Systemic benefits of Gc inhibition to preserve insulin sensitivity

Abstract

Type 2 diabetes is caused by an imbalanced supply and demand of insulin. Insulin resistance and impaired {beta}-cell function contribute to the onset of hyperglycemia. No single treatment modality can affect both aspects of diabetes pathophysiology. Thus, current treatments focus either on increasing insulin secretion (incretin mimetics, sulfonylureas) or insulin sensitivity (metformin and TZD), or reducing hyperglycemia (insulin, sglt2i). Previously, we reported that ablation of Gc, encoding a secreted protein with a primary role in vitamin D transport, improves pancreatic {beta}-cell function in models of diet-induced insulin resistance. Here, we show that Gc ablation has systemic insulin-sensitizing effects to prevent weight gain, hyperglycemia, glucose intolerance, and lower NEFA and triglyceride in mice fed a high-fat diet. Hyperinsulinemic-euglycemic clamps show that Gc ablation protects insulins ability to reduce hepatic glucose production, and increases glucose uptake in skeletal muscle and adipose tissue. Moreover, acute Gc inhibition by way of adeno-associated virus encoding a short hairpin RNA to promote Gc mRNA degradation, prevents glucose intolerance caused by high fat feeding. The data suggest that Gc inhibition can provide an approach to increase insulin production in {beta}-cells, and insulin action in peripheral tissues. RESEARCH IN CONTEXT{blacksquare} The goal was to find a therapeutic target that can improve insulin sensitivity and {beta}-cell function simultaneously. {blacksquare}Gc ablation preserves {beta}-cell insulin secretion ex vivo and in vivo. {blacksquare}Deletion of Gc prevents weight gain, reduces fat mass, lowers fasting glycemia, improves glucose tolerance, reduces hepatic glucose production after feeding, and increased glucose uptake in muscle and adipose. {blacksquare}Acute Gc inhibition improves glucose tolerance, which suggests that targeting Gc could provide an alternative way to treat type 2 diabetes.