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.
Treiber K, Carter R, Gay L, Williams C, Geor R.Inflammatory and redox signals could render lamellar tissue susceptible to damage and contribute to higher risk for laminitis in obese or insulin resistant ponies just as these factors contribute to health risks in humans with metabolic syndrome. This study evaluated circulating markers of inflammatory and redox status in ponies that had a history of recurrent bouts of pasture-associated laminitis (PL, n = 42) or had never developed clinical laminitis (NL, n = 34) under the current management conditions. There were no differences (P > 0.05) between PL and NL ponies for markers of antioxidan...
Vervuert I, Klein S, Coenen M.The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post-prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consist...
Haffner JC, Eiler H, Hoffman RM, Fecteau KA, Oliver JW.Sustained dexamethasone administration to horses results in insulin resistance, which may predispose them to laminitis. A single dose of dexamethasone is commonly used as a diagnostic aid, yet the effect of a single dose of dexamethasone on glucose homeostasis in horses is not well defined. The objective of this study was to characterize the change in glucose dynamics over time in response to a single dose of dexamethasone. A combined glucose-insulin tolerance test (CGIT) was performed on 6 adult geldings before and at 2, 24, and 72 h postdexamethasone (40 microg/kg of BW, i.v.); a minimum of ...
Vervuert I, Voigt K, Hollands T, Cí·¯ord D, Coenen M.The aim of this study was to investigate the effects of feeding oats alone before or after feeding chopped alfalfa or, in admixture with the alfalfa on the glycaemic and insulinaemic responses of horses as well as post-prandial breath hydrogen and methane excretion. Horses were fed in a randomized order, chopped alfalfa as a source of dietary fibre and unprocessed oats as a source of starch. Chopped alfalfa intake was adjusted to a crude fibre intake of 0.5 g/kg bodyweight (BW) per meal and the oats intake was adjusted to a starch intake of 2 g/kg BW per meal. The feeds were offered in three d...
Vervuert I, Voigt K, Hollands T, Cí·¯ord D, Coenen M.The aim of this study was to investigate the effect of increasing the intake of starch on the glycaemic and insulinaemic responses of horses. A cross-over study design was used in which four horses were fed increasing amounts of a compound feed (0.5-3.5 kg) to provide 0.3, 0.6, 0.8, 1.1, 1.4 and 2 starch/kg bodyweight (BW)/meal. The glycaemic response increased with starch intake (P<0.05), while feeding <1.1 g starch/kg BW resulted in a lowered response, compared to when 1.1-2 g starch/ kg BW was fed (P<0.01). The results suggested that insulin responses may be more appropriate to def...
Firshman AM, Valberg SJ, Baird JD, Hunt L, DiMauro S.To determine insulin sensitivity, proportions of muscle fiber types, and activities of glycogenolytic and glycolytic enzymes in Belgians with and without polysaccharide storage myopathy (PSSM). Methods: 10 Quarter Horses (QHs) and 103 Belgians in which PSSM status had been determined. Methods: To determine insulin sensitivity, a hyperinsulinemic euglycemic clamp (HEC) technique was used in 5 Belgians with PSSM and 5 Belgians without PSSM. Insulin was infused i.v. at 3 mU/min/kg for 3 hours, and concentrations of blood glucose and plasma insulin were determined throughout. An i.v. infusion of g...
Vervuert I, Voigt K, Hollands T, Cí·¯ord D, Coenen M.Four horses were randomly fed a diet containing rolled, micronised or extruded barley; the barley intake was adjusted to supply 2 g starch/kg bodyweight per day. During a 10-day acclimatisation period the horses were also fed 1 kg grass hay/100 kg bodyweight per day. Samples of blood and breath were collected at the end of each period after the test meal of barley had been fed after a 12-hour overnight fast. The glycaemic and insulinaemic responses of the horses were measured as an indication of the pre-caecal digestibility of starch, and postprandial breath hydrogen and methane were measured ...
Durham AE, Rendle DI, Newton JE.Laminitis in equids is a very common debilitating disease, and insulin resistance (IR) and hyperinsulinaemia are increasingly recognised as important predisposing factors. Pharmacological modification of IR and hyperinsulinaemia might reduce the risk of laminitis. Objective: Metformin, a drug commonly prescribed for treatment of human IR, may also decrease IR in equids. Methods: Eighteen horses and ponies with IR and recurrent laminitis were treated with 15 mg/kg bwt metformin per os q. 12 h. Each animal served as its own control by comparing pre- and post treatment proxies for IR, insulin sen...
