RESUMO
Although human genetic studies have implicated many susceptible genes associated with plasma lipid levels, their physiological and molecular functions are not fully characterized. Here we demonstrate that orphan G protein-coupled receptor 146 (GPR146) promotes activity of hepatic sterol regulatory element binding protein 2 (SREBP2) through activation of the extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating hepatic very low-density lipoprotein (VLDL) secretion, and subsequently circulating low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) levels. Remarkably, GPR146 deficiency reduces plasma cholesterol levels substantially in both wild-type and LDL receptor (LDLR)-deficient mice. Finally, aortic atherosclerotic lesions are reduced by 90% and 70%, respectively, in male and female LDLR-deficient mice upon GPR146 depletion. Taken together, these findings outline a regulatory role for the GPR146/ERK axis in systemic cholesterol metabolism and suggest that GPR146 inhibition could be an effective strategy to reduce plasma cholesterol levels and atherosclerosis.
Assuntos
Aterosclerose/metabolismo , Hipercolesterolemia/metabolismo , Receptores Acoplados a Proteínas G/deficiência , Animais , Aterosclerose/sangue , Sequência de Bases , Colesterol/sangue , Dependovirus/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Jejum , Feminino , Hepatócitos/metabolismo , Humanos , Hipercolesterolemia/sangue , Lipoproteínas VLDL/metabolismo , Fígado/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , RNA Interferente Pequeno/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Receptores de LDL/metabolismo , Transdução de Sinais , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Triglicerídeos/sangue , Regulação para CimaRESUMO
Autophagy is required in diverse paradigms of lifespan extension, leading to the prevailing notion that autophagy is beneficial for longevity. However, why autophagy is harmful in certain contexts remains unexplained. Here, we show that mitochondrial permeability defines the impact of autophagy on aging. Elevated autophagy unexpectedly shortens lifespan in C. elegans lacking serum/glucocorticoid regulated kinase-1 (sgk-1) because of increased mitochondrial permeability. In sgk-1 mutants, reducing levels of autophagy or mitochondrial permeability transition pore (mPTP) opening restores normal lifespan. Remarkably, low mitochondrial permeability is required across all paradigms examined of autophagy-dependent lifespan extension. Genetically induced mPTP opening blocks autophagy-dependent lifespan extension resulting from caloric restriction or loss of germline stem cells. Mitochondrial permeability similarly transforms autophagy into a destructive force in mammals, as liver-specific Sgk knockout mice demonstrate marked enhancement of hepatocyte autophagy, mPTP opening, and death with ischemia/reperfusion injury. Targeting mitochondrial permeability may maximize benefits of autophagy in aging.
Assuntos
Envelhecimento/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/fisiologia , Membranas Mitocondriais/fisiologia , Animais , Autofagia/fisiologia , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/fisiologia , Restrição Calórica , Células HEK293 , Humanos , Longevidade/fisiologia , Masculino , Camundongos , Camundongos Knockout , Mitocôndrias , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Poro de Transição de Permeabilidade Mitocondrial , Permeabilidade , Cultura Primária de Células , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/fisiologia , Traumatismo por Reperfusão/metabolismo , Transdução de SinaisRESUMO
Metformin has utility in cancer prevention and treatment, though the mechanisms for these effects remain elusive. Through genetic screening in C. elegans, we uncover two metformin response elements: the nuclear pore complex (NPC) and acyl-CoA dehydrogenase family member-10 (ACAD10). We demonstrate that biguanides inhibit growth by inhibiting mitochondrial respiratory capacity, which restrains transit of the RagA-RagC GTPase heterodimer through the NPC. Nuclear exclusion renders RagC incapable of gaining the GDP-bound state necessary to stimulate mTORC1. Biguanide-induced inactivation of mTORC1 subsequently inhibits growth through transcriptional induction of ACAD10. This ancient metformin response pathway is conserved from worms to humans. Both restricted nuclear pore transit and upregulation of ACAD10 are required for biguanides to reduce viability in melanoma and pancreatic cancer cells, and to extend C. elegans lifespan. This pathway provides a unified mechanism by which metformin kills cancer cells and extends lifespan, and illuminates potential cancer targets. PAPERCLIP.
