Glucocorticoid Resistance Increases PPARγ Activity and Drives Hepatic Lipid Accumulation via Increased Eicosanoid and Monoacylglyceride Synthesis

A diet high in fat induces adiposity and obesity, and chronic feeding can lead to multiple metabolic complications, including type II diabetes, non-alcoholic fatty liver disease, and cardiovascular disease. The glucocorticoid receptor (GR) regulates genes that control metabolism. The GR has two isoforms (GRα and GRβ) that arise from the GR gene ( NR3C1) due to the alternative splicing of exon 9. The GRα isoform is the classical receptor that binds to glucocorticoids. However, the GRβ isoform has a truncated C-terminus. It cannot bind glucocorticoid steroids, and as a result, this isoform induces a glucocorticoid-resistant state when its expression is increased. We hypothesized that increasing levels of GRβ from long-term excess glucocorticoid exposure or a high-fat diet induces adiposity by affecting lipid metabolism and lipogenesis, causing fat to accumulate in the adipose and liver tissues. We first overexpressed GRβ (GRβ-Ad) or control (Vec-Ad) using adenovirus delivery and fed the mice a normal chow diet. The GRβ-Ad mice had significantly higher lipid accumulation within five days. Western blotting analysis revealed a significant increase (p-value <0.05) in the GRβ-Ad livers for fatty acid synthase (FAS) expression, and there was a remodeling of the hepatic lipid content as measured by mass spectrometry lipidomic analysis. The data indicate an increased level of monoacylglyceride lipid species and some species of long-chain triacylglycerides and diacylglycerides. mRNA analysis revealed a significant increase (p-value <0.05) in Carbohydrate-responsive element-binding protein (ChREBP), PPARγ, and Cyp2j6, indicating an increase in de novo lipogenesis and eicosanoid synthesis. We conclude that glucocorticoid resistance due to increased levels of GRβ drives de novo lipogenesis and increases eicosanoid synthesis, possibly via synergism with PPARγ. A better understanding of the GR isoforms and glucocorticoid resistance could benefit people with obesity and other metabolic disorders to improve obesity-associated comorbidities. R01DK121797 (T.D.H.J.), R01DA058933 (T.D.H.J.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.