Supplementation comprising dietary fish oil with all-trans retinoic acid decreased blood lipids and fat accumulation in C57BL/6J mice

•All-trans retinoic acid (ATRA) and fish or soybean oil decreased body weight.•ATRA and fish/soybean oil increased expression of liver PPARδ and RARα.•ATRA reduced adipose weight, liver TG, ACC activity.•ATRA increased ACO and catalase activities.•ATRA and fish oil may suppress obesity. This study aimed to assess the effects of fish oil plus all-trans retinoic acid (ATRA) on lipid metabolism and fat accumulation. Forty male C57BL/6J mice were divided into four groups; the FO, SO, FR, and SR groups were provided with fish oil, soybean oil, fish oil with ATRA, and soybean oil with ATRA, respectively. After 16 weeks, the SR and FR groups had significantly lower body weight than the SO and FO groups. Moreover, the FR group had the lowest reproductive white adipose tissue weight, liver triglyceride level, and acetyl-CoA carboxylase activity and the highest acyl-CoA oxidase and catalase activities among all groups. Additionally, fish oil alone also showed significantly improved serum and liver lipid profiles. ATRA in combination with fish oil or soybean oil both had significantly decreased reproductive white adipose tissue and increased expression of liver peroxisome proliferator-activated receptor δ and retinoic acid receptor α. ATRA may inhibit weight gain and fat accumulation, thus preventing obesity.