Mouse lactose intolerance model experiment

Murine Lactose Intolerance Model Experiment – Preclinical Evaluation of Digestive Enzyme Products, Probiotics and Dietary Interventions

As an ISO/IEC 17025 accredited contract research laboratory, we offer specialised murine model experimentation services for the study of lactose intolerance – a common digestive disorder caused by insufficient lactase enzyme activity in the small intestine. Our models serve Bulgarian and international pharmaceutical, nutraceutical, and food ingredient companies seeking to evaluate the efficacy of lactase enzyme supplements, probiotic formulations, prebiotics, and novel dietary interventions. The mouse model of lactose intolerance reliably reproduces key clinical features – osmotic diarrhoea, abdominal distension, flatulence, and malabsorption – allowing for quantitative assessment of symptom relief, lactase activity restoration, and changes in the gut microbiome. All procedures are conducted in strict compliance with Directive 2010/63/EU, the Bulgarian Animal Welfare Act, and ARRIVE guidelines. Our reports are recognised by the Bulgarian Food Safety Agency (BFSA), the European Food Safety Authority (EFSA) reference laboratories, and pharmaceutical regulatory authorities for preclinical efficacy and safety data.

Mouse Strains and Husbandry Conditions

We use well‑characterised mouse strains that are responsive to lactose challenge and show consistent phenotypic responses. Typical models include:

• C57BL/6 and BALB/c mice – widely used immunocompetent strains with known baseline lactase activity and susceptibility to osmotic diarrhoea
• Lactase‑phlorizin hydrolase (LPH) knock‑out mice – genetically engineered to lack functional lactase, providing a robust model of severe congenital lactose intolerance
• SPF (Specific Pathogen‑Free) barrier facilities – with controlled temperature (22 ± 2 °C), humidity (55 ± 10 %), and 12‑hour light/dark cycles, with ad libitum access to standard chow and water (except during fasting periods)
• Age and sex standardisation – we use adult mice (6‑8 weeks old, males and females, as appropriate) to minimise developmental variability; gender‑specific responses are analysed separately when indicated

Lactose Challenge Protocol – Induction and Dosing

We employ a standardised acute lactose challenge protocol that reliably induces symptoms comparable to human lactose intolerance. The key parameters include:

• Fasting period – mice are fasted for 4‑6 hours before the lactose challenge to standardise baseline intestinal conditions
• Lactose dosage – a single oral gavage dose of lactose (typically 1‑2 g/kg body weight, dissolved in sterile water or phosphate‑buffered saline), chosen based on pilot dose‑finding studies to produce reproducible diarrhoea and gas accumulation
• Challenge formulation – lactose is prepared fresh, and a separate control group receives an equicaloric amount of glucose (which is readily absorbed) to differentiate between osmotic and malabsorption effects
• Duration – symptoms are monitored for 4‑8 hours post‑challenge (acute model) or repeated daily for 7‑14 days (sub‑chronic model) to evaluate adaptation and the effect of repeated dosing
• Faeces collection – we collect faeces at 0, 2, 4, and 8 hours post‑challenge for consistency scoring, moisture content measurement, and pH determination; a 4‑point faecal score (0 = normal, 3 = severe diarrhoea) is used

Assessment of Clinical and Intestinal Parameters

We use a multi‑parametric approach to capture the key effects of lactose malabsorption and to evaluate the efficacy of test interventions. The core endpoints include:

• Diarrhoea severity (faecal score) – each mouse is scored at each time point; the area under the curve (AUC) of faecal score vs. time is calculated as an integrated measure of symptom severity
• Faecal moisture content – fresh faeces are weighed, dried at 105 °C for 24 hours, and re‑weighed; percentage moisture is calculated; a moisture increase > 20 % indicates significant osmotic diarrhoea
• Abdominal distension and flatulence – assessed by measuring the abdominal circumference (at the level of the xiphoid process) and by scoring visible bloating (0‑3 scale) at 2‑hour intervals
• Intestinal transit time – we administer a non‑absorbable marker (e.g., carmine red or charcoal) together with the lactose challenge and record the time to first appearance in the faeces; a shorter transit time correlates with accelerated peristalsis due to osmotic pressure
• Lactase activity assay in small intestinal mucosa – at the end of the experiment, we dissect the proximal small intestine (duodenum and jejunum), homogenise the mucosal scrapings, and measure lactase activity using a colorimetric or fluorometric substrate (e.g., o‑nitrophenyl‑β‑D‑galactopyranoside – ONPG); results are expressed as units of activity per mg of protein
• Intestinal pH and short‑chain fatty acid (SCFA) concentration – we collect caecal contents and determine pH (using a micro‑electrode) and SCFA profiles (acetate, propionate, butyrate) by gas chromatography, which reflect fermentation of undigested lactose by the gut microbiota

Microbiome Analysis – Gut Microbiota Modulation

Lactose intolerance is closely linked to the composition and metabolic activity of the gut microbiome. We offer comprehensive microbiome profiling to evaluate product effects:

