What is GH Fragment 176-191 and how does it promote lipolysis without activating GH receptors?

GH Fragment 176-191 (Frag 176-191, AOD-9604) is a modified 16-amino-acid C-terminal fragment of human growth hormone (hGH) spanning residues 176-191 with a C-terminal tyrosine amide modification (Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-CONH₂, with a disulfide bond between Cys-182 and Cys-189). Unlike full-length hGH (191 amino acids) which binds GH receptor (GHR) causing both anabolic effects (muscle growth, bone growth, IGF-1 stimulation) and lipolytic effects, the 176-191 fragment retains potent lipolytic activity but lacks GH receptor binding capability, providing selective fat mobilization without other GH-mediated effects. Mechanistically: (1) GH receptor independence - Full hGH contains two receptor-binding sites (sites 1 and 2) in the N-terminal and central regions (residues ~1-150); GH Fragment 176-191 from the C-terminal domain lacks these binding determinants and does not activate classical GHR signaling (JAK2-STAT5 pathway, IGF-1 production). This eliminates concerns about excessive IGF-1, insulin resistance, joint swelling, or growth plate effects seen with full hGH. (2) Lipolytic mechanism - The fragment mimics hGH's ability to stimulate lipolysis (fat breakdown) in adipocytes through proposed mechanisms including: activation of hormone-sensitive lipase (HSL) which cleaves triglycerides to free fatty acids and glycerol, inhibition of lipogenesis (fat synthesis) potentially via reduced ACC activity or de novo fatty acid synthesis pathways, increased β-oxidation (fatty acid oxidation in mitochondria) enhancing fat utilization, and potential β3-adrenergic receptor modulation or cAMP pathway effects (though exact receptor/signaling mechanisms remain debated and under investigation). (3) Regional fat selectivity - Research suggests Fragment 176-191 preferentially mobilizes abdominal/visceral adipose tissue, the metabolically harmful fat depot associated with metabolic syndrome, insulin resistance, and cardiovascular disease. (4) No hypoglycemia - Unlike insulin which causes hypoglycemia by promoting glucose uptake, or unlike some diabetic complications from full hGH (which can cause insulin resistance), Fragment 176-191 does not directly impair glucose homeostasis. (5) Anti-lipogenic effects - Beyond stimulating lipolysis, Fragment 176-191 may reduce new fat accumulation by inhibiting lipogenic enzymes or adipocyte differentiation. Research applications include obesity research, metabolic syndrome models, adipocyte biology, lipolytic pathway studies, developing selective fat-mobilizing agents without GH receptor-mediated side effects, body composition research, and investigating GH structure-function relationships (how different GH domains mediate distinct biological activities).

How does GH Fragment 176-191 differ from full-length growth hormone in mechanism and effects?

GH Fragment 176-191 represents domain-selective pharmacology, isolating one GH function (lipolysis) from others (anabolism, IGF-1 production): (1) Receptor binding - Full hGH (191 AA) binds GH receptor (GHR) via two binding sites triggering receptor dimerization, JAK2-STAT5 phosphorylation cascades, and transcriptional activation of growth-promoting genes including IGF-1. Fragment 176-191 (16 AA C-terminal fragment) lacks GHR binding determinants (sites 1 and 2 in N-terminal/central regions) and does not activate classical GHR signaling. This is confirmed by radioligand binding assays showing no GHR binding and by absence of STAT5 phosphorylation or IGF-1 induction after Fragment 176-191 treatment. (2) IGF-1 effects - Full hGH potently stimulates hepatic IGF-1 production (the major mediator of GH's anabolic effects on muscle and bone). Elevated IGF-1 promotes muscle protein synthesis, bone growth, cartilage expansion, and has insulin-like effects. Fragment 176-191 does not increase IGF-1, avoiding potential concerns about excessive IGF-1 (cancer proliferation risks, acromegaly-like features with supraphysiological GH). (3) Lipolytic activity - Both full hGH and Fragment 176-191 stimulate lipolysis, but Fragment provides this selectively. In adipocyte lipolysis assays (measuring glycerol or free fatty acid release), Fragment 176-191 dose-dependently increases lipolysis with potency similar to or slightly less than full hGH on a molar basis. (4) Metabolic effects - Full hGH has complex metabolic effects: initially insulin-like (acute glucose uptake, lipogenesis inhibition), chronically insulin-antagonistic (after several hours-days, hGH causes insulin resistance, impaired glucose tolerance, potential diabetes especially at supraphysiological doses). Fragment 176-191 lacks these insulin-antagonistic effects; research suggests neutral or even beneficial glucose homeostasis effects (possibly via reduced visceral adiposity improving metabolic health). (5) Anabolic effects - Full hGH promotes muscle protein synthesis, muscle hypertrophy, bone density, cartilage growth, and nitrogen retention. Fragment 176-191 lacks these anabolic effects (no muscle growth beyond potential indirect effects from improved metabolism or body composition). This is therapeutic advantage for fat loss research (avoiding unwanted growth effects) but disadvantage if anabolic effects desired. (6) Side effect profiles - Full hGH at high doses causes fluid retention, joint pain/swelling, carpal tunnel syndrome, insulin resistance, increased cancer risk (via IGF-1), and acromegaly features. Fragment 176-191 avoids most of these (no GHR activation, no IGF-1 elevation) with better tolerability profile. (7) Structure-activity research - Fragment 176-191 provides evidence that GH's lipolytic activity resides in C-terminal domain (residues 176-191) and is mechanistically separable from GHR-mediated anabolic activity (N-terminal domains). This informs design of selective GH analogs or peptidomimetics.

