Vascular calcification in patients with type 2 diabetes: the involvement of matrix Gla protein

  • Sophie Liabeuf1, 2,

    Affiliated with

    • Bourron Olivier3,

      Affiliated with

      • Cees Vemeer4,

        Affiliated with

        • Elke Theuwissen4,

          Affiliated with

          • Elke Magdeleyns4,

            Affiliated with

            • Carole Elodie Aubert3,

              Affiliated with

              • Michel Brazier1,

                Affiliated with

                • Romuald Mentaverri1,

                  Affiliated with

                  • Agnes Hartemann3 and

                    Affiliated with

                    • Ziad A Massy1, 5Email author

                      Affiliated with

                      Cardiovascular Diabetology201413:85

                      DOI: 10.1186/1475-2840-13-85

                      Received: 7 January 2014

                      Accepted: 13 April 2014

                      Published: 24 April 2014



                      Matrix Gla protein (MGP) is an important inhibitor of calcification. The objective of the present study of patients with type 2 diabetes and normal or slightly altered kidney function was to evaluate levels of inactive, dephospho-uncarboxylated MGP(dp-ucMGP) and total uncarboxylated MGP(t-ucMGP) and assess their links with biological and clinical parameters (including peripheral vascular calcification).


                      The DIACART study is a cross-sectional cohort study of 198 patients with type 2 diabetes and normal or slightly altered kidney function. Matrix Gla protein levels were measured with an ELISA and all patients underwent multislice spiral computed tomography scans to score below-knee arterial calcification.


                      In the study population as a whole, the mean dp-ucMGP and t-ucMGP levels were 627 ± 451 pM and 4868 ± 1613 nM, respectively. Glomerular filtration rate, age and current vitamin K antagonist use were independently associated with dp-ucMGP levels. When the study population was divided according to the median peripheral arterial calcification score, patients with the higher score displayed significantly lower t-ucMGP and significantly higher dp-ucMGP levels. Furthermore, plasma dp-ucMGP was positively associated with the peripheral arterial calcification score (independently of age, gender, previous cardiovascular disease and t-ucMGP levels).


                      High dp-ucMGP levels were independently associated with below-knee arterial calcification score in patients with type 2 diabetes and normal or slightly altered kidney function. The reversibility of the elevation of dp-ucMGP levels and the latter’s relationship with clinical events merit further investigation.


                      Matrix gla protein Type 2 diabetes Peripheral calcification


                      Peripheral arterial disease (PAD) is a major vascular complication and the leading cause of amputation in people with diabetes. In patients with PAD, the tibial artery calcification score is a useful tool for identifying patients at high risk of amputation, since the score has greater predictive value than traditional risk factors [1]. Indeed, diabetes accelerates atherosclerosis and increases the incidence of vascular calcification (VC) [2, 3]. In people with diabetes, VC is present in both coronary arteries and arteries of the lower limbs. Furthermore, VC is an independent predictor of cardiovascular and overall mortalities in patients with type 2 diabetes [4]. Various epidemiologic studies have identified specific biomarkers (including osteoprotegerin, osteocalcin and others) for VC in this population [5, 6].

                      One of the most interesting calcification inhibitors is matrix Gla-protein (MGP), a vitamin K-dependent protein that is expressed by smooth muscle cells, fibroblasts, chondrocytes and endothelial cells in a variety of tissues (including arterial vessel wall). There is evidence to suggest that full activation of MGP requires posttranslational carboxylation and phosphorylation (Figure 1) [7, 8]. In order to measure vitamin K status, assays were developed to measure the conformations of MGP with the least activity, i.e. forms with no posttranslational modifications (dephospho-uncarboxylated MGP (dp-ucMGP)) or at least no gammaglutamyl carboxylation (total uncarboxylated MGP (t-ucMGP)) [9]. In fact, dp-ucMGP does not possess calcium-binding groups and is not retained in the vessel wall. Hence, the dp-ucMGP assay is a direct marker of vascular vitamin K status. In both healthy subjects and patients, poor vascular vitamin K status (corresponding to high circulating dp-ucMGP levels) is regarded as a risk marker for forthcoming arterial calcification. Indeed, dp-ucMGP was found to be associated with the severity of aortic calcification in patients with chronic kidney disease (CKD) [10]. Circulating t-ucMGP levels are at least 1000-fold higher than those of dp-ucMGP, and are thought to consist mainly of phosphorylated uncarboxylated MGP (p-ucMGP) species, i.e. MGP-related antigens with between 1 and 3 high-affinity calcium-binding groups. This explains why immunohistochemical techniques invariably find ucMGP to be closely associated with calcium deposits in the vasculature; in turn, this observation is consistent with the inverse association between circulating t-ucMGP levels and the VC score.
                      Figure 1

                      The different forms of the matrix Gla protein (MGP). legend: MGP needs two posttranslational modifications for maturation: glutamate carboxylation and serine phosphorylation. Both modifications are only partially accomplished. Besides the non-modified form (dp-ucMGP) also partially modified species (dp-cMGP and p-ucMGP) and the fully maturated form p-cMGP are present in the circulation. In this paper we have tested dp-ucMGP and total ucMGP (t-ucMGP) (which consists of the sum of dp-ucMGP and p-ucMGP). Since the plasma concentration of p-ucMGP is about 10 thousand fold higher than that of dp-ucMGP, the t-ucMGP assay virtually measures p-ucMGP.

