Biomedical subjects

F Costantini

Publications and source records attributed to F Costantini.

At least 19 recordsLinked to original sources

PubMed2003

High preprocedural non-HDL cholesterol is associated with enhanced oxidative stress and monocyte activation after coronary angioplasty: possible implications in restenosis.

OBJECTIVE: To investigate whether enhanced oxidant stress in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) is associated with a higher concentration of non-high density lipoprotein (HDL) cholesterol at baseline, and whether this contributes to the inflammatory reaction and luminal renarrowing after PTCA. DESIGN: An ex vivo and in vitro study of 46 patients who underwent PTCA and who had repeat angiograms after six months. Blood samples were collected immediately before PTCA, and at 24 hours, 48 hours, and 15 days after. SETTING: Tertiary referral centre. SUBJECTS: 46 patients (30 male, 16 female; mean (SD) age, 62 (5) years) with stable or unstable angina who underwent elective PTCA. MAIN OUTCOME MEASURES: Continuous variable luminal loss as defined by change in minimum lumen diameter during follow up, normalised for vessel size; lag phase of low density lipoprotein to in vitro oxidation; plasma fluorescent products of lipid peroxidation (FPLP); plasma vitamin C and E; interleukin (IL) 1beta secretion from unstimulated monocytes; plasma C reactive protein (CRP). RESULTS: Restenosis occurred in 12 patients (26%). Oxidant stress after PTCA was greater (p < 0.0001 at 15 days) in the patients with restenosis and showed a significant correlation with the preprocedural concentration of non-HDL cholesterol (p < 0.001). Inflammatory reaction (as reflected by IL-1beta production and CRP) and late lumen loss were linearly correlated (p < 0.001) with lag phase and FPLP throughout the study, and inversely (p < 0.05) with vitamin C and E measured at two and 15 days after PTCA. CONCLUSIONS: This study provides evidence for the critical role of cholesterol dependent oxidant stress in the pathophysiology of restenosis after PTCA. The findings raise the possibility that drugs capable of modulating oxidant status might provide a novel form of adjuvant treatment in patients with hypercholesterolaemia undergoing PTCA.

Angioplasty, Balloon, Coronary↗

PubMed2001

Impaired mammary gland and lymphoid development caused by inducible expression of Axin in transgenic mice.

Axin is a component of the canonical Wnt pathway that negatively regulates signal transduction by promoting degradation of beta-catenin. To study the role of Axin in development, we developed strains of transgenic mice in which its expression can be manipulated by the administration of doxycycline (Dox). Animals carrying both mouse mammary tumor virus (MMTV)-reverse tetracycline transactivator and tetracycline response element (TRE)2-Axin-green fluorescent protein (GFP) transgenes exhibited Dox-dependent Axin expression and, when induced from birth, displayed abnormalities in the development of mammary glands and lymphoid tissues, both sites in which the MMTV promoter is active. The transgenic mammary glands underwent normal ductal elongation and side branching during sexual maturation and early pregnancy, but failed to develop lobulo-alveoli, resulting in a defect in lactation. Axin attenuated the expression of cyclin D1, a Wnt target that promotes the growth and differentiation of mammary lobulo-alveoli. Increased apoptosis occurred in the mammary epithelia, consistent with the inhibition of a Wnt/cyclin D1 survival signal by Axin. High levels of programmed cell death also occurred in the thymus and spleen. Immature thymocytes underwent massive apoptosis, indicating that the overexpression of Axin blocks the normal development of T lymphocytes. Our data imply that the Axin tumor suppressor controls cell survival, growth, and differentiation through the regulation of an apoptotic signaling pathway.

Animals↗

PubMed2001

Differential activities of the RET tyrosine kinase receptor isoforms during mammalian embryogenesis.

