Tumor necrosis factor increases the rate of lipolysis in primary cultures of adipocytes without altering levels of hormone-sensitive lipase

Intrauterine food restriction impairs the lipogenesis process in the mesenteric adipocytes from low-birth-weight rats into adulthood

Background

Intrauterine food restriction (IFR) during pregnancy is associated with low birth weight (LBW) and obesity in adulthood. It is known that white adipose tissue (WAT) plays critical metabolic and endocrine functions; however, this tissue's behavior before weight gain and obesity into adulthood is poorly studied. Thus, we evaluated the repercussions of IFR on the lipogenesis and lipolysis processes in the offspring and described the effects on WAT inflammatory cytokine production and secretion.

Methods

We induced IFR by providing gestating rats with 50% of the necessary chow daily amount during all gestational periods. After birth, we monitored the offspring for 12 weeks. The capacity of isolated fat cells from mesenteric white adipose tissue (meWAT) to perform lipogenesis (14C-labeled glucose incorporation into lipids) and lipolysis (with or without isoproterenol) was assessed. The expression levels of genes linked to these processes were measured by real-time PCR. In parallel, Multiplex assays were conducted to analyze pro-inflammatory markers, such as IL-1, IL-6, and TNF-α, in the meWAT.

Results

Twelve-week-old LBW rats presented elevated serum triacylglycerol (TAG) content and attenuated lipogenesis and lipolysis compared to control animals. Inflammatory cytokine levels were increased in the meWAT of LBW rats, evidenced by augmented secretion by adipocytes and upregulated gene and protein expression by the tissue. However, there were no significant alterations in the serum cytokines content from the LBW group. Additionally, liver weight, TAG content in the hepatocytes and serum glucocorticoid levels were increased in the LBW group.

Conclusion

The results demonstrate that IFR throughout pregnancy yields LBW offspring characterized by inhibited lipogenesis and lipolysis and reduced meWAT lipid storage at 12 weeks. The increased serum TAG content may contribute to the augmented synthesis and secretion of pro-inflammatory markers detected in the LBW group.

A flavonoid-rich fraction of Euphorbia peplus attenuates hyperglycemia, insulin resistance, and oxidative stress in a type 2 diabetes rat model

Background: Type 2 diabetes (T2D) is a metabolic disorder characterized by insulin resistance (IR) and hyperglycemia. Plants are valuable sources of therapeutic agents for the management of T2D. Euphorbia peplus has been widely used as a traditional medicine for the treatment of various diseases, but its beneficial role in T2D has not been fully explored. Methods: The anti-diabetic efficacy of E. peplus extract (EPE) was studied using rats with T2D induced by high-fat diet (HFD) and streptozotocin (STZ). The diabetic rats received 100, 200, and 400 mg/kg EPE for 4 weeks. Results: Phytochemical fractionation of the aerial parts of E. peplus led to the isolation of seven known flavonoids. Rats with T2D exhibited IR, impaired glucose tolerance, decreased liver hexokinase and glycogen, and upregulated glycogen phosphorylase, glucose-6-phosphatase (G-6-Pase), and fructose-1,6-bisphosphatase (F-1,6-BPase). Treatment with 100, 200, and 400 mg/kg EPE for 4 weeks ameliorated hyperglycemia, IR, liver glycogen, and the activities of carbohydrate-metabolizing enzymes. EPE attenuated dyslipidemia, serum transaminases, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and liver lipid accumulation, nuclear factor (NF)-κB p65, and lipid peroxidation, nitric oxide and enhanced antioxidants. All EPE doses upregulated serum adiponectin and liver peroxisome proliferator-activated receptor γ (PPARγ) in HFD/STZ-induced rats. The isolated flavonoids showed in silico binding affinity toward hexokinase, NF-κB, and PPARγ. Conclusion: E. peplus is rich in flavonoids, and its extract ameliorated IR, hyperglycemia, dyslipidemia, inflammation and redox imbalance, and upregulated adiponectin and PPARγ in rats with T2D.

Arbutin ameliorates hyperglycemia, dyslipidemia and oxidative stress and modulates adipocytokines and PPARγ in high-fat diet/streptozotocin-induced diabetic rats

Arbutin is a glycosylated hydroquinone with antioxidant and anti-hyperglycemia effects. However, its beneficial effects in type 2 diabetes (T2D) were not clarified. This study evaluated the effect of arbutin on hyperglycemia, dyslipidemia, insulin resistance, oxidative stress, and inflammatory response in T2D. Rats induced by high fat diet and streptozotocin were treated with arbutin (25 and 50 mg/kg for 4 weeks). Diabetic rats exhibited glucose intolerance, elevated HbA1c%, reduced insulin, and high HOMA-IR. Liver glycogen and hexokinase activity were decreased in T2D rats while glucose-6-phosphatase (G6Pase), fructose-1,6- biphosphatase (FBPase), and glycogen phosphorylase were upregulated. Circulating and hepatic cholesterol and triglycerides and serum transaminases were elevated in T2D rats. Arbutin ameliorated hyperglycemia, dyslipidemia, insulin deficiency and resistance, and liver glycogen and alleviated the activity of carbohydrate-metabolizing enzymes. Both doses of arbutin decreased serum transaminases and resistin, and liver lipids, TNF-α, IL-6, malondialdehyde and nitric oxide, downregulated liver resistin and fatty acid synthase, and increased serum and liver adiponectin, and liver reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT). These effects were associated with the upregulation of hepatic PPARγ. Arbutin inhibited α-glucosidase in vitro and in silico investigations revealed the ability of arbutin to bind PPARγ, hexokinase, and α-glucosidase. In conclusion, arbutin effectively ameliorated glucose intolerance, insulin resistance, dyslipidemia, inflammation, and oxidative stress, and modulated carbohydrate-metabolizing enzymes, antioxidants, adipokines and PPARγ in T2D in rats.

Susceptibility of Fat Tissue to SARS-CoV-2 Infection in Female hACE2 Mouse Model

The coronavirus disease (COVID-19) is a highly contagious viral illness caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). COVID-19 has had a catastrophic effect globally causing millions of deaths worldwide and causing long-lasting health complications in COVID-19 survivors. Recent studies including ours have highlighted that adipose tissue can act as a reservoir where SARS-CoV-2 can persist and cause long-term health problems. Here, we evaluated the effect of SARS-CoV-2 infection on adipose tissue physiology and the pathogenesis of fat loss in a murine COVID-19 model using humanized angiotensin-converting enzyme 2 (hACE2) mice. Since epidemiological studies reported a higher mortality rate of COVID-19 in males than in females, we examined hACE2 mice of both sexes and performed a comparative analysis. Our study revealed for the first time that: (a) viral loads in adipose tissue and the lungs differ between males and females in hACE2 mice; (b) an inverse relationship exists between the viral loads in the lungs and adipose tissue, and it differs between males and females; and (c) CoV-2 infection alters immune signaling and cell death signaling differently in SARS-CoV-2 infected male and female mice. Overall, our data suggest that adipose tissue and loss of fat cells could play important roles in determining susceptibility to CoV-2 infection in a sex-dependent manner.

Lipid droplets associated perilipins protein insights into finding a therapeutic target approach to cure non-alcoholic fatty liver disease (NAFLD)

Background

Non-alcoholic fatty liver disease (NAFLD) is now the most common form of chronic liver disease in the world, and it’s linked to a slew of other risk factors including diabetes, obesity, dysbiosis and inflammatory bowel disease. More than 30 years ago, a patient was diagnosed with fatty liver with excessive fat accumulation in hepatocytes, a disorder known as hepatosteatosis. There will be no promising therapeutic medicines available from 1980 to 2021 which can reverse the fatty liver to normal liver state. In this review, we highlighted on lipid droplet associated protein which play a major role in accumulation of fat in liver cells and how these cellular pathway could be a promising therapeutic approach to treat the fatty liver disease.

Main body

Over the last few decades, Western countries follow a high-fat diet and change their lifestyle pattern due to certain metabolic disorders prevalence rate is very high all over the world. NAFLD is a major health issue and burden globally nowadays. Researchers are trying to find out the potential therapeutic target to combat the disease. The exact pathophysiology of the disease is still unclear. In the present decades. There is no Food and Drug Administration approved drugs are available to reverse the chronic condition of the disease. Based on literature survey, lipid droplets and their associated protein like perilipins play an eminent role in body fat regulation. In this review, we explain all types of perilipins such as perilipin1-5 (PLIN1-5) and their role in the pathogenesis of fatty liver which will be helpful to find the novel pharmacological target to treat the fatty liver.

