Expression of IGFBP-1 in normal and cirrhotic human livers

Structural changes of fibrinogen as a consequence of cirrhosis

Cirrhosis is a disease which may develop as a consequence of various conditions. In advanced liver disease, blood coagulation can be seriously affected. Portal hypertension, vascular abnormalities and/or a dysbalance in coagulation factors may result in bleeding disorders or in the development of thrombosis. Fibrinogen is the main protein involved in clot formation and wound healing. The aim of this work was to analyse the glycosylation pattern of the isolated fibrinogen molecules by lectin-based protein microarray, together with the carbonylation pattern of the individual fibrinogen chains, possible changes in the molecular secondary and tertiary structure and reactivity with the insulin-like growth factor-binding protein 1 (IGFBP-1) in patients with cirrhosis. The results pointed to an increase in several carbohydrate moieties: tri/tetra-antennary structures, Gal β-1,4 GlcNAc, terminal α-2,3 Sia and α-1,3 Man, and a decrease in core α-1,6 Fuc and bi-antennary galactosylated N-glycans with bisecting GlcNAc. Fibrinogen Aα chain was the most susceptible to carbonylation, followed by the Bβ chain. Cirrhosis induced additional protein carbonylation, mostly on the α chain. Spectrofluorimetry and CD spectrometry detected reduction in the α-helix content, protein unfolding and/or appearance of modified amino acid residues in cirrhosis. The amount of complexes which fibrinogen forms with IGFBP-1, another factor involved in wound healing was significantly greater in patients with cirrhosis than in healthy individuals. A more detailed knowledge of individual molecules in coagulation process may contribute to deeper understanding of coagulopathies and the results of this study offer additional information on the possible mechanisms involved in impaired coagulation due to cirrhosis.

IGFBP-1 and IGF-I as markers for advanced fibrosis in NAFLD - a pilot study

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease globally. Advanced fibrosis (stage 3-4) is the most robust marker for future mortality, but diagnosis requires liver biopsy. Current non-invasive scoring systems aimed to identify advanced fibrosis are imperfect. Insulin-like growth factor I (IGF-I) and its binding protein IGFBP-1 are liver derived proteins, that are involved in various liver disorders. The aim of this study was to examine the possible association between advanced fibrosis and IGF-I and IGFBP-1 in NAFLD.

METHODS

Fasting blood samples were obtained from 52 patients diagnosed with NAFLD by liver biopsy. Total IGF-I and IGFBP-1 concentrations were determined in serum by in-house radio-immuno-assays. IGF-I levels were age-standardized (IGF-SD). A logistic regression model was used to investigate the association of IGF-SD and IGFBP-1 with advanced fibrosis (stage 3-4).

RESULTS

Patients with advanced fibrosis (stage 3-4 vs. 0-2) had lower IGF-SD (-1.17 vs. 0.11, p = .01) and higher mean levels of IGFBP-1 (29.9 vs. 18.8 µg/l, p = .02). IGFBP-1 was associated with presence of advanced fibrosis (OR 1.04 per unit increase, 95%CI 1.0-1.07, p = .05), while IGF-1 was negatively associated with advanced fibrosis (OR 0.63 per standard deviation, 95%CI 0.44-0.92, p = .02).

CONCLUSIONS

This pilot study suggests an association between serum IGFBP-1 and IGF-I levels with advanced fibrosis in NAFLD patients. IGFBP1 and IGF-1 could be of interest as future biomarkers. Similar studies in larger cohorts are needed.

Induced secretion of insulin-like growth factor binding protein-1 (IGFBP-1) in human hepatoma cell HepG2 by rubratoxin B

The induction of insulin-like growth factor binding protein-1 (IGFBP-1) secretion by rubratoxin B was investigated using human hepatoma cell line HepG2; we also documented the involvement of stress-activated MAP kinases [c-Jun-N-terminal kinases (JNKs) and p38s] in this process. Rubratoxin B dramatically enhanced IGFBP-1 secretion, which peaked at a concentration of 40 microg/ml. The amount of IGFBP-1 mRNA increased with time and plateaued at 6 h. Compared with the amounts of IGFBP-1 secreted, the induction ratios of transcription were much smaller, indicating that IGFBP-1 secretion is regulated chiefly post-transcriptionally. The result of concomitant treatment with rubratoxin B and JNK inhibitor indicated that JNKs do not affect rubratoxin B-induced IGFBP-1 secretion. Alternatively, rubratoxin B-associated induction of IGFBP-1 secretion was marked in the absence of p38 inhibitor but attenuated in its presence. Therefore, p38s appear to stimulate rubratoxin B-induced IGFBP-1 secretion. Treatment with p38 inhibitor slightly increased the amount of rubratoxin B-induced IGFBP-1 mRNA. However this induction ratio was smaller than that of rubratoxin B-induced secretion, suggesting that p38s regulate IGFBP-1 secretion both transcriptionally and post-transcriptionally. In this study, we showed that rubratoxin B induces IGFBP-1 levels in HepG2 cells and p38s contribute to this process.

