Delineating a serotonin 1B receptor circuit for appetite suppression in mice

The Journal of experimental medicine

2022 Aug 01

Li, L;Wyler, SC;León-Mercado, LA;Xu, B;Oh, Y;Swati, ;Chen, X;Wan, R;Arnold, AG;Jia, L;Wang, G;Nautiyal, K;Hen, R;Sohn, JW;Liu, C;
PMID: 35796804 | DOI: 10.1084/jem.20212307

Triptans are a class of commonly prescribed antimigraine drugs. Here, we report a previously unrecognized role for them to suppress appetite in mice. In particular, frovatriptan treatment reduces food intake and body weight in diet-induced obese mice. Moreover, the anorectic effect depends on the serotonin (5-HT) 1B receptor (Htr1b). By ablating Htr1b in four different brain regions, we demonstrate that Htr1b engages in spatiotemporally segregated neural pathways to regulate postnatal growth and food intake. Moreover, Htr1b in AgRP neurons in the arcuate nucleus of the hypothalamus (ARH) contributes to the hypophagic effects of HTR1B agonists. To further study the anorexigenic Htr1b circuit, we generated Htr1b-Cre mice. We find that ARH Htr1b neurons bidirectionally regulate food intake in vivo. Furthermore, single-nucleus RNA sequencing analyses revealed that Htr1b marks a subset of AgRP neurons. Finally, we used an intersectional approach to specifically target these neurons (Htr1bAgRP neurons). We show that they regulate food intake, in part, through a Htr1bAgRP→PVH circuit.

Tissue-specific expression of insulin receptor isoforms in obesity/type 2 diabetes mouse models

Journal of cellular and molecular medicine

2021 Mar 19

Moruzzi, N;Lazzeri-Barcelo, F;Valladolid-Acebes, I;Moede, T;Paschen, M;Leibiger, B;Berggren, PO;Leibiger, IB;
PMID: 33742502 | DOI: 10.1111/jcmm.16452

The two insulin receptor (IR) isoforms IR-A and IR-B are responsible for the pleiotropic actions of insulin and insulin-like growth factors. Consequently, changes in IR isoform expression and in the bioavailability of their ligands will impact on IR-mediated functions. Although alteration of IR isoform expression has been linked to insulin resistance, knowledge of IR isoform expression and mechanisms underlying tissue/cell-type-specific changes in metabolic disease are lacking. Using mouse models of obesity/diabetes and measuring the mRNA of the IR isoforms and mRNA/protein levels of total IR, we provide a data set of IR isoform expression pattern that documents changes in a tissue-dependent manner. Combining tissue fractionation and a new in situ mRNA hybridization technology to visualize the IR isoforms at cellular resolution, we explored the mechanism underlying the change in IR isoform expression in perigonadal adipose tissue, which is mainly caused by tissue remodelling, rather than by a shift in IR alternative splicing in a particular cell type, e.g. adipocytes.

Macrophages and neutrophils are necessary for ER stress-induced β cell loss

Cell reports

2022 Aug 23

Yang, B;Yang, L;Wang, Y;Maddison, LA;Tang, Z;Haigh, S;Gong, Y;Zhang, Y;Covington, BA;Bosma, KJ;Tong, X;Page-McCaw, P;Gannon, M;Deng, Q;Chen, W;
PMID: 36001973 | DOI: 10.1016/j.celrep.2022.111255

Persistent endoplasmic reticulum (ER) stress induces islet inflammation and β cell loss. How islet inflammation contributes to β cell loss remains uncertain. We have reported previously that chronic overnutrition-induced ER stress in β cells causes Ripk3-mediated islet inflammation, macrophage recruitment, and a reduction of β cell numbers in a zebrafish model. We show here that β cell loss results from the intricate communications among β cells, macrophages, and neutrophils. Macrophage-derived Tnfa induces cxcl8a in β cells. Cxcl8a, in turn, attracts neutrophils to macrophage-contacted "hotspots" where β cell loss occurs. We also show potentiation of chemokine expression in stressed mammalian β cells by macrophage-derived TNFA. In Akita and db/db mice, there is an increase in CXCL15-positive β cells and intra-islet neutrophils. Blocking neutrophil recruitment in Akita mice preserves β cell mass and slows diabetes progression. These results reveal an important role of neutrophils in persistent ER stress-induced β cell loss.

