Bezafibrate on lipids and glucose metabolism in obese diabetic Otsuka Long-Evans Tokushima fatty rats

Type 2 Diabetes Mellitus: Pathogenic Features and Experimental Models in Rodents

Type 2 diabetes mellitus (T2DM) is the most common endocrine disorder (90%) in the world; it has numerous clinical, immunological, and genetic differences from type 1 diabetes mellitus. The pathogenesis of T2DM is complex and not fully clear. To date, animal models remain the main tool by which to study the pathophysiology and therapy of T2DM. Rodents are considered the best choice among animal models, because they are characterized by a small size, short induction period, easy diabetes induction, and economic efficiency. This review summarizes data on experimental models of T2DM that are currently used, evaluates their advantages and disadvantages vis-a-vis research, and describes in detail the factors that should be taken into account when using these models. Selection of a suitable model for tackling a particular issue is not always trivial; it affects study results and their interpretation.

The role of oxidative stress in the development of obesity and obesity-related metabolic disorders

Obesity is a serious medical condition, defined as excessive accumulation of fat. Abdominal fat is recognized as the major risk for obesity related diseases such as: hypertension, dyslipidemia, type 2 diabetes mellitus, coronary heart disease, stroke, non-alcoholic fatty liver disease etc. Fat accumulation is also related to pro-oxidant and pro-inflammatory states. Recently published articles suggest that oxidative stress may be a link between obesity and related complications. Adiposity leads to increased oxidative stress via several multiple biochemical processes such as superoxide generation through the action of NADPH oxidase, glyceraldehyde auto-oxidation, oxidative phosphorylation, protein kinase C (PKC) activation, and polyol and hexosamine pathways. On the other hand, oxidative stress plays a causative role in the development of obesity, by stimulating the deposition of adipose tissue, including preadipocyte proliferation, adipocyte differentiation and growth. Exercise-induced weight loss can improve the redox state by modulating both oxidative stress and antioxidant promoters, which reduce endothelial dysfunction and inflammation.

Gene polymorphisms of Patatin-like phospholipase domain containing 3 (PNPLA3), adiponectin, leptin in diabetic obese patients

Obesity leads a crucial importance in metabolic disorders, as well as type 2 diabetes mellitus. Our present study was designed to assess the potential role of irisin, adiponectin, leptin and gene polymorphism of PNPLA3, leptin and adiponectin as predictive markers of diabetes associated with obesity. One hundred eighty subjects were distributed to three groups including; healthy non-diabetic non obese volunteers as a control group, diabetic non obese group, and diabetic obese group (n = 60 for each group). Fasting blood samples of all groups were collected to determine fasting blood glucose, insulin levels, insulin resistance, total cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triacylglycerol, irisin, adiponectin, leptin; as well as, polymorphism of PNPLA3, adiponectin and leptin. The results showed that glucose, insulin resistance, total cholesterol, irisin, leptin, LDL-C, triacylglycerol concentrations were significantly increased, however, insulin, HDL-C, adiponectin were significantly decreased in diabetic obese patients in relation to diabetic non-obese patients as well as in healthy volunteers. The polymorphism of PNPLA3 rs738409 was linearly related to irisin and leptin but was not related with circulating concentrations of adiponectin. We concluded that increased irisin and leptin levels can predict the insulin resistance in obese patients. Moreover, patients who have mutant genotype of PNPLA3 I148 gene (rs738409) C>G, ADIPOQ gene (rs266729) G>C and LEP gene (rs2167270) G>A showed a significant higher susceptibility rate for DM in obese people than those with wild type. This could be considered as an adjustable retort to counter the impact of obesity on glucose homeostasis.

Prevention of Elevation in Plasma Triacylglycerol with High-Dose Bezafibrate Treatment Abolishes Insulin Resistance and Attenuates Glucose Intolerance Induced by Short-Term Treatment with Dexamethasone in Rats

OBJECTIVE

Fibrates are used as lipid-lowering drugs and are well tolerated as cotreatments when glucose metabolism disturbances are also present. Synthetic glucocorticoids (GCs) are diabetogenic drugs that cause dyslipidemia, dysglycemia, glucose intolerance, and insulin resistance when in excess. Thus, we aimed to describe the potential of bezafibrate in preventing or attenuating the adverse effects of GCs on glucose and lipid homeostasis.

