Cardiovascular risk and thiazolidinediones--what do meta-analyses really tell us?

Metabolic anomalies in vitiligo: a new frontier for drug repurposing strategies

Vitiligo is a chronic autoimmune condition characterized by the destruction of melanocytes, leading to patchy loss of skin depigmentation. Although its precise cause remains unclear, recent evidence suggests that metabolic disturbances, particularly oxidative stress and mitochondrial dysfunction, may play a significant role in the pathogenesis of the disease. Oxidative stress is thought to damage melanocytes and trigger inflammatory responses, culminating in melanocyte immune-mediate destruction. Additionally, patients with vitiligo often exhibit extra-cutaneous metabolic abnormalities such as abnormal glucose metabolism, dyslipidemia, high fasting plasma glucose levels, high blood pressure, out of range C-peptide and low biological antioxidant capacity, suggesting a potential link between metabolic impairment and vitiligo development. This implies that the loss of functional melanocytes mirrors a more general systemic targetable dysfunction. Notably, therapies targeting metabolic pathways, particularly those involving mitochondrial metabolism, such as the peroxisome proliferator-activated nuclear receptor γ (PPARγ) agonists, are currently being investigated as potential treatments for vitiligo. PPARγ activation restores mitochondrial membrane potential, mitochondrial DNA copy number and, consequently, ATP production. Moreover, PPARγ agonists counteract oxidative stress, reduce inflammation, inhibit apoptosis, and maintain fatty acid metabolism, in addition to the well-known capability to enhance insulin sensitivity. Additionally, increasing evidence of a strong relationship between metabolic alterations and vitiligo pathogenesis suggests a role for other approved anti-diabetic treatments, like metformin and fibrates, in vitiligo treatment. Taken together, these data support the use of approaches alternative to traditional immune-suppressive treatments for the treatment of vitiligo.

Stratified glucose-lowering response to vildagliptin and pioglitazone by obesity and hypertriglyceridemia in a randomized crossover trial

Background

Understanding which group of patients with type 2 diabetes will have the most glucose lowering response to certain medications (which target different aspects of glucose metabolism) is the first step in precision medicine.

Aims

We hypothesized that people with type 2 diabetes who generally have high insulin resistance, such as people of Māori/Pacific ethnicity, and those with obesity and/or hypertriglyceridemia (OHTG), would have greater glucose-lowering by pioglitazone (an insulin sensitizer) versus vildagliptin (an insulin secretagogue).

Methods

A randomised, open-label, two-period crossover trial was conducted in New Zealand. Adults with type 2 diabetes, HbA1c>58mmol/mol (>7.5%), received 16 weeks of either pioglitazone (30mg) or vildagliptin (50mg) daily, then switched to the other medication over for another 16 weeks of treatment. Differences in HbA1c were tested for interaction with ethnicity or OHTG, controlling for baseline HbA1c using linear mixed models. Secondary outcomes included weight, blood pressure, side-effects and diabetes treatment satisfaction.

Results

346 participants were randomised (55% Māori/Pacific) between February 2019 to March 2020. HbA1c after pioglitazone was lower than after vildagliptin (mean difference -4.9mmol/mol [0.5%]; 95% CI -6.3, -3.5; p<0.0001). Primary intention-to-treat analysis showed no significant interaction effect by Māori/Pacific vs other ethnicity (1.5mmol/mol [0.1%], 95% CI -0.8, 3.7), and per-protocol analysis (-1.2mmol/mol [0.1%], 95% CI -4.1, 1.7). An interaction effect (-4.7mmol/mol [0.5%], 95% CI -8.1, -1.4) was found by OHTG status. Both treatments generated similar treatment satisfaction scores, although there was greater weight gain and greater improvement in lipids and liver enzymes after pioglitazone than vildagliptin.

Conclusions

Comparative glucose-lowering by pioglitazone and vildagliptin is not different between Māori/Pacific people compared with other New Zealand ethnic groups. Presence of OHTG predicts greater glucose lowering by pioglitazone than vildagliptin.

Clinical trial registration

www.anzctr.org.au, identifier (ACTRN12618001907235).

Evaluation of the anti-diabetic effect of biogenic silver nanoparticles and intervention in PPARγ gene regulation

The current study demonstrated a green, friendly, low-cost biosynthesis of silver nanoparticles (AgNPs) from Kigelia africana leaves (Lam.) Benth. extract (KAE) as both a major capping and reducing agent. The produced AgNPs were characterized using a variety of analytical methods, like the X-ray powder diffraction (XRD), HRTEM, Fourier transforms infrared (FTIR), and UV-Vis spectrophotometer. The formation of AgNPs with maximum absorbance at max = 435 nm was endorsed by surface plasmon resonance. FTIR analysis revealed that biological macromolecules of KAE were involved in the stabilization and synthesis of AgNPs. At the same time, HRTEM images revealed that the average particle size of the spherical AgNPs ranged from about 25 nm to 35 nm. Further, cytotoxicity assessment of AgNPs was done using the RINm5F insulinoma cell line with an MTT assay. Followed by, the RINm5F insulinoma cells treated with AgNPs and KAE, the expression of the Peroxisome proliferator-activated receptor gamma (PPARγ) gene was accessed. The results showed gene expression was upregulated in the RINm5F insulinoma cell line thus confirming AgNPs and KAE anti-diabetic efficacy. Furthermore, the findings show that nanotechnology has enhanced the effectiveness of current methodologies in gene expression and regulation which has contributed to the emergence of different forms of advanced regulatory systems.