Ho EN, Wan TS, Wong AS, Lam KK, Stewart BD.Insulin administration can increase muscle glycogen by utilising hyperinsulinaemic clamps prior to sports events or during the recovery phases, and increase muscle size by its chalonic action to inhibit protein breakdown. In order to control insulin abuse in equine sports, a method to detect effectively the use of insulins in horses would be required. Besides the readily available human insulin and its synthetic analogues, structurally similar insulins from other species can also be used as doping agents. This study describes a method for the simultaneous detection of bovine, porcine and human...
Winkelsett S, Vervuert I.Laminitis is a systemic disease which is manifested as a non infectious condition in the foot. The management of feeding and housing conditions is necessary to treat the endocrinological and metabolic disturbances of laminitic horses. The Equine Metabolic Syndrome (EMS) is predisposing for developing laminitis, and it is characterised by obesity, insulin resistance, hypertension and dyslipidaemia. A genetical predisposition is supposed and EMS is accompanied by a lack of exercise and inadequate energy intake. Laboratory examinations are of great importance for diagnosis. Analyses of insulin, g...
Myers CJ, Magdesian KG, Kass PH, Madigan JE, Rhodes DM, Marks SL.This retrospective study describes the use of and complications associated with parenteral nutrition (PN) administration to 53 equine neonates at the University of California Veterinary Medical Teaching Hospital. Medical records were examined and information obtained on signalment, physical examination, clinical diagnosis, outcome, total hospitalization time, insulin administration, microbiology culture results, other complications (i.e. thrombophlebitis) and necropsy findings. Complete blood count and serum biochemistry analytes, venous blood gas, serum electrolyte and glucose concentrations,...
Carter RA, Geor RJ, Burton Staniar W, Cubitt TA, Harris PA.This study described a scoring system for the assessment of apparent neck adiposity and evaluated morphometric measurements for assessment of neck and overall adiposity. Twenty-one barren Thoroughbred mares, 13 Arabian geldings and 75 Welsh, Dartmoor, or crossbred pony mares, were clinically examined and blood samples analysed for insulin, glucose, leptin, and triglycerides. Bodyweight (BW), height, length, girth and abdominal circumferences, neck length, neck crest height and neck circumference were measured, and body condition scores (BCS) and cresty neck scores (CNS) were rated. Girth:heigh...
Rambags BP, van Rossem AW, Blok EE, de Graaf-Roelfsema E, Kindahl H, van der Kolk JH, Stout TA.Insulin is a pancreatic hormone that classically regulates carbohydrate and fat metabolism, but also appears to play a role in various reproductive processes. A preliminary study suggested insulin production by day 10 to 18 equine conceptuses. The aim of the present study was to examine the hypothesis that insulin is the conceptus signal responsible for maternal recognition of pregnancy (MRP) in the mare, or otherwise influences reproductive cyclicity during the MRP period. Six Warmblood mares were treated daily during days 7 to 17 after ovulation of two successive oestrous cycles with either ...
Kuuranne T, Thomas A, Leinonen A, Delahaut P, Bosseloir A, Schänzer W, Thevis M.Insulin is a peptide hormone consisting of two peptide chains (A- and B-chain) that are cross-linked by two disulfide bonds. To obtain improved pharmacokinetic onset of action profiles of insulin treatment in diabetic patients, recombinant long-, intermediate-, and rapid-acting insulin analogs are produced, in which the C-terminal end of the B-chain plays an especially important role.A review of the veterinary literature reveals the low prevalence of equine type I diabetes mellitus, which indicates that the therapeutic use of insulin in racing horses is unlikely. Although there is no unequivoc...
Vick MM, Murphy BA, Sessions DR, Reedy SE, Kennedy EL, Horohov DW, Cook RF, Fitzgerald BP.To determine whether an inflammatory challenge induces insulin resistance in horses and examine possible contributions of adipose tissue to inflammatory cytokine production. Methods: 15 adult mares. Methods: Lipopolysaccharide (0.045 mug/kg, IV) or saline solution was administered, and insulin sensitivity was determined by means of the hyperinsulinemic, euglycemic clamp procedure or an adipose tissue biopsy was performed. Adipose tissue samples were collected, and mature adipocytes were obtained. Mature adipocytes were stimulated with lipopolysaccharide or dedifferentiated into preadipocytes a...
