Decrease In Adipose Tissue Mass Research Articles

Hypertriglyceridemia Results From an Impaired Catabolism of Triglyceride-Rich Lipoproteins in PLIN1-Related Lipodystrophy.

Pathogenic variants in PLIN1-encoding PLIN1 (perilipin-1) are responsible for an autosomal dominant form of familial partial lipodystrophy (FPL) associated with severe insulin resistance, hepatic steatosis, and important hypertriglyceridemia. This study aims to decipher the mechanisms of hypertriglyceridemia associated with PLIN1-related FPL. We performed an in vivo lipoprotein kinetic study in 6 affected patients compared with 13 healthy controls and 8 patients with type 2 diabetes. Glucose and lipid parameters, including plasma LPL (lipoprotein lipase) mass, were measured. LPL mRNA and protein expression were evaluated in abdominal subcutaneous adipose tissue from patients with 5 PLIN1-mutated FPL and 3 controls. Patients with PLIN1-mutated FPL presented with decreased fat mass, insulin resistance, and diabetes (glycated hemoglobin A1c, 6.68±0.70% versus 7.48±1.63% in patients with type 2 diabetes; mean±SD; P=0.27). Their plasma triglycerides were higher (5.96±3.08 mmol/L) than in controls (0.76±0.27 mmol/L; P<0.0001) and patients with type 2 diabetes (2.94±1.46 mmol/L, P=0.006). Compared with controls, patients with PLIN1-related FPL had a significant reduction of the indirect fractional catabolic rate of VLDL (very-low-density lipoprotein)-apoB100 toward IDL (intermediate-density lipoprotein)/LDL (low-density lipoprotein; 1.79±1.38 versus 5.34±2.45 pool/d; P=0.003) and the indirect fractional catabolic rate of IDL-apoB100 toward LDL (2.14±1.44 versus 7.51±4.07 pool/d; P=0.005). VLDL-apoB100 production was not different between patients with PLIN1-related FPL and controls. Compared with patients with type 2 diabetes, patients with PLIN1-related FPL also showed a significant reduction of the catabolism of both VLDL-apoB100 (P=0.031) and IDL-apoB100 (P=0.031). Plasma LPL mass was significantly lower in patients with PLIN1-related FPL than in controls (21.03±10.08 versus 55.76±13.10 ng/mL; P<0.0001), although the LPL protein expression in adipose tissue was similar. VLDL-apoB100 and IDL-apoB100 indirect fractional catabolic rates were negatively correlated with plasma triglycerides and positively correlated with LPL mass. We show that hypertriglyceridemia associated with PLIN1-related FPL results from a marked decrease in the catabolism of triglyceride-rich lipoproteins (VLDL and IDL). This could be due to a pronounced reduction in LPL availability, related to the decreased adipose tissue mass.

Nitric Oxide Mobilizes Intracellular Zn2+ via the GC/cGMP/PKG Signaling Pathway and Stimulates Adipocyte Differentiation.

Plasma and tissue zinc ion levels are associated with the development of obesity. Previous studies have suggested that zinc ions may regulate adipocyte metabolism and that nitric oxide (NO) plays a pivotal role in the regulation of adipocyte physiology. Our previous study showed that chronic NO deficiency causes a significant decrease in adipose tissue mass in rats. Studies also suggested that zinc ions play an important modulatory role in regulating NO function. This study aims to explore the role of zinc ions in NO-regulated adipocyte differentiation. We hypothesized that NO could increase intracellular Zn2+ level and then stimulate adipocyte differentiation. ZnCl2 and the NO donor, NONOate, were used to explore the effects of Zn2+ and NO on adipocyte differentiation. Regulatory mechanisms of NO on intracellular Zn2+ mobilization were determined by detection. Then, Zn2+-selective chelator TPEN was used to clarify the role of intracellular Zn2+ on NO-regulated adipocyte differentiation. Furthermore, the relationship between adipocyte size, Zn2+ level, and NOS expression in human subcutaneous fat tissue was elucidated. Results showed that both ZnCl2 and NO stimulated adipocyte differentiation in a dose-dependent manner. NO stimulated intracellular Zn2+ mobilization in adipocytes through the guanylate cyclase (GC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) pathway, and NO-stimulated adipocyte differentiation was Zn2+-dependent. In human subcutaneous adipose tissue, adipocyte size was negatively correlated with expression of eNOS. In conclusion, NO treatment stimulates intracellular Zn2+ mobilization through the GC/cGMP/PKG pathway, subsequently stimulating adipocyte differentiation.

