Proteomic Identification of Target Proteins of Thiodigalactoside in White Adipose Tissue from Diet-Induced Obese Rats

Galectin-8 involves in arthritic condylar bone loss via podoplanin/AKT/ERK axis-mediated inflammatory lymphangiogenesis

OBJECTIVE

The lymphatic system plays a crucial role in the maintenance of tissue fluid homeostasis and the immunological response to inflammation. Galectin-8 (Gal-8) regulates pathological lymphangiogenesis but the effects of which on inflammation-related condylar bone loss in temporomandibular joint (TMJ) have not been well studied.

DESIGN

We used TNFα-transgenic (TNF^TG) mice and their wildtype (WT) littermates to compare their inflammatory phenotype in TMJs. Next, lymphatic endothelial cells (LECs) were used to examine the effects of which on osteoclast formation, pro-inflammatory factor expression, and inflammatory lymphangiogenesis with or without thiodigalactoside (TDG, a Gal-8 inhibitor) treatment. At last, two murine models (TNF^TG arthritic model and forced mouth opening model) were used to explore TDG as a potential drug for the treatment of inflammation-related condylar bone loss.

RESULTS

In comparison to WT mice, lymphatic areas of lymphatic vessel endothelial receptor 1 (LYVE1)⁺/podoplanin (PDPN)⁺ and Gal-8⁺/PDPN⁺, TRAP-positive osteoclast number, and condylar bone loss are increased in TNF^TG mice. Inhibition of Gal-8 in LECs by TDG, reduces TNFα-induced osteoclast formation, pro-inflammatory factor expression, and inflammatory lymphangiogenesis. In addition, Gal-8 promotes TNFα-activated AKT/ERK/NF-κB pathways by binding to PDPN. Finally, the administration of TDG attenuates inflammatory lymphangiogenesis, inhibits osteoclast activity, and reduces condylar bone loss in TNF^TG arthritic mice and forced mouth opening mice.

CONCLUSIONS

Our findings reveal the important role of Gal-8-promoted pathological lymphangiogenesis in inflammation-related condylar bone loss.

Galectin-1 in Obesity and Type 2 Diabetes

Galectin-1 is a carbohydrate-binding protein expressed in many tissues. In recent years, increasing evidence has emerged for the role of galectin-1 in obesity, insulin resistance and type 2 diabetes. Galectin-1 has been highly conserved through evolution and is involved in key cellular functions such as tissue maturation and homeostasis. It has been shown that galectin-1 increases in obesity, both in the circulation and in the adipose tissue of human and animal models. Several proteomic studies have independently identified an increased galectin-1 expression in the adipose tissue in obesity and in insulin resistance. Large population-based cohorts have demonstrated associations for circulating galectin-1 and markers of insulin resistance and incident type 2 diabetes. Furthermore, galectin-1 is associated with key metabolic pathways including glucose and lipid metabolism, as well as insulin signalling and inflammation. Intervention studies in animal models alter animal weight and metabolic profile. Several studies have also linked galectin-1 to the progression of complications in diabetes, including kidney disease and retinopathy. Here, we review the current knowledge on the clinical potential of galectin-1 in obesity and type 2 diabetes.

RNA-seq analysis reveals the positive role of KLF5 in the differentiation of subcutaneous adipocyte in goats

As the largest energy storage reservoir, subcutaneous adipose tissue (SAT) stores excess lipids by adipocytes enlargement and/or recruitment of new precursor cells. Energy overload can cause ectopic fat deposition and metabolic diseases. In this study, 6814 differentially expressed genes (DEGs) were screened in goat subcutaneous preadipocytes and mature adipocytes by RNA-seq technique. The relative expression of the DEGs were verified by qPCR, such as PLIN2, MECR, ADCY7, PEBP1 and KLF5, and their expression level was found to be consistent with the trend of RNA-seq analysis. The KLF5 was selected for further functional verification. Overexpression of KLF5 promoted both the adipogenesis and the differentiation of preadipocytes, while the expression of preadipocyte marker gene: preadipocyte factor 1(Pref1) was decreased, as well as, peroxisome proliferator activation Receptor γ(PPARγ), CCAAT enhancer binding protein β(C/EBPβ) and Sterol regulatory element binding protein isoform 1(SREBP1) were increased. On the contrary, the interference of KLF5 could reduce adipogenesis, enhance the expression of Pref1, and reduce the expression of C/EBPβ and SREBP1. Our research provides a basic reference for revealing the mechanism of subcutaneous adipocyte differentiation in goats.

