Angiotensin-converting enzyme gene single polymorphism as a genetic biomarker of diabetic peripheral neuropathy: longitudinal prospective study

BackgroundIdentifying patients at risk of developing diabetic peripheral neuropathy (DPN) is of paramount importance in those with type 2 diabetes mellitus (T2DM) to provide and anticipate secondary prevention measures as well as intensify action on risk factors, particularly so in primary care. Noteworthy, the incidence of DPN remains unknown in our environment.Aims(i) To analyze a single angiotensin-converting enzyme (ACE) gene polymorphism (D/I) as a genetic marker of risk of developing DPN, and (ii) to determine the incidence of DPN in our environment.Research design and methodsLongitudinal study with annual follow-up for 3 years involving a group of T2DM (N = 283) randomly selected. ACE gene polymorphism distribution (I = insertion; D = deletion) was determined. DPN was diagnosed using clinical and neurophysiology evaluation.ResultsBaseline DPN prevalence was 28.97% (95% CI, 23.65–34.20). ACE polymorphism heterozygous genotype D/I presence was 60.77% (95% CI, 55.05–66.5) and was independently associated with a decreased risk of DPN (RR, 0.51; 95% CI, 0.30–0.86). DPN correlated with age (P < 0.001) but not with gender (P = 0.466) or time of evolution of T2DM (P = 0.555). Regarding end point, DPN prevalence was 36.4% (95% CI, 30.76–42.04), and accumulated incidence was 10.4% 3 years thereafter. In the final Poisson regression analysis, the presence of heterozygous genotype remained independently associated with a decreased risk of DPN (RR, 0.71; (95% CI, 0.53–0.96). DPN presence remained correlated with age (P = 0.002), but not with gender (P = 0.490) or time of evolution (P = 0.630).ConclusionsIn our series, heterozygous ACE polymorphism (D/I) stands as a protective factor for DPN development. Accumulated incidence of DPN was relevant. Further prospective studies are warranted.     

转化生长因子β在糖尿病肾病发生中的作用

糖尿病肾病(DN)是糖尿病(DM)患者常见和特异的微血管并发症,其发病机制尚未完全明确,转化生长因子(TGF)-β特别是TGF-β1在DN的发病中发挥了重要作用,阻断TGF-β1的过度表达、抑制或降低其生物活性,有可能成为一种新的预防和治疗DN的有效措施.本文就TGF-β的生物学特性、在DN发生中的作用及目前所作的相关研究做一简单综述.     

Transforming growth factor beta1: implications in adrenocortical tumorigenesis

TGFbeta1, a multifunctional growth modulator, inhibits the proliferation of epithelial cells. TGFbeta1 signaling is dependent on the heterodimerization of the TGFbeta1 receptor II (TGFbeta1RII) with the TGFbeta1 receptor I (TGFbeta1RI). The cytoplasmic proteins Smads are the mediators of the TGFbeta1 signal. TGFbeta1 regulates adult and fetal adrenal growth and function. Previously we have shown by Northern analysis that TGFbeta1mRNA was well expressed in normal adrenal and in adrenocortical adenomas but reduced in carcinomas. To investigate whether TGFbeta1 receptors may act as tumor suppressors of adrenal tumorigenesis, 16 adenomas and 12 carcinomas were studied. We have used SSCP analysis to scan for inactivating mutations in carcinomas. All tumor samples were negative for somatic alterations of both genes. A competitive RT-PCR system was developed to compare the levels of expression of TGFbeta1, TGFbeta1R-I and TGFbeta1R-II, Smad-2 and Smad-4 genes in all tumors. In our study, we confirmed the presence of reduced levels of TGFbeta1 in carcinomas. On the contrary, Smad-4 gene levels were elevated in carcinomas when compared to that of adenomas. No significant differences were observed in gene expression of TGFbeta1RI and Smad-2. Our results suggest that mutations of TGFbeta1 receptors appear not to be involved in adrenal tumorigenesis. Adrenal carcinomas showed a significant reduction of the TGFbeta1 mRNA levels but on the contrary Smad 4 mRNA levels were significantly increased.     

Transforming growth factor beta as a virulence mechanism for Leishmania braziliensis.

