Supplementation with L-arginine favorably influences plasminogen activator inhibitor type 1 concentration in obese patients. A randomized, double blind trial

Steviol Glycoside, L-Arginine, and Chromium(III) Supplementation Attenuates Abnormalities in Glucose Metabolism in Streptozotocin-Induced Mildly Diabetic Rats Fed a High-Fat Diet

Stevia rebaudiana Bertoni and its glycosides are believed to exhibit several health-promoting properties. Recently, the mechanisms of the anti-diabetic effects of steviol glycosides (SG) have been the subject of intense research. The following study aims to evaluate the results of SG (stevioside (ST) and rebaudioside A (RA)) combined with L-arginine (L-Arg) and chromium(III) (CrIII) supplementation in streptozotocin- (STZ) induced mild type 2 diabetic rats fed a high-fat diet (HFD), with particular emphasis on carbohydrate and lipid metabolisms. The experiment was carried out on 110 male Wistar rats, 100 of which were fed an HFD to induce insulin resistance, followed by an intraperitoneal injection of streptozotocin to induce mild type 2 diabetes. After confirmation of hyperglycemia, the rats were divided into groups. Three groups served as controls: diabetic untreated, diabetic treated with metformin (300 mg/kg BW), and healthy group. Eight groups were fed an HFD enriched with stevioside or rebaudioside A (2500 mg/kg BW) combined with L-arginine (2000 or 4000 mg/kg BW) and Cr(III) (1 or 5 mg/kg BW) for six weeks. The results showed that supplementation with SG (ST and RA) combined with L-arg and Cr(III) could improve blood glucose levels in rats with mild type 2 diabetes. Furthermore, ST was more effective in improving blood glucose levels, insulin resistance indices, and very low-density lipoprotein cholesterol (VLDL-C) concentrations than RA. Although L-arg and Cr(III) supplementation did not independently affect most blood carbohydrate and lipid indices, it further improved some biomarkers when combined, particularly with ST. Notably, the beneficial impact of ST on the homeostatic model assessment–insulin resistance (HOMA-IR) and on the quantitative insulin-sensitivity check index (QUICKI) was strengthened when mixed with a high dose of L-arg, while its impact on antioxidant status was improved when combined with a high dose of Cr(III) in rats with mild type 2 diabetes. In conclusion, these results suggest that supplementary stevioside combined with L-arginine and Cr(III) has therapeutic potential for mild type 2 diabetes. However, further studies are warranted to confirm these effects in other experimental models and humans.

The Use and Effectiveness of Selected Alternative Markers for Insulin Sensitivity and Secretion Compared with Gold Standard Markers in Dietary Intervention Studies in Individuals without Diabetes: Results of a Systematic Review

Background: The gold-standard techniques for measuring insulin sensitivity and secretion are well established. However, they may be perceived as invasive and expensive for use in dietary intervention studies. Thus, surrogate markers have been proposed as alternative markers for insulin sensitivity and secretion. This systematic review aimed to identify markers of insulin sensitivity and secretion in response to dietary intervention and assess their suitability as surrogates for the gold-standard methodology. Methods: Three databases, PubMed, Scopus, and Cochrane were searched, intervention studies and randomised controlled trials reporting data on dietary intake, a gold standard of analysis of insulin sensitivity (either euglycaemic-hyperinsulinaemic clamp or intravenous glucose tolerance test and secretion (acute insulin response to glucose), as well as surrogate markers for insulin sensitivity (either fasting insulin, area under the curve oral glucose tolerance tests and HOMA-IR) and insulin secretion (disposition index), were selected. Results: We identified thirty-five studies that were eligible for inclusion. We found insufficient evidence to predict insulin sensitivity and secretion with surrogate markers when compared to gold standards in nutritional intervention studies. Conclusions: Future research is needed to investigate if surrogate measures of insulin sensitivity and secretion can be repeatable and reproducible in the same way as gold standards.

