Lipid and fatty acid composition of canine lipoproteins

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.

Myocardial glucose suppression may interfere with the detection of inflammatory cells with FDG-PET as suggested in a canine model of myocardial infarction

BACKGROUND

After myocardial infarction, fibrosis and an ongoing dysregulated inflammatory response have been shown to lead to adverse cardiac remodeling. FDG PET is an imaging modality sensitive to inflammation as long as suppression protocols are observed while gadolinium enhanced MRI can be used to determine extracellular volume (ECV), a measure of fibrosis. In patients, glucose suppression is achieved variously through a high fat diet, fasting and injection of heparin. To emulate this process in canines, a heparin injection and lipid infusion are used, leading to similar fatty acids in the blood. The aim of this study was to examine the effect of glucose suppression on the uptake of FDG in the infarcted myocardial tissue and also on the determination of ECV in both the infarcted tissue and in the myocardium remote to the zone of infarction during a long constant infusion of FDG and Gd-DTPA.

RESULTS

Extracellular volume was affected neither by suppression nor the length of the constant infusion in remote and infarcted tissue. Metabolic rate of glucose in infarcted tissue decreased during and after suppression of glucose uptake by lipid infusion and heparin injection. An increase in fibrosis and inflammatory cells was found in the center of the infarct as compared to remote tissue.

CONCLUSION

The decrease in the metabolic rate of glucose in the infarcted tissue suggests that inflammatory cells may be affected by glucose suppression through heparin injection and lipid infusion.

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

Removal of multiple lipids from human plasma using a hydroxyl-functionalized covalent organic framework aerogel as a new sorbent

A hydroxyl-functionalized covalent organic framework aerogel COFTHB-TAPB-aerogel was designed and prepared as an adsorbent for the removal of multiple lipids from human plasma. The applications of 1,3,5-tris(4'-hydroxy-5'-formylphenyl)benzene (THB) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as monomers, DMSO/mesitylene (v/v, 4/1) as reaction solvent, and n-propylamine as reaction regulator endow COFTHB-TAPB-aerogel with good adsorption performance for multiple lipids. The morphology, phase purity, specific surface area, pore size, surface charge, and stability of COFTHB-TAPB-aerogel were characterized. Adsorption thermodynamics and adsorption kinetics studies showed that COFTHB-TAPB-aerogel had high equilibrium adsorption capacities (> 15913 mg g-1) and fast adsorption equilibrium (≤ 10 s) for the four model lipids tested. COFTHB-TAPB-aerogel had good reusability with the removal of the model lipids being still more than 91% after 10 use cycles. The sample pretreatment conditions and adsorbent amounts used in lipids removal experiments were optimized. Under the optimized conditions, the method of ultra-high performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) using COFTHB-TAPB-aerogel as solid-phase extraction sorbent was validated with negligible matrix effects (0.4-3.0%) and good accuracy (86.7-110%) and was applied to determine  20 amino acids in human plasma samples from healthy individuals and gastric adenocarcinoma (GA) patients. The established method has been proved to have good application potential for the removal of multiple lipids in human plasma to reduce the matrix effects and improve the accuracy of clinical LC-MS analysis.

Metabolomics during canine pregnancy and lactation

During pregnancy and parturition, female dogs have to cope with various challenges such as providing nutrients for the growth of the fetuses, hormonal changes, whelping, nursing, milk production, and uterine involution. Metabolomic research has been used to characterize the influence of several factors on metabolism such as inter- and intra-individual factors, feeding, aging, inter-breed differences, drug action, behavior, exercise, genetic factors, neuter status, and pathologic processes. Aim of this study was to identify metabolites showing specific changes in blood serum at the different phases of pregnancy and lactation. In total, 27 privately owned female dogs of 21 different breeds were sampled at six time points: during heat, in early, mid and late pregnancy, at the suspected peak of lactation and after weaning. A validated and highly automated canine-specific NMR metabolomics technology was utilized to quantitate 123 measurands. It was evaluated which metabolite concentrations showed significant changes between the different time points. Metabolites were then grouped into five clusters based on concentration patterns and biochemical relationships between the metabolites: high in mid-pregnancy, low in mid-pregnancy, high in late pregnancy, high in lactation, and low in lactation. Several metabolites such as albumin, glycoprotein acetyls, fatty acids, lipoproteins, glucose, and some amino acids show similar patterns during pregnancy and lactation as shown in humans. The patterns of some other parameters such as branched-chain amino acids, alanine and histidine seem to differ between these species. For most metabolites, it is yet unstudied whether the observed changes arise from modified resorption from the intestines, modified production, or metabolism in the maternal or fetal tissues. Hence, further species-specific metabolomic research may support a broader understanding of the physiological changes caused by pregnancy that are likely to be key for the normal fetal growth and development. Our findings provide a baseline of normal metabolic changes during healthy canine pregnancy and parturition. Combined with future metabolomics findings, they may help monitor vital functions of pre-, intra-, and post-partum bitches and may allow early detection of illness.

Metabolomic Abnormalities in Serum from Untreated and Treated Dogs with Hyper- and Hypoadrenocorticism

The adrenal glands play a major role in metabolic processes, and both excess and insufficient serum cortisol concentrations can lead to serious metabolic consequences. Hyper- and hypoadrenocorticism represent a diagnostic and therapeutic challenge. Serum samples from dogs with untreated hyperadrenocorticism (n = 27), hyperadrenocorticism undergoing treatment (n = 28), as well as with untreated (n = 35) and treated hypoadrenocorticism (n = 23) were analyzed and compared to apparently healthy dogs (n = 40). A validated targeted proton nuclear magnetic resonance (¹H NMR) platform was used to quantify 123 parameters. Principal component analysis separated the untreated endocrinopathies. The serum samples of dogs with untreated endocrinopathies showed various metabolic abnormalities with often contrasting results particularly in serum concentrations of fatty acids, and high- and low-density lipoproteins and their constituents, which were predominantly increased in hyperadrenocorticism and decreased in hypoadrenocorticism, while amino acid concentrations changed in various directions. Many observed serum metabolic abnormalities tended to normalize with medical treatment, but normalization was incomplete when compared to levels in apparently healthy dogs. Application of machine learning models based on the metabolomics data showed good classification, with misclassifications primarily observed in treated groups. Characterization of metabolic changes enhances our understanding of these endocrinopathies. Further assessment of the recognized incomplete reversal of metabolic alterations during medical treatment may improve disease management.

