Direct adipotropic actions of atorvastatin: differentiation state-dependent induction of apoptosis, modulation of endocrine function, and inhibition of glucose uptake

Mevalonate biosynthesis pathway regulates the development and survival of brown adipocytes

The high thermogenic activity of brown adipose tissue (BAT) has received considerable attention. Here, we demonstrated the role of the mevalonate (MVA) biosynthesis pathway in the regulation of brown adipocyte development and survival. The inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in the MVA pathway and the molecular target of statins, suppressed brown adipocyte differentiation by suppressing protein geranylgeranylation-mediated mitotic clonal expansion. The development of BAT in neonatal mice exposed to statins during the fetal period was severely impaired. Moreover, statin-induced geranylgeranyl pyrophosphate (GGPP) deficiency led to the apoptosis of mature brown adipocytes. Brown adipocyte-specific Hmgcr knockout induced BAT atrophy and disrupted thermogenesis. Importantly, both genetic and pharmacological inhibition of HMGCR in adult mice induced morphological changes in BAT accompanied by an increase in apoptosis, and statin-treated diabetic mice showed worsened hyperglycemia. These findings revealed that MVA pathway-generated GGPP is indispensable for BAT development and survival.

Atorvastatin remodels lipid distribution between liver and adipose tissues through blocking lipoprotein efflux in fish

The regulation of cholesterol metabolism in fish is still unclear. Statins play important roles in promoting cholesterol metabolism development in mammals. However, studies on the role of statins in cholesterol metabolism in fish are currently limited. The present study evaluated the effects of statins on cholesterol metabolism in fish. Nile tilapia (Oreochromis niloticus) were fed on control diets supplemented with three atorvastatin levels (0, 12, and 24 mg/kg diet, ATV0, ATV12, and ATV24, respectively) for 4 wk. Intriguingly, the results showed that both atorvastatin treatments increased hepatic cholesterol and triglyceride contents mainly through inhibiting bile acid synthesis and efflux, and compensatorily enhancing cholesterol synthesis in fish liver (P < 0.05). Moreover, atorvastatin treatment significantly inhibited hepatic very-low-density lipoprotein (VLDL) assembly and thus decreased serum VLDL content (P < 0.05). However, fish treated with atorvastatin significantly reduced cholesterol and triglycerides contents in adipose tissue (P < 0.05). Further molecular analysis showed that atorvastatin treatment promoted cholesterol synthesis and lipogenesis pathways, but inhibited lipid catabolism and low-density lipoprotein (LDL) uptake in the adipose tissue of fish (P < 0.05). In general, atorvastatin induced the remodeling of lipid distribution between liver and adipose tissues through blocking VLDL efflux from the liver to adipose tissue of fish. Our results provide a novel regulatory pattern of cholesterol metabolism response caused by atorvastatin in fish, which is distinct from mammals: cholesterol inhibition by atorvastatin activates hepatic cholesterol synthesis and inhibits its efflux to maintain cholesterol homeostasis, consequently reduces cholesterol storage in fish adipose tissue.

Brown adipose tissue activity is modulated in olanzapine-treated young rats by simvastatin

Background

Prescription of second-generation antipsychotic drugs (SGAs) to childhood/adolescent has exponentially increased in recent years, which was associated with the greater risk of significant weight gain and dyslipidemia. Statin is considered a potential preventive and treatment approach for reducing SGA-induced weight gain and dyslipidemia in schizophrenia patients. However, the effect of statin treatment in children and adolescents with SGA-induced dyslipidemia is not clearly demonstrated.

Methods

To investigate the efficacy of statin interventions for reversing SGA-induced dyslipidemia, young Sprague Dawley rats were treated orally with either olanzapine (1.0 mg/kg, t.i.d.), simvastatin (3.0 mg/kg, t.i.d.), olanzapine plus simvastatin (O + S), or vehicle (control) for 5 weeks.

