GH influences adipocyte differentiation, but both stimulatory and inhibitory effects have been described. Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are multipotent and are able to differentiate into adipocytes, among other cells. Canonical Wnt/β-catenin signaling activation impairs adipogenesis. The aim of the present study was to elucidate the role of GH on AT-MSC adipogenesis using cells isolated from male GH receptor knockout (GHRKO), bovine GH transgenic (bGH) mice, and wild-type littermate control (WT) mice. AT-MSCs from subcutaneous (sc), epididiymal (epi), and mesenteric (mes) AT depots were identified and isolated by flow cytometry (Pdgfrα + Sca1 + Cd45 − Ter119 − cells). Their in vitro adipogenic differentiation capacity was determined by cell morphology and real-time RT-PCR. Using identical in vitro conditions, adipogenic differentiation of AT-MSCs was only achieved in the sc depot, and not in epi and mes depots. Notably, we observed an increased differentiation in cells isolated from sc-GHRKO and an impaired differentiation of sc-bGH cells as compared to sc-WT cells. Axin2, a marker of Wnt/β-catenin activation, was increased in mature sc-bGH adipocytes, which suggests that activation of this pathway may be responsible for the decreased adipogenesis. Thus, the present study demonstrates that i) adipose tissue in mice has a well-defined population of Pdgfrα + Sca1 + MSCs; ii) the differentiation capacity of AT-MSCs varies from depot to depot regardless of GH genotype; iii) the lack of GH action increases adipogenesis in the sc depot; and iv) activation of the Wnt/β-catenin pathway might mediate the GH effect on AT-MSCs. Taken together, the present results suggest that GH diminishes fat mass in part by altering adipogenesis of MSCs.
Nicoleta C Olarescu, Darlene E Berryman, Lara A Householder, Ellen R Lubbers, Edward O List, Fabian Benencia, John J Kopchick and Jens Bollerslev
Lei Zhang, Carol Paddon, Mark D Lewis, Fiona Grennan-Jones and Marian Ludgate
Since TSH receptor (TSHR) expression increases during adipogenesis and signals via cAMP/phospho-cAMP-response element binding protein (CREB), reported to be necessary and sufficient for adipogenesis, we hypothesised that TSHR activation would induce preadipocyte differentiation. Retroviral vectors introduced constitutively active TSHR (TSHR*) into 3T3L1 preadipocytes; despite increased cAMP (RIA) and phospho-CREB (western blot) there was no spontaneous adipogenesis (assessed morphologically, using oil red O and QPCR measurement of adipogenesis markers). We speculated that Gβγ signalling may be inhibitory but failed to induce adipogenesis using activated Gsα (gsp*). Inhibition of phosphodiesterases did not promote adipogenesis in TSHR* or gsp* populations. Furthermore, differentiation induced by adipogenic medium with pioglitazone was reduced in TSHR* and abolished in gsp* expressing 3T3L1 cells. TSHR* and gsp* did not inactivate PPARγ (PPARG as listed in the HUGO database) by phosphorylation but expression of PPARγ1 was reduced and PPARγ2 undetectable in gsp*. FOXO1 phosphorylation (required to inactivate this repressor of adipogenesis) was lowest in gsp* despite the activation of AKT by phosphorylation. PROF is a mediator that facilitates FOXO1 phosphorylation by phospho-Akt. Its transcript levels remained constantly low in the gsp* population. In most measurements, the TSHR* cells were between the gsp* and control 3T3L1 preadipocytes. The enhanced down-regulation of PREF1 (adipogenesis inhibitor) permits retention of some adipogenic potential in the TSHR* population. We conclude that Gsα signalling impedes FOXO1 phosphorylation and thus inhibits PPARγ transcription and the alternative promoter usage required to generate PPARγ2, the fat-specific transcription factor necessary for adipogenesis.
