A case of a mesenteric lipoma in the transverse colon / 日本農村医学会雑誌

A chest X-ray taken during a medical checkup for a 75-year-old man revealed a nodular shadow in the right middle lung field. Chest computed tomography (CT) for further examination showed an intra-abdominal tumor as an additional finding, and the patient was referred to our department. Contrast-enhanced CT revealed a tumor (16×10×5 cm) in the left upper to middle abdomen. The tumor had a clear border and uniform fat density inside. It compressed the stomach to the ventral side, but the patient had no subjective symptoms. Magnetic resonance imaging also showed the tumor contained a uniform fatty component inside, as well as no obvious non-fatty components. An intra-abdominal lipoma was suspected, but the possibility of a welldifferentiated liposarcoma could not be ruled out due to its size. During curative surgery, intraoperative findings revealed a soft tumor, weighing 612 g, with a well-defined border in the mesentery of the transverse colon. Pathological findings showed proliferation of mature adipocytes without malignancy. We report here this case of mesenteric lipoma, a rare intraabdominal tumor, and review the relevant literature.

Brown Fat as a Regulator of Systemic Metabolism beyond Thermogenesis

Brown adipose tissue (BAT) is a specialized tissue for nonshivering thermogenesis to dissipate energy as heat. Although BAT research has long been limited mostly in small rodents, the rediscovery of metabolically active BAT in adult humans has dramatically promoted the translational studies on BAT in health and diseases. Moreover, several remarkable advancements have been made in brown fat biology over the past decade: The molecular and functional analyses of inducible thermogenic adipocytes (socalled beige adipocytes) arising from a developmentally different lineage from classical brown adipocytes have been accelerated. In addition to a well-established thermogenic activity of uncoupling protein 1 (UCP1), several alternative thermogenic mechanisms have been discovered, particularly in beige adipocytes. It has become clear that BAT influences other peripheral tissues and controls their functions and systemic homeostasis of energy and metabolic substrates, suggesting BAT as a metabolic regulator, other than for thermogenesis. This notion is supported by discovering that various paracrine and endocrine factors are secreted from BAT. We review the current understanding of BAT pathophysiology, particularly focusing on its role as a metabolic regulator in small rodents and also in humans.

Brown Adipose Tissue as a Therapeutic Target for Obesity: From Mice to Humans

Brown adipose tissue (BAT) is a site of sympathetically activated non-shivering thermognenesis during cold exposure and after spontaneous hyperphagia, thereby involving in the autonomic regulation of energy balance and body fatness. Recent radionuclide studies have demonstrated the existence of metabolically active BAT in adult humans. Human BAT is activated by acute cold exposure, particularly in winter, and contributes to cold-induced increase in whole-body energy expenditure. The metabolic activity of BAT is lower in older and obese individuals. The inverse relationship between the BAT activity and body fatness suggests that BAT, because of its energy dissipating activity, is protective against body fat accumulation. In fact, either repeated cold exposure or daily ingestion of some food ingredients acting on transient receptor potential channels recruited BAT in association with increased energy expenditure and decreased body fatness. Thus, BAT is a promising target for combating obesity and related metabolic disorders in humans.

Brown Adipose Tissue as a Regulator of Energy Expenditure and Body Fat in Humans

Brown adipose tissue (BAT) is recognized as the major site of sympathetically activated nonshivering thermogenesis during cold exposure and after spontaneous hyperphagia, thereby controling whole-body energy expenditure and body fat. In adult humans, BAT has long been believed to be absent or negligible, but recent studies using fluorodeoxyglucose-positron emission tomography, in combination with computed tomography, demonstrated the existence of metabolically active BAT in healthy adult humans. Human BAT is activated by acute cold exposure, being positively correlated to cold-induced increases in energy expenditure. The metabolic activity of BAT differs among individuals, being lower in older and obese individuals. Thus, BAT is recognized as a regulator of whole-body energy expenditure and body fat in humans as in small rodents, and a hopeful target combating obesity and related disorders. In fact, there are some food ingredients such as capsaicin and capsinoids, which have potential to activate and recruit BAT via activity on the specific receptor, transient receptor potential channels, thereby increasing energy expenditure and decreasing body fat modestly and consistently.