Title: Vitamin K supplementation in patients on continuous ambulatory peritoneal dialysis
Abstract: Author's reply Sir—Biological actions of vitamin K1 (phylloquinone) and vitamins K2 (menaquinone-4, menaquinone-7) are different. We measured phylloquinone, menaquinone-4, and menaquinone-7 in 16 men and 13 women, aged 23–69 years, with chronic renal failure treated with CAPD before vitamin K2 treatment. Phylloquinone concentration was 1·8 (SE 1·9) nmol/L (one undetectable), menaquinone-4 was not detectable, and menaquinone-7 was 20 (1·3) nmol/L (12 undetectable). These concentrations were lower than reported in healthy women,1Shino M Determination of endogenous vitamin K (philloquinone and menaquinone-n) in plasma by high-performance liquid chromatography using platinum oxide catalyst reduction and fluorescence detection.Analyst. 1988; 113: 393-397Crossref PubMed Google Scholar Phylloquinone concentration showed a positive correlation with the triglycerides (r=0·789, p<0·0001), and total cholesterol (r=0·505, p<0·01) (figure). Menaquinone-7 values have a weak relation with serum lipids (menaquinone-7 vs triglyceride r=0·481, p=0·059, menaquinone-7 vs total cholesterol r=0·331, p=0·194). As Andreas Vychytil and Wilfred Druml pointed out, both vitamins K1 and vitamin K2, which are transported with lipoprotein in plasma, correlate with serum lipid concentrations. We also measured vitamins K after menaquinone-4 administration (45 mg per day) in 17 CAPD patients. Phylloquinone concentration was 1·8 (0·7) nmol/L, menaquinone-4 was 336·1 (433·4) nmol/L, and menaquinone-7 was 1085·8 (357·4) nmol/L. Menaquinone-4 in healthy old women with vitamin K2 treatment is 1431·8 (347·0) nmol/mL, which is equivalent to that in our CAPD patients after vitamin K2 treatment. This pharmacological concentration, under which bone mineral contents were improved by the action of the geranylgeraniol side chain,2Hara K Akiyama Y Nakamura T et al.The inhibitory effect of vitamin K2 (manatetrenone) on bone reabsorption may be related to its side chain.Bone. 1995; 16: 179-184Summary Full Text PDF PubMed Scopus (148) Google Scholar was much higher than physiological concentrations. In our research letter we speculated that the pharmacological, but not the physiological, concentrations of vitamin K2 suppress serum cholesterol. Vychytil and Druml raise a caution by citation of Rober's paper that plasma calcium × phosphorus (Ca×P) products as well as high vitamin K1 concentration were major risk factors of ectopic calcification.3Robert D Jorgetti V Leclercq M et al.Does vitamin K excess induce ectopic calcifications in hemodialysis patients?.Clin Nephrol. 1985; 24: 300-304PubMed Google Scholar These workers showed that high vitamin K1 concentration might be related to calcification irr haemodialysis patients. The analytical method of Leclerq et al is appropriate to measure phylloquinone but they did not analyse vitamin K2 concentration. Pharmacological concentrations of vitamin K2 ameliorate the progression of atherosclerotic plaques in rabbits on a high-cholesterol diet.4Kawashima H Nakajima Y Matsubara T et al.Effect of vitamin K2 (menatetrenone) on atherosclerosis and blood coagulation in hypercholesterolaemic rabbits.Jpn J Pharmacol. 1997; 75: 135-143Crossref PubMed Scopus (31) Google Scholar We originally started the administration of vitamin K2 to improve bone-mineral content in CAPD patients because vitamin K2 is much less harmful than vitamin D3, which raises serum CaxP products. Actually, we showed that CAPD patients had no significant change in calcium and phosphorus concentrations during vitamin K2 treatment. We would emphasise that administration of vitamin K2 reduced cholesterol concentration and may improve bone-mineral content without change of serum calcium and phosphorus concentration. Vitamin K supplementation in patients on continuous ambulatory peritoneal dialysisYasuyuki Nagasawa and colleagues (March 7, p 724)1 report that vitamin K2 supplementation (45 mg daily) in patients on continuous ambulatory peritoneal dialysis (CAPD) therapy during 1 year reduces total cholesterol concentration and conclude that vitamin K treatment might be “beneficial for patients with hyperlipidaemia and arteriosclerotic disease”. Full-Text PDF