2. Fat Burning And Weight Loss
Fragment 176-191 has earned the nickname of “lipolytic fragment” because testing in mice has revealed the peptide to have substantial fat burning and weight loss properties. It is thought that this action is mediated through an increase in production of beta-3 adrenergic receptors (β3-AR or ADRB3)
[2]. Agonist action at ADRB3 is known to directly increase fat burning in adipose tissue and is also responsible for thermogenesis in skeletal muscle
[3]. Mice that have been genetically modified to produce no ADRB3 do not respond to the lipolytic effects of hGH or fragment 176-191
[2].
Studies show that the increased fat burning associated with fragment 176-191 directly correlates with energy expenditure and thus weight reduction, leading to a nearly 50% reduction in weight gain in obese animals over a three-week course
[4]. Interestingly, the weight loss effects were seen only in obese mice, with lean mice maintaining normal body weight, on average, even when exposed to fragment 176-191
[2]. These findings indicate that there are secondary regulatory pathways for lipolysis that override ADRB3 function when body weight is at or near ideal, opening up areas for additional research into energy homeostasis.