Overexpression of SIRT1 in rat skeletal muscle does not alter glucose induced insulin resistance.

Amanda E Brandon,Edward W Kraegen,Neil B Ruderman,Jennifer Tid-Ang,Eurwin Suryana,Nicholas Bentley,Gregory J Cooney,Lauren E Wright,Ella Stuart,Nigel Turner,Makoto Kanzaki

doi:10.1371/journal.pone.0121959

Amanda E Brandon, Edward W Kraegen + Show 9 more

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https://doi.org/10.1371/journal.pone.0121959

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Abstract

SIRT1 is a NAD+-dependent deacetylase thought to regulate cellular metabolic pathways in response to alterations in nutrient flux. In the current study we investigated whether acute changes in SIRT1 expression affect markers of muscle mitochondrial content and also determined whether SIRT1 influenced muscle insulin resistance induced by acute glucose oversupply. In male Wistar rats either SIRT1 or a deacetylase inactive mutant form (H363Y) was electroprated into the tibialis cranialis (TC) muscle. The other leg was electroporated with an empty control vector. One week later, glucose was infused and hyperglycaemia was maintained at ~11mM. After 5 hours, 11mM glucose induced significant insulin resistance in skeletal muscle. Interestingly, overexpression of either SIRT1 or SIRT1 (H363Y) for 1 week did not change markers of mitochondrial content or function. SIRT1 or SIRT1 (H363Y) overexpression had no effect on the reduction in glucose uptake and glycogen synthesis in muscle in response to hyperglycemia. Therefore we conclude that acute increases in SIRT1 protein have little impact on mitochondrial content and that overexpressing SIRT1 does not prevent the development of insulin resistance during hyperglycaemia.

Highlights

Sirtuin 1 (SIRT1) is a NAD+-dependent deacetylase with a large range of target proteins that are important for apoptosis, the cell cycle, circadian rhythms, mitochondrial function, and metabolism [1]
To confirm the activity of the constructs, C2C12 myoblasts were successfully transfected with SIRT1, a deacetylase inactive mutant of SIRT1 (H363Y) or empty vector for 24h (Fig. 1A)
The current study provides evidence that increasing SIRT1 expression has no obvious impact on the development of glucose-induced insulin resistance in skeletal muscle

Summary

Introduction

Sirtuin 1 (SIRT1) is a NAD+-dependent deacetylase with a large range of target proteins that are important for apoptosis, the cell cycle, circadian rhythms, mitochondrial function, and metabolism [1]. SIRT1 is thought to be nutritionally regulated and be responsible for the beneficial effects of calorie restriction [2,3]. Levels of SIRT1 are reportedly decreased with highfat feeding and may have a role in lipid-induced insulin resistance [4]. Consistent with these results, in vitro studies has shown that SIRT1 is down regulated under hyperglycaemic conditions in liver [5,6], endothelial [7,8], mesangial [9], corneal epithelial [10] and C2C12 muscle cells [11]. Rescuing the decrease in SIRT1 via pharmacological intervention.

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