Gene Variant Review Points to Early Warning Sign for Pregnancy Diabetes

A systematic review published in the Egyptian Journal of Medical Human Genetics has brought together a decade of research on a single gene and its connection to gestational diabetes mellitus, a form of high blood sugar first recognized during pregnancy. The review, conducted by Faisal Fayaz, Ginjinder Kaur and Sarbhjit Kaur, searched the PubMed database for studies published between January 2016 and December 2025 and identified ten studies that met the authors’ inclusion criteria. According to the review, most of those studies reported a significant connection between variants of the CDKAL1 gene and a woman’s risk of developing gestational diabetes, leading the authors to propose that CDKAL1 polymorphism may serve as a potential genetic marker for early risk assessment.

Gestational diabetes mellitus is one of the most common endocrine disorders affecting pregnant women worldwide. The condition is typically recognized between 24 and 28 weeks of gestation and arises from two interlinked processes: chronic insulin resistance, in which the body’s cells no longer respond adequately to insulin, and dysfunction of the pancreatic beta cells that produce the hormone. The review notes that the global prevalence of the condition ranges from 1 percent to over 30 percent, with populations in South and Southeast Asia showing higher susceptibility, a pattern attributed to a combination of genetic predisposition, low physical activity and dietary factors. Women who develop the condition face a two-fold higher risk of developing type 2 diabetes later in life, and their children are described as predisposed to obesity and metabolic diseases.

The biological logic connecting CDKAL1 to pregnancy-related diabetes rests on the gene’s role in insulin production. The CDKAL1 gene, located on chromosome 6p22.3, contains sixteen exons and encodes a 579-amino-acid protein belonging to the methylthiotransferase family. The enzyme it produces carries out a precise chemical modification: it adds a methylthio group to the 37th base of a transfer RNA molecule, creating a modified form called 2-methylthio-N6-threonylcarbamoyladenosine. This modification helps the transfer RNA work properly during protein synthesis, and it is essential for the correct post-translational processing of pre-proinsulin into mature insulin. When this modification is disrupted, the result is beta-cell dysfunction and decreased insulin secretion, which in turn interferes with the translation of proinsulin.

The timing of this molecular failure matters during pregnancy. The review explains that women who go on to develop gestational diabetes show evidence of decreased peripheral insulin sensitivity even before conception, yet they maintain normal glucose levels in early pregnancy because their pancreatic beta cells can increase insulin output to compensate. By the end of the second trimester, however, insulin resistance rises to the point where that compensatory response becomes insufficient, and hyperglycemia appears. The authors describe how beta-cell dysfunction, once it begins, sets in motion what they call a dangerous cycle: reduced insulin effectiveness drives glucose levels up, elevated glucose overburdens the beta cells further, and the resulting glucotoxicity worsens the dysfunction.

The methodological backbone of the review was a PRISMA-reported systematic search of national and international literature. The authors screened titles, abstracts and full texts, applying filters that restricted inclusion to articles from the last ten years, published in English, available in full text, and conducted on human female subjects. From an initial pool of 37 articles identified on PubMed, ten studies fulfilled the criteria and were analyzed for the association between CDKAL1 polymorphisms and gestational diabetes. The authors report that the majority of the included studies demonstrated that CDKAL1 variants contribute to susceptibility through impaired beta-cell function, altered insulin secretion and disturbed glucose homeostasis, while also acknowledging that differences in genetic background, sample size, environmental exposure and population-specific allele frequencies may explain inconsistencies among studies.

Two variants of the gene dominated the evidence. The first, rs7754840, has been one of the most frequently investigated CDKAL1 variants in relation to gestational diabetes risk. Several studies reported that its C allele and CC genotype are associated with increased susceptibility. Huang and colleagues demonstrated a significant association of rs7754840, along with other CDKAL1 variants including rs10946398, in Chinese women, and reported strong linkage disequilibrium among multiple variants, suggesting they may collectively influence disease susceptibility. Amin and colleagues found that the GC and CC genotypes were more frequent among gestational diabetes cases in the Bangladeshi population, with genetic model analysis showing increased odds of the condition among carriers of the risk genotypes. Liang and colleagues further reported that the rs7754840 C allele interacts with metabolic and lifestyle factors, influencing fasting insulin levels and insulin resistance parameters.

