The insulin-like growth factor system in kidney diseases

Plasma levels of Th1/Th2 Type Cytokine are Associated with Change of Prolactin and GH/IGF-I in Hemodialysis Patients

Patients undergoing chronic hemodialysis (HD) have an impaired immune system involving both B and T cell-mediated immune responses. Since T helper type 1 (Th1) and type 2 (Th2) cytokines are implicated in regulating the immune responses, while the pituitary hormones, prolactin (PRL) and growth hormone (GH) are known to be involved in the regulation of the immune response, all of them may, therefore, be involved in impaired status. The aims of the present study were to estimate the serum concentrations of Th1-Th2 cytokine, GH, insulin-like growth factor-I (IGF-I) and PRL, and to determine whether there are any correlations between the release of T-cell cytokines and disturbance of hormones in a group of patients on maintenance hemodialysis (MHD). The study included 35 HD patients (23 males and 12 females, mean age 56.8±12.8 years) and a control group of 20 age-matched healthy subjects. Baseline serum concentrations of GH/IGF-I, PRL, IL-2, sIL-2R, IFN-γ, IL-4 and IL-10 were measured in all patients and control subjects. Our results demonstrate that the fasting serum concentration of IGF-I, PRL, sIL-2R and Th1-type cytokine, including IL-2 and IFN-γ, were significantly higher in HD patients compared to the healthy subjects. GH and Th2-type cytokine including IL-4 and IL-10 levels were slightly reduced, but no significant differences were observed between HD patients and the control group. In the group of HD patients, PRL correlated directly with IFN-γ and correlated inversely with IL-10; IFN-γ correlated inversely with IL-4; and GH also correlated inversely with IGF-I and IL-4. However, IGF-I correlated directly with IL-2 and IL-10. These data suggest that the Th1/Th2 imbalance in HD patients with an increase of Th1 type cytokines, associated with the altered GH/IGF-I axis and prolactin and immuno-endocrine dysfunction, probably plays a role in an impaired immune system in HD patients.

Urinary excretion of IGFBP-1 and -3 correlates with disease activity and differentiates focal segmental glomerulosclerosis and minimal change disease

The glomerular microenvironment is influenced by circulating growth factors that are filtered from the blood stream and pass the glomerular filtration barrier. In this study, we wanted to explore the role of IGF-binding proteins (IGFBPs) in two diseases that concern podocytes. We analyzed glomerular expression and urinary excretion of IGFBP-1, -2, and -3 in patients with focal segmental glomerulosclerosis (FSGS) or minimal change disease (MCD). We found that patients with active FSGS excrete high amounts of podocalyxin positive cells as well as IGFBP-1 and -3. In human podocytes, we can induce mRNA expression of IGFBP-3 in response to TGF-beta and in human microvascular endothelial cells expression of IGFBP-1 and -3 in response to TGF-beta and Bradykinin. We conclude that the local expression of IGFBPs in podocytes and endothelial cells might contribute to the pathogenesis of glomerular disease and that IGFBP-1 and -3 are potential non-invasive markers of FSGS.

Plasma levels of insulin-like growth factor-I, insulin-like growth factor binding protein-1, coenzyme Q10 and vitamin E in female populations from Poland, Serbia and Sweden

Exposure to environmental contaminants such as polycyclic aromatic hydrocarbons (PAHs), life style and nutritional status of a population are important factors that may influence normal serum levels of antioxidants and the insulin-like growth factor system. In this study we examined serum levels of insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-1(IGFBP-1), coenzyme Q10 (CoQ) and vitamin E in healthy female populations (n=4 x 100) aged 19-59 years from Poland (PL), Sweden (SE), Serbia I (SR I) and Serbia II (SR II). The last group lived in an environmental emergency area affected by the bombings of 1999 in Serbia. The Polish and SR I cohorts exhibited low IGFSD-score levels, (-2 to +/-0), compared to females from SE with IGFSD-score 0. In the SR II population, the IGFSD range was between -1 and 1. The IGFBP-1 levels of the Polish and SR I groups were lower than in the Swedish population, while the SR II levels showed a broader distribution, 20-80 microg/l. The CoQ values in the Swedish and Polish samples were around 1 nmol/ml. In contrast, the SR I cohorts exhibited higher concentrations, 1.5-3.5 nmol/ml and the SR II group had extremely low levels, <0.5 nmol/ml. The vitamin E concentrations were similar in the Polish and Swedish populations, 20-40 nmol/ml, while it was twice as high, 40-80 nmol/ml in the SR I and very low in the SR II group, which is half of the Polish and Swedish cohorts. These results suggest that different lifestyles and environmental factors affect both the IGF system and the antioxidants CoQ10 and vitamin E in female populations in Europe. The females living in the polluted area had different patterns of both the IGF and antioxidant systems. These findings may explain differences in morbidity and mortality in these countries.

