The relationship between alkaline phosphatase activity and intracellular lipid accumulation in murine 3T3-L1 cells and human preadipocytes

Relationship of Liver Blood Tests and T1 Relaxation Time With Intra-pancreatic Fat Deposition

Background

Liver is well recognised as a metabolically active organ. While intra-pancreatic fat deposition (IPFD) is emerging as an important player in the whole-body metabolism, the interplay between the liver and IPFD has been poorly investigated. This study aimed to investigate the associations of liver blood tests and non-invasive tests for hepatic fibrosis with IPFD.

Methods

Participants underwent a 3.0 Tesla magnetic resonance imaging to measure IPFD and map liver T1 (longitudinal relaxation time). Four liver tests were done on the same sample of blood. Hepatic fibrosis risk score (BARD) was calculated. Linear regression models were built, accounting for age, sex, visceral-to-subcutaneous fat ratio, and other covariates.

Results

A total of 143 individuals were studied. In the most adjusted model, alkaline phosphatase (P < 0.001), alanine aminotransferase (P < 0.001), and γ-glutamyl transferase (P = 0.042) were significantly positively associated with IPFD. The BARD score was not significantly associated with IPFD in the most adjusted model (P = 0.295). T1 relaxation time of the liver was not significantly associated with IPFD in the most adjusted model (P = 0.782).

Conclusions

Elevated alkaline phosphatase, alanine aminotransferase, and γ-glutamyl transferase are associated with increased IPFD. Hepatic fibrosis does not appear to be associated with IPFD.

Impact of obesity on liver function tests: is nonalcoholic fatty liver disease the only player? A review article

Objectives

Obesity and nonalcoholic fatty liver disease (NAFLD) are common worldwide health problems with a strong relationship in between. NAFLD is currently the most common cause of abnormal liver function tests (LFT) because of obesity pandemic. The question is NAFLD the only player of abnormal LFT in obesity?

Methodology

This article reviews the most important topics regarding the derangements of LFT in obesity through a PubMed search strategy for all English-language literature.

Results

The reported abnormal LFT in obesity were increased serum levels of transaminases (alanine aminotransaminase, aspartate aminotransaminase), gamma glutamyl transferase, and alkaline phosphatase and decreased serum levels of bilirubin and albumin. Besides novel potential hepatic markers of NAFLD/NASH such as triglycerides/high-density lipoprotein cholesterol ratio, sex hormone-binding globulin, fibroblast growth factor 21, and markers of hepatocyte apoptosis i.e. cytokeratin 18 and microribonucleic acids (miRNAs). Beyond NAFLD, there are other underlying players for the abnormal LFT in obesity such as oxidative stress, inflammation, and insulin resistance.

Conclusion

Derangements of LFT in obesity are attributed to NAFLD but also to obesity itself and its related oxidative stress, insulin resistance, and chronic inflammatory state. Abnormal LFT predict more than just liver disease.

Integrated metabolomics and transcriptomics analyses reveal the key genes regulating differential metabolites of longissimus dorsi muscle in castrated South Sichuan black goats (Capra hircus)

The main aim of the current work was to explore the differential metabolites and differentially expressed genes of longissimus dorsi muscle (LDM) between castrated and uncastrated fattening male South Sichuan black goats (Capra hircus). Then, the key genes regulating important differential metabolites (DMs) in castrated male goats were observed by integrated metabolomics and transcriptomics analyses. In addition, we evaluated the effects of castration on blood constituents, dressing percentage, and water holding capacity of LDM in male black goats. The results showed that the concentrations of alkaline phosphatase (ALP), total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) were significantly increased and testosterone was significantly decreased in castrated male goats compared with the uncastrated male goats, while dressing percentage of black goats and water holding capacity of longissimus dorsi muscle were not significant differences. Through metabolomics and transcriptomics analyses, 23 important KEGG pathways, 13 important DMs, 32 important differentially expressed genes (DEGs), and 13 key genes related to the "Metabolism" and "Organismal systems" pathways were screened. Lipid accumulation may be elevated in the blood of fattening South Sichuan black goats after castration. Castration might play a positive role in energy provision, intercellular signaling, muscle function, softening of meat, disease reduction, and anti-oxidation of LDM. P4HA2, AKR1B1, GPT2, L2HGDH, ENSCHIG00000021660, ENSCHIG00000023861, DGAT2, ULK1, SLC38A3, PLA2G4A, SLC6A1, ENSCHIG00000026624, and ND2 might be the key genes regulating important DMs in the KEGG pathways related to "Metabolism" and "Organismal systems" of castrated male goats compared with the uncastrated male goats.