Conclusion

In this review, majorly focussed on how fat is get deposited into hepatocytes follow the cellular signalling involved during lipid droplet biogenesis and leads to NAFLD. However, up to date still there mechanism of action is unclear. In this review, we hypothesized that lipid droplets associated proteins like perilipins could be better pharmacological target to reverse the chronic stage of fatty liver disease and how these lipid droplets associated proteins hide a clue to maintain the normal lipid homeostasis in the human body.

The Role of Fat Reducing Agents on Adipocyte Death and Adipose Tissue Inflammation

Deoxycholic Acid (DCA), which is an FDA-approved compound for the reduction of submental fat, has evolved through an unanticipated and surprising sequence of events. Initially, it was used as a solvent for Phosphatidylcholine (PDC), which was thought to promote lipolysis, but it was later proven to be the bioactive component of the formula and is currently widely used as Kybella. It has also been used off-label to treat other types of fat deposits like lipomas, HIV lipodystrophy, and excess orbital fat. Despite widespread clinical use, there has been no consensus clarifying the mechanisms of DCA and PDC alone or in combination. Furthermore, despite PDC's removal from the FDA-approved formula, some studies do suggest it plays an important role in fat reduction. To provide some clarity, we conducted a PubMed search and reviewed 41 articles using a comprehensive list of terms in three main categories, using the AND operator: 1) Phosphatidylcholines 2) Deoxycholic Acid, and 3) Lipoma. We isolated articles that studied PDC, DCA, and a PDC/DCA compound using cell biology, molecular and genetic techniques. We divided relevant articles into those that studied these components using histologic techniques and those that utilized specific cell death and lipolysis measurement techniques. Most morphologic studies indicated that PDC/DCA, DCA, and PDC, all induce some type of cell death with accompanying inflammation and fibrosis. Most morphologic studies also suggest that PDC/DCA and DCA alone are non-selective for adipocytes. Biochemical studies describing PDC and DCA alone indicate that DCA acts as a detergent and rapidly induces necrosis while PDC induces TNF-α release, apoptosis, and subsequent enzymatic lipolysis after at least 24 hours. Additional papers have suggested a synergistic effect between the two compounds. Our review integrates the findings of this growing body of literature into a proposed mechanism of fat reduction and provides direction for further studies.

Molecular mechanisms of fat deposition: IL-6 is a hub gene in fat lipolysis, comparing thin-tailed with fat-tailed sheep breeds

Tail fat content affects meat quality and varies significantly among different breeds of sheep. Ghezel (fat-tailed) and Zel (thin-tailed) are two important Iranian local sheep breeds with different patterns of fat storage. The current study presents the transcriptome characterization of tail fat using RNA sequencing in order to get a better comprehension of the molecular mechanism of lipid storage in the two mentioned sheep breeds. Seven (Zel  =  4 and Ghezel  =  3) 7-month-old male lambs were used for this experiment. The results of sequencing were analyzed with bioinformatics methods, including differentially expressed genes (DEGs) identification, functional enrichment analysis, structural classification of proteins, protein-protein interaction (PPI) and network and module analyses. Some of the DEGs, such as LIPG, SAA1, SOCS3, HIF-1 α , and especially IL-6, had a close association with lipid metabolism. Furthermore, functional enrichment analysis revealed pathways associated with fat deposition, including "fatty acid metabolism", "fatty acid biosynthesis" and "HIF-1 signaling pathway". The structural classification of proteins showed that major down-regulated DEGs in the Zel (thin-tailed) breed were classified under transporter class and that most of them belonged to the solute carrier transporter (SLC) families. In addition, DEGs under the transcription factor class with an important role in lipolysis were up-regulated in the Zel (thin-tailed) breed. Also, network analysis revealed that IL-6 and JUNB were hub genes for up-regulated PPI networks, and HMGCS1, VPS35 and VPS26A were hub genes for down-regulated PPI networks. Among the up-regulated DEGs, the IL-6 gene seems to play an important role in lipolysis of tail fat in thin-tailed sheep breeds via various pathways such as tumor necrosis factor (TNF) signaling and mitogen-activated protein kinase (MAPK) signaling pathways. Due to the probable role of the IL-6 gene in fat lipolysis and also due to the strong interaction of IL-6 with the other up-regulated DEGs, it seems that IL-6 accelerates the degradation of lipids in tail fat cells.

Prognostic value of dyslipidemia for sick dogs hospitalized in the intensive care unit of a veterinary teaching hospital

OBJECTIVE To evaluate the lipidemia status and serum concentrations of cholesterol and triglycerides of dogs when initially examined for hospitalization in the intensive care unit (ICU) of a veterinary teaching hospital and to determine whether these variables were predictive of survival to hospital discharge. DESIGN Retrospective cohort study. ANIMALS 549 client-owned sick (n = 398) and healthy (151) dogs. PROCEDURES Medical records of sick dogs hospitalized in the ICU at a veterinary teaching hospital between January 1, 2012, and September 30, 2015, and of healthy dogs evaluated at the teaching hospital during the same time frame were reviewed. Data collection included signalment, results of initial physical and clinicopathologic examinations, treatments, diagnosis, and survival to hospital discharge. Lipidemia status and serum concentrations of cholesterol and triglycerides were compared between healthy and sick dogs and between sick dogs that did and did not survive to hospital discharge. Regression analysis was performed to determine whether these variables were predictive of survival to hospital discharge in dogs. RESULTS Factors associated with increased odds of sick dogs not surviving to hospital discharge were hypocholesterolemia (OR, 1.87; 95% confidence interval [CI], 1.04 to 3.34), hypertriglyceridemia (OR, 3.20; 95% CI, 2.00 to 5.13), and concurrent hypocholesterolemia and hypertriglyceridemia (OR, 55.7; 95% CI, 3.2 to 959.6) at the time of initial evaluation. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that hypocholesterolemia and hypertriglyceridemia, alone or in combination, at initial examination were negative prognostic indicators for survival of dogs hospitalized in the ICU and that these conditions were easily identified with routine serum clinicopathologic analyses. (J Am Vet Med Assoc 2019;254:699-709).

Consumption of Terpenoids-Rich Padina pavonia Extract Attenuates Hyperglycemia, Insulin Resistance and Oxidative Stress, and Upregulates PPARγ in a Rat Model of Type 2 Diabetes

Seaweeds are rich in structurally diverse bioactive compounds with promising therapeutic effects. This study aimed to isolate and identify terpenes from the brown alga Padina pavonia and to investigate its antidiabetic activity, pointing to the possible involvement of peroxisome proliferator-activated receptor (PPAR)γ. Type 2 diabetes was induced by feeding rats a high fat diet (HFD) for 4 weeks followed by injection of 35 mg/kg streptozotocin (STZ). The diabetic rats received P. pavonia extract (PPE; 50, 100 and 200 mg/kg) for 4 weeks and samples were collected for analyses. HFD/STZ-induced rats showed hyperglycemia, dyslipidemia, impaired glucose tolerance, decreased insulin, and increased HbA1c and HOMA-IR. PPE ameliorated hyperglycemia and dyslipidemia, and improved glucose tolerance and insulin sensitivity in diabetic rats. Treatment with PPE increased hepatic hexokinase activity and glycogen, suppressed glucose-6-phosphatase, fructose-1,6-biphosphatase, and glycogen phosphorylase, and attenuated oxidative stress, inflammation, and liver injury and lipid infiltration in HFD/STZ-induced rats. In addition, PPE boosted antioxidants and upregulated PPARγ gene and protein expression in the liver of diabetic rats. Phytochemical investigation resulted in the isolation of six terpenes from PPE and in silico analysis revealed their binding affinity toward PPARγ. In conclusion, P. pavonia-derived terpenes attenuated hyperglycemia, dyslipidemia, oxidative stress, and inflammation, and improved insulin sensitivity and carbohydrate metabolism in type 2 diabetic rats. These beneficial effects are mediated via PPARγ activation. However, further studies to explore the exact mechanisms underlying the antidiabetic effect of PPE are recommended.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

The Potential Use of Metformin, Dipyridamole, N-Acetylcysteine and Statins as Adjunctive Therapy for Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune condition that can potentially affect every single organ during the course of the disease, leading to increased morbidity and mortality, and reduced health-related quality of life. While curative treatment is currently non-existent for SLE, therapeutic agents such as glucocorticoids, mycophenolate, azathioprine, cyclosporine, cyclophosphamide and various biologics are the mainstay of treatment based on their immunomodulatory and immunosuppressive properties. As a result of global immunosuppression, the side-effect profile of the current therapeutic approach is unfavourable, with adverse effects including myelosuppression, infection and malignancies. Hydroxychloroquine, one of the very few Food and Drug Administration (FDA)-approved medications for the treatment of SLE, has been shown to offer a number of therapeutic benefits to SLE patients independent of its immunomodulatory effect. As such, it is worth exploring drugs similar to hydroxychloroquine that confer additional clinical benefits unrelated to immunosuppressive mechanisms. Indeed, apart from hydroxychloroquine, a number of studies have explored the use of a few conventionally non-immunosuppressive drugs that are potentially useful in the management of SLE. In this review, non-immunosuppressive therapeutic agents, namely metformin, dipyridamole, N-acetylcysteine and statins, will be critically discussed with regard to their mechanisms of action and efficacy pertaining to their potential therapeutic role in SLE.

