MASLD Is Not One Disease: Genetics Reveals Distinct Biological Pathways in Diabetes
Why do some people with type 2 diabetes develop cirrhosis while others with similar obesity and glycaemic control have relatively benign fatty liver?
A new Diabetologia review argues that the answer lies in the genetics of MASLD (metabolic dysfunction-associated steatotic liver disease). Human genetic studies show that liver fat accumulation can arise through fundamentally different biological mechanisms, leading to very different clinical outcomes.
Three major genetic pathways emerge:
🔹 Liver-intrinsic lipid retention
Variants such as PNPLA3 I148M and TM6SF2 E167K impair lipid droplet turnover or VLDL export, trapping triglycerides within hepatocytes. These variants strongly increase fibrosis, cirrhosis and hepatocellular carcinoma risk while often showing surprisingly favorable lipid profiles.
🔹 Enhanced hepatic de novo lipogenesis
Variants in GCKR, TRIB1, SREBF1, and GPAM drive conversion of glucose into liver fat. These pathways closely connect MASLD with hyperglycaemia, insulin resistance and cardiometabolic disease.
🔹 Adipose tissue dysfunction
Variants affecting adipose expandability and insulin signaling promote excessive fatty acid spillover into the liver. In these individuals, hepatic steatosis reflects systemic metabolic dysfunction rather than a purely hepatic defect.
One of the most important insights is that equal liver fat does not imply equal risk.
The review highlights that:
• PNPLA3/TM6SF2 carriers often develop severe fibrosis despite relatively favorable cardiovascular profiles.
• GCKR/TRIB1-related steatosis is more tightly linked to insulin resistance, type 2 diabetes progression and cardiovascular disease.
• Similar MRI-PDFF values may therefore represent completely different biological diseases.
Genetic studies also reveal strong interactions with diabetes itself.
Hyperglycaemia, insulin resistance and obesity amplify the effects of many MASLD risk alleles. The classic example is PNPLA3, whose impact on liver fat and fibrosis becomes much stronger in individuals with obesity or diabetes.
Importantly, genetics is beginning to influence precision medicine approaches.
Protective variants such as:
✓ HSD17B13 loss-of-function
✓ MTARC1 protective alleles
reduce progression to steatohepatitis, fibrosis and hepatocellular carcinoma, making these pathways attractive therapeutic targets. Early RNA-based and antisense therapies targeting genetically validated pathways are already entering clinical development.
The review proposes a future framework where:
• Polygenic risk scores
• MRI-based liver phenotyping
• Fibrosis biomarkers
• Met