Pharmacological Treatment for Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has become the most frequently encountered chronic liver disease. NAFLD is associated with increased liver-related morbidity and mortality, but also contributes to cardiovascular disease, diabetes and non-liver-related malignancy. Non-alcoholic steatohepatitis (NASH) is considered the more severe subtype of NAFLD that drives most of these adverse outcomes. Lifestyle modification and associated weight loss can improve NASH but are not always sufficient and sustained results are difficult to obtain. There is hence an urgent need for pharmacological treatment. In this review we discuss some of the concepts and challenges in the development of pharmacological treatment. We also briefly summarise what can be achieved with some of the drugs that are currently available for other indications but have demonstrated benefit in the treatment of NASH. Finally we present an overview of some of the main drugs or types of drugs, mainly based on their mode of action, that are now being developed specifically to treat NASH and that might soon result in the availability of drugs licensed for NASH.

Cardiovascular outcome studies with incretin-based therapies: Comparison between DPP-4 inhibitors and GLP-1 receptor agonists

Dipeptidyl peptidase-4 inhibitors (DPP-4is) and glucagon-like peptide-1 receptor agonists (GLP-1RAs) represent two distinct classes of incretin-based therapies used for the treatment of type 2 diabetes. Non-inferiority versus placebo was shown in large prospective cardiovascular outcome trials in patients with high cardiovascular risk: SAVOR-TIMI 53 (saxagliptin), EXAMINE (alogliptin), and TECOS (sitagliptin); ELIXA (lixisenatide), LEADER (liraglutide) and SUSTAIN 6 (semaglutide). The promises raised by meta-analyses of phase 2-3 trials with DPP-4is were non confirmed as no cardiovascular protection could be evidenced. However, LEADER showed a significant reduction in major cardiovascular events, myocardial infarction, cardiovascular and all-cause mortality in patients treated by liraglutide compared to placebo. These positive results contrasted with the non-inferiority results with lixisenatide in ELIXA. They were partially confirmed with semaglutide in SUSTAIN 6 despite the absence of reduction in cardiovascular mortality. Hospitalisation for heart failure was not increased except with saxagliptin in SAVOR-TIMI 53. The reasons for different outcomes between trials remain largely unknown as well as the precise underlying mechanisms explaining the cardiovascular protection by liraglutide. The clinical relevance of results with DPP-4is and GLP-1RAs is discussed. Ongoing trials with linagliptin and several once-weekly GLP-1RAs should provide new insights into remaining fundamental questions.

Clinical Update: Cardiovascular Disease in Diabetes Mellitus: Atherosclerotic Cardiovascular Disease and Heart Failure in Type 2 Diabetes Mellitus - Mechanisms, Management, and Clinical Considerations

Cardiovascular disease remains the principal cause of death and disability among patients with diabetes mellitus. Diabetes mellitus exacerbates mechanisms underlying atherosclerosis and heart failure. Unfortunately, these mechanisms are not adequately modulated by therapeutic strategies focusing solely on optimal glycemic control with currently available drugs or approaches. In the setting of multifactorial risk reduction with statins and other lipid-lowering agents, antihypertensive therapies, and antihyperglycemic treatment strategies, cardiovascular complication rates are falling, yet remain higher for patients with diabetes mellitus than for those without. This review considers the mechanisms, history, controversies, new pharmacological agents, and recent evidence for current guidelines for cardiovascular management in the patient with diabetes mellitus to support evidence-based care in the patient with diabetes mellitus and heart disease outside of the acute care setting.

Non-pharmacological and pharmacological strategies of brown adipose tissue recruitment in humans

Humans maintain core temperature through a complex neuroendocrine circuitry, coupling environmental thermal and nutritional cues to heat-producing and dissipating mechanisms. Up to 40% of resting energy expenditure contributes to thermal homeostasis maintenance. Recent re-discovery of thermogenic brown adipose tissue (BAT) has brought the relation between ambient temperature, thermogenesis and systemic energy and substrate metabolism to the forefront. In addition to well-known pituitary-thyroid-adrenal axis, new endocrine signals, such as FGF21 and irisin, orchestrate crosstalk between white adipose tissue (WAT), BAT and muscle, tuning non-shivering and shivering thermogenesis responses. Cold exposure modulates the endocrine milieu, and cold-induced hormones cause bioenergetics transformation sufficient to impact whole body metabolism. This review will appraise the nature of human BAT and the basis of BAT-centred therapeutics, highlighting how the interaction between hormones and adipose tissue impacts metabolic responses. Non-pharmacological and pharmacological strategies of BAT recruitment and/or fat browning for metabolic benefits will be discussed.

