Deterioration of glucose homeostasis in type 2 diabetic patients one year after beginning of statins therapy

The Role of Perivascular Adipose Tissue in the Pathogenesis of Endothelial Dysfunction in Cardiovascular Diseases and Type 2 Diabetes Mellitus

Cardiovascular diseases (CVDs) and type 2 diabetes mellitus (T2DM) are two of the four major chronic non-communicable diseases (NCDs) representing the leading cause of death worldwide. Several studies demonstrate that endothelial dysfunction (ED) plays a central role in the pathogenesis of these chronic diseases. Although it is well known that systemic chronic inflammation and oxidative stress are primarily involved in the development of ED, recent studies have shown that perivascular adipose tissue (PVAT) is implicated in its pathogenesis, also contributing to the progression of atherosclerosis and to insulin resistance (IR). In this review, we describe the relationship between PVAT and ED, and we also analyse the role of PVAT in the pathogenesis of CVDs and T2DM, further assessing its potential therapeutic target with the aim of restoring normal ED and reducing global cardiovascular risk.

Pancreatic β-cell dysfunction in type 2 diabetes: Implications of inflammation and oxidative stress

Insulin resistance and pancreatic β-cell dysfunction are major pathological mechanisms implicated in the development and progression of type 2 diabetes (T2D). Beyond the detrimental effects of insulin resistance, inflammation and oxidative stress have emerged as critical features of T2D that define β-cell dysfunction. Predominant markers of inflammation such as C-reactive protein, tumor necrosis factor alpha, and interleukin-1β are consistently associated with β-cell failure in preclinical models and in people with T2D. Similarly, important markers of oxidative stress, such as increased reactive oxygen species and depleted intracellular antioxidants, are consistent with pancreatic β-cell damage in conditions of T2D. Such effects illustrate a pathological relationship between an abnormal inflammatory response and generation of oxidative stress during the progression of T2D. The current review explores preclinical and clinical research on the patho-logical implications of inflammation and oxidative stress during the development of β-cell dysfunction in T2D. Moreover, important molecular mechanisms and relevant biomarkers involved in this process are discussed to divulge a pathological link between inflammation and oxidative stress during β-cell failure in T2D. Underpinning the clinical relevance of the review, a systematic analysis of evidence from randomized controlled trials is covered, on the potential therapeutic effects of some commonly used antidiabetic agents in modulating inflammatory makers to improve β-cell function.

Simvastatin profoundly impairs energy metabolism in primary human muscle cells

OBJECTIVES

Simvastatin use is associated with muscular side effects, and increased risk for type 2 diabetes (T2D). In clinical use, simvastatin is administered in inactive lipophilic lactone-form, which is then converted to active acid-form in the body. Here, we have investigated if lactone- and acid-form simvastatin differentially affect glucose metabolism and mitochondrial respiration in primary human skeletal muscle cells.

METHODS

Muscle cells were exposed separately to lactone- and acid-form simvastatin for 48 h. After pre-exposure, glucose uptake and glycogen synthesis were measured using radioactive tracers; insulin signalling was detected with Western blotting; and glycolysis, mitochondrial oxygen consumption and ATP production were measured with Seahorse XFe96 analyzer.

RESULTS

Lactone-form simvastatin increased glucose uptake and glycogen synthesis, whereas acid-form simvastatin did not affect glucose uptake and decreased glycogen synthesis. Phosphorylation of insulin signalling targets Akt substrate 160 kDa (AS160) and glycogen synthase kinase 3β (GSK3β) was upregulated with lactone-, but not with acid-form simvastatin. Exposure to both forms of simvastatin led to a decrease in glycolysis and glycolytic capacity, as well as to a decrease in mitochondrial respiration and ATP production.

CONCLUSIONS

These data suggest that lactone- and acid-forms of simvastatin exhibit differential effects on non-oxidative glucose metabolism as lactone-form increases and acid-form impairs glucose storage into glycogen, suggesting impaired insulin sensitivity in response to acid-form simvastatin. Both forms profoundly impair oxidative glucose metabolism and energy production in human skeletal muscle cells. These effects may contribute to muscular side effects and risk for T2D observed with simvastatin use.

Effect of Switching from Low-Dose Simvastatin to High-Dose Atorvastatin on Glucose Homeostasis and Cognitive Function in Type 2 Diabetes

BACKGROUND

High-intensity statin is recommended in high-risk type 2 diabetes (T2D); however, statin dose dependently increases the risk of developing new-onset diabetes, can potentially worsen glycemic control in T2D, and may cause cognitive impairment. This study aimed to investigate the effect of statin intensification on glucose homeostasis and cognitive function in T2D.

MATERIALS AND METHODS

T2D patients who were taking simvastatin ≤20 mg/day were randomized to continue taking the same dosage of simvastatin (low-dose simvastatin group; LS, n=63) for 12 weeks, or to change to atorvastatin 40 mg/day for 6 weeks, and if tolerated, atorvastatin was increased to 80 mg/day for 6 weeks (high-dose atorvastatin group; HS, n=62). Fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), plasma insulin, homeostatic model assessment of insulin resistance (HOMA-IR) and of β-cell function (HOMA-B), cognitive functions using Montreal Cognitive Assessment (MoCA), and Trail Making Test (TMT) were assessed at baseline, 6 weeks, and 12 weeks.

