Nikolai N. Anitschkow and the lipid hypothesis of atherosclerosis

One hundred years ago, Nikolai N. Anitschkow published his seminal observations that rabbits fed a diet with only high-cholesterol developed atheromatous lesions in association with greatly elevated blood cholesterol. For many years, Anitschkow's observations received little recognition. However, eventually a combination of experimental work, autopsy studies, epidemiological investigation and clinical trials has led to the firm establishment of the essential role of lipids in the response to injury theory of atherosclerosis. The twists and turns in the acceptance of the lipid hypothesis of atherosclerosis is briefly reviewed. Today, it is well worth celebrating the 100th anniversary of the seminal insight into human vascular disease of the brilliant experimental pathologist, Nikolai N. Anitschkow.

LDL cholesterol and atherosclerosis: The evidence

The lipid theory of atherosclerosis dates back more than a century. Despite this, some authors have questioned the relevance of hypercholesterolaemia in its development. Multiple experimental, epidemiological, and clinical evidence underpins this association. Atherosclerotic cardiovascular disease remains as the major cause of mortality in the world. Recent genetic studies of Mendelian randomisation and randomised clinical trials aimed at LDL cholesterol reduction, are summarised in this article. They, unequivocally ratify the aetiological role of LDL cholesterol in the development of atherosclerosis. Thus, LDL cholesterol lowering is the cornerstone of lipid lowering therapy for the reduction of cardiovascular complications of atherosclerosis.

Establishment of the Meyer-Overton correlation in an artificial membrane without protein

BACKGROUND

The potency of anesthetics with various structures increases exponentially with lipophilicity, which is the Meyer-Overton (MO) correlation discovered over 120 years ago. The MO correlation was also observed with various biological effects and chemicals, including alcohols; thus, the correlation represents a fundamental relationship between chemicals and organisms. The MO correlation was explained by the lipid and protein theories, although the principle remains unknown because these are still debating.

METHODS

The gentle hydration method was used to form giant unilamellar vesicles (GUVs) consisting of high- and low-melting phospholipids and cholesterol in the presence of n-alcohols (C2-C12). Confocal fluorescence microscopy was used to determine the percentage of GUVs with domains in relation to the n-alcohol concentrations.

RESULTS

n-Alcohols inhibited the domain formation of GUVs, and the half inhibitory concentration (IC50) in the aqueous phase (Cw) decreased exponentially with increasing chain length (lipophilicity). In contrast, the membrane concentrations (Cm) of alcohols for the inhibition, which is a product of the membrane-water partition coefficient and the IC50 values, remained constant irrespective of the chain length.

CONCLUSIONS

The MO correlation is established in GUVs, which supports the lipid theory. When alcohols reach the same critical concentration in the membrane, similar biological effects appear irrespective of the chain length, which is the principle underlying the MO correlation.

GENERAL SIGNIFICANCE

The protein theory states that a highly lipophilic compound targets minor membrane proteins due to the low Cw. However, our lipid theory states that the compound targets various membrane proteins due to the high Cm.