Cardiovascular effects of dietary salt intake in aged healthy cats: a 2-year prospective randomized, blinded, and controlled study

Long-term safety of dietary salt: A 5-year ProspEctive rAndomized bliNded and controlled stUdy in healThy aged cats (PEANUT study)

BACKGROUND

High-salt diets promote urine dilution and decrease urolithiasis risk.

OBJECTIVE

Prospectively evaluate the safety of chronic high dietary salt intake (randomized controlled trial).

ANIMALS

Twenty research colony neutered, healthy aged cats (11.5 years [10.0-11.6], median [interquartile range]).

METHODS

Healthy cats were randomized to control or high-salt dry diets (sodium: 1.02 ± 0.16 [mean, SD] and 3.26 ± 0.30 g/Mcal metabolizable energy [ME], respectively; chloride: 2.26 ± 0.33 and 5.71 ± 0.28 g/Mcal ME, respectively), fed for up to 60 months. Assessments included CBC, plasma biochemistry, urinalysis, glomerular filtration rate (GFR), blood pressure, renal and cardiac (conventional Doppler and 2-dimensional color tissue Doppler) imaging, annually. Cats that died or were euthanized underwent necropsy. Diet effects over time were evaluated with linear mixed models.

RESULTS

Follow-up duration (median [Interquartile range]) was similar between the control (38.7 months [28.6-48.2]) and high-salt group (51.4 months [45.7-59.0]). Diet had no significant effect on changes in GFR, blood pressure, plasma creatinine concentration, end-diastolic left ventricular (LV) wall thicknesses, LV internal diameters, LV systolic function, left atrial size, or systolic and diastolic Doppler variables. One control cat developed hypertension. One high-salt group cat developed persistent azotemia. Serial plasma biochemistry and urine specific gravity suggested early chronic kidney disease in 4 nonazotemic cats (2 per group), consistent with necropsy findings.

CONCLUSIONS AND CLINICAL IMPORTANCE

In healthy aged cats, a commercial veterinary diet containing 3.26 ± 0.30 g/Mcal ME sodium was safe with regard to renal and cardiac function for up to 5 years.

High Intake of Sodium Chloride for 28 Days Causes No Effect on Serum FGF23 Concentrations in Cats

BACKGROUND

FGF23 is an acknowledged parameter to assess kidney health. As chronic kidney failure is one of the most common diseases in aging cats, dietary influences on renal health warrant investigation. The purpose of this study was therefore to investigate potential correlations between dietary sodium chloride and FGF23.

METHODS

In a total of two trials, 11 cats were included. In the first trial, the cats were fed a complete and balanced control diet; in the second trial, sodium chloride was added (8 g/kg/DM)). Blood, urinary, feed, and faecal samples were analysed for major minerals. FGF23 and creatinine were measured in blood and urine samples.

RESULTS

Serum phosphate and FGF23 were unaffected by high sodium chloride intake, thus showing no correlation between serum FGF23 and sodium concentrations. Apparent phosphorus digestibility was significantly increased, however, by high sodium chloride intake, whereas apparent digestibility of calcium was unaffected. The present study confirms differences in FGF23 and sodium chloride interaction in cats compared with other species. Further research regarding the correlation between sodium chloride and phosphate homeostasis is warranted.

Does the Taste and Appearance of Food Affect Food Waste in Low-Salt Diet Patients?

Large of food waste can be one indicator of nutritional deficiencies in patients. This lack of nutrition is a factor that can increase morbidity, length of stay and cost of care. The acceptance of the taste of food in patients with low-salt diets is often a problem. This study aimed to assess the effect of taste and appearance of foods on food waste in patients with low-salt diets. The study was a cross-sectional design with observational methods. Data was collection from interview using questionnaire. The study was conducted at the Jasa Kartini (JK) Hospital, Tasikmalaya in August-October 2017. Subjects (n=30) were patients in low-salt diet. The acceptance of the taste and appearance of food from JK Hospital according to the respondents, the value was quite varied, generally above the median value on a scale of 1-3. The average of food waste from patients with low-salt diets at JK Hospital was still above the PGRS (Nutritional Guideline for Hospital) standard 2013, which was 26%. Based on the analysis between variables, there was a significant relationship between food waste and food taste (p=0.002) and food waste and food appearance (p=0.000) in low-salt diets patients. The taste and appearance of food significantly affect the food waste in low-salt diet patients.

Comparison of Doppler ultrasonic and oscillometric devices (with or without proprietary optimisations) for non-invasive blood pressure measurement in conscious cats

Objectives

This study compared Doppler and oscillometric (PetMAP+) devices (with or without proprietary optimisations) for the non-invasive measurement of blood pressure in conscious cats.

