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.
Bamford NJ, Potter SJ, Baskerville CL, Harris PA, Bailey SR.The relationships between diet, obesity and insulin dysregulation in equids require further investigation due to their association with laminitis. This study examined the effect of dietary glycaemic load and increased adiposity on insulin sensitivity and adipokine concentrations in different equine breeds. Equal numbers of Standardbred horses, mixed-breed ponies and Andalusian horses were provided with ad libitum hay plus either cereal-rich (CHO; n = 12), fat-rich (FAT; n = 12) or control (CON; n = 9) meals over 20 weeks. The isocaloric CHO and FAT diets were fed to induce obesity ...
Hart KA, Wochele DM, Norton NA, McFarlane D, Wooldridge AA, Frank N.Increased free cortisol fraction is associated with insulin dysregulation (ID) in people with Metabolic Syndrome and Cushing's Disease. Free cortisol has not been investigated in equine endocrine disorders. Objective: (1) In healthy horses, sex, age, body condition score (BCS), and season impact free cortisol; (2) free cortisol is increased in horses with Pituitary Pars Intermedia Dysfunction (PPID) or Equine Metabolic Syndrome (EMS). Methods: Fifty-seven healthy horses; 40 horses and ponies with PPID (n = 20) or EMS (n = 20). Methods: Prospective study. Serum collected seasonally from healthy...
Bashir ST, Ishak GM, Gastal MO, Roser JF, Gastal EL.Changes in intrafollicular growth factors and hormones were evaluated in vivo in postdeviation and impending ovulation follicles. Mares (n = 30) were randomly assigned to five experimental groups based on target diameters of 25, 30, 35, 40 mm, and impending signs of ovulation. Furthermore, data belonging to two or more proximal diameter groups that were not different were combined and regrouped for each factor separately. Follicular fluid-free insulin-like growth factor 1 was highest (P  0.05) among groups. Additionally, follicular fluid activin A tended (P < 0.06) to be higher in i...
Köller G, Bassewitz K, Schusser GF.The aim of this study was to validate a chemiluminescence immunometric assay using the IMMULITE 2000® for the determination of adrenocorticotropic hormone (ACTH), insulin and insulin-like growth factor-1 (IGF-1) from which reference ranges were calculated for ponies. Methods: Blood samples of 130 ponies aged 3-32 years were collected in the afternoon. The reference ranges were calculated according to the Guideline EP28-A3C of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) from 2010. Results: The determined intraday precision for insulin was 3.28%, for ACTH 3...
Brøkner C, Austbø D, Næsset JA, Blache D, Bach Knudsen KE, Tauson AH.The hypothesis for this study was that a higher dietary proportion of soluble fibre would result in stable and constant plasma metabolite and regulatory hormone concentrations. The study was a 4×4 Latin Square design with a sequence of 17 days adaptation to the ration followed by 8 sampling days. The feed rations consisted of only timothy hay (H), hay plus molassed sugar beet pulp combined with either whole oats (OB) or barley (BB) and hay plus a loose chaff-based concentrate (M). Four horses were fitted with permanent caecal cannulas and liquid caecal content was withdrawn manually and blood...
Sessions-Bresnahan DR, Schauer KL, Heuberger AL, Carnevale EM.Obesity is associated with disrupted reproductive cycles in mares, but the impact of obesity on follicles and oocytes has received minimal attention. We investigated the impact of obesity on 1) expression of selected genes in follicle cells for carbohydrate metabolism, inflammatory cytokines, lipid homeostasis, endoplasmic reticulum stress, and mitochondrial function; 2) follicular fluid content of metabolic hormones and metabolites; and 3) lipid fingerprint of oocytes. Mares (9-13 yr) were classified as control (n = 8, normal weight, body condition score [BCS] 5.1, 10.4% body fat) or obese (n...
