Bacterial infection elicits hypertriglyceridemia attributed to increased hepatic production of very low-density lipoprotein (VLDL) particles and decreased peripheral metabolism. The mechanisms underlying VLDL overproduction in sepsis are as yet unclear, but seem to be fed/fasted state-dependent. To learn more about this, we investigated hepatocytes isolated from fasted rats, made endotoxic by 1 mg/kg lipopolysaccharide (LPS) injection, for their ability to secrete the VLDL protein and lipid components. The results were then related to lipogenesis markers and expression of genes critical to VLDL biogenesis. Endotoxic rats showed increased levels of serum VLDL-apoB (10-fold), -triglyceride (2-fold), and -cholesterol (2-fold), whereby circulating VLDL were lipid-poor particles. Similarly, VLDL-apoB secretion by isolated endotoxic hepatocytes was ~85% above control, whereas marginal changes in the output of VLDL-lipid classes occurred. This was accompanied by a substantial rise in apoB and a moderate rise in MTP mRNA levels, but with basal de novo formation and efficiency of secretion of triglycerides, cholesterol and cholesteryl esters. These results indicate that during periods of food restriction, endotoxin does not enhance lipid provision to accomplish normal lipidation of overproduced apoB molecules, though this does occur to a sufficient extent to pass the proteasome checkpoint and secretion of lipid-poor, type 2 VLDL takes place.
Khovidhunkit W., Kim MS, Memon RA et al. Effects of infection and inflammation on lipid and lipoprotein metabolism: mechanisms and consequences to the host . J Lipid Res2004; 45: 1169—1196.
2.
Gallay P., Heumann D., Le Roy D., Barros, Glauser MP.Lipopolysaccharide-binding protein as a major plasma protein responsible for endotoxemic shock. Proc Natl Acad Sci USA1993; 90: 9935—9938.
3.
Ulevitch RJ, Tobias PSReceptor-dependent mechanisms of cell stimulation by bacterial endotoxin. Annu Rev Immunol1995; 13: 437—457.
4.
Gangloff M., Gay NJMD-2: the Toll `gatekeeper' in endotoxin signalling. TrendsBiochem Sci2004; 29: 294—300.
5.
Visintin A., Latz E., Monks BG, Espevick T., Golenbock DTLysines 128 and 132 enable lipopolysaccharide binding to MD-2, leading to Toll-like receptor-4 aggregation and signal transduction. J Biol Chem2003; 278: 48313—48320.
6.
Levels JH, Abraham PR, Van Barreveld EP, Meijers JC, Van Deventer SJ.Distribution and kinetics of lipoprotein-bound endotoxin. Infect Immun2001; 69: 2821—2828.
7.
Harris H., Gosnell J., Kumwenda Z.The lipemia of sepsis: triglyceride-rich lipoproteins as agents of innate immunity. J Endotoxin Res2001; 6: 421—429.
8.
Esteve E., Wifredo R., Fernández-Real JMDyslipidemia and inflammation: an evolutionary conserved mechanism. Clin Nutr2005; 24: 16—31.
9.
Harris H., Eichbaum EB, Kane JP, Rapp JHDetection of endotoxin in triglyceride-rich lipoproteins in vitro. J Lab Clin Med1991; 118: 186—193.
10.
Kitchens RL , Thomsom RSImpact of sepsis-induced changes in plasma on LPS interactions with monocytes and plasma lipoproteins: roles of soluble CD14, LBP, and acute phase lipoproteins. J Endotoxin Res2003; 9: 113—118.
11.
Harris H., Grünfeld C., Feingold KR, Rapp JHHuman very low-density lipoproteins and chylomicrons can protect against endotoxin-induced death in mice. J Clin Invest1990; 86: 696—702.
12.
Harris H., Grunfeld C., Feingold KR et al. Chylomicrons alter the fate of endotoxin, decreasing tumor necrosis factor release and preventing death. J Clin Invest1993; 91: 1028—1034.
13.
Kitchens RL , Thomsom RS, Munford RS, O'Keefe N.Acute inflammation and infection maintain circulating phospholipid levels and enhance lipopolysaccharide binding to plasma lipoproteins. J Lipid Res2003; 44: 2339—2348.
