Effect of medicinal mushrooms on blood cells under conditions of diabetes mellitus

Modern clinical practice in Taiwan, Japan, China, South Korea, and other Asian countries rely on mushroom-derived preparations. These preparations have many active compounds, which identify their importance as food and as medicines. This includes mainly high-molecular weight compounds such as polysaccharides (e.g., β-D-glucans, glucuronoxylomannan), proteins, polysaccharide-protein complexes, lipopolysaccharides, glucoproteins, and lectins. Low-molecular weight metabolites include lactones, terpenoids, alkaloids, sterols, phenolic substances, and antibiotics with different active groups, metal chelating agents, etc. Also, medicinal mushrooms have enzymes - laccase, superoxide dismutase, glucose oxidase, peroxidase. As dietary supplement products, mushrooms contain a small amount of lipids and cholesterol, and low levels of carbohydrates. At the same time, they are rich in fiber, protein, minerals, and vitamins. The wide range of bioactive compounds determines antitumor, immunomodulating, antioxidant, radical scavenging, cardiovascular, antihypercholesterolemic, antiviral, antibacterial, antiparasitic, hepatoprotective, and antidiabetic properties of medicinal mushrooms.

Diabetes mellitus (DM) is the third most common non-infectious disease leading to early disability and high mortality. Moreover, the number of patients is growing every year. The main symptom of DM is hyperglycemia. Increased levels of blood glucose activate polyol, hexosamine, and protein kinase metabolic pathways cause the intensification of non-enzymatic glycosylation and nitration of macromolecules. This, in turn, leads to the development of oxidative and nitrative stresses and secondary complications, such as different kinds of micro- and macroangiopathies. Metabolic disorders caused by insulin deficiency in diabetes significantly impede the functioning of a homeostasis system, which change the physical, biochemical, morphological, and functional properties of blood cells. As a result, the oxygen-transport function of red blood cells (RBCs), rheological properties of the blood, and functions of immunocompetent cells as well as the process of apoptosis are primarily affected. Modern pharmacotherapy focuses on the search for new preparations that aim to decrease blood glucose levels. Undesirable side effects and adverse reactions caused by synthetic medicines led to the search and investigation of new preparations of natural origin.

Antidiabetic properties of Agaricus brasiliensis and Ganoderma lucidum

Research has shown that some mushrooms may have the potential to lower elevated blood sugar levels. But the explanation for this effect is limited, except for some mushrooms. Therefore, it would be necessary to carry out more research on mushrooms with a focus to identify the active compounds in specific mushrooms for the treatment of DM and its complications.

Agaricus brasiliensis (A. brasiliensis, Royal Sun Agaricus) is native to Brazil and widely grown in Japan. This mushroom is used in the treatment of atherosclerosis, hepatitis, hyperlipidemia, dermatitis, and cancer, and its polysaccharides, α-glucan and β-glucan, have been shown to have immunomodulating and antimutagenic effects both in vivo and in vitro. The possible mechanisms of natural polysaccharides to DM might base on six directions: (1) the elevation of plasma insulin, and the decline of pancreatic glucagon; (2) the increase of insulin sensitivity, and the improvement of insulin resistance; (3) the restraint of α-glycosidase enzymes in bowel, and the reduction of carbohydrates decomposition and absorption; (4) the increase of hepatic glycogen, and the inhibition of sugar dysplasia; (5) the increased glucose use of peripheral tissue; (6) the scavenging free radicals and lipid peroxidation. Also, hypoglycemic and antidiabetic properties of A. brasiliensis have been reported. But, nevertheless, additional pharmacological studies are needed to elucidate the mechanism of A. brasiliensis action as well as to assess the use of these species for the treatment of human DM.

Ganoderma lucidum (G. lucidum, Ling zhi, Reishi), has a leading place in present-day medicinal mushroom development. G. lucidum has been utilized for centuries in East Asia to prevent or treat various diseases and was used in traditional Chinese medicine as a tonic in promoting good health, perpetual youth, vitality, and longevity. It is widely grown on a commercial scale and is commonly purchased for its medicinal and spiritual properties. Worldwide, more than 250 Ganoderma species have been described. Recent studies on G. lucidum have shown many interesting biological activities including antitumor, antiinflammatory, antioxidant, and antidiabetic effects.

Antihyperglycemic effects of G. lucidum have been extensively studied and have shown potential therapeutic activities. It has been shown that oral administration of water extracts of G. lucidum significantly reduced the increase in blood glucose and insulin levels in rats following the oral glucose tolerant test. Prevention of the progression of diabetic renal complications as well as a lowering of the increased serum glucose and triglyceride levels was reported in STZ-induced diabetic rats. Another study demonstrated that polysaccharides isolated from G. lucidum significantly increased nonenzymatic and enzymatic antioxidants and serum insulin levels, and reduced lipid peroxidation and blood glucose levels in STZ-diabetic rats. In alloxan-induced diabetic rats, the aqueous extract of G. lucidum normalized blood glucose levels.

It was shown that G. lucidum consumption can provide beneficial effects in treating T2D by lowering the serum glucose levels through the suppression of the hepatic enzyme gene expression involved in gluconeogenesis in a clinical study showed that Ganopoly (polysaccharide fractions extracted from G. lucidum by a patented technique) efficaciously lowered blood glucose concentration in patients with confirmed T2D. It was shown that G. lucidum polysaccharides attenuated myocardial collagen cross-linking in diabetic rats, which was related to the decreased level of AGEs and augmented activities of antioxidant enzymes. Also, it was shown that ganoderol B (bioactive sterol from G. lucidum fruit body) has a strong inhibitory activity on α-glucosidase and can be proposed as a treatment for T2D. Orally administered proteoglycan extract, Fudan-Yueyang-G. lucidum, to STZ-induced diabetic rats showed a significant decrease in plasma glucose levels. It appears that there are a number of biologically active compounds to be explored in the mycelium, and future research should focus in that direction.

Thus, the use of medicinal mushrooms for treatment of DM and in prevention development of its secondary complications might be a new effective approach of this disease’s cure.

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