Molecular and physiologic actions of insulin related to production of nitric oxide in vascular endothelium

Molecular Aspects in the Development of Type 2 Diabetes and Possible Preventive and Complementary Therapies

The incidence of diabetes, including type 2 diabetes (T2DM), is increasing sharply worldwide. To reverse this, more effective approaches in prevention and treatment are needed. In our review, we sought to summarize normal insulin action and the pathways that primarily influence the development of T2DM. Normal insulin action involves mitogenic and metabolic pathways, as both are important in normal metabolic processes, regeneration, etc. However, through excess energy, both can be hyperactive or attenuated/inactive leading to disturbances in the cellular and systemic regulation with the consequence of cellular stress and systemic inflammation. In this review, we detailed the beneficial molecular changes caused by some important components of nutrition and by exercise, which act in the same molecular targets as the developed drugs, and can revert the damaged pathways. Moreover, these induce entire networks of regulatory mechanisms and proteins to restore unbalanced homeostasis, proving their effectiveness as preventive and complementary therapies. These are the main steps for success in prevention and treatment of developed diseases to rid the body of excess energy, both from stored fats and from overnutrition, while facilitating fat burning with adequate, regular exercise in healthy people, and together with necessary drug treatment as required in patients with insulin resistance and T2DM.

Anti-obesity and anti-diabetic effects of L-citrulline are sex-dependent

AIMS

Anti-diabetic and anti-obesity effects of L-citrulline (Cit) have been reported in male rats. This study determined sex differences in response to Cit in Wistar rats.

MAIN METHODS

Type 2 diabetes (T2D) was induced using a high-fat diet followed by low-dose of streptozotocin (30 mg/kg) injection. Male and female Wistar rats were divided into 4 groups (n = 6/group): Control, control+Cit, T2D, and T2D + Cit. Cit (4 g/L in drinking water) was administered for 8 weeks. Obesity indices were recorded, serum fasting glucose and lipid profile were measured, and glucose and pyruvate tolerance tests were performed during the Cit intervention. White (WAT) and brown (BAT) adipose tissues were weighted, and the adiposity index was calculated at the end of the study.

KEY FINDINGS

Cit was more effective in decreasing fasting glucose (18 % vs. 11 %, P = 0.0100), triglyceride (20 % vs. 14 %, P = 0.0173), and total cholesterol (16 % vs. 11 %, P = 0.0200) as well as decreasing gluconeogenesis and improving glucose tolerance, in females compared to male rats with T2D. Following Cit administration, decreases in WAT weight (16 % vs. 14 % for gonadal, 21 % vs. 16 % for inguinal, and 18 % vs. 13 % for retroperitoneal weight, all P < 0.0001) and increases in BAT weight (58 % vs. 19 %, for interscapular and 10 % vs. 7 % for axillary, all P < 0.0001) were higher in females than male rats with T2D. The decrease in adiposity index was also higher (11 % vs. 9 %, P = 0.0007) in females.

SIGNIFICANCE

The anti-obesity and anti-diabetic effects of Cit in rats are sex-dependent, with Cit being more effective in female than male rats.

Mitigation effect of galangin against aortic dysfunction and hypertrophy in rats with metabolic syndrome

Vascular alterations induced by a high-fat diet (HFD) are involved in the development of hypertension. Galangin, a flavonoid, is the major active compound isolated from galangal and propolis. The objective of this study was to investigate the effect of galangin on aortic endothelial dysfunction and hypertrophy, and the mechanisms involved in HFD-induced metabolic syndrome (MS) in rats. Male Sprague-Dawley rats (220-240 g) were separated into three groups: control + vehicle, MS + vehicle, and MS + galangin (50 mg/kg). Rats with MS received HFD plus 15% fructose solution for 16 weeks. Galangin or vehicle was orally administered daily for the final four weeks. Galangin reduced body weight and mean arterial pressure in HFD rats (p < 0.05). It also reduced circulating fasting blood glucose, insulin, and total cholesterol levels (p < 0.05). Impaired vascular responses to the exogenous acetylcholine observed in the aortic ring of HFD rats were restored by galangin (p < 0.05). However, the response to sodium nitroprusside did not differ between the groups. Galangin enhanced the expression of the aortic endothelial nitric oxide synthase (eNOS) protein and increased circulating nitric oxide (NO) levels in the MS group (p < 0.05). Aortic hypertrophy in HFD rats was alleviated by galangin (p < 0.05). Increases in tumour necrosis factor-alpha (TNF-α), interleukin (IL)-6 levels, angiotensin-converting enzyme activity and angiotensin II (Ang II) concentrations in rats with MS were suppressed in galangin treated group (p < 0.05). Furthermore, galangin reduced the upregulation of angiotensin II type I receptor (AT1R) and transforming growth factor-beta (TGF-β) expression in rats with MS (p < 0.05). In conclusion, galangin alleviates metabolic disorders and improves aortic endothelial dysfunction and hypertrophy in the MS group. These effects were consistent with increased NO availability, reduced inflammation, and suppressing Ang II/AT1R/TGF-β signalling pathway.

Vitamin C supplementation for diabetes management: A comprehensive narrative review

Growing evidence suggests that vitamin C supplementation may be an effective adjunct therapy in the management of people with diabetes. This paper critically reviews the current evidence on effects of vitamin C supplementation and its potential mechanisms in diabetes management. Evidence from meta-analyses of randomized controlled trials (RCTs) show favourable effects of vitamin C on glycaemic control and blood pressure that may be clinically meaningful, and mixed effects on blood lipids and endothelial function. However, evidence is mostly of low evidence certainty. Emerging evidence is promising for effects of vitamin C supplementation on some diabetes complications, particularly diabetic foot ulcers. However, there is a notable lack of robust and well-designed studies exploring effects of vitamin C as a single compound supplement on diabetes prevention and patient-important outcomes (i.e. prevention and amelioration of diabetes complications). RCTs are also required to investigate potential preventative or ameliorative effects of vitamin C on gestational diabetes outcomes. Oral vitamin C doses of 500-1000 mg per day are potentially effective, safe, and affordable for many individuals with diabetes. However, personalisation of supplementation regimens that consider factors such as vitamin C status, disease status, current glycaemic control, vitamin C intake, redox status, and genotype is important to optimize vitamin C's therapeutic effects safely. Finally, given a high prevalence of vitamin C deficiency in patients with complications, it is recommended that plasma vitamin C concentration be measured and monitored in the clinic setting.

Metabolic aspects of hepatitis C virus

Many metabolic factors are associated with chronic hepatitis C virus (HCV) infection and can influence the course of the illness and impact the progression of liver and non-liver-related diseases through complex interactions. Several of these factors impact the course of chronic HCV (CHC) and result in the conceptual translation of CHC from a localized to systemic disease. Besides the traditional liver manifestations associated with CHC infection, such as cirrhosis and hepatocellular carcinoma, various extrahepatic disorders are associated with HCV infection, including atherosclerosis, glucose and lipid metabolic disturbances, alterations in the iron metabolic pathways, and lymphoproliferative diseases. The coexistence of metabolic disorders and CHC is known to influence the chronicity and virulence of HCV and accelerates the progression to liver fibrosis and hepatocellular carcinoma. Insulin resistance is one of the key factors that have a tremendous metabolic impact on CHC. Therefore, there is a great need to properly evaluate patients with CHC infection and correct the modifiable metabolic risk factors. Furthermore, patients with HCV who achieved a sustained virological response showed an overall improvement in glucose metabolism, but the exact evidence still requires further studies with long-term follow-up. This review delineates the most recent evidence on the main metabolic factors associated with CHC and the possible influence of chronic HCV infection on metabolic features.

Impaired postprandial skeletal muscle vascular responses to a mixed meal challenge in normoglycaemic people with a parent with type 2 diabetes

AIMS/HYPOTHESIS

Microvascular blood flow (MBF) increases in skeletal muscle postprandially to aid in glucose delivery and uptake in muscle. This vascular action is impaired in individuals who are obese or have type 2 diabetes. Whether MBF is impaired in normoglycaemic people at risk of type 2 diabetes is unknown. We aimed to determine whether apparently healthy people at risk of type 2 diabetes display impaired skeletal muscle microvascular responses to a mixed-nutrient meal.

