For the first time, Indian researchers have been able to isolate a gene associated with obesity which is specific to the Indian population. This is important, as identifying the genetic determinants of body mass index (BMI) will go a long way in better understanding the biological basis of overweight and obesity.
The aim of a study undertaken by research team led by Dr. Kumarasamy Thangaraj of the Hyderabad-based Centre for Cellular and Molecular Biology (CCMB) was to find a novel locus in Indian population. To do that, they excluded the genes that have already been associated with obesity in other populations. A total of 204 non-smoking subjects free of chronic diseases and belonging to different BMI categories — underweight, normal and overweight and obese — were chosen for the study. The subjects were 20-30 years old.
Nearly one million SNP (single nucleotide polymorphism) markers distributed throughout the genome were analysed. “We found one SNP marker (which is within a gene) of THSD7A was significantly associated with obesity. This gene has not been associated with obesity in the Indian population,” said Dr. Thangaraj. The aim of the study was to find a novel locus in the Indian population. The results were published recently in the International Journal of Obesity.
To reconfirm its role, a replication study involving 655 people belonging to different BMI categories — underweight, normal, overweight and obese — was undertaken. “We found highly significant association between the marker and obesity in the replication study,” he said.
THSD7A is a neural N-glycoprotein, which promotes angiogenesis. Angiogenesis, in turn, modulates obesity, adipose metabolism and insulin sensitivity. And now, the authors have been able to find a correlation and this information can be used for drug target, early diagnosis of obesity and treatment. Explaining how the gene is linked to obesity, Dr. Thangaraj said: “The gene is present in everyone. But when there is a mutation to the gene, there is a likelihood that the person carrying the mutated gene will end up being obese.”
However, the gene mutation is not found in all obese people. Similarly, the gene mutation was also found in very small number of underweight people. “That is because obesity is a multigenic condition,” he explained. Despite being a multigenic condition, people carrying the mutation can always take measures to keep obesity at bay, he said. There is a possibility that the SNP marker of THSD7A may be associated with obesity in other South Asian population.
The genetic affinity Indians have with other South Asian population has already been well documented in a 2009 study. In the 2009 study, a particular gene mutation in Indians was found to increase the risk of heart failure in people with cardiomyopathy. And this mutation was found to be a risk factor implicated in South Asian people with cardiomyopathy too.