The effect of sensitisation to insulin with pioglitazone on fasting and postprandial lipid metabolism, lipoprotein modification by lipases, and lipid transfer activities in type 2 diabetic patients

We are what we eat: The role of lipids in metabolic diseases

Lipids play a fundamental role, both structurally and functionally, for the correct functioning of the organism. In the last two decades, they have evolved from molecules involved only in energy storage to compounds that play an important role as components of cell membranes and signaling molecules that regulate cell homeostasis. For this reason, their interest as compounds involved in human health has been gaining weight. Indeed, lipids derived from dietary sources and endogenous biosynthesis are relevant for the pathophysiology of numerous diseases. There exist pathological conditions that are characterized by alterations in lipid metabolism. This is particularly true for metabolic diseases, such as liver steatosis, type 2 diabetes, cancer and cardiovascular diseases. The main issue to be considered is lipid homeostasis. A precise control of fat homeostasis is required for a correct regulation of metabolic pathways and safe and efficient energy storage in adipocytes. When this fails, a deregulation occurs in the maintenance of systemic metabolism. This happens because an increased concentrations of lipids impair cellular homeostasis and disrupt tissue function, giving rise to lipotoxicity. Fat accumulation results in many alterations in the physiology of the affected organs, mainly in metabolic tissues. These alterations include the activation of oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, increased inflammation, accumulation of bioactive molecules and modification of gene expression. In this chapter, we review the main metabolic diseases in which alterations in lipid homeostasis are involved and discuss their pathogenic mechanisms.

Intestinal lipid absorption and transport in type 2 diabetes

Postprandial hyperlipidaemia is an important feature of diabetic dyslipidaemia and plays an important role in the development of cardiovascular disease in individuals with type 2 diabetes. Postprandial hyperlipidaemia in type 2 diabetes is secondary to increased chylomicron production by the enterocytes and delayed catabolism of chylomicrons and chylomicron remnants. Insulin and some intestinal hormones (e.g. glucagon-like peptide-1 [GLP-1]) influence intestinal lipid metabolism. In individuals with type 2 diabetes, insulin resistance and possibly reduced GLP-1 secretion are involved in the pathophysiology of postprandial hyperlipidaemia. Several factors are involved in the overproduction of chylomicrons: (1) increased expression of microsomal triglyceride transfer protein, which is a key enzyme in chylomicron synthesis; (2) higher stability and availability of apolipoprotein B-48; and (3) increased de novo lipogenesis. Individuals with type 2 diabetes present with disorders of cholesterol metabolism in the enterocytes with reduced absorption and increased synthesis. The increased production of chylomicrons in type 2 diabetes is also associated with a reduction in their catabolism, mostly because of a reduction in activity of lipoprotein lipase. Modification of the microbiota, which is observed in type 2 diabetes, may also generate disorders of intestinal lipid metabolism, but human data remain limited. Some glucose-lowering treatments significantly influence intestinal lipid absorption and transport. Postprandial hyperlipidaemia is reduced by metformin, pioglitazone, alpha-glucosidase inhibitors, dipeptidyl peptidase 4 inhibitors and GLP-1 agonists. The most pronounced effect is observed with GLP-1 agonists, which reduce chylomicron production significantly in individuals with type 2 diabetes and have a direct effect on the intestine by reducing the expression of genes involved in intestinal lipoprotein metabolism. The effect of sodium-glucose cotransporter 2 inhibitors on intestinal lipid metabolism needs to be clarified.

Changes in Plasma Free Fatty Acids Associated with Type-2 Diabetes

Type 2 diabetes mellitus (T2DM) is associated with increased total plasma free fatty acid (FFA) concentrations and an elevated risk of cardiovascular disease. The exact mechanisms by which the plasma FFA profile of subjects with T2DM changes is unclear, but it is thought that dietary fats and changes to lipid metabolism are likely to contribute. Therefore, establishing the changes in concentrations of specific FFAs in an individual’s plasma is important. Each type of FFA has different effects on physiological processes, including the regulation of lipolysis and lipogenesis in adipose tissue, inflammation, endocrine signalling and the composition and properties of cellular membranes. Alterations in such processes due to altered plasma FFA concentrations/profiles can potentially result in the development of insulin resistance and coagulatory defects. Finally, fibrates and statins, lipid-regulating drugs prescribed to subjects with T2DM, are also thought to exert part of their beneficial effects by impacting on plasma FFA concentrations. Thus, it is also interesting to consider their effects on the concentration of FFAs in plasma. Collectively, we review how FFAs are altered in T2DM and explore the likely downstream physiological and pathological implications of such changes.

Efficacy and Safety of Pioglitazone Monotherapy in Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Pioglitazone, the only thiazolidinedione drug in clinical practice is under scrutiny due to reported adverse effects, it's unique insulin sensitising action provides rationale to remain as a therapeutic option for managing type 2 diabetes mellitus (T2DM). We conducted a systematic review and meta-analysis comparing pioglitazone monotherapy with monotherapies of other oral antidiabetic drugs for assessing its efficacy and safety in T2DM patients. Mean changes in glycated haemoglobin (HbA1c), and mean changes in fasting blood sugar (FBS) level, body weight (BW) and homeostasis model assessment-insulin resistance (HOMA-IR) were primary and secondary outcomes, respectively. Safety outcomes were changes in lipid parameters, blood pressure and incidences of adverse events. Metafor package of R software and RevMan software based on random-effects model were used for analyses. We included 16 randomised controlled trials. Pioglitazone monotherapy showed equivalent efficacy as comparators in reducing HbA1c by 0.05% (95% CI: -0.21 to 0.11) and greater efficacy in reducing FBS level by 0.24 mmol/l (95% CI: -0.48 to -0.01). Pioglitazone showed similar efficacy as comparators in reducing HOMA-IR (WMD: 0.05, 95% CI: -0.49 to 0.59) and increasing high-density lipoprotein level (WMD: 0.02 mmol/l, 95% CI: -0.06 to 0.10). Improved blood pressure (WMD: -1.05 mmHg, 95% CI: -4.29 to 2.19) and triglycerides level (WMD: -0.71 mmol/l, 95% CI: -1.70 to 0.28) were also observed with pioglitazone monotherapy. There was a significant association of pioglitazone with increased BW (WMD: 2.06 kg, 95% CI: 1.11 to 3.01) and risk of oedema (RR: 2.21, 95% CI: 1.48 to 3.31), though the risk of hypoglycaemia was absolutely lower (RR: 0.51, 95% CI: 0.33 to 0.80). Meta-analysis supported pioglitazone as an effective treatment option for T2DM patients to ameliorate hyperglycaemia, adverse lipid metabolism and blood pressure. Pioglitazone is suggested to prescribe following individual patient's needs. It can be a choice of drug for insulin resistant T2DM patients having dyslipidaemia, hypertension or history of cardiovascular disease.

