👤 María V Hernández-Hernández

Lung type 2 pneumocytes (T2Ps) and alveolar macrophages (AMs) play crucial roles in the synthesis, recycling and catabolism of surfactant material, a lipid/protein fluid essential for respiratory function. The liver X receptors (LXR), LXRα and LXRβ, are transcription factors important for lipid metabolism and inflammation. While LXR activation exerts anti-inflammatory actions in lung injury caused by lipopolysaccharide (LPS) and other inflammatory stimuli, the full extent of the endogenous LXR transcriptional activity in pulmonary homeostasis is incompletely understood. Here, using mice lacking LXRα and LXRβ as experimental models, we describe how the loss of LXRs causes pulmonary lipidosis, pulmonary congestion, fibrosis and chronic inflammation due to defective de novo synthesis and recycling of surfactant material by T2Ps and defective phagocytosis and degradation of excess surfactant by AMs. LXR-deficient T2Ps display aberrant lamellar bodies and decreased expression of genes encoding for surfactant proteins and enzymes involved in cholesterol, fatty acids, and phospholipid metabolism. Moreover, LXR-deficient lungs accumulate foamy AMs with aberrant expression of cholesterol and phospholipid metabolism genes. Using a house dust mite aeroallergen-induced mouse model of asthma, we show that LXR-deficient mice exhibit a more pronounced airway reactivity to a methacholine challenge and greater pulmonary infiltration, indicating an altered physiology of LXR-deficient lungs. Moreover, pretreatment with LXR agonists ameliorated the airway reactivity in WT mice sensitized to house dust mite extracts, confirming that LXR plays an important role in lung physiology and suggesting that agonist pharmacology could be used to treat inflammatory lung diseases. Show less

Tocilizumab (TCZ) treatment is associated with dyslipidaemia, including a rise in triglycerides through a mechanism poorly understood. Three molecules play key roles in the regulation of triglyceride metabolism: apolipoprotein C-III (ApoC-III), angiopoietin-like protein 4(ANGPLT4) and lipoprotein lipase (LPL). The aim of this work was to analyse whether the changes in triglycerides shown by TCZ-treated RA patients could stem from the dysregulation that can occur in these regulatory molecules. Twenty-seven RA patients included in the TOCRIVAR study who received TCZ (8 mg/kg IV/q4w) were evaluated at baseline and at Weeks 12, 24 and 52 of treatment. ANGPTL4, ApoC-III and LPL, a complete lipid profile and RA disease activity, were analysed at baseline and at each visit. Multivariable linear mixed models were performed to study changes over time in lipids and regulatory molecules. After 24 weeks of TCZ treatment, HDL cholesterol, apolipoprotein A1 and triglycerides increased, whereas lipoprotein (a) decreased significantly from baseline values. However, 1 year after TCZ, no significant differences in lipid pattern were observed with respect to baseline. Serum ANGPTL4 and Apo-CIII levels decreased gradually over time, both being significantly lower than baseline values at Week 52. LPL concentration did not change significantly during TCZ treatment. Remarkably, the elevation of triglycerides at Week 24 maintained its statistical significance after adjusting for the changes in ApoC-III, ANGPTL4 and LPL. In TCZ-treated RA patients basal serum levels of ANGPLT4 and ApoC-III, but not LPL, decreased significantly. However, the elevation of triglycerides after TCZ was not related to changes in these regulatory molecules. Show less

Modulators of triglyceride metabolism include lipoprotein lipase (LPL), angiopoietin-like protein 4 (ANGPTL4), and apolipoprotein C-3 (ApoC3). There is evidence on the influence of this triangle of molecules on an increased risk of atherosclerotic cardiovascular disease (CV) in the general population. Patients with rheumatoid arthritis (RA) present changes in lipid profiles and accelerated CV disease. In the present study, we set out to study whether the ANGPTL4, ApoC3, and LPL axis differs in subjects with RA compared to controls. In a further step, we investigated the relationship of this axis with subclinical atherosclerosis in patients with RA. Cross-sectional study that included 569 individuals, 323 patients with RA and 246 age-matched controls. ANGPTL4, ApoC3 and LPL, and standard lipid profiles were analyzed in patients and controls. Carotid intima-media thickness (cIMT) and carotid plaques were assessed in RA patients. A multivariable analysis was performed to assess whether the ANGPTL4, ApoC3, and LPL axis was altered in RA and to study its relationship with RA dyslipidemia and subclinical carotid atherosclerosis. Most lipid profile molecules did not differ between patients and controls. Despite this, and after fully multivariable analysis including CV risk factors, use of statins, and changes in the lipid profile caused by the disease itself, patients with RA showed higher serum levels of ANGPTL4 (beta coef. 295 [95% CI 213-376] ng/ml, p<0.001) and ApoC3 (beta coef. 2.9 [95% CI 1.7-4.0] mg/dl, p<0.001), but lower circulating LPL (beta coef. -174 [95% CI -213 to -135] ng/ml, p<0.001). ANGPTL4 serum levels were positively and independently associated with a higher cIMT in patients with RA after fully multivariable adjustment. The axis consisting in ANGPTL4, ApoC3, and LPL is disrupted in patients with RA. ANGPTL4 serum levels are positively and independently associated with a higher cIMT in RA patients. Show less