Two recent studies looked at the potential impacts of identifying people with high genetic risk for type 2 diabetes.
The first study, published by the Journal of General Internal Medicine on July 16, reported the five-year follow-up results of a randomized trial that included 601 patients from a single Veterans Affairs medical center who, at baseline, were ages 21 to 65 years, had a body mass index (BMI) of at least 27 kg/m2, and were not actively losing weight. All received conventional type 2 diabetes risk counseling; half also received genetic testing and then counseling about their diabetes risk (low, intermediate, or high) from a licensed genetic counselor, while control patients received diabetic eye disease counseling. Thirty patients were excluded due to death or lack of data, leaving 574. At five years, type 2 diabetes incidence was 19.4% in the control arm and 22.8% in the genetic counseling arm (adjusted odds ratio, 1.17; 95% CI, 0.78 to 1.77). The groups also showed no significant differences in weight change. Among the patients who received genetic counseling, there were no differences in diabetes incidence or weight by genetic risk level. The study showed that genetic counseling about diabetes risk did not affect short- or long-term weight loss or diabetes incidence, which is consistent with other recent research, according to the study authors. “We conclude that provision of genetic risk information alone is insufficient to motivate lifestyle modification to the extent needed to prevent [type 2 diabetes] incidence,” they said.
The second study, published by The BMJ on July 25, was a meta-analysis of prospective cohort studies published between January 1970 and February 2017 with information about participants' genetic data, consumption of dietary fat, and incidence of type 2 diabetes. It included 15 studies with 102,305 participants, among whom 20,015 type 2 diabetes cases were documented after a median follow-up of 12 years. The hazard ratio of type 2 diabetes per increment of 10 risk alleles in the polygenic risk score for diabetes was 1.64 (95% CI, 1.54 to 1.75). Increased consumption of polyunsaturated fat and total omega-6 polyunsaturated fat intake in place of carbohydrate was associated with a lower risk of type 2 diabetes, but increasing monounsaturated fat in place of carbohydrates was associated with a higher risk of type 2 diabetes. The associations between fat versus carbohydrate consumption and type 2 diabetes were not significantly affected by genetic risk for diabetes. “The findings do not support tailoring recommendations on the quality of dietary fat to individual type 2 diabetes genetic risk profiles for the primary prevention of type 2 diabetes, and suggest that dietary fat is associated with the risk of type 2 diabetes across the spectrum of type 2 diabetes genetic risk,” the study authors said. They noted that “if interactions between genetic risk and dietary or lifestyle factors exist, their effects are likely to be small or undetected by conventional approaches.”