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International Journal of Molecular... Sep 2022Obesity is a complex multifactorial disorder with genetic and environmental factors. There is an increase in the worldwide prevalence of obesity in both developed and... (Review)
Review
Obesity is a complex multifactorial disorder with genetic and environmental factors. There is an increase in the worldwide prevalence of obesity in both developed and developing countries. The development of genome-wide association studies (GWAS) and next-generation sequencing (NGS) has increased the discovery of genetic associations and awareness of monogenic and polygenic causes of obesity. The genetics of obesity could be classified into syndromic and non-syndromic obesity. Prader-Willi, fragile X, Bardet-Biedl, Cohen, and Albright Hereditary Osteodystrophy (AHO) syndromes are examples of syndromic obesity, which are associated with developmental delay and early onset obesity. Non-syndromic obesity could be monogenic, polygenic, or chromosomal in origin. Monogenic obesity is caused by variants of single genes while polygenic obesity includes several genes with the involvement of members of gene families. New advances in genetic testing have led to the identification of obesity-related genes. Leptin (), the leptin receptor (), proopiomelanocortin (), prohormone convertase 1 (), the melanocortin 4 receptor (), single-minded homolog 1 (), brain-derived neurotrophic factor (), and the neurotrophic tyrosine kinase receptor type 2 gene () have been reported as causative genes for obesity. NGS is now in use and emerging as a useful tool to search for candidate genes for obesity in clinical settings.
Topics: Brain-Derived Neurotrophic Factor; Genome-Wide Association Study; Humans; Leptin; Obesity; Pro-Opiomelanocortin; Proprotein Convertase 1; Receptor, Melanocortin, Type 4; Receptor, trkB; Receptors, Leptin
PubMed: 36232301
DOI: 10.3390/ijms231911005 -
Developmental Cell Jul 2021In mammals, hematopoietic stem cells (HSCs) engage in hematopoiesis throughout adult life within the bone marrow, where they produce the mature cells necessary to... (Review)
Review
In mammals, hematopoietic stem cells (HSCs) engage in hematopoiesis throughout adult life within the bone marrow, where they produce the mature cells necessary to maintain blood cell counts and immune function. In the bone marrow and spleen, HSCs are sustained in perivascular niches (microenvironments) associated with sinusoidal blood vessels-specialized veins found only in hematopoietic tissues. Endothelial cells and perivascular leptin receptor stromal cells produce the known factors required to maintain HSCs and many restricted progenitors in the bone marrow. Various other cells synthesize factors that maintain other restricted progenitors or modulate HSC or niche function. Recent studies identified new markers that resolve some of the heterogeneity among stromal cells and refine the localization of restricted progenitor niches. Other recent studies identified ways in which niches regulate HSC function and hematopoiesis beyond growth factors. We summarize the current understanding of hematopoietic niches, review recent progress, and identify important unresolved questions.
Topics: Blood Vessels; Bone Marrow; Endothelial Cells; Hematopoiesis; Humans; Intercellular Signaling Peptides and Proteins; Receptors, Leptin; Spleen; Stem Cell Niche; Stem Cells
PubMed: 34146467
DOI: 10.1016/j.devcel.2021.05.018 -
Cell Metabolism Dec 2023The peripheral nervous system harbors a remarkable potential to regenerate after acute nerve trauma. Full functional recovery, however, is rare and critically depends on...
The peripheral nervous system harbors a remarkable potential to regenerate after acute nerve trauma. Full functional recovery, however, is rare and critically depends on peripheral nerve Schwann cells that orchestrate breakdown and resynthesis of myelin and, at the same time, support axonal regrowth. How Schwann cells meet the high metabolic demand required for nerve repair remains poorly understood. We here report that nerve injury induces adipocyte to glial signaling and identify the adipokine leptin as an upstream regulator of glial metabolic adaptation in regeneration. Signal integration by leptin receptors in Schwann cells ensures efficient peripheral nerve repair by adjusting injury-specific catabolic processes in regenerating nerves, including myelin autophagy and mitochondrial respiration. Our findings propose a model according to which acute nerve injury triggers a therapeutically targetable intercellular crosstalk that modulates glial metabolism to provide sufficient energy for successful nerve repair.
