COMPARATIVE GUT PHYSIOLOGY SYMPOSIUM: Comparative physiology of glucagon-like peptide-2: Implications and applications for production and health of ruminants

Use of Teduglutide in the Management of Gastrointestinal Graft-versus-Host Disease in Children and Young Adults

Loss of intestinal L cells and reduced levels of glucagon-like peptide-2 (GLP-2) have been implicated in acute graft-versus-host disease (GVHD) in murine models. Teduglutide, a human recombinant GLP-2 analog, may be beneficial in acute gastrointestinal (GI) GVHD owing to its known tissue protective and regenerative functions. We retrospectively reviewed patients who received teduglutide for treatment of GI GVHD. Endoscopy was performed at diagnosis and at completion of the teduglutide course. GLP-1 immunohistochemistry (IHC) was performed at diagnosis and the end of teduglutide therapy in 2 patients to evaluate L cells. We initiated daily teduglutide 0.05 mg/kg subcutaneously as adjunctive therapy in 3 pediatric patients with refractory GI GVHD. All 3 patients had resolution of GI GVHD following completion of the teduglutide course, as evidenced by reduced apoptosis and regenerative changes on post-treatment endoscopy. Reportable GLP-1 IHC in 2 patients demonstrated increased L cells at the end of teduglutide treatment compared to at diagnosis. No adverse effects to teduglutide were observed. Teduglutide is a promising adjunctive and non-immune suppressive agent for managing acute GI GVHD.

Effect of feeding sodium butyrate to beef female cows during pre- and post-partum period on concentrations of glucagon-like peptides in plasma and colostrum

The objective of this study was to evaluate the effect of feeding beef cows with sodium butyrate during the late pregnancy and early post-partum periods on concentrations of glucagon-like peptide (GLP)-1 and 2 in plasma, colostrum, and transition milk. Twelve Japanese Black female cows were fed concentrate feed without (CON; n = 6) or with (BUTY; n = 6) sodium butyrate supplementation at 1.1% of dietary dry matter from -60 d relative to the expected parturition date to 4 d after parturition. Plasma total cholesterol concentration was higher for the BUTY than for the CON (P = 0.04). In addition, plasma GLP-1 concentration was higher for the BUTY than for the CON at 3 d after calving (P < 0.05). This study showed for the first time that GLP-1 is present in the colostrum of Japanese Black cows at higher concentrations as compared to in plasma (P < 0.01). On the other hand, no treatment effect was observed for concentrations of metabolite and hormone in colostrum and transition milk. In summary, feeding beef cows with sodium butyrate during the late gestation and early post-partum period likely increases plasma GLP-1 concentrations post-partum without affecting the components of colostrum and transition milk.

Interactions between corticotropin releasing factor signaling and prophylactic antibiotics on measures of intestinal function in weaned and transported pigs

The study objective was to evaluate the interaction between corticotrophin releasing factor (CRF) receptor signaling and prophylactic antibiotic administration on intestinal physiology in newly weaned and transported pigs. Pigs (n = 56; 5.70 ± 1.05 kg) were weaned (20.49 ± 0.64 d), a blood sample was taken, and then pigs were given an intraperitoneal injection of saline (SAL; n = 28 pigs) or a CRF receptor antagonist (CRFA; n = 28 pigs; 30 μg/kg body weight; Astressin B), and then were transported in a livestock trailer for 12 h and 49 min. A second and third intraperitoneal injection was given at 4 h 42 min and 11 h 36 min into the transport process, respectively. Following transport, 4 SAL and 4 CRFA pigs were blood sampled and euthanized. The remaining 48 pigs were individually housed and given dietary antibiotics [AB; n = 12 SAL and 12 CRFA pigs; chlortetracycline (441 ppm) + tiamulin (38.6 ppm)] or no dietary antibiotics (NAB; n = 12 SAL and 12 CRFA pigs) for 14 d post-transport. Blood was collected at 12 h and on d 3, 7, and 14, and then pigs were euthanized on d 7 (n = 24) and d 14 (n = 24) post-weaning and transport. Circulating cortisol was reduced (p = 0.05) in CRFA pigs when compared to SAL pigs post-weaning and transport. On d 7, jejunal villus height and crypt depth was greater overall (p < 0.05) in AB-fed pigs versus NAB-fed pigs. On d 14, ileal crypt depth was reduced (p = 0.02) in CRFA pigs when compared to SAL pigs. Jejunal CRF mRNA abundance tended to be reduced (p = 0.09) on d 7 in CRFA pigs versus SAL pigs. On d 14, jejunal tumor necrosis factor-alpha was reduced (p = 0.01) in AB-fed pigs versus NAB-fed pigs. On d 7, change in glucose short-circuit current tended to be increased (p = 0.07) in CRFA pigs fed the AB diet when compared to CRFA pigs fed the NAB diet. In conclusion, CRFA pigs and pigs fed AB had some similar biological intestinal function measures post-weaning and transport.

Effects of medium-chain fatty acids and tributyrin supplementation in milk replacers on growth performance, blood metabolites, and hormone concentrations in Holstein dairy calves

