ß Cell GLP-1R Signaling Alters α Cell Proglucagon Processing after Vertical Sleeve Gastrectomy in Mice.

Bariatric surgery, such as vertical sleeve gastrectomy (VSG), causes high rates of type 2 diabetes remission and remarkable increases in postprandial glucagon-like peptide-1 (GLP-1) secretion. GLP-1 plays a critical role in islet function by potentiating glucose-stimulated insulin secretion; however, the mechanisms remain incompletely defined. Therefore, we applied a murine VSG model to an inducible ß cell-specific GLP-1 receptor (GLP-1R) knockout mouse model to investigate the role of the ß cell GLP-1R in islet function. Our data show that loss of ß cell GLP-1R signaling decreases α cell GLP-1 expression after VSG. Furthermore, we find a ß cell GLP-1R-dependent increase in α cell expression of the prohormone convertase required for the production of GLP-1 after VSG. Together, the findings herein reveal two concepts. First, our data support a paracrine role for α cell-derived GLP-1 in the metabolic benefits observed after VSG. Second, we have identified a role for the ß cell GLP-1R as a regulator of α cell proglucagon processing.

An innate immune response and altered nuclear receptor activation defines the spinal cord transcriptome during alpha-tocopherol deficiency in Ttpa-null mice.

Mice with deficiency in tocopherol (alpha) transfer protein gene develop peripheral tocopherol deficiency and sensory neurodegeneration. Ttpa-/- mice maintained on diets with deficient α-tocopherol (α-TOH) had proprioceptive deficits by six months of age, axonal degeneration and neuronal chromatolysis within the dorsal column of the spinal cord and its projections into the medulla. Transmission electron microscopy revealed degeneration of dorsal column axons. We addressed the potential pathomechanism of α-TOH deficient neurodegeneration by global transcriptome sequencing within the spinal cord and cerebellum. RNA-sequencing of the spinal cord in Ttpa-/- mice revealed upregulation of genes associated with the innate immune response, indicating a molecular signature of microglial activation as a result of tocopherol deficiency. For the first time, low level Ttpa expression was identified in the murine spinal cord. Further, the transcription factor liver X receptor (LXR) was strongly activated by α-TOH deficiency, triggering dysregulation of cholesterol biosynthesis. The aberrant activation of transcription factor LXR suppressed the normal induction of the transcription factor retinoic-related orphan receptor-α (RORA), which is required for neural homeostasis. Thus we find that α-TOH deficiency induces LXR, which may lead to a molecular signature of microglial activation and contribute to sensory neurodegeneration.

RNA-seq transcriptome analysis of formalin fixed, paraffin-embedded canine meningioma.

Meningiomas are the most commonly reported primary intracranial tumor in dogs and humans and between the two species there are similarities in histology and biologic behavior. Due to these similarities, dogs have been proposed as models for meningioma pathobiology. However, little is known about specific pathways and individual genes that are involved in the development and progression of canine meningioma. In addition, studies are lacking that utilize RNAseq to characterize gene expression in clinical cases of canine meningioma. The primary objective of this study was to develop a technique for which high quality RNA can be extracted from formalin-fixed, paraffin embedded tissue and then used for transcriptome analysis to determine patterns of gene expression. RNA was extracted from thirteen canine meningiomas-eleven from formalin fixed and two flash-frozen. These represented six grade I and seven grade II meningiomas based on the World Health Organization classification system for human meningioma. RNA was also extracted from fresh frozen leptomeninges from three control dogs for comparison. RNAseq libraries made from formalin fixed tissue were of sufficient quality to successfully identify 125 significantly differentially expressed genes, the majority of which were related to oncogenic processes. Twelve genes (AQP1, BMPER, FBLN2, FRZB, MEDAG, MYC, PAMR1, PDGFRL, PDPN, PECAM1, PERP, ZC2HC1C) were validated using qPCR. Among the differentially expressed genes were oncogenes, tumor suppressors, transcription factors, VEGF-related genes, and members of the WNT pathway. Our work demonstrates that RNA of sufficient quality can be extracted from FFPE canine meningioma samples to provide biologically relevant transcriptome analyses using a next-generation sequencing technique, such as RNA-seq.

Naturally Acquired Canine Herpesvirus-Associated Meningoencephalitis.

Canid alphaherpesvirus 1 (CHV) causes morbidity and mortality in susceptible puppies. While the neuropathology of experimentally infected puppies has been detailed, characterization of naturally acquired infections is limited. The aim of this study was to describe the histologic, immunohistochemical, and in situ hybridization features of CHV encephalitis in the dog. Six female and 11 male puppies ranging in age from stillborn to 57 days old were included. Histologically, lesions included multifocal glial nodules (16/17, 94%), meningeal infiltrates (15/17, 88%), and cerebellar cortical necrosis (6/9, 67%); however, robust inflammation was not a significant feature in any of the cases. Immunohistochemistry for CD3, CD20, MAC387, and Iba1 was performed. Although T cells predominated over B cells, the overall number of cells was small in all cases both within the glial nodules and the meninges. In 16 of 16 (100%) cases, glial nodules were diffusely immunoreactive for Iba1; however, limited or no immunoreactivity for MAC387 was present. In situ hybridization directed at the CHV thymidine kinase gene revealed CHV nucleic acid in the granule neurons of the cerebellar folia (8/9; 89%), endothelial cells in the meninges and parenchyma (12/17, 71%), and individual randomly distributed neurons (6/17, 35%). These results clarify the pathology of naturally acquired CHV infection and indicate that developing cerebellar granule neurons are an important site of viral replication.

Kir7.1 immunoreactivity in canine choroid plexus tumors.

Choroid plexus neoplasms are uncommon brain tumors in dogs. Choroid plexus carcinomas often spread diffusely throughout the ventricular system and subarachnoid space and, in aggressive forms, can mimic histologic patterns of other carcinomas, including being embedded in a desmoplastic reaction. Although choroid plexus tumors (CPTs) heterogeneously express pan-cytokeratin, little is known about other markers to identify choroid plexus and their associated tumors. Kir7.1, an inward-rectifier potassium channel, is reported to have high diagnostic utility in human neuropathology to distinguish CPTs from other primary brain tumors and cerebral metastases. To determine Kir7.1 expression in the dog brain, we analyzed the immunoreactivity of Kir7.1 in normal brain, gliomas, ependymomas, CPTs, meningiomas, and carcinomas. In normal brain tissue, the immunostaining was restricted to the choroid plexus where there was robust membrane immunoreactivity along the apical border of the cells with less intense cytoplasmic staining. Similar strong immunoreactivity was detected in 12 of 12 CPTs, whereas 5 of 5 gliomas, 4 of 5 ependymomas, 5 of 5 meningiomas, and 5 of 6 carcinomas had no immunoreactivity. One ependymoma and 1 nasal carcinoma with squamous metaplasia were up to 75% immunopositive, with moderate cytoplasmic and membranous immunoreactivity, but lacking the robust apical immunoreactivity pattern. Analysis for immunoreactivity in a tissue microarray failed to yield any other locations in which immunoreactivity was detected. These results, including the distinctive pattern of immunostaining in CPTs, suggest that Kir7.1 is an excellent marker for CPTs in the dog.