Associations of serum sclerostin and Dickkopf-related protein-1 proteins with future cardiovascular events and mortality in haemodialysis patients: a prospective cohort study

The Relationship between Sclerostin and Kidney Transplantation Mineral Bone Disorders: A Molecule of Controversies

Kidney transplantation is the most effective treatment option for most patients with end-stage kidney disease due to reduced mortality, decreased cardiovascular events and increased quality of life compared to patients treated with dialysis. However, kidney transplantation is not devoid of both acute and chronic complications including mineral bone disorders (MBD) which are already present in patients with chronic kidney disease (CKD) before kidney transplantation. The natural history of MBD after kidney transplantation is variable and new markers are needed to define MBD after kidney transplantation. One of these promising molecules is sclerostin. The main action of sclerostin is to inhibit bone formation and mineralization by blocking osteoblast differentiation and function. In kidney transplant recipients (KTRs), various studies have shown that sclerostin is associated with graft function, bone parameters, vascular calcification, and arterial stiffness although non-uniformly. Furthermore, data for inhibition of sclerostin with monoclonal antibody romosozumab for treatment of osteoporosis is available for general population but not in KTRs which osteoporosis is highly prevalent. In this narrative review, we have summarized the studies investigating the change of sclerostin before and after kidney transplantation, the relationship between sclerostin and laboratory parameters, bone metabolism and vascular calcification in the context of kidney transplantation. We also pointed out the uncertainties, explained the causes of divergent findings and suggest further potential study topics regarding sclerostin in kidney transplantation.

Role of Sclerostin in Cardiovascular Disease

Sclerostin is most recognized for its role in controlling bone formation but is also expressed in the heart, aorta, coronary, and peripheral arteries. This review summarizes research on sclerostin's role in cardiovascular disease. Rodent studies have found sclerostin to be expressed at sites of arterial calcification. In contrast, aortic sclerostin was reported to be downregulated in a mouse model of abdominal aortic aneurysm, and transgenic upregulation or administration of sclerostin was found to prevent abdominal aortic aneurysm and atherosclerosis formation. Sclerostin deficiency was reported to stimulate cardiac rupture in one rodent model. In humans, 7 of 11 studies reported a significant association between high serum sclerostin and high carotid intima media thickness. Ten of 15 studies reported a significant association between high serum sclerostin and severe arterial calcification. Twelve of 14 studies reported a significant association between high serum sclerostin and high arterial stiffness or atherosclerosis severity. Four of 9 studies reported a significant association between high serum sclerostin and high risk of cardiovascular events. A meta-analysis of randomized controlled trials suggested that administration of the sclerostin blocking antibody romosozumab did not significantly increase the risk of major adverse cardiovascular events (risk ratio, 1.14 [95% CI, 0.83-1.57]; P=0.54) or cardiovascular death (risk ratio, 0.92 [95% CI, 0.53-1.59]; P=0.71). Human genetic studies reported variants predisposing to low arterial sclerostin expression were associated with a high risk of cardiovascular events. Overall, past research suggests a cardiovascular protective role of sclerostin but findings have been inconsistent, possibly due to variations in study design, the unique populations and models studied, and the heterogeneous methods used.

Activation of Wnt/Beta-Catenin Signaling Pathway as a Promising Therapeutic Candidate for Cerebral Ischemia/Reperfusion Injury

Stroke is one of the leading causes of mortality, and survivors experience serious neurological and motor behavioral deficiencies. Following a cerebral ischemic event, substantial alterations in both cellular and molecular activities occur because of ischemia/reperfusion injury. Wnt signaling is an evolutionarily conserved signaling pathway that has been manifested to play a key role in embryo development and function maintenance in adults. Overactivation of Wnt signaling has previously been investigated in cancer-based research studies. Recently, abnormal Wnt signaling activity has been observed in ischemic stroke, which is accompanied by massive blood–brain barrier (BBB) disruption, neuronal apoptosis, and neuroinflammation within the central nervous system (CNS). Significant therapeutic effects were observed after reactivating the adynamic signaling activity of canonical Wnt signaling in different cell types. To better understand the therapeutic potential of Wnt as a novel target for stroke, we reviewed the role of Wnt signaling in the pathogenesis of stroke in different cell types, including endothelial cells, neurons, oligodendrocytes, and microglia. A comprehensive understanding of Wnt signaling among different cells may help to evaluate its potential value for the development of novel therapeutic strategies based on Wnt activation that can ameliorate complications and improve functional rehabilitation after ischemic stroke.

Role of Fracture Risk Assessment Tool and Bone Turnover Markers in Predicting All-Cause and Cardiovascular Mortality in Hemodialysis Patients

Background

Fracture Risk Assessment Tool (FRAX) and bone turnover markers (BTMs) predict fractures in the general population. However, the role of FRAX and BTMs in predicting mortality remains uncertain in hemodialysis (HD) patients.

Methods

One hundred and sixty-four HD patients stratified by low or high risk of 10-year fracture probability using FRAX. High risk of fracture was defined as 10-year probability of hip fracture ≥3% or major osteoporotic fracture ≥20%. The association of high risk of fracture and BTMs with all-cause mortality and cardiovascular (CV) mortality were evaluated using multivariate-adjusted Cox regression analysis.

Results

Eighty-five (51.8%) patients were classified as high risk of fracture based on FRAX among 164 HD patients. During a mean follow-up period of 3.5 ± 1.0 years, there were 39 all-cause deaths and 23 CV deaths. In multivariate-adjusted Cox regression, high risk of fracture based on FRAX was independently associated with all-cause mortality [hazard ratio (HR): 2.493, 95% confidence interval (CI): 1.026–6.056, p = 0.044) but not with CV mortality (HR: 2.129, 95% CI: 0.677–6.700, p = 0.196). There were no associations between BTMs and mortality risk. Furthermore, lower geriatric nutritional risk index (GNRI) was significantly associated with increased CV mortality (HR: 0.888, 95% CI: 0.802–0.983, p = 0.022) after adjusting by confounding variables.

Conclusion

High risk of fracture using FRAX was an independent predictor of all-cause mortality in patients undergoing HD. FRAX, rather than BTMs, has an important role of prognostic significance in HD patients.

Cardiovascular Safety of Anti-Sclerostin Therapy in Chronic Kidney Disease

The significance of sclerostin for bone and cardiovascular health in patients with chronic kidney disease (CKD) is complex and incompletely understood. Experimental evidence suggests that anti-sclerostin therapy shows diminished efficacy on bone in the setting of CKD. Limited clinical evidence suggests that the osteoanabolic and anti-resorptive activity is attenuated, but hypocalcemia is more prevalent in patients with advanced CKD (eGFR < 30 mL/min) treated with anti-sclerostin (romosozumab) therapy as compared to patients without kidney disease. Furthermore, sclerostin is prominently expressed in uremic arteries. Whether the inhibition of sclerostin has adverse effects on cardiovascular health in CKD is currently unknown. This review summarizes the current understanding of the physiology and pathophysiology of sclerostin in CKD, with a focus on the cardiovascular safety of anti-sclerostin therapy in patients with or without CKD.