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

Ketogenic diets (KDs) are very high-fat low-carbohydrate diets that promote nutritional ketosis and are widely used for weight loss, although concerns about potential adverse cardiovascular effects remain. We investigated a very high-fat KD's vascular impact and plasma metabolic signature compared to a non-ketogenic high-fat diet (HFD). Apolipoprotein E deficient (ApoE -/-) mice were fed a KD (%kcal:81:1:18, fat/carbohydrate/protein), a non-ketogenic high-fat diet with half of the fat content (HFD) (%kcal:40:42:18, fat/carbohydrate/protein) for 12 weeks. Plasma samples were used to quantify the major ketone body beta-hydroxybutyrate (BHB) and several pro-inflammatory cytokines (IL-6, MCP-1, MIP-1alpha, and TNF alpha), and to targeted metabolomic profiling by mass spectrometry. In addition, aortic atherosclerotic lesions were quantified ex-vivo by magnetic resonance imaging (MRI) on a 14-tesla system. KD was atherogenic when compared to the control diet, but KD mice, when compared to the HFD group (1) 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; (2) displayed significant changes in the plasma metabolome that included a decrease in lipophilic metabolites and an increase in hydrophilic metabolites; (3) had significantly lower levels of several atherogenic lipid metabolites, including phosphatidylcholines, cholesterol esters, sphingomyelins, and ceramides; and (4) presented significantly lower aortic plaque burden. KD was atherogenic and was associated with specific metabolic changes but alleviated the fat-induced inflammation and lessened the progression of atherosclerosis when compared to the HFD.

Diallyl disulfide alleviates hypercholesterolemia induced by a western diet by suppressing endoplasmic reticulum stress in apolipoprotein E-deficient mice

BACKGROUND

The endoplasmic reticulum (ER) plays a pivotal role in maintaining cellular metabolic homeostasis. ER stress refers to the accumulation of misfolded proteins, which can trigger an unfolded protein response for survival or death in the cells. Diallyl disulfide (DADS), a major active compound in garlic, has many health benefits for patients with metabolic diseases, especially cardiovascular or fatty liver diseases. However, its role in attenuating hypercholesterolemia by suppressing ER stress remains unknown. Therefore, in this study, we determined whether DADS supplementation could reduce ER stress in apolipoprotein E-deficient (ApoE^-/-) mice fed a Western-type diet (WD).

METHODS

ApoE^-/- mice were fed either a WD alone or a WD supplemented with 0.1% DADS for 12 weeks (n = 10). Levels of plasma total cholesterol, triglyceride, leptin, and insulin were determined. Western blotting was performed to measure protein levels involved in ER stress markers. Histology and Immunostaining were performed on aortic root sections to confirm the effect of DADS on histology and expression of ER chaperone protein GRP78.

RESULTS

The metabolic parameters showed that increases in fat weight, leptin resistance, and hypercholesterolemia were reversed in DADS-supplemented mice (p < 0.05). In addition, DADS ameliorated not only the protein of ER stress markers, phospho-eukaryotic initiation factor 2 subunit alpha and C/EBP homologous protein in the liver (p < 0.05) but also glucose-related protein 78 localization in the aorta.

CONCLUSIONS

This indicates that DADS inhibits diet-induced hypercholesterolemia, at least in parts by regulating ER stress markers. DADS may be a good candidate for treating individuals with diet-induced hypercholesterolemia.

Calcification of the cavernosal bodies may be responsible for development of erectile dysfunction in uremic apolipoprotein E deficient (apoE-/-) mice

INTRODUCTION AND OBJECTIVE

Erectile dysfunction's physiopathology in uremia is complex and multifactorial, involving a combination of classical risk factors and specific uremia-related risk factors such as increased oxidative stress, endothelial dysfunction and inflammation. The aim of the study is to investigate the effect of chronic kidney disease (CKD) on vascular calcification and endothelial function of cavernosal bodies in apolipoprotein E deficient (apoE^-/-) mice, a well known model of erectile dysfunction.

