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Free access

Chunyu Wang, Li Tian, Kun Zhang, Yaxi Chen, Xiang Chen, Ying Xie, Qian Zhao and Xijie Yu

The purpose of the study was to determine the roles of interleukin-6 (IL6) in fat and bone communication. Male wild-type (WT) mice and IL6 knockout (IL6−/−) mice were fed with either regular diet (RD) or high-fat diet (HFD) for 12 weeks. Bone mass and bone microstructure were evaluated by micro-computed tomography. Gene expression related to lipid and bone metabolisms was assayed with real-time quantitative polymerase chain reaction. Bone marrow cells from both genotypes were induced to differentiate into osteoblasts or osteoclasts, and treated with palmitic acid (PA). HFD increased the body weight and fat pad weight, and impaired lipid metabolism in both WT and IL6−/− mice. The dysregulation of lipid metabolism was more serious in IL6−/− mice. Trabecular bone volume fraction, trabecular bone number and trabecular bone thickness were significantly downregulated in WT mice after HFD than those in the RD (P < 0.05). However, these bone microstructural parameters were increased by 53%, 34% and 40%, respectively, in IL6−/− mice than those in WT mice on the HFD (P < 0.05). IL6−/− osteoblasts displayed higher alkaline phosphatase (ALP) activity and higher mRNA levels of Runx2 and Colla1 than those in WT osteoblasts both in the control and PA treatment group (P < 0.05). IL6−/− mice showed significantly lower mRNA levels of PPARγ and leptin and higher mRNA levels of adiponectin in comparison with WT mice on HFD. In conclusion, these findings suggested that IL6 gene deficiency antagonized HFD-induced bone loss. IL6 might bridge lipid and bone metabolisms and could be a new potential therapeutic target for lipid metabolism disturbance-related bone loss.

Free access

AW Kung and KS Lau

The release of interferon-gamma (IFNgamma) has been demonstrated from the infiltrating T lymphocytes of the thyroid gland from patients with autoimmune thyroid disease (AITD). We have shown previously that IFNgamma inhibited thyroglobulin (Tg) gene transcription, and that its action was mediated by an increase in intracellular calcium and inositol phosphates. In the present study, we tried to determine the specific site of action of IFNgamma on the Tg gene. A 565 bp fragment (position -530 to +34) spanning the transcriptional start site of the human Tg promoter was ligated to the luciferase plasmid and transiently transfected into human thyrocytes. Stimulation with TSH (10 mIU/l) and IFNgamma (500 IU/l) resulted in a twofold increase and a 60% reduction in the luciferase activity respectively, similar to the effect observed with the endogenous Tg gene. Deletion studies revealed that the region with the strongest suppression by IFNgamma lay between 5' -388 to -258. Mobility gel shift experiments and DNA footprinting experiments demonstrated that the action of IFNgamma was mediated through a trans-acting protein which complexed to position -282 to -262 TTGAGCCTGTTCCCTC CAAA. Position -272 to -261 TTCCCTCCAA corresponded to the gamma-interferon activation site (GAS) consensus sequence TTNC(C)T NNNA. The turnover time of the nuclear protein lasted for only 4 h although the suppressive effect of IFNgamma on Tg gene transcription lasted for 48 h. The effect of IFNgamma was lost when the thyrocytes were co-treated with genistein, a specific tyrosine kinase inhibitor. The presence of the GAS in the promoter sequence of the Tg gene confirms the specific action of IFNgamma in thyroid hormone metabolism. In conclusion, apart from its regulatory role in T cell development and perpetuation of the immune response in AITD, IFNgamma may also play a role in altering cellular function of the thyrocytes by its action on the Tg gene promoter.

