Scaling up polarized RPE cell supernatant production on parylene membrane.

Age-related macular degeneration (AMD), a leading cause of vision loss, primarily arises from the degeneration of retinal pigment epithelium (RPE) and photoreceptors. Current therapeutic options for dry AMD are limited. Encouragingly, cultured RPE cells on parylene-based biomimetic Bruch's membrane demonstrate characteristics akin to the native RPE layer. In this study, we cultivated human embryonic stem cell-derived polarized RPE (hESC-PRPE) cells on parylene membranes at both small- and large-scale settings, collecting conditioned supernatant, denoted as PRPE-SF. We conducted a comprehensive analysis of the morphology of the cultured hESC-RPE cells and the secreted growth factors in PRPE-SF. To evaluate the in vivo efficacy of these products, the product was administered via intravitreal injections of PRPE-SF in immunodeficient Royal College of Surgeons (iRCS) rats, a model for retinal degeneration. Our study not only demonstrated the scalability of PRPE-SF production while maintaining RPE cell phenotype but also showed consistent protein concentrations between small- and large-scale batches. We consistently identified 10 key factors in PRPE-SF, including BMP-7, IGFBP-2, IGFBP-3, IGFBP-4, IGFBP-6, MANF, PEDF, PDGF-AA, TGFß1, and VEGF. Following intravitreal administration of PRPE-SF, we observed a significant increase in the thickness of the outer nuclear layer (ONL) and photoreceptor preservation in iRCS rats. Furthermore, correlation analysis revealed that IGFBP-3, IGFBP-4, MANF, PEDF, and TGFß1 displayed positive associations with in vivo bioactivity, while GDF-15 exhibited a negative correlation. Overall, this study highlights the feasibility of scaling up PRPE-SF production on parylene membranes without compromising its essential constituents. The outcomes of PRPE-SF administration in an animal model of retinal degeneration present substantial potential for photoreceptor preservation. Moreover, the identification of candidate surrogate potency markers, showing strong positive associations with in vivo bioactivity, lays a solid foundation for the development of a promising therapeutic intervention for retinal degenerative diseases.

Reduction in Pappalysin-2 Levels and Lower IGF-I Bioavailability in Female Adolescents With Anorexia Nervosa.

CONTEXT: Anorexia nervosa (AN) can cause severe undernutrition associated with alterations in the IGF axis. Pappalysins (PAPP-A, PAPP-A2) and stanniocalcins (STC-1, STC-2) modulate IGF binding-protein (IGFBP) cleavage and IGF bioavailability, but their implications in AN are unknown. OBJECTIVE: We determined serum levels of PAPP-As and STCs in relationship with classical IGF axis parameters in female adolescents with AN and their association with nutritional status and secondary amenorrhea. METHODS: Parameters of the IGF axis were determined in fasting serum samples of 68 female adolescents with AN at diagnosis and 62 sex- and age-matched controls. Standardized body mass index (BMI) and bone mineral density (BMD) were calculated. RESULTS: Patients with AN had lower concentrations of total and free IGF-I, total IGFBP-3, acid-labile subunit (ALS), insulin, PAPP-A2, STC-1, and STC-2 and higher levels of IGF-II and IGFBP-2. Their free/total IGF-I ratio was decreased and the intact/total IGFBP-3 and -4 ratios increased. BMI was directly related to total IGF-I and intact IGFBP-3 and inversely with IGFBP-2 and intact IGFBP-4. Weight loss was directly correlated with intact IGFBP-4 and negatively with intact IGFBP-3, ALS, STC-2, and PAPP-A2 concentrations. BMD was directly related to intact IGFBP-3 and inversely with intact IGFBP-4 and PAPP-A2 levels. Patients with amenorrhea had lower levels of total IGF-I and IGFBP-3 than those with menses. CONCLUSION: The reduction of PAPP-A2 in patients with AN may be involved in a decline in IGFBP cleavage, which could underlie the decrease in IGF-I bioavailability that is influenced by nutritional status and amenorrhea.

Increased Levels of Circulating IGFBP4 and ANGPTL8 with a Prospective Role in Diabetic Nephropathy.

