Sirt3 negatively regulates Glut4 in skeletal muscle insulin resistance in old male offspring rats fed with maternal high fat diet

Abstract

High fat (HF) diet intake during pregnancy is linked to insulin resistance (IR) in offspring, but the molecular mechanism still needs to be clarified. In the present study, pregnant rats were fed either HF diet (45% energy from fat) or normal control (CON) diet (10% energy from fat) during gestation from day 5-21. Experiments were performed in 20 months old male offspring rats. The results showed that the fasting insulin levels of old male offspring in HF increased compared with CON. However, the fasting glucose levels was unchanged. Besides, the glucose tolerance tests (GTTs) and insulin tolerance tests (ITTs) were impaired, and the AUC of GTT in HF and CON was 44.62±5.12, 33.58±3.98, with significant differences (P<.05). Furthermore, the AUC of ITT in HF and CON was 16.62±2.07 and 12.44±2.28, which showed an obvious difference (P<.05). Additionally, Sirt3 transcript and protein expressions were found up-regulated in both of the HF old male offspring skeletal muscle (1.42-fold) (P<.05) and palmitic acid (PA) treated L6 myotubes (1.32-fold) (P<.05), accompanied with increase in nicotinamide adenine dinucleotide (NAD⁺) in HF old male offspring skeletal muscle (P<.05). What's more, Glut4 transcript and protein expressions were found decreased significantly in both of the HF old male offspring skeletal muscle (0.45-fold) (P<.01) and PA treated L6 myotubes (0.49-fold) (P<.01). Transfection of Sirt3 gene in differentiated L6 myocytes indicated that Sirt3 negatively regulated Glut4 in L6 cells. However, AcK-103 protein, an indicator of acetylation, was found decreased in HF old male offspring skeletal muscle and L6 myotubes as a result of up-regulation of Sirt3 (P<.05). Thus, our findings suggest that HF diet intake during pregnancy induced IR in the skeletal muscle of old male offspring rats, probably occurred through Sirt3-Glut4 retrograde regulation, providing novel information concerning the molecular mechanism of IR in old male offspring rats.

Keywords: Glut4; L6 myotubes; Sirt3; insulin resistance; maternal high fat diet; old male offspring.