Muscle and adipose tissue insulin resistance: malady without mechanism?

Insulin resistance is a major risk factor for numerous diseases, including type 2 diabetes and cardiovascular disease. These disorders have dramatically increased in incidence with modern life, suggesting that excess nutrients and obesity are major causes of "common" insulin resistance. Despite considerable effort, the mechanisms that contribute to common insulin resistance are not resolved. There is universal agreement that extracellular perturbations, such as nutrient excess, hyperinsulinemia, glucocorticoids, or inflammation, trigger intracellular stress in key metabolic target tissues, such as muscle and adipose tissue, and this impairs the ability of insulin to initiate its normal metabolic actions in these cells. Here, we present evidence that the impairment in insulin action is independent of proximal elements of the insulin signaling pathway and is likely specific to the glucoregulatory branch of insulin signaling. We propose that many intracellular stress pathways act in concert to increase mitochondrial reactive oxygen species to trigger insulin resistance. We speculate that this may be a physiological pathway to conserve glucose during specific states, such as fasting, and that, in the presence of chronic nutrient excess, this pathway ultimately leads to disease. This review highlights key points in this pathway that require further research effort.

Modulation of hyperglycemia and dyslipidemia in experimental type 2 diabetes by gallic acid and p-coumaric acid: The role of adipocytokines and PPARγ

There are many indications that confirm the vital role of adipocytokines and PPARγ in diabetics. Hence, the current investigation aimed to study the modulatory effects of gallic acid and p-coumaric acid on adipocytokines secretion and PPARγ mRNA expression in type 2 diabetic rats. After induction of type 2 diabetes, diabetic rats were orally treated with 20 mg/kg body mass gallic acid and 40 mg/kg body mass p-coumaric acid for six weeks. Among treatment diabetic rats, glucose and glycosylated hemoglobin levels significantly declined in diabetic rats, while insulin level and body weight significantly increased as compared to control group. Gallic acid and p-coumaric acid markedly decreased the level of TNF-α and increased the levels of PPARγ mRNA and adiponectin. In addition, the tested agents improved markedly lipid profile parameters, cardiovascular indices 1 and 2 and anti-atherogenic index. In conclusion, gallic acid and p-coumaric acid exhibited marked antidiabetic action that could be mediated via modulation of TNF-α and adipocytokines secretions as well as upregulation of PPARγ mRNA expression.

Differential expression of sirtuin 2 and adipocyte maturation restriction: an adaptation process during hypoxia in fish

Sirtuins have received widespread attention due to their diverse physiological role in metabolism. Among sirtuins, SIRT2 is more abundant in adipocytes and exerts effects on adipocyte differentiation, a process which involves conversion of preadipocytes to mature adipocytes orchestrated by adipokines and adipogenic transcription factors. Grey mullet (Mugil cephalus) was chosen as a study organism due to its excellent service as a biomonitor. Adipocytes isolated from natural field conditions were termed as field-hypoxic (Ennore) and -normoxic (Kovalam) based on dissolved oxygen (DO) level in the estuary. A previous study portrayed the hypoxic instance of Ennore estuary (low DO) and grey mullet [HIF1α in adipocytes, brain endothelial cell (EC) and hepatocytes] inhabiting this estuary ( Padmini et al., 2016a, b; Padmini and Tharani, 2015). In this context, fish adipocytes of both conditions were subjected to in vitro hypoxia for 1 h (in the pre/trigassed incubator with the supply of 1% O₂; 94% N₂; 5% CO₂) and were analysed for the expression of adipokines, adipogenic transcription factors and anti-adipogenic markers in fish adipocytes. Elevation of asymmetric dimethylarginine (ADMA), TNFα and leptin along with decreased adiponectin, adipogenic transcription factors and altering sirtuins were observed in test adipocytes and in control adipocytes on in vitro hypoxia. This suggests that adipocytes may follow internal caloric restriction as portrayed from cytomorphological/ultrastructural analysis, limiting adipocyte maturation process, one of the adaptive mechanisms triggered by adipocyte of fish surviving in Ennore estuary. Prolonged exposure to hypoxia (test on in vitro hypoxia for 1 h) showed a drastic alteration in these components leading to both structural and biological fluctuation when compared to limited hypoxic condition (field-hypoxic and control on in vitro hypoxia). Our study concludes that hypoxia may serve as the chief molecular cue in eliciting adipocyte maturation restriction though metabolic reprogramming and it also shows the significance of adipocyte maturation restriction in imparting survival mechanism.

Summary: Adipocyte maturation restriction is tightly regulated by SIRT2 activation which downregulates preadipocytes from the maturation process as adaptation strategy in fish surviving in the polluted (hypoxic) environment.

Metabolic Changes During Cancer Cachexia Pathogenesis

Wasting of adipose tissue and skeletal muscle is a hallmark of metastatic cancer and a major cause of death. Like patients with cachexia caused by other chronic infections or inflammatory diseases, the cancer subject manifests both malnutrition and metabolic stress. Both carbohydrate utilization and amino acid incorporation are decreased in the muscles of cancer cachexia patients. Cancer cells affect host metabolism in two ways: (a) their own metabolism of nutrients into other metabolites and (b) circulating factors they secrete or induce the host to secrete. Accelerated glycolysis and lactate production, i.e., the Warburg effect and the resultant increase in Cori cycle activity, are the most widely discussed metabolic effects. Meanwhile, although a large number of pro-cachexia circulating factors have been found, such as TNFa, IL-6, myostatin, and PTHrp, none have been shown to be a dominant factor that can be targeted singly to treat cancer cachexia in humans. It is possible that given the complex multifactorial nature of the cachexia secretome, and the personalized differences between cancer patients, targeting any single circulating factor would always be insufficient to treat cachexia for all patients. Here we review the metabolic changes that occur in response to tumor growth and tumor-secreted factors during cachexia.

Association Between Aerobic Exercise and Rosiglitazone Avoided the NAFLD and Liver Inflammation Exacerbated in PPAR-α Knockout Mice

Nonalcoholic fatty liver disease (NAFLD) is one of the main liver diseases today, and may progress to steatohepatitis, cirrhosis, and hepatocellular carcinoma. Some studies have shown the beneficial effects of aerobic exercise on reversing NAFLD. To verify whether chronic aerobic exercise improves the insulin resistance, liver inflammation, and steatohepatitis caused by a high fat diet (HF) and whether PPARα is involved in these actions. C57BL6 wild type (WT) and PPAR-α knockout (KO) mice were fed with a standard diet (SD) or HF during 12 weeks; the HF mice were trained on a treadmill during the last 8 weeks. Serum glucose and insulin tolerances, serum levels of aspartate aminotransferase, hepatic content of triacylglycerol, cytokines, gene expression, and protein expression were evaluated in all animals. Chronic exposure to HF diet increased triacylglycerol accumulation in the liver, leading to NAFLD, increased aminotransferase in the serum, increased peripheral insulin resistance, and higher adiposity index. Exercise reduced all these parameters in both animal genotypes. The liver lipid accumulation was not associated with inflammation; trained KO mice, however, presented a huge inflammatory response that was probably caused by a decrease in PPAR-γ expression. We conclude that exercise improved the damage caused by a HF independently of PPARα, apparently by a peripheral fatty acid oxidation in the skeletal muscle. We also found that the absence of PPARα together with exercise leads to a decrease in PPAR-γ and a huge inflammatory response. J. Cell. Physiol. 232: 1008-1019, 2017. © 2016 Wiley Periodicals, Inc.