This study aimed to evaluate the effects of triglycerides containing medium-chain fatty acids (MCT) and tributyrin (TB) supplementation in a milk replacer (MR) on growth performance, plasma metabolites, and hormone concentrations in dairy calves. Sixty-three Holstein heifer calves (body weight at 8 d of age, 41.1 ± 2.91 kg; mean ± SD) were randomly assigned to 1 of 4 experimental MR (28% crude protein and 18% fat): (1) containing 3.2% C8:0 and 2.8% C10:0 (in fat basis) without TB supplementation (CONT; n = 15), (2) containing 6.7% C8:0 and 6.4% C10:0 without TB supplementation (MCT; n = 16), (3) containing 3.2% C8:0 and 2.8% C10:0 with 0.6% (dry matter basis) TB supplementation (CONT+TB; n = 16), (4) containing 6.7% C8:0 and 6.4% C10:0 with 0.6% TB supplementation (MCT+TB; n = 16). The MR were offered at 600 g/d (powder basis) from 8 to 14 d, up to 1,300 g/d from 15 to 21 d, 1,400 g/d from 22 to 49 d, down to 700 g/d from 50 to 56 d, 600 g/d from 57 to 63 d, and weaned at 64 d of age. All calves were fed calf starter, chopped hay, and water ad libitum. The data were analyzed using a 2-way ANOVA via the fit model procedure of JMP Pro 16 (SAS Institute Inc.). Medium-chain fatty acid supplementation did not affect the total dry matter intake. However, calves that were fed MCT had greater feed efficiency (gain/feed) before weaning (0.74 ± 0.098 vs. 0.71 ± 0.010 kg/kg) compared with non-MCT calves. The MCT calves also had a lower incidence of diarrhea compared with non-MCT calves during 23 to 49 d of age and the weaning period (50 to 63 d of age; 9.2% vs. 18.5% and 10.5% vs. 17.2%, respectively). Calves fed with TB had a greater total dry matter intake during postweaning (3,465 vs. 3,232 g/d). Calves fed TB also had greater body weight during the weaning (90.7 ± 0.97 vs. 87.9 ± 1.01 kg) and postweaning period (116.5 ± 1.47 vs. 112.1 ± 1.50 kg) compared with that of non-TB calves. The plasma metabolites and hormone concentrations were not affected by MCT or TB. These results suggest that MCT and TB supplementation in the MR may improve the growth performance and gut health of dairy calves.

Effect of kraft pulp inclusion in calf starter on performance, health, and plasma concentration of glucagon-like peptide 2 in calves

Kraft pulp (KP), an intermediate product obtained when wood chips are converted to paper, contains highly digestible fiber. This study evaluated the effect of KP inclusion in calf starters on growth performance, health, and plasma glucagon-like peptide 2 (GLP-2) concentration in calves. Twenty-five Holstein heifer calves were raised on a high plane of nutrition program using milk replacer containing 29% crude protein and 18% fat until 49 d after birth, and were fed calf starters containing KP at 0 (CON; n = 14) or 12% (KPS; n = 11) on a dry matter basis. All calves were fed the treatment calf starters and timothy hay ad libitum. Blood was collected at 4, 14, 21, 35, 49, 70, and 91 d after birth. Dry matter intake (DMI) of milk replacer and hay was not affected by treatment, whereas calf starter DMI was lower for KPS (0.93 kg/d) than for CON (1.03 kg/d). Higher neutral detergent fiber (NDF) content in KPS (31.7%) than in the CON starter (22.1%) resulted in higher NDF intake for KPS (0.55 kg/d) than for CON (0.47 kg/d). However, the consumption of starch was lower for KPS (0.29 kg/d) than for CON (0.33 kg/d). Despite the lower starter intake for KPS, body weight and average daily gain did not differ between treatments. No significant difference was observed in the plasma concentrations of metabolites, except for β-hydroxybutyrate (BHB); BHB concentration was lower for KPS (216 μmol/L) than for CON (257 μmol/L). The area under the curve for plasma GLP-2 concentration was higher for KPS (54.1 ng/mL × d) than for CON (36.0 ng/mL × d). Additionally, the fecal score postweaning (1.19 and 1.48 for KPS and CON, respectively) and the number of days that calves developed diarrhea throughout the experimental period (2.50 d and 8.10 d for KPS and CON, respectively) were lower for KPS than for CON. These results indicate that feeding KP reduces the severity and frequency of diarrhea without adversely affecting growth performance. This could be attributed to the increased plasma GLP-2 concentration induced by higher NDF intake.

A Promising Insight: The Potential Influence and Therapeutic Value of the Gut Microbiota in GI GVHD

Allogeneic hematopoietic cell transplantation (allo-HSCT) is a reconstruction process of hematopoietic and immune functions that can be curative in patients with hematologic malignancies, but it carries risks of graft-versus-host disease (GVHD), thrombotic microangiopathy (TMA), Epstein–Barr virus (EBV) infection, cytomegalovirus infection, secondary hemophagocytic lymphohistiocytosis (sHLH), macrophage activation syndrome (MAS), bronchiolitis obliterans, and posterior reversible encephalopathy syndrome (PRES). Gastrointestinal graft-versus-host disease (GI GVHD), a common complication of allo-HSCT, is one of the leading causes of transplant-related death because of its high treatment difficulty, which is affected by preimplantation, antibiotic use, dietary changes, and intestinal inflammation. At present, human trials and animal studies have proven that a decrease in intestinal bacterial diversity is associated with the occurrence of GI GVHD. Metabolites produced by intestinal bacteria, such as lipopolysaccharides, short-chain fatty acids, and secondary bile acids, can affect the development of GVHD through direct or indirect interactions with immune cells. The targeted damage of GVHD on intestinal stem cells (ISCs) and Paneth cells results in intestinal dysbiosis or dysbacteriosis. Based on the effect of microbiota metabolites on the gastrointestinal tract, the clinical treatment of GI GVHD can be further optimized. In this review, we describe the mechanisms of GI GVHD and the damage it causes to intestinal cells and we summarize recent studies on the relationship between intestinal microbiota and GVHD in the gastrointestinal tract, highlighting the role of intestinal microbiota metabolites in GI GVHD. We hope to elucidate strategies for immunomodulatory combined microbiota targeting in the clinical treatment of GI GVHD.

Glucagon-like peptide 2 (GLP-2) in bovine colostrum and transition milk

Bovine colostrum contains growth factors, cytokines, hormones, and enzymes, which have important roles in stimulating gastrointestinal development of neonatal calves. In the present study, we measured the concentration of glucagon-like peptide 2 (GLP-2), one of the gut-derived peptides secreted from intestinal L-cells, in colostrum and transition milk of Japanese black cattle. All colostrum samples were collected within 24 h after calving (d 0) and transition milk was collected at 24, 48 and 72 h relative to the time at colostrum sampling (d 1, d 2 and d 3, respectively). Concentrations of GLP-2 in colostrum were 5.53 ± 1.07 ng/mL on average (range = 0.94–9.60 ng/mL) and decreased from d 0 to 3 (P < 0.01). Furthermore, concentrations of GLP-2 in colostrum and transition milk were quadratically decreased with the elapsed time from parturition until colostrum sampling (R² = 0.48, P < 0.01). Our results show for the first time that GLP-2 is present in bovine colostrum and transition milk and that concentrations decreased with elapsed time from parturition.

