Actions Of Insulin-like Growth factor-I Research Articles

The Role of Insulin-like Growth Factor I in Mechanisms of Resilience and Vulnerability to Sporadic Alzheimer's Disease.

Despite decades of intense research, disease-modifying therapeutic approaches for Alzheimer's disease (AD) are still very much needed. Apart from the extensively analyzed tau and amyloid pathological cascades, two promising avenues of research that may eventually identify new druggable targets for AD are based on a better understanding of the mechanisms of resilience and vulnerability to this condition. We argue that insulin-like growth factor I (IGF-I) activity in the brain provides a common substrate for the mechanisms of resilience and vulnerability to AD. We postulate that preserved brain IGF-I activity contributes to resilience to AD pathology as this growth factor intervenes in all the major pathological cascades considered to be involved in AD, including metabolic impairment, altered proteostasis, and inflammation, to name the three that are considered to be the most important ones. Conversely, disturbed IGF-I activity is found in many AD risk factors, such as old age, type 2 diabetes, imbalanced diet, sedentary life, sociality, stroke, stress, and low education, whereas the Apolipoprotein (Apo) E4 genotype and traumatic brain injury may also be influenced by brain IGF-I activity. Accordingly, IGF-I activity should be taken into consideration when analyzing these processes, while its preservation will predictably help prevent the progress of AD pathology. Thus, we need to define IGF-I activity in all these conditions and develop a means to preserve it. However, defining brain IGF-I activity cannot be solely based on humoral or tissue levels of this neurotrophic factor, and new functionally based assessments need to be developed.

Insulin-like growth factor I sensitization rejuvenates sleep patterns in old mice.

Sleep disturbances are common during aging. Compared to young animals, old mice show altered sleep structure, with changes in both slow and fast electrocorticographic (ECoG) activity and fewer transitions between sleep and wake stages. Insulin-like growth factor I (IGF-I), which is involved in adaptive changes during aging, was previously shown to increase ECoG activity in young mice and monkeys. Furthermore, IGF-I shapes sleep architecture by modulating the activity of mouse orexin neurons in the lateral hypothalamus (LH). We now report that both ECoG activation and excitation of orexin neurons by systemic IGF-I are abrogated in old mice. Moreover, orthodromical responses of LH neurons are facilitated by either systemic or local IGF-I in young mice, but not in old ones. As orexin neurons of old mice show dysregulated IGF-I receptor (IGF-IR) expression, suggesting disturbed IGF-I sensitivity, we treated old mice with AIK3a305, a novel IGF-IR sensitizer, and observed restored responses to IGF-I and rejuvenation of sleep patterns. Thus, disturbed sleep structure in aging mice may be related to impaired IGF-I signaling onto orexin neurons, reflecting a broader loss of IGF-I activity in the aged mouse brain.

INFLUENCE OF INSULIN-LIKE GROWTH FACTOR-I LEVELS ON THE COURSE OF ACUTE MYOCARDIAL INFARCTION: review

Over the last many years, cardiovascular disease has reached epidemic proportions among chronic noncommunicable diseases worldwide. According to the latest tendencies, cardiovascular diseases play the leading role in the formation of current negative health and demographic trends in Ukraine and all over the world: they significantly affect the main health indicators: morbidity, mortality, disability, life expectancy and quality of life. If we take the last 20 years, we can see that the prevalence of CVDs among the Ukrainian population has tripled, and the mortality rate from them has risen by 40%. Review was analysed serum level insulin-like growth factor-I (IGF-I) in patients with acute myocardial infarction and his role in left ventricular remodelling was established. The scientific data regarding the neurohumoral component of acute myocardial infarction pathogenesis have been expanded by increasing levels of the angiogenesis marker IGF-I, which can be explained by his properties as markers of the acute phase of inflammation. An analysis of the relationship between troponin I and IGF-I, a marker of myocardial damage, showed a direct relationship, indicating an increase in troponin I concentration with rising serum IGF-I levels. This indicates that the activity of the angiogenesis marker IGF-I may be associated with the severity and depth of myocardial damage.

Insulin-like Growth Factor I Couples Metabolism with Circadian Activity through Hypothalamic Orexin Neurons.