METHODS

In this cross-sectional study, participants with no family history of type 2 diabetes (FH-) for two generations (n = 18), participants with a positive family history of type 2 diabetes (FH+; i.e. a parent with type 2 diabetes; n = 16) and those with type 2 diabetes (n = 12) underwent a mixed meal challenge (MMC). Metabolic responses (blood glucose, plasma insulin and indirect calorimetry) were measured before and during the MMC. Skeletal muscle large artery haemodynamics (2D and Doppler ultrasound, and Mobil-O-graph) and microvascular responses (contrast-enhanced ultrasound) were measured at baseline and 1 h post MMC.

RESULTS

Despite normal blood glucose concentrations, FH+ individuals displayed impaired metabolic flexibility (reduced ability to switch from fat to carbohydrate oxidation vs FH-; p < 0.05) during the MMC. The MMC increased forearm muscle microvascular blood volume in both the FH- (1.3-fold, p < 0.01) and FH+ (1.3-fold, p < 0.05) groups but not in participants with type 2 diabetes. However, the MMC increased MBF (1.9-fold, p < 0.01), brachial artery diameter (1.1-fold, p < 0.01) and brachial artery blood flow (1.7-fold, p < 0.001) and reduced vascular resistance (0.7-fold, p < 0.001) only in FH- participants, with these changes being absent in FH+ and type 2 diabetes. Participants with type 2 diabetes displayed significantly higher vascular stiffness (p < 0.001) compared with those in the FH- and FH+ groups; however, vascular stiffness did not change during the MMC in any participant group.

CONCLUSIONS/INTERPRETATION

Normoglycaemic FH+ participants display impaired postprandial skeletal muscle macro- and microvascular responses, suggesting that poor vascular responses to a meal may contribute to their increased risk of type 2 diabetes. We conclude that vascular insulin resistance may be an early precursor to type 2 diabetes in humans, which can be revealed using an MMC.

Short-Term Effects of Supplemental L-Arginine, Diosmin, Troxerutin, and Hesperidin in Diabetic Patients: A Pilot Study

Background and Aims

Inflammatory, oxidative stress, and endothelial dysfunction play a key role in the pathogenesis of long-term cardiovascular complications in patients with diabetes. The present observational prospective study is aimed at evaluating the effects of micronutrients and phytochemicals contained in the dietary supplement Flebotrofine® (AMNOL Chimica Biologica) on biochemical markers of inflammation, endothelial dysfunction, and glycemic control in patients with diabetes.

Methods

105 type 1 or type 2 diabetes patients regularly took a daily dose of the dietary supplement Flebotrofine® for three consecutive months, and haematological and biochemical parameters were checked at baseline, after three months of treatment, and one month after its suspension. Statistical comparison of the laboratory parameters was performed using the two-tailed ANOVA test for repeated samples with a statistical significance level set at p < 0.05.

Results

The daily use of Flebotrofine® did not change the glycemic metabolic compensation of enrolled patients. After three months of regular Flebotrofine® intake, the plasma levels of the antioxidant β-carotene and of arginine were significantly higher compared with the baseline values, with a decrease in the ADMA/arginine ratio. In contrast, apolipoprotein B, ApoB/ApoA1 ratio, and platelet and leukocyte counts significantly dropped.

Conclusion

The daily use of Flebotrofine® might be a valid supplement of arginine, the precursor of NO, and essential in the prevention of endothelial dysfunction. The regular intake of arginine and phytochemicals also improved the antioxidant and antithrombotic profile of enrolled patients. Therefore, Flebotrofine® could be a useful dietary supplement to prevent long-term complications in patients with diabetes.

Hyperinsulinemia negatively affects the association between insulin resistance and blood pressure

BACKGROUND AND AIMS

Although hyperinsulinemia and insulin resistance (IR) together cause metabolic diseases, the available evidence fails to link hyperinsulinemia with blood pressure (BP) elevation. To further understand the role of hyperinsulinemia in the pathophysiology of hypertension, we conducted this study to investigate the moderating effect of fasting insulin (FINS) on the association between IR and BP.

METHODS AND RESULTS

The health screening data of 72,076 individuals were analyzed for this moderation analysis. IR was indicated by the homeostatic model assessment of insulin resistance (HOMA-IR), triglyceride-glucose index (TyG), and triglyceride to high-density lipoprotein cholesterol ratio (TG/HDLc). In the adjusted model, three IR indicators were considered independent variables; FINS was used as a moderator, and systolic BP (SBP) and diastolic BP (DBP) were used as dependent variables. The regression coefficient of the interaction term between the three IR indicators and FINS was significantly negative in all moderation models. Simple slope tests and the Johnson-Neymann technique also indicated that FINS negatively moderated the association between IR and BP.

CONCLUSIONS

This moderation analysis showed that FINS negatively mediated the association between IR and BP, suggesting that hyperinsulinemia may buffer, not reinforce, the effect of IR on hypertension.

Peroxisome proliferator-activated receptor agonist (pioglitazone) with exogenous adiponectin ameliorates arterial stiffness and oxidative stress in diabetic Wistar Kyoto rats

Oxidative stress causes hypoadiponectemia and reactive oxygen species production. This study investigates the pathophysiological role and potential effects of adiponectin with partial and full peroxisome proliferator-activated receptor-gamma agonists on modulation of metabolic dysregulation and oxidative stress in diabetic model of Wistar Kyoto rats (WKY). Forty two male WKY rats were randomized equally into 7 groups (n = 6), Group I serve as control, group II as WKY diabetic control, groups III, IV and V treated with irbesartan (30 mg/kg), pioglitazone (10 mg/kg) and adiponectin (2.5 μg/kg), groups VI and VII were co-treated as: irbesartan + adiponectin, pioglitazone + adiponectin, respectively. Streptozotocin @ 40 mg/kg was administered intraperitoneally to induce diabetes. Plasma adiponectin, metabolic indices, pulse wave velocity, oxidative stress and antioxidant enzymatic activities were measured. Streptozotocin induced WKYs expressed hyperglycaemia, hypertriglyceridemia, hypercholesterolemia, hypoadiponectemia, increased arterial stiffness and decreased antioxidant enzymatic levels (P<0.05). Treatment with adiponectin or pioglitazone alone showed improvements in metabolic indices, antioxidant enzymes, and abrogated arterial stiffness, attenuated generation of reactive oxygen species and dyslipidaemic effects of streptozotocin better as compared to irbesartan sets of treatment (all P<0.05). Co-treatment of adiponectin with pioglitazone significantly amplified the improvement in plasma triglycerides, adiponectin concentration, pulse wave velocity and antioxidant enzymatic activities indicating synergistic effects of adiponectin with full PPAR-γ agonist.

How Perturbated Metabolites in Diabetes Mellitus Affect the Pathogenesis of Hypertension?

The presence of hypertension (HTN) in type 2 diabetes mellitus (DM) is a common phenomenon in more than half of the diabetic patients. Since HTN constitutes a predictor of vascular complications and cardiovascular disease in type 2 DM patients, it is of significance to understand the molecular and cellular mechanisms of type 2 DM binding to HTN. This review attempts to understand the mechanism via the perspective of the metabolites. It reviewed the metabolic perturbations, the biological function of perturbated metabolites in two diseases, and the mechanism underlying metabolic perturbation that contributed to the connection of type 2 DM and HTN. DM-associated metabolic perturbations may be involved in the pathogenesis of HTN potentially in insulin, angiotensin II, sympathetic nervous system, and the energy reprogramming to address how perturbated metabolites in type 2 DM affect the pathogenesis of HTN. The recent integration of the metabolism field with microbiology and immunology may provide a wider perspective. Metabolism affects immune function and supports immune cell differentiation by the switch of energy. The diverse metabolites produced by bacteria modified the biological process in the inflammatory response of chronic metabolic diseases either. The rapidly evolving metabolomics has enabled to have a better understanding of the process of diseases, which is an important tool for providing some insight into the investigation of diseases mechanism. Metabolites served as direct modulators of biological processes were believed to assess the pathological mechanisms involved in diseases.

Dietary Flavonoids and Insulin Signaling in Diabetes and Obesity

Type 2 diabetes (T2D) and obesity are relevant worldwide chronic diseases. A common complication in both pathologies is the dysregulation of the insulin-signaling pathway that is crucial to maintain an accurate glucose homeostasis. Flavonoids are naturally occurring phenolic compounds abundant in fruits, vegetables and seeds. Rising evidence supports a role for the flavonoids against T2D and obesity, and at present, these compounds are considered as important potential chemopreventive agents. This review summarizes in vitro and in vivo studies providing data related to the effects of flavonoids and flavonoid-rich foods on the modulation of the insulin route during T2D and obesity. Notably, few human studies have evaluated the regulatory effect of these phenolic compounds at molecular level on the insulin pathway. In this context, it is also important to note that the mechanism of action for the flavonoids is not fully characterized and that a proper dosage to obtain a beneficial effect on health has not been defined yet. Further investigations will contribute to solve all these critical challenges and will enable the use of flavonoids to prevent, delay or support the treatment of T2D and obesity.

