The septin modifier, forchlorfenuron, activates NLRP3 via a potassium-independent mitochondrial axis.

The Nod-like receptor protein 3 (NLRP3) inflammasome is activated by stimuli that induce perturbations in cell homeostasis, which commonly converge on cellular potassium efflux. NLRP3 has thus emerged as a sensor for ionic flux. Here, we identify forchlorfenuron (FCF) as an inflammasome activator that triggers NLRP3 signaling independently of potassium efflux. FCF triggers the rearrangement of septins, key cytoskeletal proteins that regulate mitochondrial function. We report that FCF triggered the rearrangement of SEPT2 into tubular aggregates and stimulated SEPT2-independent NLRP3 inflammasome signaling. Similar to imiquimod, FCF induced the collapse of the mitochondrial membrane potential and mitochondrial respiration. FCF thereby joins the imidazoquinolines as a structurally distinct class of molecules that triggers NLRP3 inflammasome signaling independent of potassium efflux, likely by inducing mitochondrial damage.

Reversing the mitochondrial hex that bewitches NLRP3.

Hexokinase dissociation from mitochondria triggers calcium-induced oligomerization of VDAC within the outer mitochondrial membrane, leading to NLRP3 recruitment and inflammasome signaling (see related Research Article by Baik et al.).

Updating the British Geriatrics Society recommended undergraduate curriculum in geriatric medicine: a curriculum mapping and nominal group technique study.

BACKGROUND: medical education must adapt to meet the challenges and demands of an ageing population, ensuring that graduates are equipped to look after older patients with complex health and social care needs. Recommended curricula in geriatric medicine in the United Kingdom and Europe offer guidance for optimal undergraduate education in ageing. The UK version, written by the British Geriatrics Society (BGS), requires updating to take account of innovations in the specialty, changing guidance from the General Medical Council (GMC), and the need to support medical schools preparing for the introduction of the national Medical Licensing Assessment (MLA). METHODS: the BGS recommended curriculum was mapped to the most recent European curriculum (2014) and the MLA content map, to compare and contrast between current recommendations and nationally mandated guidance. These maps were used to guide discussion through a virtual Nominal Group Technique (NGT), including 21 expert stakeholders, to agree consensus on the updated BGS curriculum. RESULTS: the curriculum has been re-structured into seven sections, each with 1-2 overarching learning outcomes (LOs) that are expanded in multiple sub-LOs. Crucially, the curriculum now reflects the updated GMC/MLA requirements, having incorporated items flagged as missing in the mapping stages. CONCLUSION: the combined mapping exercise and NGT have enabled appropriate alignment and benchmarking of the UK national curriculum. These recommendations will help to standardise and enhance teaching and learning around the care of older persons with complexity.

Mitochondrial dynamics in macrophages: divide to conquer or unite to survive?

Mitochondria have long been appreciated as the metabolic hub of cells. Emerging evidence also posits these organelles as hubs for innate immune signalling and activation, particularly in macrophages. Macrophages are front-line cellular defenders against endogenous and exogenous threats in mammals. These cells use an array of receptors and downstream signalling molecules to respond to a diverse range of stimuli, with mitochondrial biology implicated in many of these responses. Mitochondria have the capacity to both divide through mitochondrial fission and coalesce through mitochondrial fusion. Mitochondrial dynamics, the balance between fission and fusion, regulate many cellular functions, including innate immune pathways in macrophages. In these cells, mitochondrial fission has primarily been associated with pro-inflammatory responses and metabolic adaptation, so can be considered as a combative strategy utilised by immune cells. In contrast, mitochondrial fusion has a more protective role in limiting cell death under conditions of nutrient starvation. Hence, fusion can be viewed as a cellular survival strategy. Here we broadly review the role of mitochondria in macrophage functions, with a focus on how regulated mitochondrial dynamics control different functional responses in these cells.

Parkinson's disease: connecting mitochondria to inflammasomes.

