Predictors of insulin sensitivity in Type 2 diabetes mellitus.
OBJECTIVE
To identify the independent predictors of insulin sensitivity in Type 2 diabetes, and to establish whether isolated Type 2 diabetes (i.e. diabetes without overweight, dyslipidaemia and hypertension) is a condition of insulin resistance.


METHODS
We examined 45 patients with non-insulin-treated Type 2 diabetes undergoing a 4-h euglycaemic hyperinsulinaemic clamp (20 mU/m2 per min) combined with 3H-3-D-glucose and 14C-U-glucose infusions and indirect calorimetry. We also examined 1366 patients with non-insulin-treated Type 2 diabetes randomly selected among those attending the Diabetes Clinic and in whom insulin resistance was estimated by Homeostasis Model Assessment (HOMA-IR).


RESULTS
In the 45 patients undergoing glucose clamp studies, insulin-mediated total glucose disposal (TGD) was independently and negatively associated with systolic blood pressure (standardized beta coefficient = -0.407, P = 0.003), plasma triglycerides (beta= -0.355, P = 0.007), and HbA1c (beta= -0.350, P = 0.008). The overall variability of TGD explained by these variables was 53%. Overweight diabetic subjects with central fat distribution, hypertension, hypertriglyceridaemia and poor glycometabolic control had insulin-mediated TGD values markedly lower than their lean counterparts without hypertension, with normal triglycerides, and with good glycometabolic control (16 +/- 5 vs. 31 +/- 10 micromol/min per kg lean body mass, P < 0.01). Nevertheless, the latter still were markedly insulin-resistant when compared with sex- and age-matched non-diabetic control subjects (31 +/- 10 vs. 54 +/- 13 micromol/min per kg lean body mass, P < 0.01). In the 1366 Type 2 diabetic patients of the epidemiological study, HOMA-IR value was independently associated with HbA1c (beta = 0.283, P < 0.0001), plasma triglycerides (beta = 0.246, P < 0.0001), body mass index (beta = 0.139, P < 0.001), waist girth (beta = 0.124, P < 0.001) and hypertension (beta = 0.066, P = 0.006).


CONCLUSIONS
Overweight, central fat distribution, dyslipidaemia, hypertension and poor glycometabolic control are strong independent predictors of insulin resistance in Type 2 diabetes. However, reduced insulin sensitivity can be found even when Type 2 diabetes is isolated and well controlled.
Bonora
E
E
Division of Endocrinology and Metabolic Diseases, University of Verona Medical School, Italy. enbonor@tin.it
Targher
G
G
Alberiche
M
M
Formentini
G
G
Calcaterra
F
F
Lombardi
S
S
Marini
F
F
Poli
M
M
Zenari
L
L
Raffaelli
A
A
Perbellini
S
S
Zenere
M B
MB
Saggiani
F
F
Bonadonna
R C
RC
Muggeo
M
M
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D008076:Cholesterol, HDL / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000503:physiopathology; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000503:physiopathology; D015228:Hypertriglyceridemia / Q000097:blood / Q000503:physiopathology; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000503:physiopathology; D011237:Predictive Value of Tests; D012044:Regression Analysis
D001786:Blood Glucose; D008076:Cholesterol, HDL