ASGSB 1998 Annual Meeting Abstracts

[39]
EFFECTS OF 2G ON LEAN AND OBESE ZUCKER RATS.  L.E. Warren, B.A. Horwitz and C.A. Fuller. Section of Neurobiology, Physiology and Behavior, University of California, Davis.

Changes in the ambient force environment alter the regulation of food intake and body fatness. Since fat regulation underlies human survival capacity, an understanding of the related regulatory pathways and their responsiveness to the ambient force environment may be critical to long duration spaceflight. We have studied the effects of 2G on food intake and body mass of both lean (Fa/Fa) (n=19) and obese (fa/fa) (n=22) male Zucker rats. Rats were individually housed in metabolism cages with food and water provided ad libitum. The control rats were similarly maintained at 1G. Following a 2-week baseline period at 1G, the 2G group was subjected to centrifugation on a 1.5-m diameter centrifuge for 8 weeks. Food intake and body mass measurements were obtained weekly. All animals were sacrificed immediately post-centrifugation. The lean rats' response to 2G included an initial reduction in body mass, and a resump-tion of growth at a rate greater than the controls (though at a decreased mass). In addition, the leans exhibited a 50% reduction in percent body fat after 8 weeks of 2G. In contrast, obese rats exhibited a decrease in body mass with resumption in growth at a slower rate, and a smaller decrease in body fat than the leans. In both lean and obese rats, mass adjusted food intake decreased upon centrifugation and then recovered to control levels within 4-5 weeks. Percent body fat differed significantly (p<0.05) for each of the following comparisons: 1G obese> 2G obese> 1G lean> 2G lean. As expected, obese rats had significantly higher circu-lating leptin levels (ng/ml) than did the leans. Additionally, lean rats at 1G had significantly higher leptin levels than lean rats at 2G. While this trend persisted in the obese rats, the difference did not reach significance. There was a differential response to 2G in the obese vs. lean rats, indicat-ing that while both genotypes responded to hypergravity, the response of obese Zucker rats was quantitatively different from that of their lean counterparts. The observed differences necessitates further investigation into the effects of altered ambient force environments on regulatory pathways mediating food intake, body mass and body fatness. (Supported by NASA: NAG5-3959 to BAH and GSRP-98-009 to LEW)

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