The insulin-like growth factor system in chronic kidney disease: Pathophysiology and therapeutic opportunities

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.

Glycosylation Analysis of Urinary Peptidome Highlights IGF2 Glycopeptides in Association with CKD

Chronic kidney disease (CKD) is prevalent in 10% of world’s adult population. The role of protein glycosylation in causal mechanisms of CKD progression is largely unknown. The aim of this study was to identify urinary O-linked glycopeptides in association to CKD for better characterization of CKD molecular manifestations. Urine samples from eight CKD and two healthy subjects were analyzed by CE-MS/MS and glycopeptides were identified by a specific software followed by manual inspection of the spectra. Distribution of the identified glycopeptides and their correlation with Age, eGFR and Albuminuria were evaluated in 3810 existing datasets. In total, 17 O-linked glycopeptides from 7 different proteins were identified, derived primarily from Insulin-like growth factor-II (IGF2). Glycosylation occurred at the surface exposed IGF2 Threonine 96 position. Three glycopeptides (DVStPPTVLPDNFPRYPVGKF, DVStPPTVLPDNFPRYPVG and DVStPPTVLPDNFPRYP) exhibited positive correlation with Age. The IGF2 glycopeptide (tPPTVLPDNFPRYP) showed a strong negative association with eGFR. These results suggest that with aging and deteriorating kidney function, alterations in IGF2 proteoforms take place, which may reflect changes in mature IGF2 protein. Further experiments corroborated this hypothesis as IGF2 increased plasma levels were observed in CKD patients. Protease predictions, considering also available transcriptomics data, suggest activation of cathepsin S with CKD, meriting further investigation.

Genetic and Physiological Effects of Insulin-Like Growth Factor-1 (IGF-1) on Human Urate Homeostasis

SIGNIFICANCE STATEMENT

Hyperinsulinemia induces hyperuricemia by activating net renal urate reabsorption in the renal proximal tubule. The basolateral reabsorptive urate transporter GLUT9a appears to be the dominant target for insulin. By contrast, IGF-1 infusion reduces serum urate (SU), through mechanisms unknown. Genetic variants of IGF1R associated with reduced SU have increased IGF-1R expression and interact with genes encoding the GLUT9 and ABCG2 urate transporters, in a sex-specific fashion, which controls the SU level. Activation of IGF-1/IGF-1R signaling in Xenopus oocytes modestly activates GLUT9a and inhibits insulin's stimulatory effect on the transporter, which also activates multiple secretory urate transporters-ABCG2, ABCC4, OAT1, and OAT3. The results collectively suggest that IGF-1 reduces SU by activating secretory urate transporters and inhibiting insulin's action on GLUT9a.

BACKGROUND

Metabolic syndrome and hyperinsulinemia are associated with hyperuricemia. Insulin infusion in healthy volunteers elevates serum urate (SU) by activating net urate reabsorption in the renal proximal tubule, whereas IGF-1 infusion reduces SU by mechanisms unknown. Variation within the IGF1R gene also affects SU levels.

METHODS

Colocalization analyses of a SU genome-wide association studies signal at IGF1R and expression quantitative trait loci signals in cis using COLOC2, RT-PCR, Western blotting, and urate transport assays in transfected HEK 293T cells and in Xenopus laevis oocytes.

RESULTS

Genetic association at IGF1R with SU is stronger in women and is mediated by control of IGF1R expression. Inheritance of the urate-lowering homozygous genotype at the SLC2A9 locus is associated with a differential effect of IGF1R genotype between men and women. IGF-1, through IGF-1R, stimulated urate uptake in human renal proximal tubule epithelial cells and transfected HEK 293T cells, through activation of IRS1, PI3/Akt, MEK/ERK, and p38 MAPK; urate uptake was inhibited in the presence of uricosuric drugs, specific inhibitors of protein tyrosine kinase, PI3 kinase (PI3K), ERK, and p38 MAPK. In X. laevis oocytes expressing ten individual urate transporters, IGF-1 through endogenous IGF-1R stimulated urate transport mediated by GLUT9, OAT1, OAT3, ABCG2, and ABCC4 and inhibited insulin's stimulatory action on GLUT9a and OAT3. IGF-1 significantly activated Akt and ERK. Specific inhibitors of PI3K, ERK, and PKC significantly affected IGF-1 stimulation of urate transport in oocytes.

