Hormonal regulation of acetyl-CoA carboxylase isoenzyme gene transcription

Glucocorticoid resistance remodels liver lipids and prompts lipogenesis, eicosanoid, and inflammatory pathways

We have previously demonstrated that the glucocorticoid receptor β (GRβ) isoform induces hepatic steatosis in mice fed a normal chow diet. The GRβ isoform inhibits the glucocorticoid-binding isoform GRα, reducing responsiveness and inducing glucocorticoid resistance. We hypothesized that GRβ regulates lipids that cause metabolic dysfunction. To determine the effect of GRβ on hepatic lipid classes and molecular species, we overexpressed GRβ (GRβ-Ad) and vector (Vec-Ad) using adenovirus delivery, as we previously described. We fed the mice a normal chow diet for 5 days and harvested the livers. We utilized liquid chromatography-mass spectrometry (LC-MS) analyses of the livers to determine the lipid species driven by GRβ. The most significant changes in the lipidome were monoacylglycerides and cholesterol esters. There was also increased gene expression in the GRβ-Ad mice for lipogenesis, eicosanoid synthesis, and inflammatory pathways. These indicate that GRβ-induced glucocorticoid resistance may drive hepatic fat accumulation, providing new therapeutic advantages.

Adipose tissue in cortisol excess: What Cushing's syndrome can teach us?

Endogenous Cushing's syndrome (CS) is a rare condition due to prolonged exposure to elevated circulating cortisol levels that features its typical phenotype characterised by moon face, proximal myopathy, easy bruising, hirsutism in females and a centripetal distribution of body fat. Given the direct and indirect effects of hypercortisolism, CS is a severe disease burdened by increased cardio-metabolic morbidity and mortality in which visceral adiposity plays a leading role. Although not commonly found in clinical setting, endogenous CS is definitely underestimated leading to delayed diagnosis with consequent increased rate of complications and reduced likelihood of their reversal after disease control. Most of all, CS is a unique model for systemic impairment induced by exogenous glucocorticoid therapy that is commonly prescribed for a number of chronic conditions in a relevant proportion of the worldwide population. In this review we aim to summarise on one side, the mechanisms behind visceral adiposity and lipid metabolism impairment in CS during active disease and after remission and on the other explore the potential role of cortisol in promoting adipose tissue accumulation.

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

Dexamethasone-Induced Adipose Tissue Redistribution and Metabolic Changes: Is Gene Expression the Main Factor? An Animal Model of Chronic Hypercortisolism

Chronic hypercortisolism has been associated with the development of several metabolic alterations, mostly caused by the effects of chronic glucocorticoid (GC) exposure over gene expression. The metabolic changes can be partially explained by the GC actions on different adipose tissues (ATs), leading to central obesity. In this regard, we aimed to characterize an experimental model of iatrogenic hypercortisolism in rats with significant AT redistribution. Male Wistar rats were distributed into control (CT) and GC-treated, which received dexamethasone sodium phosphate (0.5 mg/kg/day) by an osmotic minipump, for 4 weeks. GC-treated rats reproduced several characteristics observed in human hypercortisolism/Cushing’s syndrome, such as HPA axis inhibition, glucose intolerance, insulin resistance, dyslipidemia, hepatic lipid accumulation, and AT redistribution. There was an increase in the mesenteric (meWAT), perirenal (prWAT), and interscapular brown (BAT) ATs mass, but a reduction of the retroperitoneal (rpWAT) mass compared to CT rats. Overexpressed lipolytic and lipogenic gene profiles were observed in white adipose tissue (WAT) of GC rats as BAT dysfunction and whitening. The AT remodeling in response to GC excess showed more importance than the increase of AT mass per se, and it cannot be explained just by GC regulation of gene transcription.

Glucose and lipid metabolism abnormalities in Cushing's syndrome

Prolonged excess of glucocorticoids (GCs) has adverse systemic effects leading to significant morbidities and an increase in mortality. Metabolic alterations associated with the high level of the GCs are key risk factors for the poor outcome. These include GCs causing excess gluconeogenesis via upregulation of key enzymes in the liver, a reduction of insulin sensitivity in skeletal muscle, liver and adipose tissue by inhibiting the insulin receptor signalling pathway, and inhibition of insulin secretion in beta cells leading to dysregulated glucose metabolism. In addition, chronic GC exposure leads to an increase in visceral adipose tissue, as well as an increase in lipolysis resulting in higher circulating free fatty acid levels and in ectopic fat deposition. Remission of hypercortisolism improves these metabolic changes, but very often does not result in full resolution of the abnormalities. Therefore, long-term monitoring of metabolic variables is needed even after the resolution of the excess GC levels.

Adaptive immune cells shape obesity-associated type 2 diabetes mellitus and less prominent comorbidities

Obesity and type 2 diabetes mellitus (T2DM) are increasing in prevalence owing to decreases in physical activity levels and a shift to diets that include addictive and/or high-calorie foods. These changes are associated with the adoption of modern lifestyles and the presence of an obesogenic environment, which have resulted in alterations to metabolism, adaptive immunity and endocrine regulation. The size and quality of adipose tissue depots in obesity, including the adipose tissue immune compartment, are critical determinants of overall health. In obesity, chronic low-grade inflammation can occur in adipose tissue that can progress to systemic inflammation; this inflammation contributes to the development of insulin resistance, T2DM and other comorbidities. An improved understanding of adaptive immune cell dysregulation that occurs during obesity and its associated metabolic comorbidities, with an appreciation of sex differences, will be critical for repurposing or developing immunomodulatory therapies to treat obesity and/or T2DM-associated inflammation. This Review critically discusses how activation and metabolic reprogramming of lymphocytes, that is, T cells and B cells, triggers the onset, development and progression of obesity and T2DM. We also consider the role of immunity in under-appreciated comorbidities of obesity and/or T2DM, such as oral cavity inflammation, neuroinflammation in Alzheimer disease and gut microbiome dysbiosis. Finally, we discuss previous clinical trials of anti-inflammatory medications in T2DM and consider the path forward.

