A potential pathway that links intron retention with the physiological recovery by a Japanese herbal medicine

Our previous experiments with klotho mice (i.e., klotho knockout mice) showed that aberrant intron retention (IR) occurs in a pre-symptomatic state of aging and can be restored to the normal state by administration of Juzentaihoto (JTT), a formula of the Japanese herbal medicine (referred to as kampo; Okada et al., 2021). To explain that this phenomenon is not just a specific example observed in klotho mice, but is due to a universal cause that may be common in a pre-symptomatic state, we re-analyzed the data for genes that were differentially expressed in the klotho liver in response to JTT. Our data showed that AMPK signaling was activated in these mice, resulting in inhibition of anabolic pathways including protein synthesis and activation of catabolic pathways including lipolysis in various organs. These data were consistent with the observation that klotho mice appeared to be in a perpetual state of pseudo-starvation, i.e., based on their overall metabolic profile. The abnormally increased incidence of IR (IncIR) in the liver of klotho mice could be classified into three types according to their transcriptional status, revealing that each of all the three types of IncIR was caused by AMPK activation, a consequence of the pseudo-starvation state exhibited by these mice. Furthermore, we showed that both the transcriptional drift variance and the IR drift variance can be useful for visually assessing recovery from the pseudo-starvation state of klotho mice after administration of JTT. With these data, we propose a novel pathway linking intron retention to changes in the physiological state such as starvation, resulting in the maintenance of cellular homeostasis.