rs10305492 — GLP1R A316T

GLP-1 Receptor A316T -- A Rare Protective Variant with Drug Response Implications

Among the thousands of genetic variants linked to type 2 diabetes, very few are genuinely protective. The rs10305492 variant in the GLP-1 receptor gene¹¹ GLP-1 receptor gene
GLP1R encodes the receptor targeted by semaglutide (Ozempic/Wegovy) and liraglutide (Victoza/Saxenda) is one of them. This low-frequency missense variant (about 1.6% allele frequency in Europeans, rare or absent in other populations) substitutes alanine with threonine at position 316 in the receptor's fifth transmembrane domain. Carriers enjoy lower fasting glucose, reduced risk of type 2 diabetes, and protection against coronary heart disease -- but may respond differently to the very drugs that target this receptor.

The Mechanism

The A316T substitution sits in the fifth transmembrane helix²² fifth transmembrane helix
One of seven helices that span the cell membrane and form the receptor's signaling core of the GLP-1 receptor, a region critical for receptor activation. Functional studies in mice expressing the human A316T variant reveal that this change causes constitutive activation³³ constitutive activation
The receptor signals at a low level even without GLP-1 binding of the receptor at baseline. This means the receptor is partially "switched on" all the time, maintaining a tonic signal that improves fasting metabolic parameters. However, this same constitutive activity leads to receptor desensitization, which dampens responses to pharmacological GLP-1 receptor agonists⁴⁴ dampens responses to pharmacological GLP-1 receptor agonists
Drugs like semaglutide and liraglutide may have reduced effect because the receptor is already partially activated when they are administered.

The Evidence

The protective effect was first identified in a large exome chip meta-analysis⁵⁵ large exome chip meta-analysis
Wessel et al. Low-frequency and rare exome chip variants associate with fasting glucose and T2D susceptibility. Nature Comms, 2015 of 60,564 non-diabetic individuals, where the A allele was associated with lower fasting glucose (beta = -0.09 mmol/L per allele, P = 3.4 x 10^-12) and reduced T2D risk (OR 0.86, 95% CI 0.76-0.96, P = 0.010) in 16,491 cases and 81,877 controls. Notably, the variant was also associated with higher 2-hour glucose (beta = +0.16 mmol/L, P = 4.3 x 10^-4) and lower early insulin secretion, suggesting the protective effect operates through improved fasting state rather than enhanced meal-time response.

A subsequent therapeutic target validation study⁶⁶ therapeutic target validation study
Scott et al. A genomic approach to therapeutic target validation identifies a glucose-lowering GLP1R variant protective for CHD. Sci Transl Med, 2016 extended these findings to cardiovascular outcomes. In 61,846 coronary heart disease cases and 163,728 controls, the glucose-lowering allele was associated with CHD protection -- and the protective effect was larger than what would be predicted from glucose lowering alone, suggesting direct cardiovascular benefits of GLP-1R signaling.

In vivo functional profiling⁷⁷ In vivo functional profiling
In vivo functional profiling and structural characterization of the human GLP1R A316T variant. Sci Adv, 2024 in a knock-in mouse model confirmed that A316T causes constitutive receptor activation with improved fasting metabolic parameters but blunted responses to pharmacological GLP-1 receptor agonists. This is a critical finding for pharmacogenomics: the same variant that protects against diabetes may reduce the effectiveness of the drugs designed to mimic its natural ligand.

Practical Actions

If you carry the A allele, your natural GLP-1 receptor function is protective -- your fasting glucose tends to be lower and your cardiovascular risk is reduced compared to non-carriers. However, if you are prescribed a GLP-1 receptor agonist (semaglutide, liraglutide, exenatide, dulaglutide, or tirzepatide), your response may be attenuated because your receptor is already constitutively active. This does not mean these drugs won't work at all -- it means you may need different expectations for dose-response and should discuss your genotype with your prescriber.

Interactions

This variant interacts with rs3765467 (GLP1R R131Q), another missense variant in the same receptor that alters the extracellular binding domain. While A316T causes constitutive activation in the transmembrane domain, R131Q changes ligand binding in the extracellular domain. Carriers of both variants would have a GLP-1 receptor altered at two distinct functional regions, potentially compounding effects on both endogenous GLP-1 signaling and pharmacological response. No studies have yet characterized this combined genotype, but it represents a plausible compound pharmacogenomic interaction for GLP-1 receptor agonist therapy.