Glucocorticoid-Induced Fatty Liver Disease

Glucocorticoids (GCs) are commonly used at high doses and for prolonged periods (weeks to months) in the treatment of a variety of diseases. Among the many side effects are increased insulin resistance with disturbances in glucose/insulin homeostasis and increased deposition of lipids (mostly triglycerides) in the liver. Here, we review the metabolic pathways of lipid deposition and removal from the liver that become altered by excess glucocorticoids. Pathways of lipid deposition stimulated by excess glucocorticoids include 1) increase in appetite and high caloric intake; 2) increased blood glucose levels due to GC-induced stimulation of gluconeogenesis; 3) stimulation of de novo lipogenesis that is augmented by the high glucose and insulin levels and by GC itself; and 4) increased release of free fatty acids from adipose stores and stimulation of their uptake by the liver. Pathways that decrease hepatic lipids affected by glucocorticoids include a modest stimulation of very-low-density lipoprotein synthesis and secretion into the circulation and inhibition of β-oxidation of fatty acids. Role of 11β-hydroxysteroid dehydrogenases-1 and -2 and the reversible conversion of cortisol to cortisone on intracellular levels of cortisol is examined. In addition, GC control of osteocalcin expression and the effect of this bone-derived hormone in increasing insulin sensitivity are discussed. Finally, research focused on gaining a better understanding of the dose and duration of treatment with glucocorticoids, which leads to increased triglyceride deposition in the liver, and the reversibility of the condition is highlighted.

When fats commit crimes: fatty acid metabolism, cancer stemness and therapeutic resistance

The role of fatty acid metabolism, including both anabolic and catabolic reactions in cancer has gained increasing attention in recent years. Many studies have shown that aberrant expression of the genes involved in fatty acid synthesis or fatty acid oxidation correlate with malignant phenotypes including metastasis, therapeutic resistance and relapse. Such phenotypes are also strongly associated with the presence of a small percentage of unique cells among the total tumor cell population. This distinct group of cells may have the ability to self-renew and propagate or may be able to develop resistance to cancer therapies independent of genetic alterations. Therefore, these cells are referred to as cancer stem cells/tumor-initiating cells/drug-tolerant persisters, which are often refractory to cancer treatment and difficult to target. Moreover, interconversion between cancer cells and cancer stem cells/tumor-initiating cells/drug-tolerant persisters may occur and makes treatment even more challenging. This review highlights recent findings on the relationship between fatty acid metabolism, cancer stemness and therapeutic resistance and prompts discussion about the potential mechanisms by which fatty acid metabolism regulates the fate of cancer cells and therapeutic resistance.

Histone deacetylase inhibition attenuates hepatic steatosis in rats with experimental Cushing's syndrome

Cushing's syndrome (CS) is a collection of symptoms caused by prolonged exposure to excess cortisol. Chronically elevated glucocorticoid (GC) levels contribute to hepatic steatosis. We hypothesized that histone deacetylase inhibitors (HDACi) could attenuate hepatic steatosis through glucocorticoid receptor (GR) acetylation in experimental CS. To induce CS, we administered adrenocorticotropic hormone (ACTH; 40 ng/kg/day) to Sprague-Dawley rats by subcutaneous infusion with osmotic mini-pumps. We administered the HDACi, sodium valproate (VPA; 0.71% w/v), in the drinking water. Treatment with the HDACi decreased steatosis and the expression of lipogenic genes in the livers of CS rats. The enrichment of GR at the promoters of the lipogenic genes, such as acetyl-CoA carboxylase (Acc), fatty acid synthase (Fasn), and sterol regulatory element binding protein 1c (Srebp1c), was markedly decreased by VPA. Pan-HDACi and an HDAC class I-specific inhibitor, but not an HDAC class II a-specific inhibitor, attenuated dexamethasone (DEX)-induced lipogenesis in HepG2 cells. The transcriptional activity of Fasn was decreased by pretreatment with VPA. In addition, pretreatment with VPA decreased DEX-induced binding of GR to the glucocorticoid response element (GRE). Treatment with VPA increased the acetylation of GR in ACTH-infused rats and DEX-induced HepG2 cells. Taken together, these results indicate that HDAC inhibition attenuates hepatic steatosis hrough GR acetylation in experimental CS.

Choline Supplementation Normalizes Fetal Adiposity and Reduces Lipogenic Gene Expression in a Mouse Model of Maternal Obesity

Maternal obesity increases fetal adiposity which may adversely affect metabolic health of the offspring. Choline regulates lipid metabolism and thus may influence adiposity. This study investigates the effect of maternal choline supplementation on fetal adiposity in a mouse model of maternal obesity. C57BL/6J mice were fed either a high-fat (HF) diet or a control (NF) diet and received either 25 mM choline supplemented (CS) or control untreated (CO) drinking water for 6 weeks before timed-mating and throughout gestation. At embryonic day 17.5, HF feeding led to higher (p < 0.05) percent total body fat in fetuses from the HFCO group, while the choline supplemented HFCS group did not show significant difference versus the NFCO group. Similarly, HF feeding led to higher (p < 0.05) hepatic triglyceride accumulation in the HFCO but not the HFCS fetuses. mRNA levels of lipogenic genes such as Acc1, Fads1, and Elovl5, as well as the transcription factor Srebp1c that favors lipogenesis were downregulated (p < 0.05) by maternal choline supplementation in the HFCS group, which may serve as a mechanism to reduce fat accumulation in the fetal liver during maternal HF feeding. In summary, maternal choline supplementation improves indices of fetal adiposity in obese dams at late gestation.

Obesity and the dysregulation of fatty acid metabolism: implications for healthy aging

The population of the world is aging. In 2010, an estimated 524 million people were aged 65 years or older representing eight percent of the global population. By 2050, this number is expected to nearly triple to approximately 1.5 billion, 16 percent of the world's population. Although people are living longer, the quality of their lives are often compromised due to ill-health. Areas covered: Of the conditions which compromise health as we age, obesity is at the forefront. Over half of the global older population were overweight or obese in 2010, significantly increasing the risk of a range of metabolic diseases. Although, it is well recognised excessive calorie intake is a fundamental driver of adipose tissue dysfunction, the relationship between obesity; intrinsic aging; and fat metabolism is less understood. In this review we discuss the intersection between obesity, aging and the factors which contribute to the dysregulation of whole-body fat metabolism. Expert commentary: Being obese disrupts an array of physiological systems and there is significant crosstalk among these. Moreover it is imperative to acknowledge the contribution intrinsic aging makes to the dysregulation of these systems and the onset of disease.

