Fasting and postprandial liver glycogen content in patients with type 1 diabetes mellitus after successful pancreas-kidney transplantation with systemic venous insulin delivery

BACKGROUND

In patients with type 1 diabetes mellitus (T1DM), insulin is usually replaced systemically (subcutaneously) and not via the physiological portal route. According to previous studies, the liver's capacity to store glycogen is reduced in T1DM patients, but it remains unclear whether this is due to hyperglycaemia, or whether the route of insulin supply could contribute to this phenomenon. T1DM patients after successful pancreas-kidney transplantation with systemic venous drainage (T1DM-PKT) represent a suitable human model to further investigate this question, because they are normoglycaemic, but their liver receives insulin from the pancreas transplant via the systemic route.

MATERIALS AND METHODS

In nine T1DM-PKT, nine controls without diabetes (CON) and seven patients with T1DM (T1DM), liver glycogen content was measured at fasting and after two standardized meals employing (13) C-nuclear-magnetic-resonance-spectroscopy. Circulating glucose and glucoregulatory hormones were measured repeatedly throughout the study day.

RESULTS

The mean and fasting concentrations of peripheral plasma glucose, insulin, glucagon and C-peptide were comparable between T1DM-PKT and CON, whereas T1DM were hyperglycaemic and hyperinsulinaemic (P < 0·05 vs T1DM-PKT and CON). Total liver glycogen content at fasting and after breakfast did not differ in the three groups. After lunch, T1DM-PKT and T1DM had a 14% and 21% lower total liver glycogen content than CON (P < 0·02).

CONCLUSION

In spite of normalized glycaemic control, postprandial liver glycogen content was reduced in T1DM-PKT with systemic venous drainage. Thus, not even optimized systemic insulin substitution is able to resolve the defect in postprandial liver glycogen storage seen in T1DM patients.

Reduction of both number and proliferative activity of human endothelial progenitor cells in obesity

OBJECTIVE

Circulating endothelial progenitor cells (EPCs), responsible for neoangiogenesis and vascular repair, negatively correlate with vascular dysfunction and atherosclerotic risk factors. Because obesity may have a crucial role in the development of endothelial dysfunction, this study evaluated the number and proliferative activity of circulating human EPCs in obese (body mass index (BMI)=48+/-9, n=45) compared with lean (23+/-2, n=45) volunteers.

METHODS

EPCs were quantified after isolation of peripheral blood mononuclear cells (PBMCs) using fluorescence-activated cell sorting analyses. In addition, plated PBMCs developed colony-forming units (CFUs) from which 'outgrowth' endothelial cells (OECs) sprouted and differentiated into mature endothelial cells. Growth rates were monitored by periodical microscopic evaluation. Cell-cycle protein expression was determined by western blot analyses.

RESULTS

BMI negatively correlated (P<0.01) with the number of CD34(+)/CD133(+)/KDR(+) (r=-0.442), CD34(+)/KDR(+) (r=-0.500) and CD133(+)/KDR(+) (r=-0.282) EPCs. Insulin, leptin, HbA(1c), high-sensitivity C-reactive protein and hypertension, as well as diminished high-density lipoprotein and apolipoprotein A1, were not only associated with obesity but also with significantly reduced EPC levels. Applying selective culture conditions, EPC-CFUs differentiated into OECs that proliferated more slowly when derived from obese compared with lean subjects (obese: 19.9+/-2.2% vs lean: 30.9+/-3.2% grown area per week, P<0.01). The reduced proliferation was reflected by decreased (P<0.05, n=24 for each group) expression of cell-cycle-promoting cyclins and E2F-1, by hypophosphorylation of retinoblastoma protein and by increased (P<0.05, n=24 for each group) expression of the cell-cycle inhibitor p21(WAF-1/Cip1).

CONCLUSIONS

Reduced numbers of EPCs along with their premature senescence, as shown in this study, could function as early contributors to the development and progression of vascular dysfunction in obesity.

