rs11605924 — CRY2 Intron Variant

CRY2 — Your Circadian Glucose Regulator

Cryptochrome 2 (CRY2) is a core component of the molecular circadian clock¹¹ molecular circadian clock
The transcription-translation feedback loop that generates ~24-hour rhythms in virtually every cell, governing sleep-wake cycles, hormone release, and metabolism. Like its partner CRY1, CRY2 acts as a transcriptional repressor that shuts down the CLOCK:BMAL1 complex — but CRY2 has a distinct role in metabolism. The rs11605924 variant was identified in the landmark MAGIC consortium GWAS²² MAGIC consortium GWAS
Meta-analysis of 21 genome-wide association studies in 46,186 non-diabetic participants as one of nine new loci associated with fasting glucose, placing CRY2 at the intersection of circadian biology and metabolic disease.

The Mechanism

CRY2 encodes a flavin adenine dinucleotide (FAD)-binding protein³³ flavin adenine dinucleotide (FAD)-binding protein
The FAD cofactor is essential for CRY2's light-independent repressor function in mammals, distinguishing it from light-sensing cryptochromes in other organisms that forms repressive complexes with PER proteins to suppress CLOCK:BMAL1-driven transcription. This feedback loop generates rhythmic expression of thousands of metabolic genes, including those controlling hepatic glucose production⁴⁴ hepatic glucose production
CRY proteins directly regulate gluconeogenic gene expression through interaction with the glucocorticoid receptor and FOXO1 transcription factors and insulin secretion.

The rs11605924 variant sits within an intron of CRY2 on chromosome 11. While intronic, the variant appears to affect CRY2 expression or splicing efficiency, as carriers show measurable differences in both glucose homeostasis and hepatic lipid handling. CRY2 is expressed rhythmically in the liver, pancreatic beta cells, and adipose tissue, all key sites of glucose regulation.

A fascinating finding links this variant to hepatic metabolism: Machicao et al. 2016⁵⁵ Machicao et al. 2016
Machicao F et al. Glucose-Raising Polymorphisms in the Human Clock Gene Cryptochrome 2 (CRY2) Affect Hepatic Lipid Content. PLoS One, 2016 showed that the glucose-raising alleles concomitantly reduced liver fat content by approximately 30%, suggesting that the variant redirects intermediary metabolites from hepatic triglyceride synthesis toward gluconeogenesis. This metabolic shunting effect explains how the same variant can raise fasting glucose while paradoxically reducing fatty liver.

The Evidence

The MAGIC consortium GWAS⁶⁶ MAGIC consortium GWAS
Dupuis J et al. New genetic loci implicated in fasting glucose homeostasis and their impact on type 2 diabetes risk. Nat Genet, 2010 identified rs11605924 among nine new fasting glucose loci in a meta-analysis of 46,186 non-diabetic individuals, with follow-up in 76,558 additional subjects. CRY2 was the only core circadian clock gene among these loci, providing the first direct genetic link between the circadian machinery and population-level glucose variation.

The GLACIER Study⁷⁷ GLACIER Study
Renstrom F et al. Season-dependent associations of circadian rhythm-regulating loci and glucose homeostasis. Diabetologia, 2015 from northern Sweden revealed a remarkable finding: the association between rs11605924 and 2-hour glucose levels (beta = 0.07 mmol/L per A allele, P = 0.0008, n = 9,605) was present only during the dark season (P for interaction = 0.006). During the light season, no association was detected. This season-dependent effect is biologically plausible: CRY2 is a light-responsive clock protein, and extreme photoperiod variation in northern latitudes may unmask its metabolic effects.

In the hepatic lipid study⁸⁸ hepatic lipid study
Machicao et al. 2016, four CRY2 SNPs including rs11605924 showed study-wide significant associations with fasting glucose (P < 0.0005) and concomitant associations with liver fat content (P < 0.015) in 1,715 non-diabetic individuals. In vivo MRS measurements in 375 subjects confirmed approximately 30% reduced liver fat in carriers of the glucose-raising alleles.

Replication in non-European populations came from Liu et al. 2011⁹⁹ Liu et al. 2011
Liu C et al. Variants in GLIS3 and CRY2 Are Associated with Type 2 Diabetes and Impaired Fasting Glucose in Chinese Hans. PLoS One, 2011, where the A allele was associated with combined impaired fasting glucose and type 2 diabetes (OR 1.15, 95% CI 1.01-1.30, P = 0.04) in 3,210 Chinese participants, though this association was attenuated after adjustment for additional confounders.

The POUNDS LOST Trial¹⁰¹⁰ POUNDS LOST Trial
2014 demonstrated that CRY2 rs11605924 influenced metabolic responses to weight-loss diets, with significant associations between genotype and changes in respiratory quotient, resting metabolic rate, and energy expenditure during a 2-year intervention, suggesting the variant modulates how effectively different dietary strategies work.

Practical Implications

The CRY2 variant affects glucose regulation through a circadian mechanism, which means its metabolic consequences are amplified by circadian disruption — shift work, irregular meal timing, jet lag, or insufficient light exposure. Carriers of the risk allele who maintain regular circadian rhythms may show minimal glucose elevation, while those with disrupted rhythms may see larger effects.

The seasonal modulation of the glucose effect suggests that latitude and light exposure are modifiers. People in northern latitudes carrying the A allele may benefit from light therapy during dark winter months to stabilize their circadian-metabolic coupling.

Interactions

CRY2 operates in the same circadian feedback loop as CRY1 (rs2287161), CLOCK (rs1801260), and MTNR1B (rs10830963). The GLACIER Study tested interactions between these loci and found season-dependent effects for all three circadian variants (CRY1, CRY2, MTNR1B), suggesting they converge on a shared photoperiod-sensitive metabolic pathway. Carriers of glucose-raising alleles at multiple circadian loci may show amplified seasonal glucose variation.

Compound implication for CRY2 rs11605924 + MTNR1B rs10830963: Both variants affect circadian glucose regulation — MTNR1B through melatonin-mediated suppression of insulin secretion, CRY2 through transcriptional control of gluconeogenic genes. Carriers of the risk allele at both loci may show the strongest seasonal glucose fluctuation and the greatest benefit from stabilizing circadian rhythms during dark months. They should consider monitoring fasting glucose in both summer and winter to detect seasonal variation.