Assuntos
Metformina/farmacologia , Acil-CoA Desidrogenase/genética , Envelhecimento , Animais , Tamanho Corporal , Caenorhabditis elegans/crescimento & desenvolvimento , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/metabolismo , Humanos , Longevidade , Alvo Mecanístico do Complexo 1 de Rapamicina , Mitocôndrias/metabolismo , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Complexos Multiproteicos/metabolismo , Neoplasias/tratamento farmacológico , Poro Nuclear/metabolismo , Fosforilação Oxidativa , Transdução de Sinais/efeitos dos fármacos , Serina-Treonina Quinases TOR/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Both hedgehog (Hh) and target of rapamycin complex 2 (TORC2) are central, evolutionarily conserved signaling pathways that regulate development and metabolism. In C. elegans, loss of the essential TORC2 component RICTOR (rict-1) causes delayed development, shortened lifespan, reduced brood, small size and increased fat. Here, we report that knockdown of both the hedgehog-related morphogen grd-1 and its patched-related receptor ptr-11 rescues delayed development in TORC2 loss-of-function mutants, and grd-1 and ptr-11 overexpression delays wild-type development to a similar level to that in TORC2 loss-of-function animals. These findings potentially indicate an unexpected role for grd-1 and ptr-11 in slowing developmental rate downstream of a nutrient-sensing pathway. Furthermore, we implicate the chronic stress transcription factor pqm-1 as a key transcriptional effector in this slowing of whole-organism growth by grd-1 and ptr-11. We propose that TORC2, grd-1 and ptr-11 may act linearly or converge on pqm-1 to delay organismal development.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Animais , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas Hedgehog/genética , Proteínas Hedgehog/metabolismo , Alvo Mecanístico do Complexo 2 de Rapamicina/genética , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Transdução de Sinais/genética , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Receptores PatchedRESUMO
Starvation is among the most ancient of selection pressures, driving evolution of a robust arsenal of starvation survival defenses. In order to survive starvation stress, organisms must be able to curtail anabolic processes during starvation and judiciously activate catabolic pathways. Although the activation of metabolic defenses in response to nutrient deprivation is an obvious component of starvation survival, less appreciated is the importance of the ability to recover from starvation upon re-exposure to nutrients. In order for organisms to successfully recover from starvation, cells must be kept in a state of ready so that upon the return of nutrients, activities such as growth and reproduction can be resumed. Critical to this state of ready is the lysosome, an organelle that provides essential signals of nutrient sufficiency to cell growth-activating pathways in the fed state. In this issue, Murphy and colleagues provide evidence that exposure of Caenorhabditis elegans roundworms to 2 simple nutrients, glucose and the polyunsaturated fatty acid linoleate, is able to render lysosomal function competent to activate key downstream starvation recovery pathways, bypassing the need for a master transcriptional regulator of lysosomes. These findings provide a quantum leap forward in our understanding of the cellular determinants that permit organisms to survive cycles of feast and famine.
Assuntos
Proteínas de Caenorhabditis elegans , Lisossomos , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Caenorhabditis elegans , NutrientesRESUMO
Early host responses toward pathogens are essential for defense against infection. In Caenorhabditis elegans, the transcription factor, SKN-1, regulates cellular defenses during xenobiotic intoxication and bacterial infection. However, constitutive activation of SKN-1 results in pleiotropic outcomes, including a redistribution of somatic lipids to the germline, which impairs health and shortens lifespan. Here, we show that exposing C. elegans to Pseudomonas aeruginosa similarly drives the rapid depletion of somatic, but not germline, lipid stores. Modulating the epigenetic landscape refines SKN-1 activity away from innate immunity targets, which alleviates negative metabolic outcomes. Similarly, exposure to oxidative stress redirects SKN-1 activity away from pathogen response genes while restoring somatic lipid distribution. In addition, activating p38/MAPK signaling in the absence of pathogens, is sufficient to drive SKN-1-dependent loss of somatic fat. These data define a SKN-1- and p38-dependent axis for coordinating pathogen responses, lipid homeostasis, and survival and identify transcriptional redirection, rather than inactivation, as a mechanism for counteracting the pleiotropic consequences of aberrant transcriptional activity.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Ligação a DNA/metabolismo , Epigênese Genética , Metabolismo dos Lipídeos , Infecções por Pseudomonas/genética , Fatores de Transcrição/metabolismo , Animais , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Proteínas de Ligação a DNA/genética , Imunidade Inata , Sistema de Sinalização das MAP Quinases , Estresse Oxidativo , Infecções por Pseudomonas/metabolismo , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/patogenicidade , Fatores de Transcrição/genética , Transcriptoma , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Fatty acids affect a number of physiological processes, in addition to forming the building blocks of membranes and body fat stores. In this study, we uncover a role for the monounsaturated fatty acid oleate in the innate immune response of the nematode Caenorhabditis elegans. From an RNAi screen for regulators of innate immune defense genes, we identified the two stearoyl-coenzyme A desaturases that synthesize oleate in C. elegans. We show that the synthesis of oleate is necessary for the pathogen-mediated induction of immune defense genes. Accordingly, C. elegans deficient in oleate production are hypersusceptible to infection with diverse human pathogens, which can be rescued by the addition of exogenous oleate. However, oleate is not sufficient to drive protective immune activation. Together, these data add to the known health-promoting effects of monounsaturated fatty acids, and suggest an ancient link between nutrient stores, metabolism, and host susceptibility to bacterial infection.
