Effects of aging and weaning on mRNA expression of leptin and CCK receptors in the calf rumen and abomasum

Expression of Genes Encoding Selected Orexigenic and Anorexigenic Peptides and Their Receptors in the Organs of the Gastrointestinal Tract of Calves and Adult Domestic Cattle (Bos taurus taurus)

The regulation of food intake occurs at multiple levels, and two of the components of this process are orexigenic and anorexigenic peptides, which stimulate or inhibit appetite, respectively. The study of the function of these compounds in domestic cattle is essential for production efficiency, animal welfare, and health, as well as for economic benefits, environmental protection, and the contribution to a better understanding of physiological aspects that can be applied to other species. In this study, the real-time PCR method was utilized to determine the expression levels of GHRL, GHSR, SMIM20, GPR173, LEP, LEPR, and NUCB2 (which encode ghrelin, its receptor, phoenixin-14, its receptor, leptin, its receptor, and nesfatin-1, respectively) in the gastrointestinal tract (GIT) of Polish Holstein-Friesian breed cattle. In all analyzed GIT segments, mRNA for all the genes was present in both age groups, confirming their significance in these tissues. Gene expression levels varied distinctly across different GIT segments and between young and mature subjects. The differences between calves and adults were particularly pronounced in areas such as the forestomachs, ileum, and jejunum, indicating potential changes in peptides regulating food intake based on the developmental phase. In mature individuals, the forestomachs predominantly displayed an increase in GHRL expression, while the intestines had elevated levels of GHSR, GPR173, LEP, and NUCB2. In contrast, the forestomachs in calves showed upregulated expressions of LEP, LEPR, and NUCB2, highlighting the potential importance of peptides from these genes in bovine forestomach development.

Diet-ruminal microbiome-host crosstalk contributes to differential effects of calf starter and alfalfa hay on rumen epithelial development and pancreatic α-amylase activity in yak calves

Dietary supplementation of alfalfa hay or calf starter during the preweaning period was beneficial to the gastrointestinal development in dairy calves and lambs. In the present study, we designed 2 experiments using weaning with calf starter and alfalfa hay to investigate the diet-ruminal microbiome-host crosstalk in yak calves by analyzing the ruminal microbiota and rumen epithelial transcriptome. During the preweaning period, supplementation with either alfalfa hay or the starter significantly promoted animal growth and organ development in yak calves, including increases in body weight, body height, body length, chest girth, and development of liver, spleen, and thymus. These improvements could be attributed to increased dry matter intake, rumen fermentation, and development. Butyrate concentration increased in yak calves fed alfalfa hay or the starter, which could further promote ruminal epithelium development. Using 16S rRNA gene amplicon sequencing, we determined that butyrate-producing genera were increased by the supplementation with alfalfa hay or the starter. Transcriptomic analysis of the rumen epithelia revealed that the PI3K-Akt signaling pathway, which is critical in mediating many aspects of cellular function such as cell growth, was upregulated in response to alfalfa hay or the starter supplementation. The starter supplementation also increased the jejunal α-amylase activity, whereas alfalfa hay supplementation reduced the ileal α-amylase activity. Furthermore, the co-supplementation of both the starter and alfalfa hay reduced intestinal α-amylase activity. The starter increased ruminal propionate concentration, whereas alfalfa hay exhibited the opposite trend. The observed opposite effects of the starter and alfalfa hay on rumen propionate concentration corresponded with up- and downregulation, respectively, of the ruminal cholecystokinin involved in pancreatic secretion pathway, and thereby increased and decreased pancreatic α-amylase activity. In conclusion, both alfalfa hay and the starter could promote the growth and ruminal epithelial development of yak calves. The starter and alfalfa hay also differentially affected the intestinal α-amylase activities due to their different chemical components and different effects on ruminal fermentation, especially the ruminal propionate production.

