Surface tension-driven sorting of human perilipins on lipid droplets.

Perilipins (PLINs), the most abundant proteins on lipid droplets (LDs), display similar domain organization including amphipathic helices (AH). However, the five human PLINs bind different LDs, suggesting different modes of interaction. We established a minimal system whereby artificial LDs covered with defined polar lipids were transiently deformed to promote surface tension. Binding of purified PLIN3 and PLIN4 AH was strongly facilitated by tension but was poorly sensitive to phospholipid composition and to the presence of diacylglycerol. Accordingly, LD coverage by PLIN3 increased as phospholipid coverage decreased. In contrast, PLIN1 bound readily to LDs fully covered by phospholipids; PLIN2 showed an intermediate behavior between PLIN1 and PLIN3. In human adipocytes, PLIN3/4 were found in a soluble pool and relocated to LDs upon stimulation of fast triglyceride synthesis, whereas PLIN1 and PLIN2 localized to pre-existing LDs, consistent with the large difference in LD avidity observed in vitro. We conclude that the PLIN repertoire is adapted to handling LDs with different surface properties.

Ozenoxacin suppresses sebum production by inhibiting mTORC1 activation in differentiated hamster sebocytes.

Acne vulgaris is a complex condition involving factors that affect the pilosebaceous unit. A primary manifestation of acne pathology is the development of comedones, often linked to the overproduction of sebum resulting from 5α-dihydrotestosterone (5α-DHT) and insulin activity. Ozenoxacin is a topical quinolone that exhibits potent antibacterial activity against Cutibacterium acnes (C. acnes). It is commonly used to treat acne associated with this bacterium; however, its effect on sebum production within the sebaceous glands remains unclear. In this study, the effects of ozenoxacin on sebum production were examined using insulin- and 5α-DHT-differentiated hamster sebocytes. Ozenoxacin showed a dose-dependent inhibition of lipid droplet formation and triacylglycerol (TG) production, which is a major component of sebum. In addition, it suppressed the expression of diacylglycerol acyltransferase 1, stearoyl-CoA desaturase-1, and perilipin-1 mRNA, all important factors involved in sebum synthesis, in a dose-dependent manner. Moreover, ozenoxacin decreased phosphorylated 40S ribosomal protein S6 levels downstream of the mechanistic/mammalian target of rapamycin complex 1 (mTORC1), without altering the phosphorylation of Akt, an upstream regulator of mTORC1, in both insulin- and 5α-DHT-treated hamster sebocytes. Interestingly, nadifloxacin, but not clindamycin, exhibited a similar suppression of sebum production, albeit with lesser potency compared with ozenoxacin. Furthermore, a topical application of a 2% ozenoxacin-containing lotion to the auricle skin of hamsters did not affect the size of the sebaceous glands or epidermal thickness. Notably, it decreased the amount of TG on the skin surface. The results provide novel insights into the sebum-inhibitory properties of ozenoxacin, indicating its potential efficacy in controlling microbial growth and regulating sebum production for acne management.

Inhibitory Activity of Sparassis latifolia on the Lipid Accumulation through Suppressing Adipogenesis and Activating Lipolysis in 3T3-L1 Cells.

Sparassis latifolia (SL) has been reported to exhibit anti-obesity effects in high-fat diet animal models, yet research into its mechanisms of action remains limited. Therefore, this study aimed to elucidate the mechanisms behind the anti-obesity activity of SL's 30% ethanol extract (SL30E) using 3T3-L1 cells in an in vitro setting. SL30E effectively mitigated the accumulation of lipid droplets and triacylglycerol. SL30E downregulated PPARγ and CEBPα protein levels. The diminishment of PPARγ and C/EBPα, facilitated by SL30E, was impeded by the knockdown of ß-catenin using ß-catenin-specific siRNA. Furthermore, SL30E was observed to increase the protein levels of ATGL and p-HSL, while it concurrently decreased the protein levels of perilipin-1. SL30E downregulated p62/SQSTM1 protein level and upregulated LC3-II protein level. Moreover, SL30E was demonstrated to elevate the protein levels of p-AMPK and PGC-1α. The results indicate that SL30E inhibits lipid accumulation by suppressing adipogenesis and inducing lipolysis, lipophagy, and thermogenesis in 3T3-L1 cells. These observations provide potential insights into the mechanisms underlying the anti-obesity effects of SL, contributing valuable information to the existing body of knowledge.

