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Parallel activation of de novo lipogenesis and stearoyl-CoA desaturase activity after 3 d of high-carbohydrate feeding^1,2,3,4

¹ From the Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom

Background:High-carbohydrate (HC) diets increase de novo lipogenesis (DNL), but effects on stearoyl-CoA desaturase (SCD) are not so well studied.

Objective:The objective was to investigate DNL and SCD in liver and adipose tissue by using fatty acid ratios after short-term dietary intervention.

Design:Eight subjects consumed isoenergetic 3-d HC (10% fat; 75% carbohydrates) or higher fat (HF; 40% fat; 45% carbohydrates) diets (sugar to starch ratio: 60:40 for both) in a crossover study. Blood was taken from an artery and a vein draining subcutaneous adipose tissue. DNL and SCD activity were investigated by using the ratios of 16:0 to 18:2n–6 and of 16:1n–7 to 16:0, respectively. A test meal, including [U-¹³C]palmitate was given to trace dietary fatty acid incorporation into VLDL-triacylglycerol (TG). The conversion of intravenously infused [²H₂]palmitic acid to [²H₂]palmitoleic acid in VLDL-TG was quantified as a specific marker of hepatic SCD activity.

Results:The VLDL-TG 16:0/18:2n–6 ratio, which reflects hepatic DNL, was greater after the HC diet than after the HF diet (P = 0.02). With the HC diet, increased plasma TG concentrations correlated with 16:0/18:2n–6 ratios (r = 0.76, P = 0.028). Plasma VLDL-TG and adipose venous nonesterified fatty acid (NEFA) 16:1n–7/16:0 ratios were higher after the HC diet (fasting: P = 0.01 and P = 0.05, respectively; postprandial: P = 0.03 and P = 0.05, respectively). Changes in fasting VLDL-TG 16:0/18:2n–6 and 16:1n–7/16:0 ratios were associated (P = 0.06). The contribution of total fatty acids from splanchnic sources (including DNL) was higher after the HC diet (P = 0.02). Expression of lipogenic genes in subcutaneous adipose tissue was not significantly affected by diet.

Conclusion:Parallel activation of DNL and SCD was found after a short period of HC feeding.

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				R. Roberts, A. S Bickerton, B. A Fielding, E. E Blaak, A. J Wagenmakers, M. F-F Chong, M. Gilbert, F. Karpe, and K. N Frayn Reduced oxidation of dietary fat after a short term high-carbohydrate diet Am. J. Clinical Nutrition, April 1, 2008; 87(4): 824 - 831. [Abstract] [Full Text] [PDF]