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Stomatin modulates adipogenesis through ERK pathway and regulates fatty acid uptake and lipid droplet growth

ABSTRACT: Controlling fatty acid uptake, lipid production and storage, and metabolism of lipid droplets (LDs), is closely related to lipid homeostasis, adipocyte hypertrophy and obesity. We report here that stomatin, a major constituent of lipid rafts, participates in adipogenesis and adipocyte maturation by modulating related signaling pathways. In adipocyte-like cells, increased stomatin promotes LD growth or enlargements by facilitating LD-LD fusion, as well as fatty acid uptake from extracellular environment by recruiting effector molecules, such as FAT/CD36 translocase, to lipid rafts to promote internalization of fatty acids. Stomatin transgenic mice fed with high-fat diets exhibit obesity, insulin resistance and hepatic impairments; however, such phenotypes are not seen if feeding the transgenic animals with regular diets. Inhibitions of stomatin by gene knockdown or OB-1 pharmacological treatments inhibit adipogenic differentiation and LD growth through downregulation of PPARγ pathway. Effects of stomatin on PPARγ involve ERK signaling; however, an alternate pathway may also exist. Differential expression analyses by microarray were performed comparing stomatin-knockdown and control 3T3-L1 adipocyte-like cells.

ORGANISM(S): Mus musculus

PROVIDER: GSE205011 | GEO | 2022/05/28

REPOSITORIES: GEO

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Project description:Background. Obesity and body fat distribution are important risk factors for the development of type 2 diabetes and metabolic syndrome. Evidence has accumulated that this risk is related to intrinsic differences in behavior of adipocytes in different fat depots. LIM Domain Only 3 (LMO3) plays a crucial role in adipogenesis modulating the key adipogenic master switch PPARγ in human, but not mouse, visceral adipose progenitors; however, despite high expression in mature adipocytes, its function in these cells is currently unknown. Aims/Hypothesis. The aim of this study was to determine the potential involvement of LMO3-dependent pathways in the modulation of key functions of mature adipocytes during obesity. Methods. Based on a recently engineered hybrid rAAV serotype Rec2 shown to efficiently transduce both brown adipose tissue (BAT) and white adipose tissue (WAT), we delivered YFP or Lmo3 to epididymal WAT (eWAT) of C57Bl6/J mice on a high fat diet (HFD). The effects of eWAT transduction on metabolic parameters were evaluated 10 weeks later. To further define the role of LMO3 in insulin-stimulated glucose uptake, insulin signaling, adipocyte bioenergetics as well as endocrine function, experiments were conducted in 3T3-L1 adipocytes and newly differentiated human primary mature adipocytes, engineered for transient gain- or loss of LMO3 expression, respectively.Results. AAV transduction of eWAT results in strong and stable Lmo3 expression specifically in the adipocyte fraction over a course of 10 weeks with HFD feeding. Lmo3 expression in eWAT significantly improved glucose clearance and insulin sensitivity in diet-induced obesity, paralleled by increased serum adiponectin. In vitro, Lmo3 expression in 3T3-L1 adipocytes increased insulin-stimulated GLUT4 translocation and glucose uptake as well as mitochondrial oxidative capacity in addition to fatty acid oxidation. On a molecular level, LMO3 augmented PPARg activity, oxidative mitochondrial gene expression, which depended on and the expression of the PPARg co-activator Ncoa1, which was required for LMO3 effects on mitochondria and glucose uptake. In human mature adipocytes, LMO3 overexpression promoted, while silencing of LMO3 suppressed mitochondrial oxidative capacity. Conclusions. LMO3 expression in visceral adipose tissue regulates multiple genes that preserve adipose tissue functionality during obesity, such as glucose tolerance, insulin sensitivity and adiponectin secretion. Together with increased PPARγ activity, these gene expression changes promote insulin-induced GLUT4 translocation, glucose uptake in addition to increased mitochondrial oxidative capacity, limiting HFD-induced adipose dysfunction. These data add LMO3 as a novel regulator improving visceral adipose tissue function during obesity.

Project description:Growing evidence suggests that chemicals in disparate structural classes activate specific subsets of PPARγ’s transcriptional programs to generate adipocytes with distinct phenotypes. Our objectives were to 1) establish a novel classification method to predict PPARγ-interacting and modifying chemicals and 2) create taxonomy labels to group chemicals based on their effects on PPARγ’s transcriptome and downstream metabolic functions. We tested the hypothesis that an environmental ligand highly ranked by the taxonomy, but that segregated from the therapeutic ligands, would induce white but not brite adipogensis. 3T3-L1 cells were differentiated in the presence of 76 chemicals (negative controls, synthetic nuclear receptor ligands known to influence adipocyte biology, suspected environmental PPARγ ligands). Differentiation was assessed by measuring lipid accumulation. mRNA expression was determined by highly multiplexed RNA-Seq and validated by RT-qPCR. A novel classification model was developed using an amended random forest procedure. A subset of environmental contaminants identified as strong PPARγ agonists were characterized further for lipid handling, mitochondrial biogenesis and cellular respiration in 3T3-L1 cells and primary human preadipocytes. The 76 chemicals generated a spectrum of adipogenic differentiation. We used lipid accumulation and RNA sequencing data to develop a classification system that 1) identified PPARγ agonists and 2) sorted agonists into likely white or brite adipocyte inducers. Expression of Cidec, was the most efficacious indicator for strong PPARγ activation. Two known environmental PPARγ ligands, tetrabromobisphenol A, and triphenyl phosphate, which sorted distinctly from therapeutic ligands, induced white but not brite adipocyte genes and induced fatty acid uptake but not mitochondrial biogenesis in 3T3-L1 cells. The highly ranked agonists, tonalid and quinoxyfen, also induced white adipogenesis in 3T3-L1 cells and primary human preadipocytes. A novel classification procedure accurately identified environmental chemicals as PPARγ-modifying chemicals distinct from known PPARγ-modifying therapeutics.

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Stomatin modulates adipogenesis through ERK pathway and regulates fatty acid uptake and lipid droplet growth

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