FRINK Linked Data Fragments server

Matches in SemOpenAlex for { <https://semopenalex.org/work/W2017604923> ?p ?o ?g. }

• W2017604923 endingPage "244" @default.
• W2017604923 startingPage "237" @default.
• W2017604923 abstract "Studies with I125-labeled low-density lipoproteins (LDLs) have shown the presence of high-affinity LDL receptors on insulin-producing β cells but not on neighboring α cells. By using gold-labeled lipoproteins, we demonstrate receptor-mediated endocytosis of LDLs and very low-density lipoproteins in rat and human β cells. Specific for human β cells is the fusion of LDL-containing endocytotic vesicles with lipid-storing vesicles (LSVs. diameter, 0.6–3.6 μm), which are absent in rodent β cells. LSVs also occur in human pancreatic α and duct cells, but these sequester little gold-labeled LDL. In humans <25 years old, LSVs occupy 1% of the cytoplasmic surface area in β, α, and duct cells. In humans >50 years old, LSV surface area in β cells (11 ± 2% of cytoplasmic surface area) is fourfold higher than in α and duct cells and 10-fold higher than in β cells at younger ages (P < 0.001); the mean LSV diameter in these β cells (1.8 ± 0.04 μm) is larger than at younger ages (1.1 ± 0.2 μm; P < 0.005). Oil red O staining on pancreatic sections confirms that neutral lipids accumulate in β cells of older donors. We conclude that human β cells can incorporate LDL and very low-density lipoprotein material in LSVs. The marked increase in the LSV area of aging human β cells raises the question whether it is caused by prolonged exposure to high lipoprotein levels such as occurs in Western populations and whether it is causally related to the higher risk for type 2 diabetes with aging. Studies with I125-labeled low-density lipoproteins (LDLs) have shown the presence of high-affinity LDL receptors on insulin-producing β cells but not on neighboring α cells. By using gold-labeled lipoproteins, we demonstrate receptor-mediated endocytosis of LDLs and very low-density lipoproteins in rat and human β cells. Specific for human β cells is the fusion of LDL-containing endocytotic vesicles with lipid-storing vesicles (LSVs. diameter, 0.6–3.6 μm), which are absent in rodent β cells. LSVs also occur in human pancreatic α and duct cells, but these sequester little gold-labeled LDL. In humans <25 years old, LSVs occupy 1% of the cytoplasmic surface area in β, α, and duct cells. In humans >50 years old, LSV surface area in β cells (11 ± 2% of cytoplasmic surface area) is fourfold higher than in α and duct cells and 10-fold higher than in β cells at younger ages (P < 0.001); the mean LSV diameter in these β cells (1.8 ± 0.04 μm) is larger than at younger ages (1.1 ± 0.2 μm; P < 0.005). Oil red O staining on pancreatic sections confirms that neutral lipids accumulate in β cells of older donors. We conclude that human β cells can incorporate LDL and very low-density lipoprotein material in LSVs. The marked increase in the LSV area of aging human β cells raises the question whether it is caused by prolonged exposure to high lipoprotein levels such as occurs in Western populations and whether it is causally related to the higher risk for type 2 diabetes with aging. Type 2 diabetes is frequent in several aging populations.1Zimmet PZ McCarty DJ de Courten MP The global epidemiology of non-insulin-dependent diabetes mellitus and the metabolic syndrome.J Diab Comp. 1997; 11: 60-68Abstract Full Text PDF Scopus (230) Google Scholar A diagnosis of type 2 diabetes indicates that the pancreatic β cells are no longer capable of meeting metabolic demands for insulin. Nutritional factors in Western life style can contribute to this development by increasing the need for insulin and/or by reducing the functional reserve of the β cells. Fat consumption is an established risk factor.2Marshall JA Hamman RF Baxter J High-fat, low-carbohydrate diet, and the etiology of non-insulin-dependent diabetes mellitus: the San Luis Valley Diabetes Study.Am J Epidemiol. 1991; 134: 590-603PubMed Google Scholar, 3Marshall JA Hoag S Shetterly S Hamman RF Dietary fat predicts conversion from impaired glucose tolerance to NIDDM.Diabetes Care. 1994; 17: 50-56Crossref PubMed Scopus (204) Google Scholar Elevated fatty acid levels are responsible for reduced peripheral sensitivity to insulin.4McGarry JD What if Minkowski had been ageusic? An alternative angle on diabetes.Science. 