S-allylcysteine Improves Streptozotocin-Induced Alterations of Blood Glucose, Liver Cytochrome P450 2E1, Plasma Antioxidant System, and Adipocytes Hormones in Diabetic Rats

Garlic (Allium sativum L.) in diabetes and its complications: Recent advances in mechanisms of action

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia and impaired islet secretion that places a heavy burden on the global health care system due to its high incidence rate, long disease course and many complications. Fortunately, garlic (Allium sativum L.), a well-known medicinal plant and functional food without the toxicity and side effects of conventional drugs, has shown positive effects in the treatment of diabetes and its complications. With interdisciplinary development and in-depth exploration, we offer a clear and comprehensive summary of the research from the past ten years, focusing on the mechanisms and development processes of garlic in the treatment of diabetes and its complications, aiming to provide a new perspective for the treatment of diabetes and promote the efficient development of this field.

Nelsonia canescens (Acanthaceae) aqueous extract and partitioned fractions ameliorates type-2 diabetes in alloxan-induced diabetic rats

Background

Diabetes mellitus is a metabolic disorder that affects the body’s ability to produce or use insulin. There is a continuous rise of this disease particularly in developing countries due to changes in life style and poverty among the people. In this study, antidiabetic activities of aqueous extract of Nelsonia canescens and its partitioned fractions in alloxan-induced diabetic rats were evaluated. Male albino rats were divided into 9 groups (diabetic and non-diabetic) of 5 rats each. Diabetes was induced by single intraperitoneal administration of alloxan (90 mg/kgbwt). The experimental design consists of a diabetic control group (untreated), a normal control group (1 mL saline), a standard diabetic drug (Glibenclamide; 5 mg/kgbwt), two doses (50 and 300 mg/kgbwt) of aqueous extract, ethyl acetate and methanol fractions of Nelsonia canescens were orally administered for a period 21 days. Blood glucose of the rats was monitored at 3-days intervals while biochemical and in vivo antioxidant assays of serum and liver were determined after 21 days.

Results

The hypoglycemic effect of the extract observed was in a dose dependent manner with a significant reduction (p < 0.05) of blood glucose in ethylaceate fraction > aqueous extract > methanol fraction compared with the diabetic control group. A significant difference (p < 0.05) in lipid profiles and serum enzyme activity of rats in the diabetic control group was observed compared with the extract and fraction treated groups.

Conclusion

The results suggest that the aqueous extract and fractions of N. canescens showed hypoglycemic and hypolipidemic potentials and significantly (p < 0.05) reduced the progression of oxidative stress.

S-methyl cysteine sulfoxide mitigates histopathological damage, alleviate oxidative stress and promotes immunomodulation in diabetic rats

OBJECTIVES

S-methyl cysteine sulfoxide (SMCS) is a hydrophilic cysteine-containing natural compound found in plants and is known to possess antidiabetic and antioxidant properties. We investigated the antioxidant and immunomodulatory properties of SMCS, as well as histopathological changes in the liver and pancreas in streptozotocin (STZ)-induced diabetic rats.

METHODS

The rats were divided into the following groups: control (CG), comprising non-diabetic rats; STZ-DB, comprising STZ-induced diabetic rats; and STZ-SMCS, comprising STZ-induced diabetic rats treated with SMCS. SMCS (200 mg/kg) was administered by gavage daily for 30 days. Biochemical and cytokine analyses, catalase (CAT) and superoxide dismutase (SOD) activities assays and histopathological analysis of liver and pancreas tissues were performed.

RESULTS

SMCS treatment reduced glycemia (p<0.05), decreased triglyceride (p<0.01) and very-low-density lipoprotein (VLDL) levels (p<0.01), and increased SOD and CAT activity in the liver (both p<0.01) compared with STZ-DB group. Higher activity values of IL-10 were observed in the STZ-SMCS group than in the other groups (p<0.001). Liver glycogen was significantly improved in the STZ-SMCS group compared with the STZ-DB group. SMCS also ameliorated damage to pancreatic islets, which resulted in restoration of their morphology.

CONCLUSIONS

Oral treatment of SMCS showed improvement of the morphological alterations in liver and pancreatic islet in diabetic rats. These beneficial morphological effects of SMCS can be partially explained by IL-10 modulation associated with antioxidant action.

