Abstract
Elevated hepatic lipid content (IntraHepatic Lipid, IHL) increases the risk of metabolic complications. Although prolonged exercise training lowers IHL, it is unknown if acute exercise has the same effect. Furthermore, hepatic ATP content may be related to insulin resistance and IHL. We aimed to investigate if acute exercise leads to changes in IHL and whether this is accompanied by changes in hepatic ATP. Twenty-one men (age 54.8 ± 7.2 years, BMI 29.7 ± 2.2 kg/m2) performed a 2 h cycling protocol, once while staying fasted and once while ingesting glucose. IHL was determined at baseline, 30 min post-exercise and 4 h post-exercise. Additionally ATP/Total P ratio was measured at baseline and 4 h post-exercise. Compared with baseline values we did not observe any statistically significant changes in IHL within 30 min post-exercise in neither the fasted nor the glucose-supplemented condition. However, IHL was elevated 4 h post-exercise compared with baseline in the fasted condition (from 8.3 ± 1.8 to 8.7 ± 1.8%, p = 0.010), an effect that was blunted by glucose supplementation (from 8.3 ± 1.9 to 8.3 ± 1.9%, p = 0.789). Acute exercise does not decrease liver fat in overweight middle-aged men. Moreover, IHL increased 4 h post-exercise in the fasted condition, an increase that was absent in the glucose-supplemented condition. These data suggest that a single bout of exercise may not be able to lower IHL.
Highlights
Elevated hepatic lipid content (IntraHepatic Lipid, IHL) increases the risk of metabolic complications
Eleven subjects met the clinical criteria for Non-alcoholic fatty liver disease (NAFLD) (.5.6% liver fat)[19], while in ten subjects hepatic fat content was within the normal physiological range (,5.6% liver fat)
There were no significant differences in body weight, BMI, whole body fat percentage and fasting plasma glucose levels between subjects that would qualify as NAFLD and subjects with a normal liver fat content, but the NAFLD subjects were somewhat younger than the subjects with normal liver fat content (51.7 6 5.4 years vs 58.2 6 7.7 years, p 5 0.036) and had a higher diastolic blood pressure (p 5 0.011)
Summary
Elevated hepatic lipid content (IntraHepatic Lipid, IHL) increases the risk of metabolic complications. Recent studies have suggested that prolonged exercise training reduces liver fat content and may thereby contribute to the beneficial effects of exercise on metabolic risk[3,4,5,6]. Plasma FFA is an important source for hepatic triglyceride[17], and high levels of plasma FFA during exercise might mask a potential exercise-lowering effect To circumvent this bias, we here investigated the effect of acute exercise on IHL in middle-aged overweight sedentary subjects with a wide range of liver fat content under conditions with high and low plasma FFA concentrations. We studied if changes in IHL are accompanied by changes in hepatic ATP concentration To this end, we employed 1H-MRS to determine IHL before and after exercise performed with and without glucose ingestion to suppress plasma FFA levels, as well as 4 h post exercise. We employed 1H-MRS to determine IHL before and after exercise performed with and without glucose ingestion to suppress plasma FFA levels, as well as 4 h post exercise. 31P-MRS was employed before exercise and 4 h post exercise to determine hepatic ATP concentrations
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