To date, husbandry categories are defined based on the human concept of animal needs, however, to objectively assess animal welfare in defined husbandry systems, animal-related indicators must be evaluated. Here, we studied the impact of differential housing conditions on factors of the insulin-like growth factor system (IGF-system) in mother sows either housed in a conventional husbandry system corresponding to the regulations of the German husbandry form 1, or in the associated ecological facility, corresponding to the German husbandry form 4/5. Utilizing a proprietary bioassay that determines the activity of the IGF system at the level of intracellular signal transduction, we revealed altered serum IGF bioactivities in differentially housed sows. Moreover, we present a comprehensive analysis of the individual factors of the IGF system in serum of pregnant and lactating sows to elucidate which of these are modified depending on the housing conditions. An unsupervised principal component analysis suggests that IGF system factors might distinguish sows based on their housing environment. These results imply that the IGF system provides a solid basis for the documentation and objective assessment of animal health and welfare. However, a robust biomarker system for animal welfare assessment will likely require a multifactorial and integrative approach.

Thyroid hormones (THs) are fundamental regulators of skeletal muscle energy metabolism and protein turnover. Instead of directly stimulating muscle growth, they create the intracellular environment required for effective adaptation to exercise. Adequate TH availability supports mitochondrial integrity, ribosome biogenesis, and coordinated protein turnover, thereby enabling the translation of anabolic signaling into structural adaptation and remodeling. Accordingly, reduced translational efficiency during hypothyroidism may blunt hypertrophic responses. In contrast, hyperthyroidism accelerates proteolytic pathways and compromises net protein gain despite elevated turnover. Training modalities determine the physiological outcome within this endocrine context, with endurance exercise primarily enhancing oxidative remodeling, while resistance training, when sufficient biosynthetic capacity is present, can stimulate myofibrillar accretion. Reduced energy availability lowers T3 concentrations and may attenuate adaptive efficiency across both modalities. Overall, thyroid status emerges as a critical determinant of muscle remodeling capacity, underscoring the clinical relevance of thyroid assessment in exercise-based interventions.

The insulin-like growth factor (IGF) system represents the most important endocrine system for controlling muscle accretion. Substantial evidence has been provided to demonstrate the importance of exercise and amino acid supply for its activation in skeletal muscle. However, expression and activity of the IGF system in muscle are also controlled by secondary plant metabolites (SPMs). SPMs are abundantly present in plants and, therefore, in plant-based nutrition. SPMs are formulated, sometimes at high doses, in food supplements designed to support immune functions or increase muscle accretion. In the present manuscript, recent evidence on the effects of SPMs on the expression and activation of the IGF system in skeletal muscle is collected and discussed. In fact, SPMs exert positive effects on muscle mass and accretion not only during growth and development in a wide spectrum of vertebrate species but also have great potential to protect muscle mass during stress, illness, and aging.

The implantation period is crucial for the establishment of pregnancies in cows. Interferon τ (IFNτ) is produced during early implantation and acts in autocrine, paracrine and endocrine fashions on other endocrine systems. One of these is the insulin-like growth factor 1 (IGF-1) system, which is important for cell growth, proliferation, and therefore pregnancy establishment. This study investigated the effect of IFNτ on the expression of hepatic IGF-binding proteins (IGFBPs) in vitro. Primary bovine hepatocytes in a 2D sandwich culture model were stimulated with recombinant bovine IFNτ (rbIFNτ; 0.1-10.0 ng/mL) for six hours. The mRNA expression of IGFBP-1 to -7 and acid labile subunit (ALS) was measured using qRT‒PCR, and protein production was confirmed using western ligand blotting. All the IGFBPs (1-7) and ALS were expressed at basal levels in primary bovine hepatocytes, with IGFBP-2 to -4 secreted at appreciable concentrations in the medium. The expression of IGFBP-2 to -6 was stimulated by IFNτ, (treatment with rbIFNτ vs. control; IGFBP-2: for 0.5 ng/mL rbIFNτ, p = 0.0166; IGFBP-3: for 0.5 ng/mL, 5.0 ng/mL, and 10.0 ng/mL rbIFNτ, p = 0.0293, p = 0.0252, and p = 0.0099; IGFBP-4: for 0.5 ng/mL rbIFNτ, p = 0.0024; IGFBP-5: for 0.5 ng/mL and 10 ng/mL rbIFNτ, p = 0.0008 and p = 0.0421; IGFBP-6: for 0.1-10.0 ng/mL rbIFNτ, p = 0.0498-0.0022). These results indicate modulation of the IGF-system through IFNτ, which may contribute to adaptations supporting the early establishment of pregnancies in cattle.

