High extracellular calcium attenuates adipogenesis in 3T3-L1 preadipocytes

Vitamin A mediates FABP4 to regulate intramuscular fat production: a new target and strategy for optimizing beef quality

Beef quality is critically determined by intramuscular fat (IMF) deposition. Retinoic acid (RA), the active metabolite of vitamin A, plays an essential regulatory role in IMF development. To systematically investigate RA-mediated regulation of IMF formation in cattle, we established a concentration gradient of RA supplementation and employed a systematic screening approach to identify the optimal dosage for modulating bovine intramuscular adipocytes (IMAs) proliferation and differentiation. Subsequently, leveraging integrated multi-omics approaches, we screened the key downstream molecular targets through which RA governs IMF biosynthesis, and clarified the potential regulatory mechanism of this target. Our experimental data establish that RA promotes the proliferation of IMAs through modulation of G1/S phase progression. Concurrently, RA enhances triglyceride biosynthesis in IMAs by activating PPARγ-mediated cell differentiation and LPL-mediated intracellular lipid accumulation. Integrated transcriptomics and metabonomics analyses identified FABP4, CD36, EBF2, LRP1 and CAV1 as key candidate genes involved in RA-mediated IMF production. Functional interrogation revealed that FABP4 knockdown markedly attenuated lipid accumulation in IMAs, a phenotype rescued through RA supplementation, confirming FABP4 as the critical effector mediating vitamin A's regulation of bovine IMF deposition. These results provide a new understanding of how nutritional factors affect beef quality at the molecular level.

Low serum calcium promotes traumatic intracerebral hematoma expansion by the response of immune cell: A multicenter retrospective cohort study

To explore the potential role of serum calcium levels at admission in the expansion of acute traumatic intracerebral hematoma (tICH) and to construct a novel nomogram to predict tICH expansion. In this multicenter retrospective study, 640 and 237 patients were included in the training and validation datasets, respectively. Risk factors for acute tICH expansion were selected by logistic regression analysis. Causal mediation and interaction analysis were used to explore the relationship between serum calcium promotion of tICH expansion and inflammatory response. Receiver operating characteristic, calibration and clinical decision curves were applied to estimate the performance of multivariate models. Low serum calcium level was strongly associated with acute tICH expansion in patients with brain contusion. There was no significant interaction of hypocalcemia across multiple subgroups including sex, age, and coagulation dysfunction. 24.5% of the mechanisms by which hypocalcemia promotes acute tICH expansion can be explained by an inflammatory response. The addition of serum calcium made the modified model (serum calcium plus basic model) more accurate than basic model with subdural hematoma, multihematoma fuzzy sign, time to baseline CT, level on Glasgow Coma Scale score, platelet count, baseline tICH volume ≥ 5 mL, and monocyte-to-lymphocyte ratio. Low serum calcium level is a novel risk factor for acute tICH expansion, the mechanism of which may be mediated in part through the response of immune cell. The online dynamic nomogram provides a user-friendly tool for the prediction of acute tICH expansion.

Fulvic acid inhibits the differentiation of 3T3-L1 adipocytes by activating the Ca2+/CaMKⅡ/AMPK pathway

Type 2 diabetes increases the risk of developing obesity. Although fulvic acid alleviates back fat thickness in pigs, the mechanism underlying its anti-obesity effect remains unclear. Therefore, we investigated the anti-obesity mechanism of fulvic acid using 3T3-L1 adipocytes. We examined the effects of fulvic acid on adipocyte differentiation, cell viability, and lipid accumulation using molecular techniques. Fulvic acid treatment significantly decreased intracellular lipid accumulation in 3T3-L1 cells during the differentiation compared with that in the control group. Western blotting revealed fulvic acid-induced downregulated expression of the adipocyte differentiation-related markers peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein alpha, and sterol regulatory element-binding protein 1. The fulvic acid treatment decreased the expression of the lipid uptake-related markers fatty acid-binding protein 4 and the cluster of differentiation 36 in 3T3-L1 cells. Moreover, fulvic acid significantly increased cytosolic Ca2+ concentration via Ca2+ sequestration from the endoplasmic reticulum, enhanced Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, and upregulated AMP-activated protein kinase (AMPK), thereby reducing adipocyte differentiation. Conclusively, fulvic acid attenuates adipocyte differentiation by activating the Ca2+/CaMKⅡ/AMPK pathway, suggesting its anti-obesity potential.

Purple Butter Clam (Saxidomus Purpurata) as a Potential Functional Food Source for Obesity Treatment

Saxidomus purpurata extract (SPE) is a highly consumable seafood worldwide with known health-related benefits. However, there are no reports of its' anti-obesity effect. This study explores the potential of SPE for anti-obesity effects by modulating adipogenesis and lipolysis. SPE reduced intracellular lipid and triglyceride accumulation while increasing free glycerol release in adipocytes. SPE inhibited lipogenesis protein expressions and increased the phosphorylation of hormone-sensitive lipase and Adenosine monophosphate-activated protein kinase (AMPK) to promote lipolysis. In addition, SPE suppressed adipogenesis by downregulating protein expression of key adipogenic markers, peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP1) via Wnt/β-catenin signaling. SPE augmented the heme oxygenase-1 (HO-1) expression. Thus, pharmacological intervention with Zinc protoporphyrin (ZnPP-HO-1 antagonist) was employed to validate the HO-1 role. The presence of ZnPP increased the lipid accumulation and reduced the free glycerol release. At the molecular level, adipogenic transcription factors (PPARγ, C/EBPα, and SREBP1) expressions were restored in the presence of ZnPP. GC-MS analysis revealed that SPE was comprised of several fatty acids, contributing to its anti-obesity activity. SPE is an effective nutraceutical that can be used to reduce the progression of obesity. HO-1 expression during adipogenesis might be the mechanism of action for the anti-obesity effect of SPE.

Translatomics reveals the role of dietary calcium addition in regulating muscle fat deposition in pigs

Intramuscular fat (IMF) in pork holds significant importance for economic performance within the pig industry and dietary calcium supplementation enhances the accumulation of intramuscular fat. Additionally, calcium ions inhibit translation and reduce protein synthesis. However, the mechanism by which calcium regulates IMF deposition in muscle through translation remains largely unknown. In this study, we compared the ribosome profiles of the longissimus dorsi muscles of Duroc × Landrace × Large white pigs from the normal calcium (NC) group or calcium supplement (HC) group by Ribo-seq, and RNA-seq. By integrating multiple-omics analysis, we further discovered 437 genes that were transcriptionally unchanged but translationally altered and these genes were significantly enriched in the oxidative phosphorylation signaling pathway. Furthermore, experimental data showed that inhibiting the expression of COX10 and mtND4L increased triglyceride accumulation in C2C12 cells, providing new targets for intramuscular fat deposition. Finally, this work links dietary calcium, translation regulation and IMF deposition, providing a new strategy for both meat quality and economic performance within the pig industry.

