Autoantibodies against type I IFNs in humans with alternative NF-κB pathway deficiency.

Patients with autoimmune polyendocrinopathy syndrome type 1 (APS-1) caused by autosomal recessive AIRE deficiency produce autoantibodies that neutralize type I interferons (IFNs)1,2, conferring a predisposition to life-threatening COVID-19 pneumonia3. Here we report that patients with autosomal recessive NIK or RELB deficiency, or a specific type of autosomal-dominant NF-κB2 deficiency, also have neutralizing autoantibodies against type I IFNs and are at higher risk of getting life-threatening COVID-19 pneumonia. In patients with autosomal-dominant NF-κB2 deficiency, these autoantibodies are found only in individuals who are heterozygous for variants associated with both transcription (p52 activity) loss of function (LOF) due to impaired p100 processing to generate p52, and regulatory (IκBδ activity) gain of function (GOF) due to the accumulation of unprocessed p100, therefore increasing the inhibitory activity of IκBδ (hereafter, p52LOF/IκBδGOF). By contrast, neutralizing autoantibodies against type I IFNs are not found in individuals who are heterozygous for NFKB2 variants causing haploinsufficiency of p100 and p52 (hereafter, p52LOF/IκBδLOF) or gain-of-function of p52 (hereafter, p52GOF/IκBδLOF). In contrast to patients with APS-1, patients with disorders of NIK, RELB or NF-κB2 have very few tissue-specific autoantibodies. However, their thymuses have an abnormal structure, with few AIRE-expressing medullary thymic epithelial cells. Human inborn errors of the alternative NF-κB pathway impair the development of AIRE-expressing medullary thymic epithelial cells, thereby underlying the production of autoantibodies against type I IFNs and predisposition to viral diseases.

Thymic tuft cells promote an IL-4-enriched medulla and shape thymocyte development.

The thymus is responsible for generating a diverse yet self-tolerant pool of T cells1. Although the thymic medulla consists mostly of developing and mature AIRE+ epithelial cells, recent evidence has suggested that there is far greater heterogeneity among medullary thymic epithelial cells than was previously thought2. Here we describe in detail an epithelial subset that is remarkably similar to peripheral tuft cells that are found at mucosal barriers3. Similar to the periphery, thymic tuft cells express the canonical taste transduction pathway and IL-25. However, they are unique in their spatial association with cornified aggregates, ability to present antigens and expression of a broad diversity of taste receptors. Some thymic tuft cells pass through an Aire-expressing stage and depend on a known AIRE-binding partner, HIPK2, for their development. Notably, the taste chemosensory protein TRPM5 is required for their thymic function through which they support the development and polarization of thymic invariant natural killer T cells and act to establish a medullary microenvironment that is enriched in the type 2 cytokine, IL-4. These findings indicate that there is a compartmentalized medullary environment in which differentiation of a minor and highly specialized epithelial subset has a non-redundant role in shaping thymic function.

Effect of race distance on performance fatigability in male trail and ultra-trail runners.

The etiology of changes in lower-limb neuromuscular function, especially to the central nervous system, may be affected by exercise duration. Direct evidence is lacking as few studies have directly compared different race distances. This study aimed to investigate the etiology of deficits in neuromuscular function following short versus long trail-running races. Thirty-two male trail runners completed one of five trail-running races as LONG (>100 km) or SHORT (<60 km). Pre- and post-race, maximal voluntary contraction (MVC) torque and evoked responses to electrical nerve stimulation during MVCs and at rest were used to assess voluntary activation and muscle contractile properties of knee-extensor (KE) and plantar-flexor (PF) muscles. Transcranial magnetic stimulation (TMS) was used to assess evoked responses and corticospinal excitability in maximal and submaximal KE contractions. Race distance correlated with KE MVC (ρ = -0.556) and twitch (ρ = -0.521) torque decreases (p ≤ .003). KE twitch torque decreased more in LONG (-28 ± 14%) than SHORT (-14 ± 10%, p = .005); however, KE MVC time × distance interaction was not significant (p = .073). No differences between LONG and SHORT for PF MVC or twitch torque were observed. Maximal voluntary activation decreased similarly in LONG and SHORT in both muscle groups (p ≥ .637). TMS-elicited silent period decreased in LONG (p = .021) but not SHORT (p = .912). Greater muscle contractile property impairment in longer races, not central perturbations, contributed to the correlation between KE MVC loss and race distance. Conversely, PF fatigability was unaffected by race distance.

