Fig 1: The effect of dibutyryl (db)‐cAMP‐driven stimulation of thermogenesis on the expression of iron transport‐related proteins in human ex vivo differentiated subcutaneous (SubQ) and deep cervical (DeepC)‐derived adipocytes. (A) Schematic figure displaying the iron transport proteins. Figure was created by Biorender under licencing rights for open access publication with agreement number WV29EBDIBT. (B) Protein–protein interactions between transferrin receptor (TFRC), transferrin (TF), melanotransferrin (MELTF), and ferroportin based on STRING (www.string‐db.org) analysis was generated by gephi 0.9. The thickness of the edges represents the confidence level of the interaction. Red: the mRNA expression was induced by db‐cAMP in both SubQ and DeepC‐derived adipocytes, blue: the mRNA expression was suppressed by db‐cAMP in both adipocyte types, and gray: no change in expression [11]. (C, E, G, I) Normalized mRNA counts of TFRC (C), TF (E), SLC40A1/ferroportin (G), and MELTF (I) based on RNA‐sequencing data, n = 4. The RNA‐sequencing datasets generated and analyzed for this study can be found in the Sequence Read Archive (SRA) database [https://www.ncbi.nlm.nih.gov/sra] under accession number PRJNA1093362 [11]. Statistical analysis of FASTQ files aligned to BAM were performed by DESeq2. ****P < 0.0001. (D, F, H, J) mRNA expression of TFRC (D), TF (F), ferroportin (H), and MELTF (J) validated by RT‐qPCR. Data are presented as mean ± SD, n = 3, statistical analysis was performed by one‐way ANOVA followed by Tukey's post hoc test, *P < 0.05, **P < 0.01, and *** P < 0.001.
Fig 2: Correlation of MELTF and TF expression in abdominal SubQ white adipose tissue with clinical parameters. Data were retrieved from adiposetissue.org [44]. (A) Meta‐analysis forest plot comparing the MELTF mRNA levels in people living with or without obesity (< 30 kg·m−2 vs. ≥ 30 kg·m−2 BMI). SMD: Standardized mean differences (Data referenced from [45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60]). (B) Boxplots displaying the expression of MELTF after diet restriction (Data referenced from [49, 50]). (C) The transcriptome (upper panels) and proteome (bottom panels) analyses were categorized into three groups: anthropometric (left panels), focusing on TF gene and protein expression in correlation with measurements of body distribution parameters; circulating diagnostic markers (middle panels) examining molecules present in the bloodstream (e.g., hormones); and tissue‐specific responses (right panels). BMI, body mass index; CRP, C‐reactive protein; HbA1c, hemoglobin A1c; HDL, high‐density lipoprotein; HOMA‐IR, Homeostatic Model Assessment for Insulin Resistance; iso, isoproterenol; LDL, low‐density lipoprotein; LEP, leptin; TG, triglyceride; TNF, tumor necrosis factor; WHR, waist‐hip ratio.
Fig 3: Structure of human TFRC and its interactions with TF, MELTF, and homeostatic iron regulator (HFE). (A) Overall structure of human TFRC. The domain organization and boundaries are shown based on UniProt database (UniProt ID: P02786) and Testi et al. [42]. The structure of the extracellular domain (122‐756 residues) is shown by ribbon representation based on an electron microscopy structure (PDB ID: 1SUV) [37]. The helical, apical, and protease‐like domains are shown by different colors, and the cysteine residues forming disulfide bonds are shown by yellow. (B) Structural alignment of TF and MELTF. TF and MELTF are shown by ribbon representation, based on experimentally determined structures. The complex of TFRC and TF is represented based on an electron microscopy structure (PDB ID: 1SUV) [37]. The N‐ and C‐lobes of TF have blue and red colors, respectively. (C) Binding of TF, MELTF, and HFE to TFRC. TFRC is shown in side view and is colored by green; the interaction partners have different colors. The N‐ and C‐lobes of TF have blue and red colors, respectively. The complex of TFRC and MELTF is shown based on a proposed model that was prepared in this work by using alphafold. The binding of HFE to TFRC is shown based on a crystal structure (PDB ID: 1DE4) [22]. RMS, Root Mean Square deviation.
Fig 4: TF and MELTF were expressed and secreted by ex vivo differentiated human adipocytes. (A, B) Dot plot displaying the expression of TF (A) and MELTF (B) in single‐nuclei RNA‐sequencing (snRNA‐seq) data for human brown adipose tissue. (C, D) Embedding plots showing the expression of TF (C) and MELTF (D) by snRNA‐seq from isolated brown adipocytes from 8 donors. Data displayed in panels A–D were retrieved from batnetwork.org [33]. (E, F) Protein secretion of TF (E) and MELTF (F) by control (ctrl) and db‐cAMP‐activated SubQ and DeepC‐derived adipocytes detected by ELISA. Data are presented as mean ± SD, n = 3, Statistical analysis was performed by one‐way ANOVA followed by Tukey's post hoc test, ***P < 0.001. UM, unconditioned medium.
Supplier Page from Novus Biologicals, a Bio-Techne Brand for Human Melanotransferrin/CD228/MFI2 ELISA Kit (Colorimetric)
Available conjugates: Sizes Available: 1 Kit