Antiobesogenic role of endothelial nitric oxide synthase

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.

Effects of circulating endothelial microvesicles isolated from adults with obesity on endothelial cell inflammation, apoptosis, and nitric oxide production

Circulating endothelial cell-derived microvesicles (EMVs) have been shown to be elevated with obesity and associated with endothelial dysfunction; however, their direct effect on endothelial cells is unknown. The experimental aim of this study was to determine the effect of EMVs isolated from adults with obesity on endothelial cell inflammation, apoptosis, and nitric oxide (NO) production. EMVs (CD144+ microvesicles) were identified, enumerated, and isolated from plasma by flow cytometry from 24 sedentary adults: 12 normal-weight adults [8 M/4 F; age: 55 ± 6 yr; body mass index (BMI): 24.3 ± 0.7 kg/m2; EMV: 144 ± 53 EMVs/µL] and 12 adults with obesity (6 M/6 F; 59 ± 7 yr; BMI: 31.0 ± 1.1 kg/m2; EMV: 245 ± 89 EMVs/µL). Human umbilical vein endothelial cells were cultured and treated with EMVs from either normal-weight adults or adults with obesity. EMVs from obese adults induced significantly higher release of interleukin (IL)-6 (108.2 ± 7.7 vs. 90.9 ± 10.0 pg/mL) and IL-8 (75.4 ± 9.8 vs. 59.5 ± 11.5 pg/mL) from endothelial cells vs. EMVs from normal-weight adults, concordant with greater intracellular expression of phosphorylated NF-κB p65 (Ser536; active NF-κB) [145.0 ± 34.1 vs. 114.5 ± 30.4 arbitrary units (AU)]. Expression of phosphorylated p38-MAPK (15.4 ± 5.7 vs. 9.2 ± 2.5 AU) and active caspase-3 (168.2 ± 65.5 vs. 107.8 ± 40.5 AU), markers of cell apoptosis, was higher in cells treated with obesity-related EMVs. Phosphorylated endothelial nitric oxide synthase (eNOS) (Ser1177) expression (23.5 ± 7.2 vs. 34.7 ± 9.7 AU) and NO production (6.9 ± 1.4 vs. 8.7 ± 0.7 µmol/L) were significantly lower in the cells treated with EMVs from obese adults. These data indicate that circulating EMVs from adults with obesity promote a proinflammatory, proapoptotic, and NO-compromised endothelial phenotype. Circulating EMVs are a potential mediator of obesity-related endothelial dysfunction.NEW & NOTEWORTHY In the present study, we determined the effect of circulating endothelial cell-derived microvesicles (EMVs) isolated from adults with obesity on endothelial cell inflammation, apoptosis, and nitric oxide (NO) production in vitro. Circulating EMVs harvested from adults with obesity promoted a proinflammatory, proapoptotic, and NO-compromised endothelial phenotype. Elevated circulating EMVs in adults with obesity, independent of other cardiometabolic risk factors, are a potential novel systemic mediator of obesity-related endothelial dysfunction and vascular risk.

Mitochondria as a target for exercise-mitigated type 2 diabetes

Type 2 diabetes mellitus (T2DM) is one of most common metabolic diseases and continues to be a leading cause of death worldwide. Although great efforts have been made to elucidate the pathogenesis of diabetes, the underlying mechanism still remains unclear. Notably, overwhelming evidence has demonstrated that mitochondria are tightly correlated with the development of T2DM, and the defects of mitochondrial function in peripheral insulin-responsive tissues, such as skeletal muscle, liver and adipose tissue, are crucial drivers of T2DM. Furthermore, exercise training is considered as an effective stimulus for improving insulin sensitivity and hence is regarded as the best strategy to prevent and treat T2DM. Although the precise mechanisms by which exercise alleviates T2DM are not fully understood, mitochondria may be critical for the beneficial effects of exercise.

Endothelial nitric oxide synthase gene polymorphism (786T/C) in childhood acute lymphoblastic leukemia survivors

OBJECTIVES

To detect eNOS gene polymorphism and its relation to cardiovascular complications in pediatric acute lymphoblastic leukemia (ALL) survivors.

METHODS

CBC, renal and liver function tests, lipid profile, Carotid artery Intima Media Thickness (CIMT), and Brachial artery Intima Media Thickness (BIMT). eNOS gene polymorphism was done in 40 childhood ALL survivors and 40 controls.

