Background-Low plasma high-density lipoprotein (HDL) is associated with elevated cardiovascular risk and aspects of the metabolic syndrome. We hypothesized that HDL modulates glucose metabolism via elevation of plasma insulin and through activation of the key metabolic regulatory enzyme, AMP-activated protein kinase, in skeletal muscle. Methods and Results-Thirteen patients with type 2 diabetes mellitus received both intravenous reconstituted HDL (rHDL: 80 mg/kg over 4 hours) and placebo on separate days in a double-blind, placebo-controlled crossover study. A greater fall in plasma glucose from baseline occurred during rHDL than during placebo (at 4 hours rHDLϭϪ2.6Ϯ0.4; placeboϭϪ2.1Ϯ0.3mmol/L; Pϭ0.018). rHDL increased plasma insulin (at 4 hours rHDLϭ3.4Ϯ10.0; placeboϭ Ϫ19.2Ϯ7.4 pmol/L; Pϭ0.034) and also the homeostasis model assessment ␤-cell function index (at 4 hours rHDLϭ18.9Ϯ5.9; placeboϭ8.6Ϯ4.4%; Pϭ0.025). Acetyl-CoA carboxylase ␤ phosphorylation in skeletal muscle biopsies was increased by 1.7Ϯ0.3-fold after rHDL, indicating activation of the AMP-activated protein kinase pathway. Both HDL and apolipoprotein AI increased glucose uptake (by 177Ϯ12% and 144Ϯ18%, respectively; PϽ0.05 for both) in primary human skeletal muscle cell cultures established from patients with type 2 diabetes mellitus (nϭ5). The mechanism is demonstrated to include stimulation of the ATP-binding cassette transporter A1 with subsequent activation of the calcium/calmodulin-dependent protein kinase kinase and the AMP-activated protein kinase pathway. Conclusions-rHDL reduced plasma glucose in patients with type 2 diabetes mellitus by increasing plasma insulin and activating AMP-activated protein kinase in skeletal muscle. These findings suggest a role for HDL-raising therapies beyond atherosclerosis to address type 2 diabetes mellitus. Key Words: glucose Ⅲ insulin Ⅲ lipoproteins Ⅲ metabolism Ⅲ muscles H igh-density lipoprotein (HDL) is associated with protection from adverse cardiovascular outcomes in large epidemiological trials. 1 Type 2 diabetes mellitus and the cluster of pathologies including glucose intolerance/insulin resistance, obesity, and high plasma triglycerides that constitute the metabolic syndrome are associated with low and dysfunctional HDL. 2,3 In contrast, aerobically trained individuals have high HDL and display enhanced glucose tolerance. 4 Although the mechanisms linking low HDL to atherosclerosis are well characterized, the links between low HDL and disordered energy metabolism remain relatively unexplored. Given the high and escalating prevalence of type 2 diabetes mellitus, obesity, and the metabolic syndrome and the associated marked elevation in cardiovascular morbidity and mortality, this is an important area of investigation. Clinical Perspective p 2111Recent cell-based studies suggest that HDL may modulate plasma glucose through both insulin-dependent 5,6 and -independent mechanisms. 7 The ATP-binding cassette transporter A1 (ABCA1) has been shown to modulate insulin secretion, 6 and HDL can reverse ...

Abstract-Large artery stiffening increases cardiovascular risk and promotes isolated systolic hypertension which is more prevalent in elderly women than men. Variation in sex steroid levels between males and females and throughout life may modulate arterial stiffness. We hypothesized that sex steroids directly influence expression of important structural proteins which determine arterial biomechanical properties. Human aortic smooth muscle cells were incubated with physiological concentrations of 17␤-estradiol, progesterone, 17␤-estradiol and progesterone, or testosterone for 4 weeks. Collagen, elastin, and fibrillin-1 deposition was examined (histochemistry/immunohistochemistry). Gene and protein expression of 2 important matrix metalloproteinases (MMPs), MMPs 2 and 3, regulating matrix turnover was assessed. All sex steroids reduced collagen deposition relative to control (100%). However, the reduction was greater with female sex steroids than testosterone (control, 100%; 17␤-estradiol plus progesterone, 20Ϯ2%; testosterone 74Ϯ12%, PϽ0.001). Female sex steroids increased elastin deposition compared with control (control, 100%; 17␤-estradiol, 540Ϯ60%; progesterone, 290Ϯ40%; 17␤-estradiol plus progesterone, 400Ϯ80%, all PϽ0.01). The elastin/collagen ratio was Ͼ11-fold higher in the presence of 17␤-estradiol and progesterone compared with testosterone. Fibrillin-1 deposition was doubled in the presence of female sex steroids (17␤-estradiol plus progesterone) compared with testosterone (PϽ0.01). MMP-2 gene and protein expression was unaffected by any sex steroid. Testosterone increased both gene and protein expression of MMP-3 relative to both control and female sex steroids (PϽ0.01). This may contribute to degradation of elastic matrix proteins. In conclusion, female sex steroids promote an elastic matrix profile, which likely contributes to variation in large artery stiffness observed between sexes and with changes in hormonal status across the lifespan. Key Words: collagen Ⅲ elastin Ⅲ sex Ⅲ arterial stiffness S tiffness of the large arteries is a key determinant of pulse pressure 1 and independently related to cardiovascular outcome. [2][3][4][5] Sex has an important influence on arterial stiffness, which may be mediated in part via the influence of sex steroids on arterial structure and function. Before menarche and after menopause, when female sex steroid secretion is low, females have stiffer large arteries and higher pulse pressure than age-matched males. 6 -9 In elderly females, this manifests as an elevated prevalence of isolated systolic hypertension. 9 -11 Furthermore, higher levels of female sex steroids associated with the reproductive years or hormonal therapy have been linked to lower arterial stiffness. 6,7,12,13 In contrast, during the pubertal transition, male sex steroids have been associated with increased large artery stiffness. 8 We hypothesize that sex steroids may influence large artery stiffness through modulation of expression of extracellular matrix proteins and their regulators.There i...