Methods

Twenty-three cats were enrolled; however, five were excluded as fewer than five measurements were obtained for each assessment. All measurements were obtained according to American College of Veterinary Internal Medicine consensus guidelines. Oscillometric device modes A and B were operated according to the manufacturer’s guidelines. Doppler and oscillometric devices were used alternately as the first device.

Results

Systolic arterial blood pressure (SAP) measurements were obtained by Doppler (SAPd) and oscillometry; the mean of each set of five values was used for statistical analysis. There was a significant difference between SAPd and SAP measurements in oscillometric modes A (P <0.001) and B (P <0.001). While both modes measured SAP higher than SAPd, B had a smaller bias (+15.72 mmHg) and narrower limits of agreement (LOA). There was also a significant difference between SAPd and mean arterial pressure (MAP) on oscillometric modes A (P = 0.002) and B (P <0.001). Both modes’ MAP readings were lower than SAPd and oscillometric A MAP was closer to SAPd (–14.94 mmHg), with a smaller bias and narrower LOA.

Conclusions and relevance

The findings support that Doppler and oscillometric devices cannot be used interchangeably, with or without proprietary optimisations. Methodology should always be taken into account and reference intervals (RIs) need to be defined for the different methodologies. Until methodology-specific RIs are published, definitive diagnosis of hypertension and sub-staging of patients with kidney disease according to the International Renal Interest Society guidelines remains challenging.

Effects of crude protein and sodium intake on water turnover in cats fed extruded diets

The comprehension of strategies to increase urine production may be important, especially in kibble diets to prevent urolithiasis in cats. The effects of increasing amounts of crude protein (CP) and sodium on the water turnover of cats were evaluated using the water balance (WB) method and the deuterium dilution technique. The study followed a randomized block design, with three blocks of eight cats, two cats per food type in each block, and six cats per food. Four extruded diets with different amounts of CP and sodium were evaluated (on DM basis): 28% CP and 0.58% sodium; 39% CP and 0.64% sodium; 52% CP and 0.76% sodium; and 64% CP and 0.87% sodium. Cats were individually housed in cages for 8 days to measure WB, urea excretion, and faecal and urine characteristics. Deuterium oxide was used to evaluate water turnover, and during the period cats were housed in a collective cattery. The data were analysed by an F test, and the means were compared by polynomial contrasts. The ɑ level of significance was set at 0.05. The methods were compared by Pearson correlation, and Bland and Altman analysis. The increase in the CP content elevated linearly the renal excretion of urea (p < .001), and, together with the higher sodium intake, elevated the renal solute load, which resulted in a linear increase in urine production and water intake (p < .01). The urine density, metabolic water, and faecal and insensible water losses did not differ (p > .05). The water flux increased linearly when using the deuterium method (p < .001), but the obtained values were 20.85 ± 11.11 ml/cat/day higher than those verified using the WB method (p = .001). Higher CP and sodium amounts in dry diets increased the urine production and water consumption of cats, and this can be explored as a possible option to increase urination.

Evidence in Guidelines for Treatment of Coronary Artery Disease

In this chapter, we focus on evidences in current guidelines for treatment of coronary artery disease (CAD). In Part 1, diet and lifestyle management is discussed, which plays an important role in CAD risk control, including forming healthy dietary pattern, maintaining proper body weight, physical exercise, smoking cessation, and so on. Part 2 elaborated on revascularization strategies and medical treatments in patients presenting with acute coronary syndrome (ACS), including specific AHA and ESC guidelines on ST elevation myocardial infarction (STEMI) and non-ST elevation ACS (NSTE-ACS). Part 3 discussed chronic stable coronary artery disease (SCAD), the treatment objective of which is a combination of both symptomatic and prognostic improvement. Yet many of the recommendations for SCAD are expert-based rather than evidence-based. Initial medical treatment is safe and beneficial for most patients. While cumulating studies have focused on optimizing pharmacological therapy (referring to nitrates, beta-blockers, calcium channel blockers, antiplatelet agents, ACEI/ARB, statins, etc.), education, habitual modification, and social support matters a lot for reducing cardiac morbidity and mortality. Patients with moderate-to-severe symptoms and complex lesions should be considered for revascularization. But practical management of revascularization shall take individual characteristics, preference, and compliance into consideration as well.

