The correlation of cytophotometrically and biochemically measured enzyme activities: changes in the myocardium of diabetic and hypoxic diabetic rats, with and without Ginkgo biloba extract treatment

Protective effects of medicinal plant against diabetes induced cardiac disorder: A review

ETHNOPHARMACOLOGY RELEVANCE

Nowadays, there is an increase in global tendency to use medicinal plants as preventive and therapeutic agents to manage diabetes and its long-term complications such as cardiovascular disorders owing to their availability and valuable traditional background.

AIM OF STUDY

This review aims to introduce common medicinal plants, which have been demonstrated to have cardioprotective effects on diabetes and their mechanisms of action.

MATERIALS AND METHODS

Online literature databases, including Web of Sciences, PubMed, Science Direct, Scopus and Google Scholar were searched without date limitation by May 2020. The following keywords (natural products or medicinal plants or herbal medicine or herb or extract) and (diabetes or antidiabetic or hyperglycemic) and (cardiomyopathy or heart or cardioprotective or cardiac or cardio) were used, and after excluding non-relevant articles, 81 original English articles were selected.

RESULTS

The surveyed medicinal plants induced cardioprotective effects mostly through increasing antioxidant effects leading to attenuating ROS production as well as by inhibiting inflammatory signaling pathways and related cytokines. Moreover, they ameliorated the Na+/K + ATPase pump, the L-type Ca₂⁺ channel current, and the intracellular ATP. They also reduced cardiac remodeling and myocardial cell apoptosis through degradation of caspase-3, Bax, P53 protein, enhancement of Bcl-2 protein expression as well as downregulation of TGFβ1 and TNFα expression. In addition, the extracts improved cardiac function through increasing EF% and FS% as well as restoring hemodynamic parameters.

CONCLUSIONS

The reviewed medicinal plants demonstrated cardioprotective manifestations in diabetes through intervention with mechanisms involved in the diabetic heart to restore cardiovascular complications.

Effect of Low Temperature on Globin Expression, Respiratory Metabolic Enzyme Activities, and Gill Structure of Litopenaeus vannamei

Low temperature frequently influences growth, development, and even survival of aquatic animals. In the present study, physiological and molecular responses to low temperature in Litopenaeus vannamei were investigated. The cDNA sequences of two oxygen-carrying proteins, cytoglobin (Cygb) and neuroglobin (Ngb), were isolated. Protein structure analysis revealed that both proteins share a globin superfamily domain. Real-time PCR analysis indicated that Cygb and Ngb mRNA levels gradually increased during decrease in temperatures from 25 to 15°C and then decreased at 10°C in muscle, brain, stomach, and heart, except for a continuing increase in gills, whereas they showed a different expression trend in the hepatopancreas. Hemocyanin concentration gradually reduced as the temperature decreased. Moreover, the activities of respiratory metabolic enzymes including lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) were measured, and it was found that LDH activity gradually increased while SDH activity decreased after low-temperature treatment. Finally, damage to gill structure at low temperature was also observed, and this intensified with further decrease in temperature. Taken together, these results show that low temperature has an adverse influence in L. vannamei, which contributes to systematic understanding of the adaptation mechanisms of shrimp at low temperature.

The different mechanisms of hypoxic acclimatization and adaptation in Lizard Phrynocephalus vlangalii living on Qinghai-Tibet Plateau

Phrynocephalus vlangalii is a species of lizard endemic in China, which lives on Qinghai-Tibet Plateau ranging from 2000 to 4600 m above sea level. In this study, P. vlangalii were collected from low altitude (2750 m) and high altitude (4564 m). The lizards from low altitude were acclimatized in simulated hypoxic chamber (equivalent to 4600 m) for 7, 15, and 30 days. The hematological parameters, heart weight, myocardial capillary density, and myocardial enzyme activities were examined. The results showed that acclimatization to hypoxia significantly increased hemoglobin concentration ([Hb]), hematocrit (Hct), heart weight (HW), heart weight to body mass (HW/BM), lactate dehydrogenase (LDH) activity, but markedly decreased mean corpuscular hemoglobin concentration (MCHC) and succinate dehydrogenase (SDH) activity. Red blood cell (RBC) count, body mass (BM), myocardial capillary density did not change markedly during hypoxic acclimatization. On the other hand, [Hb], Hct, MCHC, HW/BM, myocardium capillary density, and SDH activity of P. vlangalii from high altitude were remarkably higher than those from low-altitude; however, LDH activity of high-altitude P. vlangalii was lower than that of low-altitude lizards. There was no significant difference in HW or BM between populations of high-altitude and low-altitude. Based on the present data, we suggest that P. vlangalii has special anatomical, physiological, and biochemical accommodate mechanisms to live in hypoxic environment, and the regulative mechanisms are different between hypoxic acclimatization and adaptation.

