Expression of the Bitter Taste Receptor, T2R38, in Enteroendocrine Cells of the Colonic Mucosa of Overweight/Obese vs. Lean Subjects.
Level 4 - case-series / case-control
Cross-sectional comparative human tissue biopsy study
PubMed 26866366 · doi:10.1371/journal.pone.0147468
What was done
Researchers evaluated colonic mucosal biopsies obtained during colonoscopy from 35 healthy subjects: 20 overweight/obese (OW/OB) and 15 normal-weight (NW) individuals. Biopsies were analyzed using quantitative RT-PCR for T2R38 mRNA expression and immunohistochemistry to quantify T2R38 immunoreactivity and examine colocalization with enteroendocrine markers including chromogranin A (CgA), GLP-1, CCK, and PYY.
What was found
T2R38 mRNA levels in colonic mucosa were increased > 2-fold in OW/OB versus NW subjects, but this did not reach statistical significance (P = 0.06). The number of T2R38-immunoreactive (IR) cells was significantly higher in OW/OB compared to NW individuals (P = 0.01) and correlated positively with BMI (r = 0.7557; P = 0.001). All T2R38-IR cells contained CgA and colocalized with CCK, GLP-1, or PYY in both groups. Total CgA-IR cell counts did not differ between groups.
Why it matters
This study shows that the bitter taste receptor T2R38 is localized to human colonic enteroendocrine cells and upregulated in obesity, identifying a potential mucosal chemosensory pathway related to energy balance.
Limits
The study is small (n = 35), cross-sectional, and observational, precluding any causal conclusions. Functional peptide secretion and downstream metabolic effects were not directly measured in vivo.
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