Diabetic nephropathy (DN) is a complicated condition related to type 2 diabetes mellitus (T2D). ANGPTL8 is a hepatic protein highlighted as a risk factor for DN in patients with T2D; additionally, recent evidence from DN studies supports the involvement of growth hormone/IGF/IGF-binding protein axis constituents. The potential link between ANGPTL8 and IGFBPs in DN has not been explored before. Here, we assessed changes in the circulating ANGPTL8 levels in patients with DN and its association with IGFBP-1, -3, and -4. Our data revealed a significant rise in circulating ANGPTL8 in people with DN, 4443.35 ± 396 ng/mL compared to 2059.73 ± 216 ng/mL in people with T2D (p < 0.001). Similarly, levels of IGFBP-3 and -4 were significantly higher in people with DN compared to the T2D group. Interestingly, the rise in ANGPTL8 levels correlated positively with IGFBP-4 levels in T2DM patients with DN (p < 0.001) and this significant correlation disappeared in T2DM patients without DN. It also correlated positively with serum creatinine and negatively with the estimated glomerular filtration rate (eGFR, All < 0.05). The area under the curve (AUC) on receiver operating characteristic (ROC) analysis of the combination of ANGPTL8 and IGFBP4 was 0.76 (0.69-0.84), p < 0.001, and the specificity was 85.9%. In conclusion, our results showed a significant increase in ANGPTL8 in patients with DN that correlated exclusively with IGFBP-4, implicating a potential role of both proteins in the pathophysiology of DN. Our findings highlight the significance of these biomarkers, suggesting them as promising diagnostic molecules for the detection of diabetic nephropathy.

Stanniocalcin-2 inhibits skeletal muscle growth and is upregulated in functional overload-induced hypertrophy.

AIMS: Stanniocalcin-2 (STC2) has recently been implicated in human muscle mass variability by genetic analysis. Biochemically, STC2 inhibits the proteolytic activity of the metalloproteinase PAPP-A, which promotes muscle growth by upregulating the insulin-like growth factor (IGF) axis. The aim was to examine if STC2 affects skeletal muscle mass and to assess how the IGF axis mediates muscle hypertrophy induced by functional overload. METHODS: We compared muscle mass and muscle fiber morphology between Stc2-/- (n = 21) and wild-type (n = 15) mice. We then quantified IGF1, IGF2, IGF binding proteins -4 and -5 (IGFBP-4, IGFBP-5), PAPP-A and STC2 in plantaris muscles of wild-type mice subjected to 4-week unilateral overload (n = 14). RESULTS: Stc2-/- mice showed up to 10% larger muscle mass compared with wild-type mice. This increase was mediated by greater cross-sectional area of muscle fibers. Overload increased plantaris mass and components of the IGF axis, including quantities of IGF1 (by 2.41-fold, p = 0.0117), IGF2 (1.70-fold, p = 0.0461), IGFBP-4 (1.48-fold, p = 0.0268), PAPP-A (1.30-fold, p = 0.0154) and STC2 (1.28-fold, p = 0.019). CONCLUSION: Here we provide evidence that STC2 is an inhibitor of muscle growth upregulated, along with other components of the IGF axis, during overload-induced muscle hypertrophy.

Circulating miR-4739 and IGFBP-4 Levels in Postmenopausal Women with Osteoporosis and Osteoporotic Vertebral Fracture.

Objective: This study aimed to investigate the potential plasma miRNA-mRNA regulatory networks in postmenopausal women with osteoporosis (OP) and osteoporotic vertebral fracture (OVF). Methods: The study employed a cross-sectional design, and the microarray dataset GSE93883 was acquired from the Gene Expression Omnibus (GEO) to assess plasma miRNA profiles in postmenopausal women with osteoporosis (OP) and osteoporotic vertebral fracture (OVF). Subsequently, plasma microRNA-4739 (miR-4739) and Insulin-like Growth Factor Binding Protein-4 (IGFBP-4) levels were validated in a well-defined cohort comprising 210 postmenopausal women. This cohort consisted of three distinct groups: healthy controls (HC, n = 70), OP patients (n = 70), and OVF patients (n = 70). Results: Analysis of the GSE93883 dataset revealed a stepwise increase in four miRNAs (hsa-miR-4739, hsa-miR-4505, hsa-miR-4459, hsa-miR-665) in plasma samples from HC to OP patients to OVF patients. Conversely, plasma miR-4666a-3p showed a gradual decrease. We predicted six genes targeted by miR-4739 using six online databases. Plasma miR-4739 levels were significantly higher in OP and OVF patients compared to HC, especially in OVF patients. However, plasma IGFBP-4 exhibited an inverse pattern. Pearson analysis demonstrated a significant negative correlation between plasma miR-4739 and plasma IGFBP-4 in OP and OVF patients. Receiver operating characteristic (ROC) curve analysis of plasma miR-4739 yielded a sensitivity of 35.71% and specificity of 95.71% for predicting the presence of OP and a sensitivity of 71.43% and specificity of 95.71% for predicting OVF, with an AUC of 0.865. Moreover, the area under the curve (AUC) for IGFBP-4 was higher than that for plasma miR-4739 when differentiating OP patients from OVF patients. Conclusions: Circulating miR-4739 and IGFBP-4 demonstrated a negative correlation in OP and OVF patients, suggesting their potential as diagnostic biomarkers for OP and OVF in the future.