Phosphorus and sodium contents in commercial wet foods for dogs and cats

It has been reported that wet foods for dogs and cats have high levels of sodium and phosphorus due to their composition. Therefore, this study aimed to evaluate the sodium and phosphorus contents in wet pet foods, and compare it to daily requirements for both species. Twenty‐five commercial wet foods for adult animals were evaluated, 13 for dogs and 12 for cats. The analyses’ results were compared to the European Pet Food Industry Federation (FEDIAF 2018) recommendations. All foods contained phosphorus and sodium amounts above minimum requirements. Three wet foods for dogs exceeded the safe upper limit for phosphorus, and four wet foods for dogs and three for cats exceeded 3.75 g of sodium/1,000 kcal metabolizable energy (ME), considered safe by FEDIAF. No studies were found at the present time evaluating whether higher sodium levels are safe for dogs and cats; however, consumption of high phosphorus diets has been associated with adverse effects on renal function parameters. Therefore, more studies are necessary to investigate the health implications of phosphorus and sodium concentrations observed in some foods evaluated in this research.

It has been reported that wet foods for dogs and cats have high levels of sodium and phosphorus due to their composition. Therefore, this study aimed to evaluate the sodium and phosphorus contents in wet pet foods, and compared to daily requirements for both species.

Nutritional Management of Urolithiasis

Dietary management of urolithiasis in dogs and cats is designed to dissolve calculi when possible and/or reduce the risk of recurrence. The diet must reduce urine relative supersaturation for the particular salt in order to prevent crystallization. To decrease urinary concentrations of crystal precursors, increasing water intake is essential regardless of the stone type. Altering the amounts of dietary precursors of the stone and controlling urine pH is mostly effective for struvite, urate, xanthine, and cystine, but still subject to controversy for calcium oxalate. The investigation of underlying metabolic disorders and close monitoring of animals at risk is recommended.

ACVIM consensus statement: Guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats

An update to the 2007 American College of Veterinary Internal Medicine (ACVIM) consensus statement on the identification, evaluation, and management of systemic hypertension in dogs and cats was presented at the 2017 ACVIM Forum in National Harbor, MD. The updated consensus statement is presented here. The consensus statement aims to provide guidance on appropriate diagnosis and treatment of hypertension in dogs and cats.

Echocardiographic evaluation of left ventricular diastolic function in cats: Hemodynamic determinants and pattern recognition

Left ventricular (LV) diastolic dysfunction is highly prevalent in cats and is a functional hallmark of feline cardiomyopathy. The majority of cats with hypertrophic, restrictive, and dilated cardiomyopathy have echocardiographic evidence of abnormal LV filling, even during the occult (preclinical) phase. Moderate and severe diastolic dysfunction is an indicator of advanced myocardial disease, is associated with clinical signs including exercise intolerance and congestive heart failure, affects outcome, and influences therapeutic decisions. Therefore, identification and quantification of LV diastolic dysfunction are clinically important. Surrogate measures of diastolic function determined by transthoracic two-dimensional, M-mode, and Doppler echocardiographic (DE) methods have been used widely for such purpose. Major functional characteristics of LV diastole, including global function, relaxation and untwist, chamber compliance, filling volume, and the resultant filling pressures can be semi-quantified by echocardiographic methods, and variables retrieved from transmitral flow, pulmonary vein flow, and tissue Doppler recordings are most frequently used. Although there is still a critical lack of well-designed studies in the field, knowledge has steadily accumulated over the past 20 years, reference ranges of diastolic echocardiographic variables have been determined, epidemiological studies have been conducted, and new treatments of diastolic dysfunction in cats have been evaluated. This report will give the reader a summary of the current status in the field of feline diastology with focus on the noninvasive diagnostic methods and interpretation of echocardiographic surrogate measures of LV diastolic function. Lastly, a grading system using a composite of left atrial size and various DE variables potentially useful in the functional classification of LV diastole in cats is introduced.

Feline Calcium Oxalate Urolithiasis: Risk factors and rational treatment approaches

PRACTICAL RELEVANCE

Uroliths occur commonly in the bladder and/or urethra of cats and can be lifethreatening if urethral obstruction occurs. Calcium oxalate accounts for 40-50% of urocystoliths and these stones are not amenable to medical dissolution; therefore, removal by surgery or minimally invasive techniques is required if uroliths must be treated. Medical protocols for prevention involve decreasing urine saturation for minerals that form uroliths.

ETIOPATHOGENESIS

Formation of uroliths is not a disease, but rather a complication of several disorders. Some disorders can be identified and corrected (such as infection-induced struvite urolith formation); others can be identified but not corrected (such as idiopathic hypercalcemia). In most cats with calcium oxalate urolith formation the underlying etiopathogenesis is not known. A common denominator of all these disorders is that they can from time to time create oversaturation of urine with one or more crystal precursors, resulting in formation of crystals.

