Machine Learning Study of SNPs in Noncoding Regions to Predict Non-small Cell Lung Cancer Susceptibility

Non-small cell lung cancer (NSCLC) is the most common pathological subtype of lung cancer. Both environmental and genetic factors have been reported to impact the lung cancer susceptibility. We conducted a genome-wide association study (GWAS) of 287 NSCLC patients and 467 healthy controls in a Chinese population using the Illumina Genome-Wide Asian Screening Array Chip on 712,095 SNPs (single nucleotide polymorphisms). Using logistic regression modeling, GWAS identified 17 new noncoding region SNP loci associated with the NSCLC risk, and the top three (rs80040741, rs9568547, rs6010259) were under a stringent p-value (<3.02e-6). Notably, rs80040741 and rs6010259 were annotated from the intron regions of MUC3A and MLC1, respectively. Together with another five SNPs previously reported in Chinese NSCLC patients and another four covariates (e.g., smoking status, age, low dose CT screening, sex), a predictive model by machine learning methods can separate the NSCLC from healthy controls with an accuracy of 86%. This is the first time to apply machine learning method in predicting the NSCLC susceptibility using both genetic and clinical characteristics. Our findings will provide a promising method in NSCLC early diagnosis and improve our understanding of applying machine learning methods in precision medicine.

Analysis of microbial diversity in the feces of Arborophila rufipectus

Introduction

Intestinal microbiota composition plays a crucial role in modulating the health of the host. This evaluation indicator is very sensitive and profoundly impacts the protection of endangered species. Currently, information on the gut microbiota of wild birds remains scarce. Therefore, this study aimed to describe the gut microbial community structure and potentially, the pathogen composition of wild Arborophila rufipectus.

Methods

To guarantee comprehensive data analysis, we collected fecal samples from wild A. rufipectus and Lophura nycthemera in their habitats for two quarters. The 16S rRNA gene was then sequenced using high-throughput sequencing technology to examine the intestinal core microbiota, microbial diversity, and potential pathogens with the aim of determining if the composition of the intestinal microflora varies seasonally.

Results and Discussion

The gut microbiota of A. rufipectus and L. nycthemera primarily comprised four phyla: Proteobacteria (45.98%), Firmicutes (35.65%), Bacteroidetes (11.77%), and Actinobacteria (3.48%), which accounted for 96.88% of the total microbial composition in all samples. At the genus level, core microorganisms were found, including Shigella (10.38%), Clostridium (6.16%), Pseudomonas (3.03%), and Rickettsiella (1.99%). In these genera, certain microbial species have been shown to be pathogenic. This study provides important indicators for analyzing the health status of A. rufipectus and formulating protective measures.

Sodium MRI at 7T for Early Response Evaluation of Intracranial Tumors following Stereotactic Radiotherapy Using the CyberKnife

BACKGROUND AND PURPOSE

Conventionally, early treatment response to stereotactic radiotherapy in intracranial tumors is often determined by structural MR imaging. Tissue sodium concentration is altered by cellular integrity and energy status in cells. In this study, we aimed to investigate the feasibility of sodium MR imaging at 7T for the preliminary evaluation of radiotherapeutic efficacy for intracranial tumors.

MATERIALS AND METHODS

Data were collected from 16 patients (12 men and 4 women, 24-75 years of age) with 22 intracranial tumors who were treated with stereotactic radiation therapy using CyberKnife at our institution between December 1, 2016, and August 15, 2019. Sodium MR imaging was performed at 7T before and 48 hours, 1 week, and 1 month after CyberKnife radiation therapy. Tissue sodium concentration (TSC) was calculated and analyzed based on manually labeled regions of tumors.

RESULTS

Ultra-high-field sodium MR imaging clearly showed the intratumoral signal, which is significantly higher than that of normal tissue (t = 5.250, P <.001)., but the edema zone has some influence. The average TSC ratios of tumor to CSF in the 22 tumors, contralateral normal tissues, edema zones, frontal cortex, and frontal white matter were 0.66 (range, 0.23-1.5), 0.30 (range, 0.15-0.43), 0.58 (range, 0.25-1.21), 0.25 (range, 0.17-0.42), and 0.30 (range, 0.19-0.49), respectively. A total of 12 tumors in 8 patients were scanned at 48 hours, 1 week, and 1 month after treatment. The average TSC at 48 hours after treatment was 0.06 higher than that before treatment and began to decrease at 1 week. The TSC ratios of 10 continued to decline and 2 tumors increased at 1 month, respectively. Tumor volume decreased by 2.4%-99% after 3 months.

CONCLUSIONS

Changes in the TSC can be quantified by sodium MR imaging at 7T and used to detect radiobiologic alterations in intracranial tumors at early time points after CyberKnife radiation therapy.

P1022Upstream therapy using preoperative renin-angiotensin system inhibitors in prevention of postoperative atrial fibrillation and adverse events: a collaborative pooled-analysis over 27,000 patients

Background

Renin-angiotensin-system inhibitors (RASIs) have been suggested as an upstream therapy for selected AF patients; however, the evidence in surgical setting is limited.

Objective

We aimed to evaluate the role of preoperative RASIs in prevention of postoperative atrial fibrillation (POAF) and adverse events for patients undergoing cardiac surgery.

