UNIPROT:P61278 - FACTA Search

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Query: UNIPROT:P61278 (somatostatin)
22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As the long-acting somatostatin analog octreotide attenuates polypeptide hormone hypersecretion, it has recently been used to effectively treat acromegaly and gastrointestinal carcinoid tumors. Most growth-promoting actions of GH are mediated by insulin-like growth factor-I (IGF-I), which circulates complexed with multiple binding proteins (IGFBPs). IGFBP-1, a nonglycosylated peptide, competes with the IGF-I receptor for ligand binding and also regulates IGF action. To examine GH-independent mechanisms for octreotide regulation of the GH axis, circulating levels of IGFBP-1 were measured hourly after sc octreotide or saline administration in normal and GH-deficient adults. As IGFBP-1 is inhibited by insulin and GH, the dynamic pattern of alterations in GH and insulin levels was also assessed. After octreotide (100 micrograms) administration to 10 normal subjects, mean IGFBP-1 concentrations were stimulated from 23 +/- 4 to 72 +/- 18 micrograms/L (P < 0.007 vs. saline) after 2 h. Maximal induction of IGFBP-1 levels occurred after 3 h (325 +/- 115 micrograms/L; P < 0.02 vs. saline) and remained elevated (P < 0.005) for 6 h. IGFBP-1 was induced by octreotide in all subjects and was confirmed by Western ligand blotting. Insulin and GH levels preceding the rise in IGFBP-1 were unaltered by octreotide. Octreotide stimulated IGFBP-1 5-fold during a sustained fast in 4 normal subjects, despite equally suppressed insulin levels in both saline- and octreotide-treated groups. In 4 GH-deficient adults, IGFBP-1 levels were stimulated by octreotide from 16 +/- 3 to 146 +/- 36 and 154 +/- 28 micrograms/L after 3 and 4 h, respectively. In conclusion, the somatostatin analog octreotide induces IGFBP-1 independently of GH and insulin. As IGFBP-1 regulates the action of IGF-I, octreotide stimulation of IGFBPs may represent an additional pharmacological mechanism for attenuating the GH-IGF-I axis.
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PMID:Octreotide stimulates insulin-like growth factor-binding protein-1: a potential pituitary-independent mechanism for drug action. 128 85

As the somatostatin analog octreotide suppresses pituitary GH secretion and circulating IGF-1 levels, we examined its effects on human hepatoma (hep G2) cells which selectively express IGFBP-1. Octreotide (60 nM) stimulated IGFBP-1 up to 4.1-fold (p < 0.001 after 24 hrs). Induction of IGFBP-1 was first detectable after 12 hrs of 6 nM octreotide (1.5-fold, p < 0.03), and was confirmed by ligand blotting. Cholera toxin and forskolin induced IGFBP-1 independently and were also additive with octreotide. IGFBP-1 mRNA expression was induced 2.7-fold by octreotide. Thus, octreotide induces basal and stimulated IGFBP-1 in hepatocytes independently of insulin and GH. As IGFBP-1 may regulate peripheral IGF-1 action, induction of IGFBP-1 represents a novel pituitary-independent mechanism for octreotide action.
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PMID:Somatostatin analog induces insulin-like growth factor binding protein-1 (IGFBP-1) expression in human hepatoma cells. 138 3

The insulin-like growth factors (IGFs) exist primarily bound to cell surface receptors or complexed to specific binding proteins (IGFBPs). The IGFBPs modulate the bioavailability of the IGFs and may enhance or inhibit IGF actions. Several distinct forms of IGFBPs have been described on the basis of size, immunological determinants, and distribution in biological fluids; the IGFBPs may differ as well in their biological function. Sheep thyroid cells produce IGFBPs under hormonal regulation. Cells grown in basal medium or with six-hormone (6H) medium supplements (transferrin, glycyl-histidyl-lysine, hydrocortisone, somatostatin, insulin, and TSH) release nonglycosylated BPs that migrate at 24, 27, 29, and 32 kDa on Western ligand blot. Cells cultured with the thyroid mitogens epidermal growth factor and phorbol ester release additional glycosylated IGFBPs of 40-44 kDa. Immunoprecipitation experiments indicate that 29- and 32-kDa IGFBPs are antigenically related to IGFBP-2, and the 40- to 44-kDa proteins are related to IGFBP-3. Using specific cDNA probes IGFBP-1, -2, and -3, we examined the regulation of IGFBP mRNA levels in sheep thyroid cultures. The rat IGFBP-2 cDNA probe hybridized to an approximately 1.6-kilobase mRNA species in cells under all culture conditions. However, IGFBP-3 mRNA was detectable only in epidermal growth factor- or phorbol ester-treated cells and appeared within 4 h, preceding the release of IGFBP-3 protein into the medium. The 6H additives, which stimulate differentiated function in thyroid cells, inhibited the mRNA levels of both IGFBP-2 and IGFBP-3. IGFBP-1 mRNA was not detectable. The distinct regulation of these IGFBPs suggest that they may play different biological roles in modulating thyroid physiology.
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PMID:Regulation of insulin-like growth factor-binding protein messenger ribonucleic acid levels in sheep thyroid cells. 170 62

