Several studies have shown that elevated plasma FGF21 levels are found in subjects with disorders related to obesity and insulin
resistance. We aimed to assess the role of FGF21 as a potential biomarker for the diagnosis of NAFLD and/or NASH. Methods: We recruited 204 patients with and 24 without NAFLD (51 ±1 vs.50±3 years [p=0.69], male: 72% vs.58% PI3K Inhibitor Library research buy [p=0.24], 34.1 ±0.3 vs.29.3±1.0 kg/m2 [p<0.01]) and measured: 1)plasma FGF21 and cytokeratin-18 fragments (CK-18) levels, 2) liver fat by magnetic resonance imaging and spectroscopy (MRS), 3) hepatic insulin resistance index (HIRi=fasting plasma insulin x endogenous glucose production) and adipose EX 527 molecular weight tissue insulin resistance index (ATIR= fasting plasma insulin x free fatty acids), 4) muscle insulin sensitivity (Rd) during a high-dose insulin euglycemic clamp, and 5) liver histology (biopsy) (n=159). Results: Plasma levels of FGF21 were significantly
increased in patients with NAFLD (337 [217-526] vs.153 [92-323] pg/ml, p<0.001). However, FGF21 only showed moderate correlations with liver fat (r=0.26, p<0.001), HIRi (r=0.26, p=0.002), ATIR (r=0.23, p<0.001) and Rd (r=-0.35, p<0.0001). As a stand-alone test for the diagnosis of NAFLD, FGF21 had rather disappointing results. With the optimal cut-off point of 205 pg/ml we obtained a sensitivity of 78% (71-84%) and specificity of 63% (41一81%). Positive and negative predictive values were 94% (89-97%) and 28% (17-42%),
respectively. Patients with NASH had higher levels of FGF21 when compared to patients with simple steatosis on liver biopsy (386 [252-581] vs.328 [170—451] pg/ml, p=0.03). However, correlations between check details FGF21 and NAFLD activity score (r=0.22, p<0.01) and fibrosis stage (r=0.30, p<0.001) were weak. As a tool for the diagnosis of NASH (optimal cut-off point: 376 pg/ml), FGF21 also showed unsatisfactory results, with low sensitivity (53% [43 62%]) and specificity (67% [50 一 81%]). With the combined use of CK-18 and FGF21 for the diagnosis of NASH, sensitivity improved slightly to 57% (49-66%) and specificity to 85% (70-94%). However, these results were similar to the ones of CK-18 alone (sensitivity 46% [38-53%] and specificity 86% [73-95%]). Conclusions: Plasma FGF21 levels were only moderately correlated with different measures of insulin resistance, hepatic steatosis and liver histology. Based on these findings, FGF21 is not a useful stand-alone test (or combined with CK-18) for the diagnosis of NAFLD or NASH.