Aguiar FL, Lunardi FO, Lima LF, Rocha RM, Bruno JB, Magalhães-Padilha DM, Cibin FW, Rodrigues AP, Gastal MO, Gastal EL, Figueiredo JR.This study investigated the effect of insulin concentration on the in vitro culture of equine preantral follicles enclosed in ovarian tissue. Ovarian tissue samples were immediately fixed (noncultured control) or cultured for 1 or 7 days in α-MEM(+) supplemented with 0 ng/mL, 10 ng/mL, or 10 μg/mL insulin. Ovarian tissues were processed and analyzed by classical histology. Culture medium samples were collected after 1 and 7 days of culture for steroid and reactive oxygen species (ROS) analyses. The percentage of morphologically normal follicles was greater (P < 0.001) in insulin-treated grou...
Marycz K, Kornicka K, Basinska K, Czyrek A.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...
Campolo A, de Laat MA, Keith L, Gruntmeir KJ, Lacombe VA.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...
de Laat MA, McGree JM, Sillence MN.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...
Kawasumi K, Yamamoto M, Koide M, Okada Y, Mori N, Yamamoto I, Arai T.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...
Glunk EC, Hathaway MR, Grev AM, Lamprecht ED, Maher MC, Martinson KL.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...
Coverdale JA, Hammer CJ, Walter KW.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...
Bamford NJ, Baskerville CL, Harris PA, Bailey SR.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...
Banse HE, Frank N, Kwong GP, McFarlane D.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...
Brennan KM, Graugnard DE, Spry ML, Brewster-Barnes T, Smith AC, Schaeffer RE, Urschel KL.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...
Lotstra RJ, van den Broek J, Power T, Marr CM, Wijnberg ID.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...
Kullmann A, Weber PS, Bishop JB, Roux TM, Norby B, Burns TA, McCutcheon LJ, Belknap JK, Geor RJ.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...
Spelta CW.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...
Mendoza FJ, Aguilera-Aguilera R, Gonzalez-De Cara CA, Toribio RE, Estepa JC, Perez-Ecija A.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...
Mizukami H, Suzuki T, Nambo Y, Ishimaru M, Naito H, Korosue K, Akiyama K, Miyata K, Yamanobe A, Nagaoka K, Watanabe G, Taya K.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...
Morgan RA, Keen JA, McGowan CM.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 ...
Karikoski NP, Patterson-Kane JC, Singer ER, McFarlane D, McGowan CM.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 ...
de Laat MA, Robinson MA, Gruntmeir KJ, Liu Y, Soma LR, Lacombe VA.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...
Bamford NJ, Potter SJ, Harris PA, Bailey SR.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 ...
Smith S, Harris PA, Menzies-Gow NJ.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€...
Selim S, Elo K, Jaakkola S, Karikoski N, Boston R, Reilas T, Särkijärvi S, Saastamoinen M, Kokkonen T.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...
McFarlane D, Hill K, Anton J.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...
Peugnet P, Robles M, Mendoza L, Wimel L, Dubois C, Dahirel M, Guillaume D, Camous S, Berthelot V, Toquet MP, Richard E, Sandersen C, Chaffaux S....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...
Delarocque J, Reiche DB, Meier AD, Warnken T, Feige K, Sillence MN.Insulin dysregulation (ID) is a key risk factor for equine endocrinopathic laminitis, but in many cases ID can only be assessed accurately using dynamic tests. The identification of other biomarkers could provide an alternative or adjunct diagnostic method, to allow early intervention before laminitis develops. The present study characterised the metabolome of ponies with varying degrees of ID using basal and postprandial plasma samples obtained during a previous study, which examined the predictive power of blood insulin levels for the development of laminitis, in ponies fed a high-sugar diet...
Noble GK, Houghton E, Roberts CJ, Faustino-Kemp J, de Kock SS, Swanepoel BC, Sillence MN.Insulin-like growth factor-1 could be a useful marker in the horse for diagnostic, selection, or forensic purposes, provided its physiological regulation is well understood. The objective of this study was to investigate factors, such as acute exercise, fitness training, time of day, sex, and age, that may influence serum IGF-1 in normal, healthy horses. Throughout a 9-wk training program, 6 geldings maintained a mean (+/- SEM) IGF-1 concentration of 302 +/- 29 ng/mL. Moderate or high intensity exercise had no effect on IGF-1 concentrations, when pre- and postexercise values were compared. Ove...
