Search

Objective To explore whether hepatocyte Perilipin-2 (Plin2) is involved in the development of fatty liver related to comparative gene identification-58 (CGI-58) deficiency mice and compare the effects of Plin2 and Plin3 on lipid droplet formation and lipid accumulation. Methods Based on CGI-58Flox/Flox mice as animal model, the adeno-associated viruses targeting mouse liver, CGI-58 knockout and Plin2 knockdown were achieved by co-expression Cre protein and micro-RNA targeting Plin2 (Mi-KD). Then CGI-58 deficiency mice were used as control (NC) to detect the differences in metabolic phenotype and liver pathology. AML-12 mouse hepatocytes were used as cellular model and interfered with siRNA to achieve Plin2/Plin3 knockdown in AML-12 cells. Lipid droplet formation and lipid accumulation were compared with Bodipy staining and enzyme colorimetry in basal condition or lipid-overloaded condition (OA inducement) after Plin2/Plin3 knockdown. Results Plin2 knockdown (Mi-KD) reduced PLIN2 protein level by >99% in mouse livers. Mi-KD decreased hepatomegaly (P=0.019 5) and liver injury (P=0.000 4), while reduced the histological NAS score (P=0.000 2) and hepatic triglyceride content (P=0.016 6) in the CGI-58 deficiency female mice. Mi-KD prevented microvesicular hepatic steatosis in the CGI-58 deficient female mice. Plin3 knockdown significantly reduced the triglyceride content in basal condition of hepatocytes (P=0.001 4), and Plin2 knockdown just showed a decreased trend. Plin2 or Plin3 knockdown significantly reduced the triglyceride content separately in lipid-overloaded hepatocytes (P < 0.05). Conclusion Hepatocyte Plin2 is essential in the development of microvesicular hepatic steatosis caused by CGI-58 deficiency. Both Plin2 and Plin3 are involved in lipid droplet formation and lipid accumulation in hepatocytes, and Plin3 shows a stronger effect.

Background: Perilipin 2 (PLIN2) is a protein that contributes to the formation and stability of lipid droplets. It has been associated with the development of several diseases, particularly related to glucose and lipid metabolism. In infants of diabetic mother (IDM), fetal hyperinsulinaemia leads to increased adipose tissue and macrosomia. The aim of this study was to investigate the relationship between PLIN2 levels and anthropometric measurements in the IDM and to investigate the relationship between PLIN2 levels and IGF-1, IGF-2 and leptin levels. Methods: The study group consisted of IDMs, while the control group consisted of infants born to non-diabetic mother, matched for gestational week and gender. Cord blood samples were collected from all patients to determine PLIN2, IGF-1, IGF-2 and leptin levels. Anthropometric measurements were taken for all patients at birth. Results: There were no differences between the groups in birth weight, birth length, head circumference and body mass index (BMI), but middle arm circumference, triceps, biceps, subscapular and suprailiac skinfold thickness were significantly higher in the IDM. While PLIN2, IGF-1, IGF-2 and leptin levels were similar between groups, there was a strong correlation between PLIN2 levels and IGF-2 and leptin levels. Conclusions: Even if IDMs were not macrosomic, the presence of high subcutaneous adipose tissue was not associated with PLIN2. [ABSTRACT FROM AUTHOR]

Steroidogenic tissues contain cytosolic lipid droplets that are important for steroidogenesis. Perilipin 2 (PLIN2), a structural coat protein located on the surface of lipid droplets in mammalian cells, plays a crucial role in regulating lipid droplet formation and contributing to various cellular processes such as lipid storage and energy homeostasis. Herein, we examine the role that PLIN2 plays in regulating progesterone synthesis in the bovine corpus luteum. Utilizing gene array databases and Western blotting, we have delineated the expression pattern of PLIN2 throughout the follicular to luteal transition. Our findings reveal the presence of PLIN2 in both ovarian follicular and steroidogenic luteal cells, demonstrating an increase in its levels as follicular cells transition into the luteal phase. Moreover, the depletion of PLIN2 via siRNA enhanced progesterone production in small luteal cells, whereas adenovirus‐mediated overexpression of both PLIN2 and Perilipin 3 (PLIN3) induced an increase in cytosolic lipid droplet accumulation and decreased hormone‐induced progesterone synthesis in these cells. Lastly, in vivo administration of the luteolytic hormone prostaglandin F2α resulted in an upregulation of PLIN2 mRNA and protein expression, accompanied by a decline in serum progesterone. Our findings highlight the pivotal role of PLIN2 in regulating progesterone synthesis in the bovine corpus luteum, as supported by its dynamic expression pattern during the follicular to luteal transition and its responsiveness to luteotropic and luteolytic hormones. We suggest PLIN2 as a potential therapeutic target for modulating luteal function. [ABSTRACT FROM AUTHOR]