Insulin-like growth factors (IGFs) circulate in a complexed state with several binding proteins (BPs). Of these, IGFBP-1 is regulated by hormonal and nutritional factors. The somatostatin analogue, octreotide, has been used to effectively control hypersomaototropism in acromegaly. IGFBP-1 levels were measured by RIA in 17 acromegalic patients receiving octreotide. Serum hormone sampling was conducted hourly for 8 hr periods. Among 13 octreotide responders, mean pre-treatment basal GH, IGF-1, and IGFBP-1 levels were 19 +/- 5 micrograms/L, 1021 +/- 168 micrograms/L, and 36 +/- 8 micrograms/L respectively. One month following octreotide treatment, an acute subcutaneous injection (100 micrograms) maximally attenuated GH to 3 +/- 0.6 microgram/L (18% of control, P less than 0.03) and IGF-1 to 467 +/- 75 micrograms/L (46% of control, P less than 0.008) after 4 hrs. IGFBP-1 levels, however, were stimulated to 95 +/- 16 micrograms/L (297% of control, P less than 0.003) during the same time period. A significant increase in IGFBP-1 levels occurred within 2 hrs (158% of baseline, P less than 0.03), and was sustained until the 7th hr following injection. Insulin, a known suppressor of IGFBP-1, did not change during this time. Among the 4 octreotide non-responders, mean basal IGFBP-1 levels were 42 +/- 4 micrograms/L, and 4 hrs following octreotide administration IGFBP-1 was 40 +/- 7 micrograms/L. Octreotide induced a dynamic inverse relationship between circulating GH and IGFBP-1 levels (r = -0.73, P less than 0.001). The absence of IGFBP-1 changes in octreotide non-responders and the non-suppression of insulin in octreotide responsive patients, suggest a direct GH-mediated mechanism of IGFBP-1 regulation in octreotide treated patients with acromegaly. IGFBP-1 may be another useful marker in evaluating the response of acromegaly to octreotide treatment in patients who experience clinical benefit but equivocal GH and IGF-1 attenuation.
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PMID:Octreotide stimulates insulin-like growth factor binding protein-1 (IGFBP-1) levels in acromegaly. 171 20

It was demonstrated recently that administration of lanreotide and octreotide, two somatostatin octapeptide analogs, increased circulating insulin-like growth factor binding protein 1 (IGFBP-1) levels. The present study demonstrates that native somatostatin 14 shares this ability and that the increase in abolished by concomitant hyperinsulinemia within the physiological range. Five fasting healthy volunteers underwent a hyperinsulinemic as well as a normo-insulinemic (i.e. basal insulinemic) euglycemic clamp lasting 8 h (serum insulin levels remained constant, about 570 vs. 16 pmol/L). Immediately before the clamps, a somatostatin infusion (500 micrograms/h) was started and continued throughout. During normo-insulinemia, IGFBP-1 levels increased slowly from 6.3 +/- 6.2 to 36.1 +/- 14.8 micrograms/L (P < 0.05) reaching maximum after 7 h constant somatostatin infusion, whereas hyperinsulinemia induced a significant decrease from basal levels (from 4.7 +/- 5.4 to 1.1 +/- 1.5 micrograms/L) after 8 h (mean +/- SD, n = 5). These results may indicate hitherto unnoticed interactions of somatostatin and insulin on IGFBP-1 release with possible impact on IGF-I action at the cellular level.
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PMID:Somatostatin-stimulated insulin-like growth factor binding protein-1 release is abolished by hyperinsulinemia. 750 19

