Hepatic fat during fasting and refeeding by MRI fat quantification

Abstract

Purpose To explore the sensitivity of high-field small animal magnetic resonance imaging to dynamic changes in fat content in the liver and to characterize the effect of prandial state on imaging studies of hepatic fat. Materials and Methods A total of 3 time-points were acquired using asymmetric spin-echo acquisitions for 12 mice with 24 hour spacing. After the first scan, half of the cohort was placed on a water-only diet. The second half of the cohort continued to have access to their high-fat chow. The scans were repeated after 24 hours. All animals were then returned to the high-fat diet, and the scans were again repeated after 24 hours. Fat fraction maps were computed using previously described methods. Regions of interests were manually drawn in the livers, and the patterns of the two groups over time were compared. Results Five out of six of the animals in the starved group showed an increase in hepatic fat fraction during the fasting period (average increase 0.54±0.48), which decreased on refeeding. ANOVA analysis indicated that the results significantly depended on both the group and the time-point (p=0.003). Conclusion Fat-water imaging methods are able to measure hepatic fat changes caused by short-term dietary perturbations.

Acute Fasting Induces Expression of Acylglycerophosphate Acyltransferase (AGPAT) Enzymes in Murine Liver, Heart, and Brain

“…Among these changes, the largest effect was a 92-fold up-regulation of Agpat2, which is consistent with prior reports of a role for this enzyme specifically in triacylglycerol storage [13,14]. These data are therefore consistent with reports that hepatic TAG synthesis is increased [15], and hepatic TAG stores are enriched following an acute fast [16][17][18][19], and that the liver acts as the main site of phospholipid synthesis in the fasted state [20].…”

Fasting enriches liver triacylglycerol with n-3 polyunsaturated fatty acids: implications for understanding the adipose–liver axis in serum docosahexaenoic acid regulation

“…As expected (Ryu et al 2005;Leone et al 1999;Narayan et al 2014), fasting more than tripled the total hepatic content of TAG from 13.41 ± 3.42 lg fatty acid/mg liver in ad libitum fed mice to 44.53 ± 9.52 lg fatty acid/mg liver in fasted mice (Supplementary Table 3). As a result, the total concentration of all major fatty acid classes and most individual fatty acid species also increased.…”