Cuong D. Tran

Early life events influence whole-of-life metabolic health via gut microflora and gut permeability.

Abstract The capacity of our gut microbial communities to maintain a stable and balanced state, termed ‘resilience’, in spite of perturbations is vital to our achieving and maintaining optimal health. A loss of microbial resilience is observed in a number of diseases including obesity, diabetes and metabolic syndrome. There are large gaps in our understanding of why an individual’s co-evolved microflora consortium fail to develop resilience thereby establishing a trajectory towards poor metabolic health. This review examines the connections between the developing gut microbiota and intestinal barrier function in the neonate, infant and during the first years of life. We propose that the effects of early life events on the gut microflora and permeability, whilst it is in a dynamic and vulnerable state, are fundamental in shaping the microbial consortia’s resilience and that it is the maintenance of resilience that is pivotal for metabolic health throughout life. We review the literature supporting this concept suggesting new potential research directions aimed at developing a greater understanding of the longitudinal effects of the gut microflora on metabolic health and potential interventions to recalibrate the ‘at risk’ infant gut microflora in the direction of enhanced metabolic health.

N-Acetylcysteine, a Novel Treatment for Helicobacter pylori Infection

N-Acetylcysteine (NAC), being both a mucolytic agent and a thiol-containing antioxidant, may affect the establishment and maintenance of H. pylori infection within the gastric mucus layer and mucosa. Agar and broth dilution susceptibility tests determined the MIC of H. pylori strain SSI to NAC. H. pylori load in SSI strain-infected C57BL mice was determined as colony forming units per gram of gastric tissue. Gastritis assessment was scored and gastric surface hydrophobicity was determined by contact angle measurement. MICs of NAC were 5 to 10 and 10 to 15 mg/ml using the agar dilution and broth dilution methods, respectively. NAC (120 mg per day for 14 days) reduced the H. pylori load in mice by almost 1 log compared with sham treatment. Pretreatment with NAC (40 mg/day) also significantly reduced the H. pylori load but did not prevent H. pylori colonization. Both H. pylori infection and NAC reduced the surface hydrophobicity of murine gastric mucosa. No significant differences were observed in the gastritis scores of H. felis- or H. pylori-infected mice receiving either NAC or sham treatments. This study demonstrates that NAC inhibits the growth of H. pylori in both agar and broth susceptibility tests and in H. pylori-infected mice. NAC did not alter the severity of H. pylori- or H. felis-induced gastritis.

Small bowel bacterial overgrowth is a common cause of chronic diarrhea

Background and Aims:  Often a cause for chronic non‐specific diarrhea (≥3 stools per day for more than 4 weeks) is not identified. Small bowel bacterial overgrowth (SBO) can occur without morphological damage and remains difficult to diagnose. Often diarrhea is treated empirically with antibiotics with a good response. The aims of the present study were first to investigate the prevalence of SBO in a consecutive series of patients with chronic diarrhea and second to compare the utility of duodenal fluid culture and 14C‐d‐xylose breath/lactulose test in diagnosing SBO.

Interaction of dietary zinc and intracellular binding protein metallothionein in postnatal bone growth.

Zinc and its binding protein, metallothionein (MT), are important in regulating growth and development, and yet it is unclear how dietary Zn and MT interact in regulating bone growth. Here, 3.5-week female MT-I&II knockout (MT(-/-)) and wild type (MT(+/+)) mice were fed diets containing 2.5 (limiting, Zn-L), 15 or 50 mg Zn/kg (Zn adequate) for 5 or 9 weeks, and effects were analysed on structure and function of growth plate and metaphysis, two structures important for bone growth. Zn limitation did not affect bone growth in MT(+/+) mice. However, MT(-/-) mice, having lower Zn concentrations in plasma and long bone, showed growth retardation as demonstrated by lower body length gain, shorter and smaller tibia/femur, lower chondrocyte proliferation, reduced metaphysis heights, but increased osteoclast densities on trabecular bone, particularly in mice fed Zn-L diet. Interestingly, mRNA expression of MT-I&II was induced in the growth plate of MT(+/+) mice fed the Zn-L diet possibly compensating for Zn limitation. Growth plate MT-III expression increased in MT(-/-) mice fed the adequate Zn diet, whereas metaphyseal MT-III was significantly upregulated in MT(-/-) mice fed Zn-L diet, possibly as a compensatory mechanism or exacerbating effects of Zn limitation. Consistent with the increased osteoclast numbers, a higher ratio of RANKL/OPG gene expression was found in bone of mutant mice fed lower Zn diets. These results indicate that interaction between dietary Zn and endogenous MT is important for maximal bone growth, and MT is particularly important in the regulation of Zn pool for bone growth during moderate Zn limitation.

