Microvascular responses to hypercholesterolemia: the interactions between innate and adaptive immune responses

Plasma proteins and psoriatic arthritis: a proteome-wide Mendelian randomization study

Background

Previous epidemiological studies have identified a correlation between serum protein levels and Psoriatic Arthritis (PsA). However, the precise nature of this relationship remains uncertain. Therefore, our objective was to assess whether circulating levels of 2,923 plasma proteins are associated with the risk of PsA, utilizing the Mendelian randomization (MR) approach.

Methods

Two-sample MR analysis was performed to assess the causal impact of proteins on PsA risk. Exposure data for plasma proteins were sourced from a genome-wide association study (GWAS) conducted within the UK Biobank Pharma Proteomics Project, which encompassed 2,923 unique plasma proteins. The outcome data for PsA were sourced from the FinnGen study, a large-scale genomics initiative, comprising 3,537 cases and 262,844 controls. Additionally, colocalization analysis, Phenome-wide MR analysis, and candidate drug prediction were employed to identify potential causal circulating proteins and novel drug targets.

Results

We thoroughly assessed the association between 1,837 plasma proteins and PsA risk, identifying seven proteins associated with PsA risk. An inverse association of Interleukin-10 (IL-10) with PsA risk was observed [odds ratio (OR)=0.45, 95% confidence interval (CI), 0.28 to 0.70, P FDR=0.072]. Additionally, Apolipoprotein F (APOF) has a positive effect on PsA risk (OR=2.08, 95% CI, 1.51 to 2.86, P FDR=0.005). Subsequently, we found strong evidence indicating that IL-10 and APOF were colocalized with PsA associations (PP.H4 = 0.834 for IL-10 and PP.H4 = 0.900 for APOF). Phenome-wide association analysis suggested that these two proteins may have dual effects on other clinical traits (P FDR<0.1).

Conclusion

This study identified 7 plasma proteins associated with PsA risk, particularly IL-10 and APOF, which offer new insights into its etiology. Further studies are needed to assess the utility and effectiveness of these candidate proteins.

The causal relationship between pure hypercholesterolemia and psoriasis: A bidirectional, two-sample Mendelian randomization study

BACKGROUND

Several studies have reported the association between pure hypercholesterolemia (PH) and psoriasis, but the causal effect remains unclear.

METHODS

We explored the causal effect between PH and psoriasis using two-sample bidirectional Mendelian randomization (MR) analysis using data from genome-wide association studies. Single nucleotide polymorphisms related with exposures at the genome-wide significance level (p < 5×10-8 ) and less than the linkage disequilibrium level (r2  < 0.001) were chosen as instrumental variables. Subsequently, we used inverse variance weighting (IVW), MR-Egger and weighted median (WM) methods for causal inference. p < 0.05 was considered statistically significant. Heterogeneity was tested using Cochran's Q-test, and horizontal pleiotropy was examined using the MR-Egger intercept. Leave-one-out analyses were performed to assess the robustness and reliability of the results.

RESULTS

MR results showed a positive causal effect of PH on psoriasis [IVW: odds ratios (OR): 1.139, p = 0.032; MR-Egger: OR: 1.434, p = 0.035; WM: OR: 1.170, p = 0.045] and psoriatic arthritis (PsA) (IVW: OR: 1.210, p = 0.049; MR-Egger regression: OR: 1.796, p = 0.033; WM: OR: 1.317, p = 0.028). However, there is no causal relationship between PH and psoriasis vulgaris as well as other unspecified psoriasis. Inverse MR results suggested a negative causal relationship between PsA and PH (IVW: OR: 0.950, p = 0.037). No heterogeneity and horizontal pleiotropy exist, and these results were confirmed to be robust.

CONCLUSION

PH has a positive casual effect on psoriasis and PsA, and PsA may reduce the risk of having PH.

The association between retinal microvasculature derived from optical coherence tomography angiography and systemic factors in type 2 diabetics

Aims

To investigate the correlation between the retinal microvasculature using optical coherence tomography angiography (OCTA) and systemic factors in type 2 diabetes mellitus (T2DM) patients.