1992; 258: 766-770Crossref PubMed Scopus (567) Google Scholar, 5McGarry JD Disordered metabolism in diabetes: have we underemphasized the fat component?.J Cell Biochem. 1994; 55: 29-38Crossref PubMed Scopus (100) Google Scholar, 6Groop LC Saloranta C Shank M Bonadonna RC Ferrannini E DeFronzo RA The role of free fatty acid metabolism in the pathogenesis of insulin resistance in obesity and noninsulin-dependent diabetes mellitus.J Clin Endocrinol Metab. 1991; 72: 96-107Crossref PubMed Scopus (288) Google Scholar They can also lead to reduced capacity of the β cells to maintain an adequate hyperinsulinemia in this condition.7Zhou Y-P Grill VE Long-term exposure of rat pancreatic islets to fatty acids inhibits glucose-induced insulin secretion and biosynthesis through a glucose fatty acid cycle.J Clin Invest. 1994; 93: 870-876Crossref PubMed Scopus (625) Google Scholar Studies in diabetes-prone rodents have demonstrated that prolonged elevation of fatty acids can cause β-cell dysfunctions, as well as β-cell death by apoptosis.8Lee Y Hirose H Ohneda M Johnson JH McGarry JD Unger RH β-Cell lipotoxicity in the pathogenesis of non-insulin-dependent diabetes mellitus of obese rats: impairment in adipocyte-β-cell relationships.Proc Natl Acad Sci USA. 1994; 91: 10878-10882Crossref PubMed Scopus (703) Google Scholar, 9Shimabukuro M Zhou Y-T Levi M Unger RH Fatty acid-induced β-cell apoptosis: a link between obesity and diabetes.Proc Natl Acad Sci USA. 1998; 95: 2498-2502Crossref PubMed Scopus (1006) Google Scholar The higher prevalence of type 2 diabetes in societies with a high fat intake also raises the question whether low-density lipoproteins (LDL. and very low-density lipoproteins (VLDL) exert any direct effects on the pancreatic β cells. We therefore investigated the interactions of LDL and VLDL with normal β cells. It was first shown that both rat and human β cells express high-affinity LDL receptors that also bind VLDL and can internalize both lipoproteins.10Grupping AY Cnop M Van Schravendijk CFH Hannaert J-C Van Berkel TJC Pipeleers DG Low density lipoprotein binding and uptake by human and rat islet β cells.Endocrinology. 1997; 138: 4064-4068Crossref PubMed Scopus (66) Google Scholar In this study, we demonstrate that this internalization contributes to the marked lipid accumulation that is noticed in β cells of aging individuals.Materials and MethodsPreparation of Islet CellsAdult male Wistar rats were housed according to the guidelines of the Belgian Regulations for Animal Care. The protocol was approved by the Ethical Committee for Animal Experiments of the Vrije Universiteit Brussel. Rats were sedated and killed with CO2 followed by decapitation. Islets were isolated by collagenase digestion and dissociated in a calcium-free medium containing trypsin and DNase (both from Boehringer Mannheim, Mannheim, Germany).11Pipeleers DG in't Veld PA Van De Winkel M Maes E Schuit FC Gepts W A new in vitro model for the study of pancreatic A and B cells.Endocrinology. 1985; 117: 806-816Crossref PubMed Scopus (323) Google Scholar Purified β and non-β cells were obtained by autofluorescence-activated cell sorting as described previously.11Pipeleers DG in't Veld PA Van De Winkel M Maes E Schuit FC Gepts W A new in vitro model for the study of pancreatic A and B cells.Endocrinology. 1985; 117: 806-816Crossref PubMed Scopus (323) Google Scholar Cells were cultured in Ham's-F10 medium supplemented with 2 mmol/L l-glutamine, 50 μmol/L 3-isobutyl-1-methylxanthine, 0.075 g/L penicillin, 0.1 g/L streptomycin, 10 mmol/L glucose, and 5 g/L charcoal-treated bovine serum albumin (fraction V, radioimmunoassay grade; Sigma Chemical Co., St. Louis, MO).Human islets were isolated from donor pancreas procured by European hospitals affiliated with Eurotransplant-Bioimplant Services (Leiden, The Netherlands) and β Cell Transplant, a multicenter program on islet cell transplantation in diabetes.12Keymeulen B Ling Z Gorus FK Delvaux G Bouwens L Grupping AY Hendrieckx C Pipeleers-Marichal M Van Schravendijk CFH Salmela K Pipeleers DG Implantation of standardized β-cell grafts in a liver segment of IDDM patients: graft and recipient characteristics in two cases of insulin-independence under maintenance immunosuppression for prior kidney graft.Diabetologia. 