The role of postprandial very-low-density lipoprotein in the development of atrial remodeling in metabolic syndrome

Neglected cardiometabolic risk factors and subclinical target organ damage in post-menopausal women with normal glucose tolerance

BACKGROUND

Menopausal transition is a crucial step in the women's cardiovascular health, and the risk stratification in apparently health post-menopausal females has been rarely assessed. Heart ultrasonography, unusually performed in such subjects, would be able to detect initial signs of organ damage. We described the cardiovascular risk profile of non-diabetic post-menopausal women, evaluating how easily computed, biochemistry-derived scores were related to ultrasonographic measures of target organ damage.

METHODS

We analyzed the characteristics of a cohort of two-hundred and seventy-three women consecutively referring to a prevention program of Azienda Ospedaliero-Universitaria Pisana (years 2017-2022) who underwent clinical evaluation, complete routine biochemical analyses with proxies of insulin resistance, heart and carotid ultrasonography. The cohort was further divided into four groups according to presence of isolated hypercholesterolemia (HC, 37%), isolated hypertension (HT, 5%), both HC/HT (38%), or none of them.

RESULTS

In HC and HC/HT, LDL cholesterol was sharply above the recommended values (149 [134-171] mg/dL and 141 [123-159] mg/dL, respectively). E/e' ratio and left atrium size were augmented in HT women and further worsened in HT/HC, with an independent effect of hypertension (E/e' ß=0.055, P=0.013, left atrium volume ß=0.059, P=0.003). Presence of carotid plaques was independently linked to hypertension (ß=0.474, P=0.003). In HC and HC/HT, the Triglycerides-Glucose Index, a surrogate of insulin resistance, was higher than in the other classes (P=0.0013), and it was associated with E/A in HC and HT/HC, with a significative interaction (P=0.0004) with hypertension. Past hormone replacement therapy did not influence clinical, biochemical or echocardiographic parameters.

CONCLUSIONS

Postmenopausal women display a high cardiovascular risk burden; a simple clinical and biochemistry screening would be advisable to identify and treat those more at risk. Cardiac ultrasonographic parameters were worse in hypertensive, hypercholesterolemic and insulin-resistant subjects, who may also deserve a deep and early instrumental characterization, especially when these conditions are associated.

Up-regulated small-conductance calcium-activated potassium currents contribute to atrial arrhythmogenesis in high-fat feeding mice

AIMS

Metabolic syndrome (MetS) is associated with arrhythmias and cardiovascular mortality. Arrhythmogenesis in MetS results from atrial structural and electrical remodelling. The small-conductance Ca2+-activated K+ (SK) currents modulate atrial repolarization and may influence atrial arrhythmogenicity. This study investigated the regulation of SK current perturbed by a high-fat diet (HFD) to mimic MetS.

METHODS AND RESULTS

Thirty mice were divided into two groups that were fed with normal chow (CTL) and HFD for 4 months. Electrocardiography and echocardiography were used to detect cardiac electrical and structure remodelling. Atrial action potential duration (APD) and calcium transient duration (CaTD) were measured by optical mapping of Langendorff-perfused mice hearts. Atrial fibrillation (AF) inducibility and duration were assessed by burst pacing. Whole-cell patch clamp was performed in primarily isolated atrial myocytes for SK current density. The SK current density is higher in atrial myocytes from HFD than in CTL mice (P ≤ 0.037). The RNA and protein expression of SK channels are increased in HFD mice (P ≤ 0.041 and P ≤ 0.011, respectively). Action potential duration is shortened in HFD compared with CTL (P ≤ 0.015). The shortening of the atrial APD in HFD is reversed by the application of 100 nM apamin (P ≤ 0.043). Compared with CTL, CaTD is greater in HFD atria (P ≤ 0.029). Calcium transient decay (Tau) is significantly higher in HFD than in CTL (P = 0.001). Both APD and CaTD alternans thresholds were higher in HFD (P ≤ 0.043), along with higher inducibility and longer duration of AF in HFD (P ≤ 0.023).

CONCLUSION

Up-regulation of apamin-sensitive SK currents plays a partial role in the atrial arrhythmogenicity of HFD mice.