Methods

This cross-sectional study obtained OCTA data from patients with T2DM administered at hospital and referred to ophthalmic services. Patient data about demographics, comorbid conditions, and blood biomarkers were extracted from electronic medical records. Data from OCTA scans obtained by CIRRUS HD-OCT Model 5,000 were obtained. Vessel density (VD) and perfusion density (PD) within the superficial capillary plexus, and foveal avascular zone (FAZ) area were automatically segmented. These parameters were tested for their correlations with systemic factors by univariate and multivariable linear regression analyses.

Results

A total of 144 T2DM patients (236 eyes) were available for analysis, with mean age of 53.6 (SD = 10.34) and 56.9% were male. Chronic kidney disease, cardiovascular disease, increased serum creatinine (Scr), red blood cell count (RBC), platelets (PLT), apolipoprotein B (APOB), and decreased urine albumin to creatinine ratio (UACR) were significantly associated with lower VD and PD (all p &lt; 0.013). UACR and triglyceride (TRIG) were significantly correlated with FAZ area (all p &lt; 0.017). In multivariate analyses, PLT, eGFR, and APOB were independent risk factors for retinal rarefaction, and UACR was a significant predictor of FAZ area.

Conclusion

We found several systemic risk factors, such as PLT, renal function and lipid profiles were associated with PD, VD, and FAZ area among Chinese T2DM patients.

Cardiovascular Comorbidities in Psoriatic Disease

Psoriatic disease (PsD) is a multisystem inflammatory disorder with a high prevalence of cardiovascular (CV) risk factors contributing to accelerated atherosclerosis and its sequelae. Imaging studies, notably with ultrasound, computed tomography, and positron emission tomography (PET) scanning have confirmed significant atherosclerotic change with plaque formation and vessel stenosis. Atherosclerosis is likely driven by a combination of traditional risk factors which occur more frequently in PsD and by systemic inflammation with associated pro-inflammatory cytokine production. While the mechanisms driving atherosclerosis in PsD are incompletely understood, it is now best practice to try to minimize the impact of CV risk factors by regular assessment, prevention, and treatment and also by ensuring that inflammatory musculoskeletal and cutaneous disease is adequately suppressed. Future studies need to focus on improving our understanding of the mechanisms driving atherosclerosis and, as a consequence, developing more rationale approaches to prevention and treatment.

Effect of Anthocyanin Supplementations on Lipid Profile and Inflammatory Markers: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Purpose

To assess combined data from seventeen randomized controlled trials studying effect of anthocyanin consumption on levels of various lipids and inflammatory markers with meta-analysis approach.

Methods

Various databases, namely, PubMed, MEDLINE, EMBASE, and Cochrane Trial Register were used to identify randomized controlled trials (RCTs) investigating an association between anthocyanins and lipid profile and inflammatory markers. Heterogeneity was assessed using Q and I² statistics and data was expressed using mean difference with 95% confidence interval.

Results

Statistically significant reduction in triglyceride [mean difference (MD) = −9.16, 95% CI: −14.02 to −4.31 mg/dL, I² = 33.54%, P = 0.149], low density lipoprotein [MD = −8.86, 95% CI: −11.17 to −20.02 mg/dL, I² = 37.75%, P = 0.098], and apolipoprotein B [MD = −7.13, 95% CI: −8.66 to −5.59 mg/dL, I² = 20.42%, P = 0.287] levels and increase in high-density lipoprotein [MD = 1.67, 95% CI: 0.8 to 2.54 mg/dL, I² = 44.88%, P = 0.053] and apolipoprotein A-1 [MD = 6.1, 95% CI: 4.51 to 7.69 mg/dL, I² = 6.95%, P = 0.358] levels were observed with anthocyanin supplementation. Levels of inflammatory markers were found to reduce [TNF-∞ - MD = −1.98, 95% CI: −2.40 to −1.55 pg/mL, I² = 0%, P = 0.975; IL-6 - MD = 1.17, 95% CI: 0.8 to 1.53 pg/mL, I² = 0%, P = 0.825; hs-CRP - MD = 0.164, 95% CI: −0.06 to 0.39 mg/dL, I² = 0%, P = 0.569]. Though the effect on TC, IL-6, and hs-CRP was positive, it was nonsignificant in nature.