Assuntos
Infecções Bacterianas/imunologia , Caenorhabditis elegans/imunologia , Imunidade Inata/efeitos dos fármacos , Ácidos Oleicos/farmacologia , Animais , Ácidos Oleicos/imunologiaRESUMO
Animals in nature are continually challenged by periods of feast and famine as resources inevitably fluctuate, and must allocate somatic reserves for reproduction to abate evolutionary pressures. We identify an age-dependent lipid homeostasis pathway in Caenorhabditis elegans that regulates the mobilization of lipids from the soma to the germline, which supports fecundity but at the cost of survival in nutrient-poor and oxidative stress environments. This trade-off is responsive to the levels of dietary carbohydrates and organismal oleic acid and is coupled to activation of the cytoprotective transcription factor SKN-1 in both laboratory-derived and natural isolates of C. elegans. The homeostatic balance of lipid stores between the somatic and germ cells is mediated by arachidonic acid (omega-6) and eicosapentaenoic acid (omega-3) precursors of eicosanoid signaling molecules. Our results describe a mechanism for resource reallocation within intact animals that influences reproductive fitness at the cost of somatic resilience.
Assuntos
Caenorhabditis elegans/metabolismo , Ácidos Graxos Ômega-3/farmacologia , Ácidos Graxos Ômega-6/farmacologia , Alimentos , Células Germinativas/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Envelhecimento/efeitos dos fármacos , Animais , Caenorhabditis elegans/efeitos dos fármacos , Proteínas de Caenorhabditis elegans/metabolismo , Células Germinativas/efeitos dos fármacos , Ácido Oleico/deficiência , Reprodução/efeitos dos fármacos , Análise de Sobrevida , Vitelogênese/efeitos dos fármacosRESUMO
Rictor is a component of the target of rapamycin complex 2 (TORC2). While TORC2 has been implicated in insulin and other growth factor signaling pathways, the key inputs and outputs of this kinase complex remain unknown. We identified mutations in the Caenorhabditis elegans homolog of rictor in a forward genetic screen for increased body fat. Despite high body fat, rictor mutants are developmentally delayed, small in body size, lay an attenuated brood, and are short-lived, indicating that Rictor plays a critical role in appropriately partitioning calories between long-term energy stores and vital organismal processes. Rictor is also necessary to maintain normal feeding on nutrient-rich food sources. In contrast to wild-type animals, which grow more rapidly on nutrient-rich bacterial strains, rictor mutants display even slower growth, a further reduced body size, decreased energy expenditure, and a dramatically extended life span, apparently through inappropriate, decreased consumption of nutrient-rich food. Rictor acts directly in the intestine to regulate fat mass and whole-animal growth. Further, the high-fat phenotype of rictor mutants is genetically dependent on akt-1, akt-2, and serum and glucocorticoid-induced kinase-1 (sgk-1). Alternatively, the life span, growth, and reproductive phenotypes of rictor mutants are mediated predominantly by sgk-1. These data indicate that Rictor/TORC2 is a nutrient-sensitive complex with outputs to AKT and SGK to modulate the assessment of food quality and signal to fat metabolism, growth, feeding behavior, reproduction, and life span.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiologia , Proteínas de Transporte/metabolismo , Comportamento Alimentar/fisiologia , Metabolismo dos Lipídeos/fisiologia , Longevidade/fisiologia , Proteínas Adaptadoras de Transdução de Sinal , Tecido Adiposo/metabolismo , Animais , Compostos de Boro/metabolismo , Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Transporte/genética , Dieta , Fixadores/metabolismo , Proteínas Imediatamente Precoces/metabolismo , Insulina/metabolismo , Mucosa Intestinal/metabolismo , Mutação/genética , Proteína Oncogênica v-akt/metabolismo , Oxazinas/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteína Companheira de mTOR Insensível à Rapamicina , Reprodução/fisiologia , Transdução de Sinais , Somatomedinas/metabolismoRESUMO
