Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic adp-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients

Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca²⁺ mobilization for insulin secretion by glucose in pancreatic β cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD⁺ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P ≤ 0.05). Insulin secretion from pancreatic islets by glucose is significantly inhibited by the addition of the NIDDM sera with anti-CD38 antibodies (P ≤ 0.04-0.0001), and the inhibition of insulin secretion is abolished by the addition of recombinant CD38 (P ≤ 0.02). The increase of cADPR levels in pancreatic islets by glucose was also inhibited by the addition of the sera (P ≤ 0.05). These results strongly suggest that the presence of anti-CD38 autoantibodies in NIDDM patients can be one of the major causes of impaired glucose-induced insulin secretion in NIDDM.