Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
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.
IGF -I plasma concentrations in non-treated horses and horses administered with methionyl equine somatotropin. Insulin-like growth factor-I (IGF -I) is likely to be an indicator of somatotropin (ST) administration in the horse. To investigate the different ways ST administration may be detected, the following aspects of IGF -I concentrations in plasma were studied: (i) the daily variation; (ii) variation following a treadmill test; (iii) concentrations at rest and after exercise; and (iv) concentrations in plasma from two young horses and two adults treated with methionyl equine somatotropin (e ST). In the population of horses at rest, IGF -I mean concentration (SEM) was 261 (104) ng ml(-1). In post ra...
Blood plasma concentrations of insulin-like growth factor-I (IGF-I) in resting standardbred horses. A survey of standardbred horses was conducted to build up a normal population profile for insulin like growth factor-I (IGF-I) concentrations in racing standardbreds and to ascertain how age, sex and geographic location affect IGF-I. Blood samples were drawn by jugular venepuncture from 202 racing standardbred horses aged one to eight years located in five different geographic regions of New Zealand. IGF-I concentrations were determined by insulin like growth factor-I binding protein (IGFBP)-blocked radioimmunoassay validated for the horse. As described in other species, age played a significa...
Glycemic index of a meal fed before exercise alters substrate use and glucose flux in exercising horses. In a randomized, balanced, crossover study each of six fit, adult horses ran on a treadmill at 50% of maximal rate of oxygen consumption for 60 min after being denied access to food for 18 h and then 1) fed corn (51.4 kJ/kg digestible energy), or 2) fed an isocaloric amount of alfalfa 2-3 h before exercise, or 3) not fed before exercise. Feeding corn, compared with fasting, resulted in higher plasma glucose and serum insulin and lower serum nonesterified fatty acid concentrations before exercise (P < 0.05) and in lower plasma glucose, serum glycerol, and serum nonesterified fatty acid conce...
Effect of partial replacement of oats with sugar beet pulp and maize oil on nutrient utilisation in horses. The objective of the present work was to assess the influence of partial replacement of oats with dried unmolassed sugar beet pulp (SBP) and/or maize oil on nutrient utilisation in horses fed a traditional hay and concentrate diet. The total tract digestibility of nutrients, urinary excretion and plasma parameters were studied in a 4 x 4 Latin-square design experiment with purebred Arabian geldings. Horses fed the SBP diets responded with a reduced (P<0.05) apparent digestibility of crude protein and feeding of maize oil resulted in an increased (P<0.05) apparent digestibility of crude f...
Measurement of basal serum insulin concentration in the diagnosis of Cushing’s disease in ponies. A high basal plasma or serum insulin concentration is commonly accepted as an indicator of Cushing's disease in horses. The results of the combined dexamethasone suppression test and thyrotropin-releasing hormone stimulation test were compared with the basal insulin concentrations and insulin response tests of eight hyperinsulinaemic and insulin-resistant ponies with clinical histories of chronic or recurrent laminitis that were suspected of having Cushing's disease. Seven of the eight ponies had normal responses to the combined test indicating that basal insulin concentrations are not a speci...
Insulin responsiveness of sheep, ponies, miniature pigs and camels: results of hyperinsulinemic clamps using porcine insulin. It had been suggested that marked species differences in glucose tolerance tests were due to differences in insulin resistance. To compare insulin responsiveness, euglycemic hyperinsulinemic clamps were carried out in sheep, ponies, miniature pigs and camels. Porcine insulin was infused as primed-continuous infusions for 2 h (6 mU x kg(-1) x min(-1)). The steady state glucose infusion rates in the pigs, sheep, ponies and camels were 96.0, 18.6, 7.1 and 6.1 micromol x kg(-1) x min(-1), respectively. The maximal plasma insulin concentrations during the insulin infusions were 2,700 microU x ml(-1...
