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Topic:Insulin
Insulin is a hormone produced by the pancreas that plays a pivotal role in regulating glucose metabolism in horses. It facilitates the uptake of glucose by cells, thus maintaining blood sugar levels within a normal range. Insulin's function is integral to energy balance and metabolic processes in equines. Disruptions in insulin regulation can lead to metabolic disorders such as Equine Metabolic Syndrome (EMS), characterized by insulin resistance and associated with obesity and laminitis. This page aggregates peer-reviewed research studies and scholarly articles that explore the physiological role, regulatory mechanisms, and clinical implications of insulin in equine health and disease management.
Equine Metabolic Syndrome Affects Viability, Senescence, and Stress Factors of Equine Adipose-Derived Mesenchymal Stromal Stem Cells: New Insight into EqASCs Isolated from EMS Horses in the Context of Their Aging. Currently, equine metabolic syndrome (EMS), an endocrine disease linked to insulin resistance, affects an increasing number of horses. However, little is known about the effect of EMS on mesenchymal stem cells that reside in adipose tissue (ASC). Thus it is crucial to evaluate the viability and growth kinetics of these cells, particularly in terms of their application in regenerative medicine. In this study, we investigated the proliferative capacity, morphological features, and accumulation of oxidative stress factors in mesenchymal stem cells isolated from healthy animals (ASCN) and horses s...
Prolonged hyperinsulinemia affects metabolic signal transduction markers in a tissue specific manner. Insulin dysregulation is common in horses although the mechanisms of metabolic dysfunction are poorly understood. We hypothesized that insulin signaling in striated (cardiac and skeletal) muscle and lamellae may be mediated through different receptors as a result of receptor content, and that transcriptional regulation of downstream signal transduction and glucose transport may also differ between tissues sites during hyperinsulinemia. Archived samples from horses treated with a prolonged insulin infusion or a balanced electrolyte solution were used. All treated horses developed marked hyperin...
Equine hyperinsulinemia: investigation of the enteroinsular axis during insulin dysregulation. Compared with some other species, insulin dysregulation in equids is poorly understood. However, hyperinsulinemia causes laminitis, a significant and often lethal disease affecting the pedal bone/hoof wall attachment site. Until recently, hyperinsulinemia has been considered a counterregulatory response to insulin resistance (IR), but there is growing evidence to support a gastrointestinal etiology. Incretin hormones released from the proximal intestine, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide, augment insulin secretion in several species but require invest...
Aging effect on plasma metabolites and hormones concentrations in riding horses. Age effects on plasma metabolites, hormone concentrations, and enzyme activities related to energy metabolism were investigated in 20 riding horses. Animals were divided into two groups: Young (3-8 years) and aged (11-18 years). They were clinically healthy, and not obese. Plasma adiponectin (ADN) concentrations in aged horses were significantly lower than those in young horses (mean±SE, 6.5±1.3 µg mL(-1) vs, 10.9±1.7 µg mL(-1), Mann-Whitney U test, respectively; P=0.0233). Plasma non-esterified fatty acid levels and Insulin and malondialdehyde concentrations in aged group tended to incre...
The effect of a limit-fed diet and slow-feed hay nets on morphometric measurements and postprandial metabolite and hormone patterns in adult horses. Modern horse management systems tend to limit a horse's opportunity to forage, rely on meal feeding, and may contribute to the increase in equine obesity. The use of slow-feed hay nets represents an opportunity to extend foraging time while feeding a restricted diet. The objectives of this study were to determine if limit feeding combined with a slow-feed hay net would affect morphometric measurements and postprandial metabolite and hormone patterns in overweight adult horses. Eight adult Quarter horses (BW 563 kg ± 4.6 kg; BCS 7.2 ± 0.3) were used in a randomized complete block design, with...
