Diabetes and mitochondrial bioenergetics: alterations with age

Several studies have been carried out to evaluate the alterations in mitochondrial functions of diabetic rats. However, some of the results reported are controversial, since experimental conditions, such as aging, and/or strain of animals used were different. The purpose of this study was to evaluate the metabolic changes in liver mitochondria, both in the presence of severe hyperglycaemia (STZ-treated rats) and mild hyperglycaemia (Goto-Kakizaki (GK) rats). Moreover, metabolic alterations were evaluated both at initial and at advanced states of the disease. We observed that both models of type 1 and type 2 diabetes presented alterations on respiratory chain activity. Because of continual severe hyperglycaemia, 9 weeks after the induction of diabetes, the respiratory function declined in STZ-treated rats, as observed by membrane potential and respiratory ratios (RCR, P/O, and FCCP-stimulated respiration) assessment. In contrast, GK rats of 6 months age presented increased respiratory ratios. To localize which respiratory complexes are affected by diabetes, enzymatic respiratory chain activities were evaluated. We observed that succinate dehydrogenase and cytochrome c oxidase activities were significantly augmented both in STZ-treated rats and GK rats of 6 months age. Moreover, H(+)-ATPase activity was also significantly increased in STZ-treated rats with 3 weeks of diabetes and in GK rats of 6 months age as compared to controls. Therefore, these results clearly suggest that both animal models of diabetes present some metabolic adjustments in order to circumvent the deleterious effects promoted by the high glucose levels typical of the disease.     

Decreased susceptibility of heart mitochondria from diabetic GK rats to mitochondrial permeability transition induced by calcium phosphate

Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease in man. The Goto-Kakizaki (GK) rat has been designed as a NIDDM model. Previous studies with this strain have shown differences at the mitochondrial level. The mitochondrial permeability transition (MPT) is a widely studied phenomenon but yet poorly understood, that leads to mitochondrial dysfunction and cell death. The aim of this work was to compare the differences in susceptibility of induction of the MPT with calcium phosphate in GK and Wistar rats. Our results show that heart mitochondria from GK rats are less susceptible to the induction of MPT, and show a larger calcium accumulation before the overall loss of mitochondrial impermeability.     

Promoter characterization and expression of the gene coding for the human GM2 activator protein

Type 2 diabetes (or non-insulin dependent diabetes mellitus, NIDDM) is a common metabolic disease in man. The Goto–Kakizaki (GK) rat has been designed as a NIDDM model. Previous studies with this strain have shown differences at the mitochondrial level. The mitochondrial permeability transition (MPT) is a widely studied phenomenon but yet poorly understood, that leads to mitochondrial dysfunction and cell death. The aim of this work was to compare the differences in susceptibility of induction of the MPT with calcium phosphate in GK and Wistar rats. Our results show that heart mitochondria from GK rats are less susceptible to the induction of MPT, and show a larger calcium accumulation before the overall loss of mitochondrial impermeability.     

Enhanced permeability transition explains the reduced calcium uptake in cardiac mitochondria from streptozotocin-induced diabetic rats

Cardiac dysfunction is associated with diabetes. It was previously shown that heart mitochondria from diabetic rats have a reduced calcium accumulation capacity. The objective of this work was to determine whether the reduction in calcium accumulation by cardiac mitochondria from diabetic rats is related to an enhanced susceptibility to induction of the mitochondrial permeability transition. Streptozotocin-induced diabetic rats were used as a model to study the alterations caused by diabetes in the permeability transition, 21 days after streptozotocin administration. Heart mitochondria were isolated to evaluate respiratory parameters and susceptibility to the calcium-dependent permeability transition. Our results show that streptozotocin diabetes facilitates the mitochondrial permeability transition in cardiac mitochondria, resulting in decreased mitochondrial calcium accumulation. We also observed that heart mitochondria from diabetic rats had depressed oxygen consumption during the phosphorylative state. The reduced mitochondrial calcium uptake observed in heart mitochondria from diabetic rats is related to an enhanced susceptibility to the permeability transition rather than to damage to the calcium uptake machinery.     