Metabolic Syndrome and Atrial Fibrillation: Different Entities or Combined Disorders

Obesity, hypertension, insulin resistance, and dyslipidemia are all clusters of an entity called "Metabolic Syndrome". The global trends of this syndrome's incidence/prevalence continue to increase reciprocally, converting it into a massive epidemic problem in the medical community. Observing the risk factors of atrial fibrillation, a medical condition that is also converted to a scourge, almost all parts of the metabolic syndrome are encountered. In addition, several studies demonstrated a robust correlation between metabolic syndrome and the occurrence of atrial fibrillation. For atrial fibrillation to develop, a combination of the appropriate substrate and a trigger point is necessary. The metabolic syndrome affects the left atrium in a multifactorial way, leading to atrial remodeling, thus providing both the substrate and provoking the trigger needed, which possibly plays a substantial role in the progression of atrial fibrillation. Due to the remodeling, treatment of atrial fibrillation may culminate in pernicious sequelae, such as repeated catheter ablation procedures. A holistic approach of the patient, with simultaneous treatment of both entities, is suggested in order to ensure better outcomes for the patients.

Association of lipid composition and unsaturated fatty acids of VLDL with atrial remodeling in metabolic syndrome

Subjects with metabolic syndrome (MetS) commonly have atrial remodeling, which indicates a risk for atrial fibrillation. This study determined MetS-related changes in lipid components in very-low-density lipoprotein (VLDL), which has been shown to cause atrial remodeling, the effect of statins on these changes, and the correlation between atrial remodeling and VLDL lipid compositions. Blood samples were collected from 12 non-MetS and 27 sex- and age-matched MetS subjects. Fourteen patients with MetS (MetS-off statin) discontinued statin therapy 14 days before the study, while the remaining 13 remained on it (MetS-on statin). The VLDLs were isolated and processed for mass-based lipid profiling. Lipidomic analyses were performed and associated with atrial remodeling markers measured using standard echocardiography and electrocardiography. Compared with the VLDL components of the non-MetS group, glucosyl/galactosyl ceramide, lyso-phosphatidylcholine, lyso-phosphatidylethanolamine, and triglycerides were enriched in the MetS-off statin group. Statin therapy attenuated all abnormally abundant lipid classes in MetS, except for triglycerides. In addition, lyso-phosphatidylcholine, lyso-phosphatidylethanolamine, and triglycerides were significantly correlated with atrial dilatation, and the latter two were also correlated with the PR interval. Enrichment of double bonds, which indicate unsaturated fatty acids, was also significantly correlated with atrial remodeling and P-wave duration. This study suggests that the pathological lipid payload of MetS-VLDL may contribute to atrial remodeling in patients.

Spotlight on very-low-density lipoprotein as a driver of cardiometabolic disorders: Implications for disease progression and mechanistic insights

Very-low-density lipoprotein (VLDL) is the only lipoprotein containing apolipoprotein B that is secreted from the liver, where VLDL is assembled from apolipoproteins, cholesterol, and triglycerides. The primary function of VLDL is to transport cholesterol and other lipids to organs and cells for utilization. Apart from its role in normal biologic processes, VLDL is also known to contribute to the development of atherosclerotic cardiovascular disease. Large VLDL particles, which are subclassified according to their size by nuclear magnetic resonance spectrometry, are significantly correlated not only with atherosclerosis, but also with insulin resistance and diabetes incidence. VLDL can also be subclassified according to surface electrical charge by using anion-exchange chromatography. The most electronegative VLDL subclass is highly cytotoxic to endothelial cells and may contribute to coronary heart disease. In addition, electronegative VLDL contributes to the development of atrial remodeling, especially in patients with metabolic syndrome, which is an established risk factor for atrial fibrillation. In this review, we focus on the VLDL subclasses that are associated with apolipoprotein alterations and are involved in cardiometabolic disease. The postprandial enhancement of VLDL’s pathogenicity is a critical medical issue, especially in patients with metabolic syndrome. Therefore, the significance of the postprandial modification of VLDL’s chemical and functional properties is extensively discussed.

QTc Interval is Associated with Atrial Fibrillation in Individuals with Metabolic Syndrome Phenotype

Purpose

Manifestations of metabolic syndrome (MetS) carry risks for atrial fibrillation (AF). The study determined whether any electrocardiographic parameter can reflect increased AF risk in individuals with MetS.

Patients and Methods

From our University Hospital database, we examined the presence of AF and its correlation with MetS manifestations, renal function, lipid profiles, and electrocardiographic parameters (P wave duration, PR interval, QRS width, and QTc intervals). Between January 2008 and December 2015, data from 4479 adults (women 41.6% vs men 58.4%) were identified.

Results

The overall prevalence of AF was 12.4%, without sex differences (women, 12.8% vs men, 12.1%). Patients with AF were older (age 73.9 ± 11.8 vs non-AF 67 ± 13.5 years), with lower lipid levels (TG, total cholesterol, and LDL-cholesterol, all p < 0.0001), and at lower eGFR level (64.1 ± 30.9 vs non-AF 68.8 ± 41.4 mL/min/1.73m2, p < 0.0001). Besides, sex differences were present in all electrocardiographic parameters (all p < 0.05). Hypertension had the highest odds ratio (1.33; p = 0.026) for AF. Comparing AF to non-AF, the QTc of quartiles was significantly different (p < 0.0089). The shortest and longest QTc quartiles had an increased incidence of AF.