Effects of exchanging lactose for fat in milk replacer on ad libitum feed intake and growth performance in dairy calves

The recent trend in the dairy industry toward ad libitum feeding of young calves merits reconsideration of calf milk replacer (CMR) formulations. Additionally, feed intake regulation in young calves provided with ad libitum milk and solid feeds is insufficiently understood. This study was designed to determine the effect of exchanging lactose for fat in CMR on voluntary feed intake and growth performance. Lactose was exchanged for fat on a weight/weight basis, resulting in different energy contents per kilogram of CMR. Thirty-two male calves (1.7 ± 0.12 d of age, 47.6 ± 0.83 kg of body weight) were assigned to 1 of 16 blocks based on arrival date. Within each block, calves were randomly assigned to 1 of 2 treatments. The experimental period was divided into 4 periods. In period 1, until 14 ± 1.7 d of age, calves were individually housed, restricted-fed their assigned CMR treatments at 2.5 to 3 L twice daily, and provided with unlimited access to water, chopped straw, and starter. In period 2, calves were group-housed with 8 calves per pen and received ad libitum access to their assigned CMR treatments, starter feed, chopped wheat straw, and water. During period 3, from 43 until 63 d of age, calves were weaned by restricting CMR allowance in 2 steps, maintaining access to all other feeds. All calves were completely weaned at d 64 of age and were monitored until 77 d of age (period 4). Measurements included the intake of all dietary components, body weight gain, and a selection of blood traits. Increasing fat content at the expense of lactose decreased CMR intake by 10%, whereas total calculated metabolizable energy intake and growth remained equal between treatments. Total solid feed (starter and straw) consumption was not affected by CMR composition. These data indicate that calves fed ad libitum regulate their CMR intake based on energy content. High-fat CMR increased plasma phosphate, nonesterified fatty acids, triglycerides, and bilirubin, whereas plasma glucose remained unchanged. Despite the limited animal numbers in the present experiment, there was a significant decrease in the total number of health events (mainly respiratory) requiring therapeutic intervention and in the total number of therapeutic interventions in calves fed high-fat CMR. Calves appeared to consume CMR based on energy content, with a difference in ad libitum intake proportional to the difference in energy content of the CMR, maintaining equal body weight gain and solid feed intake.

Sulfated cholecystokinin-8 increases ghrelin secretion but does not affect oxyntomodulin in Holstein steers

The effect of appetite regulatory hormone cholecystokinin (CCK) on the secretions of oxyntomodulin (OXM) and ghrelin, and the effect of ghrelin on the secretions of CCK and OXM were studied in ruminants. Eight Holstein steers, 7 months old, 243 ± 7 kg body weight (BW), were arranged in an incomplete Latin square design (8 animals × 4 treatments × 4 days of sampling). Steers were intravenously injected with 10 µg of sulfated CCK-8/kg BW, 20 µg of acyl ghrelin/kg BW, 100 µg of des-acyl ghrelin/kg BW or vehicle. Blood samples were collected from -60 min to 120 min relative to time of injection. Plasma concentrations of ghrelin, sulfated CCK and OXM were measured by double-antibody radioimmunoassay. Plasma acyl ghrelin was increased to peak level (428.3 ± 6 pg/mL) at 60 min after injection of CCK compared with pre-injected levels (203.3 ± 1 pg/mL). These results showed for the first time, that intravenous bolus injection of CCK increased ghrelin secretion in ruminants. In contrast, injection of ghrelin did not change CCK secretion. Administration of ghrelin or CCK has no effect on plasma OXM concentrations. In conclusion, our results show that administration of CCK increased ghrelin secretion but did not affect OXM release in ruminants. Ghrelin did not affect the secretions of CCK and OXM.