Enhanced Proliferative and Osteogenic Potential of Periodontal Ligament Stromal Cells

Cell-based therapies using periodontal ligament stromal cells (PDLSC) for periodontal regeneration may represent an alternative source for mesenchymal stromal cells (MSC) to MSC derived from bone marrow (MSC(M)) and adipose tissue (MSC(AT)). We aimed to characterize the osteogenic/periodontal potential of PDLSC in comparison to MSC(M) and MSC(AT). PDLSC were obtained from surgically extracted healthy human third molars, while MSC(M) and MSC(AT) were obtained from a previously established cell bank. Flow cytometry, immunocytochemistry, and cell proliferation analyses provided cellular characteristics from each group. Cells from the three groups presented MSC-like morphology, MSC-related marker expression, and multilineage differentiation capacity (adipogenic, chondrogenic, and osteogenic). In this study, PDLSC expressed osteopontin, osteocalcin, and asporin, while MSC(M) and MSC(AT) did not. Of note, only PDLSC expressed CD146, a marker previously applied to identify PDLSC, and presented higher proliferative potential compared to MSC(M) and MSC(AT). Upon osteogenic induction, PDLSC exhibited higher calcium content and enhanced upregulation of osteogenic/periodontal genes compared to MSC(M) and MSC(AT), such as Runx2, Col1A1 and CEMP-1. However, the alkaline phosphatase activity of PDLSC did not increase. Our findings suggest that PDLSC might be a promising cell source for periodontal regeneration, presenting enhanced proliferative and osteogenic potential compared to MSC(M) and MSC(AT).

Evaluation of Liver Metabolism Biomarkers in Metabolic Associated Fatty Liver Disease According to Obesity Phenotype

OBJECTIVE

To analyze the relationship between the biochemical markers of liver metabolism in different stages of Metabolic Associated Fatty Liver Disease (MAFLD) according to the obesity phenotype.

METHODOLOGY

This is a cross-sectional study with individuals with class III obesity classified according to the obesity phenotypes proposed by the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria. Biochemical and anthropometric variables were analyzed according to the staging of MAFLD and obesity phenotype.

RESULTS

A total of 50 subjects with MAFLD, 62% (n = 31) with steatosis and 38% (n = 19) with steatohepatitis without fibrosis; 36% were classified as metabolically healthy obesity (MHO) and 64% as metabolically unhealthy obesity (MUHO), respectively. Mean values of alkaline phosphatase were 85.44 ± 27.27 vs. 61.92 ± 17.57 (p = 0.006); gamma-glutamyl transpeptidase, 25.77 ± 15.36 vs. 30.63 ± 19.49 (p = 0.025); and albumin, 3.99 ± 0.34 vs. 4.24 ± 0.23 (p = 0.037), were lower and statistically significant in the MHO group with steatosis. The results show when considering individuals with IR, only AP is a predictor of unhealthy phenotype (B-0.934, 0.848- 1.029, p = 0.031).

CONCLUSION

MHO individuals with steatosis present lower severe changes related to markers of liver damage and function and AP is considered the predictor of MUHO phenotype.

Differential glycosylation of tissue non-specific alkaline phosphatase in mesenchymal stromal cells differentiated into either an osteoblastic or adipocytic phenotype

It has long been known that tissue non-specific alkaline phosphatase (TNAP) is essential for the correct formation of bone, as altered expression or function of this enzyme results in hypophosphatasia, a disease characterised by compromised bone structure, density and strength. However, recent evidence strongly suggests that the enzyme also has a role in lipid accrual and adipogenesis, a function that seems far removed from bone formation. Given that mesenchymal stromal cells (MSCs) are progenitors of both osteoblasts and adipocytes, the question arises of how TNAP is regulated to potentially have a different function when MSCs undergo either osteogenesis or adipogenesis. As the primary protein sequence is unchanged for the enzyme during both types of differentiation, any differences in function must be attributed to post-translational modification and/or localisation. We therefore examined the location of TNAP in bone- or adipose-derived MSCs differentiated into an adipocytic phenotype and compared the glycosylation state of the enzyme in MSCs differentiated into either osteoblasts or adipocytes. TNAP was found to co-locate with perilipin around lipid droplets in MSCs from bone, subcutaneous- and visceral adipose tissue during adipocytic differentiation. Treatment of TNAP with wheat germ lectin followed by electrophoresis showed minor differences in glycosylation between the phosphatase isolated from cells from these tissues, whereas electrophoresis after neuraminidase digestion highlighted differential glycosylation between cell types and during adipogenesis and osteoblastogenesis. This infers that post-translational modification of TNAP is altered during differentiation and is dependent on the eventual phenotype of the cells.

A new perspective on the function of Tissue Non-Specific Alkaline Phosphatase: from bone mineralization to intra-cellular lipid accumulation

Tissue-nonspecific alkaline phosphatase (TNAP) is one of four isozymes, which include germ cell, placental and intestinal alkaline phosphatases. The TNAP isozyme has 3 isoforms (liver, bone and kidney) which differ by tissue expression and glycosylation pattern. Despite a long history of investigation, the exact function of TNAP in many tissues is largely unknown. Only the bone isoform has been well characterised during mineralization where the enzyme hydrolyses pyrophosphate to inorganic phosphate, which combines with calcium to form hydroxyapatite crystals deposited as new bone. The inorganic phosphate also increases gene expression of proteins that support tissue mineralization. Recent studies have shown that TNAP is expressed in preadipocytes from several species, and that inhibition of TNAP activity causes attenuation of intracellular lipid accumulation in these and other lipid-storing cells. The mechanism by which TNAP stimulates lipid accumulation is not known; however, proteins that are important for controlling phosphate levels in bone are also expressed in adipocytes. This review examines the evidence that inorganic phosphate generated by TNAP promotes transcription that enhances the expression of the regulators of lipid storage and consequently, that TNAP has a major function of lipid metabolism.

