Activation of Gs signaling in mouse enteroendocrine K-cells greatly improves obesity- and diabetes-related metabolic deficits

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Abstract

Following a meal, glucagon-like peptide-1 (GLP1) and glucose-dependent insulinotropic polypeptide (GIP), the two major incretins promoting insulin release, are secreted from specialized enteroendocrine cells (L- and K-cells, respectively). Although GIP is the dominant incretin in humans, the detailed molecular mechanisms governing its release remain to be explored. GIP secretion is regulated by the activity of G protein-coupled receptors (GPCRs) expressed by K-cells. GPCRs couple to one or more specific classes of heterotrimeric G proteins. In the present study, we focused on the potential metabolic roles of K-cell Gs. First, we generated a mouse model that allowed us to selectively stimulate K-cell Gs signaling. Second, we generated a mouse strain harboring an inactivating mutation of Gnas, the gene encoding the alpha-subunit of Gs, selectively in K-cells. Metabolic phenotyping studies showed that acute or chronic stimulation of K-cell Gs signaling greatly improved impaired glucose homeostasis in obese mice and in a mouse model of type 2 diabetes, due to enhanced GIP secretion. In contrast, K-cell-specific Gnas knockout mice displayed markedly reduced plasma GIP levels. These data strongly suggest that strategies aimed at enhancing K-cell Gs signaling may prove useful for the treatment of diabetes and related metabolic diseases.

Authors

Antwi-Boasiako Oteng, Liu Liu, Yinghong Cui, Oksana Gavrilova, Huiyan Lu, Min Chen, Lee S. Weinstein, Jonathan E. Campbell, Jo E. Lewis, Fiona M. Gribble, Frank Reimann, Jürgen Wess

MOGAT3-Mediated DAG Accumulation Drives Acquired Resistance to Anti-BRAF/EGFR Therapy in BRAFV600E-Mutant Metastatic Colorectal Cancer

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Abstract

BRAFV600E-mutant metastatic colorectal cancer (mCRC) is associated with poor prognosis. The combination of anti-BRAF/EGFR (encorafenib/cetuximab) treatment for patients with BRAFV600E-mutant mCRC improved clinical benefits; unfortunately, inevitable acquired resistance limits the treatment outcome, and the mechanism has not been validated. Here, we discovered that monoacylglycerol O-Acyltransferase 3 (MOGAT3) mediated diacylglycerol (DAG) accumulation contributed to acquired resistance to encorafenib/cetuximab by dissecting BRAFV600E-mutant mCRC patient-derived xenograft (PDX) model exposed to encorafenib/cetuximab administration. Mechanistically, upregulated MOGAT3 promotes DAG synthesis and reduces fatty acid oxidation (FAO)-promoting DAG accumulation and activating PKCα-CRAF-MEK-ERK, driving acquired resistance. Resistance-induced hypoxia promotes MOGAT3 transcriptional elevation; simultaneously, MOGAT3-mediated DAG accumulation increases HIF1A expression in translation level through PKCα-CRAF-eIF4E activation, strengthening the resistance status. Intriguingly, reducing intratumoral DAG by fenofibrate or Pf-06471553 restores the antitumor efficacy of encorafenib/cetuximab on resistant BRAFV600E-mutant mCRC, interrupted PKCα-CRAF-MEK-ERK signaling. These findings reveal the critical metabolite DAG as a modulator of encorafenib/cetuximab efficacy in BRAFV600E-mutant mCRC, suggesting that fenofibrate may prove beneficial for resistant BRAFV600E-mutant mCRC patients.

Authors

Jiawei Wang, Huogang Wang, Wei Zhou, Xin Luo, Huijuan Wang, Qing Meng, Jiaxin Chen, Xiaoyu Chen, Yinqiang Liu, David W. Chan, Zhenyu Ju, Zhangfa Song

Delayed reinforcement of costimulation improves the efficacy of mRNA vaccines in mice