Effects of Na-butyrate supplementation in milk formula on plasma concentrations of GH and insulin, and on rumen papilla development in calves

Although the growth-promoting action of sodium-butyrate (Na-butyrate) used as a feed additive has been observed in calves and pigs, the precise mechanisms involved remain to be clarified. In this study, pre-weaning calves were given milk formula (MF) supplemented with butyrate for 6 weeks to investigate its effects on postprandial changes in the plasma concentrations of metabolic hormones, and, simultaneously, on growth performance, the weight of the digestive organs and rumen papilla development. Ingestion of MF increased (P<0.05) the plasma concentrations of GH and insulin as well as the glucose level, but decreased the non-esterified fatty acid concentration. Na-butyrate supplementation in MF or in lactose solution (with the same quantity of lactose contained in the MF, 5%) suppressed the increase in plasma insulin and GH concentrations, and the plasma IGF1 level was not changed. The length of the rumen papilla and the weight of the perirenal fat tended to increase in the calves fed with Na-butyrate-supplemented MF, but the weight of the liver, spleen, and stomach were not changed. In addition, there was no difference in the expression of mRNA for sodium-dependent glucose transporter-1 in the small intestinal epithelial tissues. We conclude that the accelerated growth performance related to the intake of Na-butyrate used as a feed additive reported previously in several species is partly due to improved insulin sensitivity and a better digestive functional development. These data could be applicable to animal and human nutrition.

Characterization and expression of Ailuropoda melanoleuca leptin (ob gene)

Leptin, an adipocyte-derived hormone, plays important roles in metabolism and reproduction. In this article, we report the cloning, expression, and identification of the giant panda leptin (gLeptin) gene and its variants. The gLeptin cDNA was 504 bp long, encoding a precursor peptide of 167 amino acids including 21 residues of signal peptide. A short variant of gLeptin was 501 bp long, encoding a 166-aa peptide and also including a 21-aa signal peptide. Giant panda leptin was 99.4%, 94.6%, and 92.8% identical to that of black bear, dog, and cat, respectively, but was only 81.4% and 80.8% identical to that of human and rat. The cloned gLeptin gene was expressed in Escherichia coli, with expression confirmed by Western blotting and MALDI-TOF-TOF MS PMF. After purification, renaturation, and condensation, the gLeptin protein was injected into Kunming mice. The recombinant gLeptin significantly inhibited food intake by 41.8% and reduced body weight by 5.1% in the mice.

Gastrin, cholecystokinin and gastrointestinal tract functions in mammals

The aim of the present review is to synthesise and summarise our recent knowledge on the involvement of cholecystokinin (CCK) and gastrin peptides and their receptors in the control of digestive functions and more generally their role in the field of nutrition in mammals. First, we examined the release of these peptides from the gut, focusing on their molecular forms, the factors regulating their release and the signalling pathways mediating their effects. Second, general physiological effects of CCK and gastrin peptides are described with regard to their specific receptors and the role of CCK on vagal mucosal afferent nerve activities. Local effects of CCK and gastrin in the gut are also reported, including gut development, gastrointestinal motility and control of pancreatic functions through vagal afferent pathways, including NO. Third, some examples of the intervention of the CCK and gastrin peptides are exposed in diseases, taking into account intervention of the classical receptor subtypes (CCK1 and CCK2 receptors) and their heterodimerisation as well as CCK-C receptor subtype. Finally, applications and future challenges are suggested in the nutritional field (performances) and in therapy with regards to the molecular forms or in relation with the type of receptor as well as new techniques to be utilised in detection or in therapy of disease. In conclusion, the present review underlines recent developments in this field: CCK and gastrin peptides and their receptors are the key factor of nutritional aspects; a better understanding of the mechanisms involved may increase the efficiency of the nutritional functions and the treatment of abnormalities under pathological conditions.