Regulation of myogenesis and adipogenesis by the electromagnetic perceptive gene

Obesity has been increasing in many regions of the world, including Europe, USA, and Korea. To manage obesity, we should consider it as a disease and apply therapeutic methods for its treatment. Molecular and therapeutic approaches for obesity management involve regulating biomolecules such as DNA, RNA, and protein in adipose-derived stem cells to prevent to be fat cells. Multiple factors are believed to play a role in fat differentiation, with one of the most effective factor is Ca2+. We recently reported that the electromagnetic perceptive gene (EPG) regulated intracellular Ca2+ levels under various electromagnetic fields. This study aimed to investigate whether EPG could serve as a therapeutic method against obesity. We confirmed that EPG serves as a modulator of Ca2+ levels in primary adipose cells, thereby regulating several genes such as CasR, PPARγ, GLU4, GAPDH during the adipogenesis. In addition, this study also identified EPG-mediated regulation of myogenesis that myocyte transcription factors (CasR, MyoG, MyoD, Myomaker) were changed in C2C12 cells and satellite cells. In vivo experiments carried out in this study confirmed that total weight/ fat/fat accumulation were decreased and lean mass was increased by EPG with magnetic field depending on age of mice. The EPG could serve as a potent therapeutic agent against obesity.

The Synthesis of Europium-Doped Calcium Carbonate by an Eco-Method as Free Radical Generator Under Low-Intensity Ultrasonic Irradiation for Body Sculpture

Body sculpture is a common method to remove excessive fat. The diet and exercise are the first suggestion to keep body shape; however, those are difficult to keep adherence. Ultrasound has been developed for fat ablation; however, it could only serve as the side treatment along with liposuction. In the study, a sonosensitizer of europium-doped calcium carbonate (CaCO₃: Eu) would be synthesized by an eco-method and combined with low-intensity ultrasound for lipolysis. The crystal structure of CaCO₃: Eu was identified by x-ray diffractometer (XRD). The morphology of CaCO₃: Eu was analyzed by scanning electron microscope (SEM). The chemical composition of CaCO₃: Eu was evaluated by energy-dispersed spectrophotometer (EDS) and inductively coupled plasma mass spectrometer (ICP-MS). The electronic diffraction pattern was to further check crystal structure of the synthesized individual grain by transmission electron microscope (TEM). The particle size was determined by Zeta-sizer. Water-soluble tetrazolium salt (WST-1) were used to evaluate the cell viability. Chloromethyl-2′,7′-dichlorofluorescein diacetate (CM-H₂DCFDA) and live/dead stain were used to evaluate feasibility in vitro. SD-rat was used to evaluate the safety and efficacy in vivo. The results showed that CaCO₃: Eu had good biocompatibility and could produce reactive oxygen species (ROS) after treated with low-intensity ultrasound. After 4-weeks, the CaCO₃: Eu exposed to ultrasound irradiation on SD rats could significantly decrease body weight, waistline, and subcutaneous adipose tissue. We believe that ROS from sonoluminescence, CO₂-bomb and locally increasing Ca²⁺ level would be three major mechanisms to remove away adipo-tissue and inhibit adipogenesis. We could say that the combination of the CaCO₃: Eu and low-intensity ultrasound would be a non-invasive treatment for the body sculpture.

Dietary calcium supplementation promotes the accumulation of intramuscular fat

BACKGROUND

In the livestock industry, intramuscular fat content is a key factor affecting meat quality. Many studies have shown that dietary calcium supplementation is closely related to lipid metabolism. However, few studies have examined the relationship between dietary calcium supplementation and intramuscular fat accumulation.

METHODS

Here, we used C2C12 cells, C57BL/6 mice (n = 8) and three-way cross-breeding pigs (Duroc×Landrace×Large white) (n = 10) to study the effect of calcium addition on intramuscular fat accumulation. In vitro, we used calcium chloride to adjust the calcium levels in the medium (2 mmol/L or 3 mmol/L). Then we measured various indicators. In vivo, calcium carbonate was used to regulate calcium levels in feeds (Mice: 0.5% calcium or 1.2% calcium) (Pigs: 0.9% calcium or 1.5% calcium). Then we tested the mice gastrocnemius muscle triglyceride content, pig longissimus dorsi muscle meat quality and lipidomics.

RESULTS

In vitro, calcium addition (3 mmol/L) had no significant effect on cell proliferation, but promoted the differentiation of C2C12 cells into slow-twitch fibers. Calcium supplementation increased triglyceride accumulation in C2C12 cells. Calcium addition increased the number of mitochondria and also increased the calcium level in the mitochondria and reduced the of key enzymes activity involved in β-oxidation such as acyl-coenzyme A dehydrogenase. Decreasing mitochondrial calcium level can alleviate lipid accumulation induced by calcium addition. In addition, calcium addition also reduced the glycolytic capacity and glycolytic conversion rate of C2C12 cells. In vivo, dietary calcium supplementation (1.2%) promoted the accumulation of triglycerides in the gastrocnemius muscle of mice. Dietary calcium supplementation (1.5%) had no effect on pig weight, but significantly improved the flesh color of the longissimus dorsi muscle, reduced the backfat thickness and increased intramuscular fat content in pigs. Besides, calcium addition had no effect on longissimus dorsi pH, electrical conductivity and shear force.

CONCLUSIONS

These results suggest that calcium addition promotes intramuscular fat accumulation by inhibiting the oxidation of fatty acids. These findings provide a new tool for increasing intramuscular fat content and an economical strategy for improving meat quality.

Exploration of Hypoglycemic Activity of Saccharomyces pastorianus Extract and Evaluation of the Molecular Mechanisms

Although the hypoglycemic potential of brewer’s yeast extract has been reported, there is limited information pertaining to the hypoglycemic ingredients of Saccharomyces pastorianus extract and their mechanisms of action available. This study aimed to investigate the in vivo and in vitro hypoglycemic effect of S. pastorianus extract and to elucidate its molecular mechanisms. S. pastorianus extract was mainly composed of proteins followed by carbohydrates. In diabetic rats, oral administration of S. pastorianus extract significantly reduced the levels of plasma glucose and enhanced the activity of hepatic glucose-6-phosphatase dehydrogenase. Treatment with S. pastorianus extract increased the localization of type 4 glucose transporter (GLUT4), PTP, and insulin receptor at 3T3-L1 cell membranes and raised the levels of P38 MAPK, PI3K, and AKT in the cytosol. In agreement with these results, pretreatment of 3T3-L1 cells with inhibitors of PTP, PI3K, Akt/PKB, and p38 MAPK inhibited glucose uptake induced by application of S. pastorianus extract. Most importantly, a 54 kDa protein with hypoglycemic activity was identified and suggested as the major ingredient contributing to the hypoglycemic activity of S. pastorianus extract. In summary, these results clearly confirm the hypoglycemic activity of S. pastorianus extract and provide critical insights into the underlying molecular mechanisms.