AIM: To investigate whether the expression of perilipin 2 (PLIN2) in renal tubular cells could predict a decline in renal function in diabetic kidney disease (DKD) patients, and to explore the potential mechanisms involved in renal tubular cell injury induced by PLIN2 during the progression of DKD. METHODS: Control individuals (n= 12) and DKD patients (n=51) were enrolled in this retrospective cohort study. Demographic and laboratory data were collected. A simplified linear mixed-effects model was applied to assess the estimated glomerular filtration rate (eGFR) slope. The relationship between PLIN2 and renal function decline in DKD patients was predicted by Spearman correlation analysis and a generalized linear model. BKS-db/db diabetic mice and streptozotocin-induced diabetic mice were used. Primary renal tubular cells were treated with glucose and transfected with small interfering RNA or plasmid. Western blotting and immunofluorescence staining were used to detect PLIN2 expression. Lipid droplets were stained with oil red O. The oxygen consumption rate (OCR) of mitochondria was measured using an extracellular flux analyser. RESULTS: The expression of PLIN2 was markedly higher in the tubules of DKD patients than in those of control subjects. After 24 (12, 39) months of follow-up, the eGFR slope of DKD patients was −7. 42 (−19. 77，−2. 09) mL/ (min·1. 73 m² ·year). An increase in the baseline percentage of PLIN2-positive tubules was significantly associated with the eGFR slope during the follow-up period ［hazard ratio (HR)=1. 90，95% confidence interval (CI): 1. 00~3. 58], indicating that tubular PLIN2 could predict a decrease in renal function in DKD patients. Both the accumulation of lipid droplets and the expression of PLIN2 were markedly greater in the tubules of diabetic mice than in those of control mice. Glucose treatment induced lipid droplet accumulation and PLIN2 expression in renal tubular cells. Knockdown of PLIN2 significantly alleviated glucose-induced lipid droplet accumulation, whereas PLIN2 overexpression aggravated glucose-induced lipid droplet accumulation. The decrease in mitochondrial OCR in renal tubular cells induced by glucose treatment was alleviated after PLIN2 knockdown. However, overexpression of PLIN2 directly decreased the mitochondrial OCR. CONCLUSION: The PLIN2 expression in tubules predicts a decline in renal function in patients with DKD. The PLIN2 suppresses mitochondrial aerobic respiration and contributes to the accumulation of lipid droplets in renal tubular cells to promote the progression of DKD. [ABSTRACT FROM AUTHOR]

Aim To investigate the mechanism of perilipin 2 (PLIN2) increasing lipid accumulation in macrophages. Methods The experiments were divided into oxidized low density lipoprotein (ox-LDL) group, different PLIN2 expression groups, and different activity Rab18 groups, the levels of Rab18 and acyl-CoA long chain synthetase 3 (ACSL3) protein in high expression and silent expression of PLIN2 macrophages were measured, and the levels of PLIN2, Rab18, and ACSL3 protein expression in high expression PLIN2 macrophages with different activity Rab18 were measured. Western blot was used to detect protein expression levels, immunofluorescence was used to observe the localization of intracellular related proteins, and oil red O staining was used to observe intracellular lipid accumulation. Results The expression levels of Rab18 and ACSL3 in cells with high expression of PLIN2 were increased significantly (P<0. 05), and there was an intracellular phenomenon of co-localization of PLIN2 with Rab18 and ACSL3. The expression level of ACSL3 in high expression macrophages of PLIN2 after transfection with the Rab18 dominant mutant Q67L plasmid (Rab18 activity increased) was increased significantly (P<0. 05), and the number of intracellular lipid droplets was also increased significantly (P < 0. 05). Conclusion PLIN2 promotes macrophage lipid accumulation through Rab18 by up-regulating ACSL3. [ABSTRACT FROM AUTHOR]

Background: Perilipin 2 (PLIN2) is a protein that contributes to the formation and stability of lipid droplets. It has been associated with the development of several diseases, particularly related to glucose and lipid metabolism. In infants of diabetic mother (IDM), fetal hyperinsulinaemia leads to increased adipose tissue and macrosomia. The aim of this study was to investigate the relationship between PLIN2 levels and anthropometric measurements in the IDM and to investigate the relationship between PLIN2 levels and IGF-1, IGF-2 and leptin levels. Methods: The study group consisted of IDMs, while the control group consisted of infants born to non-diabetic mother, matched for gestational week and gender. Cord blood samples were collected from all patients to determine PLIN2, IGF-1, IGF-2 and leptin levels. Anthropometric measurements were taken for all patients at birth. Results: There were no differences between the groups in birth weight, birth length, head circumference and body mass index (BMI), but middle arm circumference, triceps, biceps, subscapular and suprailiac skinfold thickness were significantly higher in the IDM. While PLIN2, IGF-1, IGF-2 and leptin levels were similar between groups, there was a strong correlation between PLIN2 levels and IGF-2 and leptin levels. Conclusions: Even if IDMs were not macrosomic, the presence of high subcutaneous adipose tissue was not associated with PLIN2.

