Insulin-like growth factor-II and bioactive proteins containing a part of the E-domain of pro-insulin-like growth factor-II

Clinical characteristics of gastrointestinal stromal tumors with hypoglycemia

The development of tyrosine-kinase inhibitors has improved survival rates for patients with gastrointestinal stromal tumors (GISTs). Despite the progress, not all the patients can universally receive the benefit from treatment due to the individual underlying conditions in a real-world setting. The present study focused on the well-known but understudied condition of GIST with hypoglycemia. Hypoglycemia in GIST is characterized by hypoglycemic symptoms such as dizziness, sweating and confusion. It is caused by several factors such as multiple liver metastases, drug adverse effects, postoperative complications and paraneoplastic syndrome [non-islet cell tumor hypoglycemia (NICTH)]. Comprehensive analysis of this condition has been hindered due to its rarity, and has been mostly limited to case reports. In the present study, a single-institution retrospective analysis of GIST with hypoglycemia was conducted to investigate its prevalence and prognosis, and the cause of this condition. The present study identified that the prevalence of hypoglycemic episodes of GIST was 4.1% in all patients with GIST, and recurrent hypoglycemic cases had a poor prognosis. The present study identified 1 case with recurrent hypoglycemia due to NICTH. Since NICTH is a rare hypoglycemic cause and requires further evaluation, an autopsy and genetic sequencing were performed using the available clinical materials. Through this histological and genetic investigation, the histological diversity of NICTH-GIST was revealed and insulin-like growth factor II (IGF-II) amplification was identified. Furthermore, a chronological analysis was performed using multiple resected archived samples from the same case, and revealed that diffuse IGF-II expression may have occurred in the early phase of tumor development. The present study catalogued the characteristics of GIST with hypoglycemia with a focus on NICTH-GIST.

Differential expression and significance of cytokines in cerebrospinal fluid of patients with viral encephalitis

To extensively identify cerebrospinal fluid (CSF) cytokine profiles related to the occurrence, development and prognosis of viral encephalitis (VE) patients by using a high-throughput proteomic approach. We measured 80 cytokines in the CSF of acute-phase VE patients (n = 11) using high-throughput protein chip technology, comparing them to controls (n = 6). ELISA validated these findings and assessed additional cytokines from prior literature in a larger cohort (15 VE patients, 15 controls). Correlations between biomarkers and clinical characteristics were also examined. In the initial stage, we identified two differentially expressed cytokines: cathepsin-L (CTSL), which was up-regulated, and Fractalkine, which was down-regulated. Functional enrichment analysis revealed that these proteins are linked to inflammation, apoptosis, autophagy, and blood-brain barrier disruption. In stage2, the elevations of cathepsin-L (CTSL), fractalkine, interleukin-6 (IL-6), IL-1β, macrophage migration inhibitory factor (MIF), tumor necrosis factor-α (TNF-α), insulin-like growth factor Ⅱ (IGF-2) and CXC chemokine ligand 10 (CXCL10) in VE were validated by ELISA. The results of linear regression indicated that these cytokines was positively correlated with CSF reactive lesions (p < 0.05). In this study, some biomarkers related with CSF level changes and prognosis were obtained. Although these cytokines are not specific, they may be related to the occurrence and development of VE. CTSL, MIF, IL-1β, TNF-α and CXCL10 can be used as VE potential biomarkers. These cytokines may participate in the pathogenesis of VE through inflammatory response, cell apoptosis, autophagy, blood-brain barrier disruption and cytokine-cytokine receptor interaction pathway.