RESULTS

Mean age of patients was 58.8±8.9 years, and 72% were female. Mean baseline FPG and HbA1c were 124.0±27.5 mg/dl and 6.9±0.8%, respectively. No differences in baseline characteristics between groups were observed. Change in HbA1c from baseline in the LS and HS groups was -0.1% and +0.1% (p=0.03) at 6 weeks, and -0.1% and +0.1% (p=0.07) at 12 weeks. There were no significant differences in FPG, fasting plasma insulin, HOMA-B, HOMA-IR, MoCA score, or TMT between groups at 6 or 12 weeks.

CONCLUSION

Switching from low-dose simvastatin to high-dose atorvastatin in T2D resulted in a slight increase in HbA1c (0.1%) without causing cognitive decline.

Mechanisms of statin‐induced new‐onset diabetes

Statins, with their lipid‐lowering properties, are a first‐line therapy for the prevention of cardiovascular diseases. Recent evidence, however, suggests that statins can increase the risk of new‐onset diabetes (NOD). The molecular mechanisms of statin‐induced NOD are not precisely known, although some pathophysiologic mechanisms have been suggested. Specific to the beta cell, these mechanisms include alterations in insulin secretion, changes in ion channels, modulation of signaling pathways, and inflammation/oxidative stress. Outwith the beta cell, other suggested mechanisms involve adipocytes, including alterations in adipocyte differentiation and modulation of leptin and adiponectin, and genetic and epigenetic mechanisms, including alterations in microRNA. The evidence supporting these and other mechanisms will be discussed. Greater understanding of the underlying mechanisms linking the onset of diabetes to statin therapy is essential and clinically relevant, as it may enable novel preventative or therapeutic approaches to be instituted and guide the production of a new generation of statins lacking this side effect.

Glucose homeostasis in statin users-The LIFESTAT study

BACKGROUND

Statins are widely used to lower cholesterol concentrations in both primary and secondary prevention of cardiovascular disease. The treatment increases the risk of muscle pain (myalgia) and of type 2 diabetes. However, the underlying mechanisms remain disputed.

METHODS

We investigated whether statin induced myalgia is coupled to impaired glucose homeostasis using oral glucose tolerance test (OGTT), intravenous glucose tolerance test (IVGTT), and the hyperinsulinemic euglycemic clamp. We performed a cross-sectional study of statin users without CVD (primary prevention) stratified into a statin myalgic (M; n = 25) and a non-myalgic (NM; n = 39) group as well as a control group (C; n = 20) consisting of non-statin users.

RESULTS

A reduction in the insulin secretion rate during the OGTT was observed in the myalgic group compared with the non-myalgic group (AUC ISR_OGTT , C: 1032 (683 - 1500); M: 922 (678 - 1091); NM: 1089 (933 - 1391) pmol·L^-1 ·min (median with 25%-75% percentiles), but no other measurements indicated impaired β-cell function. We found no other differences between the three groups for other measurements in the OGTT, IVGTT, and euglycemic clamp. Muscle protein content of GLUT4 and hexokinase II was similar between the three groups.

CONCLUSIONS

We conclude that statin users in primary prevention experiencing myalgia do not have impaired glucose homeostasis compared with other statin users or non-users. We consider this an important aspect in the dialogue between physician and patient regarding statin treatment and adverse effects.

Statins decrease leptin expression in human white adipocytes

Statin use is associated with increased calorie intake and consequent weight gain. It is speculated that statin‐dependent improvements in lipid profile may undermine the perceived need to follow lipid‐lowering and other dietary recommendations leading consequently to increased calorie intake. However, increases in calorie intake in statin users may also be related to statin‐dependent decreases in satiety factors such as leptin, an adipocyte‐derived adipokine. The objective of our study was to examine the direct effects of statins on leptin expression. Adipocytes are the main source of circulating leptin. Therefore, we examined the effects of atorvastatin and simvastatin on leptin expression in cultured human white adipocytes. We show that treatment of white adipocytes with simvastatin and atorvastatin decreases leptin mRNA expression (simvastatin: P = 0.008, atorvastatin: P = 0.03) and leptin secretion (simvastatin: P = 0.0001, atorvastatin: P = 0.0001). Both simvastatin and atorvastatin mediate decreases in leptin expression via extracellular‐signal‐regulated kinases 1/2 and peroxisome proliferator‐activated receptor gamma pathways (simvastatin: P = 0.01, atorvastatin: P = 0.026). Additionally, statin treatment also induced expected increases in adiponectin, while decreasing monocyte chemoattractant protein 1 (MCP1) mRNA. Furthermore, statins increased secretion of both total as well as high molecular weight adiponectin while decreasing MCP1 secretion. To conclude, statins act directly on human white adipocytes to regulate adipokine secretion and decrease leptin expression. Leptin is an important satiety factor. Hence, statin‐dependent decreases in leptin may contribute, at least in part, to increases in food intake in statin users.

Leptin levels predict the development of insulin resistance in a sample of adult men-The Olivetti Heart Study

BACKGROUND AND AIMS

Leptin (LPT) is associated with unfavourable cardio-metabolic risk profile. Although a number of studies have found a positive association between LPT and insulin resistance (IR), no observational study has evaluated a prospective association to detect a predictive role of LPT in IR. Therefore, the aim of this study was to estimate the role of LPT on the incidence of IR in an 8-year follow-up of a sample of adult men (The Olivetti Heart Study).

