bluuebunny/crossref_metadata_2025 huggingface dataset:
Alpha 2‐Adrenergic Receptor Modulation of Calcium Current is Impaired in Mesenteric Artery Projecting Sympathetic Neurons in DOCA‐Salt Hypertensive Rats
Authors: Mui Ryan , Fernandes Roxanne , Galligan James
Published: June 2021

In sympathetic neurons, activation of the prejunctional alpha 2‐adrenergic receptor (a2‐AR) inhibits nerve terminal N‐type Ca2+ channels and norepinephrine (NE) release onto blood vessels. In rats, a2‐AR dysfunction contributes to DOCA‐salt hypertension; however, the mechanism responsible for a2‐AR dysfunction is unknown. We tested the hypothesis that a2‐AR coupling to inhibition of N‐type Ca2+ channels is disrupted in DOCA‐salt hypertension.

Methods

We used cholera toxin (CTx)‐conjugated Alexafluor 588 to retrogradely label mesenteric artery projecting sympathetic neurons of the celiac ganglion (CG). We used whole‐cell patch clamp to study Ca2+ currents in these neurons. RT‐PCR and immunohistochemistry were used to evaluate a2‐AR subtype expression in CG neurons.

Results

Ca2+ current amplitudes were similar in neurons from normotensive and DOCA‐salt hypertensive rats. The a2‐AR agonists NE and UK14304 decreased calcium currents to a greater degree in normotensive rats than in DOCA‐salt hypertensive rats. The a2‐AR antagonist yohimbine blocked inhibition of Ca2+ currents caused by NE in all neurons. Immunohistochemistry revealed that CG sympathetic neurons express predominantly a2‐AR subtypes 2A and 2C. RT‐PCR revealed that gene expression levels of a2‐AR subtype 2A are comparable in normotensive and DOCA‐salt hypertensive rats.

Conclusions

In DOCA‐salt sensitive hypertension, a2‐AR dysfunction results in impaired modulation of Ca2+ calcium current. This is not due to down regulation of the a2‐AR. Supported by NIH (P01 HL070687).
β3‐ Adrenergic Receptor Activation and Endoplasmic Reticulum Stress via Modulation of Intracellular Free Zn2+in Hyperglycemic Cardiomyocytes
Authors: Turan Belma , Tuncay Erkan , Toy Aysegul , Cicek Figen
Published: June 2021

Beta‐adrenergic receptor (β‐AR)‐signaling plays important role in normal cardiac function while β3‐AR activation depresses cardiac contractile force. Since intracellular free Zn2+releases are originated either from metallothionin‐nitrolisation or endoplasmic reticulum (ER) and disturbing excitation‐contraction cyclying in cardiomyocytes, we examined role of β3‐AR activation on modulation of intracellular free Zn2+and ER stress (ERS) in hyperglycemic cardiomyocytes. Protein and mRNA levels of β3‐AR were increased in diabetic cardiomyocytes being associated with depressed left ventricular developed pressure. β3‐AR stimulation with BRL37344 induced significant increase in intracellular free Zn2+in diabetic cardiomyocytes which was diminished either with NOS inhibitor L‐NAME or β3‐AR antagonist SR59230 while it was further increased with non‐selective β‐blocker nadolol. Additionally, either BRL37344 or NO‐donor SNP induced significant increases in intracellular free Zn2+in normal cardiomyocytes while they were diminished either with L‐NAME or ODQ. These data are strongly demonstrated an association between increased intracellular free Zn2+ and β3‐AR activation in diabetic cardiomyocytes. BRL37344 stimulation of only diabetic cardiomyocytes presented also marked increases in ERS‐associated proteins which are very similar to those of diabetics. Taken together, our data demonstrated that β3‐AR activation in cardiomyocytes under hyperglycemia induces marked increase in intracellular free Zn2+which seems to be closely related with ERS, thereby both actions can underlie the depressed cardiac function in diabetics.

(Supported by TUBITAK‐SBAG‐113S466)
Improvement in cardiac function 1‐week post gastric bypass surgery
Authors: DeVallance Evan , Lee Kyuwan , Grogg Kristen , LeMaster Kent , Hull Robert , Tabone Lawrence , Rosati Kristen , Quinlin Robert , Moore Corey , Brader Alan , Frisbee Jefferson , Chantler Paul
Published: June 2021

Obesity is associated with increases in afterload causing remodeling and alterations in left ventricle (LV) function. This makes obese individuals at a greater risk of developing LV impairments and a higher risk of cardiac events. LV stiffness is common with obesity. This is reflected by hypertrophy in the LV myocardium. Gastric by‐pass an intervention for rapid weight loss is commonly implemented in individuals with obesity. We aimed to evaluate the changes in LV function after gastric bypass surgery via echocardiography. We found a reduction in body weight (pre: 132 ±6 to post: 125 ±5 Kg) and waist circumference (pre: 122 ±5 to post: 112 ± 3cm). These anthropometric changes were accompanied by improvements in LV function. Improvements in pump efficiency are shown by decreases in LV end‐systolic volume (pre: 66 ±4 to post: 55 ±3 mmHg) and LV ejection time (pre: 291 ±10 to post: 211 ± 30ms). Accompanied by an increase in early diastolic annular velocity (e': pre: 0.14 ±0.01 to post: 0.16 ±0.01 p<0.05) and a decrease in LV end diastolic pressure (E/e': pre: 5.9 ±0.7 to post: 4.8 ±0.7 p=0.06) suggesting LV destiffening and improved diastolic function. The significant weight lost after gastric by‐pass surgery causes quick improvement in cardiac function. This may be attributed to the loss of visceral adipose tissue and change in CV risk factors relieving some burden on the heart allowing for more efficient LV work
Evaluation of Cardiac ACE in Rats with Experimental Model of Metabolic Syndrome Induced by Fructose Intake
Authors: Souza Marina , Araujo Iara , Americo Anna , Muller Cynthia , Fiorino Patricia , Farah Vera
Published: June 2021

