RESUMO
The risk of chronic diseases caused by aging is reduced by caloric restriction (CR)-induced immunometabolic adaptation. Here, we found that the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), was inhibited by 2 years of 14% sustained CR in humans and elevated by obesity. SPARC converted anti-inflammatory macrophages into a pro-inflammatory phenotype with induction of interferon-stimulated gene (ISG) expression via the transcription factors IRF3/7. Mechanistically, SPARC-induced ISGs were dependent on toll-like receptor-4 (TLR4)-mediated TBK1, IRF3, IFN-ß, and STAT1 signaling without engaging the Myd88 pathway. Metabolically, SPARC dampened mitochondrial respiration, and inhibition of glycolysis abrogated ISG induction by SPARC in macrophages. Furthermore, the N-terminal acidic domain of SPARC was required for ISG induction, while adipocyte-specific deletion of SPARC reduced inflammation and extended health span during aging. Collectively, SPARC, a CR-mimetic adipokine, is an immunometabolic checkpoint of inflammation and interferon response that may be targeted to delay age-related metabolic and functional decline.
Assuntos
Envelhecimento , Interferons , Macrófagos , Osteonectina , Humanos , Inflamação/metabolismo , Interferons/metabolismo , Macrófagos/metabolismo , Osteonectina/genética , Osteonectina/metabolismoRESUMO
Integrated immunometabolic responses link dietary intake, energy utilization, and storage to immune regulation of tissue function and is therefore essential for the maintenance and restoration of homeostasis. Adipose-resident leukocytes have non-traditional immunological functions that regulate organismal metabolism by controlling insulin action, lipolysis, and mitochondrial respiration to control the usage of substrates for production of heat versus ATP. Energetically expensive vital functions such as immunological responses might have thus evolved to respond accordingly to dietary surplus and deficit of macronutrient intake. Here, we review the interaction of dietary intake of macronutrients and their metabolism with the immune system. We discuss immunometabolic checkpoints that promote healthspan and highlight how dietary fate and regulation of glucose, fat, and protein metabolism might affect immunity.
Assuntos
Tecido Adiposo/metabolismo , Dieta , Metabolismo Energético/fisiologia , Sistema Imunitário/fisiologia , Imunidade/fisiologia , Restrição Calórica , Gorduras na Dieta , Glucose/metabolismo , Humanos , Leucócitos/imunologia , Macrófagos/imunologia , Obesidade/patologiaRESUMO
The role of the immune system in homeostasis of pancreatic ß cells in type 2 diabetes mellitus is poorly characterized. In a recent issue of Cell Metabolism, Ying et al. (2018) report that two subpopulations of macrophages expand during obesity to impair ß cell function.
Assuntos
Diabetes Mellitus Tipo 2 , Ilhotas Pancreáticas , Proliferação de Células , Humanos , Inflamação , Insulina , Macrófagos , ObesidadeRESUMO
Thermogenesis in brown and beige adipose tissue has important roles in maintaining body temperature and countering the development of metabolic disorders such as obesity and type 2 diabetes1,2. Although much is known about commitment and activation of brown and beige adipose tissue, its multiple and abundant immunological factors have not been well characterized3-6. Here we define a critical role of IL-27-IL-27Rα signalling in improving thermogenesis, protecting against diet-induced obesity and ameliorating insulin resistance. Mechanistic studies demonstrate that IL-27 directly targets adipocytes, activating p38 MAPK-PGC-1α signalling and stimulating the production of UCP1. Notably, therapeutic administration of IL-27 ameliorated metabolic morbidities in well-established mouse models of obesity. Consistently, individuals with obesity show significantly decreased levels of serum IL-27, which can be restored after bariatric surgery. Collectively, these findings show that IL-27 has an important role in orchestrating metabolic programs, and is a highly promising target for anti-obesity immunotherapy.
