Chronic exposure to high fatty acids impedes receptor agonist-induced nitric oxide production and increments of cytosolic Ca2+ levels in endothelial cells

Lipotoxicity: a driver of heart failure with preserved ejection fraction?

Heart failure with preserved ejection fraction (HFpEF) is a growing public health concern, with rising incidence alongside high morbidity and mortality. However, the pathophysiology of HFpEF is not yet fully understood. The association between HFpEF and the metabolic syndrome (MetS) suggests that dysregulated lipid metabolism could drive diastolic dysfunction and subsequent HFpEF. Herein we summarise recent advances regarding the pathogenesis of HFpEF in the context of MetS, with a focus on impaired lipid handling, myocardial lipid accumulation and subsequent lipotoxicity.

Does a strict glycemic control during acute coronary syndrome play a cardioprotective effect? Pathophysiology and clinical evidence

A hyperglycemic state, also in non-diabetic subjects, may be associated with acute coronary syndrome (ACS). Aim of this review is to describe the pathophysiologic association between ACS and hyperglycemic state, the protective mechanisms of a tight glycaemic control in ACS on CV outcomes, and the supporting clinical evidence. Several mechanisms may be responsible of a poor CV outcome in subjects with hyperglycemia during ACS. Endothelial NAPDH oxidase-2 (NOX2) activation in response to high glucose alters the balance between Raf/MAPK-dependent vasoconstriction and PI3K/Akt-dependent vasodilation in favour of constriction. Hyperglycaemia induces an overproduction of superoxide by the mitochondrial electron transport chain through different molecular mechanisms. Moreover, hyperglycaemia increases the size of the infarct by causing myocardial cell death through apoptosis and reducing the collateral blood flow. High FFA concentrations lead to toxicity mechanisms in acutely ischemic myocardium. On the other hand, a tight glycaemic control in ACS exerts a cardioprotective action by anti-inflammatory and anti-apoptotic mechanisms, anti-oxidative stress, endothelium protection, FFA reduction, anti-glucotoxic effect, IR and cardiac fuel metabolisms improvement, heart stem cells protection and reduced activation of adrenergic system. Unfortunately, the clinical studies supporting the above pathophysiological background are few and sometimes controversial, more likely due the risk of hypoglycemia linked to the insulin therapy generally used during ACS. Intriguingly, GLP-1 RA and SGLT2i, demonstrated highly effective in the cardiovascular prevention in high-risk subjects without the risk of hypoglycemia, might keep this cardioprotective effect even in acute conditions such as ASC.

The role of serum monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in cardiovascular disease risk

Free fatty acids (FFA) observed as independent risk factors of cardiovascular diseases (CVD). In this study we investigated FFA levels in patients with CVD, and its risk factors. In this case-control study, 214 patients experienced coronary angiography and 222 healthy subjects were enrolled. Participants were categorized into two groups: who had >50% and <30% stenosis were assigned to the angiogram positive (N=90) and negative (N=124) group, respectively. Several risk factors were assessed and the levels of FFAs were determined using gas chromatography. Serum FFA concentrations were compared between healthy and patients with positive and negative angiograms. The association of serum FFA levels with four major risk factors (hypertension, FBG level, high BMI and WHR) were also assessed. Our data showed that median of FFAs was higher in patients than healthy subjects (p<0.0001), such as SFA and n6-FFAs (in patients; 1.59 (1.27) and 1.22 (1.06) and in healthy subjects 0.33 (0.38) and 0.36 (0.35), respectively). According to anthropometric and biochemical data, there were not statistical differences between the groups, except FBG, SBP and hs-CRP that showed significantly higher levels in patients than controls (p<0.0001, p=0.001). Also, lower median levels of total cholesterol, LDL-C, HDL-C and DBP were observed in patients which can due to lipid-lowering medication use like Statins. High serum levels of FFAs are considered as an independent risk factor for CVDs, while various types of FFAs can have different influences on CVD risk factors. Therefore, longitudinal studies are needed to clarify the association between FFAs and CVD risk factors. (www.actabiomedica.it)

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

A high concentration of fatty acids induces TNF-α as well as NO release mediated by the P2X4 receptor, and the protective effects of puerarin in RAW264.7 cells