Transforming growth factor beta (TGF-beta) has potent down-regulating effects on macrophages and is thus capable of influencing the fate of intramacrophage parasites, including leishmanias. We report the development of a mouse model for the study of the human pathogen Leishmania braziliensis and demonstrate, both in vitro and in vivo, a key regulatory role for TGF-beta in the pathogenesis of infection with this parasite. Recombinant TGF-beta added to cultures of murine peritoneal macrophages led to increased intracellular L. braziliensis replication, whereas addition of neutralizing anti-TGF-beta monoclonal antibody decreased levels of infection. Macrophages infected with L. braziliensis produced biologically active TGF-beta, with a direct correlation between amounts of TGF-beta induced by two parasite isolates and their relative virulence. In vivo, treatment with recombinant TGF-beta rendered avirulent parasites virulent and activated latent L. braziliensis infection. Activation of parasite replication was observed in mice which had been infected with L. braziliensis 15 weeks previously but had not developed lesions or had healed lesions, depending on the parasite isolate used to infect the mice. The exacerbation of L. braziliensis infection in vivo was associated with an increase of interleukin 10 mRNA in the draining lymph node. These results demonstrate that TGF-beta is able to alter the course of in vitro and in vivo infections with L. braziliensis, the latter being characterized by an increase in interleukin 10, an important Th2 helper-T-cell cytokine.     

Transforming growth factor beta 1: an autocrine regulator of adrenocortical steroidogenesis

Transforming growth factor beta 1 (TGF beta 1) is a member of a large family of structurally related regulatory polypeptides which comprises both functionally similar (TGF beta 1, TGF beta 2, TGF beta 3, TGF beta 4 and TGF beta 5) and functionally distinct proteins. In the past few years, TGF beta 1 has emerged as a multifunctional protein. One of its remarkable properties is its capacity to negatively modulate the differentiated, steroidogenic adrenocortical functions. We present here a review of the results from our recent work related to the effects of TGF beta 1 on bovine adrenocortical cell (zona fasciculata-reticularis) functions. We identified the steroid 17 alpha-hydroxylase (P-450 17 alpha) biosynthetic enzyme and the angiotensin II receptor as major targets whose expression are negatively regulated by TGF beta 1 in these cells. We characterized TGF beta 1 receptors at the surface of adrenocortical cells (mainly type I and type III receptors) and observed that their number is increased under ACTH treatment. Furthermore, we could detect the presence of immunoreactive TGF beta 1 in the bovine adrenal cortex whereas it was undetectable in the adrenal medulla and in the capsule. We also observed that adrenocortical cells secrete TGF beta 1 under a latent form together with large amounts of alpha 2-macroglobulin, a protease inhibitor known to be implied in the latency of TGF beta in serum. Taken together, these observations led us to a working hypothesis, proposing TGF beta 1 as an autocrine and/or paracrine regulator of adrenocortical steroidogenic functions. This concept points out the physiological activation of the latent TGF beta 1 complex as the important limiting step controlling its action in the adrenal cortex.     

Transforming growth factor beta induces fibroblast fibrillin-1 matrix formation

OBJECTIVE: Fibrillin, an extracellular matrix protein implicated in dermal fibrosis, is increased in the reticular dermis of systemic sclerosis (SSc) skin. We undertook this study to investigate the hypothesis that transforming growth factor beta (TGFbeta) or other cytokines regulate fibrillin matrix formation by normal and SSc fibroblasts. We further investigated the mechanism of TGFbeta-induced fibrillin fibrillogenesis and its relationship to myofibroblasts. METHODS: Fibrillin and fibronectin matrix deposition and alpha-smooth muscle actin expression by fibroblast cultures from normal and SSc skin treated with TGFbeta or other cytokines were analyzed by immunofluorescence. Supernatant and extracellular matrix from normal and SSc fibroblasts treated with or without TGFbeta were evaluated by Western blot and Northern blot for fibrillin protein and messenger RNA (mRNA) expression, respectively. RESULTS: Immunofluorescence demonstrated increased fibrillin matrix formation by normal and scleroderma fibroblasts after TGFbeta treatment. Other cytokines, including tumor necrosis factor alpha, interleukin-1beta (IL-1beta), IL-4, granulocyte-macrophage colony-stimulating factor, and platelet-derived growth factor, did not affect fibrillin fibrillogenesis. Fibrillin matrix formed in proximity to myofibroblasts and independently of up-regulation of fibronectin matrix or cell number. Western blot analysis of extracellular matrix confirmed increased fibrillin after TGFbeta stimulation of normal or scleroderma fibroblasts. However, TGFbeta did not alter the expression of either soluble fibrillin protein or fibrillin mRNA. CONCLUSION: Our data show that TGFbeta induces fibrillin protein incorporation into the extracellular matrix without affecting fibrillin gene expression or protein synthesis, suggesting that fibrillin matrix assembly is regulated extracellularly. TGFbeta might increase fibrillin matrix by activating myofibroblasts. Such TGFbeta-mediated effects could account for the increased fibrillin matrix observed in SSc skin.     

