Biology subjects

Sommer, N.

Publications and source records attributed to Sommer, N..

8 recordsLinked to original sources

bioRxiv2026

AAV-mediated delivery of leptin but not adiponectin improves metabolic health in a mouse model of congenital generalised lipodystrophy

Lipodystrophies are a group of disorders featuring reduced adipose tissue mass or function, which often leads to significant metabolic disease, reduced lifespan and impaired quality of life. Individuals with congenital generalised lipodystrophy (CGL) have severely reduced adipose tissue mass. The loss of healthy systemic lipid storage typically causes hepatic steatosis and lipoatrophic diabetes. In addition, adipocyte-secreted hormones including leptin and adiponectin are dramatically reduced. Leptin has critical roles regulating appetite and broader effects on lipid and glucose metabolism. Daily injection with recombinant leptin is currently the only specific, approved treatment for CGL. The consequences of adiponectin loss in these patients are not fully understood. Likewise, the potential therapeutic benefit of adiponectin delivery is unclear. Here we examine the effect of delivering leptin or adiponectin by adeno-associated virus (AAV) as potential gene therapy treatment for metabolic disease in CGL using a well-characterised murine model of the condition. AAV-mediated leptin delivery significantly improved hepatic steatosis and hyperinsulinemia. However, adiponectin delivery did not lead to any observed beneficial effects. This demonstrates the potential of gene therapy approaches for long-term delivery of leptin in individuals with lipodystrophy, without the need for continuous supply of perishable therapeutics and painful daily injections.

physiology↗

bioRxiv2026

Mitochondrial COX4I2 drives pericyte-dependent inflammation and emphysema

Chronic obstructive pulmonary disease (COPD) is characterized by neutrophilic inflammation, emphysema, and mild pulmonary hypertension (PH). Oxidative/nitrosative stress are key drivers, but specific mitochondrial mechanisms remain unclear. We show increased expression of the regulatory mitochondrial cytochrome c oxidase subunit 4 isoform 2 (COX4I2) in an early murine model and human COPD. After 8 months of cigarette smoke exposure, Cox4i2-/- mice were completely protected from emphysema but not from PH, associated with reduced nitrosative stress, inflammation, and apoptosis. Using a novel Cox4i2 reporter mouse and in situ hybridization of human lungs, COX4I2 was detected in precapillary ACTA2+ cells and capillary pericytes. COX4I2 promotes mitochondrial reactive oxygen species (mtROS) production in these cells, thereby enhancing neutrophil migration and alveolar type II cell apoptosis, and modulates angiogenesis. In contrast to Cox4i2-/-, mitochondria-targeted antioxidant MitoQ reversed emphysema and PH, suggesting pericyte-specific regulation of COPD pathologies and mtROS inhibition as a therapeutic approach in COPD. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/703513v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@83bca4org.highwire.dtl.DTLVardef@d5ebaborg.highwire.dtl.DTLVardef@632d1borg.highwire.dtl.DTLVardef@1267a13_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Long-Term Intestinal Epithelial Remodeling Induced by Acute Protein-Energy Malnutrition

Protein-energy malnutrition (PEM) is a global health burden with lasting effects that extend well beyond the initial nutrient deficiency. To systematically investigate the long-term effects of a single episode of PEM on the structure and function of the intestinal epithelium and its associated microbiota, we employed a comprehensive multi-omics approach, including (spatial) transcriptomics, DNA methylation analysis, fecal metagenomics, and metabolomics. Our findings show that PEM persistently alters the intestinal epithelium by depleting Paneth cells and suppressing antimicrobial gene expression - changes linked to DNA methylation that persist despite dietary recovery. In germ-free mice, the sustained epithelial phenotype after was absent. We identified the microbial lipid metabolite 9-HODE and epigenetically deregulated PPAR-driven GDF15 expression as key molecular drivers of the persistent PEM-induced Paneth cell dysfunction. Targeting microbial lipid production and its link to the host GDF15 pathway could offer novel therapeutic strategies for long-term consequences of malnutrition and other Paneth cell-associated diseases.

