Résumé :
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BackgroundInsulin resistance (IR) is a characteristic feature of dysglycaemia in myotonic dystrophy type 1 (DM1). Although the abnormal splicing of insulin receptor mRNA in DM1 muscles reported, the mechanism of IR remained obscure. The aim of this study was to investigate liver and muscle IR in DM1 by means of some indexes derived from oral glucose tolerance test (OGTT), compared with age and body mass index (BMI) matched controls.MethodsSeventy-seven non-diabetic patients with DM1 (the median value: age; 47 years, BMI; 22.4, the number of CTG repeat; 1467) were classified into the normal glucose response group (NGTDM1) and the impaired glucose tolerance group (IGTDM1) by 75g OGTT. For age and BMI matched controls, 100 normal glucose response subjects (NGTCT) and 130 impaired glucose tolerance cases (IGTCT) were picked up from our diabetic database. Liver and muscle insulin resistance indexes derived from OGTT supposed by Abdul-Ghani et al were calculated: AUCgi30 for liver; glucose0-30[AUC] x insulin0-30[AUC], dG/dt/I for muscle; the rate of decay of plasma glucose concentration from its peak value to its nadir during OGTT divided by the mean plasma insulin concentration, AUC; area under curve. AUCgi30, dG/dt/I, during OGTT, fasting plasma glucose (FPG) and insulin (FIRI), plasma glucose (PG120) and insulin (IRI120) level at 120 minutes after oral glucose load, and Insulinogenic-Index (I-I) in each group were statistically analyzed.ResultsThere was no significant difference between NGTDM1 and NGTCT for AUCgi30 or dG/dt/I. I-I in NGTDM1 was significantly lower than that in NGTCT. FPG and PG120 in NGTDM1 were significantly lower than those in NGTCT, whereas there was no significant difference in FIRI and IRI120. AUCgi30 in IGTDM1 was significantly higher than that in IGTCT, and dG/dt/I in IGTDM1 was significantly lower. I-I in IGTDM1 was also significantly lower than that in IGTCT. FPG in IGTDM1 was significantly lower than that in IGTCT. There was no significant difference between IGTDM1 and IGTCT for PG120, FIRI and IRI120.ConclusionsDM1 patients with impaired glucose tolerance showed liver IR as well as muscle IR. Lower I-I in DM1 could represent abnormality of insulin secretion. Lower FPG should be noticed as one of interesting features in early stage of dysglycaemia in DM1. Our data suggested IR in DM1 might result in multiple metabolic defects. Different mechanism of impaired glucose regulation in DM1 from that of type 2 Diabetes seemed exists.
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