Fragment 176-191 is a small C-terminal segment of human growth hormone (hGH) that has been used as a laboratory research reagent in studies focused on fat metabolism (lipolysis) and energy-balance pathways. In research discussions, Fragment 176-191 is often described within the same investigative lineage as related hGH-derived lipolytic domains (including AOD9604), and it is used to explore adipose-tissue signaling under controlled experimental conditions.

Fragment 176-191 has drawn interest in mechanistic research because preclinical work has evaluated whether a lipolytic hGH fragment can preserve aspects of fat-related signaling while minimizing other endocrine outputs commonly associated with full-length hGH (e.g., broader anabolic or growth-associated effects) within specific study designs.

Sequence: Phe–Leu–Arg–Ile–Val–Gln–Cys–Arg–Ser–Val–Glu–Gly–Ser–Cys–Gly–Phe
Molecular Formula: C₇₈H₁₂₃N₂₃O₂₂S₂
Molecular Weight: 1799.1 g/mol
CAS Number: 66004-57-7

Source: PubChem

In laboratory settings, Fragment 176-191 is typically treated as a defined-sequence peptide input for metabolic pathway interrogation, adipocyte signaling assays, and preclinical energy-balance model designs.

Fragment 176-191 may be used as a research reagent in controlled studies investigating:

• Adipose biology & lipolysis: pathway mapping of lipid mobilization, adipose mass changes, and fat oxidation endpoints in preclinical models.
• Energy homeostasis: mechanistic studies of weight trajectories, energy expenditure proxies, and substrate utilization signatures.
• Receptor/pathway attribution designs: evaluating candidate upstream drivers (e.g., adrenergic signaling involvement) using knockout models, pharmacologic controls, or comparator peptides.
• Comparative hGH-fragment research: contrasting full-length hGH versus fragment-based inputs to distinguish lipolytic-focused effects from broader endocrine outputs in defined experimental systems.
• Exploratory connective tissue models: related hGH-fragment lineages have been explored in cartilage and joint-tissue paradigms to interrogate tissue-response mechanisms in preclinical settings.

These examples describe research uses only and are not intended as medical, diagnostic, or therapeutic claims.

Fragment 176-191 is commonly discussed in metabolic research as a lipolytic hGH-derived fragment used to probe fat-mobilization pathways. In obesity-model literature, a proposed mechanistic linkage has included beta-3 adrenergic receptor (β3-AR / ADRB3)–associated signaling in adipose tissue, a pathway frequently studied for roles in lipolysis and thermogenesis in certain preclinical systems.^[2]

Because metabolic phenotypes can be influenced by multiple overlapping control loops (adrenergic tone, endocrine signaling, diet, genetics, and tissue-specific receptor expression), studies often incorporate comparator groups (e.g., placebo/saline, full-length hGH, related fragments or domains) and, in some cases, knockout models to support attribution of observed lipid-handling endpoints.

1) Glucose-Related Signaling Exploration (Preclinical)

Earlier animal work evaluating multiple synthetic C-terminal fragments of hGH explored glucose-related effects, and Fragment 176-191 was described as comparatively active in those experimental conditions, with reported changes occurring alongside sustained increases in plasma insulin levels in the study’s model system.^[1] This line of research contributed to broader interest in how specific hGH-derived regions may interact with metabolic signaling readouts.

2) Lipid Mobilization, Weight Trajectories, and β3-AR Discussion (Preclinical)

Obesity-model studies have reported reduced weight gain and adipose-tissue changes following chronic treatment paradigms involving the hGH lipolytic fragment lineage, with mechanistic discussions that include β3-AR pathway involvement in certain experimental contexts.^[2] Additional preclinical literature has discussed β3-AR agonism and its relationship to lipid stores and fat oxidation in rodent models.^[3]

Related metabolic studies of AOD9604 (a synthetic lipolytic domain in the same research lineage) reported outcomes consistent with changes in energy expenditure and weight-related endpoints under their study designs, including discussion of measured parameters such as glucose tolerance, insulin sensitivity, and IGF-1 within that framework.^[4]

Body weight in genetically obese mice after two weeks of treatment with a single daily dose of Fragment 176-191
Source: Oxford Academic