1998; 41: 452-459Crossref PubMed Scopus (149) Google Scholar Islets were prepared in the central unit, Medical Campus, Vrije Universiteit Brussel (Brussels, Belgium) using collagenase digestion and Ficoll gradient purification. The islet-enriched gradient interface was harvested, washed, and cultured in Ham's-F10 medium supplemented as previously described.13Ling Z Pipeleers DG Prolonged exposure of human β cells to elevated glucose levels results in sustained cellular activation leading to a loss of glucose regulation.J Clin Invest. 1996; 98: 2805-2812Crossref PubMed Scopus (170) Google Scholar After culture, the human islet cell preparations consisted of 55 to 65% β cells, 6 to 12% α cells, and 20 to 30% nongranulated cells, which have been identified as duct cells.12Keymeulen B Ling Z Gorus FK Delvaux G Bouwens L Grupping AY Hendrieckx C Pipeleers-Marichal M Van Schravendijk CFH Salmela K Pipeleers DG Implantation of standardized β-cell grafts in a liver segment of IDDM patients: graft and recipient characteristics in two cases of insulin-independence under maintenance immunosuppression for prior kidney graft.Diabetologia. 1998; 41: 452-459Crossref PubMed Scopus (149) Google Scholar, 13Ling Z Pipeleers DG Prolonged exposure of human β cells to elevated glucose levels results in sustained cellular activation leading to a loss of glucose regulation.J Clin Invest. 1996; 98: 2805-2812Crossref PubMed Scopus (170) Google Scholar The cultured preparations were dissociated by the same trypsin treatment as described for rat islets.Rat and human islet cell preparations were cultured for 48 hours in polylysine-coated (1 μg/ml, Sigma) wells (Falcon, Franklin Lakes, NJ. at a density of 105 cells/ml before exposure to gold-labeled lipoproteins.Preparation of LDLHuman lipoproteins were prepared from serum of healthy volunteers after an overnight fast. The VLDL and LDL fractions were isolated by ultracentrifugation,14Redgrave TG Roberts DCK West CE Separation of plasma lipoproteins by density-gradient ultracentrifugation.Anal Biochem. 1975; 65: 42-49Crossref PubMed Scopus (865) Google Scholar with one additional run for LDL. The electrophoretic mobility of LDL on 75% agarose exhibited an Rf of 0.24 ± 0.02 SEM (n = 7). All lipoprotein preparations were filtered through a 22-μm filter (Millipore, Molsheim, France) before use. Their protein concentration was determined with the Pierce BCA kit using bovine serum albumin as standard. Colloidal gold particles were conjugated to LDL by electrostatic surface adsorption of their negative charge. This was accomplished by rapid mixing of 1 ml of colloidal gold (20-nm particle size, British BioCell International, Cardiff, UK) per 100 μl of LDL (concentration, 100–150 μg LDL-protein/ml).15Handley DA Arbeeny CM Witte LD Chien S Colloidal gold-low density lipoprotein conjugates as membrane receptor probes.Proc Natl Acad Sci USA. 1981; 78: 368-371Crossref PubMed Scopus (99) Google Scholar Conjugates were examined by negative-stain electron microscopy before use. A similar procedure was used for preparing gold-labeled VLDL.Incubation of Cells with LipoproteinsExperiments with gold-labeled LDL or VLDL were carried out at 4°C for studies on binding and at 37°C for studies on uptake. After incubation, cells were fixed in cacodylate-buffered glutaraldehyde (4.5%, pH 7.3), postfixed in osmium tetroxide (1%), and embedded in Spurr's resin. Ultrathin sections were stained with uranylacetate and lead citrate and examined in a Zeiss EM 109 electron microscope.Ultrastructural localization of acid phosphatase was performed using a modified Gomori reaction.16De Jong ASH Mechanisms of metal-salt methods in enzyme cytochemistry with special reference to acid phosphatase.Histochem J. 1982; 14: 1-33Crossref PubMed Scopus (31) Google Scholar After incubation with the gold-labeled lipoprotein and short fixation of the cells, the reaction medium, containing 0.067 mol/L Tris-maleate, 0.36% β-glycerophosphate, and 0.11% lead nitrate, was added. After a 1-hour incubation at 37°C, cells were prepared for routine transmission electron microscopy, omitting the final uranylacetate-lead citrate staining step.Characterization of Lipid-Storing Vesicles in Human β CellsMorphometric analysis was conducted to determine the individual diameters and surface areas of vesicles containing large (diameter > 0.6 μm) electron-lucent droplets and a peripheral