Identification of the atherosclerosis phenotype in vivo by vascular duplex ultrasonography in ApoE-deficient dogs

Background and aims

This study evaluated the atherosclerosis phenotype by vascular duplex ultrasonography (VDU) in ApoE-deficient dogs.

Methods

A total of 108 beagle dogs were examined by VDU, which included 32 wild-type, 68 heterozygous (ApoE-/+) mutant and 8 homozygous (ApoE-/-) mutant dogs. According to age, wild-type and ApoE-/+ dogs were divided into two subgroups: young (6-15 months) and adult dogs (18-29 months). All homozygous dogs were young dogs. Dogs were feed with normal diet. The plasma lipid levels were tested. The diameter of the common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA), abdominal aorta and common iliac artery (CIA) and the intima-media thickness (IMT) of the CCA and abdominal aorta were measured by VDU. The artery sections of ApoE-/- and control dogs were analyzed by histological analysis.

Results

The plasma triglycerides (2.5-3 fold), total cholesterol (4-5 fold) and LDL levels (35-40 fold) of ApoE-/- dogs were higher than those of the wild-type and ApoE-/+ dogs. Compared with the wild-type and young ApoE-/+ dogs, the IMT of CCA and aorta in ApoE-/- dogs were increased (p<0.05). The occurrence of atherosclerosis in ApoE-/- dogs was higher than that in ApoE-/+ dogs (50% vs. 10.3%, p=0.013) and the occurrence time was earlier. Histology confirmed that the aorta, carotid arteries and CIA had atherosclerotic lesions in ApoE-/- dogs.

Conclusions

The ApoE-deficient dogs were a reliable animal model of atherosclerosis. VDU is an optimal in vivo noninvasive method for evaluating atherosclerosis phenotypes in large animal models.

The highly unnatural fatty acid profile of cells in culture

The fatty acid profile of cells in culture are unlike those of natural cells with twice the monounsaturated (MUFA) and half the polyunsaturated fatty acids (PUFA) level (Mol%). This is not due to cell lines primarily being derived from cancers but is due to limited access to lipid and an inability to make PUFA de novo as vertebrate cells. Classic culture methods use media with 10% serum (the only exogenous source of lipid). Fetal bovine serum (FBS), the serum of choice has a low level of lipid and cholesterol compared to other sera and at 10% of media provides 2-3% of the fatty acid and cholesterol, 1% of the PUFA and 0.3% of the essential fatty acid linoleic acid (18:2n-6) available to cells in the body. Since vertebrate cell lines cannot make PUFA they synthesise MUFA, offsetting their PUFA deficit and reducing their fatty acid diversity. Stem and primary cells in culture appear to be similarly affected, with a rapid loss of their natural fatty acid compositions. The unnatural lipid composition of cells in culture has substantial implications for examining natural stems cell in culture, and for investigations of cellular mechanisms using cell lines based on the pervasive influence of fats.

Fast LC-ESI-MS/MS analysis and influence of sampling conditions for gut metabolites in plasma and serum

In the past few years, the gut microbiome has been shown to play an important role in various disorders including in particular cardiovascular diseases. Especially the metabolite trimethylamine-N-oxide (TMAO), which is produced by gut microbial metabolism, has repeatedly been associated with an increased risk for cardiovascular events. Here we report a fast liquid chromatography tandem mass spectrometry (LC-MS/MS) method that can analyze the five most important gut metabolites with regards to TMAO in three minutes. Fast liquid chromatography is unconventionally used in this method as an on-line cleanup step to remove the most important ion suppressors leaving the gut metabolites in a cleaned flow through fraction, also known as negative chromatography. We compared different blood matrix types to recommend best sampling practices and found citrated plasma samples demonstrated lower concentrations for all analytes and choline concentrations were significantly higher in serum samples. We demonstrated the applicability of our method by investigating the effect of a standardized liquid meal (SLM) after overnight fasting of 25 healthy individuals on the gut metabolite levels. The SLM did not significantly change the levels of gut metabolites in serum.

Association of acute Babesia canis infection and serum lipid, lipoprotein, and apoprotein concentrations in dogs

BACKGROUND

Babesia canis infection induces a marked acute phase response (APR) that might be associated with alteration in lipid and lipoprotein metabolism and disease prognosis.

HYPOTHESIS

Dogs with B. canis-induced APR develop dyslipidemia with altered lipoprotein concentration and morphology.

ANIMALS

Twenty-nine client-owned dogs with acute B. canis infection and 10 clinically healthy control dogs.

METHODS

Observational cross-sectional study. Serum amyloid A (SAA) was measured using ELISA. Cholesterol, phospholipids, and triglycerides were determined biochemically. Lipoproteins were separated using agarose gel electrophoresis. Lipoprotein diameter was assessed by polyacrylamide gradient gel electrophoresis; correlation with ApoA-1 (radioimmunoassay) and SAA was determined.