IGF-I and GH Genes polymorphism and their association with milk yields, composition and reproductive performance in Holstein-Friesian dairy cattle

BACKGROUND

The insulin-like growth factor (IGF-I) and growth hormone (GH) genes have been identified as major regulators of milk yield and composition, and reproductive performance in cattle. Genetic variations/polymorphism in these genes have been found to influence milk production, yield and quality. This investigation aimed to explore the association between IGF-I and GH polymorphisms and milk yield and composition, and reproductive performance in a herd consisting of 1000 Holstein-Friesian (HF) dairy cattle from El-Alamia farm. The experimental animals were 76 ± 7.25 months in age, with an average live weight of 750 ± 50.49 kg, and raised under the same conditions of feeding and weather. The studied animals were divided into three categories; high producers (n = 280), medium producers (n = 318) and low producers (n = 402).

RESULTS

The digestion of 249 bp for IGF-I-SnaBI using the Restriction-fragment-length-polymorphism (RFLP) technique yielded two alleles; T (0.59) and C (0.41) and three genotypes; TT (0.52), TC (0.39) and CC (0.09) and this agrees with the results of DNA/gene sequencing technique. The sequencing analysis of the IGF-I gene revealed polymorphism in position 472 (C > T). Nucleotide sequencing of the amplified fragment of the IGF-I gene of different genotypes was done and submitted to the NCBI GenBank with Accession no. MH156812.1 and MH156811.1. While the digestion of 432 bp for GH-AluI using the RFLP technique yielded two alleles; A (0.81) and G (0.19) and two genotypes; AA (0.77) and AG (0.23) and this agrees with the results of DNA/gene sequencing technique. The sequencing analysis of the GH gene revealed polymorphism in the position 1758 C > G and in turn led to changes in amino acid sequence as Alanine for (A) compared to Glycine for (G). Nucleotide sequencing of the amplified fragment of the GH gene was done and submitted to the NCBI GenBank with Accession no. MH156810.1. The results of this study demonstrate the effects of variants of the GH-IGF-I somatotrophic axis on milk production and composition traits in commercial HF cattle. The greatest values of milk yield and reproductive performance were observed on IGF-I-SnaBI-TC and GH-AluI-AG genotypes. While the greatest % fat and % protein values were observed on IGF-I-SnaBI-CC and GH-AluI-AA genotyped individuals.

CONCLUSION

The genetic variation of the studied genes can be utilized in selecting animals with superior milk yield, composition and reproductive performance in Holstein-Friesian Dairy Cattle under subtropical conditions.

Recurrent Hypoglycemia in a Non-diabetic Female: A Case Study on Doege-Potter Syndrome

Solitary fibrous tumors (SFT) are mesenchymal cell tumors that may arise from any site throughout the body. A small percentage of patients with SFT develop non-islet cell tumor-induced hypoglycemia (NICTH), eponymously termed Doege-Potter Syndrome (DPS). DPS is characterized by severe, refractory hypoinsulinemic hypoglycemia. Diagnosis of SFT is dependent on histologic findings and immunohistochemistry (IHC). NAB2-STAT6 gene fusions are pathognomonic for SFT but may be difficult to identify in routine cytogenetic studies. STAT6 IHC is a highly sensitive and specific surrogate for the NAB2-STAT6 gene fusion. Total resection of the tumor remains the gold-standard definitive treatment of SFT of the pleura. Palliative tumor debulking is recommended if total resection is not feasible. We here report a case of DPS in a 73-year-old female, managed with palliative care.

Recurrent Non-islet Cell Tumor Hypoglycemia Secondary to Hepatocellular Carcinoma: Case Report and Literature Review

RATIONALE

Non-islet cell tumor hypoglycemia (NICTH) is a paraneoplastic syndrome caused by tumors other than insulinoma that is primarily due to excessive production of insulin-like growth factor-II (IGF-II). The prevalence of NICTH is likely underestimated because of a lack of clinical recognition.

PATIENT CONCERNS

A 41-year-old male with massive malignant liver tumors presented with recurrent severe hypoglycemia, weight loss, and liver cirrhosis.

DIAGNOSIS

NICTH related to IGF-II produced by hepatocellular carcinoma was diagnosed based on clinical symptoms, biochemical tests, and elevated IGF-II/IGF-I ratio.

