Occurrence of equine metabolic syndrome, clinical manifestations, and associated risk factors in Nigeria.

Insulin dysregulation (ID) is central to the pathophysiology of equine metabolic syndrome (EMS), putting the horse at risk of laminitis. There is a paucity of information on the status of EMS in Nigeria. This study aimed to determine the occurrence of EMS, clinical manifestations, and associated risk factors in Nigeria. A cross-sectional study was carried out. Selected horses underwent an insulin 2-step response test to ascertain insulin dysregulation; a physical examination was carried out to diagnose laminitis and obesity. Risk factors were assessed using a questionnaire. The overall prevalence of EMS was 43.10%. Breed and sex were significantly associated with EMS, but age was not. Horses diagnosed with laminitis showed two signs of laminitis, namely, divergent hoof rings and widened white lines. Risk factors significantly associated with the prevalence of EMS were as follows: being a West African Barb horse (60.00%), being a stallion (67.86%), being a leisure horse (67.86%), only walking horses during exercise (68.00%), exercising horses once every 5 months (82.76%), tethering horses to a stake in the ground (67.86%), obesity (92.86%), and abnormal neck crest (83.33%). The risk of ID remains higher in obese horses. However, some of the horses with ID were not obese, indicating that there are other possible underlying causes of EMS.

Sphingolipidome of plasma, liver, and adipose tissues and its association with insulin response to oral glucose testing in Icelandic horses.

Insulin dysregulation (ID) is a determinant of equine metabolic syndrome. Among the sphingolipids, ceramides contribute to the development of ID; however, the cross talk between the liver and adipose tissue (AT) depots and the variation among AT depots in terms of ceramide metabolism are not well understood. We aimed to characterize the sphingolipidome of plasma, liver, and AT (nuchal, NUAT; subcutaneous, SCAT; omental, OMAT; retroperitoneal, RPAT) and their associations with insulin response to oral glucose testing (OGT) in normoinsulinemic and hyperinsulinemic horses. Plasma, liver, and AT samples were collected from 12 Icelandic horses upon euthanasia and analyzed by liquid chromatography-mass spectrometry. Eighty-four targeted compounds were effectively quantified. Comparing the AT depots, greater (false discovery rate, FDR < 0.05) ceramide, dihydroceramide, and sphingomyelin concentrations and lower glucosyl- and galactosyl-ceramides were found in RPAT and OMAT than in NUAT and SCAT. Hyperinsulinemic response to OGT was associated with sphingolipidome alterations primarily in the RPAT and OMAT, whereas the NUAT sphingolipidome did not show signs of ceramide accumulation, which was inconsistent with the previously proposed role of nuchal adiposity in ID. The plasma sphingolipidome was not significantly associated with the liver or AT sphingolipidomes, indicating that plasma profiles are determined by an interplay of various organs. Furthermore, hepatic sphingolipid profiles were not correlated with the profiles of AT depots. Finally, statistically valid partial least square regression models predicting insulin response were found in the plasma (Q2 = 0.58, R2 = 0.98), liver (Q2 = 0.64, R2 = 0.74), and RPAT (Q2 = 0.68, R2 = 0.79) sphingolipidome, but not in the other adipose tissues.

Effect of a GLP-1 mimetic on the insulin response to oral sugar testing in horses.

