Most insulin is secreted in discrete pulses at an interval of ϳ6 min. Increased insulin secretion after meal ingestion is achieved through the mechanism of amplification of the burst mass. Conversely, in type 2 diabetes, insulin secretion is impaired as a consequence of decreased insulin pulse mass. ␤-cell mass is reported to be deficient in type 2 diabetes. We tested the hypothesis that decreased ␤-cell mass leads to decreased insulin pulse mass. Insulin secretion was examined before and after an ϳ60% decrease in ␤-cell mass achieved by a single injection of alloxan in a porcine model. Alloxan injection resulted in stable diabetes (fasting plasma glucose 7.4 ؎ 1.1 vs. 4.4 ؎ 0.1 mmol/l; P < 0.01) with impaired insulin secretion in the fasting and fed states and during a hyperglycemic clamp (decreased by 54, 80, and 90%, respectively). Deconvolution analysis revealed a selective decrease in insulin pulse mass (by 54, 60, and 90%) with no change in pulse frequency. Rhythm analysis revealed no change in the periodicity of regular oscillations after alloxan administration in the fasting state but was unable to detect stable rhythms reliably after enteric or intravenous glucose stimulation. After alloxan administration, insulin secretion and insulin pulse mass (but not insulin pulse interval) decreased in relation to ␤-cell mass. However, the decreased pulse mass (and pulse amplitude delivered to the liver) was associated with a decrease in hepatic insulin clearance, which partially offset the decreased insulin secretion. Despite hyperglycemia, postprandial glucagon concentrations were increased after alloxan administration (103.4 ؎ 6.3 vs. 92.2 ؎ 2.5 pg/ml; P < 0.01). We conclude that an alloxan-induced selective decrease in ␤-cell mass leads to deficient insulin secretion by attenuating insulin pulse mass, and that the latter is associated with decreased hepatic insulin clearance and relative hyperglucagonemia, thereby emulating the pattern of islet dysfunction observed in type 2 diabetes. Diabetes 50: [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012] 2001 T ype 2 diabetes is characterized by impaired glucose-mediated insulin secretion (1,2). This has been documented by demonstrating reduced first-phase insulin release in response to intravenous glucose (3,4) and impaired insulin release after glucose ingestion (1,5) and during a hyperglycemic clamp (6). Further analyses indicate that most insulin secretion is derived from discrete insulin secretory bursts (7,8), the mass of which is diminished in patients with type 2 diabetes (9). In addition, it has been reported that ␤-cell mass may be decreased in patients with type 2 diabetes (10), although this remains controversial. Indeed, the role of any decrease in the ␤-cell mass in the pathogenesis of impaired insulin secretion and the pathogenesis of hyperglycemia in type 2 diabetes remains uncertain.In the present study, we addressed the hypothesis that defective insulin secretion in type 2 diabetes can be recapitulated by a selective decreas...

Angiotensin II (ANG II) can activate the mitogen-activated protein kinases (MAPKs) and stress-activated protein kinases in several cell types. We have previously shown that the 12-lipoxygenase (12-LO) pathway of arachidonic acid metabolism is a mediator of ANG II-induced aldosterone synthesis in adrenal glomerulosa cells. To evaluate the role of MAPK activation in ANG II and the effects of LO on aldosterone synthesis, experiments were performed using the human adrenocortical cell line H295R, which secretes aldosterone in response to ANG II. MAPK activities were determined by Western immunoblotting using specific antibodies to their activated phosphorylated forms. ANG II led to a dose-dependent increase in extracellular signal-regulated kinase (ERK1/2) activity in these cells, with a peak at 5 min and lasting up to 3 h. The effects of ANG II were blocked by the ANG-II Type 1 receptor antagonist losartan. A specific 12-LO product, 12(S)-hydroxyeicosatetraenoic acid (12-HETE), had no direct effect on ERK activity. However, both ANG II and 12-HETE led to significant dose-dependent increases in p38 MAPK activity with peak effects at 5 min. By contrast, the 15-LO product, 15-HETE, had no effect on p38 MAPK activity. Furthermore, two dissimilar 12-LO inhibitors, CDC and baicalein, blocked ANG II-induced p38 MAPK activation. ANG II significantly increased aldosterone release, and this effect was inhibited by the LO inhibitor baicalein, as well as a specific p38 MAPK inhibitor, SB202190, but not by PD098059, a specific inhibitor of the ERK activator MEK. In summary, in H295R cells, ANG II activated ERK and p38 MAPKs, ANG II-induced p38 MAPK was mediated by 12-LO activation, and ANG II-induced aldosterone synthesis was prevented by 12-LO- and p38 MAPK-specific inhibitors. These results suggest, for the first time, that activation of p38 MAPK, either directly or via LO activation, participates in aldosterone's stimulatory effects of ANG II in adrenal cells.

No abstract

Hepatic ischemia/reperfusion (I/R) injury is very important in transplant surgery. To study the mechanism of receptor activator for nuclear factor kappa B-Fc (RANK-Fc) in protection against I/R injury, 90 male BALB/c mice were randomly divided into 3 groups: a phosphate-buffered saline (PBS) (sham) group, a pLNCX2-IRES-eGFPþI/R (Negative-control) group (where IRES means internal ribosome entry site and eGFP means enhanced green fluorescent protein), and a pLNCX2-RANK-Fc-IRES-eGFPþI/R (RANK-Fc) group. All mice were injected with 2.5 mL of PBS (with or without plasmids) within 6 seconds via the tail vein. After 3 days, hepatic I/R was induced under warm conditions by partial occlusion of the left and median lobes for 90 minutes followed by various periods of reperfusion. Hepatic injury was assessed by the levels of liver aminotransferases and histopathology. Tumor necrosis factor alpha, interleukin 6, and interleukin 1b were measured by enzyme-linked immunosorbent assay, whereas RANK-Fc, phospho-c-Jun, c-Jun N-terminal kinase (JNK), hypoxia inducible factor 1 alpha (HIF-1a), nuclear p65, and total p65 were assessed with western blotting. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling. RANK-Fc was efficiently expressed in the liver. In comparison with the negative-control group, RANK-Fc reduced nuclear factor kappa B (NF-jB) p65 nuclear translocation, JNK phosphorylation, and HIF-1a expression during I/R. RANK-Fc effectively suppressed proinflammatory cytokine expression. The results indicated that RANK-Fc could protect against hepatic I/R injury in mice at least in part via the inhibition of the proinflammatory NF-jB pathway as well as proapoptotic JNK and HIF-1a pathway activation. Liver Transpl 16:611-620,

Transduction of latent membrane protein 2 (LMP2)-specific T-cell receptors into activated T lymphocytes may provide a universal, MHC-restricted mean to treat EBV-associated tumors in adoptive immunotherapy. We compared TCR-specific promoters of distinct origin in lentiviral vectors, that is, Vβ6.7, delta, luria, and Vβ5.1 to evaluate TCR gene expression in human primary peripheral blood monocytes and T cell line HSB2. Vectors containing Vβ 6.7 promoter were found to be optimal for expression in PBMCs, and they maintained expression of the transduced TCRs for up to 7 weeks. These cells had the potential to recognize subdominant EBV latency antigens as measured by cytotoxicity and IFN-γ secretion. The nude mice also exhibited significant resistance to the HLA-A2 and LMP2-positive CNE tumor cell challenge after being infused with lentiviral transduced CTLs. In conclusion, LMP2-specific CTLs by lentiviral transduction have the potential use for treatment of EBV-related tumors.