Ectopic calcification in diabetic vascular disease

Elevated glucose levels increase vascular calcification risk by disrupting extracellular pyrophosphate metabolism

BACKGROUND

Vascular calcification is a major contributor to cardiovascular disease, especially diabetes, where it exacerbates morbidity and mortality. Although pyrophosphate is a recognized natural inhibitor of vascular calcification, there have been no prior studies examining its specific deficiency in diabetic conditions. This study is the first to analyze the direct link between elevated glucose levels and disruptions in extracellular pyrophosphate metabolism.

METHODS

Rat aortic smooth muscle cells, streptozotocin (STZ)-induced diabetic rats, and diabetic human aortic smooth muscle cells were used to assess the effects of elevated glucose levels on pyrophosphate metabolism and vascular calcification. The techniques used include extracellular pyrophosphate metabolism assays, thin-layer chromatography, phosphate-induced calcification assays, BrdU incorporation for DNA synthesis, aortic smooth muscle cell viability and proliferation assays, and quantitative PCR for enzyme expression analysis. Additionally, extracellular pyrophosphate metabolism was examined through the use of radiolabeled isotopes to track ATP and pyrophosphate transformations.

RESULTS

Elevated glucose led to a significant reduction in extracellular pyrophosphate across all diabetic models. This metabolic disruption was marked by notable downregulation of both the expression and activity of ectonucleotide pyrophosphatase/phosphodiesterase 1, a key enzyme that converts ATP to pyrophosphate. We also observed an upregulation of ectonucleoside triphosphate diphosphohydrolase 1, which preferentially hydrolyzes ATP to inorganic phosphate rather than pyrophosphate. Moreover, tissue-nonspecific alkaline phosphatase activity was markedly elevated across all diabetic models. This shift in enzyme activity significantly reduced the pyrophosphate/phosphate ratio. In addition, we noted a marked downregulation of matrix Gla protein, another inhibitor of vascular calcification. The impaired pyrophosphate metabolism was further corroborated by calcification experiments across all three diabetic models, which demonstrated an increased propensity for vascular calcification.

CONCLUSIONS

This study demonstrated that diabetes-induced high glucose disrupts extracellular pyrophosphate metabolism, compromising its protective role against vascular calcification. These findings identify pyrophosphate deficiency as a potential mechanism in diabetic vascular calcification, highlighting a new therapeutic target. Strategies aimed at restoring or enhancing pyrophosphate levels may offer significant potential in mitigating cardiovascular complications in diabetic patients, meriting further investigation.

A miR-125/Sirtuin-7 pathway drives the pro-calcific potential of myeloid cells in diabetic vascular disease

AIMS/HYPOTHESIS

Ectopic calcification is a typical feature of diabetic vascular disease and resembles an accelerated ageing phenotype. We previously found an excess of myeloid calcifying cells in diabetic individuals. We herein examined molecular and cellular pathways linking atherosclerotic calcification with calcification by myeloid cells in the diabetic milieu.

METHODS

We first examined the associations among coronary calcification, myeloid calcifying cell levels and mononuclear cell gene expression in a cross-sectional study of 87 participants with type 2 diabetes undergoing elective coronary angiography. Then, we undertook in vitro studies on mesenchymal stem cells and the THP-1 myeloid cell line to verify the causal relationships of the observed associations.

RESULTS

Coronary calcification was associated with 2.8-times-higher myeloid calcifying cell levels (p=0.037) and 50% elevated expression of the osteogenic gene RUNX2 in mononuclear cells, whereas expression of Sirtuin-7 (SIRT7) was inversely correlated with calcification. In standard differentiation assays of mesenchymal stem cells, SIRT7 knockdown activated the osteogenic program and worsened calcification, especially in the presence of high (20 mmol/l) glucose. In the myeloid cell line THP-1, SIRT7 downregulation drove a pro-calcific phenotype, whereas SIRT7 overexpression prevented high-glucose-induced calcification. Through the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, high glucose induced miR-125b-5p, which in turn targeted SIRT7 in myeloid cells and was directly associated with coronary calcification.

CONCLUSIONS/INTERPRETATION

We describe a new pathway elicited by high glucose through the JAK/STAT cascade, involving regulation of SIRT7 by miR-125b-5p and driving calcification by myeloid cells. This pathway is associated with coronary calcification in diabetic individuals and may be a target against diabetic vascular disease.

