Nazo, the Drosophila homolog of the NBIA-mutated protein-c19orf12, is required for triglyceride homeostasis

Lipid dyshomeostasis has been implicated in a variety of diseases ranging from obesity to neurodegenerative disorders such as Neurodegeneration with Brain Iron Accumulation (NBIA). Here, we uncover the physiological role of Nazo, the Drosophila melanogaster homolog of the NBIA-mutated protein-c19orf12, whose function has been elusive. Ablation of Drosophila c19orf12 homologs leads to dysregulation of multiple lipid metabolism genes. nazo mutants exhibit markedly reduced gut lipid droplet and whole-body triglyceride contents. Consequently, they are sensitive to starvation and oxidative stress. Nazo is required for maintaining normal levels of Perilipin-2, an inhibitor of the lipase-Brummer. Concurrent knockdown of Brummer or overexpression of Perilipin-2 rescues the nazo phenotype, suggesting that this defect, at least in part, may arise from diminished Perilipin-2 on lipid droplets leading to aberrant Brummer-mediated lipolysis. Our findings potentially provide novel insights into the role of c19orf12 as a possible link between lipid dyshomeostasis and neurodegeneration, particularly in the context of NBIA.

Lysine tRNA fragments and miR-194-5p co-regulate hepatic steatosis via β-Klotho and perilipin 2

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) involves hepatic accumulation of intracellular lipid droplets via incompletely understood processes. Here, we report distinct and cooperative NAFLD roles of LysTTT-5'tRF transfer RNA fragments and microRNA miR-194-5p.

METHODS

Combined use of diet induced obese mice with human-derived oleic acid-exposed Hep G2 cells revealed new NAFLD roles of LysTTT-5'tRF and miR-194-5p.

RESULTS

Unlike lean animals, dietary-induced NAFLD mice showed concurrent hepatic decrease of both LysTTT-5'tRF and miR-194-5p levels, which were restored following miR-132 antisense oligonucleotide treatment which suppresses hepatic steatosis. Moreover, exposing human-derived Hep G2 cells to oleic acid for 7 days co-suppressed miR-194-5p and LysTTT-5'tRF levels while increasing lipid accumulation. Inversely, transfecting fattened cells with a synthetic LysTTT-5'tRF mimic elevated mRNA levels of the metabolic regulator β-Klotho while decreasing triglyceride amounts by 30% within 24 h. In contradistinction, antisense suppression of miR-194-5p induced accumulation of its novel target, the NAFLD-implicated lipid droplet-coating PLIN2 protein. Further, two out of 15 steatosis-alleviating screened drug-repurposing compounds, Danazol and Latanoprost, elevated miR-194-5p or LysTTT-5'tRF levels.

CONCLUSION

Our findings highlight the different yet complementary roles of miR-194-5p and LysTTT-5'tRF and offer new insights into the complex roles of small non-coding RNAs and the multiple pathways involved in NAFLD pathogenesis.

Ceramide synthase 6 (CerS6) is upregulated in alcohol-associated liver disease and exhibits sex-based differences in the regulation of energy homeostasis and lipid droplet accumulation

OBJECTIVE

Alcohol-associated liver disease (ALD) is the leading cause of liver-related mortality worldwide. Current strategies to manage ALD focus largely on advanced stage disease, however, metabolic changes such as glucose intolerance are apparent at the earliest stage of alcoholic steatosis and increase the risk of disease progression. Ceramides impair insulin signaling and accumulate in ALD, and metabolic pathways involving ceramide synthase 6 (CerS6) are perturbed in ALD during hepatic steatosis. In this study, we aimed to investigate the role of CerS6 in ALD development and the relevance of CerS6 to human ALD.

METHODS

C57BL/6 WT and CerS6 KO mice of both sexes were fed either a Lieber-DeCarli control (CON) or 15% ethanol (EtOH) diet for six weeks. In vivo metabolic tests including glucose and insulin tolerance tests (GTT and ITT) and energy expenditure were performed. The mice were euthanized, and serum and liver lipids and liver histology were examined. For in vitro studies, CerS6 was deleted in human hepatocytes, VL17A and cells were incubated with EtOH and/or C16:0-ceramides. RNAseq analysis was performed in livers from mice and human patients with different stages of ALD and diseased controls.

RESULTS

After six weeks on an EtOH diet, CerS6 KO mice had reduced body weight, food intake, and %fat mass compared to WT mice. Energy expenditure increased in both male and female KO mice, however, was only statistically significant in male mice. In response to EtOH, WT mice developed mild hepatic steatosis, while steatosis was ameliorated in KO mice as determined by H&E and ORO staining. KO mice showed significantly decreased long-chain ceramide species, especially C16:0-ceramides, in the serum and liver tissues compared to WT mice. CerS6 deletion decreased serum TG and NEFA only in male not female mice. CerS6 deletion improved glucose tolerance and insulin resistance in EtOH-fed mice of both sexes. RNAseq analysis revealed that 74 genes are significantly upregulated and 66 genes are downregulated by CerS6 deletion in EtOH-fed male mice, with key network pathways including TG biosynthetic process, positive regulation of lipid localization, and fat cell differentiation. Similar to RNAseq results, absence of CerS6 significantly decreased mRNA expression of lipid droplet associated proteins in EtOH-fed mice. In vitro, EtOH stimulation significantly increased PLIN2 protein expression in VL17A cells while CerS6 deletion inhibited EtOH-mediated PLIN2 upregulation. C16:0-ceramide treatment significantly increased PLIN2 protein expression compared to CON. Notably, progression of ALD in humans was associated with increased hepatic CerS6 expression.

CONCLUSIONS

Our findings demonstrate that CerS6 deletion improves glucose homeostasis in alcohol-fed mice and exhibits sex-based differences in the attenuation of EtOH-induced weight gain and hepatic steatosis. Additionally, we unveil that CerS6 plays a major role as a regulator of lipid droplet biogenesis in alcohol-induced intra-hepatic lipid droplet formation, identifying it as a putative target for early ALD management.

Methacrylated Gelatin as a Scaffold for Mechanically Isolated Stromal Vascular Fraction for Cutaneous Wound Repair

Mechanically processed stromal vascular fraction (mSVF) is a highly interesting cell source for regenerative purposes, including wound healing, and a practical alternative to enzymatically isolated SVF. In the clinical context, SVF benefits from scaffolds that facilitate viability and other cellular properties. In the present work, the feasibility of methacrylated gelatin (GelMA), a stiffness-tunable, light-inducible hydrogel with high biocompatibility is investigated as a scaffold for SVF in an in vitro setting. Lipoaspirates from elective surgical procedures were collected and processed to mSVF and mixed with GelMA precursor solutions. Non-encapsulated mSVF served as a control. Viability was measured over 21 days. Secreted basic fibroblast growth factor (bFGF) levels were measured on days 1, 7 and 21 by ELISA. IHC was performed to detect VEGF-A, perilipin-2, and CD73 expression on days 7 and 21. The impact of GelMA-mSVF on human dermal fibroblasts was measured in a co-culture assay by the same viability assay. The viability of cultured GelMA-mSVF was significantly higher after 21 days (p < 0.01) when compared to mSVF alone. Also, GelMA-mSVF secreted stable levels of bFGF over 21 days. While VEGF-A was primarily expressed on day 21, perilipin-2 and CD73-positive cells were observed on days 7 and 21. Finally, GelMA-mSVF significantly improved fibroblast viability as compared with GelMA alone (p < 0.01). GelMA may be a promising scaffold for mSVF as it maintains cell viability and proliferation with the release of growth factors while facilitating adipogenic differentiation, stromal cell marker expression and fibroblast proliferation.

HPV-associated Vulvar Intraepithelial Carcinoma With Sebaceous Differentiation: Report of 2 Cases

Sebaceous carcinoma (SC) is a malignant neoplasm demonstrating sebocytic differentiation, commonly in the periocular area. Sebocytic differentiation is recognized by multivesicular cytoplasmic clearing with frequent nuclear scalloping. The vesicles can be highlighted by immunohistochemical stains against the perilipin family proteins including adipophilin. Extraocular SC is uncommon but well reported, often in the setting of Muir-Torre syndrome; however, vulvar SC is exceptionally rare. The literature review yielded only 12 prior cases of vulvar SC, all of which showed invasion. Here we report 2 additional similar cases from 2 different institutions of an intraepithelial carcinoma with sebaceous differentiation. Histologic examination of multiple specimens from both patients showed similar features: a multifocal intraepithelial basaloid nodular neoplasm sparing the basal layer with occasional pagetoid spread. The tumor cells demonstrated a high nuclear to cytoplasmic ratio, mitoses, variably foamy vacuolated cytoplasm, and nuclear indentation. Multiple specimens from both patients showed evidence of sebaceous differentiation (substantiated by adipophilin positivity in a membranous vesicular pattern in case 1 and by androgen receptor and epithelial membrane antigen positivity in case 2), and squamous differentiation (substantiated by p63/p40 and weak CK 5/6 expression), as well as human papillomavirus (HPV) association (substantiated by p16 block positivity and detection of high-risk HPV by in situ hybridization). One case was a true in situ lesion without evidence of invasion, and the other case was predominantly an in situ carcinoma with prominent adnexal extension and focal superficial invasion of <1 mm seen in one of multiple specimens. To our knowledge, these 2 cases are the first to show a vulvar SC/carcinoma with sebaceous differentiation that is predominantly limited to the epidermis, and the first documentation of HPV infection in vulvar sebaceous neoplasms. Vulvar intraepithelial carcinoma with sebaceous differentiation is the umbrella term we chose for this entity. Whether this is a true SC in situ that is HPV positive/driven, or a vulvar intraepithelial neoplasia with sebaceous differentiation, is not entirely clear. We emphasize the importance of looking for this morphology to avoid misclassification. Due to the rarity of cases, optimal treatment at this site has not been established.

