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LIVER AND BILIARY TRACT

Effects of yo-yo diet, caloric restriction, and olestra on tissue distribution of hexachlorobenzene

Department of Pathology and Laboratory Medicine, University of Cincinnati School of Medicine, Cincinnati, Ohio

Submitted 2 July 2004 ; accepted in final form 7 October 2004

Chlorinated hydrocarbons are lipophilic, toxic, and persistent in the environment and animal tissues. They enter the body in food and are stored in adipose tissue. Loss of body fat through caloric restriction mobilizes stored lipophilic xenobiotics and results in distribution to other tissues. We have studied the reversibility of this process in mice that followed a regimen of body weight cycling. Weight gain was followed by weight loss, a second gain, and a second loss ("yo-yo diet regimen"). We measured the distribution of orally gavaged [¹⁴C]hexachlorobenzene, which is sparingly metabolized. We found that weight cycling has different effects in different organs. Continued weight loss resulted in a threefold increase of ¹⁴C amount and concentration in the brain. After weight regain, ¹⁴C in the brain decreased but then increased again after a second weight loss. Weight loss resulted in an increase in the concentration of ¹⁴C in adipose tissue without changing the total amount in that tissue. Weight loss and regain resulted in an increase of ¹⁴C in the liver, which reflected an increase of fat in the liver. The regimen of weight gain and loss was repeated in mice gavaged with [¹⁴C]hexachlorobenzene, with one group receiving the nonabsorbable fat olestra in the diet. Combined dietary olestra and caloric restriction caused a 30-fold increase in the rate of excretion of ¹⁴C relative to an ad libitum diet or a reduced caloric diet alone. Distribution of ¹⁴C into the brain resulting from the restricted diet was reduced by 50% by dietary olestra.

body weight; xenobiotics; lipophilic; cycling; high fat