Effects of caloric restriction on O-GlcNAcylation, Ca(2+) signaling, and learning impairment in the hippocampus of ob/ob mice.

Diabetes may adversely affect cognitive function and, conversely, caloric restriction (CR) increases longevity and improves memory. To shed light on the unknown underlying mechanisms involved in these observations, we examined the effects of CR on serum metabolic parameters and hippocampal protein expression in the ob/ob mice model of obesity-induced diabetes. We found that CR reduced hepatic steatosis and insulin resistance in ob/ob mice. In addition, CR increased the levels of hippocampal O-linked-N-acetylglucosamine (O-GlcNAc) and GlcNAc transferase and decreased the expression of calcium/calmodulin-dependent protein kinase II, lipocalin-2, and phosphorylated tau. Furthermore, CR lessened the learning deficits that are typically seen in ob/ob mice. These findings indicate that CR may reverse obesity-related brain glucose impairment and intracellular Ca(2+) dysfunction and relieve learning impairment associated with diabetes.