-cationic peptide having mu-opioid receptor agonist activity is preferred. For example, during short-term treatment, such as in an acute disease or condition, it may be beneficial to use an aromatic-cationic peptide that activates the mu-opioid receptor. Such acute diseases and conditions are often associated with moderate or severe pain. In these instances, the analgesic effect of the aromatic-cationic peptide may be beneficial in the treatment regimen of the human patient or other mammal. An aromatic-cationic peptide which does not activate the mu-opioid receptor, however, may also be used with or without an analgesic, according to clinical requirements.

Alternatively, in other instances, an aromatic-cationic peptide that does not have mu-opioid receptor agonist activity is preferred. For example, during long-term treatment, such as in a chronic disease state or condition, the use of an aromatic-cationic peptide that activates the mu-opioid receptor may be contraindicated. In these instances the potentially adverse or addictive effects of the aromatic-cationic peptide may preclude the use of an aromatic-cationic peptide that activates the mu-opioid receptor in the treatment regimen of a human patient or other mammal. Potential adverse effects may include sedation, constipation and respiratory depression. In such instances an aromatic-cationic peptide that does not activate the mu-opioid receptor may be an appropriate treatment.

Peptides useful in the methods of the present invention which have mu-opioid receptor agonist activity are typically those peptides which have a tyrosine residue or a tyrosine derivative at the N-terminus (i.e., the first amino acid position). Preferred derivatives of tyrosine include 2'-methyltyrosine (Mmt); 2',6'-dimethyltyrosine (2'6'Dmt); 3',5'-dimethyltyrosine (3'5'Dmt); N,2',6'-trimethyltyrosine (Tmt); and 2'-hydroxy-6'-methyltyrosine (Hmt).

In one embodiment, a peptide that has mu-opioid receptor agonist activity has the formula Tyr-D-Arg-Phe-Lys-NH.sub.2 (referred to herein as "SS-01"). SS-01 has a net positive charge of three, contributed by the amino acids tyrosine, arginine, and lysine and has two aromatic groups contributed by the amino acids phenylalanine and tyrosine. The tyrosine of SS-01 can be a modified derivative of tyrosine such as in 2',6'-dimethyltyrosine to produce the compound having the formula 2',6'-Dmt-D-Arg-Phe-Lys-NH.sub.2 (referred to herein as "SS-02"). SS-02 has a molecular weight of 640 and carries a net three positive charge at physiological pH. SS-02 readily penetrates the plasma membrane of several mammalian cell types in an energy-independent manner (Zhao et al., J. Pharmacol Exp Ther. 304: 425-432, 2003).

Peptides that do not have mu-opioid receptor agonist activity generally do not have a tyrosine residue or a derivative of tyrosine at the N-terminus (i.e., amino acid position 1). The amino acid at the N-terminus can be any naturally occurring or non-naturally occurring amino acid other than tyrosine. In one embodiment, the amino acid at the N-terminus is phenylalanine or its derivative. Exemplary derivatives of phenylalanine include 2'-methylphenylalanine (Mmp), 2',6'-dimethylphenylalanine (Dmp), N,2',6'-trimethylphenylalanine (Tmp), and 2'-hydroxy-6'-methylphenylalanine (Hmp).

An example of a aromatic-cationic peptide that does not have mu-opioid receptor agonist activity has the formula Phe-D-Arg-Phe-Lys-NH.sub.2 (referred to herein as "SS-20"). Alternatively, the N-terminal phenylalanine can be a derivative of phenylalanine such as 2',6'-dimethylphenylalanine (2'6'Dmp). SS-01 containing 2',6'-dimethylphenylalanine at amino acid position 1 has the formula 2',6'-Dmp-D-Arg-Phe-Lys-NH.sub.2. In one embodiment, the amino acid sequence of SS-02 is rearranged such that Dmt is not at the N-terminus. An example of such an aromatic-cationic peptide that does not have mu-opioid receptor agonist activity has the formula D-Arg-2'6'Dmt-Lys-Phe-NH.sub.2 (SS-31).

