Understanding How Dogs Age: Longitudinal Analysis of Markers of Inflammation, Immune Function, and Oxidative Stress

The potential for senotherapy as a novel approach to extend life quality in veterinary medicine

Cellular senescence, a condition where cells undergo arrest and can assume an inflammatory phenotype, has been associated with initiation and perpetuation of inflammation driving multiple disease processes in rodent models and humans. Senescent cells secrete inflammatory cytokines, proteins, and matrix metalloproteinases, termed the senescence associated secretory phenotype (SASP), which accelerates the aging processes. In preclinical models, drug interventions termed "senotherapeutics" selectively clear senescent cells and represent a promising strategy to prevent or treat multiple age-related conditions in humans and veterinary species. In this review, we summarize the current available literature describing in vitro evidence for senotheraputic activity, preclinical models of disease, ongoing human clinical trials, and potential clinical applications in veterinary medicine. These promising data to date provide further justification for future studies identifying the most active senotherapeutic combinations, dosages, and routes of administration for use in veterinary medicine.

Transcriptomic and intervention evidence reveals domestic dogs as a promising model for anti-inflammatory investigation

Domestic dogs have great potential to expand our understanding of the determinants of aging. To understand the aging pattern of domestic dogs and evaluate whether they can be used as an aging model, we performed RNA sequencing on white blood cells from domestic dogs aged 1-9 years and treated aged dogs with classical antiaging approaches. We obtained 30 RNA sequencing libraries and identified 61 age-associated genes with dynamic changes, the majority of which were related to metabolism and immune function, which may be predominant biomarkers for aging in dogs. We next treated aged dogs with canine mesenchymal stem cells (cMSCs), nicotinamide mononucleotide, and rapamycin to determine whether and how they responded to the antiaging interventions. The results showed that these treatments can significantly reduce the level of inflammatory factors (IL-6 and TNF-α). MSCs effectively improved the heart functions of aged dogs. Three key potential age-related genes (PYCR1, CCRL2, and TOX) were reversed by MSC treatment, two of which (CCRL2 and TOX) are implicated in immunity. Overall, we profiled the transcriptomic pattern of domestic dogs and revealed that they may be a good model of aging, especially in anti-inflammatory investigations.

A revisiting of "the hallmarks of aging" in domestic dogs: current status of the literature

A progressive decline in biological function and fitness is, generally, how aging is defined. However, in 2013, a description on the "hallmarks of aging" in mammals was published, and within it, it described biological processes that are known to alter the aging phenotype. These include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication (inflammation), and changes within the microbiome. This mini-review provides a detailed account of the progress on each of these hallmarks of aging in the domestic dog within the last 5 years. Additionally, when there are gaps in the literature between other mammalian species and dogs, I highlight the aging biomarkers that may be missing for dogs as aging models. I also argue for the importance of dog aging studies to include several breeds of dogs at differing ages and for age corrections for breeds with differing mean lifespans throughout.

Betaine and L-Carnitine Synergistically Influence the Metabolome and Immune Response in Dogs

This study used thirty-two dogs, which were assigned to a preferred period of 14 days and then assigned to one of the four treatment foods: control (containing no added betaine, no added L-carnitine), control with 0.5% added betaine (Treatment 2), control with no added betaine and 300 ppm added L-carnitine (Treatment 3), or control with 0.5% added betaine and 300 ppm added L-carnitine (Treatment 4). All treatment foods were fed for ninety days. Untargeted blood metabolomic analysis and immune response were measured at the beginning and end of the 90-day feeding trial. Feeding betaine increased single-carbon metabolites while decreasing many carnitine-containing metabolites. Feeding L-carnitine increased many carnitine metabolites, while the combination synergistically influenced the metabolome. The combination of betaine and L-carnitine increased the cytokines released in a Tru-culture system in response to stimulation while numerically decreasing their release when unstimulated. Therefore, the combination of dietary betaine and L-carnitine could have the dual positive effects of reducing cytokine stimulation, controlling inflammation during health, and providing a robust response to bacterial infection.

Association between bacterial pathogenicity, endometrial histological changes and clinical prognosis in canine pyometra

Despite the high frequency and clinical relevance of canine pyometra, its pathogenesis remains poorly understood. In this study, the clinical data, histopathological alterations, and microbiological findings of 39 dogs with pyometra were analyzed to assess possible associations. The mean age of the affected animals was 9.6 ± 3.8 years; 76.3 % (29/38) had open cervix pyometra, 88 % (22/25) had tachypnea, 71 % (27/38) had anorexia, and 60.5 % (23/38) had leukocytosis. Histopathological analysis revealed that 66.5 % (26/39) of the uteri had a high degree of inflammation (score 4). Third-degree hyperplasia of the endometrial epithelium (72 %, 28/39) and intralesional or intrauterine bacteria (66.5 %, 26/39) were identified in most animals. Bacterial isolates were obtained from 82 % (32/39) of the uterine contents and five bacterial species were identified. Escherichia coli, classified in phylogroup B2, is associated with virulent adhesion genes (fimH, focG, and papC), and serum resistance (traT) was the most common isolate. There was an association between the detection of papC in E. coli isolates and higher necrosis scores. Additionally, the necrosis score was positively associated with the length of hospitalization, with each point increase in the necrosis score leading to two more days of hospitalization. These results suggest that papC-positive E. coli play an important role in the severity of pyometra in dogs. The present study revealed the possibility of using this virulence gene to better understand the prognosis of the disease in an affected animal.

