Adipose TBX1 regulates β-adrenergic sensitivity in subcutaneous adipose tissue and thermogenic capacity in vivo

Brain and behavioural anomalies caused by Tbx1 haploinsufficiency are corrected by vitamin B12

The brain-related phenotypes observed in 22q11.2 deletion syndrome (DS) patients are highly variable, and their origin is poorly understood. Changes in brain metabolism might contribute to these phenotypes, as many of the deleted genes are involved in metabolic processes, but this is unknown. This study shows for the first time that Tbx1 haploinsufficiency causes brain metabolic imbalance. We studied two mouse models of 22q11.2DS using mass spectrometry, nuclear magnetic resonance spectroscopy, and transcriptomics. We found that Tbx1 +/- mice and Df1/+ mice, with a multigenic deletion that includes Tbx1, have elevated brain methylmalonic acid, which is highly brain-toxic. Focusing on Tbx1 mutants, we found that they also have a more general brain metabolomic imbalance that affects key metabolic pathways, such as glutamine-glutamate and fatty acid metabolism. We provide transcriptomic evidence of a genotype-vitamin B12 treatment interaction. In addition, vitamin B12 treatment rescued a behavioural anomaly in Tbx1 +/- mice. Further studies will be required to establish whether the specific metabolites affected by Tbx1 haploinsufficiency are potential biomarkers of brain disease status in 22q11.2DS patients.

Hypercalcemia and co-occurring TBX1 mutation in Glycogen Storage Disease Type Ib: case report

Glycogen Storage Disease Type Ib (GSD-Ib) is a rare autosomal recessive metabolic disorder caused by mutations in SLC37A4, leading to a deficiency in glucose-6-phosphate translocase. This disorder is characterized by impaired glycogenolysis and gluconeogenesis, resulting in clinical and metabolic manifestations. We report a three-month-old Moroccan female patient presenting with doll-like facies, hepatomegaly, dysmorphic features, and developmental delays. Laboratory analysis revealed hypoglycemia, elevated triglyceride levels, hypercalcemia, and neutropenia. Genetic testing confirmed a homozygous pathogenic variant in SLC37A4 and a heterozygous variant of uncertain significance in TBX1. Initial management included a lactose-free and galactose-free diet, multivitamin supplementation, and granulocyte colony-stimulating factor (G-CSF) therapy to address neutropenia. A novel aspect of this case involves hypercalcemia as an unusual finding in GSD-Ib and the co-occurrence of a variant in the TBX1 gene, which is not typically associated with the disease but may contribute to the patient's clinical presentation. These findings add a new dimension to our understanding of GSD-Ib and suggest potential avenues for future research to elucidate these genetic interactions and their impact on clinical outcomes.

A novel selenoglycoside compound GlcSeCys alleviates diets-induced obesity and metabolic dysfunctions with the modulation of Galectin-1 and selenoproteins

Selenium, an essential trace element in human, has been shown to play protective roles in obesity and metabolic disorders despite insufficient understanding of mechanisms. Moreover, it's well known that biological actions of selenium compounds differed greatly due to divergent chemical forms. Selenoglycoside is a type of organoselenium compounds with excellent hydrophilicity, but biological activity of which in vivo are almost unknown. We have designed and synthesized Se-β-d-glucopyranosyl-D-selenocysteine, a novel selenoglycoside compound named GlcSeCys. Herein, GlcSeCys was given to high fat high cholesterol (HFHC) fed mice to determine its actions as well as relevant molecular mechanisms using transcriptome and multiple molecular biological methods. It was revealed that GlcSeCys displayed pronounced anti-obesity effect and significantly alleviated hyperglycemia, hyperinsulinemia along with hepatic steatosis in HFHC diets-induced mice. Mechanistically, GlcSeCys was found to inhibit lipogenesis, lipid uptake and inflammation in liver, along with attenuation of Galectin-1 and induction of selenoprotein S (SELENOS). With regard to adipose tissues, GlcSeCys ameliorated hypertrophy of adipocytes, suppressed lipids biosynthesis and stimulated WAT browning along with abrogated WAT inflammation activation, which were in line with repression of Galectin-1 and increase of GPx3. Collectively, our results uncovered, for the first time, that selenoglycoside compound GlcSeCys possessed excellent protective effects against obesity and metabolic disorders, and the mechanisms were correlated with modulation of Galectin-1 and selenoproteins, shedding lights upon molecular biology of selenium and novel therapeutic for obesity and relevant metabolic disorders.