The target of rapamycin complex 2 (TORC2) pathway is evolutionarily conserved and regulates cellular energetics, growth and metabolism. Loss of function of the essential TORC2 subunit Rictor (RICT-1) in Caenorhabditis elegans results in slow developmental rate, reduced brood size, small body size, increased fat mass and truncated lifespan. We performed a rict-1 suppressor RNAi screen of genes encoding proteins that possess the phosphorylation sequence of the AGC family kinase SGK, a key downstream effector of TORC2. Only RNAi to dpy-21 suppressed rict-1 slow developmental rate. DPY-21 functions canonically in the ten-protein dosage compensation complex (DCC) to downregulate the expression of X-linked genes only in hermaphroditic worms. However, we find that dpy-21 functions outside of its canonical role, as RNAi to dpy-21 suppresses TORC2 mutant developmental delay in rict-1 males and hermaphrodites. RNAi to dpy-21 normalized brood size and fat storage phenotypes in rict-1 mutants, but failed to restore normal body size and normal lifespan. Further dissection of the DCC via RNAi revealed that other complex members phenocopy the dpy-21 suppression of rict-1, as did RNAi to the DCC effectors set-1 and set-4, which methylate histone 4 on lysine 20 (H4K20). TORC2/rict-1 animals show dysregulation of H4K20 mono- and tri-methyl silencing epigenetic marks, evidence of altered DCC, SET-1 and SET-4 activity. DPY-21 protein physically interacts with the protein kinase SGK-1, suggesting that TORC2 directly regulates the DCC. Together, the data suggest non-canonical, negative regulation of growth and reproduction by DPY-21 via DCC, SET-1 and SET-4 downstream of TORC2 in C. elegans.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/crescimento & desenvolvimento , Proteínas de Transporte/metabolismo , Mecanismo Genético de Compensação de Dose/genética , Metabolismo Energético/fisiologia , Complexos Multiproteicos/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Western Blotting , Tamanho Corporal/genética , Proteínas de Caenorhabditis elegans/genética , Proteínas de Transporte/genética , Tamanho da Ninhada/genética , Primers do DNA/genética , Metabolismo Energético/genética , Epigênese Genética/fisiologia , Feminino , Histona-Lisina N-Metiltransferase/metabolismo , Longevidade/genética , Masculino , Alvo Mecanístico do Complexo 2 de Rapamicina , Metiltransferases/metabolismo , Complexos Multiproteicos/genética , Proteínas Serina-Treonina Quinases/metabolismo , Interferência de RNA , Proteína Companheira de mTOR Insensível à RapamicinaRESUMO
Lysosomes are membrane-bound organelles that contain acid hydrolases that degrade cellular proteins, lipids, nucleic acids, and oligosaccharides, and are important for cellular maintenance and protection against age-related decline. Lysosome related organelles (LROs) are specialized lysosomes found in organisms from humans to worms, and share many of the features of classic lysosomes. Defective LROs are associated with human immune disorders and neurological disease. Caenorhabditis elegans LROs are the site of concentration of vital dyes such as Nile red as well as age-associated autofluorescence. Even though certain short-lived mutants have high LRO Nile red and high autofluorescence, and other long-lived mutants have low LRO Nile red and low autofluorescence, these two biologies are distinct. We identified a genetic pathway that modulates aging-related LRO phenotypes via serotonin signaling and the gene kat-1, which encodes a mitochondrial ketothiolase. Regulation of LRO phenotypes by serotonin and kat-1 in turn depend on the proton-coupled, transmembrane transporter SKAT-1. skat-1 loss of function mutations strongly suppress the high LRO Nile red accumulation phenotype of kat-1 mutation. Using a systems approach, we further analyzed the role of 571 genes in LRO biology. These results highlight a gene network that modulates LRO biology in a manner dependent upon the conserved protein kinase TOR complex 2. The results implicate new genetic pathways involved in LRO biology, aging related physiology, and potentially human diseases of the LRO.