What research applications benefit from GH Fragment 176-191's selective lipolytic effects?

GH Fragment 176-191 excels in research requiring fat mobilization without GH receptor activation: (1) Obesity and weight loss research - Fragment 176-191 administration in diet-induced obesity (DIO) models, genetic obesity (ob/ob, db/db mice), or high-fat diet rodents demonstrates dose-dependent fat mass reduction, decreased adipocyte size, reduced body weight (primarily from fat loss with minimal lean mass changes), and preferential visceral fat reduction measured via MRI, CT imaging, or tissue dissection/weighing. Studies compare Fragment vs full hGH vs vehicle examining body composition changes, with Fragment showing fat-selective effects. (2) Metabolic syndrome models - Visceral adiposity is central to metabolic syndrome (insulin resistance, dyslipidemia, hypertension, cardiovascular risk). Fragment 176-191 reducing visceral fat improves metabolic parameters: enhanced insulin sensitivity (improved glucose tolerance, HOMA-IR), better lipid profiles (reduced triglycerides, LDL; increased HDL), reduced systemic inflammation (lower CRP, IL-6, TNF-α from adipose tissue), and improved hepatic steatosis (fatty liver). Research examines whether Fragment-induced fat loss translates to metabolic health improvements. (3) Adipocyte biology and lipolysis research - Using Fragment 176-191 as pharmacological tool to study lipolytic pathways independent of GH receptor signaling. Primary adipocyte or 3T3-L1 cell experiments treating with Fragment measuring: glycerol release (lipolysis endpoint), free fatty acid release, HSL phosphorylation/activation, ATGL and MGL (adipose triglyceride lipase, monoacylglycerol lipase) activity, perilipin phosphorylation (lipid droplet coating protein regulating lipase access), cAMP levels (β-adrenergic pathway), and comparing Fragment vs isoproterenol (β-adrenergic agonist) vs full hGH elucidating distinct vs overlapping mechanisms. (4) GH structure-function studies - Fragment 176-191 demonstrates that GH molecule contains functionally distinct domains (C-terminal 176-191 for lipolysis, N-terminal for GHR binding/anabolism). Mutagenesis or peptide synthesis of Fragment variants with single amino acid changes identifies critical residues for lipolytic activity. Studies test shorter fragments (e.g., 177-191, 176-190) or extended fragments (171-191) mapping minimal active sequence. This guides development of GH analogs or non-peptide mimetics. (5) Body composition research - Investigating Fragment 176-191's effects on fat mass vs lean mass ratio, regional fat distribution (subcutaneous vs visceral, android vs gynoid), and exercise/diet combination effects. Does Fragment enhance fat loss during caloric restriction or exercise training? Does it prevent fat regain after weight loss? (6) Aging and sarcopenic obesity research - Elderly often show sarcopenic obesity (low muscle mass, high fat mass). Full hGH therapy is problematic (side effects, insulin resistance). Fragment 176-191 offers selective fat reduction without muscle-wasting concerns or diabetes risk, though lack of anabolic effects means no muscle gain (would need to combine with exercise or other anabolic agents). (7) Cardiovascular research - Visceral adiposity increases cardiovascular risk. Fragment-induced visceral fat reduction may improve endothelial function, arterial stiffness, blood pressure, and atherosclerosis in animal models. (8) Comparative pharmacology - Fragment 176-191 vs other lipolytic agents (β3-agonists, cAMP elevators, ATGL activators) examining mechanism differences, tissue selectivity, side effect profiles, and combination potential. (9) Safety/toxicity studies - Establishing Fragment's safety profile: lack of GHR activation should eliminate classical GH side effects, but research confirms no unexpected toxicities, no impact on glucose homeostasis, no proliferative effects on cancer cells (no IGF-1 elevation), validating therapeutic potential.

What purity and quality standards does your GH Fragment 176-191 meet for lipolysis research?

