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Endothelial cell senescence is the main risk factor contributing to vascular dysfunction and the progression of aging-related cardiovascular diseases. However, the relationship between endothelial cell metabolism and endothelial senescence remains unclear. The present study provides novel insight into fatty acid metabolism in the regulation of endothelial senescence. In the replicative senescence model and H2O2-induced premature senescence model of primary cultured human umbilical vein endothelial cells (HUVECs), fatty acid oxidation (FAO) was suppressed and fatty acid profile was disturbed, accompanied by downregulation of proteins associated with fatty acid uptake and mitochondrial entry, in particular the FAO rate-limiting enzyme carnitine palmitoyl transferase 1A (CPT1A). Impairment of fatty acid metabolism by silencing CPT1A or CPT1A inhibitor etomoxir facilitated the development of endothelial senescence, as implied by the increase of p53, p21, and senescence-associated β-galactosidase, as well as the decrease of EdU-positive proliferating cells. In the contrary, rescue of FAO by overexpression of CPT1A or supplement of short chain fatty acids (SCFAs) acetate and propionate ameliorated endothelial senescence. In vivo, treatment of acetate for 4 weeks lowered the blood pressure and alleviated the senescence-related phenotypes in aortas of Ang II-infused mice. Mechanistically, fatty acid metabolism regulates endothelial senescence via acetyl-coenzyme A (acetyl-CoA), as implied by the observations that suppression of acetyl-CoA production using the inhibitor of ATP citrate lyase NDI-091143 accelerated senescence of HUVECs and that supplementation of acetyl-CoA prevented H2O2-induced endothelial senescence. Deficiency of acetyl-CoA resulted in alteration of acetylated protein profiles which are associated with cell metabolism and cell cycle. These findings thus suggest that improvement of fatty acid metabolism might ameliorate endothelial senescence-associated cardiovascular diseases.

A decentralized sewage treatment reactor was designed to treat wastewater in rural areas. To examine the factors influencing nitrogen removal, experiments were carried out at three levels of hydraulic surface load, three sludge concentrations, and three environment temperatures at low dissolved oxygen concentrations. The rate of denitrification decreased, and the rate of nitrification increased as the surface load rose. The maximum denitrification rate was 20.01 ± 3.02 g/(m3·d) at a surface load of 1.11 ± 0.13 m3/(m2·h). The total nitrogen (TN) removal, efficiency initially increased and then decreased as the sludge concentration rose. When the sludge concentration increased to 3.5 ± 0.3 g/L, the system showed a good level of TN removal and a denitrification rate of 28.58 ± 1.22 g/(m3·d) was achieved. Low temperature had a negative effect on the removal and transformation of nitrogenous pollutants.