The mechanism and regulation of fat mobilization from adipose tissue: desnutrin, a newly discovered lipolytic enzyme

A new member of a family of proteins functioning in the regulation of lipolysis in adipose tissue has been discovered and named "desnutrin." Desnutrin is transiently induced by fasting and decreased by re-feeding. A close homolog, termed adiponutrin, has the opposite expression pattern, being induced by feeding and disappearing upon fasting. Desnutrin functions by acting as the first enzyme in lipolysis, hydrolyzing triglycerides to diglycerides, whereas the well-known hormone-sensitive lipase takes the diglycerides to monoglycerides and on to free fatty acids.     

Clinicopathological features of hepatocellular carcinoma with fatty change: Tumors with macrovesicular steatosis have better prognosis and aberrant expression patterns of perilipin and adipophilin

The clinicopathological characteristics of steatosis in hepatocellular carcinoma (HCC) remain unclear. Here, we elucidate the features of macrovesicular steatosis (MaS) and microvesicular steatosis (MiS) in HCC and their relationships with background liver steatosis. A total of 165 HCC lesions were classified as MaS‐HCC, MiS‐HCC, or conventional HCC (cHCC) according to the cutoff value of 30% MaS or MiS in tumor cells. We analyzed the clinicopathological differences among these groups. MaS‐HCC had less portal vein invasion, a higher proportion of HCC with intratumoral fibrosis, and a lower cumulative risk of recurrence than MiS‐HCC or cHCC. Moreover, both MaS‐HCC and MiS‐HCC had lower incidences of hepatitis virus infection and higher levels of HbA1c than cHCC. Background liver steatosis was also higher in MaS‐HCC than in cHCC. Immunohistochemical expression of perilipin (Plin1) and adipophilin (ADRP), major proteins expressed on lipid droplet membranes, revealed that almost all lipid droplets in HCC were Plin1 negative, whereas those in background liver were positive. In contrast, ADRP was expressed on lipid droplets in both HCC and background liver. We concluded that MaS‐HCC and MiS‐HCC were associated with metabolic abnormalities but exhibited different biologic behaviors. Furthermore, lipid droplets in HCC were pathophysiologically different from those in background liver.     

Efficient non-viral transfection of THP-1 cells

Macrophages are an important part of the cellular immune system and play a key role during immune responses. Thus, macrophages are interesting targets in basic and clinical research. Primary monocytes or monocyte-derived macrophages do not proliferate on a suitable scale so that their use for functional studies invitro is limited. Immortal proliferating cell lines, such as the human THP-1 monocytic leukemia cell line, are therefore often used instead of primary cells. Transfection is a useful tool to study the function of gene products, but transfection of THP-1 monocytes and pre-differentiated THP-1 macrophages with subsequent differentiation into mature THP-1 macrophages using phorbol esters is usually accompanied by a progressive loss of cell viability. In this study, we describe a simple and rapid approach for efficient transfection of THP-1 monocytes and pre-differentiated THP-1 macrophages using a modified Nucleofection-based approach. The protocol maintains cell viability and functionality, thus allowing efficient transfection of THP-1 cells combined with subsequent differentiation of transfected THP-1 cells into mature macrophages.     

Mitochondrial E3 ubiquitin ligase 1 promotes autophagy flux to suppress the development of clear cell renal cell carcinomas

Clear cell renal cell carcinoma (ccRCC) is one of the most common malignant tumors in the urinary system. Surgical intervention is the preferred treatment for ccRCC, but targeted biological therapy is required for postoperative recurrent or metastatic ccRCC. Autophagy is an intracellular degradation system for misfolded/aggregated proteins and dysfunctional organelles. Defective autophagy is associated with many diseases. Mul1 is a mitochondrion‐associated E3 ubiquitin ligase and involved in the regulation of divergent pathophysiological processes such as mitochondrial dynamics, and thus affects the development of various diseases including cancers. Whether Mul1 regulates ccRCC development and what is the mechanism remain unclear. Histochemical staining and immunoblotting were used to analyze the levels of Mul1 protein in human renal tissues. Statistical analysis of information associated with tissue microarray and The Cancer Genome Atlas (TCGA) database was conducted to show the relationship between Mul1 expression and clinical features and survival of ccRCC patients. Impact of Mul1 on rates of cell growth and migration and autophagy flux were tested in cultured cancer cells. Herein we show that Mul1 promoted autophagy flux to facilitate the degradation of P62‐associated protein aggresomes and adipose differentiation‐related protein (ADFP)‐associated lipid droplets and suppressed the growth and migration of ccRCC cells. Levels of Mul1 protein and mRNA were significantly reduced so that autophagy flux was likely blocked in ccRCC tissues, which is potentially correlated with enhancement of malignancy of ccRCC and impairment of patient survival. Therefore, Mul1 may promote autophagy to suppress the development of ccRCC.     