rim of electron-dense material. Isolated islet tissue was examined from donors of different ages. The surface area of these vesicles was expressed as total per cell and as percentage of cellular cytoplasmic surface area (CSA). For each donor preparation, we performed measurements in 20 to 50 cells per cell type and averaged them to one value per cell type. We then averaged these values per donor age group, choosing arbitrarily a young (<25 years) and an old (>50 years) age group. The results are expressed as means ± SEM. The statistical significance of differences was calculated by unpaired Student's t-test, assuming equal variances.Staining for Lipids in Intact Pancreatic TissuePancreatic tissue was examined for the presence of neutral lipids by an oil red O reaction on frozen material. The sections were first briefly immersed in 60% isopropanol, then incubated at room temperature for 1 hour in an oil red O solution,17Ramirez-Zacarias J Castro-Munozledo F Kuri-Harcuch W Quantitation of adipose conversion and triglycerides by staining intracytoplasmic lipids with oil red O.Histochemistry. 1992; 97: 493-497Crossref PubMed Scopus (818) Google Scholar briefly discriminated in 60% isopropanol, and finally rinsed with water. The oil red O reaction was followed by hematoxylin staining. Consecutive sections were stained for insulin to localize the neutral lipids versus the endocrine tissue. Tissue was fixed for 10 minutes in 4% formaldehyde prepared in phosphate-buffered saline (PBS). After washing with PBS, the sections were incubated for 15 minutes in 90. methanol–10% H2O2, washed again with PBS, and incubated for 30 minutes with 10% normal goat serum. The insulin antibody11Pipeleers DG in't Veld PA Van De Winkel M Maes E Schuit FC Gepts W A new in vitro model for the study of pancreatic A and B cells.Endocrinology. 1985; 117: 806-816Crossref PubMed Scopus (323) Google Scholar was then applied at a final concentration of 1:5000 for an overnight incubation at 4°C. After washing with PBS, the biotinylated anti-guinea pig antibody (Vector Laboratories, Burlingame, CA) was added at a concentration of 1:1000 for a 30-minute incubation at room temperature. Positivity was visualized after reaction with diaminobenzidine. Insulin staining was also followed by a standard hematoxylin staining.ResultsBinding and Uptake of Gold-Labeled LDL by Rat β CellsIncubation of rat β cells with gold-labeled LDL at 4°C for 2 hours resulted in an association of gold particles with the plasma membrane but not with the intracellular compartment. Single as well as clustered particles occurred along both coated and noncoated regions of the membrane and, occasionally, in coated pits. No membrane-associated particles were noticed when incubation was carried out in calcium-free medium or when unconjugated colloidal gold was used. Membrane binding of gold-LDL was also negligible in the presence of excess unlabeled LDL and was markedly lower after 24 hours of preincubation with 100 to 400 μg/ml LDL at 37°C. No membrane binding was seen in islet endocrine non-β cells that were incubated in parallel, not even after 4 hours.Incubation at 37°C resulted in a time-dependent increase in the number of intracellular gold particles. After 5 minutes, particles were still associated with the plasma membrane, but, compared with 4°C incubations, a larger proportion occurred in coated pits and coated vesicles (Figure 1a). From 10 minutes on, increasing proportions of particles were found in uncoated vesicles, first as a rim at the inner vesicle membrane and, later on, dissociated from the membrane. The vesicles containing gold particles varied in size and in electron-lucent or electron-dense content (Figure 1b). Some vesicles exhibited a positivity for acid phosphatase. The diameter of vesicles containing gold-labeled LDL was always smaller than 0.6 μm.Binding and Uptake of Gold-Labeled Lipoproteins by Human β CellsIncubation of human β cell preparations with gold-labeled LDL led to the same observations as with rat β cells, namely, association of gold particles with the plasma membrane at 4°C and their uptake in coated and uncoated vesicles at 37°C. After 3 to 6 hours, gold-containing vesicles appeared in the vicinity of larger (diameter > 0.6 μm) vesicles that contained both electron-lucent and electron-dense material, the latter often forming