DATA AVAILABILITY

RNA sequencing data are deposited in GEO (accession number GSE193510; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE193510 ).

The Emerging Role of Nutraceuticals in Cardiovascular Calcification: Evidence from Preclinical and Clinical Studies

Cardiovascular calcification is the ectopic deposition of calcium-phosphate crystals within the arterial wall and the aortic valve leaflets. This pathological process leads to increased vascular stiffness, reduced arterial elasticity, and aortic valve stenosis, increasing the risk of cardiovascular diseases. Although cardiovascular calcification is an increasing health care burden, to date no medical therapies have been approved for treating or preventing it. Considering the current lack of therapeutic strategies and the increasing prevalence of cardiovascular calcification, the investigation of some nutraceuticals to prevent this pathological condition has become prevalent in recent years. Recent preclinical and clinical studies evaluated the potential anti-calcific role of nutraceuticals (including magnesium, zinc, iron, vitamin K, and phytate) in the progression of vascular calcification, providing evidence for their dietary supplementation, especially in high-risk populations. The present review summarizes the current knowledge and latest advances for nutraceuticals with the most relevant preclinical and clinical data, including magnesium, zinc, iron, vitamin K, and phytate. Their supplementation might be recommended as a cost-effective strategy to avoid nutritional deficiency and to prevent or treat cardiovascular calcification. However, the optimal dose of nutraceuticals has not been identified and large interventional trials are warranted to support their protective effects on cardiovascular disease.

Diagnostic methods for measurement of peripheral blood flow during exercise in patients with type 2 diabetes and peripheral artery disease: a systematic review

INTRODUCTION

Measurement of systolic ankle and to some extent toe pressure in patients suffering from combined type 2 diabetes mellitus (T2DM) and peripheral arterial disease (PAD) face several obstacles due to complex changes in the vascular bed. The aim of this review was to address the current literature on blood flow during exercise in patients with PAD and T2DM and assess the feasibility of these methods to diagnose and grade arterial insufficiency.

EVIDENCE ACQUISITION

A systematic review of the PubMed and EMBASE databases, supplemented by hand searching was performed according to PRISMA guidelines. Clinical studies evaluating methods to investigate peripheral blood flow in patients with PAD and T2DM during exercise were included.

EVIDENCE SYNTHESIS

In total nine eligible studies consisting of 1105 non-diabetic PAD patients, 336 diabetic PAD patients, 161 diabetic patients without PAD and 69 healthy controls were included in the review. Near-infrared spectroscopy (NIRS) was described in three studies, transcutaneous oxygen pressure measurement (TcpO2) in two and the following methods described in single studies: thermodilution, contrast enhanced ultrasound (CEUS), scintigraphy and TcpO2 in combination with ultrasound. These studies shows that patients with PAD and T2DM compared with patients with only PAD suffers different atherosclerotic lesions characterised by increased arterial stiffness and microcirculation abnormalities, not well differentiated by pressure measurement alone. Investigating patients with PAD and T2DM during exercise reveals that NIRS, TcpO2, CEUS, and scintigraphy have distinct advantages over ankle and toe-pressure.

CONCLUSIONS

Using methods like NIRS, TcpO2, CEUS and scintigraphy, peripheral blood flow during exercise can be measured at a detailed level and potentially improve future severity grading in patients with combined T2DM and PAD.

High glucose induces the expression of osteopontin in blood vessels in vitro and in vivo

Osteopontin (OPN) is involved in mineral metabolism and the inflammatory response while diabetes mellitus is associated with severe and extensive vascular calcification. Therefore, we speculated that OPN could be a key factor in the calcification and dysfunction of blood vessels exposed to high glucose. To identify the relationship between high glucose and OPN, we used high glucose medium to stimulate smooth muscle cells (SMCs) and vascular endothelial cells (VECs) in vitro and diabetic rats for in vivo analyses. As assessed by flow cytometry and western blots, SMC and VEC apoptosis levels increased with high glucose. Potassium and calcium uptake by cells were also increased with high glucose. These findings demonstrated the relationship between mineral metabolism and high glucose. Western blot and quantitative real time polymerase chain reaction analyses demonstrated that OPN increased in vitro with high glucose stimulation. The inflammatory factor ICAM1 and the inhibitory phosphorylation of endothelial nitric-oxide synthase (eNOS) (Thr495) were also upregulated by high glucose. In contrast, the anti-inflammatory factor Nrf2 and the activating phosphorylation of eNOS (Ser1177) were downregulated. Similar to the change of OPN, phosphorylated P38 was increased with high glucose. SB203580, an inhibitor of P38 phosphorylation, downregulated the expression of OPN and related inflammatory factors. Additionally, OPN was increased in the aortas and plasma of diabetic rats. In conclusion, our findings demonstrate that high glucose can induce the expression of OPN, which may be a key factor in the calcification and dysfunction of the vascular wall in diabetes.