Elevated insulin, proinsulin and insulin-like growth factor-binding protein-1 in liver disease

Insulin-like growth factor-binding protein-1 (IGFBP-1) is one of six soluble binding proteins that regulate the actions of the insulin-like growth factors (IGFs). Liver is the major source of IGFBP-1 in non-pregnant humans. In normal physiology, IGFBP-1 transcription is potently inhibited by insulin and serum levels are limited by a rapid clearance rate. Elevated levels of IGFBP-1 in liver disease have been attributed to insulin resistance; however, the relationships between these analytes have not been defined. We studied insulin, proinsulin and IGFBP-1 in normal subjects (NL, N=47, 43+/-12 yr), cirrhosis (CIR, N=29, 54+/-14 yr), hepatocellular carcinoma (HCC, N=42, 61+/-11 yr), and other liver tumors (TUM, N=8, 60+/-17 yr). All three analytes were significantly increased in liver disease (mean+/-SEM; p-values relative to normals): IGFBP-1 (NL 24+/-4 ng/ml; CIR 235+/-53, p<0.0001; HCC 505+/-105, p<0.0001; TUM 118+/-36, p<0.0001), insulin (NL 72+/-4 pM; CIR 261+/-62, p<0.0002; HCC 180+/-25, p<0.0001; TUM 189+/-58, p<0.0001), proinsulin (NL 6.5+/-0.7 pM; CIR 36.8+/-7.7, p<0.0001; HCC 26.2+/-3.8, p<0.0001; TUM 32.1+/-9.7, p<0.0001). The ratio of proinsulin to insulin was also significantly elevated in liver disease. A typical curvilinear inverse relationship of insulin and IGFBP-1 was observed, but was shifted several fold higher for the liver disease groups. Our results demonstrate that insulin and proinsulin are elevated in liver disease. However, these elevations are paradoxically accompanied by elevated IGFBP-1 levels, indicating disruption of normal regulatory mechanisms. IGFBP-1 is postulated to play a dynamic role in metabolic substrate utilization via regulation of free IGF. Therefore, inappropriate elevation of IGFBP-1 could play an important role in the metabolic disturbances associated with liver disease.

GH/IGF system, cirrhosis and liver transplantation

The GH-related effects are primarily mediated by insulin-like growth factor I (IGF-I), a peptide hormone almost completely produced by the liver. Liver cirrhosis is usually accompanied by a fall in protein turnover. Furthermore, an important consequence of chronic liver disease (CLD) is growth hormone/insulin-like growth factor (GH/IGF) axis modification and growth failure. Nutritional status also suffers in this condition, and IGF-I has been proposed as a marker of hepatocellular dysfunction, malnutrition and survival. CLD is characterised by alterations of various clinical biochemistry laboratory parameters. Aminotransferases, bilirubin, plasma proteins, together with prothrombin time and gamma globulins, are usually examined for laboratory diagnostic and/or monitoring purposes. These traditional parameters are also used in the perioperative liver transplantation, but an early signal of graft functioning has still not been established. The aim of the present work is a review of the possibility offered by the clinical biochemistry laboratory GH/IGF investigation in the outcome of liver transplantation.

