AI Article Synopsis
- The study investigates the relationship between aging, circulating IGF-1 levels, and erythrocyte IGF-1 binding in older versus younger males.
- Older subjects (ages 61-68) exhibited significantly lower circulating IGF-1 and variations in IGF binding proteins compared to younger subjects (ages 15-19).
- Surprisingly, while erythrocyte IGF-1 binding sites were higher in older individuals, the increase may not be due to a rise in IGF-1 receptors, suggesting the involvement of unidentified erythrocyte membrane-associated IGF binding proteins.
Article Abstract
Objective: Insulin-like growth factor-1 (IGF-l) levels are lower in older compared with younger subjects. We tested the hypothesis that the reduction in circulating IGF-l would be accompanied by upregulation in tissue IGF-l binding in at least some tissues. We tested erythrocyte IGF-l binding since blood is an accessible tissue in humans, and there is growing evidence to suggest that erythrocyte IGF-l binding is influenced by circulating IGF-l.
Design And Patients: We compared 9 healthy older males (61-68 years old) with 9 healthy younger males (15-19 years old).
Measurements: Standard techniques were used to assay circulating IGF-l and IGF binding proteins 1-5 (IGFBPs 1-5). Erythrocyte IGF-l binding was first measured by studies in which native [125l]-IGF-l was displaced with unlabelled native IGF-l. In order to determine a possible role for IGF binding proteins (IGFBP), native [125l]-IGF-l was displaced with des-(1-3)IGF-1, which binds with IGF receptors but not IGFBPs.
Results: As expected, circulating IGF-l was significantly lower in the older compared with the younger subjects. In addition, IGFBP-3 and 5 were significantly lower, and IGFBP-4 higher, in older compared with younger subjects. When native [125l]-IGF-l was displaced with unlabelled native IGF-l, the number of IGF-l binding sites per erythrocyte was higher in the older subjects (43 +/- 5 vs. 18 +/- 2, older vs. younger, respectively; P < 0.05). In contrast, when native [125l]-IGF-l was displaced with des-(1-3), IGF-l binding capacity was not different between the two age groups.
Conclusions: Erythrocyte IGF binding was increased in older compared with younger subjects. Surprisingly, the mechanism of the increase may not be a simple up regulation of IGF-l receptors in response to reduced circulating IGF-l, but possibly by an increase in the levels of as yet unidentified erythrocyte membrane-associated IGF binding proteins.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1046/j.1365-2265.1998.00395.x | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Adipocyte and adipogenesis.
Eur J Cell Biol
March 2014
Department of Chemical Pathology, Tygerberg Hospital, Cape Town, South Africa.
Adipocytes are the main constituent of adipose tissue and are considered to be a corner stone in the homeostatic control of whole body metabolism. Their primary function is to control energy balance by storing triacylglycerol in periods of energy excess and mobilizing it during energy deprivation. Besides the classical function of storing fat, adipocytes secrete numerous lipid and protein factors.
View Article and Find Full Text PDFDefective thymopoiesis and poor peripheral homeostatic replenishment of T-helper cells cause T-cell lymphopenia in cirrhosis.
J Hepatol
October 2013
Departamento de Medicina, Universidad de Alcalá, Madrid, Spain.
Background & Aims: Depletion of circulating CD4(+) T-helper (Th) lymphocytes, especially naive Th cells, is common in cirrhosis. Little is known about the pathogenetic mechanisms involved in Th-cell depletion in cirrhosis. We investigated the mechanisms involved in circulating Th-cell lymphopenia in cirrhosis.
View Article and Find Full Text PDF[The structural organization of binding determinants in insulin-like growth factor-I (IGF-I) molecule].
Zh Evol Biokhim Fiziol
May 2010
Insulin-like growth factor I (IGF-I) is a peptide related to insulin and IGF-II. These three related peptides produce similar biological effects, but each of them has its irreplaceable physiological significance in the organism. Multisided functional role of IGF-I in the organisms is due to its unique binding properties.
View Article and Find Full Text PDFGrowth hormone and insulin-like growth factor I insensitivity of fibroblasts isolated from a patient with an I{kappa}B{alpha} mutation.
J Clin Endocrinol Metab
March 2010
St. Christopher's Hospital for Children, 3601 A Street, Philadelphia, Pennsylvania 19134, USA.
Context: NF-kappaB is a family of transcription factors involved in cell proliferation, differentiation, and apoptosis.
Objective: We have recently demonstrated that NF-kappaB is expressed in the growth plate and it mediates the growth-promoting effects of IGF-I on chondrogenesis and longitudinal bone growth. Humans with defects of the NF-kappaB pathway exhibit growth failure, which suggests a possible regulatory role for NF-kappaB in statural growth.
[Growth hormone deficiency in adulthood: how to diagnose and when to treat?].
Arq Bras Endocrinol Metabol
July 2008
Unidade de Neuroendocrinologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo, SP, Brazil.
Adult growth hormone deficiency (AGHD) is a well-established clinical entity with heterogeneous characteristics, in which the main causes are hypothalamus-pituitary tumors and/or their treatment. The diagnosis of ADGH should be considered in patients with a prior history of childhood-onset GH deficiency or a history of organic hypothalamus-pituitary disease. In these patients diagnosis is performed biochemically by provocative tests of GH secretion, once the measurement of the biological markers for GH action:IGF-l and IGFBP-3 levels, can be in the normal range in an important percentage of AGHD patients.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!