Molecular Regulation of Thermogenic Mechanisms in Beige Adipocytes

Adipose tissue is conventionally recognized as a metabolic organ responsible for storing energy. However, a proportion of adipose tissue also functions as a thermogenic organ, contributing to the inhibition of weight gain and prevention of metabolic diseases. In recent years, there has been significant progress in the study of thermogenic fats, particularly brown adipose tissue (BAT). Despite this progress, the mechanism underlying thermogenesis in beige adipose tissue remains highly controversial. It is widely acknowledged that beige adipose tissue has three additional thermogenic mechanisms in addition to the conventional UCP1-dependent thermogenesis: Ca2+ cycling thermogenesis, creatine substrate cycling thermogenesis, and triacylglycerol/fatty acid cycling thermogenesis. This paper delves into these three mechanisms and reviews the latest advancements in the molecular regulation of thermogenesis from the molecular genetic perspective. The objective of this review is to provide readers with a foundation of knowledge regarding the beige fats and a foundation for future research into the mechanisms of this process, which may lead to the development of new strategies for maintaining human health.

Supraclavicular brown adipocytes originate from Tbx1+ myoprogenitors

Brown adipose tissue (BAT) dissipates energy as heat, contributing to temperature control, energy expenditure, and systemic homeostasis. In adult humans, BAT mainly exists in supraclavicular areas and its prevalence is associated with cardiometabolic health. However, the developmental origin of supraclavicular BAT remains unknown. Here, using genetic cell marking in mice, we demonstrate that supraclavicular brown adipocytes do not develop from the Pax3+/Myf5+ epaxial dermomyotome that gives rise to interscapular BAT (iBAT). Instead, the Tbx1+ lineage that specifies the pharyngeal mesoderm marks the majority of supraclavicular brown adipocytes. Tbx1Cre-mediated ablation of peroxisome proliferator-activated receptor gamma (PPARγ) or PR/SET Domain 16 (PRDM16), components of the transcriptional complex for brown fat determination, leads to supraclavicular BAT paucity or dysfunction, thus rendering mice more sensitive to cold exposure. Moreover, human deep neck BAT expresses higher levels of the TBX1 gene than subcutaneous neck white adipocytes. Taken together, our observations reveal location-specific developmental origins of BAT depots and call attention to Tbx1+ lineage cells when investigating human relevant supraclavicular BAT.

Identification of a Novel Long Non-Coding RNA G8110 That Modulates Porcine Adipogenic Differentiation and Inflammatory Responses

Long non-coding RNAs (lncRNAs) have been extensively studied, and their crucial roles in adipogenesis, lipid metabolism, and gene expression have been revealed. However, the exact regulatory or other mechanisms by which lncRNAs influence the functioning of mesenteric adipose tissue (MAT) remain largely unknown. In this paper, we report the identification of a new lncRNA, named G8110, from the MAT of Bama pigs. The coordinated expression levels of lncRNA G8110 and NFE2L1 were significantly decreased in the MAT of obese Bama pigs compared with those in the MAT of lean pigs. Using a bone mesenchymal stem cell adipogenic differentiation model, we found that lncRNA G8110 played a role in adipocyte differentiation by positively regulating NFE2L1. We also found that lncRNA G8110 inhibited the formation of intracellular lipid synthesis, promoted lipid metabolism, and inhibited the expression of inflammatory cytokines. Our findings regarding lipid synthesis may further promote the role of lncRNAs in driving adipose tissue remodeling and maintaining metabolic health.

