Pituitary insulin receptors key to obesity-induced infertility
MedWire News: Study results indicate that obesity-induced infertility may be caused by rising insulin levels interfering with gonadotroph hormones in the pituitary gland.
Study author Andrew Wolfe (Johns Hopkins University School of Medicine, Baltimore, Maryland, USA) explained that, traditionally, reproductive dysfunction among obese patients is thought to be a result of insulin resistance throughout the body.
"What we propose is a fundamentally new model showing that different tissues respond differently, and that while cells in the liver and muscle become insulin resistant, cells in the pituitary remain sensitive to insulin," he added.
Wolfe and colleagues created a mouse model lacking pituitary insulin receptors, and compared its reproductive ability with that of normal mice. All mice were fed either a standard diet or a high-fat obesity-inducing diet for 3 months.
The wild type obese mice displayed the hallmarks of insulin resistance, and had fewer ovulations and an impaired breeding capacity compared with all normal-weight mice.
Furthermore, the normal-weight mice had six times the number of successful pregnancies compared with obese mice, and the obese mice with missing insulin receptors fared almost as well, with five times the number of successful pregnancies than typically obese mice.
Wolfe believes that the finding may be most relevant in humans for women with polycystic ovary syndrome, which is often characterized by obesity and insulin resistance.
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By Sarah Guy