MIF-2/D-DT is an atypical atherogenic chemokine that promotes advanced atherosclerosis and hepatic lipogenesis

Atherosclerosis is the underlying cause of cardiovascular diseases (CVDs) such as myocardial infarction and ischemic stroke. It is a lipid-triggered chronic inflammatory condition of the arterial vascular wall that is driven by various inflammatory pathways including atherogenic cytokines and chemokines. D-dopachrome tautomerase (D-DT), also known as macrophage migration inhibitory factor-2 (MIF-2), belongs to the MIF protein family, which is best known for its pathogenic role in a variety of inflammatory and immune conditions including CVDs. While MIF is well known as a promoter of atherogenic processes, MIF-2 has not been studied in atherosclerosis. Here, we investigated atherosclerosis in hyperlipidemic Mif-2-/-Apoe-/- mice and studied the role of MIF-2 in various atherogenic assays in vitro. We found that global Mif-2 deficiency as well as its pharmacological blockade by 4-CPPC protected against atherosclerotic lesion formation and vascular inflammation in models of early and advanced atherogenesis. On cellular level, MIF-2 promoted monocyte migration in 2D and 3D and monocyte arrest on aortic endothelial monolayers, promoted B-cell chemotaxis in vitro and B-cell homing in vivo, and increased macrophage foam cell formation. Dose curves and direct comparison in a 3D migration set-up suggest that MIF-2 may be a more potent chemokine than MIF for monocytes and B cells. We identify CXCR4 as a novel receptor for MIF-2. The evidence relies on a CXCR4 inhibitor, CXCR4 internalization experiments, MIF-2/CXCR4 binding studies by yeast-CXCR4 transformants, and fluorescence spectroscopic titrations with a soluble CXCR4 surrogate. Of note, Mif-2-/- Apoe-/- mice exhibited decreased plasma cholesterol and triglyceride levels, lower body weights, smaller livers, and profoundly reduced hepatic lipid accumulation compared to Apoe-/- mice. Mechanistic experiments in Huh-7 hepatocytes suggest that MIF-2 regulates the expression and activation of sterol-regulatory element binding protein-1 and -2 (SREBP-1, SREBP-2) to induce lipogenic downstream genes such as FASN and LDLR, while it attenuated the activation of the SREBP inhibiting AMPK pathway. Studies using receptor Inhibitors showed that SREBP activation and hepatic lipoprotein uptake by MIF-2 is mediated by both CXCR4 and CD74. Lastly and in line with a combined role of MIF-2 in vascular inflammation and hepatic lipid accumulation, MIF-2 was found to be profoundly upregulated in unstable human carotid plaques, underscoring a critical role for MIF-2 in advanced stages of atherosclerosis. Together, these data identify MIF-2 as a novel atherogenic chemokine and CXCR4 ligand that not only promotes lesion formation and vascular inflammation but also strongly affects hepatic lipogenesis in an SREBP-mediated manner, possibly linking atherosclerosis and hepatic steatosis.

Differential Influence of Soluble Dietary Fibres on Intestinal and Hepatic Carbohydrate Response

Refined foods are commonly depleted in certain bioactive components that are abundant in ‘natural’ (plant) foods. Identification and addition of these ‘missing’ bioactives in the diet is, therefore, necessary to counteract the deleterious impact of convenience food. In this study, multiomics approaches were employed to assess the addition of the popular supplementary soluble dietary fibers inulin and psyllium, both in isolation and in combination with a refined animal feed. A 16S rRNA sequencing and 1H NMR metabolomic investigation revealed that, whilst inulin mediated an increase in Bifidobacteria, psyllium elicited a broader microbial shift, with Parasutterella and Akkermansia being increased and Enterorhabdus and Odoribacter decreased. Interestingly, the combination diet benefited from both inulin and psyllium related microbial changes. Psyllium mediated microbial changes correlated with a reduction of glucose (R −0.67, −0.73, respectively, p < 0.05) and type 2 diabetes associated metabolites: 3-methyl-2-oxovaleric acid (R −0.72, −0.78, respectively, p < 0.05), and citrulline (R −0.77, −0.71, respectively, p < 0.05). This was in line with intestinal and hepatic carbohydrate response (e.g., Slc2a2, Slc2a5, Khk and Fbp1) and hepatic lipogenesis (e.g., Srebf1 and Fasn), which were significantly reduced under psyllium addition. Although established in the liver, the intestinal response associated with psyllium was absent in the combination diet, placing greater significance upon the established microbial, and subsequent metabolomic, shift. Our results therefore highlight the heterogeneity that exists between distinct dietary fibers in the context of carbohydrate uptake and metabolism, and supports psyllium containing combination diets, for their ability to negate the impact of a refined diet.

Consumption of Non-Nutritive Sweetener, Acesulfame Potassium Exacerbates Atherosclerosis through Dysregulation of Lipid Metabolism in ApoE−/− Mice

Obesity is associated with the risk of cardiovascular disease, and non-nutritive sweetener, such as acesulfame potassium (AceK) has been used to combat obesity. However, the effects of AceK on cardiovascular disease are still unclear. In this study, high cholesterol diet (HCD)-fed ApoE−/− mice had dysregulated plasma lipid profile, and developed atherosclerosis, determined by atherosclerotic plaque in the aorta. Supplement of AceK in HCD worsened the dyslipidemia and increased atherosclerotic plaque, as compared with HCD-fed ApoE−/− mice. Since treatment of AceK in RAW264.7 macrophages showed no significant effects on inflammatory cytokine expressions, we then investigated the impacts of AceK on lipid metabolism. We found that AceK consumption enhanced hepatic lipogenesis and decreased β-oxidation in ApoE−/− mice. In addition, AceK directly increased lipogenesis and decreased β-oxidation in HepG2 cells. Taken together, a concurrent consumption of AceK exacerbated HCD-induced dyslipidemia and atherosclerotic lesion in ApoE−/− mice, and AceK might increase the risk of atherosclerosis under HCD.

Cinnamic Acid Ameliorates Nonalcoholic Fatty Liver Disease by Suppressing Hepatic Lipogenesis and Promoting Fatty Acid Oxidation

Background. Cinnamic acid (CA) has been shown to have many beneficial effects including regulating lipid metabolism and reducing obesity. However, its effect on nonalcoholic fatty liver disease (NAFDL) has not been investigated in detail. Thus, we performed this study in order to explore CA’s effect on hepatic lipid metabolism and the underlying mechanisms. Method. Oleic acid (OA) was used to induce lipid accumulation in HepG2 cells. After coincubation with CA, the cells were stained with oil red O and the triglyceride (TG) content was assessed. Key genes in lipogenesis and fatty acid oxidation pathways were tested. Additionally, db/db and wt/wt mice were divided into three groups, with the wt/wt mice representing the normal group and the db/db mice being divided into the NAFLD and CA groups. After 4 weeks of oral treatment, all mice were sacrificed and the blood lipid profile and liver tissues were assessed. Results. CA treatment reduced the lipid accumulation in HepG2 cells and in db/db mouse livers. ACLY, ACC, FAS, SCD1, PPARγ, and CD36 were significantly downregulated, while CPT1A, PGC1α, and PPARα were significantly upregulated. Conclusion. CA’s therapeutic effect on NAFLD may be attributed to its ability to lower hepatic lipid accumulation, which is mediated by suppression of hepatic lipogenesis and fatty acid intake, as well as increased fatty acid oxidation.