The signaling pathway for beta1-integrin/ERKs is involved in the adaptation of adipocyte functions to cell size.
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Adipocytes↗
Biomedical subjects
R Bazin
Publications and source records attributed to R Bazin.
Cholesterol, a cell size-dependent signal that regulates glucose metabolism and gene expression in adipocytes.
Enlarged fat cells exhibit modified metabolic capacities, which could be involved in the metabolic complications of obesity at the whole body level. We show here that sterol regulatory element-binding protein 2 (SREBP-2) and its target genes are induced in the adipose tissue of several models of rodent obesity, suggesting cholesterol imbalance in enlarged adipocytes. Within a particular fat pad, larger adipocytes have reduced membrane cholesterol concentrations compared with smaller fat cells, demonstrating that altered cholesterol distribution is characteristic of adipocyte hypertrophy per se. We show that treatment with methyl-beta-cyclodextrin, which mimics the membrane cholesterol reduction of hypertrophied adipocytes, induces insulin resistance. We also produced cholesterol depletion by mevastatin treatment, which activates SREBP-2 and its target genes. The analysis of 40 adipocyte genes showed that the response to cholesterol depletion implicated genes involved in cholesterol traffic (caveolin 2, scavenger receptor BI, and ATP binding cassette 1 genes) but also adipocyte-derived secretion products (tumor necrosis factor alpha, angiotensinogen, and interleukin-6) and proteins involved in energy metabolism (fatty acid synthase, GLUT 4, and UCP3). These data demonstrate that altering cholesterol balance profoundly modifies adipocyte metabolism in a way resembling that seen in hypertrophied fat cells from obese rodents or humans. This is the first evidence that intracellular cholesterol might serve as a link between fat cell size and adipocyte metabolic activity.
3T3 Cells↗
Bilateral severe keratoconus after laser in situ keratomileusis in a patient with forme fruste keratoconus.
We report a case of bilateral keratoconus after laser in situ keratomileusis (LASIK). Before surgery, the patient had a forme fruste keratoconus, which evolved rapidly to a severe form of keratoconus in the months following LASIK. From this case, we conclude that forme fruste keratoconus is a contraindication to LASIK.
Cornea↗
Impaired beta-adrenergic signaling pathway in white adipocytes of suckling fa/fa Zucker rats: a defect in receptor coupling.
BACKGROUND: In fa/fa Zucker rats, leptin receptor deficiency is responsible for both a deficit of energy expenditure and hyperphagia which lead to massive obesity and insulin resistance in adulthood. This obesity is also characterised by alterations of the beta-adrenergic signaling pathway. OBJECTIVE: To determine whether alterations in beta-adrenergic pathway could occur at the onset of obesity when fa/fa rats are not yet hyperinsulinemic. ANIMALS: Fourteen-day-old suckling fa/fa and Fa/fa littermates (from heterozygous lean (Fa/fa) female and homozygous obese (fa/fa) male mating). MEASUREMENTS: Membranes were prepared from isolated adipocytes after collagenase treatment of inguinal adipose tissue. The response of adenylyl-cyclase activity to stimulation by isoprenaline, GTPgamma-S or forskolin was studied. Bmax and Kd of (beta1+beta2) and of beta3 adrenoceptors were measured using 3H-CGP saturation binding experiments. mRNA concentration of beta1- and beta3-AR was determined by semi-quantitative RT-PCR. G(s)alpha protein was quantified by Western blotting and Gi protein by ADP-ribosylation. RESULTS: Despite an almost normal body weight, inguinal fat pad weight was increased two-fold by the expression of fa mutation. This increase was entirely accounted for by fat cell hypertrophy (x2.5 in volume). In fa/fa compared to Fa/fa pups, response of adenylyl cyclase to isoprenaline was decreased two-fold but responses to GTPgammaS or forskolin were unchanged. Density of (beta1+beta2) and beta3-AR was not affected by the fa/fa genotype, as well as G(s)alpha and Gi concentration. CONCLUSION: Response of inguinal fat cells to catecholamines was decreased without any quantitative modifications of the different elements of the adenylyl cyclase cascade. This suggests an alteration in the coupling between beta-AR and G proteins. Due to the important increase in fat cell volume we hypothesize that changes in the physical properties of plasma membranes and/or changes in cytoskeleton-extracellular-matrix interactions could disturb the beta-adrenergic pathway responsiveness. In addition to the excess of lipid storage, which occurs very early at the onset of obesity, the impairment of the responsiveness to catecholamines reported in this study might worsen the obesity syndrome.
