Molecular and Cellular Bases of Lipodystrophy Syndromes

Lipodystrophy syndromes are rare diseases originating from a generalized or partial loss of adipose tissue. Adipose tissue dysfunction results from heterogeneous genetic or acquired causes, but leads to similar metabolic complications with insulin resistance, diabetes, hypertriglyceridemia, nonalcoholic fatty liver disease, dysfunctions of the gonadotropic axis and endocrine defects of adipose tissue with leptin and adiponectin deficiency. Diagnosis, based on clinical and metabolic investigations, and on genetic analyses, is of major importance to adapt medical care and genetic counseling. Molecular and cellular bases of these syndromes involve, among others, altered adipocyte differentiation, structure and/or regulation of the adipocyte lipid droplet, and/or premature cellular senescence. Lipodystrophy syndromes frequently present as systemic diseases with multi-tissue involvement. After an update on the main molecular bases and clinical forms of lipodystrophy, we will focus on topics that have recently emerged in the field. We will discuss the links between lipodystrophy and premature ageing and/or immuno-inflammatory aggressions of adipose tissue, as well as the relationships between lipomatosis and lipodystrophy. Finally, the indications of substitutive therapy with metreleptin, an analog of leptin, which is approved in Europe and USA, will be discussed.

miR-214-5p Regulating Differentiation of Intramuscular Preadipocytes in Goats via Targeting KLF12

Intramuscular fat (i.m.) is an adipose tissue that is deposited between muscle bundles. An important type of post-transcriptional regulatory factor, miRNAs, has been observed as an important regulator that can regulate gene expression and cell differentiation through specific binding with target genes, which is the pivotal way determining intramuscular fat deposition. Thus, this study intends to use RT-PCR, cell culture, liposome transfection, real-time fluorescent quantitative PCR (qPCR), dual luciferase reporter systems, and other biological methods clarifying the possible mechanisms on goat intramuscular preadipocyte differentiation that is regulated by miR-214-5p. Ultimately, our results showed that the expression level of miR-214-5p peaked at 48 h after the goat intramuscular preadipocytes were induced for adipogenesis. Furthermore, after inhibition of the expression of miR-214-5p, the accumulation of lipid droplets and adipocyte differentiation in goat intramuscular adipocytes were promoted by the way of up-regulation of the expression level of lipoprotein lipase (LPL) (p < 0.05) and peroxisome proliferator-activated receptor gamma (PPARγ) (p < 0.01) but inhibited the expression of hormone-sensitive lipase (HSL) (p < 0.01). Subsequently, our study confirmed that Krüppel-like factor 12 (KLF12) was the target gene of miR-214-5p. Inhibition of the expression of KLF12 promoted adipocyte differentiation and lipid accumulation by upregulation of the expression of LPL and CCAAT/enhancer binding protein (C/EBPα) (p < 0.01). Overall, these results indicated that miR-214-5p and its target gene KLF12 were negative regulators in progression of goat preadipocyte differentiation. Our research results provided an experimental basis for finally revealing the mechanism of miR-214-5p in adipocytes.

Integrated Study of Transcriptome-wide m6A Methylome Reveals Novel Insights Into the Character and Function of m6A Methylation During Yak Adipocyte Differentiation

