S-Methyl Cysteine Sulfoxide Does Not Ameliorate Weight Gain or Hyperlipidemia in Mice Fed a High-Fat Diet.

SCOPE: Higher intake of cruciferous and allium vegetables is associated with lower cardiometabolic risk. Little research has investigated the cardiometabolic effects of S-methyl cysteine sulfoxide (SMCSO), found abundant in these vegetables. This study hypothesizes that SMCSO will blunt development of metabolic syndrome features in mice fed high-fat feed. METHODS AND RESULTS: Fifty C57BL/6 male mice are randomly assigned to standard-chow, high-fat, or high-fat supplemented with low-SMCSO (43 mg kg-1 body weight [BW] day-1), medium-SMCSO (153 mg kg-1 BW day-1), or high-SMCSO (256 mg kg-1 BW day-1) for 12-weeks. High-fat with SMCSO did not prevent diet-induced obesity, glucose intolerance, or hypercholesterolemia. Mice fed high-fat with SMCSO has higher hepatic lipids than mice fed standard-chow or high-fat alone. Urinary SMCSO increases at 6- and 12-weeks in the low-SMCSO group, before reducing 46% and 28% in the medium- and high-SMCSO groups, respectively, at 12-weeks, suggesting possible tissue saturation. Interestingly, two SMCSO-fed groups consume significantly more feed, without significant weight gain. Due to limitations in measuring consumed feed, caution should be taken interpreting these results. CONCLUSION: SMCSO (43-256 mg kg-1 BW day-1) does not ameliorate metabolic syndrome features in high-fat fed mice. Substantial knowledge gaps remain. Further studies should administer SMCSO separately (i.e., gavage), with metabolic studies exploring tissue levels to better understand its physiological action.

TNFSF14-Derived Molecules as a Novel Treatment for Obesity and Type 2 Diabetes.

Obesity is one of the most prevalent metabolic diseases in the Western world and correlates directly with glucose intolerance and insulin resistance, often culminating in Type 2 Diabetes (T2D). Importantly, our team has recently shown that the TNF superfamily (TNFSF) member protein, TNFSF14, has been reported to protect against high fat diet induced obesity and pre-diabetes. We hypothesized that mimics of TNFSF14 may therefore be valuable as anti-diabetic agents. In this study, we use in silico approaches to identify key regions of TNFSF14 responsible for binding to the Herpes virus entry mediator and Lymphotoxin ß receptor. In vitro evaluation of a selection of optimised peptides identified six potentially therapeutic TNFSF14 peptides. We report that these peptides increased insulin and fatty acid oxidation signalling in skeletal muscle cells. We then selected one of these promising peptides to determine the efficacy to promote metabolic benefits in vivo. Importantly, the TNFSF14 peptide 7 reduced high fat diet-induced glucose intolerance, insulin resistance and hyperinsulinemia in a mouse model of obesity. In addition, we highlight that the TNFSF14 peptide 7 resulted in a marked reduction in liver steatosis and a concomitant increase in phospho-AMPK signalling. We conclude that TNFSF14-derived molecules positively regulate glucose homeostasis and lipid metabolism and may therefore open a completely novel therapeutic pathway for treating obesity and T2D.

Metabolic dysfunction induced by a high-fat diet modulates hematopoietic stem and myeloid progenitor cells in brown adipose tissue of mice.

Brown adipose tissue (BAT) may be an important metabolic regulator of whole-body glucose. While important roles have been ascribed to macrophages in regulating metabolic functions in BAT, little is known of the roles of other immune cells subsets, particularly dendritic cells (DCs). Eating a high-fat diet may compromise the development of hematopoietic stem and progenitor cells (HSPCs)-which give rise to DCs-in bone marrow, with less known of its effects in BAT. We have previously demonstrated that ongoing exposure to low-dose ultraviolet radiation (UVR) significantly reduced the 'whitening' effect of eating a high-fat diet upon interscapular (i) BAT of mice. Here, we examined whether this observation may be linked to changes in the phenotype of HSPCs and myeloid-derived immune cells in iBAT and bone marrow of mice using 12-colour flow cytometry. Many HSPC subsets declined in both iBAT and bone marrow with increasing metabolic dysfunction. Conversely, with rising adiposity and metabolic dysfunction, conventional DCs (cDCs) increased in both of these tissues. When compared with a low-fat diet, consumption of a high-fat diet significantly reduced proportions of myeloid, common myeloid and megakaryocyte-erythrocyte progenitors in iBAT, and short-term hematopoietic stem cells in bone marrow. In mice fed the high-fat diet, exposure to low-dose UVR significantly reduced proportions of cDCs in iBAT, independently of nitric oxide release from irradiated skin [blocked using the scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO)], but did not significantly modify HSPC subsets in either tissue. Further studies are needed to determine whether changes in these cell populations contribute towards metabolic dysfunction .

