Membrane glycoprotein plasma cell 1 (PC-1) has been shown to be increased in type 2 diabetes and involved in insulin resistance through inhibiting the insulin receptor tyrosine kinase, which was demonstrated using cultured breast cancer cells. However, other reports have shown contradictory results in Chinese hamster ovary cells and in vitro kinase assay. Thus, we considered it necessary to investigate the effect of PC-1 using highly insulin-sensitive cells. Here, we used two of the following approaches: 1) investigating PC-1 expression levels in insulin-responsive tissues in rat models of diabetes and 2) overexpressing PC-1 in 3T3-L1 adipocytes. We found that PC-1 was highly expressed in insulin-responsive tissues, such as liver and adipose tissue, in normal rats. However, high-fat feeding or streptozotocin-induced diabetes did not change its expression levels in liver, adipose tissue, and skeletal muscle. Thus, PC-1 expression levels were not associated with high-fat-diet-induced insulin resistance or hyperglycemia. Although PC-1 was increased in adipose tissue in Zucker fatty rats (protein level, by 50%; mRNA level, by 90%), its expression levels in liver and skeletal muscle, tissues that are more responsible for whole body glucose metabolism than adipose tissue, did not significantly differ from those in normal rats. Next, we overexpressed PC-1 in 3T3-L1 adipocytes using an adenovirus transfection system. PC-1 expression was markedly increased to a level 16-fold greater than that in normal human adipose tissue, which is higher than the previously reported levels in diabetic patients. However, insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrate 1, activation of phosphatidylinositol 3-kinase, and glucose uptake were not affected by PC-1 overexpression. These results strongly suggest that increased PC-1 expression is not causally related to insulin resistance.
Abstract|
July 01 1999
No correlation of plasma cell 1 overexpression with insulin resistance in diabetic rats and 3T3-L1 adipocytes.
H Sakoda;
H Sakoda
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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T Ogihara;
T Ogihara
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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M Anai;
M Anai
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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M Funaki;
M Funaki
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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K Inukai;
K Inukai
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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H Katagiri;
H Katagiri
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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Y Fukushima;
Y Fukushima
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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Y Onishi;
Y Onishi
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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H Ono;
H Ono
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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Y Yazaki;
Y Yazaki
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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M Kikuchi;
M Kikuchi
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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Y Oka;
Y Oka
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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T Asano
T Asano
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
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Citation
H Sakoda, T Ogihara, M Anai, M Funaki, K Inukai, H Katagiri, Y Fukushima, Y Onishi, H Ono, Y Yazaki, M Kikuchi, Y Oka, T Asano; No correlation of plasma cell 1 overexpression with insulin resistance in diabetic rats and 3T3-L1 adipocytes.. Diabetes 1 July 1999; 48 (7): 1365–1371. https://doi.org/10.2337/diabetes.48.7.1365
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