Decreased susceptibility to lipid peroxidation of Goto-Kakizaki rats: relationship to mitochondrial antioxidant capacity.

The respiratory function and the antioxidant capacity of liver mitochondrial preparations isolated from Goto-Kakizaki non-insulin dependent diabetic rats and from Wistar control rats, with the age of 6 months, were compared. It was found that Goto-Kakizaki mitochondrial preparations presented a higher coupling between oxidative and phosphorylative systems, compared to non-diabetic preparations. Goto-Kakizaki mitochondria presented a lower susceptibility to lipid peroxidation induced by ADP/Fe2+, as evaluated by the formation of thiobarbituric acid substances. The decreased susceptibility to peroxidation in diabetic rats was correlated with an increase in mitochondrial vitamin E (alpha-tocopherol) content and GSH/GSSG ratio. Moreover, the glutathione reductase activity was significantly increased, whereas the glutathione peroxidase was decreased. Superoxide dismutase activity was unchanged in diabetic rats. Fatty acid analyses showed that the content in polyunsaturated fatty acids of Goto-Kakizaki mitochondrial membranes was significantly higher compared to controls. These results indicate that the lower susceptibility to lipid peroxidation of mitochondria from diabetic rats was related to their antioxidant defense systems, and may correspond to an adaptative response of the cells against oxidative stress in the early phase of diabetes.     

Decreased activity and impaired induction of nitric oxide synthase by lipopolysaccharides in streptozotocin-induced diabetic rats

The effect of diabetes was determined on nitric oxide synthase (NOS) activity in rat heart and liver. The diabetes was induced by streptozotocin (STZ) and NOS activity was determined after 1 or 12 weeks post-STZ injection. In both tissues, the majority of NOS activity was associated with endothelial constitutive calcium-sensitive NOS (ecNOS) isoform and found in the particulate (100,000xg pellet) fraction in young rats. The diabetes as well as age reduced this activity significantly in heart, whereas only the age caused a decrease in ecNOS activity in liver tissue. Lipopolysaccharides (LPS) induced calcium-insensitive iNOS activity in both young and old rats. The induction was significantly higher (up to 10-fold) in liver as compared to heart. Although the maximum induction of iNOS in young rats was almost similar in diabetic tissues as compared to control animals, there was a lag period for induction of iNOS in diabetic tissues. In old diabetic rats, the induction by LPS was almost completely abolished. These results suggest that diabetes causes either no change or a decrease in ecNOS activity and impairment in the induction of iNOS by LPS in rat heart and liver.     

Lipoperoxidation in hepatic subcellular compartments of diabetic rats

It is known that an accumulation of lipoperoxidative aldehydes malondialdehyde (MDA) and 4-hydroxynonenal (HNE) takes place in liver mitochondria during aging. The existence and role of an increased extra- and intra-cellular oxidative stress in diabetes, an aging-accelerating disease, is currently under discussion. This report offers evidence that lipoperoxidative aldehydes accumulate in liver microsomes and mitochondria at a higher rate in spontaneously diabetic BB/WOR rats than in control non-diabetic animals (HNE content, diabetes vs. control: microsomes 80.6+/-19.9 vs. 25.75+/-3.6 pmol/mg prot, p = .024; mitochondria 77.4+/-15.4 vs. 26.5+/-3.5 pmol/mg prot, p = .0103). Liver subcellular fractions from diabetic rats, when exposed to the peroxidative stimulus ADP/Fe, developed more lipoperoxidative aldehydes than those from non diabetic rats (HNE amount, diabetes vs. control: microsomes 3.60+/-0.37 vs. 2.33+/-0.22 nmol/mg prot, p = .014; mitochondria 3.62+/-0.26 vs. 2.30+/-0.17 nmol/mg prot, p = .0009). Liver subcellular fractions of diabetic rats developed more fluorescent chromolipids related to HNE-phospholipid adducts, either after in vitro peroxidation (microsomes: p = .0045; mitochondria: p = .0023) or by exposure to exogenous HNE (microsomes: p = .049; mitochondria: p = .0338). This higher susceptibility of diabetic liver membranes to the non-enzymatic attack of HNE may be due to an altered phospholipid composition. Moreover, a decreased activity of the HNE-metabolizing systems can be involved: diabetic liver mitochondria and microsomes were unable to consume exogenous HNE at the same rate as non-diabetic membranes; the difference was already significant after 5' incubation (microsomes p<.001; mitochondria p<.001). These data show an increased oxidative stress inside the hepatocytes of diabetic rats; the impairment of the HNE-metabolizing systems can play a key role in the maintenance and propagation of the damage.     