Clinical pathological significance and biological function of PLIN1 in hepatocellular carcinoma: bioinformatics analysis and in vitro experiments.

BACKGROUND & AIMS: Perilipin 1 (PLIN1) is an essential lipid droplet surface protein that participates in cell life activities by regulating energy balance and lipid metabolism. PLIN1 has been shown to be closely related to the development of numerous tumor types. The purpose of this work was to elucidate the clinicopathologic significance of PLIN1 in hepatocellular carcinoma (HCC), as well as its impact on the biological functions of HCC cells, and to investigate the underlying mechanisms involved. METHODS: Public high-throughput RNA microarray and RNA sequencing data were collected to examine PLIN1 levels and clinical significance in patients with HCC. Immunohistochemistry (IHC) and real-time quantitative reverse transcription polymerase chain reaction (RT‒qPCR) were conducted to assess the expression levels and the clinicopathological relevance of PLIN1 in HCC. Then, SK and Huh7 cells were transfected with a lentivirus overexpressing PLIN1. CCK8 assay, wound healing assay, transwell assay, and flow cytometric analysis were conducted to explore the effects of PLIN1 overexpression on HCC cell proliferation, migration, invasion, and cell cycle distribution. Ultimately, Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to investigate the underlying mechanisms of PLIN1 in HCC progression based on HCC differentially expressed genes and PLIN1 co-expressed genes. RESULTS: PLIN1 was markedly downregulated in HCC tissues, which correlated with a noticeably worse prognosis for HCC patients. Additionally, PLIN1 overexpression inhibited the proliferation, migration, and invasion of SK and Huh7 cells in vitro, as well as arresting the HCC cell cycle at the G0/G1 phase. More significantly, energy conversion-related biological processes, lipid metabolism, and cell cycle signalling pathways were the three most enriched molecular mechanisms. CONCLUSION: The present study revealed that PLIN1 downregulation is associated with poor prognosis in HCC patients and accelerated HCC progression by promoting cellular proliferation, migration, and metastasis, as well as the mechanisms underlying the regulation of lipid metabolism-related pathways in HCC.

Perilipin2 depletion causes lipid droplet enlargement in the ovarian corpus luteum in mice.

Lipid droplets (LDs) are endoplasmic reticulum-derived organelles that store neutral lipids (mostly triglycerides and cholesterol esters) within a phospholipid monolayer and appear in most eukaryotic cells. Perilipins (PLINs, comprising PLIN1-5) are abundant LD-associated proteins with highly variable expression levels among tissues. Although PLINs are expressed in the mammalian ovaries, little is known about their subcellular localization and physiological functions. In this study, we investigated the localization of PLIN1-3 and their relationship with LD synthesis using mCherry-HPos reporter mice, thereby enabling the visualization of LD biogenesis in vivo. PLIN2 and PLIN3 were localized as puncta in granulosa cells with low levels of LD synthesis in developing follicles. This localization pattern was quite different from that of PLIN1, which was mainly localized in the theca and interstitial cells with high levels of LD synthesis. In the corpus luteum, where LD synthesis is highly induced, PLIN2 and PLIN3 are abundant in the particulate structures, whereas PLIN1 is poorly distributed. We also generated global Plin2-deficient mice using the CRSPR/Cas9 system and demonstrated that the lack of PLIN2 did not alter the distribution of PLIN1 and PLIN3 but unexpectedly induced LD enlargement in the corpus luteum. Collectively, our results suggest that the localization of PLIN1-3 is spatiotemporally regulated and that PLIN2 deficiency influences LD mobilization in the corpus luteum within the ovaries.

Hypertriglyceridemia Results From an Impaired Catabolism of Triglyceride-Rich Lipoproteins in PLIN1-Related Lipodystrophy.

