Nehra, Vandana

INTRODUCTION: Treated patients with celiac disease (CeD) and nonceliac gluten sensitivity (NCGS) report acute, transient, incompletely understood symptoms after suspected gluten exposure. To determine whether (i) blinded gluten exposure induces symptoms, (ii) subjects accurately identify gluten exposure, and (iii) serum interleukin-2 (IL-2) levels distinguish CeD from NCGS subjects after gluten exposure. METHODS: Sixty subjects (n = 20 treated, healed CeD; n = 20 treated NCGS; n = 20 controls) were block randomized to a single, double-blind sham (rice flour) or 3-g gluten challenge with 72-hours follow-up. Twelve serial questionnaires (100 mm visual analog scale; pain, bloating, nausea, and fatigue) and 10 serial plasma samples were collected. Mucosal permeability was assessed using both urinary lactulose- 13 C mannitol ratios and endoscopic mucosal impedance. RESULTS: Thirty-five of 40 (83%) subjects with CeD and NCGS reported symptoms with gluten (8 CeD, 9 NCGS) and sham (9 CeD, 9 NCGS) compared with 9 of 20 (45%) controls after gluten (n = 6) and sham (n = 3). There was no significant difference in symptoms among groups. Only 2 of 10 subjects with CeD and 4 of 10 NCGS identified gluten, whereas 8 of 10 subjects with CeD and 5 of 10 NCGS identified sham. A significant plasma IL-2 increase occurred only in subjects with CeD after gluten, peaking at 3 hours and normalizing within 24 hours postchallenge despite no significant intestinal permeability change from baseline. DISCUSSION: Symptoms do not reliably indicate gluten exposure in either subjects with CeD or NCGS. IL-2 production indicates a rapid-onset gluten-induced T-cell activation in CeD despite long-standing treatment. The effector site is unknown, given no increased intestinal permeability after gluten.

It has been shown ingestion of whey protein (WP) results in rapid systemic appearance rates of amino acids (AA) but in higher amino acid (AA) oxidation and whole body protein synthesis than in with casein (cas) ingestion which inhibits protein breakdown. To determine whether combined ingestion of both cas and WP in a meal containing carbohydrate has any disparate effects on protein economy in splanchnic and muscle beds we studied 12 healthy volunteers who ingested intrinsically labeled WP and Cas protein fractions. Following ingestion of 0.625 g·kg FFM −1 each of [ 15 N]WP and [ 13 C]Cas and 0.9 g·kg FFM −1 of lactose; or 0.625 g·kg FFM −1 each of [ 13 C]WP and [ 15 N]CAS and 0.9 g·kg FFM −1 of lactose blood samples were collected from femoral artery and vein and hepatic vein at frequent intervals. At 80–120 min, the rate of appearance (PheRa) of Phe at hepatic vein from WP and Cas were similar (5.5 (0.9) vs 5.2 (0.7) μmol, min −1 , but at 220–260 min, PheRa from WP was slower than PheRa from Cas (2.4 (0.5) vs 5.3 (1.2) μmol, min −1 , P<0.05). Retention rates of Phe in muscle (PheRd) absorbed from WP and Cas were similar at 80–120 min (0.8 (0.1) vs 0.9 (0.2) μmol, min −1 , ns) but was significantly lower for WP than Cas at 220–260 min (0.5 (0.1) vs 1.1 (0.3) μmol, min −1 , P<0.05). In conclusion Cas has more sustained systemic effects and muscle protein accretion than WP. The different metabolic effects of co‐ingested protein fractions have potential implications in designing appropriate nutritional support.

Many factors are involved in weight gain and metabolic disturbances associated with obesity. The gut microbiota has been of particular interest in recent years, since both human and animal studies have increased our understanding of the delicate symbiosis between the trillions of microbes that reside in the GI tract and the host. It has been suggested that disruption of this mutual tolerance may play a significant role in modulating host physiology during obesity. Environmental influences such as diet, exercise, and early life exposures can significantly impact the composition of the microbiota, and this dysbiosis can in turn lead to increased host adiposity via a number of different mechanisms. The ability of the microbiota to regulate host fat deposition, metabolism, and immune function makes it an attractive target for achieving sustained weight loss.

We have previously shown that voluntary wheel running (VWR) attenuates, whereas forced treadmill running (FTR) exacerbates, intestinal inflammation and clinical outcomes in a mouse model of colitis. As the gut microbiome is implicated in colitis, we hypothesized that VWR and FTR would differentially affect the gut microbiome. Mice (9-10/treatment) were randomly assigned to VWR, FTR, or sedentary home cage control (SED) for 6 wk. VWR were given running wheel access, whereas FTR ran on a treadmill for 40 min/day at 8–12 m/min, 5% grade. Forty-eight hours after the last exercise session, DNA was isolated from the fecal pellets and cecal contents, and the conserved bacterial 16S rRNA gene was amplified and sequenced using the Illumina Miseq platform. Permutational multivariate analysis of variance based on weighted UniFrac distance matrix revealed different bacterial clusters between feces and cecal contents in all groups ( P < 0.01). Interestingly, the community structures of the three treatment groups clustered separately from each other in both gut regions ( P < 0.05). Contrary to our hypothesis, the α-diversity metric, Chao1, indicated that VWR led to reduced bacterial richness compared with FTR or SED ( P < 0.05). Taxonomic evaluation revealed that both VWR and FTR altered many individual bacterial taxa. Of particular interest, Turicibacter spp., which has been strongly associated with immune function and bowel disease, was significantly lower in VWR vs. SED/FTR. These data indicate that VWR and FTR differentially alter the intestinal microbiome of mice. These effects were observed in both the feces and cecum despite vastly different community structures between each intestinal region.

When consumed separately, whey protein (WP) is more rapidly absorbed into circulation than casein (Cas), which prompted the concept of rapid and slow dietary protein. It is unclear whether these proteins have similar metabolic fates when coingested as in milk. We determined the rate of appearance across the splanchnic bed and the rate of disappearance across the leg of phenylalanine (Phe) from coingested, intrinsically labeled WP and Cas. Either [15N]Phe or [13C- ring C6]Phe was infused in lactating cows, and the labeled WP and Cas from their milk were collected. To determine the fate of Phe derived from different protein sources, 18 healthy participants were studied after ingestion of one of the following: 1) [15N]WP, [13C]Cas, and lactose; 2) [13C]WP, [15N]Cas, and lactose; 3) lactose alone. At 80–120 min, the rates of appearance (Ra) across the splanchnic bed of Phe from WP and Cas were similar [0.068 ± 0.010 vs. 0.070 ± 0.009%/min; not significant (ns)]. At time 220–260 min, Phe appearance from WP had slowed (0.039 ± 0.008%/min, P < 0.05) whereas Phe appearance from Cas was sustained (0.068 ± 0.013%/min). Similarly, accretion rates across the leg of Phe absorbed from WP and Cas were not different at 80–120 min (0.011 ± 0.002 vs. 0.012 ± 0.003%/min; ns), but they were significantly lower for WP (0.007 ± 0.002%/min) at 220–260 min than for Cas (0.013 ± 0.002%/min) at 220–260 min. Early after meal ingestion, amino acid absorption and retention across the leg were similar for WP and Cas, but as rates for WP waned, absorption and assimilation into skeletal muscle were better retained for Cas.