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Increased adipose tissue fibrogenesis, not impaired expandability, is associated with nonalcoholic fatty liver disease

ABSTRACT: BACKGROUND AND AIMS: It is proposed that impaired expansion of subcutaneous adipose tissue (SAT), caused in part by an increase in adipose tissue fibrosis, redirects fatty acids to the liver and other organs, leading to ectopic lipid accumulation and insulin resistance. We therefore evaluated whether a decrease in SAT expandability, assessed by measuring SAT lipogenesis (triglyceride production), and an increase in SAT fibrogenesis (collagen production) are associated with nonalcoholic fatty liver disease (NAFLD) and insulin resistance in people with obesity. APPROACH AND RESULTS: In vivo SAT lipogenesis and fibrogenesis, the expression of SAT genes involved in extracellular matrix (ECM) formation, and insulin sensitivity were assessed in three groups stratified by adiposity, insulin sensitivity and intrahepatic triglyceride (IHTG) content: 1) healthy lean (Lean-NL; n=12); 2) obese with normal IHTG content and normal glucose tolerance (Ob-NL; n=25); and 3) obese with NAFLD and abnormal glucose metabolism (Ob-NAFLD; n=25). Abdominal SAT total triglyceride synthesis rates were greater in the Ob-NL (65.9±4.6 g/wk) and Ob-NAFLD (71.1±6.7 g/wk) than the Lean-NL group (16.2±2.8 g/wk), without a difference between the obese groups. Abdominal SAT collagen synthesis rate and the composite expression of collagen genes progressively increased from Lean-NL to Ob-NL to Ob-NAFLD and were greater in the Ob-NAFLD than the Ob-NL group (P<0.05). Collagen synthesis rate and the composite expression of collagen genes correlated with factors that regulate collagen production, including circulating insulin and fibrogenic factors in SAT (all P<0.001). CONCLUSIONS: Adipose tissue lipogenesis and expandability are not impaired in people with obesity and NAFLD. However, SAT fibrogenesis and extracellular matrix remodeling are greater in people with obesity and NAFLD than in those with obesity and normal IHTG content. ClinicalTrials.gov number: NCT02706262.

ORGANISM(S): Homo sapiens

PROVIDER: GSE159924 | GEO | 2021/10/01

REPOSITORIES: GEO

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Project description:A time course of the effect of overexpressing GPI-PLD on global gene expression in HepG2 cells was compared to control virus. Experiment Overall Design: This experiment compares the global gene expression in HepG2 cells that were either transduced with an adenovirus expressing GPI-phospholipase D or an adenovirus expressing beta galactosidase as a control. Treatment was for 6 or 12 hrs. Four replicates for each condition were used. 10 micrograms of total RNA was assayed per genechip using standard Affymetrix protocols. CONTEXT: Recent studies demonstrated that de novo lipogenesis is increased in patients with nonalcoholic fatty liver disease (NAFLD). Patients with NAFLD also have plasma lipid abnormalities. These lipid abnormalities may in part be related to insulin resistance, which is common in patients with NAFLD. Insulin resistance is associated with alterations in proteins involved in lipid metabolism including glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), which is involved in triglyceride metabolism. OBJECTIVE: The objective of the study was to determine whether alterations in serum and hepatic levels of GPI-PLD occur in patients with NAFLD. DESIGN AND PATIENTS: We examined the following: 1) levels of serum GPI-PLD in nondiabetics with nonalcoholic steatohepatitis, compared with matched controls; 2) hepatic expression of GPI-PLD mRNA in patients with normal liver or NAFLD; and 3) effect of overexpressing GPI-PLD vs. beta-galactosidase (control) on global gene expression in a human hepatoma cell line. RESULTS: The serum levels of GPI-PLD were significantly higher in patients with nonalcoholic steatohepatitis than in matched controls (119 +/- 24 vs.105 +/- 15 microg/ml, P = 0.047). The hepatic expression of GPI-PLD mRNA was increased nearly 3-fold in NAFLD patients, compared with patients with normal liver (3.1 +/- 2.6 vs. 1.1 +/- 1.0 arbitrary units per microgram total RNA, P = 0.026). Finally, overexpressing GPI-PLD was associated with an increase in de novo lipogenesis genes. CONCLUSIONS: Patients with NAFLD have elevated serum levels and hepatic expression of GPI-PLD, and its overexpression in vitro is associated with increased expression of de novo lipogenesis genes. These results suggest that GPI-PLD may play a role in the pathogenesis of NAFLD and/or its metabolic features and warrants further investigation.

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Increased adipose tissue fibrogenesis, not impaired expandability, is associated with nonalcoholic fatty liver disease

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