Abstract:

Objective   To investigate the relationship between the alteration of the serum melatonin (MT)level and its secretion rhythm and oxidative stress in patients with type 2 diabetes. Methods   32 patients with type 2 diabetic mellitus (DM group) and 16 cases of normal controls (NC group)were selected as study subjects. The DM group was further divided into the macrovascular subgroup (MV) and the nonmacrovascular subgroup (NMV). The levels of melatonin(MT), superoxide dismutase (SOD)and nitric oxide (NO)in the serum were measured at 02:00(t2)and 08:00(t8) respectively, and the t2 to t8 ratio of every above index was used to indicate its circadian rhythm change. Results   ① The serum MTt2 level and the ratio of MTt2/t8 were significantly lower in the DM group than in the NC group(P<0.01 ), also the serum MTt2 level and the ratio of MTt2/t8 in the MV group were apparently lower compared with those in the NMV group(P<0.01). ② Compared with the NC group, the DM group had lower SODt2and SODt8 activities (P<0.01)and higher NOt2and  NOt8 levels(P<0.05). The same changes were also found in the MV group when compared with the NMV group. ③ Multiple linear regression analysis showed that MTt2 was negatively correlated with disease duration, HbA1c, and NOt2(P<0.05) and  positively correlated with SODt2(P<0.01). MTt2, however, was negatively correlated with NOt8 only (P<0.05). Conclusion   Type 2 diabetic patients have lower serum melatonin levels at night and abnormal circadian secretion rhythm.  These changes are associated with the enhanced  oxidative stress in the body and may result in the onset and development of diabetic macrovascular complications.

Key words: Diabetes， type 2； Melatonin； Circadian rhythm； Oxidative stress