The Role of Estrogen in Insulin Resistance: A Review of Clinical and Preclinical Data

Insulin resistance results when peripheral tissues, including adipose, skeletal muscle, and liver, do not respond appropriately to insulin, causing the ineffective uptake of glucose. This represents a risk factor for the development of type 2 diabetes mellitus. Along with abdominal obesity, hypertension, high levels of triglycerides, and low levels of high-density lipoproteins, insulin resistance is a component of a condition known as the metabolic syndrome, which significantly increases the risk of developing cardiometabolic disorders. Accumulating evidence shows that biological sex has a major influence in the development of cardiometabolic disturbances, with females being more protected than males. This protection appears to be driven by female sex hormones (estrogens), as it tends to disappear with the onset of menopause but can be re-established with hormone replacement therapy. This review evaluates current knowledge on the protective role of estrogens in the relevant pathways associated with insulin resistance. The importance of increasing our understanding of sex as a biological variable in cardiometabolic research to promote the development of more effective preventative strategies is emphasized.

Ginsenoside Rc Ameliorates Endothelial Insulin Resistance via Upregulation of Angiotensin-Converting Enzyme 2

Type 2 diabetes mellitus (T2DM) is a major health concern which may cause cardiovascular complications. Insulin resistance (IR), regarded as a hallmark of T2DM, is characterized by endothelial dysfunction. Ginsenoside Rc is one of the main protopanaxadiol-type saponins with relatively less research on it. Despite researches confirming the potent anti-inflammatory and antioxidant activities of ginsenoside Rc, the potential benefits of ginsenoside Rc against vascular complications have not been explored. In the present study, we investigated the effects of ginsenoside Rc on endothelial IR and endothelial dysfunction with its underlying mechanisms using high glucose- (HG-) cultured human umbilical vein endothelial cells (HUVECs) in vitro and a type 2 diabetic model of db/db mice in vivo. The results showed that ginsenoside Rc corrected the imbalance of vasomotor factors, reduced the production of Ang (angiotensin) II, and activated angiotensin-converting enzyme 2 (ACE2)/Ang-(1–7)/Mas axis in HG-treated HUVECs. Besides, ginsenoside Rc improved the impaired insulin signaling pathway and repressed oxidative stress and inflammatory pathways which constitute key factors leading to IR. Interestingly, the effects of ginsenoside Rc on HG-induced HUVECs were abolished by the selective ACE2 inhibitor MLN-4760. Furthermore, ginsenoside Rc exhibited anti-inflammatory as well as antioxidant properties and ameliorated endothelial dysfunction via upregulation of ACE2 in db/db mice, which were confirmed by the application of MLN-4760. In conclusion, our findings reveal a novel action of ginsenoside Rc and demonstrate that ginsenoside Rc ameliorated endothelial IR and endothelial dysfunction, at least in part, via upregulation of ACE2 and holds promise for the treatment of diabetic vascular complications.

NLRP3 Inflammasome at the Interface of Inflammation, Endothelial Dysfunction, and Type 2 Diabetes

Type 2 diabetes mellitus (T2DM), accounting for 90-95% cases of diabetes, is characterized by chronic inflammation. The mechanisms that control inflammation activation in T2DM are largely unexplored. Inflammasomes represent significant sensors mediating innate immune responses. The aim of this work is to present a review of links between the NLRP3 inflammasome, endothelial dysfunction, and T2DM. The NLRP3 inflammasome activates caspase-1, which leads to the maturation of pro-inflammatory cytokines interleukin 1β and interleukin 18. In this review, we characterize the structure and functions of NLRP3 inflammasome as well as the most important mechanisms and molecules engaged in its activation. We present evidence of the importance of the endothelial dysfunction as the first key step to activating the inflammasome, which suggests that suppressing the NLRP3 inflammasome could be a new approach in depletion hyperglycemic toxicity and in averting the onset of vascular complications in T2DM. We also demonstrate reports showing that the expression of a few microRNAs that are also known to be involved in either NLRP3 inflammasome activation or endothelial dysfunction is deregulated in T2DM. Collectively, this evidence suggests that T2DM is an inflammatory disease stimulated by pro-inflammatory cytokines. Finally, studies revealing the role of glucose concentration in the activation of NLRP3 inflammasome are analyzed. The more that is known about inflammasomes, the higher the chances to create new, effective therapies for patients suffering from inflammatory diseases. This may offer potential novel therapeutic perspectives in T2DM prevention and treatment.

Correlation of serum betatrophin levels with disease severity and the emergence of insulin resistance in cirrhotic patients

Background

Insulin resistance (IR) is frequently associated with chronic liver disease. There has been an increased interest in betatrophin protein and its involvement in the compensatory response to IR. We aimed to investigate the correlation of serum betatrophin levels with disease severity and the emergence of IR in cirrhotic patients. This study included 27 cirrhotic patients and 30 healthy participants who served as a control group. IR was assessed by the Homeostasis Model Assessment (HOMA-IR). Serum insulin and betatrophin levels were measured using Enzyme-Linked Immunosorbent Assay (ELISA).

Results

IR was existing in 74% of cirrhotic patients (p < 0.001). Subjects with IR had higher serum betatrophin levels than those without IR (p = 0.04). Serum betatrophin levels were significantly higher in cirrhotic patients than controls (p < 0.001). In addition, Child-Pugh class C patients had higher serum betatrophin levels than those with Child-Pugh class B cirrhosis (p = 0.01). Moreover, the highest serum betatrophin levels were detected in patients with tense ascites followed by those with moderate and mild ascites (p = 0.01). In the cirrhosis group, serum betatrophin levels correlated positively with fasting blood glucose levels (p < 0.001), fasting insulin levels (p = 0.006), HOMA-IR (p = 0.006), Child-Pugh score (p = 0.023), MELD score (p < 0.001), and INR (p = 0.005), and correlated negatively with platelets count (p = 0.01).

Conclusion

Cirrhotic patients have higher serum betatrophin levels; moreover, these levels are positively correlated with disease severity as well as the emergence of insulin resistance.

The impact of preconditioning exercise on the vascular response to an oral glucose challenge

Exercise elicits direct benefits to insulin sensitivity but may also indirectly improve glucose uptake by hemodynamic conditioning of the vasculature. The purpose of this study was to examine the modifying effect of 3 different types of exercise on the vascular response to an oral glucose challenge. Twenty healthy adults (9 women, 11 men; aged 23 ± 3 years) completed a standard oral glucose tolerance test (OGTT) at rest, as well as 1.5 hours after moderate continuous cycling exercise (30 min; 65% peak oxygen consumption), high-intensity interval cycling exercise (10 × 1 min at 90% peak heart rate), and lower-load higher-repetition resistance exercise (25-35 repetitions/set, 3 sets). Brachial and superficial femoral artery blood flow, conductance, and oscillatory shear index were measured throughout the OGTT. Regardless of rested state or exercise preconditioning, the OGTT induced reductions in brachial artery blood flow and conductance (p < 0.001), and transient increases in brachial and superficial femoral artery oscillatory shear index and retrograde blood flow (p < 0.01). Continuous cycling and resistance exercise were followed with a small degree of protection against prolonged periods of oscillatory flow. Our findings imply transient peripheral vasoconstriction and decreased limb blood flow during a standard OGTT, for which prior exercise was unable to prevent in healthy adults. Novelty: We investigated the impact of continuous, interval, and resistance exercise on the hemodynamic response to an OGTT. Our findings suggest decreased upper-limb blood flow during an OGTT is not prevented by prior exercise in healthy adults.

The impact of triglyceride-glucose index on incident cardiovascular events during 16 years of follow-up: Tehran Lipid and Glucose Study

BACKGROUND

To investigate whether the Triglyceride-Glucose index (TyG-index) is associated with increased risk of cardiovascular diseases (CVD)/coronary heart disease (CHD).