Frisbie DD, Nixon AJ.To evaluate potential stimulatory or matrix-sparing effects of insulin-like growth factor 1 (IGF-1), alone or in combination with a corticosteroid, in an interleukin 1 (IL-1)-induced model of cartilage degradation. Methods: Cartilage from the weightbearing surfaces of trochlea and condyles of clinically normal 2-year-old male horses. Methods: Triamcinolone acetonide and IGF-1 effects were evaluated by assessing: matrix responses by sulfated glycosaminoglycan (GAG) assay and [35S]sulfated GAG synthesis; collagen content by hydroxyproline assay; and mitogenic response by [3H]thymidine incorporat...
Navas de Solis C, Foreman JH.To describe the clinical presentation, treatment, and outcome of a neonatal foal diagnosed with transient Type 1 diabetes mellitus. Methods: A 3-day-old Thoroughbred foal presented with a 24-hour history of diarrhea and depression. Coronavirus particles were observed in the feces via electron microscopy. During hospitalization the foal developed hyperglycemia concomitantly with low insulin concentration and an adequate response to exogenous insulin therapy supported a diagnosis of Type 1 diabetes mellitus. The foal required SC insulin for 26 days, but developed complications associated with in...
Samimi AS, Samimi K, Karimiafshar M, Tajik J.The objective of this study was to comparatively evaluate the anti-inflammatory effects of intravenous administration of insulin (in different doses) and flunixin on physiological variables, acute-phase responses, and cardiovascular biomarkers during inflammatory phase which was induced by Escherichia coli lipopolysaccharide (LPS) serotype O55:B5 in miniature donkeys. A total of twenty-four clinically healthy male adult miniature donkeys aged 5 ± 1 year and weighing 120 ± 10 kg were studied. The animals were assigned randomly to four experimental groups (three treatment and one positive co...
Bourebaba N, Sikora M, Qasem B, Bourebaba L, Marycz K.Equine metabolic syndrome (EMS), which encompasses insulin resistance, low-grade inflammation and predisposition to laminitis is a critical endocrine disorder among the most prevalent conditions affecting horses from different breeds. According to the most recent research, low human sex hormone-binding globulin (SHBG) serum levels correlate with an increased risk of obesity, insulin resistance and diabetes, and may contribute to overall metabolic dysregulations. This study aimed to test whether exogenous SHBG could protect EMS affected adipose-derived stromal stem cells (EqASC) from apoptosis,...
Colmer SF, Adams AA, Adam E, Miller R, Stefanovski D, Kulp JC, van Eps A.A single dose of metformin administered 1 h prior to oral glucose challenge was previously shown to reduce insulinaemic responses in horses with experimentally-induced insulin dysregulation (ID). Targeted administration could be useful for controlling post-prandial hyperinsulinaemia in horses with naturally-occurring ID.
Dybdal NO, Gribble D, Madigan JE, Stabenfelt GH.The effects of prolonged exercise on plasma concentrations of corticosteroids, insulin, glucose, lactate and beta-hydroxybutrate were studied in a group of horses competing in a 160 km endurance ride. Of the 53 horses included in the study at the outset, 23 completed the course. Plasma corticosteroids increased while glucose and insulin decreased during exercise. Little change occurred in plasma lactate or beta-hydroxybutyrate. The parameters studied did not result in the finding of any consistent significant differences beteeen individuals that completed and those that did not complete the co...
Clark BL, Stewart AJ, Kemp KL, Bamford NJ, Bertin FR.Field tests and their association with laminitis have not been evaluated in large cohorts. The objectives of this study were to evaluate the performance of basal insulin (BI), the oral sugar test (OST) and the insulin tolerance test (ITT) to diagnose ID and investigate their association with laminitis. Insulin dysregulation status was determined in 146 ponies using BI (insulin concentration >20 µIU/mL), an OST (insulin concentration >65 µIU/mL at 60 or 90min after oral administration of 0.45mL/kg corn syrup) and an ITT (< 50% reduction in glucose concentration 30min after intravenous adminis...