Impact of glucose-lowering drugs on cardiovascular disease in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is characterized by multiple pathophysiologic abnormalities. With time, multiple glucose-lowering medications are commonly required to reduce and maintain plasma glucose concentrations within the normal range. Type 2 diabetes mellitus individuals also are at a very high risk for microvascular complications and the incidence of heart attack and stroke is increased two- to three-fold compared with non-diabetic individuals. Therefore, when selecting medications to normalize glucose levels in T2DM patients, it is important that the agent not aggravate, and ideally even improve, cardiovascular risk factors (CVRFs) and reduce cardiovascular morbidity and mortality. In this review, we examine the effect of oral (metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP4 inhibitors, SGLT2 inhibitors, and α-glucosidase inhibitors) and injectable (glucagon-like peptide-1 receptor agonists and insulin) glucose-lowering drugs on established CVRFs and long-term studies of cardiovascular outcomes. Firm evidence that in T2DM cardiovascular disease can be reversed or prevented by improving glycaemic control is still incomplete and must await large, long-term clinical trials in patients at low risk using modern treatment strategies, i.e., drug combinations designed to maximize HbA1c reduction while minimizing hypoglycaemia and excessive weight gain.

A step ahead of PPARγ full agonists to PPARγ partial agonists: therapeutic perspectives in the management of diabetic insulin resistance

Described since long as a member of the nuclear receptor superfamily, peroxisome proliferator-activated receptors (PPARs) regulate the gene expression of proteins involved in glucose and lipid metabolism. PPARs indeed regulate several physiologic processes, including lipid homeostasis, adipogenesis, inflammation, and wound healing. PPARs bind natural or synthetic PPAR ligands can function as cellular sensors to regulate the gene transcription. Dyslipidemia, and type 2 diabetes mellitus (T2DM) with insulin resistance are treated using agonists of PPARα and PPARγ, respectively. The PPARγ is a key regulator of insulin sensitization and glucose metabolism, and therefore is considered as an imperative pharmacological target to combat diabetic metabolic disease and insulin resistance. Of note, currently available PPARγ full agonists like rosiglitazone display serious adverse effects such as fluid retention/oedema, weight gain, and increased incidence of cardiovascular events. On the other hand, PPARγ partial agonists are being suggested to devoid or having less incidence of these undesirable events, and are under developmental stages. Current research is on the way for the development of novel PPARγ partial agonists with enhanced therapeutic efficacy and reduced adverse effects. This review sheds lights on the current status of development of PPARγ partial agonists, for the management of T2DM, having comparatively less or no adverse effects to that of PPARγ full agonists.

Role of protein farnesylation in burn-induced metabolic derangements and insulin resistance in mouse skeletal muscle

Objective

Metabolic derangements, including insulin resistance and hyperlactatemia, are a major complication of major trauma (e.g., burn injury) and affect the prognosis of burn patients. Protein farnesylation, a posttranslational lipid modification of cysteine residues, has been emerging as a potential component of inflammatory response in sepsis. However, farnesylation has not yet been studied in major trauma. To study a role of farnesylation in burn-induced metabolic aberration, we examined the effects of farnesyltransferase (FTase) inhibitor, FTI-277, on burn-induced insulin resistance and metabolic alterations in mouse skeletal muscle.

Methods

A full thickness burn (30% total body surface area) was produced under anesthesia in male C57BL/6 mice at 8 weeks of age. After the mice were treated with FTI-277 (5 mg/kg/day, IP) or vehicle for 3 days, muscle insulin signaling, metabolic alterations and inflammatory gene expression were evaluated.

Results

Burn increased FTase expression and farnesylated proteins in mouse muscle compared with sham-burn at 3 days after burn. Simultaneously, insulin-stimulated phosphorylation of insulin receptor (IR), insulin receptor substrate (IRS)-1, Akt and GSK-3β was decreased. Protein expression of PTP-1B (a negative regulator of IR-IRS-1 signaling), PTEN (a negative regulator of Akt-mediated signaling), protein degradation and lactate release by muscle, and plasma lactate levels were increased by burn. Burn-induced impaired insulin signaling and metabolic dysfunction were associated with increased inflammatory gene expression. These burn-induced alterations were reversed or ameliorated by FTI-277.

Conclusions

Our data demonstrate that burn increased FTase expression and protein farnesylation along with insulin resistance, metabolic alterations and inflammatory response in mouse skeletal muscle, all of which were prevented by FTI-277 treatment. These results indicate that increased protein farnesylation plays a pivotal role in burn-induced metabolic dysfunction and inflammatory response. Our study identifies FTase as a novel potential molecular target to reverse or ameliorate metabolic derangements in burn patients.

Observational follow-up of the PROactive study: a 6-year update

AIMS

The PROactive study investigated pioglitazone for secondary prevention of macrovascular events in type 2 diabetes mellitus. Pioglitazone showed a 10% (non-significant) relative risk (RR) reduction for the primary composite endpoint and a significant 16% reduction for the main secondary endpoint (death, myocardial infarction, stroke) after a mean 34.5 months. There was no difference in cumulative malignancy incidence, but an imbalance in bladder malignancies (pioglitazone 14, placebo 5). We present a pre-specified 6-year interim analysis of a 10-year observational follow-up.