Microvascular changes at different stages of chronic kidney disease.

Patients with progressing chronic kidney disease (CKD) are more likely to experience cardio- and cerebrovascular events than progressing to end-stage renal disease. The authors explored whether retinal microvascular calibers differed with the degree of renal impairment and between the standard and extended optic disk and may serve as a simple additional tool for risk stratification in this highly vulnerable patient cohort. The authors analyzed central retinal arteriolar and venular equivalent calibers (CRAE, CRVE) at different retinal zones (zone B&C) using digital retinal imaging in hypertensive patients with stage 2 (n = 66) or stage 3 CKD (n = 30). Results were adjusted for age, sex, HbA1c, and 24-hour diastolic blood pressure. Mean eGFR was 77.7 ± 8.9 and 48.8 ± 7.9 ml/min/1.73 m2 for stage 2 and 3 CKD, respectively. CRAE and CRVE in zones B and C were significantly lower in patients with stage 3 CKD compared to patients with stage 2 CKD (CRAE-B:141.1 ± 21.4 vs. 130.5 ± 18.9 µm, p = .030; CRAE-C:137.4 ± 19.4 vs 129.2 ± 18.2 µm, p = .049; CRVE-B:220.8 ± 33.0 vs. 206.0 ± 28.4 µm, p = .004; and CRVE-C:215.9 ± 33.0 vs. 201.2 ± 25.1µm, p = .003). In patients with stage 2 CKD, CRAE-B was higher than CRAE-C (141.1 ± 21.4 vs. 137.4 ± 19.4µm, p < .001). In contrast, such a difference was not found in patients with stage 3 CKD. CRAE of both retinal zones correlated with eGFR for the entire cohort. In patients with stage 3 CKD, retinal narrowing is more pronounced compared to patients with stage 2 CKD. Whether the novel observation of difference in arteriolar caliber between zones B and C in stage 2 CKD could serve as an early marker of CKD progression warrants further investigation.

Low-dose UV radiation before running wheel access activates brown adipose tissue.

In previous preclinical studies, low (non-burning) doses of UV radiation (UVR) limited weight gain and metabolic dysfunction in mice fed with a high-fat diet. Here, we explored the effects of low-dose UVR on physical activity and food intake and mechanistic pathways in interscapular brown adipose tissue (iBAT). Young adult C57Bl/6J male mice, housed as individuals, were fed a high-fat diet and exposed to low-dose UVR (sub-oedemal, 1 kJ/m2 UVB, twice-a-week) or 'mock' treatment, with or without running wheel access (2 h, for 'moderate' physical activity) immediately after phototherapy. There was no difference in distance run in mice exposed to UVR or mock-treated over 12 weeks of exposure to running wheels (P = 0.14). UVR (alone) did not significantly affect food intake, adiposity, or signs of glucose dysfunction. Access to running wheels increased food intake (after 10 weeks, P ≤ 0.02) and reduced gonadal white adipose tissue and iBAT mass (P ≤ 0.03). Body weight and hepatic steatosis were lowest in mice exposed to UVR with running wheel access. In the iBAT of mice exposed to UVR and running wheels, elevated Atgl, Cd36, Fasn, Igf1, Pparγ, and Ucp1 mRNAs and reduced CD11c on F4-80 + MHC class II+ macrophages were observed, while renal Sglt2 mRNA levels were increased, compared to high-fat diet alone (P ≤ 0.03). Blood levels of 25-hydroxyvitamin D were not increased by exposure to UVR and/or access to running wheels. In conclusion, when combined with physical activity, low-dose UVR may more effectively limit adiposity (specifically, body weight and hepatic steatosis) and modulate metabolic and immune pathways in iBAT.

