Are Pears Healthier than Apples?
According to a new study published in the journal Frontiers of Immunology by researchers at the University of California, Riverside, it's healthier to be a pear than an apple! As we age, we tend to accumulate fat: women experience fat build up around the hips, yielding a pear shape, and men have increased abdominal fat resulting in an apple shape.
In this study, male and female mice were fed a high fat diet but only male mice experienced changes in the reproductive system (low testosterone and reduced sperm count) as well as response of the immune system in the brain, or neuroinflammation. Females were unaffected and this study suggested that they were not affected because of the protective effect of ovarian estrogen as well as other factors.
Dr. Djurdjica Coss, the study leader, stated, “The findings, derived from the mouse study, are likely to have applications in humans.” Much like humans, mice on high-fat diet develop metabolic syndrome — a collection of endocrine problems that includes Type 2 diabetes and insulin resistance. Obese men have decreased testosterone (associated with lowered sperm production, fatigue, decreased libido and less muscle mass and strength). Similarly, obese male mice demonstrated nearly 50 percent decreases in testosterone and sperm count, and analogous to humans, obese female mice showed abnormal ovulation patterns, contributing to decreased fertility.
Obesity is a likely a factor in the increased incidence of infertility in the United States. Now, more than 30 percent of people are obese (BMI > 30 kg/m2), and more than two-thirds are overweight (BMI 25-30 kg/m2).
Also similar to humans, female mice deposit fat differently than their male counterparts. Females deposit fat right below the skin, while males accumulate fat deeper, within the body's visceral region, which may affect internal organs. Even in women, however, when fat overwhelms the subcutaneous storage capability, it then accumulates in the abdominal region, resulting in neuroinflammation.
Another fascinating finding reported in this study is that macrophages, (large, engulfing peripheral white blood cells), cross the blood-brain barrier — the protective barrier that prevents most compounds in the blood from entering the brain. This infiltration of macrophages into the brain occurs in addition to the activation of immune cells within the brain. "We know the immune cells secrete cytokines, which are inflammatory markers, in the blood. It's possible these cytokines travel in blood from the fat tissue and activate the immune cells to cross the blood-brain barrier," Coss said.
- Nancy M. Lainez, Carrie R. Jonak, Meera G. Nair, Iryna M. Ethell, Emma H. Wilson, Monica J. Carson, Djurdjica Coss. Diet-Induced Obesity Elicits Macrophage Infiltration and Reduction in Spine Density in the Hypothalami of Male but Not Female Mice. Frontiers in Immunology, 2018; 9 DOI: 10.3389/fimmu.2018.01992