BASIC CONCEPTS

In order to develop rational and effective approaches to treatment, abnormalities that promote urolith formation must be identified, with the goal of eliminating or modifying them. It is important, therefore, to understand several basic concepts associated with urolithiasis and the factors that promote urolith formation that may be modified with medical treatment; for example, the state of urinary saturation, modifiers of crystal formation, potential for multiple crystal types, and presence of bacterial infection or urinary obstruction.

Sodium in feline nutrition

High sodium levels in cat food have been controversial for a long time. Nonetheless, high sodium levels are used to enhance water intake and urine volume, with the main objective of reducing the risk of urolithiasis. This article is a review of current evidence of the putative risks and benefits of high dietary sodium levels. Its secondary aim is to report a possible safe upper limit (SUL) for sodium intake. The first part of the manuscript is dedicated to sodium physiology, with a focus on the mechanisms of sodium homeostasis. In this respect, there is only few information regarding possible interactions with other minerals. Next, the authors address how sodium intake affects sodium balance; knowledge of these effects is critical to establish recommendations for sodium feed content. The authors then review the consequences of changes in sodium intake on feline health, including urolithiasis, blood pressure changes, cardiovascular alterations and kidney disease. According to recent, long-term studies, there is no evidence of any deleterious effect of dietary sodium levels as high as 740 mg/MJ metabolizable energy, which can therefore be considered the SUL based on current knowledge.

Chronic Kidney Disease in Aged Cats: Clinical Features, Morphology, and Proposed Pathogeneses

Chronic kidney disease (CKD) is the most common metabolic disease of domesticated cats, with most affected cats being geriatric (>12 years of age). The prevalence of CKD in cats exceeds that observed in dogs, and the frequency of the diagnosis of CKD in cats has increased in recent decades. Typical histologic features include interstitial inflammation, tubular atrophy, and fibrosis with secondary glomerulosclerosis. In contrast to people and dogs, primary glomerulopathies with marked proteinuria are remarkably rare findings in cats. Although a variety of primary renal diseases have been implicated, the disease is idiopathic in most cats. Tubulointerstitial changes, including fibrosis, are present in the early stages of feline CKD and become more severe in advanced disease. A variety of factors-including aging, ischemia, comorbid conditions, phosphorus overload, and routine vaccinations-have been implicated as factors that could contribute to the initiation of this disease in affected cats. Factors that are related to progression of established CKD, which occurs in some but not all cats, include dietary phosphorus intake, magnitude of proteinuria, and anemia. Renal fibrosis, a common histologic feature of aged feline kidneys, interferes with the normal relationship between peritubular capillaries and renal tubules. Experimentally, renal ischemia results in morphologic changes similar to those observed in spontaneous CKD. Renal hypoxia, perhaps episodic, may play a role in the initiation and progression of this disease.

Effects of two calculolytic diets on parameters of feline mineral metabolism

OBJECTIVES

To evaluate the influence of two feline calculolytic diets on selected parameters of mineral metabolism.

MATERIALS AND METHODS

Two dry commercial diets designed for struvite urolith dissolution were evaluated in 14 cats. The study was designed as a two-sequence, four-period crossover protocol with a baseline period, two 60-day "run-in" periods in which calculolytic diets (Diet 1 and Diet 2) were fed and one 30-day "wash-out" period. Data are expressed as median (range).

RESULTS

Feeding the calculolytic diets for two months did not alter plasma concentrations of calcium, phosphorus, magnesium and parathyroid hormone. A significant (P < 0.05 in each case) decline in calcitriol was observed after administering both diets from 236.4 (122.4-429.6) to 170.4 (108.0-394.3) pmol/L (Diet 1) and from 278.4 (153.6-492.0) to 177.1 (87.6-392.4) pmol/L (Diet 2). Cats fed Diet 1 showed a significant increase in urine calcium concentration (from 0.3 (0.2-0.5) to 0.4 (0.3-0.7) mmol/L). Magnesium concentration in urine was significantly increased with both diets, from 1.4 (0.1-1.7) to 1.5 (1.3-2.4) mmol/L (Diet 1) and from 1.1 (0.4-1.9) to 2.0 (0.1-3.1) mmol/L (Diet 2).

CLINICAL SIGNIFICANCE

Both diets resulted in an increased urinary concentration of magnesium, through different mechanisms: urine acidification (Diet 1) and increased sodium load (Diet 2).