Despite the early recognition that individuals living with obesity are more prone to develop adverse outcomes during COVID-19, the mechanisms underlying these conditions are still unclear. During obesity, an accumulation of free fatty acids (FFAs) in the circulation promotes low-grade inflammation. Here, we show that FFAs induce epigenetic reprogramming of monocytes, exacerbating their inflammatory profile after SARS-CoV-2 infection, a mechanism named metabolic-primed immunity. Monocytes from people with obesity or primed with palmitate, a central component of circulating FFAs, presented elevated viral load and higher gene expression of IL-6. Palmitate-primed monocytes upregulate fatty acid oxidation and FFAs entry into the mitochondria. FFA-derived acetyl-CoA is then converted into citrate, exiting the mitochondria and is used to support H3K18 histone acetylation, which regulates IL-6 accessibility. Ingestion of palm oil by lean and healthy individuals increased circulating FFAs levels and was sufficient to exacerbate the inflammatory profile of monocytes upon SARS-CoV-2 infection. Our findings demonstrate that obesity-derived FFAs induce the metabolic priming of monocytes, which exacerbates the inflammatory response observed in people with severe COVID-19.
Keywords: COVID‐19; inflammation; innate immunity; monocyte; obesity.
© 2025 The Author(s). Immunology published by John Wiley & Sons Ltd.