Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin-like growth factors (IGF-I and IGF-II) are produced in most tissues, particularly liver. Via endocrine and paracrine or autocrine mechanisms, they play an essential role in cell proliferation and differentiation and complement the metabolic effects of insulin. Similarities between the effects of insulin and IGF in vitro are largely due to cross-reaction, owing to their structural homology as well as that of their receptors. At physiological concentrations, insulin is not mitogenic. Compared with insulin, IGFs have negligible metabolic effects on hepatocytes or adipocytes. However, the presence of the IGF-I receptor in muscle accounts for IGF physiological effects in vivo on glucose uptake and glycogen synthesis. Moreover, recombinant IGF-I administered subcutaneously to healthy subjects or patients with Type 2 diabetes causes a drop in plasma levels of triglycerides and VLDL as well as cholesterol and LDL, but not HDL, and also increases insulin sensitivity. All these responses reflect IGF-I inhibition of insulin and GH secretion. In biological media, IGF-I and IGF-II are reversibly associated with specific high-affinity (10(9)-10(11) M-1) binding proteins (IGFBP-1 to -6) differing in expression according to tissue of origin and playing a variety of roles in IGF transport and half-lives, delivery of IGFs to their target cells and modulation of IGF interactions with their receptors. In the blood, where IGF concentrations are 1,000 times those of insulin, IGFBP-3 (the major form) binds at least 80% of IGFs as 140-kDa complexes which do not cross the capillary endothelium and therefore prevent the insulin-like action of IGFs. Nevertheless, these circulating IGF reserves may be mobilized in response to metabolic needs via limited proteolysis of IGFBP-3 by serine proteases. In the case of IGFBP-1, whose hepatic synthesis is negatively regulated by insulin, plasma concentrations are subject to extensive nycthemeral variation, rising with fasting and dropping after feeding, which may be involved in controlling the access of free IGF-I to its cellular receptors and hence IGF-I-regulated glucose and amino acid uptake. Therapeutic applications of recombinant human IGF-I, currently under trial in the treatment of growth retardation resulting from GH receptor abnormalities, hypercatabolic states and would repair, may also be envisaged for cases of insulin resistance, particularly type 2 diabetes.
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PMID:The IGF system in metabolism regulation. 858 49

We have examined the regulation of endothelial IGFBP-3 production by IGF-I and TGF-beta, two growth factors thought to play a major roles in the complications of diabetes mellitus. In addition, we developed a sensitive method for IGFBP-3 mRNA quantitation by adapting the fluorescent modification of the competitive PCR strategy. Our results using both Northern analysis and the fluorescent competitive PCR method indicate that: (1) IGFBP-3 mRNA is increased 2- to 10-fold by IGF-I and maximally reduced to 20% of control by TGF-beta; (2) the changes in mRNA levels correlate with the levels of IGFBP-3 protein secreted into the media by these cells; (3) the induction of IGFBP-3 mRNA and protein by IGF-I analogs was directly related to their ability to bind to the type I IGF receptor, reflecting an IGF-I receptor-mediated process; and (4) steady state IGFBP-3 mRNA levels did not change significantly after a 6 h incubation with actinomycin D in the presence or absence of the growth factors suggesting that the observed IGF-I/TGF-beta effects occur at the level of gene transcription rather than mRNA stability.
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PMID:Regulation of endothelial IGFBP-3 synthesis and secretion by IGF-I and TGF-beta. 871 44

Renal hypertrophy is a characteristic and early manifestation of diabetes in humans and experimental animals. We examined the precise distribution of insulin-like growth factor-I (IGF-I) mRNA and IGF-I receptor mRNA in the experimental diabetic rat kidney using a nonradioactive in situ hybridization technique. No significant difference in the distribution of IGF-I mRNA was found between the diabetic and control rats. IGF-I mRNA-positive cells were found in the collecting ducts and in scattered single cells in the distal tubules. The number of IGF-I mRNA-positive cells was very low in the glomeruli. Expression of IGF-I receptor mRNA was rarely seen in the glomeruli of control rats. IGF-I receptor mRNA was detected after induction of diabetes in glomerular mesangial, visceral epithelial, and parietal epithelial cells. The number of IGF-I receptor mRNA-positive cells in a glomerulus increased significantly, peaking at 4 weeks as compared with the control rats. Overexpression of IGF-I receptor in glomerular cells, especially mesangial and visceral epithelial cells, may contribute to glomerular hypertrophy in diabetic nephropathy.
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PMID:Increased gene expression of insulin-like growth factor-i receptor in experimental diabetic rat glomeruli. 873 Apr 36