An inverted U-shaped relationship between parathyroid hormone and body weight, body mass index, body fat

PURPOSE

To investigate the relationship between parathyroid hormone (PTH) levels and body weight, body mass index (BMI), lipid profiles, and fat distribution in subjects with primary hyperparathyroidism (PHPT) and controls.

METHODS

This was a cross-sectional study in 192 patients with PHPT and 202 controls. Serum concentrations of calcium, 25-hydroxyvitamin D (25(OH)D), PTH, lipids profiles, and other hormones were quantified. Bone mineral density was assessed by dual-energy X-ray absorptiometry. Fat distribution evaluation utilizing quantitative computed tomography was conducted in another 66 patients with PHPT and 155 controls.

RESULTS

PHPT patients were older (P < 0.001) and had less body weight (P < 0.001), lower BMI (P = 0.019), lower serum concentrations of 25(OH)D (P < 0.001), total cholesterol (P = 0.036), low-density lipoprotein-cholesterol (P = 0.036), and higher circulating concentration of free fatty acid (FFA) (P = 0.047) as compared with controls. After adjusting multiple confounders, PTH was positively correlated with weight (r = 0.311, P < 0.001), BMI (r = 0.268, P < 0.01), and visceral adipose tissue area (VAA) (r = 0.191, P < 0.05) in the first tertile of PTH. However, these associations were not observed in the second tertile. While in the third tertile, PTH was negatively correlated with weight (r = -0.200, P < 0.05), BMI (r = -0.223, P < 0.05) and marginally with VAA (r = -0.306, P = 0.065), it showed positive association with FFA (r = 0.230, P < 0.05).

CONCLUSIONS

The inverted U-shape relationship between PTH and body weight, BMI, VAA found in this study is helpful to explain the conflicting results among these parameters, and extend our understanding of the metabolic effects of PTH.

Involvement of calcium channels in the regulation of adipogenesis

As an important second messenger in adipocytes, calcium ions (Ca²⁺) are essential in regulating various intracellular signalling pathways that control critical cellular functions. Calcium channels show selective permeability to Ca²⁺ and facilitate Ca²⁺ entry into the cytoplasm, which are normally located in the plasmatic and intracellular membranes. The increase of cytosolic Ca²⁺ modulates a variety of signalling pathways and results in the transcription of target genes that contribute to adipogenesis, a key cellular event includes proliferation and differentiation of adipocyte. In the past decades, the involvement of some Ca²⁺-permeable ion channels, such as Ca²⁺ release-activated Ca²⁺ channels, transient receptor potential channels, voltage-gated calcium channels and others, in adipogenesis has been extensively explored. In the present review, we provided a summary of the expression and contributions of these Ca²⁺-permeable channels in mediating Ca²⁺ influxes that drive adipogenesis. Moreover, we discussed their potentials as future therapeutic targets.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

γ-Glutamylvaline Prevents Low-Grade Chronic Inflammation via Activation of a Calcium-Sensing Receptor Pathway in 3T3-L1Mouse Adipocytes

The calcium-sensing receptor (CaSR), a G-protein receptor, is well recognized for its role in the regulation of adipocyte proliferation, in modulating adipose tissue dysfunction, and as a potential target for therapeutic intervention. In the present study, we investigate the anti-inflammatory effect of γ-glutamylvaline (γ-EV) on mouse adipocytes and explore the role of γ-EV-activated CaSR in the regulation of cellular homeostasis using the mouse 3T3-L1 cell line in vitro model. Our results indicate that the 3T3-L1 adipocyte-like cells accumulated lipids and expressed CaSR after 2 days of differentiation and 7 days of maturation period. The pretreatment with γ-EV (10 μM) suppressed the production of TNF-α-induced pro-inflammatory cytokines, i.e., IL-6 (23.92 ± 5.45 ng/mL, p < 0.05)) and MCP-1 (101.17 ± 39.93 ng/mL, p < 0.05), while enhancing the expression of PPARγ (1.249 ± 0.109, p < 0.001) and adiponectin (7.37 ± 0.59 ng/mL, p < 0.05). Elevated expression of Wnt5a was detected in γ-EV-treated cells (115.90 ± 45.50, p < 0.001), suggesting the involvement of the Wnt/β-catenin pathway. Also, phosphorylation of β-catenin was shown to be significantly inhibited (0.442 ± 0.034) by TNF-α but restored when cells were pretreated with γ-EV (0.765 ± 0.048, p < 0.05). These findings suggest that γ-EV-induced CaSR activation not only prevents TNF-α-induced inflammation in adipocytes but also modulates the cross-talk between Wnt and PPARγ pathways. Concentrations of serine phosphorylated IRS-1 were shown to be lower in γ-EV-treated cells, indicating γ-EV may also prevent inflammation in the context of insulin resistance. Thus, γ-EV-activated CaSR plays a significant role in the cross-talk between adipocyte inflammatory and metabolic pathways through the regulation of extracellular sensing.

Ca2+ entry via TRPC1 is essential for cellular differentiation and modulates secretion via the SNARE complex

Properties of adipocytes, including differentiation and adipokine secretion, are crucial factors in obesity-associated metabolic syndrome. Here, we provide evidence that Ca²⁺ influx in primary adipocytes, especially upon Ca²⁺ store depletion, plays an important role in adipocyte differentiation, functionality and subsequently metabolic regulation. The endogenous Ca²⁺ entry channel in both subcutaneous and visceral adipocytes was found to be dependent on TRPC1–STIM1, and blocking Ca²⁺ entry with SKF96365 or using TRPC1^−/− knockdown adipocytes inhibited adipocyte differentiation. Additionally, TRPC1^−/− mice have decreased organ weight, but increased adipose deposition and reduced serum adiponectin and leptin concentrations, without affecting total adipokine expression. Mechanistically, TRPC1-mediated Ca²⁺ entry regulated SNARE complex formation, and agonist-mediated secretion of adipokine-loaded vesicles was inhibited in TRPC1^−/− adipose. These results suggest an unequivocal role of TRPC1 in adipocyte differentiation and adiponectin secretion, and that loss of TRPC1 disturbs metabolic homeostasis.

This article has an associated First Person interview with the first author of the paper.

Summary: TRPC1 modulates Ca²⁺ entry, which is essential in adipocyte differentiation and adiponectin secretion, through facilitating SNARE complex formation, thereby maintaining metabolic homeostasis.

Anti-Obesity Effects of Dietary Calcium: The Evidence and Possible Mechanisms

Obesity is a serious health challenge worldwide and is associated with various comorbidities, including dyslipidemia, type 2 diabetes, and cardiovascular disease. Developing effective strategies to prevent obesity is therefore of paramount importance. One potential strategy to reduce obesity is to consume calcium, which has been implicated to be involved in reducing body weight/fat. In this review, we compile the evidence for the anti-obesity roles of calcium in cells, animals, and humans. In addition, we summarize the possible anti-obesity mechanisms of calcium, including regulation of (a) adipogenesis, (b) fat metabolism, (c) adipocyte (precursor) proliferation and apoptosis, (d) thermogenesis, (e) fat absorption and excretion, and (f) gut microbiota. Although the exact anti-obesity roles of calcium in different subjects and how calcium induces the proposed anti-obesity mechanisms need to be further investigated, the current evidence demonstrates the anti-obesity effects of calcium and suggests the potential application of dietary calcium for prevention of obesity.

