Reduced mitochondrial function in obesity-associated fatty liver: SIRT3 takes on the fat

Aging is associated with various metabolic disorders that may have their origin in the liver, including nonalcoholic fatty liver disease, obesity, type 2 diabetes mellitus, and atherosclerosis. Although well-characterized in models of caloric restriction, relatively little is known about the role of sirtuins and acetylation under conditions of caloric excess. Sirtuins are NAD (+)-dependent protein deacetylases that mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized within the mitochondrial matrix, where it regulates acetylation levels of a diverse set of metabolic enzymes. When normal mice are fed a high fat diet they demonstrate reduced SIRT3 activity, impaired mitochondrial function, and hyperacetylation of a diverse set of proteins in their livers. Furthermore, SIRT3 knockout mice have signs of accelerated aging and cancer. Understanding SIRT3's biochemical function and regulation in the liver under conditions of caloric excess may potentially increase our understanding of the normal aging process and diseases associated with aging, such as diabetes, fatty liver disease, or cancer.