Influence of white fat browning on nonalcoholic fatty liver disease / 临床肝胆病杂志

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease in which a large amount of fat accumulates in hepatocytes due to lipid metabolism disorders. Conventional anti-inflammatory and transaminase-lowering treatment regimens often have an unsatisfactory therapeutic effect, and restoring the normal biosynthesis and metabolism of lipids is the key to the treatment of NAFLD. Studies have shown that brown adipose tissue can improve metabolic diseases by enhancing insulin sensitivity and regulating lipid metabolism, and the treatment of NAFLD by promoting white fat browning has attracted wide attention in the medical field. This article reviews the mechanism of white fat browning in improving NAFLD and summarizes the hepatokines that can promote white fat browning, so as to provide new ideas for the clinical treatment of NAFLD.

Research progress of brown adipose tissue imaging technology / 中华核医学与分子影像杂志

Diabetes, obesity, and metabolic diseases are globally prevalent, and induction and increase of endogenous energy consumption, especially activation of brown adipose tissue (BAT), is a new therapeutic target. Non-invasive imaging techniques, including radionuclide imaging, MRI, ultrasound imaging, and optical imaging, have attracted wide attention in BAT monitoring and have good application prospects. This article reviews the progress and application of these imaging techniques in BAT monitoring.

Correlations between brown adipose tissue in adults and metabolic indicators / 中华核医学与分子影像杂志

Objective To examine the distribution,volume and glucose-uptake activity of brown adipose tissue (BAT) in adults and investigate their correlations with metabolic indicators.Methods 18F-flurodeoxyglucose (FDG) PET/CT was used to analyze the distribution,volume and glucose-uptake activity of BAT.The clinical and metabolic differences between BAT positive group (n =121) and BAT negative group (n=257) were compared.The influences of metabolic indicators (fast blood glucose (FBG),triglyceride (TG),total cholesterol (TC),high density lipoprotein cholesterol (HDL-C),low density lipoprotein cholesterol (LDL-C),uric acid (UA)) on the distribution,volume and activity of BAT were investigated.Logistic regression analysis,two-sample t test,x2 test and multiple linear regression were used to analyze the data.Results The distribution,volume and glucose-uptake activity of BAT were found to be significantly higher in subjects being tested in colder seasons than those who were tested in warmer seasons:2.91％ (87/2 991) vs 1.68％(34/2018),(433±402) vs (329±298) ml,(212±183) vs (169±145) g (x2=7.66,t values:3.36 and 2.98,all P＜0.05).The female proportion was significantly higher in BAT positive group than that in BAT negative group:68.60％ (83/121) vs 31.91％ (82/257) (x2 =16.10,P＜0.01).The average levels of age,body mass index (BMI),FBG,TG,TC,LDL-C and UA in BAT positive group were significantly low-er than those in BAT negative group:(41.30±10.90) vs (48.70±9.60) years,(21.30±2.40) vs (24.50± 3.10) kg/m2,(4.56±0.74) vs (5.34±1.33) mmol/L,(0.94±0.36) vs (2.06±1.64) mmol/L,(4.42± 0.79) vs (4.88±0.87) mmol/L,(1.99±0.58) vs (3.10±0.77) mmol/L,(285.11±70.00) vs (347.70± 101.10) μmol/L (t values:from-6.25 to-2.94,all P＜0.01).Logistic regression analysis revealed that season,gender,age,BMI,FBG,TG and LDL-C levels were all independent influencing factors of BAT distribution in adults (odds ratios:5.36,2.06,0.95,0.79,0.49,0.23,0.02;P＜0.01 or P＜0.05).Among BAT positive adults,gender and FBG levels were found to be strongly affected by the volume and glucose-uptake activity of BAT (β values:0.28,-0.21,both P＜0.05).Conclusions The distribution,volume and glucose-uptake activity of BAT in adults are associated with multiple metabolic indicators including BMI,levels of glucose,lipid and UA.The distribution of BAT is affected by gender,age,season,BMI,blood glucose,and blood lipids.

