Hindsight: Bound Leptin and Sympathetic ActivitySaturday, June 23, 2012
As readers are probably well aware, leptin is one of the key hormones (secreted by fat cells), that regulate energy balance – not just by affecting food intake but also energy output. The latter happens in part through stimulation of the sympathetic nervous system.
In a paper we published in the Journal of Clinical Endocrinology and Metabolism in 2003, we examined the relationship between both free and protein-bound plasma leptin levels and sympathetic activity as assessed by microneurography.
Study participants included 25 healthy normal weight men, 8 individuals with central (multiple system atrophy) and 4 individuals with peripheral (pure) autonomic failure. Baroreflex sensitivity was measured using phenylephrine and nitroprusside infusions.
MSNA was consistently correlated with protein-bound leptin concentrations but not with free leptin levels. MSNA at baseline was about 15 bursts per minute in subjects with lower and about 24 bursts per minute in subjects with higher bound leptin concentrations.
We concluded that protein-bound rather than free leptin levels are correlated with basal sympathetic outflow, a relationship that was difficult to explain through a direct central nervous effect of protein-bound leptin. Rather, we suggested that protein-bound leptin may increase sympathetic vasomotor tone indirectly via a baroreflex mechanism.
According to Google Scholar, this paper has been cited 26 times.