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Streptococcus gordonii is a commensal Gram-positive bacterium that acts as an opportunistic pathogen that can cause apical periodontitis, endocarditis, and pneumonia. Biofilm formation of bacteria is important for the initiation and progression of such diseases. Although lipoproteins play key roles in physiological functions, the role of lipoproteins of S. gordonii in its biofilm formation has not been clearly understood. In this study, we investigated the role of lipoproteins of S. gordonii in the bacterial biofilm formation using its lipoprotein-deficient strain (Δlgt). The S. gordonii Δlgt exhibited increased biofilm formation on the human dentin slices or on the polystyrene surfaces compared to the wild-type strain, while its growth rate did not differ from that of the wild-type. In addition, the S. gordonii Δlgt strain exhibited the enhanced LuxS mRNA expression and AI-2 production, which is known to be a positive regulator of biofilm formation, compared to the wild-type. Concordantly, the augmented biofilm formation of S. gordonii Δlgt was attenuated by an AI-2 inhibitor, D-ribose. In addition, lipoproteins from purified S. gordonii inhibited the biofilm formation of S. gordonii wild-type and Δlgt. Taken together, these results suggest that lipoprotein-deficient S. gordonii form biofilms more effectively than the wild-type strain, which might be related to the AI-2 quorum-sensing system.

This review will provide an update on the structure of GPIHBP1, a 28-kDa glycosylphosphatidylinositol-anchored glycoprotein, and its role in the lipolytic processing of triglyceride-rich lipoproteins.Gpihbp1 knockout mice on a chow diet have milky plasma and plasma triglyceride levels of more than 3000 mg/dl. GPIHBP1 is located on the luminal surface of endothelial cells in tissues where lipolysis occurs: heart, skeletal muscle, and adipose tissue. The pattern of lipoprotein lipase (LPL) release into the plasma after an intravenous injection of heparin is abnormal in Gpihbp1-deficient mice, suggesting that GPIHBP1 plays a direct role in binding LPL within the tissues of mice. Transfection of CHO cells with a GPIHBP1 expression vector confers on cells the ability to bind both LPL and chylomicrons. Two regions of GPIHBP1 are required for the binding of LPL - an amino-terminal acidic domain and the cysteine-rich Ly6 domain. GPIHBP1 expression in mice changes with fasting and refeeding and is regulated in part by peroxisome proliferator-activated receptor-gamma.GPIHBP1, an endothelial cell-surface glycoprotein, binds LPL and is required for the lipolytic processing of triglyceride-rich lipoproteins.

Apolipoprotein E2 (apoE2)-associated hyperlipidemia is characterized by a disturbed clearance of apoE2-enriched VLDL remnants. Because excess apoE2 inhibits LPL-mediated triglyceride (TG) hydrolysis in vitro, we in vestigated whether direct or indirect stimulation of LPL activity in vivo reduces the apoE2-associated hypertriglyc-eridemia. Here, we studied the role of LPL and two potent modifiers, the LPL inhibitor apoC-III and the LPL activator apoA-V, in APOE2-knockin (APOE2) mice. Injection of heparin in APOE2 mice reduced plasma TG by 53% and plasma total cholesterol (TC) by 18%. Adenovirus-mediated overexpression of LPL reduced plasma TG by 85% and TC by 40%. Both experiments indicate that the TG in apoE2-enriched particles is a suitable substrate for LPL. Indirect activation of LPL activity via deletion of Apoc3 in APOE2 mice did not affect plasma TG levels, whereas overexpression of Apoa5 in APOE2 mice did reduce plasma TG by 81% and plasma TC by 41%. In conclusion, the hypertriglyc-eridemia in APOE2 mice can be ameliorated by the direct activation of LPL activity. Indirect activation of LPL via overexpression of apoA-V does, whereas deletion of apoC-III does not, affect the plasma TGs in APOE2 mice.Qfl These data indicate that changes in apoA-V levels have a dominant effect over changes in apoC-III levels in the improvement of APOE2-associated hypertriglyceridemia. Copyright © 2008 by the American Society for Biochemistry and Molecular Biology, Inc.

