Key-genes regulating the liposecretion process of mature adipocytes

Obesity-induced tissue alterations resist weight loss: A mechanistic review

Interventions aimed at weight control often have limited effectiveness in combating obesity. This review explores how obesity-induced dysfunction in white (WAT) and brown adipose tissue (BAT), skeletal muscle, and the brain blunt weight loss, leading to retention of stored fat. In obesity, increased adrenergic stimulation and inflammation downregulate β-adrenoreceptors and impair catecholaminergic signalling in adipocytes. This disrupts adrenergic-mediated lipolysis, diminishing lipid oxidation in both white and brown adipocytes, lowering thermogenesis and blunting fat loss. Emerging evidence suggests that WAT fibrosis is associated with worse weight loss outcomes; indeed, limiting collagen and laminin-α4 deposition mitigates WAT accumulation, enhances browning, and protects against high-fat-diet-induced obesity. Obesity compromises mitochondrial oxidative capacity and lipid oxidation in skeletal muscle, impairing its ability to switch between glucose and lipid metabolism in response to varying nutrient levels and exercise. This dysfunctional phenotype in muscle is exacerbated in the presence of obesity-associated sarcopenia. Additionally, obesity suppresses sarcolipin-induced sarcoplasmic reticulum calcium ATPase (SERCA) activation, resulting in reduced oxidative capacity, diminished energy expenditure, and increased adiposity. In the hypothalamus, obesity and overnutrition impair insulin and leptin signalling. This blunts central satiety signals, favouring a shift in energy balance toward energy conservation and body fat retention. Moreover, both obese animals and humans demonstrate impaired dopaminergic signalling and diminished responses to nutrient intake in the striatum, which tend to persist after weight loss. This may result in enduring inclinations toward overeating and a sedentary lifestyle. Collectively, the tissue adaptations described pose significant challenges to effectively achieving and sustaining weight loss in obesity.

Overexpression of GPX2 gene regulates the development of porcine preadipocytes and skeletal muscle cells through MAPK signaling pathway

Glutathione peroxidase 2 (GPX2) is a selenium-dependent enzyme and protects cells against oxidative damage. Recently, GPX2 has been identified as a candidate gene for backfat and feed efficiency in pigs. However, it is unclear whether GPX2 regulates the development of porcine preadipocytes and skeletal muscle cells. In this study, adenoviral gene transfer was used to overexpress GPX2. Our findings suggest that overexpression of GPX2 gene inhibited proliferation of porcine preadipocytes. And the process is accompanied by the reduction of the p-p38. GPX2 inhibited adipogenic differentiation and promoted lipid degradation, while ERK1/2 was reduced and p-p38 was increased. Proliferation of porcine skeletal muscle cells was induced after GPX2 overexpression, was accompanied by activation in JNK, ERK1/2, and p-p38. Overexpression methods confirmed that GPX2 has a promoting function in myoblastic differentiation. ERK1/2 pathway was activated and p38 was suppressed during the process. This study lays a foundation for the functional study of GPX2 and provides theoretical support for promoting subcutaneous fat reduction and muscle growth.

Muscle-UCP3 in the regulation of energy metabolism

Uncoupling protein-3 (UCP3) is a mitochondria-regulatory protein with potential energy- homeostatic functions. This study explores the role of UCP3 in the regulation of muscle- and energy metabolism. UCP3 is critical for tuning substrate utilization, favoring lipid oxidation, particularly in conditions of high-fat availability. While UCP3 is non-essential for lipid oxidation during energy excess, it proves vital during fasting, indicating an energy-homeostatic trait. Preliminary evidence indicates UCP3' promotion of glucose uptake and oxidation, at least in conditions of high glucose/low fat availability. However, the dynamics of how fats and glucose differentially influence UCP3 remain undefined. UCP3 exhibits inducible proton transport and uncoupling activity, operating in a dual manner: a resting state with no/low activity and an activated state in the presence of activators. Uncoupling may enhance thermogenesis in specific conditions and in the presence of activators such as fatty acids, thyroid hormones, and catecholamines. This energy-dissipative activity adapts to varying energy availability, balancing energy dissipation with fatty acid oxidation to optimize whole-body energy homeostasis: fasting triggers UCP3 upregulation, enhancing lipid utilization while suppressing uncoupling. Additionally, UCP3 upregulation induces glucose and lipid disposal from the bloodstream and decreases tri-/diglyceride storage in muscle. This process improves mitochondrial functionality and insulin signaling, leading to enhanced systemicgluco-metabolic balance and protection from metabolic conditions. Reviewed evidence suggests that UCP3 plays a crucial role in adapting the system to changing energy conditions. However, the precise role of UCP3 in regulating metabolism requires further elucidation.

