Pathogenesis of hypertension in diabetes

Extracellular Vesicles: Investigating the Pathophysiology of Diabetes-Associated Hypertension and Diabetic Nephropathy

Extracellular vesicles (EVs) include exosomes, microvesicles, and apoptotic bodies. EVs are released by all cell types and are found in biological fluids including plasma and urine. Urinary extracellular vesicles (uEVs) are a mixed population of EVs that comprise small EVs that are filtered and excreted, EVs secreted by tubular epithelial cells, and EVs released from the bladder, urethra, and prostate. The packaged cargo within uEVs includes bioactive molecules such as metabolites, lipids, proteins, mRNAs, and miRNAs. These molecules are involved in intercellular communication, elicit changes in intracellular signaling pathways, and play a role in the pathogenesis of various diseases including diabetes-associated hypertension and diabetic nephropathy. uEVs represent a rich source of biomarkers, prognosis markers, and can be loaded with small-molecule drugs as a vehicle for delivery.

Ethnic variation of IL-4 intron 3 VNTR gene polymorphism; its association with type 2 diabetes mellitus and its complication (neuropathy) in Egyptian subjects

Type 2 diabetes mellitus (T2DM) has multigenetic and environmental interactive factors. Although diabetic neuropathies (DPN) are the most common, but at the same time, the least recognized and understood long-term complication of diabetes. This study aimed to investigate the association of IL-4 VNTR gene polymorphism with T2DM complicated with neuropathy in Egyptian subjects. This is a case control study including 102 T2DM Egyptian patients, plus 188 unrelated healthy individuals as controls. They were evaluated for variable number tandem repeat (VNTR); 70 base pair repeats located in the intron 3; of IL-4 gene using the PCR technique. Homozygote frequency of the three-repeat allele (A1/A1) genotype of IL-4 VNTR was nearly equal among diabetic cases and controls (60.8% vs. 62.2%, respectively). Heterozygous frequency of (A1/A2) genotype was higher among controls compared to cases (33.5% vs. 19.6%, respectively) but not statistically significant. The (A2) allele had a significantly higher frequency in diabetic cases compared to controls (29.3% vs. 21.0%, respectively) while the (A1) allele had lower frequency but not significant one (70.7% vs. 79.0%, respectively). Comparing cases complicated with diabetic neuropathy vs. noncomplicated cases regarding their polymorphic IL-4 (VNTR) genotypes revealed a nonsignificant lower frequency of (A1A1) genotype (57.1% vs. 65.1%, respectively, p = .57) with a higher combined (A2A2 + A1/A2) genotype frequency (42.9% vs. 34.9%, respectively). Only two haplotypes (A1) & (A2) of IL-4 (VNTR) gene were recognized among Egyptian population; (A2) allele may influence in diabetes but not its complication (neuropathy) among Egyptian diabetic patients.

Renin-angiotensin-aldosterone system in insulin resistance and metabolic syndrome

Obesity and its consequent complications such as hypertension and metabolic syndrome are increasing in incidence in almost all countries. Insulin resistance is common in obesity. Renin- angiotensin system (RAS) is an important target in the treatment of hypertension and drugs that act on RAS improve insulin resistance and decrease the incidence of type 2 diabetes mellitus, explaining the close association between hypertension and type 2 diabetes mellitus. RAS influences food intake by modulating the hypothalamic expression of neuropeptide Y and orexins via AMPK dephosphorylation. Estrogen reduces appetite by its action on the brain in a way similar to leptin, an anorexigenic action that seems to be mediated via hypothalamic pro-opiomelanocortin (POMC) neurons in the arcuate nucleus and synaptic plasticity in the arcuate nucleus similar to leptin. Estrogen stimulates lipoxin A₄, a potent vasodilator and platelet anti-aggregator. Since both RAS and estrogen act on the hypothalamic neuropeptides and regulate food intake and obesity, it is likely that RAS modulates LXA₄ synthesis. Thus, it is proposed that Angiotensin-II receptor blockers and angiotensin-converting enzymes and angiotensin-II antagonists may have the ability to augment LXA₄ synthesis and thus bring about their beneficial actions.

