INS and obesity disorder: Increases in obesity and changes in fat accumulation are associated with aging, and obesity also accelerates aging by inducing inflammation in several tissues.122 During aging, NAD levels decrease in various tissues, including liver and adipose tissues.123,124 Therefore, all the pathways and metabolic reactions in which NAD is involved are also altered by aging, and this decreased metabolic activity has been associated with numerous aging-related metabolic diseases, such as diabetes.86,125 NAD levels are also related to insulin secretion and sensitivity.