Intestinal antimicrobial gene expression: impact of micronutrients in malnourished adults during a randomized trial.

BACKGROUND: Because both micronutrients and antimicrobial peptides protect against diarrhea, we looked for an effect on intestinal antimicrobial peptide gene expression during a randomized controlled trial of multiple micronutrient (MM) supplementation. METHODS: Consenting adults (n=287) in Lusaka, Zambia, were randomized to receive a daily MM supplement or placebo and were followed up for 3.3 years, with a crossover after 2 years. Intestinal biopsy samples were obtained at annual intervals, and messenger RNA of the intestinal antimicrobial peptides human alpha defensin (HD) 5, HD6, human beta-defensin (hBD) 1, hBD2, and LL-37 were quantified by real-time reverse-transcriptase polymerase chain reaction. Samples were also obtained during diarrhea episodes and after convalescence. RESULTS: There was no effect overall of treatment allocation. However, in malnourished adults (body mass index < or =18.5), HD5 mRNA was increased by 0.8 log transcripts/microg total RNA in MM recipients, compared with HD5 mRNA in placebo recipients (P=.007). During diarrhea, HD5 expression was reduced by 0.8 log transcripts in placebo recipients (P=.02) but was not reduced in MM recipients, nor was it reduced after the crossover. Correlations between HD5 and nutritional status were found that were sex-specific but not explained by serum leptin or adiponectin concentrations. CONCLUSIONS: Micronutrient supplementation was associated with up-regulation of HD5 only in malnourished adults. Interactions between antimicrobial gene expression and nutritional status may help to explain the increased risk of infection in individuals with malnutrition.

Cytokine activation is predictive of mortality in Zambian patients with AIDS-related diarrhoea.

BACKGROUND: Mortality in Zambian AIDS patients is high, especially in patients with diarrhoea, and there is still unacceptably high mortality in Zambian patients just starting anti-retroviral therapy. We set out to determine if high concentrations of serum cytokines correlate with mortality. METHODS: Serum samples from 30 healthy controls (HIV seropositive and seronegative) and 50 patients with diarrhoea (20 of whom died within 6 weeks) were analysed. Concentrations of tumour necrosis factor receptor p55 (TNFR p55), macrophage migration inhibitory factor (MIF), interleukin (IL)-6, IL-12, interferon (IFN)-gamma and C-reactive protein (CRP) were measured by ELISA, and correlated with mortality after 6 weeks follow-up. RESULTS: Apart from IL-12, concentrations of all cytokines, TNFR p55 and CRP increased with worsening severity of disease, showing highly statistically significant trends. In a multivariable analysis high TNFR p55, IFN-gamma, CRP and low CD4 count (CD4 count <100) were predictive of mortality. Although nutritional status (assessed by body mass index, BMI) was predictive in univariate analysis, it was not an independent predictor in multivariate analysis. CONCLUSION: High serum concentrations of TNFR p55, IFN-gamma, CRP and low CD4 count correlated with disease severity and short-term mortality in HIV-infected Zambian adults with diarrhoea. These factors were better predictors of survival than BMI. Understanding the cause of TNFR p55, IFN-gamma and CRP elevation may be useful in development of interventions to reduce mortality in AIDS patients with chronic diarrhoea in Africa.

Distribution, proliferation, and function of Paneth cells in uncomplicated and complicated adult celiac disease.

Paneth cells, granulated epithelial cells located at the base of small bowel crypts, have a crucial role in innate immunity. Because controversies remain concerning Paneth cell numbers and function in celiac disease (CD), we quantified Paneth cells and human alpha-defensin (HD)-5 and HD-6 in 28 patients with uncomplicated CD, 8 patients with complicated CD (3 with ulcerative jejunoileitis, 2 with refractory sprue, and 3 with enteropathy-associated T-cell lymphoma), and 14 control subjects. Paneth cell numbers and proliferation did not differ in uncomplicated untreated and treated CD and control cases. However, the number of Paneth cells was significantly reduced in complicated CD. Mucosal HD-5 and HD-6 were comparable in uncomplicated untreated and treated CD and control cases. Ex vivo gliadin challenge of treated CD biopsy specimens had no effect on mucosal HD-5 and HD-6 transcripts. Paneth cell numbers and alpha-defensins are unchanged in the mucosa in uncomplicated CD. Further studies are needed to clarify the implications of reduction of numbers of Paneth cells in complicated CD.

Reduced gene expression of intestinal alpha-defensins predicts diarrhea in a cohort of African adults.

BACKGROUND: Human defensin (HD) 5 and HD6, both Paneth cell alpha-defensins, contribute to the antimicrobial barrier against intestinal infection. We have previously demonstrated that levels of both HD5 and HD6 mRNA were reduced in adults living in urban Zambia, compared with those in adults living in London. The aim of the present study was to determine, during 2 years of follow-up, whether alpha-defensin expression in Zambian adults is related to susceptibility to diarrhea. METHODS: We analyzed intestinal biopsy samples from a longitudinal cohort study conducted in 83 Zambian adults by quantitative reverse-transcription polymerase chain reaction, Western blotting, immunohistochemistry, and in situ hybridization, and we measured the incidence of diarrhea. RESULTS: Levels of HD5 and HD6 mRNA in Paneth cells varied between participants, over time, and seasonally and were strongly correlated with mucosal architecture. Gene expression was almost exclusively restricted to Paneth cells. The median (interquartile range) HD5 mRNA level was 6.0 (5.6-6.7) log10 transcripts/microg of total RNA among 18 participants who experienced diarrhea within 2 months after biopsy-sample collection, compared with 6.8 (6.2-7.3) log10 transcripts/microg of total RNA among 94 participants who did not (P=.006). A similar observation was made for HD6. CONCLUSIONS: These data indicate that intestinal alpha-defensin expression is dynamic and seasonal and suggest that susceptibility to intestinal infection is related to alpha-defensin expression.

Intestinal defensin gene expression in human populations.

Defensins are thought to play a major role in the defence of small intestinal crypts against colonisation by potential pathogens. In humans two alpha-defensins, HD5 and HD6 and two beta-defensins, hBD1 and hBD2, probably contribute to the antimicrobial barrier, but there are no data to indicate how the expression of these defensin genes might vary in individuals and in populations. To begin to address this question we developed a competitive reverse transcriptase polymerase chain reaction (RT-PCR) assay to quantify HD5 and HD6 mRNA and used it to measure transcripts in small intestinal biopsy tissue from adults living in London, UK, or in Lusaka, Zambia. We also measured alpha- and beta-defensin mRNA in biopsies collected in London from different regions of the small intestine. Jejunal biopsies (n=169) from 83 adults in Lusaka contained approximately one order of magnitude less HD5 and HD6 mRNA than biopsies (n=33) obtained from 27 adults in London. HD5 and HD6 transcript levels were high throughout duodenum, jejunum and ileum. hBD1 and hBD2 mRNA were detected in some, but not all, biopsies from normal small intestine. These data suggest that alpha-defensin expression is down-regulated in tropical populations, and that there are distinct pathways regulating transcription of alpha- and beta-defensins.