The roles of IGF-I and IGFBP-3 in the regulation of proximal tubule, and renal cell carcinoma cell proliferation

BACKGROUND: Insulin-like growth factor I (IGF-I), a potent proximal tubule cell (PTC) mitogen, has been implicated in the progression of many human cancers. Our previous work on human renal tissues has suggested that IGF-I and several of its binding proteins (IGFBP-3 and -6) are up-regulated in clear cell renal cell carcinoma (RCC). METHODS: To further elucidate the role of IGF-I and IGFBPs in RCC growth, immunohistochemistry, thymidine incorporation, and Western analysis were performed in primary cultures of normal PTC (priPTC) and clear-cell RCC (priRCC), as well as in SN12K1 cells (a cell line derived from metastatic RCC). RESULTS: By immunohistochemistry, IGFBP-3 and IGF-I were prominently expressed in SN12K1 cells, and weakly expressed in priPTC and priRCC. Incubation with 100 ng/mL IGF-I significantly augmented DNA synthesis by priPTC (mean +/- SD 120.7%+/- 19.7% of controls, P < 0.05), priRCC (238.7%+/- 279.9% of controls, P < 0.01), and SN12K1(120.0%+/- 22.9% of controls, P < 0.05). Neutralizing antibodies to IGF-I and IGF-I receptor significantly suppressed SN12K1 growth (81.9%+/- 13.5% of control, P < 0.01 and 87.4%+/- 16.2% of control, P < 0.05, respectively). Removal of endogenous IGFBP-3 by an anti-IGFBP-3 increased SN12K1 DNA synthesis (243.9%+/- 35.3% of control, P < 0.001), which was partially abrogated by coincubation with exogenous IGFBP-3 (135.97%+/- 5.9% of controls, P < 0.001). Using Western analysis, IGFBP-3 expression was enhanced in IGF-I-stimulated SN12K1 cells exposed to exogenous IGF-I. Coincubation with anti-IGFBP-3 further enhanced IGF-I-induced DNA synthesis. CONCLUSION: RCC cells express IGF-I and IGFBP-3, and are responsive to exogenous IGF-I stimulation. Moreover, in SN12K1 cells (derived from metastatic RCC), autocrine IGF-I and IGFBP-3 actions, respectively, stimulated and inhibited growth. These results suggest that IGF-I and IGFBP-3 may be potential candidates for therapeutic manipulation in patients with advanced RCC.     

Growth hormone, insulin-like growth factors and their binding proteins in adult hemodialysis patients treated with recombinant human growth hormone.

BACKGROUND: Growth deficiency and malnutrition in uremic children are often caused by malfunction of the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis and can be corrected by treatment with GH. The purpose of this study was to evaluate the levels of GH, IGF-I and II and their binding proteins compared to changes in body composition in adult, enfeebled, uremic patients in chronic hemodialysis (HD), treated for 6 months with recombinant human growth hormone (rhGH). METHODS: 31 patients were included in a controlled, randomized, double-blinded study using either 4 IU/m2/day of rhGH or placebo injected subcutaneously every evening for 6 months. RESULTS: Fasting levels of GH were normal at start and increased significantly from 2.2 to 13.5 microg/l (p = 0.01) within the first 4 months of rhGH treatment. Before treatment IGF-I was at the upper limit of normal range (130 to 220 microg/l) in both groups, and it increased significantly from 213 to 348 microg/l (p = 0.01) during rhGH treatment. IGF-II was above the normal range in both groups, and remained unchanged throughout. IGFBP-1 decreased in the rhGH-treated group from 53.1 to 24.7 microg/l (p = 0.004), while IGFBP-3 increased from 5620 to 7100 microg/l (p = 0.004). The molar ratio of IGF-I/IGFBP-3 increased significantly from 14 to 25% (p = 0.01), while the ratio decreased in the placebo group (p = 0.01). During the treatment with rhGH the patients increased their lean body mass (= muscle mass) by a median of 3.18 kg (range 0.82 to 5.12 kg) (p = 0.0001) while their fat mass decreased by a median of 3.33 kg (range 0.18 to 5.82 kg) (p = 0.004). Total body mass (= weight) remained stable. No significant changes were observed in the placebo group. CONCLUSION: The baseline GH and IGF-I concentrations were normal in malnourished HD patients. When treated with rhGH in a dosage as used in growth-retarded uremic children, IGF-I increased to the levels seen in acromegalic persons. IGF-I increased more than IGFBP-3 whereby its biological activity obviously improved. This was reflected in an increased muscle mass and a decreased fat mass. The rhGH treatment was well tolerated.     