Emu oil expedites small intestinal repair following 5-fluorouracil-induced mucositis in rats.

Mucositis resulting from cancer chemotherapy is characterized by intestinal inflammation and ulceration. Previously, emu oil (EO) improved intestinal architecture (Br J Nutr, 2010) in a rat model of chemotherapy-induced mucositis. We investigated EO for its further potential to promote intestinal repair in this mucositis model. Female Dark Agouti rats (n = 8/group) were gavaged with water, olive oil (OO) or EO once daily (1 mL), injected with 5-fluorouracil (5-FU) or saline on day 5 and euthanized on day 8, 9, 10 or 11. Intestinal villus height (VH) and crypt depth (CD), neutral mucin-secreting goblet cell (GC) count, myeloperoxidase (MPO) activity and selected cytokines were quantified; P < 0.05 was considered significant. In 5-FU-injected rats, only EO administration significantly increased VH in the ileum (day 8), jejunum and jejunum–ileum junction (days 8 and 9) compared to 5-FU controls (P < 0.05). GC count was significantly reduced by 5-FU (jejunum: days 8 and 9; ileum: day 8; P < 0.05) and EO increased ileal GC on days 10 and 11 compared to 5-FU controls. MPO activity was significantly increased in jejunum (days 8 and 9) and ileum (day 8) following 5-FU injection, compared to normal controls (P < 0.05). Both EO and OO significantly reduced jejunal MPO on days 8 and 9; however, only EO decreased ileal MPO on day 8. Cytokine levels were not significantly affected by either oil or 5-FU administration at the day 8 time point. Promotion of repair from injury could represent a new mechanism of action for EO, suggesting potential as an adjunct to conventional treatment approaches for cancer management.

Efficacy of Lactobacillus GG in aboriginal children with acute diarrhoeal disease: a randomised clinical trial.

Objective: The effectiveness of probiotic therapy for acute rotavirus infectious diarrhoea in an indigenous setting with bacterial/parasitic diarrhoea is unclear. In the present study, we assessed the efficacy of probiotics in Australian Aboriginal children in the Northern Territory admitted to hospital with diarrhoeal disease. Patients and Methods: A randomised double-blind placebo-controlled study was conducted in Aboriginal children (ages 4 months–2 years), admitted to hospital with acute diarrhoeal disease (>3 loose stools per day). Children received either oral Lactobacillus GG (5 × 109 colony-forming units 3 times per day for 3 days; n = 33) or placebo (n = 31). Small intestinal functional capacity was assessed by the noninvasive 13C-sucrose breath test on days 1 and 4. Results: Both groups showed mean improvement in the sucrose breath test after 4 days; however, there was no difference (mean, 95% confidence interval) between probiotic (2.9 [cumulative percentage of dose recovered at 90 minutes]; 1.7–4.2) and placebo (3.7; 2.3–5.2) groups. Probiotics did not change the duration of diarrhoea, total diarrhoea stools, or diarrhoea score compared with placebo. There was a significant (P < 0.05) difference in diarrhoea frequency on day 2 between probiotics (3.3 [loose stools]; 2.5–4.3) and placebo (4.7; 3.8–5.7) groups. Conclusions: Lactobacillus GG did not appear to enhance short-term recovery following acute diarrhoeal illness in this setting.

Measurements of zinc absorption : Application and interpretation in research designed to improve human zinc nutriture

The focus of this paper is on the application of measurements of zinc absorption in human research, especially studies designed to assess the efficacy of intervention strategies to prevent and manage zinc deficiency in populations. Emphasis is given to the measurement of quantities of zinc absorbed rather than restricting investigations to measurements of fractional absorption of zinc. This is especially important when determining absorption of zinc from the diet, whether it be the habitual diet or an intervention diet under evaluation. Moreover, measurements should encompass all meals for a minimum of one day with the exception of some pilot studies. Zinc absorption is primarily via an active saturable transport process into the enterocytes of the proximal small intestine. The relationship between quantity of zinc absorbed and the quantity ingested is best characterized by saturable binding models. When applied to human studies that have sufficient data to examine dose-response relationships, efficiency of absorption is high until approximately 50-60% maximal absorption is achieved, even with moderate phytate intakes. This also coincides approximately with the quantity of absorbed zinc necessary to meet physiologic requirements. Efficiency of absorption with intakes that exceed this level is low or very low. These observations have important practical implications for the design and interpretation of intervention studies to prevent zinc deficiency. They also suggest the potential utility of measurements of the quantity of zinc absorbed when evaluating the zinc status of populations.