Epidemiological studies have observed associations between frequent interruptions of sitting time with physical activity bouts and beneficial metabolic outcomes, even in individuals who regularly exercise. Frequent interruptions to prolonged sitting reduce postprandial plasma glucose. Here we studied potential skeletal muscle mechanisms accounting for this improved control of glycemia in overweight adults under conditions of one day uninterrupted sitting and sitting interrupted with light-intensity or moderate-intensity walking every 20-min (n = 8); and, after three days of either uninterrupted sitting or light-intensity walking interruptions (n = 5). Contraction- and insulin-mediated glucose uptake signaling pathways as well as changes in oxidative phosphorylation proteins were examined. We showed that 1) both interventions reduce postprandial glucose concentration, 2) acute interruptions to sitting over one day stimulate the contraction-mediated glucose uptake pathway, 3) both acute interruptions to sitting with moderate-intensity activity over one day and light-intensity activity over three days induce a transition to modulation of the insulin-signaling pathway, in association with increased capacity for glucose transport. Only the moderate-intensity interruptions resulted in greater capacity for glycogen synthesis and likely for ATP production. These observations contribute to a mechanistic explanation of improved postprandial glucose metabolism with regular interruptions to sitting time, a promising preventive strategy for metabolic diseases.

IntroductionBrown 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.MethodsAdipogenic 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.ResultsThere 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).ConclusionHuman subcutaneous WAT cells can be induced to attain BAT characteristics, but this capacity is reduced in WAT cells from obese individuals.

Background— Experimental studies suggest that deferoxamine (DFO) limits the generation of reactive oxygen species by chelating redox-active iron and thereby may reduce ischemia-reperfusion injury and myocardial infarct (MI) size. We investigated whether DFO administered before reperfusion by primary percutaneous coronary intervention (PPCI) would ameliorate oxidative stress and MI size. Methods and Results— We randomly assigned 60 patients with ST-elevation–MI to receive an intravenous bolus of DFO (500 mg) immediately before PPCI followed by a 12-hour infusion (50 mg/kg of body weight) (n=28) or normal saline bolus and infusion (placebo group, n=32). MI size was measured by contrast-enhanced cardiac MRI (CMRI; day 3±1), creatine kinase and troponin I area-under-the-curve, and severity of wall motion abnormality on echocardiography. Clinical follow-up including repeat CMRI and echocardiography were performed at 3 months (100±17 days). Oxidative stress was assessed by plasma F 2 -isoprostane levels. DFO and placebo groups were well balanced with respect to baseline characteristics, symptom- and door-to-balloon times, pre-PPCI coronary patency, and infarct-related artery location. Serum iron levels were decreased with DFO treatment after PPCI compared with placebo (3.0±2.5 versus 12.6±5.5 μmol/L, P <0.0001), which persisted until the end of the infusion. In DFO-treated patients, there was a significant reduction in plasma F 2 -isoprostane levels immediately after PPCI (2878±1461 versus 2213±579 pmol/L, P =0.04). However, there was no difference in CMRI-determined infarct size (DFO, 17.4±10.8%, versus placebo, 18.6±10.2%; P =0.73), myocardial salvage index at 3 days or at 3 months, or the area-under-the-curve for creatine kinase or troponin I. Conclusions— Adjunctive DFO treatment after the onset of ischemia and continued periprocedurally ameliorates oxidative stress without limiting infarct size. Clinical Trial Registration— URL: http://www.anzctr.org.au/ . Unique identifier: ACTRN12608000308392.