The RET receptor tyrosine kinase has a critical role in kidney organogenesis and the development of the enteric nervous system. Two major isoforms, RET9 and RET51, differ in the amino acid sequence of the C-terminal tail as a result of alternative splicing. To determine the roles of these isoforms in vivo, we used targeted mutagenesis to generate mice that express either RET9 or RET51. Monoisoformic RET9 mice, which lack RET51, are viable and appear normal. In contrast, monoisoformic RET51 animals, which lack RET9, have kidney hypodysplasia and lack enteric ganglia from the colon. To study the differential activities of the two RET isoforms further, we generated transgenic mice expressing ligand-dependent and constitutively active forms of RET9 or RET51 under the control of the Hoxb7 regulatory sequences. Such RET9 transgenes are capable of rescuing the kidney agenesis in RET-deficient mice or causing kidney hypodysplasia in wild-type animals. In contrast, similar RET51 transgenes fail to rescue the kidney agenesis or cause hypodysplasia. Our findings show that RET9 and RET51 have different signaling properties in vivo and define specific temporal and spatial requirements of c-Ret function during renal development and histogenesis of the enteric nervous system.

Alternative Splicing↗

PubMed2001

The human erythropoietin receptor gene rescues erythropoiesis and developmental defects in the erythropoietin receptor null mouse.

Erythropoietin and its receptor are required for definitive erythropoiesis and maturation of erythroid progenitor cells. Mice lacking the erythropoietin receptor exhibit severe anemia and die at about embryonic day 13.5. This phenotype can be rescued by the human erythropoietin receptor transgene. Animals expressing only the human erythropoietin receptor survived through adulthood with normal hematologic parameters and appeared to respond appropriately to induced anemic stress. In addition to restoration of erythropoiesis during development, the cardiac defect associated with embryos lacking the erythropoietin receptor was corrected and the increased apoptosis in fetal liver, heart, and brain in the erythropoietin receptor null phenotype was markedly reduced. These studies indicate that no species barrier exists between mouse and human erythropoietin receptor and that the human erythropoietin receptor transgene is able to provide specific expression in hematopoietic and other selected tissues to rescue erythropoiesis and other organ defects observed in the erythropoietin receptor null mouse.

Anemia↗

PubMed2001

Cre reporter strains produced by targeted insertion of EYFP and ECFP into the ROSA26 locus.

BACKGROUND: Several Cre reporter strains of mice have been described, in which a lacZ gene is turned on in cells expressing Cre recombinase, as well as their daughter cells, following Cre-mediated excision of a loxP-flanked transcriptional "stop" sequence. These mice are useful for cell lineage tracing experiments as well as for monitoring the expression of Cre transgenes. The green fluorescent protein (GFP) and variants such as EYFP and ECFP offer an advantage over lacZ as a reporter, in that they can be easily visualized without recourse to the vital substrates required to visualize beta-gal in living tissue. RESULTS: In view of the general utility of targeting the ubiquitously expressed ROSA26 locus, we constructed a generic ROSA26 targeting vector. We then generated two reporter lines of mice by inserting EYFP or ECFP cDNAs into the ROSA26 locus, preceded by a loxP-flanked stop sequence. These strains were tested by crossing them with transgenic strains expressing Cre in a ubiquitous (beta-actin-Cre) or a cell-specific (Isl1-Cre and En1-Cre) pattern. The resulting EYFP or ECFP expression patterns indicated that the reporter strains function as faithful monitors of Cre activity. CONCLUSIONS: In contrast to existing lacZ reporter lines, where lacZ expression cannot easily be detected in living tissue, the EYFP and ECFP reporter strains are useful for monitoring the expression of Cre and tracing the lineage of these cells and their descendants in cultured embryos or organs. The non-overlapping emission spectra of EYFP and ECFP make them ideal for double labeling studies in living tissues.

Animals↗

PubMed2001

Second generation knockout sickle mice: the effect of HbF.

