[The influence of yeast β-glucans on the assimilation of vitamins and mineral elements in rats].

Abstract

Despite the use of yeast β-glucans in food and dietary supplements, there is insufficient data on their effect on the metabolism of vitamins and mineral elements. The aim of the study was to evaluate the effect of β-glucans from Saccharomyces cerevisiae in the diet of growing rats on the absorption of micronutrients in animals deficient in vitamins D, group B and trace elements (iron, copper, zinc). Material and methods. Micronutrient deficiency in male Wistar rats (initial body weight 61.6±0.8 g) was induced for 24 days by decreasing the content of vitamin D and all B vitamins in the vitamin mixture of the semi-synthetic diet by 5 times and the content of iron, copper and zinc in the mineral mixture by 2 times. After confirming the development of micronutrient deficiency in the animals, the missing vitamins and trace elements were added to the deficient diet for 5 days either along with β-glucan diet enrichment (1.5%) (+Vit+Met+βG) or without it addition (+Vit+Met). Vitamins B1 and B2 in the liver, riboflavin in the blood serum, thiamine, riboflavin and 4-pyridoxic acid (4-PA) in the urine collected for 18 hours were determined fluorimetrically; retinol, retinol palmitate, α-tocopherol in blood serum and liver - by high-performance liquid chromatography; minerals and trace elements in liver, serum and urine - by atomic absorption spectrometry or by standard methods on a biochemical analyzer. Results. A deficient diet for 24 days resulted in a decrease of B-vitamin status markers: riboflavin decreased in urine by 17.8- fold, in serum by 27.3% and in liver by 7.8%, vitamin B1 in liver by 3-fold, 4-PA in urine reduced by 2.8-fold (p<0.05). Urinary excretion of copper diminished by 25.7%, while the liver content of vitamin A increased by 44% and manganese by 19.2% (p<0.05). Replenishment of missing micronutrients in the diet, regardless of β-glucans presence, completely eliminated the deficiency of vitamin B2, while in the presence of the polysaccharide, rats of the +Vit+Met+βG group showed a statistically significant increase in vitamin B2 liver content by 7.5% (p<0.05) relative to the control, with an increased excretion of riboflavin by 19.1% (p<0.10) compared to excretion in +Vit+Met rats. Vitamin B1 liver level in animals of +Vit+Met and +Vit+Met+βG groups didn't completely restore to the control level but it was higher by 14.5% (p<0.05) in the presence of β-glucans. Urinary excretion of thiamine and 4-PA in rats fed β-glucan enriched diet reached the level of the control rats, while in rats from +Vit+Met group it amounted to 60.8-69.2% of the control. The diet with β-glucans caused a decrease in vitamin E liver content by 36.2% (p<0.05) compared to the level in +Vit+Met animals. Urinary excretion of iron and copper in the absence of β-glucans did not fully recover (amounting to 60.9-74.0% of the control), while in their presence it no longer differed from the value in animals of the control group. Zinc excretion in animals of the +Vit+Met+βG group, on the contrary, was lower than in the control by 29.2% (p<0.01). A decrease in serum magnesium (by 9.0%, p<0.05) with simultaneous increase (by 12.7%, p<0.10) in its urinary excretion under β-glucans' diet inclusion indicate a decrease in its retention and a deterioration in magnesium supply. Conclusion. The presence of yeast β-glucans in the diet improved the absorption of B vitamins, promoted the absorption of iron and copper, but worsened the supply with vitamin E and magnesium, and reduced zinc assimilation.