Thurmon JC, Neff-Davis C, Davis LE, Stoker RA, Benson GJ, Lock TF.The effects of intravenous xylazine (1.1 mg/kg) were studied in six thoroughbred horses (five mares and a stallion). Plasma glucose concentration increased to 168% of control at 45 min and decreased to 112% of control at 180 min. Insulin had decreased to 31% of control at 15 min. Thereafter, insulin concentration increased, reaching its highest concentration at 150 min. The mechanism for these changes is not fully understood and further investigation is indicated.
Jánosi S, Huszenicza G, Kulcsár M, Kóródi P.After giving an overview of the general pathology of endotoxin-mediated diseases, the authors summarise the endotoxin-induced endocrine changes and their clinical consequences, with particular regard to reproduction. The consequences of temporary activation of the cyclooxygenase-2 and lipoxygenase enzyme systems resulting in elevated release of various prostanoids are discussed in cyclic and pregnant ruminants, sows and mares. The clinical failures attributable to increased glucocorticoid secretion as well as the endotoxin-induced changes in thyroid function and in peripheral level of some oth...
Aguiar FL, Lunardi FO, Lima LF, Rocha RM, Bruno JB, Magalhães-Padilha DM, Cibin FW, Rodrigues AP, Gastal MO, Gastal EL, Figueiredo JR.This study investigated the effect of insulin concentration on the in vitro culture of equine preantral follicles enclosed in ovarian tissue. Ovarian tissue samples were immediately fixed (noncultured control) or cultured for 1 or 7 days in α-MEM(+) supplemented with 0 ng/mL, 10 ng/mL, or 10 μg/mL insulin. Ovarian tissues were processed and analyzed by classical histology. Culture medium samples were collected after 1 and 7 days of culture for steroid and reactive oxygen species (ROS) analyses. The percentage of morphologically normal follicles was greater (P < 0.001) in insulin-treated grou...
Panzani S, Comin A, Galeati G, Romano G, Villani M, Faustini M, Veronesi MC.Thyroid hormones, insulin growth factor I (IGF-I) and non-esterified fatty acids (NEFA) represent important hormonal and metabolic factors associated with perinatal growth and maturation. Their action could be influenced by the type of parturition and the health status of the foal and therefore the aim of this work is to evaluate their plasma concentrations in newborn foals during the first 2 wks of life. Three groups of subjects were enrolled: 15 healthy foals born by spontaneous parturition, 24 healthy foals born by induced parturition and 26 pathologic foals. From each of the healthy foals,...
Fowden AL, Silver M, Ellis L, Ousey J, Rossdale PD.The factors influencing beta cell function in the foetal and neonatal foal have been investigated in chronically catheterised foetal foals and in newborn foals delivered either spontaneously at term or by induction at different gestational ages. Insulin was detected in the foetal plasma from as early as 150 days of gestation (term = 340 days) and during the last third of gestation the foetal beta cells responded to exogenous administration of glucose and arginine and to endogenous variations in the glucose level. Insulin secretion by the foetal beta cells was depressed by anaesthesia and surge...
Fradinho MJ, Mateus L, Bernardes N, Bessa RJB, Caldeira RM, Ferreira-Dias G.Development of a healthy musculoskeletal system is of high concern for horse breeders and users. A longitudinal field study was performed in order to: (i) evaluate growth patterns and long-term changes on bone quality, bone metabolism, growth factors and metabolic variables in the Lusitano horse; and (ii) retrospectively assess whether these changes were related with radiographic findings regarding osteochondrosis-like lesions (OC) at the onset of training. Thirty-four Lusitano foals born and raised at four stud-farms, were periodically weighed (BW), and measured (withers height-WH) from birth...
Wearn JM, Crisman MV, Davis JL, Geor RJ, Hodgson DR, Suagee JK, Ashraf-Khorassani M, McCutcheon LJ.Pioglitazone is a thiazolidinedione class of antidiabetic agent with proven efficacy in increasing insulin sensitivity in humans with noninsulin-dependent diabetes mellitus, a syndrome of insulin resistance sharing similarities with equine metabolic syndrome. The purpose of this study was to determine the pharmacokinetics of pioglitazone in adult horses following multiple oral dose administration. Pioglitazone hydrochloride (1 mg/kg) was administered orally for 11 doses at 24-h intervals, and plasma samples were collected. Initially, a pilot study was performed using one horse; and thereafter ...