The high consuming of fructose sugar is a concern for public health, since factors such as cardiovascular diseases, obesity, type‐2 diabetes and metabolic syndrome are related to this new food habits. The Renin‐Angiotensin System (RAS), an endocrine system responsible for regulating blood pressure, is widely studied since its components are sensitive to hyperglycemia and hyperinsulinemia, events that occur in the diet rich in fructose. The aim of the study was to evaluate an important marker of RAS, the angiotensin‐converting enzyme (ACE), in the heart of animals treated with fructose. Weaned Wistar rats were divided into control group (CG) and fructose group (FG, 10% in drinking water) and treated for 8 weeks. FG showed changes in lipid profile when compared to GC, with increased triglycerides (CG=39±3 vs FG=49±2*) and LDL (CG=48±2 vs FG=50±3*) and decreased HDL (CG=35±2 vs FG=24±1*). FG showed lower glucose tolerance than CG on GTT (CG=113±4 vs FG=169±2*), featuring the experimental model. Mean arterial pressure was increased in FG (CG=110±1 vs FG=125±1*)and quantification of ACE showed a significant increase in CG vs. FG (p<0.05), suggesting the increased activation of the RAS in GF than in GC, concluding that chronic ingestion of fructose may induce harmful and important metabolic changes that can lead to serious diseases, such as hypertension and type 2 diabetes. (*p<0,05 vs CG). Support by: PIBIC/Mackenzie
Downregulation of the Vascular Insulin Signaling Pathway may Contribute to Hyperglycemia Following High Fat Intake
Authors: Ricklefs Kristin , Simperova Anna , Reaven Peter , Sweazea Karen
Published: June 2021

Type 2 diabetes (T2D) prevalence worldwide has increased markedly and is a major threat to global health. Insulin resistance is a key factor in the pathogenesis of T2D. Prior studies in our laboratory have shown that feeding rats a high fat diet (HFD) for 6 weeks results in increased adiposity, hyperglycemia, insulin resistance, and impaired nitric oxide (NO)‐dependent vasodilation of small resistance arteries, all major risk factors for T2D and CVD. While HFD induced insulin resistance is well‐characterized in skeletal muscle, the impacts of HFD on insulin‐mediated vasodilation is less understood. We hypothesized that feeding adult male Sprague‐Dawley rats a HFD (60% kcal from fat) for 6 weeks would downregulate the insulin‐mediated vasodilatory pathway (i.e., IRS‐1, PI3K, Akt, and eNOS) in comparison to chow‐fed controls. Western blot analyses of isolated aorta indicate that protein expression of IRS‐1, p‐PI3K(p85), total Akt, p‐Akt(t308), and p‐Akt (s473) were not significantly affected by HFD. In contrast, p‐IRS‐1 expression was modestly but not significantly (p=0.089) decreased. The expression of p‐PI3K(p55) and p‐eNOS were significantly diminished (p=0.045 and p=0.032, respectively) in HFD aortas compared to chow‐fed controls. These results suggest that endothelial dysfunction and hyperglycemia observed in rats fed a HFD may be attributed in part to reduced expression of vascular insulin signaling pathway intermediates resulting in reduced blood flow and glucose delivery. This study was funded in part by the Graduate and Professional Student Association, ASU.
Acute IP Phlorizin Normalizes Cortical PO2 But Causes Medullary Hypoxia in The Diabetic Rat Kidney
Authors: O Neill Julie , Patinha Daniela , Fasching Angelica , Pihl Liselotte , Franzen Stephanie , Palm Fredrik
Published: June 2021

Diabetic nephropathy is characterized by glomerular hyperfiltration and reduced renal cortical oxygen tension (CPO2). Recent, observations indicate that increased tubular sodium glucose linked transport (SGLT) plays a role in the development of hyperfiltration in diabetic mice (Sällstrom et al 2014). The aim of the current study was to determine how inhibition of SGLT impacts upon renal tissue PO2 in the diabetic rat kidney.

Diabetes was induced by intraperitoneal (IP) STZ (50mg/kg) injection in Sprague Dawley rats (n=9), 2 weeks prior to experimentation. Animals were surgically prepared for intravenous infusion of [3H]Inulin and [14C]PAH, the IP delivery of Phlorizin (sodium‐glucose transport inhibitor; 200mg/Kg) and the measurement of mean arterial pressure (MAP), left kidney function, CPO2 and medullary (M) PO2 (Clark electrode). Data± SEM was analyzed using a two‐way RM ANOVA. Baseline MAP, urinary glucose excretion (UGE) fractional sodium excretion (FENa), CPO2 and MPO2 was 118±2 mmHg, 0.26±0.07 mg/min, 0.09±0.03%, 36±1 mmHg and 27±2 mmHg respectively. IP Phlorizin had no effect on MAP but significantly increased UGE, FENa and CPO2 to 0.6±0.2 mg/min, 0.6±0.1 % and 49±1 mmHg respectively and reduced MPO2 to 23±1mmHg (all P<0.05).

SGLT inhibition normalizes CPO2, which implies that increased proximal tubule transport contributes to the development of hypoxia in the diabetic kidney. However,SGLT inhibition reduced oxygen availability in the medulla. This may result from the diversion of sodium reabsorption to more distal nephron segments within the medulla, where sodium transport requires more oxygen consumption.
SGLT2 Inhibition Is Predicted to Increase NaCl Delivery to the Medullary Thick Ascending Limb But Not to Significantly Elevate Its Oxygen Consumption
Authors: Edwards Aurelie , Vallon Volker , Layton Anita
Published: June 2021

