Abstract: A large body of evidence from clinical and experimental studies is aiding to understand the close relationships between obesity and rheumatic diseases. For instance, it is generally accepted that obesity contributes to the development of osteoarthritis by increasing mechanical load of the joints, at least in weight bearing joints. However, besides mechanical effects, recent studies demonstrated that white adipose tissue is able to secrete a plethora of soluble factors, called adipokines, which have a critical role in the development and progression of some rheumatic diseases such as osteoarthritis and rheumatoid arthritis. In this article, we summarize the recent findings on the interaction of certain adipokines with the two most common rheumatic diseases: osteoarthritis and rheumatoid arthritis. ... Read more

Abstract: Caloric restriction is associated with a reduction in body weight and temperature, as well as a reduction in trabecular bone volume and paradoxically an increase in adipocytes within the bone marrow. The nature of these adipocytes is uncertain, although there is emerging evidence of a direct relationship between bone remodeling and brown adipocytes. For example, in heterotrophic ossification, brown adipocytes set up a hypoxic gradient that leads to vascular invasion, chondrocyte differentiation, and subsequent bone formation. Additionally, deletion of retinoblastoma protein in an osteosarcoma model leads to increased hibernoma (brown fat tumor). Brown adipose tissue (BAT) becomes senescent with age at a time when thermoregulation is altered, bone loss becomes apparent, and sympathetic activity increases. Interestingly, heart rate is an unexpected but good predictor of fracture risk in elderly individuals, pointing to a key role for the sympathetic nervous system in senile osteoporosis. Hence the possibility exists that BAT could play an indirect role in age-related bone loss. However, evidence of an indirect effect from thermogenic dysfunction on bone loss is currently limited. Here, we present current evidence for a relationship between brown adipose tissue and bone as well as provide novel insights into the effects of thermoregulation on bone mineral density. ... Read more

Abstract: No truly effective drugs exist to treat obesity, which is reaching pandemic proportions. The search for new treatments has led to an interest into the homeostatic system of central appetite regulation. Key components of this system include the hypothalamus and brainstem, the gut, and adipose tissue. It is now recognized that food intake leads to the release of various gut hormones. There are several anorectic (appetite suppressing) gut hormones released, including cholecystokinin, glucagon like peptide-1, oxyntomodulin, peptide tyrosine tyrosine, and pancreatic polypeptide. To date, only one example is known of an orexigenic (appetite stimulating) hormone, ghrelin. These hormones circulate in the blood and signal via vagal nerve afferents to communicate with the hypothalamus and brainstem. This information is integrated and processed in key hypothalamic nuclei. The arcuate nucleus appears to be a central controller of the appetite circuit, integrating both peripheral and central signals. This information is translated into downstream signals affecting body metabolism and food intake. Increased understanding and successful manipulation of this system should enable the design of a successful and much needed anti-obesity treatment. ... Read more

Abstract: The proper maintenance of body weight and mood are two of the most prevalent health issues present in society today. Obese humans display higher levels of mood-related disorders and the causality of such an association is unknown. A common feature of obesity is the imbalance of regulatory hormones which normally act to maintain stable energy balance and body weight. The adiposity hormone leptin is one such signal elevated in obesity with the capacity to dampen feeding behavior through action on brain circuits which regulate appetite and metabolism. Recent evidence suggests that leptin may regulate motivation through its actions within brain reward circuitry. In addition, leptin signaling within central nervous system regions that regulate cognition and emotion elicits anti-depressant like effects. Together, these data indicate that leptin may regulate the decreased motivation and mood present in obesity and depression. This review describes the capacity of leptin to regulate motivation and depression through actions within brain circuits that modulate effort-based behavior and emotion, respectively. ... Read more