Tissue non-specific alkaline phosphatase mediates the accumulation of cholesterol esters in the murine Y1 adrenal cortex cell line

BACKGROUND

Cholesterol esters (CEs) accumulate in the cells of the adrenal cortex and are used for the synthesis of steroid hormones. The full molecular pathways involved in mediating the accumulation of CEs within the adrenal cortex are yet to be elucidated. Tissue non-specific alkaline phosphatase (TNAP) is needed for intracellular lipid accumulation of triglycerides in adipocytes and is also expressed in the cortical cells of the adrenal gland. Therefore we aimed to determine if TNAP is needed for the accumulation of CEs within the murine Y1 adrenal cortex cell line.

METHODS

Y1 cells were induced to accumulate lipids. Lipid accumulation and TNAP activity and expression were determined throughout intracellular lipid accumulation. The location of TNAP within the cell was determined through immunohistochemical analysis. Lipid accumulation in the cells was associated with a rise in TNAP activity and TNAP was localised to lipid droplets within the Y1 cells. Inhibition of TNAP with a specific inhibitor (levamisole) resulted in the cessation of CE accumulation.

DISCUSSION AND CONCLUSIONS

These data demonstrate that TNAP plays a role in the control of lipid accumulation in this adrenal cortex cell line. Therefore, in both triglyceride and CE storing cell types TNAP would seem to be essential for intra-cellular lipid storage.

Early maternal circulating alkaline phosphatase with subsequent gestational diabetes mellitus and glucose regulation: a prospective cohort study in China

PURPOSE

Emerging clinical evidence has implied that alkaline phosphatase (ALP) may contribute to gestational diabetes mellitus (GDM). However, there were no studies to reveal the independent and prospective associations between ALP and GDM. Our aim was to explore the independent and prospective associations between early maternal ALP level and GDM risk and glucose regulation.

METHODS

In a prospective cohort study with 2073 singleton mothers at four maternity units in China, maternal serum ALP levels were measured before 20 gestational weeks. Using logistic regression, we analyzed the relationship between maternal ALP level and risk of GDM. We further explored the relationships of ALP level to fasting blood glucose (FBG), 1-h and 2-h post-load blood glucose (1-h, 2-h PBG) with multiple linear regression. Finally, we analyzed the association between maternal ALP level and isolated impaired fasting glucose (i-IFG) and isolated impaired glucose tolerance (i-IGT) risk.

RESULTS

The maximum value of maternal ALP level was 90 U/L, within the normal range. After adjustment for confounding factors, the odds ratio (ORs) of GDM increased linearly with ALP level (p for overall association = 0.002, p for nonlinear association = 0.799), with the OR comparing the highest versus lowest quartile of 2.47 (95% CI 1.47, 4.15). Moreover, each additional of 10 U/L ALP level was associated with a 2% higher FBG (p = 0.043) and a 12% higher 1-h PBG (p = 0.004). Higher ALP level also increased the risk of i-IFG (OR 3.73, 95% CI 1.17-11.86) and i-IGT (OR 2.03, 95% CI 1.07-3.84).

CONCLUSIONS

Even within the upper limit of normal, higher early maternal ALP level could increase the risk of GDM. Moreover, both FBG and PBG were increased with early maternal ALP.

Osteogenic potential of adipogenic predifferentiated human bone marrow-derived multipotent stromal cells for bone tissue-engineering

In the present study, we evaluated the benefits of an adipogenic predifferentiation, the pathway most closely related to osteoblastogenesis, on the pro-osteogenic potential of human adult multipotent bone marrow stromal cells (hBMSCs), both in vitro and in vivo. Adipogenic differentiation of hBMSCs for 14 days resulted in a heterogeneous cell population from which the most adipogenic-committed cells were eliminated by their lack of readhesion ability. Our results provided evidence that the select adherent adipogenic differentiated hBMSCs (sAD+ cells) express a gene profile characteristic of both adipogenic and osteogenic lineages. In vitro, when cultured in osteogenic medium, sAD+ differentiated along the osteogenic lineage faster than undifferentiated hBMSCs. In vivo, in an ectopic mouse model, sAD+ exhibited a significantly higher bone formation capability compared with undifferentiated hBMSCs. We sought, then, to investigate the underlying mechanisms responsible for such beneficial effects of adipogenic predifferentiation on bone formation and found that this outcome was not linked to a better cell survival post-implantation. The secretome of sAD+ was both proangiogenic and chemoattractant, but its potential did not supersede the one of undifferentiated hBMSCs. However, using co-culture systems, we observed that the sAD+ paracrine factors were pro-osteogenic on undifferentiated hBMSCs. In conclusion, adipogenic priming endows hBMSCs with high osteogenic potential as well as pro-osteogenic paracrine-mediated activity. This preconditioning appears as a promising strategy for bone tissue engineering technology in order to improve the hBMSC osteogenic potency in vivo.

