The biology of obesity #5

Fifth in Series on Obesity Topic:

Future trends

One of the most important future issues in the field of lipogenesis is the confirmation of its regulatory role in food intake and in the fatty acid oxidation and hence resistance to obesity. Decreased lipogenesis in liver and muscle should favour fatty acid oxidation. This in turn would favour weight loss by a yet unknown mechanism but which could be linked to an uncoupling effect of fatty acids on the mitochondrial respiratory chain. However, an inhibition of lipogenesis in specific hypothalamic nuclei would mimic starvation and thus should increase food intake and favour weight gain. Activation of the lipogenic pathway would thus have an opposite effect on weight.

Part of the problem would then be to find a way of reaching only one of the two regulatory systems. PUFAs might be one possibility. Indeed, they reduce hepatic lipogenesis in animal models and do not enter readily into the brain. However, the reality of this effect needs to be studied convincingly in humans.

Concerning fructans, a number of problems have to be solved. The links between fructan fermentation and effects on gene expression are not entirely clear and this kind of experiment must be repeated and further analysed in different models. The effects of fructans on human lipid metabolism must be addressed in a more systematic way.

The effect of fructans on hepatic steatosis in obese rats is particularly interesting since in humans, Non-Alcoholic Steato-Hepatitis is diagnosed in a large percentage of obese people and has been associated with the metabolic syndrome.23 Whether such an effect of nondigestible oligosaccharides can be observed on the steatosis of patients is also an interesting issue that needs to be documented.

Camilla Verdich, PhD, and TIA Sorensen, PhD, are at Copenhagen University Hospital, Denmark. Karine Clement, Fabienne Foufelle, PhD, and P Ferre are with INSERM, France, the French National Institute for Health and Medical Research. Excerpted from Functional Foods, Ageing and Degenerative Disease, C Remacle and B Reusens, editors. ISBN 0-8493-2538-2. Published by Woodhead Publishing Ltd, England. www.woodheadpublishing.com

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