Table 1.
Actions of Adipokines
| Adipokine | Source and Nutritional Regulation | Energy, Glucose, and Lipid Metabolism |
|---|---|---|
| Leptin | Mainly adipose tissue; low levels in gastric fundus, intestine, and muscle. Obesity: adipose mRNA and protein ↑↑; plasma ↑↑. Fasting: adipose mRNA and protein ↓; plasma ↓. Refeeding: adipose mRNA and protein ↑; plasma ↓ | Inhibits feeding and increases energy expenditure; insulin sensitizer; stimulates fatty acid oxidation |
| Adiponectin | Adipose tissue. Obesity: adipose mRNA and protein ↓; plasma ↓. Fasting: adipose mRNA and protein ↑; plasma ↑. Refeeding: adipose mRNA and protein ↓; plasma ↓ | Insulin sensitizer; stimulates fatty acid oxidation; may increase or decrease adiposity |
| Resistin | Adipose tissue in rodents and macrophages in human. Obesity: rodent adipose mRNA ↓ and protein ↑; plasma ↑. Fasting: rodent adipose mRNA and protein ↓; plasma ↓. Refeeding: rodent adipose mRNA and protein ↑; plasma ↑ | Induces insulin resistance in rodents |
| TNFα | Adipose tissue and immune cells. Obesity: adipose and plasma protein ↑ | Inhibits feeding, induces cachexia, and inhibits insulin sensitivity |
| IL-6 | Adipose tissue, immune cells and muscle. Obesity: adipose and plasma protein ↑ | Inhibits feeding, increases energy expenditure, and induces insulin resistance |
| Adipsin; complement factor D | Adipose tissue. Obesity: adipose mRNA and protein ↓ in rodents; ↑ in humans; adipsin levels are linked to acylation stimulating protein (ASP) | ASP promotes fatty acid and glucose uptake by adipocytes and stimulates insulin secretion |
| Plasminogen-activator inhibitor-1 | Adipose tissue and liver. Obesity: adipose and plasma protein ↑; suppressed by thiazolidinediones | Increases adiposity and insulin resistance in rodents |
| Renin-angiotensin system | Adipose tissue, kidney, and vasculature | Angiotensin II increases adipogenesis and reduces insulin sensitivity |
| Retinol binding protein-4 | Adipose tissue and liver. Obesity: adipose and plasma protein ↑ in rodents; not consistently elevated in humans | Enhances insulin action in rodents |
| Fasting-induced adipose factor; angiopoeitin-like protein 4 | Expressed in adipose tissue, liver, and intestinal epithelium. mRNA and protein ↑ by calorie restriction, PPAR-α, and fenofibrate | Increases triglycerides by inhibiting lipoprotein lipase; stimulates cholesterol synthesis; implicated in obesity and insulin resistance induced by gut bacteria |
| Visfatin; pre-B cell colony-enhancing factor 1; extracellular nicotinamide phosphoribosyltransferase | Adipose tissue, liver, and various tissues. Obesity: adipose and plasma protein ↑ | Not an insulin mimetic as originally proposed |
| Vaspin | Adipose tissue and liver. Obesity: adipose and plasma protein ↑ | Insulin sensitizer in rodents |
↑, Increased; ↓, decreased.