Effects of Dietary Supplementation with Myo-inositol on Hepatic Expression of Glycolytic and Fructolytic Enzyme Genes in Rats Fed a High-sucrose Diet.

We examined effects of a major lipotrope, myo-inositol, on the expression of primary glycolytic (glucokinase and phosphofructokinase) and fructolytic enzyme (ketohexokinase [KHK] and aldolase B) genes in the livers of rats fed a control diet, high-sucrose diet, or high-sucrose diet supplemented with 0.5% myo-inositol for 14 d. Supplementation with myo-inositol decreased the hepatic expression of fructolytic enzyme genes, but not that of glycolytic enzyme genes, and the levels of triglycerides, fatty acid synthase, and KHK proteins in high-sucrose diet-induced fatty liver. The study results suggest that myo-inositol represses primary fructlysis, but not glycolysis, in high-sucrose diet-induced fatty liver.

High-fructose diet-induced hepatic expression of the Scd1 gene is associated with increased acetylation of histones H3 and H4 and the binding of ChREBP at the Scd1 promoter in rats.

Stearoyl-CoA desaturase-1 (SCD1) is a key enzyme in the biosynthesis of monounsaturated fatty acids, and the expression of the Scd1 gene is induced by the intake of the lipogenic sugar fructose. We examined the effects of a high-fructose diet on hepatic acetylation of histones H3 and H4 and the binding of carbohydrate response element-binding protein (ChREBP) on the Scd1 gene promoter in rats. Rats were fed a control diet or a high-fructose diet for 10 days. The intake of a high-fructose diet significantly increased histone H3 and H4 acetylation and ChREBP binding to the Scd1 gene promoter as well as the amount of triglyceride and the expression of the Scd1 gene. These results suggest that short-term intake of high fructose upregulates expression of Scd1 by enhancing acetylation of histones H3 and H4 and binding of ChREBP at the Scd1 promoter.

Dietary supplementation with myo-inositol reduces high-fructose diet-induced hepatic ChREBP binding and acetylation of histones H3 and H4 on the Elovl6 gene in rats.

ELOVL fatty acid elongase 6 (ELOVL6) is a long-chain fatty acid elongase, and the hepatic expression of the Elovl6 gene and accumulation of triglycerides (TG) are enhanced by long-term high-fructose intake. Fatty acid synthesis genes, including Elovl6, are regulated by lipogenic transcription factors, sterol regulatory element-binding protein 1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP). In addition, carbohydrate signals induce the expression of fatty acid synthase not only via these transcription factors but also via histone acetylation. Since a major lipotrope, myo-inositol (MI), can repress short-term high-fructose-induced fatty liver and the expression of fatty acid synthesis genes, we hypothesized that MI might influence SREBP-1c, ChREBP, and histone acetylation of Elovl6 in fatty liver induced by even short-term high-fructose intake. This study aimed to investigate whether dietary supplementation with MI affects Elovl6 expression, SREBP-1 and ChREBP binding, and acetylation of histones H3 and H4 at the Elovl6 promoter in short-term high-fructose diet-induced fatty liver in rats. Rats were fed a control diet, high-fructose diet, or high-fructose diet supplemented with 0.5% MI for 10 days. This study showed that MI supplementation reduced short-term high-fructose diet-induced hepatic expression of the Elovl6 gene, ChREBP binding, but not SREBP-1 binding, and acetylation of histones H3 and H4 at the Elovl6 promoter.