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Appears in Collections:Faculty of Health Sciences and Sport Journal Articles
Peer Review Status: Refereed
Title: Effects of oral L-Carnitine supplementation on insulin sensitivity indices in response to glucose feeding in lean and overweight/obese males
Author(s): Galloway, S D
Craig, Thomas P
Cleland, Stephen J
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Keywords: carnitine
glucose disposal
Issue Date: 2011
Citation: Galloway SD, Craig TP & Cleland SJ (2011) Effects of oral L-Carnitine supplementation on insulin sensitivity indices in response to glucose feeding in lean and overweight/obese males, Amino Acids, 41 (2), pp. 507-515.
Abstract: Infusion of carnitine has been observed to increase non-oxidative glucose disposal in several studies but the effect of oral carnitine on glucose disposal in non-diabetic lean vs. overweight/obese humans has not been examined. This study examined the effects of 14 days L-Carnitine L-Tartrate oral supplementation (LC) on blood glucose, insulin, NEFA and GLP-1 responses to an oral glucose tolerance test (OGTT). Sixteen male participants were recruited (lean (n=8) and overweight/obese (n=8)). After completing a submaximal predictive exercise test, participants were asked to attend three experimental sessions. These three visits were conducted, in the morning to obtain fasting blood samples and to conduct 2hr OGTT’s. The first visit was a familiarisation trial and the final two visits were conducted two weeks apart following 14 days of ingestion of placebo (PL, 3g glucose/day) then LC (3g LC/day) ingested as 2 capsules 3x/day with meals. On each visit blood was drawn at rest, at intervals during the OGTT for analysis of glucose, insulin, non-esterified fatty acids (NEFA) and total glucagon-like peptide-1 (GLP-1). Data obtained were used for determination of usual insulin sensitivity indices (HOMA-IR, AUC glucose, AUC insulin, 1st phase and 2nd phase β-cell function, estimated insulin sensitivity index, and estimated metabolic clearance rate). Data were analysed using RMANOVA and post-hoc comparisons where appropriate. There was a significant difference between groups for body mass, % fat and BMI with no significant difference in age and height. Mean (SEM) plasma glucose concentration at 30 minutes was significantly lower (p < 0.05) in the lean group on the LC trial compared with PL (8.71(0.70) PL; 7.32(0.36) LC; mmol/L). Conversely, plasma glucose concentration was not different at 30 minutes but was significantly higher at 90 minutes (p < 0.05) in the overweight/obese group on the LC trial (5.09(0.41) PL; 7.11(0.59) LC; mmol/L). Estimated 1st phase and 2nd phase β-cell function both tended to be greater following LC in the lean group only. No effects of LC were observed on NEFA or total GLP-1 response to OGTT. It is concluded that LC supplementation induces changes in blood glucose handling/disposal during an OGTT which is not influenced by GLP-1. The glucose handling/disposal response to oral LC is different between lean and overweight/obese suggesting further investigation is required. LC effects on gastric emptying and/or direct ‘insulin-like’ actions on tissues should be examined in larger samples of overweight/obese and lean participants, respectively.
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Rights: Published in Amino Acids by Springer.; The original publication is available at

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