Conclusion

Anthocyanin supplementation significantly improves lipid profile and inflammatory status. However, future trials with sufficient sample size are recommended to substantiate the findings especially for the parameters showing nonsignificant improvement.

The vascular endothelium: A regulator of arterial tone and interface for the immune system

As the primary interface between the blood and various tissues of the body, the vascular endothelium exhibits a diverse range of roles and activities, all of which contribute to the overall health and function of the cardiovascular system. In this focused review, we discuss several key aspects of endothelial function, how this may be compromised and subsequent consequences. Specifically, we examine the dynamic regulation of arterial contractility and distribution of blood flow through the generation of chemical and electrical signaling events that impinge upon vascular smooth muscle. The endothelium can generate a diverse range of vasoactive compounds and signals, most of which act locally to adjust blood flow in a dynamic fashion to match tissue metabolism. Disruption of these vascular signaling processes (e.g. reduced nitric oxide bioavailability) is typically referred to as endothelial dysfunction, which is a recognized risk factor for cardiovascular disease in patients and occurs early in the development and progression of hypertension, atherosclerosis and tissue ischemia. Endothelial dysfunction is also associated with type-2 Diabetes and aging and increased mechanistic knowledge of the cellular changes contributing to these effects may provide important clues for interventional strategies. The endothelium also serves as the initial site of interaction for immune cells entering tissues in response to damage and acts to facilitate the actions of both the innate and acquired immune systems to interact with the vascular wall. In addition to representing the main cell type responsible for the formation of new blood vessels (i.e. angiogenesis) within the vasculature, the endothelium is also emerging as a source of extracellular vesicle or microparticles for the transport of signaling molecules and other cellular materials to nearby, or remote, sites in the body. The characteristics of released microparticles appear to change with the functional status of the endothelium; thus, these microparticles may represent novel biomarkers of endothelial health and more serious cardiovascular disease.

An endothelial link between the benefits of physical exercise in dementia

The current absence of a disease-modifying treatment for Alzheimer's disease (AD) and vascular cognitive impairment and dementia (VCID) highlights the necessity for investigating the benefits of non-pharmacological approaches such as physical exercise (PE). Although evidence exists to support an association between regular PE and higher scores on cognitive function tests, and a slower rate of cognitive decline, there is no clear consensus on the underlying molecular mechanisms of the advantages of PE. This review seeks to summarize the positive effects of PE in human and animal studies while highlighting the vascular link between these benefits. Lifestyle factors such as cardiovascular diseases, metabolic syndrome, and sleep apnea will be addressed in relation to the risk they pose in developing AD and VCID, as will molecular factors known to have an impact on either the initiation or the progression of AD and/or VCID. This will include amyloid-beta clearance, oxidative stress, inflammatory responses, neurogenesis, angiogenesis, glucose metabolism, and white matter integrity. Particularly, this review will address how engaging in PE can counter factors that contribute to disease pathogenesis, and how these alterations are linked to endothelial cell function.

Increased CD160 expression on circulating natural killer cells in atherogenesis

BACKGROUND

Atherosclerosis (AS) presents characteristic of a chronic inflammatory disease in which both adaptive and innate immune cells play roles. Accumulating evidence has showed the impairment of natural killer (NK) cells in atherosclerosis, however, the mechanisms of this impairment remain unclear. In this study, we investigated the expression of CD160 on NK cells and assessed its pathological roles in NK loss during atherogenesis.

METHODS

CD160 expression on NK cells was measured in 49 AS patients and 41 healthy controls (HC) by flow cytometry, their inflammatory cytokine levels in sera were determined by ELSIA, and the effect of CD160 engagement on NK cells was evaluated by in vitro culture experiments.

