The effects of lipid lowering drugs on metabolic control and lipoprotein composition in type 2 diabetic patients with mild hyperlipidaemia

Protective effect of bezafibrate on streptozotocin-induced oxidative stress and toxicity in rats

The present study was aimed to find out the protective effect of bezafibrate on lipid peroxidation (LPO), activities of both enzymatic and non-enzymatic antioxidants and histopathological examination of pancreas in streptozotocin (STZ)-induced diabetic rats. Experimental diabetes was induced by a single dose of STZ (60mg/kg, i.p.) injection. The oxidative stress was measured by tissue LPO level, reduced glutathione (GSH) content and by enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) in liver and pancreas. Biochemical observations were further substantiated with histological examination of pancreas. The increase in blood glucose, LPO level with reduction in GSH content and decreased enzymatic activities were the salient features observed in diabetic control rats. Administration of bezafibrate (30mg/kg day, p.o.) for 15 days caused a significant reduction in blood glucose and LPO level in STZ treated rats (group III) when compared with diabetic control rats (group II). Furthermore, bezafibrate treated diabetic rats (group III) showed significant increase in the activities of both enzymatic and non-enzymatic antioxidants when compared to diabetic control rats (group II). Degenerative changes of pancreatic beta-cells in STZ treated rats were minimized to near normal morphology by administration of bezafibrate as evident by histopathological examination. The results obtained clearly indicate the role of oxidative stress in the induction of diabetes and suggest a protective effect of bezafibrate in this animal model.

No effect of simvastatin treatment on insulin sensitivity in patients with primary hypercholesterolemia

OBJECTIVE

Statins, in addition to cholesterol lowering, have nonlipid effects on formation and progression of atheromatous plaque. Insulin resistance and hyperinsulinemia may have detrimental influences on the arterial wall. Statins (may also) inhibit insulin signal transferring in vascular smooth cell cultures. However, their effect on insulin sensitivity remains controversial. Therefore, we decided to investigate the effect of simvastatin on insulin sensitivity in hypercholesterolemic patients.

PATIENTS AND METHODS

Eighteen patients with primary hypercholesterolemia were divided into simvastatin group (n = 9; 4 females, 5 males; BMI 30.6 +/- 4 kg/m2; mean ages 57 +/- 6 years) and placebo group (n = 9; 4 females, 5 males; BMI 28 +/- 2.9 kg/m2; mean ages 49 +/- 10 years). Simvastatin (20 mg/day) or placebo were given for 2 months. Total and HDL cholesterol were measured and LDL cholesterol was calculated by Friedewald formula. Insulin sensitivity was determined by using euglycemic hyperinsulinemic clamp technique [40 microU/m2/min insulin infusion rate; glucose disposal rate (M)= mg/kg/min] before and after treatment.

RESULTS

Plasma levels of total, LDL and HDL cholesterol decreased significantly in simvastatin group after treatment (p = 0.000, p = 0.000, and p = 0.048, respectively). Plasma levels of total cholesterol decreased significantly (p = 0.032), whereas LDL and HDL levels remained unchanged in placebo group. M value (mg/kg/min) decreased insignificantly in simvastatin group (4.32 +/- 1.57 vs. 3.71 +/- 1.91) and increased in placebo group (3.55 +/- 1.91 vs. 3.95 +/- 0.95).

CONCLUSION

Short-term simvastatin treatment did not affect insulin sensitivity determined by "gold standard" euglycemic hyperinsulinemic clamp method in hypercholesterolemic patients in this research. Further studies with simvastatin using higher doses and longer duration should be performed.

Bezafibrate, a peroxisome proliferator-activated receptor (PPAR)-alpha activator, prevents pancreatic degeneration in obese and diabetic rats

INTRODUCTION

Damage to the exocrine pancreas has been observed in patients and animals with hyperlipidemia and hyperglycemia. Bezafibrate, a peroxisome proliferator-activated receptor (PPAR)-alpha activator, has been shown to improve lipid and glucose metabolism, and to interfere with the inflammatory response.

