Post-developmental deletion of adipocytes autophagy
Ontology highlight
ABSTRACT: Autophagy is a homeostatic cellular process involved in the degradation of long-lived/damaged cellular components. The role of autophagy in adipogenesis is well recognized, but its role in mature adipocyte function is largely unknown. We show that the autophagy proteins Atg3 and Atg16L1 are required for proper mitochondrial function in mature adipocytes. In contrast to previous studies, we found that post-developmental ablation of autophagy causes peripheral insulin resistance independently of diet or adiposity. Finally, lack of adipocyte autophagy reveals a - cross talk between fat and liver mediated by lipid peroxide-induced Nrf2 signaling. Our data reveal a - role for autophagy in preventing lipid peroxide formation and their transfer in insulin-sensitive peripheral tissues
Project description:Susceptibility to Crohn's disease, a complex inflammatory disease involving the small intestine, is controlled by over 30 loci. One Crohn's disease risk allele is in ATG16L1, a gene homologous to the essential yeast autophagy gene ATG16 (ref. 2). It is not known how ATG16L1 or autophagy contributes to intestinal biology or Crohn's disease pathogenesis. To address these questions, we generated and characterized mice that are hypomorphic for ATG16L1 protein expression, and validated conclusions on the basis of studies in these mice by analysing intestinal tissues that we collected from Crohn's disease patients carrying the Crohn's disease risk allele of ATG16L1. Here we show that ATG16L1 is a bona fide autophagy protein. Within the ileal epithelium, both ATG16L1 and a second essential autophagy protein ATG5 are selectively important for the biology of the Paneth cell, a specialized epithelial cell that functions in part by secretion of granule contents containing antimicrobial peptides and other proteins that alter the intestinal environment. ATG16L1- and ATG5-deficient Paneth cells exhibited notable abnormalities in the granule exocytosis pathway. In addition, transcriptional analysis revealed an unexpected gain of function specific to ATG16L1-deficient Paneth cells including increased expression of genes involved in peroxisome proliferator-activated receptor (PPAR) signalling and lipid metabolism, of acute phase reactants and of two adipocytokines, leptin and adiponectin, known to directly influence intestinal injury responses. Importantly, Crohn's disease patients homozygous for the ATG16L1 Crohn's disease risk allele displayed Paneth cell granule abnormalities similar to those observed in autophagy-protein-deficient mice and expressed increased levels of leptin protein. Thus, ATG16L1, and probably the process of autophagy, have a role within the intestinal epithelium of mice and Crohn's disease patients by selective effects on the cell biology and specialized regulatory properties of Paneth cells. Experiment Overall Design: 4 Samples: 2 replicates of Atg16-hypomorph Paneth cells and 2 replicates of Wildtype Paneth cells.
Project description:Susceptibility to Crohn's disease, a complex inflammatory disease involving the small intestine, is controlled by over 30 loci. One Crohn's disease risk allele is in ATG16L1, a gene homologous to the essential yeast autophagy gene ATG16 (ref. 2). It is not known how ATG16L1 or autophagy contributes to intestinal biology or Crohn's disease pathogenesis. To address these questions, we generated and characterized mice that are hypomorphic for ATG16L1 protein expression, and validated conclusions on the basis of studies in these mice by analysing intestinal tissues that we collected from Crohn's disease patients carrying the Crohn's disease risk allele of ATG16L1. Here we show that ATG16L1 is a bona fide autophagy protein. Within the ileal epithelium, both ATG16L1 and a second essential autophagy protein ATG5 are selectively important for the biology of the Paneth cell, a specialized epithelial cell that functions in part by secretion of granule contents containing antimicrobial peptides and other proteins that alter the intestinal environment. ATG16L1- and ATG5-deficient Paneth cells exhibited notable abnormalities in the granule exocytosis pathway. In addition, transcriptional analysis revealed an unexpected gain of function specific to ATG16L1-deficient Paneth cells including increased expression of genes involved in peroxisome proliferator-activated receptor (PPAR) signalling and lipid metabolism, of acute phase reactants and of two adipocytokines, leptin and adiponectin, known to directly influence intestinal injury responses. Importantly, Crohn's disease patients homozygous for the ATG16L1 Crohn's disease risk allele displayed Paneth cell granule abnormalities similar to those observed in autophagy-protein-deficient mice and expressed increased levels of leptin protein. Thus, ATG16L1, and probably the process of autophagy, have a role within the intestinal epithelium of mice and Crohn's disease patients by selective effects on the cell biology and specialized regulatory properties of Paneth cells.