BACKGROUND: Insulin dysregulation (ID) is the most important risk factor for the development of laminitis in horses and therapies to control it are needed. HYPOTHESIS/OBJECTIVES: To assess the effects of a single dose of the synthetic GLP-1 analog exenatide on postprandial insulin dynamics. We hypothesized that exenatide would improve insulin sensitivity and lower postprandial blood insulin concentrations. STUDY DESIGN: Randomized, crossover, experimental study. ANIMALS: Six horses (3 mares, 3 geldings; 2 with normal insulin regulation [NIR] and 4 with mild ID). METHODS: Horses completed both study arms: subcutaneous administration of exenatide (or no treatment) 30 min before an oral sugar test (0.15 ml/kg of Karo Syrup). Blood samples obtained over 240 min were assayed for glucose, insulin, lactate, c-peptide and total GLP-1. The area under the curve (AUC) was calculated using the trapezoidal rule. Insulin sensitivity (SI) was estimated using a mathematical model. RESULTS: Exenatide resulted in a postprandial decrease of 20% (effect size: 2673 µU·min/ml; 95% CI: 900 - 4446 µU·min/ml; P = 0.003) in AUC of plasma insulin (control; mean AUC insulin: 11,989 µU·min/ml; 95% CI: 9673 - 14,305 µU·min/ml, exenatide; mean AUC insulin: 9316 µU·min/ml; 95% CI: 7430 - 11,202 µU·min/ml). Exenatide resulted in an approximately threefold increase (effect size: 5.56 10-4· µU/ml-1·min-1; 95% CI: 0.95 - 10.1 10-4· µU/ml-1·min-1; P = 0.02) in estimated insulin sensitivity (control mean SI: 1.93 10-4· µU/ml-1·min-1; 95% CI: 0.005 - 3.86 10-4·µU/ml-1·min-1 vs. exenatide mean SI: 7.49 10-4· µU/ml-1·min-1; 95% CI: 3.46 - 11.52 10-4· µU/ml-1·min-1). CONCLUSIONS: The decrease in insulin response to carbohydrates was due to an increase in whole-body insulin sensitivity. GLP-1 agonists may have therapeutic potential for ID in horses.

Evaluation of fasting plasma insulin and proxy measurements to assess insulin sensitivity in horses.

BACKGROUND: Proxies are mathematical calculations based on fasting glucose and/or insulin concentrations developed to allow prediction of insulin sensitivity (IS) and ß-cell response. These proxies have not been evaluated in horses with insulin dysregulation. The first objective of this study was to evaluate how fasting insulin (FI) and proxies for IS (1/Insulin, reciprocal of the square root of insulin (RISQI) and the quantitative insulin sensitivity check index (QUICKI)) and ß-cell response (the modified insulin-to-glucose ratio (MIRG) and the homeostatic model assessment of ß-cell function (HOMA-ß)) were correlated to measures of IS (M index) using the euglycemic hyperinsulinemic clamp (EHC) in horses with insulin resistance (IR) and normal IS. A second objective was to evaluate the repeatability of FI and proxies in horses based on sampling on consecutive days. The last objective was to investigate the most appropriate cut-off value for the proxies and FI. RESULTS: Thirty-four horses were categorized as IR and 26 as IS based on the M index. The proxies and FI had coefficients of variation (CVs) ≤ 25.3 % and very good reliability (intraclass correlation coefficients ≥ 0.89). All proxies and FI were good predictors of the M index (r = 0.76-0.85; P < 0.001). The proxies for IS had a positive linear relationship with the M index whereas proxies for ß-cell response and FI had an inverse relationship with the M index. Cut-off values to distinguish horses with IR from horses with normal IS based on the M index were established for all proxies and FI using receiver operating characteristic curves, with sensitivity between 79 % and 91 % and specificity between 85 % and 96 %. The cut-off values to predict IR were < 0.32 (RISQI), < 0.33 (QUICKI) and > 9.5 µIU/mL for FI. CONCLUSIONS: All proxies and FI provided repeatable estimates of horses' IS. However, there is no advantage of using proxies instead of FI to estimate IR in the horse. Due to the heteroscedasticity of the data, proxies and FI in general are more suitable for epidemiological studies and larger clinical studies than as a diagnostic tool for measurement of IR in individual horses.

Metabolic profile distinguishes laminitis-susceptible and -resistant ponies before and after feeding a high sugar diet.