DNA methylation of insulin signaling pathways is associated with HOMA2-IR in primary myoblasts from older adults

BACKGROUND

While ageing is associated with increased insulin resistance (IR), the molecular mechanisms underlying increased IR in the muscle, the primary organ for glucose clearance, have yet to be elucidated in older individuals. As epigenetic processes are suggested to contribute to the development of ageing-associated diseases, we investigated whether differential DNA methylation was associated with IR in human primary muscle stem cells (myoblasts) from community-dwelling older individuals.

METHODS

We measured DNA methylation (Infinium HumanMethylationEPIC BeadChip) in myoblast cultures from vastus lateralis biopsies (119 males/females, mean age 78.24 years) from the Hertfordshire Sarcopenia Study extension (HSSe) and examined differentially methylated cytosine phosphate guanine (CpG) sites (dmCpG), regions (DMRs) and gene pathways associated with HOMA2-IR, an index for the assessment of insulin resistance, and levels of glycated hemoglobin HbA1c.

RESULTS

Thirty-eight dmCpGs (false discovery rate (FDR) < 0.05) were associated with HOMA2-IR, with dmCpGs enriched in genes linked with JNK, AMPK and insulin signaling. The methylation signal associated with HOMA2-IR was attenuated after the addition of either BMI (6 dmCpGs), appendicular lean mass index (ALMi) (7 dmCpGs), grip strength (15 dmCpGs) or gait speed (23 dmCpGs) as covariates in the model. There were 8 DMRs (Stouffer < 0.05) associated with HOMA2-IR, including DMRs within T-box transcription factor (TBX1) and nuclear receptor subfamily-2 group F member-2 (NR2F2); the DMRs within TBX1 and NR2F2 remained associated with HOMA2-IR after adjustment for BMI, ALMi, grip strength or gait speed. Forty-nine dmCpGs and 21 DMRs were associated with HbA1c, with cg13451048, located within exoribonuclease family member 3 (ERI3) associated with both HOMA2-IR and HbA1c. HOMA2-IR and HbA1c were not associated with accelerated epigenetic ageing.

CONCLUSIONS

These findings suggest that insulin resistance is associated with differential DNA methylation in human primary myoblasts with both muscle mass and body composition making a significant contribution to the methylation changes associated with IR.

Proteomic and Transcriptomic Landscapes of Alström and Bardet-Biedl Syndromes

Alström syndrome (ALMS) and Bardet-Biedl syndrome (BBS) are rare genetic diseases with a number of common clinical features ranging from early-childhood obesity and retinal degeneration. ALMS and BBS belong to the ciliopathies, which are known to have the expression products of genes, encoding them as cilia-localized proteins in multiple target organs. The aim of this study was to perform transcriptomic and proteomic analysis on cellular models of ALMS and BBS syndromes to identify common and distinct pathological mechanisms present in both syndromes. For this purpose, epithelial cells were isolated from the urine of patients and healthy subjects, which were then cultured and reprogrammed into induced pluripotent stem (iPS) cells. The pathways of genes associated with the metabolism of lipids and glycosaminoglycan and the transport of small molecules were found to be concomitantly downregulated in both diseases, while transcripts related to signal transduction, the immune system, cell cycle control and DNA replication and repair were upregulated. Furthermore, protein pathways associated with autophagy, apoptosis, cilium assembly and Gli1 protein were upregulated in both ciliopathies. These results provide new insights into the common and divergent pathogenic pathways between two similar genetic syndromes, particularly in relation to primary cilium function and abnormalities in cell differentiation.

PPARγ and NOTCH Regulate Regional Identity in the Murine Cardiac Outflow Tract

BACKGROUND

The arterial pole of the heart is a hotspot for life-threatening forms of congenital heart defects (CHDs). Development of this cardiac region occurs by addition of Second Heart Field (SHF) progenitor cells to the embryonic outflow tract (OFT) and subsequently the base of the ascending aorta and pulmonary trunk. Understanding the cellular and genetic mechanisms driving arterial pole morphogenesis is essential to provide further insights into the cause of CHDs.