Assuntos
Envelhecimento/genética , Redes Reguladoras de Genes , Lisossomos/genética , Organelas/genética , Acetil-CoA C-Aciltransferase/genética , Envelhecimento/patologia , Animais , Caenorhabditis elegans , Regulação da Expressão Gênica , Humanos , Lisossomos/metabolismo , Lisossomos/patologia , Alvo Mecanístico do Complexo 2 de Rapamicina , Redes e Vias Metabólicas , Mitocôndrias/genética , Mitocôndrias/metabolismo , Complexos Multiproteicos/genética , Organelas/metabolismo , Serina-Treonina Quinases TOR/genéticaRESUMO
Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as nonalcoholic fatty liver disease [NAFLD]) and metabolic dysfunction-associated steatohepatitis (MASH, formerly known as nonalcoholic steatohepatitis [NASH]) are leading chronic liver diseases, driving cirrhosis, hepatocellular carcinoma, and mortality. MASLD/MASH is associated with increased senescence proteins, including Activin A, and senolytics have been proposed as a therapeutic approach. To test the role of Activin A, we induced hepatic expression of Activin A in a murine MASLD/MASH model. Surprisingly, overexpression of hepatic Activin A dramatically mitigated MASLD, reducing liver steatosis and inflammation as well as systemic fat accumulation, while improving insulin sensitivity. Further studies identified a dramatic decrease in the lipid-associated macrophages marker glycoprotein NMB (Gpnmb) by Activin A, and Gpnmb knockdown in the same model produced similar benefits and transcriptional changes to Activin A expression. These studies reveal a surprising protective role for Activin A in MASLD and the potential for SASP proteins to have context-specific beneficial effects. Moreover, they implicate both Activin A and Gpnmb as potential therapeutic targets for this condition.
Assuntos
Ativinas , Doenças Metabólicas , Hepatopatia Gordurosa não Alcoólica , Animais , Camundongos , Ativinas/genética , Ativinas/metabolismo , Proteínas do Olho , Glicoproteínas de Membrana/genética , Fatores de TranscriçãoRESUMO
Mammalian target of rapamycin complex 2 (mTORC2) is a key activator of protein kinases that act downstream of insulin and growth factor signaling. Here we report that mice lacking the essential mTORC2 component rictor in liver (Lrictor(KO)) are unable to respond normally to insulin. In response to insulin, Lrictor(KO) mice failed to inhibit hepatic glucose output. Lrictor(KO) mice also fail to develop hepatic steatosis on a high fat diet and manifest half-normal serum cholesterol levels. This is accompanied by lower levels of expression of SREBP-1c and SREBP-2 and genes of fatty acid and cholesterol biosynthesis. Lrictor(KO) mice had defects in insulin-stimulated Akt Ser-473 and Thr-308 phosphorylation, leading to decreased phosphorylation of Akt substrates FoxO, GSK-3ß, PRAS40, AS160, and Tsc2. Lrictor(KO) mice also manifest defects in insulin-activated mTORC1 activity, evidenced by decreased S6 kinase and Lipin1 phosphorylation. Glucose intolerance and insulin resistance of Lrictor(KO) mice could be fully rescued by hepatic expression of activated Akt2 or dominant negative FoxO1. However, in the absence of mTORC2, forced Akt2 activation was unable to drive hepatic lipogenesis. Thus, we have identified an Akt-independent relay from mTORC2 to hepatic lipogenesis that separates the effects of insulin on glucose and lipid metabolism.