Wild blueberries (Vaccinium myrtillus) alleviate inflammation and hypertension associated with developing obesity in mice fed with a high-fat diet

Background

Low-grade metabolic inflammation and hypertension are primary mechanisms involved in obesity-associated adverse health effects. Berries, especially Nordic wild blueberries (hereafter referred to as bilberries), represent an important source of dietary anthocyanins, a group of polyphenols with potential beneficial effects to combat obesity-associated metabolic disturbances.

Methods

The effects of 5% or 10% (w/w) of whole bilberries (BB) were studied on the development of obesity and its metabolic disturbances in C57BL mice fed with a high-fat diet (HFD) for three months. Cytokines, inflammatory cells, systolic blood pressure, glucose tolerance, insulin sensitivity, weight gain, body fat, food consumption and energy metabolism were assessed.

Results

Bilberries ameliorated type 1 pro-inflammatory responsiveness induced by HFD. This was indicated by the altered cytokine profile and the reduced prevalence of interferon gamma -producing T-cells, in particular T helper type 1 cells. Bilberries also prevented the progression of obesity associated long term increase in systolic blood pressure in mice.

Conclusions

Bilberries reduce the development of systemic inflammation and prevent the progression of chronic hypertension, thus supporting their potential role in alleviating the adverse health effects associated with developing obesity.

Coenzyme Q10 attenuates diastolic dysfunction, cardiomyocyte hypertrophy and cardiac fibrosis in the db/db mouse model of type 2 diabetes

AIMS/HYPOTHESIS

An increase in the production of reactive oxygen species is commonly thought to contribute to the development of diabetic cardiomyopathy. This study aimed to assess whether administration of the antioxidant coenzyme Q(10) would protect the diabetic heart against dysfunction and remodelling, using the db/db mouse model of type 2 diabetes. Furthermore, we aimed to compare the efficacy of coenzyme Q(10) to that of the ACE inhibitor ramipril.

METHODS

Six-week-old non-diabetic db/+ mice and diabetic db/db mice received either normal drinking water or water supplemented with coenzyme Q(10) for 10 weeks. Endpoint cardiac function was assessed by echocardiography and catheterisation. Ventricular tissue was collected for histology, gene expression and protein analysis.

RESULTS

Untreated db/db diabetic mice exhibited hyperglycaemia, accompanied by diastolic dysfunction and adverse structural remodelling, including cardiomyocyte hypertrophy, myocardial fibrosis and increased apoptosis. Systemic lipid peroxidation and myocardial superoxide generation were also elevated in db/db mice. Coenzyme Q(10) and ramipril treatment reduced superoxide generation, ameliorated diastolic dysfunction and reduced cardiomyocyte hypertrophy and fibrosis in db/db mice. Phosphorylation of Akt, although depressed in untreated db/db mice, was restored with coenzyme Q(10) administration. We postulate that preservation of cardioprotective Akt signalling may be a mechanism by which coenzyme Q(10)-treated db/db mice are protected from pathological cardiac hypertrophy.

CONCLUSIONS/INTERPRETATION

These data demonstrate that coenzyme Q(10) attenuates oxidative stress and left ventricular diastolic dysfunction and remodelling in the diabetic heart. Addition of coenzyme Q(10) to the current therapy used in diabetic patients with diastolic dysfunction warrants further investigation.

The metabolic syndrome and mind-body therapies: a systematic review

The metabolic syndrome, affecting a substantial and increasing percentage of the worldwide population, is comprised of a cluster of symptoms associated with increased risk of type 2 diabetes, cardiovascular disease, and other chronic conditions. Mind-body modalities based on Eastern philosophy, such as yoga, tai chi, qigong, and meditation, have become increasingly popular worldwide. These complementary therapies have many reported benefits for improving symptoms and physiological measures associated with the metabolic syndrome. However, clinical trial data concerning the effectiveness of these practices on the syndrome as a whole have not been evaluated using a systematic and synthesizing approach. A systematic review was conducted to critically evaluate the data from clinical trials examining the efficacy of mind-body therapies as supportive care modalities for management of the metabolic syndrome. Three clinical trials addressing the use of mind-body therapies for management of the metabolic syndrome were identified. Findings from the studies reviewed support the potential clinical effectiveness of mind-body practices in improving indices of the metabolic syndrome.