HORSE SPECIES SYMPOSIUM: Nutritional programming and the impact on mare and foal performance. Many environmental factors can alter the phenotype of offspring when applied during critical periods of early development. In most domestic species, maternal nutrition influences fetal development and the fetus is sensitive to the nutrition of the dam during pregnancy. Many experimental models have been explored including both under- and overnutrition of the dam. Both nutritional strategies have yielded potential consequences including altered glucose tolerance, pancreatic endocrine function, insulin sensitivity, body composition, and colostrum quality. Although the impact of maternal nutritio...
Postprandial glucose, insulin, and glucagon-like peptide-1 responses of different equine breeds adapted to meals containing micronized maize. The enteroinsular axis is a complex system that includes the release of incretin hormones from the gut to promote the absorption and utilization of glucose after a meal. The insulinogenic effect of incretin hormones such as glucagon-like peptide-1 (GLP-1) remains poorly characterized in the horse. The aim of this study was to compare postprandial glucose, insulin, and GLP-1 responses of different equine breeds adapted to twice-daily meals containing micronized maize. Four Standardbred horses, 4 mixed-breed ponies, and 4 Andalusian cross horses in moderate BCS (5.5 ± 0.2 out of 9) were fed mea...
Relationship of oxidative stress in skeletal muscle with obesity and obesity-associated hyperinsulinemia in horses. In horses, hyperinsulinemia and insulin resistance (insulin dysregulation) are associated with the development of laminitis. Although obesity is associated with insulin dysregulation, the mechanism of obesity-associated insulin dysregulation remains to be established. We hypothesized that oxidative stress in skeletal muscle is associated with obesity-associated hyperinsulinemia in horses. Thirty-five light breed horses with body condition scores (BCS) of 3/9 to 9/9 were studied, including 7 obese, normoinsulinemic (BCS ≥ 7, resting serum insulin < 30 μIU/mL) and 6 obese, hyperinsulinemic...
Effects of a docosahexaenoic acid-rich microalgae nutritional product on insulin sensitivity after prolonged dexamethasone treatment in healthy mature horses. To determine effects of a microalgae nutritional product on insulin sensitivity in horses. Methods: 8 healthy mature horses. PROCEDURES :Horses (n = 4/group) received a basal diet without (control diet) or with docosahexaenoic acid-rich microalgae meal (150 g/d) for 49 days (day 0 = first day of diet). On day 28, an isoglycemic hyperinsulinemic clamp procedure was performed. Horses then received dexamethasone (0.04 mg/kg/d) for 21 days. On day 49, the clamp procedure was repeated. After a 60-day washout, horses received the alternate diet, and procedures were repeated. Plasma fatty acid, gluco...
Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015. Andalusian horses have been proposed as a breed predisposed to equine metabolic syndrome (EMS) phenotype [1] because they are prone to exhibiting regional, generalised adiposity and tendency to laminitis [2]. Insulin dysregulation represents the main pathophysiological cause for all the features of EMS, however there are no epidemiological studies in this breed. Objective: To assess insulin dysregulation through insulin proxies in Andalusian horses with different levels of obesity. Methods: Cross-sectional study. Methods: One hundred and sixty-four Andalusians (78 stallions and 86 mares, 2-15 ...
Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015. Atrial fibrillation is a common equine arrhythmia. Quinidine alone, or with digoxin are common treatments. Studies on outcome in Warmblood populations in which duration of the AF is often unknown are limited. Objective: To identify the factors that are associated with the success of full treatment cardioversion with oral medication, and establish whether there are differences in these factors between institutions. Methods: Retrospective case series using patient records of Equine University Clinic of Utrecht University and Rossdales Equine Hospital, Newmarket. Methods: Forty-nine horses treate...
