HCAR2 and Hyperglycemia: Of interest in this context is our recent data showing that such a niacin-induced hyperglycemia is probably mediated via the activation of niacin receptor GPR109A-mediated ROS-PPARγ-UCP2 (reactive oxygen species-peroxisome proliferator-activated receptor-γ-uncoupling protein 2) signaling pathway in the pancreatic islet β-cells [10].