Assuntos
Adipócitos/metabolismo , Metabolismo Energético , Interleucina-27/metabolismo , Termogênese , Animais , Cirurgia Bariátrica , Modelos Animais de Doenças , Feminino , Humanos , Resistência à Insulina , Interleucina-27/sangue , Interleucina-27/uso terapêutico , Masculino , Camundongos , Obesidade/sangue , Obesidade/tratamento farmacológico , Obesidade/metabolismo , Obesidade/prevenção & controle , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Receptores de Interleucina/metabolismo , Transdução de Sinais , Proteína Desacopladora 1/biossíntese , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Aging is accompanied by chronic low-grade inflammation, but the mechanisms that allow this to persist are not well understood. Ketone bodies are alternative fuels produced when glucose is limited and improve indicators of healthspan in aging mouse models. Moreover, the most abundant ketone body, ß-hydroxybutyrate, inhibits the NLRP3 inflammasome in myeloid cells, a key potentiator of age-related inflammation. Given that myeloid cells express ketogenic machinery, we hypothesized this pathway may serve as a metabolic checkpoint of inflammation. To test this hypothesis, we conditionally ablated ketogenesis by disrupting expression of the terminal enzyme required for ketogenesis, 3-Hydroxy-3-Methylglutaryl-CoA Lyase (HMGCL). By deleting HMGCL in the liver, we validated the functional targeting and establish that the liver is the only organ that can produce the life-sustaining quantities of ketone bodies required for survival during fasting or ketogenic diet feeding. Conditional ablation of HMGCL in neutrophils and macrophages had modest effects on body weight and glucose tolerance in aging but worsened glucose homeostasis in myeloid cell-specific Hmgcl-deficient mice fed a high-fat diet. Our results suggest that during aging, liver-derived circulating ketone bodies might be more important for deactivating the NLRP3 inflammasome and controlling organismal metabolism.
Assuntos
Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Camundongos , Animais , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Corpos Cetônicos , Inflamação/genética , Glucose/metabolismo , Imunidade InataRESUMO
Current approaches for the treatment of obesity, including diet and lifestyle changes, have not been successful in curtailing the obesity epidemic. The higher incidence of inflammation-associated chronic disease and greater susceptibility to infection in obese people represents a growing health threat. Improved understanding of the immunological processes that regulate obesity may yield new treatments for obesity-associated disorders.
Assuntos
Tecido Adiposo/imunologia , Leucocitose , Obesidade/imunologia , Linfócitos B/imunologia , Evolução Biológica , Dieta , Humanos , Inflamassomos/imunologia , Inflamassomos/metabolismo , Estilo de Vida , Ativação de Macrófagos , Macrófagos/imunologia , Mastócitos/imunologia , Neutrófilos/imunologia , Obesidade/complicações , Linfócitos T/imunologiaRESUMO
Cholesterol biosynthetic intermediates, such as lanosterol and desmosterol, are emergent immune regulators of macrophages in response to inflammatory stimuli or lipid overloading, respectively. However, the participation of these sterols in regulating macrophage functions in the physiological context of atherosclerosis, an inflammatory disease driven by the accumulation of cholesterol-laden macrophages in the artery wall, has remained elusive. Here, we report that desmosterol, the most abundant cholesterol biosynthetic intermediate in human coronary artery lesions, plays an essential role during atherogenesis, serving as a key molecule integrating cholesterol homeostasis and immune responses in macrophages. Depletion of desmosterol in myeloid cells by overexpression of 3ß-hydroxysterol Δ24-reductase (DHCR24), the enzyme that catalyzes conversion of desmosterol to cholesterol, promotes the progression of atherosclerosis. Single-cell transcriptomics in isolated CD45+CD11b+ cells from atherosclerotic plaques demonstrate that depletion of desmosterol increases interferon responses and attenuates the expression of antiinflammatory macrophage markers. Lipidomic and transcriptomic analysis of in vivo macrophage foam cells demonstrate that desmosterol is a major endogenous liver X receptor (LXR) ligand involved in LXR/retinoid X receptor (RXR) activation and thus macrophage foam cell formation. Decreased desmosterol accumulation in mitochondria promotes macrophage mitochondrial reactive oxygen species production and NLR family pyrin domain containing 3 (NLRP3)-dependent inflammasome activation. Deficiency of NLRP3 or apoptosis-associated speck-like protein containing a CARD (ASC) rescues the increased inflammasome activity and atherogenesis observed in desmosterol-depleted macrophages. Altogether, these findings underscore the critical function of desmosterol in the atherosclerotic plaque to dampen inflammation by integrating with macrophage cholesterol metabolism and inflammatory activation and protecting from disease progression.