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Abstract

mRNA vaccines have demonstrated efficacy during the COVID-19 pandemic and are now being investigated for multiple diseases. However, concerns linger about the durability of immune responses, and the high incidence of breakthrough infections among vaccinated individuals highlights the need for improved mRNA vaccines. In this study, we investigated the effects of reinforcing costimulation via 4-1BB, a member of the TNF receptor superfamily, on immune responses elicited by mRNA vaccines. We first immunized mice with mRNA vaccines, followed by treatment with 4-1BB costimulatory antibodies to reinforce the 4-1BB pathway at different timepoints post-vaccination. Consistent with prior studies, reinforcing 4-1BB costimulation on the day of vaccination did not result in a substantial improvement of vaccine responses. However, reinforcing 4-1BB costimulation at day 4 post-vaccination, when 4-1BB expression levels were highest, resulted in a profound improvement of CD8 T cell responses associated with enhanced protection against pathogen challenges. A similar clinical benefit was observed in a therapeutic cancer vaccine model. We also report time-dependent effects with OX40, another costimulatory molecule of the TNF receptor superfamily. These findings demonstrate that delayed reinforcement of costimulation may exert an immunologic benefit, providing insights for the development of more effective mRNA vaccines for infectious diseases and cancer.

Authors

Sarah Sanchez, Tanushree Dangi, Bakare Awakoaiye, Min Han Lew, Nahid Irani, Slim Fourati, Pablo Penaloza-MacMaster

Androgen signaling restricts glutaminolysis to drive sex-specific Th17 metabolism in allergic airway inflammation

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Abstract

Females have an increased prevalence of many Th17 cell-mediated diseases, including asthma. Androgen signaling decreases Th17 cell-mediated airway inflammation, and Th17 cells rely on glutaminolysis. However, it remains unclear whether androgen receptor (AR) signaling modifies glutamine metabolism to suppress Th17 cell-mediated airway inflammation. We show that Th17 cells from male humans and mice had decreased glutaminolysis compared to females, and that AR signaling attenuated Th17 cell mitochondrial respiration and glutaminolysis in mice. Using allergen-induced airway inflammation mouse models, we determined females had a selective reliance upon glutaminolysis for Th17-mediated airway inflammation, and AR signaling attenuated glutamine uptake in CD4+ T cells by reducing expression of glutamine transporters. Minimal reliance on glutamine uptake in male Th17 cells compared to female Th17 cells was also found in circulating T cells from patients with asthma. AR signaling thus attenuates glutaminolysis, demonstrating sex-specific metabolic regulation of Th17 cells with implications for Th17 or glutaminolysis targeted therapeutics.

Authors

Nowrin U. Chowdhury, Jacqueline-Yvonne Cephus, Emely Henriquez Pilier, Melissa M. Wolf, Matthew Z. Madden, Shelby N. Kuehnle, Kaitlin E. McKernan, Erin Q. Jennings, Emily N. Arner, Darren R. Heintzman, Channing Chi, Ayaka Sugiura, Matthew T. Stier, Kelsey Voss, Xiang Ye, Kennedi L. Scales, Evan S. Krystofiak, Vivek D. Gandhi, Robert D. Guzy, Katherine N. Cahill, Anne I. Sperling, R. Stokes Peebles Jr., Jeffrey C. Rathmell, Dawn C. Newcomb

EMC3 regulates trafficking and pulmonary toxicity of the SFTPC^I73T mutation associated with interstitial lung disease

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Abstract

The most common mutation in surfactant protein C gene (SFTPC), SFTPCI73T, causes interstitial lung disease with few therapeutic options. We previously demonstrated that EMC3, an important component of the multiprotein endoplasmic reticulum membrane complex (EMC), is required for surfactant homeostasis in alveolar type 2 epithelial (AT2) cells at birth. In the present study, we investigated the role of EMC3 in the control of SFTPCI73T metabolism and its associated alveolar dysfunction. Using a knock-in mouse model phenocopying the I73T mutation, we demonstrated that conditional deletion of Emc3 in AT2 cells rescued alveolar remodeling/simplification defects in neonatal and adult mice. Proteomic analysis revealed that Emc3 depletion reversed the disruption of vesicle trafficking pathways and rescued the mitochondrial dysfunction associated with I73T mutation. Affinity purification-mass spectrometry analysis identified potential EMC3 interacting proteins in lung AT2 cells, including Valosin Containing Protein (VCP) and its interactors. Treatment of SftpcI73T knock-in mice and SFTPCI73T expressing iAT2 cells derived from SFTPCI73T patient-specific iPSCs with the specific VCP inhibitor CB5083 restored alveolar structure and SFTPCI73T trafficking respectively. Taken together, the present work identifies the EMC complex and VCP in the metabolism of the disease-associated SFTPCI73T mutant, providing novel therapeutical targets for SFTPCI73T-associated interstitial lung disease.

