Interactions of IGF-1 with the blood-brain barrier in vivo and in situ

The Possible Role of Postnatal Biphasic Dysregulation of IGF-1 Tone in the Etiology of Idiopathic Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a pervasive condition of neurodevelopmental origin with an increasing burden on society. Idiopathic ASD is notorious for its heterogeneous behavioral manifestations, and despite substantial efforts, its etiopathology is still unclear. An increasing amount of data points to the causative role of critical developmental alterations in the first year of life, although the contribution of fetal, environmental, and genetic factors cannot be clearly distinguished. This review attempts to propose a narrative starting from neuropathological findings in ASD, involving insulin-like growth factor 1 (IGF-1) as a key modulator and demonstrates how the most consistent gestational risk factors of ASD-maternal insulin resistance and fetal growth insufficiency-converge at the perinatal dysregulation of offspring anabolism in the critical period of early development. A unifying hypothesis is derived, stating that the co-occurrence of these gestational conditions leads to postnatal biphasic dysregulation of IGF-1 tone in the offspring, leading first to insulin-dependent accelerated development, then to subsequent arrest of growth and brain maturation in ASD as an etiologic process. This hypothesis is tested for its explanation of various widely reported risk factors and observations of idiopathic ASD, including early postnatal growth abnormalities, the pervasive spectrum of symptoms, familial predisposition, and male susceptibility. Finally, further directions of research are outlined.

The IGF System and Aging

There is strong evidence that IGF signaling is involved in fundamental aspects of the aging process. However, the extracellular part of the IGF system is complex with various receptors, ligand effectors, high-affinity IGF-binding proteins, proteinases, and endogenous inhibitors that all, along with their biological context, must be considered. The IGF system components are evolutionarily conserved, underscoring the importance of understanding this system in physiology and pathophysiology. This review will briefly describe the different components of the IGF system and then discuss past and current literature regarding IGF and aging, with a focus on cellular senescence, model organisms of aging, centenarian genetics, and 3 age-related diseases-pulmonary fibrosis, Alzheimer disease, and macular degeneration-in appropriate murine models and in humans. Commonalities in mechanism suggest conditions where IGF system components may be disease drivers and potential targets in promoting healthy aging in humans.

Insulin-Like Growth Factor Signaling in Alzheimer's Disease: Pathophysiology and Therapeutic Strategies

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population, posing a significant public health challenge due to limited therapeutic options that merely delay cognitive decline. AD is associated with impaired energy metabolism and reduced neurotrophic signaling. The insulin-like growth factor (IGF) signaling pathway, crucial for central nervous system (CNS) development, metabolism, repair, cognition, and emotion regulation, includes IGF-1, IGF-2, IGF-1R, IGF-2R, insulin receptor (IR), and six insulin-like growth factor binding proteins (IGFBPs). Research has identified abnormalities in IGF signaling in individuals with AD and AD models. Dysregulated expression of IGFs, receptors, IGFBPs, and disruptions in downstream phosphoinositide 3-kinase-protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) pathways collectively increase AD susceptibility. Studies suggest modulating the IGF pathway may ameliorate AD pathology and cognitive decline. This review explores the CNS pathophysiology of IGF signaling in AD progression and assesses the potential of targeting the IGF system as a novel therapeutic strategy. Further research is essential to elucidate how aberrant IGF signaling contributes to AD development, understand underlying molecular mechanisms, and evaluate the safety and efficacy of IGF-based treatments.

Insulin-like growth factor-1 and cognitive health: Exploring cellular, preclinical, and clinical dimensions

Age and insulin-like growth factor-1 (IGF-1) have an inverse association with cognitive decline and dementia. IGF-1 is known to have important pleiotropic functions beginning in neurodevelopment and extending into adulthood such as neurogenesis. At the cellular level, IGF-1 has pleiotropic signaling mechanisms through the IGF-1 receptor on neurons and neuroglia to attenuate inflammation, promote myelination, maintain astrocytic functions for homeostatic balances, and neuronal synaptogenesis. In preclinical rodent models of aging and transgenic models of IGF-1, increased IGF-1 improves cognition in a variety of behavioral paradigms along with reducing IGF-1 via knockout models being able to induce cognitive impairment. At the clinical levels, most studies highlight that increased levels of IGF-1 are associated with better cognition. This review provides a comprehensive and up-to-date evaluation of the association between IGF-1 and cognition at the cellular signaling levels, preclinical, and clinical levels.

Choroid plexus extracellular vesicle transport of blood-borne insulin-like growth factor 1 to the hippocampus of the immature brain

Reduced serum level of insulin-like growth factor 1 (IGF-1), a major regulator of perinatal development, in extremely preterm infants has been shown to be associated with neurodevelopmental impairment. To clarify the mechanism of IGF-1 transport at the blood-cerebrospinal fluid (CSF) barrier of the immature brain, we combined studies of in vivo preterm piglet and rabbit models with an in vitro transwell cell culture model of neonatal primary murine choroid plexus epithelial (ChPE) cells. We identified IGF-1-positive intracellular vesicles in ChPE cells and provided data indicating a directional transport of IGF-1 from the basolateral to the apical media in extracellular vesicles (EVs). Exposure of the ChPE cells to human IGF-1 on the basolateral side increased the secretion of IGF-1-positive EVs in the apical media. Mass spectrometry analysis displayed similarities in protein content between EVs derived from preterm piglet CSF-derived and ChPE cell-derived EVs. Furthermore, exposure of ChPE cells to human IGF-1 caused an enrichment of human IGF-1 and transmembrane p24 trafficking protein 2, proteins important for perinatal development, in apical media-derived EVs. Moreover, intraventricular injections of ChPE cell-derived EVs in preterm rabbit pups resulted in an uptake of EVs in the brain, displaying penetration through the ependymal lining and deep into the hippocampus. Finally, exposure of rat hippocampus neurons to ChPE cell-derived EVs resulted in internalization of the EVs in hippocampal soma and neurites. In summary, we describe a transport pathway for blood-borne IGF-1 in EVs through the blood-CSF barrier to the hippocampus in the immature brain.

White matter protection with insulin-like growth factor-1 after hypoxia-ischaemia in preterm foetal sheep

Perinatal hypoxia-ischaemia in extremely preterm infants is associated with long-term neurodevelopmental impairment, for which there is no specific treatment. Insulin-like growth factor-1 can reduce acute brain injury, but its effects on chronic white matter injury after hypoxia-ischaemia are unclear. Preterm-equivalent foetal sheep (0.6 gestation) received either sham-asphyxia or asphyxia induced by umbilical cord occlusion for 30 min, and recovered for either 3 or 35 days after asphyxia. The 35 day recovery groups received either an intracerebroventricular infusion of insulin-like growth factor-1 (1 µg/24 h) or vehicle, from 3 to 14 days after asphyxia. Asphyxia was associated with ventricular enlargement, and loss of frontal and parietal white matter area (P < 0.05 versus sham-asphyxia). This was associated with reduced area fraction of myelin basic protein and numbers of oligodendrocyte transcription factor 2 and mature, anti-adenomatous polyposis coli-positive oligodendrocytes in periventricular white matter (P < 0.05), with persistent inflammation and caspase-3 activation (P < 0.05). Four of eight foetuses developed cystic lesions in temporal white matter. Prolonged infusion with insulin-like growth factor-1 restored frontal white matter area, improved numbers of oligodendrocyte transcription factor 2-positive and mature, anti-adenomatous polyposis coli-positive oligodendrocytes, with reduced astrogliosis and microgliosis after 35 days recovery (P < 0.05 versus asphyxia). One of four foetuses developed temporal cystic lesions. Functionally, insulin-like growth factor-1-treated foetuses had faster recovery of EEG power, but not spectral edge. Encouragingly, these findings show that delayed, prolonged, insulin-like growth factor-1 treatment can improve functional maturation of periventricular white matter after severe asphyxia in the very immature brain, at least in part by suppressing chronic neural inflammation.

