Carbohydrate-induced manipulation of insulin sensitivity independently of intramyocellular lipids

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), P¼0·02). 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.

A prospective randomised trial to determine the efficacy of a low glycaemic index diet given in addition to healthy eating and weight loss advice in patients with coronary heart disease

“…This may be important as most breads sold in the UK have HGI. This drop in GI of 20% was not achieved; however, new data from our centre have shown changes in insulin sensitivity, with a 15% decrease in dietary GI (Goff et al, 2003). Also, although the LGI group demonstrated a significantly lower GI after 12 weeks, there was no significant difference in the glycaemic load.…”

The influence of fasting insulin level in post-gestational diabetes mellitus women receiving low-glycaemic-index diets

“…Hence, even though a 15% difference in dietary GI between the groups (about 9 units based on baseline GI), thought to have clinical significance, 19 could not be achieved after 12 months of intervention, significant differences in FBG and TG were seen among subjects with high/normal INS levels. Nevertheless, it is also interesting to observe that much smaller differences in the GI (among the quintiles compared in observational studies), than the 10 GI unit difference thought to be of clinical significance, 19, 20 show significant reductions in cardio-metabolic risks.…”

Determining the relationship between dietary carbohydrate intake and insulin resistance

“…Indeed, a very recent systematic review of low-carbohydrate diets found that weight loss is associated with the duration of the diet and restriction of energy intake, but not the restriction of carbohydrates (Astrup et al 2004). Also, when considering the literature on dietary intervention studies it is important to consider that Studies in which low-GI diet was associated with improved metabolic control Fontvieille et al (1988) 8 T1DM Brand et al (1991 16 T1DM Fontvieille et al (1992) 18 DM Wolever et al (1992) 6 T2DM Frost et al (1994) 51 T2DM Behall & Howe (1995) 10 ND and 14 HI Howe et al (1996) 9 ND and 13 HI Frost et al (1996) 28 HD Frost et al (1998) 28 ND Jarvi et al (1999) 20 T2DM Wolever & Mehling (2002, 2003 34 IGT Brynes et al (2003) 17 ND Goff et al (2003) 21 ND Studies in which low-GI diet was associated with worsening of metabolic control Kiens & Richter (1996) 7 ND Studies in which low-GI diet had no association with metabolic control Calle-Pascual et al (1988) 35 DM Luscombe et al (1999) 21 T2DM Tsihlias et al (2000) 91 DM Herrmann et al (2001) 9 ND T1DM, type 1 diabetes mellitus; DM, diabetes mellitus; T2DM, type 2 diabetes mellitus; ND, non-diabetic; HI, hyperinsulinaemic; HD, heart disease; IGT, impaired glucose tolerance.…”