Marked differences in the IGF system that are associated with migration in comparable populations of Gujaratis living in Sandwell, UK, and Gujarat, India

Abstract

Aims/hypotheses: We previously reported independent links between the IGF system and the development of impaired glucose tolerance and cardiovascular risk. This study tests the hypothesis that the lifestyle change which accompanies population migration, with attendant increases in cardiovascular risk, is reflected by changes in the IGF system. Materials and methods: We compared a specific Gujarati community in Sandwell, UK (n=205), with people still resident in the same villages of origin near Navsari, India (n=246). We performed anthropometry and measured fasting plasma insulin, IGF-I, insulin-like growth factor binding protein (IGFBP)-1 and IGFBP-3. Results: Daily calorie intake, BMI and WHR were significantly higher in UK Gujaratis than in Indian Gujaratis. IGFBP-1 was significantly lower in UK migrants (mean 29.5 [95% CI 25.9-33.0] vs 56.5 [50.6-62.5]μg/l; F=48.4, p<0.001). Conversely, fasting insulin, IGFBP-3 and IGF-I were all higher in UK Gujaratis (mean IGF-I 145.9 [138.1-153.6]ng/ml in UK Gujaratis and 100.9 [94.6-107.3] ng/ml in Navsari Gujaratis; F=76.6, p<0.001). These differences were still apparent when adjustment was made for BMI by location for IGF-I (F=57.4, p<0.001) and IGFBP-3 (F=5.7, p=0.02), but were no longer apparent for IGFBP-1 and insulin. At the population level, the decrease in IGFBP-1 for a given increase in insulin was significantly smaller in UK Gujaratis, suggesting greater hepatic insulin resistance in this group. Conclusions/interpretation: Environmental factors have profound effects on circulating IGF system components and on the relationship between IGFBP-1, IGF-I and related metabolic variables. This may have long-term implications for the development of worsening glucose tolerance and cardiovascular disease.

Migration is associated with lower total, but not free testosterone levels in South Asian men

“…SHBG levels were also lower in Pakistani men, in keeping with their poorer insulin sensitivity and greater abdominal adiposity. In a separate cross‐sectional study of two Gujarati populations from the same site of origin (Gujarat, Northwest India), 6 we found marked differences in relation to migration in levels of circulating IGF‐I, IGFBP‐3 and IGFBP‐1. The significant cross‐site differences in individuals from the same extended families suggest that environmental exposure and lifestyle factors profoundly influence IGF‐I bioavailability, with potential implications for the risk of developing diabetes and cardiovascular disease in this population.…”

“…Twenty‐two per cent of Sandwell participants had migrated to the UK before puberty. The Gujarati men whose androgen levels are reported here are all those of Gujarati origin for whom serum was available for analysis from the Gujarati cross‐sectional sample on which we have reported previously 6 …”

Insulin Resistance and Truncal Obesity as Important Determinants of the Greater Incidence of Diabetes in Indian Asians and African Caribbeans Compared With Europeans

“…Changes in fat distribution over the life-course appear to differ by ethnicity (29,30). Although a genetic susceptibility may be an obvious explanation for ethnic differences in metabolic and obesity characteristics, and for the different trajectories over the life-course, it is notable that total energy intake is higher compared with British Europeans in largely first-generation Indian Asian migrants to the U.K. (35) and in Indian Asian children in the U.K. (36). Within India, migrants from rural to urban areas also have higher energy intakes compared with those of the rural population (37).…”

“…This is associated with greater obesity, ectopic fat distribution, and IR. Further, age-related changes in adverse patterns of IR are more marked in Indian Asian migrant populations compared with Indian Asian nonmigrant populations (35). Such rapid changes in metabolic characteristics are likely to be environmentally rather than genetically driven.…”

The insulin‐like growth factor system and diabetes—an overview

“…We found that the IGF system differed between three ethnic groups (European, African-Caribbean and Pakistani) and that there were significant modulating effects of dietary carbohydrate, fat and protein intake on IGF concentration [23]. Furthermore, in a recent study comparing a specific Gujarati community in Sandwell, UK, with people residing in the same villages of origin in India [24], we found that the environmental changes that accompany migration to the UK have effects on circulating IGF system components consistent with a predisposition to diabetes and heart disease.…”