MTTP rs1800591: Understanding the -493G/T Promoter Variant
The rs1800591 variant is a common genetic change located in the promoter region of the MTTP gene. It has been studied for its potential role in modulating lipid metabolism and its association with nonalcoholic fatty liver disease (NAFLD) risk.
What each genotype means
Typical MTTP transcription
You carry two copies of the common G allele, historically described as the -493G promoter sequence. In cellular assays, this genotype shows standard basal MTTP transcription compared to the enhanced promoter activity seen with the T allele. Evidence regarding postprandial lipemia, LDL responsiveness to dietary fats, and liver fat accumulation is mixed across published cohorts, with many population studies finding no significant baseline lipid differences.
Found in approximately 55% to 65% of individuals of European ancestry, and represents the predominant genotype across most global populations.
Intermediate MTTP promoter activity
You carry one copy of the common G allele and one copy of the -493T promoter variant. In laboratory models, the T allele has been associated with increased MTTP transcription and subtle shifts in lipoprotein particle production. However, published clinical findings on dietary lipid response, cardiovascular risk, and hepatic fat accumulation remain conflicting and show limited overall effect.
Carried by approximately 30% to 38% of people of European ancestry, with lower frequencies observed in East Asian populations.
Increased MTTP promoter activity
You carry two copies of the -493T promoter variant, which in vitro correlates with approximately twofold higher MTTP transcription compared to the wild-type sequence. Some studies report altered postprandial lipid handling, lower IDL and LDL production, or modest differences in LDL response to dietary fats, while others find no measurable impact on lipid levels. Because scientific evidence is limited and inconsistent across ancestries, this genotype should not be interpreted as a diagnostic indicator.
Present in roughly 4% to 6% of individuals of European ancestry and is relatively uncommon in most other ancestral backgrounds.
What is the rs1800591 Variant?
The rs1800591 variant, often referred to as the -493G/T polymorphism, is a single nucleotide polymorphism (SNP) located in the promoter region of the MTTP gene on human chromosome 4. A promoter region is a specific sequence of DNA that acts as a control switch, determining how much of a protein is produced by a gene. Because this variant sits in a regulatory area, researchers have long hypothesized that it may influence the expression levels of the MTTP protein. By altering the efficiency of this switch, the G or T allele may lead to variations in the amount of protein synthesized within liver cells, which in turn could impact how the body processes and transports fats.
The Role of the MTTP Gene
The MTTP gene provides the instructions for creating the microsomal triglyceride transfer protein. This protein is essential for the assembly and secretion of very-low-density lipoproteins (VLDL) in the liver. Essentially, the MTTP protein acts as a chaperone, helping to load triglycerides onto lipoproteins so they can be transported out of the liver and into the bloodstream. When this process functions correctly, it prevents the excessive buildup of fat within liver cells. If the function of this protein is compromised or altered, it can disrupt lipid homeostasis, potentially leading to the accumulation of fat in the liver, a condition often studied in the context of metabolic health.
Research and Associations
The association between rs1800591 and liver health, particularly nonalcoholic fatty liver disease (NAFLD), has been a subject of significant scientific investigation. Some meta-analyses have suggested that the G allele may be linked to an increased risk of hepatic steatosis, or fatty liver. However, the evidence remains controversial and inconsistent across different global populations. While some studies indicate that this variant modulates lipid homeostasis and influences serum lipid levels, other research has failed to establish a definitive causal link. The complexity of liver disease, which involves a mix of genetic, environmental, and lifestyle factors, makes it difficult to isolate the specific impact of this single variant. Consequently, the scientific community views the evidence for this SNP as moderate, requiring further validation in diverse cohorts.
Understanding Your Results
If you have received information about your rs1800591 genotype, it is important to interpret it within the context of your overall health. This variant is a common genetic feature, and having a particular genotype does not mean you will develop a specific condition. Genetic associations are statistical observations made across large groups of people and cannot predict individual health outcomes. You cannot use this information to diagnose yourself or to make medical decisions. If you are concerned about your liver health or lipid levels, the most effective approach is to consult with a healthcare professional. They can evaluate your clinical history, blood work, and lifestyle factors to provide personalized guidance that is far more accurate than any single genetic marker.
How common is this variant?
The rs1800591 variant is a common polymorphism with varying frequencies observed across different global ancestries, with the GG genotype often being the most prevalent.
Frequently asked questions
Is rs1800591 a diagnostic test for fatty liver?
No, rs1800591 is not a diagnostic test. It is a genetic variant associated with statistical trends in research, not a clinical tool for diagnosing liver disease.
Does the T allele cause liver disease?
No, the T allele does not directly cause liver disease. While some studies suggest a statistical association with lipid levels, liver health is influenced by many complex genetic and environmental factors.
Should I change my diet based on my MTTP genotype?
You should not change your diet based solely on this genotype. Always consult with a doctor or a registered dietitian before making significant changes to your nutrition or lifestyle.
Where can I find more information on MTTP?
You can find reliable information on the MTTP gene and its functions through resources like MedlinePlus Genetics or the NCBI Gene database.
Sources & further reading
Educational information only, last refreshed 10/16/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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