Vitamin D metabolism in critically ill patients with acute kidney injury: a prospective observational study.

BACKGROUND: Vitamin D deficiency in critically ill patients is associated with poor outcomes, and vitamin D supplementation is recommended for patients with chronic kidney disease. Whether acute kidney injury (AKI) is associated with altered Vitamin D metabolism is unknown. We aimed to compare the longitudinal profiles of serum 25(OH)D and 1,25(OH)2D concentrations in critically ill patients with and without moderate to severe AKI and explore the impact of renal recovery and parathyroid hormone (PTH). METHODS: In this prospective, observational study in two centres in the UK, critically ill patients with and without AKI underwent serial measurement of serum 25(OH)D and 1,25(OH)2D and plasma PTH concentrations for 5 days. Linear mixed model analysis and sensitivity analyses were performed. RESULTS: Serial data of 137 patients were analysed. Seventy-one patients had AKI stage II/III of whom 23 recovered kidney function during the 5-day study period; 66 patients did not have AKI at enrolment of whom 14 developed new AKI. On day of enrolment, patients' serum 25(OH)D concentrations were low (median 18 nmol/L) but there was no significant difference between patients with and without AKI. Median serum 1,25(OH)2D levels were significantly lower in patients with AKI II/III (41 pmol/L [IQR 26, 58]) compared to similarly unwell patients without AKI (54 pmol/L [IQR 33, 69]) during the 5-day period. Recovery of kidney function in patients with AKI was associated with a rise in 1,25(OH)2D concentrations. Plasma PTH results were impacted by serum calcium and magnesium levels but not associated with 1,25(OH)2D levels. CONCLUSIONS: Critically ill patients with moderate-to-severe AKI have significantly lower serum 1,25(OH)2D concentrations than similarly sick patients without AKI but there was no difference in serum 25(OH)D concentrations. Recovery of AKI was associated with a rise in serum 1,25(OH)2D concentrations. More research is needed to investigate the health benefits and safety of supplementation with active vitamin D in critically ill patients with moderate-to-severe AKI. Trial registration Clinicaltrials.gov (NCT02869919), registered on 16 May 2016.

The additive effect of vitamin K supplementation and bisphosphonate on fracture risk in post-menopausal osteoporosis: a randomised placebo controlled trial.

This study assessed whether vitamin K, given with oral bisphosphonate, calcium and/or vitamin D has an additive effect on fracture risk in post-menopausal women with osteoporosis. No difference in bone density or bone turnover was observed although vitamin K1 supplementation led to a modest effect on parameters of hip geometry. PURPOSE: Some clinical studies have suggested that vitamin K prevents bone loss and may improve fracture risk. The aim was to assess whether vitamin K supplementation has an additive effect on bone mineral density (BMD), hip geometry and bone turnover markers (BTMs) in post-menopausal women with osteoporosis (PMO) and sub-optimum vitamin K status receiving bisphosphonate, calcium and/or vitamin D treatment. METHODS: We conducted a trial in 105 women aged 68.7[12.3] years with PMO and serum vitamin K1 ≤ 0.4 µg/L. They were randomised to 3 treatment arms; vitamin K1 (1 mg/day) arm, vitamin K2 arm (MK-4; 45 mg/day) or placebo for 18 months. They were on oral bisphosphonate and calcium and/or vitamin D. We measured BMD by DXA, hip geometry parameters using hip structural analysis (HSA) software and BTMs. Vitamin K1 or MK-4 supplementation was each compared to placebo. Intention to treat (ITT) and per protocol (PP) analyses were performed. RESULTS: Changes in BMD at the total hip, femoral neck and lumbar spine and BTMs; CTX and P1NP did not differ significantly following either K1 or MK-4 supplementation compared to placebo. Following PP analysis and correction for covariates, there were significant differences in some of the HSA parameters at the intertrochanter (IT) and femoral shaft (FS): IT endocortical diameter (ED) (% change placebo:1.5 [4.1], K1 arm: -1.02 [5.07], p = 0.04), FS subperiosteal/outer diameter (OD) (placebo: 1.78 [5.3], K1 arm: 0.46 [2.23] p = 0.04), FS cross sectional area (CSA) (placebo:1.47 [4.09],K1 arm: -1.02[5.07], p = 0.03). CONCLUSION: The addition of vitamin K1 to oral bisphosphonate with calcium and/or vitamin D treatment in PMO has a modest effect on parameters of hip geometry. Further confirmatory studies are needed. TRIAL REGISTRATION: The study was registered at Clinicaltrial.gov:NCT01232647.

Prevalence of elevated serum concentrations of biotin in patients from South East England, Korea, Singapore and Thailand and risk of immunoassay interference.

