Porniece Kumar, M;Cremer, AL;Klemm, P;Steuernagel, L;Sundaram, S;Jais, A;Hausen, AC;Tao, J;Secher, A;Pedersen, TÅ;Schwaninger, M;Wunderlich, FT;Lowell, BB;Backes, H;Brüning, JC;
PMID: 34931084 | DOI: 10.1038/s42255-021-00499-0
Insulin acts on neurons and glial cells to regulate systemic glucose metabolism and feeding. However, the mechanisms of insulin access in discrete brain regions are incompletely defined. Here we show that insulin receptors in tanycytes, but not in brain endothelial cells, are required to regulate insulin access to the hypothalamic arcuate nucleus. Mice lacking insulin receptors in tanycytes (IR∆Tan mice) exhibit systemic insulin resistance, while displaying normal food intake and energy expenditure. Tanycytic insulin receptors are also necessary for the orexigenic effects of ghrelin, but not for the anorexic effects of leptin. IR∆Tan mice exhibit increased agouti-related peptide (AgRP) neuronal activity, while displaying blunted AgRP neuronal adaptations to feeding-related stimuli. Lastly, a highly palatable food decreases tanycytic and arcuate nucleus insulin signalling to levels comparable to those seen in IR∆Tan mice. These changes are rooted in modifications of cellular stress responses and of mitochondrial protein quality control in tanycytes. Conclusively, we reveal a critical role of tanycyte insulin receptors in gating feeding-state-dependent regulation of AgRP neurons and systemic insulin sensitivity, and show that insulin resistance in tanycytes contributes to the pleiotropic manifestations of obesity-associated insulin resistance.
RSPO3 is important for trabecular bone and fracture risk in mice and humans
Nilsson, KH;Henning, P;Shahawy, ME;Nethander, M;Andersen, TL;Ejersted, C;Wu, J;Gustafsson, KL;Koskela, A;Tuukkanen, J;Souza, PPC;Tuckermann, J;Lorentzon, M;Ruud, LE;Lehtimäki, T;Tobias, JH;Zhou, S;Lerner, UH;Richards, JB;Movérare-Skrtic, S;Ohlsson, C;
PMID: 34389713 | DOI: 10.1038/s41467-021-25124-2
With increasing age of the population, countries across the globe are facing a substantial increase in osteoporotic fractures. Genetic association signals for fractures have been reported at the RSPO3 locus, but the causal gene and the underlying mechanism are unknown. Here we show that the fracture reducing allele at the RSPO3 locus associate with increased RSPO3 expression both at the mRNA and protein levels, increased trabecular bone mineral density and reduced risk mainly of distal forearm fractures in humans. We also demonstrate that RSPO3 is expressed in osteoprogenitor cells and osteoblasts and that osteoblast-derived RSPO3 is the principal source of RSPO3 in bone and an important regulator of vertebral trabecular bone mass and bone strength in adult mice. Mechanistic studies revealed that RSPO3 in a cell-autonomous manner increases osteoblast proliferation and differentiation. In conclusion, RSPO3 regulates vertebral trabecular bone mass and bone strength in mice and fracture risk in humans.
SLITRK5 is a negative regulator of hedgehog signaling in osteoblasts
Sun, J;Shin, DY;Eiseman, M;Yallowitz, AR;Li, N;Lalani, S;Li, Z;Cung, M;Bok, S;Debnath, S;Marquez, SJ;White, TE;Khan, AG;Lorenz, IC;Shim, JH;Lee, FS;Xu, R;Greenblatt, MB;
PMID: 34326333 | DOI: 10.1038/s41467-021-24819-w
Hedgehog signaling is essential for bone formation, including functioning as a means for the growth plate to drive skeletal mineralization. However, the mechanisms regulating hedgehog signaling specifically in bone-forming osteoblasts are largely unknown. Here, we identified SLIT and NTRK-like protein-5(Slitrk5), a transmembrane protein with few identified functions, as a negative regulator of hedgehog signaling in osteoblasts. Slitrk5 is selectively expressed in osteoblasts and loss of Slitrk5 enhanced osteoblast differentiation in vitro and in vivo. Loss of SLITRK5 in vitro leads to increased hedgehog signaling and overexpression of SLITRK5 in osteoblasts inhibits the induction of targets downstream of hedgehog signaling. Mechanistically, SLITRK5 binds to hedgehog ligands via its extracellular domain and interacts with PTCH1 via its intracellular domain. SLITRK5 is present in the primary cilium, and loss of SLITRK5 enhances SMO ciliary enrichment upon SHH stimulation. Thus, SLITRK5 is a negative regulator of hedgehog signaling in osteoblasts that may be attractive as a therapeutic target to enhance bone formation.