Anaesthesia in Veterinary Oncology: The Effects of Surgery, Volatile and Intravenous Anaesthetics on the Immune System and Tumour Spread

Throughout the course of oncological disease, the majority of patients require surgical, anaesthetic and analgesic intervention. However, during the perioperative period, anaesthetic agents and techniques, surgical tissue trauma, adjuvant drugs for local pain and inflammation and other non-pharmacological factors, such as blood transfusions, hydration, temperature and nutrition, may influence the prognosis of the disease. These factors significantly impact the oncologic patient's immune response, which is the primary barrier to tumour progress, promoting a window of vulnerability for its dissemination and recurrence. More research is required to ascertain which anaesthetics and techniques have immunoprotective and anti-tumour effects, which will contribute to developing novel anaesthetic strategies in veterinary medicine.

Seasonal patterns of oxidative stress markers in captive Asian elephants in Thailand and relationships to elephant endotheliotropic herpesvirus shedding

Introduction

Oxidative stress refers to an imbalance between oxidant and antioxidant activity and accumulation of reactive oxygen species, which can have detrimental effects on animal health. Annual fluctuations in oxidative stress status can occur, increasing disease susceptibility during certain time periods. However, a full understanding of factors related to oxidative stress in Asian elephants and how to mitigate the negative consequences is lacking.

Methods

This study measured six serum oxidative stress markers [reactive oxygen species (ROS), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), albumin, glutathione peroxidase (GPx), and catalase] and two stress markers [serum cortisol and fecal glucocorticoid metabolites (fGCM)] in 23 captive Asian elephants in Thailand over a 12 months period to examine relationships with age and season.

Results

Seasonal variations were observed, with several markers exhibiting significantly higher concentrations in the summer (ROS, MDA, 8-OHdG, albumin) and lower values during the rainy/winter seasons (MDA, 8-OHdG, albumin, catalase). By contrast, GPx was the only marker to be highest during the rainy season. For the stress markers, higher fGCM concentrations were noted during the rainy season, which contrasts with earlier studies showing more activity in the winter (tourist season). Positive correlations were found between the temperature-humidity index and ROS, GPx, and fGCM, while a negative correlation was observed with serum albumin. Elephant endotheliotropic herpesvirus (EEHV) shedding events were associated with higher concentrations of ROS and MDA. A moderate negative correlation was observed between 8-OHdG and the PCR threshold cycle of EEHV shedding (Ct), indicating DNA damage may be involved in EEHV shedding in elephants.

Discussion

Results revealed significant age and seasonal effects on several oxidative stress markers, indicating those factors should be considered in study design and data interpretation. There also may be physiological adaptations in oxidative stress conditions in relation to environmental changes that could impact health outcomes.

Molecular Profile of Canine Hemangiosarcoma and Potential Novel Therapeutic Targets

Canine hemangiosarcoma (HSA) is a relatively common neoplasia, occurring mainly in the skin, spleen, liver and right atrium. Despite the numerous studies investigating the treatment of canine HSA, no significant improvement in survival has been achieved in the last 20 years. Advancements in genetic and molecular profiling presented molecular similarities between canine HSA and human angiosarcoma. It could therefore serve as a valuable model for investigating new and more effective treatments in people and dogs. The most common genetic abnormalities in canine HSA have been found in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) and neuroblastoma RAS viral oncogene homolog (NRAS) pathways. Mutations are also found in tumor protein p53 (TP53), phosphatase and tensin homolog (PTEN) and cyclin dependent kinase inhibitor 2A (CDKN2A). Known abnormal protein expression could be exploited to trial new target treatments that could be beneficial for both canine and human patients. Despite the high expression of vascular endothelial growth factor (VEGF) and its receptor (VEGFR), no correlation with overall survival time has ever been found. In this review, we explore the most recent developments in molecular profiling in canine HSA and discuss their possible applications in the prognosis and treatment of this fatal disease.

Spray-Dried Animal Plasma as a Multifaceted Ingredient in Pet Food

Plasma is a co-product from pork and beef obtained during the processing of animals for human consumption. The spray-drying process maintains the solubility of spray-dried animal plasma (SDAP) and its nutritional and functional properties, making this ingredient multifunctional in human and animal nutrition. In pet food, SDAP has been used in the production of wet foods (pates and chunks in gravy) as an emulsifying and binding agent, with the potential to replace hydrocolloids partially or totally, which have some negative implications for digestibility, fecal quality, and intestinal inflammation. From a nutritional point of view, SDAP has high digestibility and an amino acid profile compatible with high-quality ingredients, such as powdered eggs. Studies in companion animals, especially in cats, have shown that SDAP is an ingredient with high palatability. Despite the immunomodulatory, anti-inflammatory, prebiotic, and neuroprotective properties demonstrated in some animal models, there are still few publications demonstrating these effects in dogs and cats, which limits its use as a functional ingredient for these species. In this review, the potential use of SDAP in pet food, aspects related to the sustainability of this ingredient, and opportunities for studies in companion animals are discussed.