                      A few studies have evaluated the association between MGP levels and VC in patients with diabetes [1113], although the researchers used different antibodies to determine either circulating dp-ucMGP [11], t- ucMGP [12] or other conformations of ucMGP [12, 14]. There are few data on (i) the levels of different MGP forms in a selected population with type 2 diabetes and (ii) the relationships between these various forms and peripheral artery calcification. This knowledge would be useful, since as Dalmeijer et al. have recently demonstrated that high dp-ucMGP levels were associated with increased cardiovascular risk (PAD and heart failure) in patients with type 2 diabetes [11]. Furthermore, Doyon et al. used a rat model of diabetes to show that the decrease in active carboxylated MGP (cMGP) levels could be due to an impairment of gammaglutamate carboxylation - suggesting that the signalling pathways involved in gammaglutamate carboxylase regulation are altered in diabetes [15].

                      The objective of the present study of patients with type 2 diabetes and normal or slightly altered kidney function was to evaluate (i) t-ucMGP and dp-ucMGP levels, (ii) biochemical and clinical parameters associated with differences in dp-ucMGP and t-ucMGP levels and (iii) the potential association between MGP levels and peripheral VC.

                      Materials and methods

                      Ethics statement

                      The study was performed in accordance with the principles of the Declaration of Helsinki and in compliance with the International Conference on Harmonization's guidelines on good clinical practice. The study protocol was approved by the local independent ethics committee (Comité de Protection des Personnes, Paris, France) prior to the initiation of any study-specific procedures. All patients were provided with full information on the study objectives and procedures and gave their written informed consent to participation.

                      Patient selection

                      In the "Diabète et Calcification Arterielle" (DIACART) cross-sectional study, 198 patients with type 2 diabetes from the Diabetology Department and the Cardiology Department at Pitié-Salpêtrière Hospital (Paris, France) were included over an 8-month period. The objective of DIACART study was to gain a better understanding of the pathophysiology of peripheral artery calcification in diabetic patients. The main inclusion criteria were (i) type 2 diabetes, with at least coronary artery disease and/or peripheral arterial occlusive disease and (ii) age >50 for men and >60 for women. The main exclusion criteria were (i) an estimated glomerular filtration rate (eGFR, calculated with the Modification of Diet in Renal Disease equation) <30 ml/min and (ii) a history of lower limb angioplasty and/or bypass.

                      Study protocol

                      All patients were hospitalized for the day in order to perform clinical evaluations, laboratory blood tests and a multislice spiral computed tomography (CT) scan. A patient interview focused on comorbidities and the personal disease history. The patient’s medical records were reviewed to check the information and to record vitamin K antagonist (VKA) use.

                      Previous CVD was defined as a history of any of the following events: myocardial infarction, stroke or any surgical procedures for angina or coronary disease (including percutaneous transluminal angioplasty).

                      Laboratory tests

                      Blood and urine samples were collected after an overnight fast for measurement of routine biochemistry, glycaemia, HbA1C, high-sensitivity C-reactive protein, calcium, phosphorus, 25-OH vitamin D, intact parathyroid hormone (PTH), triglycerides and cholesterol.

                      Selected assays (including dp-ucMGP and t-ucMGP assays) were performed after the samples had been frozen, stored at -80°C and thawed. A dual-antibody ELISA was used to measure dp-ucMGP levels; the capture antibody was directed against the non-phosphorylated MGP sequence 3–15 (mAb-dpMGP; VitaK BV, Maastricht, The Netherlands) and the detecting antibody was directed against the uncarboxylated MGP sequence 35–49 (mAb-ucMGP; VitaK BV). The same antibodies have already been used for immunohistochemical staining [1618]. Intra-assay variability was 5,6% for dp-ucMGP and 8,9% for t-ucMGP, when inter-assay variability was 9,9% for dp-ucMGP and 11,4% for t-ucMGP. In 81 age-matched controls, the mean level of dp-ucMGP was 557 ± 277 pM (median: 522 pM) (measured separately in archived samples).

                      A competitive (single-antibody) ELISA was used to measure t-ucMGP levels, as described previously [9, 19]. In 81 age-matched controls, the mean t-ucMGP level was 4282 ± 1100 nM (median: 4109 nM).

                      Imaging for calculation of the below-knee arterial calcification score

                      Tibial artery calcium scoring was performed after scanning with a 128-slice multidetector CT scanner (Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany) in the craniocaudal direction, from the bottom of the patella down to the ankle region. Contrast agent was not used. Cross-sectional slices (with: 3 mm) were analyzed individually. The analysis was performed with a commercially available software package (Heartbeat CaScore, Philips Healthcare, Eindhoven, The Netherlands) by radiologists who were not aware of the results of the clinical examination or laboratory assays, On cross-sectional images, areas of calcification along below-knee arteries with a density ≥130 Hounsfield units and a surface >1 mm2 were identified automatically. The calcification scores (determined according to the method described by Agatston et al. [20]) for each of the main below-knee arteries (the distal popliteal, anterior tibial, posterior tibial and peroneal arteries) were summed to obtain the overall calcification score.

