Plasma Docosahexaenoic Acid and Eicosapentaenoic Acid Concentrations Are Positively Associated with Brown Adipose Tissue Activity in Humans.

Brown adipose tissue (BAT) activation is a possible therapeutic strategy to increase energy expenditure and improve metabolic homeostasis in obesity. Recent studies have revealed novel interactions between BAT and circulating lipid species-in particular, the non-esterified fatty acid (NEFA) and oxylipin lipid classes. This study aimed to identify individual lipid species that may be associated with cold-stimulated BAT activity in humans. A panel of 44 NEFA and 41 oxylipin species were measured using mass-spectrometry-based lipidomics in the plasma of fourteen healthy male participants before and after 90 min of mild cold exposure. Lipid measures were correlated with BAT activity measured via 18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT), along with norepinephrine (NE) concentration (a surrogate marker of sympathetic activity). The study identified a significant increase in total NEFA concentration following cold exposure that was positively associated with NE concentration change. Individually, 33 NEFA and 11 oxylipin species increased significantly in response to cold exposure. The concentration of the omega-3 NEFA, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) at baseline was significantly associated with BAT activity, and the cold-induced change in 18 NEFA species was significantly associated with BAT activity. No significant associations were identified between BAT activity and oxylipins.

Apo AI Nanoparticles Delivered Post Myocardial Infarction Moderate Inflammation.

RATIONALE: Decades of research have examined immune-modulatory strategies to protect the heart after an acute myocardial infarction and prevent progression to heart failure but have failed to translate to clinical benefit. OBJECTIVE: To determine anti-inflammatory actions of n-apo AI (Apo AI nanoparticles) that contribute to cardiac tissue recovery after myocardial infarction. METHODS AND RESULTS: Using a preclinical mouse model of myocardial infarction, we demonstrate that a single intravenous bolus of n-apo AI (CSL111, 80 mg/kg) delivered immediately after reperfusion reduced the systemic and cardiac inflammatory response. N-apo AI treatment lowered the number of circulating leukocytes by 30±7% and their recruitment into the ischemic heart by 25±10% (all P<5.0×10-2). This was associated with a reduction in plasma levels of the clinical biomarker of cardiac injury, cardiac troponin-I, by 52±17% (P=1.01×10-2). N-apo AI reduced the cardiac expression of chemokines that attract neutrophils and monocytes by 60% to 80% and lowered surface expression of integrin CD11b on monocytes by 20±5% (all P<5.0×10-2). Fluorescently labeled n-apo AI entered the infarct and peri-infarct regions and colocalized with cardiomyocytes undergoing apoptosis and with leukocytes. We further demonstrate that n-apo AI binds to neutrophils and monocytes, with preferential binding to the proinflammatory monocyte subtype and partially via SR-BI (scavenger receptor BI). In patients with type 2 diabetes, we also observed that intravenous infusion of the same n-apo AI (CSL111, 80 mg/kg) similarly reduced the level of circulating leukocytes by 12±5% (all P<5.0×10-2). CONCLUSIONS: A single intravenous bolus of n-apo AI delivered immediately post-myocardial infarction reduced the systemic and cardiac inflammatory response through direct actions on both the ischemic myocardium and leukocytes. These data highlight the anti-inflammatory effects of n-apo AI and provide preclinical support for investigation of its use for management of acute coronary syndromes in the setting of primary percutaneous coronary interventions.

Matrix-Induced Autologous Chondrocyte Implantation (MACI) Grafting for Osteochondral Lesions of the Talus.

BACKGROUND: Matrix-induced autologous chondrocyte implantation (MACI) is an established treatment method for larger joints and has shown promising results in the ankle as well. We present a series of patients after ankle MACI with long-term follow-up of clinical and radiological outcomes. METHODS: We present the follow-up of 15 patients who underwent MACI grafting from August 2003 to February 2006. The mean follow-up was 12.9 years. Clinical evaluations were conducted using the American Orthopaedic Foot & Ankle Society (AOFAS), Foot and Ankle Activity Measurement (FAAM), and visual analog scale (VAS) scoring systems and the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system for radiological evaluation. RESULTS: The mean size of the talar osteochondral defects was 204 mm2. We found a significant improvement in mean AOFAS score from 60 preoperatively to a mean of 84 at 12 years postoperatively. The 12-year FAAM score for Activities of Daily Living was 89% (range, 62%-99%). The mean 12-year MOCART score was 65 points (range, 30-100 points) with significant agreement between assessors (P < .001). However, the MOCART scores did not correlate with the FAAM scores (P = .86). CONCLUSION: Considering our long-term follow-up, we believe MACI is a reliable treatment method for talar osteochondral defects providing lasting pain relief and satisfying clinical results. However, with an equivalent outcome, but at higher costs, and the requirement for 2 operative procedures, the results do not seem to be superior to other established methods. The clinical utility of the MOCART score requires further scrutiny since we were not able to show any correlation between the score and clinical outcome. LEVEL OF EVIDENCE: Level IV, case series.