人参皂苷Rb1改善高脂喂养肥胖小鼠胰岛素抵抗和脂肪异位沉积

人参皂苷Rb₁是人参的主要活性成分,前期体外实验显示人参皂苷Rb₁能够抑制脂肪细胞脂肪分解和促进葡萄糖转运的作用。本研究利用高脂饮食诱导的肥胖小鼠,研究人参皂苷Rb₁对胰岛素抵抗和脂肪异位沉积的影响及其作用的分子机制。将高脂喂养的肥胖雄性C57/L小鼠,随机分为高脂组（DIO组）,人参皂苷Rb₁组（Rb₁组）和罗格列酮组（Rog组）,继续给予高脂饲料喂养,另设立正常饲料喂养的C57/L小鼠为正常组（NC组）;分别按20,10 mg·kg^-1体重给予Rb₁组和Rog组小鼠每天腹腔注射人参皂苷Rb₁和罗格列酮,NC组和DIO组以等量的生理盐水腹腔注射。治疗2周后,进行腹腔注射葡萄糖耐量试验（IPGTT）,3 d后,处死小鼠,留取血清,检测胰岛素、游离脂肪酸（FFA）及生化指标;称取肝脏质量,检测肝脏内甘油三酯含量和病理检测;称取附睾脂肪质量,蛋白印迹检测PDE3B,HSL,周脂素。结果显示人参Rb₁治疗2周明显改善肥胖小鼠的葡萄糖耐量,除了0~120 min,Rb₁组葡萄糖耐量曲线下面积（0~30,0~60,0~90 min）较DIO组均显著下降（P<0.05,n=5）,胰岛素抵抗指数（HOMA-IR）显著下降（P<0.05,n=5）;并且Rb₁显著降低了肥胖小鼠肝脏内的脂肪水平（P<0.05,n=5）,肝脏质量/体重也明显下降（P<0.05,n=8）;Rb₁治疗后,肥胖小鼠血中升高的FFA水平也明显下降（P<0.05,n=8）;附睾脂肪中周脂素表达水平得到部分恢复,但对PDE3B的表达以及HSL的表达和磷酸化激活未见明显影响。以上研究结果表明人参皂苷Rb₁能够通过上调脂肪组织周脂素的表达,减少游离脂肪酸的释放和甘油三酯的异位沉积,这可能是其改善机体胰岛素抵抗和糖代谢异常的作用机制之一。     

The significance of lipid accumulation in breast carcinoma cells through perilipin 2 and its clinicopathological significance

Both systemic and intratumoral lipid metabolism have been recently reported to play pivotal roles in both tumor development and progression in various human malignancies including breast cancer. However, its details have remained largely unknown in breast cancer patients. Therefore, in this study, we focused on perilipin 2, which is involved in constituting the intracellular lipid composition. Perilipin 2 was first immunolocalized in 105 cases of breast cancer. The status of perilipin 2 immunoreactivity was significantly positively associated with histological grade, Ki‐67 labeling index and HER2 status and negatively with estrogen receptor status of these patients. Subsequent in vitro study also revealed that its mRNA expression in triple negative breast carcinoma cells was higher than cells of other subtypes. We then examined the correlation between perilipin 2 immunoreactivity and intracellular lipid droplet evaluated by Oil‐red O stating in 13 cases of breast carcinoma tissues. A significantly positive correlation was detected between the status of perilipin 2 and Oil‐red O staining. These findings above did indicate that perilipin 2 could represent the status of intracellular lipid droplets in surgical pathology specimens of breast cancer and perilipin 2 was also associated with its more aggressive biological phenotypes.     

