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Mediobasal hypothalamic SIRT1 is essential for resveratrol's effects on insulin action in rats.

Knight CM, Gutierrez-Juarez R, Lam TK, Arrieta-Cruz I, Huang L, Schwartz G, Barzilai N, Rossetti L - Diabetes (2011)

Bottom Line: Selective inhibition of hypothalamic SIRT1 using a cell-permeable SIRT1 inhibitor or SIRT1-shRNA negated the effect of central and peripheral resveratrol on glucose production.Blockade of the K(ATP) channel and hepatic vagotomy significantly attenuated the effect of central resveratrol on hepatic glucose production.In addition, we found no evidence for hypothalamic AMPK activation after MBH resveratrol administration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Diabetes Research Center, Albert EinsteinCollege of Medicine, Bronx, New York, USA. colette.knight@einstein.yu.edu

ABSTRACT

Objective: Sirtuin 1 (SIRT1) and its activator resveratrol are emerging as major regulators of metabolic processes. We investigate the site of resveratrol action on glucose metabolism and the contribution of SIRT1 to these effects. Because the arcuate nucleus in the mediobasal hypothalamus (MBH) plays a pivotal role in integrating peripheral metabolic responses to nutrients and hormones, we examined whether the actions of resveratrol are mediated at the MBH.

Research design and methods: Sprague Dawley (SD) male rats received acute central (MBH) or systemic injections of vehicle, resveratrol, or SIRT1 inhibitor during basal pancreatic insulin clamp studies. To delineate the pathway(s) by which MBH resveratrol modulates hepatic glucose production, we silenced hypothalamic SIRT1 expression using a short hairpin RNA (shRNA) inhibited the hypothalamic ATP-sensitive potassium (K(ATP)) channel with glibenclamide, or selectively transected the hepatic branch of the vagus nerve while infusing resveratrol centrally.

Results: Our studies show that marked improvement in insulin sensitivity can be elicited by acute administration of resveratrol to the MBH or during acute systemic administration. Selective inhibition of hypothalamic SIRT1 using a cell-permeable SIRT1 inhibitor or SIRT1-shRNA negated the effect of central and peripheral resveratrol on glucose production. Blockade of the K(ATP) channel and hepatic vagotomy significantly attenuated the effect of central resveratrol on hepatic glucose production. In addition, we found no evidence for hypothalamic AMPK activation after MBH resveratrol administration.

Conclusions: Taken together, these studies demonstrate that resveratrol improves glucose homeostasis mainly through a central SIRT1-dependent pathway and that the MBH is a major site of resveratrol action.

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Related in: MedlinePlus

SIRT1 expression and acetylation of p53 in hypothalamic nuclei. A: Representative Western blot and quantification of SIRT1 expression in hypothalamic nuclei paraventricular nucleus, dorsomedial hypothalamus, ventromedial hypothalamus, and arcuate nucleus of male rats. B: SIRT1 expression and acetylation of p53 after MBH administration of vehicle (5% DMSO) or resveratrol. Experiment represents n = 3–4 per group. PVN, paraventricular nucleus; DMH, dorsomedial hypothalamus; VMH, ventromedial hypothalamus; ARC, arcuate nucleus. All values are mean ± SEM. **P < 0.005 compared with control.
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Figure 1: SIRT1 expression and acetylation of p53 in hypothalamic nuclei. A: Representative Western blot and quantification of SIRT1 expression in hypothalamic nuclei paraventricular nucleus, dorsomedial hypothalamus, ventromedial hypothalamus, and arcuate nucleus of male rats. B: SIRT1 expression and acetylation of p53 after MBH administration of vehicle (5% DMSO) or resveratrol. Experiment represents n = 3–4 per group. PVN, paraventricular nucleus; DMH, dorsomedial hypothalamus; VMH, ventromedial hypothalamus; ARC, arcuate nucleus. All values are mean ± SEM. **P < 0.005 compared with control.

Mentions: To determine the role of MBH SIRT1, we first analyzed the expression of the protein in multiple hypothalamic nuclei in SD male rats by Western blot analysis. We found that SIRT1 expression is markedly increased in the arcuate nucleus of the MBH compared with the surrounding nuclei (Fig. 1A). These findings are similar to those of recent reports in mice (22,25). We then investigated the effect of acute MBH administration of resveratrol on SIRT1 activity. SD male rats received acute infusions of vehicle (5% DMSO) or resveratrol (200 μmol/L). Acetylation of lysine 379 in p53 (Acp53) was used as a marker of SIRT1 activity (14,36). Resveratrol infusion resulted in the deacetylation of p53 primarily in the arcuate nucleus and the ventromedial hypothalamus. Neither resveratrol nor DMSO altered SIRT1 expression in the MBH (Fig. 1B). The studies indicate that acute administration of resveratrol is effective in activating hypothalamic SIRT1.


