Iron chelation increases beige fat differentiation and metabolic activity, preventing and treating obesity

Beige and brown fat consume glucose and lipids to produce heat, using uncoupling protein 1 (UCP1). It is thought that full activation of brown adipose tissue (BAT) may increase total daily energy expenditure by 20%. Humans normally have more beige and potentially beige-able fat than brown fat. Strategies to increase beige fat differentiation and activation may be useful for the treatment of obesity and diabetes. Mice were fed chow or high-fat diet (HFD) with or without the iron chelator deferasirox. Animals fed HFD + deferasirox were markedly lighter than their HFD controls with increased energy expenditure (12% increase over 24 h, p < 0.001). Inguinal fat from HFD + deferasirox mice showed increased beige fat quantity with greater Ucp1 and Prdm16 expression. Inguinal adipose tissue explants were studied in a Seahorse bioanalyser and energy expenditure was significantly increased. Deferasirox was also effective in established obesity and in ob/ob mice, indicating that intact leptin signalling is not needed for efficacy. These studies identify iron chelation as a strategy to preferentially activate beige fat. Whether activating brown/beige fat is effective in humans is unproven. However, depleting iron to low-normal levels is a potential therapeutic strategy to improve obesity and related metabolic disorders, and human studies may be warranted.

Proses Pencokelatan Jaringan Adiposa

Obesity is a common, serious, and detrimental condition. In 2014, more than 1.9 billion adults were overweight. Obesity is associated with many diseases and the increase in obesity has become a major health problem. Obesity is caused by an imbalance between energy intake and energy consumption. Adipose tissue is an endocrine organ that secretes many hormones and cytokines that can affect metabolism. There are two types of adipose tissue in the body with different functions, namely white adipose tissue and brown adipose tissue. White fat has a major function in storing energy and is increased in obesity, while brown fat produces heat (thermogenesis) and then increases energy consumption. Therefore, brown fat and the induction of brown fat-like properties in white fat, have been considered as targets in the fight against obesity. The complex process of cell differentiation leading to the appearance of active brown adipocytes has been identified. There are classic brown adipocytes and cream adipocytes. Beige adipocytes are brown adipocytes that appear on precursor cells of white adipose tissue due to stimuli. Brown adipocytes are equipped with mitochondria containing uncoupling protein 1 (UCP1), which, when activated, controls ATP synthesis and stimulates respiratory chain activity. The browning process of adipose tissue is controlled by factors such as exercise. Obesitas merupakan keadaan yang umum, serius, dan merugikan. Tahun 2014, lebih dari 1,9 milyar orang dewasa mengalami kelebihan berat badan. Obesitas berasosiasi dengan banyak penyakit dan peningkatan obesitas telah menjadi masalah kesehatan utama. Obesitas disebabkan oleh ketidakseimbangan antara energi yang masuk dan konsumsi energi. Jaringan adiposa dalam tubuh ada dua tipe yang fungsinya berbeda, yakni jaringan adiposa putih dan jaringan adiposa cokelat. Lemak putih berfungsi utama dalam menyimpan energi dan meningkat pada obesitas, sedangkan lemak cokelat menghasilkan panas (termogenesis) dan kemudian meningkatkan konsumsi energi. Oleh karena itu, lemak cokelat dan induksi sifat seperti lemak cokelat pada lemak putih, telah dipertimbangkan sebagai target dalam melawan obesitas. Tujuan penelitian ini adalah untuk mengetahui proses pencoklatan jaringan adiposa putih. Metode penelitian yang digunakan adalah metode penelusuran ilmiah. Hasil penelitian diperoleh bahwa adiposit krem merupakan adiposit cokelat yang muncul pada sel prekursor dari jaringan adiposa putih karena adanya stimuli. Adiposit krem sama seperti adiposit cokelat dilengkapi dengan mitokondria yang mengandung uncoupling protein 1 (UCP1), yang ketika teraktivasi akan mengendalikan sintesis ATP dan menstimulasi aktivitas rantai respirasi. Beberapa regulator seperti PPAR γ, PGC-1α, dan PRDM16 muncul sebagai pelaku utama dalam proses diferensiasi adiposit krem.

Brown Fat Dnmt3b Deficiency Ameliorates Obesity in Female Mice

Obesity results from a chronic energy imbalance due to energy intake exceeding energy expenditure. Activation of brown fat thermogenesis has been shown to combat obesity. Epigenetic regulation, including DNA methylation, has emerged as a key regulator of brown fat thermogenic function. Here we aimed to study the role of Dnmt3b, a DNA methyltransferase involved in de novo DNA methylation, in the regulation of brown fat thermogenesis and obesity. We found that the specific deletion of Dnmt3b in brown fat promotes the thermogenic and mitochondrial program in brown fat, enhances energy expenditure, and decreases adiposity in female mice fed a regular chow diet. With a lean phenotype, the female knockout mice also exhibit increased insulin sensitivity. In addition, Dnmt3b deficiency in brown fat also prevents diet-induced obesity and insulin resistance in female mice. Interestingly, our RNA-seq analysis revealed an upregulation of the PI3K-Akt pathway in the brown fat of female Dnmt3b knockout mice. However, male Dnmt3b knockout mice have no change in their body weight, suggesting the existence of sexual dimorphism in the brown fat Dnmt3b knockout model. Our data demonstrate that Dnmt3b plays an important role in the regulation of brown fat function, energy metabolism and obesity in female mice.