Uncoupling of metabolism and circadian activity is associated with an increased risk of a wide spectrum of pathologies. Recently, insulin and the closely related insulin-like growth factor I (IGF-I) were shown to entrain feeding patterns with circadian rhythms. Both hormones act centrally to modulate peripheral glucose metabolism; however, whereas central targets of insulin actions are intensely scrutinized, those mediating the actions of IGF-I remain less defined. We recently showed that IGF-I targets orexin neurons in the lateral hypothalamus, and now we evaluated whether IGF-I modulates orexin neurons to align circadian rhythms with metabolism. Mice with disrupted IGF-IR activity in orexin neurons (Firoc mice) showed sexually dimorphic alterations in daily glucose rhythms and feeding activity patterns which preceded the appearance of metabolic disturbances. Thus, Firoc males developed hyperglycemia and glucose intolerance, while females developed obesity. Since IGF-I directly modulates orexin levels and hepatic expression of KLF genes involved in circadian and metabolic entrainment in an orexin-dependent manner, it seems that IGF-I entrains metabolism and circadian rhythms by modulating the activity of orexin neurons.

Insulin-like growth factor I mitigates post-traumatic stress by inhibiting AMP-kinase in orexin neurons

Maladaptive coping behaviors are probably involved in post-traumatic stress disorders (PTSD), but underlying mechanisms are incompletely understood. We now report that mice lacking functional insulin-like growth factor I (IGF-I) receptors in orexin neurons of the lateral hypothalamus (Firoc mice) are unresponsive to the anxiolytic actions of IGF-I and develop PTSD-like behavior that is ameliorated by inhibition of orexin neurons. Conversely, systemic IGF-I treatment ameliorated PTSD-like behavior in a wild-type mouse model of PTSD (PTSD mice). Further, systemic IGF-I modified the GABA/Glutamate synaptic structure in orexin neurons of naïve wild-type mice by increasing the dephosphorylation of GABA(B) receptor subunit through inhibition of AMP-kinase (AMPK). Significantly, pharmacological inhibition of AMPK mimicked IGF-I, normalizing fear behavior in PTSD mice. Thus, we suggest that IGF-I enables coping behaviors by balancing E/I input onto orexin neurons in a context-dependent manner. These observations provide a novel therapeutic approach to PTSD through modulation of AMPK.

Loss of sensitivity to insulin-like growth factor I in orexin neurons is associated to perturbed sleep patterns during aging.

Sleep disturbances are common during aging. Old mice show altered sleep structure, with changes in both slow and fast electro-corticographic (ECG) activity, and less transitions between sleep and wake stages, as compared to young animals. Insulin-like growth factor I (IGF-I), that is involved in hormonal changes during aging, was previously shown to increase ECG patterns in young mice and monkeys. More recently, we observed that IGF-I shapes sleep architecture through modulation of the activity of mouse orexin neurons in the lateral hypothalamus (LH). We now report that both stimulation of ECG patterns and activation of orexin neurons by systemic IGF-I were abrogated in old mice. Further, activation of orthodromically stimulated LH neurons by either systemic or local IGF-I in young mice was absent in old mice. As orexin neurons of old mice show markedly increased IGF-I receptor (IGF-IR) levels, suggesting loss of sensitivity to IGF-I, we treated them with AIK3a305, a novel IGF-IR sensitizer, and observed restored responses to IGF-I and rejuvenation of ECG patterns. Thus, disturbed sleep structure in aging mice may be related to IGF-I resistance in orexin neurons, reflecting a broader loss of IGF-I activity in the aged mouse brain.

Astrocytic IGF-IRs Induce Adenosine-Mediated Inhibitory Downregulation and Improve Sensory Discrimination.