SS-01, SS-20, SS-31, and their derivatives can further include functional analogs. A peptide is considered a functional analog of SS-01, SS-20, or SS-31 if the analog has the same function as SS-01, SS-20, or SS-31. The analog may, for example, be a substitution variant of SS-01, SS-20, or SS-31, wherein one or more amino acids are substituted by another amino acid.

Suitable substitution variants of SS-01, SS-20, or SS-31 include conservative amino acid substitutions. Amino acids may be grouped according to their physicochemical characteristics as follows:

(a) Non-polar amino acids: Ala(A) Ser(S) Thr(T) Pro(P) Gly(G) Cys (C);

(b) Acidic amino acids: Asn(N) Asp(D) Glu(E) Gln(Q);

(c) Basic amino acids: His(H) Arg(R) Lys(K);

(d) Hydrophobic amino acids: Met(M) Leu(L) Ile(I) Val(V); and

(e) Aromatic amino acids: Phe(F) Tyr(Y) Trp(W) His (H).

Substitutions of an amino acid in a peptide by another amino acid in the same group is referred to as a conservative substitution and may preserve the physicochemical characteristics of the original peptide. In contrast, substitutions of an amino acid in a peptide by another amino acid in a different group is generally more likely to alter the characteristics of the original peptide.

In some embodiments, one or more naturally occurring amino acids in the aromatic-cationic peptides are substituted with amino acid analogs. Examples of analogs useful in the practice of the present invention that activate mu-opioid receptors include, but are not limited to, the aromatic-cationic peptides shown in Table 5 -- see Original Patent.

Examples of analogs useful in the practice of the present invention that do not activate mu-opioid receptors include, but are not limited to, the aromatic-cationic peptides shown in Table 6 -- see Original Patent.

The amino acids of the peptides shown in Table 5 and 6 (see Original Patent) may be in either the L-or the D-configuration.

Synthesis of the Peptides

The peptides useful in the methods of the present invention may be synthesized by any of the methods well known in the art. Suitable methods for chemically synthesizing the protein include, for example, those described by Stuart and Young in Solid Phase Peptide Synthesis, Second Edition, Pierce Chemical Company (1984), and in Methods Enzymol. 289, Academic Press, Inc, New York (1997).

Prophylactic and Therapeutic Uses of Aromatic-Cationic Peptides.

General. The aromatic-cationic peptides of the present invention are useful to prevent or treat disease. Specifically, the invention provides for both prophylactic and therapeutic methods of treating a subject at risk of (or susceptible to) a disorder or having a disorder associated with insulin resistance. Insulin resistance is generally associated with type II diabetes, coronary artery disease, renal dysfunction, atherosclerosis, obesity, hyperlipidemia, and essential hypertension. Insulin resistance is also associated with fatty liver, which can progress to chronic inflammation (NASH; "nonalcoholic steatohepatitis"), fibrosis, and cirrhosis. Cumulatively, insulin resistance syndromes, including, but not limited to diabetes, underlie many of the major causes of morbidity and death of people over age 40. Accordingly, the present invention provides methods for the prevention and/or treatment of insulin resistance and associated syndromes in a subject comprising administering an effective amount of an aromatic-cationic peptide to a subject in need thereof. For example, a subject can be administered an aromatic-cationic peptide compositions of the present invention in an effort to improve the sensitivity of mammalian skeletal muscle tissues to insulin. In one embodiment, the aromatic-cationic peptides of the invention are useful to prevent drug-induced obesity, insulin resistance, and/or diabetes, when the peptide is administered with a drug that shows a side-effect of causing one or more of these conditions (e.g., olanzapine, Zyprexa.RTM.).