Inflammaging in domestic dogs: basal level concentrations of IL-6, IL-1β, and TNF-α in serum of healthy dogs of different body sizes and ages

Inflammaging, a "hallmark of aging," refers to a chronic, progressive increase in the proinflammatory status of mammals as they age, and this phenotype has been associated with many age-related diseases, including cardiovascular disease, arthritis and cancer. Though, inflammaging research is common in humans, there is a lack of data for this process for the domestic dog. Here, serum concentrations of IL-6, IL-1β and TNF-α in healthy dogs of different body sizes and ages were measured to determine whether inflammaging may play a mechanistic role in aging rates in dogs, similar to those found in humans. Using a four-way ANOVA, a significant decrease in IL-6 concentrations in young dogs with the rest of the age categories showing increased IL-6 concentrations was found, similar to humans. However, only young dogs have decreased IL-6 concentrations, with adult dogs having similar IL-6 concentrations to senior and geriatric dogs, implying differences in aging rates between humans and dogs. And, there was a marginally significant interaction between sex*spayed or neutered status and IL-1β concentrations with intact females having the lowest IL-1β concentrations compared with intact males, and spayed and neutered dogs. The presence of estrogen in intact females may, overall, decrease inflammatory pathways. This implies that age at spaying or neutering may be an important aspect to consider for inflammaging pathways in dogs. Furthermore, sterilized dogs often die of immune-related diseases, which could be linked to the increases in IL-1β in sterilized dogs found in this study.

Selected biomarkers of oxidative stress in healthy Beagle dogs: A preliminary study

Introduction

While oxidative stress has been studied in pathologic conditions in dogs, data in presumably healthy dogs and standardized protocols are lacking. This work purposed to bridge the gap by presenting provisional physiological ranges for oxidative stress biomarkers in a group of Beagle dogs.

Methods

Based on our long-standing clinical expertise in the field of oxidative stress, nine plasma biomarkers of oxidative stress were evaluated for their concentrations (mean ± SD) in 14 healthy adult Beagle dogs.

Results

Selected biomarkers were: vitamins C (7.90 ± 1.36 μg/mL) and E (34.1 ± 6.63 μg/mL), zinc (0.80 ± 0.17 mg/L), copper (0.54 ± 0.048 mg/L), selenium (256 ± 25.7 μg/L), total and oxidized glutathione (822 ± 108 μM and 3.56 ± 1.76 μM), myeloperoxidase (67.4 ± 56.2 ng/mL), and isoprostanes (340 ± 95.3 ng/mL). Glutathione peroxidase activity and superoxide anion production in whole blood were also measured. Glutathione peroxidase activity was 473 ± 34.0 IU/g of hemoglobin and superoxide anion production in whole blood was 18,930 ± 12,742 counts per 30 min. Reduced glutathione/oxidized glutathione and copper/zinc ratios were, respectively, 280 ± 139 and 0.70 ± 0.15. Sex-related differences were recorded for zinc (p = 0.0081), copper/zinc ratio (p = 0.0036) and plasma isoprostanes (p = 0.0045).

Conclusion

Provisional physiological norms covering 95% of our group were proposed for each biomarker and should be of interest for future studies of canine oxidative stress.

Astragalus polysaccharide (APS) supplement in beagle dogs after castration: Effects on the haematology and serum chemistry profiles, immune response, and oxidative stress status

BACKGROUND

Castration is one of the most common surgical procedures performed in dogs. However, based on increasing evidence, male animals experience significant pain after castration. Astragalus polysaccharide (APS), one of the main bioactive components in A. membranaceus bunge, has been widely used as part of Fu-Zheng therapy to enhance natural defense mechanisms.

INTRODUCTION

This study was carried out to determine the effects of supplementing different doses of Astragalus polysaccharide (APS; control, 0 mg/kg; APSL, 400 mg/kg; and APSH, 800 mg/kg) for 8 weeks on the haematology and serum chemistry profiles, immune response, and oxidative stress status in weanling beagle dogs.

METHODS

After adapting to the experimental environment for 1 week, 18 male beagle dogs (Sichuan Institute of Musk Deer Breeding, China; average initial weight, 3.80 ± 0.43 g; age, 3-month-old) were randomly allotted to diets supplemented with three doses of APS (Control, 0 mg/kg; low, 400 mg/kg; and high, 800 mg/kg), referred to as control, APSL, and APSH, respectively; six dogs were assigned to each treatment. The dogs were fed the respective diets twice daily at 08:30 and 16:30 h in sufficient quantity to supply the metabolizable energy requirements for 8 weeks. On day 43 (19 weeks old), the dogs were castrated. On days 42 (prior to castration, 19 weeks old), 50 (day 7 after castration, 20 weeks old), and 57 (day 14 after castration, 21 weeks old) to measure the haematology, blood chemistry, immune response, and oxidative stress status parameters.

