Biology subjects

Bartelt, A.

Publications and source records attributed to Bartelt, A..

16 recordsLinked to original sources

bioRxiv2026

Direct interaction between miR-210-5p and HIF-1α regulates HIF-dependent transcription

Hypoxia-inducible factors (HIFs) coordinate cellular adaptation to oxygen deprivation, yet whether hypoxia-induced microRNAs directly regulate HIF-dependent transcription remains unknown. Here, we identify miR-210-5p as a nuclear hypoxamiR that directly binds HIF-1 and enhances HIF-dependent transcription. Hypoxia induced rapid, HIF-dependent nuclear accumulation of mature miR-210-5p across multiple cell types. Biophysical analyses demonstrated direct interaction between miR-210-5p and the HIF-1 bHLH-PAS domain, while mutational studies identified a conserved 5'motif required for HIF-1 binding but dispensable for repression of the canonical cytoplasmic target ISCU. Functionally, transcriptional activity closely correlated with HIF-1-binding affinity, as binding-deficient variants failed to activate HIF reporters or endogenous target genes. Although AGO2 contributed to hypoxic transcriptional responses, miR-210-5p interacted directly with HIF-1 independently of AGO2. In ischemic myocardium, nuclear enrichment of miR-210-5p and its proximity to HIF-1 support the physiological relevance of this mechanism, revealing a previously unrecognized RNA-mediated layer of HIF transcriptional regulation.

molecular biology↗

bioRxiv2026

ATGL-catalyzed lipid catabolism promotes DNA repair

An imbalance of DNA damage over DNA repair contributes to the genomic instability that drives aging and numerous age-related diseases. While numerous DNA repair mechanisms have been elucidated over decades of study, little is known about the contribution of metabolism to genomic stability. We report that adipose triglyceride lipase (ATGL), a lipolytic enzyme, promotes DNA repair. We show that lipid droplets (LDs) accumulate in response to DNA damage and that inhibition of LD biogenesis before genotoxic stress increases the persistence of DNA damage. Overexpression of ATGL, which increases lipolysis, reduces DNA damage following etoposide and ionizing radiation, thereby promoting genomic stability. Further, ATGL expression prior to DNA damage attenuates the long-term consequences of DNA damage, reducing senescence and enhancing viability. Mechanistically, ATGL promotes double-strand break repair via NHEJ and HR to mitigate DNA damage. Overall, these studies reveal a novel role for LDs and their proteins in DNA damage and repair, thereby unveiling a mechanism by which lipid metabolism contributes to genomic stability.

biochemistry↗

bioRxiv2025

A cellular cross-species RNA-seq atlas captures the transcriptional dynamics of myogenesis

Skeletal muscle formation and regeneration is a tightly regulated process involving extensive transcriptional reprogramming as proliferating myoblasts fuse into mature myotubes. However, a comparative comprehensive analysis of the transcriptional landscape of humans and mouse myogenesis is missing. Here, we present a high-quality RNA-sequencing dataset profiling this transition in both mouse (C2C12) and human (LHCN-M2) myogenic cells. Samples were collected from proliferating myoblasts, the early differentiation phase, and from mature myocytes using identical protocols, ensuring stringent comparability. This unified dataset captures the major transcriptional shifts occurring in myoblasts, marking the onset of differentiation. Quality metrics, including PCA, read distribution, and clustering, confirmed high internal consistency across samples and species. Comparative analyses revealed shared global features of myogenesis but also distinct regulatory trajectories. Human differentiation showed early upregulation followed by suppression of metabolic and stress-related pathways, while structural and ECM-associated programs remained persistently elevated. In contrast, mouse C2C12 cells displayed early inflammatory activation and later enrichment of metabolic and contractile pathways typical of mature myotubes. Ortholog-based integration demonstrated decreasing cross-species correlation over time, indicating progressive reinforcement of species-specific differentiation programs. We additionally compared this bulk RNA-seq with tissue-derived myotubes from single-cell muscle datasets to determine which transcriptional programs are conserved in the in vitro models or which emerge only in vivo. This analysis delineates the conserved and context-specific features of myogenesis, identifying pathways that reflect culture-specific artifacts in both human and mouse muscle cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=197 SRC="FIGDIR/small/691954v1_ufig1.gif" ALT="Figure 1000"> View larger version (48K): org.highwire.dtl.DTLVardef@a2d5f1org.highwire.dtl.DTLVardef@8be571org.highwire.dtl.DTLVardef@849563org.highwire.dtl.DTLVardef@6bc1ee_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