METHODS AND RESULTS

The study included 527 not diabetic men without IR (homeostasis model assessment - HOMA index < 2.77 UI) at baseline. Baseline LPT was significantly and positively associated with HOMA index, body mass index (BMI), waist circumference and blood pressure. At the end of the 8-year follow-up period, a positive and significant association was detected between baseline LPT and changes in HOMA index (r = 0.25, p < 0.01) and incidence of IR (OR: 2.6, 95%CI: 1.9-3.4). This trend was also confirmed after adjustment for potential confounders. In addition, the predictive value of LPT was found in subjects who had not experienced any weight increase over the years, and for normal weight and excess body weight participants, separately.

CONCLUSIONS

The results of this prospective study suggest a predictive role of circulating LPT levels on a reduction of insulin sensitivity over time, independently of main potential confounders, in non-diabetic men without IR at baseline. In addition, in normal weight individuals, LPT levels were associated with development of IR.

Risk and Benefits of Statins in Glucose Control Management of Type II Diabetes

Worldwide statins are considered to be the first-line pharmacological treatment for dyslipidemia and reducing the risk of coronary heart disease. However, recently various studies have shown its adverse effect on glucose control among diabetic patients and the U.S. Food and Drug Administration have revised statin drug labels to include information that increases in fasting serum glucose and glycated hemoglobin levels have been reported. This systematic review objective is to evaluate the risks and benefits of statins in glucose control management of type 2 diabetes patients based on the 44 published journal articles included and obtained through MEDLINE full text, PubMed, Science Direct, Pro Quest, SAGE, Taylor and Francis Online, Google Scholar, High Wire, and Elsevier Clinical Key. Statins were found to affect glucose control through several ways, namely, by affecting insulin production and secretion by β-pancreatic cells, insulin resistance, insulin uptake by the muscles and adipocytes and production of adipokines. Current evidence available shows that most of the statins give unfavorable side effects with regards to glucose control among diabetic patients. A dose-dependent and time-dependent effect was also observed in some statins which may be present among other statins as well.

Pravastatin improves risk factors but not ischaemic tolerance in obese rats

Statins are effective in management of dyslipidaemia, and a cornerstone of CVD prevention strategies. However, the impacts of their pleiotropic effects on other cardiovascular risk factors and myocardial responses to infarction are not well characterised. We hypothesised that pravastatin treatment in obesity improves lipid profiles, insulin-resistance and myocardial resistance to ischaemia/reperfusion (I/R) injury. Wistar rats were fed a control (C) chow or high carbohydrate and fat diet (HCFD) for 16 weeks with vehicle or pravastatin (prava 7.5 mg/kg/day) treatment for 8 weeks. At 16 weeks HOMAs were performed, blood samples collected and hearts excised for Langendorff perfusions/biochemical analyses. Anti-oxidant activity and proteins regulating mitochondrial fission/fusion and apoptosis were assessed. The HCFD increased body weight (736±15 vs. 655±12 g for C; P<0.001), serum triglycerides (2.91±0.52 vs. 1.64±0.26 mmol/L for C; P<0.001) and insulin-resistance (HOMA- 6.9±0.8 vs. 4.2±0.5 for C; P<0.05) while prava prevented diet induced changes and paradoxically increased lipid peroxidation. The HCFD increased infarct size (34.1±3.1% vs. 18.8±3.0% of AAR for C; P<0.05), which was unchanged by prava in C and HCFD animals. The HCFD decreased cardiac TxR activity and mitochondrial MFN-1 and increased mitochondrial DRP-1 (reducing MFN-1:DRP-1 ratio) and Bax expression, with the latter changes prevented by prava. While unaltered by diet, cytosolic levels of Bax and caspase-3 were reduced by prava in C and HCFD hearts (without changes in cleaved caspase-3). We conclude that obesity, hyper-triglyceridemia and impaired glycemic control in HCFD rats are countered by prava. Despite improved risk factors, prava did not reduce myocardial infarct size, potentially reflecting its complex pleiotropic impacts on cardiac GPX activity and MFN-1, DRP-1, caspase-3 and Bcl-2 proteins.

Cardiorespiratory Fitness and Incidence of Type 2 Diabetes in United States Veterans on Statin Therapy

BACKGROUND

Impact of cardiorespiratory fitness on statin-related incidence of type 2 diabetes has not been assessed. We assessed the cardiorespiratory fitness and diabetes incidence association in dyslipidemic patients on statins.

METHODS

We identified dyslipidemic patients with a normal exercise test performed during 1986 and 2014 at the Veterans Affairs Medical Centers in Washington, DC or Palo Alto, Calif. The statin-treated patients (n = 4092; age = 58.8 ± 10.9 years) consisted of 2701 Blacks and 1391 Whites. None had evidence of type 2 diabetes prior to statin therapy. We formed 4 fitness categories based on age and peak metabolic equivalents achieved: Least-fit (n = 954), Low-fit (n = 1201), Moderate-fit (n = 1242), and High-fit (n = 695). The non-statin-treated cohort (n = 3001; age = 57.2 ± 11.2 years) with no evidence of type 2 diabetes prior to the exercise test served as controls.

