Brain insulin sensitivity may change during menstrual cycle, study finds

A collaborative team of diabetes specialists hailing from Eberhard Karls University Tübingen and Heinrich Heine University Düsseldorf in Germany has uncovered intriguing evidence indicating that the responsiveness of the brain to insulin in women may be influenced by their menstrual cycle.

Published in the journal Nature Metabolism, their study involved a clinical trial where they closely monitored the insulin levels of female volunteers. Nils Kroemer, affiliated with the University of Bonn, penned a News & Views piece within the same journal issue, providing insights into the team’s groundbreaking research.

Historically, studies have suggested that insulin’s presence in the brain can trigger alterations in eating behavior, overall metabolism, and fat storage. However, the exact mechanisms remain shrouded in mystery, partly due to the fact that most prior investigations focused on insulin’s impact on the male brain.

In this innovative study, the research team set out to shed light on how insulin affects the female brain. To achieve this, they conducted a clinical trial involving 11 female volunteers during two distinct phases of their menstrual cycle: the first day of ovulation and just after ovulation.

To gauge the brain’s response to insulin, the volunteers underwent hyperinsulinemic-euglycemic clamps, a procedure used to measure insulin sensitivity. During this process, some women received intranasal insulin doses while others were administered a placebo. The results revealed that the brain exhibited higher sensitivity to insulin on the first day of ovulation but not in the days immediately following ovulation.

Furthermore, the research team conducted MRI scans on 15 different female volunteers to delve deeper into how insulin affects the hypothalamus during menstrual cycles. These scans yielded the same outcome—greater hypothalamus sensitivity to insulin just before ovulation, but not thereafter.

The researchers propose that their findings could elucidate why many women experience increased hunger before their menstrual period, why their metabolism slows down, and why weight gain becomes more probable. Kroemer suggests that this response in the female body might serve as a way to stockpile energy in preparation for a potential pregnancy.

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