Adenovirus-mediated overexpression of human apolipoprotein E (apoE) induces hyperlipidemia by stimulating the VLDL-triglyceride (TG) production rate and inhibiting the LPL-mediated VLDL-TG hydrolysis rate. Because apoC-III is a strong inhibitor of TG hydrolysis, we questioned whether Apoc3 deficiency might prevent the hyperlipidemia induced by apoE overexpression in vivo. Injection of 2 × 109 plaque-forming units of AdAPOE4 caused severe combined hyperlipidemia in Apoe-/- mice [TG from 0.7 ± 0.2 to 57.2 ± 6.7 mM; total cholesterol (TC) from 17.4 ± 3.7 to 29.0 ± 4.1 mM] that was confined to VLDL/intermediate density lipoprotein-sized lipoproteins. In contrast, Apoc3 deficiency resulted in a gene dose-dependent reduction of the apoE4-associated hyperlipidemia (TG from 57.2 ± 6.7 mM to 21.2 ± 18.5 and 1.5 ± 1.4 mM; TC from 29.0 ± 4.1 to 16.4 ± 9.8 and 2.3 ± 1.8 mM in Apoe-/-, Apoe -/-.Apoc3+/-, and Apoe-/-.Apoc3-/- mice, respectively). In both Apoe-/- mice and Apoe -/-.Apoc3-/- mice, injection of increasing doses of AdAPOE4 resulted in up to a 10-fold increased VLDL-TG production rate. However, Apoc3 deficiency resulted in a significant increase in the uptake of TG-derived fatty acids from VLDL-like emulsion particles by white adipose tissue, indicating enhanced LPL activity. In vitro experiments showed that apoC-III is a more specific inhibitor of LPL activity than is apoE. Thus, Apoc3 deficiency can prevent apoE-induced hyperlipidemia associated with a 10-fold increased hepatic VLDL-TG production rate, most likely by alleviating the apoE-induced inhibition of VLDL-TG hydrolysis. Copyright © 2005 by the American Society for Biochemistry and Molecular Biology, Inc. Chemicals / CAS: cholesterol, 57-88-5; lipid, 66455-18-3; lipoprotein lipase, 83137-80-8, 9004-02-8; Apolipoprotein C-III; Apolipoprotein E4; Apolipoproteins C; Apolipoproteins E; Lipids; Lipoprotein Lipase, EC 3.1.1.34; Lipoproteins; Lipoproteins, VLDL; Triglycerides

Adenovirus-mediated overexpression of human apolipoprotein E (apoE) induces hyperlipidemia by stimulating the VLDL-triglyceride (TG) production rate and inhibiting the LPL-mediated VLDL-TG hydrolysis rate. Because apoC-III is a strong inhibitor of TG hydrolysis, we questioned whether Apoc3 deficiency might prevent the hyperlipidemia induced by apoE overexpression in vivo. Injection of 2 × 109 plaque-forming units of AdAPOE4 caused severe combined hyperlipidemia in Apoe-/- mice [TG from 0.7 ± 0.2 to 57.2 ± 6.7 mM; total cholesterol (TC) from 17.4 ± 3.7 to 29.0 ± 4.1 mM] that was confined to VLDL/intermediate density lipoprotein-sized lipoproteins. In contrast, Apoc3 deficiency resulted in a gene dose-dependent reduction of the apoE4-associated hyperlipidemia (TG from 57.2 ± 6.7 mM to 21.2 ± 18.5 and 1.5 ± 1.4 mM; TC from 29.0 ± 4.1 to 16.4 ± 9.8 and 2.3 ± 1.8 mM in Apoe-/-, Apoe -/-.Apoc3+/-, and Apoe-/-.Apoc3-/- mice, respectively). In both Apoe-/- mice and Apoe -/-.Apoc3-/- mice, injection of increasing doses of AdAPOE4 resulted in up to a 10-fold increased VLDL-TG production rate. However, Apoc3 deficiency resulted in a significant increase in the uptake of TG-derived fatty acids from VLDL-like emulsion particles by white adipose tissue, indicating enhanced LPL activity. In vitro experiments showed that apoC-III is a more specific inhibitor of LPL activity than is apoE. Thus, Apoc3 deficiency can prevent apoE-induced hyperlipidemia associated with a 10-fold increased hepatic VLDL-TG production rate, most likely by alleviating the apoE-induced inhibition of VLDL-TG hydrolysis. Copyright © 2005 by the American Society for Biochemistry and Molecular Biology, Inc. Chemicals / CAS: cholesterol, 57-88-5; lipid, 66455-18-3; lipoprotein lipase, 83137-80-8, 9004-02-8; Apolipoprotein C-III; Apolipoprotein E4; Apolipoproteins C; Apolipoproteins E; Lipids; Lipoprotein Lipase, EC 3.1.1.34; Lipoproteins; Lipoproteins, VLDL; Triglycerides

