Deletion of GPIHBP1 causing severe chylomicronemia

Lipoprotein lipase (LPL) is a hydrolase that cleaves circulating triglycerides to release fatty acids to the surrounding tissues. The enzyme is synthesized in parenchymal cells and is transported to its site of action on the capillary endothelium by glycophosphatidylinositol (GPI)-anchored high-density lipoprotein-binding protein 1 (GPIHBP1). Inactivating mutations in LPL; in its cofactor, apolipoprotein (Apo) C2; or in GPIHBP1 cause severe hypertriglyceridemia. Here we describe an individual with complete deficiency of GPIHBP1. The proband was an Asian Indian boy who had severe chylomicronemia at 2 months of age. Array-based copy-number analysis of his genomic DNA revealed homozygosity for a 17.5-kb deletion that included GPIHBP1. A 44-year-old aunt with a history of hypertriglyceridemia and pancreatitis was also homozygous for the deletion. A bolus of intravenously administered heparin caused a rapid increase in circulating LPL and decreased plasma triglyceride levels in control individuals but not in two GPIHBP1-deficient patients. Thus, short-term treatment with heparin failed to attenuate the hypertriglyceridemia in patients with GPIHBP1 deficiency. The increasing resolution of copy number microarrays and their widespread adoption for routine cytogenetic analysis is likely to reveal a greater role for submicroscopic deletions in Mendelian conditions. We describe the first neonate with complete GPIHBP1 deficiency due to homozygosity for a deletion of GPIHBP1

Controlled release nanoparticle-embedded coatings reduce the tissue reaction to neuroprostheses

Controlled release coatings were developed for neuroprostheses with the aim of combating the tissue reaction following implantation in the brain. The coatings consist of poly(propylene sulfide) drug-eluting nanoparticles embedded in a poly(ethylene oxide) matrix. The nanoparticles are loaded with dexamethasone, an anti-inflammatory drug known to have an effect on the cells activated during the damage caused by implantation. The nanoparticles are not affected by the coating process and the drug remains bioactive after it is released. The coating was applied to microfabricated cortical neuroprostheses consisting of platinum and polyimide. Coated drug-eluting devices were implanted in the cortex of rats. After implantation the matrix dissolves, exposing the electrode surfaces, while the nanoparticles remain in the vicinity of the tissue–implant interface. Using electrical impedance spectroscopy and comparative histology, a long-term decrease in the tissue response in comparison to control devices was observed. These coatings can therefore be used to increase the reliability and long-term efficacy of neuroprostheses

Monoclonal antibodies to avian lipoprotein lipase. Purification of the enzyme by immunoaffinity chromatography

Three monoclonal antibodies to avian lipoprotein lipase have been isolated by fusing spleen cells from immunized BALB/c mice with myeloma P3X-63 Ag 8. The antibodies were detected by their ability to bind immobilized lipoprotein lipase in enzyme-linked immunosorbent assay (ELISA) and by immunoprecipitation of purified enzyme in the presence of second (rabbit anti-mouse) antibodies. Two of these antibodies, CAL1-7 and CAL1-11, inhibited catalytic activity, whereas with CAL1-2 interaction with lipoprotein lipase could be demonstrated only in ELISA and in Western blot assays following denaturation of the enzyme with sodium dodecyl sulfate. An immunoadsorbent column was prepared by coupling immunopurified CAL1-11 to Sepharose-4B. When acetone powder extracts of adipose tissue were applied on the column, 70% of the catalytic activity bound to the matrix. Effective elution was achieved with 1.8 M NaCl, 40% glycerol, 5% acetone, 20 mM Chaps (3[(3-holamidopropyl)dimethylammonio]propanesulfonate), 0.5 mM EDTA, 1 mM phosphate (pH 6.5). After concentration of the active fractions on a heparin-Sepharose 4B column, the purified enzyme was obtained with an overall recovery of 25%. Sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrates that the preparation is homogeneous with a major band at M r 60900. Thus, avian adipose lipoprotein lipase has been purified by a one-step immunoaffinity followed by a concentrating step on heparin-Sepharose 4B

Hepatic lipase treatment of chylomicron remnants increases exposure of apolipoprotein E