Advances in the research of relationship between brown or beige fat and hypermetabolism after severe burn / 中华烧伤杂志

Hypermetabolism is one of the remarkable characteristics of burn injury. Prolonged hypermetabolism causes insufficient energy supply, which leads to delayed wound healing, immune system dysfunction, increased infection rate, and multi-organ failure. In recent years, it is concerned that the activation of brown or beige adipose tissue may be related to hypermetabolism in severe burn patients. Brown or beige adipose tissue could be regulated by stress hormones and some cytokines which increase and persist in high level for several months after severe burn. This paper reviews the current knowledge of brown or beige adipocytes developmental lineages, molecular regulation mechanism, and regulation of brown or beige adipocytes activation after severe burn.

The Role of Circulating Slit2, the One of the Newly Batokines, in Human Diabetes Mellitus

BACKGROUND: Slit2 is a new secreted protein from adipose tissue that improves glucose hemostasis in mice; however, there is no study about the serum levels and precise role of Slit2 in human. The aim of this study is to explore the serum level of Slit2 in human, and to identify the role of Slit2 in diabetes mellitus (DM). METHODS: The participants of this study consist of 38 subjects with newly diagnosed DM, and 75 healthy subjects as a control group. Serum Slit2 levels were measured using an enzyme-linked immunosorbent assay. Relationship between circulating Slit2 and diabetic related factors was investigated in diabetic group compared with non-diabetic group. Additionally, the correlations between the serum level of Slit2 and diverse metabolic parameters were analyzed. RESULTS: Circulating Slit2 level was more decreased in diabetic group than in control group, but there was no significant difference statistically. Interestingly, serum levels of Slit2 were significantly negatively correlated to the serum concentrations of fasting glucose (coefficient r=–0.246, P=0.008), the serum concentrations of postprandial glucose (coefficient r=–0.233, P=0.017), and glycosylated hemoglobin (HbA1c; coefficient r=–0.357, P<0.001). CONCLUSION: From our study, the first report of circulating Slit2 levels in human, circulating Slit2 level significantly negatively correlated with serum glucose and HbA1c. Our results suggest that the circulating Slit2 may play a role in maintainence of glucose homeostasis in human, even though exact contribution and mechanism are not yet known.

Brown Fat and Browning for the Treatment of Obesity and Related Metabolic Disorders

Brown fat is a specialized fat depot that can increase energy expenditure and produce heat. After the recent discovery of the presence of active brown fat in human adults and novel transcription factors controlling brown adipocyte differentiation, the field of the study of brown fat has gained great interest and is rapidly growing. Brown fat expansion and/or activation results in increased energy expenditure and a negative energy balance in mice and limits weight gain. Brown fat is also able to utilize blood glucose and lipid and results in improved glucose metabolism and blood lipid independent of weight loss. Prolonged cold exposure and beta adrenergic agonists can induce browning of white adipose tissue. The inducible brown adipocyte, beige adipocyte evolving by thermogenic activation of white adipose tissue have different origin and molecular signature from classical brown adipocytes but share the characteristics of high mitochondria content, UCP1 expression and thermogenic capacity when activated. Increasing browning may also be an efficient way to increase whole brown fat activity. Recent human studies have shown possibilities that findings in mice can be reproduced in human, making brown fat a good candidate organ to treat obesity and its related disorders.

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.

The Mechanism of White and Brown Adipocyte Differentiation

Obesity gives vent to many diseases such as type 2 diabetes, hypertension, and hyperlipidemia, being considered as the main causes of mortality and morbidity worldwide. The pathogenesis and pathophysiology of metabolic syndrome can well be understood by studying the molecular mechanisms that control the development and function of adipose tissue. In human body, exist two types of adipose tissue, the white and the brown one, which are reported to play various roles in energy homeostasis. The major and most efficient storage of energy occurs in the form of triglycerides in white adipose tissue while brown adipose tissue actively participates in both basal and inducible energy consumption in the form of thermogenesis. Recent years have observed a rapid and greater interest towards developmental plasticity and therapeutic potential of stromal cells those isolated from adipose tissue. The adipocyte differentiation involves a couple of regulators in the white or brown adipogenesis. Peroxisome proliferators-activated receptor-gamma actively participates in regulating carbohydrate and lipid metabolism, and also acts as main regulator of both white and brown adipogenesis. This review based on our recent research, seeks to highlight the adipocyte differentiation.