May Measurement Month 2017: an analysis of blood pressure screening results from Australia-South-East Asia and Australasia.

Increased blood pressure (BP) is the single biggest contributing risk factor to the global disease burden. May Measurement Month (MMM) is a global initiative of the International Society of Hypertension aimed at raising awareness of high BP. In Australia, hypertension affects around six million adults and continues to remain the greatest attributable cause of cardiovascular mortality and morbidity (48.3%), stroke deaths (28%), and kidney disease (14%). An opportunistic cross-sectional survey was carried out during May 2017 predominantly in capital cities across Australia which included adult volunteers. Blood pressure measurement, the definition of hypertension and statistical analysis followed the standard MMM protocol. Additional information obtained included anthropometric data and responses to questionnaires on demographic, lifestyle, and environmental factors. Data were collected from 3817 individuals. After multiple imputation, of the 3758 individuals for whom a mean of the second and third BP reading was available, 1188 (31.2%) had hypertension. Of 3213 individuals not receiving antihypertensive treatment, 591 (18.4%) were hypertensive, and 239 (40.1%) of the 596 individuals receiving treatment had uncontrolled BP. Adjusted BP was higher in association with antihypertensive medication, cerebrovascular disease, smoking, and alcohol consumption. Blood pressure was higher when measured on the right arm and on Tuesdays. MMM17 was one of the largest BP screening campaigns undertaken in Australia using standardized BP measurements. In line with previous surveys, around one-third of screened adults had hypertension and approximately 40% of treated individuals remained uncontrolled. These results suggest that opportunistic screening can identify significant numbers with raised BP.

Maternal high fat diet compromises survival and modulates lung development of offspring, and impairs lung function of dams (female mice).

BACKGROUND: Epidemiological studies have identified strong relationships between maternal obesity and offspring respiratory dysfunction; however, the causal direction is not known. We tested whether maternal obesity alters respiratory function of offspring in early life. METHODS: Female C57Bl/6 J mice were fed a high or low fat diet prior to and during two rounds of mating and resulting pregnancies with offspring lung function assessed at 2 weeks of age. The lung function of dams was measured at 33 weeks of age. RESULTS: A high fat diet caused significant weight gain prior to conception with dams exhibiting elevated fasting glucose, and glucose intolerance. The number of surviving litters was significantly less for dams fed a high fat diet, and surviving offspring weighed more, were longer and had larger lung volumes than those born to dams fed a low fat diet. The larger lung volumes significantly correlated in a linear fashion with body length. Pups born from the second pregnancy had reduced tissue elastance compared to pups born from the first pregnancy, regardless of the dam's diet. As there was reduced offspring survival born to dams fed a high fat diet, the statistical power of lung function measures of offspring was limited. There were signs of increased inflammation in the bronchoalveolar lavage fluid of dams (but not offspring) fed a high fat diet, with more tumour necrosis factor-α, interleukin(IL)-5, IL-33 and leptin detected. Dams that were fed a high fat diet and became pregnant twice had reduced fasting glucose immediately prior to the second mating, and lower levels of IL-33 and leptin in bronchoalveolar lavage fluid. CONCLUSIONS: While maternal high fat diet compromised litter survival, it also promoted somatic and lung growth (increased lung volume) in the offspring. Further studies are required to examine downstream effects of this enhanced lung volume on respiratory function in disease settings.

Sympathetic Activation in Hypertensive Chronic Kidney Disease - A Stimulus for Cardiac Arrhythmias and Sudden Cardiac Death?

