Low dietary fiber promotes enteric expansion of a Crohn's disease-associated pathobiont independent of obesity.

Obesity is associated with metabolic, immunological, and infectious disease comorbidities, including an increased risk of enteric infection and inflammatory bowel disease such as Crohn's disease (CD). Expansion of intestinal pathobionts such as adherent-invasive Escherichia coli (AIEC) is a common dysbiotic feature of CD, which is amplified by prior use of oral antibiotics. Although high-fat, high-sugar diets are associated with dysbiotic expansion of E. coli, it is unknown if the content of fat or another dietary component in obesogenic diets is sufficient to promote AIEC expansion. Here, we found that administration of an antibiotic combined with feeding mice an obesogenic low-fiber, high-sucrose, high-fat diet (HFD) that is typically used in rodent-obesity studies promoted AIEC intestinal expansion. Even a short-term (i.e., 1 day) pulse of HFD feeding before infection was sufficient to promote AIEC expansion, indicating that the magnitude of obesity was not the main driver of AIEC expansion. Controlled-diet experiments demonstrated that neither dietary fat nor sugar were the key determinants of AIEC colonization, but that lowering dietary fiber from approximately 13% to 5%-6% was sufficient to promote the intestinal expansion of AIEC when combined with antibiotics in mice. When combined with antibiotics, lowering fiber promoted AIEC intestinal expansion to a similar extent as widely used HFDs in mice. However, lowering dietary fiber was sufficient to promote AIEC intestinal expansion without affecting body mass. Our results show that low dietary fiber combined with oral antibiotics are environmental factors that promote the expansion of Crohn's disease-associated pathobionts in the gut.NEW & NOTEWORTHY It is commonly thought that obesity or a high-fat diet alters pathogenic bacteria and promotes inflammatory gut diseases. We found that lower dietary fiber is a key factor that expands a gut pathobiont linked to Crohn's disease, independent of obesity status in mice.

The NLRP3 inflammasome contributes to sarcopenia and lower muscle glycolytic potential in old mice.

The mechanisms underpinning decreased skeletal muscle strength and slowing of movement during aging are ill-defined. "Inflammaging," increased inflammation with advancing age, may contribute to aspects of sarcopenia, but little is known about the participatory immune components. We discovered that aging was associated with increased caspase-1 activity in mouse skeletal muscle. We hypothesized that the caspase-1-containing NLRP3 inflammasome contributes to sarcopenia in mice. Male C57BL/6J wild-type (WT) and NLRP3-/- mice were aged to 10 (adult) and 24 mo (old). NLRP3-/- mice were protected from decreased muscle mass (relative to body mass) and decreased size of type IIB and IIA myofibers, which occurred between 10 and 24 mo of age in WT mice. Old NLRP3-/- mice also had increased relative muscle strength and endurance and were protected from age-related increases in the number of myopathic fibers. We found no evidence of age-related or NLRP3-dependent changes in markers of systemic inflammation. Increased caspase-1 activity was associated with GAPDH proteolysis and reduced GAPDH enzymatic activity in skeletal muscles from old WT mice. Aging did not alter caspase-1 activity, GAPDH proteolysis, or GAPDH activity in skeletal muscles of NLRP3-/- mice. Our results show that the NLRP3 inflammasome participates in age-related loss of muscle glycolytic potential. Deletion of NLRP3 mitigates both the decline in glycolytic myofiber size and the reduced activity of glycolytic enzymes in muscle during aging. We propose that the etiology of sarcopenia involves direct communication between immune responses and metabolic flux in skeletal muscle.

One swab, two tests: Validation of dual SARS-CoV-2 testing on the Abbott ID NOW™.