Methods

In this collaborative pooled-analysis, both randomized and nonrandomized controlled trials comparing preoperative RASIs with no preoperative RASIs treatment on the incidence of POAF were identified. Sensitivity and subgroup analyses of RCTs were performed to test the stability of the overall-effect, and meta-regression to explore the potential risk of bias. The primary outcome was POAF, and the secondary outcomes includes rate of stroke, mortality and duration of hospitalization.

Results

Eleven trials involving 27885 patients (male 74%, median age 65yrs) were included. As compared to the control group, preoperative RASIs did not significantly reduce the risk of POAF (OR: 1.04, 95% CI: 0.91–1.19), stroke (OR: 0.86, 95% CI: 0.62–1.19), death (OR: 1.07, 95% CI: 0.85–1.35), composite adverse cardiac events (OR: 1.04, 95% CI: 0.91–1.18), and hospital stay (WMD: −0.04, 95% CI: −1.05 to 0.98). Pooled-analysis of randomized trials showed consistent results. The primary overall-effect was maintained in sensitivity and subgroup analyses. Meta-regression showed that male-gender was a significant risk-factor of POAF and use of Beta-blockers was associated with a significantly reduced risk in developing POAF.

Conclusion and relevance

This study demonstrates that preoperative RASIs do not offer additional benefit in reducing the risk of postoperative AF, stroke, death and hospitalization in the setting of cardiac surgery. The results provide no support for use of RASIs for the prevention of POAF and adverse events in patients undergoing cardiac surgery.

Ultrafast extreme rejuvenation of metallic glasses by shock compression

Structural rejuvenation of glasses not only provides fundamental insights into their complicated dynamics but also extends their practical applications. However, it is formidably challenging to rejuvenate a glass on very short time scales. Here, we present the first experimental evidence that a specially designed shock compression technique can rapidly rejuvenate metallic glasses to extremely high-enthalpy states within a very short time scale of about 365 ± 8 ns. By controlling the shock stress amplitude, the shock-induced rejuvenation is successfully frozen at different degrees. The underlying structural disordering is quantitatively characterized by the anomalous boson heat capacity peak of glasses. A Deborah number, defined as a competition of time scales between the net structural disordering and the applied loading, is introduced to explain the observed ultrafast rejuvenation phenomena of metallic glasses.

Tilmicosin- and florfenicol-loaded hydrogenated castor oil-solid lipid nanoparticles to pigs: Combined antibacterial activities and pharmacokinetics

The combined antibacterial effects of tilmicosin (TIL) and florfenicol (FF) against Actinobacillus pleuropneumoniae (APP) (n = 2), Streptococcus suis (S. suis) (n = 2), and Haemophilus parasuis (HPS) (n = 2) were evaluated by chekerboard test and time-kill assays. The pharmacokinetics (PKs) of TIL- and FF-loaded hydrogenated castor oil (HCO)-solid lipid nanoparticles (SLN) were performed in healthy pigs. The results indicated that TIL and FF showed synergistic or additive antibacterial activities against APP, S. suis and HPS with the fractional inhibitory concentration (FIC) ranging from 0.375 to 0.75. The time-kill assays showed that 1/2 minimum inhibitory concentration (MIC) TIL combined with 1/2 MIC FF had a stronger ability to inhibit the growth of APP, S. suis, and HPS than 1 MIC TIL or 1 MIC FF, respectively. After oral administration, plasma TIL and FF concentrations could maintain about 0.1 μg/ml for 192 and 176 hr. The SLN prolonged the last time point with detectable concentrations (T_last ), area under the concentration-time curve (AUC_0-t ), elimination half-life (T_½ke ), and mean residence time (MRT) by 3.1, 5.6, 12.7, 3.4-fold of the active pharmaceutical ingredient (API) of TIL and 11.8, 16.5, 18.1, 12.1-fold of the API of FF, respectively. This study suggests that the TIL-FF-SLN could be a useful oral formulation for the treatment of APP, S. suis, and HPS infection in pigs.

Caspase-3 feedback loop enhances Bid-induced AIF/endoG and Bak activation in Bax and p53-independent manner

Chemoresistance in cancer has previously been attributed to gene mutations or deficiencies. Bax or p53 deficiency can lead to resistance to cancer drugs. We aimed to find an agent to overcome chemoresistance induced by Bax or p53 deficiency. Here, we used immunoblot, flow-cytometry analysis, gene interference, etc. to show that genistein, a major component of isoflavone that is known to have anti-tumor activities in a variety of models, induces Bax/p53-independent cell death in HCT116 Bax knockout (KO), HCT116 p53 KO, DU145 Bax KO, or DU145 p53 KO cells that express wild-type (WT) Bak. Bak knockdown (KD) only partially attenuated genistein-induced apoptosis. Further results indicated that the release of AIF and endoG also contributes to genistein-induced cell death, which is independent of Bak activation. Conversely, AIF and endoG knockdown had little effect on Bak activation. Knockdown of either AIF or endoG alone could not efficiently inhibit apoptosis in cells treated with genistein, whereas an AIF, endoG, and Bak triple knockdown almost completely attenuated apoptosis. Next, we found that the Akt-Bid pathway mediates Bak-induced caspase-dependent and AIF- and endoG-induced caspase-independent cell death. Moreover, downstream caspase-3 could enhance the release of AIF and endoG as well as Bak activation via a positive feedback loop. Taken together, our data elaborate the detailed mechanisms of genistein in Bax/p53-independent apoptosis and indicate that caspase-3-enhanced Bid activation initiates the cell death pathway. Our results also suggest that genistein may be an effective agent for overcoming chemoresistance in cancers with dysfunctional Bax and p53.