The mechanism of TNF-alpha to regulate glucose metabolism remains unclear. To further delineate the TNF-alpha signal transduction pathway mediating glucose metabolism, we utilized L6 rat myoblasts which contain the receptors for the insulin-like growth factor-I (IGF-I) and TNF-alpha, and the ability of both ligands to stimulate glucose uptake was compared. IGF-I (6.5 nM) maximally stimulated glucose uptake 7-fold after 24 h incubation, while 23 nM TNF-alpha maximally stimulated glucose uptake 3-fold only after 48 h incubation. IGF-I receptor beta-subunit, insulin receptor substrate-1 (IRS-1), and mitogen-activated protein (MAP) kinase were all phosphorylated in response to 6.5 nM IGF-I after 10 min incubation. In contrast, the treatment with 23 nM TNF-alpha failed to phosphorylate either IGF-I receptor beta-subunit or IRS-1 but did phosphorylate MAP kinase as much as IGF-I did. Despite a similar extent to which TNF-alpha induced MAP kinase phosphorylation as IGF-I did, TNF-alpha stimulated glucose uptake less compared to IGF-I. The results indicate that MAP kinase phosphorylation is not sufficient for glucose uptake in L6 myoblasts. TNF-alpha-elicited signal transduction to glucose uptake may utilize a different pathway from that seen with IGF-I.
Diabetes Res Clin Pract 1996 Apr
PMID:TNF-alpha stimulates glucose uptake in L6 myoblasts. 880 77

Recent evidence suggests that several growth factors participate in diabetic glomerular disease by mediating increased extracellular matrix accumulation and altered cell growth and turnover leading to mesangial expansion. Transforming growth factor (TGF)-beta has been demonstrated to be upregulated both in vivo and in vitro, whereas studies on the activity of the renal insulin-like growth factor (IGF) system in experimental diabetes have provided conflicting results. We investigated the effects of prolonged exposure (4 weeks) of cultured human and rat mesangial cells to high (30 mmol/l) glucose vs iso-osmolar mannitol or normal (5.5 mmol/l) glucose levels on: 1) the autocrine/paracrine activity of the IGF system (as assessed by measuring IGF-I and II, IGF-I and II receptors, and IGF binding proteins); and, in parallel, on 2) TGF-beta 1 gene expression; 3) matrix production; and 4) cell proliferation. High glucose levels progressively increased the medium content of IGF-I and the mRNA levels for IGF-I and IGF-II, increased IGF-I and IGF-II binding and IGF-I receptor gene expression, and reduced IGF binding protein production. TGF-beta 1 transcripts and matrix accumulation and gene expression were increased in parallel, whereas cell proliferation was reduced. Iso-osmolar mannitol did not affect any of the above parameters. These experiments demonstrated that high glucose levels induce enhanced mesangial IGF activity, together with enhanced TGF-beta 1 gene expression, increased matrix production, and reduced cell proliferation. It is possible that IGFs participate in mediating diabetes-induced changes in matrix turnover leading to mesangial expansion, by acting in a paracrine/autocrine fashion within the glomerulus.
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PMID:Increased activity of the insulin-like growth factor system in mesangial cells cultured in high glucose conditions. Relation to glucose-enhanced extracellular matrix production. 881 1