Tóth F, Frank N, Elliott SB, Geor RJ, Boston RC.To evaluate the effects of endotoxin administered IV on glucose and insulin dynamics in horses. Methods: 16 healthy adult mares. Methods: Each week of a 2-week randomized crossover study, each horse received an IV injection (duration, 30 minutes) of Escherichia coli O55:B5 lipopolysaccharide (LPS) in 60 mL of sterile saline (0.9% NaCl) solution (20 ng/kg) or sterile saline solution alone (control treatment). Frequently sampled IV glucose tolerance test procedures were performed at 24 hours before (baseline) and 24 and 48 hours after injection; glucose and insulin dynamics were assessed via min...
Tiley HA, Geor RJ, McCutcheon LJ.To determine the effects of dexamethasone treatment on selected components of insulin signaling and glucose metabolism in skeletal muscle obtained from horses before and after administration of a euglycemic-hyperinsulinemic clamp (EHC). Methods: 6 adult Standardbreds. Methods: In a balanced crossover study, horses received either dexamethasone (0.08 mg/kg, IV, q 48 h) or an equivalent volume of saline (0.9% NaCl) solution, IV, for 21 days. A 2-hour EHC was administered for measurement of insulin sensitivity 1 day after treatment. Muscle biopsy specimens obtained before and after the EHC were a...
Bailey SR, Habershon-Butcher JL, Ransom KJ, Elliott J, Menzies-Gow NJ.To determine the metabolic phenotype of a group of laminitis-prone ponies when at pasture in summer, compared with when at pasture in winter. Methods: 40 ponies of various breeds predisposed to recurrent pasture-associated laminitis and 40 unaffected control ponies. Methods: Body condition score and size of the crest of the neck were assessed, blood samples obtained, and blood pressure measured by use of an indirect oscillometric technique, while ponies were kept on winter pasture (last week of November or beginning of December) and again on summer pasture (June). Serum insulin concentration a...
Frank N, Elliott SB, Boston RC.To determine the effects of long-term oral administration of levothyroxine sodium (L-T(4)) on glucose dynamics in adult euthyroid horses. Methods: 6 healthy adult mares. Methods: Horses received L-T(4) (48 mg/d) orally for 48 weeks. Frequently sampled IV glucose tolerance test procedures were performed on 3 occasions (24-hour intervals) before and at 16, 32, and 48 weeks during the treatment period. Data were assessed via minimal model analysis. The repeatability of measurements was evaluated. Results: During treatment, body weight decreased significantly from the pretreatment value; mean +/- ...
Firshman AM, Valberg SJ.Insulin resistance is thought to be involved in the pathogenesis of many equine conditions such as pars intermedia dysfunction, equine metabolic syndrome, diabetes mellitus, hyperlipaemia, laminitis, endotoxaemia and osteochondrosis dissecans (OCD); whereas polysaccharide storage myopathy in Quarter Horses and equine motor neuron disease (EMD) have been associated with increased insulin sensitivity. However, it is clear that there is not one ideal test, in terms of both practicality and accuracy, for evaluating insulin sensitivity in horses and improved diagnostic techniques are required. This...
Bailey SR, Menzies-Gow NJ, Harris PA, Habershon-Butcher JL, Crawford C, Berhane Y, Boston RC, Elliott J.To determine whether pasture, and specifically the addition of fructan carbohydrate to the diet, induces exaggerated changes in serum insulin concentration in laminitispredisposed (LP) ponies, compared with ponies with no history of the condition, and also to determine insulin responses to the dexamethasone suppression test. Methods: Prospective study. Methods: 10 LP and 11 control adult nonobese mixed-breed ponies. Methods: Insulin-modified IV glucose tolerance tests were performed (5 ponies/group). In diet studies, ponies were kept on pasture and then changed to a hay diet (10 ponies/group)....
Staniar WB, Kronfeld DS, Akers RM, Harris PA.The objective of this longitudinal study was to characterize growth and plasma insulin-like growth factor I (IGF-I) concentrations in pasture-raised thoroughbreds fed two sources of dietary energy. Mares and foals were randomly assigned to either a sugar and starch (SS) or fat and fibre (FF)-rich feed, and plasma IGF-I and growth were measured once a month from 1 to 16 months of age. These dependent variables were also compared with day length and ambient temperature. There was an association between plasma IGF-I concentration and average daily gain (ADG) (r = 0.32, p 0.10) in the FF group wh...
