Peptide Therapies

Peptides have become increasingly discussed in recent years in the fields of metabolic health, body composition, muscle function, tissue repair, and healthy aging. In fact, peptides are not foreign molecules to our bodies. They are short protein chains formed by the linking of amino acids in specific sequences, and many naturally occurring peptides exist in our bodies that function as hormones, neurotransmitters, or intercellular signaling molecules.

GLP-1, GIP, growth hormone-releasing hormone (GHRH), VIP, and many other signaling molecules are all parts of this vast biological system. The basic idea in peptide therapies is to mimic, enhance, or, if necessary, reorganize a specific signaling pathway already present in the body.

However, an important distinction must be made here. “Peptide” alone is not an indicator of quality or efficacy. It is not correct to evaluate a peptide-based drug, such as semaglutide or tirespatite (Ozempic and Mounjaro), which has been studied in tens of thousands of patients and received FDA approval, on the same scientific level as an experimental peptide that is only being investigated in animal studies.

Compounded Peptides and "Grey Market" Products Sold Online

While some peptides are produced as standard commercial drugs, others can be prepared by compounding pharmacies based on a doctor's prescription. Compounding refers to the preparation of a custom formulation or dosage to meet the specific needs of a particular patient. In the United States, this area is regulated specifically through 503A compounding pharmacies and 503B outsourcing facilities. The FDA also evaluates usable bulk drug substances on a substance-by-substance basis.

The most important issue for me here is the source of the product. There are many gray-market products sold online with labels like "research use only," "laboratory peptide," or similar terms. It's impossible for the patient to know whether these products actually contain the peptide described, whether they are at the correct concentration, whether there are peptide impurities that may have occurred during synthesis, the amount of bacterial endotoxin, or the sterility of the injection product.

This is especially important for products administered via injection. In peptide synthesis, it is not enough for the molecule to have the correct amino acid sequence; purity, stability, aggregation, sterility, and endotoxin control are also crucial. The FDA, in its assessments of compounded peptides, particularly emphasizes peptide impurities, aggregation, and related immunogenicity issues.

Therefore, if peptide therapy is to be considered, my approach is to obtain the products under the supervision of a doctor from reliable and regulated compounding pharmacies, and to ensure that the peptides used have undergone COA analysis, rather than sourcing them from the internet or unknown sales channels.

Peptides that can help with weight loss, fat burning, and muscle mass increase.

Not all peptides in this group function in the same way. Some affect appetite. Some stimulate the growth hormone and IGF-1 axis. Others are being investigated directly through their involvement of mitochondria and cellular energy metabolism.

MOTS-c

MOTS-c is quite different from many other peptides because the gene it is encoded by is located not in the cell nucleus, but in mitochondrial DNA. Therefore, it is defined as a mitochondrial-derived peptide.

The first significant work on MOTS-c was done in 2015. Cell Metabolism It was published in the journal. In animal models, MOTS-c administration was shown to reduce weight gain caused by high-fat diets, increase glucose utilization and improve insulin sensitivity [1].

It is particularly interesting that MOTS-c can activate metabolic pathways associated with AMPK, one of the cellular energy sensors. As a result, changes may occur in glucose utilization, fatty acid metabolism and the cell's adaptation to metabolic stress. It has also been shown in animal studies to affect exercise capacity and skeletal muscle metabolism [2].

Therefore, MOTS-c is not a classic "appetite suppressant" for me. It is more of a peptide being investigated in terms of metabolic plasticity, insulin sensitivity, mitochondrial function, and exercise capacity.

Human treatment data are still far more limited than animal data. However, the issue is no longer limited to laboratory research; MOTS-c has reached the FDA's 503A compounding review, particularly for obesity and metabolic health. In July 2026, it was formally reviewed by the FDA Pharmacy Compounding Advisory Committee for use in obesity and osteoporosis, and its acceptance within this scope was recommended.

SS-31 / Elamipretide

SS-31 interacts with cardiolipin, a component of the mitochondrial inner membrane that is crucial for energy production. This interaction is being investigated as a mechanism that could help maintain the structure of the mitochondrial membrane, improve the efficiency of the electron transport chain, and reduce excessive reactive oxygen species.

In a randomized study in humans, a rapid increase in mitochondrial ATP production capacity in skeletal muscle was demonstrated after a single dose of elamipretide was given to elderly adults [3].

Therefore, it is more accurate to consider SS-31 not directly as a fat burner, but as an experimental mitochondrial peptide that can support body composition programs through energy production, muscle function, and mitochondrial health.

