Glitazones and the cardiovascular system

Development and validation of a sensitive LC-MS/MS method for pioglitazone: application towards pharmacokinetic and tissue distribution study in rats

In the present study, a sensitive LC-MS/MS method was developed and validated to measure pioglitazone (PGZ) concentrations in rat plasma and tissues. The chromatographic separation was achieved by using a YMC Pro C₁₈ column (100 mm × 4.6 mm, 3μ) with a mobile phase consisting of formic acid (0.1% v/v) and acetonitrile (5 : 95) at a flow rate of 0.7 mL min⁻¹ and injection volume of 10 μL (IS: rosiglitazone). Mass spectrometric detection was done using triple quadrupole mass spectrometry using the ESI interface operating in a positive ionization mode. The developed method was validated over a linearity range of 1–500 ng mL⁻¹ with detection and a lower quantification limit of 0.5 ng mL⁻¹ and 1 ng mL⁻¹. The method accuracy ranged from 95.89–98.78% (inter-day) & 93.39–97.68% (intra-day) with a precision range of 6.09–8.12% for inter-day & 7.55–9.87% for intra-day, respectively. The PGZ shows the highest C_max of 495.03 ng mL⁻¹ in plasma and the lowest C_max, 24.50 ± 2.71 ng mL⁻¹ in bone. The maximum T_max of 5.00 ± 0.49 h was observed in bone and a minimum of 1.01 ± 0.05 h in plasma. The AUC_{(0–24 h and 0–∞)} values are highest in plasma (1056.58 ± 65.78 & 1069.38 ± 77.50 ng h⁻¹ mL⁻¹) and lowest in brain (166.93 ± 15.70 &167.12 ± 16.77 ng h⁻¹ mL⁻¹), and the T_1/2 was highest in plasma (5.62 ± 0.74 h) and lowest in kidney (2.78 ± 0.19). The developed method was successfully used to measure the PGZ pharmacokinetic and tissue distribution. Further, the developed method could be utilized for validating target organ (adipose tissue) specific delivery of PGZ (nano-formulations) in addition to conventional dosage forms.

The developed method was investigated for target and off-target distribution of pioglitazone and could be applied to validate the site-specific delivery systems.

The Pioglitazone Trek via Human PPAR Gamma: From Discovery to a Medicine at the FDA and Beyond

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.

Evaluation and treatment of hypertriglyceridemia: an Endocrine Society clinical practice guideline

OBJECTIVE

The aim was to develop clinical practice guidelines on hypertriglyceridemia.

PARTICIPANTS

The Task Force included a chair selected by The Endocrine Society Clinical Guidelines Subcommittee (CGS), five additional experts in the field, and a methodologist. The authors received no corporate funding or remuneration.

CONSENSUS PROCESS

Consensus was guided by systematic reviews of evidence, e-mail discussion, conference calls, and one in-person meeting. The guidelines were reviewed and approved sequentially by The Endocrine Society's CGS and Clinical Affairs Core Committee, members responding to a web posting, and The Endocrine Society Council. At each stage, the Task Force incorporated changes in response to written comments.

CONCLUSIONS

The Task Force recommends that the diagnosis of hypertriglyceridemia be based on fasting levels, that mild and moderate hypertriglyceridemia (triglycerides of 150-999 mg/dl) be diagnosed to aid in the evaluation of cardiovascular risk, and that severe and very severe hypertriglyceridemia (triglycerides of > 1000 mg/dl) be considered a risk for pancreatitis. The Task Force also recommends that patients with hypertriglyceridemia be evaluated for secondary causes of hyperlipidemia and that subjects with primary hypertriglyceridemia be evaluated for family history of dyslipidemia and cardiovascular disease. The Task Force recommends that the treatment goal in patients with moderate hypertriglyceridemia be a non-high-density lipoprotein cholesterol level in agreement with National Cholesterol Education Program Adult Treatment Panel guidelines. The initial treatment should be lifestyle therapy; a combination of diet modification and drug therapy may also be considered. In patients with severe or very severe hypertriglyceridemia, a fibrate should be used as a first-line agent.