Functional characteristics of neonatal rat β cells with distinct markers

Neonatal β cells are considered developmentally immature and hence less glucose responsive. To study the acquisition of mature glucose responsiveness, we compared glucose-regulated redox state, insulin synthesis, and secretion of β cells purified from neonatal or 10-week-old rats with their transcriptomes and proteomes measured by oligonucleotide and LC-MS/MS profiling. Lower glucose responsiveness of neonatal β cells was explained by two distinct properties: higher activity at low glucose and lower activity at high glucose. Basal hyperactivity was associated with higher NAD(P)H, a higher fraction of neonatal β cells actively incorporating (3)H-tyrosine, and persistently increased insulin secretion below 5 mM glucose. Neonatal β cells lacked the steep glucose-responsive NAD(P)H rise between 5 and 10 mM glucose characteristic for adult β cells and accumulated less NAD(P)H at high glucose. They had twofold lower expression of malate/aspartate-NADH shuttle and most glycolytic enzymes. Genome-wide profiling situated neonatal β cells at a developmental crossroad: they showed advanced endocrine differentiation when specifically analyzed for their mRNA/protein level of classical neuroendocrine markers. On the other hand, discrete neonatal β cell subpopulations still expressed mRNAs/proteins typical for developing/proliferating tissues. One example, delta-like 1 homolog (DLK1) was used to investigate whether neonatal β cells with basal hyperactivity corresponded to a more immature subset with high DLK1, but no association was found. In conclusion, the current study supports the importance of glycolytic NADH-shuttling in stimulus function coupling, presents basal hyperactivity as novel property of neonatal β cells, and provides potential markers to recognize intercellular developmental differences in the endocrine pancreas.

Sustained function of alginate-encapsulated human islet cell implants in the peritoneal cavity of mice leading to a pilot study in a type 1 diabetic patient

AIMS/HYPOTHESIS

Alginate-encapsulated human islet cell grafts have not been able to correct diabetes in humans, whereas free grafts have. This study examined in immunodeficient mice whether alginate-encapsulated graft function was inferior to that of free grafts of the same size and composition.

METHODS

Cultured human islet cells were equally distributed over free and alginate-encapsulated grafts before implantation in, respectively, the kidney capsule and the peritoneal cavity of non-obese diabetic mice with severe combined immunodeficiency and alloxan-induced diabetes. Implants were followed for in vivo function and retrieved for analysis of cellular composition (all) and insulin secretory responsiveness (capsules).

RESULTS

Free implants with low beta cell purity (19 ± 1%) were non-functional and underwent 90% beta cell loss. At medium purity (50 ± 1%), they were functional at post-transplant week 1, evolving to normoglycaemia (4/8) or to C-peptide negativity (4/8) depending on the degree of beta cell-specific losses. Encapsulated implants immediately and sustainably corrected diabetes, irrespective of beta cell purity (16/16). Most capsules were retrievable as single units, enriched in endocrine cells that exhibited rapid secretory responses to glucose and glucagon. Single capsules with similar properties were also retrieved from a type 1 diabetic recipient at post-transplant month 3. However, the vast majority were clustered and contained debris, explaining the poor rise in plasma C-peptide.

CONCLUSIONS/INTERPRETATION

In immunodeficient mice, i.p. implanted alginate-encapsulated human islet cells exhibited a better outcome than free implants under the kidney capsule. They did not show primary non-function at low beta cell purity and avoided beta cell-specific losses by rapidly establishing normoglycaemia. Retrieved capsules presented secretory responses to glucose, which was also observed in a type 1 diabetic recipient.

Contribution of postnatally formed small beta cell aggregates to functional beta cell mass in adult rat pancreas

AIMS/HYPOTHESIS

Neogenesis of beta cells and their clustering to small aggregates is a key process in prenatal development of beta cell mass. We investigated the contribution of postnatally formed small aggregates to functional beta cell mass in adult rats.

METHODS

Conditions were defined for (1) counting total beta cell number in pancreases with relative error of <10% and (2) determining their distribution over aggregates of different size and over functionally different subpopulations.

RESULTS

Pancreases of 10-week-old male Wistar rats contained 2.8 ± 0.2 × 10⁶ beta cells, of which >90% was generated postnatally, involving: (1) neo-formation of 30,000 aggregates with diameter <50 μm including single cells; and (2) growth of 5,500 aggregates to larger sizes, accounting for 90% of the increase in cell number, with number of growing aggregates in the tail 50% greater than elsewhere. At 10 weeks, 86% of aggregates were <50 μm; compared with aggregates >200 μm, their beta cells exhibited a higher basal insulin content that was also resistant to glibenclamide-induced degranulation. The pool of Ki67-positive beta cells was sixfold larger than at birth and distributed over all aggregate sizes.

CONCLUSIONS/INTERPRETATION

We describe a method for in situ counting of beta cell numbers and subpopulations with low relative error. In adult rats, >90% of beta cells and beta cell aggregates are formed after birth. Aggregates <50 μm are more than 100-fold more abundant than aggregates >200 μm, which are selected for isolated islet studies. Their topographic and functional properties contribute to the functional heterogeneity of the beta cell population; their growth to larger aggregates with characteristic beta cell functions may serve future metabolic needs.

