HFD-induced Hypertension Research Articles

Inhibition of HDAC6 mitigates high-fat diet-induced kidney inflammation and hypertension via reduced infiltration of macrophages

Obesity-mediated hypertension is a worldwide problem. Recent research has indicated that chronic inflammation is associated with the pathogenesis of obese hypertension. Activated immune cells infiltrate target organs, such as arteries, kidneys, and brain, causing end-organ damage and hypertension. Histone deacetylase 6 (HDAC6) regulates the inflammatory cell activity mediating the production of inflammatory cytokines and may play a role in the crosstalk between inflammation and hypertension. In this study, we investigated the roles of HDAC6 in high-fat diet (HFD)-induced kidney inflammation and hypertension. Nine-week-old male C57BL/6 mice were fed either a normal diet (ND) or HFD for 15 weeks. HFD-induced hypertension with increased HDAC6 activities in the kidney and bone marrow-derived macrophages (BMDM). When HFD group reached the hypertensive phase, each group of mice was intraperitoneally injected with vehicle or selective HDAC6 inhibitor Tubacin (1 mg/kg/day) for 14 days. Tubacin treatment lowered blood pressure (BP) of HFD-fed mice to the normal level with successful inhibition of HDAC6 activity. Immunohistochemical staining of F4/80, which is known as a macrophage marker, revealed that HFD promoted macrophage infiltration into the kidney. Consequently, pro-inflammatory factors TNFα and IL-6 gene expressions in the kidney were increased by HFD. Tubacin canceled HFD-induced macrophage infiltration and inflammation in the kidney. HDAC6 gene silencing and Tubacin treatment in Raw 264.7 cells also blocked the chemoattractant-stimulated cell migration in vitro. The results reveal the novel role of HDAC6 in BMDM migration, kidney inflammation, and high BP induced by HFD providing HDAC6 inhibitors as a therapeutic option for obesity-mediated hypertension.

Geraniin Ameliorates Hypertensive Vascular Remodelling in a Diet-Induced Obese Animal Model through Antioxidant and Anti-Inflammatory Effects.

Geraniin, an ellagitannin, has shown a potent blood pressure-lowering effect in vivo. Therefore, this study aims to further characterize the ability of geraniin to attenuate hypertensive vascular dysfunction, a key feature of cardiovascular disease (CVD) development. Hypertension was induced in male Sprague-Dawley rats through feeding a high-fat diet (HFD) for eight weeks, followed by oral administration of 25 mg/kg/day geraniin for four weeks. The parameters of vascular dysfunction such as the structure and function of blood vessels as well as the vascular oxidative stress and inflammation were evaluated. The outcomes of geraniin-treated rats were compared with those of untreated rats on either a normal diet (ND) or HFD and with HFD-fed rats treated with captopril (40 mg/kg/day). We found that geraniin supplementation effectively ameliorated HFD-induced hypertension and abnormal remodelling of the thoracic aorta by suppressing excessive vascular superoxide (O2-) radical generation and overexpression of pro-inflammatory mediators in the circulating leukocytes. Furthermore, compared to the ND-fed rats, geraniin also independently promoted the significant enlargement of the thoracic aortic lumen for blood pressure reduction. Notably, the vascular benefits of geraniin were comparable to that of captopril. Collectively, these data suggest that geraniin can mitigate hypertensive vascular remodelling caused by overnutrition, which potentially abrogates the further development of CVDs.

Pathologic HDAC1/c-Myc signaling axis is responsible for angiotensinogen transcription and hypertension induced by high-fat diet