Activated microglia foster a neurotoxic, inflammatory environment in the mammalian central nervous system (CNS) that drives the pathology of neurodegenerative diseases including Parkinson's disease (PD). Moreover, mitochondrial fission promotes microglial inflammatory responses in vitro. Given that the NLRP3 inflammasome and mitochondria are central regulators of both inflammation and PD, we explore potential functions for the NLRP3 inflammasome and mitochondrial dynamics in PD. Specifically, we propose that inducible microglial mitochondrial fission can promote NLRP3-dependent neuroinflammation in hereditary and idiopathic PD. Further in-depth exploration of this topic can prompt valuable discoveries of the underlying molecular mechanisms of PD neuroinflammation, identify novel candidate anti-inflammatory therapeutics for PD, and ideally provide better outcomes for PD patients.

Transforming undergraduate education in geriatric medicine: an innovative curriculum at Bristol Medical School.

The World Health Organization (WHO) advocates investment in high-quality undergraduate education in geriatric medicine as a means of meeting the future needs of the aging population. However, there is a lack of evidence for the optimal delivery of training in this area. Rigorous pedagogical research is required to determine the most effective way to equip tomorrow's doctors with the skills and knowledge to care for older adults with complex health and social care needs. The transition between two undergraduate medical curricula meant that Bristol Medical School (BMS) was uniquely positioned to innovate and evaluate undergraduate education in geriatric medicine. This transition marked BMS' departure from a 'traditional' curriculum to case-based learning. The outgoing curriculum included a 4-week unit in geriatrics, whilst the new programme includes an 18-week clerkship titled 'Complex Medicine in Older People' (CMOP). CMOP is a clinical clerkship with 18 cases at its core, covering the fundamental aspects of geriatric medicine. The core cases and clinical learning are enhanced with five expert lectures, six tutorials and three journal clubs. Reflective practice is modelled and promoted with Balint groups and a book club. Consolidative workplace-based assessments and clinical portfolio mirror those used in postgraduate training, preparing students for professional practice. CMOP is iteratively improved in real-time using staff and student feedback. This marked shift in mode and duration of teaching affords the opportunity to evaluate the impact of differing education in geriatrics, providing an evidence-based model for teaching on aging.

Rats with high aerobic capacity display enhanced transcriptional adaptability and upregulation of bile acid metabolism in response to an acute high-fat diet.

Rats selectively bred for the high intrinsic aerobic capacity runner (HCR) or low aerobic capacity runner (LCR) show pronounced differences in susceptibility for high-fat/high sucrose (HFHS) diet-induced hepatic steatosis and insulin resistance, replicating the protective effect of high aerobic capacity in humans. We have previously shown multiple systemic differences in energy and substrate metabolism that impacts steatosis between HCR and LCR rats. This study aimed to investigate hepatic-specific mechanisms of action via changes in gene transcription. Livers of HCR rats had a greater number of genes that significantly changed in response to 3-day HFHS compared with LCR rats (171 vs. 75 genes: >1.5-fold, p < 0.05). HCR and LCR rats displayed numerous baseline differences in gene expression while on a low-fat control diet (CON). A 3-day HFHS diet resulted in greater expression of genes involved in the conversion of excess acetyl-CoA to cholesterol and bile acid (BA) synthesis compared with the CON diet in HCR, but not LCR rats. These results were associated with higher fecal BA loss and lower serum BA concentrations in HCR rats. Exercise studies in rats and mice also revealed higher hepatic expression of cholesterol and BA synthesis genes. Overall, these results suggest that high aerobic capacity and exercise are associated with upregulated BA synthesis paired with greater fecal excretion of cholesterol and BA, an effect that may play a role in protection against hepatic steatosis in rodents.

Come on mtDNA, light my fire.

Oxidized mitochondrial DNA (ox-mtDNA) activates NLRP3 inflammasome signaling through an ill-defined mechanism. In this issue of Immunity, Xian et al. reveal FEN1 endonuclease cleaves ox-mtDNA into fragments that escape mitochondria, igniting NLRP3 and cGAS-STING signaling and inflammation.

Use of Singapore's "Standard Details of Road Elements" for distance estimation in traffic crash reconstruction: A comparison with onsite measurements and Google Earth Pro.

