Scientists link gene to diabetes

By SIMON COLLINS, science reporter

Scientists have found the first clear proof of genetic variations that make Maori people more likely to get diabetes.

A team led by Auckland University Professor Garth Cooper (Waikato) and doctoral student Nicola Poa (Ngapuhi) has found three minor variations in one gene in 7 per cent of Maori people with diabetes, but in only 1 per cent of Maori without the disease.

They believe that further research will find other variations which will help to explain a skyrocketing Maori rate of diabetes - one of the highest in the world.

More than one in five (21.4 per cent) Maori men over 45 have diabetes, compared with 8.6 per cent of Pakeha men of the same age.

Among women over 45, the rates are 13 per cent for Maori and 7.5 per cent for Pakeha.

"There are areas of New Zealand where upwards of half of older people have diabetes, such as parts of the East Coast," Dr Cooper said.

Genetic variations programmed from birth have long been suspected as among the causes of the discrepancy, along with lifestyle factors such as diet and lack of exercise. But no one has found the variations before.

Similar variations have been found among diabetics in China, Japan, Korea, Taiwan and various European countries. Dr Cooper's study of 131 Maori patients with diabetes and 258 Maori who do not have the disease has found two already-known variations, and two completely new ones.

One of the known variations turned out to have no effect on diabetes in Maori, because it was as common among those without diabetes as it was among those with the disease.

The other three variations were found in a total of nine of the 131 patients with diabetes (7 per cent).

Dr Cooper said a bigger study of about 1000 Maori diabetics would be needed to confirm the findings. That would identify about 70 people with the genetic variations, and it would then be possible to test other members of their families to see if they also have the variations.

If local Maori agree, this may be done in the Counties-Manukau area, where a taskforce led by former regional public health service manager Paul Stephenson is working on a long-term strategy to "beat diabetes".

Dr Cooper said the wider study would also look for other genetic variations affecting more than the initial 7 per cent of Maori diabetics.

"I suspect we'll find a series of them that will put the percentage up to 20 or 30 per cent or something."

He said it would cost between $10,000 and $20,000 to develop a genetic test and then $30 to $50 to test each person. He wants feedback from the Maori community on whether this would be worthwhile.

The medical director of South Auckland Maori health provider Te Kupenga o Hoturoa, Dr Guy Naden, said the test would provide another tool to encourage people to eat better and exercise to overcome their genetic susceptibility to the disease.

"It's going to open up a whole new screening process and I think it's exciting. It's quite revolutionary.

"We'll take a tool like this and try to use it as productively as we can."

But a Northland District Health Board member and GP who has made a major study of diabetes in Northland, Dr Shane Reti, said screening for genetic variations affecting 7 per cent of Maori diabetics might not be as worthwhile as spending the same amount of money on dietary advice - especially if screening encouraged those who did not have the variations to relax.

"At 7 per cent, it's well below obesity and other risk factors," he said.

He also questioned whether the genetic variations might actually be caused by diet and other lifestyle factors.

"We can change DNA by giving you a blast of radiation, so can lifestyle induce a form of gene mutation?" he asked. Dr Cooper said the genetic variations were in the inherited "germ line" of patients and could not be affected by lifestyle.

But he acknowledged that whether money would be better spent on nutritional education rather than genetic testing was "a good question".

Although he is of the Waikato iwi himself, he has not tested his own blood to see if he has the variation making him susceptible to diabetes.

"It's good practice not to do that. I know that I don't have diabetes, and I know that I have very good glucose tolerance."

DIABETES EPIDEMIC

More than 100,000 New Zealanders are diagnosed with type 2 diabetes.

More than 50,000 further cases may be undiagnosed.

The number diagnosed is expected to pass 145,000 by 2011.

The epidemic costs the health system more than $170 million a year.

Obesity is a leading risk factor for the disease.

17 per cent of New Zealanders were obese in 1996.

This is predicted to rise to 29 per cent by 2011.