Peter J. Markwell

Survival of Cats with Naturally Occurring Chronic Renal Failure Is Related to Severity of Proteinuria

BACKGROUND Tubulointerstitial kidney disease is a common cause of illness and death in pet cats and is typically not associated with overt proteinuria. HYPOTHESIS Proteinuria would be independently related to survival in cats with renal failure, with or without hypertension. ANIMALS The study included 136 client-owned cats; 28 apparently normal, 14 hypertensive but not azotemic, 66 azotemic but not hypertensive, and 28 both hypertensive and azotemic. METHODS Coxs proportional hazards model was used to determine the influence of initial plasma creatinine concentration, proteinuria (urine protein-to-creatinine ratio or albumin-to-creatinine ratio), age, and systemic hypertension on the risk of death or euthanasia during the follow-up period. Multivariable linear regression was used to determine the relation between severity of proteinuria and predictive variables, including age, plasma creatinine concentration, systolic blood pressure, sex, and urine specific gravity. RESULTS Plasma creatinine concentration and proteinuria were very highly related to survival. The hazard ratio (95% confidence intervals) for death or euthanasia was 2.9 (1.4-6.3) and 4.0 (2.0-8.0) for urine protein-to-creatinine ratio 0.2-0.4 and >0.4, respectively, compared with the baseline group with a urine protein-to-creatinine ratio of <0.2 and were 2.4 (1.2-4.8) and 4.9 (2.3-10.2) for an albumin-to-creatinine ratio of 30-82 mg/g and <82 mg/g, respectively, compared with a baseline group with albumin-to-creatinine ratio of <30 mg/g. Treated hypertensive cats did not have reduced survival, although systolic blood pressure, together with plasma creatinine concentration was positively related to the magnitude of proteinuria. CONCLUSIONS AND CLINICAL IMPORTANCE Despite the relatively low concentrations of proteinuria typical of chronic renal disease in cats, this measurement is of prognostic significance.

The Effect of Diet on Lower Urinary Tract Diseases in Cats

Because dietary ingredients and feeding patterns influence the volume, pH and solute concentration of urine, diet can contribute to the etiology, management or prevention of recurrence of some causes of lower urinary tract disease. Most research assessing the effect of diet has focused on the latter two aspects, primarily because of interest in struvite urolithiasis. Manipulation of urine pH through dietary means has proven an effective tool for the management and prevention of struvite urolithiasis; acidification of urine, however, may be a risk factor for calcium oxalate urolithiasis, which now appears to occur with approximately equal frequency in cats. Prediction of urine pH from dietary analysis would thus be a valuable tool, but considerable further research is required before this can be achieved with commercial canned foods. With the growing importance of urolith types other than struvite, alternatives to the measurement of urine pH are required to assess critically the likely beneficial (or detrimental) effects of manipulation of nutrient profile. Measurement of urinary saturation may permit the development and fine tuning of nutrient profiles aimed at controlling lower urinary tract diseases in cats that are associated with a range of different mineral types. The majority of cats with signs of lower urinary tract disease do not, however, have urolithiasis; indeed, no specific cause can be established in most of these cats. Recent observations suggest that recurrence rates of signs in cats classified as having idiopathic lower urinary tract disease may be more than halved if affected animals are maintained on high, rather than low moisture content diets. J. Nutr. 2753S-2757S, 1998

A blood test for intestinal permeability and function: A new tool for the diagnosis of chronic intestinal disease in dogs

We demonstrate that rhamnose, 3-O-methyl-D-glucose, D-xylose and lactulose may be quantified accurately in blood by HPLC and pulsed amperometric detection, thus enabling studies of intestinal permeability and function to be carried out using plasma samples. Prior to HPLC, the endogenous glucose was enzymatically modified to gluconic acid and the protein precipitated. The precision of the quantification of the sugars in plasma (CV: 2.2-5.7%; 8.7-10.6% at very low concentrations) compared well with the quantification in urine. The results for groups of 8 dogs with small intestinal bacterial overgrowth and 12 dogs with inflammatory bowel disease were shown to be significantly different from a group of 20 normal control dogs (P < 0.001), demonstrating the tests value as a diagnostic tool. The normal ranges in blood 2 h post oral administration were determined to be 0.05-0.17 for the lactulose/rhamnose ratio and 0.45-0.65 for the xylose/3-O-methylglucose ratio. This method may be employed advantageously when the collection of urine in intestinal permeability and function tests is difficult.