In vitro effect of endotoxin on lipolysis and lipoprotein lipase activity in adipocytes from lean, obese and obese diabetic Zucker rats

Endotoxemia and sepsis in non diabetic rats are associated with alterations in adipose tissue metabolism evidenced by an increase in lipolysis and decrease in lipoprotein lipase (LPL) activity. The purpose of this study was to determine the in vitro effect of endotoxin (LPS) on lipolysis and the activities of LPL in epididymal adipocytes isolated from 11-12-week-old obese diabetic, obese, and lean rats. Epinephrine-stimulated lipolysis was higher in the adipocytes from obese diabetic and obese rats than lean rats. Maximal lipolytic response for all groups occurred with 10-5 M of epinephrine. LPS increased the lipolytic rate in adipocytes from the obese and obese diabetic rats by 58% and 97%, respectively, in comparison to the lean rats. Heparin-releasable and extractable LPL activities were suppressed in LPS-treated adipocytes from lean rats; heparin-releasable, but not extractable LPL activity, was depressed in adipocytes from obese rats. The LPS-induced depression in LPL activities did not occur in adipocytes from obese diabetic rats. Since LPL is not altered, adipose tissue from the obese diabetic rats may not become depleted when challenged with endotoxin as is the case for the normal endotoxin-treated lean rat with diminished LPL activity.

Excessive fatty acid oxidation induces muscle atrophy in cancer cachexia

Cachexia is a devastating muscle-wasting syndrome that occurs in patients who have chronic diseases. It is most commonly observed in individuals with advanced cancer, presenting in 80% of these patients, and it is one of the primary causes of morbidity and mortality associated with cancer. Additionally, although many people with cachexia show hypermetabolism, the causative role of metabolism in muscle atrophy has been unclear. To understand the molecular basis of cachexia-associated muscle atrophy, it is necessary to develop accurate models of the condition. By using transcriptomics and cytokine profiling of human muscle stem cell-based models and human cancer-induced cachexia models in mice, we found that cachectic cancer cells secreted many inflammatory factors that rapidly led to high levels of fatty acid metabolism and to the activation of a p38 stress-response signature in skeletal muscles, before manifestation of cachectic muscle atrophy occurred. Metabolomics profiling revealed that factors secreted by cachectic cancer cells rapidly induce excessive fatty acid oxidation in human myotubes, which leads to oxidative stress, p38 activation and impaired muscle growth. Pharmacological blockade of fatty acid oxidation not only rescued human myotubes, but also improved muscle mass and body weight in cancer cachexia models in vivo. Therefore, fatty acid-induced oxidative stress could be targeted to prevent cancer-induced cachexia.

Tumor invasion depth is a useful pathologic assessment for predicting outcomes in cervical squamous cell carcinoma after neoadjuvant radiotherapy

Background

To evaluate whether tumor invasion depth can be a reliable and easily applicable pathologic assessment strategy to predict outcomes using surgically resected cervical squamous cell carcinoma specimens from patients who have received neoadjuvant radiotherapy (RT) or concurrent chemoradiotherapy (CCRT).

Methods

We included 173 patients with cervical squamous cell carcinoma who received neoadjuvant CCRT (n = 125) or RT (n = 48) and underwent subsequent radical hysterectomy. Data for the pre-operative clinical International Federation of Gynecology and Obstetrics (FIGO) stage, post-operative pathologic FIGO stage, World Health Organization (WHO) double diameter measurement evaluation, response evaluation criteria in solid tumors (RECIST 1.1) criteria, tumor necrosis rate (TNR), and tumor regression grade (TRG) were investigated to identify correlations with outcomes related to distant metastasis and survival. The tumor invasion depth (TID) and the tumor invasion depth with cytokeratin immunostaining correction (TIDC) at the cervical internal surface were measured to assess their relations to patients’ outcomes.

Results

Based on measurements taken via transvaginal ultrasound, the pre-operative clinical and post-operative pathologic FIGO staging as well as the WHO double diameter measurement evaluation and RECIST 1.1 criteria were predictive of distant metastasis and survival-related outcomes. Also, lymph node involvement was found to be an independent prognostic factor for recurrence and distant metastasis. Finally, univariate analysis showed both the TID and TIDC were highly related to distant metastasis, overall survival, and progression-free survival, irrespective of the clinical stage of carcinomas.

Conclusion

The TID or TIDC measured at the cervical internal surface is a useful and easily applied pathologic prognostic factor for distant metastasis and survival outcomes in patients with cervical squamous cell carcinoma treated with neoadjuvant RT or CCRT.

Electronic supplementary material

The online version of this article (doi:10.1186/s13000-015-0426-6) contains supplementary material, which is available to authorized users.

Fat in flames: influence of cytokines and pattern recognition receptors on adipocyte lipolysis

Adipose tissue has the largest capacity to store energy in the body and provides energy through the release of free fatty acids during times of energy need. Different types of immune cells are recruited to adipose tissue under various physiological conditions, indicating that these cells contribute to the regulation of adipose tissue. One major pathway influenced by a number of immune cells is the release of free fatty acids through lipolysis during both physiological (e.g., cold stress) and pathophysiological processes (e.g., obesity, type 2 diabetes). Adipose tissue expansion during obesity leads to immune cell infiltration and adipose tissue remodeling, a homeostatic process that promotes inflammation in adipose tissue. The release of proinflammatory cytokines stimulates lipolysis and causes insulin resistance, leading to adipose tissue dysfunction and systemic disruptions of metabolism. This review focuses on the interactions of cytokines and other inflammatory molecules that regulate adipose tissue lipolysis during physiological and pathophysiological states.

Transmembrane tumor necrosis factor-alpha sensitizes adipocytes to insulin

Transmembrane TNF-α (tmTNF-α) acts both as a ligand, delivering 'forward signaling' via TNFR, and as a receptor, transducing 'reverse signaling'. The contradiction of available data regarding the effect of tmTNF-α on insulin resistance may be due to imbalance in both signals. Here, we demonstrated that high glucose-induced impairment of insulin-stimulated glucose uptake by 3T3-L1 adipocytes was concomitant with decreased tmTNF-α expression and increased soluble TNF-α (sTNF-α) secretion. However, when TACE was inhibited, preventing the conversion of tmTNF-α to sTNF-α, this insulin resistance was partially reversed, indicating a salutary role of tmTNF-α. Treatment of 3T3-L1 adipocytes with exogenous tmTNF-α promoted insulin-induced phosphorylation of IRS-1 and Akt, facilitated GLUT4 expression and membrane translocation, and increased glucose uptake while addition of sTNF-α resulted in the opposite effect. Furthermore, tmTNF-α downregulated the production of IL-6 and MCP-1 via NF-κB inactivation, as silencing of A20, an inhibitor for NF-κB, by siRNA, abolished this effect of tmTNF-α. However, tmTNF-α upregulated adiponectin expression through the PPAR-γ pathway, as inhibition of PPAR-γ by GW9662 abrogated both tmTNF-α-induced adiponectin transcription and glucose uptake. Our data suggest that tmTNF-α functions as an insulin sensitizer via forward signaling.

Chronic helminth infection and helminth-derived egg antigens promote adipose tissue M2 macrophages and improve insulin sensitivity in obese mice

Chronic low-grade inflammation associated with obesity contributes to insulin resistance and type 2 diabetes. Helminth parasites are the strongest natural inducers of type 2 immune responses, and short-lived infection with rodent nematodes was reported to improve glucose tolerance in obese mice. Here, we investigated the effects of chronic infection (12 weeks) with Schistosoma mansoni, a helminth that infects millions of humans worldwide, on whole-body metabolic homeostasis and white adipose tissue (WAT) immune cell composition in high-fat diet-induced obese C57BL/6 male mice. Our data indicate that chronic helminth infection reduced body weight gain (-62%), fat mass gain (-89%), and adipocyte size; lowered whole-body insulin resistance (-23%) and glucose intolerance (-16%); and improved peripheral glucose uptake (+25%) and WAT insulin sensitivity. Analysis of immune cell composition by flow cytometry and quantitative PCR (qPCR) revealed that S. mansoni promoted strong increases in WAT eosinophils and alternatively activated (M2) macrophages. Importantly, injections with S. mansoni-soluble egg antigens (SEA) recapitulated the beneficial effect of parasite infection on whole-body metabolic homeostasis and induced type 2 immune responses in WAT and liver. Taken together, we provide novel data suggesting that chronic helminth infection and helminth-derived molecules protect against metabolic disorders by promoting a T helper 2 (Th2) response, eosinophilia, and WAT M2 polarization.

