Transcriptomic changes underlying the anti-steatotic effects of DHA supplementation in aged obese female mice
The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) increases with age and obesity. The aim of this study is to characterize the transcriptomic changes in liver underlying the beneficial effects of docosahexaenoic acid (DHA) supplementation on MASLD progression in aged obese female mice. Two-month-old C57BL/6J female mice were fed ad libitum with high fat saturated diet (HFD, 45%) for 4 months. These diet-induced obese (DIO) mice were divided into two groups: the DIO group that continued with HFD and the DIO + DHA mice fed up to 18 months with the HFD containing a DHA-rich concentrate. High quality RNA from liver was used to perform RNA sequencing analysis. Further functional and clustering analyses of differentially expressed genes (DEGs) in liver between treatments revealed that DHA regulated processes related to lipid metabolic processes such as fatty acid beta oxidation, lipid storage, fatty acid transport and lipid localization. DHA treatment also affects PPAR signaling pathway and the regulation of inflammatory response. These data suggest that long-term DHA supplementation ameliorates MASLD progression in aged obese female mice by promoting transcriptomic changes in genes related to lipid metabolism and inflammatory response. Overall design: RNAseq profiling of livers from 18 month-old DIO and DIO+DHA female mice. Two months-old C57BL/6J mice  were fed ad libi-tum for 4 months with high fat diet (HFD) containing as energy: 20% proteins, 35% carbohydrates, and 45% lipids (D12451 diet, Research Diets, Inc., New Brunswick, NJ USA). Then, DIO mice were divided into two groups: (1) the DIO group  continued with the HFD up to 18 months and (2) the DIO + DHA group, which was fed up to 18 months with the HFD containing a DHA-rich n-3 PUFA concentrate obtained from fish oil, replacing 15% wt/wt of dietary lipids (Research Diets Inc., New Brunswick, NJ, USA). The DHA-rich n-3 PUFA concentrate contained 683.4 mg DHA/g, 46.7 mg EPA/g, with a total content of n-3 PUFA of 838.9 mg/g as triglycerides.