a peripheral rim under the vesicle membrane or delineating several spherical electron-lucent compartments within the same vesicle (Figure 2, a and b). With longer incubation periods, gold-containing vesicles were found to fuse with these large vesicles (Figure 2c). After incorporation, gold particles were mainly present in the peripheral rim of electron-dense material (Figure 2c). At higher magnifications, this gold-containing dense material at the periphery was dispersed between two membranes, the outer one surrounding the large vesicle and the inner one surrounding an intravesicular compartment with mostly electron-lucent material (Figure 3). Gold particles remained sequestered in these large vesicles during subsequent culture for 7 days. A similar uptake and fusion process was noticed with gold-labeled VLDL. Incubation with free gold particles did not result in their uptake and sequestration by the β cells. In non-β cells, only little uptake of gold-labeled LDL or VLDL was seen. The presence of rod-shaped granules in secretory vesicles18Lacy PE The pancreatic β cell: structure and function.N Engl J Med. 1967; 276: 187-195Crossref PubMed Scopus (56) Google Scholar allows the identification of β cells from other endocrine islet cells, even when their relative proportion is decreased as a result of culture.Figure 2Electron micrographs of β cells from a 52-year-old donor. a: Presence of large (1.1–2.6 μm diameter) lipid vesicles with electron-lucent and electron-dense content (original magnification, ×2700). b: After 3 hours of incubation with gold-labeled LDL at 37°C, gold-containing vesicles are found in the proximity of these lipid vesicles (original magnification, ×20,000). c: Fusion of both vesicles with localization of gold particles under the membrane of the lipid-containing vesicles (original magnification, ×20,000). d: Gomori reaction results in lead precipitation in the peripheral rim of some lipid vesicles, indicating acid phosphatase activity (original magnification, ×12,000).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Electron micrograph of large LSV in human β cell that was exposed to gold-labeled LDL. Gold particles are sequestered in the peripheral electron-dense rim of the vesicle, between the outer membrane and the membrane that delineates electron-lucent material. Original magnification, ×32,000.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The large vesicles with which gold-containing vesicles can fuse are apparently filled with lipids because fixation without osmium caused large electron-lucent compartments; after fixation with osmium, they did not present a dense granulation or finger-print structures, suggesting absence of peroxidized lipofuscin. In some of them, the peripheral rim yielded a positive Gomori reaction, indicating the presence of acid phosphatase activity (Figure 2d). The diameter of these membrane-bound vesicles varied widely, from 0.6 to 3.6 μm. Smaller lipid accumulations were occasionally found in the cytoplasm, closely associated with endoplasmic reticulum. These lipid accumulations in vesicles or cytoplasm were not detected in β cells isolated and/or cultured from adult (10-week-old) rats or mice (data not shown).Age-Dependent Accumulation of Lipid-Storing Vesicles in Human β CellsElectron microscopy of intact human pancreatic tissue demonstrated the presence of the same lipid-containing vesicles in the β cells, indicating that they were not formed as an artifact during the isolation or culture procedure. On routine examination of isolated human islets, we noticed that their abundance markedly increased with the age of the donor (Table 1). No correlation was found with donor sex or body mass index. When the surface area of the lipid-storing vesicles (LSVs) was plotted against the age of the donors, a positive correlation was detected (Figure 4; r = 0.938; P < 0.001). We then arbitrarily selected the age limits for comparing morphometric parameters in young (<25 years) and older (>50 years) donors. In the donors of the younger age categories, LSV surface area occupied 0.9 ± 0.5 μm2 per β cell, which corresponds to 1.2% of CSA (Table 2). These absolute and relative surface areas were comparable to those measured in α cells and in nongranulated cells of the same preparations (Table 2). In β cells from donors of the older age category (>50 