Adenylyl Cyclases↗
Conjugated dienes: a critical trait of lipoprotein oxidizability in renal fibrosis.
BACKGROUND: We assessed whether a differential oxidizability of apolipoprotein B (apo B)-containing lipoproteins (LDL and VLDL) may explain the oxidative stress that we had observed at the onset of renal fibrosis in Zucker obese (ZO) rats (Nephrol Dial Transplant 2000, 15: 467--476). METHODS: Ex vivo copper-induced oxidation of lipoproteins was performed in 1-, 3-, and 9-month-old ZO and age-matched lean (ZL) rats. LDL/VLDL oxidizability was determined by spectrophotometry at 234 nm by monitoring the formation of conjugated diene hydroperoxides. RESULTS: A significant increase in lag time (reflecting the resistance to oxidation) was observed in ZO rats at 3 months while the maximal diene production (reflecting the amount of hydroperoxides formed during oxidation) was higher in ZO than in ZL rats as early as 1 month. Lipoproteins were larger in ZO than in ZL rats, as shown by their core to surface component ratio. Furthermore, ZO lipoproteins had increased vitamin E and polyunsaturated fatty acid (PUFA) content, with no change in vitamin E/PUFA ratio. CONCLUSIONS: Rather than oxidizability of apo B-containing lipoproteins, the ability of these molecules to produce high levels of conjugated dienes, which can act as toxic tissue messengers, appears to be a critical trait in the development of renal fibrosis in this rat model of obesity and renal fibrosis.
Alkenes↗
Inflammation is probably not a prerequisite for renal interstitial fibrosis in normoglycemic obese rats.
We examined the role of inflammation in the development of renal interstitial fibrosis in Zucker obese rats, which rapidly present kidney lesions in the absence of hypertension and hyperglycemia. Type I and III collagens were quantified using a polarized light and computer-assisted image analyzer. The expression of mRNA encoding matrix components, adhesion molecules, chemokines, and growth factors was followed by RT-PCR. The presence of synthesized proteins as well as lymphocytes and macrophages was determined by immunohistochemistry. Interstitial fibrosis developed in two phases. The first phase occurred as early as 3 mo and resulted from a neosynthesis of type III collagen and fibronectin and a reduction of extracellular matrix catabolism, in parallel with an overexpression of transforming growth factor-beta(1) and in the absence of any lymphocyte or macrophage infiltration. After 6 mo, interstitial fibrosis worsened with a large accumulation of type I collagen, concomitantly with a large macrophage infiltration. Thus inflammation cannot explain the onset of interstitial fibrosis that developed in young, insulinoresistant, normoglycemic, obese Zucker rats but aggravated this process afterward.
Animals↗
Assays of lipogenic enzymes.
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ATP Citrate (pro-S)-Lyase↗
Oxidative stress occurs in absence of hyperglycaemia and inflammation in the onset of kidney lesions in normotensive obese rats.
BACKGROUND: Several factors favour the development of kidney lesions. We examined the role of oxidative stress in the onset of renal alterations that occur in Zucker obese (ZO) fa/fa rats. METHODS: Kidney structure, biological data, glycation parameters, advanced glycation end products (AGE), thiobarbituric acid-reactive substances (TBARS), circulating antibodies anti-malondialdehyde (MDA)-modified low-density lipoprotein (LDL), antioxidant defenses (Cu/Zn and Mn superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) activities, glutathione level), were determined in plasma and/or kidney of young and old ZO rats and lean (ZL) Fa/fa littermates. RESULTS: Renal lesions and functional decline appeared at 3 months in hyperlipidaemic, hyperinsulinaemic, normotensive ZO rats, independently of any macrophage-ED(1)(+)-cell infiltration. At 6 months and thereafter, kidney lesions and functional impairment worsened while numerous ED(1)(+)-cells invaded the interstitium. At 3 and 9 months, TBARS level in the LDL/very low-density lipoprotein fraction and in the kidney was higher in ZO than in ZL rats. Anti-MDA-LDL antibodies were increased in ZO rats. At 3 months, renal activity of Cu/Zn SOD was higher, and activities of catalase and GPx lower in ZO than in ZL rats, leading to an accumulation of hydrogen peroxide (H(2)O(2)). At 9 months, a decrease in Cu/Zn SOD activity and an increase in glutathione level were observed. Blood glucose and glycated proteins, as well as AGE in kidney, remained similar in both ZL and ZO rats, whatever their age. CONCLUSION: These data suggest that oxidative stress triggers, at an early age, the onset of kidney lesions and functional impairment in ZO rats, in absence of hyperglycaemia, hypertension and inflammation.