Assuntos
Lipogênese/fisiologia , Fígado/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transativadores/metabolismo , Fatores de Transcrição/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Colesterol/biossíntese , Colesterol/genética , Ácidos Graxos/genética , Ácidos Graxos/metabolismo , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Proteínas Ativadoras de GTPase/genética , Proteínas Ativadoras de GTPase/metabolismo , Regulação da Expressão Gênica/fisiologia , Glucose/genética , Glucose/metabolismo , Quinase 3 da Glicogênio Sintase/genética , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Células Hep G2 , Humanos , Insulina/genética , Insulina/metabolismo , Resistência à Insulina/fisiologia , Camundongos , Camundongos Transgênicos , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Fosforilação/fisiologia , Proteínas Proto-Oncogênicas c-akt/genética , Proteína de Ligação a Elemento Regulador de Esterol 1/genética , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 2/genética , Proteína de Ligação a Elemento Regulador de Esterol 2/metabolismo , Transativadores/genética , Fatores de Transcrição/genética , Proteína 2 do Complexo Esclerose Tuberosa , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
The mitochondrial permeability transition (mPT) describes a Ca2+-dependent and cyclophilin D (CypD)-facilitated increase of inner mitochondrial membrane permeability that allows diffusion of molecules up to 1.5 kDa in size. It is mediated by a non-selective channel, the mitochondrial permeability transition pore (mPTP). Sustained mPTP opening causes mitochondrial swelling, which ruptures the outer mitochondrial membrane leading to subsequent apoptotic and necrotic cell death, and is implicated in a range of pathologies. However, transient mPTP opening at various sub-conductance states may contribute several physiological roles such as alterations in mitochondrial bioenergetics and rapid Ca2+ efflux. Since its discovery decades ago, intensive efforts have been made to identify the exact pore-forming structure of the mPT. Both the adenine nucleotide translocase (ANT) and, more recently, the mitochondrial F1FO (F)-ATP synthase dimers, monomers or c-subunit ring alone have been implicated. Here we share the insights of several key investigators with different perspectives who have pioneered mPT research. We critically assess proposed models for the molecular identity of the mPTP and the mechanisms underlying its opposing roles in the life and death of cells. We provide in-depth insights into current controversies, seeking to achieve a degree of consensus that will stimulate future innovative research into the nature and role of the mPTP.
Assuntos
Proteínas de Transporte da Membrana Mitocondrial , Poro de Transição de Permeabilidade Mitocondrial , Poro de Transição de Permeabilidade Mitocondrial/análise , Poro de Transição de Permeabilidade Mitocondrial/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Consenso , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismoRESUMO
Biguanides, including the world's most prescribed drug for type 2 diabetes, metformin, not only lower blood sugar, but also promote longevity in preclinical models. Epidemiologic studies in humans parallel these findings, indicating favorable effects of metformin on longevity and on reducing the incidence and morbidity associated with aging-related diseases. Despite this promise, the full spectrum of molecular effectors responsible for these health benefits remains elusive. Through unbiased screening in Caenorhabditis elegans, we uncovered a role for genes necessary for ether lipid biosynthesis in the favorable effects of biguanides. We demonstrate that biguanides prompt lifespan extension by stimulating ether lipid biogenesis. Loss of the ether lipid biosynthetic machinery also mitigates lifespan extension attributable to dietary restriction, target of rapamycin (TOR) inhibition, and mitochondrial electron transport chain inhibition. A possible mechanistic explanation for this finding is that ether lipids are required for activation of longevity-promoting, metabolic stress defenses downstream of the conserved transcription factor skn-1/Nrf. In alignment with these findings, overexpression of a single, key, ether lipid biosynthetic enzyme, fard-1/FAR1, is sufficient to promote lifespan extension. These findings illuminate the ether lipid biosynthetic machinery as a novel therapeutic target to promote healthy aging.