RESULTS

Diabetes incidence was 24% higher in statin-treated compared with non-statin-treated patients (P <.001). In the statin-treated cohort, 1075 (26.3%) developed diabetes (average annual incidence rate of 30.6 events/1000 person-years). Compared with the Least-fit, adjusted risk decreased progressively with increasing fitness and was 34% lower for High-fit patients (hazard ratio [HR] 0.66; 95% confidence interval [CI], 0.53-0.82; P <.001). Compared with the nonstatin cohort, elevated risk was evident only in the Least-fit (HR 1.50; 95% CI, 1.30-1.73; P <.001) and Low-fit patients (HR 1.22; 95% CI, 1.06-1.41; P = .006).

CONCLUSIONS

Risk of diabetes in statin-treated dyslipidemic patients was inversely and independently associated with cardiorespiratory fitness. The increased risk was evident only in relatively low-fitness patients. Improving fitness may modulate the potential diabetogenic effects of statins.

Statin use and risk of developing diabetes: results from the Diabetes Prevention Program

OBJECTIVE

Several clinical trials of cardiovascular disease prevention with statins have reported increased risk of type 2 diabetes (T2DM) with statin therapy. However, participants in these studies were at relatively low risk for diabetes. Further, diabetes was often based on self-report and was not the primary outcome. It is unknown whether statins similarly modify diabetes risk in higher risk populations.

RESEARCH DESIGN AND METHODS

During the Diabetes Prevention Program Outcomes Study (n=3234), the long-term follow-up to a randomized clinical trial of interventions to prevent T2DM, incident diabetes was assessed by annual 75 g oral glucose tolerance testing and semiannual fasting glucose. Lipid profile was measured annually, with statin treatment determined by a participant's own physician outside of the protocol. Statin use was assessed at baseline and semiannual visits.

RESULTS

At 10 years, the cumulative incidence of statin initiation prior to diabetes diagnosis was 33%-37% among the randomized treatment groups (p=0.36). Statin use was associated with greater diabetes risk irrespective of treatment group, with pooled HR (95% CI) for incident diabetes of 1.36 (1.17 to 1.58). This risk was not materially altered by adjustment for baseline diabetes risk factors and potential confounders related to indications for statin therapy.

CONCLUSIONS

In this population at high risk for diabetes, we observed significantly higher rates of diabetes with statin therapy in all three treatment groups. Confounding by indication for statin use does not appear to explain this relationship. The effect of statins to increase diabetes risk appears to extend to populations at high risk for diabetes.

TRIAL REGISTRATION NUMBER

NCT00038727; Results.

Lower and higher-potency statins on glycemic control in type 2 diabetes: A retrospective cohort study

AIMS

Evidences showed a link between statins and new-onset diabetes and large clinical trials in type 2 diabetes (T2DM) suggested a mild glycemic progression in statin treated. Since this effect has not yet elucidated in real world, we investigated the effects of different statins on glycemia in T2DM clinic outpatients.

METHODS

In a retrospective cohort study, we recorded at 6 and 12months modifications of fasting glucose (FPG), HbA1c, diabetes intensification therapy and target rate for HbA1c in 421 T2DM non-users and new statin users. Statins were categorized with low or high potency.

RESULTS

Compared to statin users, no statin group showed a significant HbA1c reduction from 52.8±14.0mmol/mol to 48.2±8.5 (p=0.003) at 6months and 48.6±8.8 (p=0.007) at 12months. This trend without statins was also observed in FPG starting from 7.1±2.0mmol/l to 6.7±1.6 (p=0.12) at 6months and 6.6±1.5 (p=0.032) at 12months. Statins determined a significant diabetes treatment intensification: 48.7% vs 27.4% (p=0.002) with hazard ratio 2.4 [95% CI 1.14-5.2], p=0.022. HbA1c target was significantly lower in statin users 62.0% vs 75.4%, p=0.042. Only lower-potency statins showed a significant reduction of HbA1c from 52.0±11.1mmol/mol to 50.7±9.0 (p=0.017) and 50.7±9.5 (p=0.038) at 6 and 12months, respectively. The same effect for these statins was registered in FPG from 7.5±2.2mmol/l to 7.0±1.6 (p=0.021) at 6months and 7.2±1.5 (p=0.026) at 12months.

CONCLUSIONS

In patients receiving statin therapy a greater intensification diabetes therapy is need. This impact seems to be less pronounced by statins with lower potency.

Chronic use of pravastatin reduces insulin exocytosis and increases β-cell death in hypercholesterolemic mice

