Long-term effect of a chronic low-protein multideficient diet on the heart: Hypertension and heart failure in chronically malnourished young adult rats

The isolated, perfused working heart preparation of the mouse-Advantages and pitfalls

Isolated, perfused hearts are viable for hours outside the body, and important research findings have been made using mouse hearts ex vivo. In the Langendorff perfusion mode, the coronary tree is perfused via retrograde flow of a perfusate down the ascending aorta. Although the Langendorff setup is generally simpler and quicker to establish, the working heart mode allows the heart to function in a more physiologically relevant manner, where the perfusate is directed into the left ventricle via the left atrium. The contracting, fluid-filled ventricle will eject the perfusate into the aorta in a more physiologically relevant manner, lifting the physiological relevance of the contractile and energetic data. The workload on the heart (preload, afterload and heart rate) can be precisely adjusted in the working, isolated heart, and the ventricular performance, for example, end-diastolic and end-systolic pressures, stroke volume, cardiac output, and oxygen consumption can be determined. Moreover, using pressure-volume catheters, ventricular performance can be assessed in great detail. With the present review, we highlight the benefits and drawbacks of the technique and indicate where particular attention must be put when building the working heart setup, designing experiments, executing the studies, and analyzing the obtained data.

Rostafuroxin, the inhibitor of endogenous ouabain, ameliorates chronic undernutrition-induced hypertension, stroke volume, cardiac output, left-ventricular fibrosis and alterations in Na+-transporting ATPases in rats

Our aim has been to investigate the effect of Rostafuroxin, an inhibitor of endogenous cardiotonic steroids (EO/CTS), on cardiac structure and function and cardiac Na+ transport in undernourished hypertensive Wistar rats, and to determine whether chronic undernutrition is a modifiable risk factor for cardiovascular-kidney-metabolic (CKM) syndrome. Echocardiographic studies evaluated stroke volume cardiac output, ejection fraction, mitral valve early diastolic blood flow/late diastolic blood flow (E/A) ratio, and right renal resistive index. The cardiomyocyte area and collagen infiltration of cardiac tissue were investigated, as also the activities of the cardiac ouabain-sensitive (Na++K+)ATPase ((Na++K+)ATPase Sens) and ouabain-resistant Na+-ATPase (Na+-ATPase Res). Undernourished hypertensive rats presented tachycardia, reduced stroke volume, decreased cardiac output, preserved fractional shortening and ejection fraction, unmodified mitral valve E/A ratio, and increased right renal resistive index. Cardiomyocyte size decreased and intense collagen infiltration had occurred. The (Na++K+)ATPase Sens activity decreased, whereas that of Na+-ATPase Res increased. Rostafuroxin selectively modified some of these echocardiographic and molecular parameters: it increased stroke volume and cardiac output and prevented histopathological alterations. The drug decreased and increased the activities of (Na++K+)ATPase Sens and Na+-ATPase Res, respectively, in normonourished rats, and the opposite trend was found in the undernourished group. It is concluded that chronic undernutrition in rats can provoke structural, functional, histological, and molecular cardiovascular alterations that, with the simultaneous changes in renal parameters described in this and in previous studies, configure an undescribed type of CKM syndrome. The data also demonstrate that the blockade of EO/CTS ameliorates stroke volume and cardiac output, thus preventing or delaying the worsening of the syndrome.

Different antihypertensive and metabolic responses to rostafuroxin in undernourished and normonourished male rats: Outcomes on bodily Na+ handling

Hypertension is a pandemic nowadays. We aimed to investigate whether chronic undernutrition modifies the response to the antihypertensive drug rostafuroxin in juvenile hypertensive rats. Chronic undernutrition was induced in male rats using a multideficient diet known as the Regional Basic Diet (RBD), mimicking alimentary habits in impoverished regions worldwide. Animals were given RBD-or a control/CTRL normal diet for rodents-from weaning to 90 days, and rostafuroxin (1 mg/kg body mass) was orally administered from day 60 onwards. For the last 2 days, the rats were hosted in metabolic cages to measure food/energy, water, Na+ ingestion, and urinary volume. Rostafuroxin increased food/energy/Na+ intake in CTRL and RBD rats but had opposite effects on Na+ balance (intake minus urinary excretion). The drug normalized the decreased plasma Na+ concentration in RBD rats, increased urinary volume in RBD but not in CTRL, and decreased and increased urinary Na+ concentration in the RBD and CTRL groups, respectively. Rostafuroxin decreased the ouabain-sensitive (Na+ +K+ )ATPase and increased the ouabain-resistant Na+ -ATPase from proximal tubule cells in both groups and normalized the systolic blood pressure in RBD without effect in CTRL rats. We conclude that chronic undernutrition modifies the response of blood pressure and metabolic responses to rostafuroxin.

