Physiological Effects of Different Types of Β-glucan

Natural products, useful in treating or preventing various diseases, have been sought throughout the history of mankind. Most of these natural products are plagued with a common problem, i.e., the fact that they often represent a complex mixture of individual ingredients each of which can contribute to their biological activity. Natural (1,3)-beta-D-glucans from yeast, grain and mushrooms are well-established biological response modifiers, representing highly conserved structural components of cell walls in yeast, fungi, seaweed or grain seeds. 1,3-Glucan’s role as a biologically active immunomodulator has been well documented for over 40 years. Interest in the immunomodulatory properties of polysaccharides was initially raised after experiments showing that a crude yeast cell preparation stimulated macrophages via activation of the complement system. Numerous types of glucans have been isolated from almost every species of yeast, grain and fungi. (1,3)-betaD-glucans have been extensively studied for their immunological and pharmacological effects. More than 2,000 papers describing the mostly immunological activities of glucans exist in the literature (for review see). However, multiple reports established additional effects of glucans. Nearly 50 years ago the possible effects of dietary fiber were first suggested by Keys and these effects were later found to be associated with glucans. The cholesterol-lowering effects of fibers are routinely associated with beta-glucans. Due to the high consumption of oats or oat bran, most of the attention has been focused on the relationship of oat-derived glucan to cholesterol levels. These glucans were shown to reduce serum cholesterol in both hypercholesterolemic animals and humans, however there are some studies that found no such effects. In addition, fiber-containing glucans, particularly the ones in human food, gained attention for their role in the metabolic control of diabetes. However, most of these studies were accomplished using only partly purified glucans, making evaluation of the glucan role rather difficult. Despite extensive investigations, no consensus on the source, size and other biochemical or physicochemical properties of beta-1,3-glucan has been achieved. In addition, numerous concentrations and routes of administration have been tested – including oral, intraperitoneal, subcutaneous and intravenous applications. Besides, there are probably more than a hundred of different samples on the U.S. market alone, which leads to a confusion about the quality, biological effects and overall efficiency of glucan. Therefore, we decided to compare the basic biological and immunological activities of a group of glucans. The collection of techniques including phagocytosis and stimulation of IL-2 synthesis effects on cholesterol and blood sugar levels represents a general approach to the biological characteristics of tested glucans thus offering insight as to their biological activities. PHYSIOLOGICAL EFFECTS OF DIFFERENT TYPES OF β-GLUCAN