BACKGROUND: Pathogenic variants in PLIN1-encoding PLIN1 (perilipin-1) are responsible for an autosomal dominant form of familial partial lipodystrophy (FPL) associated with severe insulin resistance, hepatic steatosis, and important hypertriglyceridemia. This study aims to decipher the mechanisms of hypertriglyceridemia associated with PLIN1-related FPL. METHODS: We performed an in vivo lipoprotein kinetic study in 6 affected patients compared with 13 healthy controls and 8 patients with type 2 diabetes. Glucose and lipid parameters, including plasma LPL (lipoprotein lipase) mass, were measured. LPL mRNA and protein expression were evaluated in abdominal subcutaneous adipose tissue from patients with 5 PLIN1-mutated FPL and 3 controls. RESULTS: Patients with PLIN1-mutated FPL presented with decreased fat mass, insulin resistance, and diabetes (glycated hemoglobin A1c, 6.68±0.70% versus 7.48±1.63% in patients with type 2 diabetes; mean±SD; P=0.27). Their plasma triglycerides were higher (5.96±3.08 mmol/L) than in controls (0.76±0.27 mmol/L; P<0.0001) and patients with type 2 diabetes (2.94±1.46 mmol/L, P=0.006). Compared with controls, patients with PLIN1-related FPL had a significant reduction of the indirect fractional catabolic rate of VLDL (very-low-density lipoprotein)-apoB100 toward IDL (intermediate-density lipoprotein)/LDL (low-density lipoprotein; 1.79±1.38 versus 5.34±2.45 pool/d; P=0.003) and the indirect fractional catabolic rate of IDL-apoB100 toward LDL (2.14±1.44 versus 7.51±4.07 pool/d; P=0.005). VLDL-apoB100 production was not different between patients with PLIN1-related FPL and controls. Compared with patients with type 2 diabetes, patients with PLIN1-related FPL also showed a significant reduction of the catabolism of both VLDL-apoB100 (P=0.031) and IDL-apoB100 (P=0.031). Plasma LPL mass was significantly lower in patients with PLIN1-related FPL than in controls (21.03±10.08 versus 55.76±13.10 ng/mL; P<0.0001), although the LPL protein expression in adipose tissue was similar. VLDL-apoB100 and IDL-apoB100 indirect fractional catabolic rates were negatively correlated with plasma triglycerides and positively correlated with LPL mass. CONCLUSIONS: We show that hypertriglyceridemia associated with PLIN1-related FPL results from a marked decrease in the catabolism of triglyceride-rich lipoproteins (VLDL and IDL). This could be due to a pronounced reduction in LPL availability, related to the decreased adipose tissue mass.

CTRP9 Promotes Brown Adipose Tissue Lipolysis in Mice Fed a High-Fat Diet.

BACKGROUND: This study aimed to elucidate the molecular mechanism through which C1q/tumor necrosis factor (TNF)-related protein 9 (CTRP9) acts in the formation and differentiation of brown adipose tissue (BAT). METHODS: Adenovirus particles encoding CTRP9 and green fluorescent protein were inoculated into the scapula of C57BL/6J mice and fed a high-fat diet for 8 weeks; the body weight, lipid droplet morphology, glucose tolerance, insulin tolerance, and protein expression levels were analyzed. In addition, CTRP9 adenovirus was transfected into brown preadipocytes, and differentiation was induced to identify the effect of CTRP9 overexpression on adipocyte differentiation. RESULTS: CTRP9 overexpression significantly increased the weight gain of mice. Additionally, the CTRP9 overexpression group exhibited significantly increased adipose tissue weight and glucose clearance rates and decreased insulin sensitivity and serum triglyceride levels compared to the control group. Furthermore, CTRP9 overexpression significantly upregulated the adipose triglyceride lipase (ATGL) and perilipin 1 protein expression levels in BAT. The cell experiment results confirmed that CTRP9 overexpression significantly inhibited the adipogenesis of brown adipocytes as evidenced by the downregulation of uncoupling protein 1, beta-3 adrenergic receptor, ATGL, and hormone-sensitive lipase mRNA levels and the significant suppression of uncoupling protein 1, ATGL, and perilipin 1 protein levels in brown adipocytes. CONCLUSIONS: The finding of this study demonstrated that CTRP9 promotes lipolysis by upregulating ATGL expression in vivo and inhibits the differentiation of brown preadipocytes in vitro.

Increased FGF-21 Improves Ectopic Lipid Deposition in the Liver and Skeletal Muscle.