Glucagon-like peptide 2 for intestinal stem cell and Paneth cell repair during graft-versus-host disease in mice and humans

Acute graft-versus-host disease (GVHD) is a life-threatening complication after allogeneic hematopoietic cell transplantation (allo-HCT). Although currently used GVHD treatment regimens target the donor immune system, we explored here an approach that aims at protecting and regenerating Paneth cells (PCs) and intestinal stem cells (ISCs). Glucagon-like-peptide-2 (GLP-2) is an enteroendocrine tissue hormone produced by intestinal L cells. We observed that acute GVHD reduced intestinal GLP-2 levels in mice and patients developing GVHD. Treatment with the GLP-2 agonist, teduglutide, reduced de novo acute GVHD and steroid-refractory GVHD, without compromising graft-versus-leukemia (GVL) effects in multiple mouse models. Mechanistically GLP-2 substitution promoted regeneration of PCs and ISCs, which enhanced production of antimicrobial peptides and caused microbiome changes. GLP-2 expanded intestinal organoids and reduced expression of apoptosis-related genes. Low numbers of L cells in intestinal biopsies and high serum levels of GLP-2 were associated with a higher incidence of nonrelapse mortality in patients undergoing allo-HCT. Our findings indicate that L cells are a target of GVHD and that GLP-2-based treatment of acute GVHD restores intestinal homeostasis via an increase of ISCs and PCs without impairing GVL effects. Teduglutide could become a novel combination partner for immunosuppressive GVHD therapy to be tested in clinical trials.

Dynamic progression of the calf's microbiome and its influence on host health

The first year of a calf's life is a critical phase as its digestive system and immunity are underdeveloped. A high level of stress caused by separation from mothers, transportation, antibiotic treatments, dietary shifts, and weaning can have long-lasting health effects, which can reduce future production parameters, such as milk yield and reproduction, or even increase the mortality of calves. The early succession of microbes throughout the gastrointestinal tract of neonatal calves follows a sequential pattern of colonisation and is greatly influenced by their physiological state, age, diet, and environmental factors; this leads to the establishment of region- and site-specific microbial communities. This review summarises the current information on the various potential factors that may affect the early life microbial colonisation pattern in the gastrointestinal tract of calves. The possible role of host-microbe interactions in the development and maturation of host gut, immune system, and health are described. Additionally, the possibility of improving the health of calves through gut microbiome modulation and using antimicrobial alternatives is discussed. Finally, the trends, challenges, and limitations of the current research are summarised and prospective directions for future studies are highlighted.

Effects of pre- and postpartum dietary starch content on productivity, plasma energy metabolites, and serum inflammation indicators of dairy cows

The objective of this study was to evaluate the effects of the starch content of pre- and postpartum diets on productivity, plasma energy metabolites, and serum markers of inflammation of dairy cows during the calving transition period. Eighty-eight primiparous and multiparous cows were randomly assigned to pre- and postpartum dietary treatments balanced for parity and pretrial body condition score at d 28 ± 3 before expected calving date. Cows were fed either a control [Control; 14.0% starch, dry matter (DM) basis] or high-starch (High; 26.1% starch, DM basis) prepartum diet commencing 28 ± 3 d before expected calving date. Following calving, cows were fed either a high-fiber (HF; 33.8% neutral detergent fiber, 25.1% starch, DM basis) or high-starch (HS; 27.2% neutral detergent fiber, 32.8% starch, DM basis) postpartum diet for the first 20 ± 2 d following calving. Cows fed the High prepartum diet had greater DM intake (12.4 vs. 10.2 kg/d), plasma concentrations of insulin (1.72 vs. 14.2 ng/mL), glucose (68.1 vs. 65.0 mg/dL), and glucagon-like peptide-2 (0.41 vs. 0.32 ng/mL) before parturition, but increased plasma free fatty acid concentration (452 vs. 363 µEq/L) and milk fat yield (1.64 vs. 1.48 kg/d) after parturition. Cows fed the HS postpartum diet had lower plasma free fatty acid (372 vs. 442 µEq/L) and serum haptoglobin (0.46 vs. 0.70 mg/mL) concentrations over a 3-wk period after calving. In addition, there was a tendency for interaction between prepartum and postpartum diets for milk yield, where feeding the HS postpartum diet increased milk yield compared with the HF diet for cows fed the Control prepartum diet (40.8 vs. 37.9 kg/d) but not for cows fed the High prepartum diet. These results suggest that management efforts to minimize the change in diet fermentability during the calving transition by feeding the High prepartum diet, the HF postpartum diet, or both did not increase productivity of dairy cows but increased fat mobilization after calving. Our findings also suggest that feeding high-starch postpartum diets can decrease fat mobilization and serum indicators of systemic inflammation and increase milk production even with the transition from a low-starch prepartum diet.

Effects of feeding a moderate- or high-energy close-up diet to cows on response of newborn calves to milk replacer feeding and intravenous injection of glucagon-like peptide 1