High-fat diet (HFD)-induced obesity is a cause of resistant hypertension. We have shown a possible link between histone deacetylases (HDACs) and renal angiotensinogen (Agt) upregulation in the HFD-induced hypertension, whereas the underlying mechanisms remain to be elucidated. Here, using a HDAC1/2 inhibitor romidepsin (FK228) and siRNAs, we determined roles of HDAC1 and HDAC2 in HFD-induced hypertension and found the pathologic signaling axis between HDAC1 and Agt transcription. Treatment with FK228 canceled the increased blood pressure of male C57BL/6 mice induced by HFD. FK228 also blocked upregulation of renal Agt mRNA, protein, angiotensin II (Ang II) or serum Ang II. Activation and nuclear accumulation of both HDAC1 and HDAC2 occurred in the HFD group. The HFD-induced HDAC activation was associated with an increase in deacetylated c-Myc transcription factor. Silencing of HDAC1, HDAC2 or c-Myc in HRPTEpi cells decreased Agt expression. However, only HDAC1 knockdown, but not HDAC2, increased c-Myc acetylation, suggesting selective roles in two enzymes. Chromatin immunoprecipitation assay revealed that HFD induced the binding of HDAC1 and deacetylated c-Myc at the Agt gene promoter. A putative c-Myc binding sequence in the promotor region was necessary for Agt transcription. Inhibition of c-Myc downregulated Agt and Ang II levels in kidney and serum, ameliorating HFD-induced hypertension. Thus, the abnormal HDAC1/2 in the kidney may be responsible for the upregulation of the Agt gene expression and hypertension. The results expose the pathologic HDAC1/c-myc signaling axis in kidney as a promising therapeutic target for obesity-associated resistant hypertension.

Abstract MP05: The Mechanism Of The Pvat Pro-inflammatory Micro-environment Formation During The Development Of High Fat Diet-induced Hypertension

There is considerable evidence for a causative role for T cells in hypertension, including studies with immunosuppressive drugs and T cell-deficient models. Our previous studies showed that soluble mediators from mesenteric perivascular adipose tissue (mPVAT) modulate T cell function. Specifically, conditioned media from mPVAT (mPVAT-CM) from Dahl S rats on a high fat diet (HFD) promoted expression of the pro-inflammatory cytokines, IFNg, IL-17a and GM-CSF, by activated T cells. Furthermore, the Dahl S rats on HFD will later develop hypertension. Hypothesis: mPVAT is stimulated to produce immunomodulatory mediators that promotes Th1/17 differentiation preceding the development of HFD-induced hypertension. We conducted bulk RNA-seq on activated splenocytes cultured in mPVAT-CM from Dahl S rats on either control or HFD for 10 weeks. In accordance with our previous studies, PVAT-CM from HFD-fed rats significantly upregulated many genes associated with IFNg/IL-17 induction, including Mpeg1, Lyz2 and Tnfsf4 (5.0±1.78, 3.70±0.53 and 1.78±0.42 fold over Control diet, respectively). In contrast, Th2/Treg-associated genes, such as Ctla2a (-0.27±0.02) and Ccr4 (-0.41±0.03) were downregulated. We also performed single cell (sc) RNA-seq on the PVAT stromal vascular fraction (SVF) and found that acute inflammatory genes were enriched in the HFD group. Together with the bulk RNA-seq on mPVAT, these data strongly suggest that the pro-inflammatory mPVAT micro-environment may promote Th1/Th17 differentiation. To identify mediators in PVAT-CM that may induce Th1/Th17 differentiation, we compared the bulk RNA-seq on splenocytes cultured in PVAT-CM with bulk RNA-seq conducted on the whole mPVAT itself. We found that a T cell co-stimulatory receptor DPP4 (CD26), which is closely associated with T cell activation was significantly increased in mPVAT from HFD-fed rats (33.4±2.3 HFD vs. 15.3±1.8 Control diet). We also observed an increase in DPP4 global expression from mPVAT SVF in HFD-fed rats, as determined by scRNA-seq. Conclusion: The data suggest that HFD promotes the IFNg and IL-17a pathways in PVAT, which precedes hypertension in Dahl S rats and correlates with an increase in expression of DPP-4, a gene that promotes T cell activation. (NIH P01 HL070687).

Inhibition of HDACs (Histone Deacetylases) Ameliorates High-Fat Diet-Induced Hypertension Through Restoration of the MsrA (Methionine Sulfoxide Reductase A)/Hydrogen Sulfide Axis.

[Figure: see text].

NLRP3 Contributes to High Fat Diet‐Induced Increases In Blood Pressure And Adiposity In Female Dahl Rats