BACKGROUND: 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. Samples from 10 pre-laminitic (PL - subsequently developed laminitis) and 10 non-laminitic (NL - did not develop laminitis) ponies were used in a targeted metabolomic assay. Differential concentration and pathway analysis were performed using linear models and global tests. RESULTS: Significant changes in the concentration of six glycerophospholipids (adj. P ≤ 0.024) and a global enrichment of the glucose-alanine cycle (adj. P = 0.048) were found to characterise the response of PL ponies to the high-sugar diet. In contrast, the metabolites showed no significant association with the presence or absence of pituitary pars intermedia dysfunction in all ponies. CONCLUSIONS: The present results suggest that ID and laminitis risk are associated with alterations in the glycerophospholipid and glucose metabolism, which may help understand and explain some molecular processes causing or resulting from these conditions. The prognostic value of the identified biomarkers for laminitis remains to be investigated in further metabolomic trials in horses and ponies.

Endocrinopathic Laminitis.

Endocrinopathic laminitis (EL) primarily occurs because of insulin dysregulation (ID) mediated through downstream effects of insulin on IGF-1R in lamellar tissues. There is likely contributing vascular and metabolic dysfunction within the lamellae, but EL is relatively non-inflammatory. EL is associated with lamellar stretching, proliferation, and failure, ultimately causing failure of the suspensory apparatus of the distal phalanx. Proper education regarding mitigating risk factors makes this a largely preventable cause of laminitis. Annual hoof evaluation plus screening geriatric horses for pituitary pars intermedia dysfunction and ID, and younger horses for ID, can significantly decrease the incidence of this devastating condition.

"Feeding the Foot": Nutritional Influences on Equine Hoof Health.

Nutrition plays an important role in equine health, including that of the foot. Deficiencies and excesses of dietary components can affect the growth and function of the foot and have been associated with important podiatric diseases. The recognition, prevention, and treatment of specific notable nutritional diseases of the foot are discussed, as well as information regarding specific ingredients included in supplements meant to improve equine hoof quality. Ensuring provision of a balanced diet, maintaining horses in appropriate body condition, and seeking guidance from an equine nutritionist when creating dietary recommendations will prevent most equine foot disease related to nutrition.

The equine gastrointestinal microbiome: impacts of weight-loss.

BACKGROUND: Obesity is an important equine welfare issue. Whilst dietary restriction is the most effective weight-loss tool, individual animals range in their weight-loss propensity. Gastrointestinal-derived bacteria play a fundamental role in host-health and have been associated with obesity and weight-loss in other species. This study evaluated the faecal microbiome (next-generation sequencing of 16S rRNA genes) of 15 obese Welsh Mountain pony mares, in the same 11-week period across 2 years (n = 8 Year 1; n = 7 Year 2). Following a 4-week acclimation period (pre-diet phase) during which time individuals were fed the same hay to maintenance (2% body mass (BM) as daily dry matter (DM) intake), animals underwent a 7-week period of dietary restriction (1% BM hay as daily DM intake). Faeces were sampled on the final 3 days of the pre-diet phase and the final 3 days of the dietary restriction phase. Bacterial communities were determined using Next Generation Sequencing of amplified V1-V2 hypervariable regions of bacterial 16S rRNA. RESULTS: Losses in body mass ranged from 7.11 to 11.59%. Changes in the faecal microbiome composition following weight-loss included a reduction in the relative abundance of Firmicutes and Tenericutes and a reduction in indices of bacterial diversity. Pre-diet diversity was negatively associated with weight-loss. Pre-diet faecal acetate concentration was a strong predictor of subsequent weight-loss and negatively associated with Sphaerochaeta (Spirochaetes phylum) abundance. When animals were divided into 3 groups (high, mid, low) based overall weight loss, pre-diet bacterial community structure was found to have the greatest divergence between the high and low weight-loss groups (R = 0.67, p <  0.01), following PERMANOVA and ANOSIM analysis. CONCLUSIONS: Weight-loss in this group of ponies was associated with lower pre-diet faecal bacterial diversity and greater pre-diet acetate concentration. Overall, these data support a role for the faecal microbiome in weight-loss propensity in ponies and provide a baseline for research evaluating elements of the faecal microbiome in predicting weight-loss success in larger cohorts.

Weight loss is linearly associated with a reduction of the insulin response to an oral glucose test in Icelandic horses.

