A very-low carbohydrate content in a high-fat diet modifies the plasma metabolome and alleviates experimental atherosclerosis

Ketogenic diets (KD) are very low-carbohydrate diets that promote nutritional ketosis and are widely used for weight loss, although concerns about potential adverse cardiovascular effects remain. In this study, we used apolipoprotein E deficient (ApoE -/-) mice to investigate the vascular impact and plasma metabolic signature of a very high-fat KD compared to a non-ketogenic high-fat diet (HFD). Plasma samples were collected after 4, 8, and 12 weeks on the experimental diets and used to quantify the major ketone body {beta}-hydroxybutyrate (BHB), inflammatory cytokines (interleukin 6, IL-6; monocyte chemoattractant protein 1, MCP-1; and tumor necrosis factor , TNF-), and targeted metabolomic profiling by mass spectrometry. Moreover, aortic atherosclerotic lesions were quantified ex vivo by magnetic resonance imaging (MRI) on a 14-tesla system. The results showed that, relative to HFD mice, the KD mice had markedly higher levels of BHB and lower levels of cytokines, confirming the presence of ketosis that alleviated the well-established fat-induced systemic inflammation. Moreover, mice under nutritional ketosis displayed a distinct plasma amino acid profile evidencing a KD-induced alteration in protein metabolism. Significant changes in the plasma metabolome in KD mice included a decrease in lipophilic and increase in hydrophilic metabolites. Despite the higher fat content of the KD versus the HFD, KD mice presented significantly lower levels of several lipid metabolites, including phosphatidylcholines, cholesterol esters, sphingomyelins, and ceramides. Consistent with the shift in energy metabolism toward fatty acid oxidation caused by the KD, the ratio of acylcarnitines to free carnitine was significantly higher in KD than in HFD mice., the aortic plaque burden was significantly lower in the KD versus the HFD group. In conclusion, nutritional ketosis induced by the KD was associated with specific metabolic changes and an atheroprotective phenotype versus the HFD.