INTERVENTION

Initial treatment with intravenous glucose and parenteral nutrition showed limited efficacy. Glucocorticoids and recombinant human growth hormone led to progressive improvement in blood glucose levels.

OUTCOME

Due to extensive tumor burden and liver failure, surgical resection was not feasible, and the patient ultimately succumbed to refractory hypoglycemia and passed away in two weeks.

LESSONS

Early recognition and diagnosis of NICTH are crucial in patients with recurrent hypoglycemia and large tumors. Surgical resection is the preferred treatment option, but supportive care and pharmacological interventions, such as glucocorticoids and growth hormone, can help manage refractory hypoglycemia. Further research is needed to explore novel treatment options, including anti-IGF-I and -IGF-II neutralizing antibodies.

Dysfunction in IGF2R Pathway and Associated Perturbations in Autophagy and WNT Processes in Beckwith-Wiedemann Syndrome Cell Lines

Beckwith-Wiedemann Syndrome (BWS) is an imprinting disorder characterized by overgrowth, stemming from various genetic and epigenetic changes. This study delves into the role of IGF2 upregulation in BWS, focusing on insulin-like growth factor pathways, which are poorly known in this syndrome. We examined the IGF2R, the primary receptor of IGF2, WNT, and autophagy/lysosomal pathways in BWS patient-derived lymphoblastoid cell lines, showing different genetic and epigenetic defects. The findings reveal a decreased expression and mislocalization of IGF2R protein, suggesting receptor dysfunction. Additionally, our results point to a dysregulation in the AKT/GSK-3/mTOR pathway, along with imbalances in autophagy and the WNT pathway. In conclusion, BWS cells, regardless of the genetic/epigenetic profiles, are characterized by alteration of the IGF2R pathway that is associated with the perturbation of the autophagy and lysosome processes. These alterations seem to be a key point of the molecular pathogenesis of BWS and potentially contribute to BWS's characteristic overgrowth and cancer susceptibility. Our study also uncovers alterations in the WNT pathway across all BWS cell lines, consistent with its role in growth regulation and cancer development.

Targeting androgen receptor (AR) with a synthetic peptide increases apoptosis in triple negative breast cancer and AR-expressing prostate cancer cell lines

BACKGROUND

The androgen receptor (AR) has been studied as an approach to cancer therapy.

AIMS

We used human breast cancer-derived cells with high, low, and very low expression levels of AR, in addition to prostate cancer-derived LNCaP and DU-145 cells as a positive and negative controls to examine apoptosis caused by a synthetic peptide that targets ARs.

METHODS AND RESULTS

The peptide was produced to inhibit AR transactivation in breast cancer cell lines. We then measured cell viability, caspase-3 activity, and the ratio of Bax/Bcl-2. The findings indicated that the peptide (100-500 nM) in the presence of dihydrotestosterone (DHT) reduced cell growth in cells with high and low expression level of AR (p < .001), but not in cells with very low levels of AR. Treatment with 100-500 nM of peptide activated caspase-3 and increased the ratio of Bax/Bcl-2 in cells with high and low expression levels of AR. Also, increasing concentrations of the peptide (100-500 nM) reduced BrdU incorporation in the presence of DHT and promoted apoptosis in cells with high and low expression levels of AR (p < .001).

CONCLUSION

The findings indicate the peptide significantly increased apoptosis in cancer cells.

Autocrine IGF-II-Associated Cancers: From a Rare Paraneoplastic Event to a Hallmark in Malignancy