The docosahexaenoic acid derivatives, diHEP-DPA and TH-DPA, synthesized via recombinant lipoxygenase, ameliorate disturbances in lipid metabolism and liver inflammation in high fat diet-fed mice

7S,15R-Dihydroxy-16S,17S-epoxy-docosapentaenoic acid (diHEP-DPA) and 7S,15R,16S,17S-tetrahydroxy-docosapentaenoic acid (TH-DPA) are two novel lipid mediators derived from docosahexaenoic acid (DHA) that we previously synthesized via combined enzymatic and chemical reactions. In the present study, we investigated the effects of these compounds on disturbances in lipid metabolism and liver inflammation induced by a high fat diet (HFD) in mice. Male BALB/c mice were randomly divided into four groups (n = 10/group): controls, HFD only, HFD + diHEP-DPA, and HFD + TH-DPA. Mice in HFD + diHEP-DPA and HFD + TH-DPA groups were orally administered 20 μg/kg of diHEP-DPA or TH-DPA, respectively. Measurements of adipose accumulation and liver inflammation showed that both diHEP-DPA and TH-DPA decreased adipose tissue mass and liver color depth, as well as total cholesterol, triglycerides, and low-density lipoprotein-cholesterol in the serum of HFD-fed mice compared with mice in the HFD-only group, while elevating high-density lipoprotein-cholesterol. Both of them also decreased hepatic expression of genes encoding lipid synthesis-related proteins (PPARγ, SIRT1, SREBP-1c and FASN) and increased the expression of genes encoding proteins involved in lipid degradation (PPARα and CPT-1) in the liver. Western blotting and quantitative RT-PCR confirmed that diHEP-DPA or TH-DPA administration modulated the expression of inflammation-related genes (TNF-α and IL-6) and inhibited activation of the NF-κB signaling pathway in livers of HFD-fed mice. Taken together, our data indicate that diHEP-DPA and TH-DPA ameliorate liver inflammation and inhibit HFD-induced obesity in mice.

Proto-oncoprotein Zbtb7c and SIRT1 repression: implications in high-fat diet-induced and age-dependent obesity

Zbtb7c is a proto-oncoprotein that controls the cell cycle and glucose, glutamate, and lipid metabolism. Zbtb7c expression is increased in the liver and white adipose tissues of aging or high-fat diet-fed mice. Knockout or knockdown of Zbtb7c gene expression inhibits the adipocyte differentiation of 3T3-L1 cells and decreases adipose tissue mass in aging mice. We found that Zbtb7c was a potent transcriptional repressor of SIRT1 and that SIRT1 was derepressed in various tissues of Zbtb7c-KO mice. Mechanistically, Zbtb7c interacted with p53 and bound to the proximal promoter p53RE1 and p53RE2 to repress the SIRT1 gene, in which p53RE2 was particularly critical. Zbtb7c induced p53 to interact with the corepressor mSin3A-HADC1 complex at p53RE. By repressing the SIRT1 gene, Zbtb7c increased the acetylation of Pgc-1α and Pparγ, which resulted in repression or activation of Pgc-1α or Pparγ target genes involved in lipid metabolism. Our study provides a molecular target that can overexpress SIRT1 protein in the liver, pancreas, and adipose tissues, which can be beneficial in the treatment of diabetes, obesity, longevity, etc.

Oral Probiotic Bifidobacterium Longum Supplementation Improves Metabolic Parameters and Alters the Expression of the Renin-Angiotensin System in Obese Mice Liver.