Results

Olanzapine treatment increased weight gain, food intake and feeding efficiency compared to the control, while O + S co-treatment significantly reversed body weight gain but without significant effects on food intake. Moreover, olanzapine treatment induced a slight but significant reduction in body temperature, with a decrease in locomotor activity. Fasting plasma glucose, triglycerides (TG), and total cholesterol (TC) levels were markedly elevated in the olanzapine-only group, whereas O + S co-treatment significantly ameliorated these changes. Pronounced activation of lipogenic gene expression in the liver and down-regulated expression of uncoupling protein-1 (UCP1) and peroxisome-proliferator-activated receptor-γ co-activator-1α (PGC-1α) in brown adipose tissue (BAT) was observed in the olanzapine-only group. Interestingly, these protein changes could be reversed by co-treatment with O + B.

Conclusions

Simvastatin is effective in ameliorating TC and TG elevated by olanzapine. Modulation of BAT activity by statins could be a partial mechanism in reducing metabolic side effects caused by SGAs in child and adolescent patients.

Graphical abstract

Inhibition of Mevalonate Pathway Prevents Adipocyte Browning in Mice and Men by Affecting Protein Prenylation

Recent research focusing on brown adipose tissue (BAT) function emphasizes its importance in systemic metabolic homeostasis. We show here that genetic and pharmacological inhibition of the mevalonate pathway leads to reduced human and mouse brown adipocyte function in vitro and impaired adipose tissue browning in vivo. A retrospective analysis of a large patient cohort suggests an inverse correlation between statin use and active BAT in humans, while we show in a prospective clinical trial that fluvastatin reduces thermogenic gene expression in human BAT. We identify geranylgeranyl pyrophosphate as the key mevalonate pathway intermediate driving adipocyte browning in vitro and in vivo, whose effects are mediated by geranylgeranyltransferases (GGTases), enzymes catalyzing geranylgeranylation of small GTP-binding proteins, thereby regulating YAP1/TAZ signaling through F-actin modulation. Conversely, adipocyte-specific ablation of GGTase I leads to impaired adipocyte browning, reduced energy expenditure, and glucose intolerance under obesogenic conditions, highlighting the importance of this pathway in modulating brown adipocyte functionality and systemic metabolism.

DAXX promotes ovarian cancer ascites cell proliferation and migration by activating the ERK signaling pathway

BACKGROUND

The death-domain-associated protein (DAXX) was originally identified as a protein that binds to the transmembrane death receptor FAS and enhances both FAS-induced and transforming growth factor-β-dependent apoptosis. In a previous study, we found that nude mice injected with DAXX-overexpressing cells (ES-2-DAXX) accumulated large concentrations of first-generation ascites cells (I ascites cells). The role of DAXX in the development of ascites is unknown. The aim of this study was to analyze the effect of DAXX on proliferation and migration of ascites cells in ovarian cancer in vitro and in vivo.

METHODS

Nude mice were housed in cages with a 14:10 h light:dark cycle; water and food were provided ad libitum. ES-2-DAXX cells (1×106) were injected intraperitoneally into athymic nude mice (8-week-old female mice). After 4 weeks, I ascites cells were collected. The I ascites cells were injected intraperitoneally into athymic nude mice (8-week-old female mice). After 4 weeks, II ascites cells were collected and cultured. Ascites cell survival, migration, and colony formation were measured using colony formation and cell growth assays. Immunofluorescent staining revealed the co-localization of DAXX and promyelocytic leukemia protein (PML) in ascites cell nuclei. Western blotting and immunohistochemistry showed that extracellular signal-related kinase (p-ERK) 1/2 and CEBP-β were highly expressed in tumor tissues formed by II ascites cells. Through immunoprecipitation, we also found that DAXX can interact with CEBP-β.

RESULTS

DAXX enhanced ascites cell survival, migration, and colony formation. DAXX and PML nuclear foci dramatically increased in a passage-dependent manner in ascites cells, DAXX promoted the tumor growth of ascites cells in vivo, increased ascites cell proliferation in vivo, and enhanced ascites cell survival and migration by activating the ERK signalling pathway and integrating with CEBP-β.