BACKGROUND: Insulin dysregulation (ID) goes along with lasting or transient hyperinsulinemia able to trigger equine laminitis, a painful and crippling foot condition. Promoting weight loss through dietary changes and physical activity is currently the main option to prevent this disease. This study aimed at describing the relationship between weight variations and the level of ID as determined by oral glucose tests (OGT). Therefore, the insulin response of 19 Icelandic horses to repeated OGTs was retrospectively analysed considering the variations in their body weight. RESULTS: There was a strong linear relationship between variations in body weight and variations in the total insulin response to OGT as approximated by the area under the curve of insulin (p < 0.001). As indicated by a weighted least squares model, the insulin response decreased by 22% for 5% weight loss on average. However some horses did not respond to weight loss with a reduction of their insulin response to OGT. Additionally, a high correlation between 120 min serum insulin concentration and total insulin response was observed (r = 0.96, p < 0.001). CONCLUSIONS: The results corroborate that weight loss is effective against ID and allow for a better quantification of the expected improvement of the insulin response after weight loss. However, it is unclear why some horses did not respond as expected. The high correlation between the 120 min insulin concentration and total insulin response suggests that insulin status can be accurately determined and monitored with only few samples in a practical setting.

Assessment of the FAM174A 11G allele as a risk allele for equine metabolic syndrome.

An 11G nucleotide repeat in the 3' UTR of FAM174A was recently postulated as a risk allele with a dominant mode of inheritance for equine metabolic syndrome (EMS) and laminitis status in Arabian horses. The objective of this project was to evaluate this hypothesis in a large and diverse across-breed population. A total of 301 ponies, 292 Morgans, 64 Arabians, 49 Tennessee Walking Horses and 59 Quarter Horses were genotyped for six observed G repeat alleles in the FAM174A 3' UTR. Phenotype data included laminitis status, baseline insulin, glucose, non-esterified fatty acids, triglycerides, adiponectin, leptin, ACTH, insulin and glucose post oral sugar test, and two proxies for insulin resistance. The 11G allele frequencies were 18.8, 6.9, 1.8, 0.2 and 0.0% in the Arabians, Tennessee Walkers, ponies, Morgans and Quarter Horses respectively. Association analyses between FAM174A genotype and EMS phenotypes, and between allele count and EMS phenotypes, identified no statistically significant associations. When a dominant effect for the 11G allele was evaluated, a statistically significant association with adiponectin levels was identified in the ponies, and pairwise comparisons revealed that the estimated marginal means were higher in ponies with the 11G allele vs. alternative alleles (i.e. the allele had a protective effect). In conclusion, our data do not support the FAM174A 11G allele as a risk allele for EMS in our studied breeds.

The effect of different grazing conditions on the insulin and incretin response to the oral glucose test in ponies.

BACKGROUND: The oral glucose test (OGT) is a useful tool for diagnosing insulin dysregulation (ID) and is somewhat repeatable in ponies under consistent management. This study aimed to determine whether the insulin and incretin responses to an OGT in ponies differed after short-term access to fertilised pasture, compared to unfertilised pasture, by using a randomised, repeated measures study design. Sixteen mixed-breed ponies were classified as severely insulin-dysregulated (SD; post-prandial insulin ≥80 µIU/mL) or not severely insulin-dysregulated (NSD; post-prandial insulin < 80 µIU/mL) using an OGT prior to the study. The ponies accessed pasture that was fertilised, or unfertilised, for 5 days (4 h/day, with supplemental hay provided at 0.7% bodyweight), with a 10 day period between phases. An OGT was performed after each phase. Glucose, insulin, active glucagon-like peptide-1 (aGLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured in post-prandial blood samples. RESULTS: The volume of fertilised pasture was five-fold greater than unfertilised pasture, with % non-structural carbohydrates (NSC) similar between all forages. Consuming fertilised pasture increased (P = 0.018) the serum insulin response to an OGT, compared to grazing unfertilised pasture. A limitation of the study was that pasture intake was unable to be quantified. Insulin responses were greater in SD, compared to NSD, ponies (P < 0.001) and remained well above the test cut-off at all times. A subset of ponies, initially screened as NSD, became (more) insulin-dysregulated after pasture access. Further, aGLP-1 was a significant predictor of insulin concentration in this cohort. CONCLUSIONS: Whereas some insulin-dysregulated ponies were comparatively resistant to dietary intervention, others showed markedly different OGT responses following subtle changes in their forage-based diet. This implies that mild/early ID might be unmasked by dietary change, and that dietary management is important in these ponies. However, dietary management alone may not be adequate for all cases of ID.

