Clustering analysis of lipoprotein profiles to identify subtypes of hypertriglyceridemia in Miniature Schnauzers

BACKGROUND

Hypertriglyceridemia (HTG) is prevalent in Miniature Schnauzers, predisposing them to life-threatening diseases. Varied responses to management strategies suggest the possibility of multiple subtypes.

HYPOTHESIS/OBJECTIVE

To identify and characterize HTG subtypes in Miniature Schnauzers through cluster analysis of lipoprotein profiles. We hypothesize that multiple phenotypes of primary HTG exist in this breed.

ANIMALS

Twenty Miniature Schnauzers with normal serum triglyceride concentration (NTG), 25 with primary HTG, and 5 with secondary HTG.

METHODS

Cross-sectional study using archived samples. Lipoprotein profiles, generated using continuous lipoprotein density profiling, were clustered with hierarchical cluster analysis. Clinical data (age, sex, body condition score, and dietary fat content) was compared between clusters.

RESULTS

Six clusters were identified. Dogs with primary HTG were dispersed among 4 clusters. One cluster showed the highest intensities for triglyceride-rich lipoprotein (TRL) and low-density lipoprotein (LDL) fractions and also included 4 dogs with secondary HTG. Two clusters had moderately high TRL fraction intensities and low-to-intermediate LDL intensities. The fourth cluster had high LDL but variable TRL fraction intensities with equal numbers of NTG and mild HTG dogs. The final 2 clusters comprised only NTG dogs with low TRL intensities and low-to-intermediate LDL intensities. The clusters did not appear to be driven by differences in the clinical data.

CONCLUSIONS AND CLINICAL IMPORTANCE

The results of this study support a spectrum of lipoprotein phenotypes within Miniature Schnauzers that cannot be predicted by triglyceride concentration alone. Lipoprotein profiling might be useful to determine if subtypes have different origins, clinical consequences, and response to treatment.

Lipoprotein profiles in Miniature Schnauzer dogs with idiopathic hypertriglyceridemia and hypercortisolism

Miniature Schnauzer dogs (MSs) are predisposed to both idiopathic hypertriglyceridemia (iHTG) and hypercortisolism (HCort). To our knowledge, the lipoprotein profiles of MSs with iHTG have not been compared to those with HCort. We analyzed cholesterol and triglyceride concentrations and lipoprotein fractions in 4 groups of MSs: normotriglyceridemia (NTG) without concurrent disease (Healthy-NTG), HCort and NTG (HCort-NTG), HCort and HTG (HCort-HTG), and iHTG. Lipoprotein fractions were assessed by lipoprotein electrophoresis and compared between groups. Fifty-one plasma samples were analyzed. Twenty-five dogs had NTG (16 Healthy-NTG, 9 HCort-NTG) and 26 dogs had HTG (7 iHTG, 19 HCort-HTG). Dogs with iHTG or HCort-HTG had significantly higher cholesterol concentrations than Healthy-NTG dogs. Dogs with HCort-HTG had higher cholesterol than HCort-NTG dogs. There was a significantly higher low-density lipoprotein (LDL) percentage in iHTG and HCort-HTG dogs than HCort-NTG dogs. HCort-HTG dogs also had lower high-density lipoproteins (HDL) than HCort-NTG dogs. It was not possible to readily distinguish MSs with iHTG from MSs with HCort-HTG or Healthy-NTG using lipoprotein electrophoresis fractions. The diagnosis of iHTG remains a diagnosis by exclusion.

Changes in Serum Lipid Profiles among Canine Patients Suffering from Chronic Hepatitis