Specific knock-down of tissue non-specific alkaline phosphatase mRNA levels inhibits intracellular lipid accumulation in 3T3-L1 and HepG2 cells

The use of non-specific inhibitors of tissue non-specific alkaline phosphatase (TNSALP) in pre-adipocytes blocks intracellular lipid accumulation. TNSALP is also expressed in hepatocytes, which are known to accumulate lipid in a similar manner to pre-adipocytes. The purpose of this study was to use specific silencing of TNSALP mRNA, using short interfering (si) RNA, to investigate the role of TNSALP in intracellular lipid accumulation in 3T3-L1 and HepG2 cells. Cellular activity of TNSALP was measured using an automated colorimetric assay, and intracellular lipid accumulation was determined using the lipid-specific dye, Oil Red O. Cells were transfected with siRNA directed against TNSALP mRNA, and expression of the TNSALP gene was determined at selected time points postinduction of lipid droplet formation. Expression of the TNSALP gene was inhibited by a maximum of 88 ± 1.9% (P < 0.005 vs. control) 11 days after initiation of lipid droplet formation in the 3T3-L1 cells and 80 ± 8.9% (P < 0.05 vs. control) after 4 days in the HepG2 cells. This led to significant inhibition of both TNSALP activity and intracellular lipid accumulation in both cell lines. These data demonstrates that TNSALP plays an important role in the control of lipid droplet formation in both pre-adipocyte and hepatocyte cell lines.

The role of alkaline phosphatase in intracellular lipid accumulation in the human hepatocarcinoma cell line, HepG2

Inhibition of tissue non-specific alkaline phosphatase (TNALP) decreases intracellular lipid accumulation in human preadipocytes and the murine preadipocyte cell line, 3T3-L1. Therefore, the current study was performed to determine if TNALP is required for intracellular lipid deposition in the human hepatocyte cell line, HepG2. Intracellular lipid accumulation, TNALP activity and peroxisome proliferator activated receptor (PPAR) γ gene expression were measured in HepG2 and 3T3-L1 cells in the presence and absence of the TNALP inhibitors levamisole and histidine. Sub-cellular TNALP activity was localized using cytochemical analysis. Both PPARγ gene expression and TNALP activity increased during intracellular lipid accumulation in HepG2 and 3T3-L1 cells. Inhibition of TNALP blocked intracellular lipid accumulation but did not alter expression of the PPARγ gene. In HepG2 cells, TNALP co-localized with adipophilin on the lipid droplet membrane. These data suggest a role for TNALP in lipid droplet formation, possibly downstream from PPARγ, within HepG2 and 3T3-L1 cells.

Presentation of functional groups on self-assembled supramolecular peptide nanofibers mimicking glycosaminoglycans for directed mesenchymal stem cell differentiation

Organizational complexity and functional diversity of the extracellular matrix regulate cellular behaviors.

Sulforaphane induces adipocyte browning and promotes glucose and lipid utilization

SCOPE

Obesity is closely related to the imbalance of white adipose tissue storing excess calories, and brown adipose tissue dissipating energy to produce heat in mammals. Recent studies revealed that acquisition of brown characteristics by white adipocytes, termed "browning," may positively contribute to cellular bioenergetics and metabolism homeostasis. The goal was to investigate the putative effects of natural antioxidant sulforaphane (1-isothiocyanate-4-methyl-sulfonyl butane; SFN) on browning of white adipocytes.

METHODS AND RESULTS

3T3-L1 mature white adipocytes were treated with SFN for 48 h, and then the mitochondrial content, function, and energy utilization were assessed. SFN was found to induce 3T3-L1 adipocytes browning based on the increased mitochondrial content and activity of respiratory chain enzymes, whereas the mechanism involved the upregulation of nuclear factor E2-related factor 2/sirtuin1/peroxisome proliferator activated receptor gamma coactivator 1 alpha signaling. SFN enhanced uncoupling protein 1 expression, a marker for brown adipocyte, leading to the decrease in cellular ATP. SFN also enhanced glucose uptake and oxidative utilization, lipolysis, and fatty acid oxidation in 3T3-L1 adipocytes.

CONCLUSION

SFN-induced browning of white adipocytes enhanced the utilization of cellular fuel, and application of SFN is a promising strategy to combat obesity and obesity-related metabolic disorder.

Glycerol Production from Glucose and Fructose by 3T3-L1 Cells: A Mechanism of Adipocyte Defense from Excess Substrate

Cultured adipocytes (3T3-L1) produce large amounts of 3C fragments; largely lactate, depending on medium glucose levels. Increased glycolysis has been observed also in vivo in different sites of rat white adipose tissue. We investigated whether fructose can substitute glucose as source of lactate, and, especially whether the glycerol released to the medium was of lipolytic or glycolytic origin. Fructose conversion to lactate and glycerol was lower than that of glucose. The fast exhaustion of medium glucose was unrelated to significant changes in lipid storage. Fructose inhibited to a higher degree than glucose the expression of lipogenic enzymes. When both hexoses were present, the effects of fructose on gene expression prevailed over those of glucose. Adipocytes expressed fructokinase, but not aldolase b. Substantive release of glycerol accompanied lactate when fructose was the substrate. The mass of cell triacylglycerol (and its lack of change) could not justify the comparatively higher amount of glycerol released. Consequently, most of this glycerol should be derived from the glycolytic pathway, since its lipolytic origin could not be (quantitatively) sustained. Proportionally (with respect to lactate plus glycerol), more glycerol was produced from fructose than from glucose, which suggests that part of fructose was catabolized by the alternate (hepatic) fructose pathway. Earlier described adipose glycerophophatase activity may help explain the glycolytic origin of most of the glycerol. However, no gene is known for this enzyme in mammals, which suggests that this function may be carried out by one of the known phosphatases in the tissue. Break up of glycerol-3P to yield glycerol, may be a limiting factor for the synthesis of triacylglycerols through control of glycerol-3P availability. A phosphatase pathway such as that described may have a potential regulatory function, and explain the production of glycerol by adipocytes in the absence of lipolytic stimulation.