Assuntos
Aterosclerose/tratamento farmacológico , Desmosterol/farmacologia , Inflamassomos/metabolismo , Inflamação/tratamento farmacológico , Ativação de Macrófagos/efeitos dos fármacos , Animais , Aterosclerose/metabolismo , Aterosclerose/patologia , Colesterol/metabolismo , Vasos Coronários , Células Espumosas/metabolismo , Humanos , Inflamação/metabolismo , Metabolismo dos Lipídeos , Receptores X do Fígado/metabolismo , Macrófagos/metabolismo , Masculino , Camundongos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Placa Aterosclerótica/metabolismo , Esteróis/metabolismoRESUMO
Catecholamine-induced lipolysis, the first step in the generation of energy substrates by the hydrolysis of triglycerides, declines with age. The defect in the mobilization of free fatty acids in the elderly is accompanied by increased visceral adiposity, lower exercise capacity, failure to maintain core body temperature during cold stress, and reduced ability to survive starvation. Although catecholamine signalling in adipocytes is normal in the elderly, how lipolysis is impaired in ageing remains unknown. Here we show that adipose tissue macrophages regulate the age-related reduction in adipocyte lipolysis in mice by lowering the bioavailability of noradrenaline. Unexpectedly, unbiased whole-transcriptome analyses of adipose macrophages revealed that ageing upregulates genes that control catecholamine degradation in an NLRP3 inflammasome-dependent manner. Deletion of NLRP3 in ageing restored catecholamine-induced lipolysis by downregulating growth differentiation factor-3 (GDF3) and monoamine oxidase A (MAOA) that is known to degrade noradrenaline. Consistent with this, deletion of GDF3 in inflammasome-activated macrophages improved lipolysis by decreasing levels of MAOA and caspase-1. Furthermore, inhibition of MAOA reversed the age-related reduction in noradrenaline concentration in adipose tissue, and restored lipolysis with increased levels of the key lipolytic enzymes adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL). Our study reveals that targeting neuro-immunometabolic signalling between the sympathetic nervous system and macrophages may offer new approaches to mitigate chronic inflammation-induced metabolic impairment and functional decline.
Assuntos
Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Envelhecimento/metabolismo , Catecolaminas/metabolismo , Inflamassomos/metabolismo , Lipólise , Macrófagos/metabolismo , Tecido Adiposo/citologia , Tecido Adiposo/efeitos dos fármacos , Envelhecimento/efeitos dos fármacos , Envelhecimento/genética , Animais , Caspase 1/metabolismo , Catecolaminas/farmacologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Fator 3 de Diferenciação de Crescimento/deficiência , Fator 3 de Diferenciação de Crescimento/genética , Fator 3 de Diferenciação de Crescimento/metabolismo , Lipase/metabolismo , Lipólise/efeitos dos fármacos , Lipólise/genética , Camundongos , Monoaminoxidase/metabolismo , Inibidores da Monoaminoxidase/farmacologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/deficiência , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Norepinefrina/metabolismo , Esterol Esterase/metabolismoRESUMO
Hypothyroidism, a metabolic disease characterized by low thyroid hormone (TH) and high thyroid-stimulating hormone (TSH) levels in the serum, is strongly associated with nonalcoholic fatty liver disease (NAFLD). Hypothyroidism-induced NAFLD has generally been attributed to reduced TH signaling in the liver with a consequent decrease in lipid utilization. Here, we found that mildly hypothyroid mice develop NAFLD without down-regulation of hepatic TH signaling or decreased hepatic lipid utilization. NAFLD was induced by impaired suppression of adipose tissue lipolysis due to decreased insulin secretion and to a reduced response of adipose tissue itself to insulin. This condition leads to increased shuttling of fatty acids (FAs) to the liver, where they are esterified and accumulated as triglycerides. Lipid accumulation in the liver induces hepatic insulin resistance, which leads to impaired suppression of endogenous glucose production after feeding. Hepatic insulin resistance, synergistically with lowered insulin secretion, increases serum glucose levels, which stimulates de novo lipogenesis (DNL) in the liver. Up-regulation of DNL also contributes to NAFLD. In contrast, severely hypothyroid mice show down-regulation of TH signaling in their livers and profound suppression of adipose tissue lipolysis, which decreases delivery of FAs to the liver. The resulting lack of substrates for triglyceride esterification protects severely hypothyroid mice against NAFLD. Our findings demonstrate that NAFLD occurs when TH levels are mildly reduced, but, paradoxically, not when they are severely reduced. Our results show that the pathogenesis of hypothyroidism-induced NAFLD is both intra- and extrahepatic; they also reveal key metabolic differences between mild and severe hypothyroidism.
