Role of TG-interacting factor (Tgif) in lipid metabolism

Effect of myristic acid supplementation on triglyceride synthesis and related genes in the pectoral muscles of broiler chickens

Fatty acids (FAs) can serve as energy for poultry, maintain normal cell structure and function, and support a healthy immune system. Although the addition of polyunsaturated fatty acids (PUFAs) to the diet has been extensively studied and reported, the mechanism of action of saturated fatty acids (SFAs) remains to be elucidated. We investigated the effect of 0.04% dietary myristic acid (MA) on slaughter performance, lipid components, tissue FAs, and the transcriptome profile in chickens. The results showed that dietary MA had no effect on slaughter performance (body weight, carcass weight, eviscerated weight, and pectoral muscle weight) (P > 0.05). Dietary MA enrichment increased MA (P < 0.001) and triglycerides (TGs) (P < 0.01) levels in the pectoral muscle. The levels of palmitic acid, linoleic acid (LA), arachidonic acid (AA), SFAs, monounsaturated fatty acids (MUFAs), and PUFAs were significantly higher (P < 0.01) in the MA supplementation group compared to the control group. However, there were no significant differences in the ratios of PUFA/SFA and n6/omega-3 (n3) between the two groups. The MA content was positively correlated with the contents of palmitic acid, LA, linolenic acid (ALA), n3, n6, SFAs, and unsaturated fatty acids (UFA). DHCR24, which is known to be involved in steroid metabolism and cholesterol biosynthesis pathways, was found to be a significantly lower in the MA supplementation group compared to the control group (P < 0.05, log2(fold change) = -0.85). Five overlapping co-expressed genes were identified at the intersection between the differential expressed genes and Weighted Gene Co‑expression Network Analysis-derived hub genes associated with MA phenotype, namely BHLHE40, MSL1, PLAGL1, SRSF4, and ENSGALG00000026875. For the TG phenotype, a total of 28 genes were identified, including CHKA, KLF5, TGIF1, etc. Both sets included the gene PLAGL1, which has a negative correlation with the levels of MA and TG. This study provides valuable information to further understand the regulation of gene expression patterns by dietary supplementation with MA and examines at the molecular level the phenotypic changes induced by supplementation with MA.

Phosphorylation of TG-interacting factor 1 at carboxyl-terminal sites in response to insulin regulates adipocyte differentiation

TG-interacting factor 1 (TGIF1) contributes to the differentiation of murine white preadipocyte and human adipose tissue-derived stem cells; however, its regulation is not well elucidated. Insulin is a component of the adipogenic cocktail that induces ERK signaling. TGIF1 phosphorylation and sustained stability in response to insulin were reduced through the use of specific MEK inhibitor U0126. Mutagenesis at T235 or T239 residue of TGIF1 in preadipocytes led to dephosphorylation of TGIF1. The reduced TGIF1 stability resulted in an increase in p27kip1 expression, a decrease in phosphorylated Rb expression and cellular proliferation, and a reduced accumulation of lipids compared to the TGIF1-overexpressed cells. These findings highlight that insulin/ERK-driven phosphorylation of the T235 or T239 residue at TGIF1 is crucial for adipocyte differentiation.

Estradiol-driven metabolism in transwomen associates with reduced circulating extracellular vesicle microRNA-224/452

OBJECTIVE

Sex steroid hormones like estrogens have a key role in the regulation of energy homeostasis and metabolism. In transwomen, gender-affirming hormone therapy like estradiol (in combination with antiandrogenic compounds) could affect metabolism as well. Given that the underlying pathophysiological mechanisms are not fully understood, this study assessed circulating estradiol-driven microRNAs (miRs) in transwomen and their regulation of genes involved in metabolism in mice.

METHODS

Following plasma miR-sequencing (seq) in a transwomen discovery (n = 20) and validation cohort (n = 30), we identified miR-224 and miR-452. Subsequent systemic silencing of these miRs in male C57Bl/6 J mice (n = 10) was followed by RNA-seq-based gene expression analysis of brown and white adipose tissue in conjunction with mechanistic studies in cultured adipocytes.

RESULTS

Estradiol in transwomen lowered plasma miR-224 and -452 carried in extracellular vesicles (EVs) while their systemic silencing in mice and cultured adipocytes increased lipogenesis (white adipose) but reduced glucose uptake and mitochondrial respiration (brown adipose). In white and brown adipose tissue, differentially expressed (miR target) genes are associated with lipogenesis (white adipose) and mitochondrial respiration and glucose uptake (brown adipose).