METHODS

A synergistic combination of bioinformatic analysis and mouse genetics as well as embryo and explant culture experiments were used to dissect the cross-regulatory transcriptional circuitry operating in future subaortic and subpulmonary OFT myocardium.

RESULTS

Here, we show that the lipid sensor PPARγ (peroxisome proliferator-activated receptor gamma) is expressed in future subpulmonary myocardium in the inferior wall of the OFT and that PPARγ signaling-related genes display regionalized OFT expression regulated by the transcription factor TBX1 (T-box transcription factor 1). Modulating PPARγ activity in ex vivo cultured embryos treated with a PPARγ agonist or antagonist or deleting Pparγ in cardiac progenitor cells using Mesp1-Cre reveals that Pparγ is required for addition of future subpulmonary myocardium and normal arterial pole development. Additionally, the non-canonical DLK1 (delta-like noncanonical Notch ligand 1)/NOTCH (Notch receptor 1)/HES1 (Hes family bHLH transcription factor 1) pathway negatively regulates Pparγ in future subaortic myocardium in the superior OFT wall.

CONCLUSIONS

Together these results identify Pparγ as a regulator of regional transcriptional identity in the developing heart, providing new insights into gene interactions involved in congenital heart defects.

Chronic cAMP activation induces adipocyte browning through discordant biphasic remodeling of transcriptome and chromatin accessibility

OBJECTIVE

Adipose tissue thermogenesis has been suggested as a new therapeutic target to promote energy metabolism for obesity and metabolic disease. Cold-inducible thermogenic adipocytes, called beige adipocytes, have attracted significant attention for their potent anti-obesity activity in adult humans. In this study, we identified the mechanisms underlying beige adipocyte recruitment, so-called adipocyte browning, by different stimuli.

METHODS

We generated a new adipocyte cell line with enhanced browning potentials and determined its transcriptomic and epigenomic responses following cAMP (forskolin, FSK) versus PPARγ activation (rosiglitazone). We performed time-course RNA-seq and compared the treatments and in vivo adipocyte browning. We also developed an improved protocol for Assay for Transposase Accessible Chromatin-sequencing (ATAC-seq) and defined changes in chromatin accessibility in a time course. The RNA-seq and ATAC-seq data were integrated to determine the kinetics of their coordinated regulation and to identify a transcription factor that drives these processes. We conducted functional studies using pharmacological and genetic approaches with specific inhibitors and shRNA-mediated knockdown, respectively.

RESULTS

FSK, not rosiglitazone, resulted in a biphasic transcriptomic response, resembling the kinetics of in vivo cold-induced browning. FSK promoted tissue remodeling first and subsequently shifted energy metabolism, concluding with a transcriptomic profile similar to that induced by rosiglitazone. The thermogenic effects of FSK were abolished by PPARγ antagonists, indicating PPARγ as a converging point. ATAC-seq uncovered that FSK leads to a significant chromatin remodeling that precedes or persists beyond transcriptomic changes, whereas rosiglitazone induces minimal changes. Motif analysis identified nuclear factor, interleukin 3 regulated (NFIL3) as a transcriptional regulator connecting the biphasic response of FSK-induced browning, as indicated by disrupted thermogenesis with NFIL3 knockdown.

CONCLUSIONS

Our findings elucidated unique dynamics of the transcriptomic and epigenomic remodeling in adipocyte browning, providing new mechanistic insights into adipose thermogenesis and molecular targets for obesity treatment.

A Comparative Analysis of the Wound Healing-Related Heterogeneity of Adipose-Derived Stem Cells Donors

Adipose-derived Stem cells (ASCs) are on the verge of being available for large clinical trials in wound healing. However, for developing advanced therapy medicinal products (ATMPs), potency assays mimicking the mode of action are required to control the product consistency of the cells. Thus, greater effort should go into the design of product assays. Therefore, we analyzed three ASC-based ATMPs from three different donors with respect to their surface markers, tri-lineage differentiation, proliferation, colony-forming unit capacity, and effect on fibroblast proliferation and migration, endothelial proliferation, migration, and angiogenesis. Furthermore, the transcriptome of all three cell products was analyzed through RNA-sequencing. Even though all products met the criteria by the International Society for Cell and Gene Therapy and the International Federation for Adipose Therapeutics and Science, we found one product to be consistently superior to others when exploring their potency in the wound healing specific assays. Our results indicate that certain regulatory genes associated with extracellular matrix and angiogenesis could be used as markers of a superior ASC donor from which to use ASCs to treat chronic wounds. Having a panel of assays capable of predicting the potency of the product would ensure the patient receives the most potent product for a specific indication, which is paramount for successful patient treatment and acceptance from the healthcare system.

