Estrogen prevents increased hepatic aquaporin-9 expression and glycerol uptake during starvation

In starvation, glycerol is released from adipose tissue and serves as an important precursor for hepatic gluconeogenesis. By unknown sex-specific mechanisms, women suppress the endogenous glucose production better than men and respond to metabolic stress with higher plasma glycerol levels. Hepatic glycerol uptake is facilitated by aquaporin-9 (AQP9), a broad-selectivity neutral solute channel, and represents an insulin-regulated step in supplying gluconeogenesis with glycerol. In the present study, hepatic AQP9 abundance was increased 2.6-fold in starved male rats as assessed by immunoblotting and immunohistochemistry. By contrast, starvation had no significant effect on hepatic AQP9 expression in female rats. Coordinately, plasma glycerol levels remained unchanged with starvation in male rats, whereas it was increased in female rats. The different responses to starvation were paralleled by higher glycerol permeability in basolateral hepatocyte membranes from starved male rats compared with starved females. Ovariectomy led to a starvation-response pattern identical to that observed in male rats with increased hepatic AQP9 expression and unchanged plasma glycerol levels. In cultured hepatocytes, 17β-estradiol and the selective estrogen receptor α-agonist, propyl pyrazole triol, caused a decrease in AQP9 expression. Our results support that a sex-specific regulation of the hepatic glycerol channel AQP9 during starvation contributes to the higher plasma glycerol levels observed in women during fasting and possibly results in a lower cytosolic availability of glycerol. Furthermore, the sexual dimorphism in the hepatic handling of glycerol during starvation might be explained by 17β-estradiol preventing the starvation-induced increase in hepatic AQP9 abundance.     

The rare peat moss Sphagnum wulfianum (Sphagnaceae) did not survive the last glacial period in northern European refugia

? Premise of the study: Organisms may survive unfavorable conditions either by moving to more favorable areas by means of dispersal or by adapting to stressful environments. Pleistocene glacial periods represent extremely unfavorable conditions for the majority of life forms, especially sessile organisms. Many studies have revealed placements of refugial areas and postglacial colonization patterns of seed plants, but little is still known about areas of long-term survival and historical migration routes of bryophytes. Given overall differences in stress tolerance between seed plants and bryophytes, it is of interest to know whether bryophytes have survived periods of extreme climatic conditions better then seed plants in northern areas. ? Methods: The haploid and rarely spore-producing peat moss Sphagnum wulfianum is mostly found in areas that were covered by ice during the last glacial maximum. Twelve microsatellite markers were amplified from 43 populations (367 shoots) of this species, and data were analyzed using population genetic diversity statistics, Bayesian clustering methods, and coalescence-based inference tools to estimate historical and demographic parameters. ? Key results: Genetic diversity within populations was low, but populations were highly differentiated, with two main genetic clusters being recognized. ? Conclusion: The two main genetic groups have diverged quite recently in the Holocene, and the pattern of genetic variability and structuring gives no support for survival in Scandinavian refugia during the last glacial period in this species. The dispersal ability of this plant thus seems surprisingly high despite its infrequent spore production.     

Development of ultra-high erucic acid oil in the industrial oil crop Crambe abyssinica

Erucic acid (22 : 1) is a major feedstock for the oleochemical industry. In this study, a gene stacking strategy was employed to develop transgenic Crambe abyssinica lines with increased 22 : 1 levels. Through integration of the LdLPAAT, BnFAE1 and CaFAD2-RNAi genes into the crambe genome, confirmed by Southern blot and qRT-PCR, the average levels of 18 : 1, 18 : 2 and 18 : 3 were markedly decreased and that of 22 : 1 was increased from 60% in the wild type to 73% in the best transgenic line of T4 generation. In single seeds of the same line, the 22 : 1 level could reach 76.9%, an increase of 28.0% over the wild type. The trierucin amount was positively correlated to 22 : 1 in the transgenic lines. Unlike high erucic rapeseed, the wild-type crambe contains 22 : 1 in the seed phosphatidylcholine and in the sn-2 position of triacylglycerols (5% and 8%, respectively). The transgenic line with high 22 : 1 had decreased 22 : 1 level in phosphatidylcholine, and this was negatively correlated with the 22 : 1 level at the sn-2 position of TAG. The significances of this study include (i) achieving an unprecedented level of 22 : 1 in an oil crop; (ii) disclosing mechanisms in the channelling of a triacylglycerol-specific unusual fatty acid in oil seeds; (iii) indicating potential limiting factors involved in the erucic acid biosynthesis and paving the way for further increase of this acid and (iv) development of an added value genetically modified oil crop having no risk of gene flow into feed and food crops.     