Assuntos
Hipotireoidismo/complicações , Resistência à Insulina , Células Secretoras de Insulina/metabolismo , Hepatopatia Gordurosa não Alcoólica/etiologia , Tecido Adiposo/metabolismo , Tecido Adiposo/fisiopatologia , Animais , Modelos Animais de Doenças , Hipotireoidismo/etiologia , Insulina/metabolismo , Secreção de Insulina , Metabolismo dos Lipídeos , Lipólise/fisiologia , Fígado/fisiopatologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/complicações , Simportadores/genéticaRESUMO
KEY POINTS: Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Insulin sensitivity is greater in premenopausal women compared with age-matched men, and metabolism-related cardiovascular diseases and type 2 diabetes are less frequent in these same women. Both female and male mice treated with oestradiol are protected against obesity-induced insulin resistance. The protection against obesity-induced insulin resistance is associated with reduced ectopic lipid content in liver and skeletal muscle. These results were associated with increased insulin-stimulated suppression of white adipose tissue lipolysis and reduced inflammation. ABSTRACT: Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Overall, females are protected against obesity-induced insulin resistance; yet, the mechanisms responsible for this protection are not well understood. Therefore, the aim of the present work was to evaluate the underlying mechanism(s) by which female mice are protected against obesity-induced insulin resistance compared with male mice. We studied male and female mice in age-matched or body weight-matched conditions. They were fed a high-fat diet (HFD) or regular chow for 4 weeks. We also studied HFD male mice treated with oestradiol or vehicle. Both HFD female and HFD male mice treated with oestradiol displayed increased whole-body insulin sensitivity, associated with reduction in ectopic hepatic and muscle lipid content compared to HFD male mice. Reductions in ectopic lipid content in these mice were associated with increased insulin-stimulated suppression of white adipose tissue (WAT) lipolysis. Both HFD female and HFD male mice treated with oestradiol also displayed striking reductions in WAT inflammation, represented by reductions in plasma and adipose tissue tumour necrosis factor α and interleukin 6 concentrations. Taken together these data support the hypothesis that HFD female mice are protected from obesity-induced insulin resistance due to oestradiol-mediated reductions in WAT inflammation, leading to improved insulin-mediated suppression of WAT lipolysis and reduced ectopic lipid content in liver and skeletal muscle.
Assuntos
Estrogênios/farmacologia , Resistência à Insulina , Interleucina-6/metabolismo , Caracteres Sexuais , Tecido Adiposo Branco/efeitos dos fármacos , Tecido Adiposo Branco/metabolismo , Animais , Peso Corporal , Linhagem Celular , Células Cultivadas , Dieta Hiperlipídica/efeitos adversos , Estrogênios/metabolismo , Feminino , Lipólise , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
The bidirectional communication between innate immune cells and energy metabolism is now widely appreciated to regulate homeostasis as well as chronic diseases that emerge from dysregulated inflammation. Macronutrients-derived from diet or endogenous pathways that generate and divert metabolites into energetic or biosynthetic pathways regulate the initiation, duration and cessation of the inflammatory response. The NLRP3 inflammasome is an important innate sensor of structurally diverse metabolic damage-associated molecular patterns (DAMPs) that has been implicated in a wide range of inflammatory disorders associated with caloric excess, adiposity and aging. Understanding the regulators of immune-metabolic interactions and their contribution towards chronic disease mechanisms, therefore, has the potential to reduce disease pathology, improve quality of life in elderly and promote the extension of healthspan. Just as specialized subsets of immune cells dampen inflammation through the production of negative regulatory cytokines; specific immunoregulatory metabolites can deactivate inflammasome-mediated immune activation. Here, we highlight the role of energy substrates, alternative fuels and metabolic DAMPs in the regulation of the NLRP3 inflammasome and discuss potential dietary interventions that may impact sterile inflammatory disease.