Associations between blood gastrin, ghrelin, leptin, pepsinogen and Ostertagia ostertagi antibody concentrations and voluntary feed intake in calves exposed to a trickle infection with O. ostertagi

Twenty-five, castrated male Holstein-cross calves, between 4 and 5 months of age, weighing 156.5+/-12.2 kg and reared under conditions designed to minimise the risk of parasitic infection, were allocated to one of the five treatment groups on the basis of initial bodyweight. The groups were (1) ad libitum (ad lib) fed controls (ALC); (2) ad lib fed infected (INF) and treated with topical eprinomectin on Day 56; (3) controls pair-fed with the INF group (PFC); (4) ad lib fed controls treated with eprinomectin on Days 0 and 56 (E-ALC) and (5) ad lib fed, infected and treated with eprinomectin on Days 0 and 56 (E-INF). Infection comprised a trickle infection with the equivalent of 10,000 larvae of Ostertagia ostertagi per day from Day 0 to Day 56 and the study concluded on Day 77. Parameters measured throughout the study included: liveweight, feed intake, faecal egg counts; plasma pepsinogen, gastrin, ghrelin and leptin; plasma antibodies to adult O. ostertagi. No significant differences in feed intake or liveweight gain were observed between any of the different groups, a finding thought to result from the high quality of feed offered. Significant differences between the INF and control groups however were observed in faecal egg counts, plasma pepsinogen, gastrin and O. ostertagi antibodies, which were all elevated, and leptin, which was reduced. Values of these parameters for the E-INF group were intermediate between the INF and ALC groups. Plasma ghrelin showed no association with either feed intake or parasitism. Further studies are needed to fully elucidate the roles of various biochemical and neuroendocrine mediators for inappetence in ruminants with parasitic gastroenteritis.

Combined administration of ghrelin and GHRH synergistically stimulates GH release in Holstein preweaning calves

Ghrelin is a gut peptide which participates in growth regulation through its somatotropic, lipogenic and orexigenic effects. Synergism of ghrelin and growth hormone-releasing hormone (GHRH) on growth hormone (GH) secretion has been reported in humans and rats, but not in domestic animals in vivo. In this study, effects of a combination of ghrelin and GHRH on plasma GH and other metabolic parameters, and changes in plasma active and total ghrelin levels were studied in Holstein bull calves before and after weaning. Six calves were intravenously injected with vehicle (0.1% BSA-saline), ghrelin (1 microg/kg BW), GHRH (0.25 microg/kg BW) or a combination of ghrelin plus GHRH at the age of 5 weeks and 10 weeks (weaning at 6 weeks of age). Ghrelin stimulated GH release with similar potency as GHRH and their combined administration synergistically stimulated GH release in preweaning calves. After weaning, GH responses to ghrelin and GHRH became greater compared with the values of preweaning calves, but a synergistic effect of ghrelin and GHRH was not observed. The GH areas under the concentration curves for 2h post-injection were greater in weaned than in preweaning calves (P<0.05) if ghrelin or GHRH were injected alone, but were similar if ghrelin and GHRH were injected together. Basal plasma active and total ghrelin levels did not change around weaning, but transiently increased after ghrelin injection. Basal plasma insulin, glucose and non-esterified fatty acid levels were reduced after weaning, but no changes by treatments were observed. In conclusion, ghrelin and GHRH synergistically stimulated GH release in preweaning calves, but this effect was lost after weaning.

Identification of differentially expressed transcripts in bovine rumen and abomasum using a differential display method

The rumen has several important physiological functions: absorption, transport, metabolic activity, and protection. To clarify the molecular basis underlying the physiological function of the rumen, reticulum, omasum, and abomasum, we used mRNA differential display to isolate and identify differentially expressed genes in these tissues. We isolated 18 transcripts that coexpressed in the rumen, reticulum, and omasum. Five genes, ribosomal protein 19 (RPS19), basic helix-loop-helix domain containing class B2 (BHLHB2), NADH dehydrogenase flavoprotein 2 (NDUFV2), exosome component 9 (EXOSC9), and ribosomal protein 23 (RPS23), were highly expressed in the rumen of adult Holstein and Japanese Black cattle. Significant differences of expression were observed in the abomasum compared with the rumen, reticulum, and omasum. To investigate the expression pattern of these genes during the neonatal growth stage, the relative levels of gene expression were analyzed in the rumen and abomasum of 3-wk-, 13-wk-, and 18- to 20-mo-old Holstein cattle. The expression level of RPS19 did not change with age in the rumen and abomasum. The levels of BHLHB2, NDUFV2, and EXOSC9 mRNA in the abomasum decreased (P < 0.05) after weaning and declined (P < 0.05) further in adults; in contrast, expression in the rumen was not altered. Interestingly, the levels of RPS23 mRNA in the rumen increased (P < 0.05) after weaning and further increased in the adult; however, the level of expression of this gene decreased (P < 0.05) in the abomasum with weaning and age. This indicates that the 4 tissues, especially the rumen and abomasum, have different developmental pathways after birth and subsequent onset of rumination.