Duplications of the functional CYP21A2 gene are primarily restricted to Q318X alleles: evidence for a founder effect

CONTEXT

Rare haplotypes with Q318X mutations and duplicated CYP21A2 genes have been reported to occur in different populations to a varying extent. Discrimination between a normal (Q318X mutation on one of the duplicated CYP21A2 genes) and a congenital adrenal hyperplasia (CAH, Q318X mutation without duplicated functional gene) allele is of importance, particularly for prenatal diagnosis and the respective genetic counseling. Although methods to differentiate between such alleles have been published only recently, it remains unclear with which frequency Q318X mutations are associated with duplicated CYP21A2 genes and whether these haplotypes have a common ancestry.

SUBJECTS AND METHODS

Human leukocyte antigen (HLA) typing has been performed in 38 unrelated individuals and in 11 family members detected to carry a Q318X mutation in the course of CYP21 genotyping using sequence, multiplex ligation-dependent probe amplification, and Southern blot analyses.

RESULTS

The majority (n = 32, 84.2%) of the 38 unrelated individuals carrying the Q318X mutation had the trimodular RCCX haplotype, carrying the Q318X mutation on a duplicated CYP21A2 gene. Twenty-two individuals of these 32 (68.8%) were of the rare HLA-B*50-Cw*06 haplotype, suggesting a common ancestry of this haplotype. In five (13.2%) of the 38 subjects, the Q318X mutation was not associated with a duplicated CYP21A2 gene and thus represents a CAH allele. None of these five patients had the above mentioned HLA haplotype.

CONCLUSION

The majority of individuals in whom Q318X mutations are detected carry a duplicated functional CYP21A2 gene and the rare HLA-B*50-Cw*06 haplotype.

Insulin does not regulate glucose transport and metabolism in human endothelium

BACKGROUND

Although endothelial cells express insulin receptors, it is controversially discussed whether the endothelium represents an insulin-responsive tissue. Since available data are primarily restricted to animal endothelial cells, this study tested (i) whether insulin affects glucose metabolism in human endothelium; (ii) whether insulin sensitivity is different in micro- versus macrovascular endothelial cells; and (iii) whether glucose concentration in the incubation medium affects the cells' response to insulin.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs), human adult saphenous vein endothelial cells (HAVECs), human aortic endothelial cells (HAEC), and human retinal endothelial cells (HRECs) as well as human smooth muscle cells were incubated with/without insulin (0.3 nmol L(-1) or 1 micromol L(-1)). Glucose transport, glycogen synthesis, glycogen content, lactate release, and expression of phospho-Akt, Akt, and endothelial nitric oxide synthase (eNOS) were determined.

RESULTS

In HUVECs and HRECs, insulin (1 micromol L(-1)) increased (P < 0.05) eNOS expression by ~70% and doubled Akt phosphorylation, but the latter was by far more pronounced in human smooth muscle cells (+1093 +/- 500%, P < 0.05). In human smooth muscle cells, insulin (1 micromol L(-1)) stimulated glycogen synthesis by 67 +/- 11% (P < 0.01). In human micro- (HRECs) and macrovascular endothelial cells (HUVECs, HAVECs and HAECs), insulin, however, failed to stimulate glucose transport, glycogen synthesis, glycogen content, or lactate release under various conditions, i.e. after glucose deprivation or in medium with normal (5.5 mmol L(-1)) or high glucose (30 mmol L(-1)).

CONCLUSIONS

Insulin stimulated glycogen synthesis and Akt phosphorylation in human smooth muscle cells. In human micro- and macrovascular endothelial cells, insulin, however, failed to affect glucose uptake and metabolism under all experimental conditions applied, whereas it increased Akt phosphorylation and eNOS expression.

