Augmentation of Ca2+-induced microsomal triglyceride transfer protein activity by glucose supply enhances hypertriglyceridemia in vivo.
We have investigated possible roles of intra-glucose supply on microsomal triglyceride (TG) transfer protein (MTP) in the secretion of TG-rich very low-density lipoprotein (VLDL) from the liver. Due to the activation of MTP, TG and apolipoprotein B (apoB) in the liver are assembled into VLDL and then the VLDL is transferred into the blood stream. High MTP activity can increase the release of VLDL into the blood stream, and this would lead high levels of TG and apoB in the blood. High MTP activity was found when the liver (or hepatocytes) contained a high level of total Ca2+ as a response of glucose administration. However, the MTP activity was reduced in response to the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7, Ki=25 microM), the intracellular Ca2+ chelator BAPTA-AM, and the extracellular Ca2+ chelator EDTA. These suggested that there might be a very close relationship between high MTP activity and high Ca2+ level in the liver by glucose administration. Glucose-derived hyperglycemic condition resulted from those elevations of TG and total cholesterol in the liver. This hyperglycemic phenomenon may be associated with the increase of TG and apoB levels in blood. The possibility for the regulation of VLDL formation in the liver and, further, those related circulatory diseases due to the excess of VLDL in the blood stream by controlling MTP activity in association with Ca2+ was investigated.
Cho
Hyun-Jeong
HJ
Department of Biomedical Laboratory Science, College of Biomedical Science and Engineering, and Regional Research Center, Inje University, Gimhae, Gyungnam, Korea.
Kang
Hyo-Chan
HC
Ju
Young-Cheol
YC
Lee
Hyun-Sub
HS
Kim
Hyeong-Soo
HS
Park
Hwa-Jin
HJ
D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry; D004435:Eating / Q000187:drug effects; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D015228:Hypertriglyceridemia / Q000097:blood / Q000139:chemically induced*; D007328:Insulin / Q000097:blood; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D013449:Sulfonamides / Q000494:pharmacology
D001055:Apolipoproteins B; D002147:Calmodulin; D002352:Carrier Proteins; D002614:Chelating Agents; D003470:Culture Media; D007328:Insulin; D013449:Sulfonamides; C106092:microsomal triglyceride transfer protein; D004533:Egtazic Acid; C017967:W 7; D005947:Glucose; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium