Table 1.

Tissue expression and maternal circulating levels of the main adipokines during normal pregnancy and gestational diabetes mellitus

Adipokine	Normal pregnancy levels	GDM pregnancy levels	Expression	Function	References
Leptin	Levels two to three times higher than in non-pregnant women; the peak occurs around the 28th week of gestation	Further increase ↑↑	Maternal adipose tissue Fetal adipose tissue Placenta	Promotion of fetal growth through greater placental lipolysis and transport of transplacental macronutrients Increased availability of fuel	[9, 22, 26, 30, 35]
Adiponectin	Progressively reduced levels	Further reduction ↓↓	Maternal adipose tissue Placenta, primarly in syncytiotrophoblast	Increased insulin-sensitivity Anti-inflammatory activity	[16, 48-50, 57, 64]
TNF-α	Higher levels than non-pregnant women, particularly in third trimester	Further increase ↑↑	Maternal adipose tissue Placenta	Aggravation of insulin resistance Regulation of placental development	[64, 76, 80, 81, 82, 83]
Resistin	Higher levels than non-pregnant women, particularly at the end of pregnancy	Further increase ↑↑	Maternal adipose tissue	Prevention of neonatal hypoglycemia Increased hepatic glucose production	[85-89]
Visfatin	Higher levels than non-pregnant women; the peak occurs between the 19th and 26th week of gestation	Further increase ↑↑	Maternal adipose tissue	Increased insulin-sensitivity Anti-inflammatory activity	[92-95]

The biological functions of the adipokines are also reported