Melatonin inhibits insulin secretion in rat insulinoma β-cells (INS-1) heterologously expressing the human melatonin receptor isoform MT2.
Level 5 - mechanism / opinion, no new human data
In vitro bench research using a cell line model
PubMed 21585522 · doi:10.1111/j.1600-079X.2011.00898.x
What was done
The authors examined the signaling pathways and impact on insulin secretion of the human recombinant melatonin receptor isoform MT2 (hMT2) expressed heterologously in a rat insulinoma beta-cell line (INS-1). INS-1 cells expressing hMT2 and control clones were incubated with melatonin (1 or 100 nM), with or without pertussis toxin pretreatment. Insulin secretion was assessed using radioimmunoassay, and cAMP and cGMP levels were measured via enzyme-linked immunosorbent assays.
What was found
Melatonin at 1 or 100 nM reduced insulin secretion more strongly in hMT2-expressing clones than in control INS-1 cells. Similarly, cAMP and cGMP levels decreased to a greater extent in hMT2 clones following melatonin treatment. The inhibitory effect of melatonin on insulin secretion was blocked by pertussis toxin pretreatment in hMT2-expressing cells. No specific numerical values or effect sizes were reported in the abstract.
Why it matters
These findings indicate that human MT2 receptor activation inhibits insulin release through Gi-protein-dependent suppression of cyclic nucleotide signaling, providing a mechanistic link between MT2 receptor function and type 2 diabetes pathogenesis.
Limits
This is an in vitro cell culture study in a transformed rat beta-cell line with heterologous human receptor expression, which may not reflect human in vivo islet physiology. The abstract provides no quantitative data, error ranges, or sample sizes.
Cited by
- supports Melatonin receptors are expressed on pancreatic beta cells, and melatonin binding to these receptors inhibits insulin secretion.