Augmented endothelial-specific L-arginine transport prevents obesity-induced hypertension

Relationship between socioeconomic status and hypertension incidence among adults in southwest China: a population-based cohort study

PURPOSE

To investigate the correlation between socioeconomic status (SES) and the incidence of hypertension among adults aged 18 or above in southwest China.

METHODS

A multistage proportional stratified cluster sampling method was employed to recruited 9280 adult residents from 12 counties in southwest China, with all participants in the cohort tracked from 2016 to 2020. The questionnaire survey gathered information on demographics, lifestyle habits, and household income. The physical exam recorded height, weight, and blood pressure. Biochemical tests measured cholesterol levels. The chi-square test was employed to assess the statistical differences among categorical variables, while the Cox proportional hazards regression model was applied to evaluate the association between socioeconomic status (SES) and the incidence of hypertension.

RESULTS

The finally effective sample size for the cohort study was 3546 participants, after excluding 5734 people who met the exclusion criteria. Adults in the highest household income group had a significantly lower risk of hypertension compared to those in the lowest income group (HR = 0.636, 95% CI: 0.478-0.845). Besides, when compared to individuals in the illiterate population, the risk of hypertension among adults with elementary school, junior high school, senior high school and associate degree educational level decreased respectively by 34.4% (HR = 0.656, 95%CI: 0.533-0.807), 44.9% (HR = 0.551, 95%CI: 0.436-0.697), 44.9% (HR = 0.551, 95%CI: 0.405-0.750), 46.1% (HR = 0.539, 95%CI: 0. 340-0.854). After conducting a thorough analysis of socioeconomic status, compared with individuals with a score of 6 or less, the risk of hypertension in participants with scores of 8, 10, 11, 12, and greater than 12 decreased respectively by 23.9% (HR = 0.761, 95%CI: 0.598-0.969), 29.7% (HR = 0.703, 95%CI: 0.538-0.919), 34.0% (HR = 0.660, 95%CI: 0.492-0.885), 34.3% (HR = 0.657, 95%CI: 0.447-0.967), 43.9% (HR = 0.561, 95%CI: 0.409-0.769).

CONCLUSION

The findings indicate a negative correlation between socioeconomic status and hypertension incidence among adults in southwest China, suggesting that individuals with higher socioeconomic status are less likely to develop hypertension.

Prevalence of Hypertension and Obesity: Profile of Mitochondrial Function and Markers of Inflammation and Oxidative Stress

Obesity and hypertension are health problems of increasing prevalence in developed countries. The link between obesity and hypertension is not yet fully determined. Oxidative stress (OS) and mitochondrial function may play a role in obesity-associated hypertension. A cross-sectional study with 175 subjects with normal weight, overweight, or obese who attended a medical check-up was included. The subjects were divided according to the body mass index (BMI) into normal-weight (n-53), overweight (n-84), and obesity (n-38). Hypertension was also evaluated. To measure mitochondrial function, ATP hydrolysis and ATP synthesis in platelets and serum, respectively, were determined. Superoxide dismutase (SOD), catalase, lipohydroperoxides, 8-isoprostanes, carbonyl groups in proteins, nitric oxide (NO) metabolites, 8-hydroxy-2′-deoxyguanosine (8-OHG), 8-oxoguanine glycosylase (hOGG1), tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6) were measured by standard colorimetric or immunoassay methods. Obese subjects showed lower ATP hydrolysis activity than normal weight and overweight subjects (p < 0.01). No differences between those groups were found in ATP synthase and catalase activities, lipid hydroperoxides, carbonyl groups in proteins, 8-isoprostanes, and NO metabolites. In the obesity group, SOD activity (p < 0.01) was decreased while 8-OHG (p < 0.01) was increased. Subjects with hypertension showed increased 8-OHG (p < 0.01) and less reparative enzyme (hOGG1 p = 0.04) than subjects with normal weight. Moreover, we found a decrease of SOD (p < 0.01), catalase activities (p = 0.04), NO metabolites (p < 0.01), and increases of carbonyl groups in proteins (p = 0.01), TNF-α (p < 0.01) and IL-6 (p < 0.01 in hypertensive subjects. Obese subjects show a decrease in ATP hydrolysis. The decrease in ATP hydrolysis rate and ATP synthesis and an increase in OS and inflammation markers were associated with the hypertensive state.

