Background Quantification of pancreatic fat (PF) and intrahepatic lipids (IHL) is of increasing interest in subjects at risk for metabolic diseases. There is limited data available on short‐ and medium‐term variability of PF/IHL and on their dependence on nutritional status. Purpose To assess short‐term intraday variations of PF/IHL after a high‐fat meal as well as medium‐term changes after 5 days of high‐caloric diet. Study Type Prospective cohort study. Subjects A total of 12 subjects (six males) for intraday variations study, 15 male subjects for medium‐term high‐caloric diet study and 11 age‐ and body mass index (BMI)‐matched controls. Field Strength/Sequence A 3 T; chemical‐shift encoded multiecho gradient echo sequence. Assessment For the intraday study, subjects were scanned after overnight fasting and after a high fat meal on the same day. For the medium‐term study, 26 subjects were scanned after overnight fasting with 15/11 rescanned after 5 days of high‐calorie diet/isocaloric diet. Proton density fat fraction (PDFF) maps were generated inline on the scanner. Regions of interest were manually drawn in head, body, and tail of pancreas and in the liver by a medical physicist and a doctoral student (26/4 years of experience). PF was calculated as the average of the head, body, and tail measurements. Statistical Tests Repeated measurements ANOVA for assessing changes in PF/IHL, linear correlation analyses for assessing relationships of PF/IHL with BMI. Significance level P < 0.05 for all. Results Nonsignificant changes in PF (2.6 ± 1.0 vs. 2.7 ± 0.9% after high‐fat meal, 1.4 ± 0.8 vs. 1.5 ± 0.6% [high‐caloric diet] and 1.5 ± 0.8 vs. 1.8 ± 1.0% [isocaloric control group]), nonsignificant changes in IHL after high‐fat meal (2.6 ± 1.3 vs. 2.5 ± 0.9%) and in the control group (1.1 ± 0.6 vs. 1.2 ± 1.1%), significantly increased IHL after high‐caloric diet (1.7 ± 2.2% vs. 2.7 ± 3.6%). Nonsignificant changes in PF (2.6 ± 1.0 vs. 2.7 ± 0.9% after high‐fat meal, 1.4 ± 0.8 vs. 1.5 ± 0.6% [high‐caloric diet] and 1.5 ± 0.8 vs. 1.8 ± 1.0% [isocaloric control group]), nonsignificant changes in IHL after high‐fat meal (2.6 ± 1.3 vs. 2.5 ± 0.9%) and in the control group (1.1 ± 0.6 vs. 1.2 ± 1.1%), significantly increased IHL after 5‐days of high‐caloric diet (1.7 ± 2.2% vs. 2.7 ± 3.6%). Data Conclusion Time of day and nutritional status have no significant influence on PF/IHL and are therefore not likely to be major confounders in epidemiologic or clinical studies. Evidence Level 2 Technical Efficacy Stage 1
BACKGROUND Quantification of pancreatic fat (PF) and intrahepatic lipids (IHL) is of increasing interest in cross-sectional epidemiological and interventional studies in subjects at risk for metabolic diseases. Up to now, short- and medium-term variations as well as their dependence on actual nutritional status are almost unknown. PURPOSE or HYPOTHESIS To assess short-term intraday variations of PF/IHL after a high-fat meal as well as medium-term changes after 5 days of high-caloric diet with a 1500 kcal surplus on individual daily energy requirement. STUDY TYPE Prospective cohort study. SUBJECTS Twelve healthy subjects (6m/6f) for intraday variations, 15 healthy male subjects for medium-term high-caloric diet and 11 age- and BMI-matched controls. FIELDSTRENGTH/SEQUENCE 3 T whole-body imager (Magnetom Vida, Siemens Healthineers, Erlangen, Germany), assessment of proton density fat fraction by chemical-shift encoded MRI (multi-echo gradient echo sequence, qDixon). ASSESSMENT Manually drawn regions of interest in head, body and tail of pancreas as well as in liver by an experienced medical physicist carefully avoiding inclusion of surrounding visceral fat (pancreas) or blood-vessels (liver). STATISTICAL TESTS Repeated measurements Anova for variabilities of PF and IHL, linear correlation analyses for relation of PF, IHL and BMI. Significance level p < 0.05 for all. RESULTS (must have numerical data and statistical testing for each phrase) Non-significant changes in PF in both studies (2.5±0.9 vs. 2.5±1.0% after high-fat meal, 1.4±0.8 vs. 1.6±0.6% after high-caloric diet and 1.6±0.7 vs. 1.8±1.0% in the isocaloric control group), unchanged IHL after high-fat meal (2.5±0.9 vs. 2.4±1.0 %) and in the control group (1.1±0.6 vs. 1.2±1.1%), but significantly increased IHL after 5-day high-caloric diet (1.6±2.2% vs. 2.6±3.6%, p < 0.05). DATA CONCLUSION Daytime and nutritional status have no significant influence on ectopic fat depots in pancreas and liver and will therefore represent no major confounders in epidemiologic or clinical studies.
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