Combined elevated midpregnancy tumor necrosis factor alpha and hyperlipidemia in pregnancies resulting in early preterm birth

OBJECTIVE

The objective of the study was to determine whether pregnancies resulting in early preterm birth (PTB) (<30 weeks) were more likely than term pregnancies to have elevated midtrimester serum tumor necrosis factor alpha (TNF-α) levels combined with lipid patterns suggestive of hyperlipidemia.

STUDY DESIGN

In 2 nested case-control samples drawn from California and Iowa cohorts, we examined the frequency of elevated midpregnancy serum TNF-α levels (in the fourth quartile [4Q]) and lipid patterns suggestive of hyperlipidemia (eg, total cholesterol, low-density-lipoproteins, or triglycerides in the 4Q, high-density lipoproteins in the first quartile) (considered independently and by co-occurrence) in pregnancies resulting in early PTB compared with those resulting in term birth (n = 108 in California and n = 734 in Iowa). Odds ratios (ORs) and 95% confidence intervals (CIs) estimated in logistic regression models were used for comparisons.

RESULTS

Early preterm pregnancies were 2-4 times more likely than term pregnancies to have a TNF-α level in the 4Q co-occurring with indicators of hyperlipidemia (37.5% vs 13.9% in the California sample (adjusted OR, 4.0; 95% CI, 1.1-16.3) and 26.3% vs 14.9% in the Iowa sample (adjusted OR, 2.7; 95% CI, 1.1-6.3). No differences between early preterm and term pregnancies were observed when TNF-α or target lipid abnormalities occurred in isolation. Observed differences were not explicable to any maternal or infant characteristics.

CONCLUSION

Pregnancies resulting in early PTB were more likely than term pregnancies to have elevated midpregnancy TNF-α levels in combination with lipid patterns suggestive of hyperlipidemia.

Lack of platelet-activating factor receptor protects mice against diet-induced adipose inflammation and insulin-resistance despite fat pad expansion

OBJECTIVE

The role of platelet-activating factor (PAF) on diet-induced inflammatory and metabolic dysfunction is unknown. The effects of diet-induced metabolic and inflammatory dysfunction in mice with deletion of the PAF receptor (PAFR(-/-) ) were evaluated in this study.

METHODS

Wild-type and PAFR(-/-) mice were fed chow (WT-C and PAFR(-/-) -C) or high-refined carbohydrate-containing diet (WT-HC and PAFR(-/-) -HC). PAFR(-/-) - RESULTS: HC mice gained more weight and adiposity than PAFR(-/-) -C and WT-HC mice. Lipogenesis increased and hormone-sensitive lipase expression decreased in PAFR(-/-) -HC compared to WT-HC mice. WT-HC mice had impaired glucose tolerance and insulin sensitivity compared to WT-C mice. In contrast, glucose tolerance and insulin sensitivity in PAFR(-/-) -HC mice were similar to that of lean littermates. PAFR(-/-) -HC mice expressed significantly more peroxisome proliferator-activator receptor gamma (PPARγ) than PAFR(-/-) -C and WT-C mice. Resistin increased in WT-HC mice compared to WT-C mice. However, the levels of resistin were 35% lower in PAFR(-/-) -HC mice than WT-HC mice. PAFR(-/-) presented with less HC diet-induced adipose tissue inflammation than WT mice. Adipocytes isolated from PAFR(-/-) mice incubated in media containing normal or high levels of glucose secreted less interleukin-6 and tumor necrosis factor alpha and presented lower rate of lipolysis than WT mice.

CONCLUSION

PAFR deficiency resulted in less inflammation in adipose tissue and improvement in glucose homeostasis when fed the HC diet. The higher adiposity observed in PAFR(-/-) mice fed HC diet could be owing to the maintenance of insulin sensitivity, decreased adipocyte lipolysis rate, high lipogenesis and PPARγ expression, and lower inflammatory milieu in adipose tissue.

The brain–adipose axis: A review of involvement of molecules

Many molecules are involved in the regulation of feeding behavior, and they and their receptors are located in the brain hypothalamus and adipocytes. On the basis of evidence suggesting an association between the brain and adipose tissue, we propose the concept of the brain-adipose axis. This model consists of (l) the expression of endogenous molecules and/or their receptors in the hypothalamus and peripheral adipose tissue, (2) the function of these molecules as appetite regulators in the brain, (3) their existence in the general circulation as secreted proteins and (4) the physiological affects of these molecules on fat cell size and number. These molecules can be divided into two anorexigenic and orexigenic classes. In adipose tissue, all orexigenic molecules possess adipogenic activity, and almost all anorexigenic molecules suppress fat cell proliferation. Although the manner, in which they present in the circulating blood connect the brain and peripheral adipocytes, remains to be well-organized, these observations suggest the positive feedback axis affecting molecules in the hypothalamus and adipose tissue. Analysis of the disturbance and dysregulation of this axis might promote the development of new anti-obesity drugs useful in treating the metabolic syndrome.

High fat diet accelerates pathogenesis of murine Crohn's disease-like ileitis independently of obesity

BACKGROUND

Obesity has been associated with a more severe disease course in inflammatory bowel disease (IBD) and epidemiological data identified dietary fats but not obesity as risk factors for the development of IBD. Crohn's disease is one of the two major IBD phenotypes and mostly affects the terminal ileum. Despite recent observations that high fat diets (HFD) impair intestinal barrier functions and drive pathobiont selection relevant for chronic inflammation in the colon, mechanisms of high fat diets in the pathogenesis of Crohn's disease are not known. The aim of this study was to characterize the effect of HFD on the development of chronic ileal inflammation in a murine model of Crohn's disease-like ileitis.

METHODS

TNF(ΔARE/WT) mice and wildtype C57BL/6 littermates were fed a HFD compared to control diet for different durations. Intestinal pathology and metabolic parameters (glucose tolerance, mesenteric tissue characteristics) were assessed. Intestinal barrier integrity was characterized at different levels including polyethylene glycol (PEG) translocation, endotoxin in portal vein plasma and cellular markers of barrier function. Inflammatory activation of epithelial cells as well as immune cell infiltration into ileal tissue were determined and related to luminal factors.

RESULTS

HFD aggravated ileal inflammation but did not induce significant overweight or typical metabolic disorders in TNF(ΔARE/WT). Expression of the tight junction protein Occludin was markedly reduced in the ileal epithelium of HFD mice independently of inflammation, and translocation of endotoxin was increased. Epithelial cells showed enhanced expression of inflammation-related activation markers, along with enhanced luminal factors-driven recruitment of dendritic cells and Th17-biased lymphocyte infiltration into the lamina propria.

CONCLUSIONS

HFD feeding, independently of obesity, accelerated disease onset of small intestinal inflammation in Crohn's disease-relevant mouse model through mechanisms that involve increased intestinal permeability and altered luminal factors, leading to enhanced dendritic cell recruitment and promoted Th17 immune responses.

Curcumin attenuates lipolysis stimulated by tumor necrosis factor-α or isoproterenol in 3T3-L1 adipocytes

BACKGROUND AND AIM

Curcumin, an active component derived from dietary spice turmeric (Curcuma longa), has been demonstrated antihyperglycemic, antiinflammatory and hypocholesterolemic activities in obesity and diabetes. These effects are associated with decreased level of circulating free fatty acids (FFA), however the mechanism has not yet been elucidated. The flux of FFA and glycerol from adipose tissue to the blood stream primarily depends on the lipolysis of triacylglycerols in the adipocytes. Adipocyte lipolysis is physiologically stimulated by catecholamine hormones. Tumor necrosis factor-α (TNFα) stimulates chronic lipolysis in obesity and type 2 diabetes. In this study, we examined the role of curcumin in inhibiting lipolytic action upon various stimulations in 3T3-L1 adipocytes.