Obesity and non-alcoholic fatty liver disease (NAFLD) have been increasing at an alarming rate worldwide. Bifidobacterium longum (BL), a common member of the human gut microbiota, has important health benefits through several mechanisms. We evaluated the BL supplementation effects on body metabolism and renin-angiotensin components hepatic expression in mice fed a high-fat diet. Thirty-two male mice were divided into four groups: standard diet + placebo (ST), standard diet + Bifidobacterium longum (ST + BL), high-fat diet + placebo (HFD) and high-fat diet + Bifidobacterium longum (HFD + BL). Following the obesity induction period, the ST + BL and HFD + BL groups were supplemented with Bifidobacterium longum for 4 weeks. Then, body, biochemical, histological and molecular parameters were evaluated. HFD + BL mice had a significant decrease in adipose tissue mass and blood glucose levels, as well as a significant reduction in blood glucose during an intraperitoneal glucose tolerance test. The treatment also resulted in reduced levels of total cholesterol and hepatic fat accumulation. Moreover, we observed an increase in angiotensin converting enzyme 2 (ACE2) and Mas receptor (MASR) expression levels in BL-treated obese mice. These data demonstrate that BL may have the potential to prevent obesity and NAFLD by modulating the mRNA expression of renin-angiotensin system components.

Apple polyphenols induce browning of white adipose tissue

We and others have shown that apple polyphenols decrease adipose tissue mass. To better understand the underlying mechanisms and to expand clinical applicability, we herein examine whether apple polyphenols induce adipose thermogenic adaptations (browning) and prevent diet-induced obesity and related insulin resistance. In mice fed a standard diet, daily apple polyphenol consumption induced thermogenic adaptations in inguinal white adipose tissue (iWAT), based on increases in the expression of brown/beige adipocyte selective genes (Ucp1, Cidea, Tbx1, Cd137) and protein content of uncoupling protein 1 and mitochondrial oxidative phosphorylation enzymes. Among the upstream regulatory factors of browning, fibroblast growth factor 21 (FGF21) and peroxisome proliferator-activated receptor gamma coactivator 1 α (PGC-1α) levels were concomitantly up-regulated by apple polyphenols. In the primary cell culture experiment, the results did not support a direct action of apple polyphenols on beige adipogenesis. Instead, apple polyphenols increased tyrosine hydroxylase (a rate-limiting enzyme of catecholamine synthesis) in iWAT, which activates the adipocyte thermogenic program possibly via intratissue cellular communications. In high-fat fed mice, apple polyphenols induced beige adipocyte development in iWAT, reduced fat accumulation, and increased glucose disposal rates in the glucose and insulin tolerance tests. Taken together, dietary administration of apple polyphenols induced beige adipocyte development in iWAT possibly via activation/induction of the peripheral catecholamine synthesis–FGF21–PGC-1α cascade. Results from diet-induced obese mice indicate that apple polyphenols have therapeutic potential for obesity and related metabolic disorders.

Effect of SGLT2 inhibitors on body composition, fluid status and renin\u2013angiotensin\u2013aldosterone system in type 2 diabetes: a prospective study using bioimpedance spectroscopy

BackgroundSGLT2-inhibitors are potent antihyperglycemic drugs for patients with type 2 diabetes and have been shown to reduce body weight. However, it is unclear which body compartments are reduced and to what extent.MethodsIn this longitudinal observational study, we analyzed the body composition of 27 outpatients with type 2 diabetes mellitus during the first week and up to 6 months after initiation of treatment with SGLT2-inhibitors (n = 18 empagliflozin, n = 9 dapagliflozin) using bioimpedance spectroscopy (BCM, Fresenius). Fluid status of hypertensive patients taking medication with hydrochlorothiazide (n = 14) and healthy persons (n = 16) were analyzed for comparison.ResultsAt 6 months, HbA1c decreased by 0.8% (IQR 2.3; 0.4), body weight and BMI by 2.6 kg (1.5; 9.3) and 0.9 kg/m2 (0.4; 3.3), respectively. Bioimpedance spectroscopy revealed significant decrease in adipose tissue mass and fat tissue index while lean tissue parameters remained stable. Overhydration (OH) and extracellular water (ECW) decreased by − 0.5 L/1.73 m2 (− 0.1; − 0.9) and − 0.4 L/1.73 m2 (− 0.1; − 0.8) at day 3, respectively, and returned to the initial value after 3 and 6 months. Plasma renin activity increased by 2.1-fold (0.5; 3.6) at 1 month and returned to the initial level at month 3 and 6. Fluid status of patients with SGLT2 inhibitors after 6 months showed no difference from that of hypertensive patients taking hydrochlorothiazide or healthy persons.ConclusionsBody weight reduction under the treatment with SGLT2-inhibitors is caused by reduction of adipose tissue mass and transient loss of extracellular fluid, which is accompanied by upregulation of renin–angiotensin–aldosterone system (RAAS). Permanent loss of extracellular water does not occur under SGLT2 inhibition.

