Microbial exposures in infancy predict levels of the immunoregulatory cytokine interleukin-4 in Filipino young adults

Prenatal household size and composition are associated with infant fecal bacterial diversity in Cebu, Philippines

OBJECTIVES

The gut microbiome (GM) connects physical and social environments to infant health. Since the infant GM affects immune system development, there is interest in understanding how infants acquire microbes from mothers and other household members.

MATERIALS AND METHODS

As a part of the Cebu Longitudinal Health and Nutrition Survey (CLHNS), we paired fecal samples (proxy for the GM) collected from infants living in Metro Cebu, Philippines at 2 weeks (N = 39) and 6 months (N = 36) with maternal interviews about prenatal household composition. We hypothesized that relationships between prenatal household size and composition and infant GM bacterial diversity (as measured in fecal samples) would vary by infant age, as well as by household member age and sex. We also hypothesized that infant GM bacterial abundances would differ by prenatal household size and composition.

RESULTS

Data from 16 S rRNA bacterial gene sequencing show that prenatal household size was the most precise estimator of infant GM bacterial diversity, and that the direction of the association between this variable and infant GM bacterial diversity changed between the two time points. The abundances of bacterial families in the infant GM varied by prenatal household variables.

CONCLUSIONS

Results highlight the contributions of various household sources to the bacterial diversity of the infant GM, and suggest that prenatal household size is a useful measure for estimating infant GM bacterial diversity in this cohort. Future research should measure the effect of specific sources of household bacterial exposures, including social interactions with caregivers, on the infant GM.

Maternal serum cytokine levels and risk of bipolar disorder

Prenatal exposure to influenza has previously been associated with increased risk of bipolar disorder (BD), an association that may be mediated by maternal cytokines. The objective of this study was to determine the association between maternal levels of cytokines measured during each trimester of pregnancy and the risk of BD in offspring. We conducted a case-control study nested in the Child Health and Development Study, a birth cohort that enrolled pregnant women in 1959-1966. Potential cases with DSM-IV-TR bipolar I disorder, bipolar II disorder, BD not otherwise specified, and BD with psychotic features were ascertained through electronic medical records, a public agency database, and a mailing to the cohort. Diagnoses were confirmed by clinical interview. Nine cytokines (IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IFN-γ, TNF-α and GM-CSF) were measured simultaneously by Luminex assays in archived prenatal maternal serum samples from 85 cases and 170 matched controls. Data were analyzed using conditional logistic regression. In the overall study sample, there were no significant associations between prenatal maternal cytokine levels and BD after adjustment for confounders. The risk of BD without psychotic features was decreased among subjects with higher maternal levels of first trimester log-transformed IL-4 (OR (95% CI)=0.76 (0.58, 0.98); p=0.04) and third trimester log-transformed IL-6 (OR (95% CI)=0.64 (0.42, 0.98); p=0.04). In conclusion, higher levels of prenatal maternal cytokines were not associated with increased risk for BD. Further studies with larger samples are necessary to confirm the finding.

Hygiene and the world distribution of Alzheimer's disease: Epidemiological evidence for a relationship between microbial environment and age-adjusted disease burden

People living in sanitized environments may be at greater Alzheimer's risk. We compare Alzheimer's rates in different countries in light of countries' historical and contemporary pathogen prevalence, sanitation, and urbanization. We find that countries that are less urbanized, with more pathogens and lower degree of sanitation have lower Alzheimer's rates.

Background and objectives: Alzheimer’s disease (AD) shares certain etiological features with autoimmunity. Prevalence of autoimmunity varies between populations in accordance with variation in environmental microbial diversity. Exposure to microorganisms may improve individuals’ immunoregulation in ways that protect against autoimmunity, and we suggest that this may also be the case for AD. Here, we investigate whether differences in microbial diversity can explain patterns of age-adjusted AD rates between countries.

Methodology: We use regression models to test whether pathogen prevalence, as a proxy for microbial diversity, across 192 countries can explain a significant amount of the variation in age-standardized AD disability-adjusted life-year (DALY) rates. We also review and assess the relationship between pathogen prevalence and AD rates in different world populations.

Results: Based on our analyses, it appears that hygiene is positively associated with AD risk. Countries with greater degree of sanitation and lower degree of pathogen prevalence have higher age-adjusted AD DALY rates. Countries with greater degree of urbanization and wealth exhibit higher age-adjusted AD DALY rates.

Conclusions and implications: Variation in hygiene may partly explain global patterns in AD rates. Microorganism exposure may be inversely related to AD risk. These results may help predict AD burden in developing countries where microbial diversity is rapidly diminishing. Epidemiological forecasting is important for preparing for future healthcare needs and research prioritization.