1
|
Fitzgerald DM, Cash CM, Dudley KJ, Sibthorpe PEM, Sillence MN, de Laat MA. Expression of the GCG gene and secretion of active glucagon-like peptide-1 varies along the length of intestinal tract in horses. Equine Vet J 2024; 56:352-360. [PMID: 37853957 DOI: 10.1111/evj.14020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 09/24/2023] [Indexed: 10/20/2023]
Abstract
BACKGROUND Active glucagon-like peptide-1 (aGLP-1) has been implicated in the pathogenesis of equine insulin dysregulation (ID), but its role is unclear. Cleavage of proglucagon (coded by the GCG gene) produces aGLP-1 in enteral L cells. OBJECTIVES The aim in vivo was to examine the sequence of the exons of GCG in horses with and without ID, where aGLP-1 was higher in the group with ID. The aims in vitro were to identify and quantify the expression of GCG in the equine intestine (as a marker of L cells) and determine intestinal secretion of aGLP-1. STUDY DESIGN Genomic studies were case-control studies. Expression and secretion studies in vitro were cross-sectional. METHODS The GCG gene sequence of the exons was determined using a hybridisation capture protocol. Expression and quantification of GCG in samples of stomach duodenum, jejunum, ileum, caecum and ascending and descending colon was achieved with droplet digital PCR. For secretory studies tissue explants were incubated with 12 mM glucose and aGLP-1 secretion was measured with an ELISA. RESULTS Although the median [IQR] post-prandial aGLP-1 concentrations were higher (p = 0.03) in animals with ID (10.2 [8.79-15.5]), compared with healthy animals (8.47 [6.12-11.7]), there was 100% pairwise identity of the exons of the GCG sequence for the cohort. The mRNA concentrations of GCG and secretion of aGLP-1 differed (p < 0.001) throughout the intestine. MAIN LIMITATIONS Only the exons of the GCG gene were sequenced and breeds were not compared. The horses used for the study in vitro were not assessed for ID and different horses were used for the small, and large, intestinal studies. CONCLUSIONS Differences in post-prandial aGLP-1 concentration were not due to a variant in the exons of the GCG gene sequence in this cohort. Both the large and small intestine are sites of GLP-1 secretion.
Collapse
Affiliation(s)
- Danielle M Fitzgerald
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Christina M Cash
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Kevin J Dudley
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Poppy E M Sibthorpe
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Martin N Sillence
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Melody A de Laat
- Faculty of Science, Queensland University of Technology, Brisbane, Queensland, Australia
| |
Collapse
|
2
|
Sibthorpe PEM, Fitzgerald DM, Sillence MN, de Laat MA. Associations between feeding and glucagon-like peptide-2 in healthy ponies. Equine Vet J 2024; 56:309-317. [PMID: 37705248 DOI: 10.1111/evj.14004] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 08/25/2023] [Indexed: 09/15/2023]
Abstract
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.
Collapse
Affiliation(s)
- Poppy E M Sibthorpe
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Danielle M Fitzgerald
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Martin N Sillence
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Melody A de Laat
- School of Biology and Environmental Science, Queensland University of Technology, Brisbane, Queensland, Australia
| |
Collapse
|
3
|
Macon EL, Harris P, McClendon M, Perron B, Adams A. Insulin dysregulated horses metabolic responses to forage pellets. J Equine Vet Sci 2024; 133:104991. [PMID: 38159582 DOI: 10.1016/j.jevs.2023.104991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/22/2023] [Accepted: 12/28/2023] [Indexed: 01/03/2024]
Abstract
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.
Collapse
Affiliation(s)
- Erica Lyn Macon
- Department of Animal Science, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, USA.
| | - Patricia Harris
- Equine studies Group, Waltham Petcare Science Institute, Freeby Lane, Waltham-on-the-Wold, Leics. LE14 4RT
| | - Margaret McClendon
- 108 M. H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, 40546, USA
| | - Brittany Perron
- 108 M. H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, 40546, USA
| | - Amanda Adams
- Department of Veterinary Science, M. H. Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546, USA
| |
Collapse
|
4
|
de Laat MA, Fitzgerald DM. Equine metabolic syndrome: Role of the enteroinsular axis in the insulin response to oral carbohydrate. Vet J 2023; 294:105967. [PMID: 36858344 DOI: 10.1016/j.tvjl.2023.105967] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 01/17/2023] [Accepted: 02/26/2023] [Indexed: 03/02/2023]
Abstract
Equine insulin dysregulation (ID) comprises amplified insulin responses to oral carbohydrates or insulin resistance, or both, which leads to sustained or periodic hyperinsulinaemia. Hyperinsulinaemia is important in horses because of its clear association with laminitis risk, and the gravity of this common sequela justifies the need for a better understanding of insulin and glucose homoeostasis in this species. Post-prandial hyperinsulinaemia is the more commonly identified component of ID and is diagnosed using tests that include an assessment of the gastrointestinal tract (GIT). There are several factors present in the GIT that either directly, or indirectly, enhance insulin secretion from the endocrine pancreas, and these factors are collectively referred to as the enteroinsular axis (EIA). A role for key components of the EIA, such as the incretin peptides glucagon-like peptide-1 and 2, in the pathophysiology of ID has been investigated in horses. By comparison, the function (and even existence) of many EIA peptides of potential importance, such as glicentin and oxyntomodulin, remains unexplored. The incretins that have been examined all increase insulin responses to oral carbohydrate through one or more mechanisms. This review presents what is known about the EIA in horses, and discusses how it might contribute to ID, then compares this to current understanding derived from the extensive studies undertaken in other species. Future directions for research are discussed and knowledge gaps that should be prioritised are suggested.