Determinants of stem cell lineage differentiation toward chondrogenesis versus adipogenesis

Adult stem cells, also termed as somatic stem cells, are undifferentiated cells, detected among differentiated cells in a tissue or an organ. Adult stem cells can differentiate toward lineage specific cell types of the tissue or organ in which they reside. They also have the ability to differentiate into mature cells of mesenchymal tissues, such as cartilage, fat and bone. Despite the fact that the balance has been comprehensively scrutinized between adipogenesis and osteogenesis and between chondrogenesis and osteogenesis, few reviews discuss the relationship between chondrogenesis and adipogenesis. In this review, the developmental and transcriptional crosstalk of chondrogenic and adipogenic lineages are briefly explored, followed by elucidation of signaling pathways and external factors guiding lineage determination between chondrogenic and adipogenic differentiation. An in-depth understanding of overlap and discrepancy between these two mesenchymal tissues in lineage differentiation would benefit regeneration of high-quality cartilage tissues and adipose tissues for clinical applications.

Dairy product consumption and its association with metabolic disturbance in a prospective study of urban adults

The role of dairy foods and related nutrients in cardiometabolic health aetiology is poorly understood. We investigated longitudinal associations between the metabolic syndrome (MetS) and its components with key dairy product exposures. We used prospective data from a bi-racial cohort of urban adults (30-64 years at baseline (n 1371)), the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS), in Baltimore City, MD (2004-2013). The average of two 24-h dietary recalls measured 4-10 d apart was computed at baseline (V1) and follow-up (V2) waves. Annual rates of change (Δ) in dairy foods and key nutrients were estimated. Incident obesity, central obesity and the MetS were determined. Among key findings, in the overall urban adult population, both cheese and yogurt (V1 and Δ) were associated with an increased risk of central obesity (hazard ratio (HR) 1·13; 95 % CI 1·05, 1·23 per oz equivalent of cheese (V1); HR 1·21; 95 % CI 1·01, 1·44 per fl oz equivalent of yogurt (V1)]. Baseline fluid milk intake (V1 in cup equivalents) was inversely related to the MetS (HR 0·86; 95 % CI 0·78, 0·94), specifically to dyslipidaemia-TAG (HR 0·89; 95 % CI 0·81, 0·99), although it was directly associated with dyslipidaemia-HDL-cholesterol (HR 1·10; 95 % CI 1·01, 1·21). Furthermore, ΔCa and ΔP were inversely related to dyslipidaemia-HDL and MetS incidence, respectively, whereas Δdairy product fat was positively associated with incident TAG-dyslipidaemia and HDL-cholesterol-dyslipidaemia and the MetS. A few of those associations were sex and race specific. In sum, various dairy product exposures had differential associations with metabolic disturbances. Future intervention studies should uncover how changes in dairy product components over time may affect metabolic disorders.

An ameloblastin C-terminus variant is present in human adipose tissue

Objective

Transcriptional regulatory elements in the ameloblastin (AMBN) promoter indicate that adipogenesis may influence its expression. The objective here was to investigate if AMBN is expressed in adipose tissue, and have a role during differentiation of adipocytes.

Design

AMBN expression was examined in adipose tissue and adipocytes by real-time PCR and ELISA. Distribution of ameloblastin was investigated by immunofluorescence in sections of human subcutaneous adipose tissue. The effect of recombinant proteins resembling AMBN and its processed products on proliferation of primary human pre-adipocytes and murine 3T3-L1 cell lines was measured by [³H]-thymidine incorporation. The effect on adipocyte differentiation was evaluated by the expression profile of the adipogenic markers PPARγ and leptin, and the content of lipids droplets (Oil-Red-O staining).

Results

AMBN was found to be expressed in human adipose tissue, human primary adipocytes, and in 3T3-L1 cells. The C-terminus of the AMBN protein and a 45 bp shorter splice variant was identified in human subcutaneous adipose tissue. The expression of AMBN was found to increase four-fold during differentiation of 3T3-L1 cells. Administration of recombinant AMBN reduced the proliferation, and enhanced the expression of PPARγ and leptin in 3T3-L1 and human pre-adipocytes, respectively.

Conclusions

The AMBN C-terminus variant was identified in adipocytes. This variant may be encoded from a short splice variant. Increased expression of AMBN during adipogenesis and its effect on adipogenic factors suggests that AMBN also has a role in adipocyte development.

Role of Thermo-Sensitive Transient Receptor Potential Channels in Brown Adipose Tissue

Brown and beige adipocytes are a major site of mammalian non-shivering thermogenesis and energy dissipation. Obesity is caused by an imbalance between energy intake and expenditure and has become a worldwide health problem. Therefore modulation of thermogenesis in brown and beige adipocytes could be an important application for body weight control and obesity prevention. Over the last few decades, the involvement of thermo-sensitive transient receptor potential (TRP) channels (including TRPV1, TRPV2, TRPV3, TRPV4, TRPM4, TRPM8, TRPC5, and TRPA1) in energy metabolism and adipogenesis in adipocytes has been extensively explored. In this review, we summarize the expression, function, and pathological/physiological contributions of these TRP channels and discuss their potential as future therapeutic targets for preventing and combating human obesity and obesity-related metabolic disorders.

The Role of Calcium in Differentiation of Human Adipose-Derived Stem Cells to Adipocytes

Differentiation process of mesenchymal stem cells (MSCs) into adipocyte is involved in obesity. Multiple factors such as Ca²⁺ play important roles in different stages of this process. Because of the complicated roles of Ca²⁺ in adipogenesis, the aim of present investigation was to study the influx and efflux of Ca²⁺ into and out of the cells during adipogenesis. Adipose-derived MSCs were used to differentiate into adipocytes. MSCs were exposed to 2.5 mM Ca²⁺ or 1.8 mM Ca²⁺ plus calcium ionophore, A23187, for 3 days. Lipid staining, triglycerides (TG) content, and glyceraldehyde phosphate dehydrogenase (GAPDH) activity were evaluated to confirm the efficiency of the differentiation. Gene expression of GLUT4, PPARγ2, RAR-α, and calreticulin, as well as the protein levels of GLUT4 and PPARγ2 were determined. Ca²⁺ and in particular Ca²⁺ plus A23187 significantly lowered the efficiency of differentiation accompanied by decrease in intracellular TG deposits, GAPDH activity and alleviation of gene, and protein levels of GLUT4 and PPARγ2. While calreticulin and RAR-α were remarkably upregulated in A23187 group. This study showed the inhibitory effects of calcium in adipogenesis. Additionally, it indicated the greater inhibitory effect of calreticulin and RAR-α in controlling adipogenesis by higher levels of calcium.