Tissue Transglutaminase Knock-Out Preadipocytes and Beige Cells of Epididymal Fat Origin Possess Decreased Mitochondrial Functions Required for Thermogenesis

Beige adipocytes with thermogenic function are activated during cold exposure in white adipose tissue through the process of browning. These cells, similar to brown adipocytes, dissipate stored chemical energy in the form of heat with the help of uncoupling protein 1 (UCP1). Recently, we have shown that tissue transglutaminase (TG2) knock-out mice have decreased cold tolerance in parallel with lower utilization of their epididymal adipose tissue and reduced browning. To learn more about the thermogenic function of this fat depot, we isolated preadipocytes from the epididymal adipose tissue of wild-type and TG2 knock-out mice and differentiated them in the beige direction. Although differentiation of TG2 knock-out preadipocytes is phenotypically similar to the wild-type cells, the mitochondria of the knock-out beige cells have multiple impairments including an altered electron transport system generating lower electrochemical potential difference, reduced oxygen consumption, lower UCP1 protein content, and a higher portion of fragmented mitochondria. Most of these differences are present in preadipocytes as well, and the differentiation process cannot overcome the functional disadvantages completely. TG2 knock-out beige adipocytes produce more iodothyronine deiodinase 3 (DIO3) which may inactivate thyroid hormones required for the establishment of optimal mitochondrial function. The TG2 knock-out preadipocytes and beige cells are both hypometabolic as compared with the wild-type controls which may also be explained by the lower expression of solute carrier proteins SLC25A45, SLC25A47, and SLC25A42 which transport acylcarnitine, Co-A, and amino acids into the mitochondrial matrix. As a consequence, the mitochondria in TG2 knock-out beige adipocytes probably cannot reach the energy-producing threshold required for normal thermogenic functions, which may contribute to the decreased cold tolerance of TG2 knock-out mice.

Male and female high-fat diet-fed Dahl SS rats are largely protected from vascular dysfunctions: PVAT contributions reveal sex differences

Vascular dysfunctions are observed in the arteries from hypertensive subjects. The establishment of the Dahl salt-sensitive (SS) male and female rat models to develop a reproducible hypertension with high-fat (HF) diet feeding from weaning allows addressing the question of whether HF diet-associated hypertension results in vascular dysfunction similar to that of essential hypertension in both sexes. We hypothesized that dysfunction of three distinct vascular layers, i.e., endothelial, smooth muscle, and perivascular adipose tissue (PVAT), would be present in the aorta from HF diet-fed versus control diet-fed male and female rats. Dahl SS rats were fed a control (10% kcal of fat) or HF (60%) diet from weaning for 24 wk. Male and female Dahl SS rats became equally hypertensive when placed on a HF diet. For male and female rats, the thoracic aorta exhibited medial hypertrophy in HF diet-induced hypertension versus control, but neither displayed a hyperresponsive contraction to the α-adrenergic agonist phenylephrine nor an endothelial cell dysfunction as measured by acetylcholine-induced relaxation. A beneficial PVAT function, support of stress relaxation, was reduced in the male versus female rats fed a HF diet. PVAT in the aorta of males but not in females retained the anticontractile activity. We conclude that this HF model does not display the same vascular dysfunctions observed in essential hypertension. Moreover, both male and female show significantly different vascular dysfunctions in this HF feeding model.NEW & NOTEWORTHY Although the aorta exhibits medial hypertrophy in response to HF diet-induced hypertension, it did not exhibit hyperresponsive contraction to an α-adrenergic agonist nor endothelial cell dysfunction; this was true for both sexes. Unlike other hypertension models, PVAT around aorta from (male) rats on the HF diet retained significant anticontractile activity. PVAT around aorta of the male on a HF diet was modestly more fibrotic and lost the ability to assist in arterial stress relaxation.

