Inhibition of protein kinase Cε prevents hepatic insulin resistance in nonalcoholic fatty liver disease
Varman T. Samuel, Zhen-Xiang Liu, Amy Wang, Sara A. Beddow, John G. Geisler, Mario Kahn, Xian-man Zhang, Brett P. Monia, Sanjay Bhanot, Gerald I. Shulman
Varman T. Samuel, Zhen-Xiang Liu, Amy Wang, Sara A. Beddow, John G. Geisler, Mario Kahn, Xian-man Zhang, Brett P. Monia, Sanjay Bhanot, Gerald I. Shulman
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Research Article Metabolism

Inhibition of protein kinase Cε prevents hepatic insulin resistance in nonalcoholic fatty liver disease

Abstract

Nonalcoholic fatty liver disease is strongly associated with hepatic insulin resistance and type 2 diabetes mellitus, but the molecular signals linking hepatic fat accumulation to hepatic insulin resistance are unknown. Three days of high-fat feeding in rats results specifically in hepatic steatosis and hepatic insulin resistance. In this setting, PKCε, but not other isoforms of PKC, is activated. To determine whether PKCε plays a causal role in the pathogenesis of hepatic insulin resistance, we treated rats with an antisense oligonucleotide against PKCε and subjected them to 3 days of high-fat feeding. Knocking down PKCε expression protects rats from fat-induced hepatic insulin resistance and reverses fat-induced defects in hepatic insulin signaling. Furthermore, we show that PKCε associates with the insulin receptor in vivo and impairs insulin receptor kinase activity both in vivo and in vitro. These data support the hypothesis that PKCε plays a critical role in mediating fat-induced hepatic insulin resistance and represents a novel therapeutic target for type 2 diabetes.

Authors

Varman T. Samuel, Zhen-Xiang Liu, Amy Wang, Sara A. Beddow, John G. Geisler, Mario Kahn, Xian-man Zhang, Brett P. Monia, Sanjay Bhanot, Gerald I. Shulman

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Figure 4

PKCε ASO therapy improves hepatic insulin signaling and preserves insulin receptor kinase activity.

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PKCε ASO therapy improves hepatic insulin signaling and preserves insuli...
Insulin receptor (IR) tyrosine phosphorylation, IRS2 tyrosine phosphorylation, and AKT2 activity were assessed in the basal, fasted state, and after 20 minutes of hyperinsulinemic-euglycemic clamping. (A) Insulin receptor tyrosine phosphorylation. (B) IRS2 tyrosine phosphorylation. *P < 0.05 versus saline; †P < 0.05 versus control ASO. (C) AKT2 activity. †P < 0.05 versus control ASO. (D) Immunoprecipitation of the insulin receptor also precipitates PKCε and vice versa. (E) Incubation of active insulin receptor kinase with increasing molar ratios of PKCε results in a dose-dependent decrease in insulin receptor kinase activity. (F) Activity of lecithin-purified insulin receptor kinase from rats fed a normal low-fat diet and high-fat-fed (HFF) rats treated with saline, control ASO, and PKCε ASO. #P < 0.01 versus HFF/saline; ΧP < 0.001 versus HFF.