Background Chronic ingestion of a high-fat diet (HFD) is pro-inflammatory and has been linked to the development of hypertension. The NLRP3 inflammasome contributes to adipose tissue inflammation with a chronic HFD in males, yet the role in blood pressure (BP) control is unknown. Interestingly, there is increasing evidence that females are highly susceptible to cardiovascular complications following a chronic HFD. The Dahl rat is a model of HFD-induced hypertension and adiposity. The goal of the current study was to test the hypothesis that NLRP3 contributes to HFD-induced increases in BP in female Dahl rats. Methods 5-week-old female wildtype (WT; n=4-8) and NLRP3 knockout (KO; n=3-6) Dahl rats were randomized to either a control normal fat diet (NFD; 7.2% calories from fat) or high fat diet (HFD; 36% of calories from fat). Body weights were measured weekly. At 15 weeks of age, body fat mass was measured via nuclear magnetic resonance. Rats were then implanted with telemetry devices and BP was measured from 16-17 weeks of age. Results Following 10 weeks of treatment with HFD, body fat percentage increased in female WT Dahl rats, however HFD-induced increases in body fat were attenuated in NLRP3 KO rats (Table, PInteraction=0.04, PDiet=0.01, Pgenotype<0.0001). Despite significant differences in body fat, all groups had similar body weights following 10 weeks of dietary treatment (PInteraction=0.56, PDiet=0.24, Pgenotype=0.09). We confirmed that chronic consumption of HFD increased MAP in female WT Dahl rats vs rats on NFD. HFD-induced increases in MAP were attenuated in NLRP3 KO rats (PInteraction=0.02, PDiet=0.001, Pgenotype=0.28). Discussion Our findings indicate that NLRP3 contributes to chronic HFD-induced increases in body fat and MAP in female Dahl rats. Most Americans eat more than the recommended amount of saturated fat. Since decreasing the intake of saturated fats is difficult, more basic science research like this project is necessary to understand the mechanisms through which females on a HFD have compromised cardiovascular health.

Pyrogallol-Phloroglucinol-6 6-Bieckol on Attenuates High-Fat Diet-Induced Hypertension by Modulating Endothelial-to-Mesenchymal Transition in the Aorta of Mice.

Endothelial-to-mesenchymal transition (EndMT), which is involved in the development of various cardiovascular diseases, is induced by dyslipidemia or obesity. In dyslipidemia, the increased levels of oxidized low-density lipoproteins (oxLDL) upregulated the lectin-type oxidized LDL receptor 1 (Lox-1), which then upregulated the down signaling pathways of PKC-α/MMPs/TGF-β/SMAD2 or 3 and increased the EndMT. In this study, we investigated the effect of pyrogallol-phloroglucinol-6,6-bieckol (PPB), which is a compound of Ecklonia cava (E. cava), on decreased blood pressure (BP) by attenuating the EndMT in a high-fat diet- (HFD-) fed animal model. We also investigated PPB's attenuation effect on EndMT in oxLDL-treated mouse endothelial cells as an in vitro model. The results indicated that, in the aorta or endothelial cells of mice, the HFD or oxLDL treatment significantly increased the expression of Lox-1/PKC-α/MMP9/TGF-β/SMAD2/SMAD3. The PPB treatment significantly decreased its expression. In contrast, the HFD or oxLDL treatment significantly decreased the expression of the EC markers (PECAM-1 and vWF) while the PPB treatment significantly increased them. Moreover, the HFD or oxLDL treatment significantly increased the expression of the mesenchymal cell markers (α-SMA and vimentin) while PPB treatment significantly decreased them. PPB decreased the intima-media thickness and extracellular matrix amount of the aorta and attenuated the BP, which was increased by the HFD. In conclusion, PPB attenuated the upregulation of Lox-1/PKC-α/MMP9/TGF-β/SMAD2 and 3 and restored the EndMT in HFD-fed animals. Moreover, PPB showed a restoring effect on HFD-induced hypertension.

Abstract P142: Sex-differences In M1-like Macrophage Counts In Aortic Perivascular Adipose Tissue Precedes High Fat Diet-induced Hypertension In Dahl S Rats