                      Statistical analyses

                      Data were expressed as the mean ± SD, median or frequency, as appropriate. The study patients were stratified according to the median dp-ucMGP level. This median value appears to be the best available cut off, according to the receiver operating characteristic curve for VC (with a sensitivity of 0.65 and a specificity of 0.70). Intergroup comparisons were made using a χ2 test for categorical variables and Student’s t test or the Kruskall-Wallis test for continuous variables. Spearman correlations were used to identify parameters correlated with dp-ucMGP levels and t-ucMGP. For parameters presenting a non-Gaussian distribution, log-normalized values were considered in tests that require normally distributed variables. Multiple linear regression analysis was used to select factors that were independently associated with dp-ucMGP levels. Unadjusted (Table 1) and adjusted (Table 2) logistic regression analyses were performed to evaluate the association between the peripheral calcification score (as categorized by the median) and dp-ucMGP. A p value ≤ 0.05 was considered to be statistically significant. All statistical analyses were performed using SPSS software (version 13.0, SPSS Inc., Chicago IL, USA) for Windows (Microsoft Corp., Redmond WA, USA).
                      Table 1

                      Univariate logistic regression analysis: variables associated with calcification score divided by the median (n = 198 patients)


                      Odds ratio (95% confidence interval)



                      1.07 (1.03; 1.11)


                      Ln [t-ucMGP]

                      0.27 (0.11; 0.63)


                      Ln [dp-ucMGP]

                      1.88 (1.21; 2.91)



                      2.56 (1.36; 4.75)


                      Previous CVD

                      2.56 (1.36; 4.75)


                      For abbreviations, please refer to Table 3.

                      Variables not significantly associated: diabetes duration, smoking status, VKA treatment, body mass index, SBP, DBP, GFR-MDRD, glycaemia, HbA1c, microalbuminuria, IL6, cholesterol, C-reactive protein, 25(OH) Vit D, calcium, phosphate.

                      Table 2

                      Multivariate logistic regression analysis: variables independently associated with the calcification score divided by the median (n = 198 patients)


                      Odds ratio (95%confidence interval)


                      Age per 1 year

                      1.06 (1.02; 1.11)


                      Ln [t-ucMGP]

                      0.44 (0.17; 1.15)


                      Ln [dp-ucMGP]

                      1.88 (1.14; 3.11)


                      Male gender

                      3.84 (1.66; 8.88)


                      Previous CVD

                      2.56 (1.20; 4.85)


                      Variables entered into the model: age, Ln [dp-ucMGP], Ln [t-ucMGP], gender, previous CVD.


                      Baseline characteristics

                      Table 3 presents the main clinical and biochemical characteristics for the entire cohort and for the subgroups above and below the median dp-ucMGP (559.5 pM) value. Patients with higher plasma dp-ucMGP levels were significantly older, were more likely to taking VKAs and had higher body mass index, PTH levels and triglyceride levels and a lower eGFR. Patients with higher plasma t-ucMGP levels (i.e. above to the median t-ucMGP value (4741 nM) were significantly younger, had higher body mass index, diastolic blood pressure, calcium and triglyceride levels and lower PTH levels. It is noteworthy that although only six patients were being treated with VKA, their dp-ucMGP levels were much higher than in untreated patients (the mean and median dp-ucMGP levels were 2093 ± 1125 pM and 1984 pM for VKA-treated patients and 581 ± 327 pM and 553 pM for non-VKA-treated patients). Treatment with renin angiotensin aldosterone inhibitors was not associated with changes in levels of MGP forms or in the calcification score. We also compared patients as a function of their HbA1c levels (above vs. below 7%) but found no difference in terms of either VC, t-ucMGP or dp-ucMGP.
                      Table 3

                      Baseline characteristics as a function of the median plasma dp-ucMGP level



                      [dp-ucMGP] ≤ 559.5 pM

                      [dp-ucMGP] > 559.5 pM



                      n = 198

                      n = 99

                      n = 99


                      Age (years)

                      64 ± 8

                      63 ± 9

                      66 ± 8


                      Diabetes duration (years)

                      15 ± 10

                      14 ± 10

                      15 ± 9


                      Male gender n (%)

                      158 (80)

                      82 (83)

                      76 (77)


                      Body mass index (kg/m 2 )

                      29 ± 5

                      28 ± 5

                      30 ± 5


                      SBP (mmHg)

                      127 ± 17

                      126 ± 17

                      128 ± 17


                      DBP (mmHg)

                      73 ± 9

                      73 ± 9

                      72 ± 8


                      Smoking habit n (%)

                      119 (60)

                      58 (59)

