The Safety and Efficacy of Growth Hormone Secretagogues

Insights on discovery, efficacy, safety and clinical applications of ghrelin receptor agonist capromorelin in veterinary medicine

Growth hormone and insulin like growth factor-1 plays an important role in the regulation of body composition and metabolism. Growth Hormone is released from the pituitary through a specific G-protein coupled receptor (GPCR) called growth hormone secretagogue receptor 1a expressed in the hypothalamus. Ghrelin is a peptide hormone released from the cells in the stomach, which stimulates appetite and food intake in mammals, regulates gut motility, gastric acid secretion, taste sensation, circadian rhythm, learning and memory, oxidative stress, autophagy, glucose metabolism etc. When the release of the endogenous ligand GHSR-1a, i.e., ghrelin is malfunctioned or stopped, external substitutes are administrated to induce the stimulation of growth hormone and appetite. A class of compound known as ghrelin receptor agonists are developed as an external substitute of ghrelin for regulation and stimulation of growth hormone in frailty, for body weight gain, muscle mass gain, prevention of cachexia and for the treatment of chronic fatigue syndromes. Capromorelin [Entyce™ (Aratana Therapeutics, Leawood, KS, USA)] is the only FDA (Food and Drug Administration) approved (May 2016) drug used for stimulating appetite in dogs and was marketed in the fall of 2017. In 2020, USFDA approved Capromorelin [Elura™ (Elanco US Inc.)] for the management of weight loss in chronic kidney disease of cats. This article reviews the discovery of the ghrelin receptor agonist capromorelin, its efficacy, safety, clinical applications and aims to delineate its further scope of use in veterinary practice.

Targeting PPARs for therapy of atherosclerosis: A review

Atherosclerosis, a chief pathogenic factor of cardiovascular disease, is associated with many factors including inflammation, dyslipidemia, and oxidative stress. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and are widely expressed with tissue- and cell-specificity. They control multiple genes that are involved in lipid metabolism, inflammatory response, and redox homeostasis. Given the diverse biological functions of PPARs, they have been extensively studied since their discovery in 1990s. Although controversies exist, accumulating evidence have demonstrated that PPAR activation attenuates atherosclerosis. Recent advances are valuable for understanding the mechanisms of action of PPAR activation. This article reviews the recent findings, mainly from the year of 2018 to present, including endogenous molecules in regulation of PPARs, roles of PPARs in atherosclerosis by focusing on lipid metabolism, inflammation, and oxidative stress, and synthesized PPAR modulators. This article provides information valuable for researchers in the field of basic cardiovascular research, for pharmacologists that are interested in developing novel PPAR agonists and antagonists with lower side effects as well as for clinicians.

Establishment of a Cell Line Stably Expressing the Growth Hormone Secretagogue Receptor to Identify Crocin as a Ghrelin Agonist

The growth hormone secretagogue receptor-1a (GHSR1a) is the endogenous receptor for ghrelin. Activation of GHSR1a participates in many physiological processes including energy homeostasis and eating behavior. Due to its transitory half-life, the efficacy of ghrelin treatment in patients is restricted; hence the development of new adjuvant therapy is an urgent need. This study aimed to establish a cell line stably expressing GHSR1a, which could be employed to screen potential ghrelin agonists from natural compounds. First, by means of lentiviral transduction, the genome of a human HEK293T cell was modified, and a cell platform stably overexpressing GHSR1a was successfully established. In this platform, GHSR1a was expressed as a fusion protein tagged with mCherry, which allowed the monitoring of the dynamic cellular distribution of GHSR1a by fluorescent microscopy. Subsequently, the authenticity of the GHSR1a mediated signaling was further characterized by using ghrelin and teaghrelin, two molecules known to stimulate GHSR1a. The results indicated that both ghrelin and teaghrelin readily activated GHSR1a mediated signaling pathways, presumably via increasing phosphorylation levels of ERK. The specific GHSR1a signaling was further validated by using SP-analog, an antagonist of GHSR1a as well as using a cell model with the knockdown expression of GHSR1a. Molecular modeling predicted that crocin might be a potential ghrelin agonist, and this prediction was further confirmed by the established platform.

