≥98%HPLC Purity
COAIncluded
USAShipped
HGH Fragment 176-191 Peptide
Human Growth Hormone full-length 191 amino acid sequence. Recombinant somatotropin for growth hormone receptor binding research.
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| SKU | ACR-HGH191 |
|---|---|
| CAS Number | 221231-10-3 |
| Molecular Formula | C78H125N23O23S2 |
| Molecular Weight | 1,817.12 g/mol |
| Sequence | 191-amino acid sequence |
| Purity | ≥99% |
| Physical Form | Lyophilized Powder |
| Storage | Store at -20°C |
What is HGH 191AA?
HGH 191AA (Somatotropin) is recombinant human growth hormone consisting of 191 amino acids in a single polypeptide chain with two disulfide bonds. It is structurally identical to endogenous pituitary-derived growth hormone, which is the most abundant anterior pituitary hormone.
Growth hormone is synthesized, stored, and secreted by somatotroph cells within the anterior pituitary gland. Its secretion follows a pulsatile pattern regulated by the opposing actions of GHRH (stimulatory) and somatostatin (inhibitory). Published research has extensively characterized its receptor binding, signaling cascades, and downstream effects.
For laboratory research use only.
Mechanism of Action
GH Receptor (GHR) Activation
GH binds to the growth hormone receptor (GHR), a type I cytokine receptor. GH binding induces receptor dimerization, bringing two intracellular JAK2 kinase molecules into proximity. This triggers JAK2 trans-phosphorylation and activation, which subsequently phosphorylates STAT5a/5b transcription factors.
JAK2-STAT5 Signaling
The JAK2-STAT5 pathway is the primary signaling cascade for GH action. Phosphorylated STAT5 dimerizes and translocates to the nucleus, where it activates transcription of target genes including IGF-1, the principal mediator of many GH effects. This GH-IGF-1 axis is fundamental to growth physiology.
MAPK and PI3K Pathways
Beyond STAT5, GH activates additional signaling cascades including the MAPK/ERK pathway (cell proliferation) and PI3K/Akt pathway (metabolic effects, cell survival). These pathways mediate the diverse metabolic effects of GH including lipolysis, glucose regulation, and protein synthesis.
Mechanism of Action: Lipolytic Pathway
HGH Fragment 176-191 reproduces the lipolytic (fat-burning) action of growth hormone without its diabetogenic, growth-promoting, or IGF-1-elevating effects. The mechanism involves:
- Beta-3 adrenergic receptor activation: Fragment 176-191 stimulates beta-3 AR on white adipocytes, triggering cAMP/PKA signaling cascade
- Hormone-sensitive lipase (HSL) activation: PKA phosphorylates HSL, which hydrolyzes stored triglycerides into free fatty acids and glycerol
- Perilipin phosphorylation: PKA also phosphorylates perilipin on the lipid droplet surface, exposing triglycerides to HSL access
- Enhanced fatty acid oxidation: Released free fatty acids are directed to mitochondrial beta-oxidation rather than re-esterification
Critically, Fragment 176-191 does NOT activate the GH receptor (GHR), meaning it does not trigger JAK2/STAT5 signaling, does not increase hepatic IGF-1 production, and does not impair insulin signaling. This makes it a pure lipolytic research tool isolated from the complex pleiotropic effects of full-length GH.
Research & Clinical Studies
HGH Fragment and Lipolysis Research
HGH Fragment 176-191 stimulates lipolysis through activation of beta-3 adrenergic receptors on adipocytes, mimicking the fat-burning portion of GH activity without affecting glucose metabolism, insulin sensitivity, or IGF-1 levels. In obese mouse models, Fragment 176-191 reduced body fat by 50% over 3 weeks without affecting lean mass, food intake, or blood glucose — demonstrating pure lipolytic activity isolated from GH anabolic effects.
[1] Ng FM, Sun J, Sharma L, et al. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Horm Res. 2000;53(6):274-278. PubMed ↗
Fragment 176-191 vs AOD-9604 Comparison
AOD-9604 is a tyrosinated version of Fragment 176-191 with an additional N-terminal tyrosine residue (Tyr-hGH177-191). Both compounds share the same lipolytic mechanism (beta-3 AR activation) but AOD-9604 showed slightly enhanced stability and was the variant advanced to clinical trials. Research comparing both fragments shows similar lipolytic potency in vitro, with AOD-9604 having marginally better pharmacokinetics due to the tyrosine modification.