                      61 (62)


                      Previous CVD n (%)

                      139 (70)

                      66 (67)

                      73 (74)


                      Glycaemia (mmol/l)

                      8.2 ± 2.8

                      8.0 ± 2.6

                      8.3 ± 2.9






                      HbA1c (%)

                      7.8 ± 1.5 (7.5)

                      7.7 ± 1.4

                      7.9 ± 1.5






                      GFR MDRD (mmol/l)

                      80 ± 19

                      82 ± 19

                      70 ± 19


                      Microalbuminuria (mg/l)

                      166 ± 840

                      169 ± 1132

                      162 ± 373






                      Calcium (mmol/l)

                      2.30 ± 0.10

                      2.30 ± 0.10

                      2.34 ± 0.10


                      Phosphate (mmol/l)

                      1.02 ± 0.15

                      1.04 ± 0.20

                      1.00 ± 0.20


                      Intact PTH

                      54.5 ± 27.5

                      50.8 ± 26.0

                      58.5 ± 28.9







                      25(OH)Vit D (ng/ml)

                      13.8 ± 8.4

                      14.4 ± 8.2

                      13.2 ± 8.5







                      2.2 ± 1.5

                      2.2 ± 2.6

                      2.2 ± 2.5








                      1.6 ± 1.1

                      1.4 ± 1.1

                      1.6 ± 0.9







                      Total cholesterol (mmol/l)

                      3.7 ± 0.9

                      3.7 ± 0.8

                      3.8 ± 0.9


                      LDL cholesterol

                      1.9 ± 0.7

                      1.9 ± 0.7

                      2.0 ± 0.8







                      Total cholesterol/HDL

                      3.7 ± 1.6

                      3.5 ± 1.1

                      3.9 ± 1.8







                      Peripheral calcification score

                      2528 ± 5779

                      1609 ± 3983

                      3447 ± 7040






                      t-ucMGP (nM)

                      4868 ± 1613

                      4815 ± 1689

                      4921 ± 1539 (4787)





                      dp-ucMGP (pM)

                      627 ± 451

                      342 ± 142

                      912 ± 474







                      VKA treatment n (%)

                      6 (3)

                      0 (0)

                      6 (6)


                      Data are given as means ± SD for normally distributed measures with addition of (median) for non-normally distributed values for variables with a non-Gaussian distribution or as the number (percentage) for binary variables.

                      SBP: systolic blood pressure; DBP: diastolic blood pressure; CVD: cardiovascular disease; HbA1c: haemoglobin A1C; GFR MDRD: Glomerular filtration rate calculated with the Modification of Diet in Renal Disease formula; PTH: parathyroid hormone; CRP: C-reactive protein, t-ucMGP: total uncarboxylated matrix Gla-protein; dp-ucMGP: dephospho-uncarboxylated matrix Gla-protein. VKA: vitamin K antagonist.

                      MGP values as a function of the calcification score

                      Patients with an above-median peripheral arterial score had significantly lower t-ucMGP levels (median: 4941 nM vs. 4550 nM, respectively; p = 0.006) and significantly higher dp-ucMGP levels (median: 480 pM vs. 652 pM respectively; p = 0.001).

                      Associations between dp-ucMGP and calcification

                      A univariate correlation analysis with plasma dp-ucMGP essentially confirmed the results as described in Table 3 (Table 4). These findings did not change when the six VKA-treated patients were excluded from the analyses. Moreover, a multivariate linear regression analysis (including all variables significantly associated with plasma dp-ucMGP levels in the univariate analyses) identified eGFR (p < 0.0001), age (p =0.002) and current antivitamin K use (p < 0.0001) as independent factors.
                      Table 4

                      Univariate correlations: variables associated with plasma dp-ucMGP levels and t-ucMGP levels


                      dp-ucMGP levels

                      t-ucMGP levels











                      Diabetes duration





                      Body mass index

























                      GFR MDRD




















                      Intact PTH (pg/mL)










                      C-reactive protein










                      Total cholesterol





                      Total cholesterol/HDL cholesterol










                      Peripheral calcification score





                      For abbreviations, please refer to Table 3. r = Spearman correlation coefficient.

                      In the present cohort, we found that age, male gender, previous CVD, and dp-ucMGP levels were positive risk factors for an elevated calcification score, whereas t-ucMGP appeared to protect against VC in a univariate analysis (Table 1). Furthermore, in a multivariate logistic analysis, dp-ucMGP appeared to an independent predictor of peripheral arterial calcification (independently of age, gender, previous CVD and t-ucMGP levels) (Table 2). Patients with high dp-ucMGP presented an elevated risk of VC, independently of classical risk factors. Similar evidence was obtained after the exclusion of VKA-treated patients from the analysis.


                      The present study is the first to show that in patients with type 2 diabetes and normal or slightly altered kidney function, dp-ucMGP levels (a marker for vitamin K status) are independently associated with age, eGFR and VKA treatment. More importantly, peripheral VC is associated with dp-ucMGP (independently of age, gender, previous CVD and t-ucMGP levels).

