GLP1R Pro7Leu — Your GLP-1 Medication Efficacy and Side Effect Profile
The GLP-1 receptor (GLP1R) is the molecular target of semaglutide (Ozempic,
Wegovy), tirzepatide (Mounjaro, Zepbound), liraglutide (Saxenda), and other
GLP-1 agonist medications prescribed for weight loss and type 2 diabetes.
rs10305420 causes a proline-to-leucine substitution at position 7 of the
receptor's signal peptide | a short amino acid sequence that directs newly
synthesized proteins to the cell surface. Unlike other GLP1R
pharmacogenomic variants that alter the drug-binding domain, this variant
affects how efficiently the receptor reaches the cell membrane.
The Mechanism
The Pro7Leu substitution replaces proline — which introduces a structural
kink — with leucine, a more hydrophobic amino acid that strengthens the
signal peptide's
hydrophobic core | the water-repelling central region that is recognized
by cellular machinery for membrane insertion. This is predicted to
enhance
signal recognition particle (SRP) binding | the molecular complex that
captures newly made proteins and directs them into the endoplasmic
reticulum for processing and improve receptor trafficking to the
plasma membrane. The result is
more GLP-1 receptor molecules on the cell surface | Su et al. Genetic predictors of GLP1 receptor agonist weight loss and side effects. Nature, 2026,
amplifying the cellular response to both natural GLP-1 and pharmaceutical
agonists.
This mechanism explains a dual pharmacogenomic effect: more receptor on
the cell surface means both greater drug efficacy (more weight loss) and
greater susceptibility to GI side effects (more nausea and vomiting).
Co-localization analysis in the Nature 2026 study confirmed that the
efficacy, nausea, and vomiting signals at this locus share the same
underlying causal variant.
The Evidence
The definitive evidence comes from a
GWAS of 27,885 GLP-1 medication users | Su et al. Nature, 2026
conducted by the 23andMe Research Institute. The T allele (leucine) was
associated with an additional 0.641% BMI loss per allele, equivalent to
approximately 0.76 kg of extra weight loss per copy (P = 2.9 x 10-10).
The effect was additive with no evidence of dominance — two copies
confer roughly twice the benefit. A trans-ancestry meta-analysis
strengthened the signal further (P = 1.1 x 10-12), with consistent
directionality across European, Latino, African American, East Asian,
South Asian, and Middle Eastern populations.
The association was
independently replicated in 4,855 participants | All of Us Research
Program cohort using EHR data
with EHR-derived weight measurements (P = 0.001, effect = -0.47% BMI).
The same study identified an important
gene-gene interaction with GIPR | rs1800437 Glu354Gln in near-perfect
LD with rs10423928: individuals homozygous for risk alleles at both
the GLP1R and GIPR loci had 14.8-fold increased odds of
tirzepatide-induced vomiting (95% CI 6.2-35.8). This interaction was
specific to tirzepatide, which targets both GLP1R and GIPR, and was
absent in semaglutide-treated patients.
Two earlier, smaller studies reported opposite directionality —
Jensterle et al. 2015
(n=57 PCOS women, liraglutide) and
Yu et al. 2019 (n=285
Chinese T2D patients, exenatide) both found the T allele associated
with less weight loss. These studies used different drugs, different
populations, and had limited statistical power. The 23andMe study is
approximately 100-fold larger and was independently replicated.
Practical Implications
This variant is common — approximately 48% of Europeans are
heterozygous and 15% are homozygous for the T allele. Unlike rare
pharmacogenomic variants, this affects a substantial fraction of GLP-1
medication users. The enhanced efficacy is clinically meaningful:
homozygous TT carriers can expect roughly 1.5 kg more weight loss
than CC carriers on the same regimen.
The trade-off is gastrointestinal tolerability. Carriers experiencing
significant nausea or vomiting on GLP-1 agonists may benefit from
slower dose titration. For tirzepatide users specifically, the
interaction with GIPR variants can dramatically amplify vomiting risk —
making GIPR genotype (rs10423928/rs1800437) clinically relevant
information for prescribers choosing between semaglutide and
tirzepatide.
Interactions
The GLP1R locus harbors multiple pharmacogenomic variants. rs6923761
(Gly168Ser) alters the extracellular binding domain, primarily affecting
gastric emptying and glycemic response. rs3765467 (Arg131Gln) changes
the ligand-binding pocket, modifying drug affinity. rs10305492
(Ala316Thr) affects intracellular signaling. Pro7Leu acts through
a distinct mechanism — receptor trafficking rather than receptor
function — and its effects are largely independent of these binding-site
variants.
The tirzepatide-specific interaction with GIPR is unique to this
variant among known GLP1R pharmacogenomic markers. The GIPR variant
rs10423928 (in near-perfect LD with the coding variant rs1800437
Glu354Gln) reduces GIP receptor function. When combined with increased
GLP1R surface expression from Pro7Leu, the balance between GLP-1 and
GIP signaling is disrupted, unmasking the nausea-inducing effects of
the GLP-1 component that GIP receptor activation normally buffers.
Alla genotyper
Standard GLP-1 receptor trafficking; typical weight loss and side effect profile on GLP-1 agonists
You have two copies of proline at position 7 of the GLP-1 receptor signal peptide. Your receptor trafficking to the cell surface follows the standard pathway. About 37% of Europeans and 41% of people globally share this genotype. On GLP-1 agonist medications like semaglutide (Ozempic/Wegovy) or tirzepatide (Mounjaro/Zepbound), your weight loss response and side effect profile should match published clinical trial averages. The large 23andMe GWAS used this genotype as the reference point for measuring the enhanced efficacy seen in T allele carriers.
One copy of enhanced-trafficking variant; approximately 0.76 kg extra weight loss on GLP-1 agonists with modestly increased nausea risk
You carry one copy of the leucine variant at position 7 of the GLP-1 receptor signal peptide. This is the most common genotype in Europeans, found in approximately 48% of people of European descent and 46% globally. In a GWAS of 27,885 GLP-1 medication users, each copy of your variant allele was associated with an additional 0.76 kg of weight loss (P = 2.9 x 10^-10), equivalent to approximately 0.6% extra BMI reduction. The association co-localizes with increased susceptibility to nausea and vomiting on these medications.
Two copies of enhanced-trafficking variant; approximately 1.5 kg extra weight loss on GLP-1 agonists with increased nausea and vomiting risk
You carry two copies of the leucine variant at position 7 of the GLP-1 receptor signal peptide. About 15% of Europeans and 13% of people globally share this genotype. In a GWAS of 27,885 GLP-1 medication users, each copy of your variant allele added approximately 0.76 kg of extra weight loss. With two copies, you can expect roughly 1.5 kg more weight loss than people with the CC genotype on the same GLP-1 agonist regimen. However, the same variant significantly increases your risk of medication-related nausea and vomiting.