Predisposition for de novo gene aberrations in the offspring of mothers with a duplicated CYP21A2 gene

CONTEXT

Although CYP21A2 de novo mutations are assumed to account for 1 to 2% of congenital adrenal hyperplasia (CAH) alleles and CYP21 genotyping has been done worldwide, there are only a few well-documented cases of CYP21A2 de novo mutations. The majority of these are deletions resulting from unequal crossings over owing to misalignment of homologous chromosomes during meiosis. Whereas so far, only heterozygous deletions of the CYP21A1P pseudogene were seen as premutations for de novo aberrations, the present report addresses such a predisposing role for parental duplicated CYP21A2 genes.

SUBJECTS AND METHODS

As part of routine diagnostic procedures, CYP21 genotyping has been performed in two unrelated female CAH index patients and in their clinically asymptomatic parents and siblings.

RESULTS

Both patients have inherited the paternal Intron2splice mutation and have harbored a de novo gene aberration (large deletion and I271N/exon 4) on their maternal haplotype. Surprisingly, both mothers were carriers of rare duplicated CYP21A2 haplotypes carrying CAH alleles, which were not detected in the daughters. Among 133 CAH alleles that were detected in patients and that could be traced to the respective family members by genotyping, these two de novo aberrations (representing 1.5% of 133 traced CAH alleles) were the only ones identified.

CONCLUSION

Because both de novo CYP21A2 gene aberrations so far identified in our laboratory occurred in the gametes of mothers carrying rare duplicated CYP21A2 haplotypes, we hypothesize that duplicated CYP21A2 genes could predispose for de novo mutations in the offspring, which is of relevance for prenatal CYP21 genotyping and genetic counseling.

Polymorphisms in exon 13 and intron 14 of the RET protooncogene: genetic modifiers of medullary thyroid carcinoma?

CONTEXT

Single-nucleotide polymorphisms (SNPs) of the RET protooncogene (RET) could modify disease susceptibility and clinical phenotype in patients with sporadic or familial medullary thyroid carcinoma (FMTC). OBJECTIVE/DESIGN OF THE STUDY: Because frequencies of RET SNPs have not yet been evaluated in patients with elevated serum concentrations of calcitonin (hCt), a biochemical marker for medullary thyroid carcinoma (MTC), we studied RET SNPs in patients with FMTC (n = 22), patients with sporadic MTC (n = 45), and 71 subjects presenting with moderately elevated hCt concentrations (basal, >10 pg/ml; pentagastrin stimulated, > 50 < 100 pg/ml) in comparison with an age- and gender-matched control group (n = 79) with basal hCt concentrations in the normal range (<5 pg/ml).

METHODS

After DNA extraction from citrated whole blood, RET exons 10, 11, 13, 14, 15, and 16 and exon/intron boundaries were analyzed by PCR-based cycle sequencing for RET germ line mutations, exonic (G691S, L769L, S836S, S904S) and intronic (IVS13+158; NCBI rs2472737 = IVS14-24) SNPs.

RESULTS

In FMTC patients, the F791Y mutation was found to be associated (P = 0.001) with the L769L SNP. The exonic SNPs (G691S, L769L, S836S, and S904S) were not different among the four groups. The intron 14 SNP (IVS14-24), however, was more frequent in individuals with elevated hCt serum concentrations (P = 0.016) and patients with sporadic MTC (P < 0.001) when compared with the control group.

CONCLUSIONS

These data suggest that the exon 13 (L769L) and the intron 14 (IVS14-24) SNPs could act as genetic modifiers in the development of some forms of hereditary and sporadic MTC, respectively.

Mutational spectrum of steroid 21-hydroxylase and the genotype-phenotype association in Middle European patients with congenital adrenal hyperplasia

OBJECTIVE

To analyze the mutational spectrum of steroid 21-hydroxylase (CYP21) and the genotype- phenotype correlation in patients with congenital adrenal hyperplasia (CAH) registered in the Middle European Society for Pediatric Endocrinology CAH database, and to design a reliable and rational approach for CYP21 mutation detection in Middle European populations.