Circulating levels of free fatty acids (FFAs) are often found to be increased in patients with type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS). High plasma FFA levels may give rise to maladaptive macrophage activation and promote inflammatory responses, which has been proposed as a potential mechanism for the development of DM and MS. P2X4 receptor (P2X4R), a ligand-gated cation channel activated by extracellular adenosine triphosphate (ATP), plays a primary role in the regulation of inflammatory responses. Puerarin has been reported to possess potential anti-inflammatory activity. However, the anti-inflammatory activity of puerarin and the underlying molecular mechanisms in a setting of a high concentration of FFAs remain unknown. In this study, we found that a high concentration of FFAs increased the expression of P2X4R, cytosolic Ca²⁺ concentration and the phosphorylation of extracellular signal-regulated kinase (ERK) and induced the expression of tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) mRNA and the release of TNF-α and nitric oxide (NO) in RAW264.7 macrophages. Such a high concentration FFA-induced inflammation may be reversed by the P2X4R selective antagonist 5-BDBD, which manifests the important role of P2X4R in the TNF-α and NO release caused by the high concentration of FFAs in RAW264.7 cells. Molecular docking data showed that puerarin could interfere with the activation of P2X4R by forming hydrogen bonding towards residue Arg267, an important residue essential for the canonical activation of P2X4R. Treatment with puerarin dose-dependently reduced high concentration FFA-elevated P2X4R expression and inhibited P2X4R-mediated inflammatory signalling, including high concentration FFA-evoked [Ca²⁺]_i, ERK phosphorylation, expression of TNF-α and iNOS mRNA and release of TNF-α and NO. Our findings emphasize the critical role of P2X4R in high concentration FFA-induced TNF-α and NO release of RAW264.7 macrophages. Puerarin notably counteracts these high concentration FFA-induced adverse effects through its inhibition of P2X4R expression and P2X4R-mediated inflammatory signalling.

Role of Tight Glycemic Control during Acute Coronary Syndrome on CV Outcome in Type 2 Diabetes

Both incidence and mortality of acute coronary syndrome (ACS) among diabetic patients are much higher than those among nondiabetics. Actually, there are many studies that addressed glycemic control and CV risk, whilst the literature on the role of tight glycemic control during ACS is currently poor. Therefore, in this review, we critically discussed the studies that investigated this specific topic. Hyperglycemia is implicated in vascular damage and cardiac myocyte death through different molecular mechanisms as advanced glycation end products, protein kinase C, polyol pathway flux, and the hexosamine pathway. Moreover, high FFA concentrations may be toxic in acute ischemic myocardium due to several mechanisms, thus leading to endothelial dysfunction. A reduction in free fatty acid plasma levels and an increased availability of glucose can be achieved by using a glucose-insulin-potassium infusion (GIKi) during AMI. The GIKi is associated with an improvement of either long-term prognosis or left ventricular mechanical performance. DIGAMI studies suggested blood glucose level as a significant and independent mortality predictor among diabetic patients with recent ACS, enhancing the important role of glucose control in their management. Several mechanisms supporting the protective role of tight glycemic control during ACS, as well as position statements of Scientific Societies, were highlighted.

In-hospital free fatty acids levels predict the severity of myocardial ischemia of acute coronary syndrome

Background

We aimed to assess whether the levels of FFAs (free fatty acids) in ACS (acute coronary syndrome) patients depend on the extent of myocardial ischemia during the subacute phase of ACS attack.

Methods

A total of 892 consecutive CAD (coronary artery disease) subjects undergoing coronary angiography were enrolled. The FFAs contents were measured based on enzymatic assay. The relationship between FFAs and Gensini score and ACS susceptibility was assessed.

Results

In the overall population, the upper FFAs quartile was accompanied with higher ischemia parameters and increased occurrence of ACS and STEMI (ST-segment elevation myocardial infarction) (P < 0.05). The FFAs concentrations were approximately 1.5-fold higher in ACS than in stable CAD patients, roughly 1.3-fold higher in STEMI than non-STEMI ACS patients and probably 1.3-fold higher in non-STEMI ACS than in stable CAD patients. After adjusted for traditional cardiovascular risk factors, the FFAs level remained a risk factor for a higher Gensini score with more than 40 (P < 0.001) and prevalent ACS (P < 0.001). After adjusted for traditional risk factors, FFAs levels after natural logarithm transformation were associated with hs-CRP and WBC counts in ACS patients. A multiplicative interaction was found between hs-CRP, WBC counts and FFAs in incident ACS and higher Gensini score (P < 0.001).

Conclusions

Higher in-hospital levels of FFAs persist and may reflect the severity of ischemia and necrosis during the subacute phase of ACS attack.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0199-1) contains supplementary material, which is available to authorized users.

