Clusterin decreases hepatic SREBP-1c expression and lipid accumulation

ASGR1 deficiency diverts lipids toward adipose tissue but results in liver damage during obesity

BACKGROUND

Asialoglycoprotein receptor 1 (ASGR1), primarily expressed on hepatocytes, promotes the clearance and the degradation of glycoproteins, including lipoproteins, from the circulation. In humans, loss-of-function variants of ASGR1 are associated with a favorable metabolic profile and reduced incidence of cardiovascular diseases. The molecular mechanisms by which ASGR1 could affect the onset of metabolic syndrome and obesity are unclear. Therefore, here we investigated the contribution of ASGR1 in the development of metabolic syndrome and obesity.

METHODS

ASGR1 deficient mice (ASGR1-/-) were subjected to a high-fat diet (45% Kcal from fat) for 20 weeks. The systemic metabolic profile, hepatic and visceral adipose tissue were characterized for metabolic and structural alterations, as well as for immune cells infiltration.

RESULTS

ASGR1-/- mice present a hypertrophic adipose tissue with 41% increase in fat accumulation in visceral adipose tissue (VAT), alongside with alteration in lipid metabolic pathways. Intriguingly, ASGR1-/- mice exhibit a comparable response to an acute glucose and insulin challenge in circulation, coupled with notably decreased in circulating cholesterol levels. Although the liver of ASGR1-/- have similar lipid accumulation to the WT mice, they present elevated levels of liver inflammation and a decrease in mitochondrial function.

CONCLUSION

ASGR1 deficiency impacts energetic homeostasis during obesity leading to improved plasma lipid levels but increased VAT lipid accumulation and liver damage.

A low-carbohydrate diet with different fatty acids' sources in the treatment of obesity: Impact on insulin resistance and adipogenesis

BACKGROUND

The search for nutritional intervention strategies against obesity has grown, highlighting the low-carbohydrate diet model. However, little is known about the impact of the quality of fatty acids consumed in this diet. Thus, we aim to investigate the influence of fatty acid quality on dietary strategy on obesity.

METHODS

Male Swiss mice were diet-induced to obesity. Afterward, mice consume a low-carb diet with different types of fat: saturated, polyunsaturated ω-3, ω-6, and monounsaturated ω-9 fatty acids. Weight gain and food consumption were monitored weekly. An oral glucose tolerance test was performed and blood and tissue samples were collected for analysis of insulin resistance markers. Protein expression of insulin signaling pathway molecules, lipid metabolism, mitochondrial function, macrophage polarization, and cytokine production were analyzed.

RESULTS

The high-fat diet was able to induce obesity and glucose intolerance. The switch to a low-carbohydrate dietary pattern reversed the glucose intolerance, with better results in the ω-3 and ω-9 groups. After the low-carbohydrate diet, groups ω-3 and ω-9 presented improved fasting serum glucose, insulin, and HOMA indexes. The low-carbohydrate diet also increased the activity of insulin pathway proteins such as IR, IRS1, and AKT. Furthermore, the ω-3 diet group showed greater activity of mitochondrial complexes and AMPK signaling pathway proteins. The ω-6 and ω-9 -rich diet induced M2-type macrophage polarization, as well as cytokine production modulation by the low-carbohydrate diet in the ω-3 and ω-9 groups.

CONCLUSIONS

Consuming a low-carbohydrate diet pattern promotes weight loss and improves glucose intolerance in obesity. Also, the quality of lipids has a direct influence, demonstrating that the consumption of ω-3 polyunsaturated and ω-9 monounsaturated lipids can lead to more favorable outcomes for the improvement of glucose intolerance, lipid metabolism, and anti-inflammatory effects.

Antagonizing apolipoprotein J chaperone promotes proteasomal degradation of mTOR and relieves hepatic lipid deposition

BACKGROUND AND AIMS

Overnutrition-induced activation of mammalian target of rapamycin (mTOR) dysregulates intracellular lipid metabolism and contributes to hepatic lipid deposition. Apolipoprotein J (ApoJ) is a molecular chaperone and participates in pathogen-induced and nutrient-induced lipid accumulation. This study investigates the mechanism of ApoJ-regulated ubiquitin-proteasomal degradation of mTOR, and a proof-of-concept ApoJ antagonist peptide is proposed to relieve hepatic steatosis.