RESULTS

Dogs with B. canis infection had a marked APR (median SAA, 168.3 μg/mL; range, 98.1-716.2 μg/mL) compared with controls (3.2 μg/mL, 2.0-4.2 μg/mL) (P < .001). Dogs with B. canis infection had significantly lower median cholesterol (4.79 mmol/L, 1.89-7.64 mmol/L versus 6.15 mmol/L, 4.2-7.4 mmol/L) (P = .02), phospholipid (4.64 mmol/L, 2.6-6.6 mmol/L versus 5.72 mmol/L, 4.68-7.0 mmol/L) (P = .02), and α-lipoproteins (77.5%, 27.7%-93.5% versus 89.2%, 75.1%-93.5%) (P = .04), and higher ApoA-1 (1.36 U, 0.8-2.56 U versus 0.95 U, 0.73-1.54 U) concentrations (P = .02). Serum amyloid A correlated with high-density lipoproteins (HDLs) diameter (rho = .43; P = .03) and ApoA-1 (rho = .63, P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Major changes associated with B. canis-induced APR in dogs are related to concentration, composition, and morphology of HDL particles pointing to an altered reverse cholesterol transport. Parallel ApoA-1 and SAA concentration increase is a unique still unexplained pathophysiological finding.

Comparison of the systemic phospholipid profile in dogs diagnosed with idiopathic inflammatory bowel disease or food-responsive diarrhea before and after treatment

BACKGROUND

Inflammatory bowel disease (IBD) and food-responsive diarrhea (FRD) are common chronic enteropathies in dogs, of which the exact pathogenesis has not been fully understood. In people dyslipidemia has been reported in patients with IBD, and potential therapeutic benefits of polyunsaturated fatty acids (PUFA) in the treatment of IBD have been investigated. Studies on the phospholipid profile in dogs with IBD and FRD are still lacking.

AIM

To investigate the systemic phospholipid profile of dogs with IBD or FRD and to evaluate possible differences in phospholipids before and after treatment.

METHODS

The phospholipids in whole blood and EDTA plasma of 32 dogs diagnosed with either IBD (n = 16) or FRD (n = 16) were analyzed by hydrophilic interaction liquid chromatography (HILIC) prior to and after initiation of treatment, which included an elimination diet enriched with PUFAs.

RESULTS

A clear separation of the phospholipids between whole blood and plasma was demonstrated on principal component analysis plots. In addition to the type of specimen, treatment and disease severity were the most significant factors determining the variance of the phospholipid profile. An increase in lysolipids was observed after treatment. The phosphatidylcholine (PC) species changed from PC 38:4 before treatment to mainly lysophosphatidylcholine 18:0 after treatment. Furthermore, several differences in the abundance of individual phospholipids were identified between dogs with IBD and dogs with FRD and between treatment statuses using random forest analysis.

CONCLUSION

Significant variances were identified in the phospholipid profiles of dogs with IBD and FRD. These were particularly determined by type of specimen used, disease severity and treatment status. After treatment, a shift of phospholipid species towards lysophosphatidylcholine 18:0 was observed. Future studies should further investigate the role of lipids in the pathophysiology of IBD and FRD as well as their potential therapeutic benefits.

Indication of metabolic inflexibility to food intake in spontaneously overweight Labrador Retriever dogs

Background

Obesity in dogs is an increasing problem associated with morbidity, shortened life span and poor life quality. Overweight dogs exhibit postprandial hyperlipidaemia, highlighting the need to identify potential dysregulations in lipid metabolism. This study investigated metabolites related to lipid metabolism (i.e. acylcarnitines and taurine) and phospholipids in a feed-challenge test and aimed to identify metabolic variations in spontaneously overweight dogs. Twenty-eight healthy male Labrador Retriever dogs were included, 12 of which were classified as lean (body condition score (BCS) 4–5 on a 9-point scale) and 16 as overweight (BCS 6–8). After overnight fasting (14–17 h), fasting blood samples were collected and dogs were fed a high-fat meal followed by postprandial blood sample collection hourly for 4 h. Liquid chromatography-time of flight mass spectrometry (LC-TOFMS) was used to identify plasma metabolites and phospholipids. Multivariate models, mixed model repeated measures and linear regression analyses were used for data interpretation.

Results

In all dogs, propionylcarnitine, stearoylcarnitine and nine phospholipids increased in response to food intake, while vaccenylcarnitine decreased (P ≤ 0.005 for all). Overall, carnitine and acetylcarnitine signal areas in the feed-challenge test were lower in overweight dogs (P ≤ 0.004). Notably, fasting plasma acetylcarnitine was lower in overweight dogs than in lean dogs (P = 0.001) and it did not change in response to feeding. The latter finding was in contrast to the decreased acetylcarnitine signal area found in lean dogs at one hour postprandially (P < 0.0001). One fasting phosphatidylcholine (PCaa C38:4) was higher in prominently overweight dogs (BCS > 6) than in lean dogs (P < 0.05).

Conclusions

Plasma carnitine status was overall lower in spontaneously overweight dogs than in lean dogs in this cohort of healthy Labrador Retriever dogs, indicating a potential carnitine insufficiency in the overweight group. The acetylcarnitine response in overweight dogs indicated decreased fatty acid oxidation at fasting and metabolic inflexibility to food intake. Further studies on metabolic inflexibility and its potential role in the metabolism of overweight dogs are warranted.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1845-5) contains supplementary material, which is available to authorized users.

Association of serum calprotectin (S100A8/A9) concentrations and idiopathic hyperlipidemia in Miniature Schnauzers

BACKGROUND

Idiopathic hyperlipidemia (IH) is a common condition in Miniature Schnauzers (MS). Studies in people have linked IH to low-grade inflammation, which plays an important role in the pathogenesis of IH complications. The role of inflammation in MS with IH is unknown.

OBJECTIVE

Evaluation of the inflammatory markers serum calprotectin and S100A12 in MS with IH and in response to dietary intervention for IH management.

ANIMALS

One-hundred fifty clinically healthy MS.

