Effects of D-beta-hydroxybutyrate and long- and medium-chain triglycerides on leucine metabolism in humans.
Ketone bodies and/or fatty acids might play a protein-sparing role during prolonged fasting or parenteral nutrition. To assess this problem, we studied whole body leucine metabolism, using L-[1-13C]leucine in normal postabsorptive volunteers who received either long-chain triglycerides (LCT, 0.15 g.kg-1.h-1, 6 subjects), a 50-50 mixture of medium-chain triglycerides (MCT) and LCT (0.15 g.kg-1.h-1, 6 subjects), D-beta-hydroxybutyrate (540 mumol.kg-1.h-1, 6 subjects), or saline (4 subjects). Leucine concentration decreased only with MCT-LCT. Leucine flux decreased by 10-20% from basal in all groups. Leucine oxidation, which was corrected for the contribution to 13CO2 of the 13C natural abundance of the infused substrates, decreased during LCT infusion (0.31 +/- 0.02 to 0.24 +/- 0.01 mumol.kg-1.min-1, P less than 0.01), but was unaffected by MCT-LCT (despite plasma free fatty acid levels similar to those obtained with LCT), D-beta-hydroxybutyrate, or saline infusion. Therefore, 1) the effect of fatty acids on amino acid oxidation is not mediated by ketone bodies, 2) it depends on the fatty acid chain length, 3) long-chain fatty acids but not medium-chain fatty acids could play a protein-sparing role during parenteral nutrition.
Beaufrère
B
B
Institut National de la Santé et de la Recherche Medicale U. 197, Faculté de Médecine Alexis Carrel, Lyon, France.
Chassard
D
D
Broussolle
C
C
Riou
J P
JP
Beylot
M
M
D020155:3-Hydroxybutyric Acid; D000328:Adult; D001639:Bicarbonates / Q000097:blood; D002096:C-Peptide / Q000097:blood; D002247:Carbon Isotopes; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood; D006801:Humans; D006885:Hydroxybutyrates / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D007700:Kinetics; D007930:Leucine / Q000097:blood*; D008297:Male; D010084:Oxidation-Reduction; D012016:Reference Values; D012964:Sodium / Q000097:blood; D017693:Sodium Bicarbonate; D013329:Structure-Activity Relationship; D014280:Triglycerides / Q000494:pharmacology*
D001639:Bicarbonates; D002096:C-Peptide; D002247:Carbon Isotopes; D005230:Fatty Acids, Nonesterified; D006885:Hydroxybutyrates; D007328:Insulin; D014280:Triglycerides; D017693:Sodium Bicarbonate; D005934:Glucagon; D012964:Sodium; D007930:Leucine; D020155:3-Hydroxybutyric Acid