CCND1 and type 2 diabetes mellitus: In the islets of obese and diabetic mice, as well as in the serum of patients with T2D, reduced expression of LncRNA Kcnq1ot1 leads to decreased levels of cyclin D1 (Ccnd1) and cyclin D2 (Ccnd2) through the targeting of miR‐15b‐5p.133