Association of Circulating Omentin-1 with Osteoporosis in a Chinese Type 2 Diabetic Population

Omentin reduces venous neointimal hyperplasia in arteriovenous fistula through hypoxia-inducible factor-1 alpha inhibition

Arteriovenous fistula (AVF) failure often involves venous neointimal hyperplasia (VNH) driven by elevated hypoxia-inducible factor-1 alpha (HIF-1α) in the venous wall. Omentin, known for its anti-inflammatory and anti-hyperplasia properties, has an uncertain role in early AVF failure. This study investigates omentin's impact on VNH using a chronic renal failure (CRF) rabbit model. The CRF rabbit model of AVF received omentin-expressing adenoviral vector or control β-gal vector to assess omentin's effects on VNH. Human vascular smooth muscle cells (HVSMCs), stimulated with tumor necrosis factor-α (TNF-α), were exposed to recombinant human omentin (Rh-OMT) to study its influence on cell proliferation and migration. The AMP-activated protein kinase (AMPK) inhibitor compound C and the mammalian target of rapamycin (mTOR) activator MHY1485 were employed to explore omentin's mechanisms in VNH reduction through HIF-1α inhibition. Omentin treatment reduced VNH in CRF rabbits, concomitant with HIF-1α down-regulation and the suppression of downstream factors, including vascular endothelial growth factor and matrix metalloproteinases. Rh-OMT inhibited TNF-α-induced HVSMC proliferation and migration by modulating both cell cycle and cell adhesion proteins. Additionally, omentin reduced HIF-1α expression through the AMPK/mTOR pathway activation. Notably, the blockade of AMPK/mTOR signaling reversed omentin-mediated inhibition of VNH, cell proliferation, and migration, both in vivo and in vitro. In conclusion, omentin mitigates VNH post-AVF creation by restraining HIF-1α via AMPK/mTOR signaling. Strategies boosting circulating omentin levels may offer promise in averting AVF failure.

The role of adipokines in osteoporosis management: a mini review

The prevalence of osteoporosis has been on the rise globally. With ageing populations, research has sought therapeutic solutions in novel areas. One such area is that of the adipokines. Current literature points to an important role for these chemical mediators in relation to bone metabolism. Well-established adipokines have been broadly reported upon. These include adiponectin and leptin. However, other novel adipokines such as visfatin, nesfatin-1, meteorin-like protein (Metrnl), apelin and lipocalin-2 are starting to be addressed pre-clinically and clinically. Adipokines hold pro-inflammatory and anti-inflammatory properties that influence the pathophysiology of various bone diseases. Omentin-1 and vaspin, two novel adipokines, share cardioprotective effects and play essential roles in bone metabolism. Studies have reported bone-protective effects of omentin-1, whilst others report negative associations between omentin-1 and bone mineral density. Lipocalin-2 is linked to poor bone microarchitecture in mice and is even suggested to mediate osteoporosis development from prolonged disuse. Nesfatin-1, an anorexigenic adipokine, has been known to preserve bone density. Animal studies have demonstrated that nesfatin-1 treatment limits bone loss and increases bone strength, suggesting exogenous use as a potential treatment for osteopenic disorders. Pre-clinical studies have shown adipokine apelin to have a role in bone metabolism, mediated by the enhancement of osteoblast genesis and the inhibition of programmed cell death. Although many investigations have reported conflicting findings, sufficient literature supports the notion that adipokines have a significant influence on the metabolism of bone. This review aims at highlighting the role of novel adipokines in osteoporosis while also discussing their potential for treating osteoporosis.

Novel Adipokines and Their Role in Bone Metabolism: A Narrative Review

The growing burden of obesity and osteoporosis is a major public health concern. Emerging evidence of the role of adipokines on bone metabolism has led to the discovery of novel adipokines over the last decade. Obesity is recognized as a state of adipose tissue inflammation that adversely affects bone health. Adipokines secreted from white adipose tissue (WAT) and bone marrow adipose tissue (BMAT) exerts endocrine and paracrine effects on the survival and function of osteoblasts and osteoclasts. An increase in marrow fat is implicated in osteoporosis and, hence, it is crucial to understand the complex interplay between adipocytes and bone. The objective of this review is to summarize recent advances in our understanding of the role of different adipokines on bone metabolism.

METHODS

This is a comprehensive review of the literature available in PubMED and Cochrane databases, with an emphasis on the last five years using the keywords.

RESULTS

Leptin has shown some positive effects on bone metabolism; in contrast, both adiponectin and chemerin have consistently shown a negative association with BMD. No significant association was found between resistin and BMD. Novel adipokines such as visfatin, LCN-2, Nesfatin-1, RBP-4, apelin, and vaspin have shown bone-protective and osteoanabolic properties that could be translated into therapeutic targets.

CONCLUSION

New evidence suggests the potential role of novel adipokines as biomarkers to predict osteoporosis risk, and as therapeutic targets for the treatment of osteoporosis.