Outcomes of pre-operative brachytherapy followed by hysterectomy for early cervical cancer.

OBJECTIVE: The standard of care for early cervical cancer is radical hysterectomy; however, consideration of pre-operative brachytherapy has been explored. We report our experience using pre-operative brachytherapy plus Wertheim-type hysterectomy to treat early stage cervical cancer. METHODS: This single-center study evaluated consecutive patients with histologically proven node-negative early stage cervical cancer (International Federation of Gynecology and Obstetrics 2009 stage IB1-IIB) that was treated using pre-operative brachytherapy and hysterectomy. Pre-brachytherapy staging was performed using magnetic resonance imaging (MRI) and pelvic lymph node assessment was performed using lymphadenectomy. The tumor and cervical tissues were treated using brachytherapy (total dose 60 Gy) followed by Wertheim-type hysterectomy. The study included patients from January 2000 to December 2013. RESULTS: A total of 80 patients completed a median follow-up of 6.7 years (range 5.4-8.5). The surgical specimens revealed a pathological complete response for 61 patients (76%). Patients with incomplete responses generally had less than 1 cm residual tumor at the cervix, and only one patient had lymphovascular space involvement. The estimated 5-year rates were 88% for overall survival (95% CI 78% to 94%) and 82% for disease-free survival (95% CI 71% to 89%). Toxicities were generally mild-to-moderate, including 26 cases (33%) of grade 2 late toxicity and 10 cases (13%) of grade 3 late toxicity. Univariate analyses revealed that poor disease-free survival was associated with overweight status (≥25 kg/m2, HR 3.05, 95% CI 1.20 to 7.76, p=0.019) and MRI tumor size >3 cm (HR 3.05, 95% CI 1.23 to 7.51, p=0.016). CONCLUSIONS: Pre-operative brachytherapy followed by Wertheim-type hysterectomy may be safe and effective for early stage cervical cancer, although poorer outcomes were associated with overweight status and MRI tumor size >3 cm.

Controlled induction of human pancreatic progenitors produces functional beta-like cells in vitro.

Directed differentiation of human pluripotent stem cells into functional insulin-producing beta-like cells holds great promise for cell replacement therapy for patients suffering from diabetes. This approach also offers the unique opportunity to study otherwise inaccessible aspects of human beta cell development and function in vitro. Here, we show that current pancreatic progenitor differentiation protocols promote precocious endocrine commitment, ultimately resulting in the generation of non-functional polyhormonal cells. Omission of commonly used BMP inhibitors during pancreatic specification prevents precocious endocrine formation while treatment with retinoic acid followed by combined EGF/KGF efficiently generates both PDX1(+) and subsequent PDX1(+)/NKX6.1(+) pancreatic progenitor populations, respectively. Precise temporal activation of endocrine differentiation in PDX1(+)/NKX6.1(+) progenitors produces glucose-responsive beta-like cells in vitro that exhibit key features of bona fide human beta cells, remain functional after short-term transplantation, and reduce blood glucose levels in diabetic mice. Thus, our simplified and scalable system accurately recapitulates key steps of human pancreas development and provides a fast and reproducible supply of functional human beta-like cells.

Elevated Hedgehog/Gli signaling causes beta-cell dedifferentiation in mice.

Although Hedgehog (Hh) signaling regulates cell differentiation during pancreas organogenesis, the consequences of pathway up-regulation in adult ß-cells in vivo have not been investigated. Here, we elevate Hh signaling in ß-cells by expressing an active version of the GLI2 transcription factor, a mediator of the Hh pathway, in ß-cells that are also devoid of primary cilia, a critical regulator of Hh activity. We show that increased Hh signaling leads to impaired ß-cell function and insulin secretion, resulting in glucose intolerance in transgenic mice. This phenotype was accompanied by reduced expression of both genes critical for ß-cell function and transcription factors associated with their mature phenotype. Increased Hh signaling further correlated with increased expression of the precursor cell markers Hes1 and Sox9, both direct Hh targets that are normally excluded from ß-cells. Over time, the majority of ß-cells down-regulated GLI2 levels, thereby regaining the full differentiation state and restoring normoglycemia in transgenic mice. However, sustained high Hh levels in some insulin-producing cells further eroded the ß-cell identity and eventually led to the development of undifferentiated pancreatic tumors. Summarily, our results indicate that deregulation of the Hh pathway impairs ß-cell function by interfering with the mature ß-cell differentiation state.