Cerebral ischemia/reperfusion (CI/R) usually causes neuroinflammation within the central nervous system, further prompting irreversible cerebral dysfunction. Perilipin 2 (Plin2), a lipid droplet protein, has been reported to exacerbate the pathological process in different diseases, including inflammatory responses. However, the role and mechanism of Plin2 in CI/R injury are unclear. In this study, the rat models of transient middle cerebral artery occlusion followed by reperfusion (tMCAO/R) were established to mimic I/R injury, and we found that Plin2 was highly expressed in the ischemic penumbra of tMCAO/R rats. The siRNA-mediated knockdown of Plin2 significantly decreased neurological deficit scores and reduced infarct areas in rats induced by I/R. Detailed investigation showed that Plin2 deficiency alleviated inflammation of tMCAO/R rats as evidenced by reduced secretion of proinflammatory factors and the blockade of NLR family pyrin domain containing 3 (NLRP3) inflammasome activation. In vitro experiments showed that Plin2 expression was upregulated in mouse microglia subjected to oxygen–glucose deprivation/reoxygenation (OGD/R). Plin2 knockdown inhibited OGD/R-induced microglia activation and the accumulation of inflammation-related factors. Taken together, this study demonstrates that lipid droplet protein Plin2 contributes to the pathologic process of CI/R damage by impacting inflammatory response and NLRP3 inflammasome activation. Thus, Plin2 may provide a new therapeutic direction for CI/R injury. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are intracellular organelles that are ubiquitous in many types of cells. The LD core consists of triacylglycerols (TGs) surrounded by a phospholipid monolayer and surface proteins such as perilipin 2 (PLIN2). Although TGs accumulate in the phospholipid bilayer of the endoplasmic reticulum (ER) and subsequently nascent LDs buds from ER, the mechanism by which LD proteins are transported to LD particles is not fully understood. Sar1 is a GTPase known as a regulator of coat protein complex Ⅱ (COPⅡ) vesicle budding, and its role in LD formation was investigated in this study. HuH7 human hepatoma cells were infected with adenoviral particles containing genes coding GFP fused with wild-type Sar1 (Sar1 WT) or a GTPase mutant form (Sar1 H79G). When HuH7 cells were treated with oleic acid, Sar1 WT formed a ring-like structure around the LDs. The transient expression of Sar1 did not significantly alter the levels of TG and PLIN2 in the cells. However, the localization of PLIN2 to the LDs decreased in the cells expressing Sar1 H79G. Furthermore, the effects of Sar1 on PLIN2 localization to the LDs were verified by the suppression of endogenous Sar1 using the short hairpin RNA technique. In conclusion, it was found that Sar1 has some roles in the intracellular distribution of PLIN2 to LDs in liver cells. [ABSTRACT FROM AUTHOR]

Ubiquitin C-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme that was originally found in neurons. We found that UCHL1 is highly expressed in slow oxidative skeletal muscles, but its functions remain to be fully understood. In this study, we observed that UCHL1 protein levels in skeletal muscle and C2C12 myotubes were downregulated by fasting or glucose starvation respectively. Skeletal muscle selective knockout (smKO) of UCHL1 resulted in a significant reduction of lipid content in skeletal muscle and improved glucose tolerance. UCHL1 smKO did not significantly change the levels of key proteins involved in oxidative metabolism such as SDHA, Akt, or PDH. Interestingly, while the levels of the major lipases and lipid transporters were unchanged, perilipin 2 was significantly downregulated in UCHL1 smKO muscle. Consistently, in C2C12 myotubes, UCHL1 siRNA knockdown also reduced perilipin 2 protein level. This data suggests that UCHL1 may stabilize perilipin 2 and thus lipid storage in skeletal muscle. [ABSTRACT FROM AUTHOR]

Ubiquitin C-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme that was originally found in neurons. We found that UCHL1 is highly expressed in slow oxidative skeletal muscles, but its functions remain to be fully understood. In this study, we observed that UCHL1 protein levels in skeletal muscle and C2C12 myotubes were downregulated by fasting or glucose starvation respectively. Skeletal muscle selective knockout (smKO) of UCHL1 resulted in a significant reduction of lipid content in skeletal muscle and improved glucose tolerance. UCHL1 smKO did not significantly change the levels of key proteins involved in oxidative metabolism such as SDHA, Akt, or PDH. Interestingly, while the levels of the major lipases and lipid transporters were unchanged, perilipin 2 was significantly downregulated in UCHL1 smKO muscle. Consistently, in C2C12 myotubes, UCHL1 siRNA knockdown also reduced perilipin 2 protein level. This data suggests that UCHL1 may stabilize perilipin 2 and thus lipid storage in skeletal muscle.

Abstract Background Hepatic lipidosis is increasing in incidence in the Western world, with cats being particularly sensitive. When cats stop eating and start utilizing their fat reserves, free fatty acids (FFAs) increase in blood, causing an accumulation of triacylglycerol (TAG) in the liver. Objective Identifying potential new drugs that can be used to treat hepatic lipidosis in cats using a feline hepatic organoid system. Animals Liver organoids obtained from 6 cats. Methods Eight different drugs were tested, and the 2 most promising were further studied using a quantitative TAG assay, lipid droplet staining, and qPCR. Results Both T863 (a diacylglycerol O‐acyltransferase 1 [DGAT1] inhibitor) and 5‐aminoimidazole‐4‐carboxamide 1‐β‐D‐ribofuranoside (AICAR; an adenosine monophosphate kinase activator) decreased TAG accumulation by 55% (P

Perilipin 2 (PLIN2) regulates intracellular lipid metabolism in macrophages, and thus, plays a role in atherosclerosis. Aim of the study was to evaluate whether PLIN2 dysregulation is involved in the onset of preclinical atherosclerosis in children with overweight/obesity and to explore dysregulation mechanisms. Sixty-three children with overweight/obesity and 21 normal weight children (controls) of the same age and sex were enrolled. Carotid intima media thickness (cIMT) was evaluated; mRNA expression of PLIN2 and proteasome subunits (PSMD3 , PSMC4) was determined by Real Time PCR, and protein expression of PLIN2, LAMP2A and Hsc70 by Western blot analysis; fluorimetric assay was used to measure proteasome chymotrypsin like activity. We performed transient LAMP2A downregulation by siRNA and quantified intracellular lipids in monocytes by Nile Red staining and flow cytometry analysis. PLIN2 protein levels were significantly higher in children with overweight/obesity and correlated with cIMT after adjusting for confounders. Accordingly, monocytes of children with overweight/obesity showed a higher intracellular amount of lipids compared with controls. mRNA expression of the regulatory subunits PSMC4 and PSMD3 and proteasome activity were lower in children with overweight/obesity, while expression of LAMP2A and Hsc70 proteins, which belong to the chaperone-mediated autophagy (CMA) pathway, was not different, suggesting that PLIN2 dysregulation in monocytes was due to an impairment of proteasome efficiency and was not CMA related. PLIN2 was overexpressed in monocytes of children with overweight/obesity and could contribute to the onset of arteropathy. Our data suggest that proteasome impairment could contribute to PLIN2 overexpression. [Display omitted] • Lipid droplets Plin2 protein is overexpressed in monocytes of children with obesity. • Early arterial injury in children with obesity is associated with increased Plin2 protein expression in monocytes. • Plin2 upregulation could depend on proteasome impairment in children with obesity. [ABSTRACT FROM AUTHOR]