CONCLUSIONS

The combined results of infusion, genetics, and transport experiments suggest that IGF-1 reduces SU by activating urate secretory transporters and inhibiting insulin's action.

Mendelian randomization reveals causal effects of kidney function on various biochemical parameters

The kidney is a vital organ with diverse biological effects and the burden of kidney function impairment is increasing in modern medicine. As the effects from kidney function on diverse biochemical parameters are yet fully understood, additional investigation to reveal the causal effects is warranted. Here we show the causal estimates from kidney function parameter, estimated glomerular filtration rate (eGFR), on 60 biochemical parameters by performing two-sample Mendelian randomization (MR) study in 337,138 white British UK Biobank participants. A higher genetically predicted eGFR was significantly associated with higher lymphocyte percentage, HDL cholesterol, and alanine aminotransferase. The causal estimates indicated that a higher genetically predicted eGFR was associated with lower urea, urate, insulin growth factor-1, and triglycerides levels. The parameters with significant but non-linear causal estimates were hemoglobin concentration, calcium, vitamin D, and urine creatinine values, identified by non-linear MR. Healthcare providers should understand that changes in eGFR may affect the identified biochemical parameters in diverse patterns. Future study is warranted to expand the knowledge of the mechanisms and clinical implications of the causal effects of eGFR on various biochemical parameters.

Stage II of Chronic Kidney Disease-A Tipping Point in Disease Progression?

Chronic kidney disease (CKD) is the progressive loss of renal function. Although advances have been made in understanding the progression of CKD, key molecular events in complex pathophysiological mechanisms that mark each stage of renal failure remain largely unknown. Changes in plasma protein profiles in different disease stages are important for identification of early diagnostic markers and potential therapeutic targets. The goal of this study was to determine the molecular profile of each CKD stage (from 1 to 5), aiming to specifically point out markedly expressed or downregulated proteins. We performed a cross-sectional shotgun-proteomic study of pooled plasma across CKD stages and compared them to healthy controls. After sample pooling and heparin-column purification we analysed proteomes from healthy to CKD stage 1 through 5 participants' plasma by liquid-chromatography/mass-spectrometry. We identified 453 proteins across all study groups. Our results indicate that key events, which may later affect the course of disease progression and the overall pathophysiological background, are most pronounced in CKD stage 2, with an emphasis on inflammation, lipoprotein metabolism, angiogenesis and tissue regeneration. We hypothesize that CKD stage 2 is the tipping point in disease progression and a suitable point in disease course for the development of therapeutic solutions.

Biochemical discrepancies in the evaluation of the somatotroph axis: Elevated GH or IGF-1 levels do not always diagnose acromegaly

The most frequent diagnosis underlying the finding of an elevated growth hormone (GH) and insulin-like growth factor-1 (IGF-1) is acromegaly due to a GH-secreting pituitary tumour. However, GH and IGF-1 levels can be discordant in patients with acromegaly due to early or partially treated disease, or there might be another cause of high GH or high IGF-1 unrelated to acromegaly, such as pre-analytical and technical pitfalls, physiological circumstances and pathological conditions. High GH and normal or low serum IGF-1, or alternatively, normal GH with elevated serum IGF-1, should be carefully assessed to avoid misinterpreting the activity of acromegaly or misdiagnosing a patient with acromegaly. We summarise here these biochemical discrepancies in the evaluation of the somatotroph axis.

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02692-z.

Insulin-Like Growth Factor Binding Proteins in Kidney Disease

The seven members of the insulin-like growth factor (IGF) binding protein family (IGFBPs) were initially considered to be the regulatory proteins of IGFs in the blood circulation, mainly as the subsequent reserve for bidirectional regulation of IGF function during environmental changes. However, in recent years, IGFBPs has been found to have many functions independent of IGFs. The role of IGFBPs in regulating transcription, inducing cell migration and apoptosis is closely related to the occurrence and development of kidney disease. IGFBP-1, IGFBP-3, IGFBP-4 are closely associated with diabetes and diabetic nephropathy. IGFBP-3, IGFBP-4, IGFBP-5, IGFBP-6 are involved in different kidney disease such as diabetes, FSGS and CKD physiological process as apoptosis proteins, IGFBP-7 has been used in clinical practice as a biomarker for early diagnosis and prognosis of AKI. This review focuses on the differential expression and pathogenesis of IGFBPs in kidney disease.

