Keiko Sakuma

Short-Chain Fatty Acids Induce Intestinal Transient Receptor Potential Vanilloid Type 6 Expression in Rats and Caco-2 Cells

Fructooligosaccharides (FOS) are indigestible oligosaccharides that increase calcium absorption by the colorectum in rats, but the underlying mechanisms remain unclear. We therefore investigated the effects of FOS on expressions of genes involved with calcium absorption in rat colorectal mucosa cells. After feeding a diet containing FOS (100 g/kg diet) to rats for 2 d, we investigated gene transcripts of transient receptor potential vanilloid type 6 (TRPV6), calbindin-D9k, and plasma membrane calcium-ATPase 1b (PMCA1b). The FOS diet increased expression of TRPV6 and calbindin-D9k but did not affect PMCA1b expression. Because FOS could not directly affect gene expression, SCFA formed as fermentation products of FOS were considered as likely intermediates. SCFA (2.0 mmol/L) were thus added to Caco-2 human colonic epithelial cells, resulting in significantly increased mRNA expression of TRPV6. To ascertain the effects of SCFA on mRNA expression, a genomic clone of TRPV6 was isolated. Using luciferase reporter assay, a segment between -71 nucleotides and the translation start site was found to contain a positive responsive element to SCFA. These results suggest that FOS increase calcium absorption by increasing mRNA expression of TRPV6 in rat colorectum, and cell culture analysis indicated that SCFA, as fermentation products of FOS, are involved in the increased mRNA expression of TRPV6. We found for the first time, to our knowledge, that regulation of TRPV6 gene expression by SCFA may be a molecular mechanism involved in the promotion of calcium absorption by FOS in rats.

Dietary short-chain fructooligosaccharides increase calbindin-D9k levels only in the large intestine in rats independent of dietary calcium deficiency or serum 1,25 dihydroxy vitamin D levels.

Dietary short-chain fructooligosaccharides (Sc-FOS) increase mucosal calbindin-D9k (CaBP) levels in the large intestine whereas levels in the small intestine are decreased in rats. In the present study, we investigated the mechanism by which Sc-FOS induce this increase in CaBP in the large intestine by measuring intestinal CaBP levels in rats fed normal and calcium-deficient diets. Dietary groups included a calcium-containing (0.5%) diet with or without Sc-FOS (100 g/kg diet) and a calcium-deficient (abt. 0.01%) diet with or without Sc-FOS (100 g/kg diet). The rats were fed these diets for 10 days following which they were killed and the intestine removed for collection of the entire mucosa which was divided into four segments, i.e., proximal and distal segments of the small intestine, the cecum and the colorectum. Mucosal CaBP and plasma calcium (Ca), 1,25-dihydroxycholecalciferol (1,25(OH)2D3), 25-hydroxycholecalciferol (25(OH)D3), parathyroid hormone (PTH) and calcitonin levels were measured. Feeding of calcium deficient diet resulted in an increase in CaBP levels in the small intestine, but did not influence levels in the large intestine. Moreover, a significant positive correlation between plasma 1,25(OH)2D3 and CaBP levels in the case of both small intestinal segments (proximal, r = 0.77012, p < 0.00007; distal, r = 0.75056, p < 0.00014) was observed, but not in the case of the large intestinal segments. Sc-FOS increased CaBP levels in the large intestine. These results suggest that the large intestinal CaBP levels do not change in response to dietary calcium conditions and are not regulated by circulating 1,25(OH)2D3 indicating that the effect of Sc-FOS on CaBP levels in the large intestine is independent of the action of 1,25(OH)2D3.

Association between Sleep Duration and Personality-Gene Variants: Sleep Duration is Longer in S/S Homozygotes of Serotonin Transporter than in L Allele Genotypes

Heavy Issue: Clarifying AHI Elevation after Contemporary Airway Surgery for OSA – The MACHO Graph Objective: Personality genes and lifestyle and depression scores of young women were analyzed to reevaluate conflicting findings regarding the relationship between worry and sleep schedule (sleep duration, bedtime etc.). Methods: Genes encoding serotonin transporter (5-HTT; S/S, S/L, L/L, and S/XL genotypes) and dopamine D4 receptor (DRD4; 2/4, 4/4, and other genotypes) and three clock genes were genotyped for 42 healthy female Japanese students (age range: 20-21). Their mood was assessed via the Center for Epidemiologic Studies Depression Scale (CES-D). Their personalities were assessed via the NEO Five-Factor Inventory (NEO-FFI). They maintained a diary and completed a questionnaire about sleep and dietary intake. Results: The variant frequencies for S/S homozygote of 5-HTT and 4/4 homozygote of DRD4 were higher among this group than among Caucasians. Sleep duration was 40.8 min longer (7.13 ± .94 hrs) in 5-HTT S/S homozygotes than in others (6.45 ± .69 hrs) (p=0.018), and the bedtime was earlier (0:16 ± 1:05 h:min) for 5-HTT S/S homozygotes than for L allele genotypes (1:14 ± 0:41 h:min) (p=0.005). A “delayed bedtime phenotype” was evident in 55% of S/S homozygotes and 100% of L allele-bearing individuals. Sleep duration was also 42.0 min longer in 4/4 homozygotes (7.09 ± 0.94 hrs) of DRD4 than that in 4/2 heterozygotes (6.39 ± .77 hrs) (p=0.042). An inverse correlation (r=-.316, p=.043) between ppppsleep duration and CES-D score was detected. When groups with high and low CES-D scores were compared, “Delayed bedtime phenotypes”, Neuroticism, and Conscientiousness of NEO-FFI were 100%:59.3%, 34.0:25.5, and 24.6:28.2, respectively. Conclusion: Both stress-susceptible genotypes, S/S homozygotes of 5-HTT and 4/4 homozygotes of DRD4, slept longer than genotypes with the L-allele of 5-HTT, and 4/2 heterozygotes of DRD4, respectively. The high CES-D group comprised short sleepers, irrespective of genotype.