Abstract Background Perilipin2 (Plin2) belongs to a family of five highly conserved proteins, known for their role in lipid storage. Recent data indicate that Plin2 has an important function in cell metabolism and is involved in several human pathologies, including liver steatosis and Type II diabetes. An association between Plin2 and lower muscle mass and strength has been found in elderly and inactive people, but its function in skeletal muscle is still unclear. Here, we addressed the role of Plin2 in adult muscle by gain and loss of function experiments. Methods By mean of in vivo Plin2 down‐regulation (shPlin2) and overexpression (overPlin2) in murine tibialis anterior muscle, we analysed the effects of Plin2 genetic manipulations on myofiber size and lipid composition. An analysis of skeletal muscle lipid composition was also performed in vastus lateralis samples from young and old patients undergoing hip surgery. Results We found that Plin2 down‐regulation was sufficient to induce a 30% increase of myofiber cross‐sectional area, independently of mTOR pathway. Alterations of lipid content and modulation of genes involved in lipid synthesis occurred in hypertrophic muscles. In particular, we showed a decrease of triglycerides, ceramides, and phosphatidylcoline:phosphatidylethanolamine ratio, a condition known to impact negatively on muscle function. Plin2 overexpression did not change fibre size; however, lipid composition was strongly affected in a way that is similar to that observed in human samples from old patients. Conclusions Altogether these data indicate that Plin2 is a critical mediator for the control of muscle mass, likely, but maybe not exclusively, through its critical role in the regulation of intracellular lipid content and composition.

Lipid droplets (LDs) are intracellular organelles that are ubiquitous in many types of cells. The LD core consists of triacylglycerols (TGs) surrounded by a phospholipid monolayer and surface proteins such as perilipin 2 (PLIN2). Although TGs accumulate in the phospholipid bilayer of the endoplasmic reticulum (ER) and subsequently nascent LDs buds from ER, the mechanism by which LD proteins are transported to LD particles is not fully understood. Sar1 is a GTPase known as a regulator of coat protein complex Ⅱ (COPⅡ) vesicle budding, and its role in LD formation was investigated in this study. HuH7 human hepatoma cells were infected with adenoviral particles containing genes coding GFP fused with wild-type Sar1 (Sar1 WT) or a GTPase mutant form (Sar1 H79G). When HuH7 cells were treated with oleic acid, Sar1 WT formed a ring-like structure around the LDs. The transient expression of Sar1 did not significantly alter the levels of TG and PLIN2 in the cells. However, the localization of PLIN2 to the LDs decreased in the cells expressing Sar1 H79G. Furthermore, the effects of Sar1 on PLIN2 localization to the LDs were verified by the suppression of endogenous Sar1 using the short hairpin RNA technique. In conclusion, it was found that Sar1 has some roles in the intracellular distribution of PLIN2 to LDs in liver cells.

Vaginal delivery (VD) and elective cesarean (CS) delivery modes may cause significant differences in maternal and fetal metabolism. In this study, we aimed to investigate changes in lipid metabolism, oxidative and apoptotic signaling pathways during VD and CS in maternal and cord blood and placenta tissue. The study included two groups of participants delivered via 90 CS and 90 VD. Maternal and cord blood samples were collected from the participants. In addition, placenta samples were also taken after delivery. Total oxidant (TOS), malondialdehyde (MDA), total antioxidant (TAS), glutathione (GSH), cleaved caspase 3 (CASP3) and perilipin 2 (PLIN2) levels were measured to determine oxidative stress, antioxidant levels and apoptosis status in the VD and CS groups. Besides, PLIN2 mRNA expressions in placental specimens were analyzed. We found no statistically significant difference in maternal age, body mass index, gestational age, birth weight and Apgar scores in both groups (P > 0.05). The increase in MDA, TOS, GSH and TAS levels was higher in the VD group compared to the CS group (P < 0.05). Similarly, PLIN2 levels and lipid profiles showed an increase in the VD group (P < 0.05 vs CS group). Likewise, PLIN2 expression enhanced in the VD group (P < 0.05 vs CS group). However, CASP3 activity reduced in maternal and cord blood in the VD group compared to the CS group. Our results support that the delivery mode may cause differences in lipid profile, oxidative and apoptotic status by affecting PLIN2 levels in both maternal and cord blood and placenta tissue. [ABSTRACT FROM AUTHOR]