CONCLUSIONS

DAXX can interact with CEBP-β. DAXX can induce ovarian cancer ascites formation by activating the ERK signal pathway and binding to CEBP-β.

Quantitative assessment of adipocyte differentiation in cell culture

Adipocyte cell culture is an important tool for mechanistic studies of energy metabolism. Many factors affect the differentiation of adipocytes in culture. Oil red O staining can be used to assess the degree of differentiation. However, the validity of this method for quantitative analysis has not yet been established. Here we show that a protocol with arbitrarily chosen parameters does not measure in the linear range and is not suitable for quantitative analysis (R² = 0.077, p = 0.382), and develop and validate an optimized protocol for quantitative oil red O staining of cultured adipocytes. 3T3-L1 preadipocytes and adipocytes are fixed with 4% formaldehyde and stained with 0.2% oil red O solution in 40% 2-propanol for 30 minutes. Dye is eluted with 2-propanol, and absorption of the eluate is measured photometrically at 510 nm. This optimized protocol achieves excellent correlation between defined amounts of differentiated adipocytes on constant-size culture plates and photometric absorption (R² = 0.972, p = 6.585E-14). The performance of the method is independent of the culture plates used. Thus, the optimized oil red O staining protocol can be universally employed to quantitatively assess adipocyte differentiation.

Mevalonate deprivation mediates the impact of lovastatin on the differentiation of murine 3T3-F442A preadipocytes

The statins competitively inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activity and consequently the synthesis of mevalonate. The use of statins is associated with insulin resistance, presumably due to the impaired differentiation and diminished glucose utilization of adipocytes. We hypothesize that mevalonate is essential to adipocyte differentiation and adipogenic gene expression. Adipo-Red assay and Oil Red O staining showed that an eight-day incubation with 0-2.5 µmol/L lovastatin dose-dependently reduced the intracellular triglyceride content of murine 3T3-F442A adipocytes. Concomitantly, lovastatin downregulated the expression of peroxisome proliferator-activated receptor γ (Pparγ), leptin (Lep), fatty acid binding protein 4 (Fabp4), and adiponectin (AdipoQ) as measured by quantitative real-time polymerase chain reaction (real-time qPCR). The expression of sterol regulatory element binding protein 1 (Srebp-1), a transcriptional regulator of Pparγ and Lep genes, was also suppressed by lovastatin. Western-blot showed that lovastatin reduced the level of CCAAT/enhancer binding protein α (C/EBPα) while inducing a compensatory over-expression of HMG CoA reductase. The impact of lovastatin on intracellular triglyceride content and expression of the adipogenic genes was reversed by supplemental mevalonate. Mevalonate-derived metabolites have essential roles in promoting adipogenic gene expression and adipocyte differentiation.

Roles and relation between C/EBPα and PARs in the activation of hepatic stellate cells

Protease activated receptors (PARs) are main components of the fibrotic cascade mediated by the trypsin and thrombin that amplifies liver inflammation and fibrosis. Gene transcription initiation induced by PARs plays an important role in the activation of hepatic stellate cells (HSCs). HSC activation can be inhibited by the expression of transcription factor CCAAT enhancer binding proteins α (C/EBPα). Further research of the relation between C/EBPα and PARs will contribute to the understanding of the pathogenesis of liver fibrosis and provide a theoretical basis for further exploration of anti-fibrotic strategies.

RLIP76, a glutathione-conjugate transporter, plays a major role in the pathogenesis of metabolic syndrome

PURPOSE

Characteristic hypoglycemia, hypotriglyceridemia, hypocholesterolemia, lower body mass, and fat as well as pronounced insulin-sensitivity of RLIP76⁻/⁻ mice suggested to us the possibility that elevation of RLIP76 in response to stress could itself elicit metabolic syndrome (MSy). Indeed, if it were required for MSy, drugs used to treat MSy should have no effect on RLIP76⁻/⁻ mice.