RESULTS

Based on our findings, the APSH diet decreased weight gain and increased the feed to gain ratio in dogs (P < 0.05). At 14 days after castration, the wound was almost closed, slightly swollen, dry, and clean in the groups supplemented with APS. In addition, optimal APS supplementation was found to decrease erythrocyte count (RBC), haematocrit (HCT), alkaline phosphatase (ALP), alanine aminotransferase (ALT), C-reactive protein (CRP), interleukin 1β (IL-1β), and tumor necrosis factor-α (TNF-α) levels, and cortisol and protein carbonyl (PC) concentrations (P < 0.05). Moreover, the mean corpuscular haemoglobin (MCH) and platelet (PLT) levels, interleukin 10 (IL-10) and glutathione (GSH) content, and Cu/Zn superoxide dismutase (SOD1), catalase (CAT), and glutathione peroxidase (Se-GPx) activities were increased in the APS supplemented groups (P < 0.05) CONCLUSION: This study demonstrated that supplementing weanling beagle dogs with optimum APS could positively affect wound healing by improving their haematological profile (decreased RBC and HCT content, increased MCH and PLT levels), serum biochemical parameters (decreased ALP and ALT content), immune status (decreased CRP, IL-1β, and TNF-α levels; increased IL-10 content), and antioxidant defense (decreased cortisol and PC content; increased GSH content, and SOD1, CAT, and Se-GPx activities). However, the detailed mechanism whereby APS regulates these changes requires further investigation. In addition, the results of this study suggest that 400 mg/kg diet is the optimum APS dose for beagle dogs.

Evaluation of cognitive function in the Dog Aging Project: associations with baseline canine characteristics

Canine cognitive dysfunction (CCD) is a neurodegenerative disease in aging dogs. It has been described previously in relatively small cohorts of dogs using multiple different rating scales. This study aimed to use a minimally modified CCD rating scale developed by previous researchers to describe the prevalence of CCD more thoroughly in a large, nationwide cohort of companion dogs participating in the Dog Aging Project (DAP) (n = 15,019). Associations between various canine characteristics, predicted lifespan quartiles, and CCD were examined using univariable and multivariable logistic regression models and receiver operating curve (ROC) analysis. When controlling for all other characteristics, the odds of CCD increased 52% with each additional year of age. Among dogs of the same age, health status, breed type, and sterilization status, odds of CCD were 6.47 times higher in dogs who were not active compared to those who were very active. When controlling for age, breed type, activity level, and other comorbidities, dogs with a history of neurological, eye, or ear disorders had higher odds of CCD. Lifespan quartile analysis showed excellent discriminating ability between CCD positive and negative dogs. Weight-based lifespan quartile estimation could therefore serve as a tool to inform CCD screening by veterinarians.

First report on clinical aspects, blood profiles, bacterial isolation, antimicrobial susceptibility, and histopathology in canine pyometra in Thailand

Background and Aim:

Canine pyometra, either the closed (closed pyometra [CP]) or open (open pyometra [OP]) cervix type, is a frequent uterine disease in intact old age bitches. Therefore, early diagnosis and appropriate medical and surgical treatments are crucial to avoid the life-threatening condition in these bitches. This study aimed to investigate clinical alterations, blood parameters, causative bacteria, antimicrobial susceptibility, and uterine histopathology obtained during aseptic surgical treatment on bitches with pyometra.

Materials and Methods:

Sixty bitches of various breeds and ages with presumptive pyometra diagnoses were included in the study. The diagnoses were based on history, clinical examination, blood parameters, radiography, and ultrasonography. All pyometra bitches were ovariohysterectomized as an emergency surgical treatment. In addition, uterine content and tissues were submitted for bacterial isolation, antimicrobial susceptibility, and uterine histopathological analysis.

Results:

Except for abdominal CP distention, no specific clinical signs were linked to the pyometra type. The mean values of total white blood cell count (WBC) and plasma protein were predominantly raised in pyometra bitches regarding hematological parameters. Leukocytosis was found in both types; however, the WBC in CP was markedly higher than in OP. The mean value of blood urea nitrogen increased in the CP group. Klebsiella pneumoniae and Escherichia coli were the most frequent causative bacteria isolated in CP and OP, respectively. All isolated bacteria were 100% susceptible to imipenem, meropenem, and carbapenem. Marbofloxacin was the second most effective drug against isolated bacteria from both groups. Uncomplicated cystic endometrial hyperplasia (CEH) was not presented in the CP group. CEH and chronic endometritis (type IV), the most severe uterine histopathological changes, were discovered in the CP and OP.

Conclusion:

The CP and OP groups presented leukocytosis, increased plasma protein, and CEH and chronic endometritis. Depression, abdominal distention, and enlarged uterine size were the major characteristics of the CP group. Furthermore, abdominal distension is presented in other abnormalities in clinical practices, providing a differential diagnosis. Drugs in the carbapenem group were the most effective against isolated bacteria; however, they are not routinely used due to bacterial resistance concerns. Thus, marbofloxacin was recommended as an alternative medical treatment because it is convenient to manage by both oral and injection routes.

Canine Cytokines Profile in an Endemic Region of L. infantum: Related Factors

Canine leishmaniosis is caused by infection with parasite Leishmania infantum, which are transmitted by sandflies Phlebotomus. Canine leishmaniosis is an endemic disease in the Mediterranean region. The immune response could vary between hosts and determines the severity of the disease and clinical features. The aim of this study was to analyze the serum levels of cytokines TNF-α, IFN-γ, IL-2, IL-6, and IL-8, which are related to the activation of Th1 or Th2 immune responses in dogs living in the L. infantum endemic region. Moreover, we intend to relate and correlate these levels with different factors, such as sex, age, diet, lifestyle, and breed. Epidemiological data and serum were recovered for seventy-eight dogs, and serum levels of cytokines described previously were analyzed by using the ELISA method. The results showed differences in serum levels of IFN-γ, IL-2, and IL-8 between breeds. The lifestyle also affected serum levels of IL-2. The main conclusion of this study is that Ibizan hounds and crossbred dogs have a serological profile of cytokines that seems to indicate certain protections against infection by L. infantum compared to boxer and purebred breeds.