Intramuscular triglycerides (IMTG) are a key substrate during prolonged exercise, but little is known about the rate of IMTG resynthesis in the postexercise period. We investigated the hypothesis that the distribution of the lipid droplet (LD)-associated perilipin (PLIN) proteins is linked to IMTG storage following exercise. Fourteen elite male triathletes (27 ± 1 yr, 66.5 ± 1.3 mL·kg−1·min−1) completed 4 h of moderate-intensity cycling. During the first 4 h of recovery, subjects received either carbohydrate or H2O, after which both groups received carbohydrate. Muscle biopsies collected pre- and postexercise and 4 and 24 h postexercise were analyzed using confocal immunofluorescence microscopy for fiber type-specific IMTG content and PLIN distribution with LDs. Exercise reduced IMTG content in type I fibers (−53%, P = 0.002), with no change in type IIa fibers. During the first 4 h of recovery, IMTG content increased in type I fibers (P = 0.014), but was not increased more after 24 h, where it was similar to baseline levels in both conditions. During recovery the number of LDs labeled with PLIN2 (70%), PLIN3 (63%), and PLIN5 (62%; all P < 0.05) all increased in type I fibers. Importantly, the increase in LDs labeled with PLIN proteins only occurred at 24 h postexercise. In conclusion, IMTG resynthesis occurs rapidly in type I fibers following prolonged exercise in highly trained individuals. Furthermore, increases in IMTG content following exercise preceded an increase in the number of LDs labeled with PLIN proteins. These data, therefore, suggest that the PLIN proteins do not play a key role in postexercise IMTG resynthesis. [ABSTRACT FROM AUTHOR]

Background: Hepatic lipidosis is increasing in incidence in the Western world, with cats being particularly sensitive. When cats stop eating and start utilizing their fat reserves, free fatty acids (FFAs) increase in blood, causing an accumulation of triacylglycerol (TAG) in the liver. Objective: Identifying potential new drugs that can be used to treat hepatic lipidosis in cats using a feline hepatic organoid system. Animals: Liver organoids obtained from 6 cats. Methods: Eight different drugs were tested, and the 2 most promising were further studied using a quantitative TAG assay, lipid droplet staining, and qPCR. Results: Both T863 (a diacylglycerol O‐acyltransferase 1 [DGAT1] inhibitor) and 5‐aminoimidazole‐4‐carboxamide 1‐β‐D‐ribofuranoside (AICAR; an adenosine monophosphate kinase activator) decreased TAG accumulation by 55% (P <.0001) and 46% (P =.0003), respectively. Gene expression of perilipin 2 (PLIN2) increased upon the addition of FFAs to the medium and decreased upon treatment with AICAR but not significantly after treatment with T863. Conclusions and Clinical Importance: Two potential drugs useful in the treatment of hepatic lipidosis in cats were identified. The drug T863 inhibits DGAT1, indicating that DGAT1 is the primary enzyme responsible for TAG synthesis from external fatty acids in cat organoids. The drug AICAR may act as a lipid‐lowering compound via decreasing PLIN2 mRNA. Liver organoids can be used as an in vitro tool for drug testing in a species‐specific system and provide the basis for further clinical testing of drugs to treat steatosis. [ABSTRACT FROM AUTHOR]

Fatty liver is a condition of excessive triglyceride accumulation in hepatocytes. Additionally, hepatocytes exhibit a high degree of fat droplet accumulation during excessive alcohol consumption and metabolic syndrome. However, the molecular mechanisms involved in fat droplet formation remain unknown. The present study used an in vitro fatty liver formation model of the human liver cancer cell line, HepG2, to comprehensively search for fat droplet formation-related genes, and which exhibit changes in expression during fat droplet formation. Microarray analysis with extracted total RNA determined the genes that are involved in fat droplet formation and their expression was confirmed using quantitative polymerase chain reaction following the culture of the HepG2 cells in culture medium containing 0, 50, 200 and 500 µM of oleic acid for 24 h. The results revealed 142 genes demonstrating increased expression levels by >2.0-fold with oleic acid treatment and 426 genes demonstrating decreased expression levels. Perilipin 2 ( PLIN2 ) was estimated as the gene most closely associated with fatty liver. Lipid droplet formation in the HepG2 cells induced by oleic acid led to the upregulation of PLIN2 in a concentration-dependent manner. On the whole, the findings of the present study indicate the involvement of genes in oleic acid-induced lipid droplet formation in HepG2 cells; PLIN2 in particular may play a crucial role in this process., Competing Interests: The authors declare that they have no competing interests., (Copyright: © Chiba et al.)

Milk fat globules (MFGs) are a remarkable example of nature's ingenuity. Human milk (HM) carries contains 3-5% fat, 0.8-0.9% protein, 6.9-7.2% carbohydrate calculated as lactose, and 0.2% mineral constituents. Most of these nutrients are carried in these MFGs, which are composed of an energy-rich triacylglycerol (TAG) core surrounded by a triple membrane structure. The membrane contains polar lipids, specialized proteins, glycoproteins, and cholesterol. Each of these bioactive components serves important nutritional, immunological, neurological, and digestive functions. These MFGs are designed to release energy rapidly in the upper gastrointestinal tract and then persist for some time in the gut lumen so that the protective bioactive molecules are conveyed to the colon. These properties may shape the microbial colonization and innate immune properties of the developing gastrointestinal tract. Milk fat globules in milk from humans and ruminants may resemble in structure but there are considerable differences in size, profile, composition, and specific constituents. There are possibilities to not only enhance the nutritional composition in a goal-oriented fashion to correct specific deficiencies in the infant but also to use these fat globules as a nutraceutical in infants who require specific treatments. To mention a few, there might be possibilities in enhancing neurodevelopment, in defense against gastrointestinal and respiratory tract infections, improving insulin sensitivity, treating chronic inflammation, and altering plasma lipids. This review provides an overview of the composition, structure, and biological activities of the various components of the MFGs. We have assimilated research findings from our own laboratory with an extensive review of the literature utilizing key terms in multiple databases including PubMed, EMBASE, and Science Direct. To avoid bias in the identification of studies, keywords were short-listed a priori from anecdotal experience and PubMed's Medical Subject Heading (MeSH) thesaurus., Competing Interests: Conflict of interest: Dr Akhil Maheshwari is associated as the Editor-in-Chief of this journal and this manuscript was subjected to this journal’s standard review procedures, with this peer review handled independently of the Editor-in-Chief and his research group.