Perivascular adipose tissue (PVAT) may connect adiposity to hypertension because of its functions and proximity to blood vessels. Immune cells in adipose tissue are proposed to couple adiposity to hypertension development in a sex-specific fashion. It is unknown if sex-differences exist in PVAT’s immune community during the onset of adiposity-induced hypertension. Both sexes of the Dahl S rat strain become equally hypertensive (table) when fed a high fat (HFD) diet. We hypothesized that both sexes have similar immune cell composition in PVAT with the development and progression of HFD-induced hypertension. Male and female Dahl S rats were fed a regular (10% calories from fat; CD) diet or a HFD (60%) from weaning. Thoracic aorta PVAT (APVAT) was harvested at 10 (pre-hypertension), 17 (onset) or 24 (chronic) weeks (w) of diet. Macrophages (subtypes), neutrophils, mast, T (subtypes), B, NK cells were measured by flow cytometry. At 10 w, HFD females had 5X the number of M1-like macrophages vs HFD males. At 17 w, CD females had 10X the number of M2-like macrophages vs CD males. At 17 w and 24 w, males had greater number of CD4 (2X) and CD8 (1.5X) memory T cells vs females, independent of the diet (table). In summary, sex-differences in M1-like macrophage counts in APVAT precedes the development of HFD-induced hypertension in Dahl S rats. The progression of hypertension is associated with memory T cells in males and M2-like macrophages in females. This study is foundational to understand the sex-specific roles of these immune cells in regulating vascular tone in HFD-induced hypertension, underscoring the need for novel sex-specific anti-hypertensive immune modulators.

Fetal programming effects of pentaerythritol tetranitrate in a rat model of superimposed preeclampsia

Preeclampsia is a common medical condition during pregnancy and a major cause of maternal and prenatal mortality. The present study was conducted to investigate the effects of maternal treatment with pentaerythritol tetranitrate (PETN) in Dahl salt-sensitive rats (DSSR), a model of superimposed preeclampsia. F0 parental DSSR were treated with PETN (50 mg/kg) from the time point of mating to the end of lactation. Maternal PETN treatment improved fetal growth and had no effect on blood pressure in DSSR offspring fed with normal chow or high-salt diet. Upon high-fat diet (HFD) feeding, offspring from PETN-treated mother showed improved glucose tolerance despite similar weight gain. Unexpectedly, maternal PETN treatment significantly potentiated the HFD-induced blood pressure elevation in male DSSR offspring. Endothelium-derived hyperpolarization factor (EDHF)-mediated vasodilation was similar between NCD-fed and HFD-fed control offspring but was markedly reduced in HFD-fed PETN offspring. EDHF genes were downregulated in the vasculature of HFD-fed PETN offspring, which was associated with epigenetic changes in histone modifications. In conclusion, maternal PETN treatment in DSSR shows both beneficial and unfavorable effects. It improves fetal growth and ameliorates glucose tolerance in the offspring. Although maternal PETN treatment has no effect on blood pressure in offspring fed with normal chow or high-salt diet, the offspring is at higher risk to develop HFD-induced hypertension. PETN may potentiate the blood pressure response to HFD by epigenetic modifications of EDHF genes.Key messagesThe core findings of this article suggest that maternal PETN treatment of DSSR, a rat model of a spontaneous superimposed preeclampsia, leads to• Improvement of fetal growth;• No changes of maternal blood pressure or markers of preeclampsia;• Amelioration of HFD-induced glucose intolerance in adult offspring;• No changes in blood pressure development of the offspring on normal chow or high salt-diet;• Potentiation of blood pressure elevation of the offspring on HFD.

Effects of high-fat diet on sympathetic neurotransmission in mesenteric arteries from Dahl salt-sensitive rat.

Obesity hypertension is driven by sympathetic neurotransmission to the heart and blood vessels. We tested the hypothesis that high-fat diet (HFD)-induced hypertension is driven by sympathetic neurotransmission to mesenteric arteries (MA) in male but not female Dahl salt-sensitive (Dahl ss) rat. Rats were fed a control diet (CD; 10 kcal% from fat) or HFD (60 kcal% from fat) beginning at 3 weeks (wk) of age; measurements were made at 10-, 17- and 24-wk. Body weight increased with HFD, age and sex. Mean arterial pressure (MAP) was higher in HFD versus CD rats from both sexes at 17- and 24-wk. MA constriction measured using pressure myography, and electrical field stimulation (EFS, 0.2-30 Hz) was greater in HFD versus CD in males at 17-wk; this was not due to changes in α2 autoreceptor or norepinephrine transporter (NET) function. Prazosin (α1-AR antagonist) and suramin (P2 receptor antagonist) inhibited neurogenic MA constriction equally in all groups. Arterial reactivity to exogenous norepinephrine (NE; 10-8 - 10-5 M) was lower in HFD versus CD at 10-wk in males. Female MA reactivity to exogenous ATP was lower at 24-weeks compared to earlier time points. HFD did not affect tyrosine hydroxylase (TH) or the vesicular nucleotide transporter (VNUT) nerve density in MA from both sexes. NE content was lower in MA but higher in plasma at 24-wk compared to 10- and 17-wk in both sexes. In conclusion, HFD-induced hypertension is not driven by increased sympathetic neurotransmission to MA in male and female Dahl ss rats.

