Aging leads to increased levels of protein O-linked N-acetylglucosamine in heart, aorta, brain and skeletal muscle in Brown-Norway rats - PubMed (original) (raw)

Aging leads to increased levels of protein O-linked N-acetylglucosamine in heart, aorta, brain and skeletal muscle in Brown-Norway rats

Norbert Fülöp et al. Biogerontology. 2008 Jun.

Abstract

Changes in the levels of O-linked N-acetyl-glucosamine (O-GlcNAc) on nucleocytoplasmic protein have been associated with a number of age-related diseases such as Alzheimer's and diabetes; however, there is relatively little information regarding the impact of age on tissue O-GlcNAc levels. Therefore, the goal of this study was to determine whether senescence was associated with alterations in O-GlcNAc in heart, aorta, brain and skeletal muscle and if so whether there were also changes in the expression of enzymes critical in regulating O-GlcNAc levels, namely, O-GlcNAc transferase (OGT), O-GlcNAcase and glutamine:fructose-6-phosphate amidotransferase (GFAT). Tissues were harvested from 5- and 24-month old Brown-Norway rats; UDP-GlcNAc, a precursor of O-GlcNAc was assessed by HPLC, O-GlcNAc and OGT levels were assessed by immunoblot analysis and GFAT1/2, OGT, O-GlcNAcase mRNA levels were determined by RT-PCR. In the 24-month old animals serum insulin and triglyceride levels were significantly increased compared to the 5-month old group; however, glucose levels were unchanged. Protein O-GlcNAc levels were significantly increased with age (30-107%) in all tissues examined; however, paradoxically the expression of OGT, which catalyzes O-GlcNAc formation, was decreased by approximately 30% in the heart, aorta and brain. In the heart increased O-GlcNAc was associated with increased UDP-GlcNAc levels and elevated GFAT mRNA while in other tissues we found no difference in UDP-GlcNAc or GFAT mRNA levels. These results demonstrate that senescence is associated with increased O-GlcNAc levels in multiple tissues and support the notion that dysregulation of pathways leading to O-GlcNAc formation may play an important role in the development of age-related diseases.

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Figures

Figure 1

Figure 1

Anti O-GlcNAc and anti OGT Western blot results from hearts (A,B,C) and aortae (D,E,F) of 5- and 24-month old Brown-Norway rats. (A,D), representative Western blots; (B,E), mean area densities of anti O-GlcNAc blots; and (C,F), mean area densities of anti OGT blots. * p<0.05 vs. control.

Figure 2

Figure 2

Anti O-GlcNAc and anti OGT Western blot results from brains (A,B,C) and skeletal muscles (D,E,F) of 5- and 24-month old Brown-Norway rats. (A,D), representative Western blots; (B,E), mean area densities of anti O-GlcNAc blots; and (C,F), mean area densities of anti OGT blots. * p<0.05 vs. control.

Figure 3

Figure 3

GFAT1 mRNA levels, GFAT2 mRNA levels as % of 5-month group and UDP-GlcNAc levels in A) heart; B); brain and C) skeletal muscle isolated from 5 and 24 month old Brown-Norway rats, * p<0.05 vs. 5 month old.

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