Losartan reduces mortality in a genetic model of heart failure

Altered Ca(2+) homoeostasis accompanies heart failure. As a model of heart failure, transgenic mice (TG) with selective overexpression of calsequestrin (CSQ) in the heart were used. CSQ is the main Ca(2+) binding protein in the lumen of the junctional sarcoplasmic reticulum. Overexpression of CSQ leads to hypertrophy, fibrosis, heart failure, cardiac arrhythmias, and ultimately premature death compared to littermate controls (WT). In the present study, cardiac hypertrophy was noted at 2 months of age (relative heart weight 6.4 +/- 0.2 mg/g in WT and 11.2 +/- 0.3 mg/g in TG, n = 7, p < 0.05) which progressed at 5 months of age (relative heart weight 15.5 +/- 1.1 mg/g in TG, n = 11). Furthermore, an increased degree of fibrosis (from 0.29 +/- 0.04 in WT to 0.77 +/- 0.06 in TG, n = 8, p < 0.05) was quantified by sirius red staining. Cardiac function was greatly impaired in TG as exemplified by reduced pressure development and cardiac arrhythmias. It is hypothesized that losartan, an inhibitor of angiotensin II receptors, might be able to attenuate these detrimental effects. Hence, TG and WT were treated for 1 or 4 months perorally with losartan (5 mg/kg/day) or solvent alone (control conditions) starting at 4 weeks of age. Under control conditions, none of the WT died within the observation period whereas all TG died within 9 months. Losartan treatment reduced the mortality of TG: Mean life span was raised from 116 to 193 days (n = 18 end, p < 0.05). Likewise, losartan reduced relative heart weight and the degree of fibrosis. In addition, losartan improved hemodynamic parameters, like left ventricular pressure and its first derivative. However, losartan treatment did not modify overexpression of CSQ in the heart of TG. These results imply that the angiotensin II receptor (type 1) contributes to heart failure due to CSQ overexpression, as its blockade improved survival.

Alterations in renal mitochondrial respiration in response to the reactive oxoaldehyde methylglyoxal

Chronic hyperglycemia has been linked to alterations in mitochondrial function, suggesting an important role in the pathophysiology of the complications of diabetes mellitus. In the diabetic kidney, ultrastructural changes in mitochondria are associated with impaired tubular function. The goal of this study was to determine if methylglyoxal (MGO), a dicarbonyl compound reaching high levels in hyperglycemic conditions, has direct toxicity for renal mitochondria. Intact mitochondria isolated from the renal cortex of rats were incubated with MGO to determine 1) its effect on mitochondrial respiration, 2) the conditions under which MGO exerts these effects, and 3) the potential mitochondrial targets of MGO influence. This study demonstrates that MGO has an inhibitory effect on both the tricarboxylic acid cycle and the electron respiratory chain. The modifications appear to be specific to certain mitochondrial proteins. Alterations of these proteins lead to disturbances in mitochondria that may play an important role in renal cellular toxicity and in the development of diabetic nephropathy.

The influence of hypoxia on the myocardium of experimentally diabetic rats with and without protection by Ginkgo biloba extract. III: Ultrastructural investigations on mitochondria

Completing our preceding ultrastructural studies on diabetes and additional acute hypoxia of rat myocardium and the protective effect of Ginkgo extract (EGb) we investigated specific ultrastructural-morphometric parameters of corresponding mitochondria. Aim of the study was to answer the question whether mitochondria of diabetic myocardium are more sensitive to hypoxia than in normal condition, and whether antioxidative protection by EGb is effective. Further we compared the ultrastructural reactions of mitochondria of different intracellular locations. Voluminal parameters of mitochondria indicated a moderate swelling after diabetes and a further slight swelling after additional hypoxia, which was slightly reduced after EGb pretreatment. Decrease of volume density of mitochondrial cristae was less expressed after diabetes and much stronger after additional hypoxia; slight protection by EGb was only visible after diabetes. Degenerative intramitochondrial areas increased significantly after diabetes and after hypoxia; EGb was protective only after additional hypoxia. The relative number of ATPase particles (F1-coupling factors) at the inner mitochondrial membranes was slightly but significantly reduced after diabetes and stronger reduced after additional hypoxia; only in the latter condition Ginkgo extract was slightly protective. The product of volume density of mitochondria x volume density of cristae x relative number of ATPase particles at the inner mitochondrial membrane (as structural equivalent of the myocardial capacity for ATP production) indicated better than single parameters the increasing mitochondrial damage after diabetes of 4 months duration and subsequent acute hypoxia of 20 min duration. After hypoxia this capacity amounted only to 46% of the normal and was improved by EGb to 53%.