Prolonged breastfeeding protects from obesity by hypothalamic action of hepatic FGF21

Nature metabolism

2022 Jul 01

Pena-Leon, V;Folgueira, C;Barja-Fernández, S;Pérez-Lois, R;Da Silva Lima, N;Martin, M;Heras, V;Martinez-Martinez, S;Valero, P;Iglesias, C;Duquenne, M;Al-Massadi, O;Beiroa, D;Souto, Y;Fidalgo, M;Sowmyalakshmi, R;Guallar, D;Cunarro, J;Castelao, C;Senra, A;González-Saenz, P;Vázquez-Cobela, R;Leis, R;Sabio, G;Mueller-Fielitz, H;Schwaninger, M;López, M;Tovar, S;Casanueva, FF;Valjent, E;Diéguez, C;Prevot, V;Nogueiras, R;Seoane, LM;
PMID: 35879461 | DOI: 10.1038/s42255-022-00602-z

Early-life determinants are thought to be a major factor in the rapid increase of obesity. However, while maternal nutrition has been extensively studied, the effects of breastfeeding by the infant on the reprogramming of energy balance in childhood and throughout adulthood remain largely unknown. Here we show that delayed weaning in rat pups protects them against diet-induced obesity in adulthood, through enhanced brown adipose tissue thermogenesis and energy expenditure. In-depth metabolic phenotyping in this rat model as well as in transgenic mice reveals that the effects of prolonged suckling are mediated by increased hepatic fibroblast growth factor 21 (FGF21) production and tanycyte-controlled access to the hypothalamus in adulthood. Specifically, FGF21 activates GABA-containing neurons expressing dopamine receptor 2 in the lateral hypothalamic area and zona incerta. Prolonged breastfeeding thus constitutes a protective mechanism against obesity by affecting long-lasting physiological changes in liver-to-hypothalamus communication and hypothalamic metabolic regulation.

An H2R-dependent medial septum histaminergic circuit mediates feeding behavior

Current biology : CB

2022 Mar 23

Xu, L;Lin, W;Zheng, Y;Chen, J;Fang, Z;Tan, N;Hu, W;Guo, Y;Wang, Y;Chen, Z;
PMID: 35338850 | DOI: 10.1016/j.cub.2022.03.010

Novel targets for treating feeding-related diseases are of great importance, and histamine has long been considered an anorexigenic agent. However, understanding its functions in feeding in a circuit-specific way is still limited. Here, we report a medial septum (MS)-projecting histaminergic circuit mediating feeding behavior. This MS-projecting histaminergic circuit is functionally inhibited during food consumption, and bidirectionally modulates feeding behavior via downstream H2, but not H1, receptors on MS glutamatergic neurons. Further, we observed a pathological decrease of histamine 2 receptors (H2Rs) expression in MS glutamatergic neurons in diet-induced obesity (DIO) mice. Genetically, down-regulation of H2Rs expression in MS glutamatergic neurons accelerates body-weight gain. Importantly, chronic activation of H2Rs in MS glutamatergic neurons (with its clinical agonist amthamine) significantly slowed down the body-weight gain in DIO mice, providing a possible clinical utility to treat obesity. Together, our results demonstrate that this MS-projecting histaminergic circuit is critically involved in feeding, and H2Rs in MS glutamatergic neurons is a promising target for treating body-weight problems.

Respiratory chain dysfunction in perifascicular muscle fibres in patients with dermatomyositis is associated with mitochondrial DNA depletion

Neuropathology and applied neurobiology

2022 Jul 27

Hedberg-Oldfors, C;Lindgren, U;Visuttijai, K;Lööf, D;Roos, S;Thomsen, C;Oldfors, A;
PMID: 35894812 | DOI: 10.1111/nan.12841

Patients with dermatomyositis suffer from reduced aerobic metabolism contributing to impaired muscle function, which has been linked to cytochrome c oxidase (COX) deficiency in muscle tissue. This mitochondrial respiratory chain dysfunction is typically seen in perifascicular regions, which also show the most intense inflammatory reaction along with capillary loss and muscle fibre atrophy. The objective of this study was to investigate the pathobiology of the oxidative phosphorylation deficiency in dermatomyositis.Muscle biopsy specimens with perifascicular COX deficiency from five juveniles and seven adults with dermatomyositis were investigated. We combined immunohistochemical analyses of subunits in the respiratory chain including complex I (subunit NDUFB8), complex II (succinate dehydrogenase, subunit SDHB) and complex IV (COX, subunit MTCO1) with in situ hybridization, next generation deep sequencing and quantitative PCR.There was a profound deficiency of complexes I and IV in the perifascicular regions with enzyme histochemical COX deficiency, whereas succinate dehydrogenase activity and complex II were preserved. In situ hybridization of mitochondrial RNA showed depletion of mitochondrial DNA (mtDNA) transcripts in the perifascicular regions. Analysis of mtDNA by next generation deep sequencing and quantitative PCR in affected muscle regions showed an overall reduction of mtDNA copy number particularly in the perifascicular regions.The respiratory chain dysfunction in dermatomyositis muscle is associated with mtDNA depletion causing deficiency of complexes I and IV, which are partially encoded by mtDNA, whereas complex II, which is entirely encoded by nuclear DNA is preserved. The depletion of mtDNA indicates a perturbed replication of mtDNA explaining the muscle pathology and the disturbed aerobic metabolism.This article is protected by

Chemogenetic strategies at whole-body, or specifically within VMH, confirm phenotype Relaxin/insulin-like family peptide receptor 4 (Rxfp4) expressing hypothalamic neurons modulate food intake and preference in mice

Molecular metabolism

2022 Sep 29

Lewis, JE;Woodward, OR;Nuzzaci, D;Smith, CA;Adriaenssens, AE;Billing, L;Brighton, C;Phillips, BU;Tadross, JA;Kinston, SJ;Ciabatti, E;Göttgens, B;Tripodi, M;Hornigold, D;Baker, D;Gribble, FM;Reimann, F;
PMID: 36184065 | DOI: 10.1016/j.molmet.2022.101604

Insulin-like peptide 5 (INSL5) signalling, through its cognate receptor relaxin/insulin-like-family-peptide-receptor-4 (RXFP4), has been reported to be orexigenic, and the preference for high fat diet (HFD) observed in wildtype mice is altered in Rxfp4 knock-out mice. In this study, we used a new Rxfp4-Cre mouse model to investigate the mechanisms underlying these observations.We generated transgenic Rxfp4-Cre mice and investigated central expression of Rxfp4 by RT-qPCR, RNAscope and intraparenchymal infusion of INSL5. Rxfp4-expressing cells were chemogenetically manipulated in global Cre-reporter mice using designer receptors exclusively activated by designer drugs (DREADDs) or after stereotactic injection of Cre-dependent AAV-DIO-Dq-DREADD targeting a population located in the ventromedial hypothalamus (RXFP4VMH). Food intake and feeding motivation were assessed in the presence and absence of a DREADD agonist. Rxfp4-expressing cells in the hypothalamus were characterised by single-cell RNA-sequencing (scRNAseq) and the connectivity of RXFP4VMH cells was investigated using viral tracing.Rxfp4-Cre mice displayed Cre-reporter expression in the hypothalamus and active expression of Rxfp4 in the adult mouse brain was confirmed by RT-qPCR and RNAscope. Functional receptor expression was supported by cAMP-responses to INSL5 application in ex vivo brain slices and increased HFD and highly palatable liquid meal (HPM), but not chow, intake after intra-VMH INSL5 infusion. scRNAseq of hypothalamic RXFP4 neurons defined a cluster expressing VMH markers, alongside known appetite-modulating neuropeptide receptors (Mc4r, Cckar and Nmur2). Viral tracing demonstrated RXFP4VMH neural projections to nuclei implicated in hedonic feeding behaviour. Whole body chemogenetic inhibition (Di-DREADD) of Rxfp4-expressing cells, mimicking physiological INSL5-RXFP4 Gi-signalling, increased intake of HFD and HPM, but not chow, whilst activation (Dq-DREADD), either at whole body level or specifically within the VMH, reduced HFD and HPM intake and motivation to work for HPM.These findings identify RXFP4VMH neurons as regulators of food intake and preference and reveal hypothalamic RXFP4 signalling as a target for feeding behaviour manipulation.