Sickle transgenic mice expressing exclusively human globins are desirable for studying pathophysiology and testing gene therapy strategies, but they must have significant pathology and show evidence of amelioration by antisickling hemoglobins. Mice were generated that expressed exclusively human sickle hemoglobin with 3 levels of HbF using their previously described sickle constructs (cointegrated human miniLCRalpha2 and miniLCRbeta(S) [PNAS 89:12150, 1992]), mouse alpha- and beta-globin-knockouts, and 3 different human gamma-transgenes. It was found that, at all 3 levels of HbF expression, these mice have balanced chain synthesis, nearly normal mean corpuscular hemoglobin, and, in some cases, F cells. Mice with the least adult HbF expression were the most severe. Progressive increase in HbF from less than 3% to 20% to 40% correlated with progressive increase in hematocrit (22% to 34% to 40%) and progressive decrease in reticulocyte count (from 60% to 30% to 13%). Urine concentrating ability was normalized at high HbF, and tissue damage detected by histopathology and organ weight were ameliorated by increased HbF. The gamma-transgene that produces intermediate levels of HbF was introduced into knockout sickle mice described by Pàszty and coworkers that express the miniLCRalpha1(G)gamma(A)gammadeltabeta(S) transgene and have fetal but not adult expression of HbF. It was found that the level of HbF required to ameliorate low hematocrit and normalize urine concentrating defect was different for the miniLCRalpha2beta(S) and miniLCRalpha1(G)gamma(A)gammadeltabeta(S) mice. We conclude that knockout mice with the miniLCRalpha2beta(S) transgene and postnatal expression of HbF have sufficiently faithful sickle pathology to serve as a platform for testing antisickling interventions.

2,3-Diphosphoglycerate↗

PubMed2001

Developmental mosaicism may explain spontaneous reappearance of the Axin(Fu) mutation in mice.

The Axin(Fu) mutation is caused by an IAP insertion. In a small percentage of mice, the Axin(Fu) mutation disappears and is not observed in the next generation. In these mice, [Axin(Fu)]/+, the IAP is absent and Axin(Fu) has reverted to the wild allele. Concomitantly with the loss of IAP, there is widespread reorganisation of numerous microsatellite loci across the surrounding region of chromosome. In rare cases, spontaneous reappearance of the mutation can be observed in progeny of [Axin(Fu)]/+ mice. It is revealed here that reappearance of Axin(Fu) was associated with restoration of the IAP insertion. In such mice, alleles of the surrounding microsatellite loci were identical to the alleles observed on chromosomes that carried Axin(Fu). Developmental mosaicism can potentially explain spontaneous reappearance of the Axin(Fu) mutation. Mosaicism can also explain other observations including postnatal changes at the Axin locus, unusual segregation in progeny, and the appearance of [Axin(Fu)]/+ mice that were phenotypically mutant. 2001.

Animals↗

PubMed2001

Vitamin A controls epithelial/mesenchymal interactions through Ret expression.

Mutations or rearrangements in the gene encoding the receptor tyrosine kinase RET result in Hirschsprung disease, cancer and renal malformations. The standard model of renal development involves reciprocal signaling between the ureteric bud epithelium, inducing metanephric mesenchyme to differentiate into nephrons, and metanephric mesenchyme, inducing the ureteric bud to grow and branch. RET and GDNF (a RET ligand) are essential mediators of these epithelial-mesenchymal interactions. Vitamin A deficiency has been associated with widespread embryonic abnormalities, including renal malformations. The vitamin A signal is transduced by nuclear retinoic acid receptors (RARs). We previously showed that two RAR genes, Rara and Rarb2, were colocalized in stromal mesenchyme, a third renal cell type, where their deletion led to altered stromal cell patterning, impaired ureteric bud growth and downregulation of Ret in the ureteric bud. Here we demonstrate that forced expression of Ret in mice deficient for both Rara and Rarb2 (Rara(-/-)Rarb2(-/-)) genetically rescues renal development, restoring ureteric bud growth and stromal cell patterning. Our studies indicate the presence of a new reciprocal signaling loop between the ureteric bud epithelium and the stromal mesenchyme, dependent on Ret and vitamin A. In the first part of the loop, vitamin-A-dependent signals secreted by stromal cells control Ret expression in the ureteric bud. In the second part of the loop, ureteric bud signals dependent on Ret control stromal cell patterning.