Growth Hormone Axis:

Another important system when it comes to body composition is the growth hormone and IGF-1 axis. Growth hormone pulsatility and IGF-1 levels generally decrease with age. This system affects many areas, including muscle protein synthesis, fat tissue metabolism, bone, and connective tissue.

SermorelinIt is a GHRH analog that mimics the active part of natural GHRH. Instead of directly delivering growth hormone to the pituitary gland, it stimulates the person to increase their own GH secretion. Human studies with GHRH analogs have shown that the GH/IGF-1 axis can be activated and an increase in lean body mass can be seen in some groups [4].

tesamorelin It is one of the peptides with the strongest human data regarding visceral fat. The strongest human data on altering body composition via the growth hormone axis is found for tesamorelin. Tesamorelin is a GHRH analogue and was specifically developed for reducing visceral fat in HIV-associated abdominal lipodystrophy.

Randomize çalışmalarda tesamorelin ile abdominal visseral yağda yaklaşık %15-20 oranında azalma gösterilmiş ve bu azalmanın 12 aya kadar korunabildiği görülmüştür [7].

In another randomized study, tesamorelin reduced not only visceral fat but also liver fat [8].

*** Growth hormone secretagogues other than sermorelin and tesamorelin are not subject to FDA compounding approval. Therefore, peptides other than sermorelin and tesamorelin are listed on this page for informational purposes only.

CJC-1295 It has been developed as a much longer-acting GHRH analog. Controlled studies in healthy adults have shown that after a single injection, GH levels can remain elevated for days and IGF-1 levels for even longer [5].

Ipamorelin It uses a different mechanism. It stimulates the release of growth hormone from the pituitary gland via the ghrelin/GH secretagogue receptor rather than the GHRH receptor. Human pharmacokinetic studies have shown that ipamoreline can induce a dose-related GH response [6].

The rationale behind using CJC-1295 and ipamorelin together stems from this: one targets the GHRH receptor, the other the ghrelin receptor, aiming to support the same GH pulse through two different signaling pathways. When combined with exercise, a significant increase in muscle mass is observed.

However, the compounding status of these molecules has been re-evaluated by the FDA over time. Specifically, the FDA has current safety/compounding assessments for ipamorelin and CJC-1295.

Peptides Commonly Used Aside from Weight or Fat Control

The application of peptide therapies is not limited to metabolism and body composition. Peptides are being researched in many different areas, including tissue repair, inflammation, the gastrointestinal system, vascular function, and neurological diseases.

BPC-157BPC-157 is probably one of the most talked-about regenerative molecules in the peptide world. Numerous animal studies exist, particularly on its effect on the healing of tendons, ligaments, muscles, and gastrointestinal tissues. In a rat Achilles tendon transection model, BPC-157 application accelerated tendon healing and increased tendocyte growth [9]. Other experimental studies have reported improved tendon-bone junction healing, ligament healing, and better regeneration after muscle injury [10,11].

There are also interesting results in terms of muscle tissue. In crush injury and complete muscle transection models created in rats, BPC-157 has been reported to accelerate functional and histological recovery [11,12].

It is thought that the effects of BPC-157 are not mediated solely through a single growth factor. Its effects on different regenerative mechanisms such as the nitric oxide system, VEGF signaling, cell migration and GH receptor expression are being investigated [13].

Human data still lags considerably behind animal data. However, the BPC-157 issue re-entered the FDA's official 503A review process in 2026, and BPC-157 free base and BPC-157 acetate were evaluated and recommended for approval by the Pharmacy Compounding Advisory Committee.

VIP (Vasoactive Intestinal Peptide) It is a neuropeptide consisting of 28 amino acids that occurs naturally in our bodies and has effects on the nervous system, intestines, lungs, blood vessels, and immune system.

The word "intestinal" in its name makes its scope of use seem a bit narrower than it actually is. VIP has strong vasodilator properties and may also affect smooth muscle, inflammatory signaling, and some immune cells.

Aviptadyl, a synthetic form of VIP, has been investigated in humans, particularly in relation to pulmonary hypertension and lung diseases. In a human study of patients with pulmonary hypertension, inhalation of VIP resulted in a transient decrease in pulmonary vascular resistance and an improvement in right ventricular workload [14].

VIP's position in terms of compounding differs from many other popular peptides. Vasoactive Intestinal Peptide is among the substances on the FDA's 503A Category 1 list, dated May 2026. This means it is one of the substances that may fall under enforcement discretion under certain 503A conditions while the FDA review continues.

Thymosin alpha-1 (Tα1) It is a 28-amino acid peptide that has effects on the regulation of the immune system. It is developed from thymosin fractions that occur naturally in the thymus and has been investigated for many years, especially because of its effects on the function of T cells, dendritic cell activity and the regulation of the innate immune response [15,16].