Animals↗
Evidence for the presence of several phosphodiesterase isoforms in brown adipose tissue of Zucker rats: modulation of PDE2 by the fa gene expression.
The present study was undertaken to characterise the phosphodiesterases (PDEs) present in brown adipose tissue (BAT) of Zucker rat pups and to determine whether the capacity for degradation of cyclic nucleotides was affected by the fatty genotype. Regardless of the genotype, PDE2-4 contributed to total PDE activity, the PDE3 activity equalling the sum of PDE2 and 4 activities. In fa/fa compared to Fa/fa rats, (a) PDE2 activity was significantly increased, (b) Western blot analysis of PDE2 revealed two signals at 71 and 105 kDa, with changes in protein being in good parallelism with changes in activity, (c) the PDE2 mRNA concentration was also significantly increased. In good agreement, the cGMP concentration was decreased in BAT from fa/fa pups.
Adipose Tissue, Brown↗
Production of a diagnostic monoclonal antibody in perennial alfalfa plants.
The increasing use of monoclonal antibodies (mAbs) in diagnostic reagents necessitates efficient and cost-effective mAb production methods. In blood banks, one of the most routinely used reagents is the anti-human IgG reagent used for the detection of non-agglutinating antibodies. Here we report the production of a functional, purified anti-human IgG, through the expression of its encoding genes in perennial transgenic alfalfa. Transgenic plants expressing the light- and heavy-chain encoding mRNAs were obtained, and plants from crosses were found to express fully assembled C5-1. The purification procedure yielded mainly the H2L2 form with specificity and affinity identical to those of hybridoma-derived C5-1. The ability to accumulate the antibody was maintained both in parental F1 lines during repeated harvesting and in clonal material; the antibody was stable in the drying hay as in extracts made in pure water. Also, plant and hybridoma-derived C5-1 had similar in vivo half-lives in mice. These results indicate that plant C5-1 could be used in a diagnostic reagent as effectively as hybridoma-derived C5-1, and demonstrates the usefulness of perennial systems for the cost-effective, stable, and reliable production of large amounts of mAbs.
Animals↗
The VF-14 index of functional visual impairment in candidates for a corneal graft.
PURPOSE: To validate the Visual Function-14 (VF-14) index of functional visual impairment in candidates for a corneal graft. METHODS: One hundred thirty-four patients who were candidates for a corneal graft participated in this study between August 1996 and February 1997. Demographic, ocular history, best-corrected visual acuity, and detailed ocular examination data were collected. Functional visual impairment information was obtained by telephone interviews using the following: VF-14, SF-36 (Short Form-36, a more generic measure of general health function), and Visual Symptom Score, and four questions measuring the overall amount of trouble with vision, dissatisfaction with vision, ocular pain, and discomfort. RESULTS: The average age of corneal graft candidates was 64 +/- 18 years (range, 18 to 90 years) and 60% were women. The most frequent corneal disease was pseudophakic bullous keratopathy (41%). Ocular comorbidities included glaucoma or ocular hypertension (30%) and cataract (19%). The mean best-corrected visual acuity of the eye scheduled for surgery was 1.33 +/- 0.56 logMAR whereas the best eye best-corrected visual acuity was 0.36 +/- 0.44 logMAR. The mean VF-14 score was 73% +/- 26%, and the internal consistency was high, with a Cronbach alpha value of 0.94. The VF-14 correlated strongly with the best eye best-corrected visual acuity. It also correlated strongly with the Visual Symptom Score, the global measures of trouble and dissatisfaction with vision. Candidates for a corneal graft had low scores for all eight general health concepts evaluated with the SF-36, and the VF-14 correlated with seven of the eight SF-36 subscales. CONCLUSION: The VF-14 is a valid measure of functional visual impairment in candidates for a corneal graft. The Visual Symptom Score and the SF-36 are also useful indices in such patients.
Adolescent↗
Interaction of amiodarone and triiodothyronine on the expression of beta-adrenoceptors in brown adipose tissue of rat.