Metformin is the drug most prescribed to treat type 2 diabetes around the world and has been in clinical use since 1950. The drug belongs to a family of compounds known as biguanides which reduce blood sugar, making them an effective treatment against type 2 diabetes. More recently, biguanides have been found to have other health benefits, including limiting the growth of various cancer cells and improving the lifespan and long-term health of several model organisms. Epidemiologic studies also suggest that metformin may increase the lifespan of humans and reduce the incidence of age-related illnesses such as cardiovascular disease, cancer and dementia. Given the safety and effectiveness of metformin, understanding how it exerts these desirable effects may allow scientists to discover new mechanisms to promote healthy aging. The roundworm Caenorhabditis elegans is an ideal organism for studying the lifespan-extending effects of metformin. It has an average lifespan of two weeks, a genome that is relatively easy to manipulate, and a transparent body that enables scientists to observe cellular and molecular events in living worms. To discover the genes that enable metformin's lifespan-extending properties, Cedillo, Ahsan et al. systematically switched off the expression of about 1,000 genes involved in C. elegans metabolism. They then screened for genes which impaired the action of biguanides when inactivated. This ultimately led to the identification of a set of genes involved in promoting a longer lifespan. Cedillo, Ahsan et al. then evaluated how these genes impacted other well-described pathways involved in longevity and stress responses. The analysis indicated that a biguanide drug called phenformin (which is similar to metformin) increases the synthesis of ether lipids, a class of fats that are critical components of cellular membranes. Indeed, genetically mutating the three major enzymes required for ether lipid production stopped the biguanide from extending the worms' lifespans. Critically, inactivating these genes also prevented lifespan extension through other known strategies, such as dietary restriction and inhibiting the cellular organelle responsible for producing energy. Cedillo, Ahsan et al. also showed that increasing ether lipid production alters the activity of a well-known longevity and stress response factor called SKN-1, and this change alone is enough to extend the lifespan of worms. These findings suggest that promoting the production of ether lipids could lead to healthier aging. However, further studies, including clinical trials, will be required to determine whether this is a viable approach to promote longevity and health in humans.
Assuntos
Antimaláricos , Diabetes Mellitus Tipo 2 , Metformina , Humanos , Animais , Caenorhabditis elegans/genética , Longevidade , Etil-Éteres , Éteres , LipídeosRESUMO
Riboflavin is an essential cofactor in many enzymatic processes and in the production of flavin adenine dinucleotide (FAD). Here, we report that the partial depletion of riboflavin through knockdown of the C. elegans riboflavin transporter 1 (rft-1) promotes metabolic health by reducing intracellular flavin concentrations. Knockdown of rft-1 significantly increases lifespan in a manner dependent upon AMP-activated protein kinase (AMPK)/aak-2, the mitochondrial unfolded protein response, and FOXO/daf-16. Riboflavin depletion promotes altered energetic and redox states and increases adiposity, independent of lifespan genetic dependencies. Riboflavin-depleted animals also exhibit the activation of caloric restriction reporters without any reduction in caloric intake. Our findings indicate that riboflavin depletion activates an integrated hormetic response that promotes lifespan and healthspan in C. elegans.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Animais , Caenorhabditis elegans/metabolismo , Longevidade/genética , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Hormese , Riboflavina/metabolismo , Fatores de Transcrição Forkhead/metabolismoRESUMO
BACKGROUND: Obesity affects more than one-third of adults in the U.S., and effective treatment options are urgently needed. Oxytocin administration induces weight loss in animal models of obesity via effects on caloric intake, energy expenditure, and fat metabolism. We study intranasal oxytocin, an investigational drug shown to reduce caloric intake in humans, as a potential novel treatment for obesity. METHODS: We report the rationale, design, methods, and biostatistical analysis plan of a randomized, double-blind, placebo-controlled clinical trial of intranasal oxytocin for weight loss (primary endpoint) in adults with obesity. Participants (aged 18-45 years) were randomly allocated (1:1) to oxytocin (four times daily over eight weeks) versus placebo. Randomization was stratified by biological sex and BMI (30 to <35, 35 to <40, ≥40 kg/m2). We investigate the efficacy, safety, and mechanisms of oxytocin administration in reducing body weight. Secondary endpoints include changes in resting energy expenditure, body composition, caloric intake, metabolic profile, and brain activation via functional magnetic resonance imaging in response to food images and during an impulse control task. Safety and tolerability (e.g., review of adverse events, vital signs, electrocardiogram, comprehensive metabolic panel) are assessed throughout the study and six weeks after treatment completion. RESULTS: Sixty-one male and female participants aged 18-45 years were randomized (mean age 34 years, mean BMI 37 kg/m2). The study sample is diverse with 38% identifying as non-White and 20% Hispanic. CONCLUSION: Investigating intranasal oxytocin's efficacy, safety, and mechanisms as an anti-obesity medication will advance the search for optimal treatment strategies for obesity and its associated severe sequelae.
