17-Hydroxylase/C17,20-lyase (CYP17) is not the enzyme responsible for side-chain cleavage of cortisol and its metabolites

The question addressed in this study was the nature of the enzyme required to remove the side-chain of 17-hydroxycorticosteroids, leading in the case of cortisol to the excretion of 11β-hydroxyandrosterone, 11-oxo-androsterone and the corresponding etiocholanolones. We questioned whether it could be CYP17, the 17-hydroxylase/17,20-lyase utilized in androgen synthesis. The conversion of exogenous cortisol to C₁₉ steroids in patients with complete 17-hydroxylase deficiency (17HD) was studied rationalizing that if CYP17 was involved no C₁₉ steroids would be formed. The urinary excretion of the four 11-oxy-C₁₉ steroids as well as many of the major C₂₁ cortisol metabolites were measured by GC/MS. Our results showed that the conversion of cortisol to C₁₉ steroids was normal in 17HD indicating that a currently unidentified enzyme must be responsible for this transformation.

A secondary goal was to determine to what extent 11-oxy-C₁₉ steroids were metabolites of cortisol or adrenal synthesized 11β-hydroxyandrostenedione. Since cortisol-treated 17HD patients cannot produce androstenedione, all C₁₉ 11-oxy-metabolites excreted must be derived from exogenous cortisol. The extent to which 17HD patients have lower relative excretion of C₁₉ steroids should reflect the absence of 11β-hydroxyandrostenedione metabolites. Our results showed almost all of 11-oxo-etiocholanolone and 11β-hydroxyetiocholanolone were cortisol metabolites, but in contrast the excretion of 11β-hydroxyandrosterone was less than 10% that of normal individuals, indicating that in excess of 90% must be a metabolite of 11β-hydroxyandrostenedione.     

Microphytobenthos in the Oosterschelde estuary (The Netherlands), 1981–1990; consequences of a changed tidal regime

During the period 1981–1990 the functioning of microphytobenthos in the carbon cycle was studied in the Oosterschelde, a mesotidal, euhaline estuary (SW Netherlands), both before and after completion of a storm-surge barrier in the sea ward entrance of the estuary in 1986, which reduced the tidal range to 88% and current velocities to 70% of their former values on average.The annual biomass cycle has changed from small spring and autumn peaks into a much larger summer peak. The average biomass during summer has increased from 70 to 170 mg Chlorophyll-a m². The average annual biomass has increased from 115 to 195 mg Chlorophyll-a m². As a consequence the (calculated) primary production by microphytobenthos has increased also, from 150 to 242 gC m^–2 y^–1 (14 045 to 22 265 tonnes C y^–1), and its share in the total primary production of the Oosterschelde has increased from 16 to 30%. These increases in biomass and primary production are mainly ascribed to a decrease in the dynamic forces (water current velocities) over the intertidal flats in most parts of the basin. Increased water transparency in parts of the estuary and increased import of inorganic carbon from the water column towards shoals may have contributed as well.The rate of reworking of the top layer of the soil (0–10 cm) has not changed significantly, as the decrease in Chlorophyll-a biomass with depth has hardly changed.     

The effect of nutrients on carbon and nitrogen fixation by the UCYN-A–haptophyte symbiosis

Symbiotic relationships between phytoplankton and N₂-fixing microorganisms play a crucial role in marine ecosystems. The abundant and widespread unicellular cyanobacteria group A (UCYN-A) has recently been found to live symbiotically with a haptophyte. Here, we investigated the effect of nitrogen (N), phosphorus (P), iron (Fe) and Saharan dust additions on nitrogen (N₂) fixation and primary production by the UCYN-A–haptophyte association in the subtropical eastern North Atlantic Ocean using nifH expression analysis and stable isotope incubations combined with single-cell measurements. N₂ fixation by UCYN-A was stimulated by the addition of Fe and Saharan dust, although this was not reflected in the nifH expression. CO₂ fixation by the haptophyte was stimulated by the addition of ammonium nitrate as well as Fe and Saharan dust. Intriguingly, the single-cell analysis using nanometer scale secondary ion mass spectrometry indicates that the increased CO₂ fixation by the haptophyte in treatments without added fixed N is likely an indirect result of the positive effect of Fe and/or P on UCYN-A N₂ fixation and the transfer of N₂-derived N to the haptophyte. Our results reveal a direct linkage between the marine carbon and nitrogen cycles that is fuelled by the atmospheric deposition of dust. The comparison of single-cell rates suggests a tight coupling of nitrogen and carbon transfer that stays balanced even under changing nutrient regimes. However, it appears that the transfer of carbon from the haptophyte to UCYN-A requires a transfer of nitrogen from UCYN-A. This tight coupling indicates an obligate symbiosis of this globally important diazotrophic association.     

Adiponectin receptor agonist AdipoRon attenuates calcification of osteoarthritis chondrocytes by promoting autophagy

Cartilage calcification contributes to the development and progression of osteoarthritis (OA). It has been well-investigated adiponectin regulates vascular calcification. The purpose of this study is to investigate the therapeutic value and the molecular mechanism of AdipoRon, an adiponectin receptor agonist, on the chondrocytes calcification. Primary chondrocytes were isolated and cultured from normal cartilage and OA cartilage. The calcification in tissues was evaluated by inductively coupled plasma/atomic emission spectroscopy and alizarin red S staining. The calcification in chondrocytes was determined using the alkaline phosphatase (ALP) staining and an ALP assay kit. The cellular effects of AdipoRon were assessed by immunofluorescence staining and Western blot analysis. We found that calcification was significantly increased in OA cartilage tissues and cells. Importantly, the degree of calcification and ALP activity of the OA chondrocytes was decreased upon the treatment with AdipoRon. The AdipoRon-induced cellular effects, including the reduction of the calcification of chondrocytes and improvement of autophagy, were blocked by dorsomorphin, an 5′-adenosine monophosphate-activated protein kinase (AMPK) inhibitor. Moreover, autophagy activation by AdipoRon was mediated by the AMPK-mammalian target of rapamycin (mTOR) signaling pathway. Our results suggest that AdipoRon significantly alleviates the calcification of OA chondrocytes via activating AMPK-mTOR signaling to promote autophagy. Therefore, AdipoRon could be a potential therapeutic agent for the prevention and treatment of OA.     

Renal Carcinogenesis After Uninephrectomy

Nephrectomized rats have widely been used to study chronic renal failure. Interestingly, renal cell carcinoma occurred in the remnant kidney after uninephrectomy (UNX). In this study, we probed insulin-like growth factor (IGF)-1 signaling pathway in UNX-induced renal cancer. Adult male Sprague-Dawley rats were randomized into two groups: UNX rats (n = 22) and sham-operated rats (n = 12). Rats were killed at 3, 7, and 10 months. After 7 months after nephrectomy, the UNX rats developed renal cell carcinoma with increased expression of proliferating cell nuclear antigen, and 68.2% (15/22) of the animals exhibited invasive carcinoma. Western blot demonstrated significant down-regulation of IGF binding protein 3 contrasting with the up-regulation of protein kinase Cζ and Akt/protein kinase B in the renal cancer tissues. These findings indicate a unique rat model of UNX-induced renal cancer associated with enhanced IGF-1 signaling pathway.