Melatonin reduces body weight gain in Sprague Dawley rats with diet-induced obesity.

Melatonin is involved in the regulation of seasonal obesity in various species, including some rodents. This involvement has been demonstrated in nonphotoperiodic rodents like rats, but only in models of enhanced body weight such as genetically obese or middle-aged rats. The aim of this investigation was to determine the effects of melatonin on body weight and metabolic parameters in a model closer to that observed in Western populations, i.e. Sprague Dawley rats fed a high-fat diet. They were treated for 3 wk with melatonin (30 mg/kg) 4 h after lights-on [Zeitgeber time (ZT) 4] or 1 h before lights-out (ZT11). Given at ZT11, melatonin decreased body weight gain and feed efficiency by half. Melatonin had no effect on plasma insulin level, but it decreased plasma glucose (13%), leptin (28%), and triglyceride (28%) levels. Furthermore, in pinealectomized high-fat diet rats, body weight gain and feed efficiency were increased 4 wk after surgery. Adipose tissue weight, insulinemia, and glycemia had a tendency to increase. Treatment with melatonin prevented in part these changes. These data demonstrate that melatonin may act as a regulator of body weight in a model of obesity and may prevent some of the side effects on glucose homeostasis such as decreased insulin sensitivity.

Virilizing sclerosing-stromal tumor of the ovary in a young woman with McCune Albright syndrome: clinical, pathological, and immunohistochemical studies.

CONTEXT: McCune-Albright syndrome (MAS) is characterized by polyostotic fibrous dysplasia, café-au-lait skin pigmentations, and gonadotropin-independent sexual precocious puberty, resulting from a somatic postzygotic activating mutation of the GNAS1 gene. SETTING: We report a virilizing sclerosing-stromal tumor of the ovary in a young female with MAS. PATIENT: She presented polyostotic fibrous dysplasia of the left upper and lower limbs and a café-au-lait skin spot in the posterior area of the neck. She had a history of precocious puberty, diagnosed at the age of 6 years and treated with cyproterone acetate until the age of 10 years; then she developed central puberty with severe oligomenorrhea. At the age of 23 years, she was hospitalized for a virilization syndrome including hirsutism, acne, deepening of the voice, amenorrhea, and clitoromegaly. Serum levels of T were dramatically increased (1293 ng/dl; normal range, 10-80). The abdominal computed tomography scan revealed a solid mass located on the left ovary. INTERVENTION: An ovariectomy was performed, and histological examination revealed a sclerosing-stromal tumor with pseudolobular pattern. RESULTS: Immunohistochemical studies revealed that the tumor cells expressed all steroidogenic enzymes involved in androgen synthesis. Molecular analysis revealed that ovarian tumor cells harbored the Arg 201 activating mutation in the GNAS1 gene. After surgery, T levels returned to normal, the patient retrieved a normal gonadal function, and she was able to become pregnant. CONCLUSION: This observation extends the clinical spectrum of ovarian pathology of women with MAS. However, the mechanisms causing this ovarian tumor remain unclear, even if the gsp oncogene has been implicated in the pathogenesis of some gonadal tumors.