Effects of dietary protein on lipid metabolism in high fructose fed humans.
OBJECTIVE
It has been reported that a high protein diet improves insulin sensitivity and reduces ectopic lipids in animals and humans with the metabolic syndrome. We therefore tested the hypothesis that a high dietary protein content may stimulate whole body lipid oxidation and alter post-prandial triglyceride (TG) after fructose ingestion.


METHODS
The post-prandial metabolism of 8 young males was studied after two 6-day periods of hyper-energetic, high fructose diet (HiFruD), and after two 6-day periods of hyper-energetic high fructose high protein diet (HiFruHiProD). The order with which these periods were applied was randomized. At the end of each period, either a low protein, (13)C fructose test meal (Fru meal) or a high protein, (13)C fructose test meal (HiPro Fru meal) was administered. This resulted in the monitoring of metabolic parameters at 4 occasions in random order: a) with Fru meal ingested after HiFruD, b) with HiPro Fru meal ingested after HiFruD, c) with Fru meal ingested after HiFruHiProD or d) with HiPro Fru meal ingested after HiFruHiProD. On each occasion, post-prandial TG concentrations were monitored, energy expenditure and substrate metabolism were measured by indirect calorimetry, and fructose-induced gluconeogenesis was evaluated by measuring plasma (13)C-labeled glucose.


RESULTS
TG responses to fructose ingestion were significantly higher after a hyper-energetic HiFruHiProD and after HiPro Fru meals than after a Fru meal ingested after a hyper-energetic HiFruD. Compared to low protein meals, high protein meals increased post-prandial energy expenditure, inhibited post-prandial lipid oxidation, and enhanced fructose-induced gluconeogenesis. These effects were similar with HiFruD and HiFruHiProD.


CONCLUSIONS
Dietary proteins did not increase lipid oxidation and increased fructose-induced post-prandial TG in healthy humans fed an hyper-energetic, high fructose diet.
Department of Physiology, University of Lausanne, 7 rue du Bugnon, 1005 Lausanne, Switzerland. murielle.bortolotti@unil.ch
Murielle
M
Bortolotti
Julien
J
Dubuis
Philippe
P
Schneiter
Luc
L
Tappy
D001786:Blood Glucose / Q000032:analysis; D002153:Calorimetry, Indirect; D018592:Cross-Over Studies; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage*; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005632:Fructose / Q000008:administration & dosage* / Q000378:metabolism; D005934:Glucagon / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D050356:Lipid Metabolism / Q000187:drug effects*; D008297:Male; D019518:Postprandial Period / Q000187:drug effects; D014280:Triglycerides / Q000097:blood*; D055815:Young Adult
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D005632:Fructose; D005934:Glucagon