In the heart, insulin stimulates a variety of kinase cascades and controls glucose utilization. Because insulin is able to activate Akt and inactivate AMP-activated protein kinase (AMPK) in the heart, we hypothesized that Akt can regulate the activity of AMPK. To address the potential existence of this novel signaling pathway, we used a number of experimental protocols to activate Akt in cardiac myocytes and monitored the activation status of AMPK. Mouse hearts perfused in the presence of insulin demonstrated accelerated glycolysis and glucose oxidation rates as compared with non-insulin-perfused hearts. In addition, insulin caused an increase in Akt phosphorylation and a decrease in AMPK phosphorylation at its major regulatory site (threonine 172 of the ␣ catalytic subunit). Transgenic mice overexpressing a constitutively active mutant form of Akt1 displayed decreased phosphorylation of cardiac ␣-AMPK. Isolated neonatal cardiac myocytes infected with an adenovirus expressing constitutively active mutant forms of either Akt1 or Akt2 also suppressed AMPK phosphorylation. However, Akt-dependent depression of ␣-AMPK phosphorylation could be overcome in the presence of the AMPK activator, metformin, suggesting that an override mechanism exists that can restore AMPK activity. Taken together, this study suggests that there is crosstalk between the AMPK and Akt pathways and that Akt activation can lead to decreased AMPK activity. In addition, our data suggest that the ability of insulin to inhibit AMPK may be controlled via an Akt-mediated mechanism.The insulin signaling cascade is an important signaling pathway responsible for controlling substrate preference in the heart. Indeed, insulin has been shown to stimulate myocardial glucose uptake (1, 2) and accelerate glycolysis (2, 3) and glucose oxidation rates (2, 4) as well as promote glycogen synthesis (5, 6). These effects of insulin on glucose metabolism are particularly important because a significant amount of glucose-derived ATP is used for maintaining proper cardiac function. In addition, the stimulation of myocardial glucose utilization and subsequent decrease in fatty acid oxidation has been proven to be efficacious in reducing ischemic injury (7-11). Moreover, insulin-stimulated glucose utilization may be a central component of the beneficial effects of glucose-insulin-potassium therapy on the ischemic heart (12). Two kinases that can be regulated by insulin are Akt and AMPK. 1 Akt is a serine/threonine protein kinase that can be activated by insulin via a multistep pathway involving a phosphatidylinositol 3-kinase-dependent mechanism (see Ref. 13 for review). Once Akt is phosphorylated and activated, it can promote glucose uptake and subsequent metabolism via translocation of glucose transporter (GLUT) 4 to the plasma membrane (14 -18). In addition, the phosphorylation and inhibition of glycogen synthase kinase (GSK) 3 by Akt activates glycogen synthase and thereby promotes glycogen synthesis (19). Recent evidence in heart indicates that the presence of...

Whereas studies involving animal models of cardiovascular disease demonstrated that resveratrol is able to inhibit hypertrophic growth, the mechanisms involved have not been elucidated. Because studies in cells other than cardiomyocytes revealed that AMP-activated protein kinase (AMPK) and Akt are affected by resveratrol, we hypothesized that resveratrol prevents cardiac myocyte hypertrophy via these two kinase systems. Herein, we demonstrate that resveratrol reduces phenylephrine-induced protein synthesis and cell growth in rat cardiac myocytes via alterations of intracellular pathways involved in controlling protein synthesis (p70S6 kinase and eukaryotic elongation factor-2). Additionally, we demonstrate that resveratrol negatively regulates the calcineurin-nuclear factor of activated T cells pathway thus modifying a critical component of the transcriptional mechanism involved in pathological cardiac hypertrophy. Our data also indicate that these effects of resveratrol are mediated via AMPK activation and Akt inhibition, and in the case of AMPK, is dependent on the presence of the AMPK kinase, LKB1. Taken together, our data suggest that resveratrol exerts anti-hypertrophic effects by activating AMPK via LKB1 and inhibiting Akt, thus suppressing protein synthesis and gene transcription.Pathological left ventricular hypertrophy is associated with coronary heart disease and all-cause mortality (1) and is a major clinical concern in cardiovascular medicine. At the cellular level, enlargement of the cardiac myocyte involves multiple events, including gene transcription and protein translation/ synthesis, which are regulated by protein kinase signaling cascades. For gene transcription, the calcineurin-nuclear factor of activated T cells (NFAT) 6 signaling pathway has been shown to play a major role in the development of pathological cardiac hypertrophy (2). Upon dephosphorylation by calcineurin, NFAT translocates to the nucleus of the cardiac myocyte where it mediates the transcription of numerous targets involved in hypertrophic growth (see Ref. 3 for review). In conjunction with alterations in gene expression, an important cellular process that must also occur during hypertrophy is enhanced protein synthesis. While the list of proteins involved in regulating protein synthesis in the cardiac myocyte is extensive, the p70S6 kinase (p70S6K) and eukaryotic elongation factor-2 (eEF2) play key roles in this process (4 -8). Although the p70S6K, eEF2, and NFAT pathways are distinct in many ways, their regulation, in some instances, appears to intersect as all three of these proteins can be regulated by two upstream kinases, AMP-activated protein kinase (AMPK) and Akt.Activation of Akt has been shown to promote cardiac hypertrophy via a number of pathways including the indirect activation of p70S6K (6) and the inhibition of glycogen synthase kinase-3␤ (GSK-3␤) (9). Whereas the pro-hypertrophic effects of Akt activation in the heart are well-established (10 -12), much less is known about the role of AMPK in the hypertrophic...