Involvement of shedding induced by ADAM17 on the nitric oxide pathway in hypertension

A Disintegrin and Metalloprotease 17 (ADAM17), also called tumor necrosis factor-ɑ (TNF-ɑ) convertase (TACE), is a well-known protease involved in the sheddase of growth factors, chemokines and cytokines. ADAM17 is also enrolled in hypertension, especially by shedding of angiotensin converting enzyme type 2 (ACE2) leading to impairment of angiotensin 1–7 [Ang-(1–7)] production and injury in vasodilation, induction of renal damage and cardiac hypertrophy. Activation of Mas receptor (MasR) by binding of Ang-(1–7) induces an increase in the nitric oxide (NO) gaseous molecule, which is an essential factor of vascular homeostasis and blood pressure control. On the other hand, TNF-ɑ has demonstrated to stimulate a decrease in nitric oxide bioavailability, triggering a disrupt in endothelium-dependent vasorelaxation. In spite of the previous studies, little knowledge is available about the involvement of the metalloprotease 17 and the NO pathways. Here we will provide an overview of the role of ADAM17 and Its mechanisms implicated with the NO formation.

Nuclear receptor ligand screening in an iPSC-derived in vitro blood-brain barrier model identifies new contributors to leptin transport

BACKGROUND

The hormone leptin exerts its function in the brain to reduce food intake and increase energy expenditure to prevent obesity. However, most obese subjects reflect the resistance to leptin even with elevated serum leptin. Considering that leptin must cross the blood-brain barrier (BBB) in several regions to enter the brain parenchyma, altered leptin transport through the BBB might play an important role in leptin resistance and other biological conditions. Here, we report the use of a human induced pluripotent stem cell (iPSC)-derived BBB model to explore mechanisms that influence leptin transport.

METHODS

iPSCs were differentiated into brain microvascular endothelial cell (BMEC)-like cells using standard methods. BMEC-like cells were cultured in Transwell filters, treated with ligands from a nuclear receptor agonist library, and assayed for leptin transport using an enzyme-linked immune sorbent assay. RNA sequencing was further used to identify differentially regulated genes and pathways. The role of a select hit in leptin transport was tested with the competitive substrate assay and after gene knockdown using CRISPR techniques.

RESULTS

Following a screen of 73 compounds, 17β-estradiol was identified as a compound that could significantly increase leptin transport. RNA sequencing revealed many differentially expressed transmembrane transporters after 17β-estradiol treatment. Of these, cationic amino acid transporter-1 (CAT-1, encoded by SLC7A1) was selected for follow-up analyses due to its high and selective expression in BMECs in vivo. Treatment of BMEC-like cells with CAT-1 substrates, as well as knockdown of CAT-1 expression via CRISPR-mediated epigenome editing, yielded significant increases in leptin transport.

CONCLUSIONS

A major female sex hormone, as well as an amino acid transporter, were revealed as regulators of leptin BBB transport in the iPSC-derived BBB model. Outcomes from this work provide insights into regulation of hormone transport across the BBB.