Lower plasma trans-4-hydroxyproline and methionine sulfoxide levels are associated with insulin dysregulation in horses.

BACKGROUND: Insulin dysregulation in horses is a metabolic condition defined by high insulin concentrations in the blood and peripheral insulin resistance. This hyperinsulinemia is often associated with severe damage in the hooves, resulting in laminitis. However, we currently lack detailed information regarding the potential involvement of particular metabolic pathways in pathophysiological causes and consequences of equine insulin dysregulation. This study aimed to assess the dynamic metabolic responses given to an oral glucose test (OGT) in insulin-sensitive and insulin-dysregulated horses by a targeted metabolomics approach to identify novel metabolites associated with insulin dysregulation. RESULTS: Oral glucose testing triggered alterations in serum insulin (26.28 ± 4.20 vs. 422.84 ± 88.86 µIU/mL, p < 0.001) and plasma glucose concentrations (5.00 ± 0.08 vs. 9.43 ± 0.44 mmol/L, p < 0.001) comparing basal and stimulated conditions after 180 min. Metabolome analyses indicated OGT-induced changes in short-chain acylcarnitines (6.00 ± 0.53 vs. 3.99 ± 0.23 µmol/L, p < 0.001), long-chain acylcarnitines (0.13 ± 0.004 vs. 0.11 ± 0.002 µmol/L, p < 0.001) and amino acids (2.18 ± 0.11 vs. 1.87 ± 0.08 µmol/L, p < 0.05). Kynurenine concentrations increased (2.88 ± 0.18 vs. 3.50 ± 0.19 µmol/L, p < 0.01), whereas spermidine concentrations decreased during OGT (0.09 ± 0.004 vs. 0.08 ± 0.002 µmol/L, p < 0.01), indicating proinflammatory conditions after oral glucose load. Insulin dysregulation was associated with lower concentrations of trans-4-hydroxyproline (4.41 ± 0.29 vs. 6.37 ± 0.71 µmol/L, p < 0.05) and methionine sulfoxide (0.40 ± 0.06 vs. 0.87 ± 0.13 µmol/L, p < 0.01; mean ± SEM in insulin-dysregulated vs. insulin-sensitive basal samples, respectively), two metabolites which are related to antioxidant defense mechanisms. CONCLUSION: Oral glucose application during OGT resulted in profound metabolic and proinflammatory changes in horses. Furthermore, insulin dysregulation was predicted in basal samples (without OGT) by pathways associated with trans-4-hydroxyproline and methionine sulfoxide, suggesting that oxidative stress and oxidant-antioxidant disequilibrium are contributing factors to insulin dysregulation. The present findings provide new hypotheses for future research to better understand the underlying pathophysiology of insulin dysregulation in horses.

Endocrine Disorders of the Equine Athlete.

Equine athletes are affected by 2 major endocrine/metabolic disorders, insulin dysregulation (ID) and pituitary pars intermedia dysfunction. ID is a risk factor for laminitis in horses, which poses the greatest threat to performance because of the damage that it causes to hoof structures. This article includes an in-depth discussion of ID and other risk factors for laminitis that are grouped together as equine metabolic syndrome. As horses age, the risk of pituitary pars intermedia dysfunction increases, and this endocrine disorder may exacerbate preexisting ID and further increase the risk of laminitis.

Tributyltin exposure at noncytotoxic doses dysregulates pancreatic ß-cell function in vitro and in vivo.