Histone deacetylase inhibitor CG200745 ameliorates high-fat diet-induced hypertension via inhibition of angiotensin II production

Obesity is growing rapidly worldwide due to consumption of westernized diet and lack of exercise. Obesity is one of the major risk factors of hypertension. The novel histone deacetylase (HDAC) inhibitor CG200745 was originally developed to treat various cancers. Previous studies showed that CG200745 attenuated hypertension through inhibition of cardiac hypertrophy and fibrosis in deoxycorticosterone acetate-induced hypertensive rat. The purpose of this study is to investigate the role and underlying mechanism of CG200745 in high-fat diet (HFD)-induced hypertension. Nine-week old C57BL/6 mice were fed a normal diet (ND) or HFD for 17 weeks. Each group of mice was treated with vehicle or CG200745 by intraperitoneal injection for 9 days. HFD group showed higher body weight, blood pressure (BP), HDAC activities, angiotensinogen and renin expressions in kidney, angiotensin-converting enzyme (ACE) expression in the lung, serum angiotensin II (Ang II) concentration, and myosin light chain20 (MLC20) phosphorylation in mesenteric artery compared with ND group. CG200745 lowered BP, HDAC activity, renin and angiotensinogen in the kidney, ACE in the lung, serum Ang II level, and phosphorylation of MLC20 in HFD group. In conclusion, CG200745 ameliorated HFD-induced hypertension through inhibition of HDAC/Ang II/vascular contraction axis. Our results offer CG200745 as a novel therapeutic option for HFD-induced hypertension.

Tipping the scales: Are females more at risk for obesity- and high-fat diet-induced hypertension and vascular dysfunction?

Obesity is a common metabolic disorder that has become a widespread epidemic in several countries. Sex and gender disparities in the prevalence of cardiovascular disease (CVD) have been well documented with premenopausal women having a lower incidence of CVD than age-matched men. However, women are more likely than men to suffer from obesity, which can predispose them to a greater risk of CVD. The mechanisms underlying high-fat diet (HFD)- or obesity-induced hypertension are not well defined, although immune system activation and inflammation have been implicated in several studies. Further, the sex of the subject can have a profound influence on the immune response to hypertensive stimuli. Therefore, the purpose of this review is to examine the effects of sex and gender on the role of the immune system in HFD-induced hypertension and vascular dysfunction. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Targeting on Gut Microbial Metabolite Trimethylamine-N-Oxide and Short-Chain Fatty Acid to Prevent Maternal High-Fructose-Diet-Induced Developmental Programming of Hypertension in Adult Male Offspring.

Alterations of gut metabolites, such as SCFAs and trimethylamine (TMA), and microbial composition are associated with the development of hypertension. Whether maternal 3,3-dimethyl-1-butanol (DMB, an inhibitor for TMA formation) treatment or the predominant SCFA acetate supplementation can prevent programed hypertension induced by a high-fructose diet (HFD) exposure during pregnancy and lactation in adult male offspring is examined. Male offspring are divided into four groups: ND, normal diet; HFD, 60% HFD; ACE, HFD plus 200mmolL-1 magnesium acetate in drinking water; and DMB: HFD plus 1% DMB in drinking water. Maternal HFD induces programed hypertension in adult male offspring, which is prevented by maternal acetate supplementation or DMB treatment. HFD-induced hypertension is relevant to increased plasma levels of TMA and acetate, and alterations of gut microbial composition. The protective effects of acetate supplementation are associated with decreased plasma TMA level and TMA-to-trimethylamine-N-oxide (TMAO) ratio, and increased renal expression of SCFA receptors. Maternal DMB treatment reduces plasma TMA, TMAO, acetate, and propionate levels. Early intervention targeting on gut-microbiota-derived metabolites TMAO and SCFAs to reprogram hypertension may have significant impact to reduce the burden of hypertension.

Sex Differences in Renal Inflammation and Injury in High-Fat Diet-Fed Dahl Salt-Sensitive Rats.