Actions of Esomeprazole on the Maternal Vasculature in Lean and Obese Pregnant Mice with Impaired Nitric Oxide Synthesis: A Model of Preeclampsia

Preeclampsia is a devastating, multisystem disorder of pregnancy. It has no cure except delivery, which if premature can impart significant neonatal morbidity. Efforts to repurpose pregnancy-safe therapeutics for the treatment of preeclampsia have led to the assessment of the proton pump inhibitor, esomeprazole. Preclinically, esomeprazole reduced placental secretion of anti-angiogenic sFlt-1, improved endothelial dysfunction, promoted vasorelaxation, and reduced maternal hypertension in a mouse model. Our understanding of the precise mechanisms through which esomeprazole works to reduce endothelial dysfunction and enhance vasoreactivity is limited. Evidence from earlier studies suggested esomeprazole might work via the nitric oxide pathway, upregulating endothelial nitric oxide synthase (eNOS). Here, we investigated the effect of esomeprazole in a mouse model of L-NAME-induced hypertension (decreased eNOS activity). We further antagonised the model by addition of diet-induced obesity, which is relevant to both preeclampsia and the nitric oxide pathway. Esomeprazole did not decrease blood pressure in this model, nor were there any alterations in vasoreactivity or changes in foetal outcomes in lean mice. We observed similar findings in the obese mouse cohort, except esomeprazole treatment enhanced ex vivo acetylcholine-induced vasorelaxation. As acetylcholine induces nitric oxide production, these findings hint at a function for esomeprazole in the nitric oxide pathway.

Impact of Obesity in Kidney Diseases

The clinical consequences of obesity on the kidneys, with or without metabolic abnormalities, involve both renal function and structures. The mechanisms linking obesity and renal damage are well understood, including several effector mechanisms with interconnected pathways. Higher prevalence of urinary albumin excretion, sub-nephrotic syndrome, nephrolithiasis, increased risk of developing CKD, and progression to ESKD have been identified as being associated with obesity and having a relevant clinical impact. Moreover, renal replacement therapy and kidney transplantation are also influenced by obesity. Losing weight is key in limiting the impact that obesity produces on the kidneys by reducing albuminuria/proteinuria, declining rate of eGFR deterioration, delaying the development of CKD and ESKD, and improving the outcome of a renal transplant. Weight reduction may also contribute to appropriate control of cardiometabolic risk factors such as hypertension, metabolic syndrome, diabetes, and dyslipidemia which may be protective not only in renal damage but also cardiovascular disease. Lifestyle changes, some drugs, and bariatric surgery have demonstrated the benefits.

Endothelial-specific overexpression of cationic amino acid transporter-1 prevents loss of kidney function in heart failure

Heart failure (HF) is associated with impaired L-arginine transport. In the present study, we tested the hypothesis that augmented L-arginine transport prevents the loss of kidney function in HF. Renal function was assessed in wildtype mice (WT), transgenic mice with HF (dilated cardiomyopathy, DCM) and double transgenic mice (double transgenic mice with DCM and CAT-1 overexpression, HFCAT-1) with HF and endothelial-specific overexpression of the predominant L-arginine transporter, cationic amino acid transporter-1 (CAT-1) (n=4-8/group). Cardiac function was assessed via echocardiography and left ventricular catheterisation. Renal function was assessed via quantification of albuminuria and creatinine clearance. Plasma nitrate and nitrite levels together with renal fibrosis and inflammatory markers were also quantified at study end. Albumin/creatinine ratio was two-fold greater in DCM mice than in WT mice (P=0.002), and tubulointerstitial and glomerular fibrosis were approximately eight- and three-fold greater, respectively, in DCM mice than in WT mice (P≤0.02). Critically, urinary albumin/creatinine ratio and tubulointerstitial and glomerular fibrosis were less in HFCAT-1 mice than in DCM mice (P<0.05). Renal CAT-1 expression and plasma nitrate and nitrite levels were less in DCM mice compared with WT (P≤0.03) but was greater in HFCAT-1 mice than in DCM mice (P≤0.009). Renal expression of IL-10 was less in DCM mice compared with WT (P<0.001) but was greater in HFCAT-1 mice compared with DCM mice (P=0.02). Our data provide direct evidence that augmented L-arginine transport prevents renal fibrosis, inflammation and loss of kidney function in HF.