Lili Men, Junjie Yao, Shanshan Yu, Yu Li, Siyuan Cui, Shi Jin, Guixin Zhang, Decheng Ren and Jianling Du
The induction of endoplasmic reticulum (ER) stress is associated with adipogenesis, during which the inositol-requiring enzyme 1 alpha (IRE1α)-X-box-binding protein 1 (XBP1) pathway is involved. Selenoprotein S (SelS), which is an ER resident selenoprotein, is involved in ER homeostasis regulation; however, little is known about the role of SelS in regulating adipogenesis. In vivo studies showed that SelS protein levels in white adipose tissue were increased in obese subjects and high-fat diet (HFD)-fed mice. Moreover, we identified that SelS protein levels increased in the early phase of adipogenesis and then decreased in the late phase during adipogenesis. Overexpression of SelS promoted adipogenesis. Conversely, knockdown (KD) of SelS resulted in the inhibition of adipogenesis, which was related to increasing cell death, decreased mitotic clonal expansion, and cell cycle G1 arrest. In vivo studies also showed that ER stress markers (p-IRE1α/IRE1α, XBP1s, and Grp78) were significantly increased with upregulating of SelS expression in subcutaneous and visceral adipose tissues in the obese subjects and HFD-fed mice. Furthermore, in SelS KD cells, the levels of Grp78 were increased and the levels of p-IRE1α/IRE1α were unchanged , but mRNA levels of spliced XBP1 (XBP1s) produced by IRE1α-mediated splicing were decreased, suggesting a role of SelS in the modulation of IRE1α-XBP1 pathway. Moreover, inhibition of adipogenesis by SelS suppression can be rescued by overexpression of XBP1s. Thus, SelS appears to function as a novel regulator of adipogenesis through the IRE1α-XBP1 signaling pathway.
Uxía Gurriarán-Rodríguez, Omar Al-Massadi, Ana Belén Crujeiras, Carlos S Mosteiro, María Amil-Diz, Daniel Beiroa, Rubén Nogueiras, Luisa María Seoane, Rosalía Gallego, Yolanda Pazos, Felipe F Casanueva and Jesús P Camiña
This study aimed to investigate the role of preproghrelin-derived peptides in adipogenesis. Immunocytochemical analysis of 3T3-L1 adipocyte cells showed stronger preproghrelin expression compared with that observed in 3T3-L1 preadipocyte cells. Insulin promoted this expression throughout adipogenesis identifying mTORC1 as a critical downstream substrate for this profile. The role of preproghrelin-derived peptides on the differentiation process was supported by preproghrelin knockdown experiments, which revealed its contribution to adipogenesis. Neutralization of endogenous O-acyl ghrelin (acylated ghrelin), unacylated ghrelin, and obestatin by specific antibodies supported their adipogenic potential. Furthermore, a parallel increase in the expression of ghrelin-associated enzymatic machinery, prohormone convertase 1/3 (PC1/3) and membrane-bound O-acyltransferase 4 (MBOAT4), was dependent on the expression of preproghrelin in the course of insulin-induced adipogenesis. The coexpression of preproghrelin system and their receptors, GHSR1a and GPR39, during adipogenesis supports an autocrine/paracrine role for these peptides. Preproghrelin, PC1/3, and MBOAT4 exhibited dissimilar expression depending on the white fat depot, revealing their regulation in a positive energy balance situation in mice. The results underscore a key role for preproghrelin-derived peptides on adipogenesis through an autocrine/paracrine mechanism.
Ana María Pino, Juan Manuel Rodríguez, Susana Ríos, Pablo Astudillo, Laura Leiva, Germán Seitz, Mireya Fernández and J Pablo Rodríguez
Human mesenchymal stem cells (hMSCs) are multipotent cells present in bone marrow, which differentiate into osteoblasts and adipocytes, among other lineages. Oestrogens play a critical role in bone metabolism; its action may affect the adipocyte to osteoblast ratio in the bone marrow. In hMSCs, oestrogens are synthesized from C19 steroids by the enzyme aromatase cytochrome P450. In this study, we assessed whether aromatase enzymatic activity varied through early osteogenic (OS) and adipogenic (AD) differentiation. Also, we studied the effect of leptin and 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) on aromatase cell activity. Finally, we analysed whether conditions that modify oestrogen generation by cells affected hMSCs differentiation. For these purposes, hMSCs derived from post-menopausal women (65–86 years old) were cultured under basal, OS or AD conditions, in the presence or the absence of leptin and 1,25(OH)2D3. Aromatase activity was measured by the tritiated water release assay and by direct measurement of steroids synthesized from 3H-labelled androstenedione or testosterone. Our results showed that different OS and AD patterns of aromatase activity developed during the first period of differentiation (up to 7 days). A massive and sharp surge of aromatase activity at 24 h characterized early OS differentiation, while increased but constant aromatase activity was increased through adipogenesis. Both leptin and vitamin D increased aromatase activity during osteogenesis, but not during adipogenesis; finally, we showed that favourable aromatase substrates concentration restrained MSCs adipogenesis but improved osteogenesis. Thus, it could be inferred that a high and early increase of local oestrogen concentration in hMSCs affects their commitment either restraining AD or facilitating OS differentiation, or both.
