Age-related changes in functional adaptation to bolus characteristics during chewing.

We investigated how the physical properties of food affect chewing kinematics, and examined the effects of aging on behavior. Twenty young and 21 older volunteers were asked to freely chew rice crackers and spit the food out at their average chewing duration. We compared chewing characteristics among the conditions (age × rice cracker), and examined the area of rectified masseter and suprahyoid electromyographic bursts per chewing cycle. We also evaluated temporal changes in those values. In addition, the bolus properties at the end of chewing were compared. The harder/larger the rice cracker, the longer the chewing duration and the greater the number of chewing cycles. These values also increased with age. Chewing cycle time was not affected by age and rice cracker properties, except in one condition: for the rice cracker with the lowest hardness and density, the chewing cycle time was longer than for the other rice crackers. Chewing cycle time decreased at the middle stage of chewing, followed by an increase, with increasing suprahyoid electromyographic activity at the late stage. The physical properties of the bolus at the end of chewing did not differ between age groups, and depended on the initial properties. The water absorption rate of the bolus was significantly greater for the rice cracker with the lowest hardness and density compared with other rice crackers. The results demonstrated that not only hardness, but also other factors, such as density, significantly affected chewing behaviors.

Rice Endosperm Protein Administration to Juvenile Mice Regulates Gut Microbiota and Suppresses the Development of High-Fat Diet-Induced Obesity and Related Disorders in Adulthood.

Obesity and related disorders, which are increasing in adults worldwide, are closely linked to childhood diet and are associated with chronic inflammation. Rice endosperm protein (REP) intake during adulthood has been reported to improve lipid metabolism and suppress the progression of diabetic kidney disease in animal models. However, the effects of REP intake during childhood on adulthood health are unclear. Therefore, we used a mouse model to experimentally investigate the preconditioning effects of REP intake during childhood on the development of obesity and related disorders in adulthood. Male C57BL/6J mice were pair-fed a normal-fat diet containing casein or REP during the juvenile period and then a high-fat diet (HFD) containing casein or REP during adulthood. Mice fed REP during the juvenile period showed better body weight, blood pressure, serum lipid profiles, lipopolysaccharide (LPS)-binding protein levels, and glucose tolerance in adulthood than those fed casein during the juvenile period. HFD-induced renal tubulo-glomerular alterations and hepatic microvesicular steatosis were less evident in REP-fed mice than in casein-fed ones. REP intake during the juvenile period improved HFD-induced dysbiosis (i.e., Escherichia genus proliferation and reduced gut microbiota diversity), thereby suppressing endotoxin-related chronic inflammation. Indeed, REP-derived peptides showed antibacterial activity against Escherichia coli, a major producer of LPS. In conclusion, REP supplementation during the juvenile period may regulate the gut microbiota and thus suppress the development of obesity and related disorders in adulthood in mice.