Galectin-1 impacts on glucose homeostasis by modulating pancreatic insulin release

Type-2 diabetes mellitus (T2DM) is an expanding global health problem, involving defective insulin secretion by pancreatic β-cells and peripheral insulin resistance, leading to impaired glucose regulation. Galectin-1, an endogenous lectin with affinity for N-acetyllactosamine (LacNAc)-containing glycans, has emerged as a regulator of inflammatory and metabolic disorders. However, the role of galectin-1 in glucose homeostasis and pancreatic β-cell function, independently of hypercaloric diets, has not been explored. Here, we identified a phenotype compatible with T2DM, involving alterations in glucose metabolism and pancreatic insulin release, in female but not male mice lacking galectin-1 (Lgals1-/-). Compared with age-matched controls, Lgals1-/female mice exhibited higher body weight and increased food intake ad libitum as well as after fasting and acute re-feeding. Although fasted serum insulin levels and insulin sensitivity were similar in both genotypes, Lgals1-/- female mice presented altered glucose tolerance and higher basal glucose levels depending on the fasting period. Insulin response to glucose overload was impaired, while pancreatic insulin content was enhanced in the absence of galectin-1. Accordingly, recombinant galectin-1 enhanced glucose-stimulated insulin release in vitro. Our study identifies a role for galectin-1 in regulating glucose metabolism through modulation of pancreatic insulin secretion, highlighting novel opportunities to control T2DM.

Proteomic screening identifies the direct targets of chrysin anti-lipid depot in adipocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Overweight/obesity was mentioned by many countries as an obstacle to good health and long life, which increases risk of diseases and disorders. Previous studies suggested that the chronic low-grade inflammation present in the body was considered as the essential pathogenesis for obesity. Chrysin is extracted from traditional Chinese medicine Oroxylum indicum (Linn.) Kurz and plays a superior anti-obesity role. Chrysin could reduce the lipid depot by inhibiting the obesity-related inflammation in adipose tissue. However, the target protein for chrysin to exert its anti-obesity role are not verified.

AIM OF STUDY

The present study aimed to screen and validate the target protein for chrysin to reduce the lipid depot in palmitic acid-induced 3T3-L1 adipocytes.

MATERIALS AND METHODS

Obesity model was established employing 0.5 mmol/L palmitic acid-induced 3T3-L1 adipocytes through "Cocktails" method. Two-dimensional gel electrophoresis (2-DE) combined with liquid chromatography-mass spectrometry (LC-MS) was applied to analyze the differentially expressed proteins for chrysin intervention by lipid formation in adipocytes. Gene silencing was utilized to decrease gene expression of the candidate proteins, then production of triglyceride in 3T3-L1 was detected by triglycerides assay to determine the target proteins. Ultraviolet (UV) absorption together with fluorescence spectra validated the direct target proteins of chrysin. They also computed the correlation constants of combination between chrysin and the target proteins. Molecular docking was further employed to identify the main binding amino acids between chrysin and the target protein.

RESULTS

2-DE combined with LC-MS screened four candidate proteins which were related to metabolism and inflammation. The production of triglycerides in 3T3-L1 was reduced after decreasing gene expression of Annexin A2 (ANXA2), 60 kDa heat shock protein (HSP-60) and succinyl-CoA:3-ketoacid coenzyme A transferase 1 (SCOT-S), respectively. UV spectrum showed that the absorbance spectra of ANXA2 from 260 to 300 nm shifted upwards along with the increase in chrysin concentration, meanwhile the absorbance spectra of HSP-60 from 200 to 220 nm and from 265 to 280 nm shifted slightly upwards along with the increase in chrysin concentrations. The results indicated the conjugated structures between chrysin and ANXA2 or HSP-60. Fluorescence quenching further suggested a spontaneous interaction between chrysin and ANXA2 or HSP-60. Finally, molecular docking identified the main binding amino acids between ANXA2 and chrysin were Ser22, Tyr24, Pro267, Val298, Asp299, and Lys302.

CONCLUSIONS

Chrysin can reduce the amount of triglycerides by directly downregulating the inflammation-related target proteins ANXA2 and HSP-60, exerting an anti-obesity role.