Clinical impact of coexisting retinopathy and vascular calcification on chronic kidney disease progression and cardiovascular events

BACKGROUND AND AIMS

Retinopathy and vascular calcification (VC) are representative markers of microvascular and macrovascular dysfunction in patients with chronic kidney disease (CKD). However, their relationship and combined effects on clinical outcomes remain undetermined.

METHODS AND RESULTS

We included 523 patients with nondialysis-dependent CKD stage 3-5 who had been examined with fundus photography for diabetic or hypertensive retinopathy. Simple radiographs were analyzed for the presence of VC. The clinical significance of VC of the abdominal aorta and iliofemoral artery (apVC) and retinopathy was evaluated in terms of the rate of renal function decline and composite of any cardiovascular event or death. CKD patients with retinopathy showed higher prevalence of apVC than those without retinopathy (25.6% vs. 12.5%, P < 0.001).The presence of retinopathy was independently associated with apVC (OR 2.13, 95% CI 1.31, 3.49). In multivariate analysis, compared with subjects with neither apVC nor retinopathy, the coexistence of both apVC and retinopathy were independently associated with rapid renal function decline (β = -1.51; 95% CI -2.40, -0.61), whereas apVC or retinopathy alone were not. Compared with subjects with neither apVC nor retinopathy, the HRs for composite end points were 1.05 (95% CI 0.48, 2.27), 1.79 (95% CI 1.14, 2.80), and 2.07 (95% CI 1.17, 3.67) for patients with apVC only, those with retinopathy only, and those with both apVC and retinopathy, respectively.

CONCLUSION

The coexistence of VC and retinopathy was independently associated with CKD progression and cardiovascular events or deaths, and its combined effect was stronger than any separate condition.

HMGB1 Induces Secretion of Matrix Vesicles by Macrophages to Enhance Ectopic Mineralization

Numerous clinical conditions have been linked to ectopic mineralization (EM). This process of pathological biomineralization is complex and not fully elucidated, but thought to be started within matrix vesicles (MVs). We hypothesized that high mobility group box 1 (HMGB1), a cytokine associated with biomineralizing process under physiological and pathological conditions, induces EM via promoting MVs secretion from macrophages. In this study, we found that HMGB1 significantly promoted secretion of MVs from macrophages and subsequently led to mineral deposition in elevated Ca/Pi medium in vitro. Transmission electron microscopy of calcifying MVs showed formation of hydroxyapatite crystals in the vesicle interior. Subcutaneous injection into mice with MVs derived from HMGB1-treated cells showed a greater potential to initiate regional mineralization. Mechanistic experiments revealed that HMGB1 activated neutral sphingomyelinase2 (nSMase2) that involved the receptor for advanced glycation end products (RAGE) and p38 MAPK (upstream of nSMase2). Inhibition of nSMase2 with GW4869 or p38 MAPK with SB-239063 prevented MVs secretion and mineral deposition. Collectively, HMGB1 induces MVs secretion from macrophages at least in part, via the RAGE/p38 MAPK/nSMase2 signaling pathway. Our findings thus reveal a novel mechanism by which HMGB1 induces ectopic mineralization.

Mechanisms of ectopic calcification: implications for diabetic vasculopathy

Vascular calcification (VC) is the deposition of calcium/phosphate in the vasculature, which portends a worse clinical outcome and predicts major adverse cardiovascular events. VC is an active process initiated and regulated via a variety of molecular signalling pathways. There are mainly two types of calcifications: the media VC and the intima VC. All major risk factors for cardiovascular disease (CVD) have been linked to the presence/development of VC. Besides the risk factors, a genetic component is also operative to determine arterial calcification. Several events take place before VC is established, including inflammation, trans-differentiation of vascular cells and homing of circulating pro-calcific cells. Diabetes is an important predisposing factor for VC. Compared with non-diabetic subjects, patients with diabetes show increased VC and higher expression of bone-related proteins in the medial layer of the vessels. In this review we will highlight the mechanisms underlying vascular calcification in diabetic patients.

