4.1.5. Cholesterol

Cholesterol is a fatty substance either obtained from food in the gu<sup>t</sup> or produced in the liver when needed. It is a necessary component of all cell membranes and a fundamental component of many molecules, such as steroid hormones; it is also involved in the transport of lipids between different tissues in the body and the blood [47]. This study revealed more considerable reductions in the concentrations of blood cholesterol in the cold-blooded knotweed-fed horses. There are many studies describing different mechanisms by which resveratrol decreased the cholesterol concentration in blood, e.g., by reducing the basal and insulin-induced glucose conversion to total lipids in white adipose tissue [55]. There are also studies which found no effect of resveratrol on cholesterol concentration in horse blood [30]. Again, it seems that different active compounds are behind these diverse effects of knotweed. Another study [50] reported that a piceatannol-enriched diet decreased the cholesterol concentration in blood due to lowering its absorption in the intestine resulting from higher excretion of bile acids to the intestine. Piceid is also known for decreasing cholesterol concentrations [49].

All of the animals involved in the experiments reported here were healthy; no lipid metabolism disorders were noted. Nevertheless, their metabolisms were improved due to the reduction in cholesterol concentration. Knotweed, owing to its content of resveratrol possessing hepatoprotective effects, can help prevent steatosis, which is an abnormal retention of fat in an organ, usually the liver [56,57].