PAPP-A-Specific IGFBP-4 Proteolysis in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

The insulin-like growth factors IGF-I and IGF-II-as well as their binding proteins (IGFBPs), which regulate their bioavailability-are involved in many pathological and physiological processes in cardiac tissue. Pregnancy-associated plasma protein A (PAPP-A) is a metalloprotease that preferentially cleaves IGFBP-4, releasing IGF and activating its biological activity. Previous studies have shown that PAPP-A-specific IGFBP-4 proteolysis is involved in the pathogenesis of cardiovascular diseases, such as ischemia, heart failure, and acute coronary syndrome. However, it remains unclear whether PAPP-A-specific IGFBP-4 proteolysis participates in human normal cardiomyocytes. Here, we report PAPP-A-specific IGFBP-4 proteolysis occurring in human cardiomyocytes derived from two independent induced pluripotent cell lines (hiPSC-CMs), detected both on the cell surface and in the cell secretome. PAPP-A was measured by fluoroimmune analysis (FIA) in a conditioned medium of hiPSC-CMs and was detected in concentrations of up to 4.3 ± 1.33 ng/mL and 3.8 ± 1.1 ng/mL. The level of PAPP-A-specific IGFBP-4 proteolysis was determined as the concentration of NT-IGFBP-4 proteolytic fragments using FIA for a proteolytic neo-epitope-specific assay. We showed that PAPP-A-specific IGFBP-4 proteolysis is IGF-dependent and inhibited by EDTA and 1,10-phenanthroline. Therefore, it may be concluded that PAPP-A-specific IGFBP-4 proteolysis functions in human normal cardiomyocytes, and hiPSC-CMs contain membrane-bound and secreted forms of proteolytically active PAPP-A.

Further Evidence that an Episode of Premature Labor Is a Pathologic State: Involvement of the Insulin-Like Growth Factor System.

INTRODUCTION: Approximately 47% of women with an episode of preterm labor deliver at term; however, their infants are at greater risk of being small for gestational age and for neurodevelopmental disorders. In these cases, a pathologic insult may disrupt the homeostatic responses sustaining pregnancy. We tested the hypothesis of an involvement of components of the insulin-like growth factor (IGF) system. METHODS: This is a cross-sectional study in which maternal plasma concentrations of pregnancy-associated plasma protease (PAPP)-A, PAPP-A2, insulin-like growth factor-binding protein 1 (IGFBP-1), and IGFBP-4 were determined in the following groups of women: (1) no episodes of preterm labor, term delivery (controls, n = 100); (2) episode of preterm labor, term delivery (n = 50); (3) episode of preterm labor, preterm delivery (n = 100); (4) pregnant women at term not in labor (n = 61); and (5) pregnant women at term in labor (n = 61). Pairwise differences in maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 among study groups were assessed by fitting linear models on log-transformed data and included adjustment for relevant covariates. Significance of the group coefficient in the linear models was assessed via t-scores, with p < 0.05 deemed a significant result. RESULTS: Compared to controls, (1) women with an episode of premature labor, regardless of a preterm or a term delivery, had higher mean plasma concentrations of PAPP-A2 and IGFBP-1 (each p < 0.05); (2) women with an episode of premature labor who delivered at term also had a higher mean concentration of PAPP-A (p < 0.05); and (3) acute histologic chorioamnionitis and spontaneous labor at term were not associated with significant changes in these analytes. CONCLUSION: An episode of preterm labor involves the IGF system, supporting the view that the premature activation of parturition is a pathologic state, even in those women who delivered at term.

Potent antitumor effects of the conditioned medium of bone marrow-derived mesenchymal stem cells via IGFBP-4.