Canine Geriatric Syndrome: A Framework for Advancing Research in Veterinary Geroscience

Biological aging is the single most important risk factor for disease, disability, and ultimately death in geriatric dogs. The effects of aging in companion dogs also impose significant financial and psychological burdens on their human caregivers. The underlying physiologic processes of canine aging may be occult, or early signs of aging may be ignored because of the misconception that biological aging is natural and therefore inevitable. The ability to detect, quantify, and mitigate the deleterious processes of canine aging would greatly enhance veterinary preventative medicine and animal welfare. In this paper we propose a new conceptual framework for aging in dogs, the Canine Geriatric Syndrome (CGS). CGS consists of the multiple, interrelated physical, functional, behavioral, and metabolic changes that characterize canine aging as well as the resulting clinical manifestations, including frailty, diminished quality of life, and age-associated disease. We also identify potential key components of a CGS assessment tool, a clinical instrument that would enable veterinarians to diagnose CGS and would facilitate the development and testing of interventions to prolong healthspan and lifespan in dogs by directly targeting the biological mechanisms of aging. There are many gaps in our knowledge of the mechanisms and phenotype of aging in dogs that must be bridged before a CGS assessment tool can be deployed. The conceptual framework of CGS should facilitate identifying these gaps and should stimulate research to better characterize the processes and effects of aging in dogs and to identify the most promising preventative strategies to target these.

Spectrophotometric assays for evaluation of Reactive Oxygen Species (ROS) in serum: general concepts and applications in dogs and humans

Reactive oxygen species (ROS) are reactive compounds derived from oxygen. In biological systems, an excessive amount of ROS can cause oxidative damage to biological macromolecules being involved in different diseases. Several assays have been developed in the last 30 years for ROS evaluation. The objective of this article will be to provide an update about the spectrophotometric methods currently used in the assessment of ROS in serum. The chemical basis of four different techniques will be reviewed, and examples of their possible applications will be provided. A particular emphasis about the practical applications of these assays in the dog will be made, but selected information about their use in humans will also be presented for comparative purposes, following a One-Health approach. The information about the spectrophotometric assays presented in this paper should be interpreted with caution once limited information about them is available yet, and further studies should be performed to clarify what they measure and their clinical application. Ideally, when applied to evaluate a sample's oxidative status, they should be incorporated in a panel of analytes where other oxidants, antioxidants, and biomarkers of inflammation were also included.

Is signalment associated with clinicopathological findings in dogs with leishmaniosis?

BACKGROUND

Canine leishmaniosis (CanL) is a common infectious disease. Age, sex and breed might influence the type of clinical and pathological manifestations that dogs develop. The main objective of this retrospective cross-sectional study was to determine if an association between age, sex, breed and size and the clinical findings of CanL exists.

MATERIAL AND METHODS

Dogs with a diagnosis of leishmaniosis were enrolled (n = 123). Clinical information, including signalment, clinical signs and laboratory abnormalities, was retrieved from medical records from different veterinary facilities from Catalonia.

RESULTS

Young dogs developed less frequently systemic signs (p = 0.0046), renal (p = 0.0019) and haematologic (p = 0.0275) abnormalities, while dermatologic signs were more common in young and adult dogs compared with old ones (p = 0.0451). Young dogs showed proteinuria less often than adult and old dogs (p = 0.0029). Young dogs did not present renal azotemia, while old dogs showed occasionally renal azotemia (p = 0.0478). Young dogs were mainly classified as mild-moderate LeishVet clinical stages of the disease, and very rarely as severe-very severe LeishVet clinical stages, compared with adult and old dogs (p = 0.0457). Purebred dogs significantly developed ulcerative dermatitis more frequently than crossbred dogs (p = 0.0460).

CONCLUSION

This study describes that age is associated with differences in clinicopathological findings of CanL.

Cellular metabolism and IL-6 concentrations during stimulated inflammation in primary fibroblasts from small and large dog breeds as they age

The immune system undergoes marked changes during aging characterized by a state of chronic, low-grade inflammation termed 'inflammaging'. We explore this phenomenon in domestic dogs, which are the most morphologically and physiologically diverse group of mammals, with the widest range in body sizes for a single species. Additionally, smaller dogs tend to live significantly longer than larger dogs across all breeds. Body size is intricately linked to mass-specific metabolism and aging rates, which suggests that dogs are exemplary for studies in inflammaging. Dermal fibroblast cells play an important role in skin inflammation, making them a good model for inflammatory patterns across dog breed, body sizes and ages. Here, we examined aerobic and glycolytic cellular metabolism, and IL-6 concentrations in primary fibroblast cells isolated from small and large dog breeds, that were either recently born puppies or old dogs after death. We found no differences in cellular metabolism when isolated fibroblasts were treated with lipopolysaccharide (LPS) from Escherichia coli to stimulate an inflammatory phenotype. Unlike responses observed in mice and humans, there was a less drastic amplification of IL-6 concentration after LPS treatment in the geriatric population of dogs compared with recently born dogs. In young dogs, we also found evidence that untreated fibroblasts from large breeds had significantly lower IL-6 concentrations than observed for smaller breeds. This implies that the patterns of inflammaging in dogs may be distinct and different from other mammals commonly studied.