Intensive rehabilitation combined with HBO2 therapy in children with cerebral palsy: a controlled longitudinal study.

OBJECTIVE: The present study aimed to assess the effect of intensive rehabilitation combined with hyperbaric oxygen (HBO2) therapy on gross motor function in children with cerebral palsy (CP). METHODS: We carried out an open, observational, platform-independent study in 150 children with cerebral palsy with follow-up over eight months to compare the effects of standard intensive rehabilitation only (control group n = 20) to standard intensive rehabilitation combined with one of three different hyperbaric treatments. The three hyperbaric treatments used were: air (FiO2 = 21%) pressurized to 1.3 atmospheres absolute/atm abs (n = 40); 100% oxygen pressurized at 1.5 atm abs (n = 32); and 100% oxygen, pressurized at 1.75 atm abs (n = 58). Each subject assigned to a hyperbaric arm was treated one hour per day, six days per week during seven weeks (40 sessions). Gross motor function measure (GMFM) was evaluated before the treatments and at two, four, six and eight months after beginning the treatments. RESULTS: All four groups showed improvements over the course of the treatments in the follow-up evaluations (p < 0.001). However, GMFM improvement in the three hyperbaric groups was significantly superior to the GMFM improvement in the control group (p < 0.001). There was no significant difference between the three hyperbaric groups. CONCLUSION: The eight-month-long benefits we have observed with combined treatments vs. rehabilitation can only have been due to a beneficial effect of hyperbaric treatment.

Redox regulation of m6A methyltransferase METTL3 in ß-cells controls the innate immune response in type 1 diabetes.

Type 1 diabetes (T1D) is characterized by the destruction of pancreatic ß-cells. Several observations have renewed the interest in ß-cell RNA sensors and editors. Here, we report that N6-methyladenosine (m6A) is an adaptive ß-cell safeguard mechanism that controls the amplitude and duration of the antiviral innate immune response at T1D onset. m6A writer methyltransferase 3 (METTL3) levels increase drastically in ß-cells at T1D onset but rapidly decline with disease progression. m6A sequencing revealed the m6A hypermethylation of several key innate immune mediators, including OAS1, OAS2, OAS3 and ADAR1 in human islets and EndoC-ßH1 cells at T1D onset. METTL3 silencing enhanced 2'-5'-oligoadenylate synthetase levels by increasing its mRNA stability. Consistently, in vivo gene therapy to prolong Mettl3 overexpression specifically in ß-cells delayed diabetes progression in the non-obese diabetic mouse model of T1D. Mechanistically, the accumulation of reactive oxygen species blocked upregulation of METTL3 in response to cytokines, while physiological levels of nitric oxide enhanced METTL3 levels and activity. Furthermore, we report that the cysteines in position C276 and C326 in the zinc finger domains of the METTL3 protein are sensitive to S-nitrosylation and are important to the METTL3-mediated regulation of oligoadenylate synthase mRNA stability in human ß-cells. Collectively, we report that m6A regulates the innate immune response at the ß-cell level during the onset of T1D in humans.

WDR36 acts as a scaffold protein tethering a G-protein-coupled receptor, Gαq and phospholipase Cß in a signalling complex.

We identified the WD-repeat-containing protein, WDR36, as an interacting partner of the ß isoform of thromboxane A(2) receptor (TPß) by yeast two-hybrid screening. We demonstrated that WDR36 directly interacts with the C-terminus and the first intracellular loop of TPß by in vitro GST-pulldown assays. The interaction in a cellular context was observed by co-immunoprecipitation, which was positively affected by TPß stimulation. TPß-WDR36 colocalization was detected by confocal microscopy at the plasma membrane in non-stimulated HEK293 cells but the complex translocated to intracellular vesicles following receptor stimulation. Coexpression of WDR36 and its siRNA-mediated knockdown, respectively, increased and inhibited TPß-induced Gαq signalling. Interestingly, WDR36 co-immunoprecipitated with Gαq, and promoted TPß-Gαq interaction. WDR36 also associated with phospholipase Cß (PLCß) and increased the interaction between Gαq and PLCß, but prevented sequestration of activated Gαq by GRK2. In addition, the presence of TPß in PLCß immunoprecipitates was augmented by expression of WDR36. Finally, disease-associated variants of WDR36 affected its ability to modulate Gαq-mediated signalling by TPß. We report that WDR36 acts as a new scaffold protein tethering a G-protein-coupled receptor, Gαq and PLCß in a signalling complex.

