# Diet induced insulin resistance is due to induction of PTEN expression

## TL;DR

A high-fat diet causes insulin resistance by increasing PTEN, which blocks insulin signaling and leads to type 2 diabetes symptoms.

## Contribution

The study identifies PTEN induction as a key mechanism driving insulin resistance and type 2 diabetes in diet-induced obesity.

## Key findings

- PTEN levels increase in fat, muscle, and liver tissues in diet-induced obesity.
- Inhibiting PTEN prevents or reverses hyperglycemia and glucose intolerance.
- mTORC1 inhibition reverses most but not all symptoms of insulin resistance.

## Abstract

Type 2 Diabetes (T2D) is a condition that is often associated with obesity and defined by reduced sensitivity of PI3K signaling to insulin (insulin resistance), hyperinsulinemia and hyperglycemia. Molecular causes and early signaling events underlying insulin resistance are not well understood. Insulin activation of PI3K signaling causes mTOR dependent induction of PTEN translation, a negative regulator of PI3K signaling. We speculated that insulin resistance is due to insulin dependent induction of PTEN protein that prevent further increases in PI3K signaling. Here we show that in a diet induced model of obesity and insulin resistance, PTEN levels are increased in fat, muscle and liver tissues. Onset of hyperinsulinemia and PTEN induction in tissue is followed by hyperglycemia, hepatic steatosis and severe glucose intolerance. Treatment with a PTEN phosphatase inhibitor prevents and reverses these phenotypes, whereas an mTORC1 kinase inhibitor reverses all but the hepatic steatosis. These data suggest that induction of PTEN by increasing levels of insulin elevates feedback inhibition of the pathway to a point where downstream PI3K signaling is reduced and hyperglycemia ensues. PTEN induction is thus necessary for insulin resistance and the type 2 diabetes phenotype and a potential therapeutic target.