DESIGN AND METHODS

Molecular analysis of the CYP21 gene was performed in 432 CAH patients and 298 family members. Low-resolution genotyping was performed to detect the eight most common point mutations. High-resolution genotyping, including Southern blotting and sequencing was performed to detect CYP21 gene deletions, conversions, point mutations or other sequence changes.

RESULTS

CYP21 gene deletion and In2 and Ile172Asn mutation accounted for 72.7% of the affected alleles in the whole study group. A good genotype-phenotype correlation was observed, with the exception of Ile172Asn and Pro30Leu mutations. In 37% of patients low resolution genotyping could not identify the causative mutation or distinguish homozygosity from hemizygosity. Using high-resolution genotyping, the causative mutations could be identified in 341 out of 348 analyzed patients. A novel mutation Gln315Stop was found in one simple virilising CAH (SV-CAH) patient from Austria. In the remaining seven patients polymorphisms were identified as the leading sequence alteration. The presence of elevated basal and ACTH-stimulated 17-hydroxyprogesterone, premature pubarche, advanced bone age and clitoral hypertrophy directly implicated Asn493Ser polymorphism in the manifestation of nonclassical- (NC) and even SV-CAH.

CONCLUSIONS

By genotyping for the most common point mutations, CYP21 gene deletion/conversion and the 8 bp deletion in exon 3, it should be possible to identify the mutation in 94-99% of the diseased alleles in any investigated Middle European population. In patients with a mild form of the disease and no detectable mutation CYP21 gene polymorphisms should be considered as a plausible disease-causing mutation.

Thiazolidinediones inhibit proliferation of microvascular and macrovascular cells by a PPARgamma-independent mechanism

AIMS/HYPOTHESIS

This study evaluated the hypothesis that peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists, including thiazolidinediones (TZDs) and the rexinoid LG100268 (LG), directly affect human vascular cell function (proliferation, cell cycle, protein expression, lactate release) independently of (1) their PPARgamma-activating potential and (2) the cells' vascular origin.

METHODS

Human umbilical vein endothelial cells (HUVECs), human adult vein endothelial cells (HAVECs), human retinal endothelial cells (HRECs) and human retinal pericytes (HRPYCs) were incubated (48 h) with 2-50 micromol/l rosiglitazone (RSG), RWJ241947 (RWJ), pioglitazone (PIO), troglitazone (TRO), 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2) and LG. Proliferation, cell cycle distribution, protein expression, peroxisome proliferator-activated receptor responsive element (PPRE) transcriptional activity and mitochondrial effects were determined by [3H]thymidine incorporation, FACS analyses, western blots, reporter assays and lactate release respectively.

RESULTS

In HUVECs, RSG, RWJ, PIO, TRO, PGJ2 and LG reduced (p<0.01) proliferation (due to a G0/G1 cell cycle arrest) by up to 23%, 36%, 38%, 86%, 99% and 93% respectively. The antiproliferative response was similar in HRPYCs and HAVECs, but was attenuated in HRECs. Whereas p21WAF-1/Cip1 and p27Kip were differently affected in HUVECs, all agents reduced (p<0.05) expression of cyclins (D3, A, E, B), cyclin-dependent kinase-2 and hyperphosphorylated retinoblastoma protein. The rank order of the antiproliferative effects of TZDs in HUVECs (RSG approximately PIO approximately RWJ<TRO) contrasted their PPRE transcriptional activities (TRO<PIO<RSG<RWJ), but correlated with cellular lactate release. Proliferation inhibition and lactate release were mimicked by rotenone (mitochondrial complex I inhibitor).

CONCLUSIONS/INTERPRETATION

In conclusion, this study suggests that the antiproliferative action of the TZDs in vascular cells is independent of their PPARgamma-activating and associated insulin-sensitising potential, but could relate to mitochondrial mechanisms.

