Sirtuin1 (SIRT1) protein uses NAD+ as a substrate to deacetylate transcription factors, cofactors, and histones to enhance mitochondrial function. We tested the hypothesis whether increased expression of SIRT1 protein in dorsal root ganglion (DRG) neurons would rescue mice from peripheral neuropathy induced by a high fat diet (HFD). Neuron-specific, doxycycline (DOX)-inducible, SIRT1 protein over expressing C57BL6 transgenic mouse (nSIRT1OE Tg) were generated. Expression of SIRT1 protein was observed in small to medium sized DRG neurons. nSIRT1OE was shut off by feeding, weaned Tg mice, with DOX in the diet for 12 weeks. The Tg mice were divided into 3 groups. Group # 1: nSIRT1OE Tg mice fed with standard diet (STD) plus DOX for 4 months; Group # 2: nSIRT1OE Tg mice fed with HFD plus DOX for 4 months; Group # 3: nSIRT1OE Tg mice fed with HFD plus DOX for 2 months until they develop neuropathy and then switched to HFD minus DOX for additional 2 months. Neuropathy was determined by mechanical allodynia thresholds (MAT) and nerve conduction velocity (NCV) at 0, 2 and 4 months. Intraepidermal nerve fiber density (IENFD) was measured at 4 months. MAT, NCV and IENFD were decreased in HFD-fed (Group # 2) mice compared to STD-fed mice (Group # 1) at 2 and 4 months. In Group # 3 mice, 2 months after turning on nSIRT1OE, we observed a reversal of mechanical allodynia, NCV and attenuation of IENFD (Group # 3 compared to Group # 2). Western blot of protein extracts from DRG neurons showed that HFD increased acetylation of proteins and SIRT1OE abolished the HFD-induced acetylation of proteins. The mitochondrial bioenergetics profile of cultured adult DRG neurons showed that hyperglycemia induced a decrease in the spare respiratory capacity in wild type (WT) DRG neurons. This was corrected in nSIRT1OE Tg DRG neurons. In type 2 diabetic neuropathy, altered acetylation of proteins and reduced mitochondrial function via a defective SIRT1 pathway may contribute to developing distal axonopathy.
K. Chandrasekaran: None. C. Ho: None. M. Salimian: None. P.H. Kumar: None. S. Konduru: None. J.W. Russell: None.