Mitochondrial activity in different regions of the brain at the onset of streptozotocin-induced diabetes in rats

Diabetes affects a variety of tissues including the central nervous system; moreover, some evidence indicates that memory and learning processes are disrupted. Also, oxidative stress triggers alterations in different tissues including the brain. Recent studies indicate mitochondria dysfunction is a pivotal factor for neuron damage. Therefore, we studied mitochondrial activity in three brain regions at early type I—diabetes induction. Isolated mitochondria from normal hippocampus, cortex and cerebellum revealed different rates of oxygen consumption, but similar respiratory controls. Oxygen consumption in basal state 4 significantly increased in the mitochondria from all three brain regions from diabetic rats. No relevant differences were observed in the activity of respiratory complexes, but hippocampal mitochondrial membrane potential was reduced. However, ATP content, mitochondrial cytochrome c, and protein levels of β-tubulin III, synaptophysin, and glutamine synthase were similar in brain regions from normal and diabetic rats. In addition, no differences in total glutathione levels were observed between normal and diabetic rat brain regions. Our results indicated that different regions of the brain have specific metabolic responses. The changes in mitochondrial activity we observed at early diabetes induction did not appear to cause metabolic alterations, but they might appear at later stages. Longer-term streptozotocin treatment studies must be done to elucidate the impact of hyperglycemia in brain metabolism and the function of specific brain regions.     

Melatonin and succinate reduce rat liver mitochondrial dysfunction in diabetes

Mitochondrial dysfunction and an increase in mitochondrial reactive oxygen species in response to hyperglycemia during diabetes lead to pathological consequences of hyperglycemia. The aim of the present work was to investigate the role of a specific functional damage in rat liver mitochondria during diabetes as well as to evaluate the possibility of metabolic and antioxidative correction of mitochondrial disorders by pharmacological doses of succinate and melatonin. In rat liver mitochondria, streptozotocin-induced diabetes was accompanied by marked impairments of metabolism: we observed a significant activation of α-ketoglutarate dehydrogenase (by 60%, p<0.05) and a damage of the respiratory function. In diabetic animals, melatonin (10 mg/kg b.w., 30 days) or succinate (50 mg/kg b.w., 30 days) reversed the oxygen consumption rate V(3) and the acceptor control ratio to those in nondiabetic animals. Melatonin enhanced the inhibited activity of catalase in the cytoplasm of liver cells and prevented mitochondrial glutathione-S-transferase inhibition while succinate administration prevented α-ketoglutarate dehydrogenase activation. The mitochondria dysfunction associated with diabetes was partially remedied by succinate or melatonin administration. Thus, these molecules may have benefits for the treatment of diabetes. The protective mechanism may be related to improvements in mitochondrial physiology and the antioxidative status of cells.     