Trip13 Depletion in Liver Cancer Induces a Lipogenic Response Contributing to Plin2-Dependent Mitotic Cell Death

Aberrant energy metabolism and cell cycle regulation both critically contribute to malignant cell growth and both processes represent targets for anticancer therapy. It is shown here that depletion of the AAA+-ATPase thyroid hormone receptor interacting protein 13 (Trip13) results in mitotic cell death through a combined mechanism linking lipid metabolism to aberrant mitosis. Diminished Trip13 levels in hepatocellular carcinoma cells result in insulin-receptor-/Akt-pathway-dependent accumulation of lipid droplets, which act as functional acentriolar microtubule organizing centers disturbing mitotic spindle polarity. Specifically, the lipid-droplet-coating protein perilipin 2 (Plin2) is required for multipolar spindle formation, induction of DNA damage, and mitotic cell death. Plin2 expression in different tumor cells confers susceptibility to cell death induced by Trip13 depletion as well as treatment with paclitaxel, a spindle-interfering drug commonly used against different cancers. Thus, assessment of Plin2 levels enables the stratification of tumor responsiveness to mitosis-targeting drugs, including clinically approved paclitaxel and Trip13 inhibitors currently under development.

Dihydroartemisinin reduced lipid droplet deposition by YAP1 to promote the anti-PD-1 effect in hepatocellular carcinoma

BACKGROUND

Anti-PD-1 was used to treat for many cancers, but the overall response rate of monoclonal antibodies blocking the inhibitory PD-1/PD-L1 was less than 20%. Lipid droplet (LD) deposition reduced chemotherapy efficacy, but whether LD deposition affects anti-PD-1 treatment and its mechanism remains unclear. Dihydroartemisinin (DHA) was FDA proved antimalarial medicine, but its working mechanism on LD deposition has not been clarified.

PURPOSE

This study aimed to elucidate the mechanism of DHA reducing LDs deposition and improving the efficacy of anti-PD-1.

METHODS

LD numbers and area were separately detected by electron microscopy and oil Red O staining. The expression of YAP1 and PLIN2 was detected by immunohistochemical staining in liver cancer tissues. Transcription and protein expression levels of YAP1 and PLIN2 in cells were detected by qRT-PCR and Western blot after DHA treated HepG2215 cells and Yap1^LKO mice.

RESULTS

LD accumulation was found in the liver tumor cells of DEN/TOPBCOP-induced liver tumor mice with anti-PD-1 treatment. But DHA treatment or YAP1 knockdown reduced LD deposition and PLIN2 expression in HepG2215 cells. Furthermore, DHA reduced the LD deposition, PLIN2 expression and triglycerides (TG) content in the liver tumor cells of Yap1^LKO mice with liver tumor.

CONCLUSION

Anti-PD-1 promoted LD deposition, while YAP1 knockdown/out reduced LD deposition in HCC. DHA reduced LD deposition by inhibiting YAP1, enhancing the effect of anti-PD-1 therapy.

Evaluation of perilipin 2 and melanocortin 5 receptor serum levels with sebogenesis in acne vulgaris patients

INTRODUCTION

Acne vulgaris is a multifactorial disease. One of the main factors that plays a role in acne pathogenesis is an increase in sebum secretion. For sebum secretion, sebocyte differentiation followed by sebogenesis is essential. Sebocyte differentiation and proliferation, and sebum synthesis are controlled by complex pathways. Studies have shown that perilipin 2 and melanocortin 5 receptors play a role in sebogenesis. This study sought to determine whether levels of perilipin 2 and melanocortin 5 receptors have an impact on the development of acne vulgaris.

METHODS

A total of 65 patients diagnosed with acne and 43 healthy control subjects were included in the study. Perilipin 2 and melanocortin 5 receptor levels were analyzed using the enzyme-linked immunosorbent assay (ELISA) technique.

RESULTS

No significant differences were observed between the acne group and the control group in serum perilipin 2 (p = 0.594) and melanocortin 5 receptor (p = 0.213) levels. In the moderate acne group, perilipin 2 and melanocortin 5 receptor levels were significantly higher than in the mild acne group (p = 0.0014, p = 0.003). The levels in the severe acne group were not higher compared to the moderate and mild acne groups.

CONCLUSION

This study failed to detect any association between acne pathogenesis and perilipin 2 and melanocortin 5 receptor serum levels. However, these proteins may have an influence on acne severity.

Regulation of lipid droplets via the PLCβ2-PKCα-ADRP pathway in granulosa cells exposed to cadmium

In steroidogenic cells, steroids are synthesized de novo from cholesterol stored in lipid droplets (LDs). The size of LDs regulated by adipose differentiation-related protein (ADRP) is closely related to cholesterol ester hydrolysis. Many studies reported that cadmium (Cd) had dual effects on steroidogenesis in granulosa cells (GCs). However, the role of LD and its regulation in abnormal steroidogenesis caused by Cd exposure remain unknown. In current study, female rats were exposed to CdCl₂ during gestation and lactation, and influence of such exposure was investigated in ovarian GCs of female offspring. The size of LDs was found much smaller than normal in GCs; ADRP was down-regulated and hormone-sensitive lipase (HSL) phosphorylation was increased, followed by up-regulation of steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (CYP11A1); the expression of 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase beta-2 (PLCβ2) and protein kinase C alpha type (PKCα) were both decreased accompanying the ADRP down-regulation. This series of events resulted in a high level of progesterone in serum. Similar results were demonstrated in GCs treated with 20 μM CdCl₂ for 24 h in vitro. The protein level of ADRP was decreased after gene silencing of PLCβ2/PKCα, and the knockdown of PLCβ2/PKCα/ADRP led to micro-sized LD formation. We found that Cd exposure down-regulated ADRP by inhibiting the PLCβ2-PKCα signaling pathway, reduced the size of LDs, and promoted HSL phosphorylation. StAR and CYP11A1 were both up-regulated following the hydrolysis of cholesterol ester, which led to a high production of progesterone. LD thereby is a target subcellular organelle for Cd to affect steroid hormone synthesis in ovarian GCs. These findings might help to uncover the mechanism of ovarian dysfunction and precocious puberty caused by Cd pollution.

Impaired adipogenic capacity in induced pluripotent stem cells from lipodystrophic patients with BSCL2 mutations

OBJECTIVE

Congenital generalized lipodystrophy (CGL) is an autosomal recessive disorder characterized by marked scarcity of adipose tissue, extreme insulin resistance, hypertriglyceridemia, hepatic steatosis and early-onset diabetes. Mutation of the BSCL2/SEIPIN gene causes the most severe form of CGL. The aim of this study was to generate induced pluripotent stem (iPS) cells from patients with CGL harboring BSCL2/SEIPIN mutations.

METHODS

Skin biopsies were obtained from two Japanese patients with CGL harboring different nonsense mutations (E189X and R275X) in BSCL2/SEIPIN. The fibroblasts thus obtained were infected with retroviruses encoding OCT4, SOX2, c-MYC, and KLF4. The generated iPS cells were evaluated for pluripotency by examining the expression of pluripotency markers (alkaline phosphatase, SSEA-4, TRA-1-60, and NANOG) and their ability to differentiate to three germ layers in vitro by forming embryoid bodies, and to form teratomas in vivo. Adipogenic capacity of differentiated BSCL2-iPS cells was determined by oil red O and adipose differentiation-related protein (ADRP) staining. Rescue experiments were also performed using stable expression of wild-type BSCL2. A coimmunoprecipitation assay was conducted to investigate the interaction of SEIPIN with ADRP.

RESULTS

iPS cells were generated from fibroblasts of the two patients with CGL. Each of the patient-derived iPS (BSCL2-iPS) clones showed all of the hallmarks of pluripotency and could differentiate into derivatives of all three germ layers in vitro by forming embryoid bodies, and form teratomas after injection into mouse testes. BSCL2-iPS cells maintained the mutations in BSCL2 and lacked intact BSCL2. Upon adipogenic differentiation, BSCL2-iPS cells exhibited marked reduction of lipid droplet formation concomitant with diffuse cytoplasmic distribution of ADRP, compared with iPS cells from healthy individuals. Forced expression of BSCL2 not only rescued the lipid accumulation defects, but also restored cytoplasmic punctate localization of ADRP in BSCL2-iPS cells. Coimmunoprecipitation indicated SEIPIN interacted with ADRP.

CONCLUSION

BSCL2-iPS cells that recapitulate the lipodystrophic phenotypes in vitro could provide valuable models with which to study the physiology of lipid accumulation and the pathology of human lipodystrophy. We found that BSCL2 defines the localization of ADRP, which has a role in lipid accumulation and adipogenic differentiation.

Conserved Amphipathic Helices Mediate Lipid Droplet Targeting of Perilipins 1-3

Perilipins (PLINs) play a key role in energy storage by orchestrating the activity of lipases on the surface of lipid droplets. Failure of this activity results in severe metabolic disease in humans. Unlike all other lipid droplet-associated proteins, PLINs localize almost exclusively to the phospholipid monolayer surrounding the droplet. To understand how they sense and associate with the unique topology of the droplet surface, we studied the localization of human PLINs inSaccharomyces cerevisiae,demonstrating that the targeting mechanism is highly conserved and that 11-mer repeat regions are sufficient for droplet targeting. Mutations designed to disrupt folding of this region into amphipathic helices (AHs) significantly decreased lipid droplet targetingin vivoandin vitro Finally, we demonstrated a substantial increase in the helicity of this region in the presence of detergent micelles, which was prevented by an AH-disrupting missense mutation. We conclude that highly conserved 11-mer repeat regions of PLINs target lipid droplets by folding into AHs on the droplet surface, thus enabling PLINs to regulate the interface between the hydrophobic lipid core and its surrounding hydrophilic environment.

[Metformin inhibits THP-1 macrophage-derived foam cell formation induced by lipopolysaccharide]

OBJECTIVE

To investigate the impact of metformin (Met) on THP-1 macrophage-derived foam cell formation induced by lipopolysaccharide (LPS) and observe the changes of lipid droplets (LDs) and LDs-associated proteins.

METHODS

THP-1 cells were induced to differentiate into macrophages by 100 ng/mL phorbol 12-myristate 13-acetate (PMA) for 48 hours, and then the macrophages were further induced to generate foam cells by 50 μg/mL oxidized low-density lipoprotein (ox-LDL) and 1 μg/mL LPS. During this process, these foam cells were treated with 0, 100, 200 μmol/L Met. Under the fluorescence microscope, the effect of Met on foam cell formation was evaluated by Oil red O staining and the number and morphology of LDs were observed by BODIPY493/503 staining. Intracellular triglyceride (TG) were extracted and measured by TG quantitative kits. The expressions of adipose differentiation-related protein (ADRP) and tail-interacting protein of 47 kDa (TIP47) were detected by Western blotting.