Polymorphisms of PLIN1 and MOGAT1 genes and their association with feed efficiency in Hu sheep

Feed cost accounts for a high proportion of sheep production, and improving sheep's utilization of feed will reduce production costs and improve economic benefits. The purpose of this study was to investigate the expression characteristics of PLIN1 and MOGAT1 genes and the relationship between their polymorphisms and feed efficiency traits in Hu sheep, and to find molecular Genetic marker that can be used in breeding. The expression levels of PLIN1 and MOGAT1 genes in various tissues were determined using quantitative real-time PCR (qRT-PCR). The results showed that PLIN1 and MOGAT1 genes were widely expressed in heart, liver, spleen, lungs, kidneys, rumen, duodenum, muscle, lymph, and tail fat. The PLIN1 gene had the highest expression level in in the tail fat compared to the other nine tissues. The expression levels of MOGAT1 gene in liver, tail fat, lung and heart was significantly higher than in kidney, muscle and lymph. The expression level of MOGAT1 was lowest in muscle compared to the other tissues (heart, liver, spleen, lung, rumen and tail fat). We recorded the body weight (BW80 and BW180) and feed intake (FI) information of 985 male Hu sheep at 80 and 180 days of age, and calculated the daily average feed intake (ADFI), average daily gain (ADG), and feed conversion rate (FCR) from 80 to 180 days of age. Two intronic mutations, g.18517910 A > G and g.224856118 G > C, were identified in PLIN1 and MOGAT1 genes by PCR amplification and Sanger sequencing. MassARRAY ® SNP detection technology was used to genotype the DNA of 985 Hu sheep and analyze its association with feed efficiency traits. The results showed that the SNP g.18517910 A > G was significantly associated with BW80, BW180, FI, ADFI and FCR (P < 0.05), while SNP g.2248561118 G > C was significantly associated with FCR (P < 0.05). Meanwhile, significant differences were also observed in different combinations of genotypes (P < 0.05). Therefore, these two polymorphic loci can serve as candidate molecular markers for improving feed utilization efficiency in Hu sheep.

Transcriptomic analysis of the longissimus thoracis muscle in pigs has identified molecular regulatory patterns associated with meat quality

Meat quality is a critical aspect of pig breeding. In addition to genetics, meat quality is also influenced by nutritional and environmental factors. In this study, three pig breeds, Shengxianhua, Jiaxing, and Qinglian Black (SXH, JXB and QLB), were used as experimental animals. Transcriptional analysis was performed on the longissimus thoracis (LT) muscle to investigate variations in intramuscular fat (IMF), inosine monophosphate (IMP), amino acids, and muscle fiber morphology across different breeds. Ingenuity canonical pathway analysis (IPA) identified biological processes and key driver genes related to metabolism and muscle development. Additionally, weighted gene co-expression network analysis (WGCNA) revealed gene modules associated with IMP. KEGG and GO analyses identified specific biological processes and signaling pathways related to IMP, including the Oxidative Phosphorylation pathway and rRNA Metabolic Processes. These findings provide novel insights into the molecular regulatory mechanisms underlying meat quality variations among pig breeds.