The CAT-1 is out of the bag: endothelial Cationic Amino Acid Transporter-1 is a critical player in cardiorenal syndrome type 2

Although the numbers of patients affected by cardiorenal syndrome keeps increasing, we lack a complete understanding of the molecular pathways involved in its development and progression. Nitric oxide synthase (NOS) may play a role in cardiorenal syndrome, particularly cardiorenal syndrome type 2 (CRS2). However, complexities and paradoxical clinical findings have limited translation. In the current Clinical Science, Giam et al. (Clinical Science (2020) 134, 2755-2769) highlight the role of a key NOS substrate transporter, the cationic amino acid transporter-1, in preserving renal function in CRS2. In this commentary, we introduce the cardiorenal syndrome and the putative role that nitric oxide (NO) may play in the development of this disease and discuss the exciting findings of Giam et al. (Clinical Science (2020) 134, 2755-2769) and their tantalizing translational implications.

Impaired l-arginine-nitric oxide pathway contributes to the pathogenesis of resistant hypertension

The precise mechanisms underlying resistant hypertension remain elusive. Reduced nitric oxide (NO) bioavailability is frequently documented in chronic kidney disease, obesity, diabetes and advanced age, all of which are risk factors for resistant hypertension. Sympathetic overactivity and chronic activation of the renin-angiotensin system are salient features of resistant hypertension. Interestingly, recent data indicate that renal sympathetic overactivity can reduce the expression of neuronal nitric oxide synthase in the paraventricular nucleus. Reduced NO levels in the paraventricular nucleus can increase sympathetic outflow and this can create a vicious cycle contributing to resistant hypertension. Angiotensin II can reduce l-arginine transport and hence NO production. Reduced NO levels may reduce the formation of angiotensin 1-7 dampening the cardio-protective effects of the renin-angiotensin system contributing to resistant hypertension. In addition, interleukin-6 (IL-6) is demonstrated to be independently associated with resistant hypertension, and IL-6 can reduce NO synthesis. Despite this, NO levels have not been quantified in resistant hypertension. Findings from a small proof of concept study indicate that NO donors can reduce blood pressure in patients with resistant hypertension but more studies are required to validate these preliminary findings. In the present paper, we put forward the hypothesis that reduced NO bioavailability contributes substantially to the development of resistant hypertension.

Thyroid hormones stimulate L-arginine transport in human endothelial cells

Thyroid hormone activity is associated with L-arginine metabolism and nitric oxide (NO) production, which participate in the cardiovascular manifestations of thyroid disorders. L-arginine transporters play an important role in activating L-arginine uptake and NO production. However, the effects of thyroid hormones on L-arginine transporters in endothelial cells have not yet been evaluated. The following methods were used. We measured L-arginine uptake, mRNA expression of L-arginine transporters, endothelial nitric oxide synthase (eNOS) mRNA and NO generation after the administration of T3, T4 and the T3 analog, 3,3′,5-triiodothyroacetic acid TRIAC in human umbilical vein endothelial cells (HUVECs). We also analyzed the role of αvβ3 integrin and of phosphatidyl-inositol-3 kinase (PI3K), mitogen-activated protein kinases (MAPKs: ERK1/2, p38 and SAPK-JNK) and intracellular calcium signaling pathways as underlying mechanisms. To this end, αvβ3 integrin was pharmacologically inhibited by tetraiodothyroacetic acid (TETRAC) or genetically blocked by silencing αv mRNA and PI3K, MAPKs and intracellular calcium by selective inhibitors. The following results were obtained. Thyroid hormones and the T3 analog TRIAC increased L-arginine uptake in HUVECs, the sodium-independent y+/CAT isoforms, except CAT2b, sodium-dependent y+L system and sodium-independent system b0,+L-arginine transporters, eNOS mRNA and NO production. These effects were suppressed by αvβ3 integrin inhibition with TETRAC or αv integrin downregulation or by PI3K, MAPK or intracellular Ca2+ signaling inhibitors. In conclusion, we report for the first time that activation of L-arginine uptake by thyroid hormones is related to an upregulation of L-arginine transporters. This effect seems to be mediated by activation of αvβ3 integrin receptor and subsequent PI3K, MAPK and intracellular Ca2+ signaling pathways.