Weyenberg SV, Hesta M, Buyse J, Papadopoulos GA, Janssens GP.To determine whether plasma leptin concentrations and glucose tolerance are affected by changes in energy balance, nine healthy Shetland ponies were fed at 140% followed by 75% of their maintenance requirements for 13 days in each of the two periods. Bodyweight was recorded every three days. Blood samples were taken every two days and analysed for leptin and cortisol. An oral glucose tolerance test was performed on day 7 of each period. Serial blood samples were analysed for glucose and insulin. Although bodyweight was not affected, plasma leptin concentrations increased (P<0.001) initially...
Asplin KE, Sillence MN, Pollitt CC, McGowan CM.The purpose of this study was to determine the effects of prolonged administration of insulin, whilst maintaining normal glucose concentrations, on hoof lamellar integrity in vivo on healthy ponies with no known history of laminitis or insulin resistance. Nine clinically healthy, unrelated ponies were randomly allocated to either a treatment group (n =5; 5.9+/-1.7 years) or control group (n =4; 7.0+/-2.8 years). The treatment group received insulin via a euglycaemic hyperinsulinaemic clamp technique modified and prolonged for up to 72 h. Control ponies were infused with an equivalent volume of...
Ralston SL.One of the most difficult problems in equine nutrition research is often the lack of objective and clinically relevant end points. Nevertheless, this article attempts to present the best evidence (or lack thereof) for some of the most common clinical questions pertaining to such topics as the evaluation of glucose and insulin tolerance and factors that may confound results, dietary management of horses prone to laminitis and rhabdomyolysis, nutritional prevention of gastric ulcers and developmental orthopedic disease, the efficacy of commonly used herbal products, and feeding geriatric horses....
Tiley HA, Geor RJ, McCutcheon LJ.To determine effects of dexamethasone on glucose dynamics and insulin sensitivity in healthy horses. Methods: 6 adult Standardbreds. Methods: In a balanced crossover study, horses received dexamethasone (0.08 mg/ kg, IV, q 48 h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment) during a 21-day period. Horses underwent a 3-hour frequently sampled IV glucose tolerance test (FSIGT) 2 days after treatment. Minimal model analysis of glucose and insulin data from FSIGTs were used to estimate insulin sensitivity (Si), glucose effectiveness (Sg), acute insulin response to gluc...
Storer WA, Thompson DL, Waller CA, Cartmill JA.We previously reported that a rise in plasma leptin concentrations followed the rise in insulin and glucose in meal-fed horses, whereas horses maintained on pasture had little fluctuations in hormonal patterns. We have also described a hyperleptinemic-hyperinsulinemic condition that occurs in about 30% of our light horse mares of high body condition maintained on pasture. The present experiment was designed to 1) study the effect of 3 common feeding-housing regimens on leptin and other metabolic hormones in mares and 2) determine whether the hyperleptinemic condition interacted with these regi...
Pratt SE, Geor RJ, Spriet LL, McCutcheon LJ.The time course of insulin sensitivity, skeletal muscle glycogen and GLUT4 content, and glycogen synthase (GS) activity after a single bout of intense exercise was examined in eight horses. On separate days, a euglycemic-hyperinsulinemic clamp (EHC) was undertaken at 0.5, 4, or 24 h after exercise or after 48 h of rest [control (Con)]. There was no increase in mean glucose infusion rate (GIR) with exercise (0.5-, 4-, and 24-h trials), and GIR was significantly decreased at 0.5 h postexercise (GIR: 8.6 +/- 2.7, 6.7 +/- 2.0, 9.0 +/- 2.0, and 10.6 +/- 2.2 mg.kg(-1).min(-1) for Con and at 0.5, 4, ...
Porter RM, Akers RM, Howard RD, Forsten-Williams K.Alginate hydrogel culture has been shown to reestablish chondrocytic phenotype following monolayer expansion; however, previous studies have not adequately addressed how culture conditions affect the signaling systems responsible for chondrocyte metabolic activity. Here we investigate whether chondrocyte culture history influences the insulin-like growth factor-I (IGF-I) signaling system and its regulation by interleukin-1 (IL-1). Articular chondrocytes (ACs) from equine stifle joints were expanded by serial passage and were either encapsulated in alginate beads or maintained in monolayer cult...
Vervuert I, Bothe C, Coenen M.This study was conducted to evaluate the effects of different barley processing techniques on the glycaemic and insulinaemic responses in horses. It was hypothesized that the changes in pre-caecal starch digestibility caused by barley processing would affect metabolic responses. Six horses were fed in random order: whole (WB), finely ground (FGB), steamed (SB), steam-flaked (SFB) and popped barley (PB). The total barley intake was adjusted to 630 g starch/horse/day (1.2-1.5 g starch/kg BW/day). During a 10-day stabilization period, the horses also received 6 kg grass hay/horse/day. On the bloo...
