Effect of troglitazone on plasma lipid metabolism and lipoprotein lipase.
OBJECTIVE
To clarify how troglitazone, an insulin-sensitizing agent, affects lipid metabolism and postheparin plasma lipoprotein lipase (LPL).


METHODS
Fifteen patients (3 male, 12 female) (the average age 62+/-7 years; the mean body mass index (BMI) 25+/-3 kg/m2 ) were recruited for this study. The serum lipids and postheparin plasma lipoprotein lipase (LPL) mass before and 4 weeks after oral administration of troglitazone (200 mg day-1 ) were measured. A mouse preadipocyte cell line, 3T3-L1, was incubated with troglitazone and LPL enzyme protein mass in the culture media was measured by an enzyme linked immunosorbent assay. A reverse transcription polymerase chain reaction (RT-PCR) using primers specific for the carboxyl terminal 135 amino acid of mouse LPL cDNA was used to evaluate the effect of troglitazone on expression of LPL and Northern blot analysis carried out to determine expression of LPL.


RESULTS
The average levels before treatment of fasting serum total cholesterol, triglycerides, high density lipoprotein cholesterol, plasma glucose and glycohaemoglobin A1c were 5.6+/-0.9, 1.8+/-1.0, 1.5+/-0.5, 8.1+/-1.7 mmol l-1 and 7.8+/-1.6% respectively. Four weeks after treatment, those levels were 5.4+/-0.9, 1.2+/-0.3 (P=0.004), 1.6+/-0.5 (P=0.02) mmol l-1, 7.7+/-2.3 mmol l-1 and 7. 3+/-0.6% (P=0.01), respectively. The postheparin plasma LPL mass increased from 226+/-39 to 257+/-68 ng ml-1 (P=0.03) during that period. The LPL mass in the media of 3T3 L1 cells cultured in the presence of 10, 20 or 30 microm of this compound increased in a dose dependent manner. RT-PCR revealed that the area of the bands of the RT-PCR products on 1.5% agarose gel analyzed with NIH image from the cell extracts cultured in the presence of 10 microm troglitazone was significantly larger (P=0.0069) than that in the absence of this compound. Northern blot analysis revealed that in the cultured 3T3-L1 cells, the expression of LPL was enhanced in the presence of 10 microm troglitazone.


CONCLUSIONS
Troglitazone improves plasma triglyceride-rich lipoproteins metabolism by enhancing the expression of LPL in adipocytes.
Kobayashi
J
J
Second Department of Internal Medicine, Chiba University School of Medicine, Health Sciences Center, Chiba University, 1-8-1 Inohana Chuo-Ku, Chiba City, Chiba 260-0856, Japan.
Nagashima
I
I
Hikita
M
M
Bujo
H
H
Takahashi
K
K
Otabe
M
M
Morisaki
N
N
Saito
Y
Y
D016475:3T3 Cells; D017667:Adipocytes / Q000201:enzymology; D000368:Aged; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D015152:Blotting, Northern; D002839:Chromans / Q000494:pharmacology*; D003920:Diabetes Mellitus / Q000097:blood; D005260:Female; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008055:Lipids / Q000097:blood*; D008071:Lipoprotein Lipase / Q000097:blood* / Q000235:genetics; D008099:Liver / Q000187:drug effects; D008297:Male; D051379:Mice; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D000077288:Troglitazone
D001786:Blood Glucose; D002839:Chromans; D007004:Hypoglycemic Agents; D008055:Lipids; D012333:RNA, Messenger; D013844:Thiazoles; D045162:Thiazolidinediones; D008071:Lipoprotein Lipase; D000077288:Troglitazone