Conclusion

AF risk in patients with MetS phenotypes can be reflected by QTc quartiles.

Left Atrial Cardiomyopathy - A Challenging Diagnosis

Left atrial cardiomyopathy (LACM) has been an ongoing focus of research for several years. There is evidence that LACM is responsible for atrial fibrillation and embolic strokes of undetermined sources. Therefore, the correct diagnosis of LACM is of clinical importance. Various techniques, including electrocardiography, echocardiography, cardiac magnetic resonance imaging, computed tomography, electroanatomic mapping, genetic testing, and biomarkers, can both identify and quantify structural, mechanical as well as electrical dysfunction in the atria. However, the question arises whether these techniques can reliably diagnose LACM. Because of its heterogeneity, clinical diagnosis is challenging. To date, there are no recommendations for standardized diagnosis of suspected LACM. However, standardization could help to classify LACM more precisely and derive therapeutic directions to improve individual patient management. In addition, uniform diagnostic criteria for LACM could be important for future studies. Combining several parameters and relating them seems beneficial to approach the diagnosis of LACM. This review provides an overview of the current evidence regarding the diagnosis of LACM, in which several potential parameters are discussed and, consequently, a proposal for a diagnostic algorithm is presented.

Determinants of Left Atrial Compliance in the Metabolic Syndrome: Insights from the "Linosa Study"

The association between left atrial (LA) impairment and cardiovascular diseases (CVD) and between dyslipidaemia and CVD are well known. The present study aims to investigate the relationships between metabolic factors and LA dimensions and compliance, as well as test the hypothesis that metabolic factors influence LA function independent from hemodynamic mechanisms. Arterial blood pressure (BP), waist and hip circumference, metabolic indices, and a complete echocardiographic assessment were obtained from 148 selected inhabitants (M/F 89/59; age 20−86 years) of Linosa Island, who had no history of CVD. At enrollment, 27.7% of the subjects met the criteria for metabolic syndrome (MetS) and 15.5% for arterial hypertension (HTN). LA compliance was reduced in subjects with MetS compared to those without (53 ± 27% vs. 71 ± 29%, p = 0.04) and was even lower (32 ± 17%, p = 0.01) in those with MetS and HTN. At multiple regression analysis, the presence of MetS independently determined LA maximal area (r = 0.56, p < 0.001), whereas systolic BP and the total cholesterol/HDL cholesterol ratio determined LA compliance (r = 0.41, p < 0.001). In an apparently healthy population with a high prevalence of MetS, dyslipidaemia seems to independently influence LA compliance. At a 5-year follow-up, LA compliance was reduced in both all-cause and CVD mortality groups, and markedly impaired in those who died of CVD. These findings may contribute to understanding the prognostic role of LA function in CVD and strengthen the need for early and accurate lipid control strategies.

Emerging Evidence of Pathological Roles of Very-Low-Density Lipoprotein (VLDL)

Embraced with apolipoproteins (Apo) B and Apo E, triglyceride-enriched very-low-density lipoprotein (VLDL) is secreted by the liver into circulation, mainly during post-meal hours. Here, we present a brief review of the physiological role of VLDL and a systemic review of the emerging evidence supporting its pathological roles. VLDL promotes atherosclerosis in metabolic syndrome (MetS). VLDL isolated from subjects with MetS exhibits cytotoxicity to atrial myocytes, induces atrial myopathy, and promotes vulnerability to atrial fibrillation. VLDL levels are affected by a number of endocrinological disorders and can be increased by therapeutic supplementation with cortisol, growth hormone, progesterone, and estrogen. VLDL promotes aldosterone secretion, which contributes to hypertension. VLDL induces neuroinflammation, leading to cognitive dysfunction. VLDL levels are also correlated with chronic kidney disease, autoimmune disorders, and some dermatological diseases. The extra-hepatic secretion of VLDL derived from intestinal dysbiosis is suggested to be harmful. Emerging evidence suggests disturbed VLDL metabolism in sleep disorders and in cancer development and progression. In addition to VLDL, the VLDL receptor (VLDLR) may affect both VLDL metabolism and carcinogenesis. Overall, emerging evidence supports the pathological roles of VLDL in multi-organ diseases. To better understand the fundamental mechanisms of how VLDL promotes disease development, elucidation of the quality control of VLDL and of the regulation and signaling of VLDLR should be indispensable. With this, successful VLDL-targeted therapies can be discovered in the future.