BACKGROUND: Point-of-care tests (POCT) are promising tools to detect SARS-CoV-2 in specific settings. Initial reports suggest the ID NOW™ COVID-19 assay (Abbott Diagnostics Inc, USA) is less sensitive than standard real-time reverse transcription polymerase chain reaction (rRT-PCR) assays. This has raised concern over false negatives in SARS-CoV-2 POCT. OBJECTIVES: We compared the performance of the ID NOW™ COVID-19 assay to our in-house rRT-PCR assay to assess whether dry swabs used in ID NOW™ testing could be stored in transport media and be re-tested by rRT-PCR for redundancy and to provide material for further investigation. METHODS: Paired respiratory swabs collected from patients at three acute care hospitals were used. One swab in transport media (McMaster Molecular Media (MMM)) was tested for SARS-CoV-2 by a laboratory-developed two-target rRT-PCR assay. The second was stored dry in a sterile container and tested by the ID NOW™ COVID-19 assay. Following ID NOW™ testing, dry swabs were stored in MMM for up to 48 h and re-tested by rRT-PCR. Serially diluted SARS-CoV-2 particles were used to assess the impact of heat inactivation and storage time. RESULTS: Respiratory swabs (n = 343) from 179 individuals were included. Using rRT-PCR results as the comparator, the ID NOW™ COVID-19 assay had positive (PPA) and negative (NPA) percent agreements of 87.0% (95% CI:0.74-0.94) and 99.7% (95% CI:0.98-0.99). Re-tested swabs placed in MMM following ID NOW testing had PPA and NPA of 88.8% (95% CI:0.76-0.95) and 99.7% (95% CI:0.98-0.99), respectively. CONCLUSIONS: Storing spent dry swabs in transport media for redundancy rRT-PCR testing is a potential approach to address possible false negatives with the ID NOW™ COVID-19 assay.

Gut microbiota impairs insulin clearance in obese mice.

OBJECTIVE: Hyperinsulinemia can be both a cause and consequence of obesity and insulin resistance. Hyperinsulinemia can result from increased insulin secretion and/or reduced insulin clearance. While many studies have focused on mechanisms triggering insulin secretion during obesity, the triggers for changes in insulin clearance during obesity are less defined. In this study, we investigated the role of the microbiota in regulating insulin clearance during diet-induced obesity. METHODS: Blood glucose and insulin clearance were tested in conventional male mice treated with antibiotics and germ-free mice colonized with microbes from mice that were fed a control (chow) diet or an obesogenic high-fat diet (HFD). The composition of the fecal microbiota was analyzed using 16S rRNA sequencing. RESULTS: Short-term HFD feeding and aging did not alter insulin clearance in the mice. Oral antibiotics mitigated impaired blood insulin clearance in the mice fed an HFD for 12 weeks or longer. Germ-free mice colonized with microbes from HFD-fed donor mice had impaired insulin but not C-peptide clearance. Microbe-transmissible insulin clearance impairment was only observed in germ-free mice after more than 6 weeks post-colonization upon HFD feeding. Five bacterial taxa predicted >90% of the variance in insulin clearance. Mechanistically, impaired insulin clearance was associated with lower levels of hepatic Ceacam-1 but increased liver and skeletal muscle insulin-degrading enzyme (IDE) activity. CONCLUSIONS: Gut microbes regulate insulin clearance during diet-induced obesity. A small cluster of microbes or their metabolites may be targeted for mitigating defects in insulin clearance and hyperinsulinemia during the progression of obesity and type 2 diabetes.

TNF, but not hyperinsulinemia or hyperglycemia, is a key driver of obesity-induced monocytosis revealing that inflammatory monocytes correlate with insulin in obese male mice.

