Parallel activation of de novo lipogenesis and stearoyl-CoA desaturase activity after 3 d of high-carbohydrate feeding.
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.


METHODS
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-(13)C]palmitate was given to trace dietary fatty acid incorporation into VLDL-triacylglycerol (TG). The conversion of intravenously infused [(2)H(2)]palmitic acid to [(2)H(2)]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.


CONCLUSIONS
Parallel activation of DNL and SCD was found after a short period of HC feeding.
Chong
Mary F-F
MF
Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom.
Hodson
Leanne
L
Bickerton
Alex S
AS
Roberts
Rachel
R
Neville
Matt
M
Karpe
Fredrik
F
Frayn
Keith N
KN
Fielding
Barbara A
BA
D000328:Adult; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D003903:Deuterium; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis* / Q000378:metabolism; D005260:Female; D006801:Humans; D050155:Lipogenesis / Q000187:drug effects / Q000502:physiology*; D008079:Lipoproteins, VLDL / Q000097:blood / Q000737:chemistry; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D013230:Stearoyl-CoA Desaturase / Q000187:drug effects / Q000378:metabolism*; D050151:Subcutaneous Fat / Q000098:blood supply / Q000737:chemistry; D014280:Triglycerides / Q000097:blood / Q000737:chemistry
D002247:Carbon Isotopes; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005227:Fatty Acids; D008079:Lipoproteins, VLDL; D014280:Triglycerides; C030106:very low density lipoprotein triglyceride; D003903:Deuterium; D013230:Stearoyl-CoA Desaturase