RESULTS

Compared to HC, AS patients had a significantly increased CD160 expression on peripheral NK cells and concomitantly decreased peripheral NK cell number, and increased CD160 expression was positively related to the levels of serum lipids and IFN-γ, TNF-α and IL-6 inflammation cytokines, which all are risk factors for atherogenesis, and inversely correlated with peripheral NK cell number. Furthermore, engagement of CD160 receptor on NK cells from AS patients triggers a significantly increased production of inflammation cytokines and subsequent NK cell apoptosis, and blockade of TNF-α prevented the increased apoptosis of NK cells from AS patients after CD160 engagement, indicating a critical role of TNF-α in mediating NK cell loss by CD160 engagement.

RESULTS

Our results provide evidence that elevated CD160 expression on NK cells plays an important role in NK cell loss in atherosclerosis. The increased CD160 expression on NK cells might be used as an indicator for disease progression.

Flavan-3-ols, anthocyanins, and inflammation

The process of inflammation constitutes a reactive response of the organism to tissue damage and is an important factor making part of a number of degenerative pathologies as insulin resistance, dyslipidemia, and hypertension, all of them comprised in the metabolic syndrome. There is an increasing interest in plant products rich in flavan-3-ols and anthocyanins because of their potential beneficial effects observed in epidemiological studies against inflammatory-related diseases. Their anti-inflammatory effects are exerted by modulation of cell redox status and inhibition of signaling pathways as NF-κB activation. The effects depend on their concentrations in target tissues and hence the bioavailability pathways followed by each particular compound. In this sense, in vitro studies performed with parental compounds at doses exceeding to those found in vivo may be drawing erroneous conclusions about their real efficacy. Contradictory results have been observed in human intervention trials, which may be ascribed to the type of population studied, length of study, source of flavan-3-ol/anthocyanin, and dose provided. Human studies are required to confirm the positive effects found in vitro and in animal models. Future research should be focused on the understanding of dose/flavonoid intake-response relationship with pharmacokinetic studies, evaluating proper biomarkers of intake. Long-term dietary interventions are necessary to observe effects on markers of late activation as well as the possible preventive effects of these compounds on long-term inflammation-related diseases.

Hypercholesterolemia and risk of incident psoriasis and psoriatic arthritis in US women

OBJECTIVE

Psoriasis is a systemic inflammatory disorder associated with an increased risk of cardiovascular disease. Hypercholesterolemia is a major risk factor for cardiovascular disease, and patients with psoriasis or psoriatic arthritis (PsA) have been shown to have elevated cholesterol levels. However, it is not known whether hypercholesterolemia is associated with an increased risk of psoriasis or psoriasis with PsA. We undertook this study to determine whether a history of hypercholesterolemia is associated with the risk of developing incident psoriasis and psoriasis with PsA in a cohort of US women.

METHODS

We included a total of 95,540 participants from the Nurses' Health Study II (1991-2005). Information on personal history of physician-diagnosed hypercholesterolemia and related medication use was collected during the followup period. Clinician-diagnosed psoriasis and psoriasis with PsA were ascertained and confirmed using supplementary questionnaires. Hazard ratios (HRs) were calculated with 95% confidence intervals (95% CIs).

RESULTS

During 1,320,765 person-years of followup, we documented 646 participants with incident psoriasis, 165 of whom had concomitant PsA. Hypercholesterolemia was associated with elevated risks of incident psoriasis (HR 1.25 [95% CI 1.04-1.50]) and psoriasis with PsA (HR 1.58 [95% CI 1.13-2.23]) in multivariate-adjusted models. Participants with hypercholesterolemia lasting for ≥7 years were at a higher risk of developing psoriasis (HR 1.29 [95% CI 1.03-1.61]) (P for trend = 0.0002) and psoriasis with PsA (HR 1.68 [95% CI 1.12-2.52]) (P for trend = 0.002). These associations persisted among participants who never took cholesterol-lowering medications. There was no association between cholesterol-lowering drugs and risk of psoriasis or psoriasis with PsA.

