May 10, 2017
Adele Fowler, doctoral candidate in the Department of Biology and pre-doctoral trainee in the Nutrition Obesity Research Center (NORC), won second place in the American Society for Nutrition (ASN) Emerging Leaders in Nutrition Science Poster Competition, which was held at ASN’s 2017 annual meeting in Chicago, April 22–26. Fowler presented the prizewinning study “Sex-Specific Differences in the Development of Diet-Induced Obesity in a Zebrafish Model” at the event, which is designed to feature the most notable research submitted to ASN’s Scientific Sessions by students and young investigators.
In response to the National Institutes of Health recent emphasis on examining sexual dimorphisms relating to diet-induced obesity and associated diseases to improve treatment and prevention strategies, Fowler and her team used the zebrafish Danio rerio as a model for human nutrition to evaluate sex-specific differences in response to dietary lipid composition, in addition to comparing rates of fat accumulation relative to body mass between males and females. They fed newly hatched larvae live feeds until 21 days post fertilization and then switched them to one of nine experimental diet treatments—prepared by varying the ratios of n-6:n-3 fatty acids within three levels of total fat—and provided each tank with a daily ration for the next 16 weeks. Fourteen fish per tank were kept in the 16 tanks utilized per treatment. Each treatment was evaluated at the end of the 16-week period, based on body weight gain and body composition (total body lipid [fat mass], body triglyceride [TAG], and fat free mass, measured by chemical carcass analysis). Sex-specific fat mass thresholds in which the slope of fat mass begins to increase rapidly in relation to body mass was determined by segmented linear regression.
A significant interaction by gender was observed in the response to dietary fat: in males, total body lipid was significantly influenced by the n-6:n-3 fatty acid ratio; in females, it was affected by total dietary fat. Interactions by sex were also noted in the relationship between total body mass with total body lipid and TAG. Females also had a higher fat mass threshold than male study subjects for both total body lipid and TAG. These variations in the association between total body mass and fat mass indicate that male and female zebrafish may develop obesity at different rates. The sex-specific fat mass thresholds and responses to dietary lipid identified in the study signify sexual dimorphisms in nutrient partitioning and utilization. Fowler concluded that these differences may explain, in part, disparities between males and females in the development of obesity and its co-morbidities.
“Zebrafish are an excellent model for diet-induced obesity in humans, and results from this study may indicate a need for gender-targeted therapies in obesity treatment,” says Fowler. “It is such an honor to have received second place in this competition.”
UAB co-investigators in the study are R. Jeff Barry, Yuan Yuan, and Michael B. Williams in the Department of Biology, as well as department colleagues Mickie L. Powell, PhD, and Stephen A. Watts, PhD, who are also members of NORC.
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