Insulin-like growth factor-I (IGF-I) signaling plays a key role in learning and memory processes. While the effects of IGF-I on neurons have been studied extensively, the involvement of astrocytes in IGF-I signaling and the consequences on synaptic plasticity and animal behavior remain unknown. We have found that IGF-I induces long-term potentiation (LTPIGFI) of the postsynaptic potentials that is caused by a long-term depression of inhibitory synaptic transmission in mice. We have demonstrated that this long-lasting decrease in the inhibitory synaptic transmission is evoked by astrocytic activation through its IGF-I receptors (IGF-IRs). We show that LTPIGFI not only increases the output of pyramidal neurons, but also favors the NMDAR-dependent LTP, resulting in the crucial information processing at the barrel cortex since specific deletion of IGF-IR in cortical astrocytes impairs the whisker discrimination task. Our work reveals a novel mechanism and functional consequences of IGF-I signaling on cortical inhibitory synaptic plasticity and animal behavior, revealing that astrocytes are key elements in these processes.SIGNIFICANCE STATEMENT Insulin-like growth factor-I (IGF-I) signaling plays key regulatory roles in multiple processes of brain physiology, such as learning and memory. Yet, the underlying mechanisms remain largely undefined. Here we demonstrate that astrocytes respond to IGF-I signaling, elevating their intracellular Ca2+ and stimulating the release of ATP/adenosine, which triggers the LTD of cortical inhibitory synapses, thus regulating the behavioral task performance related to cortical sensory information processing. Therefore, the present work represents a major conceptual advance in our knowledge of the cellular basis of IGF-I signaling in brain function, by including for the first time astrocytes as key mediators of IGF-I actions on synaptic plasticity, cortical sensory information discrimination and animal behavior.

Expression and effect of microRNA-627 in human hypertrophic scar

Objective: To investigate the expression and effect of microRNA-627 (miR-627) in human hypertrophic scar. Methods: The experimental research method was used. From October 2019 to January 2020, hypertrophic scar tissue from 6 patients with hypertrophic scar (2 males and 4 females, aged (34±11) years) and the remaining normal skin tissue from 6 trauma patients (3 males and 3 females, aged (35±13) years) after flap transplantation were collected. The above-mentioned 12 patients were admitted to the General Hospital of Northern Theater Command and met the inclusion criteria. The mRNA expression of miR-627 was detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction. The 3rd to 5th passages of fibroblasts (Fbs) were isolated from hypertrophic scar tissue and cultured for subsequent experiments after identification. Fbs from hypertrophic scar were divided into miR-627 negative control group, miR-627 mimic group, and miR-627 inhibitor group. The corresponding sequences were transfected respectively. At 0 (immediately), 12, 24, 36, and 48 h after transfection, the cell viability was detected by thiazolyl blue method; at 24 h after transfection, the apoptosis was detected by flow cytometry; at 24 h after transfection, the protein expression levels of insulin-like growth factor Ⅰ (IGF-Ⅰ), type Ⅰ collagen, and α smooth muscle actin (α-SMA) were detected by Western blotting. Two batches of Fbs from hypertrophic scar were used, one batch was divided into IGF-Ⅰ wild type+miR-627 negative control group and IGF-Ⅰ wild type+miR-627 mimic group, and the other batch was divided into IGF-Ⅰ mutant+miR-627 negative control group and IGF-Ⅰ mutant+miR-627 mimic group. The corresponding sequences were transfected respectively. At 48 h after transfection, the expressions of luciferase and renal luciferase were detected by luciferase reporter gene detection kit, and the ratio of the two was calculated to reflect the activity of IGF-Ⅰ. Fbs from hypertrophic scar were divided into miR-627 negative control group, miR-627 mimic alone group, and miR-627 mimic+IGF-Ⅰ group, and were transfected with the corresponding sequences respectively. At 24 h after transfection, the protein expression levels of IGF-Ⅰ, type Ⅰ collagen, and α-SMA were detected by Western blotting. The number of samples in cell experiment was 3. Data were statistically analyzed with analysis of variance for factorial design, one-way analysis of variance, independent sample t test, and chi-square test. Results: The expression of miR-627 mRNA in hypertrophic scar tissue was 0.47±0.06, which was significantly lower than 1.12±0.23 in normal skin tissue (t=15.090, P<0.01). At 12, 24, 36, and 48 hours after transfection, the cell viability of miR-627 mimic group was significantly lower than that of miR-627 negative control group (t=9.918, 34.370, 13.580, 61.550, P<0.05 or P<0.01); the cell viability of miR-627 inhibitor group was significantly higher than that of miR-627 negative control group (t=4.722, 8.616, 13.330, 14.000, P<0.05 or P<0.01). At 24 h after transfection, compared with the apoptosis rate (8.42±0.47)% in miR-627 negative control group, (10.89±0.35)% in miR-627 mimic group was significantly higher (t=7.301, P<0.01), and (5.00±0.22)% in miR-627 inhibitor group was significantly lower (t=11.510, P<0.01). At 24 h after transfection, compared with the cell protein expressions of IGF-Ⅰ, type Ⅰ collagen, and α-SMA in miR-627 negative control group, those in miR-627 mimic group were significantly lower (t=25.470, 5.282, 7.415, P<0.01), and those in miR-627 inhibitor group were significantly higher (t=15.930, 8.857, 9.763, P<0.01). At 48 h after transfection, the luciferase/renal luciferase ratio of IGF-Ⅰ of cells in IGF-Ⅰ wild type+miR-627 mimic group was 0.463±0.061, which was significantly lower than 0.999±0.011 in IGF-Ⅰ wild type+miR-627 negative control group (t=16.852, P<0.01); the luciferase/renal luciferase ratio of IGF-Ⅰ of cells in IGF-Ⅰ mutant+miR-627 mimic group was 0.934±0.021, which was similar to 0.930±0.023 in IGF-Ⅰ mutant+miR-627 negative control group (t=1.959, P>0.05). At 24 h after transfection, the protein expressions of IGF-Ⅰ, type Ⅰ collagen, and α-SMA of cells in miR-627 mimic alone group were 1.623±0.070, 1.363±0.042, and 1.617±0.025, which were significantly lower than 2.723±0.045, 2.147±0.067, and 2.533±0.055 in miR-627 negative control group (t=22.831, 7.280, 26.220, P<0.01); the protein expressions of IGF-Ⅰ, type Ⅰ collagen, and α-SMA of cells in mimic+IGF-Ⅰ group were 2.477±0.102, 1.760±0.046, and 2.387±0.049, which were significantly higher than those of miR-627 mimic alone group (t=3.830, 8.286, 3.436, P<0.05 or P<0.01). Conclusions: miR-627 expression in human hypertrophic scars is down-regulated; miR-627 can inhibit the proliferation and promote the apoptosis of Fbs in human hypertrophic scar by targeted inhibition of IGF-Ⅰ expression.