METHODS

Serum triglyceride, cholesterol, calprotectin, and S100A12 concentrations were measured before and after placing the dogs on an ultra-low fat diet.

RESULTS

Hypertriglyceridemia (HTGL, P < .001) and hypercholesterolemia (HCHOL, P = .01) were independently associated with increased serum calprotectin but not S100A12 concentrations. Compared to normolipidemic MS, serum calprotectin concentrations were significantly higher in MS with HTGL (P < .001) or combined hyperlipidemia (P = .02), but not those with isolated HCHOL (P = 1.0000). Presence (P = .005) and severity (P = .003) of HTGL and serum cholesterol concentrations (P = .04) decreased in MS with IH within 14-26 weeks after being placed on the ultra-low fat diet, but neither serum calprotectin nor S100A12 concentrations changed significantly with this dietary intervention.

CONCLUSIONS AND CLINICAL IMPORTANCE

Subclinical (low-grade) inflammation appears to be present in some MS with IH, and an ultra-low fat diet does not decrease serum concentrations of inflammatory proteins in those dogs. Whether this presumed inflammatory phenotype in MS with IH is associated with the development of IH complications (eg, insulin resistance) requires further research.

Cardiac and Metabolic Variables in Obese Dogs

Background

The etiology of obesity‐related cardiac dysfunction (ORCD) is linked to metabolic syndrome in people. Studies have indicated that obese dogs have components of metabolic syndrome, warranting evaluation for ORCD in obese dogs.

Objectives

To evaluate cardiac structure and function and metabolic variables in obese dogs compared to ideal weight dogs.

Animals

Forty‐six healthy, small‐breed (<25 pounds), obese dogs (n = 29) compared to ideal weight dogs (n = 17).

Methods

A cross‐sectional study of cardiac structure and function by standard and strain echocardiographic measurements and quantification of serum metabolic variables (insulin:glucose ratios, lipid analysis, adiponectin, inflammatory markers).

Results

Compared to the ideal weight controls, obese dogs had cardiac changes characterized by an increased interventricular septal width in diastole to left ventricular internal dimension in diastole ratio, decreased ratios of peak early to peak late left ventricular inflow velocities, and ratios of peak early to peak late mitral annular tissue velocities, and increased fractional shortening and ejection fraction percentages. The left ventricular posterior wall width in diastole to left ventricular internal dimension in diastole ratios were not significantly different between groups. Systolic blood pressure was not significantly different between groups. Obese dogs had metabolic derangements characterized by increased insulin:glucose ratios, dyslipidemias with increased cholesterol, triglyceride, and high‐density lipoprotein concentrations, decreased adiponectin concentrations, and increased concentrations of interleukin 8 and keratinocyte‐derived chemokine‐like inflammatory cytokines.

Conclusions and Clinical Importance

Compared to ideal weight controls, obese dogs have alterations in cardiac structure and function as well as insulin resistance, dyslipidemia, hypoadiponectinemia, and increased concentrations of inflammatory markers. These findings warrant additional studies to investigate inflammation, dyslipidemia, and possibly systemic hypertension as potential contributing factors for altered cardiac function.

Markers of Oxidative Stress in Dogs with Myxomatous Mitral Valve Disease are Influenced by Sex, Neuter Status, and Serum Cholesterol Concentration

Background

Cardiovascular disease has been associated with oxidative stress, which has been suggested to contribute to myocardial remodeling in human patients. Little is known about the relationship between myxomatous mitral valve disease (MMVD) and oxidative stress in dogs.

Objective

To determine whether clinical stage of MMVD is associated with changes in the plasma concentrations of certain markers of oxidative stress in clinically healthy dogs and dogs with MMVD.

Animals

Seventy five privately owned dogs: 59 cavalier King Charles Spaniels (CKCS) with different severities of MMVD and 16 dogs of different breeds with clinical signs of congestive heart failure (CHF) caused by MMVD.

Methods

Markers of oxidative stress including malondialdehyde (MDA), oxidized low‐density lipoprotein (oxLDL), and vitamin E (α‐tocopherol and γ‐tocopherol) were measured in plasma and their association with clinical stage of MMVD was assessed by regression analyses.

Results

Plasma oxLDL concentration was significantly lower in female dogs compared with males (P = .01). Significantly higher plasma γ‐tocopherol concentrations were found in neutered (P = .003) dogs. Vitamin E (α‐tocopherol [P = .0004] and γ‐tocopherol [P = .003]) was associated with body condition score (BCS), but the association disappeared when cholesterol was included in the analyses. All markers of oxidative stress (MDA, oxLDL, and vitamin E) were positively associated with serum cholesterol concentration (P ≤ .04), but none were associated with clinical stage of MMVD.

Conclusions

In conclusion, markers of oxidative stress are associated with sex, BCS, neuter status, and cholesterol. The results cannot confirm a relationship between oxidative stress and clinical stage of the disease in dogs with MMVD.

Do small differences in hydration status affect mood and mental performance?

Although it has been suggested that many in the general population are dehydrated to the extent that mood and cognition are disrupted, there has been little research investigating mild levels of dehydration. When dehydration reduces body mass by more than 2%, it has been consistently reported that mood is influenced, fatigue is greater, and alertness is lower. In contrast, the effects on cognition have been less consistent. Only a few studies have looked at females and these studies made little attempt to consider hormones that influence kidney functioning. In particular, there has been virtually no attempt to look at changes in hydration status in the range that occurs in individuals with a sedentary lifestyle in a temperate climate. There is a consequent need to study individuals who have lost up to 1% of body mass due to dehydration. While 4 intervention trials have found that the cognition of children improved in response to water consumption, the effects of water consumption on cognition in older adults, another high-risk group, have been largely ignored.

