Exacerbation of chronic inflammatory diseases by infectious agents: Fact or fiction?

Dual amyloid cross-seeding reveals steric zipper-facilitated fibrillization and pathological links between protein misfolding diseases

Amyloid cross-seeding, as a result of direct interaction and co-aggregation between different disease-causative peptides, is considered as a main mechanism for the spread of the overlapping pathology across different cells and tissues between different protein-misfolding diseases (PMDs). Despite the biomedical significance of amyloid cross-seeding in amyloidogenesis, it remains a great challenge to discover amyloid cross-seeding systems and reveal their cross-seeding structures and mechanisms. Herein, we are the first to report that GNNQQNY - a short fragment from yeast prion protein Sup35 - can cross-seed with both amyloid-β (Aβ, associated with Alzheimer's disease) and human islet amyloid polypeptide (hIAPP, associated with type II diabetes) to form β-structure-rich assemblies and to accelerate amyloid fibrillization. Dry, steric β-zippers, formed by the two β-sheets of different amyloid peptides, provide generally interactive and structural motifs to facilitate amyloid cross-seeding. The presence of different steric β-zippers in a variety of GNNQQNY-Aβ and GNNQQNY-hIAPP assemblies also explains amyloid polymorphism. In addition, alteration of steric zipper formation by single-point mutations of GNNQQNY and interactions of GNNQQNY with different Aβ and hIAPP seeds leads to different amyloid cross-seeding efficiencies, further confirming the existence of cross-seeding barriers. This work offers a better structural-based understanding of amyloid cross-seeding mechanisms linked to different PMDs.

The Microbiome in Posttraumatic Stress Disorder and Trauma-Exposed Controls: An Exploratory Study

OBJECTIVE

Inadequate immunoregulation and elevated inflammation may be risk factors for posttraumatic stress disorder (PTSD), and microbial inputs are important determinants of immunoregulation; however, the association between the gut microbiota and PTSD is unknown. This study investigated the gut microbiome in a South African sample of PTSD-affected individuals and trauma-exposed (TE) controls to identify potential differences in microbial diversity or microbial community structure.

METHODS

The Clinician-Administered PTSD Scale for DSM-5 was used to diagnose PTSD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria. Microbial DNA was extracted from stool samples obtained from 18 individuals with PTSD and 12 TE control participants. Bacterial 16S ribosomal RNA gene V3/V4 amplicons were generated and sequenced. Microbial community structure, α-diversity, and β-diversity were analyzed; random forest analysis was used to identify associations between bacterial taxa and PTSD.

RESULTS

There were no differences between PTSD and TE control groups in α- or β-diversity measures (e.g., α-diversity: Shannon index, t = 0.386, p = .70; β-diversity, on the basis of analysis of similarities: Bray-Curtis test statistic = -0.033, p = .70); however, random forest analysis highlighted three phyla as important to distinguish PTSD status: Actinobacteria, Lentisphaerae, and Verrucomicrobia. Decreased total abundance of these taxa was associated with higher Clinician-Administered PTSD Scale scores (r = -0.387, p = .035).

CONCLUSIONS

In this exploratory study, measures of overall microbial diversity were similar among individuals with PTSD and TE controls; however, decreased total abundance of Actinobacteria, Lentisphaerae, and Verrucomicrobia was associated with PTSD status.

Association of Helicobacter pylori infection with the metabolic syndrome among HIV-infected black Africans receiving highly active antiretroviral therapy

INTRODUCTION

The metabolic syndrome (MetS) is common in human immune deficiency virus (HIV)-infected individuals receiving highly active antiretroviral therapy (HAART). Immune deficiencies caused by HIV give rise to numerous opportunistic gastrointestinal pathogens such as Helicobacter pylori, the commonest cause of chronic gastritis. The study sought to determine the relationship between H pylori infection and the MetS among HIV-infected clinic attendees.

METHODS

This cross-sectional study was carried out in a specialised heart clinic in Kinshasa, DR Congo. Between January 2004 and December 2008, 116 HIV-infected patients (61 with MetS and 55 without MetS) who underwent upper gastrointestinal endoscopy for dyspeptic symptoms were included in the study following an informed consent. Univariate associations were determined by odds ratios (OR), while multivariate logistic regression analysis was used to identify factors associated with the MetS.

RESULTS

H pylori infection (OR = 13.5, 95% CI: 10.3-17.6; p < 0.0001) and peripheral obesity (median hip circumference ≥ 97 cm) (OR = 4.7, 95% CI: 1.2-18.8; p = 0.029) were identified as MetS-related factors in HIV-infected patients. Higher rates of the MetS were associated with increased incidence of HIV-related immunocompromise using World Health Organisation (WHO) staging criteria. There was a univariate significant difference in the prevalence of the MetS between antiretroviral therapy (ART)-naïve patients and patients treated by means of a first-line HAART regimen of stavudine (d4T), lamivudine (3TC) and nevirapine (NVP). However, this difference was not significant in multivariate logistic analysis.

CONCLUSION

H pylori infection was significantly associated with the MetS in HIV-infected patients.

Spontaneous Obesity-Linked Type 2 Diabetes in the Absence of Islet Amyloid in a Cynomolgus Monkey Infected With Bovine Spongiform Encephalopathy

A 9-year-old cynomolgus monkey ( Macaca fascicularis) infected orally with bovine spongiform encephalopathy (BSE) was presented for necropsy following euthanasia 4 years post infection (p.i.). This macaque R984 was exposed to a BSE dose that causes a simian form of variant Creutzfeldt-Jakob disease (vCJD) within 5 years p.i. in other macaques. All orally BSE-infected macaques developed a significant weight gain within the first 2 years p.i. compared with non-BSE-infected age- and sex-matched control animals, suggesting increased risk of type 2 diabetes (T2D). In contrast, macaque R984 developed rapid weight loss, hyperglycemia, and glucosuria and had to be euthanatized 4 years p.i. before clinical signs of vCJD. Pancreas histopathological evaluation revealed severe islet degeneration but, remarkably, no islet amyloid deposits were present. Immunostaining of pancreas sections for insulin and glucagon confirmed the loss of endocrine cells. In addition, prions were present in the adenohypophysis but not in other areas of the brain, indicating centripetal prion spread from the gut during the preclinical phase of BSE infection. Plasma glucose and insulin concentrations of macaque R984 became abnormal with age and resembled T2D. This unusual case of spontaneous T2D in the absence of islet amyloid deposits could have been due to early prion spread from the periphery to the endocrine system or could have occurred spontaneously.