Urayama S, Arima D, Mizobe F, Shinzaki Y, Nomura M, Minamijima Y, Kusano K.Although hyperglycemia at admission with colic has been reported to have a poor prognosis, there is no report specifically about acute colitis with systemic inflammatory response syndrome (SIRS) in horses. In this study, we measured blood glucose (Glu), insulin (Ins), and cortisol (Cor) levels in 17 Thoroughbred racehorses diagnosed as having acute colitis with SIRS, and examined the relationship between time-dependent changes in Glu, Ins, and Cor and prognosis. Glu levels were high in 3 horses at admission, but thereafter no horses had persistently high Glu levels. There was no significant di...
Burns TA, Watts MR, Weber PS, McCutcheon LJ, Geor RJ, Belknap JK.In EMS-associated laminitis, laminar failure may occur in response to energy failure related to insulin resistance (IR) or to the effect of hyperinsulinemia on laminar tissue. 5'-Adenosine-monophosphate-activated protein kinase (AMPK) is a marker of tissue energy deprivation, which may occur in IR. Objective: To characterize tissue AMPK regulation in ponies subjected to a dietary carbohydrate (CHO) challenge. Methods: Twenty-two mixed-breed ponies. Methods: Immunohistochemistry and immunoblotting for total AMPK and phospho(P)-AMPK and RT-qPCR for AMPK-responsive genes were performed on laminar...
Duren SE, Pagan JD, Harris PA, Crandell KG.Six Thoroughbreds were used to evaluate time of feeding on changes in exercise response in horses receiving either a textured feed or a fat-supplemented textured feed. Using a crossover design, 3 horses were fed a fat-supplemented diet while 3 horses received a control ration of textured feed. Horses performed a standardised exercise test (SET) on a high speed treadmill. The SET was performed at 3 different times: 1) following an overnight 12 h fast, 2) 3 h after feeding and 3) 8 h after feeding. The SET consisted of a 2 min walk at 1.4 m/s, 800 m trot at 4.2 m/s, 800 m gallop at 7.7 m/s, 1600...
de Laat MA, Kheder MH, Pollitt CC, Sillence MN.Hyperinsulinemia is a major risk factor for equine laminitis, a debilitating and painful foot condition. Sweet taste receptor (T1R2/3) inhibitors have been used to reduce the insulin and glucose responses to oral carbohydrates in other species. However, their effect in horses has not been investigated. It would be useful to be able to attenuate the large post-prandial insulin response that typically occurs when a carbohydrate-rich meal is fed to insulin-dysregulated horses. Here we have determined the efficacy of two T1R2/3 inhibitors, lactisole and Gymnema sylvestre, for reducing glucose upta...
Wagner AL, Urschel KL.To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age. Methods: 6 yearlings, six 2-year-old horses, and 6 mature horses. Methods: After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state). Blood samples were collected for the duration of the experimental ...
Gauff FC, Patan-Zugaj B, Licka TF.To determine the effect of short-term hyperinsulinemia on the localization and expression of endothelin receptor (ETR)-A and ETR-B in lamellar tissue of the forelimbs of horses. Methods: Distal portion of 15 cadaveric forelimbs from healthy adult horses (1 limb/horse) obtained immediately after slaughter at an abattoir. Methods: Each forelimb was assigned to 1 of 3 treatment groups (perfused with autologous blood for 10 hours [control perfusion; n = 5], perfused with an insulin [142 ± 81 μU/mL] perfusate for 10 hours [insulinemic perfusion; 5], or not perfused [unperfused control; 5]). Immun...
Waller CA, Thompson DL, Cartmill JA, Storer WA, Huff NK.Previous results from our laboratory indicated that a majority of mares with high body condition scores (BCS) displayed estrous cycles or had considerable follicular activity during the winter. Among these high BCS mares, about 35% of them exhibited a persistent hyperleptinemia and hyperinsulinemia. The current experiment was designed to compare the reproductive characteristics of high BCS mares with hyperleptinemia to those with normal (low) plasma concentrations of leptin during the winter and the first estrous cycle (or the first full cycle encountered for those already cycling). Light hors...