Mouse Embryonic Fibroblasts Protect ob/ob Mice From Obesity and Metabolic Complications.

The global obesity epidemic is fueling alarming rates of diabetes, associated with increased risk of cardiovascular disease and cancer. Leptin is a hormone secreted by adipose tissue that is a key regulator of body weight (BW) and energy expenditure. Leptin-deficient humans and mice are obese, diabetic, and infertile and have hepatic steatosis. Although leptin replacement therapy can alleviate the pathologies seen in leptin-deficient patients and mouse models, treatment is costly and requires daily injections. Because adipocytes are the source of leptin secretion, we investigated whether mouse embryonic fibroblasts (MEFs), capable of forming adipocytes, could be injected into ob/ob mice and prevent the metabolic phenotype seen in these leptin-deficient mice. We performed a single subcutaneous injection of MEFs into leptin-deficient ob/ob mice. The MEF injection formed a single fat pad that is histologically similar to white adipose tissue. The ob/ob mice receiving MEFs (obRs) had significantly lower BW compared with nontreated ob/ob mice, primarily because of decreased adipose tissue mass. Additionally, obR mice had significantly less liver steatosis and greater glucose tolerance and insulin sensitivity. obR mice also manifested lower food intake and greater energy expenditure than ob/ob mice, providing a mechanism underlying their metabolic improvement. Furthermore, obRs have sustained metabolic protection and restoration of fertility. Collectively, our studies show the importance of functional adipocytes in preventing metabolic abnormalities seen in leptin deficiency and point to the possibility of cell-based therapies for the treatment of leptin-deficient states.

Subchronic dietary exposure to ethoxyquin dimer induces microvesicular steatosis in male BALB/c mice

The use of the synthetic antioxidant ethoxyquin (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; EQ) in animal feed results in the presence of EQ residues and metabolites, including the EQ dimer (1,8′-bi(6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline); EQDM) in animal food products. To investigate the toxicity and dose-response of dietary exposure to EQDM, male BALB/c mice were exposed to one of six dietary doses of EQDM, ranging from 0.015 to 518 mg/kg body weight/day for 90 days. Doses above 10 mg/kg body weight/day affected whole body lipid metabolism resulting in increased liver weights and decreased adipose tissue mass. Metabolomic screening of livers revealed alterations indicating incomplete fatty acid β-oxidation and hepatic oxidative stress. Histopathological evaluation and biochemical analyses of the liver confirmed the development of microvesicular steatosis and activation of the glutathione system. Hepatic protein profiling and pathway analyses suggested that EQDM-induced responses are mediated through activation of CAR/PXR nuclear receptors and induction of a NRF2-mediated oxidative stress response. Based on the development of microvesicular steatosis as the critical endpoint, a Reference Point for dietary EQDM exposure was established at 1.1 mg/kg body weight/day (BMDL10) from benchmark dose modelling. Applying an uncertainty factor of 200, an Acceptable Daily Intake of 0.006 mg EQDM/kg body weight was proposed.

Exercise Prescription in Patients with Different Combinations of Cardiovascular Disease Risk Factors: A Consensus Statement from the EXPERT Working Group.

Whereas exercise training is key in the management of patients with cardiovascular disease (CVD) risk (obesity, diabetes, dyslipidaemia, hypertension), clinicians experience difficulties in how to optimally prescribe exercise in patients with different CVD risk factors. Therefore, a consensus statement for state-of-the-art exercise prescription in patients with combinations of CVD risk factors as integrated into a digital training and decision support system (the EXercise Prescription in Everyday practice & Rehabilitative Training (EXPERT) tool) needed to be established. EXPERT working group members systematically reviewed the literature for meta-analyses, systematic reviews and/or clinical studies addressing exercise prescriptions in specific CVD risk factors and formulated exercise recommendations (exercise training intensity, frequency, volume and type, session and programme duration) and exercise safety precautions, for obesity, arterial hypertension, type 1 and 2 diabetes, and dyslipidaemia. The impact of physical fitness, CVD risk altering medications and adverse events during exercise testing was further taken into account to fine-tune this exercise prescription. An algorithm, supported by the interactive EXPERT tool, was developed by Hasselt University based on these data. Specific exercise recommendations were formulated with the aim to decrease adipose tissue mass, improve glycaemic control and blood lipid profile, and lower blood pressure. The impact of medications to improve CVD risk, adverse events during exercise testing and physical fitness was also taken into account. Simulations were made of how the EXPERT tool provides exercise prescriptions according to the variables provided. In this paper, state-of-the-art exercise prescription to patients with combinations of CVD risk factors is formulated, and it is shown how the EXPERT tool may assist clinicians. This contributes to an appropriately tailored exercise regimen for every CVD risk patient.