Flavonoids in the Treatment of Diabetes: Clinical Outcomes and Mechanism to Ameliorate Blood Glucose Levels

BACKGROUND

For thousands of years, natural food products have been used as a medicine for treating diseases that affect the human body, including diabetes mellitus (DM). Lately, several investigations have been performed on the flavonoid derivatives of plant origin, and their biological activity has been extensively studied.

METHODS

Given our need to know more mechanisms for treating DM, we performed a thorough research review on treating diabetes mellitus based on flavonoids, their therapeutic potential, and biological action.

RESULTS

Flavonoids reduce complications in addition to their vital role as effective supplements for preventing diabetes mellitus by regulating glucose metabolism, lipid profile, liver enzyme activity, a protein kinase inhibitor, PPAR, and AMPK with NF-κB.

CONCLUSION

The articles that we reviewed showed the positive role of flavonoids, which in a certain way reduce diabetes, but their side effects still need to be studied further.This review is focused on describing the different types of dietary flavonoids along with their mechanisms of reducing blood glucose and enhancing insulin sensitivity, as well as their side effects.

Streptozotocin-induced diabetes in rats: effects of White Butterfly (Clerodendrum volubile) leaves on blood glucose levels, lipid profile and antioxidant status

White Butterfly (Clerodendrum volubile) leaf is commonly used in traditional medicine for the management of various diseases including diabetes without the full understanding of the scientific basis for its use. This study sought to evaluate the antihyperglycemic, antihyperlipidemic and antioxidant effect of C. volubile leaves in streptozotocin (STZ)-induced diabetic rats. Aqueous extract of C. volubile was prepared and its effect assessed on relevant enzymes associated with diabetes. Fifty male Wistar rats were randomly separated into 10 groups each containing five rats. The induction of diabetes in rats was by a single intraperitoneal injection of STZ (65 mg/kg body weight) while C. volubile extract was administered orally to diabetic and non-diabetic animals, at the doses of 50, 100 and 200 mg/kg body weight for 14 days. Metformin (100 mg/kg body weight) served as positive control. Clerodendrum volubile extract inhibited α-glucosidase (IC₅₀ = 0.20 mg/ml) and α-amylase (IC₅₀ = 0.58 mg/ml). Furthermore, administration of C. volubile extract significantly reduced the elevated plasma glucose level and body weight, improved kidney functions, attenuated oxidative stress by decreasing MDA levels, enhancing superoxide dismutase, catalase and glutathione peroxidase activities, reinstated the lipid profile to nearly normal level and restored pancreatic histological integrity in diabetic rats. The results reveal that C. volubile represents a source of phytochemicals that exerts their antidiabetic effects through the modulation of glycemic and atherogenic indices as well as mitigation of free-radical-mediated damage.

Insulinotropic Effect of S-Allyl Cysteine in Rat Pups

S-Allyl cysteine (SAC) is found in garlic and has been reported to exert antidiabetic and antiobesity properties in drug-induced adult experimental models of metabolic dysfunction, but its potential beneficial effects in high-fructose diet neonatal rat models have not been determined. This study investigated the potential prophylactic effects of SAC in high-fructose diet fed suckling rat pups modelling human neonates fed a high-fructose diet. Four-day-old male (n=32) and female (n=32) Wistar rat pups, were randomly assigned to and administered the following treatment regimens daily for 15 days: group I, distilled water; group II, 20% fructose solution (FS); group III, SAC; group IV, SAC+FS. The pups' blood glucose, triglyceride, cholesterol, plasma leptin and insulin concentration, liver lipid content, and liver histology were determined at termination. In female rat pups, orally administered SAC prevented FS-induced hypoinsulinemia but significantly increased (P≤0.05) liver lipid content. Oral administration of SAC significantly increased (P≤0.05) plasma insulin concentration and homeostasis model assessment for insulin resistance in the male pups. The potential sexually dimorphic effects of SAC (insulinotropic effects in male pups and protection of female pups against fructose-induced hypoinsulinemia) suggest that SAC could be potentially exploited as an antidiabetic and insulinotropic agent. Caution should, however, be exercised in the use of SAC during suckling as it could result in excessive liver lipid accumulation and insulin resistance.