Claflin KE, Sandgren JA, Lambertz AM, Weidemann BJ, Littlejohn NK, Burnett CM, Pearson NA, Morgan DA, Gibson-Corley KN, Rahmouni K, Grobe JL.
PMID: 28263184 | DOI: 10.1172/JCI88641
Leptin contributes to the control of resting metabolic rate (RMR) and blood pressure (BP) through its actions in the arcuate nucleus (ARC). The renin-angiotensin system (RAS) and angiotensin AT1 receptors within the brain are also involved in the control of RMR and BP, but whether this regulation overlaps with leptin's actions is unclear. Here, we have demonstrated the selective requirement of the AT1A receptor in leptin-mediated control of RMR. We observed that AT1A receptors colocalized with leptin receptors (LEPRs) in the ARC. Cellular coexpression of AT1A and LEPR was almost exclusive to the ARC and occurred primarily within neurons expressing agouti-related peptide (AgRP). Mice lacking the AT1A receptor specifically in LEPR-expressing cells failed to show an increase in RMR in response to a high-fat diet and deoxycorticosterone acetate-salt (DOCA-salt) treatments, but BP control remained intact. Accordingly, loss of RMR control was recapitulated in mice lacking AT1A in AgRP-expressing cells. We conclude that angiotensin activates divergent mechanisms to control BP and RMR and that the brain RAS functions as a major integrator for RMR control through its actions at leptin-sensitive AgRP cells of the ARC.
Central anorexigenic actions of bile acids are mediated by TGR5
Perino, A;Velázquez-Villegas, LA;Bresciani, N;Sun, Y;Huang, Q;Fénelon, VS;Castellanos-Jankiewicz, A;Zizzari, P;Bruschetta, G;Jin, S;Baleisyte, A;Gioiello, A;Pellicciari, R;Ivanisevic, J;Schneider, BL;Diano, S;Cota, D;Schoonjans, K;
PMID: 34031591 | DOI: 10.1038/s42255-021-00398-4
Bile acids (BAs) are signalling molecules that mediate various cellular responses in both physiological and pathological processes. Several studies report that BAs can be detected in the brain1, yet their physiological role in the central nervous system is still largely unknown. Here we show that postprandial BAs can reach the brain and activate a negative-feedback loop controlling satiety in response to physiological feeding via TGR5, a G-protein-coupled receptor activated by multiple conjugated and unconjugated BAs2 and an established regulator of peripheral metabolism3-8. Notably, peripheral or central administration of a BA mix or a TGR5-specific BA mimetic (INT-777) exerted an anorexigenic effect in wild-type mice, while whole-body, neuron-specific or agouti-related peptide neuronal TGR5 deletion caused a significant increase in food intake. Accordingly, orexigenic peptide expression and secretion were reduced after short-term TGR5 activation. In vitro studies demonstrated that activation of the Rho-ROCK-actin-remodelling pathway decreases orexigenic agouti-related peptide/neuropeptide Y (AgRP/NPY) release in a TGR5-dependent manner. Taken together, these data identify a signalling cascade by which BAs exert acute effects at the transition between fasting and feeding and prime the switch towards satiety, unveiling a previously unrecognized role of physiological feedback mediated by BAs in the central nervous system.
Lui, JC;Raimann, A;Hojo, H;Dong, L;Roschger, P;Kikani, B;Wintergerst, U;Fratzl-Zelman, N;Jee, YH;Haeusler, G;Baron, J;
PMID: 35121733 | DOI: 10.1038/s41467-022-28318-4
SP7/Osterix is a transcription factor critical for osteoblast maturation and bone formation. Homozygous loss-of-function mutations in SP7 cause osteogenesis imperfecta type XII, but neomorphic (gain-of-new-function) mutations of SP7 have not been reported in humans. Here we describe a de novo dominant neomorphic missense variant (c.926 C > G:p.S309W) in SP7 in a patient with craniosynostosis, cranial hyperostosis, and long bone fragility. Histomorphometry shows increased osteoblasts but decreased bone mineralization. Mice with the corresponding variant also show a complex skeletal phenotype distinct from that of Sp7-null mice. The mutation alters the binding specificity of SP7 from AT-rich motifs to a GC-consensus sequence (typical of other SP family members) and produces an aberrant gene expression profile, including increased expression of Col1a1 and endogenous Sp7, but decreased expression of genes involved in matrix mineralization. Our study identifies a pathogenic mechanism in which a mutation in a transcription factor shifts DNA binding specificity and provides important in vivo evidence that the affinity of SP7 for AT-rich motifs, unique among SP proteins, is critical for normal osteoblast differentiation.