Fowden AL, Ellis L, Rossdale PD.Plasma concentrations of insulin and glucose were measured in Pony and Thoroughbred foals at birth and at intervals thereafter for up to 7 days. The plasma concentrations of insulin in foals of both breeds at birth were 11.2 +/- 2.5 microU/ml (N = 6) and 13.5 +/- 1.5 microU/ml (N = 16) respectively. These values were similar to those obtained for foals in utero but were significantly less than those in adult animals. There was little variation in the plasma concentrations of insulin and glucose during the first 2 h of life and both concentrations tended to rise in the next 24-48 h. Although th...
Robertson SA, Steele CJ, Chen CL.The effect of general anaesthesia and arthroscopic surgery on blood glucose and lactate, plasma non-esterified fatty acids, insulin, beta-endorphin and cortisol was investigated in seven horses. Animals were premedicated with xylazine and anaesthesia was induced with guaifenesin and sodium thiamylal and maintained with halothane vaporised in oxygen. Blood samples were collected in the pre-, intra- and post operative period. Induction of anaesthesia was associated with a transient hyperglycaemia and a significant rise in plasma insulin levels. Plasma insulin values fell during surgery but showe...
Heidler B, Parvizi N, Sauerwein H, Bruckmaier RM, Heintges U, Aurich JE, Aurich C.In this study, growth hormone (GH), insulin-like growth factor 1 (IGF-1), leptin, luteinising hormone (LH) and prolactin were analyzed in mares from late pregnancy throughout lactation (group 1, n=46) and in non-lactating mares (group 2, n=11). Plasma GH concentrations in group 1 mares during gestation and lactation were lower than in mares of group 2 (P<0.05). Highest IGF-1 levels were found in lactating mares in the week of foaling. IGF-1 concentrations decreased continuously thereafter. Plasma leptin concentrations decreased after foaling and, for 4 weeks, were lower in lactating than in...
Delarocque J, Frers F, Huber K, Jung K, Feige K, Warnken T.Insulin dysregulation (ID) is an equine endocrine disorder, which is often accompanied by obesity and various metabolic perturbations. The relationship between weight variations and fluctuations of the insulin response to oral glucose tests (OGT) as well as the metabolic impact of ID have been described previously. The present study seeks to characterize the concomitant metabolic impact of variations in the insulin response and bodyweight during repeated OGTs using a metabolomics approach. Methods: Nineteen Icelandic horses were subjected to five OGTs over one year and their bodyweight, insuli...
Glatter M, Bochnia M, Goetz F, Gottschalk J, Koeller G, Mielenz N, Hillegeist D, Greef JM, Einspanier A, Zeyner A.This study aimed to investigate the impact of the supplementation of a pre-biotic compound [Jerusalem artichoke meal (JAM)] on the glycaemic and insulinaemic response in healthy, non-obese warm-blooded horses. Six adult mares [mean body weight (bwt) 529 ± 38.7 kg; body condition score 5.1 ± 0.49/9] were used. In two equal meals per day, the horses received crushed oat grains (1 g starch/kg bwt per day) and meadow hay (2 kg/100 kg bwt per day) which together were likely to meet the energy recommendation for light work (GfE, ). Additionally, they received either 0.15 g fructo-oligosac...
Vervuert I, Klein S, Coenen M.The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post-prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consist...
Baskerville CL, Bamford NJ, Harris PA, Bailey SR.Insulin-like growth factor-1 (IGF-1) plays several important physiological roles, and IGF-related pathways have been implicated in developmental osteochondral disease and endocrinopathic laminitis. This factor is also a downstream marker of growth hormone activity and its peptide mimetics. Unfortunately, previously used assays for measuring equine IGF-1 (radioimmunoassays and ELISAs) are no longer commercially available, and many of the kits on the market give poor results when used on horse samples. The aim of the present study was to compare three different ELISA assays (two human and one ho...
Newkirk KM, Ehrensing G, Odoi A, Boston RC, Frank N.OBJECTIVE To assess insulin, glucagon, and somatostatin expression within pancreatic islets of horses with and without insulin resistance. ANIMALS 10 insulin-resistant horses and 13 insulin-sensitive horses. PROCEDURES For each horse, food was withheld for at least 10 hours before a blood sample was collected for determination of serum insulin concentration. Horses with a serum insulin concentration 20 μU/mL underwent a frequently sampled IV glucose tolerance test to determine sensitivity to insulin by minimal model analysis. Horses with a sensitivity to insulin < 1.0 × 10 L•min•mU w...