Phagocytosis in the retina promotes local insulin production in the eye

Nature metabolism

2023 Feb 01

Iker Etchegaray, J;Kelley, S;Penberthy, K;Karvelyte, L;Nagasaka, Y;Gasperino, S;Paul, S;Seshadri, V;Raymond, M;Marco, AR;Pinney, J;Stremska, M;Barron, B;Lucas, C;Wase, N;Fan, Y;Unanue, E;Kundu, B;Burstyn-Cohen, T;Perry, J;Ambati, J;Ravichandran, KS;
PMID: 36732622 | DOI: 10.1038/s42255-022-00728-0

The retina is highly metabolically active, relying on glucose uptake and aerobic glycolysis. Situated in close contact to photoreceptors, a key function of cells in the retinal pigment epithelium (RPE) is phagocytosis of damaged photoreceptor outer segments (POS). Here we identify RPE as a local source of insulin in the eye that is stimulated by POS phagocytosis. We show that Ins2 messenger RNA and insulin protein are produced by RPE cells and that this production correlates with RPE phagocytosis of POS. Genetic deletion of phagocytic receptors ('loss of function') reduces Ins2, whereas increasing the levels of the phagocytic receptor MerTK ('gain of function') increases Ins2 production in male mice. Contrary to pancreas-derived systemic insulin, RPE-derived local insulin is stimulated during starvation, which also increases RPE phagocytosis. Global or RPE-specific Ins2 gene deletion decreases retinal glucose uptake in starved male mice, dysregulates retinal physiology, causes defects in phototransduction and exacerbates photoreceptor loss in a mouse model of retinitis pigmentosa. Collectively, these data identify RPE cells as a phagocytosis-induced local source of insulin in the retina, with the potential to influence retinal physiology and disease.

Dual roles of hexokinase 2 in shaping microglial function by gating glycolytic flux and mitochondrial activity

Nature metabolism

2022 Dec 01

Hu, Y;Cao, K;Wang, F;Wu, W;Mai, W;Qiu, L;Luo, Y;Ge, WP;Sun, B;Shi, L;Zhu, J;Zhang, J;Wu, Z;Xie, Y;Duan, S;Gao, Z;
PMID: 36536134 | DOI: 10.1038/s42255-022-00707-5

Microglia continuously survey the brain parenchyma and actively shift status following stimulation. These processes demand a unique bioenergetic programme; however, little is known about the metabolic determinants in microglia. By mining large datasets and generating transgenic tools, here we show that hexokinase 2 (HK2), the most active isozyme associated with mitochondrial membrane, is selectively expressed in microglia in the brain. Genetic ablation of HK2 reduced microglial glycolytic flux and energy production, suppressed microglial repopulation, and attenuated microglial surveillance and damage-triggered migration in male mice. HK2 elevation is prominent in immune-challenged or disease-associated microglia. In ischaemic stroke models, however, HK2 deletion promoted neuroinflammation and potentiated cerebral damages. The enhanced inflammatory responses after HK2 ablation in microglia are associated with aberrant mitochondrial function and reactive oxygen species accumulation. Our study demonstrates that HK2 gates both glycolytic flux and mitochondrial activity to shape microglial functions, changes of which contribute to metabolic abnormalities and maladaptive inflammation in brain diseases.

Insulin increases sensory nerve density and reflex bronchoconstriction in obese mice

JCI insight

2022 Sep 15

Calco, GN;Maung, JN;Jacoby, DB;Fryer, AD;Nie, Z;
PMID: 36107629 | DOI: 10.1172/jci.insight.161898

Obesity-induced asthma responds poorly to all current pharmacological interventions, including steroids; suggesting that classic, eosinophilic inflammation is not a mechanism. As insulin resistance and hyperinsulinemia are common in obese individuals and associated with increased risk of asthma, we used diet-induced obese mice to study how insulin induces airway hyperreactivity. Inhaled 5-HT or methacholine induced dose dependent bronchoconstriction that was significantly potentiated in obese mice. Cutting the vagus nerves eliminated bronchoconstriction in both obese and non-obese animals indicating it was mediated by a neural reflex. There was significantly greater density of airway sensory nerves in obese than in non-obese mice. Deleting insulin receptors on sensory nerves prevented the increase in sensory nerve density and prevented airway hyperreactivity in obese mice with hyperinsulinemia. Our data demonstrate that high levels of insulin drives obesity-induced airway hyperreactivity by increasing sensory innervation of the lung. Therefore, pharmacological interventions to control metabolic syndrome and limit reflex-mediated bronchoconstriction may be a more effective approach to reduce asthma exacerbations in obese and asthmatic patients.