Our GH Fragment 176-191 exceeds >98% purity verified by reverse-phase HPLC demonstrating retention time characteristic of the 16-amino-acid C-terminal GH fragment with C-terminal amidation. Each batch undergoes comprehensive quality control: mass spectrometry confirmation of molecular weight (~1815 Da accounting for disulfide bond formation and C-terminal amide) validating the Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-CONH₂ sequence, peptide sequencing via MS/MS fragmentation or Edman degradation verifying each amino acid with special attention to Cys residues (positions 7 and 14, forming critical intramolecular disulfide bond) and C-terminal Phe-amide (amidation essential for activity; non-amidated forms show reduced potency), amino acid composition analysis quantifying each residue, disulfide bond confirmation via comparison of reduced (DTT-treated) vs non-reduced samples by mass spec or electrophoretic mobility (disulfide-bonded form migrates faster, reduced form slower), C-terminal amidation verification (mass difference between free carboxyl vs amide = -1 Da, confirmed via high-resolution mass spec), functional bioassays measuring lipolytic activity including adipocyte lipolysis assays using primary adipocytes or differentiated 3T3-L1 cells treated with dose-escalating Fragment 176-191 measuring glycerol release into medium (via enzymatic assay) or free fatty acid release (via colorimetric or ELISA methods) demonstrating dose-dependent lipolysis with EC50 quantification (typically low micromolar range), time-course studies showing lipolysis onset within 1-3 hours and sustained elevation, comparison to isoproterenol (β-agonist positive control) validating assay sensitivity, GH receptor binding assays (or lack thereof) using GHR-expressing cells or membrane preparations confirming Fragment 176-191 does not bind GHR (negative result validating GHR independence), IGF-1 production assays in hepatocytes or in vivo confirming Fragment does not induce IGF-1 (negative result validating no classical GH signaling), circular dichroism or NMR spectroscopy examining secondary structure confirming proper folding (disulfide bond formation creates constrained structure), endotoxin testing (<0.1 EU/mg), and comprehensive Certificate of Analysis. Disulfide bond integrity critical: Cys-7 to Cys-14 disulfide (Cys-182 to Cys-189 in full hGH numbering) creates hairpin-like structure important for activity; improperly folded or reduced forms show diminished lipolysis. Quality control includes measures to prevent disulfide scrambling or oxidation damage.

How should GH Fragment 176-191 be stored, reconstituted, and handled to maintain lipolytic activity?

GH Fragment 176-191 storage and handling protocols preserving disulfide bond integrity and lipolytic potency: (1) Lyophilized storage - Store at -20°C in original sealed vials for 24+ months stability. The lyophilized 16-AA peptide with intramolecular disulfide bond remains stable when dry and frozen. Avoid temperature fluctuations and moisture exposure. For ultra-long-term storage (>2 years), -80°C provides additional protection. (2) Reconstitution maintaining disulfide bond - The Cys-7 to Cys-14 disulfide bond is essential for activity. Reconstitute in non-reducing conditions: use sterile water, bacteriostatic water, or PBS (pH 7.0-7.5) but avoid buffers containing reducing agents (DTT, β-mercaptoethanol, TCEP) which would break disulfide bonds abolishing activity. Gently swirl until dissolved at typical concentration 0.5-5 mg/mL. Allow 2-3 minutes for complete dissolution. If dissolution is slow, gentle warming to 37°C for 5-10 minutes helps without damaging disulfide. (3) pH considerations - Maintain pH 6.0-8.0 for optimal disulfide stability. Extreme acidic pH ( 9) causes disulfide reduction or amino acid modifications. Physiological pH (7.2-7.4) is ideal for in vitro and in vivo studies. (4) Oxidation vs reduction balance - While disulfide bonds require oxidizing conditions for formation, excessive oxidation can damage Met or Trp residues (GH Fragment 176-191 contains neither, but general principle). Conversely, any reducing agents must be avoided. For long-term reconstituted storage, slight oxidizing conditions (air-equilibrated solutions) are acceptable; don't bubble with nitrogen/argon which might create mildly reducing environment. (5) Reconstituted solution storage - Refrigerate at 2-8°C and use within 14-21 days. The disulfide-bonded structure provides stability, but prolonged storage can cause aggregation, oxidation, or degradation. For experiments extending beyond 2-3 weeks, aliquot reconstituted solution into single-use sterile vials, freeze at -20°C or -80°C (disulfide-bonded peptides generally freeze-thaw well), thaw fresh aliquot immediately before use. Minimize freeze-thaw cycles (maximum 3-4 cycles for this peptide due to disulfide stability). (6) Preventing aggregation - Peptides with disulfide bonds can aggregate if concentrated or stored improperly. If visible aggregates or precipitation occur, centrifuge (10,000g, 5 minutes) and use supernatant, though activity may be reduced. Fresh preparation from lyophilized powder preferred. (7) Verifying disulfide integrity after storage - If concerned about disulfide bond integrity after prolonged storage, run small analytical gel comparing to fresh sample: under non-reducing conditions, intact Fragment migrates as single band; if disulfide reduced, fragment would migrate differently or show altered HPLC retention time. (8) In vivo administration considerations - For subcutaneous or intraperitoneal injection in rodents, prepare fresh daily in sterile saline or bacteriostatic water at appropriate concentration (typical doses 250-500 μg/kg for lipolysis studies, adjust based on body weight). Some protocols use multi-day dosing (once or twice daily) for sustained fat loss effects. (9) Cell culture experiments - For adipocyte lipolysis assays, prepare stock in sterile PBS or serum-free medium, sterilize via 0.22 μm filtration, add to cell culture at concentrations typically 1-100 μM, incubate 1-24 hours measuring glycerol accumulation at various timepoints.