Dietary constituents are able to play a beneficial role in canine epidermal barrier function

Abstract:  Epidermal barrier function is a critical attribute of mammalian skin. The barrier is responsible for preventing skin‐associated pathologies through controlling egress of water and preventing ingress of environmental agents. Maintaining the quality and integrity of the epidermal barrier is therefore of considerable importance. Structurally, the barrier is composed of two main parts, the corneocytes and the intercellular lamellar lipid. The epidermal lamellar lipid comprises mainly ceramides, sterols and fatty acids. Twenty‐seven nutritional components were screened for their ability to upregulate epidermal lipid synthesis. Seven of the 27 nutritional components (pantothenate, choline, nicotinamide, histidine, proline, pyridoxine and inositol) were subsequently retested using an in vitro transepidermal diffusion experimental model, providing a functional assessment of barrier properties. Ultimately, the best performing five nutrients were fed to dogs at supplemented concentrations in a 12‐week feeding study. Barrier function was measured using transepidermal water loss (TEWL). It was found that a combination of pantothenate, choline, nicotinamide, histidine and inositol, when fed at supplemented concentrations, was able to significantly reduce TEWL in dogs after 9 weeks.

Effects of Dietary Modification in Dogs with Early Chronic Valvular Disease

BACKGROUND The potential benefits of nutritional modification in early canine cardiac disease are not known. HYPOTHESIS We hypothesized that echocardiographic, neuroendocrine, and nutritional variables will differ between dogs with asymptomatic chronic valvular disease (CVD) and healthy controls, and that a moderately reduced sodium diet enriched with antioxidants, n-3 fatty acids, taurine, carnitine, and arginine will alter these variables in dogs with CVD. METHODS Echocardiography was performed and blood was collected. After baseline comparison with healthy controls, all dogs with CVD were fed a low-sodium run-in diet for 4 weeks, reevaluated, and then randomized to receive either the cardiac diet or a placebo diet for 4 weeks. RESULTS At baseline, dogs with CVD (n = 29) had significantly lower circulating sodium, chloride, arginine, and methionine concentrations and higher plasma concentrations of atrial natriuretic peptide compared to healthy controls. In dogs with CVD, plasma aldosterone concentration and heart rate increased significantly after 4 weeks of eating the run-in diet. The cardiac diet group (n = 14) had larger increases in levels of cholesterol (P = .001), triglycerides (P = .02), eicosapentaenoic acid (P < .001), docosahexaenoic acid (P < .001), total omega-3 fatty acids (P < .001), vitamin C (P = 0.04), alpha-tocopherol (P < .001), and gamma-tocopherol (P < .001) compared to the placebo diet group (n = 15). The cardiac diet group also had larger reductions in maximal left-atrial dimension (P = .003), left-ventricular internal dimension in diastole (P = .03), and weight-based maximal left-atrial dimension (P = .03). CONCLUSIONS AND CLINICAL IMPORTANCE Observed changes in both blood variables and echocardiographic measurements warrant additional studies on dietary modifications in dogs with early CVD.

Clinical, echocardiographic, and neurohormonal effects of a sodium-restricted diet in dogs with heart failure.

The use of low-sodium diets in dogs with heart failure is common practice, but randomized, double-blind studies have not been conducted to examine the benefits or problems with this approach. The purpose of this study was to determine the effects of a low-sodium diet on clinical, echocardiographic, and neurohormonal parameters in dogs with heart failure. Dogs with stable chronic heart failure were fed exclusively a low-sodium (LS) and a moderate-sodium (MS) diet for 4 weeks each in a randomized, double-blind, crossover design. At days 0, 28, and 56, echocardiography and thoracic radiography were performed, and blood was analyzed for electrolytes and neurohormones. Fourteen dogs completed the study (9 with chronic valvular disease and 5 with dilated cardiomyopathy). Electrolyte abnormalities were common during the study, and serum sodium and chloride concentrations decreased significantly on the LS diet. Neurohormones did not change significantly between diet groups. Maximum left atrial (P = .05) and standard left atrial (P = .09) size decreased on the LS diet. For dogs with chronic valvular disease, vertebral heart score (P = .05), left ventricular internal dimension in diastole (P = .006) and systole (P = .02), standard left atrial dimension (P = .03), maximum left atrial dimension (P = .02), end-diastolic volume index (P = .02), and end-systolic volume index (P = .04) decreased significantly on the LS diet compared to the MS diet. Although analysis of these data suggests some benefits of a low-sodium diet, future studies with improved study design are needed to further evaluate the advantages and disadvantages of sodium restriction in dogs with heart failure.

