Abstract
In this study, we clarify that high glucose inhibits albumin uptake in cultured LLC-PK1
cells. LLC-PK1 cells cultured for 6 days with 5.5–27.8 mM d-glucose were challenged by fluorescein isothiocyanate (FITC)-conjugated human albumin
(HA). FITC-HA binding and uptake were inhibited by >5.5 mM glucose (![Math Eq]()
mM). Analysis of FITC-HA binding and uptake at 5.5 and 16.7 mM d-glucose (high glucose, HG) showed decreased affinity (Km for binding: 35.5 mg/l versus 52.6 mg/l, Km for uptake; 41.3 mg/l versus 55.6 mg/l) and maximal velocity (Bmax—0.33 μg versus 0.27 μg/30 min/mg protein; Umax—4.40 μg versus 3.48 μg/60 min/mg protein) at HG. A comparison of the time courses of FITC-HA binding and uptake
at 5.5 mM glucose and at HG showed that HG suppressed them beyond 15 min (P<0.05–0.001). Phlorizin (>0.25 mM) completely reversed the HG-induced inhibition of FITC-HA binding and uptake. High
glucose decreased mRNA of GLUT-1 and SGLT-1, but did not influence that of SGLT-2.
The simultaneous presence of Vitamin E (10−6 M), Vitamin C (10−6 M) and reduced glutathione (0.25 mM) reversed the suppressed FITC-HA binding and uptake by HG, while any one or two
of these molecules, and various inhibitors of advanced glycation end products, failed
to do so.
mM). Analysis of FITC-HA binding and uptake at 5.5 and 16.7 mM d-glucose (high glucose, HG) showed decreased affinity (Km for binding: 35.5 mg/l versus 52.6 mg/l, Km for uptake; 41.3 mg/l versus 55.6 mg/l) and maximal velocity (Bmax—0.33 μg versus 0.27 μg/30 min/mg protein; Umax—4.40 μg versus 3.48 μg/60 min/mg protein) at HG. A comparison of the time courses of FITC-HA binding and uptake
at 5.5 mM glucose and at HG showed that HG suppressed them beyond 15 min (P<0.05–0.001). Phlorizin (>0.25 mM) completely reversed the HG-induced inhibition of FITC-HA binding and uptake. High
glucose decreased mRNA of GLUT-1 and SGLT-1, but did not influence that of SGLT-2.
The simultaneous presence of Vitamin E (10−6 M), Vitamin C (10−6 M) and reduced glutathione (0.25 mM) reversed the suppressed FITC-HA binding and uptake by HG, while any one or two
of these molecules, and various inhibitors of advanced glycation end products, failed
to do so.In conclusion, a high glucose milieu causes inhibition of albumin binding and uptake
in proximal tubular cells by increasing metabolic oxidative stress through excessive
glucose flux via the sodium glucose transporter.
Keywords
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Article info
Publication history
Published online: August 19, 2004
Accepted:
February 2,
2004
Received in revised form:
January 20,
2004
Received:
September 10,
2003
Identification
Copyright
© 2004 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
