Emerging evidences for the opposite role of apolipoprotein C3 and apolipoprotein A5 in lipid metabolism and coronary artery disease.

Apolipoprotein C3 (apoC3) and apolipoprotein A5 (apoA5), encoded by APOA1/C3/A4/A5 gene cluster, are two critical regulators of plasma triglyceride (TG) metabolism. Deficiency of apoC3 or apoA5 led to significant decreased or increased plasma TG levels, respectively. Recent studies indicated apoC3 and apoA5 also played roles in plasma remnant cholesterol, high density lipoprotein (HDL) and hepatic TG metabolisms. Moreover, large scale population genetic studies indicated that loss of function mutations in APOC3 and APOA5 gene conferred decreased and increased risk of coronary artery disease (CAD), respectively. This manuscript mainly reviewed existing evidences suggesting the opposite role of apoC3 and apoA5 in lipid metabolism and CAD risk, and discussed the potential correlation between these two apolipoproteins.

[Effects of apolipoprotein A5 on adipogenic differentiation of human adipose mesenchymal stem cells].

Objective: To verify whether Apo A5 could inhibit the adipogenic differentiation of adipose mesenchymal stem cells (AMSCs). Methods: We isolated AMSCs by collagenase digestion method from the adipocyte tissue of patients underwent abdominal surgery in our hospital from February to July 2015. AMSCs were differentiated into mature adipocytes and incubated with Apo A5 (600 and 1 200 ng/ml) for 7, 14 and 21 days. Morphological changes, TG content, and gene expression levels of adipogenic differentiation markers were determined. Results: (1) The results of detecting the oil red O absorbance by spectrophotometer are as follows: At the 7th, 14th and 21st days after intervention, the absorbance of oil red O with 600 and 1 200 ng/ml Apo A5 intervention was lower than that of the control group (Day 7: 145.6±21.1, 110.5±31.5 vs. 195.4±35.7; Day 14: 289.2±24.2, 250.4±45.2 vs. 341.6±34.5; Day 21: 431.9±33.2, 374.7±26.4 vs. 488.2±22.5, all P<0.05). (2) The intracellular TG content after Apo A5 intervention were detected by TG quantitative detection kit detection. At the 7th, 14th and 21st days, intracellular TG contents in 600 and 1 200 ng/ml Apo A5 groups were lower than that in the control group (Day 7:(203.1±22.6), (174.2±25.8)nmol/mg protein in Apo A5 intervention group vs. (266.25±23.7)nmol/mg protein in control group; Day 14: (332.5±23.2), (231.1±22.2)nmol/mg protein in Apo A5 intervention group vs. (452.2±16.4)nmol/mg protein in control group; Day 21: (482.8±21.2), (294.2±29.9)nmol/mg protein vs. (597.2±22.1)nmol/mg protein in control group, P<0.05). (3) aP2 gene expression detected by real-time PCR and intracellular fatty acid synthase and lipid droplets coated protein gene expression levels determined by Western blot on day 7, 14 and 21 were significantly lower in Apo A5 groups than in control group (all P<0.05). Conclusions: Apo A5 significantly reduced intracellular TG content and modulated the gene expression levels of adipogenic differentiation marker, thus, Apo A5 treatment can inhibit the adipogenic differentiation of adipose mesenchymal stem cells.

[Effects and mechanism of apolipoprotein A5 on adipogenic differentiation of human adipose-derived mesenchymal stem cells].