We have previously demonstrated that hypercholesterolemic LDL receptor knockout (LDLr(-/-)) mice secrete less insulin than wild-type mice. Removing cholesterol from isolated islets using methyl-beta-cyclodextrin reversed this defect. In this study, we hypothesized that in vivo treatment of LDLr(-/-) mice with the HMGCoA reductase inhibitor pravastatin would improve glucose-stimulated insulin secretion. Female LDLr(-/-) mice were treated with pravastatin (400mg/L) for 1-3 months. Isolated pancreatic islets were assayed for insulin secretion rates, intracellular calcium oscillations, cholesterol levels, NAD(P)H and SNARE protein levels, apoptosis indicators and lipidomic profile. Two months pravastatin treatment reduced cholesterol levels in plasma, liver and islets by 35%, 25% and 50%, respectively. Contrary to our hypothesis, pravastatin treatment increased fasting and fed plasma levels of glucose and decreased markedly (40%) fed plasma levels of insulin. In addition, ex vivo glucose stimulated insulin secretion was significantly reduced after two and three months (36-48%, p<0.05) of pravastatin treatment. Although reducing insulin secretion and insulinemia, two months pravastatin treatment did not affect glucose tolerance because it improved global insulin sensitivity. Pravastatin induced islet dysfunction was associated with marked reductions of exocytosis-related SNARE proteins (SNAP25, Syntaxin 1A, VAMP2) and increased apoptosis markers (Bax/Bcl2 protein ratio, cleaved caspase-3 and lower NAD(P)H production rates) observed in pancreatic islets from treated mice. In addition, several oxidized phospholipids, tri- and diacylglycerols and the proapoptotic lipid molecule ceramide were identified as markers of pravastatin-treated islets. Cell death and oxidative stress (H2O2 production) were confirmed in insulin secreting INS-1E cells treated with pravastatin. These results indicate that chronic treatment with pravastatin impairs the insulin exocytosis machinery and increases β-cell death. These findings suggest that prolonged use of statins may have a diabetogenic effect.

Statin-induced decrease in ATP-binding cassette transporter A1 expression via microRNA33 induction may counteract cholesterol efflux to high-density lipoprotein

PURPOSE

Cholesterol efflux from macrophages to HDL, measured in vitro, is augmented by treatment with agents which raise HDL cholesterol. In vitro, cholesterol depletion by statins is known to trigger a positive feedback on the cholesterol synthetic pathway via sterol regulatory element-binding protein (SREBP) transcription and changes in expression of SREBP regulated genes including microRNA33 (miR33) which is co-transcribed with SREBP and down-regulates ABCA1 and ABCG1 expression.

METHODS

We investigated whether miR33 up-regulation, associated with SREBP increased transcription by statins, reduces macrophage ATP-binding cassette (ABC) transporter expression, thereby decreasing HDL-mediated cholesterol efflux at the tissue level.

RESULTS

In human macrophage THP-1 cells cholesterol-loaded with acetylated LDL, incubation with 1 μM atorvastatin increased miR33 by 33 % (P < 0.05), and decreased ABCA1 messenger RNA (mRNA) and ABCG1 mRNA by 47 % (P < 0.05) and 27 % (NS), respectively. In J774A.1 mouse macrophage, labelled with 3H-cholesterol, ABCA1 mRNA and ABCA1-mediated cholesterol efflux were decreased by 1 μM statin: simvastatin > pitavastatin > atorvastatin > rosuvastatin > pravastatin. HDL incubated with rhCETP and dalcetrapib increased ABCA1-mediated cholesterol efflux. However, incremental simvastatin concentrations decreased cholesterol efflux to HDL treated with rhCETP and dalcetrapib. When HDL was incubated with rhCETP, addition of dalcetrapib augmented ABCA1-mediated cholesterol efflux from J774A.1 macrophages. However, simvastatin ≥1 μM virtually eliminated any HDL-ABCA1-mediated cholesterol efflux and any augmentation of that process by dalcetrapib.

CONCLUSIONS

In vitro, statins increase miR33 expression, and decrease ABCA1 expression and cholesterol efflux from peripheral tissues; this may counteract the potential benefit of agents that raise HDL and apolipoprotein A-I in statin-treated patients.

Statins, glycemia, and diabetes mellitus: another point of view

Glycemic effects of statins have recently become a topic of heated debate. On closer inspection, however, the prevailing opinion regarding this issue may prove to be unsubstantiated. We suggest that the harmful effect of statin-induced diabetes is likely overestimated, and the consequences of the glycemic effects of statins may, theoretically, apply to a greater number of patients beyond just those with statin-induced diabetes. Most notably, though, careful consideration of the issue suggests, albeit surprisingly, that the clinical implications of the glycemic effects of statins may actually be rather limited.

[Statins diabetogenicity: are all the same? state of art]

Statins are the cornerstone of cardiovascular prevention for general population, and in patients with type 2 diabetes mellitus (T2DM). However, statin therapy predisposes to type 2 diabetes, particularly in patients with predisposition to this condition. Some statins have been associated with increases in blood glucose in patients with or without DM2, and others have shown to have neutral effects, varying from one another their glucose or diabetogenic capacity. In many statin trials the incidence of DM2 has not been systematically evaluated and others the power to detect differences between statins is lacking. Evidence highest quality available comes from the meta-analysis of controlled clinical trials. The only controlled clinical trial to evaluate the incidence of new-onset T2DM is the J-PREDICT conducted with pitavastatin in patients with abnormal glucose tolerance. Preliminary results of this study show that pitavastatin is associated with a significant decrease in the incidence of de novo T2DM compared to only modification lifestyle. Therefore, pitavastatin may be an appropriate therapeutic alternative of choice to reduce vascular risk in patients with T2DM or at risk of presenting it.

