Cees Vermeer

Vitamin-K-Dependent Protection of the Renal Microvasculature: Histopathological Studies in Normal and Diseased Kidneys

Vitamin-K-dependent carboxylation of matrix Gla protein (MGP) protects the macrocirculation against calcification. We recently reported in a multiethnic population study that the estimated glomerular filtration rate, a microvascular trait, decreased and the risk of chronic kidney disease increased with higher circulating levels of inactive dephospho-uncarboxylated MGP, a marker of vitamin K deficiency. These findings highlighted the possibility that vitamin K might have a beneficial effect on the renal microcirculation. To substantiate these epidemiological findings, we undertook a pilot study, in which we stained renal tissue samples obtained by biopsy from 2 healthy kidney donors and 4 patients with nephropathy for carboxylated and uncarboxylated MGP and calcium deposits. Three patients had renal calcifications, which were consistently associated with carboxylated and uncarboxylated MGP. Normal renal tissue was devoid of microcalcifications and staining for carboxylated and uncarboxylated MGP. Pending confirmation in a larger study covering a wider range of renal pathologies, these histopathological findings suggest that MGP might inhibit calcification not only in large arteries, as was known before, but in renal tissue as well, thereby highlighting potentially new avenues for promoting renal health, for instance by vitamin K supplementation.

Steady-state vitamin K2 (menaquinone-7) plasma concentrations after intake of dairy products and soft gel capsules.

Background:In a previous human intervention study, we observed an improved vitamin K status after 8 weeks of intake of a yogurt that was fortified with vitamin K2 (as menaquinone-7, MK-7) and enriched with vitamins C and D3, magnesium and polyunsaturated fatty acids. It was hypothesized that the added nutrients contributed to this improvement. Here we report on a study in which we compared the fasting plasma concentrations of MK-7 from (a) yogurt enriched with MK-7, vitamins D3 and C, magnesium, n-3 poly unsaturated fatty acids (n-3 PUFA) and fish oil (yogurt Kplus), (b) yogurt fortified with MK-7 only (yogurt K) and (c) soft gel capsules containing only MK-7.Subjects/Methods:For 42 days, healthy men and postmenopausal women between 45 and 65 years of age daily consumed either yogurt K, yogurt Kplus or capsules. Circulating MK-7, 25-hydroxy vitamin D (25(OH)D) and markers for vitamin K status (uncarboxylated osteocalcin (ucOC) and desphospho-uncarboxylated matrix Gla-protein (dp-ucMGP)) were assessed. Plasma MK-7 was also measured during the washout period of 2 weeks. MK-7 and dp-ucMGP were measured in citrated plasma, and 25(OH)D3 and ucOC were measured in the serum.Results:The increase in plasma MK-7 with the yogurt Kplus product was more pronounced than the increase in MK-7 with the capsules. Circulating dp-ucMGP and ucOC were significantly lowered after consumption of the yogurt products and the MK-7 capsules, reflecting vitamin K status improvement. No significant differences in fasting plasma concentrations of various biomarkers between the yogurts were found.Conclusions:Dairy matrix and nutrient composition may affect MK-7 delivery and improvement of vitamin K status. Yogurt fortified with MK-7 is a suitable matrix to improve the nutritional status of the fat-soluble vitamins.

YIA6 Medial Vascular Smooth Muscle Cell Cytopenia Accelerates Atherogenesis in APOE-/-MICE

Vascular smooth muscle cells (VSMC) are involved in many arterial diseases including atherosclerosis and aneurysm formation. VSMC accumulation and apoptosis have implications for atherosclerotic plaque stability and development. In a mouse model of inducible VSMC-specific apoptosis, chronic apoptosis of VSMC has been shown to induce features of plaque instability including fibrous cap thinning, plaque calcification, necrotic core enlargement, medial erosion, elastin breaks and accelerated atherogenesis of established atherosclerotic plaques. Based on previous findings, we questioned the role of medial VSMC in the development of atherosclerotic lesions. To test our research question, ApoE-/- and SM22α-hDTR/ApoE-/- mice were injected with 1 ng diphtheria toxin (DT) /gram bodyweight for 3 weeks to induce medial VSMC cytopenia. After 3 weeks, DT treatment was arrested, mice started a Western type diet (0.25% cholesterol) and were sacrificed after 6 and 18 weeks, respectively. The aortic arch including branches was excised and analysed (immune)histochemically. VSMC cytopenia after 3 weeks of DT treatment was verified by analysing vessel cellularity (cells/mm²) in both control (ApoE-/-) and SM22α-hDTR/ApoE-/- mice. A 2-fold decrease in cellularity was observed in SM22α-hDTR/ApoE-/- mice as compared to the control. Atherosclerotic plaque size was quantified on HE stained sections. SM22α-hDTR/ApoE-/- mice displayed significantly accelerated plaque development as compared to control mice. In vitro, induction of apoptosis by ABT737 significantly induced calcification of primary human VSMC whereas ZVAD significantly inhibited calcification. Additional, conditioned medium from both apoptotic and calcified VSMC cultures served as a chemoattractant for macrophages. In vivo, these in vitro findings may explain the pro-inflammatory phenotype of atherosclerotic plaques. In conclusion, medial VSMC cytopenia results in accelerated development of established atherosclerotic plaques, with increased plaque calcification and vessel stenosis.