Effects of parturition and feed restriction on concentrations and distribution of the insulin-like growth factor-binding proteins in plasma and cerebrospinal fluid of dairy cows

Effect of IGFBP-4 during In Vitro Maturation on Developmental Competence of Bovine Cumulus Oocyte Complexes

Insulin-like growth factors (IGFs) are essential for oocyte maturation. Their bioavailability is regulated by their respective binding proteins (IGFBPs) and proteases. IGFBP-4 blocks the biological effects of IGFs. High IGFBP-4 expression has been associated with follicle atresia. We hypothesized that IGFBP-4 affects oocyte developmental competence during maturation. Therefore, the aim of this study was to examine the effect of IGFBP-4 on the developmental rate of bovine cumulus-oocyte complexes (COCs) during in vitro embryo production. Abattoir-derived COCs were matured with rbIGFBP-4 (2000, 540, and 54 ng/mL) compared to a control. Cumulus expansion, oocyte maturation, cleavage, blastocyst, and hatching rates were evaluated. Furthermore, blastocyst gene expression of SOCS2, STAT3, SLC2A1, SLCA3, BAX, and POU5F1 transcripts were quantified using RT-qPCR. No statistical differences were detected among the groups for cumulus expansion, maturation, cleavage, blastocyst rates, or all gene transcripts analyzed. However, at day 8 and 9, the number of total hatching and successfully hatched blastocysts was lower in 2000 ng/mL rbIGFBP-4 compared to the control (day 8: total hatching: 17.1 ± 0.21 vs. 31.2 ± 0.11%, p = 0.02 and hatched blastocyst 6.7 ± 0.31 vs. 21.5 ± 0.14%, p = 0.004; day 9 total hatching 36.4 ± 0.18 vs. 57.7 ± 0.10%, p = 0.009 and hatched blastocyst 18.2 ± 0.21 vs. 38.1 ± 0.11%, p = 0.004). We concluded that high concentrations of rbIGFBP-4 might negatively affect the subsequent ability of the embryo to hatch and possibly compromise further elongation.

Effects of a combined essential fatty acid and conjugated linoleic acid abomasal infusion on metabolic and endocrine traits, including the somatotropic axis, in dairy cows

The objective of this study was to test the effects of essential fatty acids (EFA), particularly α-linolenic acid (ALA), and conjugated linoleic acid (CLA) supplementation on metabolic and endocrine traits related to energy metabolism, including the somatotropic axis, in mid-lactation dairy cows. Four cows (126 ± 4 d in milk) were used in a dose-escalation study design and were abomasally infused with coconut oil (CTRL; 38.3 g/d; providing saturated fatty acids), linseed and safflower oils (EFA; 39.1 and 1.6 g/d; n-6:n-3 FA ratio = 1:3), Lutalin (CLA; cis-9,trans-11 and trans-10,cis-12 CLA, 4.6 g/d of each), or EFA and CLA (EFA+CLA) for 6 wk. The initial dosage was doubled twice after 2 wk, resulting in 3 dosages (dosages 1, 2, and 3). Each cow received each fat treatment at different times. Cows were fed with a corn silage-based total mixed ration providing a low-fat content and a high n-6:n-3 fatty acid ratio. Plasma concentrations of metabolites and hormones (insulin-like growth factor-binding proteins only on wk 0 and 6) were analyzed at wk 0, 2, 4, and 6 of each treatment period. Liver biopsies were taken before starting the trial and at wk 6 of each treatment period to measure hepatic mRNA abundance of genes linked to glucose, cholesterol and lipid metabolism, and the somatotropic axis. The changes in the milk and blood fatty acid patterns and lactation performance of these cows have already been published in a companion paper. The plasma concentration of total cholesterol increased with dosage in all groups, except CLA, reaching the highest levels in EFA+CLA and CTRL compared with CLA. The high-density lipoprotein cholesterol plasma concentration increased in CTRL and was higher than that in EFA and CLA, whereas the concentration of low-density lipoprotein cholesterol increased in a dose-dependent manner in EFA and EFA+CLA, and was higher than that in CLA. Hepatic mRNA expression of 3-hydroxy-3-methyl-glutaryl-CoA synthase 1 was upregulated in all groups but was highest in EFA+CLA. Expression of sterol regulatory element-binding factor 1 tended to be lowest due to EFA treatment, whereas expression of long chain acyl-CoA-synthetase was lower in EFA than in CTRL. Hepatic mRNA expression of GHR1A tended to be higher in EFA+CLA than in CTRL. The plasma concentration of insulin-like growth factor I increased in CLA, and the plasma IGFBP-2 concentration was lower in EFA+CLA than in CTRL at wk 6. The plasma concentration of adiponectin decreased in EFA+CLA up to dosage 2. Plasma concentrations of albumin and urea were lower in CLA than in CTRL throughout the experimental period. Supplementation with EFA and CLA affected cholesterol and lipid metabolism and their regulation differently, indicating distinct stimulation after the combined EFA and CLA treatment. The decreased IGFBP-2 plasma concentration and upregulated hepatic mRNA abundance of GHR1A in EFA+CLA-supplemented cows indicated the beneficial effect of the combined EFA and CLA treatment on the somatotropic axis in mid-lactation dairy cows. Moreover, supplementation with CLA might affect protein metabolism in dairy cows.