METHODS

A total of 7521 Iranians aged ≥ 30 years (male = 3367) were included in the study. Multivariate Cox regression analyses (adjusted for age, gender, waist circumference, body mass index, educational level, smoking status, physical activity, family history of CVD, type 2 diabetes, hypertension, low and high density lipoprotein cholesterol, and lipid lowering drugs) were used to assess the risk of incident CVD/CHD across quintiles and for 1-standard deviation (SD) increase in the TyG-index. The cut off point for TyG-index was assessed by the minimum value of [Formula: see text]. We also examined the added value of the TyG-index in addition to the Framingham risk score when predicting CVD.

RESULTS

During follow-up, 1084 cases of CVD (male = 634) were recorded. We found a significant trend of TyG-index for incident CVD/CHD in multivariate analysis (both Ps for tend ≤ 0.002). Moreover, a 1-SD increase in TyG-index was associated with significant risk of CVD/CHD in multivariate analysis [1.16 (1.07-1.25) and 1.19 (1.10-1.29), respectively]. The cut-off value of TyG-index for incident CVD was 9.03 (59.2% sensitivity and 63.2% specificity); the corresponding value of TyG-index for incident CHD was 9.03 (60.0% sensitivity and 62.8% specificity), respectively. Although no interaction was found between gender and TyG-index for CVD/CHD in multivariate analysis (both Ps for interaction > 0.085), the significant trend of TyG-index was observed only among females for incident CVD (P = 0.035). A significant interaction was found between age groups (i.e. ≥ 60 vs < 60 years) and TyG-index for CVD outcomes in the multivariate model (P-value for interaction = 0.046). Accordingly, a significant association between the TyG-index and outcomes was found only among the younger age group. Among the population aged < 60 the addition of TyG-index to the Framingham risk score (FRS) did not show improvement in the predictive ability of the FRS, using integrated discrimination improvement.

CONCLUSION

The TyG-index is significantly associated with increased risk of CVD/CHD incidence; this issue was more prominent among the younger population. However, adding TyG-index to FRS does not provide better risk prediction for CVD.

Effects of a multifactorial ecosustainable isocaloric diet on liver fat in patients with type 2 diabetes: randomized clinical trial

INTRODUCTION

Treatment options for non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes (T2D) are still a matter of debate. We compared the effects of a diet including different components versus a proven beneficial diet rich in monounsaturated fatty acids (MUFAs) on liver fat in T2D.

RESEARCH DESIGN AND METHODS

According to a parallel design, 49 individuals with T2D, overweight/obese, with high waist circumference, 35-75 years-old, in satisfactory blood glucose control with diet or drugs not affecting liver fat content, were randomly assigned to an 8-week isocaloric intervention with a MUFA diet (n=26) or a multifactorial diet rich in fiber, MUFA, n-6 and n-3 polyunsaturated fatty acids, polyphenols, and vitamins D, E, and C (n=23). Before and after the intervention, liver fat content was evaluated by proton magnetic resonance spectroscopy (¹H-MRS). ¹H-MRS complete data were available for n=21 (MUFA diet) and n=18 (multifactorial diet) participants.

RESULTS

Adherence to dietary interventions was optimal. No significant differences between groups in body weight reduction, plasma glycated hemoglobin, insulin, glucose, lipids and liver enzymes were observed. Liver fat significantly decreased after both the multifactorial diet (9.18%±7.78% vs 5.22%±4.80%, p=0.003) and the MUFA diet (9.47%±8.89% vs 8.07%±8.52%, p=0.027) with a statistically significant difference between changes either in absolute terms (-4.0%±4.5% vs -1.4%±2.7%, p=0.035) or percent (-40%±33% vs -19%±25%, p=0.030).

CONCLUSIONS

An isocaloric multifactorial diet including several beneficial dietary components induced a clinically relevant reduction of liver fat in patients with T2D, more pronounced than that induced by simply replacing saturated fat with MUFA. This suggests that the 'optimal diet' for NAFLD treatment in T2D should be based on synergic actions of different dietary components on multiple pathophysiological pathways.

TRIAL REGISTRATION NUMBER

NCT03380416.

The effect of prolonged dietary sodium nitrate treatment on the hypothalamus-pituitary-gonadal axis and testicular structure and function in streptozotocin-induced diabetic male rats

The aim of this study was to evaluate the effect of prolonged dietary nitrate supplementation on the gonadotropin level, testicular histology and morphometry, expression of miR-34b and p53 mRNA, and spermatogenesis in streptozotocin-induced diabetic male rats.

METHODS

Fifty male Wistar rats were divided into 5 groups: Control (C), control + nitrate (CN), diabetes (D), diabetes + insulin (DI), and diabetes + nitrate (DN). Diabetes was induced using 45 mg kg^-1 of streptozotocin intraperitoneally. Rats in the CN and DN groups were administered sodium nitrate in drinking water (100 mg L^-1). NPH insulin (2-4 U d^-1) was injected subcutaneously in the DI group for 2 months. Nitrate and insulin supplementation was started one month after confirmation of diabetes.

RESULTS

Nitrate supplementation in the DN group significantly increased the body weight (p < 0.05), sperm parameters (p < 0.001), indices of spermatogenesis (p < 0.001), and testis histopathology as well as decreased the blood glucose level (p < 0.001) compared to the untreated diabetic group, although it had no significant effect on testicular parameters, LH and FSH levels. Nitrate administration in the DN group also decreased miR-34b (p < 0.001) and p53 mRNA (p < 0.001) expression, and increased serum insulin and NOx levels compared to the untreated diabetic rats.

CONCLUSIONS

Chronic nitrate supplementation in streptozotocin-induced diabetic rats improved fertility parameters, which may be associated with increased miR-34b and decreased p53 mRNA.

Overfeeding During Lactation in Rats is Associated with Cardiovascular Insulin Resistance in the Short-Term

Childhood obesity is associated with metabolic and cardiovascular comorbidities. The development of these alterations may have its origin in early life stages such as the lactation period through metabolic programming. Insulin resistance is a common complication in obese patients and may be responsible for the cardiovascular alterations associated with this condition. This study analyzed the development of cardiovascular insulin resistance in a rat model of childhood overweight induced by overfeeding during the lactation period. On birth day, litters were divided into twelve (L12) or three pups per mother (L3). Overfed rats showed a lower increase in myocardial contractility in response to insulin perfusion and a reduced insulin-induced vasodilation, suggesting a state of cardiovascular insulin resistance. Vascular insulin resistance was due to decreased activation of phosphoinositide 3-kinase (PI3K)/Akt pathway, whereas cardiac insulin resistance was associated with mitogen-activated protein kinase (MAPK) hyperactivity. Early overfeeding was also associated with a proinflammatory and pro-oxidant state; endothelial dysfunction; decreased release of nitrites and nitrates; and decreased gene expression of insulin receptor (IR), glucose transporter-4 (GLUT-4), and endothelial nitric oxide synthase (eNOS) in response to insulin. In conclusion, overweight induced by lactational overnutrition in rat pups is associated with cardiovascular insulin resistance that could be related to the cardiovascular alterations associated with this condition.

Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism

Nitric oxide (NO) contributes to carbohydrate metabolism and decreased NO bioavailability is involved in the development of type 2 diabetes mellitus (T2DM). NO donors may improve insulin signaling and glucose homeostasis in T2DM and insulin resistance (IR), suggesting the potential clinical importance of NO-based interventions. In this review, site-specific roles of the NO synthase (NOS)-NO pathway in carbohydrate metabolism are discussed. In addition, the metabolic effects of physiological low levels of NO produced by constitutive NOS (cNOS) versus pathological high levels of NO produced by inducible NOS (iNOS) in pancreatic β-cells, adipocytes, hepatocytes, and skeletal muscle cells are summarized. A better understanding of the NOS-NO system in the regulation of glucose homeostasis can hopefully facilitate the development of new treatments for T2DM.

High-Fat Overfeeding Impairs Peripheral Glucose Metabolism and Muscle Microvascular eNOS Ser1177 Phosphorylation

CONTEXT

The mechanisms responsible for dietary fat-induced insulin resistance of skeletal muscle and its microvasculature are only partially understood.

OBJECTIVE

To determine the impact of high-fat overfeeding on postprandial glucose fluxes, muscle insulin signaling, and muscle microvascular endothelial nitric oxide synthase (eNOS) content and activation.

DESIGN

Fifteen non-obese volunteers consumed a high-fat (64%) high-energy (+47%) diet for 7 days. Experiments were performed before and after the diet. Stable isotope tracers were used to determine glucose fluxes in response to carbohydrate plus protein ingestion. Muscle insulin signaling was determined as well as the content and activation state of muscle microvascular eNOS.

