Male Gender Aggravates Insomnia-Associated Disturbances in IPGTT, Insulin Level and Insulin Resistance, with Less Improvement on Retrieval of Normal Sleep Compared to Aged Females

Abstract Background and Aim Prevalence of type 2 diabetes is growing worldwide in the last decades. Recent studies showed that sleeping hours had decreased in the last decades amongst both young and aged population. This study was conducted to investigate the effects of chronic insomnia and its relief on the intraperitoneal glucose tolerance test (IPGTT),insulin level and insulin resistance in aged male and female rats with insight in the underlying mechanisms. Methods The study was carried out on 66 local strain aged rats of both sexes. Range of male and female rat weights was 350-400 and 250-350 gm, respectively. Range of ages of male and female rats were 23-25 and 24-26 months, respectively. Rats were allocated into two study groups, males (n°= 32) and females (n°= 34). The male group was further subdivided into the following 4 subgroups: Male one month control group (MC1, n°=7); Male sleep -deprived group for one month (MSD, n°=10); Male two -month control group (MC2, n°=7); Male sleep deprived group for one month followed by one month reversion to regular sleep (MSDR, n°=8). The female group was further subdivided into 4 subgroups; Female one month control group (FC1, n°=9); Female sleep deprived group for one month (FSD, n°=7); Female two -month control group (FC2, n°=9); Female sleep deprived group for one month followed by one month reversion to regular sleep (FSDR, n°=9). The experimental method of sleep restriction was the modified multiple platform method (MMPM) which deprives the animal from rapid eye movement (REM) sleep, while the non-REM sleep unaffected without the need for monitoring the EEG. The study duration was 2 months, Rats were assessed for IPGTT, fasting serum insulin (FSI) and homeostasis model assessment of insulin resistance (HOMA-IR) as well as serum levels of corticosterone (Cs) and melatonin (Mt). Results After one month of insomnia, male rats (MSD) became prediabetic with fasting hyperglycemia (FBG 107 mg/dl) and significantly elevated blood glucose values in the IPGTT and area under the curve (AUC), FSI and HOMA-IR as well as Cs and significant decrease of Mt. compared to their matched controls (MC1). Reversion to normal sleep normalized the FBG of MSDR group and blood glucose levels at 30, 90, 120 minutes and area under the curve (AUC), with significant decrease of FSI and HOMA-IR, although not yet normalized compared to MC2 rat group. Similarly, Cs and Mt. levels showed partial improvement compared to MSD group, but not f