Growth Hormone and Neuronal Hemoglobin in the Brain-Roles in Neuroprotection and Neurodegenerative Diseases.

In recent years, evidence for hemoglobin (Hb) synthesis in both animal and human brains has been accumulating. While circulating Hb originating from cerebral hemorrhage or other conditions is toxic, there is also substantial production of neuronal Hb, which is influenced by conditions such as ischemia and regulated by growth hormone (GH), insulin-like growth factor-I (IGF-I), and other growth factors. In this review, we discuss the possible functions of circulating and brain Hb, mainly the neuronal form, with respect to the neuroprotective activities of GH and IGF-I against ischemia and neurodegenerative diseases. The molecular pathways that link Hb to the GH/IGF-I system are also reviewed, although the limited number of reports on this topic suggests a need for further studies. In summary, GH and/or IGF-I appear to be significant determinants of systemic and local brain Hb concentrations through mediating responses to oxygen and metabolic demand, as part of the neuroprotective effects exerted by GH and IGF-I. The nature and quantity of the latter deserve further exploration in specific experiments.

Circulating Insulin-Like Growth Factor I is Involved in the Effect of High Fat Diet on Peripheral Amyloid β Clearance.

Obesity is a risk factor for Alzheimer’s disease (AD), but underlying mechanisms are not clear. We analyzed peripheral clearance of amyloid β (Aβ) in overweight mice because its systemic elimination may impact brain Aβ load, a major landmark of AD pathology. We also analyzed whether circulating insulin-like growth factor I (IGF-I) intervenes in the effects of overweight as this growth factor modulates brain Aβ clearance and is increased in the serum of overweight mice. Overweight mice showed increased Aβ accumulation by the liver, the major site of elimination of systemic Aβ, but unaltered brain Aβ levels. We also found that Aβ accumulation by hepatocytes is stimulated by IGF-I, and that mice with low serum IGF-I levels show reduced liver Aβ accumulation—ameliorated by IGF-I administration, and unchanged brain Aβ levels. In the brain, IGF-I favored the association of its receptor (IGF-IR) with the Aβ precursor protein (APP), and at the same time, stimulated non-amyloidogenic processing of APP in astrocytes, as indicated by an increased sAPPα/sAPPβ ratio after IGF-I treatment. Since serum IGF-I enters into the brain in an activity-dependent manner, we analyzed in overweight mice the effect of brain activation by environmental enrichment (EE) on brain IGF-IR phosphorylation and its association to APP, as a readout of IGF-I activity. After EE, significantly reduced brain IGF-IR phosphorylation and APP/IGF-IR association were found in overweight mice as compared to lean controls. Collectively, these results indicate that a high-fat diet influences peripheral clearance of Aβ without affecting brain Aβ load. Increased serum IGF-I likely contributes to enhanced peripheral Aβ clearance in overweight mice, without affecting brain Aβ load probably because its brain entrance is reduced.