RESULTS

Compared with the untreated group, the LDs in foam cells were reduced significantly and the size became smaller after treated with 100 or 200 μmol/L Met. What's more, the quantitative data showed that the intracellular TG content decreased markedly in a dose-dependent manner, and the TG content decreased about 25% in foam cells treated with 200 μmol/L Met. Western blotting showed that Met reduced the expression of ADRP, but not TIP47 in the THP-1 macrophage-derived foam cells.

CONCLUSION

Met could inhibit THP-1-derived foam cell formation induced by LPS, reduce intracellular lipid accumulation, and down-regulate the expression of ADRP.

Hepatitis C Virus Increases Occludin Expression via the Upregulation of Adipose Differentiation-Related Protein

The hepatitis C virus (HCV) life cycle is closely associated with lipid metabolism. In particular, HCV assembly initiates at the surface of lipid droplets. To further understand the role of lipid droplets in HCV life cycle, we assessed the relationship between HCV and the adipose differentiation-related protein (ADRP), a lipid droplet-associated protein. Different steps of HCV life cycle were assessed in HCV-infected human Huh-7 hepatoma cells overexpressing ADRP upon transduction with a lentiviral vector. HCV infection increased ADRP mRNA and protein expression levels by 2- and 1.5-fold, respectively. The overexpression of ADRP led to an increase of (i) the surface of lipid droplets, (ii) the total cellular neutral lipid content (2.5- and 5-fold increase of triglycerides and cholesterol esters, respectively), (iii) the cellular free cholesterol level (5-fold) and (iv) the HCV particle production and infectivity (by 2- and 3.5-fold, respectively). The investigation of different steps of the HCV life cycle indicated that the ADRP overexpression, while not affecting the viral replication, promoted both virion egress and entry (~12-fold), the latter possibly via an increase of its receptor occludin. Moreover, HCV infection induces an increase of both ADRP and occludin expression. In HCV infected cells, the occludin upregulation was fully prevented by the ADRP silencing, suggesting a specific, ADRP-dependent mechanism. Finally, in HCV-infected human livers, occludin and ADRP mRNA expression levels correlated with each other. Alltogether, these findings show that HCV induces ADRP, which in turns appears to confer a favorable environment to viral spread.

Pycnogenol Attenuates the Release of Proinflammatory Cytokines and Expression of Perilipin 2 in Lipopolysaccharide-Stimulated Microglia in Part via Inhibition of NF-κB and AP-1 Activation

Over activation of microglia results in the production of proinflammatory agents that have been implicated in various brain diseases. Pycnogenol is a patented extract from French maritime pine bark (Pinus pinaster Aiton) with strong antioxidant and anti-inflammatory potency. The present study investigated whether pycnogenol may be associated with the production of proinflammatory mediators in lipopolysaccharide-stimulated BV2 (mouse-derived) microglia. It was found that pycnogenol treatment was dose-dependently associated with significantly less release of nitricoxide (NO), TNF-α, IL-6 and IL-1β, and lower levels of intercellular adhesion molecule1 (ICAM-1) and perilipin 2 (PLIN2). Furthermore, this effect was replicated in primary brain microglia. Levels of inducible NO synthase mRNA and protein were attenuated, whereas there was no change in the production of the anti-inflammatory cytokine IL-10. Further evidence indicated that pycnogenol treatment led to the suppression of NF-κB activation through inhibition of p65 translocation into the nucleus and inhibited DNA binding of AP-1, suggesting that these proinflammatory factors are associated with NF-κB and AP-1. We conclude that pycnogenol exerts anti-inflammatory effects through inhibition of the NF-κB and AP-1pathway, and may be useful as a therapeutic agent in the prevention of diseases caused by over activation of microglia.

Computed tomography and magnetic resonance imaging features of lipid-rich neuroendocrine tumors of the pancreas

AIM: To clarify the computed tomography (CT) and magnetic resonance imaging (MRI) characteristics of lipid-rich pancreatic neuroendocrine tumors (PanNETs).

METHODS: Enhanced CT and MRI performed before pancreatectomy in 29 patients with 34 histologically-confirmed PanNETs was retrospectively reviewed. Tumor attenuation on CT and signal intensities on conventional (T1- and T2-weighted) and chemical shift MRI were qualitatively analyzed and compared alongside adipose differentiation-related protein (ADRP) immunostaining (ADRP-positive: lipid-rich; ADRP-negative: non-lipid-rich) results using Fisher’s exact test or the Mann-Whitney U test. Signal intensity index on chemical shift MRI was quantitatively assessed.

RESULTS: There were 15 lipid-rich PanNETs (44.1%) in 12 patients (41.4%). Tumor attenuation during the early, portal venous, and delayed phases of enhanced CT (P = 0.888, 0.443, and 0.359, respectively) and signal intensities on conventional MRI (P = 0.698 and 0.798, respectively) were not significantly different between lipid-rich and non-lipid-rich PanNETs. Four of the 15 lipid-rich PanNETs exhibited high signal intensity on subtraction chemical shift MRI, and the association of high signal intensity on subtraction imaging with lipid-rich PanNETs was significant (4 of 15 lipid-rich PanNETs, 26.73%, vs 0 of 19 non-lipid-rich PanNETs, 0%, P = 0.029). Lipid-rich PanNETs showed a significantly higher signal intensity index than non-lipid-rich PanNETs (0.6% ± 14.1% vs -10.4% ± 14.4%, P = 0.004). Eight of 15 lipid-rich PanNETs, vs 0 of 19 non-lipid-rich PanNETs, had positive signal intensity index values in concordance with lipid contents.

CONCLUSION: CT contrast enhancement and conventional MR signal intensities are similar in lipid-rich and non-lipid-rich PanNETs. Chemical shift MRI can demonstrate cytoplasmic lipids in PanNETs.

Heart Fat Infiltration In Subjects With and Without Coronary Artery Disease

CONTEXT

Fat may accumulate around the heart in epicardial adipose tissue or inside the heart as lipid droplets (LDs).

OBJECTIVE

To compare myocardial steatosis between subjects with and without coronary artery disease (CAD and non-CAD) and to identify which cells contain LDs.

DESIGN

Body mass index, waist circumference, glucose, insulin, homeostasis model assessment index, leptin, adiponectin, and high-sensitivity C-reactive protein were evaluated in CAD and non-CAD subjects. Biopsies were collected from right atrial myocardium. Immunohistochemistry for perilipin (PLIN) 1 and 2 was used to characterize LDs and their localization in adipocytes or myocardial cells, respectively. Cardiomyocytes apoptosis and hypoxia inducible factor 1 alpha were obtained in a subgroup of subjects.

SETTING

The study took place in a hospital.

PATIENTS

Male subjects consecutively undergoing elective cardiac surgery either for coronary bypass grafting (CAD, n = 23) or for valve replacement (non-CAD, n = 18).

MAIN OUTCOMES AND MEASURES

The study was designed to compare myocardial steatosis between subjects with and without coronary artery disease.

RESULTS

PLIN1 and PLIN2 resulted significantly higher in CAD than in non-CAD subjects, as did apoptosis. PLIN1 was positively associated with circulating leptin, high-sensitivity C-reactive protein, and apoptosis, and negatively with adiponectin. PLIN2 was positively associated with body mass index, waist circumference, and leptin and negatively with adiponectin. After taking into account the absence/presence of hypertension, diabetes, and CAD/non-CAD, adiponectin was negatively associated with PLIN1 (r(2) = 0.532); waist circumference and adiponectin were associated with PLIN2 (r(2) = 0.399).

CONCLUSIONS

Myocardial steatosis is greater in CAD than non-CAD subjects, depending on both metabolically active adipocytes interspersed among cardiomyocytes and higher fat deposition inside cardiomyocytes; serum adiponectin and waist circumference are independent predictors of myocardial steatosis.

Perilipin-2 Modulates Lipid Absorption and Microbiome Responses in the Mouse Intestine

Obesity and its co-morbidities, such as fatty liver disease, are increasingly prevalent worldwide health problems. Intestinal microorganisms have emerged as critical factors linking diet to host physiology and metabolic function, particularly in the context of lipid homeostasis. We previously demonstrated that deletion of the cytoplasmic lipid drop (CLD) protein Perilipin-2 (Plin2) in mice largely abrogates long-term deleterious effects of a high fat (HF) diet. Here we test the hypotheses that Plin2 function impacts the earliest steps of HF diet-mediated pathogenesis as well as the dynamics of diet-associated changes in gut microbiome diversity and function. WT and perilipin-2 null mice raised on a standard chow diet were randomized to either low fat (LF) or HF diets. After four days, animals were assessed for changes in physiological (body weight, energy balance, and fecal triglyceride levels), histochemical (enterocyte CLD content), and fecal microbiome parameters. Plin2-null mice had significantly lower respiratory exchange ratios, diminished frequencies of enterocyte CLDs, and increased fecal triglyceride levels compared with WT mice. Microbiome analyses, employing both 16S rRNA profiling and metagenomic deep sequencing, indicated that dietary fat content and Plin2 genotype were significantly and independently associated with gut microbiome composition, diversity, and functional differences. These data demonstrate that Plin2 modulates rapid effects of diet on fecal lipid levels, enterocyte CLD contents, and fuel utilization properties of mice that correlate with structural and functional differences in their gut microbial communities. Collectively, the data provide evidence of Plin2 regulated intestinal lipid uptake, which contributes to rapid changes in the gut microbial communities implicated in diet-induced obesity.