Biotin interference in immunoassays using biotin-streptavidin binding technology is well recognised by clinical laboratories, though the prevalence of elevated biotin in patient populations is largely unknown. We determined serum biotin concentrations in 4385 patient samples received sequentially by 6 laboratories for routine immunoassay analysis in England, and Korea, Singapore and Thailand (3 countries within the Asia Pacific region, APAC). Samples were initially analysed using a research use-only immunoassay, with those identified as having potentially elevated biotin concentrations referred for definitive analysis by LC-MS/MS. The prevalence of elevated serum biotin was 0.4% and 0.6% for England and APAC, respectively (range 10.0-129.0 µg/L). Our data adds to a report from a different region of England and is the first for APAC. Laboratories and clinicians benefit from an awareness of the prevalence of elevated serum biotin, which coupled with an understanding of the threshold at which interference occurs, reduces clinical impact of analytical error.

Exclusively breastmilk-fed preterm infants are at high risk of developing subclinical vitamin K deficiency despite intramuscular prophylaxis at birth.

BACKGROUND: There is near-global consensus that all newborns be given parenteral vitamin K1 (VK1 ) at birth as prophylaxis against VK deficiency bleeding (VKDB). Breastmilk has a low VK content and cases of late VKDB are reported in exclusively breastmilk-fed preterm infants despite VK prophylaxis at birth. OBJECTIVES: To assess the prevalence of functional VK insufficiency in preterm infants based on elevated under-γ-carboxylated (Glu) species of Gla proteins, factor II (PIVKA-II), and osteocalcin (GluOC), synthesized by liver and bone, respectively. PATIENTS/METHODS: Prospective, multicenter, observational study in preterm infants born <33 weeks' gestation. Blood samples and dietary history were collected before hospital discharge, and after discharge at 2-3 months' corrected age. Outcome measures were serum VK1 , PIVKA-II, and %GluOC (GluOC as a percentage of the sum of GluOC plus GlaOC) compared between exclusively breastmilk-fed and formula/mixed-fed infants after discharge. RESULTS: After discharge, breastmilk-fed babies had significantly lower serum VK1 (0.15 vs. 1.81 µg/L), higher PIVKA-II (0.10 vs. 0.02 AU/ml) and higher %GluOC (63.6% vs. 8.1%) than those receiving a formula/mixed-feed diet. Pre-discharge (based on elevated PIVKA-II), only one (2%) of 45 breastmilk-fed infants was VK insufficient. After discharge, eight (67%) of 12 exclusively breastmilk-fed babies were VK insufficient versus only one (4%) of 25 formula/mixed-fed babies. CONCLUSIONS: Preterm infants who remain exclusively or predominantly human breastmilk-fed after neonatal unit discharge are at high risk of developing subclinical VK deficiency in early infancy. Routine postdischarge VK1 supplementation of breastfed infants to provide intakes comparable to those from formula milks should prevent this deficiency.

Serum vitamin K1 (phylloquinone) is associated with fracture risk and hip strength in post-menopausal osteoporosis: A cross-sectional study.

PURPOSE: Vitamin K may play a potential role in bone metabolism, although further evidence is needed. The mechanisms behind its skeletal effects and optimum intake for maintaining bone health remain poorly defined. To elucidate these two issues, we investigated the association between circulating vitamin K1 (phylloquinone) concentrations with fracture risk, bone mineral density (BMD), hip geometry and plasma dephospho-uncarboxylated-Matrix Gla Protein (dp-ucMGP), an extra-hepatic vitamin K dependent protein (VKDP), in post-menopausal osteoporosis (PMO). METHODS: We studied 374 women aged (mean [SD]) 68.7[12.3] years with PMO. Information including demographics, lifestyle habits and previous fractures was captured through a questionnaire. Serum was analysed for vitamin K1. BMD at the lumbar spine (LS), total hip (TH) and femoral neck (FN) (n = 277) and hip structural analysis (HSA) parameters (n = 263) were derived from DXA scans. VKDPs including undercarboxylated prothrombin (PIVKA-II) and dp-ucMGP were measured in a sub-group (n = 130). RESULTS: Serum vitamin K1 was significantly lower in the group with fractures (prevalent fractures: 0.53 [0.41], no fractures; 0.65 [0.66] µg/L, p = 0.04) and independently associated with fracture risk. The adjusted odds ratio (95% CI) per µg/L increase in vitamin K1 was 0.550 (0.310-0.978, p = 0.042). Among the HSA parameters, serum vitamin K1 was positively associated with cross-sectional area (CSA) (p = 0.02), cross sectional moment of inertia (CSMI) (p = 0.028) and section modulus (Z) (p = 0.02) at the narrow neck (NN) of femur. Dp-ucMGP was detectable in 97 (75%) participants with serum vitamin K1 of 0.26 [0.15] µg/L, whilst PIVKA-II was above the clinical threshold in only 3.8%. CONCLUSIONS: Our data suggest that the positive effect of vitamin K on fracture risk may be related to its effects on bone strength. Higher concentrations of serum vitamin K1 may be required for vitamin K's skeletal effects compared to coagulation. Further prospective or interventional studies are needed for confirmation and should include measures of bone quality.

