Neuropeptides in the pathogenesis of obesity-associated benign acanthosis nigricans

The association of acanthosis nigricans with pituitary tumors and insulin-resistant diabetes suggests that a pituitary peptide may promote papillomatosis and acanthosis characteristic of acanthosis nigricans. Although such a peptide has not been isolated, it may derive by sequential cleavage from the 31,000-dalton precursor peptide to ACTH and β-lipotropin (β-LPH). In order to evaluate the role of pituitary peptides in the pathogenesis of acanthosis nigricans, we compared plasma levels of β-endorphin (β-EP) and ACTH in plasma of 8 fasting patients with obesity-associated benign acanthosis nigricans and 7 fasting normal controls utilizing sensitive radioimmunoassay procedures. Mean plasma β-EP levels for the acanthosis nigricans and control subjects were not significantly different (90 pg/ml vs. 140 pg/ml), nor was any significant difference observed between plasma ACTH levels of the 2 groups (42.3 and 31.2 pg/ml, respectively). Our data indicate that plasma levels of the pituitary-derived peptides ACTH and β-EP are not increased in obesity-associated benign acanthosis nigricans, and suggest that its proposed hormonal mediator might originate independently from the large peptide precursor of ACTH, β-LPH and their fragments.