APPROACH AND RESULTS

By using omics approaches, upregulation of ApoJ was found in high-fat medium-fed hepatocytes and livers of patients with NAFLD. Hepatic ApoJ level associated with the levels of mTOR and protein markers of autophagy and correlated positively with lipid contents in the liver of mice. Functionally, nonsecreted intracellular ApoJ bound to mTOR kinase domain and prevented mTOR ubiquitination by interfering FBW7 ubiquitin ligase interaction through its R324 residue. In vitro and in vivo gain-of-function or loss-of-function analysis further demonstrated that targeting ApoJ promotes proteasomal degradation of mTOR, restores lipophagy and lysosomal activity, thus prevents hepatic lipid deposition. Moreover, an antagonist peptide with a dissociation constant (Kd) of 2.54 µM interacted with stress-induced ApoJ and improved hepatic pathology, serum lipid and glucose homeostasis, and insulin sensitivity in mice with NAFLD or type II diabetes mellitus.

CONCLUSIONS

ApoJ antagonist peptide might be a potential therapeutic against lipid-associated metabolic disorders through restoring mTOR and FBW7 interaction and facilitating ubiquitin-proteasomal degradation of mTOR.

Increased expression of sodium-glucose cotransporter 2 and O-GlcNAcylation in hepatocytes drives non-alcoholic steatohepatitis

AIMS

Steatosis reducing effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors in non-alcoholic steatohepatitis (NASH) has been consistently reported in humans, but their mechanism remains uncertain. In this study, we examined the expression of SGLT2 in human livers and investigated the crosstalk between SGLT2 inhibition and hepatic glucose uptake, intracellular O-GlcNAcylation, and autophagic regulation in NASH.

MATERIALS AND METHODS

Human liver samples obtained from subjects with/without NASH were analyzed. For in vitro studies, human normal hepatocytes and hepatoma cells were treated with SGLT2 inhibitor under high-glucose and high-lipid conditions. NASH in vivo was induced by a high-fat, -fructose, and -cholesterol Amylin liver NASH (AMLN) diet for 10 weeks followed by an additional 10 weeks with/without SGLT2 inhibitor (empagliflozin 10 mg/kg/day).

RESULTS

Liver samples from subjects with NASH were associated with increased SGLT2 and O-GlcNAcylation expression compared with controls. Under NASH condition (in vitro condition with high glucose and lipid), intracellular O-GlcNAcylation and inflammatory markers were increased in hepatocytes and SGLT2 expression was upregulated; SGLT2 inhibitor treatment blocked these changes by directly reducing hepatocellular glucose uptake. In addition, decreased intracellular O-GlcNAcylation by SGLT2 inhibitor promoted autophagic flux through AMPK-TFEB activation. In the AMLN diet-induced NASH mice model, SGLT2 inhibitor alleviated lipid accumulation, inflammation, and fibrosis through autophagy activation related to decreased SGLT2 expression and O-GlcNAcylation in the liver.

CONCLUSIONS

This study firstly demonstrates increased SGLT2 expression in NASH and secondly reveals the novel effect of SGLT2 inhibition on NASH by activating autophagy mediated by inhibition of hepatocellular glucose uptake and consequently decreasing intracellular O-GlcNAcylation.

The clusterin connectome: Emerging players in chondrocyte biology and putative exploratory biomarkers of osteoarthritis

Introduction

Clusterin is amoonlighting protein that hasmany functions. It is amultifunctional Q6 holdase chaperone glycoprotein that is present intracellularly and extracellularly in almost all bodily fluids. Clusterin is involved in lipid transport, cell differentiation, regulation of apoptosis, and clearance of cellular debris, and plays a protective role in ensuring cellular survival. However, the possible involvement of clusterin in arthritic disease remains unclear. Given the significant potential of clusterin as a biomarker of osteoarthritis (OA), a more detailed analysis of its complex network in an inflammatory environment, specifically in the context of OA, is required. Based on the molecular network of clusterin, this study aimed to identify interacting partners that could be developed into biomarker panels for OA.

Methods

The STRING database and Cytoscape were used to map and visualize the clusterin connectome. The Qiagen Ingenuity Pathway Analysis (IPA) software was used to analyze and study clusterinassociated signaling networks in OA. We also analyzed transcription factors known to modulate clusterin expression, which may be altered in OA.