The obesity-linked peptide SP16 regulates adipocytes through GIP and insulin receptor

Obesity has emerged as a global epidemic and represents a major public health concern due to its profound implications for metabolic diseases. While recent pharmacological interventions primarily aim to reduce food intake, enhancing energy expenditure in adipose tissue offers a promising complementary approach. In this study, we identify that SP16, a synthetic 1- antitrypsin derived peptide, is a novel GIP (gastric inhibitory peptide) receptor agonist. SP16 promotes lipolysis via the cAMP pathway, resulting in increased mitochondrial oxygen consumption in adipocytes. Furthermore, SP16 binds to the insulin receptor, and at high concentrations, it attenuates insulin receptor signaling. In diet-induced obese (DIO) mice, acute SP16 treatment improved glucose clearance, elevated circulating free fatty acids, and decreased leptin levels. Ex vivo analyses of epididymal white adipose tissue corroborated these findings, demonstrating enhanced lipolysis in SP16-treated mice. In conclusion, SP16 emerges as a novel lipolytic peptide with beneficial metabolic effects. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=136 SRC="FIGDIR/small/660082v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@135f172org.highwire.dtl.DTLVardef@7e8152org.highwire.dtl.DTLVardef@15c6937org.highwire.dtl.DTLVardef@1ffc295_HPS_FORMAT_FIGEXP M_FIG C_FIG Created with Biorender.com

pharmacology and toxicology↗

bioRxiv2024

Control of cholesterol-induced adipocyte inflammation by the Nfe2l1-Atf3 pathway

While adipocytes are critical pillars of energy metabolism, their dysfunction is linked to adipose tissue (AT) inflammation, insulin resistance, and ectopic lipotoxicity in cardiometabolic diseases. However, the mechanisms causing adipocyte inflammation and insulin resistance remain unclear. Here, we show that excess cholesterol induces adipocyte dysfunction, which is suppressed by the transcription factor Nfe2l1 (nuclear factor erythroid derived-2, like-1). Nfe2l1 is required to sustain proteasome function in adipocytes and proteotoxic stress induces adipocyte inflammation via the activation of Atf3. In humans, the Nfe2l1-proteasome pathway is inversely correlated to body mass index (BMI) in an adipose-depot specific manner. In mice, loss of adipocyte Nfe2l1 caused AT inflammation with a pronounced infiltration of macrophages and T cells. Mice lacking adipocyte Nfe2l1 displayed severe adipocyte dysfunction during diet-induced obesity (DIO), characterized by lower adipokine levels, steatosis, glucose intolerance and insulin resistance. Nfe2l1{Delta}AT mice on an Apoe-deficient (Apoe-/-) background fed a cholesterol-rich Western Diet (WD), developed a lipoatrophy-like syndrome, dyslipidemia, and enhanced atherosclerosis. Our results reveal an important role for proteasome-mediated proteostasis in adipocytes and indicate that Nfe2l1 is linked to metabolic health in humans and preclinical mouse models. Promoting proteostasis in adipocytes may thus alleviate inflammation in obesity, potentially averting adverse cardiometabolic outcomes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/604614v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@145e32borg.highwire.dtl.DTLVardef@1454df1org.highwire.dtl.DTLVardef@1002383org.highwire.dtl.DTLVardef@1b7319_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Macroscopic label-free biomedical imaging withshortwave infrared Raman scattering

