The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform

Stephen J. Lolait - One of the best experts on this subject based on the ideXlab platform.

Kenichi Inui - One of the best experts on this subject based on the ideXlab platform.

  • regulatory mechanism governing the Diurnal Rhythm of intestinal h peptide cotransporter 1 pept1
    American Journal of Physiology-gastrointestinal and Liver Physiology, 2008
    Co-Authors: Hirofumi Saito, Tomohiro Terada, Jin Shimakura, Toshiya Katsura, Kenichi Inui
    Abstract:

    The intestinal H(+)/peptide cotransporter 1 (PEPT1) plays important roles as a nutrient and drug transporter. Previously, we reported that rat intestinal PEPT1 showed a Diurnal Rhythm and that this Rhythm is closely related to the feeding schedule. Furthermore, we also demonstrated that transcription factors, Sp1, Cdx2, and peroxisome proliferator-activated receptor-alpha (PPAR-alpha) contribute to the basal, intestine-specific, and fasting-induced expression of PEPT1, respectively. In this study, to clarify the molecular mechanism governing the Diurnal Rhythm of PEPT1 expression, we compared expression profiles of these transcription factors under two kinds of feeding schedules. The intestinal Sp1 and Cdx2 did not show a circadian accumulation of mRNA or response to the daytime feeding regimen. Plasma free fatty acids, endogenous PPAR-alpha ligands, exhibited a robust circadian fluctuation in phase with that of PEPT1. However, subsequent experiments using PPAR-alpha-null mice revealed the absence of any association between the circadian Rhythm of PEPT1 and PPAR-alpha. We then focused on the clock genes (Clock, Bmal1, Per1-2, and Cry1) and clock-controlled gene, albumin D site-binding protein (DBP). A robust and coordinated circadian expression of the clock genes was observed, and daytime feeding entirely inverted the phase except for Clock. The expression of DBP was in phase with that of PEPT1 in both groups. Electrophoretic mobility shift assays and reporter assays revealed that DBP has the ability to bind the DBP binding site located in the distal promoter region of the rat PEPT1 gene and induce the transcriptional activity. These findings indicate that DBP plays pivotal roles in the circadian oscillation of PEPT1.

  • the Diurnal Rhythm of the intestinal transporters sglt1 and pept1 is regulated by the feeding conditions in rats
    Journal of Nutrition, 2004
    Co-Authors: Xiaoyue Pan, Tomohiro Terada, Masahiro Okuda, Kenichi Inui
    Abstract:

    The intestinal Na + /glucose cotransporter 1 (SGLT1) and H + /peptide cotransporter 1 (PEPT1) play important roles in the absorption of carbohydrate and protein. Although they exhibit a Diurnal Rhythm in their expression and function, the factors responsible for this are unclear. In the present study, we examined the effects of various feeding conditions on the Diurnal Rhythm of intestinal SGLT1 and PEPT1. Rats were divided into 1 of 4 groups: group 1 was fed, group 2 was food deprived for 1-4 d, group 3 was food deprived for 4 d and then refed for 1 or 2 d, and group 4 was fed during the daytime (0900-1500 h) for 10 d. In fed rats, the SGLT1 protein level was significantly higher at 2000 h than at 0800 h. However, in rats deprived of food for 2-4 d, protein levels did not differ between 0800 and 2000 h. In contrast, the SGLT1 messenger RNA (mRNA) level was significantly higher at 2000 h than at 0800 h in rats deprived of food for 4 d. Refeeding for 2 d after 4 d of food deprivation returned the Diurnal variation in SGLT1 and PEPT1 protein expressions to normal. Consuming food during the daytime only shifted the peaks of SGLT1 and PEPT1 mRNAs and protein expressions from the dark phase to the light phase. These findings suggest that food intake, rather than the light cycle, greatly affects the Diurnal Rhythm of SGLT1 and PEPT1 expressions.