Rodríguez, JMM;Fonfara, S;Hetzel, U;Kipar, A;
PMID: 34955067 | DOI: 10.1177/03009858211062631
The sequence of pathological events in feline hypertrophic cardiomyopathy (fHCM) is still largely unknown, although we know that fHCM is characterized by interstitial remodeling in a macrophage-driven pro-inflammatory environment and that myocardial ischemia might contribute to its progression. This study aimed to gain further insights into the structural changes associated with interstitial remodeling in fHCM with special focus on the myocardial microvasculature and the phenotype of the interstitial cells. Twenty-eight hearts (16 hearts with fHCM and 12 without cardiac disease) were evaluated in the current study, with immunohistochemistry, RNA-in situ hybridization, and transmission electron microscopy. Morphometrical evaluations revealed a statistically significant lower microvascular density in fHCM. This was associated with structural alterations in capillaries that go along with a widening of the interstitium due to the accumulation of edema fluid, collagen fibers, and mononuclear cells that also proliferated locally. The interstitial cells were mainly of fibroblastic or vascular phenotype, with a substantial contribution of predominantly resident macrophages. A large proportion expressed CD34 mRNA, which suggests a progenitor cell potential. Our results indicate that microvascular alterations are key events in the pathogenesis of fHCM and that myocardial interstitial cell populations with CD34+ phenotype play a role in the pathogenesis of the disease.
International journal of molecular sciences
Son, M;Kim, GY;Yang, Y;Ha, S;Kim, J;Kim, D;Chung, HY;Moon, HR;Chung, KW;
PMID: 36902313 | DOI: 10.3390/ijms24054882
The peroxisome proliferator-activated receptor (PPAR) nuclear receptor has been an interesting target for the treatment of chronic diseases. Although the efficacy of PPAR pan agonists in several metabolic diseases has been well studied, the effect of PPAR pan agonists on kidney fibrosis development has not been demonstrated. To evaluate the effect of the PPAR pan agonist MHY2013, a folic acid (FA)-induced in vivo kidney fibrosis model was used. MHY2013 treatment significantly controlled decline in kidney function, tubule dilation, and FA-induced kidney damage. The extent of fibrosis determined using biochemical and histological methods showed that MHY2013 effectively blocked the development of fibrosis. Pro-inflammatory responses, including cytokine and chemokine expression, inflammatory cell infiltration, and NF-κB activation, were all reduced with MHY2013 treatment. To demonstrate the anti-fibrotic and anti-inflammatory mechanisms of MHY2013, in vitro studies were conducted using NRK49F kidney fibroblasts and NRK52E kidney epithelial cells. In the NRK49F kidney fibroblasts, MHY2013 treatment significantly reduced TGF-β-induced fibroblast activation. The gene and protein expressions of collagen I and α-smooth muscle actin were significantly reduced with MHY2013 treatment. Using PPAR transfection, we found that PPARγ played a major role in blocking fibroblast activation. In addition, MHY2013 significantly reduced LPS-induced NF-κB activation and chemokine expression mainly through PPARβ activation. Taken together, our results suggest that administration of the PPAR pan agonist effectively prevented renal fibrosis in both in vitro and in vivo models of kidney fibrosis, implicating the therapeutic potential of PPAR agonists against chronic kidney diseases.
El Mehdi, M;Takhlidjt, S;Devère, M;Arabo, A;Le Solliec, MA;Maucotel, J;Bénani, A;Nedelec, E;Duparc, C;Lefranc, B;Leprince, J;Anouar, Y;Prévost, G;Chartrel, N;Picot, M;
PMID: 35476025 | DOI: 10.1007/s00125-022-05706-5
26RFa (pyroglutamilated RFamide peptide [QRFP]) is a biologically active peptide that regulates glucose homeostasis by acting as an incretin and by increasing insulin sensitivity at the periphery. 26RFa is also produced by a neuronal population localised in the hypothalamus. In this study we investigated whether 26RFa neurons are involved in the hypothalamic regulation of glucose homeostasis.26Rfa+/+, 26Rfa-/- and insulin-deficient male C57Bl/6J mice were used in this study. Mice received an acute intracerebroventricular (i.c.v.) injection of 26RFa, insulin or the 26RFa receptor (GPR103) antagonist 25e and were subjected to IPGTTs, insulin tolerance tests, acute glucose-stimulated insulin secretion tests and pyruvate tolerance tests (PTTs). Secretion of 26RFa by hypothalamic explants after incubation with glucose, leptin or insulin was assessed. Expression and quantification of the genes encoding 26RFa, agouti-related protein, the insulin receptor and GPR103 were evaluated by quantitative reverse transcription PCR and RNAscope in situ hybridisation.Our data indicate that i.c.v.-injected 26RFa induces a robust antihyperglycaemic effect associated with an increase in insulin production by the pancreatic islets. In addition, we found that insulin strongly stimulates 26Rfa expression and secretion by the hypothalamus. RNAscope experiments revealed that neurons expressing 26Rfa are mainly localised in the lateral hypothalamic area, that they co-express the gene encoding the insulin receptor and that insulin induces the expression of 26Rfa in these neurons. Concurrently, the central antihyperglycaemic effect of insulin is abolished in the presence of a GPR103 antagonist and in 26RFa-deficient mice. Finally, our data indicate that the hypothalamic 26RFa neurons are not involved in the central inhibitory effect of insulin on hepatic glucose production, but mediate the central effects of the hormone on its own peripheral production.We have identified a novel mechanism in the hypothalamic regulation of glucose homeostasis, the 26RFa/GPR103 system, and we provide evidence that this neuronal peptidergic system is a key relay for the central regulation of glucose metabolism by insulin.