Open access

Seema Kumar, Sarah Nadeem, Marius N Stan, Michael Coenen and Rebecca S Bahn

Graves' ophthalmopathy (GO) is characterized by expanded volume of the orbital tissues associated with elevated serum levels of TSH receptor (TSHR) autoantibodies. Because previous studies have demonstrated evidence of adipogenesis within the GO orbit, we sought to determine whether M22, a human monoclonal antibody directed against TSHR, enhances adipogenesis in orbital fibroblasts from patients with GO and, if so, to identify signaling mechanisms involved. GO orbital fibroblast cultures (n=10) were treated for 10 days with bovine TSH (1 or 10.0 U/l) or M22 (1 or 10 ng/ml) in serum-free adipocyte differentiation medium. Some cultures also received a phosphoinositide 3-kinase (PI3K) inhibitor or an inhibitor of cAMP production. In other experiments, confluent cultures (n=8) were treated for between 1 and 30 min with TSH (0.1–10.0 U/l) or M22 (0.1–100 ng/ml) with measurement of cAMP production or levels of phosphorylated AKT (pAKT). We found levels of adiponectin, leptin, and TSHR mRNA to be increased in GO cultures treated for 10 days with either M22 (2.6 mean fold ±0.7; P=0.03) or TSH (13.2±5.8-fold, P=0.048). In other studies, M22 and TSH stimulated cAMP production and pAKT levels in GO cells. Inhibition of PI3K activity during 10 days in culture decreased the levels of M22-stimulated mRNA encoding adiponectin (67±12%; P=0.021), as well as adiponectin and CCAAT/enhancer-binding protein α protein levels. In conclusion, M22 is a pro-adipogenic factor in GO orbital preadipocytes. This antibody appears to act via the PI3K signaling cascade, suggesting that inhibition of PI3K signaling may represent a potential novel therapeutic approach in GO.

Restricted access

S Singh and PD Gupta

In the present study, the induction of the phosphoinositide signal transduction pathway by 17 beta-oestradiol has been demonstrated in rat vaginal epithelial cells (VEC). We have shown an increase in the metabolism of phosphoinositol lipids by 3H-myoinositol incorporation as well as production of inositol phosphate in VEC in vivo and in vitro following oestradiol administration. Concomitant changes in intracellular calcium levels have also been observed under the influence of oestradiol. To rule out the effects of cytokines, parallel studies were performed using primary cultures of VEC. Oestradiol-induced calcium uptake was seen even in the presence of actinomycin D and cycloheximide which inhibit transcription and translation respectively. Calcium uptake was blocked by neomycin, an inhibitor of phosphoinositol lipid metabolism, and by the oestrogen receptor antagonist tamoxifen. Results suggest that oestradiol induces second messenger pathways in the VEC through specific receptors. Implications of these observations in cellular differentiation processes are discussed.

Free access

Elisa Manieri and Guadalupe Sabio

Obesity is a new global pandemic, with growing incidence and prevalence. This disease is associated with increased risk of several pathologies, including diabetes, cardiovascular diseases, and cancer. The mechanisms underlying obesity-associated metabolic changes are the focus of efforts to identify new therapies. Stress-activated protein kinases (SAPK), including cJun N-terminal kinases (JNKs) and p38, are required for cellular responses to metabolic stress and therefore might contribute to the pathogenesis of obesity. Tissue-specific knockout models support a cell-type-specific role for JNK isoforms, in particular JNK1, highlighting its importance in cell homeostasis and organ crosstalk. However, more efforts are needed to elucidate the specific roles of other JNK isoforms and p38 family members in metabolism and obesity. This review provides an overview of the role of SAPKs in the regulation of metabolism.

Restricted access

Isabel Moscoso, María Cebro-Márquez, Moisés Rodríguez-Mañero, José Ramón González-Juanatey and Ricardo Lage

Irisin is a newly identified adipokine critical to modulate body metabolism, fatty acid metabolism and oxidative stress; recent evidence suggests a cardioprotective role in ischemic injury. Loss of cardiomyocytes during acute myocardial infarction is strongly associated with energetic changes and lipotoxic-induced apoptosis. Our aim was to study FNDC5/irisin’s potential protective role against hypoxia and lipotoxicity, both related with myocardial infarction environment. H9c2 cells were treated with palmitate and/or irisin in normoxic/hypoxic conditions. Cell viability and apoptosis were assessed by MTT assay and annexin V/PI staining. Immunoblotting was used to confirm apoptotic cascade regulation. Irisin counteracts lipotoxic-induced apoptosis in hypoxic cardiomyoblasts by activating Akt signaling pathway suggesting the potential therapeutic role of irisin in ischemic heart disease.

