Time-dependent alterations in rat macrovessels with type 1 diabetes

Insulin protects against type 1 diabetes mellitus-induced aortopathy associated with the inhibition of biomarkers of vascular injury in rats

BACKGROUND

We sought to investigate the protective effect of insulin against type 1 diabetes mellitus (T1DM)-induced aortic injury (aortopathy) associated with the inhibition of biomarkers of vascular injury.

MATERIAL AND METHODS

T1DM was induced in rats by streptozotocin (STZ) (65 mg/kg), and the protection group started insulin treatment 2 days post diabetic induction and continued until being sacrificed at week 8.

RESULTS

Aortopathy was developed in the diabetic rats as demonstrated by profound alterations to the aorta ultrastructure, which was substantially protected by insulin. In addition, insulin significantly inhibited diabetes-induced dyslipidaemia, soluble vascular cell adhesion molecule-1 (sVCAM-1) and soluble intercellular adhesion molecule-1 (sICAM-1), oxidative stress, and inflammation. However, blood levels of these biomarkers in the insulin-treated group were still significant (p < .05) compared with the control group, whereas insulin treatment returned blood glucose and triglyceride to control levels.

CONCLUSIONS

We demonstrate effective protection by insulin against T1DM-induced aortopathy in rats, which is associated with the inhibition of vascular injury biomarkers.

Prevalence and incidence of diabetic peripheral neuropathy in Latin America and the Caribbean: A systematic review and meta-analysis

AIMS

The objective of this systematic review and meta-analysis is to estimate the prevalence and incidence of diabetic peripheral neuropathy (DPN) in Latin America and the Caribbean (LAC).

MATERIALS AND METHODS

We searched MEDLINE, SCOPUS, Web of Science, EMBASE and LILACS databases of published observational studies in LAC up to December 2020. Meta-analyses of proportions were performed using random-effects models using Stata Program 15.1. Heterogeneity was evaluated through sensitivity, subgroup, and meta-regression analyses. Evidence certainty was performed with the GRADE approach.

RESULTS

Twenty-nine studies from eight countries were included. The estimated prevalence of DPN was 46.5% (95%CI: 38.0-55.0) with a significant heterogeneity (I2 = 98.2%; p<0.01). Only two studies reported incidence, and the pooled effect size was 13.7% (95%CI: 10.6-17.2). We found an increasing trend of cumulative DPN prevalence over time. The main sources of heterogeneity associated with higher prevalence were diagnosis criteria, higher A1c (%), and inadequate sample size. We judge the included evidence as very low certainty.

CONCLUSION

The overall prevalence of DPN is high in LAC with significant heterogeneity between and within countries that could be explained by population type and methodological aspects. Significant gaps (e.g., under-representation of most countries, lack of incidence studies, and heterogenous case definition) were identified. Standardized and population-based studies of DPN in LAC are needed.

Carvacrol protects against diabetes-induced hypercontractility in the aorta through activation of the PI3K/Akt pathway

Vascular complications induced by diabetes constitute the principal cause of morbidity and mortality in diabetic patients. It has been reported that carvacrol (CAR) possesses a wide range of biological activities. The effects of CAR on diabetes-induced vasculopathy remain unknown. In this study, diabetic mice were created by the intraperitoneal injection of streptozotocin (STZ) in male C57BL/6 J mice to investigate whether CAR provided a protective effect against diabetes-induced vasculopathy and to investigate the underlying mechanisms. We found that CAR decreased blood glucose levels in diabetic mice. Moreover, CAR ameliorated diabetes-induced aortic morphological alterations, as evidenced by an increased thickness in the intima-media width and an increased number of vascular smooth muscle cells (VSMCs) layers. Further studies revealed that CAR inhibited hypercontractility in the aortas of diabetic mice and VSMCs in response to hyperglycemia, as evidenced by the relaxation of phenylephrine(PE)-induced vasoconstriction, the decreased expression of smooth muscle (SM)-α-actin, and the increased expression of Ki67 and proliferating cell nuclear antigen (PCNA). Furthermore, the PI3K/Akt signaling pathway was inhibited in the aortas of diabetic mice and VSMCs in response to hyperglycemia, while CAR treatment activated the PI3K/Akt signaling pathway. In conclusion, our results strongly suggest that CAR plays a protective role in diabetes-induced aortic hypercontractility, possibly by activating the PI3K/Akt signaling pathway. CAR is a potential drug for the treatment of diabetic vasculopathy.