8-Hydroxy-2-deoxyguanosine ameliorates high-fat diet-induced insulin resistance and adipocyte dysfunction in mice

8-Hydroxy-2-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, has been recently shown to exert anti-inflammatory effects through inhibition of Rac1. Inflammation in adipose tissue is a hallmark of obesity-induced insulin resistance, but the therapeutic potential of 8-OHdG in treatment of metabolic diseases has not been fully elucidated. The aim of this study was to examine the effect of exogenously administered 8-OHdG on adipose tissue and whole body metabolism. In cultured adipocytes, 8-OHdG inhibited adipogenesis and reversed TNFα-induced insulin resistance. In high-fat diet (HFD)-induced obese mice, 8-OHdG administration blunted the rise in body weight and fat mass. The decrease in adipose tissue mass by 8-OHdG was due to reduced adipocyte hypertrophy through induction of adipose triglyceride lipase and inhibition of fatty acid synthase expression. 8-OHdG also inhibited the infiltration of macrophages, resulting in amelioration of adipose tissue inflammation and adipokine dysregulation. Moreover, 8-OHdG administration ameliorated adipocyte as well as systemic insulin sensitivity. Both in vivo and in vitro results showed that 8-OHdG induces AMPK activation and reduces JNK activation in adipocytes. In conclusion, our results show that orally administered 8-OHdG protects against HFD-induced metabolic disorders by regulating adipocyte metabolism.

Repin1 deficiency in adipose tissue improves whole-body insulin sensitivity, and lipid metabolism.

Replication initiator 1 (Repin1) gene encodes for a zinc-finger protein and has been implicated in the regulation of adipocyte cell size and glucose transport in vitro. Here, we investigate the consequences of reduced adipose tissue (AT) Repin1 expression in vivo. We have inactivated the Repin1 gene in adipose tissue (iARep-/-) at an age of 4 weeks using tamoxifen-inducible gene targeting strategies on the background of C57BL/6NTac mice. Furthermore, we differentiated human primary adipocytes derived from subcutaneous AT in vitro and knocked down REPIN1 using siRNA technique to measure glycerol release. Conditional Repin1 inactivation results in decreased AT mass, smaller adipocytes in both, subcutaneous and epigonadal AT compared to controls. Compared to controls, iARep-/- mice were more insulin sensitive, had better glucose tolerance and lower LDL-, HDL- and total cholesterol. Significantly lower AT expression of the Repin1 target genes Cd36 and Lcn2 may contribute to the phenotype of iARep-/- mice. Knockdown of REPIN1 in human in vitro differentiated adipocytes revealed an increased glycerol release. In conclusion, deficiency of Repin1 in AT causes alterations in AT morphology and function, which may underlay lower body weight and improved parameters of insulin sensitivity, glucose and lipid metabolism.

The Effects of Graded Levels of Calorie Restriction: X. Transcriptomic Responses of Epididymal Adipose Tissue.

Calorie restriction (CR) leads to a remarkable decrease in adipose tissue mass and increases longevity in many taxa. Since the discovery of leptin, the secretory abilities of adipose tissue have gained prominence in the responses to CR. We quantified transcripts of epididymal white adipose tissue of male C57BL/6 mice exposed to graded levels of CR (0–40% CR) for 3 months. The numbers of differentially expressed genes (DEGs) involved in NF-κB, HIF1-α, and p53 signaling increased with increasing levels of CR. These pathways were all significantly downregulated at 40% CR relative to 12 h ad libitum feeding. In addition, graded CR had a substantial impact on DEGs associated with pathways involved in angiogenesis. Of the 497 genes differentially expressed with graded CR, 155 of these genes included a signal peptide motif. These putative signaling proteins were involved in the response to ketones, TGF-β signaling, negative regulation of insulin secretion, and inflammation. This accords with the previously established effects of graded CR on glucose homeostasis in the same mice. Overall these data suggest reduced levels of adipose tissue under CR may contribute to the protective impact of CR in multiple ways linked to changes in a large population of secreted proteins.

