Effect of angiotensin receptor blockade on insulin sensitivity and endothelial function in abdominally obese hypertensive patients with impaired fasting glucose

Clinical research progress on β-cell dysfunction in T2DM development in the Chinese population

The prevalence of type-2 diabetes mellitus (T2DM) has increased over 10-fold in the past 40 years in China, which now has the largest T2DM population in the world. Insulin resistance and β-cell dysfunction are the typical features of T2DM. Although both factors play a role, decreased β-cell function and β-cell mass are the predominant factors for progression to T2DM. Considering the differences between Chinese T2DM patients and those of other ethnicities, it is important to characterize β-cell dysfunction in Chinese patients during T2DM progression. Herein, we reviewed the studies on the relationships between β-cell function and T2DM progression in the Chinese population and discussed the differences among individuals of varying ethnicities. Meanwhile, we summarized the risk factors and current treatments of T2DM in Chinese individuals and discussed their impacts on β-cell function with the hope of identifying a better T2DM therapy.

A Systematic Review on Participant Diversity in Clinical Trials-Have We Made Progress for the Management of Obesity and Its Metabolic Sequelae in Diet, Drug, and Surgical Trials

OBJECTIVE

Individuals from Black and Hispanic backgrounds represent a minority of the overall US population, yet are the populations most affected by the disease of obesity and its comorbid conditions. Black and Hispanic individuals remain underrepresented among participants in obesity clinical trials, despite the mandate by the National Institutes of Health (NIH) Revitalization Act of 1993. This systematic review evaluates the racial, ethnic, and gender diversity of clinical trials focused on obesity at a national level.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review of clinicaltrials.gov, PubMed, Cochrane Central, and Web of Science was undertaken to locate phase 3 and phase 4 clinical trials on the topic of obesity that met associated inclusion/exclusion criteria. Ultimately, 18 studies were included for review.

RESULTS

White non-Hispanic individuals represented the majority of clinical trial participants, as did females. No study classified participants by gender identity. Reporting of race/ethnicity was not uniform, with noted variability among racial/ethnic subgroups.

CONCLUSIONS

Our findings suggest that disparities remain in the diverse racial, ethnic, and gender representation of participants engaged in clinical trials on obesity relative to the prevalence of obesity in underrepresented populations. Commitment to inclusive and intentional recruiting practices is needed to increase the representation of underrepresented groups, thus increasing the generalizability of future research.

Co Q10 improves vascular reactivity in male diabetic rats by enhancing insulin sensitivity and antioxidant effect

Oxidative stress is the main player in the development of diabetic vascular complications. Co-Q10 is a natural antioxidant present in the body and in many foods. This study was designed to evaluate the effect of Co-Q10 administration to improve vascular complications and increase insulin sensitivity in diabetic rats. Fifty male rats were divided into five groups: control, diabetic untreated, diabetic insulin-treated, diabetic Co-Q10-treated, and diabetic combined-treated groups. After 8 weeks, blood pressure and vascular reactivity to NE and ACh, fasting glucose, insulin, C-peptide, MDA, TAC, HbA1c, and the HOMA-IR were measured. Diabetes increased fasting glucose, HbA1c, HOMA-IR, MDA, blood pressure, and decreased TAC and vascular reactivity. Ttreatment with insulin or Co-Q10 improved glycemic parameters and increasing antioxidant levels compared to diabetic group. Combined Co-Q10 with insulin was found to increase insulin sensitivity and decrease its resistance, which helps to decrease insulin doses in diabetic patients and reduce its side effects.

Effect of the Renin-Angiotensin System Inhibitors on Inflammatory Markers: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

To synthesize more conclusive evidence on the anti-inflammatory effects of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs).

METHODS

PubMed, Scopus, and Embase were searched from inception until March 1, 2021. We included randomized controlled trials (RCTs) that assessed the effect of ACEIs or ARBs, compared with placebo, on any of the following markers: C-reactive protein (CRP), interleukin 6 (IL-6), or tumor necrosis factor α (TNF-α). Mean changes in the levels of these markers were pooled as a weighted mean difference (WMD) with a 95% CI.