Li FI, Spence RJ, de Laat MA, Harris PA, Sonntag J, Menzies-Gow NJ, Durham AE, Bailey SR, Sillence MN.High concentrations of adrenocorticotropic hormone (ACTH) are used as an indicator of pituitary pars intermedia dysfunction (PPID), but other factors that may influence ACTH need to be understood, if diagnostic reference ranges for ACTH are to be used with confidence. Insulin dysregulation (ID) could be one such factor, as insulin affects pituitary hormones in other species. Objective: To test the hypothesis that a relationship exists between high insulin and high ACTHÂ in aged (>15-year-old) animals with no clinical signs of PPID. Methods: A cohort study. Methods: Thirteen horses and eleven p...
Beech J, Garcia M.Cortisol, triiodothyronine (T3), thyroxine (T4), insulin, and glucose responses to thyrotropin-releasing hormone (TRH) were evaluated in 12 healthy, mature horses and in 7 horses and 4 ponies with clinical signs of pituitary adenoma (PA). Within 1 hour after TRH administration, the increase in T3 and T4 was similar in healthy horses and animals with PA. Plasma cortisol in the group with PA increased (P less than 0.05) within 0.25 hours after TRH administration, and remained increased for 1.5 hours. In the control group, a significant increase in plasma cortisol concentrations did not develop a...
Van Weyenberg S, Buyse J, Janssens GP.In this study 0 or 4 g of l-carnitine was supplemented for 7 days in a cross-over design of six healthy ponies to modulate glucose metabolism and leptin production. At the end of each period, serial blood samples were taken to measure glucose and insulin response, leptin, triglyceride (TG), non-esterified fatty acids (NEFA) and creatine phosphokinase. l-carnitine supplementation was associated with a decrease in postprandial plasma glucose and insulin concentration, indicating an enhanced glucose tolerance. In contrast, postprandial plasma leptin concentration was increased when l-carnitine wa...
Elliott J, Bailey SR.Equine laminitis has both fascinated and frustrated veterinary researchers and clinicians for many years. The recognition that many ponies suffering from pasture-associated laminitis have an insulin-dysregulated phenotype (endocrinopathic laminitis, EL) and that prolonged insulin and glucose infusions can experimentally induce laminar pathology and functional failure are seminal discoveries in this field. Researchers have studied the molecular basis for disease pathogenesis in models of EL, sepsis-related laminitis and supporting limb laminitis and generated much data over the last 15 years....
Glade MJ, Gupta S, Reimers TJ.Growth-related skeletal diseases in young horses have been associated with high planes of nutrition, although the mechanisms underlying such an association have not been determined. It is likely that nutrition-induced effects on growth rate or growth quality involve the endocrine system. Hormonal and metabolic responses to the ingestion of meals containing either 80% (diet A) or 160% (diet B) of National Research Council energy and protein recommendations were examined in eight Thoroughbred weanling horses after 3 wk of dietary adaptation. After 24 h fasts, prefeeding serum concentrations of t...
Brunner J, Wichert B, Burger D, von Peinen K, Liesegang A.This study aims at the comparison of the actual feeding of horses with the recommendations from the literature, and it studies the effects of feeding and exercise on several blood metabolic parameters before and after exercise. Blood samples were collected from 25 horses during one-star eventing competitions and evaluated for blood glucose, insulin, lactate, free fatty acids and triglyceride levels. Questionnaires on the feeding practices of the horses were evaluated. The questionnaires revealed that during training, and on tournament days, horses received on average 4.3 kg of concentrate per ...