Cell transfer therapy using mesenchymal stem cells (MSCs) has pronounced therapeutic potential, but concerns remain about immune rejection, emboli formation, and promotion of tumor progression. Because the mode of action of MSCs highly relies on their paracrine effects through secretion of bioactive molecules, cell-free therapy using the conditioned medium (CM) of MSCs is an attractive option. However, the effects of MSC-CM on tumor progression have not been fully elucidated. Herein, we addressed this issue and investigated the possible underlying molecular mechanisms. The CM of MSCs derived from human bone marrow greatly inhibited the in vitro growth of several human tumor cell lines and the in vivo growth of the SCCVII murine squamous cell carcinoma cell line with reduced neovascularization. Exosomes in the MSC-CM were only partially involved in the inhibitory effects. The CM contained a variety of cytokines including insulin-like growth factor binding proteins (IGFBPs). Among them, IGFBP-4 greatly inhibited the in vitro growth of these tumors and angiogenesis, and immunodepletion of IGFBP-4 from the CM significantly reversed these effects. Of note, the CM greatly reduced the phosphorylation of AKT, ERK, IGF-1 receptor beta, and p38 MAPK in a partly IGFBP4-dependent manner, possibly through its binding to IGF-1/2 and blocking the signaling. The CM depleted of IGFBP-4 also reversed the inhibitory effects on in vivo tumor growth and neovascularization. Thus, MSC-CM has potent inhibitory effects on tumor growth and neovascularization in an IGFBP4-dependent manner, suggesting that cell-free therapy using MSC-CM could be a safer promising alternative for even cancer patients.

Insulin-like growth factor binding protein 4 loaded electrospun membrane ameliorating tendon injury by promoting retention of IGF-1.

Tendon injury is one of the most common musculoskeletal disorders that impair joint mobility and lower quality of life. The limited regenerative capacity of tendon remains a clinical challenge. Local delivery of bioactive protein is a viable therapeutic approach for tendon healing. Insulin-like growth factor binding protein 4 (IGFBP-4) is a secreted protein capable of binding and stabilizing insulin-like growth factor 1 (IGF-1). Here, we applied an aqueous-aqueous freezing-induced phase separation technology to obtain the IGFBP4-encapsulated dextran particles. Then, we added the particles into poly (L-lactic acid) (PLLA) solution to fabricate IGFBP4-PLLA electrospun membrane for efficient IGFBP-4 delivery. The scaffold showed excellent cytocompatibility and a sustained release of IGFBP-4 for nearly 30 days. In cellular experiments, IGFBP-4 promoted tendon-related and proliferative markers expression. In a rat Achilles tendon injury model, immunohistochemistry and quantitative real-time polymerase chain reaction confirmed better outcomes by using the IGFBP4-PLLA electrospun membrane at the molecular level. Furthermore, the scaffold effectively promoted tendon healing in functional performance, ultrastructure and biomechanical properties. We found addition of IGFBP-4 promoted IGF-1 retention in tendon postoperatively and then facilitated protein synthesis via IGF-1/AKT signaling pathway. Overall, our IGFBP4-PLLA electrospun membrane provides a promising therapeutic strategy for tendon injury.

The Stanniocalcin-PAPP-A-IGFBP-IGF Axis.

The pappalysin metalloproteinases, PAPP-A and PAPP-A2, have emerged as highly specific proteolytic enzymes involved in the regulation of insulin-like growth factor (IGF) signaling. The only known pappalysin substrates are a subset of the IGF binding proteins (IGFBPs), which bind IGF-I or IGF-II with high affinity to antagonize receptor binding. Thus, by cleaving IGFBPs, the pappalysins have the potential to increase IGF bioactivity and hence promote IGF signaling. This is relevant both in systemic and local IGF regulation, in normal and several pathophysiological conditions. Stanniocalcin-1 and -2 were recently found to be potent pappalysin inhibitors, thus comprising the missing components of a complete proteolytic system, the stanniocalcin-PAPP-A-IGFBP-IGF axis. Here, we provide the biological context necessary for understanding the properties of this molecular network, and we review biochemical data, animal experiments, clinical data, and genetic data supporting the physiological operation of this branch as an important part of the IGF system. However, although in vivo data clearly illustrate its power, it is a challenge to understand its subtle operation, for example, multiple equilibria and inhibitory kinetics may determine how, where, and when the IGF receptor is stimulated. In addition, literally all of the regulatory proteins have suspected or known activities that are not directly related to IGF signaling. How such activities may integrate with IGF signaling is also important to address in the future.

Structure of the proteolytic enzyme PAPP-A with the endogenous inhibitor stanniocalcin-2 reveals its inhibitory mechanism.