RESEARCH DESIGN AND METHODS

Blood glucose (BG) and lipid measurements were performed in RLIP76⁺/⁺ and RLIP76⁻/⁻ mice, using Ascensia Elite Glucometer® for glucose and ID Labs kits for cholesterol and triglycerides assays. The ultimate effectors of gluconeogenesis are the three enzymes: PEPCK, F-1,6-BPase, and G6Pase, and their expression is regulated by PPARγ and AMPK. The activity of these enzymes was tested by protocols standardized by us. Expressions of RLIP76, PPARα, PPARγ, HMGCR, pJNK, pAkt, and AMPK were performed by Western-blot and tissue staining.

RESULTS

The concomitant activation of AMPK and PPARγ by inhibiting transport activity of RLIP76, despite inhibited activity of key glucocorticoid-regulated hepatic gluconeogenic enzymes like PEPCK, G6Pase and F-1,6-BP in RLIP76⁻/⁻ mice, is a salient finding of our studies. The decrease in RLIP76 protein expression by rosiglitazone and metformin is associated with an up-regulation of PPARγ and AMPK.

CONCLUSIONS/SIGNIFICANCE

All four drugs, rosiglitazone, metformin, gemfibrozil and atorvastatin failed to affect glucose and lipid metabolism in RLIP76⁻/⁻ mice. Studies confirmed a model in which RLIP76 plays a central role in the pathogenesis of MSy and RLIP76 loss causes profound and global alterations of MSy signaling functions. RLIP76 is a novel target for single-molecule therapeutics for metabolic syndrome.

Opposite effects of pravastatin and atorvastatin on insulin sensitivity in the rat: role of vitamin D metabolites

OBJECTIVE

Recent studies indicate that pravastatin improves whereas other statins impair glucose homeostasis in humans, but the underlying mechanisms are not clear. We examined the effect of pravastatin and atorvastatin on insulin sensitivity in a rat model.

METHODS

Pravastatin (40 mg/kg/day) or atorvastatin (20mg/kg/day) were administered for 3 weeks and insulin sensitivity was assessed by measuring fasting plasma insulin, HOMA-IR, non-esterified fatty acids (NEFA) and glycerol levels, as well as by the hyperinsulinemic euglycemic clamp.

RESULTS

Pravastatin had no effect on fasting insulin and HOMA-IR but significantly reduced plasma NEFA and glycerol levels and increased glucose infusion rate (GIR) during the hyperinsulinemic clamp. Increase in GIR induced by pravastatin was not abolished by NO synthase inhibitor, l-NAME, indicating that this effect did not result from the improvement of endothelial function. Atorvastatin increased fasting insulin, HOM-IR, NEFA and glycerol levels as well as reduced GIR. Statins had no effect on leptin, HMW adiponectin, resistin, visfatin, interleukin-6 and TNF-α. Pravastatin increased plasma concentrations of 25-hydroxy- and 1,25-dyhydroxyvitamin D(3) (25-OH-D(3) and 1,25-(OH)(2)-D(3)), and its effect on insulin sensitivity was mimicked by exogenous 1,25-(OH)(2)-D(3). Atorvastatin reduced plasma 25-OH-D(3) but had no effect on 1,25-(OH)(2)-D(3). Decrease in insulin sensitivity induced by atorvastatin was not corrected by supplementation of vitamin D(3) despite normalization of plasma 25-OH-D(3) level.

CONCLUSIONS

Pravastatin and atorvastatin have opposite effects on insulin sensitivity and vitamin D(3) status. Pravastatin-induced increase in insulin sensitivity is mediated by elevation of 1,25-(OH)(2)-D(3). In contrast, atorvastatin-induced decrease in insulin sensitivity is independent of lowering 25-OH-D(3).