Hyperlipidemia is a risk factor for nonalcoholic fatty liver disease (NAFLD) in humans. However, the association between serum lipids and canine chronic hepatitis remains unknown. In this study, serum lipids, hepatic profiles, and hepatic ultrasound scores of healthy dogs and dogs with chronic hepatitis were evaluated. Serum triglyceride and cholesterol concentrations were significantly higher (p < 0.01) in dogs with chronic hepatitis. There were 62.2% of dogs with chronic hepatitis accompanied by hypertriglyceridemia, hypercholesterolemia, or both. Positive correlations were observed between serum ALT and cholesterol (r = 0.8287, p < 0.01), serum ALP and cholesterol (r = 0.8436, p < 0.01), serum GGT and cholesterol (r = 0.5640, p < 0.01), serum bile acid and cholesterol (r = 0.3310, p < 0.01) and serum ALP and triglycerides (r = 0.2582, p < 0.05). No significant differences were found between ultrasound scores of diseased dogs with and without hypertriglyceridemia and diseased dogs with and without hypercholesterolemia. Canine chronic hepatitis is associated with hyperlipidemia. A significant positive association was identified between hyperlipidemia, especially hypercholesterolemia, liver enzymes, and bile acid concentration in dogs suffering from chronic hepatitis. The underlying mechanisms connecting hyperlipidemia and canine chronic hepatitis remain elusive.

Efficacy of a micronized, nanocrystal fenofibrate formulation in treatment of hyperlipidemia in dogs

Background

Safe, effective, and readily available drug therapies are required for the management of hyperlipidemia and its associated complications in dogs.

Objectives

To investigate the efficacy of a micronized, nanocrystal formulation of fenofibrate (Tricor) in the treatment of hyperlipidemia in dogs.

Animals

Ten client‐owned dogs with primary (n = 7) and secondary (n = 3) hyperlipidemia. All dogs had hypertriglyceridemia at baseline; 3 dogs also had hypercholesterolemia.

Methods

Prospective dose‐escalation study. Dogs were treated with fenofibrate orally once daily in up to 3 cycles of 21 days each. Fenofibrate dose was increased at the end of each cycle if hypertriglyceridemia persisted and adverse effects were not documented. Complete blood count, biochemistry, and urine protein:creatinine ratio were collected serially. Baseline (T0) parameters were compared to time of maximal reduction in serum triglyceride concentrations (T1) and reported as median (range).

Results

Triglycerides normalized in all dogs (T0 = 662 mg/dL [189‐2391]; T1 = 113 mg/dL [81‐132]; P = .002). Fenofibrate dose at T1 = 6.4 mg/kg PO q24h (range, 2.2‐13.5). T1 was achieved at 3 (n = 4), 6 (n = 4), and 9 (n = 2) weeks. Serum cholesterol concentrations decreased in 9 of 10 dogs. Quiet demeanor and firm stools in 1 dog were the only reported adverse reactions. Fenofibrate administration resulted in a significant reduction in median alkaline phosphatase activity (P = .049).

Conclusions and Clinical Importance

Over 21 to 63 days, TriCor was effective in the management of primary and secondary hyperlipidemia in dogs.

Effect of a low-fat diet on serum triglyceride and cholesterol concentrations and lipoprotein profiles in Miniature Schnauzers with hypertriglyceridemia

Background

Hypertriglyceridemia is common in Miniature Schnauzer (MS). Dietary management of hypertriglyceridemia is important, but no studies are available.

Hypothesis/Objectives

To evaluate the effect of a commercially available low‐fat diet on serum triglyceride and cholesterol concentrations and lipoprotein profiles in MS with hypertriglyceridemia.

Animals

Sixteen MS with hypertriglyceridemia and 28 MS without hypertriglyceridemia.

Methods

Prospective clinical trial. Four blood samples (1‐2 months before and 1 day before diet change and 2 and 3 months after the dogs were fed the low‐fat diet) were collected from the MS with hypertriglyceridemia.

Results

Serum triglyceride concentrations for the 2 samples after the diet change (median of sample 3 = 177 mg/dL; range, 48‐498; median of sample 4 = 168 mg/dL; range, 77‐745) were significantly lower than the 2 samples before the diet change (median of sample 1 = 480 mg/dL; range, 181‐1320; median of sample 2 = 493 mg/dL; range, 114‐1395; P < .001). Serum cholesterol concentrations for the 2 samples after the diet change (mean for sample 3 = 257 mg/dL, SD = 82.2; mean for sample 4 = 178 mg/dL, SD = 87.4) were also significantly lower than the 2 samples before the diet change (mean for sample 1 = 381 mg/dL, SD = 146.1; mean for sample 2 = 380 mg/dL, SD = 134.7; P < .001). Before the diet change, 15/16 (94%) of hyperlipidemic MS were classified as hyperlipidemic based on their lipoprotein profiles alone. After the diet change, significantly fewer MS (7/16; 44%; odds ratio = 19.3; 95% CI = 2.0‐184.0; P = .006) were classified as hyperlipidemic based on lipoprotein profile analysis.