The objective of this study was to investigate how changes in sodium reabsorption in the proximal tubule affect oxygen (O2) consumption and the metabolic efficiency of the nephron. To do so, we developed a detailed mathematical model of solute transport in a short‐loop nephron of the rat kidney. Glucose is reabsorbed via sodium‐glucose cotransporters (SGLTs) in the proximal tubule, which primarily expresses the isoforms SGLT2 in S1‐S2 and SGLT1 in S3. We used the model to investigate the effect of inhibiting SGLT2, a novel treatment for reducing proximal tubule glucose uptake in diabetes, on renal Na+ transport (TNa) and renal oxygen consumption (QO2). Inhibiting SGLT2 shifts Na+ transport to downstream nephron segments, possibly increasing their QO2. Of particular concern are the S3 segment and medullary thick ascending limb (mTAL), which are at risk for hypoxic injury. Dual SGLT2‐SGLT1 inhibition protects the S3 segment, but could further reduce mTAL oxygenation. Model simulations suggest that SGLT2 inhibition substantially increases S3 TNa and QO2. In contrast, mTAL TNa and QO2 is insensitive to SGLT inhibition and the resulting increase in Na+ load, because under physiological conditions luminal [Na+] is sufficiently high that the Na+/K+‐ATPase pump is nearly carrier‐saturated. We also used the model to determine the optimal combination of SGLT1 and SGLT2 inhibition, in terms of suppressing tubular glucose uptake and maintaining a sufficiently low S3 QO2. This research was supported in part by NIH grants DK‐89066 and DK‐56248.
Renal Structure‐Function Relationship in the Obese ZSF1 Rat Model of Diabetic Nephropathy
Authors: Kuo Jay , Lee Chung Wein , Qian Hu Sheng , Fryer Ryan
Published: June 2021

Although the obese ZSF1 rat is a preclinical model of type 2 diabetic nephropathy (DN) with marked renal dysfunction and structural derangement, the course of disease progression has not been evaluated in an age‐dependent manner. This study characterizes temporal changes in renal function relative to changes in proteinuria and glomerular and tubulointerstitial structure to further understand renal disease progression in this model.

Male obese ZSF1 rats were aged to 20, 25, 30, 35, or 40 weeks of age. At those times, proteinuria (UPCR) and GFR (anesthetized, FITC‐inulin, kidney weight (KW) normalized) were measured. The left kidney was processed for histopathological analyses of glomerular lesions (% glomerulosclerosis) and tubulointerstitial damage (foci number, interstitial collagen, a‐SMA, KIM‐1, ED‐1+).

GFR was steady from 20 to 30 weeks of age (avg 0.71±0.06 mL/min/g KW). At 35 and 40 weeks, GFR declined markedly to 0.29±0.11 and 0.23±0.05 mL/min/g KW, respectively. Glomerulosclerosis increased steadily from 12±1% at 20 weeks to 71±2% by 40 weeks as did UPCR, glomerular lesion severity score, interstitial lesions, a‐SMA, and ED‐1. Interstitial collagen increased modestly from 20 weeks (1.3±0.2%) to 30 weeks (3.7±0.3%) and markedly increased at 35 and 40 weeks, to 8.3±0.6% and 13.3±0.9%, respectively. KIM‐1 increased to 30 weeks (7.5±0.6%) then declined at 40 weeks.

In aging obese ZSF1 rats, increased UPCR and glomerulosclerosis occurred prior to the decline in GFR and further increased as GFR fell. The decreased GFR also corresponded with a marked increase in tubulointerstitial fibrosis and injury. These results, consistent with observations in human DN, also support the obese ZSF1 rat as a relevant preclinical model of DN.
Interaction of Hypertension and Diabetes in Progressive Nephropathy: Role of ER Stress
Authors: Wang Zhen , do Carmo Jussara , Williams Jan , da Silva Alexandre , Hall John
Published: June 2021

To investigate the mechanisms by which hypertension (HT) and diabetes interact to promote nephropathy, 6 month‐old male Goto‐Kakizaki (GK) rats, a model of spontaneous type 2 diabetes, were used in this study. HT was induced by aorta coarctation (AC) between the renal arteries to produce HT plus diabetes in the right kidney (above AC) and normal blood pressure (BP) plus diabetes in the left kidney (below AC). Eight weeks after AC, BP above the AC and urinary albumin excretion (UAE) were significantly increased from baseline (BP: 155±4 vs 108±2 mmHg; UAE: 39.2±14.8 vs 0.9±0.7 mg/24h, n=6, p<0.05). We also observed 17% and 15% increase in protein expression of endoplasmic reticulum (ER) stress markers CHOP and GRP 78 in the HT‐diabetic right kidney compared to the normotensive‐diabetic left kidney. To examine the role of ER stress in development of nephropathy, GK‐AC rats were treated with ER stress inhibitor, tauroursodeoxycholic acid (TUDCA, 200 mg/kg/day IP), from 2 to 8 wks after AC. After 6 wks of treatment, GRP‐78 expression was significantly reduced in the right HT kidney compared to untreated rats. TUDCA treatment lowered BP above the AC (135±4 vs 155±4 mmHg, n=7, p<0.05 compared to untreated group). Also, when comparing right kidneys between treated and untreated GK‐AC rats, TUDCA increased glomerular filtration rate (0.9±0.1 vs 0.6±0.1ml/min/g of kidney weight, n=6, p<0.05) and decreased UAE (5.6±1.5 vs 18.4±5.8 ug/min, n=4‐6, p<0.05). These results suggest that ER stress contributes to kidney injury when HT is superimposed on diabetes. Pharmacological inhibition of ER stress may attenuate increases in BP and kidney injury in hypertensive‐diabetic nephropathy. (NHLBI PO1HL51971, NIGMS P20GM104357, AHA 14POST18160019)
Resveratrol Treatment Reverses Mild Angiotensin II‐Induced Hypertension, but Not by Increased Natriuresis
Authors: Gordish Kevin , Beierwaltes William
Published: June 2021

