Human relaxin inhibits division but not differentiation of 3T3-L1 cells

Human recombinant relaxin-2 (serelaxin) regulates the proteome, lipidome, lipid metabolism and inflammatory profile of rat visceral adipose tissue

Recombinant human relaxin-2 (serelaxin) has been widely proven as a novel drug with myriad effects at different cardiovascular levels, which support its potential therapeutic efficacy in several cardiovascular diseases (CVD). Considering these effects, together with the influence of relaxin-2 on adipocyte physiology and adipokine secretion, and the connection between visceral adipose tissue (VAT) dysfunction and the development of CVD, we could hypothesize that relaxin-2 may regulate VAT metabolism. Our objective was to evaluate the impact of a 2-week serelaxin treatment on the proteome and lipidome of VAT from Sprague-Dawley rats. We found that serelaxin increased 1 polyunsaturated fatty acid and 6 lysophosphatidylcholines and decreased 4 triglycerides in VAT employing ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) based platforms, and that regulates 47 phosphoproteins using SWATH/MS analysis. Through RT-PCR, we found that serelaxin treatment also caused an effect on VAT lipolysis through an increase in the mRNA expression of hormone-sensitive lipase (HSL) and a decrease in the expression of adipose triglyceride lipase (ATGL), together with a reduction in the VAT expression of the fatty acid transporter cluster of differentiation 36 (Cd36). Serelaxin also caused an anti-inflammatory effect in VAT by the decrease in the mRNA expression of tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), chemerin, and its receptor. In conclusion, our results highlight the regulatory role of serelaxin in the VAT proteome and lipidome, lipolytic function, and inflammatory profile, suggesting the implication of several mechanisms supporting the potential benefit of serelaxin for the prevention of obesity and metabolic disorders.

Identification and characterization of distinct brown adipocyte subtypes in C57BL/6J mice

Using a number of cell biological and statistical methods we identify and characterize EIF5, TCF25 and BIN1 as markers for individual brown adipocyte subtypes in C57BL/6J mice.

Brown adipose tissue (BAT) plays an important role in the regulation of body weight and glucose homeostasis. Although increasing evidence supports white adipose tissue heterogeneity, little is known about heterogeneity within murine BAT. Recently, UCP1 high and low expressing brown adipocytes were identified, but a developmental origin of these subtypes has not been studied. To obtain more insights into brown preadipocyte heterogeneity, we use single-cell RNA sequencing of the BAT stromal vascular fraction of C57/BL6 mice and characterize brown preadipocyte and adipocyte clonal cell lines. Statistical analysis of gene expression profiles from brown preadipocyte and adipocyte clones identify markers distinguishing brown adipocyte subtypes. We confirm the presence of distinct brown adipocyte populations in vivo using the markers EIF5, TCF25, and BIN1. We also demonstrate that loss of Bin1 enhances UCP1 expression and mitochondrial respiration, suggesting that BIN1 marks dormant brown adipocytes. The existence of multiple brown adipocyte subtypes suggests distinct functional properties of BAT depending on its cellular composition, with potentially distinct functions in thermogenesis and the regulation of whole body energy homeostasis.

Adipose tissue DNA methylome changes in development of new-onset diabetes after kidney transplantation

AIM

New-onset diabetes after kidney transplant (NODAT) adversely impacts kidney allograft and patient survival. Epigenetic alterations in adipose tissue like DNA methylation may play a contributory role.

METHODS

Adipose tissue DNA of the patients with NODAT and their age, sex and BMI matched controls (nine each) were sequenced by reduced representation bisulfite sequencing. Differentially methylated CpGs (DMCs) and differentially methylated regions (DMRs) were studied.

RESULTS

Adipose tissue from the patients had reduced DNA methylation in intergenic and intronic regions. DMCs were found to be more hypomethylated in repeat regions and hypermethylated in CGIs and promoter region. About 900 DMRs were found and their associated genes were significantly enriched in 32 pathways, the top ones of which were associated with insulin resistance and inflammation. Some DMR or DMC genes have known T2DM associations.

CONCLUSION

Changes in DNA methylation in adipose tissue may be suggestive of future NODAT.

Maternal relaxin concentrations in diabetic pregnancy

Maternal serum concentrations of relaxin, an insulin homologue produced both by the corpus luteum of pregnancy and by the fetoplacental unit, are highest in the first trimester and fall to their lowest level in the third trimester. Relaxin is thought to influence carbohydrate metabolism in the uterus, and it has been suggested that serum concentrations of relaxin in diabetic women are higher than those of non-diabetic women. We show that maternal serum relaxin concentrations are significantly higher at each stage of pregnancy in insulin-dependent diabetic mothers than in non-diabetic mothers. This elevation in relaxin concentrations is not related to other indices of diabetic control. The physiological importance of the higher concentrations of relaxin in the serum of diabetic women--in particular, whether they contribute to the higher incidence of major anomalies in the fetuses of diabetic mothers--is yet to be determined.

Relaxin influences the growth of MCF-7 breast cancer cells. Mitogenic and antimitogenic action depends on peptide concentration

BACKGROUND

The effects of relaxin (RLX) on the human breast adenocarcinoma cell line MCF-7 have been evaluated.

METHODS

The cells were maintained in culture with Dulbecco's modified Eagle's medium with 1% and 10% fetal calf serum. Highly purified porcine RLX was added at concentrations ranging between 10(-11) and 10(-6) M, and, after 96-hour incubation in the presence of the peptide, cell proliferation, intracellular cyclic adenosine monophosphate (cAMP) content, percent cycling cells, and structural and ultrastructural pattern were studied.

RESULTS

The results indicate that RLX is a direct modulator of MCF-7 cell proliferation, stimulating growth at low concentrations and inhibiting growth at high concentrations. Determinations of percent cycling cells and intracellular cAMP accumulation agree with the results of the growth studies. Addition of different concentrations of 8-Br-cAMP to the culture medium results in a dose-related stimulation of MCF-7 cell proliferation. Morphologic examination shows that, in the current experiments, RLX does not induce any clear-cut signs of differentiation of MCF-7 cells in terms of activation of secretion or intracellular lipid deposition.

CONCLUSION

These findings indicate that RLX should be regarded as a novel agent involved in the control of growth of human breast cancer cells.