Human islet cell implants in a nude rat model of diabetes survive better in omentum than in liver with a positive influence of beta cell number and purity

AIMS/HYPOTHESIS

Intraportal human islet cell grafts do not consistently and sustainably induce insulin-independency in type 1 diabetic patients. The reasons for losses in donor cells are difficult to assess in patients. This study in streptozotocin-diabetic nude rats examines whether outcome is better in an extra-hepatic site such as omentum.

METHODS

Intraportal and omental implants of human islet cell grafts with the same beta cell number were followed for function and cellular composition over 5 weeks. Their outcome was also compared with that of rat islet cell grafts with similar beta cell numbers but higher purity.

RESULTS

While all intraportal recipients of rat islet cell grafts were normoglycaemic until post-transplant (PT) week 5, none was with human islet cell grafts; loss of human implants was associated with early infiltration of natural killer and CD45R-positive cells. Human islet cell implants in omentum achieved plasma human C-peptide positivity and normoglycaemia in, respectively, nine of 13 and five of 13 recipients until PT week 5; failures were not associated with inflammatory infiltrates but with lower beta cell numbers and purity of the grafts. Observations in human and rat islet cell implants in the omentum suggest that a delayed revascularisation can interfere with their metabolic outcome. Irrespective of normalisation, human omental implants presented beta cell aggregates adjacent to alpha cells and duct cells.

CONCLUSIONS/INTERPRETATION

In nude rats, human islet cell implants survive better in omentum than in liver, with positive influences of the number and purity of implanted beta cells. These observations can guide studies in patients.

Catheter ablation vs. amiodarone plus losartan for prevention of atrial fibrillation recurrence in patients with paroxysmal atrial fibrillation

BACKGROUND

Although amiodarone plus angiotensin II receptor blockers (ARBs) and catheter ablation may improve sinus rhythm maintenance of paroxysmal atrial fibrillation (AF), their clinical efficacies have not been compared. This prospective cohort study was designed to compare clinical efficacy of catheter ablation and amiodarone plus losartan on sinus rhythm maintenance in patients with paroxysmal AF.

MATERIALS AND METHODS

A total of 240 patients with paroxysmal AF were assigned to four groups. CPVA group (n = 60) was treated with circumferential pulmonary vein ablation (CPVA), SPVI group (n = 60) with segmental pulmonary vein isolation, AMIO group (n = 60) with amiodarone and AMIO + LO group (n = 60) with amiodarone plus losartan. The endpoint was documented recurrence of AF > 30 s by Holter or conventional 12-lead ECG in the 1-year follow-up period.

RESULTS

During 12 months of follow-up, the primary end point was reached in 28 patients in CPVA group, 14 patients in SPVI group, 25 patients in AMIO group and 13 patients in AMIO + LO group, respectively. The sinus rhythm in SPVI and AMIO + LO group were significant higher than that in CPVA and AMIO group (P < 0.01 and 0.025), and no difference between CPVA and AMIO group. The maintenance rate of sinus rhythm in SPVI group was similar to that in AMIO + LO group.

CONCLUSIONS

This study demonstrates that segmental pulmonary vein isolation in preventing AF recurrence is similar to amiodarone plus losartan, but it is superior to CPVA and amiodarone alone in patients with paroxysmal AF. Larger multicentre studies are needed to confirm its long-term outcomes.

Glibenclamide activates translation in rat pancreatic beta cells through calcium-dependent mTOR, PKA and MEK signalling pathways

AIMS/HYPOTHESIS

Prolonged exposure of rat beta cells to the insulin secretagogue glibenclamide has been found to induce a sustained increase in basal insulin synthesis. This effect was calcium-dependent and localised in cells that had been degranulated by the drug. Since it was blocked by the translation inhibitor cycloheximide, we examined whether sustained exposure to glibenclamide activates translational factors by calcium-dependent signalling pathways.

METHODS

Purified rat beta cells were cultured with and without glibenclamide in the presence or absence of inhibitors of calcium-dependent signalling pathways before measurement of basal and stimulated protein and insulin synthesis, and assessment of abundance of (phosphorylated) translation factors.

RESULTS

A 24 h exposure to glibenclamide induced activation of four translation factors, i.e. phosphorylation of eukaryotic initiation factor (eIF) 4e binding protein 1 and ribosomal protein S6 (rpS6), and dephosphorylation of eIF-2alpha and eukaryotic elongation factor 2. The rise in phospho-rpS6 intensity was localised to a subpopulation of beta cells with low insulin content. This activation of translational factors and the associated elevation of insulin synthesis were completely blocked by the calcium channel blocker verapamil and partially blocked by the mammalian target of rapamycin (mTOR) inhibitor rapamycin, the protein kinase A (PKA) inhibitor Rp-8-Br-cAMPs and the mitogen-activated protein kinase/ extracellular signal-regulated kinase kinase (MEK) inhibitor U0126; a combination of inhibitors exhibited additive effects.

CONCLUSIONS/INTERPRETATION

Prolonged exposure to glibenclamide activates protein translation in pancreatic beta cells through the calcium-regulated mTOR, PKA and MEK signalling pathways. The observed intercellular differences in translation activation are proposed as underlying mechanism for functional heterogeneity in the pancreatic beta cell population.