RESULTS

Thirty-two RCTs (n=3489 patients) were included in the final analysis. Overall pooled analysis suggested that ACEIs significantly reduced plasma levels of CRP (WMD, -0.54 [95% CI, -0.88 to -0.21]; P=.002; I²=96%), IL-6 (WMD, -0.84 [95% CI, -1.03 to -0.64]; P<.001; I²=0%), and TNF-α (WMD, -12.75 [95% CI, -17.20 to -8.29]; P<.001; I²=99%). Moreover, ARBs showed a significant reduction only in IL-6 (WMD, -1.34 [95% CI, -2.65 to -0.04]; P=.04; I²=85%) and did not significantly affect CRP (P=.15) or TNF-α (P=.97) levels. The lowering effect of ACEIs on CRP levels remained significant with enalapril (P=.006) and perindopril (P=.01) as well as with a treatment duration of less than 24 weeks (WMD, -0.67 [95% CI, -1.07 to -0.27]; P=.001; I²=94%) and in patients with coronary artery disease (WMD, -0.75 [95% CI, -1.17 to -0.33]; P<.001; I²=96%).

CONCLUSION

Based on this meta-analysis, ACEIs showed a beneficial lowering effect on CRP, IL-6, and TNF-α, whereas ARBs were effective as a class in reduction of IL-6 only.

T Cell-Based RAS Activity and Insulin Levels in Obese Subjects with Low Grade Inflammation

BACKGROUND

Obesity is a major contributor to inflammation and oxidative stress that are key underlying causes for insulin resistance (IR) and diabetes. Accumulated evidence suggest that RAS may serve as a strong link between IR and obesity. We investigated RAS activity in circulating T cells by obese subjects with and without angiotensin (Ang) II stimulation in presence or not of IR and of low-grade inflammation.

METHODS

We studied 29 obese and 10 healthy subjects. After T-lymphocytes isolation, mRNAs for angiotensin converting enzyme (ACE) and angiotensin 1-receptor (AT1-R) were quantified by reverse transcription polymerase chain reaction (RT-PCR). High-sensitivity C-reactive protein (hs-CRP), insulin and inflammatory cytokines serum levels, plasma renin activity (PRA) and ACE activity in cell pellet and supernatant, and angiotensin (Ang) II T cell content were also measured.

RESULTS

Under baseline conditions, RAS gene expressions, ACE activity and Ang II levels in T cells, but not PRA, of obese subjects with or without IR and with or without hs-CRP ≥3mg/dl were higher than in controls (p < 0.05). The increase in all parameters induced by Ang II was significantly higher in T cells from the obese subjects with hs-CRP≥3 mg/dl than in controls or in the obese subjects with hs-CRP<3 mg/dl. In the obese subjects with low grade inflammation and IR, the cytokine serum levels and T cells RAS gene expression was inversely correlated with insulin serum concentration.

CONCLUSIONS

Low grade inflammation amplifies the T cell RAS response to Ang II stimulation. T cell RAS gene expressions and serum levels of inflammatory cytokines were inversely related with insulin serum concentration. A protective role of insulin towards the development of inflammatory events can be hypothesized.

Blockade of Renin Angiotensin System Ameliorates the Cardiac Arrhythmias and Sympathetic Neural Remodeling in Hearts of Type 2 DM Rat Model

OBJECTIVE

The present study was designed to investigate the effects of renin angiotensin system (RAS) blockade on cardiac arrhythmias and sympathetic nerve remodelling in heart tissues of type 2 diabetic rats.

METHODS

Thirty-two male Sprague Dawley rats were randomly allocated into 4 equal groups; a) normal control group: normal rats, b) DM group; after type 2 diabetes induction, rats received 2ml oral saline daily for 4 weeks, c) DM+ ACEi: after type 2 diabetes induction, rats were treated with enalapril (10 mg/kg, orally for 4 weeks) and d) DM+ ARBs: after type 2 diabetes induction, rats were treated with losartan (30 mg/kg, orally for 4 weeks).

RESULTS

In type 2 diabetic rats, the results demonstrated significant prolongation in Q-T interval and elevation of blood sugar, HOMA-IR index, TC, TGs, LDL, serum CK-MB, myocardial damage, myocardial MDA, myocardial norepinephrine and tyrosine hydroxylase (TH) density with significant reduction in serum HDL, serum insulin and myocardial GSH and CAT. On the other hand, blockade of RAS at the level of either ACE by enalapril or angiotensin (Ag) receptors by losartan resulted in significant improvement in ECG parameters (Q-T), cardiac enzymes (CK-MB), cardiac morphology, myocardial oxidative stress (low MDA, high CAT and GSH) and myocardial TH density.

CONCLUSION

RAS plays a role in the cardiac sympathetic nerve sprouting and cardiac arrhythmias induced by type 2 DM and its blockade might have a cardioprotective effect via attenuation of sympathetic nerve fibres remodelling, myocardial norepinephrine contents and oxidative stress.