In this study, we investigated the effects of feeding a moderate- or high-energy close-up diet to close-up cows on response of newborn calves to intravenously (i.v.) injected glucagon-like peptide 1 (GLP-1). Newborn Holstein heifer calves (n = 37) from cows fed with a moderate-energy [M, 1.54 Mcal/kg of dry matter (DM) NEl; 14% starch; n = 17] or high-energy (H, 1.63 Mcal/kg of DM NEl; 26% starch; n = 20) diet in the last 28 d prepartum were assigned to one of two treatment groups, which were i.v. injected with saline (MC and HC, n = 9 and 10, respectively) or GLP-1 solution at 1.0 μg/kg BW (MG and HG, n = 8 and 10, respectively) immediately after milk replacer (MR; 26% CP, 16% fat) feeding. Blood samples were obtained through a jugular vein catheter at -10, 0, 10, 20, 30, 40, 50, 60, 90, and 120 min relative to MR feeding at 2, 10, and 20 d after birth, and plasma glucose, insulin, and GLP-1 concentrations were measured. Plasma GLP-1 concentration tended to increase starting from 30 min after MR feeding in the MC relative to the HC group at 10 (0.77 ng/mL vs 0.69 ng/mL for MC and HC, respectively; P = 0.10) and 20 d after birth (0.47 ng/mL vs 0.35 ng/mL for MC and HC, respectively; P = 0.07). Plasma glucose and insulin concentrations after MR feeding did not differ between MC and HC groups at 2 and 20 d after birth but were higher (P < 0.05) in MC (158 mg/dL and 3.64 ng/mL for glucose and insulin, respectively) than in HC (143 mg/dL and 2.46 ng/mL for glucose and insulin, respectively) calves at 10 d after birth. The elevation in plasma glucose concentration after MR feeding was suppressed by direct glucose-lowering action of i.v. injected GLP-1 at 2, 10, and 20 d after birth in M and H calves; this direct glucose-lowering action by GLP-1 was greater (P < 0.05) for H than for M calves at 20 d after birth. These results indicate that feeding a high-energy close-up diet to cows affects glucose status in their female offspring via suppression of postprandial plasma concentrations of GLP-1 and insulin as well as the alteration in the glucose-lowering action of GLP-1 after feeding depending on the day after birth.

The effects of supplementing yeast fermentation products on gut permeability, hormone concentration, and growth in newborn dairy calves

The objectives of this study were to evaluate the effect of the use of yeast fermentation products (YFP) on growth, hormone concentration, and gut permeability in dairy calves. One hundred and twenty heifers were randomly assigned to one of three treatments: control group with no YFP supplementation (C), Saccharomyces cerevisiae fermentation products (SCFP) supplementation (1 g/head/d of SmartCare [Diamond V] in the milk and 0.7% on dry matter basis of NutriTek [Diamond V] on the starter feed), or Aspergillus oryzae fermentation extracts (AOFE) supplementation (3 g/head/d of LXtract1224 [Biozyme Inc.] in the milk). All calves received 6 L/d of pasteurized milk and had ad libitum access to water and dry feed along the study. Body weight (BW) was recorded at birth and on days 14, 30, and 45 and at weaning. Dry feed (starter) offered was measured daily and refusals twice a week to obtain starter intake (SI). Diarrhea events were recorded daily and fecal scores were classified by using a four-point scale. Blood was sampled on days 7 and 14 for plasma glucose, nonesterified fatty acids (NEFA), insulin, and IL-1β concentrations. Lactulose and D-mannitol were included in the morning feeding of day 14 and blood samples were taken an hour after feeding for assessment of intestinal permeability. On day 14, blood samples were taken for plasma glucagon-like peptide 2 (GLP-2) concentration. On day 30, fecal samples were collected for measurements of Salmonella and Escherichia coli concentration on feces. No treatment differences (P ≥ 0.13) were found for BW or SI. There was a time by treatment difference (P = 0.01) in average daily gain (ADG) on day 45 where C animals had a greater ADG when compared with SCFP and AOFE. Diarrhea incidence did not change between treatments (P = 0.97) and Salmonella and E. coli were not found in feces. There were no differences (P > 0.60) between treatments for plasma GLP-2, glucose, insulin, lactulose, nor D-mannitol concentrations. There was a time by treatment tendency (P = 0.06) for NEFA concentration which tended to be greater on day 7 for C and AOFE when compared with day 14. Plasma IL-1β concentration showed a treatment tendency which tended (P = 0.06) to be greater for SCFP when compared with C. Under the current conditions, supplementation with YFP did not improve performance parameters. Plasma GLP-2 concentration, intestinal permeability, and plasma metabolites did not differ after yeast fermentation products supplementation.

Effect of colostrum feeding strategies on the expression of neuroendocrine genes and active gut mucosa-attached bacterial populations in neonatal calves

Colostrum feeding is vital for the development of the immune system and gastrointestinal tract in neonatal calves; however, it is currently unknown whether different colostrum feeding strategies affect their neuroendocrine system and potentially the gut-brain axis. The present study investigated the effect of 3 different colostrum feeding regimens on the expression of neuroendocrine genes in adrenal glands and gastrointestinal tissues and on the abundance of intestinal commensal bacteria. Holstein bull calves were fed colostrum immediately after birth and randomly assigned to 3 groups: whole milk (n = 8), mixture of 50% colostrum and 50% whole milk (n = 8), and colostrum (CF; n = 8) for 72 h with 12-h intervals. Adrenal glands, ileum, and colon tissues were collected at 75 h and were subjected to the expression of 11 targeted neuroendocrine genes and the abundance of tissue mucosa-associated bacteria measurement using quantitative real-time PCR and quantitative PCR, respectively. The expressions of all targeted genes were detected, and the expression of α-adrenergic receptor (ADRA1A) gene was affected by CF in adrenal glands and gut tissues. In addition, CF upregulated the expression of HTR4 (serotonin receptor) and SLC4A4 (serotonin transporter) genes in the ileum and increased the abundance of active Lactobacillus spp. and Escherichia coli (as detected at RNA level) associated with ileum and colon tissue. Furthermore, there were positive correlations between the abundance of active Lactobacillus spp. and E. coli with expression of HTR2B and HTR4 genes in the colon, suggesting that extended colostrum feeding strategies may affect the interaction between gut microbiota and host endocrine functions in neonatal calves.