METHODS

Male Wistar rats were treated with high-dose bezafibrate (300 mg/kg, body mass (b.m.)) daily for 28 consecutive days. In the last five days, the rats were also treated with dexamethasone (1 mg/kg, b.m.).

RESULTS

Dexamethasone treatment reduced the body mass gain and food intake, and bezafibrate treatment exerted no impact on these parameters. GC treatment caused an augmentation in fasting and fed glycemia, plasma triacylglycerol and nonesterified fatty acids, and insulinemia, and bezafibrate treatment completely prevented the elevation in plasma triacylglycerol and attenuated all other parameters. Insulin resistance and glucose intolerance induced by GC treatment were abolished and attenuated, respectively, by bezafibrate treatment.

CONCLUSION

High-dose bezafibrate treatment prevents the increase in plasma triacylglycerol and the development of insulin resistance and attenuates glucose intolerance in rats caused by GC treatment, indicating the involvement of dyslipidemia in the GC-induced insulin resistance.

The impact of triglycerides on glucose tolerance: Lipotoxicity revisited

Elevated plasma triglycerides (TGs) are early key features of conditions associated with a dysregulation in glucose metabolism and may predict the development of type 2 diabetes (T2D) over time. Although the acute ingestion of lipid, either mixed with or shortly before the meal, is neutral or slightly beneficial on glucose tolerance, a short-term increase in plasma TGs induced by either an i.v. lipid infusion or a high-fat diet produces a deterioration of glucose control. Accordingly, chronic lowering of plasma TGs by fibrates improves glucose homeostasis and may also prevent T2D. The chronic effects of the elevation of dietary lipid intake are less clear, particularly in humans, being the quality of fat probably more important than total fat intake. Although on the bases of the available experimental and clinical evidence it cannot be easily disentangled, with respect to elevated non-esterified fatty acids (NEFA) the relative contribution of elevated TGs to glucose homeostasis disregulation seems to be greater and also more plausible. In conclusion, although the association between elevated plasma TGs and impaired glucose tolerance is commonly considered not causative or merely a consequence of NEFA-mediated lipotoxicity, the available data suggest that TGs per se may directly contribute to disorders of glucose metabolism.

Blood glycemia-modulating effects of melanian snail protein hydrolysates in mice with type II diabetes

Freshwater animal proteins have long been used as nutrient supplements. In this study, melanian snail (Semisulcospira libertina) protein hydrolysates (MPh) were found to exert anti-diabetic and protective effects against liver and kidney damage in mice with type II diabetes adapted to a 45% kcal high-fat diet (HFD). The hypoglycemic, hepatoprotective and nephroprotective effects of MPh were analyzed after 12 weeks of the continuous oral administration of MPh at 125, 250 and 500 mg/kg. Diabetic control mice exhibited an increase in body weight, and blood glucose and insulin levels, with a decrease in serum high-density lipoprotein (HDL) levels. In addition, an increase in the regions of steatohepatitis, hepatocyte hypertrophy, and lipid droplet deposit-related renal tubular vacuolation degenerative lesions were detected, with noticeable expansion and hyperplasia of the pancreatic islets, and an increase in glucagon- and insulin-producing cells, insulin/glucagon cell ratios in the endocrine pancreas and hepatic lipid peroxidation, as well as decreased zymogen contents. Furthermore, a deterioration of the endogenous antioxidant defense system was observed, with reduced glucose utilization related hepatic glucokinase (GK) activity and an increase in hepatic gluconeogenesis-related phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6pase) activity. However, all of these diabetic complications were significantly inhibited by oral treatment with MPh in a dose-dependent manner. In addition, the marked dose-dependent inhibition of hepatic lipid peroxidation, the depletion of the liver endogenous antioxidant defense system, and changes in hepatic glucose-regulating enzyme activities were also observed. The results of this study suggest that MPh exerts potent anti-diabetic effects, along with the amelioration of related complications in mice with type II diabetes. The overall effects of MPh at a dose of 125 mg/kg on HFD-induced diabetes and related complications were similar or more potent than those of metformin (250 mg/kg).

