Gender Affects the Stress Response, Gut Microbiome, and Obesity
There is mounting evidence confirming the role of an imbalanced gut microbiome in obesity and its related health problems – heart disease, insulin resistance/diabetes and systemic inflammation.
In addition, obesity is linked with a high prevalence of mood disorders such as anxiety and depression.
The reason why obesity seems to cause these mood disorders is not really known, but a number of reasons are possible, they are:
- Systemic inflammation caused by obesity may affect serotonin production.
- Systemic inflammation causing inflammation around the brain/nervous system.
- High-fat diet altering signaling in the hippocampus (part of the brain that regulates emotion).
Moreover, fecal microbiome transplants in mice have shown that the gut microbiome also affects mood disorders – transplanting the microbiome from obese mice into a thin mice causes behavior changes in the thin mice.
Finally, stress contributes to both mood disorders and obesity.
In a study published in the journal Scientific Reports, scientists examined the relationship between these three components in a mouse model of obesity.
The surprising finding of this study was the effect played by gender!
First, the scientists fed the mice a high-fat diet to alter the gut microbiome and make them obese. The researchers then assessed the behavior of the mice. Next, they stressed the mice out with chronic and unpredictable mild stress, analyzed their gut microbiome, and retested their behavior.
The results revealed striking gender differences in the effects of obesity and stress on anxiety, activity levels, and the gut microbiome.
The male mice were more vulnerable to developing anxiety on the high-fat diet and obese male mice moved around less than females when they were stressed.
In female mice, stress caused the gut microbiomes of the lean mice to look more like the gut microbiomes of obese mice.
This study highlights the importance of considering the effects of gender in scientific research.
Anxiety disorders occur nearly twice as frequently in women than they do in men. Major depression is also more prevalent in women. Although these gender differences are well known, there has been a real lack of studies into why.
This study suggests that the gut microbiome is one source for the differences. With the NIH 2014 mandate to include sex and gender in all preclinical animal studies, we should start to see many more.