Targeting Pyruvate Carboxylase Reduces Gluconeogenesis and Adiposity and Improves Insulin Resistance

Abstract

We measured the mRNA and protein expression of the key gluconeogenic enzymes in human liver biopsy specimens and found that only hepatic pyruvate carboxylase protein levels related strongly with glycemia. We assessed the role of pyruvate carboxylase in regulating glucose and lipid metabolism in rats through a loss-of-function approach using a specific antisense oligonucleotide (ASO) to decrease expression predominantly in liver and adipose tissue. Pyruvate carboxylase ASO reduced plasma glucose concentrations and the rate of endogenous glucose production in vivo. Interestingly, pyruvate carboxylase ASO also reduced adiposity, plasma lipid concentrations, and hepatic steatosis in high fat–fed rats and improved hepatic insulin sensitivity. Pyruvate carboxylase ASO had similar effects in Zucker Diabetic Fatty rats. Pyruvate carboxylase ASO did not alter de novo fatty acid synthesis, lipolysis, or hepatocyte fatty acid oxidation. In contrast, the lipid phenotype was attributed to a decrease in hepatic and adipose glycerol synthesis, which is important for fatty acid esterification when dietary fat is in excess. Tissue-specific inhibition of pyruvate carboxylase is a potential therapeutic approach for nonalcoholic fatty liver disease, hepatic insulin resistance, and type 2 diabetes.

Thrap3 docks on phosphoserine 273 of PPARγ and controls diabetic gene programming

“…Previous reports have shown that ASO treatment can lead to repression of specific gene expression in several tissues in vivo, particularly liver and adipose tissue (Supplemental Figs. S2, S3;Watts et al 2005;Kumashiro et al 2013). …”

Insights into Transcriptional Regulation of Hepatic Glucose Production

“…However, the levels of PC and its activity are elevated in livers of type 1 diabetic rats and mice (Wimhurst and Manchester, 1970), and in genetically obese Zucker diabetic fatty rats (Lynch et al, 1992;Jitrapakdee et al, 1998), suggesting that insulin exerts its inhibitory effect on hepatic PC expression. Furthermore, antisense oligonucleotide-mediated suppression of hepatic PC expression in rats fed with normal diet marginally reduced fasting plasma glucose and endogenous glucose production, while this effect was more pronounced in rats fed with high-fat diet, suggesting the critical role of PC in hepatic gluconeogenesis, especially during the development of diabetes (Kumashiro et al, 2013). Recent study has shown that in humans, the level of hepatic PC protein is increased in those who have hyperglycemia, supporting the role of PC being one of the key gluconeogenic enzymes in human (Kumashiro et al, 2013), while this evidence was absent for PEPCK-C and G6Pase (Samuel et al, 2009).…”

Glutathione s-transferase p in glucose homeostasis in mice.

“…It has recently been reported that hepatic expression of Pepck and G6pc mRNA was not related to fasting hyperglycemia in humans and in rodent models of T2D [168]. The authors revealed a strong association between pyruvate carboxylase protein expression and glycemia in humans [169]. Pyruvate carboxylase is allosterically activated by acetyl-CoA [170].…”