Protecting effect of vitamin E supplementation on submaximal exercise-induced oxidative stress in sedentary dogs as assessed by erythrocyte membrane fluidity and paraoxonase-1 activity

PON1 enzyme activity assays for serum and heparinized plasma in horses and stability evaluation of the enzyme activity over different freeze-thaw cycles and mimic transportation

Consistent information and standardization procedures regarding the time of storage for frozen samples and the effects of storage time on enzyme activity are still missing in the literature. Thus, we evaluated the effects of different storage temperatures (-20 °C and - 80 °C), three repetitive freeze/thaw cycles, and 24-h mimic transportation on the activities of PON1 (paraoxonase and arylesterase), enzymes involved in the protection and detoxification processes of reactive molecules. PON1 enzymes' activity was validated on serum and heparinized plasma in horses. The results revealed that conditions and time of storage of blood samples for PON1 analyses altered the activities of both enzymes in both sample types, evidencing that these conditions can lead to protein degradation or general alteration. Specifically, paraoxonase and arylesterase activities significantly decreased among storage temperatures, with major effects detected at -20 °C. The repeated freeze/thaw cycles at -20 °C and 24-h mimic transport conditions also generated an expected degradation of the arylesterase in both serum and heparinized plasma while freeze/thaw cycles at -80 °C caused an increase of both arylesterase and paraoxonase activities on both sample types. In general, similar enzyme responses were detected between serum and heparinized plasma.

Dietary Strategies for Relieving Stress in Pet Dogs and Cats

A variety of physical, emotional, and mental factors can induce a stress response in pet dogs and cats. During this process, hypothalamus-pituitary-adrenal (HPA) and sympathetic-adrenal medulla (SAM) axes are activated to produce a series of adaptive short-term reactions to the aversive situations. Meanwhile, oxidative stress is induced where there is an imbalance between the production and scavenging of reactive oxygen species (ROS). Oxidative damage is also incorporated in sustained stress response causing a series of chronic problems, such as cardiovascular and gastrointestinal diseases, immune dysfunction, and development of abnormal behaviors. In this review, the effects and mechanisms of dietary regulation strategies (e.g., antioxidants, anxiolytic agents, and probiotics) on relieving stress in pet dogs and cats are summarized and discussed. We aim to shed light on future studies in the field of pet food and nutrition.

Changes in Acute Phase Proteins in Bitches after Laparoscopic, Midline, and Flank Ovariectomy Using the Same Method for Hemostasis

Simple Summary

Ovariectomy is a common surgical procedure in veterinary medicine, with many techniques involved. The aim of this study is to objectively evaluate the acute phase response by measuring the changes in a panel of acute phase proteins after applying three different ovariectomy techniques. C-reactive protein values showed increases of lower magnitude after laparoscopic ovariectomy compared with other techniques, indicating that this surgical technique induces a reduced inflammatory response and tissue damage. The use of this procedure is in agreement with the current tendency to use minimally invasive procedures for ovariectomy.

Abstract

Acute phase proteins (APP) are biomarkers of systemic inflammation, which allow monitoring the evolution of diseases, the response to treatments, and post-operative complications. Ovariectomy (OVE) is frequently performed in veterinary medicine and can be a useful model to evaluate surgical trauma and inflammation in the bitch. The objective was to investigate and compare the acute phase response (APR) after applying three different OVE techniques by measuring serum levels of C-reactive protein (CRP), haptoglobin (Hp), albumin (Alb), and paraoxonase-1 (PON-1). Forty-five intact bitches were included in the study, being randomly distributed into three groups: laparoscopic OVE (L), midline OVE (M), and flank OVE (F). Serum CRP, Hp, Alb, and PON-1 were measured before surgery, 1, 24, 72, and 168 h post-intervention. CRP levels increased significantly 24 h post-surgery in the M and F groups, but no significant variation was observed in the L group at any time of the study period. Hp was significantly higher in group L than in group F 72 h post-surgery. Alb and PON-1 showed no statistical difference among groups or among sampling periods. CRP response suggests that the use of laparoscopic procedures produce lower inflammation compared to open conventional approaches when performing OVE in the bitch.