Experimental evolution through selection experiments is a vital tool for exploring the special features of polygenic traits. Here, we provide liver transcriptome data from a paternally selected marathon mouse model (DUhTP), characterized by exceptional running performance, and unselected controls (DUC), both descended from the same polygenic background. To study training responses, both lines were either challenged by three weeks of high-speed treadmill training or remained sedentary. For each condition, eight animals were used for liver tissue isolation and next-generation sequencing. Raw sequencing files were submitted to the ArrayExpress collection under accession number E-MTAB-12071. High data quality was confirmed by appropriate mean read lengths, high mean quality scores, and low duplication rates after adapter trimming. With an average of 16.9 million reads per sample mapping to 19,930 genes, the dataset enables comprehensive gene expression analyses. A multiQC report for the dataset, together with a sample-by-gene count matrix, is available on Figshare. The provided data offer a valuable resource for research in polygenic traits associated with physical activity.

To date, animal models with reproductive phenotypes are knockout or transgenic and typically exhibit reduced fertility or infertility. This limits research to studying single-gene effects or loss of fertility. By contrast, Dummerstorf high-fertility mouse lines 1 and 2 (FL1 and FL2) are two unique outbred selection models that demonstrate exceptional reproductive performance. After approximately 50 years of selection, both lines have doubled the number of ovulated oocytes per cycle and consequently their litter size (>20 vs ∼11) compared to the unselected mice of the same founder population (Dummerstorf FZTDU, ctrl line). FL1 and FL2 exhibit atypical estrous cycle length and altered levels of hormones, such as insulin and leptin, which are associated with GnRH release and/or increased body fat content. Unlike typical cases where these factors impair fertility, they instead contribute to the FLs' high reproductive capacity: the increased ovulation rate results from an upgrade in the quality of their oocytes, influenced by different ovarian lipid profile. In the present study, we analyzed the expression of IGF-axis marker genes linked to reproductive performance and FL-specific traits in three tissues. We found that lepr, which plays a critical role in implantation, was upregulated in the FL1 uterus (1.5-fold vs. ctrl, p < 0.05). In FL1 follicles, igf1, IGF-biding proteins (IGFBP2, IGFBP4) and hsf1-which is involved in gametogenesis-were significantly upregulated (1-4-fold vs. ctrl, p < 0.05 for igf1, hsf1 and IGFBP4; p < 0.01 for igfbp2). In FL2, uterine size was reduced relatively to the body weight (∼0.2 % FL2 vs. 0.25 % in ctrl and 0.28 % in FL1, p < 0.001), indicating that uterus dimensions do not drive their increased litter size. These findings provide new insights into the molecular basis of high fertility and could serve as a foundation for further studies on genotype-phenotype relationships in reproductive biology.

Insulin-like growth factor 1 (IGF-1) regulates dairy cow reproduction, while the paracrine IGF system locally influences fertility. In both systems, IGF-1 bioactivity is regulated through binding proteins (IGFBPs) inhibiting IGF-1 binding to its receptor (IGF1R). This study aimed to investigate a possible transfer between this endocrine and paracrine system. Therefore, blood and follicular fluid (FF) from postpartum dairy cows were analysed for ß-hydroxybutyrate (BHB), IGF-1, IGFBP-2, -3, -4, -5, and an IGFBP fragment in two study parts. The mRNA expression of IGFBP-2, IGFBP-4, IGF1R, and the pregnancy-associated plasma protein A (PAPP-A) in granulosa cells was measured. The results showed correlations between plasma and FF for IGF-1 (r = 0.57, p < 0.001) and IGFBP-2 (r = −0.57, p < 0.05). Blood BHB negatively correlated with IGF-1 in blood and FF and IGFBP-3, -5 and total IGFBP in blood (IGF-1 plasma: r = −0.26, p < 0.05; FF: r = −0.35, p < 0.05; IGFBP-3: r = −0.64, p = 0.006; IGFBP-5: r = −0.49, p < 0.05; total IGFBP: r = −0.52, p < 0.05). A negative correlation was found between IGFBP-2 expression and IGF-1 concentration in FF (r = −0.97, p = 0.001), while an IGFBP fragment positively correlated with IGF1R-mRNA in FF (r = 0.82, p = 0.042). These findings suggest a transfer and local regulation between the somatotropic axis and the follicular IGF system, linking the metabolic status with local effects on dairy cow fertility.