Fine particulate matter induces adipose tissue expansion and weight gain: Pathophysiology

Dysregulations in energy balance represent a major driver of obesity. Recent evidence suggests that environmental factors also play a pivotal role in inducing weight gain. Chronic exposure to fine particulate matter (PM_2.5 ) is associated with white adipose tissue (WAT) expansion in animals and higher rates of obesity in humans. This review discusses metabolic adaptions in central and peripheral tissues that promote energy storage and WAT accumulation in PM_2.5 -exposed animals and humans. Chronic PM_2.5 exposure produces inflammation and leptin resistance in the hypothalamus, decreasing energy expenditure and increasing food intake. PM_2.5 promotes the conversion of brown adipocytes toward the white phenotype, resulting in decreased energy expenditure. The development of inflammation in WAT can stimulate adipogenesis and hampers catecholamine-induced lipolysis. PM_2.5 exposure affects the thyroid, reducing the release of thyroxine and tetraiodothyronine. In addition, PM_2.5 exposure compromises skeletal muscle fitness by inhibiting Nitric oxide (NO)-dependent microvessel dilation and impairing mitochondrial oxidative capacity, with negative effects on energy expenditure. This evidence suggests that pathological alterations in the hypothalamus, brown adipose tissue, WAT, thyroid, and skeletal muscle can alter energy homeostasis, increasing lipid storage and weight gain in PM_2.5 -exposed animals and humans. Further studies will enrich this pathophysiological model.

SPRY4 promotes adipogenic differentiation of human mesenchymal stem cells through the MEK-ERK1/2 signaling pathway

Obesity is a chronic metabolic disorder characterized by the accumulation of excess fat in the body. Preventing and controlling obesity by inhibiting the adipogenic differentiation of mesenchymal stem cells (MSCs) and thereby avoiding the increase of white adipose tissue is safe and effective. Recent studies have demonstrated that Sprouty proteins (SPRYs) are involved in cell differentiation and related diseases. However, the role and mechanism of SPRY4 in MSC adipogenic differentiation remain to be explored. Here, we found that SPRY4 positively correlates with the adipogenic differentiation of human adipose-derived MSCs (hAMSCs). Via gain- and loss-of-function experiments, we demonstrated that SPRY4 promotes hAMSC adipogenesis both in vitro and in vivo. Mechanistically, SPRY4 functioned by activating the MEK-ERK1/2 pathway. Our findings provide new insights into a critical role for SPRY4 as a regulator of adipogenic differentiation, which may illuminate the underlying mechanisms of obesity and suggest the potential of SPRY4 as a novel treatment option.

Transcriptome analysis revealed potential genes involved in thermogenesis in muscle tissue in cold-exposed lambs

Cold tolerance is an important trait for sheep raised at high altitudes. Muscle tissue, comprising 30–40% of the total body mass, produces heat during cold exposure. However, little is known about the genetic mechanisms of this tissue and its role in thermogenesis in lambs. We examined genes in skeletal muscle tissue in a cold-adapted sheep breed, Altay, and a cold-intolerant sheep breed, Hu, when exposed to low air temperature. Three ewe-lambs of each breed were maintained at −5°C and three ewe-lambs of each breed were maintained at 20°C. After cold exposure for 25 days, the longissimus dorsi of each lamb was collected, and transcriptome profiles were sequenced and analyzed. The results of RNA-seq showed that the average reads among the four groups were 11.0 Gbase. The genome mapping rate averaged 88.1% and the gene mapping rate averaged 82.5%. The analysis of differentially expressed genes (DEGs) indicated that the peroxisome proliferator-activated receptors (PPAR), cAMP, and calcium signaling pathways and muscle contraction in muscle tissue were linked to thermogenesis in cold-exposed lambs. Furthermore, PCK1 (phosphoenolpyruvate carboxykinase1) increased glyceroneogenesis in cold-exposed Altay lambs, and APOC3 (apolipoprotein C3), LPL (lipoprotein lipase), and FABP4 (fatty acid binding protein 4, adipocyte) were involved in the intake and transport of free fatty acids. In Hu sheep, cAMP biosynthesis from ATP hydrolysis was regulated by ADCY10 (adenylate cyclase) and ADORA2a (adenosine A2a receptor). Skeletal muscle contraction was regulated by MYL2 (myosin light chain 2). In conclusion, cold exposure altered the expression level of genes involved in heat production in muscle tissue. Some potential mechanisms were revealed, including calcium ion transport in the calcium signaling pathway, fatty acid metabolism in the PPAR signaling pathway, and cAMP biosynthesis in the cAMP signaling pathway. This study implied that skeletal muscle plays an important role in thermoregulation in lambs.