Animals↗

PubMed2001

Vitamin E and lipid peroxide plasma levels predict the risk of cardiovascular events in a group of healthy very old people.

OBJECTIVES: To assess whether systemic oxidative stress can predict the risk of first myocardial infarction, ischemic stroke, and congestive heart failure. DESIGN: A longitudinal study started in 1992 and completed in 1997. SETTING: Community-based, outpatient. PARTICIPANTS: 102 apparently healthy, community-dwelling subjects age 80 and older from the Vibrata valley, Teramo, Italy. MEASUREMENTS: Plasma vitamin E, beta-carotene, vitamin C, fluorescent products of lipid peroxidation (FPLPs), and serum lipids were determined at enrollment. RESULTS: Thirty-two cardiovascular events were recorded in 47.4 months of follow-up. The subjects with vitamin E levels in the highest quartile had a risk of cardiovascular events one-sixth those with vitamin E levels in the lowest quartile (relative risk (RR) = 0.16; 95% confidence interval (CI) = 0.04-0.55). The subjects with FPLPs in the highest quartile had a risk seven times greater than those with FPLPs in the lowest quartile (RR = 7.61; 95% CI = 2.23-25.96). No association was observed for vitamin C, beta-carotene, or total cholesterol. Multivariate adjustment for known risk factors did not significantly change the results. CONCLUSIONS: Our results suggest that in apparently healthy, community-dwelling very old subjects, base-line plasma concentration of vitamin E and FPLPs predicts the risk of future cardiovascular events. We confirm previous data showing that total cholesterol is not a predictor of cardiovascular disease in people age 80 and older.

Age Distribution↗

PubMed2001

High vitamin E plasma levels and low low-density lipoprotein oxidation are associated with the absence of atherosclerosis in octogenarians.

OBJECTIVES: To identify the biological characteristics of older subjects with vascular successful aging (VASA), defined as the absence of instrumental signs and clinical symptoms of atherosclerosis in the extracoronary and coronary vessels. DESIGN: A cross-sectional study. SETTING: A university-affiliated outpatient clinic. PARTICIPANTS: Sixty older subjects (30 with VASA and 30 controls with moderate carotid atherosclerosis (AG group)) from a sample of 705 subjects age 75 and older consecutively screened. MEASUREMENTS: Clinical examination; ultrasonographic examination of carotid, vertebral, abdominal aortic, iliac, and femoral arteries; electrocardiogram; and laboratory evaluation (lipid profile, lipophilic antioxidants, and markers of low-density lipoprotein (LDL) oxidation). RESULTS: Compared with controls, there were more females in the VASA group (82% vs 50%, P <.01), and fewer previous smokers (20.5% vs 52.5%, P <.01). Vitamin E/total cholesterol levels both in plasma (4.81 vs 3.51 micromol/mmol, P <.001) and in isolated LDLs (2.71 vs 1.86 microg/mg LDL cholesterol (LDL-C), P <.01), were higher in the VASA group, as was the resistance of LDLs to in vitro oxidation (as indicated by a longer duration of the lag phase: 80.2 vs 65.6 minutes, P <.001). The level of fluorescent products of lipid peroxidation (FPLPs) in native LDLs was lower in the VASA group (13.5 vs 18.8 URF/mg LDL-C, P <.001). Multivariate logistic regression analysis showed that only plasma vitamin E level (odds ratio (OR) = 6.04, 95% confidence interval (CI) = 1.48-24.63) and FPLPs in LDLs (OR = 0.53, 95% CI = 0.31-0.91) were independently associated with VASA. CONCLUSIONS: These results suggest that an appropriate level of vitamin E and a low level of LDL oxidation might be important for reaching advanced age without developing atherosclerosis.