The ability of TSH to stimulate synthesis and release of thyroid hormones in ovine thyroid follicles in vitro depends partially on a synergy with insulin-like growth factors (IGFs). The cellular availability of IGFs may be influenced by the release of several IGF binding proteins (IGFBPs). The purposes of these studies was to 1) further characterize the species of IGFBPs synthesized by thyroid follicles, 2) examine the ability of TSH and cortisol to alter IGFBP gene expression and protein release, and 3) investigate the actions of exogenous IGFBPs on thyroid cell function. Adult sheep thyroid follicles were isolated after collagenase digestion, grown to confluence in Coon's modified Ham's F12M medium (OH) with the addition of transferrin, glycylhistidyl-lysine, somatostatin (3H), cortisol and insulin, and maintained in serum-free test media with or without further supplements for up to 48 h. Conditioned media were analyzed for IGFBP presence by Western ligand blotting, and by immunoblotting using specific antisera against bovine IGFBP-2 and human IGFBP-5. IGFBP mRNAs from follicles were identified by Northern blot hybridization using [32P]labeled complementary DNAs encoding ovine IGFBP-1 or -2, and rat IGFBP-4, -5, or -6. Uptake and organification of Na[125I] were measured by incorporation into trichloroacetic acid-precipitable material. Isolated thyroid follicles synthesized four species of IGFBPs in either 0H or 3H medium as detected by ligand blotting, of sizes 40-46, 34, 28, and 18 kilodaltons (kDa), respectively. The 32 kDa IGFBP was identified immunologically as IGFBP-2, whereas the 28 kDa and 18 kDa species were identified as IGFBP-5. Northern blot hybridization of total RNA from cells in 3H medium demonstrated an IGFBP-2 messenger RNA (mRNA) [1.4 kilobase (kb)], an IGFBP-4 mRNA (2.6 kb), and two IGFBP-5 mRNAs (6 kb and 1.8 kb). No IGFBP-1 or -6 mRNAs were detected. Incubation of cultured follicles with TSH (30-500 microU/ml) caused a dose-dependent decrease in the abundance of all IGFBP mRNAs and released proteins, which were reduced further by TSH together with cortisol (10 nM). When the inhibitory effect of TSH and cortisol was removed, IGFBP-2 mRNA increased within 3 h and was 7-fold greater within 12 h. IGFBP-2 did not appear in the conditioned medium until 12 h after TSH removal, along with the other IGFBP species.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Hormonal regulation and biological actions of insulin-like growth factor binding proteins in isolated ovine thyroid follicles. 750 36

Twenty-three patients with active acromegaly underwent serum sampling for growth hormone (GH), insulin and insulin-like growth factor binding protein 1 (IGFBP-1) after placebo or single doses of octreotide or bromocriptine. Integrated 24-h serum GH levels decreased by 90% after octreotide and 49% after bromocriptine. A statistically significant correlation between the course of GH levels after octreotide and bromocriptine was observed (p < 0.001). Octreotide, but not bromocriptine, induced a significant increase in integrated 24-h serum IGFBP-1 levels to 37.4 times the baseline values. Bromocriptine caused a non-significant increase in integrated 24-h serum IGFBP-1 levels, which argues against a direct regulatory effect of GH on IGFBP-1 production in acromegaly. In conclusion, octreotide induces in acromegaly the production of IGFBP-1, which occurs independently of the number of somatostatin receptors on the GH-secreting pituitary adenoma. The supposed inhibitory effect of IGFBP-1 on the biological effect of IGF-1 might result in an additional clinical benefit in acromegalic patients as compared to treatment directed at the pituitary level.
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PMID:Octreotide, but not bromocriptine, increases circulating insulin-like growth factor binding protein 1 levels in acromegaly. 754 70

Insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) normally circulates as a single, highly phosphorylated species. However, IGFBP-1 phosphorylation status can be altered, such as in pregnancy where non- and lesser phosphorylated isoforms are also present. We have examined how hormonal regulators of circulating IGFBP-1 influence its phosphorylation status and, hence, its ability to modulate IGF activity. In response to insulin-induced hypoglycemia (0.2 U/kg, iv), an increase in the highly phosphorylated isoform was observed after 5 h [16 (range, 11.5-35.5) to 77 (range, 63-250) microgram/L; 4.8-fold increase; P = 0.009], but no non- or lesser phosphorylated variants could be detected. Glucagon (1 mg, sc), increased IGFBP-1 from 27 (range, 13-36.5) to 112 (range, 100.5-129) micrograms/L (4.1-fold increase; P = 0.009) after 90 min despite preceding insulin concentrations of more than 500 pmol/L, but again the IGFBP-1 remained in the highly phosphorylated form. Regulation of IGFBP-1 phosphorylation by sex steroids was studied by comparing women receiving a combined oral contraceptive with women on no medication. Although plasma IGFBP-1 levels were significantly elevated in the treatment group [120 (range, 97.5-237.5) vs. 52 (range, 38-70) micrograms/L; P < 0.004], there was no difference in the form of IGFBP-1 present. The acute effect of somatostatin (500 micrograms/h) on IGFBP-1 phosphorylation status was also studied. Somatostatin only increased the phosphoform characteristic of normal subjects; the appearance of non- or lesser phosphorylated variants was not induced. The effect of rhIGF-I (80 or 120 micrograms, sc) on plasma IGFBP-1 was studied in three subjects with Laron's syndrome. A transient increase in the highly phosphorylated isoform of IGFBP-1 was noted; there was no rise in the non- and lesser phosphorylated isoforms also found in the plasma of Laron's syndrome subjects. These data suggest that only the highly phosphorylated species of IGFBP-1 is under hormonal control; regulation of the non- and lesser phosphorylated variants remains to be determined.
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PMID:Hormonal regulation of circulating insulin-like growth factor-binding protein-1 phosphorylation status. 853 May 93