Conclusions and Clinical Importance

The study diet was effective in reducing serum triglyceride and cholesterol concentrations and correcting lipoprotein profiles in MS with hypertriglyceridemia.

Improvement Effect of 5-Aminolevulinic Acid on Hyperlipidemia in Miniature Schnauzer Dogs: An Open Study in 5 Cases of One Pedigree

This is the first study to examine the long-term effect of 5-aminolevulinic acid mainly on serum lipoproteins in dogs with hyperlipidemia. We studied 5 Miniature Schnauzer cases whose fasting serum total triglyceride and very-low-density lipoprotein of triglyceride levels were extremely high (635 ± 116 and 520 ± 92 mg/dL, respectively). Although the total cholesterol values were normal, the very-low-density lipoprotein of cholesterol level was high (49 ± 7 mg/dL). Each dog received a 5-aminolevulinic acid supplement (5 mg/day) orally for 6 months. The mean values of total triglyceride, very-low-density lipoprotein of both triglyceride and cholesterol decreased significantly after the treatment period (319 ± 29, 245 ± 18, and 27 ± 2 mg/dL, respectively, P < 0.05). Our present results may present evidence that 5-ALA administration contributes to improvement of hyperlipidemia in Miniature Schnauzer.

Starch sources influence lipidaemia of diabetic dogs

BACKGROUND

Hyperlipidaemia is considered a cause of other diseases that are clinically important and potentially life threatening. Combination of pea and barley as exclusive starch sources is known to interfere with glycemic control in diabetic dogs, but their effect on lipid profile of hiperlipidaemic dogs is yet to be evaluated. Twelve adult diabetic dogs were fed three dry extruded diets with different starch sources and different fat levels: peas and barley (PB), maize (Mi), and peas, barley and rice (Ba) with 15.7, 15.6 and 9.0% of their dry matter as fat, respectively. Plasmatic cholesterol and triglycerides concentration curves over 10 h were obtained after 60 days on each diet and with the same NPH insulin dose. ANOVA test or Friedman test were used to compare the dietary effects on triglycerides and cholesterol variables among the diets.

RESULTS

Dogs presented lower mean (p = 0.05), fasting (p = 0.03), and time 8-h postprandial (p = 0.05) triglyceridemia after PB diet period than Ba diet period and time 4-h postprandial (p = 0.02) lower after PB than Mi diet. Cholesterolemia mean, minimum, maximum, area under the cholesterol curve and times points: 2, 4, 6, 8 and 10-h postprandial, had lower values after PB ingestion in comparison to Mi, without difference to Ba diet.

CONCLUSION

Inclusion of pea and barley, as exclusive starch sources, in therapeutic diets for diabetic dogs can minimize plasmatic triglycerides and cholesterol concentration at fasting and at different postprandial time, compared to the maize diet or diet with lesser fat content.

Clinical Consequences of Hypertriglyceridemia-Associated Proteinuria in Miniature Schnauzers

BACKGROUND

Primary hypertriglyceridemia is a common condition in older Miniature Schnauzers that recently has been associated with proteinuria and underlying glomerular pathology, particularly glomerular lipid thromboemboli. Consequences of glomerular disease can include hypertension, thromboembolic disease, and cardiac disease. The incidence of these sequelae in Miniature Schnauzers with hypertriglyceridemia-associated proteinuria (HTGP) is unknown.

OBJECTIVE

To investigate prevalence of hypertension, decreased antithrombin III activity, and cardiac disease in Miniature Schnauzers with and without HTGP.

ANIMALS

Thirty-two Miniature Schnauzers ≥7 years old.