Aged↗

PubMed2001

White blood cell count is associated with some features of metabolic syndrome in a very old population.

BACKGROUND AND AIMS: Although the association between white blood cell (WBC) counts and the risk of cardiovascular disease has been repeatedly described, its biological mechanism is still unclear. A significant correlation has been demonstrated in adults between WBC counts and some risk factors for coronary heart disease (CHD), including insulin resistance. The aims of this study were: 1) to investigate the association between WBC count and some risk factors for atherosclerosis in a sample of octo-nonagenarians; and 2) to test the hypothesis of an association between WBC count and "metabolic syndrome", a clinical condition mediated by insulin resistance. METHODS AND RESULTS: The study involved 160 free-living healthy octo-nonagenarians participating in the Val Vibrata Aging Project, whose WBC count, and anthropometric and metabolic parameters were measured using standardised methods. WBC count correlated positively with the logarithm of triglyceride, apoprotein B and glucose levels, and negatively with high-density lipoprotein cholesterol: the subjects with low high-density lipoprotein and high triglyceride levels had higher WBC count than normal subjects. The WBC count were significantly higher in the subjects with four or more of six features of metabolic syndrome than in those with three or less. CONCLUSIONS: The results of this study support the existence of a significant association between WBC count and some of the typical features of metabolic syndrome in very old subjects.

Aged↗

PubMed2000

Domains of axin and disheveled required for interaction and function in wnt signaling.

Disheveled blocks the degradation of beta-catenin in response to Wnt signal by interacting with the scaffolding protein, Axin. To define this interaction in detail we undertook a mutational and binding analysis of the murine Axin and Disheveled proteins. The DIX domain of Axin was found to be important for association with Disheveled and two other regions of Axin (between residues 1-168 and 600-810) were identified that can promote the association of Axin and Disheveled. We found that the DIX domain of Disheveled is critical for association with Axin in vivo and for Disheveled activity. The Disheveled DIX domain controlled the ability of Disheveled to induce the accumulation of cytosolic beta-catenin whereas the PDZ domain was not essential to this function.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Developmentally distinct effects on human epsilon-, gamma- and delta-globin levels caused by the absence or altered position of the human beta-globin gene in YAC transgenic mice.

The human beta-globin locus has been an important model system in the study of developmentally regulated transcription in multigene chromosomal domains. In this study, primer extension and sensitive real-time RT-PCR assays were used to quantify the effects of beta-globin sequence modifications on epsilon-, gamma- and delta-globin levels in transgenic mice. E11.5 primitive erythroid cells showed a surprisingly large increase in epsilon-globin in the absence of the beta-globin gene (beta- locus), which is weakly expressed at that stage of development. E17.5 fetal liver and adult erythroid cells, in which beta-globin expression approaches its maximum, showed an unexpectedly small, statistically insignificant stimulation of gamma- and delta-globin levels in the absence of beta-globin sequence. Analysis of erythroid colonies produced by in vitro differentiation of embryonic stem cells indicated that the absence of the human beta-globin gene had no effect on gamma-globin expression. These results suggest that competitive influences need not be linked directly to transcription level or distance from the locus control region (LCR), and that the large increases in gamma-globin levels seen in some human deletional beta-thalassemias and hereditary persistence of fetal hemoglobin conditions are most likely to be due to effects other than loss of beta-globin competition. In transgenic mice with beta-globin sequences inserted between epsilon and the LCR in a beta- locus (betaup), the expression of epsilon-, gamma- and delta-globins suggested that stage-specific sensitivity to loss of LCR activity may be a more important parameter than position relative to the LCR. The relationship of these measurements of transgenic globin expression to a possible binary model of globin LCR action and to mimicry from red blood cell loss due to transgenic globin imbalances are discussed.

Adult↗

PubMed2000

C-cell hyperplasia, pheochromocytoma and sympathoadrenal malformation in a mouse model of multiple endocrine neoplasia type 2B.