DOK4/IRS-5 expression is altered in clear cell renal cell carcinoma

The insulin-receptor substrate family plays important roles in cellular growth, signaling, and survival. We have previously shown the dysregulation of the IGF-axis in clear cell renal cell carcinoma. In this manuscript, we examine the expression of the insulin receptor substrate family in clear cell RCC, and demonstrate that the expression of 2 members of this family are significantly altered in tumors. The most striking finding is that expression of the new IRS family member IRS-5 is significantly upregulated in 90% of examined clear cell RCCs. Studies on this gene has shown that it is regulated through chromatin remodeling in kidney cells.

Gene expression profiling in the remnant kidney model of wild type and kinin B1 and B2 receptor knockout mice

Angiotensin-converting enzyme inhibitors are the most efficient pharmacologic agents to delay the development of end-stage renal disease (ESRD). This is a multipharmacologic approach that inhibits angiotensin II formation while increasing kinin concentrations. Considerable attention has been focused on the role of decreased angiotensin II levels; however, the role of increased kinin levels is gaining in interest. Kinins affect cellular physiology by interacting with one of two receptors being the more inducible B1 and the more constitutive B2 receptors. This study utilizes the mouse remnant kidney of 20 weeks duration as a model of ESRD. Whole mouse genome microarrays were used to evaluate gene expression in the remnant kidneys of wild type, B1 and B2 receptor knockout animals. The microarray data indicate that gene families involved in vascular damage, inflammation, fibrosis, and proteinuria were upregulated, whereas gene families involved in cell growth, metabolism, lipid, and protein biosynthesis were downregulated in the remnant kidneys. Interestingly, the microarray analyses coupled to histological evaluations are suggestive of a possible protective role of kinins operating through the B2 receptor subtype in this model of renal disease. The results highlight the potential of microarray technology for unraveling complex mechanisms contributing to chronic renal failure.

NT-proBNP, IGF-I and survival in patients with chronic heart failure

OBJECTIVE

Growth hormone (GH) resistance with a reduction of insulin-like growth factor-I (IGF-I) serum concentrations seems to be implicated in the catabolic process associated with chronic heart failure (CHF). However, data concerning the prognostic value of these alterations in CHF patients without cachexia are scant. In this study, we aimed to determine in CHF patients the prognostic value of IGF-I/GH ratio and its relationships with N-terminal brain natriuretic peptide (NT-proBNP), a known marker of prognosis in these patients.

DESIGN

We enrolled 82 non-cachectic patients, mean age 61+/-13 years, with ejection fraction <40% and predischarge New York Heart Association (NYHA) functional classes II-IV. All patients underwent clinical examination, two-dimensional echocardiography and NT-proBNP, GH and IGF-I measurement with log IGF-I/GH ratio calculation. Mortality and clinical status was documented at follow-up (18.4+/-8.1 months).

RESULTS

During follow-up 17 patients died of cardiac causes. Non-survivors were at baseline in higher NYHA class (P<0.05) and showed higher values of NT-proBNP (P<0.001) than survivors; differently IGF-I, and log IGF-I/GH ratio were lower (P<0.05). At Cox multivariate analysis, NT-proBNP (P<0.001) and IGF-I/GH ratio (P<0.05) were independent predictors of death.

CONCLUSIONS

High NT-proBNP levels and low IGH-I/GH ratio may be useful to stratify CHF patients at higher risk of cardiac death.

