Assessment of insulin resistance in normoglycemic young adults

Abstract

Detection of Insulin resistance (IR) in normoglycemic young subjects before the onset of Impaired Glucose Tolerance (IGT) is of importance as it affords implementation of preventive measures in such high risk subject. Very few studies have specifically evaluated for the presence of IR in younger age group with normal glucose tolerance. The gold standard for investigating and quantifying insulin resistance is the "hyperinsulinemic euglycemic clamp," the complicated nature of the "clamp" technique, alternatives have been sought to simplify the measurement of insulin resistance. The oral glucose tolerance test (OGTT) is one of the most commonly used methods to evaluate whole body glucose tolerance in vivo. IR & IS values of HOMA-IR, ISI 0-120, QUICKIE mathematical models derived from OGTT have been shown to produce equivalent results as in Euglycemic clamp technique we hypothesized that normoglycemic young adult who are siblings of type II diabetics (SD) probably have higher IR values than the siblings of non diabetics as they are genetically predisposed. In this study 79 normal young adult volunteers, 40 subjects with family history of diabetes (SD) and 39 subjects without family history of diabetes (SND), in the age range of 18 to 25 years were evaluated for Insulin resistance. Standard (75 g) OGTT was performed on all the study subjects after an overnight fast. Fasting (basal), 30, 120 min venous plasma glucose & Corresponding specific insulin concentration was determined by radioimmuno assay (RIA) using a human specific antibody RIA kit. In each subject, the degree of insulin resistance was estimated by various parameters of Insulin resistance & sensitivity that were calculated using physiological mathematical models like HOMA-IR, ISI0-120, IGI, QUICKIE and their formulas derived from OGTT. The mean age of the study population was 19.01 (18 to 25 years), Male: 33 (41.3%) and Female: 47 (58.8%). The normoglycemic subjects were categorized as Siblings of Diabetics (SD n = 40) and siblings of non-diabetics(SND n = 39). Both the groups were matched by physical, clinical and routine laboratory parameters and were not statistically significant different. Siblings of diabetics had a statistically significant higher values of insulin at baseline, 30 min & 120 minutes and glucose at 30 minutes. Siblings of diabetics had a significantly higher insulin resistance and lower insulin sensitivity indices as in HOMA-IR (2.01527, p < 0.017), ISIO-120 (56.27, p < 0.002) and I0/G0 ratio (0.122381, p < 0.012) and a trend towards significance for QUICKIE(0.29578, p < 0.056). Detection of insulin resistance in normoglycemic young adult subjects in pre-disease state is feasible using mathematical models like HOMA IR, ISIO-120 from OGTT. OGTT is simple and a generally acceptable test. Siblings of diabetics had higher Insulin resistance values and lower Insulin sensitivity values. Physiological models like HOMA IR, QUICKIE, I0/G0 ratio, IGI, ISIO-120 are simple & cost effective method for screening Insulin resistance. Diagnosis of Insulin resistance in pre-disease state allows initiation of preventive measures like life style modification, diet & exercise, thereby preventing the high risk subjects from progressing to disease state.