**6. Conclusions**

282 Lipid Metabolism

calculation for the wet tissue of the liver.

concentration in plasma lowers [63,64].

shown in parallelly conducted research*.* 

cholesterol concentration and LDL fraction in blood [67].

groups of fatty acids was not influenced by the type of used β-glucans. Dried spent brewer's yeast, like β-glucans, also contributed to obtaining lower concentration of cholesterol in

Beta glucans, regardless of origin, serve as dietary fibre in the body of mammals, therefore, their hipocholesterolemic effect might be associated with the mechanism recognised for dietary fibre. The influence of soluble fractions of dietary fibre on the cholesterol concentration in the body is known, by binding bile acids in the intestine and consequently increases the amount of bile acids excreted in the feces. It results in decreasing the pool of bile salt able to take part in the synthesis of cholesterol in liver and disregulation of micellas in intestines, which hampers lipid absorption. Cholesterol is used in the synthesis of bile acids instead of lipoproteid synthesis, therefore, speeding its circulation, and its

Hipocholesterolemic effect of tested β-glucans might be also compared with the activity of known prebiotic (inulin) and oat fibre. Inulin while undergoing fermentation in large intestine influences the proportions of produced SCFA [65], decreasing the amount of produced octan, and increasing the level of propionic and butyric acid. It is especially advantageous, as octan acts as a simulator and propionian as inhibitor of cholesterol synthesis [66]. Research *in vitro* showed that propionic acid hampers cholesterol and fatty acid synthesis in the liver. It seems that the combination of increased excretion of bile acid with faeces and slight lowering of cholesterol synthesis in liver aims to lower total

Supplementation of rat diets with β-glucan preparations from spent brewer's yeast examined in this work and the preparation of dried brewer's yeast contributes to advantegous lowering of cholesterol concentration in blood, at simultaneous achieving a more advantegous in relations to control group content of bowel microflora, connected particularly with increased numer of *Bifidobacterium* bacteria of lactid acid, which was

It is quite difficult to explain the estimated mechanism of lowering cholesterol concentration under the influence of prebiotics. However, increased excretion of cholesterol with faeces through hampering the creation of easily digested fatty micellas has been suggested. In rats, increased excretion of cholesterol in faeces has been confirmed, and similar research presents this mechanism also in people. It is possible that some bacteria of lactid acid can assimilate cholesterol directly. There is proof that fructooligosaccharides (FOS) lower the synthesis of triacylglycerols in liver, however, so far the mechanism has not been identified. Similar significance to probiotics is also attributed to prebiotics. Prebiotics arouse even greater interest due to practical means – they are characterised by greater durability than probiotics, their activity is not conditioned by micorbe viability after intake and they might be added to many food products as one of the ingredients. There is little research available concerning the research on people, therefore, most conclusions have been drawn based on the research on animals. In rats, for example, after a 5-week inulin administration a No significant differences have been observed in hypocholesterolemic effect of soluble βglucan – (CMG) and insoluble native β-glucan (HP). The results showed that after hydration, carboxymethylated β-glucan CMG was characterised by higher viscosity and mean particle size amounting to about 90 µm, whereas particles of insoluble HP β-glucan, established nonviscous solutions of particle size amounting to about 50 µm and about 320 µm. Examined β-glucans showed an effective hypocholesterolemic effect. It has been proven that they influenced lipid metabolism advantageously, especially in case of LDL fraction cholesterol and triacylglycerols (TG). An advantageous HDL/Chol-total factor and HDL/LDL factor has also been confirmed. Dried spent brewer's yeast were given to animals in a daily dosage of 100 mg/kg of body mass were as efficient as β-glucans isolated from them and they lowered the concentration in blood of: total cholesterol of 21.6%, LDL fraction – of 28.2% and triacylglycerols of 27.2% in relation to control group. The research also proves that advantageous influence of yeast on lipid metabolism and their level in blood might be linked with prebiotic properties of yeast on lipid metabolism, as in the research simultaneously conducted by the Author, the advantageous composition of intestine microflora was observed (a higher number of lactid acid bacteria of *Bifidobacterium* type was obtained*).* 

High nucleic acid content in yeast (supplying from 12% to 25% of total nitrogen content) [70] limits their use as a traditional ingredient in human nutrition. It has been stated that the excess of nucleic acid in the diet of people and most monogastric animals is toxic and results in excessive accumulation of uric acid in organism, leading to arthritis. Therefore, it is recommended to consume their little portions as diet supplement supplying mainly vitamins from B group.

Numerous research on fish proved that diet supplementation with yeast to a particular level (in the amount providing no more than 50% of proteins in the diet), does not show disadvantageous health effects, such as abnormal growth, improper nitrogen balance or liver diseases [71]. However, only lower diet intake was observed when spent brewer's yeast constituted more than 25% of the diet [70]

It seems that diet supplementation with dried spent brewer's yeast *S.cerevisiae* in the amount of 0.5% of the diet contributed significantly to correcting possible disorders in lipid metabolism of rats on an atherogenic diet – it enhances lipid changes in organism, enhancing their parameters.