Sarcopenia in Chronic Kidney Disease: A Scoping Review of Prevalence, Risk Factors, Association with Outcomes, and Treatment

Sarcopenia, a condition characterized by loss of skeletal muscle mass and function, has important clinical ramifications. We aimed to map the existing literature about prevalence, risk factors, associated adverse outcomes, and treatment of sarcopenia in individuals with chronic kidney disease (CKD). A scoping review of the literature was conducted to identify relevant articles published from databases' inception to September 2019. Individuals with CKD, regardless of their disease stage and their comorbidities, were included. Only studies with sarcopenia diagnosed using both muscle mass and function, based on published consensus definitions, were included. For studies on treatment, only randomized controlled trials with at least one sarcopenia parameter as an outcome were included. Our search yielded 1318 articles, of which 60 from were eligible for this review. The prevalence of sarcopenia ranged from 4 to 42% according to the definition used, population studied, and the disease stage. Several risk factors for sarcopenia were identified including age, male gender, low BMI, malnutrition, and high inflammatory status. Sarcopenia was found to be associated with several adverse outcomes, including disabilities, hospitalizations, and mortality. In CKD subjects, several therapeutic interventions have been assessed in randomized controlled trial with a muscle mass, strength, or function endpoint, however, studies focusing on sarcopenic CKD individuals are lacking. The key interventions in the prevention and treatment of sarcopenia in CKD seem to be aerobic and resistance exercises along with nutritional interventions. Whether these interventions are effective to treat sarcopenia and prevent clinical consequences in this population remains to be fully determined.

Association between insulin growth factor-1, bone mineral density, and frailty phenotype in children with chronic kidney disease

BACKGROUND

This cohort study investigates the association between insulin growth factor-1 (IGF-1), bone mineral density, and frailty phenotype in children with chronic kidney disease (CKD).

METHODS

Forty-six patients (median age 14.5 years) were prospectively enrolled. Frailty phenotype was defined as the presence ≥ 3 of the following indicators: suboptimal growth/weight gain (body mass index height age < 5th percentile or height < 3rd percentile or loss of ≥ 10 percentiles/year in at least one parameter), low muscle mass (lean tissue mass height age < 5th percentile or loss of ≥ 10 percentiles/year), general fatigue reported by parent or child, and C-reactive protein > 3 mg/l. Lumbar bone mineral apparent density (LBMAD) was measured by dual-energy X-ray absorptiometry, body composition by bioimpedance spectroscopy, and IGF-1 by enzyme-labeled chemiluminescent immunometric assay.

RESULTS

Frailty phenotype (seven patients) was more frequent in advanced CKD (estimated glomerular filtration rate < 30 ml/min/1.73m²) (p = 0.014). IGF-1 and LBMAD z-scores were lower in patients with suboptimal growth/weight gain (14 patients) (p = 0.013, p = 0.012), low muscle mass (nine patients) (p = 0.001, p = 0.009), and general fatigue (eight patients) (p < 0.001, p = 0.004). IFG-1 and LBMAD z-scores were associated with frailty phenotype (OR 0.109, 95% CI 0.015-0.798 and OR 0.277, 95% CI 0.085-0.903) after adjustment for CKD stage. IGF-1 z-score was associated with LBMAD < 5th percentile (six patients) (OR 0.020, 95% CI 0.001-0.450) after adjustment for CKD stage. The association between LBMAD and frailty phenotype lost significance after adjustment for IGF-1.

CONCLUSION

Frailty phenotype is more frequent in advanced pediatric CKD. IGF-1 is negatively associated with frailty phenotype and interferes in the association between frailty and LBMAD.

Effect of Kidney or Hepatic Impairment on the Pharmacokinetics and Pharmacodynamics of Somapacitan: Two Open-Label, Parallel-Group Trials

INTRODUCTION

Somapacitan is a long-acting growth hormone (GH) derivative being developed for once-weekly dosing in patients with GH deficiency (GHD). Our objective was to evaluate the impact of kidney or hepatic impairment on somapacitan exposure in adults.