METHODS

Any patient completing PROactive was eligible. No study treatments were provided. A Cox proportional hazard model compared non-adjudicated macrovascular events (same endpoints as PROactive excluding acute coronary syndrome) based on original randomization. Malignancies were compared using conventional RR ratios.

RESULTS

Of 5238 randomized patients, 3599 (74%) entered the follow-up. For the follow-up (mean 5.8 years) or combined double-blind and follow-up periods (≤9.5 years, mean 8.7), there were no statistically significant differences in primary or main secondary endpoints. For the combined period, a similar percentage of patients had any diagnosed malignancy (RR = 1.05, 95% CI [0.89, 1.24]) or bladder malignancy (RR = 1.06, 95% CI [0.59, 1.89]) in the pioglitazone and placebo groups. There were fewer cases of bladder malignancy with pioglitazone (15 [0.6%] vs. 19 [0.7%] for placebo) for the combined period when events diagnosed in the first 365 days were excluded, and fewer cases for the follow-up period alone (10 [0.5%] vs. 17 [1.0%] for placebo). Further analyses of pioglitazone use (including use during follow-up) found no significant difference in bladder malignancies between any and no pioglitazone use for the combined period.

CONCLUSIONS

These data suggest that improved macrovascular outcomes seen with pioglitazone subside without continued pioglitazone treatment. The double-blind period bladder cancer imbalance did not persist in follow-up.

Do thiazolidinediones still have a role in treatment of type 2 diabetes mellitus?

Thiazolidinediones have been introduced in the treatment of type 2 diabetes mellitus (T2DM) since the late 1990s. Although troglitazone was withdrawn from the market a few years later due to liver toxicity, both rosiglitazone and pioglitazone gained widespread use for T2DM treatment. In 2010, however, due to increased risk of cardiovascular events associated with its use, the European Medicines Agency recommended suspension of rosiglitazone use and the Food and Drug Administration severely restricted its use. Thus pioglitazone is the only thiazolidinedione still significantly employed for treating T2DM and it is the only molecule of this class still listed in the American Diabetes Association-European Association for the Study of Diabetes 2012 Position Statement. However, as for the other thiazolidinediones, use of pioglitazone is itself limited by several side effects, some of them potentially dangerous. This, together with the development of novel therapeutic strategies approved in the last couple of years, has made it questionable whether or not thiazolidinediones (namely pioglitazone) should still be used in the treatment of T2DM. This article will attempt to formulate an answer to this question by critically reviewing the available data on the numerous advantages and the potentially worrying shortcomings of pioglitazone treatment in T2DM.

Pleiotropic effects of thiazolidinediones: implications for the treatment of patients with type 2 diabetes mellitus

Thiazolidinediones (TZDs) are insulin-sensitizing antidiabetes agents that act through the peroxisome proliferator-activated receptor-γ to cause a durable improvement in glycemic control in patients with type 2 diabetes mellitus. Although less well recognized, TZDs also exert a protective effect on β-cell function. In addition to their beneficial effects on glucose homeostasis, TZDs-especially pioglitazone-exert a number of other pleiotropic effects that make them ideal agents as monotherapy or in combination with other oral agents, glucagon-like peptide-1 analogs, or insulin. Pioglitazone improves endothelial dysfunction, reduces blood pressure, corrects diabetic dyslipidemia, and reduces circulating levels of inflammatory cytokines and prothrombotic factors. Pioglitazone also redistributes fat and toxic lipid metabolites in muscle, liver, β cells, and arteries, and deposits the fat in subcutaneous adipocytes where it cannot exert its lipotoxic effects. Consistent with these antiatherogenic effects, pioglitazone reduced major adverse cardiac event endpoints (ie, mortality, myocardial infarction, and stroke) in the Prospective Pioglitazone Clinical Trial in Macrovascular Events and in a meta-analysis of all other published pioglitazone trials. Pioglitazone also mobilizes fat out of the liver, improving liver function and histologic abnormalities in patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis. Pioglitazone also reduces proteinuria, all-cause mortality, and cardiovascular events in patients with type 2 diabetes mellitus with a reduced glomerular filtration rate. These benefits must be weighed against the side effects of the drug, including weight gain, fluid retention, atypical fractures, and, possibly, bladder cancer. When low doses of pioglitazone are used (eg, 7.5-30 mg/d) with gradual titration, and physician recognition of the potential side effects are applied, the risk-to-benefit ratio is very favorable. Despite having similar effects on glycemic control, pioglitazone and rosiglitazone appear to have different effects on cardiovascular outcomes. Rosiglitazone has been associated with an increased risk of myocardial infarction, and its use in the United States is restricted because of cardiovascular safety concerns.