Therapeutic lifestyle change intervention improved metabolic syndrome criteria and is complementary to amlodipine/atorvastatin

AIMS

To examine whether addition of amlodipine (5 mg)/atorvastatin (10 mg) A/A to Therapeutic Lifestyle change intervention (TLC) would beneficially modulate Metabolic Syndrome (MetS) and oxidized low-density lipoprotein (Ox-LDL) levels.

METHODS

Patients with MetS (n = 53) were randomized to TLC + placebo or TLC + A/A for 12 months. Anthropometric measurements, blood pressure (BP), lipid profile, plasma Ox-LDL, and area under the curve of free fatty acid (AUC_FFA) during oral glucose tolerance test, a marker of adipose tissue health, were assessed before and after the intervention.

RESULTS

Twenty-six patients completed the study with an overall improvement of MetS (p = 0.02). TLC + placebo was beneficial in reversing MetS comparable to TLC + A/A (54% vs. 39%; p = 0.08). Both treatments decreased systolic BP (p ≤ 0.01). TLC + A/A also decreased diastolic BP and triglyceride levels. The changes in Ox-LDL levels directly correlated with changes in weight in the TLC-placebo group (r = 0.64; p = 0.04). AUC_FFA determined the loss of fat mass (r = 0.472, p = 0.03).

CONCLUSIONS

1) Addition of A/A has the advantage of improving the lipid profile and BP; but TLC alone was comparable to TLC + A/A in improving MetS; 2) weight change determines the TLC-associated change in Ox-LDL levels; and 3) AT metabolic health is a significant predictor of TLC-associated loss of body fat mass.

Correlation between renin-angiotensin system (RAS) related genes, type 2 diabetes, and cancer: Insights from metanalysis of transcriptomics data

Although studies have provided significant evidence about the role of RAS in mediating cancer risk in type 2 diabetes mellitus (DM), conclusions about the central molecular mechanisms underlying this disease remain to be reached, because this type of information requires an integrative multi-omics approach. In the current study, meta-analysis was performed on type 2 diabetes and breast, bladder, liver, pancreas, colon and rectum cancer-associated transcriptome data, and reporter biomolecules were identified at RNA, protein, and metabolite levels using the integration of gene expression profiles with genome-scale biomolecular networks in diabetes samples. This approach revealed that RAS biomarkers could be associated with cancer initiation and progression, which include metabolites (particularly, aminoacyl-tRNA biosynthesis and ABC transporters) as novel biomarker candidates and potential therapeutic targets. We detected downregulation and upregulation of differentially expressed genes (DEGs) in blood, pancreatic islets, liver and skeletal muscle from normal and diabetic patients. DEGs were combined with 211 renin-angiotensin-system related genes. Upregulated genes were enriched using Pathway analysis of cancer in pancreatic islets, blood and skeletal muscle samples. It seems that the changes in mRNA are contributing to the phenotypic changes in carcinogenesis, or that they are as a result of the phenotypic changes associated with the malignant transformation. Our analyses showed that Ctsg and Ednrb are downregulated in cancer samples. However, by immunohistochemistry experiments we observed that EDNRB protein showed increased expression in tumor samples. It is true that alterations in mRNA expression do not always reflect alterations in protein expression, since post-translational changes can occur in proteins. In this study, we report valuable data for further experimental and clinical analysis, because the proposed biomolecules have significant potential as systems biomarkers for screening or for therapeutic purposes in type 2 diabetes and cancer-associated pathways.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

POPs' effect on cardiometabolic and inflammatory profile in a sample of women with obesity and hypertension

Persistent organic pollutants (POPs) are man-made compounds with metabolic disruption impact. We investigated the effect of POP exposure in the cardiometabolic and inflammatory profile in a population of women with obesity and hypertension. In 43 premenopausal women (22 treated vs. 21 nontreated) undergoing bariatric surgery, blood and adipose tissue samples (visceral (vAT) and abdominal subcutaneous (scAT)) were collected. Median concentrations of ∑HCH and ∑POPs in vAT were significantly higher in treated women. VAT ∑HCH and scAT ∑HCH and ∑POPs concentrations were positively correlated with systolic blood pressure in the non-treated group. Our findings suggest that exposure to POPs and its accumulation in vAT and circulating in plasma may be associated to a higher cardiovascular risk in women with obesity and hypertension, with or without antihypertensive treatment.

Is Atorvastatin Associated with New Onset Diabetes or Deterioration of Glycemic Control? Systematic Review Using Data from 1.9 Million Patients

BACKGROUND

Current evidence indicates that statins increase the risk of new onset diabetes mellitus (NOD) and also deteriorate the glycemic control in patients with known diabetes mellitus (DM) after high-dose statin therapy.