The Potential of L-Arginine in Prevention and Treatment of Disturbed Carbohydrate and Lipid Metabolism—A Review

L-arginine, an endogenous amino acid, is a safe substance that can be found in food. The compound is involved in synthesis of various products responsible for regulatory functions in the body. Particularly noteworthy is, among others, nitric oxide, a signaling molecule regulating carbohydrate and lipid metabolism. The increasing experimental and clinical data indicate that L-arginine supplementation may be helpful in managing disturbed metabolism in obesity, regulate arterial blood pressure or alleviate type 2 diabetes symptoms, but the mechanisms underlying these effects have not been sufficiently elucidated. This review aims to present the up-to-date information regarding the current uses and health-promoting potential of L-arginine, its effects on nitric oxide, carbohydrate and lipid metabolisms, based on the results of in vivo, in vitro studies, and clinical human trials. Available literature suggests that L-arginine may have beneficial effects on human health. However, some studies found that higher dietary L-arginine is associated with worsening of an existing disease or may be potential risk factor for development of some diseases. The mechanisms of regulatory effects of L-arginine on carbohydrate and lipid metabolism have not been fully understood and are currently under investigation.

Effect of Cucumis sativus on Dysfunctional 3T3-L1 Adipocytes

Obesity is caused by lipid accumulation in adipose tissues inducing adipocyte dysfunction, characterized by insulin resistance, increased lipolysis, oxidative stress, and inflammation, leading to increased levels of adipokines. Herein the capacity of the subfractions (SFs) SF1, SF2, and SF3 from the Cucumis sativus aqueous fraction and their combinations (M) to control adipocyte dysfunction in vitro, in 3T3-L1 adipocytes was studied. Adipocytes, previously treated with dexamethasone or IL-1 to induce dysfunction, were incubated with different concentrations of the subfractions for 24 h. 2-deoxyglucose consumption and glycerol release were evaluated, and a surface model was constructed to determine the most effective SF concentrations to improve both parameters. Effective SF combinations were assessed in their capacity to control metabolic, pro-oxidative, and pro-inflammatory conditions. SF1, SF2 (40 μg/ml each) and SF3 (20 μg/ml) improved 2-deoxyglucose consumption by 87%, 57%, and 87%, respectively. SF1 and SF2 (5 μg/ml each) and SF3 (40 μg/mL) increased glycerol secretion by 10.6%, 18.9%, and 11.8%, respectively. Among five combinations tested, only M4 (SF1 40 μg/ml:SF2 60 μg/ml:SF3 30 μg/ml) and M5 (SF1 40 μg/ml:SF2 60 μg/mL:SF3 10 μg/ml) controlled effectively the metabolic, pro-oxidative, and proinflammatory conditions studied. Glycine, asparagine, and arginine were the main components in these SFs.

Association of l-Arginine Supplementation with Markers of Endothelial Function in Patients with Cardiovascular or Metabolic Disorders: A Systematic Review and Meta-Analysis

l-Arginine supplementation is a potential therapy for treating cardiovascular and metabolic diseases. However, the use of distinct l-arginine sources, intervened populations, and treatment regimens may have yielded confusion about their efficacy. This research constitutes a systematic review and meta-analysis summarizing the effects of l-arginine supplementation compared to placebo in individuals with cardiovascular disease (CVD), obesity, or diabetes. Eligibility criteria included randomized clinical trials and interventions based on oral supplementation of l-arginine with a minimum duration of three days; comparison groups consisted of individuals with the same disease condition receiving an oral placebo substance. The primary outcome was flow-mediated dilation, and secondary outcomes were nitrite/nitrate (NOx) rate and asymmetric dimethylarginine (ADMA). Statistical heterogeneity among studies included in the meta-analyses was assessed using the inconsistency index (I2). Fifty-four full-text articles from 3761 retrieved references were assessed for eligibility. After exclusions, 13 studies were included for data extraction. There was no difference in blood flow after post-ischemic hyperemia between the supplementation of l-arginine and placebo groups before and after the intervention period (standardized mean difference (SMD) = 0.30; 95% confidence intervals (CIs) = −0.85 to 1.46; I2 = 96%). Sensitivity analysis showed decreased heterogeneity when the studies that most favor arginine and placebo were removed, and positive results in favor of arginine supplementation were found (SMD = 0.59; 95% CIs = 0.10 to 1.08; I2 = 75%). No difference was found in meta-analytical estimates of NOx and ADMA responses between arginine or placebo treatments. Overall, the results indicated that oral l-arginine supplementation was not associated with improvements on selected variables in these patients (PROSPERO Registration: CRD42017077289).