AIM

To examine the effects of bezafibrate on exocrine pancreas in hyperlipidemic obese and diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats that have no cholecystokinin-1 receptor gene expression.

METHODOLOGY

One group of rats (n = 8) received a bezafibrate-rich diet (150 mg/100 g normal chow) from 12 weeks of age until 30 weeks of age, whereas a control group (n = 8) received standard rat chow.

RESULTS

Bezafibrate treatment significantly reduced serum triglyceride, total cholesterol, and free fatty acids levels and significantly increased the pancreatic wet weight (1,145 +/- 54 vs 874 +/- 33 mg/rat, p < 0.01), and protein (169 +/- 7 vs 128 +/- 11 mg/pancreas p < 0.01) and enzyme contents in the pancreas compared with those in untreated control rats. Immunohistochemical studies of the pancreas showed that expression of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1beta and interleukin-6, and alpha-smooth muscle actin in bezafibrate-treated rats was greatly suppressed compared with that in the untreated control rats. The histopathologic changes such as vacuolar degeneration and tubular complexes observed in the control rat pancreas were markedly improved in bezafibrate-treated rats.

CONCLUSIONS

Our results suggest that bezafibrate reduces hyperlipidemia, inhibits pancreatic inflammation, and prevents pancreatic degeneration in obese and diabetic OLETF rats.

Early vascular benefits of statin therapy

Large-scale trials established that statin administration in hypercholesterolaemic individuals and patients with coronary heart disease (CHD) significantly reduces the risk of vascular events and death. This benefit was primarily attributed to their actions on lipids. This review focuses on the benefits (clinical and experimental) of statins observed soon (approximately 12 weeks) after their administration. Statins rapidly increase nitric oxide production and improve endothelial function (e.g. increased flow-mediated dilatation). Similarly, antioxidant properties decrease the susceptibility of low density lipoprotein cholesterol to oxidation. Statins inhibit the migration of macrophages and smooth muscle cell proliferation leading to an antiproliferative effect and the stabilisation of atherosclerotic plaques. Anti-inflammatory effects include a reduction in serum C-reactive protein levels, inflammatory and proinflammatory cytokines (e.g. IL-6, IL-8), adhesion molecules (e.g. ICAM-1, VCAM-1) and other acute phase proteins. Statins influence the haemostatic system. They reduce tissue factor expression and platelet activity, whereas fibrinolysis can be enhanced. Statins improve microalbuminuria, renal function, hypertension and arterial wall stiffness. A significant reduction of the carotid intima media thickness (IMT) was also reported early after statin treatment. These early effects of statins probably contribute to the significant reduction in vascular events seen in some 'short-term' studies. There is a need to further elucidate the rapid and non-lipid lowering properties of statins.

Lipids and diabetes mellitus: a review of therapeutic options

Diabetes mellitus ia very common disease with a high cardiovascular morbidity and mortality. This articles reviews the types of lipid disorders that can accompany diabetes mellitus and the evidence that treatment of dyslipidaemia improves primary and secondary endpoints, i.e. lipid levels, cardiovascular events, and mortality. Specific lipid-lowering strategies are discussed, including diet and exercise, treatment of hyperglycaemia, and the use of lipid-lowering therapy such as statins, fibric acid derivatives, bile acid sequestrants, nicotinic acid and its derivatives, fish oil and hormone replacement therapy. An approach to the patient with diabetes mellitus and dyslipidaemia is provided.