Dominantly inherited multiple endocrine neoplasia type 2B (MEN2B) is characterized by tumors of the thyroid C-cells and adrenal chromaffin cells, together with ganglioneuromas of the gastrointestinal tract and other developmental abnormalities. Most cases are caused by substitution of threonine for Met918 in the RET receptor tyrosine kinase, which is believed to convert the RET gene to an oncogene by altering the enzyme's substrate specificity. We report the production of a mouse model of MEN2B by introduction of the corresponding mutation into the ret gene. Mutant mice displayed C-cell hyperplasia and chromaffin cell hyperplasia progressing to pheochromocytoma. Homozygotes did not develop gastrointestinal ganglioneuromas, but displayed ganglioneuromas of the adrenal medulla, enlargement of the associated sympathetic ganglia and a male reproductive defect. Surprisingly, homozygotes did not display any developmental defects attributable to a loss-of-function mutation. Thus, while our results support the conclusion that the Met918Thr substitution is responsible for MEN2B, they suggest that the substrate specificity of the RET kinase does not interfere with its normal role in the development of the kidneys and enteric nervous system.

Adrenal Gland Neoplasms↗

PubMed2000

Purification of GSK-3 by affinity chromatography on immobilized axin.

Glycogen synthase kinase 3 (GSK-3), an element of the Wnt signalling pathway, plays a key role in numerous cellular processes including cell proliferation, embryonic development, and neuronal functions. It is directly involved in diseases such as cancer (by controlling apoptosis and the levels of beta-catenin and cyclin D1), Alzheimer's disease (tau hyperphosphorylation), and diabetes (as a downstream element of insulin action, GSK-3 regulates glycogen and lipid synthesis). We describe here a rapid and efficient method for the purification of GSK-3 by affinity chromatography on an immobilized fragment of axin. Axin is a docking protein which interacts with GSK-3ss, beta-catenin, phosphatase 2A, and APC. A polyhistidine-tagged axin peptide (residues 419-672) was produced in Escherichia coli and either immobilized on Ni-NTA agarose beads or purified and immobilized on CNBr-activated Sepharose 4B. These "Axin-His6" matrices were found to selectively bind recombinant rat GSK-3 beta and native GSK-3 from yeast, sea urchin embryos, and porcine brain. The affinity-purified enzymes displayed high kinase activity. This single step purification method provides a convenient tool to follow the status of GSK-3 (protein level, phosphorylation state, kinase activity) under various physiological settings. It also provides a simple and efficient way to purify large amounts of active recombinant or native GSK-3 for screening purposes.

Amino Acid Sequence↗

PubMed2000

Unusual inheritance of the AxinFu mutation in mice is associated with widespread rearrangements in the proximal region of chromosome 17.

AxinFu is a mutation in mice that causes fused tails and other developmental abnormalities as a result of insertion of an intracisternal-A particle (IAP), a murine retrotransposon, into intron 6. In a small percentage of offspring we found that the mutant allele reverts to wild-type through loss of the insertion with concomitant disappearance of the mutant phenotype. Investigation of a series of microsatellite loci in the proximal region of chromosome 17 revealed novel alleles which arise simultaneously with disappearance of IAP from AxinFu. These novel microsatellite variants are distinct from the parental alleles and those so far discovered are organized into two haplotypes. Both haplotypes demonstrate stable Mendelian inheritance. Results show that these rearrangements, which are involved in the production of the new haplotypes, exceed millions of base pairs.

Animals↗

PubMed2000

Twenty-four-hour autonomic nervous function in sustained and "white coat" hypertension.