The Triad Na+ Activated Na+ Channel (Nax)-Salt Inducible KINASE (SIK) and (Na+ + K+)-ATPase: Targeting the Villains to Treat Salt Resistant and Sensitive Hypertension

The Na⁺-activated Na⁺ channel (Nax) and salt-inducible kinase (SIK) are stimulated by increases in local Na⁺ concentration, affecting (Na⁺ + K⁺)-ATPase activity. To test the hypothesis that the triad Nax/SIK/(Na⁺ + K⁺)-ATPase contributes to kidney injury and salt-sensitive hypertension (HTN), uninephrectomized male Wistar rats (200 g; n = 20) were randomly divided into 4 groups based on a salt diet (normal salt diet; NSD-0.5% NaCl-or high-salt diet; HSD-4% NaCl) and subcutaneous administration of saline (0.9% NaCl) or deoxycorticosterone acetate (DOCA, 8 mg/kg), as follows: Control (CTRL), CTRL-Salt, DOCA, and DOCA-Salt, respectively. After 28 days, the following were measured: kidney function, blood pressure, (Na⁺ + K⁺)-ATPase and SIK1 kidney activities, and Nax and SIK1 renal expression levels. SIK isoforms in kidneys of CTRL rats were present in the glomerulus and tubular epithelia; they were not altered by HSD and/or HTN. CTRL-Salt rats remained normotensive but presented slight kidney function decay. HSD rats displayed augmentation of the Nax/SIK/(Na⁺ + K⁺)-ATPase pathway. HTN, kidney injury, and kidney function decay were present in all DOCA rats; these were aggravated by HSD. DOCA rats presented unaltered (Na⁺ + K⁺)-ATPase activity, diminished total SIK activity, and augmented SIK1 and Nax content in the kidney cortex. DOCA-Salt rats expressed SIK1 activity and downregulation in (Na⁺ + K⁺)-ATPase activity in the kidney cortex despite augmented Nax content. The data of this study indicate that the (Na⁺ + K⁺)-ATPase activity response to SIK is attenuated in rats under HSD, independent of HTN, as a mechanism contributing to kidney injury and salt-sensitive HTN.

Ventricular Fibrosis and Coronary Remodeling Following Short-Term Exposure of Healthy and Malnourished Mice to Bisphenol A

Bisphenol-A (BPA) is an endocrine disruptor associated with higher risk of insulin resistance, type 2 diabetes, and cardiovascular diseases especially in susceptible populations. Because malnutrition is a nutritional disorder associated with high cardiovascular risk, we sought to compare the effects of short-term BPA exposure on cardiovascular parameters of healthy and protein-malnourished mice. Postweaned male mice were fed a normo- (control) or low-protein (LP) diet for 8 weeks and then exposed or not to BPA (50 μg kg⁻¹ day⁻¹) for the last 9 days. Systolic blood pressure was higher in BPA or LP groups compared with the control group. However, diastolic blood pressure was enhanced by BPA only in malnourished mice. Left ventricle (LV) end diastolic pressure (EDP), collagen deposition, and CTGF mRNA expression were higher in the control or malnourished mice exposed to BPA than in the respective nonexposed groups. Nevertheless, mice fed LP diet exposed to BPA exhibited higher angiotensinogen and cardiac TGF-β1 mRNA expression than mice treated with LP or BPA alone. Wall:lumen ratio and cross-sectional area of intramyocardial arteries were higher either in the LP or BPA group compared with the control mice. Taken together, our data suggest that short-term BPA exposure results in LV diastolic dysfunction and fibrosis, and intramyocardial arteries inward remodeling, besides potentiate protein malnutrition-induced hypertension and cardiovascular risk.

