Roles of growth hormone and insulin-like growth factor 1 in mouse postnatal growth

Novel evidence in vivo: Berberine ameliorated glucocorticoid-induced post-natal growth retardation by regulating the GH/IGF-1 axis through KMT1A downregulation

BACKGROUND

Glucocorticoids (GCs) are widely used anti-inflammatory agents that inhibit growth in children. However, their mechanisms and effect on the growth hormone (GH)/insulin-like growth factor (IGF)-1 axis remain unclear.

PURPOSE

This study, we aimed to establish a mouse model of GC-induced growth retardation during the critical growth period and explore the underlying mechanisms. Additionally, we aimed to identify novel biomarkers and potential therapeutic agents for GC-induced growth impairment.

METHODS

Four-week-old mice were treated with GCs for two weeks and subsequently assessed for body length, weight, and body composition. Immunohistochemical analysis of the growth plate in the proximal tibia and biochemical assays of blood were performed to evaluate changes in growth plate length and GH/IGF-1 axis. KMT1A expression and its effects on Ghr expression were examined, and the impact of berberine on GC-induced growth retardation was assessed.

RESULTS

GCs significantly reduced growth by impairing growth plate expansion, disrupting the GH/IGF-1 axis, and downregulation of the GH receptor (Ghr) and Igf-1 levels in the liver. These changes were attributed to the upregulation of the H3K9 trimethyltransferase KMT1A, which decreased Ghr transcription in the liver. In vitro screening of natural compounds revealed that berberine chloride hydrate decreased the KMT1A levels and increased GHR levels. Berberine chloride hydrate also effectively ameliorated GC-induced growth retardation by restoring Ghr expression via KMT1A inhibition, thereby enhancing the circulating IGF-1 levels.

CONCLUSION

Overall, our findings highlight the potential of targeting KMT1A using berberine chloride hydrate as an epigenetic modifier to treat GC-induced growth impairment.

Exploring the Bone-Liver Axis: Impact of Acute Ethanol Intoxication on Post-Traumatic Liver Inflammation and Damage Following Femur Fracture

Bone fracture activates the immune system and induces inflammation crucial for fracture healing but may also affect trauma-distant organs like the liver. Acute alcohol intoxication (AAI) dysregulates immune responses and affects organ damage post-trauma. However, the bone-liver axis and alcohol's role in this process remain poorly understood. This study explores liver inflammation and damage following fracture, with and without prior AAI. Twenty-four male C57BL/6J mice were randomly assigned to four groups (n = 6) and received either NaCl (control) or 35% ethanol via gavage. Mice underwent femur osteotomy with external fixation or sham surgery. After 24 h, liver damage was assessed using hematoxylin-eosin and activated caspase-3 staining. Liver inflammation was evaluated through CXCL1 and polymorphonuclear leukocyte (PMNL) immunostaining, cytokine gene and protein expression analyses, and immune cell profiling in the liver via flow cytometry. Western blotting assessed NF-κB and Wnt signaling. Neither fracture alone nor with AAI caused significant liver damage. However, fracture significantly increased PMNL infiltration and altered monocyte populations, effects that were amplified by AAI. The hepatic neutrophil-to-monocyte ratio significantly decreased after fracture and was absent in the fracture AAI group. CXCL1 increased post-fracture, while MCP-1 and IL-10 decreased significantly, with AAI further significantly amplifying these changes. Wnt1 and Wnt3a levels increased significantly after fracture and were further strongly elevated by AAI. AAI completely abolished fracture-induced significant β-catenin reduction and significantly increased its phosphorylation, effects that potentially involve an AAI-induced β-catenin stabilization as well as its increased degradation. NF-κB activation was significantly decreased, while A20 expression significantly increased after fracture and AAI. Fracture influences the inflammatory liver response and signaling pathways, effects which were further modulated by AAI.

Loss of the acyltransferase TMEM68 leads to growth delay and dysregulation of triacylglycerol and glycerophospholipid homeostasis in the mouse brain

Lipid droplets (LDs) are ubiquitous cellular storage organelles for triacylglycerol (TAG) that have recently been implicated in brain development and aging, and the progression of neurodegenerative diseases. However, the enzymes responsible for brain TAG synthesis are incompletely understood. Transmembrane protein 68 (TMEM68) catalyzes TAG synthesis independent of canonical diacylglycerol acyltransferase (DGAT) enzymes and is highly expressed in the brain. In the current study, we addressed the role of TMEM68 in murine brain TAG metabolism using a global Tmem68 knockout mouse model. We found that loss of TMEM68 led to decreased TAG levels in the cerebral cortex and a concomitant increase in polyunsaturated glycerophospholipid species. These changes in lipid pattern were associated with perturbed expression of genes involved in fatty acid and glycerophospholipid metabolism. While brain size and morphology were largely unaffected, TMEM68 deficiency caused reductions in white adipose tissue mass, decreased insulin-like growth factor 1 levels, and retarded weight gain. In conclusion, our study identifies TMEM68 as regulator of TAG and glycerophospholipid homeostasis in the central nervous system and discloses a requirement of the enzyme for postnatal development and energy metabolism.

Growth Hormone Action as a Target in Cancer: Significance, Mechanisms, and Possible Therapies

Growth hormone (GH) is a pituitary-derived endocrine hormone required for normal postnatal growth and development. Hypo- or hypersecretion of endocrine GH results in 2 pathologic conditions, namely GH deficiency (GHD) and acromegaly. Additionally, GH is also produced in nonpituitary and tumoral tissues, where it acts rather as a cellular growth factor with an autocrine/paracrine mode of action. An increasingly persuasive and large body of evidence over the last 70 years concurs that GH action is implicit in escalating several cancer-associated events, locally and systemically. This pleiotropy of GH's effects is puzzling, but the association with cancer risk automatically raises a concern for patients with acromegaly and for individuals treated with GH. By careful assessment of the available knowledge on the fundamental concepts of cancer, suggestions from epidemiological and clinical studies, and the evidence from specific reports, in this review we aimed to help clarify the distinction of endocrine vs autocrine/paracrine GH in promoting cancer and to reconcile the discrepancies between experimental and clinical data. Along this discourse, we critically weigh the targetability of GH action in cancer-first by detailing the molecular mechanisms which posit GH as a critical node in tumor circuitry; and second, by enumerating the currently available therapeutic options targeting GH action. On the basis of our discussion, we infer that a targeted intervention on GH action in the appropriate patient population can benefit a sizable subset of current cancer prognoses.

Insight into the Potential of Somatostatin Vaccination with Goats as a Model: From a Perspective of the Gastrointestinal Microbiota

Deciphering the gastrointestinal microbial response to oral SS DNA vaccines with different doses is helpful for identifying the mechanism for effective utilization of the vaccine for improving animal production. Here, we conduct a comparative study with different doses of vaccine (control: empty plasmid; low dose: 1 × 107 CFU vaccine; high dose: 1 × 1012 CFU vaccine) using goat as a case to investigate the potential of somatostatin vaccination from the entire gastrointestinal microbiota perspective. Our results show that body weight gain and slaughter rate are greater in the L_SS group than in the C_SS group. Compared with the C_SS group, the GH concentration is reduced, while the SS concentration is elevated in the cecum of L_SS goats. Moreover, the SCFAs concentration is elevated in the L_SS goats, the acetate molar proportion is lower in the rumen, the proportion of the acetate is decreased, and propionate is increased in the cecum of L_SS goats. Our data indicate that the low-dose somatostatin vaccine possesses a more efficient improvement in the productivity of goats, emphasizing that the dosage should be considered to reach its optimal effect on the host. Moreover, we find that different doses of the SS vaccination select distinct microbial communities in the gastrointestinal tract. Beta diversity analysis shows a significant interaction. Microorganisms capable of converting nutrients, including Ruminococcacease, Butyrivibrio, Akkermansia, and Lachnospiraceae are enriched, altering the gastrointestinal fermentation response to SS DNA vaccination of ruminants. Moreover, the correlation analysis results revealing these biomarkers have a close association with the phenotypes of productivity. These results imply that somatostatin immunoneutralization might directly alter the gastrointestinal tract commensal bacterial structure, improving gastrointestinal homeostasis, and, thus, modifying the fermentability and effected hormone level to improve the productivity of goats. Our study extends the understanding of the somatostatin vaccine regulation of ruminants' growth through the entire gastrointestinal microbial perspective.