Paula Fuentes, María José Acuña, Mariana Cifuentes and Cecilia V Rojas
Despite the importance of adipocyte formation for adipose tissue physiology, current knowledge about the mechanisms that regulate the recruitment of progenitor cells to undergo adipogenic differentiation is limited. A role for locally generated angiotensin II emerged from studies with human and murine cells. Preadipose cells from different human fat depots show reduced response to adipogenic stimuli when exposed to angiotensin II. This investigation sought to gain an insight into the intracellular mechanisms involved in the anti-adipogenic response of human preadipose cells from omental fat to angiotensin II. Its effect was evaluated on cells stimulated to adipogenic differentiation in vitro, by assessment of glycerol-3-phosphate dehydrogenase activity and expression of early markers of adipogenesis. Extracellular signal-regulated kinase1,2 (ERK1,2) pathway activation was inferred from the phosphorylated to total ERK1,2 ratio determined by western blot. Exposure to angiotensin II throughout the 10-day differentiation period resulted in a reduced adipogenic response. A similar anti-adipogenic effect was observed when this hormone was present during the first 48 h of induction to differentiation. Angiotensin II treatment had no consequences on CCAAT/enhancer-binding protein β and peroxisome proliferator-activated receptor γ (PPARG) induction, but increased the phosphorylated form of the key adipogenic regulator PPARG. Upon angiotensin II exposure, a raise of phosphorylated ERK1,2 was determined, which was more prominent 8–20 h after induction of adipogenesis (when controls reached negligible values). Chemical inhibition of ERK1,2 phosphorylation prevented angiotensin II-dependent reduction in adipogenesis. These results support the participation of the mitogen-activated protein kinase/ERK1,2 pathway in the anti-adipogenic effect of angiotensin II on preadipose cells from human omental adipose tissue.
Qinghua Wang, Jing Tang, Shujun Jiang, Zan Huang, Anying Song, Siyuan Hou, Xiang Gao and Hai-Bin Ruan
Peroxisome proliferator-activated receptor-γ (PPARγ) is a master regulator of adipogenesis and a target of the thiazolidinedione (TZD) class of antidiabetic drugs; therefore, identifying novel regulators of PPARγ action in adipocytes is essential for the future development of therapeutics for diabetes. MAGE family member D1 (MAGED1), by acting as an adaptor for ubiquitin-dependent degradation pathways and a co-factor for transcription, plays an important role in neural development, cell differentiation and circadian rhythm. Here, we showed that MAGED1 expression was downregulated during adipogenesis and loss of MAGED1 promoted preadipocyte proliferation and differentiation in vitro. MAGED1 bound to PPARγ and suppressed the stability and transcriptional activity of PPARγ. Compared to WT littermates, MAGED1-deficient mice showed increased levels of PPARγ protein and its target genes, more CD29+CD34+Sca-1+ adipocyte precursors and hyperplasia of white adipose tissues (WATs). Moreover, MAGED1-deficient mice developed late-onset obesity as a result of decreased energy expenditure and physical activity. However, these mice were metabolically healthy as shown by improved glucose clearance and insulin sensitivity, normal levels of serum lipids and enhanced secretion of adipokines such as leptin and adiponectin. Taken together, our data identify MAGED1 as a novel negative regulator of PPARγ activity, adipogenesis and insulin sensitivity in mice. MAGED1 might therefore serve as a novel pharmaceutical target to treat obesity-associated insulin resistance.
