7872 Adiponectin Enhances Hepatic Insulin Sensitivity in a Rat Model of Polycystic Ovary Syndrome: Role of PI3K/Akt/mTORC2 Pathway

Abstract Disclosure: A. Abdelhameed: None. S. Rezq: None. R.M. Vinson: None. J. Flaherty: None. B. Kim: None. D.G. Romero: None. L.L. Yanes Cardozo: None. Background: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women and is associated with a high prevalence of obesity and insulin resistance (IR). Phosphoinositide-3-kinase (PI3K)/Akt/ the mammalian target of rapamycin complex 2 (mTORC2) pathway is one major insulin signaling pathway and its impairment is involved in multiple metabolic disorders by inducing IR. Phosphorylation of protein kinase B (Akt) at (Ser)-473 by mTORC2 leads to its full activation and subsequently enhances insulin sensitivity. Adiponectin is a peptide secreted by adipocytes that increases insulin sensitivity. PEG-BHD1028 is a novel potent peptide adiponectin receptor agonist that enhances insulin sensitivity in different models of diabetes. However, its potential to attenuate androgen-mediated hepatic IR by modulating PI3K/Akt/mTORC2 pathway remains unknown in PCOS. Hypothesis: We tested the hypothesis that PEG-BHD1028 attenuates hepatic IR via modulating PI3K/Akt/mTORC2 pathway in a rat model of PCOS. Methods: To induce PCOS, four-week-old female Sprague Dawley rats were implanted with dihydrotestosterone (DHT) silastic tubes (7.5mg) or placebo (PBO) for 90 days (n=4-8/group). During the final three weeks of DHT treatment, rats received PEG-BHD1028 (25μg/kg/day) subcutaneously. Body weight (BW) by gravimetry, fat and lean mass were measured by Echo-MRI. Fasting plasma insulin was measured by ELISA while fasting plasma glucose was measured with a clinical chemistry analyzer. HOMA-IR, an index of systemic IR, was calculated. Protein levels of insulin signaling markers including IRS1, p-IRS1 (Ser1101), PI3 kinase p110, Akt, p-Akt (Ser473), mTOR, p-mTOR (Ser2481) and mTORC2 regulatory protein Rictor were quantified in the liver by Western-blot. Results: DHT significantly (p<0.05) increased BW, fat mass and lean mass by 1.4-, 2.2-, 1.4- folds, respectively compared to PBO group. DHT significantly (p<0.05) increased HOMA-IR by 3.8- fold, compared to PBO group. DHT downregulated hepatic p-Akt, Akt and mTOR protein expression by 20% to 40% while upregulating IRS-1 by 1.6- fold with no impact on PI3 kinase, p-mTOR, Rictor and p-IRS1 compared to the PBO group. PEG-BHD1028 significantly decreased BW, fat mass and lean mass while attenuating IR (34.7% reduction in HOMA-IR) in PCOS rats. Interestingly, PEG-BHD1028 significantly (p<0.05) increased PI3K, active Akt (pAKT), mTOR and Rictor levels by 1.6-, 2.2-, 1.5-, 1.8- folds, respectively with no effect on the other insulin signaling markers compared to vehicle-treated group. Conclusion: Our findings suggest that PEG-BHD1028 is a novel and effective therapeutic agent to attenuate hepatic IR in PCOS via activating PI3K/Akt/mTORC2 pathway. Significance: Targeting adiponectin signaling could be a novel and effective therapeutic approach to mitigate metabolic dysfunction in females with excess androgens. Presentation: 6/2/2024