The neurohormone tyramine stimulates the secretion of an insulin-like peptide from the Caenorhabditis elegans intestine to modulate the systemic stress response

The DAF-2/insulin/insulin-like growth factor signaling (IIS) pathway plays an evolutionarily conserved role in regulating reproductive development, life span, and stress resistance. In Caenorhabditis elegans, DAF-2/IIS signaling is modulated by an extensive array of insulin-like peptides (ILPs) with diverse spatial and temporal expression patterns. However, the release dynamics and specific functions of these ILPs in adapting to different environmental conditions remain poorly understood. Here, we show that the ILP, insulin-3 (INS-3), plays a crucial role in modulating the response to various environmental stressors in C. elegans. ins-3 mutants display increased resistance to heat, oxidative stress, and starvation; however, this advantage is countered by slower reproductive development under favorable conditions. We find that ins-3 expression is downregulated in response to environmental stressors, whereas, the neurohormone tyramine, which is released during the acute flight response, increases ins-3 expression. We show that tyramine induces intestinal calcium (Ca2+) transients through the activation of the TYRA-3 receptor. Our data support a model in which tyramine negatively impacts environmental stress resistance by stimulating the release of INS-3 from the intestine via the activation of a TYRA-3-Gαq-IP3 pathway. The release of INS-3 systemically activates the DAF-2 pathway, resulting in the inhibition of cytoprotective mechanisms mediated by DAF-16/FOXO. These studies offer mechanistic insights into a brain-gut communication pathway that weighs adaptive strategies to respond to acute and long-term stressors.

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

Growth hormone-receptor disruption in mice reduces osteoarthritis and chondrocyte hypertrophy

Excessive growth hormone (GH) has been shown to promote joint degeneration in both preclinical and clinical studies. Little is known about the effect of disrupted GH or GH receptor (GHR) on joint health. The goal of this study is to investigate joint pathology in mice with either germline (GHR-/-) or adult inducible (iGHR-/-) GHR deficiency. Knee joints from male and female GHR-/- and WT mice at 24 months of age were processed for histological analysis. Also, knee joints from male and female iGHR-/- and WT mice at 22 months of age were scanned by micro-CT (μCT) for subchondral bone changes and characterized via histology for cartilage degeneration. Joint sections were also stained for the chondrocyte hypertrophy marker, COLX, and the cartilage degeneration marker, ADAMTS-5, using immunohistochemistry. Compared to WT mice, GHR-/- mice had remarkably smooth articular joint surfaces and an even distribution of proteoglycan with no signs of degeneration. Quantitatively, GHR-/- mice had lower OARSI and Mankin scores compared to WT controls. By contrast, iGHR-/- mice were only moderately protected from developing aging-associated OA. iGHR-/- mice had a significantly lower Mankin score compared to WT. However, Mankin scores were not significantly different between iGHR-/- and WT when males and females were analyzed separately. OARSI scores did not differ significantly between WT and iGHR-/- in either individual or combined sex analyses. Both GHR-/- and iGHR-/- mice had fewer COLX+ hypertrophic chondrocytes compared to WT, while no significant difference was observed in ADAMTS-5 staining. Compared to WT, a significantly lower trabecular thickness in the subchondral bone was observed in the iGHR-/- male mice but not in the female mice. However, there were no significant differences between WT and iGHR-/- mice in the bone volume to total tissue volume (BV/TV), bone mineral density (BMD), and trabecular number in either sex. This study identified that both germline and adult-induced GHR deficiency protected mice from developing aging-associated OA with more effective protection in GHR-/- mice.

Subperiosteal delivery of transforming growth factor beta 1 and human growth hormone from mineralized PCL films

The ability to locally deliver bioactive molecules to distinct regions of the skeleton may provide a novel means by which to improve fracture healing, treat neoplasms or infections, or modulate growth. In this study, we constructed single-sided mineral-coated poly-ε-caprolactone membranes capable of binding and releasing transforming growth factor beta 1 (TGF-β1) and human growth hormone (hGH). After demonstrating biological activity in vitro and characterization of their release, these thin bioabsorbable membranes were surgically implanted using an immature rabbit model. Membranes were circumferentially wrapped under the periosteum, thus placed in direct contact with the proximal metaphysis to assess its bioactivity in vivo. The direct effects on the metaphyseal bone, bone marrow, and overlying periosteum were assessed using radiography and histology. Effects of membrane placement at the tibial growth plate were assessed via physeal heights, tibial growth rates (pulsed fluorochrome labeling), and tibial lengths. Subperiosteal placement of the mineralized membranes induced greater local chondrogenesis in the plain mineral and TGF-β1 samples than the hGH. More exuberant and circumferential ossification was seen in the TGF-β1 treated tibiae. The TGF-β1 membranes also induced hypocellularity of the bone marrow with characteristics of gelatinous degeneration not seen in the other groups. While the proximal tibial growth plates were taller in the hGH treated than TGF-β1, no differences in growth rates or overall tibial lengths were found. In conclusion, these data demonstrate the feasibility of using bioabsorbable mineral coated membranes to deliver biologically active compounds subperiosteally in a sustained fashion to affect cells at the insertion site, bone marrow, and even growth plate.

SLC30A9: an evolutionarily conserved mitochondrial zinc transporter essential for mammalian early embryonic development

SLC30A9 (ZnT9) is a mitochondria-resident zinc transporter. Mutations in SLC30A9 have been reported in human patients with a novel cerebro-renal syndrome. Here, we show that ZnT9 is an evolutionarily highly conserved protein, with many regions extremely preserved among evolutionarily distant organisms. In Drosophila melanogaster (the fly), ZnT9 (ZnT49B) knockdown results in acutely impaired movement and drastic mitochondrial deformation. Severe Drosophila ZnT9 (dZnT9) reduction and ZnT9-null mutant flies are pupal lethal. The phenotype of dZnT9 knockdown can be partially rescued by mouse ZnT9 expression or zinc chelator TPEN, indicating the defect of dZnT9 loss is indeed a result of zinc dyshomeostasis. Interestingly, in the mouse, germline loss of Znt9 produces even more extreme phenotypes: the mutant embryos exhibit midgestational lethality with severe development abnormalities. Targeted mutagenesis of Znt9 in the mouse brain leads to serious dwarfism and physical incapacitation, followed by death shortly. Strikingly, the GH/IGF-1 signals are almost non-existent in these tissue-specific knockout mice, consistent with the medical finding in some human patients with severe mitochondrial deficiecny. ZnT9 mutations cause mitochondrial zinc dyshomeostasis, and we demonstrate mechanistically that mitochondrial zinc elevation quickly and potently inhibits the activities of respiration complexes. These results reveal the critical role of ZnT9 and mitochondrial zinc homeostasis in mammalian development. Based on our functional analyses, we finally discussed the possible nature of the so far identified human SLC30A9 mutations.

Associations of co-exposure to polycyclic aromatic hydrocarbons and lead (Pb) with IGF1 methylation in peripheral blood of preschool children from an e-waste recycling area

BACKGROUND

Childhood exposure to polycyclic aromatic hydrocarbons (PAHs) or lead (Pb) is associated with epigenetic modifications. However, the effects of their co-exposures on IGF1 (Insulin-like growth factor 1) methylation and the potential role in child physical growth are unclear.

METHODS

From our previous children study (N = 238, ages of 3-6), 75 children with higher total concentrations of urinary ten hydroxyl PAH metabolites (∑10OH-PAHs) from an e-waste recycling area, Guiyu, and 75 with lower ∑10OH-PAHs from Haojiang (reference area) were included. Pb and IGF1 P2 promoter methylation in peripheral blood were also measured. Multivariable linear regression analyses were performed to estimate individual associations, overall effects and interactions of co-exposure to OH-PAHs and Pb on IGF1 methylation were further explored using Bayesian kernel machine regression.