Effective treatment with combination of peripheral 5-hydroxytryptamine synthetic inhibitor and 5-hydroxytryptamine 2 receptor antagonist on glucocorticoid-induced whole-body insulin resistance with hyperglycemia

AIMS/INTRODUCTION

Our previous study found that dexamethasone-induced insulin resistance (IR) was involved in 5-hydroxytryptamine (5-HT) synthesis and 5-hydroxytryptamine 2 receptor (5-HT₂ R) in the periphery. The present study examined the effects of inhibitions of both peripheral 5-HT synthesis and 5-HT₂ R on dexamethasone-induced IR.

MATERIALS AND METHODS

Male rats were exposed to dexamethasone for 10 days, then treated with or without a 5-HT₂ R antagonist, sarpogrelate, a 5-HT synthetic inhibitor, carbidopa, alone or in combination for 20 days.

RESULTS

Dexamethasone-induced whole-body IR, with glucose intolerance, decreased insulin sensitivity, hyperglycemia, hyperinsulinemia and dyslipidemia, could be effectively abolished by sarpogrelate or/and carbidopa, whereas IR-related actions of dexamethasone in tissues were accompanied by increased 5-HT synthesis in the liver and visceral adipose, and upregulated 5-HT₂ R (5-HT_2A R and 5-HT_2B R) expression in these two tissues as well as in skeletal muscle. Sarpogrelate or/and carbidopa treatment significantly abolished dexamethasone-caused tissue-specific IR. In the liver, increased gluconeogenesis, triglycerides and very low-density lipoprotein syntheses with steatosis, and downregulated expression of plasmalemmal glucose transporter-2 were markedly reversed. In the visceral adipose and skeletal muscle, downregulated expression of plasmalemmal glucose transporter-4 was significantly reversed, and increased lipolysis was also reversed in the visceral adipose. Dexamethasone-induced activations of hepatic mammalian target of rapamycin serine²⁴⁴⁸ , and S6K threonine^389/412 phosphorylation were also abolished markedly by sarpogrelate or/and carbidopa. Co-treatment with sarpogrelate and carbidopa showed a synergistic effect on suppressing dexamethasone actions.

CONCLUSION

Inhibitions of both peripheral 5-HT synthesis and 5-HT₂ R are expected to be a dependable target for treatment of steroid-induced diabetes.

Discovery and Structural Characterization of G-quadruplex DNA in Human Acetyl-CoA Carboxylase Gene Promoters: Its Role in Transcriptional Regulation and as a Therapeutic Target for Human Disease

Accumulating evidence suggests that G-quadruplexes play vital roles in gene expression, DNA replication, and recombination. Three distinct promoters (PI, PII, and PIII) regulate human acetyl-CoA carboxylase 1 (ACC1) gene expression. In this study, we asked whether the G-rich sequences within the human ACC1 (PI and PII) promoters can form G-quadruplex structures and regulate normal DNA transactions. Using multiple complementary methods, we show that G-rich sequences of PI and PII promoters form intramolecular G-quadruplex structures and then establish unambiguously the topologies of these structures. Importantly, G-quadruplex formation in ACC1 gene promoter region blocks DNA replication and suppresses transcription, and this effect was further augmented by G-quadruplex stabilizing ligands. Altogether, these results are consistent with the notion that G-quadruplex structures exist within the human ACC1 gene promoter region, whose activity can be suppressed by G-quadruplex stabilizing ligands, thereby revealing a novel regulatory mechanism of ACC1 gene expression and as a possible therapeutic target.

Long-term Stress with Hyperglucocorticoidemia-induced Hepatic Steatosis with VLDL Overproduction Is Dependent on both 5-HT2 Receptor and 5-HT Synthesis in Liver

Hepatic triglycerides production and adipose lipolysis are pivotal for long-term stress (LTS) or hyperglucocorticoidemia-induced insulin resistance. 5-hydroxytryptamine (5-HT) has been demonstrated to induce hepatic lipid metabolic abnormality by activating mammalian target of rapamycin (mTOR). In present study, we explored whether 5-HT is involved in LTS effects in liver using restraint stress-exposed rats and cultured primary rat hepatocytes and HepG2 cells. LTS with hyperglucocorticoidemia induced hepatic 5-HT synthetic increase with tryptophan hydroxylase 1 (Tph1) up-regulation, and 5-HT2 receptor (5-HT₂R, including 5-HT2A, 2B receptor) up-regulation in liver and visceral adipose, as well as hepatic mTOR activation with triglycerides and VLDL overproduction with steatosis, and visceral adipose lipolytic increase with high blood free fatty acids (FFAs) level. 5-HT exposure exhibited LTS-like effects in both tissues, and both LTS and 5-HT effects could be abolished significantly by blocking 5-HT₂R. In HepG2 cells dexamethasone or palmitate-induced mTOR activation with triglycerides and VLDL overproduction were accompanied by up-regulations of 5-HT synthesis and 5-HT₂R, which were significantly abolished by gene silencing Tph1 or 5-HT₂R and were almost fully abolished by co-silencing of both, especially on VLDL overproduction. Chemical inhibition of Tph1 or/and 5-HT₂R in both hepatocytes exhibited similar abolishment with genetic inhibition on dexamethason-induced effects. 5-HT-stimulated effects in both hepatocytes were fully abolished by blocking 5-HT₂R, while 5-HT itself also up-regulated 5-HT₂R. In conclusion, up-regulated hepatic 5-HT synthesis and 5-HT₂R induced by both glucocorticoid and FFAs are crucial for LTS-induced hepatic steatosis with VLDL overproduction, while 5-HT by acting on 5-HT₂R mediates mTOR activation in liver.