Reduction of free fatty acids, safety, and pharmacokinetics of oral GS-9667, an A(1) adenosine receptor partial agonist

GS-9667, a new selective, partial agonist of the A(1) adenosine receptor (AR), may represent an effective therapy for Type 2 diabetes (T2DM) and dyslipidemia via lowering of free fatty acids (FFA). The objectives of the studies were to evaluate the effects of single and multiple doses of GS-9667 on plasma FFA concentrations, its pharmacokinetics (PK) and safety/tolerability. Two studies were conducted. In the single ascending dose study, healthy, non-obese, and obese subjects received a single oral dose of GS-9667 (30-1,800 mg). In the multiple, ascending dose study, healthy, obese subjects received GS-9667 (600-2,400 mg QD, 1,200 mg BID, or 600 mg QID) for 14 days. Blood and urine samples were collected for lipid profiling and PK analyses. The ECG, vital signs, and subject tolerability were monitored. Doses of GS-9667 ≥300 mg caused dose-dependent reductions in FFA levels that were reproducible over 14 days without evidence of desensitization or rebound. All doses were well tolerated. GS-9667 was rapidly absorbed and distributed; Steady-state concentrations were achieved within 3-5 days. The A(1) AR partial agonist GS-9667 reduced plasma FFA, exhibited linear kinetics, and was well-tolerated in healthy non-obese and obese subjects.

Cardiovascular disease and glycemic control in type 2 diabetes: now that the dust is settling from large clinical trials

The relationship between glucose control and cardiovascular outcomes in type 2 diabetes has been a matter of controversy over the years. Although epidemiological evidence exists in favor of an adverse role of poor glucose control on cardiovascular events, intervention trials have been less conclusive. The Action to Control Cardiovascular Risk in Diabetes (ACCORD) study, the Action in Diabetes and Vascular Disease (ADVANCE) study, and the Veterans Affairs Diabetes Trial (VADT) have shown no beneficial effect of intensive glucose control on primary cardiovascular endpoints in type 2 diabetes. However, subgroup analysis has provided evidence suggesting that the potential beneficial effect largely depends on patients’ characteristics, including age, diabetes duration, previous glucose control, presence of cardiovascular disease, and risk of hypoglycemia. The benefit of strict glucose control on cardiovascular outcomes and mortality may be indeed hampered by the extent and frequency of hypoglycemic events and could be enhanced if glucose-lowering medications, capable of exerting favorable effects on the cardiovascular system, were used. This review examines the relationship between intensive glucose control and cardiovascular outcomes in type 2 diabetes, addressing the need for individualization of glucose targets and careful consideration of the benefit/risk profile of antidiabetes medications.

Risk of fracture with thiazolidinediones: an individual patient data meta-analysis

BACKGROUND

The use of thiazolidinediones (TZDs) has been associated with increased fracture risks. Our aim was to estimate the risk of fracture with TZDs in three different healthcare registries, using exactly the same study design, and to perform an individual patient data meta-analysis of these three studies.

METHODS

Population-based cohort studies were performed utilizing the British General Practice Research Database (GPRD), the Dutch PHARMO Record Linkage System (RLS), and the Danish National Health Registers. In all three databases, the exposed cohort consisted of all patients (aged 18+) with at least one prescription of antidiabetic (AD) medication. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture. The total period of follow-up for each patient was divided into periods of current exposure and past exposure, with patients moving between current and past use.

RESULTS

In all three registries, the risk of fracture was increased for women who were exposed to TZDs: HR 1.48 (1.37-1.60) in GPRD, HR 1.35 (1.15-1.58) in PHARMO, and HR 1.22 (1.03-1.44) in Denmark. Combining the data in an individual patient data meta-analysis resulted, for women, in a 1.4-fold increased risk of any fracture for current TZD users versus other AD drug users [adj. HR 1.44 (1.35-1.53)]. For men, there was no increased fracture risk [adj. HR 1.05 (0.96-1.14)]. Risks were increased for fractures of the radius/ulna, humerus, tibia/fibula, ankle, and foot, but not for hip/femur or vertebral fractures. Current TZD users with more than 25 TZD prescriptions ever before had a 1.6-fold increased risk of fracture compared with other AD drug users [HR 1.59 (1.46-1.74)].

CONCLUSION

In this study, we consistently found a 1.2- to 1.5-fold increased risk of fractures for women using TZDs, but not for men, across three different healthcare registries. TZD users had an increased risk for fractures of the extremities, and risks further increased for prolonged users of TZDs.

Sex-specific differences in Type 2 Diabetes Mellitus and dyslipidemia therapy: PPAR agonists

The influence of sex on the development of obesity, Type 2 Diabetes Mellitus (T2DM), and dyslipidemia is well documented, although the molecular mechanism underlying those differences reminds elusive. Ligands of peroxisome proliferator-activated receptors (PPARs) are used as oral antidiabetics (PPARgamma agonists: thiazolidinediones, TZDs), or for the treatment of dyslipidemia and cardiovascular diseases, due to their lipid-lowering properties (PPARalpha agonists: fibrates), as PPARs control transcription of a set of genes involved in the regulation of lipid and carbohydrate metabolism. Given a high prevalence of those metabolic disorders, and thus a broad use of PPAR agonists, the present review will discuss distinct aspects of sex-specific differences in antiobesity treatment using those groups of PPAR ligands.

