Microbes and healthful longevity

popularity of hand sanitizer and antibiotics shows how we feel about bacteria: an enemy that's bad for our health. Emerging data, however, suggest just the opposite-that exposures to certain kinds of bacteria are beneficial for a long and healthy life, at least in part by inhibiting a wasting syndrome termed cachexia [1]. Cachexia, a condition defined as muscle wasting associated with chronic disease, arises during cancer and chronic obstructive pulmonary disease (COPD) with debilitating consequences resulting in premature death and creating a major public health burden. A growing body of research involving the host immune system reveals great potential for commensal bacteria to treat diseases and improve quality of life in animal hosts [2]. It's an intriguing possibility that microbes may be harnessed for a long, healthy, and meaningful life. Varian et al. (2016) tested this concept involving cancer-associated cachexia using a probiotic microbe Lactobacillus reuteri [1] isolated from human breast milk and previously shown to prevent diarrhea in humans [3]. The authors used a targeted infection in mouse models for proof-of-concept and mechanistic insight, rather than to focus on one type of bacteria per se. Specifically, mice consuming probiotic L. reuteri were shown to have larger skeletal muscles than untreated age-matched controls (Figure 1). A surprising additional finding was increased thymus gland size only in mice consuming bacteria in their drinking water. The thymus was not only larger, but also had increased expression of Forkhead Box N1 [FoxN1], a feature involved in systemic programming of immune system lymphocytes. FoxN1 is most widely recognized as the factor missing in athymic nude mice [4]. Nude mice lack a functional thymus gland creating an immune deficit, with fewer cancer-fighting immune cells thus making them exquisitely susceptible to neoplasia. Thus, their thymic deficiency has been widely exploited in biomedical research to study cancer progression. It follows logically that mice with a larger thymus and with higher levels of FoxN1 would have increased resistance against tumors, as seen in Varian et al. 2016 [1]. Although cachexia was reduced, perhaps the most Editorial powerful finding in this study was that edible microbes globally increased FoxN1 expression even in mice without cancer, leading to a more balanced immune system during normal aging. Bacterial stimulation of FoxN1 and increased thymus gland size has enormous implications for host good health beyond cancer and associated cachexia. Indeed, FoxN1 protein has been touted as a " Fountain of Youth " …