Transforming growth factor beta1 gene polymorphism in rheumatoid arthritis

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic inflammatory disease and synovial cells, antigen presenting cells, lymphocytes, and their cytokines might be associated with the disease. Transforming growth factor beta1 (TGFbeta1) has been reported to have important roles in unresolved inflammation, immune suppression, fibrosing processes, and angiogenesis. TGFbeta1 is highly expressed in joints in RA and is considered to be a regulator of anti-inflammation in RA. Polymorphisms of TGFbeta1 have been reported to be associated with the production of TGFbeta1 protein, and to increase the risk of acquiring several diseases. It was speculated that these polymorphisms might also be involved in RA, and therefore the TGFbeta1 codon 10 T869C polymorphism in a series of patients and controls was investigated. METHOD: A total of 155 patients with RA and 110 healthy subjects were studied. DNA was extracted from peripheral leucocytes and TGFbeta1 codon 10 T869C polymorphism was determined by polymerase chain reaction restriction fragment polymorphism. RESULTS: A significantly higher proportion of patients with RA with the T allele (CT type or TT type) was found compared with the CC type (p=0.039). CONCLUSION: The T allele, previously reported to be linked with production of TGFbeta1, may be associated with an increased risk of RA.     

Nerve growth factor and diabetic neuropathy

Neuropathy is one of the most debilitating complications of both type 1 and type 2 diabetes, with estimates of prevalence between 50-90% depending on the means of detection. Diabetic neuropathies are heterogeneous and there is variable involvement of large myelinated fibers and small, thinly myelinated fibers. Many of the neuronal abnormalities in diabetes can be duplicated by experimental depletion of specific neurotrophic factors, their receptors or their binding proteins. In experimental models of diabetes there is a reduction in the availability of these growth factors, which may be a consequence of metabolic abnormalities, or may be independent of glycemic control. These neurotrophic factors are required for the maintenance of the neurons, the ability to resist apoptosis and regenerative capacity. The best studied of the neurotrophic factors is nerve growth factor (NGF) and the related members of the neurotrophin family of peptides. There is increasing evidence that there is a deficiency of NGF in diabetes, as well as the dependent neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) that may also contribute to the clinical symptoms resulting from small fiber dysfunction. Similarly, NT3 appears to be important for large fiber and IGFs for autonomic neuropathy. Whether the observed growth factor deficiencies are due to decreased synthesis, or functional, e.g. an inability to bind to their receptor, and/or abnormalities in nerve transport and processing, remains to be established. Although early studies in humans on the role of neurotrophic factors as a therapy for diabetic neuropathy have been unsuccessful, newer agents and the possibilities uncovered by further studies should fuel clinical trials for several generations. It seems reasonable to anticipate that neurotrophic factor therapy, specifically targeted at different nerve fiber populations, might enter the therapeutic armamentarium.     

Transforming growth factor beta 1 regulates production of acute-phase proteins.

We explored the possible role of transforming growth factor beta 1 (TGF-beta), a cytokine that appears to be an important modulator of inflammation and tissue repair, in regulation of human plasma protein synthesis during the acute-phase response. In Hep 3B cells, TGF-beta led to increased secretion of the positive acute-phase proteins alpha 1-protease inhibitor and alpha 1-antichymotrypsin and decreased secretion of the negative acute-phase protein albumin. In Hep G2 cells, after incubation with TGF-beta, the same changes in secretion of alpha 1-protease inhibitor, alpha 1-antichymotrypsin, and albumin were observed, as well as decreased secretion of both the negative acute-phase protein alpha-fetoprotein and the positive acute-phase protein fibrinogen. In addition, TGF-beta modulated the effects of interleukin 6; these cytokines, in combination, were additive in inducing synthesis and secretion of alpha 1-protease inhibitor and alpha 1-antichymotrypsin and in decreasing secretion of albumin and alpha-fetoprotein. TGF-beta inhibited the induction of fibrinogen caused by interleukin 6. The effects on alpha 1-protease inhibitor were confirmed by metabolic labeling in Hep 3B cells and by demonstrating increased accumulation of specific mRNA in Hep G2 cells, and the effects on fibrinogen were confirmed in Hep 3B cells by studies of mRNA for the alpha chain of fibrinogen. TGF-beta had no effect on haptoglobin or alpha 1-acid glycoprotein secretion, either directly or in the presence of interleukin 6, which is capable of inducing these proteins. These studies demonstrate that TGF-beta can affect hepatic synthesis and secretion of a subset of acute-phase proteins, both directly and by modulating the effect of interleukin 6. The affected group of plasma proteins is distinct from those affected by other recognized acute-phase protein-inducing cytokines. These findings support the view that combinations of cytokines mediate the response of the hepatocyte to inflammatory stimuli.     