Clinical Research: AOD-9604 Phase 2 Trials
AOD-9604 (the tyrosinated version of Fragment 176-191) advanced to Phase 2 clinical trials in Australia for obesity. Key findings from the randomized, double-blind trial (Stier et al.):
- Daily oral AOD-9604 for 12 weeks produced dose-dependent weight loss
- The 1 mg/day group lost 2.6 kg more than placebo
- No effect on IGF-1 levels, glucose tolerance, or insulin sensitivity — confirming the fragment does not activate the GH receptor
- No serious adverse events; safety profile indistinguishable from placebo
- AOD-9604 was subsequently approved in Australia (TGA) as a food substance, confirming its safety profile
[1] Heffernan M et al. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice. Endocrinology. 2001;142(12):5182-5189. PubMed ↗
Chemical Properties
| Sequence | Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe (hGH176-191) |
|---|---|
| Formula | C₇₈H₁₂₅N₂₃O₂₃S₂ |
| MW | 1,817.12 g/mol |
| CAS | 221231-10-3 |
| Amino Acids | 16 (C-terminal fragment of 191-aa human GH) |
| Disulfide Bond | Cys182-Cys189 (intramolecular) |
| Purity | ≥98% HPLC |
Handling & Reconstitution
Reconstitution: Add bacteriostatic water slowly along vial wall. Fragment 176-191 contains a disulfide bond (Cys182-Cys189) — do not use reducing agents or harsh agitation that could disrupt it.
Concentration: 5 mg vial + 1 mL BAC water = 5 mg/mL. 10 mg vial + 2 mL = 5 mg/mL.
Important: Administer on an empty stomach in research protocols — food intake (especially carbohydrates) elevates insulin, which counteracts the lipolytic signaling activated by Fragment 176-191. Most research protocols specify at least 30 minutes pre-meal or 2-3 hours post-meal timing.
Storage & Stability
Lyophilized: -20°C for 24 months. Reconstituted: 2-8°C, use within 14 days. Contains disulfide bond (Cys182-Cys189) — avoid reducing conditions. Protect from light.
Frequently Asked Questions
What is HGH 191AA?
HGH 191AA is recombinant human growth hormone consisting of 191 amino acids, structurally identical to endogenous pituitary GH. It activates the GH receptor (GHR), triggering JAK2-STAT5 signaling and IGF-1 production. For laboratory research only.
How does HGH differ from peptide secretagogues?
HGH is the actual growth hormone protein (191 amino acids, 22 kDa). Secretagogues like GHRP-6, Ipamorelin, and CJC-1295 are small peptides that stimulate the pituitary to produce and release endogenous GH. HGH directly activates GH receptors while secretagogues work indirectly through the pituitary.
Does HGH Fragment affect IGF-1 or blood sugar?
No. Fragment 176-191 isolates only the lipolytic domain of growth hormone. It does not bind the GH receptor, does not increase IGF-1, and does not affect blood glucose or insulin sensitivity. This is its primary advantage over full-length GH for fat metabolism research.
HGH Fragment vs AOD-9604?
Both share the same core sequence (hGH176-191). AOD-9604 adds an N-terminal tyrosine for stability. Lipolytic potency is similar. AOD-9604 was the variant used in clinical trials. Fragment 176-191 is the base compound often preferred in preclinical research.
Does Fragment 176-191 affect muscle growth?
No. Fragment 176-191 does not activate the GH receptor and does not increase IGF-1. It is purely lipolytic. For anabolic/muscle-building GH research, full-length GH or GH secretagogues (Ipamorelin, MK-677) are the appropriate compounds.
Why dose on empty stomach?
Insulin antagonizes lipolysis. Carbohydrate intake raises insulin, which activates phosphodiesterase (degrades cAMP) and dephosphorylates HSL — directly counteracting Fragment 176-191 mechanism. Empty stomach ensures low insulin for maximal lipolytic response.
Is Fragment 176-191 the same as AOD-9604?
Almost. Fragment 176-191 = hGH amino acids 176-191. AOD-9604 = Fragment 176-191 + additional N-terminal tyrosine residue. Same mechanism, similar potency. AOD-9604 has slightly better stability and was used in clinical trials.
For laboratory and research use only. Not intended for human or animal consumption. All product information is derived from published preclinical research and does not constitute medical advice or claims.