Mediobasal hypothalamic SIRT1 is essential for resveratrol's effects on insulin action in rats.

Knight CM, Gutierrez-Juarez R, Lam TK, Arrieta-Cruz I, Huang L, Schwartz G, Barzilai N, Rossetti L - Diabetes (2011)

SIRT1 expression and acetylation of p53 in hypothalamic nuclei. A: Representative Western blot and quantification of SIRT1 expression in hypothalamic nuclei paraventricular nucleus, dorsomedial hypothalamus, ventromedial hypothalamus, and arcuate nucleus of male rats. B: SIRT1 expression and acetylation of p53 after MBH administration of vehicle (5% DMSO) or resveratrol. Experiment represents n = 3–4 per group. PVN, paraventricular nucleus; DMH, dorsomedial hypothalamus; VMH, ventromedial hypothalamus; ARC, arcuate nucleus. All values are mean ± SEM. **P < 0.005 compared with control.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198094&req=5

Figure 1: SIRT1 expression and acetylation of p53 in hypothalamic nuclei. A: Representative Western blot and quantification of SIRT1 expression in hypothalamic nuclei paraventricular nucleus, dorsomedial hypothalamus, ventromedial hypothalamus, and arcuate nucleus of male rats. B: SIRT1 expression and acetylation of p53 after MBH administration of vehicle (5% DMSO) or resveratrol. Experiment represents n = 3–4 per group. PVN, paraventricular nucleus; DMH, dorsomedial hypothalamus; VMH, ventromedial hypothalamus; ARC, arcuate nucleus. All values are mean ± SEM. **P < 0.005 compared with control.
Mentions: To determine the role of MBH SIRT1, we first analyzed the expression of the protein in multiple hypothalamic nuclei in SD male rats by Western blot analysis. We found that SIRT1 expression is markedly increased in the arcuate nucleus of the MBH compared with the surrounding nuclei (Fig. 1A). These findings are similar to those of recent reports in mice (22,25). We then investigated the effect of acute MBH administration of resveratrol on SIRT1 activity. SD male rats received acute infusions of vehicle (5% DMSO) or resveratrol (200 μmol/L). Acetylation of lysine 379 in p53 (Acp53) was used as a marker of SIRT1 activity (14,36). Resveratrol infusion resulted in the deacetylation of p53 primarily in the arcuate nucleus and the ventromedial hypothalamus. Neither resveratrol nor DMSO altered SIRT1 expression in the MBH (Fig. 1B). The studies indicate that acute administration of resveratrol is effective in activating hypothalamic SIRT1.

Bottom Line: Selective inhibition of hypothalamic SIRT1 using a cell-permeable SIRT1 inhibitor or SIRT1-shRNA negated the effect of central and peripheral resveratrol on glucose production.Blockade of the K(ATP) channel and hepatic vagotomy significantly attenuated the effect of central resveratrol on hepatic glucose production.In addition, we found no evidence for hypothalamic AMPK activation after MBH resveratrol administration.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Diabetes Research Center, Albert EinsteinCollege of Medicine, Bronx, New York, USA. colette.knight@einstein.yu.edu

ABSTRACT

Objective: Sirtuin 1 (SIRT1) and its activator resveratrol are emerging as major regulators of metabolic processes. We investigate the site of resveratrol action on glucose metabolism and the contribution of SIRT1 to these effects. Because the arcuate nucleus in the mediobasal hypothalamus (MBH) plays a pivotal role in integrating peripheral metabolic responses to nutrients and hormones, we examined whether the actions of resveratrol are mediated at the MBH.

Research design and methods: Sprague Dawley (SD) male rats received acute central (MBH) or systemic injections of vehicle, resveratrol, or SIRT1 inhibitor during basal pancreatic insulin clamp studies. To delineate the pathway(s) by which MBH resveratrol modulates hepatic glucose production, we silenced hypothalamic SIRT1 expression using a short hairpin RNA (shRNA) inhibited the hypothalamic ATP-sensitive potassium (K(ATP)) channel with glibenclamide, or selectively transected the hepatic branch of the vagus nerve while infusing resveratrol centrally.

Results: Our studies show that marked improvement in insulin sensitivity can be elicited by acute administration of resveratrol to the MBH or during acute systemic administration. Selective inhibition of hypothalamic SIRT1 using a cell-permeable SIRT1 inhibitor or SIRT1-shRNA negated the effect of central and peripheral resveratrol on glucose production. Blockade of the K(ATP) channel and hepatic vagotomy significantly attenuated the effect of central resveratrol on hepatic glucose production. In addition, we found no evidence for hypothalamic AMPK activation after MBH resveratrol administration.

Conclusions: Taken together, these studies demonstrate that resveratrol improves glucose homeostasis mainly through a central SIRT1-dependent pathway and that the MBH is a major site of resveratrol action.

Show MeSH
Related in: MedlinePlus