HDL Phospholipids, but Not Cholesterol Distinguish Acute Coronary Syndrome From Stable Coronary Artery Disease.

Background Although acute coronary syndromes (ACS) are a major cause of morbidity and mortality, relationships with biologically active lipid species potentially associated with plaque disruption/erosion in the context of their lipoprotein carriers are indeterminate. The aim was to characterize lipid species within lipoprotein particles which differentiate ACS from stable coronary artery disease. Methods and Results Venous blood was obtained from 130 individuals with de novo presentation of an ACS (n=47) or stable coronary artery disease (n=83) before coronary catheterization. Lipidomic measurements (533 lipid species; liquid chromatography electrospray ionization/tandem mass spectrometry) were performed on whole plasma as well as 2 lipoprotein subfractions: apolipoprotein A1 (apolipoprotein A, high-density lipoprotein) and apolipoprotein B. Compared with stable coronary artery disease, ACS plasma was lower in phospholipids including lyso species and plasmalogens, with the majority of lipid species differing in abundance located within high-density lipoprotein (high-density lipoprotein, 113 lipids; plasma, 73 lipids). Models including plasma lipid species alone improved discrimination between the stable and ACS groups by 0.16 (C-statistic) compared with conventional risk factors. Models utilizing lipid species either in plasma or within lipoprotein fractions had a similar ability to discriminate groups, though the C-statistic was highest for plasma lipid species (0.80; 95% CI, 0.75-0.86). Conclusions Multiple lysophospholipids, but not cholesterol, featured among the lipids which were present at low concentration within high-density lipoprotein of those presenting with ACS. Lipidomics, when applied to either whole plasma or lipoprotein fractions, was superior to conventional risk factors in discriminating ACS from stable coronary artery disease. These associative mechanistic insights elucidate potential new preventive, prognostic, and therapeutic avenues for ACS which require investigation in prospective analyses.

Acute effects of active breaks during prolonged sitting on subcutaneous adipose tissue gene expression: an ancillary analysis of a randomised controlled trial.

Active breaks in prolonged sitting has beneficial impacts on cardiometabolic risk biomarkers. The molecular mechanisms include regulation of skeletal muscle gene and protein expression controlling metabolic, inflammatory and cell development pathways. An active communication network exists between adipose and muscle tissue, but the effect of active breaks in prolonged sitting on adipose tissue have not been investigated. This study characterized the acute transcriptional events induced in adipose tissue by regular active breaks during prolonged sitting. We studied 8 overweight/obese adults participating in an acute randomized three-intervention crossover trial. Interventions were performed in the postprandial state and included: (i) prolonged uninterrupted sitting; or prolonged sitting interrupted with 2-minute bouts of (ii) light- or (iii) moderate-intensity treadmill walking every 20 minutes. Subcutaneous adipose tissue biopsies were obtained after each condition. Microarrays identified 36 differentially expressed genes between the three conditions (fold change ≥0.5 in either direction; p < 0.05). Pathway analysis indicated that breaking up of prolonged sitting led to differential regulation of adipose tissue metabolic networks and inflammatory pathways, increased insulin signaling, modulation of adipocyte cell cycle, and facilitated cross-talk between adipose tissue and other organs. This study provides preliminary insight into the adipose tissue regulatory systems that may contribute to the physiological effects of interrupting prolonged sitting.

Acute metabolic and cardiovascular effects of mirabegron in healthy individuals.

