MRI-PDFF在MASLD大鼠模型中准确反映肝脂肪变，不受炎症和纤维化影响

BACKGROUND: Magnetic resonance imaging-proton density fat fraction (MRI-PDFF) is a noninvasive biomarker for hepatic steatosis, but its quantitative reliability in the presence of inflammation or fibrosis remains incompletely defined.

METHODS: Forty rats were fed a methionine-and choline-deficient (MCD) diet for 2, 4, 6, 8, or 10 weeks (n = 8 per time point), while eight additional rats served as controls. All animals underwent MRI-PDFF examination immediately prior to sacrifice, followed by histopathologic assessment within 4 h using the NASH Clinical Research Network scoring system. Associations between PDFF and histologic fat content, steatosis grade, inflammation, and fibrosis were analyzed using Pearson and Spearman correlations, with subgroup analyses performed in animals with fibrosis.

RESULTS: MRI-PDFF showed a near-perfect correlation with histologic fat percentage in the entire cohort (r = 0.994, p < 0.0001), which remained strong in animals with fibrosis (r = 0.983, p < 0.0001). PDFF was also strongly associated with steatosis grade overall (ρ = 0.893, p < 0.0001) and within the fibrosis subgroup (ρ = 0.727, p < 0.0001). In contrast, PDFF values did not differ significantly across inflammation grades and were comparable between animals with and without lobular inflammation (all p > 0.05). Intra-scan reproducibility of PDFF was excellent (intraclass correlation coefficient (ICC) = 0.935).

CONCLUSIONS: MRI-PDFF provides a robust and reproducible quantitative assessment of hepatic steatosis in the MCD rat model of MASLD. Its quantitative relationship with hepatic fat burden and steatosis grade is preserved in animals with concomitant fibrosis and is not materially influenced by inflammatory activity.