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Hedi Raizer

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What markers track intestinal permeability?

Intestinal permeability is assessed with sugar-absorption probes such as the urinary lactulose:mannitol ratio, alongside barrier-protein and inflammatory readouts. This page summarises the markers and models reported in

peptides-pro Editorial

Intestinal permeability is the functional property of the gut epithelium that governs the rate at which solutes cross from the lumen into the systemic compartment, and it is tracked with a defined set of markers rather than a single measurement. The most frequently specified marker in the supplied evidence is the urinary lactulose:mannitol ratio, collected over a 5-hour test window, which is used as the primary permeability endpoint in a collagen peptide dose-comparison trial in healthy adults [6]. Other markers named across the evidence include fasting high-sensitivity C-reactive protein as a subclinical inflammation readout [5], and barrier-integrity endpoints measured in cell culture and in murine colitis models [1].

The mechanistic work in this evidence centres on the intestinal epithelial barrier and its response to dietary peptides, fibre substrates, and microbial metabolites, with the tight-junction and mucus layers as the operative structures and the gut microbiota as a modifying input [1][2][7][8].

Research Studies

Collagen peptides and barrier integrity in Caco-2 and murine colitis models

A low-molecular-weight collagen peptide fraction (LSCP-I, under 3 kDa) derived from Lutjanus erythropterus scales was evaluated in Caco-2 cell monolayers subjected to macrophage-mediated inflammatory injury and in murine models of colitis [1]. In the Caco-2 system at 50 µg/mL, the fraction increased proliferation by 35% and migration by 40%, preserved barrier integrity, reduced reactive oxygen species by 45%, decreased lipid peroxidation by 30%, and restored glutathione and superoxide dismutase [1]. These are in vitro and animal findings; they do not establish an effect in humans.

Collagen peptide and the urinary lactulose:mannitol ratio in healthy adults

A registered clinical trial is evaluating 45 days of daily collagen peptide administration at three doses (2.5 g, 5 g, and 10 g) versus placebo in healthy adults, with intestinal permeability measured by the urinary lactulose:mannitol ratio collected over 5 hours [6]. The primary comparison is the change from Day 42 to Day 45 following an acute aspirin challenge, an NSAID-based permeability provocation [6]. This is a registered protocol; results are not reported in the supplied evidence.

Oral glutamine and sex-dependent gut responses in diet-induced obesity

Male and female C57BL/6 mice received a standard or high-fat diet (60% kcal from fat) for 14 weeks, with glutamine in drinking water (2 g/kg/day) or no supplementation from week 12 onward [2]. The study characterised body composition, glucose tolerance, insulin sensitivity, intestinal permeability, and colon outcomes, and reported opposite metabolic and gut responses between male and female mice [2]. This is an animal study; the sex-dependent divergence is a finding in mice, not a human dose or recommendation.

Zein-based nanoparticles and oral peptide permeability in Danio rerio

Hybrid zein-Eudragit RS100-chitosan nanoparticles were developed for oral co-delivery of insulin and liraglutide, with the stated aim of protecting both peptides from enzymatic degradation and supporting oral administration [3]. The particles showed a nanoscale size of approximately 230 nm, a polydispersity index below 0.1, and a positive zeta potential of approximately +46 mV, with structural and thermal analysis indicating a predominantly amorphous and molecularly dispersed system [3]. Preliminary in vivo evaluation was performed in Danio rerio [3].

Inulin and Bacillus coagulans BC30 and fasting inflammation markers

A randomised, double-blind, controlled crossover study is testing a sugar-based synbiotic containing inulin and Bacillus coagulans BC30 spores in healthy overweight individuals, with 20 participants completing a 2-week run-in and two 4-week intervention periods separated by a 4-week washout [5]. Each intervention provides 1 × 10⁹ CFU/day of BC30 or a matched control sugar product containing inulin without probiotic spores [5]. The primary outcome is change in fasting markers of subclinical inflammation, including high-sensitivity C-reactive protein [5].

Inulin and pectin fibre and permeability in alcohol use disorder

A clinical trial is testing a fibre-enriched diet with a high proportion of inulin and pectin, combined with standard care, in patients with alcohol use disorder aged 19 to 65, with the stated hypothesis that modifying the gut microbiota and its metabolites will decrease intestinal permeability and restore microbiota composition [7]. Secondary targets named in the protocol include abstinence, craving, anxiety, inflammation, steatosis, and hepatic fibrosis [7].

Akkermansia muciniphila and berberine in night-shift workers

A registered trial is examining Akkermansia muciniphila and berberine supplementation in night-shift workers, a population described as having increased risk of obesity, insulin resistance, and cardiometabolic disorders due to circadian misalignment, disrupted sleep, and altered eating patterns [8]. A. muciniphila is linked in the protocol background to improved metabolic health, including enhanced insulin sensitivity, lipid regulation, and maintenance of intestinal barrier integrity, while berberine is described as upregulating A. muciniphila and improving insulin sensitivity [8].

Rowing exercise and multilevel intestinal permeability readouts

An observational study of 30 members of the Polish Youth National Rowing Team, aged 19 to 24 years, is designed to evaluate multilevel physiological, molecular, metabolic, intestinal, immunological, and psychophysiological responses to rowing-specific exercise [4]. The protocol states that it will investigate how maximal and prolonged rowing ergometer exercise, including a 2000-m maximal effort during the competitive phase, influences integrated adaptive mechanisms related to mitochondrial function, metabolic regulation, intestinal permeability, immune activation, DNA damage response, and psychological status [4].

Permeation enhancers and PROTAC transport in rats

A study examined the effects of intestinal permeation enhancers on the solubilization and epithelial transport of the proteolysis targeting chimera ARV-471 in rats [9]. The work reports that PROTAC molecular properties often fall outside the rule-of-five chemical space associated with poor intestinal solubility, permeability, and absorption, and that formulation strategies have primarily focused on solubility enhancement rather than intrinsic permeability [9].

Natural products and NSAID-induced small intestinal injury

A systematic review evaluated natural products, functional foods, and probiotics for preventing or treating NSAID-induced small intestinal injury, a complication described as clinically significant among chronic NSAID and aspirin users with limited effective treatment options [10]. The review includes mechanistic considerations of oxidative stress and microbiome modulation [10].

Marker comparison across the supplied evidence

Marker or endpointSpecimen or modelSource
Urinary lactulose:mannitol ratio (5-hour collection)Healthy adults, aspirin challenge[6]
Intestinal permeability (unspecified assay)Male and female C57BL/6 mice, high-fat diet[2]
Barrier integrity, ROS, lipid peroxidation, GSH, SODCaco-2 cells; murine colitis[1]
High-sensitivity C-reactive proteinHealthy overweight adults[5]
Intestinal permeability (multilevel panel)Elite rowers, aged 19–24[4]
Intestinal permeability (fibre intervention)Adults with alcohol use disorder, 19–65[7]
Barrier integrity (microbiota-linked)Night-shift workers[8]

Related marker contexts in the supplied evidence

Two reference items in the evidence set address adjacent marker questions. A review of diagnostic and prognostic biomarkers in polycystic ovary syndrome examines insulin resistance, systemic inflammation, and endometrial receptivity, with insulin resistance described as a central molecular driver of metabolic and reproductive complications [11]. A study of canagliflozin in indomethacin-induced peptic ulcer reports effects on inflammation, pyroptosis, autophagy, and gut integrity [12]. Neither is a permeability-marker study in its own right; they are included here as context for how barrier and inflammatory readouts are used across gastrointestinal and metabolic research.

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