Aspartame supplementation in starter accelerates small intestinal epithelial cell cycle and stimulates secretion of glucagon-like peptide-2 in pre-weaned lambs

The objective of this study was to test the hypothesis that aspartame supplementation in starter diet accelerates small intestinal cell cycle by stimulating secretion and expression of glucagon-like peptide -2 (GLP-2) in pre-weaned lambs using animal and cell culture experiments. In vivo, twelve 14-day-old lambs were selected and allocated randomly to two groups; one was treated with plain starter diet (Con, n = 6) and the other was treated with starter supplemented with 200 mg of aspartame/kg starter (APM, n = 6). Results showed that the lambs received APM treatment for 35 d had higher (p < .05) GLP-2 concentration in the plasma and greater jejunum weight/live body weight (BW) and jejunal crypt depth. Furthermore, APM treatment significantly upregulated (p < .05) the mRNA expression of cyclin D1 in duodenum; and cyclin A2, cyclin D1, cyclin-dependent kinases 6 (CDK6) in jejunum; and cyclin A2, cyclin D1, CDK4 in ileum. Moreover, APM treatment increased (p < .05) the mRNA expression of glucagon (GCG), insulin-like growth factor 1 (IGF-1) in the jejunum and ileum and mRNA expression of GLP-2 receptor (GLP-2R) in the jejunum. In vitro, when jejunal cells were treated with GLP-2 for 2 hr, the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) OD, IGF-1 concentration, and the mRNA expression of IGF-1, cyclin D1 and CDK6 were increased (p < .05). Furthermore, IGF-1 receptor (IGF-1R) inhibitor decreased (p < .05) the mRNA expression of IGF-1, cyclin A2, cyclin D1 and CDK6 in GLP-2 treatment jejunal cells. These results suggest that aspartame supplementation in starter accelerates small intestinal cell cycle that may, in part, be related to stimulate secretion and expression of GLP-2 in pre-weaning lambs. Furthermore, GLP-2 can indirectly promote the proliferation of jejunal cells mainly through the IGF-1 pathway. These findings provide new insights into nutritional interventions that promote the development of small intestines in young ruminants.

The effect of tributyrin supplementation to milk replacer on plasma glucagon-like peptide 2 concentrations in pre-weaning calves

The objective of this study was to evaluate the effect of tributyrin (TB) supplementation to milk replacer (MR) on performance, health, and blood concentrations of metabolite and glucagon-like peptide (GLP-2) in pre-weaning calves. Twenty Holstein heifer calves were raised on an intensified nursing program using MR supplemented with either palm oil (CON) or TB (TB) at 0.3% (as fed basis) for 7 weeks starting 1 week after birth. Calves were fed a calf starter and kleingrass from the beginning of the study. Blood samples were obtained weekly to measure blood glucose, serum β-hydroxybutyric acid (BHBA), insulin-like growth factor 1 (IGF-1), and plasma GLP-2 concentrations. Starter DMI and metabolizable energy (ME) intake were lower in TB calves at 46, 47, from 49 to 55 days after birth compared with the CON calves. However, any growth parameters were not affected by TB treatment. Blood glucose, serum BHBA, and IGF-1 concentrations were not affected by TB supplementation. On the other hand, mean plasma GLP-2 concentration among whole experimental period was higher for TB (0.60 ng/ml) compared with CON (0.41 ng/ml). In conclusion, feeding MR supplemented with TB increases plasma GLP-2 concentration, which might counterbalance the growth performance of TB calves despite the decreased ME intake.

Effects of ad libitum milk replacer feeding and butyrate supplementation on the epithelial growth and development of the gastrointestinal tract in Holstein calves

Intensive milk feeding and butyrate supplementation in calves stimulate body growth and affect gastrointestinal development. The aim of the present study was to investigate the synergistic effects of ad libitum milk replacer (MR) feeding and butyrate supplementation of MR on rumen and small intestinal growth and on gene expression in the small intestine related to growth and energy metabolism at weaning. Male Holstein calves (n = 32) received colostrum from birth to d 3 of age and MR either ad libitum (Adl) or restrictively (Res; 6 L of MR/d; 12.5% solids) with (AdlB+, ResB+) or without (AdlB-, ResB-) 0.24% butyrate from d 4 until wk 8 of age. From wk 9 to 10, all calves were weaned and were fed 2 L/d until the end of the trial. Concentrate, hay, and water were freely available. At d 80, calves were slaughtered, volatile fatty acids were measured in rumen fluid, and rumen and small intestine samples were taken for histomorphometric measurements. The expression of mRNA associated with the local insulin-like growth factor (IGF) system and glucose metabolism as well as lactase and maltase activities were measured in the intestinal mucosa. The small intestine was 3 m longer in Adl than in Res. In the atrium ruminis, papilla width was greater in Res than in Adl. Villus circumference, cut surface, and height in the duodenum, proximal jejunum, and ileum were greater in Adl than in Res and in the proximal, mid, and distal jejunum and ileum were greater in calves treated with butyrate. Crypt depth in the duodenum and proximal jejunum was greater in Adl than in Res and in the ileum was smaller in calves treated with butyrate. The villus height:crypt depth ratio was greatest in AdlB+ calves. In the proximal and mid jejunum, IGF1 mRNA abundance was lower in calves treated with butyrate. In the proximal jejunum, INSR mRNA abundance was greater in Res than in Adl. The abundance of PCK2 mRNA was greater in Res than in Adl in the duodenum and was greatest in ResB- in the mid jejunum. Lactase activity tended to be greater in Res than in Adl and after butyrate treatment in the proximal jejunum. The results indicated an elevated growth of the small intestinal mucosa at weaning due to intensive milk feeding and butyrate supplementation, and the local IGF system was involved in intestinal growth regulation. Rumen development was not affected by butyrate supplementation of MR and was slightly delayed due to ad libitum MR feeding.