The metzincin metalloproteinase PAPP-A plays a key role in the regulation of insulin-like growth factor (IGF) signaling by specific cleavage of inhibitory IGF binding proteins (IGFBPs). Using single-particle cryo-electron microscopy (cryo-EM), we here report the structure of PAPP-A in complex with its endogenous inhibitor, stanniocalcin-2 (STC2), neither of which have been reported before. The highest resolution (3.1 Å) was obtained for the STC2 subunit and the N-terminal approximately 1000 residues of the PAPP-A subunit. The 500 kDa 2:2 PAPP-A·STC2 complex is a flexible multidomain ensemble with numerous interdomain contacts. In particular, a specific disulfide bond between the subunits of STC2 and PAPP-A prevents dissociation, and interactions between STC2 and a module located in the very C-terminal end of the PAPP-A subunit prevent binding of its main substrate, IGFBP-4. While devoid of activity towards IGFBP-4, the active site cleft of the catalytic domain is accessible in the inhibited PAPP-A·STC2 complex, as shown by its ability to hydrolyze a synthetic peptide derived from IGFBP-4. Relevant to multiple human pathologies, this unusual mechanism of proteolytic inhibition may support the development of specific pharmaceutical agents, by which IGF signaling can be indirectly modulated.

CT-IGFBP-4 as a Predictive Novel Biomarker of Ischemic Cardiovascular Events and Mortality: A Systematic Review.

Methods: The electronic databases PubMed, medRxiv, ScienceDirect, and Google Scholar were searched for relevant literature from inception to the 10th of December, 2021. Thus, retrieved literature was screened by title and abstract, followed by full-text screening based on the eligibility criteria. The risk of bias was accessed using the quality in prognostic studies (QUIPSs) tool. The data on cardiovascular outcomes about CT-IGFBP-4 levels were studied and the results were synthesized. Results: Five studies with a total of 1,417 participants were included in our study. The studies reported a low risk of bias. The mean age of the participants was 66.14 and more than 65% were males. Elevated CT-IGFBP-4 levels were associated with poor cardiovascular outcomes and increased mortality in severely ill patients. In contrast, there were no significant findings in the case of stable patients. Sandwich ELISA using lithium-heparin plasma provided a better detection limit of 0.15 ng/ml, low cross-reactivity (<2%), and generated linear results between 12 and 500 ng/ml. Conclusion: CT-IGFBP-4 is an efficient biomarker for the prediction of MACE and mortality in patients with severe ischemic cardiovascular events.

Pappalysins and Stanniocalcins and Their Relationship With the Peripheral IGF Axis in Newborns and During Development.

CONTEXT: Pappalysins (PAPP-A, PAPP-A2) modulate body growth by increasing insulin-like growth factor I (IGF-I) bioavailability through cleavage of insulin-like growth factor binding proteins (IGFBPs) and are inhibited by stanniocalcins (STC1, STC2). Normative data on these novel factors, as well as on free IGF-I and uncleaved fractions of IGFBPs, are not well established. OBJECTIVE: This work aimed to determine serum concentrations of PAPP-A, PAPP-A2, STC1, and STC2 in relationship with other growth hormone (GH)-IGF axis parameters during development. METHODS: Full-term newborns (150; gestational age: 39.30 ±â€…1.10 weeks), 40 preterm newborns (30.87 ±â€…3.35 weeks), and 1071 healthy individuals (aged 1-30 years) were included in the study and divided according to their Tanner stages (males and females): I:163 males, 154 females; II:100 males, 75 females; III:83 males, 96 females; IV: 77 males, 86 females; and V:109 males,128 females. RESULTS: Serum concentrations of PAPP-A, PAPP-A2, STC1, STC2, IGFBP-2, total IGFBP-4, and total IGFBP-5 were elevated at birth and declined throughout childhood. In postnatal life, PAPP-A2 concentrations decreased progressively in concomitance with the free/total IGF-I ratio; however, stanniocalcin concentrations remained stable. PAPP-A2 concentrations positively correlated with the free/total IGF-I ratio (r = +0.28; P < .001) and negatively with the intact/total IGFBP-3 ratio (r = -0.23; P < .001). PAPP-A concentrations inversely correlated with intact/total IGFBP-4 ratio (r = -0.21; P < .001), with PAPP-A concentrations being lower in females at all ages. Association studies indicate the importance of stanniocalcins and pappalysins in the control of this axis in an age-specific manner. CONCLUSION: This study provides reference values of pappalysins and stanniocalcins, which modulate IGF-I activity by changing the concentrations of cleaved and uncleaved IGFBPs.