Benefits of dietary supplements on the physical fitness of German Shepherd dogs during a drug detection training course

A high standard of physical fitness is an essential characteristic of drug detection dogs because it affects not only their ability to sustain high activity levels but also their attention and olfaction efficiency. Nutritional supplements could improve physical fitness by modulating energy metabolism, oxidative processes, and perceived fatigue. The aim of this study was to investigate the physiological and biochemical changes induced by submaximal exercise on drug detection dogs (German Shepherd breed) and to assess whether a dietary supplement improves their physical fitness. During a drug detection dog training course, seven dogs were fed with a basal diet (Control Group) for three-month period, while a further seven dogs were fed with a basal diet as well as a daily nutritional supplement containing branched-chain and limiting amino acids, carnitine, vitamins, and octacosanol (Treatment Group). At the end of this period, individual physical fitness was assessed by making each subject take a graded treadmill exercise test. A human heart rate monitor system was used to record the dog's heart rate (HR) during the treadmill exercise and the subsequent recovery period. The parameters related to HR were analysed using nonparametric statistics. Blood samples were collected before starting the nutritional supplement treatment, before and after the treadmill exercise and following recovery. Linear mixed models were used. The dietary supplements accelerated HR recovery, as demonstrated by the lower HR after recovery (P<0.05) and Time constants of HR decay (P<0.05), and by the higher Absolute HR Recovered (P<0.05) recorded in the Treatment group compared with the Control dogs. The supplemented dogs showed the lowest concentrations of creatine kinase (CK; P<0.001), aspartate aminotransferase (AST, P<0.05) and non-esterified fatty acids (NEFA; P<0.01) suggesting a reduction in muscle damage and improvement of energy metabolism. These data suggest that this combined supplement can significantly enhance the physical fitness of drug detection dogs.

The Search for Dietary Supplements to Elevate or Activate Circulating Paraoxonases

Low levels of paraoxonase 1 (PON1) have been associated with the development of several pathological conditions, whereas high levels have been shown to be anti-atherosclerotic in mouse models. These findings suggest that PON1 could be a good surrogate biomarker. The other members of the family, namely PON2 and PON3, the role of which has been much less studied, deserve more attention. This paper provides a systematic review of current evidence concerning dietary supplements in that regard. Preliminary studies indicate that the response to dietary supplements may have a nutrigenetic aspect that will need to be considered in large population studies or in clinical trials. A wide range of plant preparations have been found to have a positive action, with pomegranate and some of its components being the best characterized and Aronia melanocarpa one of the most active. Flavonoids are found in the composition of all active extracts, with catechins and genistein being the most promising agents for increasing PON1 activity. However, some caveats regarding the dose, length of treatment, bioavailability, and stability of these compounds in formulations still need to be addressed. Once these issues have been resolved, these compounds could be included as nutraceuticals and functional foods capable of increasing PON1 activity, thereby helping with the long-term prevention of atherosclerosis and other chronic ailments.

Distinctive adaptive response to repeated exposure to hydrogen peroxide associated with upregulation of DNA repair genes and cell cycle arrest

Many environmental and physiological stresses are chronic. Thus, cells are constantly exposed to diverse types of genotoxic insults that challenge genome stability, including those that induce oxidative DNA damage. However, most in vitro studies that model cellular response to oxidative stressors employ short exposures and/or acute stress models. In this study, we tested the hypothesis that chronic and repeated exposure to a micromolar concentration of hydrogen peroxide (H₂O₂) could activate DNA damage responses, resulting in cellular adaptations. For this purpose, we developed an in vitro model in which we incubated mouse myoblast cells with a steady concentration of ~50 μM H₂O₂ for one hour daily for seven days, followed by a final challenge of a 10 or 20X higher dose of H₂O₂ (0.5 or 1 mM). We report that intermittent long-term exposure to this oxidative stimulus nearly eliminated cell toxicity and significantly decreased genotoxicity (in particular, a >5-fold decreased in double-strand breaks) resulting from subsequent acute exposure to oxidative stress. This protection was associated with cell cycle arrest in G2/M and induction of expression of nine DNA repair genes. Together, this evidence supports an adaptive response to chronic, low-level oxidative stress that results in genomic protection and up-regulated maintenance of cellular homeostasis.

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Repetitive stimulus with subtoxic H₂O₂ resulted in cellular adaptive response.

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Cells responded by abridged cytotoxicity and reduced intracellular ROS.

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Adaptive response mitigated the genotoxicity of acute oxidative insults.

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Adaption induced overexpression of selected genes of the BER, NER, MMR pathways.

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Chronic and repetitive H₂O₂ resulted in cell cycle checkpoint arrest.

PON1 and Mediterranean Diet

The Mediterranean diet has been proven to be highly effective in the prevention of cardiovascular diseases. Paraoxonase 1 (PON1) has been implicated in the development of those conditions, especially atherosclerosis. The present work describes a systematic review of current evidence supporting the influence of Mediterranean diet and its constituents on this enzyme. Despite the differential response of some genetic polymorphisms, the Mediterranean diet has been shown to exert a protective action on this enzyme. Extra virgin olive oil, the main source of fat, has been particularly effective in increasing PON1 activity, an action that could be due to low saturated fatty acid intake, oleic acid enrichment of phospholipids present in high-density lipoproteins that favor the activity, and increasing hepatic PON1 mRNA and protein expressions induced by minor components present in this oil. Other Mediterranean diet constituents, such as nuts, fruits and vegetables, have been effective in modulating the activity of the enzyme, pomegranate and its compounds being the best characterized items. Ongoing research on compounds isolated from all these natural products, mainly phenolic compounds and carotenoids, indicates that some of them are particularly effective, and this may enhance the use of nutraceuticals and functional foods capable of potentiating PON1 activity.

