Early vs late histological confirmation of coeliac disease in children with new-onset type 1 diabetes.

AIM: Screening for coeliac disease in asymptomatic children with new-onset type 1 diabetes is controversial. The aim of this study was to analyse whether the confirmation of coeliac disease in children with new-onset type 1 diabetes and positive screening results can be postponed. METHODS: This was a multicentre population-based cohort study based on the German/Austrian/Swiss/Luxembourgian Prospective Diabetes Follow-up Registry (Diabetes Patienten Verlaufsdokumentation [DPV]). Participants aged ≤18 years diagnosed with type 1 diabetes between 1995 and June 2021 and with elevated IgA tissue transglutaminase antibodies (anti-tTGA) at diabetes onset on screening for coeliac disease were included. We compared outcomes of participants with a diabetes duration of more than 1 year between those in whom coeliac disease was confirmed histologically within the first 6 months and those in whom coeliac disease was confirmed between 6 and 36 months after diabetes diagnosis. RESULTS: Of 92,278 children and adolescents with a diagnosis of type 1 diabetes, 26,952 (29.2%) had documented anti-tTGA data at diabetes onset. Of these, 2340 (8.7%) had an elevated anti-tTGA level. Individuals who screened positive were younger (median age 9.0 vs 9.8 years, p<0.001) and more often female (53.1% vs 44.4%, p<0.001). A total of 533 participants (22.8% of those who screened positive) had a documented biopsy, of whom 444 had documented histological confirmation of coeliac disease. Of 411 participants with biopsy-proven coeliac disease within the first 36 months of diabetes and follow-up data, histological confirmation was performed in 264 (64.2%) within the first 6 months and in 147 (35.8%) between 6 and 36 months after diabetes onset. At follow-up (median diabetes duration 5.3 years and 5.1 years, respectively), estimated median HbA1c levels (62.8 mmol/mol vs 62.2 mmol/mol [7.9% vs 7.8%]), cardiovascular risk markers (lipids, rate of microalbuminuria, blood pressure), rates of acute diabetes complications (diabetic ketoacidosis, severe hypoglycaemia) and the proportions of participants reaching anti-tTGA levels within the normal range did not differ between groups. Participants with delayed histological confirmation of coeliac disease showed no negative effects on growth or weight gain during the observation period. CONCLUSIONS: Our study suggests that the histological confirmation of coeliac disease in asymptomatic individuals with new-onset type 1 diabetes could be postponed.

Reversible severe glycogenic hepatopathy in type 1 diabetes.

CASE PRESENTATION: We report a case of severe glycogenic hepatopathy in a 17-year-old boy with poorly controlled type 1 diabetes. On presentation, major findings included unexplained pronounced hepatomegaly and increased liver enzymes, ferritin, and triglycerides. Histology and electron microscopy evaluation showed severe glycogen storage, steatosis, and signs of fibrosis, resembling the histomorphological findings of Mauriac syndrome. After information about the nature of the disease and intensification of insulin therapy with insulin pump, liver enzymes, ferritin, and triglycerides normalized within 1 month. CONCLUSION: Glycogenic hepatopathy is a rare but important potential complication in poorly controlled juvenile diabetic patients. With improved metabolic control, it is fully reversible.

Ataxin-3 consolidates the MDC1-dependent DNA double-strand break response by counteracting the SUMO-targeted ubiquitin ligase RNF4.

The SUMO-targeted ubiquitin ligase RNF4 functions at the crossroads of the SUMO and ubiquitin systems. Here, we report that the deubiquitylation enzyme (DUB) ataxin-3 counteracts RNF4 activity during the DNA double-strand break (DSB) response. We find that ataxin-3 negatively regulates ubiquitylation of the checkpoint mediator MDC1, a known RNF4 substrate. Loss of ataxin-3 markedly decreases the chromatin dwell time of MDC1 at DSBs, which can be fully reversed by co-depletion of RNF4. Ataxin-3 is recruited to DSBs in a SUMOylation-dependent fashion, and in vitro it directly interacts with and is stimulated by recombinant SUMO, defining a SUMO-dependent mechanism for DUB activity toward MDC1. Loss of ataxin-3 results in reduced DNA damage-induced ubiquitylation due to impaired MDC1-dependent recruitment of the ubiquitin ligases RNF8 and RNF168, and reduced recruitment of 53BP1 and BRCA1. Finally, ataxin-3 is required for efficient MDC1-dependent DSB repair by non-homologous end-joining and homologous recombination. Consequently, loss of ataxin-3 sensitizes cells to ionizing radiation and poly(ADP-ribose) polymerase inhibitor. We propose that the opposing activities of RNF4 and ataxin-3 consolidate robust MDC1-dependent signaling and repair of DSBs.

Alzheimer's disease-associated ubiquilin-1 regulates presenilin-1 accumulation and aggresome formation.