Shortwave infrared (SWIR) imaging provides enhanced tissue penetration and reduced autofluorescence in clinical and pre-clinical applications. However, existing applications often lack the ability to probe chemical composition and molecular specificity without the need for contrast agents. Here, we present a SWIR imaging approach that visualizes spontaneous Raman scattering with remarkable chemical contrast deep within tissue across large fields of view. Our results demonstrate that Raman scattering overcomes autofluorescence as the predominant source of endogenous tissue background at illumination wavelengths as short as 892 nm. We highlight the versatility of SWIR Raman imaging through in vivo monitoring of whole-body tissue composition dynamics and non-invasive detection of fatty liver disease in mice, and identification of calcification and lipids in unfixed human atherosclerotic plaques. Moreover, our approach facilitates the visualization of nerves embedded in fatty tissue, a major advancement for surgical applications. With a simple wide-field setup orthogonal to fluorescence, SWIR Raman imaging holds promise for rapid adoption by clinicians and biologists. This technique opens new possibilities for contrast agent-free visualization of pathophysiology in whole animals and intraoperative imaging in humans. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/597863v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@394289org.highwire.dtl.DTLVardef@13f3289org.highwire.dtl.DTLVardef@ee6f7org.highwire.dtl.DTLVardef@5d7399_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2024

Chronic intermittent fasting impairs β-cell maturation and function in adolescent mice

Intermittent fasting (IF) is a nutritional lifestyle intervention with broad metabolic benefits, but whether the impact of IF depends on the individuals age is unclear. Here, we investigated the effects of IF on systemic metabolism and pancreatic islet function in old, middle-aged, and young mice. Short-term IF improved glucose homeostasis across all age groups, without altering islet function and morphology. In contrast, while chronic IF was beneficial for adult mice, it resulted in impaired {beta}-cell function in the young. Using scRNAseq, we delineated that the {beta}-cell maturation and function score were reduced in young mice. In human islets, a similar pattern was observed in Type 1 (T1D), but not in Type 2 diabetes (T2D), suggesting that the impact of chronic IF in adolescence is linked to the development of {beta}-cell dysfunction. Our study suggests considering the duration of IF in younger people, as it may enhance rather than reduce diabetes outcomes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=164 SRC="FIGDIR/small/590140v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1676dd1org.highwire.dtl.DTLVardef@15ac993org.highwire.dtl.DTLVardef@167f577org.highwire.dtl.DTLVardef@247e4e_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LILong-term IF impairs {beta}-cell function in adolescent mice. C_LIO_LIIF-induced impaired {beta}-cell function is associated with impaired proliferative capacity and lower levels of mature cells. C_LIO_LIIF-induced impaired {beta}-cell function is associated with a transcriptional change highly conserved in type 1-, but not type 2 diabetes. C_LI

physiology↗

bioRxiv2023

IF1 controls UCP1-dependent mitochondrial bioenergetics in brown adipocytes

While mechanisms controlling mitochondrial uncoupling protein-1 (UCP1) expression and function in thermogenic adipocytes play a pivotal role in non-shivering thermogenesis (NST), it remains unclear whether F1Fo-ATP synthase function is regulated during NST. Here, we show that Inhibitory Factor 1 (IF1, encoded by Atp5if1), an inhibitor of ATP synthase hydrolytic activity, is a critical negative regulator of brown adipocyte energy metabolism. In mice, IF1 protein content is markedly diminished in brown adipose tissue (BAT) after 5 days of cold exposure. Additionally, the capacity of ATP synthase to generate mitochondrial membrane potential through ATP hydrolysis (the so-called "reverse mode" of ATP synthase) is higher in mitochondria isolated from cold- adapted mice compared to mice housed at room temperature. In vitro, IF1 overexpression results in an inability of mitochondria to sustain mitochondrial membrane potential upon adrenergic stimulation and this occurs in a UCP1-dependent manner. In brown adipocytes, IF1 silencing is sufficient to increase mitochondrial lipid oxidation and the cellular dependency on glycolysis to produce ATP. Conversely, IF1 overexpression blunts mitochondrial respiration without causing cellular energetic stress, leading to a quiescent-like phenotype in brown adipocytes. In mice, adeno-associated virus- mediated IF1 overexpression in BAT suppresses adrenergic-stimulated thermogenesis and decreases mitochondrial respiration in this tissue. Taken together, our data shows that the downregulation of IF1 upon cold serves to facilitate the reverse mode of ATP synthase to enable energetic adaptation and effectively support NST in BAT. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/550888v2_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@16146faorg.highwire.dtl.DTLVardef@17afc1corg.highwire.dtl.DTLVardef@13da476org.highwire.dtl.DTLVardef@1f86fd3_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