Obesity can lead to excessive lipid accumulation in non-adipose tissues, such as the liver and skeletal muscles, leading to ectopic lipid deposition and damaging target organ function through lipotoxicity. FGF-21 is a key factor in regulating lipid metabolism, so we aim to explore whether FGF-21 is involved in improving ectopic lipid deposition. We observed the characteristics of ectopic lipid deposition in the liver and skeletal muscles of obesity-resistant mice, detected the expression of FGF-21 and perilipin, and found that obesity-resistant mice showed a decrease in ectopic lipid deposition in the liver and skeletal muscles and increased expression of FGF-21. After inhibiting the expression of FGF-21, a more severe lipid deposition in liver cells and skeletal muscle cells was found. The results indicate that inhibiting FGF-21 can exacerbate ectopic lipid deposition via regulating lipid droplet synthesis and decomposition, as well as free fatty acid translocation and oxidation. In conclusion, FGF-21 is involved in improving ectopic lipid deposition caused by obesity in the liver and skeletal muscles.

Perilipin1 inhibits Nosema bombycis proliferation by promoting Domeless- and Hop-mediated JAK-STAT pathway activation in Bombyx mori.

Lipid droplets (LDs) are dynamic organelles that participate in the regulation of lipid metabolism and cellular homeostasis inside of cells. LD-associated proteins, also known as perilipins (PLINs), are a family of proteins found on the surface of LDs that regulate lipid metabolism, immunity, and other functions. In silkworms, pébrine disease caused by infection by the microsporidian Nosema bombycis (Nb) is a severe threat to the sericultural industry. Although we found that Nb relies on lipids from silkworms to facilitate its proliferation, the relationship between PLINs and Nb proliferation remains unknown. Here, we found Nb infection caused the accumulation of LDs in the fat bodies of silkworm larvae. The characterized perilipin1 gene (plin1) promotes the accumulation of intracellular LDs and is involved in Nb proliferation. plin1 is similar to perilipin1 in humans and is conserved in all insects. The expression of plin1 was mostly enriched in the fat body rather than in other tissues. Knockdown of plin1 enhanced Nb proliferation, whereas overexpression of plin1 inhibited its proliferation. Furthermore, we confirmed that plin1 increased the expression of the Domeless and Hop in the JAK-STAT immune pathway and inhibited Nb proliferation. Taken together, our current findings demonstrate that plin1 inhibits Nb proliferation by promoting the JAK-STAT pathway through increased expression of Domeless and Hop. This study provides new insights into the complicated connections among microsporidia pathogens, LD surface proteins, and insect immunity.IMPORTANCELipid droplets (LDs) are lipid storage sites in cells and are present in almost all animals. Many studies have found that LDs may play a role in host resistance to pathogens and are closely related to innate immunity. The present study found that a surface protein of insect lipid droplets could not only regulate the morphological changes of lipid droplets but also inhibit the proliferation of a microsporidian pathogen Nosema bombycis (Nb) by activating the JAK-STAT signaling pathway. This is the first discovery of the relationship between microsporidian pathogen and insect lipid surface protein perilipin and insect immunity.

Yeast perilipin Pet10p/Pln1p interacts with Erg6p in ergosterol metabolism.

Lipid droplets (LD) are highly dynamic organelles specialized for the regulation of energy storage and cellular homeostasis. LD consist of a neutral lipid core surrounded by a phospholipid monolayer membrane with embedded proteins, most of which are involved in lipid homeostasis. In this study, we focused on one of the major LD proteins, sterol C24-methyltransferase, encoded by ERG6. We found that the absence of Erg6p resulted in an increased accumulation of yeast perilipin Pet10p in LD, while the disruption of PET10 was accompanied by Erg6p LD over-accumulation. An observed reciprocal enrichment of Erg6p and Pet10p in pet10Δ and erg6Δ mutants in LD, respectively, was related to specific functional changes in the LD and was not due to regulation on the expression level. The involvement of Pet10p in neutral lipid homeostasis was observed in experiments that focused on the dynamics of neutral lipid mobilization as time-dependent changes in the triacylglycerols (TAG) and steryl esters (SE) content. We found that the kinetics of SE hydrolysis was reduced in erg6Δ cells and the mobilization of SE was completely lost in mutants that lacked both Erg6p and Pet10p. In addition, we observed that decreased levels of SE in erg6Δpet10Δ was linked to an overexpression of steryl ester hydrolase Yeh1p. Lipid analysis of erg6Δpet10Δ showed that PET10 deletion altered the composition of ergosterol intermediates which had accumulated in erg6Δ. In conclusion, yeast perilipin Pet10p functionally interacts with Erg6p during the metabolism of ergosterol.