Exercise, Neuroprotective Exerkines, and Parkinson's Disease: A Narrative Review

Parkinson's disease (PD) is a prevalent neurodegenerative disease in which treatment often includes an exercise regimen. Exercise is neuroprotective in animal models of PD, and, more recently, human clinical studies have verified exercise's disease-modifying effect. Aerobic exercise and resistance training improve many of PD's motor and non-motor symptoms, while neuromotor therapy and stretching/flexibility exercises positively contribute to the quality of life in people with PD. Therefore, understanding the role of exercise in managing this complex disorder is crucial. Exerkines are bioactive substances that are synthesized and released during exercise and have been implicated in several positive health outcomes, including neuroprotection. Exerkines protect neuronal cells in vitro and rodent PD models in vivo. Aerobic exercise and resistance training both increase exerkine levels in the blood, suggesting a role for exerkines in the neuroprotective theory. Many exerkines demonstrate the potential for protecting the brain against pathological missteps caused by PD. Every person (people) with Parkinson's (PwP) needs a comprehensive exercise plan tailored to their unique needs and abilities. Here, we provide an exercise template to help PwP understand the importance of exercise for treating PD, describe barriers confronting many PwP in their attempt to exercise, provide suggestions for overcoming these barriers, and explore the role of exerkines in managing PD. In conclusion, exercise and exerkines together create a powerful neuroprotective system that should contribute to slowing the chronic progression of PD.

Effect of ultrasound-mediated blood-spinal cord barrier opening on survival and motor function in females in an amyotrophic lateral sclerosis mouse model

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive loss of motor neurons. The limited efficacy of recent therapies in clinical development may be linked to lack of drug penetration to the affected motor neurons due to the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB).

METHODS

In this work, the safety and efficacy of repeated short transient opening of the BSCB by low intensity pulsed ultrasound (US, sonication) was studied in females of an ALS mouse model (B6.Cg-Tg(SOD1∗G93A)1Gur/J). The BSCB was disrupted using a 1 MHz ultrasound transducer coupled to the spinal cord, with and without injection of insulin-like growth factor 1 (IGF1), a neurotrophic factor that has previously shown efficacy in ALS models.

FINDINGS

Results in wild-type (WT) animals demonstrated that the BSCB can be safely disrupted and IGF1 concentrations significantly enhanced after a single session of transient BSCB disruption (176 ± 32 μg/g vs. 0.16 ± 0.008 μg/g, p < 0.0001). Five repeated weekly US sessions performed in female ALS mice demonstrated a survival advantage in mice treated with IGF1 and US (US IGF1) compared to treatment with IGF1 alone (176 vs. 166 days, p = 0.0038). Surprisingly, this survival advantage was also present in mice treated with US alone vs. untreated mice (178.5 vs. 166.5 days, p = 0.0061). Muscle strength did not show difference among the groups. Analysis of glial cell immunoreactivity and microglial transcriptome showing reduced cell proliferation pathways, in addition to lymphocyte infiltration, suggested that the beneficial effect of US or US IGF1 could act through immune cell modulation.

INTERPRETATION

These results show the first step towards a possible beneficial impact of transient BSCB opening for ALS therapy and suggest implication of immune cells.

FUNDING

Fondation pour la Recherche Médicale (FRM). Investissements d'avenirANR-10-IAIHU-06, Société Française de Neurochirurgie (SFNC), Fond d'étude et de Recherche du Corps Medical (FERCM), Aide à la Recherche des Maladies du Cerveau (ARMC), SLA Fondation Recherche (SLAFR), French Ministry for High Education and Research (MENR), Carthera, Laboratoire de Recherche en Technologies Chirurgicales Avancées (LRTCA).

Palmitic Acid Modulation of the Insulin-Like Growth Factor System in Hypothalamic Astrocytes and Neurons

INTRODUCTION

Insulin-like growth factor (IGF)1 and IGF2 have neuroprotective effects, but less is known regarding how other members of the IGF system, including IGF binding proteins (IGFBPs) and the regulatory proteinase pappalysin-1 (PAPP-A) and its endogenous inhibitor stanniocalcin-2 (STC2) participate in this process. Here, we analyzed whether these members of the IGF system are modified in neurons and astrocytes in response to palmitic acid (PA), a fatty acid that induces cell stress when increased centrally.

METHODS

Primary hypothalamic astrocyte cultures from male and female PND2 rats and the pro-opiomelanocortin (POMC) neuronal cell line, mHypoA-POMC/GFP-2, were treated with PA, IGF1 or both. To analyze the role of STC2 in astrocytes, siRNA assays were employed.

RESULTS

In astrocytes of both sexes, PA rapidly increased cell stress factors followed by increased Pappa and Stc2 mRNA levels and then a decrease in Igf1, Igf2, and Igfbp2 expression and cell number. Exogenous IGF1 did not revert these effects. In mHypoA-POMC/GFP-2 neurons, PA reduced cell number and Pomc and Igf1 mRNA levels, and increased Igfbp2 and Stc2, again with no effect of exogenous IGF1. PA increased STC2 expression, but no effects of decreasing its levels by interference assays or exogenous STC2 treatment in astrocytes were found.

CONCLUSIONS

The response of the IGF system to PA was cell and sex specific, but no protective effects of the IGFs were found. However, the modifications in hypothalamic PAPP-A and STC2 indicate that further studies are required to determine their role in the response to fatty acids and possibly in metabolic control.

PEAK Mood, Mind, and Marks: a pilot study of an intervention to support university students' mental and cognitive health through physical exercise

Introduction

Regular exercise has the potential to enhance university students' mental and cognitive health. The PEAK Mood, Mind and Marks program (i.e., PEAK) is a neuroscience-informed intervention developed using the Behaviour Change Wheel to support students to exercise three or more times per week to benefit their mental and cognitive health. This pilot study assessed the impact of PEAK on exercise, mental and cognitive health, and implementation outcomes.

Methods

PEAK was delivered to 115 undergraduate university students throughout a 12-week university semester. The primary outcome was weekly exercise frequency. Secondary outcomes were: time spent engaged in moderate-vigorous exercise, sedentary behaviour and perceived mental health and cognitive health. All were measured via online self-report questionnaires. Qualitative interviews with 15 students investigated influences on engagement, the acceptability and appropriateness of PEAK, and its mechanisms of behaviour change. Paired t-tests, Wilcoxon Signed-Rank tests and template analysis were used to analyse quantitative and qualitative data, respectively.

Results

On average, 48.4% of students engaged in the recommended frequency of three or more exercise sessions per week. This proportion decreased towards the end of PEAK. Sedentary behaviour significantly decreased from baseline to end-point, and moderate-vigorous exercise significantly increased among students' who were non-exercisers. Mental wellbeing, stress, loneliness, and sense of belonging to the university significantly improved. There were no significant changes in psychological distress. Concentration, memory, and productivity significantly improved. Sixty-eight percent of students remained engaged in one or more components of PEAK at end-point. Qualitative data indicated students found PEAK to be acceptable and appropriate, and that it improved aspects of their capability, opportunity, and motivation to exercise.

Conclusions

Students are receptive to an exercise-based program to support their mental and cognitive health. Students exercise frequency decreased; however, these figures are likely a conservative estimate of students exercise engagement. Students valued the neuroscience-informed approach to motivational and educational content and that the program's goals aligned with their academic goals. Students identified numerous areas PEAK's content and implementation can be optimised, including use of a single digital delivery platform, more opportunities to connect with peers and to expand the content's cultural inclusivity.

Targeting the Multiple Complex Processes of Hypoxia-Ischemia to Achieve Neuroprotection

Hypoxic-ischemic encephalopathy (HIE) is a major cause of newborn brain damage stemming from a lack of oxygenated blood flow in the neonatal period. Twenty-five to fifty percent of asphyxiated infants who develop HIE die in the neonatal period, and about sixty percent of survivors develop long-term neurological disabilities. From the first minutes to months after the injury, a cascade of events occurs, leading to blood-brain barrier (BBB) opening, neuronal death and inflammation. To date, the only approach proposed in some cases is therapeutic hypothermia (TH). Unfortunately, TH is only partially protective and is not applicable to all neonates. This review synthesizes current knowledge on the basic molecular mechanisms of brain damage in hypoxia-ischemia (HI) and on the different therapeutic strategies in HI that have been used and explores a major limitation of unsuccessful therapeutic approaches.

Perioperative growth hormone levels as an early predictor of new-onset secondary adrenal insufficiency following transsphenoidal pituitary tumor resection

OBJECTIVE

This study aims to predict new-onset secondary adrenal insufficiency (NOSAI) after transsphenoidal pituitary tumor resection surgery using perioperative growth hormone (GH) and prolactin (PRL) levels, among other factors.