PPAR agonists for the treatment of cardiovascular disease in patients with diabetes

Diabetes is a complex disease defined by hyperglycaemia; however, strong associations with abdominal obesity, hypertension and dyslipidaemia contribute to the high risk of cardiovascular disease. Although aggressive glycaemic control reduces microvascular complications, the evidence for macrovascular complications is less certain. The theoretical benefits of the mode of action of peroxisome proliferator-activated receptor (PPAR) agonists are clear. In clinical practice, PPAR-α agonists such as fibrates improve dyslipidaemia, while PPAR-γ agonists such as thiazolidinediones improve insulin resistance and diabetes control. However, although these agents are traditionally classed according to their target, they have different and sometimes conflicting clinical benefit and adverse event profiles. It is speculated that this is because of differing properties and specificities for the PPAR receptors (each of which targets specific genes). This is most obvious in the impact on cardiovascular outcomes--in clinical trials pioglitazone appeared to reduce cardiovascular events, whereas rosiglitazone potentially increased the risk of myocardial infarction. The development of a dual PPAR-α/γ agonist may prove beneficial in effectively managing glycaemic control and improving dyslipidaemia in patients with type 2 diabetes. Yet, development of agents such as muraglitazar and tesaglitazar has been hindered by various serious adverse events. Aleglitazar, a balanced dual PPAR-α/γ agonist, is currently the most advanced in clinical development and has shown promising results in phase II clinical trials with beneficial effects on glucose and lipid variables. A phase III study, ALECARDIO, is ongoing and will establish whether improvements in laboratory test profiles translate into an improvement in cardiovascular outcomes.

Spirulina improves non-alcoholic steatohepatitis, visceral fat macrophage aggregation, and serum leptin in a mouse model of metabolic syndrome

BACKGROUND

Nutritional approaches are sought to overcome the limits of pioglitazone in metabolic syndrome and non-alcoholic fatty liver disease. Spirulina, a filamentous unicellular alga, reduces serum lipids and blood pressure while exerting antioxidant effects.

AIM

To determine whether Spirulina may impact macrophages infiltrating the visceral fat in obesity characterizing our metabolic syndrome mouse model induced by the subcutaneous injection treatment of monosodium glutamate.

METHODS

Mice were randomized to receive standard food added with 5% Spirulina, 0.02% pioglitazone, or neither. We tested multiple biochemistry and histology (both liver and visceral fat) readouts at 24 weeks of age.

RESULTS

Data demonstrate that both the Spirulina and the pioglitazone groups had significantly lower serum cholesterol and triglyceride levels and liver non-esterified fatty acid compared to untreated mice. Spirulina and pioglitazone were associated with significantly lower leptin and higher levels, respectively, compared to the control group. At liver histology, non-alcoholic fatty liver disease activity score and lipid peroxide were significantly lower in mice treated with Spirulina.

CONCLUSIONS

Spirulina reduces dyslipidaemia in our metabolic syndrome model while ameliorating visceral adipose tissue macrophages. Human studies are needed to determine whether this safe supplement could prove beneficial in patients with metabolic syndrome.

Risk of fracture with thiazolidinediones: disease or drugs?

The use of thiazolidinediones (TZDs) has been associated with an increased fracture risk. In addition, type 2 diabetes mellitus (T2DM) has been linked with fracture. We evaluated to what extent the association between TZD use and fracture risk is related to the drug or to the underlying disease. We conducted a population-based cohort study using the Danish National Health Registers (1996-2007), which link pharmacy data to the national hospital registry. Oral antidiabetic users (n = 180,049) were matched 1:3 by year of birth and sex to nonusers. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture. Time-dependent adjustments were made for age, comorbidity, and drug use. We created a proxy indicator for the severity of disease. The first stage was defined as current use of either a biguanide or a sulfonyluerum, the second stage as current use of a biguanide and a sulfonyluerum at the same time, the third stage as patients using TZDs, and the fourth stage as patients using insulin. The risk of osteoporotic fracture was increased 1.3-fold for stages 3 and 4 compared with controls. Risk with current TZD use (stage 3 HR = 1.27, 95 % CI 1.06-1.52) and risk with current use of insulin (stage 4 HR = 1.25, 95 % CI 1.20-1.31) were similar. In the first (HR = 1.15, 95 % CI 1.13-1.18) and second (HR = 1.00, 95 % CI 0.96-1.04) stages risks were lower. Risk of osteoporotic fracture was similar for TZD users and insulin users. When studying fracture risk with TZDs, the underlying T2DM should be taken into account.

Metabolic syndrome in South Asians

Metabolic syndrome (MS) is a cluster of multiple cardio-metabolic risk factors in the same individual. People with MS are at high risk for the development of cardiovascular disease (CVD), chronic kidney disease (CKD), and cerebrovascular disease (CeVD). The excessive presence of MS in South Asians is likely responsible for significant morbidity in this population. This review discusses the scope of MS in South Asians and measures to combat its effects by preventive and therapeutic measures.