Phenotypical Conversions of Dermal Adipocytes as Pathophysiological Steps in Inflammatory Cutaneous Disorders

Adipocytes from the superficial layer of subcutaneous adipose tissue undergo cyclic de- and re-differentiation, which can significantly influence the development of skin inflammation under different cutaneous conditions. This inflammation can be connected with local loading of the reticular dermis with lipids released due to de-differentiation of adipocytes during the catagen phase of the hair follicle cycle. Alternatively, the inflammation parallels a widespread release of cathelicidin, which typically takes place in the anagen phase (especially in the presence of pathogens). Additionally, trans-differentiation of dermal adipocytes into myofibroblasts, which can occur under some pathological conditions, can be responsible for the development of collateral scarring in acne. Here, we provide an overview of such cellular conversions in the skin and discuss their possible involvement in the pathophysiology of inflammatory skin conditions, such as acne and psoriasis.

Analysis of genome-wide DNA methylation patterns in obesity

Obesity is a chronic and complex psychosomatic disease that is becoming increasingly prevalent worldwide. This study aimed to analyze whole methylation profiles to uncover the epigenetic mechanisms associated with obesity. DNA methylation profiles in blood samples from patients with obesity and normal controls were studied using the Illumina 850 K methylation microarray. The diagnostic value of the differentially methylated genes was determined using receiver operating characteristic (ROC) analysis. The expression of selected candidate genes was verified using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and pyrosequencing. A total of 9,371 significantly differentially methylated sites (7,974 hypermethylated sites and 1,397 hypomethylated sites) were identified in 4,571 genes. A difference in the distribution of differentially methylated sites (hypermethylated and hypomethylated) in both gene structures and CpG islands was observed. A total of 114 key differentially methylated sites were identified in the CpG islands. ROC results indicated that Inhibin Subunit Beta B (INHBB), Homeobox A9 (HOXA9), Troponin T3 (TNNT3), Cyclic adenosine monophosphate (cAMP)-responsive element binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) and Zinc finger and BTB domain-containing 7 B (ZBTB7B) could discriminate patients with obesity from normal controls. RT-qPCR results of CRTC1 and ZBTB7B were consistent with our methylation profile results. The pyrosequencing results showed that the methylation levels of CRTC1 CpG sites (CpG1 and CpG2-cg11660071) and INHBB CpG sites (CpG2) were significantly changed in patients with obesity compared with normal controls, which was consistent with our DNA methylation profile results. Our study provides new insights into the pathological mechanism of obesity.

Perilipin2 is an Earlier Marker Than Perilipin1 for Identifying Adipocyte Regeneration in Fat Grafts

BACKGROUND

Both perilipin1 (Plin1) and perilipin2 (Plin2) play a crucial role in regulating lipid droplet (LD) formation in fat cells. Plin2 is expressed early in the adipocyte differentiation process but is replaced by Plin1 after cell maturation. In free fat grafts, only a small number of adipocytes remain alive or are replaced by newly regenerated fat cells. It is known that Plin1-positive adipocytes participate in regeneration, but the characteristics of Plin2 expression during this process are still poorly understood.

OBJECTIVES

The aim of this study was to investigate whether Plin2 is a more precise early marker for detecting adipocyte regeneration in fat grafts than Plin1.