l-Citrulline Supplementation: Impact on Cardiometabolic Health

Diminished bioavailability of nitric oxide (NO), the gaseous signaling molecule involved in the regulation of numerous vital biological functions, contributes to the development and progression of multiple age- and lifestyle-related diseases. While l-arginine is the precursor for the synthesis of NO by endothelial-nitric oxide synthase (eNOS), oral l-arginine supplementation is largely ineffective at increasing NO synthesis and/or bioavailability for a variety of reasons. l-citrulline, found in high concentrations in watermelon, is a neutral alpha-amino acid formed by enzymes in the mitochondria that also serves as a substrate for recycling l-arginine. Unlike l-arginine, l-citrulline is not quantitatively extracted from the gastrointestinal tract (i.e., enterocytes) or liver and its supplementation is therefore more effective at increasing l-arginine levels and NO synthesis. Supplementation with l-citrulline has shown promise as a blood pressure lowering intervention (both resting and stress-induced) in adults with pre-/hypertension, with pre-clinical (animal) evidence for atherogenic-endothelial protection. Preliminary evidence is also available for l-citrulline-induced benefits to muscle and metabolic health (via vascular and non-vascular pathways) in susceptible/older populations. In this review, we examine the impact of supplementing this important urea cycle intermediate on cardiovascular and metabolic health outcomes and identify future directions for investigating its therapeutic impact on cardiometabolic health.

Arginase inhibition prevents the development of hypertension and improves insulin resistance in obese rats

This study investigated the temporal activation of arginase in obese Zucker rats (ZR) and determined if arginase inhibition prevents the development of hypertension and improves insulin resistance in these animals. Arginase activity, plasma arginine and nitric oxide (NO) concentration, blood pressure, and insulin resistance were measured in lean and obese animals. There was a chronological increase in vascular and plasma arginase activity in obese ZR beginning at 8 weeks of age. The increase in arginase activity in obese animals was associated with a decrease in insulin sensitivity and circulating levels of arginine and NO. The rise in arginase activity also preceded the increase in blood pressure in obese ZR detected at 12 weeks of age. Chronic treatment of 8-week-old obese animals with an arginase inhibitor or L-arginine for 4 weeks prevented the development of hypertension and improved plasma concentrations of arginine and NO. Arginase inhibition also improved insulin sensitivity in obese ZR while L-arginine supplementation had no effect. In conclusion, arginase inhibition prevents the development of hypertension and improves insulin sensitivity while L-arginine administration only mitigates hypertension in obese animals. Arginase represents a promising therapeutic target in ameliorating obesity-associated vascular and metabolic dysfunction.

Factors Responsible for Obesity-Related Hypertension

PURPOSE OF REVIEW

The major health issue of being overweight or obese relates to the development of hypertension, insulin resistance and diabetic complications. One of the major underlying factors influencing the elevated blood pressure in obesity is increased activity of the sympathetic nerves to particular organs such as the kidney.

RECENT FINDINGS

There is now convincing evidence from animal studies that major signals such as leptin and insulin have a sympathoexcitatory action in the hypothalamus to cause hypertension. Recent studies suggest that this may involve 'neural plasticity' within hypothalamic signalling driven by central actions of leptin mediated via activation of melanocortin receptor signalling and activation of brain neurotrophic factors. This review describes the evidence to support the contribution of the SNS to obesity related hypertension and the major metabolic and adipokine signals.