Comparison of 2 electrophoretic methods and a wet-chemistry method in the analysis of canine lipoproteins

BACKGROUND

The evaluation of lipoprotein metabolism in small animal medicine is hindered by the lack of a gold standard method and paucity of validation data to support the use of automated chemistry methods available in the typical veterinary clinical pathology laboratory. The physical and chemical differences between canine and human lipoproteins draw into question whether the transference of some of these human methodologies for the study of canine lipoproteins is valid. Validation of methodology must go hand in hand with exploratory studies into the diagnostic or prognostic utility of measuring specific lipoproteins in veterinary medicine.

OBJECTIVE

The goal of this study was to compare one commercially available wet-chemistry method to manual and automated lipoprotein electrophoresis in the analysis of canine lipoproteins.

METHODS

Canine lipoproteins from 50 dogs were prospectively analyzed by 2 electrophoretic methods, one automated and one manual method, and one wet-chemistry method.

RESULTS

Electrophoretic methods identified a higher proportion of low-density lipoproteins than the wet-chemistry method. Automated electrophoresis occasionally failed to identify very low-density lipoproteins.

CONCLUSIONS

Wet-chemistry methods designed for evaluation of human lipoproteins are insensitive to canine low-density lipoproteins and may not be applicable to the study of canine lipoproteins. Automated electrophoretic methods will likely require significant modifications if they are to be used in the analysis of canine lipoproteins. Studies aimed at determining the impact of a disease state on lipoproteins should thoroughly investigate the selected methodology prior to the onset of the study.

Biopterin status in dogs with myxomatous mitral valve disease is associated with disease severity and cardiovascular risk factors

BACKGROUND

Endothelial dysfunction (ED) has been suggested to be associated with myxomatous mitral valve disease (MMVD) in dogs. Tetrahydrobiopterin (BH4) is an important cofactor for production of the endothelium-derived vasodilator nitric oxide (NO). Under conditions of oxidative stress, BH4 is oxidized to the biologically inactive form dihydrobiopterin (BH2). Thus, plasma concentrations of BH2 and BH4 may reflect ED and oxidative stress.

OBJECTIVE

To determine plasma concentrations of BH2 and BH4 in dogs with different degrees of MMVD.

ANIMALS

Eighty-four privately owned dogs grouped according to ACVIM guidelines (37 healthy control dogs including 13 Beagles and 24 Cavalier King Charles Spaniels [CKCSs], 33 CKCSs with MMVD of differing severity including 18 CKCSs [group B1] and 15 CKCSs [group B2], and 14 dogs of different breeds with clinical signs of congestive heart failure [CHF] because of MMVD [group C]).

METHODS

Dogs underwent clinical examination including echocardiography. Plasma concentrations of BH2 and BH4 were measured using high-performance liquid chromatography with fluorescence detection.

RESULTS

Higher plasma BH4 and BH2 concentrations were found with dogs in CHF compared with all other groups (control, B1 and B2; P ≤ .001). Females had higher concentrations of BH4 and BH4/BH2 (P ≤ .0003). BH4/BH2 was found to decrease with age (P < .0001). Cardiovascular risk factors in humans such as passive smoking (P ≤ .01) and increased body weight (P ≤ .009) were associated with lower BH4 concentrations.

CONCLUSIONS AND CLINICAL IMPORTANCE

Age, sex, body weight, passive smoking, and cardiac status are associated with plasma biopterin concentration in dogs. Additional studies should clarify the clinical implications of the findings.

Interfacial tension and surface pressure of high density lipoprotein, low density lipoprotein, and related lipid droplets

Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively) are essentially lipid droplets surrounded by specific proteins, their main function being to transport cholesterol. Interfacial tension and surface pressure of these particles are of great interest because they are related to the shape and the stability of the droplets and to protein adsorption at the interface. Here we use coarse-grained molecular-dynamics simulations to consider a number of related issues by calculating the interfacial tension in protein-free lipid droplets, and in HDL and LDL particles mimicking physiological conditions. First, our results suggest that the curvature dependence of interfacial tension becomes significant for particles with a radius of ∼5 nm, when the area per molecule in the surface region is <1.4 nm(2). Further, interfacial tensions in the used HDL and LDL models are essentially unaffected by single apo-proteins at the surface. Finally, interfacial tensions of lipoproteins are higher than in thermodynamically stable droplets, suggesting that HDL and LDL are kinetically trapped into a metastable state.

Role of lipids in spheroidal high density lipoproteins

We study the structure and dynamics of spherical high density lipoprotein (HDL) particles through coarse-grained multi-microsecond molecular dynamics simulations. We simulate both a lipid droplet without the apolipoprotein A-I (apoA-I) and the full HDL particle including two apoA-I molecules surrounding the lipid compartment. The present models are the first ones among computational studies where the size and lipid composition of HDL are realistic, corresponding to human serum HDL. We focus on the role of lipids in HDL structure and dynamics. Particular attention is paid to the assembly of lipids and the influence of lipid-protein interactions on HDL properties. We find that the properties of lipids depend significantly on their location in the particle (core, intermediate region, surface). Unlike the hydrophobic core, the intermediate and surface regions are characterized by prominent conformational lipid order. Yet, not only the conformations but also the dynamics of lipids are found to be distinctly different in the different regions of HDL, highlighting the importance of dynamics in considering the functionalization of HDL. The structure of the lipid droplet close to the HDL-water interface is altered by the presence of apoA-Is, with most prominent changes being observed for cholesterol and polar lipids. For cholesterol, slow trafficking between the surface layer and the regimes underneath is observed. The lipid-protein interactions are strongest for cholesterol, in particular its interaction with hydrophobic residues of apoA-I. Our results reveal that not only hydrophobicity but also conformational entropy of the molecules are the driving forces in the formation of HDL structure. The results provide the first detailed structural model for HDL and its dynamics with and without apoA-I, and indicate how the interplay and competition between entropy and detailed interactions may be used in nanoparticle and drug design through self-assembly.