Effects of combined therapy with glipizide and Aralia root bark extract on glycemic control and lipid profiles in patients with type 2 diabetes mellitus

BACKGROUND

The root bark of Aralia is a rich source of bioactive components that may improve glycemic control and lipid status. In this study, 148 patients with type 2 diabetes mellitus (T2DM) were assigned randomly to receive either glipizide alone or glipizide plus Aralia root bark extract (ARBE) for 8 weeks to test the effects of ARBE plus glipizide therapy on glycemic control and lipid profiles in these patients.

RESULTS

Levels of HbA1c, fasting plasma glucose (FPG) and 2 h postprandial plasma glucose (2-h PPG) in both groups significantly decreased from baseline. Glycated hemoglobin (HbA1c) decreased marginally significantly in participants taking glipizide plus ARBE compared with the glipizide group (P = 0.06). Participants in the combination group had significant decreases in total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), and the between-group difference achieved statistical significance for LDL-C (P = 0.04). Reduction in HbA1c in the combination group was significantly associated with changes in TC (r = 0.32; P = 0.006) and LDL-C (r = 0.34; P = 0.005), and the change in FPG was inversely correlated with LDL-C reduction (r = 0.34; P = 0.004).

CONCLUSIONS

In patients with T2DM, combination therapy with glipizide and ARBE resulted in moderately lowering HbA1c and LDL-C levels compared with glipizide alone.

Saxagliptin efficacy and safety in patients with type 2 diabetes receiving concomitant statin therapy

AIMS

To examine whether concomitant statin therapy affects glycemic control with saxagliptin 2.5 and 5mg/d in patients with type 2 diabetes mellitus (T2DM).

METHODS

Efficacy and safety were analyzed post hoc for pooled data from 9 saxagliptin randomized, placebo-controlled trials with a primary 24-week treatment period (4 monotherapy, 2 add-on to metformin, 1 each add-on to a sulfonylurea, thiazolidinedione, or insulin±metformin). Safety was also assessed in an 11-study, 24-week pool and an extended 20-study pool, which included 9 additional 4- to 52-week randomized studies. Comparisons were performed for patient groups defined by baseline statin use.

RESULTS

Saxagliptin produced greater mean reductions in glycated hemoglobin than placebo, with no interaction between treatment and baseline statin use (P=0.47). In patients receiving saxagliptin 2.5 and 5mg and placebo, the proportion of patients with ≥1 adverse event (AE) was 78.1%, 64.0%, and 63.2%, respectively, in patients with any statin use and 70.6%, 57.9%, and 55.0% in patients with no statin use. Serious AEs, deaths, and symptomatic confirmed hypoglycemia (fingerstick glucose ≤50mg/dL) were few and similar, irrespective of baseline statin use.

CONCLUSIONS

Saxagliptin improves glycemic control and is generally well tolerated in patients with T2DM, irrespective of concomitant statin therapy.

Statin treatment and new-onset diabetes: a review of proposed mechanisms

New-onset diabetes has been observed in clinical trials and meta-analyses involving statin therapy. To explain this association, three major mechanisms have been proposed and discussed in the literature. First, certain statins affect insulin secretion through direct, indirect or combined effects on calcium channels in pancreatic β-cells. Second, reduced translocation of glucose transporter 4 in response to treatment results in hyperglycemia and hyperinsulinemia. Third, statin therapy decreases other important downstream products, such as coenzyme Q10, farnesyl pyrophosphate, geranylgeranyl pyrophosphate, and dolichol; their depletion leads to reduced intracellular signaling. Other possible mechanisms implicated in the effect of statins on new-onset diabetes are: statin interference with intracellular insulin signal transduction pathways via inhibition of necessary phosphorylation events and reduction of small GTPase action; inhibition of adipocyte differentiation leading to decreased peroxisome proliferator activated receptor gamma and CCAAT/enhancer-binding protein which are important pathways for glucose homeostasis; decreased leptin causing inhibition of β-cells proliferation and insulin secretion; and diminished adiponectin levels. Given that the magnitude of the risk of new-onset diabetes following statin use remains to be fully clarified and the well-established beneficial effect of statins in reducing cardiovascular risk, statins remain the first-choice treatment for prevention of CVD. Elucidation of the mechanisms underlying the development of diabetes in association with statin use may help identify novel preventative or therapeutic approaches to this problem and/or help design a new generation statin without such side-effects.

Utilization of glucose, blood pressure, and lipid lowering medications among people with type II diabetes in the United States, 1999-2010

PURPOSE

Changes in relation to drug treatment to various control targets for diabetes were studied using the National Health and Nutrition Examination Survey, 1999-2010.

METHODS

Data on 3094 participants aged 20 years or older with diagnosed type II diabetes were analyzed. Use of medications for lowering glucose, blood pressure, and lipids in the past month was assessed by questionnaire. Data from two survey cycles were combined together to produce estimates for each 4-year period.

RESULTS

Usage of metformin increased from 34.8% to 53.8% and was the most prevalent medications during this period (P < .001), and half of subjects taking metformin could achieve glycated hemoglobin less than 7.0% in 2007-2010. Dipeptidyl peptidase-4 inhibitors were used by 7.4% of participants in 2007-2010. Usage of angiotensin receptor blockers and beta-blockers increased significantly from 7.4% to 21.4% and from 15.3% to 31.8%, respectively from 1999 to 2010 (P ≤ .001). A total of 64.7% of participants could attain blood pressure control by 2007-2010. Usage of statins doubled in 1999-2010 and 52.2% of subjects took statins by 2007-2010 (P < .001).

