LPS and proinflammatory cytokines decrease lipin-1 in mouse adipose tissue and 3T3-L1 adipocytes

Infection and inflammation affect adipose triglyceride metabolism, resulting in increased plasma free fatty acid (FFA) and VLDL levels during the acute-phase response. Lipin-1, a multifunctional protein, plays a critical role in adipose differentiation, mitochondrial oxidation, and triglyceride synthesis. Here, we examined whether LPS [a Toll-like receptor (TLR)-4 activator], zymosan (a TLR-2 activator), and proinflammatory cytokines regulate lipin-1 in adipose tissue. LPS administration caused a marked decrease in the levels of lipin-1 mRNA and protein in adipose tissue. The decrease in lipin-1 mRNA levels occurred rapidly and lasted for at least 24 h. In contrast, lipin-2 and -3 mRNA levels did not change, suggesting specific repression of lipin-1. Zymosan similarly decreased lipin-1 mRNA without affecting lipin-2 or lipin-3 mRNA levels. To determine the pathways by which LPS repressed lipin-1, we examined the effect of proinflammatory cytokines on cultured adipocytes. In 3T3-L1 adipocytes, TNF-alpha, IL-1beta, and IFN-gamma, but not LPS or IL-6, caused a decrease in lipin-1 mRNA levels. Furthermore, TNF-alpha and IL-1beta administration also decreased mRNA levels of lipin-1 in adipose tissue in mice. Importantly, the LPS-induced decrease in lipin-1 mRNA levels was significantly but not totally blunted in TNF-alpha/IL-1 receptor-null mice compared with controls, suggesting key roles for TNF-alpha/IL-1beta and other cytokines in mediating LPS-induced repression of lipin-1. Together, our results demonstrate that expression of lipin-1, one of the essential triglyceride synthetic enzymes, was suppressed by LPS, zymosan, and proinflammatory cytokines in mouse adipose tissue and in cultured 3T3-L1 adipocytes, which could contribute to a decrease in the utilization of FFA to synthesize triglycerides in adipose tissue, thus promoting the release of FFA into the circulation.     

Interleukin-1ß is a positive regulator of TIARP/STAMP2 gene and protein expression in adipocytes in vitro

The impact of interleukin (IL)-1ß on tumor necrosis factor α-induced adipose-related protein (TIARP)/six-transmembrane protein of prostate 2 (STAMP2) was determined in adipocytes. TIARP/STAMP2 mRNA synthesis was significantly stimulated by IL-1ß in a dose- and time-dependent fashion in 3T3-L1 adipocytes. Signaling studies suggested that janus kinase 2, nuclear factor κB, and p44/42 mitogen-activated protein kinase are involved in IL-1ß-induced TIARP/STAMP2 mRNA expression. Furthermore, IL-1ß, TNFα, and IL-6 showed synergistic stimulatory effects on TIARP/STAMP2 gene expression. Moreover, both TIARP/STAMP2 mRNA synthesis and protein expression were induced by IL-1ß in fully differentiated human mesenchymal stem cell-derived adipocytes (hMSC-Ad). Taken together, TIARP/STAMP2 is highly upregulated in 3T3-L1 cells and hMSC-Ad by IL-1ß and might, therefore, modulate proinflammatory and insulin resistance-inducing effects of IL-1ß.     

Cytokines promote Wnt signaling and inflammation and impair the normal differentiation and lipid accumulation in 3T3-L1 preadipocytes

Obesity with enlarged fat cells is associated with high local concentrations of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFalpha) in the adipose tissue. We examined the effects of this inflammatory state on 3T3-L1 preadipocyte development and differentiation to mature adipose cells. Both IL-6 and TNFalpha impaired the normal differentiation pattern and lipid accumulation. However, IL-6 allowed a normal early induction of differentiation with inhibition of Wnt10b and Pref-1, whereas expression of CCAAT/enhancer-binding protein alpha, in contrast to peroxisome proliferator-activated receptor gamma, was markedly reduced. TNFalpha also allowed a normal early induction of differentiation, whereas the terminal differentiation to adipose cells was completely prevented. However, both cytokines induced an inflammatory phenotype of the cells but with different profiles. Remarkably, both IL-6 and TNFalpha maintained and augmented the canonical Wnt signaling associated with low axin and high low density lipoprotein receptor-related protein (LRD), Dishevelled, and beta-catenin levels. TNFalpha, but not IL-6, activated Wnt10b expression, whereas IL-6 increased the apparent phosphorylation of Dishevelled. Thus, both IL-6 and TNFalpha prevent the normal development of preadipocytes to fully differentiated adipose cells and, instead, promote an inflammatory phenotype of the adipocytes. These results provide an explanation as to why obesity and diabetes are associated with both local and systemic inflammation, insulin resistance, and ectopic lipid accumulation.     