Peisker, F;Halder, M;Nagai, J;Ziegler, S;Kaesler, N;Hoeft, K;Li, R;Bindels, EMJ;Kuppe, C;Moellmann, J;Lehrke, M;Stoppe, C;Schaub, MT;Schneider, RK;Costa, I;Kramann, R;
PMID: 35641541 | DOI: 10.1038/s41467-022-30682-0
The cardiac vascular and perivascular niche are of major importance in homeostasis and during disease, but we lack a complete understanding of its cellular heterogeneity and alteration in response to injury as a major driver of heart failure. Using combined genetic fate tracing with confocal imaging and single-cell RNA sequencing of this niche in homeostasis and during heart failure, we unravel cell type specific transcriptomic changes in fibroblast, endothelial, pericyte and vascular smooth muscle cell subtypes. We characterize a specific fibroblast subpopulation that exists during homeostasis, acquires Thbs4 expression and expands after injury driving cardiac fibrosis, and identify the transcription factor TEAD1 as a regulator of fibroblast activation. Endothelial cells display a proliferative response after injury, which is not sustained in later remodeling, together with transcriptional changes related to hypoxia, angiogenesis, and migration. Collectively, our data provides an extensive resource of transcriptomic changes in the vascular niche in hypertrophic cardiac remodeling.
International journal of molecular sciences
Torz, L;Niss, K;Lundh, S;Rekling, JC;Quintana, CD;Frazier, SED;Mercer, AJ;Cornea, A;Bertelsen, CV;Gerstenberg, MK;Hansen, AMK;Guldbrandt, M;Lykkesfeldt, J;John, LM;Villaescusa, JC;Petersen, N;
PMID: 35328681 | DOI: 10.3390/ijms23063260
Restoring the control of food intake is the key to obesity management and prevention. The arcuate nucleus (ARC) of the hypothalamus is extensively being studied as a potential anti-obesity target. Animal studies showed that neuropeptide FF (NPFF) reduces food intake by its action in neuropeptide Y (NPY) neurons of the hypothalamic ARC, but the detailed mode of action observed in human neurons is missing, due to the lack of a human-neuron-based model for pharmacology testing. Here, we validated and utilized a human-neural-stem-cell-based (hNSC) model of ARC to test the effects of NPFF on cellular pathways and neuronal activity. We found that in the human neurons, decreased cAMP levels by NPFF resulted in a reduced rate of cytoplasmic calcium oscillations, indicating an inhibition of ARC NPY neurons. This suggests the therapeutic potential of NPFFR2 in obesity. In addition, we demonstrate the use of human-stem-cell-derived neurons in pharmacological applications and the potential of this model to address functional aspects of human hypothalamic neurons.
Ramírez, S;Haddad-Tóvolli, R;Radosevic, M;Toledo, M;Pané, A;Alcolea, D;Ribas, V;Milà-Guasch, M;Pozo, M;Obri, A;Eyre, E;Gómez-Valadés, AG;Chivite, I;Van Eeckhout, T;Zalachoras, I;Altirriba, J;Bauder, C;Imbernón, M;Garrabou, G;Garcia-Ruiz, C;Nogueiras, R;Soto, D;Gasull, X;Sandi, C;Brüning, JC;Fortea, J;Jiménez, A;Fernández-Checa, JC;Claret, M;
PMID: 35108514 | DOI: 10.1016/j.cmet.2021.12.023
Obesity and type 2 diabetes are associated with cognitive dysfunction. Because the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggest that pregnenolone's effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically unhealthy patients with obesity. Our data reveal an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders.
