The Association of Serum Irisin with Bone Mineral Density and Turnover Markers in New-Onset Type 2 Diabetic Patients

Effects of metformin on bone mineral density and bone turnover markers: a systematic review and meta-analysis

OBJECTIVES

Metformin is associated with osteoblastogenesis and osteoclastogenesis. This study aims to investigate the impacts of metformin therapy on bone mineral density (BMD) and bone turnover markers.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

METHODS

Searches were carried out in PubMed, EMBASE, Web of science, Cochrane library, ClinicalTrials.gov from database inception to 26 September 2022. Two review authors assessed trial eligibility in accordance with established inclusion criteria. The risk of bias was assessed using the Cochrane Risk of Bias tool (RoB V.2.0). Data analysis was conducted with Stata Statistical Software V.16.0 and Review Manager Software V.5.3.

RESULTS

A total of 15 studies with 3394 participants were identified for the present meta-analysis. Our pooled results indicated that metformin had no statistically significant effects on BMD at lumbar spine (SMD=-0.05, 95% CI=-0.19 to 0.09, p=0.47, participants=810; studies=7), at femoral (MD=-0.01 g/cm2, 95% CI=-0.04 to 0.01 g/cm2, p=0.25, participants=601; studies=3) and at hip (MD=0.01 g/cm2, 95% CI=-0.02 to 0.03 g/cm2, p=0.56, participants=634; studies=4). Metformin did not lead to significant change in osteocalcin, osteoprotegerin and bone alkaline phosphatase. Metformin induced decreases in N-terminal propeptide of type I procollagen (MD=-6.09 µg/L, 95% CI=-9.38 to -2.81 µg/L, p=0.0003, participants=2316; studies=7) and C-terminal telopeptide of type I collagen (MD=-55.80 ng/L, 95% CI=-97.33 to -14.26 ng/L, p=0.008, participants=2325; studies=7).

CONCLUSION

This meta-analysis indicated that metformin had no significant effect on BMD. Metformin decreased some bone turnover markers as N-terminal propeptide of type I procollagen and C-terminal telopeptide of type I collagen. But the outcomes should be interpreted with caution due to several limitations.

Irisin and Bone in Sickness and in Health: A Narrative Review of the Literature

Irisin is a hormone-like myokine produced by the skeletal muscle in response to exercise. Upon its release into the circulation, it is involved in the browning process and thermogenesis, but recent evidence indicates that this myokine could also regulate the functions of osteoblasts, osteoclasts, and osteocytes. Most human studies have reported that serum irisin levels decrease with age and in conditions involving bone diseases, including both primary and secondary osteoporosis. However, it should be emphasized that recent findings have called into question the importance of circulating irisin, as well as the validity and reproducibility of current methods of irisin measurement. In this review, we summarize data pertaining to the role of irisin in the bone homeostasis of healthy children and adults, as well as in the context of primary and secondary osteoporosis. Additional research is required to address methodological issues, and functional studies are required to clarify whether muscle and bone damage per se affect circulating levels of irisin or whether the modulation of this myokine is caused by the inherent mechanisms of underlying diseases, such as genetic or inflammatory causes. These investigations would shed further light on the effects of irisin on bone homeostasis and bone disease.

Exercise-induced modulation of myokine irisin in bone and cartilage tissue—Positive effects on osteoarthritis: A narrative review

Osteoarthritis is a chronic degenerative musculoskeletal disease characterized by pathological changes in joint structures along with the incidence of which increases with age. Exercise is recommended for all clinical treatment guidelines of osteoarthritis, but the exact molecular mechanisms are still unknown. Irisin is a newly discovered myokine released mainly by skeletal muscle in recent years—a biologically active protein capable of being released into the bloodstream as an endocrine factor, the synthesis and secretion of which is specifically induced by exercise-induced muscle contraction. Although the discovery of irisin is relatively recent, its role in affecting bone density and cartilage homeostasis has been reported. Here, we review the production and structural characteristics of irisin and discuss the effects of the different types of exercise involved in the current study on irisin and the role of irisin in anti-aging. In addition, the role of irisin in the regulation of bone mineral density, bone metabolism, and its role in chondrocyte homeostasis and metabolism is reviewed. A series of studies on irisin have provided new insights into the mechanisms of exercise training in improving bone density, resisting cartilage degeneration, and maintaining the overall environmental homeostasis of the joint. These studies further contribute to the understanding of the role of exercise in the fight against osteoarthritis and will provide an important reference and aid in the development of the field of osteoarthritis prevention and treatment.

Metabolic properties of irisin in health and in diabetes mellitus

Irisin is a polypeptide hormone of muscle tissue (myokine), the synthesis and secretion of which increase against the background of physical exertion, which plays a significant role in the metabolism of fat, muscle and bone tissues. It is known that irisin promotes the transformation of white adipose tissue into brown adipose tissue. It has also been experimentally proven that the introduction of irisin contributed to an increase in bone mass and the prevention of osteoporosis and muscular atrophy. There are works indicating a positive effect of irisin in the functioning of bone, fat and muscle tissues in humans. Diabetes mellitus (DM) is an independent risk factor for osteoporotic fractures and the development of specific diabetic myopathy, at the cellular level similar to the aging of muscle tissue, and type 2 diabetes is also associated with the presence of obesity. Thus, it is of particular interest to study the effect of irisin on the state of bone, muscle and adipose tissues and glucose homeostasis in patients with diabetes. This literature review highlights the biological functions of irisin in healthy people and patients with DM.