Annual Report HS02243-01 We hypothesized that the metabolic effects of resveratrol may be mediated by AMPK. To test this, we treated AMPKa1 and a2 knockout mice with resveratrol. In the absence of either AMPKa1 or a2, resveratrol failed to increase insulin sensitivity, glucose tolerance, mitochondrial mitochondrial biogenesis and physical endurance. Consistent with this, the expression of genes important for mitochondrial biogenesis was not induced by resveratrol in AMPK-deficient mice. In addition, resveratrol increased the NAD/NADH ratio in an AMPK-dependent manner, which may explain how resveratrol may activate Sirt1 indirectly.We also discovered that both AMPKa1 and a2 knockout mice are able to maintain a circadian rhythm of activity, but AMPKa1 knockout mice have a shorter circadian period whereas AMPKa2 knockout mice have a slightly longer circadian period. In the absence of light que (i.e. 24 hr darkness), AMPKa1 knockout mice cannot maintain the circadian rhythm of core body temperature or heart rate. The circadian pattern of gene expression is severely disrupted in fat in AMPKa1 knockout mice, but it is severely disrupted in the heart and skeletal muscle of AMPKa2 knockout mice. The circadian rhythm of nicotinamide phosphoryl-transferase (NAMPT) activity, which converts nicotinamide (NAM) to NAD+, is an important regulator of the circadian clock. We find that the NAMPT rhythm is absent in AMPK-deficient tissues and cells. Thus, AMPK regulates circadian rhythm in vivo in an isoform-specific manner.These findings indicate that energy pathways affect circadian rhythm. To investigate whether circadian clock affects energy metabolism, we examined the metabolic parameters of mice deficient in mPer2, one of the clock components that regulate circadian rhythm. Our findings indicate that mPer2 knockout mice do not have a glucocorticoid rhythm even though the corticosterone response to hypoglycemia, ACTH and restraint stress is intact. In addition, the diurnal feeding rhythm is absent in mPer2 knockout mice. On high fat diet, they eat as much during the light period as they do during the dark period and develop significant obesity. The diurnal rhythm of neuroendocrine peptide aMSH, a major effector of appetite control, is disrupted in the hypothalamus of mPer2 knockout mice even though the diurnal rhythm of ACTH, the aMSH precursor, is intact. Peripheral injection of aMSH, which has been shown to enter the brain, restored the feeding rhythm and induced weight loss in mPer2 knockout mice. These findings emphasize the requirement of mPer2, and the circadian clock, in appetite control during the inactive period.