Assuntos
Obesidade , Ocitocina , Adulto , Animais , Feminino , Humanos , Masculino , Administração Intranasal , Método Duplo-Cego , Obesidade/tratamento farmacológico , Ocitocina/uso terapêutico , Resultado do Tratamento , Redução de Peso , Pessoa de Meia-IdadeRESUMO
A hallmark of type 2 diabetes (T2D) is hepatic resistance to insulin's glucose-lowering effects. The serum- and glucocorticoid-regulated family of protein kinases (SGK) is activated downstream of mechanistic target of rapamycin complex 2 (mTORC2) in response to insulin in parallel to AKT. Surprisingly, despite an identical substrate recognition motif to AKT, which drives insulin sensitivity, pathological accumulation of SGK1 drives insulin resistance. Liver-specific Sgk1-knockout (Sgk1Lko) mice display improved glucose tolerance and insulin sensitivity and are protected from hepatic steatosis when fed a high-fat diet. Sgk1 promotes insulin resistance by inactivating AMP-activated protein kinase (AMPK) via phosphorylation on inhibitory site AMPKαSer485/491. We demonstrate that SGK1 is dominant among SGK family kinases in regulation of insulin sensitivity, as Sgk1, Sgk2, and Sgk3 triple-knockout mice have similar increases in hepatic insulin sensitivity. In aggregate, these data suggest that targeting hepatic SGK1 may have therapeutic potential in T2D.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Proteínas Imediatamente Precoces/metabolismo , Fígado/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Animais , Diabetes Mellitus Tipo 2/patologia , Dieta Hiperlipídica , Proteína Forkhead Box O1/metabolismo , Glucose/metabolismo , Proteínas Imediatamente Precoces/deficiência , Proteínas Imediatamente Precoces/genética , Insulina/metabolismo , Resistência à Insulina , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosforilação , Proteínas Serina-Treonina Quinases/deficiência , Proteínas Serina-Treonina Quinases/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Guia de Cinetoplastídeos/metabolismo , Transdução de SinaisRESUMO
Gas chromatography-mass spectrometry (GC-MS) enables sensitive detection and relative quantification of fatty acids. In Caenorhabditis elegans, the use of GC-MS can corroborate findings from common staining methodologies, providing great resolution on the lipid species altered in abundance in aging, genetic mutants, or with dietary or pharmacologic manipulation. Here we describe a method to quantitate relative abundance of fatty acids in total worm lipid extracts, as well as a method that quantitates fatty acids following separation into neutral lipid pools (triacylglycerols and cholesteryl esters) versus more polar lipids (phospholipids) by solid-phase extraction (SPE).
Assuntos
Caenorhabditis elegans/genética , Ácidos Graxos/genética , Cromatografia Gasosa-Espectrometria de Massas/métodos , Lipídeos/genética , Animais , Ácidos Graxos/química , Ácidos Graxos/isolamento & purificação , Lipídeos/química , Lipídeos/isolamento & purificaçãoRESUMO
PURPOSE OF REVIEW: Metformin has multiple benefits for health beyond its anti-hyperglycemic properties. The purpose of this manuscript is to review the mechanisms that underlie metformin's effects on obesity. RECENT FINDINGS: Metformin is a first-line therapy for type 2 diabetes. Large cohort studies have shown weight loss benefits associated with metformin therapy. Metabolic consequences were traditionally thought to underlie this effect, including reduction in hepatic gluconeogenesis and reduction in insulin production. Emerging evidence suggests that metformin-associated weight loss is due to modulation of hypothalamic appetite regulatory centers, alteration in the gut microbiome, and reversal of consequences of aging. Metformin is also being explored in the management of obesity's sequelae such as hepatic steatosis, obstructive sleep apnea, and osteoarthritis. Multiple mechanisms underlie the weight loss-inducing and health-promoting effects of metformin. Further exploration of these pathways may be important in identifying new pharmacologic targets for obesity and other aging-associated metabolic diseases.