Specific changes in circulating levels of insulin-like growth factor I (IGF-I) and various IGF-binding proteins are known to occur in insulin-dependent diabetic patients and laboratory animals. However, little attention has been paid to the effects of this chronic metabolic disease on the IGF system of the central nervous system. Because various types of human cerebellar degeneration are accompanied by changes in the peripheral IGF-I system which are similar, although not identical, to those found in diabetes, we tested whether diabetes results in changes in the cerebellar IGF-I system. Streptozotocin-induced diabetic rats were divided into two groups: 1) well controlled diabetics, which received twice daily injections of insulin and had mean glucose levels in the normal range; and 2) poorly controlled diabetic animals, which received 1 U of insulin once a day and had glucose levels above 300 mg/dl. As previously described, there were significant decreases in circulating levels of IGF-I and IGFBP-3 (38-42 kDa band), and an increase in the 30-kDa IGFBP (likely corresponding to IGFBP-1) in poorly controlled diabetic animals. All these parameters were normal in well controlled diabetic rats. In addition, significant modifications in the cerebellar IGF-I system were found. Poorly controlled diabetic animals had significantly lower levels of IGF-I protein in the cerebellum, whereas no change in cerebellar IGF-I messenger RNA (mRNA) levels was found. A significant reduction in IGFBP-2 (31 kDa-band) protein and mRNA levels was also found in poorly controlled diabetics. Well controlled rats had normal cerebellar IGF-I levels, whereas levels of IGFBP-2 protein and mRNA were still significantly low. Finally, mRNA levels for the IGF-I receptor were similar in all experimental groups. These changes appear to be anatomically specific because other brain areas did not show the same alterations. The present results indicate that in the diabetic animal changes in circulating IGF-I and IGFBPs are accompanied by, and possibly implicated in, modifications of the IGF-I system in the cerebellum and possibly other brain regions. We suggest that modifications in the cerebellar, IGF-I system, which plays an important trophic role in postnatal life, may underlie, at least in part, specific neuronal losses known to occur in diabetic patients.
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PMID:Specific alterations of the insulin-like growth factor I system in the cerebellum of diabetic rats. 889 71

Streptozotocin (STZ)-induced diabetes in the rat causes early renal enlargement preceded by a transient elevation in IGF-I content and an increase in IGF-I tissue binding. The effects of IGF-I are mainly mediated through the IGF-I receptor (IGF-IR) and modulated by six specific IGF-binding proteins (IGFBPs). We investigated the gene expression of IGF-I, IGF-IR and IGFBPs at a cellular level within the kidney using in situ hybridisation techniques in short-term (7 day) STZ-diabetic, insulin-treated euglycaemic and normal rats. In diabetes, IGFBP-1 mRNA showed markedly increased expression in distal tubules, collecting ducts and thick ascending limbs of Henle (TALs). IGF-I, and IGFBP-4 and -5 mRNAs showed site-specific tubular changes whilst remaining unchanged in other parts of the kidney normally expressing the genes: IGF-I and IGFBP-4 mRNAs were reduced in TALs and proximal tubules respectively; IGFBP-5 mRNA was reduced in most distal tubular cells but strongly expressed in a few of these cells. IGF-IR mRNA and the mRNAs for IGFBP-2, -3 and -6 were unchanged in STZ diabetes. There was no difference between control and insulin-treated kidneys. These complex changes suggest possible involvement of the IGF/IGFBP system in the early stages of diabetic renal hypertrophy.
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PMID:Cell-specific regulation of mRNAs for IGF-I and IGF-binding proteins-4 and -5 in streptozotocin-diabetic rat kidney. 906 2