Epidemiological studies initially demonstrated that maternal undernutrition leading to low birth weight may predispose for energy balance disorders throughout life. High birth weight due to maternal obesity or diabetes, inappropriate early post-natal nutrition and rapid catch-up growth may also sensitise to increased risk of obesity. As stated by the Developmental Origin of Health and Disease concept, the perinatal perturbation of foetus/neonate nutrient supply might be a crucial determinant of individual programming of body weight set point. The hypothalamus–adipose axis plays a pivotal role in the maintenance of energy homoeostasis controlling the nutritional status and energy storage level. The perinatal period largely corresponds to the period of brain maturation, neuronal differentiation and active adipogenesis in rodents. Numerous dams and/or foetus/neonate dietary manipulation models were developed to investigate the mechanisms underlying perinatal programming in rodents. These models showed several common offspring hypothalamic consequences such as impaired neurogenesis, neuronal functionality, nuclei structural organisation and feeding circuitry hardwiring. These alterations led to a persistent reprogrammed appetite system that favoured the orexigenic pathways, leptin/insulin resistance and hyperphagia. Impaired hypothalamic sympathetic outflow to adipose tissue and/or reduced innervation may also account for modified fat cell metabolism. Thus, enhanced adipogenesis and/or lipogenesis capacities may predispose the offspring to fat accumulation. Abnormal hypothalamus–adipose axis circadian rhythms were also evidenced. This review mainly focuses on studies in rodents. It highlights hormonal and epigenetic mechanisms responsible for long-lasting programming of energy balance in the offspring. Dietary supplementation may provide a therapeutic option using a specific regimen for reversing adverse programming outcomes in humans.
M A Hyatt, D H Keisler, H Budge and M E Symonds
Maternal parity influences size at birth, postnatal growth and body composition with firstborn infants being more likely to be smaller with increased fat mass, suggesting that adiposity is set in early life. The precise effect of parity on fat mass and its endocrine sensitivity remains unclear and was, therefore, investigated in the present study. We utilised an established sheep model in which perirenal–abdominal fat mass (the major fat depot in the neonatal sheep) increases ∼10-fold over the first month of life and focussed on the impact of parity on glucocorticoid sensitivity and adipokine expression in the adipocyte. Twin-bearing sheep of similar body weight and adiposity that consumed identical diets were utilised, and maternal blood samples were taken at 130 days of gestation. One offspring from each twin pair was sampled at 1 day of age, coincident with the time of maximal recruitment of uncoupling protein 1 (UCP1), whilst its sibling was sampled at 1 month, when UCP1 had disappeared. Plasma leptin was lower in nulliparous mothers than in multiparous mothers, and offspring of nulliparous mothers possessed more adipose tissue with increased mRNA abundance of leptin, glucocorticoid receptor and UCP2, adaptations that persisted up to 1 month of age when gene expression for interleukin-6 and adiponectin was also raised. The increase in fat mass associated with firstborn status is therefore accompanied by a resetting of the leptin and glucocorticoid axis within the adipocyte. Our findings emphasise the importance of parity in determining adipose tissue development and that firstborn offspring have an increased capacity for adipogenesis which may be critical in determining later adiposity.
I J Bujalska, L L Gathercole, J W Tomlinson, C Darimont, J Ermolieff, A N Fanjul, P A Rejto and P M Stewart
Glucocorticoid excess increases fat mass, preferentially within omental depots; yet circulating cortisol concentrations are normal in most patients with metabolic syndrome (MS). At a pre-receptor level, 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activates cortisol from cortisone locally within adipose tissue, and inhibition of 11β-HSD1 in liver and adipose tissue has been proposed as a novel therapy to treat MS by reducing hepatic glucose output and adiposity. Using a transformed human subcutaneous preadipocyte cell line (Chub-S7) and human primary preadipocytes, we have defined the role of glucocorticoids and 11β-HSD1 in regulating adipose tissue differentiation. Human cells were differentiated with 1.0 μM cortisol (F), or cortisone (E) with or without 100 nM of a highly selective 11β-HSD1 inhibitor PF-877423. 11β-HSD1 mRNA expression increased across adipocyte differentiation (P<0.001, n=4), which was paralleled by an increase in 11β-HSD1 oxo-reductase activity (from nil on day 0 to 5.9±1.9 pmol/mg per h on day 16, P<0.01, n=7). Cortisone enhanced adipocyte differentiation; fatty acid-binding protein 4 expression increased 312-fold (P<0.001) and glycerol-3-phosphate dehydrogenase 47-fold (P<0.001) versus controls. This was abolished by co-incubation with PF-877423. In addition, cellular lipid content decreased significantly. These findings were confirmed in the primary cultures of human subcutaneous preadipocytes. The increase in 11β-HSD1 mRNA expression and activity is essential for the induction of human adipogenesis. Blocking adipogenesis with a novel and specific 11β-HSD1 inhibitor may represent a novel approach to treat obesity in patients with MS.