Effects of ketoacidosis on rat apolipoprotein A1 gene expression: a link with acidosis but not with ketones.
To determine if ketoacidosis contributes to reduced apolipoprotein A1 (apoA1) expression in insulin-deficient diabetic rats, we examined the regulation of apoA1 gene expression in response to changes in ambient pH or ketone body concentrations. Hepatic apoAI mRNA levels were reduced 42% in diabetic rats relative to nondiabetic controls (means+/-s.d.; 321.8+/-43.7 vs 438.7+/-58.8 arbitrary units; P<0.03). Neither endogenous apoA1 mRNA nor transcriptional activity of the rat apoA1 gene promoter (from -474 to -7) were altered by sodium butyrate or isobutyramide (0.3 mM to 10 mM) in Hep G2 or Caco-2 cells. Rat hepatic and intestinal apoA1 mRNA levels, and plasma apoA1 concentration, were not altered 24 h after isobutyramide administration (500 mg/kg by gavage). When the effect of altering ambient pH within a wide range commonly encountered in vivo was studied, acidosis (pH 6.7), relative to alkalosis (pH 7.9), decreased apoAI mRNA levels relative to glyceraldehyde-3-phosphate dehydrogenase mRNA by 47% in Hep G2 cells (P<0.025) and by 24% in Caco-2 cells (P<0.017). Acidosis did not alter cytomegalo virus (CMV)-beta-galactosidase activity, or the activity of the simian virus (SV40) early-region promoter, in either cell line transfected with the respective constructs. The lowering of ambient pH was associated with a graded reduction in apoAI promoter activity. At pH 6.7, apoAI promoter activity was reduced by 75% compared with promoter activity at pH 7.9. These observations indicate that acidosis, but not ketosis, contributes to the reduction in apoA1 expression during diabetic ketoacidosis by down-regulating apoAI promoter activity.
Haas
M J
MJ
Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, Saint Louis University Medical School, St Louis, Missouri 63104, USA.
Pun
K
K
Reinacher
D
D
Wong
N C
NC
Mooradian
A D
AD
D000577:Amides / Q000008:administration & dosage; D000818:Animals; D016632:Apolipoprotein A-I / Q000097:blood / Q000235:genetics*; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000378:metabolism; D016883:Diabetic Ketoacidosis / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D015870:Gene Expression; D017930:Genes, Reporter; D006863:Hydrogen-Ion Concentration; D007657:Ketone Bodies / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D014162:Transfection
D000577:Amides; D016632:Apolipoprotein A-I; D007657:Ketone Bodies; D012333:RNA, Messenger; C030197:isobutyramide