Expression of insulin-like growth factors systems in cloned cattle dead within hours after birth

Cloning by somatic nuclear transfer is an inefficient process in which many of the cloned animals die shortly after birth and display organ abnormalities. In an effort to determine the possible roles IGFs played in neonatal death and organ abnormalities, we have examined expression patterns of eight genes in insulin-like growth factor (IGF) systems (IGF1, IGF2, IGF1R, IGF2R, IGFBP-1, IGFBP-2, IGFBP-3, and IGFBP-4) in six organs (heart, liver, spleen, lung, kidney, and brain) of both neonatal death cloned bovines (n = 9) and normal control calves (n = 3) produced by artificial insemination (AI) using real-time quantitative RT-PCR. The effect of the age of the fibroblast donor cell on the gene expression profiles was also investigated. Aberrant expressions of six genes (IGF2, IGF1R, IGF2R, IGFBP-2, IGFBP-3, and IGFBP-4) were found in some studied tissues, but the expression of two genes (IGF1 and IGFBP-1) had similar levels with the normal controls. For the studied genes, kidney was the organ that was most affected (five genes) by gene downregulation, whereas spleen was the organ that was not affected. The two upregulation genes were in brain, but both of downregulation and upregulation were found in the heart, liver, and lung. The expression of three genes (IGF2R, IGFBP-4, and IGF2) in some tissues showed significant differences between AF cell-derived and FF cell-derived clones. Our results suggest that aberrations in gene expression within IGF systems were found in most cloned bovine tissues of neonatal death. Because IGF systems play an important role in embryo development and organogenesis, the aberrant transcription patterns detected in these clones may contribute to the defects of organs reported in neonatal death of clones.

The IGF-I system and the renal and haemodynamic effects of losartan in normotensive patients with type 2 diabetes mellitus: a randomized clinical trial

OBJECTIVE

Losartan has been shown to protect the diabetic kidney, at least partly independent of changes in blood pressure. Imbalances in the IGF-I system are associated with the development of diabetic nephropathy. We investigated whether renal as well as haemodynamic effects of losartan are associated with changes in the IGF-I system in normotensive patients with type 2 diabetes mellitus (T2DM).

DESIGN AND PATIENTS

This randomized, double-blind placebo-controlled clinical trial involved 74 normotensive patients with T2DM and microalbuminuria. Thirty-eight patients were assigned to receive losartan and 36 patients were assigned to receive placebo for 10 weeks.

MEASUREMENTS

Serum levels of total and free IGF-I, IGFBP-3, creatinine and haemoglobin A(1c) (HbA(1c)), as well as urinary albumin excretion rate, creatinine clearance and blood pressure, were measured prior to the start of treatment and after 10 weeks of treatment.

RESULTS

At baseline, serum levels of IGFBP-3 were elevated and serum levels of free IGF-I were reduced. Losartan tended to reduce IGFBP-3 levels and to increase free IGF-I levels, although neither effect was statistically significant. These effects were more pronounced in a subanalysis of 18 losartan-treated patients with stable metabolic parameters, with a decrease in IGFBP-3 from 133.2 to 122.6 nmol/l (P=0.006) and an increase in free IGF-I levels by 8% (ns). Serum levels of total IGF-I were unaffected. The change in IGFBP-3 was inversely correlated to the change in creatinine clearance (r=-0.4; P=0.02). Total and free IGF-I inversely correlated to systolic blood pressure (r= -0.46; P=0.007 and r=0.26; P=0.14 respectively). Furthermore, changes in total IGF-I and IGFBP-3 correlated to changes in serum creatinine levels in the metabolically stable patients (r=0.58, P=0.02 and r=0.6, P=0.01, respectively). Changes in the IGF-I system were unrelated to a reduction in microalbuminuria associated with losartan.

CONCLUSIONS

Losartan lowered the elevated levels of IGFBP-3, although only significantly in the metabolically stable patients. A tendency towards an increase in free IGF-I levels was also observed, but this change was small and not statistically significant. These changes were not related to reduction in microalbuminuria, but might contribute to effects of losartan on creatinine clearance and blood pressure of losartan in normotensive patients with T2DM.

