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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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Hypothalamic KATP channel inhibition and hepatic branch vagotomy significantly reduce resveratrol action. A: Representative schematic of the sagittal section of the brain at the level of the arcuate nucleus. KATP channels in the arcuate nucleus have a role in regulating glucose production. Neural activity from the arcuate nucleus is transferred to the nucleus of solitary tract/dorsal motor vagal nucleus of the brain stem and subsequently relayed to the liver via the vagus nerve. B: Experimental protocol for resveratrol-glibenclamide studies. C–F: Central glibenclamide significantly attenuated the effect of resveratrol on hepatic glucose production. G and H: Timeline and basal insulin clamp protocol for hepatic vagotomy and sham studies. I–L: Effect of hepatic vagotomy or sham operation on GIR, glucose production, and glucose uptake after resveratrol treatment. For all studies n = 4–6 per group. All values are mean ± SEM. *P < 0.05, **P < 0.005 compared with control. ARC, arcuate nucleus; KATP, potassium sensitive ATP channel; NTS, nucleus of solitary tract; DMX, dorsal motor vagal nucleus; SHAM, sham-operated; HVG, hepatic vagotomy. For all studies: control, white bars; resveratrol, black bars; resveratrol and glibenclamide, striped bars; glibenclamide only, hatched bars.
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Figure 4: Hypothalamic KATP channel inhibition and hepatic branch vagotomy significantly reduce resveratrol action. A: Representative schematic of the sagittal section of the brain at the level of the arcuate nucleus. KATP channels in the arcuate nucleus have a role in regulating glucose production. Neural activity from the arcuate nucleus is transferred to the nucleus of solitary tract/dorsal motor vagal nucleus of the brain stem and subsequently relayed to the liver via the vagus nerve. B: Experimental protocol for resveratrol-glibenclamide studies. C–F: Central glibenclamide significantly attenuated the effect of resveratrol on hepatic glucose production. G and H: Timeline and basal insulin clamp protocol for hepatic vagotomy and sham studies. I–L: Effect of hepatic vagotomy or sham operation on GIR, glucose production, and glucose uptake after resveratrol treatment. For all studies n = 4–6 per group. All values are mean ± SEM. *P < 0.05, **P < 0.005 compared with control. ARC, arcuate nucleus; KATP, potassium sensitive ATP channel; NTS, nucleus of solitary tract; DMX, dorsal motor vagal nucleus; SHAM, sham-operated; HVG, hepatic vagotomy. For all studies: control, white bars; resveratrol, black bars; resveratrol and glibenclamide, striped bars; glibenclamide only, hatched bars.

Mentions: Activation of the hypothalamic KATP channel has been shown to lower hepatic glucose production in response to hormonal stimuli, such as leptin, insulin, and nutritional substrates, whereas blockade of the KATP channel with sulfonylureas has the opposite effect (19,28,44). Thus, we asked whether resveratrol’s action on glucose production was dependent on KATP activation (Fig. 4A). SD male rats received MBH infusion of vehicle (5% DMSO), resveratrol (200 μmol/L), a coinfusion of resveratrol (200 μmol/L), and the KATP inhibitor glibenclamide (100 μmol/L) or glibenclamide alone (100 µmol/L) during basal pancreatic clamp study (Fig. 4B). We found that IH infusion of glibenclamide significantly reversed the effect of resveratrol on hepatic glucose production in a manner that was similar to what was observed with the SIRT1-specific inhibitor. However, glibenclamide alone had no appreciable effect compared with vehicle-treated controls (Fig. 4C–F). These findings suggest that the acute effects of resveratrol on hepatic glucose production are dependent on the activation of KATP channels in the MBH.


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)

Hypothalamic KATP channel inhibition and hepatic branch vagotomy significantly reduce resveratrol action. A: Representative schematic of the sagittal section of the brain at the level of the arcuate nucleus. KATP channels in the arcuate nucleus have a role in regulating glucose production. Neural activity from the arcuate nucleus is transferred to the nucleus of solitary tract/dorsal motor vagal nucleus of the brain stem and subsequently relayed to the liver via the vagus nerve. B: Experimental protocol for resveratrol-glibenclamide studies. C–F: Central glibenclamide significantly attenuated the effect of resveratrol on hepatic glucose production. G and H: Timeline and basal insulin clamp protocol for hepatic vagotomy and sham studies. I–L: Effect of hepatic vagotomy or sham operation on GIR, glucose production, and glucose uptake after resveratrol treatment. For all studies n = 4–6 per group. All values are mean ± SEM. *P < 0.05, **P < 0.005 compared with control. ARC, arcuate nucleus; KATP, potassium sensitive ATP channel; NTS, nucleus of solitary tract; DMX, dorsal motor vagal nucleus; SHAM, sham-operated; HVG, hepatic vagotomy. For all studies: control, white bars; resveratrol, black bars; resveratrol and glibenclamide, striped bars; glibenclamide only, hatched bars.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

Figure 4: Hypothalamic KATP channel inhibition and hepatic branch vagotomy significantly reduce resveratrol action. A: Representative schematic of the sagittal section of the brain at the level of the arcuate nucleus. KATP channels in the arcuate nucleus have a role in regulating glucose production. Neural activity from the arcuate nucleus is transferred to the nucleus of solitary tract/dorsal motor vagal nucleus of the brain stem and subsequently relayed to the liver via the vagus nerve. B: Experimental protocol for resveratrol-glibenclamide studies. C–F: Central glibenclamide significantly attenuated the effect of resveratrol on hepatic glucose production. G and H: Timeline and basal insulin clamp protocol for hepatic vagotomy and sham studies. I–L: Effect of hepatic vagotomy or sham operation on GIR, glucose production, and glucose uptake after resveratrol treatment. For all studies n = 4–6 per group. All values are mean ± SEM. *P < 0.05, **P < 0.005 compared with control. ARC, arcuate nucleus; KATP, potassium sensitive ATP channel; NTS, nucleus of solitary tract; DMX, dorsal motor vagal nucleus; SHAM, sham-operated; HVG, hepatic vagotomy. For all studies: control, white bars; resveratrol, black bars; resveratrol and glibenclamide, striped bars; glibenclamide only, hatched bars.
Mentions: Activation of the hypothalamic KATP channel has been shown to lower hepatic glucose production in response to hormonal stimuli, such as leptin, insulin, and nutritional substrates, whereas blockade of the KATP channel with sulfonylureas has the opposite effect (19,28,44). Thus, we asked whether resveratrol’s action on glucose production was dependent on KATP activation (Fig. 4A). SD male rats received MBH infusion of vehicle (5% DMSO), resveratrol (200 μmol/L), a coinfusion of resveratrol (200 μmol/L), and the KATP inhibitor glibenclamide (100 μmol/L) or glibenclamide alone (100 µmol/L) during basal pancreatic clamp study (Fig. 4B). We found that IH infusion of glibenclamide significantly reversed the effect of resveratrol on hepatic glucose production in a manner that was similar to what was observed with the SIRT1-specific inhibitor. However, glibenclamide alone had no appreciable effect compared with vehicle-treated controls (Fig. 4C–F). These findings suggest that the acute effects of resveratrol on hepatic glucose production are dependent on the activation of KATP channels in the MBH.

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