years), LSV surface area was more than 10-fold higher (11.9 ± 1.2 μm2/β cell; P < 0.001), corresponding now to 11.1% of CSA (P < 0.001). Higher surface areas were also measured in α cells and in nongranulated cells from the older donors, but they remained, in both absolute and relative terms, 4- to 10-fold smaller than in the β cells (Table 2). In β cells from the older donors, the mean diameter of these vesicles was larger than in β cells from the younger donors (1.8 ± 0.04 versus 1.1 ± 0.2 μm; P < 0.005). In view of their ultrastructural characteristics, these vesicles were denoted as lipid-storing vesicles.Table 1Correlation Between Surface Area of LSVs and Clinical Characteristics of DonorsDonor age (years)Cause of deathSexBody mass index (kg/m2)LSV-SA in β cells (% of CSA)1MeningitisM18.10.035Brain traumaM20.71.0314Brain traumaM23.41.4025Brain traumaM21.92.2933Brain traumaM24.76.4240StrokeM24.65.9452StrokeF24.89.4055StrokeM23.59.6557Brain hemorrhageF22.512.7262Brain hemorrhageM26.19.5881Brain hemorrhageF23.014.24Mean LSV surface area (LSV-SA) in β cells expressed as percentage of cytoplasmic surface area (CSA); none of the donors presented a history of diabetes mellitus or drug treatment for a particular disease. M, male; F, female. Open table in a new tab Figure 4Correlation between donor age and the mean surface area of LSVs, expressed as percentage of the β cell CSA. By linear regression, a correlation coefficient r of 0.938 was calculated (P < 0.001).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Table 2Surface Area of LSVs in Human Pancreatic CellsSurface area per cellVesicles with lipid inclusionsCytoplasmDonor age (years)Cell typeTotal (μm2)% of cytoplasmic surface areaTotal (μm2)<25β0.9 ± 0.51.2 ± 0.779 ± 5α0.4 ± 0.20.6 ± 0.461 ± 7*Nongranulated0.3 ± 0.20.6 ± 0.342 ± 7*>50β11.9 ± 1.2†P < 0.005;11.1 ± 1.6†P < 0.005;107 ± 14‡P < 0.05; P for comparison with β cells in same age category: *, P < 0.005.α2.3 ± 0.5*†P < 0.005;2.8 ± 0.8*‡P < 0.05; P for comparison with β cells in same age category: *, P < 0.005.83 ± 10‡P < 0.05; P for comparison with β cells in same age category: *, P < 0.005.Nongranulated1.6 ± 0.4*‡P < 0.05; P for comparison with β cells in same age category: *, P < 0.005.2.6 ± 0.6*†P < 0.005;51 ± 5*Data are means ± SEM of measurements in islet tissue isolated from four donors younger than 25 years (body mass index, 18.1–23.4) and five donors older than 50 years (body mass index, 22.5–26.1). Statistical significance of differences is calculated by unpaired Student's t test assuming equal variances:P for comparison with same cell type of donors <25 years old:† P < 0.005;‡ P < 0.05; P for comparison with β cells in same age category: *, P < 0.005. Open table in a new tab In the older donors, the α and β cells exhibited larger CSAs than in donors younger than 25 years (P < 0.05. Table 2). In β cells, the increase (28 ± 10 μm2/cell) is 40% attributable to the increase in LSV area (increase of 11 ± 0.9 μm2/cell; Table 2). This is not the case in α cells, in which the increase in LSV surface area is marginal (1.9 ± 0.4 μm2/cell) to the increase in CSA (22 ± 8 μm2/cell). Higher age was not associated with a larger CSA in nongranulated cells (P > 0.05).Lipid Accumulation in Pancreatic Islets from Older DonorsIn cryostat sections of frozen pancreatic tissue, a positive oil red O staining was observed in the islets, as indicated by its colocalization with the insulin-positive regions (Figure 5, a and b). This staining pattern was found in all sections from donors older than 50 years, but was absent in tissue from donors younger than 25 years (Figure 5, c and d). No oil red O staining was noticed in rat or mouse pancreatic tissue, regardless of age (data not shown). When the oil red O staining was performed on human tissue that was embedded in paraffin before sectioning, no positive reaction was obtained, indicating that its positivity in frozen tissue was not caused by the presence of lipofuscin.19Majno G Symptoms of cellular disease: intracellular accumulations.in: Majno G Joris I Cells, Tissues, and Disease: Principles of General Pathology. Blackwell Science, Cambridge, MA1996: 76-90Google ScholarFigure 5Oil red O staining on pancreatic tissue from a donor aged 67 years (a) and a donor aged 6 years (c). Consecutive sections were stained for insulin (b, d). a: Presence of an oil red O-positive cell group, which is insulin-positive on a consecutive section (b). c: Absence of oil red O positivity in a 6-year-old donor, with insulin-positive cells shown in d. Original magnification, ×145.View Large Image Figure ViewerDownload Hi-res image Download (PPT)DiscussionLDLs have been previously found to be taken up by pancreatic β cells but not by their neighboring α cells.10Grupping AY Cnop M Van Schravendijk CFH Hannaert J-C Van Berkel TJC Pipeleers DG Low density lipoprotein binding and uptake by human and rat islet β cells.Endocrinology. 