Cholesterol-induced changes

SIRIKCI, O., OZER, N. K. AZZI, A. 1996. Dietary cholesterol-induced changes of protein kinase C and the effect of vitamin E in rabbit aortic smooth muscle cells. Atherosclerosis, 126, 253-63. 

To identify further which substance, cafestol or kahweol, or both, was inducing changes in serum cholesterol, the investigators attempted, but failed due to technical limitations, to separate the two chemical compounds. Alternatively, they compared coffee oil from Arabica vs. Robusta coffee beans. Arabica beans contain both cafestol and kahweol, while Robusta beans contain cafestol, but almost no kahweol. The investigators found that Arabica and Robusta oils both increased serum cholesterol and triglyceride levels comparably. They thus concluded that cafestol is, and kahweol might be, a serum cholesterol raising factor. 

Kim, E.D. (1974). Annual and age-induced changes in the cholesterol and phospholipid content of full-grown reproductive products of carp (In Russian). In Different Quality of Early Ontogenesis in Fish (VJ. Vladimirov, ed.), pp.l 14-127. Naukova Dumka, Kiev. 

An aliphatic ketone (9-heptadecanone) and two keto derivatives of stearic acid (as potassium salts) containing a ketone functionality either at position 5 or 12 were incorporated into bilayers of the phospholipid l,2-dihexadecyl-sn-glycero-3-phosphocholine. Infrared spectra of these mixtures were measured as a function of temperature and amount of added cholesterol. It was found that the presence of cholesterol in these bilayers induces changes in the location of the guest ketone and that these changes are dependent on both temperature and cholesterol concentration. It is also demonstrated that, in the gel phase, the presence of cholesterol induces larger intersheadgroup separations and, therefore, water penetrates deeper into the lipid bilayer. 

From the data presented here several conclusions may be reached regarding the effect of cholesterol on lipid bilayers. It is shown that, even if the presence of cholesterol in bilayers serves to moderate temperature-induced changes, its ability to affect the location of solubilized molecules is highly temperature dependent We have also shown, in accord with previous work (11), that the presence of cholesterol in the gel phase results in a larger separation between the lipid polar groups and this in turn allows water to penetrate into the lipid hydrophobic core. 

Mechanisms of Exercise-Induced Changes in Plasma Lipids Lipoprotein Lipase, Hepatic Triglyceride Lipase and Lecithin Cholesterol Acyl Transferase... 

The importance of investigating how cholesterol content and acyl chain composition alter the physical properties of membranes is highlighted by the functional deficits associated with 22 6n-3-deficient diets and the antisocial behavior associated with varied cholesterol levels. In the context of psychological disease and neurotransmitter receptor function, it is important to investigate how compositionally induced changes in membrane physical properties influence membrane-associated signaling processes. 

In contrast to lipid bilayer membranes, it has been found [4] that the permeability coefficient of the human red-cell membrane to water did not change when the free cholesterol content in the membrane was varied from 0.84 to 1.87 mg/ml cells. Furthermore, the permeability of the human red-cell membrane to sulfate and some nonelectrolytes remained constant when membrane cholesterol was partially removed (for review, see [6]). These results, however, should not be taken as evidence that water transport in human red cells is independent of membrane cholesterol, since this degree of variation may be insufficient to produce alteration. In fact, extensive depletion of membrane cholesterol induces a marked increase in nonelectrolyte permeability. The effect of membrane cholesterol on the transport of water is also found in other membrane systems. For example, the polyene antibiotic. Amphotericin B, which interacts specifically with sterol-containing membranes, increases the permeability of the mucosal but not the serosal membrane of toad bladder to water and other solutes [32]. It is possible that membrane cholesterol only effects the movements through the lipid bilayer pathway. This may explain the findings that the permeabiUty coefficient of the human red cell membrane to water... 

The same PDA fusion methodology was also used to study attaehment, perturbation of the membrane, and entry of vaeeinia virus to the cell membrane. The PDA patch was introduced on epithelial cell membranes and polymerized. Attachment of viral particle to the membranes induced changes in color (blue to red) and emission spectra. It was observed that the lipid composition of the membrane had a profound effect for the interactions of the PDA labeled cells with the virus particles. Membrane domains or lipid rafts rich in cholesterol and sphingomylein favored the interactions with the vaccinia virus. 

---