Alcohol intake and late-stage promotion of breast cancer

Breast cancer risk in women rises with increasing alcohol intake and is widely assumed to be mediated by increased oestrogen concentrations. However, observations that mechanisms and risk are likely to differ between pre- and postmenopausal women suggest that the postmenopausal disease in particular, may involve a promoting role for concomitants of hyperinsulinaemia which is commonly associated with alcoholic cirrhosis of the liver. The MEDLINE database and ongoing studies were examined for clinical, epidemiological and laboratory data on; (a) alcohol-related increase in the incidence of breast cancer in relation to menopausal status, oestrogen concentrations and the oestrogen receptor (ER) status of the tumour; (b) activation of insulin-like growth factor 1 receptor (IGF1R) in mammary tissue by alcohol-related hyperinsulinaemia; (c) interaction between ER and IGF1R in breast cancer cell systems. Epidemiological association between alcohol intake and increased breast cancer risk is more clearly seen in postmenopausal than premenopausal women, and a significant risk is associated with intake of more than two drinks (over 30 g) daily over a period of years. Alcohol-related hyperinsulinaemia is reported to increase with increasing degrees of cirrhosis and damage to liver function. Laboratory evidence suggests that hyperinsulinaemia can stimulate expression of IGF1R in mammary tissue, and this protein is likely to have a crucial role in mitogenesis and transformation to an oestrogen-independent malignant phenotype. It is postulated that in women with a history of long-term intake of moderate quantities of alcohol, the concomitants of hyperinsulinaemia may help to stimulate progression in precancerous breast lesions in the years leading up to the menopause and may increase the risk of breast cancer manifesting after the menopause.

Biliary cirrhosis induces type IIx/b fiber atrophy in rat diaphragm and skeletal muscle, and decreases IGF-I mRNA in the liver but not in muscle

BACKGROUND/AIMS

Patients with cirrhosis complain of fatigue, which in part may be due to the progressive muscle atrophy, noted especially when signs of decompensation appear. In addition, weaning from mechanical ventilation may be difficult in some patients following liver transplantation. Since little is known about the peripheral muscles and the diaphragm in cirrhosis, we investigated diaphragm and gastrocnemius histochemical properties, and diaphragm contractile properties in male rats with biliary cirrhosis. In addition, the extent to which insulin-like growth factor I (IGF-I) was involved in the regulation of muscle function was also examined, since IGF-I is known to induce growth and regeneration as well as to exert a protein anabolic action.

METHODS

Ten rats underwent a sham operation, while another ten underwent bile duct ligation and excision. After 5 weeks, biliary cirrhosis was confirmed histologically in random liver biopsies.

RESULTS

Compared to sham animals, diaphragm mass in cirrhotic rats was decreased by 10% (p<0.05), while masses of other respiratory (e.g. scalenus medius -21%, p<0.001) or peripheral muscles (e.g. gastrocnemius -24%, p<0.0001) decreased more. No changes in diaphragm force nor in its endurance were observed between the two groups. However, a clear decrease in the cross-sectional area of type IIx/b muscle fiber was present in both diaphragm (1360+/-147 vs 1112+/-167 microm2, p<0.02) and gastrocnemius (1954+/-265 vs 2328+/-245 microm2, p<0.02). Finally, hybridization of Northern blot with a rat cDNA IGF-I probe (gift from Dr D. Leroith, Bethesda, USA) labeled with alpha-32P revealed that in cirrhotic rats, the relative expression of IGF-I was markedly reduced by 45% in the liver (p<0.05) but was unchanged in the two muscles studied.

CONCLUSIONS

In this model of biliary cirrhosis: (i) muscle wasting was less pronounced in the diaphragm than in other muscles; (ii) type IIx/b fiber atrophy in respiratory (diaphragm) and peripheral muscles (gastrocnemius) developed while diaphragm contractile properties remained unchanged; and (iii) the relative expression of IGF-I was reduced in the liver only, while it remained unchanged in the muscle. The functional significance of these changes, their pathogenesis and presence in other models and in human cirrhosis remain to be elucidated.

Serum insulin-like growth factors and their binding proteins in patients with hepatic failure and after liver transplantation

