Noninvasive assessment of hepatic lipid composition: Advancing understanding and management of fatty liver disorders
✍ Scribed by Nathan A. Johnson; David W. Walton; Toos Sachinwalla; Campbell H. Thompson; Kate Smith; Patricia A. Ruell; Stephen R. Stannard; Jacob George
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 365 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0270-9139
No coin nor oath required. For personal study only.
✦ Synopsis
Nonalcoholic fatty liver is frequently observed in obese individuals, yet the factors that predict its development and progression to liver disease are poorly understood. We proposed that proton magnetic resonance spectroscopy ( 1 H-MRS) might allow noninvasive assessment of hepatic lipid composition. Lipid saturation (SI) and polyunsaturation (PUI) indices measured by 1 H-MRS were in agreement with those expected in oils of known composition. Hepatic triglyceride concentration (HTGC) and composition were then measured in healthy lean (LEAN) men, obese men with normal HTGC (OB), and obese men with hepatic steatosis (OB؉HS). The effect of marked changes in dietary fat consumption on hepatic lipids were also compared in lean men after 67 hours of a normal mixed (NM) diet versus a low-carbohydrate, high-saturated-fat (LCHF) diet. SI was significantly higher in OB؉HS (0.970 ؎ 0.004) and OB (0.944 ؎ 0.008) versus LEAN (0.818 ؎ 0.025) (P < 0.01 for both). PUI was significantly lower in OB؉HS (0.003 ؎ 0.001) and OB (0.022 ؎ 0.005) versus LEAN (0.120 ؎ 0.021) (P < 0.01), and significantly lower in OB؉HS versus OB (P < 0.05). LCHF diet did not alter HTGC, SI, or PUI (P > 0.05). The 1 H-MRS method provides for rapid, qualitative assessment of lipid composition. Application of this technique in the liver produces results that are consistent with biopsy-based approaches demonstrating that relative hepatic lipid saturation increases and polyunsaturation decreases with obesity. Obesity-related hepatic steatosis is characterized by further depletion of polyunsaturated hepatic lipids. Conclusion: This readily available and noninvasive approach should promote further study into interactions between hepatic and whole-body lipid metabolism and help to elucidate the pathogenesis of disorders characterized by lipid accumulation within the liver. (HEPATOLOGY 2008;47:1513-1523.)
N onalcoholic fatty liver disease (NAFLD) encompasses a spectrum of liver disorders ranging from simple hepatic steatosis (nonalcoholic fatty liver) to steatohepatitis (NASH), with or without fibrosis. Hepatic steatosis is characterized by excessive storage of triglyceride within the liver and may affect 30% of the adult population 1,2 and up to 75% of obese individuals 3 in affluent nations. Hepatic steatosis is an independent risk factor for cardiovascular disease, 4 and more recently, NAFLD has been considered the hepatic manifestation of the metabolic syndrome. 5 In a proportion of individuals, steatosis in the liver may progress to hepatic fibrosis and cirrhosis, yet the host and environmental factors mediating this progression remain ill-defined.
Liver biopsy and histological evaluation is the gold standard for the precise diagnosis and categorization of fatty liver disorders. However, the low tissue yield of this method and its invasive nature limits biopsy as a tool to screen the large number of individuals at risk of NAFLD and to monitor treatment and disease progression. These difficulties, in part, explain the limited research concerning treatments for NAFLD and interactions between hepatic and whole-body lipid metabolism.