Resveratrol is a phenol that reduces blood pressure in animal models of hypertension, but a mechanism is unknown. We reported resveratrol is a renal vasodilator that increases nitric oxide bioavailability, and increases sodium excretion independent of its hemodynamic effects. Angiotensin II (AngII), a potent vasoconstrictor, also induces sodium retention. We hypothesized chronic resveratrol treatment may blunt AngII‐induced hypertension by its natriuretic effects. We infused male Sprague Dawley rats with vehicle or 80 μg AngII/day via osmotic minipumps over 4 weeks. Vehicle or AngII infused rats were individually housed, pair fed and placed on a diet of normal chow or chow plus 146 mg resveratrol/day. Groups included: 1) Control, 2) Resveratrol‐fed, 3) AngII‐treated, and 4) AngII plus Resveratrol. Systolic blood pressure (sBP) was measured by tail cuff plethsmography. During the 4th week rats were placed in metabolic caging for urine collection. AngII increased sBP in the first week by +14 ±5 mmHg (p<0.05) in group 3 and +10 ±3 mmHg (p<0.05) in the group 4, respectively. sBP was unchanged in groups 1 and 2. After 4 weeks, sBP remained elevated in group 3 rats with AngII, (+9 ±3 mmHg, p<0.05), but in group 4 with AngII plus Resveratrol, sBP was no longer elevated (+2 ±2 mmHg). We found no significant differences between groups in urine volume, sodium excretion or 7 day cumulative sodium balance (18.49 ±0.12, 17.75 ±0.16, 17.97±0.17, 18.46±0.18 mEq Na+/7 days in groups 1‐4 respectively). We conclude resveratrol did not blunt the initial pressor effect of Ang II, but sustained resveratrol ingestion reversed mild Ang II‐induced hypertension. The mechanism is not due to changes in sodium balance or volume status, and remains undefined.
Flow‐Stimulated NO Production is Altered in Thick Ascending Limbs of Dahl Salt‐Sensitive Rats Fed Either normal or High‐Salt Diets
Authors: Gonzalez‐Vicente Agustin , Hong Nancy , Garvin Jeffrey
Published: June 2021

Thick ascending limbs (TALs) of the loop of Henle reabsorb 30% of the filtered NaCl, regulating extracellular fluid volume and electrolyte excretion, thereby affecting blood pressure. NO produced by NO synthase 3 (NOS3) inhibits NaCl transport by TALs and luminal flow increases NO production. Reductions in TAL NO are associated with salt‐sensitive hypertension. In TALs of Sprague‐Dawley rats, dietary salt increases NOS3 expression by day 7, and animals don't become hypertensive. We hypothesized that Dahl salt‐sensitive rat (SS) TALs produce less NO in response to luminal flow than those from Dahl‐salt resistant rats (SR) due to altered NOS3 expression. We used SS or SR fed either normal or high‐salt diets for 7 days. We measured flow‐induced NO in isolated perfused TALs and performed Western blots of renal medullary lysates. On normal‐salt, flow‐induced NO was 32 ± 2 AFU/min in SR TALs and 12 ± 2 AFU/min in SS TALs (Δ 267 ± 63 %; p<0.03; n=6). In the presence of the superoxide (O2‐)scavenger TEMPOL, flow‐induced NO was 35 ± 5 AFU/min in SR TALs and 19 ± 2 AFU/min (p<0.05; n=9) in SS TALs, indicating that NO scavenging by O2‐ plays a minor role in this difference. NOS3 expression was not different between strains fed normal salt. When animals were given a high‐salt diet, flow‐induced NO was 44 ± 10 AFU/min (n = 11) in SR TALs and 9 ± 2 AFU/min (n=8) in SS TALs (Δ 389 ± 110 %; p<0.01). NOS3 expression was 69 ± 15 % (p<0.02; n=5) higher in TALs from SR compared to SS. We conclude that on a normal‐salt diet SR TALs produce more NO in response to luminal flow than those from SS, and that factors other than NOS3 expression or increased O2‐ are involved. On a high‐salt diet NO production is further affected in SS TALs by differences in NOS3 expression.
Effects of Combined Endothelin A Receptor and Renin‐Angiotensin System Blockade on The Regression of Chronic Kidney Disease in 5/6 Nephrectomized Ren‐2 Transgenic Rats
Authors: Sedlakova Lenka , Kopkan Libor , Cervenka Ludek
Published: June 2021

Study objective

We tested the hypothesis where the combined renin‐angiotensin system (RAS) and endothelin 1 (ETA) receptor blockade could be more effective in the slowing of progression of CKD with already established sings of renal injury than antihypertensive treatment based on isolated RAS inhibition in 5/6 nephrectomized (NX) Ren‐2 transgenic hypertensive rats (TGR).

Methods

In five groups of male rats: sham‐operated TGR; untreated 5/6 NX TGR; 5/6 NX TGR with dual RAS blockade (trandolapril 6 mg/L and losartan 100 mg/L); 5/6 NX TGR with combined treatment with RAS and ETA receptor blockade (atrasentan 5 mg/kg/day). 5/6 NX was done in age of 6 weeks and the treatments were initiated 6 weeks after 5/6 NX. Rats were placed into metabolic cages to determine albuminuria at weeks 6, 8, 12, 16, 20, 30. In other groups, concentrations of ANG II and ET1 were evaluated in the kidneys after 2 weeks of treatments.

Results

Mortality of untreated 5/6 NX TGR was 100% at 17th week compared to sham‐operated rats with mortality 0% to 30th week. Mortality of 5/6 NX TGR with RAS blockade was 32 % and in group with RAS and ETA receptor blockade 37 % at the end of 30th week. In 5/6 NX TGR, both treatments reduced enhanced albuminuria, plasma and kidney ANG II and cortical ET 1 concentrations similarly.

Conclusion

There is no additive effect of combined ETA receptor and RAS blockade on the regression of CKD in 5/6 NX TGR most likely due to efficient reduction of ET 1in the renal cortex by the dual RAS inhibition.
Stretch Increases Intracellular Calcium More in Dahl‐Salt‐Sensitive than Salt‐Resistant Rat Thick Ascending Limbs
Authors: Cabral Pablo , Gonzalez‐Vicente Agustin , Garvin Jeffrey
Published: June 2021