Results

The top hits in the clusterin network were intracellular chaperones, aggregate-forming proteins, apoptosis regulators and complement proteins. Using a text-mining approach in Cytoscape, we identified additional interacting partners, including serum proteins, apolipoproteins, and heat shock proteins.

Discussion

Based on known interactions with proteins, we predicted potential novel components of the clusterin connectome in OA, including selenoprotein R, semaphorins, and meprins, which may be important for designing new prognostic or diagnostic biomarker panels.

Human milk-derived extracellular vesicles alleviate high fat diet-induced non-alcoholic fatty liver disease in mice

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), characterized by excessive hepatic lipid accumulation, imposes serious challenges on public health worldwide. Breastfeeding has been reported to reduce the risk of NAFLD. Extracellular vesicles (EVs) are bilayer membrane vesicles released from various cells into the extracellular space, participating in multiple life processes. Whether EVs from human milk exert metabolic benefits against NAFLD is worth investigating.

METHODS AND RESULTS

In this study, the EVs were isolated from human milk collected from healthy mothers and quantified. Functional analyses were performed using the NAFLD mouse model and free fatty acid (FFA)-stimulated mouse primary hepatocytes. The results showed that human milk-derived EVs could effectively alleviate high fat diet-induced hepatic steatosis and insulin resistance in mice with NAFLD via inhibiting lipogenesis and increasing lipolysis. The FFA-induced lipid accumulation was also inhibited in hepatocytes after treatment with human milk-derived EVs. Mechanistically, the human milk derived-EVs cargo (proteins and miRNAs), which linked to lipid metabolism, may be responsible for these beneficial effects.

CONCLUSION

The findings of this study highlighted the therapeutic benefits of human milk-derived EVs and provided a new strategy for NAFLD treatment.

Dietary additive octyl and decyl glycerate modulates metabolism and inflammation under different dietary patterns with the contribution of the gut microbiota

Octyl and decyl glycerate (ODG), a medium-chain triglyceride (MCT), is widely used as a food additive. Medium-chain monoglycerides, such as glycerol monolaurate and glycerol monocaprylate, were found to change the composition of the gut microbiota and influence glucose and lipid metabolism and inflammation. However, whether ODG influences the gut microbiota and whether the alteration in the gut microbiota contributes to the metabolic phenotype remain unknown. Under a normal-chow diet, mice were treated with or without different dosages of ODG (150, 800, 1600 mg kg^-1) for 22 weeks. All doses of ODG significantly decreased the ratio of HDL to LDL cholesterol, improved the inflammation and insulin resistance, and increased the α-diversity of the gut microbiota and the abundance of Bifidobacterium and Turicibacter. Under a high-fat diet, mice were treated with or without 1600 mg kg^-1 ODG for 16 weeks. The results demonstrated that ODG significantly alleviated the increase in the ratio of HDL to LDL cholesterol, insulin resistance, and inflammation caused by HFD. The expression of related genes was consistent with the above observations. ODG also altered the composition of the gut microbiota and increased the Bifidobacterium abundance under HFD. Our findings indicated that ODG similarly improved glucose metabolism and inflammation but exhibited differential effects on lipid metabolism under different dietary patterns. Furthermore, changes in the gut microbiota caused by ODG supplementation might contribute to the alteration in glucose and lipid metabolism and inflammation, which might be influenced by dietary patterns.

Sterol O-acyltransferase 2 chaperoned by apolipoprotein J facilitates hepatic lipid accumulation following viral and nutrient stresses

The risks of non-alcoholic fatty liver disease (NAFLD) include obese and non-obese stresses such as chronic hepatitis C virus (HCV) infection, but the regulatory determinants remain obscure. Apolipoprotein J (ApoJ) served as an ER-Golgi contact-site chaperone near lipid droplet (LD), facilitating HCV virion production. We hypothesized an interplay between hepatic ApoJ, cholesterol esterification and lipid deposit in response to NAFLD inducers. Exposures of HCV or free-fatty acids exhibited excess LDs along with increased ApoJ expression, whereas ApoJ silencing alleviated hepatic lipid accumulation. Both stresses could concomitantly disperse Golgi, induce closer ApoJ and sterol O-acyltransferase 2 (SOAT2) contacts via the N-terminal intrinsically disordered regions, and increase cholesteryl-ester. Furthermore, serum ApoJ correlated positively with cholesterol and low-density lipoprotein levels in normal glycaemic HCV patients, NAFLD patients and in mice with steatosis. Taken together, hepatic ApoJ might activate SOAT2 to supply cholesteryl-ester for lipid loads, thus providing a therapeutic target of stress-induced steatosis.