The paraneoplastic syndrome referred in the literature as non-islet-cell tumor hypoglycemia (NICTH) and extra-pancreatic tumor hypoglycemia (EPTH) was first reported almost a century ago, and the role of cancer-secreted IGF-II in causing this blood glucose-lowering condition has been widely established. The landscape emerging in the last few decades, based on molecular and cellular findings, supports a broader role for IGF-II in cancer biology beyond its involvement in the paraneoplastic syndrome. In particular, a few key findings are constantly observed during tumorigenesis, (a) a relative and absolute increase in fetal insulin receptor isoform (IRA) content, with (b) an increase in IGF-II high-molecular weight cancer-variants (big-IGF-II), and (c) a stage-progressive increase in the IGF-II autocrine signal in the cancer cell, mostly during the transition from benign to malignant growth. An increasing and still under-exploited combinatorial pattern of the IGF-II signal in cancer is shaping up in the literature with respect to its transducing receptorial system and effector intracellular network. Interestingly, while surgical and clinical reports have traditionally restricted IGF-II secretion to a small number of solid malignancies displaying paraneoplastic hypoglycemia, a retrospective literature analysis, along with publicly available expression data from patient-derived cancer cell lines conveyed in the present perspective, clearly suggests that IGF-II expression in cancer is a much more common event, especially in overt malignancy. These findings strengthen the view that (1) IGF-II expression/secretion in solid tumor-derived cancer cell lines and tissues is a broader and more common event compared to the reported IGF-II association to paraneoplastic hypoglycemia, and (2) IGF-II associates to the commonly observed autocrine loops in cancer cells while IGF-I cancer-promoting effects may be linked to its paracrine effects in the tumor microenvironment. Based on these evidence-centered considerations, making the autocrine IGF-II loop a hallmark for malignant cancer growth, we here propose the functional name of IGF-II secreting tumors (IGF-IIsT) to overcome the view that IGF-II secretion and pro-tumorigenic actions affect only a clinical sub-group of rare tumors with associated hypoglycemic symptoms. The proposed scenario provides an updated logical frame towards biologically sound therapeutic strategies and personalized therapeutic interventions for currently unaccounted IGF-II-producing cancers.

Signaling Pathways of the Insulin-like Growth Factor Binding Proteins

The 6 high-affinity insulin-like growth factor binding proteins (IGFBPs) are multifunctional proteins that modulate cell signaling through multiple pathways. Their canonical function at the cellular level is to impede access of insulin-like growth factor (IGF)-1 and IGF-2 to their principal receptor IGF1R, but IGFBPs can also inhibit, or sometimes enhance, IGF1R signaling either through their own post-translational modifications, such as phosphorylation or limited proteolysis, or by their interactions with other regulatory proteins. Beyond the regulation of IGF1R activity, IGFBPs have been shown to modulate cell survival, migration, metabolism, and other functions through mechanisms that do not appear to involve the IGF-IGF1R system. This is achieved by interacting directly or functionally with integrins, transforming growth factor β family receptors, and other cell-surface proteins as well as intracellular ligands that are intermediates in a wide range of pathways. Within the nucleus, IGFBPs can regulate the diverse range of functions of class II nuclear hormone receptors and have roles in both cell senescence and DNA damage repair by the nonhomologous end-joining pathway, thus potentially modifying the efficacy of certain cancer therapeutics. They also modulate some immune functions and may have a role in autoimmune conditions such as rheumatoid arthritis. IGFBPs have been proposed as attractive therapeutic targets, but their ubiquity in the circulation and at the cellular level raises many challenges. By understanding the diversity of regulatory pathways with which IGFBPs interact, there may still be therapeutic opportunities based on modulation of IGFBP-dependent signaling.

Non-glycosylated IGF2 prohormones are more mitogenic than native IGF2

Insulin-like Growth Factor-2 (IGF2) is important for the regulation of human embryonic growth and development, and for adults' physiology. Incorrect processing of the IGF2 precursor, pro-IGF2(156), leads to the formation of two IGF2 proforms, big-IGF2(87) and big-IGF2(104). Unprocessed and mainly non-glycosylated IGF2 proforms are found at abnormally high levels in certain diseases, but their mode of action is still unclear. Here, we found that pro-IGF2(156) has the lowest ability to form its inactivating complexes with IGF-Binding Proteins and has higher proliferative properties in cells than IGF2 and other IGF prohormones. We also showed that big-IGF2(104) has a seven-fold higher binding affinity for the IGF2 receptor than IGF2, and that pro-IGF2(87) binds and activates specific receptors and stimulates cell growth similarly to the mature IGF2. The properties of these pro-IGF2 forms, especially of pro-IGF2(156) and big-IGF2(104), indicate them as hormones that may be associated with human diseases related to the accumulation of IGF-2 proforms in the circulation.