Studies have revealed a robust and independent correlation between chronic kidney disease (CKD) and cardiovascular (CV) events, including death, heart failure, and myocardial infarction. Recent clinical trials extend this range of adverse CV events, including malignant ventricular arrhythmias and sudden cardiac death (SCD). Moreover, other studies point out that cardiac structural and electrophysiological changes are a common occurrence in this population. These processes are likely contributors to the heightened hazard of arrhythmias in CKD population and may be useful indicators to detect patients who are at a higher SCD risk. Sympathetic overactivity is associated with increased CV risk, specifically in the population with CKD, and it is a central feature of the hypertensive state, occurring early in its clinical course. Sympathetic hyperactivity is already evident at the earliest clinical stage of CKD and is directly related to the progression of renal failure, being most pronounced in those with end-stage renal disease. Sympathetic efferent and afferent neural activity in kidney failure is a crucial facilitator for the perpetuation and evolvement of the disease. Here, we will revisit the role of the feedback loop of the sympathetic neural cycle in the context of CKD and how it may aggravate several of the risk factors responsible for causing SCD. Targeting the overactive sympathetic nervous system therapeutically, either pharmacologically or with newly available device-based approaches, may prove to be a pivotal intervention to curb the substantial burden of cardiac arrhythmias and SCD in the high-risk population of patients with CKD.

Shining LIGHT on the metabolic role of the cytokine TNFSF14 and the implications on hepatic IL-6 production.

The cytokine Tumor Necrosis Factor Superfamily member 14, TNFSF14 (or LIGHT), is a controversial player in numerous diseases. We investigated the role of endogenously expressed TNFSF14 in diet-induced obesity in vivo. Firstly, we studied the effects of Tnfsf14 ablation on the development of obesity, glucose intolerance, insulin resistance, steatosis, tissue inflammation, and mitochondrial respiration in the liver. Secondly, we examined the role of TNFSF14 expression in hematopoietic cells on obesity and insulin sensitivity. Male Tnfsf14 knockout (KO) and wild type mice were fed chow or high fat diet (HFD) for 12 weeks and were assessed for weight gain, glucose intolerance, insulin resistance, hepatosteatosis, mitochondrial dysfunction, and cytokine expression. Wild-type mice were also reconstituted with bone marrow cells from Tnfsf14 knockout mice and were fed chow or HFD for 12 weeks. These mice were examined for weight gain and insulin resistance. HFD fed mice had elevated circulating levels of serum TNFSF14. Liver and white adipose tissue are potential sources of this elevated TNFSF14. Tnfsf14 deficient mice displayed increased obesity, glucose intolerance, insulin resistance, hepatosteatosis, and mitochondrial dysfunction compared to control mice on a HFD. Hepatic cytokine profiling pointed to a potential novel role of decreased IL-6 in the metabolic disturbances in obesogenic Tnfsf14 knockout mice. Bone marrow cells from Tnfsf14 deficient mice appeared to promote diet-induced obesity, insulin resistance and reduced FGF21 levels in white adipose tissue and liver. Our novel data suggest that Tnfsf14 ablation exacerbates parameters of the metabolic syndrome under high fat feeding conditions and provides evidence to support the development of TNFSF14 agonists as potential therapeutics in diet-induced obesity.

Role of the sympathetic nervous system in regulation of the sodium glucose cotransporter 2.

BACKGROUND: The sympathetic nervous system (SNS) regulates glucose metabolism in various organs including the kidneys. The sodium glucose cotransporter 2 (SGLT2) mediates glucose reabsorption in renal proximal tubules and its inhibition has been shown to improve glucose control, cardiovascular and renal outcomes. We hypothesized that SNS-induced alterations of glucose metabolism may be mediated via regulation of SGLT2. METHOD: We used human renal proximal tubule cells to investigate the effects of noradrenaline on SGLT2 regulation. Mice fed a high-fat diet were oral gavaged with dapagliflozin and the expression of noradrenaline and tyrosine hydroxylase was measured in the kidney and heart. RESULTS: Noradrenaline treatment resulted in a pronounced increase in SGLT2 and interleukin (IL)-6 expression in HK2 cells and promoted translocation of SGLT2 to the cell surface. In vivo, dapagliflozin treatment resulted in marked glucosuria in high-fat diet-fed mice. SGLT2 inhibition significantly reduced high-fat diet-induced elevations of tyrosine hydroxylase and noradrenaline in the kidney and heart. We also aimed to assess the levels of hypertension-related cytokines in the kidneys of our mice treated with and without dapagliflozin. Excitingly, we demonstrate that SGLT2 inhibition with dapagliflozin promoted a trend towards reduced tumour necrosis factor-alpha and elevated IL-1ß protein levels in the kidney. CONCLUSION: Our in-vitro and in-vivo studies provide first evidence for an important cross-talk between the SNS and SGLT2 regulation that may not only account for SNS-induced alterations of glucose metabolism but potentially contribute to cardiovascular and renal protection observed with SGLT2 inhibitors.