Activating the NFE2L1-ubiquitin-proteasome system by DDI2 protects from ferroptosis

Ferroptosis is an iron-dependent, non-apoptotic form of cell death initiated by oxidative stress and lipid peroxidation. Recent evidence has linked ferroptosis to the action of the transcription factor Nuclear factor erythroid-2 derived,-like-1 (NFE2L1). NFE2L1 regulates proteasome abundance in an adaptive fashion, maintaining protein quality control to secure cellular homeostasis, but the regulation of NFE2L1 during ferroptosis and the role of the ubiquitin-proteasome system (UPS) herein are still unclear. In the present study, using an unbiased proteomic approach charting the specific ubiquitylation sites, we show that induction of ferroptosis leads to recalibration of the UPS. RSL3-induced ferroptosis inhibits proteasome activity and leads to global hyperubiquitylation, which is linked to NFE2L1 activation. As NFE2L1 resides in the endoplasmic reticulum tethered to the membrane, it undergoes complex posttranslational modification steps to become active and induce the expression of proteasome subunit genes. We show that proteolytic cleavage of NFE2L1 by the aspartyl protease DNA-damage inducible 1 homolog 2 (DDI2) is a critical step for the ferroptosis-induced feed-back loop of proteasome function. Cells lacking DDI2 cannot activate NFE2L1 in response to RSL3 and show global hyperubiquitylation. Genetic or chemical induction of ferroptosis in cells with a disrupted DDI2-NFE2L1 pathway diminishes proteasomal activity and promotes cell death. Also, treating cells with the clinical drug nelfinavir, which inhibits DDI2, sensitized cells to ferroptosis. In conclusion, our results provide new insight into the importance of the UPS in ferroptosis and highlight the role of the DDI2-NFE2L1 as a potential therapeutic target. Manipulating DDI2-NFE2L1 activity through chemical inhibition might help sensitizing cells to ferroptosis, thus enhancing existing cancer therapies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/547652v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@b3f899org.highwire.dtl.DTLVardef@18625feorg.highwire.dtl.DTLVardef@287bcborg.highwire.dtl.DTLVardef@1d758d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Nfe2l1-mediated proteasome function controls muscle energy metabolism in obesity

Muscle function is an important denominator of energy metabolism and metabolic health. Adapting the myocyte proteome to energetic challenges, in response to diet or fasting, is facilitated by programs of proteostasis, but the adaptive role of the ubiquitin-proteasome system (UPS) in muscle remains unclear. Here, we show that myocyte Nuclear factor erythroid derived 2,-like 1 (Nfe2l1, also known as Nrf1) is a key regulator of skeletal muscle proteostasis and function. In mice and humans, Nfe2l1 is highly expressed in skeletal myocytes, and its loss diminishes proteasomal activity and leads to hyperubiquitylation. Mice lacking myocyte Nfe2l1 display muscle fiber type switching and insulin resistance when fed a high-fed diet. Nfe2l1 protects myocytes from ferroptosis, which is enhanced in the presence of excess lipids. In conclusion, we define a new adaptive role for the Nfe2l1-ubiquitin proteasome system in the control of skeletal muscle function and energy metabolism.

