Carrot Juice Administration Decreases Liver Stearoyl-CoA Desaturase 1 and Improves Docosahexaenoic Acid Levels, but Not Steatosis in High Fructose Diet-Fed Weanling Wistar Rats

Abstract

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent liver diseases associated with an altered lifestyle, besides genetic factors. The control and management of NAFLD mostly depend on lifestyle modifications, due to the lack of a specific therapeutic approach. In this context, we assessed the effect of carrot juice on the development of high fructose-induced hepatic steatosis. For this purpose, male weanling Wistar rats were divided into 4 groups, fed either a control (Con) or high fructose (HFr) diet of AIN93G composition, with or without carrot juice (CJ) for 8 weeks. At the end of the experimental period, plasma biochemical markers, such as triglycerides, alanine aminotransferase, and β-hydroxy butyrate levels were comparable among the 4 groups. Although, the liver injury marker, aspartate aminotransferase, levels in plasma showed a reduction, hepatic triglycerides levels were not significantly reduced by carrot juice ingestion in the HFr diet-fed rats (HFr-CJ). On the other hand, the key triglyceride synthesis pathway enzyme, hepatic stearoyl-CoA desaturase 1 (SCD1), expression at mRNA level was augmented by carrot juice ingestion, while their protein levels showed a significant reduction, which corroborated with decreased monounsaturated fatty acids (MUFA), particularly palmitoleic (C16:1) and oleic (C18:1) acids. Notably, it also improved the long chain n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA; C22:6) content of the liver in HFr-CJ. In conclusion, carrot juice ingestion decreased the SCD1-mediated production of MUFA and improved DHA levels in liver, under high fructose diet-fed conditions. However, these changes did not significantly lower the hepatic triglyceride levels.

Keywords: PUFA; carotenoids; elongases; fatty liver; vegetables.

Fig. 1

Impacts of carrot juice on liver biochemistry and histology. Liver triglyceride (A) and retinol (B) levels. Representative liver photomicrographs of hematoxylin & eosin stained liver sections (C), immnuohistological staining of liver lipid droplet-associated proteins [abhydrolase domain containing 5 (ABHD5) and perilipin]. 1st row, 20×; 2nd and 3rd row, 40× magnification. Data were analyzed by one way ANOVA with post-hoc least significant difference test. Results are expressed as means±SE of 6 rats from each group. Significantly different at P≤0.05 compared with the ^#control and high fructose group and *with or without carrot juice groups. NC, negative control; Con, control diet; Con-CJ, control diet with carrot juice; HFr, high fructose diet; HFr-CJ, high fructose diet with carrot juice.

Fig. 2

Impacts of carrot juice on insulin sensitivity markers. Results are expressed as means±SE of 7~8 rats, except for muscle glucose uptake, 4 rats from each group. Plasma glucose, insulin, plasma C-peptide, and retinol-binding protein 4 (RBP4) levels, respectively (A~D). Area under curve (AUC) of glucose for respective oral glucose tolerance test (OGTT) (E) and intra-peritoneal insulin tolerance test (IPITT) (F). Soleus muscle insulin-stimulated glucose uptake (fold change in % over basal glucose uptake) (G). Data were analyzed by one way ANOVA with post-hoc least significant difference test. ^#Significantly different at P≤0.05 compared between control and high fructose group. Con, control diet; Con-CJ, control diet with carrot juice; HFr, high fructose diet; HFr-CJ, high fructose diet with carrot juice.

Fig. 3

Impacts of carrot juice on liver fatty acid desaturases and elongases. Results are expressed as means±SE of 3 rats for gene expression and 3~4 rats for protein expression. Respective hepatic mRNA and representative immunoblots with densitometry analyses for FADS1, FADS2 and SCD1 levels (A, B). Respective hepatic mRNA and representative immunoblots with densitometry analyses for ELOVL2 and ELOVL6 levels (C, D). Data were analyzed by one way ANOVA with post-hoc least significant difference test. Significantly different at P≤0.05 compared with the ^#control and high fructose group and *with or without carrot juice groups. Con, control diet; Con-CJ, control diet with carrot juice; HFr, high fructose diet; HFr-CJ, high fructose diet with carrot juice; FADS, fatty acid desaturase; SCD1, stearoyl-CoA desaturase 1; ELOVL, very long chain fatty acid elongase.