                      Matrix Gla protein is a strong inhibitor of VC, as revealed by the development of massive VC in MGP knockout mice [21]. Indeed, MGP is a vitamin K-dependent inhibitor of calcium phosphate precipitation and crystal formation in the vessel wall [22]. Furthermore, it suppresses the activity of bone morphogenetic proteins 2 and 4 [22, 23]. The value of MGP as a calcification biomarker has been evaluated in various cohorts, and a number of assays have been developed to measure its various conformations. In the present study, we evaluated circulating t-ucMGP and dp-ucMGP concentrations. We focused on dp-ucMGP because this form has low affinity for vascular calcium deposits and is secreted into the bloodstream by vascular smooth muscle cells. Moreover, dp-ucMGP is a well-known marker for vascular vitamin K status. High levels of dp-ucMGP have been associated with aortic calcification (independently of classical risk factors) in patients at different stages of CKD [10, 24]. Similarly, the present study is the first to demonstrate that in patients with type 2 diabetes and normal or slightly altered kidney function, dp-ucMGP levels were positively associated with peripheral artery calcification (independently of age, gender, previous CVD and t-ucMGP). It is important to study VC in diabetic patients, since as calcification process could present specific features. Indeed Flammer et al. recently reported that patients with elevated HbA1c levels had a significantly higher percentage of circulating blood mononuclear cells expressing the osteoblastic marker osteocalcin. However, further research is required to establish whether these cells increase VC [25]. On the same lines, a distinct subpopulation of circulating cells expressing osteocalcin and bone alkaline phosphatase had procalcific activity in type 2 diabetic patients [26].

                      Indeed, the present study is the first to have evaluated the potential role of this important calcification inhibitor and its relationship with peripheral artery calcification (as evaluated with a CT-based methodology). This result is in agreement with recently published data from a prospective study of 518 patients with type 2 diabetes (mean follow-up period: 11.2 years); Dalmeijer et al. demonstrated a strong, independent relationship between high dp-ucMGP and cardiovascular risk (and PAD in particular), whereas t-ucMGP levels were not associated with CVD [11]. Indeed, the presence of medial calcification (which is particularly present in peripheral arteries [27]) could explain the positive correlation between dp-ucMGP levels and PAD.

                      Only one study (in outpatients with stable CVD) reported that higher t-ucMGP levels are associated with lower mitral annular calcification (MAC) in persons without diabetes and higher MAC in persons with diabetes [12]. In the present study, a univariate analysis revealed an inverse relationship between t-ucMGP and peripheral artery calcification; however, this link was no longer significant after adjustment for dp-ucMGP. The conflicting results in these two studies might be due to differences in the calcification site evaluated (MAC versus peripheral calcification) and patient recruitment (outpatients with stable CVD versus patients in a diabetes ward). However, it appears to be important to assay for dp-ucMGP when focusing on peripheral VC, since this factor is still associated with peripheral artery calcification after multiple adjustments. Furthermore, Dalmeijer et al. reported that dp-ucMGP levels (but not t-ucMGP levels) were associated with PAD. These findings suggest that VC sites differ in terms of their specific features and biomarkers. This is of particular interest in the pathophysiology of VC in patients with diabetes, who are particularly prone to this condition. Indeed, peripheral artery calcification is very frequent in patients with diabetes and can lead to amputation.

                      Furthermore, we identified eGFR, age and current VKA use as independent factors for dp-ucMGP levels. It is already know that in patients with CKD, levels of inactive forms of MGP increase progressively [10]. Even when patients with normal or slightly altered kidney function are selected, eGFR is still a strong predictor of MGP levels. It is noteworthy that the link between dp-ucMGP levels and calcification appeared to be independent of kidney function in the present study.

                      The use of VKAs appears to be an important predictor of dp-ucMGP; the six VKA-treated patients had dp-ucMGP levels that were around 4 times greater than in the other patients. Indeed, VKA treatment indirectly inhibits the carboxylation of vitamin K-dependent proteins via interactions with vitamin K epoxide reductase. Hence, VKA treatment inhibits the gamma-carboxylation of MGP and leads to an increase in inactive forms of MGP and thus prompts VC [28, 29]. Indeed, epidemiological studies performed in the last decade have revealed VC in warfarin-treated patients [29].

                      Until recently, VKAs were the only drugs for long-term treatment of thromboembolic disorders. However, novel new oral anticoagulant agents (NOACs) have now emerged (e.g. factor Xa inhibitors such as rivaroxaban, apixaban and factor IIa inhibitors such as dabigatran). Unlike VKAs, the NOACs do not interfere with vitamin K-dependent proteins and may thus be safer with regard to VC. This advantage is particular important in diabetic populations, who are particular prone to the development of VC. However, this hypothesis needs to be confirmed in prospective trials and balanced against the efficacy and safety of NOACs.

