The central administration of C75, a fatty acid synthase inhibitor, activates sympathetic outflow and thermogenesis in interscapular brown adipose tissue.

The present work investigated the participation of interscapular brown adipose tissue (IBAT), which is an important site for thermogenesis, in the anti-obesity effects of C75, a synthetic inhibitor of fatty acid synthase (FAS). We report that a single intracerebroventricular (i.c.v.) injection of C75 induced hypophagia and weight loss in fasted male Wistar rats. Furthermore, C75 induced a rapid increase in core body temperature and an increase in heat dissipation. In parallel, C75 stimulated IBAT thermogenesis, which was evidenced by a marked increase in the IBAT temperature that preceded the rise in the core body temperature and an increase in the mRNA levels of uncoupling protein-1. As with C75, an i.c.v. injection of cerulenin, a natural FAS inhibitor, increased the core body and IBAT temperatures. The sympathetic IBAT denervation attenuated all of the thermoregulatory effects of FAS inhibitors as well as the C75 effect on weight loss and hypophagia. C75 induced the expression of Fos in the paraventricular nucleus, preoptic area, dorsomedial nucleus, ventromedial nucleus, and raphé pallidus, all of which support a central role of FAS in regulating IBAT thermogenesis. These data indicate a role for IBAT in the increase in body temperature and hypophagia that is induced by FAS inhibitors and suggest new mechanisms explaining the weight loss induced by these compounds.

Effects of neonatal castration and androgenization on sexual dimorphism in bone, leptin and corticosterone secretion.

This study investigated the role of neonatal sex steroids in rats on sexual dimorphism in bone, as well as on leptin and corticosterone concentrations throughout the lifespan. Castration of males and androgenization of females were used as models to investigate the role of sex steroids shortly after birth. Newborn Wistar rats were divided into four groups, two male groups and two female groups. Male pups were cryoanesthetized and submitted to castration or sham-operation procedures within 24 h after birth. Female pups received a subcutaneous dose of testosterone propionate (100 µg) or vehicle. Rats were euthanized at 20, 40, or 120 postnatal days. Body weight was also measured at 20, 40, and 120 days of age, and blood samples and femurs were collected. The length and thickness of the femurs were measured and the areal bone mineral density (areal BMD) was determined by dual-energy X-ray absorptiometry (DEXA). Biomechanical three-point bending testing was used to evaluate bone breaking strength, energy to fracture, and extrinsic stiffness. Blood samples were submitted to a biochemical assay to estimate calcium, phosphorus, alkaline phosphatase, leptin, and corticosterone levels. Weight gain, areal BMD and bone biomechanical properties increased rapidly with respect to age in all groups. In control animals, skeletal sexual dimorphism, leptin concentration, and dimorphic corticosterone concentration patterns were evident after puberty. However, androgen treatment induced changes in growth, areal BMD, and bone mass properties in neonatal animals. In addition, neonatally-castrated males had bone development and mechanical properties similar to those of control females. These results suggest that the exposure to neonatal androgens may represent at least one covariate that mediates dimorphic variation in leptin and corticosterone secretions. The study indicates that manipulation of the androgen environment during the critical period of sexual differentiation of the brain causes long-lasting changes in bone development, as well as serum leptin and corticosterone concentrations. In addition, this study provides useful models for the investigation of bone disorders induced by hypothalamic hypogonadism.