Tissue alkaline phosphatase is involved in lipid metabolism and gene expression and secretion of adipokines in adipocytes

BACKGROUND

Alkaline phosphatases are dimeric hydrolytic enzymes that dephosphorylate nucleotides and proteins. AP-TNAP is found primarily in skeletal tissues were it plays a major role in the mineralization of the extracellular matrix and bone formation.

METHODS

In this study we found through conventional and real time PCR assays that Alpl, the gene encoding for AP-TNAP is expressed in adipose tissue and in 3 T3-F442A adipocytes. We evaluated, using RNAi its role in adipocyte metabolism, and its cytoplasmic location by immunohistochemistry.

RESULTS

Alpl is highly expressed late in adipogenesis during adipose terminal differentiation. Knocking down Alpl increased the expression of the genes encoding for glycerophosphate dehydrogenase, and for the adipokines adiponectin, and FABP4 (aP2) but decreased that of leptin, and it also increased secretion of FABP4; these 3 proteins are important in adipocyte systemic signaling and insulin sensitivity. Inhibition of alkaline phosphatase activity in adipocytes by levamisole reduced lipolysis and the expression of various lipogenic genes. We found the enzyme intracytoplasmically, forming aggregates in close surroundings of the lipid droplets during lipolysis.

CONCLUSIONS

We suggest that AP-TNAP activity is involved in lipid and energy metabolism of fat cells, and it might regulate glucose metabolism and insulin sensitivity via adipokine synthesis and secretion.

GENERAL SIGNIFICANCE

The activity of AP-TNAP might have a critical role in the energy balance of the adipocyte, probably participating in obesity and metabolic syndrome.

Differential Properties of Human ALP+ Periodontal Ligament Stem Cells vs Their ALP- Counterparts

Characterizing subpopulations of stem cells is important to understand stem cell properties. Tissue-nonspecific alkaline phosphatase (ALP) is associated with mineral tissue forming cells as well as stem cells. Information regarding ALP subpopulation of human periodontal ligament stem cells (hPDLSCs) is limited. In the present study, we examined ALP⁺ and ALP⁻ hPDLSC subpopulations, their surface markers STRO-1 and CD146, and the expression of stemness genes at various cell passages. We found that ALP⁺ subpopulation had higher levels of STRO-1 (30.6 ± 5.6%) and CD146 (90.4 ± 3.3%) compared to ALP⁻ (STRO-1: 0.5 ± 0.1%; CD146: 75.3 ± 7.2%). ALP⁺ cells expressed significantly higher levels of stemness associated genes, NANOG, OCT4 and SOX than ALP⁻ cells at low cell passages of 2-3 (p<0.05). ALP⁺ and ALP⁻ cells had similar osteogenic, chondrogenic and neurogenic potential while ALP⁻, not ALP⁺ cells, lacked adipogenic potential. Upon continuous culturing and passaging, ALP⁺ continued to express higher stemness genes and STRO-1 and CD146 than ALP⁻ cells at ≥passage 19. Under conditions (over-confluence and vitamin C treatment) when ALP⁺ subpopulation was increased, the stemness gene levels of ALP⁺ was no longer significantly higher than those in ALP⁻ cells. In conclusion, ALP⁺ hPDLSCs possess differential properties from their ALP⁻ counterparts.

Ethnic differences in pre-adipocyte intracellular lipid accumulation and alkaline phosphatase activity

Alkaline phosphatase (ALP) increases lipid accumulation in human pre-adipocytes. This study was performed to assess whether ethnic differences in the prevalence of obesity in African and European females are related to differences in pre-adipocyte lipid accretion and ALP activity. Pre-adipocytes were isolated from 13 black and 14 white females. Adipogenesis was quantified using the lipid dye, Oil red O, whilst ALP activity was assayed in cell extracts on day zero and 12days after initiating adipogenesis. Lipid levels (OD units/mg protein) were lower in pre-adipocytes from white than black females on day 0 (0.36±0.05 versus 0.44±0.03, respectively; p<0.0005) and day 12 (1.18±0.14 versus 1.80±0.22, respectively; p<0.0005), as was ALP activity (mU/mg protein) on day zero (36.5±5.8 versus 136.4±10.9, respectively; p<0.0005) and day 12 (127±16 versus 278±27, respectively; p<0.0005). Treatment of pre-adipocytes with histidine, an ALP inhibitor, blocked lipid accumulation. Thus, lipid uptake is higher in pre-adipocytes isolated from black compared to white females which parallels the obesity prevalence rates in these population groups. The reason for higher fat accumulation in pre-adipocytes isolated from black females may be related to higher ALP activity.