METHODS

Autologous fat tissue (120 mg) harvested from inguinal fat pads was injected under the scalps of C57 mice. Samples were explanted at days 3, 7, 15, and 30 after transplantation. Changes in sample size and weight were evaluated. Hematoxylin-eosin staining, real-time polymerase chain reaction, and immunostaining of Plin1 and Plin2 expression were performed.

RESULTS

Plin1, but not Plin2, expression was detected in the freshly harvested fat, but the latter was activated after grafting. Newly regenerated Plin2-positive adipocytes increased from day 3 to day 7 and then declined, whereas the number of Plin1-positive fat cells decreased first and began to increase after day 15. The expression levels of Plin1 and Plin2 mRNA demonstrated similar changes over time. At day 30, adipocytes lost Plin2 expression and were positive for Plin1 again.

CONCLUSIONS

Our experiments showed convincing evidence that Plin2 expression could be used to detect early adipocyte regeneration in grafted fat tissue.

Oxysterol-binding protein-like 2 contributes to the developmental progression of preadipocytes by binding to β-catenin

Oxysterol-binding protein-like 2 (OSBPL2), also known as oxysterol-binding protein-related protein (ORP) 2, is a member of lipid transfer protein well-known for its role in regulating cholesterol homeostasis. A recent study reported that OSBPL2/ORP2 localizes to lipid droplets (LDs) and is associated with energy metabolism and obesity. However, the function of OSBPL2/ORP2 in adipocyte differentiation is poorly understood. Here, we report that OSBPL2/ORP2 contributes to the developmental progression of preadipocytes. We found that OSBPL2/ORP2 binds to β-catenin, a key effector in the Wnt signaling pathway that inhibits adipogenesis. This complex plays a role in regulating the protein level of β-catenin only in preadipocytes, not in mature adipocytes. Our data further indicated that OSBPL2/ORP2 mediates the transport of β-catenin into the nucleus and thus regulates target genes related to adipocyte differentiation. Deletion of OSBPL2/ORP2 markedly reduces β-catenin both in the cytoplasm and in the nucleus, promotes preadipocytes maturation, and ultimately leads to obesity-related characteristics. Altogether, we provide novel insight into the function of OSBPL2/ORP2 in the developmental progression of preadipocytes and suggest OSBPL2/ORP2 may be a potential therapeutic target for the treatment of obesity-related diseases.

Partial-Body Cryostimulation Increases Resting Energy Expenditure in Lean and Obese Women

Cryostimulation is currently seen as a potential adjuvant strategy to tackle obesity and dysmetabolism by triggering cold-induced thermogenesis. Although suggestive, the underlying mechanisms are still poorly elucidated. We tested whether single or repeated applications of partial-body cryostimulation (PBC) could influence resting energy expenditure (REE) in exposed individuals. Fifteen middle-aged obese and sixteen control lean women (body mass index 31 ± 1.6 kg/m² and 22 ± 1.7 kg/m²) underwent a daily PBC (−130 °C × 150 s) for five consecutive days. Resting energy metabolism (REE) was assessed by indirect calorimetry pre- and post-PBC on day 1 and day 5. As concerns REE, the linear mixed model revealed that REE changes were explained by session and time (F_1,29 = 5.58; p = 0.02; ƞ_p² = 0.16) independent of the group (F_1,29 = 2.9; p = 0.09; ƞ_p² = 0.09). REE pre-PBC increased from day 1 to day 5 either in leans (by 8.2%, from 1538 ± 111 to 1665 ± 106 kcal/day) or in obese women (by 5.5%, from 1610 ± 110 to 1698 ± 142 vs kcal/day). Respiratory quotient was significantly affected by the time (F_1,29 = 51.61; p < 0.000001, ƞ_p² = 0.64), as it increased from pre- to post-PBC, suggesting a shift in substrate oxidation. According to these preliminary data, cold-induced thermogenesis could be explored as a strategy to elevate REE in obese subjects. Longitudinal studies could test whether chronic PBC effects may entail favorable metabolic adaptations.