LGD-4033 and MK-677 use impacts body composition, circulating biomarkers, and skeletal muscle androgenic hormone and receptor content: A case report

NEW FINDINGS

What is the main observation in this case? Co-administration of LGD-4033 and MK-677 increased body mass, lean mass and fat mass, while negatively impacting bone, serum lipids, liver enzymes, testosterone (total and free) and, probably, follicle-stimulating hormone. What insights does it reveal? Our cross-sectional data imply that these compounds might alter intramuscular androgenic hormone and receptor concentrations along with promoting muscular strength, when compared with previously published data from trained males.

ABSTRACT

LGD-4033, a selective androgen receptor modulator, and MK-677, a growth hormone secretagogue, are being used increasingly amongst recreationally active demographics. However, limited data exist describing their effects on health- and androgen-related biomarkers. The purpose of this case study was to determine changes in body composition and biomarkers during and after continued co-administration of LGD-4033 and MK-677. We also aimed to examine muscular strength and intramuscular androgen-associated biomarkers relative to non-users. A 25-year-old male ingested LGD-4033 (10 mg) and MK-677 (15 mg) daily for 5 weeks. Blood and body composition metrics were obtained pre-, on- and post-cycle. One-repetition maximum leg and bench press, in addition to intramuscular androgens and androgen receptor content, were analysed on-cycle. We observed pre- to on-cycle changes in body composition (body mass, +6.0%; total lean body mass, +3.1%; trunk lean body mass, +6.6%; appendicular lean body mass, +4.3%; total fat mass, +15.4%; trunk fat mass, +2.8%; and appendicular fat mass, +14.8%), bone (bone mineral content, -3.60%; area, -1.1%; and bone mineral density, -2.1%), serum lipid-associated biomarkers (cholesterol, +14.8%; triglycerides, +39.2%; low-density lipoprotein-cholesterol, +40.0%; and high-density lipoprotein-cholesterol, -36.4%), liver-associated biomarkers (aspartate aminotransferase, +95.8%; and alanine aminotransferase, +205.0%) and androgen-associated biomarkers (free testosterone, -85.7%; total testosterone, -62.3%; and sex hormone-binding globulin, -79.6%); however, all variables returned to pre-cycle values post-cycle, apart from total fat mass, appendicular fat mass, bone area, total cholesterol and low-density lipoprotein-cholesterol. Follicle-stimulating hormone was below clinical reference values on- (1.2 IU/L) and post-cycle (1.3 IU/L). Intramuscular androgen receptor (-44.6%), testosterone (+47.8%) and dihydrotestosterone (+34.4%), in addition to one-repetition maximum leg press and bench press (+39.2 and +32.0%, respectively), were different in the case subject compared with non-users. These data demonstrate that LGD-4033 and MK-677 increase several body composition parameters, whilst negatively impacting bone and several serum biomarkers. Given the sparsity of data in recreationally using demographics, further research is warranted to elucidate the acute and chronic physiological effects of these anabolic agents.

Public Health Need, Molecular Targets, and Opportunities for the Accelerated Development of Function-Promoting Therapies: Proceedings of a National Institute on Aging Workshop

Background

People ≥ 65 years are expected to live a substantial portion of their remaining lives with a limiting physical condition and the numbers of affected individuals will increase substantially due to the growth of the population of older adults worldwide. The age-related loss of muscle mass, strength, and function is associated with an increased risk of physical disabilities, falls, loss of independence, metabolic disorders, and mortality. The development of function-promoting therapies to prevent and treat age-related skeletal muscle functional limitations is a pressing public health problem.

Methods

On March 20–22, 2022, the National Institute on Aging (NIA) held a workshop entitled “Development of Function-Promoting Therapies: Public Health Need, Molecular Targets, and Drug Development.”

Results

The workshop covered a variety of topics including advances in muscle biology, novel candidate molecules, findings from randomized trials, and challenges in the design of clinical trials and regulatory approval of function-promoting therapies. Leading academic investigators, representatives from the National Institutes of Health (NIH) and the U.S. Food and Drug Administration (FDA), professional societies, pharmaceutical industry, and patient advocacy organizations shared research findings and identified research gaps and strategies to advance the development of function-promoting therapies. A diverse audience of 397 national and international professionals attended the conference.