Differential alterations in mitochondrial function induced by a choline-deficient diet: understanding fatty liver disease progression

Non-alcoholic fatty liver disease (NAFLD) is an increasingly reported pathology, characterized by fat accumulation within the hepatocyte. Growing evidences suggest specific effects on mitochondrial metabolism, but it is still unclear the relationship between fatty liver progression and mitochondrial function. In the present work we have investigated the impact of fatty liver on mitochondrial bioenergetic functions and susceptibility to mitochondrial permeability transition (MPT) induction in animals fed a choline-deficient diet (CDD) for 4, 8, 12 or 16 weeks. Mitochondria isolated from CDD animals always exhibited higher state 4 respiration. Mitochondrial membrane potential was decreased in CDD animals at 4 and 16 weeks. At 12 weeks, oxidative phosphorylation was more efficient in CDD animals, suggesting a possible early response trying to revert the deleterious effect of increased triglyceride storage in the liver. However, mitochondrial dysfunction was evident in CDD animals at 16 weeks as indicated by decreased RCR and ADP/O, with a corresponding decrease in respiratory chain enzymes activities. Such loss of respiratory efficiency was associated with accumulation of protein oxidation products, in tissue and mitochondrial fraction. Additionally, although no differences in ATPase activity, the lag phase was increased in mitochondria from CDD animals at 16 weeks, associated with decreased content of the adenine nucleotide translocator. Increased susceptibility to calcium-induced MPT was evident in CDD animals at all time points. These results suggest a dynamic mechanism for the development of NALFD associated with altered mitochondrial function.     

A bioenergetic model of the mitochondrial population undergoing permeability transition

Mitochondrial permeability transition (MPT) is a highly regulated complex phenomenon that is a type of ischemia/reperfusion injury that can lead to cell death and ultimately organ dysfunction. A novel population transition and detailed permeability transition pore regulation model were integrated with an existing bioenergetics model to describe MPT induction under a variety of conditions. The framework of the MPT induction model includes the potential states of the mitochondria (aggregated, orthodox and post-transition), their transitions from one state to another as well as their interaction with the extra-mitochondrial environment. The model encodes the three basic necessary conditions for MPT: a high calcium load, alkaline matrix pH and circumstances which favor de-energization. The MPT induction model was able to reproduce the expected bioenergetic trends observed in a population of mitochondria subjected to conditions that favor MPT. The model was corroborated and used to predict that MPT in an acidic environment is mitigated by an increase in activity of the mitochondrial potassium/hydrogen exchanger. The model was also used to present the beneficial impact of reducing the duration mitochondria spend in the orthodox state on preserving the extra-mitochondrial ATP levels. The model serves as a tool for investigators to use to understand the MPT induction phenomenon, explore alternative hypotheses for PTP regulation, as well as identify endogenous pharmacological targets and evaluate potential therapeutics for MPT mitigation.     

Higher efficiency of the liver phosphorylative system in diabetic Goto-Kakizaki (GK) rats.

Liver mitochondrial bioenergetics of Goto-Kakizaki (GK) rats (a model of non-insulin dependent diabetes mellitus) reveals a Delta Psi upon energization with succinate significantly increased relatively to control animals. The repolarization rate following ADP phosphorylation is also significantly increased in GK mitochondria in parallel with increased ATPase activity. The increase in the repolarization rate and ATPase activity is presumably related to an improved efficiency of F(0)F(1)-ATPase, either from a better phosphorylative energy coupling or as a consequence of an enlarged number of catalytic units. Titrations with oligomycin indicate that diabetic GK liver mitochondria require excess oligomycin pulses to completely abolish phosphorylation, relative to control mitochondria. Therefore, accepting that the number of operational ATP synthase units is inversely proportional to the amount of added oligomycin, it is concluded that liver mitochondria of diabetic GK rats are provided with extra catalytic units relative to control mitochondria of normal rats. Other tissues (kidney, brain and skeletal muscle) were evaluated for the same bioenergetic parameters, confirming that this feature is exclusive to liver from diabetic GK rats.     

Improving effects obtained by the ovariectomy or treatment with tamoxifen of female diabetic rats over the function and enzyme activities of liver mitochondria.