Apelin gene transfer into the rostral ventrolateral medulla induces chronic blood pressure elevation in normotensive rats

The peripheral apelin system plays a significant role in cardiovascular homeostasis and in the pathophysiology of cardiovascular diseases. However, the central effect of this neurohormonal system in neural control of cardiovascular function remains poorly understood. Thus, this study was undertaken to evaluate the effect of apelin in the rostral ventrolateral medulla (RVLM) on blood pressure, cardiac function, and sympathetic nerve activity. Apelin mRNA and protein levels were detected with real-time RT-PCR and Western blots, respectively. Expression of apelin was significantly enhanced in the RVLM of spontaneously hypertensive rat (SHR) compared with normotensive Wistar-Kyoto (WKY) rats. To study the functional consequence of upregulated apelin expression, apelin was overexpressed by bilateral microinjection of the AAV2-apelin viral vector into the RVLM of WKY rats. Immunofluorescence staining and Western blots demonstrated that microinjection of AAV2-apelin into the RVLM resulted in a significant increase in apelin expression, which was associated with a chronic elevation in blood pressure and cardiac hypertrophy. In addition, direct microinjection of exogenous apelin-13 (200 pmol in 50 nL) into the RVLM caused a 20 mm Hg elevation in blood pressure and a 24% increase in sympathetic nerve activity. The present study is the first to show that apelin expression is enhanced in the RVLM of SHR versus WKY rats and that overexpression of this gene in the RVLM results in chronic blood pressure elevation and cardiac hypertrophy in normotensive rats. Thus, the apelin system in the RVLM may play a very important role in central blood pressure regulation and in the pathogenesis of hypertension.

Activation of prostaglandin E2 EP1 receptor increases arteriolar tone and blood pressure in mice with type 2 diabetes

AIMS

Type 2 diabetes mellitus is frequently associated with hypertension, but the underlying mechanisms are not completely understood. We tested the hypothesis that activation of type 1 prostaglandin E(2) (PGE(2)) receptor (EP1) increases skeletal muscle arteriolar tone and blood pressure in mice with type 2 diabetes.

METHODS AND RESULTS

In 12-week-old, male db/db mice (with homozygote mutation in leptin receptor), systolic blood pressure was significantly elevated, compared with control heterozygotes. Isolated, pressurized gracilis muscle arterioles ( approximately 90 microm) of db/db mice exhibited an enhanced pressure- and angiotensin II (0.1-10 nM)-induced tone, which was reduced by the selective EP1 receptor antagonist, AH6809 (10 microM), to the level observed in arterioles of control mice. Exogenous application of PGE(2) (10 pM-100 nM) or the selective agonist of the EP1 receptor, 17-phenyl-trinor-PGE(2) (10 pM-100 nM), elicited arteriolar constrictions that were significantly enhanced in db/db mice (max: 31 +/- 4 and 29 +/- 5%), compared with controls (max: 20 +/- 2 and 14 +/- 3%, respectively). In the aorta of db/db mice, an increased protein expression of EP1, but not EP4, receptor was also detected by western immunoblotting. Moreover, we found that oral administration of the EP1 receptor antagonist, AH6809 (10 mg/kg/day, for 4 days), significantly reduced the systolic blood pressure in db/db, but not in control mice.

CONCLUSION

Activation of EP1 receptors increases arteriolar tone, which could contribute to the development of hypertension in the db/db mice.

Analysis of renin-angiotensin aldosterone system gene polymorphisms in Malaysian essential hypertensive and type 2 diabetic subjects

BACKGROUND

The renin-angiotensin aldosterone system (RAAS) plays an important role in regulating the blood pressure and the genetic polymorphisms of RAAS genes has been extensively studied in relation to the cardiovascular diseases in various populations with conflicting results. The aim of this study was to determine the association of five genetic polymorphisms (A6G and A20C of angiotensinogen (AGT), MboI of renin, Gly460Trp of aldosterone synthase and Lys173Arg of adducin) of RAAS genes in Malaysian essential hypertensive and type 2 diabetic subjects.