Conclusions

Function-promoting therapies to prevent and treat physical disabilities associated with aging and chronic diseases are a public health imperative. Appropriately powered, well-designed clinical trials and synergistic collaboration among academic experts, patients and stakeholders, the NIH and the FDA, and the pharmaceutical industry are needed to accelerate the development of function-promoting therapies.

Liver fat metabolism of broilers regulated by Bacillus amyloliquefaciens TL via stimulating IGF-1 secretion and regulating the IGF signaling pathway

Bacillus amyloliquefaciens TL (B.A-TL) is well-known for its capability of promoting protein synthesis and lipid metabolism, in particular, the abdominal fat deposition in broilers. However, the underlying molecular mechanism remains unclear. In our study, the regulations of lipid metabolism of broilers by B.A-TL were explored both in vivo and in vitro. The metabolites of B.A-TL were used to simulate in vitro the effect of B.A-TL on liver metabolism based on the chicken hepatocellular carcinoma cell line (i.e., LMH cells). The effects of B.A-TL on lipid metabolism by regulating insulin/IGF signaling pathways were investigated by applying the signal pathway inhibitors in vitro. The results showed that the B.A-TL metabolites enhanced hepatic lipid synthesis and stimulated the secretion of IGF-1. The liver transcriptome analysis revealed the significantly upregulated expressions of four genes (SI, AMY2A, PCK1, and FASN) in the B.A-TL treatment group, mainly involved in carbohydrate digestion and absorption as well as biomacromolecule metabolism, with a particularly prominent effect on fatty acid synthase (FASN). Results of cellular assays showed that B.A-TL metabolites were involved in the insulin/IGF signaling pathway, regulating the expressions of lipid metabolism genes (e.g., FASN, ACCα, LPIN, and ACOX) and the FASN protein, ultimately regulating the lipid metabolism via the IGF/PI3K/FASN pathway in broilers.

Appearance and Performance Enhancing Drugs and Substances: The Role of the School Nurse

The purpose of this article is to provide the school nurse with the ability to recognize performance and appearance enhancing substance use and understand treatment and prevention strategies to reduce associated health risks. The use of appearance and performance enhancing drugs and substances, also known as "doping," has been an ethical and health issue in sports for many years. It is vital that school nurses learn to recognize performance and appearance enhancing substance use to ensure student athletes and exercisers receive the care and education they need. Commonly used performance and appearance enhancing substances include anabolic-androgenic steroids, stimulants, diuretics, growth hormone, and supplements. Signs and symptoms that may look similar to other health concerns include palpitations, stunted growth, acne, severe headaches, muscle cramps, dizziness, and dehydration, but some long-term severe complications occur as well. Doping can lead to severe and sometimes permanent organ damage, including liver, kidney, and heart disease. The school nurse can play a key role by working with parents, coaches, school counselors, and educators to foster an anti-doping culture.

Transcription of cytochrome P450 46A1 in NIH3T3 cells is negatively regulated by FBS

Extracellular administration of side-chain oxysterols, such as 24S-hydroxycholesterol (24S-HC), 27-hydroxycholesterol (27-HC) and 25-hydroxycholesterol (25-HC) to cells suppresses HMG-CoA reductase (Hmgcr) and CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) mRNA levels. Oxysterols are enzymatically produced in cells from cholesterol by cytochrome P450 46A1 (Cyp46A1), Cyp27A1, Cyp3A11 and cholesterol 25-hydroxylase (Ch25h). We analyzed which of these oxysterol-producing enzymes are expressed in NIH3T3 cells and found that only Cyp46A1 was expressed. When Cyp46A1 was overexpressed in NIH3T3 cells, intrinsic oxysterols increased in the order 24S-HC > 25-HC > 27-HC. We investigated the mechanism regulating the production of endogenous oxysterols in NIH3T3 cells by Cyp46A1 and found that the mRNA, relative protein levels and enzymatic activity of Cyp46A1, and the amounts of 24S-HC, 25-HC and 27-HC significantly increased under serum-starved conditions, and these increases were suppressed by FBS supplementation. The aqueous phase of FBS obtained by the Bligh & Dyer method significantly suppressed Cyp46A1 mRNA levels. Fractionation of the aqueous phase by HPLC and analysis of the inhibiting fractions by nanoLC and TripleTOF MS/MS identified insulin-like factor-II (IGF-II). Cyp46A1 mRNA levels in serum-starved NIH3T3 cells were significantly suppressed by the addition of IGFs and insulin and endogenous oxysterol levels were decreased. CYP46A1 mRNA levels in the T98G human glioblastoma cell line were also increased by serum starvation but not by FBS supplementation, and the aqueous phase did not inhibit the increase. These results suggest that mRNA levels of Cyp46A1 are regulated by factors in FBS.