MATERIALS AND METHODS

Eight-week-old male apoE^-/- mice were randomly assigned to the following 3 groups: (i) subtotally nephrectomised (SNX apoE^-/-, 12 mice), (ii) uninephrectomised (UNX apoE^-/-, 11 mice) or (iii) sham operated (sham-op apoE^-/-, 15 mice). At 16 weeks after surgery, aortas and penile erectile tissues were harvested for histological studies to assess atherosclerosis, vascular calcification, nitrotyrosine staining, total collagen content and macrophage staining.

RESULTS

At sacrifice, SNX and UNX mice had significantly higher serum urea, total cholesterol, and triglyceride concentrations than sham-op controls. Atherosclerotic lesions in thoracic aorta were significantly larger in uremic apoE^-/- mice than in controls. There were no atheromatous lesions in cavernosal bodies or penile artery observed in any group. However, SNX and UNX animals showed a significant increase in calcification score, collagen content and nitrotyrosine staining in cavernosal bodies when compared with controls. The degree of macrophage infiltration was comparable between the 3 groups.

CONCLUSION

In conclusion, even mild renal dysfunction, i.e., after uninephrectomy increases calcification score and aggravates endothelial function of cavernosal bodies in apoE^-/- mice and this effect might be linked to increased oxidative stress in penile endothelium.

ILC2 transfers to apolipoprotein E deficient mice reduce the lipid content of atherosclerotic lesions

BACKGROUND

Expansion of type 2 innate lymphoid cells (ILC2s) in hypercholesterolaemic mice protects against atherosclerosis while different ILC2 subsets have been described (natural, inflammatory) based on their suppression of tumorigenicity 2 (ST2) and killer-cell lectin like receptor G1 (KLRG1) expression. The aim of the current study is to characterize the interleukin 25 (IL25)-induced splenic ILC2 population (Lin^-CD45⁺IL17RB⁺ICOS⁺IL7ra^intermediate) and address its direct role in experimental atherosclerosis by its adoptive transfer to hypercholesterolaemic apolipoprotein E deficient (apoE^-/-) mice.

RESULTS

Immunomagnetically enriched, FACS-sorted ILC2s from the spleens of IL-25 treated apoE^-/- mice were stained for KLRG1 and ST2 directly upon cell obtainment or in vitro cell expansion for flow cytometric analysis. IL25-induced splenic ILC2s express high levels of both KLRG1 and ST2. However, both markers are downregulated upon in vitro cell expansion. In vitro expanded splenic ILC2s were intraperitoneally transferred to apoE^-/- recipients on high fat diet. ApoE^-/- mice that received in vitro expanded splenic ILC2s had decreased lipid content in subvalvular heart and brachiocephalic artery (BCA) plaques accompanied by increased peritoneal B1 cells, activated eosinophils and alternatively activated macrophages (AAMs) as well as anti-phosphorylcholine (PC) immunoglobulin (Ig) M in plasma.

CONCLUSIONS

With the current data we designate the IL25-induced ILC2 population to decrease the lipid content of atherosclerotic lesions in apoE^-/- mice and we directly link the induction of B1 cells and the atheroprotective anti-PC IgM antibodies with ILC2s.

Allergic asthma aggravated atherosclerosis increases cholesterol biosynthesis and foam cell formation in apolipoprotein E-deficient mice

Several studies have demonstrated that allergic asthma can induce atherosclerosis formation in mice. Moreover, allergic asthma and atherosclerosis have been shown to be strongly associated with dyslipidemia. In this study, we investigated the underlying mechanism of allergic asthma-aggravated atherosclerosis-induced cholesterol metabolism disorder in asthmatic apoE^-/- mice. We found that allergic asthma increased the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the liver and CD36 in the aorta during the acute and advanced stages of atherosclerosis, respectively. These results indicate that cholesterol biosynthesis is increased during acute atherosclerosis and cholesterol uptake and foam cell formation is increased during advanced atherosclerosis. Simvastatin administration significantly ameliorated the aortic root lesion size of asthmatic mice and significantly decreased HMGCR and CD36 expression. However, the expression of the low-density lipoprotein receptor and ATP-binding cassette transporter A1 was markedly increased, indicating that the beneficial effect of statins in allergic asthma and coronary artery disease was mediated, at least in part, by decreasing cholesterol biosynthesis and foam cell formation. In conclusion, allergic asthma aggravates atherosclerosis by regulating cholesterol metabolism in apoE^-/- mice. Allergic asthma selectively promotes cholesterol biosynthesis in acute atherosclerosis and increases foam cell formation in advanced atherosclerosis.

