Effect of cigarette smoke and dietary cholesterol on plasma lipoprotein composition.

The effect of acute inhalation of cigarette smoke and consumption of dietary cholesterol on plasma lipoprotein composition in atherosclerosis-susceptible White Carneau pigeons was examined. Pigeons were assigned to four treatment groups: 1) Controls fed a chow diet ad libitum and retained in their cages throughout the study; 2) Sham pigeons fed a cholesterol-saturated fat diet and exposed to fresh air by the Lorillard smoking machine; 3) Low nicotine-low carbon monoxide (LoLo) animals also fed the cholesterol diet and exposed to low concentrations of these cigarette smoke products; and 4) High nicotine-high carbon monoxide (HiHi) birds fed the cholesterol diet and subjected to high concentrations of these inhalants. Plasma very low density (VLDL), low density (LDL), and high density (HDL) lipoproteins were isolated by density gradient ultracentrifugation. Smoke-related differences appeared in HiHi HDL which contained relatively more free and esterified cholesterol and total lipid, but relatively and absolutely less total protein than HDL from Sham-smoked pigeons. Similarly, VLDL from birds exposed to cigarette smoke (LoLo and HiHi) contained relatively more total lipid, but less total protein than VLDL from Sham pigeons. Inhalation of tobacco smoke also produced a marked depression in the HDL2/HDL3 ratio resulting from an increased proportion of the HDL3 subfraction relative to HDL2. Pigeons (Sham, LoLo, HiHi) fed the cholesterol-saturated fat diet circulated HDL with greater free and esterified cholesterol mass than Controls. VLDL particles from these three treatment groups were relatively enriched with cholesterol and cholesteryl ester at the expense of triglyceride. Diet also altered the type of cholesteryl ester present in HDL with cholesteryl linoleate representing the predominant form in Control pigeons and cholesteryl oleate in cholesterol-fed birds. These results demonstrate that cigarette smoking can mediate alterations in lipoprotein composition independent of changes induced by dietary cholesterol and saturated fat.