CONCLUSION

Our study provides evidence that hypercholesterolemia, a well-known cardiovascular risk factor, is also associated with an elevated risk of psoriasis and psoriasis with PsA.

Dietary cholesterol increases ventricular volume and narrows cerebrovascular diameter in a rabbit model of Alzheimer's disease

Using structural magnetic resonance imaging in a clinical scanner at 3.0T, we describe results showing that following 12weeks on a diet of 2% cholesterol, rabbits experience a significant increase in the volume of the third ventricle compared to rabbits on a diet of 0% cholesterol. Using time-of-flight magnetic resonance angiography, we find cholesterol-fed rabbits also experience a decrease in the diameter of a number of cerebral blood vessels including the basilar, posterior communicating, and internal carotid arteries. Taken together, these data confirm that, despite the inability of dietary cholesterol to cross the blood-brain barrier, it does significantly enlarge ventricular volume and decrease cerebrovascular diameter in the rabbit - effects that are also seen in patients with Alzheimer's disease.

Anti-inflammatory effect of purified dietary anthocyanin in adults with hypercholesterolemia: a randomized controlled trial

BACKGROUND AND AIM

Atherosclerosis is a chronic inflammatory disease and previous studies have demonstrated that anthocyanin inhibits atherosclerosis. In the present study, we explored the effects of anthocyanins on inflammatory cytokines in hypercholesterolemic adults and cell lines.

METHODS AND RESULTS

A total of 150 subjects with hypercholesterolemia consumed a purified anthocyanin mixture (320 mg/d) or a placebo twice a day for 24 weeks in a randomized, double-blind trial. Anthocyanin consumption significantly decreased the levels of serum high sensitivity C-reactive protein (hsCRP) (-21.6% vs. -2.5%, P = 0.001), soluble vascular cell adhesion molecule-1 (sVCAM-1) (-12.3% vs. 0.4%, P = 0.005) and plasma IL-1β (-12.8% vs. -1.3%, P = 0.019) compared to the placebo. We also found a significant difference in the LDL-cholesterol (-10.4% vs. 0.3%, P = 0.030) and HDL-cholesterol level changes (14.0% vs. -0.9%, P = 0.036) between the two groups. In cell culture assays in vitro, purified anthocyanin mixture, delphinidin-3-Ο-β-glucoside (Dp-3g) and cyanidin-3-Ο-β-glucoside (Cy-3g) inhibited IL-6 and IL-1β-induced CRP production (P < 0.05) in HepG2 cell line and LPS-induced VCAM-1 secretion (P < 0.05) in porcine iliac artery endothelial cell line respectively in a dose-dependent manner. In addition, the reduction of inflammatory cytokines associated with anthocyanin mixture was stronger when compared with the effects of Dp-3g and Cy-3g separately (P < 0.05).

CONCLUSIONS

Anthocyanin mixture reduced the inflammatory response in hypercholesterolemic subjects. In addition, different anthocyanin compounds were found to have additive or synergistic effects in mediating anti-inflammatory responses in vitro cell culture assays.

Increased expression of T cell immunoglobulin- and mucin domain-containing molecule-3 on natural killer cells in atherogenesis

OBJECTIVE

Atherosclerosis (AS) has many features of a chronic inflammatory disease in which both adaptive and innate immune cells play roles. Increasing evidence has demonstrated the impairment of circulating natural killer (NK) cells in atherosclerosis. However, the mechanisms of this impairment remain unclear. We previously reported the suppression of NK cell functions by T cell immunoglobulin- and mucin domain-containing molecule (Tim)-3. Here, we investigated the expression of Tim-3 on NK cells and assessed its possible roles in NK loss during atherogenesis.

METHODS AND RESULTS

Flow cytometry analysis showed increased Tim-3 expression on peripheral NK cells from patients with AS. This increased expression of Tim-3 was significantly related to the levels of serum lipids and inflammation markers, C-reactive protein (CRP) and tumor necrosis factor (TNF)-α, which are risk factors for atherogenesis. We detected decreased peripheral NK cell number in patients with AS. The NK cell number showed significant inverse correlations with Tim-3 expression levels on NK cells and the level of serum TNF-α. Consistently, Tim-3 overexpression reduced NK92 cell number. Blockade of Tim-3 protected NK92 cells from TNF-α-induced cell death. Similar results were obtained with peripheral NK cells from patients with AS.