Glucocorticoid receptor gene polymorphisms and disease activity during pregnancy and the postpartum period in rheumatoid arthritis

Introduction

The mechanism underlying the spontaneous improvement of rheumatoid arthritis (RA) during pregnancy and the subsequent postpartum flare is incompletely understood, and the disease course varies widely between pregnant RA patients. In pregnancy, total and free levels of cortisol increase gradually, followed by a postpartum decrease to prepregnancy values. The glucocorticoid receptor (GR) polymorphisms BclI and N363S are associated with relatively increased glucocorticoid (GC) sensitivity, whereas the 9β and ER22/23EK polymorphisms of the GR gene are associated with a relatively decreased GC sensitivity. We examined the relation between the presence of these GR polymorphisms and level of disease activity and disease course of RA during pregnancy and postpartum.

Methods

We studied 147 participants of the PARA study (Pregnancy-Induced Amelioration of Rheumatoid Arthritis study), a prospective study investigating the natural improvement during pregnancy and the postpartum flare in women with RA. Patients were visited, preferably before pregnancy, at each trimester and at three postpartum time points. On all occasions, disease activity was scored by using DAS28. All patients were genotyped for the GR polymorphisms BclI, N363S, 9β, and ER22/23EK and divided in groups harboring either polymorphisms conferring increased GC sensitivity (BclI and N363S; GC-S patients) or polymorphisms conferring decreased GC sensitivity (9β or 9β + ER22/23EK; GC-I patients). Data were analyzed by using a mixed linear model, comparing GC-S patients with GC-I patients with respect to improvement during pregnancy and the postpartum flare. The cumulative disease activity was calculated by using time-integrated values (area under the curve, AUC) of DAS28 in GC-I patients versus GC-S patients. Separate analyses were performed according to the state of GC use.

Results

GC-S patients treated with GC had a significantly lower AUC of DAS28 in the postpartum period than did GC-I patients. This difference was not observed in patients who were not treated with GCs. During pregnancy, GC-S and GC-I patients had comparable levels of disease activity and course of disease.

Conclusions

Differences in relative GC sensitivity, as determined by GR polymorphisms, are associated with the level of disease activity in the postpartum period in GC-treated patients, but they do not seem to influence the course of the disease per se.     

Risk Factors for Loss to Follow-Up among People Who Inject Drugs in a Risk Reduction Program at Karachi,Pakistan. A Case-Cohort Study

Introduction

Retention of male people who inject drugs (PWIDs) is a major challenge for harm reduction programs that include sterile needle/syringe exchange in resource-limited settings like Pakistan. We assessed the risk factors for loss to follow-up among male PWIDs enrolled in a risk reduction program in Karachi, Pakistan.

Methods

We conducted a prospective cohort study among 636 HIV-uninfected male PWIDs enrolled during March-June 2009 in a harm reduction program for the estimation of incidence rate. At 24 months post-enrollment, clients who had dropped out of the program were defined as lost to follow-up and included as cases for case-cohort study.

Results

The median age of the participants was 29 years (interquartile range: 23–36). Active outreach accounted for 76% (483/636) of cohort recruits. Loss to follow-up at 24 months was 25.5% (162/636). In multivariable logistic regression, younger age (AOR: 0.97, 95% CI: 0.92–0.99, p = 0.028), clients from other provinces than Sindh (AOR: 1.49, 95% CI: 1.01–2.22, p = 0.046), having no formal education (AOR: 3.44, 95% CI: 2.35–4.90, p<0.001), a history of incarceration (AOR: 1.68, 95% CI: 1.14–2.46, p<0.008), and being homeless (AOR: 1.47, 95% CI: 1.00–2.19, p<0.049) were associated with loss to follow-up.

Conclusions

Our cohort retained 74.5% of male PWIDs in Karachi for 24 months. Its loss to follow up rate suggested substantial ongoing programmatic challenges. Programmatic enhancements are needed for the highest risk male PWIDs, i.e., younger men, men not from Sindh Province, men who are poorly educated, formerly incarcerated, and/or homeless.     

CASP11 – An Evaluation of a Modular BCL::Fold-Based Protein Structure Prediction Pipeline

In silico prediction of a protein’s tertiary structure remains an unsolved problem. The community-wide Critical Assessment of Protein Structure Prediction (CASP) experiment provides a double-blind study to evaluate improvements in protein structure prediction algorithms. We developed a protein structure prediction pipeline employing a three-stage approach, consisting of low-resolution topology search, high-resolution refinement, and molecular dynamics simulation to predict the tertiary structure of proteins from the primary structure alone or including distance restraints either from predicted residue-residue contacts, nuclear magnetic resonance (NMR) nuclear overhauser effect (NOE) experiments, or mass spectroscopy (MS) cross-linking (XL) data. The protein structure prediction pipeline was evaluated in the CASP11 experiment on twenty regular protein targets as well as thirty-three ‘assisted’ protein targets, which also had distance restraints available. Although the low-resolution topology search module was able to sample models with a global distance test total score (GDT_TS) value greater than 30% for twelve out of twenty proteins, frequently it was not possible to select the most accurate models for refinement, resulting in a general decay of model quality over the course of the prediction pipeline. In this study, we provide a detailed overall analysis, study one target protein in more detail as it travels through the protein structure prediction pipeline, and evaluate the impact of limited experimental data.