Influence of surgical stress and parenteral nutrition on serum leptin concentration

Experimental studies suggest that leptin may be an important metabolic signal for energy regulation.

To assess whether surgical stress produces changes in serum leptin concentration and to investigate and compare the effect of total parenteral nutrition and hypocaloric parenteral nutrition on serum leptin levels.

Twenty-two surgical patients (11 male and 11 female) in need of parenteral nutrition were recruited. Parenteral nutrition was always initiated 24 h after surgical procedure. Group I (n=15) received total parenteral nutrition, while Group II (n=7) were treated with hypocaloric parenteral nutrition. Serum leptin concentration was determined before surgical procedure (day -1), after surgery and before parenteral nutrition was started (day +1), and after 5 days of treatment with parenteral nutrition (day +6).

A tendency to increase serum leptin levels was observed after surgical procedure (6.0+/-1.9 vs 9.9+/-2.7 ng/ml;P= 0.07). After starting parenteral nutrition no significant changes on serum leptin concentrations were found in both groups, but a trend to raise serum leptin was observed in Group I (6.2+/-1.7 vs 8.3+/-2.7 ng/ml) whereas a trend to decrease serum leptin was detected in Group II (4.6+/-2.5 vs 1.6+/-0.5 ng/ml). On day +6 an increase of serum leptin and insulin levels was observed in Group I in comparison with Group II (8.3+/-2.7 vs 1.6+/-0.5 ng/ml;P<< 0.05 and 58+/-41 vs 12+/-15 microU/l;P<< 0.05 respectively). Finally, a positive correlation at day +6 between insulin and serum leptin levels was observed (r= 0.66;P<< 0.01).

a) Surgical stress is associated to an increase of serum leptin concentrations; b) Total and hypocaloric parenteral nutrition produces quite different effects on serum leptin levels that could be related to distinct insulin response.