N-Acetylcysteine derivative inhibits procoagulant activity of human islet cells

AIMS/HYPOTHESIS

The early loss of beta cells after islet cell transplantation has been attributed in part to blood coagulation at the implant site. Tissue factor expressed by beta cells and contaminating duct cells is considered to activate this process. Here, we investigated the ability of N-acetyl-L-cysteine to suppress the in vitro procoagulant activity of duct cells and human islet cell preparations.

MATERIALS AND METHODS

The effects of Nacystelyn, a salt derivative of N-acetyl-L-cysteine, were first assessed on procoagulant activity induced in human plasma by recombinant tissue factor, human primary duct cells or human islet cell preparations. The influence of Nacystelyn on clot formation, platelet counts and D-dimers were measured in a whole blood tubing loop model. Human beta cell viability and insulin synthesis after Nacystelyn treatment were assessed to exclude cytotoxicity of Nacystelyn.

RESULTS

Nacystelyn efficiently inhibited the procoagulant activity of human recombinant tissue factor, primary duct cells and human islet cell preparations at clinically relevant concentrations without cellular toxicity.

CONCLUSIONS/INTERPRETATION

Nacystelyn is a pharmaceutical candidate to reduce early beta cell loss related to tissue factor-dependent coagulation after islet transplantation.

Metabolic activation of glucose low-responsive beta-cells by glyceraldehyde correlates with their biosynthetic activation in lower glucose concentration range but not at high glucose

Insulin synthesis and release activities of beta-cells can be acutely regulated by glucose through its glycolytic and mitochondrial breakdown involving a glucokinase-dependent rate-limiting step. Isolated beta-cell populations are composed of cells with intercellular differences in acute glucose responsiveness that have been attributed to differences in glucokinase (GK) expression and activity. This study first shows that glyceraldehyde can be used as GK-bypassing oxidative substrate and then examines whether the triose can metabolically activate beta-cells with low glucose responsiveness. Glyceraldehyde 1 mm induced a similar cellular (14)CO(2) output and metabolic redox state as glucose 4 mM. Using flow cytometric analysis, glyceraldehyde (0.25-2 mM) was shown to concentration-dependently increase the percent metabolically activated cells at all tested glucose concentrations (2.5-20 mM). Its ability to activate beta-cells that are unresponsive to the prevailing glucose level was further illustrated in glucose low-responsive cells that were isolated by flow sorting. Metabolic activation by glyceraldehyde was associated with an activation of nutrient-driven translational control proteins and an increased protein synthetic response to glucose, however not beyond the maximal rates that are inducible by glucose alone. It is concluded that glucose low-responsive beta-cells can be metabolically activated by the GK-bypassing glyceraldehyde, increasing their acute biosynthetic response to glucose but not their maximal glucose-inducible biosynthetic capacity, which is considered subject to chronic regulation.

AMP-activated protein kinase can induce apoptosis of insulin-producing MIN6 cells through stimulation of c-Jun-N-terminal kinase

We have recently shown that conditions known to activate AMP-activated protein kinase (AMPK) in primary beta-cells can trigger their apoptosis. The present study demonstrates that this is also the case in the MIN6 beta-cell line, which was used to investigate the underlying mechanism. Sustained activation of AMPK was induced by culture with the adenosine analogue AICA-riboside or at low glucose concentrations. Both conditions induced a sequential activation of AMPK, c-Jun-N-terminal kinase (JNK) and caspase-3. The effects of AMPK on JNK activation and apoptosis were demonstrated by adenoviral expression of constitutively active AMPK, a condition which reproduced the earlier-described AMPK-dependent effects on pyruvate kinase and acetyl-coA-carboxylase. The effects of JNK activation on apoptosis were demonstrated by the observations that (i). its inhibition by dicumarol prevented caspase-3 activation and apoptosis, (ii). adenoviral expression of the JNK-interacting scaffold protein JIP-1/IB-1 increased AICA-riboside-induced JNK activation and apoptosis. In primary beta-cells, AMPK activation was also found to activate JNK, involving primarily the JNK 2 (p54) isoform. It is concluded that prolonged stimulation of AMPK can induce apoptosis of insulin-producing cells through an activation pathway that involves JNK, and subsequently, caspase-3.

Interleukin-1 beta inhibits proinsulin conversion in rat beta-cells via a nitric oxide-dependent pathway

Exposure of pancreatic beta-cells to interleukin-1 beta (IL-1 beta) alters their protein expression and phenotype. Previous work has shown that IL-1 beta inhibited proinsulin conversion in rat islets, but the mechanism of this inhibition remained unknown. To investigate this phenomenon further, we examined purified rat beta-cells for IL-1 beta-induced inhibition of proinsulin conversion and nitric oxide (NO)-dependency of this inhibitory process. Rat beta-cells were cultured for 24 h with or without IL-1 beta and the inducible-nitric-oxide-synthase (iNOS) inhibitor N(G)-methyl-L-arginine (NMA). Exposure to IL-1 beta suppressed proinsulin-1 and proinsulin-2 synthesis by more than 50 %. Conversion of both proinsulin isoforms was also delayed. The suppressive effects of IL-1 beta on proinsulin synthesis and conversion were prevented by addition of NMA. Exposure to IL-1 beta also decreased the expression of the proinsulin convertase (PC) PC2. This decrease in PC2 expression was NO-dependent. In conclusion, IL-1 beta inhibition of proinsulin conversion in rat beta-cells occurs via an NO-mediated pathway.

