UCSF

Disease conditions like obstructive sleep apnea (OSA) and human immunodeficiency virus (HIV) infections are characterized by chronic low-grade inflammation, leading to poor metabolic health. This work is focused on comparing MR-based fat measures to indicators of worse metabolic health, namely OSA severity and hydroxyproline, a biomarker of subcutaneous fat (SAT) fibrosis. The study also explored the utility of novel MRI methods of diffusion-weighted imaging of fat and T1 mapping to detect fibrosis in the SAT. There were 33 participants with OSA and 58 participants with or without HIV infection who had hydroxyproline measured via SAT biopsy, 13 of whom had the novel MRI measures of fibrosis. The liver, visceral, and SAT volumes were segmented using artificial intelligence-based methods, and the pancreas was manually drawn on proton density fat fraction (PDFF) images. Apparent diffusion coefficient (ADC) and T1 were measured in regions of interest drawn in the SAT. Liver fat fraction, liver fat content, and pancreatic fat fraction were higher with increased severities of sleep apnea, p0.01. Furthermore, liver fat fraction, pancreatic fat fraction, and visceral fat volume were higher in subjects with high hydroxyproline levels on biopsy, p0.03. The ADC of SAT at b-values of 3×10-3 s/mm2 were negatively correlated with hydroxyproline levels. It can be concluded that more severe OSA and higher hydroxyproline were associated with worse metabolic health. The role of diffusion-weighted imaging of fat with high b-values to detect SAT fibrosis is also encouraging and opens up avenues for future research.