CONCLUSIONS

Metformin is the first-line drug for diabetes while dipeptidyl peptidase-4 inhibitors started to be used since 2007. Blood pressure control improved in 1999-2010 partly due to increased drug prescriptions. Although statins were widely used about half of the participants did not take them.

Differential metabolic actions of specific statins: clinical and therapeutic considerations

SIGNIFICANCE

Statins, the most widely prescribed drugs in clinical practice, mainly act by reducing the plasma level of low-density lipoprotein (LDL)-cholesterol. A shift in redox homeostasis to an imbalance between reactive oxygen species generation and endogenous antioxidant mechanisms results in oxidative stress that has been implicated in the pathogenesis of various diseases, including those of the cardiovascular system. Beyond their efficacy in lowering LDL cholesterol, statins modulate redox systems that are implicated in the development of atherosclerosis, cardiovascular morbidity, and mortality.

RECENT ADVANCES

Differences in specific statins or their dosages result in differential metabolic actions arising from off-target or unknown mechanisms of action that can have important implications for overall patient morbidity and mortality.

CRITICAL ISSUES

A recent meta-analysis and a combined analysis have suggested that high doses of statins increase the risk of developing type 2 diabetes mellitus, but reduce the risk of cardiovascular events. Thus, it is important to consider the cardiovascular and metabolic context and natural history of diseases when choosing a specific statin therapy for optimal individual patient health over the long term.

FUTURE DIRECTIONS

More information is needed regarding the metabolism of statins, and the off-target or unknown actions of statins in affecting insulin resistance and metabolic homeostasis. The differential metabolic effects of specific statins should be considered in formulating optimal therapeutic strategies to reduce not just cardiovascular-related but also overall patient morbidity and mortality.

Statins impair glucose uptake in human cells

OBJECTIVE

Considering the increasing number of clinical observations indicating hyperglycemic effects of statins, this study was designed to measure the influence of statins on the uptake of glucose analogs by human cells derived from liver, adipose tissue, and skeletal muscle.

DESIGN

Flow cytometry and scintillation counting were used to measure the uptake of fluorescently labeled or tritiated glucose analogs by differentiated visceral preadipocytes, skeletal muscle cells, skeletal muscle myoblasts, and contact-inhibited human hepatocellular carcinoma cells. A bioinformatics approach was used to predict the structure of human glucose transporter 1 (GLUT1) and to identify the presence of putative cholesterol-binding (cholesterol recognition/interaction amino acid consensus (CRAC)) motifs within this transporter. Mutagenesis of CRAC motifs in SLC2A1 gene and limited proteolysis of membrane GLUT1 were used to determine the molecular effects of statins.

RESULTS

Statins significantly inhibit the uptake of glucose analogs in all cell types. Similar effects are induced by methyl-β-cyclodextrin, which removes membrane cholesterol. Statin effects can be rescued by addition of mevalonic acid, or supplementation with exogenous cholesterol. Limited proteolysis of GLUT1 and mutagenesis of CRAC motifs revealed that statins induce conformational changes in GLUTs.

CONCLUSIONS

Statins impair glucose uptake by cells involved in regulation of glucose homeostasis by inducing cholesterol-dependent conformational changes in GLUTs. This molecular mechanism might explain hyperglycemic effects of statins observed in clinical trials.

The good and bad effects of statins on insulin sensitivity and secretion

AIMS

Statins are the main lipid-lowering treatment in both primary and secondary prevention populations. Whether statins deteriorates glycemic control, predisposing to the onset of diabetes mellitus has been a matter of recent concern. Statins may accelerate progression to diabetes via molecular mechanisms that impact insulin sensitivity and secretion. In this review, we debate the relative effect of statins in driving insulin resistance and the impairment of insulin secretion.

METHODS

Narrative overview of the literature synthesizing the findings of literature was retrieved from searches of computerized databases, hand searches, and authoritative texts employing the key words "Statins", "Randomized Clinical Trial", "Insulin sensitivity", "Insulin resistance", "Insulin Secretion", "Diabetes Mellitus" alone and/or in combination.

RESULTS

The weight of clinical evidence suggests a worsening effect of statins on insulin resistance and secretion, anyway basic science studies did not find a clear molecular explanation, providing conflicting evidence regarding both the beneficial and the adverse effects of statin therapy on insulin sensitivity.

CONCLUSIONS

Although most of the clinical studies suggest a worsening of insulin resistance and secretion, the cardiovascular benefits of statin therapy outweigh the risk of developing insulin resistance, thus the data suggest the need to treat dyslipidemia and to make patients aware of the possible risk of developing type 2 diabetes or, if they already are diabetic, of worsening their metabolic control.

