[show abstract][hide abstract] ABSTRACT: The effect of dietary calcium (Ca) on fecal fat excretion in lactose maldigestion is not known.
To investigate the effect of dairy and non-dairy dietary Ca on fecal fat excretion in lactose digesters and maldigesters during moderate energy restriction.
A randomized cross-over trial comparing the effect of 500 mg versus 1500 mg dairy and non-dairy Ca on fecal fat excretion in 34 healthy adults during moderate (-30%) energy restriction induced weight loss for 12 weeks. The participants were classified as lactose digester or maldigester on the basis of breath hydrogen test.
Anthropometric parameters and body composition, resting energy expenditure, energy and nutrient intake, fecal fat, physical activity, blood pressure, blood and urine sampling for pertinent measurements.
Fecal fat loss expressed as percent of fat intake was significantly higher with 1500 mg (high Ca) as compared with 500 mg (low Ca) Ca intake per day (mean: 3.0%; 95% CI: 2.3 to 3.7%; P<0.001) independent of Ca source and lactose digestion status.
During a moderate energy restriction induced weight loss, a high-Ca diet causes an increase in fecal fat excretion independent of Ca source. Ca intake related fecal fat loss is also independent of the ability to digest lactose and it is not diminished over time (US Clinical Trial Registration: Clinicaltrials.gov NCT00808275).
International journal of obesity (2005) 10/2009; 34(1):127-35. · 4.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: To examine the relationship between the amount and patterns of physical activity (PA), body fatness, and age in a heterogeneous adult population in the free living.
Cross-sectional study of the amount of PA over a 1-week period. The amount of body movements during PA (PA counts*10(3)) and time spent on various PA intensity categories were calculated from a triaxial accelerometer and compared with subject characteristics, including body fat from hydrodensitometry.
Adult healthy men (n=48) and women (n=72) were recruited from the Nashville, Tennessee area and their PA was monitored in their free-living environment.
The average weekday PA counts (176.5+/-60.3, P=0.002, r(2)=0.294), PA counts day-to-day variability (47.3+/-32.7, P=0.002, r(2)=0.286), daily maximum PA counts (241.9+/-89.2, P=0.001, r(2)=0.327), minute-to-minute variability on weekdays (0.281+/-0.091, P=0.001, r(2)=0.362), and the difference between maximum and minimum daily PA counts (130.6+/-78.3, P=0.008, r(2)=0.243) were significantly and negatively correlated with body fatness. During awake time, both men and women spent 10-12 h on low intensity (1.0-2.9 metabolic equivalents (METs)) PA, approximately 1 h on moderate (3.0-5.9 MET), and less than 10 min on vigorous (>6.0 MET) PA each day. On weekends, men and women spent more time at rest (1 MET), less time on low-intensity PA, and men spent more time on moderate PA than on weekdays.
In adults living in the Southern US the amount of free-living PA was negatively correlated with body fatness. Both men and women spent the majority of active time on low and moderate PA. PA patterns on weekends were different than on weekdays and were related to sex and age, but not to body fatness.
National Institutes of Health, US.