The thick ascending limb (TAL) reabsorbs 30 % of the filtered NaCl. It plays a pivotal role in the regulation of salt homeostasis and abnormal reabsorption of NaCl in this segment causes salt‐sensitive hypertension. We have shown that flow‐induced stretch stimulates superoxide production. Cellular stretch increases intracellular calcium (Cai) in other cells and Dahl salt‐sensitive rat (SS) TALs produce more superoxide than those from salt‐resistant rats (SR). Thus we hypothesized that mechanical stretch of SS TALs induces greater increases in Cai than in SR TALs. We measured Cai using the ratiometric calcium‐sensitive dye Fura‐2 in isolated, perfused rat TALs. Stretching cells increased Cai by 243 ± 51 nM in SS TALs (n=9; p<0.0008 vs. no stretch conditions) and by 124 ± 27 nM in SR TALs (n=10; p<0.0005 vs no stretch conditions). The rise in Cai caused by increasing cellular stretch was significantly higher in the SS group (p<0.05 vs SR). When these animals were fed a high‐salt diet (4% NaCl) similar responses were obtained. Cellular stretch increased Cai by 236 ± 58 nM in SS TALs (n=7; p<0.004 vs no stretch conditions) and by 92 ± 15 nM in SR TALs (n=6; p<0.0008 vs no stretch conditions). We have previously reported that the mechanosensitive Transient Receptor Potential Vanilloid 4 (TRPV4) is responsible for flow‐induced increases in Cai. Thus we next tested whether TRPV4 expression was different between strains. TRPV4 was similarly expressed in TALs lysates from SS and SR that were fed either a control standard or a high‐salt diet. We conclude that SS TALs are more sensitive to increases in cellular stretch than SR TALs and that the difference is not due to TRPV4 expression.
Protective Function of Guava (Psidium guajava) Juice Combined with Trehalose in Kidney and Pancreas in Type 2 Diabetic Rats
Authors: Kuo Yen‐Ting , Chien Chiang‐Ting
Published: June 2021

Type II diabetes (T2DM) is one of the most epidemic metabolic syndrome. Guava (Psidium guajava) has been reported anti‐oxidant, anti‐inflammatory, and anti‐diabetic ability in type I diabetic rats. To further improve the metabolic parameters, we added trehalose, which can reduce apoptosis, endoplasmic reticulum stress and oxidative stress. The present study was designed to explore the protective mechanisms of guava juice combination with trehalose in the T2DM rats.

T2DM was induced in female Wistar rats by intraperitoneal nicotinamide and streptozotocin combined with high fructose diets. After successfully diabetic induction, the rats were divided into control, T2DM, T2DM with 4 ml/kg guava + trehalose (T1), 8 ml/kg guava plus trehalose (T2), 20 ml/kg guava plus trehalose (T5) or 4 ml/kg guava juice (B1) for 4 weeks. We explored the protective mechanisms by a chemiluminescence‐amplification method, immunohistochemistry, fluorescent stain and western blot.

The level of fasting blood glucose, OGTT and HbA1C was significantly elevated in T2DM compared to control rats. The insulin level measured by area under curve was significantly higher in the T5 compared to T2DM rats. The level of serum and renal reactive oxygen species, 3‐nitrotyrosine‐related oxidative stress, caspase‐3‐mediated apoptosis, IL‐1β‐mediated pyroptosis was significantly higher in T2DM rats vs control rats. These oxidative parameters were significantly depressed in the groups of B1, T1, T2 and T5. Our data showed that guava juice with trehalose in T1, T2, T5 rats had less oxidative damage in the kidney and pancreas compared to B1 rats.

The combination of guava juice and trehalose protects pancreas and kidney against hyperglycemia‐induced inflammation and oxidative injury.
Perinatal taurine supplementation followed by a high sugar diet after weaning alters renal function in adult rats via renin‐angiotensin system
Authors: Roysommuti Sanya , Lerdweeraphon Wichaporn , Wyss James
Published: June 2021

This study tests the hypothesis that perinatal taurine supplementation alters adult renal function via the renin‐angiotensin system (RAS). Female Sprague‐Dawley rats were fed normal rat chow and water alone (C) or water containing 3 % taurine (taurine supplementation, TS) from conception until weaning. Then, they received normal rat chow and tap water with (CG, TSG) or without (CW, TSW) 5 % glucose. At 7‐8 weeks of age, renal function at rest and after acute saline load (5 % of body weight) was tested in conscious, restrained female rats with or without an angiotensin converting enzyme inhibitor captopril treatment. Body weight, heart weight, kidney weight, mean arterial pressure, and heart rate were not significantly different among the eight groups. Although effective renal blood flow did not significantly differ among the groups, TSG displayed higher renal vascular resistance compared to CW, CG, and TSW groups. Further, this TSG's renal vascular resistance was normalized by captopril treatment. Captopril treatment did not alter glomerular filtration rate or sodium and water excretion in the groups. Changes in filtration fractions were similar among the eight groups. Compared to its effect in CW, saline load significantly depressed fractional water excretion in CG and TSW and fractional sodium excretion in CG, TSW, and TSG. These differences were abolished by captopril treatment. The present study indicates that in adult female rats, perinatal taurine supplementation, particularly followed by a high sugar diet after weaning, alters renal excretory function via the RAS.
Differential Effects of Sex Steroids on mRNA Expression of Renal Sodium Transporters in Mice
Authors: Fan Liming , Curtis Kathleen , Toal Sheri , Kudo Lucia , Rouch Al
Published: June 2021

Sex steroids play key roles in regulating blood pressure but their impact on renal handling of sodium is unclear. Using real‐time qt‐RT‐PCR, we investigated effects of estrogen and testosterone on the expression of renal sodium transporters in CD‐1 mice consuming 1% and 4% salt diets. Six groups (n=4) included intact female and male mice (IF & IM), ovariectomized (O) and castrated (C) mice with a placebo pellet (OP & CP), and O & C mice with a 1.5 mg estrogen or 2.5 mg testosterone pellet, respectively (OE & CT). Mice at 3 weeks old and pellets came from Harlan, Inc. and Innovative Research of America, respectively. Three days after pellet implantation, mice consumed ad libitum 1% salt diet for ten days. Four mice in each group were killed, kidneys removed, RNA extracted from 10 mg mid‐cortical sections, 1st‐strand cDNA synthesized followed by qt‐RT‐PCR using Sybr‐green and custom PCR arrays designed by Qiagen with primers of the following: NCC, NKCC, NHE2 & 3, ENaC a, b, and g, and angiotension type II receptor I (AgII‐I). Surviving mice consumed 4% salt diet for the next ten days and procedures were repeated. After the 1% salt period, we measured higher expression of AgII‐I, ENaC (a, b, g), NKCC, NCC, NHE2 & 3 from IF mice compared to IM mice (p<0.01 – 0.001), and higher expression of NCC and NHE2 in OE compared to OP (p<0.05 – 0.01). After the 4% salt period, expression of AgII‐I, ENaC (a, b, g), NKCC, NCC, NHE2 & 3 was higher in IM mice compared to the IM‐1% salt diet group (p<0.05‐0.001) with no differences between the IF 1% & IF 4% groups. Results indicate putative sex differences in the renal handling of sodium which could contribute to blood pressure regulation. Research supported by Oklahoma INBRE 8P20GM103447.
Sex Differences in Renal Inner Medullary ET‐1 Gene Expression Levels with Increasing Medullary Osmolality
Authors: Gohar Eman , Speed Joshua , Pollock David
Published: June 2021