Genetic causes of growth hormone insensitivity beyond GHR.

Growth hormone insensitivity (GHI) syndrome, first described in 1966, is classically associated with monogenic defects in the GH receptor (GHR) gene which result in severe post-natal growth failure as consequences of insulin-like growth factor I (IGF-I) deficiency. Over the years, recognition of other monogenic defects downstream of GHR has greatly expanded understanding of primary causes of GHI and growth retardation, with either IGF-I deficiency or IGF-I insensitivity as clinical outcomes. Mutations in IGF1 and signaling component STAT5B disrupt IGF-I production, while defects in IGFALS and PAPPA2, disrupt transport and release of circulating IGF-I, respectively, affecting bioavailability of the growth-promoting IGF-I. Defects in IGF1R, cognate cell-surface receptor for IGF-I, disrupt not only IGF-I actions, but actions of the related IGF-II peptides. The importance of IGF-II for normal developmental growth is emphasized with recent identification of defects in the maternally imprinted IGF2 gene. Current application of next-generation genomic sequencing has expedited the pace of identifying new molecular defects in known genes or in new genes, thereby expanding the spectrum of GH and IGF insensitivity. This review discusses insights gained and future directions from patient-based molecular and functional studies.

Pregnancy-Associated Plasma Protein-A2 Is Associated With Mortality in Patients With Lung Cancer

Pregnancy-associated plasma protein-A (PAPP-A) and its homolog PAPP-A2 are enzymes that modulate the availability and mitogenic activity of insulin-like growth factor-I (IGF-I). PAPP-A has been implicated in numerous cancers but reports on PAPP-A2 in malignancy are non-existent. In a prospective observational study of 689 patients under suspicion of lung cancer, we examined levels of PAPP-A and PAPP-A2 and their relationship with mortality. Serum PAPP-A and PAPP-A2 concentrations were determined in pre-diagnostic blood samples using ELISA, and immunohistochemical staining of PAPP-A and PAPP-A2 was performed in malignant tissue from five operable patients. A total of 144 patients were diagnosed with lung cancer, whereas the diagnosis was rejected in 545 subjects, who served as a control group. PAPP-A2 concentrations were higher in patients with lung cancer [median (IQR): 0.33 (0.21–0.56) ng/mL] than in controls [0.27 (0.17–0.39) ng/mL], p < 0.001, whereas PAPP-A levels did not differ. Presence of PAPP-A and PAPP-A2 were confirmed in tumor specimens, and staining occurred in a heterogeneous pattern. Patients were observed for a median (range) of 7 (6; 8) years, during which 114 patients (79.2%) died. Patient mortality differed according to PAPP-A2 tertile (p < 0.001). PAPP-A2 was associated with mortality with an unadjusted hazard ratio (95% CI) per doubling in protein concentration of 1.30 (1.12; 1.53), p = 0.001. In a multivariable model adjusted for age, sex, and BMI, PAPP-A2 remained predictive of the endpoint with a hazard ratio per doubling in protein concentration of 1.25 (1.05; 1.48), p = 0.013. Collectively, PAPP-A2, but not PAPP-A, is elevated in patients with lung cancer and associated with mortality. This novel role of PAPP-A2 in cancer warrants further functional studies as well as validation in external cohorts.