AIMS

The aim of this review was to explore the effect of atorvastatin in causing NOD or deteriorating glycemic control in patients with DM.

METHODS

Two independent reviewers conducted the literature search, through PubMed database searching for articles published in English until April 2015, and only primary studies were included.

RESULTS

Of the 919 articles identified in our original search, 33 met the criteria for this review encompassing 1,951,113 participants. Twenty articles examined dysregulation of DM due to atorvastatin. Half of them showed that there was no significant change in glycemic control in patients treated with atorvastatin. Other studies showed that fasting plasma glucose and HbA1c levels were increased by atorvastatin. Thirteen articles examined if atorvastatin causes NOD. The majority of these articles showed that patients who used atorvastatin had a higher dose-dependent risk of developing NOD.

CONCLUSION

This systematic review suggests that there is an association between atorvastatin treatment and NOD. Moreover, it showed that atorvastatin in high dose causes worsening of the glycemic control in patients with DM.

Association between insulin resistance and the development of cardiovascular disease

For many years, cardiovascular disease (CVD) has been the leading cause of death around the world. Often associated with CVD are comorbidities such as obesity, abnormal lipid profiles and insulin resistance. Insulin is a key hormone that functions as a regulator of cellular metabolism in many tissues in the human body. Insulin resistance is defined as a decrease in tissue response to insulin stimulation thus insulin resistance is characterized by defects in uptake and oxidation of glucose, a decrease in glycogen synthesis, and, to a lesser extent, the ability to suppress lipid oxidation. Literature widely suggests that free fatty acids are the predominant substrate used in the adult myocardium for ATP production, however, the cardiac metabolic network is highly flexible and can use other substrates, such as glucose, lactate or amino acids. During insulin resistance, several metabolic alterations induce the development of cardiovascular disease. For instance, insulin resistance can induce an imbalance in glucose metabolism that generates chronic hyperglycemia, which in turn triggers oxidative stress and causes an inflammatory response that leads to cell damage. Insulin resistance can also alter systemic lipid metabolism which then leads to the development of dyslipidemia and the well-known lipid triad: (1) high levels of plasma triglycerides, (2) low levels of high-density lipoprotein, and (3) the appearance of small dense low-density lipoproteins. This triad, along with endothelial dysfunction, which can also be induced by aberrant insulin signaling, contribute to atherosclerotic plaque formation. Regarding the systemic consequences associated with insulin resistance and the metabolic cardiac alterations, it can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to the myocardium. The aim of this review is to discuss the mechanisms associated with insulin resistance and the development of CVD. New therapies focused on decreasing insulin resistance may contribute to a decrease in both CVD and atherosclerotic plaque generation.

Inverse Association of N-terminal Pro‒B-type Natriuretic Peptide Level With Metabolic Syndrome in Kidney Transplant Patients

BACKGROUND

Low levels of natriuretic peptide may activate the renin-angiotensin-aldosterone system, which may contribute to the development of obesity. Therefore, in study we aim to evaluate the relationship between metabolic syndrome (MetS) and serum N-terminal pro‒B-type natriuretic peptide (NT-proBNP) concentration in kidney transplant recipients.

METHODS

Fasting blood samples were obtained from 66 kidney transplant recipients. MetS and its components were defined using the diagnostic criteria of the International Diabetes Federation.

RESULTS

A total of 20 patients (30.3%) had MetS. Hypertension, prevalence of diabetes, use of statin or fibrate, body weight, body mass index, waist circumference, body fat mass, and levels of systolic blood pressure, total cholesterol, triglyceride, blood urea nitrogen, insulin, and HOMA-IR were higher, whereas the levels of high-density lipoprotein cholesterol and NT-proBNP were lower in patients with MetS. Logarithmically transformed creatinine and log-HOMA-IR were associated with NT-proBNP levels in a multivariable linear regression analysis. Multivariate logistic regression analysis revealed that NT-proBNP was an independent predictor of MetS in kidney transplant recipients.

CONCLUSION

Our study has revealed that fasting level of NT-proBNP was negatively associated with MetS and that serum creatinine and HOMA-IR were independent predictors of serum NT-proBNP level in kidney transplant recipients.

Telmisartan is effective to ameliorate metabolic syndrome in rat model - a preclinical report

BACKGROUND

Metabolic syndrome (MS) is known to be associated with hypertension, insulin resistance, and dyslipidemia, and it raises the risk for cardiovascular diseases and diabetes mellitus. Telmisartan is used in clinic as an angiotensin II receptor blocker and it is also identified as activating peroxisome proliferator-activated receptors δ (PPARδ). Activation of PPARδ produced beneficial effects on fatty acid metabolism and glucose metabolism. This study aims to investigate the effects of telmisartan on the modulation of MS in rats fed a high-fat/high-sodium diet.