Structural basis of human ghrelin receptor signaling by ghrelin and the synthetic agonist ibutamoren

The hunger hormone ghrelin activates the ghrelin receptor GHSR to stimulate food intake and growth hormone secretion and regulate reward signaling. Acylation of ghrelin at Ser3 is required for its agonistic action on GHSR. Synthetic agonists of GHSR are under clinical evaluation for disorders related to appetite and growth hormone dysregulation. Here, we report high-resolution cryo-EM structures of the GHSR-G_i signaling complex with ghrelin and the non-peptide agonist ibutamoren as an investigational new drug. Our structures together with mutagenesis data reveal the molecular basis for the binding of ghrelin and ibutamoren. Structural comparison suggests a salt bridge and an aromatic cluster near the agonist-binding pocket as important structural motifs in receptor activation. Notable structural variations of the G_i and GHSR coupling are observed in our cryo-EM analysis. Our results provide a framework for understanding GHSR signaling and developing new GHSR agonist drugs.

Contribution of Ghrelin to the Pathogenesis of Growth Hormone Deficiency

In this review we described the interactions between ghrelin and the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis in children and adults with growth hormone deficiency (GHD). A possible involvement of these interactions in the pathogenesis of unexplained cases of GHD was suggested. Current research provides more and more details to the knowledge on the circadian rhythm of ghrelin. We gathered reports on the decreasing effect of Helicobacter pylori-related chronic gastritis on the number of ghrelin immunopositive cells and the consequent decrease in ghrelin serum concentration. The gastrointestinal tract microflora modification of the ghrelin action, by the mechanism of molecular mimicry, was also stressed. Moreover, the mutual relationships between ghrelin and the TSH-FT4/FT3 axis in growth and metabolic processes are described. It is to be recalled that FT4 and FT3 exert a permissive impact on IGF-1 action and, in turn, GH, in reaction mediated by IGF-1, enhances the monodeiodination of FT4 to FT3. Finally, we discussed the latest attempts to use the GH secretagogue receptor (GHS-R) analogues for possible diagnostic and therapeutic purposes.

A quantitative UHPLC-MS/MS method for the growth hormone-releasing peptide-6 determination in complex biological matrices and transdermal formulations

Growth hormone-releasing peptide-6 (GHRP-6) is part of a group of small synthetic peptides with potent GH-releasing activity that have gained attention in the last two decades by virtue of their cyto- and cardioprotective effects. Despite numerous preclinical studies highlighting the potential cardiovascular benefits of GHRP-6, confirmation of clinical efficacy is still awaited. Recent advances in transdermal drug delivery systems have been made to address challenges related to the poor skin permeation rate of peptides by using pain-free microneedle (MN) devices. Accordingly, highly sensitive and validated analytical methods are required for the potential clinical translation of MN-based peptides. The ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) methods developed in this study aimed to quantify GHRP-6 in biological matrices (plasma, skin) and dissolving polymeric MNs. UHPLC/MS-MS method detection limits of 0.1, 1.1, 0.9 and 1.5 ng/mL were achieved in neat solution, plasma, MN polymer solution, and skin matrices, respectively. Method validation also involved assessment of precision, accuracy, limits of quantification, linearity of matched calibration curves (R² > 0.990), extraction recovery, matrix effect, stability studies, selectivity, and carry-over effect. Additionally, quality control samples were analyzed at three concentration levels to determine recovery (85-109%) and accuracy/bias (3.2-14.7%). Intra- and inter-day precision were within the range of acceptance (RSDs of 3.0-13.9% and 0.4-14.5%, respectively). The validity and applicability of such methods were successfully demonstrated for transdermal GHRP-6 delivery using GHRP-6-loaded MN patches applied to pig skin.