Since insulin-like growth factor-I (IGF-I) has been shown to promote renal growth and as kidney IGF-I content increases during the early days after the onset of diabetes, it is likely that this growth factor contributes to initial diabetic renal hypertrophy. However, it is unclear whether IGF-I contributes to the continued renal growth that occurs in diabetes. Since IGF-I action is mediated through its receptor and as its bioavailability is regulated by IGF binding proteins (IGFBP), we postulated that changes in IGF-I receptor binding or IGFBP production may favor a role for IGF-I in diabetic renal growth when kidney IGF-I levels have returned to normal. To test this thesis, we studied kidneys of rats after seven days of streptozotocin diabetes. In diabetic cortex and medulla, growth hormone receptor mRNA levels and IGF-I and IGF-I receptor mRNA and protein product levels were unchanged. In cortex IGFBP-1 mRNA levels were increased while IGFBP-2 and -4 mRNA levels decreased. In medulla the only change was a fall in IGFBP-1 mRNA levels. Using Western ligand blot we observed an increase in a 32 kDa plasma membrane-associated IGFBP. Insulin therapy reversed all changes except the elevated cortical IGFBP-1 mRNA levels, indicating the presence of regional heterogeneity in the IGFBP response to diabetes in the kidney. However, the lack of change in IGF-I, IGF-I receptor and growth hormone receptor gene expression and protein products after one week of diabetes argues against a role for IGF-I in sustaining diabetic renal growth beyond the initial growth phase.
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PMID:Regional changes in the intrarenal insulin-like growth factor-I axis in diabetes. 906 15

The non-obese diabetic mouse is a model of spontaneous insulin-dependent diabetes as a result of autoimmune destruction of pancreatic beta cells, similar to the disease seen in human Type I diabetes. This mouse strain develops glomerular lesions reminiscent of those seen in human disease. The study presented here investigated the changes in renal insulin-like growth factor (IGF) system in hyperglycemic non-obese diabetic mice. Female non-obese diabetic mice and their age- and sex-matched controls were euthanized 4 days, 2 wk, and 4 wk after the onset of glycosuria. Kidney weight increased in diabetic mice, beginning at 2 wk after the onset of glycosuria. This renal hypertrophy was associated with an increase in renal extractable IGF-I protein. However, a decrease in IGF-I mRNA was observed at the same time. Serum IGF-I levels remained stable after 2 wk of diabetes and decreased at 1 month. No change was detected in renal IGF-I receptor mRNA levels. Renal cortical IGF binding protein (IGFBP)-1 mRNA levels were increased. Ligand blot analysis revealed a significant increase in serum and renal 30-kd IGFBP and a decrease in serum and kidney IGFBP-3 and IGFBP-4 at 30 days of diabetes. Insulin therapy prevented the increases in kidney weight, renal IGF-I, and 30-kd IGFBP, but did not reverse the decreased serum IGF-I levels observed at 1 month of diabetes. In summary, renal hypertrophy in non-obese diabetic mice is associated with a persistent accumulation of renal IGF-I and, IGFBP-1. These changes were partially reversed with insulin therapy, which did not correct the hyperglycemia, suggesting an important role for insulin deficiency in mediating these changes in the IGF system. These findings suggest that the IGF system may play a potential role in the development of diabetic nephropathy.
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PMID:Renal hypertrophy in hyperglycemic non-obese diabetic mice is associated with persistent renal accumulation of insulin-like growth factor I. 907 12

The structure of IGF-I is similar to that of insulin, having 43% sequence homology with human proinsulin. Both peptides can induce metabolic and mitogenic effects through their own specific receptors, which also share many structural and functional similarities. Primarily involved in the regulation of growth, IGF-I may have a role in the control of glucose homeostasis, facilitated by changes in its binding proteins. RhIGF-I can reduce hyperglycaemia in patients with severe insulin resistance by direct effects mediated via the IGF-I receptor. Improvements in insulin sensitivity, and reductions in blood glucose levels and HbA1c values have also been seen in subjects with NIDDM. Enhanced insulin sensitivity with low dose rhIGF-I has been observed in adolescents and young adults with IDDM. These effects are closely related to reductions in growth hormone levels, but there is also evidence of complex interactions with insulin at the post receptor level and with IGFBP-1. In recent randomised, double-blind, placebo controlled trials, rhIGF-I given as an adjunct to insulin therapy reduced to HbA1c values. Although the ideal dosage to obtain therapeutic efficacy without complications has yet to be determined, rhIGF-I may have an important role in the treatment of hyperglycaemia and insulin resistance in diabetes.
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PMID:Does recombinant human insulin-like growth factor-1 have a role in the treatment of diabetes? 930 Feb 21


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