CONCLUSION

This study identified an estradiol-drive post-transcriptional network that could potentially offer a mechanistic understanding of metabolism following gender-affirming estradiol therapy.

In vivo identification of novel TGIF2LX target genes in colorectal adenocarcinoma using the cDNA-AFLP method

BACKGROUND AND STUDY AIMS

Homeobox-containing genes are composed of a group of regulatory genes encoding transcription factors involved in the control of developmental processes. The homeodomain proteins could activate or repress the expression of downstream target genes. This study was conducted to in vivo identify the potential target gene(s) of TGIF2LX in colorectal adenocarcinoma.

METHODS

A human colorectal adenocarcinoma cell line, SW48, was transfected with the recombinant pEGFPN1-TGIF2LX. The cells were injected subcutaneously into the flank of the three groups of 6-week-old female athymic C56BL/6 nude mice (n = 6 per group). The transcript profiles in the developed tumours were investigated using the cDNA amplified fragment length polymorphism (cDNA-AFLP) technique.

RESULTS

The real-time RT-PCR and DNA sequencing data for the identified genes indicated that the N-terminal domain-interacting receptor 1 (Nir1) gene was suppressed whereas Nir2 and fragile histidine triad (FHIT) genes were upregulated followed by the overexpression of TGIF2LX gene.

CONCLUSION

Downregulation of Nir1 and upregulation of Nir2 and FHIT genes due to the overexpression of TGIF2LX suggests that the gene plays an important role as a suppressor in colorectal adenocarcinoma.

Overexpression of transforming growth factor β induced factor homeobox 1 represses NPC1L1 and lowers markers of intestinal cholesterol absorption

BACKGROUND AND AIMS

Transforming growth factor β induced factor homeobox 1 (TGIF1) is a transcriptional repressor that limits the response to transforming growth factor ß signaling and also represses transcription independent of this pathway. Recently, we found higher serum cholesterol levels and more hepatic lipid accumulation in mice lacking Tgif1, and showed that TGIF1 can repress the expression of Soat2, the gene encoding the cholesterol esterifying enzyme acyl-Coenzyme A:cholesterol acyltransferase 2. Although there is evidence that TGIF1 plays a role in lipid metabolism, its role in this metabolic pathway is not fully characterized. Here we investigate whether overexpression of TGIF1 affects intestinal cholesterol absorption.

METHODS AND RESULTS

TGIF1 was found to repress human and mouse Niemann-Pick C1 like 1 (Npc1l1) promoter activity in intestinal Caco2 cells. We also found TGIF1 to be able to oppose the induction of the promoter activity by sterol regulatory element binding protein 2 and hepatocyte nuclear factor 1α and 4α. To validate these effects of TGIF1 in vivo, we generated transgenic mice specifically overexpressing TGIF1 in the intestine (Villin-Tgif1). We observed lower intestinal expression levels of Npc1l1 that was associated with lower expression of ATP-binding cassette transporter (Abc) a1, Abcg5, and Abcg8. Villin-Tgif1 mice fed regular chow or a high-fat diet had lower levels of markers of intestinal cholesterol absorption than wild types.

CONCLUSIONS

We suggest TGIF1 as a new player in intestinal cholesterol metabolism.

Silencing of TGIF1 in bone mesenchymal stem cells applied to the post-operative rotator cuff improves both functional and histologic outcomes

Stem cells have long been hypothesized to improve outcomes following rotator cuff repair. However, these cells must be signaled in order to do so. TGIF1 is a transcription factor that has been found to be down-regulated in cells involved in chondrogenesis. We therefore wished to examine whether stem cells expressing lower levels of TGIF1 could better improve outcomes following rotator cuff repair than stem cells expressing normal levels of TGIF1. Bone mesenchymal stem cells (BMSCs) were transduced with TGIF1 siRNA to suppress native TGIF1. Nontransduced BMSCs were also obtained for the control group. Following suprapinatus tendon repair, rats were either treated with transduced BMSCs or nontransduced BMSCs. Histologic and functional testing were performed on both groups. Rats treated with transduced TGIF1 siRNA BMSCs following suprapinatus repair expressed significantly higher levels of chondrogenic proteins at 4 weeks than rats treated with nontransduced BMSCs. Further, rats treated with BMSCs transduced with TGIF1 siRNA had both a significantly greater maximum load at failure and stiffness. Rats treated with transduced TGIF1 siRNA BMSCs following supraspinatus repair perform better both histologically and functionally at 4 weeks.