14.
Berbee JF, Havekes LM, Rensen PCApolipoproteins modulate the inflammatory response to lipopolysaccharide. J Endotoxin Res2005; 11: 97—103.
15.
Sammalkorpi K., Valtonen V., Kerttula Y., Nikkila E., Taskinen M.Change in serum lipoprotein pattern induced by acute infections. Metabolism1988; 37: 859—865.
16.
Feingold K. , Staprans I., Memon R. et al. Endotoxin rapidly induces changes in lipid metabolism that produce hypertriglyceridemia: low doses stimulate hepatic triglyceride production while high doses inhibit clearance. J Lipid Res1992; 33: 1765—1776.
17.
Hardardottir I., Moser AH, Fuller J., Fielding C., Feingold KR, Grünfeld C.Endotoxin and cytokines decrease serum levels and extra hepatic protein and mRNA levels of cholesteryl ester transfer protein in Syrian hamsters. J Clin Invest1996; 97: 2585—2592.
18.
Phetteplace HW, Sedkova N., Hirano K., Davidson NO, Lanza-Jacoby S.Escherichia coli sepsis increases hepatic apolipoprotein B secretion by inhibiting degradation. Lipids2000; 35: 1079—1085.
19.
Aspichueta P., Pérez S., Ochoa B., Fresnedo O.Endotoxin promotes preferential periportal upregulation of VLDL secretion in the rat liver. J Lipid Res2005; 46: 1017—1026.
20.
Lanza-Jacoby S., Tabares A.Triglyceride kinetics, tissue lipoprotein lipase, and liver lipogenesis in septic rats. Am J Physiol1990; 258: E678—E685.
21.
Teng B., Burant CF, Davidson NOMolecular cloning of an apolipoprotein B messenger RNA editing protein. Science1993; 260: 1816—1819.
22.
Kulinsli A. , Rustaeus S., Vance JEMicrosomal triacylglycerol transfer protein is required for lumenal accretion of triacylglycerol not associated with apoB, as well as for apoB lipidation. J Biol Chem2002; 277: 31516—31525.
23.
Gusarova V. , Brodsky JL, Fisher EAApolipoprotein B100 exit from the endoplasmic reticulum (ER) is COPII-dependent, and its lipidation to very low density lipoprotein occurs post-ER. J Biol Chem2003 ; 278: 48051—48058.
24.
Zhou M., Wu X., Huang LS, Ginsberg HNApoprotein B100, an inefficiently translocated secretory protein, is bound to the cytosolic chaperone, heat shock protein 70. J Biol Chem1995; 270: 25220—25224.
25.
Zhou M., Fisher EA, Ginsberg HNRegulated co-translational ubiquitination of apolipoprotein B100. A new paradigm for proteasomal degradation of a secretory protein. J Biol Chem1998; 73: 24649—24653.
26.
Yeung S.J., Chen SH, Chan L.Ubiquitin-proteasome pathway mediates intracellular degradation of apolipoprotein B. Biochemistry1996; 35: 13843—13848.
27.
Fisher EA, Ginsberg HNComplexity in the secretory pathway: the assembly and secretion of apolipoprotein B-containing lipoproteins, J Biol Chem2002 ; 277: 17377—17380.
28.
Wetterau JR, Lin MC, Jamil H.Microsomal triglyceride transfer protein. Biochim Biophys Acta1997; 1345: 136—150.
29.
Hussain MM, Shi J., Dreizen P.Microsomal triglyceride transfer protein and its role in apoB-lipoprotein assembly. J Lipid Res2003; 44: 22—32.
30.
Mann J., Chrisholm A.Nutritional determinants of serum TG. Nutr Metab Cardiovasc Dis1999; 9: 1—8.
31.
Leighton JK, Joyner J., Zamarripa J., Deines M., Davis RAFasting decreases apolipoprotein B mRNA editing and the secretion of small molecular weight apoB by rat hepatocytes: evidence that the total amount of apoB is secreted post-transcriptionally. J Lipid Res1990; 31: 1663—1668.