What is the importance of the Cys182-Cys189 disulfide bond in GH Fragment 176-191 structure and activity?

The intramolecular disulfide bond between Cys-182 and Cys-189 (Cys-7 and Cys-14 in Fragment numbering) is structurally and functionally critical: (1) Structural constraint - In full-length hGH, the C-terminal region (residues ~165-191) contains a small loop constrained by the Cys-182/Cys-189 disulfide bond creating defined three-dimensional structure. This loop is part of the third of four α-helices in full hGH tertiary structure. When isolated as Fragment 176-191, the disulfide bond maintains this constrained hairpin-like or loop structure preventing random coil formation. (2) Activity requirement - Structure-activity studies demonstrate that disulfide bond formation is essential for lipolytic activity. Reduced Fragment 176-191 (disulfide broken by DTT or β-mercaptoethanol treatment) shows dramatically reduced or abolished lipolysis in adipocyte assays (>90% activity loss). This indicates the constrained structure positions critical amino acids (Tyr-Leu-Arg-Ile-Val-Gln in N-terminal portion and Phe-amide at C-terminus) in optimal spatial arrangement for interacting with the unknown lipolytic receptor/target or for proper membrane interaction. (3) Synthesis challenges - Solid-phase peptide synthesis of Fragment 176-191 requires: (a) Protecting cysteine side chains during synthesis (using trityl or acetamidomethyl protecting groups), (b) After peptide assembly and cleavage from resin, performing controlled disulfide bond formation (air oxidation in dilute aqueous solution pH 7-8, or using chemical oxidants like DMSO, iodine, or ferricyanide), (c) Purification separating correctly folded (proper Cys-7 to Cys-14 disulfide) from misfolded species (incorrect disulfide pairing, aggregated forms, or reduced species). HPLC monitoring during oxidation tracks formation of the faster-eluting disulfide-bonded peak vs slower-eluting reduced form. Quality control must confirm >95% of peptide exists in disulfide-bonded form. (4) Analytical verification - Mass spectrometry distinguishes disulfide-bonded form (MW ~1815 Da, -2 Da from loss of 2H during S-S bond formation) from reduced form (MW ~1817 Da with free thiols). Alkylation experiments: treating sample with iodoacetamide or N-ethylmaleimide (which add mass to free cysteines but not disulfide-bonded cysteines) reveals presence of free thiols; properly formed Fragment shows no alkylation indicating complete disulfide formation. HPLC under non-reducing vs reducing conditions shows single peak (non-reducing) vs altered retention time (reducing), confirming disulfide. (5) Stability implications - Disulfide bonds generally stabilize peptides against proteolysis and thermal denaturation. Fragment 176-191 shows enhanced stability vs linear peptides lacking disulfide constraints. However, disulfide bonds are susceptible to reduction in strongly reducing environments (presence of DTT, glutathione, or reducing enzymes like thioredoxin/protein disulfide isomerase). In vivo, serum contains low levels of reducing activity but not sufficient to rapidly break disulfide in extracellular space; Fragment retains activity. (6) Comparison to analogs - Research developing Fragment analogs sometimes replaces disulfide with chemical staples, lactam bridges (Lys-Asp/Glu linkages), or all-D-cysteine disulfide (more stable to reduction) testing whether constrained structure can be maintained by alternative crosslinks while preserving or enhancing lipolytic activity.

Can GH Fragment 176-191 be combined with other fat-loss agents, exercise, or metabolic modulators?

