Effects of an oral mixture containing glycine, glutamine and niacin on memory, GH and IGF-I secretion in middle-aged and elderly subjects.
Aging is associated with declining activity of the growth hormone-insulin-like growth factor-I (GH-IGF-I) axis and with a decrease in cognitive function. The stimulatory effect of an orally administered nutritional supplement, mainly containing glycine, glutamine and niacin on the GH-IGF-I axis and on mood and cognition was investigated. Forty-two healthy subjects (14 men and 28 women, aged 40-76 years) were enrolled in a randomised, double blind, placebo-controlled trial. They received 5 g of a nutritional supplement or placebo, twice daily orally for a period of 3 weeks. At baseline and after 3 weeks, blood was collected for measurement of serum GH and IGF-I levels and mood and cognitive function were tested. The nutritional supplement ingestion for 3 weeks was found to increase serum GH levels with 70% relatively to placebo, whereas circulating IGF-I levels did not change. Mean GH (+/- SD) increased in this group from 3.23 (+/- 4.78) to 4.67 mU/l (+/- 5.27) (p = 0.03). GH increase was not associated with improvement in mood or memory. Correlation analyses, however, revealed that individual increases in IGF-I, but not GH, were associated with improved memory and vigour. It is concluded that an oral mixture of glycine, glutamine and niacin can enhance GH secretion in healthy middle-aged and elderly subjects.
Arwert
L I
LI
Department of Endocrinology, VU University Medical Center, de Boelelaan 1117, 1081 HVAmsterdam, The Netherlands.
Deijen
J B
JB
Drent
M L
ML
D000284:Administration, Oral; D000328:Adult; D000339:Affect; D000368:Aged; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005973:Glutamine / Q000008:administration & dosage / Q000494:pharmacology*; D005998:Glycine / Q000008:administration & dosage / Q000494:pharmacology*; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D009525:Niacin / Q000008:administration & dosage / Q000494:pharmacology*; D010919:Placebos
D010919:Placebos; D005973:Glutamine; D019382:Human Growth Hormone; D009525:Niacin; D007334:Insulin-Like Growth Factor I; D005998:Glycine