In the present work we studied, in female chronic diabetic rats the effect of either the parenteral administration of tamoxifen (TAM) (500 micrograms.kg-1.day-1) for 15 days or the ovariectomy upon the respiration and oscillatory behaviour of intact mitochondria and the activities of 3-hydroxybutyrate dehydrogenase (HBD) and cytochrome c oxidase (Cox) of disrupted liver mitochondria. The treatment with TAM as well as the ovariectomy of diabetic animals significantly increased the respiratory control (RC) and the state 3 (S3) of respiration of intact liver mitochondria with the three substrates assayed (3-hydroxybutyrate, malate-glutamate and succinate). Both treatments also lowered significantly the damped factors of the oscillatory variation of liver intact mitochondria of diabetic rats. Moreover, the two above-mentioned treatments restored the activities of HBD and Cox of liver disrupted mitochondria to normal values. The effect of estrogens at level of its receptors in the modulation of liver mitochondrial function and liver HBD and Cox activities in chronic diabetes is discussed.     

Enhanced mitochondrial testicular antioxidant capacity in Goto-Kakizaki diabetic rats: role of coenzyme Q

Because diabetes mellitus isassociated with impairment of testicular function, ultimately leadingto reduced fertility, this study was conducted to evaluate theexistence of a cause-effect relationship between increased oxidativestress in diabetes and reduced mitochondrial antioxidant capacity. Thesusceptibility to oxidative stress and antioxidant capacity (in termsof glutathione, coenzyme Q, and vitamin E content) of testismitochondrial preparations isolated from Goto-Kakizaki (GK)non-insulin-dependent diabetic rats and from Wistar control rats, 1 yrof age, was evaluated. It was found that GK mitochondrial preparationsshowed a lower susceptibility to lipid peroxidation induced byADP/Fe²⁺, as evaluated by oxygen consumption and reactiveoxygen species generation. The decreased susceptibility to oxidativestress in diabetic rats was associated with an increase inmitochondrial glutathione and coenzyme Q9 contents, whereas vitamin Ewas not changed. These results demonstrate a higher antioxidantcapacity in diabetic GK rats. We suggest this is an adaptive responseof testis mitochondria to the increased oxidative damage in diabetes mellitus.

     

Alloxan-induced diabetes triggers the development of periodontal disease in rats

Background

Periodontal disease in diabetic patients presents higher severity and prevalence; and increased severity of ligature-induced periodontal disease has been verified in diabetic rats. However, in absence of aggressive stimuli such as ligatures, the influence of diabetes on rat periodontal tissues is incompletely explored. The aim of this study was to evaluate the establishment and progression of periodontal diseases in rats only with diabetes induction.

Methodology/Principal Findings

Diabetes was induced in Wistar rats (n = 25) by intravenous administration of alloxan (42 mg/kg) and were analyzed at 1, 3, 6, 9 and 12 months after diabetes induction. The hemimandibles were removed and submitted to radiographical and histopathological procedures. A significant reduction was observed in height of bone crest in diabetic animals at 3, 6, 9 and 12 months, which was associated with increased numbers of osteoclasts and inflammatory cells. The histopathological analyses of diabetic rats also showed a reduction in density of collagen fibers, fibroblasts and blood vessels. Severe caries were also detected in the diabetic group.

Conclusions/Significance

The results demonstrate that diabetes induction triggers, or even co-induces the onset of alterations which are typical of periodontal diseases even in the absence of aggressive factors such as ligatures. Therefore, diabetes induction renders a previously resistant host into a susceptible phenotype, and hence diabetes can be considered a very important risk factor to the development of periodontal disease.     

Decreased rate of ketone-body oxidation and decreased activity of D-3-hydroxybutyrate dehydrogenase and succinyl-CoA:3-oxo-acid CoA-transferase in heart mitochondria of diabetic rats.