The effects of age, season and fertility status on plasma and intratesticular insulin-like growth factor I concentration in stallions. The purposes of this study were to establish the basal plasma and testicular insulin-like growth factor-I (IGF-I) values for stallions ranging in age from 6 months to 23 years and to determine if IGF-I could be used as a marker for declining fertility. Blood and testes were obtained from 28 light horse stallions and colts. Of the 28 stallions, 22 were considered fertile and were categorized by age (<2 y, 5 to 10 y, 11 to 15 y, and 16 to 23 y); 12 age-matched stallions were grouped as to fertility status (fertile, subfertile, infertile); and all 28 stallions were grouped as to season of cast...
Effects of beta-aminopropionitrile on equine tendon metabolism in vitro and on effects of insulin-like growth factor-I on matrix production by equine tenocytes. To investigate effects of beta-aminopropionitrile and a combination of insulin-like growth factor (IGF)-I and beta-aminopropionitrile on metabolism of equine tendon fibroblasts. Methods: Flexor tendon explants from 3 horses. Methods: Explants received 1 of 4 treatments (control, IGF-I, beta-aminopropionitrile, and IGF-I/beta-aminopropionitrile) for 10 days, and message expression for collagen types I and III was assessed by use of in situ hybridization. Histologic findings, new protein production, and quantitative determinations of glycosaminoglycan, DNA, and de novo collagen synthesis were ma...
The role of nutritional therapy in the treatment of equine Cushing’s syndrome and laminitis. Equine Cushing's syndrome, a relatively common and complex condition, is difficult to treat with conventional medicine. Cushing's syndrome involves a hyperplasia or adenoma of the anterior pituitary gland. Biochemical alterations include increased endogenous cortisol, insulin resistance, elevated adrenocorticotrophic hormone, and decreased thyroid hormone levels. Symptoms include hirsutism with no loss of the winter coat in summer, refractory laminitis, weight problems (over- or underweight), polyuria/polydipsia (Pu/Pd), frequent infections, lowered immunity to intestinal parasites, decreased ...
Administration of bovine, porcine and equine growth hormone to the horse: effect on insulin-like growth factor-I and selected IGF binding proteins. This study investigated the biochemical effects of administration of three types of recombinant growth hormone (GH; somatotropin) to the Thoroughbred horse. Equine or bovine or porcine GH was administered at a recommended dosage to 3-5-year old Thoroughbred geldings, for up to 21 days. It was shown that, in addition to equine GH, bovine and porcine GH were active in the horse; however, porcine GH caused injection-site reactions that were so serious that administration had to be terminated. The concentrations of a range of GH-related serum protein markers were determined before, during and afte...
Effects of nandrolone treatment on recovery in horses after strenuous physical exercise. To test the effect of nandrolone on their recovery, six adult half-bred riding horses performed a competition exercise test (CET) and a standardized exercise test (SET) on consecutive days before and after a 2-week treatment with the anabolic steroid nandrolone laurate. Blood samples were collected during and between these tests for the determination of red cell volume and concentrations of blood lactate, plasma glucose, non-esterified fatty acids, glycerol, triglycrides, erythropoietin, cortisol, insulin, and glucagon. Muscle biopsy specimens were taken immediately after the CET and before th...
Plasma glucose and insulin responses of Thoroughbred mares fed a meal high in starch and sugar or fat and fiber. Plasma concentrations of glucose and insulin following a meal were compared in twelve Thoroughbred mares fed a pelleted concentrate (PC), a traditional sweet feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The feeds had similar DE and CP but differed in fat (19, 32, and 166 g/kg DM, respectively), NDF (199, 185, and 369 g/kg DM, respectively) and nonstructural carbohydrates (574, 645, and 247 g/kg, respectively). Mares were randomly assigned to two groups balanced for foaling date and weight. All mares received PC in late gestation; then, after foaling, one group was ...