CONCLUSIONS

To the best of our knowledge, for the first time, the data from our study provide evidence that augmented Tim-3 expression on NK cells plays an important role in NK cell loss in atherosclerosis. The augmented Tim-3 expression on NK cells might be used as an indicator for disease progression.

Linking cardiometabolic disorders to sporadic Alzheimer's disease: a perspective on potential mechanisms and mediators

There is increasing evidence that the incidence of Alzheimer's disease (AD) is significantly influenced by cardiovascular risk factors in association with a cluster of metabolic diseases including diabetes and atherosclerosis. The shared risk is also reflected in the dietary and lifestyle links to both metabolic disorders and AD-type cognitive dysfunction. Recent studies with genetic and diet-induced animal models have begun to illuminate convergent mechanisms and mediators between these two categories of disease conditions with distinct tissue-specific pathologies. Although it is clear that peripheral inflammation and insulin resistance are central to the pathogenesis of the disorders of metabolic syndrome, it seems that the same mechanisms are also in play across the blood-brain barrier that lead to AD-like molecular and cognitive changes. This review highlights these convergent mechanisms and discusses the role of cerebrovascular dysfunction as a conduit to brain emergence of these pathogenic processes that might also represent future therapeutic targets in AD in common with metabolic disorders.

Microvascular responses to cardiovascular risk factors

Hypertension, hypercholesterolemia, diabetes, and obesity are among a growing list of conditions that have been designated as major risk factors for cardiovascular disease (CVD). While CVD risk factors are well known to enhance the development of atherosclerotic lesions in large arteries, there is also evidence that the structure and function of microscopic blood vessels can be profoundly altered by these conditions. The diverse responses of the microvasculature to CVD risk factors include oxidative stress, enhanced leukocyte- and platelet-endothelial cell adhesion, impaired endothelial barrier function, altered capillary proliferation, enhanced thrombosis, and vasomotor dysfunction. Emerging evidence indicates that a low-grade systemic inflammatory response that results from risk factor-induced cell activation and cell-cell interactions may underlie the phenotypic changes induced by risk factor exposure. A consequence of the altered microvascular phenotype and systemic inflammatory response is an enhanced vulnerability of tissues to the deleterious effects of secondary oxidative and inflammatory stresses, such as ischemia and reperfusion. Future efforts to develop therapies that prevent the harmful effects of risk factor-induced inflammation should focus on the microcirculation.

Diet and age interactions with regards to cholesterol regulation and brain pathogenesis

Cholesterol is an essential molecule for brain homeostasis; yet, hypercholesterolemia and its numerous complications are believed to play a role in promoting multiple aspects of brain pathogenesis. An ever increasing number of individuals in modern Western Society are regularly consuming diets high in fat which promote the development of hypercholesterolemia. Additionally, modern societies are becoming increasingly aged, causing a collision between increased hypercholesterolemia and increased aging, which will likely lead to the development of increased pathological conditions due to hypercholesterolemia, thereby promoting deleterious neurochemical and behavioral changes in the brain. Lastly, while beneficial in controlling cholesterol levels, the long-term use of statins itself may potentially promote adverse effects on brain homeostasis, although specifics on this remain largely unknown. This review will focus on linking the current understanding of diet-induced hypercholesterolemia (as well as statin use) to the development of oxidative stress, neurochemical alterations, and cognitive disturbances in the aging brain.

Impact of chronic anticholesterol therapy on development of microvascular rarefaction in the metabolic syndrome

OBJECTIVE

The obese Zucker rat (OZR) model of the metabolic syndrome is partly characterized by moderate hypercholesterolemia, in addition to other contributing comorbidities. Previous results suggest that vascular dysfunction in OZR is associated with chronic reduction in vascular nitric-oxide (NO) bioavailability and chronic inflammation, both frequently associated with hypercholesterolemia. As such, we evaluated the impact of chronic cholesterol-reducing therapy on the development of impaired skeletal muscle arteriolar reactivity and microvessel density in OZR and its impact on chronic inflammation and NO bioavailability.

