Metabolism of 25-Hydroxy-Vitamin D in Human Macrophages Is Highly Dependent on Macrophage Polarization

Macrophages synthesize active vitamin D (1,25-dihydroxy-vitamin D) and express the vitamin D receptor in the nucleus; however, vitamin D metabolism in relation to macrophage polarization and function is not well understood. We studied monocyte-derived macrophages (MDMs) from human buffy coats polarized into M0, M1 (LPS + IFNγ), M2a (IL4 + IL13) and M2c (IL10) macrophage subtypes stimulated with 25-hydroxy-vitamin D (1000 and 10,000 nanomolar). We measured vitamin D metabolites (25-hydroxy-vitamin D, 1,25-dihydroxy-vitamin D, 24,25-dihydroxy-vitamin D and 3-epi-25-hydroxy-vitamin D) in cell media with liquid chromatography-mass spectrometry-mass spectrometry. The mRNA expression (CYP27B1, CYP24A1 and CYP24A1-SV) was measured with qPCR. We found that reparative MDMs (M2a) had significantly more 1,25-dihydroxy-vitamin D compared to the other MDMs (M0, M1 and M2c). All MDMs were able to produce 3-epi-25-hydroxy-vitamin D, but this pathway was almost completely attenuated in inflammatory M1 MDMs. All MDM subtypes degraded vitamin D through the 24-hydroxylase pathway, although M1 MDMs mainly expressed an inactive splice variant of CYP24A1, coding the degrading enzyme. In conclusion, this study shows that vitamin D metabolism is highly dependent on macrophage polarization and that the C3-epimerase pathway for vitamin D is active in macrophages.

Local concentrations of gentamicin obtained by microdialysis after a controlled application of a GentaColl sponge in a porcine model

Local treatment with gentamicin may be an important tool in the prevention and treatment of surgical site infections in high-risk procedures and patients. The aim of this study was to evaluate the pharmacokinetic profile of gentamicin in bone and surrounding tissue, released from a controlled application of a GentaColl sponge in a porcine model. In eight female pigs, a GentaColl sponge of 10 × 10 cm (1.3 mg gentamicin/cm² ) was placed in a cancellous bone cavity in the proximal tibia. Microdialysis was used for sampling of gentamicin concentrations over 48 hours from the cavity with the implanted GentaColl sponge, cancellous bone parallel to the cavity over and under the epiphyseal plate, cortical bone, the intramedullary canal, subcutaneous tissue, and the joint cavity of the knee. Venous blood samples were obtained as reference. The main finding was a mean peak drug concentration (95% CI) of gentamicin in the cancellous bone cavity containing the implanted GentaColl sponge of 11 315 (9049-13 581) μg/mL, persisting above 1000 μg/mL until approximately 40 hours after application. Moreover, the concentrations were low (<1 μg/mL) in the surrounding tissues as well as in plasma. The mean peak gentamicin concentration from the cancellous bone cavity after a controlled application of a GentaColl sponge was high and may be adequate for the prevention of biofilm formation. However, high MIC strains and uncontrolled application of the GentaColl sponge may jeopardize this conclusion.

Vitamin D content in human breast milk: a 9-mo follow-up study

BACKGROUND

Parents are advised to avoid the direct sun exposure of their newborns. Therefore, the vitamin D status of exclusively breastfed newborns is entirely dependent on the supply of vitamin D from breast milk.

OBJECTIVES

We explored concentrations of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) (vitamin D) and 25-hydroxivitamin D2 plus D3 (25-hydroxyvitamin D [25(OH)D]) in foremilk and hindmilk during the first 9 mo of lactation and identified indexes of importance to the concentrations.

DESIGN

We collected blood and breast-milk samples from mothers at 2 wk (n = 107), 4 mo, (n = 90), and 9 mo (n = 48) postpartum. Blood samples from infants were collected 4 and 9 mo after birth. We measured concentrations of vitamin D metabolites in blood and milk samples with the use of liquid chromatography-tandem mass spectrometry.