Clusterin overexpression in mice exacerbates diabetic phenotypes but suppresses tumor progression in a mouse melanoma model

Clusterin (CLU) is an ATP-independent small heat shock protein-like chaperone, which functions both intra- and extra-cellularly. Consequently, it has been functionally involved in several physiological (including aging), as well as in pathological conditions and most age-related diseases, e.g., cancer, neurodegeneration, and metabolic syndrome. To address CLU function at an in vivo model we established CLU transgenic (Tg) mice bearing ubiquitous or pancreas-targeted CLU overexpression (OE). Our downstream analyses in established Tg lines showed that ubiquitous or pancreas-targeted CLU OE in mice affected antioxidant, proteostatic and metabolic pathways. Targeted OE of CLU in the pancreas, which also resulted in CLU upregulation in the liver likely via systemic effects, increased basal glucose levels in the circulation and exacerbated diabetic phenotypes. Furthermore, by establishing a syngeneic melanoma mouse tumor model we found that ubiquitous CLU OE suppressed melanoma cells growth, indicating a likely tumor suppressor function in early phases of tumorigenesis. Our observations provide in vivo evidence corroborating the notion that CLU is a potential modulator of metabolic and/or proteostatic pathways playing an important role in diabetes and tumorigenesis.

Regulation of adipocyte differentiation by clusterin-mediated Krüppel-like factor 5 stabilization

Clusterin (CLU) is a heterodimeric glycoprotein involved in a range of biological processes. We investigated the function of CLU as a novel regulator of adipogenesis. CLU expression increased during 3T3-L1 preadipocyte differentiation. CLU overexpression promoted adipogenic differentiation of preadipocytes and increased the mRNA levels of adipogenic markers including peroxisome proliferator-activated receptor γ (Pparg) and CCAAT enhancer-binding protein α (Cebpa). Conversely, knockdown of CLU attenuated adipogenesis and reduced transcript levels of Pparg and Cebpa. However, the promoter activities of both the Pparg and the Cebpa gene were not affected by alteration of CLU expression on its own. Additionally, the protein level of Krüppel-like factor 5 (KLF5), an upstream transcription factor of Pparg and Cebpa involved in adipogenic differentiation, was upregulated by CLU overexpression, although the mRNA level of Klf5 was not altered by changes in the expression level of CLU. Cycloheximide chase assay showed that the increased level of KLF5 by CLU overexpression was due to decreased degradation of KLF5 protein. Interestingly, CLU increased the stability of KLF5 by decreasing KLF5 ubiquitination. CLU inhibited the interaction between KLF5 and F-box/WD repeat-containing protein 7, which is an E3 ubiquitin ligase that targets KLF5. The adipogenic role of CLU was also addressed in mesenchymal stem cells (MSCs) and Clu^-/- mouse embryonic fibroblasts (MEFs). Furthermore, CLU enhanced KLF5-mediated transcriptional activation of both the Cebpa and the Pparg promoter. Taken together, these results suggest that CLU is a novel regulator of adipocyte differentiation by modulating the protein stability of the adipogenic transcription factor KLF5.

Clusterin overexpression protects against western diet-induced obesity and NAFLD

Obesity is a significant risk factor for various metabolic diseases and is closely related to non-alcoholic fatty liver disease (NAFLD) characterized by inflammation and oxidative stress. Clusterin is a multi-functional protein that is up-regulated in the pathogenesis of various metabolic diseases, including obesity and NAFLD. Our previous studies indicated that hepatocyte-specific overexpression of clusterin alleviates methionine choline-deficient (MCD) diet-induced non-alcoholic steatohepatitis (NASH) by activating nuclear factor erythroid 2-related factor 2 (Nrf2). Here we generated transgenic mice with whole-body clusterin overexpression (wCLU-tg) and investigated the role of clusterin in Western diet-induced obesity and NAFLD. We confirmed that obesity parameters and the spectrum of NAFLD of wCLU-tg mice were improved compared to wild type mice. Contrarily, clusterin deficiency deteriorated metabolic disruptions. We also found that clusterin activates target molecules for obesity and NAFLD, namely Nrf2 and AMPK, suggesting that clusterin protects against Western diet-induced obesity and NAFLD by activating Nrf2 and AMPK.