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

Transcription factor 21 (Tcf21) is a basic helix-loop-helix transcription factor required for mesenchymal development in several organs. Others have demonstrated that Tcf21 is expressed in embryonic lung mesenchyme and that loss of Tcf21 results in a pulmonary hypoplasia phenotype. Although recent singlecell transcriptome analysis has described multiple mesenchymal cell types in the lung, few have characterized the Tcf21 expressing population. To explore the Tcf21 mesenchymal lineage, we traced Tcf21-expressing cells during embryogenesis and in the adult. Our results showed that Tcf21 progenitor cells at embryonic day (E)11.5 generated a subpopulation of fibroblasts and lipofibroblasts and a limited number of smooth muscle cells. After E15.5, Tcf21 progenitor cells exclusively become lipofibroblasts and interstitial fibroblasts. Lipid metabolism genes were highly expressed in perinatal and adult Tcf21 lineage cells. Overexpression of Tcf21 in primary neonatal lung fibroblasts led to increases in intracellular neutral lipids, suggesting a regulatory role for Tcf21 in lipofibroblast function. Collectively, our results reveal that Tcf21 expression after E15.5 delineates the lipofibroblast and a population of interstitial fibroblasts. The Tcf21 inducible Cre mouse line provides a novel method for identifying and manipulating the lipofibroblast. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the role of urine aquaporin 1 and perilipin 2 as biomarkers adjunct to renal mass biopsy in guiding the management of patients with small renal masses. Methods: Preoperative aquaporin 1 and perilipin 2 levels in 57 patients with small renal masses undergoing partial nephrectomy were analyzed and compared with postoperative tumor histology. An algorithm was created utilizing aquaporin 1 and perilipin 2 in conjunction with renal mass biopsy. Cut‐off values were implemented to maximize biomarker sensitivity and specificity. Renal mass biopsy utilization and intervention were then compared with rates in traditional renal mass biopsy algorithms. Results: All clear cell and papillary renal cell carcinomas were correctly identified and assigned to the treatment path. All benign lesions were correctly sorted to a confirmatory renal mass biopsy path. Two chromophobe masses did not have elevated aquaporin 1 and perilipin 2, and would require renal mass biopsy. Compared with protocols that call for all small renal masses to be biopsied, confirmatory renal mass biopsy could have been safely avoided in 74% of patients with elevated aquaporin 1 and perilipin 2. Compared with protocols that do not utilize renal mass biopsy, surgical intervention would have been avoided in 23% of patients with benign masses. Conclusions: Aquaporin 1 and perilipin 2 possess high sensitivity and specificity for detecting clear cell and papillary renal cell carcinoma. Use of these markers might compliment renal mass biopsy in the characterization of small renal masses. [ABSTRACT FROM AUTHOR]

Background: Perilipin2 (Plin2) belongs to a family of five highly conserved proteins, known for their role in lipid storage. Recent data indicate that Plin2 has an important function in cell metabolism and is involved in several human pathologies, including liver steatosis and Type II diabetes. An association between Plin2 and lower muscle mass and strength has been found in elderly and inactive people, but its function in skeletal muscle is still unclear. Here, we addressed the role of Plin2 in adult muscle by gain and loss of function experiments. Methods: By mean of in vivo Plin2 down‐regulation (shPlin2) and overexpression (overPlin2) in murine tibialis anterior muscle, we analysed the effects of Plin2 genetic manipulations on myofiber size and lipid composition. An analysis of skeletal muscle lipid composition was also performed in vastus lateralis samples from young and old patients undergoing hip surgery. Results: We found that Plin2 down‐regulation was sufficient to induce a 30% increase of myofiber cross‐sectional area, independently of mTOR pathway. Alterations of lipid content and modulation of genes involved in lipid synthesis occurred in hypertrophic muscles. In particular, we showed a decrease of triglycerides, ceramides, and phosphatidylcoline:phosphatidylethanolamine ratio, a condition known to impact negatively on muscle function. Plin2 overexpression did not change fibre size; however, lipid composition was strongly affected in a way that is similar to that observed in human samples from old patients. Conclusions: Altogether these data indicate that Plin2 is a critical mediator for the control of muscle mass, likely, but maybe not exclusively, through its critical role in the regulation of intracellular lipid content and composition. [ABSTRACT FROM AUTHOR]