Equine insulin receptor and insulin-like growth factor-1 receptor expression in digital lamellar tissue and insulin target tissues. Hyperinsulinaemia is implicated in the pathogenesis of endocrinopathic laminitis. Insulin can bind to different receptors: two insulin receptor isoforms (InsR-A and InsR-B), insulin-like growth factor-1 receptor (IGF-1R) and InsR/IGF-1R hybrid receptor (Hybrid). Currently, mRNA expression of these receptors in equine tissues and the influence of body type and dietary carbohydrate intake on expression of these receptors is not known. Objective: The study objectives were to characterise InsR-A, InsR-B, IGF-1R and Hybrid expression in lamellar tissue (LT) and insulin responsive tissues from horse...
Equine pituitary pars intermedia dysfunction: current perspectives on diagnosis and management. Equine pituitary pars intermedia dysfunction (PPID) is a neurodegenerative disease of the hypothalamus, resulting in the loss of dopaminergic inhibition of pars intermedia. An oxidative stress injury of unknown etiology has been suggested to initiate the neurodegeneration. While hypertrichosis (formerly known as hirsutism) is considered pathognomic for advanced disease, the antemortem diagnosis of subclinical and early disease has continued to prove difficult. Numerous tests have been used with varying sensitivities and specificities. The overnight dexamethasone suppression test, originally do...
Characterization of the intravenous glucose tolerance test and the combined glucose-insulin test in donkeys. Glucose-insulin dynamic challenges such as the intravenous glucose tolerance test (IVGTT) and combined glucose-insulin test (CGIT) have not been described in donkeys. The objectives of this study were (1) to characterize the IVGTT and CGIT in healthy adult donkeys, and (2) to establish normal glucose-insulin proxies. Sixteen donkeys were used and body morphometric variables obtained each. For the IVGTT, glucose (300 mg/kg) was given IV. For the CGIT, glucose (150 mg/kg) followed by recombinant insulin (0.1 IU/kg) were administered IV. Blood samples for glucose and insulin determinations were c...
Comparison of growth and endocrine changes in Thoroughbred colts and fillies reared under different climate conditions. Development and endocrine changes in Thoroughbreds colts and fillies were compared between those reared at two facilities of the Japan Racing Association, the Hidaka Training and Research Center (Hidaka) and Miyazaki Yearling Training Farm (Miyazaki). Thoroughbred colts and fillies born in Japan between 2003 and 2010 were used. Each colt group and filly group was divided into 2 groups, respectively, and raised in Hidaka or Miyazaki for 7 months from September at 1 year old to April at 2 years old. For the growth parameters, the body weight, height at withers, and girth and cannon circumference...
Treatment of equine metabolic syndrome: A clinical case series. Treatment of equine metabolic syndrome (EMS) is essential to improve insulin sensitivity and reduce the risk of laminitis. Calorie restriction and increased exercise are the mainstays of treatment but there is potential for poor owner compliance. Objective: To determine whether significant weight loss accompanied by improvements in measures of insulin sensitivity can be achieved in horses and ponies with EMS managed by their owners in their normal environment under veterinary guidance. Methods: Retrospective clinical case series. Methods: Horses and ponies attending 2 university hospitals for ...
Lamellar pathology in horses with pituitary pars intermedia dysfunction. Hoof lamellar pathology in horses with pituitary pars intermedia dysfunction (PPID) has not been described previously. Objective: To describe the histomorphometry and pathological lesions in hoof lamellar tissue of animals that had PPID with or without concurrent laminitis, with reference to age-matched controls. We hypothesised that lamellar lesions consistent with laminitis would be associated with PPID, even in animals without current or historical laminitis. Methods: Prospective case-control study. Methods: Mid-dorsal hoof histological sections were obtained post mortem from the forelimbs ...
AICAR administration affects glucose metabolism by upregulating the novel glucose transporter, GLUT8, in equine skeletal muscle. Equine metabolic syndrome is characterized by obesity and insulin resistance (IR). Currently, there is no effective pharmacological treatment for this insidious disease. Glucose uptake is mediated by a family of glucose transporters (GLUT), and is regulated by insulin-dependent and -independent pathways, including 5-AMP-activated protein kinase (AMPK). Importantly, the activation of AMPK, by 5-aminoimidazole-4-carboxamide-1-D-ribofuranoside (AICAR) stimulates glucose uptake in both healthy and diabetic humans. However, whether AICAR promotes glucose uptake in horses has not been established. I...