血压控制不佳是痛性糖尿病周围神经病变的危险因素:前瞻性队列研究

目的通过前瞻性研究设计明确血压控制不佳是否为痛性糖尿病周围神经病变(DPN)发病的危险因素。方法本研究为前瞻性研究。自2014年起从上海5家社区卫生中心纳入年龄≥18岁未诊断DPN的患者。记录所有患者在基线纳入和随访结束时的基本资料、实验室检查和密西根神经病变筛查量表检查结果,并在随访结束时接受神经病理性疼痛问卷评估和神经传导功能检查。根据痛性DPN标准,将患者分为非DPN组、痛性DPN组和无痛性DPN组。比较非DPN组、痛性DPN组和无痛性DPN组患者基线及随访时临床资料,分析痛性DPN组和无痛性DPN组患者基线(收缩压、舒张压)、随访(收缩压、舒张压)以及随访和基线时血压差值的差异,并采用χ²检验比较血压控制不佳组(≥130/80 mmHg,1 mmHg=0.133 kPa)和血压控制良好组(<130/80 mmHg)痛性DPN发生率的差异,采用多因素logistic回归模型进一步分析血压控制不佳与痛性DPN之间的关系。结果最终纳入315例T2DM患者,随访(5.06±1.14)年,将患者分为非DPN组152例、痛性DPN组74例和无痛性DPN组89例。与非DPN组患者相比,痛性DPN组和无痛性DPN组患者基线的年龄、腰围和空腹血糖明显升高,差异有统计学意义(P<0.05);痛性DPN组患者基线时的糖尿病病程、收缩压和舒张压明显高于非DPN组患者(P<0.05)。痛性DPN组患者随访时的收缩压(P=0.030)和舒张压(P=0.007)明显高于无痛性DPN组,差异有统计学意义(P<0.05)。基线血压控制不佳组患者132例,血压控制良好组患者30例,基线血压控制不佳组痛性DPN的发生率49.24%(65/132)高于基线血压控制良好组26.67%(8/30),差异有统计学意义(P=0.025)。校正体重指数、糖化血红蛋白、年龄、性别、吸烟、饮酒、T2DM病程、总胆固醇、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇、服用血管紧张素转化酶抑制剂、其他降压药及二甲双胍后,血压控制不佳仍然与痛性DPN相关(OR=17.921,95%CI为1.497~214.593)。结论血压控制不佳为T2DM患者痛性DPN的危险因素。     

Transforming growth factor beta1 induction of vascular endothelial growth factor receptor 1: mechanism of pericyte-induced vascular survival in vivo

Degeneration of vessels precedes and precipitates the devastating ischemia of many diseases, including retinopathy of prematurity and diabetic retinopathy. Ischemia then leads to proliferative retinopathy and blindness. Understanding the mechanisms of blood vessel degeneration is critical to prevention of these diseases. Vessel loss is associated with oxygen-induced suppression of vascular endothelial growth factor (VEGF) and with pericyte (vascular smooth muscle cell) dropout. The molecular mechanism of pericyte protection of the vasculature is unknown. We show that transforming growth factor beta1 (TGF-beta1)-expressing pericytes are specifically found on vessels resistant to oxygen-induced loss. TGF-beta1 potently induces VEGF receptor 1 (VEGFR-1) expression in endothelial cells and thereby prevents oxygen-induced vessel loss in vivo. Vessel survival is further stimulated with a VEGFR-1-specific ligand, placental growth factor 1. TGF-beta1 induction of VEGFR-1 in endothelial cells explains pericyte protection of vessels and the selective vulnerability of neonatal vessels to oxygen. These results implicate induction and activation of VEGFR-1 as critical targets to prevent vessel loss.     