Apolipoprotein D Transgenic Mice Develop Hepatic Steatosis through Activation of PPARγ and Fatty Acid Uptake

Transgenic mice (Tg) overexpressing human apolipoprotein D (H-apoD) in the brain are resistant to neurodegeneration. Despite the use of a neuron-specific promoter to generate the Tg mice, they expressed significant levels of H-apoD in both plasma and liver and they slowly develop hepatic steatosis and insulin resistance. We show here that hepatic PPARγ expression in Tg mice is increased by 2-fold compared to wild type (WT) mice. Consequently, PPARγ target genes Plin2 and Cide A/C are overexpressed, leading to increased lipid droplets formation. Expression of the fatty acid transporter CD36, another PPARgamma target, is also increased in Tg mice associated with elevated fatty acid uptake as measured in primary hepatocytes. Elevated expression of AMPK in the liver of Tg leads to phosphorylation of acetyl CoA carboxylase, indicating a decreased activity of the enzyme. Fatty acid synthase expression is also induced but the hepatic lipogenesis measured in vivo is not significantly different between WT and Tg mice. In addition, expression of carnitine palmitoyl transferase 1, the rate-limiting enzyme of beta-oxidation, is slightly upregulated. Finally, we show that overexpressing H-apoD in HepG2 cells in presence of arachidonic acid (AA), the main apoD ligand, increases the transcriptional activity of PPARγ. Supporting the role of apoD in AA transport, we observed enrichment in hepatic AA and a decrease in plasmatic AA concentration. Taken together, our results demonstrate that the hepatic steatosis observed in apoD Tg mice is a consequence of increased PPARγ transcriptional activity by AA leading to increased fatty acid uptake by the liver.

Human umbilical cord matrix mesenchymal stem cells suppress the growth of breast cancer by expression of tumor suppressor genes

Human and rat umbilical cord matrix mesenchymal stem cells (UCMSC) possess the ability to control the growth of breast carcinoma cells. Comparative analyses of two types of UCMSC suggest that rat UCMSC-dependent growth regulation is significantly stronger than that of human UCMSC. Their different tumoricidal abilities were clarified by analyzing gene expression profiles in the two types of UCMSC. Microarray analysis revealed differential gene expression between untreated naïve UCMSC and those co-cultured with species-matched breast carcinoma cells. The analyses screened 17 differentially expressed genes that are commonly detected in both human and rat UCMSC. The comparison between the two sets of gene expression profiles identified two tumor suppressor genes, adipose-differentiation related protein (ADRP) and follistatin (FST), that were specifically up-regulated in rat UCMSC, but down-regulated in human UCMSC when they were co-cultured with the corresponding species' breast carcinoma cells. Over-expression of FST, but not ADRP, in human UCMSC enhanced their ability to suppress the growth of MDA-231 cells. The growth of MDA-231 cells was also significantly lower when they were cultured in medium conditioned with FST, but not ADRP over-expressing human UCMSC. In the breast carcinoma lung metastasis model generated with MDA-231 cells, systemic treatment with FST-over-expressing human UCMSC significantly attenuated the tumor burden. These results suggest that FST may play an important role in exhibiting stronger tumoricidal ability in rat UCMSC than human UCMSC and also implies that human UCMSC can be transformed into stronger tumoricidal cells by enhancing tumor suppressor gene expression.

Perilipin1 deficiency in whole body or bone marrow-derived cells attenuates lesions in atherosclerosis-prone mice

Aims

The objective of this study is to determine the role of perilipin 1 (Plin1) in whole body or bone marrow-derived cells on atherogenesis.

Methods and Results

Accumulated evidence have indicated the role of Plin1 in atherosclerosis, however, these findings are controversial. In this study, we showed that Plin1 was assembled and colocalized with CD68 in macrophages in atherosclerotic plaques of ApoE-/- mice. We further found 39% reduction of plaque size in the aortic roots of Plin1 and ApoE double knockout (Plin1-/-ApoE-/-) females compared with ApoE-/- female littermates. In order to verify whether this reduction was macrophage-specific, the bone marrow cells from wild-type or Plin1 deficient mice (Plin1-/-) were transplanted into LDL receptor deficient mice (LDLR-/-). Mice receiving Plin1-/- bone marrow cells showed also 49% reduction in aortic atherosclerotic lesions compared with LDLR-/- mice received wild-type bone marrow cells. In vitro experiments showed that Plin1-/- macrophages had decreased protein expression of CD36 translocase and an enhanced cholesterol ester hydrolysis upon aggregated-LDL loading, with unaltered expression of many other regulators of cholesterol metabolism, such as cellular lipases, and Plin2 and 3. Given the fundamental role of Plin1 in protecting LD lipids from lipase hydrolysis, it is reasonably speculated that the assembly of Plin1 in microphages might function to reduce lipolysis and hence increase lipid retention in ApoE-/- plaques, but this pro-atherosclerotic property would be abrogated on inactivation of Plin1.

Conclusion

Plin1 deficiency in bone marrow-derived cells may be responsible for reduced atherosclerotic lesions in the mice.

Perilipin 5 regulates islet lipid metabolism and insulin secretion in a cAMP-dependent manner: implication of its role in the postprandial insulin secretion

Elevation of circulating fatty acids (FA) during fasting supports postprandial (PP) insulin secretion that is critical for glucose homeostasis and is impaired in diabetes. We tested our hypothesis that lipid droplet (LD) protein perilipin 5 (PLIN5) in β-cells aids PP insulin secretion by regulating intracellular lipid metabolism. We demonstrated that PLIN5 serves as an LD protein in human islets. In vivo, Plin5 and triglycerides were increased by fasting in mouse islets. MIN6 cells expressing PLIN5 (adenovirus [Ad]-PLIN5) and those expressing perilipin 2 (PLIN2) (Ad-PLIN2) had higher [(3)H]FA incorporation into triglycerides than Ad-GFP control, which support their roles as LD proteins. However, Ad-PLIN5 cells had higher lipolysis than Ad-PLIN2 cells, which increased further by 8-Br-cAMP, indicating that PLIN5 facilitates FA mobilization upon cAMP stimulation as seen postprandially. Ad-PLIN5 in islets enhanced the augmentation of glucose-stimulated insulin secretion by FA and 8-Br-cAMP in G-protein-coupled receptor 40 (GPR40)- and cAMP-activated protein kinase-dependent manners, respectively. When PLIN5 was increased in mouse β-cells in vivo, glucose tolerance after an acute exenatide challenge was improved. Therefore, the elevation of islet PLIN5 during fasting allows partitioning of FA into LD that is released upon refeeding to support PP insulin secretion in cAMP- and GPR40-dependent manners.

S-Adenosylmethionine increases circulating very-low density lipoprotein clearance in non-alcoholic fatty liver disease

BACKGROUND & AIMS

Very-low-density lipoproteins (VLDLs) export lipids from the liver to peripheral tissues and are the precursors of low-density-lipoproteins. Low levels of hepatic S-adenosylmethionine (SAMe) decrease triglyceride (TG) secretion in VLDLs, contributing to hepatosteatosis in methionine adenosyltransferase 1A knockout mice but nothing is known about the effect of SAMe on the circulating VLDL metabolism. We wanted to investigate whether excess SAMe could disrupt VLDL plasma metabolism and unravel the mechanisms involved.

METHODS

Glycine N-methyltransferase (GNMT) knockout (KO) mice, GNMT and perilipin-2 (PLIN2) double KO (GNMT-PLIN2-KO) and their respective wild type (WT) controls were used. A high fat diet (HFD) or a methionine deficient diet (MDD) was administrated to exacerbate or recover VLDL metabolism, respectively. Finally, 33 patients with non-alcoholic fatty-liver disease (NAFLD); 11 with hypertriglyceridemia and 22 with normal lipidemia were used in this study.

RESULTS

We found that excess SAMe increases the turnover of hepatic TG stores for secretion in VLDL in GNMT-KO mice, a model of NAFLD with high SAMe levels. The disrupted VLDL assembly resulted in the secretion of enlarged, phosphatidylethanolamine-poor, TG- and apoE-enriched VLDL-particles; special features that lead to increased VLDL clearance and decreased serum TG levels. Re-establishing normal SAMe levels restored VLDL secretion, features and metabolism. In NAFLD patients, serum TG levels were lower when hepatic GNMT-protein expression was decreased.

CONCLUSIONS

Excess hepatic SAMe levels disrupt VLDL assembly and features and increase circulating VLDL clearance, which will cause increased VLDL-lipid supply to tissues and might contribute to the extrahepatic complications of NAFLD.

Urine aquaporin 1 and perilipin 2 differentiate renal carcinomas from other imaged renal masses and bladder and prostate cancer

OBJECTIVE

To evaluate the sensitivity and specificity of urine aquaporin 1 (AQP1) and perilipin 2 (PLIN2) concentrations to diagnose clear cell or papillary renal cell carcinoma (RCC) by comparing urine concentrations of these unique biomarkers in patients with RCC, noncancer renal masses, bladder cancer, and prostate cancer.

METHODS

From February 1, 2012, through October 31, 2012, preoperative urine samples were obtained from patients with a presumptive diagnosis of RCC based on an imaged renal mass, prostate cancer, or transitional cell bladder cancer. Imaged renal masses were diagnosed postnephrectomy—as malignant or benign—by histology. Urine AQP1 and PLIN2 concentrations were measured by using a sensitive and specific Western blot and normalized to urine creatinine concentration.

RESULTS

Median concentrations of urine AQP1 and PLIN2 in patients with clear cell and papillary RCC (n=47) were 29 and 36 relative absorbance units/mg urine creatinine, respectively. In contrast, median concentrations in patients with bladder cancer (n=22) and prostate cancer (n=27), patients with chromophobe tumors (n=7), and patients with benign renal oncocytomas (n=9) and angiomyolipomas (n=7) were all less than 10 relative absorbance units/mg urine creatinine (Kruskal-Wallis test, P<.001 vs RCC for both biomarkers) and comparable with those in healthy controls. The area under the receiver operating characteristic curve ranged from 0.99 to 1.00 for both biomarkers.

CONCLUSION

These results support the specificity and sensitivity of urine AQP1 and PLIN2 concentrations for RCC. These novel tumor-specific proteins have high clinical validity and high potential as specific screening biomarkers for clear cell and papillary RCC as well as in the differential diagnosis of imaged renal masses.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00851994.

