Search Results
You are looking at 1 - 4 of 4 items for
- Author: M. Seppälä x
- Refine by access: All content x
Search for other papers by M. Angervo in
Google Scholar
PubMed
Search for other papers by R. Koistinen in
Google Scholar
PubMed
Search for other papers by M. Seppälä in
Google Scholar
PubMed
ABSTRACT
Insulin-like growth factor-I (IGF-I) enhances and epidermal growth factor (EGF) inhibits gonadotrophin-induced aromatization in granulosa cells. Our previous studies have shown that human ovarian granulosa cells synthesize insulin-like growth factor-binding protein-1 (IGFBP-1) which inhibits IGF-stimulated DNA synthesis. The present study addresses the effect of EGF and gonadotrophins in the regulation of IGFBP-1 release by human granulosa cells cultured in serum-free medium. At concentrations of 1–100 μg/l EGF was found to stimulate IGFBP-1 secretion. This was not due to cell proliferation, as the viable cell count remained unaffected. Growth hormone and gonadotrophins had no effect on IGFBP-1 secretion when added alone to culture medium. These results suggest that EGF regulates IGFBP-1 secretion in human granulosa-luteal cells.
Journal of Endocrinology (1992) 134, 127–131
Search for other papers by C Nilsson in
Google Scholar
PubMed
Search for other papers by M Seppala in
Google Scholar
PubMed
Search for other papers by K Pettersson in
Google Scholar
PubMed
Immunoassays are widely used for measuring gonadotropins, including luteinizing hormone (LH), as these are both specific and sensitive. Because LH is microheterogeneous it has been claimed that the specificity of monoclonal antibodies used in two-site immunoassays can limit their clinical utility. Furthermore, we reported earlier a common genetic variant form of LH due to amino acid alterations in the LHbeta gene that is poorly or not recognized by antibodies directed against epitopes present in the intact molecule. We here report the result of an LH epitope mapping using 30 different monoclonal antibodies. The antigenic area affected by the amino acid alterations is fairly large, as antibodies to the two intact domains are able to sandwich each other. Combinations of alpha-beta or beta-beta antibodies generally provide alternatives for unbiased detection of circulating LH and some have reasonably good discrimination of human chorionic gonadotropin. The beta-beta combinations exhibit a peculiarity in urine determinations as they detect the urinary beta-core fragment. Our aims were to study the altered immunoreactivity caused by the amino acid changes and to design two-site LH assays fully capable of recognizing the biologically active LH variant. We also conclude that the variability in recognizing the universally occurring LH variant is the most important factor contributing to the widely documented LH immunoassay discrepancies.
Search for other papers by P Ebeling in
Google Scholar
PubMed
Search for other papers by U-H Stenman in
Google Scholar
PubMed
Search for other papers by M Seppälä in
Google Scholar
PubMed
Search for other papers by V A Koivisto in
Google Scholar
PubMed
Abstract
The acute effects of hyperinsulinemia on androgen homeostasis and a possible association of androgens to insulin sensitivity, serum lipids and lipoproteins and to lipid oxidation were examined in 19 healthy males (27 ± 1 yrs, body mass index 24 ± 1 kg/m2). In each subject, a 240 min euglycemic hyperinsulinemic clamp was performed and glucose and lipid oxidation were determined by indirect calorimetry. During hyperinsulinemia serum sex hormone-binding globulin (SHBG) concentration decreased by 5% (P<0·01), insulin-like growth factor binding protein (IGFBP-1) by 88% (P<0·001) and dehydroepiandrosterone sulphate (DHEAS) by 12% (P<0·001), with no change in total or free testosterone concentrations. In the basal state, IGFBP-1 and C-peptide were inversely related (r= −0·54, P<0·05). Fasting concentrations of serum free testosterone (r=0·59, P<0·01) and DHEAS (r=0·47, P<0·05) correlated positively with serum free fatty acid (FFA) concentrations during hyperinsulinemia, but not with fasting FFA level. Lipid oxidation rate in the basal state correlated positively to the decline in SHBG (r=0·61, P<0·01) and DHEAS concentrations (r=0·62, P<0·01) during hyperinsulinemia. While the fasting serum high density lipoprotein cholesterol level correlated positively with the insulin-induced decline in DHEAS level (r=0·58, P<0·01), no associations were found between serum androgens and total cholesterol, low density lipoprotein cholesterol or triglyceride concentrations. Insulin sensitivity was not related to SHBG, IGFBP-1, DHEAS or testosterone concentrations. It is concluded that, in the healthy man with normal androgen homeostasis, (1) acute hyperinsulinemia decreases SHBG, IGFBP-1 and DHEAS concentrations, (2) the relative insulin-induced decline of IGFBP-1 level is 18-fold greater than that of the SHBG level, (3) androgens may maintain lipolysis during hyperinsulinemia and (4) there is no association between physiological androgen concentrations and insulin sensitivity.
Journal of Endocrinology (1995) 146, 63–69
Search for other papers by A. Singh in
Google Scholar
PubMed
Search for other papers by D. Hamilton-Fairley in
Google Scholar
PubMed
Search for other papers by R. Koistinen in
Google Scholar
PubMed
Search for other papers by M. Seppälä in
Google Scholar
PubMed
Search for other papers by V.H.T. James in
Google Scholar
PubMed
Search for other papers by S. Franks in
Google Scholar
PubMed
Search for other papers by M.J. Reed in
Google Scholar
PubMed
ABSTRACT
Dietary factors are known to modulate concentrations of sex hormone-binding globulin (SHBG). In the present study we have investigated the possibility that insulin like growth factor-type I (IGF-I) may be an additional regulator of SHBG using cultured human hepatoma cells which secrete SHBG. The inhibitory effect of insulin on SHBG secretion by these cells was confirmed but, in addition, IGF-I was shown to inhibit SHBG secretion by about 40% at a concentration of 100 nmol/l. A similar degree of inhibition was achieved using insulin at a concentration of 10 umol/l. Insulin, but not IGF-I, was also found to inhibit the secretion of a low molecular weight IGF-binding protein (IBP-I), which is also secreted by hepatoma cells. It is concluded that IGF-I is an additional regulator of SHBG secretion by these cells and that it may be involved in regulating SHBG secretion in vivo in response to dietary factors.