32.
Gibbons GF, Burnham FJEffect of nutritional state on the utilization of fatty acids for hepatic triacylglycerol synthesis and secretion as very-low-density lipoprotein. Biochem J1991; 275: 87—92.
33.
Marrino P., Gavish D., Shafris E., Eisenberg S.Diurnal variations of plasma lipids, tissue and plasma lipoprotein lipase, and VLDL secretion rates in the rat. A model for studies of VLDL metabolism . Biochim Biophys Acta1987; 920: 277—284.
34.
Ruiz JI, Ochoa B.Quantification in the subnanomolar range of phospholipids and neutral lipids by monodimensional thin-layer chromatography and image analysis. J Lipid Res1997; 38: 1482—1489.
35.
Seglen POPreparation of isolated rat liver cells. Methods Cell Biol1976; 13: 29—83.
36.
Vance D., Weinstein D., Steinberg D.Isolation and analysis of lipoproteins secreted by rat liver hepatocytes. Biochim Biophys Acta1984; 792: 39—47.
37.
Isusi E., Aspichueta P., Liza M. et al. Short- and long-term effects of atorvastatin, lovastatin and simvastatin on the cellular metabolism of cholesteryl esters and VLDL secretion in hepatocytes . Atherosclerosis2000; 153: 283—294.
38.
Lin Mcm, Arbeeny C., Bergquist K., Kienzle B., Gordon DA, Weterau JRCloning and regulation of hamster microsomal triglyceride transfer protein . J Biol Chem1994; 269: 29138—29145.
39.
Memon RA, Shechter I., Moser AH, Shigenaga JK, Grünfeld C., Feingold KREndotoxin, tumor necrosis factor, and interleukin-1 decrease hepatic squalene synthase activity, protein, and mRNA levels in Syrian hamsters. J Lipid Res1997; 38: 1620—1628.
40.
Memon RA, Feingold KR, Moser AH, Fuller J., Grünfeld C.Regulation of fatty acid transport protein and fatty acid translocase mRNA levels by endotoxin and cytokines. Am J Physiol1998; 274: E210—E217.
41.
Bradford MMA rapid and sensitive method for the quantification of microgram quantities of protein utilizing the principle of protein dye binding. Anal Biochem1976; 72: 248—254.
42.
FangCh, Lindros KO, Badger TM, Ronis MJJ, Ingelman-Sundberg M. Zonated expression of cytokines in rat liver: effect of chronic ethanol and cytochrome P450 2E1 inhibitor, chlormethiazole. Hepatology1998 ; 27: 1304—1310.
43.
van't Hooft FM, Jormsjö S., Lundahl B., Tornvall P., Eriksson P., Hamsten A.A functional polymorphism in the apolipoprotein B promoter that influences the level of plasma low density lipoprotein. J Lipid Res1999; 40: 1686—1694.
44.
Singh K., Batuman OA, Akman HO, Kedees MH, Vakil V., Hussain MMDifferential, tissue-specific, transcriptional regulation of apolipoprotein B secretion by transforming growth factor β. J Biol Chem2002; 277: 39515—39524.
45.
Yoo JI, Desiderio S.Innate and acquired immunity intersect in a global view of the acute-phase response. Proc Natl Acad Sci USA2003; 100: 1157—1162.
46.
Hinsdale ME , Maeda N.Complex control of mouse apolipoprotein B gene expression revealed by targeted duplication, Biochim Biophys Acta2005; 1734: 178—189.
47.
Tripp RJ, Tabares A., Wang H., Lanza-Jacoby SPAltered hepatic production of apolipoprotein B and E in the fasted septic rat: factors in the development of hypertriglyceridemia. J Surg Res1993; 55: 465—472.
48.
Yokoyama K. , Ishibashi T., Yi-Qiang L., Nagayoshi A., Teramoto T., Maruyama Y.Interleukin-1β and interleukin-6 increase levels of apolipoprotein B mRNA and decrease accumulation of its protein in culture medium of HepG2 cells. J Lipid Res1998; 39: 103—113.
