Reduced Food Intake and Body Weight in Mice Deficient for the G Protein-Coupled Receptor GPR82

G protein-coupled receptors (GPCR) are involved in the regulation of numerous physiological functions. Therefore, GPCR variants may have conferred important selective advantages during periods of human evolution. Indeed, several genomic loci with signatures of recent selection in humans contain GPCR genes among them the X-chromosomally located gene for GPR82. This gene encodes a so-called orphan GPCR with unknown function. To address the functional relevance of GPR82 gene-deficient mice were characterized. GPR82-deficient mice were viable, reproduced normally, and showed no gross anatomical abnormalities. However, GPR82-deficient mice have a reduced body weight and body fat content associated with a lower food intake. Moreover, GPR82-deficient mice showed decreased serum triacylglyceride levels, increased insulin sensitivity and glucose tolerance, most pronounced under Western diet. Because there were no differences in respiratory and metabolic rates between wild-type and GPR82-deficient mice our data suggest that GPR82 function influences food intake and, therefore, energy and body weight balance. GPR82 may represent a thrifty gene most probably representing an advantage during human expansion into new environments

Catalytic and structural properties of pheophytinase, the phytol esterase involved in chlorophyll breakdown

During leaf senescence and fruit ripening, chlorophyll is degraded in a multistep pathway into linear tetrapyrroles called phyllobilins. A key feature of chlorophyll breakdown is the removal of the hydrophobic phytol chain that renders phyllobilins water soluble, an important prerequisite for their ultimate storage in the vacuole of senescent cells. Chlorophyllases had been considered for more than a century to catalyze dephytylation in vivo; however, this was recently refuted. Instead, pheophytinase was discovered as a genuine in vivo phytol hydrolase. While chlorophyllase acts rather unspecifically towards different porphyrin substrates, pheophytinase was shown to specifically dephytylate pheophytin, namely Mg-free chlorophyll. The aim of this work was to elucidate in detail the biochemical and structural properties of pheophytinase. By testing different porphyrin substrates with recombinant pheophytinase from Arabidopsis thaliana we show that pheophytinase has high specificity for the acid moiety of the ester bond, namely the porphyrin ring, while the nature of the alcohol, namely the phytol chain in pheophytin, is irrelevant. In silico modelling of the 3-dimensional structure of pheophytinase and subsequent analysis of site-directed pheophytinase mutant forms allowed the identification of the serine, histidine, and aspartic acid residues that compose the catalytic triad, a classical feature of serine-type hydrolases to which both pheophytinase and chlorophyllase belong. Based on substantial structural differences in the models of Arabidopsis pheophytinase and chlorophyllase 1, we discuss potential differences in the catalytic properties of these two phytol hydrolases

Acute systemic rapamycin induces neurobehavioral alterations in rats

Rapamycin is a drug with antiproliferative and immunosuppressive properties, widely used for prevention of acute graft rejection and cancer therapy. It specifically inhibits the activity of the mammalian target of rapamycin (mTOR), a protein kinase known to play an important role in cell growth, proliferation and antibody production. Clinical observations show that patients undergoing therapy with immunosuppressive drugs frequently suffer from affective disorders such as anxiety or depression. However, whether these symptoms are attributed to the action of the distinct compounds remains rather elusive. The present study investigated in rats neurobehavioral consequences of acute rapamycin treatment. Systemic administration of a single low dose rapamycin (3mg/kg) led to enhanced neuronal activity in the amygdala analyzed by intracerebral electroencephalography and FOS protein expression 90min after drug injection. Moreover, behavioral investigations revealed a rapamycin-induced increase in anxiety-related behaviors in the elevated plus-maze and in the open-field. The behavioral alterations correlated to enhanced amygdaloid expression of KLK8 and FKBP51, proteins that have been implicated in the development of anxiety and depression. Together, these results demonstrate that acute blockade of mTOR signaling by acute rapamycin administration not only causes changes in neuronal activity, but also leads to elevated protein expression in protein kinase pathways others than mTOR, contributing to the development of anxiety-like behavior. Given the pivotal role of the amygdala in mood regulation, associative learning, and modulation of cognitive functions, our findings raise the question whether therapy with rapamycin may induce alterations in patients neuropsychological functioning