physiology↗

bioRxiv2022

Proteasome dysfunction disrupts adipogenesis and induces inflammation via ATF3

ObjectiveRegulation of proteasomal activity is an essential component of cellular proteostasis and function. This is evident in patients with mutations in proteasome subunits and regulators, who suffer from proteasome-associated autoinflammatory syndromes (PRAAS). These patients display lipodystrophy and fevers, which may be partly related to adipocyte malfunction and abnormal thermogenesis in adipose tissue. However, the cell-intrinsic pathways that could underlie these symptoms are unclear. Here, we investigate the impact of two proteasome subunits implicated in PRAAS, Psmb4 and Psmb8, on differentiation, function and proteostasis of brown adipocytes. MethodsIn immortalized mouse brown pre-adipocytes, levels of Psmb4, Psmb8, and downstream effectors genes were downregulated through reverse transfection with siRNA. Adipocytes were differentiated and analyzed with various assays of adipogenesis, lipogenesis, lipolysis, inflammation, and respiration. ResultsLoss of Psmb4, but not Psmb8, disrupted proteostasis and adipogenesis. Proteasome function was reduced upon Psmb4 loss, but partly recovered by the activation of Nuclear factor, erythroid-2, like-1 (Nfe2l1). In addition, cells displayed higher levels of surrogate inflammation and stress markers, including Activating transcription factor-3 (Atf3). Simultaneous silencing of Psmb4 and Atf3 lowered inflammation and restored adipogenesis. ConclusionsOur study shows that Psmb4 is required for adipocyte development and function in cultured adipocytes. These results imply that in humans with PSMB4 mutations, PRAAS-associated lipodystrophy is partly caused by disturbed adipogenesis. While we uncover a role for Nfe2l1 in the maintenance of proteostasis under these conditions, Atf3 is a key effector of inflammation and blocking adipogenesis. In conclusion, our work highlights how proteasome dysfunction is sensed and mitigated by the integrated stress response in adipocytes with potential relevance for PRAAS patients and beyond. Highlights- PRAAS-associated PSMB4 is required for brown adipocyte differentiation - Loss of PSMB4 activates NFE2L1 to counteract proteasome dysfunction - The ATF3 pathway regulates adipocyte dysfunction and inflammation - Loss of ATF3 restores adipogenesis in cells with loss of PSMB4 Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/476367v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@4c9c5eorg.highwire.dtl.DTLVardef@1ae0674org.highwire.dtl.DTLVardef@29c741org.highwire.dtl.DTLVardef@d8a584_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2021

NFE2L1-mediated proteasome function protects from ferroptosis

ObjectiveFerroptosis continues to emerge as a novel modality of cell death with important therapeutic implications for a variety of diseases, most notably cancer and degenerative diseases. While susceptibility, initiation, and execution of ferroptosis have been linked to reprogramming of cellular lipid metabolism, imbalances in iron-redox homeostasis, and aberrant mitochondrial respiration, the detailed mechanisms of ferroptosis are still insufficiently well understood. Methods and ResultsHere we show that diminished proteasome function is a new mechanistic feature of ferroptosis. The transcription factor nuclear factor erythroid-2, like-1 (NFE2L1) protects from ferroptosis by sustaining proteasomal activity. In cellular systems, loss of NFE2L1 reduced cellular viability after the induction of both chemically and genetically induced ferroptosis, which was linked to the regulation of proteasomal activity under these conditions. Importantly, this was reproduced in a Sedaghatian-type Spondylometaphyseal Dysplasia (SSMD) patient-derived cell line carrying mutated glutathione peroxidase-4 (GPX4), a critical regulator of ferroptosis. Also, reduced proteasomal activity was associated with ferroptosis in Gpx4-deficient mice. In a mouse model for genetic Nfe2l1 deficiency, we observed brown adipose tissue (BAT) involution, hyperubiquitination of ferroptosis regulators, including the GPX4 pathway, and other hallmarks of ferroptosis. ConclusionOur data highlight the relevance of the NFE2L1-proteasome pathway in ferroptosis. Manipulation of NFE2L1 activity might enhance ferroptosis-inducing cancer therapies as well as protect from aberrant ferroptosis in neurodegeneration, general metabolism, and beyond. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY HighlightsO_LIProteasome function is diminished during ferroptosis C_LIO_LINFE2L1-mediated proteasomal activity protects from ferroptosis C_LIO_LIThe ubiquitination of the GPX4-glutathione pathway is implicated in Nfe2l1 deficiency C_LIO_LINFE2L1 deficiency in brown fat is associated with hallmarks of ferroptosis C_LI