We examined the impact of sex on high-fat diet (HFD)-induced renal alterations in Dahl salt-sensitive and Sprague Dawley rats. In Dahl rats, HFD (60% kcal from fat for 24-26 weeks starting at weaning) significantly and equally increased blood pressure in males and females when compared with rats fed a control diet (10% kcal from fat). Male Dahl rats on HFD exhibited progressive renal histological injury and moderately increased renal macrophage infiltration at 10 and 24 weeks of feeding when compared with males on control diet. Female Dahl rats had lower grade renal injury and less macrophage infiltration (except at 17 weeks) than males regardless of diet. Male Dahl rats on both diets showed progressively increasing numbers of renal T-cells, a pattern not observed in females. HFD per se did not significantly affect renal T-cell number. Male Dahl rats had lower renal regulatory T-cells cell ratio than females at 24 weeks. Renal macrophage and T-cell infiltrations were highly correlated to final mean arterial pressure levels in males but not in females. Sprague Dawley rats fed HFD were normotensive without significant renal injury/inflammation after 24 weeks of feeding. In summary, HFD feeding fails to increase arterial blood pressure in Sprague Dawley rats but strongly promotes hypertension in both male and female Dahl salt-sensitive rats. Only Dahl males, however, exhibited blood pressure-associated renal inflammation and injury. Maintenance of regulatory T-cells ratio may protect against hypertension-associated renal injury/inflammation but not HFD-induced hypertension.

Abstract P162: Adiposity-Induced Hypertension is Associated With Sex-Specific Macrophage Infiltration of Mesenteric Perivascular Adipose Tissue in Dahl S Rats.

Perivascular adipose tissue (PVAT) may be a key player in mediating adiposity-associated hypertension because of its proximity to blood vessels. Although increased immune cell occupancy in adipose tissue is proposed to couple adiposity to hypertension, little is known about PVAT’s immune complement. We hypothesized that an immune complement exists in PVAT that would become pro-inflammatory with adiposity-induced hypertension. Male and female Dahl S rats were fed a regular (10% calories from fat) diet (control) or a high fat (60%) diet (HFD) from weaning through 24 weeks of age. HFD rats demonstrated significantly higher systolic blood pressure [mm Hg; control: 127±7 (M), 145±8 (F); HFD: 168±9 (M), 184±11 (F); tail cuff] and visceral adiposity (micro-CT scans). PVATs from the thoracic aorta (APVAT), mesenteric resistance vessels (MRPVAT), non-PVAT retroperitoneal fat (RP fat) and spleen (positive control) were harvested from each animal. T cells (CD4 and CD8), B cells, macrophages, mast cells and neutrophils in the stromal vascular fraction were quantified using 7-color flow cytometry. The type and number of immune cells are presented as a percentage (%) of total live singlet cells. Each immune cell type is reported as % of total immune cells, and CD4, CD8 cells as % of T cells. The table illustrates significant (P&lt;0.05) differences with HFD vs respective controls. HFD-induced hypertension in Dahl S rats leads to greater macrophage infiltration of MRPVAT and RP fat in females vs males. Further studies are needed to gain mechanistic insights into how macrophage subtypes and their associated cytokines in PVAT may alter vascular tone and blood pressure.

Abstract 653: Placental Growth Factor mediates Splenic Sympathetic Overdrive induced by Obesity and induces hypertension

Obesity is an epidemic condition associated with several cardiovascular comorbidities, as hypertension. Although the molecular mechanisms related to obesity-induced hypertension are not well understood, the sympathetic nervous system (SNS) overactivation typically accompanying obesity has been ascribed as one of the main culprits. Thus far, mechanistic studies focused on the effects of sympathetic overdrive on peripheral resistances. Recent data showing that SNS activation also dictates immune responses involved in hypertension, made us hypothesize whether obesity induced by high fat diet (HFD) could recruit splenic SNS efferent. Thus we subjected WT mice to HFD, as compared to low fat diet (LFD), and monitored the hypertensive response. Blood pressure (BP) started to rise after two months, and hypertensive disease became clearly manifest within 4 months. To gain mechanistic insights responsible for BP increase, we assessed peripheral SNS activation at a time point preceding overt hypertension (i.e. 2 months after HFD). We found elevated circulating noradrenalin levels in HFD mice and, more important, a specific pattern of activated splenic sympathetic overdrive, as recorded by microneurography. WT mice subjected by surgical removal of the left celiac ganglion (CGX) where the splenic nerve originate, before receiving HFD, were protected from hypertension, despite developing obesity the same. The fact that splenectomized mice showed an overlapping response to HFD, supported the conclusion that the sympathetic-immune axis is crucial for HFD-induced hypertension but not for weight regulation. To look for molecular determinants, we analyzed the expression of Placental Growth Factor (PlGF), previously identified as a neuroimmune mediator of other hypertensive challenges. PlGF was significantly overexpressed in the spleen upon HFD, but only when SNS innervation was intact, as CGX mice failed to induce its expression. In the end, PlGF KO mice subjected to HFD, although becoming obese as much as WT did, were protected from hypertension. Overall our results demonstrate that a splenic neuroimmune drive is crucial to allow the onset of hypertensive disease associated with obesity, although having no effect in body weight increase in response to HFD.