Serum paraoxonase 1 (PON1) measurement: an update

Paraoxonase 1 (PON1) is a widely studied enzyme based on its protective role against poisoning by organophosphate (OP) metabolites of specific OP insecticides and in vascular disease, as well as its use as biomarker of diseases involving oxidative stress, inflammation and liver diseases.

This review provides an update about the current knowledge in the field of the analytical procedures that are used for PON1 measurements. It will be specially focused on: (a) characteristics of the different substrates used for measuring PON1, with emphasis in four aspects: toxicity, polymorphism influence, rate of hydrolysis and diagnostic performance. And (b) the technical aspects of PON1 assays, in which the reagents and reaction conditions, sources of variation, quality control systems, equipment and interferences with other esterases will be discussed.

The information provided in this review can contribute to a more accurate and safe measurements of PON1 in laboratories and encourage researchers to explore the wide areas of PON1 in veterinary medicine that are still unknown.

Serum paraoxonase 1 activity in dogs: preanalytical and analytical factors and correlation with C-reactive protein and alpha-2-globulin

BACKGROUND

Serum activity of paraoxonase (PON1) decreases during inflammation in many species. Little information is available on paraoxon-based tests and the possible role of PON1 in dogs.

OBJECTIVES

The objectives of the study were to validate an automated paraoxon-based assay to measure PON1 activity in canine serum, to determine its stability under different storage conditions, to determine a reference interval (RI) in healthy dogs, and to assess whether PON1 is of comparable diagnostic value as C-reactive protein (CRP) and α2-globulins.

METHODS

Intra-assay and inter-assay imprecision, linearity under dilution (LUD), interference, and storage artifacts were evaluated. A PON1 RI was determined for healthy dogs, and PON1 activity, sensitivity, and specificity were compared with CRP and α2-globulins.

RESULTS

Intra- and inter-assay CVs were below 1.6% and 7.8%, respectively. The LUD test fitted the linear model. PON1 activity measurements were increased after addition of hemolysates and lipids, and after storage for 12 hours at room temperature, 72 hours at 4°C, and 6 months at -20°C. PON1 activity and CRP or α2-globulins did not correlate well. PON1 activity decreased significantly only in dogs with very high CRP concentrations. In contrast to CRP and α2-globulins, PON1 activity was not significantly different between dogs with and without inflammation.

CONCLUSIONS

The automated paraoxon-based method to assess serum canine PON1 activity was accurate and precise, but it was influenced by hemolysis, lipemia, and standard storage conditions. In this study, contrarily to CRP and α2-globulins, PON1 activity did not provide diagnostic value as a negative acute phase protein in dogs.

Effect of seabuckthorn (Hippophae rhamnoides ssp. sinensis) leaf extract on the swimming endurance and exhaustive exercise-induced oxidative stress of rats

BACKGROUND

Seabuckthorn (SBT) leaves have significant antioxidant, immunomodulatory and anti-inflammatory properties. The objective of this study was to assess the anti-fatigue, antioxidant and tissue-protective properties of aqueous lyophilised extracts of SBT dried leaves in the hearts of Wistar male rats undergoing exhaustive physical exercise. Doses of 50, 200 and 800 mg kg⁻¹ body weight (BW) day⁻¹ were given orally for 1 week. A week later the rats were forced to swim in barrels until they were exhausted. The times were noted to establish the effective dose of the extracts in rats. After establishing the effective dose, the rats were then sacrificed and assessed for various biochemical parameters.

RESULTS

SBT leaf aqueous extracts (200 and 800 mg kg⁻¹ BW) markedly prolonged the swim time of rats. Supplementation with SBT leaf aqueous extracts helped reduce the exhaustive exercise-induced increase in malondialdehyde level and selenium-dependent glutathione peroxidase activity. Alanine aminotransferase and creatine kinase levels were lowered in the exhaustive exercise with SBT treatment group (E + SBT) compared with the exhaustive exercise group (E).

CONCLUSION

The findings suggest that SBT leaf aqueous extract supplements can enhance exercise capacity and protect against oxidative damage caused by exhaustive exercise in rats.