FADD is a key regulator of lipid metabolism.

FADD, a classical apoptotic signaling adaptor, was recently reported to have non‐apoptotic functions. Here, we report the discovery that FADD regulates lipid metabolism. PPAR‐α is a dietary lipid sensor, whose activation results in hypolipidemic effects. We show that FADD interacts with RIP140, which is a corepressor for PPAR‐α, and FADD phosphorylation‐mimic mutation (FADD‐D) or FADD deficiency abolishes RIP140‐mediated transcriptional repression, leading to the activation of PPAR‐α. FADD‐D‐mutant mice exhibit significantly decreased adipose tissue mass and triglyceride accumulation. Also, they exhibit increased energy expenditure with enhanced fatty acid oxidation in adipocytes due to the activation of PPAR‐α. Similar metabolic phenotypes, such as reduced fat formation, insulin resistance, and resistance to HFD‐induced obesity, are shown in adipose‐specific FADD knockout mice. Additionally, FADD‐D mutation can reverse the severe genetic obesity phenotype of ob/ob mice, with elevated fatty acid oxidation and oxygen consumption in adipose tissue, improved insulin resistance, and decreased triglyceride storage. We conclude that FADD is a master regulator of glucose and fat metabolism with potential applications for treatment of insulin resistance and obesity.

Liver-Specific Silencing of Lipin1 Reduces Fat Mass as Well as Hepatic Triglyceride Biosynthesis in Mice.

Lipin1, a bifunctional protein, regulates fatty acid utilization in the triglyceride biosynthesis pathway. In the current study, using a liver-specific in vivo short interfering RNA (siRNA) delivery system, we examined the pathological and physiological roles of hepatic Lipin1 in the development of insulin resistance and the maintenance of systemic energy homeostasis. Liver-specific silencing of Lipin1 expression was achieved by the systemic administration of siRNA against Lpin1 mRNA (siLpin1)-loaded lipid nanoparticles (LNPs) to wild type mice at 3-4 d intervals for 25 d. The siLpin1-treated mice showed normal blood glucose levels and insulin sensitivity, however, triglyceride (TG) levels were reduced in liver and peripheral blood of them. The knockdown of hepatic Lipin1 in mice led to marked decrease in adipose tissue mass and adipocyte diameters in epididymal and inguinal fat depots without the undesired silencing of Lipin1 in adipose tissue. In summary, we report for the first time that the down-regulation of hepatic Lipin1 expression leads to less adiposity as well as a decrease in TG level in the liver and blood circulation, without any alterations in the glucose tolerance and blood glucose levels. Our findings may provide new insights into the physiological roles of hepatic Lipin1 in systemic energy homeostasis.

The anti-angiogenic herbal extract from Melissa officinalis inhibits adipogenesis in 3T3-L1 adipocytes and suppresses adipocyte hypertrophy in high fat diet-induced obese C57BL/6J mice

Ethnopharmacological relevanceMelissa officinalis L. (Labiatae; lemon balm) has been used traditionally and contemporarily as an anti-stress herb. Current hypotheses suggest that not only chronic stress promotes angiogenesis, but angiogenesis also modulates adipogenesis and obesity. Because the herbal extract ALS-L1023 from M. officinalis L. (Labiatae; lemon balm) has an anti-angiogenic activity, we hypothesized that ALS-L1023 could inhibit adipogenesis and adipocyte hypertrophy. Materials and methodsALS-L1023 was prepared by a two-step organic solvent fractionation from M. officinalis. The effects of ALS-L1023 on adipogenesis in 3T3-L1 adipocytes and adipocyte hypertrophy in high fat diet (HFD)-fed obese mice were measured using in vivo and in vitro approaches. ResultsALS-L1023 inhibited angiogenesis in a dose-dependent manner in the HUVEC tube formation assay in vitro. Treatment of cells with ALS-L1023 inhibited lipid accumulation and adipocyte-specific gene expression caused by troglitazone or MDI differentiation mix. ALS-L1023 reduced mRNA expression of angiogenic factors (VEGF-A and FGF-2) and MMPs (MMP-2 and MMP-9) in differentiated cells. In contrast, mRNA levels of angiogenic inhibitors (TSP-1, TIMP-1, and TIMP-2) increased. Protease activity, as measured by zymography, showed that activity of MMP-2 and MMP-9 decreased in ALS-L1023-treated cells. ALS-L1023 also inhibited MMP-2 and MMP-9 reporter gene expression in the presence of the MMP inducer phorbol 12-myristate 13-acetate. An in vivo study showed that ALS-L1023 not only decreased adipose tissue mass and adipocyte size, but also reduced mRNA levels of adipose tissue angiogenic factors and MMPs in HFD-fed obese mice. ConclusionsThese results suggest that the anti-angiogenic herbal extract ALS-L1023 suppresses adipogenesis and adipocyte hypertrophy, and this effect may be mediated by inhibiting angiogenesis and MMP activities. Thus, by curbing adipogenesis, anti-angiogenic ALS-L1023 yields a possible therapeutic choice for the prevention and treatment of human obesity and its associated conditions.