Beneficial effects of extended growth hormone treatment after hospital discharge in pediatric burn patients

OBJECTIVE: To study the efficacy of growth hormone given to severely burned children from discharge to 12 months after burn and for 12 months after the drug was discontinued. SUMMARY BACKGROUND DATA: We have previously shown that low-dose recombinant human growth hormone (rhGH), given to children after a severe thermal injury, successfully improved lean muscle mass, bone mineral content, and growth. The aim of the present study was to investigate long-term functional improvements after treatment. METHODS: Forty-four pediatric patients with over 40% total body surface area burns were studied for 24 months after burn. Patients were randomized to receive either rhGH (0.05 mg/kg body weight) or placebo. Height, weight, body composition, serum hormones, resting energy expenditure, cardiac function, muscle strength, and number of reconstructive procedures performed were measured during rhGH treatment and for 12 months after treatment was discontinued. Statistical analysis used Tukey's multiple comparison test. Significance was accepted at P < 0.05. RESULTS: Height, weight, lean body mass, bone mineral content, cardiac function, and muscle strength significantly improved during rhGH treatment compared with placebo (P < 0.05). This treatment significantly increased GH, IGF-I, and IGFBP-3, whereas serum cortisol decreased (P < 0.05). The number of operative reconstructive procedures was significantly lower with rhGH (P < 0.05). Improvements in height, bone mineral content, and IGF-1 concentrations persisted after rhGH treatment (P < 0.05). No side effects with rhGH were observed. CONCLUSIONS: Administration of rhGH for 1 year after burn was safe and improved recovery. These salutary effects continued after rhGH treatment was discontinued.     

The functional, metabolic, and anabolic responses to exercise training in renal transplant and hemodialysis patients

BACKGROUND: Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients and is related to muscle weakness. Its pathogenesis may vary between these groups leading to a different response to exercise. The aim of the study was to compare intrinsic muscular parameters between HD and RTx patients and controls, and to assess the response to exercise training on exercise capacity and muscular structure and function in these groups. METHODS: Quadriceps function (isokinetic dynamometry), body composition (dual-energy x-ray absorptiometry), and vastus lateralis muscle biopsies were analyzed before and after a 12-week lasting training-program in 35 RTx patients, 16 HD patients, and 21 healthy controls. RESULTS: At baseline, myosin heavy chain (MyHC) isoform composition and enzyme activities were not different between the groups. VO2peak and muscle strength improved significantly and comparably over the training-period in RTx, HD patients and controls (p(time)<0.05). The proportion of MyHC type I isoforms decreased (p(time)<0.001) and type IIa MyHC isoforms increased (p(time)<0.05). The 3-hydroxyacyl-CoA-dehydrogenase activity increased (p(time)=0.052). Intrinsic muscular changes were not significantly different between groups. In the HD group, changes in lean body mass were significantly related to changes in muscle insulin-like growth factor (IGF)-II and IGF binding protein-3. CONCLUSIONS: Abnormalities in metabolic enzyme activities or muscle fiber redistribution do not appear to be involved in muscle dysfunction in RTx and HD patients. Exercise training has comparable beneficial effects on functional and intrinsic muscular parameters in RTx patients, HD patients, and controls. In HD patients, the anabolic response to exercise training is related to changes in the muscle IGF system.     

Similarities in Skeletal Muscle Strength and Exercise Capacity Between Renal Transplant and Hemodialysis Patients

Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients. Aim of the study was to assess to what extent exercise capacity and skeletal muscle strength of RTx patients differ from HD patients and healthy controls and to elucidate potential determinants of exercise capacity in RTx patients. Exercise capacity, muscle strength, lean body mass (LBM) and physical activity level (PAL) were measured by cycle-ergometry, isokinetic dynamometry, DEXA and Baecke Questionnaire, respectively, in 35 RTx, 16 HD and 21 controls. VO2peak and muscle strength of the RTx patients were significantly lower compared to controls (p<0.01), but not different compared to HD patients. In RTx patients, strength (p<0.001), PAL (p=0.001) and age (p=0.045) were significant predictors of VO2peak. Muscle strength was related to LBM (p=0.001) and age (p=0.001), whereas gender (p<0.001) and renal function (p=0.01) turned out to be significant predictors of LBM. No effects of corticosteroids were observed. Exercise capacity and muscle strength seem equally reduced in RTx and HD patients compared to controls. In RTx patients, muscle strength and PAL are highly related to exercise capacity. Renal function appears to be a significant predictor of LBM, and through the LBM, of muscle strength and exercise capacity.     

Prostatic involution in men taking finasteride is associated with elevated levels of insulin-like growth factor-binding proteins (IGFBPs)-2, -4, and -5

