Abstract
Background Irisin, an exercise-induced myokine and adipocytokine, has been reported to decrease in type 2 diabetic patients. Recently, several research studies indicated that circulating levels were correlated with bone mineral density (BMD). To evaluate bone metabolism, bone turnover markers (BTMs) should be included. However, with respect to newly diagnosed T2DM patients, the relevance of their irisin levels to their BTMs and BMD remains unclear. The investigation of serum irisin levels in patients who have been newly diagnosed with type 2 diabetes and illumination of the relationship between serum irisin levels and those two indices of BMD and BTMs mentioned above are the intention of this cross-sectional study. Methods 66 new-onset type 2 diabetic patients (T2DM group), together with 82 control subjects (NGT group), were recruited in this study. Serum irisin concentrations and BTMs (including osteocalcin (OC), procollagen type 1 N-terminal propeptide (P1NP), and β-C-terminal telopeptides of type I collagen (β-CTX)) were determined by the enzyme-linked immunosorbent assay (ELISA). Glucose, lipid profile, and insulin were considered as measuring indicators as well. Dual-energy X-ray absorptiometry (DXA) was utilized to evaluate the indicator of BMD. Serum irisin, BTMs, and BMD were compared between diabetic patients and healthy individuals. Pearson and Spearman correlation analyses were applied as well to assess correlations between irisin and BTMs and BMD. Multiple stepwise regression analysis was conducted to identify the independent factors of irisin. ROC curve analyses were carried out for serum irisin prediction for osteoporosis/osteopenia (OP). Results The serum levels of irisin, procollagen type 1, intact N-terminal propeptide (P1NP), and osteocalcin (OC) were evidently lower in T2DM subjects than in NGT subjects (10.90 ± 1.88 vs .11.69 ± 2.06 ng/mL, P < 0.05; 36.42(25.68,51.70) vs. 44.52(35.73,58.05)ng/ml, P < 0.05; 16.15(12.40,21.66) vs. 18.70(15.56, 23.22)ng/ml, P < 0.05). Among patients with T2DM, the circulating irisin level of those with OP was lower than that of normal BMD (9.98 ± 2.09 vs. 11.39 ± 1.57 ng/ml, P < 0.01); irisin had a negative correlation with β-C-terminal telopeptides of type I collagen (β-CTX) (r = −0.496, P < 0.001) and came back unrelated to Lumbar BMD; Lumbar BMD was negatively relevant to OC (r = −0.274, P < 0.05) and β-CTX (r = −0.410, P < 0.01). Multiple linear regression analyses of stepwise models implied that TG, LDL-C, and β-CTX were independently associated with serum irisin concentrations (P < 0.01 or P < 0.05). Conclusion Serum irisin level was declined in patients with type 2 diabetes diagnosed in the near term and had a certain association with bone turnover markers. It is suggested to consider irisin as a potential biomarker of bone metabolic disorder in T2DM patients with the initial diagnosis.
Highlights
Skeletal muscle (SKM) and bone are anatomically and physiologically connected, and their coupling has been considered mainly a mechanical one to regulate bone metabolism
Whether there is a relationship of irisin with bone mineral density (BMD) and bone turnover markers (BTMs) in newly diagnosed T2DM patients remains unknown. In this cross-sectional study, we aim to identify the serum irisin levels in the new-onset T2DM patients and control subjects and do some investigation to confirm the existence of associations between irisin levels and the BMD and BTMs in both groups
Comprising 66 newly diagnosed T2DM patients (T2DM group, mean age 51.08 ± 12.67 years) and 82 healthy controls whose age and sex are matched (NGT group, mean age 50.04 ± 8.98 years) according to 75 g OGTT outcomes, a total amount of 148 subjects were recruited from the outpatient and inpatient of the endocrinology department of the 903rd Hospital of PLA, China, from May 2017 to December 2019. ose subjects were distributed into four subgroups in accordance with BMD levels [normal BMD subjects (−1.0 < T/Z < 1.0) and decreased BMD subjects (T/Z ≤ −1.0, including osteopenia and osteoporosis)] for further analysis
Summary
Skeletal muscle (SKM) and bone are anatomically and physiologically connected, and their coupling has been considered mainly a mechanical one to regulate bone metabolism. Residing in one of the representatives in the myokine family, irisin is mainly known for the transiting ability of white adipocytes to brown adipocytes [3] Most studies about this myokine were focused on the field of energy expenditure and adiposity or glucose homeostasis whereas recent pieces of evidence implied that irisin was involved in bone metabolism. Injection of recombinant irisin (r-irisin) was reported to increase osteoblasts and decrease the quantity of osteoclasts, which evokes the upkeep of quality and bone mass in male mice [10] and ovariectomized mice [11] All these highlighted that irisin had an underlying function as a biomarker or modulator of bone abnormalities in the T2DM patient group where they are more susceptible to fracture which was suggested to be considered one of the chronic complications of T2DM [12–14]. Serum irisin level was declined in patients with type 2 diabetes diagnosed in the near term and had a certain association with bone turnover markers. It is suggested to consider irisin as a potential biomarker of bone metabolic disorder in T2DM patients with the initial diagnosis
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