Edible mushrooms are a valuable source of nutrients and bioactive compounds in addition to a growing appeal for humans by their flavors and culinary features. Recently, they have become increasingly attractive as functional foods for their potential beneficial effects on human health. Hence, food industry is especially interested in cultivated and wild edible mushrooms. Cardiovascular diseases are one of the most prevalent causes of morbidity and mortality in the Western world. Several investigations have shown the influence of mushrooms intake on some metabolic markers (total, LDL, HDL cholesterol, fasting triacylglycerol, homocysteine, blood pressure, homeostatic function and oxidative and inflammatory damage), which potentially may reduce the risk of suffering cardiovascular diseases. Relevant nutritional aspects of mushrooms include a high fiber supply, a low fat content with low trans isomers of unsaturated fatty acids and a low concentration of sodium as well as the occurrence of components such as eritadenine, phenolic compounds, sterols (such as ergosterol), chitosan, triterpenes, etc., which are considered as important responsible agents for some hitherto healthy properties. The aims of this review are to report putative positive effects of mushrooms consumption on cardiovascular diseases risk markers and to identify some putative bioactive compounds involved in these effects.
Cardiovascular diseases are among the most common causes of death in the Western world and transition countries. The aetiological risk markers that have been shown to be specially modified by the diet are related to lipid and lipoprotein metabolism, haemostatic function, oxidative dam- age, homocysteine metabolism and blood pressure changes . LDL and HDL cholesterol, triacylglycerol, homocysteine and blood pressure are well-validated and generally accepted biomarkers, being the rest of them just recommended. However, currently only LDL and blood pressure are considered diet-related biomarkers. Traditionally, edible mushrooms have been prescribed in Oriental medicine due to their hypocholesterolemic effects . In general, the intake of edible mushroom reduces the cardiovascular risk, due to the occurrence of specific substance and other bioactive compounds.
The mechanisms related to cholesterol metabolism involved in the hypocholesterolemic effect of edible mushrooms are depicted in. The fatty acid pattern of edible mushrooms seems to contribute to reduce serum cholesterol .When the fatty acid profile of some edible mushrooms was analyzed, considerable amounts of polyunsaturated fatty acid were found. The presence of trans isomers of unsaturated fatty acids is associatedwith the strongest effects on raising the serum total cholesterol to high-density lipoprotein ratio, increasing cardiovascular diseases risk. The transisomers of unsaturated fatty acids have not been detected in mushrooms. The dietary fiber intake may affect plasma lipid concentrations and lower the cardiovascular diseases risks. The soluble dietary fiber has shown healthy effects on serum lipid levels, reducing total cholesterol and LDL-cholesterol amounts . The formation of viscous gels from soluble dietary fiber such as glucans might contribute to inhibit the cholesterol and triglycerol absorption . Their viscous properties are related to an increase on the fecal excretion of bile acids and short chain fatty acids (propionate), which inhibits acetate incorporation (substrate for sterols and fatty acid synthesis) to serum lipids. The results of some reports suggest that the hypocholesterolemic effects of some fruiting bodies of edible mushroom could be mainly attributed to the dietary fiber supply. Two mushrooms with a high dietary fiber content such as Auricularia auricula and Tremella fuciformis have proved to produce similar lowering in LDL cholesterol levels, and therefore in the serum total cholesterol. Neither of them affect serumHDL cholesterol, however the A. bisporus fiber can elevate the hepatic LDL receptor messenger RNA in male rats, reducing the HDL cholesterol concentration and serum total cholesterol by lowering VDL+ILD+LDL cholesterol concen- trations . In addition to the reduction in serum cholesterol, T. fuciformis also lowered plasma triacylglycerol levels and hepatic total cholesterol. This finding might be the result of an inhibition of the synthesis of hepatic triglycerides by increasing the short chain fatty acids production (acetate, propionate and butyrate) during the dietary fiber fermentation by colonic microflora . Mushrooms are also of interest because they contain large amounts of β-glucans polysaccharides, which exhibit hypocholesterolemic and anticoagulant functions . Other interesting fungal polysaccharide with similar characteristics to dietary fiber is chitosan (D-366 glucosamine polymer) or chitin (N acetyl-D-glucosamine polymer). The high fat diet-induced obese mice supplied with a chitosan supplement (5%) from A. bisporus during ten weeks, showed lower lipid absorption and serum adipocytokine levels . Consequently, those actions could contribute to reduce fat deposition in the liver (a decrease of triglyceride content by 39%) and muscle (a decrease of triglyceride content by 66%) besides to a lowering in fat mass. Nowadays, fungal chitosan (KiOnutrime_CsTM) is being commercialized as a dietary supplement for obesity and cholesterol management (http://ec.europa.eu./food/food/biotechnology/novelfood/ notif_list_en.pdf). Investigations in the last decade have revealed that fruiting bodies of P. ostreatus exhibit a hypocholesterolemic effect on rats with normocholesterolemia and hypercholesterolemia induced by intake of a high fat diet or alcohol intake and diabetes or hereditary cholesterol disorder . A pronounced cholesterol-lowering effect of oyster mushroom consumption (P. ostreatus) has been demonstrated on rats through a decrease in very-low-density lipoproteins and also by suppressing the activity ofHMG-CoA reductase and an enhanced fractional catabolic rate of cholesterol . Recently, it has been evidenced by Kantun et al. that P. ostreatus reduced total cholesterol, triglycerides plasma, glucose and blood pressure in diabetic subjects. The results of this trial suggest that eatingmushrooms (P. ostreatus) provides health benefits by acting on the atherogenic lipid profile under hypercholesterolemic and normocholesterolemic conditions. On the contrary, with a normocholesterolemic diet, this effect was not observed by Hossein et al.. A clinical report was carried out in a group of 57 individuals with combined dyslipidaemia, who included P. ostreatus powdered (10g/day) aspart of their dietduring 6weeks .Adecrease in total cholesterol and triglyceride levelswas observed,while the HDL-cholesterol concentration in serum remained stable . Most animal studies concerning Pleurotus spp. were especially focused on oyster mushroom, P. ostreatus, and it is clear that
enhanced effectively the effect on rate cholesterol. However, there are other flavorful edible mushrooms belonging to this species such as Pleurotus florida and Pleurotus citrinopileatus with the same beneficial effect . Feeding on dried fruiting bodies of P. florida to hypercholesterolemic rabbits resulted in a total lipids decrease, lower cholesterol and triglyceride levels of plasma and liver, whereas heart lipids were unaffected. Furthermore, HDL cholesterol/total cholesterol and HDL cholesterol/LDL cholesterol ratios increased in experimental animals providing an antiatherogenic potential. This effect was further supported by the severity of tissue damage as evidenced by histopathological studies on aorta and heart tissues. An increase in bile acid excretion in experimental animals could be taken as one of the possible mechanisms explaining in hypocholesterolemic actions of P. florida . In P. citrinopileatus, the antihyperlipidemic effect of the powdered dry fruiting bodies, ergosterol-rich and nicotinic acid-rich extracts were tested in hyperlipidemic rats by Hu et al. being serum cholesterol and triglyceride outcomes similar to
previously studies. Eritadenine or lentinacin (or lentysine) ( is an adenosine analogue alkaloid or purine alkaloid [(2R,3R)-2,3-dihydroxy-4-(9-adenyl)-butyric acid], which evidences hypo- cholesterolemic effects in L. edodes and to a lesser extent in A.bisporus . The compound lentinacin has been shown to reduce cholesterol levels in rats by 25% after 7 days of oral administration in a dose as low as 0.005% of feed intake. The main cause of the hypocholesterolemic action of eritadenine seems to be associated to a modification of the hepatic phospholipid metabolism by inducing a phosphaty-lethanolamine N-methyltransferase deficiency . Also, dietary eritadenine can alter the fatty acid andmolecular profile of liver and plasma, suppressing the metabolic conversion of linoleic acid into arachidonic acid by decreasing the Δ6-
desaturase activity , which can be affected through transcriptional regulation . Recently, Fukada et al. have demonstrated that eritadenine supplementation also counteract the hyperhomocysteinemic effect of guanidinoace-tic-acid. On the other hand, the microsomal enzyme 3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMG-CoA reductase) is the major rate-limiting enzyme in cholesterol biosynthesis, which converts HMG-CoA to mevalonate. Therefore, inhibition of HMG-CoA reductase decreases intracellular cholesterol biosynthesis. Mevinolin and also, it is a known pharmacological HMG-CoA reductase inhibitor. A high quantity of this inhibitor has been found in P. ostreatus fruiting bodies, especially in the pileus. Further- more, it has been found in sporocarps of P. cornucopiae and P. eryngii.
There is no question thatmushrooms can be considered as a functional food. Fungi contain a representative nutritional composition as well as numerous bioactive compounds, which may promote human well-being as well as the prevention and treatment of several illness. According to current dietary recommendations for preventing and treating for cardiovascular diseases, edible mushroom presents an appropriate nutritional value and its consumption can affect some known cardiovascular risk biomarkers. Mushroom intake clearly has a cholesterol-lowering effect or hypocholesterolemic effect by different mechanisms such as decreasing very-low-density lipoproteins, improving lipid metabolism, inhibiting of activity of HMG-CoA reductase, and consequently preventing the development of atherosclerosis. The antioxidant and antiinflammatory compounds occurring on mushrooms also may contribute to reduce the atherosclerosis risk. Nevertheless, renewed scientific efforts are needed in order to elucidate the mechanisms and to identify and characterize the responsible and novel bioactive compounds from edible mushrooms, in addition to long term clinical studies.