METHODS

Glycerol release from TNFα or isoproterenol-stimulated 3T3-L1 adipocytes in the absence or presence of curcumin was determined using a colorimetric assay (GPO-Trinder). Western blotting was used to investigate the TNFα-induced phosphorylation of MAPK and perilipin expression. Fatcake and cytosolic fractions were prepared to examine the isoproterenol-stimulated hormone-sensitive lipase translocation.

RESULTS

Treatment with curcumin attenuated TNFα-mediated lipolysis by suppressing phosphorylation of extracellular signal-related kinase 1/2 (ERK1/2) and reversing the downregulation of perilipin protein in TNFα-stimulated adipocytes (p<0.05). The acute lipolytic response to adrenergic stimulation of isoproterenol was also restricted by curcumin (10-20 μM, p<0.05), which was compatible with reduced perilipin phosphorylation(29%, p<0.05) and hormone-sensitive lipase translocation(20%, p<0.05).

CONCLUSIONS

This study provides evidence that curcumin acts on adipocytes to suppress the lipolysis response to TNFα and catecholamines. The antilipolytic effect could be a cellular basis for curcumin decreasing plasma FFA levels and improving insulin sensitivity.

Free fatty acids are associated with metabolic syndrome and insulin resistance but not inflammation in systemic lupus erythematosus

Free fatty acids (FFAs) are implicated in the pathogenesis of insulin resistance and atherosclerosis. Inflammatory cytokines promote lipolysis and increase FFAs, a cause of endothelial dysfunction and increased atherosclerosis risk. We hypothesized that increased inflammation is associated with increased FFAs, resulting in insulin resistance and atherosclerosis in patients with systemic lupus erythematosus (SLE). We measured clinical variables, serum FFAs, homeostasis model assessment for insulin resistance (HOMA), inflammatory cytokines, markers of endothelial activation, cholesterol concentrations and coronary artery calcium in 156 patients with SLE and 90 controls. We compared FFAs in patients with SLE and controls using Wilcoxon rank sum tests and further tested for the independent association between FFAs and disease status with adjustment for age, race and sex using multivariable regression models. We assessed the relationship between FFAs and continuous variables of interest using Spearman correlation and multivariable regression analysis. Levels of FFAs were higher in patients with SLE than controls (0.55 mmol/l (0.37-0.71) vs 0.44 mmol/l (0.32-0.60), P = 0.02). Levels of FFAs remained significantly higher among patients with SLE after adjustment for age, race and sex (P = 0.03) but not after further adjustment for body mass index (P = 0.13). FFA levels did not differ according to the usage of current immunosuppressive medications in univariate and adjusted analysis (all P > 0.05). Among patients with SLE, concentrations of FFAs were higher among those with metabolic syndrome compared to those without (0.66 mmol/l (0.46-0.81) vs 0.52 mmol/l (0.35-0.66), P < 0.001). FFAs were positively correlated with insulin resistance (HOMA) (rho = 0.23, P = 0.004, P adjusted = 0.006) and triglyceride levels (rho = 0.22, P = 0.01, P adjusted = 0.004). FFAs were not associated with inflammatory cytokines (IL-6, TNF-α) (all P > 0.05) but were positively associated with levels of E-selectin (rho = 0.33, P = < 0.001, P adjusted = 0.001) and ICAM-1 (rho = 0.35, P < 0.001, P adjusted = 0.001). FFAs were correlated with coronary artery calcium score (rho = 0.20, P = 0.01) but this was attenuated after adjustment for age, race and sex (P = 0.33). From our study we concluded that FFAs are elevated in patients with SLE, particularly those with metabolic syndrome. FFAs in patients with SLE are not associated with markers of generalized inflammation but are associated with insulin resistance and markers of endothelial activation.

Leukocyte Migration in Adipose Tissue of Mice Null for ICAM-1 and Mac-1 Adhesion Receptors

OBJECTIVE

To determine whether the leukocyte adhesion receptors ICAM-1 and Mac-1, regulators of immune cell migration, have an intrinsic role within adipose tissue by 1) analyzing the expression of ICAM-1 in adipose tissue, 2) identifying leukocyte populations within adipose tissue, and 3) determining whether ICAM-1 and Mac-1 mutant mice exhibit abnormal numbers of adipose tissue leukocytes.

RESEARCH METHODS AND PROCEDURES

Wild-type, ICAM-1(-/-), and Mac-1(-/-) mice were fed a long-term high-fat diet. ICAM-1 expression was analyzed by Northern blot and immunohistochemistry. Leukocytes within adipose tissue were identified by immunohistochemistry and flow cytometry.

RESULTS

ICAM-1 was expressed in adipose tissue and localized to the vascular endothelium. Macrophages and lymphocytes were prevalent within the stromal-vascular cell fraction of adipose tissue, and gender-specific differences were observed, with adipose tissue from female mice containing significantly more macrophages than tissue from male mice. Numbers of leukocytes in ICAM-1(-/-) and Mac-1(-/-) mice were not different from wild-types, however, indicating that these adhesion receptors are not required for leukocyte migration into adipose tissue.

DISCUSSION

Our results documented leukocyte populations within adipose tissue, which may be involved in the development of heightened inflammation that is characteristic of obesity.

Relative contribution of adipose triglyceride lipase and hormone-sensitive lipase to tumor necrosis factor-α (TNF-α)-induced lipolysis in adipocytes

TNF-α potently stimulates basal lipolysis in adipocytes, which may contribute to hyperlipidemia and peripheral insulin resistance in obesity. Recent studies show that adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) act sequentially in catalyzing the first two steps of adipose lipolysis in response to β-adrenergic stimulation. Here, we sought to determine their functional roles in TNF-α-induced lipolysis. Silencing of ATGL expression in adipocytes almost completely abolished basal and TNF-α-induced glycerol release. In comparison, the glycerol release under the same conditions was only partially decreased upon reduction in expression of either HSL or the ATGL coactivator CGI-58. Interestingly, overexpression of ATGL restored the lipolytic rates in cells with silenced HSL or CGI-58, indicating a predominant role for ATGL. While expression of ATGL, HSL and CGI-58 remains mostly unaffected, TNF-α treatment caused a rapid abrogation of the ATGL inhibitory protein G0S2. TNF-α drastically decreased the level of G0S2 mRNA, and the level of G0S2 protein could be maintained by inhibiting proteasomal protein degradation using MG-132. Furthermore, coexpression of G0S2 was able to significantly decrease TNF-α-stimulated lipolysis mediated by overexpressed ATGL or CGI-58. We propose that the early reduction in G0S2 content is permissive for TNF-α-induced lipolysis.

Mapping quantitative trait loci for metabolic and cytological fatness traits of connected F2 crosses in pigs

In the present study 3 connected F(2) crosses were used to map QTL for classical fat traits as well as fat-related metabolic and cytological traits in pigs. The founder breeds were Chinese Meishan, European Wild Boar, and Pietrain with to some extent the same founder animals in the different crosses. The different selection history of the breeds for fatness traits as well as the connectedness of the crosses led to a high statistical power. The total number of F(2) animals varied between 694 and 966, depending on the trait. The animals were genotyped for around 250 genetic markers, mostly microsatellites. The statistical model was a multi-allele, multi-QTL model that accounted for imprinting. The model was previously introduced from plant breeding experiments. The traits investigated were backfat depth and fat area as well as relative number of fat cells with different sizes and 2 metabolic traits (i.e., soluble protein content as an indicator for the level of metabolic turnover and NADP-malate dehydrogenase as an indicator for enzyme activity). The results revealed in total 37 significant QTL on chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 14, 17, and 18, with often an overlap of confidence intervals of several traits. These confidence intervals were in some cases remarkably small, which is due to the high statistical power of the design. In total, 18 QTL showed significant imprinting effects. The small and overlapping confidence intervals for the classical fatness traits as well as for the cytological and metabolic traits enabled positional and functional candidate gene identification for several mapped QTL.

Free fatty acids are associated with insulin resistance but not coronary artery atherosclerosis in rheumatoid arthritis

BACKGROUND

Free fatty acids (FFAs) affect insulin signaling and are implicated in the pathogenesis of insulin resistance and atherosclerosis. Inflammatory cytokines such as interleukin-6 (IL-6) increase lipolysis and thus levels of FFAs. We hypothesized that increased IL-6 concentrations are associated with increased FFAs resulting in insulin resistance and atherosclerosis in rheumatoid arthritis (RA).