Assuntos
Proteínas de Transporte/metabolismo , Dieta , Metabolismo Energético , Imunomodulação , Inflamassomos/metabolismo , Tecido Adiposo/imunologia , Tecido Adiposo/metabolismo , Animais , Metabolismo Energético/efeitos dos fármacos , Humanos , Imunomodulação/efeitos dos fármacos , Inflamassomos/antagonistas & inibidores , Inflamação/imunologia , Inflamação/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Doenças Metabólicas/tratamento farmacológico , Doenças Metabólicas/imunologia , Doenças Metabólicas/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR , Transdução de SinaisRESUMO
Age-related thymic degeneration is associated with loss of naïve T cells, restriction of peripheral T-cell diversity, and reduced healthspan due to lower immune competence. The mechanistic basis of age-related thymic demise is unclear, but prior evidence suggests that caloric restriction (CR) can slow thymic aging by maintaining thymic epithelial cell integrity and reducing the generation of intrathymic lipid. Here we show that the prolongevity ketogenic hormone fibroblast growth factor 21 (FGF21), a member of the endocrine FGF subfamily, is expressed in thymic stromal cells along with FGF receptors and its obligate coreceptor, ßKlotho. We found that FGF21 expression in thymus declines with age and is induced by CR. Genetic gain of FGF21 function in mice protects against age-related thymic involution with an increase in earliest thymocyte progenitors and cortical thymic epithelial cells. Importantly, FGF21 overexpression reduced intrathymic lipid, increased perithymic brown adipose tissue, and elevated thymic T-cell export and naïve T-cell frequencies in old mice. Conversely, loss of FGF21 function in middle-aged mice accelerated thymic aging, increased lethality, and delayed T-cell reconstitution postirradiation and hematopoietic stem cell transplantation (HSCT). Collectively, FGF21 integrates metabolic and immune systems to prevent thymic injury and may aid in the reestablishment of a diverse T-cell repertoire in cancer patients following HSCT.
Assuntos
Envelhecimento/imunologia , Fatores de Crescimento de Fibroblastos/fisiologia , Imunossenescência , Timo/imunologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Receptores de Antígenos de Linfócitos T/fisiologia , Linfócitos T/imunologiaRESUMO
Aging is the greatest risk factor for the development of chronic diseases such as arthritis, type 2 diabetes, cardiovascular disease, kidney disease, Alzheimer's disease, macular degeneration, frailty, and certain forms of cancers. It is widely regarded that chronic inflammation may be a common link in all these age-related diseases. This raises the question, can one alter the course of aging and potentially slow the development of all chronic diseases by manipulating the mechanisms that cause age-related inflammation? Emerging evidence suggests that pro-inflammatory cytokines interleukin-1 (IL-1) and IL-18 show an age-dependent regulation implicating inflammasome-mediated caspase-1 activation in the aging process. The Nod-like receptor (NLR) family of innate immune cell sensors, such as the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome controls the caspase-1 activation in myeloid-lineage cells in several organs during aging. The NLRP3 inflammasome is especially relevant to aging as it can get activated in response to structurally diverse damage-associated molecular patterns (DAMPs) such as extracellular ATP, excess glucose, ceramides, amyloids, urate, and cholesterol crystals, all of which increase with age. Interestingly, reduction in NLRP3-mediated inflammation prevents age-related insulin resistance, bone loss, cognitive decline, and frailty. NLRP3 is a major driver of age-related inflammation and therefore dietary or pharmacological approaches to lower aberrant inflammasome activation holds promise in reducing multiple chronic diseases of age and may enhance healthspan.