[Identification of serological biomarkers for diagnosis of rheumatoid arthritis using a protein array-based approach].

OBJECTIVE: To study the cytokine patterns in patients with rheumatoid arthritis (RA) and healthy individuals and identify candidate serum biomarkers for clinical diagnosis of RA. METHODS: This study was conducted among 59 patients diagnosed with RA in our hospital from 2015 to 2019 with 46 age- and gender-matched healthy subjects who received regular physical examinations in our hospital as the control group. Serological autoimmune profiles of 5 RA patients and 5 healthy control subjects were obtained from human cytokine microarrays. We selected 4 differentially expressed cytokines (LIMPII, ROBO3, Periostin and IGFBP-4) and 2 soluble cytokine receptors of interest (2B4 and Tie-2) and examined their serum levels using enzyme-linked immunosorbent assay in 54 RA patients and 41 healthy control subjects. Spearman correlation test was performed to assess the correlation of serum cytokine and soluble receptor expression levels with the clinical features including rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), disease activity score (DAS28) and health assessment questionnaire (HAQ). Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic capability of these cytokines. RESULTS: We identified 6 dysregulated cytokines and soluble receptors (2B4, LIMPII, Tie-2, ROBO3, periostin and IGFBP-4) in RA patients (P < 0.01). The serum levels of LIMPII, ROBO3 and periostin were significantly correlated with the disease activity indicators including RF (P < 0.001), CRP (P < 0.001), DAS28 (P < 0.001) and HAQ (P < 0.001) in RA patients. Among the 6 candidate cytokines, 2B4 showed the largest area under the curve (AUC) of 0.861 for RA diagnosis (P < 0.001), followed then by LIMPII, ROBO3, periostin, Tie-2 and IGFBP-4. CONCLUSION: Serum levels of LIMPII, ROBO3 and periostin can be indicative of the disease activity of RA, and serum 2B4, LIMPII, periostin, ROBO3, IGFBP-4 and Tie-2 levels may serve as biomarkers for the diagnosis of RA.

Functional characterization of a novel p.Ser76Thr variant in IGFBP4 that associates with body mass index in American Indians.

Insulin-like growth factor binding protein 4 (IGFBP4) is involved in adipogenesis, and IGFBP4 null mice have decreased body fat through decreased PPAR-γ expression. In the current study, we assessed whether variation in the IGFBP4 coding region influences body mass index (BMI) in American Indians who are disproportionately affected by obesity. Whole exome sequence data from a population-based sample of 6779 American Indians with longitudinal measures of BMI were used to identify variation in IGFBP4 that associated with BMI. A novel variant that predicts a p.Ser76Thr in IGFBP4 (Thr-allele frequency = 0.02) was identified which associated with the maximum BMI measured during adulthood (BMI 39.8 kg/m2 for Thr-allele homozygotes combined with heterozygotes vs. 36.2 kg/m2 for Ser-allele homozygotes, ß = 6.7% per Thr-allele, p = 8.0 × 10-5, adjusted for age, sex, birth-year and the first five genetic principal components) and the maximum age- and sex-adjusted BMI z-score measured during childhood/adolescence (z-score 0.70 SD for Thr-allele heterozygotes vs. 0.32 SD for Ser-allele homozygotes, ß = 0.37 SD per Thr-allele, p = 8.8 × 10-6). In vitro functional studies showed that IGFBP4 with the Thr-allele (BMI-increasing) had a 55% decrease (p = 0.0007) in FOXO-induced transcriptional activity, reflecting increased activation of the PI3K/AKT pathway mediated through increased IGF signaling. Over-expression and knock-down of IGFBP4 in OP9 cells during differentiation showed that IGFBP4 upregulates adipogenesis through PPARγ, CEBPα, AGPAT2 and SREBP1 expression. We propose that this American Indian specific variant in IGFBP4 affects obesity via an increase of IGF signaling.

Alterations in the fecal microbiota and serum metabolome in unstable angina pectoris patients.