Regional distribution and localization of Zinc and metallothionein in the intestine of rats fed diets differing in zinc content

BACKGROUND Zinc (Zn) is protective and enhances epithelial repair in gut diseases. In this study we investigate the localization and distribution of Zn and its binding protein, metallothionein (MT), in the gut of rats fed diets varying in Zn content. METHODS Male-Sprague Dawley rats were fed low, normal, high, or excess Zn in their diets (10, 100, 400, or 1000 mg Zn/kg, respectively) and killed 7 days later. Blood, liver, and gut tissues were collected. Tissue Zn was determined with atomic absorption spectrophotometery and MT with a Cd/haem affinity assay. Zn and MT were immunohistochemically localized in the small-intestinal wall with zinquin and an anti-MT antibody. RESULTS Most Zn in the intestinal wall was present in the mucosal scrapings, with 94% membrane-bound and 6% cytosolic, irrespective of dietary Zn. MT levels increased in all gut regions at dietary Zn levels above 100 mg Zn/kg. MT was 40% higher in the ileum than in other gut regions in rats fed low- and normal-Zn diets. The Zn content of the ileum was also 20% higher than that of other gut regions in rats fed low-, normal-, or high-Zn diets. Zn and MT were colocalized in the base of the intestinal crypts, most visibly in the ileum. CONCLUSION Mucosal cytosolic Zn and MT concentrations are increased only at high or excessive Zn intakes in all gut regions except the ileum, which can respond to a lower Zn intake. As the cytosolic Zn pool most likely influences mucosal protection and repair mechanisms, it is proposed that an increased MT may indicate the adequacy of oral Zn therapy in gut disease.

Regional Distribution of Metallothionein and Zinc in the Mouse Gut - Comparison With Metallothionien-Null Mice

Gut Zn homeostatic responses to low, replete, and excess dietary Zn (10, 150, and 400 mg Zn/kg, respectively) were compared in mice with (MT+/+) and without (MT−/−) metallothionein (MT) expression. MT concentrations decreased progressively from stomach (12.9 nmol Cd bound/g) to colon (4.6 nmol Cd bound/g). Small intestinal MT was increased in mice fed the 400-mg Zn/kg diet (+130%, duodenum; +56%, jejunum; +29%, terminal ileum), but not in the stomach, cecum and colon. Zn concentrations were much higher in the distal gut at increasing Zn intakes in MT+/+ mice but to a lesser extent in MT−/− mice. On the 10-mg Zn/kg diet, MT−/− mice had 45% more Zn in the jejunum/ileum than MT+/+ mice. In fasted (20 h) mice, Zn concentrations in all gut regions were similar to those of MT+/+ mice fed the 10-mg Zn/kg diet, irrespective of prior Zn intake or genotype. Liver MT quadrupled in mice fasted after the 10-mg Zn/kg diet but only doubled after the 400-mg Zn/kg diet, a trend also present in gut MT. Glucagon administration stimulated gut as well as liver MT, implicating it as a major component of the MT response to fasting. MT−/− mice had five times more variation than MT+/+ mice in plasma Zn over all dietary groups. Together, these findings demonstrate that without MT, there is little modification of regional gut Zn concentrations in response to extremes of dietary Zn and poorer regulation of Zn homeostasis.

Emu Oil: a novel therapeutic for disorders of the gastrointestinal tract?

Gastrointestinal diseases characterized by inflammation, including the inflammatory bowel diseases, chemotherapy‐induced mucositis and non‐steroidal anti‐inflammatory drug‐induced enteropathy, currently have variably effective treatment options, highlighting the need for novel therapeutic approaches. Recently, naturally‐sourced agents including prebiotics, probiotics, plant‐extracts and marine‐derived oils known to possess anti‐inflammatory and anti‐oxidant properties have been investigated in vitro and in vivo. However, animal‐derived oils are yet to be extensively tested. Emu Oil is extracted from the subcutaneous and retroperitoneal fat of the Emu, a flightless bird native to Australia, and predominantly comprises fatty acids. Despite the limited rigorous scientific studies conducted to date, with largely anecdotal claims, Emu Oil, when administered topically and orally, has been shown to possess significant anti‐inflammatory properties in vivo. These include a CD‐1 mouse model of croton oil‐induced auricular inflammation, experimentally‐induced polyarthritis and dextran sulfate sodium‐induced colitis. Recently, Emu Oil has been demonstrated to endow partial protection against chemotherapy‐induced mucositis, with early indications of improved intestinal repair. Emu Oil could therefore form the basis of an adjunct to conventional treatment approaches for inflammatory disorders affecting the gastrointestinal system.