Pitavastatin in cardiometabolic disease: therapeutic profile

Statins effectively lower low-density lipoprotein-cholesterol (LDL-C) and reduce cardiovascular risk in people with dyslipidemia and cardiometabolic diseases such as Metabolic syndrome (MetS) or type 2 diabetes (T2D). In addition to elevated levels of LDL-C, people with these conditions often have other lipid-related risk factors, such as high levels of triglycerides, low levels of high-density lipoprotein-cholesterol (HDL-C), and a preponderance of highly atherogenic, small, dense low-density lipoprotein particles. The optimal management of dyslipidemia in people with MetS or T2D should therefore address each of these risk factors in addition to LDL-C. Although statins typically have similar effects on LDL-C levels, differences in chemical structure and pharmacokinetic profile can lead to variations in pleiotropic effects, adverse event profiles and drug-drug interactions. The choice of statin should therefore depend on the characteristics and needs of the individual patient. Compared with other statins, pitavastatin has distinct pharmacological features that translate into a broad range of actions on both apolipoprotein-B-containing and apolipoprotein-A-containing lipoproteins. Studies show that pitavastatin 1 to 4 mg is well tolerated and significantly improves LDL-C and triglyceride levels to a similar or greater degree than comparable doses of atorvastatin, simvastatin or pravastatin, irrespective of diabetic status. Moreover, whereas most statins show inconsistent effects on HDL-C levels, pitavastatin-treated patients routinely experience clinically significant elevations in HDL-C that are maintained and even increased over the long term. In addition to increasing high-density lipoprotein quantity, pitavastatin appears to improve high-density lipoprotein function and to slow the progression of atherosclerotic plaques by modifying high-density lipoprotein-related inflammation and oxidation, both of which are common in patients with MetS and T2D. When choosing a statin, it is important to note that patients with MetS have an increased risk of developing T2D and that some statins can exacerbate this risk via adverse effects on glucose regulation. Unlike many statins, pitavastatin appears to have a neutral and even beneficial effect on glucose regulation, making it a useful treatment option in this high-risk group of patients. Together with pitavastatin’s beneficial effects on the cardiometabolic lipid profile and its low potential for drug-drug interactions, this suggests that pitavastatin might be a useful lipid-lowering option for people with cardiometabolic disease.

Statin diabetogenicity: guidance for clinicians

Type 2 diabetes (T2D) is a strong, independent risk factor for cardiovascular (CV) and cerebrovascular outcomes. Meta-analysis of five randomised clinical trials (n = 33,040) showed that, although intensive versus standard glycaemic control significantly reduced CV events in people with T2D, the reduction was less than that achieved with lipid-lowering or antihypertensive treatment. Furthermore, fasting plasma glucose (FPG) concentrations were a modest predictor for CV risk in people without T2D. Thus, although effective glycaemic control is important for the prevention/management of T2D, other risk factors must be addressed to effectively reduce CV risk. Reducing low-density lipoprotein-cholesterol levels using statins significantly reduces CV risk in people with and without T2D. Although statins are generally safe and well tolerated, conflicting data exist regarding the diabetogenic effects of some statins. Based on recent clinical trial data, the US Food and Drug Administration have changed the labelling of all statins to include 'an effect of statins on incident diabetes and increases in haemoglobin A1c and/or FPG'. However, the literature suggests that the beneficial effects of most statins on CV risk continue to outweigh their diabetogenic risks and that statins should remain as first-line therapy for the majority of people with dyslipidaemia and metabolic syndrome or T2D. Mechanisms explaining the potentially higher incidence of T2D with statin therapy have not been confirmed. However, independent predictors for statin-associated T2D appear to include elevated levels of baseline FPG, BMI, blood pressure and fasting triglycerides. Moreover, although some statins (for example, atorvastatin) are associated with increased haemoglobin A1c levels in patients receiving intensive but not moderate therapy, other statins (for example, pitavastatin) have demonstrated neutral or favourable effects on glucose control in patients with and without T2D or metabolic syndrome. The potential diabetogenic effects of statins may therefore differ between drugs. In conclusion, conflicting data exist regarding the diabetogenic effects of statins. Further studies are required to understand whether all statins have the same effect and whether some patient groups are at higher risk than others. Meanwhile, results suggest that the net CV benefit favours the use of statin therapy in patients with dyslipidaemia, irrespective of T2D risk.

Cholesterol metabolism and the pathogenesis of non-alcoholic steatohepatitis

Emerging experimental and human evidence has linked altered hepatic cholesterol homeostasis and free cholesterol (FC) accumulation to the pathogenesis of non-alcoholic steatohepatits (NASH). This review focuses on cellular mechanisms of cholesterol toxicity involved in liver injury and on alterations in cholesterol homeostasis promoting hepatic cholesterol overload in NASH. FC accumulation injures hepatocytes directly, by disrupting mitochondrial and endoplasmic reticulum (ER) membrane integrity, triggering mitochondrial oxidative injury and ER stress, and by promoting generation of toxic oxysterols, and indirectly, by inducing adipose tissue dysfunction. Accumulation of oxidized LDL particles may also activate Kupffer and hepatic stellate cells, promoting liver inflammation and fibrogenesis. Hepatic cholesterol accumulation is driven by a deeply deranged cellular cholesterol homeostasis, characterized by elevated cholesterol synthesis and uptake from circulating lipoproteins and by a reduced cholesterol excretion. Extensive dysregulation of cellular cholesterol homeostasis by nuclear transcription factors sterol regulatory binding protein (SREBP)-2, liver X-receptor (LXR)-α and farnesoid X receptor (FXR) plays a key role in hepatic cholesterol accumulation in NASH. The therapeutic implications and opportunities for normalizing cellular cholesterol homeostasis in these patients are also discussed.