Ectodysplasin A Is Increased in Non-Alcoholic Fatty Liver Disease, But Is Not Associated With Type 2 Diabetes

Abstract

Ectodysplasin A (EDA) was recently identified as a liver-secreted protein that is increased in the liver and plasma of obese mice and causes skeletal muscle insulin resistance. We assessed if liver and plasma EDA is associated with worsening non-alcoholic fatty liver disease (NAFLD) in obese patients and evaluated plasma EDA as a biomarker for NAFLD. Using a cross-sectional study in a public hospital, patients with a body mass index >30 kg/m² (n=152) underwent liver biopsy for histopathology assessment and fasting liver EDA mRNA. Fasting plasma EDA levels were also assessed. Non-alcoholic fatty liver (NAFL) was defined as >5% hepatic steatosis and nonalcoholic steatohepatitis (NASH) as NAFLD activity score ≥3. Patients were divided into three groups: No NAFLD (n=45); NAFL (n=65); and NASH (n=42). Liver EDA mRNA was increased in patients with NASH compared with No NAFLD (P=0.05), but not NAFL. Plasma EDA levels were increased in NAFL and NASH compared with No NAFLD (P=0.03). Plasma EDA was related to worsening steatosis (P=0.02) and fibrosis (P=0.04), but not inflammation or hepatocellular ballooning. ROC analysis indicates that plasma EDA is not a reliable biomarker for NAFL or NASH. Plasma EDA was not increased in patients with type 2 diabetes and did not correlate with insulin resistance. Together, we show that plasma EDA is increased in NAFL and NASH, is related to worsening steatosis and fibrosis but is not a reliable biomarker for NASH. Circulating EDA is not associated with insulin resistance in human obesity.

Clinical trial registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12615000875505, identifier ACTRN12615000875505.

Keywords: ectodysplasin A; hepatokine; insulin resistance; non-alcoholic fatty liver disease; type 2 diabetes (T2DM).

Figure 1

Liver EDA mRNA and NAFLD progression. Hepatic EDA expression by (A) patient group, (B) steatosis grade, (C) lobular inflammation score, (D) hepatocellular ballooning score and (E) fibrosis score. Shown are median and 95% confidence interval. Data were analyzed by Kruskal-Wallis test and Dunn’s multiple comparisons test. Adjoining lines indicate P<0.05.

Figure 2

Plasma EDA and NAFLD progression. Plasma EDA levels by (A) patient group, (B) steatosis grade, (C) lobular inflammation score, (D) hepatocellular ballooning score and (E) fibrosis score. Shown are median and 95% confidence interval. Data were analyzed by Kruskal-Wallis test and Dunn’s multiple comparisons test. Adjoining lines indicate P<0.05. (F) Relationship between liver EDA mRNA and plasma EDA.

Figure 3

Receiver operating characteristic (ROC) curve for the prediction of NAFL and NASH. The diagnostic accuracy of clinical markers with and without the addition of EDA was calculated for (A) NAFL, (B) NASH, and (C) NAFLD. Thicker lines represent statistically significant models with P<0.05.

Figure 4

Relationship between plasma EDA, type 2 diabetes and insulin resistance. (A) Plasma EDA in patients without NAFLD or type 2 diabetes, with NAFLD and without type 2 diabetes and with both NAFLD and type 2 diabetes. Data were analyzed by Kruskal-Wallis test and Dunn’s multiple comparisons test. Adjoining lines indicate P<0.05. (B–D) Relationship between plasma EDA and (B) HOMA-IR (insulin resistance), (C) fasting blood glucose, and (D) HbA1c.

Figure 5

EDA gene expression in various tissues. EDA tissue gene expression (shown as TPM—transcripts per million) adapted from GTEx (based on ENSG00000158813), showing that the liver is the tissue with the 6^th highest EDA expression compared to 54 tissues examined. Box plots are shown as median and 25^th/75^th percentile. Data Source: GTEx Analysis Release V8 (dbGaP Accession phs000424.v8.p2).