The biology of obesity #4

Continued from Saturday, Jan-29-11

Fourth in Series on Obesity Topic:

Foods to improve lipogenesis16

When dealing with the regulation of a specific metabolic pathway in a given direction by functional foods, it is obviously necessary that the specific nutrients chosen have no adverse consequences that will alter the global health status. The other necessity is that the functional food can be used at a reasonable dose compatible with an otherwise normal nutrition.

Is it advantageous to modulate the lipogenic rate — that is, the rate of fat formation in the body? Hyperlipidaemia with high concentrations of VLDL-triglycerides is associated with insulin resistance, obesity and cardiovascular diseases.

Plasma triglyceride concentration is dependent upon the rates of hepatic VLDL production and of clearance from the plasma. Hepatic lipogenesis from carbohydrates can contribute significantly to the rate of triglyceride production by the liver in conditions such as obesity or when ingesting simple-sugar enriched diets. It is thus reasonable to try to decrease de novo fatty acid synthesis. In addition, this could favour hepatic fatty acid oxidation by reducing malonyl-CoA concentration, thus alleviating the inhibition of CPT I, and ultimately improve hepatic insulin sensitivity.17

Small amounts of PUFAs in the diet are able to reduce the hepatic rate of lipogenesis
PUFAs: At present, two directions can be explored. The first one involves the use of polyunsaturated fatty acids (PUFAs) of the n-3 and n-6 families. Small amounts of PUFAs in the diet are able to reduce very efficiently the hepatic rate of lipogenesis at least in rodents.18 In addition, this effect is specific of hepatic lipogenesis. Moreover, PUFAs have been described as potentially beneficial for atherosclerosis.19 Thus, the use of PUFAs is an interesting clue as a beneficial modulator of hepatic lipogenesis.

Prebiotic fibres: The second possibility involves the use of nondigestible oligosaccharides belonging to the fructan class such as inulin or one of its fraction oligofructose. They are usually obtained from chicory roots or Jerusalem artichokes. These oligosaccharides are not digested in the upper intestine because the anomeric carbon 2 in their fructose momomer is in a beta configuration precluding hydrolysis by human digestive enzymes, which are specific for alpha-glycosidic bonds.20

Inulin and oligofructose are thus fermented in the caeco-colon, yielding short-chain fatty acids such as acetate, butyrate and propionate. It has been repeatedly shown in rodent models that inulin and oligofructose given in a 10 per cent range in the diet are able to modulate triglyceride metabolism at the hepatic level.21

When fed with oligofructose-enriched diets, a lower triglyceridaemia in nonobese animals and a decreased hepatic steatosis in Zucker fa/fa obese rats have been observed.21 A lower rate of lipogenesis due to a reduction in the expression and activity of lipogenic enzymes seems to be a key explanation for the effects of these oligosaccharides.21

In humans, conflicting results have been reported concerning the effect of inulin and oligofructose in lipid metabolism.20 Some studies have reported a beneficial effect on serum triglycerides where others have not. It must be underlined that the doses used in humans are much lower than in rats due to the unpleasant gastrointestinal effects when consuming doses in excess of 30g/day.

In addition, if lipogenesis is one of the key targets of their effects, then the diet fed during the study is of importance.20 It can be predicted that the antilipogenic effects of fructans would increase with the sugar content of the diet.

A recent study has addressed the question of the effects of fructans on hepatic lipogenesis in humans.22 Inulin (10g/day) was added to a moderately high carbohydrates diet (55 per cent of total energy). Plasma triglycerides and hepatic lipogenesis were indeed lower in the group consuming the inulin-enriched diet.

Fructans widely used in the food industry have no obvious adverse effects
Finally, it can be pointed out that fructans that are already widely used in the food industry (texture modifier, sweetener) have no obvious adverse effects and are even usually considered as having health-promoting properties.20

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.

http://www.woodheadpublishing.com

http://www.functionalingredientsmag.com/content/print.aspx?topic=the-biology-of-obesity

http://www.depsyl.com/

http://back2basicnutrition.com/

http://bionutritionalresearch.olhblogspace.com/