Tributyltin (TBT) is an endocrine disruptor. TBT can be found in food and in human tissues and blood. Several animal studies revealed that organotins induced diabetes with decreased insulin secretion. The detailed effect and mechanism of TBT on pancreatic ß-cell function still remain unclear. We investigated the effect and mechanism of TBT exposure at noncytotoxic doses relevant to human exposure on ß-cell function in vitro and in vivo. The ß-cell-derived RIN-m5F cells and pancreatic islets from mouse and human were treated with TBT (0.05-0.2 µM) for 0.5-4 h. Adult male mice were orally exposed to TBT (25 µg/kg/day) with or without antioxidant N-acetylcysteine (NAC) for 1-3 weeks. Assays for insulin secretion and glucose metabolism were carried out. Unlike previous studies, TBT at noncytotoxic concentrations significantly increased glucose-stimulated insulin secretion and intracellular Ca2+ ([Ca2+]i) in ß-cells. The reactive oxygen species (ROS) production and phosphorylation of protein kinase C (PKC-pan) and extracellular signal-regulated kinase (ERK)1/2 were also increased. These TBT-triggered effects could be reversed by antiestrogen ICI182780 and inhibitors of ROS, [Ca2+]i, and PKC, but not ERK. Similarly, islets treated with TBT significantly increased glucose-stimulated insulin secretion, which could be reversed by ICI182780, NAC, and PKC inhibitor. Mice exposed to TBT for 3 weeks significantly increased blood glucose and plasma insulin and induced glucose intolerance and insulin resistance, which could be reversed by NAC. These findings suggest that low/noncytotoxic doses of TBT induce insulin dysregulation and disturb glucose homeostasis, which may be mediated through the estrogen receptor-regulated and/or oxidative stress-related signaling pathways.

Type 1 diabetes modulates cyclooxygenase- and nitric oxide-dependent mechanisms governing sweating but not cutaneous vasodilation during exercise in the heat.

Both cyclooxygenase (COX) and nitric oxide synthase (NOS) contribute to sweating, whereas NOS alone contributes to cutaneous vasodilation during exercise in the heat. Here, we evaluated if Type 1 diabetes mellitus (T1DM) modulates these responses. Adults with (n = 11, 25 ± 5 yr) and without (n = 12, 24 ± 4 yr) T1DM performed two bouts of 30-min cycling at a fixed rate of heat production of 400 W in the heat (35°C); each followed by a 20- and 40-min recovery period, respectively. Sweat rate and cutaneous vascular conductance (CVC) were measured at four intradermal microdialysis sites treated with either 1) lactated Ringer (vehicle control site), 2) 10 mM ketorolac (nonselective COX inhibitor), 3) 10 mM NG-nitro-l-arginine methyl ester (nonselective NOS inhibitor), or 4) a combination of both inhibitors. In nondiabetic adults, separate and combined inhibition of COX and NOS reduced exercise sweat rate (P ≤ 0.05), and the magnitude of reductions were similar across sites. In individuals with T1DM, inhibition of COX resulted in an increase in sweat rate of 0.10 ± 0.09 and 0.09 ± 0.08 mg ·: min-1 ·: cm-2 for the first and second exercise bouts, respectively, relative to vehicle control site (P ≤ 0.05), whereas NOS inhibition had no effect on sweating. In both groups, NOS inhibition reduced CVC during exercise (P ≤ 0.05), although the magnitude of reduction did not differ between the nondiabetic and T1DM groups (exercise 1: -28 ± 10 vs. -23 ± 8% max, P = 0.51; exercise 2: -31 ± 12 vs. -24 ± 10% max, P = 0.38). We show that in individuals with T1DM performing moderate intensity exercise in the heat, NOS-dependent sweating but not cutaneous vasodilation is attenuated, whereas COX inhibition increases sweating.

Effect of Exercise Conditioning on Countering the Effects of Obesity and Insulin Resistance in Horses-A Review.