BACKGROUND: Insulin-like growth factor-binding proteins (IGFBPs)-2, -4, and -5 are associated with upregulation of apoptosis in the ovary. The purpose of this study was to assess the roles of IGF-I and IGFBPs during involution of the prostate. Frozen and fixed tissue was collected by transurethral prostatectomy from Caucasian men, aged 52-82 years, scheduled for prostatectomy for benign prostatic hyperplasia, who took either placebo (n = 7) or the 5alpha-reductase inhibitor finasteride for 6 days to 6 years (n = 15) prior to surgery. METHODS: Intraprostatic androgen levels were measured by radioimmunoassay. Tissues were immunostained for IGF-I and IGFBP-2, -3, -4, and -5, and staining was quantitated by computerized image analysis. Serial sections were stained for markers of apoptosis (TUNEL and tissue transglutaminase) and IGFBP-2, -4, or -5. RESULTS: IGF-I staining was significantly decreased in the medium-term (18-43 days) treatment group and remained so for the duration of the study (P = 0.026). IGFBP-3 staining was unchanged in the early and medium-term treatment groups; however, a transient earlier rise in the level of this proapoptotic protein cannot be ruled out. The percentage of epithelial cell area staining positively for IGFBP-2 increased significantly, from 1.6 +/- 0.5 in the placebo group to 12.0 +/- 2.0 (P < 0.0001), and 7.6 +/- 1.9 (P = 0.003) in the short (6-13 days) and medium-term treatment groups, respectively. IGFBP-4 staining increased from 2.2 +/- 0.6 to 9.8 +/- 1.9 (P < 0.0001) and 7.4 +/- 1.2 (P = 0.004) in the short and medium-term groups, respectively, and IGFBP-5 staining increased from 0.2 +/- 0.1 to 3.8 +/- 2.0 (P = 0.004) in the medium-term group. The results from serial sections showed that IGFBP-2 and -4 costained with markers of apoptosis, while IGFBP-5 did not. CONCLUSIONS: These results indicate that IGFBP-2, -4, and -5 are associated with prostatic involution. Because of the timing and distribution of expression, we hypothesize that IGFBP-2 and -4 have a role as signals for apoptosis, but that IGFBP-5 likely does not.     

Effect of exercise on mRNA levels for growth factors in skeletal muscle of hemodialysis patients.

OBJECTIVES: Muscle mass and muscle mRNA levels for certain growth factors are reduced in maintenance hemodialysis (MHD) patients. This study tested the hypothesis that in MHD patients endurance exercise training (EET) increases mRNA levels for insulin-like growth factors and reduces myostatin mRNA. DESIGN: Biopsies of the right vastus lateralis muscle were performed before and at the end of 8.9 +/- 0.9 (SEM) weeks of EET in MHD patients. Muscle tissue was analyzed histologically by electron microscopy and for fiber cross-sectional area, and, in 8 pairs of biopsies, muscle was examined for mRNA levels for the following proteins: myostatin, insulin-like growth factor-I (IGF-I), IGF-I receptor (IGF-IR), IGF binding proteins (IGFBPs)-1, -2, -3, -4, and -5, and IGF-binding protein-related protein-1 (IGFBP-rP1). SETTING: Outpatient MHD centers. PATIENTS: This was a pilot study conducted in sedentary clinically stable MHD patients undergoing EET with no control group. INTERVENTION: EET that was carefully supervised by exercise trainers. MAIN OUTCOME MEASURE: Skeletal muscle mRNA levels, especially myostatin mRNA. RESULTS: With EET, skeletal muscle myostatin mRNA decreased by 51%, mRNA levels increased significantly for IGF-IR (by 41%), IGFBP-2, -4, and -5, and IGFBP-rP1. IGF-I mRNA increased by 35%; this change was not significant. IGFBP-3 mRNA did not change, and IGFBP-1 mRNA was undetectable. There were mild to moderate alterations in skeletal muscle ultrastructure that did not change significantly with EET. Muscle fiber size, measured in 5 patients, did not change. CONCLUSION: In MHD patients who undergo approximately 9 weeks of EET, skeletal muscle mRNA for myostatin decreases and mRNA for IGF-IR, IGFBPs -2, -4, and -5 and IGFBP-rP1 increases. These changes may indicate mechanisms by which EET improves muscle exercise capacity in MHD patients.     

Muscle ubiquitin m-rNA levels in patients with end-stage renal disease on maintenance hemodialysis

BACKGROUND: Loss of lean body mass is frequently reported in patients with end-stage renal disease (ES-RD). Inadequate nutrient intake, superimposed illnesses, endocrine disorders, uremia and acidosis are some of the potential causes of muscle depletion. Previous reports on experimental models show that lean body mass depletion results from enhancement of muscle tissue protein catabolism, mainly associated with activation of ATP-ubiquitin-dependent proteolysis. Little is known, however, about the affects on this proteolytic system in ESRD patients on maintenance hemodialysis (HD). The present study was designed to investigate the expression of ubiquitin mRNAs in skeletal muscle of patients with ESRD on maintenance HD. METHODS: Biopsies from the rectus abdominis muscle were obtained from eight ESRD patients and from six control subjects undergoing surgery for benign disease. Ubiquitin mRNA levels were measured by Northern blotting analysis. RESULTS: Patients with ESRD had mild metabolic acidosis, as a result of chronic intermittent HD. There were no significant differences between HD patients and controls with regard to the 1.2kb polyubiquitin mRNA species (332.9+/-139 vs 324.2+/-60; ns), but the levels of the 2.4 kb mRNA species were significantly lower in HD patients than in controls (1687+/-542 vs 2529.9+/-325, p=0.01). No correlation was observed between ubiquitin mRNA levels and nutritional parameters and degree of acidosis. CONCLUSIONS: The present study found that the ubiquitin mRNA levels were not increased in the muscle of stable, mildly acidotic hemodialysis patients.     