Transcriptional regulation of adipogenic marker genes for the improvement of intramuscular fat in Qinchuan beef cattle

The intramuscular fat content plays a crucial role in meat quality traits. Increasing the degree of adipogenesis in beef cattle leads to an increase in the content of intramuscular fat. Adipogenesis a complex biochemical process which is under firm genetic control. Over the last three decades, the Qinchuan beef cattle have been extensively studied for the improvement of meat production and quality traits. In this study, we reviewed the literature regarding adipogenesis and intramuscular fat deposition. Then, we summarized the research conducted on the transcriptional regulation of key adipogenic marker genes, and also reviewed the roles of adipogenic marker genes in adipogenesis of Qinchuan beef cattle. This review will elaborate our understanding regarding transcriptional regulation which is a vital physiological process regulated by a cascade of transcription factors (TFs), key target marker genes, and regulatory proteins. This synergistic action of TFs and target genes ensures the accurate and diverse transmission of the genetic information for the accomplishment of central physiological processes. This information will provide an insight into the transcriptional regulation of the adipogenic marker genes and its role in bovine adipogenesis for the breed improvement programs especially for the trait of intramuscular fat deposition.

Long noncoding RNA repressor of adipogenesis negatively regulates the adipogenic differentiation of mesenchymal stem cells through the hnRNP A1-PTX3-ERK axis

BACKGROUND

Mesenchymal stem cells (MSCs) are pluripotent stem cells that can differentiate via osteogenesis and adipogenesis. The mechanism underlying MSC lineage commitment still remains incompletely elucidated. Understanding the regulatory mechanism of MSC differentiation will help researchers induce MSCs toward specific lineages for clinical use. In this research, we intended to figure out the long noncoding RNA (lncRNA) that plays a central role in MSC fate determination and explore its application value in tissue engineering.

METHODS

The expression pattern of lncRNAs during MSC osteogenesis/adipogenesis was detected by microarray and qRT-PCR. Lentivirus and siRNAs were constructed to regulate the expression of lncRNA repressor of adipogenesis (ROA). MSC osteogenesis/adipogenesis was evaluated by western blot and alizarin red/oil red staining. An adipokine array was used to select the paracrine/autocrine factor PTX3, followed by RNA interference or recombinant human protein stimulation to confirm its function. The activation of signaling pathways was also detected by western blot, and a small molecule inhibitor, SCH772984, was used to inhibit the activation of the ERK pathway. The interaction between ROA and hnRNP A1 was detected by RNA pull-down and RIP assays. Luciferase reporter and chromatin immunoprecipitation assays were used to confirm the binding of hnRNP A1 to the PTX3 promotor. Additionally, an in vivo adipogenesis experiment was conducted to evaluate the regulatory value of ROA in tissue engineering.

RESULTS

In this study, we demonstrated that MSC adipogenesis is regulated by lncRNA ROA both in vitro and in vivo. Mechanistically, ROA inhibits MSC adipogenesis by downregulating the expression of the key autocrine/paracrine factor PTX3 and the downstream ERK pathway. This downregulation was achieved through transcription inhibition by impeding hnRNP A1 from binding to the promoter of PTX3.

CONCLUSIONS

ROA negatively regulates MSC adipogenesis through the hnRNP A1-PTX3-ERK axis. ROA may be an effective target for modulating MSCs in tissue engineering.

Overexpression of PLIN1 Promotes Lipid Metabolism in Bovine Adipocytes

Perilipin 1 (PLIN1) is a protein encoded by the PLIN1 gene in eukaryotes. PLIN1 is a member of the PAT protein family, a family of proteins related to lipid droplet (LD) surface proteins. PLIN1 phosphorylation plays a vital role during fat metabolism of adipose tissue lipolysis and fat storage in adipocytes. However, to further explore the regulation of the PLIN1 gene on the proliferation, differentiation and lipid metabolism of bovine adipocytes. In this study, the mRNA expression of PLIN1, at day six, was the highest during bovine adipocyte differentiation. Moreover, PLIN1 can promote the proliferation and differentiation of preadipocytes in cattle. On the sixth day, after transfection with, and overexpression of, the PLIN1 gene in bovine preadipocytes via adenovirus, cell samples were collected, and transcriptome sequencing was performed. A total of 1923 differentially expressed genes were detected. Through GO and KEGG pathway analysis, the differentially expressed genes were established to be mainly enriched in the AMPK, Wnt, and PPAR signaling pathways related to fat proliferation and differentiation. In conclusion, at the transcriptional level, PLIN1 plays an important role in regulating fat proliferation and metabolism. Additionally, the sequencing results screened new differentially expressed genes related to fat metabolism, providing theoretical support for molecular breeding of Qinchuan beef cattle.

