Abstract
Oral supplemented nutraceuticals derived from food sources are surmised to improve the human health through interaction with the gastrointestinal bacteria. However, the lack of fundamental quality control and authoritative consensus (e.g., formulation, route of administration, dose, and dosage regimen) of these non-medical yet bioactive compounds are one of the main practical issues resulting in inconsistent individual responsiveness and confounded clinical outcomes of consuming nutraceuticals. Herein, we studied the dose effects of widely used food supplement, microalgae spirulina (Arthrospira platensis), on the colonic microbiota and physiological responses in healthy male Balb/c mice. Based on the analysis of 16s rDNA sequencing, compared to the saline-treated group, oral administration of spirulina once daily for 24 consecutive days altered the diversity, structure, and composition of colonic microbial community at the genus level. More importantly, the abundance of microbial taxa was markedly differentiated at the low (1.5 g/kg) and high (3.0 g/kg) dose of spirulina, among which the relative abundance of Clostridium XIVa, Desulfovibrio, Eubacterium, Barnesiella, Bacteroides, and Flavonifractor were modulated at various degrees. Evaluation of serum biomarkers in mice at the end of spirulina intervention showed reduced the oxidative stress and the blood lipid levels and increased the level of appetite controlling hormone leptin in a dose-response manner, which exhibited the significant correlation with differentially abundant microbiota taxa in the cecum. These findings provide direct evidences of dose-related modulation of gut microbiota and physiological states by spirulina, engendering its future mechanistic investigation of spirulina as potential sources of prebiotics for beneficial health effects via the interaction with gut microbiota.
Highlights
The gut microbiota is a complex and functional ecological community and plays an important role in influencing the physiological states, disease susceptibilities, and even therapeutic efficacies (Flint et al, 2012; Lozupone et al, 2012; Geller et al, 2017)
To assess the diversity and structural differences in the colonic microbiota of healthy mice treated with saline or spirulina at the low and high doses over 25 days of daily intervention, differential significance in α-and β-diversity of collected fecal and cecal samples were analyzed by the Wilcoxon signed-rank test and weighted UniFrac distance matrix based multiresponse permutation procedure (MRPP), respectively (Figures 2, 3)
No significant difference in Chao1 and observed species indexes were observed between samples from the treatments of saline, low, and high spirulina at all designated time points (Figures 2A,B), indicating the microbial richness within each treatment were not changed
Summary
The gut microbiota is a complex and functional ecological community and plays an important role in influencing the physiological states, disease susceptibilities, and even therapeutic efficacies (Flint et al, 2012; Lozupone et al, 2012; Geller et al, 2017). To sustain or restore the intestinal bacterial homeostasis in healthy individuals or disease states, several approaches have been implemented, including the oral supplementation of probiotics, prebiotics and synbiotics (Verdu, 2009; Quigley, 2018), fecal microbiota transplantation (Zipursky et al, 2012; Li et al, 2016; Bilinski et al, 2017), bacterial consortium transplantation (Li et al, 2015) as well as bacteriocins and bacteriophage targeted antimicrobial therapies (Mills et al, 2017). There is a large knowledge gap of cause-and-effect relationships between marketed nutraceutical products, the change of microbial population and the physiological benefits
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