The effect of prolonged metformin treatment on the activity of the adenylyl cyclase system and NO-synthase in the brain and myocardium of obese rats

The biguanide metformin, which is widely used for the treatment of type 2 diabetes, improves carbohydrate and lipid metabolism and has substantial cardioand neuroprotective effects. The positive effects of metformin on the activity of NO synthases catalyzing the synthesis of NO, a major vasodilator, and that of the hormone-sensitive adenylyl cyclase signaling system (ACSS) are believed to play an important role in the mediation of these effects. To prove this hypothesis, we initiated a study addressing the effect of prolonged metformin treatment of obese rats on metabolic parameters and the activity of ACSS and NO synthases in the myocardium and brain of the animals. Obesity was induced in Wistar rats by a high-fat diet, and the animals were subsequently treated with metformin for 2 months (the daily dose was 200 mg/kg). Metformin treatment induced a decrease in adipose tissue mass, total body mass, levels of insulin and glucose, and the insulin resistance index HOMA-IR, as well as improved glucose tolerance, and led to a decrease of the content of atherogenic forms of cholesterol. ACSS stimulation by agonists of β1/β2-adrenergic receptors (ARs) and enhancement of β3-AR signaling was detected in the myocardium of obese rats, while metformin treatment restored ACSS regulation by adrenergic agonists in the myocardium and normalized the balance between β-AR-signaling pathways. The stimulating effects of serotonin and agonists of type 4 melanocortin receptors on adenylyl cyclase, which are attenuated in obesity, were restored in the brain of rats treated with metformin. The treatment completely restored the total activity of NO synthases and the activity of endothelial NO synthase in the myocardium, which are reduced in obesity. Metformin treatment was also shown to induce hyperactivation of NO synthases in the brain and myocardium of healthy animals. It is proposed the effects of prolonged treatment of obese rats with metformin underlie the cardioand neuroprotective actions of this drug.

Chronic hindlimb suspension unloading markedly decreases turnover rates of skeletal and cardiac muscle proteins and adipose tissue triglycerides.

We previously showed that a single bolus of "doubly-labeled" water ((2)H2 (18)O) can be used to simultaneously determine energy expenditure and turnover rates (synthesis and degradation) of tissue-specific lipids and proteins by modeling labeling patterns of protein-bound alanine and triglyceride-bound glycerol (Bederman IR, Dufner DA, Alexander JC, Previs SF. Am J Physiol Endocrinol Metab 290: E1048-E1056, 2006). Using this novel method, we quantified changes in the whole body and tissue-specific energy balance in a rat model of simulated "microgravity" induced by hindlimb suspension unloading (HSU). After chronic HSU (3 wk), rats exhibited marked atrophy of skeletal and cardiac muscles and significant decrease in adipose tissue mass. For example, soleus muscle mass progressively decreased 11, 43, and 52%. We found similar energy expenditure between control (90 ± 3 kcal · kg(-1)· day(-1)) and hindlimb suspended (81 ± 6 kcal/kg day) animals. By comparing food intake (∼ 112 kcal · kg(-1) · day(-1)) and expenditure, we found that animals maintained positive calorie balance proportional to their body weight. From multicompartmental fitting of (2)H-labeling patterns, we found significantly (P < 0.005) decreased rates of synthesis (percent decrease from control: cardiac, 25.5%; soleus, 70.3%; extensor digitorum longus, 44.9%; gastrocnemius, 52.5%; and adipose tissue, 39.5%) and rates of degradation (muscles: cardiac, 9.7%; soleus, 52.0%; extensor digitorum longus, 27.8%; gastrocnemius, 37.4%; and adipose tissue, 50.2%). Overall, HSU affected growth of young rats by decreasing the turnover rates of proteins in skeletal and cardiac muscles and adipose tissue triglycerides. Specifically, we found that synthesis rates of skeletal and cardiac muscle proteins were affected to a much greater degree compared with the decrease in degradation rates, resulting in large negative balance and significant tissue loss. In contrast, we found a small decrease in adipose tissue triglyceride synthesis paired with a large decrease in degradation, resulting in smaller negative energy balance and loss of fat mass. We conclude that HSU in rats differentially affects turnover of muscle proteins vs. adipose tissue triglycerides.