IGF and IGF-binding protein system in the synovial fluid of osteoarthritic and rheumatoid arthritic patients

Various arthritic disorders result from a disruption of the equilibrium between the synthesis and degradation of tissue matrix macromolecules. Growth factors, particularly insulin-like growth factor-I (IGF-I), are believed to play an important role in maintaining this equilibrium. In this study, we determined the levels of IGF-I, IGF-II, and characterized and measured the amount of IGF-binding proteins (IGFBPs) in the synovial fluid (SF) of osteoarthritis (OA), rheumatoid arthritis (RA) patients and normal individuals. Furthermore, we characterized the IGFBP found in these SFs. The levels of IGF-I, IGF-II and IGFBP-3 were determined by specific radioimmunoassays (RIAs). IGFBP identification and measurement were carried out using the Western ligand blot (WLB) technique, and characterization performed by Western immunoblot. IGFBP-3 proteolysis was analyzed by autoradiography after incubation of SF with radiolabeled IGFBP-3. Results showed a statistically significant increase (P < 0.001) in the IGF-I level in arthritic SF vs normal controls; 75 +/- 11 ng/ml and 82 +/- 11 ng/ml were recorded for RA (N = 8) and OA (N = 10), respectively, whilst normal controls (N = 9) were at 19 +/- 7 ng/ml. No difference in the level of IGF-II was recorded between the three groups studied. Human SF demonstrated the presence of IGFBP-1, -2, -3 and -4, but not that of IGFBP-5 and -6. The level of IGFBP-3 tested either by WLB or RIA was significantly higher (P < 0.001) in RA and OA patients. Moreover, a statistical and positive correlation between the levels of IGF-I and IGFBP-3 was noted. WLB analysis indicated that the amount of IGFBP-1 did not vary among the groups. The levels of IGFBP-2 and -4 were significantly increased (P < 0.02) solely in the RA SF. Further experiments demonstrated that a limited IGFBP-3 proteolysis occurred in human SF. Moreover, the ratio of total IGF over total bioactive IGFBPs was lower in RA (P < 0.05), and to a lesser extent in OA than normal specimens. This study showed the presence of four IGFBPs (1 4) in human SF for which the IGFBP-2, -3 and -4 were enhanced in arthritic fluid. Importantly, although proteolysis occurred in the SF, an increased amount of bioactive IGFBPs were present in arthritic SF, which may affect the bioavailability of IGF-I within the articular tissues.     

Body composition, muscle strength, functional capacity, and physical disability risk in liver transplanted familial amyloidotic polyneuropathy patients

Tomás MT, Santa‐Clara MH, Monteiro E, Baynard T, Carnero EÁ, Bruno PM, Barroso E, Sardinha LB, Fernhall B. Body composition, muscle strength, functional capacity, and physical disability risk in liver transplanted familial amyloidotic polyneuropathy patients.
Clin Transplant 2011: 25: E406–E414. © 2011 John Wiley & Sons A/S. Abstract: Background: Familial amyloidotic polyneuropathy (FAP) is a neurodegenerative disease leading to sensory and motor polyneuropathies, and functional limitations. Liver transplantation is the only treatment for FAP, requiring medication that negatively affects bone and muscle metabolism. The aim of this study was to compare body composition, levels of specific strength, level of physical disability risk, and functional capacity of transplanted FAP patients (FAPTx) with a group of healthy individuals (CON). Methods: A group of patients with 48 FAPTx (28 men, 20 women) was compared with 24 CON individuals (14 men, 10 women). Body composition was assessed by dual‐energy X‐ray absorptiometry, and total skeletal muscle mass (TBSMM) and skeletal muscle index (SMI) were calculated. Handgrip strength was measured for both hands as was isometric strength of quadriceps. Muscle quality (MQ) was ascertained by the ratio of strength to muscle mass. Functional capacity was assessed by the six‐minute walk test. Results: Patients with FAPTx had significantly lower functional capacity, weight, body mass index, total fat mass, TBSMM, SMI, lean mass, muscle strength, MQ, and bone mineral density. Conclusion: Patients with FAPTx appear to be at particularly high risk of functional disability, suggesting an important role for an early and appropriately designed rehabilitation program.     

Patients receiving maintenance dialysis have more severe functionally significant skeletal muscle wasting than patients with dialysis-independent chronic kidney disease.

BACKGROUND: Chronic renal replacement therapy patients exhibit reduction in skeletal muscle function as a result of a combination of metabolic effects and muscle fibre size reduction. The aim of this study was to compare muscle mass with function in patients with chronic kidney disease (CKD) at stages 4 and 5 on haemodialysis (HD) and peritoneal dialysis (PD), and investigate the associations of muscle wasting in a cross-sectional cohort. METHODS: We studied 134 patients (60 HD, 28 PD and 46 CKD 4). The three groups were well matched for age, sex, diabetes and dialysis vintage. Cross-sectional area (CSA) of muscle and fat was measured from a standardized multi-slice CT scan of a 6 cm long section of thigh. CSA of soft tissue was taken from appropriate fat and muscle densities. Functional assessment was by the sit-to-stand 60 test, assessing both the number of sit-to-stands possible under controlled conditions in 60 s (STS 60), and the time taken to perform five sit-to-stand movements (STS 5). Data were collected on a wide range of potential determinants of muscle CSA. RESULTS: There were no significant differences in haemoglobin between males or females or between any of the groups studied. Serum phosphate and calcium-phosphate product were higher in HD patients as compared to CKD4 patients, but there were no differences in these variables when comparing PD patients with either CKD4 or HD patients. Muscle CSA correlated well with objective functional assessments in males (STS 60 R = 0.52, P<0.0001) and females (R = 0.41, P = 0.004), and STS performance was reduced in dialysed patients as compared with CKD 4. Univariate analysis demonstrated that muscle CSA was associated with serum albumin concentration (R = 0.49, P<0.0001), age (R = -0.35, P = 0.005) and C-reactive protein (R = -0.34, P = 0.004). Creatinine clearance, dialysis adequacy, dialysis vintage and time-averaged serum bicarbonate, calcium and phosphate concentrations were not correlated with muscle CSA. CONCLUSION: In conclusion, patients with dialysis-treated CKD 5 exhibited more functionally significant muscle wasting than patients with CKD 4. This may be amenable to modification with targeted exercise or amelioration of factors associated with observed differences in muscle mass.     