Glucagon-like peptide 1 receptor signaling influences topography of islet cells in mice

Glucagon-like peptide 1 (GLP-1) amplifies glucose-induced insulin release in vivo and in vitro. Activation of GLP-1 receptor (GLP-1R) signaling leads to differentiation of exocrine cells towards a beta-cell phenotype in vitro and stimulation of islet cell proliferation in vitro and in vivo, suggesting a potential role for GLP-1 in the modulation of islet growth and differentiation. To determine whether basal levels of GLP-1R signaling are essential for islet development, we examined islet cell composition and topography in GLP-1R-/- mice. Total beta-cell volume and number are not altered, but the topography of beta cells is markedly different in GLP-1R-/- mice compared with GLP-1R+/+ controls. The distribution of beta cells is shifted from large to small and medium-sized islets in the absence of GLP-1R signaling (large islets: 50 +/- 3% in GLP-1R+/+ vs 28 +/- 4% in GLP- 1R-/-, P < 0.01 and medium islets: 32 +/- 2% in GLP- 1R+/+ vs 48 +/- 3% in GLP-1R-/-, P < 0.001). Furthermore, GLP-1R-/- islets exhibit abnormalities in cell topography, with two to threefold more centrally located alpha cells detected in GLP-1R-/- islets. These alterations in alpha- and beta-cell topography indicate that basal levels of GLP-1 signaling in the normal rodent are involved in the normal cellular organization of the endocrine pancreas.

Genetic analysis of wild-type hepatitis A virus strains

OBJECTIVE

To clarify the distribution of hepatitis A virus (HAV) genotype in geographical regions of China.

METHODS

Seventeen representative HAV strains were isolated from the stool or serum of hepatitis A patients in different geographical regions. Viral RNA was recovered from stool or serum by proteinase K digestion and phenol-chloroform extraction, followed by ethanol precipitation prior to reverse transcription and polymerase chain reaction (RT-PCR) amplification. The nucleotide sequences of VP1/2A junction region were tested by using a direct sequencing technique.

RESULTS

A pairwise comparison of sequences within 168 bases at the VP1/2A junction revealed that all the sequences clustered within genotype I. About 53% of strains clustered in genotype I B, with less than 6% variability; while the others clustered in genotype I A, with less than 5.3% variability. Sequence homology between genotype I A and I B varied from 88.7% to 92.3%.

CONCLUSION

Epidemic or sporadic HAV strains in China may belong to HAV genotype I A or I B. Epidemiologically related strains may be identical or closely related in sequence.

Role of pancreatic beta-cells in the process of beta-cell death

Studies on the pathogenesis of type 1 diabetes have mainly focused on the role of the immune system in the destruction of pancreatic beta-cells. Lack of data on the cellular and molecular events at the beta-cell level is caused by the inaccessibility of these cells during development of the disease. Indirect information has been collected from isolated rodent and human islet cell preparations that were exposed to cytotoxic conditions. This article reviews in vitro experiments that investigated the role of beta-cells in the process of beta-cell death. beta-Cells rapidly die in necrosis because of toxic levels of oxidizing radicals or of nitric oxide; they progressively become apoptotic after prolonged culture at low glucose or with proinflammatory cytokines. Their susceptibility to necrosis or apoptosis varies with their functional state and thus with the environmental conditions. A change in cellular phenotype can alter its recognition of potentially cytotoxic agents and its defense mechanisms against cell death. These observations support the view that beta-cells are not necessarily passive victims of a cytotoxic process but can actively participate in a process of beta-cell death. Their role will be influenced by neighboring non-beta-cells, which can make the islet internal milieu more protective or toxic for the beta-cells. We consider duct cells as potentially important contributors to this local process.

Neurodegeneration prevented by lentiviral vector delivery of GDNF in primate models of Parkinson's disease

Lentiviral delivery of glial cell line-derived neurotrophic factor (lenti-GDNF) was tested for its trophic effects upon degenerating nigrostriatal neurons in nonhuman primate models of Parkinson's disease (PD). We injected lenti-GDNF into the striatum and substantia nigra of nonlesioned aged rhesus monkeys or young adult rhesus monkeys treated 1 week prior with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Extensive GDNF expression with anterograde and retrograde transport was seen in all animals. In aged monkeys, lenti-GDNF augmented dopaminergic function. In MPTP-treated monkeys, lenti-GDNF reversed functional deficits and completely prevented nigrostriatal degeneration. Additionally, lenti-GDNF injections to intact rhesus monkeys revealed long-term gene expression (8 months). In MPTP-treated monkeys, lenti-GDNF treatment reversed motor deficits in a hand-reach task. These data indicate that GDNF delivery using a lentiviral vector system can prevent nigrostriatal degeneration and induce regeneration in primate models of PD and might be a viable therapeutic strategy for PD patients.

Glucagon receptors on human islet cells contribute to glucose competence of insulin release

AIMS/HYPOTHESIS

Synergism between glucose and cAMP in the stimulation of insulin secretion has been suggested to regulate beta cells. This study assessed the importance of an interaction between glucose and cAMP in the stimulation of insulin secretion from human islet cells by investigating expression and functional activity of receptors recognising glucagon, glucagon-like peptide-1 (7-36)amide (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

METHODS

Expression of the glucagon, GLP-1 and GIP receptors in human islets was investigated by northern blots and reverse transcription-polymerase chain reaction analysis. Functional activity of these receptors was assessed by the effects of peptides (agonists and antagonists) on glucose-induced insulin release.

