OBJECTIVEResveratrol, a natural polyphenolic compound that is found in grapes and red wine, increases metabolic rate, insulin sensitivity, mitochondrial biogenesis, and physical endurance and reduces fat accumulation in mice. Although it is thought that resveratrol targets Sirt1, this is controversial because resveratrol also activates 5′ AMP-activated protein kinase (AMPK), which also regulates insulin sensitivity and mitochondrial biogenesis. Here, we use mice deficient in AMPKα1 or -α2 to determine whether the metabolic effects of resveratrol are mediated by AMPK.RESEARCH DESIGN AND METHODSMice deficient in the catalytic subunit of AMPK (α1 or α2) and wild-type mice were fed a high-fat diet or high-fat diet supplemented with resveratrol for 13 weeks. Body weight was recorded biweekly and metabolic parameters were measured. We also used mouse embryonic fibroblasts deficient in AMPK to study the role of AMPK in resveratrol-mediated effects in vitro.RESULTSResveratrol increased the metabolic rate and reduced fat mass in wild-type mice but not in AMPKα1−/− mice. In the absence of either AMPKα1 or -α2, resveratrol failed to increase insulin sensitivity, glucose tolerance, 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-to-NADH ratio in an AMPK-dependent manner, which may explain how resveratrol may activate Sirt1 indirectly.CONCLUSIONSWe conclude that AMPK, which was thought to be an off-target hit of resveratrol, is the central target for the metabolic effects of resveratrol.

Mitochondrial stress releases mitochondrial DNA (mtDNA) into the cytosol, thereby triggering the type Ι interferon (IFN) response. Mitochondrial outer membrane permeabilization, which is required for mtDNA release, has been extensively studied in apoptotic cells, but little is known about its role in live cells. We found that oxidatively stressed mitochondria release short mtDNA fragments via pores formed by the voltage-dependent anion channel (VDAC) oligomers in the mitochondrial outer membrane. Furthermore, the positively charged residues in the N-terminal domain of VDAC1 interact with mtDNA, promoting VDAC1 oligomerization. The VDAC oligomerization inhibitor VBIT-4 decreases mtDNA release, IFN signaling, neutrophil extracellular traps, and disease severity in a mouse model of systemic lupus erythematosus. Thus, inhibiting VDAC oligomerization is a potential therapeutic approach for diseases associated with mtDNA release.

Metformin is one of the most commonly used first line drugs for type II diabetes. Metformin lowers serum glucose levels by activating 5-AMP-activated kinase (AMPK), which maintains energy homeostasis by directly sensing the AMP/ATP ratio. AMPK plays a central role in food intake and energy metabolism through its activities in central nervous system and peripheral tissues. Since food intake and energy metabolism is synchronized to the light-dark (LD) cycle of the environment, we investigated the possibility that AMPK may affect circadian rhythm. We discovered that the circadian period of Rat-1 fibroblasts treated with metformin was shortened by 1 h. One of the regulators of the period length is casein kinase I⑀ (CKI⑀), which by phosphorylating and inducing the degradation of the circadian clock component, mPer2, shortens the period length. AMPK phosphorylates Ser-389 of CKI⑀, resulting in increased CKI⑀ activity and degradation of mPer2. In peripheral tissues, injection of metformin leads to mPer2 degradation and a phase advance in the circadian expression pattern of clock genes in wild-type mice but not in AMPK ␣2 knock-out mice. We conclude that metformin and AMPK have a previously unrecognized role in regulating the circadian rhythm.Animal behavior, including spontaneous locomotion, sleeping, eating, and drinking, follows a 24-h light-dark (LD) 2 cycle of the environment. The master pacemaker for the rhythmic behavior lies in the suprachiasmatic nucleus (SCN) of the hypothalamus (1). The SCN neurons, cued by the LD cycle, orchestrate the circadian rhythms of peripheral clocks that reside in most cells of the body. The pacemaker, both in the SCN and in peripheral tissues, consists of a self-sustaining near 24-h rhythm in the expression of core clock genes. A central component of this pacemaker is the negative-feedback loop, which results from Per and Cry proteins suppressing their own transcription with a precisely timed lag. A key regulator of the period length is casein kinase I⑀ (CKI⑀) (2). CKI⑀ and its homolog CKI␦ regulate the circadian period by phosphorylating mammalian Per proteins (3-6). The role of CKI⑀ in mammalian circadian rhythm is best illustrated by the semidominant mutation in hamster CKI⑀, tau (7). CKI⑀ tau is a highly specific gain-of-function mutation that increases the CKI⑀ kinase activity on Per proteins. CKI⑀-mediated phosphorylation induces proteasome-mediated degradation of Per proteins, leading to circadian phase advance and shortened period length (8).AMPK, by sensing the rise in AMP level under energy-deprived conditions (9), maintains energy homeostasis by stimulating ATP production and suppressing ATP-consuming processes such as synthesis of macromolecules (10). The catalytic subunit of AMPK has two isoforms, ␣1 (11) and ␣2 (12). Mice with a knockout (KO) of either AMPK ␣1 or AMPK ␣2 are viable (13,14), but mice with a KO of both ␣1 and ␣2 are not viable, 3 indicating that the two isoforms have partially redundant functions. In the hypothalamus, AMPK maintains energy homeostasis at...