Role of the histone deacetylase inhibitor valproic acid in high-fat diet-induced hypertension via inhibition of HDAC1/angiotensin II axis.

Obesity is known as an epidemic worldwide because of consumption of westernized high-fat diets and one of the major risk factors of hypertension. Histone deacetylases (HDACs) control gene expression by regulating histone/non-histone protein deacetylation. HDAC inhibitors exert anti-cancer and anti-inflammatory effects and play a protective role in cardiovascular diseases. In the present study, we tested the effect of an FDA-approved pan-HDAC inhibitor valproic acid (VPA) on high-fat diet (HFD)-induced hypertension in mice. Furthermore, we examined the mechanism of VPA-induced prevention of hypertension. Nine-week-old male C57BL/6 mice were fed either a normal diet (ND) or HFD. When the HFD group reached a pre-hypertensive phase (130-140 mm Hg systolic blood pressure), VPA was administered for 6 days (300 mg kg-1 per day). Body weights and blood pressure (BP), expression of renin-angiotensin system (RAS) components and HDAC1 were determined. The direct role of HDAC1 in the expression of RAS components was investigated using gene silencing. HFD accelerated the increase in body weight from 22.4±1.3 to 31.9±3.0 compared to in the ND group from 22.7±0.9 to 26.0±1.7 (P=0.0134 ND vs HFD), systolic BP from 118.5±5.7 to 145.0±3.0 (P<0.001), and diastolic BP from 91.0±13.6 to 121.0±5.0 (P=0.006); BP was not altered in the ND group. HFD increased RAS components and HDAC1 in the kidneys as well as leptin in the plasma. VPA administration prevented the progression of hypertension and inhibited the increase in expression of HDAC1 and RAS components. VPA did not affect plasma leptin level. Knockdown of HDAC1 in MDCK cells decreased the expression of angiotensinogen and type 1 angiotensin II receptor. VPA prevented HFD-induced hypertension by downregulating angiotensin II and its receptor via inhibition of HDAC1, offering a novel therapeutic option for HFD-induced hypertension.

High fat diet confers vascular hyper-contractility against angiotensin II through upregulation of MLCK and CPI-17.

Obesity is a critical risk factor for the hypertension. Although angiotensin II (Ang II) in obese individuals is known to be upregulated in obesity-induced hypertension, direct evidence that explains the underlying mechanism for increased vascular tone and consequent increase in blood pressure (BP) is largely unknown. The purpose of this study is to investigate the novel mechanism underlying Ang II-induced hyper-contractility and hypertension in obese rats. Eight-week old male Sprague-Dawley rats were fed with 60% fat diet or normal diet for 4 months. Body weight, plasma lipid profile, plasma Ang II level, BP, Ang II-induced vascular contraction, and expression of regulatory proteins modulating vascular contraction with/without Ang II stimulation were measured. As a result, high fat diet (HFD) accelerated age-dependent body weight gaining along with increased plasma Ang II concentration. It also increased BP and Ang II-induced aortic contraction. Basal expression of p-CPI-17 and myosin light chain (MLC) kinase was increased by HFD along with increased phosphorylation of MLC. Ang II-induced phosphorylation of CPI-17 and MLC were also higher in HFD group than control group. In conclusion HFD-induced hypertension is through at least in part by increased vascular contractility via increased expression and activation of contractile proteins and subsequent MLC phosphorylation induced by increased Ang II.

