Abstract:
There is a high prevalence of insulin and leptin resistance and increased
cortisol concentrations in sleep apnoea patients, independent of obesity.
Chronic intermittent hypoxia is used an experimental animal model to
simulate the hypoxia occurring in sleep apnoea patients. The aim of this
study was to measure plasma insulin and leptin concentrations and
hypothalamic-pituitary-axis activity in rats exposed to either intermittent
hypoxia (CIH) or sham hypoxia (SH) for fourteen days. To induce CIH
plexiglass cylinders were flushed with 100% nitrogen for nine seconds
every 90 seconds, seven hours/day. The rats were weighed each day
during the exposure period. Venous blood samples for insulin and leptin
were collected on days one, three, five, eight and fifteen. Faecal
samples were collected to measure glucocorticoid metabolites. There
was no significant difference in the daily change in body weight between
the rats exposed to CIH compared to the rats exposed to SH (unpaired
t-test). Plasma insulin concentrations were not affected by CIH. In both
groups of rats plasma leptin concentrations were significantly higher on
day fifteen compared to day five (p=0.03, unpaired t-test). Glucocorticoid
metabolites were significantly increased in the intermittent hypoxia
group on day two (p=0.003 one-way ANOVA). In conclusion, exposing
normal weight rats to CIH for fourteen days resulted in a transient
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increase in HPA axis activity on day two and an elevation in plasma
leptin levels, in both groups of rats, at day fifteen.