Metabolic Syndrome, Clusterin and Elafin in Patients with Psoriasis Vulgaris

Background: Psoriasis is a pathological condition characterized by immune system dysfunction and inflammation. Patients with psoriasis are more likely to develop a wide range of disorders associated with inflammation. Serum levels of various substances and their combinations have been associated with the presence of the disease (psoriasis) and have shown the potential to reflect its activity. The aim of the present study is to contribute to the elucidation of pathophysiological links between psoriasis, its pro-inflammatory comorbidity metabolic syndrome (MetS), and the expression of clusterin and elafin, which are reflected in the pathophysiological “portfolio” of both diseases. Material and methods: Clinical examinations (PASI score), ELISA (clusterin, elafin), and biochemical analyses (parameters of MetS) were performed. Results: We found that patients with psoriasis were more often afflicted by MetS, compared to the healthy controls. Clusterin and elafin levels were higher in the patients than in the controls but did not correlate to the severity of psoriasis. Conclusion: Our data suggest that patients with psoriasis are more susceptible to developing other systemic inflammatory diseases, such as MetS. The levels of clusterin and elafin, which are tightly linked to inflammation, were significantly increased in the patients, compared to the controls, but the presence of MetS in patients did not further increase these levels.

Apolipoprotein J is a hepatokine regulating muscle glucose metabolism and insulin sensitivity

Crosstalk between liver and skeletal muscle is vital for glucose homeostasis. Hepatokines, liver-derived proteins that play an important role in regulating muscle metabolism, are important to this communication. Here we identify apolipoprotein J (ApoJ) as a novel hepatokine targeting muscle glucose metabolism and insulin sensitivity through a low-density lipoprotein receptor-related protein-2 (LRP2)-dependent mechanism, coupled with the insulin receptor (IR) signaling cascade. In muscle, LRP2 is necessary for insulin-dependent IR internalization, an initial trigger for insulin signaling, that is crucial in regulating downstream signaling and glucose uptake. Of physiologic significance, deletion of hepatic ApoJ or muscle LRP2 causes insulin resistance and glucose intolerance. In patients with polycystic ovary syndrome and insulin resistance, pioglitazone-induced improvement of insulin action is associated with an increase in muscle ApoJ and LRP2 expression. Thus, the ApoJ-LRP2 axis is a novel endocrine circuit that is central to the maintenance of normal glucose homeostasis and insulin sensitivity.

Hepatokines are proteins secreted by the liver that can regulate whole body metabolism. Here the authors identify apolipoprotein J as a hepatokine that regulates muscle glucose metabolism and insulin resistance through a low-density lipoprotein receptor-related protein−2 mediated mechanism in mice.

Fatty liver diseases, mechanisms, and potential therapeutic plant medicines

The liver is an important metabolic organ and controls lipid, glucose and energy metabolism. Dysruption of hepatic lipid metabolism is often associated with fatty liver diseases, including nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD) and hyperlipidemia. Recent studies have uncovered the contribution of hormones, transcription factors, and inflammatory cytokines to the pathogenesis of dyslipidemia and fatty liver diseases. Moreover, a significant amount of effort has been put to examine the mechanisms underlying the potential therapeutic effects of many natural plant products on fatty liver diseases and metabolic diseases. We review the current understanding of insulin, thyroid hormone and inflammatory cytokines in regulating hepatic lipid metabolism, focusing on several essential transcription regulators, such as Sirtuins (SIRTs), Forkhead box O (FoxO), Sterol-regulatory element-binding proteins (SREBPs). We also discuss a few representative natural products with promising thereapeutic effects on fatty liver disease and dyslipidemia.