MATERIALS AND METHODS

Beginning at seven weeks of age, male OZR were treated with gemfibrozil, probucol, atorvastatin, or simvastatin (in chow) for 10 weeks. Subsequently, plasma and vascular samples were collected for biochemical/molecular analyses, while arteriolar reactivity and microvessel network structure were assessed by using established methodologies after 3, 6, and 10 weeks of drug therapy.

RESULTS

All interventions were equally effective at reducing total cholesterol, although only the statins also blunted the progressive reductions to vascular NO bioavailability, evidenced by greater maintenance of acetylcholine-induced dilator responses, an attenuation of adrenergic constrictor reactivity, and an improvement in agonist-induced NO production. Comparably, while minimal improvements to arteriolar wall mechanics were identified with any of the interventions, chronic statin treatment reduced the rate of microvessel rarefaction in OZR. Associated with these improvements was a striking statin-induced reduction in inflammation in OZR, such that numerous markers of inflammation were correlated with improved microvascular reactivity and density. However, using multivariate discriminant analyses, plasma RANTES (regulated on activation, normal T-cell expressed and secreted), interleukin-10, monocyte chemoattractant protein-1, and tumor necrosis factor alpha were determined to be the strongest contributors to differences between groups, although their relative importance varied with time.

CONCLUSIONS

While the positive impact of chronic statin treatment on vascular outcomes in the metabolic syndrome are independent of changes to total cholesterol, and are more strongly associated with improvements to vascular NO bioavailability and attenuated inflammation, these results provide both a spatial and temporal framework for targeted investigation into mechanistic determinants of vasculopathy in the metabolic syndrome.

Novel cerebrovascular pathology in mice fed a high cholesterol diet

Background

Hypercholesterolemia causes atherosclerosis in medium to large sized arteries. Cholesterol is less known for affecting the microvasculature and has not been previously reported to induce microvascular pathology in the central nervous system (CNS).

Results

Mice with a null mutation in the low-density lipoprotein receptor (LDLR) gene as well as C57BL/6J mice fed a high cholesterol diet developed a distinct microvascular pathology in the CNS that differs from cholesterol-induced atherosclerotic disease. Microvessel diameter was increased but microvascular density and length were not consistently affected. Degenerative changes and thickened vascular basement membranes were present ultrastructurally. The observed pathology shares features with the microvascular pathology of Alzheimer's disease (AD), including the presence of string-like vessels. Brain apolipoprotein E levels which have been previously found to be elevated in LDLR-/- mice were also increased in C57BL/6J mice fed a high cholesterol diet.

Conclusion

In addition to its effects as an inducer of atherosclerosis in medium to large sized arteries, hypercholesterolemia also induces a microvascular pathology in the CNS that shares features of the vascular pathology found in AD. These observations suggest that high cholesterol may induce microvascular disease in a range of CNS disorders including AD.

CD40/CD40L contributes to hypercholesterolemia-induced microvascular inflammation