Topics: Peripheral Nerves; Myelin Sheath; Neuroglia; Schwann Cells; Nerve Regeneration
PubMed: 37989315
DOI: 10.1016/j.cmet.2023.10.017 -
Nature Reviews. Nephrology Jun 2019Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity,... (Review)
Review
Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.
Topics: Adipokines; Aldosterone; Angiotensin II; Humans; Hypertension; Kidney; Kidney Tubules; Leptin; Obesity; Oxidative Stress; Pro-Opiomelanocortin; Receptor, Melanocortin, Type 4; Receptors, Mineralocorticoid; Renal Reabsorption; Renin; Sodium; Sympathetic Nervous System
PubMed: 31015582
DOI: 10.1038/s41581-019-0145-4 -
Gastroenterology Mar 2022Cancer-associated fibroblasts (CAFs) play an important role in colorectal cancer (CRC) progression and predict poor prognosis in CRC patients. However, the cellular...
BACKGROUND & AIMS
Cancer-associated fibroblasts (CAFs) play an important role in colorectal cancer (CRC) progression and predict poor prognosis in CRC patients. However, the cellular origins of CAFs remain unknown, making it challenging to therapeutically target these cells. Here, we aimed to identify the origins and contribution of colorectal CAFs associated with poor prognosis.
METHODS
To elucidate CAF origins, we used a colitis-associated CRC mouse model in 5 different fate-mapping mouse lines with 5-bromodeoxyuridine dosing. RNA sequencing of fluorescence-activated cell sorting-purified CRC CAFs was performed to identify a potential therapeutic target in CAFs. To examine the prognostic significance of the stromal target, CRC patient RNA sequencing data and tissue microarray were used. CRC organoids were injected into the colons of knockout mice to assess the mechanism by which the stromal gene contributes to colorectal tumorigenesis.
RESULTS
Our lineage-tracing studies revealed that in CRC, many ACTA2 CAFs emerge through proliferation from intestinal pericryptal leptin receptor (Lepr) cells. These Lepr-lineage CAFs, in turn, express melanoma cell adhesion molecule (MCAM), a CRC stroma-specific marker that we identified with the use of RNA sequencing. High MCAM expression induced by transforming growth factor β was inversely associated with patient survival in human CRC. In mice, stromal Mcam knockout attenuated orthotopically injected colorectal tumoroid growth and improved survival through decreased tumor-associated macrophage recruitment. Mechanistically, fibroblast MCAM interacted with interleukin-1 receptor 1 to augment nuclear factor κB-IL34/CCL8 signaling that promotes macrophage chemotaxis.
CONCLUSIONS
In colorectal carcinogenesis, pericryptal Lepr-lineage cells proliferate to generate MCAM CAFs that shape the tumor-promoting immune microenvironment. Preventing the expansion/differentiation of Lepr-lineage CAFs or inhibiting MCAM activity could be effective therapeutic approaches for CRC.
Topics: Actins; Adult; Aged; Aged, 80 and over; Animals; CD146 Antigen; Cancer-Associated Fibroblasts; Carcinogenesis; Cell Differentiation; Cell Lineage; Cell Proliferation; Colorectal Neoplasms; Disease Models, Animal; Female; Humans; Intestinal Mucosa; Ki-67 Antigen; Male; Mesenchymal Stem Cells; Mice; Mice, Transgenic; Middle Aged; Organoids; Prognosis; Receptors, Leptin; Sequence Analysis, RNA; Survival Rate; Tumor Microenvironment
PubMed: 34883119
DOI: 10.1053/j.gastro.2021.11.037 -
Nature Mar 2021Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of...
Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of haematopoietic stem cells and early restricted progenitors. LEPR cells are heterogeneous, including skeletal stem cells and osteogenic and adipogenic progenitors, although few markers have been available to distinguish these subsets or to compare their functions. Here we show that expression of an osteogenic growth factor, osteolectin, distinguishes peri-arteriolar LEPR cells poised to undergo osteogenesis from peri-sinusoidal LEPR cells poised to undergo adipogenesis (but retaining osteogenic potential). Peri-arteriolar LEPRosteolectin cells are rapidly dividing, short-lived osteogenic progenitors that increase in number after fracture and are depleted during ageing. Deletion of Scf from adult osteolectin cells did not affect the maintenance of haematopoietic stem cells or most restricted progenitors but depleted common lymphoid progenitors, impairing lymphopoiesis, bacterial clearance, and survival after acute bacterial infection. Peri-arteriolar osteolectin cell maintenance required mechanical stimulation. Voluntary running increased, whereas hindlimb unloading decreased, the frequencies of peri-arteriolar osteolectin cells and common lymphoid progenitors. Deletion of the mechanosensitive ion channel PIEZO1 from osteolectin cells depleted osteolectin cells and common lymphoid progenitors. These results show that a peri-arteriolar niche for osteogenesis and lymphopoiesis in bone marrow is maintained by mechanical stimulation and depleted during ageing.
Topics: Adipose Tissue; Aging; Animals; Arterioles; Bone Marrow Cells; Bone and Bones; Female; Hematopoietic Cell Growth Factors; Lectins, C-Type; Lymphocytes; Lymphopoiesis; Male; Mice; Osteogenesis; Receptors, Leptin; Stem Cell Factor; Stem Cell Niche; Stromal Cells
PubMed: 33627868
DOI: 10.1038/s41586-021-03298-5 -
International Journal of Molecular... May 2022Obesity is a growing worldwide health problem, affecting many people due to excessive saturated fat consumption, lack of exercise, or a sedentary lifestyle. Leptin is an... (Review)
Review
Obesity is a growing worldwide health problem, affecting many people due to excessive saturated fat consumption, lack of exercise, or a sedentary lifestyle. Leptin is an adipokine secreted by adipose tissue that increases in obesity and has central actions not only at the hypothalamic level but also in other regions and nuclei of the central nervous system (CNS) such as the cerebral cortex and hippocampus. These regions express the long form of leptin receptor LepRb, which is the unique leptin receptor capable of transmitting complete leptin signaling, and are the first regions to be affected by chronic neurocognitive deficits, such as mild cognitive impairment (MCI) and Alzheimer's Disease (AD). In this review, we discuss different leptin resistance mechanisms that could be implicated in increasing the risk of developing AD, as leptin resistance is frequently associated with obesity, which is a chronic low-grade inflammatory state, and obesity is considered a risk factor for AD. Key players of leptin resistance are SOCS3, PTP1B, and TCPTP whose signalling is related to inflammation and could be worsened in AD. However, some data are controversial, and it is necessary to further investigate the underlying mechanisms of the AD-causing pathological processes and how altered leptin signalling affects such processes.
