Exploring relationships between body condition score, body fat, activity level and inflammatory biomarkers

Relationships between total adiponectin concentrations and obesity in native-breed ponies in England

BACKGROUND

Equine metabolic syndrome is a collection of risk factors associated with an increased risk of endocrinopathic laminitis. All affected animals display insulin dysregulation and some may show adiponectin dysregulation and/or excessive adiposity. However, the relationship between obesity and hypoadiponectinaemia in equids remains unclear.

OBJECTIVES

To investigate the relationship between obesity and circulating plasma total adiponectin (TA) concentrations in native-breed ponies in England.

STUDY DESIGN

Secondary data analysis.

METHODS

Data collected for three previous studies were retrospectively analysed and cohorts were pooled where possible (maximum sample size: n = 734 ponies). Correlations between [TA], age, and morphometric measures were assessed using Spearman's correlation coefficient. [TA] was compared between animals of different body condition score (BCS) classification (ideal-weight, overweight, and obese), breed, and body shape using Kruskal-Wallis with Dunn's post hoc tests, and sex using Mann-Whitney U test. The proportions of obese and ideal-weight ponies with basal hyperinsulinaemia and/or hypoadiponectinaemia were compared using a Chi-square test of homogeneity and post hoc z-test. Logistic regression was used to identify factors that may discriminate ponies with hypoadiponectinaemia.

RESULTS

[TA] was weakly positively correlated with BCS, height, weight, and weight:height ratio (Spearman's ρ = 0.14-0.29, p < 0.05). There were significant differences in [TA] in ponies with different BCS group classification, body shape, and breed. A greater percentage of obese (54.6%) than ideal-weight ponies (33.1%, p < 0.001) had both normal [TA] and [basal insulin], and a greater percentage of ideal-weight (38.6%) than obese ponies (16.5%, p < 0.001) showed hypoadiponectinaemia. Weight:height and BCS group were significant variables in a logistic regression of hypoadiponectinaemia but model fit and predictive accuracy were poor.

MAIN LIMITATIONS

Retrospective study design, only native-breed ponies included.

CONCLUSIONS

Morphometric measures such as BCS do not closely reflect [TA]. Circulating [TA] and [basal insulin] should be determined in all animals with predisposing factors, regardless of obesity status.

Obesity during Pregnancy in the Horse: Effect on Term Placental Structure and Gene Expression, as Well as Colostrum and Milk Fatty Acid Concentration

In horses, the prevalence of obesity is high and associated with serious metabolic pathologies. Being a broodmare has been identified as a risk factor for obesity. In other species, maternal obesity is known to affect the development of the offspring. This article is a follow-up study of previous work showing that Obese mares (O, n = 10, body condition score > 4.25 at insemination) were more insulin resistant and presented increased systemic inflammation during pregnancy compared to Normal mares (N, n = 14, body condition score < 4 at insemination). Foals born to O mares were more insulin-resistant, presented increased systemic inflammation, and were more affected by osteoarticular lesions. The objective of the present study was to investigate the effect of maternal obesity on placental structure and function, as well as the fatty acid profile in the plasma of mares and foals, colostrum, and milk until 90 days of lactation, which, to our knowledge, has been poorly studied in the horse. Mares from both groups were fed the same diet during pregnancy and lactation. During lactation, mares were housed in pasture. A strong heat wave, followed by a drought, occurred during their 2nd and 3rd months of lactation (summer of 2016 in the Limousin region, France). In the present article, term placental morphometry, structure (stereology), and gene expression (RT-qPCR, genes involved in nutrient transport, growth, and development, as well as vascularization) were studied. Plasma of mares and their foals, as well as colostrum and milk, were sampled at birth, 30 days, and 90 days of lactation. The fatty acid composition of these samples was measured using gas chromatography. No differences between the N and O groups were observed for term placental morphometry, structure, or gene expression. No difference in plasma fatty acid composition was observed between groups in mares. The plasma fatty acid profile of O foals was more pro-inflammatory and indicated an altered placental lipid metabolism between birth and 90 days of age. These results are in line with the increased systemic inflammation and altered glucose metabolism observed until 18 months of age in this group. The colostrum fatty acid profile of O mares was more pro-inflammatory and indicated an increased transfer and/or desaturation of long-chain fatty acids. Moreover, O foals received a colostrum poorer in medium-chain saturated fatty acid, a source of immediate energy for the newborn that can also play a role in immunity and gut microbiota development. Differences in milk fatty acid composition indicated a decreased ability to adapt to heat stress in O mares, which could have further affected the metabolic development of their foals. In conclusion, maternal obesity affected the fatty acid composition of milk, thus also influencing the foal's plasma fatty acid composition and likely participating in the developmental programming observed in growing foals.