Impact of adipogenic differentiation on stemness and osteogenic gene expression in extensive culture of human adipose-derived stem cells

INTRODUCTION

Adipose tissue is a source of multipotent adult stem cells. Most studies on human adipose-derived stem cells (ASC) have been on the early passages. Studies in extensive expansion have not been well established yet. In this study, we aim to investigate the effects of extensive expansion on the adipogenic differentiation capability of ASC.

MATERIAL AND METHODS

The ability of ASC to undergo adipogenic differentiation in extensive expansion was evaluated by morphological changes, differentiation assay by using Oil Red O staining and changes in the genes expression levels of adipogenic genes, osteogenic genes and stemness genes using quantitative polymerase chain reaction (qPCR) after induction.

RESULTS

Morphological study showed that the formation of lipid droplets can be observed at all passages but decreased at P20 after induction. Data from qPCR showed that most adipogenicgenes expression increased significantlyat P5, P10 and P15 but decreased at P20 after induction. On the other hand, osteogenic genes showed no significant changes after adipogenic induction indicating low potentiality of adipogenic-induced ASC to become osteogenic cells. While stemness genes expression levels showed a decrease or no significant changes after adipogenic induction except Nanog3, which showed a significant increase at P15 and P20.

CONCLUSIONS

The ability of ASC to differentiate into mature adipogenic cells decreased after P10 and the decrease in the osteogenics gene expression level during adipogenic induction suggested that the osteogenesis and adipogenesis are not parallel events.

The interrelationship between bone and fat: from cellular see-saw to endocrine reciprocity

The number of mature osteoblasts and marrow adipocytes in bone is influenced by the differentiation of the common mesenchymal progenitor cell towards one phenotype and away from the other. Consequently, factors which promote adipogenesis not only lead to fatty marrow but also inhibit osteoblastogenesis, resulting in decreased osteoblast numbers, diminished bone formation and, potentially, inadequate bone mass and osteoporosis. In addition to osteoblast and bone adipocyte numbers being influenced by this skewing of progenitor cell differentiation towards one phenotype, mature osteoblasts and adipocytes secrete factors which may evoke changes in the cell fate and function of each other. This review examines the endogenous factors, such as PPAR-γ2, Wnt, IGF-1, GH, FGF-2, oestrogen, the GP130 signalling cytokines, vitamin D and glucocorticoids, which regulate the selection between osteoblastogenesis and adipogenesis and the interrelationship between fat and bone. The role of adipokines on bone, such as adiponectin and leptin, as well as adipose-derived oestrogen, is reviewed and the role of bone as an energy regulating endocrine organ is discussed.

Effects of raftilose on serum biochemistry and liver morphology in rats fed with normal or high-fat diet

Non-alcoholic fatty liver disease is the leading cause of chronic liver injury in developed countries. Oligofructose (OFS) is a prebiotic with proven benefits for health. The aim of the study is to evaluate the effect of 10% OFS on hepatic morphology and lipid metabolism in Wistar Kyoto rats submitted to normal diet (ND) or high-fat diet (FD). Animals were treated for 7 weeks. Lipid profile and serum alkaline phosphatase (ALP) activity were measured and liver histology evaluated at the end of the study. Ten percent OFS reduced triglyceride (TAG) levels when added to any of the diet regimens; 10% OFS decreased plasmatic urea in ND and plasmatic and urinary urea levels in FD; ND + 10% OFS treated rats showed lower ALP activity than controls. FD increased ALP activity, an effect not reversed by OFS. Animals submitted to FD have microscopic hepatic changes: marked steatosis with disarranged centrilobular zone structure; enlarged sinusoids; enlarged mitochondria and an increase in number and volume of adiposomes. Supplementation with 10% OFS in FD reversed those effects. In conclusion, 10% OFS supplementation prevented deleterious effects of FD such as alterations on lipid profile (TAG elevation) and hepatic morphologic changes. OFS decreased ALP activity in animals subjected to ND, which may have contributed to the differences on lipid metabolism.

Studying arrhythmogenic right ventricular dysplasia with patient-specific iPSCs

Cellular reprogramming of somatic cells to patient-specific induced pluripotent stem cells (iPSCs) enables in vitro modelling of human genetic disorders for pathogenic investigations and therapeutic screens. However, using iPSC-derived cardiomyocytes (iPSC-CMs) to model an adult-onset heart disease remains challenging owing to the uncertainty regarding the ability of relatively immature iPSC-CMs to fully recapitulate adult disease phenotypes. Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an inherited heart disease characterized by pathological fatty infiltration and cardiomyocyte loss predominantly in the right ventricle, which is associated with life-threatening ventricular arrhythmias. Over 50% of affected individuals have desmosome gene mutations, most commonly in PKP2, encoding plakophilin-2 (ref. 9). The median age at presentation of ARVD/C is 26 years. We used previously published methods to generate iPSC lines from fibroblasts of two patients with ARVD/C and PKP2 mutations. Mutant PKP2 iPSC-CMs demonstrate abnormal plakoglobin nuclear translocation and decreased β-catenin activity in cardiogenic conditions; yet, these abnormal features are insufficient to reproduce the pathological phenotypes of ARVD/C in standard cardiogenic conditions. Here we show that induction of adult-like metabolic energetics from an embryonic/glycolytic state and abnormal peroxisome proliferator-activated receptor gamma (PPAR-γ) activation underlie the pathogenesis of ARVD/C. By co-activating normal PPAR-alpha-dependent metabolism and abnormal PPAR-γ pathway in beating embryoid bodies (EBs) with defined media, we established an efficient ARVD/C in vitro model within 2 months. This model manifests exaggerated lipogenesis and apoptosis in mutant PKP2 iPSC-CMs. iPSC-CMs with a homozygous PKP2 mutation also had calcium-handling deficits. Our study is the first to demonstrate that induction of adult-like metabolism has a critical role in establishing an adult-onset disease model using patient-specific iPSCs. Using this model, we revealed crucial pathogenic insights that metabolic derangement in adult-like metabolic milieu underlies ARVD/C pathologies, enabling us to propose novel disease-modifying therapeutic strategies.