Hyperinsulinemic euglycemic clamps were performed on six patients with compensated alcoholic cirrhosis and on six normal comparison subjects. As in previous studies, glucose uptake in the cirrhotic patients was only 21% of the comparison value. The cirrhotic patients had high growth hormone (GH) and low insulin-like growth factor-I (IGF-I) levels, with low insulin-like growth factor-binding protein (IGFBP)-3 levels, but surprisingly high IGFBP-I levels (26.8 +/- 8.4 microgH vs. 3.2 +/- 0.2 microm/L, P < .001). The log IGFBP-1 level was inversely correlated with the log insulin sensitivity (r = -.95). The clamps were repeated with a somatostatin infusion to suppress GH secretion. IGFBP-1 increased in both groups, especially in the cirrhotic subjects. Insulin sensitivity increased in the normal subjects but was unchanged in the cirrhotic patients. Following GH treatment (0.13 U/kg/d for 5 days), the clamps were repeated. GH, IGF-1, and IGFBP-3 levels were now similar in the two groups; IGFBP-1 levels decreased in the cirrhotic patients but remained fivefold higher than the comparison value (10.6 +/- 3.7 vs. 2.1 +/- 0.4, P < .05). Glucose uptake in the cirrhotic patients remained only 29% of the comparison value, but the change in their insulin sensitivity was inversely correlated with the change in their IGFB-1 levels (r = -.84). These results suggests an important role for IGFBP-1 in modulating insulin sensitivity in cirrhosis.
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PMID:High insulin-like growth factor binding protein 1 levels in cirrhosis: link with insulin resistance. 870 51

Octreotide nasal powder is a delivery system of the somatostatin analogue developed to overcome the inconvenience of repeated subcutaneous administrations. Eight patients with clinically active acromegaly were treated for three months with octreotide nasal powder which was administered at the initial dosage of 0.125 mg tid, doubling the dosage up to 2 mg tid in order to obtain a mean GH value below 5 micrograms/l during 8 daytime hours. In 4 of these patients, treatment was prolonged till the sixth month. Blood samples were taken on days 15, 29, 43, 55, 90, 120, 150, 180 for GH, IGF-I, IGFBP-3, IGFBP-1 and insulin measurements. Before treatment, mean daytime GH and morning IGF-I serum levels were both increased but not correlated with each other. Serum IGFBP-3 levels were higher than normal and positively correlated with those of GH, IGF-I and insulin. Insulin levels were elevated and positively correlated with those of GH but not with those of IGF-I and IGFBP-1. Serum IGFBP-1 levels were in the low normal range and not correlated with any of the other parameters. Treatment with octreotide nasal powder induced in all patients a marked decrease of GH which lowered below 5 micrograms/l in 7/8 patients and IGF-I levels, which fell within the normal range in 1 patient. Serum IGFBP-3 and insulin concentrations decreased by 26% and 71%, respectively, and those of IGFBP-1 underwent an only transient increase in 5/8 patients. Opposite changes of insulin and IGFBP-1 levels, with a decrease of the former followed by an increase of the latter were noted during the 8 hours following an octreotide nasal insufflation. During chronic octreotide treatment, positive correlations were found between GH and IGF-I, GH and IGFBP-3, IGF-I and IGFBP-3, insulin and IGFBP-3 and insulin and IGF-I. An improvement of the clinical picture was registered in all patients after a few days of octreotide nasal powder administration. Treatment was well tolerated, with only mild side effects and no significant changes in the nasal mucosa, and the patients' compliance was excellent.
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PMID:Effect of chronic treatment with octreotide nasal powder on serum levels of growth hormone, insulin-like growth factor I, insulin-like growth factor binding proteins 1 and 3 in acromegalic patients. 890 79

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