Insulin-like growth factor system components in hyperparathyroidism and renal osteodystrophy

BACKGROUND: The insulin-like growth factor (IGF) system plays a key role in regulation of bone formation. In patients with renal osteodystrophy, an elevation of some IGF binding proteins (IGFBPs) has been described, but there is no study measuring serum levels of both IGF-I and IGF-II as well as IGFBP-1 to -6 in different forms of renal osteodystrophy and hyperparathyroidism. METHODS: In a cross-sectional study, we investigated 319 patients with mild (N = 29), moderate (N = 48), preuremic (N = 37), and end-stage renal failure (ESRF; N = 205). The ESRF group was treated by hemodialysis (HD; N = 148), peritoneal dialysis (PD; N = 27), or renal transplantation (RTX; N = 30). As controls without renal failure, we recruited age-matched healthy subjects (N = 87) and patients with primary hyperparathyroidism (pHPT; N = 25). Serum levels of total and free IGF-I, IGF-II, IGFBP-1 to -6, and biochemical bone markers including intact parathyroid hormone (PTH), bone alkaline phosphatase (B-ALP), and osteocalcin (OSC) were measured by specific immunometric assays. IGF system components and bone markers were correlated with clinical and bone histologic findings. Mean values +/- SEM are given. RESULTS: With declining renal function a significant increase was measured for IGFBP-1 (range 7- to 14-fold), IGFBP-2 (3- to 8-fold), IGFBP-3 (1.5- to 3-fold), IGFBP-4 (3- to 19-fold), and IGFBP-6 (8- to 25-fold), whereas IGFBP-5 levels tended to decrease (1.3- to 1. 6-fold). In contrast, serum levels of IGF-I, free IGF-I, and IGF-II remained constant in most patients. Compared with renal failure patients, pHPT patients showed a similar decline in IGFBP-5 levels and less elevated levels of IGFBP-1 (3.5-fold), IGFBP-2 (2-fold), IGFBP-3 (1.2-fold), and IGFBP-6 (4-fold) but no elevation of IGFBP-4 levels. In all subjects, free and total IGF-I levels showed significant negative correlations with IGFBP-1, IGFBP-2, and IGFBP-4 (that is, inhibitory IGF system components) and significant positive correlations with IGFBP-3 and IGFBP-5 (that is, stimulatory IGF system components). A positive correlation was observed between IGF-II and IGFBP-6. ESRF patients with mixed uremic bone disease and histologic evidence for osteopenia revealed significantly (P < 0.05) higher levels of IGFBP-2 and IGFBP-4 but lower IGFBP-5 levels. Histologic parameters of bone formation showed significant positive correlations with serum levels of IGF-I, IGF-II, and IGFBP-5. In contrast, IGFBP-2 and IGFBP-4 correlated positively with indices of bone loss. Moreover, dialysis patients with low bone turnover (N = 24) showed significantly (P < 0.05) lower levels of IGFBP-5, PTH, B-ALP, and OSC than patients with high bone turnover. CONCLUSION: Patients with primary and secondary hyperparathyroidism showed lower levels of the putative stimulatory IGFBP-5 but higher levels of IGFBP-1, -2, -3, and -6, whereas total IGF-I and IGF-II levels were not or only moderately increased. The marked increase in serum levels of IGFBP-4 appeared to be characteristic for chronic renal failure. IGFBP-5 correlated with biochemical markers and histologic indices of bone formation in renal osteodystrophy patients and was not influenced by renal function. Therefore, IGFBP-5 may gain significance as a serological marker for osteopenia and low bone turnover in long-term dialysis patients.     

Insulin-like growth factor binding proteins 4 and 5 and bone mineral density in elderly men and women

Insulin-like growth factor-1 (IGF-I) plays a central role in the maintenance of bone mass. To test whether two major IGF-I binding proteins, IGFBP-4 and IGFBP-5, are related to bone mineral density (BMD), we studied a sample of the Framingham Offspring Cohort participants (99 men and 101 women, ages 60-87). Serum levels of IGF-I, IGFBP-4, and IGFBP-5 were measured by previously validated radioimmunoassays (CVs approximately 10%). BMDs of the proximal femur and lumbar spine were measured using a Lunar DPX-L densitometer. In males, but not females, IGF-I and IGFBP-5 were inversely associated with age (r = 0.34 and r = -0.28, respectively; P <0.01), while IGFBP-4 levels were positively associated with age (P <0.01). Multivariate means for BMD (adjusted for age, body mass index, height, smoking, and in women, estrogen use) were computed across quartiles of IGFBP-4 and IGFBP-5 and IGFBP-4/IGFBP-5 ratio. In women, but not men, IGFBP-5 was positively associated with femoral neck BMD (P = 0.03), however, after statistical adjustment for IGF-I, this association was no longer significant. No other associations were observed for BMD at any other site. Further study is necessary for elucidation of the gender differences in the possible influence of IGF system components on bone mass.     