Inflammation contributes to obesity-related hyperinsulinemia and insulin resistance, which often precede type 2 diabetes. Inflammation is one way that obesity can promote insulin resistance. It is not clear if the extent of obesity, hyperinsulinemia, or hyperglycemia, underpins changes in cellular immunity during diet-induced obesity. In particular, the requirement for obesity or directionality in the relationship between insulin resistance and monocyte characteristics is poorly defined. Inflammatory cytokines such as tumor necrosis factor (TNF) can contribute to insulin resistance. It is unclear if TNF alters monocytosis or specific markers of cellular immunity in the context of obesity. We measured bone marrow and blood monocyte characteristics in WT and TNF-/- mice that were fed obesogenic, high fat (HF) diets. We also used hyperglycemic Akita mice and mice implanted with insulin pellets in order to determine if glucose or insulin were sufficient to alter monocyte characteristics. We found that diet-induced obesity in male mice increased the total number of monocytes in blood, but not in bone marrow. Immature, inflammatory (Ly6Chigh ) monocytes decreased within the bone marrow and increased within peripheral blood of HF-fed mice. We found that neither hyperinsulinemia nor hyperglycemia was sufficient to induce the observed changes in circulating monocytes in the absence of diet-induced obesity. In obese HF-fed mice, antibiotic treatment lowered insulin and insulin resistance, but did not alter circulating monocyte characteristics. Fewer Ly6Chigh monocytes were present within the blood of HF-fed TNF-/- mice in comparison to HF-fed wild-type (WT) mice. The prevalence of immature Ly6Chigh monocytes in the blood correlated with serum insulin and insulin resistance irrespective of the magnitude of adipocyte or adipose tissue hypertrophy in obese mice. These data suggest that diet-induced obesity instigates a TNF-dependent increase in circulating inflammatory monocytes, which predicts increased blood insulin and insulin resistance independently from markers of adiposity or adipose tissue expansion.

A patient-derived cellular model for Huntington's disease reveals phenotypes at clinically relevant CAG lengths.

The huntingtin protein participates in several cellular processes that are disrupted when the polyglutamine tract is expanded beyond a threshold of 37 CAG DNA repeats in Huntington's disease (HD). Cellular biology approaches to understand these functional disruptions in HD have primarily focused on cell lines with synthetically long CAG length alleles that clinically represent outliers in this disease and a more severe form of HD that lacks age onset. Patient-derived fibroblasts are limited to a finite number of passages before succumbing to cellular senescence. We used human telomerase reverse transcriptase (hTERT) to immortalize fibroblasts taken from individuals of varying age, sex, disease onset, and CAG repeat length, which we have termed TruHD cells. TruHD cells display classic HD phenotypes of altered morphology, size and growth rate, increased sensitivity to oxidative stress, aberrant adenosine diphosphate/adenosine triphosphate (ADP/ATP) ratios, and hypophosphorylated huntingtin protein. We additionally observed dysregulated reactive oxygen species (ROS)-dependent huntingtin localization to nuclear speckles in HD cells. We report the generation and characterization of a human, clinically relevant cellular model for investigating disease mechanisms in HD at the single-cell level, which, unlike transformed cell lines, maintains functions critical for huntingtin transcriptional regulation and genomic integrity.

Defective NOD2 peptidoglycan sensing promotes diet-induced inflammation, dysbiosis, and insulin resistance.

Pattern recognition receptors link metabolite and bacteria-derived inflammation to insulin resistance during obesity. We demonstrate that NOD2 detection of bacterial cell wall peptidoglycan (PGN) regulates metabolic inflammation and insulin sensitivity. An obesity-promoting high-fat diet (HFD) increased NOD2 in hepatocytes and adipocytes, and NOD2(-/-) mice have increased adipose tissue and liver inflammation and exacerbated insulin resistance during a HFD. This effect is independent of altered adiposity or NOD2 in hematopoietic-derived immune cells. Instead, increased metabolic inflammation and insulin resistance in NOD2(-/-) mice is associated with increased commensal bacterial translocation from the gut into adipose tissue and liver. An intact PGN-NOD2 sensing system regulated gut mucosal bacterial colonization and a metabolic tissue dysbiosis that is a potential trigger for increased metabolic inflammation and insulin resistance. Gut dysbiosis in HFD-fed NOD2(-/-) mice is an independent and transmissible factor that contributes to metabolic inflammation and insulin resistance when transferred to WT, germ-free mice. These findings warrant scrutiny of bacterial component detection, dysbiosis, and protective immune responses in the links between inflammatory gut and metabolic diseases, including diabetes.

Bacterial peptidoglycan stimulates adipocyte lipolysis via NOD1.