Obesity is an important health concern in horses, along with humans and companion animals. Adipose tissue is an inflammatory organ that alters the insulin-signaling cascade, ultimately causing insulin dysregulation and impaired glucose metabolism. These disruptions can increase the risk of metabolic disease and laminitis in horses and may also impact energy metabolism during exercise. A single bout of exercise, along with chronic exercise conditioning, increases insulin sensitivity and glucose disposal via both contraction- and insulin-mediated glucose uptake pathways. Regular exercise also increases calorie expenditure, which can facilitate weight (as body fat) loss. This paper explores the metabolic pathways affected by adiposity, as well as discusses the impact of exercise on insulin metabolism in horses.

Obesity and gestation in Criollo mares: endocrine and metabolic profiles.

The aim of this study was to determine the effect of body condition score (BCS) on metabolic and endocrine parameters in pregnant Criollo mares (n=41), which were categorized according to their BCS as obese (7 to 9 BCS, n=26) or normal (5 to 7, n=15). Blood samples were taken during gestation in 3 periods: between 3.5 and 5 months (I), 8 and 9 months (II) and in the last month of gestation (III). The data was analyzed in the statistical model by mixed procedures, including BCS, gestational period and their interaction as fixed effects. BCS was only different in period I, as normal mares increased their BCS in the later periods. Leptin concentrations were greater in obese mares when compared to non-obese mares during all sampling periods (P<0.01), while glucose concentrations were also greater in the former group (P<0.01) but only during the first sampling period. Insulin concentrations and homeostatic model assessment for insulin resistance (HOMA-IR) index were greater also in obese mares in periods I and III (P<0.05). Adiponectin concentrations in period I were lower in obese mares (P<0.05). Cholesterol concentrations increased during gestation, and obese mares tended to have greater concentrations than nonobese mares (P<0.1). Triglyceride concentrations were not affected by group or gestational period. This study revealed adaptations in carbohydrate and lipid metabolism during gestation in mares. Several parameters are dependent on the degree of body fat reserves, which are reflected in the concentrations of biomarkers such as leptin and adiponectin. Insulin concentration in obese mares was higher than non-obese mares at the end of gestation, a similar profile was observed for HOMA-IR although cutoff values are yet still to be validated.

Associations between feeding and glucagon-like peptide-2 in healthy ponies.

BACKGROUND: Gastrointestinal peptides, such as glucagon-like peptide-2 (GLP-2), could play a direct role in the development of equine hyperinsulinaemia. OBJECTIVES: To describe the secretory pattern of endogenous GLP-2 over 24 h in healthy ponies and determine whether oral administration of a synthetic GLP-2 peptide increases blood glucose or insulin responses to feeding. STUDY DESIGN: A cohort study followed by a randomised, controlled, cross-over study. METHODS: In the cohort study, blood samples were collected every 2 h for 24 h in seven healthy ponies and plasma [GLP-2] was measured. In the cross-over study, 75 µg/kg bodyweight of synthetic GLP-2, or carrier only, was orally administered to 10 ponies twice daily for 10 days. The area under the curve (AUC0-3h ) of post-prandial blood glucose and insulin were determined before and after each treatment. RESULTS: Endogenous [GLP-2] ranged from <0.55 to 1.95 ± 0.29 [CI 0.27] ng/mL with similar peak concentrations in response to meals containing 88-180 g of non-structural carbohydrate, that were ~4-fold higher (P < 0.001) than the overnight nadir. After GLP-2 treatment peak plasma [GLP-2] increased from 1.1 [0.63-1.37] ng/mL to 1.54 [1.1-2.31] ng/mL (28.6%; P = 0.002), and AUC0-3h was larger (P = 0.01) than before treatment. The peptide decreased (7%; P = 0.003) peak blood glucose responses to feeding from 5.33 ± 0.45 mmol/L to 5.0 ± 0.21 mmol/L, but not AUC0-3h (P = 0.07). There was no effect on insulin secretion. MAIN LIMITATIONS: The study only included healthy ponies and administration of a single dose of GLP-2. CONCLUSIONS: The diurnal pattern of GLP-2 secretion in ponies was similar to other species with no apparent effect of daylight. Although GLP-2 treatment did not increase post-prandial glucose or insulin responses to eating, studies using alternative dosing strategies for GLP-2 are required.

Obesity and obesity-associated metabolic disease conditions in Connemara ponies in Ireland.