METHODS

Rats were fed with a high-fat/high-sodium diet and received injections of streptozotocin at low dose to induce MS. Then, rats with MS were treated with telmisartan. The weight, glucose tolerance, and insulin sensitivity were measured. The lipid profiles were also obtained. The weights of retroperitoneal and epididymal fat pads were determined. The role of PPARδ in telmisartan treatment was identified in rats pretreated with the specific antagonist GSK0660.

RESULTS

The results showed that telmisartan, but not losartan, significantly reduced plasma glucose and plasma insulin, and improved insulin resistance in rats with MS. Telmisartan also decreased blood pressure and lipids more significantly than losartan. Moreover, GSK0660 effectively reversed the effects of telmisartan in the MS rats. In the MS group, telmisartan activated PPARδ to enhance the levels of phosphorylated GLUT4 in muscle or the expression of phosphoenolpyruvate carboxykinase (PEPCK) in the liver, which was also abolished by GSK0660. Telmisartan is useful to ameliorate hypertension and insulin resistance in rats with MS. Telmisartan improves the insulin resistance through increased expression of GLUT4 and down-regulation of PEPCK via PPARδ-dependent mechanisms.

CONCLUSION

Telmisartan has been proven to ameliorate MS, particularly in the prediabetes state. Therefore, telmisartan is suitable to develop for the management of MS in clinics.

Systemic and tissue-specific effects of aliskiren on the RAAS and carbohydrate/lipid metabolism in obese patients with hypertension

Aliskiren penetrates adipose and skeletal muscle in hypertensive patients with abdominal obesity and reduces renin-angiotensin-aldosterone system activity. After discontinuation, blood pressure-lowering effects are observed possibly through drug-tissue binding. We performed microdialysis evaluation of adipose tissue and skeletal muscle before and during an insulin-modified frequently sampled intravenous glucose tolerance test (IM-FSIGT). Aliskiren 300 mg (n = 8) or amlodipine 5 mg (n = 8) once daily were administered during a 12-week randomized treatment period. Aliskiren elicited variable changes in median interstitial angiotensin II (Ang II) in adipose (2.60-1.30 fmol/mL) and skeletal muscle (2.23-0.68 fmol/mL); amlodipine tended to increase adipose and skeletal muscle Ang II (P = .066 for skeletal muscle treatment difference). Glucose/insulin increased median plasma Ang II 1 hour after glucose injection (1.04-2.50 fmol/mL; P = .001), which was markedly attenuated by aliskiren but not amlodipine. Aliskiren increased glucose disposition index (P = .012) and tended to increase acute insulin response to glucose (P = .067). Fasting adipose glycerol (-17%; P = .064) and fasting muscle glucose dialysate (-17%; P = .025) were decreased by aliskiren but not amlodipine. In summary, aliskiren decreased Ang II production in response to glucose/insulin stimulus and elicited metabolic effects in adipose and skeletal muscle suggestive of increased whole-body glucose utilization.

Dipeptidyl peptidase-4 inhibitor sitagliptin improves pancreatic β-cell function in hypertensive diabetic patients treated with angiotensin receptor blockers

INTRODUCTION

Dipeptidyl peptidase (DPP)-4 inhibitors, a novel oral anti-diabetic agents, exert a protective effect on pancreatic β-cell function in patients with type 2 diabetic mellitus (T2DM). However, their beneficial effect in hypertensive T2DM patients treated with angiotensin receptor blockers (ARBs) has not been investigated.

METHODS

In this open-label multicenter randomized study, a total of 55 hypertensive T2DM patients treated with ARBs were randomly assigned to receive the DPP-4 inhibitor sitagliptin or sulfonylurea (SU).

RESULTS

After 24 weeks of treatment, a significant reduction in fasting blood glucose was only observed in the sitagliptin group, while HbA1c was significantly reduced in both groups. Homeostasis model assessment of insulin resistance was not significantly improved in either group. Indicators of pancreatic β-cell function, including proinsulin to insulin ratio and homeostasis model assessment of β-cell function, were significantly improved in the sitagliptin group, but not in the SU group. The beneficial effects of sitagliptin were observed in hypoglycemic drug naïve patients, but not in patients who had received SU monotherapy prior to the study.