Intensity-dependent and sex-specific alterations in hepatic triglyceride metabolism in mice following acute exercise

Precise regulation of hepatic triglyceride (TG) metabolism and secretion is critical for health, and exercise could play a significant role. We compared one session of high-intensity interval exercise (HIIE) vs. continuous exercise (CE) on hepatic TG metabolism. Female and male mice were assigned to CE, HIIE, or sedentary control (CON). HIIE was a 30-min session of 30-s running intervals (30 m/min) interspersed with 60-s walking periods (5 m/min). CE was a distance- and duration-matched run at 13.8 m/min. Hepatic content of TG and TG secretion rates, as well as expression of relevant genes/proteins, were measured at 3 h (day 1) and 28 h (day 2) postexercise. On day 1, hepatic [TG] in CE and HIIE were both elevated vs. CON in both sexes with an approximately twofold greater elevation in HIIE vs. CE in females. In both sexes, hepatic perilipin 2 (PLIN2) protein on day 1 was increased significantly by both exercise types with a significantly greater increase with HIIE than CE, whereas the increase in mRNA reached significance only after HIIE. On day 2 in both sexes the increases in hepatic TG and PLIN2 with exercise declined toward CON levels. Only HIIE on day 2 resulted in reduced hepatic TG secretion by ∼20% in females with no effect in males. Neither exercise modality altered AMPK signaling or microsomal triglyceride transfer protein expression. Females exhibited higher hepatic TG secretion than males in association with different expression levels of related metabolic enzymes. These intensity-dependent and sex-specific alterations following exercise may have implications for sex-based exercise prescription.

Structural and functional assessment of perilipin 2 lipid binding domain(s)

Although perilipin 2 (Plin2) has been shown to bind lipids with high affinity, the Plin2 lipid binding site has yet to be defined. This is of interest since Plin2's affinity for lipids has been suggested to be important for lipid droplet biogenesis and intracellular triacylglycerol accumulation. To define these regions, mouse Plin2 and several deletion mutants expressed as recombinant proteins and in mammalian cells were assessed by molecular modeling, fluorescence binding, circular dichroic, and fluorescence resonance energy transfer techniques to identify the structural and functional requirements for lipid binding. Major findings of this study indicate (1) the N-terminal PAT domain does not bind cholesterol or stearic acid; (2) Plin2 residues 119-251, containing helix α4, the α-β domain, and part of helix α6 form a Plin3-like cleft found to be important for highest affinity lipid binding; (3) both stearic acid and cholesterol interact favorably with the Plin2 cleft formed by conserved residues in helix α6 and adjacent strands, which is common to all the active lipid-binding constructs; and (4) discrete targeting of the Plin2 mutants to lipid droplets supports Plin2 containing two independent, nonoverlapping lipid droplet targeting domains in its central and C-terminal sequences. Thus, the current work reveals specific domains responsible for Plin2-lipid interactions that involves the protein's lipid binding and targeting functions.

Surface features of the lipid droplet mediate perilipin 2 localization

All eukaryotic organisms store excess lipid in intracellular lipid droplets. These dynamic structures are associated with and regulated by numerous proteins. Perilipin 2, an abundant protein on most lipid droplets, promotes neutral lipid accumulation in lipid droplets. However, the mechanism by which perilipin 2 binds to and remains anchored on the lipid droplet surface is unknown. Here we identify features of the lipid droplet surface that influence perilipin 2 localization. We show that perilipin 2 binding to the lipid droplet surface requires both hydrophobic and electrostatic interactions. Reagents that disrupt these interactions also decrease binding. Moreover, perilipin 2 binding does not depend on other lipid droplet-associated proteins but is influenced by the lipid composition of the surface. Perilipin 2 binds to synthetic vesicles composed of dioleoylphosphatidylcholine, a phospholipid with unsaturated acyl chains. Decreasing the temperature of the binding reaction, or introducing phospholipids with saturated acyl chains, decreases binding. We therefore demonstrate a role for surface lipids and acyl chain packing in perilipin 2 binding to lipid droplets. The ability of the lipid droplet phospholipid composition to impact protein binding may link changes in nutrient availability to lipid droplet homeostasis.

Absence of perilipin 2 prevents hepatic steatosis, glucose intolerance and ceramide accumulation in alcohol-fed mice

BACKGROUND

Perilipin 2 (Plin2) is a lipid droplet protein that has roles in both lipid and glucose homeostasis. An increase in Plin2 in liver is associated with the development of steatosis, glucose intolerance, and ceramide accumulation in alcoholic liver disease. We investigated the role of Plin2 on energy balance and glucose and lipid homeostasis in wildtype and Plin2 knockout (Plin2KO) mice chronically fed a Lieber-DeCarli liquid ethanol or control diet for six weeks.

METHODS

We performed in vivo measurements of energy intake and expenditure; body composition; and glucose tolerance. After sacrifice, liver was dissected for histology and lipid analysis.

RESULTS

We found that neither genotype nor diet had a significant effect on final weight, body composition, or energy intake between WT and Plin2KO mice fed alcohol or control diets. Additionally, alcohol feeding did not affect oxygen consumption or carbon dioxide production in Plin2KO mice. We performed glucose tolerance testing and observed that alcohol feeding failed to impair glucose tolerance in Plin2KO mice. Most notably, absence of Plin2 prevented hepatic steatosis and ceramide accumulation in alcohol-fed mice. These changes were related to downregulation of genes involved in lipogenesis and triglyceride synthesis.

CONCLUSIONS

Plin2KO mice chronically fed alcohol are protected from hepatic steatosis, glucose intolerance, and hepatic ceramide accumulation, suggesting a critical pathogenic role of Plin2 in experimental alcoholic liver disease.

Characterisation of the genetic effects of the ADFP gene and its association with production traits in dairy goats

Adipose differentiation-related protein (ADFP) is important for regulation of lipid metabolism and insulin secretion in beta-cells. In this study, we investigated polymorphisms within the caprine ADFP gene and determined its relationship with production traits. As there was no sequence information available for the caprine ADFP gene, we generated DNA sequence data and examined the genomic organisation. The caprine ADFP gene is organised into 7 exons and 6 introns that span approximately 8.7 kbp and is transcribed into mRNA containing 1,353 bp of sequence coding for a protein of 450 amino acids. The protein sequences showed substantial similarity (71-99%) to orthologues from cattle, human and mouse. We identified polymorphisms in the sequences using DNA sequencing, PCR-RFLP and forced PCR-RFLP methods. Seven single nucleotide polymorphisms (SNPs) were identified using samples from 4 different goat populations consisting of 1408 healthy and unrelated individuals. Six haplotypes involving the 7 SNPs from the caprine ADFP gene were identified and their effects on production traits were analysed. Haplotype 6 had the highest haplotype frequency and was highly significantly associated with chest circumference and milk yield in the analysed populations. The results of this study suggest that the ADFP gene is a strong candidate gene affecting production traits and may be used for marker-assisted selection and management in Chinese dairy goat breeding programmes.

[Effects of octreotide on fatty infiltration of the pancreas in high-fat diet induced obesity rats]

OBJECTIVE

To investigate effects of octreotide on fatty infiltration of the pancreas in high-fat diet induced obesity rats.

METHODS

SD rats were divided into control group (n = 14) and high-fat diet group (n = 36). Obese rats from the high-fat diet group were further divided into 2 groups: the obese group (n = 14) and the octreotide-treated group (n = 16). Rats in the octreotide-treated group were subcutaneously injected with octreotide per 12 h (40 mg/kg BW) for 8 days. Body weight, fasting plasma glucose (FPG), fasting serum insulin, triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) levels, pancreatic TG and FFA content were measured. Homeostatic model assessment (HOMA) index was calculated. Somatostatin (SST) and the expression of adipose differentiation-related protein (ADFP) in pancrea were measured. Pathological changes of pancreas were examined with light microscopy.

RESULTS

Body weight, Lee's index, FPG, fasting serum insulin, TG, TC levels and HOMA index in the obese group were higher than those in the control group (P < 0.05), while the level of HDL-C in the obese group was lower than that in the control group (P < 0.05). Pancreatic TG, FFA contents and expression of ADFP in the obese group were significantly higher than those in the control group (P < 0.05), while pancreatic SST level in the obese group was lower than that in the control group (P < 0.05). Obvious pancreatic intra-lobular fatty infiltration was observed in the obese group. After treatment of octreotide, body weight, HOMA index, as well as other plasma parameters as above showed decrease as compared with those in the obese group (P < 0.05). In addition, pancreatic TG, FFA contents and the expression of ADFP in the octreotide treated group were also significantly decreased compared with those in the obese group (P < 0.05), pancreatic SST level was increased in the octreotide treated group than that in the obese group (P < 0.05), and pancreatic intra-lobular fatty infiltration was alleviated.

CONCLUSION

Octreotide might improve pancreatic fatty infiltration, lipid disorder, insulin resistance and alleviate pancreatic injury by down-regulating the expression of ADFP in pancreas, and lowering the levels of plasma glucose and lipid in the high-fat diet induced obesity rats.

Androgen receptor identification in the diagnosis of eyelid sebaceous carcinomas

PURPOSE

To assess the role of androgen receptor detection in diagnosing eyelid sebaceous carcinomas and to compare it with that of adipophilin.

DESIGN

Retrospective, clinicopathologic study.

METHODS

Ten sebaceous carcinomas (8 invasive, 2 intraepithelial only) were stained immunohistochemically for androgen receptors and were compared with adipophilin staining. Receptor staining also was performed on benign sebaceous tumors (a sebaceoma and an adenoma) and as controls on eyelid basal cell carcinomas, eyelid squamous cell carcinomas, conjunctival squamous dysplasias, and conjunctival melanomas.

RESULTS

All 8 patients with an invasive component of sebaceous carcinoma underwent a biopsy in which the tumor cells showed diffusely positive results for androgen receptors (>20% of cells and usually >40%) and positive results for adipophilin. Eight cases displaying an intraepithelial (or pagetoid) component of spread also showed diffusely positive results for androgen receptors and adipophilin in at least 1 of multiple biopsy samples from each patient. However, in 8 of 21 separate conjunctival biopsy specimens with intraepithelial cytologic atypia, adipophilin results were negative. A sebaceoma and a sebaceous adenoma also showed positive results for both of these biomarkers. Among the controls, squamous carcinomas and melanomas showed negative results for androgen receptors and adipophilin. Basal cell carcinomas displayed focal receptor positivity in fewer than 5% of cells and showed negative results for adipophilin.