Large neutral amino acid levels tune perinatal neuronal excitability and survival

Cell

2023 Mar 24

Knaus, LS;Basilico, B;Malzl, D;Gerykova Bujalkova, M;Smogavec, M;Schwarz, LA;Gorkiewicz, S;Amberg, N;Pauler, FM;Knittl-Frank, C;Tassinari, M;Maulide, N;Rülicke, T;Menche, J;Hippenmeyer, S;Novarino, G;
PMID: 36996814 | DOI: 10.1016/j.cell.2023.02.037

Little is known about the critical metabolic changes that neural cells have to undergo during development and how temporary shifts in this program can influence brain circuitries and behavior. Inspired by the discovery that mutations in SLC7A5, a transporter of metabolically essential large neutral amino acids (LNAAs), lead to autism, we employed metabolomic profiling to study the metabolic states of the cerebral cortex across different developmental stages. We found that the forebrain undergoes significant metabolic remodeling throughout development, with certain groups of metabolites showing stage-specific changes, but what are the consequences of perturbing this metabolic program? By manipulating Slc7a5 expression in neural cells, we found that the metabolism of LNAAs and lipids are interconnected in the cortex. Deletion of Slc7a5 in neurons affects the postnatal metabolic state, leading to a shift in lipid metabolism. Additionally, it causes stage- and cell-type-specific alterations in neuronal activity patterns, resulting in a long-term circuit dysfunction.

Post-fast refeeding enhances intestinal stem cell-mediated regeneration and tumourigenesis through mTORC1-dependent polyamine synthesis

Research square

2023 Jan 10

Imada, S;Shin, H;Khawaled, S;Meckelmann, S;Whittaker, C;Correa, R;Pradhan, D;Calibasi, G;Nascentes, LN;Allies, G;Wittenhofer, P;Schmitz, O;Roper, J;Vinolo, M;Cheng, CW;Tasdogan, A;Yilmaz, ÃM;
PMID: 36711807 | DOI: 10.21203/rs.3.rs-2320717/v1

For more than a century, fasting regimens have improved health, lifespan, and tissue regeneration in diverse organisms, including humans. However, how fasting and post-fast refeeding impact adult stem cells and tumour formation has yet to be explored in depth. Here, we demonstrate that post-fast refeeding increases intestinal stem cell (ISC) proliferation and tumour formation: Post-fast refeeding augments the regenerative capacity of Lgr5+ intestinal stem cells (ISCs), and loss of the tumour suppressor Apc in ISCs under post-fast refeeding leads to a higher tumour incidence in the small intestine and colon than in the fasted or ad libitum (AL) fed states. This demonstrates that post-fast refeeding is a distinct state. Mechanistically, we discovered that robust induction of mTORC1 in post-fast-refed ISCs increases protein synthesis via polyamine metabolism to drive these changes, as inhibition of mTORC1, polyamine metabolite production, or protein synthesis abrogates the regenerative or tumourigenic effects of post-fast refeeding. Thus, fast-refeeding cycles must be carefully considered when planning diet-based strategies for regeneration without increasing cancer risk, as post-fast refeeding leads to a burst not only in stem cell-driven regeneration but also in tumourigenicity.

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	Description
sense Example: Hs-LAG3-sense	Standard probes for RNA detection are in antisense. Sense probe is reverse complent to the corresponding antisense probe.
Intron# Example: Mm-Htt-intron2	Probe targets the indicated intron in the target gene, commonly used for pre-mRNA detection
Pool/Pan Example: Hs-CD3-pool (Hs-CD3D, Hs-CD3E, Hs-CD3G)	A mixture of multiple probe sets targeting multiple genes or transcripts
No-XSp Example: Hs-PDGFB-No-XMm	Does not cross detect with the species (Sp)
XSp Example: Rn-Pde9a-XMm	designed to cross detect with the species (Sp)
O# Example: Mm-Islr-O1	Alternative design targeting different regions of the same transcript or isoforms
CDS Example: Hs-SLC31A-CDS	Probe targets the protein-coding sequence only
EnEm	Probe targets exons n and m
En-Em	Probe targets region from exon n to exon m
Retired Nomenclature
tvn Example: Hs-LEPR-tv1	Designed to target transcript variant n
ORF Example: Hs-ACVRL1-ORF	Probe targets open reading frame
UTR Example: Hs-HTT-UTR-C3	Probe targets the untranslated region (non-protein-coding region) only
5UTR Example: Hs-GNRHR-5UTR	Probe targets the 5' untranslated region only
3UTR Example: Rn-Npy1r-3UTR	Probe targets the 3' untranslated region only
Pan Example: Pool	A mixture of multiple probe sets targeting multiple genes or transcripts

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