Bezafibrate ameliorates diabetes via reduced steatosis and improved hepatic insulin sensitivity in diabetic TallyHo mice

OBJECTIVE

Recently, we have shown that Bezafibrate (BEZ), the pan-PPAR (peroxisome proliferator-activated receptor) activator, ameliorated diabetes in insulin deficient streptozotocin treated diabetic mice. In order to study whether BEZ can also improve glucose metabolism in a mouse model for fatty liver and type 2 diabetes, the drug was applied to TallyHo mice.

METHODS

TallyHo mice were divided into an early (ED) and late (LD) diabetes progression group and both groups were treated with 0.5% BEZ (BEZ group) or standard diet (SD group) for 8 weeks. We analyzed plasma parameters, pancreatic beta-cell morphology, and mass as well as glucose metabolism of the BEZ-treated and control mice. Furthermore, liver fat content and composition as well as hepatic gluconeogenesis and mitochondrial mass were determined.

RESULTS

Plasma lipid and glucose levels were markedly reduced upon BEZ treatment, which was accompanied by elevated insulin sensitivity index as well as glucose tolerance, respectively. BEZ increased islet area in the pancreas. Furthermore, BEZ treatment improved energy expenditure and metabolic flexibility. In the liver, BEZ ameliorated steatosis, modified lipid composition and increased mitochondrial mass, which was accompanied by reduced hepatic gluconeogenesis.

CONCLUSIONS

Our data showed that BEZ ameliorates diabetes probably via reduced steatosis, enhanced hepatic mitochondrial mass, improved metabolic flexibility and elevated hepatic insulin sensitivity in TallyHo mice, suggesting that BEZ treatment could be beneficial for patients with NAFLD and impaired glucose metabolism.

Bezafibrate Improves Insulin Sensitivity and Metabolic Flexibility in STZ-Induced Diabetic Mice

Bezafibrate (BEZ), a pan activator of peroxisome proliferator-activated receptors (PPARs), has been generally used to treat hyperlipidemia for decades. Clinical trials with type 2 diabetes patients indicated that BEZ also has beneficial effects on glucose metabolism, although the underlying mechanisms of these effects remain elusive. Even less is known about a potential role for BEZ in treating type 1 diabetes. Here we show that BEZ markedly improves hyperglycemia and glucose and insulin tolerance in mice with streptozotocin (STZ)-induced diabetes, an insulin-deficient mouse model of type 1 diabetes. BEZ treatment of STZ mice significantly suppressed the hepatic expression of genes that are annotated in inflammatory processes, whereas the expression of PPAR and insulin target gene transcripts was increased. Furthermore, BEZ-treated mice also exhibited improved metabolic flexibility as well as an enhanced mitochondrial mass and function in the liver. Finally, we show that the number of pancreatic islets and the area of insulin-positive cells tended to be higher in BEZ-treated mice. Our data suggest that BEZ may improve impaired glucose metabolism by augmenting hepatic mitochondrial performance, suppressing hepatic inflammatory pathways, and improving insulin sensitivity and metabolic flexibility. Thus, BEZ treatment might also be useful for patients with impaired glucose tolerance or diabetes.

Fermentation of Green Tea with 2% Aquilariae lignum Increases the Anti-Diabetic Activity of Green Tea Aqueous Extracts in the High Fat-Fed Mouse

Anti-diabetic effects on the metabolomic differences between green tea (GT) and Aquilariae lignum-fermented green tea (fGT) were investigated in the high fat-fed mouse. To prove the differences, hypoglycemic (blood glucose, insulin and glycated hemoglobin levels, pancreas weights and histopathological-immunohistochemistrical analysis of pancreas–insulin/glucagon cells), hepato- and nephron-protective (the changes in liver and kidney weight, histopathology of liver and kidney, serum aminotransferases (AST and ALT) levels, blood urea nitrogen, and serum creatinine levels), and hypolipidemic (the changes of serum total cholesterol, triglyceride, low- and high-density lipoprotein levels with fecal TC and TG contents) effects were evaluated. In addition, liver lipid peroxidation, the glutathione contents, and catalase and superoxide dismutase activities were measured according to the hepatic glucose-regulating enzyme activities of glucokinase (GK), glucose-6-phosphatase (G6pase) and phosphoenolpyruvate carboxykinase (PEPCK) for action mechanisms. As a result, fGT showed a stronger hypoglycemic, hepato- and nephron-protective, hypolipidemic, and anti-oxidant effect than GT in high fat-fed mice. In addition, fGT-treated mice exerted more favorable inhibitory activities against GK, G6pase, PERCK activities as compared to GT-treated mice. Taken together, fGT fermented with Aquilariae lignum, 1:49 (2%; g/g) has a stronger effect compared with GT. Therefore, fGT has the potential to increase bioactivity against type 2 diabetics.

