Serum calcification propensity is independently associated with disease activity in systemic lupus erythematosus

Worse cardiovascular and renal outcome in male SLE patients

Systemic lupus erythematosus (SLE) in males is rare and poorly understood. Thus, still little is known about sex differences in SLE. We set out to identify sex differences regarding clinical manifestations as well as renal and cardiovascular outcomes of SLE. We analyzed patient data from the Swiss SLE Cohort Study. Cumulative clinical manifestations according to the updated American College of Rheumatology criteria were recorded at inclusion. Cardiovascular events were recorded within Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SLICC-SDI). Renal failure was defined as eGFR < 15 ml/min/1.73 m2, initiation of renal replacement therapy or doubling of serum creatinine which were all assessed yearly or documented as end stage renal disease in SLICC-SDI. Risk differences were calculated using logistic regression and cox regression models. We analyzed 93 men and 529 women with a median follow up time of 2 years. Males were significantly older at diagnosis (44.4 versus 33.1 years, p < 0.001) and had less often arthritis (57% versus 74%, p = 0.001) and dermatological disorders (61% versus 76%, p < 0.01). In multivariate analysis female sex remained a significantly associated with arthritis and dermatological disorders. In multivariate analysis men had a significantly higher hazard ratio of 2.3 for renal failure (95% confidence interval (95%-CI) 1.1-5.2, p < 0.04). Total SLICC-SDI Score was comparable. Men had significantly more coronary artery disease (CAD) (17% versus 4%, p < 0.001) and myocardial infarction (10% versus 2%, p < 0.01). In multivariate analysis, male sex remained a significant risk factor for CAD (odds ratio (OR) 5.6, 95%-CI 2.3-13.7, p < 0.001) and myocardial infarction (OR 8.3, 95%-CI 2.1-32.6, p = 0.002). This first sex study in a western European population demonstrates significant sex differences in SLE. Male sex is a risk factor for cardiovascular events and renal failure in SLE. Potential etiological pathomechanisms such as hormonal or X-chromosomal factors remain to be further investigated.

ITGAM rs1143679 Variant in Systemic Lupus Erythematosus Is Associated with Increased Serum Calcification Propensity

OBJECTIVES

CD11B/ITGAM (Integrin Subunit α M) mediates the adhesion of monocytes, macrophages, and granulocytes and promotes the phagocytosis of complement-coated particles. Variants of the ITGAM gene are candidates for genetic susceptibility to systemic lupus erythematosus (SLE). SNP rs1143679 (R77H) of CD11B particularly increases the risk of developing SLE. Deficiency of CD11B is linked to premature extra-osseous calcification, as seen in the cartilage of animals with osteoarthritis. Serum calcification propensity measured by the T50 test is a surrogate marker for systemic calcification and reflects increased cardiovascular (CV) risk. We aimed to assess whether the CD11B R77H gene variant is associated with a higher serum calcification propensity (i.e., a lower T50 value) in SLE patients compared to the wild-type allele (WT).

METHODS

Cross-sectional study incorporating adults with SLE genotyped for the CD11B variant R77H and assessed for serum calcification propensity with the T50 method. Participants were included in a multicenter trans-disciplinary cohort and fulfilled the 1997 revised American College of Rheumatology (ACR) criteria for SLE. We used descriptive statistics for comparing baseline characteristics and sequential T50 measurements in subjects with the R77H variant vs. WT CD11B.

RESULTS

Of the 167 patients, 108 (65%) were G/G (WT), 53 (32%) were G/A heterozygous, and 6 (3%) were A/A homozygous for the R77H variant. A/A patients cumulated more ACR criteria upon inclusion (7 ± 2 vs. 5 ± 1 in G/G and G/A; p = 0.02). There were no differences between the groups in terms of global disease activity, kidney involvement, and chronic renal failure. Complement C3 levels were lower in A/A individuals compared to others (0.6 ± 0.08 vs. 0.9 ± 0.25 g/L; p = 0.02). Baseline T50 did not differ between the groups (A/A 278 ± 42' vs. 297 ± 50' in G/G and G/A; p = 0.28). Considering all sequential T50 test results, serum calcification propensity was significantly increased in A/A individuals compared to others (253 ± 50 vs. 290 ± 54; p = 0.008).