It is not entirely accurate to simply describe thymosin alpha-1 as an “immune system booster” peptide. A more appropriate expression is that it is an immunomodulator. It has been shown to affect different parts of the immune system such as toll-like receptor signaling, dendritic cells, natural killer cells and T cells [15]. Therefore, it has been investigated in a very wide range of areas, from chronic infections to immunodeficiency conditions and to support use in cancer treatment.

An important difference of thymosin alpha-1 is that, unlike many experimental peptides, it is not based solely on animal studies. Clinical trials have been conducted in humans for various diseases including hepatitis, serious infections, sepsis and some types of cancer [16,17].

Thymosin beta-4 (Tβ4) It is a peptide that occurs naturally in the body and plays a role particularly in cell movement, neovascularization, inflammation regulation, and tissue healing processes. TB-500 is the name used for synthetic peptide products related to thymosin beta-4.

One of the most interesting properties of thymosin beta-4 is its interaction with a cellular structural protein called actin. This mechanism can affect different stages of healing such as the movement of cells to the damaged area, the formation of new vessels and the remodeling of tissue [18].

In animal and cell studies, thymosin beta-4 has been shown to accelerate wound healing, support angiogenesis and regulate the inflammatory response [18,19]. The biological rationale behind its use in muscle, tendon and ligament injuries is largely based on these regenerative properties.

Human data for thymosin beta-4 is not entirely lacking. Clinical studies have been conducted, particularly regarding wound healing and eye surface injuries.

GHK-Cu (glycyl-L-histidyl-L-lysine-copper) It is a complex formed by copper and a small peptide of three amino acids that occurs naturally in the human body. It was first isolated from human plasma and its effects on wound healing, collagen synthesis, skin regeneration and hair follicle biology have been investigated [20].

GHK-Cu is of particular interest in regenerative medicine and dermatology due to its effects on supporting collagen and elastin synthesis, fibroblast activity, wound healing and tissue remodeling [20,21]. The fact that copper is necessary for many enzymatic reactions and that GHK can transport copper to tissues in a bioavailable form is also an important part of this effect.

GHK levels have been reported to decrease with age. Therefore, GHK-Cu is being investigated not only as a cosmetic “skin peptide” but also as a signaling molecule associated with cellular repair and extracellular matrix protection in aging tissues [21].

Human data are available on topical use, and particularly positive results have been reported in terms of skin quality, fine wrinkles, elasticity, and wound healing. However, clinical data on systemic GHK-Cu use via injection are much more limited than those for topical use.

Epithalon It is a synthetic tetrapeptide composed of four amino acids and has been studied for many years, particularly due to its potential effects on aging biology, pineal function, melatonin rhythm, and telomerase activity.

One of the most noteworthy studies on Epitalon is on telomere biology. In cell culture studies, it has been reported that Epitalon can increase telomerase activity and may be associated with telomere elongation in human somatic cells [22]. Therefore, Epitalon has become one of the experimental peptides targeting telomere biology in the field of longevity.

In animal studies, the effects of epitalon and related pineal peptides on lifespan, oxidative stress, circadian rhythm and some age-related physiological changes have been investigated [23]. Some long-term Russian studies have also reported remarkable results in terms of mortality and age-related diseases in elderly individuals.

However, it is important to consider that a significant portion of the literature on Epitalon comes from specific research groups and older Russian studies. Therefore, it would be more accurate to consider Epitalon not as a proven "anti-aging treatment" today, but as an interesting experimental peptide being investigated in terms of telomere biology, pineal function, and healthy aging.

Cerebrolysin It is a preparation consisting of low molecular weight neuroactive peptides and amino acids obtained from pig brain proteins, not a single peptide. It has been investigated for many years, especially in stroke, traumatic brain injury, Alzheimer's disease and other neurodegenerative processes, due to its neuroprotective and neurotrophic effects [24].

What makes Cerebrolysin interesting is that it is not only aimed at protecting nerve cells from damage. Experimental studies show that it can affect many mechanisms important to the brain's healing capacity, such as neuroplasticity, synaptic function, neurogenesis, neuronal survival and neuroinflammation. In a randomized controlled CARS study after stroke, adding Cerebrolysin to standard rehabilitation resulted in significantly better outcomes than placebo, particularly in the recovery of upper extremity motor function [25].

Cerebrolysin has also been the subject of several randomized, double-blind, placebo-controlled human trials in Alzheimer's disease. These studies have reported significant improvements in some cognitive and general clinical assessments [26-28]. Therefore, Cerebrolysin is particularly noteworthy among neurological peptide therapies because, unlike many experimental peptides supported only by animal studies, it also has clinical human data on neuroprotection and neuroregeneration.