Characterization of an animal model of spontaneous congenital unilateral obstructive uropathy by cDNA microarray analysis

INTRODUCTION

The pathophysiology of congenital obstructive uropathy has been studied intensively in several animal models. A reliable parameter for early detection of relevant obstruction is not yet identified. For further investigation of the complex regulatory events of obstructive uropathy, we used a cDNA microarray technology for a parallel differential expression analysis of about 15000 different genes of obstructed, contralateral and healthy kidneys of rats with spontaneous congenital obstructive uropathy.

METHODS

Total cellular RNA of obstructed, contralateral and healthy control kidneys of 32-35 days old rats was extracted and pooled. RNA quality and quantity was assessed using a Bioanalyzer 2100. mRNA expression for selected marker genes was assessed by real time PCR. High throughput gene expression profiling was performed with cDNA microarrays with differentially labeled cDNA targets.

RESULTS

Beside expected typical alterations of several growth factors such as TGF-beta, EGF, IGF-1, PDGF, we observed overexpression of extracellular matrix proteins and a decreased activity of antioxidant enzymes. Additionally, NFkappaB, a nuclear transcription factor involved in the development of interstitial fibrosis, was slightly up-regulated in the obstructed kidneys. Down-regulation of genes involved in tubular sodium transport indicated impaired concentration ability of the obstructed kidneys. Furthermore, we found up-regulation of pro-apoptotic genes including transcripts for the proapoptotic protein Siva. Interestingly, TNFalpha, another factor involved in the pathophysiology of congenital obstructive uropathy, was not differentially regulated.

CONCLUSIONS

The alterations of the genes for growth factors, extracellular matrix proteins, antioxidant enzymes, sodium transport and genes involved in apoptosis support the representative character of this animal model for congenital obstructive uropathy. In the rather advanced stage of congenital renal obstruction a possible explanation of the lacking differential regulation of TNFalpha highlights it as a possible marker of earlier stages of obstruction. Furthermore, the possible involvement of the Siva/CD27 pathway in the apoptotic cascade also offers a new possibility to find a sensitive marker to detect renal obstruction already in an earlier stage.

Growth hormone, IGF-I and its binding proteins (IGFBP-1 and -3) in adult uraemic patients undergoing peritoneal dialysis and haemodialysis

OBJECTIVE

The GH/IGF axis is altered in chronic renal failure (CRF). CRF patients usually show normal or high serum concentrations of GH and IGF-I, whereas all IGF binding proteins (IGFBP-1 to -6), except IGFBP-5, considerably increase with declining renal function. The aims of the present study were to quantify serum concentrations of GH, IGF-I, IGFBP-1 and IGFBP-3 in a group of patients with CRF, and determine whether there were differences according to the type of dialysis, that is, peritoneal dialysis (PD) and haemodialysis (HD).

DESIGN

A cross-sectional study in the setting of a dialysis unit of a general hospital.

PATIENTS AND MEASUREMENTS

We studied 108 dialysis patients treated by PD (n = 54, 32 males and 22 females, mean age 61.0 +/- 1.4 years) or HD (n = 54, 31 males and 23 females, age 62.6 +/- 1.5 years). A group of 42 healthy subjects of similar age, sex and body mass index (BMI) served as the control group. Baseline serum concentrations of GH, insulin, IGF-I, IGFBP-1 and IGFBP-3 were measured in all patients and control subjects.

RESULTS

Fasting serum concentrations of IGF-I and its binding proteins (IGFBP-1 and IGFBP-3) were significantly higher in dialysis patients than in subjects with normal renal function. IGF-I (248.9 +/- 23.4 vs. 205.5 +/- 15.5 micro g/l, NS), IGFBP-3 (5.6 +/- 0.4 vs. 5.5 +/- 0.2 mg/l, NS) and IGFBP-1 (36.1 +/- 5.9 vs. 44.1 +/- 6.5 micro g/l, NS) concentrations were similar in both groups of dialysis (PD vs. HD) patients. However, GH (2.3 +/- 0.3 vs. 1.1 +/- 0.1 micro g/l, P < 0.001) and insulin (40.4 +/- 4.5 vs. 30.1 +/- 3.1 micro U/ml, P < 0.05) levels were significantly higher in the PD group than in the HD group. Both groups of dialysis patients showed significantly higher levels of insulin than healthy subjects (14.7 +/- 1.9 micro U/ml, P < 0.0001 and P < 0.01 for PD and HD, respectively). In both groups of dialysis patients, IGF-I correlated inversely with IGFBP-1 (PD group r = -0.46, P = 0.0006; HD group r = -0.57, P = 0.0001) and directly with IGFBP-3 (PD group r = 0.44, P = 0.001; HD group r = 0.73, P = 0.001). No correlation between insulin and IGFBP-1 was found in any of the groups studied.

