Differences in Plasma Insulin Responses in Urban and Rural Indians: A Study in Southern-Indians

Abstract

Fasting and 2 h post glucose plasma immunoreactive insulin (fasting IRI and 2 h IRI) responses were measured in urban (n = 149) and rural (n = 40) individuals with normal glucose tolerance during an epidemiological survey. In this survey, 900 urban and 1038 rural subjects were screened for glucose intolerance by capillary blood sampling. The respective response rates were 91% and 88%. We had planned to collect venous blood for IRI estimation, i.e. from 180 urban and 200 rural subjects. The compliance for the same was poor from the rural subjects and therefore the number available for IRI estimation was small. The mean ± SD ages of the urban and rural groups were similar (35.3 ± 9.9 and 38.6 ± 13.1 years, respectively). The rural population had lower body mass index (BMI) and subscapular:triceps ratio compared to the urban group (p < 0.001). The total calorie consumption was lower and physical activity was higher in rural population. Fasting and 2 h insulin values in urban population were 16.6 ± 9.4 mU I⁻¹ and 60.6 ± 42.5 mU I⁻¹ and in rural 6.7 ± 5.1 mU I⁻¹ and 32.4 ± 27.8 mU I⁻¹, respectively; the values being significantly lower in the rural population (p < 0.001). Multiple regression analysis showed that in urban population the fasting insulin was correlated to the BMI and the 2h IRI to 2 h glucose, BMI and the subscapular:triceps ratio. In the rural population, similar results were obtained, except in that the 2 h IRI was influenced by the gender also. This study showed that the fasting IRI and 2 h IRI responses in normoglycaemic urban and rural populations differed widely, probably related to the differences in body mass and adiposity distribution. The higher IRI concentrations in normoglycaemic urban subjects suggest a relative insulin resistance and this may be a contributory factor for the higher prevalence of diabetes in urban Indians.