Ikaros is a principal regulator of Aire+ mTEC homeostasis, thymic mimetic cell diversity, and central tolerance.

Mutations in the gene encoding the zinc-finger transcription factor Ikaros (IKZF1) are found in patients with immunodeficiency, leukemia, and autoimmunity. Although Ikaros has a well-established function in modulating gene expression programs important for hematopoietic development, its role in other cell types is less well defined. Here, we uncover functions for Ikaros in thymic epithelial lineage development in mice and show that Ikzf1 expression in medullary thymic epithelial cells (mTECs) is required for both autoimmune regulator-positive (Aire+) mTEC development and tissue-specific antigen (TSA) gene expression. Accordingly, TEC-specific deletion of Ikzf1 in mice results in a profound decrease in Aire+ mTECs, a global loss of TSA gene expression, and the development of autoimmunity. Moreover, Ikaros shapes thymic mimetic cell diversity, and its deletion results in a marked expansion of thymic tuft cells and muscle-like mTECs and a loss of other Aire-dependent mimetic populations. Single-cell analysis reveals that Ikaros modulates core transcriptional programs in TECs that correlate with the observed cellular changes. Our findings highlight a previously undescribed role for Ikaros in regulating epithelial lineage development and function and suggest that failed thymic central tolerance could contribute to the autoimmunity seen in humans with IKZF1 mutations.

Autoantibodies to Perilipin-1 Define a Subset of Acquired Generalized Lipodystrophy.

Acquired lipodystrophy is often characterized as an idiopathic subtype of lipodystrophy. Despite suspicion of an immune-mediated pathology, biomarkers such as autoantibodies are generally lacking. Here, we used an unbiased proteome-wide screening approach to identify autoantibodies to the adipocyte-specific lipid droplet protein perilipin 1 (PLIN1) in a murine model of autoimmune polyendocrine syndrome type 1 (APS1). We then tested for PLIN1 autoantibodies in human subjects with acquired lipodystrophy with two independent severe breaks in immune tolerance (including APS1) along with control subjects using a specific radioligand binding assay and indirect immunofluorescence on fat tissue. We identified autoantibodies to PLIN1 in these two cases, including the first reported case of APS1 with acquired lipodystrophy and a second patient who acquired lipodystrophy as an immune-related adverse event following cancer immunotherapy. Lastly, we also found PLIN1 autoantibodies to be specifically enriched in a subset of patients with acquired generalized lipodystrophy (17 of 46 [37%]), particularly those with panniculitis and other features of autoimmunity. These data lend additional support to new literature that suggests that PLIN1 autoantibodies represent a marker of acquired autoimmune lipodystrophies and further link them to a break in immune tolerance.

Redox Regulation of m 6 A Methyltransferase METTL3 in Human ß-cells Controls the Innate Immune Response in Type 1 Diabetes.