Transforming growth factor beta can be a parameter of aggressiveness of pT1 colorectal cancer

AIM: To evaluate the significance of transforming growth factor beta (TGF β) expression, in correlation with histopathological parameters, at the front of invasion in T1 colorectal cancer (CRC) and presence of metastases. METHODS: TGF p immunohistochemical expression was studied in 34 specimens of colorectal adenocarcinomas (pT1). A three-step avidin-biotinylated immuno-peroxidase (ABCu-NCL) staining technique was performed on 4-μm paraffin-embedded tissue sections with a monoclonal antibody to TGF β (Novocastra, NCL-TGFB, clone TGFB 17, dilution 1:40). RESULTS: Seventeen (50%) out of 34 lesions were positive for TGF p expression. The TGF β-positive rate in patients with vascular invasion was significantly higher than in those without vascular invasion (11/14 cases, P<0.01, P= 0.005). The TGF p-positive rate was observed in 91.7% of patients with presence of tumor budding at the front of invasion (11/12 cases, P<0.01, P= 0.0003). A statistically significant correlation was found between the presence of lymph node metastases and positive expression of TGF β (14/16 cases, P<0.01, P= 0.0001). We also observed that the TGF β-positive rates in groups with distant and non-distant metastases were 92.8% and 20% respectively, and a significant correlation between TGF β expression and distant metastasis was shown (P<0.01, P= 0.00003). CONCLUSION: The evaluation of TGF β expression of protein in association with histological parameters can be used as a parameter of the aggressiveness of pT1 CRC.     

Transforming growth factor beta inhibits megakaryocyte growth and endomitosis.

Using a rat bone marrow culture system, the effect of transforming growth factor beta 1 (TGF beta 1) on megakaryocyte growth and endoreduplication has been studied. Purified human platelet TGF beta 1 inhibited the number of megakaryocytes that appeared in culture at a half-maximal concentration of 0.66 +/- 0.21 ng/mL and inhibited megakaryocyte endoreduplication at a half-maximal concentration of 0.14 +/- 0.08 ng/mL. Under identical conditions, growth of erythroid precursors was half-maximally inhibited at a concentration of 0.125 ng/mL while myeloid growth was not inhibited at concentrations of TGF beta 1 up to 25 ng/mL. These profound inhibitory effects on megakaryocyte growth and endomitosis suggested that TGF beta might play a role in megakaryocytopoiesis. Therefore, we explored the effect of TGF beta in three different experimental situations by using a neutralizing antibody to TGF beta: (1) Serum but not plasma was found to inhibit the number and ploidy of megakaryocytes that grew in vitro. This inhibitory activity was completely neutralized by antibody to TGF beta or on treatment with dithiothreitol. (2) Plasma from thrombocytotic rats was observed to decrease megakaryocyte ploidy on culture but this effect was not prevented by the addition of antibody to TGF beta. (3) Plasma from thrombocytopenic but not normal rats increased megakaryocyte ploidy on culture. Addition of antibody to TGF beta did not alter these results. Therefore, TGF beta is a potent inhibitor of the number and ploidy of megakaryocytes and accounts for all the inhibition seen when megakaryocytes are cultured in serum. However, the differences in effect on megakaryocyte growth that we observe between normal, thrombocytopenic, and thrombocytotic plasmas are not due to variations in the amount of TGF beta. Furthermore, our results show that release of TGF beta from megakaryocytes during culture does not act as an autocrine regulator of megakaryocyte ploidy in vitro.     

Transforming growth factor beta1 gene polymorphism in patients with systemic sclerosis

OBJECTIVE: To determine whether transforming growth factor beta1 (TGFbeta1) gene DNA polymorphism is associated with pathogenesis in the fibrosis of patients with systemic sclerosis (SSc). METHODS: Eighty-seven Japanese patients with SSc including 30 with diffuse type and 57 with limited type together with 110 unrelated controls were investigated. Pulmonary fibrosis was determined in 34 SSc patients using high-resolution chest computed tomography. TGFbeta1 genetic polymorphisms were analyzed in 2 loci; T869C (Leu10Pro) in codon 10 at exon 1, and C-509T in the promoter region using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: Neither the genotype of T/C polymorphism in T869C nor C/T polymorphism in C-509T revealed any difference in distribution between SSc and controls. In the group of SSc patients with pulmonary fibrosis, a weak but significantly high frequency (p = 0.05) of TC+CC (the presence of C allele) in T869C, and CT+TT (the presence of T allele) in C-509T was found. Compared with controls, the pulmonary fibrosis group showed no difference in the highly frequent alleles. CONCLUSION: Our results suggest that TGFbeta1 polymorphisms do not play a role in the pathogenesis of SSc, even though there remains the possibility of a risk factor for genetic susceptibility to pulmonary fibrosis.     

