Leptin levels in the hypertensive black African parturient.

Abstract

Background: Leptin is a new adipose-derived hormone discovered in 1994. It is vital in energy balance and weight regulation in humans. During pregnancy the placenta is an extra source of leptin. The role of leptin in pregnancy is not established. This has generated a lot of interest in leptin research in pregnancy. Leptin is being examined in pathological states that may have origin in adipose tissue and the placenta such as pre-eclampsia, intrauterine growth restriction and obesity. Aim and Method: This study measured concentrations of serum leptin in Black African women during late pregnancy in 68 women with pre-eclampsia, 92 healthy normotensive pregnant women and in 32 healthy non-pregnant women. In each group leptin levels were compared between obese (body mass index, BMI = or > than 30 kgm-2) and lean women. Serum leptin concentrations were measured by radioimmunoassay (RIA) technique. Results: Serum leptin levels were higher in pregnancy compared to non-pregnant women (26.66+/-16.13 ng/ml, 25.89+/-15.83 ng/ml vs 17.97+/-11.98 ng/ml, p=0.02). This is due to firstly, the extra fat accumulated as part of the maternal adaptation to pregnancy and secondlv, to the placenta-derived leptin. Other pregnancy hormones such as insulin, hcG, prolactin and oestrogen may modulate the serum levels of leptin in pregnancy. Simple anthropometric parameters (weight, BMI, circumferences of the mid upper arm (MAC), waist (WC), hip (HC), and thigh (TC) and waist-hip ratio (WHR)) were used to explore the relationship between leptin concentrations and obesity. All the parameters showed a positive correlation with serum leptin concentration in all the groups with the exception of WHR. Weight and BMI showed the greatest correlation both in pregnant (r=0.61 and r=0.58, respectively, p<0.001) and non-pregnant (r=0.74 and 0.79, respectively, p<0.001) women. However we did not find a significant difference in the concentrations of leptin between women with and those without pre-eclampsia (26.66 ng/ml vs 25.89 ng/ml, p=0.95). This probably means that adiposity is the predominant factor influencing levels of leptin in pregnancy. The other factors mentioned above play only a minor role. Indeed the mean serum leptin levels were higher in obese compared to lean women in both pregnant and non-pregnant women. Conclusion: Pregnancy is a hyperleptinaemic state. There is no difference in serum leptin levels between women with pre-eclampsia and healthy normotensive pregnant women. Serum leptin concentration is largely determined by the degree of adiposity both in and outside pregnancy.