AIMS: To quantify acute energy expenditure, supraclavicular skin temperature and cardiovascular responses to four doses of the ß3-adrenoceptor agonist, mirabegron. MATERIALS AND METHODS: A total of 17 individuals (11 men, six women) participated in this ascending-dose study, receiving single 50-, 100-, 150- and 200-mg doses of mirabegron on four separate days with 3 to 14 days wash-out between each dose. All variables were measured each visit from baseline to 180 minutes post mirabegron treatment. To determine brown adipose tissue (BAT) thermogenic efficacy at each dose, energy expenditure and supraclavicular skin temperature were compared from baseline to 180 minutes post mirabegron treatment. To examine safety, changes in cardiovascular variables at 100, 150 and 200 mg were compared with the standard clinical dose of 50 mg. RESULTS: Energy expenditure significantly increased after the 100- (35.6 ± 5.4 kJ/h) and 200-mg (35.6 ± 13.1 kJ/h) doses (P ≤ 0.05), and trended towards an increase after 150 mg (24.1 ± 13.6 kJ/h). Supraclavicular skin temperature increased after 50- (0.22 ± 0.1°C), 100- (0.30 ± 0.1°C) and 150-mg mirabegron doses (0.29 ± 0.1°C; P ≤ 0.05). The change in systolic blood pressure was greater after 150- (7.1 ± 1.3 mm Hg) and 200-mg doses (9.3 ± 1.9 mm Hg) than after the 50-mg dose (2.2 ± 1.3 mm Hg; P ≤ 0.05). The change in heart rate was greater after 200 mg (9.0 ± 2.2 bpm) compared with 50 mg (2.9 ± 1.4 bpm; P ≤ 0.05). CONCLUSIONS: A 100-mg dose of mirabegron increases energy expenditure and supraclavicular skin temperature in a ß3-adrenoceptor-specific manner, without the off-target elevations in blood pressure or heart rate observed at higher doses.

Brown adipose tissue and lipid metabolism: New strategies for identification of activators and biomarkers with clinical potential.

Development of therapeutic agents directed towards increasing brown adipose tissue (BAT) energy expenditure to combat obesity and its comorbidities is currently an area of intense research. Both preclinical and clinical studies have suggested a potentially significant role for BAT in regulating whole body energy expenditure as well as glucose and lipid metabolism. Lipids, particularly long chain fatty acids (LCFAs), are recognized as integral substrates in mediating the primary heat-producing functions of BAT, and to date thought to be principally sourced from stored intracellular lipid droplets. While this prior understanding is not disputed, recent evidence has demonstrated the importance of lipids derived from the circulation, including those from dietary sources and from tissue lipolysis, especially white adipose tissue lipolysis. Moreover, recent studies have shed further light on a potential role for BAT as an autocrine, paracrine and endocrine organ, with lipids as key signaling molecules. Advances in metabolomics have enabled high-resolution exploration of biomolecules that may be associated with various physiological processes and potentially pathological states. Such approaches have led to several novel lipid species recently being associated with BAT function and dysfunction. Further exploration of the circulating lipidome will likely reveal additional novel BAT biomarkers that can inform development of BAT-directed therapies. This review will address current progress and new strategies to identify and characterize BAT-associated lipids which may represent both novel activators and/or activity biomarkers with both research and clinical utility.

Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans.

AIMS/HYPOTHESIS: Increasing brown adipose tissue (BAT) activity is a possible therapeutic strategy to increase energy expenditure and glucose and lipid clearance to ameliorate obesity and associated comorbidities. The thiazolidinedione (TZD) class of glucose-lowering drugs increase BAT browning in preclinical experimental models but whether these actions extend to humans in vivo is unknown. The aim of this study was to determine the effect of pioglitazone treatment on adipocyte browning and adaptive thermogenesis in humans. METHODS: We first examined whether pioglitazone treatment of cultured human primary subacromioclavicular-derived adipocytes induced browning. Then, in a blinded, placebo-controlled, parallel trial, conducted within the Baker Institute clinical research laboratories, 14 lean male participants who were free of cardiometabolic disease were randomised to receive either placebo (lactose; n = 7, age 22 ± 1 years) or pioglitazone (45 mg/day, n = 7, age 21 ± 1 years) for 28 days. Participants were allocated to treatments by Alfred Hospital staff independent from the study via electronic generation of a random number sequence. Researchers conducting trials and analysing data were blind to treatment allocation. The change in cold-stimulated BAT activity, assessed before and after the intervention by [18F]fluorodeoxyglucose uptake via positron emission tomography/computed tomography in upper thoracic and cervical adipose tissue, was the primary outcome measure. Energy expenditure, cardiovascular responses, core temperature, blood metabolites and hormones were measured in response to acute cold exposure along with body composition before and after the intervention. RESULTS: Pioglitazone significantly increased in vitro browning and adipogenesis of adipocytes. In the clinical trial, cold-induced BAT maximum standardised uptake value was significantly reduced after pioglitazone compared with placebo (-57 ± 6% vs -12 ± 18%, respectively; p < 0.05). BAT total glucose uptake followed a similar but non-significant trend (-50 ± 10% vs -6 ± 24%, respectively; p = 0.097). Pioglitazone increased total and lean body mass compared with placebo (p < 0.05). No other changes between groups were detected. CONCLUSIONS/INTERPRETATION: The disparity in the actions of pioglitazone on BAT between preclinical experimental models and our in vivo human trial highlight the imperative to conduct human proof-of-concept studies as early as possible in BAT research programmes aimed at therapeutic development. Our clinical trial findings suggest that reduced BAT activity may contribute to weight gain associated with pioglitazone and other TZDs. TRIAL REGISTRATION: ClinicalTrials.gov NCT02236962 FUNDING: This work was supported by the Diabetes Australia Research Program and OIS scheme from the Victorian State Government.

