CREBRF missense variant rs373863828 has both direct and indirect effects on type 2 diabetes and fasting glucose in Polynesians living in Samoa and Aotearoa New Zealand.

Objective The minor allele of rs373863828 in CREBRF is associated with higher BMI, lower fasting glucose, and lower odds of type 2 diabetes. We examined the associations between BMI and rs373863828 on type 2 diabetes and fasting glucose with a large sample of adult Polynesians from Samoa, American Samoa and Aotearoa New Zealand and estimated direct and indirect (via BMI) effects of rs373863828 on type 2 diabetes and fasting glucose. Research Design and Methods We regressed type 2 diabetes and fasting glucose on BMI and rs373863828 stratified by obesity, regressed type 2 diabetes and fasting glucose on BMI stratified by rs373863828 genotype, and assessed the effects of rs373863828 on type 2 diabetes and fasting glucose with path analysis. Results Association of BMI with fasting glucose was greater in those without obesity than in those with obesity. We did not observe evidence of differences by genotype. In the path analysis, the minor allele has direct negative and indirect positive effects on type 2 diabetes risk and fasting glucose, with the indirect effect mediated through a direct positive effect on BMI. Conclusions There may be a stronger effect of BMI on fasting glucose in Polynesians without obesity than in those with obesity. Carrying the rs373863828 minor allele does not decouple higher BMI from odds of type 2 diabetes. Given the current cost of genotyping compared to the accessibility of measuring BMI, including rs373863828 as a clinical predictor of type 2 diabetes may not be indicated.