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Johnston K.L.,University of Surrey | Thomas E.L.,Metabolic and Molecular Imaging Group | Bell J.D.,Metabolic and Molecular Imaging Group | Frost G.S.,Imperial College London | Robertson M.D.,University of Surrey
Diabetic Medicine | Year: 2010

Aims Diets rich in non-viscous fibre are linked to a reduced risk of both diabetes and cardiovascular disease; however, the mechanism of action remains unclear. This study was undertaken to assess whether chronic consumption of this type of fibre in individuals with the metabolic syndrome would improve insulin sensitivity via changes in ectopic fat storage. Methods The study was a single-blind, randomized, parallel nutritional intervention where 20 insulin resistant subjects consumed either the fibre supplement (resistant starch) (40 g/day) or placebo supplement (0 g/day) for 12 weeks. Insulin sensitivity was measured by euglycaemic-hyperinsulinaemic clamp and ectopic fat storage measured by whole-body magnetic resonance spectroscopy. Results Resistant starch consumption did not significantly affect body weight, fat storage in muscle, liver or visceral depots. There was also no change with resistant starch feeding on vascular function or markers of inflammation. However, in subjects randomized to consume the resistant starch, insulin sensitivity improved compared with the placebo group (P = 0.023). Insulin sensitivity correlated significantly with changes in waist circumference and fat storage in tibialis muscle and to a lesser extent to visceral-to-subcutaneous abdominal adipose tissue ratio. Conclusion Consumption of resistant starch improves insulin sensitivity in subjects with the metabolic syndrome. Unlike in animal models, diabetes prevention does not appear to be directly related to changes in body adiposity, blood lipids or inflammatory markers. Further research to elucidate the mechanisms behind this change in insulin sensitivity in human subjects is required. © 2010 Diabetes UK.

Hankir M.,Imperial College London | Hankir M.,Metabolic and Molecular Imaging Group | Bueter M.,Imperial College London | Bueter M.,University of Zürich | And 8 more authors.
Obesity Facts | Year: 2012

Objective: To investigate whether gastric bypass induces a higher activity of brown adipose tissue and greater levels of the brown adipose tissue-specific protein uncoupling protein-1 (UCP-1) in rats. Methods: Gastric bypass rats and sham-operated controls (each n = 8) underwent whole body 1H-MR spectroscopy for analysis of body composition and 18F- fluorodeoxyglucose positron emission tomography combined with computed tomography (18F-FDG PET/CT) imaging for measurement of the metabolic activity of brown adipose tissue. Brown adipose tissue was harvested and weighed, and UCP-1 mRNA content was measured by Northern Blot technique. Results: Gastric bypass rats had a significantly lower percentage of whole body adipose tissue mass compared to sham-operated rats (p = 0.001). There was no difference in brown adipose tissue activity between the two groups (standardised uptake value sham 2.81 ± 0.58 vs. bypass 2.56 ± 0.46 ; p = 0.73). Furthermore, there was no difference in the UCP-1 mRNA content of brown adipose tissue between the two groups (sham 49.5 ± 13.2 vs. bypass 43.7 ± 13.1; p = 0.77). Conclusion: Gastric bypass does not increase the activity of brown adipose tissue in rats suggesting that other mechanisms are involved to explain the increased energy expenditure after bypass surgery. Our results cannot justify the radiation dose of 18F-FDG PET/CT studies in humans to determine potential changes in brown adipose tissue after gastric bypass surgery. Copyright © 2012 S. Karger GmbH, Freiburg.

Mehta S.R.,Clinical science Center | Louise Thomas E.,Metabolic and Molecular Imaging Group | Patel N.,Clinical science Center | Crofton M.E.,Imperial College London | And 9 more authors.
Hepatology Research | Year: 2010

Aim: The increasing prevalence of fatty liver disease requires routine assessment methods. Proton magnetic resonance spectroscopy (1H MRS) is increasingly used for steatosis measurement, but due to cost, is unlikely to become a widely-used screening tool. Ultrasound is cheaper and more widely available, although subject to observer variability. Our aim was to determine the sensitivity and specificity of ultrasound against 1H MRS, using MRS as a gold standard, for the detection and quantification of hepatic fat content. Methods: Fifty adults participated (43 men, seven women) in this study. Hepatic steatosis was assessed by ultrasound and 1H MRS. Images were graded by two independent radiologists to classify severity and distribution of liver fat. Results: Ultrasound detected liver fat infiltration in 82% of cases measurable by 1H MRS, while liver fat was detectable in 44% of cases graded absent by ultrasound. Ultrasound grading was subjective, with the radiologists in agreement in 53% of cases (κ = 0.39, P = 0.002). Considerable overlap in intrahepatocellular lipid content was observed between different grades: absent (0.0-1.58%), mild (2.2-16.2%), moderate (4.9-26.7%) and severe (8.1-76.8%) steatosis. Ultrasound could not detect liver fat levels below 2% as measured by 1H MRS Conclusion: Ultrasound is less sensitive than 1H MRS in detecting very low levels of liver fat content, but is sensitive to fatty infiltration greater than 2%. There is a tendency of higher ultrasound grades to correlate with higher degrees of fatty infiltration, although some overlap exists. Our findings are still consistent with ultrasound being useful as a low cost screening tool. © 2010 The Japan Society of Hepatology.

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