Genetic mutation lowers obesity in Cushing’s syndrome

London E. J Clin Endocrinol Metab. 2013; doi:10.1210/jc.2013-1956.

Among adult patients with Cushing’s syndrome, those with mutations in PRKAR1A, the gene that controls cAMP-dependent protein kinase, are less obese than their counterparts without these mutations, according to a recent study.

The retrospective study evaluated adrenalectomy samples from 51 patients with Cushing’s syndrome, 13 with PRKAR1A mutations and 32 without. Of the 51 patients, 40 were female and 11 were male, and patients ranged in age from 4 to 74 years.

A non-Cushing’s syndrome comparison group consisting of 6 adrenalectomy patients with aldosterone producing adenomas (APAs) was included. Additional comparison groups comprising clinical data from 89 patients with Cushing’s disease and 26 with hyperaldosteronism were also studied.

Researchers recorded the weight, height and BMI of all patients, and measured abdominal subcutaneous adipose tissue (ScAT) and periadrenal adipose tissue (PAT) using computed tomography. PAT was collected and frozen for evaluation; the extracts were assessed for levels of cAMP and protein kinase (PKA) activity, as well as for protein and mRNA expression of subunits of PKA. Diurnal cortisol levels and urine-free cortisol were also measured preoperatively.

The study found that in adults with Cushing’s syndrome, the mean BMI of those with PRKAR1A mutations was lower than that of patients with noPRKAR1A mutations (P<.05), and was not inconsistent with the hyperaldosteronism comparison group.

In pediatric patients with adrenal Cushing’s syndrome, the presence of PRKAR1A mutation did not have an impact on mean BMI z-scores. However, in comparison with pediatric patients with pituitary Cushing’s disease, the BMI z-scores were significantly lower in pediatric Cushing’s disease patients with PRKAR1Amutations (P<.05). Patients with Cushing’s syndrome without PRKAR1A mutations had significantly more PAT and ScAT than non-Cushing’s syndrome patients. Additionally, the ratio of basal-to-total (cAMP-triggered) PKA activity was significantly lower in patients with PRKAR1A mutations, suggesting greater proportions of active PKA (P<.005).

“These findings have obvious implications in the establishment of the diagnosis of CS in patients with PRKAR1A mutations: These patients may be leaner than other patients with [Cushing’s syndrome],” the study authors wrote. “Perhaps more importantly, our findings point to the importance of cAMP and or PKA signaling in the regulation of adiposity.”

Disclosures: The researchers report no relevant financial disclosures.

From http://www.healio.com/endocrinology/adrenal/news/online/%7B693f94cd-359d-4c52-8e0d-bfd0e4a51d03%7D/genetic-mutation-lowers-obesity-in-cushings-syndrome

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