Melatonin exerts an inhibitory effect on insulin gene transcription via MTNR1B and the downstream Raf‑1/ERK signaling pathway.
Level 5 - mechanism / opinion, no new human data
In vitro bench research using a mouse pancreatic beta-cell line.
PubMed 29207116 · doi:10.3892/ijmm.2017.3305
What was done
Researchers investigated the effects of exogenous melatonin on the mRNA expression of mouse insulin genes (*Ins1* and *Ins2*) and on insulin secretion in MIN6 pancreatic beta-cells. They evaluated the MAPK pathway components Raf-1 and ERK following the overexpression or silencing of *MTNR1B*. They also tested whether chemical inhibitors of Raf-1 (GW5074) and ERK (U0126) altered melatonin's regulation of insulin mRNA expression.
What was found
Exogenous melatonin inhibited insulin mRNA expression in MIN6 cells without altering insulin secretion. Both melatonin treatment and *MTNR1B* overexpression suppressed MAPK signaling pathway activity (Raf-1 and ERK). Knockdown of *MTNR1B* abolished melatonin's effect on insulin gene expression. In addition, blocking Raf-1 or ERK with chemical inhibitors attenuated the regulatory effect of melatonin on insulin mRNA. The abstract reports directional findings only and does not report specific numerical values, concentrations, or effect sizes.
Why it matters
This study outlines a downstream molecular pathway (MTNR1B/Raf-1/ERK) through which melatonin suppresses insulin gene transcription, offering mechanistic context for genetic associations between *MTNR1B* variants and type 2 diabetes risk.
Limits
The study was conducted entirely in an immortalized mouse beta-cell line (MIN6) and lacks confirmation in primary human islets or in vivo systems. The abstract omits sample sizes, experimental replicate numbers, melatonin concentrations, and quantitative effect sizes.
Cited by
- supports Melatonin inhibits insulin production in pancreatic beta cells.