Effects of oral l-carnitine supplementation on insulin sensitivity indices in response to glucose feeding in lean and overweight/obese males
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 versus overweight/obese humans has not been examined. This study examined the effects of 14 days of 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 2 h OGTTs. The first visit was a familiarisation trial and the final two visits were conducted 2 weeks apart following 14 days of ingestion of placebo (PL, 3 g glucose/day) and then LC (3 g LC/day) ingested as two capsules 3×/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 min 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 min, but was significantly higher at 90 min (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 first phase and second 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 that 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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β-cell function tended to be greater following L-carnitine supplement in the lean group only.
“In fact, β-cell function tended to be greater following L-carnitine supplement in the lean group only [38].”
From The influence of obesity on the effects of spirulina supplementation in the human metabolic response of Korean elderly (2016) · cites this paper as [38]
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- Authors
- Galloway, S. D. R., Craig, T. P., & Cleland, S. J.
- Affiliations
- University of Stirling (GB)
- Stobhill Hospital (GB)
- Corresponding author
- Galloway, Stuart D. R.
- Venue
- Amino Acids
- Published
- 2010-10-21
- Volume
- 41
- Issue
- 2
- Pages
- 507-515
- ISSN
- 0939-4451 (ISSN-L)
- 1438-2199
- OpenAlex
- W2066945797
- Cited by
- 34
- References
- 36
- Citations by year
- 2025: 4 · 2023: 1 · 2022: 1 · 2021: 2 · 2019: 3 · 2018: 3 · 2017: 2 · 2016: 3 · 2015: 5 · 2014: 2 · 2013: 4
- FWCI
- 0.98
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- www.springer.com/tdm (tdm)
- Locations
- Amino Acids (publishedVersion)
- PubMed (publishedVersion)
- Stirling Online Research Repository (University of Stirling) (submittedVersion, public-domain)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes, Cardiovascular Risks, and Lipoproteins
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diet, Metabolism, and Disease
- Keywords
- L-carnitine, oral supplementation, insulin sensitivity, insulin resistance, glucose tolerance, beta-cell function, first-phase insulin secretion, second-phase insulin secretion, glucagon-like peptide-1, free fatty acids, overweight and obesity, metabolic clearance rate, HOMA-IR
- MeSH terms
- Adipose Tissue, Administration, Oral, Adolescent, Adult, Blood Glucose, Carnitine, Physical Exertion, Fatty Acids, Nonesterified, Glucose Tolerance Test, Humans, Insulin, Male, Metabolic Clearance Rate, Obesity, Body Mass Index, Dietary Supplements, Young Adult
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