Authors

Xiaofang Tang, Wei Wei, Yuqing Sun, Timothy E. Weaver, Ernesto S. Nakayasu, Geremy Clair, John M. Snowball, Cheng-Lun Na, Karen S. Apsley, Emily P. Martin, Darrell N. Kotton, Konstantinos-Dionysios Alysandratos, Jiuzhou Huo, Jeffery D. Molkentin, William A. Gower, Xinhua Lin, Jeffrey A. Whitsett

TREM2 aggravates sepsis by inhibiting fatty acid oxidation via the SHP1/BTK axis

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Abstract

Impaired fatty acid oxidation (FAO) and the therapeutic benefits of FAO restoration have been revealed in sepsis. However, the regulatory factors contributing to FAO dysfunction during sepsis remain inadequately clarified. In this study, we identified a subset of lipid-associated macrophages characterized by high expression of trigger receptor expressed on myeloid cells 2 (TREM2) and demonstrated that TREM2 acted as a suppressor of FAO to increase the susceptibility to sepsis. TREM2 expression was markedly up-regulated in sepsis patients and correlated with the severity of sepsis. Knock out of TREM2 in macrophages improved the survival rate and reduced inflammation and organ injuries of sepsis mice. Notably, TREM2-deficient mice exhibited decreased triglyceride accumulation and an enhanced FAO rate. Further observations showed that the blockade of FAO substantially abolished the alleviated symptoms observed in TREM2 knockout mice. Mechanically, we demonstrated that TREM2 interacted with the phosphatase SHP1 to inhibit Bruton tyrosine kinas (BTK)-mediated FAO in sepsis. Our findings expand the understanding of FAO dysfunction in sepsis and reveal TREM2 as a critical regulator of FAO, which may provide a promising target for the clinical treatment of sepsis.

Authors

Siqi Ming, Xingyu Li, Qiang Xiao, Siying Qu, Qiaohua Wang, Qiongyan Fang, Pingping Liang, Yating Xu, Jingwen Yang, Yongqiang Yang, Xi Huang, Yongjian Wu

The Nr4a family regulates intrahepatic Treg proliferation and liver fibrosis in MASLD models

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Abstract

Nonalcoholic steatohepatitis (NASH) is a chronic progressive liver disease and highly prevalent worldwide. NASH is characterized by hepatic steatosis, inflammation, fibrosis and liver damage, which eventually results in liver dysfunction due to cirrhosis or hepatocellular carcinoma. However, the cellular and molecular mechanisms underlying NASH progression remain largely unknown. Here, we found an increase of Nr4a family of orphan nuclear receptors expression in intrahepatic T cells from mice with diet-induced NASH. Loss of Nr4a1 and Nr4a2 in T cell (dKO) ameliorated liver cell death and fibrosis, thereby mitigating liver dysfunction in NASH mice. dKO resulted in reduction of infiltrated macrophages and Th1/Th17 cells, whereas massive accumulation of T regulatory (Treg) cells in the liver of NASH mice. Combined single-cell RNA transcriptomic and TCR sequencing analysis revealed that intrahepatic dKO Tregs exhibited enhanced TIGIT and IL10 expression and were clonally expanded during NASH progression. Mechanistically, we found that dKO Tregs expressed high levels of Batf which promotes Treg cell proliferation and function upon TCR stimulation. Collectively, our findings not only provide an insight into the impact of intrahepatic Treg cells on NASH pathogenesis, but also suggest a therapeutic potential of targeting of Nr4a family to treat the disease.