CONCLUSIONS

SLE patients with homozygosity for the R77H variant and repeated T50 assessment displayed an increased serum calcification propensity (i.e., a lower T50) and lower C3 levels compared to heterozygous and WT CD11B, without differing with respect to global disease activity and kidney involvement. This suggests an increased CV risk in SLE patients homozygous for the R77H variant of CD11B.

Calciprotein Particles Cause Physiologically Significant Pro-Inflammatory Response in Endothelial Cells and Systemic Circulation

Calciprotein particles (CPPs) represent an inherent mineral buffering system responsible for the scavenging of excessive Ca²⁺ and PO₄^3- ions in order to prevent extraskeletal calcification, although contributing to the development of endothelial dysfunction during the circulation in the bloodstream. Here, we performed label-free proteomic profiling to identify the functional consequences of CPP internalisation by endothelial cells (ECs) and found molecular signatures of significant disturbances in mitochondrial and lysosomal physiology, including oxidative stress, vacuolar acidification, accelerated proteolysis, Ca²⁺ cytosolic elevation, and mitochondrial outer membrane permeabilisation. Incubation of intact ECs with conditioned medium from CPP-treated ECs caused their pro-inflammatory activation manifested by vascular cell adhesion molecule 1 (VCAM1) and intercellular adhesion molecule 1 (ICAM1) upregulation and elevated release of interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1/ C-C motif ligand 2 (MCP-1/CCL2). Among the blood cells, monocytes were exclusively responsible for CPP internalisation. As compared to the co-incubation of donor blood with CPPs in the flow culture system, intravenous administration of CPPs to Wistar rats caused a considerably higher production of chemokines, indicating the major role of monocytes in CPP-triggered inflammation. Upregulation of sICAM-1 and IL-8 also suggested a notable contribution of endothelial dysfunction to systemic inflammatory response after CPP injections. Collectively, our results demonstrate the pathophysiological significance of CPPs and highlight the need for the development of anti-CPP therapies.

Serum Calcification Propensity Represents a Good Biomarker of Vascular Calcification: A Systematic Review

Vascular calcification contributes to cardiovascular morbidity and mortality. A recently developed serum calcification propensity assay is based on the half-transformation time (T50) from primary calciprotein particles (CPPs) to secondary CPPs, reflecting the serum’s endogenous capacity to prevent calcium phosphate precipitation. We sought to identify and review the results of all published studies since the development of the T50-test by Pasch et al. in 2012 (whether performed in vitro, in animals or in the clinic) of serum calcification propensity. To this end, we searched PubMed, Elsevier EMBASE, the Cochrane Library and Google Scholar databases from 2012 onwards. At the end of the selection process, 57 studies were analyzed with regard to the study design, sample size, characteristics of the study population, the intervention and the main results concerning T50. In patients with primary aldosteronism, T50 is associated with the extent of vascular calcification in the abdominal aorta. In chronic kidney disease (CKD), T50 is associated with the severity and progression of coronary artery calcification. T50 is also associated with cardiovascular events and all-cause mortality in CKD patients, patients on dialysis and kidney transplant recipients and with cardiovascular mortality in patients on dialysis, kidney transplant recipients, patients with ischemic heart failure and reduced ejection fraction, and in the general population. Switching from acetate-acidified dialysate to citrate-acidified dialysate led to a longer T50, as did a higher dialysate magnesium concentration. Oral administration of magnesium (in CKD patients), phosphate binders, etelcalcetide and spironolactone (in hemodialysis patients) was associated with a lower serum calcification propensity. Serum calcification propensity is an overall marker of calcification associated with hard outcomes but is currently used in research projects only. This assay might be a valuable tool for screening serum calcification propensity in at-risk populations (such as CKD patients and hemodialyzed patients) and, in particular, for monitoring changes over time in T50.

