Women Retain Insulin Sensitivity Better Than Men

A new study shows that a protein that regulates muscle insulin resistance causes the sex differences in the risk of developing type two diabetes.

Researchers at McMaster University (Hamilton, ON, Canada) conducted a cross-sectional study of muscle biopsies in 34 women and 42 men to test for differences in the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a protein that when active prevents insulin from signaling properly in muscle, reducing the amount of sugar uptake. Real-time polymerase chain reaction (PCR) was performed to determine PTEN gene expression, and western blotting detected total and phosphorylated PTEN protein.

The results showed that while study participants were comparable in age and body mass index (BMI), women had higher adiposity (fat mass) than men for any given weight, as well as significant downregulation of PTEN gene expression and upregulation of PTEN protein phosphorylation (signifying inactivation), when compared to men. This remained true after correction for age, ethnicity, homeostatic model assessment insulin resistance (HOMA-IR), fat mass, and sex. The study was published in the March 2015 issue of Scientific Reports.

“This protein is one explanation of why women are relatively protected from type 2 diabetes, despite having more body fat content compared to men at a given weight,” said lead author pediatric endocrinologist M. Constantine Samaan, MD, an assistant professor of pediatrics at McMaster Children's Hospital. “Women's muscle appeared more efficient in neutralizing this protein, and this allows insulin to work better to move sugar from circulation to muscle.”

One of the hallmarks of obesity is the deposition of excess fat in and outside adipose tissue, with the increased adiposity associated with skeletal muscle insulin resistance. As skeletal muscle is the main organ responsible for postprandial glucose disposal, its insulin resistance is a major contributor to the global epidemic of type 2 diabetes. One of the factors that determine adiposity patterns is sex.

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