Determination of the Biological Effect of the Aromatic-Cationic Peptide-Based Therapeutic. In various embodiments of the invention, suitable in vitro or in vivo assays are performed to determine the effect of a specific aromatic-cationic peptide-based therapeutic and whether its administration is indicated for treatment of the affected tissue in a subject. In various embodiments, in vitro assays can be performed with representative cells of the type(s) involved in the subject's disorder, to determine if a given aromatic-cationic peptide-based therapeutic exerts the desired effect upon the cell type(s). Compounds for use in therapy can be tested in suitable animal model systems including, but not limited to rats, mice, chicken, cows, monkeys, rabbits, and the like, prior to testing in human subjects. Similarly, for in vivo testing, any of the animal model system known in the art can be used prior to administration to human subjects. Increased or decreased insulin resistance or sensitivity can be readily detected by quantifying body weight, fasting glucose/insulin/free fatty acid, glucose tolerance (OGTT), in vitro muscle insulin sensitivity, markers of insulin signaling (e.g., Akt-P, IRS-P), mitochondrial function (e.g., respiration or H.sub.2O.sub.2 emission), markers of intracellular oxidative stress (e.g., lipid peroxidation, GSH/GSSG ratio or aconitase activity) or mitochondrial enzyme activity.

Prophylactic Methods. In one aspect, the invention provides a method for preventing, in a subject, a disease or condition associated with insulin resistance in skeletal muscle tissues, by administering to the subject an aromatic-cationic peptide that modulates one or more signs or markers of insulin resistance, e.g., body weight, fasting glucose/insulin/free fatty acid, glucose tolerance (OGTT), in vitro muscle insulin sensitivity, markers of insulin signaling (e.g., Akt-P, IRS-P), mitochondrial function (e.g., respiration or H.sub.2O.sub.2 emission), markers of intracellular oxidative stress (e.g., lipid peroxidation, GSH/GSSG ratio or aconitase activity) or mitochondrial enzyme activity.

Subjects at risk for a disease that is caused or contributed to by aberrant mitochondrial function or insulin resistance can be identified by, e.g., any or a combination of diagnostic or prognostic assays as described herein. In prophylactic applications, pharmaceutical compositions or medicaments of aromatic-cationic peptides are administered to a subject susceptible to, or otherwise at risk of a disease or condition in an amount sufficient to eliminate or reduce the risk, lessen the severity, or delay the outset of the disease, including biochemical, histologic and/or behavioral symptoms of the disease, its complications and intermediate pathological phenotypes presenting during development of the disease. Administration of a prophylactic aromatic-cationic can occur prior to the manifestation of symptoms characteristic of the aberrancy, such that a disease or disorder is prevented or, alternatively, delayed in its progression. Depending upon the type of aberrancy, e.g., a aromatic-cationic peptide which acts to enhance or improve mitochondrial function can be used for treating the subject. The appropriate compound can be determined based on screening assays described herein.

Therapeutic Methods. Another aspect of the invention includes methods of modulating insulin resistance or sensitivity in a subject for therapeutic purposes. In therapeutic applications, compositions or medicaments are administered to a subject suspected of, or already suffering from such a disease in an amount sufficient to cure, or at least partially arrest, the symptoms of the disease (biochemical, histologic and/or behavioral), including its complications and intermediate pathological phenotypes in development of the disease. An amount adequate to accomplish therapeutic or prophylactic treatment is defined as a therapeutically-or prophylactically-effective dose. These modulatory methods can be performed in vitro (e.g., by culturing the cell with the aromatic-cationic peptide) or, alternatively, in vivo (e.g., by administering the aromatic-cationic peptide to a subject). As such, the invention provides methods of treating an individual afflicted with a insulin resistance-associated disease or disorder.

Modes of Administration and Effective Dosages

Any method known to those in the art for contacting a cell, organ or tissue with a peptide may be employed. Suitable methods include in vitro, ex vivo, or in vivo methods. In vivo methods typically include the administration of an aromatic-cationic peptide, such as those described above, to a mammal, preferably a human. When used in vivo for therapy, the aromatic-cationic peptides of the present invention are administered to the subject in effective amounts (i.e., amounts that have desired therapeutic effect). They will normally be administered parenterally or orally. The dose and dosage regimen will depend upon the degree of the insulin resistance-related disease or disorder, the characteristics of the particular aromatic-cationic peptide used, e.g., its therapeutic index, the subject, and the subject's history.

The effective amount may be determined during pre-clinical trials and clinical trials by methods familiar to physicians and clinicians. An effective amount of a peptide useful in the methods of the present invention, preferably in a pharmaceutical composition, may be administered to a mammal in need thereof by any of a number of well-known methods for administering pharmaceutical compounds. The peptide may be administered systemically or locally.