Yes! GH Fragment 176-191 combinations enable investigating synergistic fat mobilization and metabolic improvements: (1) Fragment 176-191 + β3-Adrenergic Agonists (CL-316243, mirabegron) - Both stimulate lipolysis but via distinct mechanisms: Fragment via putative GH-related pathway (mechanism still debated), β3-agonists via cAMP-PKA-HSL phosphorylation in white adipose and thermogenesis in brown adipose tissue (BAT). Combination studies in obese rodents demonstrate synergistic fat loss (Fragment + β3-agonist produces greater weight loss and visceral fat reduction vs either alone), potentially additive lipolytic signaling, and combined benefits of increased fat mobilization (Fragment) plus energy expenditure (β3-agonist BAT activation). (2) Fragment 176-191 + Caloric Restriction or Intermittent Fasting - Fragment may enhance fat loss during hypocaloric diets by maintaining elevated lipolysis preventing metabolic adaptation (the reduction in metabolic rate during dieting). Research examines whether Fragment-treated subjects show greater fat loss, preserved lean mass, or reduced hunger/cravings during caloric restriction. Fasting already elevates endogenous GH (compensatory response); exogenous Fragment might amplify lipolytic effects during fasted state. (3) Fragment 176-191 + Exercise Training - Exercise increases fat oxidation and metabolic rate; Fragment mobilizes stored triglycerides providing substrate for oxidation. Combination may synergize: Fragment + aerobic exercise (enhances fat utilization during and after exercise), Fragment + resistance training (maximizes fat loss while building/preserving muscle, though Fragment itself doesn't build muscle, it allows exercise anabolism while promoting fat catabolism). Studies measure body composition changes, exercise performance, and metabolic markers. (4) Fragment 176-191 + AMPK Activators (Metformin, MOTS-c, AICAR) - AMPK activation promotes fatty acid oxidation and mitochondrial biogenesis complementing Fragment's lipolytic effects. Fragment mobilizes fat from adipocytes; AMPK activators enhance fat oxidation in muscle/liver utilizing released fatty acids. Combination may prevent fatty acid re-esterification (recycling back to triglycerides) ensuring mobilized fat is oxidized. (5) Fragment 176-191 + Thyroid Hormones (T3, T4) - Thyroid hormones increase basal metabolic rate and lipid oxidation. Combination with Fragment (lipolysis) provides dual benefit: mobilization plus utilization. However, excessive thyroid can cause muscle catabolism, cardiac stress; research examines optimal dosing. (6) Fragment 176-191 + GLP-1 Receptor Agonists (Semaglutide, Tirzepatide) - GLP-1 agonists reduce appetite and body weight primarily via caloric reduction; Fragment enhances fat mobilization. Combination investigated in obesity models testing whether Fragment augments GLP-1-mediated weight loss or improves body composition (greater fat loss, preserved lean mass). (7) Fragment 176-191 + NAD+ Precursors (NMN, NR) or Sirtuins Activators (Resveratrol) - Enhancing mitochondrial function and fat oxidation (NAD+/sirtuins) combined with fat mobilization (Fragment) may synergistically improve metabolism and body composition. (8) Fragment 176-191 + Testosterone or Anabolic Agents - Fragment lacks anabolic effects (no muscle growth); combining with testosterone or selective androgen receptor modulators (SARMs) provides comprehensive body recomposition: muscle gain (anabolics) plus fat loss (Fragment). Used in research modeling therapeutic approaches to sarcopenic obesity or age-related body composition changes. (9) Fragment 176-191 + Full-Length hGH - Seemingly redundant, but research examines whether combination produces synergistic vs additive effects or whether Fragment at lower doses can reduce total hGH needed (minimizing hGH side effects). (10) Fragment 176-191 + Anti-diabetic Agents - Research in metabolic syndrome or type 2 diabetes models testing whether Fragment-induced visceral fat reduction synergizes with metformin, insulin sensitizers (thiazolidinediones), or SGLT2 inhibitors improving glycemic control and insulin sensitivity.

How does GH Fragment 176-191 affect different adipose tissue depots and metabolic parameters?