The expression of genes involved in jejunal lipogenesis and lipoprotein synthesis is altered in morbidly obese subjects with insulin resistance

The dyslipidemia associated with type 2 diabetes mellitus (T2DM) is an important risk factor for atherosclerotic cardiovascular disease. However, until now little attention has been paid to the role that the intestine might have. The aim of this research was to determine the relation between insulin resistance and intestinal de novo lipogenesis/lipoprotein synthesis in morbidly obese subjects and to study the effect of insulin on these processes. Jejunal mRNA expression of the different genes involved in the intestinal de novo lipogenesis/lipoprotein synthesis was analyzed in three groups of morbidly obese subjects: Group 1 with low insulin resistance (MO-low-IR), group 2 with high insulin resistance (MO-high-IR), and group 3 with T2DM and treatment with metformin (MO-metf-T2DM). In addition, intestinal epithelial cells (IECs) from MO-low-IR were incubated with different doses of insulin/glucose. In Group 2 (MO-high-IR), the jejunal mRNA expression levels of apo A-IV, ATP-citrate lyase (ACLY), pyruvate dehydrogenase (lipoamide) beta (PDHB), and sterol regulatory element-binding protein-1c (SREBP-1c) were significantly higher and acetyl-CoA carboxylase alpha (ACC1) and fatty-acid synthase lower than in Group 1 (MO-low-IR). In Group 3 (MO-metf-T2DM), only the ACLY and PDHB mRNA expressions were significantly higher than in Group 1 (MO-low-IR). The mRNA expression of most of the genes studied was significantly linked to insulin and glucose levels. The incubation of IEC with different doses of insulin and glucose produced a higher expression of diacylglycerol acyltransferase 2, microsomal triglyceride transfer protein, apo A-IV, SREBP-1c, and ACC1 when both, glucose and insulin, were at a high concentration. However, with only high insulin levels, there were higher apo A-IV, PDHB and SREBP-1c expressions, and a lower ACLY expression. In conclusion, the jejunum of MO-high-IR has a decreased mRNA expression of genes involved in de novo fatty-acid synthesis and an increase of genes involved in acetyl-CoA and lipoprotein synthesis. This effect is attenuated by metformin. In addition, the expression of most of the genes studied was found to be regulated by insulin.

Hypoxia is associated with a lower expression of genes involved in lipogenesis in visceral adipose tissue

Background

A key role for HIF-1α in the promotion and maintenance of dietary obesity has been proposed. We analyzed the association between hypoxia and de novo lipogenesis in human adipose tissue.

Methods

We studied HIF-1α mRNA and protein expression in fasting status in visceral adipose tissue (VAT) from non-obese and morbidly obese subjects, and in VAT from wild-type and ob/ob C57BL6J mice in both fasting and feeding status. We also analyzed the effect of hypoxia on the VAT mRNA expression of genes involved in lipogenesis.

Results

HIF-1α was increased in VAT from morbidly obese subjects. In fasting status, C57BL6J ob/ob mice had a higher VAT HIF-1α mRNA expression than C57BL6J wild-type mice. In feeding status, VAT HIF-1α mRNA expression significantly increased in C57BL6J wild-type, but not in C57BL6J ob/ob mice. In humans, HIF-1α mRNA expression correlated positively with body mass index and insulin resistance. VAT HIF-1α mRNA expression correlated negatively with ACC1, PDHB and SIRT3 mRNA expression, and positively with PPAR-γ. VAT explants incubated in hypoxia showed reduced SIRT3 and increased PPAR-γ, SREBP-1c, ACLY, ACC1 and FASN mRNA expression.

Conclusions

Morbidly obese subjects have a higher level of VAT HIF-1α. Postprandial status is associated with an increase in HIF-1α mRNA expression in C57BL6J wild-type mice. Hypoxia alters the mRNA expression of genes involved in de novo lipogenesis in human VAT.

Selective inhibition of liver X receptor α-mediated lipogenesis in primary hepatocytes by licochalcone A

Background

Sterol regulatory element binding protein-1c (SREBP-1c) is a regulator of the lipogenic pathway and is transcriptionally activated by liver X receptor α (LXRα). This study aims to investigate phytochemicals inhibiting the autonomous transactivity of LXRα with potentials as SREBP-1c inhibitors. Licochalcone A (LicA) is a flavonoid isolated from licorice root of Glycyrrhiza plant.

Methods

The effects of 238 natural chemicals on autonomous transactivity of LXRα were determined by the Gal4-TK-luciferase reporter system. The inclusion criteria for chemical selection was significant (P < 0.05) inhibition of autonomous transactivity of LXRα from three independent experiments. Transcript levels of mouse primary hepatocytes were measured by conventional or quantitative RT-PCR. Luciferase assay was used to assess synthetic or natural promoter activities of LXRα target genes. The effect of LicA on lipogenic activity was evaluated by measuring cellular triglycerides in mouse primary hepatocytes. The recruitment of RNA polymerase II to the LXR response element (LXRE) region was examined by chromatin immunoprecipitation.

Results

Among 238 natural compounds, LicA considerably inhibited the autonomous transactivity of LXRα and decreased the LXRα-dependent expression of SREBP-1c. LicA inhibited not only LXRα-dependent activation of the synthetic LXRE promoter but also that of the natural SREBP-1c promoter. As a consequence, LicA reduced the LXRα agonist-stimulated transcription of several lipogenic genes. Furthermore, LXRα-dependent hepatic lipid accumulation was repressed by LicA in mouse primary hepatocytes. Interestingly, the LXRα-dependent activation of ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1), other LXR target genes involved in reverse cholesterol transport (RCT), was not inhibited by LicA. LicA hindered the recruitment of RNA polymerase II to the LXRE of the SREBP-1c gene, but not of the ABCA1 gene.

Conclusions

LicA is a selective inhibitor of LXRα, repressing lipogenic LXRα target genes but not RCT-related LXRα target genes.