A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete

Endocrine disorders are associated with joint pain and tendon injury in humans, but the effects in the horse are only starting to be understood. Similar patterns of clinical signs and injury appear to affect horses and humans for both orthopedic and endocrine disorders, supporting the use of a one-health approach to tackle these issues. In this Currents in One Health, we will discuss common equine endocrinopathies, current testing recommendations, dietary management, genetic predispositions, and endocrine disorders' effects on performance. Our aim is to use a one-health lens to describe current comparative research so that veterinarians can employ cutting-edge preventative, diagnostic, and therapeutic recommendations. Identified key gaps in knowledge include whether equine metabolic osteoarthritis exists, if steroid joint injections are safe in horses with endocrine disorders, and if the return to performance percentage improves with concurrent treatment of endocrine and musculoskeletal disorders. Key takeaways include that the relationship between endocrine disorders and musculoskeletal disease in the horse goes beyond laminitis to include lameness, muscle atrophy, suspensory ligament degeneration, osteochondritis dissecans, and potentially metabolic osteoarthritis. Approaches learned from human and equine comparative studies can offer insight into injury recognition and management, thus mitigating the impact of endocrine disorders on performance in both species. Readers interested in an in-depth description of current and future research involving pathophysiology, novel interventions, and multiomic approaches to identify individuals with athletic limitations induced by endocrine disorders are invited to read the companion Currents in One Health by Manfredi et al, AJVR, February 2023.

Are Horse Owners Able to Estimate Their Animals' Body Condition Score and Cresty Neck Score?

Obesity and overconditioning are becoming more prevalent in horses, and are influencing the animal's health, activity, and reproductive efficiency. Body condition score (BCS) and cresty neck score (CNS) have been correlated with the development of various diseases. Many of the papers in the literature evaluate the prevalence of obesity and overconditioning in horse populations considering BCS given by owners. The aim of this study was to evaluate the validity of the owners' estimation of the degree of equine obesity or overconditioning by comparing BCS and CNS provided by each owner and a board-certified vet to a cohort of 259 horses and their agreement based on age, breed, sex, and activity of the animals. Overconditioning was present in 29% and 24% of horses according to the owners and the vet, respectively, and obesity in 2% and 1%, respectively. Agreement between BCS and CNS given by the owners and the vet was slight, with owners scoring horses either lower or higher than the vet. Agreement between the owners and the vet assessment was also influenced by age, breed, sex, and activity of the animals. Education of owners and caretakers to correctly assess BCS and CNS and regular evaluation of the animals throughout the year is important to prevent the development of obesity and overconditioning and related diseases.

Fecal extract from obese horses induces an inflammatory response by murine macrophages in vitro

OBJECTIVE

To compare the inflammatory response of murine macrophages exposed to the enteric microbiome of obese horses versus nonobese horses.

SAMPLE

Fecal samples from 12 obese horses (body condition score ≥ 7/9) and 12 nonobese horses (body condition score 4 to 5/9) with similar dietary management.

PROCEDURES

Fecal supernatant was prepared from frozen fecal samples. RAW 264.7 macrophage cells were exposed to the fecal extract. Inflammatory cytokine (interleukin-1β, tumor necrosis factor-α, and interleukin-6) gene expression was quantified via real-time quantitative reverse transcription PCR assay, and cytokine concentration was quantified via ELISA. Lipopolysaccharide was evaluated in fecal extract via chromo-limulus amoebocyte lysate assay.

RESULTS

Compared with fecal extracts from nonobese horses, fecal extracts from obese horses presented higher concentrations of lipopolysaccharide and induced a heightened expression of the proinflammatory cytokines interleukin-1β, tumor necrosis factor-α, and interleukin-6 from macrophages.

CLINICAL RELEVANCE

The increased levels of inflammatory markers induced in murine macrophages by the microbiome of obese horses in vitro suggested important differences in the enteric microbial composition of these horses, compared with nonobese horses. Overall, this study showed that the microbiome may play a role in mediating an inflammatory response within the gastrointestinal tract of obese horses. Mechanisms of obesity in the horse have not been fully elucidated. Improved understanding of the pathophysiology of disease will guide future research into potential diagnostic and therapeutic interventions for equine obesity.