Correction to: Pioglitazone reduces cold-induced brown fat glucose uptake despite induction of browning in cultured human adipocytes: a randomised, controlled trial in humans.

The baseline insulin data given in Table 1 for the placebo group were incorrectly reported as 51 ± 10 pmol/l instead of 48 ± 10 pmol/l. This mistake also impacts on data reported in Table 4.

High-density lipoprotein delivered after myocardial infarction increases cardiac glucose uptake and function in mice.

Protecting the heart after an acute coronary syndrome is a key therapeutic goal to support cardiac recovery and prevent progression to heart failure. A potential strategy is to target cardiac glucose metabolism at the early stages after ischemia when glycolysis is critical for myocyte survival. Building on our discovery that high-density lipoprotein (HDL) modulates skeletal muscle glucose metabolism, we now demonstrate that a single dose of reconstituted HDL (rHDL) delivered after myocardial ischemia increases cardiac glucose uptake, reduces infarct size, and improves cardiac remodeling in association with enhanced functional recovery in mice. These findings applied equally to metabolically normal and insulin-resistant mice. We further establish direct effects of HDL on cardiomyocyte glucose uptake, glycolysis, and glucose oxidation via the Akt signaling pathway within 15 min of reperfusion. These data support the use of infusible HDL preparations for management of acute coronary syndromes in the setting of primary percutaneous interventions.

Effects of the BET-inhibitor, RVX-208 on the HDL lipidome and glucose metabolism in individuals with prediabetes: A randomized controlled trial.

AIMS: High-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I) can modulate glucose metabolism through multiple mechanisms. This study determined the effects of a novel bromodomain and extra-terminal (BET) inhibitor (RVX-208) and putative apoA-I inducer on lipid species contained within HDL (HDL lipidome) and glucose metabolism. MATERIALS AND METHODS: Twenty unmedicated males with prediabetes received 100mg b.i.d. RVX-208 and placebo for 29-33days separated by a wash-out period in a randomized, cross-over design trial. Plasma HDL-cholesterol and apoA-I were assessed as well as lipoprotein particle size and distribution using NMR spectroscopy. An oral glucose tolerance test (OGTT) protocol with oral and infused stable isotope tracers was employed to assess postprandial plasma glucose, indices of insulin secretion and insulin sensitivity, glucose kinetics and lipolysis. Whole plasma and HDL lipid profiles were measured using mass spectrometry. RESULTS: RVX-208 treatment for 4weeks increased 6 sphingolipid and 4 phospholipid classes in the HDL lipidome (p≤0.05 versus placebo), but did not change conventional clinical lipid measures. The concentration of medium-sized HDL particles increased by 11% (P=0.01) and small-sized HDL particles decreased by 10% (P=0.04) after RVX-208 treatment. In response to a glucose load, after RVX-208 treatment, plasma glucose peaked at a similar level to placebo, but 30min later with a more sustained elevation (treatment effect, P=0.003). There was a reduction and delay in total (P=0.001) and oral (P=0.003) glucose rates of appearance in plasma and suppression of endogenous glucose production (P=0.014) after RVX-208 treatment. The rate of glucose disappearance was also lower following RVX-208 (P=0.016), with no effect on glucose oxidation or total glucose disposal. CONCLUSIONS: RVX-208 increased 10 lipid classes in the plasma HDL fraction, without altering the concentrations of either apoA-I or HDL-cholesterol (HDL-C). RVX-208 delayed and reduced oral glucose absorption and endogenous glucose production, with plasma glucose maintained via reduced peripheral glucose disposal. If sustained, these effects may protect against the development of type 2 diabetes.