Collapse
Affiliation(s)
- Melody A de Laat
- School of Biology and Environmental Science, Faculty of Science, Queensland University of Technology, Brisbane 4000, Australia.
| | - Danielle M Fitzgerald
- School of Biology and Environmental Science, Faculty of Science, Queensland University of Technology, Brisbane 4000, Australia
| |
Collapse
|
5
|
Mendoza FJ, Buzon-Cuevas A, Toribio RE, Perez-Ecija A. Characterisation of the oral glucose and sugar tolerance tests and the enteroinsular axis response in healthy adult donkeys. Equine Vet J 2021; 54:1123-1132. [PMID: 34897779 DOI: 10.1111/evj.13544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 10/18/2021] [Accepted: 12/09/2021] [Indexed: 11/30/2022]
Abstract
BACKGROUND Insulin dysregulation (ID) is diagnosed in horses and ponies using oral glucose (OGTT) and oral sugar (OSTT) tolerance tests. The enteroinsular axis plays a major role in postprandial glucose disposal and insulin response in horses, ponies and foals. The insulin and incretin response to oral carbohydrate challenges has not been characterised in donkeys. OBJECTIVES (a) To characterise OGTT and OSTT, and (b) to assess the plasma incretin response to OGTT and OSTT in healthy donkeys. STUDY DESIGN In vivo experiments. METHODS Six healthy adult female Andalusian donkeys were challenged with OGTT (1 g/kg glucose, 20% solution by nasogastric tube) and OSTT (0.45 mL/kg corn syrup orally by syringe) with a 1-week washout. Blood samples were collected for glucose (spectrophotometry), insulin (radioimmunoassay), glucose-dependent insulinotropic polypeptide (GIP, ELISA) and active glucagon-like peptide-1 (aGLP-1, ELISA) determination over 6 hours. Curves were analysed and proxies calculated. RESULTS Glucose and insulin concentrations peaked at 180 minutes in OGTT, but at 300 and 150 minutes in OSTT, respectively. Plasma GIP concentrations increased in the OGTT and OSTT (peaked at 180 and 360 minutes, respectively), but aGLP-1 increased only in OGTT (240 minutes). MAIN LIMITATIONS Single breed, narrow age and sample, diet, season and not having donkeys with evidence of ID to provide clinical validation. CONCLUSIONS Donkeys have a functional enteroinsular axis that is activated by enteral carbohydrates. Donkeys have evident endocrine differences with horses, supporting the validation of the OSTT and OGTT to assess insulin sensitivity in this species to avoid extrapolation from horses.
Collapse
Affiliation(s)
- Francisco J Mendoza
- Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain
| | - Antonio Buzon-Cuevas
- Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain
| | - Ramiro E Toribio
- Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio, USA
| | | |
Collapse
|
6
|
Abstract
Equine obesity is common, reducing quality of life and requiring dietary energy restriction. Equine obesity is identified using subjective body condition scoring. Considerations are given for life stage and health status when managing obese equines. Every effort should be made to maximize feeding duration, and minimize time spent without feed while meeting all essential nutrient requirements. Limiting total daily dry matter intake to 2% of current bodyweight per day of a low caloric, forage-based diet may result in adequate body weight loss. Weight loss and weight management plans should be monitored for success and potential gastrointestinal, metabolic, and/or behavioral complications.
Collapse
|
7
|
Fitzgerald DM, Spence RJ, Stewart ZK, Prentis PJ, Sillence MN, de Laat MA. The effect of diet change and insulin dysregulation on the faecal microbiome of ponies. J Exp Biol 2020; 223:jeb219154. [PMID: 32098884 DOI: 10.1242/jeb.219154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 02/12/2020] [Indexed: 12/16/2022]
Abstract
The equine microbiome can change in response to dietary alteration and may play a role in insulin dysregulation. The aim of this study was to determine the effect of adding pasture to a hay diet on the faecal bacterial microbiome of both healthy and insulin-dysregulated ponies. Faecal samples were collected from 16 ponies before and after dietary change to enable bacterial 16S rRNA sequencing of the V3-V4 region. The dominant phyla in all samples were the Firmicutes and Bacteroidetes. The evenness of the bacterial populations decreased after grazing pasture, and when a pony was moderately insulin dysregulated (P=0.001). Evenness scores negatively correlated with post-prandial glucagon-like peptide-1 concentration after a hay-only diet (r²=-0.7, P=0.001). A change in diet explained 3% of faecal microbiome variability. We conclude that metabolically healthy ponies have greater microbial stability when challenged with a subtle dietary change, compared with moderately insulin-dysregulated ponies.
Collapse
Affiliation(s)
- Danielle M Fitzgerald
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Robert J Spence
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Zachary K Stewart
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Peter J Prentis
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Martin N Sillence
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Melody A de Laat
- Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia
| |
Collapse
|