Gábor Speer

Tumor necrosis factor system in insulin resistance in gestational diabetes

OBJECTIVE The aim of the study was to investigate the pathophysiological role of the tumor necrosis factor (TNF) system in insulin resistance in patients with gestational diabetes (GDM) and during the course of normal pregnancy. PATIENTS AND METHODS Thirty women with GDM (16-39 gestational weeks), 35 healthy pregnant women (15 first, nine second and 11 third trimester) and 25 healthy age-matched non-pregnant women were studied. Serum TNF-alpha, and its soluble receptors 1 and 2 (sTNFR-1 and -2) were measured. RESULTS In non-diabetic pregnant women in the third trimester all measures were significantly higher (P<0.05 or less) than in the first trimester and in non-pregnant women (BMI 27.6 +/- 4.1 (+/- S.D.), 24.1 +/- 2.6, 22.4 +/- 2.4 kg/m(2)), serum TNF-alpha (4.6 +/- 0.6, 4.1 +/- 0.4, 4.1 +/- 0.4 ng/l), sTNFR-1 (2.7 +/- 0.9, 2.0 +/- 0.5, 2.0 +/- 0.1 microg/l), sTNFR-2 (5.6 +/- 2.6, 4.6 +/- 2.1, 3.3 +/- 0.2 microg/l), C-peptide (3.1 +/- 1.7, 1.1 +/- 0.7, 1.1 +/- 0.8 microg/l), and C-peptide:blood glucose ratio (0.6 +/- 0.2, 0.2 +/- 0.1, 0.2 +/- 0.1 microg/mmol). In GDM these measures were even higher than in any subgroup of healthy pregnant women (BMI) (33.4 +/- 6.4 kg/m(2), TNF-alpha) (6.3 +/- 0.6 microg/l), sTNFR-1 (3.0 +/- 0.5 microg/l), sTNFR-2 (10.0 +/- 6.9 microg/l, C-peptide 6.0 +/- 2.7 microg/l, C-peptide:blood glucose ratio: 1.2 +/- 0.5 microg/mmol, P<0.01). Significant (P<0.01) positive linear correlations were found in gestational diabetic and non-diabetic women between serum TNF-alpha, C-peptide levels, and BMI. In gestational diabetic women, in multivariate analysis studying the dependency of C-peptide only BMI remained significant (r(2)=0.67, P=0.01). CONCLUSIONS Our observation emphasizes the obesity-related component of insulin resistance driven by adipocytokines, such as TNF-alpha and its receptors during the course of normal pregnancy and GDM.

The Candidate Oncogene CYP24A1: A Potential Biomarker for Colorectal Tumorigenesis

The main autocrine/paracrine role of the active metabolite of vitamin D3, 1α,25-dihydroxyvitamin D3 (1,25-D3), is inhibition of cell growth and induction of cell differentiation and/or apoptosis. Synthesis and degradation of the secosteroid occurs not only in the kidney but also in normal tissue or malignant extrarenal tissues such as the colon. Because 25-hydroxyvitamin D3 24-hydroxylase (CYP24A1) is considered to be the main enzyme determining the biological half-life of 1,25-D3, we have examined expression of the CYP24A1 mRNA (by real-time RT-PCR) and protein (by immunohistochemistry) in normal human colon mucosa, colorectal adenomas, and adenocarcinomas in 111 patients. Although 76% of the normal and benign colonic tissue was either completely devoid of or expressed very low levels of CYP24A1, in the majority of the adenocarcinomas (69%), the enzyme was present at high concentrations. A parallel increased expression of the proliferation marker Ki-67 in the same samples suggests that overexpression of CYP24A1 reduced local 1,25-D3 availability, decreasing its antiproliferative effect.

Elevated serum tumor necrosis factor-alpha concentrations and bioactivity in Type 2 diabetics and patients with android type obesity

The role of tumor necrosis factor-alpha in insulin resistance has been studied in 59 patients with Type 2 diabetes, 28 with android type obesity and 35 healthy lean controls. Immunoreactive concentrations and bioactivity of serum tumor necrosis factor-alpha have repeatedly been determined in 8 weeks intervals for 12 months, five times per patients, by using ELISA and L929 cell cytotoxicity bioassay. Significantly higher immunoreactive tumor necrosis factor-alpha concentrations and bioactivity have been found in both, the Type 2 diabetic and obese groups as compared to the healthy persons. Tumor necrosis factor-alpha concentrations and bioactivity have showed a significant positive linear correlation with the elevated basal serum C-peptide levels and body mass indexes in both groups of patients. According to these data the cytokine might play a role in insulin resistance in obesity as well in Type 2 diabetes.

