An opportunistic pathogen isolated from the gut of an obese human causes obesity in germfree mice

LisaLuna Medical Primary Care

Case

• weight 174.8 kg, • body mass index 58.8 kgm2• suffering from diabetes, hypertension and other serious

metabolic deteriorations

• on a diet composed of whole grains, traditional Chinese medicinal foods and prebiotics

• lost 30.1 kg after 9 weeks, and 51.4 kg after 23 weeks• Amelioration of hyperinsulinemia, hyperglycemia and

hypertension until most metabolic parameters improved to normal ranges

How does it happen?• Biomedical Indicator

Key Point----Enterobacter

a genus of opportunistic, endotoxin producingPathogens, made up 35% of the gut bacteria in a morbidly obese volunteer

After 9 weeks on the WTP diet*, this Enterobacter population in the volunteer’s gut reduced to 1.8%, and became undetectable by the end of the 23-week trial

*WTP Diet :whole grains, traditional Chinese medicine and prebiotics

Hypothesis

The endotoxin producing Enterobacter population may have a causative role in the metabolic deteriorations of its human host

Animal Studies

Animal: Germfree (GF) male C57BL/6J mice* *germfree mice are resistant to HFD-induced obesity

Clinical isolation: • Strain Enterobacter cloacae B29 isolated from the volunteer’s gut• and nearest neighbor as E.cloacae subsp. cloacae ATCC 13047

Process: Inoculation of B29 and Luria–Bertani (LB) into GF mice

Feed:• normal chow diet (NCD) or• High fat diet(HFD)

(continued)4 groups:• NCD+B29• NCD+LB• HFD+B29 • HFD+LB

data collected at the end of 16 weeks after inoculation• Body weight• mass of epididymal, mesenteric, subcutaneous inguinal and retroperitoneal fat

pad; • oral glucose tolerance test (OGTT) and areas under the curve (AUC) for the plasma

glucose; • serum 2h post load insulin; • enzyme-linked immunosorbent assay (ELISA) analysis of serum LPS-binding protein

(LBP); • serum amyloid A (SAA); • adiponectin corrected for bodyweight

Body weight after 16 weeks of experiment

Fat pad after 16 weeks of experiment

Blood Glucose level after 16 weeks of experiment

Conclusion from the data collected

• The HFD+B29 gnotobiotic mice developed the most significant insulin resistant phenotype and body gain and other characteristics of obesity

• The NCD+B29or NCD+LB both remained lean throughout the trial

Serum LPS-binding protein after 16 weeks

*B29 was the only LPS producer in the gnotobiotic-mouse gut

Conclusion from the LBP level after 16 weeks experiment

• The serum LPS-binding protein was significantly higher in the HFD+B29 gnotobiotic mice than in the NCD+B29

• increased serum–endotoxin load in the HFD+B29 gnotobiotic mice could only come from B29.

HFD+B29 mice had the greatest increase in systemic inflammation

Serum SAA and adiponection level after the 16 weeks

Conclusion of the study

Overgrowth of an endotoxin producing gut bacterium is a contributing factor to, rather than a consequence of, the metabolic deteriorationsin its human host

Strength of the study

• for the first time, established a gnotobiotic-mouse obesity model combining HFD with a human-originated endotoxin producer

• identify more such obesity-inducing bacteria from various human populations

• develop new strategies for reducing the devastating epidemic of metabolic diseases

Several question remains uncertain

• Study is conducted for 16 weeks, it’s uncertain if the gut pathogen from the obese functions the similar way in a long term.

• B29 is probably not the only contributor to human obesity in vivo.

• More case study is required to replicate the experiments

Thank You!

We Appreciate Your Patience