Serum-free insulin-like growth factor I correlates with clearance in patients with chronic renal failure

Serum-free insulin-like growth factor I correlates with clearance in patients with chronic renal failure. BACKGROUND: Chronic renal failure (CRF) results in major changes in the circulating growth hormone (GH)/insulin-like growth factor (IGF) system. However, there are only limited data on changes in free IGF-I in CRF. METHODS: Matched groups of nondiabetic, nondialyzed patients with CRF (N = 25) and healthy controls (N = 13) were compared. The creatinine clearance (CCr) based on a 24-hour urine collection ranged from 3 to 59 and 89 to 148 ml/min/1.73 m2 in patients and controls, respectively. Overnight fasting serum samples were analyzed for free and total IGF-I and -II, and IGF-binding protein (IGFBP)-1, -2, and -3. Additionally, intact as well as proteolyzed IGFBP-3 was determined. RESULTS: The patients had reduced serum-free IGF-I (-53%) and increased levels of total IGF-II (40%), IGFBP-1 (546%), and IGFBP-2 (270%, P < 0.05). Serum total IGF-I and free IGF-II were normal. Also, serum levels of immunoreactive IGFBP-3 were elevated (33%, P < 0.05), but this could be explained by an increased abundance of IGFBP-3 fragments, as ligand blotting showed no difference in levels of intact IGFBP-3. Accordingly, patients had an increased proteolysis of IGFBP-3 in vivo (17%) and in vitro (7%, P < 0.05). In patients, free IGF-I levels correlated positively with CCr (r2 = 0.38, P < 0.002) and inversely with IGFBP-1 (r2 = 0.69, P < 0. 0001) and IGFBP-2 (r2 = 0.41, P < 0.0007), whereas CCr was inversely correlated with levels of IGFBP-1 (r2 = 0.48, P < 0.0001) and IGFBP-2 (r2 = 0.63, P < 0.0001). CONCLUSIONS: These data strongly support the hypothesis that CRF-related growth failure and tissue catabolism are caused by an increased concentration of circulating IGFBP-1 and -2, resulting in low serum levels of free IGF-I and thus IGF-I bioactivity. In addition, low levels of free IGF-I may explain the increased secretion of GH in CRF.     

Serum insulin-like growth factor-I and insulin-like growth factor-binding protein-3 in localized, metastasized prostate cancer and benign prostatic hyperplasia

OBJECTIVE: Insulin-like growth factors (IGF-I and IGF-II) are important mitogenic peptides and are thought to be significant factors involved in normal and malignant cellular proliferation including benign prostatic hyperplasia (BPH) and prostate cancer (PC). In particular, the association between IGF-I and PC has received much attention. Insulin-like growth factor binding protein-3 (IGFBP-3) is the major carrier protein in serum for the IGF-I, thus is an important functional modulator of it. On the other hand, one of the functions of prostate-specific antigen (PSA) is to cleave IGFBP-3. Epidemiological studies have shown that decreased levels of serum IGFBP-3 are associated with increased PC risk. Controversial results have also been reported on the value of serum IGF-I and/or IGFBP-3 in the detection of PC, especially of metastatic PC; as increased, decreased or unchanged when compared to BPH. The aim of the present study was to investigate whether serum IGF-I and IGFBP-3 levels change in localized and metastasized PC cases compared with BPH as the control cases. METHOD: The study included 45 BPH, 24 localized PC and 19 metastasized PC cases. Serum IGF-I and IGFBP-3 levels were measured by two-site immunoradiometric assay kits, and serum total and free PSA levels were assayed by chemiluminescence method. RESULTS: Serum IGF-I levels in both localized and metastasized PC cases were similar to BPH cases (138.3 +/- 58.2, 137.7 +/- 39.0 and 147.7 +/- 44.2 ng/ml, respectively), whereas serum IGFBP-3 levels were lower in metastasized PC group than in BPH group (1,795.6 +/- 305.6 and 2,196.0 +/- 505.7 ng/ml; p = 0.005). In localized PC, serum IGFBP-3 levels (1,911.00 +/- 349.58 ng/ml) were similar to metastasized PC. There were significant correlations between serum IGFBP-3 and serum free PSA in three groups (r = -0.46, p = 0.02 for localized PC; r = -0.56, p = 0.01 for metastasized PC, and r = -0.31, p = 0.03 for BPH). CONCLUSION: These data reveal that serum IGF-I levels may not change either in localized or metastasized PC, and that decreased serum IGFBP-3 levels may be attributed to its proteolysis by PSA which is increased in PC.     