Mechanisms of glucocorticoid-induced insulin resistance: focus on adipose tissue function and lipid metabolism

Glucocorticoids (GCs) are critical in the regulation of the stress response, inflammation and energy homeostasis. Excessive GC exposure results in whole-body insulin resistance, obesity, cardiovascular disease, and ultimately decreased survival, despite their potent anti-inflammatory effects. This apparent paradox may be explained by the complex actions of GCs on adipose tissue functionality. The wide prevalence of oral GC therapy makes their adverse systemic effects an important yet incompletely understood clinical problem. This article reviews the mechanisms by which supraphysiologic GC exposure promotes insulin resistance, focusing in particular on the effects on adipose tissue function and lipid metabolism.

Combination of lipid metabolism alterations and their sensitivity to inflammatory cytokines in human lipin-1-deficient myoblasts

Lipin-1 deficiency is associated with massive rhabdomyolysis episodes in humans, precipitated by febrile illnesses. Despite well-known roles of lipin-1 in lipid biosynthesis and transcriptional regulation, the pathogenic mechanisms leading to rhabdomyolysis remain unknown. Here we show that primary myoblasts from lipin-1-deficient patients exhibit a dramatic decrease in LPIN1 expression and phosphatidic acid phosphatase 1 activity, and a significant accumulation of lipid droplets (LD). The expression levels of LPIN1-target genes [peroxisome proliferator-activated receptors delta and alpha (PPARδ, PPARα), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), acyl-coenzyme A dehydrogenase, very long (ACADVL), carnitine palmitoyltransferase IB and 2 (CPT1B and CPT2)] were not affected while lipin-2 protein level, a closely related member of the family, was increased. Microarray analysis of patients' myotubes identified 19 down-regulated and 51 up-regulated genes, indicating pleiotropic effects of lipin-1 deficiency. Special attention was paid to the up-regulated ACACB (acetyl-CoA carboxylase beta), a key enzyme in the fatty acid synthesis/oxidation balance. We demonstrated that overexpression of ACACB was associated with free fatty acid accumulation in patients' myoblasts whereas malonyl-carnitine (as a measure of malonyl-CoA) and CPT1 activity were in the normal range in basal conditions accordingly to the normal daily activity reported by the patients. Remarkably ACACB invalidation in patients' myoblasts decreased LD number and size while LPIN1 invalidation in controls induced LD accumulation. Further, pro-inflammatory treatments tumor necrosis factor alpha+Interleukin-1beta(TNF1α+IL-1ß) designed to mimic febrile illness, resulted in increased malonyl-carnitine levels, reduced CPT1 activity and enhanced LD accumulation, a phenomenon reversed by dexamethasone and TNFα or IL-1ß inhibitors. Our data suggest that the pathogenic mechanism of rhabdomyolysis in lipin-1-deficient patients combines the predisposing constitutive impairment of lipid metabolism and its exacerbation by pro-inflammatory cytokines.

11β-Hydroxysteroid dehydrogenase 1: translational and therapeutic aspects

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) interconverts the inactive glucocorticoid cortisone and its active form cortisol. It is widely expressed and, although bidirectional, in vivo it functions predominantly as an oxoreductase, generating active glucocorticoid. This allows glucocorticoid receptor activation to be regulated at a prereceptor level in a tissue-specific manner. In this review, we will discuss the enzymology and molecular biology of 11β-HSD1 and the molecular basis of cortisone reductase deficiencies. We will also address how altered 11β-HSD1 activity has been implicated in a number of disease states, and we will explore its role in the physiology and pathologies of different tissues. Finally, we will address the current status of selective 11β-HSD1 inhibitors that are in development and being tested in phase II trials for patients with the metabolic syndrome. Although the data are preliminary, therapeutic inhibition of 11β-HSD1 is also an exciting prospect for the treatment of a variety of other disorders such as osteoporosis, glaucoma, intracranial hypertension, and cognitive decline.

Prediabetic changes in gene expression induced by aspartame and monosodium glutamate in Trans fat-fed C57Bl/6 J mice

BACKGROUND

The human diet has altered markedly during the past four decades, with the introduction of Trans hydrogenated fat, which extended the shelf-life of dietary oils and promoted a dramatic increase in elaidic acid (Trans-18.1) consumption. Food additives such as monosodium glutamate (MSG) and aspartame (ASP) were introduced to increase food palatability and reduce caloric intake. Nutrigenomics studies in small-animal models are an established platform for analyzing the interactions between various macro- and micronutrients. We therefore investigated the effects of changes in hepatic and adipose tissue gene expression induced by the food additives ASP, MSG or a combination of both additives in C57Bl/6 J mice fed a Trans fat-enriched diet.

METHODS

Hepatic and adipose tissue gene expression profiles, together with body characteristics, glucose parameters, serum hormone and lipid profiles were examined in C57Bl/6 J mice consuming one of the following four dietary regimens, commencing in utero via the mother's diet: [A] Trans fat (TFA) diet; [B] MSG + TFA diet; [C] ASP + TFA diet; [D] ASP + MSG + TFA diet.

RESULTS

Whilst dietary MSG significantly increased hepatic triglyceride and serum leptin levels in TFA-fed mice, the combination of ASP + MSG promoted the highest increase in visceral adipose tissue deposition, serum free fatty acids, fasting blood glucose, HOMA-IR, total cholesterol and TNFα levels. Microarray analysis of significant differentially expressed genes (DEGs) showed a reduction in hepatic and adipose tissue PPARGC1a expression concomitant with changes in PPARGC1a-related functional networks including PPARα, δ and γ. We identified 73 DEGs common to both adipose and liver which were upregulated by ASP + MSG in Trans fat-fed mice; and an additional 51 common DEGs which were downregulated.

CONCLUSION

The combination of ASP and MSG may significantly alter adiposity, glucose homeostasis, hepatic and adipose tissue gene expression in TFA-fed C57Bl/6 J mice.