Greene SA, Thurmon JC, Tranquilli WJ, Benson GJ.Serum insulin and plasma glucose concentrations were determined in 8 mares. Four IV treatments were studied: xylazine (1.1 mg/kg of body weight); yohimbine (0.125 mg/kg); yohimbine (0.125 mg/kg) followed 5 minutes later by xylazine (1.1 mg/kg); and 5 ml of isotonic saline solution as a control. Blood samples were collected before (time 0) and at 5, 15, 30, 60, 120, and 180 minutes after drug administration. Serum insulin concentration decreased and plasma glucose concentration increased in mares given xylazine. Plasma glucose concentration was unchanged in control mares and in mares given yohi...
Hosoya M, Inoue A, Kimura N, Arai T.Glucose, free fatty acid (FFA), triglyceride (TG) and immunoreactive insulin (IRI) concentrations in plasma and activities of enzymes related to energy metabolism in some types of peripheral leukocytes were measured in thoroughbred race horses before and after racing. Glucose, FFA, TG and IRI concentrations and enzyme activities did not change significantly in plasma. However, the activities of cytosolic hexokinase, malate dehydrogenase (MDH), mitochondrial MDH and aspartate aminotransferase decreased significantly in leukocytes of the horses after the races. The cytosolic ratio of MDH/LDH act...
Jayathilake WMNK, Furr M, Risco C, Lacombe VA.Similar to human diabetes, equine metabolic syndrome (EMS) causes insulin dysregulation leading to debilitating sequela including laminitis. The pathophysiological mechanisms underlying EMS and laminitis are not well known. Therefore, using an insulin-resistant equine model, we hypothesized that insulin dysregulation induces an increased expression of inflammatory proteins in a tissue specific manner. Two groups of horses (n = -5/group) were categorized as insulin-resistant (IR) or insulin-sensitive (IS), using a frequently sampled intra-venous glucose tolerance test. Biopsies from skeletal ...
Cartmill JA, Thompson DL, Del Vecchio RP, Storer WA, Crowley JC.Five experiments were performed to evaluate the effects of dexamethasone (DEX), gender, and testosterone on plasma leptin concentrations in horses. In experiment 1, plasma leptin, insulin, glucose, and IGF-1 concentrations were increased (P < 0.01) in stallions following five daily injections of DEX (125 microg/kg BW). In experiment 2, leptin concentrations increased (P < 0.01) in mares, geldings, and stallions following a single injection of DEX, and the response was greater (P < 0.01) in mares and geldings than in stallions. The gender effect was confounded by differences in body co...
Yoon M, Jiang J, Chung KH, Roser JF.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...
Pang DS, Panizzi L, Paterson JM.A 3-year-old, 400 kg, gelding Quarter Horse was presented for investigation of epistaxis. Methods: The horse was bright, alert and responsive with rectal temperature, heart rate and respiration rate within normal limits. Results: During a second general anaesthetic for surgical treatment of guttural pouch mycosis by balloon-tipped catheter occlusion of the right major palatine artery and ligation of the right external carotid artery, signs consistent with hyperkalaemic periodic paralysis (HYPP) were exhibited. These included concurrent hyperkalaemia, hypercapnoea, sinus tachycardia, and muscle...
Thorringer NW, Weisberg MR, Jensen RB.The competition for customers increases the search for new grain processing methods for equine feed, but the effect on starch digestibility and metabolic responses varies. Therefore, to evaluate the effect of the processing methods, toasting and micronizing, on starch digestion and the effect on metabolic responses, the mobile bag technique (MBT) and plasma glucose and insulin concentrations in the blood were used to estimate nutrient disappearance and metabolic responses pre-cecally. Further, cecal pH, ammonium nitrogen (N), and short-chain fatty acid (SCFA) concentrations were used to estima...
Manfredi JM, Jacob SI, Boger BL, Norton EM.Endocrinopathies affect multiple species in ever-increasing percentages of their populations, creating an opportunity to apply one-health approaches to determining creative preventative measures and therapies in athletes. Obesity and alterations in insulin and glucose dynamics are medical concerns that play a role in whole-body health and homeostasis in both horses and humans. The role and impact of endocrine disorders on the musculoskeletal, cardiovascular, and reproductive systems are of particular interest to the athlete. Elucidation of both physiologic and pathophysiologic mechanisms invol...