RESULTS

Concentrations of vitamin D and 25(OH)D correlated significantly and were higher in hindmilk than in foremilk. Milk concentrations were also correlated with maternal plasma 25(OH)D concentrations. In foremilk and hindmilk, concentrations were a median (IQR) of 1.35% (1.04-1.84%) and 2.10% (1.63-2.65%), respectively, of maternal plasma 25(OH)D concentrations (P < 0.01). Milk concentrations showed a significant seasonal variation. Mothers who were taking vitamin D supplements had higher concentrations than did nonusers. Medians (IQRs) of infant daily intake through breast milk of vitamin D and 25(OH)D were 0.10 μg (0.02-0.40 μg) and 0.34 μg (0.24-0.47 μg), respectively, which were equal to a median (IQR) antirachitic activity of 77 IU/d (52-110 IU/d).

CONCLUSIONS

The supply of vitamin D from breast milk is limited. Exclusively breastfed infants received <20% of the daily dose recommended by the Institute of Medicine for infants during the first year of life. This trial was registered at clinicaltrials.gov as NCT02548520.

Development of a high-resolution melting genotyping assay for the angiotensin I converting enzyme insertion/deletion polymorphism and establishment of genotype-specific reference intervals in a Danish population

BACKGROUND

The serum-angiotensin I converting enzyme (s-ACE) activity is influenced by a genetic insertion/deletion (I/D) polymorphism in the ACE gene, and the resulting large interindividual variation in s-ACE limits the use of normal reference intervals in the evaluation of sarcoidosis. In this study, we developed a new method for genotyping the I/D polymorphism in ACE and established genotype-specific reference intervals in order to improve the diagnostic accuracy and the value for treatment of sarcoidosis.

METHODS

The new genotyping assay is based on high-resolution melting (HRM) using LCGreen + and was used to genotype 400 healthy Danish individuals. The assay was compared to a real-time polymerase chain reaction (RT-PCR) assay in a validation set of 86 samples. Enzyme activity in serum was measured using the Infinity™ ACE Liquid Stable Reagent from Thermo adapted for the ABX Pentra analyzer.

RESULTS

There was full concordance between genotyping assays. The three genotypes II, ID and DD were present with a frequency of 0.23, 0.51 and 0.26. The distribution of s-ACE values in the total population was non-Gaussian (non-parametric 95% reference interval 12.0-60.0 U/L). The median activities of the genotypes differed significantly (P<0.0001). Ninety-five per cent non-parametric reference intervals for the subpopulations were determined to 6.3-38.5, 14.0-56.0 and 23.3-71.2 U/L for II, ID and DD, respectively.

CONCLUSION

We have developed a simple and robust method for ACE genotyping and determined genotype-specific reference intervals for s-ACE concentrations in the Danish population. The new reference intervals may increase the value of s-ACE measurements.

High-throughput liquid-liquid extraction and LCMSMS assay for determination of circulating 25(OH) vitamin D3 and D2 in the routine clinical laboratory

BACKGROUND

Increasing focus on vitamin D as essential to health has underscored the need for accurate and precise high-throughput measurement of serum 25(OH)D.

METHODS

Serum was denatured in acetonitrile containing hexadeuterated 25(OH)D3 as internal standard (IS) and automatically applied to filter plates packed with inert diatomous earth material for subsequent heptane extraction. Extracts were chromatographed on a C12 HPLC column, and detected on a triple quadropole mass spectrometer.

RESULTS

The inter-assay precision was 9.4% and 8.8% respectively at 32.0 and 59.7 nmol/l for 25(OH)D3 and 8.6% and 8.0% at 23.4 and 64.4 nmol/l for 25(OH)D2. The detection limit was 10 nmol/l for both metabolites. Three percent of samples contained >50 nmol/l 25(OH)D2. Total run time was 4 min. We have performed more than 200,000 routine samples and the method performs well in external control schemes.

CONCLUSION

We describe a robust, high-throughput, LLE-LCMSMS method for accurate and precise quantitation of 25(OH)D3 and 25(OH)D2 in serum. The use of diatomaceous earth material for extraction of vitamin D in 96-well format enables fast, simple and efficient sample preparation. The method offers a cost-effective alternative to immunological methods for use in the routine clinical biochemical laboratory.

Liquid chromatography tandem mass spectrometry assay for topiramate analysis in plasma and cerebrospinal fluid: validation and comparison with fluorescence-polarization immunoassay

SUMMARY

The authors report the development and validation of a liquid chromatography tandem mass spectrometry assay (LC/MS/MS assay) for the analysis of topiramate (2,3:4,5-bis-o-(-1-methyl)-beta-D-fructopyranose sulfamate) in plasma and cerebrospinal fluid (CSF). Comparison is made with the commercially available fluorescence-polarization immunoassay (FPIA).