A low-protein, high-carbohydrate diet increases de novo fatty acid synthesis from glycerol and glycerokinase content in the liver of growing rats

We had previously shown that adipose tissue increased in rats fed a low-protein, high-carbohydrate (LPHC) diet (6% protein, 74% carbohydrate) without a simultaneous increase in the de novo fatty acids (FA) synthesis. In addition, impairment in insulin signaling in adipose tissues was observed in these rats. For this study, we hypothesized that the insulin signaling pathway is preserved in the livers from these rats, which contributes to an increase in liver lipogenesis and, consequently, an increase in the weight of the adipose tissue. We also hypothesized that glycerol from triacylglycerol is an important substrate for FA synthesis. Our results showed that administration of the LPHC diet induced an increase in the in vivo rate of total FA synthesis (150%) as well as FA synthesis from glucose (270%) in the liver. There were also increased rates of [U-¹⁴C]glycerol incorporation into glyceride-FA (15-fold), accompanied by increased glycerokinase content (30%) compared with livers of rats fed the control diet. The LPHC diet did not change the glycerol-3-phosphate generation from either glucose or glyceroneogenesis. There was an increase in the insulin sensitivity in liver from LPHC-fed rats, as evidenced by increases in IR(β) (35%) levels and serine/threonine protein kinase (AKT) levels (75%), and basal (95%) and insulin-stimulated AKT phosphorylation (105%) levels. The LPHC diet also induced an increase in the liver sterol regulatory element-binding protein-1c content (50%). In summary, these data confirmed the hypothesis that lipogenesis and insulin signaling are increased in the livers of LPHC-fed rats and that glycerol is important not only for FA esterification but also for FA synthesis.

High-fat diet-induced hyperinsulinemia and tissue-specific insulin resistance in Cry-deficient mice

Perturbation of circadian rhythmicity in mammals, either by environmental influences such as shiftwork or by genetic manipulation, has been associated with metabolic disturbance and the development of obesity and diabetes. Circadian clocks are based on transcriptional/translational feedback loops, comprising positive and negative components. Whereas the metabolic effects of deletion of the positive arm of the clock gene machinery, as in Clock- or Bmal1-deficient mice, have been well characterized, inactivation of Period genes (Per1-3) as components of the negative arm have more complex, sometimes contradictory effects on energy homeostasis. The CRYPTOCHROMEs are critical interaction partners of PERs, and simultaneous deletion of Cry1 and -2 results in behavioral and molecular circadian arrhythmicity. We show that, when challenged with a high-fat diet, Cry1/2(-/-) mice rapidly gain weight and surpass that of wild-type mice, despite displaying hypophagia. Transcript analysis of white adipose tissue reveals upregulated expression of lipogenic genes, many of which are insulin targets. High-fat diet-induced hyperinsulinemia, as a result of potentiated insulin secretion, coupled with selective insulin sensitivity in adipose tissue of Cry1/2(-/-) mice, correlates with increased lipid uptake. Collectively, these data indicate that Cry deficiency results in an increased vulnerability to high-fat diet-induced obesity that might be mediated by increased insulin secretion and lipid storage in adipose tissues.

Chemical genetics of acetyl-CoA carboxylases

Chemical genetic studies on acetyl-CoA carboxylases (ACCs), rate-limiting enzymes in long chain fatty acid biosynthesis, have greatly advanced the understanding of their biochemistry and molecular biology and promoted the use of ACCs as targets for herbicides in agriculture and for development of drugs for diabetes, obesity and cancers. In mammals, ACCs have both biotin carboxylase (BC) and carboxyltransferase (CT) activity, catalyzing carboxylation of acetyl-CoA to malonyl-CoA. Several classes of small chemicals modulate ACC activity, including cellular metabolites, natural compounds, and chemically synthesized products. This article reviews chemical genetic studies of ACCs and the use of ACCs for targeted therapy of cancers.

The endocrine disrupting chemical tolylfluanid alters adipocyte metabolism via glucocorticoid receptor activation

Glucocorticoid signaling plays a critical role in regulating energy metabolism. Emerging data implicate environmental endocrine-disrupting chemicals as contributors to the obesity and diabetes epidemics. Previous studies have shown that the phenylsulfamide fungicide tolylfluanid (TF) augments glucocorticoid receptor (GR)-dependent luciferase expression in 3T3-L1 preadipocytes while modulating insulin action in primary murine and human adipocytes. Studies were performed to interrogate glucocorticoid signaling in primary adipocytes exposed to TF. TF mimicked the gene transcription profile of the murine glucocorticoid corticosterone (Cort). Cellular fractionation assays demonstrated that TF treatment promoted the activating serine phosphorylation of GR, augmenting its cytoplasmic-to-nuclear translocation as well as its enrichment at glucocorticoid response elements on the glucocorticoid-induced leucine zipper gene promoter. After acute treatment, Cort or TF promoted insulin receptor substrate-1 (IRS-1) gene and protein expression. Either treatment also enriched GR binding at an identified glucocorticoid response element in the IRS-1 gene. TF or Cort each increased insulin-stimulated lipogenesis, an effect resulting from increased lipogenic gene expression and enhanced insulin-stimulated dephosphorylation of acetyl-coenzyme A carboxylase. The augmentation of insulin-stimulated lipogenesis was mediated through a specific enhancement of Akt phosphorylation at T308. These findings support modulation of IRS-1 levels as a mechanism for glucocorticoid-mediated changes in insulin action in primary adipocytes. Albeit with less affinity than Cort, in silico analysis suggests that TF can interact with the ligand binding pocket of GR. Collectively, these studies identify TF as a structurally unique environmental glucocorticoid. Glucocorticoid signaling may thus represent a novel pathway by which environmental toxicants promote the development of metabolic diseases.