RESULTS

High-fat overfeeding impaired postprandial glycemic control as demonstrated by higher concentrations of glucose (+11%; P = 0.004) and insulin (+19%; P = 0.035). Carbohydrate plus protein ingestion suppressed endogenous glucose production to a similar extent before and after the diet. Conversely, high-fat overfeeding reduced whole-body glucose clearance (-16%; P = 0.021) and peripheral insulin sensitivity (-26%; P = 0.006). This occurred despite only minor alterations in skeletal muscle insulin signaling. High-fat overfeeding reduced eNOS content in terminal arterioles (P = 0.017) and abolished the increase in eNOS Ser1177 phosphorylation that was seen after carbohydrate plus protein ingestion.

CONCLUSION

High-fat overfeeding impaired whole-body glycemic control due to reduced glucose clearance, not elevated endogenous glucose production. The finding that high-fat overfeeding abolished insulin-mediated eNOS Ser1177 phosphorylation in the terminal arterioles suggests that impairments in the vasodilatory capacity of the skeletal muscle microvasculature may contribute to early dietary fat-induced impairments in glycemic control.

Postprandial microvascular blood flow in skeletal muscle: Similarities and disparities to the hyperinsulinaemic-euglycaemic clamp

Skeletal muscle contributes to ~40% of total body mass and has numerous important mechanical and metabolic roles in the body. Skeletal muscle is a major site for glucose disposal following a meal. Consequently, skeletal muscle plays an important role in postprandial blood glucose homeostasis. Over the past number of decades, research has demonstrated that insulin has an important role in vasodilating the vasculature in skeletal muscle in response to an insulin infusion (hyperinsulinaemic-euglycaemic clamp) or following the ingestion of a meal. This vascular action of insulin is pivotal for glucose disposal in skeletal muscle, as insulin-stimulated vasodilation increases the delivery of both glucose and insulin to the myocyte. Notably, in insulin-resistant states such as obesity and type 2 diabetes, this vascular response of insulin in skeletal muscle is significantly impaired. Whereas the majority of work in this field has focussed on the action of insulin alone on skeletal muscle microvascular blood flow and myocyte glucose metabolism, there is less understanding of how the consumption of a meal may affect skeletal muscle blood flow. This is in part due to complex variations in glucose and insulin dynamics that occurs postprandially-with changes in humoral concentrations of glucose, insulin, amino acids, gut and pancreatic peptides-compared to the hyperinsulinaemic-euglycaemic clamp. This review will address the emerging body of evidence to suggest that postprandial blood flow responses in skeletal muscle may be a function of the nutritional composition of a meal.

Almond-supplemented diet improves sexual functions beyond Phosphodiesterase-5 inhibition in diabetic male rats

Hyperglycemia, an important feature of diabetes, can cause oxidative stress, which is associated with varieties of diabetic complications including erectile dysfunction. Therefore, this study sought to investigate the effect of almond-supplemented diet on some biochemical indices relevant to erection in diabetic male rats. Forty-two male rats were divided into two groups: A (n = 6) and B (n = 36). Diabetes was induced in Group B via injection of a single dose of STZ (50 mg/kg) intraperitoneally and confirmed 72 h after induction. Diabetic rats (blood glucose ≥250 mg/dL) were subsequently divided into six groups (n = 6). Fourteen days after confirmation of diabetes, rats were fed with diets containing almond drupe and seeds (10 and 20% inclusion) for fourteen days. The effects of the diets on blood glucose, sexual behavior, sexual hormones, phosphodiesterase-5 activity, nitric oxide, H₂S, and AGEs levels were evaluated. Significant increase in blood glucose level, phosphodiesterase-5 activity, and glycated hemoglobin was observed in diabetic rats. Furthermore, diabetes caused a significant decrease in nitric oxide, H₂S, sexual hormones (testosterone, follicle-stimulating hormone and luteinizing hormone) levels, and sexual behavioral indices. However, treatment with diets supplemented with almond drupe and seeds significantly reversed these effects in diabetic rats. Findings in this study revealed that almond-supplemented diets enhance some important biomarkers relevant to erection in diabetic rats. Thus, dietary inclusion of almond (drupe and seeds) could serve as a cheap and readily available nutraceutical in the management of erectile dysfunction associated with diabetes.

The Postprandial Appearance of Features of Cardiometabolic Risk: Acute Induction and Prevention by Nutrients and Other Dietary Substances

The purpose of this review is to provide an overview of diets, food, and food components that affect postprandial inflammation, endothelial function, and oxidative stress, which are related to cardiometabolic risk. A high-energy meal, rich in saturated fat and sugars, induces the transient appearance of a series of metabolic, signaling and physiological dysregulations or dysfunctions, including oxidative stress, low-grade inflammation, and endothelial dysfunction, which are directly related to the amplitude of postprandial plasma triglycerides and glucose. Low-grade inflammation and endothelial dysfunction are also known to cluster together with insulin resistance, a third risk factor for cardiovascular diseases (CVD) and type-II diabetes, thus making a considerable contribution to cardiometabolic risk. Because of the marked relevance of the postprandial model to nutritional pathophysiology, many studies have investigated whether adding various nutrients and other substances to such a challenge meal might mitigate the onset of these adverse effects. Some foods (e.g., nuts, berries, and citrus), nutrients (e.g., l-arginine), and other substances (various polyphenols) have been widely studied. Reports of favorable effects in the postprandial state have concerned plasma markers for systemic or vascular pro-inflammatory conditions, the activation of inflammatory pathways in plasma monocytes, vascular endothelial function (mostly assessed using physiological criteria), and postprandial oxidative stress. Although the literature is fragmented, this topic warrants further study using multiple endpoints and markers to investigate whether the interesting candidates identified might prevent or limit the postprandial appearance of critical features of cardiometabolic risk.

Endothelial Dysfunction: Is There a Hyperglycemia-Induced Imbalance of NOX and NOS?

NADPH oxidases (NOX) are enzyme complexes that have received much attention as key molecules in the development of vascular dysfunction. NOX have the primary function of generating reactive oxygen species (ROS), and are considered the main source of ROS production in endothelial cells. The endothelium is a thin monolayer that lines the inner surface of blood vessels, acting as a secretory organ to maintain homeostasis of blood flow. The enzymatic production of nitric oxide (NO) by endothelial NO synthase (eNOS) is critical in mediating endothelial function, and oxidative stress can cause dysregulation of eNOS and endothelial dysfunction. Insulin is a stimulus for increases in blood flow and endothelium-dependent vasodilation. However, cardiovascular disease and type 2 diabetes are characterized by poor control of the endothelial cell redox environment, with a shift toward overproduction of ROS by NOX. Studies in models of type 2 diabetes demonstrate that aberrant NOX activation contributes to uncoupling of eNOS and endothelial dysfunction. It is well-established that endothelial dysfunction precedes the onset of cardiovascular disease, therefore NOX are important molecular links between type 2 diabetes and vascular complications. The aim of the current review is to describe the normal, healthy physiological mechanisms involved in endothelial function, and highlight the central role of NOX in mediating endothelial dysfunction when glucose homeostasis is impaired.

Insulin treatment increases brain nitric oxide and oxidative stress, but does not affect memory function in mice

Insulin increases brain nitric oxide (NO) level but the mechanism and the significance of the effect on memory are not fully understood. This study aimed to demonstrate the mechanism of insulin-induced increase in oxidative stress (OS) and its consequences on learning and memory. Twenty four mice were assigned to groups (n = 6) and treated daily for seven days with water (control), insulin, insulin+N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) and L-NAME, respectively. Memory was assessed using Y-maze; NO, malondialdehyde (MDA) and glutathione peroxidase (GPx) in brain homogenate were also determined. There was no difference between the groups in the number of entries into the arms and time spent in them, and in number of and percentage alternations performed by the mice, indicating normal memory function of the control and treated mice. NO level in the insulin group was higher compared to the control (p = .018), while those of the other groups were statistically the same compared to the control group. MDA values in the insulin group were higher (p = .001) than those of the control, while those of the other groups were statistically the same compared to those of the control group. GPx activity in the insulin group was lower compared to control (p = .004), while that of the other groups was not significantly different compared to control. It was concluded that insulin treatment increased brain level of NO and OS through increased malondialdehyde level and glutathione peroxidase activity; insulin treatment did not affect long-term visuo-spatial and short-term working memory in the animals. Insulin treatment may have deleterious effects on the brain through increased NO and OS levels.