Mechanisms of putative IGF-I receptor resistance in active acromegaly

Acromegaly is a disease characterized by overproduction of growth hormone (GH). As a consequence of excessive GH secretion, circulating insulin-like growth factor-I (IGF-I) is elevated in active (untreated) acromegaly. IGF-I is often used as a marker of disease activity and growth hormone status in acromegaly. Although IGF-I can directly improve insulin sensitivity and glucose uptake in muscles, the excessive GH secretion in active acromegaly frequently leads to insulin resistance, glucose intolerance and even diabetes. In this review evidence will be discussed that in active acromegaly chronically elevated IGF-I, insulin and soluble Klotho (S-Klotho) levels play a pathophysiological role in the development of IGF-I receptor (IGF-IR) resistance. It is postulated that as soon as circulating IGF-I, insulin and S-Klotho rise above a certain level the IGF-IR becomes relatively resistant to actions of IGF-I. The development of a degree of IGF-IR resistance for metabolic actions may help to explain why in active acromegaly diabetogenic effects of GH predominate and are not completely counteracted and neutralized by elevated circulating levels of IGF-I. Further studies are necessary in order to support this hypothesis.

Regulation of IGF-I by IGFBP3 and IGFBP5 during odontoblast differentiation in mice

ObjectivesAlthough intracellular signaling pathways of insulin-like growth factor I (IGF-I) related to the proliferation of dental pulp cells have been investigated, the switching mechanism from cell proliferation to differentiation during odontogenesis remains elusive. This study aimed to elucidate the role of IGF binding protein (IGFBP) 3 and 5 in regulation of IGF-I during odontoblast differentiation in mouse incisors. MethodsThe detailed expression patterns of IGF-I, IGF-I receptor (IGF-IR), IGFBP3, and IGFBP5 together with that of an odontoblast differentiation marker, nestin, were examined by immunohistochemistry and/or in situ hybridization using paraffinized sections of TetOP-H2B-GFP mouse incisors at postnatal 4 weeks. ResultsUndifferentiated dental papilla cells and preodontoblasts (preOB) showed intense IGF-I- and IGF-IRα-positive reactions, and the expression was observed in differentiated odontoblasts, such as immature odontoblasts (iOB) and mature odontoblasts (mOB). IGFBP3/Igfbp3 was transiently expressed in preOB and early iOB, and the intensity of expression gradually reduced with the progression of odontoblast differentiation. In contrast, immunohistochemical analysis for IGFBP5 identified a positive reaction in the undifferentiated dental papilla cells and differentiated odontoblasts, and the expression of Igfbp5 was reduced in the differentiated odontoblasts. ConclusionThe present study demonstrated the expression patterns of IGF-I, IGF-IR, IGFBP3, and IGFBP5 during odontoblast differentiation in mouse incisors. These results suggested that IGFBP3 regulates the transition from the proliferative to differentiation stage by inhibiting the action of IGF-I on the proliferation of dental papilla cells, and that IGFBP5 plays an important role in the maintenance of the differentiated odontoblasts during tooth development.

Serum Insulin-Like Growth Factor I Deficiency Associates to Alzheimer's Disease Co-Morbidities.

Increasing evidence supports the notion that Alzheimer's disease (AD), a condition that presents heterogeneous pathological disturbances, is also associated to perturbed metabolic function affecting insulin and insulin-like growth factor I (IGF-I). While impaired insulin activity leading to insulin resistance has been associated to AD, whether altered IGF-I function affects the disease is not entirely clear. Despite the limitations of mouse models to mimic AD pathology, we took advantage that serum IGF-I deficient mice (LID mice) present many functional perturbations present in AD, most prominently cognitive loss, which is reversed by treatment with systemic IGF-I. We analyzed whether these mice display other pathological traits that are usual co-morbidities of AD. We found that LID mice not only display cognitive disturbances, but also show altered mood and sociability, increased susceptibility to epileptiform activity, and a disturbed sleep/wake cycle. Collectively, these data suggest that reduced IGF-I activity contributes to heterogeneous deficits commonly associated to AD. We suggest that impaired IGF-I activity needs to be taken into consideration when modeling this condition.

