The value of the zebrafish (Danio rerio) as a model organism continues to expand. In developing the model, current feeding practice in zebrafish laboratories includes the use of commercially available diets. In this study, we compared outcomes in growth, body composition, and reproduction among zebrafish fed five highly utilized commercial diets and one formulated chemically defined reference diet. Wild-type zebrafish larvae were raised on live feed until 21 days postfertilization and then fed diets for 16 weeks. All fish received a daily ration of >5% of body weight (adjusted biweekly). Growth varied among diets throughout the feeding trial, and at study termination (week 16), significant differences among diets were observed for terminal weight gain, body condition index, body fat deposition, and reproductive outcomes. In addition, the proportion of viable embryos produced from females fed the formulated reference diet was high relative to the commercial diets. These data suggest that metabolic profiles, most likely reflecting nutrient/energy availability, utilization, and allocation, vary relative to diet in zebrafish. Undefined differences in metabolic profiles could result in erroneous predictions of health outcomes and make comparisons among laboratories more challenging. We recommend that dietary standards should be defined for zebrafish to support their common utility in biomedical research.
Background Controversial findings have been reported in human and animal studies regarding the influence of n–6 (ω-6) to n–3 (ω-3) fatty acid ratios on obesity and health. Two confounding factors may be related to interactions with other dietary lipid components or sex-specific differences in fatty acid metabolism. Objective This study investigated main and interactive effects of total dietary lipid, ratio of n–6 to n–3 fatty acids, and sex on growth, adiposity, and reproductive health in wild-type zebrafish. Methods Male and female zebrafish (3 wk old) were fed 9 diets consisting of 3 ratios of n–6 to n–3 fatty acids (1.4:1, 5:1, and 9.5:1) varied within 3 total lipid amounts (80, 110, and 140 g/kg) for 16 wk. Data were then collected on growth, body composition (determined by chemical carcass analysis), and female reproductive success (n = 32 breeding events/diet over 4 wk). Main and interactive effects of dietary lipid and sex were evaluated with regression methods. Significant differences within each dietary lipid component were relative to the intercept/reference group (80 g/kg and 1.4:1 ratio). Results Dietary lipid and sex interacted in their effects on body weight (P = 0.015), total body length (P = 0.003), and total lipid mass (P = 0.029); thus, these analyses were stratified by sex. Female spawning success decreased as dietary total lipid and fatty acid ratio increased (P = 0.030 and P = 0.026, respectively). While total egg production was not associated with either dietary lipid component, females fed the 5:1 ratio produced higher proportions of viable embryos compared with the 1.4:1 ratio [median (95% CI): 0.915 (0.863, 0.956) vs 0.819 (0.716, 0.876); P < 0.001]. Conclusions Further characterization of dietary lipid requirements will help define healthy balances of dietary lipid, while the sex-specific responses to dietary lipid identified in this study may partially explain sex disparities in the development of obesity and its comorbidities.
The interaction of dietary macronutrients in the control of growth, body composition, health, and longevity has received renewed attention. The protein leverage hypothesis proposes an inverse relationship between dietary protein levels and obesity development (low protein promoting high obesity), although the majority of laboratory studies have utilized a design modulating the protein amount within a single dietary protein source composition. We investigated whether varying the levels of dietary protein amount and sources would have impacts on growth and body composition using the Zebrafish Danio rerio model. At 28 d postfertilization, Zebrafish were fed 1 of 12 dietary treatments for 12 weeks. Diets contained different protein sources (fish protein hydrolysate [FPH], soy protein isolate [SOY], casein [CAS], or a mixture of all three sources including wheat gluten [MIX]). Sources were formulated at three protein concentrations (18, 33, or 48% as fed, substituted with wheat starch for caloric balance). Body length, height, and weight were measured over time and at termination. Contributions of macronutrients to growth and body fat outcomes were estimated by LASSO (least absolute shrinkage and selection operator) regression. Male and female length, height, and weight increased significantly in response to increasing dietary protein. Male and female fish fed SOY or FPH had the highest amount of body lipid at all protein concentrations relative to those fed CAS or MIX. Relative body lipid was highest in fish that were fed the lowest protein concentration. These data suggest an important role of macronutrient balances, including dietary protein amount and source, in relation to the protein: energy (carbohydrate and lipid) ratio on growth and body composition outcomes. These outcomes may ultimately reflect metabolic alterations that can lead to confounding interpretations of health and disease status. Furthermore, these data reinforce the need to consider and report dietary composition in establishing rigorous and reproducible nutritional guidelines for Zebrafish.
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