Targeting impaired nutrient sensing with repurposed therapeutics to prevent or treat age-related cognitive decline and dementia: A systematic review

BACKGROUND

Dementia is a debilitating syndrome that significantly impacts individuals over the age of 65 years. There are currently no disease-modifying treatments for dementia. Impairment of nutrient sensing pathways has been implicated in the pathogenesis of dementia, and may offer a novel treatment approach for dementia.

AIMS

This systematic review collates all available evidence for Food and Drug Administration (FDA)-approved therapeutics that modify nutrient sensing in the context of preventing cognitive decline or improving cognition in ageing, mild cognitive impairment (MCI), and dementia populations.

METHODS

PubMed, Embase and Web of Science databases were searched using key search terms focusing on available therapeutics such as 'metformin', 'GLP1', 'insulin' and the dementias including 'Alzheimer's disease' and 'Parkinson's disease'. Articles were screened using Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). The risk of bias was assessed using the Cochrane Risk of Bias tool v 2.0 for human studies and SYRCLE's risk of bias tool for animal studies.

RESULTS

Out of 2619 articles, 114 were included describing 31 different 'modulation of nutrient sensing pathway' therapeutics, 13 of which specifically were utilized in human interventional trials for normal ageing or dementia. Growth hormone secretagogues improved cognitive outcomes in human mild cognitive impairment, and potentially normal ageing populations. In animals, all investigated therapeutic classes exhibited some cognitive benefits in dementia models. While the risk of bias was relatively low in human studies, this risk in animal studies was largely unclear.

CONCLUSIONS

Modulation of nutrient sensing pathway therapeutics, particularly growth hormone secretagogues, have the potential to improve cognitive outcomes. Overall, there is a clear lack of translation from animal models to human populations.

Anabolic steroid misuse and male infertility: management and strategies to improve patient awareness

Introduction: Anabolic androgenic steroid use is an uncommon but important cause of male infertility. As paternal age and anabolic steroid use increases, providers are more likely than ever to encounter men with infertility and prior or concurrent anabolic steroid use. In this review, we outline the background, epidemiology and pathophysiology of anabolic steroid induced male infertility and provide recommendations regarding the diagnosis, management, and future prevention of this condition.Areas covered: Male reproductive physiology is a tightly regulated process that can be influenced by exogenous sources such as anabolic steroids and selective androgen receptor modulators (SARMs). Data suggest that a combination of selective estrogen receptor modulators (SERMs), human chorionic gonadotropin (hCG), aromatase inhibitors (AIs), and recombinant follicle-stimulating hormone (rFSH) may lead to spermatogenesis recovery.Expert opinion: Anabolic steroid and SARM users continue to exhibit lack of understanding regarding the potential side effects of their use on male fertility. Current literature suggests that spermatogenesis can be safely recovered using a combination of SERMs, hCG, AIs and rFSH although additional studies are necessary. While anabolic steroid prevention strategies have largely been focused on the individual level, further investigation is necessary and should be approached in a socioecological manner.

An in vitro assay approach to investigate the potential impact of different doping agents on the steroid profile

