Leptin levels in peripheral blood and bone marrow in orthopedic patients

Leptin is a protein with hormonal activity and is produced mainly by adipocytes. Its primary function in the human organism is regulation of the calorie intake via the anorectic action in the hypothalamus. Leptin participates also in the regulation of haematopoiesis and immunity processes. There are many data on leptin production by peripheral adipose tissue and it is also known that leptin is produced by adipocytes of bone marrow. It was assumed for a long time that adipocytes of bone marrow are not only a passive source of energy but have, similarly as stromal cells, a regulatory function. However, it is not clear in what way the adipose tissue of bone marrow participates in the regulation of haematopoiesis and what role is played in this relationship by leptin production. The authors attempted to assemble in their small study data on leptin production in bone marrow and at the same time parameters of lipids of bone marrow which can be assessed by cytological examination. The authors examined 16 patients (9 men and 7 women) subjected to orthopaedic surgery. They assessed leptin concentrations in sera obtained from peripheral blood and bone marrow, and at the same time they assessed by morphological examination in smears of bone marrow some parameters associated with lipids. The authors found that serum leptin levels from bone marrow are significantly lower than in peripheral blood (p < 0.0005). These values correlate closely (r = +0.77, p < 0.0005). The authors found also a positive correlation between serum leptin (r = +0.56, p < 0.02) and bone marrow leptin (r = +0.72, p < 0.002) and the body mass index (BMI). A positive correlation was found also between serum (r = +0.65, p < 0.006) and bone marrow leptin (r = +0.80, p < 0.0002) and age. The authors did not detect any significant correlations between parameters of the lipids of bone marrow and leptin levels in serum and bone marrow. The assembled results can in combination with data from the literature indicate that the actual amount of leptin in bone marrow is influenced rather by its consumption by haematopoietic tissue than by its production.