Serum alkaline phosphatase, body composition, and risk of metabolic syndrome in middle-aged Korean

Some papers have suggested that alkaline phosphatase (ALP) level is a predictor of the metabolic syndrome (MetS) in the general population. However, the association is still controversial, and the mechanisms underlying an association between ALP level and the MetS have not been elucidated. We analyzed the association between serum ALP level and the development of the MetS over a 4-year period. A total of 14,224 subjects who visited the Health Promotion Center for a medical examination in 2005 were followed up after 4 years. Serum ALP level correlated positively with body fat mass and visceral fat mass. The adjusted geometric mean ALP levels were higher in subjects with elevated C-reactive protein level or greater fat mass (P < 0.001). None of the subjects had the MetS at baseline, but 1,179 exhibited the MetS at the 4-year follow-up. After multiple adjustments, the odds ratio (OR) was substantially higher for development of the MetS (OR 1.56, 95% confidence intervals, 1.21-2.01) in subjects in the highest ALP quintile compared with those in the lowest quintile. After adjusting for various covariates, we found significant associations between the quintile of serum ALP level and abdominal obesity, low high-density lipoprotein cholesterol level, and high triglyceride level. Higher serum ALP level was a significant predictor of the MetS in middle-aged Koreans. Serum ALP level correlated positively with body fat mass and independently with a more atherogenic lipid profile in the general population in Korea.

Silk ionomers for encapsulation and differentiation of human MSCs

The response of human bone marrow derived human mesenchymal stem cells (hMSCs) encapsulated in silk ionomer hydrogels was studied. Silk aqueous solutions with silk-poly-L-lysine or silk-poly-L-glutamate were formed into hydrogels via ultrasonication in situ with different net charges. hMSCs were encapsulated within the hydrogels and the impact of matrix charge was assessed over weeks in osteogenic, adipogenic and maintenance growth media. These modified silk charged polymers supported cell viability and proliferative potential, and the hMSCs were able to differentiate toward osteogenic or adipogenic lineages in the corresponding differentiation media. The silk/silk-poly-L-lysine hydrogels exhibited a positive effect on selective osteogenesis of hMSCs, inducing differentiation toward an osteogenic lineage even in the absence of osteogenic supplements, while also inhibiting adipogenesis. In contrast, silk/silk fibroin-poly-L-glutamate hydrogels supported both osteogenic and adipogenic differentiation of hMSCs when cultured under induction conditions. The results demonstrate the potential utility of silk-based ionomers in gel formats for hMSCs encapsulation and for directing hMSCs long term functional differentiation toward specific lineages.

Static mechanical stretching accelerates lipid production in 3T3-L1 adipocytes by activating the MEK signaling pathway

Understanding mechanotransduction in adipocytes is important for research of obesity and related diseases. We cultured 3T3-L1 preadipocytes on elastic substrata and applied static tensile strains of 12% to the substrata while inducing differentiation. Using an image processing method, we monitored lipid production for a period of 3-4 wk. The ratio of %-lipid area per field of view (FOV) in the stretched over nonstretched cultures was significantly greater than unity (P < 0.05), reaching ∼1.8 on average starting from experimental day ∼10. The superior coverage of the FOV by lipids in the stretched cultures was due to significantly greater sizes of lipid droplets (LDs) with respect to nonstretched cultures, starting from experimental day ∼10 (P < 0.05), and due to significantly more LDs per cell between days ∼10 and ∼17 (P < 0.05). The statically stretched cells also differentiated significantly faster than the nonstretched cells within the first ∼10 days (P < 0.05). Adding peroxisome proliferator-activated receptor-γ (PPARγ) antagonist did not change these trends, as the %-lipid area per FOV in the stretched cultures that received this treatment was still significantly greater than in the nonstretched cultures without the PPARγ antagonist (14.44 ± 1.96% vs. 10.21 ± 3%; P < 0.05). Hence, the accelerated adipogenesis in the stretched cultures was not mediated through PPARγ. Nonetheless, inhibiting the MEK/MAPK signaling pathway reduced the extent of adipogenesis in the stretched cultures (13.53 ± 5.63%), bringing it to the baseline level of the nonstretched cultures without the MEK inhibitor (10.21 ± 3.07%). Our results hence demonstrate that differentiation of adipocytes can be enhanced by sustained stretching, which activates the MEK signaling pathway.