Elevated serum tumour necrosis factor-alpha levels can contribute to the insulin resistance in Type II (non-insulin-dependent) diabetes and in obesity.

Dear Sir, Tumour necrosis factor alpha (TNF-a) may play a role in the pathophysiology of obesity and also in the obesity-diabetes link [1]. The overexpression of the cytokine has been demonstrated in the adipose tissue of different rodent genetic models of obesity [2]. This overexpression of TNF-a led to the downregulation of the signal transduction of insulin receptor via the increased serin phosphorilation of the insulin receptor substrate (IRS)-1 turning it to an inhibitor of the receptor [3], although a contradictory observation has also been published [4]. Moreover, TNF-a also downregulates several genes in adipocytes, e. g. GLUT-4, lipoprotein lipase [2, 4] and adipsin [2, 4]. In TNF-a deficient obese mice the GLUT-4 protein level was significantly higher only in the muscle tissue [5]. Targeted mutations in the genes of TNF-a and the two TNF-receptors resulted in an improved insulin sensitivity in animal models of obesity [5, 6]. According to these observations the role of TNF-a can be raised in insulin resistance and hyperinsulinaemia. In a follow-up study we have investigated serum TNFa bioactivity in Type II (non-insulin-dependent) diabetes mellitus and obesity. We studied 59 (male/female 32/27, age X _ ± SE: 62 ± 3 years, BMI: 32.2 ± 3.1 kg/m2) patients with Type II diabetes (classification according to clinical data and C-peptide levels), 28 (10/ 18, 49 ± 4 years, 39.5 ± 3.0 kg/m2) with a simple, android type obesity and 35 (19/16, 59 ± 5 years, 25.4 ± 2.4 kg/m2) matched healthy control subjects for twelve months. Blood samples were taken at intervals of 8 weeks ± six times per patients ± for measuring serum basal C-peptide and glucagon levels and TNF-a bioactivity. C-peptide and glucagon levels were measured by commercial RIA kit-s (Serono, Italy, normal values for basal serum Cpeptide levels 0.66±2.50 ng/ml [0.22±0.83 nmol/l], for basal glucagon levels 60±200 pg/ml [16.8±56.0 pmol/l]) and serum TNFa bioactivity by applying the L929 (ATCC) cell cytotoxicity bioassay [7]. Recombinant human TNF-a (Sigma, St. Louis, MS, USA) was used as a standard (concentration range: 0.625 pg/ml±1.562 ng/ml). Serum TNF-a bioactivity was expressed in pg/ml, calculated according to the bioactivity of the standard curve. Monoclonal neutralizing TNF-a and -b mouse immunglobulins (Boehringer GmbH, Mannheim, Germany) were used to detect the TNF-a bioactivity in the samples. Significantly elevated serum TNF-a bioactivity and basal serum C-peptide levels were detected in both, the Type II diabetic and obese patients groups as compared with the control subjects. The values are means of six different measurements during the observation period. (Table 1). In 85 % of the cases the individual serum TNF-a bioactivity in Type II diabetic and obese patients have been found to be above 45 pg/ml (X _ + 2SD value of the controls). The individual concentrations showed an approximately 40 % difference evaluating the six measurements. No significant differences were observed between the means of the six consecutive measurements. We could not measure any significant difference between males and females, or in different age groups (30±39, 40±49, 50±59, 60±69 and above 70 years), either in control subjects or in patients. We could calculate a significantly positive linear correlation (p < 0.01) between the elevated basal serum C-peptide levels and the higher TNF-a bioactivity in both, the Type II diabetic Diabetologia (1998) 41: 860±862

Down-regulation of RpS21, a putative translation initiation factor interacting with P40, produces viable minute imagos and larval lethality with overgrown hematopoietic organs and imaginal discs.