MicroRNA-134 Contributes to Glucose-Induced Endothelial Cell Dysfunction and This Effect Can Be Reversed by Far-Infrared Irradiation

Diabetes mellitus (DM) is a metabolic disease that is increasing worldwide. Furthermore, it is associated with the deregulation of vascular-related functions, which can develop into major complications among DM patients. Endothelial colony forming cells (ECFCs) have the potential to bring about medical repairs because of their post-natal angiogenic activities; however, such activities are impaired by high glucose- (HG) and the DM-associated conditions. Far-infrared radiation (FIR) transfers energy as heat that is perceived by the thermoreceptors in human skin. Several studies have revealed that FIR improves vascular endothelial functioning and boost angiogenesis. FIR has been used as anti-inflammatory therapy and as a clinical treatment for peripheral circulation improvement. In addition to vascular repair, there is increasing evidence to show that FIR can be applied to a variety of diseases, including cardiovascular disorders, hypertension and arthritis. Yet mechanism of action of FIR and the biomarkers that indicate FIR effects remain unclear. MicroRNA-134 (miR-134-5p) was identified by small RNA sequencing as being increased in high glucose (HG) treated dfECFCs (HG-dfECFCs). Highly expressed miR-134 was also validated in dmECFCs by RT-qPCR and it is associated with impaired angiogenic activities of ECFCs. The functioning of ECFCs is improved by FIR treatment and this occurs via a reduction in the level of miR-134 and an increase in the NRIP1 transcript, a direct target of miR-134. Using a mouse ischemic hindlimb model, the recovery of impaired blood flow in the presence of HG-dfECFCs was improved by FIR pretreatment and this enhanced functionality was decreased when there was miR-134 overexpression in the FIR pretreated HG-dfECFCs. In conclusion, our results reveal that the deregulation of miR-134 is involved in angiogenic defects found in DM patients. FIR treatment improves the angiogenic activity of HG-dfECFCs and dmECFCs and FIR has potential as a treatment for DM. Detection of miR-134 expression in FIR-treated ECFCs should help us to explore further the effectiveness of FIR therapy.

Sildenafil reduces signs of oxidative stress in pulmonary arterial hypertension: Evaluation by fatty acid composition, level of hydroxynonenal and heart rate variability

Pulmonary arterial hypertension (PAH) is a rare multifactorial disease with an unfavorable prognosis. Sildenafil therapy can improve functional capacity and pulmonary hemodynamics in PAH patients. Nowadays, it is increasingly recognized that the effects of sildenafil are pleiotropic and may also involve changes of the pro-/antioxidant balance, lipid peroxidation and autonomic control. In present study we aimed to assess the effects of sildenafil on the fatty acids (FAs) status, level of hydroxynonenal (HNE) and heart rate variability (HRV) in PAH patients. Patients with PAH were characterized by an increase in HNE and changes in the FAs composition with elevation of linoleic, oleic, docosahexanoic acids in phospholipids as well as reduced HRV with sympathetic predominance. Sildenafil therapy improved exercise capacity and pulmonary hemodynamics and reduced NT-proBNP level in PAH. Antioxidant and anti-inflammatory effects of sildenafil were noted from the significant lowering of HNE level and reduction of the phopholipid derived oleic, linoleic, docosahexanoic, docosapentanoic FAs. That was also associated with some improvement of HRV on account of the activation of the neurohumoral regulatory component. Incomplete recovery of the functional metabolic disorders in PAH patients may be assumed from the persistent increase in free FAs, reduced HRV with the sympathetic predominance in the spectral structure after treatment comparing to control group. The possibilities to improve PAH treatment efficacy through mild stimulation of free radical reactions and formation of hormetic reaction in the context of improved NO signaling are discussed.

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Sildenafil showed antioxidant and anti-inflammatory effects in pulmonary hypertension.

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Sildenafil reduced hydroxynonenal level and improved fatty acid profile in serum.

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Improvement of heart rate variability and functional capacity was noted after therapy.

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Mild prooxidant activity is suggested as the mechanism to improve sildenafil efficacy.