Kranenburg LC, Westermann CM, de Sain-van der Velden MG, de Graaf-Roelfsema E, Buyse J, Janssens GP, van den Broek J, van der Kolk JH.Insulin resistance in horses is an emerging field of interest as it is thought to be a contributing factor in the pathogenesis of many equine conditions. Objective: The objectives of the present study were to determine the effects of long-term oral administration of L-carnitine on insulin sensitivity, glucose disposal, plasma leptin concentrations and acylcarnitine spectrum both in plasma and urine. Methods: Six 3-year-old healthy warmblood geldings were used. In a double blind 2 × 2 Latin square design at a dosage of 100 mg/kg body weight (BW)/day for 28 days the effects of oral supplementat...
Valencia NA, Thompson DL, Mitcham PB.Six insulin-sensitive and 6 insulin-insensitive mares were used in a replicated 3 by 3 Latin square design to determine the pituitary hormonal responses (compared with vehicle) to sulpiride and thyrotropin-releasing hormone (TRH), 2 compounds commonly used to diagnose pituitary pars intermedia dysfunction (PPID) in horses. Mares were classified as insulin sensitive or insensitive by their previous glucose responses to direct injection of human recombinant insulin. Treatment days were February 25, 2012, and March 10 and 24, 2012. Treatments were sulpiride (racemic mixture, 0.01 mg/kg BW), TRH (...
Loos CMM, McLeod KR, Stratton SC, van Doorn DA, Kalmar ID, Vanzant ES, Urschel KL.Activation of the mechanistic target of rapamycin (mTOR)-controlled anabolic signaling pathways in skeletal muscle of rodents and humans is responsive to the level of dietary protein supply, with maximal activation and rates of protein synthesis achieved with 0.2 to 0.4 g protein/kg body weight (BW). In horses, few data are available on the required level of dietary protein to maximize protein synthesis for maintenance and growth of skeletal muscle. To evaluate the effect of dietary protein level on muscle mTOR pathway activation, five mares received different amounts of a protein supplement t...
van der Kolk JH, Rijnen KE, Rey F, de Graaf-Roelfsema E, Grinwis GC, Wijnberg ID.To determine whether increased glucose metabolism is the potential cause of the decreased plasma glucose curve determined after oral glucose tolerance testing in horses with lower motor neuron degeneration. Methods: 3 horses with signs suggestive of lower motor neuron degeneration, 1 horse with malignant melanoma with multiple metastases, and an obese but otherwise healthy horse. Procedures-Glucose metabolism was assessed by use of the hyperglycemic clamp and euglycemic hyperinsulinemic clamp techniques. Results: Mean rate of glucose metabolism of horses with lower motor neuron degeneration wa...
Wilson AD, Badnell-Waters AJ, Bice R, Kelland A, Harris PA, Nicol CJ.High carbohydrate diets can affect the health and behaviour of foals, but the mechanisms are not always fully understood. The objective of this study was to compare the effects of feeding a starch and sugar (SS), or a fat (oil) and fibre (FF) rich diet to two groups of eight foals. Diets were fed from 4 to 42 weeks of age, alongside ad libitum forage. Faecal pH levels did not differ significantly between groups and endoscopic examination showed that the gastric mucosa was healthy in both groups at 25 and 42 weeks of age. At 40 weeks of age, SS foals had significantly higher total blood glucose...
Kutzner-Mulligan J, Eisemann J, Siciliano P, Smith J, Hewitt K, Sharlette J, Pratt-Phillips S.Management techniques that reduce the insulin response to feeding in horses have application in preventing insulin resistance (IR) and potential associations (e.g., laminitis). Eight mature idle horses of BCS between 5 and 6.5 and with no previous indication of IR were fed a meal of concentrate under 4 feed delivery treatments in a repeated Latin Square design. Treatments were all based on a bucket of equal dimensions. The treatments included a control (CON) and 3 treatments hypothesized to increase time to consume feed (TCF): mobile obstacles above the feed (BALL), stationary obstacles below ...
Ferraz GC, Teixeira-Neto AR, Mataqueiro MI, Lacerda-Neto JC, Queiroz-Neto A.To investigate the effect of acute administration of caffeine on the athletic performance of Arabian horses. Methods: 12 healthy adult Arabian horses that were trained for exercise on a treadmill. Methods: By use of a crossover study design, horses received each of the following treatments: IV administration of caffeine (5 mg/kg) and IV administration of approximately the same volume of saline (0.9% NaCl) solution. Order of treatment was randomized, and there was a 10-day interval between treatments. Thirty minutes after treatments, horses underwent an incremental exercise test (IET) on a trea...