Epigenetic interaction between UTX and DNMT1 regulates diet-induced myogenic remodeling in brown fat

Brown adipocytes share the same developmental origin with skeletal muscle. Here we find that a brown adipocyte-to-myocyte remodeling also exists in mature brown adipocytes, and is induced by prolonged high fat diet (HFD) feeding, leading to brown fat dysfunction. This process is regulated by the interaction of epigenetic pathways involving histone and DNA methylation. In mature brown adipocytes, the histone demethylase UTX maintains persistent demethylation of the repressive mark H3K27me3 at Prdm16 promoter, leading to high Prdm16 expression. PRDM16 then recruits DNA methyltransferase DNMT1 to Myod1 promoter, causing Myod1 promoter hypermethylation and suppressing its expression. The interaction between PRDM16 and DNMT1 coordinately serves to maintain brown adipocyte identity while repressing myogenic remodeling in mature brown adipocytes, thus promoting their active brown adipocyte thermogenic function. Suppressing this interaction by HFD feeding induces brown adipocyte-to-myocyte remodeling, which limits brown adipocyte thermogenic capacity and compromises diet-induced thermogenesis, leading to the development of obesity.

Hibernoma of Thigh: A Case Report of 39-Year-Old Male

Introduction: Hibernoma is an uncommon benign lipomatous tumor that originates from residual brown fat. It commonly affects adult patients aged between 30 and 40 with a slight predominance in male more than female and usually seen in the thigh, shoulder, back, chest, axilla, and neck. The present report aimed to highlight on a viable differential diagnosis of thigh mass including liposarcoma and atypical lipoma. Case Presentation: This is the case report with detailed history, examination of 39-year-old male patient with hibernoma over medial aspect of thigh. Marginal surgical resection was carried and sent to histopathology to confirm the diagnosis of hibernoma. Conclusion: Hibernoma is a rare benign lipomatous soft tissue tumor with no known risk for malignant transformation or metastasis. Based on imaging examination, it can mimic malignant tumors such as, liposarcoma, in which we believe that biopsy is required in order to reach the diagnosis in most of the cases. Keywords: Soft tissue tumor, hibernoma, brown fat, liposarcoma.

Exploratory Study on Expression of Fatty Tissue in Gestational Diabetes Mouse

Objective. To investigate the changes of UCP1 protein in brown fat by establishing a model of gestational diabetes mellitus through intervention of high fat and carbohydrate diet. To explore the changes of UCP1 protein in brown fat in gestational diabetic mice, and analyze the characteristics of abnormal glucose metabolism in gestational diabetic mice and its relationship with changes in adipocyte morphology and insulin resistance. Methods. Eighty C57BL/6J pregnant mice were randomly divided into a normal control group and a high-fat and high-sugar feeding group. The normal control group was fed a normal diet, while the high-fat and high-sugar group was fed a high-fat and high-sugar diet to establish a gestational diabetes mellitus (GDM) model. On the pregnancy days 0, 10, and 18, the weight and fasting glucose were measured. On the pregnancy day 18, the triglycerides (TG), the total cholesterol (TC), free fatty acid (FFA), insulin levels, and insulin resistance index (HOMA-IR) were measured or calculated. At the same time, brown fat UCP1 protein of the two groups of pregnant mice were measured using Western blot Observed the Adipose tissue pathological changes by staining HE. The adipocyte was observed, and the correlation was analyzed. Results. Twenty-one pregnant mice reach the level of gestational diabetes diagnosis (FBG ≥ 5.1 mmol/L) in the high-fat and high-sugar diet group. On the pregnancy day 10 and 18, the fasting plasma glucose and the body weight significantly increased ( P < 0.05 ). The total cholesterol, triglycerides, free fatty acid, insulin level, and insulin resistance index of the GDM group were also higher compared with that of the control group ( P < 0.05 ). The adipocyte size significantly increased in the GDM mice. TG, TC, FFA, and body weight at 18 days of gestation were significantly correlated with HOMA-IR and single-adipocyte area in the GDM mice. HOMA-IR was significantly correlated with a single-adipocyte area. Compared with the normal control group, the UCP1 proteins of GDM mice decreased significantly and negatively correlated with body weight increase. Conclusion. Feeding C57BL/6J pregnant mice with high fat and high sugar to establish a gestational diabetes mouse model has good stability and is similar to human gestational diabetes. The reduction of brown fat UCP1 protein in GDM mice has a certain correlation with obesity tendency and obvious insulin resistance.