Resveratrol in high doses has been shown to extend lifespan in some studies in invertebrates and to prevent early mortality in mice fed a high-fat diet. We fed mice from middle age (14-months) to old age (30-months) either a control diet, a low dose of resveratrol (4.9 mg kg−1 day−1), or a calorie restricted (CR) diet and examined genome-wide transcriptional profiles. We report a striking transcriptional overlap of CR and resveratrol in heart, skeletal muscle and brain. Both dietary interventions inhibit gene expression profiles associated with cardiac and skeletal muscle aging, and prevent age-related cardiac dysfunction. Dietary resveratrol also mimics the effects of CR in insulin mediated glucose uptake in muscle. Gene expression profiling suggests that both CR and resveratrol may retard some aspects of aging through alterations in chromatin structure and transcription. Resveratrol, at doses that can be readily achieved in humans, fulfills the definition of a dietary compound that mimics some aspects of CR.

T he signaling pathways that mediate insulin's many actions remain incompletely understood, but the following sequence has been well characterized: insulin binds to its receptor, leading to receptor autophosphorylation and activation of receptor tyrosine kinase, which in turn results in tyrosine phosphorylation of endogenous substrates including insulin receptor substrate proteins. These docking proteins engage downstream signaling molecules such as phosphatidylinositol (PI) 3-kinase (1-3). PI 3-kinase catalyzes the phosphorylation of phosphatidylinositol 4,5-bisphosphate on the D3 position of inositol, and the resultant PI 3,4,5-trisphosphate binds and activates more distal signaling proteins, including phosphoinositide-dependent kinase-1 and Akt, a serine/threonine kinase. Akt has been implicated as a key signaling protein for several of insulin's actions, including activation of glycogen synthesis, protein synthesis, and GLUT4 translocation to the cell surface, thereby increasing glucose transport (1-5). Identification of the intermediate signaling steps linking Akt to insulin's diverse actions remains incomplete.Recent research using 3T3-L1 adipocytes demonstrated that insulin leads to the phosphorylation of multiple proteins that contain one or more consensus sequences for phosphorylation by Akt (6). Among these Akt substrates was a 160-kDa protein, named Akt substrate of 160 kDa (AS160), which contained six Akt consensus sequences that become phosphorylated in insulin-treated adipocytes. AS160 also includes a GTPase-activating domain for small G-proteins, known as Rabs, which participate in vesicular trafficking (7). A point mutation of two or more of the consensus phosphorylation sites for Akt resulted in a marked decline in insulin-stimulated GLUT4 redistribution to the cell surface. Thus, in 3T3-L1 adipocytes, phosphorylation of AS160 was strongly implicated as an intermediate step linking insulin's activation of Akt to increased glucose transport. More recently, Zeigerer et al. (8) demonstrated that AS160 is important for insulin's activation of GLUT4 vesicle exocytosis without altering insulin-mediated inhibition of GLUT4 internalization.Insulin also activates Akt in skeletal muscle (9,10), and AS160 is expressed by this tissue (6), which is a major target for insulin action. An important question is this: Does insulin, in skeletal muscle, lead to increased phosphorylation of AS160 and/or other proteins containing the Akt phosphomotif? Accordingly, our first aim was to AICAR, 5-aminoimidazole-4-carboxamide-1-␤-D-ribofuranoside; AS160, Akt substrate of 160 kDa; KHB, Krebs-Henseleit buffer; PAS, phospho-(Ser/Thr) Akt substrate; PI, phosphatidylinositol; TBST, Tris-buffered saline plus Tween.

Earlier research on rats with normal insulin sensitivity demonstrated that acute exercise increased insulin-stimulated glucose uptake (GU) concomitant with greater phosphorylation of Akt substrate of 160 kDa (pAS160). Because mechanisms for exercise effects on GU in insulin-resistant muscle are unknown, our primary objective was to assess insulin-stimulated GU, proximal insulin signaling (insulin receptor [IR] tyrosine phosphorylation, IR substrate 1–phosphatidylinositol-3-kinase, and Akt phosphorylation and activity), and pAS160 in muscles from acutely exercised (one session) and sedentary rats fed either chow (low-fat diet [LFD]; normal insulin sensitivity) or a high-fat diet (HFD; for 2 weeks, insulin-resistant). At 3 h postexercise (3hPEX), isolated epitrochlearis muscles were used for insulin-stimulated GU and insulin signaling measurements. Although exercise did not enhance proximal signaling in either group, insulin-stimulated GU at 3hPEX exceeded respective sedentary control subjects (Sedentary) in both diet groups. Furthermore, insulin-stimulated GU for LFD-3hPEX was greater than HFD-3hPEX values. For HFD-3hPEX muscles, pAS160 exceeded HFD-Sedentary, but in muscle from LFD-3hPEX rats, pAS160 was greater still than HFD-3hPEX values. These results implicated pAS160 as a potential determinant of the exercise-induced elevation in insulin-stimulated GU for each diet group and also revealed pAS160 as a possible mediator of greater postexercise GU of insulin-stimulated muscles from the insulin-sensitive versus insulin-resistant group.

Arias EB, Kim J, Funai K, Cartee GD. Prior exercise increases phosphorylation of Akt substrate of 160 kDa (AS160) in rat skeletal muscle. Am J Physiol Endocrinol Metab 292: E1191-E1200, 2007. First published December 19, 2006; doi:10.1152/ajpendo.00602.2006.-The main purpose of this study was to determine whether the increased glucose transport (GT) found immediately postexercise (IPEX) or 4 h postexercise (4hPEX) is accompanied by increased phosphorylation of Akt substrate of 160 kDa (AS160, a protein regulator of GLUT4 translocation). Paired epitrochlearis muscles were dissected from rats (sedentary or IPEX, 2-h swim) and used to measure protein phosphorylation and insulin-independent GT. IPEX values exceeded sedentary values for GT and phosphorylations of AS160, AMP-activated protein kinase (pAMPK) and acetyl-CoA carboxylase (pACC) but not for AS160 abundance or phosphorylation of Akt serine (pSerAkt), Akt threonine (pThrAkt), or glycogen synthase kinase-3 (pGSK3). AS160 phosphorylation was significantly correlated with GT (R ϭ 0.801, P Ͻ 0.01) and pAMPK (R ϭ 0.655, P Ͻ 0.05). Muscles from other rats were studied 4hPEX along with sedentary controls. One muscle per rat was incubated without insulin, and the contralateral muscle was incubated with insulin. 4hPEX values exceeded sedentary values for insulinstimulated GT. The elevated pAMPK and pACC found IPEX had reversed by 4hPEX. Insulin caused a significant increase in pSerAkt, pThrAkt, pGSK3, and AS160 phosphorylation with or without exercise. Exercise significantly increased AS160 phosphorylation, regardless of insulin, with unchanged AS160 abundance. Among the signaling proteins studied, insulin-stimulated GT was significantly correlated only with insulin-stimulated pThrAkt (R ϭ 0.720, P Ͻ 0.0005). The results are consistent with a role for increased AS160 phosphorylation in the increased insulin-independent GT IPEX, and the exercise effects on AS160 phosphorylation and/or pThrAkt at 4hPEX are potentially relevant to the increased insulin-stimulated glucose transport at this time.