METHODS

RAAS gene polymorphisms were determined using mutagenically separated PCR and PCR-RFLP method in a total of 270 subjects consisting of 70 hypertensive subjects without type 2 diabetes mellitus (T2DM), 60 T2DM, 65 hypertensive subjects with T2DM and 75 control subjects.

RESULTS

There was significant difference found in age, body mass index, systolic/diastolic blood pressure, fasting plasma glucose and high density lipoprotein cholesterol levels between the hypertensive subjects with or without T2DM and control subjects. No statistically significant differences between groups were found in the allele frequency and genotype distribution for A20C variant of AGT gene, MboI of renin, Gly460Trp of aldosterone and Lys173Arg of adducin (p > 0.05). However, the results for A6G of AGT gene revealed significant differences in allele and genotype frequencies in essential hypertension with or without T2DM (p < 0.001).

CONCLUSION

Among the five polymorphisms of RAAS genes only A6G variant of AGT gene was significantly associated in Malaysian essential hypertensive and type 2 diabetic subjects. Therefore, A6G polymorphism of the AGT gene could be a potential genetic marker for increased susceptibility to essential hypertension with or without T2DMin Malaysian subjects.

Hypertension and disrupted blood pressure circadian rhythm in type 2 diabetic db/db mice

Human Type 2 diabetes is associated with increased incidence of hypertension and disrupted blood pressure (BP) circadian rhythm. Db/db mice have been used extensively as a model of Type 2 diabetes, but their BP is not well characterized. In this study, we used radiotelemetry to define BP and the circadian rhythm in db/db mice. We found that the systolic, diastolic, and mean arterial pressures were each significantly increased by 11, 8, and 9 mmHg in db/db mice compared with controls. In contrast, no difference was observed in pulse pressure or heart rate. Interestingly, both the length of time db/db mice were active (locomotor) and the intensity of locomotor activity were significantly decreased in db/db mice. In contrast to controls, the 12-h light period average BP in db/db mice did not dip significantly from the 12-h dark period. A partial Fourier analysis of the continuous 72-h BP data revealed that the power and the amplitude of the 24-h period length rhythm were significantly decreased in db/db mice compared with the controls. The acrophase was centered at 0141 in control mice, but became scattered from 1805 to 0236 in db/db mice. In addition to BP, the circadian rhythms of heart rate and locomotor activity were also disrupted in db/db mice. The mean arterial pressure during the light period correlates with plasma glucose, insulin, and body weight. Moreover, the oscillations of the clock genes DBP and Bmal1 but not Per1 were significantly dampened in db/db mouse aorta compared with controls. In summary, our data show that db/db mice are hypertensive with a disrupted BP, heart rate, and locomotor circadian rhythm. Such changes are associated with dampened oscillations of clock genes DBP and Bmal1 in vasculature.

High sodium intake enhances insulin-stimulated glucose uptake in rat epididymal adipose tissue

OBJECTIVE

This study investigated the effect of different sodium content diets on rat adipose tissue carbohydrate metabolism and insulin sensitivity.

METHODS AND PROCEDURES

Male Wistar rats were fed on normal- (0.5% Na(+); NS), high- (3.12% Na(+); HS),or low-sodium (0.06% Na(+); LS) diets for 3, 6, and 9 weeks after weaning. Blood pressure (BP) was measured using a computerized tail-cuff system. An intravenous insulin tolerance test (ivITT) was performed in fasted animals. At the end of each period, rats were killed and blood samples were collected for glucose and insulin determinations. The white adipose tissue (WAT) from abdominal and inguinal subcutaneous (SC) and periepididymal (PE) depots were weighed and processed for adipocyte isolation and measurement of in vitro rates of insulin-stimulated 2-deoxy-D-[(3)H]-glucose uptake (2DGU) and conversion of -[U-(14)C]-glucose into (14)CO(2).

