INS and chronic kidney disease: Compared to controls where nicotinamide levels profoundly decreased in response to OGTT, the levels of nicotinamide in participants with CKD remained elevated (Table 3) consistent with our prior findings using insulin clamp testing.14 Our data confirm findings from these other studies showing nicotinamide and other NAD + catabolites accumulating in uremic patients suggesting an insulin-mediated defect to use nicotinamide during anabolic reactions.