Impact of acute undernutrition on growth, ileal morphology and nutrient transport in a murine model

Undernutrition represents a major public health challenge for middle- and low-income countries. This study aimed to evaluate whether a multideficient Northeast Brazil regional basic diet (RBD) induces acute morphological and functional changes in the ileum of mice. Swiss mice (∼25 g) were allocated into two groups: i) control mice were fed a standard diet and II) undernourished mice were fed the RBD. After 7 days, mice were killed and the ileum collected for evaluation of electrophysiological parameters (Ussing chambers), transcription (RT-qPCR) and protein expression (western blotting) of intestinal transporters and tight junctions. Body weight gain was significantly decreased in the undernourished group, which also showed decreased crypt depth but no alterations in villus height. Electrophysiology measurements showed a reduced basal short circuit current (I_sc) in the undernourished group, with no differences in transepithelial resistance. Specific substrate-evoked I_sc related to affinity and efficacy (glutamine and alanyl-glutamine) were not different between groups, except for the maximum I_sc (efficacy) induced by glucose. Transcription of Sglt1 and Pept1 was significantly higher in the undernourished group, while SN-2 transcription was decreased. No changes were found in transcription of CAT-1 and CFTR, while claudin-2 and occludin transcriptions were significantly increased in the undernourished group. Despite mRNA changes, SGLT-1, PEPT-1, claudin-2 and occludin protein expression showed no difference between groups. These results demonstrate early effects of the RBD on mice, which include reduced body weight and crypt depth in the absence of significant alterations to villus morphology, intestinal transporters and tight junction expression.

Biomarkers of Environmental Enteropathy, Inflammation, Stunting, and Impaired Growth in Children in Northeast Brazil

Critical to the design and assessment of interventions for enteropathy and its developmental consequences in children living in impoverished conditions are non-invasive biomarkers that can detect intestinal damage and predict its effects on growth and development. We therefore assessed fecal, urinary and systemic biomarkers of enteropathy and growth predictors in 375 6–26 month-old children with varying degrees of malnutrition (stunting or wasting) in Northeast Brazil. 301 of these children returned for followup anthropometry after 2-6m. Biomarkers that correlated with stunting included plasma IgA anti-LPS and anti-FliC, zonulin (if >12m old), and intestinal FABP (I-FABP, suggesting prior barrier disruption); and with citrulline, tryptophan and with lower serum amyloid A (SAA) (suggesting impaired defenses). In contrast, subsequent growth was predicted in those with higher fecal MPO or A1AT and also by higher L/M, plasma LPS, I-FABP and SAA (showing intestinal barrier disruption and inflammation). Better growth was predicted in girls with higher plasma citrulline and in boys with higher plasma tryptophan. Interactions were also seen with fecal MPO and neopterin in predicting subsequent growth impairment.

Biomarkers clustered into markers of 1) functional intestinal barrier disruption and translocation, 2) structural intestinal barrier disruption and inflammation and 3) systemic inflammation. Principle components pathway analyses also showed that L/M with %L, I-FABP and MPO associate with impaired growth, while also (like MPO) associating with a systemic inflammation cluster of kynurenine, LBP, sCD14, SAA and K/T. Systemic evidence of LPS translocation associated with stunting, while markers of barrier disruption or repair (A1AT and Reg1 with low zonulin) associated with fecal MPO and neopterin.

We conclude that key noninvasive biomarkers of intestinal barrier disruption, LPS translocation and of intestinal and systemic inflammation can help elucidate how we recognize, understand, and assess effective interventions for enteropathy and its growth and developmental consequences in children in impoverished settings.

Glutamine and alanyl-glutamine promote crypt expansion and mTOR signaling in murine enteroids

L-glutamine (Gln) is a key metabolic fuel for intestinal epithelial cell proliferation and survival and may be conditionally essential for gut homeostasis during catabolic states. We show that L-alanyl-L-glutamine (Ala-Gln), a stable Gln dipeptide, protects mice against jejunal crypt depletion in the setting of dietary protein and fat deficiency. Separately, we show that murine crypt cultures (enteroids) derived from the jejunum require Gln or Ala-Gln for maximal expansion. Once expanded, enteroids deprived of Gln display a gradual atrophy of cryptlike domains, with decreased epithelial proliferation, but stable proportions of Paneth and goblet cell differentiation, at 24 h. Replenishment of enteroid medium with Gln selectively activates mammalian target of rapamycin (mTOR) signaling pathways, rescues proliferation, and promotes crypt regeneration. Gln deprivation beyond 48 h leads to destabilization of enteroids but persistence of EGFP-Lgr5-positive intestinal stem cells with the capacity to regenerate enteroids upon Gln rescue. Collectively, these findings indicate that Gln deprivation induces a reversible quiescence of intestinal stem cells and provides new insights into nutritional regulation of intestinal epithelial homeostasis.