Cerebrocortical proteome profile of female rats subjected to the western diet and chronic social stress

The energy-dense western diet significantly increases the risk of obesity, type 2 diabetes, cardiovascular episodes, stroke, and cancer. Recently more attention has been paid to the contribution of an unhealthy lifestyle on the development of central nervous system disorders. Exposure to long-lasting stress is one of the key lifestyle modifications associated with the increased prevalence of obesity and metabolic diseases. The main goal of the present study was to verify the hypothesis that exposure to chronic stress modifies alterations in the brain proteome induced by the western diet. Female adult rats were fed with the prepared chow reproducing the human western diet and/or subjected to chronic stress induced by social instability for 6 weeks. A control group of lean rats were fed with a standard diet. Being fed with the western diet resulted in an obese phenotype and induced changes in the serum metabolic parameters. The combination of the western diet and chronic stress exposure induced more profound changes in the rat cerebrocortical proteome profile than each of these factors individually. The down-regulation of proteins involved in neurotransmitter secretion (Rph3a, Snap25, Syn1) as well as in learning and memory processes (Map1a, Snap25, Tnr) were identified, while increased expression was detected for 14-3-3 protein gamma (Ywhag) engaged in the modulation of the insulin-signaling cascade in the brain. An analysis of the rat brain proteome reveals important changes that indicate that a combination of the western diet and stress exposure may lead to impairments of neuronal function and signaling.

Obesity Reshapes Visceral Fat-Derived MHC I Associated-Immunopeptidomes and Generates Antigenic Peptides to Drive CD8+ T Cell Responses

Adaptive CD8⁺ T cells were observed to contribute to the initiation and progression of obesity-induced visceral adipose tissue (VAT) chronic inflammation that is critically linked to metabolic disorders. Numerous peptides presented by the major histocompatibility complex (MHC) class I molecules at the cell surface are collectively termed as MHC I-associated immunopeptidome (MIP) for the interaction with CD8⁺ T cells. We conducted the in-depth mapping of MIP of VAT from lean and obese mice using large-scale high-resolution mass spectrometry and observed that obesity significantly alters the landscape of VAT MIPs. Additionally, the obese VAT-exclusive MIP source proteome reflected a distinct obesity-associated signature. A peptide derived from lactate dehydrogenase A (LDHA) or B chain, named LDHA_237-244, was identified as an obese VAT-exclusive immunogenic peptide that was capable of eliciting pro-inflammatory CD8⁺ T cells responses. Our findings suggest that certain immunogenic peptides generated by obesity may trigger CD8⁺ T cell-mediated VAT inflammation.

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Obesity reshapes the landscape of VAT-derived MIP

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The obese VAT-exclusive MIP reflects an obesity-associated signature

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An obese VAT-exclusive peptide LDHA_237-244 can stimulate CD8⁺ T cell responses

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LDHA_237-244-reactive CD8⁺ T cells were present in obese mice but not lean mice

Liver proteomics unravel the metabolic pathways related to Feed Efficiency in beef cattle

Improving nutrient utilization efficiency is essential for livestock, given the current scenario of increasing demand for animal protein and sustainable resource use. In this context, understanding the biology of feed efficiency (FE) in beef cattle allows the development of markers for identification and selection of best animals for animal production. Thus, 98 young Nellore bulls were evaluated for FE and at the end of the experiment liver samples from six High Feed Efficient (HFE) and six Low Feed Efficient (LFE) animals were collected for protein extraction, digestion and analysis by HPLC-MS/MS. Data were analyzed for differential abundant proteins (DAPs), protein networks, and functional enrichment. Serum endotoxin was also quantified. We found 42 DAPs and 3 protein networks significantly related to FE. The main pathways associated with FE were: microbial metabolism; biosynthesis of fatty acids, amino acids and vitamins; glycolysis/gluconeogenesis; xenobiotic metabolism and; antigen processing and presentation. Serum endotoxins were significantly higher in LFE animals supporting the results. Therefore, the findings presented here confirmed the altered hepatic metabolism and pronounced hepatic inflammation in LFE animals supporting that the increased bacterial load is at least in part responsible for the hepatic lesions and inflammation in LFE animals.

Autophagy in Adipocyte Browning: Emerging Drug Target for Intervention in Obesity

