Creatine may not aid insulin sensitivity: Rat study
The study, published in The Journal of Nutritional Biochemistry, claims to be the first to demonstrate that creatine supplementation blocks the accumulation of intramyocellular lipid content (IMCL) from a sugar-rich so called ‘cafeteria diet’, which provides the majority of its energy from sugars rather than carbohydrates.
However, the authors, from the Katholieke Universiteit Leuven (K.U. Leuven), Belgium, said that this effect does not lead to the improvement in insulin sensitivity, unlike exercise induced IMCL reductions.
“We show that creatine intake was effective to prevent intramyocellular lipid (IMCL) accumulation during cafeteria diet but failed to beneficially impact on insulin-stimulated muscle glucose transport or whole body insulin sensitivity,” said the authors, led by Morad Vaisy, from the Research Centre for Exercise and Health, at K.U. Leuven.
They added that the results “clearly demonstrate that exercise-induced, but not creatine-induced reduction of IMCL, is associated with improved insulin action on glucose transport in muscle cells.”
Vaisy and colleagues reported that creatine has become one of the most popular nutritional supplements to boost performance in athletes.
As such, they said that the beneficial effects of creatine supplementation in healthy individuals are well documented and have triggered interest in the potential of creatine as a therapeutic agent to improve muscular function in other populations such as the elderly or patients afflicted by neuromuscular disease.
“Theoretically, creatine supplementation could [also] improve whole body glucose homeostasis either by stimulating pancreatic insulin secretion or by facilitating peripheral glucose disposal,” explained the authors.
This idea has been supported by previous research data indicating that creatine intake can beneficially impact glucose metabolism and may affect insulin sensitivity.
The new study investigated the effects of creatine supplementation, alone or in combination with exercise training, on whole body glucose homeostasis and muscular insulin sensitivity in rats receiving a sucrose-rich cafeteria diet – which is known to induce obesity and a state of glucose intolerance and muscular insulin resistance.
“Interestingly, the addition of creatine to the cafeteria diet was very potent to preventing diet-induced IMCL accumulation in any muscle type,” said the authors.
Moreover, they reported that in rats performing exercise training, creatine intake even caused IMCL to drop below values measured in control rats on a normal diet.
The effect of creatine to inhibit IMCL during the cafeteria diet, however, did not reduce insulin sensitivity of muscle glucose transport.
“Administration of cafeteria diet for 12 weeks caused insulin resistance at whole body level and at the site of skeletal muscle glucose transport, and only 4 weeks of exercise training during the final stage of the dietary intervention period were needed to offset insulin resistance,” said the researchers.
“However, in contrast with exercise, creatine supplementation did not rescue insulin-stimulated muscle glucose transport,” they added.
Viasy and co-workers concluded that creatine supplementation showed benefit for improvement in IMCL, but “is not an effective intervention to prevent the development of muscular insulin resistance.”
Source: The Journal of Nutritional Biochemistry
Published online ahead of print, doi: 10.1016/j.jnutbio.2010.10.004
“Exercise-induced, but not creatine-induced, decrease in intramyocellular lipid content improves insulin sensitivity in rats”
Authors: M. Vaisy, K. Szlufcik, K. De Bock, B.O. Eijnde, K. Van Proeyen, K. Verbeke, et al