The aromatic-cationic peptides described herein can be incorporated into pharmaceutical compositions for administration, singly or in combination, to a subject for the treatment or prevention of a disorder described herein. Such compositions typically include the active agent and a pharmaceutically acceptable carrier. As used herein the term "pharmaceutically acceptable carrier" includes saline, solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. Supplementary active compounds can also be incorporated into the compositions.

Pharmaceutical compositions are typically formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral (e.g., intravenous, intradermal, intraperitoneal or subcutaneous), oral, inhalation, transdermal (topical), and transmucosal administration. Solutions or suspensions used for parenteral, intradermal, or subcutaneous application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. pH can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. For convenience of the patient or treating physician, the dosing formulation can be provided in a kit containing all necessary equipment (e.g. vials of drug, vials of diluent, syringes and needles) for a treatment course (e.g. 7 days of treatment).

Pharmaceutical compositions suitable for injectable use can include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. For intravenous administration, suitable carriers include physiological saline, bacteriostatic water, Cremophor EL.TM. (BASF, Parsippany, N.J.) or phosphate buffered saline (PBS). In all cases, a composition for parenteral administration must be sterile and should be fluid to the extent that easy syringability exists. It should be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi.

The aromatic-cationic peptide compositions can include a carrier, which can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prevention of the action of microorganisms can be achieved by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thiomerasol, and the like. Glutathione and other antioxidants can be included to prevent oxidation. In many cases, it will be preferable to include isotonic agents, for example, sugars, polyalcohols such as mannitol, sorbitol, or sodium chloride in the composition. Prolonged absorption of the injectable compositions can be brought about by including in the composition an agent which delays absorption, for example, aluminum monostearate or gelatin.

Sterile injectable solutions can be prepared by incorporating the active compound in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle, which contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, typical methods of preparation include vacuum drying and freeze drying, which can yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

Oral compositions generally include an inert diluent or an edible carrier. For the purpose of oral therapeutic administration, the active compound can be incorporated with excipients and used in the form of tablets, troches, or capsules, e.g., gelatin capsules. Oral compositions can also be prepared using a fluid carrier for use as a mouthwash. Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part of the composition. The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring.

For administration by inhalation, the compounds can be delivered in the form of an aerosol spray from a pressurized container or dispenser which contains a suitable propellant, e.g., a gas such as carbon dioxide, or a nebulizer. Such methods include those described in U.S. Pat. No. 6,468,798.

Systemic administration of a therapeutic compound as described herein can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, detergents, bile salts, and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays. For transdermal administration, the active compounds are formulated into ointments, salves, gels, or creams as generally known in the art. In one embodiment, transdermal administration may be performed my iontophoresis.

A therapeutic protein or peptide can be formulated in a carrier system. The carrier can be a colloidal system. The colloidal system can be a liposome, a phospholipid bilayer vehicle. In one embodiment, the therapeutic protein is encapsulated in a liposome while maintaining protein integrity. As one skilled in the art would appreciate, there are a variety of methods to prepare liposomes. (See Lichtenberg et al., Methods Biochem. Anal., 33:337-462 (1988); Anselem et al., Liposome Technology, CRC Press (1993)). Liposomal formulations can delay clearance and increase cellular uptake (See Reddy, Ann. Pharmacother., 34 (7-8):915-923 (2000)).

The carrier can also be a polymer, e.g., a biodegradable, biocompatible polymer matrix. In one embodiment, the therapeutic protein can be embedded in the polymer matrix, while maintaining protein integrity. The polymer may be natural, such as polypeptides, proteins or polysaccharides, or synthetic, such as poly .alpha.-hydroxy acids. Examples include carriers made of, e.g., collagen, fibronectin, elastin, cellulose acetate, cellulose nitrate, polysaccharide, fibrin, gelatin, and combinations thereof. In one embodiment, the polymer is poly-lactic acid (PLA) or copoly lactic/glycolic acid (PGLA). The polymeric matrices can be prepared and isolated in a variety of forms and sizes, including microspheres and nanospheres. Polymer formulations can lead to prolonged duration of therapeutic effect. (See Reddy, Ann. Pharmacother., 34 (7-8):915-923 (2000)). A polymer formulation for human growth hormone (hGH) has been used in clinical trials. (See Kozarich and Rich, Chemical Biology, 2:548-552 (1998)).