Effects of fat feeding and energy level on plasma metabolites and hormones in Shetland ponies. The aim of this study was to investigate the influence of a fat-supplemented diet compared with a carbohydrate diet on the lipid metabolism and the enteroinsular axis of Shetland ponies. The 'crossover' experiment was divided into two parts: in the first 10 weeks the diets comprised the correct number of calories according to requirements and in the following 10 weeks they were hypercaloric, in order to check the effect of a different energy content of the diets. Feeding the fat-enriched diet, independently of its energy content, led to a significant decrease in plasma triglycerides, associate...
Changes in molecular expression of aggrecan and collagen types I, II, and X, insulin-like growth factor-I, and transforming growth factor-beta1 in articular cartilage obtained from horses with naturally acquired osteochondrosis. To determine molecular changes in the expression of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta1 (TGF-beta1) in horses with osteochondrosis, and to characterize expression of matrix aggrecan and collagen types I, II, and X in articular cartilage of affected joints. Methods: Articular cartilage from affected stifle or shoulder joints of 11 horses with naturally acquired osteochondrosis and corresponding joints of 11 clinically normal horses. Methods: Harvested specimens were snap frozen in liquid nitrogen, and total RNA was isolated. Specimens were fixed in 4% paraf...
Glucose-dependent insulinotropic polypeptide (GIP) and the enteroinsular axis in equines (Equus caballus). To investigate the enteroinsular axis (EIA) in equines oral (oGTT) and intravenous (i.v.GTT) glucose tolerance tests (5.6 and 1 mmol glucose/kg BW, respectively) were performed with healthy, normal weight large horses and Shetland ponies. Plasma was analysed for concentrations of glucose, glucose-dependent insulinotropic polypeptide (GIP) and insulin. In all equines plasma GIP concentrations only increased significantly when glucose was administered orally. The insulin glucose ratio (IGR) was significantly higher during the oGTT than during the i.v.GTT in both races. Basal plasma glucose level...
Postprandial arterial vasodilation in the equine distal thoracic limb. The effects of feeding on blood flow to the equine foot are poorly understood. In a temperature-controlled room, duplex Doppler ultrasonographic observations were made pre- and postprandially of the lateral proper palmar digital artery of 5 horses, randomly assigned to twice and 4 times daily feeding in an unbalanced 2 period crossover design. Arterial diameter and blood velocity were measured over 4 h and additional observations made of heart rate, blood pressure, total plasma protein, packed cell volume, plasma glucose and insulin. There was no effect of the feeding regimen on any variable. ...
Pituitary hormone and insulin responses to infusion of amino acids and N-methyl-D,L-aspartate in horses. Thirty-nine adult light horse mares, geldings, and stallions were used in two experiments to assess the pituitary hormone and insulin responses to infusions of arginine, aspartic acid, lysine, glutamic acid, and N-methyl-D,L-aspartate (NMA). In Exp. 1, 27 horses were assigned to one of three infusion treatments: 1) physiological saline (1 L); 2) 2.855 mmol of arginine/kg BW in 1 L of water; or 3) 2.855 mmol of aspartic acid/kg BW in 1 L of water. In Exp. 2, 12 horses were assigned, in a multiple-square 4 x 4 Latin square design, to one of four infusion treatments: 1) 2 mL of saline/kg BW; 2) 2...
Effect of short-term feed restriction and calorie source on hormonal and metabolic responses in geldings receiving a small meal. The metabolic effects of short-term feed restriction and dietary calorie source were studied in horses receiving high-roughage or high-concentrate diets. Four Thoroughbred geldings were assigned to four treatment groups in a 4 x 4 Latin square experiment. The four treatments were 1) a nutritionally adequate high-roughage ration (70% roughage, 30% concentrate; AHR), 2) a nutritionally adequate high-concentrate ration (40% roughage, 60% concentrate; AHC), 3) 70% of the intake of the AHR diet (RHR), and 4) 70% of the intake of the AHC diet (RHC). Diets AHR and AHC were designed to meet the calori...