Correction of Rhytides, Peau d'Orange, and Thin Dermis of the Face by Neocollagenesis Using Novel Collagen Stimulating Slurry Protocol

We reviewed 200 patient records from 2009 to 2015 of individuals who presented at the authors offices for facial wrinkle reduction and who on physical examination had rhytides, peau d'orange, or thin dermis and underwent novel adipose slurry injections. The patients were evaluated at week 2, 1, 3 and 6 months revealing an 80, 60 and 40% improvement in rhytides and dermis density, respectively. We present the protocol and description of a reasonable alternative or adjunct to manufactured fillers that is comprised of autologous adipose, stem cells, and growth factor slurry. The slurry is easily produced and injected at the bedside in the office setting, and has remarkable and reproducible positive outcomes in skin tone, color, texture, and rhytides as judged by both patient and physician.

LEVEL OF EVIDENCE IV

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Role of mitochondrial dysfunction and dysregulation of Ca2+ homeostasis in the pathophysiology of insulin resistance and type 2 diabetes

Metabolic diseases such as obesity, type 2 diabetes (T2D) and insulin resistance have attracted great attention from biomedical researchers and clinicians because of the astonishing increase in its prevalence. Decrease in the capacity of oxidative metabolism and mitochondrial dysfunction are a major contributor to the development of these metabolic disorders. Recent studies indicate that alteration of intracellular Ca²⁺ levels and downstream Ca²⁺-dependent signaling pathways appear to modulate gene transcription and the activities of many enzymes involved in cellular metabolism. Ca²⁺ uptake into mitochondria modulates a number of Ca²⁺-dependent proteins and enzymes participating in fatty acids metabolism, tricarboxylic acid cycle, oxidative phosphorylation and apoptosis in response to physiological and pathophysiological conditions. Mitochondrial calcium uniporter (MCU) complex has been identified as a major channel located on the inner membrane to regulate Ca²⁺ transport into mitochondria. Recent studies of MCU complex have increased our understanding of the modulation of mitochondrial function and retrograde signaling to the nucleus via regulation of the mitochondrial Ca²⁺ level. Mitochondria couple cellular metabolic state by regulating not only their own Ca²⁺ levels, but also influence the entire network of cellular Ca²⁺ signaling. The mitochondria-associated ER membranes (MAMs), which are specialized structures between ER and mitochondria, are responsible for efficient communication between these organelles. Defects in the function or structure of MAMs have been observed in affected tissue cells in metabolic disease or neurodegenerative disorders. We demonstrated that dysregulation of intracellular Ca²⁺ homeostasis due to mitochondrial dysfunction or defects in the function of MAMs are involved in the pathogenesis of insulin insensitivity and T2D. These observations suggest that mitochondrial dysfunction and disturbance of Ca²⁺ homeostasis warrant further studies to assist the development of therapeutics for prevention and medication of insulin resistance and T2D.

Extracellular calcium modulates brown adipocyte differentiation and identity

Brown adipocytes are important in regulating non-shivering thermogenesis, whole body glucose and lipid homeostasis. Increasing evidence supports an important role of metabolites as well as macro- and micronutrients in brown adipocyte differentiation and function. Calcium is one of the most abundant ions in the body regulating multiple cellular processes. We observed that increasing extracellular calcium concentration during brown adipocyte differentiation blocks lipid accumulation and suppresses induction of major adipogenic transcription factors such as PPARγ and C/EBPα. In contrast, the depletion of calcium in the medium enhances adipogenesis and expression of brown adipocyte selective genes, such as UCP1. Mechanistically, we show that elevated extracellular calcium inhibits C/EBPβ activity through hyperactivation of ERK, a process that is independent of intracellular calcium levels and reversibly halts differentiation. Moreover, increased extracellular calcium solely after the induction phase of differentiation specifically suppresses gene expression of UCP1, PRDM16 and PGC1-α. Notably, depleting extracellular calcium provokes opposite effects. Together, we show that modulating extracellular calcium concentration controls brown adipocyte differentiation and thermogenic gene expression, highlighting the importance of tissue microenvironment on brown adipocyte heterogeneity and function.

Gene expression changes of thermo-sensitive transient receptor potential channels in obese mice

Adipose tissues play key roles in energy homeostasis. Brown adipocytes and beige adipocytes in white adipose tissue (WAT) share the similar characters of thermogenesis, both of them could be potential targets for obesity management. Several thermo-sensitive transient receptor potential channels (thermoTRPs) are shown to be involved in adipocyte biology. However, the expression pattern of thermoTRPs in adipose tissues from obese mice is still unknown. The mRNA expression of thermoTRPs in subcutaneous WAT (sWAT) and interscapular brown adipose tissue (iBAT) from lean and obese mice were measured using reverse transcriptase-quantitative PCRs (RT-qPCR). The results demonstrated that all 10 thermoTRPs are expressed in both iBAT and sWAT, and without significant difference in the mRNA expression level of thermoTRPs between these two tissues. Moreover, Trpv1 and Trpv3 mRNA expression levels in both iBAT and sWAT were significantly decreased in high fat diet (HFD)-induced obese mice and db/db (leptin receptor deficient) mice. Trpm2 mRNA expression level was significantly decreased only in sWAT from HFD-induced obese mice and db/db mice. On the other hand, Trpv2 and Trpv4 mRNA expression levels in iBAT and sWAT were significantly increased in HFD-induced obese mice and db/db mice. Taken together, we conclude that all 10 thermoTRPs are expressed in iBAT and sWAT. And several thermoTRPs differentially expressed in adipose tissues from HFD-induced obese mice and db/db mice, suggesting a potential involvement in anti-obesity regulations.

Obesogenic and Diabetogenic Effects of High-Calorie Nutrition Require Adipocyte BK Channels

Elevated adipose tissue expression of the Ca²⁺- and voltage-activated K⁺ (BK) channel was identified in morbidly obese men carrying a BK gene variant, supporting the hypothesis that K⁺ channels affect the metabolic responses of fat cells to nutrients. To establish the role of endogenous BKs in fat cell maturation, storage of excess dietary fat, and body weight (BW) gain, we studied a gene-targeted mouse model with global ablation of the BK channel (BK^L1/L1) and adipocyte-specific BK-deficient (adipoqBK^L1/L2) mice. Global BK deficiency afforded protection from BW gain and excessive fat accumulation induced by a high-fat diet (HFD). Expansion of white adipose tissue-derived epididymal BK^L1/L1 preadipocytes and their differentiation to lipid-filled mature adipocytes in vitro, however, were improved. Moreover, BW gain and total fat masses of usually superobese ob/ob mice were significantly attenuated in the absence of BK, together supporting a central or peripheral role for BKs in the regulatory system that controls adipose tissue and weight. Accordingly, HFD-fed adipoqBK^L1/L2 mutant mice presented with a reduced total BW and overall body fat mass, smaller adipocytes, and reduced leptin levels. Protection from pathological weight gain in the absence of adipocyte BKs was beneficial for glucose handling and related to an increase in body core temperature as a result of higher levels of uncoupling protein 1 and a low abundance of the proinflammatory interleukin-6, a common risk factor for diabetes and metabolic abnormalities. This suggests that adipocyte BK activity is at least partially responsible for excessive BW gain under high-calorie conditions, suggesting that BK channels are promising drug targets for pharmacotherapy of metabolic disorders and obesity.