CD11b Signaling Prevents Chondrocyte Mineralization and Attenuates the Severity of Osteoarthritis

Osteoarthritis (OA) is a progressive joint disease that is strongly associated with calcium-containing crystal formation (mineralization) by chondrocytes leading ultimately to cartilage calcification. However, this calcification process is poorly understood and treatments targeting the underlying disease mechanisms are lacking. The CD11b/CD18 integrin (Mac-1 or αMβ2), a member of the beta 2 integrin family of adhesion receptors, is critically involved in the development of several inflammatory diseases, including rheumatoid arthritis and systemic lupus erythematosus. We found that in a collagen-induced arthritis, CD11b-deficient mice exhibited increased cartilage degradation compared to WT control animals. However, the functional significance of CD11b integrin signaling in the pathophysiology of chondrocytes remains unknown. CD11b expression was found in the extracellular matrix and in chondrocytes in both healthy and damaged human and murine articular cartilage. Primary murine CD11b KO chondrocytes showed increased mineralization when induced in vitro by secondary calciprotein particles (CPP) and quantified by Alizarin Red staining. This increased propensity to mineralize was associated with an increased alkaline phosphatase (Alp) expression (measured by qRT-PCR and activity assay) and an enhanced secretion of the pro-mineralizing IL-6 cytokine compared to control wild-type cells (measured by ELISA). Accordingly, addition of an anti-IL-6 receptor antibody to CD11b KO chondrocytes reduced significantly the calcification and identified IL-6 as a pro-mineralizing factor in these cells. In the same conditions, the ratio of qRT-PCR expression of collagen X over collagen II, and that of Runx2 over Sox9 (both ratio being indexes of chondrocyte hypertrophy) were increased in CD11b-deficient cells. Conversely, the CD11b activator LA1 reduced chondrocyte mineralization, Alp expression, IL-6 production and collagen X expression. In the meniscectomy (MNX) model of murine knee osteoarthritis, deficiency of CD11b led to more severe OA (OARSI scoring of medial cartilage damage in CD11b: 5.6 ± 1.8, in WT: 1.2 ± 0.5, p < 0.05, inflammation in CD11b: 2.8 ± 0.2, in WT: 1.4 ± 0.5). In conclusion, these data demonstrate that CD11b signaling prevents chondrocyte hypertrophy and chondrocyte mineralization in vitro and has a protective role in models of OA in vivo.

Calciprotein Particles and Serum Calcification Propensity: Hallmarks of Vascular Calcifications in Patients with Chronic Kidney Disease

Cardiovascular complications are one of the leading causes of mortality worldwide and are strongly associated with atherosclerosis and vascular calcification (VC). Patients with chronic kidney disease (CKD) have a higher prevalence of VC as renal function declines, which will result in increased mortality. Serum calciprotein particles (CPPs) are colloidal nanoparticles that have a prominent role in the initiation and progression of VC. The T₅₀ test is a novel test that measures the conversion of primary to secondary calciprotein particles indicating the tendency of serum to calcify. Therefore, we accomplished a comprehensive review as the first integrated approach to clarify fundamental aspects that influence serum CPP levels and T₅₀, and to explore the effects of CPP and calcification propensity on various chronic disease outcomes. In addition, new topics were raised regarding possible clinical uses of T₅₀ in the assessment of VC, particularly in patients with CKD, including possible opportunities in VC management. The relationships between serum calcification propensity and cardiovascular and all-cause mortality were also addressed. The review is the outcome of a comprehensive search on available literature and could open new directions to control VC.

