A systematic review examining the impact of blended diets on the gastrointestinal symptoms of people who are enterally fed.

BACKGROUND: Adults and children who are enterally tube-fed can experience adverse gastrointestinal symptoms (GIS). Observational data suggests that blended diets (BD) could mitigate such symptoms, with potential to improve quality of life and clinical outcomes. We present a novel systematic review examining the impact of BD, compared to commercial feeds, on GIS of adults and children who are tube-fed. METHODS: The protocol was registered with PROSPERO (CRD42021261147). Four electronic databases were searched from inception to August 2021. Search terms included 'tube-fed', 'blended diet' and 'formula'. Inclusion criteria were intervention studies comparing blended and commercial feeds using quantitative measures of GIS. Heterogeneity of outcome measures precluded meta-analysis; therefore, a narrative synthesis was conducted. RESULTS: Six papers (n = 219), including two randomised control trials (RCT) and four single arm pre-post studies, were identified. Equal numbers studied in- and out-patients, adults and children. Risk of bias was notable for all studies. Equivocal and insufficient evidence prevented consensus on outcomes of vomiting, gagging, oral intake, bloating and constipation. However, one RCT and two single arm pre-post studies suggest that diarrhoea symptoms may be improved on BD. CONCLUSIONS: Diarrhoea is prevalent in tube-fed populations and associated with adverse outcomes. Improvements in diarrhoea symptoms attributed to BD may be clinically important. Our findings are congruous with the wider observational evidence base, and support recommendations of the British Dietetic Association. BD may pose a viable alternative to commercial formula, and may mitigate symptoms of diarrhoea for adults and children who are tube-fed.

Regressive evolution of an effector following a host jump in the Irish potato famine pathogen lineage.

In order to infect a new host species, the pathogen must evolve to enhance infection and transmission in the novel environment. Although we often think of evolution as a process of accumulation, it is also a process of loss. Here, we document an example of regressive evolution of an effector activity in the Irish potato famine pathogen (Phytophthora infestans) lineage, providing evidence that a key sequence motif in the effector PexRD54 has degenerated following a host jump. We began by looking at PexRD54 and PexRD54-like sequences from across Phytophthora species. We found that PexRD54 emerged in the common ancestor of Phytophthora clade 1b and 1c species, and further sequence analysis showed that a key functional motif, the C-terminal ATG8-interacting motif (AIM), was also acquired at this point in the lineage. A closer analysis showed that the P. mirabilis PexRD54 (PmPexRD54) AIM is atypical, the otherwise-conserved central residue mutated from a glutamate to a lysine. We aimed to determine whether this PmPexRD54 AIM polymorphism represented an adaptation to the Mirabilis jalapa host environment. We began by characterizing the M. jalapa ATG8 family, finding that they have a unique evolutionary history compared to previously characterized ATG8s. Then, using co-immunoprecipitation and isothermal titration calorimetry assays, we showed that both full-length PmPexRD54 and the PmPexRD54 AIM peptide bind weakly to the M. jalapa ATG8s. Through a combination of binding assays and structural modelling, we showed that the identity of the residue at the position of the PmPexRD54 AIM polymorphism can underpin high-affinity binding to plant ATG8s. Finally, we conclude that the functionality of the PexRD54 AIM was lost in the P. mirabilis lineage, perhaps owing to as-yet-unknown selection pressure on this effector in the new host environment.