Abstract P188: (Pro)renin Receptor (PRR) Mediates High Fat Diet-induced Hypertension via Upregulation of Epithelial Sodium Channel &amp; Aquaporin-2

We hypothesized that the renal prorenin receptor (PRR) mediates high fat diet (HFD)-induced hypertension via enhancing expression of epithelial sodium channel (α-ENaC) and aquaporin-2 (AQP-2). C57BL/6 mice underwent right nephrectomy (n=12) and allocated to receive regular diet (RD, 12 kcal% fat, n=6) or a high-fat diet (HFD, 45 kcal% fat, n=6) for 10 weeks. HFD group received left renal subcapsular interstitial administration of PRR shRNA (n=3) or vehicle (n=3). BW, food and water intake, BP, UV and UNaV, renal interstitial fluid (RIF) angiotensin II (Ang II), and renal expressions of PRR, α-ENaC, AQP-2 were monitored. At baseline, there were no significant differences in BW, food and water intake, BP, UV or UNaV between different animal groups. At the end of the study, HFD mice had significant increase in food intake, systolic blood pressure (HFD 154.6 ± 2.181 mmHg, vs. RD 112.21 ± 4.684 mmHg, P&lt;0.0.05), BW (HFD 43.2 ± 1.125 gm, vs. RD 31.9 ± 0.89654 gm, P&lt;0.0.05), and significant reduction in UV (HFD 0.16 ± 0.042 ml, vs. RD 0.41 ± 0.061 ml, P&lt;0.0.05) and UNaV (HFD 26.02 ± 3.652 μmol/day vs. RD 46.32 ± 5.236 μmol/day, P&lt;0.0.05). Compared to RD, there were significant increases in mRNA and protein expressions of PRR (64% and 40%, P&lt;0.01), α-ENaC (85% and 75%, P&lt;0.05), AQP-2 (105% and 80%, P&lt;0.05) in HFD alone mice respectively. Compared to HFD alone, HFD+ PRR shRNA treatment caused significant reductions in BP (108 ± 13.88 mmHg vs HFD 154.6 ± 2.181 mmHg), mRNA and protein expressions of PRR (33% and 50%, P&lt;0.01), α-ENaC (49% and 56%, P&lt;0.05), AQP-2 (30% and 29%, P&lt;0.05) respectively. There were no changes in RIF Ang II between different animal groups. We conclude that PRR mediates HFD-induced hypertension via enhancing renal α-ENaC and AQP-2 expression independent of Angiotensin II.

N-HMME Upregulates Lipolytic Proteins in the Liver to Counter NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a comorbidity associated with diet-induced obesity, diabetes, hyperlipidemia and hypertension. While the prevalence of obesity and its causal role in NAFLD continue to rise, currently, there is no strategy to counter NAFLD. It is the most common liver disease associated with chronic obesity and is one of the top concerns for clinicians as it has the potential to advance into hepatic steatosis, steatohepatitis, and cirrhosis of liver. Recent research suggests that transient receptor potential vanilloid 1 (TRPV1), a non-selective Ca2+ channel protein, is implicated in NAFLD. However, the precise mechanism underlying this remains to be elucidated. TRPV1 activation via dietary supplementation of (E)-N-[(4-hydroxy-3-methoxyphenyl) methyl]-8-methylnon-6-enamide (N-HMME; also known as capsaicin) is an emerging strategy to counter NAFLD. Protein assays from liver lysates in dietary induced obesity models indicate that high fat diet (HFD; 60% of total calories) promoted hepatic steatosis. HFD feeding caused increase in liver weight, downregulated the expression of lipolytic genes and increased triglyceride levels in blood. N-HMME supplementation prevented hepatic steatosis by increasing lipolytic genes while decreasing de novo lipogenesis of fatty acids in the liver. N-HMME increased the expression of lipolytic proteins PPARα, PGC-1α and SiRT-1 and suppressed the expression of lipogenic SCD-1 in the liver. N-HMME significantly prevented hepatic steatosis and decreased circulating triglyceride levels in blood. N-HMME supplementation also suppressed HFD-induced hypertension, hyperglycemia and improved blood glucose handling. Further, N-HMME facilitated the activation of SiRT-1 via Ca2+/Calmodulin dependent protein kinase II dependent mechanism and increased the interaction between SiRT-1 and PPARα. However, N-HMME did not prevent NAFLD in mice, which genetically lack the expression of TRPV1. Our data provide evidence for the emergence of N-HMME as a new drug molecule to counter NAFLD and its associated pathologies.