The Alzheimer's disease (AD)-associated ubiquilin-1 regulates proteasomal degradation of proteins, including presenilin (PS). PS-dependent γ-secretase generates ß-amyloid (Aß) peptides, which excessively accumulate in AD brain. Here, we have characterized the effects of naturally occurring ubiquilin-1 transcript variants (TVs) on the levels and subcellular localization of PS1 and other γ-secretase complex components and subsequent γ-secretase function in human embryonic kidney 293, human neuroblastoma SH-SY5Y and mouse primary cortical cells. Full-length ubiquilin-1 TV1 and TV3 that lacks the proteasome-interaction domain increased full-length PS1 levels as well as induced accumulation of high-molecular-weight PS1 and aggresome formation. Accumulated PS1 colocalized with TV1 or TV3 in the aggresomes. Electron microscopy indicated that aggresomes containing TV1 or TV3 were targeted to autophagosomes. TV1- and TV3-expressing cells did not accumulate other unrelated proteasome substrates, suggesting that the increase in PS1 levels was not because of a general impairment of the ubiquitin-proteasome system. Furthermore, PS1 accumulation and aggresome formation coincided with alterations in Aß levels, particularly in cells overexpressing TV3. These effects were not related to altered γ-secretase activity or PS1 binding to TV3. Collectively, our results indicate that specific ubiquilin-1 TVs can cause PS1 accumulation and aggresome formation, which may impact AD pathogenesis or susceptibility.

Accumulation of ubiquitin conjugates in a polyglutamine disease model occurs without global ubiquitin/proteasome system impairment.

Aggregation-prone proteins have been suggested to overwhelm and impair the ubiquitin/proteasome system (UPS) in polyglutamine (polyQ) disorders, such as Huntington's disease (HD). Overexpression of an N-terminal fragment of mutant huntingtin (N-mutHtt), an aggregation-prone polyQ protein responsible for HD, obstructs the UPS in cellular models. Furthermore, based on the accumulation of polyubiquitin conjugates in brains of R6/2 mice, which express human N-mutHtt and are one of the most severe polyQ disorder models, it has been proposed that UPS dysfunction is a consistent feature of this pathology, occurring in both in vitro and in vivo models. Here, we have exploited transgenic mice that ubiquitously express a ubiquitin fusion degradation proteasome substrate to directly assess the functionality of the UPS in R6/2 mice or the slower onset R6/1 mice. Although expression of N-mutHtt caused a general inhibition of the UPS in PC12 cells, we did not observe an increase in the levels of proteasome reporter substrate in the brains of R6/2 and R6/1 mice. We show that the increase in ubiquitin conjugates in R6/2 mice can be primarily attributed to an accumulation of large ubiquitin conjugates that are different from the conjugates observed upon UPS inhibition. Together our data show that polyubiquitylated proteins accumulate in R6/2 brain despite a largely operative UPS, and suggest that neurons are able to avoid or compensate for the inhibitory effects of N-mutHtt.

The Machado-Joseph disease deubiquitylase ataxin-3 interacts with LC3C/GABARAP and promotes autophagy.

The pathology of spinocerebellar ataxia type 3, also known as Machado-Joseph disease, is triggered by aggregation of toxic ataxin-3 (ATXN3) variants containing expanded polyglutamine repeats. The physiological role of this deubiquitylase, however, remains largely unclear. Our recent work showed that ATX-3, the nematode orthologue of ATXN3, together with the ubiquitin-directed segregase CDC-48, regulates longevity in Caenorhabditis elegans. Here, we demonstrate that the long-lived cdc-48.1; atx-3 double mutant displays reduced viability under prolonged starvation conditions that can be attributed to the loss of catalytically active ATX-3. Reducing the levels of the autophagy protein BEC-1 sensitized worms to the effect of ATX-3 deficiency, suggesting a role of ATX-3 in autophagy. In support of this conclusion, the depletion of ATXN3 in human cells caused a reduction in autophagosomal degradation of proteins. Surprisingly, reduced degradation in ATXN3-depleted cells coincided with an increase in the number of autophagosomes while levels of lipidated LC3 remained unaffected. We identified two conserved LIR domains in the catalytic Josephin domain of ATXN3 that directly interacted with the autophagy adaptors LC3C and GABARAP in vitro. While ATXN3 localized to early autophagosomes, it was not subject to lysosomal degradation, suggesting a transient regulatory interaction early in the autophagic pathway. We propose that the deubiquitylase ATX-3/ATXN3 stimulates autophagic degradation by preventing superfluous initiation of autophagosomes, thereby promoting an efficient autophagic flux important to survive starvation.

Sjl2p is specifically involved in early steps of endocytosis intimately linked to actin dynamics via the Ark1p/Prk1p kinases.

Sjl2p is one of three yeast phosphoinositide 5'-phosphatases that belong to the conserved family of synaptojanins. Here, we show that Sjl2p is specifically associated with cortical actin patches which aggregate upon loss of the actin-regulating kinases Ark1p and Prk1p. The Sjl2p-containing clumps overlap with clathrin and early endocytic structures generated independently of NSF/Sec18p, but not with endosome- and trans Golgi network-derived membranes. Consistent with the finding that Sjl2p can bind to clathrin heavy chain in vitro, our results suggest that Sjl2p localizes to smooth endocytic vesicles that may be derived from clathrin-coated structures.

