BDNF and diabetes mellitus: The linear correlation analysis was conducted between BDNF and indicators of islet secretion in subjects with diabetes for more than 10 years, which presented a negative relationship [FCP (r = −0.260; p = 0.022); 2hCP (r = −251; p = 0.028); HOMA-IR (r = −0.312, p = 0.006)].