Expression of the phospholipid scramblase (PLSCR) gene family during the acute phase response

Phospholipid scramblase 1 (PLSCR1) is a member of PLSCR gene family that has been implicated in multiple cellular processes including movement of phospholipids, gene regulation, immuno-activation, and cell proliferation/apoptosis. In the present study, we identified PLSCR1 as a positive intracellular acute phase protein that is upregulated by LPS in liver, heart, and adipose tissue, but not skeletal muscle. LPS administration resulted in a marked increase in PLSCR1 mRNA and protein levels in the liver. This stimulation occurred rapidly (within 2 h), and was very sensitive to LPS (half-maximal response at 0.1 microg/mouse). Moreover, two other APR-inducers, zymosan and turpentine, also produced significant increases in PLSCR1 mRNA and protein levels, indicating that PLSCR1 was stimulated in a number of models of the APR. To determine signaling pathways by which LPS stimulated PLSCR1, we examined the effect of proinflammatory cytokines in vitro and in vivo. TNFalpha, IL-1beta, and IL-6 all stimulated PLSCR1 in cultured Hep B3 hepatocytes, whereas only TNFalpha stimulated PLSCR1 in cultured 3T3-L1 adipocytes, suggesting cell type-specific effects of cytokines. Furthermore, the LPS-stimulated increase in liver PLSCR1 mRNA was greatly attenuated by 80% in TNFalpha and IL-1beta receptor null mice as compared to wild-type controls. In contrast, PLSCR1 levels in adipose tissue were induced to a similar extent in TNFalpha and IL-1beta receptor null mice and controls. These results indicate that maximal stimulation of PLSCR1 by LPS in liver required TNFalpha and/or IL-1beta, whereas the stimulation of PLSCR1 in adipose tissue is not dependent on TNFalpha and/or IL-1beta. These data provide evidence that PLSCR1 is a positive intracellular acute phase protein with a tissue-specific mechanism for up-regulation.     

Plasma PTX3 protein levels inversely correlate with insulin secretion and obesity, whereas visceral adipose tissue PTX3 gene expression is increased in obesity

Plasma acutephase protein pentraxin 3 (PTX3) concentration is dysregulated in human obesity and metabolic syndrome. Here, we explore its relationship with insulin secretion and sensitivity, obesity markers, and adipose tissue PTX3 gene expression. Plasma PTX3 protein levels were analyzed in a cohort composed of 27 lean [body mass index (BMI) ≤ 25 kg/m(2)] and 48 overweight (BMI 25-30 kg/m(2)) men (cohort 1). In this cohort, plasma PTX3 was negatively correlated with fasting triglyceride levels and insulin secretion after intravenous and oral glucose administration. Plasma PTX3 protein and PTX3 gene expression in visceral (VAT) and subcutaneous (SAT) whole adipose tissue and adipocyte and stromovascular fractions were analyzed in cohort 2, which was composed of 19 lean, 28 overweight, and 15 obese subjects (BMI >30 kg/m(2)). An inverse association with body weight and waist/hip ratio was observed in cohort 2. In VAT depots, PTX3 mRNA levels were higher in subjects with BMI >25 kg/m(2) than in lean subjects, positively correlated with IL-1β mRNA levels, and higher in the adipocyte than stromovascular fraction. Human preadipocyte SGBS cell line was used to study PTX3 production in response to factors that obesity entails. In SGBS adipocytes, PTX3 gene expression was enhanced by IL-1β and TNFα but not IL-6 or insulin. In conclusion, the negative correlation between PTX3 and glucose-stimulated insulin secretion suggests a role for PTX3 in metabolic control. PTX3 gene expression is upregulated in VAT depots in obesity, despite lower plasma PTX3 protein, and by some proinflammatory cytokines in cultured adipocytes.     

Obesity modulates the expression of haptoglobin in the white adipose tissue via TNFalpha.

Increase in adipose mass results in obesity and modulation of several factors in white adipose tissue (WAT). Two important examples are tumor necrosis factor alpha (TNFalpha) and leptin, both of which are upregulated in adipose tissue in obesity. In order to isolate genes differentially expressed in the WAT of genetically obese db/db mice compared to their lean littermates, we performed RNA fingerprinting and identified haptoglobin (Hp), which is significantly upregulated in the obese animals. Hp is a glycoprotein induced by a number of cytokines, LPS (Lipopolysaccharide), and more generally by inflammation. A significant upregulation of WAT Hp expression was also evident in several experimental obese models including the yellow agouti (/) A(y), ob/ob and goldthioglucose-treated mice (10-, 8-, and 7-fold, respectively). To identify the potential signals for an increase in Hp expression in obesity, we examined leptin and TNFalpha in vivo. Wild type animals treated with recombinant leptin did not show any alteration in WAT Hp expression compared to controls that were food restricted to the level of intake of the treated animals. On the other hand, Hp expression was induced in mice transgenically expressing TNFalpha in adipose tissue. Finally, a significant downregulation of WAT Hp mRNA was observed in ob/ob mice deficient in TNFalpha function, when compared to the ob/ob controls. These results demonstrate that haptoglobin expression in WAT is increased in obesity in rodents and TNFalpha is an important signal for this regulation.     