Blood glucose control and coronary heart disease

Epidemiologic data support the hypothesis of a direct and independent relationship between hyperglycemia and cardiovascular disease. The lack of a clear-cut threshold value in diabetic patients, and the persistence of the relationship in nondiabetic population as well, suggest that glycemia is a continuous variable, similarly to other cardiovascular risk factors. Moreover, increased plasma glucose levels contribute to cardiovascular risk by activating multiple atherogenic mechanisms. In spite of evident plausibility for hyperglycemia as a cardiovascular risk factor per se, intervention data remain controversial. Results of recent large-scale intervention trials, such as ACCORD, ADVANCE, and VADT, seem to undermine the concept that tight glycemic control confers some protection against cardiovascular disease in patients with type 2 diabetes, while maintenance of near-normal glycemic control from earlier stage of the disease and during acute coronary events seems to be more beneficial. However, individualized therapies remain the cornerstone of strategies aimed to reduce cardiovascular risk associated to hyperglycemia.

PPAR-gamma-independent inhibitory effect of rosiglitazone on glucose synthesis in primary cultured rabbit kidney-cortex tubules

Therapeutic effect of rosiglitazone has been reported to result from an improvement of insulin sensitivity and inhibition of glucose synthesis. As the latter process occurs in both liver and kidney cortex the aim of this study was to elucidate the rosiglitazone action on glucose formation in both tissues. Primary cultured cells of both liver and kidney cortex grown in defined medium were use throughout. To identify the mechanism responsible for drug-induced changes, intracellular gluconeogenic intermediates and enzyme activities were determined. In contrast to hepatocytes, the administration of a 10 micromol/L concentration of rosiglitazone to renal tubules resulted in about a 70% decrease in the rate of gluconeogenesis, accompanied by an approximately 75% decrease in alanine utilization and a 35% increase in lactate synthesis. The effect of rosiglitazone was not abolished by GW9662, the PPAR-gamma irreversible antagonist, indicating that this action is not dependent on PPAR-gamma activation. In view of rosiglitazone-induced changes in gluconeogenic intermediates and a diminished incorporation of 14CO2 into pyruvate, it is likely that the drug causes a decline in flux through pyruvate carboxylase and (or) phosphoenolpyruvate carboxykinase. It is likely that the hypoglycemic action of rosiglitazone is PPAR-gamma independent and results mainly from its inhibitory effects on renal gluconeogenesis.

Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low fat diet

We recently proposed that the biological markers improved by carbohydrate restriction were precisely those that define the metabolic syndrome (MetS), and that the common thread was regulation of insulin as a control element. We specifically tested the idea with a 12-week study comparing two hypocaloric diets (approximately 1,500 kcal): a carbohydrate-restricted diet (CRD) (%carbohydrate:fat:protein = 12:59:28) and a low-fat diet (LFD) (56:24:20) in 40 subjects with atherogenic dyslipidemia. Both interventions led to improvements in several metabolic markers, but subjects following the CRD had consistently reduced glucose (-12%) and insulin (-50%) concentrations, insulin sensitivity (-55%), weight loss (-10%), decreased adiposity (-14%), and more favorable triacylglycerol (TAG) (-51%), HDL-C (13%) and total cholesterol/HDL-C ratio (-14%) responses. In addition to these markers for MetS, the CRD subjects showed more favorable responses to alternative indicators of cardiovascular risk: postprandial lipemia (-47%), the Apo B/Apo A-1 ratio (-16%), and LDL particle distribution. Despite a threefold higher intake of dietary saturated fat during the CRD, saturated fatty acids in TAG and cholesteryl ester were significantly decreased, as was palmitoleic acid (16:1n-7), an endogenous marker of lipogenesis, compared to subjects consuming the LFD. Serum retinol binding protein 4 has been linked to insulin-resistant states, and only the CRD decreased this marker (-20%). The findings provide support for unifying the disparate markers of MetS and for the proposed intimate connection with dietary carbohydrate. The results support the use of dietary carbohydrate restriction as an effective approach to improve features of MetS and cardiovascular risk.