RESULTS

There was no significant difference between survivors and control groups regarding 786 T/C polymorphism. There was a significant increase in serum cholesterol, TGs, LDL, VLDL, and HbA1c in the TC and CC group more than in the TT group, while there was a significant decrease in serum HDL in the TC and CC group more than in the TT group. There was no significant difference as regards echocardiography findings between different polymorphisms of 786 T/C, but there was a significant difference between 786 T/C groups with regard to the carotid and brachial arteries intima media thickness (IMT) measurements being significantly higher in the TC and CC group more than in the TT group.

CONCLUSION

Carotid and brachial arteries intima media thickness measurements were higher in the survivors when compared to healthy controls. eNOS gene polymorphism may play a role in modifying or developing CVD in pediatric ALL survivors.

ASSOCIATIONS OF ENOS GLU298ASP (G894T) ENDOTHELIAL DYSFUNCTION GENE POLYMORPHISMS WITH METABOLIC DISORDERS IN PATHOLOGICAL PREGNANCY

OBJECTIVE

The aim: To determine the association between the Glu298Asp (G894T) polymorphisms of the eNOS gene with metabolic disorders in excessive gestational weight gain (GWG) pregnancy.

PATIENTS AND METHODS

Materials and methods: 97 pregnant women in 9-12, and 37-39 weeks of gestation were examined. The recommended GWG was diagnosed in 33 (34.0 %), insufficient in 19 (19.6 %), and excessive in 45 (46.4 %) patients. Genetic variants of eNOS were analyzed by real-time polymerase chain reaction, lipid profile, and carbohydrate status were performed. The results were statistically analyzed using Statistica 6.0 program pack (StatSoft Inc., USA) and Microsoft Excel statistical analysis package.

RESULTS

Results: GWG in the group of patients with gene eNOS TT polymorphism was significantly higher (1.5-fold) compared to pregnant with GG - genotype (р<0.05). Pregnant, inherited the TT allele of the eNOS gene, associated with higher levels of hypertriglyceridemia, hypercholesterolemia, of lipoprotein low density, glycemia, hyperinsulinemia, and higher HOMA-IR compared to carriers of GG and GT alleles (р<0.05) in the third trimester, which is especially manifested in excessive GWG.

CONCLUSION

Conclusions: Decreased activity of the eNOS gene in the presence of pathological alleles is the initiator of impaired lipid and carbohydrate metabolisms and, as a consequence, excessive GWG. A high risk of excessive GWG was found in pregnant women with TT polymorphism Glu298Asp (G894T) (OR=4.52; 95%CI: 1.18-17.32; р<0.05) (frequency distribution of 73.7 %). Endothelial dysfunction is a pathogenetic link of excessive body weigh in pregnancy.

Acute beetroot juice supplementation improves exercise tolerance and cycling efficiency in adults with obesity

BACKGROUND

Exercise training improves health outcomes in individuals with obesity (IO); however, it remains challenging for IO to adhere to exercise. Thus, it is critical to identify novel strategies that improve exercise tolerance (ET) and adherence in IO. Beetroot juice (BRJ), high in inorganic dietary nitrate, consistently improves exercise performance in athletes, individuals with cardiopulmonary diseases, and nonobese lean individuals. These improvements may be explained by reduced oxygen uptake (VO2 ) during exercise, enhanced blood flow, and greater mitochondrial efficiency. To date, we are aware of no studies that have compared the effects of BRJ, sodium nitrate (NaNO3), and nitrate-depleted BRJ (PLA) for improving ET and cardiometabolic health in IO.

PURPOSE

Determine if BRJ improves ET, exercise efficiency (EE), and cardiometabolic health in IO and identify possible mechanisms of action.

METHODS

Vascular hemodynamic, submaximal- and maximal-exercise VO2 , and time to exhaustion (TTE) were assessed in 16 participants 2.5 hr following consumption of: 1) BRJ, 2) NaNO3 , 3) PLA, or 4) CON.

RESULTS

A significant treatment effect was observed for submaximal exercise VO2 (p = .003), and TTE (p < .001). Post hoc analyses revealed lower VO2 during submaximal exercise in BRJ compared to PLA (p = .009) NaNO3 (p = .042) and CON (0.009), equating to an average improvement of ~ 7% with BRJ. TTE was greater for BRJ compared to other treatment arms, PLA (p = .008), NaNO3 (p = .038), and CON (p=<0.001), equating to ~ 15% improvement with BRJ. No significant changes were observed for other outcomes.

CONCLUSIONS

Consumption of BRJ improved EE during submaximal exercise by 7%, and TTE by 15% compared to other conditions. These results suggest that BRJ may improve EE and exercise tolerance in IO.

