A study to evaluate surrogate markers of insulin resistance in forty euglycemic healthy subjects.

OBJECTIVE

Insulin resistance (IR) is increasingly being recognized as an important pathophysiological determinant of not only diabetes but also a number of other clinical states. Methods for directly estimating IR like euglycemic clamp technique and Insulin suppression test (IST) are experimentally demanding and impractical tool for large scale epidemiological studies. We evaluated several surrogate markers of IR in 40 healthy subjects.

METHODS

Study included 40 euglycemic normal healthy north Indian subjects (33 males, 7 females) of mean +/- SD age 38.9 +/- 8.6 yrs, BMI 20.5 +/- 3.6 kg/m2 and WHR 0.87 +/- 0.05. All subjects were tested for fasting and postprandial (2 hr post 75 gm glucose) glucose and insulin. Then all the subjects underwent IST by modified Harano's method (simultaneous infusion of 20% dextrose @ 6mg/kg/min and plain human insulin @ 50 mU/kg/hr). Metabolic clearance rate for glucose (MCR = glucose infusion rate/steady state plasma glucose, ml/kg/min) was calculated for 120-150 min of infusion. Correlation of MCR with various surrogate markers which included fasting glucose (FG), fasting insulin (FI), fasting glucose/insulin ratio (FGIR), 120 min glucose (PPG), 120 min insulin (PPI), 120 min glucose/insulin ratio (PPGIR), homeostatic model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), fasting glucose insulin product (FIGP), insulin sensitivity index (ISI), fasting insulin resistance index (FIRI), insulin ratio (IRa) and insulinogenic index (II) were evaluated.

RESULTS

MCR was found to be significantly (p <0.05) correlated with FI (r= -0.347), PPI (r= -0.402), PPG (r= -0.317), PPGIR (r= 0.356), HOMA-IR (r= -0.348), FIGP (r= -0.348), and FIRI (r= -0.348).

CONCLUSIONS

Among the surrogate markers which were significantly correlated to MCR, there was no significant superiority of one marker over the other. We suggest that measuring insulin levels alone in a single fasting sample can serve as a simple, cheap and convenient indirect qualitative index of IR.