Mushroom Polysaccharides: Chemistry and Antiobesity, Antidiabetes, Anticancer, and Antibiotic Properties in Cells, Rodents, and Humans

More than 2000 species of edible and/or medicinal mushrooms have been identified to date, many of which are widely consumed, stimulating much research on their health-promoting properties. These properties are associated with bioactive compounds produced by the mushrooms, including polysaccharides. Although β-glucans (homopolysaccharides) are believed to be the major bioactive polysaccharides of mushrooms, other types of mushroom polysaccharides (heteropolysaccharides) also possess biological properties. Here we survey the chemistry of such health-promoting polysaccharides and their reported antiobesity and antidiabetic properties as well as selected anticarcinogenic, antimicrobial, and antiviral effects that demonstrate their multiple health-promoting potential. The associated antioxidative, anti-inflammatory, and immunomodulating activities in fat cells, rodents, and humans are also discussed. The mechanisms of action involve the gut microbiota, meaning the polysaccharides act as prebiotics in the digestive system. Also covered here are the nutritional, functional food, clinical, and epidemiological studies designed to assess the health-promoting properties of polysaccharides, individually and as blended mixtures, against obesity, diabetes, cancer, and infectious diseases, and suggestions for further research. The collated information and suggested research needs might guide further studies needed for a better understanding of the health-promoting properties of mushroom polysaccharides and enhance their use to help prevent and treat human chronic diseases.

Effects of Dietary l-Arginine on Nitric Oxide Bioavailability in Obese Normotensive and Obese Hypertensive Subjects

Obesity related hypertension is a major risk factor for resistant hypertension. We do not completely understand the mechanism(s) underlying the development of obesity related hypertension which hinders the development of novel treatment strategies for this condition. Data from experimental studies and small clinical trials indicate that transport of l-arginine, the substrate for nitric oxide (NO), and subsequent NO production are reduced in obesity induced hypertension. Reduced NO bioavailability can induce hypertension via multiple mechanisms. Mirmiran et al. recently analyzed data from a large population study and found that the association between dietary l-arginine and serum nitrate and nitrite was weakened in obese hypertensive subjects compared to obese normotensives. These data suggest that l-arginine dependent NO production is impaired in the former group compared to the latter which may represent a novel mechanism contributing to hypertension in the setting of obesity.

Augmented endothelial l-arginine transport ameliorates pressure-overload-induced cardiac hypertrophy

NEW FINDINGS

What is the central question of this study? What is the potential role of endothelial NO production via overexpression of the l-arginine transporter, CAT1, as a mitigator of cardiac hypertrophy? What is the main finding and its importance? Augmentation of endothelium-specific l-arginine transport via CAT1 can attenuate pressure-overload-dependent cardiac hypertrophy and fibrosis. Our findings support the conclusion that interventions that improve endothelial l-arginine transport may provide therapeutic utility in the setting of myocardial hypertrophy. Such modifications may be introduced by exercise training or locally delivered gene therapy, but further experimental and clinical studies are required. Endothelial dysfunction has been postulated to play a central role in the development of cardiac hypertrophy, probably as a result of reduced NO bioavailability. We tested the hypothesis that increased endothelial NO production, mediated by increased l-arginine transport, could attenuate pressure-overload-induced cardiac hypertrophy. Echocardiography and blood pressure measurements were performed 15 weeks after transverse aortic constriction (TAC) in wild-type (WT) mice (n = 12) and in mice with endothelium-specific overexpression of the l-arginine transporter, CAT1 (CAT+; n = 12). Transverse aortic constriction induced greater increases in heart weight to body weight ratio in WT (by 47%) than CAT+ mice (by 25%) compared with the respective controls (P ≤ 0.05). Likewise, the increase in left ventricular wall thickness induced by TAC was significantly attenuated in CAT+ mice (P = 0.05). Cardiac collagen type I mRNA expression was greater in WT mice with TAC (by 22%; P = 0.03), but not in CAT+ mice with TAC, compared with the respective controls. Transverse aortic constriction also induced lesser increases in β-myosin heavy chain mRNA expression in CAT+ mice compared with WT (P ≤ 0.05). Left ventricular systolic pressure after TAC was 36 and 39% greater in WT and CAT+ mice, respectively, compared with the respective controls (P ≤ 0.001). Transverse aortic constriction had little effect on left ventricular end-diastolic pressure in both genotypes. Taken together, these data indicate that augmenting endothelial function by overexpression of l-arginine transport can attenuate pressure-overload-induced cardiac hypertrophy.