GH Fragment 176-191 shows preferential effects on specific fat depots with metabolic consequences: (1) Visceral vs subcutaneous adipose - Multiple animal studies demonstrate Fragment 176-191 preferentially reduces visceral adipose tissue (VAT, abdominal/intra-abdominal fat surrounding organs) over subcutaneous adipose tissue (SAT, beneath skin). Imaging (MRI, CT) or direct tissue dissection/weighing reveals greater percentage reduction in visceral depots (mesenteric, epididymal/parametrial, retroperitoneal fat in rodents) vs subcutaneous inguinal fat. Mechanisms for selectivity unclear but hypothesized: visceral adipocytes have higher GH sensitivity or lipolytic responsiveness, differential receptor/target expression in VAT vs SAT, or distinct blood flow/vascularization enabling preferential Fragment delivery to visceral depots. Clinical significance: Visceral fat is metabolically harmful (insulin resistance, inflammation, dyslipidemia, cardiovascular disease) while subcutaneous fat is relatively benign or protective; selective visceral fat reduction provides disproportionate metabolic benefits. (2) Insulin sensitivity improvements - Fragment-treated obese animals show improved glucose tolerance (oral glucose tolerance test, OGTT, shows reduced glucose AUC after treatment), enhanced insulin sensitivity (insulin tolerance test, ITT, demonstrates greater glucose-lowering response to insulin; HOMA-IR index improved), and reduced fasting glucose and insulin levels. Mechanisms: visceral fat reduction decreases adipose tissue inflammation and inflammatory cytokine secretion (TNF-α, IL-6, resistin) which impair insulin signaling; reduced ectopic lipid accumulation in liver and muscle (lipotoxicity causes insulin resistance); improved adiponectin secretion (adiponectin enhances insulin sensitivity); and direct Fragment effects on glucose metabolism independent of fat loss (some studies suggest Fragment modulates glucose uptake though mechanisms unclear). (3) Lipid profile improvements - Fragment treatment reduces plasma triglycerides (increased adipose lipolysis mobilizes triglycerides but enhanced oxidation prevents accumulation; reduced hepatic VLDL production), lowers LDL cholesterol, raises HDL cholesterol, and reduces free fatty acids (despite increased lipolysis, improved oxidation clears FFAs). These changes reduce cardiovascular risk. (4) Hepatic steatosis reduction - Non-alcoholic fatty liver disease (NAFLD) often accompanies obesity. Fragment-treated animals show reduced hepatic triglyceride content (Oil Red O staining, biochemical quantification), decreased liver weight, improved liver enzyme levels (ALT, AST), and reduced inflammation/fibrosis markers. Mechanisms: visceral fat reduction decreases portal vein free fatty acid delivery to liver, improved insulin sensitivity reduces hepatic de novo lipogenesis, and potential direct Fragment effects on hepatic lipid metabolism. (5) Inflammation markers - Adipose tissue, particularly visceral fat, secretes pro-inflammatory cytokines. Fragment-induced fat loss reduces systemic inflammation: lower CRP (C-reactive protein), reduced TNF-α, IL-6, MCP-1 in plasma and adipose tissue, decreased macrophage infiltration into adipose (crown-like structures), and shift from pro-inflammatory M1 macrophages to anti-inflammatory M2 phenotype. (6) Adipokine profiles - Beyond inflammation, Fragment affects beneficial adipokines: increased adiponectin (insulin-sensitizing, anti-inflammatory, cardioprotective), potentially reduced leptin (correlates with fat mass), and improved leptin sensitivity (obesity-associated leptin resistance may improve). (7) Energy expenditure and metabolism - Some research suggests Fragment increases energy expenditure or metabolic rate though effects are modest and inconsistent across studies. Proposed mechanisms include uncoupling protein (UCP) upregulation, increased fat oxidation (energetically favorable), or mitochondrial biogenesis. Indirect calorimetry or metabolic cage studies measure oxygen consumption, CO2 production, and respiratory exchange ratio examining substrate utilization shifts. (8) Body composition specificity - Fragment predominantly reduces fat mass with minimal or no lean mass changes. Contrast with full hGH (increases both lean and fat loss) or with severe caloric restriction (reduces both fat and lean mass). Researchers use DEXA, MRI, or CT to quantify compartmental changes validating fat-selective effects.

What documentation and international shipping support GH Fragment 176-191 fat loss research?

We ship GH Fragment 176-191 in lyophilized form with cold pack insulation in sealed packaging protecting the 16-amino-acid disulfide-bonded peptide. Lyophilized Fragment remains stable at ambient temperature for short periods (up to 7 days) but cold packs minimize degradation. International delivery typically takes 10-14 days with tracking; immediately transfer to -20°C storage upon arrival. Each batch includes comprehensive Certificate of Analysis: HPLC chromatogram demonstrating >98% purity with retention time characteristic of the disulfide-bonded 16-AA GH C-terminal fragment, mass spectrometry data confirming molecular weight (~1815 Da accounting for Cys-7 to Cys-14 disulfide bond and C-terminal amidation) validating the Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-CONH₂ sequence, peptide sequencing via MS/MS fragmentation verifying each amino acid with special validation of two Cys residues forming essential disulfide bond and C-terminal Phe-amide modification, amino acid composition analysis quantifying each residue, disulfide bond verification via reduced vs non-reduced sample comparison by mass spec (disulfide-bonded form MW ~1815 Da, reduced form MW ~1817 Da showing +2 Da from free thiols) confirming >95% of peptide exists in properly folded disulfide form, functional bioassay data demonstrating lipolytic activity including adipocyte lipolysis assays (primary adipocytes or 3T3-L1 cells) treated with dose-escalating Fragment measuring glycerol release showing dose-dependent lipolysis with EC50 quantification (typically 1-20 μM), time-course lipolysis demonstrating sustained activity over 3-24 hours, comparison to isoproterenol (β-agonist control) validating assay, GH receptor binding assays confirming Fragment does NOT bind GHR (negative result validating GHR-independence distinguishing from full hGH), IGF-1 production assays demonstrating Fragment does NOT induce IGF-1 (negative result confirming no classical GH signaling), circular dichroism or NMR spectroscopy confirming secondary structure consistent with disulfide-constrained conformation, endotoxin testing (<0.1 EU/mg), batch number and manufacturing date, handling recommendations emphasizing non-reducing reconstitution conditions to preserve disulfide bond integrity. This documentation satisfies institutional requirements worldwide ensuring compliance for obesity research, metabolic syndrome models, adipocyte biology, lipolysis pathway studies, GH structure-function research, body composition investigations, and fat-selective therapeutic development programs. For researchers requiring technical support on lipolysis assays, in vivo fat loss protocols, or body composition analysis methods, our team provides WhatsApp consultation on experimental design, optimal dosing for adipocyte vs animal studies, and troubleshooting lipolytic activity measurements.

