Adiponectin &Resistin: Structure, Function &Effects

Albert Einstein Col Of Med Yeshiva Univ, Bronx NY

Investigators

Linked publications & trials

Abstract

DESCRIPTION (provided by applicant): Excessive hepatic glucose production is a hallmark of Type II diabetes. An important function of insulin in the liver is the suppression of hepatic glucose production. This is partly mediated via reducing the transcription of two key gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6- phosphatase (G-6-Pase). Adipocyte-specific secreted molecules, termed adipokines, have highlighted the role of adipose tissue as an active endocrine organ that regulates metabolism and maintains energy homeostasis. Adiponectin has gained significant attention recently as a mediator of hepatic insulin sensitivity. In contrast, resistin has been shown to have a potent negative impact on hepatic insulin sensitivity. The ability of both of these proteins to form higher order complex structures is an essential aspect of their bioactivity that results in the modulation of the insulin-induced transcriptional changes of PEPCK and G-6-Pase, resulting in changes in hepatic glucose output. Under the auspices of this R24 application, we propose to integrate independent efforts of the four participating laboratories towards the characterization of the underlying mechanisms by which adipokines influence hepatic glucose fluxes in vivo. A detailed structure/function analysis will be performed on adiponectin and resistin to identify the critical determinants that enable these complexes to exert their effects on the downstream targets. The bioactivity of both key mediators of this process, adiponectin and resistin, is critically dependent on the formation and disruption of essential disulfide bonds, yet how the reduction of these disulfide bonds affects conformation is not clear. Metabolic clamp studies will be performed in models of impaired or increased hepatic insulin sensitivity, obtained through perfusion of adiponectin or resistin, in combination with gain- and loss-of-function mutations of potentially critical downstream targets, AMPK and Foxo1. These experiments will be complemented with similar studies in tissue culture cells. The short-term goal of this proposal is to gain a better molecular understanding of the adipo-hepatic signaling axis and how it affects glucose fluxes within the liver. The longer-term goal consists of forging closer collaborative ties between investigators in two leading Diabetes Centers in the New York City area with a vision towards much closer inter-institutional efforts in the area of obesity and diabetes research in the future.