49.
Jura J., Wegrzyn P., Zarebski A., Wladyka B., Koj A.Identification of changes in the transcriptome profile of human hepatoma HepG2 cells stimulated with interleukin-1 beta. Biochim Biophys Acta2004; 1689: 120—133.
50.
Bush KT, Goldberg AL, Nigam SKProteasome inhibition leads to a heat-shock response, induction of endoplasmic reticulum chaperones, and thermotolerance. J Biol Chem1997; 272: 9086—9092.
51.
Linnik KM, Herscovitz H.Multiple chaperones interact with apolipoprotein B during its maturation. The network of endoplasmic reticulum-resident chaperones (Erp72, GRP94, calreticulin, and BiP) interacts with apolipoprotein B regardless of its lipidation state . J Biol Chem1998; 273: 21368—21373.
52.
Castell JV, Gomez-Lechon MJ, David M. et al. Interleukin-6 is the major regulator of acute phase protein synthesis in adult human hepatocytes. FEBS Lett1989; 242: 237—239.
53.
Ramadori G. , Christ B.Cytokines and the hepatic acute-phase response . Semin Liver Dis1999; 19: 141—155.
54.
Yang LY, Kuksis A., Myher JJ, Steiner G.Origin of triacylglycerol moiety of plasma very low density lipoproteins in the rat: structural studies. J Lipid Res1995 ; 36: 125—136.
55.
Lankester DL , Brown AM, Zammit VAUse of cytosolic triacylglycerol hydrolysis products and of exogenous fatty acid for the synthesis of triacylglycerol secreted by cultured rat hepatocytes. J Lipid Res1998; 39: 1889—1895.
56.
Gilham D., Ho S., Rasouli M., Martres P., Vance DE, Lehner R.Inhibitors of hepatic microsomal triacylglycerol hydrolase decrease VLDL secretion . FASEB J2003; 17: 1685—1687.
Pruzanski W. , Stefanski E., Beer FC, Beer MC, Ravandi A., Kuksis A.Comparative analysis of lipid composition of normal and acute-phase high density lipoproteins. J Lipid Res2000; 41: 1035—1047.
59.
Coetzee GA, Strachan AF, Van Der Westhuyzen DR, Hoppe HC, Jeenah MS, De Beer FCSerum amyloid A-containing human high density lipoprotein 3. Density, size and apolipoprotein composition. J Biol Chem1986; 261: 9644—9651.
60.
Malle E., Steinmetz A., Raynes JGSerum amyloid A (SAA): an acute phase protein and apolipoprotein. Atherosclerosis1993; 102: 131—146.
61.
Memon RA, Holleran WM, Moser AH et al. Endotoxin and cytokines increase hepatic sphingolipid biosynthesis and produce lipoproteins enriched in ceramides and sphingomyelin. Arterioscler Thromb Vasc Biol1998; 18: 1257—1265.
62.
Memon RA, Staprans I., Noor M. et al. Infection and inflammation induce LDL oxidation in vivo. Arterioscler Thromb Vasc Biol2000; 20: 1536—1542.
63.
Nigon F., Lesnik P., Rouis M., Chapman MJDiscrete subspecies of human low-density lipoproteins are heterogeneous in their interaction with the cellular LDL receptor. J Lipid Res1991; 32: 1741—1753.
64.
Connelly PW , Maguire GF, Vezina C., Hegele RA, Kuksis A. Kinetics of lipolysis of very low density lipoproteins by lipoprotein lipase. J Biol Chem1994; 269: 20554—20560.
65.
Lanza-Jacoby S., Wong SH, Tabares A., Baer D., Schneider T.Disturbances in the composition of plasma lipoproteins during gram-negative sepsis in the rat. Biochim Biophys Acta1992; 1124: 233—240.
66.
Redgrave TG , Rakiv V., Mortimer BC, Mamo JCEffects of spingomyelin and phosphatidylcholine acyl chains on the clearance of triacylglycerol-rich lipoproteins from plasma. Studies with lipid emulsions in rats. Biochim Biophys Acta1992; 1126: 65—72.