RESULTS

Methylation of IGF1 (CG-232) was lower (38.00 vs. 39.74 %, P < 0.001), but of CG-207 and CG-137 were higher (59.94 vs. 58.41 %; 57.60 vs. 56.28 %, both P < 0.05) in exposed children than the reference. The elevated urinary 2-OHPhe was associated with reduced methylation of CG-232 (B = -0.051, 95 % CI: -0.096, -0.005, P < 0.05), whereas blood Pb was positively associated with methylation of CG-108 (B = 0.106, 95 %CI: 0.013, 0.199, P < 0.05), even after full adjustment. Methylations of CG-224 and 218 significantly decreased when all OH-PAHs and Pb mixtures were set at 35th - 40th and 45th - 55th percentile compared to when all fixed at 50th percentile. There were bivariate interactions of co-exposure to the mixtures on methylations of CG-232, 224, 218, and 108. Methylations correlated with height, weight, were observed in the exposed children.

CONCLUSIONS

Childhood co-exposure to high PAHs and Pb from the e-waste may be associated with IGF1 promoter methylation alterations in peripheral blood. This, in turn, may interrupt the physical growth of preschool children.

Generation of insulin-like growth factor 1 receptor-knockout pigs as a potential system for interspecies organogenesis

BACKGROUND

To overcome organ shortage during transplantation, interspecies organ generation via blastocyst complementation has been proposed, although not yet in evolutionarily distant species. To establish high levels of chimerism, low chimerism is required early in development, followed by high chimerism, to effectively complement the organ niche. Very few human cells are expected to contribute to chimerism in heterologous animals. Previous studies had demonstrated increased donor chimerism in both intra- and interspecies chimeras in rodents, using insulin-like growth factor 1 receptor (Igf1r) knockout (KO) mice; deletion of the Igf1r gene in the mouse host embryo created a cell-competitive niche. The current study aimed to generate IGF1R-KO pigs and evaluate whether they have the same phenotype as Igf1r-KO mice.

METHODS

To generate IGF1R-KO pigs, genome-editing molecules were injected into the cytoplasm of pig zygotes. The fetuses were evaluated at 104 days of gestation.

RESULTS

IGF1R-KO pigs were generated successfully. Their phenotypes were almost identical to those of Igf1r-KO mice, including small lungs and enlarged endodermal organs in fetuses, and they were highly reproducible.

CONCLUSIONS

Pigs may allow the generation of organs using blastocyst complementation with developmentally-compatible xenogeneic pluripotent stem cells over a large evolutionary distance.

Renin-angiotensin system inhibitors positively impact on multiple aging regulatory pathways: Could they be used to protect against human aging?

The renin-angiotensin system (RAS)-a classical blood pressure regulator-largely contributes to healthy organ development and function. Besides, RAS activation promotes age-related changes and age-associated diseases, which are attenuated/abolished by RAS-blockade in several mammalian species. RAS-blockers also increase rodent lifespan. In previous work, we discussed how RAS-blockade downregulates mTOR and growth hormone/IGF-1 signaling, and stimulates AMPK activity (together with klotho, sirtuin, and vitamin D-receptor upregulation), and proposed that at least some of RAS-blockade's aging benefits are mediated through regulation of these intermediaries and their signaling to mitochondria. Here, we included RAS-blockade's impact on other aging regulatory pathways, that is, TGF-ß, NF-kB, PI3K, MAPK, PKC, Notch, and Wnt, all of which affect mitochondria. No direct evidence is available on RAS/RAS-blockade-aging regulatory pathway-mitochondria interactions. However, existing results allow to conjecture that RAS-blockers neutralize mitochondrial dysfunction by acting on the discussed pathways. The reviewed evidence led us to propose that the foundation is laid for conducting clinical trials aimed at testing whether angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB)-even at subclinical doses-offer the possibility to live longer and in better health. As ACEi and ARB are low cost and well-tolerated anti-hypertension therapies in use for over 35 years, investigating their administration to attenuate/prevent aging effects seems simple to implement.

Ablation of specific insulin-like growth factor I forms reveals the importance of cleavage for regenerative capacity and glycosylation for skeletal muscle storage

Insulin-like growth factor-I (IGF-I) facilitates mitotic and anabolic actions in all tissues. In skeletal muscle, IGF-I can promote growth and resolution of damage by promoting satellite cell proliferation and differentiation, suppressing inflammation, and enhancing fiber formation. While the most well-characterized form of IGF-I is the mature protein, alternative splicing and post-translational modification complexity lead to several additional forms of IGF-I. Previous studies showed muscle efficiently stores glycosylated pro-IGF-I. However, non-glycosylated forms display more efficient IGF-I receptor activation in vitro, suggesting that the removal of the glycosylated C terminus is a necessary step to enable increased activity. We employed CRISPR-Cas9 gene editing to ablate IGF-I glycosylation sites (2ND) or its cleavage site (3RA) in mice to determine the necessity of glycosylation or cleavage for IGF-I function in postnatal growth and during muscle regeneration. 3RA mice had the highest circulating and muscle IGF-I content, whereas 2ND mice had the lowest levels compared to wild-type mice. After weaning, 4-week-old 2ND mice exhibited higher body and skeletal muscle mass than other strains. However, by 16 weeks of age, muscle and body size differences disappeared. Even though 3RA mice had more IGF-I stored in muscle in homeostatic conditions, regeneration was delayed after cardiotoxin-induced injury, with prolonged necrosis most evident at 5 days post injury (dpi). In contrast, 2ND displayed improved regeneration with reduced necrosis, and greater fiber size and muscle mass at 11 and 21 dpi. Overall, these results demonstrate that while IGF-I glycosylation may be important for storage, cleavage is needed to enable IGF-I to be used for efficient activity in postnatal growth and following acute injury.

Maternal fiber-rich diet promotes early-life intestinal development in offspring through milk-derived extracellular vesicles carrying miR-146a-5p

BACKGROUNDS

The intestinal development in early life is profoundly influenced by multiple biological components of breast milk, in which milk-derived extracellular vesicles (mEVs) contain a large amount of vertically transmitted signal from the mother. However, little is known about how maternal fiber-rich diet regulates offspring intestinal development by influencing the mEVs.

RESULTS

In this study, we found that maternal resistant starch (RS) consumption during late gestation and lactation improved the growth and intestinal health of offspring. The mEVs in breast milk are the primary factor driving these beneficial effects, especially enhancing intestinal cell proliferation and migration. To be specific, administration of mEVs after maternal RS intake enhanced intestinal cell proliferation and migration in vivo (performed in mice model and indicated by intestinal histological observation, EdU assay, and the quantification of cyclin proteins) and in vitro (indicated by CCK8, MTT, EdU, and wound healing experiments). Noteworthily, miR-146a-5p was found to be highly expressed in the mEVs from maternal RS group, which also promotes intestinal cell proliferation in cells and mice models. Mechanically, miR-146a-5p target to silence the expression of ubiquitin ligase 3 gene NEDD4L, thereby inhibiting DVL2 ubiquitination, activating the Wnt pathway, and promoting intestinal development.

CONCLUSION

These findings demonstrated the beneficial role of mEVs in the connection between maternal fiber rich diet and offspring intestinal growth. In addition, we identified a novel miRNA-146a-5p-NEDD4L-β-catenin/Wnt signaling axis in regulating early intestinal development. This work provided a new perspective for studying the influence of maternal diet on offspring development.

Establishment of African pygmy mouse induced pluripotent stem cells using defined doxycycline inducible transcription factors

Mus minutoides is one of the smallest mammals worldwide; however, the regulatory mechanisms underlying its dwarfism have not been examined. Therefore, we aimed to establish M. minutoides induced pluripotent stem cells (iPSCs) using the PiggyBac transposon system for applications in developmental engineering. The established M. minutoides iPSCs were found to express pluripotency markers and could differentiate into neurons. Based on in vitro differentiation analysis, M. minutoides iPSCs formed embryoid bodies expressing marker genes in all three germ layers. Moreover, according to the in vivo analysis, these cells contributed to the formation of teratoma and development of chimeric mice with Mus musculus. Overall, the M. minutoides iPSCs generated in this study possess properties that are comparable to or closely resemble those of naïve pluripotent stem cells (PSCs). These findings suggest these iPSCs have potential utility in various analytical applications, including methods for blastocyst completion.