The flavonoid, naringenin, decreases adipose tissue mass and attenuates ovariectomy-associated metabolic disturbances in mice.

ObjectiveAdverse metabolic changes associated with loss of ovarian function increase the risk of developing metabolic syndrome and non-alcoholic fatty liver disease (NAFLD) in postmenopausal women. Naringenin improves metabolic disturbances in vitro and in vivo. In the present study, we tested the effects of naringenin on metabolic disturbances resulting from estrogen deficiency in ovariectomized mice.Materials/methodsOvariectomized C57BL/6 J female mice were fed a control diet (10% calories from fat) for 11 weeks. Mice either continued on the control diet (n = 9) or were switched to the control diet supplemented with 3% naringenin (n = 10) for the next 11 weeks. Energy expenditure was measured by indirect calorimetry and activity was monitored by infrared beam breaks. Intra-abdominal and subcutaneous adiposity was evaluated by magnetic resonance imaging (MRI). Blood biochemical measures of metabolic response included glucose, insulin, adipokines, and lipids. Lipid content in liver and muscle and expression of relevant genes in adipose tissue, liver, and muscle were quantified.ResultsOvariectomized mice fed naringenin exhibited lower fasting glucose and insulin levels compared to controls, with over 50% reduction of intra-abdominal and subcutaneous adiposity. Plasma leptin and leptin mRNA in adipose depots were also decreased in mice fed a naringenin diet. Monocyte chemoattractant protein-1 (MCP1/Ccl2) and interleukin 6 (IL-6/Il6) mRNA expression levels were significantly lower in perigonadal adipose tissue of naringenin-supplemented mice. We also observed that mice fed a naringenin diet had less hepatic lipid accumulation with corresponding alterations of hepatic gene expression associated with de novo lipogenesis, fatty acid oxidation, and gluconeogenesis.ConclusionDietary naringenin attenuates many of the metabolic disturbances associated with ovariectomy in female mice.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-7075-12-1) contains supplementary material, which is available to authorized users.

Endoplasmic reticulum stress in adipose tissue augments lipolysis.

The endoplasmic reticulum (ER) is an organelle important for protein synthesis and folding, lipid synthesis and Ca2+ homoeostasis. Consequently, ER stress or dysfunction affects numerous cellular processes and has been implicated as a contributing factor in several pathophysiological conditions. Tunicamycin induces ER stress in various cell types in vitro as well as in vivo. In mice, a hallmark of tunicamycin administration is the development of fatty livers within 24–48 hrs accompanied by hepatic ER stress. We hypothesized that tunicamycin would induce ER stress in adipose tissue that would lead to increased lipolysis and subsequently to fatty infiltration of the liver and hepatomegaly. Our results show that intraperitoneal administration of tunicamycin rapidly induced an ER stress response in adipose tissue that correlated with increased circulating free fatty acids (FFAs) and glycerol along with decreased adipose tissue mass and lipid droplet size. Furthermore, we found that in addition to fatty infiltration of the liver as well as hepatomegaly, lipid accumulation was also present in the heart, skeletal muscle and kidney. To corroborate our findings to a clinical setting, we examined adipose tissue from burned patients where increases in lipolysis and the development of fatty livers have been well documented. We found that burned patients displayed significant ER stress within adipose tissue and that ER stress augments lipolysis in cultured human adipocytes. Our results indicate a possible role for ER stress induced lipolysis in adipose tissue as an underlying mechanism contributing to increases in circulating FFAs and fatty infiltration into other organs.