Circulating serum preptin levels in women with polycystic ovary syndrome: A systematic review and meta-analysis

Background

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder with complex pathogenesis and metabolic complications, such as insulin resistance. Among the new markers, preptin seems to play a significant role in metabolic disorders.

Objective

This meta-analysis was conducted to determine the relationship between circulating preptin levels and PCOS.

Materials and Methods

A systematic review and meta-analysis was performed to identify relevant articles in electronic databases such as PubMed, Web of Science, Scopus, Cochrane, EMBASE, and the Google Scholar search engine, using a predefined search strategy. A random-effects model was used to combine standard mean difference (SMD) and 95% CI to compare results between groups. Meta-regression and subgroup analysis were also performed to reveal the sources of heterogeneity.

Results

The meta-analysis encompassed a total of 8 studies and 582 participants. The results indicate a statistically significant association between PCOS and serum preptin levels, with a pooled standardized mean difference (SMD = 1.35; 95% CI]: 0.63-2.08; p < 0.001). Further analysis suggested a significant difference in serum preptin levels between women with PCOS and higher homeostatic model assessment for insulin resistance ratio (SMD = 2.40; 95% CI: 1.17-3.63; p < 0.001) within the subgroup.

Conclusion

Our meta-analysis shows that increased serum preptin levels are associated with PCOS, suggesting that preptin may be related to the pathogenesis of PCOS and may be recognized as a novel diagnostic biomarker for PCOS. However, further studies are needed to confirm our results.

Doege-Potter syndrome in a patient with a giant abdominal solitary fibrous tumor: a case report and review of the literature

A 63-year-old man with spells of reduced consciousness in the morning and a giant abdominal mass presented to our institution for a second opinion. Investigation revealed non-diabetic hypoinsulinemic hypoglycemic events. Removal of the abdominal mass solved the hypoglycemia. Anatomopathological examination confirmed a solitary fibrous tumor (SFT). Doege-Potter syndrome was diagnosed. Doege-Potter syndrome is a potentially life-threatening rare paraneoplastic syndrome characterized by recurrent hypoinsulinemic hypoglycemia due to the overproduction of a prohormone form of insulin-like growth factor-II (pro-IGF-II) from a solitary fibrous tumor. First, we describe the clinical, laboratory and radiologic findings of the case. Second, a brief literature review on Doege-Potter syndrome is provided.

Doege-Potter Syndrome; A Case of Solitary Fibrous Pleura Tumor Associated with Severe Hypoglycemia: A Case Report in Internal Medicine

BACKGROUND

Doege-Potter syndrome is a rare paraneoplastic entity that is often diagnosed incidentally during the work-up of hypoglycemia of unclear etiology. It is characterized by a non-islet cell tumor hypoglycemia mostly associated with solitary fibrous tumors. These uncommon tumors have been reported in <5% of solitary fibrous tumors. Although not unique in its kind, this case is extremely important as this syndrome often conceals unrecognized tumors that can be surgically resolved.

CASE PRESENTATION

We present the case of a 59-year-old non-diabetic man with a 2-month history of severe and recurrent fasting hypoglycaemia presenting with severe dyspnea and sweating. Further workup revealed low insulin, C-peptide, and IGF-1 levels and a large right in-trathoracic solitary fibrous tumor. Unfortunately, bioassays for IGF-2 were unavailable at our hos-pital. Nevertheless, as hypoglycemia completely resolved after resection of the mass, Doege-Potter syndrome was highly suspected.

CONCLUSION

Doege-Potter syndrome is a complication of rare tumors. If hy-poglycemia is unexplained, this syndrome should always be suspected, and the presence of un-known masses should be investigated.

