APLN and osteoporosis: Moreover, a clinical trial based on T2DM patients found that the levels of Apelin-13, bone formation sensitive factor procollagen type I N-propeptide (PINP), and bone mineral density (BMD) in the serum of T2DM patients with osteoporosis were significantly lower than those in T2DM patients with normal bone mass, whereas the bone resorption marker type I collagen carboxyterminal telopeptide (ICTP) showed the opposite trend (89).