Perilipin membrane integration determines lipid droplet heterogeneity in differentiating adipocytes.

The storage of fat within lipid droplets (LDs) of adipocytes is critical for whole-body health. Acute fatty acid (FA) uptake by differentiating adipocytes leads to the formation of at least two LD classes marked by distinct perilipins (PLINs). How this LD heterogeneity arises is an important yet unresolved cell biological problem. Here, we show that an unconventional integral membrane segment (iMS) targets the adipocyte specific LD surface factor PLIN1 to the endoplasmic reticulum (ER) and facilitates high-affinity binding to the first LD class. The other PLINs remain largely excluded from these LDs until FA influx recruits them to a second LD population. Preventing ER targeting turns PLIN1 into a soluble, cytoplasmic LD protein, reduces its LD affinity, and switches its LD class specificity. Conversely, moving the iMS to PLIN2 leads to ER insertion and formation of a separate LD class. Our results shed light on how differences in organelle targeting and disparities in lipid affinity of LD surface factors contribute to formation of LD heterogeneity.

Correlational analysis of PLIN1 with inflammation in diabetic foot ulcer wounds.

BACKGROUND: The persistent presence of inflammation is a recognized pathogenic mechanisms of diabetic foot ulcers (DFUs). We aimed to investigate the expression of PLIN1 in tissues from DFU patients and assess its potential association with inflammation-induced damage. METHODS: We performed transcriptome sequencing and correlation analysis of the foot skin from patients with or without DFUs. Additionally, we examined the correlation between PLIN1 and related inflammatory indicators by analyzing PLIN1 expression in tissue and serum samples and through high-glucose stimulation of keratinocytes (HaCaT cells). RESULTS: PLIN1 is upregulated in the tissue and serum from DFU patients. Additionally, PLIN1 shows a positive correlation with leukocytes, neutrophils, monocytes, C-reactive protein, and procalcitonin in the serum, as well as IL-1ß and TNF-α in the tissues. Experiments with Cells demonstrated that reduced expression of PLIN1 leads to significantly decreased expression of iNOS, IL-1ß, IL-6, IL-18, and TNF-α. PLIN1 may mediate wound inflammatory damage through the NF-κB signaling pathway. CONCLUSION: Our findings suggest that PLIN1 mediates the inflammatory damage in DFU, offering new prospects for the treatment of DFU.

Perilipin 1: a systematic review on its functions on lipid metabolism and atherosclerosis in mice and humans.

The function of perilipin 1 in human metabolism was recently highlighted by the description of PLIN1 variants associated with various pathologies. These include severe familial partial lipodystrophy and early onset acute coronary syndrome. Additionally, certain variants have been reported to have a protective effect on cardiovascular diseases. The role of this protein remains controversial in mice and variant interpretation in humans is still conflicting. This literature review has two primary objectives (i) to clarify the function of the PLIN1 gene in lipid metabolism and atherosclerosis by examining functional studies performed in cells (adipocytes) and mice and (ii) to understand the impact of PLIN1 variants identified in humans based on the variant's location within the protein and the type of variant (missense or frameshift). To achieve these objectives, we conducted an extensive analysis of the relevant literature on perilipin 1, its function in cellular models and mice, and the consequences of its mutations in humans. We also utilized bioinformatics tools and consulted the Human Genetics Cardiovascular Disease Knowledge Portal to enhance the pathogenicity assessment of PLIN1 missense variants.

ApoL6 associates with lipid droplets and disrupts Perilipin1-HSL interaction to inhibit lipolysis.

Adipose tissue stores triacylglycerol (TAG) in lipid droplets (LD) and release fatty acids upon lipolysis during energy shortage. We identify ApoL6 as a LD-associated protein mainly found in adipose tissue, specifically in adipocytes. ApoL6 expression is low during fasting but induced upon feeding. ApoL6 knockdown results in smaller LD with lower TAG content in adipocytes, while ApoL6 overexpression causes larger LD with higher TAG content. We show that the ApoL6 affects adipocytes through inhibition of lipolysis. While ApoL6, Perilipin 1 (Plin1), and HSL can form a complex on LD, C-terminal ApoL6 directly interacts with N-terminal Plin1 to prevent Plin1 binding to HSL, to inhibit lipolysis. Thus, ApoL6 ablation decreases white adipose tissue mass, protecting mice from diet-induced obesity, while ApoL6 overexpression in adipose brings obesity and insulin resistance, making ApoL6 a potential future target against obesity and diabetes.