We report the use of the geometric design standard for road markings published in the "Standard Details of Road Elements" ('SDRE') by the Land Transport Authority ('LTA') of Singapore as a convenient and sufficiently accurate means of estimating distances between features of the roadway, particularly useful for performing speed analysis based on videos. In this study, onsite measurements (by measuring tape, total station or 3D laser scanner) from various locations in Singapore, as well as the corresponding distances based on Google Earth Pro, were compared with those estimated using the SDRE. We demonstrate herein that the SDRE estimated 85.7% of all corresponding onsite measurements to within ±5%, and can thus be relied upon for crash reconstruction. This study also evaluated the distance accuracies associated with using the geometric design standard (the SDRE) and Google Earth Pro, and determined that both methods were robust and accurate, with overall average absolute percentage errors of less than 1% and would be beneficial for obtaining measurements for crash reconstruction, especially when the site of interest is not accessible.

Intrinsic High Aerobic Capacity in Male Rats Protects Against Diet-Induced Insulin Resistance.

Low aerobic capacity increases the risk for insulin resistance but the mechanisms are unknown. In this study, we tested susceptibility to acute (3-day) high-fat, high-sucrose diet (HFD)-induced insulin resistance in male rats selectively bred for divergent intrinsic aerobic capacity, that is, high-capacity running (HCR) and low-capacity running (LCR) rats. We employed hyperinsulinemic-euglycemic clamps, tracers, and transcriptome sequencing of skeletal muscle to test whether divergence in aerobic capacity impacted insulin resistance through systemic and tissue-specific metabolic adaptations. An HFD evoked decreased insulin sensitivity and insulin signaling in muscle and liver in LCR rats, whereas HCR rats were protected. An HFD led to increased glucose transport in skeletal muscle (twofold) of HCR rats while increasing glucose transport into adipose depots of the LCR rats (twofold). Skeletal muscle transcriptome revealed robust differences in the gene profile of HCR vs LCR on low-fat diet and HFD conditions, including robust differences in specific genes involved in lipid metabolism, adipogenesis, and differentiation. HCR transcriptional adaptations to an acute HFD were more robust than for LCR and included genes driving mitochondrial energy metabolism. In conclusion, intrinsic aerobic capacity robustly impacts systemic and skeletal muscle adaptations to HFD-induced alterations in insulin resistance, an effect that is likely driven by baseline differences in oxidative capacity, gene expression profile, and transcriptional adaptations to an HFD.

Prolonged exposure of mouse and human podocytes to insulin induces insulin resistance through lysosomal and proteasomal degradation of the insulin receptor.

AIMS/HYPOTHESIS: Podocytes are insulin-responsive cells of the glomerular filtration barrier and are key in preventing albuminuria, a hallmark feature of diabetic nephropathy. While there is evidence that a loss of insulin signalling to podocytes is detrimental, the molecular mechanisms underpinning the development of podocyte insulin resistance in diabetes remain unclear. Thus, we aimed to further investigate podocyte insulin responses early in the context of diabetic nephropathy. METHODS: Conditionally immortalised human and mouse podocyte cell lines and glomeruli isolated from db/db DBA/2J mice were studied. Podocyte insulin responses were investigated with western blotting, cellular glucose uptake assays and automated fluorescent imaging of the actin cytoskeleton. Quantitative (q)RT-PCR was employed to investigate changes in mRNA. Human cell lines stably overproducing the insulin receptor (IR) and nephrin were also generated, using lentiviral constructs. RESULTS: Podocytes exposed to a diabetic environment (high glucose, high insulin and the proinflammatory cytokines TNF-α and IL-6) become insulin resistant with respect to glucose uptake and activation of phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signalling. These podocytes lose expression of the IR as a direct consequence of prolonged exposure to high insulin concentrations, which causes an increase in IR protein degradation via a proteasome-dependent and bafilomycin-sensitive pathway. Reintroducing the IR into insulin-resistant human podocytes rescues upstream phosphorylation events, but not glucose uptake. Stable expression of nephrin is also required for the insulin-stimulated glucose uptake response in podocytes and for efficient insulin-stimulated remodelling of the actin cytoskeleton. CONCLUSIONS/INTERPRETATION: Together, these results suggest that IR degradation, caused by high levels of insulin, drives early podocyte insulin resistance, and that both the IR and nephrin are required for full insulin sensitivity of this cell. This could be highly relevant for the development of nephropathy in individuals with type 2 diabetes, who are commonly hyperinsulinaemic in the early phases of their disease.

Aerobic capacity and hepatic mitochondrial lipid oxidation alters susceptibility for chronic high-fat diet-induced hepatic steatosis.