Effect of extended colostrum feeding on plasma glucagon-like peptide-1 concentration in newborn calves

Glucagon-like peptide-1 (GLP-1) plays a role in the regulation of glucose homeostasis via the stimulation of insulin secretion. The objective of this study was to evaluate the effect of extended colostrum feeding on plasma concentration of GLP-1. Holstein bull calves (n = 27) were fed pooled colostrum at 7.5% of birth body weight at 2 h after birth and then fed mature milk (M), a 50:50 mixture of pooled colostrum and milk (CM), or pooled colostrum (C; n = 9 for each treatment) at 5% of birth body weight at 12 h after birth and every 12 h thereafter until 72 h after birth. Blood samples were obtained before (1 and 2 h after birth) and after (until 72 h after birth; 42 time points) the first colostrum feeding, and plasma concentrations of glucose, insulin, and GLP-1 were measured. Data were analyzed by ANOVA of JMP 13 (SAS Institute Inc., Cary, NC) with treatment, time, and treatment × time interaction as fixed effects. Treatment × time interaction was observed for plasma insulin and glucose concentrations, which were mainly the result of lower concentrations from 1 to 2 d after birth for C compared with M. Conversely, on d 3 after birth, the difference between treatments was not observed for insulin and glucose. For the entire experimental period, plasma GLP-1 concentration was higher for C (2.25 ng/mL) compared with M (1.41 ng/mL) and tended to be higher compared with CM (1.58 ng/mL). A treatment × time interaction was observed for GLP-1, but unlike glucose and insulin, this was mainly the result of higher concentrations from 54 to 72 h after birth (on d 3 after birth) for C compared with M or CM. Postprandial plasma concentration of glucose was not correlated with that of GLP-1 but was positively correlated with that of insulin for the 4-h period after feeding on d 1 (r = 0.30) and d 3 after birth (r = 0.33). Postprandial plasma concentration of GLP-1 was positively correlated with that of insulin for the 4-h period after feeding on d 3 after birth (r = 0.20). These results indicate that extended colostrum feeding may increase plasma GLP-1 concentrations, especially 3 d after birth, but further study is necessary to determine the effect on plasma insulin and glucose concentrations.

Effects of pulse-dose ruminal infusion of butyrate on plasma glucagon-like peptide 1 and 2 concentrations in dairy calves

Feeding of butyrate was found to have a positive effects in enhancing gut development and improving growth performance of calves. Equally, glucagon-like peptide 1 and 2 (GLP-1 and GLP-2), secreted from gastrointestinal L-cells in response to nutrient intake, were found to play a significant role in regulating blood glucose homeostasis and improving gut health. However, limited information is available about the relationship between butyrate and release of GLP-1 and GLP-2 in dairy calves. The objective of this study was to evaluate the effects of a pulse-dose ruminal infusion of butyrate on plasma GLP-1 and GLP-2 concentrations in dairy calves. Five ruminally cannulated mature Holstein bull calves (7.2 ± 0.10 mo, and 330 ± 16.0 kg of body weight; mean ± standard deviation) were used in a 5 × 5 Latin square with 4-d periods. On d 1 of each period at 0800 h, calves were ruminally infused with 1 of 5 treatments: 0 (saline), 0.3, 0.6, 0.9, and 1.2 g of butyrate per kg of body weight. Before butyrate infusion, calves were not offered feed overnight, and sequential blood and rumen fluid samples were taken before and after infusion on d 1 of each period. Ruminal butyrate and total volatile fatty acid concentrations increased linearly (2.65, 12.19, 20.99, 30.19, and 36.30; 23.68, 33.07, 40.94, 51.13, and 56.31 µmol/mL, for butyrate and total volatile fatty acids, respectively) in a dose-dependent manner, whereas propionate and isobutyrate increased quadratically. Ruminal and plasma butyrate, β-hydroxybutyrate, GLP-1, GLP-2, insulin, and glucose concentrations were all affected by treatment, time (except GLP-2), and interaction of treatment with time (except GLP-1). The area under the curve (AUC) summarized at different time points relative to the baseline (AUC30, AUC60, AUC120, and AUC240) for ruminal and plasma butyrate, and BHB, increased linearly with the dose of butyrate infused. However, AUC30, AUC60, AUC120, and AUC240 for plasma GLP-2 concentration were affected in a cubic manner unlike the linear effect on AUC30 and AUC60 for GLP-1. Plasma GLP-2 was not correlated with plasma butyrate (r = 0.16), GLP-1 (r = 0.03), or BHB (r = -0.05). This findings suggest that pulse-dosing of butyrate slightly increased both GLP-1 and GLP-2 concentrations at specific time points and this might be promoted by direct or indirect effect of butyrate on the intestinal L-cells.

Effects of different starch source of starter on small intestinal growth and endogenous GLP-2 secretion in preweaned lambs

The objective of this study was to investigate the effects of different sources of starch in starter feed on small intestinal growth and endogenous glucagon-like peptide 2 (GLP-2) secretion in preweaned lambs. Twenty-four 10-d-old lambs were divided into three groups that were treated with different iso-starch diets containing purified cassava starch (CS, n = 8), maize starch (MS, n = 8), and pea starch (PS, n = 8). At 56 d old, there was no significant difference in final body weight (BW) of lambs among the three groups. However, different starch source in starter significantly affected the average daily feed intake (ADFI) and average daily gain (ADG) of lambs among three groups. Compared with the CS and MS diets, the PS diet significantly increased the GLP-2 concentration in blood plasma (P < 0.001), the crypt depth of the jejunum (P = 0.006), and the villus height of the ileum (P = 0.039). Meanwhile, PS diet significantly increased the mRNA expression of proglucagon and the glucagon-like peptide 2 receptor (GLP-2R) in the jejunum and ileum (P < 0.001). Furthermore, the PS diet significantly upregulated the mRNA expression of cyclin D1 (P < 0.001), cyclin E (P = 0.006), and cyclin-dependent kinases 6 (CDK6) (P = 0.048) in the jejunum and cyclin A (P < 0.001), cyclin D1 (P < 0.001), and CDK6 (P = 0.002) in the ileum. Correlation analysis showed that endogenous GLP-2 secretion was positively related to the mRNA levels of cell cycle proteins in small intestinal mucosa. In summary, all results showed that PS in starter feed promoted small intestinal growth that may, in part, be related to cell cycle acceleration and endogenous GLP-2 secretion in preweaned lambs. These findings provide new insights into nutritional interventions that promote the development of small intestines in young ruminants.