• 16S rRNA sequencing – we extract DNA from faecal samples (collected before and after intervention) and perform amplicon sequencing (V3‑V4 region) to characterise bacterial community composition, richness, and diversity (α and β diversity indices)
• Quantitative PCR (qPCR) for specific bacterial groups – we quantify key genera involved in lactose fermentation, such as Lactobacillus, Bifidobacterium, Bacteroides, and Clostridium clusters, using genus‑specific primers
• Metagenomic functional prediction (PICRUSt2) – based on 16S profiles, we predict the abundance of genes encoding β‑galactosidase, carbohydrate‑active enzymes (CAZymes), and short‑chain fatty acid biosynthesis pathways
• Faecal pH and gas composition – we measure hydrogen and methane production in faecal headspace using a micro‑gas chromatograph, which provides a non‑invasive indicator of fermentative activity

Intervention Efficacy Testing – Enzyme Supplements, Probiotics and Dietary Modifications

Our model is designed to screen and compare multiple therapeutic strategies. Typical interventions include:

• Lactase enzyme supplements – administered orally (by gavage) together with or immediately before the lactose challenge; we evaluate the dose‑response and the timing of enzyme delivery on diarrhoea reduction and lactase activity preservation
• Probiotic strains – we give mice a 7‑14 day pre‑treatment of the test probiotic (e.g., Lactobacillus acidophilus, Bifidobacterium longum, or a multi‑strain consortium) at 10⁹‑10¹⁰ CFU/day, and then challenge with lactose; we assess symptom reduction and changes in faecal microbial composition and β‑galactosidase activity
• Prebiotics and dietary fibres – we test the effect of oligosaccharides (e.g., galacto‑oligosaccharides – GOS, fructo‑oligosaccharides – FOS) on lactose fermentation and symptom alleviation, measured by faecal SCFA levels and abdominal distension
• Combination products – we evaluate synergistic effects of enzyme + probiotic + prebiotic combinations
• Dietary modifications – we compare the effect of low‑lactose diets, milk processing (e.g., ultra‑high temperature, fermentation), or alternative dairy sources (e.g., lactose‑free milk) on symptom occurrence

Standardisation and Quality Control

To ensure reproducibility and comparability across experiments, we implement strict quality controls:

• Positive control – a group receiving an established lactase supplement (e.g., a standard commercially available enzyme) to validate the model and demonstrate the expected clinical improvement
• Negative control – a group receiving a non‑absorbable carbohydrate (e.g., sorbitol) that produces osmotic diarrhoea but is not substrate for lactase, allowing differentiation between osmotic and enzymatic effects
• Sham gavage group – mice gavaged with water or vehicle, to assess the effect of the gavage procedure itself
• Baseline lactase activity – a cohort of untreated mice is sacrificed at the start of the experiment to establish normal lactase activity for the strain and age group
• Randomisation and blinding – animals are randomly assigned to treatment groups, and the observer (scoring symptoms) is blinded to the treatment allocation

Ethical Compliance, Welfare and Study Approval

All experiments are performed in accordance with Directive 2010/63/EU and the Bulgarian Animal Welfare Act. Our animal facility is registered with the Bulgarian Food Safety Agency (BFSA) and operates under an institutional ethics committee. We follow the 3Rs principles:

• Replacement – we use ex vivo intestinal sacs and Caco‑2 cell models for initial screening of enzyme activity and permeability before moving to in vivo studies
• Reduction – sample sizes are determined by power analysis (typically 6‑8 animals per group) to detect a clinically meaningful difference (e.g., 30 % reduction in faecal score) with 80 % power and α=0.05; we also use repeated‑measures designs to reduce inter‑animal variability
• Refinement – we use non‑invasive faecal scoring and abdominal circumference measurement to minimise handling stress; animals showing > 20 % weight loss, severe dehydration, or persistent distress are euthanised early and excluded from the analysis

Report Acceptance & Compliance with Bulgarian and EU Regulatory Frameworks

All murine lactose intolerance model experiments are performed under our ISO/IEC 17025 accreditation and in compliance with Good Laboratory Practice (GLP) principles. Our final study reports provide a complete experimental plan (including ethical approval number, study design, and statistical analysis), raw data for all endpoints (faecal scores, moisture, transit time, lactase activity, microbiome data), graphical summaries (time‑course curves, bar charts, principal coordinate analysis for microbiome), a detailed discussion of treatment efficacy and statistical significance, and a clear conclusion on whether the tested product shows promise in alleviating lactose intolerance symptoms. These reports are accepted by the Bulgarian Food Safety Agency (BFSA), the European Food Safety Authority (EFSA), and Bulgarian and international pharmaceutical and food ingredient companies for product development, label claims, and market authorisation. Bilingual (Bulgarian/English) versions are available for ease of submission to national and European regulatory bodies.