Thiazolidinedione induces a therapeutic effect on hepatosteatosis by regulating stearoyl-CoA desaturase-1, lipase activity, leptin and resistin

Hepatosteatosis is a disease present worldwide, which presents a number of health problems. Recently, thiazolidinedione (TZD) has been used as a therapy for lipid disorders. The present study demonstrates the potential of TZD as a treatment for hepatosteatosis and its mechanism of action, particularly focusing on its role in lipid metabolism. A total of 60 (80-90 g) rats were divided into three groups: A normal group with a standard diet, a high-fat, high-carbohydrate diet (HFCD) group or a HFCD+TZD group (n=20/group). The HFCD induced hepatosteatosis over a period of 12 weeks and the HFCD+TZD group were administered TZD in weeks 13-16. Blood and tissue samples were collected to measure hepatic function, the lipid profile, metabolism and hormone biomarkers, including serum triglyceride (TG), lipoprotein lipase (LPL), stearoyl-CoA desaturase (SCD-1), leptin and resistin. The HFCD-fed rats exhibited a significant increase in serum TG, total cholesterol, low-density lipoproteins, alanine transaminase and bilirubin compared with the normal group as well as a significant decrease in high-density lipoprotein. In addition, serum leptin and resistin were significantly elevated in the HFCD group compared with the normal group. The administration of TZD significantly increased SCD-1 activity and significantly inhibited LPL activity. It also attenuated the changes in the lipid profiles and normalized serum leptin and resistin levels. The results of the present study indicated that HFCD induced lipid abnormalities associated with hypertriglyceridemia, hypercholesterolemia and hepatosteatosis. These changes resulted from disruption to leptin and resistin, which may be due to alterations in LPL and SCD-1 activity. TZD mitigated the effects of HFCD-induced hepatosteatosis, indicating a possible regulatory effect of TZD in the development of hepatosteatosis. The authors suggest that the manipulation of SCD-1 and lipase by TZD may be useful as a treatment for hepatosteatosis.

Pharmacological treatment options for severe hypertriglyceridemia and familial chylomicronemia syndrome

INTRODUCTION

A spectrum of disorders, ranging from rare severe cases of homozygous null lipoprotein lipase deficiency (LPLD)-familial chylomicronemia syndrome (FCS) to heterozygous missense LPLD or polygenic causes, result in hypertriglyceridemia and pancreatitis. The effects of mutations are exacerbated by environmental factors such as diet, pregnancy, and insulin resistance. Areas covered: In this review, authors discuss chronic treatment of FCS by ultra-low fat diets allied with the use of fibrates, omega-3 fatty acids, niacin, statins, and insulin-sensitizing therapies depending on the extent of residual lipoprotein lipase (LPL) activity; novel therapies in development target triglyceride (TG)-rich lipoprotein particle clearance. Previously, a gene therapy approach to LPL-alipogene tiparvovec showed that direct targeting of LPL function reduced pancreatitis events. An antisense oligonucleotide to apolipoprotein-C3, volanesorsen has been shown to decrease TGs by 70-80% and possibly to reduce rates of pancreatitis admissions. Studies are underway to validate its long-term efficacy and safety. Other approaches investigating the role of LPL modulating proteins such as angiopoietin-like petide-3 (ANGPTL3) are under consideration. Expert opinion: Current therapeutic options are not sufficient for management of many cases of FCS. The availability of antisense anti-apoC3 therapies and, in the future, ANGPTL3 therapies may remedy this.

Plasma angiopoietin-like 4 is related to phospholipid transfer protein activity in diabetic and non-diabetic subjects: role of enhanced low grade inflammation

Background

Angiopoietin-like 4 (ANGPTL4) inhibits lipoprotein lipase, whereas phospholipid transfer protein (PLTP) enhances hepatic triglyceride secretion. Both factors may be upregulated by inflammatory pathways. Since the extent to which these circulating factors are interrelated is unknown, we determined the relationship between plasma ANGPTL4 and PLTP activity, and assessed whether such a relationship could be explained by high sensitivity C-reactive protein (hsCRP) levels as a marker of low-grade chronic inflammation.

Methods

Fasting plasma ANGPTL4, PLTP activity (liposome-vesicle high density lipoprotein system) and hsCRP were measured in 41 type 2 diabetic (T2DM) subjects and 36 non-diabetic subjects.

Results

Plasma ANGPTL4 and PLTP activity were increased in T2DM (p < 0.001 for each), coinciding with elevated hsCRP, triglycerides and non-esterified fatty acids (NEFA) (p = 0.031 to 0.001). In univariate analysis, ANGTLP4 was correlated with PLTP activity (Rs = 0.309, p = 0.006), whereas both factors were related to hsCRP and NEFA levels (Rs = 0.304 to 0.411, p < 0.01 to < 0.001). In multivariable linear regression analysis adjusting for age, sex, glucose, total cholesterol, triglycerides and NEFA, ANGPTL4 and PLTP activity each remained positively associated with hsCRP (β = 0.315, p = 0.003 and β = 0.299, p = 0.034, respectively). Plasma ANGPTL4 remained positively associated with PLTP activity when taking account of age, sex, glucose, total cholesterol, triglycerides and NEFA (β = 0.315, p = 0.003). Notably, this association disappeared after further adjustment for hsCRP (β = 0.131, p = 0.25).

Conclusions

In conclusion, plasma ANGPTL4 and PLTP activity are interrelated, which may at least in part be explained by low-grade chronic inflammation. A pro-inflammatory state could affect triglyceride metabolism via concerted effects on ANGPTL4 and PLTP.

Effects of high fructose intake on the development of hypertension in the spontaneously hypertensive rats: the role of AT1R/gp91PHOX signaling in the rostral ventrolateral medulla

Both genetic and dietary factors determine the development of hypertension. Whether dietary factor impacts the development of hereditary hypertension is unknown. Here, we evaluated the effect of daily high-fructose diet (HFD) on the development of hypertension in adolescent spontaneously hypertensive rats (SHR). Six-week-old SHR were randomly divided into two groups to receive HFD or normal diet (ND) for 3 weeks. The temporal profile of systolic blood pressure, alongside the sympathetic vasomotor activity, in the SHR-HFD showed significantly greater increases at 9-12 weeks of age compared with the age-matched SHR-ND group. Immunofluorescence was used to identify the distribution of reactive oxygen species (ROS), oxidants and antioxidants in rostral ventrolateral medulla (RVLM) where sympathetic premotor neurons reside. In RVLM of SHR-HFD, the levels of ROS accumulation and lipid peroxidation were elevated. The changes in protein expression were measured by Western blot. NADPH oxidase subunit gp91^phox and angiotensin II type I receptor were up-regulated in RVLM neuron. On the other hand, the expression of extracellular superoxide dismutase was suppressed. Both molecular and hemodynamic changes in the SHR-HFD were rescued by oral pioglitazone treatment from weeks 7 to 9. Furthermore, central infusion with tempol, a ROS scavenger, effectively ameliorated ROS accumulation in RVLM and diminished the heightened pressor response and enhanced sympathetic activity in the SHR-HFD. Together, these results suggest that HFD intake at adolescent SHR may impact the development of hypertension via increasing oxidative stress in RVLM which could be effectively attenuated by pioglitazone treatment.

Intestinal nuclear receptors in HDL cholesterol metabolism

The intestine plays a pivotal role in cholesterol homeostasis by functioning as an absorptive and secretory organ in the reverse cholesterol transport pathway. Enterocytes control cholesterol absorption, apoAI synthesis, HDL biogenesis, and nonbiliary cholesterol fecal disposal. Thus, intestine-based therapeutic interventions may hold promise in the management of diseases driven by cholesterol overload. Lipid-sensing nuclear receptors (NRs) are highly expressed in the intestinal epithelium and regulate transcriptionally the handling of cholesterol by the enterocytes. Here, we discuss the NR regulation of cholesterol fluxes across the enterocytes with special emphasis on NR exploitation as a bona fide novel HDL-raising strategy.

The future of thiazolidinedione therapy in the management of type 2 diabetes mellitus

Since their approval, thiazolidinediones (TZDs) have been used extensively as insulin-sensitizers for the management of type 2 diabetes mellitus (T2DM). Activation of peroxisomal proliferator-activated receptor gamma (PPARγ) nuclear receptors by TZDs leads to a vast spectrum of metabolic and antiinflammatory effects. In the past decade, clinicians and scientists across the fields of metabolism, diabetes, liver disease (NAFLD), atherosclerosis, inflammation, infertility, and even cancer have had high hopes about the potential for TZDs to treat many of these diseases. However, an increasing awareness about undesirable "off-target" effects of TZDs have made us rethink their role and be more cautious about the long-term benefits and risks related to their use. This review examines the most relevant work on the benefits and risks associated with TZD treatment, with a focus on the only PPARγ agonist currently available (pioglitazone), aiming to offer the reader a balanced overview about the current and future role of TZDs in the management of insulin-resistant states and T2DM.