METHODS

In two open-label, parallel-group, single-center, 6-week trials, eligible subjects (18-75 years of age, body mass index 18.5-34.9 kg/m², GH-naïve, without GHD) were divided into five kidney (total n = 44) or three hepatic (n = 34) function groups. Subjects with normal kidney/hepatic function were matched to those with kidney/hepatic impairment by age, sex, and body weight. Subjects received three subcutaneous somapacitan administrations (0.08 mg/kg) on days 1, 8, and 15. Blood samples were collected before each dose, at 28 time points throughout 2 weeks after the last dose, and at follow-up (3-4 weeks after the last dose). The primary endpoint was area under the somapacitan serum concentration-time curve up to 1 week after the last dose (AUC_0-168 h), while secondary endpoints included AUC_0-168 h of insulin-like growth factor (IGF)-I.

RESULTS

In the kidney impairment trial, somapacitan AUC_0-168 h was higher in groups with severe kidney impairment and requiring hemodialysis versus the normal kidney function group (estimated ratio and 90% confidence interval 1.75 [1.00-3.06] and 1.63 [1.01-2.61], respectively). AUC_0-168 h of IGF-I was increased in the moderate impairment group (1.35 [1.09-1.66]), severe impairment group (1.40 [1.10-1.78]), and requiring hemodialysis group (1.24 [1.01-1.52]), compared with the normal function group. In the hepatic impairment trial, somapacitan AUC_0-168 h was significantly higher in the moderate impairment group compared with the normal hepatic function group (4.69 [2.92-7.52]). IGF-I AUC_0-168 h was lower in both hepatic impairment groups (0.85 [0.67-1.08] for the mild impairment group and 0.75 [0.60-0.95] for the moderate impairment group) compared with the normal function group. No new safety or tolerability issues were observed.

CONCLUSIONS

In summary, somapacitan exposure increased with level of kidney/hepatic impairment. Clinically, this will be taken into account when treating adults with GHD with somapacitan, as doses should be individually titrated.

CLINICAL TRIAL REGISTRATION

NCT03186495 (kidney impairment trial, registered 12 June 2017); NCT03212131 (hepatic impairment trial, registered 30 June 2017).

Effects of Dietary or Supplementary Micronutrients on Sex Hormones and IGF-1 in Middle and Older Age: A Systematic Review and Meta-Analysis

Observational research suggests that micronutrients may be protective for sarcopenia, a key health issue during ageing, potentially via effects on hormone synthesis and metabolism. We aimed to carry out a systematic review of RCTs investigating effects of increasing dietary or supplemental micronutrient intake on sex hormones and IGF-1 in individuals aged 45 years or older. We searched MEDLINE, EMBASE and Cochrane databases for RCTs reporting the effects of different micronutrients (vitamins A, C, D, or E; carotenoids; iron; copper; zinc; magnesium; selenium; and potassium) on sex hormones or IGF-1. Of the 26 RCTs identified, nine examined effects of vitamin D, nine of multi-nutrients, four of carotenoids, two of selenium, one of zinc, and one of vitamin E. For IGF-1 increasing vitamin D (MD: -0.53 nmol/L, 95% CI: -1.58, 0.52), multi-nutrients (MD: 0.60 nmol/L, 95% CI -1.12 to 2.33) and carotenoids (MD -1.32 nmol/L; 95% CI -2.76 to 0.11) had no significant effect on circulating concentrations. No significant effects on sex hormones of other micronutrients were found, but data were very limited. All trials had significant methodological limitations making effects of micronutrient supplementation on sex hormones unclear. Further high quality RCTs with physiological doses of micronutrients in people with low baseline intakes or circulating concentrations, using robust methodology, are required to assess effects of supplementation adequately.

Focal segmental glomerulosclerosis in which urinary protein improved after surgical treatment for acromegaly: a case report

Background

Focal segmental glomerulosclerosis is characterized by partial (segmental) sclerotic lesions in some glomeruli (focal). Primary focal segmental glomerulosclerosis is generally considered resistant to steroid therapy. However, acromegaly is a disease that causes peculiar facial features, body types, and metabolic abnormalities due to the excessive secretion of growth hormone by a pituitary adenoma. Growth hormone has been reported to be involved in glomerular cell growth, mesangial proliferation, and glomerulosclerosis in the kidney.

Case presentation

We report a case of a Japanese patient with focal segmental glomerulosclerosis in whom decreased urinary protein was observed after surgical treatment for acromegaly.

Conclusion

The patient’s urinary protein improved as the concentration of growth hormone/insulin-like growth factor 1 decreased.

Impaired kidney structure and function in spinal muscular atrophy

Objective

To determine changes in serum profiles and kidney tissues from patients with spinal muscular atrophy (SMA) type 1 compared with age- and sex-matched controls.