Effects of colostrum instead of formula feeding for the first 2 days postnatum on whole-body energy metabolism and its endocrine control in neonatal calves

Colostrum provides high amounts of nutritive and non-nutritive substrates, which are essential for calf nutrition and passive immunization. Colostral growth factors and hormones have beneficial effects on postnatal maturation and may affect substrate utilization and energy expenditure in neonatal calves. We tested the hypothesis that energy metabolism and its endocrine regulation differ during the first 10 d of life in calves fed either colostrum or a milk-based formula with a similar nutrient composition to colostrum, but largely depleted of bioactive substances, for the first 2 d postnatum. Male Holstein calves (n = 18) were fed either pooled colostrum (COL; n = 9) or a milk-based formula (FOR; n = 9) for the first 2 d of life. From d 3 on, all calves received same milk replacer. On d 2 and 7 of life, calves were placed in a respiration chamber for indirect calorimetric measurements to calculate heat production, fat (FOX) and carbohydrate oxidation (COX), as well as respiratory quotient. Blood was sampled on d 1 before first colostrum intake and on d 2, 3, 7, 8, 9, and 10 before morning feeding, to measure plasma concentrations of immunoglobulins, metabolites, and hormones. Additional postprandial blood samples were taken on d 1 and 9 at 30, 60, 120, 240, and 420 min after milk feeding. Liver samples were collected on d 10 of life to determine gene expression related to energy metabolism. Formula-fed calves showed lower plasma concentrations of total protein, immunoglobulins, haptoglobin, leptin, adiponectin, and insulin-like growth factor (IGF) binding protein (IGFBP)-4 during the whole study but temporarily higher plasma concentrations of urea, insulin, glucagon, triglyceride, and cholesterol on the first day after feeding, compared with concentrations in COL. The temporary increase in glucagon, triglyceride, and cholesterol on d 1 reversed on d 2 or 3, showing higher concentrations in COL than in FOR calves. In FOR, IGF-I, IGFBP-2, and IGFBP-3 were lower on d 3 than in COL. Interestingly, FOR calves had higher heat production during respiratory measurements on d 2 and higher body temperature on d 2, 3, and 5 than those of COL. The hepatic mRNA abundance of cytosolic phosphoenolpyruvate carboxykinase was higher in FOR than in COL. Our results indicate that first milk feeding after birth influenced whole-body energy expenditure but not FOX and COX in neonatal calves, and the absorption of colostral leptin and adiponectin might affect insulin sensitivity on d 1 of life.

Modulation of growth hormone receptor-insulin-like growth factor 1 axis by dietary protein in young ruminants

A reduced protein intake causes a decrease in insulin-like growth factor 1 (IGF1) concentrations and modulates Ca homoeostasis in young goats. IGF1 is synthesised by the liver in response to stimulation by growth hormone (GH). Due to rumino-hepatic circulation of urea, ruminants are suitable for investigating the effects of protein reduction despite sufficient energy intake. The present study aimed to investigate the impact of a protein-reduced diet on the expression of components of the somatotropic axis. Male young goats were divided into two feeding groups receiving either a control diet (20 % crude protein (CP)) or a reduced-protein diet (9 % CP). Blood concentrations of IGF1 and GH were measured, and a 24-h GH secretion profile was compiled. Moreover, ionised Ca and insulin concentrations as well as mRNA and protein expression levels of hepatic proteins involved in GH signalling were quantified. Due to the protein-reduced diet, concentrations of ionised Ca, insulin and IGF1 decreased significantly, whereas GH concentrations remained unchanged. Expression levels of the hepatic GH receptor (GHR) decreased during protein reduction. GHR expression was down-regulated due to diminished insulin concentrations as both parameters were positively correlated. Insulin itself might be reduced due to reduced blood Ca levels that are involved in insulin release. The protein-reduced diet had an impact on the expression of components of the somatotropic axis as a disruption of the GH–IGF1 axis brought about by diminished GHR expression was shown in response to a protein-reduced diet.