Interplay between statins and PPARs in improving cardiovascular outcomes: a double-edged sword?

Statins are best-selling medications in the management of high cholesterol and associated cardiovascular complications. They inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA)-reductase in order to prevent disproportionate cholesterol synthesis. Statins slow the progression of atherosclerosis, prevent the secondary cardiovascular events and improve the cardiovascular outcomes in patients with elevated cholesterol levels. The underlying mechanisms pertaining to the cardioprotective role of statins are linked with numerous pleiotropic actions including inhibition of inflammatory events and improvement of endothelial function, besides an effective cholesterol-lowering ability. Intriguingly, recent studies suggest possible interplay between statins and nuclear transcription factors like PPARs, which should also be taken into consideration while analysing the potential of statins in the management of cardiovascular complications. It could be suggested that statins have two major roles: (i) a well-established cholesterol-lowering effect through inhibition of HMG-CoA-reductase; (ii) a newly explored PPAR-activating property, which could mediate most of cardiovascular protective pleiotropic effects of statins including anti-inflammatory, antioxidant and anti-fibrotic properties. The present review addressed the underlying principles pertaining to the modulatory role of statins on PPARs.

Use of thiazolidinediones and risk of osteoporotic fracture: disease or drugs?

PURPOSE

Clinical and observational studies suggest that use of thiazolidinediones (TZDs) is associated with an increased fracture risk. In addition, type 2 diabetes mellitus (T2DM) is a risk factor for osteoporotic fracture. Our aim was to estimate fracture risks in TZD users and users of other antidiabetic drugs, classified according to proxies of disease severity.

METHODS

We conducted a population-based cohort study utilizing the Dutch PHARMO database (1998-2008). PHARMO links pharmacy-dispensing data to the National Hospital Registry. Oral antidiabetic users (n = 123,452) were matched 1:4 by year of birth and sex to non-users. Cox proportional hazards models were used to estimate hazard ratios (HRs) of fracture in TZD users. We created a proxy indicator for disease severity. The first stage was defined as current use of either a biguanide or a sulfonylureum, the second stage as current use of a biguanide and a sulfonylureum at the same time, the third stage was assigned to patients using TZDs and the fourth stage to patients using insulin.

RESULTS

The risk of osteoporotic fracture was increased 1.5-fold (HR 1.49, 95%CI 1.28-1.73) in patients who currently used TZDs (stage 3), and for patients using insulin (stage 4), the risk was increased 1.2-fold (HR 1.24, 1.14-1.36), as compared with controls. In the first and second stages, risks were lower: HR 1.11 (1.06-1.17) for stage 1 and HR 1.03 (0.96-1.11) for stage 2.

CONCLUSIONS

When observational studies assess risk of fracture in patients with TZDs, the severity of T2DM should be taken into account.

Establishment of a cell-based drug screening model for identifying agonists of human peroxisome proliferator-activated receptor gamma (PPARγ)

OBJECTIVES

Peroxisome proliferator-activated receptor gamma (PPARγ) plays a critical role in regulation of diverse biological processes, including lipid metabolism and adipogenesis, cell division and apoptosis, and is involved in variety of disease conditions, such as obesity, atherosclerosis, inflammation and tumour. Developing a cell-based reporter gene model targeting PPARγ would be useful to screen human PPARγ agonists that could be beneficial to patients with these diseases.

METHODS

We stably co-transfected human embryonic kidney (HEK) cell line 293T cells with phPPARγ-IRES2-EGFP vector to express human PPARγ (hPPARγ), a reporter vector pPPRE×3-TK-LUC, and control vector pRL-CMV. The efficiency of the co-transfection was evaluated with flow cytometry of hPPARγ expressing cells. Specificity of hPPARγ activity was determined by dual luciferase reporter assay of co-transfected cells exposed to PPARγ agonist rosiglitazone, PPARα agonist WY14643 and retinoic acid receptor alpha (RARα) agonist all-trans-retinoic acid (ATRA).

KEY FINDINGS

The phPPARγ-IRES2-EGFP co-transfected HEK293T cells showed concentration- and time-dependent luciferase induction upon exposure to the rosiglitazone, while WY14643 and ATRA were unable to activate the co-transfected HEK293T cells.

CONCLUSIONS

These data indicated that the HEK293T cells could be stably transfected with hPPARγ. This cell-based drug screening platform could be used targeting specific nuclear receptor of hPPARγ with effectiveness and specificity for hPPARγ agonists discovery.

