Autophagy: roles in obesity-induced ER stress and adiponectin downregulation in adipocytes.

Accumulating evidence strongly suggests that autophagy, which is induced by endoplasmic reticulum (ER) stress in adipocytes, may play an important role in obesity-induced insulin resistance and type 2 diabetes. Obesity induces ER stress in mouse adipose tissue, which correlates with reduced adiponectin levels. In 3T3-L1 adipocytes, induction of ER stress is sufficient to promote autophagy-dependent adiponectin degradation. In contrast, suppressing ER stress increases adiponectin levels in 3T3-L1 adipocytes and alleviates high fat diet-induced adiponectin downregulation in mice. The ER stress-induced adiponectin downregulation can also be suppressed by overexpression of DsbA-L, a newly identified protein involved in promoting adiponectin multimerization and stability. Taken together, our results show that ER stress-induced autophagy provides an important mechanism underlying obesity-induced adiponectin downregulation in adipocytes. In addition, increasing the expression levels of DsbA-L could be an effective approach to improve adiponectin biosynthesis and stability, thus improving insulin sensitivity: in cells and in vivo.