ADAM19: A Novel Target for Metabolic Syndrome in Humans and Mice.

Obesity is one of the most prevalent metabolic diseases in the Western world and correlates directly with insulin resistance, which may ultimately culminate in type 2 diabetes (T2D). We sought to ascertain whether the human metalloproteinase A Disintegrin and Metalloproteinase 19 (ADAM19) correlates with parameters of the metabolic syndrome in humans and mice. To determine the potential novel role of ADAM19 in the metabolic syndrome, we first conducted microarray studies on peripheral blood mononuclear cells from a well-characterised human cohort. Secondly, we examined the expression of ADAM19 in liver and gonadal white adipose tissue using an in vivo diet induced obesity mouse model. Finally, we investigated the effect of neutralising ADAM19 on diet induced weight gain, insulin resistance in vivo, and liver TNF-α levels. Significantly, we show that, in humans, ADAM19 strongly correlates with parameters of the metabolic syndrome, particularly BMI, relative fat, HOMA-IR, and triglycerides. Furthermore, we identified that ADAM19 expression was markedly increased in the liver and gonadal white adipose tissue of obese and T2D mice. Excitingly, we demonstrate in our diet induced obesity mouse model that neutralising ADAM19 therapy results in weight loss, improves insulin sensitivity, and reduces liver TNF-α levels. Our novel data suggest that ADAM19 is pro-obesogenic and enhances insulin resistance. Therefore, neutralisation of ADAM19 may be a potential therapeutic approach to treat obesity and T2D.

Sub-erythemal ultraviolet radiation reduces metabolic dysfunction in already overweight mice.

Exposure to sunlight may limit cardiometabolic risk. In our previous studies, regular exposure to sub-erythemal (non-burning) ultraviolet radiation (UVR) reduced signs of adiposity and cardiometabolic dysfunction in mice fed a high-fat diet. Some of the observed effects were dependent on skin release of nitric oxide after UVR exposure. Here, we examine the effects of sub-erythemal UVR on signs of adiposity and metabolic dysfunction in already overweight mice, comparing the effects of two sunlamps with distinct emitted light spectra. Mice were fed a high-fat diet from 8 weeks of age, with UVR administered twice a week from 14 weeks of age until they were killed at 20 weeks of age. Mice were irradiated with the same dose of UVB radiation (1 kJ/m2) from either FS40 (65% UVB, 35% UVA) or CLEO (4% UVB, 96% UVA) sunlamps, but substantially more UVA from the latter. FS40 UVR (but not CLEO UVR) significantly reduced mouse weights and weight gain, compared to mice fed a high-fat diet (only). These effects were dependent on nitric oxide. Conversely, CLEO UVR (but not FS40 UVR) significantly reduced circulating LDL cholesterol. Both light sources reduced fasting insulin levels, and the extent of hepatic steatosis; the latter was reversed by topical application of cPTIO, suggesting an important role for skin release of nitric oxide in preventing hepatic lipid accumulation. These results suggest that there may be a number of benefits achieved by regular exposure to safe (non-burning) levels of sunlight or UV-containing phototherapy, with effects potentially dependent on the predominance of the wavelengths of UVR administered.

Blocking IL-6 trans-signaling prevents high-fat diet-induced adipose tissue macrophage recruitment but does not improve insulin resistance.

Interleukin-6 (IL-6) plays a paradoxical role in inflammation and metabolism. The pro-inflammatory effects of IL-6 are mediated via IL-6 "trans-signaling," a process where the soluble form of the IL-6 receptor (sIL-6R) binds IL-6 and activates signaling in inflammatory cells that express the gp130 but not the IL-6 receptor. Here we show that trans-signaling recruits macrophages into adipose tissue (ATM). Moreover, blocking trans-signaling with soluble gp130Fc protein prevents high-fat diet (HFD)-induced ATM accumulation, but does not improve insulin action. Importantly, however, blockade of IL-6 trans-signaling, unlike complete ablation of IL-6 signaling, does not exacerbate obesity-induced weight gain, liver steatosis, or insulin resistance. Our data identify the sIL-6R as a critical chemotactic signal for ATM recruitment and suggest that selectively blocking IL-6 trans-signaling may be a more favorable treatment option for inflammatory diseases, compared with current treatments that completely block the action of IL-6 and negatively impact upon metabolic homeostasis.