Plasma EBF1 as a Novel Biomarker for Postmenopausal Osteoporosis

Postmenopausal osteoporosis (OPO) is one of the most common types of primary osteoporosis. There is currently lack of a plasma biomarker for sensitive and early diagnosis of OPO. Here we aimed to explore the potential of early B cell factor 1 (EBF1) as a new plasma biomarker of OPO. Quantitative real-time PCR was used to measure the plasma EBF1 levels. Absorptiometry markers, such as lumbar spine (LS) bone mineral density (BMD) and LS T score were obtained after X-ray scans. Biochemical analyses used to measure osteopontin (OPN), β-isomerized C-terminal telopeptides and total N-terminal procollagen of type-I collagen levels of patients with osteopenia (OPE, n = 81), osteoporosis (OPO, n = 98) as well as healthy subjects (NC, n = 110). Quantitative real-time PCR was used to measure the plasma levels of PAX5 and GSTP1, which are target genes of EBF1. EBF1 was downregulated in OPO patients. Levels of EBF1 were positively correlated to clinicopathological characteristics, including LS BMD and LS T scores, and negatively correlated to OPN and total N-terminal procollagen of type-I collagen levels. Increased PAX5 and GSTP1 levels also demonstrated strong correlations with higher EBF1, LS BMD and LS T score. Anti-osteoporotic treatment resulted in significant upregulation of EBF1, PAX5 and GSTP1 at 6 mo after treatment. Our study suggests that plasma EBF1 is a potential biomarker for diagnosing and assessing treatment outcome of OPO.

Lower Visceral Fat Area in Patients with Type 2 Diabetic Peripheral Neuropathy

OBJECTIVE

There is preliminary evidence that visceral fat area (VFA) was associated with the presence of type 2 diabetic peripheral neuropathy (DPN) in the Korean population; however, no studies have reported the association in Chinese population. The purpose of this study was to explore the possible correlation of VFA with DPN in such a population.

METHODS

A total of 2498 hospitalized patients with type 2 diabetes mellitus (T2DM) undergone VFA measurement, and were divided into DPN group (n=900) and non-DPN group (n=1594). The association of VFA with the presence of DPN was evaluated by correlation and multiple logistic regression analyses, generalized additive model with a smooth curve fitting, and receiver operating characteristic (ROC) curve analysis.

RESULTS

The VFA was significantly lower in the DPN group than in the non-DPN group (P < 0.001). VFA was significantly and positively associated with sural nerve conduction velocity (SNCV) and amplitude potential (SNAP) and negatively associated with the presence of DPN (all P< 0.001); there was no significant difference in the curve fitting (P = 0.344). Multivariate logistic regression analysis showed that the risk of presence of DPN decreased progressively across the VFA quartiles (P for trend < 0.001) and was significantly lower in patients in the highest VFA quartile than in those in the lowest quartile (OR: 0.382, 95% CI 0.151-0.968, P< 0.001) after multivariate adjustment. The ROC analysis revealed that the best cut-off value of VFA for predicting the presence of DPN was 50.5cm² (sensitivity 84.40%; specificity 34.00%).

CONCLUSION

These results suggest that lower VFA level may be associated with increased risk of the presence of DPN in T2DM patients.

Association of serum levels of Visfatin, Intelectin-1, RARRES2 and their genetic variants with bone mineral density in postmenopausal females

BACKGROUND

Adipokines are engaged in bone physiology and regulate bone mineral density (BMD) by playing protective or cynical role in bone metabolism. The study is designed to measure and compare BMD, adipokines (retinoic acid receptor responder protein-2 RARRES2, visfatin and Intelectin-1) and their genetic variants in postmenopausal osteoporotic, osteopenic and non-osteoporotic females.

METHODS

This comparative study included postmenopausal non-osteoporotic (n=72), osteopenic (n=72) and osteoporotic (n=100) females with two years of amenorrhea and age between 50 to 70 years. Gold standard DXA was used to measure BMD. Hardy-Weinberg equilibrium was established. Kruskal-Wallis test for comparisons, logistic and multivariate regression analysis were used to rule out the predictors of BMD.

RESULTS

On comparing the three groups, significant differences were observed in serum RARRES2 (p <0.001) and serum visfatin (p=0.050). The significant positive predictor of BMD at lumbar spine and total hip was serum visfatin. BMD at right and left femoral neck was predicted negatively by serum chemerin while BMD at left femoral neck was also predicted positively by serum calcium levels. There was significant difference in BMD at right femoral neck (p = 0.033) between rs7806429 genotypes. The odds of having low BMD increases with increasing serum levels of chemerin and decreasing serum levels of visfatin and calcium.

CONCLUSION

The adipokines RARRES2 and visfatin are associated with BMD. RARRES2 is an independent negative and visfatin is positive predictor of BMD in postmenopausal females. BMD at right femoral neck was significantly low in RARRES2 rs7806429 TC heterozygotes.