British Journal of Nutrition

Research Article

Carbohydrate-induced manipulation of insulin sensitivity independently of intramyocellular lipids

Louise M. Goffa1a2, Gary S. Frosta2 c1, Gavin Hamiltona1, E. Louise Thomasa1, Waljit S. Dhilloa3, Anne Dornhorsta3 and Jimmy D. Bella1

a1 MRC MRI Unit, Clinical Sciences Centre, Division of Investigative Science, Hammersmith Hospital, Imperial College School of Medicine, London W12 0HS, UK

a2 Department of Nutrition & Dietetics, Division of Investigative Science, Hammersmith Hospital, Imperial College School of Medicine, London W12 0HS, UK

a3 Department of Metabolic Medicine, Division of Investigative Science, Hammersmith Hospital, Imperial College School of Medicine, London W12 0HS, UK

Abstract

Subjects with insulin resistance have been shown to have higher storage levels of intramyocellular lipid (IMCL) than their insulin-sensitive counterparts. It has been proposed that elevated IMCL stores may be the main cause of insulin resistance. The aim of the present study was to ascertain whether there is a causal relationship between IMCL storage and insulin resistance. IMCL storage was assessed using magnetic resonance spectroscopy and insulin sensitivity was assessed by performing an oral glucose tolerance test. A 4-week intervention of reduction of dietary glycaemic index was used to manipulate insulin sensitivity in a cohort of healthy volunteers; the effects of this intervention on IMCL were measured after 4 weeks of intervention. Significant improvements in the insulin sensitivity index occurred following the dietary intervention (baseline 7·8 (sem 1·11) v. post-intervention 9·7 (sem 1·11), P=0·02). However, there were no changes in IMCL storage levels, suggesting that insulin sensitivity can be manipulated independently of IMCL. This suggests that in healthy volunteers, insulin sensitivity is independent of IMCL storage and the high storage levels that have been found in insulin-resistant subjects may occur as a consequence rather than a cause of insulin resistance.

(Received February 06 2002)

(Revised October 09 2002)

(Accepted October 21 2002)

Correspondence:

c1 *Corresponding author: Dr Gary S. Frost, fax +44 20 8383 3379, email gfrost@ic.ac.uk

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