Plasma Concentration of Advanced Glycation End-Products From Wild Canids and Domestic Dogs Does Not Change With Age or Across Body Masses

Dogs provide a physiological paradox: In domestic dogs, small breeds live longer lives than large breed dogs. Comparatively, a wild canid can be a similar size than many large breed dogs and outlive their domestic cousin. We have previously shown that oxidative stress patterns between domestic and wild canids differ, so that wild canids invest in a robust antioxidant system across their lives; whereas domestic dogs tend to accumulate lipid damage with age. There is a close association between oxidative stress and the production of a carbohydrate based-damage, Advanced Glycation End-products (AGEs). AGEs can bind to their receptor (RAGE), which can lead to increases in reactive oxygen species (ROS) production, and decreases in antioxidant capacity. Here, I used plasma from wild and domestic canids to address whether blood plasma AGE-BSA concentration associated with body mass and age in domestic dogs; And whether AGE-BSA concentration patterns in blood plasma from wild canids are similar to those found in domestic dogs. I found no correlation between circulating AGE-BSA concentration and body size or age in either domestic dogs and wild canids. These data suggest that AGEs formation may be a conserved trait across the evolution of domesticated dogs from wild ancestors, in opposition to oxidative stress patterns between these two groups. And, that, in domestic dogs, lipid metabolism, rather than carbohydrate metabolism, may be upregulated to yield the previously found differences in circulating lipid damage across lifespan and body sizes.

Lack of NLRP3 Inflammasome Activation Reduces Age-Dependent Sarcopenia and Mitochondrial Dysfunction, Favoring the Prophylactic Effect of Melatonin

To investigate the role of NLRP3 inflammasome in muscular aging, we evaluated here the morphological and functional markers of sarcopenia in the NLRP3-knockout mice, as well as the beneficial effect of melatonin supplementation. The gastrocnemius muscles of young (3 months), early-aged (12 months), and old-aged (24 months) NLRP3-knockout female mice were examined. Moreover, locomotor activity and apoptosis were assessed. The results revealed early markers of sarcopenia at the age of 12 months, including reduction of lactate, ratio of muscle weight to body weight, muscle fibers number, and mitochondrial number. Increased interstitial tissues, apoptosis, and muscle fibers area, as well as mitochondrial damage were detected, with little muscular activity effects. In the old-aged, these alterations progressed with a reduction in locomotor activity, mitochondrial cristae destruction, nuclear fragmentation, tubular aggregates (TAs) formation, and increased frailty index. Oral melatonin supplementation preserved the normal muscular structure, muscle fibers number, and muscular activity in old age. Melatonin enhanced lactate production, recovered mitochondria, inhibited TAs formation, reduced apoptosis, and normalized frailty index. The fewer sarcopenic changes as well as the highly detectable prophylactic effects of melatonin treatment reported here in the muscle of NLRP3-knockout mice comparing with that previously detected in wild-type mice, confirming NLRP3 inflammasome implication in muscular aging and sarcopenia onset and progression.

The plasma proteome and the acute phase protein response in canine pyometra

Canine pyometra is a common inflammatory disease of uterus in sexually mature bitches caused by secondary bacterial infection, leading to change in plasma proteins associated with the innate immune system. Proteomic investigation is increasingly being applied to canine diseases in order to identify and quantify significant changes in the plasma proteome. The aim of the study was to assess and quantify changes in plasma proteome profiles of healthy dogs and pyometra affected bitches using a TMT-based high-resolution quantitative proteomic approach. As a result, 22 proteins were significantly down-regulated including transthyretin, antithrombin, retinol-binding protein, vitamin D binding protein, paraoxonase 1, and kallikrein, while 16 were significantly up-regulated including haptoglobin light chain, alpha-1-acid glycoprotein, C-reactive protein precursor, and lipopolysaccharide-binding protein in dogs with pyometra. Pathway analysis indicated that acute inflammatory response, regulation of body fluid levels, protein activation cascade, the humoral immune response, and phagocytosis were affected in pyometra. Validation of biological relevance of the proteomic study was evident with significant increases in the concentrations of haptoglobin, C-reactive protein, alpha-1-acid glycoprotein, and ceruloplasmin by immunoassay. Pyometra in bitches was shown to stimulate an increase in host defence system proteins in response to inflammatory disease including the acute phase proteins. SIGNIFICANCE: The label-based high-resolution quantitative proteomics analysis and bioinformatic approach used in this study provide insight into the complex pathophysiology of inflammation associated with pyometra revealing proteins with biomarker potential. Early diagnosis and therapeutic intervention may prevent severe complications associated with advancing sepsis in dogs with pyometra. Therefore the identification of diagnostic biomarkers that, after clinical validation may be used in veterinary practice and protein relevant to pathways responding to disease are important findings of the study. Data are available via ProteomeXchange with identifier PXD015951.