The liver is the major source of circulating insulin-like growth factor-I and -II (IGF-I and IGF-II) and several of their binding proteins (BPs). This study examined the effects of end-stage liver disease (ESLD) and subsequent liver transplantation (LT) on serum levels of these growth factors and their BPs in four children and six adults for up to 2 years. Serum IGF-I and IGF-II were quantified by radioimmunoassay (RIA), IGFBP-3 by immunoradiometric assay (IRMA), and changes in IGFBP-1, -2, -3, and -4 were estimated by Western ligand blotting (WLB). In severe hepatic disease, serum concentrations of IGF-I (10 +/- 5 ng/mL) and IGF-II (126 +/- 32 ng/mL) were significantly (P < .01) less than in normal controls (170 +/- 37 and 590 +/- 41 ng/mL, respectively). One year following LT, the mean levels of IGF-I (344 +/- 55 ng/mL) and IGF-II (627 +/- 38 ng/mL) were within normal limits and remained so for the duration of the study. Patients exhibited considerable variation not only in the rate of achieving normal IGF-I and IGF-II concentrations, but also in the ultimate height and stability of these peptide levels. Serum IGFBP-3 in hepatic failure (580 +/- 140 ng/mL) was significantly (P < .05) lower than in controls (2,900 +/- 220 ng/mL) and increased to normal levels (3,650 +/- 360 ng/mL) 2 to 14 weeks after LT. Serum levels of IGFBP-1, -2, and -4 before and after LT were variable but usually remained within normal limits compared with control sera. The decreases observed in IGF-I, IGF-II, and IGFBP-3 in patients with hepatic failure and their subsequent restoration after LT probably result primarily from the reduced number of functional hepatocytes in ESLD and their subsequent replacement by healthy hepatic tissue. These changes may also result from hormonal alterations and nutritional deficiencies known to exist in patients with severe liver dysfunction, which are corrected by LT. We conclude that LT in patients with severe hepatic insufficiency enhances the potential for normal cell growth and replication by restoring serum IGF-I, IGF-II, and IGFBP-3 concentrations to normal concomitantly with the improvement in hormonal and nutritional status.

Characterization and regulation of insulin-like growth factor binding proteins in human hepatic stellate cells

Cultured hepatic stellate cells (HSCs), the cell type primarily involved in the progression of liver fibrosis, secrete insulin-like growth factor-I (IGF-I) and IGF binding protein (IGFBP) activity. IGF-I exerts a mitogenic effect on HSCs, thus potentially contributing to the fibrogenic process in an autocrine fashion. However, IGF-I action is modulated by the presence of specific IGFBPs that may inhibit and/or enhance its biologic effects. Therefore, we examined IGFBP-1 through IGFBP-6 mRNA and protein expression in HSCs isolated from human liver and activated in culture. Regulation of IGFBPs in response to IGF-I and other polypeptide growth factors involved in the hepatic fibrogenic process was also assessed. RNase protection assays and ligand blot analysis demonstrated that HSCs express IGFBP-2 through IGFBP-6 mRNAs and release detectable levels of IGFBP-2 through IGFBP-5. Because IGF-I, platelet-derived growth factor-BB (PDGF-BB), and transforming growth factor-beta (TGF-beta) stimulate HSC proliferation and/or matrix production, we tested their effect on IGFBPs released by HSCs. IGF-I induced IGFBP-3 and IGFBP-5 proteins in a time-dependent manner without an increase in the corresponding mRNAs. IGFBP-4 protein levels decreased in response to IGF-I. TGF-beta stimulated IGFBP-3 mRNA and protein but decreased IGFBP-5 mRNA and protein. In contrast, PDGF-BB failed to regulate IGFBPs compared with controls. Recombinant human IGFBP-3 (rhIGFBP-3) was then tested for its effect on IGF-I-induced mitogenesis in HSCs. rhIGFBP-3 inhibited IGF-I-stimulated DNA synthesis in a dose-dependent manner, with a peak effect observed at 25 nM IGFBP-3. Because TGF-beta is highly expressed in cirrhotic liver tissue, we determined whether IGFBP-3 mRNA expression is increased in liver biopsies obtained from patients with an active fibroproliferative response due to viral-induced chronic active hepatitis. In the majority of these samples, IGFBP-3 mRNA was increased compared with normal controls. These findings indicate that human HSCs, in their activated phenotype, constitutively produce IGFBPs. IGF-I and TGF-beta differentially regulate IGFBP-3, IGFBP-4, and IGFBP-5 expression, which, in turn, may modulate the in vitro and in vivo action of IGF-I.

Critical illness is associated with low circulating concentrations of insulin-like growth factors-I and -II, alterations in insulin-like growth factor binding proteins, and induction of an insulin-like growth factor binding protein 3 protease

OBJECTIVES

To describe the sequential changes in the circulating concentrations of insulin-like growth factor-I, insulin-like growth factor-II, and insulin-like growth factor binding proteins in critically ill patients. To determine whether critical illness is associated with induction of a specific protease directed against insulin-like growth factor binding protein 3 and to relate these changes to outcome.