Adverse association between obesity and menopause in mice treated with bezafibrate, a pan peroxisome proliferator-activated receptor agonist

OBJECTIVE

The goal of this study was to investigate the combined effects of ovariectomy (OVX) and high-fat diet (HF) on insulin sensitivity and pancreatic remodeling in C57BL/6 mice treated with bezafibrate.

METHODS

Female C57BL/6 mice were subjected to OVX or surgical procedure without removal of the ovary (SHAM). Animals received standard chow (SC; 10% lipids) or HF (60% lipids). After 13 weeks on the diets, the animals were subdivided into six groups based on diet, bezafibrate treatment, or both: SHAM-SC, SHAM-HF, SHAM-HFBz, OVX-SC, OVX-HF, and OVX-HFBz. After treatment for 5 weeks, the pancreas was removed and analyzed using morphometry, stereological tools, immunostaining, and multiplex assay kits.

RESULTS

SHAM-HF and OVX-HF mice showed increased fasting glucose levels, plasma insulin levels, homeostasis model of assessment for insulin resistance index, body mass, islet hypertrophy, β-cell mass, and insulin immunostaining, but decreased GLUT2 immunostaining. Bezafibrate treatment prevented islet hypertrophy and reduced body mass, plasma insulin levels, and homeostasis model of assessment for insulin resistance index.

CONCLUSIONS

OVX combined with HF accentuates the effects of menopause, leading to the development of insulin resistance. Bezafibrate treatment reduces body mass, plasma insulin levels, and pancreatic islet hypertrophy in mice fed HF.

Localization of multidomain adaptor proteins, p140Cap and vinexin, in the pancreatic islet of a spontaneous diabetes mellitus model, Otsuka Long-Evans Tokushima Fatty rats

We have shown that two multidomain adaptor proteins, p140Cap and vinexin, interact with each other and are likely to be involved in neurotransmitter release. Because the basic molecular mechanism governing neurotransmitter and insulin secretion is conserved, these two proteins may also to play pivotal roles in insulin secretion. We therefore performed some characterization of p140Cap and vinexin in pancreas of a wild-type rat or a spontaneous type 2 diabetes mellitus (DM) model, the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. These two proteins were detected in Wistar rat pancreas by Western blotting. Immunohistochemistry revealed that p140Cap and vinexin are enriched in β and α cells, respectively, in the rat pancreas. We then found that pancreatic islet structure was disorganized in the OLETF rat with hyperinsulinemia or with hyperglycemia, based on immunohistochemical analyses of vinexin. In β cells of these model rats, p140Cap was distributed in a cytoplasmic granular pattern as in the control rats, although its expression was reduced to various extents from cell to cell. These results may suggest possible involvement of p140Cap in insulin secretion, and reduction of p140Cap might be related to abnormal insulin secretion in DM.

Murine models for pharmacological studies of the metabolic syndrome

Metabolic syndrome has been described as the association of insulin resistance, hypertension, hyperlipidemia and obesity. Its prevalence increased dramatically, mainly in developed countries. Animal models are essential to understand the pathophysiology of this syndrome. This review presents the murine models of metabolic syndrome the most often used in pharmacological studies. The most common metabolic syndrome models exhibit a non-functional leptin pathway, or metabolic disorders induced by high fat diets. In a first part, and after a short introduction on leptin, its receptor and mechanism of action, we provide a detailed description of each model: SHROB, SHHF, JCR:LA-cp, Zucker, ZDF, Wistar Ottawa Karlsburg W, and Otsuka Long-Evans Tokushima Fatty rats, ob/ob, db/db, agouti yellow and Mc4R KO mice. The second part of this review is dedicated to metabolic syndrome models obtained by high fat feeding.