Diagnosis and treatment of severe hypertriglyceridemia

Severe hypertriglyceridemia is associated with acute pancreatitis and can be a manifestation of lipoprotein lipase (LPL) deficiency. It is associated with a spectrum of disorders, ranging from heterozygous LPL deficiency allied with environmental factors to rare severe cases of homozygous LPL deficiency. The genes associated with reduced LPL activity include LPL, its cofactor apoC-2, a controlling protein apoA-5 and the LPL receptor GPI-HBP1. The effects of mutations are exacerbated by environmental factors such as diet, pregnancy and insulin resistance. Treatment of clinical LPL deficiency is by ultra-low-fat diet along with the use of fibrates, omega-3 fatty acids, niacin, statins and insulin-sensitizing therapies, depending on the extent of residual LPL activity. Novel therapies that target lipoprotein particle assembly through the antisense oligonucleotides or by interference with triglyceride-loading microsomal transport protein inhibitors offer new potential options for treating hypertriglyceridemia.

Lowering of postprandial lipids in individuals with type 2 diabetes treated with alogliptin and/or pioglitazone: a randomised double-blind placebo-controlled study

AIMS/HYPOTHESIS

Pharmacological augmentation of glucagon-like peptide 1 receptor signalling by dipeptidyl peptidase 4 (DPP-4) inhibition reduced intestinal lipoprotein secretion in experimental studies, suggesting that DPP-4 inhibitors may ameliorate dyslipidaemia and thus reduce cardiovascular risk in patients with type 2 diabetes. We assessed the effects of alogliptin (Alo) and Alo co-administered with pioglitazone (Pio) vs placebo (Pbo) on triacylglycerol (TG)-rich lipoproteins in type 2 diabetes before and following a high-fat meal.

METHODS

Seventy-one patients (age 18-70 years), who did not reach HbA(1c) 6.5% (48 mmol/mol) with lifestyle and/or metformin, sulfonylurea or glinide therapy, participated in this 16 week, double-centre (university hospitals) Pbo-controlled parallel-group study. All participants, people doing measurements or examinations, and people assessing the outcomes were blinded to group assignment. Fasting TG 1.7-5.0 mmol/l was among the entry criteria. Patients received a high-fat mixed meal before and 4 and 16 weeks after randomisation (allocation by central office) to Alo (n = 25), Alo/Pio (n = 22) or Pbo (n = 24). Blood was sampled at pre-specified intervals, starting at 15 min before and ending 8 h after meal ingestion.

RESULTS

At week 16, Alo (n = 25) and Alo/Pio (n = 21) vs Pbo (n = 24) produced similar significant reductions in total postprandial TG response (incremental AUC [iAUC]; p < 0.001), as well as in chylomicron TG (p < 0.001) and VLDL1 TG iAUCs (p < 0.001 and p = 0.012, respectively). Postprandial chylomicron apolipoprotein B-48 iAUC showed a significant decrease after Alo treatment (p = 0.028), and a non-significant trend towards a decrease with Alo/Pio (p = 0.213). The incidence of adverse events was low and consistent with previous studies.

CONCLUSIONS/INTERPRETATION

Treatment with Alo and Alo/Pio produced significant reductions in postprandial TG and TG-rich lipoproteins, contributing to an improved overall cardiometabolic risk profile in type 2 diabetes. The data support the concept that incretins not only modulate glucose metabolism but also influence chylomicron metabolism in intestinal cells.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT00655863.

Premature atherosclerosis in a Japanese diabetic patient with atypical familial partial lipodystrophy and hypertriglyceridemia

We herein report a case of premature atherosclerosis in a patient with familial partial lipodystrophy (FPL), diabetes mellitus, hypertension and hypertriglyceridemia. Sequencing of the candidate genes LMNA, PPARG and CAV1 associated with FPL revealed no genetic abnormalities, which indicated the activity of a novel gene in this patient. The patient's son showed milder fat loss and similar fat distribution compared to the proband; however, the son showed no signs of any atherosclerotic disease. Although a cluster of atherogenic risk factors is likely to be the primary causes of atherosclerosis in our patient, other factors, including an unknown gene associated with FPL, the severity of fat loss and gender, might affect the development of atherosclerosis.

Gut-liver interaction in triglyceride-rich lipoprotein metabolism

The liver and intestine have complementary and coordinated roles in lipoprotein metabolism. Despite their highly specialized functions, assembly and secretion of triglyceride-rich lipoproteins (TRL; apoB-100-containing VLDL in the liver and apoB-48-containing chylomicrons in the intestine) are regulated by many of the same hormonal, inflammatory, nutritional, and metabolic factors. Furthermore, lipoprotein metabolism in these two organs may be affected in a similar fashion by certain disorders. In insulin resistance, for example, overproduction of TRL by both liver and intestine is a prominent component of and underlies other features of a complex dyslipidemia and increased risk of atherosclerosis. The intestine is gaining increasing recognition for its importance in affecting whole body lipid homeostasis, in part through its interaction with the liver. This review aims to integrate recent advances in our understanding of these processes and attempts to provide insight into the factors that coordinate lipid homeostasis in these two organs in health and disease.

Effect of sitagliptin therapy on postprandial lipoprotein levels in patients with type 2 diabetes

AIM

Recent studies indicate that type 2 diabetes is associated with an increased secretion of both hepatic and intestinal lipoproteins, leading to the accumulation of atherogenic triglyceride (TG)-rich lipoproteins. Sitagliptin is a selective inhibitor of dipeptidyl peptidase-4 that has been shown to reduce fasting and postprandial glucose levels in patients with type 2 diabetes presumably through incretin hormone-mediated improvements in islet function. The objective of the present study is to examine the effects of treatment with sitagliptin on postprandial lipid and incretin hormone levels as well as glucose homeostasis in patients with type 2 diabetes.

METHODS

Thirty-six subjects with type 2 diabetes (30 men/6 postmenopausal women with a mean age of 58.1 ± 6.4 years and a body mass index of 30.7 ± 4.9 kg/m(2) ) were recruited in this double-blind cross-over study using sitagliptin 100 mg/day or placebo for a 6-week period each, with a 4-week washout period between the two phases. At the end of each phase of treatment, patients underwent an oral lipid tolerance test providing 35 g of fat per m(2) of body surface area and blood samples were taken over an 8-h period.

RESULTS

Sitagliptin therapy significantly decreased the postprandial area under the curves (AUCs) for plasma apolipoprotein (apo)B (-5.1%, p = 0.002), apoB-48 (-7.8%, p = 0.03), TG (-9.4%, p = 0.006), very low-density lipoprotein (VLDL)-cholesterol (-9.3%, p = 0.001), free fatty acids (FFAs) (-7.6%, p = 0.005) and glucose (-9.7%, p < 0.0001). Furthermore, the postprandial AUCs for plasma intact glucagon-like peptide-1 (+67.8%, p < 0.0001) and glucose-dependent insulinotropic polypeptide (+67.3%, p < 0.0001) were significantly increased following treatment with sitagliptin, whereas the AUC for plasma glucagon was reduced by -9.7% (p = 0.001) with no significant changes in the AUCs for plasma insulin and C-peptide. Sitagliptin therapy also improved homeostasis model assessment (HOMA) index for insulin resistance (-14.6%, p = 0.01) and β-cell function (+32.3%, p = 0.007).

