280 - Reg3g-induced Heparan Sulfate Glycosaminoglycan Formation as a Mechanism Underlying Islet Dysfunction in Offspring of Obese Mice

Poster Number: 280
Publication Number: 280.119

Abigail Toren, Indiana University School of Medicine, Indianapolis, IN, United States; Kok Lim Kua, Indiana University School of Medicine, Indianapolis, IN, United States

Background: Children born to mothers who are obese are at higher risk of developing type 2 diabetes due to inadequate islet insulin secretion. We found that offspring born to obese mice exhibit sex-differences in islet insulin secretion and heparan sulfate glycosaminoglycan (HSG). HSG is a macromolecule containing core protein (HSPG2) and carbohydrate chain that regulates islet health. HSG formation is initiated by Exostosin Like Glycosyltransferase (Extl3), which is a receptor of Regenerating islet derived protein 3-Gamma (Reg3g). However, the role of Reg3g in the regulating of sex-differences in islet HSG and subsequent downstream signals modulating islet insulin secretion is unknown.

Objective: We hypothesize that in offspring of obese mice, sex-differences in islet insulin secretion is regulated by HSG through differential expression of Reg3g.

Design/Methods: We measured Reg3g, EXTL3, HSPG2, and HPSE gene in islets isolated from 21-day-old (P21) pups of chow- (Con) or western-diet fed obese dams (MatOB). We also used INS1 β-cell line to test the effects of recombinant Reg3g (rReg) and heparinase (HPSE) during IL1B cytokine stress. For outcome, we measured glucose induced insulin secretion (GIIS) and ERK1/2 phosphorylation, a common downstream pathway regulated by Reg3g and HSG. Finally, we tested the in-vivo effect of rReg and heparan sulfate analogue (HS) on male MatOb pups glucose tolerance. All experiments had n >3/grp

Results: At P21, there were no sex-differences in islet HSPG2, EXTL3, or HSPE. Interestingly, only female MatOb pups protected from islet dysfunction had 10-fold higher islet Reg3g vs. Con female. This data suggests the differential expression of Reg3g contributes to sex-differences in offspring islet HSG and insulin secretion. Next, we found that INS1 cells treated with rReg had 3.9-fold higher HSG* and 60% increase in phospho-ERK1/2*. During IL1B stress, INS1 cells had 53% lower GIIS*, and this was rescued by rReg*. The addition of HPSE ablated the increase in phospho-ERK1/2 and insulin secretion*, indicating that the positive effects of Reg3g is mediated via HSG. Finally, we found that MatOb male mice treated with rReg and HS had improved GTT compared to MatOB male mice receiving PBS vehicle*. (*p < 0.05)Conclusion(s): Taken together, our data showed Reg3g-HSG-ERK1/2 phosphorylation as a potential pathway regulating sex-differences in MatOB offspring islet dysfunction. Notably, we show preclinical evidence that these targets can be manipulated to improve offspring glucose tolerance.