Homocysteine metabolism and the associations of global DNA methylation with selected gene polymorphisms and nutritional factors in patients with dementia.

Epigenetics (particularly DNA methylation) together with environmental and genetic factors, are key to understanding the pathogenesis of many diseases including dementia. Disturbances in DNA methylation have already been implicated in dementia. Homocysteine metabolism, with folate and vitamin B12 as essential cofactors, is integral to methylation processes. We evaluated in a case-control study the association of global DNA methylation, homocysteine, folate and vitamin B12 status with dementia. Selected polymorphisms of genes previously associated with dementia development and the influence of various factors on DNA methylation were also investigated. 102 patients with dementia (53 with Alzheimer's disease, 17 with vascular dementia and 32 with mixed dementia) were recruited. The non-demented controls consisted of 45 age-matched subjects without dementia and 47 individuals with mild cognitive impairment. Global DNA methylation was determined by Imprint Methylated DNA Quantification Kit MDQ1 (Sigma-Aldrich, Gillingham, Dorset, UK). Plasma homocysteine, serum folate and vitamin B12 were determined by chemiluminescence. Plasma and erythrocyte 5-methyltetrahydrofolate and plasma methylmalonic acid (markers of folate and vitamin B12 status) were measured by HPLC. APOE, PON1 p.Q192R, MTHFR 677C>T (c.665C>T) and IL1B-511C>T polymorphisms were identified using PCR-RFLP methods. Patients with dementia had significantly higher concentrations of homocysteine (p=0.012) and methylmalonic acid (p=0.016) and lower folate (p=0.002) and plasma 5-methyltetrahydrofolate (p=0.005) than non-demented subjects. There was no difference in DNA methylation between patients and controls. A non-significant tendency to higher DNA methylation in patients with vascular dementia (p=0.061) was observed. Multivariate regression analysis of all recruited individuals demonstrated a significant positive association between DNA methylation and folate (p=0.013), creatinine (p=0.003) concentrations and IL1B-511T (p=0.002) and PON1 192R (p=0.049) alleles and negative association with fasting glucose (p=0.004). The biochemical results showed significantly lower folate and vitamin B12 status in demented patients than controls. Global DNA methylation was associated with markers of folate status, creatinine, glucose and PON1 and IL1B polymorphisms.

Plasma and red cell reference intervals of 5-methyltetrahydrofolate of healthy adults in whom biochemical functional deficiencies of folate and vitamin B 12 had been excluded.

5-Methyltetrahydrofolate (5-MTHF) is the predominant form of folate and a strong determinant of homocysteine concentrations. There is evidence that suboptimal 5-MTHF availability is a risk factor for cardiovascular disease independent of homocysteine. The analysis of folates remains challenging and is almost exclusively limited to the reporting of "total" folate rather than individual molecular forms. The purpose of this study was to establish the reference intervals of 5-MTHF in plasma and red cells of healthy adults who had been prescreened to exclude biochemical evidence of functional deficiency of folate and/or vitamin B12. Functional folate and vitamin B12 status was assessed by respective plasma measurements of homocysteine and methylmalonic acid in 144 healthy volunteers, aged 19-64 years. After the exclusion of 10 individuals, values for 134 subjects were used to establish the upper reference limits for homocysteine (13 µ mol/L females and 15 µ mol/L males) and methylmalonic acid (430 nmol/L). Subjects with values below these cutoffs were designated as folate and vitamin B12 replete and their plasma and red cell 5-MTHF reference intervals determined, N = 126: 6.6-39.9 nmol/L and 223-1041 nmol/L, respectively. The application of these intervals will assist in the evaluation of folate status and facilitate studies to evaluate the relationship of 5-MTHF to disease.

Vitamin K status in chronic kidney disease: a report of a study and a mini-review.

Hepatic vitamin K-dependent proteins (e.g., Factors II, VII, IX and X) form part of the clotting cascade. Factor II (FII)/Prothrombin incorporates 10 Glu residues on the N-terminal region that are γ-carboxylated to Gla residues by the action of γ-glutamyl carboxylase to confer biological activity. Vitamin K is also required for the normal function of Matrix Gla Protein (MGP)--one of several non-clotting-related extra-hepatic vitamin K-dependent proteins. MGP is known to have protective action against vascular calcification--indeed it is a powerful tissue-bound inhibitory mechanism and can be found in blood vessel walls. The mature protein is also dependent on activation by γ-glutamyl carboxylase enzyme to convert Glu residues in its amino acid sequence to Gla. This reaction can only take place when the enzyme is activated in the presence of vitamin K. It is of great potential interest to investigate whether subtle deficiencies of vitamin K may, through its effect on the action of MGP, be a contributing factor to vascular calcification in CKD patients, in whom CV disease is greatly accelerated and in whom vascular calcification is not only common, but progresses aggressively, and is something for which as yet there is no clinically applicable remedy.