Pharmacokinetics and metabolic effects of triamcinolone acetonide and their possible relationships to glucocorticoid-induced laminitis in horses. Experiments were performed to establish the pharmacokinetics of triamcinolone acetonide and the effects of the glucocorticoid on glucose metabolism in horses. The pharmacokinetics after intravenous (i.v.) dosing was best described by a three-compartment open model. There was rapid distribution from the central compartment followed by two phases of elimination. The half-life of the rapid elimination phase was 83.5 min and of the slower phase was 12 h. The term (Vss/Vc)-1was 12.3 indicating extensive distribution into the tissues. Triamcinolone acetonide given i.v. or intramuscularly (i.m. ) ind...
Hormones, growth factors and other plasma variables in relation to osteochondrosis. Osteochondrosis (OC) is a multifactorial disorder with endocrinological dysfunction and mineral imbalance having a role in pathogenesis. The present study focused on a possible relationship between insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), parathyroid hormone (PTH), 1,25-dihydroxy-vitamin D (1,25(OH)2D), cortisol, copper, zinc, calcium, ionised calcium, magnesium and phosphorus and 5 different postmortem and radiographical osteochondrosis scores of hock and stifle joints in foals age 0-11 months. Osteochondrosis-positive foals showed a significantly lower IG...
The effects of bovine recombinant growth hormone administration on insulin-like growth factor-I and the haemopoietic system in thoroughbred geldings. The effect of intramuscularly administered recombinant bovine growth hormone (rbGH) on insulin-like growth factor-I (IGF-I) and white and red blood cell indices was studied in Thoroughbred geldings. An insulin-like growth factor binding protein (IGFBP)-blocked radioimmunoassay was modified and validated for the measurement of IGF-I in equine blood plasma. Baseline values of IGF-I and blood indices were determined over a 48 h period and then a single dose of 5 microg/kg, 10 microg/kg or 50 microg/kg of rbGH was administered. Insulin-like growth factor-I levels increased in a dose-dependent mann...
beta-adrenergic blockade augments glucose utilization in horses during graded exercise. To examine the role of beta-adrenergic mechanisms in the regulation of endogenous glucose (Glu) production [rate of appearance (R(a))] and utilization [rate of disappearance (R(d))] and carbohydrate (CHO) metabolism, six horses completed consecutive 30-min bouts of exercise at approximately 30% (Lo) and approximately 60% (Hi) of estimated maximum O(2) uptake with (P) and without (C) prior administration of the beta-blocker propranolol (0.22 mg/kg iv). All horses completed exercise in C; exercise duration in P was 49.9 +/- 1.2 (SE) min. Plasma Glu was unchanged in C during Lo but increased prog...
Loading-induced changes in synovial fluid affect cartilage metabolism. The object of this study was to determine whether changes in the synovial fluid (SF) induced by in vivo loading can alter the metabolic activity of chondrocytes in vitro, and, if so, whether insulin-like growth factor-I (IGF-I) is responsible for this effect. Therefore, SF was collected from ponies after a period of box rest and after they had been exercised for a week. Normal, unloaded articular cartilage explants were cultured in 20% solutions of these SFs for 4 days and chondrocyte bioactivity was determined by glycosaminoglycan (GAG) turnover (i.e., the incorporation of 35SO4 into GAG and ...
Carbohydrate supplementation of horses during endurance exercise: comparison of fructose and glucose. To delay the onset of fatigue, endurance horses are often fed at rest stops during races. The resulting increase in blood insulin may adversely inhibit lipolysis. In humans, ingestion of fructose produces a smaller insulin rise than glucose. This study compared glucose and fructose as carbohydrate supplements for endurance horses. Three Arabian geldings were given 300 g of fructose (F), glucose (G) or 50% glucose: 50% fructose (GF), in 1.5 L water, by stomach tube. In the Resting Test, carbohydrate was administered at rest. Following treatment, blood samples were taken every 30 min for 8 h, an...
