IGFBP1 Sustains Cell Survival during Spatially-Confined Migration and Promotes Tumor Metastasis

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially-confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially-confined migration, the expression of insulin-like growth factor-binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1-mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis.

Hepatic Oleate Regulates Insulin-like Growth Factor-Binding Protein 1 Partially through the mTORC1-FGF21 Axis during High-Carbohydrate Feeding

Stearoyl-CoA desaturase-1 (SCD1) catalyzes the rate-liming step of monounsaturated fatty acid biosynthesis and is a key regulator of systemic glucose metabolism. Mice harboring either a global (GKO) or liver-specific deletion (LKO) of Scd1 display enhanced insulin signaling and whole-body glucose uptake. Additionally, GKO and LKO mice are protected from high-carbohydrate diet-induced obesity. Given that high-carbohydrate diets can lead to chronic metabolic diseases such as obesity, diabetes, and hepatic steatosis, it is critical to understand how Scd1 deficiency confers metabolically beneficial phenotypes. Here we show that insulin-like growth factor-binding protein 1 (IGFBP1), a hepatokine that has been reported to enhance insulin signaling, is significantly elevated in the liver and plasma of GKO and LKO mice fed a low-fat high-carbohydrate diet. We also observed that the expression of hepatic Igfbp1 is regulated by oleic acid (18:1n9), a product of SCD1, through the mTORC1-FGF21 axis both in vivo and in vitro.

Elevated levels of insulin-like growth factor-binding protein 1 predict outcome after acute myocardial infarction: A long-term follow-up of the glucose tolerance in patients with acute myocardial infarction (GAMI) cohort

OBJECTIVE

To investigate the long-term prognostic value of insulin-like growth factor-binding protein 1 in patients with acute myocardial infarction.

METHODS

Patients ( n = 180) with admission glucose < 11 mmol/L without previously known diabetes admitted for an acute myocardial infarction in 1998-2000 were followed for mortality and cardiovascular events (first of cardiovascular mortality/acute myocardial infarction/stroke/severe heart failure) until the end of 2011 (median 11.6 years). Fasting levels of insulin-like growth factor-binding protein 1 at day 2 were related to outcome in Cox proportional hazard regression analyses.

RESULTS

Median age was 64 years, 69% were male and median insulin-like growth factor-binding protein 1 was 20 µg/L. Total mortality was 34% ( n = 61) and 44% ( n = 80) experienced a cardiovascular event during a median follow-up time of 11.6 years. After age adjustment, insulin-like growth factor-binding protein 1 was associated with all-cause (1.40; 1.02-1.93, p = 0.039) and cancer mortality (2.09; 1.15-3.79, p = 0.015) but not with cardiovascular death ( p = 0.29) or cardiovascular events ( p = 0.57). After adjustments also for previous myocardial infarction, previous heart failure and body mass index, insulin-like growth factor-binding protein 1 was still associated with all-cause mortality (1.38; 1.01-1.89, p = 0.046).

CONCLUSION

In patients with acute myocardial infarction without previously known diabetes, high insulin-like growth factor-binding protein 1 was associated with long-term all-cause and cancer mortality but not with cardiovascular events.

Branched-chain amino acids regulate insulin-like growth factor-binding protein 1 (IGFBP1) production by decidua and influence trophoblast migration through IGFBP1

STUDY QUESTION

Do branched-chain amino acids (BCAAs) influence the migration of human extravillous trophoblast (EVT) cells through changes in insulin-like growth factor-binding protein 1 (IGFBP1) production in decidual cells?

STUDY FINDING

Decidua-derived IGFBP1 had a stimulating effect on migration of EVT.

WHAT IS KNOWN ALREADY

IGFBP1 is abundantly secreted from human decidual cells and influences trophoblast migration in human placenta of early pregnancy. In hepatic cells, the expression of IGFBP1 is influenced by nutritional status and BCAAs regulate IGFBP1 production.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

This is a laboratory-based study using human decidual cells and trophoblast cells isolated from placental tissue of early pregnancy (n = 50) and grown as primary cultures. Production of IGFBP1 from decidual cells was examined by enzyme-linked immunosorbent assay and immunoblotting after incubation with or without BCAAs. EVT migration was evaluated using the media conditioned by decidual cells. The effect of conditioned media on phosphorylation of focal adhesion kinase (FAK) in EVT was also analyzed by immunoblotting. The same experiments were repeated in the presence of RGD peptide, which inhibits IGFBP1 binding to α5β1 integrin. An EVT migration assay and the immunoblotting of phosphorylated FAK were also conducted with exogenous IGFBP1. The effect of the conditioned media on cytotrophoblast cell number was also assessed using WST-1 in a cell proliferation assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Deprivation of BCAAs on decidual cells significantly suppressed IGFBP1 secretion (P < 0.05, versus BCAA+). Exogenous IGFBP1-stimulated EVT migration (P < 0.05) and phosphorylation of FAK (P < 0.05), and the RGD peptide inhibited these effects. EVT migration and phosphorylation of FAK were stimulated by the conditioned media, presumably by IGFBP1 in the media. RGD treatment abrogated the stimulating effects of conditioned media. The conditioned media deprived of BCAAs had suppressive effects on EVT migration (P < 0.05, versus BCAA+) and phosphorylation of FAK (P < 0.05, versus BCAA+). The conditioned media did not affect number of cytotrophoblast cells.