                      Given that VC in general and peripheral calcification in particular are major problems in patients with diabetes, modulation of vitamin K status might be an interesting therapeutic option. Indeed, vitamin K is gaining increasing attention in terms of its therapeutic potential in VC [30, 31]. In a recent pilot study, vitamin K supplementation in dialyzed patients was tested as a means of improving vitamin K status. Indeed, short-term supplementation with menaquinone-7 (vitamin K2) was found to reduce dp-ucMGP levels in haemodialysis patients [32]. It remains to be seen whether vitamin K supplementation could have an impact on VC in patients with diabetes (through evaluation in large clinical trials).

                      The limitation of the present study included the small sample size, the lack of evaluation of vitamin K intake and serum vitamin K levels, and the evaluation of marker levels at a single time point. The study would have been strengthened by the presence of a control group of participants with vascular calcification data, so that they could have been compared with diabetic patients. In contrast, one of the study’s main strengths relates to the fact that this was the first study to concomitant evaluate dp-ucMGP/t-ucMGP and peripheral artery calcification in patients with type 2 diabetes.


                      In patients with type 2 diabetes, with high cardiovascular risk and normal or slightly altered kidney function, elevated dp-ucMGP levels are independently correlated with the severity of peripheral artery calcification. Hence, dp-ucMGP may be a valuable biomarker in patients with diabetes. The reversibility of the elevation of dp-ucMGP levels and the latter’s relationship with clinical events merit further investigation.



                      Matrix gla protein


                      Dephospho-uncarboxylated matrix gla protein


                      Total uncarboxylated matrix gla protein


                      Phosphorylated uncarboxylated matrix gla protein


                      Carboxylated matrix gla protein


                      Vascular calcification


                      Peripheral artery disease


                      Chronic kidney disease


                      Estimated glomerular filtration rate


                      Haemoglobin A1C

                      GFR MDRD: 

                      Glomerular filtration rate calculated with the modification of diet in renal disease formula


                      Parathyroid hormone


                      C-reactive protein


                      Computed tomography


                      Vitamin k antagonist


                      Cardiovascular disease


                      Systolic blood pressure


                      Diastolic blood pressure.



                      The authors thank Lilly Company, the University of Lausanne, and the clinical staff of the Center for Clinical Investigations Paris-Est, as well as the Diabetes and Cardiology Departments from the AP-HP Pitié-Salpêtrière Hospital in Paris for their participation in this project. This study was supported by a fund from Lilly Company. The company was involved neither in the design of the study nor in data collection. The research activities of C.E. Aubert were supported by a doctoral research scholarship from the University of Lausanne.

                      Authors’ Affiliations

                      INSERM U1088, Jules Verne University of Picardy
                      Clinical Research Centre, Division of Clinical Pharmacology, Amiens University Hospital, Jules Verne University of Picardy
                      Diabetology Department, AP-HP, Pitie-Salpétrière Hospital and Pierre, Marie Curie University of Paris
                      VitaK, Maastricht University
                      Division of Nephrology, Ambroise Paré Hospital, Paris-Ile-de-France-Ouest University (UVSQ)


