Effects of dietary ascorbic acid levels on cholesterol metabolism in rainbow trout (Oncorhynchus mykiss)

Abstract

An 80-day feeding trial was conducted to evaluate the effects of dietary ascorbic acid (AA) supplementation at different levels (0, 0.2 and 0.4 g/kg l-ascorbate-2-polyphosphate; 7.6, 77.2 and 146.7 mg/kg AA, respectively) on cholesterol metabolism in rainbow trout (Oncorhynchus mykiss). Dietary AA supplementation regardless of inclusion level increased the serum total cholesterol and low-density lipoprotein (LDL) cholesterol levels and LDL cholesterol/high-density lipoprotein cholesterol ratio. No significant differences were observed in the serum triiodothyronine and thyroxine levels, faecal cholesterol content, hepatic activity and mRNA expression of acyl-coenzyme A:cholesterol acyltransferase among the dietary treatments. Dietary AA inclusion increased the faecal bile acid content, hepatic activity and mRNA expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase and hepatic cholesterol 7α-hydroxylase mRNA expression, but decreased the hepatic LDL receptor content.High level of AA supplementation (0.4 g/kg) depressed the serum cortisol levels.These results suggest that dietary supplementation with 0.2-0.4 g/kg l-ascorbate-2polyphosphate may increase the serum total cholesterol level in rainbow trout. The cholesterol-raising effect of AA may be due to the increased hepatic cholesterol production and the depressed cholesterol clearance from serum. In addition, dietary AA inclusion also facilitates the hepatic conversion of cholesterol to bile acids. K E Y W O R D Sascorbic acid, cholesterol, homeostasis, l-ascorbate-2-polyphosphate, metabolism, rainbow trout

Effects of Dietary Vitamin C on the Growth Performance, Biochemical Parameters, and Antioxidant Activity of Coho Salmon Oncorhynchus kisutch (Walbaum, 1792) Postsmolts

“…In the study, TC, LDL-C, and HDL-C contents showed dramatic increase with VC supplementation, which were similar with those in rainbow trout [36]. It was suggested that dietary VC levels increased the cholesterol synthesis and inhibited the degradation and clearance of serum LDL-C [36].…”

“…VC had synergistic effects on cholesterol synthesis and catabolism; this might be the reason that VC had variable influences on serum cholesterol contents [ 65 ]. In the study, TC, LDL-C, and HDL-C contents showed dramatic increase with VC supplementation, which were similar with those in rainbow trout [ 36 ]. It was suggested that dietary VC levels increased the cholesterol synthesis and inhibited the degradation and clearance of serum LDL-C [ 36 ].…”

“…In this study, VC supplementation obviously decreased the TG level of serum, suggesting that dietary VC levels did affect the coho salmon health. Blood TC including HDL-C as well as LDL-C levels had been documented to decrease [58][59][60][61], increase [36,62,63], or be independent [23,30,64] with dietary VC supplementation in fishes. VC had synergistic effects on cholesterol synthesis and catabolism; this might be the reason that VC had variable influences on serum cholesterol contents [65].…”

“…Inappropriate supplementation of VC would lead to lower enzyme activities, thus resulting in poor growth performance, low survival rate, and being susceptible to diseases of fish [ 1 , 8 , 30 , 35 ]. Dietary VC deficiency would also lead to some nonspecific signs, such as changes of serum triglycerides and cholesterol levels [ 1 , 36 ]. The dietary VC requirement had been investigated in many farmed fish species, and the optimal dietary VC levels are varied among fish species [ 1 ], which can be affected by the growth rates, age, size, various environmental factors, and nutrient interrelationships of the fish [ 1 , 7 , 24 ].…”

Ascorbic supplementation attenuates juglone induced metabolic derangement

“…Also, ascorbate supplementation can regulate the cholesterol homeostasis, such as LDL cholesterol, decreasing the hepatic 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR) activity, and then, the endogenous cholesterol biosynthesis (Deng et al, 2019). Our results confirmed the protective role of ascorbate over lipid metabolism.…”