Combined effects of exercise and soy isoflavone diet on paraoxonase, nitric oxide and aortic apoptosis in ovariectomized rats

Menopause is associated with an increased risk of cardiovascular disease (CVD). Exercise and soy isoflavone diets have been suggested to reduce the risk of CVD in postmenopausal women. We investigated the effects of exercise, or combined exercise and soy isoflavone diet, on plasma lipid profiles, paraoxonase (PON), nitric oxide (NO) and apoptosis in the aorta of ovariectomized (OVX) rats. Thirty-two female Sprague-Dawley rats were divided into four groups: OVX with general diet (OVX-GD), OVX with isoflavone diet (OVX-ISO), OVX-GD with exercise training (OVX-ET) and OVX-ISO with exercise training (OVX-ISO+ET). The experimental rats undertook treadmill training (30 min/day, 4 days/week) and/or were supplied a soy isoflavone diet (added to the experimental diet at 2.39 mg/g protein) for 12 weeks. Body weight and levels of total cholesterol (TC), triglyceride (TG), LDL-cholesterol (LDL-C) increased in the OVX rats and HDL-C decreased. These effects were reduced by exercise and/or soy isoflavone supplementation. PON and NO activities were higher in the OVX-ISO+ET group than in the OVX-GD group. In addition, this group had lower caspase-9 and -3 and higher Bcl-2 expression, and there was less aortic apoptotic cell death. These results suggest that a combination of exercise and a soy isoflavone diet has beneficial effects in terms of protecting against cardiovascular risk factors by controlling lipid profiles and the related enzyme, PON, as well as NO activity and apoptosis of the aorta in OVX rats.

Evaluation of oxidative stress in hunting dogs during exercise

Exercise has been shown to increase the production of reactive oxygen species (ROS) to a point that can exceed antioxidant defenses, to cause oxidative stress. The aim of our trials was to evaluate oxidative stress and recovery times in trained dogs during two different hunting exercises, with reactive oxygen metabolites-derivatives (d-ROMs) and biological antioxidant potential (BAP) tests. A group of nine privately owned Italian hounds were included. A 20-min aerobic exercise and a 4-h aerobic exercise, after 30 days of rest, were performed by the dogs. Our results show an oxidative stress after exercise due to both the high concentration of oxidants (d-ROMs) and the low level of antioxidant power (BAP). Besides, the recovery time is faster after the 4-h aerobic exercise than the 20-min aerobic exercise. Oxidative stress monitoring during dogs exercise could become an interesting aid to establish ideal adaptation to training.

Improving the ex vivo stability of drug ester compounds in rat and dog serum: inhibition of the specific esterases and implications on their identity

In drug development, it has been noticed that some drug compounds, especially esters, are unstable in serum samples ex vivo. This can lead to a substantial underestimation of the actual drug concentration. The rat and the dog, representing a rodent and non-rodent species, respectively, are widely used in preclinical studies. We studied the degradation of three structurally different drug esters in rat and dog serum. Moreover, the efficiency of selected enzyme inhibitors to prevent these degradations was investigated. Furthermore, we found indications of the identity of the drug-specific esterases by means of their inhibitor sensitivity as well as by protein purification and identification. The studied drugs were sagopilone, drospirenone, and methylprednisolone aceponate (MPA) all of which are used in (pre-)clinical drug development. The sagopilone-cleaving esterases in rat serum were inhibited by serine hydrolase inhibitors. We partly purified these esterases resulting in an activity yield of 5% and a purification factor of 472. Using matrix-assisted laser desorption ionization (MALDI)-time of flight (TOF)-mass spectrometry (MS), the rat carboxylesterase isoenzyme ES-1 was identified in these fractions, thus pointing to its involvement in sagopilone cleavage. Drospirenone cleavage in rat serum was effected by butyrylcholinesterase (BChE) and paraoxonase 1 (PON1) as we deduced from the high efficacy of certain serine hydrolase and metallohydrolase inhibitors, respectively. Likewise, some inhibition characteristics implied that MPA was cleaved in rat serum by BChE and serine proteases. Partial purification of the MPA-specific esterases resulted in activity yields of 1-2%, exhibiting up to 10,000-fold purification. In dog serum, we found that sagopilone was not degraded which was in contrast to MPA and drospirenone. MPA degradation was mainly prevented by serine hydrolase inhibitors. We used a three-step purification to isolate the esterases cleaving MPA. This procedure resulted in an activity yield of 12% and 645-fold purification. By protein identification using liquid chromatography (LC)-electrospray ionization (ESI)-MS, we identified alpha(2)-macroglobulin (alpha(2)M) in the active fractions. We therefore assumed that serine hydrolases, probably butyrylcholinesterase, known to form esteratically active complexes with alpha(2)M, were responsible for MPA cleavage. In contrast, PON1 was assumed to be involved in drospirenone cleavage due to the high efficiency of metallohydrolase inhibitors. This indication was supported by the presence of PON1 in drospirenone-cleaving fractions as we found by affinity chromatography and Western immunoblotting for isolation and detection of PON1, respectively. The identity of the assumed cleaving enzymes remains, however, to be further studied. The inhibitors we found can serve as a tool for stabilizing drug ester compounds in biological samples ex vivo.