Developmental changes in the kinetics of glucose and urea in Holstein calves

Because weaning is the point when the nutrient composition of feed changes for the neonatal ruminant, the present experiment was conducted to assess the developmental changes in the kinetics of glucose and urea over this period, using stable isotopes of glucose and urea, at 4, 13, and 24 wk in calves. Plasma concentrations of nonesterified fatty acids, amino-N, urea-N, and insulin-like growth factor-I increased, but that of growth hormone decreased with age. The plasma glucose concentration increased at 13 wk of age and thereafter decreased at 24 wk of age. The glucose irreversible loss and recycling rates were significantly higher at 4 wk of age than at 13 and 24 wk of age. On the other hand, the irreversible loss and recycling rates of urea, as well as the urea pool size, were higher at 24 wk of age than at 4 and 13 wk. It is concluded that weaning at 6 wk is the pivotal time for the alteration of glucose kinetics. However, the aging process, but not weaning, is important for changes in the kinetics of urea in calves.

Growth hormone and lactogenic hormones can reduce the leptin mRNA expression in bovine mammary epithelial cells

Leptin mRNA is expressed in not only adipocytes but also mammary epithelial cells and leptin protein is present in milk. Although milk leptin is thought to influence metabolism or the immune system in neonates, there is little information about the regulation of leptin expression in mammary epithelial cells. We examined the effect of growth hormone (GH) and/or lactogenic hormone complex (DIP; dexamethasone, insulin and prolactin) on leptin mRNA expression in mammary epithelial cells. We used a bovine mammary epithelial cell (BMEC) clonal line, which was established from a 26-day pregnant Holstein heifer. We confirmed that the mRNA was expressed in BMECs and the expression was significantly reduced by GH and/or DIP, when the cells were cultured on both plastic plates and cell culture inserts at days 2 and 7 after stimulation with lactogenic hormones. GH and/or DIP significantly increased level of alpha-casein mRNA in BMECs after 7 days on the cell culture inserts, but no mRNA expression was detected at day 2. GH and DIP significantly stimulated the secretion of alpha-casein from BMEC on cell culture inserts at 3.5 and 7 days. However, neither alpha-casein mRNA expression nor secretion was observed in the BMECs cultured on plastic dishes, even in the presence of GH or/and DIP. These results indicate that GH and DIP can directly reduce leptin mRNA expression in both undifferentiated and functionally differentiated bovine mammary epithelial cell.

Leptin expression in ruminants: nutritional and physiological regulations in relation with energy metabolism

Leptin, mainly produced in adipose tissue (AT), is a protein involved in the central and/or peripheral regulation of body homeostasis, energy intake, storage and expenditure, fertility and immune functions. Its role is well documented in rodent and human species, but less in ruminants. This review is focused on some intrinsic and extrinsic factors which regulate adipose tissue leptin gene expression and leptinemia in cattle, sheep, goat and camel: age, physiological status (particularly pregnancy and lactation) in interaction with long-term (adiposity) and short-term effects of feeding level, energy intake and balance, diet composition, specific nutrients and hormones (insulin, glucose and fatty acids), and seasonal non-dietary factors such as photoperiod. Body fatness strongly regulates leptin and its responses to other factors. For example, leptinemia is higher after underfeeding or during lactation in fat than in lean animals. Physiological status per se also modulates leptin expression, with lactation down-regulating leptinemia, even when energy balance (EB) is positive. These results suggest that leptin could be a link between nutritional history and physiological regulations, which integrates the animal's requirements (e.g., for a pregnancy-lactation cycle), predictable food availability (e.g., due to seasonal variations) and potential for survival (e.g., body fatness level). Reaching permissive leptin thresholds should be necessary for pubertal or postpartum reproductive activity. In addition to the understanding of leptin yield regulation, these data are helpful to understand the physiological significance of changes in leptin secretion and leptin effects, and how husbandry strategies could integrate the adaptative capacities of ruminant species to their environment.