Protein-energy malnutrition alters IgA responses to rotavirus vaccination and infection but does not impair vaccine efficacy in mice

BACKGROUND

Conflicting evidence links malnutrition to the reduced efficacy of rotavirus vaccines in developing countries, where diarrhea and undernutrition remain leading causes of child deaths. Here, we adapted mouse models of rotavirus vaccination (rhesus rotavirus, RRV), rotavirus infection (EDIM), and protein-energy malnutrition (PEM) to test the hypothesis that undernutrition reduces rotavirus vaccine immunogenicity and efficacy.

METHODS

We randomized wild type Balb/C dams with 3-day-old pups to a control diet (CD) or an isocaloric, multideficient regional basic diet (RBD) that produces PEM. At 3 weeks of age, we weaned CD and RBD pups to their dams' diet and subrandomized weanlings to receive a single dose of either live oral rotavirus vaccine (RRV) or PBS. At 6 weeks of age, we orally challenged all groups with murine rotavirus (EDIM). Serum and stool specimens were collected before and after RRV and EDIM administration to measure viral shedding and antibody responses by ELISA.

RESULTS

RBD pups and weanlings exhibited significant failure to thrive compared to age-matched CD mice (P<.0001). RRV vaccination induced higher levels of serum anti-RV IgA responses in RBD vs. CD mice (P<.0001). Vaccination protected CD and RBD mice equally against EDIM infection, as measured by viral shedding. In unvaccinated RBD mice, EDIM shedding peaked 1 day earlier (P<.05), however we detected no effects of undernutrition on viral clearance nor of infection on bodyweight. EDIM infection provoked higher anti-RV serum IgA levels in RBD vs. CD mice, regardless of vaccination (P<.0001). Last, RRV vaccination mitigated stool IgA responses to EDIM more in CD vs. RBD mice (P<.0001).

CONCLUSIONS

Despite modulated IgA responses to vaccination and infection, undernutrition does not impair rotavirus vaccine efficacy nor exacerbate infection in this mouse model of protein-energy malnutrition. Alternative models are needed to elucidate host-pathogen factors undermining rotavirus vaccine effectiveness in high-risk global settings.

Gastroprotective effect of mangiferin, a xanthonoid from Mangifera indica, against gastric injury induced by ethanol and indomethacin in rodents

In search of novel gastroprotective agents, mangiferin, a naturally occurring glucosylxanthone from Mangifera indica L. (Anacardiaceae), was evaluated in mice on gastric injury induced by ethanol and indomethacin. The effects of mangiferin on gastric mucosal damage were assessed by determination of changes in mean gastric lesion area or ulcer score in mice and on gastric secretory volume and total acidity in 4-h pylorus-ligated rats. Mangiferin (3, 10 and 30 mg/kg, P. O.) significantly attenuated the gastric damage induced by ethanol by 30, 35, and 63 %, and of indomethacin by 22, 23 and 57 %, respectively. N-Acetylcysteine (750 mg/kg, I. P.) and lansoprazole (30 mg/kg, P. O.) used as positive controls in these ulcerogenic models resulted in 50 % and 76 % suppression of gastric injury, respectively. In 4-h pylorus-ligated rats, intraduodenally applied mangiferin (30 mg/kg) caused significant diminutions in gastric secretory volume and total acidity. In addition, like N-acetylcysteine, a donor of sulfhydryls, mangiferin effectively prevented the ethanol-associated depletion of gastric mucosal non-protein sulfhydryl content in mice, suggesting an antioxidant action. These findings provide evidence that mangiferin affords gastroprotection against gastric injury induced by ethanol and indomethacin most possibly through the antisecretory and antioxidant mechanisms of action.

Antinociceptive and gastroprotective effects of diterpenes from the flower buds of Egletes viscosa

Centipedic acid and 12-acetoxy-hawtriwaic acid lactone, diterpenes isolated from the flower buds of Egletes viscosa (Asteraceae) were assayed for antinociceptive and gastroprotective activities in animal models of nociception and gastric ulcer. In the chemical nociception induced in mice by intraperitoneal acetic acid and subplantar formalin injections, both diterpenes (25 and 50 mg/kg, p. o.) exerted potent antinociception in a manner similar to indomethacin (5 mg/kg, p. o.). In the formalin test, only the late phase nociceptive response (20 - 25 min) and not the early phase response (0 - 5 min) was inhibited by these diterpenes. However, these compounds were found to be ineffective against thermal nociception in the hot-plate test. Further, the diterpenes reduced the severity of absolute ethanol-induced gastric lesions in rats. At the dose of 50 mg/kg, both centipedic acid and 12-acetoxy hawtriwaic acid suppressed the gastric lesions by 53 % and 63 %, respectively. Against the gastric ulceration induced by indomethacin, only centipedic acid (25 and 50 mg/kg) showed significant inhibition by about 47 - 49 %. The data suggested the gastroprotective and peripheral analgesic properties of diterpenes isolated from E. viscosa.