Project description:There is increasing evidence that autophagy contributes to the epidermal differentiation; however, the role of autophagy in epidermal tight junction (TJ) barrier remains unclear. To evaluate the role of autophagy in the maintenance of skin TJ barrier, we knocked out autophagy in human primary keratinocytes by infecting cells with autophagy-related gene 3 (Atg3) C264S mutant adenovirus.
Project description:The identification of Atg16L1 as a susceptibility gene has implicated antibacterial autophagy in the pathogenesis of Crohn's disease, a major type of inflammatory bowel disease (IBD). However, the role of Atg16L1 during extracellular bacterial infections of the intestine has not been sufficiently examined and compared to the function of other IBD susceptibility genes such as Nod2. We now find that Atg16L1 mutant mice are extraordinarily resistant to intestinal disease induced by the model bacterial pathogen Citrobacter rodentium. We further demonstrate that Atg16L1 deficiency alters the intestinal environment to mediate an enhanced immune response that is dependent on monocytic cells, and that Atg16L1/Nod2 double mutant mice lose this advantage. These results reveal an unappreciated immuno-suppressive function of an IBD gene, and raise the possibility that gene variants that affect the autophagy pathway were evolutionarily maintained to protect against certain life-threatening infections. Twenty samples have been analyzed. All are colonic tissue from mice. Controls are uninfected WT mice, uninfected Atg16L1 mutant mice (Atg16L1HM) (n=3/genotype). Treatment conditions are tissue from WT and Atg16L1 mutant mice 6 days after C. rodentium infection (n=4/genotype) and 15 days after infection (n=3/genotype).
Project description:Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can be induced by a high-fat diet. CD1d-restricted invariant natural killer T (iNKT) cells have been proposed as mediators between lipid overload and insulin resistance, but recent studies found decreased iNKT cell numbers and marginal effects of iNKT cell depletion on insulin resistance under high-fat diet conditions. Here, we focused on the role of iNKT cells under normal conditions. We showed that iNKT cell–deficient mice on a low-fat diet, considered a normal diet for mice, displayed a distinctive insulin resistance phenotype without overt adipose tissue inflammation. Insulin resistance was characterized by adipocyte dysfunction, including adipocyte hypertrophy, increased leptin, and decreased adiponectin levels. The lack of liver abnormalities in CD1d-null mice together with the enrichment of CD1d-restricted iNKT cells in both mouse and human adipose tissue indicated a specific role for adipose tissue–resident iNKT cells in the development of insulin resistance. Strikingly, iNKT cell function was directly modulated by adipocytes, which acted as lipid antigen-presenting cells in a CD1d-mediated fashion. Based on these findings, we propose that, especially under low-fat diet conditions, adipose tissue–resident iNKT cells maintain healthy adipose tissue through direct interplay with adipocytes and prevent insulin resistance. four samples
Project description:The identification of Atg16L1 as a susceptibility gene has implicated antibacterial autophagy in the pathogenesis of Crohn's disease, a major type of inflammatory bowel disease (IBD). However, the role of Atg16L1 during extracellular bacterial infections of the intestine has not been sufficiently examined and compared to the function of other IBD susceptibility genes such as Nod2. We now find that Atg16L1 mutant mice are extraordinarily resistant to intestinal disease induced by the model bacterial pathogen Citrobacter rodentium. We further demonstrate that Atg16L1 deficiency alters the intestinal environment to mediate an enhanced immune response that is dependent on monocytic cells, and that Atg16L1/Nod2 double mutant mice lose this advantage. These results reveal an unappreciated immuno-suppressive function of an IBD gene, and raise the possibility that gene variants that affect the autophagy pathway were evolutionarily maintained to protect against certain life-threatening infections.