The role of dietary protein on lipotoxicity

Lipotoxicity is a metabolic abnormality frequently observed during the development of obesity and is the main cause of several changes in the metabolic observed during metabolic syndrome. Consistent consumption of diets high in saturated fat or simple carbohydrates combined with low physical activity are the main causes of obesity and its comorbidities. However, the contribution of dietary protein and, in particular, the contribution due to the type of dietary protein, to the process of obesity and its metabolic consequences are less well-understood. In this review, we showed that the type of dietary protein has a significant contribution to the process of lipotoxicity through the modulation of insulin secretion and the regulation of adipocyte metabolic function. Consumption of soy protein stimulates insulin secretion to a lower extent than casein despite the fact that both are high-quality proteins. The amino acid profiles of soy protein and its isoflavones are responsible for the reduced insulin secretion. Also, soy protein increases insulin sensitivity, whereas casein has the opposite effect. Consequently, soy protein reduces SREBP-1 expression in the liver leading to low accumulation of hepatic triglycerides, despite the consumption of a high-fat diet. Furthermore, soy protein reduces adipocyte hypertrophy, hyperleptinemia, and free fatty acid concentration. Thus, the influx of FA into the liver decreases, and hepatic oxidation of FA increases. These metabolic changes result in a decrease in lipid depots and ceramide which reduce hepatic lipotoxicity, whereas casein produces the opposite effect. This study emphasizes that the type of dietary protein has an important effect on lipotoxicity.

Rosiglitazone aggravates nonalcoholic Fatty pancreatic disease in C57BL/6 mice fed high-fat and high-sucrose diet

OBJECTIVES

Evaluate the effect of fenofibrate, bezafibrate, and rosiglitazone on nonalcoholic fatty pancreatic disease and islet peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and PPAR-beta immunostain in mice fed high-fat high-sucrose (HFHS) diet.

METHODS

Two-month-old male mice were fed standard chow (n = 10) or HFHS chow (n = 40) for 6 weeks. Afterward, HFHS mice were grouped by treatment: untreated HFHS and HFHS treated with rosiglitazone (HFHS-Ro), fenofibrate (HFHS-Fe), or bezafibrate (HFHS-Bz). Medications were administered for 5 weeks. After treatment, the pancreas was removed and analyzed by morphometry, stereology, and immunohistochemistry.

RESULTS

The HFHS-fed mice showed altered fasting glucose (+33%) and insulin (+138%); increased body (+20%) and pancreas (+28%) masses, pancreatic fat (+700%), islet hypertrophy (+38%); and decreased GLUT2 immunostain (-60%). Rosiglitazone reduced fasting glucose and insulin but induced weight gain. Fibrates impeded weight gain, but only bezafibrate prevented islet hypertrophy. The GLUT2 stain was improved in all treatments, and there were no alterations in PPAR-alpha. There were morphological signs of pancreatitis with fenofibrate, although there were no alterations in amylase and lipase. Rosiglitazone exacerbated pancreatic fat infiltration (+75% vs HFHS group), and bezafibrate increased PPAR-beta expression in pancreatic islets.

CONCLUSIONS

Rosiglitazone is shown for the first time to exacerbate pancreatic fat infiltration; therefore, precaution has to be taken when rosiglitazone is prescribed to obese patients.

A review of islet of Langerhans degeneration in rodent models of type 2 diabetes

Type 2 diabetes mellitus (TTDM) is characterized by progressive loss of glucose control through multifactorial mechanisms. The search for an understanding of TTDM has relied on animal models since the realization of the importance of the pancreas in controlling plasma glucose concentration. Rodent models of TTDM are developed to express hyperglycemia and not islet degeneration per se. Degeneration of the islets of Langerhans with beta-cell loss is secondary to insulin resistance and is regarded as the more important lesion. Despite this, differences between models are seen in the development and progression of islet degeneration. Assessing the differences between the models is important to appreciate the various aspects of TTDM and understand their advantages as well as their deficiencies. Relevant animal models of TTDM provide opportunities to investigate important physiological and cell biological processes that may ultimately lead to development of targeted therapies. This article reviews the importance, advantages, and limitations of rodent models of TTDM in relation to the histopathological changes that characterize islet degeneration. Pathophysiological mechanisms that contribute to islet degeneration are also discussed and are placed into the context of changes in islet histological appearances.

