Effect of zinc supplementation on protein metabolism in late-middle-aged men: The Zenith study.
OBJECTIVE
Zinc (Zn) is an essential trace element that is a potent enhancer of protein metabolism due to its numerous roles in metabolic processes. Protein turnover decreases with age. We determined whether a Zn supplementation, which increases serum Zn concentration and Zn exchangeable pool mass, modifies whole-body protein turnover and albumin and fibrinogen synthesis rates in late-middle-aged men.


METHODS
Three groups of 16 healthy subjects 55-70 y of age participated in a randomized, doubled-blinded, placebo-controlled intervention. Each group received 0, 15, or 30 mg/d of supplemental Zn for 6 mo. At the end of the supplementation period, each subject received an intravenous infusion of L-[1-13C] leucine to quantify whole-body leucine fluxes and synthesis rates of albumin and fibrinogen.


RESULTS
In the placebo group, mean +/- SEM whole-body leucine fluxes to protein synthesis, to oxidation, and from protein degradation were 1.46 +/- 0.05, 0.40 +/- 0.01, and 1.73 +/- 0.06 micromol.kg(-1).min(-1), respectively. Zn supplementation did not significantly change whole-body leucine fluxes. In the placebo group, plasma concentration and fractional rate of protein synthesis were 45 +/- 1 g/L and 8.2 +/- 0.6%/d for albumin and 3.6 +/- 0.2 g/L and 16.7 +/- 1.3%/d for fibrinogen, respectively. Zn supplementation did not significantly change these parameters or the absolute rates of synthesis of these proteins.


CONCLUSIONS
Increasing Zn supply does not modify whole-body protein metabolism and synthesis rates of albumin and fibrinogen in late-middle-aged men.
Papet
Isabelle
I
INRA, Centre Clermont-Ferrand-Theix, UMR 1019 Unité de Nutrition Humaine, Saint-Genès-Champanelle, France. papet@clermont.inra.fr <papet@clermont.inra.fr>
Meunier
Nathalie
N
Béchereau
Fabienne
F
Glomot
Françoise
F
Obled
Christiane
C
Coudray
Charles
C
D000368:Aged; D000375:Aging / Q000187:drug effects / Q000378:metabolism; D000418:Albumins / Q000187:drug effects / Q000378:metabolism; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D002247:Carbon Isotopes; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005340:Fibrinogen / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011506:Proteins / Q000187:drug effects / Q000378:metabolism*; D014131:Trace Elements / Q000494:pharmacology*; D015032:Zinc / Q000494:pharmacology*
D000418:Albumins; D015415:Biomarkers; D002247:Carbon Isotopes; D011506:Proteins; D014131:Trace Elements; D005340:Fibrinogen; D007930:Leucine; D015032:Zinc