During the research on hypocholesterolemic activity of 81 different yeast strains, showed hypocholesterolemic activity of spent brewer's yeast of male Wistar rats with their

Spent Brewer's Yeast and Beta-Glucans Isolated from Them as Diet Components

peristlsis and lowering HMG (3-hydroxy-3-methylglutaryl) CoA reductase activity, since

The influence of soluble beta glucan fractions (CMG) on cholesterol concentration in the body was associated with the ability to bind bile acids in a small testine. It might have led to a decrease in bile salt pool able to participate in cholesterol synthesis in liver and disregulation of micellas creation in testine, which hampered lipid absorption. Cholesterol was then used to a larger extent in bile acid synthesis rather than lipoproteid synthesis, therefore, its concentration in blood plasma was decreased. CMG and HP β-glucans given in a higher dosage (100 mg/kg of body mass daily), protected the liver more efficiently against excessive fat layering. Dried spent brewer's yeast also contributed to obtaining lower

Present interest of consumers to a large extent concerns food that can be used in prevention of many diet-dependent diseases, whereas the interest of food industry is directed at the search for new ingredients of pro-health influence. The knowledge of functional properties of preparations containg β-glucans might be used to shape proper quality of food products

β-Glucan is a valuable functional ingredient and various extraction techniques are available for its extraction. Choice of an appropriate extraction technique is important as it may affect the quality, structure, rheological properties, molecular weight, and other functional properties of the extracted β-glucan. These properties lead to the use of β-glucan into

Diet supplementation with β-glucans from spent brewer's yeast and preparation of dried spent brewer's yeast contributed to advantageous lowering of cholesterol concentration in blood and lowering lipid concentration in liver. The results described above allow for the

1. β-glucan preparations obtained from spent brewer's yeast and dried spent brewer's yeast show efficient biological activity, connected with the improvement of blood lipid

2. Spent brewer's yeast show a similar pro-health influence to β-glucans isolated from them, therefore, they can be a valuable and much cheaper diet suplement, correcting

3. β-glucan preparations from spent brewer's yeast (CMG and HP) given in higher doses (100 mg/kg of body mass daily), efficiently protect liver against excessive fat layering.

Results obtained in the experiment described above with various yeast preparations are valuable, since they point out that β-glucans obtained from a new source, i.e. spent brewer's yeast have a hypocholesterolemic effect, similarly to other glucans described in literature. Moreover, it has been shown that each of examined β-glucans isolated from spent brewer's

also lowering of cholesterol concentration in liver was obtained.

cholesterol concentration in liver in comparison with control group.

various food systems and have important implications in human health.

**7. Requests** 

for special purposes.

formulation of the following conclusions:

profile and liver of experimental animals.

blood lipid metabolism disturbed by atherogenic diet.

Modifying Blood Lipid Metabolism Disturbed by an Atherogenic Diet 285

**Figure 13.** Probable mechanism of hypocholesterolemic effect of beta-glucans and spent brewer's yeast Saccharomyces cerevisiae.

participation of 10% in the diet [72]. The hypocholesterolemic activities of the yeast varied remarkably between strains. In contrast, brewer's yeast and baker's yeast, which have been predominantly used for food, did not exhibit hypocholesterolemic activity even when administered at concentration of 10%. Whereas, during the research on obese men with hypocholesterolemy it has been shown that the intake of spent brewer's yeast considerably lowers the concentration of total cholesterol, increasing the concentration of advantageous fraction of HDL cholesterol when consumed in the amount supplying 15 g of fiber daily. Triacylglycerol concentration in blood did not change considerably [60]. The yeast-derived bglucan fiber significantly lowered total cholesterol concentrations and was well tolerated; HDL-cholesterol concentrations rose, but only 4 weeks after the fiber was stopped. Described varied hypocholesterolemic activity of various spent brewer's yeast results among others from the kind of yeast and the amount of their supplementation in the diet. Advantageous lowering of cholesterol concentration in the blood of test animals due to diet supplementation with yeast can be caused by prebiotic properties of yeast, which corrects natural content of bacterial flora [61] or considerably high amount of squalens in yeast lipids [62].

A probable mechanism of HP beta glucan and insoluble, dried brewer's yeast influence presented in the diagram (Fig. 13) is associated with their advantageous influence on testine peristlsis and lowering HMG (3-hydroxy-3-methylglutaryl) CoA reductase activity, since also lowering of cholesterol concentration in liver was obtained.