Heart mitochondria from chronically diabetic rats ('diabetic mitochondria'), in metabolic State 3, oxidized 3-hydroxybutyrate and acetoacetate at a relatively slow rate, as compared with mitochondria from normal rats ('normal mitochondria'). No significant differences were observed, however, with pyruvate or L-glutamate plus L-malate as substrates. Diabetic mitochondria also showed decreased 3-hydroxybutyrate dehydrogenase and succinyl-CoA: 3-oxoacid CoA-transferase activities, but cytochrome content and NADH-dehydrogenase, succinate dehydrogenase, cytochrome oxidase and acetoacetyl-CoA thiolase activities proved normal. The decrease of 3-hydroxybutyrate dehydrogenase activity was observed in diabetic mitochondria subjected to different disruption procedures, namely freeze-thawing, sonication or hypoosmotic treatment, between pH 7.5 and 8.5, at temperatures in the range 6-36 degrees C, and in the presence of L-cysteine. Determination of the kinetic parameters of the enzyme reaction in diabetic mitochondria revealed diminution of maximal velocity (Vmax) as its outstanding feature. The decrease in 3-hydroxybutyrate dehydrogenase in diabetic mitochondria was a slow-developing effect, which reached full expression 2-3 months after the onset of diabetes; 1 week after onset, no significant difference between enzyme activity in diabetic and normal mitochondria could be established. Insulin administration to chronically diabetic rats for 2 weeks resulted in limited recovery of enzyme activity. G.l.c. analysis of fatty acid composition and measurement of diphenylhexatriene fluorescence anisotropy failed to reveal significant differences between diabetic and normal mitochondria. The Arrhenius-plot characteristics for 3-hydroxybutyrate dehydrogenase in membranes of diabetic and normal mitochondria were similar. It is assumed that the variation of the assayed enzymes in diabetic mitochondria results from a slow adaptation to the metabolic conditions resulting from diabetes, rather than to insulin deficiency itself.     

Circulating sphingolipid biomarkers in models of type 1 diabetes

Alterations in lipid metabolism may contribute to diabetic complications. Sphingolipids are essential components of cell membranes and have essential roles in homeostasis and in the initiation and progression of disease. However, the role of sphingolipids in type 1 diabetes remains largely unexplored. Therefore, we sought to quantify sphingolipid metabolites by LC-MS/MS from two animal models of type 1 diabetes (streptozotocin-induced diabetic rats and Ins2(Akita) diabetic mice) to identify putative therapeutic targets and biomarkers. The results reveal that sphingosine-1-phosphate (So1P) is elevated in both diabetic models in comparison to respective control animals. In addition, diabetic animals demonstrated reductions in plasma levels of omega-9 24:1 (nervonic acid)-containing ceramide, sphingomyelin, and cerebrosides. Reduction of 24:1-esterfied sphingolipids was also observed in liver and heart. Nutritional stress via a high-fat diet also reduced 24:1 content in the plasma and liver of mice, exacerbating the decrease in some cases where diabetes was also present. Subcutaneous insulin corrected both circulating So1P and 24:1 levels in the murine diabetic model. Thus, changes in circulating sphingolipids, as evidenced by an increase in bioactive So1P and a reduction in cardio- and neuro-protective omega-9 esterified sphingolipids, may serve as biomarkers for type 1 diabetes and represent novel therapeutic targets.     

Metabolic and mitochondrial disturbances in streptozotocin-treated Sprague-Dawley and Sherman rats