Obesity is associated with inflammation that can drive metabolic defects such as hyperlipidemia and insulin resistance. Specific metabolites can contribute to inflammation, but nutrient intake and obesity are also associated with altered bacterial load in metabolic tissues (i.e. metabolic endotoxemia). These bacterial cues can contribute to obesity-induced inflammation. The specific bacterial components and host receptors that underpin altered metabolic responses are emerging. We previously showed that Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) activation with bacterial peptidoglycan (PGN) caused insulin resistance in mice. We now show that PGN induces cell-autonomous lipolysis in adipocytes via NOD1. Specific bacterial PGN motifs stimulated lipolysis in white adipose tissue (WAT) explants from WT, but not NOD1⁻/⁻mice. NOD1-activating PGN stimulated mitogen activated protein kinases (MAPK),protein kinase A (PKA), and NF-κB in 3T3-L1 adipocytes. The NOD1-mediated lipolysis response was partially reduced by inhibition of ERK1/2 or PKA alone, but not c-Jun N-terminal kinase (JNK). NOD1-stimulated lipolysis was partially dependent on NF-κB and was completely suppressed by inhibiting ERK1/2 and PKA simultaneously or hormone sensitive lipase (HSL). Our results demonstrate that bacterial PGN stimulates lipolysis in adipocytes by engaging a stress kinase, PKA, NF-κB-dependent lipolytic program. Bacterial NOD1 activation is positioned as a component of metabolic endotoxemia that can contribute to hyperlipidemia, systemic inflammation and insulin resistance by acting directly on adipocytes.

Fluvastatin causes NLRP3 inflammasome-mediated adipose insulin resistance.

Statins reduce lipid levels and are widely prescribed. Statins have been associated with an increased incidence of type 2 diabetes, but the mechanisms are unclear. Activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3)/caspase-1 inflammasome, promotes insulin resistance, a precursor of type 2 diabetes. We showed that four different statins increased interleukin-1ß (IL-1ß) secretion from macrophages, which is characteristic of NLRP3 inflammasome activation. This effect was dose dependent, absent in NLRP3(-/-) mice, and prevented by caspase-1 inhibition or the diabetes drug glyburide. Long-term fluvastatin treatment of obese mice impaired insulin-stimulated glucose uptake in adipose tissue. Fluvastatin-induced activation of the NLRP3/caspase-1 pathway was required for the development of insulin resistance in adipose tissue explants, an effect also prevented by glyburide. Fluvastatin impaired insulin signaling in lipopolysaccharide-primed 3T3-L1 adipocytes, an effect associated with increased caspase-1 activity, but not IL-1ß secretion. Our results define an NLRP3/caspase-1-mediated mechanism of statin-induced insulin resistance in adipose tissue and adipocytes, which may be a contributing factor to statin-induced development of type 2 diabetes. These results warrant scrutiny of insulin sensitivity during statin use and suggest that combination therapies with glyburide, or other inhibitors of the NLRP3 inflammasome, may be effective in preventing the adverse effects of statins.

Psychiatrists in New Zealand: are they burning out, satisfied at work and, in any case, who cares?

OBJECTIVE: To explore possible contributing or mitigating factors for burnout in New Zealand psychiatrists as well as future research directions in this area. METHOD: A selective review of the literature pertaining to burnout and reports regarding New Zealand's medical workforce. RESULTS: Possible factors contributing to burnout in New Zealand psychiatrists include rapid changes in the country's health system, the challenge of recruiting and retaining psychiatrists, poor distribution of staff and funds and difficulties in psychiatric training. Potential protective factors against burnout include lifestyle factors, long experience in psychiatry, proposed long lengths of career in New Zealand and potentially positive changes in the health system. Research challenges include subject recruitment, the lack of exploration of personal protective factors and completing longitudinal studies. CONCLUSIONS: Given the current state of knowledge, it would be difficult to accurately know whether New Zealand psychiatrists were burnt out or satisfied with their work. Carefully designed studies would help to clarify this issue.