BACKGROUND: Unstable angina pectoris (UAP) is a type of Coronary artery disease (CAD) characterized by a series of angina symptoms. Insulin-like growth factor 1 (IGF-1) system may be related to CAD. However, the correlation between the IGF-1 system, metabolism, and gut microbiota has not been studied. In the present study, we investigated the alterations of serum IGF-1 system, metabolomics, and gut microbiota in patients with UAP. METHODS: Serum and stool samples from healthy volunteers and UAP patients were collected. Serum metabolomics, PAPP-A, IGF-1, IGFBP-4, STC2, hs-CRP, TNF-α, and IL-6 were detected in serum samples by LC-MS, and commercial ELISA kits, respectively. Fecal short-chain fatty acids (SCFAs) were measured by gas chromatography. 16S rDNA was used to measure the changes of the gut microbiota. The correlation of the above indicators was analyzed. RESULTS: There were 24 upregulated and 31 downregulated metabolites in the serum of UAP patients compared to those in the controls. Pathway analysis showed that these metabolites were enriched in pathways including linoleic acid metabolism, amino acid metabolism, starch metabolism, sucrose metabolism, and citrate cycle (TCA cycle), etc. Additionally, the UAP patients had lower fecal levels of 2-hydroxyisobutyric acid and succinic acid. 16S rDNA sequencing results showed that the relative abundances of Bacteroidetes, Synergistetes, Lactobacillaceae, Burkholderiaceae, Synergistaceae, and Subdoligranulum were significantly higher in the UAP patients than the healthy subjects. Moreover, the UAP patients had lower serum IGF-1, IGFBP-4, and STC2 and higher serum inflammatory cytokines (hs-CRP, TNF-α, and IL-6) levels than the healthy controls. Furthermore, there was a strong correlation between serum amino acids and IL-6, which played an important role in the development of UAP. CONCLUSIONS: These results indicated that the UAP patients had decreased serum IGF-1 level and imbalanced amino acids metabolism, which may be caused by the altered gut microbiota. It may provide a new therapeutic strategy for unstable angina pectoris.

Association of significantly elevated plasma levels of NGAL and IGFBP4 in patients with diabetic nephropathy.

BACKGROUND: Diabetic nephropathy (DN) is a type of progressive kidney disease affecting approximately 40% of patients with diabetes. Current DN diagnostic criteria predominantly rely on albuminuria and serum creatinine (sCr) levels. However, the specificity and reliability of both markers are limited. Hence, reliable biomarkers are required for early diagnosis to effectively manage DN progression. METHODS: In this study, a cohort of 159 individuals were clinically evaluated and the plasma levels of NGAL, IGFBP-1, IGFBP-3, and IGFBP-4 were determined using Multiplexing Assays. Additionally, the association between the plasma levels of NGAL, IGFBP-1, IGFBP-3, and IGFBP-4 in patients with DN were compared to those in patients with T2D without kidney disease and control participants. RESULTS: Circulating level of NGAL were significantly higher in people with DN compared to people with T2D and non-diabetic groups (92.76 ± 7.5, 57.22 ± 8.7, and 52.47 ± 2.9 mg/L, respectively; p <  0.0001). IGFBP-4 showed a similar pattern, where it was highest in people with DN (795.61 ng/ml ±130.7) compared to T2D and non-diabetic people (374.56 ng/ml ±86.8, 273.06 ng/ml ±27.8 respectively, ANOVA p <  0.01). The data from this study shows a significant positive correlation between NGAL and IGFBP-4 in people with DN (ρ = .620, p <  0.005). IGFBP-4 also correlated positively with creatinine level and negatively with eGFR, in people with DN supporting its involvement in DN. CONCLUSION: The data from this study shows a parallel increase in the plasma levels of NGAL and IGFBP-4 in DN. This highlights the potential to use these markers for early diagnosis of DN.

Pregnancy-associated plasma protein A mRNA expression as a marker for differentiated thyroid cancer: results from a "surgical" and a "cytological" series.

PURPOSE: Pregnancy-associated plasma protein A (PAPPA) is a metalloproteinase initially described for its role during pregnancy. PAPPA regulates IGF ligands 1 (IGF1) bioavailability through the degradation of IGF-binding protein 4 (IGFBP4). After the cleavage of IGFBP4, free IGF1 is able to bind IGF1 receptors (IGF1R) triggering the downstream signaling. Recently, PAPPA expression has been linked with development of several cancers. No data have been published on thyroid cancer, yet. METHODS: We evaluated PAPPA, insulin-like growth factor (IGF1), IGF1 receptors (IGF1R) and IGF-binding protein 4 (IGFBP4) mRNA expression levels in a "Surgical series" of 94 thyroid nodules (64 cancers, 16 follicular adenomas and 14 hyperplastic nodules) and in a "Cytological series" of 80 nodules from 74 patients underwent to fine-needle aspiration cytology (FNAC). In tissues, PAPPA was also evaluated by western blot. RESULTS: We found that PAPPA expression was increased in thyroid cancer specimen at mRNA and protein levels and that, adenomas and hyperplastic nodules had an expression similar to normal tissues. When applied on thyroid cytologies, PAPPA expression was able to discriminate benign from malignant nodules contributing to pre-surgical classification of the nodules. We calculated a cut-off with a good specificity (91%) which reached 100% when combined with molecular biology. CONCLUSION: These results show that PAPPA could represent a promising diagnostic marker for differentiated thyroid cancer.