Disruption of the selenocysteine lyase-mediated selenium recycling pathway leads to metabolic syndrome in mice

Selenium (Se) is an essential trace element used for biosynthesis of selenoproteins and is acquired either through diet or cellular recycling mechanisms. Selenocysteine lyase (Scly) is the enzyme that supplies Se for selenoprotein biosynthesis via decomposition of the amino acid selenocysteine (Sec). Knockout (KO) of Scly in a mouse affected hepatic glucose and lipid homeostasis. Mice lacking Scly and raised on an Se-adequate diet exhibit hyperinsulinemia, hyperleptinemia, glucose intolerance, and hepatic steatosis, with increased hepatic oxidative stress, but maintain selenoprotein levels and circulating Se status. Insulin challenge of Scly KO mice results in attenuated Akt phosphorylation but does not decrease phosphorylation levels of AMP kinase alpha (AMPKα). Upon dietary Se restriction, Scly KO animals develop several characteristics of metabolic syndrome, such as obesity, fatty liver, and hypercholesterolemia, with aggravated hyperleptinemia, hyperinsulinemia, and glucose intolerance. Hepatic glutathione peroxidase 1 (GPx1) and selenoprotein S (SelS) production and circulating selenoprotein P (Sepp1) levels are significantly diminished. Scly disruption increases the levels of insulin-signaling inhibitor PTP1B. Our results suggest a dependence of glucose and lipid homeostasis on Scly activity. These findings connect Se and energy metabolism and demonstrate for the first time a unique physiological role of Scly in an animal model.

Regulation of triglyceride metabolism by glucocorticoid receptor

Glucocorticoids are steroid hormones that play critical and complex roles in the regulation of triglyceride (TG) homeostasis. Depending on physiological states, glucocorticoids can modulate both TG synthesis and hydrolysis. More intriguingly, glucocorticoids can concurrently affect these two processes in adipocytes. The metabolic effects of glucocorticoids are conferred by intracellular glucocorticoid receptors (GR). GR is a transcription factor that, upon binding to glucocorticoids, regulates the transcriptional rate of specific genes. These GR primary target genes further initiate the physiological and pathological responses of glucocorticoids. In this article, we overview glucocorticoid-regulated genes, especially those potential GR primary target genes, involved in glucocorticoid-regulated TG metabolism. We also discuss transcriptional regulators that could act with GR to participate in these processes. This knowledge is not only important for the fundamental understanding of steroid hormone actions, but also are essential for future therapeutic interventions against metabolic diseases associated with aberrant glucocorticoid signaling, such as insulin resistance, dyslipidemia, central obesity and hepatic steatosis.

Liver X receptor α is involved in the transcriptional regulation of the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene

The activity of 6-phosphofructo-1-kinase is strictly controlled by fructose-2,6-bisphosphate, the level of which is regulated by another enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK2/FBP2). PFK2/FBP2 is a bifunctional enzyme, having kinase and phosphatase activities, and regulates both glycolysis and gluconeogenesis. Here, we examined the hormonal regulation of the PFK2/FBP2 gene in vitro using the reporter assay, the electromobility shift assay (EMSA), and the chromatin immunoprecipitation (ChIP) assay in HuH7 cells and also using the mouse liver in vivo. We found that the transcriptional activity of the PFK2/FBP2 gene was stimulated by insulin and inhibited by cAMP and glucocorticoid. Liver X receptor (LXR) α showed a potent and specific stimulatory effect on PFK2/FBP2 gene transcription. Deletion and mutagenesis analyses identified the LXR response element (LXRE) in the 5'-promoter region of the PFK2/FBP2 gene. Binding of LXRα was confirmed by the EMSA and ChIP assay. Endogenous PFK2/FBP2 mRNA in the mouse liver was increased in the fasting/refeeding state compared with the fasting state. Altogether, PFK2/FBP2 gene transcription is found to be regulated in a way that is more similar to other glycolytic enzyme genes than to gluconeogenic genes. Furthermore, our data strongly suggest that LXRα is one of the key regulators of PFK2/FBP2 gene transcription.

De novo lipogenesis in adipose tissue is associated with course of morbid obesity after bariatric surgery

Objective

De novo lipogenesis is involved in fatty acid biosynthesis and could be involved in the regulation of the triglyceride storage capacity of adipose tissue. However, the association between lipogenic and lipolytic genes and the evolution of morbidly obese subjects after bariatric surgery remains unknown. In this prospective study we analyze the association between the improvement in the morbidly obese patients as a result of bariatric surgery and the basal expression of lipogenic and lipolytic genes.

Methods

We study 23 non diabetic morbidly obese patients who were studied before and 7 months after bariatric surgery. Also, we analyze the relative basal mRNA expression levels of lipogenic and lipolytic genes in epiploic visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT).

Results

When the basal acetyl-CoA carboxylase 1 (ACC1), acetyl-CoA synthetase 2 (ACSS2) and ATP citrate lyase (ACL) expression in SAT was below percentile-50, there was a greater decrease in weight (P = 0.006, P = 0.034, P = 0.026), body mass index (P = 0.008, P = 0.033, P = 0.034) and hip circumference (P = 0.033, P = 0.021, P = 0.083) after bariatric surgery. In VAT, when the basal ACSS2 expression was below percentile-50, there was a greater decrease in hip circumference (P = 0.006). After adjusting for confounding variables in logistic regression models, only the morbidly obese patients with SAT or VAT ACSS2 expression≥P50 before bariatric surgery had a lower percentage hip circumference loss (<P50) after bariatric surgery (SAT: P = 0.039; VAT: P = 0.033).

Conclusions

A lower basal ACSS2, ACC1 and ACL expression, genes involved in de novo lipogenesis, is associated with a better evolution of anthropometric variables after bariatric surgery. Thus, the previous state of the pathways involved in fatty acid metabolism may have repercussions on the improvement of these patients.

Carbohydrates for Physical Activity

Intake of carbohydrates above the dietary guidelines to support performance of physical activity is common but may be unnecessary and counterproductive. Sports nutrition guidelines have not been designed to incorporate characteristics that may make high carbohydrate consumption a source of metabolic stress that may increase oxidative stress, inflammation, and lipogenesis. This metabolic stress is linked to the physiology underlying the development of insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases. This review describes research-based evidence to aid in bridging the gap between dietary guidelines for overall health and those to support physical activity. Characteristics that increase the likelihood of metabolic stress resulting from carbohydrate intake include overweight and obesity, central/visceral adiposity, older age, sedentary lifestyle, and caloric state. Carbohydrate-based foods that provide the most health benefits are whole grains, beans and legumes, fruits, and vegetables. Carbohydrate-based foods that most readily elicit metabolic stress are those with added sugars and refined grains or that have a high glycemic index. A checklist that incorporates both the number of these characteristics and prevailing guidelines for nutrition and physical activity is presented. This may be useful in determining whether additional carbohydrates are needed to support the physical activity level of the individual.

