Maresin 1 Regulates Hepatic FGF21 in Diet-Induced Obese Mice and in Cultured Hepatocytes

SCOPE

To study the effects of Maresin 1 (MaR1), a docosahexaenoic-acid-derived lipid mediator, on fibroblast growth factor 21 (FGF21) production and to characterize the tissue-specific regulation of Fgf21 and its signaling pathway in liver, skeletal muscle, and white adipose tissue (WAT).

METHODS AND RESULTS

Diet-induced obese (DIO) mice are treated with MaR1 (50 µg kg^-1 , 10 days, oral gavage) and serum FGF21 levels and liver, muscle and WAT Fgf21, β-Klotho, Fgfr1, Egr1, and cFos mRNA expression are evaluated. Additionally, MaR1 effects are tested in mouse primary hepatocytes, HepG2 human hepatocytes, C2C12 myotubes, and 3T3-L1 adipocytes. In DIO mice, MaR1 decreases circulating FGF21 levels and HFD-induced hepatic Fgf21 mRNA expression. MaR1 increases hepatic β-Klotho, Egr1, and cFos in DIO mice. In WAT, MaR1 counteracts the HFD-induced downregulation of Fgf21, Fgfr1, and β-Klotho. In muscle, MaR1 does not modify Fgf21 but promoted Fgfr1 expression. In mouse primary hepatocytes, MaR1 decreases Fgf21 expression and downregulated Pparα mRNA levels. In HepG2 cells, MaR1 reverses the increased production of FGF21 and the downregulation of FGFR1, Β-KLOTHO, EGR1, and cFOS induced by palmitate. Preincubation with a PPARα antagonist prevents MaR1 effects on FGF21 secretion.

CONCLUSION

The ability of MaR1 to modulate FGF21 can contribute to its beneficial metabolic effects.

Adipose tissue and serum CCDC80 in obesity and its association with related metabolic disease

Coiled-coil domain-containing 80 (CCDC80) is an adipocyte-secreted protein that modulates glucose homeostasis in response to diet-induced obesity in mice. The objective of this study is to analyze the link between human CCDC80 and obesity. CCDC80 protein expression was assessed in paired visceral (VAT) and subcutaneous (SAT) adipose tissue from 10 subjects (BMI range 22.4-38.8 kg/m²). Circulating CCDC80 levels were quantified in serum samples from two independent cross-sectional cohorts comprising 33 lean and 15 obese (cohort 1) and 32 morbid obese (cohort 2) male subjects. Insulin sensitivity, insulin secretion and blood neutrophil count were quantified in serum samples from both cohorts. Additionally, circulating free IGF-1 levels and oral glucose tolerance tests (OGTT) were assessed in cohort 1 whereas C-reactive protein levels and degree of atherosclerosis and hepatic steatosis were studied in cohort 2. In lean subjects, total CCDC80 protein content assessed by immunoblotting was lower in VAT than in SAT. In obese patients, CCDC80 was increased in VAT (P<0.05), but equivalent in SAT compared with lean counterparts. In cohort 1, serum CCDC80 correlated negatively with the acute insulin response to glucose and IGF1 levels, and positively with blood neutrophil count, independently of BMI, but not with insulin sensitivity. In cohort 2, serum CCDC80 was positively linked to the inflammatory biomarker C-reactive protein (r=0.46; P=0.009), atherosclerosis (carotid intima-media thickness, r=0.62; P<0.001) and hepatic steatosis (ANOVA P=0.025). Overall, these results suggest for the first time that CCDC80 may be a component of the obesity-altered secretome in VAT and could act as an adipokine whose circulant levels are linked to glucose tolerance derangements and related to inflammation-associated chronic complications.

HIV/antiretroviral therapy-related lipodystrophy syndrome (HALS) is associated with higher RBP4 and lower omentin in plasma

Very little information is available on the involvement of newly characterized adipokines in human immunodeficiency virus (HIV)/antiretroviral therapy (ART)-associated lipodystrophy syndrome (HALS). Our aim was to determine whether apelin, apelin receptor, omentin, RBP4, vaspin and visfatin genetic variants and plasma levels are associated with HALS. We performed a cross-sectional multicentre study that involved 558 HIV type 1-infected patients treated with a stable highly active ART regimen, 240 of which had overt HALS and 318 who did not have HALS. Epidemiologic and clinical variables were determined. Polymorphisms in the apelin, omentin, RBP4, vaspin and visfatin genes were assessed by genotyping. Plasma apelin, apelin receptor, omentin, RBP4, vaspin and visfatin levels were determined by enzyme-linked immunosorbent assay in 163 patients (81 with HALS and 82 without HALS) from whom stored plasma samples were available. Student's t test, one-way ANOVA, chi-square test, Pearson and Spearman correlations and linear regression analysis were used for statistical analyses. There were no associations between the different polymorphisms assessed and the HALS phenotype. Circulating RBP4 was significantly higher (p < 0.001) and plasma omentin was significantly lower (p 0.001) in patients with HALS compared to those without HALS; differences in plasma levels of the remaining adipokines were nonsignificant between groups. Circulating RBP4 concentration was predicted independently by the presence of HALS. Apelin and apelin receptor levels were independently predicted by body mass index. Visfatin concentration was predicted independently by the presence of acquired immunodeficiency syndrome. HALS is associated with higher RBP4 and lower omentin in plasma. These two adipokines, particularly RBP4, may be a link between HIV/ART and fat redistribution syndromes.

