Native hGH fragment 176–191 is the sixteen-residue terminal segment of human growth hormone, beginning with phenylalanine and containing a disulfide bridge between two cysteines. The direct historical research identified here concerns carbohydrate metabolism in rats: the fragment was among peptides that transiently raised glucose and changed insulin sensitivity, followed by experiments examining metabolic enzymes in rat tissues. AOD9604 has a different first residue and a separate development history. Keeping those materials distinct is essential, because otherwise human studies of a modified analogue can be misread as evidence for this native sequence.
Overview
The NLM MeSH chemical record identifies somatotropin(176–191), also called hGH(176–191), as a phenylalanine-starting peptide with a cyclic disulfide between positions 7 and 14. The sequence is Phe-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe. These positions refer to the isolated sixteen-residue peptide; the fragment name uses numbering within the mature GH protein.
Molecular profile
Forms and derivatives
Native hGH177–191
A shorter fifteen-residue terminal peptide, beginning with leucine. It was tested separately alongside native176–191 in the 1982 rat metabolic investigation.
AOD9604 / LAT8881
Tyr-hGH177–191 places tyrosine at the first position occupied by phenylalanine in native176–191. Its obesity and pain development is described on the separate modified-analogue profile.
Peptide-labeled chitosan nanoparticles
A 2022 cancer-cell paper used the 176–191 label, but its numbering and substitution descriptions do not resolve the peptide material sufficiently for assignment to this native sequence.
AOD9604 is Tyr-hGH177–191: it adds tyrosine to the fifteen-residue 177–191 sequence, occupying the first position where the native 176–191 fragment contains phenylalanine. The LAT8881 protocol gives that modified identity explicitly. Native 177–191 is also a shorter peptide. A commercial “GH fragment” label needs a sequence and form before evidence can be assigned reliably.
Uses and research areas
The original investigators used synthetic C-terminal fragments to locate GH-related metabolic activity within a smaller portion of the protein. Their measurements focused on glucose, insulin and enzymes that regulate carbohydrate storage and oxidation. This is a useful biochemical question because intact GH influences several metabolic processes, and removing most of its sequence changes both shape and signaling potential.
The selected direct-material studies do not establish a human weight-loss, muscle-growth or anti-aging effect. Related lipolytic research involved other fragments or modified analogues. That neighboring work can explain why the terminal region attracted interest, while a benefit estimate for native hGH176–191 requires direct evidence for the native preparation. Ng and Bornstein, Ma et al.
Mechanism of action
The historical experiments examined carbohydrate responses rather than establishing one modern receptor target. Insulin normally helps tissues take up and store glucose; a reduced response to insulin can leave more glucose in blood. The 1978 rat study observed a short-lived glucose increase and a more persistent insulin rise after several terminal peptides, including native 176–191. Active fragments sharing the 178–191 region also reduced insulin sensitivity in the tested system.
The 1982 investigation examined glycogen synthase, which helps store glucose as glycogen, and pyruvate dehydrogenase, which helps route carbohydrate-derived fuel into oxidation. The tested 176–191 and 177–191 peptides shifted these enzymes toward inactive forms in selected tissues. Total enzyme amount was unchanged, locating the effect in activity regulation rather than loss of the enzyme itself. The abstract groups findings across the two preparations, so it does not supply a native176–191-specific effect size.
These results describe a coherent metabolic signal but leave the initiating molecular interaction unresolved. The fragment has lost the rest of the GH protein’s receptor-binding architecture, and the GH-like origin alone cannot identify its receptor or prove a selectively favorable metabolic action.
Pharmacokinetics
A route- and analyte-specific human elimination half-life for native hGH176–191 was not established in the direct sources reviewed here. The older papers describe transient glucose effects, which involve the tissues’ response to a stimulus. Their timing does not measure intact fragment clearance.
AOD9604’s animal metabolism report concerns a tyrosine-modified peptide and several assay systems. Its estimates cannot be used as the native fragment’s exposure curve. Consequently, this profile provides no numerical PK illustration or inferred human duration of action.
Research findings
A length comparison in normal rats
Ng and Bornstein compared six synthetic fragments corresponding to hGH172–191, 176–191, 177–191, 178–191, 179–191 and 180–191 in normal rats. The first four caused a brief glucose rise and a more sustained insulin rise. The 179–191 and 180–191 peptides were inactive in the systems tested. The active fragments containing the 178–191 region also reduced insulin sensitivity during intravenous insulin-tolerance testing.
The comparison gives both positive and negative evidence about length and physical configuration. It places native176–191 among the active carbohydrate-modifying materials, with shorter terminal sequences losing activity. Sample counts and detailed time windows were not obtained from the accessible abstract, so there is no pooled animal denominator or reconstructed effect size.
Enzyme activity in whole animals and isolated tissues
Ma and colleagues tested separate native176–191 and native177–191 preparations in rats and in-vitro rat tissue systems. The publisher abstract reports transient glucose and lactate increases after injection. Glycogen-synthase activity ratios decreased in muscle, adipose tissue and liver. Pyruvate-dehydrogenase activity ratios decreased in muscle and adipose tissue, while the liver measurement was unchanged.