Rats selectively bred for high capacity running (HCR) or low capacity running (LCR) display divergence for intrinsic aerobic capacity and hepatic mitochondrial oxidative capacity, both factors associated with susceptibility for nonalcoholic fatty liver disease. Here, we tested if HCR and LCR rats display differences in susceptibility for hepatic steatosis after 16 wk of high-fat diets (HFD) with either 45% or 60% of kcals from fat. HCR rats were protected against HFD-induced hepatic steatosis, whereas only the 60% HFD induced steatosis in LCR rats, as marked by a doubling of liver triglycerides. Hepatic complete fatty acid oxidation (FAO) and mitochondrial respiratory capacity were all lower in LCR compared with HCR rats. LCR rats also displayed lower hepatic complete and incomplete FAO in the presence of etomoxir, suggesting a reduced role for noncarnitine palmitoyltransferase-1-mediated lipid catabolism in LCR versus HCR rats. Hepatic complete FAO and mitochondrial respiration were largely unaffected by either chronic HFD; however, 60% HFD feeding markedly reduced 2-pyruvate oxidation, a marker of tricarboxylic acid (TCA) cycle flux, and mitochondrial complete FAO only in LCR rats. LCR rats displayed lower levels of hepatic long-chain acylcarnitines than HCR rats but maintained similar levels of hepatic acetyl-carnitine levels, further supporting lower rates of ß-oxidation, and TCA cycle flux in LCR than HCR rats. Finally, only LCR rats displayed early reductions in TCA cycle genes after the acute initiation of a HFD. In conclusion, intrinsically high aerobic capacity confers protection against HFD-induced hepatic steatosis through elevated hepatic mitochondrial oxidative capacity.

Deficiency in the Heat Stress Response Could Underlie Susceptibility to Metabolic Disease.

Heat treatment (HT) effectively prevents insulin resistance and glucose intolerance in rats fed a high-fat diet (HFD). The positive metabolic actions of heat shock protein 72 (HSP72), which include increased oxidative capacity and enhanced mitochondrial function, underlie the protective effects of HT. The purpose of this study was to test the ability of HSP72 induction to mitigate the effects of consumption of a short-term 3-day HFD in rats selectively bred to be low-capacity runners (LCRs) and high-capacity runners (HCRs)-selective breeding that results in disparate differences in intrinsic aerobic capacity. HCR and LCR rats were fed a chow or HFD for 3 days and received a single in vivo HT (41°C, for 20 min) or sham treatment (ST). Blood, skeletal muscles, liver, and adipose tissues were harvested 24 h after HT/ST. HT decreased blood glucose levels, adipocyte size, and triglyceride accumulation in liver and muscle and restored insulin sensitivity in glycolytic muscles from LCR rats. As expected, HCR rats were protected from the HFD. Importantly, HSP72 induction was decreased in LCR rats after only 3 days of eating the HFD. Deficiency in the highly conserved stress response mediated by HSPs could underlie susceptibility to metabolic disease with low aerobic capacity.

Increased aerobic capacity reduces susceptibility to acute high-fat diet-induced weight gain.

OBJECTIVE: Aerobic capacity is the most powerful predictor of all-cause mortality in humans; however, its role in the development of obesity and susceptibility for high-fat diet (HFD)-induced weight gain is not completely understood. METHODS: Herein, a rodent model system of divergent intrinsic aerobic capacity [high capacity running (HCR) and low capacity running (LCR)] was utilized to evaluate the role of aerobic fitness on 1-week HFD-induced (45% and 60% kcal) weight gain. Food/energy intake, body composition analysis, and brown adipose tissue gene expression were assessed as important potential factors involved in modulating HFD-induced weight gain. RESULTS: HCR rats had reduced 1-week weight gain on both HFDs compared with LCR. Reduced HFD-induced weight gain was associated with greater adaptability to decrease food intake following initiation of the HFDs. Further, the HCR rats were observed to have reduced feeding efficiency and greater brown adipose mass and expression of genes involved in thermogenesis. CONCLUSIONS: Rats with high intrinsic aerobic capacity have reduced susceptibility to 1-week HFD-induced weight gain, which is associated with greater food intake adaptability to control intake of energy-dense HFDs, reduced weight gain per kcal consumed, and greater brown adipose tissue mass and thermogenic gene expression.

