An O‐Glycosylation of Fibronectin Mediates Hepatic Osteodystrophy Through α4β1 Integrin

Patients with cholestatic liver disease experience increased fracture risk. Higher circulating levels of a fibronectin isoform called oncofetal fibronectin (oFN) were detected in a subset of such patients. Administering this isoform to mice suppresses osteoblast differentiation and diminishes bone mineral density in vivo, suggesting it is responsible for bone loss in cholestatic liver disease. The aim of this study was to define the mechanism by which oFN affects osteoblast function and evaluate possible modifiers in experimental hepatic osteodystrophy. The fibronectin isoform oFN is characterized by the presence of various glycosylations. In line with this, adding oFN that underwent enzymatic O‐deglycosylation to osteoblasts normalized nodule formation in vitro. Of three possible O‐glycosylation sites in oFN, only a mutation at AA 33 of the variable region or binding of this glycosylated site with an antibody normalized osteoblast differentiation. Because the responsible site is located in the variable region of fibronectin, which binds to α4β1 or α4β7 integrins, these integrins were evaluated. We show that integrin α4β1 mediates the inhibitory effect of oFN both in vitro as well as in vivo. In a hepatic osteodystrophy mouse model, we demonstrate that liver fibrosis is associated with increased circulating oFN and diminished BMD. In addition, trabecular bone loss induced by oFN injection or fibrosis induction could be prevented by either administering an antibody that binds to α4 integrin (PS/2) or the CS1 peptide, which contains a binding site for α4β1 integrin. In summary, oFN inhibits osteoblast activity. This is because of an O‐glycosylation in the variable region that results in decreased integrin‐mediated signaling. This deleterious effect can be thwarted by binding α4β1 integrin. Thus, we have characterized the defect and the receptor mediating bone loss in patients with hepatic osteodystrophy and evaluated possible therapeutic interventions in a murine model. © 2016 American Society for Bone and Mineral Research.     

Präsentismus bei Medizinstudierenden

Background

Presenteeism is defined as the behaviour of attending work while being sick, a behaviour that appears to be especially common amongst doctors. Medical socialisation is already apparent during medical school. However, whether medical students also show above-average presenteeism has not been specifically investigated.

Objective

We aimed to provide a more detailed of presenteeism in medical school: Is presenteeism more common amongst medical students when compared to students of other subjects? Does the prevalence of presenteeism change over the course of medical studies? Is presenteeism associated with health-related outcomes and behaviour?

Materials and methods

We collected data on the prevalence of presenteeism in students, as well as on their general physical and mental health and study-related behaviour and experiences, at three different time points at one German university. We compared the prevalence of presenteeism between medical students and students of other subjects and investigated factors associated with presenteeism in medical students using logistic regression analysis.

Results

We found no differences in the prevalence of presenteeism between medical students and students of other subjects at the different survey time points. However, we did find that presenteeism was more prevalent amongst female students when compared to their male counterparts. A tendency to overcommit was consistently proven to be a predictor of presenteeism.

Conclusions

Medical students do not seem to attend classes while sick more frequently than the average student. However, the share of female students, who, as a group, show presenteeism more often, continues to increase. The reasons for presenteeism might change over the course of study and should be pursued in future studies.

     

Synthetic cathinones in Southern Germany – characteristics of users,substance-patterns,co-ingestions,and complications

Objective: To define the characteristics of synthetic cathinone users admitted to hospital including clinical and laboratory parameters and the complications of use.

Design: Retrospective single-center study of patients treated for acute cathinone intoxication and complications of cathinone use between January 2010 and January 2016.

Setting: A specialized clinical toxicology unit at an academic tertiary care center in Southern Germany serving a population of about 4 million.

Patients and methods: 81 consecutive patients with laboratory-confirmed use of cathinones who presented for acute intoxication or complications of cathinone use were retrospectively analyzed.