These tissue differences matter: the same peptide exposure need not produce the same enzymatic response in every organ. The observations help connect circulating metabolites with regulated fuel handling. They do not establish a favorable net weight effect, and the grouped abstract cannot isolate each peptide’s contribution to every assay.
Identity determines which later studies belong here
Human AOD9604 safety and LAT8881 pain trials involve the tyrosine-modified analogue. Their separate profile describes those outcomes. A 2022 nanoparticle study used a “176–191” label in its title and studied doxorubicin-containing chitosan particles in MCF-7 breast-cancer cells. Its sequence and substitution descriptions do not resolve the peptide’s identity sufficiently to assign its results to native hGH176–191. The source is retained as a screened identity-ambiguous record, without using its cancer-cell findings as exact-native evidence.
Safety and tolerability
Native hGH176–191 has no established FDA-approved therapeutic indication. The selected search did not identify a controlled human intervention study that resolves its safety or efficacy. Its direct animal findings include transient hyperglycemia and altered insulin sensitivity, making glucose regulation a concrete concern to retain in the research summary.
Those experimental effects do not determine the frequency or magnitude of a human adverse event. Human exposure, immune reactions, repeated-use consequences and interaction with existing metabolic disease remain unresolved for the native material. Safety conclusions from AOD9604 depend on its modified identity and trial formulations.
What the research means
The direct evidence is small but informative. The 1978 length comparison identifies active and inactive terminal fragments; the 1982 work connects the active sequences to enzyme regulation in particular rat tissues. Together, the rat experiments showed glucose and insulin increases, reduced insulin sensitivity and changes in enzymes that regulate carbohydrate use.
The central interpretive requirement is exact identity. A first-residue change, a shorter sequence, an altered disulfide or a different formulation can change the material under study. A useful next investigation would therefore need to specify that material, measure intact-peptide exposure and evaluate the proposed outcome alongside glucose and insulin effects. The current direct record does not support a clinical fat-loss estimate for native hGH176–191.
FAQs
Why is native176–191 separate from AOD9604?
The NLM chemical record identifies a phenylalanine-starting native sequence, while the AOD/LAT8881 sponsor protocol specifies Tyr-hGH177–191. The first-position change creates a different peptide identity, so the clinical studies remain assigned to their tested material. NLM MeSH
What did the direct native-fragment studies measure?
They examined rat glucose and insulin responses and activity regulation of carbohydrate-metabolism enzymes. The length comparison also included shorter inactive fragments. This direct evidence is useful for understanding sequence-dependent metabolism, and supplies no human fat-loss estimate. Ng and Bornstein
Does a brief glucose response mean rapid peptide elimination?
Glucose reflects metabolism across several tissues. Its return toward baseline can involve physiological compensation and changes in insulin action even when the peptide’s concentration has not been measured. Intact-peptide pharmacokinetics requires a specific assay and sampling design.
How should a product labeled GH fragment be identified?
A sequence and chemical form are needed to determine which research applies. Fragment numbering alone can conceal a changed first residue, a shorter chain or a different disulfide state. The exact native and modified records provide concrete examples of that ambiguity.
Comparisons and related reading
AOD9604’s separate profile follows the modified analogue through obesity and pain development. Ipamorelin and GHRP-2 belong to a different strategy: they stimulate the pituitary to release GH. The pharmacokinetics explainer describes why a blood-glucose response and intact-peptide elimination require different measurements.
References
The rat length comparison includes native176–191 among active glucose-modifying fragments and retains inactive shorter peptides.
Researchers tested native hGH176–191 and hGH177–191 in rats and isolated rat tissues, measuring enzymes that regulate glucose storage and oxidation. The abstract groups some results across the two peptides.
Alternate primary location gives the grouped peptide identities and tissue-specific enzyme findings.
The native sequence, phenylalanine beginning and cyclic 7–14 disulfide are specified in the chemical name.
Screened identity-ambiguous record retained for transparency; its cancer-cell results are not assigned to exact native176–191.
The sponsor protocol specifies Tyr-hGH177–191, its disulfide, the AOD9604/LAT8881 name link and the failed obesity-development endpoint.
Glossary
- Disulfide bridge
- A covalent connection between the sulfur atoms of two cysteine residues.
- Hyperglycemia
- An increase in blood glucose above its reference level.
- Insulin sensitivity
- How strongly cells and tissues respond to a given insulin signal.
- Glycogen synthase
- An enzyme involved in storing glucose as glycogen.
- Pyruvate dehydrogenase
- An enzyme complex that connects carbohydrate-derived fuel with oxidative metabolism.
- Activity ratio
- The measured active fraction or relative activity of an enzyme under the assay conditions.
- Native sequence
- The amino-acid sequence corresponding to the specified region of the original protein.