Horse conceptuses secrete insulin-like growth factor-binding protein 3. Insulin-like growth factor-I (IGF-I) promotes early embryonic development in several species. In the rabbit, IGF-I binds to the embryonic coats from Day 3 of development onward by a 38-kDa protein that is probably insulin-like growth factor-binding protein 3 (IGFBP3). In the present study, ligand, Western, and Northern blot analyses were used to demonstrate the presence of IGF-I-binding activity, several immunoreactive IGFBP3 proteins, and IGFBP3 mRNA in horse conceptuses with particularly large amounts of immunoreactive IGFBP3 in the conceptus capsule. In addition, immunoprecipitation of radi...
Epinephrine inhibits exogenous glucose utilization in exercising horses. This study examined the effects of preexercise glucose administration, with and without epinephrine infusion, on carbohydrate metabolism in horses during exercise. Six horses completed 60 min of treadmill exercise at 55 +/- 1% maximum O(2) uptake 1) 1 h after oral administration of glucose (2 g/kg; G trial); 2) 1 h after oral glucose and with an intravenous infusion of epinephrine (0.2 micromol. kg(-1). min(-1); GE trial) during exercise, and 3) 1 h after water only (F trial). Glucose administration (G and GE) caused hyperinsulinemia and hyperglycemia ( approximately 8 mM). In GE, plasma epine...
Metabolic and mitogenic activities of insulin-like growth factor-1 in interleukin-1-conditioned equine cartilage. To determine response of interleukin-1alpha (IL-1alpha)-conditioned equine articular cartilage explants to insulin-like growth factor-1 (IGF-1). Sample Population-Cartilage from the trochlea and condyles of the femur of a clinically normal 4-year-old horse. Methods: Effects of IGF-1 (0 to 500 ng/ml) after addition of IL-1alpha were evaluated by assessing matrix responses, using a sulfated glycosaminoglycan (GAG) assay, matrix 35SO4 GAG incorporation, and release of GAG. Mitogenic response was assessed by 3H-thymidine incorporation into DNA and fluorometric assay of total DNA concentration. Res...
Effect of nervous excitation on acid secretion in horses. Nervous excitation was induced by various means in horses provided with a gastric cannula. Insulin hypoglycaemia profoundly inhibited the basal acid output and volume secreted from the stomach. No clear effect on acid secretion was noted after administration of bethanechol, as the acid output was covered by the copious secretion of saliva. Atropine almost abolished the basal acid output. Sensoric stimulation by teasing caused a slight but not significant increase in the total acid output. These data suggest that cholinergic excitation might play a role in the stimulation of both volume and aci...
Urinary concentration of corticoids in ponies with hyperlipoproteinaemia or hyperadrenocorticism. The urinary corticoid:creatinine (c:c) ratio was determined in ten pony mares suffering from hyperlipoproteinaemia. The mean (+/- sd) urinary c:c ratio of these ten ponies (47 +/- 31 x 10(-6)) was not significantly different from that of twelve pony mares with a pituitary pars intermedia adenoma (31 +/- 18 x 10(-6). The correlation between the urinary concentration of corticoids and plasma total lipids, and the correlation between the urinary c:c ratio and plasma total lipids in ponies with hyperlipoproteinaemia were not significant (P > 0.05; r = 0.53 and r = 0.008, respectively). Preliminary...
Blood glucose clearance after feeding and exercise in polysaccharide storage myopathy. Polysaccharide storage myopathy (PSSM) in Quarter Horses (QH) and QH crosses is a glycogen storage disorder in which blood glucose clearance and insulin sensitivity, following an i.v. or oral glucose challenge, are enhanced. Exercise is known also to enhance glucose uptake into skeletal muscle in many animal species. Therefore, the purpose of this study was to compare the effect of exercise on glucose clearance in PSSM and control horses when an oral carbohydrate meal (8 Mcal sweet feed) was fed following either 12 h fasting alone (NEX protocol) or following fasting and a standard exercise pro...