immunology↗

bioRxiv2024

Preclinical evaluation of tissue-selective gene therapies for congenital generalised lipodystrophy

Lipodystrophy is a rare disorder which can be life-threatening. Here individuals fail to develop or maintain appropriate adipose tissue stores. This typically causes severe metabolic complications, including hepatic steatosis and lipoatrophic diabetes. There is no cure for lipodystrophy, and treatment options remain very limited. Here we evaluate whether tissue-selective adeno-associated virus (AAV) vectors can provide a targeted form of gene therapy for lipodystrophy, using a preclinical lipodystrophic mouse model of Bscl2 deficiency. We designed AAV vectors containing the mini/aP2 or thyroxine-binding globulin promoter to selectively target adipose or liver respectively. The AAV-aP2 vectors also contained the liver-specific microRNA-122 target sequence, restricting hepatic transgene expression. Systemic delivery of AAV-aP2 vectors overexpressing human BSCL2 restored adipose tissue development and metabolic health in lipodystrophic mice without detectable expression in the liver. High doses (1x1012 GCs) of liver-selective vectors led to off target expression and adipose tissue development, whilst low doses (1x1010 GCs) expressed selectively and robustly in the liver but did not improve metabolic health. This reveals that adipose tissue-selective, but not liver directed, AAV-mediated gene therapy is sufficient to substantially recover metabolic health in generalised lipodystrophy. This provides an exciting potential new avenue for an effective, targeted, and thereby safer therapeutic intervention.

molecular biology↗

bioRxiv2023

Notch3 deletion regulates HIV-1 gene expression and systemic inflammation to ameliorate chronic kidney disease

Antiretroviral therapy (ART) has decreased HIV-1 associated morbidity. However, despite ART, immune cells remain latently infected and slowly release viral proteins, leading to chronic inflammation and HIV-1 associated comorbidities. New strategies are needed to target viral proteins and inflammation. We found activation of Notch3 in several renal cells of the HIV-1 mouse model (HIV-Tg26) and in patients with HIV associated Nephropathy. We hypothesized that targeting Notch3 activation constitutes an effective therapy for HIV-related chronic kidney diseases (HIV-CKD). We generated HIV-Tg26 mice with Notch3 knocked out (Tg-N3KO). Compared to HIV-Tg26 mice at 3 months, HIV-Tg-N3KO mice showed a marked reduction in renal injury, skin lesions and mortality rate. Bulk RNA sequencing revealed that N3KO not only reduced renal infiltrating cells but significantly reduced the expression of HIV genes. Moreover, Notch3 activated the HIV-promoter and induction of HIV-1 resulted in increased Notch3 activation indicating a feedback mechanism. Further, bone marrow derived macrophages (BMDMs) from HIV-Tg26 mice showed activation of Notch3 indicating systemic effects. Consistent with that, systemic levels of TNF-, MCP-1 and other inflammatory chemokines and cytokines were reduced in Tg-N3KO mice. Thus, Notch3 inhibition/deletion has a dual therapeutic effect in HIV-CKD and may extend to other HIV-related pathologies.

molecular biology↗

bioRxiv2023

GLP-1 Receptor Agonist Improves Metabolic Disease in a Pre-clinical Model of Lipodystrophy