Autophagy, lipophagy, and mitophagy are considered to be the major recycling processes for protein aggregates, excess fat, and damaged mitochondria in adipose tissues in response to nutrient status-associated stress, oxidative stress, and genotoxic stress in the human body. Obesity with increased body weight is often associated with white adipose tissue (WAT) hypertrophy and hyperplasia and/or beige/brown adipose tissue atrophy and aplasia, which significantly contribute to the imbalance in lipid metabolism, adipocytokine secretion, free fatty acid release, and mitochondria function. In recent studies, hyperactive autophagy in WAT was observed in obese and diabetic patients, and inhibition of adipose autophagy through targeted deletion of autophagy genes in mice improved anti-obesity phenotypes. In addition, active mitochondria clearance through activation of autophagy was required for beige/brown fat whitening – that is, conversion to white fat. However, inhibition of autophagy seemed detrimental in hypermetabolic conditions such as hepatic steatosis, atherosclerosis, thermal injury, sepsis, and cachexia through an increase in free fatty acid and glycerol release from WAT. The emerging concept of white fat browning–conversion to beige/brown fat–has been controversial in its anti-obesity effect through facilitation of weight loss and improving metabolic health. Thus, proper regulation of autophagy activity fit to an individual metabolic profile is necessary to ensure balance in adipose tissue metabolism and function, and to further prevent metabolic disorders such as obesity and diabetes. In this review, we summarize the effect of autophagy in adipose tissue browning in the context of obesity prevention and its potential as a promising target for the development of anti-obesity drugs.

Trans-anethole ameliorates obesity via induction of browning in white adipocytes and activation of brown adipocytes

To treat obesity, suppression of white adipose tissue (WAT) expansion and activation of brown adipose tissue (BAT) are considered as potential therapeutic targets. Recent advances have been made in the induction of brown fat-like adipocytes (beige) in WAT, which represents an attractive potential strategy for the management and treatment of obesity. Use of natural compounds for browning of white adipocytes can be considered as a safe and novel strategy against obesity. Here, we report that trans-anethole (TA), a flavoring substance present in the essential oils of various plants, alleviated high fat diet (HFD)-induced obesity in mice models via elevation of the expression of beige-specific genes such as Ppargc1α, Prdm16, Ucp1, Cd137, Cited1, Tbx1, and Tmem26. TA also regulated lipid metabolism in white adipocytes via reduction of adipogenesis and lipogenesis as well as elevation of lipolysis and fat oxidation. Moreover, TA exhibited thermogenic activity by increasing mitochondrial biogenesis in white adipocytes and activating brown adipocytes. In addition, molecular docking analysis enabled us to successfully predict core proteins for fat browning such as β3-adrenergic receptor (β3-AR) and sirtuin1 (SIRT1) based on their low binding energy interactions with TA for promotion of regulatory mechanisms. Indeed, agonistic and antagonistic studies demonstrated that TA induced browning of 3T3-L1 adipocytes through activation of β3-AR as well as the AMPK-mediated SIRT1 pathway regulating PPARα and PGC-1α. In conclusion, TA possesses potential therapeutic implications for treatment of obesity by playing multiple modulatory roles in the induction of white fat browning, activation of brown adipocytes, and promotion of lipid catabolism.

Serum galectin-1 levels are positively correlated with body fat and negatively with fasting glucose in obese children

Galectin-1, a recently identified peptide, is primarily released from the adipose tissue. Although galectin-1 was shown to have an anti-inflammatory effect, its specific function is not clearly understood. We aimed to evaluate the relationship of serum galectin-1 levels with clinical and laboratory parameters in childhood obesity. A total of 45 obese children (mean age: 12.1±3.1years) and 35 normal-weight children (mean age: 11.8±2.2years) were enrolled. Clinical [body mass index (BMI), waist circumference (WC), percentage of body fat and blood pressure] and biochemical [glucose, insulin, lipids, galectin-1, high-sensitive C-reactive protein (hsCRP) and leptin levels] parameters were assessed. Serum galectin-1, hsCRP and leptin levels were significantly higher in obese children than those in normal-weight children (12.4 vs 10.2ng/mL, p<0.001; 3.28 vs 0.63mg/L, p<0.001; 8.3 vs 1.2ng/mL, p<0.001, respectively). In obese children, galectin-1 levels correlated negatively with fasting glucose (r=-0.346, p=0.020) and positively with fat mass (r=0.326, p=0.026) and WC standard deviation score (SDS) (r=0.451, p=0.002). The multivariate regression analysis demonstrated that serum galectin-1 levels were significantly associated with fasting glucose and WC SDS. This study showed that obese children had significantly higher galectin-1 levels in proportion to fat mass in obese cases than those in healthy children, which may be interpreted as a compensatory increase in an attempt to improve glucose metabolism.