METHODS

Clinical variables, serum FFAs and inflammatory cytokines, homeostasis model assessment for insulin resistance (HOMA-IR), and coronary artery calcium were measured in 166 patients with RA and 92 controls. We compared serum FFAs in RA and controls using Wilcoxon rank sum tests and further tested for multivariable association by adjusting for age, race, sex and BMI. Among patients with RA, we assessed the relationship between serum FFAs and inflammatory cytokines, HOMA-IR, and coronary artery calcium scores using Spearman correlation and multivariable regression analyses.

RESULTS

Serum FFAs did not differ significantly in patients with RA and controls (0.56mmol/L [0.38-0.75] and 0.56mmol/L [0.45-0.70] respectively, p=0.75). Presence of metabolic syndrome was associated with significantly increased serum FFAs in both RA and controls (p=0.035 and p=0.025). In multivariable regression analysis that adjusted for age, race, sex and BMI, serum FFAs were associated with HOMA-IR (p=0.011), CRP (p=0.01), triglycerides (p=0.005) and Framingham risk score (p=0.048) in RA, but not with IL-6 (p=0.48) or coronary artery calcium score (p=0.62).

CONCLUSIONS

Serum FFAs do not differ significantly in patients with RA and controls. FFAs may contribute to insulin resistance, but are not associated with IL-6 and coronary atherosclerosis in RA.

Adipose triglyceride lipase and hormone-sensitive lipase are involved in fat loss in JunB-deficient mice

Proteins of the activator protein-1 family are known to have roles in many physiological processes such as proliferation, apoptosis, and inflammation. However, their role in fat metabolism has yet to be defined in more detail. Here we study the impact of JunB deficiency on the metabolic state of mice. JunB knockout (JunB-KO) mice show markedly decreased weight gain, reduced fat mass, and a low survival rate compared with control mice. If fed a high-fat diet, the weight gain of JunB-KO mice is comparable to control mice and the survival rate improves dramatically. Along with normal expression of adipogenic marker genes in white adipose tissue (WAT) of JunB-KO mice, this suggests that adipogenesis per se is not affected by JunB deficiency. This is supported by in vitro data, because neither JunB-silenced 3T3-L1 cells nor mouse embryonic fibroblasts from JunB-KO mice show a change in adipogenic potential. Interestingly, the key enzymes of lipolysis, adipose triglyceride lipase and hormone-sensitive lipase, were significantly increased in WAT of fasted JunB-KO mice. Concomitantly, the ratio of plasma free fatty acids per gram fat mass was increased, suggesting an elevated lipolytic rate under fasting conditions. Furthermore, up-regulation of TNFα and reduced expression of perilipin indicate that this pathway is also involved in increased lipolytic rate in these mice. Additionally, JunB-KO mice are more insulin sensitive than controls and show up-regulation of lipogenic genes in skeletal muscle, indicating a shuttling of energy substrates from WAT to skeletal muscle. In summary, this study provides valuable insights into the impact of JunB deficiency on the metabolic state of mice.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

FFA-induced adipocyte inflammation and insulin resistance: involvement of ER stress and IKKβ pathways

Free-fatty acids (FFAs) are well-characterized factor for causing production of inflammatory factors and insulin resistance in adipocytes. Using cultured adipocytes, we demonstrate that FFAs can activate endoplasmic reticulum (ER) stress pathway by examination of ER stress sensor activation and marker gene expression. Chemical chaperone tauroursodeoxycholic acid (TUDCA) can reduce FFA-induced adipocyte inflammation and improve insulin signaling whereas overexpression of spliced X-box protein 1 (XBP-1s) only attenuates FFA-induced inflammation. PKR-like eukaryotic initiation factor 2α kinase (PERK) is one of the three major ER stress sensor proteins and deficiency of PERK alleviates FFA-induced inflammation and insulin resistance. The key downstream target of FFA-induced ER stress is IκB kinase β (IKKβ), a master kinase for regulating expression of inflammatory genes. Deficiency of PERK attenuates FFA-induced activation of IKKβ and deficiency of IKKβ alleviates FFA-induced inflammation and insulin resistance. Consistently, overexpression of IKKβ in 3T3-L1 CAR adipocytes causes inflammation and insulin resistance. In addition, IKKβ overexpression has profound effect on adipocyte lipid metabolism, including inhibition of lipogenesis and promotion of lipolysis. Furthermore, increased endogenous IKKβ expression and activation is also observed in isolated primary adipocytes from mice injected with lipids or fed on high-fat diet (HFD) acutely. These results indicate that ER stress pathway is a key mediator for FFA-induced inflammation and insulin resistance in adipocytes with PERK and IKKβ as the critical signaling components.

Ursolic acid stimulates lipolysis in primary-cultured rat adipocytes

Ursolic acid (UA) is a pentacyclic triterpenic acid with many biological functions naturally existing in many kinds of food. To investigate whether UA can accelerate lipolysis, primary-cultured rat adipocytes were treated with UA, and glycerol release in the culture medium was measured. UA stimulated lipolysis significantly. Furthermore, the lipolytic effect of UA was inhibited by the protein kinase A (PKA) specific inhibitor H89, suggesting that UA exerted its lipolytic function through the cAMP-dependent PKA pathway. Downstream targets of the PKA pathway, hormone-sensitive lipase (HSL) and perilipin A were checked, UA enhanced lipolysis by promoting the translocation of HSL from the cytosol to the lipid droplets and inhibiting the expression of perilipin A. Additionally, adipose triglyceride lipase (ATGL), a novel rate-limiting lipase in the lipolytic catabolism, was upregulated by UA. UA-induced expression of ATGL could not be blocked by H89, suggesting that ATGL upregulation is not regulated by the PKA pathway. These findings suggest that UA significantly stimulates lipolysis by translocating HSL, decreasing perilipin A expression by the PKA pathway, and up-regulating ATGL in primary cultured adipocytes. Thus, UA is a promising candidate for the treatment of obesity.

Biological effects of propionic acid in humans; metabolism, potential applications and underlying mechanisms

Undigested food is fermented in the colon by the microbiota and gives rise to various microbial metabolites. Short-chain fatty acids (SCFA), including acetic, propionic and butyric acid, are the principal metabolites produced. However, most of the literature focuses on butyrate and to a lesser extent on acetate; consequently, potential effects of propionic acid (PA) on physiology and pathology have long been underestimated. It has been demonstrated that PA lowers fatty acids content in liver and plasma, reduces food intake, exerts immunosuppressive actions and probably improves tissue insulin sensitivity. Thus increased production of PA by the microbiota might be considered beneficial in the context of prevention of obesity and diabetes type 2. The molecular mechanisms by which PA may exert this plethora of physiological effects are slowly being elucidated and include intestinal cyclooxygenase enzyme, the G-protein coupled receptors 41 and 43 and activation of the peroxisome proliferator-activated receptor γ, in turn inhibiting the sentinel transcription factor NF-κB and thus increasing the threshold for inflammatory responses in general. Taken together, PA emerges as a major mediator in the link between nutrition, gut microbiota and physiology.

TNF-alpha, a potent lipid metabolism regulator

As a multifunctional cytokine, tumor necrosis factor alpha (TNF-alpha) exerts a series of biological actions in different cells, tissues, organs, and species and has been demonstrated to regulate and interfere with energy metabolism, especially lipid homeostasis. A large body of researches suggested that the effects of TNF-alpha on lipid metabolism mainly include five aspects: (1) suppresses free fatty acid (FFA) uptake and promotes lipogenesis; (2) induces lipolysis; (3) inhibits lipid-metabolism-related enzymes activity; (4) regulates cholesterol metabolism; (5) regulates other adipocyte-derived adipokines. The molecular mechanisms underlying these actions are complex and several signal transduction pathways might be involved. Regulation of metabolism-related gene expression at transcriptional and protein levels and impact on enzymes activity might be of importance. Identification and verification of these pathways might provide novel potential strategies and drug targets for dyslipidemia therapy. However, the inconsistent and even conflict conclusions on lipid profile drawn from human subjects after infliximab therapy poses the possibility that the effect of TNF-alpha on lipid metabolism might be more complicated than it appeared to be.