Effect of adipocyte-derived IGF-I on adipose tissue mass and glucose metabolism in the Berlin Fat Mouse

Besides liver, IGF-I is expressed in adipose tissue. However, the effects of this local IGF-I on adipose tissue and metabolism are unclear. We generated adipocyte-specific knock-out mice on the background of the Berlin Fat Mouse Inbred (BFMI) line to evaluate the contribution of adipocyte-IGF-I on glucose metabolism and adipose tissue development. BFMI mice are obese, non-diabetic with elevated plasma insulin and IGF-I concentration. The knock-out in adipocytes led to a total white adipose tissue expression of 50-60% due to unaltered Igf-1 expression in stromavascular cells. The lack of IGF-I from adipocytes did not alter plasma IGF-I concentration. BFMI^Chr3-Igf-I-KO^Q-AT mice had reduced adipose tissue mass in most depots. During oral glucose tolerance tests, BFMI^Chr3-Igf-I-KO^Q-AT mice showed an impaired glucose clearance (p = .03). Interestingly, insulin action was enhanced during insulin tolerance tests (p = .05). In conclusion, adipocyte-specific IGF-I ablation in obese BFMI mice results in reduced adipose tissue mass and thereby alters glucose metabolism.

Increased Concentrations of Insulin-Like Growth Factor Binding Protein (IGFBP)-2, IGFBP-3, and IGFBP-4 Are Associated With Fetal Mortality in Pregnant Cows

Insulin-like growth factors (IGFs) play a critical role in fetal growth, and components of the IGF system have been associated with fetal growth restriction in women. In human pregnancy, the proteolytic cleavage of insulin-like growth factor binding proteins (IGFBPs), particularly IGFBP-4, releases free IGF for respective action at the tissue level. The aim of the present study was to determine IGFBP-2, IGFBP-3, and IGFBP-4 concentrations by Western ligand blotting during pregnancy until day 100 in cows and to compare these concentrations with those of non-pregnant cows and cows undergoing embryonic/fetal mortality. Therefore, two study trials (I and II) and an in vitro study were conducted. In study I, 43 cows were not pregnant, 34 cows were pregnant, and 4 cows were undergoing fm. In study II, 500 cows were examined, and 7 cases of pregnancy loss between days 24-27 and 34-37 after artificial insemination (AI, late embryonic mortality; em) and 8 cases of pregnancy loss between days 34-37 and 54-57 after AI (late embryonic mortality and early fetal mortality; em/fm) were defined from the analyses of 30 pregnant and 20 non-pregnant cows randomly selected for insulin-like growth factor 1 and IGFBP analyses. In vitro serum from pregnant (n = 3) and non-pregnant (n = 3) cows spiked after incubation with recombinant human (rh) IGFBP-4 for 24 h, and IGFBP-4 levels were analyzed before and after incubation to detect proteolytic degradation. The IGFBP-2, -3, and -4 concentrations did not decline during early pregnancy in cows, while IGFBP-4 concentrations were comparable between pregnant and non-pregnant cows, irrespective of low proteolytic activity, which was also demonstrated in cows. Interestingly, cows with em or fm showed distinct IGFBP patterns. The IGFBP-2 and -3 concentrations were higher (P < 0.05) in cows with fm compared to pregnant. The IGFBP-4 levels were significantly higher in cows developing fm. Thus, distinct differences in the circulating IGFBP concentrations could be associated with late embryonic and early fetal losses in cattle.

Analysis of the IGF-system in milk from farm animals - Occurrence, regulation, and biomarker potential

IGFs and IGF-binding proteins (IGFBPs) are abundantly present in milk and in dairy products. Compared to the IGFs, the IGFBP have received less attention in milk, although truncated IGFBPs and IGFBP-glycosylation have been described in milk. Thereby, complex control of local IGF-effects can be assumed on the levels of IGFBPs, proteases, and protease inhibitors. The present review collects the current knowledge both on presence and regulation of IGFs and IGFBPs in milk particularly from dairy animal species. As a rule higher levels of IGF-I, IGF-II, and IGFBPs are measured around parturition if compared to later time-points of lactation. In all farm animal species included in this review, it is found that the relative abundancies of IGFBPs in milk and serum are similar, with IGFBP-3 and -2 characterized by higher concentrations if compared to IGFBP-4 or -5. The concentrations of IGFs and IGFBPs in milk or dairy products can be altered by hormones, dairy processing, or fermentation. Because milk can be used for non-invasive biomarker research, quality management, and health monitoring, we discuss novel directions of IGF-analysis and potential on-site biomarker research in milk.