Assuntos
Envelhecimento/imunologia , Proteínas de Transporte/metabolismo , Inflamação/imunologia , Células Mieloides/imunologia , Animais , Proteínas de Transporte/imunologia , Caspase 1/metabolismo , Humanos , Interleucina-1/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLRRESUMO
Dietary lipid overload and calorie excess during obesity is a low grade chronic inflammatory state with diminished ability to appropriately metabolize glucose or lipids. Macrophages are critical in maintaining adipose tissue homeostasis, in part by regulating lipid metabolism, energy homeostasis, and tissue remodeling. During high fat diet-induced obesity, macrophages are activated by lipid derived "danger signals" such as ceramides and palmitate and promote the adipose tissue inflammation in an Nlrp3 inflammasome-dependent manner. Given that the metabolic fate of fatty acids in macrophages is not entirely elucidated, we have hypothesized that de novo synthesis of ceramide, through the rate-limiting enzyme serine palmitoyltransferase long chain (Sptlc)-2, is required for saturated fatty acid-driven Nlrp3 inflammasome activation in macrophages. Here we report that mitochondrial targeted overexpression of catalase, which is established to mitigate oxidative stress, controls ceramide-induced Nlrp3 inflammasome activation but does not affect the ATP-mediated caspase-1 cleavage. Surprisingly, myeloid cell-specific deletion of Sptlc2 is not required for palmitate-driven Nlrp3 inflammasome activation. Furthermore, the ablation of Sptlc2 in macrophages did not impact macrophage polarization or obesity-induced adipose tissue leukocytosis. Consistent with these data, investigation of insulin resistance using hyperinsulinemic-euglycemic clamps revealed no significant differences in obese mice lacking ceramide de novo synthesis machinery in macrophages. These data suggest that alternate metabolic pathways control fatty acid-derived ceramide synthesis in macrophage and the Nlrp3 inflammasome activation in obesity.
Assuntos
Proteínas de Transporte/genética , Ceramidas/metabolismo , Inflamassomos/metabolismo , Resistência à Insulina , Macrófagos/metabolismo , Obesidade/metabolismo , Tecido Adiposo/metabolismo , Animais , Células da Medula Óssea/citologia , Dieta Hiperlipídica , Modelos Animais de Doenças , Ácidos Graxos/química , Feminino , Inflamação/metabolismo , Lipídeos/química , Masculino , Camundongos , Camundongos Transgênicos , Mitocôndrias/patologia , Proteína 3 que Contém Domínio de Pirina da Família NLR , Estresse Oxidativo , Serina C-Palmitoiltransferase/genéticaRESUMO
Emerging evidence indicates that the immune and metabolic interactions control several aspects of the aging process and associated chronic diseases. Among several sites of immune-metabolic interactions, thymic demise represents a particularly puzzling phenomenon because even in metabolically healthy middle-aged individuals the majority of thymic space is replaced with ectopic lipids. The new T cell specificities can only be generated in a functional thymus and, peripheral proliferation of pre-existing T cell clones provides limited immune-vigilance in the elderly. Therefore, it is hypothesized that the strategies that enhance thymic-lymphopoiesis may extend healthspan. Recent data suggest that byproducts of thymic fatty acids and lipids result in accumulation of 'lipotoxic DAMPs' (damage associated molecular patterns), which triggers the innate immune-sensing mechanism like inflammasome activation which links aging to thymic demise. The immune-metabolic interaction within the aging thymus produces a local pro-inflammatory state that directly compromises the thymic stromal microenvironment, thymic-lymphopoiesis and serves a precursor of systemic immune-dysregulation in the elderly. New evidence also suggests that ectopic thymic adipocytes may develop from specific intrathymic stromal cell precursors instead of a passive process that is simply a consequence of thymic lymphopenia. Thus the complex bidirectional interactions between metabolic and immune systems may link aging to health, T cell senescence, and associated diseases. This review discusses the immune-metabolic mechanisms during aging - with implications for developing future therapeutic strategies for living well beyond the expected.