Baltic Sea harbour porpoise populations : status and conservation needs derived from recent survey results

During recent decades, the 2 distinct harbour porpoise populations of the Baltic Sea have decreased sharply in abundance. The Baltic Proper population is down to a few hundred individuals and is regarded as ‘Critically Endangered’ by IUCN; the more abundant Belt Sea population also appears to have experienced a severe decline. We summarize the results of extensive static acoustic monitoring in the German part of the Baltic Sea and compare them to published results of aerial and acoustic surveys. Acoustic monitoring confirmed seasonal changes in detection rates consistent with proposed east–west migrations. Detection rates, and thus presumably porpoise density, decrease from west to east from a long-term mean (2002 to 2012) of 94% detection-positive days per month (DPD mo-1) around the island of Fehmarn and 71% DPD mo-1 in Kadet Trench to 4.4% DPD mo-1 in Pomeranian Bay as one crosses the putative population boundary. Acoustic monitoring results show a recent increase in porpoise registration rates in the Kadet Trench and in Pomeranian Bay, although this does not necessarily indicate a population increase. This large dataset supports the previously suggested proposition that each population uses the boundary waters in Pomeranian Bay alternately, leading to the presence of registration peaks in (late) summer by Belt Sea porpoises, and in winter by Baltic Proper animals. The critical status of porpoises in the Baltic Sea highlights the urgent need for protective measures which still await national and international implementation.publishe

Extracellular Ca2+ is a danger signal activating the NLRP3 inflammasome through G protein-coupled calcium sensing receptors

Activation of the NLRP3 inflammasome enables monocytes and macrophages to release high levels of interleukin-1β during inflammatory responses. Concentrations of extracellular calcium can increase at sites of infection, inflammation or cell activation. Here we show that increased extracellular calcium activates the NLRP3 inflammasome via stimulation of G protein-coupled calcium sensing receptors. Activation is mediated by signalling through the calcium-sensing receptor and GPRC6A via the phosphatidyl inositol/Ca(2+) pathway. The resulting increase in the intracellular calcium concentration triggers inflammasome assembly and Caspase-1 activation. We identified necrotic cells as one source for excess extracellular calcium triggering this activation. In vivo, increased calcium concentrations can amplify the inflammatory response in the mouse model of carrageenan-induced footpad swelling, and this effect was inhibited in GPRC6A(−/−) mice. Our results demonstrate that G-protein-coupled receptors can activate the inflammasome, and indicate that increased extracellular calcium has a role as a danger signal and amplifier of inflammation

Risk Factors for Early Dialysis Dependency in Autosomal Recessive Polycystic Kidney Disease

© 2018 Elsevier Inc.Objective: To identify prenatal, perinatal, and postnatal risk factors for dialysis within the first year of life in children with autosomal recessive polycystic kidney disease (ARPKD) as a basis for parental counseling after prenatal and perinatal diagnosis. Study design: A dataset comprising 385 patients from the ARegPKD international registry study was analyzed for potential risk markers for dialysis during the first year of life. Results: Thirty-six out of 385 children (9.4%) commenced dialysis in the first year of life. According to multivariable Cox regression analysis, the presence of oligohydramnios or anhydramnios, prenatal kidney enlargement, a low Apgar score, and the need for postnatal breathing support were independently associated with an increased hazard ratio for requiring dialysis within the first year of life. The increased risk associated with Apgar score and perinatal assisted breathing was time-dependent and vanished after 5 and 8 months of life, respectively. The predicted probabilities for early dialysis varied from 1.5% (95% CI, 0.5%-4.1%) for patients with ARPKD with no prenatal sonographic abnormalities to 32.3% (95% CI, 22.2%-44.5%) in cases of documented oligohydramnios or anhydramnios, renal cysts, and enlarged kidneys. Conclusions: This study, which identified risk factors associated with onset of dialysis in ARPKD in the first year of life, may be helpful in prenatal parental counseling in cases of suspected ARPKD