Tmem263 deletion disrupts the GH/IGF-1 axis and causes dwarfism and impairs skeletal acquisition

Genome-wide association studies (GWAS) have identified a large number of candidate genes believed to affect longitudinal bone growth and bone mass. One of these candidate genes, TMEM263, encodes a poorly characterized plasma membrane protein. Single nucleotide polymorphisms in TMEM263 are associated with bone mineral density in humans and mutations are associated with dwarfism in chicken and severe skeletal dysplasia in at least one human fetus. Whether this genotype-phenotype relationship is causal, however, remains unclear. Here, we determine whether and how TMEM263 is required for postnatal growth. Deletion of the Tmem263 gene in mice causes severe postnatal growth failure, proportional dwarfism, and impaired skeletal acquisition. Mice lacking Tmem263 show no differences in body weight within the first 2 weeks of postnatal life. However, by P21 there is a dramatic growth deficit due to a disrupted growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis, which is critical for longitudinal bone growth. Tmem263-null mice have low circulating IGF-1 levels and pronounced reductions in bone mass and growth plate length. The low serum IGF-1 in Tmem263-null mice is associated with reduced hepatic GH receptor (GHR) expression and GH-induced JAK2/STAT5 signaling. A deficit in GH signaling dramatically alters GH-regulated genes and feminizes the liver transcriptome of Tmem263-null male mice, with their expression profile resembling wild-type female, hypophysectomized male, and Stat5b-null male mice. Collectively, our data validates the causal role for Tmem263 in regulating postnatal growth and raises the possibility that rare mutations or variants of TMEM263 may potentially cause GH insensitivity and impair linear growth.

Comparative Analysis of the GH/IGF-1 Axis during the First Sixth Months in Children with Low Birth Weight

OBJECTIVE

To analyze the relation between alterations in the growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis during the first 6 months of life and weight in children born in the lower-middle São Francisco region.

METHODS

This is an analytical cohort and exploratory. Thirty children, were formed two groups, one of low birth weight children (LBW, n = 15) and another of normal weight (NBW = 15) were initially identified in a hospital and reapproached at 3 and 6 months of age. Birth weight and alterations in GH/IGF-1 curves were measured at birth and the third and sixth months of life.

RESULTS

Weight gain during the 6 months of follow-up in newborns with a low birth weight was greater compared to newborns with a normal birth weight. All children who were born with a low birth weight had an altered GH/IGF-1 curve at birth (p = 0.002). Most newborns with a low birth weight maintained the alteration in the GH/IGF-1 curve at the third month of life (p = 0.027). Regarding the GH/IGF-1 curve at the sixth month, alteration persisted in greater proportion among children with a low birth weight.

CONCLUSIONS

Alterations in insulin resistance markers, demonstrated by increased GH without a proportional increase in IGF-1, were observed to be significant in children with a low birth weight with greater adiposity in this group which may increase the risk of metabolic diseases in later life.

Tmem263 deletion disrupts the GH/IGF-1 axis and causes dwarfism and impairs skeletal acquisition

Genome-wide association studies (GWAS) have identified a large number of candidate genes believed to affect longitudinal bone growth and bone mass. One of these candidate genes, TMEM263, encodes a poorly characterized plasma membrane protein. Single nucleotide polymorphisms in TMEM263 are associated with bone mineral density in humans and mutations are associated with dwarfism in chicken and severe skeletal dysplasia in at least one human fetus. Whether this genotype-phenotype relationship is causal, however, remains unclear. Here, we determine whether and how TMEM263 is required for postnatal growth. Deletion of the Tmem263 gene in mice causes severe postnatal growth failure, proportional dwarfism, and impaired skeletal acquisition. Mice lacking Tmem263 show no differences in body weight within the first two weeks of postnatal life. However, by P21 there is a dramatic growth deficit due to a disrupted GH/IGF-1 axis, which is critical for longitudinal bone growth. Tmem263-null mice have low circulating IGF-1 levels and pronounced reductions in bone mass and growth plate length. The low serum IGF-1 in Tmem263-null mice is associated with reduced hepatic GH receptor (GHR) expression and GH-induced JAK2/STAT5 signaling. A deficit in GH signaling dramatically alters GH-regulated genes and feminizes the liver transcriptome of Tmem263-null male mice, with their expression profile resembling a wild-type female, hypophysectomized male, and Stat5b-null male mice. Collectively, our data validates the causal role for Tmem263 in regulating postnatal growth and raises the possibility that rare mutations or variants of TMEM263 may potentially cause GH insensitivity and impair linear growth.

Hydrolyzed Collagen Tripeptide Promotes Longitudinal Bone Growth in Childhood Rats via Increases in Insulin-Like Growth Factor-1 and Bone Morphogenetic Proteins

Previous studies have reported that collagen tripeptide (CTP) derived from collagen hydrolysate has various beneficial effects on health by protecting against skin aging and improving bone formation and cartilage regeneration. Collagen-Tripep20TM (CTP20), which is a low-molecular-weight CTP derived from fish skin, contains a bioactive CTP, Gly-Pro-Hyp >3.2% with a tripeptide content >20%. Herein, we investigated the osteogenic effects and mechanisms of CTP20 (<500 Da) on MG-63 osteoblast-like cells and SW1353 chondrocytes. And we measured promoting ratio of the longitudinal bone growth in childhood rats. First, CTP20 at 100 μg/mL elevated the proliferation (15.0% and 28.2%), alkaline phosphatase activity (29.3% and 32.0%), collagen synthesis (1.25- and 1.14-fold), and calcium deposition (1.18- and 1.15-fold) in MG-63 cells and SW1353, respectively. In addition, we found that CTP20 could promote the longitudinal growth and height of the growth plate of the tibia in childhood rats. CTP20 enhanced the protein expression of insulin-like growth factor-1 (IGF-1) in MG-63 and SW1353 cells, and in the growth plate of childhood rats, along with Janus Kinase 2, and signal transducer and activator of transcription 5 activation in MG-63 and SW1353 cells. CTP20 also elevated the expression levels of bone morphogenetic proteins (BMPs) in MG-63 and SW1353 cells and in the growth plates of childhood rats. These results indicate that CTP20 may promote the endochondral ossification and longitudinal bone growth, through enhancing of IGF-1 and BMPs. (Clinical Trial Registration number: smecae 19-09-01).

Short- and long-term effects of nutritional state on IGF-1 levels in nestlings of a wild passerine

Growth trajectories of young animals are intimately connected to their fitness prospects, but we have little knowledge of growth regulation mechanisms, particularly in the wild. Insulin-like growth factor 1 (IGF-1) is a central hormone in regulating resource allocation, with higher IGF-1 levels resulting in more growth. IGF-1 levels generally increase in conjunction with nutritional state, but whether IGF-1 levels are adjusted in response to current nutrient availability or to the nutrient availability integrated over a longer term is not well known. We tested for such effects by supplementary feeding the jackdaw (Corvus monedula) nestlings in experimentally reduced or enlarged broods with either water (control) or a food solution; these manipulations have long- and short-term effects on the nutritional state, respectively. Baseline plasma IGF-1 levels were higher in reduced broods. Food supplementation induced an increase in plasma IGF-1 levels measured one hour later, and this effect was significantly more substantial in nestlings in reduced broods. Changes in plasma IGF-1 levels increased with increased retention of the supplementary food, which was higher in reduced broods, explaining the stronger IGF-1 response. Thus, IGF-1 levels respond to short-term variations in the nutritional state, but this effect is amplified by longer-term variations in the nutritional state. We discuss our findings using a graphical model that integrates the results of the two treatments.

Characteristic amino acid residues in the growth hormone receptor gene on Mus minutoides underlying dwarfism

The African pygmy mouse ( Mus minutoides ) displays a dwarfism phenotype distinctive from closely related species. This study aimed to investigate the growth hormone receptor (Ghr) gene sequence in M. minutoides . We identified several amino acid variations, including the P469L mutation. Our findings suggest that this mutation affects Ghr protein functionality, decreasing Igf1 expression and contributing to the dwarfism observed in M. minutoides . Further studies utilizing genome editing technology are necessary to elucidate the mechanisms involved in mammalian body size determination.