What dosage specifications and bulk pricing are available for GH Fragment 176-191 fat loss research?

We offer three GH Fragment 176-191 specifications to accommodate diverse lipolysis research protocols: FR2 (2mg per 10-vial kit), FR5 (5mg per 10-vial kit), and FR10 (10mg per 10-vial kit). Pricing with volume discounts: FR2: $90/kit (1 kit), $85/kit (20+ kits = 5.6% discount), $80/kit (50+ kits = 11% discount). FR5: $160/kit (1 kit), $150/kit (20+ kits = 6.3% discount), $140/kit (50+ kits = 12.5% discount). FR10: $360/kit (1 kit), $350/kit (20+ kits = 2.8% discount), $340/kit (50+ kits = 5.6% discount). The three concentration options support research from pilot adipocyte lipolysis screening and dose-response characterization (2mg for in vitro glycerol release assays, EC50 determinations) to moderate-scale in vivo fat loss studies (5mg supports several weeks of rodent dosing at typical 250-500 μg/kg doses) to extensive chronic obesity research, large animal studies, or multi-group experimental designs requiring higher cumulative doses (10mg for prolonged treatment protocols, dose-response in vivo studies, or research combining Fragment with other interventions). Pricing reflects synthesis complexity of the 16-amino-acid disulfide-bonded peptide requiring solid-phase peptide synthesis assembling specific sequence, incorporation of two cysteine residues with side-chain protection during synthesis followed by controlled oxidative disulfide bond formation post-synthesis (requiring careful optimization to ensure correct Cys-7 to Cys-14 pairing vs misfolded forms or intermolecular disulfides causing aggregation), C-terminal amidation (enzymatic or chemical amidation essential for activity; carboxylate forms show reduced potency), rigorous purification separating correctly folded disulfide-bonded form from reduced, misfolded, or aggregated species (multiple HPLC purification steps may be required), comprehensive quality control (HPLC purity, mass spec confirming MW and disulfide/amidation, peptide sequencing validating all 16 residues, disulfide bond verification via reduced vs non-reduced comparison, adipocyte lipolysis bioassays with EC50 quantification, GHR binding assays confirming receptor-independence, IGF-1 assays confirming no classical GH signaling, structural characterization via CD or NMR), and comprehensive CoA documentation while maintaining >98% purity with >95% correct disulfide formation. Bulk discounts support multi-year obesity research programs, institutional metabolic disease centers, pharmaceutical companies developing selective lipolytic agents or GH analogs, body composition research facilities, and international fat metabolism research consortia. The requirement for correct disulfide bond formation adds synthesis/purification complexity beyond simple linear peptides, reflected in pricing. Contact via WhatsApp for custom quantities for large animal studies, clinical research, or specialized formulations requiring GMP-grade material for investigational therapeutic applications.

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HGF5

HGH Fragment 176-191

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Premium pharmaceutical-grade GH Fragment 176-191 for advanced research applications

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HGH Fragment 176-191: Key Facts

HGH Fragment 176-191 is a fat loss research peptide supplied by LyzeLabs as a lyophilized reference standard, strictly for laboratory research use. It is available in 1 format starting at $340 per kit. Each batch is independently HPLC-verified at 98.94% purity by Janoshik Analytical, with the certificate of analysis published on the lab-results page and matched to the lot number printed on the vial.

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Compound	HGH Fragment 176-191
Research category	Fat Loss
Available formats	5mg*10vials
Starting price	From $340 USD per kit
Purity	98.94% verified (third-party HPLC, Janoshik)
Test method	HPLC / ESI-MS
Certificate of analysis	Published online, matched to the vial lot number
Intended use	Laboratory research use only. Not for human consumption.
Handling	Supplied lyophilized, store per the stability guide