Short communication: The effect of delayed colostrum feeding on plasma concentrations of glucagon-like peptide 1 and 2 in newborn calves

Glucagon-like peptide (GLP)-1 is involved in glucose homeostasis via its role in stimulating insulin secretion, whereas GLP-2 increases mucosal growth of the small intestine. To our knowledge, the effect of delayed colostrum feeding on plasma GLP-1 and GLP-2 in neonatal calves has not been evaluated. To investigate the effect of delayed colostrum feeding on plasma concentrations of GLP-1 and GLP-2 in newborn calves, we randomly assigned 27 Holstein bull calves to 1 of 3 treatment groups: those fed colostrum within 1 h after birth (control), 6 h after birth (6H), and 12 h after birth (12H; n = 9 for each treatment). Blood samples were obtained before the colostrum feeding and every 3 h after each colostrum feeding for a 36-h period, and plasma concentrations of GLP-1, GLP-2, insulin, and glucose were measured. Plasma GLP-1 concentration at 12 h after colostrum feeding was lower in 12H than in control calves. In addition, plasma insulin concentration was lower in the 6H and 12H calves than in the controls. Plasma glucose and GLP-2 concentrations were, however, not affected by treatment. These results indicate that delayed colostrum feeding can decrease plasma GLP-1 and insulin concentrations without affecting glucose or GLP-2 concentration.

Response of plasma glucagon-like peptide-2 to feeding pattern and intraruminal administration of volatile fatty acids in sheep

Glucagon-like peptide-2 (GLP-2), a gut peptide secreted by enteroendocrine L cells, has recently been identified as a key regulator of intestinal growth and absorptive function in ruminants. However, reports on GLP-2 secretion are few, and more information regarding its secretion dynamics is needed. In this study, two experiments were conducted to elucidate the daily rhythm of GLP-2 secretion in response to feeding regimen and to investigate the effect of volatile fatty acids (VFA) on GLP-2 release in sheep. In experiment 1, blood samples were collected over 3 d from 4 Suffolk mature wethers adapted to a maintenance diet fed once daily; day 1 sampling was preceded by 24 h of fasting to reach steady state. On days 1 and 3, samples were collected every 10 min from 11:00 to 14:00 on both days and then every 1 h until 00:00 on day 1 only; feed was offered at 12:00. On day 2, feed was withheld, and sampling was performed every hour from 01:00 to 00:00. In experiment 2, 5 Suffolk mature wethers were assigned to 5 treatment groups of intraruminal administration of saline, acetate, propionate, butyrate, or VFA mix (acetate, propionate, and butyrate in a ratio of 65:20:15) in a 5 × 5 Latin square design. Blood samples were collected at 0, 1.5, 3, 6, 9, 12, 15, 20, 25, 30, 40, 50, 60, 90, and 120 min relative to the beginning of administration at 12:00. In both experiments, plasma GLP-2, glucagon-like peptide-1 (GLP-1), glucose, insulin, and β-hydroxy butyric acid (BHBA) levels were measured. In experiment 1, incremental area under the curve was greater (P < 0.05) post-feeding than pre-feeding on days 1 and 3 for GLP-2 and tended to be greater (P < 0.1) on day 1 for GLP-1. Plasma insulin, glucose, and BHBA levels increased (P < 0.05) on day 1 post-feeding. Plasma GLP-2 was poorly correlated with GLP-1 but positively correlated with insulin, glucose, and BHBA. In experiment 2, administration of butyrate and VFA mix remarkably increased plasma GLP-2 (P = 0.05) and BHBA (P < 0.0001) levels compared with those in other treatments. Plasma GLP-1 levels were higher with butyrate administration compared with those in the saline, acetate, and VFA mix (P = 0.019). Propionate administration increased plasma glucose (P = 0.013) and insulin (P = 0.053) levels. Thus, our data confirmed that GLP-2 release is responsive to feeding and might be promoted by BHBA produced by the rumen epithelial metabolism of butyrate. Further molecular- and cellular-level studies are needed to determine the role of butyrate as a signaling molecule for GLP-2 release.

Effects of a 3 strain -based direct-fed microbial and dietary fiber concentration on growth performance and expression of genes related to absorption and metabolism of volatile fatty acids in weanling pigs

Effects of a -based direct-fed microbial (DFM) on growth performance, plasma tumor necrosis factor ɑ (TNFɑ), relative gene expression, and intestinal VFA concentrations in weanling pigs fed low- or high-fiber diets were evaluated. Two hundred pigs (initial BW: 6.31 ± 0.73 kg) were allotted to 1 of 4 dietary treatments (5 pigs per pen and 10 pens per treatment). Treatments were arranged in a 2 × 2 factorial design with 2 diet types [low-fiber (LF) or high-fiber (HF)] and 2 concentrations of DFM (0 or 60 g DFM/t of feed). The DFM contained 1.5 × 10 cfu/g and was obtained from Danisco Animal Nutrition-DuPont Industrial Biosciences, Marlborough, UK. Phase 1 diets were fed for 2 wk post-weaning and phase 2 diets were fed over the following 29 d. Low fiber diets contained corn and soybean meal as main ingredients and HF diets contained corn, soybean meal, corn distillers dried grains with solubles (7.5 and 15.0% in phase 1 and 2, respectively), and wheat middlings (10.0%). Pigs and feed were weighed at the start and at the end of each phase, and ADG, ADFI, and G:F were calculated. At the conclusion of phase 2, blood was collected from 1 pig per pen and 1 pig per pen was sacrificed. Cecum and rectum contents were analyzed for VFA, and tissue samples were collected from the ileum, cecum, rectum, and liver to determine expression of genes related to absorption and metabolism of VFA using quantitative reverse transcription-PCR. Results indicated that feeding HF diets reduced ( ≤ 0.05) ADFI and ADG of pigs compared with feeding LF diets. Pigs fed DFM diets had improved ( ≤ 0.05) G:F compared with pigs fed non-DFM diets. Pigs fed LF diets had greater ( ≤ 0.05) BW at the end of phase 2 compared with pigs fed HF diets. The concentration of VFA in rectum contents was greater ( ≤ 0.05) in pigs fed LF diets than in pigs fed HF diets. The expression of in the rectum of pigs fed HF diets was greater ( ≤ 0.05) than for pigs fed LF diets, and pigs fed DFM-containing diets had an increased ( ≤ 0.05) expression of in the liver. Pigs fed HF diets had greater ( ≤ 0.05) concentrations of urea N in plasma compared with pigs fed LF diets, but dietary fiber and DFM had no effect on plasma concentration of TNF-ɑ. In conclusion, the -based DFM improved overall G:F of weanling pigs, but pigs fed LF diets had greater final BW than pigs fed HF diets.