Inhalation exposure to cigarette smoke induces endothelial nitric oxide synthase uncoupling and enhances vascular collagen deposition in streptozotocin-induced diabetic rats

Smoking is an acknowledged risk factor for vascular disorders, and vascular complication is a main outcome of diabetes. Hence, we investigated the impact of cigarette smoke on blood vessels in diabetes, postulating that smoking might aggravate diabetic vascular impairment. Sprague-Dawley rats were divided into four groups: control, cigarette smoke-exposed, diabetic, and cigarette smoke-exposed diabetic groups. Streptozotocin-induced diabetic rats were exposed to cigarette smoke by inhalation at total particulate matter concentration of 200 μg/L for 4 h/day, 5 day/week for a total of 4 weeks. Diabetes caused structural change of aorta, but additional cigarette smoke exposure did not induce further alteration. Collagen, a marker for fibrosis, was increased in media of diabetic aorta, and this increase was augmented by cigarette smoke. Cigarette smoke induced endothelial nitric oxide synthase (eNOS) uncoupling in the diabetic group. Malondialdehyde was increased and glutathione was decreased in blood from diabetes, but these effects were not exaggerated by cigarette smoke. Cigarette smoke caused NADPH oxidase (NOX) 2 expression in diabetic aorta and enhanced diabetes-induced NOX4 expression in aorta. Taken together, cigarette smoke exposure can aggravate vascular fibrosis and induce eNOS uncoupling in diabetes under experimental condition, suggesting that smoking might exacerbate diabetic vascular impairments.

Vascular impact of quercetin administration in association with moderate exercise training in experimental type 1 diabetes

Hyperglycemia and oxidative stress have a major role in the pathogenesis of diabetic vascular complications. In this study, we investigated the efficacy of combining quercetin treatment with moderate exercise training in reversing diabetes-induced oxidative stress and ultrasound modifications in rat carotid arteries. The diabetic Wistar rats were divided into sedentary groups and trained groups. The trained animals went through a regular moderate exercise by swimming (5 weeks). Some non-diabetic and diabetic rats were daily treated with quercetin (30 mg/kg, for 5 weeks). At the end of the study, the imaging evaluation required to assess the effects of diabetes on carotid arteries was performed by micro-ultrasound (MU). The diabetic rats presented atherosclerotic plaques, with an increase in the echogenicity of the carotid artery wall, carotid intima-media thickness (CIMT), and carotid wall thickness, while the diabetic trained rats treated with quercetin presented normal values of these parameters. Malondialde-hyde (MDA) levels, superoxide dismutase (SOD) antioxidant enzyme activity, reduced glutathione (GSH) levels and the reduced (GSH) to oxidized (GSSG) glutathione ratio were determined in the carotid artery tissue. Diabetes caused elevated MDA levels and a decrease in SOD activity, GSH levels and GSH/GSSG ratio in the carotid artery tissue. Treating diabetic rats with quercetin combined with moderate exercise training reversed all these oxidative stress parameters. Our results show that this combination, quercetin and moderate exercise training, can be a good treatment strategy for the vascular complications of diabetes by attenuating hyperglycemia-mediated oxidative stress.

Sexual dimorphism on aortic remodelling in rats offspring from diabetic mothers and the role of flaxseed oil in this effect

Diabetes during pregnancy is associated with aortic remodelling in the fetus, stimulating the development of cardiovascular diseases in adult life. However, studies suggest that the use of foods high in omega-3 fatty acid, such as flaxseed oil, may reverse this effect of metabolic programming. This study aimed at investigating whether the effects of diabetes in mothers are passed on to their offspring in a gender-specific manner and whether the flaxseed oil used during pregnancy and lactation reverses or not the possible negative effects of this programming. Diabetic female rats (n = 18) were mated and allocated into three groups (n = 6): high-fat group (HG); flaxseed oil group (FOG) and control group (CG) (nondiabetic rats) during pregnancy and lactation. On the 21st day, male and female pups were weaned on a standard diet until 180 days. Aorta histomorphometry was analysed. Intima-media layer thickness was larger in FOG than CG in male (+15%) and than HG in female (+13.7%). Male FOG (+11.5%) showed higher amount of elastic fibre than CG. Maternal intake of flaxseed oil during pregnancy and lactation of diabetic mothers program the offspring to increase aorta intima-media layer thickness in adulthood and preserves aorta elastic fibres deposition in male offspring.