Brain clusterin protein isoforms and mitochondrial localization

Clusterin (CLU), or apolipoprotein J (ApoJ), is the third most predominant genetic risk factor associated with late-onset Alzheimer’s disease (LOAD). In this study, we use multiple rodent and human brain tissue and neural cell models to demonstrate that CLU is expressed as multiple isoforms that have distinct cellular or subcellular localizations in the brain. Of particular significance, we identify a non-glycosylated 45 kDa CLU isoform (mitoCLU) that is localized to the mitochondrial matrix and expressed in both rodent and human neurons and astrocytes. In addition, we show that rodent mitoCLU is translated from a non-canonical CUG (Leu) start site in Exon 3, a site that coincides with an AUG (Met) in human CLU. Last, we reveal that mitoCLU is present at the gene and protein level in the currently available CLU^–/– mouse model. Collectively, these data provide foundational knowledge that is integral in elucidating the relationship between CLU and the development of LOAD.

Clusterin Attenuates Hepatic Fibrosis by Inhibiting Hepatic Stellate Cell Activation and Downregulating the Smad3 Signaling Pathway

Clusterin is a glycoprotein that is expressed in most human tissues and found in body fluids. In our previous studies we demonstrated that clusterin has a protective effect against hepatic lipid accumulation and renal fibrosis; however, the role of clusterin in hepatic fibrosis is unknown. Here, we examined whether clusterin had protective effects against hepatic fibrosis using in vitro and in vivo models. Clusterin was upregulated in the livers of human cirrhotic patients and in thioacetamide (TAA)-induced and bile duct ligation mouse models of liver fibrosis. Loss and overexpression of clusterin promoted and attenuated hepatic fibrosis after TAA injection, respectively. In addition, we found that clusterin attenuates hepatic fibrosis by inhibiting the activation of hepatic stellate cells and Smad3 signaling pathways. Thus, clusterin plays an important role in hepatic fibrosis.

Clusterin deficiency induces lipid accumulation and tissue damage in kidney

Clusterin is a secretory glycoprotein that is involved in multiple physiopathological processes, including lipid metabolism. Previous studies have shown that clusterin prevents hepatic lipid accumulation via suppression of sterol regulatory element-binding protein (SREBP) 1. In this study, we examined the role of clusterin in renal lipid accumulation in clusterin-knockout mice and NRK52e tubular epithelial cells. Clusterin deficiency increased the expression of SREBP1 and its target genes and decreased malonyl-CoA decarboxylase protein levels in the kidney. Expression of the endocytic receptor, megalin, and scavenger receptor class A was increased in clusterin-deficient mice. Functional analysis of lipid metabolism also revealed that lipid uptake and triglyceride synthesis were increased and fatty acid oxidation was reduced, leading to increased lipid accumulation in clusterin-deficient mice. These phenomena were accompanied by mesangial expansion, fibrosis and increased urinary protein-to-creatinine ratio. High-fat feeding aggravated these clusterin deficiency-induced pathological changes. Clusterin knockdown in NRK52e cells increased lipogenic gene expression and lipid levels, whereas overexpression of clusterin by treatment with adenovirus or recombinant clusterin protein suppressed lipogenic gene expression and lipid levels. Transforming growth factor-beta 1 (TGFB1) expression increased in the kidney of clusterin-deficient mice and suppression of TGFB1 in NRK52e cells suppressed lipid accumulation. These results suggest that clusterin deficiency induces renal lipid accumulation by dysregulating the expression of lipid metabolism-related factors and TGFB1, thereby leading to chronic kidney disease. Hence, clusterin may serve as a therapeutic target for lipid-induced chronic kidney disease.

Gangjihwan, a polyherbal composition, inhibits fat accumulation through the modulation of lipogenic transcription factors SREBP1C, PPARγ and C/EBPα

ETHNOPHARMACOLOGICAL RELEVANCE

Gangjihwan (DF) which is composed of Ephedra intermedia, Lithospermum erythrorhizon, and Rheum palmatum has been used for the treatment of obesity in traditional medical clinics in Korea.

AIM OF THE STUDY

This study was conducted to standardize DF and elucidate its mechanism of action for inhibiting fat accumulation in adipocytes and adipose tissues.

MATERIALS AND METHODS

The herbal ingredients of DF were extracted in water, 30% ethanol or 70% ethanol and freeze-dried followed by HPLC analyses. 3T3-L1 adipocytes and high-fat diet-induced obese mice were treated with each of the three DF preparations. Messenger RNA and protein expression levels were measured by real-time qPCR and Western blotting. RNA-Seq analyses were conducted to examine the effects of DF treatment on whole transcriptome of adipocyte.

