Menin-regulated Pbk controls high fat diet-induced compensatory beta cell proliferation.

Pancreatic beta cells undergo compensatory proliferation in the early phase of type 2 diabetes. While pathways such as FoxM1 are involved in regulating compensatory beta cell proliferation, given the lack of therapeutics effectively targeting beta cell proliferation, other targetable pathways need to be identified. Herein, we show that Pbk, a serine/threonine protein kinase, is essential for high fat diet (HFD)-induced beta cell proliferation in vivo using a Pbk kinase deficiency knock-in mouse model. Mechanistically, JunD recruits menin and HDAC3 complex to the Pbk promoter to reduce histone H3 acetylation, leading to epigenetic repression of Pbk expression. Moreover, menin inhibitor (MI) disrupts the menin-JunD interaction and augments Pbk transcription. Importantly, MI administration increases beta cell proliferation, ameliorating hyperglycemia, and impaired glucose tolerance (IGT) in HFD-induced diabetic mice. Notably, Pbk is required for the MI-induced beta cell proliferation and improvement of IGT. Together, these results demonstrate the repressive role of the menin/JunD/Pbk axis in regulating HFD-induced compensatory beta cell proliferation and pharmacologically regulating this axis may serve as a novel strategy for type 2 diabetes therapy.

Protective Effect of Iridoid Glycosides of the Leaves of Syringa oblata Lindl. on Dextran Sulfate Sodium-Induced Ulcerative Colitis by Inhibition of the TLR2/4/MyD88/NF-κB Signaling Pathway.

Iridoid glycoside (IG) is the major active fraction extracted from the leaves of Syringa oblata Lindl. In view of its antimicrobial and antidiarrheal potential, it could be beneficial for the treatment of ulcerative colitis (UC). In the present study, IG (20, 40, and 80 mg/kg) was administered orally for 14 days to dextran sulfate sodium- (DSS-) induced colitis rats. The anti-inflammatory effects of IG on DSS-induced UC were evaluated by comparing observations in DSS-induced colitis and drug-treated groups using disease activity index (DAI), macroscopic score, histological analysis, and apoptosis assay. To elucidate the antioxidant mechanisms of IG on NOX-dependent ROS production, the activities of 8-OHdG, NOX1, and NOX2 in DSS-induced colitis were determined. The levels of proinflammatory cytokines such as IL-2, IL-4, IL-5, IL-12p40, and IL-13 were detected. The inflammation-associated protein and mRNA expressions of TLR-2, TLR-4, MyD88, and NF-κBp65 were assessed by immunohistochemistry and real-time quantitative PCR, respectively. The results suggested that IG treatment significantly reduced DAI, macroscopic score, and histological damage compared to untreated animals (p < 0.01), whereas administration of IG remarkably attenuated the upregulation of 8-OHdG, NOX1, and NOX2 and the expression of proinflammatory cytokines such as IL-2, IL-4, IL-5, IL-12p40, and IL-13 in DSS-treated rats in a concentration-dependent manner. In addition, IG treatment could dose dependently suppress the protein and mRNA levels of TLR-2, TLR-4, MyD88, and NF-κBp65. The dose of IG that produced the most significant protective effect was 80 mg/kg. The above results demonstrate that IG exerts its inhibitory effect on cell apoptosis, oxidative stress, and proinflammatory cytokines in DSS-induced colitis through modulation of the TLR2/4/MyD88/NF-κB signaling pathway.

Neutrophil-mediated and low density lipoprotein receptor-mediated dual-targeting nanoformulation enhances brain accumulation of scutellarin and exerts neuroprotective effects against ischemic stroke.