European Journal of Clinical Nutrition 06/2004; 58(5):828-37. · 2.76 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Na+/H+ exchangers at the brush border membrane (BBM) and the basolateral membrane (BLM) are each distinct with different kinetic and pharmacologic characteristics. At the BBM, Na+/H+ exchange provides an acid microenvironment necessary for nutrient transport. At the BLM, the Na+/H+ exchanger regulates intracellular pH and cell volume which affect cell growth and repair. This study was designed to determine the effect of burn injury on Na+/H+ exchange at the BBM and BLM of the rat enterocyte. Adolescent Sprague-Dawley rats were divided into control (n = 6) and 20% scald burn groups (n = 6). Using differential centrifugation and percoll density gradient techniques, BBM and BLM vesicles were prepared from the jejunum. 22Na+ uptake was measured using a rapid filtration technique. Initial rate uptake studies showed that the slope of Na+ uptake in BBM (y = 0.06x + 0.12, r2 = 0.99) and BLM (y = 0.075x + 0.1, r2 = 0.99) of the control group was higher (P < 0.05) than that in the burn group (y = 0.0345x + 0.06, r2 = 0.98 and y = 0.056x + 0.01, r2 = 0.99). To determine whether the changes in transport are related to the feeding pattern in burn rats, similar experiments were done in pair-fed animals. The initial rate uptake studies of BBM showed a similarily greater slope of Na+ uptake in pair-fed control animals compared to the burn group (y = 0.043x + 0.06, r2 = 0.99 and y = 0.062x + 0.008, r2 = 0.98; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Surgical Research 03/1995; 58(2):137-42. · 2.02 Impact Factor
[show abstract][hide abstract] ABSTRACT: Kinetically distinct Na(+)-H+ exchangers exist on the apical and basolateral membranes of rabbit ileal enterocytes. The apical Na(+)-H+ exchanger appears to function in electroneutral NaCl transport, whereas the basolateral Na(+)-H+ exchanger may function in homeostatic intravesicular pH (pHi) regulation and volume regulation. This study is designed to determine the presence and characteristics of the Na(+)-H+ exchanger in basolateral membrane vesicles (BLMV) prepared from jejunal tissues of human organ donors. A well-validated Percoll-gradient technique was used to prepare BLMV. An outwardly directed H+ gradient [pHi/extravesicular pH (pHo) = 5.2/7.5] resulted in a Na+ uptake overshoot (1.45 +/- 0.21 nmol/mg protein) 2.5-fold above equilibrium values (0.59 +/- 0.13 nmol/mg protein). Na+ uptake at equilibrium represented transport into an osmotically sensitive intravesicular space as validated by an osmolality study. Na+ uptake represented an electroneutral process, as shown by studies in which negative membrane potentials were induced by K+ and the ionophore valinomycin. Na+ uptake was linear for the first 15 s of transport as depicted by y = 0.042x + 0.002, r2 = 0.98. Dixon plot analysis of amiloride sensitivity revealed an ID50 value for amiloride of 29 microM (fourfold lower than ID50 for brush-border Na(+)-H+ exchanger). Kinetic studies of amiloride-sensitive Na+ uptake revealed a maximal velocity = 1.53 +/- 0.19 nmol.mg protein-1.5 s-1 and Michaelis constant = 9.83 +/- 3.5 mM. By varying pHi a sigmoidal effect of internal H+ on Na+ uptake was noted consistent with an internal modifier site for protons. To confirm this finding, the effect of pHi on Na+ efflux and Na(+)-Na+ exchange was studied.(ABSTRACT TRUNCATED AT 250 WORDS)
The American journal of physiology 02/1993; 264(1 Pt 1):G45-50.
[show abstract][hide abstract] ABSTRACT: The present study was designed to investigate Cl- transport across rat ileal basolateral membranes. Basolateral membrane vesicles were prepared by a well-validated technique. The purity of the basolateral membrane vesicles was verified by marker enzyme studies and by studies of d-glucose and calcium uptake. Cl- uptake was studied by a rapid filtration technique. Neither an outwardly directed pH gradient, nor a HCO3- gradient, or their combination could elicit any stimulation of Cl- transport when compared with no gradient. 4,4-Diisothiocyanostilbene-2,2-disulfonic acid at 5 mM concentration did not inhibit Cl- uptake under gradient condition. Similarly, the presence of the combination of outwardly directed Na+ and HCO3- gradients did not stimulate Cl- uptake compared with the combination of K+ and HCO3- gradients or no HCO3- gradient. This is in contrast to our results in the brush border membranes, where an outwardly directed pH gradient caused an increase in Cl- uptake. Cl- uptake was stimulated in the presence of combined Na+ and K+ gradient. Bumetanide at 0.1 mM concentration inhibited the initial rate of Cl- uptake in the presence of combined Na+ and K+ gradients. Kinetic studies of bumetanide-sensitive Cl- uptake showed a Vmax of 5.6 +/- 0.7 nmol/mg protein/5 sec and a Km of 30 +/- 8.7 mM. Cl- uptake was stimulated by an inside positive membrane potential induced by the ionophore valinomycin in the setting of inwardly directed K+ gradient compared with voltage clamp condition. These studies demonstrate two processes for Cl- transport across the rat ileal basolateral membrane: one is driven by an electrogenic diffusive process and the second is a bumetanide-sensitive Na+/K+/2 Cl- process. Cl- uptake is not enhanced by pH gradient, HCO3- gradient, their combination, or outwardly directed HCO3- and Na+ gradients.