The second variant, rs10946398, showed a broadly similar pattern with some notable exceptions. Huang and colleagues reported a significant association with gestational diabetes, with the CC genotype appearing more frequently among affected individuals, while Asghar and colleagues observed that the C allele and the CC and AC genotypes were significantly associated with increased risk in Pakistani women. Not every study agreed. Tarnowski and colleagues did not find a statistically significant association between rs10946398 genotype distribution and the occurrence of gestational diabetes, although within their affected group the CC genotype showed a tendency toward an increased requirement for insulin therapy, hinting that the variant may influence disease severity and treatment response rather than disease initiation alone. Ju and colleagues likewise reported no significant association between the variant and gestational glycemic traits in a Chinese population, despite observing strong linkage disequilibrium among CDKAL1 variants.

The negative findings extended to rs7754840 as well. Popova and colleagues reported inconsistent results for that variant, and Noury and colleagues found no significant association in an Egyptian population, although the C allele did show a relationship with type 2 diabetes risk among pregnant women. The review’s authors treat these exceptions as informative rather than dismissive. They suggest that rs7754840 may have a stronger influence on long-term metabolic susceptibility than on directly determining gestational diabetes development in certain populations, and they lay out several possible explanations for the discordant results: allele frequencies and linkage disequilibrium patterns differ among ethnic groups, modest genetic effect sizes demand large samples to detect reliably, and environmental factors such as diet, physical activity and obesity may modify the effect of the variants. They also note that some studies measured only disease occurrence, whereas the variants may influence intermediate traits such as insulin secretion capacity, beta-cell function and the need for insulin therapy, so an absence of association with diagnosis does not necessarily exclude a functional role in glucose metabolism.

The review’s conclusion is deliberately measured. Most of the included studies showed significant associations between CDKAL1 gene variants and the development or increased risk of gestational diabetes, with the variants implicated in beta-cell dysfunction and impaired insulin secretion leading to glucose intolerance during pregnancy, but a minority reported non-significant associations that point to population-specific genetic variability. The authors state that CDKAL1 polymorphisms may be usable as a potential genetic marker for early risk assessment of the condition, while emphasizing that validation in diverse populations of different ethnicities is what they call the need of the hour. They call for future studies involving larger multi-ethnic cohorts and the integration of genetic, metabolic and lifestyle factors to establish the predictive value of the two candidate variants.

For readers weighing what this means, the review is a synthesis of observational association studies rather than a clinical trial, and it establishes links between inherited variants and disease occurrence, not a validated screening test. What the work does establish is a coherent mechanistic thread: a gene that fine-tunes the chemical processing of insulin, variants that disrupt that fine-tuning, and a pregnancy-specific metabolic stress that exposes the weakness. Whether that thread can be woven into reliable early prediction for women of diverse genetic backgrounds remains the central open question the authors identify for the next decade of research.

Subject of Research: The association between CDKAL1 gene polymorphisms and susceptibility to gestational diabetes mellitus

Article Title: CDKAL1 gene polymorphism and susceptibility to gestational diabetes mellitus: a systematic review

Article References: Fayaz, F., Kaur, G., & Kaur, S. (2026). CDKAL1 gene polymorphism and susceptibility to gestational diabetes mellitus: a systematic review. Egyptian Journal of Medical Human Genetics, 27(1), Article 81. https://doi.org/10.1186/s43042-026-00901-0

Image Credits: AI Generated

DOI: 10.1186/s43042-026-00901-0

Keywords: gestational diabetes mellitus, CDKAL1, gene polymorphism, rs7754840, rs10946398, beta-cell dysfunction, insulin secretion, systematic review, genetic susceptibility, type 2 diabetes risk, pregnancy, tRNA modification