Abstract Objective Intramyocellular lipid droplets (LD) and their coat proteins PLIN2 and PLIN5 are involved in lipolysis, with a putative role for PLIN5 in mitochondrial tethering. Reportedly, these proteins co-localize and cover the surface of the LD. To provide the spatial basis for understanding how these proteins possess their distinct roles, we examined the precise location of PLIN2 and PLIN5 and explored PLIN5 presence at LD-mitochondria contact sites using Stimulated emission depletion (STED) microscopy and correlative light-electron microscopy (CLEM) in human skeletal muscle sections. Methods LDs were stained by MDH together with combinations of mitochondrial proteins and PLINs. Subcellular distribution and co-localization of PLIN proteins and mitochondria was imaged by STED microscopy (Leica TCS SP8) and quantified using Pearson's correlation coefficients and intensity profile plots. CLEM was employed to examine the presence of PLIN5 on mitochondria-LD contact sites. Results Both PLIN2 and PLIN5 localized to the LD in a dot-like, juxtaposed fashion rather than colocalizing and covering the entire LD. Both STED and CLEM revealed a high fraction of PLIN5 at the LD-mitochondria interface, but not at mitochondrial cristae, as suggested previously. Conclusion Using two super-resolution imaging approaches, this is the first study to show that in sections of human skeletal muscle PLIN2 and PLIN5 localize to the LD at distinct sites, with abundance of PLIN5 at LD-mitochondria tethering sites. This novel spatial information uncovers that PLIN proteins do not serve as lipolytic barriers but rather are docking sites for proteins facilitating selective lipase access under a variety of lipolytic conditions. Graphical abstract Unlabelled Image Highlights • MDH can be used as a blue lipid droplet dye in tissue sections. • PLIN5 is located in the cytosol and at the lipid droplet mitochondrial interface. • Super-resolution microscopy reveals that PLIN5 is not at the mitochondrial cristae. • PLIN2 and PLIN5 localize to the lipid droplet at distinct locations rather than fully decorating the lipid droplet. [ABSTRACT FROM AUTHOR]

Steatosis is a frequent histological feature of hepatitis C virus (HCV) infection. Cohort studies of patients with chronic hepatitis C identified HCV genotype 3 (HCV GT3) as the prevalent steatotic genotype. Moreover, Huh- 7 cells over- expressing HCV GT3 core protein accumulate more triglyceride in larger lipid droplets than cells expressing core proteins of other HCV genotypes. However, little is known about the relationship of steatosis and HCV infection at the cellular level in vivo. In this study, we used highly sensitive multiplex in situ hybridization methodology together with lipid staining to investigate HCV- induced lipid droplet accumulation at the cellular level in liver biopsies. Consistent with previous reports, histological steatosis grades were significantly higher in GT3 compared to GT1 infected livers, but independent of viral load. Using nile red lipid stainings, we observed that the frequency of lipid droplet containing cells was similar in HCV GT1- and HCV GT3- infected livers. Lipid droplet formation preferentially occurred in HCV- infected cells irrespective of the genotype, but was also observed in noninfected cells. These findings demonstrate that the main difference between GT1- and GT3- induced steatosis is the size of lipid droplets, but not the number or relative distribution of lipid droplets in infected vs uninfected hepatocytes. [ABSTRACT FROM AUTHOR]

Key points The lipid droplet (LD)-associated perilipin (PLIN) proteins promote intramuscular triglyceride (IMTG) storage, although whether the abundance and association of the PLIN proteins with LDs is related to the diverse lipid storage in muscle between trained and sedentary individuals is unknown., We show that lipid infusion augments IMTG content in type I fibres of both trained and sedentary individuals. Most importantly, despite there being no change in PLIN protein content, lipid infusion did increase the number of LDs connected with PLIN proteins in trained individuals only., We conclude that trained individuals are able to redistribute the pre-existing pool of PLIN proteins to an expanded LD pool during lipid infusion and, via this adaptation, may support the storage of fatty acids in IMTG., Abstract Because the lipid droplet (LD)-associated perilipin (PLIN) proteins promote intramuscular triglyceride (IMTG) storage, we investigated the hypothesis that differential protein content of PLINs and their distribution with LDs may be linked to the diverse lipid storage in muscle between trained and sedentary individuals. Trained ( n = 11) and sedentary ( n = 10) subjects, matched for age, sex and body mass index, received either a 6 h lipid or glycerol infusion in the setting of a concurrent hyperinsulinaemic-euglycaemic clamp. Sequential muscle biopsies (0, 2 and 6 h) were analysed using confocal immunofluorescence microscopy for fibre type-specific IMTG content and PLIN associations with LDs. In both groups, lipid infusion increased IMTG content in type I fibres (trained: +62%, sedentary: +79%; P < 0.05) but did not affect PLIN protein content. At baseline, PLIN2 (+65%), PLIN3 (+105%) and PLIN5 (+53%; all P < 0.05) protein content was higher in trained compared to sedentary individuals. In trained individuals, lipid infusion increased the number of LDs associated with PLIN2 (+27%), PLIN3 (+73%) and PLIN5 (+40%; all P < 0.05) in type I fibres. By contrast, in sedentary individuals, lipid infusion only increased the number of LDs not associated with PLIN proteins. Acute free fatty acid elevation therefore induces a redistribution of PLIN proteins to an expanded LD pool in trained individuals only and this may be part of the mechanism that enables fatty acids to be stored in IMTG. [ABSTRACT FROM AUTHOR]