BACKGROUND: It is unknown whether "white coat" hypertension, also known as isolated clinic hypertension, shares similarities in pathophysiologic background with sustained hypertension. Therefore we evaluated 24-hour autonomic nervous function in sustained and white coat hypertension. METHODS: We selected 12 patients with sustained hypertension (clinic blood pressure >/=140/90 mm Hg and daytime blood pressure >135/85 mm Hg) and 12 patients with white coat hypertension (clinic blood pressure >/=140/90 mm Hg and daytime blood pressure <135/85 mm Hg) from patients undergoing ambulatory blood pressure monitoring and 12 normotensives for study inclusion. Groups were matched for age, sex, and body mass index and had similar dietary pattern and occupational status (civil servants with sedentary jobs). Subjects underwent noninvasive 24-hour monitoring of blood pressure, R-R interval of the electrocardiogram, body position, activity rate, and ambient temperature. Power spectral analysis of R-R intervals was performed with an autoregressive model to obtain the low-frequency component, the high-frequency component, and their ratio. Subjects also collected 24-hour urine samples for examination of norepinephrine and epinephrine excretion by high-performance liquid chromatography. RESULTS: Work and sleep time, body position, ambient temperature, and activity were not different among the groups. Daytime, nighttime, and 24-hour low-frequency/high-frequency ratios were significantly higher in patients with sustained hypertension than in patients with white coat hypertension (3.4 +/- 0.45 vs 2.65 +/- 0.45, 2.35 +/- 0.60 vs 1. 82 +/- 0.45, and 3.04 +/- 0.45 vs 2.4 +/- 0.35, respectively, P <. 05). Urinary norepinephrine excretion (53 +/- 12 microg vs 29.5 +/- 6 microg; P <.05) and vanillylmandelic acid excretion (4.45 +/- 0.6 mg vs 3.1 +/- 0.55 mg; P <.05) during the 24 hours were significantly higher in patients with sustained hypertension than in those with white coat hypertension. There was no difference between those with white coat hypertension and normotensives concerning the aforementioned parameters. CONCLUSIONS: Our findings indicate whole-day sympathetic overactivity in sustained hypertension but not in white coat hypertension, suggesting that these conditions show some differences in pathophysiologic background.

Adult↗

PubMed2000

Increased circulating nitric oxide in young patients with type 1 diabetes and persistent microalbuminuria: relation to glomerular hyperfiltration.

Hyperglycemia has been causally linked to vascular and glomerular dysfunction by a variety of biochemical mechanisms, including a glucose-dependent abnormality in nitric oxide (NO) production and action. NO is a candidate for mediating hyperfiltration and the increased vascular permeability induced by diabetes. Serum nitrite and nitrate (NO2-+ NO3-) concentrations were assessed as an index of NO production in 30 adolescents and young adults with type 1 diabetes, 15 with and 15 without microalbuminuria (albumin excretion rate [AER] between 20 and 200 microg/min), compared with a well-balanced group of healthy control subjects. In all subjects, glomerular filtration rate (GFR) was determined by radionuclide imaging. Our study showed that NO2- + NO3- serum content and GFR values were significantly higher in microalbuminuric diabetic patients than in the other 2 groups. GFR was significantly and positively related to AER levels (r2 = 0.75, P < 0.0001), whereas NO2- + NO3- serum content was independently associated with both AER and GFR values (beta = 2.086, P = 0.05, beta = 1.273, P = 0.0085, respectively), suggesting a strong link between circulating NO, glomerular hyperfiltration, and microalbuminuria in young type 1 diabetic patients with early nephropathy. Interestingly, mean HbA1c, serum concentration was significantly higher in microalbuminuric than in normoalbuminuric diabetic subjects (P < 0.05) and was independently associated with AER values, suggesting a role for chronic hyperglycemia in the genesis of diabetic nephropathy. Moreover, HbA1c serum concentration was significantly and positively related to NO2 + NO3 serum content (r2 = 0.45, P = 0.0063) and GFR values (r2 = 0.57, P = 0.0011), suggesting that chronic hyperglycemia may act through a mechanism that involves increased NO generation and/or action. In conclusion, we suggest that in young type 1 diabetic patients with early nephropathy, chronic hyperglycemia is associated with an increased NO biosynthesis and action that contributes to generating glomerular hyperfiltration and persistent microalbuminuria.

Adolescent↗