Results and conclusions: The patients were predominantly male (64%, 52/81) with a median age of 34 years. 60 were admitted for signs of acute intoxication while 21 suffered from complications of cathinone use. 70% of acutely intoxicated patients had an increased creatinine phosphokinase. Only a minority of patients presented with a sympathomimetic toxidrome. Three patients had infectious complications, 10 prolonged psychosis, 6 rhabdomyolyses and/or kidney failure, and two patients died. Based on presentations, cathinone use has increased with the first cases seen in 2010. Opiates/opioids are the main co-ingested drugs of abuse. The pattern of cathinone use shifted from methylone in 2010/2011 to 3,4-methylenedioxypyrovalerone (MDPV) and 3-methylmethcathinone (3-MMC) in 2014/2015. We conclude that in our setting “typical“ cathinone users are males in their thirties. They are seldom drug naïve and regularly co-ingest illicit drugs. Preventive measures have to be tailored to these difficult to reach patients. Present efforts to educate young clubbers in their late teens may fail to reach the pertinent demographic.     

Resilience is strongly associated with health-related quality of life but does not buffer work-related stress in employed persons 1 year after acute myocardial infarction

Quality of Life Research - Resilience may facilitate the adaptation after experiencing a severe disease such as acute myocardial infarction (AMI) and attenuate the negative effects of stress on...     

Identification of tumor differentiation factor (TDF) in select CNS neurons

Identification of central nervous system (CNS) molecules elucidates normal and pathological brain function. Tumor differentiation factor (TDF) is a recently-found protein secreted by the pituitary into the blood. TDF mRNA was detected in brain; not heart, placenta, lung, liver, skeletal muscle, or pancreas. However, TDF has an unclear function. It is not known whether TDF is expressed only by pituitary or by other brain regions. It is also not known precisely where TDF is expressed in the brain or which cells produce TDF. Database searching revealed that this molecule shares no homology with any known protein. Therefore, we investigated the distribution of TDF in the rat brain using immunohistochemistry (IHC) and immunofluorescence (IF). TDF protein was detected in pituitary and most other brain regions. Double-staining for TDF and glial fibrillary acidic protein (GFAP), an astrocyte marker, showed no co-localization. Double-staining for TDF with NeuN, a neuronal marker, showed co-localization. Not all NeuN positive cells were positive for TDF. Western blotting (WB) using NG108 neuroblastoma and GS9L astrocytoma cell lysate revealed TDF immunoreactivity in cultured neuroblastoma, not astrocytoma. These data suggest that TDF is localized in neurons, not in astrocytes. This is the first report of any cellular localization of TDF. TDF may have specific roles as a pituitary-derived hormone and in the CNS, and appears to be produced by distinct CNS neurons, not astroglia.     

Diabetes and kidney disease: the role of sodium–glucose cotransporter-2 (SGLT-2) and SGLT-2 inhibitors in modifying disease outcomes

Patients with type 2 diabetes (T2D) often have coexisting chronic kidney disease (CKD). However, healthy renal function is crucial in maintaining glucose homeostasis, assuring that almost all of the filtered glucose is reabsorbed by the sodium glucose cotransporters (SGLTs) SGLT-1 and SGLT-2. In diabetes, an increased amount of glucose is filtered by the kidneys and SGLT-2 is upregulated, leading to increased glucose absorption and worsening hyperglycemia. Prolonged hyperglycemia contributes to the development of CKD by inducing metabolic and hemodynamic changes in the kidneys. Due to the importance of SGLT-2 in regulating glucose levels, investigation into SGLT-2 inhibitors was initiated as a glucose-dependent mechanism to control hyperglycemia, and there are three agents currently approved for use in the United States: dapagliflozin, canagliflozin, and empagliflozin. SGLT-2 inhibitors have been shown to reduce glycated hemoglobin (A1C), weight, and blood pressure, which not only affects glycemic control, but may also help slow the progression of renal disease by impacting the underlying mechanisms of kidney injury. In addition, SGLT-2 inhibitors have shown reductions in albuminuria, uric acid, and an increase in magnesium. Caution is advised when prescribing SGLT-2 inhibitors to patients with moderately impaired renal function and those at risk for volume depletion and hypotension. Published data on slowing of the development, as well as progression of CKD, is a hopeful indicator for the possible renal protection potential of this drug class. This narrative review provides an in-depth discussion of the interplay between diabetes, SGLT-2 inhibitors, and factors that affect kidney function.