Effects of Feeding Milk Replacer Ad Libitum or in Restricted Amounts for the First Five Weeks of Life on the Growth, Metabolic Adaptation, and Immune Status of Newborn Calves

The pre-weaning period is critical for calf health and growth, and intensive milk feeding programs may assist postnatal development by improving body growth and organ maturation. The aim of the present work was to study the effects of ad libitum milk replacer (MR) feeding on the growth, metabolic adaptation, health, and immune status of newborn calves. Twenty-eight newborn Holstein and Holstein x Charolais crossbred calves were fed ad libitum (ADLIB) or in restricted amounts (6 liters per day; RES) during the first five weeks of life. The MR intake in the ADLIB treatment was gradually reduced at weeks 6 and 7, and all calves then received 6 liters of MR per day until day 60. Blood samples were collected to measure the plasma concentrations of metabolites, insulin, insulin-like growth factor (IGF)-I and IGF binding proteins (IGFBP), immunoglobulins, and acute phase proteins. The expression of mRNA associated with both the somatotropic axis and gluconeogenic enzymes was measured in the liver on day 60. Intensive feeding improved MR intake and growth in ADLIB without influencing concentrate intake. Carcass weight, perirenal fat, and muscle mass were greater in ADLIB. Plasma concentrations of glucose, triglycerides, insulin, and IGF-I were greater, whereas plasma concentrations of β-hydroxybutyrate, total protein, albumin, urea, IGFBP-2 and -4, and fibrinogen were lower at distinct time points in ADLIB. The hepatic mRNA expression of cytosolic phosphoenolpyruvate carboxykinase was greater in ADLIB. Most metabolic and endocrine differences occurred during the MR feeding period, but a slightly greater concentrate intake was associated with increased plasma IGF-I and insulin at the end of the study. The immune and health status of the calves were not affected by MR feeding. However, increased plasma fibrinogen in the RES group suggested differences in the acute phase response.

Serum IGFBP4 concentration decreased in dairy heifers towards day 18 of pregnancy

This study was conducted to determine if the main components of the somatotropic axis change during the early phase of pregnancy in the maternal blood system and whether differences exist on day 18 after pregnancy recognition by the maternal organism. Blood samples of pregnant heifers (Holstein Friesian; n = 10 after embryo transfer) were obtained on the day of ovulation (day 0), as well as on days 7, 14, 16 and 18 and during pregnant, non-pregnant and negative control cycles. The oncentrations of progesterone (P₄), oestrogen, growth hormone (GH), insulin-like growth factor-1 and -2 (IGF1, -2) and IGF-binding protein-2, -3 and -4 (IGFBP2, -3, -4) were measured. The mRNA expressions of growth hormone receptor 1A, IGF1, IGF2, IGFBP2, IGFBP3 and IGFBP4 were detected using RT-qPCR in liver biopsy specimens (day 18). In all groups, total serum IGF1 decreased from day 0 to 16. Notably, IGFBP4 maternal blood concentrations were lower during pregnancy than during non-pregnant cycles and synchronized control cycles. It can be speculated that the lower IGFBP4 in maternal blood may result in an increase of free IGF1 for local action. Further studies regarding IGFBP4 concentration and healthy early pregnancy are warranted.

Quantitative Western ligand blotting reveals common patterns and differential features of IGFBP-fingerprints in domestic ruminant breeds and species

The insulin-like growth factor binding proteins (IGFBPs) are determinants of local IGF-effects and thus have an impact on growth and metabolism in vertebrate species. In farm animals, IGFBPs are associated with traits such as growth rate, body composition, milk production, or fertility. It may be assumed, that selective breeding and characteristic phenotypes of breeds are related to differential expression of IGFBPs. Therefore, the aim of the present study was to investigate the effects of selective breeding on blood IGFBP concentrations of farm animals. Breeds of the sheep, goat, and cattle species were investigated. IGFBP-3, -2, and -4 were analyzed with quantitative Western ligand blotting (qWLB), enabling comprehensive monitoring of intact IGFBPs with IGF-binding capacity. We show that in sera of all species and breeds investigated, IGFBP-3, -2, and -4 were simultaneously detectable by qWLB analysis. IGFBP-3 and the total amount of IGFBPs were significantly increased (P<0.05) in Cameroon sheep, if compared to 3 of 4 other sheep breeds, as well as in Dwarf goats versus Toggenburg and Boer goats (P<0.01). IGFBP-2 was elevated in Cameroon sheep and Boer goats, if compared to other breeds of these species (P<0.01), respectively. Holstein Friesian dairy cows had higher levels of IGFBP-4 (P<0.05), if compared to conventional crossbreeds of beef cattle. In Dwarf goats the ratio of IGFBP-3/IGFBP-2 was about 3-fold higher than in other goat breeds (P<0.001). The total IGFBP amount of Toggenburg goats was reduced (P<0.05), compared to the other goat breeds. In conclusion, our data indicate that common and specific features of IGFBP fingerprints are found in different ruminant species and breeds. Our findings may introduce quantitative Western ligand blotting as an attractive tool for biomarker development and molecular phenotyping in farm animal breeds.