Changes in cardiac parameters of renal allograft recipients: a compilation of clinical, laboratory, and echocardiographic observations

INTRODUCTION: This study was undertaken to observe changes in cardiac parameters along with clinical and laboratory changes after renal transplantation. PATIENTS AND METHODS: Cardiac parameters were evaluated by M-mode 2-dimensional echocardiography before transplantation and at monthly intervals. All subjects had functioning grafts at the time of the evaluations. RESULTS: Fifty-two allograft recipients underwent pretransplant parameters for comparison to those at posttransplant months 1, 3, 6, and 12. When changes at month 1 and 3 were observed among 22 patients, improvements were evident at month 3. Comparisons of pretransplant versus month 3 showed systolic blood pressure (SBP), 161 +/- 16 to 133 +/- 26 mmHg (P < .002); diastolic BP (DBP), 101 +/- 9 to 86 +/- 11 mmHg, (P < .006); hemoglobin (Hgb), 7.3 +/- 1.6 to 11.2 +/- 3.9 g/dL (P < .006); left atrial diameter (LAD), 41 +/- 5 to 35 +/- 3 mm (P < .001); left ventricular muscle mass index (LVMI), 379 +/- 114 to 248 +/- 58 g/m(2) (P < .001); and left ventricular end diastolic volume index (LVEDVI), 96 +/- 28 to 64 +/- 17 mL/m(2) (P < .002). When changes at months 3, 6, and 12 were observed among 30 patients, improvements evident at month 3 were maintained. Comparisons of pretransplant and 3 and 12 months observations showed SBP, 157 +/- 17, 131 +/- 14, to 126 +/- 10 mm Hg (P < .001); DBP, 97 +/- 10, 83 +/- 16, to 85 +/- 6 mmHg (P < .001); Hgb, 7 +/- 1, 13 +/- 2, to 13 +/- 2 g/dL (P < .001); LAD, 39 +/- 7, 35 +/- 3, to 34 +/- 4 mm (P < .05); LVMI, 275 +/- 91, 191 +/- 38, to 159 +/- 26 g/m(2) (P < .001); and LVEDVI, 87 +/- 29, 56 +/- 34, to 49 +/- 24 mL/m(2) (P < .001). CONCLUSION: Significant improvements in cardiac parameters were evident by the third month post-renal transplantation; the changes were maintained over a longer period among patients with functional grafts.     

Growth hormone,insulin growth factor-1, and igf binding protein-3 axis relationship with bone mineral density among healthy men

The aim of this study was to investigate serum levels of growth hormone (GH), insulin growth factor-I (IGF-I), and insulin growth factor binding protein-3 (IGFBP-3) in 363 healthy caucasian men with and without decreased bone density, who had never experienced fractures. Mean age was 51+/-8.7 years. Height and weight were measured and BMI was calculated using the formula weight (kg)/height (m(2)). Bone mineral density (BMD) was assessed: in 4 skeletal sites (lumbar spine [LS], femoral neck [FN], Ward's triangle [WT], and trochanter [T]) using dual-energy X-ray absorpsiometry (DEXA). After an overnight fasting, blood samples were taken at 8:00 a.m. Serum concentrations of GH, IGF-I, and IGFBP-3 were measured using the immunofunctional (GH) and IRMA (IGF-I and IGFBP-3) methods. The BMD at the 4 skeletal sites is expressed as mean value+/-SD in g/cm(2) and T score. Forty-four men (11%) had bone mineral density (BMD)<-2.5 SD (T score). Mean GH, IGF-I, and IGFBP-3 levels were 0.2+/-0.1, 186.1+/-177.3, and 4990+/-1460 ng/mL, respectively. There were no significant differences between men with normal BMD and men with reduced BMD concerning GH, IGF-I, and IGFBP-3 measurements. In normal men (319), mean GH, IGF-I, and IGFBP-3 levels were 0.4+/-0.1, 192+/-87, and 4960+/-1530 ng/mL, respectively. In the subgroup with reduced BMD (44), mean GH, IGF-I and IGFBP-3 levels were 0.2+/-0.1, 179+/-72 and 5230+/-1270 ng/mL, respectively. An age-dependent attenuation of GH, IGF-I, and IGFBP-3 levels was also found. No correlation was revealed between BMD and GH in the 4 skeletal sites tested. On the contrary, a positive correlation was established between BMD and IGF-I levels in 3 skeletal sites (LS, FN, T). The same was true between BMD and IGFBP-3 in 2 skeletal sites (LS, FN). In conclusion, 11% of Greek healthy males had decreased bone density. No fractures were demonstrated in any individuals. No significant differences were found between men with normal and reduced BMD, with regards to serum GH, IGF-I, and IGFBP-3, although these levels decreased with age. No correlation was found between BMD and GH levels in the 4 skeletal sites. A positive correlation was found between BMD and IGF-I levels in 3 skeletal sites and IGFBP-3 in 2 skeletal sites.     