RESULTS

(-)-Ephedrine and (+)-pseudoephedrine from E. intermedia, aloe-emodin and chrysophanol from R. palmatum and shikonin from L. erythrorhizon were identified as phytochemical components of DF. DF caused dose-dependent inhibition of fat accumulation in 3T3-L1 adipocytes. It also significantly reduced adipose tissue mass and adipocyte size in high-fat diet-induced obese mice. DF was found to down-regulate the expressions of the lipogenic transcription factors such as sterol regulatory element binding protein 1C (SREBP1C), peroxisome proliferator activated receptor gamma (PPARγ), and CCAAT/enhancer binding protein alpha (C/EBPα). Among the three preparations of DF, the 70% ethanol extract was the most effective. RNA-Seq analyses showed that DF treatment decreased the expression levels of up-regulators and increased those of down-regulators of lipogenic transcription factors.

CONCLUSIONS

DF preparations, among which 70% ethanol extract was the most effective, reduced fat accumulation in 3T3-L1 adipocytes and high-fat diet-induced obese mice through the down-regulation of lipogenic transcription factors SREBP1C, PPARγ and C/EBPα.

Clusterin: full-length protein and one of its chains show opposing effects on cellular lipid accumulation

Proteins, made up of either single or multiple chains, are designed to carry out specific biological functions. We found an interesting example of a two-chain protein where administration of one of its chains leads to a diametrically opposite outcome than that reported for the full-length protein. Clusterin is a highly glycosylated protein consisting of two chains, α- and β-clusterin. We have investigated the conformational features, cellular localization, lipid accumulation, in vivo effects and histological changes upon administration of recombinant individual chains of clusterin. We demonstrate that recombinant α- and β-chains exhibit structural and functional differences and differ in their sub-cellular localization. Full-length clusterin is known to lower lipid levels. In contrast, we find that β-chain-treated cells accumulate 2-fold more lipid than controls. Interestingly, α-chain-treated cells do not show such increase. Rabbits injected with β-chain, but not α-chain, show ~40% increase in weight, with adipocyte hypertrophy, liver and kidney steatosis. Many, sometimes contrasting, roles are ascribed to clusterin in obesity, metabolic syndrome and related conditions. Our findings of differential localization and activities of individual chains of clusterin should help in understanding better the roles of clusterin in metabolism.

Green Tea Extract Rich in Epigallocatechin-3-Gallate Prevents Fatty Liver by AMPK Activation via LKB1 in Mice Fed a High-Fat Diet

Supplementation with epigallocatechin-3-gallate has been determined to aid in the prevention of obesity. Decaffeinated green tea extract appears to restore a normal hepatic metabolic profile and attenuate high-fat diet (HFD)-induced effects, thereby preventing non-alcoholic fatty liver disease in mice. Mice were maintained on either a control diet (CD) or HFD for 16 weeks and supplemented with either water or green tea extract (50 mg/kg/day). The body mass increase, serum adiponectin level, and lipid profile were measured over the course of the treatment. Furthermore, the AMPK pathway protein expression in the liver was measured. From the fourth week, the weight gain in the CD + green tea extract (CE) group was lower than that in the CD + water (CW) group. From the eighth week, the weight gain in the HFD + water (HFW) group was found to be higher than that in the CW group. Moreover, the weight gain in the HFD + green tea extract (HFE) group was found to be lower than that in the HFW group. Carcass lipid content was found to be higher in the HFW group than that in the CW and HFE groups. Serum analysis showed reduced non-esterified fatty acid level in the CE and HFE groups as compared with their corresponding placebo groups. Increased adiponectin level was observed in the same groups. Increased VLDL-TG secretion was observed in the HFW group as compared with the CW and HFE groups. Increased protein expression of AdipoR2, SIRT1, pLKB1, and pAMPK was observed in the HFE group, which explained the reduced expression of ACC, FAS, SREBP-1, and ChREBP in this group. These results indicate that the effects of decaffeinated green tea extract may be related to the activation of AMPK via LKB1 in the liver of HFD-fed mice.