IGF-1 receptor inhibitor OSI-906 reduces growth in nestlings of a wild passerine

Young animals need to grow to a large body size fast to maximise their survival prospects until sexual maturity. However, body size varies substantially in wild populations, and neither the selection pressures maintaining this variation, nor the regulatory mechanisms are well understood. IGF-1 administration has been shown to accelerate growth, but this does not necessarily imply that natural variation in growth rate is IGF-1 dependent. To test the latter we administered OSI-906 to pied flycatcher Ficedula hypoleuca nestlings, which has an inhibitory effect on IGF-1 receptor activity. We performed the experiment in two breeding seasons to test the prediction that blocking the IGF-1 receptor downregulates growth. As predicted, OSI-906 treated nestlings had lower body mass and reached a smaller structural size than siblings receiving a vehicle only, with the mass difference being most profound at the age preceding the highest body mass growth rate. The IGF-1 receptor inhibition effect on growth varied with age and year of study, and we discuss possible explanations. The OSI-906 administration results indicate that natural variation in growth rate is regulated by IGF-1, and constitutes a novel tool to study causes and consequences of growth variation, but details of the underlying mechanism still need to be resolved.

Imprinted Dlk1 dosage as a size determinant of the mammalian pituitary gland

Co-regulated genes of the Imprinted Gene Network are involved in the control of growth and body size, and imprinted gene dysfunction underlies human paediatric disorders involving the endocrine system. Imprinted genes are highly expressed in the pituitary gland, among them, Dlk1, a paternally expressed gene whose membrane-bound and secreted protein products can regulate proliferation and differentiation of multiple stem cell populations. Dosage of circulating DLK1 has been previously implicated in the control of growth through unknown molecular mechanisms. Here we generate a series of mouse genetic models to modify levels of Dlk1 expression in the pituitary gland and demonstrate that the dosage of DLK1 modulates the process of stem cell commitment with lifelong impact on pituitary gland size. We establish that stem cells are a critical source of DLK1, where embryonic disruption alters proliferation in the anterior pituitary, leading to long-lasting consequences on growth hormone secretion later in life.

An in vivo functional assay to characterize human STAT5B genetic variants during zebrafish development

Growth hormone (GH) binding to GH receptor activates janus kinase 2 (JAK2)-signal transducer and activator of transcription 5b (STAT5b) pathway, which stimulates transcription of insulin-like growth factor-1 (IGF1), insulin-like growth factor binding protein 3 (IGFBP3) and insulin-like growth factor acid-labile subunit (IGFALS). Although STAT5B deficiency was established as an autosomal recessive disorder, heterozygous dominant-negative STAT5B variants have been reported in patients with less severe growth deficit and milder immune dysfunction. We developed an in vivo functional assay in zebrafish to characterize the pathogenicity of three human STAT5B variants (p.Ala630Pro, p.Gln474Arg and p.Lys632Asn). Overexpression of human wild-type (WT) STAT5B mRNA and its variants led to a significant reduction of body length together with developmental malformations in zebrafish embryos. Overexpression of p.Ala630Pro, p.Gln474Arg or p.Lys632Asn led to an increased number of embryos with pericardial edema, cyclopia and bent spine compared with WT STAT5B. Although co-injection of WT and p.Gln474Arg and WT and p.Lys632Asn STAT5B mRNA in zebrafish embryos partially or fully rescues the length and the developmental malformations in zebrafish embryos, co-injection of WT and p.Ala630Pro STAT5B mRNA leads to a greater number of embryos with developmental malformations and a reduction in body length of these embryos. These results suggest that these variants could interfere with endogenous stat5.1 signaling through different mechanisms. In situ hybridization of zebrafish embryos overexpressing p.Gln474Arg and p.Lys632Asn STAT5B mRNA shows a reduction in igf1 expression. In conclusion, our study reveals the pathogenicity of the STAT5B variants studied.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

Immunity and Growth Plasticity of Asian Short-Toed Lark Nestlings in Response to Changes in Food Conditions: Can It Buffer the Challenge of Climate Change-Induced Trophic Mismatch?

Passerine nestlings frequently suffer from sub-optimal food conditions due to climate change-induced trophic mismatch between the nestlings and their optimal food resources. The ability of nestlings to buffer this challenge is less well understood. We hypothesized that poor food conditions might induce a higher immune response and lower growth rate of nestlings, and such physiological plasticity is conducive to nestling survival. To test this, we examined how food (grasshopper nymphs) abundance affects the expression of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin-1 β (IL-1β) genes, plasma IGF-1 levels, body mass, and fledging rates in wild Asian short-toed lark (Alaudala cheleensis) nestlings. Linear mixed models revealed that nymph biomass significantly influenced the expression of IFN-γ, TNF-α, and IL-1β genes, and the level of plasma IGF-1. The expressions of IFN-γ, TNF-α, and IL-1β genes were negatively correlated with nymph biomass and plasma IGF-1 level. Plasma IGF-1 level, nestling body mass growth rate, was positively correlated with nymph biomass. Despite a positive correlation between the nestling fledge rate and nymph biomass, more than 60% of nestlings fledged when nymph biomass was at the lowest level. These results suggest that immunity and growth plasticity of nestlings may be an adaptation for birds to buffer the negative effects of trophic mismatch.

Bone circuitry and interorgan skeletal crosstalk

The past decade has seen significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone integrity in disease. Recent breakthroughs have arisen mainly from identifying disease-causing mutations and modeling human bone disease in rodents, in essence, highlighting the integrative nature of skeletal physiology. It has become increasingly clear that bone cells, osteoblasts, osteoclasts, and osteocytes, communicate and regulate the fate of each other through RANK/RANKL/OPG, liver X receptors (LXRs), EphirinB2-EphB4 signaling, sphingolipids, and other membrane-associated proteins, such as semaphorins. Mounting evidence also showed that critical developmental pathways, namely, bone morphogenetic protein (BMP), NOTCH, and WNT, interact each other and play an important role in postnatal bone remodeling. The skeleton communicates not only with closely situated organs, such as bone marrow, muscle, and fat, but also with remote vital organs, such as the kidney, liver, and brain. The metabolic effect of bone-derived osteocalcin highlights a possible role of skeleton in energy homeostasis. Furthermore, studies using genetically modified rodent models disrupting the reciprocal relationship with tropic pituitary hormone and effector hormone have unraveled an independent role of pituitary hormone in skeletal remodeling beyond the role of regulating target endocrine glands. The cytokine-mediated skeletal actions and the evidence of local production of certain pituitary hormones by bone marrow-derived cells displays a unique endocrine-immune-skeletal connection. Here, we discuss recently elucidated mechanisms controlling the remodeling of bone, communication of bone cells with cells of other lineages, crosstalk between bone and vital organs, as well as opportunities for treating diseases of the skeleton.

Insulin-like growth factor 1 and the hormonal mediation of sibling rivalry

In altricial animals, young are completely dependent on parents for provisioning. The ability to outcompete siblings to receive parental provisioning has clear fitness benefits, and may be mediated by hormones that influence growth. We analyzed the effects of insulin-like growth factor 1 (IGF-1) on body size, growth, and sibling rivalry in eastern bluebirds (Sialia sialis). To determine whether IGF-1 is upregulated in response to the competitive environment, we manipulated brood sizes and examined the effect on IGF-1 levels, nestling body size, growth rate, and behavior. In a separate experiment, we injected nestlings with exogenous IGF-1 to study its impacts on body size, growth rate, and sibling competition. Brood size manipulation did not influence endogenous IGF-1 levels, but male nestlings with higher IGF-1 levels early in the nestling period tended to have greater mass gain than males with lower IGF-1 levels. Nestlings with higher IGF-1 levels also tended to be fed more frequently by parents. In the injection experiment, IGF-1 injected individuals tended to be heavier than vehicle injected young by the end of the nestling period, which suggests that IGF-1 can influence mass gain in bluebirds. IGF-1 has been proposed to be a mediator of life-history strategies and post-hatching behavior. Our results suggest that although bluebird nestlings do not adaptively elevate IGF-1 in response to the presence or number of siblings, IGF-1 may influence growth during the nestling period. These findings shed light on sibling competition, life history strategies, and the hormones that underlie them.