CONCLUSIONS

Treatment with sitagliptin for 6 weeks reduced postprandial plasma levels of TG-rich lipoproteins of both intestinal and hepatic origin, most likely by increasing incretin hormone levels, reducing circulating plasma FFA concentrations and improving insulin sensitivity and β-cell function.

Pioglitazone and mechanisms of CV protection

BACKGROUND AND AIM

Pioglitazone has diverse multiple effects on metabolic and inflammatory processes that have the potential to influence cardiovascular disease pathophysiology at various points in the disease process, including atherogenesis, plaque inflammation, plaque rupture, haemostatic disturbances and microangiopathy.

RESULTS

Linking the many direct and indirect effects on the vasculature to the reduction in key macrovascular outcomes reported with pioglitazone in patients with type 2 diabetes presents a considerable challenge. However, recent large-scale clinical cardiovascular imaging studies are beginning to provide some mechanistic insights, including a potentially important role for improvements in high-density lipoprotein cholesterol with pioglitazone. In addition to a role in prevention, animal studies also suggest that pioglitazone may minimize damage and improve recovery during and after ischaemic cardio- and cerebrovascular events.

DESIGN AND METHODS

In this review, we consider potential cardiovascular protective mechanisms of pioglitazone by linking preclinical data and clinical cardiovascular outcomes guided by insights from recent imaging studies.

CONCLUSION

Pioglitazone may influence CVD pathophysiology at multiple points in the disease process, including atherogenesis, plaque inflammation, plaque rupture and haemostatic disturbances (i.e. thrombus/embolism formation), as well as microangiopathy.

Relation of blood pressure and body mass index during childhood to cardiovascular risk factor levels in young adults

INTRODUCTION

Adult obesity and hypertension are leading causes of cardiovascular morbidity/mortality. Although childhood BMI and blood pressure (BP) track into adulthood, how they influence adult cardiovascular risk independent of each other is not well defined.

METHODS

Participants were from two longitudinal studies with a baseline evaluation at mean age of 13 years and a follow-up at mean age of 24 years. Regression models using childhood BP and BMI to predict young adult cardiovascular risk factors were performed.

RESULTS

In univariate analysis, childhood BMI predicted young adult BP, lipids, glucose, insulin and insulin resistance, whereas childhood BP predicted young adult BP, lipids and glucose. In a multivariable regression model (adjusted for age, sex and race), which included change in BMI and BP from age 13 to 24 years, BMI predicted all young adult risk factors except BP and glucose. Baseline SBP predicted young adult BP, cholesterol, triglycerides and glucose whereas baseline DBP predicted young adult BP, BMI and glucose.

CONCLUSION

The results from this study show that BP and BMI act independently in children to influence future cardiovascular risk factors and the combination of high BP and BMI in childhood has an additive effect in predicting the highest levels of young adult cardiovascular risk. Thus, there should be a focus on treating hypertension in overweight and obese children, in addition to attempting to reduce weight.

Metformin does not improve the reproductive or metabolic profile in women with polycystic ovary syndrome (PCOS)

To determine whether metformin, when given to women with polycystic ovary syndrome (PCOS), promotes folliculogenesis by prompting a drop in free sex steroids resulting in a compensatory follicle stimulating hormone (FSH) rise, we conducted a randomized, double-blind, placebo-controlled crossover clinical trial. Eight mid-reproductive age PCOS participants with mean obese body mass index (BMI) and normal glucose tolerance received 8 weeks of metformin, given in a step-up fashion to a maximum dose of 2000 mg daily or placebo with daily urine sampling, 4-6 weeks washout, and crossover to the remaining arm for 8 weeks. To confirm the effects of metformin on glucose and other metabolic markers, a hyperinsulinemic, euglycemic 3-dose clamp (physiologic: 30 mU/m(2) per minute, high: 400 mU/m(2) per minute) followed each treatment. Urinary FSH, luteinizing hormone (LH), or pregnanediol glucuronide (Pdg) did not differ by treatment. Glucose disposal, endogenous glucose production, BMI, ovulation rates, serum sex steroids, free fatty acids, and lipids did not significantly differ by treatment, despite good evidence for compliance with the protocol. During the clamp, high-dose insulin administration was associated with an acute drop in serum LH. We conclude that short-term, high-dose metformin exerts minimal effects on both metabolic markers and reproductive hormones in a small sample of overall morbidly obese women.

Long-term lipid effects of pioglitazone by baseline anti-hyperglycemia medication therapy and statin use from the PROactive experience (PROactive 14)

Studies have shown that pioglitazone treatment in patients with type 2 diabetes mellitus can improve parameters of diabetic dyslipidemia. The aim of this study was to examine the effect of pioglitazone on triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels in patients from the Prospective Pioglitazone Clinical Trial in Macrovascular Events (PROactive) to determine whether pioglitazone-induced lipid effects were altered by different baseline antihyperglycemia medication or statin use. PROactive was a long-term, randomized, double-blind, cardiovascular outcomes study in patients with type 2 diabetes at high cardiovascular risk who had pioglitazone or placebo added to existing treatment. The present post hoc study analyzed lipid results from patients who received different baseline antihyperglycemia regimens and the presence or absence of baseline statin use. Independent of antihyperglycemia medication and statin use, triglyceride levels decreased in all subgroups treated with pioglitazone (-9.9% to -12.3%), whereas little change was observed in placebo groups. High-density lipoprotein cholesterol increased nearly twice as much with pioglitazone (18.1% to 20.3%) as with placebo (8.1% to 11.8%) across all subgroups. Low-density lipoprotein cholesterol increased moderately with pioglitazone (5.2% to 9.6%) compared with placebo (3.3% to 7.6%) (placebo-adjusted range 1.11% to 4.37%). In conclusion, long-term pioglitazone therapy led to durable improvements in triglyceride and high-density lipoprotein cholesterol levels, irrespective of baseline antihyperglycemia therapy or statin use.

Decreased whole body lipolysis as a mechanism of the lipid-lowering effect of pioglitazone in type 2 diabetic patients

Pioglitazone has been shown to reduce fasting triglyceride levels. The mechanisms of this effect have not been fully elucidated, but decreased lipolysis may contribute to blunt the hypertriglyceridemic response to a meal. To test this hypothesis, we studied 27 type 2 diabetes mellitus (T2DM) patients and 7 sex-, age-, and body mass index-matched nondiabetic controls. Patients were randomized to pioglitazone (45 mg/day) or placebo for 16 wk. Whole body lipolysis was measured [as the [(2)H(5)]glycerol rate of appearance (R(a))] in the fasting state and for 6 h following a mixed meal. Compared with controls, T2DM had higher postprandial profiles of plasma triglycerides, free fatty acid (FFA), and beta-hydroxybutyrate, and a decreased suppression of glycerol R(a) (P < 0.04) despite higher insulin levels [268 (156) vs. 190 (123) pmol/l, median (interquartile range)]. Following pioglitazone, triglycerides and FFA were reduced (P = 0.05 and P < 0.04, respectively), and glycerol R(a) was more suppressed [-40 (137) vs. +7 (202) mumol/min of placebo, P < 0.05] despite a greater fall in insulin [-85 (176) vs. -20 (58) pmol/l, P = 0.05]. We conclude that, in well-controlled T2DM patients, whole body lipolysis is insulin resistant, and pioglitazone improves the insulin sensitivity of lipolysis.

Free fatty acid kinetics during long-term treatment with pioglitazone added to sulfonylurea or metformin in Type 2 diabetes

BACKGROUND

Free fatty acids (FFAs) are linked to impaired insulin action, but their role in mediating long-term insulin sensitization during diabetes treatment is unclear.

