HK2 and type 1 diabetes mellitus: Previous studies have demonstrated that the LDHA is reduced in testes from T1DM patients [49], similarly, the expression of key glycolytic enzymes HK2, PKM2 and LDHA in the testis of diabetic mice are significantly reduced, which leads to glycogen accumulation, cut down of lactate production of SCs, eventually disorders the energy metabolism of spermatogenic cells and induces a significant cell apoptosis [50, 51].