Multispecies Probiotic Supplementation Favorably Affects Vascular Function and Reduces Arterial Stiffness in Obese Postmenopausal Women-A 12-Week Placebo-Controlled and Randomized Clinical Study

Obesity in the postmenopausal period is associated with an increased risk of cardiovascular diseases in women. One of the key drivers of cardiovascular risk is endothelial dysfunction; thus, this is also a crucial point for studies on new therapeutic methods of cardioprotective properties. The aim of the current study was to evaluate the effect of two doses of multispecies probiotic Ecologic® Barrier supplement on functional (primary endpoint) and biochemical parameters (secondary endpoint) of endothelial dysfunction in obese postmenopausal women in a 12-week randomized, placebo-controlled clinical trial. A total of 81 obese Caucasian women participated in the trial. The subjects were randomly assigned to three groups that received a placebo, a low dose (LD) (2.5 × 10⁸ colony forming units (CFU) per day), or a high dose (HD) (1 × 1010 CFU per day) of lyophilisate powder containing live multispecies probiotic bacteria. The probiotic supplement was administered each day for 12 weeks in two equal portions. A high dose probiotic supplementation for 12 weeks decreased systolic blood pressure, vascular endothelial growth factor, pulse wave analysis systolic pressure, pulse wave analysis pulse pressure, pulse wave analysis augmentation index, pulse wave velocity, interleukin-6, tumor necrosis factor alpha, and thrombomodulin. Low doses of probiotic supplementation decreased the systolic blood pressure and interleukin-6 levels. The mean changes in the estimated parameters, compared among the three groups, revealed significant differences in the vascular endothelial growth factor, the pulse wave analysis systolic pressure, the pulse wave analysis augmentation index, the pulse wave velocity, the tumor necrosis factor alpha, and thrombomodulin. The post hoc tests showed significant differences for all parameters between HD and the placebo group, and HD and LD (besides pulse wave analysis augmentation index). We show for the first time that supplementation with multispecies probiotic Ecologic® Barrier favorably modifies both functional and biochemical markers of vascular dysfunction in obese postmenopausal women.

Regulation of obesity and insulin resistance by nitric oxide

Obesity is a risk factor for developing type 2 diabetes and cardiovascular disease and has quickly become a worldwide pandemic with few tangible and safe treatment options. Although it is generally accepted that the primary cause of obesity is energy imbalance, i.e., the calories consumed are greater than are utilized, understanding how caloric balance is regulated has proven a challenge. Many "distal" causes of obesity, such as the structural environment, occupation, and social influences, are exceedingly difficult to change or manipulate. Hence, molecular processes and pathways more proximal to the origins of obesity-those that directly regulate energy metabolism or caloric intake-seem to be more feasible targets for therapy. In particular, nitric oxide (NO) is emerging as a central regulator of energy metabolism and body composition. NO bioavailability is decreased in animal models of diet-induced obesity and in obese and insulin-resistant patients, and increasing NO output has remarkable effects on obesity and insulin resistance. This review discusses the role of NO in regulating adiposity and insulin sensitivity and places its modes of action into context with the known causes and consequences of metabolic disease.

