Native Hawaiians of Polynesian descent are at increased risk of obesity, heart failure, and type 2 diabetes, according to a study.
The higher risk of diabetes is related to a genetic variant that is unique among native Hawaiians.
The study, “The Influence of Global and Local Polynesian Genetic Ancestry on Complex Traits in Native Hawaiians, ”Appeared in the diary PLOS genetics.
Compared to Hawaiian nationals of European or Japanese descent, native Hawaiians are at significantly higher risk of obesity, type 2 diabetes, cardiovascular disease, and other cardiometabolic risk factors such as high blood pressure. Although genetic factors such as socioeconomic status and diet do not influence the development of these conditions, they do differ genetic profiles may contribute to the disparity in disease risk among native Hawaiians from different ancestors.
Although genetics play a well-known role in obesity and related diseases, these factors are not well characterized in indigenous populations such as native Hawaiians, at least in part because of the low population size.
“Native Hawaiians have really been under-discussed from a genetic standpoint,” he said. Charleston Chiang, PhD, assistant professor at the University of Southern California and lead author on the study, said in a university news release. “My team focuses on the genetic component of health risk in geographically diverse populations.”
Chiang and his colleagues examined the genetic factors underlying an increased risk of disease among native Hawaiians of Polynesian descent by analyzing genetic variations in the population. Genetic data from 3,940 self-identified Native Hawaiians from the Multi-ethnic cohort study were used to develop a model to determine the relationship between ancestry and disease risk.
The results showed that P.Olynesian ancestry was strongly associated with an increased risk of obesity, type 2 diabetes, and heart failure, as well as higher body mass index (BMI, a measure of body fat) and lower high-density lipoprotein (HDL) or “good” levels Cholesterol. After adjusting for BMI, type 2 diabetes and heart failure showed a linear association with Polynesian ancestry, such that every 10% increase in Polynesian genetic ancestry resulted in an 8.6% increased risk of diabetes and an 11% higher risk of being Heart failure corresponded.
“While we had to quantify the proportion of Polynesian ancestry in order to conduct our research, we don’t want to create the impression that this is a way for people to define their membership in the community based on an arbitrary threshold,” said Chiang.
Interestingly, East Asian ancestry was associated with a higher risk of type 2 diabetes, high blood fat, and high blood pressure in native Hawaiians, but also a lower risk of obesity and a lower BMI. In fact, after adjusting the BMI, East Asian ancestry had a greater impact than Polynesian ancestry on type 2 diabetes risk. This suggests that both East Asian and Polynesian ancestors influence the risk of disease among native Hawaiians.
Socioeconomic status was significantly associated with the same risk factors as Polynesian ancestry, namely BMI, obesity, HDL levels, type 2 diabetes, and heart failure, and appears to explain some, but not all, of the risk. These results suggest that Polynesian genetic risk factors, at least in part, explain the higher risk of disease among native Hawaiians, the researchers said.
Further analysis revealed a relationship between Polynesian ancestry and BMI in people without type 2 diabetes, so that a 10% increase in Polynesian ancestry corresponded to an increase in BMI of 0.51 units. Notably, no such relationship was observed in patients with type 2 diabetes.
Then the team found that a genetic variant on chromosome 6 was significantly associated with type 2 diabetes. The variant, named rs370140172, is uniquely prevalent at 24.2% in people of Polynesian descent, compared with 11.2% in Native Hawaiians, 0% in Europeans, 0.9% in East Asians and 1.2% in Southeast Asians who were included in the study.
The variant was significantly less common in an independent Polynesian population from Samoa (8.7%). However, the association between rs370140172 and type 2 diabetes could not be replicated in the Samoan group due to the small sample size.
“Our results suggest that future studies could identify population-specific genetic susceptibility factors that could elucidate the underlying biological mechanisms and reduce disease risk inequality in Polynesian populations,” the researchers wrote.
Chiang added: “Genetics is a window into understanding the biology behind these diseases. Genetics doesn’t determine everything, and doesn’t necessarily make up most of the risk disparity. “