Increased Hepatic PDGF-AA Signaling Mediates Liver Insulin Resistance in Obesity Associated Type 2 Diabetes

In type 2 diabetes (T2D), hepatic insulin resistance is strongly associated with non-alcoholic fatty liver disease (NAFLD). In this study, we hypothesized that DNA methylome of livers from patients with T2D, when compared to livers of individuals with normal plasma glucose levels, can unveil some mechanism of hepatic insulin resistance that could link to NAFLD. Using DNA methylome and transcriptome analyses of livers from obese individuals, we found that both hypomethylation at a CpG site in (encoding platelet derived growth factor alpha) and overexpression are associated with increased T2D risk, hyperinsulinemia, increased insulin resistance and increased steatohepatitis risk. Both genetic risk score studies and human cell modeling pointed to a causative impact of high insulin levels on CpG site hypomethylation, overexpression, and increased PDGF-AA secretion from liver. We found that PDGF-AA secretion further stimulates its own expression through protein kinase C activity and contributes to insulin resistance through decreased expression of both insulin receptor substrate 1 and of insulin receptor. Importantly, hepatocyte insulin sensitivity can be restored by PDGF-AA blocking antibodies, PDGF receptor inhibitors and by metformin opening therapeutic avenues. Therefore, in the liver of obese patients with T2D, the increased PDGF-AA signaling contributes to insulin resistance, opening new therapeutic avenues against T2D and possibly NAFLD.