Metabolic responsiveness of different size adipocytes to fasting and refeeding in the pig

The effects of fasting (F) and fasting-refeeding (FR) on [U-¹⁴C]glucose and [1-¹⁴C]palmitate metabolism were examined in pig middle subcutaneous (MSQ) adipocytes fractionated into 20-63, 63-102 and 102-153 μm diameter ranges. Fasting caused a similar decrease in de novo glyceride fatty acid (GFA) and glyceride-glycerol (GG) synthesis from glucose among adipocytes of different size. After refeeding for 2 days, glucose metabolism significantly increased in all fractions, however, the increase did not reach non-fasting levels. There was a disparate increase in glucose metabolism among adipocyte fractions after refeeding. Adipocytes 102-153 μm in diameter had a larger increase in glucose metabolism than smaller adipocytes. Fasting suppressed palmitate esterification rates in 20-63 and 63-102 μm fractions. Esterification by adipocytes 102-153 μm in diameter was not diminished after fasting. An 'overshoot' in esterification by adipocytes 63-102 and 102-153 μm in diameter relative to control adipocytes was observed after refeeding; no 'overshoot' occurred in 20-63 μm adipocytes. These results indicate that adipocytes of different size have markedly different capacities for substrate utilization after F or FR as well as different metabolic adaptations to F or FR.