The influence of hypoxia on the myocardium of experimentally diabetic rats with and without protection by Ginkgo biloba extract. I. Ultrastructural and biochemical investigations on cardiomyocytes

The influence of acute respiratoric hypoxia in streptozotocin-diabetic rats and protective effects of Ginkgo biloba extract (EGb 761)-pretreatment were investigated by the means of ultrastructural morphometry, biochemical parameters of oxidative stress and iNOS transcription and expression. Ultrastructural parameters revealed that acute hypoxia deteriorated the morphologic condition of the diabetic cardiomyocytes: volume fractions of sarcoplasm, t-tubules, mitochondria, cytoplasmic vacuoles, and degenerative intramitochondrial areas increased after hypoxia, those of myofibrils and mitochondrial cristae decreased. Since these alterations are more striking than after hypoxia of non-diabetic animals as demonstrated in preceding studies, we regard them as indicative for reduced hypoxia tolerance of the diabetic myocardium. EGb-treatment of the diabetic animals could improve the above mentioned parameters thus indicating a gradual improvement of the hypoxia tolerance. The biochemical parameters of oxidative stress (malondialdehyde, superoxide dismutase) were decreased after hypoxia in the diabetic myocardium but increased after EGb-pretreatment. The ultrastructural damage by hypoxia and its prevention by EGb should be regarded rather as a consequence of ATP--and energy deficiency and breakdown of membrane functions and--structure resp. as membrane stabilizing and enzyme-regulating effects of EGb than as radical-related events. The hypoxia-induced deprivation of creatine kinase activity of the diabetic myocardium was not prevented by EGb-treatment. Immunohistochemical demonstration of iNOS expression was strongest in the unprotected diabetic myocardium, absent after additional hypoxia and in the controls, and very weak in the protected hypoxic specimens. Transcription of iNOS as demonstrated by RT-PCR was present in few diabetic, some of the hypoxic diabetic, in most of the EGb-treated hypoxic diabetic, and in all control animals. EGb-treatment seems to improve the hypoxia tolerance of diabetic myocardium concerning ultratructural parameters. The partly conflicting immunohistochemical and biochemical results require further investigations.

Changes of enzyme activities in the myocardium and skeletal muscle fibres of cardiomyopathic hamsters. A cytophotometrical study

Cytophotometrical measurements of enzyme activities were performed in the myocardium and skeletal muscle fibres from normal and cardiomyopathic hamsters (BIO 8262) during ageing from 12-14 to 120-190 days. Myocardium as well as vastus lateralis muscles of cardiomyopathic hamsters showed changes in enzyme activities. The skeletal muscle fibres were typed into slow-oxidative, fast-oxidative glycolytic and fast-glycolytic to investigate fibre type-related changes in muscles of cardiomyopathic hamsters. The following myopathic changes were mainly found: Myofibrillic ATPase was depressed in the myocardium of both ventricles in all investigated age stages. The ATPase activity of the right ventricle was more decreased than that of the left one. Additionally, a metabolic shift was observed in myocardium and slow-oxidative muscle fibres at the onset of clinical symptoms, which appeared from day 150 to day 190. During the period from 42 up to 190 days of life an increase of oxidative (succinate dehydrogenase) activity was measured in the myocardium of both ventricles and in slow oxidative fibres of vastus lateralis muscle as a proximal muscle. At earlier ages, the fast fibres of myopathic vastus lateralis muscle showed higher glycolytic (glycerol-3-phosphate dehydrogenase) activity than those of normal muscles. However, at the age of 120-190 days the metabolic profile of fast fibres was normalized. In gastrocnemius muscle as a distal muscle no changes of enzyme activities were measured, suggesting the investigated hereditary myopathy effected proximal, but not distal muscles.

Potential role for Ginkgo biloba extract in the treatment of glaucoma

Glaucoma is becoming recognized as a condition for which not only elevated intraocular pressure, but also non-pressure-dependent risk factors are responsible. New avenues of treatment into which investigations are being initiated include agents which could possibly improve blood flow to the eye and neuroprotective drugs. Only calcium channel blockers are presently available for such treatment in glaucoma, and these have not been widely adopted, in contrast to clinical trials involving a number of neuroprotectants in other neurologic disorders. Ginkgo biloba extract is freely available and has several biological actions which combine to make it a potentially important agent in the treatment of glaucoma: improvement of central and peripheral blood flow, reduction of vasospasm, reduction of serum viscosity, antioxidant activity, platelet activating factor inhibitory activity, inhibition of apoptosis, and inhibition of excitotoxicity. The effect of Ginkgo biloba extract as a potential antiglaucoma therapy deserves intensive scrutiny.