Free access

Salman Azhar, Dachuan Dong, Wen-Jun Shen, Zhigang Hu and Fredric B Kraemer

miRNAs are endogenous noncoding single-stranded small RNAs of ~22 nucleotides in length that post-transcriptionally repress the expression of their various target genes. They contribute to the regulation of a variety of physiologic processes including embryonic development, differentiation and proliferation, apoptosis, metabolism, hemostasis and inflammation. In addition, aberrant miRNA expression is implicated in the pathogenesis of numerous diseases including cancer, hepatitis, cardiovascular diseases and metabolic diseases. Steroid hormones regulate virtually every aspect of metabolism, and acute and chronic steroid hormone biosynthesis is primarily regulated by tissue-specific trophic hormones involving transcriptional and translational events. In addition, it is becoming increasingly clear that steroidogenic pathways are also subject to post-transcriptional and post-translational regulations including processes such as phosphorylation/dephosphorylation, protein‒protein interactions and regulation by specific miRNAs, although the latter is in its infancy state. Here, we summarize the recent advances in miRNA-mediated regulation of steroidogenesis with emphasis on adrenal and gonadal steroidogenesis.

Free access

Hyeon Young Park, Hye Suk Kang and Seung-Soon Im

Fatty acids are essential nutrients that contribute to several intracellular functions. Fatty acid synthesis and oxidation are known to be regulated by sterol regulatory element-binding proteins (SREBPs), which play a pivotal role in the regulation of cellular triglyceride synthesis and cholesterol biogenesis. Recent studies point to a multifunctional role of SREBPs in the pathogenesis of metabolic diseases, such as obesity, type II diabetes and cancer as well as in immune responses. Notably, fatty acid metabolic intermediates are involved in energy homeostasis and pathophysiological conditions. In particular, intracellular fatty acid metabolism affects an inflammatory response, thereby influencing metabolic diseases. The objective of this review is to summarize the recent advances in our understanding of the dual role of SREBPs in both lipid metabolism and inflammation-mediated metabolic diseases.

Free access

Russell A Prough, Barbara J Clark and Carolyn M Klinge

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA), secreted by the adrenal cortex, gastrointestinal tract, gonads, and brain, and its sulfated metabolite DHEA-S are the most abundant endogeneous circulating steroid hormones. DHEA actions are classically associated with age-related changes in cardiovascular tissues, female fertility, metabolism, and neuronal/CNS functions. Early work on DHEA action focused on the metabolism to more potent sex hormones, testosterone and estradiol, and the subsequent effect on the activation of the androgen and estrogen steroid receptors. However, it is now clear that DHEA and DHEA-S act directly as ligands for many hepatic nuclear receptors and G-protein-coupled receptors. In addition, it can function to mediate acute cell signaling pathways. This review summarizes the molecular mechanisms by which DHEA acts in cells and animal models with a focus on the ‘novel’ and physiological modes of DHEA action.

Free access

Charit Taneja, Sakshi Gera, Se-Min Kim, Jameel Iqbal, Tony Yuen and Mone Zaidi

FSH has a primary function in procreation, wherein it induces estrogen production in females and regulates spermatogenesis in males. However, in line with our discoveries over the past decade of non-unitary functions of pituitary hormones, we and others have described hitherto uncharacterized functions of FSH. Through high-affinity receptors, some of which are variants of the ovarian FSH receptor (FSHR), FSH regulates bone mass, adipose tissue function, energy metabolism, and cholesterol production in both sexes. These newly described actions of FSH may indeed be relevant to the pathogenesis of bone loss, dysregulated energy homeostasis, and disordered lipid metabolism that accompany the menopause in females and aging in both genders. We are therefore excited about the possibility of modulating circulating FSH levels toward a therapeutic benefit for a host of age-associated diseases, including osteoporosis, obesity and dyslipidemia, among other future possibilities.