Abstract
A 6-week feeding trial was conducted to investigate the effects of dietary retinoids, especially retinoic acid, an anti-adipogenic factor in mammals, on lipid deposition in juvenile red sea bream (initial body weight: 8.5 g). The fish were fed either a commercial diet (control: diet 1, crude protein 61.7%, crude fat 13.9%), or diets supplemented with 100 mg retinyl acetate (diet 2), 10 mg all- trans-retinoic acid (diet 3), or 100 mg all- trans-retinoic acid/kg diet (diet 4) for the test period. A low mortality (2.5%) was observed with diets 3 and 4 through the period. Weight gain, daily feed intake, feed efficiency, whole body crude protein, and crude fat content were not affected by the treatments. Visceral adiposomatic index of the fish was highest in fish fed diet 4 as follows: 2.90 in diet 1 fish, 3.46 in diet 2 fish, 3.28 in diet 3 fish, and 4.19 in diet 4. The treatments did not affect hepatosomatic index. Lipid in the dorsal white muscle was lowest and those in the visceral adipose tissue highest in fish fed diet 4. Liver lipid content was not affected by the treatments. Average plasma free fatty acid levels in fish fed diet 4 (60 μEq/l) were lower than those of the other groups (113–148 μEq/l). Plasma triacylglycerol levels in fish fed diet 2 (1845 mg/l) were lower than those of the other groups (2944–3130 mg/l). Subsequently, to confirm that dietary retinoic acid was internally absorbed, plasma retinoic acid levels at 6-h post-feeding were determined by HPLC. These were 4±0 ng/ml in diet 1, 6±0 ng/ml in diet 2, 20±0 ng/ml in diet 3, and 223±34 ng/ml in diet 4. The present results suggest that dietary retinoic acid was directly incorporated into the body, and that retinoic acid up-regulated development of the visceral adipose tissue and down-regulated lipid deposition in the dorsal white muscle.
Published Version
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