Barrett's oesophagus in Asians--are ethnic differences due to genes or the environment?

Abstract

Ethnic differences in the prevalence of gastro-oesophageal reflux disease (GORD) and its complications, including Barrett's oesophagus (BO), are well described in multiracial Asian patient populations. These findings together with familial aggregation of GORD symptoms and twin studies suggest the possibility of a genetic component to GORD. Nevertheless, environmental factors, e.g. Helicobacter pylori infection, abdominal adiposity and metabolic syndrome, could equally account for these differences. Indian (South Asian) race is a risk factor for Barrett' oesophagus. This may be related to the Caucasian genetic make-up of Indians as opposed to an Oriental one as is the case of most other Asians. The HLA-B07 gene commonly found in South Asian and Caucasian populations, but not Orientals, may confer an increased risk for BO. Nevertheless, the high prevalence of H. pylori in South Asians and the consequent atrophic gastritis and hypochlorhydria may partially ameliorate this genetic predisposition to BO. The higher prevalence of obesity and the metabolic syndrome amongst certain Asiatic races may also contribute to the observed increased risk for BO. Future research should target the search for GORD/BO genes, ethnic differences in parietal cell mass and hiatal hernia, H. pylori colonization factors (e.g. MUC1 and MUC2) and adhesion molecules (BabA). Racial differences in lifestyle factors, i.e. abdominal adiposity, consumption of fruit and vegetables as well as smoking, should all be investigated as potential causes for this interethnic variation in GORD and BO. Nature or nurture, the clues are teasing and tantalizing and illustrate the complex relationship between the genetic make-up of man and the environment.