Dietary Sugars Stimulate Fatty Acid Synthesis in Adults123

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Abstract

The goal of this study was to determine the magnitude by which acute consumption of fructose in a morning bolus would stimulate lipogenesis (measured by infusion of 13C1-acetate and analysis by GC-MS) immediately and after a subsequent meal. Six healthy subjects [4 men and 2 women; aged (mean ± SD) 28 ± 8 y; BMI, 24.3 ± 2.8 kg/m2; and serum triacylglycerols (TG), 1.03 ± 0.32 mmol/L] consumed carbohydrate boluses of sugars (85 g each) in a random and blinded order, followed by a standardized lunch 4 h later. Subjects completed a control test of glucose (100:0) and a mixture of 50:50 glucose:fructose and one of 25:75 (wt:wt). Following the morning boluses, serum glucose and insulin after 100:0 were greater than both other treatments (P < 0.05) and this pattern occurred again after lunch. In the morning, fractional lipogenesis was stimulated when subjects ingested fructose and peaked at 15.9 ± 5.4% after the 50:50 treatment and at 16.9 ± 5.2% after the 25:75 treatment, values that were greater than after the 100:0 treatment (7.8 ± 5.7%; P < 0.02). When fructose was consumed, absolute lipogenesis was 2-fold greater than when it was absent (100:0). Postlunch, serum TG were 11–29% greater than 100:0 and TG-rich lipoprotein-TG concentrations were 76–200% greater after 50:50 and 25:75 were consumed (P < 0.05). The data demonstrate that an early stimulation of lipogenesis after fructose, consumed in a mixture of sugars, augments subsequent postprandial lipemia. The postlunch blood TG elevation was only partially due to carry-over from the morning. Acute intake of fructose stimulates lipogenesis and may create a metabolic milieu that enhances subsequent esterification of fatty acids flowing to the liver to elevate TG synthesis postprandially.

Abbreviations

AUC
area under the curve
CHO
carbohydrate
iAUC
incremental area under the curve
GCRC
General Clinical Research Center
MIDA
mass isotopomer distribution analysis
Sf
Svedberg flotation rate
TG
triacylglycerol
tTRL
total triacylglycerol-rich lipoprotein
100:0
a mixture of 100% glucose and 0% fructose wt:wt
75:25
75:25 glucose: fructose wt:wt
50:50
50:50 glucose:fructose wt:wt

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1

Supported by grants from the NRC Resources/NIH General Clinical Research Center Program (M01-RR00400) at the University of Minnesota, and unrestricted research funds from the Cargill Higher Education Fund and the Sugar Association.

2

Author disclosures: E. J. Parks, L. E. Skokan, M. T. Timlin, and C. S. Dingfelder, no conflicts of interest.