Banse HE, Whitehead AE, McFarlane D, Chelikani PK.Pituitary pars intermedia dysfunction (PPID) is a common endocrine disorder of aged horses, with muscle atrophy as one of the clinical signs. We sought to compare muscle mass and regulation of skeletal muscle proteolysis between horses with PPID and muscle atrophy to older horses without PPID, and to assess the impact of treatment with pergolide (dopaminergic agonist) on PPID horses. We hypothesized that PPID-associated muscle atrophy is a result of increased proteolysis, and that markers of muscle atrophy and proteolysis would improve over time with pergolide treatment. Markers of muscle atro...
Berryhill EH, Magdesian KG, Tadros EM, Edman JE.Maintaining serum glucose concentrations is critical in neonatal foals and is often dysregulated in illness; however, few studies have assessed the effects of age, or variation of glucose and insulin, in neonates and their postpartum dams. This study aimed to serially evaluate serum glucose and insulin concentrations and glucose/insulin (G/I) ratios in seven healthy foals and their dams immediately postpartum and at 1-2 and 10-12days of age. The hypotheses were that: (1) there would be wide temporal variation in hourly glucose and insulin measurements among foals; and (2) measured parameters i...
DePew CL, Thompson DL, Fernandez JM, Sticker LS, Burleigh DW.Experiment 1 was conducted to characterize the concentrations of prolactin, growth hormone (GH), cortisol, insulin, glucagon, glucose, nonesterified fatty acids (NEFA), urea N, and 10 indispensable amino acids in the plasma of mares (n = 8) and stallions (n = 8) during the last 4 h of a 19-h period of feed deprivation and for 8 h after a noon meal. Experiment 2 was similar to Exp. 1 except that only stallions (n = 8) were used, and they were either fed (n = 4) or not fed (n = 4) at noon in a 2 x 2 Latin square design conducted over two sampling days 7 d apart. In Exp. 1, increases (P < .01)...
Serwotka-Suszczak AM, Marcinkowska KA, Smieszek A, Michalak IM, Grzebyk M, Wiśniewski M, Marycz KM.Insulin resistance (IR) is one of the characteristic features of equine metabolic syndrome (EMS). Presently, the only therapies of choice are caloric restrictions combined with mineral supplementation, which might improve insulin sensitivity. In this study we investigated the effect of Haematococcus pluvialis algae water extract enriched in bioaccumulation process in magnesium ions (Hp_Mg(II)) on equine adipose derived mesenchymal stromal stem cells, in which insulin resistance was induced by palmitic acid (IR-EqASCs). For this purpose, chemical characterization of H. pluvialis was performed w...
Fowden AL, Gardner DS, Ousey JC, Giussani DA, Forhead AJ.At birth, the endocrine pancreas becomes more directly involved in the control of glycaemia than in utero. However, compared with other tissues, relatively little is known about the maturational changes that occur in the fetal endocrine pancreas in preparation for extrauterine life. This study examined the pancreatic beta-cell response to exogenous administration of glucose and arginine in fetal horses with respect to their gestational age and concentration of cortisol, the hormone responsible for prepartum maturation of other fetal tissues. Glucose administration had no effect on fetal insuli...
Caltabilota TJ, Earl LR, Thompson DL, Clavier SE, Mitcham PB.Four experiments were conducted 1) to assess the use of glucose responses to insulin injections as a means of estimating insulin sensitivity in horses and 2) to compare the insulin sensitivities of normal horses vs. those displaying hyperleptinemia (HL). In Exp. 1, HL mares and geldings (n = 4 each) and 4 mares and geldings with normal leptin concentrations (NL) were injected intravenously with 20 and 100 mU/kg of BW of bovine insulin on 2 separate occasions in December 2008. In Exp. 2, the experimental protocol was repeated in late April 2009. In Exp. 1, the 20 mU/kg of BW dose of insulin cau...
Hess MF, Roser JF.There are several hormones and local testicular factors involved in the initiation and control of steroidogenesis and spermatogenesis during puberty. GH and its mediator, IGF-I, increase substantially during puberty, and in addition to LH, these growth-promoting hormones can have direct effects upon testicular function. The objective of this work was to investigate the effects of eLH, eGH and hrIGF-I upon Leydig cells derived from testes of colts and stallions representing different stages of development. Testes were obtained from 48 light horse colts and stallions at the time of routine castr...
