In May 2019, the International Scientific Association for Probiotics and Prebiotics (ISAPP) convened a panel of nutritionists, physiologists and microbiologists to review the definition and scope of synbiotics. The panel updated the definition of a synbiotic to “a mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host”. The panel concluded that defining synbiotics as simply a mixture of probiotics and prebiotics could suppress the innovation of synbiotics that are designed to function cooperatively. Requiring that each component must meet the evidence and dose requirements for probiotics and prebiotics individually could also present an obstacle. Rather, the panel clarified that a complementary synbiotic, which has not been designed so that its component parts function cooperatively, must be composed of a probiotic plus a prebiotic, whereas a synergistic synbiotic does not need to be so. A synergistic synbiotic is a synbiotic for which the substrate is designed to be selectively utilized by the co-administered microorganisms. This Consensus Statement further explores the levels of evidence (existing and required), safety, effects upon targets and implications for stakeholders of the synbiotic concept.

Background: The gut microbiota is essential to human health throughout life, yet the acquisition and development of this microbial community during infancy remains poorly understood. Meanwhile, there is increasing concern over rising rates of cesarean delivery and insufficient exclusive breastfeeding of infants in developed countries. In this article, we characterize the gut microbiota of healthy Canadian infants and describe the influence of cesarean delivery and formula feeding. Methods: We included a subset of 24 term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Mode of delivery was obtained from medical records, and mothers were asked to report on infant diet and medication use. Fecal samples were collected at 4 months of age, and we characterized the microbiota composition using high-throughput DNA sequencing. Results: We observed high variability in the profiles of fecal microbiota among the infants. The profiles were generally dominated by Actinobacteria (mainly the genus Bifidobacterium) and Firmicutes (with diverse representation from numerous genera). Compared with breastfed infants, formula-fed infants had increased richness of species, with overrepresentation of Clostridium difficile. Escherichia–Shigella and Bacteroides species were underrepresented in infants born by cesarean delivery. Infants born by elective cesarean delivery had particularly low bacterial richness and diversity. Interpretation: These findings advance our understanding of the gut microbiota in healthy infants. They also provide new evidence for the effects of delivery mode and infant diet as determinants of this essential microbial community in early life.

Autophagy is involved in human diseases and is regulated by reactive oxygen species (ROS) including superoxide (O₂^•−) and hydrogen peroxide (H₂O₂). However, the relative functions of O₂^•− and H₂O₂ in regulating autophagy are unknown. In this study, autophagy was induced by starvation, mitochondrial electron transport inhibitors, and exogenous H₂O₂. We found that O₂^•− was selectively induced by starvation of glucose, L-glutamine, pyruvate, and serum (GP) whereas starvation of amino acids and serum (AA) induced O₂^•− and H₂O₂. Both types of starvation induced autophagy and autophagy was inhibited by overexpression of SOD2 (manganese superoxide dismutase, Mn-SOD), which reduced O₂^•− levels but increased H₂O₂ levels. Starvation-induced autophagy was also inhibited by the addition of catalase, which reduced both O₂^•− and H₂O₂ levels. Starvation of GP or AA also induced cell death that was increased following treatment with autophagy inhibitors 3-methyladenine, and wortamannin. Mitochondrial electron transport chain (mETC) inhibitors in combination with the SOD inhibitor 2-methoxyestradiol (2-ME) increased O₂^•− levels, lowered H₂O₂ levels, and increased autophagy. In contrast to starvation, cell death induced by mETC inhibitors was increased by 2-ME. Finally, adding exogenous H₂O₂ induced autophagy and increased intracellular O₂^•− but failed to increase intracellular H₂O₂. Taken together, these findings indicate that O₂^•− is the major ROS-regulating autophagy.

Reactive oxygen species (ROS) have been identified as signaling molecules in various pathways regulating both cell survival and cell death. Autophagy, a self-digestion process that degrades intracellular structures in response to stress, such as nutrient starvation, is also involved in both cell survival and cell death. Alterations in both ROS and autophagy regulation contribute to cancer initiation and progression, and both are targets for developing therapies to induce cell death selectively in cancer cells. Many stimuli that induce ROS generation also induce autophagy, including nutrient starvation, mitochondrial toxins, hypoxia, and oxidative stress. Some of these stimuli are under clinical investigation as cancer treatments, such as 2-methoxyestrodial and arsenic trioxide. Recently, it was demonstrated that ROS can induce autophagy through several distinct mechanisms involving Atg4, catalase, and the mitochondrial electron transport chain (mETC). This leads to both cell-survival and cell-death responses and could be selective toward cancer cells. In this review, we give an overview of the roles ROS and autophagy play in cell survival and cell death, and their importance to cancer. Furthermore, we describe how autophagy is mediated by ROS and the implications of this regulation to cancer treatments. Antioxid. Redox Signal. 11, 777–790.