Biology subjects

Woller, A.

Publications and source records attributed to Woller, A..

3 recordsLinked to original sources

bioRxiv2024

Quantification of beta cell carrying capacity in prediabetes

Prediabetes, a subclinical state of high glucose, carries a risk of transition to diabetes. One cause of prediabetes is insulin resistance, which impairs the ability of insulin to control blood glucose. However, many individuals with high insulin resistance retain normal glucose due to compensation by enhanced insulin secretion by beta cells. Individuals seem to differ in their maximum compensation level, termed beta cell carrying capacity, such that low carrying capacity is associated with a higher risk of prediabetes and diabetes. Carrying capacity has not been quantified using a mathematical model and cannot be estimated directly from measured glucose and insulin levels in patients, unlike insulin resistance and beta cell function which can be estimated using HOMA-IR and HOMA-B formula. Here we present a mathematical model of beta cell compensation and carrying capacity, and develop a new formula called HOMA-C to estimate it from glucose and insulin measurements. HOMA-C estimates the maximal potential beta cell function of an individual, rather than the current beta cell function. We test this approach using longitudinal cohorts of prediabetic people, finding 10-fold variation in carrying capacity. Low carrying capacity is associated with higher risk of transitioning to diabetes. We estimate the timescales of beta cell compensation and insulin resistance using large datasets, showing that, unlike previous mathematical models, the new model can explain the slow rise in glucose over decades. Our mathematical understanding of beta cell carrying capacity may help to assess the risk of prediabetes in each individual.

systems biology↗

bioRxiv2022

Combined oral vaccination with niche competition can generate sterilizing immunity against entero-pathogenic bacteria

Colonization of the intestinal lumen precedes invasive infection for a wide range of enteropathogenic and opportunistic pathogenic bacteria. Here we show that combining oral vaccination with engineered or selected niche-competitor strains permits pathogen exclusion and strain replacement in the mouse gut lumen. This approach can be applied both prophylactically to prevent invasion of non-typhoidal Salmonella strains, or therapeutically to displace an established Escherichia coli. Both intact adaptive immunity and metabolic niche competition are necessary for efficient vaccine-enhanced competition. Our findings imply that mucosal antibodies have evolved to work in the context of gut microbial ecology, by influencing the outcome of competition. This has broad implications for the elimination of pathogenic and antibiotic-resistant bacterial reservoirs, and for rational microbiota engineering.

microbiology↗

bioRxiv2022

Fitness advantage of Bacteroides thetaiotaomicron capsular polysaccharide is dependent on the resident microbiota

Many microbiota-based therapeutics rely on our ability to introduce a microbe of choice into an already-colonized intestine. However, we remain largely blind to the quantitative effects of processes determining colonization success. In this study, we used genetically-barcoded Bacteroides thetaiotaomicron (B.theta) strains in combination with mathematical modeling to quantify population bottlenecks experienced by B.theta during gut colonization. Integrating population bottlenecks sizes with careful quantification of net growth rates in vivo and in vitro allows us to build models describing the events during intestinal colonization in the context of gnotobiotic and complex microbiotas. Using these models, we estimated the decrease in niche size for B.theta colonization with increasing microbiota complexity. In addition, our system can be applied to mechanistically dissect colonization defects of mutant strains. As a proof of concept, we demonstrated that the competitive disadvantage of a B.theta mutant lacking capsular polysaccharide is due to a combination of an increased lag-phase before growth initiation in the gut, combined with an increased clearance rate. Crucially, the requirement for the B.theta capsule depended strongly on microbiota composition, suggesting that the dominant role may be protection from bacterial or phage aggression rather than from host-induced bactericidal mechanisms.

microbiology↗