1997; 138: 4064-4068Crossref PubMed Scopus (66) Google Scholar We have now used gold-labeled LDL to monitor the intracellular track of LDLs in rat and human β cells. This technique confirmed the presence of LDL-binding sites on the plasma membrane of β cells, with characteristics that were similar to those observed in the binding studies with I125-labeled LDL. Previous data characterized these sites as high-affinity receptors for LDL and VLDL but not for acetylated LDL.10Grupping AY Cnop M Van Schravendijk CFH Hannaert J-C Van Berkel TJC Pipeleers DG Low density lipoprotein binding and uptake by human and rat islet β cells.Endocrinology. 1997; 138: 4064-4068Crossref PubMed Scopus (66) Google Scholar Half-maximal binding was reached at 10 to 15 μg LDL/ml, a concentration that is comparable to the estimated interstitial LDL levels in the rat but is fivefold lower than those levels in humans with Western life styles.20Brown MS Goldstein JL A receptor-mediated pathway for cholesterol homeostasis.Science. 1986; 232: 34-47Crossref PubMed Scopus (4308) Google Scholar In this latter condition, LDL receptors on β cells are thus expected to be down-regulated and saturated, mediating a steady uptake of LDL and VLDL. Uptake of LDL by β cells was first noticed during binding studies with I125-LDL.10Grupping AY Cnop M Van Schravendijk CFH Hannaert J-C Van Berkel TJC Pipeleers DG Low density lipoprotein binding and uptake by human and rat islet β cells.Endocrinology. 1997; 138: 4064-4068Crossref PubMed Scopus (66) Google Scholar It is now documented ultrastructurally as a receptor-mediated endocytosis, occurring in both rat and human β cells but negligible in α cells. From 30 minutes on, some of the gold-LDL-containing vesicles were positive for acid phosphatase, suggesting fusion of endocytotic vesicles with lysosomes. This process has been described for other cell types,21Paavola LG Strauss JF Boyd CO Nestler JE Uptake of gold- and [3H]cholesteryl linoleate-labeled human low density lipoprotein by cultured rat granulosa cells: cellular mechanisms involved in lipoprotein metabolism and their importance to steroidogenesis.J Cell Biol. 1985; 100: 1235-1247Crossref PubMed Scopus (31) Google Scholar in which the lysosomes have been found to degrade the lipoprotein.22Goldstein JL Brunschede GY Brown MS Inhibition of proteolytic degradation of low density lipoprotein in human fibroblasts by chloroquine, concanavalin A, and Triton WR 1339.J Biol Chem. 1975; 250: 7854-7862Abstract Full Text PDF PubMed Google ScholarIn human β cells, gold-LDL–co" @default.
• W2017604923 created "2016-06-24" @default.
• W2017604923 creator A5004287022 @default.
• W2017604923 creator A5024265898 @default.
• W2017604923 creator A5056936819 @default.
• W2017604923 creator A5075645937 @default.
• W2017604923 creator A5076858965 @default.
• W2017604923 creator A5080456562 @default.
• W2017604923 date "2000-01-01" @default.
• W2017604923 modified "2023-10-16" @default.
• W2017604923 title "Endocytosis of Low-Density Lipoprotein by Human Pancreatic β Cells and Uptake in Lipid-Storing Vesicles, Which Increase with Age" @default.
• W2017604923 cites W1530473730 @default.
• W2017604923 cites W1973068197 @default.
• W2017604923 cites W1979946833 @default.
• W2017604923 cites W2002711503 @default.
• W2017604923 cites W2002888717 @default.
• W2017604923 cites W2020468088 @default.
• W2017604923 cites W2030226450 @default.
• W2017604923 cites W2036344921 @default.
• W2017604923 cites W2054714044 @default.
• W2017604923 cites W2056384844 @default.
• W2017604923 cites W2063705161 @default.
• W2017604923 cites W2065504943 @default.
• W2017604923 cites W2069649414 @default.
• W2017604923 cites W2083643208 @default.
• W2017604923 cites W2084744450 @default.
• W2017604923 cites W2099638040 @default.
