Bone Density Is Directly Associated With Glomerular Filtration and Metabolic Acidosis but Do Not Predict Fragility Fractures in Men With Moderate Chronic Kidney Disease

Role of nutritional vitamin D in chronic kidney disease-mineral and bone disorder: A narrative review

Chronic kidney disease-mineral and bone disorder has complex and diverse clinical manifestations, including the simplest abnormalities of calcium, phosphorus and parathyroid hormone detected in blood, abnormalities of bone transformation and mineralization in bone, and calcification of blood vessels or other soft tissues detected on imaging. Patients with CKD-MBD combined low bone mineral density and fragility fractures are referred to as CKD-MBD with low bone mineral density. Vascular calcification refers to ectopic deposition of calcium phosphate in the blood vessel walls and heart valves. The degree of vascular calcification was inversely proportional to bone mineral density. The more severe the degree of vascular calcification, the lower the bone mineral density, and the higher the risk of death, indicating that the bone-vascular axis exists. Activation and alteration of the Wnt signaling pathway are central to the treatment of vascular diseases in uremia. Vitamin D supplementation can prevent secondary hyperparathyroidism, activate osteoblasts, relieve muscle weakness and myalgia, and reduce vascular calcification. Nutritional vitamin D may improve vascular calcification in uremia patients by regulating Wnt signaling pathway.

Bone material strength index is associated with prior fracture in men with and without moderate chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) are at high risk for fracture. The ability of bone mineral density (BMD) to predict fractures in CKD patients has been inconsistent. Other measures such as trabecular bone score (TBS) and impact microindentation (IMI) may be more useful in this group. This study aimed to determine if TBS or IMI values differed between men with and without CKD and examine associations between prior fracture, TBS and IMI values.

METHODS

Men (n = 343, age 33-96 yr) from the Geelong Osteoporosis Study were included. Femoral neck (FNBMD) and lumbar spine BMD (LSBMD) were measured using DXA (Lunar ProdigyPro). TBS was determined from lumbar spine scans (TBS iNsight software Version 2.2). IMI values (bone material strength index; BMSi) were measured using an OsteoProbe. CKD was defined as an eGFR<60 mL/min/1.73m² (n = 53). Prior low trauma fractures (n = 37) were ascertained from radiological reports. Associations were examined using binary logistic regression, adjusting for potential confounders. Interaction terms were tested in all models.

RESULTS

Men with CKD tended to have a higher likelihood of prior fracture (adjusted OR 2.27, 95%CI 1.02-5.01). Higher BMSi was associated with a lower likelihood of prior fracture (adjusted OR for 1SD increase: 0.70; 95%CI 0.51-0.97). This association was sustained after adjustment for FNBMD (OR 0.68; 95%CI 0.49-0.96) or LSBMD (OR 0.69; 95%CI 0.49-0.95). No interaction was detected between BMSi and CKD (p = 0.898). No associations were detected between FNBMD, LSBMD or TBS and prior fracture in either population and there were no interactions with CKD for FNBMD, LSBMD or TBS.

CONCLUSIONS

BMSi was associated with prior fracture in men with and without CKD, however, FNBMD, LSBMD and TBS were not. Lack of an interaction term suggests that BMSi performed similarly in identifying the likelihood of prior fracture, regardless of CKD status. IMI may have clinical utility for assessing fracture risk in patients with CKD.

Mineral bone disorders in chronic kidney disease

As the GFR loss aggravates, the disturbed mineral metabolism worsens the bone microstructure and remodelling - scenario, which is known as CKD-mineral bone disease (MBD). CKD-MBD is characterized by : (i) abnormal metabolism of calcium, phosphorus, parathyroid hormone (PTH), or vitamin D; (ii) abnormalities in bone turnover, mineralization, volume linear growth or strength; (iii) soft-tissue calcifications, either vascular or extra-osseous. Uremic vascular calcification and osteoporosis are the most common complications related to CKD-MBD. Disregulated bone turnover by uremic toxin or secondary hyperparathyroidism disturbed bone mineralization and makes it difficult for calcium and inorganic phosphate to enter into bone, resulting in increased serum calcium and inorganic phosphate. Vascular calcification worsens by hyperphosphatemia and systemic inflammation. Since vitamin D deficiency plays an important role in renal osteodystrophy, supplement of nutritional vitamin D is important in treating uremic osteoporosis and vascular calcification at the same time. Its pleotropic effect improves the bone remodeling initiated by osteoblast and alleviates the risk factors for vascular calcification with less hypercalcemia than vitamin D receptor analogs. Therefore, nutritional vitamin D should be considered in managing CKDMBD.

Relationship between mild-to-moderate chronic kidney disease and decreased bone mineral density in Chinese adult population

BACKGROUND

Several studies have shown ethnic differences in bone and mineral metabolism in healthy people and patients with chronic kidney disease (CKD). However, there have been few studies regarding CKD and bone mineral density (BMD) in Chinese population. We aimed to explore the relationship between mild-to-moderate CKD and decreased BMD in Chinese adult population.

METHODS

A total of 24,002 adults were enrolled in this cross-sectional study. Mild-to-moderate CKD was defined as 30 < estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m(2) or eGFR ≥ 60 mL/min/1.73 m(2) with proteinuria greater than 1+. BMD was measured by dual-energy X-ray absorptiometry at the lumbar spine. Either osteopenia or osteoporosis was defined as decreased BMD. Multivariate logistic regression analysis was used to estimate the associations with decreased BMD.

RESULTS

The subjects comprised 71.5 % men and 28.5 % women, the age was 49.9 ± 13.9 years. The overall prevalence of CKD was 2.9 %. Decreased BMD was 22.1, 19.9 % had osteopenia, and 2.2 % had osteoporosis. The percentage of patients with decreased BMD, osteopenia and osteoporosis were statistically higher (P < 0.05) in CKD patients compared with those of non-CKD participants, which was 29.5 versus 21.9 %, 25.9 versus 19.8 % and 3.6 versus 2.1 %, respectively. The risk for decreased BMD increased with CKD in a simple logistic analysis. However, the correlation disappeared after adjusted for age, sex, smoking, drinking, hypertension, diabetes and obesity.

CONCLUSIONS

Subjects with worse renal function have significantly lower BMD, but after adjusted for confounders, mild-to-moderate CKD is not independently associated with decreased BMD.