RESULTS

Human islet cells express transcripts encoding glucagon, GLP-1 and GIP receptors. Glucose (10 mmol/l) stimulated insulin release 4.5 +/- 0.6-fold over basal (2.5 mmol/l). This glucose effect was amplified by 10 nmol/l GLP-1, GIP or glucagon. It was reduced by 51 +/- 6% in the presence of 1 micromol/l of the glucagon-receptor antagonist des-His1-[Glu9]-glucagon-amide (n = 8; p < 0.05), indicating participation of endogenously released glucagon in the process of glucose-induced insulin release. The glucagon-receptor antagonist also suppressed the potentiation of glucose-induced insulin release by addition of 10 nmol/l glucagon.

CONCLUSION/INTERPRETATION

These data suggest that human beta cells express functional glucagon receptors which can, similar to incretin hormone receptors, generate synergistic signals for glucose-induced insulin secretion.

Interleukin-1beta-induced alteration in a beta-cell phenotype can reduce cellular sensitivity to conditions that cause necrosis but not to cytokine-induced apoptosis

Previous work has shown that interleukin-1beta (IL-1beta) alters protein expression in beta-cells. This alteration is associated with cell death in isolated rat islets but not in isolated rat beta-cells. We examined whether IL-1beta pretreatment of isolated beta-cells influences their sensitivity to toxic agents. After a 24-h culture with IL-1beta (30 U/ml), beta-cells exhibited a lower expression of the beta-cell-specific protein transcription factor pancreatic and duodenal homeobox gene (PDX)-1, glucose transporter GLUT2, and proinsulin convertase PC2, with a marked reduction (60-70%) in glucose-induced insulin production and selective sensitivity to the toxins alloxan (ALX) and streptozotocin (STZ). On the other hand, the cells presented an increased expression of Mn-superoxide dismutase, heat shock protein 70, inducible heme oxygenase, and inducible nitrite oxide synthase. This IL-1beta-induced alteration in beta-cell phenotype resulted in a reduced cellular sensitivity to the beta-cell-specific toxins ALX and STZ; the production of nontoxic conditions of nitric oxide (NO) also rendered the cells less susceptible to radical-induced damage. Exposure to IL-1beta can thus protect beta-cells against conditions that cause necrosis; however, it did not protect against apoptosis induced by the additional presence of interferon-gamma or tumor necrosis factor-alpha. Release of IL-1beta in the endocrine pancreas is thus not necessarily the cause of massive NO-dependent beta-cell destruction. On the contrary, IL-1beta may protect these cells against necrosis, though with a loss of their characteristic phenotype and homeostatic functions.

conZA8 encodes an abundant protein targeted to the developing macronucleus in Euplotes crassus

During macronuclear development in the ciliate Euplotes crassus, micronuclear-derived chromosomes undergo a series of rearrangements that include polytenization, DNA splicing, chromosome fragmentation, and telomere addition and processing. Although cis-acting signals that may function in the regulation of these events have been characterized, the proteins that mediate these events have not yet been identified. To identify development-specific factors that may be involved in DNA rearrangement, we previously isolated clones of a number of genes that are expressed only during early macronuclear development. Here, we report the genomic and cDNA sequences of one of these genes, conZA8. The analysis indicates that the conZA8 gene encodes a novel, 468-amino acid, proline-rich protein. Antibodies were raised against both a recombinant form of the conZA8 protein and an internal peptide. Immunoblotting and immunofluorescence analyses indicated that the conZA8 protein is highly abundant, expressed only during the polytene chromosome stage of macronuclear development, and localized to the developing macronucleus. Possible functions of the conZA8 protein are discussed.

Prenatal cocaine exposure reduces glial cell line-derived neurotrophic factor (GDNF) in the striatum and the carotid body of the rat: implications for DA neurodevelopment

Glial cell line-derived neurotrophic factor (GDNF) is a glycosylated, disulfide-bonded homodimer, and a member of the transforming growth factor-beta superfamily. GDNF has been shown to promote the survival and morphological differentiation of dopamine (DA) neurons and increase their high-affinity dopamine uptake. In order to determine whether the mechanism for our previously observed cocaine-induced DA reductions in brain and carotid body were GDNF-mediated, we exposed Sprague-Dawley rat fetuses to cocaine via maternal subcutaneous injections (30 mg/kg b.i.d., E7-E19). Brains and carotid bodies of fetuses were excised and processed for assessment of GDNF levels using an Enzyme-Linked ImmunoadSorbent Assay (ELISA). ANOVA indicated that cocaine reduced carotid body GDNF by 36% (F((1,5))=28. 11, p<0.05) and striatal GDNF by 41% (F((1,5))=41.77, p<0.01). Although there was no interaction between drug exposure and fetal uterine position, post-hoc pairwise comparisons indicated that reductions in GDNF in the cocaine groups were due to differences at more distal positions (positions 4-8). The magnitude of the reductions in striatal GDNF (but not carotid body GDNF) in both cocaine-exposed and control fetuses followed a cervical (smallest GDNF reductions) to ovarian (greatest GDNF reductions) uterine position gradient. This pattern was similar to that which we observed in prior studies examining DA reductions in brain following prenatal cocaine exposure. The finding that cocaine reduces GDNF levels in striatum and carotid body support the hypothesis that cocaine's ability to reduce striatal and carotid body DA may be indirect through its ability to reduce GDNF. These data along with previous findings support the hypothesis that cocaine's effects on DA neurons are at least partially due to its indirect effects on trophic activity. The possible mechanisms whereby cocaine affects trophic activity are discussed.