The steroid profile, that is, the urinary concentrations and concentration ratios of selected steroids, is used in sports drug testing to detect the misuse of endogenous steroids such as testosterone. Since several years, not only population-based thresholds are applied but also the steroid profile is monitored via the Athlete Biological Passport whereby the individual reference ranges derived from multiple test results of the same athlete are compared to population-based thresholds. In order to maintain a high probative force of the passport, samples collected or analyzed under suboptimal conditions should not be included in the longitudinal review. This applies to biologically affected or degraded samples and to samples excluded owing to the presence of other substances potentially (or evidently) altering the steroid profile. Nineteen different doping agents comprising anabolic steroids, selective androgen receptor modulators, selective estrogen receptor modulators, ibutamoren, and tibolone were investigated for their effect on the steroid profile using an androgen receptor activation test, an androgen receptor binding assay, an aromatase assay, and a steroidogenesis assay. The in vitro tests were coupled with well-established liquid chromatography/mass spectrometry-based analytical approaches and for a subset of steroidal analytes by gas chromatography/mass spectrometry. The variety of tests employed should produce a comprehensive data set to better understand how a compound under investigation may impact the steroid profile. Although our data set may allow an estimate of whether or not a substance will have an impact on the overall steroid metabolism, predicting which parameter in particular may be influenced remains difficult.

Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males

Male hypogonadism is an increasingly prevalent clinical condition that affects patients’ quality of life and overall health. Obesity and metabolic syndrome can both cause and result from hypogonadism. Although testosterone remains the gold standard for hypogonadism management, its benefits are not always conserved across different populations, especially with regards to changes in body composition. Partially in response to this, growth hormone secretagogues (GHS) have emerged as a potential novel adjunctive therapy for some of the symptoms of hypogonadism, although current data on their clinical efficacy largely remain lacking. The present review examines the existing literature on the use of GHS and explores their potential complementary role in the management of hypogonadal and eugonadal males with metabolic syndrome or subclinical hypogonadism (SH). The GHS that will be discussed include sermorelin, growth hormone-releasing peptides (GHRP)-2, GHRP-6, ibutamoren, and ipamorelin. All are potent GH and IGF-1 stimulators that can significantly improve body composition while ameliorating specific hypogonadal symptoms including fat gain and muscular atrophy. However, a paucity of data examining the clinical effects of these compounds currently limits our understanding of GHS’ role in the treatment of men with hypogonadism, but does open opportunities for future investigation.

Emerging evidence for the roles of peptide in hypertrophic scar

Hypertrophic scar is a dermal fibroproliferative disorder characterized by excess collagen deposition. There are many existing treatment modalities, but none works perfectly in all individuals. Recently, evidence is increasing that peptides can play crucial roles in the prevention or treatment of hypertrophic scar. The peptides may be derived from growth factors, hormones, and intracellular products of proteolysis. In vitro and in vivo studies have revealed that a number of peptides, usually topically applied, have beneficial effects on fibroblasts in rat, mouse, hamster, pig and rabbit scar models. The length of such peptides typically ranges between 10 and 15 amino acids (aa). Peptides may reduce scar progenitors, prevent excessive scarring, decrease scar growth, speed re-epithelialization and promote scar maturation through multiple mechanisms. They may target TGF-β signaling, fibroblast function or collagen modulation, inflammation, renin angiotensin system, gap junction and other pathways. However, there is a paucity of evidence regarding specific binding sites for these peptides in scar models. Here, we review current research progress on the roles of peptides and underlying mechanisms in hypertrophic scar. We also discuss the clinical potential of peptides as therapeutic agents in scarring. Finally, the functions of several peptide-related compounds in hypertrophic scar are summarized.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

The CD36-PPARγ Pathway in Metabolic Disorders

Uncovering the biological role of nuclear receptor peroxisome proliferator-activated receptors (PPARs) has greatly advanced our knowledge of the transcriptional control of glucose and energy metabolism. As such, pharmacological activation of PPARγ has emerged as an efficient approach for treating metabolic disorders with the current use of thiazolidinediones to improve insulin resistance in diabetic patients. The recent identification of growth hormone releasing peptides (GHRP) as potent inducers of PPARγ through activation of the scavenger receptor CD36 has defined a novel alternative to regulate essential aspects of lipid and energy metabolism. Recent advances on the emerging role of CD36 and GHRP hexarelin in regulating PPARγ downstream actions with benefits on atherosclerosis, hepatic cholesterol biosynthesis and fat mitochondrial biogenesis are summarized here. The response of PPARγ coactivator PGC-1 is also discussed in these effects. The identification of the GHRP-CD36-PPARγ pathway in controlling various tissue metabolic functions provides an interesting option for metabolic disorders.