The insulin receptor family in the heart: new light on old insights

Insulin was discovered over 100 years ago. Whilst the first half century defined many of the physiological effects of insulin, the second emphasised the mechanisms by which it elicits these effects, implicating a vast array of G proteins and their regulators, lipid and protein kinases and counteracting phosphatases, and more. Potential growth-promoting and protective effects of insulin on the heart emerged from studies of carbohydrate metabolism in the 1960s, but the insulin receptors (and the related receptor for insulin-like growth factors 1 and 2) were not defined until the 1980s. A related third receptor, the insulin receptor-related receptor remained an orphan receptor for many years until it was identified as an alkali-sensor. The mechanisms by which these receptors and the plethora of downstream signalling molecules confer cardioprotection remain elusive. Here, we review important aspects of the effects of the three insulin receptor family members in the heart. Metabolic studies are set in the context of what is now known of insulin receptor family signalling and the role of protein kinase B (PKB or Akt), and the relationship between this and cardiomyocyte survival versus death is discussed. PKB/Akt phosphorylates numerous substrates with potential for cardioprotection in the contractile cardiomyocytes and cardiac non-myocytes. Our overall conclusion is that the effects of insulin on glucose metabolism that were initially identified remain highly pertinent in managing cardiomyocyte energetics and preservation of function. This alone provides a high level of cardioprotection in the face of pathophysiological stressors such as ischaemia and myocardial infarction.

Functional stapled fragments of human preptin of minimised length

Preptin is a 34-amino-acid-long peptide derived from the E-domain of a precursor of insulin-like growth factor 2 (pro-IGF2) with bone-anabolic and insulin secretion amplifying properties. Here, we describe the synthesis, structures, and biological activities of six shortened analogues of human preptin. Eight- and nine-amino-acid-long peptide amides corresponding to the C-terminal part of human preptin were stabilised by two types of staples to induce a higher proportion of helicity in their secondary structure. We monitored the secondary structure of the stapled peptides using circular dichroism. The biological effect of the structural changes was determined afterwards by the ability of peptides to stimulate the release of intracellular calcium ions. We confirmed the previous observation that the stabilisation of the disordered conformation of human preptin has a deleterious effect on biological potency. However, surprisingly, one of our preptin analogues, a nonapeptide stabilised by olefin metathesis between positions 3 and 7 of the amino acid chain, had a similar ability to stimulate calcium ions' release to the full-length human preptin. Our findings could open up new ways to design new preptin analogues, which may have potential as drugs for the treatment of diabetes and osteoporosis.

Review of Novel Potential Insulin Resistance Biomarkers in PCOS Patients—The Debate Is Still Open

Research on proteins and peptides that play roles in metabolic regulation, which may be considered potential insulin resistance markers in some medical conditions, such as diabetes mellitus, obesity and polycystic ovarian syndrome (PCOS), has recently gained in interest. PCOS is a common endocrine disorder associated with hyperandrogenemia and failure of ovulation, which is often accompanied by metabolic abnormalities, including obesity, dyslipidemia, hyperinsulinemia, and insulin resistance. In this review, we focus on less commonly known peptides/proteins and investigate their role as potential biomarkers for insulin resistance in females affected by PCOS. We summarize studies comparing the serum fasting concentration of particular agents in PCOS individuals and healthy controls. Based on our analysis, we propose that, in the majority of studies, the levels of nesfastin-1, myonectin, omentin, neudesin were decreased in PCOS patients, while the levels of the other considered agents (e.g., preptin, gremlin-1, neuregulin-4, xenopsin-related peptide, xenin-25, and galectin-3) were increased. However, there also exist studies presenting contrary results; in particular, most data existing for lipocalin-2 are inconsistent. Therefore, further research is required to confirm those hypotheses, as well as to elucidate the involvement of these factors in PCOS-related metabolic complications.