CONCLUSION

Treatment with the DPP-4 inhibitor sitagliptin might exert beneficial effects on pancreatic β-cell function in ARB-treated T2DM patients and its efficacy might be more pronounced in hypoglycemic drug naïve patients.

Effect of Angiotensin Receptor Blockers on Flow-Mediated Vasodilation: A Meta-Analysis of Randomized Controlled Trials

Background: In a meta-analysis, we investigated the effects of angiotensin receptor blockers (ARBs) in comparison to placebo or other classes of antihypertensive drugs on endothelial function, which was measured by brachial flow-mediated vasodilation (FMD). Methods: We searched for randomized controlled trials that compared ARBs with placebo or other classes of antihypertensive drugs in improving FMD. A random-effect model was used to compute pooled estimates. Results: In 13 trials (n = 529), ARBs were more efficacious in improving brachial FMD than placebo [pooled weighted mean change difference (WMD) 1.34%, 95% CI, 0.93-1.75%, p < 0.001]. In 15 trials (n = 918), treatment with ARBs had a significant effect on brachial FMD when compared with other antihypertensive drugs (pooled WMD 0.59%, 95% CI, 0.20-0.98%, p = 0.003 with significant heterogeneity). ARBs were also more efficacious in improving brachial FMD than calcium channel blockers (CCBs; pooled WMD 1.61%, 95% CI, 0.72-2.49%, p < 0.001) but not the other classes of drugs (p ≥ 0.072). Conclusions: This meta-analysis shows that ARBs improve brachial FMD, a marker of endothelial function, and that they are superior to placebo and CCBs. There was no significant difference in the effect on brachial FMD between ARBs and the other antihypertensive drugs.

Improvement in endothelial function by lifestyle modification focused on exercise training is associated with insulin resistance in obese patients

A new method to evaluate endothelial function, namely, reactive hyperemia peripheral arterial tonometry (RH-PAT), has been developed. RH-PAT is an index of endothelial function, indicating initial atherosclerotic lesions. The present study aimed to investigate the effect of lifestyle modification with a focus on exercise training on RH-PAT in obese patients. We studied 43 obese patients (body mass index ≥ 30). RH-PAT was measured, and the RH-PAT index was calculated as a ratio of the digital pulse volume during reactive hyperemia divided by that at baseline. Further, we assessed body composition, arterial stiffness, insulin resistance, adipocytokine levels, and exercise tolerance. The exercise program consisted of 30 min on a cycle ergometer or treadmill, 3 times per week for 6 months. Training intensity was adjusted to the anaerobic threshold. Significant improvements were observed in the RH-PAT index following exercise training. We noted a significant reduction in weight, body fat percentage, and leptin values, and a significant increase in adiponectin levels and exercise tolerance. An abnormal baseline RH-PAT index was observed in 24 patients (55.8%); however, the improvement rate was higher in these patients than in patients with normal RH-PAT index values. Stepwise multiple regression analysis revealed that changes in insulin resistance (Δ”HOMA-IR) were independently correlated with changes in the RH-PAT index. Our results indicate that lifestyle modification with a focus on exercise training improved the RH-PAT index in obese patients. Patients with abnormal RH-PAT index values before lifestyle modification with exercise training demonstrated a high rate of improvement following exercise. Further, our results suggest that insulin resistance was the only independent factor influencing improvement in endothelial function.

Endothelial function testing and cardiovascular disease: focus on peripheral arterial tonometry

During recent decades, a number of methods have been developed to assess endothelial function, contributing to a better understanding of the pathophysiology of cardiovascular disease. Recently, the advent of noninvasive, reproducible techniques for assessment of endothelial function has opened novel possibilities of application in the clinical setting. Peripheral arterial tonometry is a relatively novel, user-friendly technique measuring finger pulse volume amplitude changes induced by reactive hyperemia following 5 minutes of ischemia in the upper limb. Current evidence indicates that this technique has the potential to significantly impact the field of cardiovascular research and prevention of cardiovascular disease. However, a number of methodological, pathophysiological, and clinical aspects still need to be clarified before widespread application of this promising technique. This review focuses on the current knowledge and future perspectives of peripheral arterial tonometry, in comparison with the most widely used noninvasive technique, ie, flow-mediated dilation.

Renin-angiotensin system blockers protect pancreatic islets against diet-induced obesity and insulin resistance in mice

Background

The associations between obesity, hypertension and diabetes are well established, and the renin-angiotensin system (RAS) may provide a link among them. The effect of RAS inhibition on type 2 diabetes is still unclear; however, RAS seems to play an important role in the regulation of the pancreas and glucose intolerance of mice fed high-fat (HF) diet.

