Metabolic endotoxemia initiates obesity and insulin resistance.
Level 5 - mechanism / opinion, no new human data
Animal (mouse) model and mechanistic laboratory research
PubMed 17456850 · doi:10.2337/db06-1491
What was done
Researchers measured circulating lipopolysaccharide (LPS) levels during fed, fasted, and 4-week high-fat diet conditions in mice, and assessed gut microbiota composition. To test causality, they induced chronic metabolic endotoxemia in mice via continuous subcutaneous infusion of LPS for 4 weeks and compared outcomes to high-fat-fed mice and controls. They also evaluated metabolic outcomes and inflammatory markers in CD14 mutant mice subjected to LPS infusion or a high-fat diet.
What was found
A 4-week high-fat diet chronically increased plasma LPS concentrations 2- to 3-fold (defined as metabolic endotoxemia) and increased gut LPS-bearing bacteria. Continuous subcutaneous LPS infusion for 4 weeks increased fasting glycemia, fasting insulinemia, whole-body weight gain, liver weight, and adipose tissue weight to levels comparable to high-fat-fed mice. LPS infusion also increased adipose tissue F4/80-positive cells, inflammatory markers, liver triglyceride content, and hepatic insulin resistance (whole-body insulin resistance was not detected). CD14 mutant mice were resistant to most features induced by LPS infusion and the high-fat diet. Exact numerical values for glycemia, weight, and inflammatory markers were not reported in the abstract.
Why it matters
This study introduced the concept of metabolic endotoxemia, proposing gut-derived bacterial LPS and CD14 pathway activation as an upstream driver connecting dietary fat intake to low-grade inflammation, hepatic insulin resistance, and weight gain.
Limits
The abstract reports only mouse data with no human participants, limiting direct clinical translation. Sample sizes (n), precise quantitative effect estimates, and statistical dispersion metrics are not provided in the abstract.
Cited by
- partial The American Diabetes Association published a paper stating that the primary insult starting insulin resistance is endotoxins (LPS).