Vascular and metabolic effects of treatment of combined hyperlipidemia: focus on statins and fibrates

Combined hyperlipidemia results from overproduction of hepatically synthesized apolipoprotein B in very low-density lipoproteins in association with reduced lipoprotein lipase activity. Thus, this condition is typically characterized by concurrent elevations in total cholesterol and triglycerides with decreased high-density lipoprotein cholesterol. High levels of apolipoprotein B-containing lipoproteins, most prominently carried by low-density lipoprotein (LDL) particles, are an important risk factor for coronary heart disease. Statin therapy is highly effective at lowering LDL cholesterol. Despite the benefits of statin treatment for lowering total and LDL cholesterol, many statin-treated patients still have initial or recurrent coronary heart disease events. In this regard, combined therapy with statins and fibrates is more effective in controlling atherogenic dyslipidemia in patients with combined hyperlipidemia than either drug alone. Furthermore, statins and fibrates activate PPARalpha in a synergistic manner providing a molecular rationale for combination treatment in coronary heart disease. Endothelial dysfunction associated with cardiovascular diseases may contribute to insulin resistance so that there may also be additional beneficial metabolic effects of combined statin/fibrates therapy. However, there has been little published evidence that combined therapy is synergistic or even better than monotherapy alone in clinical studies. Therefore, there is a great need to study the effects of combination therapy in patients. When statins are combined with gemfibrozil therapy, this is more likely to be accompanied by myopathy. However, this limitation is not observed when fenofibrate, bezafibrate, or ciprofibrate are used in combination therapy.

Pancreatic Insulin Secretion in Rats Fed a Soy Protein High Fat Diet Depends on the Interaction between the Amino Acid Pattern and Isoflavones

Obesity is frequently associated with the consumption of high carbohydrate/fat diets leading to hyperinsulinemia. We have demonstrated that soy protein (SP) reduces hyperinsulinemia, but it is unclear by which mechanism. Thus, the purpose of the present work was to establish whether SP stimulates insulin secretion to a lower extent and/or reduces insulin resistance, and to understand its molecular mechanism of action in pancreatic islets of rats with diet-induced obesity. Long-term consumption of SP in a high fat (HF) diet significantly decreased serum glucose, free fatty acids, leptin, and the insulin:glucagon ratio compared with animals fed a casein HF diet. Hyperglycemic clamps indicated that SP stimulated insulin secretion to a lower extent despite HF consumption. Furthermore, there was lower pancreatic islet area and insulin, SREBP-1, PPARgamma, and GLUT-2 mRNA abundance in comparison with rats fed the casein HF diet. Euglycemic-hyperinsulinemic clamps showed that the SP diet prevented insulin resistance despite consumption of a HF diet. Incubation of pancreatic islets with isoflavones reduced insulin secretion and expression of PPARgamma. Addition of amino acids resembling the plasma concentration of rats fed casein stimulated insulin secretion; a response that was reduced by the presence of isoflavones, whereas the amino acid pattern resembling the plasma concentration of rats fed SP barely stimulated insulin release. Infusion of isoflavones during the hyperglycemic clamps did not stimulate insulin secretion. Therefore, isoflavones as well as the amino acid pattern seen after SP consumption stimulated insulin secretion to a lower extent, decreasing PPARgamma, GLUT-2, and SREBP-1 expression, and ameliorating hyperinsulinemia observed during obesity.

Long-term effect of bezafibrate on pancreatic beta-cell function and insulin resistance in patients with diabetes

OBJECTIVE

Development of insulin resistance (IR) and the progressive failure of the pancreatic beta-cell function (BCF) may be important in the pathogenesis of type 2 diabetes. Influence of peroxisome proliferator-activated receptors ligand bezafibrate on BCF and IR in patients with diabetes is unknown. The present study was aimed to investigate the long-term effect of bezafibrate on these parameters in diabetic patients enrolled in the Bezafibrate Infarction Prevention (BIP) Study.

METHODS

Metabolic and inflammatory parameters were analyzed from stored frozen plasma samples obtained from 351 diabetic patients (168 treated by bezafibrate and 183 by placebo) who completed a 2-year of randomized, double-blind, placebo-controlled study period. The homeostatic indexes of BCF (HOMA-BCF) and IR (HOMA-IR) were calculated according to the homeostasis model of assessment.