Yak (Bos grunniens) is considered an iconic symbol of Tibet and high altitude, but they suffer from malnutrition during the cold season that challenges the metabolism of energy. Adipocytes perform a crucial role in maintaining the energy balance, and adipocyte differentiation is a complex process involving multiple changes in the expression of genes. N6-methyladenosine (m6A) plays a dynamic role in post-transcription gene expression regulation as the most widespread mRNA modification of the higher eukaryotes. However, currently there is no research existing on the m6A transcriptome-wide map of bovine animals and their potential biological functions in adipocyte differentiation. Therefore, we performed methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) to determine the distinctions in m6A methylation and gene expression during yak adipocyte differentiation. In yak adipocyte and preadipocyte the content of m6A and m6A-associated enzymes was substantially different. In the two groups, a total of 14,710 m6A peaks and 13,388 m6A peaks were identified. For the most part, m6A peaks were enriched in stop codons, 3′-untranslated regions, and coding regions with consensus motifs of GGACU. The functional enrichment exploration displayed that differentially methylated genes participated in some of the pathways associated with adipogenic metabolism, and several candidate genes (KLF9, FOXO1, ZNF395, and UHRF1) were involved in these pathways. In addition to that, there was a positive association between m6A abundance and levels of gene expression, which displayed that m6A may play a vital role in modulating gene expression during yak adipocyte differentiation. Further, in the adipocyte group, several methylation gene protein expression levels were significantly higher than in preadipocytes. In short, it can be concluded that the current study provides a comprehensive explanation of the m6A features in the yak transcriptome, offering in-depth insights into m6A topology and associated molecular mechanisms underlying bovine adipocyte differentiation, which might be helpful for further understanding its mechanisms.

Polysaccharide CM1 from Cordyceps militaris hinders adipocyte differentiation and alleviates hyperlipidemia in LDLR(+/−) hamsters

Background Cordyceps militaris is cultured widely as an edible mushroom and accumulating evidence in mice have demonstrated that the polysaccharides of Cordyceps species have lipid-lowering effects. However, lipid metabolism in mice is significantly different from that in humans, making a full understanding of the mechanisms at play critical. Methods After 5 months, the hamsters were weighed and sampled under anesthesia after overnight fasting. The lipid-lowering effect and mechanisms of the polysaccharide CM1 was investigated by cellular and molecular technologies. Furthermore, the effect of the polysaccharide CM1 (100 μg/mL) on inhibiting adipocyte differentiation was investigated in vitro. Results CM1, a polysaccharide from C. militaris, significantly decreased plasma total cholesterol, triglyceride and epididymal fat index in LDLR(+/−) hamsters, which have a human-like lipid profile. After 5 months’ administration, CM1 decreased the plasma level of apolipoprotein B48, modulated the expression of key genes and proteins in liver, small intestine, and epididymal fat. CM1 also inhibited preadipocyte differentiation in 3T3-L1 cells by downregulating the key genes involved in lipid droplet formation. Conclusions The polysaccharide CM1 lowers lipid and adipocyte differentiation by several pathways, and it has potential applications for hyperlipidemia prevention.

Effects of Thymoquinone on Adipocyte Differentiation in Human Adipose-Derived Stem Cells

Background: Obesity is one of the most important public health problems worldwide. Stem cells are primary cells capable of differentiating into different types of cells, and can be used to treat various diseases. Thymoquinone (TQ) has antioxidant, anti-inflammatory, anti-diabetic and anti-obesity properties. Herein, we aim to investigate the effect of TQ on the process of lipid differentiation in human adipose tissue-derived stem cells (ADSCs). Methods and Results: Quantification of cell surface markers was used by Flow-Cytometry and then, the effect of TQ on cell viability was assessed using alamarBlue test. ADSCs were then subjected to induction of differentiation in the presence of non-cytotoxic concentrations of TQ (6.25, 12.5 and 25 μg/mL). ADSCs differentiation was assessed using Oil-Red staining technique. Moreover, expression of PPARγ (Peroxisome proliferator activated receptor γ) and FAS (Fatty Acid Synthetase) proteins was evaluated using Western blotting analysis. Flow-cytometric analysis demonstrated the expression of CD44 and CD90 markers as mesenchymal stem cells markers on the surface of ADSCs. At concentrations≤100 μg/mL of TQ, no significant difference in cell viability of ADSCs was observed compared to the control. Adipocyte differentiation process significantly decreased at 25 μg/mL (P<0.001) and 12.5 μg/mL (P<0.01) of TQ. The results of the qualitative examination of Lipid Droplets also confirmed these results. Western-blot analysis showed that TQ at 12.5 (p<0.05) and 25 μg/mL (p<0.01) reduced FAS/β-actin ratio compared to the positive group.Conclusions: This study showed that TQ can reduce the process of differentiation of fat stem cells into fat cells and might be considered as an anti-obesity compound.