Parathyroid hormone-related protein protects against kainic acid excitotoxicity in rat cerebellar granule cells by regulating L-type channel calcium flux

The parathyroid hormone-related peptide (PTHrP) and PTH/PTHrP receptor genes are widely expressed in the CNS and both are highly expressed in the cerebellar granule cell. We have shown previously that PTHrP gene expression in granule cells is depolarization-dependent in vitro and is regulated specifically by Ca2+ influx via L-type voltage-sensitive calcium channels (L-VSCCs). Kainic acid induces long-latency excitotoxicity in granule cells via L-VSCC-mediated Ca2+ influx. Here, we show that PTHrP is just as effective as the L-VSCC blocker, nitrendipine (NTR), in preventing kainate excitotoxicity. A competitive inhibitor of PTHrP binding abrogates its neuroprotective effect. Both NTR and PTHrP decrease 45Ca2+ influx to the same degree. These findings suggest that PTHrP functions in an autocrine/paracrine neuroprotective feedback loop that can combat L-VSCC-mediated excitotoxcity.

Exposure of human islets to cytokines can result in disproportionately elevated proinsulin release

Infiltration of immunocytes into pancreatic islets precedes loss of beta cells in type 1 diabetes. It is conceivable that local release of cytokines affects the function of beta cells before their apoptosis. This study examines whether the elevated proinsulin levels that have been described in prediabetes can result from exposure of beta cells to cytokines. Human beta-cell preparations were cultured for 48 or 72 hours with or without IL-1beta, TNF-alpha, or IFN-gamma, alone or in combination. None of these conditions were cytotoxic, nor did they reduce insulin biosynthetic activity. Single cytokines did not alter medium or cellular content in insulin or proinsulin. Cytokine combinations, in particular IL-1beta plus IFN-gamma, disproportionately elevated medium proinsulin levels. This effect expresses an altered functional state of the beta cells characterized by preserved proinsulin synthesis, a slower hormone conversion, and an increased ratio of cellular proinsulin over insulin content. The delay in proinsulin conversion can be attributed to lower expression of PC1 and PC2 convertases. It is concluded that disproportionately elevated proinsulin levels in pre-type 1 diabetic patients might result from exposure of their beta cells to cytokines released from infiltrating immunocytes. This hormonal alteration expresses an altered functional state of the beta cells that can occur independently of beta-cell death.

Inhibition of human pancreatic islet insulin release by receptor-selective somatostatin analogs directed to somatostatin receptor subtype 5

Somatostatin (SS)-14 and SS28 are produced by pancreatic D cells and gut mucosa and inhibit pancreatic islet insulin and glucagon release. There are five distinct SS receptor (SSTR) subtypes, namely SSTR1-5, which show different affinities for SS14 and SS28. In order to identify the subtype responsible for inhibition of insulin release by human B cells, SSTR-selective SS analogs were tested in isolated human islets. Glucose-stimulated insulin secretion in human islets incubated for 1 hr at 20 mM glucose, and in islets cultured for 24 hr at a near-physiological (6.1 mM) glucose concentration, was inhibited (<50% of the control) by SSTR5-specific analogs and by SS14 and SS28. SS14, SS28, and different SSTR5 preferential analogs also inhibited islet amyloid polypeptide release during the 24-hr culture. On the other hand, a group of SSTR2-selective analogs failed to inhibit insulin release. Analysis by reverse transcription-polymerase chain reaction indicated that human islets express similar amounts of SSTR2 and SSTR5 mRNAs, while human pancreatic ductal cells express much lower levels of these mRNAs. In conclusion, our data suggest that SSTR5 is an important mediator of the insulin inhibitory action of SS in cultured human islets.

Prolonged exposure of human beta-cells to high glucose increases their release of proinsulin during acute stimulation with glucose or arginine

The disproportionate hyperproinsulinemia in type 2 diabetes has been attributed to either a primary beta-cell defect or a secondary dysregulation of beta cells under sustained hyperglycemia. This study examines the effect of a 10- to 13-day exposure to 20 mmol/L glucose on subsequent proinsulin and insulin release by human islets isolated from nondiabetic donors. Compared to control preparations kept at 6 mmol/L glucose, the high glucose cultured beta-cells released more proinsulin and less insulin during perifusion at 5, 10, or 20 mmol/L glucose. The lower amounts of secreted insulin resulted from a marked reduction in cellular insulin content (5-fold lower than in controls). The higher amount of secreted proinsulin is attributed to the sustained state of cellular activation that is known to occur after prolonged exposure to high glucose levels. This activated state of the beta-cell population is also held responsible for its higher secretory responsiveness to 5 mmol/L arginine at a submaximal (5 mmol/L) glucose concentration (8-fold higher proinsulin levels than in the control population). It results, together with the reduction in cellular insulin content, in 7- to 10-fold higher proinsulin over insulin ratios in the medium; at 5 mmol/L glucose, this extracellular ratio is similar to that in the cells. These data add direct support to the view that a disproportionate hyperproinsulinemia can result from a sustained activation of human beta-cells after prolonged exposure to elevated glucose levels.