Effect of α2-adrenoceptor antagonist on platelet activation during insulin-induced hypoglycaemia in Type 2 (non-insulin-dependent) diabetes mellitus

Summary The role of epinephrine in platelet activation and the effect of an ₂-adrenoceptor antagonist, midaglizole, during insulin-induced hypoglycaemia in Type 2 (noninsulin-dependent) diabetes mellitus were examined. The action of midaglizole as a platelet ₂-antagonist was confirmed by in vitro studies using platelet-rich plasma and washed platelet suspension. Hypoglycaemia was induced by a bolus injection of short-acting insulin in 24 diabetic patients. They were divided into two groups, a control group (n=12) and an ₂-group (n=12), and midaglizole was administered orally 60 min before insulin injection in the latter. Blood glucose and plasma C-peptide levels were significantly decreased (p<0.005) by insulin injection in both groups. Counter-regulatory hormones, including epinephrine, and arginine vasopressin were similarly increased at the hypoglycaemic nadir compared with the levels at 0 min in both groups. Plasma -thromboglobulin was increased at the hypoglycaemic nadir (165.5±12.6ng/ml) compared with the level at 0 min (121.0±11.5, p<0.005) in the control group, whereas no significant increase was demonstrated in the ₂ group. These results suggest that plasma epinephrine plays an important role in platelet activation during hypoglycaemia in Type 2 diabetes mellitus, and that the platelet activation is prevented by ₂-adrenoceptor antagonist.     

Metabolic programming and PDHK1 control CD4+ T cell subsets and inflammation

Activation of CD4⁺ T cells results in rapid proliferation and differentiation into effector and regulatory subsets. CD4⁺ effector T cell (Teff) (Th1 and Th17) and Treg subsets are metabolically distinct, yet the specific metabolic differences that modify T cell populations are uncertain. Here, we evaluated CD4⁺ T cell populations in murine models and determined that inflammatory Teffs maintain high expression of glycolytic genes and rely on high glycolytic rates, while Tregs are oxidative and require mitochondrial electron transport to proliferate, differentiate, and survive. Metabolic profiling revealed that pyruvate dehydrogenase (PDH) is a key bifurcation point between T cell glycolytic and oxidative metabolism. PDH function is inhibited by PDH kinases (PDHKs). PDHK1 was expressed in Th17 cells, but not Th1 cells, and at low levels in Tregs, and inhibition or knockdown of PDHK1 selectively suppressed Th17 cells and increased Tregs. This alteration in the CD4⁺ T cell populations was mediated in part through ROS, as N-acetyl cysteine (NAC) treatment restored Th17 cell generation. Moreover, inhibition of PDHK1 modulated immunity and protected animals against experimental autoimmune encephalomyelitis, decreasing Th17 cells and increasing Tregs. Together, these data show that CD4⁺ subsets utilize and require distinct metabolic programs that can be targeted to control specific T cell populations in autoimmune and inflammatory diseases.     

Direct Transmission of H. pylori from Challenged to Nonchallenged Mice in a Single Cage

To understand whether direct transmission of H. pylori occurs from infected mouse to noninfected mouse, the system using a mouse model we developed previously was tested. Six nude mice were challenged with H. pylori inocula; one group consisted of one challenged nude mouse 1 week after inoculation raised with four nonchallenged nude mice in a single cage. For the single cage, a polycarbonate cage or a mesh-floor cage was used. Then three groups were kept in a polycarbonate cage and the other three groups kept in a mesh-floor cage to avoid H. pylori transmission through stool. After coraising for 1, 2, or 3 weeks, all mice were sacrificed to determine the existence of H. pylori in the stomach, saliva, and stool by culture or PCR and H. pylori-associated gastritis. RAPD fingerprinting patterns using different primers of isolated strains from challenged and nonchallenged mice were compared to understand the origin of transmitted strains. During 3 weeks after coraising of H. pylori challenged and nonchallenged mice, H. pylori was detected in the stomachs in 3 of 12 nonchallenged mice in the polycarbonate cage and in 2 of 12 nonchallenged mice in the cage with a steel mesh floor. H. pylori was detected from saliva or stool in two nonchallenged, infected mice in the polycarbonate cage. Moreover, RAPD fingerprinting using different primers of the total five strains isolated from five nonchallenged, infected mice in both cages showed the same pattern and concordance with that of the challenged strain and the strains isolated from challenged mice. It is demonstrated that intimate interaction is the cause of H. pylori transmission via saliva and stool.     

Susceptibility of muridae cell lines to ecotropic murine leukemia virus and the cationic amino acid transporter 1 viral receptor sequences: implications for evolution of the viral receptor

Ecotropic murine leukemia viruses (Eco-MLVs) infect mouse and rat, but not other mammalian cells, and gain access for infection through binding the cationic amino acid transporter 1 (CAT1). Glycosylation of the rat and hamster CAT1s inhibits Eco-MLV infection, and treatment of rat and hamster cells with a glycosylation inhibitor, tunicamycin, enhances Eco-MLV infection. Although the mouse CAT1 is also glycosylated, it does not inhibit Eco-MLV infection. Comparison of amino acid sequences between the rat and mouse CAT1s shows amino acid insertions in the rat protein near the Eco-MLV-binding motif. In addition to the insertion present in the rat CAT1, the hamster CAT1 has additional amino acid insertions. In contrast, tunicamycin treatment of mink and human cells does not elevate the infection, because their CAT1s do not have the Eco-MLV-binding motif. To define the evolutionary pathway of the Eco-MLV receptor, we analyzed CAT1 sequences and susceptibility to Eco-MLV infection of other several murinae animals, including the southern vole (Microtus rossiaemeridionalis), large Japanese field mouse (Apodemus speciosus), and Eurasian harvest mouse (Micromys minutus). Eco-MLV infection was enhanced by tunicamycin in these cells, and their CAT1 sequences have the insertions like the hamster CAT1. Phylogenetic analysis of mammalian CAT1s suggested that the ancestral CAT1 does not have the Eco-MLV-binding motif, like the human CAT1, and the mouse CAT1 is thought to be generated by the amino acid deletions in the third extracellular loop of CAT1.