Antiresistin RNA Oligonucleotide Ameliorates Diet-Induced Nonalcoholic Fatty Liver Disease in Mice through Attenuating Proinflammatory Cytokines

The aim of this study was to determine whether inhibition of resistin by a synthetic antiresistin RNA (oligonucleotide) oligo ameliorates metabolic and histological abnormalities in nonalcoholic fatty liver disease (NAFLD) induced by high-fat diet (HFD) in mice. The antiresistin RNA oligo and a scrambled control oligo (25 mg/kg of body weight) were i.p. injected to HFD mice. Serum metabolic parameters and hepatic enzymes were measured after 4-week treatment. The treatment significantly reduced epididymal fat and attenuated the elevated serum resistin, cholesterol, triglycerides, glucose, and insulin with an improved glucose tolerance test. Antiresistin RNA oligo also normalized serum AST and ALT levels with improved pathohistology of NAFLD. Immunoblotting and qRT-PCR revealed that decreased protein and mRNA expression of resistin in fat and liver tissues of the treated mice were associated with reduction of adipose TNF-α and IL-6 expression and secretion into circulation. mRNA and protein expression of hepatic phosphoenolpyruvate carboxykinase (PEPCK) and sterol regulatory element-binding protein-1c (SREBP-1c) were also significantly decreased in the treated mice. Our results suggest that resistin may exacerbate NAFLD in metabolic syndrome through upregulating inflammatory cytokines and hepatic PEPCK and SREBP-1c. Antiresistin RNA oligo ameliorated metabolic abnormalities and histopathology of NAFLD through attenuating proinflammatory cytokines.

Deficiency of clusterin exacerbates high-fat diet-induced insulin resistance in male mice

The present study examined the role of clusterin in insulin resistance in high fat-fed wild-type and clusterin knockout (KO) mice. The plasma levels of glucose and C-peptide and islet size were increased in clusterin KO mice after an 8-week high-fat diet. In an ip glucose tolerance test, the area under the curve for glucose was not different, whereas the area under the curve for insulin was higher in clusterin KO mice. In a hyperinsulinemic-euglycemic clamp, the clamp insulin levels were higher in clusterin KO mice after the high-fat diet. After adjusting for the clamp insulin levels, the glucose infusion rate, suppression of hepatic glucose production, and glucose uptake were lower in clusterin KO mice in the high fat-fed group. The plasma levels of clusterin and clusterin mRNA levels in the skeletal muscle and liver were increased by the high-fat diet. The mRNA levels of the antioxidant enzymes were lower, and the mRNA levels of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 1 and cytokines and protein carbonylation were higher in the skeletal muscle and liver in clusterin KO mice after the high-fat diet. Palmitate-induced gene expressions of NOX1 and cytokines were higher in the primary cultured hepatocytes of clusterin KO mice compared with the wild-type mice. Clusterin inhibited the gene expression and reactive oxygen species generation by palmitate in the hepatocytes and C2C12. AKT phosphorylation by insulin was reduced in the hepatocytes of clusterin KO mice. These results suggest that clusterin plays a protective role against high-fat diet-induced insulin resistance through the suppression of oxidative stress and inflammation.

The physiological roles of apolipoprotein J/clusterin in metabolic and cardiovascular diseases

Several isoforms of apolipoprotein J/clusterin (CLU) are encoded from a single gene located on chromosome 8 in humans. These isoforms are ubiquitously expressed in the tissues, and have been implicated in aging, neurodegenerative disorders, cancer progression, and metabolic/cardiovascular diseases including dyslipidemia, diabetes, atherosclerosis and myocardial infarction. The conventional secreted form of CLU (sCLU) is thought to be a component of high density lipoprotein-cholesterol. sCLU functions as a chaperone for misfolded proteins and it is thought to promote survival by reducing oxidative stress. Nuclear CLU, a truncated CLU formed by alternative splicing, is responsible for promoting apoptosis via a Bax-dependent pathway. There are putative regulatory sites in the promoter regions of CLU, which are occupied by transcription factors such as transforming growth factor (TGF)-β inhibitory element, activator protein-1, CLU-specific elements, and carbohydrate response element. However, the molecular mechanisms underlying the distinct roles of CLU in a variety of conditions remain unclear. Although the function of CLU in cancer or neurological disease has been studied intensively for three decades, physiological roles of CLU seem unexplored in the cardiovascular system and metabolic diseases. In this review, we will discuss general characteristics and regulations of CLU based on previous literature and assess the recent findings associated with its physiological roles in different tissues including the vasculature, heart, liver, kidney, adipose tissue, and brain.