Description and validation of an equilibrium dialysis ID-LC-MS/MS candidate reference measurement procedure for free thyroxine in human serum.

OBJECTIVES: Free thyroxine (FT4) in serum is routinely measured in clinical practice to diagnose and monitor thyroid disease. Due to its concentration in picomolar range and the delicate equilibrium of free and protein-bound T4, accurate measurement is challenging. As a consequence, large inter-method differences in FT4 results exists. Optimal method design and standardization of the FT4 measurement is therefore necessary. The IFCC Working Group for Standardization of Thyroid Function Tests proposed a reference system with a conventional reference measurement procedure (cRMP) for FT4 in serum. In this study, we describe our FT4 candidate cRMP and its validation in clinical samples. METHODS: This candidate cRMP is based on equilibrium dialysis (ED) combined with determination of T4 with an isotope-dilution liquid chromatography tandem mass-spectrometry (ID-LC-MS/MS) procedure and was developed according to the endorsed conventions. Its accuracy, reliability, and comparability was investigated using human sera. RESULTS: It was shown that the candidate cRMP adhered to the conventions and its accuracy, precision, and robustness were adequate in serum of healthy volunteers. CONCLUSIONS: Our candidate cRMP measures FT4 accurately and performs well in serum matrix.

Diurnal salivary androstenedione and 17-hydroxyprogesterone levels in healthy volunteers for monitoring treatment efficacy of patients with congenital adrenal hyperplasia.

OBJECTIVE: Treatment of congenital adrenal hyperplasia (CAH) patients with glucocorticoids is often challenging since there is a delicate balance between over- and undertreatment. Treatment can be monitored noninvasively by measuring salivary androstenedione (A4) and 17-hydroxyprogesterone (17-OHP). Optimal treatment monitoring requires the establishment of reference values in saliva. DESIGN: A descriptive study. PATIENTS: For this study saliva of 255 healthy paediatric and adult volunteers with an age range of 4-75 years old was used. MEASUREMENTS: We developed a sensitive liquid chromatography-tandem mass spectrometry method, assessed salivary A4 and 17-OHP stability, and measured A4 and 17-OHP concentrations in saliva collected in the morning, afternoon, and evening. RESULTS: We quantified A4 and 17-OHP concentrations in the morning, afternoon, and evening and demonstrated that there is a significant rhythm with the highest levels in the morning and decreasing levels over the day. A4 and 17-OHP concentrations display an age-dependent pattern. These steroids remain stable in saliva at ambient temperature for up to 5 days. CONCLUSIONS: Good stability of the steroids in saliva enables saliva collection by the patient at home. Since salivary A4 and 17-OHP display a diurnal rhythm and age-dependent pattern, we established reference values for both children and adults at three time points during the day. These reference values support treatment monitoring of children and adults with CAH.

Load dissipation by corn residue on tilled soil in laboratory and field-wheeling conditions.

Crop residues may partially dissipate applied loads and reduce soil compaction. We evaluated the effect of corn residue on energy-applied dissipation during wheeling. The experiment consisted of a preliminary laboratory test and a confirmatory field test on a Paleaudalf soil. In the laboratory, an adapted Proctor test was performed with three energy levels, with and without corn residue. Field treatments consisted of three 5.1 Mg tractor wheeling intensities (0, 2, and 6), with and without 12 Mg ha(-1) corn residue on the soil surface. Corn residue on the soil surface reduced soil bulk density in the adapted Proctor test. By applying energy of 52.6 kN m m(-3) , soil dissipated 2.98% of applied energy, whereas with 175.4 kN m m(-3) a dissipation of 8.60% was obtained. This result confirms the hypothesis that surface mulch absorbs part of the compaction effort. Residue effects on soil compaction observed in the adapted Proctor test was not replicated under subsoiled soil field conditions, because of differences in applied pressure and soil conditions (structure, moisture and volume confinement). Nevertheless, this negative result does not mean that straw has no effect in the field. Such effects should be measured via stress transmission and compared to soil load-bearing capacity, rather than on bulk deformations. Wheeling by heavy tractor on subsoiled soil increased compaction, independently of surface residue. Two wheelings produced a significantly increase, but six wheelings did not further increase compaction. Reduced traffic intensity on recently tilled soil is necessary to minimize soil compaction, since traffic intensity show a greater effect than surface mulch on soil protection from excessive compaction. © 2015 Society of Chemical Industry.

Dutasteride and enzalutamide synergistically suppress prostate tumor cell proliferation.