Objective: To investigate the effect and related mechanism of apolipoprotein A5 (ApoA5) on adipogenic differentiation of human adipose-derived mesenchymal stem cells (AMSC). Methods: Subcutaneous adipose tissue was obtained from 40 patients undergoing abdominal surgery at our hospital from February to July 2015. After induction of human AMSC by collagenase digestion, the adipose tissue was induced to differentiate into mature adipocytes and treated with ApoA5 at 600 and 1 200 ng/ml, respectively (ApoA5 intervention groups). Cells treated without ApoA5 protein were used as control group. The cells were harvested on the 7th and 14th day of differentiation, and the following assays were performed: (1) the effect of ApoA5 on TG content was measured by a TG assay kit; (2) RT-qPCR assay was used to detect the effect of ApoA5 on aP2 and FAS mRNA expression; (3) the effect of ApoA5 on the expression of CIDEC mRNA and protein was detected by RT-qPCR and Western blot; (4) the effect of ApoA5 on the expression of C/EBPß mRNA and protein was detected by RT-qPCR and Western blot; (5) using lentiviral transfection technique, we overexpressed the gene of CIDEC in AMSC and cells were divided into lentiviral negative control group, lentiviral over-expressed CIDEC group and lentiviral over-expressed CIDEC+ApoA5 intervention group (the ApoA5 intervention concentration was 1 200 ng/ml). Thereby, we examined the effect of ApoA5 on the above indicators in adipogenic differentiation of AMSC in the case of CIDEC overexpression. Results: (1) Effect of ApoA5 on TG content in AMSC: on the 7th and 14th day after the intervention, the TG levels were lower in ApoA5 600 and 1 200 ng/ml group AMSC than those in the control group (all P<0.05). (2) The effect of ApoA5 on the expression of aP2 and FAS mRNA in AMSC: on the 7th day after intervention, the expression levels of aP2 and FAS mRNA were significantly lower in ApoA5 600 and 1 200 ng/ml group than those in the control group (all P<0.05). On the 14th day after intervention, the expression levels of aP2 and FAS mRNA were lower in ApoA5 600 and 1 200 ng/ml group than those in the control group (all P<0.05). (3) The effect of ApoA5 on the mRNA and protein expression of CIDEC in AMSC: on the 7th day after intervention, the mRNA and relative protein expression levels of CIDEC were significantly lower in AMSC of ApoA5 600 and 1 200 ng/ml group than those of the control group (all P<0.05). On the 14th day after intervention, the mRNA and relative protein levels of CIDEC were further reduced in ApoA5 600 and 1 200 ng/ml AMSC groups than those in the control group (all P<0.05). (4) The effect of ApoA5 on C/EBPß mRNA and protein expression in AMSC: on the 7th day after intervention, C/EBPß mRNA and relative protein expression levels were significantly lower in ApoA5 600 and 1 200 ng/ml group than those in the control group (all P<0.05). On the 14th day after intervention, the levels of C/EBPß mRNA and relative protein were lower in ApoA5 600 and 1 200 ng/ml group than those in the control group (all P<0.05). (5) The effect of ApoA5 on the content of TG in AMSC after CIDEC overexpression: on the 7th and 14th day after intervention, the TG contents in AMSC were higher in the lentivirus over-expressed CIDEC group than in the lentivirus negative control group (both P<0.05). However, TG contents in AMSC were similar between the over-expressed CIDEC group and the CIDEC+ApoA5 over-expression group (both P>0.05). (6) The effect of ApoA5 on the expression of aP2 and FAS mRNA in AMSC after CIDEC overexpression: on the 7th day after intervention, the expression levels of aP2 and FAS mRNA in AMSC were higher in the lentivirus over-expressed CIDEC group than in the lentivirus negative control group (both P<0.05). On the 14th day after intervention, the expression level of aP2 mRNA in the AMSC was higher in the lentivirus over-expressed CIDEC group than in the lentivirus negative control group (P<0.05). On the 7th and 14th day after intervention, the expression levels of aP2 and FAS mRNA in AMSC were similar between the lentivirus over-expressed CIDEC group and the lentivirus over-expressed CIDEC+ApoA5 group (all P>0.05). (7) The effect of ApoA5 on the expression of C/EBPß mRNA and protein in AMSC after CIDEC overexpression: on the 7th day after intervention, the mRNA and relative protein expressions of C/EBPß in AMSC were higher in lentivirus-overexpressed CIDEC group than in lentivirus negative control group (both P <0.05). On the 14th day after intervention, C/EBPß mRNA and protein expression levels in AMSC were higher in the lentivirus over-expressed CIDEC group than in the lentivirus negative control group (both P<0.05). On the 7th and 14th day after intervention, the expressions of C/EBPß mRNA and protein in AMSC were similar between lentivirus over-expressed CIDEC group and lentivirus over-expression CIDEC+ApoA5 intervention group (all P>0.05). Conclusions: ApoA5 can inhibit the adipogenic differentiation of AMSC,and this effect may be mediated by down-regulating the expression of CIDEC. Furthermore, our results indicate that CIDEC could be considered as a key factor in adipogenic differentiation.

New Insights into Apolipoprotein A5 and the Modulation of Human Adipose-derived Mesenchymal Stem Cells Adipogenesis.

BACKGROUND: The hallmark of obesity is the excessive accumulation of triglyceride (TG) in adipose tissue. Apolipoprotein A5 (ApoA5) has been shown to influence the prevalence and pathogenesis of obesity. However, the underlying mechanisms remain to be clarified. METHODS: Human adipose-derived mesenchymal stem cells (AMSCs) were treated with 600 ng/ml human recombinant ApoA5 protein. The effect of ApoA5 on intracellular TG content and adipogenic related factors expression were determined. Furthermore, the effect of ApoA5 on CIDE-C expression was also observed. RESULTS: During the process of adipogenesis, ApoA5 treatment reduced the intracellular accumulation of lipid droplets and the TG levels; meanwhile, ApoA5 down-regulated the expression levels of adipogenic related factors, including CCAAT enhancer-binding proteins α/ß (C/EBPα/ß), fatty acid synthetase (FAS), and fatty acid-binding protein 4 (FABP4). Furthermore, the suppression of adipogenesis by ApoA5 was mediated through the inhibition of CIDE-C expression, an important factor which promotes the process of adipogenesis. However, over-expressing intracellular CIDE-C could lead to the loss-of-function of ApoA5 in inhibiting AMSCs adipogenesis. CONCLUSIONS: In conclusion, ApoA5 inhibits the adipogenic process of AMSCs through, at least partly, down-regulating CIDE-C expression. The present study provides novel mechanisms whereby ApoA5 prevents obesity via AMSCs in humans.