The IGF system in patients with inflammatory bowel disease treated with prednisolone or infliximab: potential role of the stanniocalcin-2 / PAPP-A / IGFBP-4 axis

BackgroundPatients with inflammatory bowel disease (IBD) present with reduced serum insulin-like growth factor I (IGF-I). Anti-inflammatory treatment with prednisolone or infliximab ameliorates symptoms and increases circulating IGF-I, but prednisolone induces catabolism, whereas infliximab may promote protein synthesis. Recently, stanniocalcin-2 (STC2) was discovered as a novel inhibitor of the enzyme pregnancy-associated plasma protein-A (PAPP-A), which modulates IGF-I activity. PAPP-A can cleave IGF binding protein-4 (IGFBP-4), upon which IGF-I is liberated. We hypothesized that prednisolone and infliximab exert different effects on levels of STC2, PAPP-A, and IGFBP-4, thereby explaining the distinct metabolic effects of prednisolone and infliximab.MethodsThirty-eight patients with active IBD treated with either prednisolone (n = 17) or infliximab (n = 21) were examined before and after 7 days of treatment. Circulating levels of IGF-I, IGF-II, IGFBP-3, PAPP-A, and STC2 were measured by immunoassays. Intact IGFBP-4 and two IGFBP-4 fragments were determined by a novel immunoassay. Bioactive IGF was assessed by cell-based IGF receptor activation assay. Concentrations of IGFBP-4, PAPP-A, and STC2 on day 0 and 7 were compared to healthy control subjects.ResultsFollowing seven days of prednisolone treatment, total and bioactive IGF-I were increased (p < 0.001 and p < 0.05, respectively). Upon infliximab treatment, total IGF-I levels were augmented (p < 0.05), yet IGF bioactivity remained unaltered. Intact IGFBP-4 and the two IGFBP-4 fragments generated upon cleavage by PAPP-A were all decreased following treatment with either prednisolone or infliximab (all p < 0.05). PAPP-A levels were only increased by infliximab (p = 0.005), whereas the inhibitor STC2 did not respond to any of the treatments.ConclusionIGF-I and IGFBP-4 concentrations were markedly altered in patients with IBD and near-normalized with disease remission following treatment with prednisolone or infliximab. Thus, IGFBP-4 may modulate IGF bioavailability in IBD. The effect of immunosuppression did not appear to extend beyond the regulation of IGF and IGFBP-4, as neither PAPP-A nor STC2 were discernibly affected.Trial registrationClinicalTrials.gov: NCT00955123. Date of registration: August 7, 2009 (retrospectively registered).

Influence of green tea constituents on cultured porcine luteinized granulosa cell functions

The aim of the study was to examine the action of green tea polyphenols (GTPP) and their main constituent, epigallocatechin-3-gallate (EGCG), on porcine ovarian granulosa cells. For this purpose, the effect of GTPP and EGCG on cultured porcine ovarian granulosa cell functions, including proliferation, apoptosis, steroidogenesis and response to insulin-like growth factor I (IGF-I) was examined. Proliferation (the accumulation of proliferating cell nuclear antigen (PCNA) and cyclin B1), apoptosis (the accumulation of bax and caspase 3) and the release of steroid hormones (progesterone and testosterone) were evaluated by using immunocytochemistry and enzyme immunoassay. The addition of both GTPP and EGCG reduced the percentage of both PCNA- and cyclin B1-positive cells, increased the proportion of cells containing bax and caspase 3 and stimulated progesterone release. GTPP had a biphasic effect on testosterone output – stimulating at dose 1 μg/ml and inhibiting at doses 10 and 100 μg/ml, whilst EGCG did not affect testosterone secretion. IGF-I, when administered alone, promoted % of cells containing PCNA, suppressed bax accumulation, and stimulated progesterone release (only at dose 100 ng/ml). Testosterone release increased after the addition of IGF-I at 1 ng/ml, but decreased after IGF-I addition at 10 or 100 ng/ml. Both GTPP and EGCG suppressed or even reversed the effects of IGF-I on percentage of PCNA-positive cells, bax, testosterone output, and promoted IGF-I action on progesterone release. These observations suggested the inhibitory actions of green tea constituents on porcine ovarian granulosa cell functions were mediated through various regulatory mechanisms: suppression of the ovarian cell cycle in the S and G2 phases; promotion of cytoplasmic apoptosis; alteration of steroid hormone release; and, predominantly, prevention of the action of the hormonal stimulator IGF-I on ovarian cells. It can be also suggested that the major GTPP effects may result from the presence of EGCG.