Carrier frequency of congenital adrenal hyperplasia (21-hydroxylase deficiency) in a middle European population

Based on newborn screening data, the carrier frequency of congenital adrenal hyperplasia (CAH) in the general population has been estimated to be 1:55. The higher CAH frequency (particularly of milder forms of the disease) reported for certain populations including Yugoslavs (1.6%) relates to population genetic and hormonal data. However, so far, true carrier frequency for CAH due to 21-OH deficiency has not been determined by comprehensive mutation analysis of the 21-OH gene (CYP21A2) in an unselected European population. This study used CYP21A2 genotyping (sequence/Southern blot analysis) to determine CAH carrier frequency in a middle European (Austrian) population. The study included 100 migrants from the former Yugoslavia and 100 individuals of non-Yugoslavian origin. None of these individuals showed clinical hyperandrogenism or had a family history of CAH. Genotyping 400 unrelated alleles from 200 clinically unaffected individuals, this study revealed a carrier frequency of 9.5%, including so-called "classic" (5.5%) and "nonclassic" (4%) CYP21A2-gene aberrations. The observed heterozygosity for CAH in Yugoslavs was not different (P = 0.8095) from that in non-Yugoslavs. In conclusion, the observed CAH carrier frequency of 9.5% suggests a higher prevalence of CAH heterozygosity in a middle European population than hitherto estimated independently of the individuals' Yugoslav or non-Yugoslav origin.

A rare duplicated 21-hydroxylase haplotype and a de novo mutation: a family analysis

21-Hydroxylase (21-OH) genotyping was performed in clinically unaffected family members of a congenital adrenal hyperplasia (CAH) index patient (Prader stage 3), who is a compound heterozygous carrier of the I172N (exon 4) and the intron2 splicing mutations. Whereas the latter mutation could be traced to the father, the exon 4 aberration represents a de novo mutation (accounting for 1% of CAH alleles) harbored on an unaffected allele, which was inherited from the mother. Although clinically and biochemically unaffected, the patient's brother was found to be compound heterozygous for intron2splice (paternal allele) and Q318X in exon 8 (maternal allele). As shown by PCR-based sequence and Southern blot analysis, the maternal haplotype, inherited by the brother, has a duplicated CYP21B (functional) gene, one of which carries a Q318X mutation. This duplicated Q318X-affected haplotype is the first of its kind among 800 alleles screened for 21-OH deficiency in our laboratory and has to date been reported only in three Swedish CAH patients, all of them bearing an intron2splice and a Q318X mutation. This family analysis highlights the complexity of the CYP21/CYP21P(pseudogene) loci and the difficulties of 21-OH genotyping.

Increased prevalence of heterozygous 21-OH germline mutations in patients with adrenal incidentalomas

OBJECTIVE

As a result of the widespread use and the enhanced quality of high-resolution radiological techniques [computed tomography (CT), magnetic resonance imaging (MRI)] a high frequency (4-10%) of adrenal incidentalomas has been detected in the general population. It is still debated whether undiagnosed 21-hydroxylase (21-OH) deficiency, accounting for more than 90% of congenital adrenal hyperplasia (CAH) cases, predisposes for adrenal tumours. We therefore performed an analysis of the prevalence of 21-OH germline mutations in patients with non-functional adrenal incidentalomas.

SUBJECTS AND METHODS

Fifty Austrian patients with non-functional adrenal adenomas detected by CT for unrelated reasons were screened by PCR-based sequencing for the most common point mutations and by Southern blot analysis for large gene deletion/conversion events of the 21-OH gene.

RESULTS

Heterozygosity for large gene conversions was shown in 5 (10%), for Q318 point mutations in 2 (4%) and for the Intron2splice mutation in 1 (2%) of the 50 patients with adrenal adenomas. One (2%) patient (70 years of age), identified to have a chimeric CYP21AB gene with a junction site before Intron 2 on one and a large (30 kb) deletion on the other allele, was diagnosed to be affected by CAH.

