Rationale: Obstructive sleep apnea, a condition leading to chronic intermittent hypoxia (CIH), is associated with hyperlipidemia, atherosclerosis, and a high cardiovascular risk. A causal link between obstructive sleep apnea and atherosclerosis has not been established. Objectives: The objective of the present study was to examine whether CIH may induce atherosclerosis in C57BL/6J mice. Methods: Forty male C57BL/6J mice, 8 weeks of age, were fed either a high-cholesterol diet or a regular chow diet and subjected either to CIH or intermittent air (control conditions) for 12 weeks. Measurements and Main Results: Nine of 10 mice simultaneously exposed to CIH and high-cholesterol diet developed atherosclerotic lesions in the aortic origin and descending aorta. In contrast, atherosclerosis was not observed in mice exposed to intermittent air and a high-cholesterol diet or in mice exposed to CIH and a regular diet. A high-cholesterol diet resulted in significant increases in serum total and low-density lipoprotein cholesterol levels and a decrease in high-density lipoprotein cholesterol. Compared with mice exposed to intermittent air and a high-cholesterol diet, combined exposure to CIH and a high-cholesterol diet resulted in marked progression of dyslipidemia with further increases in serum total cholesterol and low-density lipoprotein cholesterol (124 ؎ 4 vs. 106 ؎ 6 mg/dl; p Ͻ 0.05), a twofold increase in serum lipid peroxidation, and up-regulation of an important hepatic enzyme of lipoprotein secretion, stearoyl-coenzyme A desaturase-1. Conclusions: CIH causes atherosclerosis in the presence of dietinduced dyslipidemia.Keywords: obstructive sleep apnea; lipids; hypoxia; mouse; stearoylcoenzyme A desaturaseObstructive sleep apnea (OSA) is characterized by recurrent collapse of the upper airway during sleep, leading to chronic intermittent hypoxia (CIH) (1). OSA has been associated with an increased risk of hypertension, type II diabetes, angina, myocardial infarction, congestive heart failure, stroke, and fatal cardiovascular events, independent of underlying obesity (2-5).Poor cardiovascular outcomes may be related to the high prevalence of atherosclerosis in patients with OSA. Studies have shown independent associations between hypoxic stress of OSA and increased carotid artery intima-media thickness (6) as well as progressive narrowing of the coronary artery lumens (7).

Abstract-Obstructive sleep apnea, a syndrome leading to recurrent intermittent hypoxia (IH), has been associated previously with hypercholesterolemia, independent of underlying obesity. We examined the effects of experimentally induced IH on serum lipid levels and pathways of lipid metabolism in the absence and presence of obesity. Lean C57BL/6J mice and leptin-deficient obese C57BL/6J-Lep ob mice were exposed to IH for five days to determine changes in serum lipid profile, liver lipid content, and expression of key hepatic genes of lipid metabolism. In lean mice, exposure to IH increased fasting serum levels of total cholesterol, high-density lipoprotein (HDL) cholesterol, phospholipids (PLs), and triglycerides (TGs), as well as liver TG content. These changes were not observed in obese mice, which had hyperlipidemia and fatty liver at baseline. In lean mice, IH increased sterol regulatory element binding protein 1 (SREBP-1) levels in the liver, increased mRNA and protein levels of stearoyl-coenzyme A desaturase 1 (SCD-1), an important gene of TG and PL biosynthesis controlled by SREBP-1, and increased monounsaturated fatty acid content in serum, which indicated augmented SCD-1 activity. In addition, in lean mice, IH decreased protein levels of scavenger receptor B1, regulating uptake of cholesterol esters and HDL by the liver. We conclude that exposure to IH for five days increases serum cholesterol and PL levels, upregulates pathways of TG and PL biosynthesis, and inhibits pathways of cholesterol uptake in the liver in the lean state but does not exacerbate the pre-existing hyperlipidemia and metabolic disturbances in leptin-deficient obesity. Key Words: obstructive sleep apnea Ⅲ cholesterol homeostasis Ⅲ lipids Ⅲ hypoxia Ⅲ mouse Ⅲ gene expression O bstructive sleep apnea (SA) is the most common form of sleep-disordered breathing and is characterized by recurrent collapse of the upper airway during sleep, leading to periods of intermittent hypoxia (IH) and sleep fragmentation. 1 SA is present in 2% of women and 4% of men in the general US population, but it is more common in obese individuals. 2,3 SA is an independent risk factor for increased cardiovascular morbidity and mortality. 4 -7 It has been postulated that metabolic dysfunction in SA may provide an intermediate step linking IH and sleep disturbances to cardiovascular disease. Although several recent studies have focused on the effects of SA on dysregulating glucose and insulin metabolism, 2,8 -10 little information is available about the impact of SA on lipid metabolism. Abnormalities in lipid regulation that occur in response to SA may act to increase the cardiovascular risk in an already susceptible population. Although obesity is one of the risk factors for elevations in total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels, 11 recent clinical studies indicate that SA may also contribute to hypercholesterolemia. [12][13][14][15] Thus, obesity and IH may interact to alter lipid metabolism in SA.Key steps of lipid metaboli...

The prevalence of the MS increased with aging, and this was associated with lower androgen levels. Lower total T and SHBG predicted a higher incidence of the MS.