Chronic ephedrine administration decreases brown adipose tissue activity in a randomised controlled human trial: implications for obesity.

AIMS/HYPOTHESIS: Brown adipose tissue (BAT) activation increases energy expenditure and may have therapeutic potential to combat obesity. The primary activating and adaptive signal for BAT is via ß-adrenergic signalling. We previously demonstrated that human BAT is acutely responsive to oral administration of the sympathomimetic, ephedrine. Here we aimed to determine whether adaptive thermogenesis can be induced via chronic treatment with ephedrine. METHODS: Twenty-three healthy young men, recruited from the general public in Melbourne, Australia, who were non-smokers, physically inactive and non-medicated with no prior history of cardiovascular disease or diabetes were recruited for this study. They were assigned to receive either 1.5 mg kg(-1) day(-1) ephedrine ('active' group; n = 12, age 23 ± 1 years, BMI 24 ± 1 kg/m(2)) or placebo (n = 11; 22 ± 2 years, 23 ± 2 kg/m(2)) for 28 days in a randomised (computer-generated random order sequence), placebo-controlled, parallel-group trial. Participants and all investigators were blinded to treatments. Body composition was measured before and after the intervention by dual energy X-ray absorptiometry. BAT activity, measured via (18)F-fluorodeoxyglucose positron emission tomography-computed tomography, in response to a single dose of 2.5 mg/kg ephedrine, was the primary outcome measure to be determined before and after the 28 day treatment period. RESULTS: Twenty-eight individuals were randomised and consented to the study. Twenty-three completed the trial and only these participants were included in the final analyses. After 28 days of treatment, the active group lost a significant amount of total body fat (placebo 1.1 ± 0.3 kg, ephedrine -0.9 ± 0.5 kg; p < 0.01) and visceral fat (placebo 6.4 ± 19.1 g, ephedrine -134 ± 43 g; p < 0.01), with no change in lean mass or bone mineral content compared with the placebo group. In response to acute ephedrine, BAT activity (change in mean standardised uptake value: placebo -3 ± 7%, ephedrine -22 ± 6%) and the increase in systolic blood pressure were significantly reduced (p < 0.05) in the active group compared with placebo. CONCLUSIONS/INTERPRETATION: Chronic ephedrine treatment reduced body fat content, but this was not associated with an increase in BAT activity. Rather, chronic ephedrine suppressed BAT glucose disposal, suggesting that chronic ephedrine treatment decreased, rather than increased, BAT activity. TRIAL REGISTRATION: ClinicalTrials.gov NCT02236962 FUNDING: This study was funded by the National Health and Medical Research Council of Australia Program Grant (1036352) and the OIS scheme from the Victorian State Government.

Reduced UCP-1 content in in vitro differentiated beige/brite adipocytes derived from preadipocytes of human subcutaneous white adipose tissues in obesity.

INTRODUCTION: Brown adipose tissue (BAT) is a potential therapeutic target to reverse obesity. The purpose of this study was to determine whether primary precursor cells isolated from human adult subcutaneous white adipose tissue (WAT) can be induced to differentiate in-vitro into adipocytes that express key markers of brown or beige adipose, and whether the expression level of such markers differs between lean and obese young adult males. METHODS: Adipogenic precursor cells were isolated from lean and obese individuals from subcutaneous abdominal WAT biopsies. Cells were grown to confluence, differentiated for 2.5 weeks then harvested for measurement of gene expression and UCP1 protein. RESULTS: There was no difference between groups with respect to differentiation into adipocytes, as indicated by oil red-O staining, rates of lipolysis, and expression of adipogenic genes (FABP4, PPARG). WAT genes (HOXC9, RB1) were expressed equally in the two groups. Post differentiation, the beige adipose specific genes CITED1 and CD137 were significantly increased in both groups, but classic BAT markers ZIC1 and LHX8 decreased significantly. Cell lines from both groups also equally increased post-differentiation expression of the thermogenic-responsive gene PPARGC1A (PGC-1α). UCP1 gene expression was undetectable prior to differentiation, however after differentiation both gene expression and protein content were increased in both groups and were significantly greater in cultures from lean compared with obese individuals (p<0.05). CONCLUSION: Human subcutaneous WAT cells can be induced to attain BAT characteristics, but this capacity is reduced in WAT cells from obese individuals.