Methods

In this cohort study, we investigated renal structure and function in infants and children with SMA type 1 in comparison with age- and sex-matched controls.

Results

Patients with SMA had alterations in serum creatinine, cystatin C, sodium, glucose, and calcium concentrations, granular casts and crystals in urine, and nephrocalcinosis and fibrosis. Nephrotoxicity and polycystic kidney disease PCR arrays revealed multiple differentially expressed genes, and immunoblot analysis showed decreased calcium-sensing receptors and calbindin and increased insulin-like growth factor-binding proteins in kidneys from patients with SMA.

Conclusions

These findings demonstrate that patients with SMA type 1, in the absence of disease-modifying therapies, frequently manifest impaired renal function as a primary or secondary consequence of their disease. This study provides new insights into systemic contributions to SMA disease pathogenesis and the need to identify coadjuvant therapies.

Regenerative potential of platelets in patients with chronic kidney disease

INTRODUCTION

Chronic kidney disease (CKD) is a systemic disease affecting many organs. Progression of renal failure aggravates ongoing inflammation and increases oxidative stress. In the final stage of CKD, it is necessary to use renal replacement therapy. A side effect of dialysis therapy is the synthesis of proinflammatory factors and increased oxidative stress, which activates platelets and immune cells.

AIM OF THE STUDY

To determine the regenerative potential of platelets in patients with CKD based on the analysis of the relationships between substances with potential regenerative action, as well as analysis of the influence of the type of renal replacement therapy used on regeneration of platelets.

MATERIALS AND METHODS

The study group consisted of 117 patients. Based on the type of therapy used, patients were divided into four groups: hemodialysis, peritoneal dialysis, kidney transplant patients, and conservative treatment (30, 30, 27, and 30 patients). The control group consisted of 30 healthy volunteers. The concentrations of IGF-1, TGF-β, and PDGF-B in the blood serum were measured by ELISA methods.

RESULTS

It was shown that renal replacement therapy significantly influences the concentration of platelet growth factors (IGF-1: p = 0.025 and PDGF-B: p = 0.012). There was a relationship between the type of renal replacement therapy and the duration of dialysis, and the concentration of IGF-1, PDGF-B (p < 0.00001, p < 0.001).

CONCLUSIONS

The type of renal replacement therapy has a different effect on the concentration of platelet-derived growth factors IGF-1 and PDGF-B. PD patients had the highest concentrations of all growth factors, and this may be due to the presence of inflammation induced by dialysis-related advanced end-products of glycosylation (AGE).

Changes in hepato-renal gene expression in microminipigs following a single exposure to a mixture of perfluoroalkyl acids

It is evident that some perfluoroalkyl acids (PFAAs), a group of globally dispersed pollutants, have long biological half-lives in humans and farm animals. However, the effects of PFAAs in domestic animals have not been fully elucidated. The present study investigated how exposure to a single dose of a mixture of 10 PFAAs influenced hepatic and renal gene expression and histopathology, as well as plasma clinical biochemistry, in microminipigs (MMPigs) over 21 days. In animals treated with PFAAs, the mRNA expression of twelve genes related to fatty acid metabolism was upregulated in the kidney, while only few of these genes were induced in the liver. The expression of several kidney injury-associated genes such as, IGFBP1, IGFBP6, GCLC X2, GCLC X3, MSGT1, OLR1 was upregulated in the kidney. Interestingly, the expression of IGFBP-genes was differentially altered in the liver and kidney. Our findings thus identified hepato-renal gene expression changes in MMPigs that were associated with various molecular pathways including peroxisome proliferation, lipid metabolism, kidney injury, and apoptosis. Furthermore, serum HDL levels were significantly decreased following exposure to PFAAs, whereas no significant histopathological changes were detected, as compared to the vehicle group. Taken together, the present study provided the first indication that a single exposure to a mixture of PFAAs can produce changes in MMPig renal gene expression that were observed three weeks post exposure, suggesting that more attention should be paid to the kidney as a primary target organ of PFAAs.

