TABLE 4.
Tissue-specific effects of adipokines on lipid metabolism and flux
| Adipokine | Food Intake (Energy Intake) | Fat Utilization, β-Oxidation, Thermogenesis (Energy Expenditure) | Fat Storage, Adipogenesis, Nonadipose Lipogenesis (Excess Energy Storage Capacity) | Levels in Common Forms of Obesity |
|---|---|---|---|---|
| Leptin | Anorexigenic | Enhances β-oxidation via AMPK activation in muscle and liver; reduces intracellular lipids; promotes thermogenesis in BAT | Antiadipogenic in vitro, promotes adipose lipolysis in vivo via the sympathetic nervous system | High (but evidence of leptin resistance) |
| Adiponectin | No effect on food intake, but ICV leads to increased energy expenditure; present in human cerebrospinal fluid | Enhances via AMPK activation in muscle and liver; reduces intracellular lipids | Promotes lipogenesis in adipocytes in vitro | Low |
| TNF-α | Anorexigenic | Inhibits muscle AMPK; increased FA incorporation into diacylglycerol, and increase in intracellular ceramide levels; reduces BAT function and promotes BAT atrophy | Antiadipogenic and stimulates lipolysis via TNFR1-mediated transcriptional signals; increases hepatic de novo synthesis of fatty acid and triglycerides | High (but with autocrine/paracrine activity) |
| IL-6 | Anorexigenic | Stimulates fat oxidation via AMPK activation | Stimulates adipose tissue lipolysis; increases hepatic de novo synthesis of fatty acid and cholesterol | High |
| Resistin | Potentially anorexigenic; present in human cerebrospinal fluid | Decreases fatty acid uptake and metabolism in muscle in vitro | Antiadipogenic and stimulates lipolysis in adipocytes | High |
| RBP4 | Unknown | Unknown | Promotes liver steatosis | High |
| PBEF/visfatin | Unknown | Unknown | Promotes lipogenesis in adipocytes | Controversial: may be higher in visceral fat |
| Omentin (humans, not mice) | Unknown | Unknown | Unknown | Increased in human visceral fat |
BAT, brown adipose tissue.