Carotid plaque calcification predicts future cardiovascular events in type 2 diabetes

OBJECTIVE

The presence of carotid plaques is associated with future cardiovascular events, with local plaque composition being an independent outcome predictor. We examined the association between ultrasonographically determined carotid plaque calcification and incident major adverse cardiovascular events (MACE) and death in type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

We enrolled 581 patients with T2D who underwent routine carotid ultrasonography. Plaques were classified as echolucent (lipid rich), heterogenous, and echogenic (calcific). We collected demographic, anthropometric, and clinical data at baseline and followed the patients for up to 9 years.

RESULTS

Plaques were detected in 81.8% of the patients (echolucent in 16.4%, heterogenous in 43.2%, and echogenic in 22.2%). During follow-up (4.3 ± 0.1 years), 58 deaths (27 cardiovascular) and 236 fatal and nonfatal MACE occurred. In univariate analyses, presence versus absence of any carotid plaque was associated with incident MACE, and the hazard ratio (95% CI) progressively increased from echolucent (1.97 [0.93-3.44]), to heterogeneous (3.10 [2.09-4.23]), to echogenic (3.71 [2.09-5.59]) plaques. Compared with echolucent plaques, echogenic plaques were associated with incident MACE independently from confounders. This association was attenuated after adjusting for the degree of stenosis, but in patients with stenosis ≤30%, echogenic plaque type still predicted total and atherosclerotic MACE, even after further adjusting for mean intima-media thickness.

CONCLUSIONS

In T2D, carotid plaque calcification predicts MACE, especially in patients with a low degree of stenosis. The biology of atherosclerotic calcification in diabetes needs to be further elucidated to understand the basis of this association.

Diabetes modifies the relationships among carotid plaque calcification, composition and inflammation

BACKGROUND AND AIMS

Diabetes is traditionally associated with vascular calcification, but the molecular mechanisms are largely unknown. We herein explored the relationships among carotid plaque calcification, composition and gene expression, and how these are modified by diabetes.

METHODS

We collected carotid endoarterectomy specimen from 59 patients, of whom 23 had diabetes. We analysed histology with pentachromic staining, calcification with Alizarin red and Von Kossa's staining, chemical calcium extraction and quantification, as well as gene expression by quantitative PCR.

RESULTS

We detected no differences in the extent of plaque calcification and in plaque composition between diabetic and non-diabetic patients. In non-diabetic plaques, calcium content was directly correlated with the area occupied by muscle/fibrinoid tissue and inversely correlated with collagen, but such correlations were not seen in plaques from diabetic patients. While consistent correlations were found between calcium content and RUNX2 (direct), as well as Osteopontin (inverse), diabetes modified the association between plaque calcification and inflammatory gene expression. Only in diabetic plaques, calcium content was inversely correlated with MCP1 and IL1b, whereas the direct correlation with TNF-alpha expression seen in non-diabetic plaques was lost in diabetes.

CONCLUSIONS

Though plaque composition and calcification were not quantitatively affected, diabetes modified the relationships between plaque calcium, composition and inflammation. These results suggest that the mechanisms and the clinical significance of atherosclerotic calcification in diabetic may be different than in non-diabetic patients.

Molecular mechanisms of vascular dysfunction and cardiovascular biomarkers in type 2 diabetes

Prevalence of obesity and type 2 diabetes (T2DM) is alarmingly increasing worldwide. Albeit advances in therapy have reduced morbidity and mortality in T2DM, cardiovascular risk is far to be eradicated and mechanism-based therapeutic approaches are in high demand. In this perspective, deciphering novel molecular networks of vascular disease will be instrumental to develop novel diagnostic and therapeutic strategies in people affected by diabetes. There is therefore a need to address current knowledge gaps in disease aetiology in order to support innovation in diagnosis and treatment. Unfortunately, we are still lacking cost-effective markers able to identify atherosclerotic vascular disease at an early stage. The issue of risk stratification deserves attention because not every T2DM patient carries the same degree of inflammation and oxidative stress. The diversity of metabolic phenotypes with different outcomes underscores the need for cardiovascular risk stratification within such heterogeneous population. Early predictors of vascular damage are mandatory to implement intensive treatment strategies and, hence, reduce cardiovascular disease burden in this setting. In this review we critically discuss novel molecular mechanisms of diabetic vascular disease and their possible translation to the clinical setting.