Frag 176-191

This foundational study synthesized the C-terminal hGH sequence 177-191 (the fragment structurally corresponding to Frag 176-191) and demonstrated that it possesses antilipogenic activity essentially identical to that of the intact human growth hormone molecule, indicating that the domain governing hGH's inhibition of lipogenesis resides in this carboxyl-terminal region. In rat adipose tissue, the fragment produced minimal direct lipolytic (glycerol-releasing) effect, so the authors framed inhibition of lipogenesis, rather than active lipolysis, as the principal lipid-metabolic action detected for this peptide. The work established the C-terminal fragment as the isolable functional unit later developed into the AOD analog series.

Scientists made a short piece of growth hormone (the same C-terminal fragment marketed as Frag 176-191) and found it blocked the body from building new fat about as effectively as the whole hormone. In this early rat-tissue experiment the fragment mainly stopped fat from being made rather than actively burning existing fat. This study is important because it first pinned down that growth hormone's fat-related activity comes from this specific tail-end region of the molecule.

Using obese Zucker rats, oral administration of AOD9604 (the stabilized analog of the hGH 176-191 lipolytic domain) at 500 micrograms/kg/day for 19 days reduced body-weight gain by over 50% relative to controls and increased lipolytic activity in adipose tissue. Critically, unlike chronic treatment with intact hGH, AOD9604 produced no adverse effect on insulin sensitivity as assessed by euglycemic clamp, suggesting the lipolytic domain retains fat-metabolic activity while shedding the diabetogenic liability of the full hormone. The authors proposed the fragment as a candidate orally bioavailable anti-obesity agent.

In obese rats, the fragment-derived compound AOD9604 given by mouth cut weight gain by more than half over about three weeks and boosted fat breakdown in fat tissue. Unlike the full growth hormone, it did not worsen blood-sugar control, which is a key safety advantage. The researchers suggested it could potentially become a fat-loss drug that works when taken orally.

Chronic 14-day treatment with either human GH or its C-terminal lipolytic fragment AOD9604 reduced body weight and fat mass in obese mice, an effect correlated with restoration of beta(3)-adrenergic receptor (beta3-AR) expression in adipose tissue toward normal levels. In beta3-AR knock-out mice the weight-loss and increased-lipolysis effects were abolished, indicating dependence on a functional beta3-AR pathway; however, AOD9604 still acutely raised energy expenditure in knock-outs, so the peptide's action was interpreted as enhancing lipolytic sensitivity via receptor upregulation rather than direct receptor activation. This study mechanistically links the 176-191/AOD fragment's fat-reducing effect to beta3-AR signaling in fat cells.

In obese mice, both growth hormone and its fragment (AOD9604) lowered body weight and fat over two weeks, and this tracked with the fragment restoring a key fat-burning receptor (beta3) in fat cells back to normal levels. When mice were genetically engineered to lack that receptor, the weight-loss effect largely disappeared, showing the receptor is required. This helped explain how the fragment works: it seems to make fat cells more responsive to fat-burning signals rather than flipping the switch directly.