1. This study was undertaken to evaluate in vivo the influence of amiodarone on the effects of triiodothyronine (T3) in brown adipose tissue (BAT) which are independent of thyroid hormone synthesis and of the conversion of thyroxine (T4) to T3. Thyroidectomized rats were given a replacement dose of T3 (0.5 mg kg(-1) p.o. daily for 3 days) with or without amiodarone (50 mg kg(-1) p.o. daily for 1 week). 2. As assessed by RT-PCR, treatment of thyroidectomized rats with T3 caused a 2 fold decrease in beta3-adrenoceptor (beta3-AR) mRNA levels and a 2 fold increase in beta1-AR mRNA levels. 3. Binding studies using [3H]-CGP 12177 as a ligand showed that treatment of thyoidectomized rats with T3 resulted in a 70% decrease in beta3-AR number and in an 80% increase in beta1-AR in BAT membranes. 4. T3-treatment abolished the increase in BAT adenylyl cyclase (AC) activity induced by CGP12177 in thyroidectomized rats. It also decreased the amount of Gi protein (ADP-ribosylation) by 30%. 5. At variance with the literature on the heart, amiodarone administration did not inhibit the positive effect of T3 on beta1-AR expression in BAT in thyroidectomized rats. However, it antagonized the effect of T3 on beta3-AR number, but not on AC activity or on Gi expression. 6. These results indicate that the effects of thyroid hormones on the responsiveness of BAT to catecholamines involves both receptor and post-receptor mechanisms, they also suggest that interaction between amiodarone and thyroid hormones is highly tissue-specific and depends on the beta-AR subtype.
Adenylyl Cyclases↗
Production and utilization of polyclonal antibodies against nisin in an ELISA and for immuno-location of nisin in producing and sensitive bacterial strains.
Specific nisin polyclonal antibodies (PAb) were produced in rabbits using nisin Z produced by Lactococcus lactis subsp. lactis biovar diacetylactis UL 719. Antisera were obtained from white female New Zealand rabbits that were first immunized with a nisin Z-keyhole limpet haemocyanin conjugate and boosted with free nisin Z. Nisin-specific PAb were purified by affinity chromatography with a yield of 15 mg specific antinisin 100 ml-1 serum. The detection limit of the ELISA test for nisin Z was 0.75 ng ml-1 in buffer but was 1.7 and 3.5 ng ml-1 in milk and complex media broth spiked (5, 10, 20 microg ml-1) with nisin Z, respectively. In nisin Z-spiked samples, the average concentration was between 90 and 107% of actual added amount. In contrast, when the bioassay (microtitration method) was used, only 50-63% of nisin Z biological activity could be detected. In addition, the affinity-purified nisin PAb, antirabbit IgG gold conjugate and transmission electron microscopy were successfully used to locate nisin Z on producing cells and to observe its bactericidal effects against sensitive cells.
Animals↗
Role of presensitization and donor-recipient crossmatching in corneal graft outcome.
PURPOSE: A positive donor-recipient crossmatch (CM) due to preexisting recipient lymphocytotoxic antibodies is known to be an important factor in allograft failure in the majority of organ transplantations. However, the effect of positive CM on corneal graft outcome is less known. METHOD: Between 1982 and 1994, CM was performed by the microlymphocytotoxicity method using donor lymphocytes and recipient pretransplant serum in 759 consecutive corneal transplantations (maximal follow-up, 36 months). Patients were evaluated regarding the type of allospecificity of antibodies involved and their role on corneal graft outcome (rejection and failure). RESULTS: A positive CM was found in 61 patients (8%) and a negative CM in 698 patients (92%). The positive and negative CM groups had similar graft rejection rates at 36 months. Patients with a positive CM due to antibodies directed against donor human leukocyte antigen (HLA) (as defined on the basis of private and public or CREG HLA allele specificities) did not have an increased risk of rejection. However, patients with positive CM and presensitization (previous graft or rejection history) had a statistically significant increase in risk of corneal endothelial rejection. CONCLUSION: This study shows that donor-recipient CM could be a useful procedure for the selection of recipients for corneal transplantation in patients presensitized by anterior graft or previous corneal rejection.
Adult↗
Analysis of IgM structures involved in J chain incorporation.
J chain is associated with pentameric IgM and polymeric IgA. In IgM, J chain is disulfide bonded to the C575 residue of the mu-chain, located in the mu tail piece (mu tp). Previous studies indicated that mu tp is not sufficient to mediate J chain incorporation into polymeric Ig. In this study, we analyzed which other C mu domains are involved in J chain incorporation. Three altered forms of mouse IgM were analyzed: IgM lacking the C mu 1 domain, IgM in which the C mu 2 and C mu 3 domains were replaced by the hinge region and the C gamma 2 domain of IgG2b, and IgM, in which the C mu 4 domain was replaced by C gamma 3. We found that neither C mu 1, C mu 2, nor C mu 3 was absolutely required for J chain incorporation. The importance of C mu 4 could not be fully analyzed because the C gamma 3 replacement mutant failed to form polymers. Also, we found that the glycosylation site at asparagine 563 of mu tp was important for J chain incorporation. Disruption of this site by replacement of either asparagine 563 by tyrosine or serine 565 by phenylalanine resulted in diminished J chain incorporation and increased production of hexameric IgM. These results demonstrate the importance of structural elements located close to mu tp in the incorporation of J chain into IgM.