Role of IL-6 in exercise training- and cold-induced UCP1 expression in subcutaneous white adipose tissue.

Expression of brown adipose tissue (BAT) associated proteins like uncoupling protein 1 (UCP1) in inguinal WAT (iWAT) has been suggested to alter iWAT metabolism. The aim of this study was to investigate the role of interleukin-6 (IL-6) in exercise training and cold exposure-induced iWAT UCP1 expression. The effect of daily intraperitoneal injections of IL-6 (3 ng/g) in C57BL/6 mice for 7 days on iWAT UCP1 expression was examined. In addition, the expression of UCP1 in iWAT was determined in response to 3 days of cold exposure (4°C) and 5 weeks of exercise training in wild type (WT) and whole body IL-6 knockout (KO) mice. Repeated injections of IL-6 in C57BL/6 mice increased UCP1 mRNA but not UCP1 protein content in iWAT. Cold exposure increased iWAT UCP1 mRNA content similarly in IL-6 KO and WT mice, while exercise training increased iWAT UCP1 mRNA in WT mice but not in IL-6 KO mice. Additionally, a cold exposure-induced increase in iWAT UCP1 protein content was blunted in IL-6 KO mice, while UCP1 protein content in iWAT was lower in both untrained and exercise trained IL-6 KO mice than in WT mice. In conclusion, repeated daily increases in plasma IL-6 can increase iWAT UCP1 mRNA content and IL-6 is required for an exercise training-induced increase in iWAT UCP1 mRNA content. In addition IL-6 is required for a full induction of UCP1 protein expression in response to cold exposure and influences the UCP1 protein content iWAT of both untrained and exercise trained animals.

Plasma sphingosine-1-phosphate is elevated in obesity.

BACKGROUND: Dysfunctional lipid metabolism is a hallmark of obesity and insulin resistance and a risk factor for various cardiovascular and metabolic complications. In addition to the well known increase in plasma triglycerides and free fatty acids, recent work in humans and rodents has shown that obesity is associated with elevations in the bioactive class of sphingolipids known as ceramides. However, in obesity little is known about the plasma concentrations of sphinogsine-1-phosphate (S1P), the breakdown product of ceramide, which is an important signaling molecule in mammalian biology. Therefore, the purpose of this study was to examine the impact of obesity on circulating S1P concentration and its relationship with markers of glucose metabolism and insulin sensitivity. METHODOLOGY/PRINCIPAL FINDINGS: Plasma S1P levels were determined in high-fat diet (HFD)-induced and genetically obese (ob/ob) mice along with obese humans. Circulating S1P was elevated in both obese mouse models and in obese humans compared with lean healthy controls. Furthermore, in humans, plasma S1P positively correlated with total body fat percentage, body mass index (BMI), waist circumference, fasting insulin, HOMA-IR, HbA1c (%), total and LDL cholesterol. In addition, fasting increased plasma S1P levels in lean healthy mice. CONCLUSION: We show that elevations in plasma S1P are a feature of both human and rodent obesity and correlate with metabolic abnormalities such as adiposity and insulin resistance.

Effects of high-density lipoprotein elevation with cholesteryl ester transfer protein inhibition on insulin secretion.

RATIONALE: High-density lipoprotein cholesterol elevation via cholesteryl ester transfer protein (CETP) inhibition represents a novel therapy for atherosclerosis, which also may have relevance for type 2 diabetes mellitus. OBJECTIVE: The current study assessed the effects of a CETP inhibitor on postprandial insulin, ex vivo insulin secretion, and cholesterol efflux from pancreatic ß-cells. METHODS AND RESULTS: Healthy participants received a daily dose of CETP inhibitor (n=10) or placebo (n=15) for 14 days in a randomized double-blind study. Insulin secretion and cholesterol efflux from MIN6N8 ß-cells were determined after incubation with treated plasma. CETP inhibition increased plasma high-density lipoprotein cholesterol, apolipoprotein AI, and postprandial insulin. MIN6N8 ß-cells incubated with plasma from CETP inhibitor-treated individuals (compared with placebo) exhibited an increase in both glucose-stimulated insulin secretion and cholesterol efflux over the 14-day treatment period. CONCLUSIONS: CETP inhibition increased postprandial insulin and promoted ex vivo ß-cell glucose-stimulated insulin secretion, potentially via enhanced ß-cell cholesterol efflux.