Identification of serological biomarkers for diagnosis of rheumatoid arthritis using a protein array-based approach / 南方医科大学学报

OBJECTIVE@#To study the cytokine patterns in patients with rheumatoid arthritis (RA) and healthy individuals and identify candidate serum biomarkers for clinical diagnosis of RA.@*METHODS@#This study was conducted among 59 patients diagnosed with RA in our hospital from 2015 to 2019 with 46 age- and gender-matched healthy subjects who received regular physical examinations in our hospital as the control group. Serological autoimmune profiles of 5 RA patients and 5 healthy control subjects were obtained from human cytokine microarrays. We selected 4 differentially expressed cytokines (LIMPII, ROBO3, Periostin and IGFBP-4) and 2 soluble cytokine receptors of interest (2B4 and Tie-2) and examined their serum levels using enzyme-linked immunosorbent assay in 54 RA patients and 41 healthy control subjects. Spearman correlation test was performed to assess the correlation of serum cytokine and soluble receptor expression levels with the clinical features including rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), disease activity score (DAS28) and health assessment questionnaire (HAQ). Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic capability of these cytokines.@*RESULTS@#We identified 6 dysregulated cytokines and soluble receptors (2B4, LIMPII, Tie-2, ROBO3, periostin and IGFBP-4) in RA patients (P < 0.01). The serum levels of LIMPII, ROBO3 and periostin were significantly correlated with the disease activity indicators including RF (P < 0.001), CRP (P < 0.001), DAS28 (P < 0.001) and HAQ (P < 0.001) in RA patients. Among the 6 candidate cytokines, 2B4 showed the largest area under the curve (AUC) of 0.861 for RA diagnosis (P < 0.001), followed then by LIMPII, ROBO3, periostin, Tie-2 and IGFBP-4.@*CONCLUSION@#Serum levels of LIMPII, ROBO3 and periostin can be indicative of the disease activity of RA, and serum 2B4, LIMPII, periostin, ROBO3, IGFBP-4 and Tie-2 levels may serve as biomarkers for the diagnosis of RA.

IGFBP-4 Proteolysis by PAPP-A in a Primary Culture of Rat Neonatal Cardiomyocytes under Normal and Hypertrophic Conditions.

Cardiovascular diseases (CVD) are among the leading causes of death and disability worldwide. Pregnancy-associated plasma protein-A (PAPP-A) is a matrix metalloprotease localized on the cell surface. One of the substrates that PAPP-A cleaves is the insulin-like growth factor binding protein-4 (IGFBP-4), a member of the family of proteins that bind insulin-like growth factor (IGF). Proteolysis of IGFBP-4 by PAPP-A occurs at a specific site resulting in formation of two proteolytic fragments - N-terminal IGFBP-4 (NT-IGFBP-4) and C-terminal IGFBP-4 (CT-IGFBP-4), and leads to the release of IGF activating various cellular processes including migration, proliferation, and cell growth. Increased levels of the proteolytic IGFBP-4 fragments correlate with the development of CVD complications and increased risk of death in patients with the coronary heart disease, acute coronary syndrome, and heart failure. However, there is no direct evidence that PAPP-A specifically cleaves IGFBP-4 in the cardiac tissue under normal and pathological conditions. In the present study, using a primary culture of rat neonatal cardiomyocytes as a model, we have demonstrated that: 1) proteolysis of IGFBP-4 by PAPP-A occurs in the conditioned medium of cardiomyocytes, 2) PAPP-A-specific IGFBP-4 proteolysis is increased when cardiomyocytes are transformed to a hypertrophic state. Thus, it can be assumed that the enhancement of IGFBP-4 cleavage by PAPP-A and hypertrophic changes in cardiomyocytes accompanying CVD are interrelated, and PAPP-A appears to be one of the activators of the IGF-dependent processes in normal and hypertrophic-state cardiomyocytes.