A Proposed Inflammatory Score of Circulating Cytokines/Adipokines Associated with Resistant Hypertension, but Dependent on Obesity Parameters

Background

There is evidence that subclinical systemic inflammation is present in resistant hypertension (RHTN).

Objective

The aim of the study was to develop an integrated measure of circulating cytokines/adipokines involved in the pathophysiology of RHTN.

Methods

RHTN (n = 112) and mild to moderate hypertensive (HTN) subjects (n=112) were studied in a cross-sectional design. Plasma cytokines/adipokines (TNF-alpha, interleukins [IL]-6, -8, -10, leptin and adiponectin) values were divided into tertiles, to which a score ranging from 1 (lowest tertile) to 3 (highest tertile) was assigned. The inflammatory score (IS) of each subject was the sum of each pro-inflammatory cytokine scores from which anti-inflammatory cytokines (adiponectin and IL-10) scores were subtracted. The level of significance accepted was alpha = 0.05.

Results

IS was higher in RHTN subjects compared with HTN subjects [4 (2-6) vs. 3 (2-5); p = 0.02, respectively]. IS positively correlated with body fat parameters, such as body mass index (r = 0.40; p < 0.001), waist circumference (r = 0.30; p < 0.001) and fat mass assessed by bioelectrical impedance analysis (r = 0.31; p < 0.001) in all hypertensive subjects. Logistic regression analyses revealed that IS was an independent predictor of RHTN (OR = 1.20; p = 0.02), independent of age, gender and race, although it did not remain significant after adjustment for body fat parameters.

Conclusion

A state of subclinical inflammation defined by an IS including TNF-alpha, IL-6, IL-8, IL-10, leptin and adiponectin is associated with obese RHTN. In addition, this score correlates with obesity parameters, independently of hypertensive status. The IS may be used for the evaluation of conditions involving low-grade inflammation, such as obesity-related RHTN. Indeed, it also highlights the strong relationship between obesity and inflammatory process.

Hyperglycemia modulates redox, inflammatory and vasoactive markers through specific signaling pathways in cerebral endothelial cells: Insights on insulin protective action

Type 2 diabetes is associated with major vascular dysfunctions, leading to clinical complications such as stroke. It is also known that hyperglycemia dysregulates blood-brain barrier homeostasis by altering cerebral endothelial cell function. Oxidative stress may play a critical role. The aim of this study was to evaluate the effect of hyperglycemia and insulin on the production of redox, inflammatory and vasoactive markers by cerebral endothelial cells. Murine bEnd.3 cerebral endothelial cells were exposed to hyperglycemia in the presence or not of insulin. Results show that hyperglycemia altered the expression of genes encoding the ROS-producing enzyme Nox4, antioxidant enzymes Cu/ZnSOD, catalase and HO-1 as well as Cu/ZnSOD, MnSOD and catalase enzymatic activities, leading to a time-dependent modulation of ROS levels. Cell preconditioning with inhibitors targeting PI3K, JNK, ERK, p38 MAPK or NFĸB signaling molecules partly blocked hyperglycemia-induced oxidative stress. Conversely, AMPK inhibitor exacerbated ROS production, suggesting a protective role of AMPK on the antioxidant defense system. Hyperglycemia also modulated both gene expression and nuclear translocation of the redox-sensitive transcription factor Nrf2. Moreover, hyperglycemia caused a pro-inflammatory response by activating NFĸB-AP-1 pathway and IL-6 secretion. Hyperglycemia reduced eNOS gene expression and NO levels, while increasing ET-1 gene expression. Importantly, insulin counteracted all the deleterious effects of hyperglycemia. Collectively, these results demonstrate that hyperglycemia dysregulated redox, inflammatory and vasoactive markers in cerebral endothelial cells. Insulin exerted a protective action against hyperglycemia effects. Thus, it will be of high interest to evaluate the benefits of antioxidant and anti-inflammatory strategies against hyperglycemia-mediated vascular complications in type 2 diabetes.

Oral glucose challenge impairs skeletal muscle microvascular blood flow in healthy people

Skeletal muscle microvascular (capillary) blood flow increases in the postprandial state or during insulin infusion due to dilation of precapillary arterioles to augment glucose disposal. This effect occurs independently of changes in large artery function. However, acute hyperglycemia impairs vascular function, causes insulin to vasoconstrict precapillary arterioles, and causes muscle insulin resistance in vivo. We hypothesized that acute hyperglycemia impairs postprandial muscle microvascular perfusion, without disrupting normal large artery hemodynamics, in healthy humans. Fifteen healthy people (5 F/10 M) underwent an oral glucose challenge (OGC, 50 g glucose) and a mixed-meal challenge (MMC) on two separate occasions (randomized, crossover design). At 1 h, both challenges produced a comparable increase (6-fold) in plasma insulin levels. However, the OGC produced a 1.5-fold higher increase in blood glucose compared with the MMC 1 h postingestion. Forearm muscle microvascular blood volume and flow (contrast-enhanced ultrasound) were increased during the MMC (1.3- and 1.9-fold from baseline, respectively, P < 0.05 for both) but decreased during the OGC (0.7- and 0.6-fold from baseline, respectively, P < 0.05 for both) despite a similar hyperinsulinemia. Both challenges stimulated brachial artery flow (ultrasound) and heart rate to a similar extent, as well as yielding comparable decreases in diastolic blood pressure and total vascular resistance. Systolic blood pressure and aortic stiffness remained unaltered by either challenge. Independently of large artery hemodynamics, hyperglycemia impairs muscle microvascular blood flow, potentially limiting glucose disposal into skeletal muscle. The OGC reduced microvascular blood flow in muscle peripherally and therefore may underestimate the importance of skeletal muscle in postprandial glucose disposal.

Molecular and cellular insights into the pathogenesis of coronary artery ectasia

Coronary artery ectasia describes a local or diffuse dilatation of the epicardial coronary arteries. This review summarizes the molecular and cellular mechanisms involved in the pathogenesis of coronary artery ectasia. Better identification of the pathophysiologic steps will shed light into the clinical significance and may have direct implications for the management strategies of this disease. Additionally, understanding the underlying etiology may help to improve treatment modalities specific to coronary artery ectasia.

Gastrointestinal hormones in regulation of memory

The connection between the gastrointestinal hormones and the brain has been established many years ago. This relation is termed the gut-brain axis (GBA). The GBA is a bidirectional communication which not only regulates gastrointestinal homeostasis but is also linked with higher emotional and cognitive functions. Hypothalamus plays a critical role in the regulation of energy metabolism, nutrient partitioning and control of feeding behaviors. Various gut hormones are released inside the gastrointestinal tract on food intake. These hormones act peripherally and influence the different responses of the tissues to the food intake, but do also have effects on the brain. The hypothalamus, in turn, integrates visceral function with limbic system structures such as hippocampus, amygdala, and cerebral cortex. The hippocampus has been known for its involvement in the cognitive function and the modulation of synaptic plasticity. This review aims to establish the role of various gut hormones in learning and memory, through the interaction of various receptors in the hippocampus. Understanding their role in memory can also aid in finding novel therapeutic strategies for the treatment of the neurological disorders associated with memory dysfunctions.

Pathophysiological Role of Adiponectin, Leptin and Asymmetric Dimethylarginine in the Process of Atherosclerosis

Adipose tissue is recognized as a rich source of proinflammatory mediators that may directly contribute to vascular injury, insulin resistance, and atherogenesis. Many studies have shown that adiponectin has antiatherogenic and anti-inflammatory properties. Adiponectin acts not only as a factor increasing insulin sensitivity, and the protective effect may result from its ability to suppress production of proinflammatory cytokines. It negatively regulates the expression of TNF-alpha and C-reactive protein (CRP) in adipose tissue; reduces expression of vascular and intracellular adhesion molecules (VCAM-1, ICAM-1), E-selectin, interleukin-8 (IL-8). Hyperleptinemia has been linked with the development of hypertension and endothelial dysfunction/atherosclerosis, two main pathophysiological conditions associated with cardiovascular disease development. Leptin-mediated increases in sympathetic nervous system activity may be among the principal mechanisms evoking obesity related hypertension. Leptin stimulates the secretion of proinflammatory cytokines, and increases the release of endothelin-1 (ET-1), which may promote hypertension. Increased serum levels of asymmetric dimethylarginine (ADMA), a physiological regulator of the biosynthesis of nitric oxide (NO), promote the process of atherosclerosis, leading to the occurrence of endothelial dysfunction and cardiovascular disease.