CONCLUSIONS

Androgen receptors and adipophilin can separate sebaceous tumors immunohistochemically from squamous carcinomas and melanomas, which showed negative results for both, and from basal cell carcinomas, which showed positive receptor results in a distant minority of cells. Regarding intraepithelial (or pagetoid) spread, androgen receptor detection was more sensitive and reliable than adipophilin in highlighting this component of the disease.

Effect of different culture systems on adipocyte differentiation-related protein (ADRP) in bovine embryos

Bovine embryos cultured in serum-containing media abnormally accumulate lipid droplets, compared to their in vivo counterparts. The objective of this study was to investigate the effect of different culture systems on the mRNA expression and on the quantification and localisation of adipocyte differentiation-related protein (ADRP), a protein associated with lipid accumulation in bovine blastocysts. Two experiments were independently performed for ADRP mRNA expression analysis. In experiment A, blastocysts were produced in modified synthetic oviduct fluid (mSOF)+10% foetal calf serum (FCS), in coculture (bovine oviduct epithelial cells, Boec) and in ewe oviducts, whereas in experiment B, they were produced in mSOF+10μM docosahexaenoic acid (DHA) and in vivo. Control groups were also performed. ADRP mRNA expression was downregulated in the Boec, ewe oviduct and in vivo groups compared to the 10% FCS or DHA groups, respectively. Moreover, the expression of this protein was downregulated in the Boec group compared to the control group (P<0.05). A third experiment (experiment C) was performed to quantify and localise ADRP protein. Boec, in vivo and control groups were tested. After immunofluorescence staining followed by confocal microscopy analysis, embryonic ADRP was clearly localised around lipid droplets, indicating that ADRP is also a lipid droplet coat protein in bovine embryos. In conclusion, our results demonstrate that bovine embryos at the blastocyst stage expressed ADRP mRNA and protein, and that the embryonic culture system modified this expression.

Eyelid sebaceous carcinoma: clinicopathologic and multiparametric immunohistochemical analysis that includes adipophilin

PURPOSE

To evaluate the fine cytopathologic features and immunohistochemistry of eyelid sebaceous carcinoma.

DESIGN

Retrospective clinicopathologic study.

METHODS

Clinical records and microscopic glass slides of 12 patients diagnosed with sebaceous carcinoma were reviewed. Paraffin-embedded tissue recuts were immunoreacted for epithelial membrane antigen (EMA), Ber-EP4, p53, Ki-67, and adipophilin for cytoplasmic lipid. Invasive growth and intraepithelial spread were analyzed separately. Cytoplasmic and nuclear characteristics were correlated with the results of the immunohistochemical profiling.

RESULTS

Five patients experienced recurrences, but no metastases or tumor-related deaths were discovered. The nuclei in 11 invasive tumor cells were typically round with finely divided, granular, or smudgy chromatin without prominent margination at the nuclear membrane; they exhibited small punctate nucleoli. Positivity for EMA (both diffuse and focal), p53 (72% of nuclei), and Ki-67 (45% proliferation index) was demonstrated. Adipophilin positivity in vesicular and granular forms was detected in paraffin sections in all invasive tumors, most prominently in moderately differentiated and well-differentiated lesions. Among 9 cases exhibiting intraepithelial extensions, 6 showed mostly granular positivity and 3 vesicular positivity. p53 identified residual atypical intraepithelial cells when conjunctival epithelial sloughing occurred.

CONCLUSIONS

Immunohistochemistry can make significant contributions to the diagnosis of sebaceous carcinoma. p53 and vesicular granular adipophilin positivity were highly reliable in supplementing the routine microscopic diagnosis of infiltrative tumors and both can be used in paraffin sections, thereby obviating cumbersome oil red O staining of frozen sections. The cells found in intraepithelial spread were strongly EMA and p53 positive, with more granular than vesicular adipophilin positivity.

Delayed liver regeneration after partial hepatectomy in adipose differentiation related protein-null mice

BACKGROUND & AIMS

Adult hepatocytes undergo cell cycle progression and proliferation in response to partial hepatectomy (PH). Transient lipid accumulation within hepatocytes preceding the peak proliferative phase is a characteristic feature of regenerating livers. However, the molecular mediators and mechanisms responsible for lipid accumulation in regenerating livers are not well understood. Adipose differentiation related protein (ADRP; Plin2) regulates hepatic triglyceride storage and Plin2-deficient (Plin2(-/-)) mice have significantly reduced triglyceride (TG) content in the liver. We sought to determine the functional significance of PLIN2 in liver regeneration in response to PH and toxic liver injury and examined whether absence of Plin2 expression modulates hepatocyte proliferation and liver regeneration.

METHODS

We subjected wild-type (WT) and Plin2(-/-) mice to 70% PH or acute carbon tetrachloride (CCL4) treatment and examined the hepatic lipid content, the expression profile of lipid metabolism-related genes, the rate of cellular proliferation and the dynamics of liver regeneration in the treated animals.

RESULTS

In response to PH, Plin2(-/-) mice showed decreased hepatic triglyceride accumulation and delayed cell cycle progression, which was associated with impaired liver regeneration. Fatty acid (FA) synthesis and lipid transfer gene expression profile were comparable between Plin2(-/-) and wild-type mice, while VLDL secretion rate was higher in the Plin2(-/-) mice. Downregulated β-oxidation and reduced cytosolic FA level in Plin2(-/-) mice may have contributed to the attenuation of the liver regeneration capacity in these animals. In parallel experiments, we also observed attenuated hepatic lipid accumulation and proliferation in response to CCl4-mediated acute toxic liver injury in Plin2(-/-) mice.

CONCLUSIONS

We conclude that PLIN2-mediated lipid accumulation and utilization by the liver is important for efficient liver regeneration in response to PH and toxic liver injury.

Plin2 inhibits cellular glucose uptake through interactions with SNAP23, a SNARE complex protein

Although a link between excess lipid storage and aberrant glucose metabolism has been recognized for many years, little is known what role lipid storage droplets and associated proteins such as Plin2 play in managing cellular glucose levels. To address this issue, the influence of Plin2 on glucose uptake was examined using 2-NBD-Glucose and [(3)H]-2-deoxyglucose to show that insulin-mediated glucose uptake was decreased 1.7- and 1.8-fold, respectively in L cell fibroblasts overexpressing Plin2. Conversely, suppression of Plin2 levels by RNAi-mediated knockdown increased 2-NBD-Glucose uptake several fold in transfected L cells and differentiated 3T3-L1 cells. The effect of Plin2 expression on proteins involved in glucose uptake and transport was also examined. Expression of the SNARE protein SNAP23 was increased 1.6-fold while levels of syntaxin-5 were decreased 1.7-fold in Plin2 overexpression cells with no significant changes observed in lipid droplet associated proteins Plin1 or FSP27 or with the insulin receptor, GLUT1, or VAMP4. FRET experiments revealed a close proximity of Plin2 to SNAP23 on lipid droplets to within an intramolecular distance of 51 Å. The extent of targeting of SNAP23 to lipid droplets was determined by co-localization and co-immunoprecipitation experiments to show increased partitioning of SNAP23 to lipid droplets when Plin2 was overexpressed. Taken together, these results suggest that Plin2 inhibits glucose uptake by interacting with, and regulating cellular targeting of SNAP23 to lipid droplets. In summary, the current study for the first time provides direct evidence for the role of Plin2 in mediating cellular glucose uptake.

Increased Plin2 expression in human skeletal muscle is associated with sarcopenia and muscle weakness

Human aging is associated with a progressive loss of muscle mass and strength and a concomitant fat accumulation in form of inter-muscular adipose tissue, causing skeletal muscle function decline and immobilization. Fat accumulation can also occur as intra-muscular triglycerides (IMTG) deposition in lipid droplets, which are associated with perilipin proteins, such as Perilipin2 (Plin2). It is not known whether Plin2 expression changes with age and if this has consequences on muscle mass and strength. We studied the expression of Plin2 in the vastus lateralis (VL) muscle of both healthy subjects and patients affected by lower limb mobility limitation of different age. We found that Plin2 expression increases with age, this phenomenon being particularly evident in patients. Moreover, Plin2 expression is inversely correlated with quadriceps strength and VL thickness. To investigate the molecular mechanisms underpinning this phenomenon, we focused on IGF-1/p53 network/signalling pathway, involved in muscle physiology. We found that Plin2 expression strongly correlates with increased p53 activation and reduced IGF-1 expression. To confirm these observations made on humans, we studied mice overexpressing muscle-specific IGF-1, which are protected from sarcopenia. These mice resulted almost negative for the expression of Plin2 and p53 at two years of age. We conclude that fat deposition within skeletal muscle in form of Plin2-coated lipid droplets increases with age and is associated with decreased muscle strength and thickness, likely through an IGF-1- and p53-dependent mechanism. The data also suggest that excessive intramuscular fat accumulation could be the initial trigger for p53 activation and consequent loss of muscle mass and strength.

A white opaque substance-positive gastric hyperplastic polyp with dysplasia

The endoscopic findings of gastric hyperplastic polyps (HPs) with dysplasia have not been well-defined, and the clinical significance of these lesions, including their malignant potential, is unclear. In this report, we describe a case of a white opaque substance (WOS)-positive gastric HP with dysplasia. A 76-year-old woman was referred to our hospital for endoscopic resection of a gastric HP. Upper endoscopy revealed a 25-mm whitish and reddish polypoid lesion on the greater curvature in the lower third of the stomach. The whitish part was diagnosed as a WOS using conventional and magnifying endoscopy with narrow band imaging. An examination of the biopsy specimen indicated that the lesion was a typical gastric HP. However, because of its color and the presence of a WOS, we suspected that this lesion was an atypical gastric HP. Therefore, we performed a polypectomy. Histopathologically, diffuse low- to high-grade dysplasia was found on the surface of the polyp. We performed immunohistochemical staining using a monoclonal antibody specific for adipophilin as a marker of lipid droplets (LDs). LDs were detected in approximately all of the neoplastic cells, especially in the surface epithelium of the intervening apical parts and were located in the subnuclear cytoplasm of the neoplastic cells. According to endoscopic and histopathological findings, the WOS-positive epithelium indicated dysplasia of the gastrointestinal phenotype, which could absorb lipids. The presence of a WOS in a gastric HP may be considered an endoscopic finding that is predictive of the neoplastic transformation of a gastric HP. We suggest that a WOS-positive gastric HP should be resected endoscopically to investigate its neoplastic transformation.