The function of apolipoprotein (apo) C1 in vivo is not well understood. From in vitro studies it has been reported that an excess of apoC1 relative to apoE inhibits receptor-mediated uptake of remnant lipoproteins. In order to gain a better understanding of the role of apoC1 in lipoprotein metabolism in vivo, we have generated apoC1-deficient mice by gene targeting in embryonic stem cells. Homozygous mutant mice are viable and do not show overt abnormalities. Serum triacylglycerol levels are increased by 60% on both a standard mouse diet and a mild hypercholesterolaemic diet compared with controls. Total serum cholesterol levels are similar to controls on the two diets. However, the level of high-density lipoprotein cholesterol in the apoC1-deficient mice fed on the mild hypercholesterolaemic diet is slightly decreased, which is accompanied by a 3-fold increase in very-low-density plus low-density lipoprotein (VLDL + LDL) cholesterol. On a severe atherogenic diet, the homozygous apoC1-deficient mice become hypercholesterolaemic, with a serum cholesterol level of 10.7 ± 3.3 mM compared with 6.7 ± 1.8 mM and 5.1 ± 1.6 mM in heterozygous and control mice respectively. The increase in cholesterol is mainly confined to the VLDL + LDL-sized fractions. Binding experiments revealed that lipoproteins lacking apoC1 with d < 1.006 g/ml are poor competitors for 125I-labelled LDL binding to the LDL receptor on HepG2 cells. This suggests that total apoC1 deficiency leads to impaired receptor-mediated clearance of remnant lipoproteins rather than enhanced uptake, as was expected from data reported in the literature. Chemicals/CAS: apolipoprotein C-I; Apolipoproteins C; Cholesterol, 57-88-5; Cholesterol, Dietary; Lipoproteins, HDL Cholesterol; Lipoproteins, LDL Cholesterol; Lipoproteins, VLDL Cholesterol; Receptors, LDL; Triglycerides

The function of apolipoprotein (apo) C1 in vivo is not well understood. From in vitro studies it has been reported that an excess of apoC1 relative to apoE inhibits receptor-mediated uptake of remnant lipoproteins. In order to gain a better understanding of the role of apoC1 in lipoprotein metabolism in vivo, we have generated apoC1-deficient mice by gene targeting in embryonic stem cells. Homozygous mutant mice are viable and do not show overt abnormalities. Serum triacylglycerol levels are increased by 60% on both a standard mouse diet and a mild hypercholesterolaemic diet compared with controls. Total serum cholesterol levels are similar to controls on the two diets. However, the level of high-density lipoprotein cholesterol in the apoC1-deficient mice fed on the mild hypercholesterolaemic diet is slightly decreased, which is accompanied by a 3-fold increase in very-low-density plus low-density lipoprotein (VLDL + LDL) cholesterol. On a severe atherogenic diet, the homozygous apoC1-deficient mice become hypercholesterolaemic, with a serum cholesterol level of 10.7 ± 3.3 mM compared with 6.7 ± 1.8 mM and 5.1 ± 1.6 mM in heterozygous and control mice respectively. The increase in cholesterol is mainly confined to the VLDL + LDL-sized fractions. Binding experiments revealed that lipoproteins lacking apoC1 with d < 1.006 g/ml are poor competitors for 125I-labelled LDL binding to the LDL receptor on HepG2 cells. This suggests that total apoC1 deficiency leads to impaired receptor-mediated clearance of remnant lipoproteins rather than enhanced uptake, as was expected from data reported in the literature. Chemicals/CAS: apolipoprotein C-I; Apolipoproteins C; Cholesterol, 57-88-5; Cholesterol, Dietary; Lipoproteins, HDL Cholesterol; Lipoproteins, LDL Cholesterol; Lipoproteins, VLDL Cholesterol; Receptors, LDL; Triglycerides

Sir .—Issues have been raised involving the use of drugs that lower the lipid level and reduce the serum cholesterol level in the general adult population, 1 as well as in infants and children at risk for future development of high serum cholesterol levels. 2 Toward the same goal, dietary modifications have been introduced in the United States that have resulted in increased consumption of polyunsaturated fats (USF) between 1960 and 1975. 3 Linoleic acid intakes from infant formulas have also increased since 1970. 4 This approach to the treatment of hypercholesterolemia may shift a patient's balance toward lipoprotein deficiency, especially during growth and development, and while a great deal is known about the pathologic consequences of hypercholesterolemia, the consequences of hypocholesterolemia are unknown. We wish to bring the following experimental results to the attention of clinicians interested in reducing serum cholesterol levels. Diets rich in USF 5 and diets

The clinical features of plasma lipoprotein disorders have already taught us much about the function of lipoproteins, but certain aspects remain unexplained, notably the relationship of lipoprotein deficiency to neurological function. We can still learn more from nature’s experiments than from our own.