Short-term regulation of tumor necrosis factor-alpha-induced lipolysis in 3T3-L1 adipocytes is mediated through the inducible nitric oxide synthase/nitric oxide-dependent pathway

TNF-alpha has several effects on adipocytes that may be related to the development of type 2 diabetes in obese subjects. Many studies demonstrated that long-term treatment with TNF-alpha increases lipolysis in adipocytes. However, the short-term (<4 h) effects of TNF-alpha on lipolysis have not been well investigated. The aim of this study was to investigate the short-term regulatory mechanism of TNF-alpha-induced lipolysis in 3T3-L1 adipocytes. Well-differentiated 3T3-L1 adipocytes were used. Lipolysis was determined by measuring glycerol release. Expression of inducible nitric oxide (iNOS) and nitric oxide (NO) production were measured, respectively, by Western blots and the Griess reagent. A selective iNOS inhibitor (s-ethylisothiourea . HBr), an adenylyl cyclase inhibitor (SQ22536), and a guanylyl cyclase inhibitor (LY83583) were used to investigate the involvement of iNOS, cAMP, and cGMP in TNF-alpha-induced lipolysis. Transient transfection with iNOS short hairpin RNA was performed to confirm the involvement of iNOS in TNF-alpha-induced lipolysis. Phosphorylation of hormone-sensitive lipase (HSL) was measured by immunoprecipitation and Western blotting. Results showed that short-term TNF-alpha treatment significantly increased lipolysis, iNOS expression, and NO production in a time- and dose-dependent manner. Furthermore, treatment with the NO donor S-nitroso-N-acetylpenicillamine also stimulated lipolysis and HSL phosphorylation in 3T3-L1 adipocytes. Moreover, pretreatment with inhibitors of iNOS and guanylate cyclase, but not an adenylate cyclase inhibitor, abolished TNF-alpha-induced lipolysis and HSL phosphorylation. Suppression of TNF-alpha-induced iNOS expression using short hairpin RNA significantly reduced TNF-alpha-induced lipolysis. In conclusion, short-term TNF-alpha treatment induces lipolysis in 3T3-L1 adipocytes by increasing iNOS expression and NO production, which activates the guanylyl cyclase/cGMP-dependent pathway and induces phosphorylation of HSL.

Molecular mechanisms involved in obesity-associated insulin resistance: therapeutical approach

Insulin resistance is an important contributor to the pathogenesis of T2D and obesity is a risk factor for its development. It has been demonstrated that these obesity-related metabolic disorders are associated with a state of chronic low-intensity inflammation. Several mediators released from adipocytes and macrophages, such as the pro-inflammatory cytokines TNF-alpha and IL-6, have been suggested to impair insulin action in peripheral tissues, including fat and skeletal muscle. Such insulin resistance can initially be compensated by increased insulin secretion, but the prolonged presence of the hormone is detrimental for insulin sensitivity. Stress and pro-inflammatory kinases as well as more recent players, phosphatases, seem to be involved in the molecular mechanisms by which pro-inflammatory cytokines and hyperinsulinemia disrupt insulin signalling at the level of IRSs. Pharmacological approaches, such as treatment with PPAR and LXR agonists, overcome such insulin resistance, exerting anti-inflammatory properties as well as controlling the expression of cytokines with tissular specificity.

The protein kinase IKKepsilon regulates energy balance in obese mice

Obesity is associated with chronic low-grade inflammation that negatively impacts insulin sensitivity. Here, we show that high-fat diet can increase NF-kappaB activation in mice, which leads to a sustained elevation in level of IkappaB kinase epsilon (IKKepsilon) in liver, adipocytes, and adipose tissue macrophages. IKKepsilon knockout mice are protected from high-fat diet-induced obesity, chronic inflammation in liver and fat, hepatic steatosis, and whole-body insulin resistance. These mice show increased energy expenditure and thermogenesis via enhanced expression of the uncoupling protein UCP1. They maintain insulin sensitivity in liver and fat, without activation of the proinflammatory JNK pathway. Gene expression analyses indicate that IKKepsilon knockout reduces expression of inflammatory cytokines, and changes expression of certain regulatory proteins and enzymes involved in glucose and lipid metabolism. Thus, IKKepsilon may represent an attractive therapeutic target for obesity, insulin resistance, diabetes, and other complications associated with these disorders.

eNOS, metabolic syndrome and cardiovascular disease

Large epidemiologic studies have established that diabetes, hyperlipidemia and obesity all increase the risk for cardiovascular disease. However, the precise mechanisms by which these metabolic disorders increase the propensity to develop atherosclerosis are not known. Recently, the concept of the metabolic syndrome - a constellation of conditions including obesity, hypertension, hyperlipidemia and insulin resistance - has received much attention. Studies on the metabolic syndrome might enable a better understanding of the underlying biological mechanisms that lead to cardiovascular disease. This review focuses on endothelial nitric oxide synthase and summarizes evidence that a reduction in the bioavailability of endothelium-derived nitric oxide serves as a key link between metabolic disorders and cardiovascular risk.

Bacterial endotoxin stimulates adipose lipolysis via toll-like receptor 4 and extracellular signal-regulated kinase pathway

Bacterial endotoxin/lipopolysaccharide elicits inflammatory responses and also elevates circulating levels of free fatty acids (FFAs) and impairs insulin sensitivity. Serum FFA elevation in acute endotoxemia has long been thought to be due to endotoxin dysregulating lipid disposal and counterregulatory hormones and cytokines. Here, we investigated the direct lipolysis effect of endotoxin in rodents and in isolated primary adipocytes. Endotoxin increases lipolysis in vivo in adipose tissues, elevates circulating FFA level, induces insulin resistance in rats, and directly stimulates chronic lipolysis in vitro in adipocytes. The lipolytic action of endotoxin is mediated via its lipid A moiety and is blocked by anti-endotoxin peptides. Neither adipocytokine secretion nor nuclear factor-kappaB activation is involved in endotoxin-induced lipolysis. Different from catecholamine, endotoxin stimulates lipolysis without elevating cAMP production and activating protein kinase A and protein kinase C. Instead, endotoxin induces phosphorylation of Raf-1, MEK1/2, and ERK1/2. Upon inhibition of ERK1/2 but not JNK and p38 MAPK, endotoxin-stimulated lipolysis ceases. Endotoxin causes perilipin down-regulation and phosphorylation and increases the activity and protein levels of hormone-sensitive lipase and adipose triglyceride lipase but does not induce hormone-sensitive lipase translocation to intracellular lipid droplets. In TLR4 (Toll-like receptor 4)-deficient mice and adipocytes, endotoxin fails to increase in vivo and in vitro lipolysis. These findings suggest that endotoxin stimulates lipolysis via TLR4 and ERK1/2 signaling in adipocytes. The lipolytic action of endotoxin liberates FFA efflux from adipocytes to the bloodstream, which is a possible basis for systemic FFA elevation and insulin resistance in endotoxemia or Gram-negative bacterial infection.

Mild mitochondrial uncoupling induces 3T3-L1 adipocyte de-differentiation by a PPARgamma-independent mechanism, whereas TNFalpha-induced de-differentiation is PPARgamma dependent

Impairment of mitochondrial activity affects lipid-metabolizing tissues and mild mitochondrial uncoupling has been proposed as a possible strategy to fight obesity and associated diseases. In this report, we characterized the 3T3-L1-adipocyte ;de-differentiation' induced by carbonyl cyanide (p-trifluoromethoxy)-phenylhydrazone (FCCP), a mitochondrial uncoupler. We found a decrease in triglyceride (TG) content in adipocytes incubated with this molecule. We next analyzed the expression of genes encoding adipogenic markers and effectors and compared the differentially expressed genes in adipocytes treated with FCCP or TNFalpha (a cytokine known to induce adipocyte de-differentiation). Furthermore, a significant decrease in the transcriptional activity of PPARgamma and C/EBPalpha transcription factors was found in adipocytes with impaired mitochondrial activity. However, although these modifications were also found in TNFalpha-treated adipocytes, rosiglitazone and 9-cis retinoic acid (PPARgamma and RXR ligands) were unable to prevent triglyceride loss in FCCP-treated cells. Metabolic assays also revealed that TG reduction could be mediated by a downregulation of lipid synthesis rather than an upregulation of fatty acid oxidation. Finally, lipolysis stimulated by the uncoupler also seems to contribute to the TG reduction, a process associated with perilipin A downregulation. These results highlight some new mechanisms that might potentially be involved in adipocyte de-differentiation initiated by a mitochondrial uncoupling.