Young Indian diabetics suffering from a hitherto overlooked form of the disease may now stand a chance of getting more precise treatment. Medical scientists at a well-known hospital in south India have devised a test that can screen them for predisposing genetic aberrations.

Scientists have known for a while that defective genes rather than lifestyle choices trigger maturity onset diabetes of the young (Mody), earlier called type 1.5 diabetes. But the techniques to identify these gene defects at best are cumbersome even in the West, and almost non-existent in India.

A team of researchers led by Dr Nihal Thomas, professor and head of endocrinology at the Christian Medical College (CMC), Vellore, in Tamil Nadu, has developed a powerful gene screen test that can look for defective variants of all 13 genes that are so far known to be associated with Mody; and all at one go.

A major characteristic of Mody is that the onset occurs at a very young age and is often misdiagnosed as the more predominant type 2 diabetes (T2D). This is because the mean onset age of T2D has of late come down drastically and is in the range of 25 to 34 years. “Besides, there are many overlapping clinical symptoms between Mody and classical T2D, which are caused by the impairment of multiple genes (unlike a single gene normally implicated in Mody). This poses a major diagnostic challenge for physicians,” says Dr Thomas.

According to studies conducted in the West, up to two per cent of diabetics actually suffer from Mody. “In India, the share of Mody in the diabetic population may probably be higher, as there is a great deal of consanguinity (marriage among close relatives) in many Indian communities,” says Dr Thomas. As of 2011, as many as 62 million Indians are estimated to suffer from diabetes and another 77 million from pre-diabetes.

The best way to distinguish Mody from T2D is to do genetic testing. Unfortunately, the genetic screening techniques currently available are not only expensive but also time consuming. These tests cannot check more than three defective genes at a time, and it would take 40 days to complete each test. With 13 genes known to be associated with Mody, labs will have to run a number of tests, each time with a different set of genes.

This is why a new genetic screening technique developed by Aaron Chapla, a doctoral student of Dr Thomas, becomes significant. Using a specially-designed, postage stamp-sized semiconductor chip, Chapla, together with other colleagues at CMC’s department of endocrinology, diabetes and metabolism, demonstrated that it is possible to screen for all known 13 genes simultaneously.

For the study, reported recently in the journal Clinical Endocrinology, the CMC researchers carried out tests using DNA samples from 80 volunteers, who seemed to be suffering from diabetes from a young age. Studies confirmed that 56 of the patients suffered from Mody.

The genetic analysis showed that samples had one or another of 10 Mody genes. “In fact, this study was the first to report the presence of mutations of four Mody genes, known to be prevalent in other populations,in Indians,” says Dr Thomas.

Costing less than Rs 10,000, this might be the cheapest such genetic test available for screening all known Mody genes, says a confident Chapla. As these genes are passed on from one generation to another, it is important to screen all close relatives for Mody, if any of the family members is known to suffer from it, he says. And the new test makes it cheaper to do so.

Mody is caused normally by the dysfunction of the beta cells, which produce insulin in the pancreas. All the genes so far implicated in Mody are known to impair normal development of beta cells.

According to Dr Thomas, it is important to identify whether a diabetic patient is suffering from Mody or not because the treatment is actually different from those who suffer from typical diabetes.

For instance, says Dr Thomas, those who have a defective glucokinase — a common Mody gene — can control the blood glucose levels by diet alone. And usually, a Mody patient does not require insulin treatment.

“Identifying a person prone to Mody at an early stage is important because even the slightest of stress can trigger the disorder,” says Chapla.

“This is a meaningful work. Currently many physicians send patient samples abroad for Mody genetic screening. They should know that sending samples not only make it expensive for patients, but also allow medical scientists in those countries to have easy access to unique mutations present in our country,” says Dwaipayan Bharadwaj, a scientist who studies the genetic basis of diabetes and obesity at the New Delhi-based Institute of Genomics and Integrative Biology.

The studies have thrown up some surprises as well. Though Mody is normally caused by a single gene defect, the CMC researchers discovered more than one defective gene co-existing in a few patients.