Purpose: Liposarcomas are the most common soft tissue sarcomas of adults. The identification of lipoblastic cells in soft tissue sarcomas is mandatory for the diagnosis of most subtypes of liposarcomas but may be difficult in conventional histology. The present study focuses on the expression and possible diagnostic impact of two PAT family proteins, perilipin 1/perilipin and perilipin 2/adipophilin in human liposarcomas. Methods: Eighty-seven cases of liposarcomas and 30 cases of non-lipomatous sarcomas were investigated immunohistochemically for perilipin 1 and 2 using entire tissue sections. Statistical analyses were performed using appropriate tests. Results: Most liposarcomas and non-lipomatous sarcomas displayed positivity for perilipin 2. In contrast, while more than two-thirds of liposarcomas presented perilipin 1 positivity, all non-lipomatous sarcomas studied were negative for this marker, with statistical significance ( p < 0.001). Perilipin 1 expression increased with adipocytic differentiation of liposarcoma subtypes showing statistical significance ( p < 0.001). Non-lipomatous sarcomas demonstrated variable expression levels of perilipin 2. The expression level of perilipin 2 appeared to be correlated with tumor cell degeneration, e.g., through hypoxia. Conclusions: Perilipin 2 is not well suitable for distinction between liposarcomas and non-lipomatous sarcomas. However, perilipin 1 appeared to be a highly specific marker for liposarcoma and adipocytic differentiation in sarcomas with intermediate sensitivity. [ABSTRACT FROM AUTHOR]

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins widely found in food contaminants, and its target organ is the liver. It poses a major food security and public health threat worldwide. However, the lipotoxicity mechanism of AFB1 exposure-induced liver injury remains unclear and requires further elucidation. Herein, we investigated the potential hepatic lipotoxicity of AFB1 exposure using in vitro and in vivo models to assess the public health hazards of high dietary AFB1 exposure. We demonstrated that low-dose of AFB1 (1.25 μM for 48 h, about one-fifth of the IC50 in HepG2 and HepaRG cells, IC50 are 5.995 μM and 5.266 μM, respectively) exposure significantly induced hepatic lipotoxicity, including abnormal lipid droplets (LDs) growth, mitochondria-LDs contacts increase, lipophagy disruption, and lipid accumulation. Mechanistically, we showed that AFB1 exposure promoted the mitochondrial p53 (mito-p53) and LDs-associated protein perilipin 2 (PLIN2) interaction-mediated mitochondria-LDs contacts, resulting in lipid accumulation in hepatocytes. Mito-p53-targeted inhibition, knockdown of PLIN2, and rapamycin application efficiently promoted the lysosome-dependent lipophagy and alleviated the hepatic lipotoxicity and liver injury induced by AFB1 exposure. Overall, our study found that mito-p53 and PLIN2 interaction mediates three organelles-mitochondria, LDs, and lysosomal networks to regulate lipid homeostasis in AFB1 exposure-induced hepatotoxicity, revealing how this unique trio of organelles works together and provides a novel insight into the targeted intervention in inter-organelle lipid sensing and trafficking for alleviating hazardous materials-induced hepatic lipotoxicity. [Display omitted] • Aflatoxin B1 (AFB1) exposure-induced inter-organelle lipid trafficking mediates hepatic lipotoxicity. • Mito-p53 and perilipin 2 interaction mediates mitochondria and lipid droplets (LDs) communication. • AFB1 exposure promotes LDs growth via inhibiting lysosome-associated lipophagy. • Targeted intervention on mito-p53 alleviates AFB1-induced hepatic lipotoxicity and liver injury. [ABSTRACT FROM AUTHOR]

Perilipin 2 (Plin2), a protein associated with the metabolism of intracellular lipid droplets (LDs), has long been considered only for its role in lipid storage. However, the manipulation of its expression affects the severity of a variety of metabolic and age-related diseases, such as fatty liver, insulin resistance and type 2 diabetes (T2D), cardiovascular disease, atherosclerosis, sarcopenia, and cancer, suggesting that this protein may play a role in these pathological conditions. In particular, its downregulation in mice prevents or mitigates some of the above mentioned diseases. Conversely, in humans high levels of Plin2 are present in sarcopenia, hepatic steatosis, atherosclerosis, and some types of cancer. We propose that inhibition of Plin2 might be a strategy to counteract several metabolic and age-related diseases. [ABSTRACT FROM AUTHOR]

Hepatic inflammation and fibrosis are key elements in the pathogenesis of nonalcoholic steatohepatitis (NASH), a progressive liver disease initiated by excess hepatic lipid accumulation. Lipid droplet protein Perilipin 2 (Plin2) alleviates dietary-induced hepatic steatosis when globally ablated; however, its role in the progression of NASH remains unknown. To investigate this further, we challenged Plin2 liver-specific knockout mice (designated L-KO) and their respective wild-type (WT) controls with a methionine-choline-deficient (MCD) diet for 15 days to induce a NASH phenotype of increased hepatic triglyceride levels through impaired phosphatidylcholine (PC) synthesis and very-low-density lipoprotein (VLDL) secretion. Results on liver weights, body weights, fat tissue mass, and histology in WT and L-KO mice fed the MCD diet revealed signs of hepatic steatosis, fibrosis, and inflammation; however, these effects were blunted in L-KO mice. In addition, levels of PC and VLDL were unchanged, and hepatic steatosis was reduced in L-KO mice fed the MCD diet, due in part to an increase in remodeling of PE to PC via the enzyme phosphatidylethanolamine N-methyltransferase (PEMT). These mice also exhibited decreased hepatic expression of proinflammatory markers cyclooxygenase 2, IL-6, TNF-α, IL-1β, and reduced expression of endoplasmic reticulum (ER) stress proteins C/EBP homologous protein and cleaved caspase-1. Taken together, these results suggest that Plin2 liver-specific ablation alleviates diet-induced hepatic steatosis and inflammation via a PEMT-mediated mechanism that involves compensatory changes in proteins involved in phospholipid remodeling, inflammation, and ER stress that work to alleviate diet-induced NASH. Overall, these findings support a role for Plin2 as a target for NASH therapy. [ABSTRACT FROM AUTHOR]