Assuntos
Envelhecimento , Senescência Celular , Linfócitos T/imunologia , Timo/imunologia , Animais , Humanos , Transdução de Sinais , Linfócitos T/metabolismo , Timo/metabolismoRESUMO
Successful adaptation to periods of chronic caloric excess is a highly coordinated event that is critical to the survival and propagation of species. Transcription factor C/ebp homologous protein (Chop) is thought to be an important molecular mediator that integrates nutrient signals to endoplasmic reticulum (ER) stress and innate immune activation. Given that aberrant ER stress response is implicated in inducing metabolic inflammation and insulin resistance, we hypothesized that ER stress target gene Chop integrates immune and metabolic systems to adapt to chronic positive energy balance. Here we report that inactivation of Chop in mice fed a high fat diet led to significant increase in obesity caused by a reduction in energy expenditure without any change in food intake. Importantly, ablation of Chop does not induce metabolically healthy obesity, because Chop-deficient mice fed a high fat diet had increased hepatic steatosis with significantly higher insulin resistance. Quantification of adipose tissue leukocytosis revealed that elimination of Chop during obesity led to substantial increase in number of adipose tissue T and B lymphocytes. In addition, deficiency of Chop led to increase in total number of myeloid subpopulations like neutrophils and F4/80(+) adipose tissue macrophages without any alterations in the frequency of M1- or M2-like adipose tissue macrophages. Further investigation of inflammatory mechanisms revealed that ablation of Chop increases the sensitivity of macrophages to inflammasome-induced activation of IL-ß in macrophages. Our findings indicate that regulated expression of Chop during obesity is critical for adaptation to chronic caloric excess and maintenance of energy homeostasis via integration of metabolic and immune systems.
Assuntos
Tecido Adiposo/imunologia , Leucocitose/imunologia , Leucocitose/metabolismo , Obesidade/imunologia , Obesidade/metabolismo , Fator de Transcrição CHOP/metabolismo , Animais , Metabolismo Energético , Deleção de Genes , Inflamassomos/metabolismo , Macrófagos/imunologia , Masculino , Camundongos , Linfócitos T/imunologia , Fator de Transcrição CHOP/deficiência , Fator de Transcrição CHOP/genéticaRESUMO
Dietary interventions such as caloric restriction (CR)1 and methionine restriction2 that prolong lifespan induce the 'browning' of white adipose tissue (WAT), an adaptive metabolic response that increases heat production to maintain health3,4. However, how diet influences adipose browning and metabolic health is unclear. Here, we identified that weight-loss induced by CR in humans5 reduces cysteine concentration in WAT suggesting depletion of this amino-acid may be involved in metabolic benefits of CR. To investigate the role of cysteine on organismal metabolism, we created a cysteine-deficiency mouse model in which dietary cysteine was eliminated and cystathionine γ-lyase (CTH)6, the enzyme that synthesizes cysteine was conditionally deleted. Using this animal model, we found that systemic cysteine-depletion causes drastic weight-loss with increased fat utilization and browning of adipose tissue. The restoration of dietary cysteine in cysteine-deficient mice rescued weight loss together with reversal of adipose browning and increased food-intake in an on-demand fashion. Mechanistically, cysteine deficiency induced browning and weight loss is dependent on sympathetic nervous system derived noradrenaline signaling via ß3-adrenergic-receptors and does not require UCP1. Therapeutically, in high-fat diet fed obese mice, one week of cysteine-deficiency caused 30% weight-loss and reversed inflammation. These findings thus establish that cysteine is essential for organismal metabolism as removal of cysteine in the host triggers adipose browning and rapid weight loss.
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The authors have requested that this preprint be removed from Research Square.
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The comprehensive assessment of long-term effects of reducing intake of energy (CALERIE-II; NCT00427193) clinical trial established that caloric restriction (CR) in humans lowers inflammation. The identity and mechanism of endogenous CR-mimetics that can be deployed to control obesity-associated inflammation and diseases are not well understood. Our studies have found that 2 years of 14% sustained CR in humans inhibits the expression of the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), in adipose tissue. In mice, adipose tissue remodeling caused by weight loss through CR and low-protein diet feeding decreased, while high-fat diet-induced (HFD-induced) obesity increased SPARC expression in adipose tissue. Inducible SPARC downregulation in adult mice mimicked CR's effects on lowering adiposity by regulating energy expenditure. Deletion of SPARC in adipocytes was sufficient to protect mice against HFD-induced adiposity, chronic inflammation, and metabolic dysfunction. Mechanistically, SPARC activates the NLRP3 inflammasome at the priming step and downregulation of SPARC lowers macrophage inflammation in adipose tissue, while excess SPARC activated macrophages via JNK signaling. Collectively, reduction of adipocyte-derived SPARC confers CR-like metabolic and antiinflammatory benefits in obesity by serving as an immunometabolic checkpoint of inflammation.