Increased renal methylglyoxal formation with down-regulation of PGC-1α-FBPase pathway in cystathionine γ-Lyase knockout mice

We have previously reported that hydrogen sulfide (H ₂S), a gasotransmitter and vasodilator has cytoprotective properties against methylglyoxal (MG), a reactive glucose metabolite associated with diabetes and hypertension. Recently, H ₂S was shown to up-regulate peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, a key gluconeogenic regulator that enhances the gene expression of the rate-limiting gluconeogenic enzyme, fructose-1,6-bisphosphatase (FBPase). Thus, we sought to determine whether MG levels and gluconeogenic enzymes are altered in kidneys of 6-22 week-old cystathionine γ-lyase knockout (CSE ^-/-; H ₂S-producing enzyme) male mice. MG levels were determined by HPLC. Plasma glucose levels were measured by an assay kit. Q-PCR was used to measure mRNA levels of PGC-1α and FBPase-1 and -2. Coupled-enzymatic assays were used to determine FBPase activity, or triosephosphate levels. Experimental controls were either age-matched wild type mice or untreated rat A-10 cells. Interestingly, we observed a significant decrease in plasma glucose levels along with a significant increase in plasma MG levels in all three age groups (6-8, 14-16, and 20-22 week-old) of the CSE ^-/- mice. Indeed, renal MG and triosephosphates were increased, whereas renal FBPase activity, along with its mRNA levels, were decreased in the CSE ^-/- mice. The decreased FBPase activity was accompanied by lower levels of its product, fructose-6-phosphate, and higher levels of its substrate, fructose-1,6-bisphosphate in renal extracts from the CSE ^-/- mice. In agreement, PGC-1α mRNA levels were also significantly down-regulated in 6-22 week-old CSE ^-/- mice. Furthermore, FBPase-1 and -2 mRNA levels were reduced in aorta tissues from CSE ^-/- mice. Administration of NaHS, a H ₂S donor, increased the gene expression of PGC-1α and FBPase-1 and -2 in cultured rat A-10 cells. In conclusion, overproduction of MG in CSE ^-/- mice is due to a H ₂S-mediated down-regulation of the PGC-1α-FBPase pathway, further suggesting the important role of H ₂S in the regulation of glucose metabolism and MG generation.