Hypercholesterolemia is associated with phenotypic changes in endothelial cell function that lead to a proinflammatory and prothrombogenic state in different segments of the microvasculature. CD40 ligand (CD40L) and its receptor CD40 are ubiquitously expressed and mediate inflammatory responses and platelet activation. The objective of this study was to determine whether CD40/CD40L, in particular T-cell CD40L, contributes to microvascular dysfunction induced by hypercholesterolemia. Intravital microscopy was used to quantify blood cell adhesion in cremasteric postcapillary venules, endothelium-dependent vasodilation responses in arterioles, and microvascular oxidative stress in wild-type (WT) C57BL/6, CD40-deficient ((-/-)), CD40L(-/-), or severe combined immune deficient (SCID) mice placed on a normal (ND) or high-cholesterol (HC) diet for 2 wk. WT-HC mice exhibited an exaggerated leukocyte and platelet recruitment in venules and impaired vasodilation responses in arterioles compared with ND counterparts. A deficiency of CD40, CD40L, or lymphocytes attenuated these responses to HC. The HC phenotype was rescued in CD40L(-/-) and SCID mice by a transfer of WT T cells. Bone marrow chimeras revealed roles for both vascular- and blood cell-derived CD40 and CD40L in the HC-induced vascular responses. Hypercholesterolemia induced an oxidative stress in both arterioles and venules of WT mice, which was abrogated by either CD40 or CD40L deficiency. The transfer of WT T cells into CD40L(-/-) mice restored the oxidative stress. These results implicate CD40/CD40L interactions between circulating cells and the vascular wall in both the arteriolar and venular dysfunction elicited by hypercholesterolemia and identify T-cell-associated CD40L as a key mediator of these responses.

Atherogenic diet-induced hepatitis is partially dependent on murine TLR4

Diets high in cholesterol and cholate such as the Paigen diet have been used to study atherogenesis, lithogenesis, and proinflammatory microvascular changes induced by nutritional hypercholesterolemia. Although these diets lead to chronic hepatic inflammation and fibrosis, the early inflammatory changes have been poorly characterized. TLR4, a known receptor for LPS, is also a receptor for a variety of endogenous ligands and has been implicated in atheroma formation. Here, we specifically examined the early inflammatory response of the liver to the atherogenic (ATH) diet and the possible contribution of TLR4. Animals fed the high-cholesterol/cholate diet for 3 weeks developed a significant, predominantly mononuclear leukocyte infiltration in the liver, hepatic steatosis, elevated hepatic expression of MCP-1, RANTES, and MIP-2, and increased serum levels of liver enzymes. In TLR4-deleted animals, there was a 30% attenuation in the serum alanine transaminase levels and a 50% reduction in the leukocyte infiltration with a fourfold reduction in chemokine expression. In contrast, hepatic steatosis did not differ from wild-type controls. TLR2 deletion had no effect on diet-induced hepatitis but increased the amount of steatosis. We conclude that the early inflammatory liver injury but not hepatic lipid loading induced by the ATH diet in mice is mediated in part by TLR4.

Steatocholecystitis: the influence of obesity and dietary carbohydrates

INTRODUCTION

We have recently demonstrated that obese and lean mice fed a high fat diet have increased gallbladder wall fat and decreased gallbladder contractility, cholecystosteatosis. Animal and human data also suggest that diets high in refined carbohydrates lead to gallstone formation. However, no data are available on the role of dietary carbohydrates on gallbladder wall fat and inflammation. Therefore, we tested the hypothesis that both obesity and dietary carbohydrates would increase gallbladder fat and cytokines, steatocholecystitis.

METHODS

At 8 wk of age, 47 lean and 22 obese female mice were fed a 45% carbohydrate (CHO) diet while an equal number of lean and obese mice were fed a 75% CHO diet for 4 wk. All mice underwent cholecystectomy, and the gallbladders were snap-frozen. Individual and total lipids were measured by gas chromatography. Interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-6 were measured by enzyme-linked immunosorbent assay. Data were analyzed by analysis of variance and Tukey test.

RESULTS

Gallbladder total fat, triglycerides, and cholesterol were maximum (P < 0.001) in obese mice on the 75% CHO diet. Gallbladder TNF-alpha and IL-1beta as well as serum cholesterol levels showed a similar pattern (P < 0.001). Gallbladder saturated free fatty acids and IL-6 levels were highest (P < 0.001) in obese mice on the 45% CHO diet.

CONCLUSIONS

These data suggest that (1) both obesity and dietary carbohydrates increase gallbladder total fat, triglycerides, cholesterol, TNF-alpha, and IL-1beta and (2) obesity also increases gallbladder free fatty acids and IL-6. Therefore, we conclude that obesity is associated with steatocholecystitis and that a high carbohydrate diet exacerbates this phenomenon.