The Role of NAD+ in Metabolic Regulation of Adipose Tissue: Implications for Obesity-Induced Insulin Resistance

Obesity-induced insulin resistance is among the key factors in the development of type 2 diabetes, atherogenic dyslipidemia and cardiovascular disease. Adipose tissue plays a key role in the regulation of whole-body metabolism and insulin sensitivity. In obesity, adipose tissue becomes inflamed and dysfunctional, exhibiting a modified biochemical signature and adipokine secretion pattern that promotes insulin resistance in peripheral tissues. An important hallmark of dysfunctional obese adipose tissue is impaired NAD(+)/sirtuin signaling. In this chapter, we summarize the evidence for impairment of the NAD(+)/sirtuin pathway in obesity, not only in white adipose tissue but also in brown adipose tissue and during the process of beiging, together with correlative evidence from human studies. We also describe the role of PARPs and CD38 as important NAD(+) consumers and discuss findings from experimental studies that investigated potential NAD(+) boosting strategies and their efficacy in restoring impaired NAD(+) metabolism in dysfunctional obese adipose tissue. In sum, these studies suggest a critical role of NAD(+) metabolism in adipose biology and provide a basis for the potential development of strategies to restore metabolic health in obesity.