ABSTRACT Down-regulation of the Drosophila ribosomal protein S21 gene (rpS21) causes a dominant weak Minutephenotype and recessively produces massive hyperplasia of the hematopoietic organs and moderate overgrowth of the imaginal discs during larval development. Here, we show that the S21 protein (RpS21) is bound to native 40S ribosomal subunits in a salt-labile association and is absent from polysomes, indicating that it acts as a translation initiation factor rather than as a core ribosomal protein. RpS21 can interact strongly with P40, a ribosomal peripheral protein encoded by the stubarista(sta) gene. Genetic studies reveal that P40 underexpression drastically enhances imaginal disc overgrowth inrpS21-deficient larvae, whereas viable combinations betweenrpS21 and sta affect the morphology of bristles, antennae, and aristae. These data demonstrate a strong interaction between components of the translation machinery and showed that their underexpression impairs the control of cell proliferation in both hematopoietic organs and imaginal discs.

Increased interleukin-12 plasma concentrations in both, insulin-dependent and non-insulin-dependent diabetes mellitus.

Dear Sir, The pathogenetic role of the Th 1 type inflammatory cytokine interleukin-12 (IL-12) in insulin-dependent diabetes mellitus (IDDM) of the non-obese diabetic (NOD) mice has repeatedly been emphasized by Rothe et al. [1, 2] and others [3]. Moreover IL-12 proved to be a potent inhibitor of angiogenesis [4]. Theoretically genetically lower IL-12 level might be a predisposing factor for the development of diabetic retinopathy. Alternatively, elevated IL-12 levels can be a consequence of the retinopathic complication in diabetes as a part of the consecutive immunological mechanism. Therefore we have studied plasma IL-12 levels in Caucasian (Hungarian) patients, 15 of them with IDDM (age X ± ± SE years, 36 ± 2.8, male/female 7/8) and 35 with non-insulin-dependent diabetes mellitus (NIDDM, 58 ± 1.2 years, 19/16) with and without diabetic retinopathy, as well as in 30 healthy blood donors (55 ± 2.1 years, 16/14). Quantikine ELISA kit (R&D Systems, Minneapolis, Minn. USA) recognizing only the 75 kDa heterodimer, not cross-reactive with the individual subunits of the dimer was used for the IL-12 determination. Blood samples were collected from a cubital vein, using EDTA-coated tubes. Elevated IL-12 plasma levels were detected in both types of diabetes (IDDM: X ± ± SE, pg/ml 2.40 ± 0.16, NIDDM: 2.35 ± 0.10, p < 0.01) as compared to healthy control subjects (1.86 ± 0.07). Higher IL-12 levels were found in patients with diabetic retinopathy (background and proliferative as well) both in IDDM (2.53 ± 0.14) and NIDDM (2.63 ± 0.16, p < 0.02) as compared to those without retinopathic complications (IDDM: 2.25 ± 0.10, NIDDM: 2.08 ± 0.10, Fig.1). We could not find any significant correlation between plasma IL-12 levels and duration of the disease, neither in IDDM, nor in NIDDM. Beside its emphasized role in the pathophysiology of IDDM, IL-12 may also contribute to the pathogenesis of the diabetic retinopathy more likely as a part of the consecutive immunological response mechanisms rather than a predisposing factor.

The pathophysiological influence of leptin and the tumor necrosis factor system on maternal insulin resistance: negative correlation with anthropometric parameters of neonates in gestational diabetes

The contribution of the tumor necrosis factor (TNF) system and leptin was studied in insulin resistance and neonatal development during the course of normal pregnancy and gestational diabetes mellitus (GDM). Thirty patients with GDM and their neonates (n = 30), 35 healthy pregnant women (15 in the first, nine in the second and 11 in the third trimester) and their neonates (n = 20), and 25 healthy matched non-pregnant women participated in the study. Significantly elevated levels of maternal TNF-α, sTNF receptor (R)-1 and R-2, leptin (detected by enzyme-linked immunosorbent assay) and fasting C-peptide (measured by radioimmunossay and raised body mass index (BMI) were found in GDM patients and in the third trimester of normal pregnancies. TNF-α, sTNFR-2, C-peptide, leptin concentrations and BMI positively correlated with each other in GDM. An inverse relationship between the body length, head circumference and body weight of the newborns, and maternal TNF-α, leptin and C-peptide concentrations was shown in GDM. In healthy pregnancies the maternal serum leptin level was in a negative linear correlation with the head circumference of the newborns. In conclusion, increased TNF-α and leptin levels may contribute to insulin resistance in GDM and in the third trimester of normal pregnancy and may negatively influence the anthropometric parameters of the newborns.