Methods

C57BL/6 mice fed a HF diet (8 weeks) were treated with aliskiren (50 mg/kg/day), enalapril (30 mg/kg/day) or losartan (10 mg/kg/day) for 6 weeks, and the protective effects were extensively compared among groups by morphometry, stereological tools, immunostaining, Western blotting and hormonal analysis.

Results

All RAS inhibitors significantly attenuated the increased blood pressure in mice fed a HF diet. Treatment with enalapril, but not aliskiren or losartan, significantly attenuated body mass (BM) gain, glucose intolerance and insulin resistance, improved the alpha and beta cell mass and prevented the reduction of plasma adiponectin. Furthermore, enalapril treatment improved the protein expression of the pancreatic islet Pdx1, GLUT2, ACE2 and Mas receptors. Losartan treatment showed the greatest AT2R expression.

Conclusion

Our findings indicate that ACE inhibition with enalapril attenuated several of the deleterious effects of the HF diet. In summary, enalapril appears to be responsible for the normalization of islet morphology and function, of alpha and beta cell mass and of Pdx1 and GLUT2 expression. These protective effects of enalapril were attributed, primarily, to the reduction in body mass gain and food intake and the enhancement of the ACE2/Ang (1-7) /Mas receptor axis and adiponectin levels.

The renin angiotensin aldosterone system and insulin resistance in humans

Alterations in the renin angiotensin aldosterone system (RAAS) contribute to the underlying pathophysiology of insulin resistance in humans; however, individual differences in the treatment response of insulin resistance to RAAS blockade persist. Thus, understanding inter-individual differences in the relationship between the RAAS and insulin resistance may provide insights into improved personalized treatments and improved outcomes. The effects of the systemic RAAS on blood pressure regulation and glucose metabolism have been studied extensively; however, recent discoveries on the influence of local tissue RAAS in the skeletal muscle, heart, vasculature, adipocytes, and pancreas have led to an improved understanding of how activated tissue RAAS influences the development of insulin resistance and diabetes in humans. Angiotensin II (ANGII) is the predominant RAAS component contributing to insulin resistance; however, other players such as aldosterone, renin, and ACE2 are also involved. This review examines the role of local ANGII activity on insulin resistance development in skeletal muscle, adipocytes, and pancreas, followed by a discussion of the other RAAS components implicated in insulin resistance, including ACE2, Ang1-7, renin, and aldosterone.

Angiotensin II receptor blockade and insulin sensitivity in overweight and obese adults with elevated blood pressure

We tested the hypothesis that olmesartan, an angiotensin II receptor blocker (ARB) devoid of peroxisome proliferator-activated receptor γ agonist activity, would improve whole-body insulin sensitivity in overweight and obese individuals with elevated blood pressure (BP). Sixteen individuals (8 women, 8 men; age=49.5 ± 2.9 years; body mass index=33.0 ± 1.7 kg/m2) were randomly assigned in a crossover manner to control and ARB interventions. Insulin sensitivity was determined from intravenous glucose tolerances tests before and after each 8-week intervention. BP, body weight, body fat, lipid and lipoprotein concentrations, and insulin sensitivity were similar at baseline for both treatments (all p > 0.05). Diastolic BP and triglyceride concentrations were higher ( p = 0.007 and 0.042 respectively) at baseline for the ARB compared with the control intervention. Systolic (−11.7 mmHg; p = 0.008) and diastolic (−12.1 mmHg; p = 0.0001) BP decreased, however insulin sensitivity did not change ( p > 0.05) following ARB treatment. Furthermore, there were no significant correlates of changes in insulin sensitivity following the ARB intervention. In summary, our findings indicate that short-term ARB treatment did not affect whole-body insulin sensitivity in overweight or obese individuals with elevated BP. Future studies are needed to clarify the effect of individual ARBs on insulin sensitivity in obesity.

Angiotensin II type 2 receptor promotes adipocyte differentiation and restores adipocyte size in high-fat/high-fructose diet-induced insulin resistance in rats