KPV (Lysine-Proline-Valine) KPV is a small peptide consisting of only three amino acids and is derived from the C-terminal portion of the α-MSH (alpha-melanocyte stimulating hormone) molecule, which occurs naturally in our bodies. The most interesting feature of KPV is that, despite possessing some of the potent anti-inflammatory properties of α-MSH, it does not exhibit any of the pigmentation-related effects.

KPV is being investigated particularly in terms of intestinal inflammation, mucosal healing and suppression of inflammatory signaling pathways. In cell and animal studies, KPV has been shown to reduce inflammatory signaling pathways such as NF-κB and MAPK and to suppress the release of inflammatory mediators such as IL-8 [29]. In experimental colitis models, oral KPV administration significantly reduced intestinal inflammation and disease activity [29,30].

A particularly interesting feature of KPV from an intestinal perspective is its ability to be taken up by intestinal cells with inflammation via a peptide transporter called PepT1. Therefore, KPV is being investigated not only for systemic use but also for oral or local treatments directly targeting the gastrointestinal system. In experimental ulcerative colitis models, highly potent anti-inflammatory effects have been demonstrated in targeted KPV applications to the colon within nanoparticles [31].

Scientific data on KPV is still largely based on cell and animal studies, but the FDA's Pharmacy Compounding Advisory Committee recommended the addition of KPV free base and KPV acetate to the 503A Bulks List in July 2026. The uses being evaluated have primarily been in wound healing and inflammatory diseases.

Therefore, KPV is one of the small peptides that I most expect to see in human studies in the coming years, especially in terms of chronic inflammation, the gut barrier, and inflammatory bowel diseases.

***

All information presented here is for general informational and educational purposes only. This content is not intended to diagnose any disease, provide personalized medical assessments, or initiate, modify, or discontinue any treatment.

The information provided does not replace a doctor's examination, personal medical evaluation, or professional healthcare. Because health conditions and treatment needs vary from person to person, it is recommended that you consult your own doctor or relevant healthcare professional before starting any medication, supplement, treatment, or medical practice, or making any changes to your current treatment.

Because medical information and scientific data can change over time, the information presented here should not be assumed to be applicable to every individual or every clinical situation.

I wish you healthy days,

***

Dr. Ahmet Özyiğit, MD, MSc, PgDip, FAAMM, ABAARM
Longevity Physician

Elite Research and Surgical Hospital

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23. For your actual website, I think GHK-Cu deserves slightly more space than the other three. There is an interesting story to tell around copper signaling, collagen remodeling, gene expression and the age-related decline in circulating GHK, which fits your longevity theme particularly well.
    
24. Ladurner G, Kalvach P, Moessler H. Neuroprotective treatment with cerebrolysin in patients with acute stroke: a randomized controlled trial. Journal of Neural Transmission. 2005;112:415-428. DOI: 10.1007/s00702-004-0248-2A randomized study in which cerebrolysin was identified as a neurotrophic/neuroprotective preparation composed of low molecular weight peptides and amino acids. 
    
25. Muresanu DF, Heiss WD, Hoemberg V, et al. Cerebrolysin and Recovery After Stroke (CARS): A Randomized, Placebo-Controlled, Double-Blind, Multicenter Trial. Stroke. 2016;47:151-159. DOI: 10.1161/STROKEAHA.115.009416A large effect size in favor of Cerebrolysin was reported in upper extremity motor recovery at the three-month evaluation. 
    
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27. Alvarez XA, Cacabelos R, Sampedro C, et al. A 24-week, double-blind, placebo-controlled study of three dosages of Cerebrolysin in patients with mild to moderate Alzheimer's disease. European Journal of Neurology. 2006. DOI: 10.1111/j.1468-1331.2006.01222.xThe study included 279 patients, and cognitive/global clinical outcomes were evaluated for up to 24 weeks. 
    
28. Alvarez XA, Cacabelos R, Sampedro C, et al. Efficacy and safety of Cerebrolysin in moderate to moderately severe Alzheimer's disease: results of a randomized, double-blind, controlled trial investigating three dosages of Cerebrolysin.European Journal of Neurology. 2011;18:59-68. DOI: 10.1111/j.1468-1331.2010.03092.x. 
    
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31. Xiao B, Xu Z, Viennois E, et al. Orally Targeted Delivery of Tripeptide KPV via Hyaluronic Acid-Functionalized Nanoparticles Efficiently Alleviates Ulcerative Colitis. Molecular Therapy. 2017;25:1628–1640. DOI: 10.1016/j.ymthe.2016.11.020.