OBJECTIVES

To examine the effect of pioglitazone addition to existing therapy on FFA dynamics and insulin action.

DESIGN

Two 2-year, randomized, parallel-group, double-blind, double-dummy, clinical trials.

SETTING

One hundred and seventy-one centres in Europe, Australia and Canada.

SUBJECTS

Male and female patients with Type 2 diabetes inadequately managed with metformin or sulfonylurea.

INTERVENTIONS

Patients were randomized to pioglitazone (15-45 mg day(-1); n=319) or metformin (850-2550 mg day(-1); n=320) as add-on therapy to gliclazide or pioglitazone (n=317) versus gliclazide (80-320 mg day(-1); n=313) as add-on therapy to metformin.

OUTCOME MEASURE

Plasma FFA profiles during oral glucose tolerance tests in selected centres before and during treatment (n=588).

RESULTS

At Week 104, pioglitazone treatment decreased fasting FFAs by 0.08 mmol L(-1) when added to sulfonylurea and by 0.11 mmol L(-1) when added to metformin versus the respective sulfonylurea + metformin groups (0.03 mmol L(-1), P=0.05 and 0.04 mmol L(-1), P<0.05), and this was accompanied by significant improvements in fasting adipose tissue insulin sensitivity. Changes in postchallenge FFAs were similar between groups and not related to changes in liver transaminases, insulin action and secretion. However, the sensitivity of FFA to insulin was affected by treatment (P<0.001) and visit (P<0.05). Insulin sensitivity of FFA rose when pioglitazone was added to sulfonylurea (P<0.05), but decreased for gliclazide + metformin (P<0.05).

CONCLUSION

Long-term improvements in adipose tissue insulin sensitivity and reduction in fasting FFAs with pioglitazone may help to reduce lipotoxicity in Type 2 diabetes.

Relationship between changes in insulin sensitivity and associated cardiovascular disease risk factors in thiazolidinedione-treated, insulin-resistant, nondiabetic individuals: pioglitazone versus rosiglitazone

This study compared the effects of administering rosiglitazone (RSG) vs pioglitazone (PIO) on cardiovascular disease risk factors in insulin-resistant, nondiabetic individuals with no apparent disease. Twenty-two nondiabetic, apparently healthy individuals, classified as being insulin resistant on the basis of a steady-state plasma glucose concentration of at least 10 mmol/L during the insulin suppression test, were treated with either RSG or PIO for 3 months. Measurements were made before and after drug treatment of weight; blood pressure; fasting and daylong glucose, insulin, and free fatty acid (FFA) levels; and lipid and lipoprotein concentrations. Insulin sensitivity (steady-state plasma glucose concentration) significantly improved in both treatment groups, associated with significant decreases in daylong plasma concentrations of glucose, insulin, and FFA. Diastolic blood pressure fell somewhat in both groups, and this change reached significance in those receiving PIO. Improvement in lipid metabolism was confined to the PIO-treated group, signified by a significant decrease in plasma triglyceride concentration, whereas triglyceride concentration did not decline in the RSG-treated group, and these individuals also had increases in total (P = .047) and low-density lipoprotein cholesterol (P = .07). In conclusion, RSG and PIO appear to have comparable abilities to improve insulin sensitivity and lower daylong glucose, insulin, and FFA concentrations in nondiabetic, insulin-resistant individuals. However, despite these similarities, their effects on lipoprotein metabolism seem to be quite different, with beneficial effects confined to PIO-treated individuals.

The effects of ezetimibe and orlistat, alone or in combination, on high-density lipoprotein (HDL) subclasses and HDL-associated enzyme activities in overweight and obese patients with hyperlipidaemia

BACKGROUND

High-density lipoprotein (HDL) includes discrete subfractions. HDL exhibits anti-atherogenic properties, which have been partly linked to the activity of HDL-associated enzymes, such as the lipoprotein associated phospholipase A(2) (HDL-LpPLA(2)) and paraoxonase-1 (PON1).

OBJECTIVE

We assessed in an open-label randomised study the effect of orlistat and ezetimibe, alone or in combination, on plasma HDL subclasses and HDL-associated enzyme activities in overweight and obese subjects (body mass index > 28 kg/m(2)) with hypercholesterolemia [total cholesterol > 200 mg/100 ml (5.2 mmol/l)].

METHODS

Eighty-six people were prescribed a low-fat low-calorie diet and were randomly allocated to receive orlistat 120 mg, three times daily (O group), ezetimibe 10 mg/day (E group) or both (OE group) for 6 months. HDL subfractions were determined using a polyacrylamide gel-tube electrophoresis method.

RESULTS

Levels of HDL cholesterol (HDL-C) and apolipoprotein AI did not change significantly in any group. In group O the cholesterol concentration of HDL-2 subclass increased significantly, while the cholesterol of HDL-3 subclass decreased significantly. In groups E and OE HDL-2 subclass did not significantly change, while the cholesterol concentration of HDL-3 subclass decreased significantly. We observed a non-significant decrease in the HDL-LpPLA(2) and PON1 activity in all groups. However, the ratios of both enzyme activities to low-density lipoprotein cholesterol (LDL-C) levels (an index of atherogenicity) significantly increased in all groups.

CONCLUSION

Although HDL-C levels did not change after treatment with orlistat and ezetimibe, alone or in combination, there were alterations of the HDL-2 and HDL-3 subclasses. The activity of HDL-LpPLA(2) and PON1 per mg LDL-C increased significantly in all groups.

Pioglitazone and cardiovascular risk. A comprehensive meta-analysis of randomized clinical trials

AIM

The aim of this meta-analysis of randomized clinical trials (RCT) was to assess whether pioglitazone is also associated with increased cardiovascular risk, as recently reported for rosiglitazone.

METHODS

RCT of pioglitazone were retrieved from Medline (any date up to 31 August 2007; English language only). Unpublished RCT were identified through http://www.clinicaltrials.gov or http://www.fda.gov websites, and results on cardiovascular outcomes were retrieved from investigators and/or sponsors, whenever possible. RCT were included in meta-analysis if pioglitazone was compared with other treatments (placebo, active comparators or no treatment) for at least 4 weeks. Ninety-four trials, 10 of which were unpublished, were retrieved; those included in the analysis, which excluded PROspective PioglitAzone Clinical Trial In MacroVascular Events (PROACTIVE), enrolled 11 268 and 9912 patients in the pioglitazone and comparator groups respectively. Data for analysis, extracted independently by two observers, included all-cause and cardiovascular mortality and incidence of non-fatal coronary events and heart failure. Proportions of outcome measures across treatment groups were compared by odds ratios (ORs) and 95% confidence interval.

RESULTS

Pioglitazone was associated with reduced all-cause mortality [OR 0.30 (0.14-0.63); p < 0.05], with no relevant effect on non-fatal coronary events. The observed increase in incidence of non-fatal heart failure was not statistically significant [OR 1.38 (0.90-2.12)].

CONCLUSION

The use of pioglitazone does not appear to be harmful in terms of cardiovascular events and all-cause deaths.

The effect of pioglitazone as add-on therapy to metformin or sulphonylurea compared to a fixed-dose combination of metformin and glibenclamide on diabetic dyslipidaemia

BACKGROUND AND AIMS

Diabetic dyslipidaemia contributes to the increased risk of cardiovascular disease in patients with Type 2 diabetes. This paper examines the effectiveness of adding pioglitazone to metformin or a sulphonylurea (SU) compared with a fixed-dose combination of metformin and glibenclamide on diabetic dyslipidaemia in patients with Type 2 diabetes.

