Role of insulin resistance in decreasing lipoprotein lipase activity in tumor-bearing rats.
The role of insulin resistance in the tumor-induced decrease in tissue lipoprotein lipase (LPL) activity was studied in vivo and vitro in methylcholanthrene-induced sarcoma-bearing rats. Intraperitoneal (i.p.) injection of 2U of regular insulin resulted in high-adipose LPL activity in control rats (CTR) of 122.0 +/- 42.4 U/mg tissue, but it had little effect on tumor-bearing rats (TBR), which showed a value of only 9.6 +/- 5.5 U/mg tissue (P = 0.002). When adjusted for serum insulin concentrations, adipose LPL activity remained significantly different between the TBR and CTR at 0.19 +/- 0.17 and 0.78 +/- 0.29 U/mg tissue, respectively (P = 0.02). Following the in vitro incubation with either 1.44 g/l glucose of 1 x 10-8 U insulin of adipose tissue fragments obtained from the TBR and the CTR, measurable LPL activity was maintained in the tissue from the CTR for 2 h but not in that from the TBR. These results suggest that the decreased LPL activities seen in the tumor-bearing state may be mediated by insulin resistance.
Noguchi
Y
Y
First Department of Surgery, Yokohama City University School of Medicine, Japan.
Nomura
K
K
Yoshikawa
T
T
Fukuzawa
K
K
Makino
T
T
Tsuburaya
A
A
Matsumoto
A
A
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002100:Cachexia / Q000201:enzymology; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008071:Lipoprotein Lipase / Q000097:blood*; D008297:Male; D008748:Methylcholanthrene; D051381:Rats; D011916:Rats, Inbred F344; D012513:Sarcoma, Experimental / Q000139:chemically induced / Q000201:enzymology*; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D014280:Triglycerides; D008748:Methylcholanthrene; D008071:Lipoprotein Lipase