The Ca(2+)/Calmodulin/CaMKK2 Axis: Nature's Metabolic CaMshaft

Calcium (Ca(2+)) is an essential ligand that binds its primary intracellular receptor calmodulin (CaM) to trigger a variety of downstream processes and pathways. Central to the actions of Ca(2+)/CaM is the activation of a highly conserved Ca(2+)/CaM kinase (CaMK) cascade that amplifies Ca(2+) signals through a series of subsequent phosphorylation events. Proper regulation of Ca(2+) flux is necessary for whole-body metabolism and disruption of Ca(2+) homeostasis has been linked to various metabolic diseases. Here we provide a synthesis of recent advances that highlight the roles of the Ca(2+)/CaMK axis in key metabolic tissues. An appreciation of this information is critical to understanding the mechanisms by which Ca(2+)/CaM-dependent signaling contributes to metabolic homeostasis and disease.

Effect of Pulsed Electromagnetic Field on Bone Formation and Lipid Metabolism of Glucocorticoid-Induced Osteoporosis Rats through Canonical Wnt Signaling Pathway

Pulsed electromagnetic field (PEMF) has been suggested as a promising method alternative to drug-based therapies for treating osteoporosis (OP), but the role of PEMF in GIOP animal models still remains unknown. This study was performed to investigate the effect of PEMF on bone formation and lipid metabolism and further explored the several important components and targets of canonical Wnt signaling pathway in GIOP rats. After 12 weeks of intervention, bone mineral density (BMD) level of the whole body increased significantly, serum lipid levels decreased significantly, and trabeculae were thicker in GIOP rats of PEMF group. PEMF stimulation upregulated the mRNA and protein expression of Wnt10b, LRP5, β-catenin, OPG, and Runx2 and downregulated Axin2, PPAR-γ, C/EBPα, FABP4, and Dkk-1. The results of this study suggested that PEMF stimulation can prevent bone loss and improve lipid metabolism disorders in GIOP rats. Canonical Wnt signaling pathway plays an important role in bone formation and lipid metabolism during PEMF stimulation.

Role of mitochondrial dysfunction and dysregulation of Ca(2+) homeostasis in insulin insensitivity of mammalian cells

Mitochondria and endoplasmic reticulum (ER) play an important role in the maintenance of intracellular Ca(2+) homeostasis, and their defects may be etiological factors contributing to insulin resistance and type 2 diabetes (T2D). Recent studies indicate that alterations of Ca(2+) levels and Ca(2+) -dependent signaling pathways can impede the insulin signaling cascade, resulting in insulin resistance of β cells and insulin-responsive cells. Mitochondria-associated ER membranes (MAMs) are essential for efficient communication between the ER and mitochondria. Thus, abnormalities in the structure and function of MAMs in affected tissue cells in T2D are an important area of study. Recently, we demonstrated that a deficiency of Cisd2, an iron-sulfur protein localized on MAMs, could lead to mitochondrial dysfunction and disturbance of intracellular Ca(2+) homeostasis. Moreover, we first elucidated that defects in the function of MAMs in Ca(2+) uptake resulted in insulin insensitivity of adipocytes, which plays an important role in the pathogenesis of diabetes in Cisd2 knockout mice. On the basis of these observations, we suggest improving the bioenergetic function of mitochondria and the function of MAMs in maintaining Ca(2+) homeostasis as a novel strategy for the development of new therapeutics aimed at preventing and treating insulin resistance and T2D.

Extracellular Calcium Modulates Chondrogenic and Osteogenic Differentiation of Human Adipose-Derived Stem Cells: A Novel Approach for Osteochondral Tissue Engineering Using a Single Stem Cell Source

We have previously shown that elevating extracellular calcium from a concentration of 1.8 to 8 mM accelerates and increases human adipose-derived stem cell (hASC) osteogenic differentiation and cell-mediated calcium accretion, even in the absence of any other soluble osteogenic factors in the culture medium. However, the effects of elevated calcium on hASC chondrogenic differentiation have not been reported. The goal of this study was to determine the effects of varied calcium concentrations on chondrogenic differentiation of hASC. We hypothesized that exposure to elevated extracellular calcium (8 mM concentration) in a chondrogenic differentiation medium (CDM) would inhibit chondrogenesis of hASC when compared to basal calcium (1.8 mM concentration) controls. We further hypothesized that a full osteochondral construct could be engineered by controlling local release of calcium to induce site-specific chondrogenesis and osteogenesis using only hASC as the cell source. Human ASC was cultured as micromass pellets in CDM containing transforming growth factor-β1 and bone morphogenetic protein 6 for 28 days at extracellular calcium concentrations of either 1.8 mM (basal) or 8 mM (elevated). Our findings indicated that elevated calcium induced osteogenesis and inhibited chondrogenesis in hASC. Based on these findings, stacked polylactic acid nanofibrous scaffolds containing either 0% or 20% tricalcium phosphate (TCP) nanoparticles were electrospun and tested for site-specific chondrogenesis and osteogenesis. Histological assays confirmed that human ASC differentiated locally to generate calcified tissue in layers containing 20% TCP, and cartilage in the layers with no TCP when cultured in CDM. This is the first study to report the effects of elevated calcium on chondrogenic differentiation of hASC, and to develop osteochondral nanofibrous scaffolds using a single cell source and controlled calcium release to induce site-specific differentiation. This approach holds great promise for osteochondral tissue engineering using a single cell source (hASC) and single scaffold.

Biomineralized matrices dominate soluble cues to direct osteogenic differentiation of human mesenchymal stem cells through adenosine signaling

Stem cell differentiation is determined by a repertoire of signals from its microenvironment, which includes the extracellular matrix (ECM) and soluble cues. The ability of mesenchymal stem cells (MSCs), a common precursor for the skeletal system, to differentiate into osteoblasts and adipocytes in response to their local cues plays an important role in skeletal tissue regeneration and homeostasis. In this study, we investigated whether a bone-specific calcium phosphate (CaP) mineral environment could induce osteogenic differentiation of human MSCs, while inhibiting their adipogenic differentiation, in the presence of adipogenic-inducing medium. We also examined the mechanism through which the mineralized matrix suppresses adipogenesis of hMSCs to promote their osteogenic differentiation. Our results show that hMSCs cultured on mineralized matrices underwent osteogenic differentiation despite being cultured in the presence of adipogenic medium, which indicates the dominance of matrix-based cues of the mineralized matrix in directing osteogenic commitment of stem cells. Furthermore, the mineralized matrix-driven attenuation of adipogenesis was reversed with the inhibition of A2b adenosine receptor (A2bR), implicating a role of adenosine signaling in mineralized environment-mediated inhibition of adipogenesis. Such synthetic matrices with an intrinsic ability to direct differentiation of multipotent adult stem cells toward a targeted phenotype while inhibiting their differentiation into other lineages not only will be a powerful tool in delineating the role of complex microenvironmental cues on stem cell commitment but also will contribute to functional tissue engineering and their translational applications.