Basic techniques in human mesenchymal stem cell cultures: differentiation into osteogenic and adipogenic lineages, genetic perturbations, and phenotypic analyses

This unit describes basic techniques in human mesenchymal stem cell (hMSC) cultures. It includes protocols for the differentiation of hMSCs into osteogenic and adipogenic lineages, genetic perturbations, and phenotypic analyses. hMSCs can be differentiated with dexamethasone and β-glycerophosphate into mineralizing osteoblasts within 2 to 3 weeks, or with dexamethasone, indomethacin, and 3-isobutyl-1-methylxanthine into lipid vesicle-containing adipocytes within 1 to 2 weeks. Phenotypic changes during those highly dynamic differentiation processes can be detected by biochemical and histological assays and gene expression analyses of differentiation markers. In addition, this unit describes an electroporation method that allows the transient genetic perturbation of hMSCs.

Depot-specific differences in the insulin response of adipose-derived stromal cells

Visceral adiposity is more strongly linked to insulin resistance than subcutaneous adiposity. High insulin levels can be mitogenic or adipogenic to adipocytes, but little is known regarding these effects of insulin on stromal cells from visceral and subcutaneous fat depots. Consequently, we measured adipogenesis and mitosis in response to elevated insulin levels in rat adipose-derived stromal cells (ADSCs) from visceral (perirenal) and subcutaneous depots. Insulin alone, at 10 microM, did not stimulate adipogenesis in naïve perirenal visceral (pvADSCs) or subcutaneous ADSCs (scADSCs), although a significant increase in proliferation occurred in both. Adipogenesis, induced using adipocyte differentiation medium (AM), resulted in greater lipid accumulation in pvADSCs, but the associated decrease in proliferation was less than in scADSCs. Omission of insulin from AM significantly reduced lipid accumulation in pvADSCs, but had little effect in scADSC, whilst proliferation was inhibited more in scADSCs than pvADSCs. Consequently, insulin is more lipogenic and less mitogenic in differentiating pvADSCs compared to scADSCs.

Chronic mineral dysregulation promotes vascular smooth muscle cell adaptation and extracellular matrix calcification

In chronic kidney disease (CKD) vascular calcification occurs in response to deranged calcium and phosphate metabolism and is characterized by vascular smooth muscle cell (VSMC) damage and attrition. To gain mechanistic insights into how calcium and phosphate mediate calcification, we used an ex vivo model of human vessel culture. Vessel rings from healthy control subjects did not accumulate calcium with long-term exposure to elevated calcium and/or phosphate. In contrast, vessel rings from patients with CKD accumulated calcium; calcium induced calcification more potently than phosphate (at equivalent calcium-phosphate product). Elevated phosphate increased alkaline phosphatase activity in CKD vessels, but inhibition of alkaline phosphatase with levamisole did not block calcification. Instead, calcification in CKD vessels most strongly associated with VSMC death resulting from calcium- and phosphate-induced apoptosis; treatment with a pan-caspase inhibitor ZVAD ameliorated calcification. Calcification in CKD vessels was also associated with increased deposition of VSMC-derived vesicles. Electron microscopy confirmed increased deposition of vesicles containing crystalline calcium and phosphate in the extracellular matrix of dialysis vessel rings. In contrast, vesicle deposition and calcification did not occur in normal vessel rings, but we observed extensive intracellular mitochondrial damage. Taken together, these data provide evidence that VSMCs undergo adaptive changes, including vesicle release, in response to dysregulated mineral metabolism. These adaptations may initially promote survival but ultimately culminate in VSMC apoptosis and overt calcification, especially with continued exposure to elevated calcium.

Effect of shanzha, a Chinese herbal product, on obesity and dyslipidemia in hamsters receiving high-fat diet

AIM

The present study is designed to investigate the effect of shanzha (Crataegus pinnatifida) on obesity or dyslipidemia induced by high-fat diet in hamsters and characterize the role of PPARalpha in this action of shanzha.

MATERIALS AND METHODS

We induced dyslipidemia and obesity in hamsters using high-fat diet and treated hamsters with shanzha or vehicle for 7 days. We measured the body weight, adipose tissue weights, and food intake of hamsters. Plasma total cholesterol (TC), triglyceride (TG), LDL-cholesterol (LDL-C) and HDL-cholesterol (HDL-C) were determined at the beginning and end of this treatment. Effect of shanzha on adipogenesis was examined in vitro and change of PPARalpha was analyzed using Western blot.

RESULTS

The food intake, body weights, and weights of both brown and white adipose tissues were markedly reduced in hamsters receiving shanzha as compared with the vehicle-treated control. Plasma levels of TC, TG and LDL-C were decreased by this shanzha treatment while HDL-C was elevated. The effects of shanzha were reversed by the combined treatment with PPARalpha antagonist, MK886. Shanzha inhibited the fat droplet accumulation in 3T3-L1 adipocytes in a dose-dependent manner and this effect was abolished by MK886. Western blot results showed activation of PPARalpha by shanzha in hamster adipose tissue.

CONCLUSION

We suggest that shanzha could activate PPARalpha to improve dyslipidemia or obesity.