Abstract
Purpose: :
To study normo- and hyperglycemic electrophysiological retinal function in healthy subjects before and after induction of temporary insulin resistance.
Methods: :
Dark-adapted full field electroretinography (ffERG) was made in 10 eyes in 10 healthy men (age 25±3 years (mean±SD); body mass index 22±3 kg/m2; fasting plasma glucose 4.9±0.2 mM), while fasting and 2-3 hours later while plasma glucose was clamped at 10 mM. A baseline session in the subjects’ habitual state was followed by a second session after being on a high-caloric diet with minimal physical activity while taking prednisolone 37.5 mg/day for 9.1±1.4 days.
Results: :
The intervention had no impact on fasting plasma glycemia, but the postprandial increase in glycemia 2 h into an oral glucose tolerance test rose from 4.2±0.8 to 5.5±1.5 mM (P=0.023) and the area under curve increased from 154±81 to 250±40 mM·120 min (P=0.021) concomitantly with increases in insulin resistance according to the homeostatic model assessment (P=0.011) and fasting plasma insulin levels (P=0.003). The amplitudes and implicit times of the ffERG did not vary significantly (P<0.05) in any components between normo- and hyperglycemia, nor did they vary with insulin resistance. Thus, the fasting b-wave amplitude of the combined rod-cone response was 432±84 mV at baseline and 463±71 mV (P=0.13) during increased insulin resistance while the hyperglycemic b-wave amplitude was 449±91 mV at baseline and 478±119 mV (P=0.55) during increased insulin resistance. Also, differences in b-wave amplitude between normo- and hyperglycemia at the baseline visit (P=0.62) and during insulin resistance (P=0.62) were non-significant.
Conclusions: :
Neither hyperglycemia, nor short-term prednisolone-induced insulin resistance had any measurable effect on the components of the ffERG in healthy subjects.
Clinical Trial: :
http://www.clinicaltrials.gov NCT01140932
Keywords: retina • electroretinography: clinical • drug toxicity/drug effects