Recombinant Buckwheat Trypsin Inhibitor Improves the Protein and Mitochondria Homeostasis in <b><i>Caenorhabditis elegans</i></b> Model of Aging and Age-Related Disease

<b><i>Background:</i></b> With the acceleration of aging process in human society, improvements of the physical functionality and life quality in the elderly population are more meaningful than pure longevity. Buckwheat trypsin inhibitor is a low molecular weight polypeptide extracted from buckwheat, which is a beneficial food for improving the health in the elderly. <b><i>Objectives:</i></b> The aim of the current study was to evaluate the potential beneficial effects of recombinant buckwheat trypsin inhibitor (rBTI) on age-dependent function decline and the primary mechanism. <b><i>Method:</i></b> Day 10 N2 <i>Caenorhabditis elegans</i> and day 6 AM140 <i>C. elegan</i>s cultured at 25°C were used as models of aging and age-related disease, respectively. Motor function was as an indicator of age-dependent function. ATP content and damage mitochondrial DNA mass were detected to assess mitochondrial damage and function by ATP Assay Kit and agarose gel electrophoresis, respectively. Soluble protein content was quantified by SDS polyacrylamide gel electrophoresis. Autophagy-related genes transcription levels, autophagy marker proteins <i>lgg-1</i>, and lysosomal content were analyzed to quantify autophagy levels by qRT-PCR, transgenic <i>C. elegans</i>, and lysosomal staining. Autophagy inhibitor chloroquine, <i>daf-16</i> mutant, and RNA Interference were used to determine the roles of autophagy and DAF-16 in rBTI-mediated effects. <b><i>Results:</i></b> In this study, we found that rBTI could decrease the proportions of insoluble protein and impaired mitochondria, finally reduce motility deficits in both models. Further study indicated that rBTI activated the autophagy, and the inhibition of autophagy reduced rBTI-mediated beneficial effects. Genetic analyses showed the transcriptional activity of DAF-16 was increased by rBTI and was required for rBTI-mediated beneficial effects. <b><i>Conclusions:</i></b> These data indicated that rBTI might promote the autophagy to alleviate the age-related functional decline via DAF-16 in <i>C. elegans</i> and suggested a potential role of rBTI as a nutraceutical for the improvement of age-related complications.