CONCLUSIONS

These findings demonstrate that adult dialysis patients have elevated IGF-I, IGFBP-1 and IGFBP-3 serum concentrations compared with subjects with normal renal function. Only GH and insulin show statistically significant differences in relation to type of dialysis. Finally, the negative correlation between IGF-I and IGFBP-1 and the positive correlation between IGF-I and IGFBP-3 are maintained in both groups of adult dialysis patients.

IGF-I system responses during 12 weeks of resistance training in end-stage renal disease patients

OBJECTIVE

To examine the hypothesis that 12 weeks of resistance training would alter circulating concentrations of IGF-I system components in end-stage renal disease (ESRD) patients.

DESIGN

Ten ESRD patients underwent 12 weeks of resistance training after a 6 week control period and had morning fasted blood drawn on four occasions (weeks - 6, 0, 6, 12). Immunoassays were performed for serum total and free IGF-I, IGF binding proteins (IGFBPs) 2 and 3, and the acid labile subunit (ALS). Immunoaffinity depletion of ALS-based complexes allowed measurement of non-ternary (i.e., binary) IGF-I and IGFBP-3.

RESULTS

Significant improvements in strength and functional performance were observed. All IGF-I measures were stable during the control period and no changes were observed for the first 6 weeks of resistance training. At week 12, total IGF-I (-15.4+/-28.9%), ternary IGF-I (-16.4+/-36.7%), and the IGF-I/IGFBP-3 ratio had significantly (p < or = 0.05) declined from week 0 values. No changes were observed for free IGF-I, IGFBPs 2 and 3, or the acid labile subunit. The proportion of IGF-I in ternary ( approximately 76.3+/-6.8%), non-ternary ( approximately 22.5+/-6.6%), and free ( approximately 1.2+/-0.5%) forms remained constant throughout the training.

CONCLUSIONS

12 weeks of resistance training in ESRD patients induced a decline in total IGF-I, but did not alter the proportion of IGF-I circulating in free, ternary or non-ternary molecular complexes. The decline in IGF-I occurs in the presence of positive training adaptations on physical performance and we conclude that this response pattern appears to be reflective of favorable neuromuscular anabolic adaptations.

A method to improve selection of molecular targets by circumventing the ADME pharmacokinetic system utilizing PharmArray DNA microarrays

DNA microarrays may be used to identify potential molecular targets for drug discovery. Yet, DNA microarray experiments provide massive amounts of data. To limit the choice of potential molecular targets, it may be desirable to eliminate genes coincidentally up-regulated in tissues implicated in absorption, distribution, metabolism, and excretion (ADME) pharmacokinetics. DNA microarray experiments were performed to demonstrate a gene-exclusion approach using as an example RNA samples of neural origin, i.e., a human neuroblastoma cell line (SK-N-SH) and brain tissue, as the intended hypothetical site(s) of drug action. Biomarkers were identified using PharmArray DNA microarrays. The lists of neuroblastoma and neural biomarkers were constrained by limiting selection to the subset of genes that were not highly expressed in three transformed cell lines from liver, colon, and kidney (HepG2, Caco-2, and 786-O, respectively) that are routinely used as representatives of the ADME system during in vitro pharmacology and toxicology experiments. Principal component analysis methods with likelihood ratio-related bioinformatic tools were utilized to identify robust potential biomarker genes for the three ADME-related cell lines, neuroblastoma, and normal brain. Biomarkers of each sample were identified and selected genes were validated by qRT-PCR. Hundreds of biomarkers of the three ADME-related cell types, representing hepatocytes, kidney epithelium, and gastrointestinal tract, may now be used as a valuable database to restrict selection of biomarkers as potential molecular targets from the intended samples (e.g., neuroblastoma in this work). In addition to biomarker discovery per se, this demonstration suggests that our model method may be viable to help restrict gene lists during selection of potential molecular targets for subsequent drug discovery.