Adaptation of colonic uptake of hexoses and lipids following ileal resection: effect of variations in the fat content of the diet

Human rectal absorption of short- and medium-chain C2-C10 fatty acids

BACKGROUND

Current knowledge on the colonorectal absorption of medium-chain fatty acids is limited. The purpose of the present study was to evaluate and compare the human rectal absorption of short- and medium-chain C2-C10 fatty acids in healthy volunteers.

METHODS

Dialysis bags containing 20 mmol x l(-1) of the fatty acids acetate, butyrate, hexanoate, octanoate, or decanoate in a phosphate-buffered (pH neutral) isoosmotic electrolyte solution were placed in the rectum for 30 min in 14 healthy volunteers. Absorption rates were calculated for all fatty acids, sodium, potassium, and water.

RESULTS

Absorption rates of the fatty acids acetate, butyrate, hexanoate, octanoate or decanoate were the same (1.9 +/- 0.1 = 2.5 +/- 0.2 = 1.7 +/- 0.2 = 1.9 +/- 0.2 = 2.2 +/- 0.1 micromol x cm(-2) x h(-1) (mean +/- standard error of the mean), respectively; P = 0.24).

CONCLUSIONS

Medium-chain fatty acids were absorbed in the human rectum at a rate similar to that for short-chain fatty acids. If results can be applied to the human colon, colonic absorption of medium-chain fatty acids could possibly become an important secondary site of absorption in abnormal intestinal conditions such as massive small-intestinal resection or malabsorption syndromes.

Inhibition of lipid absorption as an approach to the treatment of obesity

A reduction in fat intake may be achieved by making educated choices to reduce total calorie intake, to consume a lower quantity of total fats, or to modify the ratio of saturated-to-polyunsaturated lipids. Leptin agonists or NPY or CCK antagonists may prove to be useful to diminish appetite and thereby reduce the total intake of food. But eating has such cultural, social, and hedonistic attributes that such a single-pronged approach is unlikely to be successful. The use of fat substitutes may prove to be popular to provide a wide range of snack food options, but these are likely to be of minimal use in weight reduction programs because of their distribution of additives in only a limited number of foods. The inhibitors of lipid digestion will be modestly successful in the short term; their long-term success will be influenced by gastrointestinal adverse effects and the need to consume fat-soluble vitamin supplements to prevent the development of fat-soluble vitamin deficiencies. The inhibition of lipid absorption is an attractive targeted approach for the treatment of obesity, since this would reduce the uptake of visible as well as invisible fats, which would potentially offer convenient dosing, and could also be a means to inhibit secondarily the uptake of carbohydrate calories.