MicroRNAs and obesity-induced endothelial dysfunction: key paradigms in molecular therapy

The endothelium plays a pivotal role in maintaining vascular health. Obesity is a global epidemic that has seen dramatic increases in both adult and pediatric populations. Obesity perturbs the integrity of normal endothelium, leading to endothelial dysfunction which predisposes the patient to cardiovascular diseases. MicroRNAs (miRNAs) are short, single-stranded, non-coding RNA molecules that play important roles in a variety of cellular processes such as differentiation, proliferation, apoptosis, and stress response; their alteration contributes to the development of many pathologies including obesity. Mediators of obesity-induced endothelial dysfunction include altered endothelial nitric oxide synthase (eNOS), Sirtuin 1 (SIRT1), oxidative stress, autophagy machinery and endoplasmic reticulum (ER) stress. All of these factors have been shown to be either directly or indirectly caused by gene regulatory mechanisms of miRNAs. In this review, we aim to provide a comprehensive description of the therapeutic potential of miRNAs to treat obesity-induced endothelial dysfunction. This may lead to the identification of new targets for interventions that may prevent or delay the development of obesity-related cardiovascular disease.

Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies

Emerging data suggest that impaired nitric oxide (NO) homeostasis has a key role in development of cardiometabolic disorders. The association between circulating levels of NO metabolites, i.e. nitrate and nitrite (NOx), and risk of chronic diseases has not yet been fully clarified. This work aims to address epidemiologic aspects of NO metabolism and discusses different physiologic and pathophysiologic conditions influencing circulating NOx. Further, cross-sectional associations of serum NOx with metabolic disorders are described and along the way, potential short-term and long-term power of serum NOx for predicting cardiometabolic outcomes are reviewed. Results from population-based studies show that circulating NOx is affected by aging, smoking habits, pregnancy, menopause status, thyroid hormones, and various pathologic conditions including type 2 diabetes, insulin resistance, hypertension, and renal dysfunction. Lifestyle factors, especially dietary habits, but also smoking habits and the degree of physical activity influence NO homeostasis and the circulating levels of NOx. Elevated serum NOx, due to increased iNOS activity, is associated with increased incidence of metabolic syndrome, different obesity phenotypes, and cardiovascular events.

Luteolin Prevents Cardiometabolic Alterations and Vascular Dysfunction in Mice With HFD-Induced Obesity

Purpose: Luteolin exerts beneficial effects against obesity-associated comorbidities, although its influence on vascular dysfunction remains undetermined. We examined the effects of luteolin on endothelial dysfunction in a mouse model of diet-induced obesity. Methods: Standard diet (SD) or high-fat diet (HFD)-fed mice were treated daily with luteolin intragastrically. After 8 weeks, body and epididymal fat weight, as well as blood cholesterol, glucose, and triglycerides were evaluated. Endothelium-dependent relaxations of resistance mesenteric vessels was assessed by a concentration-response curve to acetylcholine, repeated upon N^w-nitro-L-arginine methylester (L-NAME) or ascorbic acid infusion to investigate the influence of nitric oxide (NO) availability and reactive oxygen species (ROS) on endothelial function, respectively. Intravascular ROS production and TNF levels were measured by dihydroethidium dye and ELISA, respectively. Endothelial NO synthase (eNOS) and superoxide dismutase 1 (SOD1), as well as microRNA-214-3p expression were examined by Western blot and RT-PCR assays, respectively. Results: HFD animals displayed elevated body weight, epididymal fat weight and metabolic indexes. Endothelium-dependent relaxation was resistant to L-NAME and enhanced by ascorbic acid, which restored also the inhibitory effect of L-NAME, suggesting a ROS-dependent reduction of NO availability in HFD vessels. Moreover, media-lumen ratio, intravascular superoxide anion and TNF levels were increased, while vascular eNOS, SOD1, and microRNA-214-3p expression were decreased. In HFD mice, luteolin counteracted the increase in body and epididymal fat weight, and metabolic alterations. Luteolin restored vascular endothelial NO availability, normalized the media-lumen ratio, decreased ROS and TNF levels, and normalized eNOS, SOD1 and microRNA-214-3p expression. Conclusion: Luteolin prevents systemic metabolic alterations and vascular dysfunction associated with obesity, likely through antioxidant and anti-inflammatory mechanisms.