Two factors influencing female reproduction have been repeatedly studied in different animal species and humans, namely, 1. secondary plant compounds, especially phytoestrogens (mainly isoflavones (IFs)), and 2. the physical constitution/metabolic phenotype (e.g., obesity). So far, these research results have only been considered separately. In this study, we investigated the influence on reproduction of both phytochemicals, mainly dietary IFs, and the metabolic phenotype represented by three mouse models considered as three distinct genetic groups (a control group, a mouse model with high metabolic activity, and a mouse line with obese body weight). The IF content in different investigated standard chows with similar macronutrient profiles varied significantly (p < 0.005), leading to high mean total plasma IF levels of up to 5.8 µmol/L in juvenile and 6.7 µmol/L in adult female mice. Reproductive performance was only slightly affected; only an IF dose-dependent effect on gestation length was observed in all genetic groups, as well as an effect on pregnancy rate in obese mice. Dietary IF exposure, however, caused earlier onset of vaginal opening by 4–10 days in juvenile mice (p < 0.05), dependent on the genetic group, resulting in a slight acceleration of sexual maturation in the already precocious obese model and to a strong earlier maturation in the otherwise late-maturing sporty model, bred for high treadmill performance. Therefore, our results may help to draw the missing line between the effect of dietary secondary plant constituents, such as IFs, and metabolic phenotype on sexual development.

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.

Metabolic flexibility describes the capability to switch between oxidative fuels depending on their availability during diet or exercise. In a previous study, we demonstrated that in response to training, marathon (DUhTP) mice, paternally selected for high treadmill performance, are metabolically more flexible than unselected control (DUC) mice. Since exercise-associated metabolic flexibility can be assessed by indirect calorimetry or partially by circulating lactate concentrations, we investigated these parameters in DUhTP and DUC mice. Therefore, males of both lines completed a three-week high-speed treadmill training or were physically inactive (sedentary) before being placed in a metabolic cage for three days (one day of acclimatization, two days with monitoring), measuring CO2 and O2 to calculate respiratory quotient (RQ) and fatty acid oxidation (FATox). Circulating blood lactate concentrations were determined. Training resulted in a lower RQ in DUhTP and an increased RQ in DUC mice compared to their sedentary counterparts. Increased FATox rates and lower lactate concentrations were observed in exercised DUhTP but not in DUC mice, indicating a shift to oxidative metabolism in DUhTP and a glycolytic one in DUC mice. Therefore, improved metabolic flexibility in DUhTP mice is verifiable up to three days after training.

https://doi.org/10.1093/af/vfad024 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. © Hoeflich, Galow, Brenmoehl, Hadlich Feature Article Growth and development of the mammary gland in mice—control of the insulin-like growth factor system by hormones and metalloproteases, and putative interference with micro RNAs

In contracting muscles, carbohydrates and fatty acids serve as energy substrates; the predominant utilization depends on the workload. Here, we investigated the contribution of non-mitochondrial and mitochondrial metabolic pathways in response to repeated training in a polygenic, paternally selected marathon mouse model (DUhTP), characterized by exceptional running performance and an unselected control (DUC), with both lines descended from the same genetic background. Both lines underwent three weeks of high-speed treadmill training or were sedentary. Both lines’ muscles and plasma were analyzed. Muscle RNA was sequenced, and KEGG pathway analysis was performed. Analyses of muscle revealed no significant selection-related differences in muscle structure. However, in response to physical exercise, glucose and fatty acid oxidation were stimulated, lactate dehydrogenase activity was reduced, and lactate formation was inhibited in the marathon mice compared with trained control mice. The lack of lactate formation in response to exercise appears to be associated with increased lipid mobilization from peripheral adipose tissue in DUhTP mice, suggesting a specific benefit of lactate avoidance. Thus, results from the analysis of muscle metabolism in born marathon mice, shaped by 35 years (140 generations) of phenotype selection for superior running performance, suggest increased metabolic flexibility in male marathon mice toward lipid catabolism regulated by lactate dehydrogenase.

The limited endogenous regenerative capacity of the human heart renders cardiovascular diseases a major health threat, thus motivating intense research on in vitro heart cell generation and cell replacement therapies. However, so far, in vitro-generated cardiomyocytes share a rather fetal phenotype, limiting their utility for drug testing and cell-based heart repair. Various strategies to foster cellular maturation provide some success, but fully matured cardiomyocytes are still to be achieved. Today, several hormones are recognized for their effects on cardiomyocyte proliferation, differentiation, and function. Here, we will discuss how the endocrine system impacts cardiomyocyte maturation. After detailing which features characterize a mature phenotype, we will contemplate hormones most promising to induce such a phenotype, the routes of their action, and experimental evidence for their significance in this process. Due to their pleiotropic effects, hormones might be not only valuable to improve in vitro heart cell generation but also beneficial for in vivo heart regeneration. Accordingly, we will also contemplate how the presented hormones might be exploited for hormone-based regenerative therapies.

