Fructose consumption has been associated with the surge in obesity and dyslipidemia. This may be mediated by the fructose effects on hepatic lipids and ATP levels. Fructose metabolism provides carbons for de novo lipogenesis (DNL) and stimulates enterocyte secretion of apoB48. Thus, fructose-induced hepatic triglyceride (HTG) accumulation can be attributed to both DNL stimulation and dietary lipid absorption. The aim of this study was to assess the effects of fructose diet on HTG and ATP content and the contributions of dietary lipids and DNL to HTG. Measurements were performed in vivo in mice by magnetic resonance imaging (MRI) and novel magnetic resonance spectroscopy (MRS) approaches. Abdominal adipose tissue volume and intramyocellular lipid levels were comparable between 8-wk fructose- and glucose-fed mice. HTG levels were ∼1.5-fold higher in fructose-fed than in glucose-fed mice (P<0.05). Metabolic flux analysis by (13)C and (2)H MRS showed that this was not due to dietary lipid absorption, but due to DNL stimulation. The contribution of oral lipids to HTG was, after 5 h, 1.60 ± 0.23% for fructose and 2.16 ± 0.35% for glucose diets (P=0.26), whereas that of DNL was higher in fructose than in glucose diets (2.55±0.51 vs.1.13±0.24%, P=0.01). Hepatic energy status, assessed by (31)P MRS, was similar for fructose- and glucose-fed mice. Fructose-induced HTG accumulation is better explained by DNL and not by dietary lipid uptake, while not compromising ATP homeostasis.
Keywords: de novo lipogenesis; in vivo hepatic lipid metabolism; magnetic resonance spectroscopy.