Zinc alpha-2 glycoprotein is implicated in dyslipidaemia in HIV-1-infected patients treated with antiretroviral drugs

OBJECTIVES

Treated HIV-1-infected patients with lipodystrophy often develop insulin resistance and proatherogenic dyslipidaemia. Zinc alpha-2 glycoprotein (ZAG) is a recently characterized adipokine which has been shown to be involved in the development of obesity and metabolic syndrome in uninfected subjects. We assessed the relationship between circulating ZAG levels and metabolic derangements in HIV-1-infected patients receiving antiretroviral drugs.

METHODS

Plasma ZAG levels were assessed in 222 individuals: 166 HIV-1-infected patients treated with antiretroviral drugs (77 with lipodystrophy and 89 without lipodystrophy) and 56 uninfected controls. Plasma ZAG levels were assessed by enzyme-linked immunosorbent assay (ELISA) and were correlated with fat distribution abnormalities and metabolic parameters.

RESULTS

HIV-1-infected patients had lower plasma ZAG levels compared with uninfected controls (P < 0.001). No differences were found in ZAG plasma levels according to the presence of lipodystrophy, components of the metabolic syndrome or type of antiretroviral treatment regimen. Circulating ZAG levels were strongly determined by high-density lipoprotein cholesterol (HDLc) in men (B = 0.644; P < 0.001) and showed a positive correlation with total cholesterol (r = 0.312; P < 0.001) and HDLc (r = 0.216; P = 0.005).

CONCLUSIONS

HIV-1-infected patients have lower plasma ZAG levels than uninfected controls. In infected patients, plasma ZAG levels are in close relationship with total cholesterol and HDLc.

Paired subcutaneous and visceral adipose tissue aquaporin-7 expression in human obesity and type 2 diabetes: differences and similarities between depots

CONTEXT

AQP7 is considered to be the sole adipose glycerol channel, and its regulation is crucial for glycemia control.

OBJECTIVES

In this work, we aimed to further characterize AQP7 in human adipose tissue in obesity and type 2 diabetes (T2D): 1) to assess AQP7 expression levels in paired abdominal adipose tissue depots (sc and visceral); 2) to relate it with gene expression of genes involved in lipid metabolism; and 3) to confirm that AQP7 is mainly expressed in the adipocytes.

DESIGN

We conducted a transversal study of gene expression in paired samples of sc adipose tissue (SAT) and visceral adipose tissue (VAT).

PATIENTS

Caucasian lean and obese subjects (n = 62, matched for age and gender) and T2D subjects (n = 11, matched for age, gender, and BMI with their control group) participated in the study.

MAIN OUTCOME MEASURE

We measured AQP7 expression levels in paired SAT and VAT.

RESULTS

We have proved the presence of AQP7 mRNA and protein in the adipocyte rather than the stromovascular fraction of adipose tissue (P = 0.001) and in mature adipocytes when differentiated in vitro. Increased AQP7 mRNA expression levels in VAT from T2D obese subjects (P < 0.05) were found. AQP7 transcript levels ratio of SAT vs. VAT changed with the presence of obesity and T2D. Interestingly, there were positive associations between AQP7 and both lipogenic and lipolytic genes in a similar manner in both adipose depots.

CONCLUSIONS

Taken together, these data suggest a subtle regulation between adipose depots of the sole adipose aquaporin, AQP7, which is unbalanced in obesity and T2D.

Circulating and adipose tissue gene expression of zinc-alpha2-glycoprotein in obesity: its relationship with adipokine and lipolytic gene markers in subcutaneous and visceral fat

CONTEXT

Zinc-alpha2-glycoprotein (ZAG) is a soluble protein similar to the class I major histocompatibility complex heavy chain, which has been implicated in lipid catabolism. We hypothesized that ZAG mRNA expression in adipose tissue may be linked with lipolytic and adipokine gene expression and have a close relationship with clinical phenotype.

OBJECTIVES

The objective of the study was to analyze ZAG gene expression in human adipose tissue from lean and obese subjects. ZAG circulating plasma levels and its relationship with cardiometabolic risk factors were also studied.

DESIGN

Seventy-three Caucasian (43 male and 30 female) subjects were included. Plasma and adipose tissue [sc (SAT) and visceral (VAT)] from the same patient were studied. mRNA of PPARgamma, hormone-sensitive lipase (HSL), adipose triglyceride lipase, adiponectin, omentin, visfatin, and ZAG were quantified. Plasma concentrations of ZAG were determined with ELISA.

RESULTS

ZAG plasma levels showed a negative correlation with insulin (r = -0.39; P = 0.008) and the homeostasis model assessment for insulin resistance index (r = -0.36; P = 0.016). No differences in ZAG circulating levels according to body mass index classification were observed. ZAG expression in SAT was significantly reduced in overweight and obese individuals compared with lean subjects (P < 0.001 and P = 0.007, respectively). ZAG mRNA expression in both SAT and VAT depots were negatively correlated with many clinical and metabolic cardiovascular risk factors. After multiple linear regression analysis, SAT ZAG was mainly predicted by adiponectin mRNA expression (B = 0.993; P < 0.0001) and plasma triglyceride levels (B = -0.565; P = 0.006). VAT ZAG expression was predicted by adiponectin expression (B = 0.449; P < 0.0001), and HSL VAT expression (B = 0.180; P = 0.023).

CONCLUSIONS

The present study provides evidence of a role of ZAG gene in adipose tissue metabolism, with a close association with adiponectin gene expression in sc and visceral fat.