Nephrotoxicity Induced by Cisplatin Intake in Experimental Rats and Therapeutic Approach of Using Mesenchymal Stem Cells and Spironolactone

Chronic kidney disease may lead to subsequent tissue fibrosis. However, many factors can combat injurious stimuli in these tissues aiming to repair, heal, and alleviate any disturbance. Chemokines release, migration of inflammatory cells to the affected site, and activation of fibroblasts for the production of extracellular matrix are commonly observed in this disease. In the last years, many studies have focused on spironolactone (SPL), a mineralocorticoid receptor antagonist, and its pharmacological effects. In the present study, SPL was selected as an anti-inflammatory agent to combat nephrotoxicity and renal fibrosis induced by cisplatin. Mesenchymal stem cells (MSCs) were also selected in addition as a referring agent. Renal fibrosis induced by cisplatin intake significantly increased creatinine, urea, nuclear factor kappa B, insulin-like growth factor-1, fibroblast growth factor-23, and kidney malondialdehyde (MDA) content. Hepatocyte growth factor and renal content of reduced glutathione demonstrated a significant decrease. Histopathological examination of kidney tissues demonstrated marked cellular changes which are correlated with the biochemical results. Oral SPL intake (20 mg/kg/body weight) daily for 4 weeks and MSCs administration (3 × 10⁶ cell/rat) intravenous to the experimental rats resulted in a significant improvement of both the biomarkers studied and the histopathological profile of the renal tissue. Individual administration of spironolactone and MSCs exhibited a marked anti-inflammatory potential and alleviated to a great extent the nephrotoxicity and renal fibrotic pattern induced by cisplatin.

Novel Actions of Growth Hormone in Podocytes: Implications for Diabetic Nephropathy

The kidney regulates water, electrolyte, and acid-base balance and thus maintains body homeostasis. The kidney’s potential to ensure ultrafiltered and almost protein-free urine is compromised in various metabolic and hormonal disorders such as diabetes mellitus (DM). Diabetic nephropathy (DN) accounts for ~20–40% of mortality in DM. Proteinuria, a hallmark of renal glomerular diseases, indicates injury to the glomerular filtration barrier (GFB). The GFB is composed of glomerular endothelium, basement membrane, and podocytes. Podocytes are terminally differentiated epithelial cells with limited ability to replicate. Podocyte shape and number are both critical for the integrity and function of the GFB. Podocytes are vulnerable to various noxious stimuli prevalent in a diabetic milieu that could provoke podocytes to undergo changes to their unique architecture and function. Effacement of podocyte foot process is a typical morphological alteration associated with proteinuria. The dedifferentiation of podocytes from epithelial-to-mesenchymal phenotype and consequential loss results in proteinuria. Poorly controlled type 1 DM is associated with elevated levels of circulating growth hormone (GH), which is implicated in the pathophysiology of various diabetic complications including DN. Recent studies demonstrate that functional GH receptors are expressed in podocytes and that GH may exert detrimental effects on the podocyte. In this review, we summarize recent advances that shed light on actions of GH on the podocyte that could play a role in the pathogenesis of DN.

High Serum Insulin-Like Growth Factor-Binding Protein 1 (IGFBP-1) is Associated with High Fracture Risk Independent of Insulin-Like Growth Factor 1 (IGF-I)

High serum levels of IGFBP-1 are related both to low body mass index (BMI) and to low insulin-like growth factor 1 (IGF-I), which both in turn are related to low bone mineral density (BMD) and to increased fracture risk. However, we have found no previous prospective studies on IGFBP-1 and fracture risk. Despite its name, IGFBP-1 is not only just a binding protein but also has its own IGF-independent effects, e.g., stimulating osteoclast differentiation. IGFBP-1 might have an IGF-related and/or an IGF-independent association to fracture risk. This is a population-based prospective cohort study with a ten-year follow-up of 351 women aged 69-79 at inclusion. Fracture and mortality data were collected from national health care registers. IGFBP-1 had a positive linear relation to the risk of both hip fractures and "major osteoporotic fractures" including fractures of the hip, spine, shoulder, and wrist. The age-adjusted hazard ratio (HR) for a hip fracture was 1.46 (95 % CI 1.08-1.99) for one SD increase in IGFBP-1. The corresponding age-adjusted HR for major osteoporotic fractures was 1.33 (95 % CI 1.05-1.69). The relation between IGFBP-1 and fracture risk was not confounded by either IGF-I or BMI. Femoral neck BMD, however, mediated 56 % of the total "effect" of IGFBP-1 on hip fracture risk. In conclusion, IGFBP-1 had a positive linear relation to fracture risk, partly mediated by BMD but not related to IGF-I or BMD. This implies that IGFBP-1 might be an important factor in bone turnover and that further studies on this would be valuable.

