Diabetes Is Predicted by Fatty Liver Indices

Fatty liver is known to be linked with insulin resistance, alcohol intake, diabetes and obesity. Biopsy and even scan-assessed fatty liver are not always feasible in clinical practice. This report evaluates the predictive ability of two recently published markers of fatty liver: the Fatty Liver Index (FLI) and the NAFLD fatty liver score (NAFLD-FLS), for 9-year incident diabetes.

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver injury in Western countries and about 20 to 30% of people with NAFLD have non-alcoholic steatohepatitis (NASH), which is associated with fibrosis and can progress to cirrhosis, terminal liver failure and hepatocellular carcinoma. The obese, the insulin resistant and the diabetic patient have a higher prevalence of NAFLD, and metabolic steatosis may be a major risk factor for disease progression. A liver biopsy is the only way to reliably diagnose NAFLD, but even this technique is not 100% precise due to the sampling variability of biopsies. Clearly a biopsy is very invasive and carries a risk, thus proxy markers are often used. However while the extent of liver fat correlates with liver enzymes: alanine aminotransferase (ALT), asparate aminotransferase (AST), gamma glutamyl transferase (GGT), there are other commonly measured factors such as obesity which are also associated. Thus to aid in screening for fatty liver, Bedogni et al., developed a simple score, from a cohort of patients with suspected liver disease and a group of controls. Their Fatty Liver Index (FLI) uses an equation with GGT, triglycerides, body mass index (BMI) and waist circumference. Another score has recently been published by a Finnish group, the NAFLD fatty liver score (NAFLD-FLS). This includes in its definition, the presence of diabetes, the metabolic syndrome, and levels of ALT, AST and fasting insulin.

At baseline, there were 1,861 men and 1,950 women, non-diabetic, aged 30 to 65 years. Over the follow-up, 203 incident diabetes cases (140 men, 63 women) were identified by diabetes-treatment or fasting plasma glucose ≥ 126mg/dL.(7.0 mmol/l). The FLI includes: BMI, waist circumference, triglycerides and gamma glutamyl transferase, and the NAFLD-FLS: the metabolic syndrome, diabetes, insulin, alanine aminotransferase, and asparate aminotransferase. Logistic regression was used to determine the odds ratios for incident diabetes associated with categories of the fatty liver indices.

In comparison to those with a FLI < 20, the age-adjusted odds ratio (95% confidence interval) for diabetes for a FLI ≥ 70 was 9.33 (5.05–17.25) for men and 36.72 (17.12–78.76) for women; these were attenuated to 3.43 (1.61–7.28) and 11.05 (4.09 29.81), after adjusting on baseline glucose, insulin, hypertension, alcohol intake, physical activity, smoking and family antecedents of diabetes; odds ratios increased to 4.71 (1.68–13.16) and 22.77 (6.78–76.44) in those without an excessive alcohol intake. The NAFLD-FLS also predicted incident diabetes, but with odds ratios much lower in women, similar in men.

The novel finding of the study is that these two recently published indices of liver fat are predictive of diabetes in both men and women. These fatty liver indexes are simple clinical tools for evaluating the extent of liver fat and they are predictive of incident diabetes. Physicians should screen for diabetes in patients with fatty liver.