CONCLUSION

21-OH mutation screening indicates a higher frequency of classic CAH carriers (16%) and of manifest CAH (2%) due to 21-OH-deficiency among patients with adrenal adenomas than in the general population (1-2% carrier frequency for classic CAH).

Modulation by leptin of proliferation and apoptosis in vascular endothelial cells

AIM

Plasma leptin concentrations not only correlate with body fat mass, but also with the degree of hypertensive retinopathy. The present study was designed to further examine, whether leptin's proliferative, proangiogenic activity relates to a yet uncovered anti-apoptotic effect.

RESULTS

Leptin (10-50 nmol/l) concentration-dependently reduced apoptosis in HUVECs (human umbilical vein endothelial cells), HAVECs (human adult vein endothelial cells) and HMECs (human microvascular endothelial cells) by 20% (P < or = 0.05). These findings were supported by increased expression of the apoptosis inhibitor bcl-2 (+55%, P < or = 0.05) as well as by differential modulation of the respective cell cycle checkpoint genes/proteins p53 (-20%, P < or = 0.01), p21(WAF-1/Cip1) (-23%, P < or = 0.05) and the Retinoblastoma protein (+123%, P < or = 0.01).

CONCLUSION

bcl-2 dependent anti-apoptotic action might contribute to leptin's proangiogenic activity and thereby promote the development of vascular proliferative disease in obesity.

The endothelium as a metabolic and endocrine organ: its relation with insulin resistance

The vascular endothelium, building the inner layer of capillaries and blood vessels of all sorts, represents a highly active metabolic and endocrine organ producing a multitude of different molecules, including vasoactive peptide hormones, growth factors, coagulation factors and adhesion molecules. In addition, it expresses many of the respective endocrine, paracrine and cytokine/growth factor receptors. It thereby regulates the delicate balance between vasoconstriction and vasodilation, between coagulation and fibrinolysis, proliferation and apoptosis, as well as between transient adhesion and diapedesis of blood borne leukocytes. This minireview addresses the potential interactions of these important functions in the states of diabetes and of insulin resistance including obesity, hypertension and dyslipidaemia, all of which characterized by endothelial dysfunction.

Mutational spectrum of the steroid 21-hydroxylase gene in Austria: identification of a novel missense mutation

This study attempted an analysis of the mutational spectrum of 21-hydroxylase deficiency in 79 unrelated Austrian patients with classical and nonclassical forms of congenital adrenal hyperplasia and their respective 112 family members. Apparent large gene deletions/conversions were present in 31% of the 158 unrelated congenital adrenal hyperplasia alleles, whereas the most frequent point mutations were intron 2 splice (22.8%), I172N (15.8%), V281L (12%), and P30L (7.6%), in line with the frequencies reported for other countries. In 5 of the 12 congenital adrenal hyperplasia alleles carrying a P30L mutation the aberration is based on a single base substitution, whereas the remaining 7 represent part of a CYP21B conversion (1 allele) or CYP21B/21A hybrid gene (6 alleles), the latter characterized by a junction site before intron 2 as indicated by Southern blot, PCR, and sequence analyses. Previously described mutations were not present in 1.2% of unrelated congenital adrenal hyperplasia alleles, including one female patient presenting with severe genital virilization. Sequence analysis of the complete functional 21-hydroxylase gene revealed an as yet undescribed mutation in exon 10-Arg(426)His, which has not yet been described to represent a common pseudogene sequence. In vitro expression experiments showed the Arg(426)His mutant to exhibit only low enzyme activity toward the natural substrate 17-hydroxyprogesterone corresponding to the degree of disease manifestation in the patient in whom it was found.