Brown adipose tissue in humans: therapeutic potential to combat obesity.

Harnessing the considerable capacity of brown adipose tissue (BAT) to consume energy was first proposed as a potential target to control obesity nearly 40years ago. The plausibility of this approach was, however, questioned due to the prevailing view that BAT was either not present or not functional in adult humans. Recent definitive identification of functional BAT in adult humans as well as a number of important advances in the understanding of BAT biology has reignited interest in BAT as an anti-obesity target. Proof-of-concept evidence demonstrating drug-induced BAT activation provides an important foundation for development of targeted pharmacological approaches with clinical application. This review considers evidence from both human and relevant animal studies to determine whether harnessing BAT for the treatment of obesity via pharmacological intervention is a realistic goal.

Skeletal muscle insulin resistance associated with cholesterol-induced activation of macrophages is prevented by high density lipoprotein.

BACKGROUND: Emerging evidence suggests that high density lipoprotein (HDL) may modulate glucose metabolism through multiple mechanisms including pancreatic insulin secretion as well as insulin-independent glucose uptake into muscle. We hypothesized that HDL may also increase skeletal muscle insulin sensitivity via cholesterol removal and anti-inflammatory actions in macrophages associated with excess adiposity and ectopic lipid deposition. METHODS: Human primary and THP-1 macrophages were treated with vehicle (PBS) or acetylated low density lipoprotein (acLDL) with or without HDL for 18 hours. Treatments were then removed, and macrophages were incubated with fresh media for 4 hours. This conditioned media was then applied to primary human skeletal myotubes derived from vastus lateralis biopsies taken from patients with type 2 diabetes to examine insulin-stimulated glucose uptake. RESULTS: Conditioned media from acLDL-treated primary and THP-1 macrophages reduced insulin-stimulated glucose uptake in primary human skeletal myotubes compared with vehicle (primary macrophages, 168±21% of basal uptake to 104±19%; THP-1 macrophages, 142±8% of basal uptake to 108±6%; P<0.05). This was restored by co-treatment of macrophages with HDL. While acLDL increased total intracellular cholesterol content, phosphorylation of c-jun N-terminal kinase and secretion of pro- and anti-inflammatory cytokines from macrophages, none were altered by co-incubation with HDL. Insulin-stimulated Akt phosphorylation in human skeletal myotubes exposed to conditioned media was unaltered by either treatment condition. CONCLUSION: Inhibition of insulin-stimulated glucose uptake in primary human skeletal myotubes by conditioned media from macrophages pre-incubated with acLDL was restored by co-treatment with HDL. However, these actions were not linked to modulation of common pro- or anti-inflammatory mediators or insulin signaling via Akt.

Effects of breaking up prolonged sitting on skeletal muscle gene expression.

Breaking up prolonged sitting has been beneficially associated with cardiometabolic risk markers in both observational and intervention studies. We aimed to define the acute transcriptional events induced in skeletal muscle by breaks in sedentary time. Overweight/obese adults participated in a randomized three-period, three-treatment crossover trial in an acute setting. The three 5-h interventions were performed in the postprandial state after a standardized test drink and included seated position with no activity and seated with 2-min bouts of light- or moderate-intensity treadmill walking every 20 min. Vastus lateralis biopsies were obtained in eight participants after each treatment, and gene expression was examined using microarrays validated with real-time quantitative PCR. There were 75 differentially expressed genes between the three conditions. Pathway analysis indicated the main biological functions affected were related to small-molecule biochemistry, cellular development, growth and proliferation, and carbohydrate metabolism. Interestingly, differentially expressed genes were also linked to cardiovascular disease. For example, relative to prolonged sitting, activity bouts increased expression of nicotamide N-methyltransferase, which modulates anti-inflammatory and anti-oxidative pathways and triglyceride metabolism. Activity bouts also altered expression of 10 genes involved in carbohydrate metabolism, including increased expression of dynein light chain, which may regulate translocation of the GLUT-4 glucose transporter. In addition, breaking up sedentary time reversed the effects of chronic inactivity on expression of some specific genes. This study provides insight into the muscle regulatory systems and molecular processes underlying the physiological benefits induced by interrupting prolonged sitting.