Dynamic regulation of hepatic lipid droplet properties by diet

Cytoplasmic lipid droplets (CLD) are organelle-like structures that function in neutral lipid storage, transport and metabolism through the actions of specific surface-associated proteins. Although diet and metabolism influence hepatic CLD levels, how they affect CLD protein composition is largely unknown. We used non-biased, shotgun, proteomics in combination with metabolic analysis, quantitative immunoblotting, electron microscopy and confocal imaging to define the effects of low- and high-fat diets on CLD properties in fasted-refed mice. We found that the hepatic CLD proteome is distinct from that of CLD from other mammalian tissues, containing enzymes from multiple metabolic pathways. The hepatic CLD proteome is also differentially affected by dietary fat content and hepatic metabolic status. High fat feeding markedly increased the CLD surface density of perilipin-2, a critical regulator of hepatic neutral lipid storage, whereas it reduced CLD levels of betaine-homocysteine S-methyltransferase, an enzyme regulator of homocysteine levels linked to fatty liver disease and hepatocellular carcinoma. Collectively our data demonstrate that the hepatic CLD proteome is enriched in metabolic enzymes, and that it is qualitatively and quantitatively regulated by diet and metabolism. These findings implicate CLD in the regulation of hepatic metabolic processes, and suggest that their properties undergo reorganization in response to hepatic metabolic demands.

The specificity of urinary aquaporin 1 and perilipin 2 to screen for renal cell carcinoma

PURPOSE

Renal cancer is frequently asymptomatic until late stages of the disease and it has a poor prognosis when not discovered early. AQP1 and PLIN2 are recently discovered, sensitive urine biomarkers of clear cell and papillary kidney cancer. We validated these biomarkers in a second cohort of patients and determined the effect of common kidney diseases on specificity.

MATERIALS AND METHODS

Urine samples were obtained from 36 patients with clear cell or papillary kidney cancer, 43 controls, 44 patients with documented urinary tract infection, 24 diagnosed with diabetic nephropathy and 18 diagnosed with glomerulonephritis. Urine levels of AQP1 and PLIN2 normalized to urine creatinine were determined by a sensitive, specific Western blot procedure.

RESULTS

Compared with controls, urine AQP1 and PLIN2 levels in patients with kidney cancer were 23-fold and fourfold greater, respectively, and they decreased 83% to 84% after tumor excision. There was a linear correlation between urine AQP1 and PLIN2 levels, and tumor size (each p <0.001). Urine AQP1 and PLIN2 levels in patients with kidney cancer were 11 to 23-fold and 17 to 25-fold greater, respectively, than in patients with the common kidney diseases.

CONCLUSIONS

The ability of urine AQP1 and PLIN2 to identify patients with kidney cancer compared to controls was validated in a second cohort of patients. Common kidney diseases do not adversely increase urine AQP1 and PLIN2 levels or decrease their specificity to screen for renal cancer.

High-fat diet-mediated lipotoxicity and insulin resistance is related to impaired lipase expression in mouse skeletal muscle

Elevated expression/activity of adipose triglyceride lipase (ATGL) and/or reduced activity of hormone-sensitive lipase (HSL) in skeletal muscle are causally linked to insulin resistance in vitro. We investigated here the effect of high-fat feeding on skeletal muscle lipolytic proteins, lipotoxicity, and insulin signaling in vivo. Five-week-old C3H mice were fed normal chow diet (NCD) or 45% kcal high-fat diet (HFD) for 4 weeks. Wild-type and HSL knockout mice fed NCD were also studied. Whole-body and muscle insulin sensitivity, as well as lipolytic protein expression, lipid levels, and insulin signaling in skeletal muscle, were measured. HFD induced whole-body insulin resistance and glucose intolerance and reduced skeletal muscle glucose uptake compared with NCD. HFD increased skeletal muscle total diacylglycerol (DAG) content, protein kinase Cθ and protein kinase Cε membrane translocation, and impaired insulin signaling as reflected by a robust increase of basal Ser1101 insulin receptor substrate 1 phosphorylation (2.8-fold, P < .05) and a decrease of insulin-stimulated v-Akt murine thymoma viral oncogene homolog Ser473 (-37%, P < .05) and AS160 Thr642 (-47%, P <.01) phosphorylation. We next showed that HFD strongly reduced HSL phosphorylation at Ser660. HFD significantly up-regulated the muscle protein content of the ATGL coactivator comparative gene identification 58 and triacylglycerol hydrolase activity, despite a lower ATGL protein content. We further show a defective skeletal muscle insulin signaling and DAG accumulation in HSL knockout compared with wild-type mice. Together, these data suggest a pathophysiological link between altered skeletal muscle lipase expression and DAG-mediated insulin resistance in mice.

Immunohistochemistry of LAMP-2 and adipophilin for phospholipidosis in liver and kidney in ketoconazole-treated mice

Drug-induced phospholipidosis is an abnormal accumulation of phospholipids in the lysosomes following repeated administration of cationic amphiphilic drugs. Phospholipidosis is detected histopathologically as cytoplasmic vacuolation; however, it is difficult to distinguish from lipid accumulation since their morphological features are similar. In this study, we investigated the usefulness of immunohistochemistry for lysosome-associated membrane protein-2 (LAMP-2) and adipophilin, a membrane protein of cytosolic non-lysosomal lipid droplets, in the liver and kidneys of mice orally administered ketoconazole, an inducer of hepatic phospholipidosis. In 7-week-old mice administered ketoconazole (300 mg/kg/day) for 7 days, cytoplasmic vacuolation was histopathologically observed in centrilobular hepatocytes and proximal tubular epithelial cells under the fasted condition. The cytoplasmic vacuolation consisted of foamy vacuoles, which were revealed to be phospholipidosis-characteristic lamellar bodies by electron microscopy. Furthermore, lipid-like vacuoles were observed in the perilobular hepatocytes, and revealed to be lipid droplets by electron microscopy. In immunohistochemistry, the foamy vacuoles and lipid-like vacuoles were positive for LAMP-2 and adipophilin, respectively. These results indicate that immunohistochemistry for LAMP-2 and adipophilin could distinguish between phospholipidosis and lipid accumulation. Additionally, it could detect ketoconazole-induced phospholipidosis in the glycogen-rich livers of non-fasted mice. In conclusion, ketoconazole induced phospholipidosis in not only the liver but also the kidneys, and immunohistochemistry for LAMP-2 and adipophilin could be useful for the pathological evaluation of drug-induced phospholipidosis in mice.

Prolonged exercise training increases intramuscular lipid content and perilipin 2 expression in type I muscle fibers of patients with type 2 diabetes

The aim of the present study was to investigate changes in intramuscular triglyceride (IMTG) content and perilipin 2 expression in skeletal muscle tissue following 6 mo of endurance-type exercise training in type 2 diabetes patients. Ten obese male type 2 diabetes patients (age 62 ± 1 yr, body mass index BMI 31 ± 1 kg/m²) completed three exercise sessions/week consisting of 40 min of continuous endurance-type exercise at 75% V(O₂ peak) for a period of 6 mo. Muscle biopsies collected at baseline and after 2 and 6 mo of intervention were analyzed for IMTG content and perilipin 2 expression using fiber type-specific immunofluorescence microscopy. Endurance-type exercise training reduced trunk body fat by 6 ± 2% and increased whole body oxygen uptake capacity by 13 ± 7% (P < 0.05). IMTG content increased twofold in response to the 6 mo of exercise training in both type I and type II muscle fibers (P < 0.05). A threefold increase in perilipin 2 expression was observed from baseline to 2 and 6 mo of intervention in the type I muscle fibers only (1.1 ± 0.3, 3.4 ± 0.6, and 3.6 ± 0.6% of fibers stained, respectively, P < 0.05). Exercise training induced a 1.6-fold increase in mitochondrial content after 6 mo of training in both type I and type II muscle fibers (P < 0.05). In conclusion, this is the first study to report that prolonged endurance-type exercise training increases the expression of perilipin 2 alongside increases in IMTG content in a type I muscle fiber-type specific manner in type 2 diabetes patients.

Perilipin 2 improves insulin sensitivity in skeletal muscle despite elevated intramuscular lipid levels

Type 2 diabetes is characterized by excessive lipid storage in skeletal muscle. Excessive intramyocellular lipid (IMCL) storage exceeds intracellular needs and induces lipotoxic events, ultimately contributing to the development of insulin resistance. Lipid droplet (LD)-coating proteins may control proper lipid storage in skeletal muscle. Perilipin 2 (PLIN2/adipose differentiation-related protein [ADRP]) is one of the most abundantly expressed LD-coating proteins in skeletal muscle. Here we examined the role of PLIN2 in myocellular lipid handling and insulin sensitivity by investigating the effects of in vitro PLIN2 knockdown and in vitro and in vivo overexpression. PLIN2 knockdown decreased LD formation and triacylglycerol (TAG) storage, marginally increased fatty-acid (FA) oxidation, and increased incorporation of palmitate into diacylglycerols and phospholipids. PLIN2 overexpression in vitro increased intramyocellular TAG storage paralleled with improved insulin sensitivity. In vivo muscle-specific PLIN2 overexpression resulted in increased LD accumulation and blunted the high-fat diet-induced increase in protein content of the subunits of the oxidative phosphorylation (OXPHOS) chain. Diacylglycerol levels were unchanged, whereas ceramide levels were increased. Despite the increased IMCL accumulation, PLIN2 overexpression improved skeletal muscle insulin sensitivity. We conclude that PLIN2 is essential for lipid storage in skeletal muscle by enhancing the partitioning of excess FAs toward TAG storage in LDs, thereby blunting lipotoxicity-associated insulin resistance.