In Vivo Effects of Quercetin in Association with Moderate Exercise Training in Improving Streptozotocin-Induced Aortic Tissue Injuries

Background: Diabetes mellitus (DM) is a chronic endocrine-metabolic disorder associated with endothelial dysfunction. Hyperglycemia, dyslipidemia and abnormal nitric oxide-mediated vasodilatation are the major causal factors in the development of endothelial dysfunction in DM. The prevention of endothelial dysfunction may be a first target against the appearance of atherosclerosis and cardiovascular diseases. We have investigated the synergistic protective effects of quercetin administration and moderate exercise training on thoracic aorta injuries induced by diabetes. Methods: Diabetic rats that performed exercise training were subjected to a swimming training program (1 h/day, 5 days/week, 4 weeks). The diabetic rats received quercetin (30 mg/kg body weight/day) for 4 weeks. At the end of the study, the thoracic aorta was isolated and divided into two parts; one part was immersed in 10% formalin for histopathological evaluations and the other was frozen for the assessment of oxidative stress markers (malondialdehyde, MDA and protein carbonyls groups, PC), the activity of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT), nitrite plus nitrate (NOx) production and inducible nitric oxide synthase (iNOS) protein expression. Results: Diabetic rats showed significantly increased MDA and PC levels, NOx production and iNOS expression and a reduction of SOD and CAT activity in aortic tissues. A decrease in the levels of oxidative stress markers, NOx production and iNOS expression associated with elevated activity of antioxidant enzymes in the aortic tissue were observed in quercetin-treated diabetic trained rats. Conclusions: These findings suggest that quercetin administration in association with moderate exercise training reduces vascular complications and tissue injuries induced by diabetes in rat aorta by decreasing oxidative stress and restoring NO bioavailability.

Maternal exposure to diets containing flaxseed flour or flaxseed oil during pregnancy and lactation protects the aortic remodeling in adult male offspring of diabetic rat dams

BACKGROUND

Diabetes during pregnancy is associated with cardiovascular complications in the fetus and extends into adulthood. Therapeutic applications of flaxseed have been studied in cardiovascular disorders, because its oilseed is the best plant source of omega-3 fatty acid, which is currently considered by researchers to be an essential protective against cardiovascular disease. The aim of this study was to evaluate the influence of flaxseed flour and oil on cardiovascular biochemical parameters and the histoarchitecture of the aorta in adult rats which were offspring of diabetic mothers.

RESULTS

At 100 days of age in offspring it was observed that maternal consumption of a high-fat diet containing flaxseed oil (FOG) and flaxseed flour (FFG) did not affect the serum concentration of monocyte chemoattractant protein-1, vascular endothelial growth factor, cholesterol, triglycerides, high-density-, low-density- or very-low-density-lipoprotein cholesterol. However, the thickness of the intima media layer of the aorta was significantly smaller in FOG and FFG groups; the lumen area was similar among the groups; and a higher percentage of elastic fiber was found in FOG and FFG groups.

CONCLUSION

These data suggest that the use of both flaxseed flour and its oil reduces the remodeling of the aorta; however; it has not been possible to modify the cardiovascular biochemical parameters.

Silencing of activin receptor-like kinase 7 alleviates aortic stiffness in type 2 diabetic rats

AIM

Arterial stiffness is an important feature of diabetic macrovascular complications. Activin receptor-like kinase 7 (ALK7), a member of type I transforming growth factor-β (TGF-β) receptors, is correlated with pathogenic risks of type 2 diabetes mellitus and cardiovascular diseases and may be involved in cardiovascular remodeling. We aimed to investigate whether ALK7 is implicated in diabetes-induced aortic stiffness.