Flower perianth: first observations on a novel diet item for the ponerine ant Odontomachus chelifer (Latreille)

Abstract Ants are known to feed on a variety of plant resources. Nevertheless, there are very few reports in the literature on ants using flower parts. Here, we describe how two Odontomachus chelifer (Latreille) ants teared and removed a part of an inner tepal of a Neomarica candida (Hassl.) (Iridaceae) flower at the restinga sandy forest in the Cardoso Island State Park, Brazil. To determine which part of the perianth attracted these ants, we performed two independent two-choice field assays: tepals (inner and outer tepals) were cut in two parts (basal and apical), with contrasting colors, which were offered to ants leaving a colony. Our results show that ants significantly preferred to remove or lick the basal part of the inner tepal. Based on the knowledge of N. candida's floral anatomy, we hypothesize that ants were attracted by the nectar produced by trichomatic nectaries at the basal part of the inner tepals. These tepal parts containing nectar are likely to be used as an alternative food resource amid the scarcity of arthropods usually preyed or scavenged by O. chelifer, since the restinga forest is known as an arthropod-poor habitat.

Family system dynamics and type 1 diabetic glycemic variability: a vector-auto-regressive model.

Statistical approaches rooted in econometric methodology, so far foreign to the psychiatric and psychological realms have provided exciting and substantial new insights into complex mind-body interactions over time and individuals. Over 120 days, this structured diary study explored the mutual interactions of emotions within a classic 3-person family system with its Type 1 diabetic adolescent's daily blood glucose variability. Glycemic variability was measured through daily standard deviations of blood glucose determinations (at least 3 per day). Emotions were captured individually utilizing the self-assessment manikin on affective valence (negative-positive), activation (calm-excited), and control (dominated-dominant). Auto- and cross-correlating the stationary absolute (level) values of the mutually interacting parallel time series data sets through vector autoregression (VAR, grounded in econometric theory) allowed for the formulation of 2 concordant models. Applying Cholesky Impulse Response Analysis at a 95% confidence interval, we provided evidence for an adolescent being happy, calm, and in control to exhibit less glycemic variability and hence diabetic derailment. A nondominating mother and a happy father seemed to also reduce glycemic variability. Random shocks increasing glycemic variability affected only the adolescent and her father: In 1 model, the male parent felt in charge; in the other, he calmed down while his daughter turned sad. All reactions to external shocks lasted for less than 4 full days. Extant literature on affect and glycemic variability in Type 1 diabetic adolescents as well as challenges arising from introducing econometric theory to the field were discussed.

Mutant p62/SQSTM1 UBA domains linked to Paget's disease of bone differ in their abilities to function as stabilization signals.

We show that the ubiquitin-associated domain (UBA) of human p62/sequestosome-1 (SQSTM1) can delay degradation of proteasome substrates in yeast. Taking advantage of naturally occurring mutant UBA domains that are linked to Paget's disease of bone (PDB), we found that three of the four mutant UBA domains tested in this study were able to inhibit proteasomal degradation, albeit not to the same extent as the wild-type domain. Interestingly, the stability measured as the fraction of folded protein, and not the ubiquitin binding properties, of the PDB-associated UBA domains correlated with their protective effects. These data suggest that the protective effect of UBA domains depends on their structural integrity rather than ubiquitin binding capabilities.

Selective accumulation of aggregation-prone proteasome substrates in response to proteotoxic stress.

Conditions causing an increase in misfolded or aberrant proteins can impair the activity of the ubiquitin/proteasome system (UPS). This observation is of particular interest, given the fact that proteotoxic stress is closely associated with a large variety of disorders. Although impairment of the UPS appears to be a general consequence of proteotoxic insults, the underlying mechanisms remain enigmatic. Here, we show that heat shock-induced proteotoxic stress resulted in conjugation of ubiquitin to detergent-insoluble protein aggregates, which coincided with reduced levels of free ubiquitin and impediment of ubiquitin-dependent proteasomal degradation. Interestingly, whereas soluble proteasome substrates returned to normal levels after a transient accumulation, the levels of an aggregation-prone substrate remained high even when the free ubiquitin levels were restored. Consistently, overexpression of ubiquitin prevented accumulation of soluble but not aggregation-prone substrates in thermally stressed cells. Notably, cells were also unable to resume degradation of aggregation-prone substrates after treatment with the translation inhibitor puromycin, indicating that selective accumulation of aggregation-prone proteins is a consistent feature of proteotoxic stress. Our data suggest that the failure of the UPS to clear aggregated proteins in the aftermath of proteotoxic stress episodes may contribute to the selective deposition of aggregation-prone proteins in conformational diseases.