Adipose and liver expression of interleukin (IL)-1 family members in morbid obesity and effects of weight loss

Morbid obesity is associated with a state of chronic inflammation. Interleukin-1 family (IL-1F) cytokine members are produced by human adipose tissue in obesity. Whereas certain IL-1F members such as IL-1β or IL-18 are potently proinflammatory, others such as IL-1 receptor antagonist (IL-1Ra) or IL-37 (formerly IL-1F7) are antiinflammatory. The NLRP3 inflammasome plays a key role in the processing of bioactive IL-1β and IL-18. We investigated the effect of excessive weight loss on subcutaneous adipose tissue and liver expression of IL-1α, IL-1β, IL-18, IL-1Ra, IL-37 and NLRP3. Twenty-one severely obese patients undergoing laparoscopic adjustable gastric banding were studied. Tissue samples were collected before and 6 months after laparoscopic adjustable gastric banding surgery. mRNA expression of all studied IL-1F members, but especially of IL-37, was much higher in subcutaneous/visceral adipose tissue compared with their liver expression. Subcutaneous adipose tissue mRNA expression of IL-1β decreased significantly after extensive weight loss; expression of IL-18 and IL-1Ra did not change, whereas IL-37 expression increased. Weight loss led to a significant reduction in liver IL-1β, IL-18 and IL-1Ra expression, whereas hepatic IL-37 mRNA expression remained stable. Adipose/liver NLRP3 inflammasome and IL-1α expression were not affected by weight loss. Tissue expression of IL-1β, IL-18 and IL-37 were significantly higher in subcutaneous/visceral adipose tissue compared with the liver. In conclusion, expression of IL-1F members is more pronounced in adipose compared with liver tissue in patients with severe obesity. Excessive weight loss changes the adipose and liver expression profile of IL-1F members toward a more antiinflammatory direction.     

Interleukin-17F affects cartilage matrix turnover by increasing the expression of collagenases and stromelysin-1 and by decreasing the expression of their inhibitors and extracellular matrix components in chondrocytes

Interleukin (IL)-17, a proinflammatory cytokine, is produced primarily by activated Th17 cells. IL-17 consists of six ligands that signal through five receptors (IL-17Rs); IL-17A and IL-17F share the highest homology in the family. Matrix metalloproteinases (MMPs) degrade the extracellular matrix during cartilage remodeling whereas tissue inhibitor of metalloproteinases (TIMPs) inhibit the action of MMPs. In the present study, we examined the effect of IL-17F on the degradation and synthesis of the extracellular matrix in cartilage using human articular chondrocytes. We examined the effect of IL-17F on the expression of IL-17Rs, MMPs, TIMPs, type II collagen, aggrecan, link protein, and cyclooxygenases (COXs), as well as on prostaglandin E₂ (PGE₂) production. We also examined the indirect effect of PGE₂ on the above IL-17F-induced/reduced components using NS-398, a specific inhibitor of COX-2. Cells were cultured with or without IL-17F in the presence or absence of either an IL-17R antibody or NS-398 for up to 28 days. Expression of IL-17Rs, MMPs, TIMPs, type II collagen, aggrecan, link protein, and COXs at mRNA and protein levels was determined using real-time polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA), respectively. PGE₂ production was determined by ELISA. The expression of all types of IL-17Rs was detected in chondrocytes. However, IL-17RE expression was extremely low, compared with other IL-17Rs. The expression of MMP-1, MMP-3, MMP-13, and COX-2 as well as PGE₂ production were increased by addition of IL-17F, whereas the expression of IL-17RD, TIMP-2, TIMP-4, type II collagen, aggrecan, link protein, and COX-1 was decreased. The expression of IL-17RA, IL-17RB, IL-17RC, MMP-2, MMP-14, TIMP-1, and TIMP-3 was unaffected by addition of IL-17F. The IL-17R antibody blocked the stimulating/reducing effect of IL-17F on the expression of MMP-1, MMP-3, MMP-13, TIMP-2, TIMP-4, type II collagen, aggrecan, and link protein. NS-398 blocked the reducing effect of IL-17F on aggrecan expression, whereas it did not completely block the stimulating/reducing effects of IL-17F on the expression of MMP-1, MMP-3, MMP-13, TIMP-2, TIMP-4, type II collagen, and link protein. Our results suggest that IL-17F stimulates cartilage degradation by increasing the expression of collagenases (MMP-1 and -13) and stromelysin-1 (MMP-3) and by decreasing expression of their inhibitors (TIMP-2 and -4), type II collagen, aggrecan, and link protein in chondrocytes. Furthermore, our results suggest that the expression of aggrecan, link protein, and TIMP-4 decrease through the autocrine action of PGE₂ in chondrocytes.     