Transient elastography in healthy subjects and factors influencing liver stiffness in non-alcoholic fatty liver disease: An Italian community-based population study

BACKGROUND

Few studies have been performed to explore parameters that influence liver stiffness measurement (LSM) using transient elastography in general population.

AIM

To explore factors influencing LSM in healthy and in subjects with non-alcoholic fatty liver disease (NAFLD).

METHODS

LSM was performed in a well-characterized cohort of subjects aged between 30 and 63 years. After exclusion of any causes of liver disease, the healthy cohort was defined and was compared with participants with NAFLD. The 95th percentile value of LSM in healthy was used as a cutoff suggesting relevant fibrosis.

RESULTS

Among 780 subjects evaluated, 331 were defined as healthy. The median value was 4.4kPa (3.7-5.2) and the 95th percentile was 6.8kPa. LSM was not influenced by gender, age, anthropometrics and biochemical parameters. Only insulin resistance was independently associated with increasing of LSM. In the cohort of 157 subjects with NAFLD, LSM was higher than in healthy (5.6±1.9 vs 4.6±1.3kPa; p<0.001). On multivariate analysis, the degree of steatosis was independently associated with increasing of LSM in NAFLD cohort (β=0.271; 95% CI=0.026-0.095; p<0.001). Participants with diabetes and/or severe steatosis had the highest probabilities of relevant fibrosis.

CONCLUSIONS

LSM varies between 3.7 and 5.2kPa in healthy Caucasians and is influenced only by insulin resistance. In NAFLD, severe steatosis and diabetes are factors influencing LSM.

A Slow- Compared with a Fast-Release Form of Oral Arginine Increases Its Utilization for Nitric Oxide Synthesis in Overweight Adults with Cardiometabolic Risk Factors in a Randomized Controlled Study

BACKGROUND

Oral l-arginine supplements can have a beneficial effect on nitric oxide (NO)-related functions when subjects have cardiovascular disease risk factors.

OBJECTIVE

The study was designed to determine the utilization for NO synthesis of oral l-arginine as a function of the cardiometabolic risk and the speed of absorption by comparing immediate-release arginine (IR-Arg), as in supplements, and sustained-release arginine (SR-Arg), which mimics the slow release of dietary arginine.

METHODS

In a randomized, single-blind, 2-period crossover, controlled trial (1 wk of treatment, >2 wk of washout), using [(15)N-(15)N-(guanidino)]-arginine for the first morning dose, we compared the bioavailability (secondary outcome) and utilization for NO synthesis (primary outcome) of 1.5 g IR- and SR-Arg 3 times/d in 12 healthy overweight [body mass index (BMI; in kg/m(2)): 25-30] adults with the hypertriglyceridemic waist phenotype [HTW; plasma triglycerides (TGs): >150 mg/dL; waist circumference: >94 cm (men) or >80 cm (women)] and 15 healthy control adults (CON; BMI: 18.5-25; no elevated TGs and waist circumference).

RESULTS

Plasma oral arginine areas under the curve were lower after supplementation with SR-Arg than with IR-Arg (112 ± 52.3 and 142 ± 50.8 μmol ⋅ h/L; P < 0.01). The utilization of oral arginine for NO synthesis was 58% higher in HTW subjects than in CON subjects and higher with SR-Arg than with IR-Arg (P < 0.05 both), particularly in HTW subjects (group-by-treatment interaction, P < 0.05). In HTW subjects administered the SR form, utilization for NO synthesis was 32% higher than with the IR form and 87% higher than in CON subjects who were administered the SR form.

CONCLUSION

In overweight adults with the HTW phenotype, a slow- compared with a fast-release form of oral arginine markedly favors the utilization of arginine for NO synthesis. The utilization of low-dose, slow-release arginine for NO synthesis is higher in overweight adults with the HTW phenotype than in healthy controls, suggesting that the sensitivity of NO synthesis to the dietary arginine supply increases with cardiometabolic risk. The trial was registered at clinicaltrials.gov as NCT02352740.

l-Arginine Supplementation Alleviates Postprandial Endothelial Dysfunction When Baseline Fasting Plasma Arginine Concentration Is Low: A Randomized Controlled Trial in Healthy Overweight Adults with Cardiometabolic Risk Factors

BACKGROUND

Vascular endothelial dysfunction, the hallmark of early atherosclerosis, is induced transiently by a high-fat meal. High doses of free l-arginine supplements reduce fasting endothelial dysfunction.

OBJECTIVE

We sought to determine the effects of a low dose of a sustained-release (SR) l-arginine supplement on postprandial endothelial function in healthy overweight adults with cardiometabolic risk factors and to investigate whether this effect may vary by baseline arginine status.

METHODS

In a randomized, double-blind, 2-period crossover, placebo-controlled trial (4-wk treatment, 4-wk washout), we compared the effects of 1.5 g SR-l-arginine 3 times/d (4.5 g/d) with placebo in 33 healthy overweight adults [body mass index (BMI, in kg/m(2)): 25 to >30] with the hypertriglyceridemic waist (HTW) phenotype [plasma triglycerides > 150 mg/dL; waist circumference > 94 cm (men) or > 80 cm (women)]. The main outcome variable tested was postprandial endothelial function after a high-fat meal (900 kcal), as evaluated by use of flow-mediated dilation (FMD) and Framingham reactive hyperemia index (fRHI), after each treatment. By use of subgroup analysis, we determined whether the effect was related to the baseline plasma arginine concentration.

RESULTS

In the total population, the effects of SR-arginine supplementation on postprandial endothelial function were mixed and largely varied with baseline fasting arginine concentration (P-interaction < 0.05). In the lower half of the population (below the median of 78.2 μmol arginine/L plasma), but not the upper half, SR-arginine supplementation attenuated the postprandial decrease in both FMD (29% decrease with SR-arginine compared with 50% decrease with placebo) and fRHI (5% increase with SR-arginine compared with 49% decrease with placebo), resulting in significantly higher mean ± SEM values with SR-arginine (FMD: 4.0% ± 0.40%; fRHI: 0.41 ± 0.069) than placebo (FMD: 2.9% ± 0.31%; fRHI: 0.21 ± 0.060) at the end of the postprandial period (P < 0.05).

CONCLUSIONS

Supplementation with low-dose SR-arginine alleviates postprandial endothelial dysfunction in healthy HTW adults when the baseline plasma arginine concentration is relatively low. The benefits of arginine supplementation may be linked to a lower ability to mobilize endogenous arginine for nitric oxide synthesis during a postprandial challenge. This trial was registered at clinicaltrials.gov as NCT02354794.

Insulin resistance is associated with esophageal varices in alcoholic liver disease patients

BACKGROUND AND AIM

Insulin resistance plays an important role in chronic liver disease, where it has been associated with the progression of fibrosis and correlated with portal hypertension in cirrhotic patients with mixed etiology. However, the impact of insulin resistance in alcoholic liver disease remains mostly unknown. The aim of this study was to evaluate the association between insulin resistance, portal hypertension, severity of liver disease, and mortality in patients with alcoholic cirrhosis.

PATIENTS AND METHODS

A total of 106 consecutive alcoholic cirrhotic patients undergoing hepatic venous pressure gradient measurement at Erasme Hospital were included. Insulin resistance was estimated using the homeostatic model assessment-2 index.

RESULTS

The median model for end-stage liver disease (MELD) score was 15 (9-21) and the mean hepatic venous pressure gradient was16.3±6 mmHg. Twenty-six percent of the patients had compensated cirrhosis. Insulin resistance was significantly associated with portal hypertension in compensated cirrhotic patients and with the presence of esophageal varices, but was not associated with the MELD score and mortality. MELD score was the only independent covariate associated with mortality at 6 (P<0.001) and 12 months (P<0.001).

CONCLUSION

Insulin resistance is associated with the presence of esophageal varices, suggesting that the presence of insulin resistance could be harmful to alcoholic liver disease patients.

Serum nitric oxide levels in patients with coronary artery ectasia

Objective:

Serum levels of nitric oxide (NO) are decreased in patients with atherosclerosis and also are a risk factor for the development of atherosclerosis. Endothelial dysfunction and diffuse atherosclerosis have been proposed for the etiology of coronary artery ectasia (CAE). The purpose of this clinical trial was to determine the relationship between CAE and serum NO levels.

