AJP - Renal Physiology, Vol 259, Issue 4 704-F714, Copyright © 1990 by American Physiological Society
High glucose induces cell hypertrophy and stimulates collagen gene transcription in proximal tubule
F. N. Ziyadeh, E. R. Snipes, M. Watanabe, R. J. Alvarez, S. Goldfarb and T. P. Haverty
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104.
Tubulointerstitial changes in the diabetic kidney correlate closely with
the decline in glomerular filtration. In this study, we used a cell culture
system of mouse proximal tubule epithelial cells to test the effects of
glucose on cell growth, size, and matrix biosynthesis. [3H]thymidine
incorporation was significantly inhibited in cells grown in 450 mg/dl
glucose, compared with cells grown in 100 mg/dl glucose. The cells grown in
the higher glucose concentration were slightly larger, their protein
content and the total protein synthetic rate were significantly increased,
and they secreted approximately twice as much procollagens type IV and type
I. Concordantly, steady-state procollagen mRNA levels were also increased:
2.6-fold for the alpha 1(IV) and 2.2-fold for the alpha 2(I) procollagens.
Additionally, nuclear run-off studies demonstrated that procollagen gene
transcription rate was stimulated approximately 50%; beta-actin
transcription rate was not altered. We used chloramphenicol
acetyltransferase (CAT) reporter gene constructs to determine whether the
increased transcription rate of alpha 2(I) gene was associated with
activation of its enhancer sequence. Cells transfected with the enhancer
demonstrated more than fivefold increase in CAT activity when cultured in
the high-glucose medium. These studies demonstrate a multitude of effects
of high ambient glucose concentrations on proximal tubule cell growth and
collagen biosynthesis; cell proliferation is decreased although cell
hypertrophy occurs. Procollagen gene transcription rate is stimulated and
this response contributes to the observed increase in procollagen mRNA
content. Activation of an enhancer sequence may be one possible mode
through which high glucose levels increase the transcription of procollagen
type I, presumably involving trans-acting factor(s).