Proteomic analysis of cAMP-mediated signaling during differentiation of 3 T3-L1 preadipocytes

Initiation of adipocyte differentiation is promoted by the synergistic action of insulin/insulin-like growth factor, glucocorticoids, and agents activating cAMP-dependent signaling. The action of cAMP is mediated via PKA and Epac, where at least part of the PKA function relates to strong repression of Rho kinase activity, whereas Epac counteracts the reduction in insulin/insulin-like growth factor signaling associated with complete repression of Rho kinase activity. However, detailed knowledge of the Epac-dependent branch and the interplay with PKA is still limited. In the present study, we present a comprehensive evaluation of Epac-mediated processes and their interplay with PKA during the initiation of 3 T3-L1 preadipocyte differentiation using a combination of proteomics, molecular approaches, and bioinformatics. Proteomic analyses revealed 7 proteins specifically regulated in response to Epac activation, 4 in response to PKA activation, and 11 in response to the combined activation of Epac and PKA during the initial phase of differentiation. Network analyses indicated that the identified proteins are involved in pathways of importance for glucose metabolism, inositol metabolism, and calcium-dependent signaling thereby adding a novel facet to our understanding of cAMP-mediated potentiation of adipocyte differentiation.

Cisd2 modulates the differentiation and functioning of adipocytes by regulating intracellular Ca2+ homeostasis

CISD2 is a causative gene associated with Wolfram syndrome (WFS). However, it remains a mystery as to how the loss of CISD2 causes metabolic defects in patients with WFS. Investigation on the role played by Cisd2 in specific cell types may help us to resolve these underlying mechanisms. White adipose tissue (WAT) is central to the maintenance of energy metabolism and glucose homeostasis in humans. In this study, adipocyte-specific Cisd2 knockout (KO) mice showed impairment in the development of epididymal WAT (eWAT) in the cell autonomous manner. A lack of Cisd2 caused defects in the biogenesis and function of mitochondria during differentiation of adipocytes in vitro. Insulin-stimulated glucose uptake and secretion of adiponectin by the Cisd2 KO adipocytes were decreased. Moreover, Cisd2 deficiency increased the cytosolic level of Ca(2+) and induced Ca(2+)-calcineurin-dependent signaling that inhibited adipogenesis. Importantly, Cisd2 was found to interact with Gimap5 on the mitochondrial and ER membranes and thereby modulate mitochondrial Ca(2+) uptake associated with the maintenance of intracellular Ca(2+) homeostasis in adipocytes. Thus, it would seem that Cisd2 plays an important role in intracellular Ca(2+) homeostasis, which is required for the differentiation and functioning of adipocytes as well as the regulation of glucose homeostasis in mice.

Role of transient receptor potential channels in adipocyte biology

The transient receptor potential (TRP) channel superfamily is a family of 28 nonselective cation channels expressed on the plasma membrane with a high permeability to calcium. Role of TRP channels, especially TRP vanilloid 1, TRP ankyrin 1 and TRP melastatin 8, is widely documented in nociception. During the last few years, there has been a consistent increase in reports indicating the presence and significance of these channels in different tissues including bladder, skin, respiratory system and brain. Based on calcium permeability of these channels and the much published role of calcium and its signaling in adipogenesis, there is a potential for importance of these ion channels in adipocyte biology. This review provides insight into the involvement of TRP channels in adipocyte differentiation, obesity and associated complications. Furthermore, the authors will focus to evaluate these channels as potential therapeutic targets for the management of obesity.

Layer-shaped alginate hydrogels enhance the biological performance of human adipose-derived stem cells

BACKGROUND

The reconstruction of adipose tissue defects is often challenged by the complications that may occur following plastic and reconstructive surgery, including donor-site morbidity, implant migration and foreign body reaction. To overcome these problems, adipose tissue engineering (ATE) using stem cell-based regeneration strategies has been widely explored in the last years. Mounting evidence has shown that adipose-derived stem cells (ADSCs) represent a promising cell source for ATE. In the context of a small number of reports concerning adipose tissue regeneration using three-dimensional (3-D) systems, the present study was designed to evaluate the biological performance of a novel alginate matrix that incorporates human ADSCs (hADSCs).

RESULTS

Culture-expanded cells isolated from the stromal vascular fraction (SVF), corresponding to the third passage which showed the expression of mesenchymal stem cell (MSC) markers, were used in the 3-D culture systems. The latter represented a calcium alginate hydrogel, obtained by the diffusion of calcium gluconate (CGH matrix), and shaped as discoid-thin layer. For comparative purposes, a similar hADSC-laden alginate hydrogel cross-linked with calcium chloride was considered as reference hydrogel (RH matrix). Both hydrogels showed a porous structure under scanning electron microscopy (SEM) and the hADSCs embedded displayed normal spherical morphologies, some of them showing signs of mitosis. More than 85% of the entrapped cells survived throughout the incubation period of 7 days. The percentage of viable cells was significantly higher within CGH matrix at 2 days post-seeding, and approximately similar within both hydrogels after 7 days of culture. Moreover, both alginate-based hydrogels stimulated cell proliferation. The number of hADSC within hydrogels has increased during the incubation period of 7 days and was higher in the case of CGH matrix. Cells grown under adipogenic conditions for 21 days showed that both analyzed 3-D culture systems support adipogenic differentiation in terms of neutral lipid accumulation and perillipin expression. Furthermore, the cells encapsulated in CGH matrix displayed a more differentiated phenotype.

CONCLUSIONS

The results of this study suggest that both CGH and RH matrices successfully support the survival and adipogenesis of hADSC. An enhancement of biological performance was detected in the case of CGH matrix, suggesting its promising application in ATE.

Calreticulin signaling in health and disease

Calreticulin is an endoplasmic reticulum Ca(2+) binding chaperone that has multiple functions inside and outside of the endoplasmic reticulum. It is involved in the quality control of newly synthesized proteins and glycoproteins, interacting with various other endoplasmic reticulum chaperones, specifically calnexin and ER protein of 57-kDa in the calreticulin/calnexin cycle. Calreticulin also plays a crucial role in regulating intracellular Ca(2+) homeostasis, associating calreticulin with a wide variety of signaling processes, such as cardiogenesis, adipocyte differentiation and cellular stress responses. The role of calreticulin outside of the endoplasmic reticulum is also extensive, including functions in wound healing and immunity. Therefore, calreticulin has important implications in health and disease. Signaling facts.