Examples of polymer microsphere sustained release formulations are described in PCT publication WO 99/15154 (Tracy et al.), U.S. Pat. Nos. 5,674,534 and 5,716,644 (both to Zale et al.), PCT publication WO 96/40073 (Zale et al.), and PCT publication WO 00/38651 (Shah et al.). U.S. Pat. Nos. 5,674,534 and 5,716,644 and PCT publication WO 96/40073 describe a polymeric matrix containing particles of erythropoietin that are stabilized against aggregation with a salt.

In some embodiments, the therapeutic compounds are prepared with carriers that will protect the therapeutic compounds against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylacetic acid. Such formulations can be prepared using known techniques. The materials can also be obtained commercially, e.g., from Alza Corporation and Nova Pharmaceuticals, Inc. Liposomal suspensions (including liposomes targeted to specific cells with monoclonal antibodies to cell-specific antigens) can also be used as pharmaceutically acceptable carriers. These can be prepared according to methods known to those skilled in the art, for example, as described in U.S. Pat. No. 4,522,811.

The therapeutic compounds can also be formulated to enhance intracellular delivery. For example, liposomal delivery systems are known in the art, see, e.g., Chonn and Cullis, "Recent Advances in Liposome Drug Delivery Systems," Current Opinion in Biotechnology 6:698-708 (1995); Weiner, "Liposomes for Protein Delivery: Selecting Manufacture and Development Processes," Immunomethods 4 (3) 201-9 (1994); and Gregoriadis, "Engineering Liposomes for Drug Delivery: Progress and Problems," Trends Biotechnol. 13 (12):527-37 (1995). Mizguchi et al., Cancer Lett. 100:63-69 (1996), describes the use of fusogenic liposomes to deliver a protein to cells both in vivo and in vitro.

Dosage, toxicity and therapeutic efficacy of the therapeutic agents can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Compounds which exhibit high therapeutic indices are preferred. While compounds that exhibit toxic side effects may be used, care should be taken to design a delivery system that targets such compounds to the site of affected tissue in order to minimize potential damage to uninfected cells and, thereby, reduce side effects.

The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the method of the invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose can be formulated in animal models to achieve a circulating plasma concentration range that includes the IC50 (i.e., the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma may be measured, for example, by high performance liquid chromatography.

Typically, an effective amount of the aromatic-cationic peptides of the present invention, sufficient for achieving a therapeutic or prophylactic effect, range from about 0.000001 mg per kilogram body weight per day to about 10,000 mg per kilogram body weight per day. Preferably, the dosage ranges are from about 0.0001 mg per kilogram body weight per day to about 100 mg per kilogram body weight per day. For example dosages can be 1 mg/kg body weight or 10 mg/kg body weight every day, every two days or every three days or within the range of 1-10 mg/kg every week, every two weeks or every three weeks. In one embodiment, a single dosage of peptide ranges from 0.1-10,000 micrograms per kg body weight. In one embodiment, aromatic-cationic peptide concentrations in a carrier range from 0.2 to 2000 micrograms per delivered milliliter. An exemplary treatment regime entails administration once per day or once a week. Intervals can also be irregular as indicated by measuring blood levels of glucose or insulin in the subject and adjusting dosage or administration accordingly. In some methods, dosage is adjusted to achieve a desired fasting glucose or fasting insulin concentration. In therapeutic applications, a relatively high dosage at relatively short intervals is sometimes required until progression of the disease is reduced or terminated, and preferably until the subject shows partial or complete amelioration of symptoms of disease. Thereafter, the patient can be administered a prophylactic regime.

In some embodiments, a therapeutically effective amount of an aromatic-cationic peptide may be defined as a concentration of peptide at the target tissue of 10.sup.-11 to 10.sup.-6 molar, e.g., approximately 10.sup.-7 molar. This concentration may be delivered by systemic doses of 0.01 to 100 mg/kg or equivalent dose by body surface area. The schedule of doses would be optimized to maintain the therapeutic concentration at the target tissue, most preferably by single daily or weekly administration, but also including continuous administration (e.g. parenteral infusion or transdermal application).