Delivery of poorly permeable drugs across the blood-brain barrier (BBB) is a great challenge in the treatment of ischemic stroke. In order to construct a suitable delivery system for this purpose, we developed a dual-targeting nanoformulation to transfer therapeutic agents targeting the inflammatory sites of the ischemic brain. The matrix of this system is a hydroxyl-terminated polyamidoamine dendrimer with excellent biodegradability. The surface of the matrix is functionalized with two targeting peptides: Angiopep-2 is a low density lipoprotein receptor-mediated peptide with high BBB transcytosis capacity with ligands expressed on brain endothelial cells; N-acetylated proline-glycine-proline (PGP) has high affinity to CXCR2 expressed on infiltrating neutrophils. This system proved to be a high-loading formulation for the neuroprotective compound, scutellarin (STA), and significantly improved its therapeutic efficacy in a rodent model of ischemic stroke. The molecular mechanism underlying the therapeutic efficacy of this formulation is associated with significant down-regulation of the inflammatory cytokines, neutrophils infiltration and intracellular calcium overload and blockade of the inflammatory signaling pathway HMGB1/TLRs/MyD88/TRIF/NF-κB. Our results suggest that this dual-targeting delivery system is a promising drug delivery vehicle for ischemic stroke, and possibly other CNS diseases where neuroinflammation is involved.

Kinase inhibitors of HER2/AKT pathway induce ERK phosphorylation via a FOXO-dependent feedback loop.

Inhibitors of the HER2/PI3K/AKT pathway are being developed, and shown promise in clinical trials for various types of cancers. However, development of drug resistance is a challenging problem for therapy. Elucidating various adaptive pathways leading to resistance or reduced sensitivity to drugs targeting the HER2/PI3K/AKT pathway may provide new insights into countering the resistance. Epidermal growth factor receptor (EGFR, aka HER1), which can dimerize with HER2, can activate a cascade consisting of Ras/RAF/MEK/ERK, promoting tumorigenesis. Lapatinib inhibits the kinase activity of both HER1 and HER2. In the current study, we found that repeated treatment of HER2+ breast cancer cells with HER1/2 inhibitor Lapatinib led to increased phosphorylation of RAF, MEK, and ERK, while suppressing HER1 phosphorylation and reduced the active form of Ras, indicating existence of factor(s) activating RAF/MEK/ERK by bypassing RAS activation. Notably, the Lapatinib treatment-induced phosphorylation of ERK was dependent on FOXO transcription factors, which are also activated by Lapatinib-mediated suppression of AKT. Moreover, the Lapatinib-induced phosphorylation of RAF and ERK is inhibited by a pan-PKC inhibitor. Furthermore, the Lapatinib induced increased ERK phosphorylation is correlated with increased stability of c-Myc, which is known to be stabilized by ERK-mediated phosphorylation. Together, these results suggest that chronic inhibition of the HER1/2 by Lapatinib triggers a feedback loop to activate RAF/MEK/ERK pathway, in a FOXO dependent but Ras-independent manner.

BRD4 inhibitor IBET upregulates p27kip/cip protein stability in neuroendocrine tumor cells.

The prevalence of neuroendocrine tumors (NETs) has recently been increasing. Although various drugs such as Octreotide and its analogs show certain efficacy, NETs in many patients progress and metastasize. It is desirable to develop new interventions to improve the therapy. Here we show that human neuroendocrine tumor BON cells are resistant to several drugs commonly used for NET therapy, including Octreotide that activates somatostatin receptor-induced anti-proliferation, and Capecitabine and Temozolimide that damage DNA. In contrast, an inhibitor (IBET) to an epigenetic regulator, Brd4 that binds acetylated histones and upregulates transcription of multiple genes including protooncogene c-Myc, potently inhibited the NET cells. We found that IBET increased the protein levels of cyclin-dependent kinase (CDK) inhibitor p27kip/cip (or p27), but not its mRNA levels. Moreover, the p27 induction at protein level by IBET was at least partly through increasing the protein stability of p27. The increased protein stability of p27 likely resulted from IBET-mediated suppression of Skp2, an E3 ligase that can mediate p27 degradation by increasing its ubiquitinylation. These findings unravel a new mechanism whereby the IBET-induced repression of proliferation of neuroendocrine cells.

Menin and Daxx Interact to Suppress Neuroendocrine Tumors through Epigenetic Control of the Membrane Metallo-Endopeptidase.