LIMITATIONS, REASONS FOR CAUTION

The conclusions are based on in vitro experiments with human decidual cells and trophoblast cells isolated from placental tissue of early pregnancy, and we were unable to ascertain whether these mechanisms actually operate in vivo. We investigated the effect of decidua-derived IGFBP1 on EVT migration, however, we cannot completely rule out the possibility that endogenous IGF could also influence cell migration.

WIDER IMPLICATIONS OF FINDINGS

Interruption of the BCAA supply to uterine decidual cells in early pregnancy may suppress EVT migration through reduced IGFBP1 secretion, which may be one of the pathophysiological conditions responsible for pre-eclampsia.

LARGE SCALE DATA

None.

STUDY FUNDING/ AND COMPETING INTERESTS

All funds were obtained through Kyorin University School of Medicine. The authors have no conflict of interest to declare.

O-GlcNAcylation of FoxO1 in pancreatic β cells promotes Akt inhibition through an IGFBP1-mediated autocrine mechanism

O-GlcNAcylation on serine/threonine is a post-translational modification that controls the activity of nucleocytoplasmic proteins according to glucose availability. We previously showed that O-GlcNAcylation of FoxO1 in liver cells increases its transcriptional activity. In the present study, we evaluated the potential involvement of FoxO1 O-GlcNAcylation in the context of pancreatic β-cell glucotoxicity. FoxO1 was O-GlcNAcylated in INS-1 832/13 β cells and isolated rat pancreatic islets. O-GlcNAcylation of FoxO1 resulted in a 2-fold increase in its transcriptional activity toward a FoxO1 reporter gene and a 3-fold increase in the expression of the insulin-like growth factor-binding protein 1 (Igfbp1) gene at the mRNA level, resulting in IGFBP1 protein oversecretion by the cells. Of note, increased IGFBP1 in the culture medium inhibited the activity of the insulin-like growth factor 1 receptor (IGF1R)/phosphatidyl inositol 3 kinase (PI3K)/Akt pathway. We reveal in this report a novel mechanism by which O-GlcNAcylation inhibits Akt activity through an autocrine mechanism. However, although inhibition of IGFBP1 expression using siRNA restored the PI3 kinase/Akt pathway, it did not rescue INS-1 832/13 cells from high-glucose- or O-glcNAcylation-induced cell death. In contrast, FoxO1 down-regulation by siRNA led to 30 to 60% protection of INS-1 832/13 cells from death mediated by glucotoxic conditions. Therefore, whereas FoxO1 O-GlcNAcylation inhibits Akt through an IGFBP1-mediated autocrine pathway, the deleterious effects of FoxO1 O-GlcNAcylation on cell survival appeared to be independent of this pathway.

Gender-specific transcriptional profiling of marine medaka (Oryzias melastigma) liver upon BDE-47 exposure

Marine medaka (Oryzias melastigma) were exposed to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) to investigate the gender-specific transcriptional profiles of liver tissue in response to this flame retardant. A cDNA library of O. melastigma was constructed, and 2304 clones were amplified from the library to fabricate a cDNA microarray. Sequences of these genes were assembled into 1800 sequences using Geneious, a bioinformatics software. Corresponding expressed sequence tags were blasted against the National Centre for Biotechnology Information non-redundant database and further classified into various biological categories according to the Gene Ontology project. Male and female three-month-old were fed a diet of BDE-47 contaminated Artemia at low dosage (290.3±172.3ng BDE-47/day) and high dosage (580.5±344.6ng BDE-47/day) for 5 and 21 days, respectively. The transcriptional profiles of O. melastigma liver were then generated by the species-specific cDNA microrarray. The results from microarray analysis suggested very different gene expression patterns between males and females for both BDE-47 exposure-dose and exposure-time, with male livers having stronger gene regulatory responses than female livers. Importantly, our results revealed that in male O. melastigma only, BDE-47 exposure may activate phosphoinositide-3-kinase and mitogen-activated protein kinase, proteins that play importance roles in cell growth, proliferation and survival.