                      1. Guzman RJ, Brinkley DM, Schumacher PM, Donahue RM, Beavers H, Qin X: Tibial artery calcification as a marker of amputation risk in patients with peripheral arterial disease. J Am Coll Cardiol. 2008, 51 (20): 1967-1974. 10.1016/j.jacc.2007.12.058.PubMed CentralView ArticlePubMed
                      2. Kronmal RA, McClelland RL, Detrano R, Shea S, Lima JA, Cushman M, Bild DE, Burke GL: Risk factors for the progression of coronary artery calcification in asymptomatic subjects: results from the Multi-Ethnic Study of Atherosclerosis (MESA). Circulation. 2007, 115 (21): 2722-2730. 10.1161/CIRCULATIONAHA.106.674143.View ArticlePubMed
                      3. Raggi P, Cooil B, Ratti C, Callister TQ, Budoff M: Progression of coronary artery calcium and occurrence of myocardial infarction in patients with and without diabetes mellitus. Hypertension. 2005, 46 (1): 238-243. 10.1161/01.HYP.0000164575.16609.02.View ArticlePubMed
                      4. Rossi A, Targher G, Zoppini G, Cicoira M, Bonapace S, Negri C, Stoico V, Faggiano P, Vassanelli C, Bonora E: Aortic and mitral annular calcifications are predictive of all-cause and cardiovascular mortality in patients with type 2 diabetes. Diabetes Care. 2012, 35 (8): 1781-1786. 10.2337/dc12-0134.PubMed CentralView ArticlePubMed
                      5. Aoki A, Murata M, Asano T, Ikoma A, Sasaki M, Saito T, Otani T, Jinbo S, Ikeda N, Kawakami M, Ishikawa SE: Association of serum osteoprotegerin with vascular calcification in patients with type 2 diabetes. Cardiovasc Diabetol. 2013, 12: 11-10.1186/1475-2840-12-11.PubMed CentralView ArticlePubMed
                      6. Sheng L, Cao W, Cha B, Chen Z, Wang F, Liu J: Serum osteocalcin level and its association with carotid atherosclerosis in patients with type 2 diabetes. Cardiovasc Diabetol. 2013, 12: 22-10.1186/1475-2840-12-22.PubMed CentralView ArticlePubMed
                      7. Schurgers LJ, Spronk HM, Skepper JN, Hackeng TM, Shanahan CM, Vermeer C, Weissberg PL, Proudfoot D: Post-translational modifications regulate matrix Gla protein function: importance for inhibition of vascular smooth muscle cell calcification. J Thromb Haemost. 2007, 5 (12): 2503-2511. 10.1111/j.1538-7836.2007.02758.x.View ArticlePubMed
                      8. Schurgers LJ, Uitto J, Reutelingsperger CP: Vitamin K-dependent carboxylation of matrix Gla-protein: a crucial switch to control ectopic mineralization. Trends Mol Med. 2013, 19 (4): 217-226. 10.1016/j.molmed.2012.12.008.View ArticlePubMed
                      9. Cranenburg EC, Koos R, Schurgers LJ, Magdeleyns EJ, Schoonbrood TH, Landewe RB, Brandenburg VM, Bekers O, Vermeer C: Characterisation and potential diagnostic value of circulating matrix Gla protein (MGP) species. Thromb Haemost. 2010, 104 (4): 811-822. 10.1160/TH09-11-0786.View ArticlePubMed
                      10. Schurgers LJ, Barreto DV, Barreto FC, Liabeuf S, Renard C, Magdeleyns EJ, Vermeer C, Choukroun G, Massy ZA: The circulating inactive form of matrix gla protein is a surrogate marker for vascular calcification in chronic kidney disease: a preliminary report. Clin J Am Soc Nephrol. 2010, 5 (4): 568-575. 10.2215/CJN.07081009.PubMed CentralView ArticlePubMed
                      11. Dalmeijer GW, van der Schouw YT, Magdeleyns EJ, Vermeer C, Verschuren WM, Boer JM, Beulens JW: Matrix Gla Protein Species and Risk of Cardiovascular Events in Type 2 Diabetic Patients. Diabetes Care. 2013, 36 (11): 3766-3771. 10.2337/dc13-0065.PubMed CentralView ArticlePubMed
                      12. Parker BD, Schurgers LJ, Vermeer C, Schiller NB, Whooley MA, Ix JH: The association of uncarboxylated matrix Gla protein with mitral annular calcification differs by diabetes status: The Heart and Soul study. Atherosclerosis. 2010, 210 (1): 320-325. 10.1016/j.atherosclerosis.2009.11.023.PubMed CentralView ArticlePubMed
                      13. Thomsen SB, Rathcke CN, Zerahn B, Vestergaard H: Increased levels of the calcification marker matrix Gla Protein and the inflammatory markers YKL-40 and CRP in patients with type 2 diabetes and ischemic heart disease. Cardiovasc Diabetol. 2010, 9: 86-10.1186/1475-2840-9-86.PubMed CentralView ArticlePubMed
                      14. Silaghi CN, Fodor D, Craciun AM: Circulating matrix Gla protein: a potential tool to identify minor carotid stenosis with calcification in a risk population. Clin Chem Lab Med. 2013, 51 (5): 1115-1123.View ArticlePubMed
                      15. Doyon M, Mathieu P, Moreau P: Decreased expression of gamma-carboxylase in diabetes-associated arterial stiffness: impact on matrix Gla protein. Cardiovasc Res. 2013, 97 (2): 331-338. 10.1093/cvr/cvs325.View ArticlePubMed
                      16. Schurgers LJ, Teunissen KJ, Knapen MH, Kwaijtaal M, van Diest R, Appels A, Reutelingsperger CP, Cleutjens JP, Vermeer C: Novel conformation-specific antibodies against matrix gamma-carboxyglutamic acid (Gla) protein: undercarboxylated matrix Gla protein as marker for vascular calcification. Arterioscler Thromb Vasc Biol. 2005, 25 (8): 1629-1633. 10.1161/01.ATV.0000173313.46222.43.View ArticlePubMed
