When incubated with methylglyoxal (MG) alone, the insulin peak on the HPLC chromatogram weakened in a concentration-dependent manner with increasing MG concentration until it completely disappeared at 100 equivalents, as shown in Figure 1a. However, under the same conditions, incubation of insulin with MG in the presence of D-Dap-L-Leu (dipeptide/MG = 1.1 equivalents) significantly reduced this trend (Figure 1b).

If insulin was incubated with 10 equivalents of MG, it took about 7 days to observe complete degradation (Figure 2b).

Potent and selective piperazine sulfonamides as 11β-HSD1 inhibitors.