The skilled artisan will appreciate that certain factors may influence the dosage and timing required to effectively treat a subject, including but not limited to, the severity of the disease or disorder, previous treatments, the general health and/or age of the subject, and other diseases present. Moreover, treatment of a subject with a therapeutically effective amount of the therapeutic compositions described herein can include a single treatment or a series of treatments.

The mammal treated in accordance with the invention can be any mammal, including, for example, farm animals, such as sheep, pigs, cows, and horses; pet animals, such as dogs and cats; laboratory animals, such as rats, mice and rabbits. In a preferred embodiment, the mammal is a human.

Labeled Aromatic-Cationic Peptides and Diagnostic Methods

Disclosed herein are methods comprising providing a labeled aromatic-cationic peptide to a cell or a subject, wherein the peptide has a detectable label conjugated to a peptide. In one embodiment, a specific combination of a particular label with a particular peptide allows for detecting localization of the peptide within a cell.

Labeled Aromatic Cationic Peptides. In one embodiment, the aromatic-cationic peptides of the present invention are coupled with a label moiety, i.e., detectable group. The particular label or detectable group conjugated to the aromatic-cationic peptide of the invention is not a critical aspect of the invention, so long as it does not significantly interfere with the specific activity of the aromatic cationic peptide of the present invention. The detectable group can be any material having a detectable physical or chemical property. Such detectable labels have been well-developed in the field of immunoassays and imaging, in general, most any label useful in such methods can be applied to the present invention. Thus, a label is any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. Useful labels in the present invention include magnetic beads (e.g., Dynabeads.TM.), fluorescent dyes (e.g., fluorescein isothiocyanate, Texas red, rhodamine, and the like), radiolabels (e.g., .sup.3H, .sup.14C, .sup.35S, .sup.125I, .sup.121I, .sup.112In, .sup.99mTc), other imaging agents such as microbubbles (for ultrasound imaging), .sup.18F, .sup.11C, .sup.15O, (for Positron emission tomography), .sup.99mTC, .sup.111In (for Single photon emission tomography), enzymes (e.g., horse radish peroxidase, alkaline phosphatase and others commonly used in an ELISA), and calorimetric labels such as colloidal gold or colored glass or plastic (e.g., polystyrene, polypropylene, latex, and the like) beads. Patents that described the use of such labels include U.S. Pat. Nos. 3,817,837; 3,850,752; 3,939,350; 3,996,345; 4,277,437; 4,275,149; and 4,366,241, each incorporated herein by reference in their entirety and for all purposes. See also Handbook of Fluorescent Probes and Research Chemicals (6.sup.th Ed., Molecular Probes, Inc., Eugene Oreg.).

The label can be coupled directly or indirectly to the desired component of an assay according to methods well known in the art. As indicated above, a wide variety of labels can be used, with the choice of label depending on sensitivity required, ease of conjugation with the compound, stability requirements, available instrumentation, and disposal provisions.

Non-radioactive labels are often attached by indirect means. Generally, a ligand molecule (e.g., biotin) is covalently bound to the molecule. The ligand then binds to an anti-ligand (e.g., streptavidin) molecule which is either inherently detectable or covalently bound to a signal system, such as a detectable enzyme, a fluorescent compound, or a chemiluminescent compound. A number of ligands and anti-ligands can be used. Where a ligand has a natural anti-ligand, e.g., biotin, thyroxine, and cortisol, it can be used in conjunction with the labeled, naturally-occurring anti-ligands.

The molecules can also be conjugated directly to signal generating compounds, e.g., by conjugation with an enzyme or fluorophore. Enzymes of interest as labels will primarily be hydrolases, particularly phosphatases, esterases and glycosidases, or oxidoreductases, particularly peroxidases. Fluorescent compounds useful as labeling moieties, include, but are not limited to, e.g., fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelliferone, and the like. Chemiluminescent compounds useful as labelling moieties, include, but are not limited to, e.g., luciferin, and 2,3-dihydrophthalazinediones, e.g., luminol. For a review of various labeling or signal-producing systems which can be used, see, U.S. Pat. No. 4,391,904.