Anti-obesity and anti-diabetic effects of nitrate and nitrite

Prevalence of obesity is increasing worldwide and type 2 diabetes to date is the most devastating complication of obesity. Decreased nitric oxide bioavailability is a feature of obesity and diabetes that links these two pathologies. Nitric oxide is synthesized both by nitric oxide synthase enzymes from l-arginine and nitric oxide synthase-independent from nitrate/nitrite. Nitric oxide production from nitrate/nitrite could potentially be used for nutrition-based therapy in obesity and diabetes. Nitric oxide deficiency also contributes to pathogeneses of cardiovascular disease and hypertension, which are associated with obesity and diabetes. This review summarizes pathways for nitric oxide production and focuses on the anti-diabetic and anti-obesity effects of the nitrate-nitrite-nitric oxide pathway. In addition to increasing nitric oxide production, nitrate and nitrite reduce oxidative stress, increase adipose tissue browning, have favorable effects on nitric oxide synthase expression, and increase insulin secretion, all effects that are potentially promising for management of obesity and diabetes. Based on current data, it could be suggested that amplifying the nitrate-nitrite-nitric oxide pathway is a diet-based strategy for increasing nitric oxide bioavailability and the management of these two interlinked conditions. Adding nitrate/nitrite to drugs that are currently used for managing diabetes (e.g. metformin) and possibly anti-obesity drugs may also enhance their efficacy.

Assisted Reproductive Technologies Predispose to Insulin Resistance and Obesity in Male Mice Challenged With a High-Fat Diet

Assisted reproductive technology (ART) alters glucose homeostasis in mice and humans, but the underlying mechanisms are incompletely understood. ART induces endothelial dysfunction and arterial hypertension by epigenetic alteration of the endothelial nitric oxide synthase (eNOS) gene. In eNOS-deficient mice, insulin resistance is related to impaired insulin stimulation of muscle blood flow and substrate delivery and defective intrinsic skeletal muscle glucose uptake. We therefore assessed glucose tolerance, insulin sensitivity (euglycemic clamp), insulin stimulation of muscle blood flow in vivo, and muscle glucose uptake in vitro in male ART and control mice fed a normal chow (NC) or challenged with a high-fat diet (HFD) during 8 weeks. Glucose tolerance and insulin sensitivity were similar in NC-fed animals. When challenged with a HFD, however, ART mice developed exaggerated obesity, fasting hyperinsulinemia and hyperglycemia, and a 20% lower insulin-stimulated glucose utilization than did control mice (steady-state glucose infusion rate (GIR), 51.3 ± 7.3 vs 64.0 ± 10.8 mg/kg/min, P = 0.012). ART-induced insulin resistance was associated with defective insulin stimulation of muscle blood flow, whereas intrinsic skeletal muscle glucose uptake was normal. In conclusion, ART-induced endothelial dysfunction, when challenged with a metabolic stress, facilitates glucose intolerance and insulin resistance. Similar mechanisms may contribute to ART-induced alterations of the metabolic phenotype in humans.

Anti-Obesity Effect of Bombus ignitus Queen Glycosaminoglycans in Rats on a High-Fat Diet

The mechanism of functional insect glycosaminoglycan (GAG) on obesity caused a high fat diet has not yet been elucidated. Therefore, insect glycosaminoglycans derived from Isaria sinclairii, Bombus ignitus (a type of bumblebee) queen, and Gryllus bimaculatus were purified and investigated as a potential functional food. 14-week old male Wistar rats were fed a high-fat diet (HFD) for 6 weeks. There were five groups that received daily intraperitoneal administration of phosphate buffered saline (PBS, control), GbG (GAG from Gryllus bimaculatus) 10 mg/kg, ISG (GAG from Isaria sinclairii) 10 mg/kg, IQG (GAG from Bombus ignites) 10 mg/kg, or Pravastatin (2 mg/kg). All treatments were performed for one month. IQG produced a potential anti-inflammatory effect with the inhibition of c-reactive protein and sero-biochemical parameters of phospholipids and free fatty acids indicative of an anti-hyperlipidemic effect. Abdominal and epididymidal fat weight were reduced in conjunction with a mild increase in body weight. The level of laminin in HMVEC-C cells or fibronectin in HFD rat hepatocytes was significantly affected by these GAG treatments, which regulated adipogenesis and adipocyte function. Compared to the control rats, IQG-treated rats displayed up-regulation of 87 genes (test:control ratio >2.0) including fatty acid synthase and 3-hydroxy-3-methylglutaryl-coenzyme A reductase, with the down-regulation of 47 genes including the uridine diphosphate (UDP) glycosyltransferase 2 families, polypeptidase B, and insulin-like growth factor binding protein 1. The data suggest that IQG could potentially prevent or treat fatty liver or hyperlipidemia.