Abstract
Obesity and alterations of lipid homeostasis are hallmarks of the metabolic syndrome
and largely influenced by the dietary conditions of the individual. Although heritability
is considered to be a major risk factor, the almost 40 candidate genes identified
by genome-wide association studies (GWAS) so far account for only 5–10% of the observed
variance in BMI in human subjects. Alternatively, diet-induced changes of epigenetic
gene regulation might be involved in disturbed lipid homeostasis and weight development.
The aim of this study was to investigate how a high-carbohydrate diet (HCD; 70 kcal%
from carbohydrates, 10 kcal% from fat) or a high-fat diet (HFD; 20 kcal% from carbohydrates,
60 kcal% from fat) affects hepatic expression of genes involved in fatty acid metabolism
and if these alterations are correlated to changes in promoter methylation. Expression
of stearoyl-CoA desaturase 1 (Scd1) was lower in livers from HFD-fed C57BL/6 J mice compared to HCD-fed animals and
correlated inversely with the degree of DNA methylation at 2 distinct, adjacent CpG
sites in the Scd1 promoter. In contrast, expression of transcription factors peroxisome proliferator
activated receptor alpha and gamma (Ppara, Pparg), and sterol regulatory element binding transcription factor 1 (Srebf1) was not affected. The degree of hepatic Scd1 promoter methylation at these CpG sites correlated positively to fat mass and serum
leptin levels, whereas serum ghrelin levels were inversely correlated with methylation
at both CpG sites. Taken together, hepatic expression of Scd1 is differentially affected by carbohydrate- and lipid content of the diet. These
differences in Scd1 expression are associated with altered promoter methylation, indicating that diets
affect lipid metabolism in the liver via epigenetic mechanisms.
Key words
obesity - lipid metabolism - epigenetic gene regulation - DNA methylation