Administrators' perspectives of the challenges in recruiting and retaining psychiatrists for New Zealand: a national study.

OBJECTIVE: Administrators' perceptions of significant factors that might affect the recruitment and retention of psychiatrists for New Zealand's public mental health Services have not been previously investigated. METHODS: A postal questionnaire was sent to managers of all 21 of New Zealand's mental health Services. The questionnaire requesting information about any difficulties managers experienced in recruiting and retaining psychiatrists, factors they thought attract psychiatrists to join and stay, reasons why psychiatrists left, strategies they had tried to alleviate any psychiatrist shortages, and their relative success. RESULTS: Responses were received from 3 of 8 metropolitan Services and 8 of 13 non-metropolitan Services. Every service had experienced problems in recruiting and retaining psychiatrists over the past 5 years. New Zealand's general shortage of psychiatrists and limitations on recreational activities available in their area were reasons unanimously held to account for this. Factors unanimously identified as significant in influencing psychiatrists to join a mental health service were lifestyle, professional opportunities, functional multidisciplinary teams, and adequate staffing and training activities. Factors unanimously identified in retaining psychiatrists were levels of professional satisfaction, a reasonable on-call roster, functional multidisciplinary teams, adequate resources, and the ability to practise safely and within their area of expertise. There was no unanimity as to why psychiatrists would leave a service. Every service which attempted to assist psychiatrists with their relocation, and which found locums to cover so that they could take leave when they wanted, reported that these strategies had been wholly or partially successful in alleviating their psychiatrist shortage. CONCLUSIONS: Administrators' perspectives (which are often different to those of psychiatrists) about factors affecting recruitment and retention are worth investigating.

New Zealand's psychiatrist workforce: profile, recruitment and retention.

OBJECTIVE: New Zealand is suspected of sharing other countries' difficulties of having inadequate numbers of practising psychiatrists and attracting psychiatrists to work outside its main urban centres, but there is no contemporary data on the socio-demographic and professional practice profile of its psychiatrists. This paper highlights some interesting trends about New Zealand's psychiatric workforce. METHOD: A postal questionnaire was sent to all actively practising vocationally registered psychiatrists with a New Zealand mailing address requesting information about basic demographic data, professional training experiences, current professional status, practise intentions, why they chose to work where they do and what factors might influence them to leave for another region of New Zealand or overseas. RESULTS: Of the 277 doctors on the vocational register for psychiatry, 159 responded, giving a response rate of 59.8%. Most psychiatrists were male (n = 102; 64.2%), European (n = 144; 90.6%), aged between 41 and 60 (69.2%), born overseas (n = 90; 56%), had English as their primary language (n = 142; 89.3%) and were in a long-term relationship with dependent children (n = 99; 62.3%). Nearly all (n = 149; 95%) did their psychiatry training in a metropolitan area and most (n = 108; 67.9%) held the Fellowship of the Royal Australian and New Zealand College of Psychiatry (FRANZCP). Most worked in a metropolitan area (n = 136; 85.5%) and either wholly or partly in the public sector (n = 145; 93%). Nearly one-quarter expected to retire over the next decade. Professional factors were rated more important as a reason for staying by metropolitan psychiatrists compared with their non-metropolitan counterparts (p < 0.001). Psychiatrists who did not have an FRANZCP (57%vs. 27%, p = 0.05), those who had spent more than 50% of their professional life in New Zealand (86%vs. 74%, p = 0.02) or those who had obtained their primary medical degree outside New Zealand were more likely to be in non-metropolitan areas (81%vs. 49%, p = 0.04). Metropolitan psychiatrists rated personal and social reasons more highly than non-metropolitan psychiatrists did for factors which might induce them to leave for another area, whereas professional development was ranked lower. CONCLUSIONS: This is the first contemporary study of New Zealand's psychiatric workforce and it highlights some interesting trends and has significant implications for those concerned with the recruitment and retention of psychiatrists. Further investigation is suggested, as a more complete picture of New Zealand's specialist psychiatric workforce would be gained by including psychiatrists who are not vocationally registered.