Means of detecting labels are well known to those of skill in the art. Thus, for example, where the label is a radioactive label, means for detection include a scintillation counter or photographic film as in autoradiography. Where the label is a fluorescent label, it can be detected by exciting the fluorochrome with the appropriate wavelength of light and detecting the resulting fluorescence. The fluorescence can be detected visually, by means of photographic film, by the use of electronic detectors such as charge coupled devices (CCDs) or photomultipliers and the like. Similarly, enzymatic labels can be detected by providing the appropriate substrates for the enzyme and detecting the resulting reaction product. Finally simple colorimetric labels can be detected simply by observing the color associated with the label. Thus, in various dipstick assays, conjugated gold often appears pink, while various conjugated beads appear the color of the bead.

Diagnostic Applications of Labeled Aromatic Cationic Peptides

In one embodiment, the method comprising administering the labeled aromatic-cationic peptide to a cell or a subject and achieving a desired localization. In one embodiment of the invention, the method comprising administering the labeled aromatic-cationic peptide to a human cell and achieving a desired localization. A desired localization refers to a labeled aromatic-cationic peptide being specifically sequestered in a desired cellular component, e.g., the mitochondrion. Those skilled in the art will recognize that any number of labeled aromatic-cationic peptides of the present invention may be delivered to a cell and the method remains within the spirit and scope of the present invention. In addition, those skilled in the art will recognize that cellular imaging various types of cells from various types of sources are within the spirit and scope of the present invention.

Labeled aromatic-cationic peptides of the invention can be used in vitro and/or in vivo to detect target molecules of interest. In many cases, the labeled aromatic-cationic peptides can simply be added to test samples in a homogenous assay, not requiring addition of multiple reagents and/or wash steps before detection of the target. Labeled aromatic-cationic peptides of the invention may contact target molecules or cellular compartments in vitro by simple addition to a test sample containing the target molecules or cells. Test samples for in vitro assays can be, e.g., molecular libraries, cell lysates, analyte eluates from chromatographic columns, and the like. The in vitro assay often takes place in a chamber, such as, e.g., a well of a multiwell plate, a test tube, an Eppendorf tube, a spectrophotometer cell, conduit of an analytical system, channels of a microfluidic system, an open array, and the like.

Where labeled aromatic-cationic peptides of the invention are administered to living cells, binding can take place with targets on the cell surface or within the cell itself, e.g., the labeled aromatic-cationic peptide is transferred into the cell to make contact with an intracellular target molecule. In some cases, the labeled aromatic-cationic peptide can penetrate a cell suspected of containing a selected target passively by mere exposure of the cell to a medium containing the labeled aromatic-cationic peptides. In other embodiments, the labeled aromatic-cationic peptide is actively transferred into the cell by mechanisms known in the art, such as, e.g., poration, injection, transduction along with transfer peptides, and the like.

Following contact of the cells with the labeled aromatic-cationic peptides, the methods may comprise irradiating the cell with an energy source. In one embodiment, the energy source is a light source. In one embodiment, the imaging agent of the labeled aromatic-cationic peptide is activated by the energy source. In one embodiment, the imaging agent of the labeled aromatic-cationic peptide gives off a detectable signal when it is illuminated by the energy source. In one embodiment of the invention, the imaging agent gives off a detectable fluorescence in response to the energy source.

In one embodiment of the invention, the fluorescence given off by the imaging agent in response to the light source may be observed and measured. In one embodiment of the invention, the fluorescence is observed and measured with a confocal microscope. Those skilled in the art will recognize that various devices used to observe and measure fluorescence are within the spirit and scope of the present invention.
 

Claim 1 of 12 Claims

1. A method for reducing the risk, lessening the symptoms, or delaying the outset of insulin resistance in a mammalian subject in need thereof, comprising administering to the mammalian subject a therapeutically effective amount of the peptide D-Arg-2'6'Dmt-Lys-Phe-NH.sub.2 (SS-31).
 

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