ABSTRACT
In the pig, as in other species, leptin gene expression in adipose tissue is restricted to developing pre-adipocytes and adipocytes. Therefore, adipose tissue leptin gene expression is linked to adipocyte genesis and subsequent adipocyte hypertrophy. Hormone and growth factors influence adipocyte leptin expression much in the same way as they influence adipogenesis and adipocyte size. Insulin and glucocorticoids are the major regulators of adipocyte leptin gene expression in vitro and in vivo. Anatomical location of depots can also influence leptin gene expression with the lowest gene expression evident in intramuscular adipocytes (Table 3).[2]
LEPTIN AND ENERGY BALANCE
Circulating leptin concentrations are positively correlated with adiposity and positive energy balance in pigs and with
LeptinM
eat
Table 1 Collective reports on the effect of leptin treatment on serum metabolites, metabolic hormones, adipose gene expression, and immune and intestine function in the pig. Gender/BWa Peripheral metabolism Leptin dose Route Result Male castrate 27 kg Serum NEFAb, Glycerol,
Triglycerides, Glucose 0.03, 0.01, 0.03 mg/kg/day, 15 day
i.m. No effect
Male castrate 27 kg Adipose tissue PPARg1c, PPARg2 mRNA
0.01, 0.03 mg/kg/day, 15 day
i.m. Decreased
Male castrate 53 kg Serum NEFA 0.05 mg/kg/day, 14 day i.m. Increased Glycerol, Triglycerides, Glucose
No effect No effect
Adipose PPARg1 mRNA Increased
Male castrate 53 kg Adipose PPARg2 mRNA 0.05 mg/kg/day, 14 day i.m. No effect Adipose, Liver, Skeletal muscle: PPARa mRNA
No effect
Blood urea nitrogen Decreased Female 6 kg Feed Intake 100 mg/kg BW Carotid No effect
200, 500 mg/kg BW artery Decreased
Glucose and Insulin 100 mg/kg BW Carotid No effect
200 mg, 500 mg/kg BW artery Decreased
GHd 200 mg/kg BW Cartoid Increased
NEFA 200, 500 mg/kg BW artery Increased
Neonatal meishan Hind limb bone and Growth rate
4 mg/ml/hg BW day 3-8 i.m. Increased
Barrow 3-5 mo. old Lymphocyte proliferation 0.025 mg/kg BW 2 × day for 21 day
i.m. No effect
Neonatal pig Small intestine length and motility
10 mg/kg/BW Gastric infusion Increased
Table 2 In vitro effects of leptin on adipocyte, hepatic, and C2C12 myotube cells. Type culture Metabolic effect Dose of leptin Result Adipose tissue cell culture Lipolysis 40 ng leptin for 8 hr Increased Neonatal subcutaneous adipose tissue Lipid synthesis 100 ng/ml media Decreased Male castrate subcutaneous adipose tissue
Fatty acid esterification 100 nM leptin Decreased
C2C12myotubes Fatty acid oxidation 5, 50, 500 ng/ml for 4 hr No effect 5, 50, 500 ng/ml for 24 hr Increased
Adipocyte cell culture Glucose oxidation 1000 ng/ml media for 4 hr Inhibited Hepatpocyte cell Gluconeogensis 50 or 100 nM for 3 hr No effect
Glycogen synthesis No effect Ketogenesis No effect
Adipose tissue explants UCP2 mRNAa 100 ng/ml media 24 hr Increased Adipose tissue explants UCP3 mRNA 100 ng/ml media 24 hr Decreased aUncoupling protein.
