Research uncovers specific genetic factor responsible for serious under-diagnosis of type 2 diabetes in Inuit population
The discovery that a significant percentage of the Inuit population in Greenland has a particular genetic factor that makes it likely for prediabetes and type 2 diabetes to go undiagnosed inspired Dr. Brent Richards, of the Lady Davis Institute at the Jewish General Hospital, to investigate whether the same is true of Inuit in North America (Canada has the largest Inuit population in the world). He and his collaborators found that 27% of Inuit in Nunavik and Alaska have a variant in the TBC1D4 gene that lowers glucose slightly before a meal while raising it after eating. The latter effect is known to be a strong risk factor for complications from diabetes (including heart attack, stroke, loss of limbs, kidney failure, and blindness). Moreover, this curious effect means that diabetes can only be detected if a test known as an oral glucose tolerance test (OGTT) is administered. Less than one-percent of diabetes testing employs this method because it requires that patients wait to have their glucose level tested until two hours after consuming a sugary beverage in the clinic.
“This is a cumbersome test,” Dr. Richards, an Associate Professor of Medicine at McGill University, admits, “but it’s the only way to detect the disease in Inuit with this genetic variable because their fasting glucose is low.”
Unless an OGTT is administered, a significant number of individuals who, in fact, have diabetes, or pre-diabetes, will not be diagnosed until they begin to suffer the complications caused by the disease. Thus, they will never be afforded the opportunity to effectively manage their diabetes by making adjustments to their lifestyle and diet, thereby decreasing the risk of future health crises.
“Because of the prevalence of this genetic variant, as many as 10% of all Inuit may have diabetes, or pre-diabetes, without knowing it unless they are administered an OGTT,” Dr. Richards said. “It is, therefore, highly likely that we have underestimated the prevalence of diabetes among this population.
“Interestingly,” Dr. Despoina Manousaki, the lead author on the study stated, “until recently very few Inuit got diabetes. Now, however, through the adoption of more processed food, starches, and carbohydrates in their diet, they have matched the rate for the rest of Canada. Given that we now believe we are failing to diagnose many diabetic Inuit, it may be more prevalent in this population than the Canadian average.”
”The impact of such a finding that may affect diagnosis and treatment plans and, in turn, put pressure on health care capacity is of concern in northern communities and has to be evaluated in collaboration with the Inuit communities,” says Dr Paul Brassard , a public health physician at the Jewish General Hospital and one of the co-authors of the study. Inuit could be offered genetic testing to see whether they have the particular variant of TBC1D4 that causes this glucose anomaly and/or they could be given an OGTT to accurately assess whether they are diabetic.
This genetic change is only manifest among Inuit. One hypothesis is that it was a necessary adaptation that helps their muscles feed off a diet that was traditionally rich in fat and protein, but lacking in glucose. As the Inuit’s traditional hunting and fishing lifestyle has changed and they consume different foods, a genetic evolution that allowed them to survive in a very adverseenvironment may now be having negative consequences.
“A better understanding of the cultural-specific causes under which common diseases occur within indigenous populations can only lead to better care, and in this case, the implementation of precision medicine” Dr. Richards concludes.
This study is published in the November issue of Diabetes Care.
For further information or to arrange interviews with Dr. Richards, contact:
Research Communications Officer
Lady Davis Institute at the Jewish General Hospital
Office: 514-340-8222, ext. 8661