METHODS

A cohort of 124 adult patients who underwent transsphenoidal resection for non-functioning pituitary adenoma, with routine perioperative glucocorticoid use, was used to develop the predictive regression model. An additional 46 patients served as the validation cohort. Generalized additive models were used to identify optimal cut-off points for the variables.

RESULTS

The GH level on postoperative day one (POD1) can be a simple predictor by implementing a cut-off point of 0.41 ng/ml. A value ≤ 0.41 ng/mL predicted NOSAI with 0.6316 sensitivity and 0.7810 specificity for the original cohort and 1.0000 sensitivity and 0.7143 specificity for the validation cohort. The multiple logistic regression model included perioperative PRL level difference, perioperative GH level difference, intraoperative cerebrospinal fluid (CSF) leakage, tumor size, and the combined effect of diabetes insipidus (DI) and relative perioperative GH level difference. The areas under the receiver operating characteristic curves were 0.9410 (original cohort) and 0.9494 (validation cohort) for the regression model.

CONCLUSION

Early morning GH level on POD1 can predict NOSAI with fair accuracy when perioperative stress dose glucocorticoid is administered. Prediction accuracy can be improved by considering CSF leakage, DI, and perioperative changes in GH and PRL in the final regression model.

Insulin and the blood-brain barrier

The blood-brain barrier (BBB) predominantly regulates insulin transport into and levels within the brain. The BBB is also an important site of insulin binding and mediator of insulin receptor (INSR) signaling. The insulin transporter is separate from the INSR, highlighting the important, unique role of each protein in this structure. After a brief introduction on the structure of insulin and the INSR, we discuss the importance of insulin interactions at the BBB, the properties of the insulin transporter and the role of the BBB insulin transporter in various physiological conditions. We go on to further describe insulin BBB signaling and the impact not only within brain endothelial cells but also the cascade into other cell types within the brain. We close with future considerations to advance our knowledge about the importance of insulin at the BBB.

Phenotype-structured model of intra-clonal heterogeneity and drug resistance in multiple myeloma

Multiple myeloma (MM) is a genetically complex hematological cancer characterized by the abnormal proliferation of malignant plasma cells in the bone marrow. This disease progresses from a premalignant condition known as monoclonal gammopathy of unknown significance (MGUS) through sequential genetic alterations involving various genes. These genetic changes contribute to the uncontrolled growth of multiple clones of plasma cells. In this study, we present a phenotype-structured model that captures the intra-clonal heterogeneity and drug resistance in multiple myeloma (MM). The model accurately reproduces the branching evolutionary pattern observed in MM progression, aligning with a previously developed multiscale model. Numerical simulations reveal that higher mutation rates enhance tumor phenotype diversity, while access to growth factors accelerates tumor evolution and increases its final size. Interestingly, the model suggests that further increasing growth factor access primarily amplifies tumor size rather than altering clonal dynamics. Additionally, the model emphasizes that higher mutation frequencies and growth factor availability elevate the chances of drug resistance and relapse. It indicates that the timing of the treatment could trajectory of tumor evolution and clonal emergence in the case of branching evolutionary pattern. Given its low computational cost, our model is well-suited for quantitative studies on MM clonal heterogeneity and its interaction with chemotherapeutic treatments.

Molecular mechanisms underlying physical exercise-induced brain BDNF overproduction

Accumulating evidence supports that physical exercise (EX) is the most effective non-pharmacological strategy to improve brain health. EX prevents cognitive decline associated with age and decreases the risk of developing neurodegenerative diseases and psychiatric disorders. These positive effects of EX can be attributed to an increase in neurogenesis and neuroplastic processes, leading to learning and memory improvement. At the molecular level, there is a solid consensus to involve the neurotrophin brain-derived neurotrophic factor (BDNF) as the crucial molecule for positive EX effects on the brain. However, even though EX incontestably leads to beneficial processes through BDNF expression, cellular sources and molecular mechanisms underlying EX-induced cerebral BDNF overproduction are still being elucidated. In this context, the present review offers a summary of the different molecular mechanisms involved in brain's response to EX, with a specific focus on BDNF. It aims to provide a cohesive overview of the three main mechanisms leading to EX-induced brain BDNF production: the neuronal-dependent overexpression, the elevation of cerebral blood flow (hemodynamic hypothesis), and the exerkine signaling emanating from peripheral tissues (humoral response). By shedding light on these intricate pathways, this review seeks to contribute to the ongoing elucidation of the relationship between EX and cerebral BDNF expression, offering valuable insights into the potential therapeutic implications for brain health enhancement.

Modulation of neurotrophic factors in the treatment of dementia, stroke and TBI: Effects of Cerebrolysin

Neurotrophic factors (NTFs) are involved in the pathophysiology of neurological disorders such as dementia, stroke and traumatic brain injury (TBI), and constitute molecular targets of high interest for the therapy of these pathologies. In this review we provide an overview of current knowledge of the definition, discovery and mode of action of five NTFs, nerve growth factor, insulin-like growth factor 1, brain derived NTF, vascular endothelial growth factor and tumor necrosis factor alpha; as well as on their contribution to brain pathology and potential therapeutic use in dementia, stroke and TBI. Within the concept of NTFs in the treatment of these pathologies, we also review the neuropeptide preparation Cerebrolysin, which has been shown to resemble the activities of NTFs and to modulate the expression level of endogenous NTFs. Cerebrolysin has demonstrated beneficial treatment capabilities in vitro and in clinical studies, which are discussed within the context of the biochemistry of NTFs. The review focuses on the interactions of different NTFs, rather than addressing a single NTF, by outlining their signaling network and by reviewing their effect on clinical outcome in prevalent brain pathologies. The effects of the interactions of these NTFs and Cerebrolysin on neuroplasticity, neurogenesis, angiogenesis and inflammation, and their relevance for the treatment of dementia, stroke and TBI are summarized.

Application of In vitro transcytosis models to brain targeted biologics

The blood brain barrier (BBB) efficiently limits the penetration of biologics drugs from blood to brain. Establishment of an in vitro BBB model can facilitate screening of central nervous system (CNS) drug candidates and accelerate CNS drug development. Despite many established in vitro models, their application to biologics drug selection has been limited. Here, we report the evaluation of in vitro transcytosis of anti-human transferrin receptor (TfR) antibodies across human, cynomolgus and mouse species. We first evaluated human models including human cerebral microvascular endothelial cell line hCMEC/D3 and human colon epithelial cell line Caco-2 models. hCMEC/D3 model displayed low trans-epithelial electrical resistance (TEER), strong paracellular transport, and similar transcytosis of anti-TfR and control antibodies. In contrast, the Caco-2 model displayed high TEER value and low paracellular transport. Anti-hTfR antibodies demonstrated up to 70-fold better transcytosis compared to control IgG. Transcytosis of anti-hTfR.B1 antibody in Caco-2 model was dose-dependent and saturated at 3 μg/mL. Enhanced transcytosis of anti-hTfR.B1 was also observed in a monkey brain endothelial cell based (MBT) model. Importantly, anti-hTfR.B1 showed relatively high brain radioactivity concentration in a non-human primate positron emission tomography study indicating that the in vitro transcytosis from both Caco-2 and MBT models aligns with in vivo brain exposure. Typically, brain exposure of CNS targeted biologics is evaluated in mice. However, antibodies, such as the anti-human TfR antibodies, do not cross-react with the mouse target. Therefore, validation of a mouse in vitro transcytosis model is needed to better understand the in vitro in vivo correlation. Here, we performed transcytosis of anti-mouse TfR antibodies in mouse brain endothelial cell-based models, bEnd3 and the murine intestinal epithelial cell line mIEC. There is a good correlation between in vitro transcytosis of anti-mTfR antibodies and bispecifics in mIEC model and their mouse brain uptake. These data strengthen our confidence in the predictive power of the in vitro transcytosis models. Both mouse and human in vitro models will serve as important screening assays for brain targeted biologics selection in CNS drug development.