A case of nonislet cell tumor hypoglycemia associated with malignant mesothelioma requiring a multifaceted approach for optimal glycemic control

Nonislet tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome characterized by refractory hypoglycemia, which often requires multifaceted therapy. We reported a case of a patient with pleural malignant mesothelioma and developed NICTH, for which chemotherapy, glucocorticoids, and nutrition were given to achieve optimal glycemic control.

Severe recurrent hypoglycaemia in a patient with aggressive melanoma

We present a case of hypoglycemia in a young patient without diabetes mellitus who presented initially with enlarging neck mass and weight loss, and was found to have aggressive melanoma with metastasis to multiple organs and diffuse lymphadenopathy. He had presented to the emergency room two times with neuroglycopenic symptoms that required admission and intravenous dextrose continuously. Evaluation of hypoglycemia included C-peptide, insulin levels, insulin-like growth factor (IGF) -I and -II, and ß- hydroxybutyrate. Insulin levels were suppressed appropriately during hypoglycemia, however, IGF-II:IGF-I ratio was high, suggesting non-islet tumour induced hypoglycemia. The presence of IGF-II produced by large tumors results in a low hepatic glucose output and increased uptake by skeletal muscle, resulting in hypoglycemia especially in a patient with extremely low appetite such as our patient. Treating the culprit malignancy leads to resolution of hypoglycemia, but corticosteroids have been used to suppress IGF-II levels and alleviate symptoms.

Hepatitis C-Associated Osteosclerosis: Improvement After Treatment with Sofosbuvir, Daclatasvir, and Ibandronate: Case Report and Literature Review

Hepatitis C-associated osteosclerosis (HCAO) remains a rare condition despite the growing prevalence of hepatitis C virus (HCV) infection worldwide. Since the first case reported in 1992, this is the twenty-second case described. Patients with HCAO present with severe bone pain and elevated serum levels of bone markers, especially alkaline phosphatase (ALP), with increased bone density. We report here the case of a 59-year-old man with generalized bone pain and diagnosis of HCV infection. Biochemical tests showed elevated bone turnover markers, specifically, ALP, carboxy-terminal collagen crosslinks and osteocalcin. Imaging studies revealed generalized bone sclerosis. Bone mineral density was elevated in all validated sites. His clinical symptoms and bone-related findings were attributed to HCAO. He was sequentially treated with cholecalciferol, prednisone, sofosbuvir associated with daclatasvir and ibandronate, and progressed with undetectable viral load after HCV treatment, normalization of ALP levels after introduction of ibandronate, and pain improvement 1 year after discontinuation of the bisphosphonate. Bone pain complaints must be investigated in patients with HCV. HCAO is a differential diagnosis of increased bone mass.

Insulin-like growth factors: Ligands, binding proteins, and receptors

BACKGROUND

The insulin-like growth factor family of ligands (IGF-I, IGF-II, and insulin), receptors (IGF-IR, M6P/IGF-IIR, and insulin receptor [IR]), and IGF-binding proteins (IGFBP-1-6) play critical roles in normal human physiology and disease states.

SCOPE OF REVIEW

Insulin and insulin receptors are the focus of other chapters in this series and will therefore not be discussed further. Here we review the basic components of the IGF system, their role in normal physiology and in critical pathology's. While this review concentrates on the role of IGFs in human physiology, animal models have been essential in providing understanding of the IGF system, and its regulation, and are briefly described.

MAJOR CONCLUSIONS

IGF-I has effects via the circulation and locally within tissues to regulate cellular growth, differentiation, and survival, thereby controlling overall body growth. IGF-II levels are highest prenatally when it has important effects on growth. In adults, IGF-II plays important tissue-specific roles, including the maintenance of stem cell populations. Although the IGF-IR is closely related to the IR it has distinct physiological roles both on the cell surface and in the nucleus. The M6P/IGF-IIR, in contrast, is distinct and acts as a scavenger by mediating internalization and degradation of IGF-II. The IGFBPs bind IGF-I and IGF-II in the circulation to prolong their half-lives and modulate tissue access, thereby controlling IGF function. IGFBPs also have IGF ligand-independent cell effects.

