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A transcriptomic analysis of primary mature adipocytes from lean, obese, and type 2 diabetic subjects: role of the extracellular matrix

ABSTRACT: Type 2 diabetes is associated with obesity, and is characterized by insulin resistance in target tissues of the hormone combined with insufficient systemic insulin. Insulin resistance apparently begins in subcutaneous adipocytes that fail to further accumulate triacylglycerol. To understand the pathogenesis of transition from lean to obesity and to diabetes, we performed transcriptome profiling by RNA-sequencing of isolated primary human adipocytes. Half of identified transcripts were protein-coding and shared between individuals, while non-protein-coding transcripts were subject specific. Differential gene expression between lean and diabetes reflected corresponding changes in 7 of 12 characterized insulin-signaling proteins. In the tissue, adipocytes are surrounded by extracellular matrix (ECM) providing a dynamic scaffold. However, excess ECM is implicated in obesity and diabetes. Bioinformatic analyses of transcriptomes revealed major upregulation of genes related to ECM in obese compared with lean, which was reversed in diabetes. However, biochemical analysis of adipose tissue demonstrated reduced ECM in obesity or diabetes compared with lean. We conclude that marked changes in the adipocyte transcriptome related to ECM do not reflect global adipose tissue fibrosis, but likely control the pericellular milieu surrounding the adipocyte; and excess ECM is not a feature of subcutaneous adipose tissue in obesity or diabetes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE133099 | GEO | 2019/06/21

REPOSITORIES: GEO

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Project description:Development of insulin resistance is a key pathogenic component underlying metabolic syndrome and Type 2 diabetes (T2DM). Despite its importance, the molecular mechanisms underlying insulin resistance are poorly understood. Genome-wide association studies for T2DM and other metabolic traits have led to the identification of many candidate SNPs, but the majority of these SNPs are noncoding and determination of associated causal genes and/or specific tissue sites of action have been difficult. Adipocytes are critical regulators of mammalian metabolic homeostasis, with important effects on appetite, satiety, glucose and lipid homeostasis, energy expenditure, blood pressure, and immune function. Although insulin resistance (IR) in skeletal muscle, the major source of glucose disposal, is responsible for the bulk of the hyperglycemia observed in T2DM, muscle IR KO mice are generally healthy, IR also occurs in adipocytes, and inflammation within adipose tissue has been proposed as a primary mediator of IR, resulting in excess release of free fatty acids as well as alterations in adipokine release. Absence of adipose tissue, as observed in various lipodystrophies, or adipocyte-specific knockout of genes such as GLUT4 or insulin receptor, also alter systemic IR and T2DM risk. Transcriptional changes in adipocytes associated with metabolic disease. Despite the importance of adipocytes to metabolic disease, we have a poor understanding of how the adipocyte transcriptome changes in the disease state. Studies investigating transcriptional changes in whole adipose tissue have shown decreases in genes involved in adipogenesis, as well as alterations in inflammation, mitochondrial metabolism, lipid metabolism, detoxification, and insulin signaling. However, the vast majority of these studies use total adipose tissue samples, which does not allow for the exclusive evaluation of gene expression in mature adipocytes due to the substantial number of nonadipocyte cells (immune cells, fibroblasts, endothelial cells, pre-adipocytes, and mesenchymal cells) that also reside in adipose tissue. This is particularly relevant when studying metabolic disorders related to obesity-associated insulin resistance because these conditions are characterized by an increased influx of inflammatory cells into the adipose tissue.

Project description:The expression of adipogenic genes is decreased in obesity and diabetes mellitus ; Samuel T. Nadler*, Jonathan P. Stoehr*, Kathryn L. Schueler*, Gene Tanimoto, Brian S. Yandell, and Alan D. Attie*,Â§ ; Departments of * Biochemistry, and Statistics and Horticulture, University of Wisconsin, Madison, WI, 53706; and Affymetrix, Inc., Santa Clara, CA 95051 ; Communicated by Neal L. First, University of Wisconsin, Madison, WI, July 13, 2000 (received for review April 3, 2000) ; Obesity is strongly correlated with type 2 diabetes mellitus, a common disorder of glucose and lipid metabolism. Although adipocytes are critical in obesity, their role in diabetes has only recently been appreciated. We conducted studies by using DNA microarrays to identify differences in gene expression in adipose tissue from lean, obese, and obese-diabetic mice. The expression level of over 11,000 transcripts was analyzed, and 214 transcripts showed significant differences between lean and obese mice. Surprisingly, the expression of genes normally associated with adipocyte differentiation were down-regulated in obesity. Not all obese individuals will become diabetic; many remain normoglycemic despite profound obesity. Understanding the transition to obesity with concomitant diabetes will provide important clues to the pathogenesis of type 2 diabetes. Therefore, we examined the levels of gene expression in adipose tissue from five groups of obese mice with varying degrees of hyperglycemia, and we identified 88 genes whose expression strongly correlated with diabetes severity. This group included many genes that are known to be involved in signal transduction and energy metabolism as well as genes not previously examined in the context of diabetes. Our data show that a decrease in expression of genes normally involved in adipogenesis is associated with obesity, and we further identify genes important for subsequent development of type 2 diabetes mellitus. Experiment Overall Design: For obesity study, lean samples include C57BL/6J lean, (C57BL/6J X BTBR) F1 and BTBR lean, obese sampples incluse C57BL/6J-ob/ob, (C57BL/6J X BTBR) F2-ob/ob and BTBR-ob/ob. All samples are subjected to Mu11K A and B arrays. Experiment Overall Design: For diabetes study, B6-ob/ob, (C57BL/6J X BTBR) F2-ob/ob low glucose, (C57BL/6J X BTBR) F2-ob/ob medium glucose, (C57BL/6J X BTBR) F2-ob/ob high glucose, and BTBR-ob/ob samples were analyzed for genes whose expression levels changes correlated with the plasma glucose levels in these mice. All samples are subjected to Mu11K A and B arrays.

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A transcriptomic analysis of primary mature adipocytes from lean, obese, and type 2 diabetic subjects: role of the extracellular matrix

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