Elderly patients on haemodialysis have 50% less functional capacity than gender- and age-matched healthy subjects

OBJECTIVE: Patients on haemodialysis (HD) are by necessity inactive for 3-6 h three times a week. The aim of this prospective controlled study was to investigate the level of functional capacity of elderly HD patients using simple measures. MATERIAL AND METHODS: A total of 11 consecutive HD patients aged > 60 years (median age 75 years) were included in the study. They were compared with 22 gender- and age-matched healthy subjects using a prospective 1:2 case:healthy subject study design. As tests of functional capacity and maximal exercise capacity we used a "sit-to-stand" test (number of cycles within 10 s) and a staircase test (the number of cycles completed per second was used as the effect variable), respectively. RESULTS: The patients managed significantly fewer cycles than the healthy subjects in the staircase test (median 2 vs 10; p<0.003) and performed approximately 50% fewer cycles in the sit-to-stand test (p<0.014). The work performed in a given time in the staircase test was 54% less for the patients (p<0.017). CONCLUSIONS: The HD patients in the study had a considerably lower functional capacity than the healthy subjects, which may have interfered with their daily living activities. The tests used are easy to apply and need no specialized equipment. The importance of investigating functional capacity and instituting rehabilitation programmes is emphasized.     

Haemodialysis patients with sleep apnoea syndrome experience increased central adiposity and altered muscular composition and functionality.

BACKGROUND: Sleep apnoea frequently affects patients with end-stage renal disease. However, it is still unclear whether or to what extent sleep disorders may affect functional capacity and quality of life in haemodialysis patients. We tested the hypothesis that apneic dialysis patients due to the lack of restorative sleep will have a further reduced functional capacity and further compromised quality of life compared to their non-apneic counterparts. METHODS: Forty-three clinically stable haemodialysis patients (13 F, 56.6+/-19.4 years) were examined. After polysomnographic analysis, patients were divided in two groups according to their calculated apnoea hypopnoea index (AHI; cutoff 5). Primary outcomes were intergroup differences in the following: (1) physical capacity and muscle performance, assessed by functional tests, (2) quality of life, assessed by the SF-36, (3) body composition, measured by DEXA and (4) muscle composition and size, as well as (5) visceral (VAT) and subcutaneous (SAT) adipose tissue, calculated by computed tomography. RESULTS: Twenty-two patients had AHI >5 (4 F, AHI=28.8+/-22.3). The adjusted analysis for age, BMI and years in dialysis therapy, showed that the low-AHI group (N=21, 9 F, AHI=1.8+/-1.3) had better functional capacity, and performed better in muscle strength and endurance tests compared to the high-AHI group. There were no differences in lean body mass and % total body fat between groups, however, values for VAT, VAT/TAT ratio and thigh muscles' fat infiltration were increased in the high-AHI group. VAT correlated with BMI (r=0.682, P=0.001), functional capacity (r=0.558, P=0.001) apnoea hypopnoea index (r=0.530, P=0.001). There were no statistical significant differences in quality of life between the two groups. To further account for age and BMI differences, a subgroup of patients was matched by age, sex and BMI (N=10/group). In the matched analysis, all the above statistical differences remained, between the low-AHI and high-AHI groups. CONCLUSIONS: Haemodialysis patients with sleep apnoea syndrome demonstrate poorer functional capacity, physical performance and muscle composition, compared to non-apneic dialysis patients. Overall, sleep apnoea appears to partly contribute to the total diminished functional capacity of haemodialysis patients.     

Myosin heavy-chain isoform distribution, fibre-type composition and fibre size in skeletal muscle of patients on haemodialysis

OBJECTIVE: Chronic uraemia is associated with abnormalities in skeletal muscles, which can affect their working capacity. It is also well known that the fibre-type composition of skeletal muscles influences endurance, muscle strength and power. In this study we therefore determined the size and distribution of muscle fibres and the myosin heavy-chain (MHC) isoform composition in patients on haemodialysis (HD) in order to establish any differences with values for untrained control subjects. MATERIAL AND METHODS: Muscle biopsies were obtained from the vastus lateralis muscle of 14 non-diabetic patients on HD. The size and distribution of muscle fibres were evaluated using adenosine triphosphate synthase (ATPase) histochemistry, whilst MHC isoform composition was determined in muscle homogenates using sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Values were compared to those for a group of age-, gender- and BMI-matched untrained control subjects. The aerobic work capacity of the patients was also determined. RESULTS: The MHC composition for I, IIA and IIX isoforms was found to be 35.3% +/- 18.2%, 35.9% +/- 7.1% and 28.9% +/- 15.6%, respectively, findings supported by the ATPase histochemically determined fibre-type composition of the vastus lateralis muscle. The mean fibre area of type 1 and 2 fibres was 3283 +/- 873 and 3594 +/- 1483 MICROm2, respectively. The MHC composition and the size of the type 1 fibres of the patients on HD were significantly different from those of the control subjects. CONCLUSIONS: The data demonstrate relatively fewer type 1 and consequently more type 2x fibres, with a corresponding change in MHC isoforms (MHC I and MHC IIX) in the skeletal muscle of patients on HD. Several patients on HD were found to have <15% type 1 (or relative percentage of MHC I) fibres. Such a low percentage of type 1 fibres is very rarely observed in normal untrained subjects. Chronic uraemia more severely affects the composition than the size of fibres.