Renoprotective Effect of Lactoferrin against Chromium-Induced Acute Kidney Injury in Rats: Involvement of IL-18 and IGF-1 Inhibition

Hexavalent chromium (CrVI) is a heavy metal widely used in more than 50 industries. Nephrotoxicity is a major adverse effect of chromium poisoning. The present study investigated the potential renoprotective effect of lactoferrin (Lf) against potassium dichromate (PDC)-induced acute kidney injury (AKI) in rats. Beside, because previous studies suggest that interlukin-18 (IL-18) and insulin-like growth factor-1 (IGF-1) play important roles in promoting kidney damage, the present work aimed to evaluate the involvement of these two cytokines in PDC model of AKI and in the potential renoprotective effect of lactoferrin. Adult male albino Wistar rats were pretreated with Lf (200mg/kg/day, p.o.) or (300mg/kg/day, p.o.); the doses that are usually used in the experiment studies, for 14 days followed by a single dose of PDC (15mg/kg, s.c.). PDC caused significant increase in serum urea, creatinine, and total protein levels. This was accompanied with decreased renal glutathione content, and increased renal malondialdehyde, IL-18, IL-4, nuclear factor kappa B (NFκB), IGF-1, and the phosphorylated form of forkhead box protein O1 (FoxO1) levels. Moreover, normal expression IFN-γ mRNA and enhanced expression of TNF-α mRNA was demonstrated in renal tissues. Histopathological investigations provoked deleterious changes in the renal tissues. Tubular epithelial hyperplasia and apoptosis were demonstrated immunohistochemically by positive proliferating cell nuclear antigen (PCNA), Bax, and Caspase-3 expression, respectively. Pretreatment of rats with Lf in both doses significantly corrected all previously mentioned PDC-induced changes with no significant difference between both doses. In conclusion, the findings of the present study demonstrated the involvement of oxidative stress, inflammatory reactions, tubular hyperplasia and apoptosis in PDC-induced AKI. It suggested a role of IL-18 through stimulation of IL-4-induced inflammatory pathway, and IGF-1 through triggering FoxO1-induced cell proliferation. Moreover, the study revealed that Lf protected the kidney against Cr-induced AKI in rats and significantly showed antioxidant, anti-inflammatory, and anti-proliferative properties with down-regulation of IL-18 and IGF-1.

Association between the ratio of insulin-like growth factor-I to insulin-like growth factor binding protein-3 and inflammation in incident automated peritoneal dialysis patients

BACKGROUND

The insulin-like growth factor (IGF) system is known to be associated with inflammation in various populations. However, the association between the IGF system and inflammation has not previously been investigated in automated peritoneal dialysis (APD) patients. Therefore, the aim of this study was to investigate whether the IGF system correlates with inflammation in APD patients.

METHODS

We prospectively determined IGF-I activity, the ratio of serum IGF-I concentrations to those of IGF binding protein-3 (IGFBP-3), and inflammatory markers at initiation of APD and after 6 months of follow-up in 21 incident APD patients.

RESULTS

The mean age was 55.2 ± 13.1 years, and 11 patients (52.3%) were male. Continuous cyclic PD (CCPD) was performed in 11 patients, and nocturnal intermittent PD (NIPD) in 10 patients. The mean value of IGF-I/IGFBP-3 was 0.21 ± 0.13. At baseline, IGF-I/IGFBP-3 was negatively correlated with high-sensitivity C-reactive protein (hs-CRP) (r = -0.27, P = 0.032) and interleukin-6 (IL-6) (r = -0.19, P = 0.046) concentrations. After 6 months, IGF-I/IGFBP-3 (P = 0.048) had decreased significantly, while the hs-CRP (P = 0.036) increased significantly in the CCPD group. However, there were no significant changes in IGF-I/IGFBP-3 (P = 0.59) and hs-CRP (P = 0.14) during 6 months in the NIPD group. Furthermore, compared with the NIPD group, IGF-I/IGFBP-3 (P = 0.041) decreased greater, whereas hs-CRP (P = 0.048) concentrations increased greater in the CCPD group.

CONCLUSIONS

The IGF system was significantly associated with inflammatory markers in incident APD patients, and different APD modalities modulate the IGF system and inflammation.