RESULTS

After 6 weeks, HS diet significantly increased the BP, SC and PE WAT masses, PE adipocyte size, and plasma insulin concentration. The sodium dietary content did not influence the whole-body insulin sensitivity. A higher half-maximal effective insulin concentration (EC(50)) from the dose-response curve of 2DGU and an increase in the insulin-stimulated glucose oxidation rate were observed in the isolated PE adipocytes from HS rats.

DISCUSSION

The chronic salt overload enhanced the adipocyte insulin sensitivity for glucose uptake and the insulin-induced glucose metabolization, contributing to promote adipocyte hypertrophy and increase the mass of several adipose depots, particularly the PE fat pad.

The influence of yoga-based programs on risk profiles in adults with type 2 diabetes mellitus: a systematic review

There is growing evidence that yoga may offer a safe and cost-effective intervention for Type 2 Diabetes mellitus (DM 2). However, systematic reviews are lacking. This article critically reviews the published literature regarding the effects of yoga-based programs on physiologic and anthropometric risk profiles and related clinical outcomes in adults with DM 2. We performed a comprehensive literature search using four computerized English and Indian scientific databases. The search was restricted to original studies (1970-2006) that evaluated the metabolic and clinical effects of yoga in adults with DM 2. Studies targeting clinical populations with cardiovascular disorders that included adults with comorbid DM were also evaluated. Data were extracted regarding study design, setting, target population, intervention, comparison group or condition, outcome assessment, data analysis and presentation, follow-up, and key results, and the quality of each study was evaluated according to specific predetermined criteria. We identified 25 eligible studies, including 15 uncontrolled trials, 6 non-randomized controlled trials and 4 randomized controlled trials (RCTs). Overall, these studies suggest beneficial changes in several risk indices, including glucose tolerance and insulin sensitivity, lipid profiles, anthropometric characteristics, blood pressure, oxidative stress, coagulation profiles, sympathetic activation and pulmonary function, as well as improvement in specific clinical outcomes. Yoga may improve risk profiles in adults with DM 2, and may have promise for the prevention and management of cardiovascular complications in this population. However, the limitations characterizing most studies preclude drawing firm conclusions. Additional high-quality RCTs are needed to confirm and further elucidate the effects of standardized yoga programs in populations with DM 2.

Anti-diabetic properties of the Canadian lowbush blueberry Vaccinium angustifolium Ait

Incidence of type II diabetes is rapidly increasing worldwide. In order to identify complementary or alternative approaches to existing medications, we studied anti-diabetic properties of Vaccinium angustifolium Ait., a natural health product recommended for diabetes treatment in Canada. Ethanol extracts of root, stem, leaf, and fruit were tested at 12.5 microg/ml for anti-diabetic activity in peripheral tissues and pancreatic beta cells using a variety of cell-based bioassays. Specifically, we assessed: (1) deoxyglucose uptake in differentiated C2C12 muscle cells and 3T3-L1 adipocytes; (2) glucose-stimulated insulin secretion (GSIS) in beta TC-tet pancreatic beta cells; (3) beta cell proliferation in beta TC-tet cells; (4) lipid accumulation in differentiating 3T3-L1 cells; (5) protection against glucose toxicity in PC12 cells. Root, stem, and leaf extracts significantly enhanced glucose transport in C2C12 cells by 15-25% in presence and absence of insulin after 20 h of incubation; no enhancement resulted from a 1 h exposure. In 3T3 cells, only the root and stem extracts enhanced uptake, and this effect was greater after 1 h than after 20 h; uptake was increased by up to 75% in absence of insulin. GSIS was potentiated by a small amount in growth-arrested beta TC-tet cells incubated overnight with leaf or stem extract. However, fruit extracts were found to increase 3H-thymidine incorporation in replicating beta TC-tet cells by 2.8-fold. Lipid accumulation in differentiating 3T3-L1 cells was accelerated by root, stem, and leaf extracts by as much as 6.5-fold by the end of a 6-day period. Stem, leaf, and fruit extracts reduced apoptosis by 20-33% in PC12 cells exposed to elevated glucose for 96 h. These results demonstrate that V. angustifolium contains active principles with insulin-like and glitazone-like properties, while conferring protection against glucose toxicity. Enhancement of proliferation in beta cells may represent another potential anti-diabetic property. Extracts of the Canadian blueberry thus show promise for use as a complementary anti-diabetic therapy.