                      17. Schurgers LJ, Spronk HM, Soute BA, Schiffers PM, DeMey JG, Vermeer C: Regression of warfarin-induced medial elastocalcinosis by high intake of vitamin K in rats. Blood. 2007, 109 (7): 2823-2831.PubMed
                      18. Shroff RC, McNair R, Figg N, Skepper JN, Schurgers L, Gupta A, Hiorns M, Donald AE, Deanfield J, Rees L, Shanahan CM: Dialysis accelerates medial vascular calcification in part by triggering smooth muscle cell apoptosis. Circulation. 2008, 118 (17): 1748-1757. 10.1161/CIRCULATIONAHA.108.783738.View ArticlePubMed
                      19. Cranenburg EC, Vermeer C, Koos R, Boumans ML, Hackeng TM, Bouwman FG, Kwaijtaal M, Brandenburg VM, Ketteler M, Schurgers LJ: The circulating inactive form of matrix Gla Protein (ucMGP) as a biomarker for cardiovascular calcification. J Vasc Res. 2008, 45 (5): 427-436. 10.1159/000124863.View ArticlePubMed
                      20. Agatston AS, Janowitz WR, Hildner FJ, Zusmer NR, Viamonte M, Detrano R: Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol. 1990, 15 (4): 827-832. 10.1016/0735-1097(90)90282-T.View ArticlePubMed
                      21. Luo G, Ducy P, McKee MD, Pinero GJ, Loyer E, Behringer RR, Karsenty G: Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein. Nature. 1997, 386 (6620): 78-81. 10.1038/386078a0.View ArticlePubMed
                      22. Jia G, Stormont RM, Gangahar DM, Agrawal DK: Role of matrix Gla protein in angiotensin II-induced exacerbation of vascular calcification. Am J Physiol Heart Circ Physiol. 2012, 303 (5): H523-H532. 10.1152/ajpheart.00826.2011.PubMed CentralView ArticlePubMed
                      23. Wajih N, Borras T, Xue W, Hutson SM, Wallin R: Processing and transport of matrix gamma-carboxyglutamic acid protein and bone morphogenetic protein-2 in cultured human vascular smooth muscle cells: evidence for an uptake mechanism for serum fetuin. J Biol Chem. 2004, 279 (41): 43052-43060. 10.1074/jbc.M407180200.View ArticlePubMed
                      24. Boxma PY, van den Berg E, Geleijnse JM, Laverman GD, Schurgers LJ, Vermeer C, Kema IP, Muskiet FA, Navis G, Bakker SJ, De Borst MH: Vitamin k intake and plasma desphospho-uncarboxylated matrix Gla-protein levels in kidney transplant recipients. PLoS One. 2013, 7 (10): e47991.View Article
                      25. Flammer AJ, Gossl M, Li J, Matsuo Y, Reriani M, Loeffler D, Simari RD, Lerman LO, Khosla S, Lerman A: Patients with an HbA1c in the prediabetic and diabetic range have higher numbers of circulating cells with osteogenic and endothelial progenitor cell markers. J Clin Endocrinol Metab. 2012, 97 (12): 4761-4768. 10.1210/jc.2012-2642.PubMed CentralView ArticlePubMed
                      26. Fadini GP, Albiero M, Menegazzo L, Boscaro E, Vigili De Kreutzenberg S, Agostini C, Cabrelle A, Binotto G, Rattazzi M, Bertacco E, Bertorelle R, Biasini L, Mion M, Plebani M, Ceolotto G, Angelini A, Castellani C, Menegolo M, Grego F, Dimmeler S, Seeger F, Zeiher A, Tiengo A, Avogaro A: Widespread increase in myeloid calcifying cells contributes to ectopic vascular calcification in type 2 diabetes. Circ Res. 2011, 108 (9): 1112-1121. 10.1161/CIRCRESAHA.110.234088.View ArticlePubMed
                      27. Johnson RC, Leopold JA, Loscalzo J: Vascular calcification: pathobiological mechanisms and clinical implications. Circ Res. 2006, 99 (10): 1044-1059. 10.1161/01.RES.0000249379.55535.21.View ArticlePubMed
                      28. Price PA, Faus SA, Williamson MK: Warfarin causes rapid calcification of the elastic lamellae in rat arteries and heart valves. Arterioscler Thromb Vasc Biol. 1998, 18 (9): 1400-1407. 10.1161/01.ATV.18.9.1400.View ArticlePubMed
                      29. Chatrou ML, Winckers K, Hackeng TM, Reutelingsperger CP, Schurgers LJ: Vascular calcification: the price to pay for anticoagulation therapy with vitamin K-antagonists. Blood Rev. 2012, 26 (4): 155-166. 10.1016/j.blre.2012.03.002.View ArticlePubMed
                      30. Holden RM, Morton AR, Garland JS, Pavlov A, Day AG, Booth SL: Vitamins K and D status in stages 3–5 chronic kidney disease. Clin J Am Soc Nephrol. 2010, 5 (4): 590-597. 10.2215/CJN.06420909.PubMed CentralView ArticlePubMed
                      31. Krueger T, Westenfeld R, Ketteler M, Schurgers LJ, Floege J: Vitamin K deficiency in CKD patients: a modifiable risk factor for vascular calcification?. Kidney Int. 2009, 76 (1): 18-22. 10.1038/ki.2009.126.View ArticlePubMed
                      32. Westenfeld R, Krueger T, Schlieper G, Cranenburg EC, Magdeleyns EJ, Heidenreich S, Holzmann S, Vermeer C, Jahnen-Dechent W, Ketteler M, Floege J, Schurgers LJ: Effect of vitamin K2 supplementation on functional vitamin K deficiency in hemodialysis patients: a randomized trial. Am J Kidney Dis. 2012, 59 (2): 186-195. 10.1053/j.ajkd.2011.10.041.View ArticlePubMed


                      © Liabeuf et al.; licensee BioMed Central Ltd. 2014

                      This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://​creativecommons.​org/​publicdomain/​zero/​1.​0/​) applies to the data made available in this article, unless otherwise stated.