We previously reported that exposing the renal medulla to hyperosmotic solutions enhances urinary ET‐1 excretion in male rats. We have also seen that female rats have a more robust renal ET‐1 natriuretic capacity compared to males. Therefore, we determined whether intramedullary infusion of hyperosmotic saline has a differential effect on ET‐1 gene expression in inner medullas from anesthetized male and female rats. Isosmotic saline (284 mosmol/kgH2O) was infused into the renal medullary interstitium (500 μl/h) during a 60 min equilibration period and 30 min baseline urine collection period, followed by isosmotic or hyperosmotic saline (1800 mosmol/kgH2O) for two further 30 min periods. At the end of each experiment, the renal inner medulla was isolated for ET‐1 mRNA assessment using the real‐time quantitative polymerase chain reaction (RT‐PCR) technique. Compared with isosmotic saline, hyperosmotic saline infused in the renal medulla caused significant increases in urine flow in both male and female rats (from 6.3±0.9 to 12.2±1.7 and from 8.2±1.3 to 15.0±2.8 μl/min, respectively). Sodium excretion was also significantly enhanced, in both males and females (from 0.6±0.1 to 8.3±1.9 and from 0.9±0.2 to 5.8±1.0 μl/min, respectively). Inner medullary ET‐1 expression in male rats was significantly increased after 60 min of medullary interstitial infusion of hyperosmotic saline (from 1.0± 0.1 to 1.4± 0.1 fold change, p<0.05). In contrast, ET‐1 expression did not change with medullary hyperosmotic infusion in females. These data indicate that an increase in renal inner medullary ET‐1 could play a more important role in the diuretic and natriuretic response to intramedullary hyperosmolality in male compared to female rats.
Postmenopausal Hypertension Is Blunted Following Chronic Flutamide Treatment in Intrauterine Growth Restricted Female Rat
Authors: Dasinger John Henry , Intapad Suttira , Rudsenske Benjamin , Carter Anthony , Alexander Barbara
Published: June 2021

Intrauterine growth restriction (IUGR) programs the development of hypertension associated with increased adiposity and accelerated reproductive senescence by 12 months of age in female IUGR rats. At 12 months of age the estradiol (E) to testosterone (T) ratio is shifted with E levels remaining similar whereas T levels are increased in female IUGR relative to control. Postmenopausal women have a higher prevalence of hypertension associated with increased adiposity. In addition, blood pressure (BP) is increased in association with increased serum T in postmenopausal women. Thus, we tested the hypothesis that chronic blockade of the androgen receptor would attenuate hypertension in female IUGR rats at 12 months of age. Rats were treated with flutamide (8mg/kg/day), an androgen receptor antagonist, or vehicle subcutaneously for two weeks. BP was measured in conscious, chronically catheterized rats. T levels were measured via radioimmunoassay. BP was increased in IUGR relative to control at 12 months of age (Δ15 mmHg, P<0.05); T levels were also elevated in IUGR vs. control (45.33±3.48 vs. 37.56 ±1.72 pg/ml; P<0.05). Flutamide decreased BP in IUGR relative to untreated IUGR (Δ7 mmHg) with no impact in control (Δ0 mmHg). Flutamide did not alter fat mass. Thus, these data indicate that T contributes to the etiology of hypertension that develops with age following IUGR in the female rat. NIH: HL074927, HL51971, P20GM104357, AHA GRNT19900004
Effect of Water and/or Food Deprivation on Renal Function
Authors: Pessoa Thaissa , Malnic Gerhard
Published: June 2021

Acute water (WD) and/or food (FD) deprivation can occur in a variety of situations, eg. natural disasters. The knowledge of these conditions is important to improve therapies, thus the aim of the present work was to determine the effect of 24 hours WD, FD or both on renal function.

Animals kept in WD presented body weight reduction and total plasma protein, hematocrit and plasma sodium increase (vs CTRL), indicating that WD causes a significant decrease in plasma volume. Animals kept in WD + FD presented no changes in all these parameters, indicating that FD has an important role in the ability to maintain plasma volume during WD. Besides, WD, FD and WD + FD decreased glomerular filtration rate (vs CTRL) but FD had the strongest effect. These results show that food intake is an important element related to glomerular control and may modify the vascular tone that can be involved with the ability to maintain plasma volume during WD.

Although Na+ intake (NaI) in WD was 37% smaller, urinary Na+ excretion (UNa) had not changed (vs CTRL), showing that WD animals were in a negative Na+ balance. Besides, WD animals showed a high positive correlation between NaI, UNa and urine flow (UF), i.e. the volume of urine was higher, as urinary Na+ excretion increased and this last was higher, as NaI increased. These results show that in WD the ability to retain volume is influenced by NaI.

Surprisingly, animals kept in WD + FD presented the same UF as animals in WD, although UNa decreased by 79% (vs WD) and they ingested no Na+. Besides, although in FD the UNa had decreased by 75% (vs CTRL), FD animals presented marked diuresis (UF increased 47% vs CTRL). These results show that FD modulates water excretion independently of UNa. This mechanism may influence the renal ability to retain volume when animals are kept in WD + FD.