Brown/Beige adipose tissues and the emerging role of their secretory factors in improving metabolic health: The batokines

Brown and beige adipose tissues are the primary sites for adaptive non-shivering thermogenesis. Although they have been known principally for their thermogenic effects, in recent years, it has emerged that, just like white adipose tissue (WAT), brown and beige adipose tissues also play an important role in the regulation of metabolic health through secretion of various brown adipokines (batokines) in response to various physiological cues. These secreted batokines target distant organs and tissues such as the liver, heart, skeletal muscles, brain, WAT, and perform various local and systemic functions in an autocrine, paracrine, or endocrine manner. Brown and beige adipose tissues are therefore now receiving increasing levels of attention with respect to their effects on various other organs and tissues. Identification of novel secreted factors by these tissues may help in the discovery of drug candidates for the treatment of various metabolic disorders such as obesity, type-2 diabetes, skeletal deformities, cardiovascular diseases, dyslipidemia. In this review, we comprehensively describe the emerging secretory role of brown/beige adipose tissues and the metabolic effects of various brown/beige adipose tissues secreted factors on other organs and tissues in endocrine/paracrine manners, and as well as on brown/beige adipose tissue itself in an autocrine manner. This will provide insights into understanding the potential secretory role of brown/beige adipose tissues in improving metabolic health.

Homeobox A5 and C10 genes modulate adaptation of brown adipose tissue during exercise training in juvenile rats

NEW FINDINGS

What is the central question of this study? Exercise can stimulate brown adipose tissue (BAT) with subsequent increase in uncoupling protein 1 expression and mitochondrial biogenesis. In that case, do BAT-specific Hox genes modify BAT functioning and cause uncoupling protein expression changes due to exercise? What is the main finding and its importance? Exercise enhanced brown adipocyte markers, with significant upregulation of HoxA5 and downregulation of HoxC10 mRNA expression in rat BAT. HoxA5 and HoxC10 are thus likely to play distinct roles in exercise-induced changes in BAT markers during the early postnatal period. These findings provide new insight into the mechanisms underlying exercise-induced changes in BAT function.

ABSTRACT

Brown adipose tissue (BAT) recruitment is involved in increased energy expenditure associated with cold exposure and exercise training. We explored whether exercise training induced changes in expression levels of brown adipocyte-selective factors and Homeobox (Hox) genes during the post-weaning growth period of male Wistar rats. Relative to total body weight, BAT weights alone were lower in exercise-trained (EX) rats compared to sedentary control (SED) rats. mRNA expression of HoxA5 was higher and that of HoxC10 was lower in EX rats than in SED rats, accompanied by both higher citrate synthase activity and protein expression levels for uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor (PPAR) α, and PPARγ-coactivator (PGC)-1α. HoxA5 knockdown with siRNA reduced the expression of PR-domain containing 16 (Prdm16), cell death-inducing DNA fragmentation factor-α-like effector A (Cidea) gene, type 2 deiodinase mRNA, and PRDM16 protein. Comparatively, HoxC10 knockdown with siRNA enhanced mRNA expression of Prdm16, Pparα and Pgc1α and protein expression of UCP1, PPARα and PGC1α in brown adipocytes. The stimulation of brown adipocytes with isoproterenol, a β-adrenoceptor agonist, caused a phenomenon similar to the effect of exercise training on the genes tested: upregulation of HoxA5 mRNA, downregulation of HoxC10 mRNA, and increased protein expression for UCP1 and PGC1α. Collectively, HoxA5 and HoxC10 may have unique functions that contribute to modulating the expression of BAT-selective markers in BAT of juvenile rats during exercise training. The study findings regarding activation and recruitment of BAT during exercise training have implications for anti-obesity management.