Primary Research · 2013
Meta-analysis: Lactobacillus GG for treating acute gastroenteritis in children
Szajewska et al. · Alimentary Pharmacology & Therapeutics, 2013
Key finding
LGG reduced diarrhea duration by roughly 25 hours in pediatric gastroenteritis across multiple RCTs.
Abstract
PubMed · PMID 17521331 →Cathepsin E (CatE) and D (CatD) are the major aspartic proteinases in the endolysosomal pathway. They have similar specificity and therefore it is difficult to distinguish between them, as known substrates are not exclusively specific for one or the other. In this paper we present a substrate-based assay, which is highly relevant for immunological investigations because it detects both CatE and CatD in antigen-processing organelles. Therefore it could be used to study the involvement of these proteinases in protein degradation and the processing of invariant chain. An assay combining a new monospecific CatE antibody and the substrate, MOCAc-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys(Dnp)-D-Arg-NH2[where MOCAc is (7-methoxycoumarin-4-yl)acetyl and Dnp is dinitrophenyl], is presented. This substrate is digested by both proteinases and therefore can be used to detect total aspartic proteinase activity in biological samples. After depletion of CatE by immunoprecipitation, the remaining activity is due to CatD, and the decrease in activity can be assigned to CatE. The activity of CatE and CatD in cytosolic, endosomal and lysosomal fractions of B cells, dendritic cells and human keratinocytes was determined. The data clearly indicate that CatE activity is mainly located in endosomal compartments, and that of CatD in lysosomal compartments. Hence this assay can also be used to characterize subcellular fractions using CatE as an endosomal marker, whereas CatD is a well-known lysosomal marker. The highest total aspartic proteinase activity was detected in dendritic cells, and the lowest in B cells. The assay presented exhibits a lower detection limit than common antibody-based methods without lacking the specificity.
Abstract sourced from PubMed, a database of the U.S. National Library of Medicine. Displayed in the authors’ own words for context; our critique is in the sections below.
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How to read a study like this
The same questions worth asking about any research paper, not just this one. Worth a minute even if you trust the grade.
Who was studied, and do you resemble them?
Supplement effects often depend on baseline status. Vitamin D helps people who are deficient; iron helps people who are anemic. A result in people unlike you may not apply to you.
What was measured, and does it matter in daily life?
A study that shows a blood marker moved isn't the same as a study that shows people felt or functioned better. Ask what the outcome means in practice.
How large was the effect — not just whether it was significant.
'Statistically significant' only means the effect is unlikely to be zero. It doesn't tell you the effect is large enough to notice. Look for effect sizes, not just p-values.
Who paid for the trial, and what did they stand to gain?
Industry-funded trials are several times more likely to report positive results than independent ones. It's not usually fraud — it's subtle design and reporting choices. Weight accordingly.
Has anyone else replicated this?
Single positive trials are hypotheses. Replication by independent groups is what turns a hypothesis into reliable evidence. If the only positive trial is the one you're reading, wait.
Does the dose in the trial match what's being sold?
Supplement marketing routinely cites trials that used 5–10× the dose in the product. If the effective dose was 2 g/day and the capsule has 200 mg, expect roughly no effect.
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