Protective effects of Gingko biloba extract EGb 761 on myocardium of experimentally diabetic rats. I: ultrastructural and biochemical investigation on cardiomyocytes

Chronic diabetes in man and animal models develops cardiomyopathic alterations which cannot be absolutely avoided by insuline therapy. Since diabetic damage is partly attributed to oxidative stress antioxidative treatment could be able to reduce the alterations. Aim of this study was to investigate the cardioprotective effects of EGb 761, known as a radical scavenger, against diabetic alterations in rats. The diabetes was induced by i.p. injection of 60 mg/kg body weight streptozotocin. Duration of diabetes was 4 months, the protected group received 100 mg/kg body weight EGb 761 with the drinking water over 3 months. Electron and light microscopic morphometry of left-ventricular samples revealed typical diabetic alterations consisting in decrease of volume fraction of myofibrils, SR and t-tubules and diminishing of cardiomyocyte diameter, increase of interstitial volume, mitochondrial size and volume fraction, and of vacuoles and of lipid drops. EGb treatment could gradually prevent the loss of myofibrils and reduction of myocyte diameter but has only little influence on interstitial and mitochondria volume. The diabetic-induced increase of lipid and vacuoles and the decrease of SR and t-tubules were not influenced. Biochemical parameters of oxidative stress: malondialdehyde (MDA) was only insignificantly altered by diabetes and EGb. The superoxide dismutase (SOD) activity was increased by diabetes and more increased by EGb treatment. Creatine kinase (CK) activity was diminished by diabetes but slightly increased by EGb. The polymerase chain reaction (PCR) of i-NOS was not different between the diabetic and protected diabetic groups.

Effects on skeletal muscle fibres of diabetes and Ginkgo biloba extract treatment

Combined cytophotometric and morphometric analysis of muscle fibre properties and myosin heavy chain electrophoresis were performed on extensor digitorum longus and soleus muscles from healthy rats and rats with streptozotocin-induced diabetes. Moreover, the protective effect of Ginkgo biloba extract, a potent oxygen radical scavenger, on diabetic muscles was investigated. Changes in fibre type-related enzyme activities, fibre type distribution, fibre cross areas and myosin isoforms were found. In muscles of diabetic rats, a metabolic shift was measured mainly in fibres with oxidative metabolism. Fast-oxidative glycolytic fibres showed a shift to more glycolytic metabolism and about a third transformed into fast-glycolytic fibres. Slow-oxidative fibres became more oxidative. Fibre atrophy was measured in diabetic muscles dependent on fibre type and muscle. Different fibre types atrophied to a different degree. Therefore, a decreased area percentage of slow fibres and an increased area percentage of fast fibres of the whole muscle cross section in both muscles were found. This is supported by reduced slow and increased fast myosin heavy chain isoforms. These alterations of diabetic muscle fibres could be due to less motion of diabetic rats and diabetic neuropathy. After treatment with Ginkgo biloba extract, enzyme activities were increased mainly in oxidative fibres of diabetic muscles, which was interpreted as protective effect. Generally, the soleus muscle with predominant oxidative metabolism was more vulnerable to diabetic alterations and Ginkgo biloba extract treatment than the extensor digitorum longus muscle with predominant glycolytic metabolism.

Region- and age-dependent variations of muscle fibre properties

The cytophotometric-morphometrical analysis of extensor digitorum longus and soleus muscles of 2.5 and 18 months old rats revealed regional and age-dependent differences in fibre type distribution, fibre area and fibre type related-enzyme activities which characterize contractility and metabolic profile. Variations along the longitudinal axis from the origin to the insertion and along three transversal axes from superficial to deep were found dependent on the muscle investigated. For example, the fibres of extensor digitorum longus muscle showed increased contractile and glycolytic capacities near insertion and the fibres of soleus muscle increased oxidative capacity in its middle part. Furthermore, the contribution of the fibre type that is dominant in a muscle (fast-glycolytic fibre type in extensor digitorum longus and slow-oxidative fibre type in soleus muscle) to the total number of fibres increased from origin to insertion by 15 and 30%, respectively. Along the superficial-deep axes the oxidative capacity of all fibres increased, the most in fast fibres of the soleus muscle by approximately 50%. In soleus muscle, a decrease of cross areas of all fibre types from superficial to deep was found, correlating negatively with the succinate dehydrogenase activity of the fibres. In extensor digitorum longus muscle the change in cross areas of slow-oxidative and fast-oxidative glycolytic fibres was dependent on the position of the transversal axis in the muscle. The results suggest that distribution patterns of fibre types and the metabolic make up of individual muscle fibres are adapted on the basis of local functional demands. In both muscles, higher numbers and increased oxidative capacity of fast-glycolytic fibres were found during ageing, but variations from superficial to deeper regions were irrespective of age.