Metformin and atorvastatin combination further protect the liver in type 2 diabetes with hyperlipidaemia

BACKGROUND

non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes are associated with dyslipidaemia, inflammation and oxidative stress. However, the pathophysiology of NAFLD in type 2 diabetes with hyperlipidaemia is not fully known, as well as the utility of the commonly prescribed anti-diabetic and lipid-lowering drugs in ameliorating liver injury markers.

METHODS

hepatic complications of type 2 diabetes with hyperlipidaemia and the effects of atorvastatin and metformin, isolated and in association, in systemic and hepatic inflammatory and oxidative stress markers were tested using genetic type 2 diabetic Goto-Kakizaki rats fed with a high-fat diet.

RESULTS

the high-fat diet aggravated the overall metabolic state and the hepatic markers of injury. All treatments decreased fasting glycaemia, insulin resistance and free fatty acid levels. Combined treatment further decreased C-reactive protein (CRP), adiponectin, liver tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6), systemic and hepatic oxidative stress and portal inflammation.

CONCLUSIONS

our data provides evidence of a greater benefit with a combination of atorvastatin and metformin in improving liver injury in type 2 diabetes with hyperlipidaemia.

Simvastatin inhibits goblet cell hyperplasia and lung arginase in a mouse model of allergic asthma: a novel treatment for airway remodeling?

Airway remodeling in asthma contributes to airway hyperreactivity, loss of lung function, and persistent symptoms. Current therapies do not adequately treat the structural airway changes associated with asthma. The statins are cholesterol-lowering drugs that inhibit the enzyme 3-hydroxy-3-methyl-glutaryl-CoA reductase, which is the rate-limiting step of cholesterol biosynthesis in the mevalonate (MA) pathway. These drugs have been associated with improved respiratory health, and ongoing clinical trials are testing their therapeutic potential in asthma. We hypothesized that simvastatin treatment of ovalbumin (OVA)-exposed mice would attenuate early features of airway remodeling by a mevalonate-dependent mechanism. BALB/c mice initially were sensitized to OVA and then exposed to 1% OVA aerosol for 2 weeks after sensitization for 6 exposures. Simvastatin (40 mg/kg) or simvastatin plus MA (20 mg/kg) were injected intraperitoneally before each OVA exposure. Treatment with simvastatin attenuated goblet cell hyperplasia, arginase-1 protein expression, and total arginase enzyme activity, but it did not alter airway hydroxyproline content or transforming growth factor-β1. Inhibition of goblet cell hyperplasia by simvastatin was mevalonate-dependent. No appreciable changes to airway smooth muscle cells were observed in any control or treatment groups. In conclusion, in an acute mouse model of allergic asthma, simvastatin inhibited early hallmarks of airway remodeling, which are indicators that can lead to airway thickening and fibrosis. Statins are potentially novel treatments for airway remodeling in asthma. Additional studies using subchronic or chronic allergen exposure models are needed to extend these initial findings.

Statin treatment reduces oxidative stress-associated apoptosis of sciatic nerve in diabetes mellitus

Statins are lipid-lowering drugs that are widely used for treating hyperlipidemia, especially in diabetic patients. The aim of our study was to explore the effects of atorvastatin on oxidative stress and apoptosis in the sciatic nerve due to hyperglycemia. Diabetes was induced by streptozotocin. Atorvastatin was given orally for two weeks beginning from the sixth week. Microscopic examination of sciatic nerve revealed that normal tissue organization was disrupted in streptozotocin induced diabetic rats. Treatment with Atorvastatin reduced the histological damage and protected the morphological integrity of the sciatic nerve in streptozotocin induced diabetes. Increased expressions of transforming growth factor beta-1, endothelial nitric oxide synthase and TUNEL in sciatic nerve from streptozotocin induced diabetes were reduced by Atorvastatin. Atorvastatin could improve the effects of oxidative stress and apoptosis on the sciatic nerve due to diabetes.