Serum osteoprotegerin level, carotid-femoral pulse wave velocity and cardiovascular survival in haemodialysis patients

BACKGROUND Osteoprotegerin (OPG) is a marker and regulator of arterial calcification, and it is related to cardiovascular survival in haemodialysis patients. The link between OPG and aortic stiffening--a consequence of arterial calcification--has not been previously evaluated in this population, and it is not known whether OPG-related mortality risk is mediated by arterial stiffening. METHODS At baseline, OPG and aortic pulse wave velocity (PWV) were measured in 98 chronic haemodialysis patients who were followed for a median of 24 months. The relationship between OPG and PWV was assessed by multivariate linear regression. The role of PWV in mediating OPG related cardiovascular mortality was evaluated by including both OPG and PWV in the same survival model. RESULTS At baseline mean (standard deviation) PWV was 11.2 (3.3) m/s and median OPG (interquartile range) was 11.1 (7.5-15.9) pmol/L. There was a strong, positive, linear relationship between PWV and lnOPG (P = 0.009, model R(2) = 0.540) independent of covariates. During follow-up 23 patients died of cardiovascular causes. In separate univariate survival models both PWV and lnOPG were related to cardiovascular mortality [hazard ratios 1.31 (1.14-1.50) and 8.96 (3.07-26.16), respectively]. When both PWV and lnOPG were entered into the same model, only lnOPG remained significantly associated with cardiovascular mortality [hazard ratio 1.11 (0.93-1.33) and 7.18 (1.89-27.25), respectively). CONCLUSION In haemodialysis patients OPG is strongly related to PWV and OPG related cardiovascular mortality risk is, in part, mediated by increased PWV.

Oestrogen and vitamin D receptor (VDR) genotypes and the expression of ErbB-2 and EGF receptor in human rectal cancers

Oestrogen/oestrogen receptor (ER) and vitamin D/vitamin D receptor (VDR) systems have been implicated in the pathogenesis of colorectal cancers. The expression of erbB-2 and epidermal growth factor receptor (EGFR) in colorectal cancers has been suggested to have diagnostic and prognostic significance. In our study, XbaI and PvuII polymorphisms of the ER gene and the BsmI polymorphism of the VDR gene were studied in 56 Caucasian patients with rectal cancer. The relationship between the ER and VDR genotypes and the expression of oncogenes was also investigated. The presence of the x allele of ER gene significantly correlated with the overexpression of the erbB-2 and EGFR oncogenes. Significantly increased erbB-2 expression was observed in patients with the VDR B allele. The XXbb allelic combination of the ER/VDR genes was associated with a significantly lower erbB-2 expression, whereas in the other genotypes significantly higher oncogene expression was seen. Our data raise the possibility that ER/VDR gene polymorphisms accompanied by variable oncogene expression might influence the pathogenetic processes of colorectal cancers.

Lack of association between interleukin-1 receptor antagonist protein gene polymorphism and bone mineral density in Hungarian postmenopausal women.

The major determinant for risk of osteoporosis in later life is bone mineral density (BMD) attained during early adulthood. Bone mineral density is a complex trait that is presumably influenced by multiple genes. Interleukin-1 receptor antagonist protein (IL-1RN) is an attractive candidate gene for osteoporosis susceptibility, because IL-1RN completely inhibits the stimulatory effects of interleukin-1 (IL-1) on bone resorption in organ cultures and has been implicated in the pathogenesis of osteoporosis. In addition, the IL-1RN gene contains a variable-number tandem repeat polymorphism (VNTR) in intron 2 with three potential protein-binding sites. Recently, an association has been found between this polymorphism and postmenopausal bone loss in the spine. In this study, we use the previously described IL-1RN polymorphism to test for an association between this polymorphism and bone mineral density in our population of postmenopausal women. There was no correlation between alleles or genotypes and BMD in the 286 subjects. Dividing subjects into osteoporotic and healthy groups (osteoporotics and controls), we found no difference in the distribution of alleles or genotypes between groups. We found no association between IL-1RN alleles or genotypes and BMD either at the lumbar spine or the femoral neck within groups. Our data do not support the hypothesis that this IL-1RN gene VNTR polymorphism has an impact on bone mass in postmenopausal women.