Determination of plasma ET-1 by RIA--risks and limitations

Plasma concentrations of the vasoconstrictor peptide endothelin-1 (ET-1) were determined in nonobese healthy subjects as well as in unspecified patients using three different commercially available radioimmunoassays (RIAs) and the respective recommended prepurification procedures. Depending on the antibody and extraction procedure applied different ET-1 concentrations were measured in identical plasma samples. Thus, this study clearly documents that ET-1 concentrations measured in plasma samples represent apparent concentrations which have to be interpreted with caution.

Glycemia and regulation of endothelial adhesion molecules

Hyperglycemia is one of the most prominent factors associated with diabetic vascular disease, the development of which is initated by functional and morphological alterations of the endothelium. The review summarizes several issues of glycemia and advanced glycation end products induced changes concerning soluble as well as cell bound endothelial adhesion molecules, and further addresses the aspect of apoptosis in the light of diabetic vascular complications.

Increase by tri-iodothyronine of endothelin-1, fibronectin and von Willebrand factor in cultured endothelial cells

Hyperthyroidism is associated with elevated plasma levels of endothelium-derived proteins such as von Willebrand factor (vWF), fibronectin (FN) and endothelin-1 (ET-1). This study was designed to characterize the mechanisms involved in this phenomenon at the cellular level. vWF, FN and ET-1 secretion and mRNA expression were measured in human umbilical vein endothelial cells (HUVECs) exposed to tri-iodothyronine (T3) for 13 +/- 1 days, using ELISA, Western blot, RIA and Northern blot analysis respectively. Exposure of HUVECs to T3 significantly increased vWF secretion (50 ng T3/ml: 117 +/- 5%, P < 0.01; 100 ng T3/ml: 127 +/- 26%, P < 0.01) as well as vWF mRNA expression (50 ng/ml: 116 +/- 13%, P < 0.001; 100 ng/ml: 136 +/- 30%, P < 0.002) (results are means +/- S.D. analysed by the Wilcoxon signed rank test). FN secretion was significantly affected by 50 (145 +/- 42% of control, P < 0.05) and 100 (116.8 +/- 16% of control, P < 0.05) ng T3/ml, and FN mRNA expression by 50 ng T3/ml (123 +/- 20%, P < 0.05). Long-term incubation with T3 increased both ET-1 secretion (25 ng/ml: 124 +/- 25%, P < 0.001; 50 ng/ml: 165 +/- 53%, P < 0.05; 100 ng/ml: 116 +/- 17%, P < 0.05) and prepro-ET-1 mRNA expression (25 ng/ml: 112 +/- 16%, P < 0.05; 50 ng/ml: 134 +/- 43%, P < 0.02; 100 ng/ml: 120 +/- 20%, P < 0.02). Protein kinase C (PKC) isoforms epsilon and beta II were not significantly affected by T3, whereas PKC alpha was increased in whole cell lysates and in membrane fractions of cells incubated with 100 but not 50 ng T3/ml. Prepro-ET-1 mRNA stability, cell numbers and proliferation, measured by [3H]thymidine assays, remained unaffected in HUVECs after exposure to T3. These data indicate thyroid hormone-induced upregulation of mRNA expression and protein synthesis of vWF, FN and ET-1, by PKC alpha-, beta II- and epsilon-independent pathways, explaining, at least in part, increased plasma concentrations of endothelial proteins and peptides in the hyperthyroid state.

