Ctrp4, a new adipokine, promotes the differentiation of osteoblasts

CTRP family in diseases associated with inflammation and metabolism: molecular mechanisms and clinical implication

C1q/tumor necrosis factor (TNF) related proteins (CTRPs) is a newly discovered adipokine family with conservative structure and ubiquitous distribution and is secreted by adipose tissues. Recently, CTRPs have attracted increasing attention due to the its wide-ranging effects upon inflammation and metabolism. To-date, 15 members of CTRPs (CTRP1-15) with the characteristic C1q domain have been characterized. Earlier in-depth phenotypic analyses of mouse models of CTRPs deficiency have also unveiled ample function of CTRPs in inflammation and metabolism. This review focuses on the rise of CTRPs, with a special emphasis on the latest discoveries with regards to the effects of the CTRP family on inflammation and metabolism as well as related diseases. We first introduced the structure of characteristic domain and polymerization of CTRPs to reveal its pleiotropic biological functions. Next, intimate association of CTRP family with inflammation and metabolism, as well as the involvement of CTRPs as nodes in complex molecular networks, were elaborated. With expanding membership of CTRP family, the information presented here provides new perspectives for therapeutic strategies to improve inflammatory and metabolic abnormalities.

Osteometabolism: Metabolic Alterations in Bone Pathologies

Renewing interest in the study of intermediate metabolism and cellular bioenergetics is brought on by the global increase in the prevalence of metabolic illnesses. Understanding of the mechanisms that integrate energy metabolism in the entire organism has significantly improved with the application of contemporary biochemical tools for quantifying the fuel substrate metabolism with cutting-edge mouse genetic procedures. Several unexpected findings in genetically altered mice have prompted research into the direction of intermediate metabolism of skeletal cells. These findings point to the possibility of novel endocrine connections through which bone cells can convey their energy status to other metabolic control centers. Understanding the expanded function of skeleton system has in turn inspired new lines of research aimed at characterizing the energy needs and bioenergetic characteristics of these bone cells. Bone-forming osteoblast and bone-resorbing osteoclast cells require a constant and large supply of energy substrates such as glucose, fatty acids, glutamine, etc., for their differentiation and functional activity. According to latest research, important developmental signaling pathways in bone cells are connected to bioenergetic programs, which may accommodate variations in energy requirements during their life cycle. The present review article provides a unique perspective of the past and present research in the metabolic characteristics of bone cells along with mechanisms governing energy substrate utilization and bioenergetics. In addition, we discussed the therapeutic inventions which are currently being utilized for the treatment and management of bone-related diseases such as osteoporosis, rheumatoid arthritis (RA), osteogenesis imperfecta (OIM), etc., by modulating the energetics of bone cells. We further emphasized on the role of GUT-associated metabolites (GAMs) such as short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs), indole derivates, bile acids, etc., in regulating the energetics of bone cells and their plausible role in maintaining bone health. Emphasis is importantly placed on highlighting knowledge gaps in this novel field of skeletal biology, i.e., "Osteometabolism" (proposed by our group) that need to be further explored to characterize the physiological importance of skeletal cell bioenergetics in the context of human health and bone related metabolic diseases.

Diagnosis of Low Bone Mass Density: Serological versus Radiological Methods

Context

Bone remodeling comprises balanced coupling of bone formation and resorption, and low bone mineral density (BMD) demonstrates high rates of bone resorption. Osteoporosis is a chronic asymptomatic disease with fragile bones and impending risk of fractures mediated by minor trauma. Whereas bone mineralization and integrity are determined by calcium and vitamin D, specific serum markers such as bone specific alkaline phosphatase (ALP) and osteocalcin (OC) play a vital role in bone formation.

Materials and Methods

Serum calcium, vitamin D, ALP, and OC levels were measured in 2,145 Saudi students aged 18–22 years at Umm Al-Qura University. The BMD was measured by dual-energy X-ray absorptiometry (DEXA), and the findings were statistically evaluated. The following statistics were utilized in the analysis: the SPSS software was used to record, tabulate, and statistically evaluate the results.

Results

Low BMD cases accounted for 27.46% of all cases investigated, with considerably higher serum calcium, bone-specific ALP, and OC levels compared to control cases, but significantly lower serum vitamin D levels. In low BMD instances, there was no association between serum markers and DEXA findings.

Conclusion

Serum indicators by themselves may be useful for screening and predicting patients at risk of osteoporosis, as well as assessing treatment response. The combination of serum markers and DEXA measures is more effective in detecting low BMD.

Role of the CTRP family in tumor development and progression

C1q tumor necrosis factor-related proteins (CTRPs), which are members of the adipokine superfamily, have gained significant interest in the recent years. CTRPs are homologs of adiponectin with numerous functions and are closely associated with metabolic diseases, such as abnormal glucose and lipid metabolism and diabetes. Previous studies have demonstrated that CTRPs are highly involved in the regulation of numerous physiological and pathological processes, including glycolipid metabolism, protein kinase pathways, cell proliferation, cell apoptosis and inflammation. CTRPs also play important roles in the development and progression of numerous types of tumor, including liver, colon and lung cancers. This observation can be attributed to the fact that diabetes, obesity and insulin resistance are independent risk factors for tumorigenesis. Numerous CTRPs, including CTRP3, CTRP4, CTRP6 and CTRP8, have been reported to be associated with tumor progression by activating multiple signal pathways. CTRPs could therefore be considered as diagnostic markers and therapeutic targets in some cancers. However, the underlying mechanisms of CTRPs in tumorigenesis remain unknown. The present review aimed to determine the roles and underlying mechanisms of CTRPs in tumorigenesis, which may help the development of novel cancer treatments in the future.