Abstract
The aim of this study is to evaluate the changes in soy isoflavones and peptides in soy milk after lactic acid bacterial fermentation, and explore the positive effects of fermented soy milk on an oxidative aging mouse model induced with D-galactose. We found that free soybean isoflavones and peptides increased after soy milk was fermented by Lactobacillus fermentum CQPC04. The in vivo results indicated that L. fermentum CQPC04-fermented soy milk enhanced the organ index of the liver and spleen, and improved the pathological morphology of the liver, spleen, and skin. L. fermentum CQPC04-fermented soy milk increased the enzymatic activity of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD), and catalase (CAT), increased glutathione (GSH), but decreased the levels of nitric oxide (NO) and malondialdehyde (MDA) in serum, liver, and brain tissues of oxidative aging mice. The above mentioned fermented soy milk also increased the levels of collagen I (Col I), hyaluronic acid (HA), and collagen III (Col III), and decreased the levels of advanced glycation End products (AGEs) and hydrogen peroxide (H2O2). The RT-qPCR results showed that L. fermentum CQPC04-fermented soy milk upregulated the mRNA expression of nuclear factor erythroid 2?related factor (Nrf2), heme oxygenase-1 (HMOX1), quinone oxido-reductase 1 (Nqo1), neuronal nitric oxide synthase (NOS1), endothelial nitric oxide synthase (NOS3), Cu/Zn–superoxide dismutase (Cu/Zn-SOD), Mn–superoxide dismutase (Mn-SOD), and CAT, but downregulated the expression of inducible nitric oxide synthase (NOS2) and glutamate cysteine ligase modifier subunit (Gclm) in liver and spleen tissues. Lastly, the fermented soy milk also increased the gene expression of Cu/Zn-SOD, Mn-SOD, CAT, GSH-Px, matrix metalloproteinases 1 (TIMP1), and matrix metalloproteinases 2 (TIMP2), and decreased the expression of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) in skin tissue. In conclusion, L. fermentum CQPC04-fermented soy milk was able to satisfactorily delay oxidative aging effects, and its mechanism may be related to the increase in free soy isoflavones and peptides.
Highlights
The United Nations (UN) predicted that there would be an average annual increase rate of 2.5% in the elderly population from 1990 to 2020, and over the same period, the proportion of the world’s aging population has risen from 6.6% in 1995 to 9.3% in 2020 [1]
In order to further evaluate the effect of L. fermentum CQPC04fermented soy milk on D-galactose-induced aging mice, we measured the amounts of advanced glycation End products (AGEs), hyaluronic acid, collagen I (Col I), hydrogen peroxide, and collagen III (Col III) in skin tissues (Figure 5)
We found that the levels of Col I, hyaluronic acid, and Col III were the highest, and AGEs and hydrogen peroxide were the lowest in the normal group, but these indicators were absolutely in reverse in the
Summary
The United Nations (UN) predicted that there would be an average annual increase rate of 2.5% in the elderly population from 1990 to 2020, and over the same period, the proportion of the world’s aging population has risen from 6.6% in 1995 to 9.3% in 2020 [1]. The increasing aging population will strain the economy and health care, and decrease the amount of available people in the labor pool [3]. Research on how to delay aging or how to maintain health while aging is of great significance because it can improve the quality of life of the elderly, and reduce the burden on countries and families. When soy milk is fermented by lactic acid bacteria or yeast, there is an increase in nutrients with greater bioavailability for the human body [4]. The flavonoids are transformed into the aglycone form that is more absorbed by the human body, and the protein is broken down into amino acids and bioactive peptides, which thereby improve the nutritional value of soy milk [6]
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