biochemistry↗

bioRxiv2021

The obesity-linked human lncRNA AATBC regulates adipocyte plasticity by stimulating mitochondrial dynamics and respiration

Adipocytes are critical regulators of metabolism and energy balance. While white adipocyte dysfunction is a hallmark of obesity-associated disorders, the activation of thermogenic brown and beige adipocytes is linked to improved cardiometabolic health. As adipocytes dynamically adapt to environmental cues by functionally switching between white and thermogenic phenotypes, a molecular understanding of this adipocyte plasticity could help improving energy balance and weight loss. Here, we show that the long non-coding RNA (lncRNA) Apoptosis associated transcript in bladder cancer (AATBC) is a human-specific regulator of adipocyte plasticity. Searching for new human lncRNAs implicated in adipocyte biology we compared transcriptional profiles of human adipose tissues and cultured adipocytes and discovered that AATBC was enriched in thermogenic conditions. Using primary human adipocytes and immortalized human adipocytes we found that gain-of-function of AATBC enhanced the thermogenic phenotype whereas loss-of-function diminished this effect. The AATBC-mediated increase in mitochondrial respiration was linked to a more fragmented mitochondrial network and vice versa. While we found that AATBC is predominantly located in the nucleus, its effect on global transcription was only marginal. As AATBC is specific to humans, we expressed AATBC in adipose tissue of mice to study its systemic impact, which led to lower plasma leptin levels. Interestingly, this association was also present in human subjects, as AATBC in adipose tissue was inversely correlated with plasma leptin levels, body mass index and other measures of metabolic health. In conclusion, AATBC is a novel obesity-linked regulator of adipocyte plasticity and mitochondrial function in humans.

molecular biology↗

bioRxiv2020

ADH5-mediated NO Bioactivity Maintains Metabolic Homeostasis in Brown Adipose Tissue

Brown adipose tissue (BAT) thermogenic activity is tightly regulated by cellular redox status but the molecular mechanisms underlying this regulation are incompletely understood. Protein S-nitrosylation, the nitric oxide-mediated cysteine thiol modification of proteins, plays important roles in cellular redox regulation. Here we show that both diet-induced obesity (DIO) and acute cold exposure elevates protein S-nitrosylation of BAT proteins, including UCP1, to regulate thermogenesis. This effect in BAT is regulated largely by S-nitrosoglutathione reductase (GSNOR, ADH5), a denitrosylase that balances the intracellular nitroso-redox status. Loss of ADH5 specifically in BAT impairs UCP1-dependent thermogenesis during acute cold challenge and worsens metabolic dysfunction during diet-induced obesity. Mechanistically, we demonstrate that Adh5 expression in BAT is controlled by the transcription factor heat shock factor 1 (HSF1) and administration of an HSF1 activator to the BAT of mice with DIO increased Adh5 expression and significantly improved UCP1-mediated mitochondrial respiration. Together, these data demonstrate that ADH5 controls BAT nitroso-redox homeostasis to regulate adipose thermogenesis which may be therapeutically targeted to improve metabolic health. HighlightsO_LIThermogenesis induces protein S-nitrosylation modification in the BAT; C_LIO_LIADH5, a major cellular denitrosylase, is required for maintaining BAT metabolic homeostasis under both overnutrition and cold stress conditions; C_LIO_LIDiet-induced obesity suppresses HSF1-mediated activation of Adh5 in the BAT; C_LIO_LIADH5 overexpression in BAT improves whole-body glucose homeostasis in obesity. C_LI

molecular biology↗

bioRxiv2020

HAND2 is a novel obesity-linked adipogenic transcription factor regulated by glucocorticoid signaling