Polymorphism of the PLIN1 gene and its association with body measures and ultrasound carcass traits in Qinchuan beef cattle

The PLIN1 gene produces a phosphorylated protein wrapped in lipid droplets in adipocytes. This phosphorylation assists the mobilization of fat into adipose tissue. The purpose of the experiment was to study the polymorphism of the PLIN1 gene and its relationship with the body and carcass characteristics of Qinchuan cattle to find molecular genetic markers that can be used for breeding. The expression level of the PLIN1 gene was determined in various tissues by qRT-PCR. The results showed that the highest level of PLN1 expression was found in subcutaneous fat, followed by the heart and longissimus muscle, and the lowest level was found in the kidney. Five SNP loci of the PLIN1 gene were identified in 510 Qinchuan cattle, including g.3580T>C (SNP1), g.3898G>A (SNP2), g.8333G>A (SNP3), g.10517T>C (SNP4), and g.10538G>T (SNP5). The results show that SNP1, SNP2, SNP3, and SNP4 were moderately polymorphic (0.25 < PIC < 0.5), while SNP5 was minimally polymorphic (PIC < 0.25). SNP2, SNP3, and SNP5 were within Hardy-Weinberg equilibrium (P > 0.05), but SNP1 and SNP4 were not (P < 0.05). Correlation analysis showed that the five SNPs of the PLIN1 gene were correlated with back-fat depth, intramuscular fat, and chest depth of Qinchuan cattle. The double haplotype H2H4 in Qinchuan beef was associated with body and carcass traits. We conclude that variants mapped within PLIN1 can be used in marker-assisted selection for carcass quality and body traits in breed improvement programs for Qinchuan cattle.

Characterization and visualization of the liposecretion process taking place during ceiling culture of human mature adipocytes

OBJECTIVE

To investigate and further characterize the process of mature adipocyte dedifferentiation. Our hypothesis was that dedifferentiation does not involve mitosis but rather a phenomenon of liposecretion.

METHODS

Mature adipocytes were isolated by collagenase digestion of human adipose tissue samples. Ceiling cultures were established using our six-well plate model. Cells were treated with cytosine β-d-arabinofuranoside (AraC) or vincristine (VCR), two agents blocking cell division, and were compared with vehicle. Liposecretion events were visualized by time-lapse microscopy, with and without AraC in adipocytes transducted with a baculovirus. Microscopic analyses were performed after labeling phosphorylated histone 3 and cyclin B1 in ceiling cultures.

RESULTS

Treatment with AraC almost entirely prevented the formation of fibroblasts up to 12 days of ceiling culture. Similar results were obtained with VCR. The antimitotic effectiveness of the treatment was confirmed in fibroblast cultures from the adipose tissue stromal-vascular fraction by proliferation assays and colony-forming unit experiments. Using time-lapse microscopy, we visualized liposecretion events in which a large lipid droplet was rapidly secreted from isolated mature adipocytes. The same phenomenon was observed with AraC. This was observed in conjunction with histone 3 phosphorylation and cyclin B1 segregation to the nucleus.

CONCLUSION

Our results support the notion that dedifferentiation involves rapid secretion of the lipid droplet by the adipocytes with concomitant generation of fibroblast-like cells that subsequently proliferate to generate the dedifferentiated adipocyte population during ceiling culture. The presence of mitotic markers suggests that this process involves cell cycle progression, although cell division does not occur.