Relationship between 24-hour urinary-free cortisol excretion and salivary cortisol levels sampled from awakening to bedtime in healthy subjects

The utility of repeated salivary cortisol sampling as a substitute for 24-hour urinary-free cortisol (UFC) assessment was examined. Forty-four participants completed both 24-hour collections and 6 salivary collections at wake-up, 08:00, 12:00, 16:00, 20:00 and bedtime, during the same 24-hour period. The results demonstrated that mean, maximum, and amplitude (maximum minus minimum) for salivary cortisol all correlated positively with urinary cortisol, but the associations of these variables with urinary-free cortisol excretion were relatively small. Furthermore, a single salivary sample taken at wake-up was as good an indicator of overall cortisol production as the measures derived from multiple salivary samples. An examination of subject compliance indicated that many subjects failed to collect the timed salivary collections as instructed. The authors conclude that diurnal salivary cortisol sampling versus 24-hour urinary cortisol collections are likely to provide different information about ambient hypothalamic-pituitary-adrenal productivity, and therefore these measures should not be used interchangeably. In addition, subject compliance is a serious consideration in designing studies that employ home salivary collections. Published by Elsevier Science Inc.

The effect of dietary nitrate on salivary, plasma, and urinary nitrate metabolism in humans

Dietary nitrate is metabolized to nitrite by bacterial flora on the posterior surface of the tongue leading to increased salivary nitrite concentrations. In the acidic environment of the stomach, nitrite forms nitrous acid, a potent nitrating/nitrosating agent. The aim of this study was to examine the pharmacokinetics of dietary nitrate in relation to the formation of salivary, plasma, and urinary nitrite and nitrate in healthy subjects. A secondary aim was to determine whether dietary nitrate increases the formation of protein-bound 3-nitrotyrosine in plasma, and if dietary nitrate improves platelet function. The pharmacokinetic profile of urinary nitrate excretion indicates total clearance of consumed nitrate in a 24 h period. While urinary, salivary, and plasma nitrate concentrations increased between 4- and 7-fold, a significant increase in nitrite was only detected in saliva (7-fold). High dietary nitrate consumption does not cause a significant acute change in plasma concentrations of 3-nitrotyrosine or in platelet function.

A randomised, double-blind, placebo controlled cross-over study to determine the gastrointestinal effects of consumption of arabinoxylanoligosaccharides enriched bread in healthy volunteers

BACKGROUND: Prebiotics are food ingredients, usually non-digestible oligosaccharides, that are selectively fermented by populations of beneficial gut bacteria. Endoxylanases, altering the naturally present cereal arabinoxylans, are commonly used in the bread industry to improve dough and bread characteristics. Recently, an in situ method has been developed to produce arabinoxylan-oligosaccharides (AXOS) at high levels in breads through the use of a thermophilic endoxylanase. AXOS have demonstrated potentially prebiotic properties in that they have been observed to lead to beneficial shifts in the microbiota in vitro and in murine, poultry and human studies. METHODS: A double-blind, placebo controlled human intervention study was undertaken with 40 healthy adult volunteers to assess the impact of consumption of breads with in situ produced AXOS (containing 2.2 g AXOS) compared to non-endoxylanase treated breads. Volatile fatty acid concentrations in faeces were assessed and fluorescence in situ hybridisation was used to assess changes in gut microbial groups. Secretory immunoglobulin A (sIgA) levels in saliva were also measured. RESULTS: Consumption of AXOS-enriched breads led to increased faecal butyrate and a trend for reduced iso-valerate and fatty acids associated with protein fermentation. Faecal levels of bifidobacteria increased following initial control breads and remained elevated throughout the study. Lactobacilli levels were elevated following both placebo and AXOS-breads. No changes in salivary secretory IgA levels were observed during the study. Furthermore, no adverse effects on gastrointestinal symptoms were reported during AXOS-bread intake. CONCLUSIONS: AXOS-breads led to a potentially beneficial shift in fermentation end products and are well tolerated.

Dietary supplementation with Bifidobacterium lactis NCC2818 from weaning reduces local immunoglobulin production in lymphoid-associated tissues but increases systemic antibodies in healthy neonates

Weaning is associated with a major shift in the microbial community of the intestine, and this instability may make it more acquiescent than the adult microbiota to long-term changes. Modulation achieved through dietary interventions may have potentially beneficial effects on the developing immune system, which is driven primarily by the microbiota. The specific aim of the present study was to determine whether immune development could be modified by dietary supplementation with the human probiotic Bifidobacterium lactis NCC2818 in a tractable model of weaning in infants. Piglets were reared by their mothers before being weaned onto a solid diet supplemented with B. lactis NCC2818, while sibling controls did not receive supplementation. Probiotic supplementation resulted in a reduction in IgA (P,0·0005) and IgM (P,0·009) production by mucosal tissues but had no effect on IgG production (P.0·05). Probiotic- supplemented pigs had more mast cells than unsupplemented littermates (P,0·0001), although numbers in both groups were low. In addition, the supplemented piglets made stronger serum IgG responses to fed and injected antigens (P,0·05). The present findings are consistent with B. lactis NCC2818 reducing intestinal permeability induced by weaning, and suggest that the piglet is a valuable intermediate between rodent models and human infants. The results also strongly suggest that measures of the effect of probiotic supplementation on the immune system need to be interpreted carefully as proxy measures of health benefit. However, they are useful in developing an understanding of the mechanism of action of probiotic strains, an important factor in predicting favourable health outcomes of nutritional intervention.