Adiponectin and PPARγ: cooperative and interdependent actions of two key regulators of metabolism

The recent advances in the understanding of adiponectin and other adipokines have highlighted the role of adipose tissue as an active endocrine organ. One of the central regulators of adipocyte biology is peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor that induces the adipogenic gene expression program during development, promotes adipose remodeling, and regulates the functions of adipocytes in lipid storage, adipokine secretion, and energy homeostasis. Activation of PPARγ results in increased insulin sensitivity in skeletal muscle and liver and improves the secretory profile of adipose tissue, favoring release of insulin-sensitizing adipokines, such as adiponectin, and reducing inflammatory cytokines. Increased adiponectin production is likely a significant mediator of the systemic effects of PPARγ activation. This chapter will review the interplay between PPARγ and adiponectin in regulating metabolism, presenting evidence that PPARγ regulates adiponectin gene expression, processing, and secretion and that the two proteins have overlapping effects on downstream metabolic pathways.

Dual role of insulin-like growth factor-1 in acetyl-CoA carboxylase-alpha activity in human colon cancer cells HCT-8: downregulating its expression and phosphorylation

Insulin-like growth factor-1 (IGF-1) plays the role in cellular lipid synthesis and cell proliferation. However, the role of IGF-1 on the growth of colon cancer cell line HCT-8 is not clear. In this study, HCT-8 cells were exposed to IGF-1 at 0, 10, 50, or 100 ng/ml in serum-free medium. Fatty acid/lipid synthesis in HCT-8 cells was examined by 2-14C-acetate incorporation. HCT-8 cell growth and proliferation were determined by MTT assay and Trypan blue exclusive viable cell counting. We found that in serum starvation conditions, IGF-1 at 10-100 ng/ml induced dose-dependent down regulation of both the ACCα expression and the phosphorylation in HCT-8 cells, maintaining a balance in ACCα activity and lipid synthesis. IGF-1 reduced p-ATM, p-AMPK, and then p-ACCα protein levels in HCT-8 cells. IGF-1 increased p-Akt levels, but decreased p-ERK1/2 levels, leading to the decrease in ACCα protein and mRNA levels. Similarly, ERK1/2 inhibitor PD98059 reduced ACCα expression. IGF-1 influences neither HCT-8 cell growth nor their p53 protein levels and PARP cleavage. In a word, IGF-1 reduced ACCα phosphorylation via an ATM/AMPK signaling pathway and suppressed ACCα expression through an ERK1/2 transduction, playing a dual role in regulating ACCα activity and lipogenesis. This may render a cell with survival advantages under a serum starvation crisis, representing a novel mitogenic role of IGF-1.

Dietary manipulation reveals an unexpected inverse relationship between fat mass and adipose 11β-hydroxysteroid dehydrogenase type 1

Increased dietary fat intake is associated with obesity, insulin resistance, and metabolic disease. In transgenic mice, adipose tissue-specific overexpression of the glucocorticoid-amplifying enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) exacerbates high-fat (HF) diet-induced visceral obesity and diabetes, whereas 11β-HSD1 gene knockout ameliorates this, favoring accumulation of fat in nonvisceral depots. Paradoxically, in normal mice HF diet-induced obesity (DIO) is associated with marked downregulation of adipose tissue 11β-HSD1 levels. To identify the specific dietary fats that regulate adipose 11β-HSD1 and thereby impact upon metabolic disease, we either fed mice diets enriched (45% calories as fat) in saturated (stearate), monounsaturated (oleate), or polyunsaturated (safflower oil) fats ad libitum or we pair fed them a low-fat (11%) control diet for 4 wk. Adipose and liver mass and glucocorticoid receptor and 11β-HSD1 mRNA and activity levels were determined. Stearate caused weight loss and hypoinsulinemia, partly due to malabsorption, and this markedly increased plasma corticosterone levels and adipose 11β-HSD1 activity. Oleate induced pronounced weight gain and hyperinsulinemia in association with markedly low plasma corticosterone and adipose 11β-HSD1 activity. Weight gain and hyperinsulinemia was less pronounced with safflower compared with oleate despite comparable suppression of plasma corticosterone and adipose 11β-HSD1. However, with pair feeding, safflower caused a selective reduction in visceral fat mass and relative insulin sensitization without affecting plasma corticosterone or adipose 11β-HSD1. The dynamic depot-selective relationship between adipose 11β-HSD1 and fat mass strongly implicates a dominant physiological role for local tissue glucocorticoid reactivation in fat mobilization.

Next generation sequencing in functional genomics

Genome-wide sequencing has enabled modern biomedical research to relate more and more events in healthy as well as disease-affected cells and tissues to the genomic sequence. Now next generation sequencing (NGS) extends that reach into multiple almost complete genomes of the same species, revealing more and more details about how individual genomes as well as individual aspects of their regulation differ from each other. The inclusion of NGS-based transcriptome sequencing, chromatin-immunoprecipitation (ChIP) of transcription factor binding and epigenetic analyses (usually based on DNA methylation or histone modification ChIP) completes the picture with unprecedented resolution enabling the detection of even subtle differences such as alternative splicing of individual exons. Functional genomics aims at the elucidation of the molecular basis of biological functions and requires analyses that go far beyond the primary analysis of the reads such as mapping to a genome template sequence. The various and complex interactions between the genome, gene products and metabolites define biological function, which necessitates inclusion of results other than sequence tags in quite elaborative approaches. However, the extra efforts pay off in revealing mechanisms as well as providing the foundation for new strategies in systems biology and personalized medicine. This review emphasizes the particular contribution NGS-based technologies make to functional genomics research with a special focus on gene regulation by transcription factor binding sites.