Benzyl isothiocyanate inhibits TNFα-driven lipolysis via suppression of the ERK/PKA/HSL signaling pathway in 3T3-L1 adipocytes.

Tumor necrosis factor α (TNFα), an inflammatory cytokine, induces lipolysis and increases circulating concentrations of free fatty acids. In addition, TNFα is the first adipokine produced by adipose tissue in obesity, contributing to obesity-associated metabolic disease. Given that benzyl isothiocyanate (BITC) is a well-known anti-inflammatory agent, we hypothesized that BITC can ameliorate TNFα-induced lipolysis and investigated the working mechanisms involved. We first challenged 3T3-L1 adipocytes with TNFα to induce lipolysis, which was confirmed by increased glycerol release, decreased protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and perilipin 1 (PLIN1), and increased phosphorylation of ERK, protein kinase A (PKA), and hormone-sensitive lipase (HSL). However, inhibition of ERK or PKA significantly attenuated the lipolytic activity of TNFα. Meanwhile, pretreatment with BITC significantly ameliorated the lipolytic activity of TNFα; the TNFα-induced phosphorylation of ERK, PKA, and HSL; the TNFα-induced ubiquitination of PPARγ; the TNFα-induced decrease in PPARγ nuclear protein binding to PPAR response element; and the TNFα-induced decrease in PLIN1 protein expression. Our results indicate that BITC ameliorates TNFα-induced lipolysis by inhibiting the ERK/PKA/HSL signaling pathway, preventing PPARγ proteasomal degradation, and maintaining PLIN1 protein expression.

Molecular mechanisms of perilipin protein function in lipid droplet metabolism.

Perilipins are abundant lipid droplet (LD) proteins present in all metazoans and also in Amoebozoa and fungi. Humans express five perilipins, which share a similar domain organization: an amino-terminal PAT domain and an 11-mer repeat region, which can fold into amphipathic helices that interact with LDs, followed by a structured carboxy-terminal domain. Variations of this organization that arose during vertebrate evolution allow for functional specialization between perilipins in relation to the metabolic needs of different tissues. We discuss how different features of perilipins influence their interaction with LDs and their cellular targeting. PLIN1 and PLIN5 play a direct role in lipolysis by regulating the recruitment of lipases to LDs and LD interaction with mitochondria. Other perilipins, particularly PLIN2, appear to protect LDs from lipolysis, but the molecular mechanism is not clear. PLIN4 stands out with its long repetitive region, whereas PLIN3 is most widely expressed and is used as a nascent LD marker. Finally, we discuss the genetic variability in perilipins in connection with metabolic disease, prominent for PLIN1 and PLIN4, underlying the importance of understanding the molecular function of perilipins.

RS2289487 variation in PERILIPIN gene is a predictor of weight loss and protection against impaired glucose metabolism after a meal-replacement diet in postmenopausal obese females.

OBJECTIVE: The PERILIPIN1 (PLIN1) gene encodes an adipocyte-associated protein that modulates weight. The objective was to evaluate the role of the rs2289487 genetic variant of the PLIN1 gene on weight loss and glucose metabolism secondary to a partial meal replacement (pMR) hypocaloric diet. PATIENTS AND METHODS: We conducted an interventional study in 111 postmenopausal obese females with body mass index (BMI) > 35 kg/m2. The subjects received two intakes per day of a normocaloric hyperproteic formula for 12 weeks. RESULTS: After the pMR diet, body weight, (BMI), fat mass, waist circumference, fasting insulin levels and HOMA-IR decreased in both genotype groups. The improvements in these parameters were higher in C allele carriers than in subjects with TT genotype. The percentage of patients who achieved 7.5% weight loss was higher in the C carriers (57.4% vs. 27.6%), (adjusted Odds Ratio 2.14, 95% CI = 1.33-9.40; p = 0.02). The decrease in the percentage of diabetes mellitus or impaired fasting glucose decrease was statistically significant in C allele carriers (30.2% vs. 18.9%; p = 0.01) (OR 0.54, 95% CI = 0.22-0.78; p = 0.02). CONCLUSIONS: The C allele of rs2289487 predicts the magnitude of weight loss resulting from a pMR diet. These adiposity improvements produce a better improvement in insulin resistance and the percentage of impaired glucose metabolism.