Undernutrition - thirty years of the Regional Basic Diet: the legacy of Naíde Teodósio in different fields of knowledge

Undernutrition is characterized by an imbalance of essential nutrients with an insufficient nutritional intake, a disorder in which the clinical manifestations in most cases are the result of the economic and social context in which the individual lives. In 1990, the study by the medical and humanitarian Naíde Teodósio (1915-2005) and coworkers, which formulated the Regional Basic Diet (RBD) model for inducing undernutrition, was published. This diet model took its origin from the observation of the dietary habits of families that inhabited impoverished areas from the Pernambuco State. RBD mimics an undernutrition framework that extends not only to the Brazilian population, but to populations in different regions worldwide. The studies based on RBD-induced deficiencies provide a better understanding of the impact of undernutrition on the pathophysiological mechanisms underlying the most diverse prevalent diseases. Indexed papers that are analyzed in this review focus on the importance of using RBD in different areas of knowledge. These papers reflect a new paradigm in translational medicine: they show how the study of pathology using the RBD model in animals over the past 30 years has and still can help scientists today, shedding light on the mechanisms of prevalent diseases that affect impoverished populations.

Sympathetic overactivation predicts body weight loss in patients with heart failure

Neurohumoral activation is frequently observed in chronic heart failure (HF) patients who develop body weight (BW) loss. We therefore hypothesized that sympathetic overactivation can predict progression of BW loss in HF patients with reduced ejection fraction. We prospectively evaluated BW loss in 108 non-edematous HF in whom muscle sympathetic nerve activity (MSNA) was measured. Follow-up began on the day of first MSNA measurement. Patients with BW loss of ≥5% of baseline BW during the first year of follow-up were considered to be experiencing BW loss. Maximal BW loss (%) and time to first BW loss (i.e., ≥5%) were assessed. Primary cardiovascular endpoints included cardiovascular death and HF hospitalization. Predictors of outcomes were assessed on univariate, multivariate, and Kaplan-Meier analyses. BW loss ≥5% occurred in 14% of enrolled patients. Mean MSNA was significantly higher in the BW loss group than in the no-BW loss group (80 versus 58 bursts/100 beats; p < 0.001). Moreover, multivariate Cox proportional hazard regression analysis revealed MSNA as the only independent predictor of BW loss. Multiple linear regression analysis identified MSNA as the strongest independent marker of maximal BW loss, even after adjusting for univariate predictors. BW loss, MSNA and several variables also correlated significantly with poor outcomes in univariate analyses. However, multivariate analysis only showed MSNA and NYHA III/IV as independent prognostic predictors, while BW loss did not predict prognosis. MSNA offered the most sensitive marker of BW loss in HF patients, but MSNA, not BW loss, was an independent predictor of poor outcome.

Cardiac metabolic modulation upon low-carbohydrate low-protein ketogenic diet in diabetic rats studied in vivo using hyperpolarized 13 C pyruvate, butyrate and acetoacetate probes

AIM

To investigate the effects of long-term low-carbohydrate low-protein ketogenic diet (KD) on cardiac metabolism and diabetic cardiomyopathy status in lean diabetic Goto-Kakizaki (GK) rats.

MATERIALS AND METHODS

Diabetic GK rats were fed with KD for 62 weeks. Cardiac function and metabolism were assessed using magnetic resonance imaging and ¹³ C magnetic resonance spectroscopy (¹³ C-MRS), at rest and under dobutamine stress. ¹³ C-MRS was performed following injection of hyperpolarized [3-¹³ C]acetoacetate, [1-¹³ C]butyrate or [1-¹³ C]pyruvate to assess ketone body, short-chain fatty acid or glucose utilization, respectively. Protein expression and cardiomyocyte structure were determined via Western blotting and histology, respectively.

RESULTS

KD lowered blood glucose, triglyceride and insulin levels while increasing blood ketone body levels. In KD-fed diabetic rats, myocardial ketone body and glucose oxidation were lower than in chow-fed diabetic rats, while myocardial glycolysis and short-chain fatty acid oxidation were unaltered. Dobutamine stress revealed an increased cardiac preload and reduced cardiac compliance in KD-fed diabetic rats. Dobutamine-induced stimulation of myocardial glycolysis was more enhanced in KD-fed diabetic rats than in chow-fed diabetic rats, which was potentially facilitated via an upregulation in basal expression of proteins involved in glucose transport and glycolysis in the hearts of KD-fed rats. The metabolic profile induced by KD was accompanied by cardiac hypertrophy, a trend for increased myocardial lipid and collagen content, and an increased marker of oxidative stress.

CONCLUSION

KD seems to exacerbate diabetic cardiomyopathy in GK rats, which may be associated with maladaptive cardiac metabolic modulation and lipotoxicity.