Effect of antioxidants, mitochondrial cofactors and omega-3 fatty acids on telomere length and kinematic joint mobility in young and old shepherd dogs - A randomized, blinded and placebo-controlled study

In dogs, decreasing telomere length is a biomarker for cellular aging. On a systemic level, aging affects the locomotor system in particular, leading to restricted joint mobility. As aging is thought to be related to oxidative stress, it may be counteracted by a diet enriched with antioxidants, mitochondrial cofactors and omega-3 fatty acids. This randomized, blinded and placebo-controlled study examined the influence of an accordingly enriched diet compared to a control diet on 36 young and 38 old shepherd dogs. At the outset, after 3 and after 6 months, mean and minimum telomere lengths were measured. Furthermore, minimum and maximum joint angles and range of motion of the shoulder, elbow, carpal, hip, stifle and tarsal joints were measured by computer-assisted gait analysis. A positive influence of the enriched diet on old dogs could be verified for minimum telomere length and all three parameters of the shoulder joint on the side with the higher vertical ground reaction force after 6 months. In the other joints there were less significant differences; in some cases they indicated a contrary influence of the enriched diet on young dogs, probably due to its reduced protein content. The greater effect of the enriched diet on minimum than on mean telomere length may be due to the higher preference of telomerase for short telomeres. The greater effect on shoulder joint mobility is explained by the greater influence of musculature and connective tissue in this joint. For elderly dogs it is advisable to feed these nutritional supplements.

Active fractions of mannoproteins derived from yeast cell wall stimulate innate and acquired immunity of adult and elderly dogs

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Aging can promote changes in the immune system in dogs.

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Nutritional intervention in older dogs aims to increase lifespan.

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The yeast cell wall comprises β-(1,3)-D-glucan, β-(1,6)-D-glucan and mannoproteins.

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Elderly dogs when compared to adult dogs had lower absolute T and B lymphocyte counts.

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Mannoproteins stimulated acquired and innate immune responses in adult and elderly dogs.

Nutritional intervention in older dogs aims to increase lifespan and improve life quality as well as delay the development of diseases related to ageing. It is believed that active fractions of mannoproteins (AFMs) obtained through extraction and fractionation of yeast cell walls (Saccharomyces cerevisiae) may beneficially modulate the immune system. However, studies that have evaluated this component and the effects of ageing on the immune system of dogs are scarce. This study aimed to evaluate the immunological effects of AFMs in adult and elderly dogs. Three extruded iso-nutrient experimental diets were formulated: without addition of AFM (T0); with AFM at 400 mg/kg (T400); and with AFM at 800 mg/kg (T800). Thirty-six beagle dogs were used, and six experimental treatments, resulting in combinations of age (adult and elderly) and diet (T0, T400, and T800), were evaluated. On days zero, 14, and 28, blood samples were obtained for leucocyte phenotyping and phagocytosis assays. On days zero and 28, a lymphoproliferation test, quantification of reactive oxygen (H₂O₂) and nitrogen (NO) intermediate production, evaluation of faecal immunoglobulin A (IgA) content, and a delayed cutaneous hypersensitivity test (DCHT) were performed. Statistical analyses were performed with SAS software. Repeated measure variance analyses were performed, and means were compared by the Tukey test. Values of P ≤ 0.05 were considered significant, and values of P ≤ 0.10 were considered tendencies. Dogs fed T400 tended to have higher neutrophilic phagocytic activity than dogs fed T800 (P = 0.073). Regarding reactive oxygen intermediates, bacterial lipopolysaccharide (LPS)-stimulated neutrophils from animals that were fed T400 had a tendency to produce more H₂O₂ than those from animals fed the control diet (P = 0.093). Elderly dogs, when compared to adult dogs, had lower absolute T and B lymphocyte counts, lower auxiliary T lymphocyte counts, and higher cytotoxic T lymphocyte counts (P < 0.05). A significant effect of diet, age, and time with saline inoculation was noted for the DCHT. There was no effect of diet or age on faecal IgA content in dogs. This study suggests beneficial effects of mannoproteins on the specific and nonspecific immune responses in adult and elderly dogs.

A Frailty Index based on clinical data to quantify mortality risk in dogs

Frailty is defined as a decline in an organism’s physiological reserves resulting in increased vulnerability to stressors. In humans, a single continuous variable, the so-called Frailty Index (FI), can be obtained by multidimensionally assessing the biological complexity of an ageing organism. Here, we evaluate this variability in dogs and compare it to the data available for humans. In dogs, there was a moderate correlation between age and the FI, and the distribution of the FI increased with age. Deficit accumulation was strongly related to mortality. The effect of age, when combined with the FI, was negligible. No sex-related differences were evident. The FI could be considered in epidemiological studies and/or experimental trials to account for the potential confounding effects of the health status of individual dogs. The age-related deficit accumulation reported in dogs is similar to that demonstrated in humans. Therefore, dogs might represent an excellent model for human aging studies.

Development of Dog Immune System: From in Uterus to Elderly

Immune system recognize and fight back foreign microorganisms and inner modifications that lead to deficient cell and tissue functions. During a dog's life, the immune system needs to adapt to different physiological conditions, assuring surveillance and protection in a careful and controlled way. Pregnancy alters normal homeostasis, requiring a balance between immunity and tolerance. The embryos and fetus should be protected from infections, while the female dog must tolerate the growing of semi-allografts in her uterus. After birth, newborn puppies are at great risk of developing infectious diseases, because their immune system is in development and immune memory is absent. Passive transfer of immunity through colostrum is fundamental for puppy survival in the first weeks of life, but hampers the development of an active immune response to vaccination. At the end of life, dogs experience a decline in the structure and functional competence of the immune system, compromising the immune responses to novel antigenic challenges, such as infections and vaccines. Therefore, the current article reviews the general processes related to the development of the dog´s immune system, providing an overview of immune activity throughout the dog's life and its implications in canine health, and highlighting priority research goals.