High-glucose--triggered apoptosis in cultured endothelial cells

High ambient glucose concentration, linked to vascular complications in diabetes in vivo, modulates mRNA expression of fibronectin, collagen, tissue-type plasminogen activator, and plasminogen activator inhibitor and induces delayed replication and excess cell death in cultured vascular endothelial cells. To determine the role of high ambient glucose (30 mmol/l) in apoptosis, paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were exposed to both high (30 mmol/l) and low (5 mmol/l) concentrations of glucose for short-term (24, 48, and 72 h) and long-term (13 +/- 1 days) experiments. Incubation of HUVECs with high glucose for > 48 h increased DNA fragmentation (13.7 +/- 6.5% of total DNA, mean +/- SD) versus cultures kept in 5 mmol/l glucose (10.9 +/- 5.6%, P < 0.005), as measured by [3H]thymidine assays. Data were confirmed by apoptosis-specific fluorescence-activated cell sorter analysis of confluent HUVEC cultures, which displayed after long-term exposure to 30 mmol/l glucose a 1.5-fold higher prevalence of apoptosis than control cultures exposed to 5 mmol/l glucose (P < 0.005). In contrast, no increase in DNA fragmentation in response to 30 mmol/l glucose was seen for standardized cell lines (K 562, P 815, YT) and fibroblasts. Expression of clusterin mRNA, originally reported to be a molecular marker of apoptosis, was only slightly affected by short-term (24-h) high-glucose exposure but was significantly reduced after long-term incubation in 30 mmol/l glucose (82.2 +/- 13.8% of control) versus 5 mmol/l glucose, which questions the role of clusterin gene expression as a marker of apoptosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation by high glucose of adhesion molecule expression in cultured endothelial cells

We evaluated the influence of high ambient glucose on cellular expression of adhesion molecules, known to mediate endothelial interaction of leucocytes and monocytes. Paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were studied by fluorescence activated cell sorter analysis after exposure to 30 vs 5 mmol/l glucose. Incubation of HUVECs for 24h in 30 mmol/l glucose increased ICAM-1 (intercellular adhesion molecule-1; 116.4 +/- 16.9% of control, p < or = 0.05), but not PECAM (platelet endothelial cell adhesion molecule) expression, compared to cultures kept in 5 mmol/l glucose. Long-term exposure (13 +/- 1 days) of HUVECs to 30 mmol/l glucose increased expression of ICAM-1 to 122.5 +/- 32.2% (p < 0.002) and reduced that of PECAM to 86.9 +/- 21.3% vs the respective control culture in 5 mmol/l glucose (p < 0.02). Stimulation of confluent HUVECs, kept in 30 vs 5 mmol/l glucose for 13 +/- 1 days, with 20 U/ml interleukin-1 for 24 h (ICAM-1) and 4 h (endothelial leukocyte adhesion molecule 1) resulted in reduced ICAM-1 (84.8 +/- 27.0%, p < 0.05) and endothelial leukocyte adhesion molecule-1 (87.6 +/- 22.4%, p < 0.05) expression vs control cells, while that of PECAM (t:24 h) and vascular cell adhesion molecule-1 (t: 16 h) remained unchanged. In conclusion, it appears that differences in expression of adhesion molecules on HUVECs in response to high glucose reflects endothelial glucose toxicity, which may also induce endothelial dysfunction in diabetes.

Possible clinical effects of the interaction of hemodialysis membranes with adhesion proteins

In this study data obtained in an in vitro hemodialysis model are related to various parameters measured in patients' plasma during hemodialysis in a clinical crossover study. In vitro, blood from healthy volunteers was dialyzed under standardized conditions using the capillaries Fresenius MTS C (Cuprophane) and Hospal AN 69 (Polyacrylonitrile). Following dialysis, surface bound proteins were eluted with saline, 1 M Tris and 2% SDS, and analyzed by immunoblotting. Depending on the capillary, different protein patterns could be identified in the eluates. Intact forms of adhesion proteins were predominantly (fibrinogen) or exclusively (vitronectin) found in PA eluates. In contrast, low molecular weight products of fibrinogen as well as high molecular weight components containing antithrombin III (AT III) were present in CP eluates. Their presence may reflect fibrinolytic and procoagulatory activity during dialysis with CP capillaries. A microscopic investigation of CP membranes demonstrated fibrin lined platelet conglomerates. In the plasmas of patients dialyzed with CP capillaries high D-Dimer concentrations were found. We also noticed that during dialysis with PA membranes less heparin was consumed than during dialysis with CP membranes. Our study showed a good correlation of the observations in the vitro system and the measurements in patient samples.