Oral administration of resveratrol is able to improve glucose homeostasis in obese individuals. Herein we show that resveratrol ingestion produces taxonomic and predicted functional changes in the gut microbiome of obese mice. In particular, changes in the gut microbiome were characterized by a decreased relative abundance of Turicibacteraceae, Moryella, Lachnospiraceae, and Akkermansia and an increased relative abundance of Bacteroides and Parabacteroides Moreover, fecal transplantation from healthy resveratrol-fed donor mice is sufficient to improve glucose homeostasis in obese mice, suggesting that the resveratrol-mediated changes in the gut microbiome may play an important role in the mechanism of action of resveratrol.

Background— Although resveratrol has multiple beneficial cardiovascular effects, whether resveratrol can be used for the treatment and management of heart failure (HF) remains unclear. In the current study, we determined whether resveratrol treatment of mice with established HF could lessen the detrimental phenotype associated with pressure-overload–induced HF and identified physiological and molecular mechanisms contributing to this. Methods and Results— C57Bl/6 mice were subjected to either sham or transverse aortic constriction surgery to induce HF. Three weeks post surgery, a cohort of mice with established HF (% ejection fraction <45) was administered resveratrol (≈320 mg/kg per day). Despite a lack of improvement in ejection fraction, resveratrol treatment significantly increased median survival of mice with HF, lessened cardiac fibrosis, reduced gene expression of several disease markers for hypertrophy and extracellular matrix remodeling that were upregulated in HF, promoted beneficial remodeling, and improved diastolic function. Resveratrol treatment of mice with established HF also restored the levels of mitochondrial oxidative phosphorylation complexes, restored cardiac AMP-activated protein kinase activation, and improved myocardial insulin sensitivity to promote glucose metabolism and significantly improved myocardial energetic status. Finally, noncardiac symptoms of HF, such as peripheral insulin sensitivity, vascular function, and physical activity, were improved with resveratrol treatment. Conclusions— Resveratrol treatment of mice with established HF lessens the severity of the HF phenotype by lessening cardiac fibrosis, improving molecular and structural remodeling of the heart, and enhancing diastolic function, vascular function, and energy metabolism.

AMP-activated protein kinase (AMPK) plays a major role in the regulation of cardiac energy substrate utilization and can be negatively regulated by Akt activation in the heart. It has recently been shown that Akt directly phosphorylates AMPKalpha(1)/alpha(2) on Ser(485/491) in vitro and prevents the AMPK kinase (AMPKK) LKB1 from phosphorylating AMPKalpha at its primary activation site, Thr(172) (S Horman, D Vertommen, R Heath, D Neumann, V Mouton, A Woods, U Schlattner, T Wallimann, D Carling, L Hue, and MH Rider. J Biol Chem 281: 5335-5340, 2006). To determine whether this is also the case in the cardiac myocyte, neonatal rat cardiac myocytes (NRCM) were infected with a recombinant adenovirus expressing a constitutively active mutant of Akt1 (myrAkt1) and then with or without adenoviruses expressing the active LKB1 complex. Expression of myrAkt1 blunted LKB1-induced phosphorylation of AMPKalpha at Thr(172), which resulted in a dramatic decrease in phosphorylation of AMPK's target, acetyl CoA-carboxylase. This decrease in AMPK activity was associated with prior Akt1-dependent phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491). To investigate whether Akt1 activation was also able to prevent other AMPKKs from phosphorylating AMPKalpha, we subjected NRCM to chemical hypoxia and noted a marked increase in phosphorylation of AMPKalpha at Thr(172), despite no change in LKB1 activity. NRCM expressing myrAkt1 demonstrated increased phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491) and a complete inhibition of chemical hypoxia-induced phosphorylation of AMPKalpha at Thr(172). Taken together, our data show that activation of Akt1 is able to prevent activation of cardiac AMPK by LKB1 and at least one other AMPKK, likely by prior phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491).