Therefore, the alteration in circulating BDNF levels after oral glucose intake might not be directly responsive to hyperglycemia, suggesting that the source of cerebral BDNF output might also play an important role.[31, 51] For example, in animal studies, the expression of BDNF in the brain has been shown to be induced by vagal afferents or humoral interactions.[33, 52]. This evidence concerns the gene BDNF and Hyperglycemia.