Genetic Pathways of Aging and Their Relevance in the Dog as a Natural Model of Human Aging

Aging research has experienced a burst of scientific efforts in the last decades as the growing ratio of elderly people has begun to pose an increased burden on the healthcare and pension systems of developed countries. Although many breakthroughs have been reported in understanding the cellular mechanisms of aging, the intrinsic and extrinsic factors that contribute to senescence on higher biological levels are still barely understood. The dog, Canis familiaris, has already served as a valuable model of human physiology and disease. The possible role the dog could play in aging research is still an open question, although utilization of dogs may hold great promises as they naturally develop age-related cognitive decline, with behavioral and histological characteristics very similar to those of humans. In this regard, family dogs may possess unmatched potentials as models for investigations on the complex interactions between environmental, behavioral, and genetic factors that determine the course of aging. In this review, we summarize the known genetic pathways in aging and their relevance in dogs, putting emphasis on the yet barely described nature of certain aging pathways in canines. Reasons for highlighting the dog as a future aging and gerontology model are also discussed, ranging from its unique evolutionary path shared with humans, its social skills, and the fact that family dogs live together with their owners, and are being exposed to the same environmental effects.

Body weight at 10 years of age and change in body composition between 8 and 10 years of age were related to survival in a longitudinal study of 39 Labrador retriever dogs

BACKGROUND

Overweight and obesity have been adversely associated with longevity in dogs but there is scarce knowledge on the relation between body composition and lifespan. We aimed to investigate the effects of body composition, and within-dog changes over time, on survival in adult Labradors using a prospective cohort study design. The dogs had a median age of 6.5 years at study start and were kept in similar housing and management conditions throughout. The effects of the various predictors, including the effect of individual monthly-recorded change in body weight as a time varying covariate, were evaluated using survival analysis.

RESULTS

All dogs were followed to end-of-life; median age at end-of-life was 14.0 years. Body composition was measured annually with dual-energy x-ray absorptiometer (DEXA) scans between 6.2 and 17.0  years. All 39 dogs had DEXA recorded at 8, 9 and 10 years of age. During the study the mean (± SD) percent of fat (PF) and lean mass (PL) was 32.8 (± 5.6) and 64.2 (± 5.5) %, respectively, with a mean lean:fat ratio (LFR) of 2.1 (± 0.6); body weight (BW) varied from 17.5 to 44.0 kg with a mean BW change of 9.9 kg (± 3.0). There was increased hazard of dying for every kg increase in BW at 10 years of age; for each additional kg of BW at 10 years, dogs had a 19% higher hazard (HR = 1.19, P = 0.004). For the change in both lean mass (LM) and LFR variables, it was protective to have a higher lean and/or lower fat mass (FM) at 10 years of age compared to 8 years of age, although the HR for change in LM was very close to 1.0. For age at study start, older dogs had an increased hazard. There was no observed effect for the potential confounders sex, coat colour and height at shoulders, or of the time-varying covariate.

CONCLUSIONS

These results suggest that even rather late-life control efforts on body weight and the relationship between lean and fat mass may influence survival in dogs. Such "windows of opportunity" can be used to develop healthcare strategies that would help promote an increased healthspan in dogs.

Longevity: Lesson from Model Organisms

Research on longevity and healthy aging promises to increase our lifespan and decrease the burden of degenerative diseases with important social and economic effects. Many aging theories have been proposed, and important aging pathways have been discovered. Model organisms have had a crucial role in this process because of their short lifespan, cheap maintenance, and manipulation possibilities. Yeasts, worms, fruit flies, or mammalian models such as mice, monkeys, and recently, dogs, have helped shed light on aging processes. Genes and molecular mechanisms that were found to be critical in simple eukaryotic cells and species have been confirmed in humans mainly by the functional analysis of mammalian orthologues. Here, we review conserved aging mechanisms discovered in different model systems that are implicated in human longevity as well and that could be the target of anti-aging interventions in human.

The companion dog as a model for human aging and mortality

Around the world, human populations have experienced large increases in average lifespan over the last 150 years, and while individuals are living longer, they are spending more years of life with multiple chronic morbidities. Researchers have used numerous laboratory animal models to understand the biological and environmental factors that influence aging, morbidity, and longevity. However, the most commonly studied animal species, laboratory mice and rats, do not experience environmental conditions similar to those to which humans are exposed, nor do we often diagnose them with many of the naturally occurring pathologies seen in humans. Recently, the companion dog has been proposed as a powerful model to better understand the genetic and environmental determinants of morbidity and mortality in humans. However, it is not known to what extent the age‐related dynamics of morbidity, comorbidity, and mortality are shared between humans and dogs. Here, we present the first large‐scale comparison of human and canine patterns of age‐specific morbidity and mortality. We find that many chronic conditions that commonly occur in human populations (obesity, arthritis, hypothyroidism, and diabetes), and which are associated with comorbidities, are also associated with similarly high levels of comorbidity in companion dogs. We also find significant similarities in the effect of age on disease risk in humans and dogs, with neoplastic, congenital, and metabolic causes of death showing similar age trajectories between the two species. Overall, our study suggests that the companion dog may be an ideal translational model to study the many complex facets of human morbidity and mortality.