This study was aimed at establishing whether specific activation of angiotensin II (ANG II) type 2 receptor (AT2R) modulates adipocyte differentiation and function. In primary cultures of subcutaneous (SC) and retroperitoneal (RET) preadipocytes, both AT2R and AT1R were expressed at the mRNA and protein level. Cells were stimulated with ANG II or the AT2R agonist C21/M24, alone or in the presence of the AT1R antagonist losartan or the AT2R antagonist PD123,319. During differentiation, C21/M24 increased PPARγ expression in both RET and SC preadipocytes while the number of small lipid droplets and lipid accumulation solely increased in SC preadipocytes. In mature adipocytes, C21/M24 decreased the mean size of large lipid droplets. Upon abolishment of AT2R expression using AT2R-targeted shRNAs, expressions of AT2R, aP2, and PPARγ remained very low, and cells were unable to differentiate. In Wistar rats fed a 6-wk high-fat/high-fructose (HFHF) diet, a significant shift toward larger adipocytes was observed in RET and SC adipose tissue depots. C21/M24 treatments for 6 wk restored normal adipocyte size distribution in both these tissue depots. Moreover, C21/M24 and losartan decreased hyperinsulinemia and improved insulin sensitivity impaired by HFHF diet. A strong correlation between adipocyte size area and glucose infusion rate during euglycemic-hyperinsulinemic clamp was observed. These results indicate that AT2R is involved in early adipocyte differentiation, while in mature adipocytes and in a model of insulin resistance AT2R activation restores normal adipocyte morphology and improves insulin sensitivity.

Angiotensin receptor blockade recovers hepatic UCP2 expression and aconitase and SDH activities and ameliorates hepatic oxidative damage in insulin resistant rats

Metabolic syndrome (MetS) is commonly associated with elevated renin-angiotensin system, oxidative stress, and steatohepatitis with down-regulation of uncoupling proteins (UCPs). However, the mechanisms linking renin-angiotensin system, steatosis, and UCP2 to hepatic oxidative damage during insulin resistance are not described. To test the hypothesis that angiotensin receptor activation contributes to decreased hepatic UCP2 expression and aconitase activity and to increased oxidative damage after increased glucose intake in a model of MetS, lean and obese Long Evans rats (n = 10/group) were randomly assigned to the following groups: 1) untreated Long Evans Tokushima Otsuka (lean, strain control), 2) untreated Otsuka Long Evans Tokushima Fatty (OLETF) (MetS model), 3) OLETF + angiotensin receptor blocker (ARB) (10 mg olmesartan/kg·d × 6 wk), 4) OLETF + high glucose (HG) (5% in drinking water × 6 wk), and 5) OLETF + ARB + HG (ARB/HG × 6 wk). HG increased body mass (37%), plasma triglycerides (TGs) (35%), plasma glycerol (87%), plasma free fatty acids (28%), and hepatic nitrotyrosine (74%). ARB treatment in HG decreased body mass (12%), plasma TG (15%), plasma glycerol (23%), plasma free fatty acids (14%), and hepatic TG content (42%), suggesting that angiotensin receptor type 1 (AT1) activation and increased adiposity contribute to the development of obesity-related dyslipidemia. ARB in HG also decreased hepatic nitrotyrosine and increased hepatic UCP2 expression (59%) and aconitase activity (40%), as well as antioxidant enzyme activities (50-120%), suggesting that AT1 activation also contributes to protein oxidation, impaired lipid metabolism, and antioxidant metabolism in the liver. Thus, in addition to promoting obesity-related hypertension, AT1 activation may also impair lipid metabolism and antioxidant capacity, resulting in steatosis via decreased UCP2 and tricarboxylic acid cycle activity.

Link between the renin-angiotensin system and insulin resistance: implications for cardiovascular disease

The incidence of metabolic syndrome is rapidly increasing in the United States and worldwide. The metabolic syndrome is a complex metabolic and vascular disorder that is associated with inappropriate activation of the renin-angiotensin-aldosterone system (RAAS) in the cardiovascular (CV) system and increased CV morbidity and mortality. Insulin activation of the phosphatidylinositol-3-kinase (PI3K) pathway promotes nitric oxide (NO) production in the endothelium and glucose uptake in insulin-sensitive tissues. Angiotensin (Ang) II inhibits insulin-mediated PI3K pathway activation, thereby impairing endothelial NO production and Glut-4 translocation in insulin-sensitive tissues, which results in vascular and systemic insulin resistance, respectively. On the other hand, Ang II enhances insulin-mediated activation of the mitogen-activated protein kinase (MAPK) pathway, which leads to vasoconstriction and pathologic vascular cellular growth. Therefore, the interaction of Ang II with insulin signaling is fully operative not only in insulin-sensitive tissues but also in CV tissues, thereby linking insulin resistance and CV disease. This notion is further supported by an increasing number of experimental and clinical studies indicating that pharmacological blockade of RAAS improves insulin sensitivity and endothelial function, as well as reduces the incidence of new-onset diabetes in high-risk patients with CV disease. This article reviews experimental and clinical data elucidating the physiological and pathophysiological role of the interaction between insulin and RAAS in the development of insulin resistance as well as CV disease.