METHODS

Type 2 diabetes was induced by high-fat diet and low-dose streptozotocin (STZ; 27.5 mg/kg). Forty rats were separated into four groups: control, diabetes, diabetes with empty virus and diabetes treated with ALK7-shRNA. The metabolic index, ALK 7 expression and aortic stiffness were evaluated. We used gene silencing method to investigate the role of ALK7 in the pathological development.

RESULTS

Diabetic rats showed increased blood glucose, cholesterol, triglyceride levels, severe insulin resistance and ALK7 overexpression. Diabetes enhanced aortic stiffness, as demonstrated by the loss and disruption of elastic fibers as well as by an increase in collagen fibers in the aortic media. ALK7 gene silencing ameliorated metabolic hyperlipidemia and insulin resistance. With ALK7 gene silencing, collagen content, elastin to collagen ratio, as well as collagen I-to-collagen III content ratio in diabetic rats were significantly decreased. Moreover, the phosphorylation level of Smad2/3 was markedly decreased after ALK7 gene silencing.

CONCLUSIONS

ALK7 gene silencing has a protective effect on diabetes-induced aortic stiffness, insulin resistance and hyperlipidemia, thus implicating a new potential therapeutic approach to diabetic macrovascular stiffness.

Prevalence of diabetic peripheral neuropathy in Iran: a systematic review and meta-analysis

Diabetic peripheral neuropathy (DPN) is an important microvascular complication of diabetes mellitus (DM). It is a major contributor to foot ulceration and lower limb amputation in persons with DM and have also a significant negative effect on patient's quality of life. This meta-analysis reviews prevalence of DPN among patients with type 1 and 2 DM in Iran. Using PubMed and NLM Gateway (for MEDLINE), Institute of Scientific Information (ISI), and SCOPUS as the main international electronic data sources, and Iranmedex, Irandoc, and Scientific Information Database (SID), as the main domestic databases with systematic search capability, we systematically searched surveys, papers, and reports on the prevalence of DPN (between January 1991 to February 2013). Heterogeneity of reported prevalence’s between studies was assessed by the Chi-square-based Q test and due to heterogeneity; overall prevalence of DPN was estimated using random-effect meta-analysis model. We found 304 records; from them a total of 21 studies comprising 5540 diabetic patients were included. The prevalence of diabetic neuropathy (reported) from 16% to 87%. In overall the prevalence of DPN estimated 53% (95% CI: 41-65) by using random-effect. This study show that the prevalence of DPN seems very high among the population with diabetes in Iran and more than half of the patients with DM has any type of diabetic neuropathy.

Angiotensin II receptor blocker telmisartan attenuates aortic stiffening and remodelling in STZ-diabetic rats

BACKGROUND

Prevention or attenuation of diabetic vascular complications includes anti-hypertensive treatment with renin-angiotensin system inhibitors on account of their protective effects beyond blood pressure reduction. The present study aimed to investigate the effects of telmisartan, an angiotensin II type 1 receptor blocker (ARB), on blood pressure, aortic stiffening, and aortic remodelling in experimental type 1 diabetes in rats.

METHODS

Diabetes was induced by streptozotocin (STZ) (65 mg/kg) in male Wistar rats. One diabetic group was treated for 10 weeks with telmisartan (10 mg/kg/day p/o). Pressure-independent aortic pulse wave velocity (PWV) was measured under anaesthesia after intravenous infusion of phenylephrine and nitroglycerine. Aortic wall samples were collected for histomorphometrical analysis.

RESULTS

Untreated diabetes imposed differential effects on aortic stiffening, as demonstrated by increased isobaric PWV over a range of high blood pressures, but not at lower blood pressures. This was associated with loss and disruption of elastin fibres and an increase in collagen fibres in the aortic media. Treatment with telmisartan decreased resting blood pressure, reduced aortic stiffness, and partially prevented the degradation of elastin network within the aortic wall.

CONCLUSIONS

Telmisartan improved the structural and functional indices of aortic stiffening induced by untreated STZ-diabetes, demonstrating the importance of ARBs in the therapeutic approach to diabetic vascular complications.