Financial support: FAPESP; CNPq
Contribution of Brain Gαq and Gα12 Protein Pathways in Mediating Angiotensin II (Ang II) Dependent Hypertension
Authors: Gao Juan , Kapusta Daniel
Published: June 2021

Our previous studies demonstrated that down‐regulation of brain Gα12 proteins blunted Ang II‐induced hypertension in rats. In this study, we examined whether brain Gαq proteins also contribute to Ang II‐dependent hypertension and whether the combined down‐regulation of brain Gαq and Gα12 proteins further attenuates the increase in blood pressure (BP) to Ang II. Methods: Sprague Dawley rats were implanted with telemetry transmitters for measurement of BP. After 3 days of baseline BP recording, rats were distributed into 3 groups (n=6/group) for i.c.v. infusion (mini‐osmotic pump) of scrambled (SCR) oligodeoxynucleotide (ODN; 50 µg/day), Gαq ODN (50 µg/day), or Gαq ODN + Gα12 ODN (50 µg/day each). Each group also received subcutaneous mini‐osmotic pump Ang II infusion (350 ng/kg/min). BP recording was then performed daily for 14 days. Results: After 7 days of Ang II treatment, Gαq ODN infusion decreased mean blood pressure (MBP) compared to that of SCR ODN (day 7, 151±7 vs 170±10 mmHg), and i.c.v. Gαq ODN + Gα12 ODN infusion reduced MBP further (133±4 mmHg, n=6). At day 14, there was no significant difference in MAP between Ang II + Gαq ODN and Ang II + SCR ODN (163±8 vs 176±12 mmHg), but there remained a significant decrease in MBP in the Gαq ODN + Gα12 ODN group (142±6 mmHg).

Conclusions

These findings demonstrate that brain Gαq protein pathways mediate the early phase increase in BP produced by systemic administration of Ang II, whereas brain Gα12 pathways supersede in the late phase. Therapeutically, these findings also demonstrate that down‐regulation of both brain Gαq and Gα12 protein pathways is necessary to maximally attenuate Ang II‐dependent hypertension. AHA 14POST20450173 to JG; 12GRNT12060613 and P20 GM103514 to DRK
The Succinate Receptor 1 is a Physiological Regulator of the Renin‐Angiontensin Aldosterone System
Authors: Carmone Claudia , Robben Joris , Ariza Ana , Bekkenkamp Melissa , Kurstjens Steef , Devuyst Olivier , Deen Peter
Published: June 2021

It has been shown that oxidative cell stress in diabetes type I (DMI) induces tubular release of mitochondrial succinate and that subsequent activation of the SUCNR1 in the juxta‐glomerular apparatus is needed for renin release and DMI‐induced hypertension. Here, we tested whether the SUCNR1 also has a physiological role in renal water and electrolyte handling.

Blood and urine analysis of wild‐type and SUCNR1‐/‐ mice showed that loss of SUCNR1 increased sodium and albumin excretion, and reduced renal renin and plasma angiotensin II (AngII) levels. Immunoblotting revealed decreased proximal tubular and inversely related medullary abundance of sodium‐hydrogen exchanger (NHE)‐3, and decreased abundance of the epithelial sodium channel ENaC. Nitric Oxide (NO) release, and fractional excretion of urea and water were increased, coinciding with reduced AQP2 abundance. With an unchanged overall morphology, wet, but not dry, weights of kidneys of SUCNR1‐/‐ mice were significantly higher than of wild‐type littermates.

Our data reveal that the SUCNR1 is essential for the physiological maintenance of renin and AngII levels, and proper proximal tubule and collecting duct sodium reabsorption. Albumin release may be secondary to the decreased cortical NHE3 expression in proximal tubules, due to reduced AngII levels. Increased NO may underlie water loss.The increased wet kidney mass is likely due to tubular dilation due to increased tubular pressure because of life‐long diuresis. Our data thus indicate that the mammalian SUCNR1 is a physiological regulator of water and volume homeostasis.
Dynamic Response to Long‐Term Sodium Loading and Restriction
Authors: Karaaslan Fatih , Hester Robert
Published: June 2021

Plasma sodium concentration is controlled within very narrow limits. During changes in sodium intake, plasma sodium concentration deviates minimally from its normal value. Sodium intake was increased from a normal to a high level (208 % of normal) for 5 days and then dropped to a low level (13% of normal) for subsequent 5 days in He et al's experimental study (Hypertension.38:321‐325, 2001). Plasma renin, aldosterone and sodium concentrations were measured. He et al. reported decreases in renin and aldosterone concentrations and a small increase in plasma sodium concentration during sodium loading. During the subsequent 5 days of sodium intake decrease, there was an increase in plasma renin and aldosterone concentrations and a small decrease in plasma sodium concentration. The mathematical model we developed was tested with He et al.'s experimental findings in our previous study. And it was shown that the model gave similar results to the experimental work. In this study, to analyze the response dynamics in detail, the rate of change (derivative) of plasma renin, aldosterone and sodium concentrations during sodium loading and restriction were calculated by using the same model. According to the model, the maximum value of the rate of change of plasma renin, aldosterone and sodium concentrations during sodium restriction is larger than during the sodium loading condition. The possible reason of this simulation result is that the absolute change in the sodium intake from a high level to a low level is larger than the change in the sodium intake from a normal to a high level during sodium loading in the model.
Gender‐Specific Multidrug‐Resistance Transporter Expression in Choroid Plexus
Authors: Flores Katiria , Renfro J Larry , Manautou Jose
Published: June 2021

Multidrug efflux transporters of the ATP‐Binding cassette (ABC) family, ABCC1 (Mrp1) and ABCC4 (Mrp4) located on the basolateral membrane of the CP, play important roles in clearing the brain of unwanted substances and protecting it from potentially harmful material in the circulation. Previous research has shown gender‐specific patterns and compensatory responses in liver and kidney. However, little is known about the gender differences and their function in brain. In the present study we examine Mrp1 and Mrp4 mRNA expression in CP using a Mrp4 knockout mouse (Mrp4‐/‐) model and also investigate whether Abcc transporters are expressed in a gender dependent pattern as in kidney and liver. We hypothesized that the female predominant Mrp1 and Mrp4 expression will remain in CP and that in the absence of Mrp4, the activity of Mrp1 will increase. qPCR and immunoblot analysis showed that Mrp4 mRNA and protein are expressed at much higher levels in the female than in male CP. Immunoblot analysis on CP of Mrp4‐/‐ mice showed higher protein expression of Mrp1 in males supporting our hypothesis that the activity of the Mrp1 would increase. Abcc transporters share a wide variety of substrates: therefore, compensation by Mrp1 in the absence of Mrp4 and gender divergent transporter expression could manifest in differential disposition of endogenous substrates, toxicants, and therapeutic drugs, from the CSF to the blood. These sex‐specific differences in the CP highlight the need to evaluate sex differences in neurological disorders, especially those that differ in prevalence and symptoms between men and women.
Tight Junction Elaboration Aids Hypersaline Secretion in Euryhaline Teleost Fish
Authors: Marshall William , Zaparilla Gabriella , Robertson George , Cozzi Regina
Published: June 2021

