Abstract
Introduction
Diabetes mellitus (DM) is a major health problem worldwide. Approximately 10% of all DM cases are type 1 (Juvenile onset) and the prevalence of type 1 DM among the under 20s continuously rise. DM is known to be an important etiologic factor for premature disc degeneration. Previous studies have reported higher incidence of degenerative disc diseases in patients with DM, relatively young age, than in the patients without DM. A glucose-mediated increase of oxidative stress is a major causative factor for the development of diseases associated with DM through senescence. However, little is known about relationship among DM, mitochondrial damage, oxidative stress, senescence of young intervertebral disc cells, and disc degeneration. The aim of this study was to investigate the effect of high glucose on mitochondrial damage, oxidative stress, senescence of nucleus pulposus (NP) cells, and disc degeneration.
Material and Methods
Young nucleus pulposus (NP) and annulus fibrosus (AF) cells were isolated from 4-week-old rats, cultured and placed in either 10% FBS (normal control) or 10% FBS plus two high glucose concentrations (0.1 and 0.2 M) (experimental conditions) for 1 and 3 days. We identified and quantified the mitochondrial damage (mitochondrial transmembrane potential) and reactive oxygen species (ROS) for 1 and 3 days. We also identified and quantified the occurrence of senescence and telomerase activity. Finally, we determined the expressions of proteins related to replicative senescence (p53–p21) and stress-induced senescence (p16–pRB) pathways.
Results
Two high glucoses enhanced the disruption of mitochondrial transmembrane potential (mitochondrial damage) in young NP and AF cells for 1 and 3 days compared with normal control. Two high glucoses increased the occurrence of senescence of young NP and AF cells in a dose- and time-dependent manner. Telomerase activity declined in a dose- and time-dependent manner. Both high glucoses increased the expression of p16 and pRB proteins in young NP and AF cells for 1 and 3 days. However, compared to normal control, the expressions of p53 and p21 proteins were decreased in young NP and AF cells treated with both high glucoses for 1 and 3 days.
Conclusion
The current study demonstrated that high glucose-induced oxidative stress accelerates premature stress-induced senescence of young NP and AF cells in a dose- and time-dependent manner rather than replicative stress. This may result in dysfunction of young NP and AF cells, leading to accelerated premature disc degeneration. Therefore, the prevention of excessive generation of oxidative stress by strict blood glucose control is important to prevent or to delay premature disc degeneration in young patients with DM.