microRNAs in Human Adipose Tissue Physiology and Dysfunction

In recent years, there has been a large amount of evidence on the role of microRNA (miRNA) in regulating adipose tissue physiology. Indeed, miRNAs control critical steps in adipocyte differentiation, proliferation and browning, as well as lipolysis, lipogenesis and adipokine secretion. Overnutrition leads to a significant change in the adipocyte miRNOME, resulting in adipose tissue dysfunction. Moreover, via secreted mediators, dysfunctional adipocytes may impair the function of other organs and tissues. However, given their potential to control cell and whole-body energy expenditure, miRNAs also represent critical therapeutic targets for treating obesity and related metabolic complications. This review attempts to integrate present concepts on the role miRNAs play in adipose tissue physiology and obesity-related dysfunction and data from pre-clinical and clinical studies on the diagnostic or therapeutic potential of miRNA in obesity and its related complications.

Chlorogenic Acids Inhibit Adipogenesis: Implications of Wnt/β-Catenin Signaling Pathway

In our previous in vitro study, we found that chlorogenic acid (CGA) inhibited adipocyte differentiation and triglyceride (TG) accumulation, but the underlying mechanism is still unclear. Accumulative genetic evidence supports that canonical Wnt signaling is a key modulator on adipogenesis. Methods. In this study, 3T3-L1 cells were induced adipogenic differentiation and then treated with CGA. We investigate the effect of CGA in inhibiting adipogenesis and evaluate its role in modulating Wnt10b (wingless integration1 10b), β-catenin, glycogen synthase kinase-3β (GSK-3β), and peroxisome proliferator-activated receptor γ (PPAR-γ) involved in the Wnt (wingless integration1)/β-catenin signaling pathway. Results. The result showed that after CGA treatment, lipid accumulation and TG level decreased significantly in 3T3-L1 cells, indicating that CGA could inhibit adipogenesis. In addition, CGA repressed the induction of adipocyte differentiation biomarkers as PPAR-γ, adipocyte protein 2 (aP2), fatty acid synthase (FAS), and lipoprotein lipase (LPL), and the secretion of GSK-3β in a dose-dependent manner upregulated the expression of β-catenin and Wnt10b both in gene and protein levels. Moreover, CGA induced phosphorylation of GSK-3β and promoted the accumulation of free cytosolic β-catenin in 3T3-L1 adipocytes. Conclusion. Overall, these findings gave us the implications that CGA inhibits adipogenesis via the canonical Wnt signaling pathway.

Evaluation of Fermented Extracts of Aloe vera Processing Byproducts as Potential Functional Ingredients

Aloe is widely used as a cosmetic and medicinal plant. Numerous studies have reported that aloe gel extract has antioxidant, anticancer, antidiabetic, immunity, and skin antiaging properties. However, few studies have investigated the properties of fermentation products of aloe processing byproducts. Aloe stalks and leaves remain as byproducts after the aloe beverage manufacturing process. This study evaluated whether fermentation products of blender and press extracts of aloe processing byproducts (BF and PF, respectively) that remain after beverage manufacturing were useful as functional biomaterial by investigating their effects on adipocyte differentiation, hyaluronic acid (HA) production, tyrosinase activity, and antioxidant activity. Co-fermentation of G. xylinus and S. cerevisiae was conducted for fermentation of aloe processing byproducts. The BF and PF products did not induce observable cytotoxicity effects. However, BF and PF products did inhibit a 3T3-L1 adipocyte differentiation compared with control, with the BF product displaying greater inhibition of 3T3-L1 adipocyte differentiation than the PF product. HA production increased in HaCaT cell cultures as the concentration of the MF product increased, as compared with the untreated control. The levels of tyrosinase inhibition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and superoxide dismutase (SOD)-like activity also depended on the MF product concentration. This study indicates that the fermented products of aloe processing byproducts have biological potential for applications in the manufacturing of cosmetics, pharmaceuticals, and beverages. These laboratory bench results provide the foundation for future studies of scaling and practical applications at the industrial level.