Project description:The clear role of autophagy in human inflammatory diseases such as Crohn’s disease was first identified by genome-wide association studies and subsequently dissected in multiple mechanistic studies. ATG16L1 has been particularly well studied in knockout and hypomorph settings as well as models recapitulating the Crohn’s disease-associated T300A polymorphism. Interestingly, ATG16L1 has a single homolog, ATG16L2, which is independently implicated in diseases including Crohn’s disease and systemic lupus erythematosus. However, the contribution of ATG16L2 to canonical autophagy pathways and other cellular functions is poorly understood.To better understand its role, we generate and analyze the first, to our knowledge, ATG16L2 knockout mouse. Our results show that ATG16L1 and ATG16L2 contribute very distinctly to autophagy and cellular ontogeny in myeloid, lymphoid and epithelial lineages. Dysregulation of any of these lineages could contribute to complex diseases like Crohn’s disease and systemic lupus erythematosus, highlighting the value of examining cell-specific effects. We also identify a novel genetic interaction between ATG16L2 and epithelial ATG16L1. These findings are discussed in the context of how these genes may contribute distinctly to human disease.
Project description:In order to unravel the functional role of autophagy in skin homeostasis, we performed single-cell RNA-sequencing on total skin of 10-weeks-old male mice lacking ATG16L1 selectively in keratinocytes. Keratinocyte-specific ATG16L1 knock-out (KO) mice do not show an overt skin phenotype. By performing single-cell analysis on total skin of control mice and mice lacking ATG16L1 in keratinocytes, we could identify a crucial role for keratinocyte autophagyin mediating the timing of hair follicle stem cell activation in hair growth.
Project description:Cell membrane phosphatidylcholine composition is regulated by lysophosphatidylcholine acyltransferase (LPCAT); changes in membrane phosphatidylcholine saturation are implicated in metabolic disorders. Here, we identified LPCAT3 as the major isoform of LPCAT in adipose tissues and created adipocyte-specific Lpcat3-knockout mice to study adipose tissue lipid metabolism. Transcriptome sequencing and plasma adipokine profiling were used to investigate how LPCAT3 regulates adipose tissue insulin signaling. LPCAT3 deficiency reduced polyunsaturated phosphatidylcholines in adipocyte plasma membranes, increasing insulin sensitivity. LPCAT3 deficiency influenced membrane lipid rafts, which activated insulin receptors and AKT in adipose tissue, and attenuated diet-induced insulin resistance. Conversely, higher LPCAT3 activity in adipose tissues from ob/ob, db/db, and high-fat diet-fed mice reduced insulin signaling. Adding polyunsaturated phosphatidylcholines to mature human or mouse adipocytes in vitro worsened insulin signaling. We suggest that targeting LPCAT3 in adipose tissues to manipulate membrane phospholipid saturation is a new strategy to treat insulin resistance.
Project description:Cell membrane phosphatidylcholine composition is regulated by lysophosphatidylcholine acyltransferase (LPCAT); changes in membrane phosphatidylcholine saturation are implicated in metabolic disorders. Here, we identified LPCAT3 as the major isoform of LPCAT in adipose tissues and created adipocyte-specific Lpcat3-knockout mice to study adipose tissue lipid metabolism. Transcriptome sequencing and plasma adipokine profiling were used to investigate how LPCAT3 regulates adipose tissue insulin signaling. LPCAT3 deficiency reduced polyunsaturated phosphatidylcholines in adipocyte plasma membranes, increasing insulin sensitivity. LPCAT3 deficiency influenced membrane lipid rafts, which activated insulin receptors and AKT in adipose tissue, and attenuated diet-induced insulin resistance. Conversely, higher LPCAT3 activity in adipose tissues from ob/ob, db/db, and high-fat diet-fed mice reduced insulin signaling. Adding polyunsaturated phosphatidylcholines to mature human or mouse adipocytes in vitro worsened insulin signaling. We suggest that targeting LPCAT3 in adipose tissues to manipulate membrane phospholipid saturation is a new strategy to treat insulin resistance.