Metabolic development of liver and adipose tissue in pre-obese and control pig fetuses

The metabolic development of the liver and adipose tissue was examined in 75 and 110 day fetuses from genetically obese and control sows. In the liver, glucose and palmitate utilization was influenced by both age and strain. Higher rates of glucose oxidation and palmitate oxidation and esterification were observed in the 75 day compared to the 110 day fetuses. Hepatic palmitate oxidation was greater in pre-obese than in control fetuses at both fetal ages, while hepatic palmitate esterification was greater in pre-obese than in control fetuses at 75 days of gestation only. In subcutaneous adipose tissue, de novo lipogenesis increased with age and was higher in pre-obese than in control fetuses by 110 days of gestation. At 75 days of gestation, glucose oxidation and incorporation into fatty acids was similar in adipose tissue from both strains. However, by 110 days of gestation, both basal and insulin-stimulated rates of glucose metabolism were greater in pre-obese compared to control fetuses. Palmitate esterification increased with age but was similar in pre-obese and control fetuses. Basal lipolysis was not affected by strain or age. Isoproterenol had no effect on lipolysis in the 75 day fetuses while stimulating glycerol release to a comparable degree in 110 day fetuses of both strains. This study demonstrates that metabolic differences between genetically obese and control pigs are already apparent in the pre-obese state prior to birth. Such alterations in hepatic and adipose tissue carbohydrate and lipid metabolism, which promote early lipid storage by the pre-obese fetuses, may serve as useful metabolic markers for the development of obesity.