Antimicrobial drug resistance

This chapter provides an overview of our current understanding of the mechanisms associated with the development of antimicrobial drug resistance, international differences in definitions of resistance, ongoing efforts to track shifts in drug susceptibility, and factors that can influence the selection of therapeutic intervention. The latter presents a matrix of complex variables that includes the mechanism of drug action, the pharmacokinetics (PK) of the antimicrobial agent in the targeted patient population, the pharmacodynamics (PD) of the bacterial response to the antimicrobial agent, the PK/PD relationship that will influence dose selection, and the integrity of the host immune system. Finally, the differences between bacterial tolerance and bacterial resistance are considered, and the potential for non-traditional anti-infective therapies is discussed.

Choline or CDP-choline alters serum lipid responses to endotoxin in dogs and rats: involvement of the peripheral nicotinic acetylcholine receptors

We showed previously that choline administration protects dogs from endotoxin-induced multiple organ injury and platelet dysfunctions. Because sepsis/endotoxemia is associated with alterations in lipid metabolism, we have investigated whether choline or cytidine-5'-diphosphate choline, a choline donor, alters serum lipid responses to endotoxin in dogs and rats. In response to endotoxin, serum concentrations of triglycerides, choline-containing phospholipids, total cholesterol, and high-density lipoprotein cholesterol increased in a dose- and time-related manner. Administration of choline (20 mg/kg i.v. in dogs or 90 mg/kg i.p. in rats) or cytidine-5'-diphosphate choline (70 mg/kg i.v. in dogs) 5 min before and 4 and 8 h after endotoxin blocked or attenuated the increases in serum triglycerides, total cholesterol, and nonesterified fatty acids. Endotoxin-induced elevations in serum phospholipid levels did not change in rats and were enhanced in dogs by choline. In rats, serum lipid response to endotoxin was accompanied by severalfold elevations in serum levels of hepatorenal injury markers; their elevations were also blocked by choline. Pretreatment with hexamethonium blocked choline's effects on serum lipids and hepatorenal injury markers. Pretreatment with atropine blocked endotoxin-induced elevations in serum lipid and hepatorenal injury markers, but failed to alter choline's actions on these parameters. Choline treatment improved survival rate of rats in lethal endotoxin shock. In conclusion, these data show that choline treatment alters serum lipid responses to endotoxin and prevents hepatorenal injury during endotoxemia through a nicotinic acetylcholine receptor-mediated mechanism. Hence, choline and choline-containing compounds may have a therapeutic potential in the treatment of endotoxemia/sepsis.

Chromatographic Analysis of Lipid Fractions in Healthy Dogs and Dogs with Obesity or Hyperadrenocorticism

Obesity and endogenous hyperadrenocorticism (HAC) are common clinical conditions in veterinary practice, and both conditions have clinical and laboratory similarities, such as weight gain and dyslipidemia. The objective of the present study was to characterize and compare the lipid profiles and plasma lipoprotein fractions in healthy dogs ( n = 10), in obese dogs ( n = 10), and in dogs with HAC ( n = 6). All of the dogs were client owned. The lipoproteins were separated by fast protein liquid chromatography, and the plasma concentrations of total cholesterol and total triacylglycerol (TAG) were determined by enzymatic methods. When compared with the healthy and obese groups, dogs with HAC had a significant increase ( P < 0.01) in the total concentrations of TAGs and cholesterol (CHOL), with higher distribution in the very low-density lipoprotein (VLDL)–CHOL fractions. In addition, the distributions of the high-density lipoprotein (HDL)–CHOL and HDL–TAG fractions were significantly lower ( P < 0.01) in dogs with HAC than in healthy dogs. Considering the animals in this study, it was determined that the dogs with HAC differed significantly from the healthy and obese dogs regarding the metabolism of CHOL and TAG, as well as their VLDL and HDL fractions. Similar laboratory findings could allow veterinarians to distinguish obese dogs from those with HAC. In addition, dogs with HAC may be at higher risk for developing metabolic and atherosclerotic complications.

Solid intraocular xanthogranuloma in three Miniature Schnauzer dogs

OBJECTIVE

Macrophages that contain abundant intracytoplasmic lipid are called 'foam cells'. In four canine globes submitted to the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW), foam cells formed a solid intraocular mass. The purpose of this study was to describe the histopathologic findings in these cases.

PROCEDURE

The electronic COPLOW database (1993-2006) was searched for the diagnosis of 'foam cell tumor'. Clinical history, gross pathology and histopathology (5-micron sections, hematoxylin and eosin and Alcian blue periodic acid Schiff) were reviewed in all cases. Cases were included if the globe was grossly filled by a solid mass and if all intraocular structures were effaced by lipid-laden foam cell macrophages admixed with birefringent, Alcian blue-positive crystals oriented in stellate patterns.

RESULTS

All three patients (four globes) satisfying the selection criteria were Miniature Schnauzers. In all cases the clinical history included diabetes mellitus, hyperlipidemia and chronic bilateral uveitis that was interpreted to be lens-induced. All globes were enucleated because of glaucoma.

CONCLUSIONS

The term solid intraocular xanthogranuloma was used to describe these cases because the intraocular contents were effaced by a solid mass of foam cells and birefringent crystals. The cases in this report suggest that diabetic Miniature Schnauzers with hyperlipidemia are at risk for lipid and macrophage-rich uveitis, which may in some cases form a solid inflammatory intraocular mass, precipitate glaucoma, and lead to enucleation.

Serum concentrations of adiponectin and characterization of adiponectin protein complexes in dogs

OBJECTIVE

To assess serum concentrations of adiponectin and characterize adiponectin protein complexes in healthy dogs.

ANIMALS

11 healthy dogs.