The intravenous injection of oxidized LDL- or Apolipoprotein B100--Coupled splenocytes promotes Th1 polarization in wildtype and Apolipoprotein E--Deficient mice

BACKGROUND

Th1 responses in atherosclerosis are mainly associated with the aggravation of atherosclerotic plaques, whereas Th2 responses lead to a less pronounced disease in mouse models. The fixation of antigens on cells by means of ethylene carbodiimide (ECDI), and subsequent injection of these antigen-coupled splenocytes (Ag-SP) to induce tolerance against the attached antigens, has been successfully used to treat murine type 1 diabetes or encephalomyelitis in. We analyzed this approach in a mouse model for atherosclerosis.

METHODS AND RESULTS

OTII-transgenic mice that were treated with a single dose of 5 × 10(7) OVA-coupled splenocytes (OVA-SP), had decreased splenocyte proliferation, and lower IFNγ production in vitro upon antigen recall. However, in vivo CD4 cell activation was increased. To try lipoprotein-derived, "atherosclerosis-associated" antigens, we first tested human oxidized LDL. In wild type mice, an increase of IFNγ production upon in vitro recall was detected in the oxLDL-SP group. In Apolipoprotein E - deficient (ApoE-/-) mice that received oxLDL-SP every 5 weeks for 20 weeks, we did not find any difference of atherosclerotic plaque burden, but again increased IFNγ production. To overcome xenogenous limitations, we then examined the effects of mouse Apolipoprotein B100 peptides P3 and P6. ApoB100-SP treatment again promoted a more IFNγ pronounced response upon in vitro recall. Flow cytometry analysis of cytokine secreting spleen cells revealed CD4 positive T cells to be mainly the source for IFNγ. In ApoE-/- mice that were administered ApoB100-SP during 20 weeks, the atherosclerotic plaque burden in aortic roots as well as total aorta was unchanged compared to PBS treated controls. Splenocyte proliferation upon antigen recall was not significantly altered in ApoB100-SP treated ApoE-/- mice.

CONCLUSION

Although we did not observe a relevant anti-atherosclerotic benefit, the treatment with antigen-coupled splenocytes in its present form already impacts the immune responses and deserves further exploration.

Allergic asthma accelerates atherosclerosis dependent on Th2 and Th17 in apolipoprotein E deficient mice

AIMS

The chronic inflammation of atherosclerosis is regulated by Th1, while allergic asthma is controlled by Th2. The direct relationship between atherosclerosis and asthma is contradictory. The aim of this study was to investigate the role of allergic asthma in atherosclerotic plaque formation and the change of CD4(+) T cells subsets.

METHODS AND RESULTS

Six-week C57BL/6J or apoE(-/-) mice were sensitized on day 0, 7 and 14, then exposed to aerosolized 1% Ovalbumin (OVA) or PBS 30min/day, 3 times/week for 8 or 16weeks from day 14 onward. The results showed that allergic asthma mice models were successfully established and the accelerated atherosclerosis induced by allergic asthma accompanied with increased Th2 and Th17 cells but not Th1 cells in spleen. Moreover, the expression and production of Th2 and Th17 biomarkers including IL-4 and IL-17A were significantly elevated in asthmatic apoE(-/-) mice. After 8-week treated with the neutralizing antibody of IL-4 or IL-17A, the lesion area in the aortic root of asthmatic apoE(-/-) mice was markedly decreased, and more dramatical result was observed after the combined treatment with IL-4 and IL-17A mAbs. The expression of IgE and FcεRIα in the aortic root of apoE(-/-) mice was markedly increased but was significantly reduced after 8-week treatment with IL-4 mAb.

CONCLUSION

Allergic asthma accelerates atherosclerosis by modulating the balance of Teff/Treg cells in apoE(-/-) mice, which is associated with increased Th2 and Th17 cells but not Th1 cells.