Inflammatory response and matrix metalloproteinases in chronic kidney failure: Modulation by adropin and spexin

Chronic kidney disease is a major global public health problem. The peptide hormones adropin and spexin modulate many physiological functions such as energy balance and glucose, lipid and protein metabolism. However, it is unclear whether these peptides may exert effects on renal damage, tissue remodeling, and inflammatory conditions. In view of the limited information, we aimed to investigate the effect of adropin and spexin on matrix metalloproteinase and inflammatory response genes a rat model of adenine-induced chronic kidney failure. Chronic kidney failure was induced in rats by administering adenine hemisulfate. Renal function was determined in an autoanalyzer. Histopathological modifications were assessed by H&E staining. mRNA expression levels of ALOX 15, COX 1, COX 2, IL-1β, IL-10, IL-17A, IL-18 IL-21, IL-33, KIM-1, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, NGAL, TGFβ1, TIMP-1, and TNFα in kidney tissue were measured by qPCR. Our results showed an increase of 24-h urine volume, serum creatinine, BUN, and urine protein levels in group with adenine-induced CKF. Adropin and spexin treatments decreased urine protein and 24-h urine volume. Renal damage, TIMP-1, IL-33, and MMP-2 increased after CKF induction, while COX 1, MMP-9, and MMP-13 levels were significantly reduced. Furthermore, KIM-1, TIMP-1, IL-33, and MMP-2 were downregulated by spexin treatment. Renal damage, NGAL, TIMP-1 IL-17A, IL-33, MMP-2, and MMP-3 decreased after adropin treatment, while MMP-13 levels were upregulated. Treatment with adropin+spexin decreased KIM-1, NGAL, TIMP-1, IL-1β, IL-17A, IL-18, IL-33, ALOX 15, COX 1, COX 2, TGFβ1, TNFα, MMP-2, MMP-3, and MMP-7, but increased MMP-13 levels. Our findings revealed that inflammatory response and MMP genes were modulated by adropin and spexin. These peptides may have protective effects on inflammation and chronic kidney damage progression.     

Glucocorticoid-regulated adipose tissue secretion of PAI-1, but not IL-6, TNFalpha or leptin in vivo.

OBJECTIVE: Glucocorticoids are well-known regulators of adipose tissue metabolism and endocrine function. The aim of this study was to examine glucocorticoid effect on plasminogen activator inhibitor 1 (PAI-1), tumour necrosis factor alpha (TNFalpha), leptin and interleukin-6 (IL-6) adipose tissue secretion. MATERIAL AND METHODS: Twelve healthy postmenopausal women with mean BMI of 28.9 kg/m(2) (+/- 0.8 SEM) received 25 mg prednisolone daily for 7 days. Before and after glucocorticoid treatment adipose tissue secretion of PAI-1, leptin, IL-6 and TNFalpha were measured, and adipocyte PAI-1 mRNA as well as anthropometrical and bio-chemical data were obtained. RESULTS: Anthropometric measurements remained unaffected. Analyses of venous blood-samples showed a borderline increase of insulin levels (p = 0.062). PAI-1 secretion from adipose tissue increased (1.9 +/- 0.2 vs. 3.5 +/- 0.5 ng/g triglycerides, p = 0.012), but PAI-1 mRNA levels did not (0.19 +/- 0.02 vs. 0.21 +/- 0.04 arbitrary units after normalised to beta-actin, p = 0.51). There were no apparent differences in IL-6, TNFalpha or leptin secretion after glucocorticoid exposure. CONCLUSION: This study shows an increased secretion of PAI-1, but not IL-6, TNFalpha or leptin, from abdominal adipose tissue after in vivo glucocorticoid treatment, which may be a finding of pathophysiological importance given the well-known effect of glucocorticoid excess on metabolic aberrations and cardiovascular morbidity.     

IL-1 family in breast cancer: Potential interplay with leptin and other adipocytokines

Obesity is associated with an increased risk of breast cancer. interleukin-1 (IL-1), a pro-inflammatory cytokine secreted by adipose tissue, is involved in breast cancer development. There is also convincing evidence that other adipocytokines including leptin not only have a role in haematopoiesis, reproduction and immunity but are also growth factors in cancer. Therefore, IL-1 family and leptin family are adipocytokines which could represent a major link between obesity and breast cancer progression. This minireview provides insight into recent findings on the prognostic significance of IL-1 and leptin in mammary tumours, and discusses the potential interplay between IL-1 family members and adipocyte-derived hormones in breast cancer.