Effects of dietary 1,3-butylene glycol on adipose tissue metabolism from lean and obese swine.

One,three-butylene glycol (BG) was isocalorically substituted for glucose and fed ad libitum to lean (XB) and obese (HL) swine at 0, 10, and 20% of the total dietary ME from 25 kg body weight until slaughter at 90 kg. BG depressed rate and efficiency of gain in both groups. Plasma beta-hydroxybutyrate concentration was increased by the ketogenic energy substitution. Plasma glucose and free fatty acids were not influenced by diet composition. Adipose tissue utilization of glucose for lipogenesis was depressed by BG in both XB and HL animals after 4 wk of treatment. Insulin added in vitro increased glucose utilization by approximately 20% in adipose tissue from both breed groups; however, the BG induced depression of glucose utilization for fatty acid synthesis was still evident. Insulin-stimulated glucose utilization was greater in XB then in L swine. After 12 wk of dietary treatment, animals given BG had significantly increased plasma insulin concentration and decreased plasma urea concentrations. Although the absolute rates of lipogenesis had decreased after 12 wk of treatment, similar diet-related results were obtained. Insulin did not stimulate glucose utilization by adipose tissue from animals of either breed group at this latter sampling. Fatty acid esterification was slightly depressed by BG at the 4 wk sampling, but after 12 wk of treatment, only a significantly breed group effect was evident. Subcutaneous fat thickness, loineye area and carcass percentage lean cuts were not influenced by diet composition. This experiment demonstrated that ketogenic energy and substitution in the diet does depress the rate of de novo lipogenesis from glucose as measured by in vitro incubation of swine adipose tissue. Supplementation of the incubation media with massive quantities of insulin did not reverse the dietary treatment effects, and animals of both lean and obese phenotypes responded similarly to the dietary treatment. The absence of dietary treatment effects on indices of body fat content suggest that ketone bodies may be substituted for glucose as a lipogenic substrate in swine.