Influence of glucagon-like peptide 2 on energy homeostasis

Glucagon like peptide-2 (GLP-2) is a gastrointestinal hormone released from enteroendocrine L-type cells together with glucagon like peptide-1 in response to dietary nutrients. GLP-2 acts through a specific receptor, the GLP-2 receptor, mainly located in the gut and in the brain. Classically, GLP-2 is considered a trophic hormone involved in the maintenance of intestinal epithelial morphology and function. This role has been targeted for therapies promoting repair and adaptive growth of the intestinal mucosa. Recently, GLP-2 has been shown to exert beneficial effects on glucose metabolism specially in conditions related to increased uptake of energy, such as obesity. Several actions of GLP-2 are related to a positive energy balance: GLP-2 increases not only the absorptive surface, but also expression and activity of epithelial brush-border nutrient transporters and digestive enzymes, intestinal blood flow, postprandial chylomicron secretion and it inhibits gastrointestinal motility, providing the opportunity to increase absorption of nutrients. Other actions, including anorexigenic effects, appear in opposition to the energy intake. In this review, we discuss the GLP-2 functions related to energy homeostasis. GLP-2 could be considered an hormone causing positive energy balance, which, however has the role to mitigate the metabolic dysfunctions associated with hyper-adiposity.

Generation of glucagon-like peptide-2-expressing Saccharomyces cerevisiae and its improvement of the intestinal health of weaned rats

We aimed to assess the feasibility of enhancing the intestinal development of weaned rats using glucagon-like peptide-2 (GLP-2)-expressing Saccharomyces cerevisiae (S. cerevisiae). GLP-2-expressing S. cerevisiae (GLP2-SC) was generated using a recombinant approach. The diet of weaned rats was supplemented with the GLP2-SC strain. The average daily gain (ADG), the intestinal morphology and the activities of the digestive enzymes in the jejunum were tested to assess the influence of the GLP2-SC strain on intestinal development. The proliferation of rat enterocytes was also assessed in vitro. The study revealed that the ADG of the weaned rats that received GLP2-SC was significantly greater than that of the controls fed a basal diet (Control) and S. cerevisiae harbouring an empty vector (EV-SC) (P < 0.05) but was equivalent to that of positive control rats fed recombinant human GLP-2 (rh-GLP2) (P > 0.05). Furthermore, GLP2-SC significantly increased villous height (P < 0.01) and digestive enzyme activity (P < 0.05) in the jejunum. Immunohistochemistry analysis further affirmed that enterocyte proliferation was stimulated in rats fed the GLP2-SC strain, as indicated by the greater number of enterocytes stained with proliferative cell nuclear antigen (P < 0.05). In vitro, the proliferation of rat enterocytes was also stimulated by GLP-2 expressed by the GLP2-SC strain (P < 0.01). Herein, the combination of the GLP-2 approach and probiotic delivery constitute a possible dietary supplement for animals after weaning.

Glucagon-like peptide 2 and its beneficial effects on gut function and health in production animals

Numerous endocrine cell subtypes exist within the intestinal mucosa and produce peptides contributing to the regulation of critical physiological processes including appetite, energy metabolism, gut function, and gut health. The mechanisms of action and the extent of the physiological effects of these enteric peptides are only beginning to be uncovered. One peptide in particular, glucagon-like peptide 2 (GLP-2) produced by enteroendocrine L cells, has been fairly well characterized in rodent and swine models in terms of its ability to improve nutrient absorption and healing of the gut after injury. In fact, a long-acting form of GLP-2 recently has been approved for the management and treatment of human conditions like inflammatory bowel disease and short bowel syndrome. However, novel functions of GLP-2 within the gut continue to be demonstrated, including its beneficial effects on intestinal barrier function and reducing intestinal inflammation. As knowledge continues to grow about GLP-2's effects on the gut and its mechanisms of release, the potential to use GLP-2 to improve gut function and health of food animals becomes increasingly more apparent. Thus, the purpose of this review is to summarize: (1) the current understanding of GLP-2's functions and mechanisms of action within the gut; (2) novel applications of GLP-2 (or stimulators of its release) to improve general health and production performance of food animals; and (3) recent findings, using dairy calves as a model, that suggest the therapeutic potential of GLP-2 to reduce the pathogenesis of intestinal protozoan infections.

Gastroduodenal mucosal defense mechanisms

PURPOSE OF REVIEW

To highlight recent developments in the field of gastroduodenal mucosal defense with emphasis on lumen-gut interactions.

RECENT FINDINGS

There has been a growing interest in the physiological functions of luminal chemosensors present from tongue to colon that detect organic molecules in the luminal content associated with nutrient ingestion, usually associated with specialized cells, in particular the enteroendocrine cells. These receptors transduce the release of peptide hormones, in particular proglucagon-derived products such as the glucagon-like peptides (GLPs), which have profound effects on gut function and on metabolism. Luminal chemosensors transduce GLP release in response to changes in the cellular environment, as part of the mechanism of nutrient chemosensing. GLP-2 has important trophic effects on the intestinal mucosa, including increasing the proliferation rate of stem cells and reducing transmucosal permeability to ions and small molecules, in addition to increasing the rate of duodenal bicarbonate secretion. GLP-1, although traditionally considered an incretin that enhances the effect of insulin on peripheral tissues, also has trophic effects on the intestinal epithelium.

SUMMARY

A better understanding of the mechanisms that mediate GLP release can further illuminate the importance of nutrient chemosensing as an important component of the mechanism that mediates the trophic effects of luminal nutrients. GLP-1 and GLP-2 are already in clinical use for the treatment of diabetes and intestinal failure. Improved understanding of the control of their release and their end-organ effects will identify new clinical indications and interventions that enhance their release.