INS and type 2 diabetes mellitus: 23). In addition to glucose-induced insulin secretion, L-arginine-induced insulin secretion (in the presence of low glucose levels) is also impaired in TRPM5-knockout mice, but this effect can be suppressed by the TRPM5 inhibitor triphenylphosphine oxide (TPPO). Furthermore, TPPO blockade of TRPM5 inhibits GLP-1-enhanced glucose-induced insulin release (Refs 24, 25, 26). These findings suggest that TRPM5 expression levels inversely correlate with T2DM development (Ref. 27).