Identification of novel biomarkers to monitor β-cell function and enable early detection of type 2 diabetes risk

A decline in β-cell function is a prerequisite for the development of type 2 diabetes, yet the level of β-cell function in individuals at risk of the condition is rarely measured. This is due, in part, to the fact that current methods for assessing β-cell function are inaccurate, prone to error, labor-intensive, or affected by glucose-lowering therapy. The aim of the current study was to identify novel circulating biomarkers to monitor β-cell function and to identify individuals at high risk of developing β-cell dysfunction. In a nested case-control study from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) cohort (n = 1157), proteomics and miRNA profiling were performed on fasting plasma samples from 43 individuals who progressed to impaired glucose tolerance (IGT) and 43 controls who maintained normal glucose tolerance (NGT) over three years. Groups were matched at baseline for age, gender, body mass index (BMI), insulin sensitivity (euglycemic clamp) and β-cell glucose sensitivity (mathematical modeling). Proteomic profiling was performed using the SomaLogic platform (Colorado, USA); miRNA expression was performed using a modified RT-PCR protocol (Regulus Therapeutics, California, USA). Results showed differentially expressed proteins and miRNAs including some with known links to type 2 diabetes, such as adiponectin, but also novel biomarkers and pathways. In cross sectional analysis at year 3, the top differentially expressed biomarkers in people with IGT/ reduced β-cell glucose sensitivity were adiponectin, alpha1-antitrypsin (known to regulate adiponectin levels), endocan, miR-181a, miR-342, and miR-323. At baseline, adiponectin, cathepsin D and NCAM.L1 (proteins expressed by pancreatic β-cells) were significantly lower in those that progressed to IGT. Many of the novel prognostic biomarker candidates were within the epithelial-mesenchymal transition (EMT) pathway: for example, Noggin, DLL4 and miR-181a. Further validation studies are required in additional clinical cohorts and in patients with type 2 diabetes, but these results identify novel pathways and biomarkers that may have utility in monitoring β-cell function and/ or predicting future decline, allowing more targeted efforts to prevent and intercept type 2 diabetes.

Microdialysis and proteomics of subcutaneous interstitial fluid reveals increased galectin-1 in type 2 diabetes patients

OBJECTIVE

To identify a potential therapeutic target for type 2 diabetes by comparing the subcutaneous interstitial fluid from type 2 diabetes patients and healthy men.

METHODS

Proteomics was performed on the interstitial fluid of subcutaneous adipose tissue obtained by microdialysis from 7 type 2 diabetes patients and 8 healthy participants. 851 proteins were detected, of which 36 (including galectin-1) showed significantly altered expression in type 2 diabetes. We also measured galectin-1 expression in: (1) adipocytes isolated from adipose tissue biopsies from these participants; (2) subcutaneous adipose tissue of 24 obese participants before, during and after 16weeks on a very low calorie diet (VLCD); and (3) adipocytes isolated from 6 healthy young participants after 4weeks on a diet and lifestyle intervention to promote weight gain. We also determined the effect of galectin-1 on glucose uptake in human adipose tissue.

RESULTS

Galectin-1 protein levels were elevated in subcutaneous dialysates from type 2 diabetes compared with healthy controls (p<0.05). In agreement, galectin-1 mRNA expression was increased in adipocytes from the type 2 diabetes patients (p<0.05). Furthermore, galectin-1 mRNA expression was decreased in adipose tissue after VLCD (p<0.05) and increased by overfeeding (p<0.05). Co-incubation of isolated human adipocytes with galectin-1 reduced glucose uptake (p<0.05) but this was independent of the insulin signal.

CONCLUSION

Proteomics of the interstitial fluid in subcutaneous adipose tissue in vivo identified a novel adipokine, galectin-1, with a potential role in the pathophysiology of type 2 diabetes.

Beef quality with different intramuscular fat content and proteomic analysis using isobaric tag for relative and absolute quantitation of differentially expressed proteins

Intramuscular fat (IMF) is an important trait for beef eating quality. The mechanism of how IMF is deposited in beef cattle muscle is not clear at the molecular level. The muscle (M. longissimus lumborum: LL) of a group of Xiangxi yellow×Angus cattle with high fat levels (HF), was compared to the muscle of a low fat group (LF). The meat quality and the expressed protein patterns were compared. It was shown that LL from the HF animals had a greater fat content (P<0.05) and lower moisture content (P<0.05) than LL from LF animals. Forty seven sarcoplasmic proteins were differentially expressed and identified between the two groups. These proteins are involved in 6 molecular functions and 16 biological processes, and affect the Mitogen-activated protein kinases pathway, insulin pathway and c-Jun N-terminal kinases leading to greater IMF deposition. Cattle in the HF group had greater oxidative capacity and lower glycolytic levels suggesting a greater energetic efficiency.