Hepatic triglyceride content and its relation to body adiposity: a magnetic resonance imaging and proton magnetic resonance spectroscopy study

Abstract

Background: Hepatic steatosis is associated with obesity and type II diabetes. Proton magnetic resonance spectroscopy (1H MRS) is a non-invasive method for measurement of tissue fat content, including intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL).

Patients and methods: We used 1H MRS and whole body magnetic resonance imaging (MRI) to assess the relationship between IHCL accumulation, total body adipose tissue (AT) content/distribution, and IMCL content in 11 subjects with biopsy proven hepatic steatosis and 23 normal volunteers.

Results: IHCL signals were detectable in all subjects but were significantly greater in hepatic steatosis (geometric mean (GM) 11.5 (interquartile range (IQR) 7.0-39.0)) than in normal volunteers (GM 2.7 (IQR 0.7-9.3); p=0.02). In the study group as a whole, IHCL levels were significantly greater in overweight compared with lean subjects (body mass index (BMI) >25 kg/m2 (n=23): GM 7.7 (IQR 4.0-28.6) v BMI <25 kg/m2 (n=11): GM 1.3 (IQR 0.3-3.6; p=0.004)). There was a significant association between IHCL content and indices of overall obesity (expressed as a percentage of body weight) for total body fat (p=0.001), total subcutaneous AT (p=0.007), and central obesity (subcutaneous abdominal AT (p=0.001) and intra-abdominal AT (p=0.001)), after allowing for sex and age. No correlation between IHCL content and IMCL was observed. A significant correlation was observed between serum alanine aminotransferase and liver fat content (r=0.57, p=0.006).

Conclusions: Our results suggest that hepatic steatosis appears to be closely related to body adiposity, especially central obesity. MRS may be a useful method for monitoring IHCL in future interventional studies.

Figures

Figure 1

A transverse image through the abdomen showing the two voxel positions used to study regional variation in hepatic fat content.

Figure 2

Typical proton magnetic resonance liver spectra from three volunteers showing progressive degrees of fatty infiltration. Spectrum (a) shows a liver with minimal fatty infiltration (1.0%), (b) a liver with moderate fatty infiltration (10.2%), and spectrum (c) shows a liver with severe fatty infiltration (74.9%). Resonances from water and IHCL-(CH2)n- can be clearly identified. Values refer to the peak area of the IHCL peak with reference to the water peak after correcting for T1 and T2. IHCL, intrahepatocellular lipids.

Figure 3

Difference in intrahepatocellular lipid (IHCL) content between voxels placed in different positions in the left lobe of the liver.

Figure 4

Relationship between intrahepatocellular lipid (IHCL) content and serum alanine aminotransferase (ALT): loge IHCL = −3.271+1.3377×loge ALT (r = 0.57, p = 0.006).