Sibutramine effect on metabolic control of obese patients with type 2 diabetes mellitus treated with pioglitazone

Thiazolidinediones are supposed to be the pharmacologic agents that more physiologically fight the insulin resistance, but a possible adverse effect may be a weight increase. The aim of the study was to test the efficacy and tolerability of sibutramine on the metabolic effect of pioglitazone in obese patients with type 2 diabetes mellitus. All enrolled patients were required to have been diagnosed as being diabetic for at least 6 months and did not have glycemic control with diet and oral hypoglycemic agents such as sulfonylureas or metformin, both to the maximum tolerated dose. After a run-in period in which the eligible patients took a fixed dose of pioglitazone (30 mg/d), the patients were randomized to receive also sibutramine (10 mg/d) or placebo for 6 months. We assessed body mass index, hemoglobin A(1c) (HbA(1c)), fasting plasma glucose (FPG), postprandial plasma glucose (PPG), fasting plasma insulin (FPI), postprandial plasma insulin (PPI), lipid profile, lipoprotein parameters, and lipoprotein (a) at baseline and after 3 and 6 months. No body mass index change was observed after 3 and 6 months in the pioglitazone + placebo (pp) group. Significant decrease was present in the pioglitazone + sibutramine (ps) group after 3 (P < .05) and 6 months (P < .01) compared with the baseline values, and this variation was significant (P < .05) between groups. A significant HbA(1c) decrease was observed after 3 (P < .05) and 6 months (P < .01) in both groups with respect to the baseline values. There was no difference in HbA(1c) value between the 2 groups. No FPG, PPG, FPI, PPI, and homeostasis model assessment index change was observed at 3 months, whereas a significant decrease was present after 6 months (P < .05), in both groups with respect to the baseline values. There was no difference in FPG, PPG, FPI, PPI, and homeostasis model assessment index value between the pp and ps groups. No significant low-density lipoprotein cholesterol change was observed at 3 months, whereas a significant decrease was present after 6 months (P < .05), in both groups with respect to the baseline values. There was no difference in low-density lipoprotein cholesterol value between the pp and ps groups. No triglyceride variation was present at 3 and 6 months in the pp group and at 3 months in the ps group, whereas a significant decrease was observed at 6 months (P < .05) in the ps group with respect to the baseline values. There was no difference in triglyceride value between both groups. No high-density lipoprotein cholesterol, apolipoprotein A-I, apolipoprotein B, and lipoprotein (a) changes were present in both groups with respect to the baseline values. Sibutramine appears to be a tolerable and efficacious drug when added to pioglitazone for the global management of obese diabetic patients.

Design, synthesis, and structure-activity relationships of novel insulin receptor tyrosine kinase activators

A novel series of symmetrical ureas of [(7-amino(2-naphthyl))sulfonyl]phenylamines were designed, synthesized, and tested for their ability to increase glucose transport in mouse 3T3-L1 adipocytes, a surrogate readout for activation of the insulin receptor (IR) tyrosine kinase (IRTK). A structure-activity relationship was established that indicated glucose transport activity was dependent on the presence of two acidic functionalities, two sulfonamide linkages, and a central urea or 2-imidazolidinone core. Compound 30 was identified as a potent and selective IRTK activator. At low concentrations, 30 was able to increase the tyrosine phosphorylation of the IR stimulated by submaximal insulin. At higher concentrations, 30 was able to increase tyrosine the phosphorylation levels of the IR in the absence of insulin. When administered intraperitoneally (ip) and orally (po), 30 improved glucose tolerance in hypoinsulinemic, streptozotocin-treated rats. These data provide pharmacological validation that small molecule IRTK activators represent a potential new class of antidiabetic agents.