Effect of plasma NOx values on cardiac function in obese hypertensive and normotensive pediatric patients

BACKGROUND

Hypertension (HT) is a major comorbidity of obesity that is associated with an increased risk of cardiovascular disease and higher mortality. The aim of our study was to evaluate cardiac function in obese hypertensive (OHT) and obese normotensive (ONT) pediatric patients and determine the effects of plasma nitric oxide (NOx) values on cardiac function, while demonstrating the role of plasma NOx in HT in obese pediatric patients.

METHODS

The study population consisted of 62 patients (27 boys, 35 girls), aged 13-18 years and 21 age-matched healthy controls. All subjects enrolled in the study underwent echocardiography (Echo) evaluation and ambulatory blood pressure monitoring for HT. Plasma NOx and biochemical values were studied in both patient groups separately.

RESULTS

Plasma NOx levels were found to be lower in the OHT group than in the ONT and control groups (p < 0.001) and to be negatively correlated with left ventricular mass index values (p < 0.05). Both the OHT and ONT groups had concentric hypertrophy of the heart.

CONCLUSIONS

Plasma NOx plays an essential role in obesity-induced HT. Concentric hypertrophy of the left ventricle was found in both the OHT and ONT groups, indicating structural deformation of the heart.

Augmented Endothelial-Specific L-Arginine Transport Blunts the Contribution of the Sympathetic Nervous System to Obesity Induced Hypertension in Mice

Augmenting endothelial specific transport of the nitric oxide precursor L-arginine via cationic amino acid transporter-1 (CAT1) can prevent obesity related hypertension. We tested the hypotheses that CAT1 overexpression prevents obesity-induced hypertension by buffering the influence of the sympathetic nervous system (SNS) on the maintenance of arterial pressure and by buffering pressor responses to stress. Wild type (WT; n=13) and CAT1 overexpressing mice (CAT+; n=13) were fed a normal or a high fat diet for 20 weeks. Mice fed a high fat diet were returned to the control diet before experiments commenced. Baseline mean arterial pressure (MAP) and effects of restraint-, shaker- and almond feeding-stress and ganglionic blockade (pentolinium; 5 mg/kg; i.p.) on MAP were determined in conscious mice. Fat feeding increased body weight to a similar extent in WT and CAT+ but MAP was greater only in WT compared to appropriate controls (by 29%). The depressor response to pentolinium was 65% greater in obese WT than lean WT (P < 0.001), but was similar in obese and lean CAT+ (P = 0.65). In lean WT and CAT+, pressor responses to shaker and feeding stress, but not restraint stress, were less in the latter genotype compared to the former (P ≤ 0.001). Pressor responses to shaker and feeding stress were less in obese WT than lean WT (P ≤ 0.001), but similar in obese and lean CAT+. The increase in MAP in response to restraint stress was less in obese WT (22 ± 2%), but greater in obese CAT+ (37 ± 2%), when compared to respective lean WT (31 ± 3%) and lean CAT+ controls (27 ± 2%; P ≤ 0.02). We conclude that CAT1 overexpression prevents obesity-induced hypertension by reducing the influence of the SNS on the maintenance of arterial pressure but not by buffering pressor responses to stress.