Female rats selectively bred for high intrinsic aerobic fitness are protected from ovariectomy-associated metabolic dysfunction.

Ovariectomized rodents model human menopause in that they rapidly gain weight, reduce spontaneous physical activity (SPA), and develop metabolic dysfunction, including insulin resistance. How contrasting aerobic fitness levels impacts ovariectomy (OVX)-associated metabolic dysfunction is not known. Female rats selectively bred for high and low intrinsic aerobic fitness [high-capacity runners (HCR) and low-capacity runners (LCR), respectively] were maintained under sedentary conditions for 39 wk. Midway through the observation period, OVX or sham (SHM) operations were performed providing HCR-SHM, HCR-OVX, LCR-SHM, and LCR-OVX groups. Glucose tolerance, energy expenditure, and SPA were measured before and 4 wk after surgery, while body composition via dual-energy X-ray absorptiometry and adipose tissue distribution, brown adipose tissue (BAT), and skeletal muscle phenotype, hepatic lipid content, insulin resistance via homeostatic assessment model of insulin resistance and AdipoIR, and blood lipids were assessed at death. Remarkably, HCR were protected from OVX-associated increases in adiposity and insulin resistance, observed only in LCR. HCR rats were ∼30% smaller, had ∼70% greater spontaneous physical activity (SPA), consumed ∼10% more relative energy, had greater skeletal muscle proliferator-activated receptor coactivator 1-alpha, and ∼40% more BAT. OVX did not increase energy intake and reduced SPA to the same extent in both HCR and LCR. LCR were particularly affected by an OVX-associated reduction in resting energy expenditure and experienced a reduction in relative BAT; resting energy expenditure correlated positively with BAT across all animals (r = 0.6; P < 0.001). In conclusion, despite reduced SPA following OVX, high intrinsic aerobic fitness protects against OVX-associated increases in adiposity and insulin resistance. The mechanism may involve preservation of resting energy expenditure.

Intrinsic aerobic capacity impacts susceptibility to acute high-fat diet-induced hepatic steatosis.

Aerobic capacity/fitness significantly impacts susceptibility for fatty liver and diabetes, but the mechanisms remain unknown. Herein, we utilized rats selectively bred for high (HCR) and low (LCR) intrinsic aerobic capacity to examine the mechanisms by which aerobic capacity impacts metabolic vulnerability for fatty liver following a 3-day high-fat diet (HFD). Indirect calorimetry assessment of energy metabolism combined with radiolabeled dietary food was employed to examine systemic metabolism in combination with ex vivo measurements of hepatic lipid oxidation. The LCR, but not HCR, displayed increased hepatic lipid accumulation in response to the HFD despite both groups increasing energy intake. However, LCR rats had a greater increase in energy intake and demonstrated greater daily weight gain and percent body fat due to HFD compared with HCR. Additionally, total energy expenditure was higher in the larger LCR. However, controlling for the difference in body weight, the LCR has lower resting energy expenditure compared with HCR. Importantly, respiratory quotient was significantly higher during the HFD in the LCR compared with HCR, suggesting reduced whole body lipid utilization in the LCR. This was confirmed by the observed lower whole body dietary fatty acid oxidation in LCR compared with HCR. Furthermore, LCR liver homogenate and isolated mitochondria showed lower complete fatty acid oxidation compared with HCR. We conclude that rats bred for low intrinsic aerobic capacity show greater susceptibility for dietary-induced hepatic steatosis, which is associated with a lower energy expenditure and reduced whole body and hepatic mitochondrial lipid oxidation.

Reduced hepatic mitochondrial respiration following acute high-fat diet is prevented by PGC-1α overexpression.