The Ca2+/calmodulin-dependent protein kinase kinase, CaMKK2, inhibits preadipocyte differentiation

When fed a standard chow diet, CaMKK2 null mice have increased adiposity and larger adipocytes than do wild-type mice, whereas energy balance is unchanged. Here, we show that Ca(2+)/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is expressed in preadipocytes, where it functions as an AMP-activated protein kinase (AMPK)α kinase. Acute inhibition or deletion of CaMKK2 in preadipocytes enhances their differentiation into mature adipocytes, which can be reversed by 5-aminoimidazole-4-carboxamide ribonucleotide-mediated activation of AMPK. During adipogenesis, CaMKK2 expression is markedly decreased and temporally accompanied by increases in mRNA encoding the early adipogenic genes CCAAT/enhancer binding protein (C/EBP) β and C/EBP δ. Preadipocyte factor 1 has been reported to inhibit adipogenesis by up-regulating sex determining region Y-box 9 (Sox9) expression in preadipocytes and Sox9 suppresses C/EBPβ and C/EBPδ transcription. We show that inhibition of the CaMKK2/AMPK signaling cascade in preadipocytes reduces preadipocyte factor 1 and Sox9 mRNA resulting in accelerated adipogenesis. We conclude that CaMKK2 and AMPK function in a signaling pathway that participates in the regulation of adiposity.

p38 MAPK regulates calcium signal-mediated lipid accumulation through changing VDR expression in primary preadipocytes of mice

In the present study we have examined whether p38 mitogen activated protein kinase (p38 MAPK) signal pathway interacts with calcium signal on lipid accumulation in primary preadipocytes of mice. The primary preadipocytes were treated with p38 MAPK inhibitor SB203580, blockers and excitomotors of calcium channel for 24 h, respectively. Intracellular triglyceride (TG) content was measured by triglyceride kit and lipid accumulation was determined by Oil Red O staining. Meanwhile, the mRNA expressions of peroxisome proliferators-activated receptor gamma (PPARγ) gene, fatty acid synthetase (FAS) gene, lipoprotein lipase (LPL) gene, vitamin D receptor (VDR) gene and extracellular Ca(2+)-sensing receptor (CaSR) gene were analyzed with real-time PCR. The protein content and phosphorylation of VDR and p38 were tested with Western Blotting. The data showed that intracellular TG content and the mRNA expression levels of PPARγ, FAS, LPL in N group and L group as well as FAS, LPL in C group were increased significantly (P < 0.01) compared to the control. On the contrary, intracellular TG content and the mRNA expression levels of PPARγ, FAS in B group as well as intracellular TG content and PPARγ, FAS, LPL in SB group and B+SB group were decreased significantly (P < 0.01). VDR mRNA expression and protein content were decreased in B, C, and SB added groups (P < 0.01). In addition, p38 phosphorylation levels increased in N and L groups (P < 0.01) and decreased in SB added groups (P < 0.01). These findings suggest that p38 MAPK pathway through regulating VDR mRNA expression participates in mediation of calcium signal and affects calcium signal regulating lipid accumulation in mice preadipocytes through changing PPARγ, FAS and LPL mRNA expression. In addition, calcium signal have a feedback effect in phosphorylation of p38.

Calcium ameliorates obesity induced by high-fat diet and its potential correlation with p38 MAPK pathway

To investigate whether and on which pathway dietary calcium influence the obesity induced by high-fat diet, thirty male Kunming mice were fed in six groups for 4 weeks and mouse preadipocytes were divided into eight groups for different treatment. Body weight gain was measured each week. Calcium in serum and tissues, intracellular free Ca(2+) concentration ([Ca(2+)]i), blood fat and intracellular lipid content were also measured. The expression of Lipid metabolism-related genes were measured by q RT-PCR. Compared with control group, body weight gain (P < 0.05) and fat pad weight (P < 0.01) in Low calcium group decreased. Triglycerides (TG) and total Cholesterol (TC) level decreased (P < 0.01), while HDL-Cholesterol (HDL) level increased (P < 0.01). And calcium supply increased calcium content in blood serum and tissues. In tissues, adipogenesis and vitamin D receptor (VDR) genes expression decreased but lipoclasis genes expression increased. These anti-obesity effects were more obvious when supplying with 2.8% calcium, but the effects were reduced while supplying Nifedipine at the same time. The results in preadipocytes indicated that calcium-treated can reduce intracellular lipid content, along with adipogenesis and lipoclasis genes expression decrease, promoted the expression levels of p38 MAPK pathway upstream gene MKK6 (P < 0.01) and downstream gene MAPKAPK2 (P < 0.01). Treated with SB203580 could increase adipogenesis genes expression, decrease lipoclasis genes expression and ([Ca(2+)]i) (P < 0.01). These results implied that dietary calcium had remarkable effect on anti-obesity effect and p38 MAPK pathway potentially participated in calcium-mediated lipid accumulation and lipolysis in mouse preadipocytes.

Gene expression profiles in Atlantic salmon adipose-derived stromo-vascular fraction during differentiation into adipocytes

BACKGROUND

Excessive fat deposition is one of the largest problems faced by salmon aquaculture industries, leading to production losses due to high volume of adipose tissue offal. In addition, increased lipid accumulation may impose considerable stress on adipocytes leading to adipocyte activation and production and secretion of inflammatory mediators, as observed in mammals.

RESULTS

Microarray and qPCR analyses were performed to follow transcriptome changes during adipogenesis in the primary culture of adipose stromo-vascular fraction (aSVF) of Atlantic salmon. Cellular heterogeneity decreased by confluence as evidenced by the down-regulation of markers of osteo/chondrogenic, myogenic, immune and vasculature lineages. Transgelin (TAGLN), a marker of the multipotent pericyte, was prominently expressed around confluence while adipogenic PPARgamma was up-regulated already in subconfluent cells. Proliferative activity and subsequent cell cycle arrest were reflected in the fluctuations of pro- and anti-mitotic regulators. Marked regulation of genes involved in lipid and glucose metabolism and pathways producing NADPH and glycerol-3-phosphate (G3P) was seen during the terminal differentiation, also characterised by diverse stress responses. Activation of the glutathione and thioredoxin antioxidant systems and changes in the iron metabolism suggested the need for protection against oxidative stress. Signs of endoplasmic reticulum (ER) stress and unfolded protein response (UPR) occured in parallel with the increased lipid droplet (LD) formation and production of secretory proteins (adipsin, visfatin). The UPR markers XBP1 and ATF6 were induced together with genes involved in ubiquitin-proteasome and lysosomal proteolysis. Concurrently, translation was suppressed as evidenced by the down-regulation of genes encoding elongation factors and components of the ribosomal machinery. Notably, expression changes of a panel of genes that belong to different immune pathways were seen throughout adipogenesis. The induction of AP1 (Jun, Fos), which is a master regulator of stress responses, culminated by the end of adipogenesis, concurrent with the maximal observed lipid deposition.

CONCLUSIONS

Our data point to an intimate relationship between metabolic regulation and immune responses in white adipocytes of a cold-blooded vertebrate. Stress imposed on adipocytes by LD formation and expansion is prominently reflected in the ER compartment and the activated UPR response could have an important role at visceral obesity in fish.