Effect of increased adiposity on insulin sensitivity and adipokine concentrations in horses and ponies fed a high fat diet, with or without a once daily high glycaemic meal. The relative influences of obesity and adaptation to high glycaemic diets on the development of insulin dysregulation in equids are unclear. Objective: To determine whether increased adiposity per se is responsible for the decreased insulin sensitivity often observed in obese horses or whether a dietary glycaemic response is critically important. Methods: Randomised controlled trial. Methods: Eighteen horses and ponies were studied over a 20-week period. They received ad libitum hay plus either a high fat (low glycaemic) diet (FAT; n = 6) or a similar (isocaloric) diet containing 1.5 g/kg bwt ...
Comparison of the in-feed glucose test and the oral sugar test. The in-feed oral glucose test (OGT) and oral sugar test (OST) are advocated as field tests of insulin sensitivity in horses and ponies but have not been directly compared. Objective: To compare the insulin response to OGT and OST in 8 ponies and 5 horses of unknown insulin sensitivity. Methods: Experimental, randomised crossover study. Methods: Animals were fasted for 8 h overnight before and throughout testing. They were fed 1 g/kg bwt glucose powder with chaff (OGT) or 0.15 ml/kg bwt corn syrup (Karoâ„¢ Light Syrup; OST) was administered per os in a randomised crossover study with 48â€...
Relationships among Body Condition, Insulin Resistance and Subcutaneous Adipose Tissue Gene Expression during the Grazing Season in Mares. Obesity and insulin resistance have been shown to be risk factors for laminitis in horses. The objective of the study was to determine the effect of changes in body condition during the grazing season on insulin resistance and the expression of genes associated with obesity and insulin resistance in subcutaneous adipose tissue (SAT). Sixteen Finnhorse mares were grazing either on cultivated high-yielding pasture (CG) or semi-natural grassland (NG) from the end of May to the beginning of September. Body measurements, intravenous glucose tolerance test (IVGTT), and neck and tailhead SAT gene exp...
Neutrophil function in healthy aged horses and horses with pituitary dysfunction. Immunosuppression leading to opportunist bacterial infection is a well-recognized sequela of equine pituitary pars intermedia dysfunction (PPID). The mechanisms responsible for immune dysfunction in PPID however, are as of yet poorly characterized. Horses with PPID have high concentrations of hormones known to impact immune function including α-melanocyte stimulating hormone (α-MSH) and insulin. α-MSH and related melanocortins have been shown in rodents and people to impair neutrophil function by decreasing superoxide production (known as oxidative burst activity), migration and adhesion. T...
Effects of moderate amounts of barley in late pregnancy on growth, glucose metabolism and osteoarticular status of pre-weaning horses. In stud management, broodmares are commonly fed concentrates in late pregnancy. This practice, however, was shown to correlate with an increased incidence of osteochondrosis in foals, which may be related to insulin sensitivity. We hypothesized that supplementation of the mare with barley in the last trimester of pregnancy alters the pre-weaning foal growth, glucose metabolism and osteoarticular status. Here, pregnant multiparous saddlebred mares were fed forage only (group F, n=13) or both forage and cracked barley (group B, n=12) from the 7th month of pregnancy until term, as calculated to c...
Energy-related parameters and their association with age, gender, and morphometric measurements in healthy donkeys. Donkeys are commonly afflicted by endocrine and metabolic disturbances but few studies have investigated endocrine variables involved in energy regulation and their association with morphometric indices, age or gender in this species. Hemostatic and clinical differences have been demonstrated between horses and donkeys, so to consider both species as metabolically and endocrinologically similar could lead to misdiagnosis. In this study, plasma concentrations of glucose, triglycerides and endocrine factors involved in energy homeostasis (insulin, glucagon, leptin, adiponectin, ghrelin and insul...