Methylating micronutrient supplementation during pregnancy influences foetal hepatic gene expression and IGF signalling and increases foetal weight

PURPOSE

Maternal diet during pregnancy impacts foetal growth and development. In particular, dietary levels of methylating micronutrients (methionine, folate, choline, vitamins B6, and B12) interfere with the availability and allocation of methyl groups for methylation reactions, thereby influencing normal transcription. However, the currently recommended methylating micronutrient supplementation regimen is haphazard and arbitrary at best.

METHODS

To investigate the effects of a methylating micronutrient-rich maternal diet, pregnant Pietrain sows were fed either a standard diet (CON) or a diet supplemented with methionine, folate, choline, B6, B12, and zinc (MET). Foetal liver and muscle (M. longissimus dorsi) tissues were collected at 35, 63, and 91 days post-conception. Transcriptional responses to diet were assessed in foetal liver. Altered insulin-like growth factor (IGF) signalling in transcriptome analyses prompted investigation of IGF-2 and insulin-like growth factor binding proteins (IGFBPs) levels in muscle and liver.

RESULTS

Maternal diet enriched with methylating micronutrients was associated with increased foetal weight in late gestation. Hepatic transcriptional patterns also revealed differences in vitamin B6 and folate metabolism between the two diets, suggesting that supplementation was effective. Additionally, shifts in growth-supporting metabolic routes of the lipid and energy metabolism, including IGF signalling, and of cell cycle-related pathways were found to occur in liver tissue in supplemented individuals. Weight differences and modulated IGF pathways were also reflected in the muscle content of IGF-2 (increased in MET) and IGFBP-2 (decreased in MET).

CONCLUSIONS

Maternal dietary challenges provoke stage-dependent and tissue-specific transcriptomic modulations in the liver pointing to molecular routes contributing to the organismal adaptation. Subtle effects on late foetal growth are associated with changes in the IGF signalling mainly in skeletal muscle tissue that is less resilient to dietary stimuli than liver.

Validation of serum IGF-I as a biomarker to monitor the bioactivity of exogenous growth hormone agonists and antagonists in rabbits

The development of new growth hormone (GH) agonists and growth hormone antagonists (GHAs) requires animal models for pre-clinical testing. Ideally, the effects of treatment are monitored using the same pharmacodynamic marker that is later used in clinical practice. However, intact rodents are of limited value for this purpose because serum IGF-I, the most sensitive pharmacodynamic marker for the action of GH in humans, shows no response to treatment with recombinant human GH and there is little evidence for the effects of GHAs, except when administered at very high doses or when overexpressed. As an alternative, more suitable model, we explored pharmacodynamic markers of GH action in intact rabbits. We performed the first validation of an IGF-I assay for the analysis of rabbit serum and tested precision, sensitivity, linearity and recovery using an automated human IGF-I assay (IDS-iSYS). Furthermore, IGF-I was measured in rabbits of different strains, age groups and sexes, and we monitored IGF-I response to treatment with recombinant human GH or the GHA Pegvisomant. For a subset of samples, we used LC-MS/MS to measure IGF-I, and quantitative western ligand blot to analyze IGF-binding proteins (IGFBPs). Although recovery of recombinant rabbit IGF-I was only 50% in the human IGF-I assay, our results show that the sensitivity, precision (1.7–3.3% coefficient of variation) and linearity (90.4–105.6%) were excellent in rabbit samples. As expected, sex, age and genetic background were major determinants of IGF-I concentration in rabbits. IGF-I and IGFBP-2 levels increased after single and multiple injections of recombinant human GH (IGF-I: 286±22 versus 434±26 ng/ml; P<0.01) and were highly correlated (P<0.0001). Treatment with the GHA lowered IGF-I levels from the fourth injection onwards (P<0.01). In summary, we demonstrated that the IDS-iSYS IGF-I immunoassay can be used in rabbits. Similar to rodents, rabbits display variations in IGF-I depending on sex, age and genetic background. Unlike in rodents, the IGF-I response to treatment with recombinant human GH or a GHA closely mimics the pharmacodynamics seen in humans, suggesting that rabbits are a suitable new model to test human GH agonists and antagonists.