Treatment of metabolic bone disease in patients with chronic renal disease: A perspective for rheumatologists

The autonomic nervous system and bone health in chronic kidney disease

Besides the well-known role of hormonal factors in mineral and bone metabolism, the sympathetic nervous system participates in this regulation by inhibiting bone formation and promoting bone resorption, primarily via β-adrenergic receptors expressed on osteoblasts. Conversely, the parasympathetic system, through cholinergic signalling, inhibits osteoclast activity, promoting bone formation and maintaining skeletal homeostasis. This review presents the role of the autonomic nervous system, with particular focus on the potential role of β-blockers, especially β1-selective blockers, in modulating bone health in people with normal kidney function and those with CKD. While early studies with non-selective β-blockers like propranolol showed mixed results, recent findings in postmenopausal women suggested that β1-selective β-blockers could enhance bone density by modulating sympathetic activity. Trial emulation using large databases and eventually randomized controlled trials are needed to test the hypothesis that β-blockade can favourably impact bone disease in patients with kidney failure.

Treatment of Diabetes and Osteoporosis—A Reciprocal Risk?

Diabetes mellitus is a metabolic and systematic disorder that requires individualized therapy. The disease leads to various consequences, resulting in the destruction of tissues and organs. The aforementioned outcomes also include bone mineral disorders, caused by medications as well as diet therapy and physical activity. Some drugs may have a beneficial effect on both bone mineral density and the risk of fractures. Nevertheless, the impact of other medications remains unknown. Focusing on pharmacotherapy in diabetes may prevent bone mineral disorders and influence both the treatment and quality of life in patients suffering from diabetes mellitus. On the other hand, anti-osteoporosis drugs, such as antiresorptive or anabolic drugs, as well as drugs with a mixed mechanism of action, may affect carbohydrate metabolism, particularly in patients with diabetes. Therefore, the treatment of diabetes as well as osteoporosis prevention are vital for this group of patients.

Effect of alendronate on vascular calcification in CKD stages 3 and 4: a pilot randomized controlled trial

BACKGROUND

Vascular calcification contributes to cardiovascular disease in patients with chronic kidney disease (CKD). Few studies have addressed interventions to decrease vascular calcification; however, experimental studies report benefits of bisphosphonates. Recent studies of hemodialysis patients also suggest benefits of bisphosphonates on vascular calcification; however, no study exists in nondialysis patients with CKD.

STUDY DESIGN

We conducted a randomized controlled trial to determine the effect of bisphosphonates on vascular calcification in patients with CKD.

SETTING & PARTICIPANTS

51 patients with CKD stages 3-4 were recruited from a hospital outpatient setting; 50 were treated with study medication.

INTERVENTIONS

Patients were randomly assigned to either alendronate, 70 mg (n = 25), or matching placebo (n = 25), administered weekly.

OUTCOMES

The primary outcome was change in aortic vascular calcification after 18 months. Secondary outcomes included superficial femoral artery vascular calcification, arterial compliance, bone mineral density (BMD), renal function, and serum markers of mineral metabolism.

MEASUREMENTS

At baseline and 12 and 18 months, computed tomography, pulse wave velocity using SphygmoCor (AtCor Medical, PWV Inc, www.atcormedical.com), and dual-energy x-ray absorptiometry were performed to measure vascular calcification, arterial compliance, and BMD, respectively. Analysis was by intention to treat, with a random-effect linear regression model to assess differences.

RESULTS

46 patients completed the study (24 alendronate, 22 placebo); baseline mean age was 63.1 +/- 1.8 years, estimated glomerular filtration rate was 34.5 +/- 1.4 mL/min/1.73 m(2), 59% had diabetes, and 65% were men. 91% had aortic vascular calcification at the start and 78% showed progression. At 18 months, there was no difference in vascular calcification progression with alendronate compared with placebo (adjusted difference, -24.2 Hounsfield units [95% CI, -77.0 to 28.6]; P = 0.4). There was an increase in lumbar spine BMD (T score difference, +0.3 [95% CI, 0.03-0.6]; P = 0.04) and a trend toward better pulse wave velocity (-1 m/s [95% CI, -2.1 to 0.1]; P = 0.07) with alendronate. Femoral BMD was similar between groups. There was a nonsignificant decrease in kidney function in patients on alendronate therapy compared with placebo (-1.2 mL/min/1.73 m(2) [95% CI, -4.0 to 1.7]).

LIMITATIONS

Small sample size and baseline differences, especially with aortic vascular calcification, may have diminished any potential difference between groups.

CONCLUSIONS

Unlike previous studies of hemodialysis patients, alendronate did not decrease the progression of vascular calcification compared with placebo in patients with CKD during 18 months.

Non-crystalline and crystalline rheumatic disorders in chronic kidney disease

Rheumatic syndromes are cause for morbidity in patients with end-stage renal disease. Recent advances in understanding the role of tissue remodeling have provided insight into the pathogenic mechanisms responsible for some of these manifestations. Here, we survey recent and clinically relevant advances in translational research that impact our understanding of rheumatic syndromes seen in patients with significant renal disease. The management of acute and chronic crystalline arthropathies in chronic kidney disease and hemodialysis patients is discussed.

[Metabolic bone diseases]

Osteomalacia is caused by impaired vitamin D receptor (VDR) signaling, calcium deficiency, and altered bone mineralization. This can be due to insufficient sunlight exposure, malabsorption, reduced D hormone activation in chronic kidney disease, and rare alterations of VDR signaling and phosphate metabolism. Leading symptoms are bone pain, muscular cramps, and increased incidence of falls in the elderly. The adequate respective countermeasures are to optimize the daily intake of calcium and vitamin D3 and to replace active D hormone and phosphate if deficient. Osteoporosis is characterized by bone fragility fractures upon minor physical impact. Indications for diagnosis and treatment can be established by estimating the absolute fracture risk, taking into account bone mineral density, age, gender, and individual risk factors. Exercise, intervention programs to avoid falls, and specific drugs are capable of substantially reducing fracture risk even in the elderly. Secondary osteoporosis primarily requires both bone-altering medications and effective treatment of underlying diseases.

Is there a role for bisphosphonates in chronic kidney disease?

Patients with stage 5 chronic kidney disease (CKD) including those on dialysis can and do develop osteoporosis. They also develop a wide range of other metabolic bone diseases that may look like osteoporosis when it is defined by either the World Health Organization bone mineral density (BMD) criteria or by the development of fragility fractures. Those dialysis patients with osteoporosis that is due to gonadal hormone deficiency such as postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, or male osteoporosis may benefit from the administration of bisphosphonates (BPs). The challenges lie in the diagnosis of osteoporosis in this population where adynamic, osteomalacic, hyperparathyroid, or aluminum bone disease are also prevalent, with concommitant low BMD and low trauma fractures, but where BPs may be contraindicated. The only secure means to diagnose osteoporosis in this patient population is by quantitative bone histomorphometry demonstrating low trabecular bone volume and disrupted microarchitecture. Once the diagnosis of osteoporosis is established, BPs should be considered for a well-defined brief period of time (e.g., 2-3 years), even though there is no evidence for a fracture reduction benefit in this population. If a BP is chosen there may be a need for dose adjustment or slower infusion rates (for the intravenous formulations), as a greater bone retention may occur for these renally cleared agents. While it is unknown what consequences could develop from increased bone retention in patients with little renal function, data are needed if more bone retention of BP might lead to a greater risk of the development of adynamic bone disease and lower bone strength. More data are needed to define the risks and benefits of BPs in patients with stage 5 CKD.