This study provides explanation for conflicting evidence in the literature relating to changes in mitochondrial function and metabolic parameters during chemically induced diabetes. Diabetes of 3 days' duration (early ketosis) did not alter heart, kidney, or liver mitochondrial respiratory rates with glutamate or succinate even though serum glucose and triglycerides were elevated. Diabetes of 5 weeks' duration did not alter kidney or liver mitochondrial function in the fed adult rat although weight gain was depressed. The amount of kidney mitochondrial protein isolated per gram of tissue was increased by 30% in the diabetic. This increase was reversed by insulin treatment as were the other biochemical modalities measured. Superimposition of a 24-hr fast resulted in enhanced gluconeogenesis as measured by an animal weight loss of 17% within 24 hr (liver weight loss, 21%) and an elevation of serum urea nitrogen by 180% compared to fasted control. Respiratory rates of diabetic kidney mitochondria with glutamate were unaffected in the fasted animal whereas diabetic liver mitochondrial respiratory rates during succinate oxidation were reduced by 43%. Respiratory control was unchanged in the fasted diabetic rat. All the observed changes were reversed by insulin. Variation in the serum and liver metabolic indices (urea nitrogen, creatinine, glycerol, free fatty acids, free amino acids, triglycerides, and glucose) and liver mitochondrial responses to 7 weeks of chemically induced diabetes was affected by the rat strain, Sprague-Dawley versus Sherman, and rat weight, 72 g versus 222 g. Liver mitochondrial respirations in fed Sherman rats were not depressed by diabetes. Both rat strains had elevated liver free fatty acids and glutamate dehydrogenase activity in the diabetic state. Serum leucine, isoleucine, and valine were more elevated and serum lysine and arginine were more depressed in the diabetic Sprague-Dawley rat than in the Sherman rat. Conjectures on these results are presented in the text.     

Comparative study of three angiotensin II type 1 receptor antagonists in preventing liver fibrosis in diabetic rats: stereology, histopathology, and electron microscopy

The presence of liver disease in patients with progressively worsening insulin resistance may not be recognized until patients develop manifestations of the metabolic syndrome such as diabetes, hypertension, hyperlipidemia, and vascular disease. It was aimed to investigate whether three angiotensin II type 1 receptor antagonists (ARBs) (olmesartan, losartan, and valsartan) had preventive effect against hepatic fibrosis and this was a common characteristic among ARBs. In current study, 25 adult male rats were used and divided into five groups: the non-diabetic healthy group, alloxan induced diabetic (AID) control group, AID losartan group, AID valsartan group and AID olmesartan group. According to numerical density of hepatocytes, significant difference was found between the non-diabetic healthy group and diabetic control group. All treatments groups were significant when compared to diabetic control group. In diabetic control group it was examined swelling, irregular cristae arrangement in some of mitochondria. It was also determined mitochondria membrane degeneration in some areas of section profiles. In diabetic rats treated with losartan group, there were necrotic hepatocytes. In diabetic rats treated with valsartan group, predominantly, findings were similar to losartan group. In diabetic rats treated with olmesertan group, plates of hepatocytes were quite regular. There were hardly necrotic cells. Not only other organelles such as RER, SER and lysosom but also mitochondrial structures had normal appearance. In the diabetic control group electron microscopy revealed edema in both the cytoplasm and perinuclear area and the nuclear membranes appeared damaged. In conclusion, it was established that the most protective ARB the liver in diabetic rats was olmesartan, followed by losartan.     

Appearance and metabolic development of diabetes mellitus in the sand rat, Psammomys obesus

The aim of this study was to examine the long-term effects of synthetic chow diet on the metabolic pattern of diabetic syndrome in a large group of sand rats. Few animals had a fulminating reaction with markedly decreased glucose tolerance, low plasma insulin levels and death within 3-4 weeks. But the most of sand rats developed obesity and elevated plasma insulin levels. From the third month, 40% of sand rats presented a diabetic syndrome with hyperinsulinemia, hyperglycemia, markedly decreased glucose tolerance and insulin resistance. Plasma lipids were increased; the lipid and glycogen accumulation in the liver was high. So this diabetic syndrome can be compared to maturity onset diabetes. If this synthetic chow diet lasted more than 6 months, the most of animals lost considerable weight with a strong lipid depletion of fat stores. Serum immunoreactive insulin levels fall and the blood glucose rose over 500 mg/100 ml with glycosuria and ketonuria . The elevated triglyceride content of plasma and the lipid deposits in the liver were exaggerated; glycogen had disappeared. Animals developed an overtly insulin- dependent diabetes, the latter phase of the disease. The sand rat appears to us as a potentially interesting model for investigation both maturity onset and ketotic-type diabetic syndrome.