Beneficial direct adipotropic actions of pitavastatin in vitro and their manifestations in obese mice

OBJECTIVE

Prevention of cardiovascular complications in obese patients frequently includes statin administration for coexisting dyslipidemia. Herein, we investigated the impacts of pitavastatin at clinically relevant doses on adipose dysfunction and insulin resistance.

METHODS

We treated 3T3-L1 preadipocytes with 10-100 ng/ml pitavastatin from initiation of differentiation (Day 0) to Day 8 (differentiation/maturation phase) or from Day 8 to Day 16 (post-maturation phase). Subsequently, we administered pitavastatin (6.2mg/day/kg) to 7-week-old female KKAy mice for 6 weeks; untreated KKAy mice served as obese controls.

RESULTS

Pitavastatin impaired neither lipogenesis nor adiponectin expression during the differentiation/maturation phase. During the post-maturation phase, pitavastatin prevented excessive triglyceride accumulation, which was associated with attenuated glucose transporter-4 expression, and dose-dependently upregulated hormone-sensitive lipase expression. Decrements in the adiponectin/plasminogen activator-1 ratio were also dose-dependently inhibited. In KKAy mice, Coulter counter analyses revealed that pitavastatin treatment significantly decreased (by 16.8%) the frequency of hypertrophic adipocytes (>150 microm in diameter) in parametrial adipose pads, of which total weight remained unaltered. Correspondingly, plasma adiponectin was significantly higher in pitavastatin-treated KKAy mice than in the untreated KKAy mice (12.5+/-3.8 microg/ml vs. 8.3+/-1.5 microg/ml, p<0.05). Moreover, the area under the time-glucose curve after intraperitoneal insulin was decreased by 16% in pitavastatin-treated KKAy mice (p<0.05 vs. untreated controls).

CONCLUSIONS

Pitavastatin did not impair differentiation/maturation of preadipocytes and prevented their deterioration with hypertrophy after maturation at clinical concentrations in vitro. These effects likely contributed to improved insulin sensitivity, in an obese model, via prevention of adipocyte hypertrophy and adipocytokine dysregulation.

Impact of simvastatin on adipose tissue: pleiotropic effects in vivo

Statins belong to a class of drugs well known for their ability to reduce circulating low-density lipoprotein cholesterol. In addition to cholesterol lowering, they also exhibit potential antiinflammatory and antioxidant properties, suggesting that tissues other than liver may be targeted by statins to exert their beneficial metabolic effects. Adipocytes have received very little attention as a potential target of these drugs, possibly because adipocytes are not a major source of biosynthetic cholesterol. Here, we examine the effects of simvastatin on the secretory pathway, inflammation, and cellular metabolism of adipocytes as well as on whole-body insulin sensitivity. We find that statins have a selective effect on the secretion of the insulin-sensitizing adipokine adiponectin by reducing circulating levels of the high-molecular-weight form of adiponectin specifically with a concomitant increase in intracellular adiponectin levels. However, these effects on adiponectin do not translate into changes in metabolism or whole-body insulin sensitivity, potentially due to additional antiinflammatory properties of statins. In addition, ob/ob mice treated with statins have reduced adiposity and an altered ultrastructure of the plasma membrane with respect to caveolar histology. Our data demonstrate that statins have major effects on the cellular physiology of the adipocyte on multiple levels.

Active visfatin is elevated in serum of maintenance haemodialysis patients and correlates inversely with circulating HDL cholesterol

BACKGROUND

Increased circulating visfatin may be associated both with endothelial damage and with increased mortality in end-stage renal disease (ESRD). HDL cholesterol is an independent, strong inverse predictor of cardiovascular events. However, associations between visfatin and parameters of lipid metabolism are unclear. Moreover, serum concentrations of visfatin measured by an enzyme immuno assay (EIA) are conflicting and do not correlate with ELISA (enzyme-linked immunosorbent assay) data, which predominantly detect enzymatically active visfatin.