PROCEDURES

Sera collected from 10 dogs were evaluated via velocity sedimentation and ultracentrifugation, SDS-PAGE, western immunoblotting, and radioimmunoassay. Visceral adipose tissue (approx 90 g) was collected from the falciform ligament of a healthy dog undergoing elective ovariohysterectomy, and adiponectin gene expression was assessed via a real-time PCR procedure.

RESULTS

Adiponectin gene expression was detected in visceral adipose tissue. Serum adiponectin concentrations ranged from 0.85 to 1.5 microg/mL (mean concentration, 1.22 microg/mL). In canine serum, adiponectin was present as a multimer, consisting of a low-molecular-weight complex (180 kd); as 3 (180-, 90-, and 60-kd) complexes under denaturing conditions; as 2 (90- and 60-kd) complexes under reducing conditions; and as a dimer, a monomer, and globular head region (60, 30, and 28 kd, respectively) under reducing-denaturing conditions. It is likely that adiponectin also circulates as a high-molecular-weight (360- to 540-kd) complex in canine serum, but resolution of this complex was not possible via SDS-PAGE.

CONCLUSIONS AND CLINICAL RELEVANCE

After exposure to identical experimental conditions, adiponectin protein complexes in canine serum were similar to those detected in human and rodent sera. Circulating adiponectin concentrations in canine serum were slightly lower than concentrations in human serum. Adiponectin gene expression was identified in canine visceral adipose tissue. Results suggest that adiponectin could be used as an early clinical marker for metabolic derangements, including obesity, insulin resistance, and diabetes mellitus in dogs.

Interplay between lipoproteins and bee venom phospholipase A2 in relation to their anti-plasmodium toxicity

We previously showed that the in vitro intraerythrocytic development of the malarial agent Plasmodium falciparum is strongly inhibited by secreted phospholipases A(2) (sPLA(2)s) from animal venoms. Inhibition is dependent on enzymatic activity and requires the presence of serum lipoproteins in the parasite culture medium. To evaluate the potential involvement of host lipoproteins and sPLA(2)s in malaria, we investigated the interactions between bee venom phospholipase A(2) (bvPLA(2)), human triglyceride-rich lipoproteins, and infected erythrocytes. Even at high enzyme concentration (100x IC(50)), bvPLA(2) binding to Plasmodium-infected or normal erythrocytes was not detected. On the contrary, tight association with lipoproteins was observed through the formation of buoyant bvPLA(2)/lipoprotein complexes. Direct involvement of the hydrolysis lipid products in toxicity was demonstrated. Arachidonic acid (C20:4), linoleic acid (C18:2), and, to a lesser extent, docosahexaenoic acid (C22:6) appeared as the main actors in toxicity. Minimal oxidation of lipoproteins enhanced toxicity of the lipolyzed particles and induced their interaction with infected or normal erythrocytes. Fresh or oxidized lipolyzed lipoproteins induced the parasite degeneration without host cell membrane disruption, ruling out a possible membranolytic action of fatty acids or peroxidation products in the death process. In conclusion, our data enlighten on the capability of secreted PLA(2)s to exert cytotoxicity via the extracellular generation of toxic lipids, and raise the question of whether such mechanisms could be at play in pathophysiological situations such as malaria.

8302A/C and (TTA)n polymorphisms in the HMG-CoA reductase gene may be associated with some plasma lipid metabolic phenotypes in patients with coronary heart disease

HMG-CoA reductase (HMGCR) is a rate-limiting enzyme that participates in cholesterol metabolism. Here we analyzed the 8302A/C and the (TTA)n polymorphisms in the HMGCR gene in 169 Chinese patients with coronary heart disease (CHD) and 161 age-matched controls. Results indicated that the levels of plasma VLDL and TG in patients with the AA genotype of the 8302A/C locus were significantly higher than in patients with other genotypes (P < 0.05). In addition, the frequency of allele A4 of the (TTA)n locus was higher (P < 0.05) and the frequency of allele A5 was lower (P = 0.002) in CHD patients than in the controls. This suggests that both polymorphisms in the HMGCR gene may be associated with lipid and lipoprotein abnormalities in CHD in the Chinese.

Selective uptake of high density lipoproteins cholesteryl ester in the dog, a species lacking in cholesteryl ester transfer protein activity

Amongst the processes involved in the reverse cholesterol transport (RCT) from organs to liver, including high density lipoproteins-apolipoprotein AI (HDL-apoAI) dependent tissue uptake and cholesteryl ester transfer protein (CETP)-mediated transfers, the selective uptake of cholesteryl ester (CE) is of increasing interest through its antiatherogenic role. The purpose of this report is to develop a simple protocol allowing study of this process in an animal model with easier quantification of CE selective uptake. The dog was chosen essentially because this animal has a low CETP activity and an appropriate size to conduce a kinetic study. Tracer kinetics were performed to estimate in vivo the contributions of the pathways involved in HDL-CE turnover in dogs. Stable isotopes, 13C-acetate and D3-leucine as labeled precursors of CE and apoAI, were infused to fasting dogs. Isotopic enrichments were monitored in plasma unesterified cholesterol and in HDL-CE and apoAI by mass spectrometry. Kinetics were analyzed using compartmental modeling. Results concerned the measurement of the activity of cholesterol esterification (0.13+/-0.032 h(-1)), rate of HDL-apoAI catabolism (0.024+/-0.012 h(-1)), HDL-CE turnover (0.062+/-0.010 h(-1)) and CE selective uptake (0.038+/-0.014 h(-1)). Our results show that CE in dogs is mainly eliminated by selective uptake of HDL-CE (60% of HDL-CE turnover), unlike in other species studied by similar methods in our laboratory. This study shows that among species used to analyze cholesterol metabolism, the dog appears to be the animal in whom HDL-CE selective uptake represents the largest part of HDL-CE turnover.