Type 1 Diabetes (T1D) is characterized by autoimmune-mediated destruction of insulin-producing ß-cells. Several observations have renewed interest in the innate immune system as an initiator of the disease process against ß-cells. Here, we show that N 6 -Methyladenosine (m 6 A) is an adaptive ß-cell safeguard mechanism that accelerates mRNA decay of the 2'-5'-oligoadenylate synthetase (OAS) genes to control the antiviral innate immune response at T1D onset. m 6 A writer methyltransferase 3 (METTL3) levels increase drastically in human and mouse ß-cells at T1D onset but rapidly decline with disease progression. Treatment of human islets and EndoC-ßH1 cells with pro-inflammatory cytokines interleukin-1 ß and interferon α mimicked the METTL3 upregulation seen at T1D onset. Furthermore, m 6 A-sequencing revealed the m 6 A hypermethylation of several key innate immune mediators including OAS1, OAS2, and OAS3 in human islets and EndoC-ßH1 cells challenged with cytokines. METTL3 silencing in human pseudoislets or EndoC-ßH1 cells enhanced OAS levels by increasing its mRNA stability upon cytokine challenge. Consistently, in vivo gene therapy, to prolong Mettl3 overexpression specifically in ß-cells, delayed diabetes progression in the non-obese diabetic (NOD) mouse model of T1D by limiting the upregulation of Oas pointing to potential therapeutic relevance. Mechanistically, the accumulation of reactive oxygen species blocked METTL3 upregulation in response to cytokines, while physiological levels of nitric oxide promoted its expression in human islets. Furthermore, for the first time to our knowledge, we show that the cysteines in position C276 and C326 in the zinc finger domain of the METTL3 protein are sensitive to S-nitrosylation (SNO) and are significant for the METTL3 mediated regulation of OAS mRNA stability in human ß-cells in response to cytokines. Collectively, we report that m 6 A regulates human and mouse ß-cells to control the innate immune response during the onset of T1D and propose targeting METTL3 to prevent ß-cell death in T1D.

Static Postural Control Deficits in Adults with Myotonic Dystrophy Type 1, Steinert Disease.

BACKGROUND: Myotonic dystrophy type 1 (DM1) is characterized by progressive and predominantly distal muscle atrophy and myotonia. Gait and balance impairments, resulting in falls, are frequently reported in this population. However, the extent to which individuals with DM1 rely more on a specific sensory system for balance than asymptomatic individuals (AI) is unknown. OBJECTIVE: Evaluate postural control performance in individuals with DM1 and its dependence on vision compared to AI. METHODS: 20 participants with DM1, divided into two groups based on their diagnosis, i.e. adult and congenital phenotype, and 12 AI participants were recruited. Quiet standing postural control was assessed in two visual conditions: eyes-open and eyes-closed. The outcomes measures were: center of pressure (CoP), mean velocity, CoP range of displacement in anteroposterior and mediolateral axis, and the 95% confidence ellipse's surface. Friedman and Kruskal-Wallis analysis of variance were used to compare outcomes between conditions and groups, respectively. RESULTS: Significant group effect and condition effect were observed on postural control performance. No significant difference was observed between the two DM1 groups. The significant differences observed between the AI group and the two DM1 groups in the eyes-open condition were also observed in the eyes-closed condition. CONCLUSIONS: The result revealed poorer postural control performance in people with DM1 compared to AI. The DM1 group also showed similar decrease in performance than AI in eyes-closed condition, suggesting no excessive visual dependency.

Stem cell-based multi-tissue platforms to model human autoimmune diabetes.

BACKGROUND: Type 1 diabetes (T1D) is an autoimmune disease in which pancreatic insulin-producing ß cells are specifically destroyed by the immune system. Understanding the initiation and progression of human T1D has been hampered by the lack of appropriate models that can reproduce the complexity and heterogeneity of the disease. The development of platforms combining multiple human pluripotent stem cell (hPSC) derived tissues to model distinct aspects of T1D has the potential to provide critical novel insights into the etiology and pathogenesis of the human disease. SCOPE OF REVIEW: In this review, we summarize the state of hPSC differentiation approaches to generate cell types and tissues relevant to T1D, with a particular focus on pancreatic islet cells, T cells, and thymic epithelium. We present current applications as well as limitations of using these hPSC-derived cells for disease modeling and discuss efforts to optimize platforms combining multiple cell types to model human T1D. Finally, we outline remaining challenges and emphasize future improvements needed to accelerate progress in this emerging field of research. MAJOR CONCLUSIONS: Recent advances in reprogramming approaches to create patient-specific induced pluripotent stem cell lines (iPSCs), genome engineering technologies to efficiently modify DNA of hPSCs, and protocols to direct their differentiation into mature cell types have empowered the use of stem cell derivatives to accurately model human disease. While challenges remain before complex interactions occurring in human T1D can be modeled with these derivatives, experiments combining hPSC-derived ß cells and immune cells are already providing exciting insight into how these cells interact in the context of T1D, supporting the viability of this approach.

Relationship between lower limb strength and walking capacities in children with spastic bilateral cerebral palsy.