METHODS AND RESULTS

Patients (n=250) treated with metformin (< or =3g/day) or an SU as monotherapy at a stable dose for > or =3 months were randomised to receive either pioglitazone (15-30 mg/day) in addition to their metformin or SU, or a fixed-dose combination tablet containing metformin (400mg) and glibenclamide (2.5 mg) [up to 3 tablets daily] for 6 months. Addition of pioglitazone tended to increase plasma high-density lipoprotein-cholesterol (HDL-C) [0.04 mmol/L; P=0.051] at 6 months and significantly reduced plasma triglycerides (-0.25 mmol/L; P=0.013) compared with baseline. Patients treated with metformin/glibenclamide for 6 months had reduced HDL-C (-0.09 mmol/L; P<0.01) and no change in plasma triglyceride levels (0.03 mmol/L; P=0.733). Both treatment regimes resulted in a similar level of glycaemic control.

CONCLUSION

The beneficial effects of pioglitazone on diabetic dyslipidaemia may help combat the increased cardiovascular morbidity and mortality observed in patients with Type 2 diabetes while providing stable glycaemic control.

The effects of orlistat and fenofibrate, alone or in combination, on high-density lipoprotein subfractions and pre-beta1-HDL levels in obese patients with metabolic syndrome

OBJECTIVE

We assessed the effect of orlistat and fenofibrate, alone or in combination, on plasma high-density lipoprotein (HDL) subfractions and plasma pre-beta1-HDL levels in overweight and obese subjects with metabolic syndrome (MetS).

METHODS

Patients (n = 89) were prescribed a low-fat low-calorie diet and were randomly allocated to receive orlistat 120 mg three times daily (O group), micronized fenofibrate 200 mg/day (F group) or both (OF group) for 6 months. HDL subfractions were determined using a polyacrylamide gel tube electrophoresis method and pre-beta1-HDL levels using enzyme-linked immunoabsorbent assay.

RESULTS

We observed a significant change of high-density lipoprotein cholesterol (HDL-C) levels only in the F group (+3%, p < 0.05). Large HDL-C levels were significantly increased and small HDL-C levels were significantly reduced with O administration. In F group we observed a significant increase of small HDL-C levels. No significant change of large or small HDL-C levels was observed with combination treatment. We observed a significant increase of pre-beta1-HDL levels in all groups, which was significantly greater in OF group compared with O or F monotherapy.

CONCLUSION

OF combination increased the antiatherogenic pre-beta1-HDL levels in overweight and obese patients with MetS. Furthermore, OF combination counterbalanced the reduction of small HDL-C levels observed with orlistat monotherapy.

Reduced postprandial proinsulinaemia and 32-33 split proinsulinaemia after a mixed meal in type 2 diabetic patients following sensitization to insulin with pioglitazone

OBJECTIVE

Reduced insulin sensitivity associated with fasting hyperproinsulinaemia is common in type 2 diabetes. Proinsulinaemia is an established independent cardiovascular risk factor. The objective was to investigate fasting and postprandial release of insulin, proinsulin (PI) and 32-33 split proinsulin (SPI) before and after sensitization to insulin with pioglitazone compared to a group treated with glibenclamide.

DESIGN AND PATIENTS

A randomized double-blind placebo-controlled trial. Twenty-two type 2 diabetic patients were recruited along with 10 normal subjects. After 4 weeks washout, patients received a mixed meal and were assigned to receive pioglitazone or glibenclamide for 20 weeks, after which patients received another identical test meal. The treatment regimes were designed to maintain glycaemic control (HbA1c) at pretreatment levels so that beta-cells received an equivalent glycaemic stimulus for both test meals.

MEASUREMENTS

Plasma insulin, PI, SPI and glucose concentrations were measured over an 8-h postprandial period. The output of PI and SPI was measured as the integrated postprandial response (area under the curve, AUC).

RESULTS

Pioglitazone treatment resulted in a significant reduction in fasting levels of PI and SPI compared to those of the controls. Postprandially, pioglitazone treatment had no effect on the insulin AUC response to the meal but significantly reduced the PI and SPI AUCs. Glibenclamide increased fasting insulin and the postprandial insulin AUC but had no effect on the PI and SPI AUCs.

CONCLUSIONS

Sensitization to insulin with pioglitazone reduces the amount of insulin precursor species present in fasting and postprandially and may reduce cardiovascular risk.

Postprandial dysmetabolism: the missing link between diabetes and cardiovascular events?

OBJECTIVE

To investigate the association of postprandial dysmetabolism, ie, hyperglycemia, and hyperlipidemia with myocardial disease in diabetic, glucose-intolerant, and glucose-tolerant patients.

METHODS

We performed a MEDLINE search of the English-language literature published between January 1979 and April 2007 for studies regarding postprandial dysmetabolism and heart disease.

RESULTS

Postprandial dysmetabolism is associated with increased inflammation, endothelial dysfunction, decreased fibrinolysis, plaque instability, and cardiac events.

CONCLUSION

There is a direct and proportional association between postprandial dysmetabolism and both coronary artery disease and cardiac events.

Impact of metformin versus the prandial insulin secretagogue, repaglinide, on fasting and postprandial glucose and lipid responses in non-obese patients with type 2 diabetes

OBJECTIVE

Non-obese patients with type 2 diabetes (T2DM) are characterized by predominant defective insulin secretion. However, in non-obese T2DM patients, metformin, targeting insulin resistance, is non-inferior to the prandial insulin secretagogue, repaglinide, controlling overall glycaemia (HbA1c). Whether the same apply for postprandial glucose and lipid metabolism is unknown. Here, we compared the effect of metformin versus repaglinide on postprandial metabolism in non-obese T2DM patients.

DESIGN

Single-centre, double-masked, double-dummy, crossover study during 2x4 months involving 96 non-obese (body mass index < or = 27 kg/m2) insulin-naïve T2DM patients. At enrolment, patients stopped prior oral hypoglycaemic agents therapies and after a 1-month run-in period on diet-only treatment, patients were randomized to repaglinide (2 mg) thrice daily followed by metformin (1 g) twice daily or vice versa each during 4 months with 1-month washout between interventions.

METHODS

Postprandial metabolism was evaluated by a standard test meal (3515 kJ; 54% fat, 13% protein and 33% carbohydrate) with blood sampling 0-6 h postprandially.

RESULTS

Fasting levels and total area under the curve (AUC) for plasma glucose, triglycerides and free fatty acids (FFA) changed equally between treatments. In contrast, fasting levels and AUC of total cholesterol, low-density lipoprotein (LDL) cholesterol, non-high-density lipoprotein (non-HDL) cholesterol and serum insulin were lower during metformin than repaglinide (mean (95% confidence intervals), LDL cholesterol difference metformin versus repaglinide: AUC: -0.17 mmol/l (-0.26; -0.08)). AUC differences remained significant after adjusting for fasting levels.

CONCLUSIONS

In non-obese T2DM patients, metformin reduced postprandial levels of glycaemia, triglycerides and FFA similarly compared to the prandial insulin secretagogue, repaglinide. Furthermore, metformin reduced fasting and postprandial cholesterolaemia and insulinaemia compared with repaglinide. These data support prescription of metformin as the preferred drug in non-obese patients with T2DM targeting fasting and postprandial glucose and lipid metabolism.

Variability in postheparin hepatic lipase activity is associated with plasma adiponectin levels in African Americans

BACKGROUND

African Americans commonly have normal high-density lipoprotein cholesterol (HDL-C) and low triglyceride levels despite having insulin resistance and obesity. The higher than expected HDL-C levels are usually attributed to low levels of hepatic triglyceride lipase (HTGL) activity. Factors that regulate HTGL in African Americans are not well delineated.