Liver-bone crosstalk in non-alcoholic fatty liver disease: Clinical implications and underlying pathophysiology

Osteoporosis is a common complication of many types of chronic liver diseases (CLDs), such as cholestatic liver disease, viral hepatitis, and alcoholic liver disease. Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent metabolic liver disease, affecting almost one third of adults around the world, and is emerging as the dominant cause of CLDs. Liver serves as a hub for nutrient and energy metabolism in the body, and its crosstalk with other tissues, such as adipose tissue, heart, and brain, has been well recognized. However, much less is known about the crosstalk that occurs between the liver and bone. Moreover, the mechanisms by which CLDs increase the risk for osteoporosis remain unclear. This review summarizes the latest research on the liver-bone axis and discusses the relationship between NAFLD and osteoporosis. We cover key signaling molecules secreted by liver, such as insulin-like growth factor-1 (IGF-1), fibroblast growth factor 21 (FGF21), insulin-like growth factor binding protein 1 (IGFBP1), fetuin-A, tumor necrosis factor-alpha (TNF-α), and osteopontin (OPN), and their relevance to the homeostasis of bone metabolism. Finally, we consider the disordered liver metabolism that occurs in patients with NAFLD and how this disrupts signaling to the bone, thereby perturbing the balance between osteoclasts and osteoblasts and leading to osteoporosis or hepatic osteodystrophy (HOD).

A Poly(dA:dT) Tract in the IGF1 Gene Is a Genetic Marker for Growth Traits in Pigs

Insulin-like growth factor 1 (IGF1) is an important regulator of body growth, development, and metabolism. The poly(dA:dT) tract affects the accessibility of transcription factor binding sites to regulate transcription. Therefore, this study assessed the effects of two poly(dA:dT) tracts on the transcriptional activity of porcine IGF1. The luciferase assay results demonstrated that the poly(dA:dT) tract 2 (−264/−255) was a positive regulatory element for IGF1 gene expression, and the activities between the different lengths of the poly(dA:dT) tract 2 were significant (p<0.01). The transcription factor C/EBPα inhibited the transcription of IGF1 by binding to tract 2, and the expression levels between the lengths of tract 2 after C/EBPα binding were also statistically different (p<0.01). Only the alleles 10T and 11T were found in the tract 2 in commercial pig breeds, while the 9T, 10T, and 11T alleles were found in Chinese native pig breeds. The allele frequencies were in Hardy−Weinberg equilibrium in all pig breeds. The genotypes of tract 2 were significantly associated with the growth traits (days to 115 kg and average daily gain) (p<0.05) in commercial pig breeds. Based on these findings, it can be concluded that the tract 2 mutation could be applied as a candidate genetic marker for growth trait selection in pig breeding programs.

Hallmarks of cancer: The insulin-like growth factors perspective

The identification of a series of attributes or hallmarks that are shared by virtually all cancer cells constitutes a true milestone in cancer research. The conceptualization of a catalogue of common genetic, molecular, biochemical and cellular events under a unifying Hallmarks of Cancer idea had a major impact in oncology. Furthermore, the fact that different types of cancer, ranging from pediatric tumors and leukemias to adult epithelial cancers, share a large number of fundamental traits reflects the universal nature of the biological events involved in oncogenesis. The dissection of a complex disease like cancer into a finite directory of hallmarks is of major basic and translational relevance. The role of insulin-like growth factor-1 (IGF1) as a progression/survival factor required for normal cell cycle transition has been firmly established. Similarly well characterized are the biochemical and cellular activities of IGF1 and IGF2 in the chain of events leading from a phenotypically normal cell to a diseased one harboring neoplastic traits, including growth factor independence, loss of cell-cell contact inhibition, chromosomal abnormalities, accumulation of mutations, activation of oncogenes, etc. The purpose of the present review is to provide an in-depth evaluation of the biology of IGF1 at the light of paradigms that emerge from analysis of cancer hallmarks. Given the fact that the IGF1 axis emerged in recent years as a promising therapeutic target, we believe that a careful exploration of this signaling system might be of critical importance on our ability to design and optimize cancer therapies.

Identification of Potential miRNA-mRNA Regulatory Network Associated with Pig Growth Performance in the Pituitaries of Bama Minipigs and Landrace Pigs

Pig growth performance is one of the criteria for judging pork production and is influenced by genotype and external environmental factors such as feeding conditions. The growth performance of miniature pigs, such as Bama minipigs, differs considerably from that of the larger body size pigs, such as Landrace pigs, and can be regarded as good models in pig growth studies. In this research, we identified differentially expressed genes in the pituitary gland of Bama minipigs and Landrace pigs. Through the pathway enrichment analysis, we screened the growth-related pathways and the genes enriched in the pathways and established the protein-protein interaction network. The RNAHybrid algorithm was used to predict the interaction between differentially expressed microRNAs and differentially expressed mRNAs. Four regulatory pathways (Y-82-ULK1/CDKN1A, miR-4334-5p-STAT3/PIK3R1/RPS6KA3/CAB39L, miR-4331-SCR/BCL2L1, and miR-133a-3p-BCL2L1) were identified via quantitative real-time PCR to detect the expression and correlation of candidate miRNAs and mRNAs. In conclusion, we revealed potential miRNA-mRNA regulatory networks associated with pig growth performance in the pituitary glands of Bama minipigs and Landrace pigs, which may help to elucidate the underlying molecular mechanisms of growth differences in pigs of different body sizes.

Independent Skeletal Actions of Pituitary Hormones

Over the past years, pituitary hormones and their receptors have been shown to have non-traditional actions that allow them to bypass the hypothalamus-pituitary-effector glands axis. Bone cells-osteoblasts and osteoclasts-express receptors for growth hormone, follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin, oxytocin, and vasopressin. Independent skeletal actions of pituitary hormones on bone have been studied using genetically modified mice with haploinsufficiency and by activating or inactivating the receptors pharmacologically, without altering systemic effector hormone levels. On another front, the discovery of a TSH variant (TSH-βv) in immune cells in the bone marrow and skeletal action of FSHβ through tumor necrosis factor α provides new insights underscoring the integrated physiology of bone-immune-endocrine axis. Here we discuss the interaction of each pituitary hormone with bone and the potential it holds in understanding bone physiology and as a therapeutic target.

Combining Gene Mutation with Expression of Candidate Genes to Improve Diagnosis of Escobar Syndrome

Escobar syndrome is a rare, autosomal recessive disorder that affects the musculoskeletal system and the skin. Mutations in the CHRNG and TPM2 genes are associated with this pathology. In this study, we conducted a clinical and genetic investigation of five patients and also explored via in silico and gene expression analysis their phenotypic variability. In detail, we identified a patient with a novel composite heterozygous variant of the CHRNG gene and two recurrent mutations in both CHRNG and TPM2 in the rest of the patients. As for the clinical particularities, we reported a list of modifier genes in a patient suffering from myopathy. Moreover, we identified decreased expression of IGF-1, which could be related to the short stature of Escobar patients, and increased expression of POLG1 specific to patients with TPM2 mutation. Through this study, we identified the genetic spectrum of Escobar syndrome in the Tunisian population, which will allow setting up genetic counseling and prenatal diagnosis for families at risk. In addition, we highlighted relevant biomarkers that could differentiate between patients with different genetic defects.

Covert actions of growth hormone: fibrosis, cardiovascular diseases and cancer

Since its discovery nearly a century ago, over 100,000 studies of growth hormone (GH) have investigated its structure, how it interacts with the GH receptor and its multiple actions. These include effects on growth, substrate metabolism, body composition, bone mineral density, the cardiovascular system and brain function, among many others. Recombinant human GH is approved for use to promote growth in children with GH deficiency (GHD), along with several additional clinical indications. Studies of humans and animals with altered levels of GH, from complete or partial GHD to GH excess, have revealed several covert or hidden actions of GH, such as effects on fibrosis, cardiovascular function and cancer. In this Review, we do not concentrate on the classic and controversial indications for GH therapy, nor do we cover all covert actions of GH. Instead, we stress the importance of the relationship between GH and fibrosis, and how fibrosis (or lack thereof) might be an emerging factor in both cardiovascular and cancer pathologies. We highlight clinical data from patients with acromegaly or GHD, alongside data from cellular and animal studies, to reveal novel phenotypes and molecular pathways responsible for these actions of GH in fibrosis, cardiovascular function and cancer.