DESIGN

Prospective, descriptive study.

SETTING

Intensive care unit (ICU) of a university hospital.

PATIENTS

Eighteen heterogeneous critically ill patients, requiring ventilatory support.

INTERVENTIONS

Serial daily blood samples were collected until death or discharge from the ICU. In five patients, samples were also obtained on the ward before discharge from the hospital.

MEASUREMENTS AND MAIN RESULTS

Serum concentrations of insulin-like growth factor-I, insulin-like growth factor-II, and insulin-like growth factor binding proteins 1, 2, and 3 were measured by radioimmunoassay. After 5 days, insulin-like growth factor binding protein 3 concentrations were measured on alternate days. Alterations in binding of insulin-like growth factor-I to insulin-like growth factor binding protein 3 and the presence of protease activity directed against insulin-like growth factor binding protein 3 were investigated by Western ligand blotting. Circulating concentrations of insulin-like growth factor-I and insulin-like growth factor-II were low and remained low throughout the 7-day study period. Insulin-like growth factor binding protein 1 concentrations were initially increased to within the fasting range, but subsequently decreased. There was considerable variability in insulin-like growth factor binding protein 2 concentrations, but generally, concentrations were at the upper end of the normal range throughout. Insulin-like growth factor binding protein 3 concentrations were consistently low and Western ligand blotting at the nadir of the insulin-like growth factor-I concentration demonstrated the presence of a protease directed against insulin-like growth factor binding protein 3. The last recorded concentrations of insulin-like growth factor-I and insulin-like growth factor binding protein 3 were higher in survivors than in nonsurvivors (p < .05). Two patients were also studied for a prolonged period. In one patient, a survivor, insulin-like growth factor-I and insulin-like growth factor binding protein 3 were low initially, but later increased in association with recovery and cessation of protease activity over a period of 33 days. In another patient, a nonsurvivor, insulin-like growth factor-I and insulin-like growth factor binding protein 3 remained low and protease activity persisted until the patient died 38 days after admission to the ICU.

CONCLUSIONS

Critical illness is associated with low circulating concentrations of insulin-like growth factor-I, insulin-like growth factor-II, and insulin-like growth factor binding protein 3 and these low values are associated with induction of protease activity specifically directed against insulin-like growth factor binding protein 3. In survivors, recovery is associated with increasing insulin-like growth factor-I and insulin-like growth factor binding protein 3 concentrations and cessation of protease activity. The therapeutic effects of exogenous growth factors are likely to be influenced by these changes.

Insulin-like growth factor bioactivity and its modification in growth hormone resistant states

Acquired growth hormone (GH) resistance is an increasingly recognized feature of catabolic states. Low circulating levels of the insulin-like growth factors (IGF-I and II) have been shown to be associated with changes in the IGF binding proteins (IGFBP-1 to -6) that may significantly impact on IGF bioactivity. IGFBP-3 binds IGF and a third glycoprotein, the acid labile subunit (ALS), to form a stable 150 kDa ternary complex that serves as an intravascular store for IGFs and prolongs IGF half-life. IGFBP-1 is present at much lower concentration in serum but levels fluctuate acutely, suggesting regulation of IGF bioactivity in response to short-term metabolic changes. The function of IGFBP-2 remains unclear, but studies suggest that this protein may act as an alternative carrier for IGF when IGFBP-3 levels are low. Multiple regulatory influences on circulating IGFBP levels have been identified but three appear prominent. Nutritional influences, in particular substrate availability, appear to be a central regulatory influence on IGFBP levels in catabolic states. Low substrate availability increases IGFBP-1 levels acutely and decreases IGFBP-3 and IGFBP-2 levels in the intermediate term, with each of these changes likely to further limit IGF bioactivity. End organ failure, particularly of liver and kidney significantly affects production and clearance rates of the circulating IGFBPs and may contribute to the catabolism frequently seen in these states. Severe protein catabolism often accompanies malignancy and chronic sepsis and it is likely that additional ill-defined factors influence IGF bioactivity in this setting. Recent studies have identified post-translational modifications to the IGFBPs such as proteolysis and phosphorylation, which appear to further impact on IGF bioactivity. The relative contributions of these changes to the overall impairment of IGF bioactivity in GH-resistant states remains to be fully elucidated.