Effect on Canine Oral Health of Adding Chlorhexidine to a Dental Hygiene Chew

A study to compare the effect of a dental hygiene chew with or without 0.2% chlorhexidine on the development of gingivitis and the accumulation of dental deposits was performed using 11 small dogs. Confirming previous data, the daily addition of a standard chew to a dry diet resulted in significantly less gingivitis and calculus after 3 weeks compared with feeding the dry diet alone. Addition of chlorhexidine to the chew made no difference to the degree of gingivitis or the amount of calculus that accumulated, but did result in significantly less plaque accumulation after 3 weeks. The abrasiveness of the chew, rather than the antibacterial activity of chlorhexidine, is likely to have contributed the most to the maintenance of oral health in dogs with mild gingivitis.

Taurine: An essential nutrient for the cat. A brief review of the biochemistry of its requirement and the clinical consequences of deficiency

Abstract Taurine, an amino-sulphonic acid, is an essential dietary constituent for the cat as a result of limited biosynthetic capability, and its bile salt metabolism. Dietary deficiency of taurine has been associated with a range of serious clinical problems, including retinal degeneration (2, 8), poor reproductive performance and developmental abnormalities (22, 24), and dilated cardiomyopathy (18). Knowledge of the importance of taurine in feline nutrition has helped understanding of the role that taurine may play in other mammalian species, including man.

Effect of Level and Source of Dietary Fiber on Food Intake in the Dog

The effects of dietary fiber on challenge meal intake and on the perception of hunger in dogs were evaluated. A program of testing variants of a standard low energy diet, to which one of five fiber containing raw materials was added, was undertaken. Diets were fed to a group of six dogs for 12-d periods in a latin square design and in amounts that corresponded to the food allowance for weight reduction. Behavioral characteristics of dogs were recorded on videotape for 30-min periods after introduction of test diets. On two occasions during each 12-d feeding period dogs were presented with a challenge meal. At the end of each 12-d feeding period all dogs entered a 6-d washout period. There was no significant effect of diet on the intake of the challenge meal or on intake of food during the subsequent washout period. In addition, diet had no apparent effect on the perception of hunger, as represented by behavioral characteristics during the 30-min period after presentation of test diets. It was concluded that inclusion of moderate levels of raw materials, composed primarily of insoluble fiber, in a commercial low energy diet had no apparent beneficial effects on satiety, when fed to dogs on an energy intake corresponding to allowances for weight reduction.

Molecular species of cholesteryl esters formed via plasma lecithin: Cholesterol acyltransferase in fish oil supplemented dogs

Abstract Effects of a dietary supplement containing n-3 polyunsaturated fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), on molecular species of cholesteryl ester (CE) formed via the plasma lecithin: cholesterol acyltransferase (LCAT; EC 2.3.1.43) reaction was studied. A commercially available basal diet was initially fed to 18 normal adult dogs for 10 days prior to supplementing the dogs, divided into two groups of nine, using either menhaden fish (MHO) or safflower (SAF) oil capsules for a 22 day period. Fatty acid compositions of plasma phospholipid (PL) and CE were measured at days 0, 10 and 32. Characterization of the plasma LCAT-derived reaction products formed in vitro was performed using a radiolabeled cholesterol substrate and molecular species formed were separated by argentation thin-layer chromatography. Significant differences in PL EPA, DHA, and docosapentaenoic acid (DPA) were found in the MHO group. The CE fatty acid distributions revealed a greater than 20-fold elevation in EPA and a nearly 6-fold increase in DHA after MHO supplements. However, DPA was not detected in any CE fatty acid samples suggesting that this fatty acid is not a substrate for cholesterol esterification. The CE molecular species in plasma and those formed via the plasma LCAT reaction in vitro support the possibility that LCAT is responsible, at least in part, for the plasma CE fatty acid distribution. Ratios of selected plasma CE and LCAT derived CE n-6 and n-3 fatty acids using the MHO group data resulted in 3-fold elevations of both DHA/EPA and DHA/AA in the LCAT-derived in vitro CE fraction compared to CE in whole plasma. It is concluded that while both EPA and DHA are suitable substrates for CE formation, relatively lower amounts of plasma CE-DHA compared to the LCAT derived CE-DHA indicates that this fatty acid may be selectively taken up by the tissues compared to CE-EPA and AA.