Authors

Daisuke Aki, Taeko Hayakawa, Tanakorn Srirat, Shigeyuki Shichino, Minako Ito, Shin-Ichiroh Saitoh, Setsuko Mise-Omata, Akihiko Yoshimura

Adipocyte lipin 1 expression associates with human metabolic health and regulates systemic metabolism in mice

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Abstract

Dysfunctional adipose tissue is believed to promote the development of hepatic steatosis and systemic insulin resistance, but many of the mechanisms involved are still unclear. Lipin 1 catalyzes the conversion of phosphatidic acid to diacylglycerol (DAG), the penultimate step of triglyceride synthesis, which is essential for lipid storage. Herein we found that adipose tissue LPIN1 expression is decreased in people with obesity compared to lean subjects, and low LPIN1 expression correlated with multi-tissue insulin resistance and increased rates of hepatic de novo lipogenesis. Comprehensive metabolic and multi-omic phenotyping demonstrated that adipocyte-specific Lpin1–/– mice had a metabolically-unhealthy phenotype, including liver and skeletal muscle insulin resistance, hepatic steatosis, increased hepatic de novo lipogenesis, and transcriptomic signatures of metabolically associated steatohepatitis that was exacerbated by high-fat diets. We conclude that adipocyte lipin 1-mediated lipid storage is vital for preserving adipose tissue and systemic metabolic health, and its loss predisposes mice to metabolically associated steatohepatitis.

Authors

Andrew LaPoint, Jason M. Singer, Daniel Ferguson, Trevor M. Shew, M. Katie Renkemeyer, Hector H. Palacios, Rachael L. Field, Sireeesha Yerrathota, Roshan Kumari, Mahalakshmi Shankaran, Gordon I. Smith, Jun Yoshino, Mai He, Gary J. Patti, Marc K. Hellerstein, Samuel Klein, E. Matthew Morris, Jonathan R. Brestoff, Brian N. Finck, Andrew Lutkewitte

Transcription factor KROX20 marks epithelial stem cells for hair follicle formation

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Abstract

Epidermal stem cells control homeostasis and regeneration of skin and hair. In the hair follicle (HF) bulge of mammals, populations of slow-cycling stem cells regenerate the HF during cyclical rounds of anagen (growth), telogen (quiescence), and catagen (regression). Multipotent epidermal cells are also present in the HF above the bulge area, contributing to the formation and maintenance of sebaceous gland and upper and middle portions of the HF. Here, we report that the transcription factor Krox20 is enriched in an epidermal stem cell population located in the upper/ middle HF. Expression analyses and lineage tracing using inducible Krox20-CreERT showed that Krox20-lineage cells migrate out of this HF region and contribute to the formation of bulge in the HF, serving as ancestors of bulge stem cells. In vivo depletion of these cells arrests HF morphogenesis. This study identifies a novel marker for an epidermal stem cell population that is indispensable for hair homeostasis.

Authors

Elnaz Ghotbi, Edem Tchegnon, Zhiguo Chen, Stephen Li, Tracey Shipman, Yong Wang, Jenny Raman, Yumeng Zhang, Renee M. McKay, Chung-Ping Liao, Lu Q. Le

Reactive microglia partially envelop viable neurons in prion diseases

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Abstract

Microglia are recognized as the main cells in the central nervous system responsible for phagocytosis. The current study demonstrated that in prion disease, microglia effectively phagocytose prions or PrPSc during early preclinical stages. However, a critical shift occured in microglial activity during the late preclinical stage, transitioning from PrPSc uptake to establishing extensive neuron-microglia body-to-body cell contacts. This change was followed by a rapid accumulation of PrPSc in the brain. Microglia that enveloped neurons exhibited hypertrophic, cathepsin D-positive lysosomal compartments. However, most neurons undergoing envelopment were only partially encircled by microglia. Despite up to 40% of cortical neurons being partially enveloped at clinical stages, only a small percentage of envelopment proceeded to full engulfment. Partially enveloped neurons lacked apoptotic markers but showed signs of functional decline. Neuronal envelopment was independent of the CD11b pathway, previously associated with phagocytosis of newborn neurons during neurodevelopment. This phenomenon of partial envelopment was consistently observed across multiple prion-affected brain regions, various mouse-adapted strains, and different subtypes of sporadic Creutzfeldt-Jakob disease (sCJD) in humans. The current work describes a new phenomenon of partial envelopment of neurons by reactive microglia in the context of an actual neurodegenerative disease, not a disease model.

Authors

Natallia Makarava, Tarek Safadi, Olga Bocharova, Olga Mychko, Narayan P. Pandit, Kara Molesworth, Simone Baiardi, Li Zhang, Piero Parchi, Ilia V. Baskakov