Deficiency of mature lipoprotein fractions, be it the consequence of an abnormality of the apolipoprotein(s) or of a deficient synthesis, can have a significant clinical impact in some cases whereas in others it may go almost unnoticed. The study of lipoprotein deficiency syndromes has received considerable help from the recent advances in molecular cloning both of apolipoproteins and of major enzymes involved in lipid metabolism. This type of information has allowed the conclusion that lipoprotein deficiency syndromes are very often associated with well-characterized abnormalities in the processing and/or transformation of lipoproteins or apolipoproteins in the carriers.

The pore properties of PhoE protein channels in the outer membrane of a lipoprotein-deficient mutant and in a mutant with heptose-deficient lipopolysaccharide were investigated. The absence of lipoprotein neither affects the rate of permeation of glucose 6-phosphate or of the beta-lactam antibiotic cephsulodin through the PhoE pore nor the inhibition of cephsulodin permeation by polyphosphate. In contrast, heptose deficiency results in a 6- to 8-fold increase in the rates of permeation of glucose 6-phosphate and cephsulodin. Possible explanations for these data are discussed. It is argued that the lipopolysaccharide structure synthesized under phosphate limitation may be similar to that of the heptoseless mutant and hence that not only the structure of the PhoE protein pore but also the structure of the lipopolysaccharide may promote the uptake of Pi and Pi-containing solutes under phosphate limitation.

A case of xanthomatous skin changes and an abnormal serum lipoprotein pattern is described. The clinical and histological findings are those of diffuse "normolipemic" plane xanthoma. The main features of the case are intracellular cholesterol deposits in the skin, and in serum, a reduced level of total high-density lipoproteins and also an abnormally low cholesterol content of the low-density and very low-density lipoprotein fractions. The case does not correspond to any of the types of lipoprotein abnormality in the classification of Fredrickson and Lees. It shows some similarities to the two conditions of α-lipoprotein deficiency, Tangier disease, and familial lecithin-cholesterol-acyltransferase deficiency. The case appears to represent a type of lipoprotein abnormality, not previously reported.

A patient with α-lipoprotein deficiency presented with widespread dissociated loss of pain and temperature sensation and progressive focal muscle wasting and weakness. Electrical and histological investigations revealed disordered function and structure of the peripheral nerves. The typical pharyngeal appearance was present, and cholesterol ester was demonstrated in the sternal marrow and rectal mucosa. The small amount of α-lipoprotein present contained an excessive proportion of triglyceride. An increased proportion of triglyceride was also present in β-lipoprotein. Studies of the serum-lipoproteins in relatives confirmed the familial nature of the defect.

Dermal deposition of cholesterol esters was found in cutaneous papules or clinically normal skin in four of the five known living patients with Tangier disease (familial α- or high-density lipoprotein deficiency). Five patients with Niemann-Pick disease and three normal patients studied in like manner exhibited no evidence of cutaneous cholesterol ester deposition. These cutaneous findings will be useful in the diagnosis, follow-up, and study of this rare and interesting syndrome.

FAMILIAL recurrent neuropathy is an unusual condition. When it does occur, a specific biochemical abnormality is occasionally detected when the clinical syndrome is part of Refsum's disease, acute intermittent porphyria, or possibly Fabry's disease. In this paper is presented another biochemical abnormality associated with familial recurrent neuropathy, namely, αlipoprotein deficiency or Tangier disease. One of the two patients had additional features of prominent intestinal lipid storage. In the past, a low plasma cholesterol has been associated with neurologic disease in hereditary abetalipoproteinemia. This report is intended to alert the physician to the existence of another lipid deficiency state associated with a neurologic disorder, signaled by a low plasma cholesterol and readily diagnosed by careful study of the plasma lipids and lipoproteins. Clinical Description The first patient (NIH 06-63-22) is 16 years old. She had an essentially unremarkable childhood except for removal of enlarged tonsils at age 3; and