Urethral striated muscle and extracellular matrix morphological characteristics among mildly diabetic pregnant rats: translational approach

INTRODUCTION AND HYPOTHESIS

Diabetes mellitus (DM) during pregnancy is associated with high levels of urinary incontinence (UI) and pelvic floor muscle dysfunction. Mild DM can lead to changes in urethral striated muscle and extracellular matrix (ECM) in pregnant rats considering both structures as an entire system responsible for urinary continence.

METHODS

Ninety-two female Wistar rats were distributed in four experimental groups: virgin, pregnant, diabetic, and diabetic pregnant. In adult life, parental nondiabetic female rats were mated with nondiabetic male rats to obtain newborns. At the first day of birth, newborns received citrate buffer (nondiabetic group) or streptozotocin 100 mg/kg body weight, subcutaneous route (mild DM group). At day 21 of the pregnancy, the rats were lethally anesthetized and the urethra and vagina were extracted as a unit. Urethral and vaginal sections were cut and analyzed by: (a) cytochemical staining for ECM and muscle structural components, (b) immunohistochemistry to identify fast- and slow-muscle fibers, and (c) transmission electron microscopy for ultrastructural analysis of urethral striated muscle.

RESULTS

In comparison with the three control groups, variations in the urethral striated muscle and ECM from diabetic pregnant rats were observed including thinning, atrophy, fibrosis, increased area of blood vessels, mitochondria accumulation, increased lipid droplets, glycogen granules associated with colocalization of fast and slow fibers, and a steady decrease in the proportion of fast to slow fibers.

CONCLUSIONS

Mild DM and pregnancy can lead to a time-dependent disorder and tissue remodeling in which the urethral striated muscle and ECM has a fundamental function.

Organ-based response to exercise in type 1 diabetes

While significant research has clearly identified sedentary behavior as a risk factor for type 2 diabetes and its subsequent complications, the concept that inactivity could be linked to the complications associated with type 1 diabetes (T1D) remains underappreciated. This paper summarizes the known effects of exercise on T1D at the tissue level and focuses on the pancreas, bone, the cardiovascular system, the kidneys, skeletal muscle, and nerves. When possible, the molecular mechanisms underlying the benefits of exercise for T1D are elucidated. The general benefits of increased activity on health and the barriers to increased exercise specific to people with T1D are discussed.

Roles of polyuria and hyperglycemia in bladder dysfunction in diabetes

PURPOSE

Diabetes mellitus causes diabetic bladder dysfunction. We identified the pathogenic roles of polyuria and hyperglycemia in diabetic bladder dysfunction in rats.

MATERIALS AND METHODS

A total of 72 female Sprague-Dawley® rats were divided into 6 groups, including age matched controls, and rats with sham urinary diversion, urinary diversion, streptozotocin induced diabetes mellitus after sham urinary diversion, streptozotocin induced diabetes mellitus after urinary diversion and 5% sucrose induced diuresis after sham urinary diversion. Urinary diversion was performed by ureterovaginostomy 10 days before diabetes mellitus induction. Animals were evaluated 20 weeks after diabetes mellitus or diuresis induction. We measured 24-hour drinking and voiding volumes, and cystometry. Bladders were harvested to quantify smooth muscle, urothelium and collagen. We measured nitrotyrosine and Mn superoxide dismutase in the bladder.

RESULTS

Diabetes and diuresis caused increases in drinking and voiding volume, and bladder weight. Bladder weight decreased in the urinary diversion group and the urinary diversion plus diabetes group. The intercontractile interval, voided volume and compliance increased in the diuresis and diabetes groups, decreased in the urinary diversion group and further decreased in the urinary diversion plus diabetes group. Total cross-sectional tissue, smooth muscle and urothelium areas increased in the diuresis and diabetes groups, and decreased in the urinary diversion and urinary diversion plus diabetes groups. As a percent of total tissue area, collagen decreased in the diuresis and diabetes groups, and increased in the urinary diversion and urinary diversion plus diabetes groups. Smooth muscle and urothelium decreased in the urinary diversion and urinary diversion plus diabetes groups. Nitrotyrosine and Mn superoxide dismutase increased in rats with diabetes and urinary diversion plus diabetes.

CONCLUSIONS

Polyuria induced bladder hypertrophy, while hyperglycemia induced substantial oxidative stress in the bladder, which may have a pathogenic role in late stage diabetic bladder dysfunction.