We examined how the Na+ conductive paracellular pathway between ionocytes and accessory cells is modified in hypersaline conditions to allow Na+ secretion in extreme environments. Mummichogs (Fundulus heteroclitus) were acclimated to seawater (SW) or hypersaline conditions (2SW, 64 ‰) for 30 days. In 2SW fish, invasive cellular projections of accessory cells with increased area of simple tight junctions were detected by the punctate distribution of CFTR immunofluorescence and by TEM ultrastructure of the opercular epithelium (OE), a gill‐like tissue rich in mitochondrion‐rich ionocytes. Punctate CFTR distribution was not explained by membrane raft organization, as chlorpromazine (50 μM) and filipin (1.5 μM) were ineffective in changing electrophysiology of OE. Isolated OE from SW fish with SW on the mucosal side had a transepithelial potential (Vt) of +40.1 + 0.9 mV (n = 24), sufficient to allow passive Na+ secretion (Nernst equilibrium potential ≡ ENa = +24.11 mV). OE from fish acclimated to 2SW and bathed in 2SW (mucosal side) had significantly higher Vt of +45.1 + 1.2 mV (n = 24; P < 0.001) and plasma Na+ was slightly elevated, sufficient for passive Na+ secretion (ENa = +40.74 mV), but with a severely diminished net driving force. Paradoxically, estimates of shunt conductance from epithelial conductance (Gt ) vs. short‐circuit current (Isc) plots (extrapolation to zero Isc) revealed significant reduction in total epithelial shunt conductance in 2SW acclimated fish. We conclude that whereas most epithelial tight junctions become less conductive in hypersaline conditions, those localized to the paracellular Na+ exit pathway become more conductive, compensating for lower driving force. Funded by NSERC and CFI.
AMPK Stimulates Urea Permeability and Urine Osmolality
Authors: Wang Yanhua , Klein Janet , Sands Jeff
Published: June 2021

Vasopressin is a key regulator of urine concentration through its actions on water and urea transporters, but what happens when vasopressin signaling breaks down‾ We investigated adenosine monophosphate activated kinase (AMPK) as a possible alternate, vasopressin‐independent regulatory pathway for urea and water transport. Mice lacking a vasopressin receptor (V2R‐KO) are polyuric. Injection of metformin to stimulate AMPK significantly increased urine osmolality from 196 (control) to 399 mOsM at 1h, and 586 mOsM at 5h post treatment in the V2R‐KO mice. We further investigated the role of AMPK using isolated perfused rat inner medullary collecting ducts (IMCDs). We showed that metformin and AICAR, AMPK activators, significantly increased urea permeability (control:metformin 16.4 ± 2.3 to 22.3 ± 3.5 x10‐5 cm/s; control:AICAR 19.3 ± 2.4 to 23.3 ± 3.0 x10‐5 cm/s). Hypertonicity stimulates urea transport though PKC. To determine if AMPK is additive to hypertonic stimulation, 400µM metformin was added to the tubule bath either before or after subjecting the IMCDs to hypertonic stimulation. Increasing the osmolality of perfusate and bath from 290 to 690 mOsM increased urea permeability from 18.9 ± 1.4 to 48.4 ± 3.1 x10‐5 cm/s. Addition of metformin further increased urea permeability from 48.4 ± 3.1 to 57.0 ± 4.1 x10‐5 cm/s. Initial stimulation with metformin raised urea permeability from 23.6 ± 1.9 to 32.2 ± 2.5 x10‐5 cm/s. Subsequent increase of the osmolality from 290 to 690 mOsM in the presence of metformin significantly increased urea permeability from 32.2 ± 2.5 to 68.0 ± 7.9 x10‐5 cm/s. We conclude that AMPK signaling may provide a means to increase urea permeability in addition to, or in place of, PKA and PKC. AMPK activation may be useful to increase urine concentrating ability when vasopressin signaling breaks down.
Short and Long‐term dysfunction induced TLR5 upon intestinal Na+/H+ exchange
Authors: Cabral Jose , Grácio Daniela , Soares‐da‐Silva Patricio , Magro Fernando
Published: June 2021

It is well known that intestinal microflora play an important role during inflammatory flares in Inflammatory Bowel Disease. However, the cellular mechanisms set in motion are still not completely understood. The immune system relies on Toll‐like receptor (TLR) 5 to detect any pathogenic flagellated microorganisms, as it is activated by flagellin.

Aims

evaluate the effect of TLR5 activation by flagellin on activity of Na+/H+ exchanger (NHE) in T84 intestinal epithelial cells as well the signal transduction set in motion.

Methods

NHE activity and kinetics were measured using fluorimetric assays and protein expression was determined by western blotanalysis.

Results

Shor‐term (st) cell exposure to Flagellin induced NHE1 activity reduction concentration dependent (2.1±2 to ‐14.9±2%). Cell signal set in motion triggered AC3, PKA, PLC and PKC signal molecules. As to the long‐term (lt) exposure, it induced rather opposite effects upon NHE1 and NHE3 activities. NHE1 activity was inhibited (‐1.7±3 to ‐19.1±2%). Whereas, NHE3 activity increased when cells were exposed to Flagellin (~ 10% at 100 ng/ml). Moreover, this NHE3 activity increase was accompanied by a NHE3 expression increase (16.74 ± 2%). During st exposure AC3, PKA, PLC and PKC were recruited while lt exposure to Flagellin activated AC3 and PKA. Flagellin induced an impaired recover of pHi.

Conclusions

Activation of TLR5 exerts marked inhibition of NHE1 activity and stimulates NHE3 activity in intestinal epithelial cells. While st Flagellin exposure (that leads to NHE1 inhibition) activates AC3, PKA, PKC and PLC, the lt activation (that leads to NHE3 stimulation) only triggers AC3 and PKA.