Exerkines and long-term synaptic potentiation: Mechanisms of exercise-induced neuroplasticity

Physical exercise may improve cognitive function by modulating molecular and cellular mechanisms within the brain. We propose that the facilitation of long-term synaptic potentiation (LTP)-related pathways, by products induced by physical exercise (i.e., exerkines), is a crucial aspect of the exercise-effect on the brain. This review summarizes synaptic pathways that are activated by exerkines and may potentiate LTP. For a total of 16 exerkines, we indicated how blood and brain exerkine levels are altered depending on the type of physical exercise (i.e., cardiovascular or resistance exercise) and how they respond to a single bout (i.e., acute exercise) or multiple bouts of physical exercise (i.e., chronic exercise). This information may be used for designing individualized physical exercise programs. Finally, this review may serve to direct future research towards fundamental gaps in our current knowledge regarding the biophysical interactions between muscle activity and the brain at both cellular and system levels.

Considerations for and against dosing rodent pups before 7 days of age in juvenile toxicology studies

This review focuses on preweaning ontogenic and developmental processes that can influence the selection of the appropriate age at which to start dosing rodent pups in juvenile animal studies (JAS). The ICH S11 guideline on 'Nonclinical Safety Testing in Support of Development of Paediatric Medicines' highlights the need to adapt the age from which animals are dosed according to the stage of development in the target organs/tissues of concern in the youngest pediatric patients. Rodents (rat or mouse) are the most common species for JAS. Despite previous practices, based on comparative ontogeny, it is rarely necessary to dose rodents younger than one week of age since postnatal day (PND)7 is appropriate to address concern for the vast majority of organs. In exceptional cases, earlier dosing (e.g., PND4) can be appropriate to address specific concern in preterm neonates and when a tissue of concern has a particularly early developmental trajectory in the rodent compared to humans. The comparative development of the CNS is particularly complex. While exposure of rodents from PND10 covers most CNS development stages relevant to human neonates, a later dosing start (yet, not later than PND14) can sometimes be appropriate to reflect specific aspects (e.g., transformation of GABAergic transmission). An extended study design including subsets of several ages can be helpful to address multiple concerns within a preweaning JAS. Such design can allow for individual assessment of each concern, whilst minimizing (potentially irrelevant) signals from tissues exposed at a developmental stage that do not match the human situation.

Growth hormone modulates Trypanosoma cruzi infection in vitro

OBJECTIVE

Chagas disease (CD) is caused by the protozoan parasite, Trypanosoma cruzi. It affects 7 to 8 million people worldwide and leads to approximately 50,000 deaths per year. In vitro and in vivo studies had demonstrated that Trypanosoma cruziinfection causes an imbalance in the hypothalamic-pituitary-adrenal (HPA) axis that is accompanied by a progressive decrease in growth hormone (GH) and prolactin (PRL) production. In humans, inactivating mutations in the GH receptor gene cause Laron Syndrome (LS), an autosomal recessive disorder. Affected subjects are short, have increased adiposity, decreased insulin-like growth factor-I (IGFI), increased serum GH levels, are highly resistant to diabetes and cancer, and display slow cognitive decline. In addition, CD incidence in these individuals is diminished despite living in highly endemic areas. Consequently, we decided to investigate the in vitro effect of GH/IGF-I on T. cruzi infection.

DESIGN

We first treated the parasite and/or host cells with different peptide hormones including GH, IGFI, and PRL. Then, we treated cells using different combinations of GH/IGF-I attempting to mimic the GH/IGF-I serum levels observed in LS subjects.

RESULTS

We found that exogenous GH confers protection against T. cruzi infection. Moreover, this effect is mediated by GH and not IGFI. The combination of relatively high GH (50 ng/ml) and low IGF-I (20 ng/ml), mimicking the hormonal pattern seen in LS individuals, consistently decreased T. cruzi infection in vitro.

CONCLUSIONS

The combination of relatively high GH and low IGF-I serum levels in LS individuals may be an underlying condition providing partial protection against T. cruzi infection.

Combination treatment with growth hormone and zoledronic acid in a mouse model of Osteogenesis imperfecta

INTRODUCTION

Osteogenesis imperfecta (OI) or brittle bone disease is a genetic disorder that results in bone fragility. Bisphosphonates such as zoledronic acid (ZA) are used clinically to increase bone mass and reduce fracture risk. Human growth hormone (hGH) has been used to promote long bone growth and forestall short stature in children with OI. The potential for hGH to improve bone quality, particularly in combination with ZA has not been robustly studied.

METHODS

A preclinical study was performed using n = 80 mice split evenly by genotype (WT, Col1a2^+/G610C). Groups of n = 10 were treated with +/-ZA and +/-hGH in a factorial design for each genotype. Outcome measures included bone length, isolated muscle mass, bone parameters assessed by microCT analysis, dynamic histomorphometry, and biomechanical testing.

RESULTS

Treatment with hGH alone led to an increase in femur length in WT but not OI mice, however bone length was increased in both genotypes with the combination of hGH/ZA. MicroCT showed that hGH/ZA treatment increased cortical BV in both WT (+15%) and OI mice (+14.3%); hGH/ZA were also found to be synergistic in promoting cortical thickness in OI bone. ZA was found to have a considerably greater positive impact on trabecular bone than hGH. ZA was found to suppress bone turnover, and this was rescued by hGH treatment in terms of cortical periosteal perimeter, but not by dynamic bone remodeling. Statistically significant improvements in long bone by microCT did not translate into improvements in mechanical strength in a 4-point bending test, nor did vertebral strength improve in L4 compression testing in WT/OI bone.

DISCUSSION/CONCLUSION

These data support hGH/ZA combination as a treatment for short stature, however the improvements granted by hGH alone and in combination with ZA on bone quality are modest. Increased periosteal perimeter does show promise in improving bone strength in OI, however a longer treatment time may be required to see effects on bone strength through mechanical testing.

Musculoskeletal Effects of Altered GH Action

Growth hormone (GH) is a peptide hormone that can signal directly through its receptor or indirectly through insulin-like growth factor 1 (IGF-1) stimulation. GH draws its name from its anabolic effects on muscle and bone but also has distinct metabolic effects in multiple tissues. In addition to its metabolic and musculoskeletal effects, GH is closely associated with aging, with levels declining as individuals age but GH action negatively correlating with lifespan. GH’s effects have been studied in human conditions of GH alteration, such as acromegaly and Laron syndrome, and GH therapies have been suggested to combat aging-related musculoskeletal diseases, in part, because of the decline in GH levels with advanced age. While clinical data are inconclusive, animal models have been indispensable in understanding the underlying molecular mechanisms of GH action. This review will provide a brief overview of the musculoskeletal effects of GH, focusing on clinical and animal models.

Essential Amino Acid Intake Is Required for Sustaining Serum Insulin-like Growth Factor-I Levels but Is Not Necessarily Needed for Body Growth

Essential amino acids (EAAs) are those that cannot be synthesized enough to meet organismal demand; therefore, it is believed that they must be taken from the diet for optimal growth. The growth hormone (GH)/insulin-like growth factor-I (IGF-I) system is also considered significant for growth regulation in mammals. This study aimed to evaluate the relative contributions of protein nutrition and the GH/IGF-I system to body growth regulation. Experiments using rodents and hepatocyte-derived cell lines subjected to EAA deficiency showed that a reduction in the serum EAA concentration hinders Igf1 transcription in the liver in a cell-autonomous manner, thereby decreasing serum IGF-I levels. Remarkably, when the serum IGF-I level of mice on a low-protein diet was restored by the recombinant IGF-I infusion, the body growth was mostly rescued, although the mice were still deficient in EAA intake. Meanwhile, the GH signal activation and subsequent Igf1 transcription were also dramatically diminished by EAA deprivation in the cell culture model. Altogether, we demonstrate that EAAs are not strictly necessary for animal growth as building blocks but are required as IGF-I-tropic cues. The results will bring a paradigm shift regarding the definition of “essential” amino acids.