BACKGROUND: Equine obesity combined with insulin dysregulation (ID) is a major risk factor associated with laminitis. Some pony breeds appear to be at increased risk. However, little is known regarding the prevalence of obesity or hyperinsulinaemia as evidence of ID in Irish ponies. OBJECTIVE: To investigate the prevalence of obesity and associated endocrine/metabolic disease conditions in Connemara ponies and to determine if hyperinsulinaemia in these ponies could be predicted by morphometric or metabolic markers. STUDY DESIGN: Cross-sectional study. METHODS: The study population included registered Connemara ponies recruited through public and veterinary social media posts. Ponies underwent a physical examination and information on their management and clinical history was obtained via owner questionnaire. The body condition score (BCS) was measured using the Henneke system; cresty neck score (CNS) and regionalised adiposity were also assessed. Hyperinsulinaemia was confirmed by measuring serum basal insulin concentration (BIC) or insulin concentration after an oral sugar test (OST). Blood glucose and triglyceride concentrations were measured. Characteristics of hyperinsulinaemic and insulin-sensitive ponies were compared by logistic regression. RESULTS: Two hundred ponies were included; 59 ponies (29.5%) had a BCS ≥7, 58 (29.0%) had a CNS ≥2.5 and 135 (67.5%) had regionalised adiposity; 137 (68.5%) ponies had at least one of these abnormalities. Owner-reported history or clinical evidence of chronic laminitis was found in 92 ponies (46.0%). Hyperinsulinaemia was confirmed in 32 ponies (16.0%), including 23 of 91 (25.3%) detected by OST and 9 of 109 (8.3%) by BIC. Hypertriglyceridaemia was observed in 12 of 198 ponies (6.1%) ponies and hyperglycaemia in 11 of 197 ponies (5.6%) ponies. The odds of hyperinsulinaemia increased by a factor of 6.53 (95% confidence interval: 2.95, 15.21) when BCS was ≥7. MAIN LIMITATIONS: The OST was not performed in all ponies. CONCLUSIONS: Increased adiposity, laminitis and metabolic derangements are prevalent in this native Irish pony breed.

Insulin dysregulated horses metabolic responses to forage pellets.

Hyperinsulinemia-associated laminitis (HAL) is the primary concern for insulin dysregulated (ID) equids and their insulin response to the consumption of oral, nonstructural carbohydrates (NSC) has been shown to be a risk predictor for HAL development. This randomized, crossover study's objective was to examine the insulinemic responses to 3 forage pellets (1 g/kg BW) (timothy hay, TH, 9.5 % CP & 10 % NSC DM; alfalfa hay, AH, 16.3 % CP & 9.8 % NSC DM; timothy-alfalfa hay; TAH, 17.2 % CP & 9.8 % NSC DM) along with a positive (dehulled oats; OG, 14.7 % CP & 59.7 % NSC DM) and negative dietary challenge control (low-NSC; LNSC, 12.8 % CP & 5.4 % NSC DM) of ID (n = 8; 16.1 ± 2.2 yr; 565.4 ± 99.1 kgs.) and non-ID (NID; n = 7; 17.0 ± 2.8 yr; 583.6 ± 57.9 kgs.) horses. ID horses had higher positive incremental area under the curve for insulin (IAUCi) (ID: 890 ± 925 µIU/mL*minute vs. NID: 225 ± 228 µIU/mL*minute), peak (ID: 101.5 ± 80.72 µIU/mL vs. NID: 25.7 ± 7.2 µIU/mL), and delta (ID: 45.5 ± 77.1 µIU/mL vs. NID: 4.9 ± 5.3 µIU/mL) insulin for all forage pellets compared to NID (p < 0.01). ID horses IAUCi for the forage pellets was not different compared to the LNSC (218 ± 327 µIU/mL*minute) but was different from OG (10,522 ± 4,565 µIU/mL*minute). ID horses' lack of an augmented insulinemic response to the low NSC forage pellets (fed in small amounts) indicates that they could be a safe feedstuff for ID animals.