Protection of vascular endothelial cells from high glucose-induced cytotoxicity by emodin

Induction of endothelial cytotoxicity by hyperglycemia in diabetes has been widely accepted. Emodin is a natural anthraquinone in rhubarb used for treatment of diabetes, but its mechanism of action is not fully understood. This study aimed to examine the potential beneficial effects of emodin on endothelial cytotoxicity caused by high glucose milieu. Culture of human umbilical vein endothelial cells (HUVECs) with high concentrations of glucose resulted in damage to the cells, leading to decreased formazan products by 14-27%, reduced DNA contents by 12-19%, and increased hypodiploid apoptosis by 40-109%. These adverse effects of high glucose could be prevented to a large extent by co-culture with 3 μM of emodin which per se did not affect HUVECs viability. In addition, CCL5 expression of HUVECs cultured in high glucose medium was significantly elevated at both mRNA and protein levels, an effect abolished after treatment with emodin. Moreover, the enhanced adhesion of monocytes to HUVECs (2.1-2.2 fold over control) and elevated chemotaxis activities (2.3-2.4 fold over control) in HUVECs cultured in high glucose medium were completely reversed by emodin. Emodin also suppressed activation of p38 MAPK and ERK1/2 due to high glucose. Our data demonstrated that endothelial cytotoxicity occurred clearly when HUVECs were exposed to high glucose milieu and emodin was able to alleviate the impairments. The protective effects of emodin might be related to the inhibition of CCL5 expression and subsequent cell stress/inflammatory events possibly mediated by activation of MAPK signaling pathways.

The production of nitric oxide, IL-6, and TNF-alpha in palmitate-stimulated PBMNCs is enhanced through hyperglycemia in diabetes

We examined nitric oxide (NO), IL-6, and TNF-α secretion from cultured palmitate-stimulated PBMNCs or in the plasma from type 2 diabetes mellitus (T2MD) patients or nondiabetic (ND) controls. Free fatty acids (FFA) have been suggested to induce chronic low-grade inflammation, activate the innate immune system, and cause deleterious effects on vascular cells and other tissues through inflammatory processes. The levels of NO, IL-6, TNF-α, and MDA were higher in supernatant of palmitate stimulated blood cells (PBMNC) or from plasma from patients. The results obtained in the present study demonstrated that hyperglycemia in diabetes exacerbates in vitro inflammatory responses in PBMNCs stimulated with high levels of SFA (palmitate). These results suggest that hyperglycemia primes PBMNCs for NO, IL-6, and TNF-alpha secretion under in vitro FFA stimulation are associated with the secretion of inflammatory biomarkers in diabetes. A combined therapy targeting signaling pathways activated by hyperglycemia in conjunction with simultaneous control of hyperglycemia and hypertriglyceridemia would be suggested for controlling the progress of diabetic complications.

Mechanisms of lipotoxicity in the cardiovascular system

Cardiovascular diseases account for approximately one third of all deaths globally. Obese and diabetic patients have a high likelihood of dying from complications associated with cardiovascular dysfunction. Obesity and diabetes increase circulating lipids that upon tissue uptake, may be stored as triglyceride, or may be metabolized in other pathways, leading to the generation of toxic intermediates. Excess lipid utilization or activation of signaling pathways by lipid metabolites may disrupt cellular homeostasis and contribute to cell death, defining the concept of lipotoxicity. Lipotoxicity occurs in multiple organs, including cardiac and vascular tissues, and a number of specific mechanisms have been proposed to explain lipotoxic tissue injury. In addition, recent data suggests that increased tissue lipids may also be protective in certain contexts. This review will highlight recent progress toward elucidating the relationship between nutrient oversupply, lipotoxicity, and cardiovascular dysfunction. The review will focus in two sections on the vasculature and cardiomyocytes respectively.

Lipotoxicity contributes to endothelial dysfunction: a focus on the contribution from ceramide

Cardiovascular complications are the leading causes of morbidity and mortality in individuals with obesity, type 2 diabetes mellitus (T2DM), and insulin resistance. Complications include pathologies specific to large (atherosclerosis, cardiomyopathy) and small (retinopathy, nephropathy, neuropathy) vessels. Common among all of these pathologies is an altered endothelial cell phenotype i.e., endothelial dysfunction. A crucial aspect of endothelial dysfunction is reduced nitric oxide (NO) bioavailability. Hyperglycemia, oxidative stress, activation of the renin-angiotensin system, and increased pro-inflammatory cytokines are systemic disturbances in individuals with obesity, T2DM, and insulin resistance and each of these contribute independently and synergistically to decreasing NO bioavailability. This review will examine the contribution from elevated circulating fatty acids in these subjects that lead to lipotoxicity. Particular focus will be placed on the fatty acid metabolite ceramide.