Characterization of choroid plexus in the preterm rabbit pup following subcutaneous administration of recombinant human IGF-1/IGFBP-3

Insulin-like growth factor-1 (IGF-1) is essential for normal brain development and regulates essential processes of vascular maturation and stabilization. Importantly, preterm birth is associated with reduced serum levels of IGF-1 as compared to in utero levels. Using a preterm rabbit pup model, we investigated the uptake of systemic recombinant human (rh) IGF-1 in complex with its main binding protein IGF-binding protein 3 (BP-3) to the brain parenchyma via the choroid plexus. Five hours after subcutaneous administration, labeled rhIGF-1/rhIGFBP-3 displayed a widespread presence in the choroid plexus of the lateral and third ventricle, however, to a less degree in the fourth, as well as in the perivascular and subarachnoid space. We found a time-dependent uptake of IGF-1 in cerebrospinal fluid, decreasing with postnatal age, and a translocation of IGF-1 through the choroid plexus. The impact of systemic rhIGF-1/rhIGFBP-3 on IGF-1 receptor activation in the choroid plexus decreased with postnatal age, correlating with IGF-1 uptake in cerebrospinal fluid. In addition, choroid plexus gene expression was observed to increase with postnatal age. Moreover, using choroid plexus in vitro cell cultures, gene expression and protein synthesis were further investigated upon rhIGF-1/rhIGFBP-3 stimulation as compared to rhIGF-1 alone, and found not to be differently altered. Here, we characterize the uptake of systemic rhIGF-1/rhIGFBP-3 to the preterm brain, and show that the interaction between systemic rhIGF-1/rhIGFBP-3 and choroid plexus varies over time.

The metabolic effects of resumption of a high fat diet after weight loss are sex dependent in mice

Dietary restriction is a frequent strategy for weight loss, but adherence is difficult and returning to poor dietary habits can result in more weight gain than that previously lost. How weight loss due to unrestricted intake of a healthy diet affects the response to resumption of poor dietary habits is less studied. Moreover, whether this response differs between the sexes and if the insulin-like growth factor (IGF) system, sex dependent and involved in metabolic control, participates is unknown. Mice received rodent chow (6% Kcal from fat) or a high-fat diet (HFD, 62% Kcal from fat) for 4 months, chow for 3 months plus 1 month of HFD, or HFD for 2 months, chow for 1 month then HFD for 1 month. Males and females gained weight on HFD and lost weight when returned to chow at different rates (p < 0.001), but weight gain after resumption of HFD intake was not affected by previous weight loss in either sex. Glucose metabolism was more affected by HFD, as well as the re-exposure to HFD after weight loss, in males. This was associated with increases in hypothalamic mRNA levels of IGF2 (p < 0.01) and IGF binding protein (IGFBP) 2 (p < 0.05), factors involved in glucose metabolism, again only in males. Likewise, IGF2 increased IGFBP2 mRNA levels only in hypothalamic astrocytes from males (p < 0.05). In conclusion, the metabolic responses to dietary changes were less severe and more delayed in females and the IGF system might be involved in some of the sex specific observations.

Insulin-like growth factor 1 supplementation supports motor coordination and affects myelination in preterm pigs

Introduction

Preterm infants have increased risk of impaired neurodevelopment to which reduced systemic levels of insulin-like growth factor 1 (IGF-1) in the weeks after birth may play a role. Hence, we hypothesized that postnatal IGF-1 supplementation would improve brain development in preterm pigs, used as a model for preterm infants.

Methods

Preterm pigs delivered by cesarean section received recombinant human IGF-1/IGF binding protein-3 complex (rhIGF-1/rhIGFBP-3, 2.25 mg/kg/day) or vehicle from birth to postnatal day 19. Motor function and cognition were assessed by monitoring of in-cage and open field activities, balance beam test, gait parameters, novel object recognition and operant conditioning tests. Collected brains were subject to magnetic resonance imaging (MRI), immunohistochemistry, gene expression analyses and protein synthesis measurements.

Results

The IGF-1 treatment increased cerebellar protein synthesis rates (both in vivo and ex vivo). Performance in the balance beam test was improved by IGF-1 but not in other neurofunctional tests. The treatment decreased total and relative caudate nucleus weights, without any effects to total brain weight or grey/white matter volumes. Supplementation with IGF-1 reduced myelination in caudate nucleus, cerebellum, and white matter regions and decreased hilar synapse formation, without effects to oligodendrocyte maturation or neuron differentiation. Gene expression analyses indicated enhanced maturation of the GABAergic system in the caudate nucleus (decreased NKCC1:KCC2 ratio) with limited effects in cerebellum or hippocampus.

Conclusion

Supplemental IGF-1 during the first three weeks after preterm birth may support motor function by enhancing GABAergic maturation in the caudate nucleus, despite reduced myelination. Supplemental IGF-1 may support postnatal brain development in preterm infants, but more studies are required to identify optimal treatment regimens for subgroups of very or extremely preterm infants.

Diabetic vascular diseases: molecular mechanisms and therapeutic strategies

Vascular complications of diabetes pose a severe threat to human health. Prevention and treatment protocols based on a single vascular complication are no longer suitable for the long-term management of patients with diabetes. Diabetic panvascular disease (DPD) is a clinical syndrome in which vessels of various sizes, including macrovessels and microvessels in the cardiac, cerebral, renal, ophthalmic, and peripheral systems of patients with diabetes, develop atherosclerosis as a common pathology. Pathological manifestations of DPDs usually manifest macrovascular atherosclerosis, as well as microvascular endothelial function impairment, basement membrane thickening, and microthrombosis. Cardiac, cerebral, and peripheral microangiopathy coexist with microangiopathy, while renal and retinal are predominantly microangiopathic. The following associations exist between DPDs: numerous similar molecular mechanisms, and risk-predictive relationships between diseases. Aggressive glycemic control combined with early comprehensive vascular intervention is the key to prevention and treatment. In addition to the widely recommended metformin, glucagon-like peptide-1 agonist, and sodium-glucose cotransporter-2 inhibitors, for the latest molecular mechanisms, aldose reductase inhibitors, peroxisome proliferator-activated receptor-γ agonizts, glucokinases agonizts, mitochondrial energy modulators, etc. are under active development. DPDs are proposed for patients to obtain more systematic clinical care requires a comprehensive diabetes care center focusing on panvascular diseases. This would leverage the advantages of a cross-disciplinary approach to achieve better integration of the pathogenesis and therapeutic evidence. Such a strategy would confer more clinical benefits to patients and promote the comprehensive development of DPD as a discipline.

Insulin‐like growth factor‐2 is a promising candidate for the treatment and prevention of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. Current AD treatments slow the rate of cognitive decline, but do not restore lost function. One reason for the low efficacy of current treatments is that they fail to target neurotrophic processes, which are thought to be essential for functional recovery. Bolstering neurotrophic processes may also be a viable strategy for preventative treatment, since structural losses are thought to underlie cognitive decline in AD. The challenge of identifying presymptomatic patients who might benefit from preventative treatment means that any such treatment must meet a high standard of safety and tolerability. The neurotrophic peptide insulin-like growth factor-2 (IGF2) is a promising candidate for both treating and preventing AD-induced cognitive decline. Brain IGF2 expression declines in AD patients. In rodent models of AD, exogenous IGF2 modulates multiple aspects of AD pathology, resulting in (1) improved cognitive function; (2) stimulation of neurogenesis and synaptogenesis; and, (3) neuroprotection against cholinergic dysfunction and beta amyloid-induced neurotoxicity. Preclinical evidence suggests that IGF2 is likely to be safe and tolerable at therapeutic doses. In the preventative treatment context, the intranasal route of administration is likely to be the preferred method for achieving the therapeutic effect without risking adverse side effects. For patients already experiencing AD dementia, routes of administration that deliver IGF2 directly access the CNS may be necessary. Finally, we discuss several strategies for improving the translational validity of animal models used to study the therapeutic potential of IGF2.