Neuroendocrine tumors (NET) often harbor loss-of-function mutations in the MEN1 and DAXX tumor suppressor genes. Here, we report that the products of these genes, menin and Daxx, interact directly with each other to suppress the proliferation of NET cells, to a large degree by inhibiting expression of the membrane metallo-endopeptidase (MME). Menin and Daxx were required to enhance histone H3 lysine9 trimethylation (H3K9me3) at the MME promoter, as mediated partly by the histone H3 methyltransferase SUV39H1. Notably, the menin T429K mutation associated with a NET syndrome reduced Daxx binding, MME repression, and proliferation of NET cells. Conversely, inhibition of MME in NET cells repressed proliferation and tumor growth in vivo Our findings reveal a previously unappreciated cross-talk between two crucial tumor suppressor genes thought to work by independent pathways, focusing on MME as a common target of menin/Daxx to treat NET. Cancer Res; 77(2); 401-11. ©2016 AACR.

The effect of cationic albumin-conjugated PEGylated tanshinone IIA nanoparticles on neuronal signal pathways and neuroprotection in cerebral ischemia.

Targeted treatment of ischemic stroke remains problem due to the complex pathogenesis of this disease and the difficulty in drug delivery across the blood-brain barrier (BBB). In the present study, the delivery efficiency of cationic bovine serum albumin-conjugated tanshinone IIA PEGylated nanoparticles (CBSA-PEG-TIIA-NPs) in rat brain was investigated. We further explored whether the protective mechanism of CBSA-PEG-TIIA-NPs in cerebral ischemia was associated with modulating neuronal signaling pathways. The experimental cerebral ischemia model was established to evaluate the treatment efficacy of CBSA-PEG-TIIA-NPs. The pharmacokinetics demonstrated that CBSA-PEG-TIIA-NPs could obviously prolong circulation time and increase plasma concentration compared with intravenously administrated TIIA solution. The biodistribution and brain uptake study confirmed that CBSA-PEG-TIIA-NPs possessed better brain delivery efficacy with a high drug accumulation and fluorescence quantitative level in brain. CBSA-PEG-TIIA-NPs effectively reduced infarction volume, neurological dysfunctions, neutrophils infiltration and neuronal apoptosis. Moreover, CBSA-PEG-TIIA-NPs significantly suppressed the expression of pro-inflammatory cytokines TNF-α and IL-8; upregulated the expression of anti-inflammatory cytokines IL-10 and increase TGF-ß1 level in the ischemic brain. In addition, treatment with CBSA-PEG-TIIA-NPs markedly inhibited the mRNA expressions of GFAP, MMP-9, COX-2, p38MAPK, ERK1/2 and JNK, downregulated the protein levels of GFAP, MMP-9 and COX-2, as well as decreased the phosphorylation of ERK1/2, p38MAPK and JNK. These results demonstrated that CBSA-PEG-TIIA-NPs displayed remarkable neuroprotective effects on ischemic stroke through modulation of MAPK signal pathways involved in the cascades of neuroinflammation.

Protective effects of cationic bovine serum albumin-conjugated PEGylated tanshinone IIA nanoparticles on cerebral ischemia.

Tanshinone IIA is a good candidate for treating cerebral ischemia, but its short half-life and poor permeability across the blood-brain-barrier (BBB) limit its curative efficacy. In this study, we successfully developed cationic bovine serum albumin-conjugated tanshinone IIA PEGylated nanoparticles (CBSA-PEG-TIIA-NPs). A cerebral ischemia rat model was established to evaluate the treatment efficacy and protective mechanism of CBSA-PEG-TIIA-NPs. CBSA-PEG-TIIA-NPs showed the mean particle size 118 ± 14 nm with drug loaded ratio and encapsulation efficiency 5.69 ± 0.6% and 83.2 ± 2.6%, respectively. The pharmacokinetics demonstrated that CBSA-PEG-TIIA-NPs could significantly prolong circulation time and increase plasma concentration compared with intravenously administrated TIIA solution. The biodistribution and brain uptake study confirmed that CBSA-PEG-TIIA-NPs possessed better brain delivery efficacy with a high accumulation in brain. CBSA-PEG-TIIA-NPs obviously ameliorated infarct volume, neurological deficit and histopathological severity. Treatment with CBSA-PEG-TIIA-NPs markedly inhibited the levels of the MPO, TNF-α, IL-1ß and IL-6. Furthermore, CBSA-PEG-TIIA-NPs significantly decreased the mRNA expressions of iNOS and p38MAPK, upregulated PPARγ expression, and inhibited the protein levels of iNOS, GFAP and p38MAPK phosphorylation. These results demonstrated that CBSA-PEG-TIIA-NPs possessed remarkable neuroprotective effects on ischemic stroke through modulation of inflammatory cascades and neuronal signal pathways involved in cerebral ischemia.