• W2017604923 cites W2103219617 @default.
• W2017604923 cites W2108709856 @default.
• W2017604923 cites W2115583439 @default.
• W2017604923 cites W2125733587 @default.
• W2017604923 cites W2140341996 @default.
• W2017604923 cites W2166648967 @default.
• W2017604923 cites W2312513482 @default.
• W2017604923 cites W4317707609 @default.
• W2017604923 doi "https://doi.org/10.1016/s0002-9440(10)64724-4" @default.
• W2017604923 hasPubMedCentralId "https://www.ncbi.nlm.nih.gov/pmc/articles/1868647" @default.
• W2017604923 hasPubMedId "https://pubmed.ncbi.nlm.nih.gov/10623672" @default.
• W2017604923 hasPublicationYear "2000" @default.
• W2017604923 type Work @default.
• W2017604923 sameAs 2017604923 @default.
• W2017604923 citedByCount "62" @default.
• W2017604923 countsByYear W20176049232012 @default.
• W2017604923 countsByYear W20176049232013 @default.
• W2017604923 countsByYear W20176049232014 @default.
• W2017604923 countsByYear W20176049232017 @default.
• W2017604923 countsByYear W20176049232018 @default.
• W2017604923 countsByYear W20176049232019 @default.
• W2017604923 countsByYear W20176049232020 @default.
• W2017604923 countsByYear W20176049232021 @default.
• W2017604923 countsByYear W20176049232022 @default.
• W2017604923 countsByYear W20176049232023 @default.
• W2017604923 crossrefType "journal-article" @default.
• W2017604923 hasAuthorship W2017604923A5004287022 @default.
• W2017604923 hasAuthorship W2017604923A5024265898 @default.
• W2017604923 hasAuthorship W2017604923A5056936819 @default.
• W2017604923 hasAuthorship W2017604923A5075645937 @default.
• W2017604923 hasAuthorship W2017604923A5076858965 @default.
• W2017604923 hasAuthorship W2017604923A5080456562 @default.
• W2017604923 hasBestOaLocation W20176049231 @default.
• W2017604923 hasConcept C130316041 @default.
• W2017604923 hasConcept C1491633281 @default.
• W2017604923 hasConcept C185592680 @default.
• W2017604923 hasConcept C2778163477 @default.
• W2017604923 hasConcept C2779620165 @default.
• W2017604923 hasConcept C2780072125 @default.
• W2017604923 hasConcept C28005876 @default.
• W2017604923 hasConcept C41625074 @default.
• W2017604923 hasConcept C55493867 @default.
• W2017604923 hasConcept C86803240 @default.
• W2017604923 hasConcept C95444343 @default.
• W2017604923 hasConceptScore W2017604923C130316041 @default.
• W2017604923 hasConceptScore W2017604923C1491633281 @default.
• W2017604923 hasConceptScore W2017604923C185592680 @default.
• W2017604923 hasConceptScore W2017604923C2778163477 @default.
• W2017604923 hasConceptScore W2017604923C2779620165 @default.
• W2017604923 hasConceptScore W2017604923C2780072125 @default.
• W2017604923 hasConceptScore W2017604923C28005876 @default.
• W2017604923 hasConceptScore W2017604923C41625074 @default.
• W2017604923 hasConceptScore W2017604923C55493867 @default.
• W2017604923 hasConceptScore W2017604923C86803240 @default.
• W2017604923 hasConceptScore W2017604923C95444343 @default.
• W2017604923 hasIssue "1" @default.
• W2017604923 hasLocation W20176049231 @default.
• W2017604923 hasLocation W20176049232 @default.
• W2017604923 hasLocation W20176049233 @default.
• W2017604923 hasLocation W20176049234 @default.
• W2017604923 hasOpenAccess W2017604923 @default.
• W2017604923 hasPrimaryLocation W20176049231 @default.
• W2017604923 hasRelatedWork W1528852332 @default.
• W2017604923 hasRelatedWork W1999944142 @default.
• W2017604923 hasRelatedWork W2027010109 @default.
• W2017604923 hasRelatedWork W2043225747 @default.
• W2017604923 hasRelatedWork W2084525109 @default.
• W2017604923 hasRelatedWork W2146234479 @default.
• W2017604923 hasRelatedWork W2235380040 @default.
• W2017604923 hasRelatedWork W2320520566 @default.
• W2017604923 hasRelatedWork W2438187491 @default.

• next