Reduced oxidation of dietary fat after a short term high-carbohydrate diet.
BACKGROUND
Short-term high-carbohydrate (HC) diets induce metabolic alterations, including hypertriacylglycerolemia, in both the fasting and postprandial states. The underlying tissue-specific alterations in fatty acid metabolism are not well understood.


OBJECTIVE
We investigated alterations in exogenous and endogenous fatty acid metabolism by using stable isotope tracers to label meal triacylglycerol and plasma fatty acids.


METHODS
Eight healthy subjects consumed isocaloric diets containing a high percentage of energy from carbohydrates or a higher percentage of energy from fat for 3 d in a randomized crossover dietary intervention study. A test meal containing [U-13C] palmitate was combined with intravenous infusion of [2H2] palmitate to label plasma fatty acids and VLDL triacylglycerol. Blood and breath samples were taken before the meal and for 6 h postprandially. Blood samples were drawn from the femoral artery and from veins draining subcutaneous adipose tissue and forearm muscle for monitoring of tissue-specific metabolic substrate partitioning.


RESULTS
Systemic triacylglycerol concentrations were increased in both fasting (P = 0.02) and postprandial (P = 0.02) periods, and a greater amount of infused labeled fatty acid appeared in VLDL triacylglycerol after the HC diet than after the higher-fat diet (P = 0.05). Significantly less 13CO2 was exhaled after the HC diet (P = 0.04) and significantly less production of 13CO2 was seen across forearm muscle (P = 0.04). Systemic 3-hydroxybutyrate was significantly lower, postprandially, after the HC diet (P = 0.02).


CONCLUSIONS
Metabolic alterations suggestive of repartitioning of fatty acids away from oxidation toward esterification in both liver and muscle occur in response to short-term adaptation to a HC diet.
Roberts
Rachel
R
Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom.
Bickerton
Alex S
AS
Fielding
Barbara A
BA
Blaak
Ellen E
EE
Wagenmakers
Anton J
AJ
Chong
Mary F-F
MF
Gilbert
Marjorie
M
Karpe
Fredrik
F
Frayn
Keith N
KN
D000222:Adaptation, Physiological; D000328:Adult; D001944:Breath Tests; D002247:Carbon Isotopes; D018592:Cross-Over Studies; D003903:Deuterium; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005215:Fasting / Q000097:blood; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D006801:Humans; D015228:Hypertriglyceridemia / Q000209:etiology; D008079:Lipoproteins, VLDL / Q000097:blood; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010084:Oxidation-Reduction; D019518:Postprandial Period; D014280:Triglycerides / Q000097:blood*
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