Serum retinol-binding protein 4 is elevated and positively associated with insulin resistance in postmenopausal women.

Retinol-binding protein 4 (RBP4) is a newly discovered adipokine, which is reported to be correlated with insulin resistance (IR) and type 2 diabetes (T2DM). The aim of this study was to evaluate the influence of menopausal status on RBP4 concentration and to investigate serum RBP4 with IR and the prevalence of T2DM in postmenopausal women. We conducted a cross-sectional study and enrolled 34 healthy premenopausal women, 41 healthy postmenopausal women and 37 postmenopausal women with T2DM. Serum RBP4 concentration was measured by an enzyme-linked immunosorbent assay. Anthropometric parameters, plasma glucose, insulin and sex hormones concentrations were measured, and IR was assessed by HOMA2-IR. We found RBP4 was significantly elevated after menopause, even after adjustment for age and BMI. In postmenopausal women, RBP4 correlated positively with BMI, WHR, FPI, HOMA2-IR, TG and FAI, while negatively with SHBG (p<0.05). Furthermore, RBP4 was positively associated with 17beta-estradiol in only diabetic postmenopausal women. In healthy premenopausal group, age, BMI, and TG were the independent determinants of RBP4. In two postmenopausal groups, the independent determinants of RBP4 were BMI, WHR, HOMA2-IR, TG and FAI in healthy subjects, and in group with T2DM, the determinants were BMI, WHR, FPI, HOMA2-IR, TG and FAI (p<0.05). However, serum RBP4 was not significantly associated with increased odds of T2DM in postmenopausal women (OR 0.979, 95% CI 0.610-1.637). The findings suggested serum RBP4 concentration is influenced by menopausal status and closely related to IR but not to the prevalence of T2DM in postmenopausal women.

Effect of ScrF I polymorphism in the 2nd intron of the HMGCR gene on lipid-lowering response to simvastatin in Chinese diabetic patients.

OBJECTIVE: To investigate whether ScrF I polymorphism in the 2nd intron of the HMG-COA reductase gene (HMGCR) influences serum lipid levels and whether this polymorphism affects the efficiency of the cholesterol lowering HMG-CoA reductase inhibitor, simvastatin. METHODS: One hundred sixty-eight patients with type 2 diabetes mellitus (T2DM) prospectively received simvastatin as a single-agent therapy (20mg day-1 p.o.) for 12 weeks. Serum lipid levels were determined before and after simvastatin treatment. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: Subjects with the AA homozygotes had significantly higher serum very low-density lipoprotein cholesterol (VLDL-C) levels than those with the aa homozygotes. In addition, in 168 patients with T2DM who took 20mg simvastatin, the VLDL-C lowering effect by simvastatin in subjects with the aa homozygotes was significantly lower than in those with the Aa heterozygotes and AA homozygotes. CONCLUSIONS: Simvastatin treatment significantly decreased plasma lipids in all patients (P<0.01). Importantly, we demonstrate that ScrF I polymorphism of the HMGCR gene in patients with T2DM groups is associated with significant elevation of serum VLDL-C levels. Subjects with the AA homozygotes had significantly higher serum high VLDL-C levels than those with the Aa heterozygotes and aa homozygotes (AA: 2.18+/-0.51; Aa: 2.04+/-0.59, aa: 1.86+/-0.43, P<0.05 for comparison among three genotypes and P<0.01 for difference between AA and aa). Furthermore, this polymorphism tends to show an enhanced response to an HMG-CoA reductase inhibitor in terms of the cholesterol-lowering effect. In 168 patients with T2DM who took 20mg simvastatin, the VLDL-C lowering effect by simvastatin in subjects with the AA homozygotes was significantly lower than in those with the Aa heterozygotes and aa homozygotes (the reduction in serum VLDL-C levels; 37.03+/-5.67 versus 28.97+/-4.96, P<0.01; 34.62+/-5.87 versus 28.97+/-4.96, P<0.05). These results suggest that the HMGCR gene may serve as a modifier gene for hypercholesterolemia in Chinese diabetic patients.