Carbohydrate Ingestion Augments L-carnitine Retention in Humans

J Appl Physiol (1985). 2007 Mar;102(3):1065-70. doi: 10.1152/japplphysiol.01011.2006. Epub 2006 Nov 30.

Abstract

Maintaining hyperinsulinemia (approximately 150 mU/l) during steady-state hypercarnitinemia (approximately 550 micromol/l) increases skeletal muscle total carnitine (TC) content by approximately 15% within 5 h. The present study aimed to investigate whether an increase in whole body carnitine retention can be achieved through L-carnitine feeding in conjunction with a dietary-induced elevation in circulating insulin. On two randomized visits (study A), eight men ingested 3 g/day L-carnitine followed by 4 x 500-ml solutions, each containing flavored water (Con) or 94 g simple sugars (glucose syrup; CHO). In addition, 14 men ingested 3 g/day L-carnitine followed by 2 x 500 ml of either Con or CHO for 2 wk (study B). Carbohydrate ingestion in study A resulted in a fourfold greater serum insulin area under the curve when compared with Con (P < 0.001) and in a lower plasma TC concentration throughout the CHO visit (P < 0.05). Twenty-four-hour urinary TC excretion in the CHO visit was lower than in the Con visit in study A (155.0 +/- 10.7 vs. 212.1 +/- 17.2 mg; P < 0.05). In study B, daily urinary TC excretion increased after 3 days (65.9 +/- 18.0 to 281.0 +/- 35.0 mg; P < 0.001) and remained elevated throughout the Con trial. During the CHO trial, daily urinary TC excretion increased from a similar basal value of 53.8 +/- 9.2 to 166.8 +/- 17.3 mg after 3 days (P < 0.01), which was less than during the Con trial (P < 0.01), and it remained lower over the course of the study (P < 0.001). The difference in plasma TC concentration in study A and 24-h urinary TC excretion in both studies suggests that insulin augmented the retention of carnitine in the CHO trials.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Carnitine / administration & dosage
  • Carnitine / metabolism*
  • Dietary Carbohydrates / administration & dosage
  • Dietary Carbohydrates / metabolism*
  • Dietary Supplements
  • Eating
  • Energy Metabolism
  • Humans
  • Insulin / blood*
  • Male
  • Muscle, Skeletal / metabolism*

Substances

  • Dietary Carbohydrates
  • Insulin
  • Carnitine