Insulinaemic and glycaemic responses to a second meal of a fibre- or starch-enriched compound feed in healthy horses. This study aimed to investigate the effect of a second meal of a fibre- or starch-enriched compound feed on glycaemic and insulinaemic responses in healthy horses. In a cross-over design, horses were fed either a starch-enriched compound feed (SCF) or a fibre-enriched compound feed (FCF). On days of blood collection, test diets were fed in the morning (0800 h, first meal) and a second meal was fed 510 min after the first meal was finished (second meal). Significantly higher glycaemic and insulinaemic responses were associated with SCF compared with FCF. Feeding FCF for the second meal yiel...
Comparison among the euglycemic-hyperinsulinemic clamp, insulin-modified frequently sampled intravenous glucose tolerance test, and oral glucose tolerance test for assessment of insulin sensitivity in healthy Standardbreds. To compare, in horses, estimates of insulin sensitivity obtained from minimal model analysis (MMA) of a frequently sampled IV glucose tolerance test (FSIGTT) with estimates from the euglycemic-hyperinsulinemic clamp (EHC) and to evaluate the validity of surrogate estimates of insulin sensitivity derived from an oral glucose tolerance test (OGTT). Methods: 18 mature Standardbreds (mean ± SD body weight, 428.9 ± 35.9 kg; mean ± SD body condition score, 4.4 ± 1.0 [on a scale of 1 to 9]). Methods: All horses underwent at least 2 of the 3 procedures (EHC [n = 15], insulin-modified FSIGTT [18], ...
Feeding practice and influence on selected blood parameters in show jumping horses competing in Switzerland. The aim of this study was to compare the nutritional management of show jumping horses in practice with recommendations from the literature. Additionally, the effects of these feeding practices on several blood metabolic parameters before and after exercise were studied. Blood samples were collected in the field from 27 different horses at 71 trials on the level M1 to S2 show jumping competitions in Switzerland and questionnaires on feeding practice of the studied horses were evaluated. The questionnaires revealed that during training and on tournament days horses received on average 3.1Â kg o...
Immunolocalization of insulin-like growth factor-I (IGF-I) and its receptors (IGF-IR) in the equine epididymis. Insulin-like growth factor plays a paracrine/autocrine role in regulating testicular function in the stallion, but its presence in the equine epididymis remains unknown. The aim of this study was to test the hypothesis that insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) are localized in the caput, corpus, and cauda of the epididymis in an age-dependent manner. Immediately after castration, epididymal tissue was fixed, paraffin-embedded, and processed for immunohistochemistry (IHC). Western blot was also performed using equine epididymal extracts to verify the specificity of t...
Pathology of Natural Cases of Equine Endocrinopathic Laminitis Associated With Hyperinsulinemia. Laminitis in equids is a clinical syndrome usually associated with systemic disease. Endocrinopathies recently have been recognized as the most common cause of laminitis, with hyperinsulinemia playing a key role. Descriptions of laminitis-associated lesions have been confusing due to the wide range of experimental models used, failure of adequate clinical documentation for naturally occurring cases, lack of separate analysis of inflammatory and endocrinopathic laminitis, and uncertainty regarding normal morphological variation of lamellae. In this study, lamellar morphology and pathology were ...
The impact of prolonged hyperinsulinaemia on glucose transport in equine skeletal muscle and digital lamellae. An increased incidence of metabolic disease in horses has led to heightened recognition of the pathological consequences of insulin resistance. Laminitis, failure of the weightbearing digital lamellae, is an important consequence. Altered trafficking of specialised glucose transporters (GLUTs), responsible for glucose uptake, is central to the dysregulation of glucose metabolism and may play a role in the pathophysiology of laminitis. Objective: We hypothesised that prolonged hyperinsulinaemia alters the regulation of glucose transport in insulin-sensitive tissue and digital lamellae. Our obje...