Proceedings of The Society for Experimental Biology and Medicine 01/1993; 201(3):254-60.
[show abstract][hide abstract] ABSTRACT: The spontaneously hypertensive rats and their genetically matched controls, Wistar-Kyoto, serve as models of essential hypertension. The present study was undertaken to determine whether brush border membrane vesicles obtained from jejunal enterocytes of spontaneously hypertensive rats show increased Na(+)-H+ exchange as part of a generalized membrane disorder. Brush border membrane vesicles were prepared from the jejunum of adult spontaneously hypertensive rats and Wistar-Kyoto rats using an Mg2+/ethylene glycol tetraacetic acid precipitation method. Uptake of 22Na by these vesicles was found to be into an osmotically sensitive intravesicular space rather than mere binding. Initial Na+ uptake by brush border membrane vesicles was greater in spontaneously hypertensive rats than in Wistar-Kyoto rats (P less than 0.05). Higher total and amiloride-sensitive Na+ uptake in spontaneously hypertensive rats occurred in the presence of an outwardly directed pH gradient, and uptake became statistically similar to that of Wistar-Kyoto rats in the absence of a pH gradient. Moreover, amiloride-insensitive Na+ uptake under an outwardly directed pH gradient did not differ significantly between the two groups. The enhanced Na(+)-H+ activity in spontaneously hypertensive rats is not due to altered membrane permeability to protons, as is shown by acridine orange-quenching studies. Kinetic studies for amiloride-sensitive Na+ uptake showed a greater Vmax in spontaneously hypertensive rats compared with Wistar-Kyoto rats (1.46 +/- 0.05 vs. 1.08 +/- 0.08 nmol.mg protein-1.7 s-1) but the Km values were similar in the two groups. These finding, along with similar findings previously reported in vascular smooth muscle and renal tissue of SHR, strongly suggest that an increased Na(+)-H+ exchange is related to the development of hypertension.
[show abstract][hide abstract] ABSTRACT: This study was designed to examine the activity of the Na(+)-H+ exchanger across the basolateral membranes of the ileal enterocyte and its developmental pattern. The function of the Na(+)-H+ exchanger was studied using a well validated basolateral membrane vesicle technique. Na+ uptake represented transport into the vesicle rather than binding as validated by initial rate studies. Na+ uptake represented an electroneutral process as shown by studies in which negative membrane potential was induced by the ionophore valinomycin. Various outwardly directed pH gradients significantly stimulated Na+ uptake compared with no pH gradient conditions at all age groups. However, the magnitude of stimulation was significantly different between the age groups with more marked stimulation of amiloride-sensitive Na+ uptake occurring in adolescent rats as compared to weanling or suckling rats. The amiloride sensitivity of the pH stimulated Na+ uptake was investigated using [Amiloride] = 10(-2)-10(-5) M at pHi/pHo = 5.2/7.5. At 10(-2) M amiloride concentration, Na+ uptake was inhibited by 80%, 70%, 77%, in the basolateral membranes of adolescent, weanling and suckling rats, respectively. Dixon plot analysis in both adolescent and weanling rats was consistent with two amiloride binding sites, a low affinity system and a high affinity system. In the suckling rat, on the other hand, the data supported a single high affinity binding site. Kinetic studies revealed a Km for amiloride-sensitive Na+ uptake of 12.6 +/- 6.6, 10.2 +/- 1.77, 9.46 and Vmax of 4.83 +/- 1.22, 4.47 +/- 0.36 and 8.08 +/- 1.92 n.mol.mg.protein-1.7 s-1 in suckling, weanling and adolescent rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of developmental physiology 04/1991; 15(3):175-81.