Using naso- and oro-intestinal catheters in physiological research for intestinal delivery and sampling in vivo: practical and technical aspects to be considered

Intestinal catheters have been used for decades in human nutrition, physiology, pharmacokinetics, and gut microbiome research, facilitating the delivery of compounds directly into the intestinal lumen or the aspiration of intestinal fluids in human subjects. Such research provides insights about (local) dynamic metabolic and other intestinal luminal processes, but working with catheters might pose challenges to biomedical researchers and clinicians. Here, we provide an overview of practical and technical aspects of applying naso- and oro-intestinal catheters for delivery of compounds and sampling luminal fluids from the jejunum, ileum, and colon in vivo. The recent literature was extensively reviewed, and combined with experiences and insights we gained through our own clinical trials. We included 60 studies that involved a total of 720 healthy subjects and 42 patients. Most of the studies investigated multiple intestinal regions (24 studies), followed by studies investigating only the jejunum (21 studies), ileum (13 studies), or colon (2 studies). The ileum and colon used to be relatively inaccessible regions in vivo. Custom-made state-of-the-art catheters are available with numerous options for the design, such as multiple lumina, side holes, and inflatable balloons for catheter progression or isolation of intestinal segments. These allow for multiple controlled sampling and compound delivery options in different intestinal regions. Intestinal catheters were often used for delivery (23 studies), sampling (10 studies), or both (27 studies). Sampling speed decreased with increasing distance from the sampling syringe to the specific intestinal segment (i.e., speed highest in duodenum, lowest in ileum/colon). No serious adverse events were reported in the literature, and a dropout rate of around 10% was found for these types of studies. This review is highly relevant for researchers who are active in various research areas and want to expand their research with the use of intestinal catheters in humans in vivo.

A Proinflammatory Gut Microbiota Increases Systemic Inflammation and Accelerates Atherosclerosis

Supplemental Digital Content is available in the text.

Rationale:

Several studies have suggested a role for the gut microbiota in inflammation and atherogenesis. A causal relation relationship between gut microbiota, inflammation, and atherosclerosis has not been explored previously.

Objective:

Here, we investigated whether a proinflammatory microbiota from Caspase1^−/− (Casp1^−/−) mice accelerates atherogenesis in Ldlr^−/− mice.

Method and Results:

We treated female Ldlr^−/− mice with antibiotics and subsequently transplanted them with fecal microbiota from Casp1^−/− mice based on a cohousing approach. Autologous transplantation of fecal microbiota of Ldlr^−/− mice served as control. Mice were cohoused for 8 or 13 weeks and fed chow or high-fat cholesterol–rich diet. Fecal samples were collected, and factors related to inflammation, metabolism, intestinal health, and atherosclerotic phenotypes were measured. Unweighted Unifrac distances of 16S rDNA (ribosomal DNA) sequences confirmed the introduction of the Casp1^−/− and Ldlr^−/− microbiota into Ldlr^−/− mice (referred to as Ldlr^−/−(Casp1^−/−) or Ldlr^−/−(Ldlr^−/−) mice). Analysis of atherosclerotic lesion size in the aortic root demonstrated a significant 29% increase in plaque size in 13-week high-fat cholesterol–fed Ldlr^−/−(Casp1^−/−) mice compared with Ldlr^−/−(Ldlr^−/−) mice. We found increased numbers of circulating monocytes and neutrophils and elevated proinflammatory cytokine levels in plasma in high-fat cholesterol–fed Ldlr^−/−(Casp1^−/−) compared with Ldlr^−/−(Ldlr^−/−) mice. Neutrophil accumulation in the aortic root of Ldlr^−/−(Casp1^−/−) mice was enhanced compared with Ldlr^−/−(Ldlr^−/−) mice. 16S-rDNA-encoding sequence analysis in feces identified a significant reduction in the short-chain fatty acid–producing taxonomies Akkermansia, Christensenellaceae, Clostridium, and Odoribacter in Ldlr^−/−(Casp1^−/−) mice. Consistent with these findings, cumulative concentrations of the anti-inflammatory short-chain fatty acids propionate, acetate and butyrate in the cecum were significantly reduced in 13-week high-fat cholesterol–fed Ldlr^−/−(Casp1^−/−) compared with Ldlr^−/−(Ldlr^−/−) mice.

Conclusions:

Introduction of the proinflammatory Casp1^−/− microbiota into Ldlr^−/− mice enhances systemic inflammation and accelerates atherogenesis.