Insulin-Like Growth Factor 2 As a Possible Neuroprotective Agent and Memory Enhancer-Its Comparative Expression, Processing and Signaling in Mammalian CNS

A number of studies performed on rodents suggest that insulin-like growth factor 2 (IGF-2) or its analogs may possibly be used for treating some conditions like Alzheimer’s disease, Huntington’s disease, autistic spectrum disorders or aging-related cognitive impairment. Still, for translational research a comparative knowledge about the function of IGF-2 and related molecules in model organisms (rats and mice) and humans is necessary. There is a number of important differences in IGF-2 signaling between species. In the present review we emphasize species-specific patterns of IGF-2 expression in rodents, humans and some other mammals, using, among other sources, publicly available transcriptomic data. We provide a detailed description of Igf2 mRNA expression regulation and pre-pro-IGF-2 protein processing in different species. We also summarize the function of IGF-binding proteins. We describe three different receptors able to bind IGF-2 and discuss the role of IGF-2 signaling in learning and memory, as well as in neuroprotection. We hope that comprehensive understanding of similarities and differences in IGF-2 signaling between model organisms and humans will be useful for development of more effective medicines targeting IGF-2 receptors.

The Roles of Insulin-Like Growth Factor Binding Protein Family in Development and Diseases

The insulin-like growth factor (IGF) system comprises ligands of IGF-I/II, IGF receptors (IGFR), IGF binding proteins (IGFBPs), and IGFBP hydrolases. The IGF system plays multiple roles during various disease development as IGFs are widely involved in cell proliferation and differentiation through regulating DNA transcription. Meanwhile, IGFBPs, which are mainly synthesized in the liver, can bind to IGFs and perform two different functions: either inhibition of IGFs by forming inactive compounds with IGF or enhancement of the function of IGFs by strengthening the IGF-IGFR interaction. Interestingly, IGFBPs may have wider functions through IGF-independent mechanisms. Studies have shown that IGFBPs play important roles in cardiovascular disease, tumor progression, fetal growth, and neuro-nutrition. In this review, we emphasize that different IGFBP family members have common or unique functions in numerous diseases; moreover, IGFBPs may serve as biomarkers for disease diagnosis and prediction.

Insulin-like growth factor-II and bioactive proteins containing a part of the E-domain of pro-insulin-like growth factor-II

Insulin-like growth factor (IGF)-II is considered to function as an important fetal growth factor, which is structurally and functionally related to IGF-I and proinsulin. At least in vitro, IGF-II actions are mediated through the IGF-I receptor and to a lesser extent the insulin receptor. After birth, the function of IGF-II is less clear although in adults the serum level of IGF-II exceeds that of IGF-I several fold. The IGF-II gene is maternally imprinted, with exception of the liver and several parts of the brain, where it is expressed from both alleles. The regulation, organization, and translation of the IGF-II gene is complex, with five different putative promotors leading to a range of noncoding and coding mRNAs. The 180-amino acid pre-pro-IGF-II translation product can be divided into five domains and include a N-terminal signal peptide of 24 amino acid residues, the 67 amino acid long mature protein, and an 89 residues extension at the COOH terminus, designated as the E-domain. After removal of the signal peptide, the processing of pro-IGF-II into mature IGF-II requires various steps including glycosylation of the E-domain followed by the action of endo-proteases. Several of these processing intermediates can be found in the human circulation. There is increasing evidence that, besides IGF-II, several incompletely processed precursor forms of the protein, and even a 34-amino acid peptide (preptin) derived from the E-domain of pro-IGF-II, exhibit distinct biological activities. This review will focus on the current insights regarding the specific roles of the latter proteins in cancer, glucose homeostasis, and bone physiology. To address this topic clearly in the right context, a concise overview of the biological and biochemical properties of IGF-II and several relevant aspects of the IGF system will be provided.