The effects of dietary retinoic acid on body lipid deposition in juvenile red sea bream

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 Ž . Ž initial body weight: 8.5 g . The fish were fed either a commercial diet control: diet 1, crude . Ž . protein 61.7%, crude fat 13.9% , or diets supplemented with 100 mg retinyl acetate diet 2 , 10 Ž . Ž . mg all-trans-retinoic acid diet 3 , or 100 mg all-trans-retinoic acidrkg diet diet 4 for the test Ž . 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 Ž . by the treatments. Average plasma free fatty acid levels in fish fed diet 4 60 mEqrl were lower Ž . than those of the other groups 113–148 mEqrl . Plasma triacylglycerol levels in fish fed diet 2 Ž . Ž . 1845 mgrl were lower than those of the other groups 2944–3130 mgrl . 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 ngrml in diet 1, 6"0 ngrml in diet 2, 20"0 ngrml in diet 3, and 223"34 ngrml 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. q 2001 Elsevier Science B.V. All rights reserved.