Insulin-like growth factor I (IGF-I) is a growth-promoting anabolic hormone that fosters cell growth and tissue homeostasis. IGF-I deficiency is associated with several diseases, including growth disorders and neurological and musculoskeletal diseases due to impaired regeneration. Despite the vast regenerative potential of IGF-I, its unfavorable pharmacokinetic profile has prevented it from being used therapeutically. In this study, we resolved these challenges by the local administration of IGF-I mRNA, which ensures desirable homeostatic kinetics and non-systemic, local dose-dependent expression of IGF-I protein. Furthermore, IGF-I mRNA constructs were sequence engineered with heterologous signal peptides, which improved in vitro protein secretion (2- to 6-fold) and accelerated in vivo functional regeneration (16-fold) over endogenous IGF-I mRNA. The regenerative potential of engineered IGF-I mRNA was validated in a mouse myotoxic muscle injury and rabbit spinal disc herniation models. Engineered IGF-I mRNA had a half-life of 17-25 h in muscle tissue and showed dose-dependent expression of IGF-I over 2-3 days. Animal models confirm that locally administered IGF-I mRNA remained at the site of injection, contributing to the safety profile of mRNA-based treatment in regenerative medicine. In summary, we demonstrate that engineered IGF-I mRNA holds therapeutic potential with high clinical translatability in different diseases.

Sialylated milk oligosaccharides and glycoconjugates have several positive effects on the mucosal barrier, the gut microbiome, and an effective immune system. For this reason, they are important biomolecules for mammary gland health and optimal development of offspring. In milk, the major sialic acid, N-acetylneuraminic acid (Neu5Ac), can be attached as monosialyl-residues or as polymers. To investigate the sialylation processes during lactation of German Holstein cows, we analyzed udder tissue in addition to milk at different time points of lactation. The analysis of the milk samples revealed that both the levels of Neu5Ac and its polymer, polysialic acid (polySia), rapidly decreased during the first three days of lactation, and a high interindividual variance was observed. In mature milk, however, the sialylation status remains relatively constant. The results indicate that mammary gland epithelial cells are one source for milk polySia, since immunohistochemistry of udder tissue exhibited strong polySia staining in these cells. Furthermore, both polysialyltransferases, ST8SiaII and ST8SiaIV, are expressed. Based on known functions of monosialyl residues and polySia, we discuss the potential impact of these biomolecules and the consequences of the heterogeneous sialylation status of milk in relation to udder health and offspring health.

Suitable animal models are essential for translational research, especially in the case of complex, multifactorial conditions, such as obesity. The non-inbred mouse (Mus musculus) line Titan, also known as DU6, is one of the world's longest selection experiments for high body mass and was previously described as a model for metabolic healthy (benign) obesity. The present study further characterizes the geno- and phenotypes of this non-inbred mouse line and tests its suitability as an interventional obesity model. In contrast to previous findings, our data suggest that Titan mice are metabolically unhealthy obese and short-lived. Line-specific patterns of genetic invariability are in accordance with observed phenotypic traits. Titan mice also show modifications in the liver transcriptome, proteome, and epigenome linked to metabolic (dys)regulations. Importantly, dietary intervention partially reversed the metabolic phenotype in Titan mice and significantly extended their life expectancy. Therefore, the Titan mouse line is a valuable resource for translational and interventional obesity research.

ObjectiveWe aimed to investigate the short and long-term metabolic consequences of IGF1R systemic gene deficiency in mice. MethodsUBC-CreERT2, Igf1r(fl/fl) mutant mice were used to suppress IGF1R signaling in adult tissues by inducing postnatal generalized Igf1r deletion with tamoxifen. Animals were analyzed at two different ages: i) 13-weeks old young mice, and ii) 12-months old middle-aged mice. In addition, the effects of 10 weeks-long high-fat diet (HFD) were investigated in middle-aged mice. ResultsYoung IGF1R-deficient mice were insulin-resistant, with high IGF1, growth hormone (GH) and IGFBP3, as well as low IGFBP2 circulating levels. Males also presented increased triglycerides in liver. In contrast, middle-aged mice did not clearly show all of these alterations, suggesting possible compensatory effects. Middle-aged IGF1R-deficient male mice were able to counteract the negative effects induced by aging and HFD in adiposity, inflammation and glucose metabolism. A metabolic sexual dimorphism dependent on IGF1R was observed, especially in middle-aged mice. ConclusionsThese results demonstrate that IGF1R is involved in metabolic homeostasis, with effects modulated by diet-induced obesity and aging in a sex dependent manner. Thus, IGF1R deficiency in mice is proposed as a useful tool to understand metabolic alterations observed in patients with IGF1R gene deletions.