Influence of the fatty acid composition of lipids in chylomicron remnants derived from fish or corn oil on the lipid profile of cultured rat hepatocytes

The aim of this work was to characterise the lipid and fatty acid composition of chylomicron remnants enriched in n-3 or n-6 polyunsaturated fatty acids (PUFA) and to investigate their influence on the fatty acid profiles of the lipids of rat hepatocytes cultured in monolayers. Chylomicrons were prepared from the lymph collected from the thoracic duct of rats given an oral dose of fish or corn oil (high in n-3 and n-6 PUFA, respectively), and remnants were prepared in vitro from such chylomicrons using rat plasma containing lipoprotein lipase. The fatty acids predominating in the oils abounded also in their respective chylomicrons and remnants, especially in triacylglycerols. Chylomicrons as well as remnants contained small amounts of phospholipids and long-chain PUFA that were minor in, or absent from, the dietary oils, evidently provided by the intestinal epithelium. The incubation of hepatocytes for 6 h, with either n-3 or n-6 PUFA-rich remnants (0.25-0.75 mM triacylglycerol) resulted in a dose-dependent increase in the amount of triacylglycerols and phospholipids in the cells, which was not affected further by increasing the incubation time to 19 h. Whereas hepatocyte triacylglycerols mostly incorporated the PUFA predominating in each remnant type, the fatty acid profile of cell phospholipids was virtually unchanged. In addition, irrespective of whether they were enriched in n-3 or n-6 PUFA, remnants promoted a relative decrease in the amount of cholesteryl esters, a minor hepatocyte lipid class poor in PUFA. The results demonstrate that the hepatocyte fatty acid profile is modulated in a lipid-class specific way by the amount and type of dietary PUFA delivered to cells in chylomicron remnants.

Lipoproteins abnormalities in obese insulin-resistant dogs

Many studies have shown that obesity and low insulin sensitivity are associated with lipoprotein abnormalities, which are risk factors for coronary heart disease. The effects of insulin resistance on lipoprotein metabolism were investigated in hyperenergetic-fed beagle dogs, a new model of insulin resistance. Insulin resistance was assessed by the 3-hour euglycemic-hyperinsulinemic glucose clamp technique. Lipoproteins were separated by fast-protein liquid chromatography (FPLC) and lipid composition of the different lipoproteins was determined by enzymatic methods. Hyperenergetic diet was associated with a 43% +/- 5% increase in dog body weight and a reduction in insulin-mediated glucose uptake (28 +/- 3 to 16 +/- 1 mg. kg(-1). min(-1), P <.05). Low insulin sensitivity associated with obesity was related to an increase in plasma triglyceride (TG) through an increase in very-low-density lipoprotein (VLDL)-TG (0.071 +/- 0.020 v 0.382 +/- 0.242 mmol/L, P <.05) and high-density lipoprotein (HDL)-TG (0.025 +/- 0.012 v 0.242 +/- 0.143 mmol/L, P <.05). Other lipid abnormalities common in insulin resistant humans were also found: lower plasma HDL-cholesterol (4.690 +/- 0.151 v 3.937 +/- 0.141 mmol/L, P <.05) and higher plasma nonesterified fatty acids (NEFA) (0.974 +/- 0.094 v 1.590 +/- 0.127 mmol/L, P <.05) levels. These data show that this model of the insulin-resistant obese dog could be useful in studying insulin resistance-associated dyslipidemia.

Major plasma lipids and fatty acids in four HDL mammals

Lipid classes and their fatty acids were compared in plasma from four mammals: a laboratory rodent, the mouse; two domestic animals, the cat and dog; and a wild animal, the South American armadillo, Chaetophractus villosus. In all, the most abundant lipoprotein was high-density lipoprotein (HDL). In the total lipid of plasma, phospholipids (PL) predominated in all four species, in correlation with the proportion of HDL, both being largest in dogs. The major PL was phosphatidylcholine (PC), followed by sphingomyelin (SM) and lysophosphatidylcholine. The total plasma lipid from the four species contained long-chain n-6 polyunsaturated fatty acids as the predominant acyl groups, followed by comparable proportions of total saturated and monoenoic fatty acids and small percentages of n-3 PUFA. The percentages of these four major groups of fatty acids in PC, SM, triacylglycerols and cholesterol esters were similar among species, but showed significant differences in the ratios between major individual fatty acids composing these groups.

Reversibility of the changes induced by n-3 fatty acids in mouse plasma, liver and blood cell lipids

The changes induced by dietary n-3 fatty acids (FA) in the lipids and FA of plasma, liver and blood cells, and their reversibility, was studied in mice given a diet containing 9% fish oil (FO) for 2 weeks and then returned to, and kept for another 2 weeks on, the usual standard lab chow diet. In plasma, the concentrations of phospholipids (PL), mostly phosphatidylcholine (PC), triacylglycerols (TG), cholesterol and cholesterol esters (CE) decreased rapidly after starting the FO diet, and remained low from day 3 onwards. This decrease was concomitant with a remarkable reduction in the n-6 FA, especially 18:2n-6, not compensated for by the relative enrichment in n-3 FA induced by FO. In liver, TG and CE decreased and PL slightly increased, all of them showing reduced n-6/n-3 ratios. Sphingomyelin, which lacks polyunsaturated FA other than small amounts of 18:2 and 24:2n-6, showed altered ratios between its very long chain monoenes and saturates. In the washout phase, the most rapid event was an immediate increase in 18:2n-6 and after a few days in 20:4n-6 in plasma and liver, where most of the lipid and FA changes were reversed completely in about 10 days. In the case of blood cells even 2 weeks were insufficient for a reversal to the initial n-6/n-3 ratios. The lipid class responsible for this lack of reversibility was phosphatidylethanolamine, PC having returned to the initial fatty acid composition during the stated period.