METHODS

Prospective case-control study. Data collected from dogs included a CBC, biochemistry panel, urinalysis, urine protein-to-creatinine ratio, urine cortisol-to-creatinine ratio, serum total thyroxine concentration, fasting serum triglyceride concentration, indirect blood pressure, antithrombin III activity, and serum cardiac troponin I concentration. Results from dogs with HTGP (serum triglyceride concentration ≥ 100 mg/dL and urine protein-to-creatinine ratio >0.5) were statistically compared to normotriglyceridemic, nonproteinuric dogs.

RESULTS

Eighteen of the 32 dogs (56%) had primary hypertriglyceridemia. Of those dogs, 8 of 18 had proteinuria. None of the HTGP dogs were azotemic or hypoalbuminemic. Serum albumin concentration, alkaline phosphatase activity, and cholesterol concentration were significantly increased in dogs with HGTP compared to those without HGTP. No increased risk of hypertension, decreased antithrombin III activity, or cardiac disease was noted. Limited data from 8 dogs with HTGP showed no development of hypoalbuminemia or azotemia over a median follow-up period of 18 months.

CONCLUSIONS AND CLINICAL IMPORTANCE

Geriatric Miniature Schnauzers with HGTP may have a good prognosis overall, and are not typically azotemic or hypoalbuminemic.

Therapy of Canine Hyperlipidemia with Bezafibrate

BACKGROUND

Bezafibrate (BZF) is effective in the treatment of hypertriglyceridemia in human patients, but there are no data on its use in dogs.

OBJECTIVE

To assess the safety of BZF in hyperlipidemic dogs and its efficacy in decreasing serum triglyceride (TG) and cholesterol (CHO) concentrations.

ANIMALS

Forty-six dogs, 26 females and 20 males, mean (±SD) age of 9 (±3) years, with TG ≥150 mg/dL (33 dogs also were hypercholesterolemic [>300 mg/dL]).

METHODS

Prospective, uncontrolled clinical trial. Dogs were treated with bezafibrate once daily, using 200 mg tablets at a dosage of 4-10 mg/kg (depending on body weight). Serum TG and CHO concentrations and alanine aminotransferase (ALT) and creatine kinase (CK) activity before and after 30 days of treatment were compared.

RESULTS

Sixteen dogs (34.8%) had primary hyperlipidemia, and 30 dogs (65.2%) had secondary hyperlipidemia (including spontaneous hyperadrenocorticism [41.3%, n = 19/46], chronic treatment with glucocorticoids [10.8%, n = 5/46], and hypothyroidism [15.2%, n = 7/46]). After 30 days, serum TG concentration normalized (<150 mg/dL) in 42 dogs (91.3%) and CHO concentration normalized (<270 mg/dL) in 22 of 33 dogs (66.7%). There was no difference in baseline TG concentration between the primary and secondary hyperlipidemia subgroups, but the decrease in TG concentration after treatment was greater in the primary hyperlipidemia subgroup. No adverse effects were observed, but ALT activity decreased significantly after 30 days of treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

Over 30 days, BZF was safe and effective in treatment of primary and secondary hyperlipidemia in dogs.

Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs

Miniature Schnauzer dogs are predisposed to idiopathic hypertriglyerceridemia, which increases risk for diseases such as pancreatitis and gallbladder mucocele. Recently, elevated triglyceride concentrations have been associated with proteinuria in this breed, although it is difficult to determine which abnormality is primary. Retrospective review of renal tissue from 27 proteinuric Miniature Schnauzers revealed that 20 dogs had ultrastructural evidence of osmophilic globules consistent with lipid in glomerular tufts. Seven of these dogs had lipid thromboemboli in glomerular capillary loops that distorted their shape and compressed circulating erythrocytes. Triglyceride concentrations were reported in 6 of these 7 dogs, and all were hypertriglyceridemic. In addition, glomerular lipidosis (defined as accumulation of foam cells within peripheral capillary loops) was identified in a single dog. The remaining 12 dogs had smaller amounts of lipid that could only be identified ultrastructurally. Neither signalment data nor clinicopathologic parameters (serum albumin, serum creatinine, urine protein-to-creatinine ratio, and blood pressure) differed among the various types of lipid lesions. During the time course of this study, all dogs diagnosed with glomerular lipid thromboemboli were Miniature Schnauzers, underscoring the importance of recognizing these clear spaces within capillary loops as lipid.