The effects of L-arginine, alone and combined with vitamin C, on mineral status in relation to its antidiabetic, anti-inflammatory, and antioxidant properties in male rats on a high-fat diet

The aim of this study was to evaluate the influence of the intake of L-arginine alone and of L-arginine with vitamin C on mineral concentration in rats fed with a high-fat diet, and to assess the lipid glucose, insulin, and total antioxidant status (TAS) and tumor necrosis factor (TNF) alpha serum levels that result. Wistar rats were assigned to groups fed with either a standard control diet (C), a diet high in fat (FD), a diet high in fat with L-arginine, or a diet high in fat with L-arginine and vitamin C. After 6 weeks, the length and weight of the rats were measured, and the animals were euthanized. The liver, spleen, kidneys, pancreas, heart, and gonads were collected, as were blood samples. The total serum cholesterol, triglyceride, fasting glucose, insulin, TAS, and TNF alpha levels were measured. The tissue calcium, magnesium, iron, zinc, and copper concentrations were determined. It was found that L-arginine supplementation diminished the effect of the modified diet on the concentration of iron in the liver and spleen and of copper in heart. At the same time, it was observed that L-arginine supplementation reduced the effect of the high-fat diet on insulin, TNF alpha, and TAS. The combination of L-arginine and vitamin C produced a similar effect on the mineral levels in the tissues as did L-arginine used alone. Moreover, positive correlations between serum insulin and iron in the liver, between TNF alpha and iron in the liver, and between TNF alpha and copper in the heart were observed. The level of TAS in serum was inversely correlated with the copper level in the heart and the iron level in the liver. We concluded that the beneficial influence of L-arginine on insulin, TAS, and TNF alpha serum level is associated with changes in the iron and copper status in rats fed with a high-fat diet. No synergistic effect of L-arginine and vitamin C in the biochemical parameters or in the mineral status in rats fed with the modified diet was observed.

Antiobesogenic role of endothelial nitric oxide synthase

The prevalence of obesity has increased remarkably in the past four decades. Because obesity can promote the development of type 2 diabetes and cardiovascular disease, understanding the mechanisms that engender weight gain and discovering safe antiobesity therapies are of critical importance. In particular, the gaseous signaling molecule, nitric oxide (NO), appears to be a central factor regulating adiposity and systemic metabolism. Obese and diabetic states are characterized by a deficit in bioavailable NO, with such decreases commonly attributed to downregulation of endothelial NO synthase (eNOS), loss of eNOS activity, or quenching of NO by its reaction with oxygen radicals. Gain-of-function studies, in which vascular-derived NO has been increased pharmacologically or genetically, reveal remarkable actions of NO on body composition and systemic metabolism. This review addresses the metabolic actions of eNOS and the potential therapeutic utility of harnessing its antiobesogenic effects.

Changes in mineral status are associated with improvements in insulin sensitivity in obese patients following L-arginine supplementation

PURPOSE

The aim of this study is to evaluate the long-term influence of L-arginine intake on mineral concentration in patients with obesity and to assess the changes in lipid serum levels, fat content, and insulin resistance that result.

METHODS

A randomized double-blind placebo-controlled study was conducted. 88 obese patients were randomly assigned to receive either 9 g of L-arginine or placebo daily, for 6 months. At baseline and after 6 months, selected anthropometrical measurements and blood biochemical analyses were performed and mineral levels were assessed. To assess insulin sensitivity, the gold-standard euglycemic clamp methodology was used.

RESULTS

We found that 6 months of L-arginine supplementation resulted in significant increases in insulin sensitivity (Δ1.1 mg/kg/min, P < 0.01) and zinc levels (Δ1.5 μmol/L, P < 0.001). Moreover, a positive correlation between the change in zinc concentration in serum and the change in insulin sensitivity was observed (R = 0.80, P < 0.01). In the group of patients treated with L-arginine, a negative correlation between the change in zinc concentration in serum and the change in body fat content was noted (R = -0.38, P < 0.05).

CONCLUSIONS

L-Arginine supplementation affects zinc status in obese patients. One beneficial influence is related to the improvements in insulin sensitivity.