β-cell metabolic alterations under chronic nutrient overload in rat and human islets

The aim of this study was to assess multifactorial β-cell responses to metabolic perturbations in primary rat and human islets. Treatment of dispersed rat islet cells with elevated glucose and free fatty acids (FFAs, oleate:palmitate = 1:1 v/v) resulted in increases in the size and the number of lipid droplets in β-cells in a time- and concentration-dependent manner. Glucose and FFAs synergistically stimulated the nutrient sensor mammalian target of rapamycin complex 1 (mTORC1). A potent mTORC1 inhibitor, rapamycin (25 nM), significantly reduced triglyceride accumulation in rat islets. Importantly, lipid droplets accumulated only in β-cells but not in α-cells in an mTORC1-dependent manner. Nutrient activation of mTORC1 upregulated the expression of adipose differentiation related protein (ADRP), known to stabilize lipid droplets. Rat islet size and new DNA synthesis also increased under nutrient overload. Insulin secretion into the culture medium increased steadily over a 4-day period without any significant difference between glucose (10 mM) alone and the combination of glucose (10 mM) and FFAs (240 μM). Insulin content and insulin biosynthesis, however, were significantly reduced under the combination of nutrients compared with glucose alone. Elevated nutrients also stimulated lipid droplet formation in human islets in an mTORC1-dependent manner. Unlike rat islets, however, human islets did not increase in size under nutrient overload despite a normal response to nutrients in releasing insulin. The different responses of islet cell growth under nutrient overload appear to impact insulin biosynthesis and storage differently in rat and human islets.

An undifferentiated embryonal sarcoma of the liver containing adipophilin-positive vesicles in an adult with massive sinusoidal invasion

Undifferentiated embryonal sarcoma of the liver (UESL) is a malignant mesenchymal tumor that occurs typically in children and rarely in adults. Here we describe a case of UESL in a 51-year-old woman who presented with a cystic lesion in the liver. Because it grew slowly, the anterior segment of the liver was resected to check the lesion. Histologically, the lesion looked like a telangiectatic hepatic adenoma. Two years after resection, the tumor recurred, and she died 3 years later due to liver failure. The autopsy revealed that these lesions were UESL with massive sinusoidal invasion, and a review of the case indicated the primary lesion was also UESL. We also confirmed these tumor cells by staining with CD56, alpha-smooth muscle actin (SMA), and adipophilin, suggesting that they have a character similar to that of stellate cells in the space of Disse. The histological result of our patient revealed atypical UESL. Therefore, UESL should be considered when a hepatic lesion with degeneration is seen, even in an adult. In addition, the immunohistochemical appearance of this case implies that UESL is perhaps derived from stellate cells or stellate cells with myofibroblast differentiation in the space of Disse.

[Effects of resveratrol on the morphology of lipid droplets and the expression of lipid droplet-associated proteins in mouse primary hepatocytes]

AIM

To investigate the effects of resveratrol on the morphology of lipid droplet (LD) and the expression of lipid droplet-associated proteins in primary hepatocytes of mice.

METHODS

We isolated and cultured the primary hepatocytes of mice using collagenase perfusion. The primary hepatocytes were stimulated with 200 μmol/L oleic acid (OA) for 12 h, and then added with 0 (control), 20, 50, 100 μmol/L resveratrol, respectively. Another 12 h later, we utilized Bodipy 493/503 staining to observe the morphology and amount of intracellular lipid droplets under fluorescence microscope. The Folch method and triglyceride (TG) quantitative kit were used to extract the total intracellular lipids and determine the TG contents. Western blotting was applied to analyze the expression levels of perilipin, adipophilin and TIP-47.

RESULTS

Compared with the control, the size and amount of lipid droplets in primary hepatocytes were reduced after treated with different concentrations of resveratrol. The quantitative analysis showed that the intracellular TG contents decreased markedly in a dose-dependent manner, but the most significant decrease was in 50 μmol/L resveratrol group. Western blotting showed that resveratrol reduced the expressions of perilipin, adipophilin and TIP-47 in the primary hepatocytes, especially the perilipin.

CONCLUSION

Resveratrol could inhibit intracellular lipid accumulation, which is most significant in 50 μmol/L concentration. The inhibiting effect of resveratrol may be caused by mediating the expression levels of lipid droplet-associated proteins in primary hepatocytes of mice.

The alteration of lipid metabolism in Burkitt lymphoma identifies a novel marker: adipophilin

Background

Recent evidence suggests that lipid pathway is altered in many human tumours. In Burkitt lymphoma this is reflected by the presence of lipid droplets which are visible in the cytoplasm of neoplastic cells in cytological preparations. These vacuoles are not identifiable in biopsy section as lipids are “lost” during tissue processing.

Methods and Results

In this study we investigated the expression of genes involved in lipid metabolism, at both RNA and protein level in Burkitt lymphoma and in other B-cell aggressive lymphoma cases. Gene expression profile indicated a significant over-expression of the adipophilin gene and marked up-regulation of other genes involved in lipid metabolism in Burkitt lymphoma. These findings were confirmed by immunohistochemistry on a series od additional histological samples: 45 out of 47 BL cases showed strong adipophilin expression, while only 3 cases of the 33 of the not-Burkitt lymphoma category showed weak adipophilin expression (p<0.05).

Conclusions

Our preliminary results suggest that lipid metabolism is altered in BL, and this leads to the accumulation of lipid vacuoles. These vacuoles may be specifically recognized by a monoclonal antibody against adipophilin, which may therefore be a useful marker for Burkitt lymphoma because of its peculiar expression pattern. Moreover this peptide might represent an interesting candidate for interventional strategies.

Lipid homeostasis and the formation of macrophage-derived foam cells in atherosclerosis

Atherosclerosis is a chronic, inflammatory disorder characterized by the deposition of excess lipids in the arterial intima. The formation of macrophage-derived foam cells in a plaque is a hallmark of the development of atherosclerosis. Lipid homeostasis, especially cholesterol homeostasis, plays a crucial role during the formation of foam cells. Recently, lipid droplet-associated proteins, including PAT and CIDE family proteins, have been shown to control the development of atherosclerosis by regulating the formation, growth, stabilization and functions of lipid droplets in macrophage-derived foam cells. This review focuses on the potential mechanisms of formation of macrophage-derived foam cells in atherosclerosis with particular emphasis on the role of lipid homeostasis and lipid droplet-associated proteins. Understanding the process of foam cell formation will aid in the future discovery of novel therapeutic interventions for atherosclerosis.

Perilipin 2 (PLIN2)-deficiency does not increase cholesterol-induced toxicity in macrophages

Interventions on macrophages/foam cells to redirect intracellular cholesterol towards efflux pathways could become a very valuable addition to our therapeutic arsenal against atherosclerosis. However, certain manipulations of the cholesteryl ester cycle, such as the inhibition of ACAT1, an ER-resident enzyme that re-esterifies cholesterol, are not well tolerated. Previously we showed that targeting perilipin-2 (PLIN2), a major lipid droplet (LD)-associated protein in macrophages, prevents foam cell formation and protects against atherosclerosis. Here we have assessed the tolerance of PLIN2-deficient bone marrow derived macrophages (BMM) to several lipid loading conditions similar to the found during atherosclerosis development, including exposure to modified low-density lipoprotein (mLDL) and 7-ketocholesterol (7-KC), a free cholesterol (FC) metabolite, in media with or without cholesterol acceptors. BMM isolated from mice that do or do not express PLIN2 were tested for apoptosis (TUNEL and cleaved caspase-3), ER stress (CHOP induction and XBP-1 splicing), and inflammation (TNF-α and IL-6 mRNA levels). Like in other cell types, PLIN2 deficiency impairs LD buildup in BMM. However, while most stress parameters were elevated in macrophages under ACAT inhibition and 7-KC loading, PLIN2 inactivation was well tolerated. The data support the safety of targeting PLIN2 to prevent foam cell formation and atherosclerosis.

Distinct cellular pools of perilipin 5 point to roles in lipid trafficking

The PAT family of lipid storage droplet proteins comprised five members, each of which has become an established regulator of cellular neutral lipid metabolism. Perilipin 5 (also known as lsdp-5, MLDP, PAT-1, and OXPAT), the most recently discovered member of the family, has been shown to localize to two distinct intracellular pools: the lipid storage droplet (LD), and a poorly characterized cytosolic fraction. We have characterized the denser of these intracellular pools and find that a population of perilipin 5 not associated with large LDs resides in complexes with a discrete density (~1.15 g/ml) and size (~575 kDa). Using immunofluorescence, western blotting of isolated sucrose density fractions, native gradient gel electrophoresis, and co-immunoprecipitation, we have shown that these small (~15 nm), perilipin 5-encoated structures do not contain the PAT protein perilipin 2 (ADRP), but do contain perilipin 3 and several other as of yet uncharacterized proteins. The size and density of these particles as well as their susceptibility to degradation by lipases suggest that like larger LDs, they have a neutral lipid rich core. When treated with oleic acid to promote neutral lipid deposition, cells ectopically expressing perilipin 5 experienced a reorganization of LDs in the cell, resulting in fewer, larger droplets at the expense of smaller ones. Collectively, these data demonstrate that a portion of cytosolic perilipin 5 resides in high density lipid droplet complexes that participate in cellular neutral lipid accumulation.

3,5-Diiodo-L-thyronine modulates the expression of genes of lipid metabolism in a rat model of fatty liver

Recent reports demonstrated that 3,5-diiodo-l-thyronine (T(2)) was able to prevent lipid accumulation in the liver of rats fed a high-fat diet (HFD). In this study, we investigated how the rat liver responds to HFD and T(2) treatment by assessing the transcription profiles of some genes involved in the pathways of lipid metabolism: oxidation, storage and secretion. The mRNA levels of the peroxisome proliferator-activated receptors (PPARα, PPARγ and PPARδ), and of their target enzymes acyl-CoA oxidase and stearoyl-CoA desaturase were evaluated by real-time RT-PCR. Moreover, the expression of the adipose triglyceride lipase involved in lipid mobilisation, of the main PAT proteins acting in lipid droplet (LD) turnover, and of apoprotein B (apo B), the major protein component of very low-density lipoproteins (VLDLs) were analysed. Overall, our data demonstrated that T(2) administration to HFD rats counteracts most of the hepatic transcriptional changes that occurred in response to the excess exogenous fat. In particular, our results suggest that T(2) may prevent the pathways leading to lipid storage in LDs, promote the processes of lipid mobilisation from LDs and secretion as VLDL, in addition to the stimulation of pathways of lipid oxidation. In conclusion, our findings might give an insight into the mechanisms underlying the anti-steatotic ability of T(2) and help to define the potential therapeutic role of T(2) for preventing or treating liver steatosis.