PURPOSE: Evaluate the relationship between different walking capacities and muscle strength in children with bilateral cerebral palsy (BCP) and assess these relationships in stronger and weaker children. MATERIALS AND METHODS: Thirty-two children with spastic BCP were included. All participants walked under three speed conditions: comfortable, fast, and for a longer period (6 min). Walking speeds, Energy Expenditure Index (EEI), and lower limb muscle strength were measured. A global strength index (GSI) was computed as the sum of each muscle group strength. Pearson's coefficient and regression models were computed between walking capacities and the GSI. RESULTS: GSI was correlated with the EEI and all walking speeds. Logarithmic regressions models explained between 24 and 34% of the variance of walking capacities. Then, the group was divided in two subgroups (weaker and stronger children). GSI was correlated with comfortable and endurance waking speed in weaker children, but not in stronger children. CONCLUSION: This study reports logarithmic relationship between muscle strength and walking capacities in children with BCP. The subgroup analysis implies that muscle strength has an impact on walking capacities solely in weaker children, suggesting that muscle strength must be preserved and reinforced in interventions targeting motor function in weaker children with BCP.Implications for rehabilitationIn a sample of children with spastic bilateral cerebral palsy, this study shows that global muscle strength is associated with walking capacities and the relationship seems more complex than linear.Based on the results, interventions should focus on maintaining or improving muscle strength in weaker children as no association was observed between muscle strength and walking capacities in stronger children.In stronger children, intervention should focus on factors other than muscle strength as it does not influence walking capacities.Based on this study, a more accurate screening of children who could benefit from strength training could be completed by initial global muscle strength.

Development of a scalable method to isolate subsets of stem cell-derived pancreatic islet cells.

Cell replacement therapy using ß cells derived from stem cells is a promising alternative to conventional diabetes treatment options. Although current differentiation methods produce glucose-responsive ß cells, they can also yield populations of undesired endocrine progenitors and other proliferating cell types that might interfere with long-term islet function and safety of transplanted cells. Here, we describe the generation of an array of monoclonal antibodies against cell surface markers that selectively label stem cell-derived islet cells. A high-throughput screen identified promising candidates, including three clones that mark a high proportion of endocrine cells in differentiated cultures. A scalable magnetic sorting method was developed to enrich for human pluripotent stem cell (hPSC)-derived islet cells using these three antibodies, leading to the formation of islet-like clusters with improved glucose-stimulated insulin secretion and reduced growth upon transplantation. This strategy should facilitate large-scale production of functional islet clusters from stem cells for disease modeling and cell replacement therapy.

Performance fatigability during isometric vs. concentric quadriceps fatiguing tasks in men and women.

In the present study, we aimed to provide a robust comparison of the fatigability of the knee extensors following isometric (ISO) and concentric (CON) tasks. Twenty young adults (25 ± 4 yr, 10 women) randomly performed the ISO and CON quadriceps intermittent fatigue test, consisting of ten (5 s on/5-s off, ISO) or one-hundred (0.5-s on/0.5-s off, CON) contractions with 10 % increments per stage until exhaustion. Performance fatigability was quantified as maximal isometric (MVIC) and concentric (MVCC) torque loss. Voluntary activation and contractile function (peak-twitch) were investigated using peripheral nerve stimulation. Number of stages (6.2 ± 0.7 vs. 4.9 ± 0.8; P < 0.001) and torque-time integral (20,166 ± 7,821 vs. 11,285 ± 4,933 Nm.s; P < 0.001) were greater for ISO than CON. MVIC, MVCC and voluntary activation decreased similarly between sessions (P > 0.05) whereas peak-twitch amplitude decreased more for CON (P < 0.001). The number of contractions was similar across sexes (ISO: men = 62 ± 8, women = 61 ± 5; CON: men = 521 ± 67, women = 458 ± 76, P > 0.05). MVCC was more reduced in women for both sessions (all P < 0.05), while MVIC loss was similar between sexes. We concluded that, despite greater torque-time integral and duration for ISO, both sessions induced a similar performance fatigability at exhaustion. Contractile function was more altered in CON. Finally, sex-related difference in fatigability depends on the contraction mode used during testing.

Fatigue Measured in Dynamic Versus Isometric Modes After Trail Running Races of Various Distances.