Changes in substrate utilization and reduced mitochondrial respiratory capacity following exposure to energy-dense, high-fat diets (HFD) are putatively key components in the development of obesity-related metabolic disease. We examined the effect of a 3-day HFD on isolated liver mitochondrial respiration and whole body energy utilization in obesity-prone (OP) rats. We also examined if hepatic overexpression of peroxisomal proliferator-activated receptor-γ coactivator-1α (PGC-1α), a master regulator of mitochondrial respiratory capacity and biogenesis, would modify liver and whole body responses to the HFD. Acute, 3-day HFD (45% kcal) in OP rats resulted in increased daily energy intake, energy balance, weight gain, and adiposity, without an increase in liver triglyceride (triacylglycerol) accumulation. HFD-fed OP rats also displayed decreased whole body substrate switching from the dark to the light cycle, which was paired with reductions in hepatic mitochondrial respiration of multiple substrates in multiple respiratory states. Hepatic PGC-1α overexpression was observed to protect whole body substrate switching, as well as maintain mitochondrial respiration, following the acute HFD. Additionally, liver PGC-1α overexpression did not alter whole body dietary fatty acid oxidation but resulted in greater storage of dietary free fatty acids in liver lipid, primarily as triacylglycerol. Together, these data demonstrate that a short-term HFD can result in a decrease in metabolic flexibility and hepatic mitochondrial respiratory capacity in OP rats that is completely prevented by hepatic overexpression of PGC-1α.

PGC-1α overexpression results in increased hepatic fatty acid oxidation with reduced triacylglycerol accumulation and secretion.

Studies have shown that decreased mitochondrial content and function are associated with hepatic steatosis. We examined whether peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) overexpression and a subsequent increase in mitochondrial content and function in rat primary hepatocytes (in vitro) and Sprague-Dawley rats (in vivo) would comprehensively alter mitochondrial lipid metabolism, including complete (CO(2)) and incomplete (acid-soluble metabolites) fatty acid oxidation (FAO), tricarboxylic acid cycle flux, and triacylglycerol (TAG) storage and export. PGC-1α overexpression in primary hepatocytes produced an increase in markers of mitochondrial content and function (citrate synthase, mitochondrial DNA, and electron transport system complex proteins) and an increase in FAO, which was accompanied by reduced TAG storage and TAG secretion compared with control. Also, the PGC-1α-overexpressing hepatocytes were protected from excess TAG accumulation following overnight lipid treatment. PGC-1α overexpression in hepatocytes lowered expression of genes critical to VLDL assembly and secretion (apolipoprotein B and microsomal triglyceride transfer protein). Adenoviral transduction of rats with PGC-1α resulted in a liver-specific increase in PGC-1α expression and produced an in vivo liver phenotype of increased FAO via increased mitochondrial function that also resulted in reduced hepatic TAG storage and decreased plasma TAG levels. In conclusion, overexpression of hepatic PGC-1α and subsequent increases in FAO through elevated mitochondrial content and/or function result in reduced TAG storage and secretion in the in vitro and in vivo milieu.

Oxidative stress-mediated mitochondrial dysfunction contributes to angiotensin II-induced nonalcoholic fatty liver disease in transgenic Ren2 rats.

Emerging evidence indicates that impaired mitochondrial fatty acid beta-oxidation plays a key role in liver steatosis. We have recently demonstrated that increased angiotensin (ANG) II causes progressive hepatic steatosis associated with oxidative stress; however, the underlying mechanisms remain unclear. We hypothesized that ANG II causes hepatic mitochondrial oxidative damage and impairs mitochondrial beta-oxidation, thereby leading to hepatic steatosis. We used the Ren2 rat with elevated endogenous ANG II levels to evaluate mitochondrial ultrastructural changes, gene expression levels, and beta-oxidation. Compared with Sprague-Dawley littermates, Ren2 livers exhibited mitochondrial damage and reduced beta-oxidation, as evidenced by ultrastructural abnormalities, decrease of mitochondrial content, percentage of palmitate oxidation to CO(2), enzymatic activities (beta-HAD and citrate synthase), and the expression levels of cytochrome c, cytochrome c oxidase subunit 1, and mitochondrial transcription factor A. These abnormalities were improved with either ANG II receptor blocker valsartan or superoxide dismutase/catalase mimetic tempol treatment. Both valsartan and tempol substantially attenuated mitochondrial lipid peroxidation in Ren2 livers. Interestingly, there was no difference in the expression of key enzymes (ACC1 and FAS) for fatty acid syntheses and their transcription factors (SREBP-1c and ChREBP) between Sprague-Dawley, untreated Ren2, and valsartan- or tempol-treated Ren2 rats. These results document that ANG II induces mitochondrial oxidative damage and impairs mitochondrial beta-oxidation, contributing to liver steatosis.