LC/MS/MS ASSAY

Using the internal standard, 1,2:3,4-bis-o-(1-methylethylidene-alpha-D-galactopyranose sulfamate), a structural isomer, the calibration curve in plasma was linear in the concentration range of 0.02-20.0 mg/L (r(2) = 0.9998). The coefficients of variation in plasma were < or = 3%, and the accuracy ranged from 100% to 101% in the therapeutically relevant concentration range of 0.4-16.0 mg/L. In CSF, the mean recovery was 98%, and there was linearity between the nominal and the estimated concentration in the range of 1.5-20.0 mg/L (r(2)= 0.9996). FPIA: The calibration curve was linear in the concentration interval of 1.6-24.3 mg/L (r(2) = 0.9994), and the mean recovery was 96%. Accuracy in plasma was 99- 104%, and precision was 3.2-6.0%. In CSF, there was linearity between the nominal concentration and the estimated concentration in the range of 1.5-20.0 mg/L (r(2) = 0.9995), and the mean recovery was 100%. COMPARISON BETWEEN FPIA AND LC/MS/MS: There was a high correlation between the FPIA and the LC/MS/MS assay (r(2) = 0.9965 in plasma and r(2) = 0.9996 in CSF, P < 0.001 for both). In plasma and CSF, the two methods showed equal results, evaluated as the ratio between the two methods (plasma: median ratio = 1.00; 95% confidence interval [CI], 0.98-1.02, paired-sample test, P = 0.79; and CSF: median ratio = 1.00, 95% CI, 0.99-1.02, paired-sample test, P = 0.75). The coefficient of variation on the ratios between the two methods had similar levels: 5% in plasma and 3% in CSF.

CONCLUSION

The new LC/MS/MS assay has favorable characteristics, being highly precise and accurate. FPIA also proved precise and accurate, and there was a high agreement with the LC/MS/MS assay in plasma and CSF. Either method displayed sufficient precision and accuracy and may thus be implemented in daily routine.

Plasma concentration of topiramate correlates with cerebrospinal fluid concentration

The authors examined the ratio between the plasma and the cerebrospinal fluid (CSF) concentration of topiramate in 14 adults with epilepsy. Simultaneous trough samples of venous blood and CSF were collected and analyzed as total and unbound concentrations. Concomitant levels were also analyzed of lamotrigine (n = 5) and the relevant oxcarbazepine metabolite, 10-hydroxycarbazepine (n = 3). There was a close correlation between the plasma and the CSF concentration for both the total and unbound concentration of topiramate. The median CSF/plasma ratio of total topiramate was 0.85. The free topiramate concentration in plasma was not different from the free topiramate concentration in CSF. The CSF/plasma ratios showed little variation and were independent of the plasma level for both the total and the unbound levels. The unbound fraction of topiramate was 84% in plasma and 97% in CSF. The CSF concentrations of lamotrigine and 10-hydroxycarbazepine were 50% and 61% of the plasma concentrations, respectively. For topiramate, there is a close correlation between the plasma concentration and the CSF concentration. There does not seem to be a saturable carrier mechanism restricting topiramate transport across the blood-brain barrier. The concentration of topiramate in CSF is equal to the unbound proportion of topiramate in plasma, implying that the delivery of topiramate to the brain occurs via transfer from the unbound plasma pool. Plasma is thus a relevant matrix for therapeutic drug monitoring of topiramate.

Reduction of organochlorine contaminants from fish oil during refining

Samples of crude fish oil have been refined, and the crude fish oil together with samples taken out after each step of the refining process have been analysed for organochlorine pesticides and PCB (quantified both as CB congeners and total PCB). The levels of organochlorine contaminants in fish oils remain almost constant during the neutralisation and bleaching steps of the refining process. The deodorisation step seems to cause a decrease in the amount of contaminants, especially for the most volatile compounds (alpha-HCH, lindane, HCB) where the levels were reduced to below the detection level. Concentrations of the less volatile organochlorine pesticides (dieldrin, p,p'-DDE and p,p'-DDD) and PCB are reduced to about half the concentration in the crude fish oil.