Pathogenesis and treatment of the cardiorenal syndrome: Implications of L-arginine-nitric oxide pathway impairment

A highly complex interplay exists between the heart and kidney in the setting of both normal and abnormal physiology. In the context of heart failure, a pathophysiological condition termed the cardiorenal syndrome (CRS) exists whereby dysfunction in the heart or kidney can accelerate pathology in the other organ. The mechanisms that underpin CRS are complex, and include neuro-hormonal activation, oxidative stress and endothelial dysfunction. The endothelium plays a central role in the regulation of both cardiac and renal function, and as such impairments in endothelial function can lead to dysfunction of both these organs. In particular, reduced bioavailability of nitric oxide (NO) is a key pathophysiologic component of endothelial dysfunction. The synthesis of NO by the endothelium is critically dependent on the plasmalemmal transport of its substrate, L-arginine, via the cationic amino acid transporter-1 (CAT1). Impaired L-arginine-NO pathway activity has been demonstrated individually in heart and renal failure. Recent findings suggest abnormalities of the L-arginine-NO pathway also play a role in the pathogenesis of CRS and thus this pathway may represent a potential new target for the treatment of heart and renal failure.

Fibroblast growth factor 10 protects neuron against oxygen-glucose deprivation injury through inducing heme oxygenase-1

Fibroblast growth factors (FGFs) are a family of structurally related heparin-binding proteins with diverse biological functions. FGFs participate in mitogenesis, angiogenesis, cell proliferation, development, differentiation and cell migration. Here, we investigated the potential effect of FGF10, a member of FGFs, on neuron survival in oxygen-glucose deprivation (OGD) model. In primary cultured mouse cortical neurons upon OGD, FGF10 treatment (100 and 1000 ng/ml) attenuated the decrease of cell viability and rescued the LDH release. Tuj-1 immunocytochemistry assay showed that FGF10 promoted neuronal survival. Apoptosis assay with Annexin V+PI by flow cytometry demonstrated that FGF10 treatment reduced apoptotic cell proportion. Moreover, immunoblotting showed that FGF10 alleviated the cleaved caspase-3 upregulation caused by OGD. FGF10 treatment also depressed the OGD-induced increase of caspase-3, -8 and -9 activities. At last, we found FGF10 triggered heme oxygenase-1 (HO-1) protein expression rather than hypoxia-inducible factor-1 (HIF-1), AMP-activated protein kinase (AMPK) signaling and extracellular signal-regulated kinases 1/2 (ERK1/2) signaling. Knockdown of HO-1 by siRNA partly abolished the neuroprotection of FGF10 in OGD model. In summary, our observations provide the first evidence for the neuroprotective function of FGF10 against ischemic neuronal injury and suggest that FGF10 may be a promising agent for treatment of ischemic stroke.

Overexpression of mitochondrial antioxidant manganese superoxide dismutase (MnSOD) provides protection against AZT- or 3TC-induced endothelial dysfunction

Nucleoside reverse transcriptase inhibitors (NRTIs) are considered the backbone of current combination therapies for HIV. These therapies have significantly decreased mortality and morbidity in HIV-infected patients, but some are associated with cardiovascular complications, including endothelial dysfunction, an early marker for atherosclerosis. Our prior studies demonstrated that co-treatment of cells with an antioxidant therapy reversed NRTI-induced endothelial injury. Thus, as a proof of concept that mitochondrially-targeted antioxidants may be useful in preventing NRTI toxicity, in the current study, mice overexpressing a mitochondrial antioxidant, manganese superoxide dismutase (MnSOD), were compared with wild-type (WT) mice. Mice were treated chronically with either zidovudine (AZT), lamivudine (3TC), or tenofovir (TDF) to determine whether overexpression of MnSOD protected them from endothelial dysfunction. Endothelial function was assessed using vessel reactivity experiments on thoracic aortas as well as measures of endothelium derived factors nitric oxide (NO), endothelin-1 (ET-1), and prostacyclin. Oxidative stress was evaluated as levels of plasma 8-isoprostane. Alterations in vessel reactivity, NO, and ET-1 in WT mice treated with AZT or 3TC were noted. Overexpression of MnSOD offered protection from decreases in vessel reactivity and increases in ET-1. These findings indicate that mitochondrial oxidative stress induced by AZT or 3TC plays a major role in mediating NRTI-induced endothelial dysfunction, and suggest that the use of targeted antioxidants administered in conjunction with NRTIs may attenuate these effects.