Adipocytes are critical cornerstones of energy metabolism. While obesity-induced adipocyte dysfunction is associated with insulin resistance and systemic metabolic disturbances, adipogenesis, the formation of new adipocytes and healthy adipose tissue expansion are associated with metabolic benefits. Understanding the molecular mechanisms governing adipogenesis is of great clinical potential to efficiently restore metabolic health in obesity. Here we show that Heart- and neural crest derivatives-expressed protein 2 (HAND2) is an obesity-linked adipocyte transcription factor regulated by glucocorticoids and required for adipocyte differentiation in vitro. In a large cohort of humans with obesity, white adipose tissue (WAT) HAND2 expression was correlated to body-mass-index (BMI). The HAND2 gene was enriched in white adipocytes, induced early in differentiation and responded to dexamethasone, a typical glucocorticoid receptor (GR, encoded by NR3C1) agonist. Silencing of NR3C1 in human multipotent adipose-derived stem cells (hMADS) or deletion of GR in a transgenic conditional mouse model results in diminished HAND2 expression, establishing that adipocyte HAND2 is regulated by glucocorticoids via GR in vitro and in vivo. Using a combinatorial RNAseq approach we identified gene clusters regulated by the GR-HAND2 pathway. Interestingly, silencing of HAND2 impaired adipocyte differentiation in hMADS and primary mouse adipocytes. However, a conditional adipocyte Hand2 deletion mouse model using Cre under control of the Adipoq promoter did not mirror these effects on adipose tissue differentiation, indicating that Hand2 was required at stages prior to Adipoq expression. In summary, our study identifies HAND2 as a novel obesity-linked adipocyte transcription factor, highlighting new mechanisms of GR-dependent adipogenesis in human and mice.

molecular biology↗

bioRxiv2020

An unexpected lack of difference in superoxide/H2O2 production rates in isolated heart and skeletal muscle mitochondria from a mouse model of Barth Syndrome

Barth Syndrome (BTHS) is a rare X-linked genetic disorder caused by mutations in tafazzin and characterized by loss of cardiolipin and severe cardiomyopathy. Mitochondrial superoxide/H2O2 production has been implicated in the cardiomyopathy observed in different BTHS models. There are at least 11 mitochondrial sites that produce superoxide/H2O2 at significant rates. Which of these sites generate oxidants at excessive rates in BTHS is unknown. Here, we measured the maximum capacity of superoxide/H2O2 production from each site in mitochondria isolated from heart and skeletal muscle of the tafazzin knockdown mice (tazkd) at 3, 7 and 12 months of age. Strikingly, the superoxide/H2O2 production capacities of these sites were overall indistinguishable between tazkd mice and their wildtype littermates across the time points analyzed. The only exception was site GQ in glycerol phosphate dehydrogenase, which was increased in the skeletal muscle of 7 months old tazkd mice. Mitochondrial superoxide/H2O2 production was also measured ex vivo during the oxidation of a complex mixture of substrates mimicking either heart or skeletal muscle cytosol and was found to be indistinguishable between wildtype and tazkd mice. However, we consistently measured decreased FAD-linked respiration in mitochondria isolated from tazkd mice. We conclude that the maximum capacity and ex vivo rates of superoxide/H2O2 production were not increased in mitochondria isolated from heart and skeletal muscle of tazkd mice, despite reduced oxidative capacity. Therefore, it seems unlikely that mitochondrial oxidants contribute to the development of cardiomyopathy in tazkd mice. These observations raise questions about the involvement of mitochondrial oxidants in BTHS pathology.

biochemistry↗