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Impact of Diet Induced Obesity on Hyperoxic Lung Injury

ABSTRACT: Background: Obesity has become a worldwide concern. Acute respiratory distress syndrome (ARDS) comprises 10.4% of total intensive care unit admissions and is associated with very high mortality. ARDS incidence is increased in obese patients. Exposure of rodents to hyperoxia mimics many of the clinical and pathologic features observed in patients with ARDS. The aim of this study was to determine the impact of high fat diet-induced obesity on the susceptibility to hyperoxic acute lung injury in mice. Methods: Male C57BL/6 mice received 60% fat versus ingredient matched 10% fat diet. Mice were exposed to >95% oxygen to induce lung damage. RNA was isolated from lung homogenates and by comparing RNA sequencing results with mouse Mitocarta, an inventory of genes encoding proteins with mitochondrial localization, we identified fatty acid synthase (FASN), an enzyme catalyzing de novo fatty acid synthesis, as one of the mitochondrial genes significantly changed with diet and with hyperoxia. We generated mice deficient in FASN in alveolar epithelial cells by using a tamoxifen inducible Cre recombinase construct (FASNflox/flox SPC Cre+/-) and subjected them to hyperoxia and high fat diet. Results: Mice receiving 60% fat diet had significantly higher weight, serum cholesterol and fasting glucose. High fat diet mice had significantly reduced survival and increased lung damage, as assessed by BAL protein and LDH, histology and TUNEL staining. By RNA sequencing of lung homogenates we identified FASN as one of the mitochondrial genes significantly reduced in mice receiving 60% compared to 10% fat diet and further reduced with hyperoxia. We confirmed that FASN protein levels in the lung of high fat diet mice were lower by immunoblotting and immunohistochemistry. After 48 hours of hyperoxia FASNflox/flox SPC Cre+/- mice displayed increased levels of BAL protein and LDH and more severe histologic lung injury. FASNflox/flox SPC Cre+/- mice remained more prone to lung injury after hyperoxic exposure even when they received 60% fat diet. Conclusions: These results demonstrate that obesity increases the severity of hyperoxia induced acute lung injury in mice by altering FASN levels in the lung of high fat diet fed rodents. To our knowledge, this is the first study to show that high fat diet leads to altered FASN expression in the lung and that both high fat diet and reduced FASN in alveolar epithelial cells lead to increased lung injury under hyperoxic conditions.

ORGANISM(S): Mus musculus

PROVIDER: GSE123938 | GEO | 2019/07/25

REPOSITORIES: GEO

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Project description:Maternal obesity is linked with increased adverse outcomes for mother and fetus. However, the metabolic impact of excessive fat accumulation within the altered hormonal context of pregnancy is not well understood. We used a murine model of obesity, the high fat diet-fed C57BL/6J mouse to determine adipose tissue-mediated molecular mechanisms driving metabolic dysfunction throughout pregnancy. Remarkably, obese mice exhibited a normalization of visceral fat accumulation at late-stage pregnancy (-53%, P<0.001 E18.5) to achieve levels comparable in mass (per gram of body weight) to that of non pregnant, control diet fed mice. Moreover, whilst obese pregnant mice showed a marked glucose intolerance and apparent insulin resistance at mid-stage pregnancy (E14.5), glucose homeostasis converged with that of lean pregnant mice at late-stage pregnancy, suggesting an unexpected amelioration of the worsening metabolic dysfunction in obese pregnant mice. Transcriptomic analysis of the late-stage visceral fat indicated reduced de novo lipogenic drive (Me1, Fasn, Scd1, Dgat2), retinol metabolism (Rdh11, Rbp4) and inflammation (Mcp1, Tnfα) in obese pregnant mice that was confirmed functionally by their lower adipose proinflammatory macrophage density. Elevated expression of estrogen receptor a (ERα) in visceral adipose tissue was identified as potential unifying mechanism for the transcriptional changes and reduced adiposity of late stage obese pregnancy. Support for a role for ERα was provided by experiments showing that the ERα selective agonist PPT suppressed lipogenesis in primary mouse adipocytes and suppressed Me1, Fasn, SCD1 and Dgat2 mRNA levels in mature female human ChubS7 clonal fat cells. Our data reveal a novel role for elevated visceral adipocyte estrogen signaling as a protective mechanism against visceral fat hypertrophy and inflammation in late pregnancy. Pregnant high fat, pregnant control fat, non pregnant high fat, non pregnant control fat. Five biologial replictes each (20 samples).

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Impact of Diet Induced Obesity on Hyperoxic Lung Injury

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