Previous cellular, animal, and human studies suggest that increasing plasma HDL cholesterol may modulate insulin secretion. 5,[20][21][22] Cholesteryl ester transfer protein (CETP) inhibition increases plasma HDL cholesterol via a reduction in the transfer of neutral lipids (triglycerides and cholesteryl esters) between HDL and triglyceride-rich lipoprotein particles. The efficacy of this strategy to improve cardiovascular outcomes has not yet been determined, and there is controversy regarding whether CETP inhibition might produce a dysfunctional form of HDL cholesterol, which is less efficient at promoting reverse cholesterol transport than native HDL. 23 This controversy has arisen, in part, because of the early termination of 2 CETP inhibitor trials resulting from adverse events in the case of torcetrapib 24

BackgroundThe regulation of microRNAs (miRNAs) at different stages of the progression of type 2 diabetes mellitus (T2DM) and their role in glucose homeostasis was investigated.MethodsMicroarrays were used to assess miRNA expression in skeletal muscle biopsies taken from healthy individuals and patients with pre-diabetes or T2DM, and insulin resistant offspring of rat dams fed a high fat diet during pregnancy.ResultsTwenty-three miRNAs were differentially expressed in patients with T2DM, and 7 in the insulin resistant rat offspring compared to their controls. Among these, only one miRNA was similarly regulated: miR-194 expression was significantly reduced by 25 to 50% in both the rat model and in human with pre-diabetes and established diabetes. Knockdown of miR-194 in L6 skeletal muscle cells induced an increase in basal and insulin-stimulated glucose uptake and glycogen synthesis. This occurred in conjunction with an increased glycolysis, indicated by elevated lactate production. Moreover, oxidative capacity was also increased as we found an enhanced glucose oxidation in presence of the mitochondrial uncoupler FCCP. When miR-194 was down-regulated in vitro, western blot analysis showed an increased phosphorylation of AKT and GSK3β in response to insulin, and an increase in expression of proteins controlling mitochondrial oxidative phosphorylation.ConclusionsType 2 diabetes mellitus is associated with regulation of several miRNAs in skeletal muscle. Interestingly, miR-194 was a unique miRNA that appeared regulated across different stages of the disease progression, from the early stages of insulin resistance to the development of T2DM. We have shown miR-194 is involved in multiple aspects of skeletal muscle glucose metabolism from uptake, through to glycolysis, glycogenesis and glucose oxidation, potentially via mechanisms involving AKT, GSK3 and oxidative phosphorylation. MiR-194 could be down-regulated in patients with early features of diabetes as an adaptive response to facilitate tissue glucose uptake and metabolism in the face of insulin resistance.

Abstract-Ramipril improves cardiovascular outcome in patients with peripheral arterial disease; however, the precise mechanisms of benefit remain to be elucidated. The effect of ramipril on large-artery stiffness in patients with peripheral arterial disease was examined. In addition, we determined the effect of ramiprilat on extracellular matrix from human aortic smooth muscle cell culture. Forty patients with peripheral arterial disease were randomized to receive ramipril, 10 mg once daily or placebo for 24 weeks. Arterial stiffness was assessed globally via systemic arterial compliance and augmentation index (carotid tonometry and Doppler velocimetry), and regionally via carotid-femoral pulse wave velocity. Angiotensin-converting enzyme inhibition increased arterial compliance by 0.10Ϯ0.02 mL/mm Hg, (PϽ0.001, all probability values relative to placebo) and reduced pulse wave velocity by 1.7Ϯ0.2 m/s (PϽ0.001), augmentation index by 4.1Ϯ0.3% (PϽ0.001), and systolic blood pressure by 5Ϯ1 mm Hg (PϽ0.001). Ramipril did not reduce mean arterial pressure significantly compared with placebo (Pϭ0.59). In cell culture, ramiprilat decreased collagen deposition by Ͼ50% and increased elastin and fibrillin-1 deposition by Ͼ3-and 4-fold respectively (histochemistry and immunohistochemistry). Fibrillin-1 gene expression was increased 5-fold (real-time reverse-transcriptase polymerase chain reaction). Ramiprilat also reduced gene and protein (Western) expression of both matrix metalloproteinase (MMP)-2 and MMP-3. In conclusion, ramipril promoted an elastogenic matrix profile that may contribute to the observed clinical reduction in large-artery stiffness and carotid pressure augmentation, which occurred independently of mean arterial blood pressure reduction in patients with peripheral arterial disease.