Epitope mapping of a blood-brain barrier crossing antibody targeting the cysteine-rich region of IGF1R using hydrogen-exchange mass spectrometry enabled by electrochemical reduction

Pathologies of the central nervous system impact a significant portion of our population, and the delivery of therapeutics for effective treatment is challenging. The insulin-like growth factor-1 receptor (IGF1R) has emerged as a target for receptor-mediated transcytosis, a process by which antibodies are shuttled across the blood-brain barrier (BBB). Here, we describe the biophysical characterization of VHH-IR4, a BBB-crossing single-domain antibody (sdAb). Binding was confirmed by isothermal titration calorimetry and an epitope was highlighted by surface plasmon resonance that does not overlap with the IGF-1 binding site or other known BBB-crossing sdAbs. The epitope was mapped with a combination of linear peptide scanning and hydrogen-deuterium exchange mass spectrometry (HDX-MS). IGF1R is large and heavily disulphide bonded, and comprehensive HDX analysis was achieved only through the use of online electrochemical reduction coupled with a multiprotease approach, which identified an epitope for VHH-IR4 within the cysteine-rich region (CRR) of IGF1R spanning residues W244-G265. This is the first report of an sdAb binding the CRR. We show that VHH-IR4 inhibits ligand induced auto-phosphorylation of IGF1R and that this effect is mediated by downstream conformational effects. Our results will guide the selection of antibodies with improved trafficking and optimized IGF1R binding characteristics.

Evidence for an alternative insulin transporter at the blood-brain barrier

Accumulating evidence suggests there is an alternative insulin transporter besides the insulin receptor at the blood-brain barrier (BBB), responsible for shuttling insulin from the circulation into the brain. In this review, we summarize key features of the BBB and what makes it unique compared to other capillary beds; summarize what we know about insulin BBB transport; provide an extensive list of diseases, physiological states, and serum factors tested in modifying insulin BBB transport; and lastly, highlight potential alternative transport systems that may be involved in or have already been tested in mediating insulin BBB transport. Identifying the transport system for insulin at the BBB would aide in controlling central nervous system (CNS) insulin levels in multiple diseases and conditions including Alzheimer's disease (AD) and obesity, where availability of insulin to the CNS is limited.

Age-related decline in circulating IGF-1 associates with impaired neurovascular coupling responses in older adults

Impairment of moment-to-moment adjustment of cerebral blood flow (CBF) to the increased oxygen and energy requirements of active brain regions via neurovascular coupling (NVC) contributes to the genesis of age-related cognitive impairment. Aging is associated with marked deficiency in the vasoprotective hormone insulin-like growth factor-1 (IGF-1). Preclinical studies on animal models of aging suggest that circulating IGF-1 deficiency is causally linked to impairment of NVC responses. The present study was designed to test the hypotheses that decreases in circulating IGF-1 levels in older adults also predict the magnitude of age-related decline of NVC responses. In a single-center cross-sectional study, we enrolled healthy young (n = 31, 11 female, 20 male, mean age: 28.4 + / - 4.2 years) and aged volunteers (n = 32, 18 female, 14 male, mean age: 67.9 + / - 4.1 years). Serum IGF-1 level, basal CBF (phase contrast magnetic resonance imaging (MRI)), and NVC responses during the trail making task (with transcranial Doppler sonography) were assessed. We found that circulating IGF-1 levels were significantly decreased with age and associated with decreased basal CBF. Age-related decline in IGF-1 levels predicted the magnitude of age-related decline in NVC responses. In conclusion, our study provides additional evidence in support of the concept that age-related circulating IGF-1 deficiency contributes to neurovascular aging, impairing CBF and functional hyperemia in older adults.

Growth Hormone Increases BDNF and mTOR Expression in Specific Brain Regions after Photothrombotic Stroke in Mice

Aims

We have shown that growth hormone (GH) treatment poststroke increases neuroplasticity in peri-infarct areas and the hippocampus, improving motor and cognitive outcomes. We aimed to explore the mechanisms of GH treatment by investigating how GH modulates pathways known to induce neuroplasticity, focusing on association between brain-derived neurotrophic factor (BDNF) and mammalian target of rapamycin (mTOR) in the peri-infarct area, hippocampus, and thalamus.

Methods

Recombinant human growth hormone (r-hGH) or saline was delivered (0.25 μl/hr, 0.04 mg/day) to mice for 28 days, commencing 48 hours after photothrombotic stroke. Protein levels of pro-BDNF, total-mTOR, phosphorylated-mTOR, total-p70S6K, and phosporylated-p70S6K within the peri-infarct area, hippocampus, and thalamus were evaluated by western blotting at 30 days poststroke.

Results

r-hGH treatment significantly increased pro-BDNF in peri-infarct area, hippocampus, and thalamus (p < 0.01). r-hGH treatment significantly increased expression levels of total-mTOR in the peri-infarct area and thalamus (p < 0.05). r-hGH treatment significantly increased expression of total-p70S6K in the hippocampus (p < 0.05).

Conclusion

r-hGH increases pro-BDNF within the peri-infarct area and regions that are known to experience secondary neurodegeneration after stroke. Upregulation of total-mTOR protein expression in the peri-infarct and thalamus suggests that this might be a pathway that is involved in the neurorestorative effects previously reported in these animals and warrants further investigation. These findings suggest region-specific mechanisms of action of GH treatment and provide further understanding for how GH treatment promotes neurorestorative effects after stroke.

Research Progress on Neuroprotection of Insulin-like Growth Factor-1 towards Glutamate-Induced Neurotoxicity

Insulin-like growth factor-1 (IGF-1) and its binding proteins and receptors are widely expressed in the central nervous system (CNS), proposing IGF-1-induced neurotrophic actions in normal growth, development, and maintenance. However, while there is convincing evidence that the IGF-1 system has specific endocrine roles in the CNS, the concept is emerging that IGF-I might be also important in disorders such as ischemic stroke, brain trauma, Alzheimer’s disease, epilepsy, etc., by inducing neuroprotective effects towards glutamate-mediated excitotoxic signaling pathways. Research in rodent models has demonstrated rescue of pathophysiological and behavioral abnormalities when IGF-1 was administered by different routes, and several clinical studies have shown safety and promise of efficacy in neurological disorders of the CNS. Focusing on the relationship between IGF-1-induced neuroprotection and glutamate-induced excitatory neurotoxicity, this review addresses the research progress in the field, intending to provide a rationale for using IGF-I clinically to confer neuroprotective therapy towards neurological diseases with glutamate excitotoxicity as a common pathological pathway.

Preclinical and clinical evidence of IGF-1 as a prognostic marker and acute intervention with ischemic stroke

Ischemic strokes are highly prevalent in the elderly population and are a leading cause of mortality and morbidity worldwide. The risk of ischemic stroke increases in advanced age, corresponding with a noted decrease in circulating insulin growth factor-1 (IGF-1). IGF-1 is a known neuroprotectant involved in embryonic development, neurogenesis, neurotransmission, cognition, and lifespan. Clinically, several studies have shown that reduced levels of IGF-1 correlate with increased mortality rate, poorer functional outcomes, and increased morbidities following an ischemic stroke. In animal models of ischemia, administering exogenous IGF-1 using various routes of administration (intranasal, intravenous, subcutaneous, or topical) at various time points prior to and following insult attenuates neurological damage and accompanying behavioral changes caused by ischemia. However, there are some contrasting findings in select clinical and preclinical studies. This review discusses the role of IGF-1 as a determinant factor of ischemic stroke outcomes, both within the clinical settings and preclinical animal models. Furthermore, the review provides insight on the role of IGF-1 in mechanisms and cellular processes that contribute to stroke damage.

How alcohol affects insulin-like growth factor-1's influences on the onset of puberty: A critical review

Alcohol (ALC) is capable of delaying signs associated with pubertal development in laboratory animals, as well as in humans. The normal onset of puberty results from a timely increase in gonadotropin‐releasing hormone (GnRH) secretion, which is associated with a gradual decline in prepubertal inhibitory influences, and the establishment of excitatory inputs that increase GnRH release, which together drive pubertal development. In recent years, insulin‐like growth factor‐1 (IGF‐1) has emerged as a pivotal contributor to prepubertal GnRH secretion and pubertal development, whose critical actions are interfered with by ALC abuse. Here we review the neuroendocrine research demonstrating the important role that IGF‐1 plays in pubertal development, and describe the detrimental effects and mechanisms of action of ALC on the onset and progression of pubertal maturation.

Association between the serum insulin-like growth factor-1 concentration in the first trimester of pregnancy and postpartum depression

AIM

Patients with major depression present with an increased serum insulin-like growth factor-1 (IGF-1) concentration. However, the longitudinal relationship between serum IGF-1 levels and depression development remains unclear. This study aimed to investigate the longitudinal association between the serum IGF-1 concentration in the first trimester of pregnancy and postpartum depression development using data obtained from the Japan Environment and Children's Study (JECS).