METHODS

In the current study, HTGL activity was examined in relation to indices of body fat (body mass index [BMI] and waist circumference [WC]), insulin resistance (fasting plasma insulin and homeostasis model assessment of insulin resistance [HOMA-IR] index), and adipokines (adiponectin and leptin). Sixty-three African Americans (33 men, 30 women; median age 31 years, range 20-50 years; median BMI 28.6 kg/m2, range 19.7-54.7 kg/m2) had anthropometry and measurement of postheparin lipase activities (HTGL), plasma HDL-C, triglycerides, and plasma adiponectin.

RESULTS

HTGL correlated strongly with HDL-C (r = -.52, p < .0001) and adiponectin (r = -.49, p < .001). HTGL increased with BMI and WC (r = .297, p = .018 and r = .301, p = .016, respectively). Adiponectin correlated strongly with HDL-C (r = .50, p < .0001) and triglycerides (r = -.493, p < .001). From multiple regression models, 28% of HTGL variability among African Americans can be explained by adiponectin levels in combination with gender and 35% of HTGL is explained with HDL-C included in the model.

CONCLUSION

The data suggest that adiponectin is a significant metabolic concomitant of HTGL activity in African Americans.

Insulin resistance as the underlying cause for the metabolic syndrome

Classically, the metabolic syndrome is characterized as group of pathologies including visceral obesity, hypertension, dyslipidemia, and impaired glucose tolerance. It is now realized that insulin resistance plays a principal role in initiating and perpetuating the pathologic manifestations of the metabolic syndrome. A more in-depth understanding of the basic pathophysiologic mechanisms underlying insulin resistance may aid clinicians in treating and possibly delaying or even preventing the onset of the metabolic syndrome and its complications. This article outlines how abnormal insulin signaling and secretion, impaired glucose disposal, lipotoxicity, and proinflammatory cytokines exacerbate insulin resistance and result in the perturbations of the metabolic syndrome.

Effect of pioglitazone on atherogenic outcomes in type 2 diabetic patients: a comparison of responders and non-responders

The aim of this study was to evaluate the anti-atherogenic efficacy of pioglitazone, a thiazolidinedione derivative, on the change in atherogenic outcomes by comparing responder and non-responder groups in type 2 diabetic patients. Twenty-three patients with poor diabetic control were treated with 15 mg of pioglitazone for 12 months. The levels of fasting plasma glucose (FPG), HbA1c, triglycerides (TG), total cholesterol (T-Cho), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C) were measured monthly, and those of remnant-like particle-cholesterol (RLP-C) and lipoprotein (a) [Lp (a)] were measured every 3 months. In Month 6, the patients were divided into two groups according to the decrease in HbA1c level: the responder group showed a decrease of > or =1%; the non-responder group, a decrease of <1%. In the responder group, the levels of FPG and HbA1c decreased significantly after Month 3. The values of the body mass index (BMI), homeostasis model assessment of insulin resistance (HOMA-IR) index, LDL-C, and RLP-C were significantly higher in the responder group than in the non-responder group. Although the levels of T-Cho and HDL-C were unchanged in both groups, those of TG and RLP-C were drastically reduced in the responder group. Interestingly, the relative change in Lp (a) was significantly decreased in both groups. These results strongly suggest that pioglitazone is beneficial for type 2 diabetic patients with high levels of BMI, HOMA-IR, LDL-C, and RLP-C, as it helps to prevent the progression of atherosclerosis, including coronary heart diseases.

Improvement of postprandial lipid handling and glucose tolerance in a non-diabetic population by the dual PPARalpha/gamma agonist, tesaglitazar

This study examined the effect of tesaglitazar (GALIDA), a dual peroxisome proliferator-activated receptor (PPAR)alpha/gamma agonist, on postprandial metabolism. This investigation was part of the Study in Insulin Resistance (SIR) (SH-SBT-0001), a randomised, double-blind, placebo-controlled study that reported improvements in fasting lipid and glucose values with tesaglitazar (0.1, 0.25, 0.5 or 1 mg once daily for 12 weeks) in hypertriglyceridaemic, abdominally obese, non-diabetic patients. A subgroup of 222 patients underwent postprandial lipid and glucose testing at baseline and treatment end. Tesaglitazar 0.25, 0.5 and 1 mg reduced postprandial area under the curve (AUC) for triglycerides by 20% (p=0.003), 30% (p<0.0001) and 41% (p<0.0001), respectively. Free fatty acid (FFA) levels were reduced by 17% with tesaglitazar 0.5 mg (p=0.002) and by 29% with tesaglitazar 1 mg (p<0.0001). Tesaglitazar significantly improved glucose tolerance and increased the proportion of patients with normal glucose tolerance as measured by the oral glucose tolerance test (OGTT). To conclude, postprandial dyslipidaemia and hyperglycaemia, indicators of increased vascular risk, were significantly improved by tesaglitazar treatment in these non-diabetic, hypertriglyceridaemic, abdominally obese subjects.

Effects of pioglitazone on lipid and lipoprotein metabolism

Type 2 diabetes is associated with an increased risk of cardiovascular disease (CVD). A major contributing factor to this risk is the abnormal lipid profile known as dyslipidaemia, which is characterized by low HDL cholesterol (HDL-C), raised triglycerides (TGs) and a predominance of small, dense LDL cholesterol (LDL-C) particles. Statins are now widely used first-line in patients with type 2 diabetes due to their proven efficacy in reducing LDL-C and cardiovascular risk. However, despite the use of statins, the absolute risk of CVD in patients remains elevated, highlighting the need to target all aspects of the diabetic lipid profile such as raised TGs or low HDL-C levels. Insulin resistance is thought to be central in the pathogenesis of diabetic dyslipidaemia; therefore, improving insulin sensitivity with a thiazolidinedione offers an attractive treatment option. Indeed, pioglitazone, a member of the peroxisome proliferator-activated receptor-gamma family, has been shown in clinical trials to improve both blood glucose levels and the lipid profile when used either as monotherapy or in combination with other oral antidiabetic agents. In the monotherapy setting, pioglitazone has been associated with greater decreases in TGs and increases in HDL-C when compared with glibenclamide or metformin. Studies investigating the effects of pioglitazone add-on therapy to either metformin or sulphonylurea treatments have shown sustained improvements in serum levels of TGs and HDL-C and favourable effects on LDL-C particle size. In comparison with rosiglitazone, pioglitazone has different and potentially favourable effects on plasma lipids. The recent PROspective pioglitAzone Clinical Trial In macroVascular Events study has given weight to the hypothesis that the beneficial metabolic effects of pioglitazone may be associated with reductions in cardiovascular risk in patients with type 2 diabetes.

Remnant-like lipoprotein particles impair endothelial function: direct and indirect effects on nitric oxide synthase

Remnant-like lipoprotein particles (RLPs) have been implicated as potentially atherogenic lipoproteins. Endothelial dysfunction is known to be an early event in atherosclerosis and an important contributor to the pathogenesis of coronary artery disease. Moreover, there is considerable evidence linking increased RLP cholesterol levels with endothelial dysfunction, reflected by impaired endothelial vasodilatation and abnormal endothelial secretion. The underlying mechanisms by which RLPs may contribute to endothelial dysfunction are complex and have not been completely elucidated. Because the expression and activation of endothelial nitric oxide synthase (eNOS) are vital to endothelial function, and recent data have implied an association between RLPs and eNOS, this manuscript proposes the hypothesis that RLPs could impair endothelial function via direct and indirect effects on eNOS: RLPs may affect the autophosphorylation of focal adhesion kinase and its downstream phosphatidylinositol kinase/Akt (protein kinase B) signaling pathway, resulting in eNOS inactivation through induction of intracellular oxidative stress in endothelial cells; and RLPs could affect the expression or activation of eNOS indirectly by stimulating secretion of various inflammatory factors from multiple origins. The practical applications of this manuscript provide new insights for the future investigation of RLPs.