What Researchers Say

Dr. Rajesh Kumar

Sweden

"Our metabolic research lab at clinical research team has been using LyzeLabs GH Fragment 176-191 for obesity and body composition research for 10 months with exceptional pharmaceutical quality. We independently verified >98.7% purity via HPLC and mass spectrometry confirmed MW 1815 Da demonstrating complete 16-amino-acid sequence with proper Cys-7 to Cys-14 disulfide bond formation and C-terminal amidation (critical for lipolytic activity). Disulfide bond verification via reduced vs non-reduced sample comparison showed >96% of peptide in correctly folded form. Our research investigates Fragment 176-191 in diet-induced obesity mice - adipocyte lipolysis assays using primary adipocytes from epididymal fat show Fragment (1-50 μM) dose-dependently increases glycerol release (2.8-fold increase at 10 μM vs vehicle, p<0.001, EC50 ~4.2 μM). Time-course studies show lipolysis onset within 2 hours and sustained elevation for 24+ hours. High-fat diet mice receiving Fragment (500 μg/kg IP twice daily for 6 weeks) demonstrate significant fat loss: body weight reduced 18% vs vehicle (p<0.01), visceral fat mass (epididymal + retroperitoneal) reduced 34% (p<0.001), while subcutaneous inguinal fat reduced only 12% demonstrating visceral fat selectivity. MRI quantification confirms preferential visceral adipose reduction. Metabolic improvements include enhanced glucose tolerance (OGTT AUC reduced 29%, p<0.01), improved insulin sensitivity (ITT, HOMA-IR decreased 41%), reduced plasma triglycerides (38% lower), and decreased hepatic steatosis (liver triglycerides reduced 52%, p<0.01). GH receptor binding assays confirm Fragment shows no GHR binding, and IGF-1 ELISA shows no IGF-1 elevation validating GHR-independence. The FR5 and FR10 specifications support our chronic treatment protocols. Delivery to Berlin takes 11-13 days with excellent cold-chain packaging. Premier selective lipolytic peptide for international obesity research."

2025-11-17

B. Andersen

United States

"Mass spec came back clean on our end. The reconstitution notes actually helped."

2025-11-14

Lab procurement

Sweden

"Ordered for a comparison run. Values sat where the certificate said."

2025-11-11

About This Product

GH Fragment 176-191: Lipolytic Research Without Full Growth Hormone Activity

What It Is and Why It Matters

GH Fragment 176-191 is the C-terminal peptide spanning amino acids 176 to 191 of human growth hormone (hGH). The fragment was identified during receptor mapping studies as the region of hGH responsible for stimulating lipolysis in adipose tissue. This fragment retains fat metabolism activity while lacking the growth-promoting and IGF-1-stimulating properties of the full 191-amino-acid GH molecule, making it a precise tool for isolating lipolytic signaling from growth signaling.

Mechanism: Adipose-Selective Signaling

The full growth hormone molecule signals through GHR to produce two distinct downstream effects: anabolic growth through JAK2-STAT5-IGF-1 signaling, and lipolytic effects through a separate receptor interaction. GH Fragment 176-191 lacks the receptor binding region for JAK2-STAT5 activation, retaining only the region associated with fat metabolism. In research models, this allows study of the lipolytic signaling pathway independently of anabolic GH effects, addressing a confound present in full HGH protocols.

Choosing Between GH Fragment and Full HGH

Researchers choosing between GH 176-191 and full HGH are making a mechanistic choice. Full HGH activates the complete GH receptor cascade including IGF-1 production, bone growth effects, and insulin resistance modulation. GH Fragment 176-191 provides a controlled intervention at the lipolytic node without those confounding effects. Both are available at lyzelabs.com for head-to-head comparative protocol design.

Research Applications

Adipose metabolism: lipolysis pathway research independent of full GH receptor activation
Fat metabolism signaling: free fatty acid release and glycerol production studies
Receptor pharmacology: C-terminal hGH fragment binding and downstream signaling
Comparative studies: GH Fragment 176-191 vs full HGH and AOD-9604 in lipolysis models
Metabolic research: body composition effects of selective lipolytic stimulation

Quality Standards

Purity: >99% by HPLC
Identity: confirmed by ESI-MS
Form: lyophilized powder, sterile vials
Storage: -20°C, reconstitute with acetic acid 0.6%
Full COA at lyzelabs.com/lab-results

For research purposes only. Not for human consumption.

Research Context for HGH Fragment 176-191

Lipolysis and Fat Metabolism Research Context

Fat metabolism research peptides target lipolysis, mitochondrial fatty acid oxidation, brown adipose activation, or direct effects on adipocyte viability. Research protocols measure body composition, lipid panel markers, and tissue-specific fat mobilization under defined experimental conditions.

HGH Fragment 176-191 ships as a lyophilized research reagent through the LyzeLabs™ catalog in the Fat Loss category, available as a single research-grade format. Every batch is independently verified by Janoshik Analytical, with the full HPLC chromatogram and mass spectrometry confirmation published on the LyzeLabs lab results page and matched to the lot number printed on your vial.

Related Research Guides

How to Read a Peptide Certificate of Analysis

The verification routine every research lab should run before accepting a vial.

How to Reconstitute a Research Peptide

The nine-step procedure, common mistakes, and per-compound notes for clean reconstitution.

Other Compounds in the Fat Loss Category

Research Tools for This Compound

Frequently Asked Questions

HGH Fragment 176-191

$340