METHODS

The JECS included 97 415 pregnant women; among them, 8791 were enrolled in this study. Data regarding depression in the first trimester, postpartum depression development at 1 month after childbirth, and other covariates were collected using a self-administered questionnaire. Serum IGF-1 levels were measured in the first trimester of pregnancy. The participants were divided into four groups according to the serum IGF-1 level.

RESULTS

In the first trimester, serum IGF-1 levels were not significantly associated with psychological distress in pregnant women. In the longitudinal analyses, however, postpartum depression development in mothers within the highest quartile for serum IGF-1 concentration in the first trimester was significantly less common than in those within the lowest quartile (odds ratio 0.48, 95% confidence interval 0.30-0.79).

CONCLUSION

Pregnant women with a high serum IGF-1 concentration in the first trimester were less likely to develop postpartum depression than those with a low concentration. A high serum IGF-1 concentration during pregnancy may help to protect against postpartum depression development.

Insulin-Like Growth Factor 1 Increases GABAergic Neurotransmission to GnRH Neurons via Suppressing the Retrograde Tonic Endocannabinoid Signaling Pathway in Mice

INTRODUCTION

Hypophysiotropic gonadotropin-releasing hormone (GnRH) neurons orchestrate various physiological events that control the onset of puberty. Previous studies showed that insulin-like growth factor 1 (IGF-1) induces the secretion of GnRH and accelerates the onset of puberty, suggesting a regulatory role of this hormone upon GnRH neurons.

METHODS

To reveal responsiveness of GnRH neurons to IGF-1 and elucidate molecular pathways acting downstream to the IGF-1 receptor (IGF-1R), in vitro electrophysiological experiments were carried out on GnRH-GFP neurons in acute brain slices from prepubertal (23-29 days) and pubertal (50 days) male mice.

RESULTS

Administration of IGF-1 (13 nM) significantly increased the firing rate and frequency of spontaneous postsynaptic currents and that of excitatory GABAergic miniature postsynaptic currents (mPSCs). No GABAergic mPSCs were induced by IGF-1 in the presence of the GABAA-R blocker picrotoxin. The increase in the mPSC frequency was prevented by the use of the IGF-1R antagonist, JB1 (1 µM), or the intracellularly applied PI3K blocker (LY294002, 50 µM), showing involvement of IGF-1R and PI3K in the mechanism. Blockade of the transient receptor potential vanilloid 1, an element of the tonic retrograde endocannabinoid machinery, by AMG9810 (10 µM) or antagonizing the cannabinoid receptor type-1 by AM251 (1 µM) abolished the effect.

DISCUSSION/CONCLUSION

These findings indicate that IGF-1 arrests the tonic retrograde endocannabinoid pathway in GnRH neurons, and this disinhibition increases the release of GABA from presynaptic terminals that, in turn, activates GnRH neurons leading to the fine-tuning of the hypothalamo-pituitary-gonadal axis.

The impact of trophic and immunomodulatory factors on oligodendrocyte maturation: Potential treatments for encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a major cause of morbidity in preterm neonates, causing neurodevelopmental adversities that can lead to lifelong impairments. Preterm birth-related insults, such as cerebral oxygen fluctuations and perinatal inflammation, are believed to negatively impact brain development, leading to a range of brain abnormalities. Diffuse white matter injury is a major hallmark of EoP and characterized by widespread hypomyelination, the result of disturbances in oligodendrocyte lineage development. At present, there are no treatment options available, despite the enormous burden of EoP on patients, their families, and society. Over the years, research in the field of neonatal brain injury and other white matter pathologies has led to the identification of several promising trophic factors and cytokines that contribute to the survival and maturation of oligodendrocytes, and/or dampening neuroinflammation. In this review, we discuss the current literature on selected factors and their therapeutic potential to combat EoP, covering a wide range of in vitro, preclinical and clinical studies. Furthermore, we offer a future perspective on the translatability of these factors into clinical practice.

Impact of Long-Term HFD Intake on the Peripheral and Central IGF System in Male and Female Mice

The insulin-like growth factor (IGF) system is responsible for growth, but also affects metabolism and brain function throughout life. New IGF family members (i.e., pappalysins and stanniocalcins) control the availability/activity of IGFs and are implicated in growth. However, how diet and obesity modify this system has been poorly studied. We explored how intake of a high-fat diet (HFD) or commercial control diet (CCD) affects the IGF system in the circulation, visceral adipose tissue (VAT) and hypothalamus. Male and female C57/BL6J mice received HFD (60% fat, 5.1 kcal/g), CCD (10% fat, 3.7 kcal/g) or chow (3.1 % fat, 3.4 kcal/g) for 8 weeks. After 7 weeks of HFD intake, males had decreased glucose tolerance (p < 0.01) and at sacrifice increased plasma insulin (p < 0.05) and leptin (p < 0.01). Circulating free IGF1 (p < 0.001), total IGF1 (p < 0.001), IGF2 (p < 0.05) and IGFBP3 (p < 0.01) were higher after HFD in both sexes, with CCD increasing IGFBP2 in males (p < 0.001). In VAT, HFD reduced mRNA levels of IGF2 (p < 0.05), PAPP-A (p < 0.001) and stanniocalcin (STC)-1 (p < 0.001) in males. HFD increased hypothalamic IGF1 (p < 0.01), IGF2 (p < 0.05) and IGFBP5 (p < 0.01) mRNA levels, with these changes more apparent in females. Our results show that diet-induced changes in the IGF system are tissue-, sex- and diet-dependent.

Ionizing radiation-induced risks to the central nervous system and countermeasures in cellular and rodent models

PURPOSE

Harmful effects of ionizing radiation on the Central Nervous System (CNS) are a concerning outcome in the field of cancer radiotherapy and form a major risk for deep space exploration. Both acute and chronic CNS irradiation induce a complex network of molecular and cellular alterations including DNA damage, oxidative stress, cell death and systemic inflammation, leading to changes in neuronal structure and synaptic plasticity with behavioral and cognitive consequences in animal models. Due to this complexity, countermeasure or therapeutic approaches to reduce the harmful effects of ionizing radiation include a wide range of protective and mitigative strategies, which merit a thorough comparative analysis.

MATERIALS AND METHODS

We reviewed current approaches for developing countermeasures to both targeted and non-targeted effects of ionizing radiation on the CNS from the molecular and cellular to the behavioral level.

RESULTS

We focus on countermeasures that aim to mitigate the four main detrimental actions of radiation on CNS: DNA damage, free radical formation and oxidative stress, cell death, and harmful systemic responses including tissue death and neuroinflammation. We propose a comprehensive review of CNS radiation countermeasures reported for the full range of irradiation types (photons and particles, low and high linear energy transfer) and doses (from a fraction of gray to several tens of gray, fractionated and unfractionated), with a particular interest for exposure conditions relevant to deep-space environment and radiotherapy. Our review reveals the importance of combined strategies that increase DNA protection and repair, reduce free radical formation and increase their elimination, limit inflammation and improve cell viability, limit tissue damage and increase repair and plasticity.

CONCLUSIONS

The majority of therapeutic approaches to protect the CNS from ionizing radiation have been limited to acute high dose and high dose rate gamma irradiation, and few are translatable from animal models to potential human application due to harmful side effects and lack of blood-brain barrier permeability that precludes peripheral administration. Therefore, a promising research direction would be to focus on practical applicability and effectiveness in a wider range of irradiation paradigms, from fractionated therapeutic to deep space radiation. In addition to discovering novel therapeutics, it would be worth maximizing the benefits and reducing side effects of those that already exist. Finally, we suggest that novel cellular and tissue models for developing and testing countermeasures in the context of other impairments might also be applied to the field of CNS responses to ionizing radiation.

Peripheral Circulation and Astrocytes Contribute to the MSC-Mediated Increase in IGF-1 Levels in the Infarct Cortex in a dMCAO Rat Model

Materials and Methods

Ischemic brain injury was induced by dMCAO in Sprague-Dawley rats. The transplantation group received MSC infusion 1 h after dMCAO. Expression of IGF-1 in GFAP+ astrocytes, Iba-1+ microglia/macrophages, CD3+ lymphocytes, Ly6C+ monocytes/macrophages, and neutrophil elastase (NE)+ neutrophils was examined to determine the contribution of these cells to the increase of IGF-1. ELISA was performed to examine IGF-1 levels in blood plasma at days 2, 4, and 7 after ischemia onset.

