Biomedical subjects

Elio F De Palo

Publications and source records attributed to Elio F De Palo.

7 recordsLinked to original sources

PubMed2005

Growth hormone isoforms and segments/fragments: molecular structure and laboratory measurement.

Endocrine diagnostic tests are dependent on the molecular characteristics of protein hormones, a property that is also intimately tied to function. The structure-function relationship is of particular importance for multifunctional protein hormones such as growth hormone (GH). For clinical diagnosis, it is imperative to understand the relationship between GH structure (and its molecular fragments) and function and their potential interaction with single or multiple receptors. The existence of a single or aggregated intact GH 22 kDa form such as the 20 kDa GH isoform has been described, but GH fragments cannot be excluded a priori. Recent advances and probable similarity of GH with other protein hormones such as natriuretic peptides (ANP, BNP and their proANP and proBNP fragments) and POMC (ACTH, beta-endorphin, etc.) lend support to the hypothesis that GH fragments should also be present. This brief review focuses on GH heterogeneity and feasible post-synthesis events. The aim of the review is to describe which GH forms/fragments have already been recognized and/or are potentially present in the circulation. The impacts of GH isoforms (namely the intact 20 and 22 kDa isoforms) and fragments thereof on quantitative measurement are discussed with reference to traditional immunoassay technology and innovative immunofunctional laboratory assays.

Human Growth Hormone↗

PubMed2005

Growth hormone isoforms, segments/fragments: does a link exist with multifunctionality?

Understanding the relationship between growth hormone (GH) structure (its molecular fragments) and function via interaction with single or multiple receptors is of particular importance in clinical diagnostics and physiologic biochemistry. Direct and indirect actions of GH are numerous ranging from carbohydrate and lipid metabolism to growth effects at muscle and vessels. To this end, we have focused on the influence of physical exercise on GH synthesis and release into the circulation. Physical exercise is a physiological condition to which GH multifunctionality is inextricably linked and is thus important physiologically and pathologically. This review describes the potential human GH fragments with respect to protein hormone multifunctionality and the molecular regions of potential action. The intent of the review is to highlight human GH fragments and hypothesize their potential physiologic role. GH fragmentation is also reviewed in relation to the effects of physical exercise and hormone multifunctionality.

Energy Metabolism↗

PubMed2005

Urinary insulin-like growth factor-I measurement in an actual sport competition, an additional approach in laboratory antidoping tests.

BACKGROUND: The insulin-like growth factor hormone (IGF-I) is an important protein hormone under investigation with physical exercise and for doping detection. Urinary IGF-I level in fact represents a relevant measurement when the postexercise proteinuria is under analysis. To verify the IGF-I level variation in the circulation and in urinary excretion in the occasion of a competition, the plasma and urine IGF-I in athletes before and after an actual competitive event were measured. METHODS: Twenty well-trained cyclists took part in a competition (102 km) and concluded the intense physical exercise in approximately 2(1/2) h. Urine and blood samples were collected from each athlete 10-20 min before and at the end of the competition. Plasma and urine total IGF-I (pIGF, uIGF), total urinary proteins (uPr), and creatinine (uCr) concentrations were measured. RESULTS: The uIGF [from 76.2+/-15.8 to 256.9+/-29.1 ng/l (p<0.001)], uPr [from 29.4+/-6.7 to 325.9+/-95.1 mg/l (p<0.005)], and uCr [from 6.3+/-1.0 to 10.0+/-0.8 mmol/l (p<0.005)] significantly increased. The pIGF was 262.6+/-14.3 and 247.3+/-11.8 microg/l before and end-exercise, respectively. A statistical correlation between uIGF and uPr was demonstrated (p<0.001). The pIGF/uIGF ratio was significantly (p<0.05) decreased comparing the end with before the competition. CONCLUSIONS: The pIGF/uIGF significantly decreased at the end, compared with before the competition, suggesting a changed uIGF excretion. This increment appeared to be increased, although not significantly, considering the ratio with uCr.

Adolescent↗

PubMed2004

Effect of prolonged physical exercise on urinary proANP1-30 and proANP31-67.