周脂素及运动对其影响研究进展

周脂素（Perilipin）是包被于脂滴表面的一种磷蛋白,特异表达于脂肪细胞和类甾醇生成细胞中。周脂素对脂肪分解具有双重调控作用,可能与肥胖、胰岛素抵抗和动脉粥样硬化等的发生有关。本研究对周脂素的研究进展进行综述,并提出一些假设,以期为周脂素的深入研究提供参考。     

Dieckol-Attenuated High-Fat Diet Induced Muscle Atrophy by Modulating Muscular Deposition of Lipid Droplets

An excessive fat diet induces intramuscular fat deposition that accumulates as a form of lipid droplet (LD) and leads to lipotoxicity, including muscle atrophy or decreasing muscle strength. Lipotoxicity depends on the number of LDs, subcellular distribution (intermyofibrillar, IMF, LDs or subsarcolemmal, SS), and fiber type-specific differences (type I or type II fiber) as well as the size of LD. Ecklonia cava extracts (ECE), which is known to increase peroxisome proliferator-activated receptor alpha (PPAR-α), which leads to decreasing expression level of perilipin2 (PLIN2). PLIN2 is involved in modulating the size of LDs. This study shows that ECE and dieckol could decrease PLIN2 expression and decrease the size and number of LDs in the muscle of high-fat diet (HF)-fed animals and lead to attenuating muscle atrophy. Expression level of PPAR-α was decreased, and PLIN2 was increased by HF. ECE and dieckol increased PPAR-α expression and decreased PLIN2. The diameter of LDs was increased in high-fat diet condition, and it was decreased by ECE or dieckol treatment. The number of LDs in type II fibers/total LDs was increased by HF and it was decreased by ECE or dieckol. The SS LDs were increased, and IMF LDs were decreased by HF. ECE or dieckol decreased SS LDs and increased IMF LDs. The ECE or dieckol attenuated the upregulation of muscle atrophy-related genes including Murf1, Atrogin-1, and p53 by HF. ECE or dieckol increased the cross-sectional area of the muscle fibers and grip strength, which were decreased by HF. In conclusion, ECE or dieckol decreased the size of LDs and modulated the contribution of LDs to less toxic ones by decreasing PLIN2 expression and thus attenuated muscle atrophy and strength, which were induced by HF.     

黄连提取物对ApoE基因敲除小鼠主动脉易损斑块Perilipin和PPAR-γ基因表达的影响

目的 观察黄连提取物对ApoE基因敲除小鼠动脉粥样硬化（AS）易损斑块内周脂素（perilipin）和过氧化物酶体增殖物激活受体γ（PPAR-γ）基因表达的影响,探讨黄连提取物稳定AS斑块的作用及可能机制。方法 33只6～8周龄ApoE基因敲除小鼠予高脂饮食喂养13周,待其形成成熟的AS斑块后,随机分为3组：模型组、黄连提取物组、辛伐他汀组（阳性对照组）,每组11只。继续高脂喂养,并按体重比折算给予小鼠临床推荐剂量的相应药物治疗13周,处死动物,每只小鼠分别取主动脉根部的4个切面,分别行HE染色和Movat染色,观察并计算各组小鼠主AS斑块内埋藏纤维帽的平均数目,实时荧光定量PCR法检测主动脉内perilipin和PPAR-γmRNA的表达。结果 给药13周后,黄连提取物组斑块内埋藏纤维帽的数目与模型组比较明显减少（P<0.05）,并且斑块内perilipin mRNA的表达与模型组比较显著降低（P<0.05）,而PPAR-γmRNA的表达较模型组显著增加（P<0.01）。结论 在临床推荐剂量上,黄连提取物可显著减少ApoE基因敲除小鼠主动脉粥样斑块破裂次数,有助于稳定易损斑块,其机制可能与促进小鼠AS斑块内PPAR-γmRNA表达,抑制perilipin mRNA表达有关。     

Endocrine modulation of brain-skeleton axis driven by neural stem cell-derived perilipin 5 in the lipid metabolism homeostasis for bone regeneration

1. Download : Download high-res image (264KB)
2. Download : Download full-size image