Results

In total, only 5-6% of Iba-1+ microglia were colabeled with IGF-1 in the infarct cortex, corpus callosum, and striatum at day 2 post-dMCAO. MSC transplantation did not lead to a higher proportion of Iba-1+ cells that coexpressed IGF-1. In the infarct cortex, all Iba-1+/IGF-1+ double-positive cells were also positive for CD68. In the infarct, corpus callosum, and striatum, the majority (50-80%) of GFAP+ cells were colabeled with ramified IGF-1 signals. The number of GFAP+/IGF-1+ cells was further increased following MSC treatment. In the infarct cortex, approximately 15% of IGF-1+ cells were double-positive for CD3. MSC treatment reduced the number of infiltrated CD3+/IGF-1+ cells by 70%. In the infarct, few Ly6C+ monocytes/macrophages or NE+ neutrophils expressed IGF-1, and MSC treatment did not induce a higher percentage of these cells that coexpressed IGF-1. The IGF-1 level in peripheral blood plasma was significantly higher in the MSC group than in the ischemia control group.

Conclusion

The MSC-mediated increase in IGF-1 levels in the infarct cortex mainly derives from two sources, astrocytes in brain and blood plasma in periphery. Manipulating the IGF-1 level in the peripheral circulation may lead to a higher level of IGF-1 in brain, which could be conducive to recovery at the early stage of dMCAO.

Effects of adipokine administration to the hypothalamic preoptic area on body temperature in rats

The effects of adipokine administration to the hypothalamic preoptic area (POA), which is one of the body temperature (BT) regulation centers in the central nervous system, on BT were investigated in male Wistar rats. BT was measured in conscious rats using telemetry. Insulin-like growth factor-1 (IGF-1), interleukin-1β (IL-1β), monocyte chemoattractant protein-1 and lipocalin-2 produced hyperthermia, and the effects induced by IL-1β (25 ng) and IGF-1 (5 μg) were sustainable and remarkable. IL-6 did not show any significant effect. The IGF-1-induced effect was inhibited by pretreatment with IGF binding protein 3 (IGFBP3) or NVP-AEW541 (NVP, a selective inhibitor of type 1 IGF receptor tyrosine kinase, IGF1R TK). NVP-induced inhibition was observed only in the early phase of IGF-1-induced hyperthermia. In addition, IGF-1 increased the IL-1β concentration in the microdialysate of POA perfusion, but did not increase the IL-1β concentration in the plasma or the PGE₂ concentration in the microdialysate. These findings suggested that IGF-1 produced hyperthermia, which was mediated, at least a part, through an increased IL-1β concentration after activation of IGF1R TK in the POA, and the IGF-IGFBP system possibly participates in BT homeostasis in the POA.

LC-MS/MS analysis of partial structure of Panax ginseng protein and its distribution in vivo

Protein from Panax ginseng can improve learning, memory, and analgesia. Here, we investigated a fluorescence labeling method that can be used to determine the in vivo distribution of P. ginseng protein (PGP). High-performance liquid chromatography (HPLC) was used to define the amino acid composition and molecular weight of PGP; LC-MS/MS was used to identify the PGP structure, which was fluorescently-labeled using a fluorescein isothiocyanate (FITC) probe. The connection form of the PGP fluorescent marker (PGP-FITC) was identified by ultraviolet and infrared spectrophotometry. The in vivo distribution of PGP was observed by fluorescence imaging, and tissue content was determined. Results showed that PGP was enriched in the brain and that vascular epithelial cells showed specific uptake. We provide an experimental method to label and identify the in vivo distribution of PGP, which forms the basis for future studies to determine whether PGP can penetrate the blood-brain barrier (BBB) and elucidate the transport mechanism.

Combined Treatment with Insulin-Like Growth Factor 1 and AMD3100 Improves Motor Outcome in a Murine Model of Neonatal Hypoxic-Ischemic Encephalopathy

Stem cell transplantation is a promising intervention for neonatal hypoxic-ischemic encephalopathy (HIE); however, universal feasibility and safety have not been thoroughly evaluated. AMD3100 and insulin-like growth factor 1 (IGF1) mobilize progenitor cells into peripheral circulation. The objective of this study was to assess the short-term efficacy of inducing endogenous stem cell mobilization after injury in a model of neonatal HIE. Postnatal day 9 CD1 pups received sham surgery or unilateral carotid artery ligation and 30 min of hypoxia followed by saline, AMD3100, IGF1, or both agents. Intraperitoneal injections of 5-ethynyl-2'-deoxy-uridine (EdU) and 5-bromo-2'-deoxyuridine were used to -label replicating progenitor cells. At P14, animals underwent rotarod testing, and the brains were sectioned for area measurements and immunofluorescence staining. Comparisons were made using one-way analysis of variance. Spearman's rho was calculated to assess correlation between rotarod results and markers of brain injury. Pups treated with both agents had improved rotarod performance (p = 0.02) and increased EdU+ progenitor cells in the subgranular zone (SGZ) compared to injured controls (p = 0.10). An increase in active cells within the SGZ was correlated with improved rotarod performance (r = 0.84, p = 0.04). There were no differences in overall injury score or in brain area or number of activated cells in the subventricular zone between the treatment groups. Combined treatment with AMD3100 and IGF1 shows promise for decreasing brain injury and improving motor function in pups after HIE which correlated with changes in the number of active progenitor cells in the SGZ.

Neurobiological effects of aerobic exercise, with a focus on patients with schizophrenia

Schizophrenia is a severe neuropsychiatric disease that is associated with neurobiological alterations in multiple brain regions and peripheral organs. Negative symptoms and cognitive deficits are present in about half of patients and are difficult to treat, leading to an unfavorable functional outcome. To investigate the impact of aerobic exercise on various neurobiological parameters, we conducted a narrative review. Add-on aerobic exercise was shown to be effective in improving negative and general symptoms, cognition, global functioning, and quality of life in schizophrenia patients. Based on findings in healthy individuals and animal models, this qualitative review gives an overview of different lines of evidence on how aerobic exercise impacts brain structure and function and molecular mechanisms in patients with schizophrenia and how its effects could be related to clinical and functional outcomes. Structural magnetic resonance imaging studies showed a volume increase in the hippocampus and cortical regions in schizophrenia patients and healthy controls after endurance training. However, results are inconsistent and individual risk factors may influence neuroplastic processes. Animal studies indicate that alterations in epigenetic mechanisms and synaptic plasticity are possible underlying mechanisms, but that differentiation of glial cells, angiogenesis, and possibly neurogenesis may also be involved. Clinical and animal studies also revealed effects of aerobic exercise on the hypothalamus-pituitary-adrenal axis, growth factors, and immune-related mechanisms. Some findings indicate effects on neurotransmitters and the endocannabinoid system. Further research is required to clarify how individual risk factors in schizophrenia patients mediate or moderate the neurobiological effects of exercise on brain and cognition. Altogether, aerobic exercise is a promising candidate in the search for pathophysiology-based add-on interventions in schizophrenia.

Growth Hormone Deficiency Following Traumatic Brain Injury

Traumatic brain injury (TBI) is fairly common and annually affects millions of people worldwide. Post traumatic hypopituitarism (PTHP) has been increasingly recognized as an important and prevalent clinical entity. Growth hormone deficiency (GHD) is the most common pituitary hormone deficit in long-term survivors of TBI. The pathophysiology of GHD post TBI is thought to be multifactorial including primary and secondary mechanisms. An interplay of ischemia, cytotoxicity, and inflammation post TBI have been suggested, resulting in pituitary hormone deficits. Signs and symptoms of GHD can overlap with those of TBI and may delay rehabilitation/recovery if not recognized and treated. Screening for GHD is recommended in the chronic phase, at least six months to a year after TBI as GH may recover in those with GHD in the acute phase; conversely, it may manifest in those with a previously intact GH axis. Dynamic testing is the standard method to diagnose GHD in this population. GHD is associated with long-term poor medical outcomes. Treatment with recombinant human growth hormone (rhGH) seems to ameliorate some of these features. This review will discuss the frequency and pathophysiology of GHD post TBI, its clinical consequences, and the outcomes of treatment with GH replacement.