Proteinuria and lipoprotein lipase activity in Miniature Schnauzer dogs with and without hypertriglyceridemia

Spontaneous hyperlipidemia in rats causes glomerular disease. Idiopathic hypertriglyceridemia (HTG) is prevalent in Miniature Schnauzers, but its relationship with proteinuria is unknown. Decreased activity of major lipid metabolism enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL), may play a role in the cyclic relationship between hyperlipidemia and proteinuria. These enzymes have also not been previously investigated in Miniature Schnauzers. The aims of this study were to determine the relationship between HTG and proteinuria in Miniature Schnauzers and to measure LPL and HL activities in a subset of dogs. Fifty-seven Miniature Schnauzers were recruited (34 with and 23 without HTG). Fasting serum triglyceride concentrations and urine protein-to-creatinine ratios (UPC) were measured in all dogs, and LPL and HL activities were determined in 17 dogs (8 with and 9 without HTG). There was a strong positive correlation between triglyceride concentration and UPC (r = 0.77-0.83, P < 0.001). Proteinuria (UPC ≥ 0.5) was present in 60% of dogs with HTG and absent from all dogs without HTG (P < 0.001). Proteinuric dogs were not azotemic or hypoalbuminemic. Dogs with HTG had a 65% reduction in LPL activity relative to dogs without HTG (P < 0.001); HL activity did not differ. Proteinuria occurs with HTG in Miniature Schnauzers and could be due to lipid-induced glomerular injury. Reduced LPL activity may contribute to the severity of HTG, but further assay validation is required.

Breed-specific biochemical reference intervals for the adult Dogue de Bordeaux

BACKGROUND

Breed-specific reference intervals are of increasing interest in veterinary medicine. The health monitoring of the Dogue de Bordeaux, a breed predisposed to familial juvenile glomerulonephropathy and hypothyroidism, would benefit from specific reference intervals.

OBJECTIVE

The purpose of this study was to establish breed-specific biochemical reference intervals for the Dogue de Bordeaux in accordance with the International Federation of Clinical Chemistry and Clinical and Laboratory Standards Institute guidelines.

METHODS

One hundred and twenty Dogues de Bordeaux from France and Belgium were recruited. Complete urinalysis and chemistry panels, venous blood gas variables, total thyroxin and thyroid stimulating hormone, and fibrinogen and antithrombin were measured for each dog. Reference intervals were determined using the non-parametric method. Confounding variables such as sex, age and color of facial mask were analyzed.

RESULTS

Due to pre-defined criteria for exclusion, 62 healthy dogs were finally selected for the reference intervals determination. Using the instrument manufacturer's generic canine RI for most analytes did not have a significant impact on potential clinical decisions, except for total proteins, ALT, AST, total cholesterol, lipase and total thyroxin, for which possible clinically relevant differences were noted.

CONCLUSION

Specific reference intervals for biochemical analytes in the Dogue de Bordeaux were determined under controlled pre-analytical and analytical conditions, and according to international recommendations. The use of these breed-specific reference intervals is recommended when using the specified analytic instruments, especially for the 6 analytes for which the reference intervals differed considerably from those provided by manufacturers.

Novel lipoprotein density profiling in healthy dogs of various breeds, healthy Miniature Schnauzers, and Miniature Schnauzers with hyperlipidemia

BACKGROUND

Despite the importance of abnormalities in lipoprotein metabolism in clinical canine medicine, the fact that most previously used methods for lipoprotein profiling are rather laborious and time-consuming has been a major obstacle to the wide clinical application and use of lipoprotein profiling in this species. The aim of the present study was to assess the feasibility of a continuous lipoprotein density profile (CLPDP) generated within a bismuth sodium ethylenediaminetetraacetic acid (NaBiEDTA) density gradient to characterize and compare the lipoprotein profiles of healthy dogs of various breeds, healthy Miniature Schnauzers, and Miniature Schnauzers with primary hypertriacylglycerolemia. A total of 35 healthy dogs of various breeds with serum triacylglycerol (TAG) and cholesterol concentrations within their respective reference intervals were selected for use as a reference population. Thirty-one Miniature Schnauzers with serum TAG and cholesterol concentrations within their respective reference intervals and 31 Miniature Schnauzers with hypertriacylglyceridemia were also included in the study.

