Intermittent hypoxia (low oxygen) of sleep apnea exacerbates insulin resistance and inflammation

New research just published in the journal Obesity contributes to the evidence for weighty metabolic consequences of the hypoxia (reduced oxygen saturation) that occurs with sleep disordered breathing. The authors state:

"The main aim of this study is to evaluate the effects of chronic intermittent hypoxia (CIH), a hallmark of sleep apnea, on IR [insulin resistance] and NAFLD [non-alcoholic fatty liver disease] in lean mice and mice with diet-induced obesity (DIO)."

They fed the study subjects either a high fat or regular diet for 12 weeks, after which they were exposed to CIH or normal room air as a control condition for 4 weeks. Then they measured fasting blood glucose, insulin, homeostasis model assessment (HOMA) index, liver enzymes, and performed an intraperitoneal glucose tolerance test. Their data paints an interesting picture:

"In DIO mice, body weight remained stable during CIH and did not differ from control conditions...Compared to lean mice, DIO mice had higher fasting levels of blood glucose, plasma insulin, the HOMA index, and had glucose intolerance and hepatic steatosis at baseline. In lean mice, CIH slightly increased HOMA index, whereas glucose tolerance was not affected. In contrast, in DIO mice, CIH doubled HOMA index, and induced severe glucose intolerance. In DIO mice, CIH induced NAFLD, inflammation, and oxidative stress, which was not observed in lean mice."

In other words, even though hypoxia did not further increase the body weight of the subjects with diet induced obesity, the metabolic effects including glucose intolerance, inflammation, fatty liver disease and oxidative stress were severe. I often find that the possibility of sleep disordered breathing has been overlooked in the work-up of patients with overweight or metabolic syndrome. This research adds to the compelling evidence that clinicians should bear this in mind.

"In conclusion, CIH exacerbates IR and induces steatohepatitis in DIO mice, suggesting that CIH may account for metabolic dysfunction in obesity."