The Neuroprotective Effects of Exercise: Maintaining a Healthy Brain Throughout Aging

Physical activity plays an essential role in maintaining a healthy body, yet it also provides unique benefits for the vascular and cellular systems that sustain a healthy brain. While the benefit of exercise has been observed in humans of all ages, the availability of preclinical models has permitted systematic investigations into the mechanisms by which exercise supports and protects the brain. Over the past twenty-five years, rodent models have shown that increased physical activity elevates neurotrophic factors in the hippocampal and cortical areas, facilitating neurotransmission throughout the brain. Increased physical activity (such as by the voluntary use of a running wheel or regular, timed sessions on a treadmill) also promotes proliferation, maturation and survival of cells in the dentate gyrus, contributing to the process of adult hippocampal neurogenesis. In this way, rodent studies have tremendous value as they demonstrate that an 'active lifestyle' has the capacity to ameliorate a number of age-related changes in the brain, including the decline in adult neurogenesis. Moreover, these studies have shown that greater physical activity may protect the brain health into advanced age through a number of complimentary mechanisms: in addition to upregulating factors in pro-survival neurotrophic pathways and enhancing synaptic plasticity, increased physical activity promotes brain health by supporting the cerebrovasculature, sustaining the integrity of the blood-brain barrier, increasing glymphatic clearance and proteolytic degradation of amyloid beta species, and regulating microglia activation. Collectively, preclinical studies demonstrate that exercise initiates diverse and powerful neuroprotective pathways that may converge to promote continued brain health into old age. This review will draw on both seminal and current literature that highlights mechanisms by which exercise supports the functioning of the brain, and aids in its protection.

Neurotrophic factors and neuroplasticity pathways in the pathophysiology and treatment of depression

Depression is a major health problem with a high prevalence and a heavy socioeconomic burden in western societies. It is associated with atrophy and impaired functioning of cortico-limbic regions involved in mood and emotion regulation. It has been suggested that alterations in neurotrophins underlie impaired neuroplasticity, which may be causally related to the development and course of depression. Accordingly, mounting evidence suggests that antidepressant treatment may exert its beneficial effects by enhancing trophic signaling on neuronal and synaptic plasticity. However, current antidepressants still show a delayed onset of action, as well as lack of efficacy. Hence, a deeper understanding of the molecular and cellular mechanisms involved in the pathophysiology of depression, as well as in the action of antidepressants, might provide further insight to drive the development of novel fast-acting and more effective therapies. Here, we summarize the current literature on the involvement of neurotrophic factors in the pathophysiology and treatment of depression. Further, we advocate that future development of antidepressants should be based on the neurotrophin theory.

Pregnancy-Associated Plasma Protein-aa Regulates Photoreceptor Synaptic Development to Mediate Visually Guided Behavior

To guide behavior, sensory systems detect the onset and offset of stimuli and process these distinct inputs via parallel pathways. In the retina, this strategy is implemented by splitting neural signals for light onset and offset via synapses connecting photoreceptors to ON and OFF bipolar cells, respectively. It remains poorly understood which molecular cues establish the architecture of this synaptic configuration to split light-onset and light-offset signals. A mutant with reduced synapses between photoreceptors and one bipolar cell type, but not the other, could reveal a critical cue. From this approach, we report a novel synaptic role for pregnancy-associated plasma protein aa (pappaa) in promoting the structure and function of cone synapses that transmit light-offset information. Electrophysiological and behavioral analyses indicated pappaa mutant zebrafish have dysfunctional cone-to-OFF bipolar cell synapses and impaired responses to light offset, but intact cone-to-ON bipolar cell synapses and light-onset responses. Ultrastructural analyses of pappaa mutant cones showed a lack of presynaptic domains at synapses with OFF bipolar cells. pappaa is expressed postsynaptically to the cones during retinal synaptogenesis and encodes a secreted metalloprotease known to stimulate insulin-like growth factor 1 (IGF1) signaling. Induction of dominant-negative IGF1 receptor expression during synaptogenesis reduced light-offset responses. Conversely, stimulating IGF1 signaling at this time improved pappaa mutants' light-offset responses and cone presynaptic structures. Together, our results indicate Pappaa-regulated IGF1 signaling as a novel pathway that establishes how cone synapses convey light-offset signals to guide behavior.SIGNIFICANCE STATEMENT Distinct sensory inputs, like stimulus onset and offset, are often split at distinct synapses into parallel circuits for processing. In the retina, photoreceptors and ON and OFF bipolar cells form discrete synapses to split neural signals coding light onset and offset, respectively. The molecular cues that establish this synaptic configuration to specifically convey light onset or offset remain unclear. Our work reveals a novel cue: pregnancy-associated plasma protein aa (pappaa), which regulates photoreceptor synaptic structure and function to specifically transmit light-offset information. Pappaa is a metalloprotease that stimulates local insulin-like growth factor 1 (IGF1) signaling. IGF1 promotes various aspects of synaptic development and function and is broadly expressed, thus requiring local regulators, like Pappaa, to govern its specificity.

On the Run for Hippocampal Plasticity

Accumulating research in rodents and humans indicates that exercise benefits brain function and may prevent or delay onset of neurodegenerative conditions. In particular, exercise modifies the structure and function of the hippocampus, a brain area important for learning and memory. This review addresses the central and peripheral mechanisms underlying the beneficial effects of exercise on the hippocampus. We focus on running-induced changes in adult hippocampal neurogenesis, neural circuitry, neurotrophins, synaptic plasticity, neurotransmitters, and vasculature. The role of peripheral factors in hippocampal plasticity is also highlighted. We discuss recent evidence that systemic factors released from peripheral organs such as muscle (myokines), liver (hepatokines), and adipose tissue (adipokines) during exercise contribute to hippocampal neurotrophin and neurogenesis levels, and memory function. A comprehensive understanding of the body-brain axis is needed to elucidate how exercise improves hippocampal plasticity and cognition.

Insulin-like Growth Factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: A review

Insulin-like Growth Factor 1 (IGF-1) and its signaling pathway play a primary role in normal growth and ageing, however serum IGF-1 is known to reduce with advancing age. Recent findings suggest IGF-1 is essential for neurogenesis in the adult brain, and this reduction of IGF-1 with ageing may contribute to age-related cognitive decline. Experimental studies have shown manipulation of the GH/GF-1 axis can slow rates of cognitive decline in animals, making IGF-1 a potential biomarker of cognition, and/or its signaling pathway a possible therapeutic target to prevent or slow age-related cognitive decline. A systematic literature review and qualitative narrative summary of current evidence for IGF-1 as a biomarker of cognitive decline in the ageing brain was undertaken. Results indicate IGF-1 concentrations do not confer additional diagnostic information for those with cognitive decline, and routine clinical measurement of IGF-1 is not currently justified. In cases of established cognitive impairment, it remains unclear whether increasing circulating or brain IGF-1 may reverse or slow down the rate of further decline. Advances in neuroimaging, genetics, neuroscience and the availability of large well characterized biobanks will facilitate research exploring the role of IGF-1 in both normal ageing and age-related cognitive decline.

Efficient expression of stable recombinant human insulin-like growth factor-1 fusion with human serum albumin in Chinese hamster ovary cells

Insulin-like growth factor-1 (IGF-1) plays a crucial role in cell development, differentiation, and metabolism, and has been a potential therapeutic agent for many diseases. Chinese hamster ovary (CHO) cells are widely used for production of recombinant therapeutic proteins, but the expression level of IGF-1 in CHO cells is very low (1,500 µg/L) and the half-life of IGF-1 in blood circulation is only 4.5 min according to previous studies. Therefore, IGF-1 was fused to long-circulating serum protein human serum albumin (HSA) and expressed in CHO cells. After 8-day fed-batch culture, the expression level of HSA-IGF-1 reached 100 mg/L. The fusion protein HSA-IGF-1 was purified with a recovery of 35% using a two-step chromatographic procedure. According to bioactivity assay, the purified HSA-IGF-1 could stimulate the proliferation of NIH3T3 cells in a dose-dependent fashion and promote the cell-cycle progression. Besides this, HSA-IGF-1 could bind to IGF-1 receptor on cell membrane and activate the intracellular PI3K/AKT signaling pathway. Our study suggested that HSA fusion technology carried out in CHO cells not only provided bioactivity in HSA-IGF-1 for further research but also offered a beneficial strategy to produce other similar cytokines in CHO cells.