RESULTS

The results suggest that CLPDP using NaBiEDTA provides unique diagnostic information in addition to measurements of serum TAG and cholesterol concentrations and that it is a useful screening method for dogs with suspected lipoprotein metabolism disorders. Using the detailed and continuous density distribution information provided by the CLPDP, important differences in lipoprotein profiles can be detected even among dogs that have serum TAG and cholesterol concentrations within the reference interval. Miniature Schnauzers with serum TAG and cholesterol concentrations within the reference interval had significantly different lipoprotein profiles than dogs of various other breeds. In addition, it was further established that specific lipoprotein fractions are associated with hypertriacylglyceridemia in Miniature Schnauzers.

CONCLUSIONS

The results of the present study suggest that density gradient ultracentrifugation using NaBiEDTA is a useful screening method for the study of lipoprotein profiles in dogs. Therefore, this method could potentially be used for diagnostic purposes for the separation of dogs suspected of having lipoprotein abnormalities from healthy dogs.

Use of a meal challenge test to estimate peak postprandial triglyceride concentrations in dogs

OBJECTIVE

To develop a standardized meal challenge test by assessing associations between food-withheld preprandial (ie, fasting) and postprandial triglyceride concentrations, determining the most appropriate sampling time to detect the peak concentration (highest postprandial concentration), and estimating reference intervals for fasting and postprandial concentrations in healthy dogs.

ANIMALS

12 lean healthy mixed-breed dogs.

PROCEDURES

Dogs were fed a dry commercially available diet (fat, 31% metabolizable energy) for 3 weeks. After food was withheld for 23 to 24 hours, plasma triglyceride concentrations were measured 1 and 0.083 hours before and 1, 2, 3, 4, 5, 6, 9, and 12 hours after feeding of a standardized challenge meal (median amount eaten, 63 kcal/kg [127 kcal/kg⁰.⁷⁵]). Correlation and agreement between concentrations at peak and other time points were assessed by use of correlation coefficients and Bland-Altman limits of agreement. Reference intervals were calculated by use of a robust method.

RESULTS

Fasting and peak triglyceride concentrations were not closely associated. The highest concentration among samples obtained 2, 5, and 6 hours after meal consumption had closest agreement with peak concentration. In 5 of 12 dogs, concentrations 12 hours after eating were still significantly above baseline concentration (mean of each dog's fasting concentrations).

CONCLUSIONS AND CLINICAL RELEVANCE

Fasting triglyceride concentration could not be used to accurately predict peak concentration. When estimating peak concentration, multiple samples should be collected 2, 5, and 6 hours after consumption of a standardized meal. Food may need to be withheld for > 12 hours when assessing fasting concentrations in healthy dogs.

Association Between Serum Triglyceride and Canine Pancreatic Lipase Immunoreactivity Concentrations in Miniature Schnauzers

The objective of this study was to investigate possible associations between serum triglyceride and canine pancreatic lipase immunoreactivity (cPLI) concentrations in miniature schnauzers. One hundred and ninety-five miniature schnauzers were enrolled and divided into two groups based on whether they had normal (group 1) or increased (group 2) serum triglyceride concentrations. Serum cPLI concentrations were measured and compared between groups. A significant positive correlation was seen between serum triglyceride and cPLI concentrations (Spearman r=0.321; P&lt;0.0001). Miniature schnauzers with hypertriglyceridemia had a significantly higher median serum cPLI concentration (99.5 μg/L) than miniature schnauzers with normal serum triglyceride concentrations (median cPLI concentration 39.3 μg/L; P=0.0001). A cutoff value of 862 mg/dL was selected for serum triglyceride concentrations based on receiver operator characteristic analysis. Miniature schnauzers with severe hypertriglyceridemia (≥862 mg/dL) were 4.5 times more likely to have a serum cPLI concentration consistent with pancreatitis (≥200 μg/L) than miniature schnauzers with a normal serum triglyceride concentration. The present study supports an association between hypertriglyceridemia (especially when severe [≥862 mg/dL]) and high cPLI concentrations in miniature schnauzers.