Growth control of the kidney

The functional mass of kidney tissue in an adult is an important determinant of human health. Kidney formation during development is an essential determinant of the final nephron endowment of the adult organ, and no evidence has been reported that mice or humans are able to generate new nephrons after the developmental period. Mechanisms controlling organ growth after development are essential to establish the final adult organ size. The potential for organ growth is maintained in adult life and the size of one kidney may be significantly increased by loss of the contralateral kidney. The mouse has provided a model system for investigators to critically explore genetic, cell biological, and hormonal control of developmental and juvenile kidney growth. This article reviews three basic aspects of kidney size regulation: (1) Mechanisms that control nephron formation and how these are altered by the cessation of nephrogenesis at the end of the developmental period. (2) Applicability of the general model for growth hormone-insulin like growth factor control to kidney growth both pre- and postnatally. (3) Commonalities between mechanisms of juvenile kidney growth and the compensatory growth that is stimulated in adult life by reduction of kidney mass. Understanding the mechanisms that determine set-points for cell numbers and size in the kidney may inform ongoing efforts to generate kidney tissue from stem cells.

Combined growth hormone and insulin-like growth factor-1 rescues growth retardation in glucocorticoid-treated mdxmice but does not prevent osteopenia

Short stature and osteoporosis are common in Duchenne muscular dystrophy (DMD) and its pathophysiology may include an abnormality of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, which is further exacerbated by long-term glucocorticoid (GC) treatment. Hence, an agent that has anabolic properties and may improve linear growth would be beneficial in this setting and therefore requires further exploration. A 5-week-old x-linked muscular dystrophy (mdx) mice were used as a model of DMD. They were treated with prednisolone ± GH + IGF-1 for 4 weeks and then compared to control mdx mice to allow the study of both growth and skeletal structure. GC reduced cortical bone area, bone fraction, tissue area and volume and cortical bone volume, as assessed by micro computed tomography (CT) In addition, GC caused somatic and skeletal growth retardation but improved grip strength. The addition of GH + IGF-1 therapy rescued the somatic growth retardation and induced additional improvements in grip strength (16.9% increase, P < 0.05 compared to control). There was no improvement in bone microarchitecture (assessed by micro-CT and static histomorphometry) or biomechanical properties (assessed by three-point bending). Serum bone turnover markers (Serum procollagen 1 intact N-terminal propeptide (P1NP), alpha C-terminal telopeptide (αCTX)) also remained unaffected. Further work is needed to maximise these gains before proceeding to clinical trials in boys with DMD.

Key pituitary miRNAs mediate the expression of pig GHRHR splice variants by regulating splice factors

The growth hormone releasing hormone receptor (GHRHR) is well documented in organism growth and its alternative splicing may generate multiple functional GHRHR splice variants (SVs). Our previous study has demonstrated the key pituitary miRNAs (let-7e and miR-328-5p) in pig regulated the expression of GHRHR SVs by directly targeting to them. And according to recent reports, the interplay between miRNA-based silencing of mRNAs and alternative splicing of pre-mRNAs is a crucial post-transcriptional mechanism. In this study, SF3B3 and CPSF4 were firstly excavated as the splice factors that involved in the formation of GHRHR SVs mediated by let-7e and miR-328-5p through the comparation of the expression relations of GHRHR SVs, let-7e/miR-328-5p and SF3B3/CPSF4 in pituitary tissues between Landrace pigs and BaMa pigs, as well as the prediction of the target relations of let-7e/miR-328-5p with SF3B3 and/or CPSF4. SF3B3 and CPSF4 targeted by let-7e and miR-328-5p were further verified by performing dual-luciferase reporter assays and detecting the expression of target transcripts. Then the RT-PCR, RT-qPCR and Western blot assays were used to confirm SF3B3 and CPSF4 were involved in the formation of the GHRHR SVs, and in this process, let-7e and miR-328-5p mediated GHRHR SVs by regulating SF3B3 and CPSF4. Finally, the target site of SF3B3 on pre-GHRHR was on the Exon 12 to Exon14, while CPSF4 acted on the other fragments of the pre-GHRHR, which were explored by dual-luciferase reporter system preliminarily. To the best of our knowledge, this paper is the first to report the miRNAs regulate GHRHR SVs indirectly by splice factors.

Mice with gene alterations in the GH and IGF family

Much of our understanding of GH's action stems from animal models and the generation and characterization of genetically altered or modified mice. Manipulation of genes in the GH/IGF1 family in animals started in 1982 when the first GH transgenic mice were produced. Since then, multiple laboratories have altered mouse DNA to globally disrupt Gh, Ghr, and other genes upstream or downstream of GH or its receptor. The ability to stay current with the various genetically manipulated mouse lines within the realm of GH/IGF1 research has been daunting. As such, this review attempts to consolidate and summarize the literature related to the initial characterization of many of the known gene-manipulated mice relating to the actions of GH, PRL and IGF1. We have organized the mouse lines by modifications made to constituents of the GH/IGF1 family either upstream or downstream of GHR or to the GHR itself. Available data on the effect of altered gene expression on growth, GH/IGF1 levels, body composition, reproduction, diabetes, metabolism, cancer, and aging are summarized. For the ease of finding this information, key words are highlighted in bold throughout the main text for each mouse line and this information is summarized in Tables 1, 2, 3 and 4. Most importantly, the collective data derived from and reported for these mice have enhanced our understanding of GH action.

The imprinted Zdbf2 gene finely tunes control of feeding and growth in neonates

Genomic imprinting refers to the mono-allelic and parent-specific expression of a subset of genes. While long recognized for their role in embryonic development, imprinted genes have recently emerged as important modulators of postnatal physiology, notably through hypothalamus-driven functions. Here, using mouse models of loss, gain and parental inversion of expression, we report that the paternally expressed Zdbf2 gene controls neonatal growth in mice, in a dose-sensitive but parent-of-origin-independent manner. We further found that Zdbf2-KO neonates failed to fully activate hypothalamic circuits that stimulate appetite, and suffered milk deprivation and diminished circulating Insulin Growth Factor 1 (IGF-1). Consequently, only half of Zdbf2-KO pups survived the first days after birth and those surviving were smaller. This study demonstrates that precise imprinted gene dosage is essential for vital physiological functions at the transition from intra- to extra-uterine life, here the adaptation to oral feeding and optimized body weight gain.

Effect of Growth Hormone Secretagogue Receptor Deletion on Growth, Pulsatile Growth Hormone Secretion, and Meal Pattern in Male and Female Mice

INTRODUCTION

While the vast majority of research investigating the role of ghrelin or its receptor, GHS-R1a, in growth, feeding, and metabolism has been conducted in male rodents, very little is known about sex differences in this system. Furthermore, the role of GHS-R1a signaling in the control of pulsatile GH secretion and its link with growth or metabolic parameters has never been characterized.

METHODS

We assessed the sex-specific contribution of GHS-R1a signaling in the activity of the GH/IGF-1 axis, metabolic parameters, and feeding behavior in adolescent (5-6 weeks old) or adult (10-19 weeks old) GHS-R KO (Ghsr-/-) and WT (Ghsr+/+) male and female mice.

RESULTS

Adult Ghsr-/- male and female mice displayed deficits in weight and linear growth that were correlated with reduced GH pituitary contents in males only. GHS-R1a deletion was associated with reduced meal frequency and increased meal intervals, as well as reduced hypothalamic GHRH and NPY mRNA in males, not females. In adult, GH release from Ghsr-/- mice pituitary explants ex vivo was reduced independently of the sex. However, in vivo pulsatile GH secretion decreased in adult but not adolescent Ghsr-/- females, while in males, GHS-R1a deletion was associated with reduction in pulsatile GH secretion during adolescence exclusively. In males, linear growth did not correlate with pulsatile GH secretion, but rather with ApEn, a measure that reflects irregularity of the rhythmic secretion. Fat mass, plasma leptin concentrations, or ambulatory activity did not predict differences in GH secretion.

DISCUSSION/CONCLUSION

These results point to a sex-dependent dimorphic effect of GHS-R1a signaling to modulate pulsatile GH secretion and meal pattern in mice with different compensatory mechanisms occurring in the hypothalamus of adult males and females after GHS-R1a deletion. Altogether, we show that GHS-R1a signaling plays a more critical role in the regulation of pulsatile GH secretion during adolescence in males and adulthood in females.