Treating dyslipidaemia in non-insulin-dependent diabetes mellitus -- a special reference to statins

Patients with non-insulin-dependent diabetes (NIDDM) have an increased incidence of ischaemic heart disease (IHD) when compared with nondiabetic subjects. In addition, they have a worse prognosis after their first myocardial infarction (MI). According to the recent USA recommendations, the threshold for initiation of dietary intervention in diabetic subjects is an LDL greater than 2.6 mmol/l, with the goal to achieve levels less than 2.6 mmol/l (100 mg/dl). This is also the threshold for initiation and treatment goal for pharmacological intervention in diabetic subjects, unless they are completely free of IHD, peripheral vascular disease or cerebrovascular disease and have no other IHD risk factors. In the latter circumstances, the threshold for treatment is an LDL greater than 3.38 mmol/l (130 mg/dl), with the goal to achieve levels less than 3.38 mmol/l. The HMG-CoA reductase inhibitors (statins) can improve the lipid profile effectively and safely in NIDDM. Results from post hoc analyses of diabetic subgroups in the large intervention trials suggest that some statins significantly reduce the risk for IHD-related mortality/morbidity. However, because these results are derived from secondary prevention trials, we cannot be sure if these benefits apply to all diabetic subjects or only to those who already have IHD. Nevertheless, it seems logical to assume that this benefit also applies to NIDDM patients who do not have IHD because they share a similar vascular risk as nondiabetic subjects who have IHD. Intervention trials using statins and fibrates, alone or in combination, in NIDDM are under way. In a few years these trials will provide definitive end-point-based evidence in this high-risk group of patients.

Effects of comicronised fenofibrate on lipid and insulin sensitivity in patients with polymetabolic syndrome X

BACKGROUND

This study investigated the effects of comicronised fenofibrate in patients with dyslipidemia and polymetabolic syndrome X.

DESIGN

After a 6-week dietary run-in phase, 37 male patients eligible on lipid criteria entered a 12-week treatment phase consisting of diet plus one capsule daily containing 200 mg of comicronised fenofibrate (Lipanthyl(R)).

RESULTS

A significant reduction in plasma concentrations of total cholesterol, LDL cholesterol and triglyceride was observed after 4, 8 and 12 weeks of treatment with fenofibrate. The improvement in the atherogenic index LDL/HDL cholesterol from a pretreatment 3.8 to 3.0 after treatment was highly statistically significant and may be judged as satisfactory. Significant changes were also observed in haemostatic factors (fibrinogen reduced by 19%, factor VII activity reduced by 18%). Fasting serum insulin levels and insulin response (area under the curve) after oral glucose load were significantly reduced by 26.8% and 18.7%, respectively, indicating an improvement of insulin sensitivity. Systolic and diastolic blood pressure were significantly reduced. Uric acid was significantly reduced by 21.6%.

CONCLUSION

These favourable effects of comicronised fenofibrate both on lipid and non lipid parameters, including insulin sensitivity, may confer to this product a particular interest in the treatment of patients with polymetabolic syndrome X.

Complementary measures for promoting insulin sensitivity in skeletal muscle

Insulin resistance of skeletal muscle is fundamental to both syndrome X and its frequent sequel, type II diabetes. In these disorders, excessive exposure of muscle to free fatty acids (FFAs) and their metabolic derivatives appears to play a prominent role in the induction of insulin resistance. Recent evidence suggests that activation of novel isoforms of protein kinase C (PKC) by diacylglycerol may mediate at least part of the adverse impact of FFAs on muscle insulin sensitivity. Vitamin E and fish oil omega-3s, by promoting the activity of diacylglycerol kinase and inhibiting that of phosphatidate phosphohydrolase, should reduce diacylglycerol levels, thus accounting for their documented favorable impact on insulin sensitivity. Thiazolidinediones such as troglitazone, on the other hand, appear to intervene in the signaling pathway whereby PKC down-regulates insulin function. The insulin-sensitizing activity of chromium picolinate may be attributable, at least in part, to increased expression of insulin receptors. In combination with lifestyle modifications which reduce FFA exposure--weight loss, very-low-fat eating, excessive training--these measures can be expected to work in a complementary way to promote increased numbers of insulin receptors that are more functionally competent. As these measures appear to be safe and well-tolerated, they may have utility for the prevention of diabetes as well as its therapy. When they do not prove sufficient to achieve optimal glycemic control, excessive hepatic glucose output and impaired cell response to glucose can be addressed with metformin and sulfonylureas, respectively. The prospects for a rational medical management of type II diabetes, obviating the need for injectible insulin, have never been brighter.