Topics: Alzheimer Disease; Humans; Leptin; Obesity; Receptors, Leptin; Risk Factors
PubMed: 35563589
DOI: 10.3390/ijms23095202 -
Nature Reviews. Endocrinology Oct 2022Obesity is a multifactorial and complex disease that often manifests in early childhood with a lifelong burden. Polygenic and monogenic obesity are driven by the... (Review)
Review
Obesity is a multifactorial and complex disease that often manifests in early childhood with a lifelong burden. Polygenic and monogenic obesity are driven by the interaction between genetic predisposition and environmental factors. Polygenic variants are frequent and confer small effect sizes. Rare monogenic obesity syndromes are caused by defined pathogenic variants in single genes with large effect sizes. Most of these genes are involved in the central nervous regulation of body weight; for example, genes of the leptin-melanocortin pathway. Clinically, patients with monogenic obesity present with impaired satiety, hyperphagia and pronounced food-seeking behaviour in early childhood, which leads to severe early-onset obesity. With the advent of novel pharmacological treatment options emerging for monogenic obesity syndromes that target the central melanocortin pathway, genetic testing is recommended for patients with rapid weight gain in infancy and additional clinical suggestive features. Likewise, patients with obesity associated with hypothalamic damage or other forms of syndromic obesity involving energy regulatory circuits could benefit from these novel pharmacological treatment options. Early identification of patients affected by syndromic obesity will lead to appropriate treatment, thereby preventing the development of obesity sequelae, avoiding failure of conservative treatment approaches and alleviating stigmatization of patients and their families.
Topics: Child, Preschool; Genetic Predisposition to Disease; Humans; Hyperphagia; Leptin; Melanocortins; Obesity; Phenotype; Receptors, Leptin
PubMed: 35902734
DOI: 10.1038/s41574-022-00716-0 -
Nature Communications Mar 2023Leptin is an adipocyte-derived protein hormone that promotes satiety and energy homeostasis by activating the leptin receptor (LepR)-STAT3 signaling axis in a subset of...
Leptin is an adipocyte-derived protein hormone that promotes satiety and energy homeostasis by activating the leptin receptor (LepR)-STAT3 signaling axis in a subset of hypothalamic neurons. Leptin signaling is dysregulated in obesity, however, where appetite remains elevated despite high levels of circulating leptin. To gain insight into the mechanism of leptin receptor activation, here we determine the structure of a stabilized leptin-bound LepR signaling complex using single particle cryo-EM. The structure reveals an asymmetric architecture in which a single leptin induces LepR dimerization via two distinct receptor-binding sites. Analysis of the leptin-LepR binding interfaces reveals the molecular basis for human obesity-associated mutations. Structure-based design of leptin variants that destabilize the asymmetric LepR dimer yield both partial and biased agonists that partially suppress STAT3 activation in the presence of wild-type leptin and decouple activation of STAT3 from LepR negative regulators. Together, these results reveal the structural basis for LepR activation and provide insights into the differential plasticity of signaling pathways downstream of LepR.
Topics: Humans; Leptin; Receptors, Leptin; Obesity; Hypothalamus; Neurons
PubMed: 37002197
DOI: 10.1038/s41467-023-37169-6 -
Nature Metabolism Aug 2021Metabolic health depends on the brain's ability to control food intake and nutrient use versus storage, processes that require peripheral signals such as the...
Metabolic health depends on the brain's ability to control food intake and nutrient use versus storage, processes that require peripheral signals such as the adipocyte-derived hormone, leptin, to cross brain barriers and mobilize regulatory circuits. We have previously shown that hypothalamic tanycytes shuttle leptin into the brain to reach target neurons. Here, using multiple complementary models, we show that tanycytes express functional leptin receptor (LepR), respond to leptin by triggering Ca waves and target protein phosphorylation, and that their transcytotic transport of leptin requires the activation of a LepR-EGFR complex by leptin and EGF sequentially. Selective deletion of LepR in tanycytes blocks leptin entry into the brain, inducing not only increased food intake and lipogenesis but also glucose intolerance through attenuated insulin secretion by pancreatic β-cells, possibly via altered sympathetic nervous tone. Tanycytic LepRb-EGFR-mediated transport of leptin could thus be crucial to the pathophysiology of diabetes in addition to obesity, with therapeutic implications.
Topics: Brain; Diabetes Mellitus; Energy Metabolism; Ependymoglial Cells; ErbB Receptors; Insulin-Secreting Cells; Leptin; Lipid Metabolism; Pancreas; Phosphorylation; Receptors, Leptin
PubMed: 34341568
DOI: 10.1038/s42255-021-00432-5