Favourable serum calcification propensity with intraperitoneal as compared with subcutaneous insulin administration in type 1 diabetes

BACKGROUND

Serum calcification propensity can be monitored using the maturation time of calciprotein particles in serum (T₅₀ test). A shorter T₅₀ indicates greater propensity to calcify; this is an independent determinant of cardiovascular disease. As the intraperitoneal (IP) route of insulin administration mimics the physiology more than the subcutaneous (SC) route in persons with type 1 diabetes (T1DM), we hypothesized that IP insulin influences determinants of calcium propensity and therefore result in a longer T₅₀ than SC insulin administration.

METHODS

Prospective, observational case-control study. Measurements were performed at baseline and at 26 weeks in age and gender matched persons with T1DM.

RESULTS

A total of 181 persons, 39 (21.5%) of which used IP and 142 (78.5%) SC insulin were analysed. Baseline T₅₀ was 356 (45) minutes. The geometric mean T₅₀ significantly differed between both treatment groups: 367 [95% confidence interval (CI) 357, 376] for the IP group and 352 (95% CI 347, 357) for the SC group with a difference of -15 (95% CI -25, -4) minutes, in favour of IP treatment. In multivariable analyses, the IP route of insulin administration had a positive relation on T₅₀ concentrations while higher age, triglycerides and phosphate concentrations had an inverse relation.

CONCLUSION

Among persons with T1DM, IP insulin administration results in a more favourable calcification propensity time then SC insulin. It has yet to be shown if this observation translates into improved cardiovascular outcomes.

Serum calcification propensity in type 1 diabetes associates with mineral stress

AIMS

Increased vascular calcification could be an underlying mechanism of cardiovascular complications in type 1 diabetes mellitus (T1DM). Calcificationpropensitycan be monitored by the maturation time of calciprotein particles in serum (T₅₀ test). A high calcification propensity (i.e. low T₅₀-value) is an independent determinant of mortality in various populations. Aim was to investigate T₅₀levels with indices of calcium metabolism and disease status in T1DM patients.

METHODS

As part of a prospective cohort study, T1DM patients were examined annually. At baseline T₅₀ was determined in 216 (77%) patients (57% male) with a mean age of 45 (12) years, diabetes duration 22 [15.8, 30.4] years and HbA1c of 60 (12) mmol/mol (7.6 (1.0) %). Baseline data were collected in 2002 and follow-up data were collected in 2018.

RESULTS

The T₅₀ time was normally distributed with a mean of 339 (60) minutes. Patients in the highest tertile of T₅₀ (range 369-466) were older, had lower phosphate and PTH and higher magnesium and vitamin D concentrations as compared to the middle (range 317-368) and lowest (range 129-316) tertiles, while eGFR was comparable between groups. During follow-up of 15 years, 43 patients developed a macrovascular complication and 26 patients died. In regression analysis, T₅₀ was not a prognostic factor for the development of complications or mortality.

CONCLUSIONS

The T₅₀ time was associated with indices of increased mineral stress, but not with the development of long-term macrovascular complications.

The importance of being amorphous: calcium and magnesium phosphates in the human body

This article focuses on the relevance of amorphous calcium (and magnesium) phosphates in living organisms. Although crystalline calcium phosphate (CaP)-based materials are known to constitute the major inorganic constituents of human hard tissues, amorphous CaP-based structures, often in combination with magnesium, are frequently employed by Nature to build up components of our body and guarantee their proper functioning. After a brief description of amorphous calcium phosphate (ACP) formation mechanism and structure, this paper is focused on the stabilization strategies that can be used to enhance the lifetime of the poorly stable amorphous phase. The various locations of our body in which ACP (pure or in combination with Mg²⁺) can be found (i.e. bone, enamel, small intestine, calciprotein particles and casein micelles) are highlighted, showing how the amorphous nature of ACP is often of paramount importance for the achievement of a specific physiological function. The last section is devoted to ACP-based biomaterials, focusing on how these materials differ from their crystalline counterparts in terms of biological response.