Methods:

This prospective controlled study was conducted between January 2008 and March 2012. Serum levels of NO were compared in 40 patients with CAE (mean age 60.1±7.3 years) and 40 patients with normal coronary arteries (mean age 57.6±5 years) as a control group. CAE was diagnosed when a segment of coronary artery was more than 1.5 times the diameter of the adjacent healthy segment. Patients with stenotic atherosclerotic plaques, slow coronary flow, previous history of revascularization, acute coronary syndromes, left ventricular dysfunction, valvular heart disease, and systemic diseases were not included in the study. The effect of NO on the outcome was studied by constructing a receiver operating characteristic (ROC) curve with CAE as the primary variable. Effects of different variables on CAE were calculated using binary logistics regression analysis.

Results:

Serum NO concentrations were significantly lower in patients with CAE than in the control group (42.1±20.1 µmol/L vs. 77.3±15.7 µmol/L, p<0.001). According to the results of the multivariate regression analysis, LDL and NO levels were identified as independent factors associated with CAE (OR=1.02, 95% CI 1–1.04, p=0.02 and OR=0.88, 95% CI 0.83–0.93, p=0.001, respectively). ROC analysis revealed that using a cut-off point of 63.3, NO level predicts CAE with a sensitivity of 87.5% and specificity of 90%.

Conclusion:

Our study indicates that decreased levels of NO are present in patients with CAE compared to patients with normal coronary arteries, supporting the hypothesis that decreased levels of NO might be associated with CAE development. (Anatol J Cardiol 2016; 16: 947-52)

Nitric oxide and the cardiovascular system

Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.

Cocoa, glucose tolerance, and insulin signaling: cardiometabolic protection

Experimental and clinical evidence reported that some polyphenol-rich natural products may offer opportunities for the prevention and treatment of type 2 diabetes, due to their biological properties. Natural products have been suggested to modulate carbohydrate metabolism by various mechanisms, such as restoring β-cell integrity and physiology and enhancing insulin-releasing activity and glucose uptake. Endothelium is fundamental in regulating arterial function, whereas insulin resistance plays a pivotal role in pathophysiological mechanisms of prediabetic and diabetic states. Glucose and insulin actions in the skeletal muscle are improved by insulin-dependent production of nitric oxide, favoring capillary recruitment, vasodilatation, and increased blood flow. Endothelial dysfunction, with decreased nitric oxide bioavailability, is a critical step in the development of atherosclerosis. Furthermore, insulin resistance has been described, at least in part, to negatively affect endothelial function. Consistent with this, conditions of insulin resistance are usually linked to endothelial dysfunction, and the exposure of the endothelial cells to cardiovascular risk factors such as hypertension, dyslipidemia, and hyperglycemia is associated with reduced nitric oxide bioavailability, resulting in impaired endothelial-dependent vasodilatation. Moreover, endothelial dysfunction has been described as an independent predictor of cardiovascular risk and events. Cocoa and cocoa flavonoids may positively affect the pathophysiological mechanisms involved in insulin resistance and endothelial dysfunction with possible benefits in the prevention of cardiometabolic diseases.

Toll-like receptor 4-induced endoplasmic reticulum stress contributes to impairment of vasodilator action of insulin

Impairment of vasodilator action of insulin is associated with endothelial dysfunction and insulin resistance. Activation of Toll-like receptor 4 (TLR4) induces proinflammatory response and endoplasmic reticulum (ER) stress. Saturated fatty acids (SFA) activate TLR4, which induces ER stress and endothelial dysfunction. Therefore, we determined whether TLR4-mediated ER stress is an obligatory step mediating SFA-induced endothelial dysfunction. Palmitate stimulated proinflammatory responses and ER stress, and this was suppressed by knockdown of TLR4 in primary human aortic endothelial cells (HAEC). Next, we examined the role of TLR4 in vasodilatory responses in intact vessels isolated from wild-type (WT, C57BL/6) and TLR4-KO mice after feeding high-fat (HFD) or normal chow diet (NCD) for 12 wk. Arterioles isolated from HFD WT mice exhibited impaired insulin-stimulated vasodilation compared with arterioles isolated from NCD WT mice. Deficiency of TLR4 was protective from HFD-induced impairment of insulin-stimulated vasodilation. There were no differences in acetylcholine (Ach)- or sodium nitroprusside (SNP)-stimulated vasodilation between the two groups. Furthermore, we examined whether ER stress is involved in SFA-induced impairment of vasodilator actions of insulin. Infusion of palmitate showed the impairment of vasodilatory response to insulin, which was ameliorated by coinfusion with tauroursodeoxycholic acid (TUDCA), an ER stress suppressor. Taken together, the results suggest that TLR4-induced ER stress may be an obligatory step mediating the SFA-mediated endothelial dysfunction.

Effect of Sancaijiangtang on plasma nitric oxide and endothelin-1 levels in patients with type 2 diabetes mellitus and vascular dementia: a single-blind randomized controlled trial

OBJECTIVE

To observe the effect of Sancaijiangtang powders on plasma nitric oxide and endothelin-1 levels. We sought to identify the common pathological link and mechanism of action for Traditional Chinese medicine in type 2 diabetes mellitus and vascular dementia, and to explicate the material basis for treating the different diseases with the same method in Traditional Chinese Medicine.

METHODS

In total, 168 patients with type 2 diabetes mellitus and vascular dementia were enrolled in the study, and randomly divided into two groups by simple randomization. Patients in the treatment group received oral Sancaijiangtang powders with pioglitazone hydrochloride three times daily, while patients in the control group received pioglitazone hydrochloride alone. The treatment course was for 12 weeks. Mini-mental state examinations (Chinese version) and Montreal Cognitive Assessments (Beijing version) were performed, and fasting plasma glucose, fasting insulin, hemoglobin A1c, homeostasis model assessment of insulin resistance, plasma nitric oxide and endothelin-1 levels were measured before and after the treatment.

RESULTS

The post-treatment levels for all measurements in both groups were better than pre-treat- ment levels (P < 0.05). The post-treatment levels for all measurements in the treatment group were better than the levels measured in the control group (P < 0.05).

CONCLUSION

Type 2 diabetes mellitus and vascular dementia have common pathological mechanisms for insulin resistance and endothelium dysfunction. Sancaijiangtang powders could improve the release of nitric oxide and inhibit the secretion of endothelin-1. Therefore, the material basis exists for treating the different diseases with the same method in Traditional Chinese Medicine.

Plasma betatrophin levels in patients with liver cirrhosis

AIM: To investigate the plasma levels of betatrophin in patients with cirrhosis.

METHODS: Forty patients diagnosed at the clinic with liver cirrhosis according to biological, ultrasonographic, or histological criteria were included. The severity of cirrhosis was classified according to Pugh’s modification of Child’s classification and MELD score. Insulin resistance (IR) was assessed by the Homeostasis Model Assessment. A total of 20 patients showed a MELD score higher than 14. The control group consisted in 15 sex-and aged-matched subjects. Fasting blood samples were obtained for subsequent analysis. Serum insulin was determined by Liaison automated immune chemiluminiscence assay (DiaSorin S.p.A.) using a sandwich assay. The sensitivity of the assay was 0.2 μU/mL. The intra and interassay variation coefficients were < 4% and < 10%, respectively. The normal values were between 2 and 17 μU/mL. Human active betatrophin was analyzed by specific quantitative sandwich ELISA (Aviscera Bioscience^®). The sensitivity of the assay was 0.4 ng/mL, and the intra and interassay reproducibility were < 6% and < 10%, respectively.

RESULTS: Plasma betatrophin levels were significantly increased in patients with cirrhosis compared with those in healthy subjects (P = 0.0001). Betatrophin levels were also associated with disease severity, being higher in Child-Pugh C patients compared to Child-Pugh B (P < 0.0005) and in patients who displayed a MELD score higher than 14 points compared to patients with lower punctuation (P = 0.01). In addition, we found a positive correlation between plasma betatrophin levels and the severity of cirrhosis according to Child-Pugh classification (r = 0.53; P < 0.01) or MELD score (r = 0.45; P < 0.01). In the overall cohort, a moderate correlation between serum betatrophin and plasmatic bilirrubin (r = 0.39; P < 0.01) has been observed, as well as an inverse correlation between betatrophin and albumin (r = -0.41; P < 0.01) or prothrombin time (r = -0.44; P <0.01). Moreover, insulin resistance was observed in 82.5% of the cirrhotic patients. In this group of patients, betatrophin levels were significantly higher than those in the group of patients without IR (P < 0.05).

CONCLUSION: Plasma betatrophin is increased in patients with cirrhosis. This increase is related to the severity of cirrhosis, as well as with the emergence of insulin resistance.