Dynamic exercise strongly affects atrial natriuretic peptides (ANP), in particular the mature bioactive alphaANP and the proANP fragments, namely proANP1-98, proANP1-30 and proANP31-67. The proANPs influence kidney functions and their plasma levels increase after physical exercise. We measured urinary proANP1-30 and proANP31-67 levels before and at the end of physical exercise in 28 well-trained male cyclists. For the first time, the proANP1-30 and proANP31-67 urinary levels in athletes before and at the end of a prolonged agonistic bicycle race were measured. Urinary creatinine and total proteins were also measured. The urinary proANP31-67, creatinine and total protein levels were significantly higher at the end of exercise than before. In contrast, proANP1-30/protein and proANP31-67/protein ratios decreased after exercise. Even proANP1-30/creatinine and proANP31-67/creatinine ratios were lower after exercise. A significant correlation between proANP1-30 and proANP31-67 urinary levels at the end of exercise was found. The proANP31-67/creatinine ratio before and after exercise also showed a significant correlation. The variation of urinary proANP fragments confirmed their possible role in physical exercise. In particular, it could be interpreted as a response of the body or kidney to renal impairment occurring during exercise.

Adolescent↗

PubMed2003

Effects of acute, heavy-resistance exercise on urinary peptide hormone excretion in humans.

To examine physical exercise-related changes in urinary excretion of protein/peptide hormones and to correlate modifications with the general increase in post-exercise proteinuria, urine C-peptide, insulin and insulin-like growth factor-I (IGF-I) and their plasma concentrations were measured. Plasma and urinary C-peptide, insulin and IGF-I before (Bex) and at the end (Eex) of physical exercise (a 2.5-hour competition, 102 km) were analysed in 20 young cyclists. At Eex compared with Bex, concentration of urinary C-peptide decreased slightly but significantly (21.3 +/- 2.7 vs. 13.5 +/- 1.7 nmol/l), but urinary insulin and urinary IGF-I concentrations significantly increased at Eex (92.5 +/- 4.2 vs. 131.4 +/- 15.7 pmol/l and 10.0 +/- 2.1 vs. 33.6 +/- 3.8 pmol/l, respectively). Plasma insulin and plasma C-peptide significantly decreased, whereas plasma IGF-I was unchanged. Urinary concentrations of total proteins and creatinine significantly increased. Both Eex urinary C-peptide/urinary protein and urinary C-peptide/urinary creatinine ratios were significantly reduced. The correlation between C-peptide and insulin in plasma was confirmed at Bex as well as Eex, but in urine only at Bex. An increased renal tubular reabsorption of C-peptide at the end of exercise might be suggested, but the expected values considering creatinine excretion were almost three times less. The Eex urinary insulin concentration was higher than expected, considering the circulation levels, but lower when compared with the expected concentration considering creatinine excretion. Physical exercise proteinuria, related to an increased protein filtration and a saturation of the mechanisms responsible for the reabsorption, does not appear similar for all peptide hormones.

Adolescent↗

PubMed2002

Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects.

BACKGROUND: Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise. METHODS: Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively. RESULTS: The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively. CONCLUSIONS: uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.

Adolescent↗

PubMed2002

The measurement of insulin-like growth factor-I (IGF-I) concentration in random urine samples.

The aim of the present study was to assess a suitable expression of the urinary concentration of a protein/ peptide hormone such as insulin-like growth factor-I (IGF-I), measured in the urine of healthy individuals when the specimen collection is executed randomly. One hundred and twenty male subjects were divided by age into four groups, namely healthy sedentary young (SYA) and older (SOA) adults, older (OC) and young (YC) children. In a single urine specimen, randomly collected during the morning from each individual, total urinary IGF-I was measured by immunoradiometric method, and urinary creatinine (uCr) and total proteins (utPr) were measured by capillary electrophoresis and spectrophotometric methods, respectively. The urinary IGF-I concentrations were not significantly different in all groups investigated and they were (mean +/- SD): 82.7 +/- 82.8 ng/l, 103.5 +/- 83.3 ng/l, 80.4 +/- 64.4 ng/l in OC, SYA and SOA, respectively; only in the YC group there was a tendency to higher values (125.2 +/- 93.2 ng/l) compared with the other groups. utPr ranged from 26 to 40 mg/l and did not demonstrate significant differences between groups. The urinary IGF-I correlated with uCr and utPr, and statistical significance was observed in all measurements. The measurement of urinary IGF-I in random urine and its ratio to utPr is an innovative, useful way of investigation of urinary protein/peptide hormones.

Adolescent↗