The influence of soluble beta glucan fractions (CMG) on cholesterol concentration in the body was associated with the ability to bind bile acids in a small testine. It might have led to a decrease in bile salt pool able to participate in cholesterol synthesis in liver and disregulation of micellas creation in testine, which hampered lipid absorption. Cholesterol was then used to a larger extent in bile acid synthesis rather than lipoproteid synthesis, therefore, its concentration in blood plasma was decreased. CMG and HP β-glucans given in a higher dosage (100 mg/kg of body mass daily), protected the liver more efficiently against excessive fat layering. Dried spent brewer's yeast also contributed to obtaining lower cholesterol concentration in liver in comparison with control group.

#### **7. Requests**

284 Lipid Metabolism

Saccharomyces cerevisiae.

**Figure 13.** Probable mechanism of hypocholesterolemic effect of beta-glucans and spent brewer's yeast

participation of 10% in the diet [72]. The hypocholesterolemic activities of the yeast varied remarkably between strains. In contrast, brewer's yeast and baker's yeast, which have been predominantly used for food, did not exhibit hypocholesterolemic activity even when administered at concentration of 10%. Whereas, during the research on obese men with hypocholesterolemy it has been shown that the intake of spent brewer's yeast considerably lowers the concentration of total cholesterol, increasing the concentration of advantageous fraction of HDL cholesterol when consumed in the amount supplying 15 g of fiber daily. Triacylglycerol concentration in blood did not change considerably [60]. The yeast-derived bglucan fiber significantly lowered total cholesterol concentrations and was well tolerated; HDL-cholesterol concentrations rose, but only 4 weeks after the fiber was stopped. Described varied hypocholesterolemic activity of various spent brewer's yeast results among others from the kind of yeast and the amount of their supplementation in the diet. Advantageous lowering of cholesterol concentration in the blood of test animals due to diet supplementation with yeast can be caused by prebiotic properties of yeast, which corrects natural content of

bacterial flora [61] or considerably high amount of squalens in yeast lipids [62].

A probable mechanism of HP beta glucan and insoluble, dried brewer's yeast influence presented in the diagram (Fig. 13) is associated with their advantageous influence on testine Present interest of consumers to a large extent concerns food that can be used in prevention of many diet-dependent diseases, whereas the interest of food industry is directed at the search for new ingredients of pro-health influence. The knowledge of functional properties of preparations containg β-glucans might be used to shape proper quality of food products for special purposes.

β-Glucan is a valuable functional ingredient and various extraction techniques are available for its extraction. Choice of an appropriate extraction technique is important as it may affect the quality, structure, rheological properties, molecular weight, and other functional properties of the extracted β-glucan. These properties lead to the use of β-glucan into various food systems and have important implications in human health.

Diet supplementation with β-glucans from spent brewer's yeast and preparation of dried spent brewer's yeast contributed to advantageous lowering of cholesterol concentration in blood and lowering lipid concentration in liver. The results described above allow for the formulation of the following conclusions:


Results obtained in the experiment described above with various yeast preparations are valuable, since they point out that β-glucans obtained from a new source, i.e. spent brewer's yeast have a hypocholesterolemic effect, similarly to other glucans described in literature. Moreover, it has been shown that each of examined β-glucans isolated from spent brewer's yeast was as efficient. Final effect correcting lipid metabolism, particularly various fractions of lipids, was more connected with the dose, rather than physic-chemical properties.

Spent Brewer's Yeast and Beta-Glucans Isolated from Them as Diet Components

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[14] Zhang P., hang L., Cheng S. Solution properties of an alpha-(1→3)-D-glucan from *Lentinus edodes* and its sulfated derivatives. Carbohyd. Res. 2002;337(2) 155-60. [15] Colleoni-Sirghie M., Kovalenko I.V., Briggs J.L., Fulton B., White P.J. Rheological and molecular properties of water soluble (1,3)/(1,4)-β-D-glucans from high-β-glucan and

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Modifying Blood Lipid Metabolism Disturbed by an Atherogenic Diet 287

Health advantages contributing to significant cholesterol reduction in blood obtained in experiments on animals, might constitute the basis for assuming that similar influence will be observed in case of a human body. Therefore, it would be recommended to supplement human diet with β-glucans, particularly for people whose diet is abundant in fat and cholesterol. Spent brewer's yeast constituting a serious problem for brewing plants (waste material), can be used successfully as a valuable source of beta glucans, which can be used as diet supplements or as food additives, e.g. in yoghurts, breakfast desserts or snacks.

Currently conducted research is the continuation of a presented experiment. It shows that atherogenic diet supplementation with beta-glucans or spent brewer's yeast contributed to simultaneous obtaining more advantageous content of testine microflara in relation to control group, connected with the increased number of lactid acid bacteria *Bifidobacterium*  and *Lactobacillus* and limited growth frequency of disadvantageous yeast fungi *Candida albicans*. Conducted research on functional properties and biological experiment proves the complexity of β-glucan and other fibre preparation influence on experimental animals.