Expression of leptin and its receptors in various tissues of ruminants

The energy metabolism of domestic animals is under the control of hormonal factors, which include thyroid hormones and leptin. Leptin signals from the periphery to the centre. It is mostly produced in the white adipose tissue and informs the central nervous system (CNS) about the total fat depot of the body. Low and high levels of leptin induce anabolic and catabolic processes, respectively. Besides controlling the food uptake and energy expenditure leptin is also involved in regulation of the reproduction and the immune system. Leptin is produced in several tissues other than fat. In the present paper the leptin expression of ruminant (Egyptian water buffalo, cow, and one-humped camel) tissues are examined. The mammary gland produces leptin in each species investigated. The local hormone production contributes to milk leptin and most probably helps to maintain lactation. Considerable leptin receptor expression was observed in the milk-producing epithelial cells, which is the same cell type that produces most of the udder leptin. Based on the results tissues participating in production have an autoregulative mechanism through which tissues can be relatively independent of the plasma leptin levels in order to maintain the desired function.

Effects of long-chain fatty acids on cytosolic triacylglycerol accumulation and lipid droplet formation in primary cultured bovine mammary epithelial cells

Mammary epithelial cells have recently been shown to express and secrete leptin into milk and to accumulate triacylglycerol (TAG) in cytosol. We examined the effects on the accumulation of cytosolic TAG of free fatty acid addition to the medium bathing bovine mammary epithelial cells (bMEC). Both saturated (palmitic and stearic) and unsaturated (oleic and linoleic) fatty acids stimulated the accumulation of TAG in a concentration-dependent manner from 50 to 400 microM and the expression of mRNA expression for CD36, which is involved in the uptake and secretion of long-chain fatty acids. However, leptin mRNA expression and lipid droplet formation were significantly increased only by the addition of unsaturated, but not saturated, fatty acids. Interestingly, both types of fatty acids stimulated alphas1-casein mRNA expression. These data suggest that the expression of leptin is related to droplet formation, whereas CD36 is related to cytosolic TAG accumulation, and that fatty acids or cytosolic TAG accumulation also have a role to accelerate differentiation of bMEC as shown by casein synthesis.

Partial cloning and localization of leptin and leptin receptor in the mammary gland of the Egyptian water buffalo

Originally an overall metabolic control was attributed to the leptin hormone, which is produced mainly by the adipose tissue. Recently, leptin gene expression was demonstrated in several additional peripheral tissues. Furthermore, several isoforms of leptin receptor were found both in the central nervous system and in the peripheral tissues. Using reverse transcription and polymerase chain reaction analysis we demonstrate that leptin is expressed both in the adipose tissue and in the lactating mammary gland tissue of Egyptian water buffalo. Our results show that, short and long isoforms of leptin receptor are expressed in buffalo mammary gland tissue. We have partially cloned the buffalo leptin and its short and long isoforms of receptor, which show a high sequence homology to previously published sequences of other mammalian species especially to that of other ruminants. Localization of leptin and its receptor mRNA transcripts, as determined by in situ hybridization procedure, revealed that leptin and its receptor transcripts are expressed specifically in the alveolar epithelial cells of the mammary gland. These morphological data support that leptin could also act as an autocrine and paracrine mediator for mammary gland metabolism and as a facilitator of alveolar epithelial cell activity during lactation.