Transforming growth factor beta at clinical onset of Type 1 diabetes mellitus. A pilot study.

AIMS: The aims of the study were to determine whether transforming growth factor beta1 TGF-beta1 levels are raised at diagnosis of Type 1 diabetes mellitus and are related to blood glucose. SUBJECTS AND METHODS: Fourteen patients (mean age 24.3 +/- 4.9 years) admitted to hospital for onset of Type 1 diabetes were studied. On the first day of hospitalization, before insulin therapy, and at 1, 4 and 16 weeks, fasting blood glucose, HbA(1c), lipid profile and TGF-beta1 levels and TGF-beta1 levels in 24-h urine were determined. The control group included 14 non-diabetic subjects with similar characteristics to those of the diabetic group. RESULTS: Plasma and urinary TGF-beta1 levels were significantly lower in controls (4.7 (1.6-6.8) ng/ml P < 0.001; 5.7 (1.5-8.5) ng/mg urinary creatinine, P < 0.01) than in patients with Type 1 diabetes mellitus [10.5 (1.8-24.9) ng/ml; 10.1 (4.2-29.8) ng/mg urinary creatinine]. On study completion, HbA(1c) fell from 11.6 +/- 2.0 to 5.4 +/- 0.6% (P < 0.001). Improved metabolic control was not associated with changes in plasma (9.4 (2.6-19.5)/5.9 (1.6-21.5)/7.0 (2.3-30.2)/10.5 (1.8-24.9) ng/ml at baseline, 1, 4 and 16 weeks, respectively) or urinary (12.0 (4.7-29.5)/10.9 (1.5-20.5)/8.7 (4.3-16.9)/10.1 (4.2-29.8) ng/mg urinary creatinine) TGF-beta1 levels. A statistically significant correlation was observed between plasma TGF-beta1 and insulin dosage (U/kg/day) (r = 0.52, P = 0.037). CONCLUSIONS: The increased TGF-beta1 production observed herein was not modulated by glycaemic reduction and could be a response to immuno-inflammatory activation present at the onset of Type 1 diabetes.     

Elevated plasma insulin-like growth factor binding protein-1 levels in Type 1 (insulin-dependent) diabetic patients with peripheral neuropathy

Summary Previous studies have suggested that nerve regeneration may be defective in patients with diabetic polyneuropathy. Since insulin-like growth factor I (IGF-I) has been shown to stimulate nerve regeneration, and IGF binding protein-1 is acutely regulated by plasma insulin we have investigated the relationships between plasma IGF-I, IGFBP-1, glucose and insulin in Type 1 (insulin-dependent) diabetic patients with peripheral polyneuropathy. Plasma samples were taken at hourly intervals over an 11-h period (08.00–19.00 hours) in order to characterise secretory profiles for 15 Type 1 diabetic patients (eight neuropathic and seven non-neuropathic) and eight non-diabetic control subjects. In the non-diabetic subjects, mean plasma IGF-I levels were stable throughout the 11-h period with a range of 97 g/l–169 g/l. In contrast, mean plasma IGFBP-1 levels declined steadily from a high level of 1.99 g/l at 08.00 hours to approximately one half (0.86 g/l) at 15.00 hours. Comparison of areas under the curves revealed significant negative correlations between IGFBP-1 and glucose (–0.88, p=0.01), IGFBP-1 and insulin (–0.75, p=0.016), and IGFBP-1 and IGF-I (–0.68, p=0.03). A significant positive correlation was found between insulin and IGF-I (+ 0.89, p=0.001). The diabetic patients had markedly elevated plasma IGFBP-1 levels (area under curve, p=0.01) and lower plasma IGF-I levels (p=0.033) even though these patients were hyperinsulinaemic throughout the study period. The neuropathic diabetic patients had grossly elevated IGFBP-1 levels (–X=40 g/l at 08.00 hours) which were significantly higher (area under curve, p=0.05) than in patients without neuropathy (¯X=15 g/l at 08.00 hours). However, plasma levels of insulin and IGF-I in neuropathic and non-neuropathic subjects were similar, suggesting that the regulation of IGFBP-1 is more resistant to insulin in the neuropathic patients. In contrast to the non-diabetic subjects comparison of area under curve values revealed no positive correlation between insulin and IGF-I or negative correlations between IGF-I and IGFBP-1, and IGFBP-1 and glucose. We conclude that in Type 1 diabetes the relationships between plasma glucose, insulin, IGF-I and IGFBP-1 are clearly abnormal, and these abnormalities are more pronounced in patients with peripheral neuropathy.