Lamin A is involved in the development of vascular calcification induced by chronic kidney failure and phosphorus load

Vascular calcification remains one of the main factors associated to morbidity and mortality in both ageing and chronic kidney disease. Both hyperphosphataemia, a well-known promoter of vascular calcification, and abnormal processing defects of lamin A/C have been associated to ageing. The main aim of this study was to analyse the effect of phosphorus load in the differential expression pattern of genes and proteins, particularly of lamin A/C, which are involved in phenotypic change of the vascular smooth muscle cells to osteoblast-like cells. The in vivo study of the calcified abdominal aortas from nephrectomized rats receiving a high phosphorus diet showed among others, a repression of muscle related proteins and overexpression of lamin A/C. Similar results were observed in vitro, where primary vascular smooth muscle cells cultured in calcifying medium showed increased expression of prelamin A and lamin A and abnormalities in the nuclear morphology. Co-immunoprecipitation assays showed novel and important physical interactions between lamin A and RUNX2 during the process of calcification. In fact, the knockdown of prelamin A and lamin A inhibited the increase of Runx2, osteocalcin and osteopontin gene expression, calcium deposition, nuclear abnormalities and the RUNX2 protein translocation into the nucleus of the cell. These in vivo and in vitro results highlight the important role played by lamin A in the process of vascular calcification.

Vitamin D receptor activation, left ventricular hypertrophy and myocardial fibrosis

BACKGROUND

Left ventricular hypertrophy (LVH), a common complication in chronic kidney disease (CKD), is associated with high cardiovascular mortality. The aim of this experimental study was to analyze the effect of different vitamin D receptor activators (VDRAs) on both LVH and myocardial fibrosis in chronic renal failure (CRF).

METHODS

Male Wistar rats with CRF, carried out by 7/8 nephrectomy, were treated intraperitoneally with equivalent doses of VDRAs (calcitriol, paricalcitol and alfacalcidol, 5 days per week) during 4 weeks. A placebo group (CRF + vehicle) and a Sham group with normal renal function served as controls. Biochemical, morphological, functional and molecular parameters associated with LVH were evaluated, as well as cardiac fibrosis, collagen I, transforming growth factor β1 (TGFβ1) and matrix metalloproteinase-1 (MMP1) expression.

RESULTS

All VDRAs treatment prevented LVH, with values of cardiomyocyte size, LV wall and septum thickness and heart-body weight ratio similar to those observed in the Sham group. At molecular levels, all VDRAs attenuated atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression compared with CRF + vehicle. The phosphorylation of ERK1/2, a signal for activating growth, was stimulated in the CRF + vehicle group; VDRAs use prevented this activation. Paricalcitol was the only VDRA used that maintained in the normal range all parameters associated with myocardial fibrosis (total collagen, collagen I, TGFβ1 and MMP1).

CONCLUSIONS

Our findings demonstrated that the three VDRAs used induced similar changes in bone metabolic parameters and LVH. In addition, paricalcitol was the only VDRA which showed a relevant beneficial effect in the reduction of myocardial fibrosis, a key factor in the myocardial dysfunction in CKD patients.

Low calcidiol levels and risk of progression of aortic calcification

In this observational study, we found a positive relationship between low calcidiol levels and the risk of aortic calcification progression. A 10-ng/mL increase of calcidiol was associated with a decrease in the risk of progression by 44%. This figure was higher than that observed if we increased age by 10 years.

INTRODUCTION

The aim of this study was to investigate the relationship between serum calcidiol levels and the onset and progression of aortic calcifications in a community-based sample of ambulatory subjects.

METHODS

Three hundred two men and women aged 50 and over underwent two lateral X-rays and were followed up for 4 years. Abdominal aortic calcifications were classified as absent, mild-moderate, and severe. The biochemical measurements of serum calcium, phosphorus, parathyroid hormone, total alkaline phosphatase, tartrate-resistant acid phosphatase, creatinine, calcidiol, calcitriol, and osteocalcin were determined. Subjects who had received anti-osteoporotic treatments were excluded from the analysis.

RESULTS

Subjects with progression of aortic calcifications had significantly lower serum calcidiol levels than those without progression. In the multivariate analysis, using the agreed upon serum levels for calcidiol (>30 ng/mL) as the reference, those subjects with calcidiol levels between 10 and 20 ng/mL showed a higher risk of progression of aortic calcification (odds ratio (OR) = 3.95; 95% confidence interval (CI) = 1.16 to 13.40). An even higher OR was observed in subjects with calcidiol values <10 ng/mL (OR = 4.10; 95% CI = 1.12 to 14.99). In addition, an increase by 1 ng/mL in osteocalcin levels was associated with a 17% reduction of the risk of aortic calcification progression.

CONCLUSIONS

An increase by 10 ng/mL of calcidiol was associated with a decrease in the risk of aortic calcifications progression by 44%. This figure was even higher than that observed if we increased age by 10 years. Levels of calcidiol higher than 30 ng/mL seem to be desirable to reduce the progression of aortic calcification and to maintain bone turnover.