PURPOSE: Dihydrotestosterone is the main active androgen in the prostate and it has a role in prostate cancer progression. After androgen deprivation therapy androgen receptor signaling is still active in tumor cells. Persistent intratumor steroidogenesis and androgen receptor changes are responsible for this continued activity, which influences the efficacy of prostate cancer treatment. We hypothesized that combining a 5α-reductase inhibitor and an antiandrogen would block intratumor androgen synthesis and androgen receptor protein activity. Thus, it would act synergistically to reduce tumor cell proliferation. MATERIALS AND METHODS: The expression level of 5α-reductase and androgen receptor in endocrine therapy naïve prostate cancer and castration resistant prostate cancer tissues, and cell line models was determined by microarray and quantitative polymerase chain reaction analysis. Intracellular androgen was measured with radioimmunoassay. Tumor cell proliferation was determined using coloric MTT assay. The synergistic effects of combination treatments on tumor cell proliferation were calculated using the Chou-Talalay equation. RESULTS: In all prostate cancer cases 5α-reductase-1 and 3 were up-regulated. Androgen receptor was up-regulated in metastatic prostate cancer and castration resistant prostate cancer cases. The 5α-reductase inhibitor dutasteride effectively decreased dihydrotestosterone production in prostate cancer and castration resistant prostate cancer cell lines. Furthermore, dutasteride combined with the novel antiandrogen enzalutamide synergistically suppressed endocrine therapy naïve prostate cancer and castration resistant prostate cancer cell proliferation. CONCLUSIONS: In this study the combination of a 5α-reductase inhibitor and (novel) antiandrogens synergistically inhibited tumor cell proliferation. These findings support clinical studies of combinations of a 5α-reductase inhibitor and (novel) antiandrogens as first line treatment of prostate cancer and castration resistant prostate cancer.

Aldo-keto reductase family 1 member C3 (AKR1C3) is a biomarker and therapeutic target for castration-resistant prostate cancer.

Current endocrine treatment for advanced prostate cancer does not result in a complete ablation of adrenal androgens. Adrenal androgens can be metabolized by prostate cancer cells, which is one of the mechanisms associated with progression to castration-resistant prostate cancer (CRPC). Aldo-keto reductase family 1 member C3 (AKR1C3) is a steroidogenic enzyme that plays a crucial role in the conversion of adrenal androgen dehydroepiandrosterone (DHEA) into high-affinity ligands for the androgen receptor (testosterone [T] and dihydrotestosterone [DHT]). The aim of this study was to examine whether AKR1C3 could be used as a marker and therapeutic target for CRPC. AKR1C3 mRNA and protein levels were upregulated in CRPC tissue, compared with benign prostate and primary prostate cancer tissue. High AKR1C3 levels were found only in a subset of CRPC patients. AKR1C3 can be used as a biomarker for active intratumoral steroidogenesis and can be measured in biopsy or transurethral resection of the prostate specimens. DuCaP (a CRPC cell line that has high AKR1C3 expression levels) used and converted DHEA under hormone-depleted conditions into T and DHT. The DHEA-induced growth of DuCaP could be antagonized by indomethacine, an inhibitor of AKR1C3. This study indicates that AKR1C3 can be considered a therapeutic target in a subgroup of patients with high AKR1C3 expression.

Serum FGF21 levels in adult m.3243A>G carriers: clinical implications.

OBJECTIVES: To determine the value of fibroblast growth factor 21 (FGF21), a recently discovered biomarker for mitochondrial disease, in predicting clinical disease severity and disease progression in adult carriers of the m.3243A>G mutation. METHODS: In the context of a national inventory, the heteroplasmy levels of the m.3243A>G mutation were measured in leukocytes and urinary epithelial cells. The Newcastle Mitochondrial Disease Adult Scale score was determined and blood was drawn for measuring FGF21 concentration. Twenty-five of the included initial patients studied were then selected randomly for a follow-up study. RESULTS: This prognostic study included 99 adult carriers of the m.3243A>G mutation. Our analysis revealed a moderate, significant correlation between FGF21 concentration and disease severity (r = 0.49; p = <0.001). No significant correlations were found between disease severity and the heteroplasmy percentage determined in urinary epithelial cells or the heteroplasmy percentage determined in leukocytes. Weak but significant correlations were also found between FGF21 concentration and the severity of the myopathy (r = 0.38; p = <0.001) and between the concentration of FGF21 and the severity of the encephalopathy (r = 0.30; p = <0.001). Repeated measurements following 25 subjects for 2 years revealed no significant correlation between FGF21 concentration and disease progression. CONCLUSIONS: Measuring FGF21 concentration had little added value in monitoring and predicting the disease course in this specific patient group.

Liver afferents contribute to water drinking-induced sympathetic activation in human subjects: a clinical trial.

UNLABELLED: Water drinking acutely increases sympathetic activity in human subjects. In animals, the response appears to be mediated through transient receptor potential channel TRPV4 activation on osmosensitive hepatic spinal afferents, described as osmopressor response. We hypothesized that hepatic denervation attenuates water drinking-induced sympathetic activation. We studied 20 liver transplant recipients (44±2.6 years, 1.2±0.1 years post transplant) as model of hepatic denervation and 20 kidney transplant recipients (43±2.6 years, 0.8±0.1 years post transplant) as immunosuppressive drug matched control group. Before and after 500 ml water ingestion, we obtained venous blood samples for catecholamine analysis. We also monitored brachial and finger blood pressure, ECG, and thoracic bioimpedance. Plasma norepinephrine concentration had changed by 0.01±0.07 nmol/l in liver and by 0.21±0.07 nmol/l in kidney transplant recipients (p<0.05 between groups) after 30-40 minutes of water drinking. While blood pressure and systemic vascular resistance increased in both groups, the responses tended to be attenuated in liver transplant recipients. Our findings support the idea that osmosensitive hepatic afferents are involved in water drinking-induced sympathetic activation in human subjects. TRIAL REGISTRATION: ClinicalTrials.gov NCT01237431.