Supplementation of a high-fat diet with chlorogenic acid is associated with insulin resistance and hepatic lipid accumulation in mice.

The increasing prevalence of the metabolic syndrome requires a greater need for therapeutic and prevention strategies. Higher coffee consumption is consistently associated with a lower risk of type 2 diabetes in population studies. Dietary polyphenols have been linked to benefits on several features of the metabolic syndrome. Chlorogenic acid (CGA), a major component of coffee, is one of the most consumed polyphenols in the diet. In our study, we conducted a controlled dietary intervention over 12 weeks in male mice. There were three dietary groups: (i) normal diet, (ii) high-fat diet, and (iii) high-fat diet + CGA. We assessed the effect of CGA at a physiologically obtainable dose (1 g/kg of diet) on high-fat-diet-induced obesity, glucose intolerance, insulin resistance, and also fatty acid oxidation and insulin signaling in C57BL/6 male mice. Supplementation of CGA in the high-fat diet did not reduce body weight compared to mice fed the high-fat diet alone (p = 0.32). CGA resulted in increased insulin resistance compared to mice fed a high-fat diet only (p < 0.05). CGA resulted in decreased phosphorylation of AMP-activated protein kinase (AMPK) (p < 0.001) and acetyl carboxylase ß (ACCß), a downstream target of AMPK (p < 0.05), in liver. The liver of mice fed a high-fat diet supplemented with CGA had a higher lipid content (p < 0.05) and more steatosis relative to mice fed a high-fat diet only, indicating impaired fatty acid oxidation. This study suggests that CGA supplementation in a high-fat diet does not protect against features of the metabolic syndrome in diet-induced obese mice.

ADAM28 is elevated in humans with the metabolic syndrome and is a novel sheddase of human tumour necrosis factor-α.

Metalloproteinases are implicated in cleaving numerous proinflammatory mediators from the cell surface. Interestingly, the elevated levels of tumour necrosis factor-α (TNF-α) have been associated with the metabolic syndrome. We aimed to ascertain whether the human metalloproteinase ADAM28 correlates with parameters of the metabolic syndrome and whether ADAM28 is a novel sheddase of human TNF-α. To identify novel metalloproteinases associated with the metabolic syndrome, we conducted microarray studies on peripheral blood mononuclear cells from a well characterised human cohort. Human ADAM28 and TNF-α were overexpressed and ADAM28 expression or activity was reduced with small-interfering RNA (siRNA) or pharmacological inhibition. TNF-α levels were measured in cell supernatant by enzyme-linked immunosorbent assay. We also conducted ADAM28 inhibition studies in human THP-1 macrophages. Human ADAM28 expression levels were positively correlated with parameters of the metabolic syndrome. When human ADAM28 and TNF-α were overexpressed in HEK293 cells, both proteins co-localised, co-immunoprecipitated and promoted TNF-α shedding. The shedding was significantly reduced when ADAM28 activity was inhibited or ADAM28 expression was downregulated. In human THP-1 macrophages, endogenous ADAM28 and TNF-α were co-expressed and TNF-α shedding was significantly reduced when ADAM28 was inhibited by pharmacological inhibition or siRNA knockdown. Our data suggest a novel mechanistic role for the metalloproteinase ADAM28 in inflammation, obesity and type 2 diabetes.

Contraction-induced interleukin-6 gene transcription in skeletal muscle is regulated by c-Jun terminal kinase/activator protein-1.

