A search was made for functional food factors that prevent or improve lifestyle-related diseases resulting from disorders of lipid metabolism. We established assay systems utilizing molecular cell biological methods for evaluating food factors that are capable of affecting the activities and functions of bio-functional molecules involved in lipid metabolism. Several types of nuclear receptors, transcription factors, and receptors considered to be bio-functional molecules were examined using our own food chemical library composed of commercially available chemical compounds derived from foods. These assays allowed us to establish a clear link between functional food factors and bio-functional molecules. This review illustrates the functions of the food factors found in these assays in a comprehensible way.

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The aim of this study was to investigate the influence of folic acid restriction during pre-pregnancy on maternal skeletal metabolism. Female Sprague-Dawley rats (6 weeks old) were divided into two groups: a basal control diet group (Cont) and a folic acid restriction diet group (FR) . The rats were then given a basal control diet after mating. On the 29th day of the experimental diet, the serum level of folic acid was significantly lower in the FR group than in the Cont group. After delivery, the femoral trabecular bone mineral density (BMD) in the pregnant FR group was significantly lower than that in the pregnant Cont group or non-pregnant FR group. In addition, there was a significant difference in the femoral cortical BMD between the pregnant FR and non-pregnant FR groups. These results suggest that folic acid restriction during pre-pregnancy influences recovery of the circulating folic acid concentration, and that even if folic acid is given during pregnancy, the maternal BMD is significantly decreased after delivery. An adequate intake of folic acid during pre-pregnancy should be considered in order to maintain maternal bone health and prevent osteoporosis.

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Isothiocyanates, membrane-permeable electrophiles that form adducts with thiol, have been suggested to have important medical benefits. 6- (Methylsulfinyl) hexyl isothiocyanate (6-HITC) , the major isothiocyanate compound in wasabi, has been identified as an inducer of detoxification enzymes in rat liver epithelial RL34 cells. We have reported that the expression level of genes encoding detoxification enzymes in human intestinal Caco-2 cells is regulated by the enterocyte differentiation process. The present study was conducted to evaluate the effect of 6-HITC on proliferating and differentiated Caco-2 cells exposed to a wide variety of orally-ingested compounds including chemoprotective compounds. Treatment with 6-HITC decreased the level of proteasome activity in proliferating Caco-2 cells and induced HO-1 expression in those that had undifferentiated and differentiated. Proteasome inhibition with MG132 also induced HO-1 expression in proliferating Caco-2 cells, but not in those that had differentiated. These results indicate that 6-HITC induces HO-1 gene expression via a distinct pathway that differs between the proliferation and differentiation stages in Caco-2 cells.

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Isomaltulose, a structural isomer of sucrose, is digested slowly in the small intestine. Although various factors affect feeding behavior, the relationship between the digestion rate of nutrients in food and feeding regulation is unknown. We examined the effect of isomaltulose on feeding behavior in rats. Food and total energy intakes were measured during the light (7：00-19：00) and dark (19：00-7：00) periods after administration of the test sugar at 7：00 and 19：00. It was found that the food and total energy intakes during 24 hours were significantly decreased in the isomaltulose group relative to the control (sucrose) group. We also measured the gastric emptying rate and blood components after administration of the test sugar. The gastric emptying rate in the isomaltulose group had a tendency to be lower than that in the control group. The isomaltulose group showed significantly lower plasma glucose and insulin levels than the control group. These results suggest that isomaltulose has a prolonged effect on satiety and would likely be beneficial for appetite control.

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