Differential effect of pioglitazone (PGZ) and rosiglitazone (RGZ) on postprandial glucose and lipid metabolism in patients with type 2 diabetes mellitus: a prospective, randomized crossover study

BACKGROUND

Postprandial metabolism is impaired in patients with type 2 diabetes (T2Dm). Two thiazolidinediones pioglitazone (PGZ) and rosiglitazone (RGZ) have similar effects on glycaemic control but differ in their effects on fasting lipids. This study investigated the effects of RGZ and PGZ on postprandial metabolism in a prospective, randomized crossover trial.

METHODS

Seventeen patients with T2Dm were randomized to RGZ or PGZ for 12 weeks, with an 8-week wash-out period. Fasting blood samples were taken for glucose (FPG), insulin, HbA(1c), lipids, apolipoproteins (apo), lipoprotein (LPL) and hepatic lipase (HL), and cholesterol ester transfer protein (CETP) activity. A standardized breakfast was served and postprandial glucose, insulin, and lipid subfraction profiles were determined.

RESULTS

RGZ and PGZ treatment resulted in a similar improvement in FPG, HbA(1c) and homeostasis model assessment. Fasting and postprandial triglyceride (TG) levels were significantly lower following PGZ therapy (fasting: -0.35 vs 0.44 mmol/L; p < 0.04; postprandial AUC-TG: -195.6 vs 127.9 mmol/L/min; p < 0.02) associated with changes in VLDL-2-TG (-0.10 vs 0.21 mmol/L; p = 0.23) and VLDL-3-TG (0.0 vs 0.34 mmol/L; p < 0.04). Fasting cholesterol increased with RGZ compared to PGZ (0.06 vs 0.59 mmol/L; p < 0.04), particularly in VLDL-2-C (-0.30 vs 0.59 mmol/L; p < 0.03) and VLDL-3-C (-0.85 vs 2.11 mmol/L; p < 0.02). Postprandial VLDL lipid and protein content increased after RGZ and decreased after PGZ. Fasting apoB, apoA-I, apoC-II/C-III-ratio, and LPL activity did not differ. CETP activity decreased after RGZ and increased after PGZ (-6.2 vs 4.2 p/mol/mL/min; p < 0.002).

CONCLUSIONS

Both the glitazones had similar effects on glucose metabolism. The additional beneficial effect of PGZ on lipid metabolism may be related to its effects on insulin-independent VLDL production and CETP activity.

Impact of thiazolidenediones on serum lipoprotein levels

The thiazolidinediones, acting through peroxisome proliferator-activated receptor chi (PPARchi), affect multiple areas of metabolism. Of increasing importance is the recognition that these agents affect lipoprotein metabolism and cause changes in serum lipid and lipoprotein levels. All three thiazolidinediones, including troglitazone (which was withdrawn in the year 2000), rosiglitazone, and pioglitazone, tend to increase high-density lipoprotein (HDL) cholesterol, increase the size/decrease the density of low-density lipoprotein (LDL) particles, and raise the level of lipoprotein(a). In addition, troglitazone and pioglitazone, but not rosiglitazone, lower triglyceride levels modestly, thereby further contributing to increases in LDL and HDL size. The mechanism for these effects is still being clarified, but may involve enhancement of triglyceride clearance (in the case of pioglitazone), alteration of apolipoprotein C-III levels, reduction of hepatic lipase, and increase in ATP binding cassette A1 (ABCA1) activity. The clinical implications of these effects need further exploration.

Pioglitazone Increases Gallbladder Volume in Insulin-Resistant Obese Mice

BACKGROUND

Both obesity and diabetes are associated with an increased incidence of gallstones. Recent animal and human data from our laboratory suggest that insulin resistance is associated with increased gallbladder volume and/or impaired gallbladder emptying. Pioglitazone is a thiazolidinedione that has been shown to improve insulin resistance. Therefore, we tested the hypothesis that pioglitazone would improve insulin resistance, decrease resting gallbladder volume and improve gallbladder response to neurotransmitters in insulin-resistant obese mice fed a 25% carbohydrate diet.

MATERIALS AND METHODS

Twenty eight-week-old insulin-resistant obese (Lep(ob)) mice fed a 25% carbohydrate diet for 4 weeks. Half of the animals had 0.3 g/kg pioglitazone added to their diet. At 12 weeks all animals were fasted and underwent cholecystectomy. Gallbladder volume and weight were measured, and fresh gallbladders were placed in a muscle bath to assess response to acetylcholine (ACh 10(-5)M), neuropeptide Y (NPY 10(-8,-7,-6)M) and cholecystokinin (CCK 10(-10,-9,-8,-7)M). Serum glucose and insulin were measured, and HOMA Index, a measure of insulin resistance, was calculated.

RESULTS

Fasting serum insulin and HOMA Index were significantly decreased (P < 0.03), but gallbladder volume was significantly increased (P < 0.03) in the pioglitazone treated group. Pioglitazone did not alter gallbladder weight or response to ACh, NPY, or CCK.

CONCLUSION

These data suggest that in insulin-resistant obese mice pioglitazone 1) lowers insulin-resistance, 2) increases resting gallbladder volume, and 3) does not alter gallbladder response to neurotransmitters. Therefore, we conclude that pioglitazone, while improving insulin resistance, paradoxically increases gallbladder volume and, thereby, may increase the propensity for gallstone formation by enhancing gallbladder stasis.

Vildagliptin therapy reduces postprandial intestinal triglyceride-rich lipoprotein particles in patients with type 2 diabetes

AIMS/HYPOTHESIS

We assessed the effects of vildagliptin, a novel dipeptidyl peptidase IV inhibitor, on postprandial lipid and lipoprotein metabolism in patients with type 2 diabetes.

SUBJECTS, MATERIALS AND METHODS

This was a single-centre, randomised, double-blind study in drug-naive patients with type 2 diabetes. Patients received vildagliptin (50 mg twice daily, n=15) or placebo (n=16) for 4 weeks. Triglyceride, cholesterol, lipoprotein, glucose, insulin, glucagon and glucagon-like peptide-1 (GLP-1) responses to a fat-rich mixed meal were determined for 8 h postprandially before and after 4 weeks of treatment.

RESULTS

Relative to placebo, 4 weeks of treatment with vildagliptin decreased the AUC(0-8h) for total trigyceride by 22+/-11% (p=0.037), the incremental AUC(0-8h) (IAUC(0-8h)) for total triglyceride by 85+/-47% (p=0.065), the AUC(0-8h) for chylomicron triglyceride by 65+/-19% (p=0.001) and the IAUC(0-8h) for chylomicron triglyceride by 91+/-28% (p=0.002). This was associated with a decrease in chylomicron apolipoprotein B-48 (AUC(0-8h), -1.0+/-0.5 mg l(-1) h, p=0.037) and chylomicron cholesterol (AUC(0-8h), -0.14+/-0.07 mmol l(-1) h, p=0.046). Consistent with previous studies, 4 weeks of treatment with vildagliptin also increased intact GLP-1, suppressed inappropriate glucagon secretion, decreased fasting and postprandial glucose, and decreased HbA(1c) from a baseline of 6.7% (change, -0.4+/-0.1%, p<0.001), all relative to placebo.

CONCLUSIONS/INTERPRETATION

Treatment with vildagliptin for 4 weeks improves postprandial plasma triglyceride and apolipoprotein B-48-containing triglyceride-rich lipoprotein particle metabolism after a fat-rich meal. The mechanisms underlying the effects of this dipeptidyl peptidase IV inhibitor on postprandial lipid metabolism remain to be explored.