Amino Acid Sequence↗
Role of ABO and Lewis blood group antigens in donor-recipient compatibility of corneal transplantation rejection.
PURPOSE: There are conflicting results regarding the role of human leukocyte antigen (HLA) matching and ABO compatibility in corneal graft rejection for low- and high-risk patients. Lewis blood group antigens could be an important histocompatibility system. Beneficial effects of Lewis antigens matching have been reported in renal transplantation, but its effect is still unknown in corneal allografting. METHODS: Between 1987 and 1993, ABO, Lewis and HLA phenotypes were determined in 697 consecutive grafts of corneal transplantations. The effect of Lewis matching on corneal endothelial rejection was evaluated over a 3-year period. Data analysis was done by plotting survival curves with the Kaplan-Meier method for survivorship data and performing statistical analysis with the log-rank test (Mantel-Haenszel test) for curve comparison. RESULTS: In vascularized recipients, the ABO, Lewis, and HLA systems did not influence the graft outcome. However, for the unvascularized recipients, the endothelial 3-year rejection rate was significantly lower for both Lewis compatible patients (84% vs. 68%; log rank = 0.03) and HLA compatible patients (86% vs 72%; log rank = 0.001), but not for the ABO-matched patients (82% vs. 79%; log rank = 0.56). CONCLUSIONS: The authors' study suggests that Lewis antigens and HLA matching could positively influence corneal graft survival for the unvascularized recipients, but it did not seem to have any effect in vascularized recipients.
ABO Blood-Group System↗
Effects of triiodothyronine administration on the adenylyl cyclase system in brown adipose tissue of rat.
This study was undertaken to investigate the effect of triiodothyronine (T3) administration to euthyroid rats on beta 3-adrenoceptor (beta 3-AR) expression and on the different components of the adenylyl cyclase (AC) system in brown adipose tissue (BAT). In rats treated with T3, the beta 3-AR density (assessed by the binding of [3H]CGP-12177) showed a decrease of 50%, as did their mRNA, as analyzed by reverse transcriptase-polymerase chain reaction. In hyperthyroid rats, compared with control rats, there was a 40% increase in G alpha s activity (stimulated by NaF or GTP gamma S) and a fourfold increase in the protein concentration (Western blotting). In contrast, the level of the pertussis toxin substrate Gi declined by 35% in response to T3. Analysis of dose-response curves for isoproterenol and CGP-12177 revealed that neither basal nor stimulated AC activities nor 50% stimulatory concentration for these agonists was changed by T3 administration. In conclusion, these results suggest that downregulation of the beta 3-AR by T3 was counter-balanced by changes in other components of the AC cascade (i.e., Gs and Gi), so no change occurred in the capacity of BAT to generate adenosine 3',5'-cyclic monophosphate.
Adenylyl Cyclases↗
Early influx of glomerular macrophages precedes glomerulosclerosis in the obese Zucker rat model.
Because hyperlipidemia and macrophage influx appear to play a key role in the genesis of renal glomerulosclerosis, this study examined the temporal relationship between hyperlipidemia (triglycerides and cholesterol), mononuclear cell influx, changes in glomerular structure, and expansion of the extracellular matrices in obese Zucker rats, which rapidly develop hyperlipidemia and spontaneous glomerulosclerosis. Lean and obese Zucker rats were fed a standard diet, and were euthanized at 14 days, 1, 3, 6, 9, and 12 months. Plasma lipid, insulin, and creatinine levels were measured, and the presence of inflammatory cells in the glomerulus was assessed by immunohistochemistry on kidney sections. Plasma lipids and insulin and macrophage density were significantly greater in obese than in lean rats as early as 1 month. Computer-assisted image analysis was used to evaluate the glomerular domain surface areas. The morphometric measurements showed that glomeruli of obese rats rapidly became hypertrophied after 3 months, as a result of a very large increase in the mesangial domain. The expression of genes for extracellular matrix components and inhibitors of extracellular matrix proteinases (TIMP-1 and TIMP-2) was monitored in microdissected glomeruli. Reverse transcription-polymerase chain reaction showed increases in mRNA for Type IV collagen and fibronectin and for the two metalloproteinase inhibitors, each of which might participate in this matrix expansion. Thus, the development of hyperlipidemia plus macrophage influx at a very early age may initiate a sequence of events leading to glomerulosclerosis later on.
Age Factors↗