Direct inhibitory effect of flaxseed on porcine ovarian granulosa cell functions.

Flaxseed is useful as a functional food and alternative medicine owing to its beneficial health effects. Its action on ovarian cell functions and interrelationships with the upstream hormonal regulators remain unknown. Our aim was to examine the direct influence of flaxseed extract on basal porcine ovarian functions (proliferation, apoptosis), leptin release, and response to insulin-like growth factor I (IGF-I). First, we examined the effect of flaxseed extract on the accumulation of proliferation (PCNA) and apoptosis (Bax) markers and on leptin release in cultured porcine ovarian granulosa cells. Next, granulosa cells were cultured with IGF-I with and without flaxseed extract and analyzed for PCNA and Bax accumulation by quantitative immunocytochemistry and for leptin release by radioimmunoassay. Flaxseed decreased the accumulation of PCNA and increased that of Bax at all doses and reduced leptin output at 100 μg/mL. In contrast, IGF-I promoted PCNA accumulation and suppressed Bax. Flaxseed did not modify IGF-I action on these parameters. Thus, we showed that flaxseed influences porcine reproductive processes, having a direct effect on the ovary and the ability to affect ovarian cell proliferation, apoptosis, and leptin release. Furthermore, we confirmed the pro-proliferative and antiapoptotic actions of IGF-I but showed that flaxseed action on ovarian cell proliferation and apoptosis is not due to changes in the cell response to IGF-I. The potential direct anti-reproductive action of flaxseed needs to be considered during its application in nutrition, medicine, and animal production.

Regulatory Role for Growth Hormone in Statural Growth: IGF-Dependent and IGF-Independent Effects on Growth Plate Chondrogenesis and Longitudinal Bone Growth.

It was initially thought that the growth-promoting effects of GH were exclusively mediated by liver-derived Insulin-like Growth Factor-I (IGF-I). Subsequent studies demonstrated that GH promotes IGF-I synthesis and activity in other organs and in the growth plate. GH has also IGF-I-independent growth-promoting effects. In Igf1 null mice, high circulating GH levels may be responsible for normal chondrocyte proliferation. Furthermore, tibial growth is reduced more in Ghr null mice than in Igf1 null mice, while the body of mice lacking both Ghr and Igf1 is smaller than that of mice lacking Igf1 or Ghr. The increased IGF-II expression in the growth plate in Igf1 null mice suggests that the IGF-I-independent effects of GH may be mediated by IGF-II. The effects of Igf1 receptor (Igf1r) gene deletion in chondrocytes indicate that GH may promote growth directly at the growth plate even when the local effects of IGF-I and IGF-II are abrogated.

Expression of Insulin-like Growth Factor Binding Protein-3 and Regulation of the Insulin-like Growth Factor-I Axis in Pig Testis

The stem cell niche is a complex unit comprising key components, such as the extracellular matrix and various paracrine factors, which regulate the differentiation of adult stem cells. In our previous study, we established pig spermatogonial stem cells (pSSCs) in culture and identified the expression of insulin-like growth factor binding protein-3 (IGFBP-3) in pSSCs. The present study investigated not only the expression of IGFBP-3, but also its possible role in pSSCs. In this study, IGFBP-3-expressing cells responded positively to protein gene product 9.5 (PGP9.5), which is a marker for pig spermatogonia. IGFBP-3 expression was significantly increased in 60-dayold pig testes. Additionally, the expression levels of insulinlike growth factor I (IGF-I) and its receptor (IGF-IR) were observed in pSSCs and pig Sertoli cells (pSCs). Furthermore, IGF-I treatment enhanced the proliferation of pSCs and pSSCs when they were co-cultured. Blocking the IGF-I pathway using a specific IGF-IR inhibitor dramatically reduced the proliferation of pSCs. In addition, when heparan sulfate was used to sequester IGFBP-3 from IGF-I binding, a significant increase in the proliferation of pSCs was observed. Exogenous IGF-I treatment also increased the expression level of IGFBP-3 in cultured pSSCs. Furthermore, pSSCs grew well in IGF-I-treated pSC conditioned media. In summary, IGF-I and IGF-IR signaling are important for the proliferation of pSCs, and the germ cell-derived IGFBP-3 had an inhibitory effect on the mitotic activity of IGF-I in pSCs.