The consequences of hepatic lipase treatment of chylomicron remnants were studied. Rats were fed corn oil to induce production and secretion of chylomicrons and were then injected with polyclonal antiserum raised against hepatic lipase to specifically and quantitatively inhibit hepatic lipase activity in vivo. A fraction enriched in chylomicron remnants was isolated from rat plasma by a brief centrifugation step that preferentially isolates triglyceride-rich apolipoprotein (apo) B-48-containing lipoproteins. The chylomicron remnants were then treated with hepatic lipase in vitro, or incubated under identical conditions in the absence of enzyme (control incubations). Hepatic lipase-treated and control chylomicron remnants were isolated by a second brief centrifugation step using discontinuous salt gradients. Control lipoproteins were collected from one discrete band at d \u3c 1.02 g/ml. Hepatic lipase-treated chylomicron remnants formed two discrete bands and were collected at two densities: d \u3c 1.02 g/ml and 1.02 \u3c d \u3c 1.04 g/ml. The buoyant (d \u3c 1.02 g/ml) subfraction of hepatic lipase-treated chylomicron remnants was depleted of 62% of the total phospholipid when compared to control d \u3c 1.02 g/ml lipoproteins. The dense (1.02 \u3c d \u3c 1.04 g/ml) subfraction of hepatic lipase-treated chylomicron remnants was depleted of 65% of particle phospholipid content and 90% of particle triglyceride content when compared to control d \u3c 1.02 g/ml lipoproteins. The dense (1.02 \u3c d \u3c 1.04 g/ml) subfraction of hepatic lipase-treated chylomicron remnants showed 5- to 7-fold greater immunoreactivity of apoE when compared to control lipoproteins in competitive displacement immunoassays. These data suggest that extensive hydrolysis of chylomicron remnant phospholipid and triglyceride leads to the formation of a dense remnant particle that contains highly exposed apoE. This increased exposure of apoE may be the key to the previously observed increased degradation of chylomicron remnants treated with hepatic lipase because more exposed apoE may bind better to cell surface lipoprotein receptors. Furthermore, the data imply that hepatic lipase cleaves chylomicron remnant phospholipid and triglyceride in a sequential fashion; hydrolytic intermediates depleted only of phospholipid precede the formation of a smaller dense remnant particle depleted of phospholipid and triglyceride

Hepatic lipase treatment of chylomicron remnants increases exposure of apolipoprotein E

The consequences of hepatic lipase treatment of chylomicron remnants were studied. Rats were fed corn oil to induce production and secretion of chylomicrons and were then injected with polyclonal antiserum raised against hepatic lipase to specifically and quantitatively inhibit hepatic lipase activity in vivo. A fraction enriched in chylomicron remnants was isolated from rat plasma by a brief centrifugation step that preferentially isolates triglyceride-rich apolipoprotein (apo) B-48-containing lipoproteins. The chylomicron remnants were then treated with hepatic lipase in vitro, or incubated under identical conditions in the absence of enzyme (control incubations). Hepatic lipase-treated and control chylomicron remnants were isolated by a second brief centrifugation step using discontinuous salt gradients. Control lipoproteins were collected from one discrete band at d \u3c 1.02 g/ml. Hepatic lipase-treated chylomicron remnants formed two discrete bands and were collected at two densities: d \u3c 1.02 g/ml and 1.02 \u3c d \u3c 1.04 g/ml. The buoyant (d \u3c 1.02 g/ml) subfraction of hepatic lipase-treated chylomicron remnants was depleted of 62% of the total phospholipid when compared to control d \u3c 1.02 g/ml lipoproteins. The dense (1.02 \u3c d \u3c 1.04 g/ml) subfraction of hepatic lipase-treated chylomicron remnants was depleted of 65% of particle phospholipid content and 90% of particle triglyceride content when compared to control d \u3c 1.02 g/ml lipoproteins. The dense (1.02 \u3c d \u3c 1.04 g/ml) subfraction of hepatic lipase-treated chylomicron remnants showed 5- to 7-fold greater immunoreactivity of apoE when compared to control lipoproteins in competitive displacement immunoassays. These data suggest that extensive hydrolysis of chylomicron remnant phospholipid and triglyceride leads to the formation of a dense remnant particle that contains highly exposed apoE. This increased exposure of apoE may be the key to the previously observed increased degradation of chylomicron remnants treated with hepatic lipase because more exposed apoE may bind better to cell surface lipoprotein receptors. Furthermore, the data imply that hepatic lipase cleaves chylomicron remnant phospholipid and triglyceride in a sequential fashion; hydrolytic intermediates depleted only of phospholipid precede the formation of a smaller dense remnant particle depleted of phospholipid and triglyceride

in vivo Electrical Impedance Spectroscopy of Tissue Reaction to Microelectrode Arrays

The goal of this experiment was to determine the electrical properties of the tissue reaction to implanted microelectrode arrays. We describe a new method of analyzing electrical impedance spectroscopy data to determine the complex impedance of the tissue reaction as a function of postimplantation time. A model is used to extract electrical model parameters of the electrode-tissue interface, and is used to isolate the impedance of the tissue immediately surrounding the microelectrode. The microelectrode arrays consist of microfabricated polyimide probes, incorporating four 50-mum- diameter platinum microelectrodes. The devices were implanted in the primary motor cortex of adult rats, and measurements were performed for 12 weeks. Histology was performed on implants at three time points in one month. Results demonstrate that the tissue reaction causes a rapid increase in bioimpedance over the first 20 days, and then stabilizes. This result is supported by histological data

Angiopoietin-like 4 promotes intracellular degradation of lipoprotein lipase in adipocytes

International audienc

Zilversmit, Donald B.

Also available as a printed booklet and from the Dean of Faculty website https://theuniversityfaculty.cornell.edu/Memorial Statement for Donald B. Zilversmit, who died in 2010. The memorial statements contained herein were prepared by the Office of the Dean of the University Faculty of Cornell University to honor its faculty for their service to the university