Exercise increases the expression of the prototypical myokine IL-6, but the precise mechanism by which this occurs has yet to be identified. To mimic exercise conditions, C2C12 myotubes were mechanically stimulated via electrical pulse stimulation (EPS). We compared the responses of EPS with the pharmacological Ca(2+) carrier calcimycin (A23187) because contraction induces marked increases in cytosolic Ca(2+) levels or the classical IκB kinase/NFκB inflammatory response elicited by H(2)O(2). We demonstrate that, unlike H(2)O(2)-stimulated increases in IL-6 mRNA, neither calcimycin- nor EPS-induced IL-6 mRNA expression is under the transcriptional control of NFκB. Rather, we show that EPS increased the phosphorylation of JNK and the reporter activity of the downstream transcription factor AP-1. Furthermore, JNK inhibition abolished the EPS-induced increase in IL-6 mRNA and protein expression. Finally, we observed an exercise-induced increase in both JNK phosphorylation and IL-6 mRNA expression in the skeletal muscles of mice after 30 min of treadmill running. Importantly, exercise did not increase IL-6 mRNA expression in skeletal muscle-specific JNK-deficient mice. These data identify a novel contraction-mediated transcriptional regulatory pathway for IL-6 in skeletal muscle.

Obesity-induced renal impairment is exacerbated in interleukin-6-knockout mice.

AIM: Interleukin-6 (IL-6) is secreted from adipose tissue and thought to contribute to obesity-related disorders. The aim of this study was to assess if IL-6-knockout (IL-6-/-) mice would develop obesity-induced renal impairment. METHODS: Wild-type (WT) and IL-6-/- mice were high-fat fed (HFF) for 16 weeks to induce obesity. At the end of the study, renal function was measured via albumin/creatinine ratio and serum creatinine levels, using enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). Glomerulosclerotic index (GSI) was scored in periodic acid Schiff-stained sections and collagen IV accumulation was assessed by immunohistochemistry. Renal cortical tumour growth factor beta (TGF-ß(1) ) activity and monocyte chemotactic protein-1 (MCP-1) levels were measured via ELISA. RESULTS: Renal IL-6 concentrations were increased with obesity. Although both WT HFF and IL-6-/- HFF mice exhibited renal impairment as measured by increased serum creatinine and urinary albumin/creatinine ratios, this was exacerbated in IL-6-/- mice. Obese mice had renal activation of cortical TGF-ß(1) , which was also higher in IL-6-/- mice. Collagen IV staining was not affected by obesity. GSI was increased with obesity in both WT and IL-6-/- mice. CONCLUSION: Obese IL-6-/- mice demonstrated renal functional and structural abnormalities above that seen in obese WT mice. We suggest that absence or low IL-6 levels may be an important accelerating factor implicated in the development and progression of obesity-induced renal disease.

Interleukin-6 attenuates insulin-mediated increases in endothelial cell signaling but augments skeletal muscle insulin action via differential effects on tumor necrosis factor-alpha expression.

OBJECTIVE: The cytokine interleukin-6 (IL-6) stimulates AMP-activated protein kinase (AMPK) and insulin signaling in skeletal muscle, both of which result in the activation of endothelial nitric oxide synthase (eNOS). We hypothesized that IL-6 promotes endothelial cell signaling and capillary recruitment in vivo, contributing to increased glucose uptake. RESEARCH DESIGN AND METHODS: The effect of IL-6 with and without insulin on AMPK, insulin, and eNOS signaling in and nitric oxide (NO) release from human aortic endothelial cells (HAECs) was examined. The physiological significance of these in vitro signaling events was assessed by measuring capillary recruitment in rats during control and euglycemic-hyperinsulinemic clamps with or without IL-6 infusion. RESULTS: IL-6 blunted increases in insulin signaling, eNOS phosphorylation (Ser1177), and NO production and reduced phosphorylation of AMPK in HAEC in vitro and capillary recruitment in vivo. In contrast, IL-6 increased Akt phosphorylation (Ser473) in hindlimb skeletal muscle and enhanced whole-body glucose disappearance and glucose uptake during the clamp. The differences in endothelial cell and skeletal muscle signaling were mediated by the cell-specific, additive effects of IL-6 and insulin because this treatment markedly increased tumor necrosis factor (TNF)-alpha protein expression in HAECs without any effect on TNF-alpha in skeletal muscle. When HAECs were incubated with a TNF-alpha-neutralizing antibody, the negative effects of IL-6 on eNOS signaling were abolished. CONCLUSIONS: In the presence of insulin, IL-6 contributes to aberrant endothelial cell signaling because of increased TNF-alpha expression.