Effect of saline (control), Fragment 176-191, and hGH on white adipose tissue mass in obese mice over 14 days
Source: Oxford Academic

3) Safety/Tolerability Framing and Study Design Considerations

Because long-term exogenous hGH exposure is discussed clinically in association with potential adverse outcomes (e.g., insulin resistance and related metabolic issues), research has evaluated whether lipolytic fragments or domains can be studied with a more targeted profile in defined settings. A publication assessing safety and tolerability of the hexadecapeptide AOD9604 in humans is included among the cited sources.^[5] Additional cited metabolic studies reported no meaningful differences versus placebo in several measured parameters under their study designs, including glucose tolerance, insulin sensitivity, and IGF-1 levels.^[4]

Preclinical work has also discussed selection of lipolytic fragments for studying fat oxidation and weight outcomes rather than anabolic signaling, including discussion of endpoints related to proliferation in specific experimental contexts.^[6]

4) Exploratory Connective Tissue / Cartilage Models (Preclinical)

Beyond metabolism, related hGH-fragment research has been explored in connective tissue models. A rabbit osteoarthritis study investigated intra-articular AOD9604 (with or without hyaluronic acid) and reported findings consistent with changes in cartilage-related measures in that experimental context.^[7]

Note: The studies summarized above describe mechanistic or experimental endpoints in laboratory and preclinical systems and are not intended as medical claims.

In laboratory supply and research environments, peptide identity and quality are commonly evaluated using standard analytical approaches such as chromatographic purity profiling and mass-based identity confirmation. These methods support controlled experimental use and batch-to-batch documentation within the purchaser’s research quality framework.

This section is provided for general informational context regarding common laboratory quality practices and does not represent a medical, diagnostic, or clinical application.

The above literature was researched, edited and organized by Dr. Logan, M.D. Dr. Logan holds a doctorate degree from Case Western Reserve University School of Medicine and a B.S. in molecular biology.

Frank Ng, M.D. has been cited for contributions to research exploring growth-hormone–derived lipolytic domains and fragments (including AOD9604 and Fragment 176-191 lineage), with published work spanning lipid metabolism in obesity models and related metabolic endpoints under experimental control.

This reference is provided to acknowledge scientific contributions and does not imply endorsement or advocacy of purchase, sale, or use of this product. No affiliation or relationship is implied between the seller and this scientist. The cited work appears in the references below.

1. F. M. Ng and J. Bornstein, “Hyperglycemic action of synthetic C-terminal fragments of human growth hormone,” Am. J. Physiol., vol. 234, no. 5, pp. E521–526, May 1978.
2. M. Heffernan et al., “The Effects of Human GH and Its Lipolytic Fragment (AOD9604) on Lipid Metabolism Following Chronic Treatment in Obese Mice and β3-AR Knock-Out Mice,” Endocrinology, vol. 142, no. 12, pp. 5182–5189, Dec. 2001.
3. R. Ferrer-Lorente, C. Cabot, J.-A. Fernández-López, and M. Alemany, “Combined effects of oleoyl-estrone and a beta3-adrenergic agonist (CL316,243) on lipid stores of diet-induced overweight male Wistar rats,” Life Sci., vol. 77, no. 16, pp. 2051–2058, Sep. 2005.
4. F. M. Ng, J. Sun, L. Sharma, R. Libinaka, W. J. Jiang, and R. Gianello, “Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone,” Horm. Res., vol. 53, no. 6, pp. 274–278, 2000.
5. H. Stier, E. Vos, and D. Kenley, “Safety and Tolerability of the Hexadecapeptide AOD9604 in Humans,” J. Endocrinol. Metab., vol. 3, no. 1–2, pp. 7–15, Apr. 2013.
6. M. A. Heffernan et al., “Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment,” Int. J. Obes., vol. 25, no. 10, pp. 1442–1449, Oct. 2001.
7. D. R. Kwon and G. Y. Park, “Effect of Intra-articular Injection of AOD9604 with or without Hyaluronic Acid in Rabbit Osteoarthritis Model,” Ann. Clin. Lab. Sci., vol. 45, no. 4, pp. 426–432, Jul. 2015.

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