PURPOSE: Fatigue has previously been investigated in trail running by comparing maximal isometric force before and after the race. Isometric contractions may not entirely reflect fatigue-induced changes, and therefore dynamic evaluation is warranted. The aim of the present study was to compare the magnitude of the decrement of maximal isometric force versus maximal power, force, and velocity after trail running races ranging from 40 to 170 km. METHODS: Nineteen trail runners completed races shorter than 60 km, and 21 runners completed races longer than 100 km. Isometric maximal voluntary contractions (IMVCs) of knee extensors and plantar flexors and maximal 7-second sprints on a cycle ergometer were performed before and after the event. RESULTS: Maximal power output (Pmax; -14% [11%], P < .001), theoretical maximum force (F0; -11% [14%], P < .001), and theoretical maximum velocity (-3% [8%], P = .037) decreased significantly after both races. All dynamic parameters but theoretical maximum velocity decreased more after races longer than 100 km than races shorter than 60 km (P < .05). Although the changes in IMVCs were significantly correlated (P < .05) with the changes in F0 and Pmax, reductions in IMVCs for knee extensors (-29% [16%], P < .001) and plantar flexors (-26% [13%], P < .001) were larger (P < .001) than the reduction in Pmax and F0. CONCLUSIONS: After a trail running race, reductions in isometric versus dynamic forces were correlated, yet they are not interchangeable because the losses in isometric force were 2 to 3 times greater than the reductions in Pmax and F0. This study also shows that the effect of race distance on fatigue measured in isometric mode is true when measured in dynamic mode.

Performance Determinants in Trail-Running Races of Different Distances.

PURPOSE: While the physiological determinants of road running have been widely studied, there is a lack of research in trail-running racing performance. The aim of our study was to determine the physiological predictors of trail-running performance in races of different distances in similar terrain and weather conditions. METHODS: Seventy-five trail runners participating in one of the races of the Ultra-Trail du Mont-Blanc were recruited. Previous to the race, each runner was evaluated with (1) an incremental treadmill test to determine maximal oxygen uptake, ventilatory thresholds, cost of running, and substrate utilization; (2) a power-force-velocity profile on a cycle ergometer; (3) maximal voluntary contractions of the knee extensors and plantar flexors; and (4) anthropometric characteristics. Neuromuscular fatigue was evaluated after the races. Twenty-four runners finished a SHORT (<55 km), 16 finished a MEDIUM (101 km), and 14 finished a LONG (>145 km) race. Correlations and multiple linear regressions were used to find the determinants of performance in each race distance. RESULTS: Performance in SHORT was explained by maximal oxygen uptake and lipid utilization at 10 km/h (r2 = .825, P < .001). Performance in MEDIUM was determined by maximal oxygen uptake, maximal isometric strength, and body fat percentage (r2 = .917, P < .001). A linear model could not be applied in LONG, but performance was correlated to peak velocity during the incremental test. CONCLUSIONS: Performance in trail running is mainly predicted by aerobic capacity, while lipid utilization also influences performance in races <60 km and performance in approximately 100 km is influenced by muscle strength and body composition.

Modeling human T1D-associated autoimmune processes.

BACKGROUND: Type 1 diabetes (T1D) is an autoimmune disease characterized by impaired immune tolerance to ß-cell antigens and progressive destruction of insulin-producing ß-cells. Animal models have provided valuable insights for understanding the etiology and pathogenesis of this disease, but they fall short of reflecting the extensive heterogeneity of the disease in humans, which is contributed by various combinations of risk gene alleles and unique environmental factors. Collectively, these factors have been used to define subgroups of patients, termed endotypes, with distinct predominating disease characteristics. SCOPE OF REVIEW: Here, we review the gaps filled by these models in understanding the intricate involvement and regulation of the immune system in human T1D pathogenesis. We describe the various models developed so far and the scientific questions that have been addressed using them. Finally, we discuss the limitations of these models, primarily ascribed to hosting a human immune system (HIS) in a xenogeneic recipient, and what remains to be done to improve their physiological relevance. MAJOR CONCLUSIONS: To understand the role of genetic and environmental factors or evaluate immune-modifying therapies in humans, it is critical to develop and apply models in which human cells can be manipulated and their functions studied under conditions that recapitulate as closely as possible the physiological conditions of the human body. While microphysiological systems and living tissue slices provide some of these conditions, HIS mice enable more extensive analyses using in vivo systems.