Metabolic safety of antihypertensive drugs: Myth versus reality

Treatment of hypertension with the major available antihypertensive classes results in a significant improvement in cardiovascular morbidity and mortality. However, there is controversy about whether specific classes of drug therapy have deleterious or beneficial effects on glucose and lipid metabolism. Myths and misconceptions have thus arisen. Although "old" classes of antihypertensives, such as diuretics and beta-blockers, seem to have deleterious effects on glucose and lipid metabolism, the "newer" agents appear to have either neutral or beneficial profiles. The long-term significance of these metabolic changes is still debated. It is known that insulin resistance plays a major role in the pathogenesis of hypertension and type 2 diabetes mellitus. There is increasing evidence that blocking the renin-angiotensin-aldosterone system by using angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers favorably affects insulin sensitivity and, accordingly, decreases the incidence of new-onset type 2 diabetes mellitus.

Citocinas, disfunção endotelial e resistência à insulina

A disfunção endotelial está associada a diversas alterações vasculares, como a aterosclerose, hipertensão arterial, hiperlipidemia e diabetes mellitus, que têm em comum a resistência à insulina (RI). Citocinas são proteínas de baixo peso molecular, com diversas funções metabólicas e endócrinas, que participam da inflamação e resposta do sistema imune. Várias dessas citocinas são consideradas como fatores de risco independentes para doenças da artéria coronária e cerebrovascular. As principais fontes de citocinas (adipocinas) são os tecidos adiposos subcutâneo e visceral. Assim, aumento da massa de tecido adiposo está associado com alterações da produção de adipocina com aumento da expressão de fator de necrose tumoral alfa (TNF-alfa), interleucina 6 (IL-6), inibidor do fator ativador de plasminogênio 1 (PAI-1), e diminuição da expressão de adiponectina no tecido adiposo. A condição pró-inflamatória associada a essas alterações sugere ligação entre RI e disfunção endotelial no estágio inicial do processo de aterosclerose, em indivíduos obesos e em pacientes diabéticos tipo 2. A redução da massa de tecido adiposo, por redução de peso associada a exercício físico, reduz TNF-alfa, IL-6 e PAI-1, aumenta adiponectina, e melhora tanto a sensibilidade à insulina quanto a função endotelial. A interação entre adipocinas e insulina no controle da função endotelial será discutida, bem como o conceito de que a alteração da secreção de adiponectinas na RI e/ou obesidade piora a função endotelial, além de diminuir ainda mais a sensibilidade à insulina.

Vascular complications in diabetes mellitus: the role of endothelial dysfunction

The endothelium is a complex organ with a multitude of properties essential for control of vascular functions. Dysfunction of the vascular endothelium is regarded as an important factor in the pathogenesis of diabetic micro- and macro-angiopathy. Endothelial dysfunction in Type I and II diabetes complicated by micro- or macro-albuminuria is generalized in that it affects many aspects of endothelial function and occurs not only in the kidney. The close linkage between microalbuminuria and endothelial dysfunction in diabetes is an attractive explanation for the fact that microalbuminuria is a risk marker for atherothrombosis. In Type I diabetes, endothelial dysfunction precedes and may cause diabetic microangiopathy, but it is not clear whether endothelial dysfunction is a feature of the diabetic state itself. In Type II diabetes, endothelial function is impaired from the onset of the disease and is strongly related to adverse outcomes. It is not clear whether impaired endothelial function is caused by hyperglycaemia or by other factors. Impaired endothelial function is closely associated with and may contribute to insulin resistance regardless of the presence of diabetes. Endothelial dysfunction in diabetes originates from three main sources. Hyperglycaemia and its immediate biochemical sequelae directly alter endothelial function or influence endothelial cell functioning indirectly by the synthesis of growth factors, cytokines and vasoactive agents in other cells. Finally, the components of the metabolic syndrome can impair endothelial function.