METHODS

A total of 74 haemodialysis (HD) patients and 35 control individuals (C) were studied. All subjects (mean age 62.9 years) provided fasted blood samples (HD patients after 66-69 h without dialysis). Circulating visfatin was measured by the ELISA. Body composition was evaluated using waist circumference, skinfold thickness and body impedance analysis. Results obtained by the ELISA were compared with EIA data.

RESULTS

Active serum visfatin was increased in HD (5.58 +/- 6.50 ng/ml) versus C [0.97 +/- 1.79 ng/ml, mean +/- SD; P < 0.0001 by multiple regression analysis (MRA)] independently of plasma glucose, serum insulin, diabetes, HDL cholesterol and body composition. Within the HD group, only plasma HDL cholesterol (4% lower per additional mg/dl HDL; P = 0.001) and insulin-treated diabetes mellitus [subgroup of n = 18; 119% higher compared with patients without diabetes (n = 40); P = 0.011] were independently (by MRA) associated with active serum visfatin. Visfatin measured by an EIA showed no correlation with ELISA data.

CONCLUSIONS

Our study provides reliable data on active visfatin in HD patients using a well-characterized ELISA. Loss of renal function is accompanied by increased circulating active visfatin concentrations in our patients. Furthermore, decreased HDL cholesterol may hint at an increased probability of cardiovascular events in HD patients with elevated serum visfatin.

Increased serum visfatin in patients with metabolic syndrome and carotid atherosclerosis

OBJECTIVE

Visfatin is a newly identified adipocytokine and recent studies indicated that visfatin may have potential proinflammatory effect. However, its pathophysiological role in the metabolic syndrome (MetS) is not fully understood. In this study we investigated whether serum visfatin levels is altered in patients with the MetS, and compared the levels of visfatin between patients with and without carotid plaques.

DESIGN AND METHOD

A total of 139 patients with MetS and 105 controls were included. The patients were further divided into two groups: 40 with carotid plaques and 99 without carotid plaques. Serum visfatin was measured by using enzyme immunoassay method and carotid intimal-media thickness (IMT) was measured by ultrasound in all subjects.

RESULTS

Serum visfatin was elevated in both MetS patients with and without carotid plaques compared to controls (log visfatin: 1.14 +/- 0.14 vs. 0.99 +/- 0.17 ng/ml vs. 0.93 +/- 0.23 ng/ml, P < 0.001 and P < 0.05 vs. control group, respectively), and in patients with carotid plaques more than in patients without carotid plaques (P < 0.001). Multiple stepwise regression analysis revealed that only LDL-cholesterol correlated with visfatin, and visfatin independently correlated with max IMT in the patients with MetS. A log visfatin > 1.08 ng/ml had 70% sensitivity and 67% specificity for detecting patients with carotid plaques.

CONCLUSIONS/INTERPRETATION

Our results showed that serum visfatin was increased in patients with MetS, especially in those with carotid plaques. Visfatin may be an inflammatory marker of MetS.

A novel membrane-based anti-diabetic action of atorvastatin

We recently found that chromium picolinate (CrPic), a nutritional supplement thought to improve insulin sensitivity in individuals with impaired glucose tolerance, enhances insulin action by lowering plasma membrane (PM) cholesterol. Recent in vivo studies suggest that cholesterol-lowering statin drugs benefit insulin sensitivity in insulin-resistant patients, yet a mechanism is unknown. We report here that atorvastatin (ATV) diminished PM cholesterol by 22% (P<0.05) in 3T3-L1 adipocytes. As documented for CrPic, this small reduction in PM cholesterol enhanced insulin action. Replenishment of cholesterol mitigated the positive effects of ATV on insulin sensitivity. Co-treatment with CrPic and ATV did not amplify the extent of PM cholesterol loss or insulin sensitivity gain. In addition, analyses of insulin signal transduction suggest a non-signaling basis of both therapies. Our data reveal an unappreciated beneficial non-hepatic effect of statin action and highlight a novel mechanistic similarity between two recently recognized therapies of impaired glucose tolerance.