Human SIRT3 blocking peptide

Hyperinsulinemia plays a causal role in adipose tissue expansion. Mice with reduced insulin have increased energy expenditure. but the mechanisms remained unclear. Here we investigated the effects of genetically reducing insulin production on uncoupling and oxidative mitochondrial proteins in liver, skeletal muscle, white adipose tissue (WAT), and brown adipose tissue (BAT). Male Ins1(+/+) or Ins1(+/-) littermates were fed either a low-fat diet (LFD) or a high-fat diet (HFD) for 4 wk, starting at 8 wk of age. Replicating our previous observations, HFD increased fasting hyperinsulinemia, and Ins1(+/-) mice had significantly lower circulating insulin compared with Ins1(+/+) littermates. Fasting glucose and body weight were not different between genotypes. We did not observe robust significant differences in liver or skeletal muscle. In mesenteric WAT, Ins1(+/-) mice had reduced Ndufb8 and Sdhb, while Ucp1 was increased in the context of HFD. HFD alone had a dramatic inhibitory effect on Pparg abundance. In inguinal WAT, Ins1(+/-) mice exhibited significant increases in oxidative complex proteins, independent of diet, without affecting Ucp1. Pparg, or Prdm16:Pparg association. In BAT, lowered insulin increased Sdhb protein levels that had been reduced by HFD. Ucp1 protein. Prdml6:Pparg association, and Sirt3 abundance were all increased in the absence of diet-induced hyperinsulinemia. Our data show that reducing insulin upregulates oxidative proteins in inguinal WAT without affecting Ucp1, whereas in mesenteric WAT and BAT, reducing insulin upregulates Ucp1 in the context of HFD. Preventing hyperinsulinemia has early depot-specific effects on adipose tissue metabolism and helps explain the increased energy expenditure previously reported in Ins1(+/-) mice.

Sirtuin-3 (SIRT3) is a mitochondria] NAD + -dependent deacetylase that is essential in regulating mitochondrial proteins and maintaining cellular antioxidant properties. It has been reported that icariin (ICA) is neuroprotective over various neurotoxicant induced oxidative stress. This study aimed to determine whether ICA exerts neuroprotective effects on rotenone (ROT)-induced neurotoxicity through activation of SIRT3. Rats treated with ROT exhibited a marked loss of dopamine (DA) neurons and a decline in motor function, along with a decrease in protein expressions of SIRT3 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha) in the substantia nigra (SN). Administration of ICA significantly alleviated the loss of DA neurons, improved behavioral function, and concomitantly enhanced SIRT3 and PGC-1 alpha expressions. The neuroprotective effect of ICA on ROT-induced cytotoxicity was further confirmed in the PC12 cell model, which showed significant improvement in the survival of ROT-treated cells with ICA pretreatment. The cytoprotective effect of ICA was abolished in ROT-treated cells by SIRT3 inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP), along with a resultant decrease in PGC-1 alpha expression. In addition, knockdown of PGC-1 alpha by siRNA suppressed ICA-mediated protective effects but did not affect SIRT3 expression, indicating the role of regulation of PGC-1 alpha by SIRT3 in the protective action of ICA. Furthermore, we showed that ICA improved mitochondrial respiration, oxidative status, enhanced antioxidant enzyme SOD activity and GSH/GSSG ratio in cells treated with ROT. However, these protective effects of ICA on ROT-treated cells was markedly abolished by SIRT3 inhibitor 3-TYP. Our findings demonstrate that ICA exerts a neuroprotective role through upregulation of SIRT3.