Hepatic Steatosis in Morbidly Obese Patients Undergoing Gastric Bypass Surgery: Assessment With Open-System H-1-MR Spectroscopy
ABSTRACT The purpose of this study was to assess, with histopathologic control, the use of open-system 1-T (1)H MR spectroscopy for the evaluation of hepatic steatosis in morbidly obese patients undergoing gastric bypass surgery.
Patients underwent (1)H MR spectroscopy (MRS) for the assessment of steatosis before and 3 months after surgery. Liver biopsy was performed during surgery. Hepatic steatosis was expressed as the ratio of fat peak area to cumulative water and fat peak areas. Histopathologic percentage of steatosis was graded as none (0-5%), mild (5-33%), moderate (33-66%), or severe (> 66%). The accuracy of (1)H-MRS and Spearman correlation coefficient were calculated. Differences between groups were assessed with the Wilcoxon signed rank and Mann-Whitney tests.
The study included 38 patients (median age, 45.5 years; median body mass index, 47.7). Before surgery, median steatosis measured with (1)H-MRS was 5.8%. The accuracy of (1)H-MRS was 89% (32/36), and the (1)H-MRS findings correlated with the histopathologic assessment of steatosis (r = 0.85, p < 0.001). With (1)H-MRS, no steatosis was discriminated from mild steatosis (p = 0.011), mild was discriminated from moderate steatosis (p < 0.001), and moderate was discriminated from severe steatosis (p = 0.021). Three months after surgery, steatosis had decreased to 3.1% (p < 0.001). The prevalence of hepatic steatosis measured with (1)H-MRS decreased from 53% to 32%.
In the care of morbidly obese patients undergoing assessment of hepatic steatosis and changes in steatosis after gastric bypass surgery, (1)H-MRS with an open 1-T MRI system is feasible. Measurements of hepatic fat with (1)H-MRS are accurate and correlate with clinical and histopathologic results.
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ABSTRACT: Background: The recently identified circulating sCD36 has been proposed to reflect tissue CD36 expression, and is upregulated in case of obesity, insulin resistance and hepatic steatosis. The aim of this study was to explore the effect of weight loss secondary to bariatric surgery in relation to sCD36 among morbidly obese individuals. Furthermore, we investigated the levels of sCD36 in relation to obesity-related metabolic complications, low-grade inflammation and fat distribution. Methods: Twenty morbidly obese individuals (body mass index (BMI) 43.0±5.4 kg m−2) with a referral to Roux-en-Y gastric bypass were included. Anthropometric measurements and fasting blood samples were collected at a preoperative baseline visit and 3 months after surgery. sCD36 was measured by an in-house assay, whereas insulin sensitivity and the hepatic fat accumulation were estimated by the homeostasis model assessment (HOMA-%S) and liver fat percentage (LF%), respectively. Results: Postoperatively, BMI was reduced by 20% to 34.3±5.2 kg m−2 (P<0.001). sCD36 was reduced by 31% (P=0.001) and improvements were observed in the amount of fat mass (P<0.001), truncal fat mass (P<0.001), circulating triglycerides (P=0.001), HOMA-%S (P=0.007), LF% (P=0.001) and the inflammatory marker high-sensitive C-reactive protein (P=0.005). sCD36 correlated with triglycerides (ρ=0.523, P=0.001) and truncal fat mass (ρ=0.357, P=0.026), and triglycerides were found to be an independent predictor of sCD36. At baseline, participants with the metabolic syndrome had a higher LF% and higher levels of the inflammatory biomarker YKL-40 (P=0.003 and P=0.014) as well as a tendency towards higher levels of sCD36. Conclusion: sCD36 was reduced by weight loss and associated with an unhealthy fat accumulation and circulating triglycerides, which support the proposed role of sCD36 as a biochemical marker of obesity-related metabolic complications and risks.Nutrition & Diabetes 04/2014; 4(4):e114. DOI:10.1038/nutd.2014.11 · 1.52 Impact Factor
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ABSTRACT: Rationale and Objectives To diagnose hepatic steatosis with noninvasive magnetic resonance (MR)–based measurements, threshold values of liver fat percentages are used. However, these differ between studies. Consequently, the choice of threshold values influences diagnostic accuracy, especially in subjects with borderline hepatic steatosis. In this study, we compared 1H-MR spectroscopy (MRS) and biochemically determined liver fat content in mice with moderately elevated fat content and studied the diagnostic accuracy of 1H-MRS using two literature-based threshold values. Materials and Methods Fifty mice were divided into three groups: 21 C57Bl/6OlaHSD (B6) mice on a high-fat diet, 20 B6 mice on a control diet, and 9 LDLr−/− mice on a high-fat high-cholesterol diet. 1H-MRS was performed using multi-echo STEAM at 3T to derive a fat mass fraction (1H-MRS fat content). Biochemical fat content was determined from liver homogenates. Correlation and agreement were assessed with the Pearson correlation coefficient and the Bland–Altman analysis and diagnostic accuracy by calculating sensitivity, specificity, and positive and negative predictive values. Results All mice were pooled to form a single cohort. Mean (±standard deviation) biochemical fat content was 32.2 (±13.9) mg/g. Mean 1H-MRS fat content did not differ at 30.2 (±12.0) mg/g (P = .13). Correlation r was 0.74 (P < .0001). Bland–Altman analysis indicated that 1H-MRS fat content underestimated biochemical fat content by 2.1 mg/g. The diagnostic accuracy of 1H-MRS depended to a great extent on the chosen reference threshold value. Conclusions 1H-MRS measurement of moderately elevated liver fat content in mice correlated substantially with biochemical fat content measurement. Contrary to earlier studies, diagnostic accuracy of 1H-MRS fat content in borderline liver fat content appears limited.Academic Radiology 11/2014; 21(11):1446–1454. DOI:10.1016/j.acra.2014.06.009 · 2.08 Impact Factor
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ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) is the most common, chronic liver disease worldwide. Within this spectrum, steatosis alone is apparently benign, while nonalcoholic steatohepatitis may progress to cirrhosis and hepatocellular carcinoma. NAFLD is strongly associated with obesity, dyslipidemia, type 2 diabetes mellitus, and cardiovascular disease. The pathogenesis of hepatic steatosis is not clearly known, but its main characteristics are considered insulin resistance, mitochondrial dysfunction, increased free fatty acids reflux from adipose tissue to the liver, hepatocyte lipotoxicity, stimulation of chronic necroinflammation, and fibrogenic response. With recent advances in technology, advanced imaging techniques provide important information for diagnosis. There is a significant research effort in developing noninvasive monitoring of disease progression to fibrosis and response to therapy with potential novel biomarkers, in order to facilitate diagnosis for the detection of advanced cirrhosis and to minimize the need of liver biopsy. The identification of NAFLD should be sought as part of the routine assessment of type 2 diabetics, as sought the microvascular complications and cardiovascular disease, because it is essential for the early diagnosis and proper intervention. Diet, exercise training, and weight loss provide significant clinical benefits and must be considered of first line for treating NAFLD.International Journal of Endocrinology 04/2013; 2013:450639. DOI:10.1155/2013/450639 · 1.52 Impact Factor