Binding of perilipin 3 to membranes containing diacylglycerol is mediated by conserved residues within its PAT domain.

Perilipins (PLINs) constitute an evolutionarily conserved family of proteins that specifically associate with the surface of lipid droplets (LDs). These proteins function in LD biogenesis and lipolysis and help to stabilize the surface of LDs. PLINs are typically composed of three different protein domains. They share an N-terminal PAT domain of unknown structure and function, a central region containing 11-mer repeats that form amphipathic helices, and a C-terminal domain that adopts a 4-helix bundle structure. How exactly these three distinct domains contribute to PLIN function remains to be determined. Here, we show that the N-terminal PAT domain of PLIN3 binds diacylglycerol (DAG), the precursor to triacylglycerol, a major storage lipid of LDs. PLIN3 and its PAT domain alone bind liposomes with micromolar affinity and PLIN3 binds artificial LDs containing low concentrations of DAG with nanomolar affinity. The PAT domain of PLIN3 is predicted to adopt an amphipathic triangular shaped structure. In silico ligand docking indicates that DAG binds to one of the highly curved regions within this domain. A conserved aspartic acid residue in the PAT domain, E86, is predicted to interact with DAG, and we found that its substitution abrogates high affinity binding of DAG as well as DAG-stimulated association with liposome and artificial LDs. These results indicate that the PAT domain of PLINs harbor specific lipid-binding properties that are important for targeting these proteins to the surface of LDs and to ER membrane domains enriched in DAG to promote LD formation.

Perilipin 1 Deficiency Prompts Lipolysis in Lipid Droplets and Aggravates the Pathogenesis of Persistent Immune Activation in Drosophila.

Lipid droplets (LDs) are highly dynamic intracellular organelles, which are involved in lots of biological processes. However, the dynamic morphogenesis and functions of intracellular LDs during persistent innate immune responses remain obscure. In this study, we induce long-term systemic immune activation in Drosophila through genetic manipulation. Then, the dynamic pattern of LDs is traced in the Drosophila fat body. We find that deficiency of Plin1, a key regulator of LDs' reconfiguration, blocks LDs minimization at the initial stage of immune hyperactivation but enhances LDs breakdown at the later stage of sustained immune activation via recruiting the lipase Brummer (Bmm, homologous to human ATGL). The high wasting in LDs shortens the lifespan of flies with high-energy-cost immune hyperactivation. Therefore, these results suggest a critical function of LDs during long-term immune activation and provide a potential treatment for the resolution of persistent inflammation.

Perilipin-1 immunostaining improves semi-automated digital quantitation of bone marrow adipocytes in histological bone sections.

Bone marrow adipocytes (BMAds) are not just passive fillers inside the bone marrow compartment but respond to various metabolic changes. Assessment of those responses requires evaluation of the number of BMAds and their morphology for which laborious and error-prone manual histological analysis remains the most widely used method. Here, we report an alternative image analysis strategy to semi-automatically quantitate and analyse the morphology of BMAds in histological bone sections. Decalcified, formalin-fixed paraffin-embedded histological sections of long bones of Sprague-Dawley rats were stained with either haematoxylin and eosin (HE) or by immunofluorescent staining for adipocyte-specific protein perilipin-1 (PLIN1). ImageJ-based commands were constructed to detect BMAds sized 200 µm2 or larger from standardized 1 mm2 analysis regions by either classifying the background colour (HE) or the positive and circular PLIN1 fluorescent signal. Semi-automated quantitation strongly correlated with independent, single-blinded manual counts regardless of the staining method (HE-based: r=0.85, p<0.001; PLIN1 based: r=0.95, p<0.001). The detection error was higher in HE-stained sections than in PLIN1-stained sections (14% versus 5%, respectively; p<0.001), which was due to false-positive detections of unstained adipocyte-like circular structures. In our dataset, the total adiposity area from standardised ROIs in PLIN-1-stained sections correlated with that in whole-bone sections (r=0.60, p=0.02).