RESULTS

Both groups displayed similar baseline characteristics. During follow-up, in the placebo group there was 28% rise of HOMA-IR (p<0.001). In contrast, HOMA-IR in patients in the bezafibrate group did not change (p=0.99). The intergroup differences in HOMA-IR percentage changes were in favor of bezafibrate (p=0.01). HOMA-BCF values have significantly decreased by 13.9% (p=0.04) in patients of placebo group, whereas in patients of bezafibrate group HOMA-BCF was stable during follow-up and its alterations (-2.9%) were non-significant (p=0.59).

CONCLUSIONS

Diabetic patients from the placebo group demonstrated a progressive declining of BCF and an increasing of IR over 2 years of follow-up. These longitudinal changes were attenuated when patients used bezafibrate.

Activity of the Chinese prescription Hachimi-jio-gan against renal damage in the Otsuka Long-Evans Tokushima fatty rat: a model of human type 2 diabetes mellitus

Currently, in Japan, approximately 95% of patients with diabetes mellitus have non-insulin-dependent (type 2) diabetes mellitus (NIDDM), and diabetic nephropathy is a major cause of patients requiring chronic haemodialysis. A previous study showed that Hachimi-jio-gan has a protective effect in rats subjected to subtotal nephrectomy plus streptozotocin injection, a model of insulin-dependent (type 1) diabetic nephropathy. In this study, we used the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of human NIDDM, to investigate whether long-term administration of Hachimi-jio-gan affects glycaemic control and renal function in NIDDM. Male OLETF rats, aged 22 weeks, were divided into 4 groups of 10 and given Hachimi-jio-gan (50, 100 or 200 mg kg(-1) daily) orally or no treatment for 32 weeks. Male Long-Evans Tokushima Otsuka (LETO) rats (n = 6) were used as non-diabetic normal controls. Hachimi-jio-gan reduced hyperglycaemia dose-dependently from 16 weeks of the administration period. Urinary protein excretion decreased significantly from an early stage, and creatinine clearance levels improved at 32 weeks. In addition, the levels of serum glycosylated protein and renal advanced glycation end-products were effectively reduced. Hachimi-jio-gan also significantly reduced the levels of thiobarbituric acid-reactive substances in renal mitochondria, although it showed only a tendency to reduce these in serum. Furthermore, long-term administration of Hachimi-jio-gan reduced renal cortical expression of proteins, such as transforming growth factor-beta1 (TGF-beta1), fibronectin, inducible nitric oxide synthase and cyclooxygenase-2. The 100- and 200-mg kg(-1) daily doses of Hachimi-jio-gan significantly reduced TGF-beta1 and fibronectin protein expression to levels below those of LETO rats. These data suggest that Hachimi-jio-gan may have a beneficial effect on the progression of diabetic nephropathy in OLETF rats by attenuating glucose toxicity and renal damage.

Effects of fenofibrate on lipid metabolism in adipose tissue of rats

The effect of fenofibrate, a peroxisome proliferator-activated receptor alpha agonist, on body weight gain and on reduction of adipose tissue pads has been ascribed to increased fat catabolism in liver mainly through the induction of target enzymes involved in hepatic lipid metabolism. The aim of this study was to investigate whether peroxisome proliferator-activated receptor alpha activation also affects metabolic pathways in adipose tissue of rats treated with fenofibrate (100 mg/kg body weight) for 9 days. Fenofibrate lowered body weight gain and plasma triglyceride, total cholesterol, and high-density lipoprotein cholesterol but had no influence on food intake and on plasma glucose levels. The activity of lipoprotein lipase of treated animals decreased 50% in epididymal, 29% in retroperitoneal, and was not affected in the mesenteric fat pads. In this study, we show a 34% decrease in epididymal adipose tissue de novo lipogenesis by fenofibrate. The results demonstrate that insulin sensitivity of lipolysis is decreased in fenofibrate-treated rats which resulted in 30% higher rate of glycerol release when compared to the control group. These findings suggest that besides its effects on liver, fenofibrate exerts effects on lipid metabolism in adipose tissue which may contribute to decreasing adiposity.