  • altered Diurnal Rhythm of intestinal peptide transporter by fasting and its effects on the pharmacokinetics of ceftibuten
    Journal of Pharmacology and Experimental Therapeutics, 2003
    Co-Authors: Xiaoyue Pan, Tomohiro Terada, Masahiro Okuda, Kenichi Inui
    Abstract:

    We previously demonstrated that H+/peptide cotransporter PEPT1 shows a Diurnal Rhythm in the rat small intestine. In the present study, we examined the effect of food intake on the Diurnal Rhythm of intestinal PEPT1 using fed and fasted rats and also determined whether such variation affected the pharmacokinetics of peptide-like drugs. In fed rats, PEPT1 protein level was significantly higher at 8:00 PM than at 8:00 AM. However, during fasting for 2 to 4 days, the differences of PEPT1 protein levels between 8:00 AM and 8:00 PM gradually disappeared. Intestinal absorption of an oral antibiotic ceftibuten (CETB), a pharmacological substrate for PEPT1, was also greater at 8:00 PM than at 8:00 AM in fed rats, but not different in 4-day fasted rats. In contrast to PEPT1 protein levels, PEPT1 mRNA levels retained a Diurnal Rhythm after 4 days of fasting. Pharmacokinetic analyses of CETB after intraintestinal administration demonstrated that both Cmax and area under the plasma concentration-time curve from 0 to 3 h were greater at 8:00 PM than at 8:00 AM in fed rats. In contrast, pharmacokinetic parameters showed no significant difference between 8:00 AM and 8:00 PM for intraintestinal administration in 4-day fasted rats and for intravenous administration in fed and 4-day fasted rats. These findings suggested that the Diurnal Rhythm of intestinal PEPT1 transport activity was disrupted by fasting and that Diurnal variation of intestinal PEPT1 functionality could influence the pharmacokinetics of peptide-like drugs such as CETB.

  • Diurnal Rhythm of h peptide cotransporter in rat small intestine
    American Journal of Physiology-gastrointestinal and Liver Physiology, 2002
    Co-Authors: Xiaoyue Pan, Tomohiro Terada, Megumi Irie, Hideyuki Saito, Kenichi Inui
    Abstract:

    In mammals, most physiological, biochemical, and behavioral processes show a circadian Rhythm. In the present study, we examined the Diurnal Rhythm of the H+-peptide cotransporter (PEPT1), which tr...

W S Young - One of the best experts on this subject based on the ideXlab platform.

Christos S Mantzoros - One of the best experts on this subject based on the ideXlab platform.

  • sleep loss reduces Diurnal Rhythm amplitude of leptin in healthy men
    Journal of Neuroendocrinology, 2003
    Co-Authors: Janet Mullington, J L Chan, H P A Van Dongen, Martin P Szuba, J Samaras, Nick J Price, Hans K Meierewert, David F Dinges, Christos S Mantzoros
    Abstract:

    The aim of the current study was to investigate the effects of sleep loss on the Diurnal Rhythm of circulating leptin levels. An indwelling forearm catheter was used to sample blood at 90-min intervals for a total of 120 h, which included 88 h of sustained sleeplessness, in 10 healthy men. The Diurnal amplitude of leptin was reduced during total sleep deprivation and returned toward normal during the period of recovery sleep. This finding provides evidence that sleep influences the nocturnal leptin profile, and may have implications for the understanding of the role of sleep in metabolic regulation and the aetiologies of obesity and the night eating syndrome.

Arthur A Stone - One of the best experts on this subject based on the ideXlab platform.

  • effect of chronic stress associated with unemployment on salivary cortisol overall cortisol levels Diurnal Rhythm and acute stress reactivity
    Psychosomatic Medicine, 1995
    Co-Authors: Margit C Ockenfels, Laura S Porter, Joshua M Smyth, Clemens Kirschbaum, Dirk H Hellhammer, Arthur A Stone
    Abstract:

    This study examined the effect of chronic stress associated with unemployment on the magnitude of salivary cortisol excretion, on the Diurnal Rhythm of cortisol, and on cortisol reactivity to acute naturalistic stressors using Experience Sampling Methodology (ESM). Employed (N = 60) and unemployed (N = 60) subjects were studied for 2 days. Subjects were beeped 6 times per day by a preprogrammed wristwatch to assess acute stressors; 25 minutes after each ESM-beep, subjects were beeped a second time for saliva samples. The groups did not differ in their overall cortisol excretion or in cortisol reactivity to acute daily stressors. Compared to employed subjects, unemployed subjects had a Diurnal pattern of cortisol excretion with relatively higher morning and lower evening levels. Subjects' daily activities and their locations were associated with Diurnal Rhythm differences.