Individuals with lipodystrophies typically suffer from significant metabolic disease linked to adipose tissue dysfunction including severe insulin resistance and lipoatrophic diabetes, hepatic steatosis and hyperphagia. Current treatment options are limited and beter therapies for affected individuals are urgently needed. No systematic, detailed analyses exist of the effects of glucagon like peptide-1 receptor (GLP-1R) agonists in the treatment of lipoatrophic diabetes. Here we examined the effects of the GLP-1R agonist liraglutide in seipin knockout mice, a pre-clinical model of generalised lipodystrophy. Acute liraglutide treatment of seipin knockout mice significantly improved insulin, glucose and pyruvate tolerance. Once-daily injection of seipin knockout mice with liraglutide for 14 days led to a modest reduction in food intake but significant improvements in hepatomegaly associated with steatosis and significantly reduced markers of liver fibrosis. Detailed examination of the pancreas revealed that liraglutide enhanced insulin secretion in response to glucose challenge with concomitantly improved glucose control. Thus, GLP-1R agonist liraglutide significantly improved multiple aspects of lipoatrophic diabetes and hepatic steatosis in mice with congenital generalised lipodystrophy. This provides important insights regarding the benefits of GLP-1R agonists for treating lipodystrophy, informing more widespread use to improve the health of individuals with this condition.

pharmacology and toxicology↗

bioRxiv2023

Neutrophil efferocytosis reprograms mitochondrial metabolism to switch alveolar macrophages to a pro-resolution phenotype at the cost of bacterial control

Resolution of lung injuries is vital to maintain gas exchange. Concurrently, there is an increased risk of secondary bacterial infections. Alveolar macrophages (AMs) are crucial to clear bacteria and control initiation and resolution of inflammation, but environmental cues that switch functional phenotypes of AMs remain elusive. Here, we discovered an incapacity of AMs to mount an effective immune response to bacteria during resolution of inflammation. AM efferocytosis of neutrophils (PMNs), a hallmark of resolution of inflammation, switched mitochondrial metabolism to shift AM functions. Mechanistically, PMN-derived myeloperoxidase (MPO) fueled canonical glutaminolysis via uncoupling protein 2 (UCP2) resulting in decreased mtROS-dependent killing of bacteria and secretion of pro-inflammatory cytokines. Instead, MPO-enhanced UCP2 expression inhibited mitochondrial hyperpolarization and boosted efferocytosis irrespective of the presence of bacterial pathogens. In contrast, efferocytosis of epithelial cells resulted in a distinct anti-inflammatory phenotype of AMs maintaining phenotypic plasticity towards bacteria. Overall, uptake of apoptotic PMNs switches AMs to prioritize resolution of inflammation over antibacterial responses and similarly affects murine macrophages at extra-pulmonary sites, and human AMs. One sentence summaryNeutrophil efferocytosis reprograms mitochondrial metabolism to switch alveolar macrophages to a pro-resolution phenotype at the cost of bacterial control.

immunology↗

bioRxiv2020

Microbial regulation of hexokinase 2 links mitochondrial metabolism and cell death in colitis

Hexokinases (HK) catalyze the first step of glycolysis and thereby limit its pace. HK2 is highly expressed in the gut epithelium, plays a role in immune responses and is upregulated in inflammation and ulcerative colitis 1-3. Here, we examined the microbial regulation of HK2 and its impact on intestinal inflammation by generating mice lacking HK2 specifically in intestinal epithelial cells (Hk2{Delta}IEC). Hk2{Delta}IEC mice were less susceptible to acute intestinal inflammation upon challenge with dextran sodium sulfate (DSS). Analyzing the epithelial transcriptome from Hk2{Delta}IEC mice during acute colitis revealed downregulation of cell death signaling and mitochondrial dysfunction dependent on loss of HK2. Using intestinal organoids derived from Hk2{Delta}IEC mice and Caco-2 cells lacking HK2, we identified peptidyl-prolyl cis-trans isomerase (PPIF) as a key target of HK2-mediated regulation of mitochondrial permeability and repression of cell-death during intestinal inflammation. The microbiota strongly regulated HK2 expression and activity. The microbially-derived short-chain fatty acid (SCFA) butyrate repressed HK2 expression and oral supplementation protected wildtype but not Hk2{Delta}IEC mice from DSS colitis. Our findings define a novel mechanism how butyrate may act as a protective factor for intestinal barrier homeostasis and suggest targeted HK2 inhibition as a promising therapeutic avenue in intestinal inflammation.

immunology↗