Effect of active vitamin-D on left ventricular mass index: Results of a randomized controlled trial in type 2 diabetes and chronic kidney disease.

BACKGROUND: Active vitamin-D deficiency is a potential modifiable risk factor for increased ventricular mass. We explored the effects of active vitamin-D (calcitriol) treatment on left ventricular mass in patients with type-2 diabetes (T2D) and chronic kidney disease (CKD). METHODS: We performed a 48-week duration single center randomized double-blind parallel group trial examining the impact of calcitriol, 0.5 mcg once daily, as compared to placebo on a primary endpoint of change from baseline in left ventricular mass index (LVMI) measured by magnetic resonance imaging . Patients with T2D, CKD stage-3 and raised left ventricular mass on stable renin angiotensin aldosterone system blockade, who all had elevated intact parathyroid hormone were eligible. Secondary endpoints included interstitial myocardial fibrosis, assessed with cardiac magnetic resonance imaging. In total, 45 (male 73%) patients with T2D and stage-3 CKD were studied (calcitriol n = 19, placebo n = 26). RESULTS: Following 48-weeks calcitriol treatment, the median difference and the (95% CI) of LVMI between the 2 treatment arms was 1.84 (-1.28, 4.96), similar between the 2 groups studied. Intact parathyroid hormone fell only in the calcitriol group from 142 pg/mL (80-293) to 76 pg/mL (41-204)(median, interquartile range, P= .04). No significant differences were observed in interstitial myocardial fibrosis or other secondary endpoints. CONCLUSIONS: The study did not provide evidence that treatment with calcitriol as compared to placebo might improve LVMI in patients with T2D, mild left ventricular hypertrophy and stable CKD. Our data does not support the routine use of active vitamin-D for LVMI regression and cardiovascular protection in patients with T2D and stage-3 CKD.

Mucus physically restricts influenza A viral particle access to the epithelium.

Prior work suggests influenza A virus (IAV) crosses the airway mucus barrier in a sialic acid-dependent manner through the actions of the viral envelope proteins, hemagglutinin and neuraminidase. However, host and viral factors that influence how efficiently mucus traps IAV remain poorly defined. In this work, we assessed how the physicochemical properties of mucus influence its ability to effectively capture IAV with altered sialic acid preference using fluorescence video microscopy and multiple particle tracking. We found an airway mucus gel layer must be produced with pores on the order of size of the virus to physically constrain IAV. Sialic acid binding by IAV also improves mucus trapping efficiency, but interestingly, sialic acid preferences had little impact on the fraction of IAV particles expected to penetrate the mucus barrier. Together, this work provides new insights on mucus barrier function toward IAV with important implications on innate host defense and interspecies transmission.

Dopaminergic and glutamatergic signaling crosstalk in Huntington's disease neurodegeneration: the role of p25/cyclin-dependent kinase 5.

Altered glutamatergic and dopaminergic signaling has been proposed as contributing to the specific striatal cell death observed in Huntington's disease (HD). However, the precise mechanisms by which mutant huntingtin sensitize striatal cells to dopamine and glutamate inputs remain unclear. Here, we demonstrate in knock-in HD striatal cells that mutant huntingtin enhances dopamine-mediated striatal cell death via dopamine D(1) receptors. Moreover, we show that NMDA receptors specifically potentiate the vulnerability of mutant huntingtin striatal cells to dopamine toxicity as pretreatment with NMDA increased D(1)R-induced cell death in mutant but not wild-type cells. As potential underlying mechanism of increased striatal vulnerability, we identified aberrant cyclin-dependent kinase 5 (Cdk5) activation. We demonstrate that enhanced Cdk5 phosphorylation and increased calpain-mediated conversion of the Cdk5 activator p35 into p25 may account for the deregulation of Cdk5 associated to dopamine and glutamate receptor activation in knock-in HD striatal cells. Moreover, supporting a detrimental role of Cdk5 in striatal cell death, neuronal loss can be widely prevented by roscovitine, a potent Cdk5 inhibitor. Significantly, reduced Cdk5 expression together with enhanced Cdk5 phosphorylation and p25 accumulation also occurs in the striatum of mutant Hdh(Q111) mice and HD human brain suggesting the relevance of deregulated Cdk5 pathway in HD pathology. These findings provide new insights into the molecular mechanisms underlying the selective vulnerability of striatal cells in HD and identify p25/Cdk5 as an important mediator of dopamine and glutamate neurotoxicity associated to HD.

Ultrastructural analysis of the functional domains in FMRP using primary hippocampal mouse neurons.

Fragile X syndrome is caused by lack of the protein FMRP. FMRP mediates mRNA binding, dendritic mRNA transport and translational control at spines. We examined the role of functional domains of FMRP in neuronal RNA-granule formation and dendritic transport using different FMRP variants, including the mutant FMRP_I304N and the splice-variant FMRP_Iso12. Both variants are absent from dendritic RNA-granules in Fmr1 knockout neurons. Co-transfection experiments showed that wild-type FMRP recruits both FMRP variants into dendritic RNA-granules. Co-transfection of FXR2, an FMRP homologue, also resulted in redistribution of both variants into dendritic RNA-granules. Furthermore, the capacity of the variants to transport their mRNAs and the mRNA localization of an FMR1 construct containing silent point-mutations affecting only the G-quartet-structure were investigated. In conclusion, we show that wild-type FMRP and FXR2P are able to recruit FMRP variants into RNA-granules and that the G-quartet-structure in FMR1 mRNA is not essential for its incorporation in RNA-granules.

Transport kinetics of FMRP containing the I304N mutation of severe fragile X syndrome in neurites of living rat PC12 cells.

Lack of fragile X mental retardation protein (FMRP) causes the fragile X syndrome, a common form of inherited mental retardation. The syndrome usually results from the expansion of a CGG repeat in the FMR1 gene with consequent transcriptional silencing of FMR1. However, one missense mutation (Ile304Asn) was reported in the second KH domain of the protein involved in RNA binding. The protein containing this mutation showed an impaired function, leading to an extremely severe phenotype. In the present report, we have studied the role of FMRP I304N in living PC12 cells to better understand the (dys) function of this mutant FMRP. We have generated an FMR1 I304N-EGFP stably transfected PC12 cell line with an inducible expression system (Tet-On) for regulated expression of the FMRP I304N-EGFP fusion protein. After Dox-induction, FMRP I304N-EGFP was localized in the neurites of PC12 cells; however, no granules were formed as has been recently demonstrated for the normal FMRP. Time-lapse microscopy in combination with bleaching technology illustrated that although FMRP I304N-EGFP does not form visible granules, the transport into the neurites is microtubule dependent. Immunoprecipitation with antibodies against GFP demonstrates that FMRP I304N-EGFP coprecipitate with both the 60S ribosomal protein P0 and FXR1P, suggesting that the mutant FMRP is still able to form complexes, however, with different characteristics compared to normal FMRP.