Cancer-preventive rexinoid modulates neutral lipid contents of mammary epithelial cells through a peroxisome proliferator-activated receptor γ-dependent mechanism

Synthetic rexinoids effectively suppress both estrogen receptor-positive and estrogen receptor-negative mammary tumors in animal models, which makes them prime candidates for a novel class of cancer-preventive agents. When used in combination with chemotherapy for non-small-cell lung cancer, the rexinoid bexarotene was most effective for patients who developed hypertriglyceridemia as a side effect. Although serum triglycerides originate from the liver, the effect of bexarotene on lipogenesis in breast epithelial cells is not known. Gene expression studies with normal mammary epithelial cells indicated that rexinoids modulate lipid metabolism, particularly enzymes involved in triglyceride synthesis. High-content analysis revealed dose-dependent accumulation of neutral lipids within adipocyte differentiation-related protein-associated cytoplasmic lipid droplets after long-term bexarotene treatment. Bexarotene also induced mRNA and protein levels for peroxisome proliferator-activated receptor (PPAR) γ, whereas selective knockdown of PPARγ attenuated the induction of both lipid droplets and adipocyte differentiation-related protein. Pharmacological activation of PPARγ, but not PPARα or retinoic acid receptors, effectively induced lipid accumulation. Furthermore, the combination of the PPARγ agonist rosiglitazone with bexarotene synergistically suppressed the growth of human mammary epithelial cells and revealed a strong, nonlinear, inverse correlation of cell growth with lipid droplet accumulation in the cell population. These findings indicate that rexinoids activate a lipogenic program in mammary epithelial cells through a retinoid X receptor/PPARγ-mediated mechanism. It is noteworthy that combining low doses of bexarotene with the PPARγ agonist rosiglitazone provides effective growth suppression of mammary epithelial cells, potentially dissociating systemic adverse effects associated with standard bexarotene treatment from the antiproliferative effects on mammary epithelium.

The inhibitory effect of celecoxib and rosiglitazone on experimental endometriosis

OBJECTIVE

To evaluate the effects of celecoxib and rosiglitazone on the implantation and growth of endometriotic-like lesions in a murine model of endometriosis.

DESIGN

Prospective experimental study.

SETTING

Animal research and laboratory facility.

ANIMAL(S)

Two-month-old female BALB/c mice.

INTERVENTION(S)

Surgically induced endometriosis in female BALB/C mice; 28 days of treatment with celecoxib, rosiglitazone, or their combination; counting, measuring, excising, and fixing lesions.

MAIN OUTCOME MEASURE(S)

Immunohistochemical examination for proliferating cell nuclear antigen (PCNA), CD31, and CD34 to assess cell proliferation and vascularization, with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) technique for apoptosis evaluation.

RESULT(S)

Celecoxib and the combined treatment (celecoxib and rosiglitazone) statistically significantly reduced the mean number of lesions established per mouse, and all treatments diminished the implant volume. In addition, cell proliferation within the implants was statistically significantly reduced, and apoptosis was statistically significantly enhanced by all treatments. Also, we found that all treatments diminished the vascularized area in the lesion.

CONCLUSION(S)

These results are promising and reveal that celecoxib and rosiglitazone, combined or separately, have a beneficial effect on overall endometriotic growth.

In vitro characterization of rosiglitazone metabolites and determination of the kinetic parameters employing rat liver microsomal fraction

Rosiglitazone (RSG), a thiazolidinedione antidiabetic drug, is metabolized by CYP450 enzymes into two main metabolites: N-desmethyl rosiglitazone (N-Dm-R) and ρ-hydroxy rosiglitazone (ρ-OH-R). In humans, CYP2C8 appears to have a major role in RSG metabolism. On the other hand, the in vitro metabolism of RSG in animals has not been described in literature yet. Based on these concerns, the kinetic metabolism study of RSG using rat liver microsomal fraction is described for the first time. Maximum velocity (V (max)) values of 87.29 and 51.09 nmol/min/mg protein were observed for N-Dm-R and ρ-OH-R, respectively. Michaelis-Menten constant (K(m)) values were of 58.12 and 78.52 μM for N-Dm-R and ρ-OH-R, respectively. Therefore, these results demonstrated that this in vitro metabolism model presents the capacity of forming higher levels of N-Dm-R than of ρ-OH-R, which also happens in humans. Three other metabolites were identified employing mass spectrometry detection under positive electrospray ionization: ortho-hydroxy-rosiglitazone (ο-OH-R) and two isomers of N-desmethyl hydroxy-rosiglitazone. These metabolites have also been observed in humans. The results observed in this study indicate that rats could be a satisfactory model for RSG metabolism.

Effects of specific chemical suppressors of plasminogen activator inhibitor-1 in cardiovascular diseases

INTRODUCTION

plasminogen activator inhibitor-1 (PAI-1) is critical in thrombus formation and inflammation. Although these are essential pathological features of cardiovascular diseases, the effects of PAI-1 inhibition against the development of cardiovascular remodeling have not been well studied.

AREAS COVERED

the review explores the therapeutic value of PAI-1 in the progression of various cardiovascular diseases. To date, the authors have reported that a novel PAI-1 inhibitor suppressed the development of experimental autoimmune myocarditis, vascular remodeling after arterial injury, and heart transplant rejection using rodent models. Pathologically, the PAI-1 inhibitor improved histological remodeling of myocardium and arteries with suppression of inflammation and thrombus formation.

EXPERT OPINION

PAI-1 inhibitors appear to exhibit potent effects on the prevention of adverse tissue remodeling. However, PAI-1 is a multifunctional protein and more research is needed to further elucidate the association between PAI-1 expression and cardiovascular disease.