Effect of neonatal orally administered S-allyl cysteine in high-fructose diet fed Wistar rats

S-allyl cysteine (SAC) has antioxidant, antidiabetic and antiobesity properties. We hypothesized that neonatal oral administration of SAC would protect rats against neonatal and adulthood high-fructose diet-induced adverse metabolic outcomes in adulthood. In total, 112 (males=56; females=56), 4-day-old Wistar rat pups were randomly allocated to groups and administered the following treatment regimens daily for 15 days from postnatal day (PND) 6-20: group I - 10 ml/kg distilled water, group II - 10 ml/kg 20% fructose solution (FS), group III - 150 mg/kg SAC and group IV - SAC+FS. On PND 21, the pups were weaned and allowed to grow on a standard rat chow (SRC) until PND 56. The rats from each treatment regimen were then randomly split into two subgroups: one on a SRC and plain drinking water and another on SRC and 20% FS as drinking fluid and then subjected to these treatment regimens for 8 weeks after which they were euthanized and tissues collected for analyzes. Neonatal oral administration of SAC attenuated the neonatal high-fructose diet-induced programming for hepatic lipid accretion in adulthood but not against adulthood high-fructose diet-induced visceral obesity. Neonatal oral administration of SAC programmes for protection against neonatal fructose-induced programming for hepatic lipid accumulation thus could potentially protect against fat-mediated liver derangements in adult life.

Ameliorative Effects of Allium sativum Extract on iNOS Gene Expression and NO Production in Liver of Streptozotocin + Nicotinamide-Induced Diabetic Rats

Diabetes mellitus (DM) is one of the most prevalent diseases in the world, which is strongly associated with liver dysfunction. Hyperglycemia, through an oxidative stress pathway, damages various tissues. Herbal medicine is a good candidate to ameliorate hyperglycemia and oxidative stress. In this study, the effects of aqueous Allium sativum (garlic) extract (AGE) on gene expression of inducible nitric oxide synthases (iNOS) and production of nitric oxide (NO) were evaluated in the liver tissue of diabetic rats. Four groups of rats contained normal control rats, garlic control rats (AGE), Streptozotocin (STZ) + nicotinamide-induced diabetic rats (DM), and diabetic rats treated with garlic (DM + AGE). Glucose levels and liver enzymes activities were determined by colorimetric assay in the serum. Gene expression of iNOS by real-time PCR, NO levels by Griess method, oxidative stress parameters by spectrophotometric method and histopathological examination by hematoxylin and eosin staining method were evaluated in the liver tissues. Glucose levels, activities of liver enzymes, oxidative stress markers, iNOS gene expression, and NO production increased significantly in diabetic rats in comparison with control rats, whereas after oral administration of garlic, these parameters decreased significantly, close to the normal levels. Hence, the beneficial effects of garlic on the liver injury of diabetes could be included in the hypoglycaemic and antioxidant properties of garlic via a decrease in gene expression of iNOS and subsequent NO production.

Preparation of S-Allylcysteine-Enriched Black Garlic Juice and Its Antidiabetic Effects in Streptozotocin-Induced Insulin-Deficient Mice

S-Allylcysteine (SAC), produced in large amounts during the aging process of garlic via enzymatic hydrolysis, is known as a key compound responsible for the multiple pharmacological activities of aged black garlic. This study investigated the effects of enzyme- and high hydrostatic pressure (HHP)-assisted extraction on the content of the bioactive compounds, including SAC, in black garlic juice (BGJ) and evaluated the antidiabetic effects of SAC-enriched BGJ in streptozotocin (STZ)-treated mice. The aging process increased the contents of SAC, total polyphenols, and total flavonoids in garlic juice. More importantly, pretreatment of pectinase cocktail with HHP resulted in a greater increase in those compounds during aging. Enzyme-treated BGJ reduced hyperglycemia and improved islet architecture and β-cell function in STZ-treated mice. Moreover, these effects were more potent than those of BGJ prepared by the conventional aging process. These findings provide useful information for the production of black garlic with improved bioactivities.

Hypoglycemic activity of Gleditsia caspica extract and its saponin-containing fraction in streptozotocin-induced diabetic rats

The fruits of Gleditsia species (Fabaceae) have been known in traditional medicine as a saponin-rich herbal medicine. The present study aimed to investigate the effects of the total methanolic extract of Gleditsia caspica (MEGC) and its saponin-containing fractions (SFGC) on hyperglycemia in streptozotocin (STZ)-induced diabetic rats. A single intraperitoneal injection of STZ (55 mg/kg body weight) was used to induce hyperglycemia in male albino rats. MEGC (15, 30 and 60 mg/kg, p.o.) and SFGC (15, 30 and 60 mg/kg, p.o.) were administered to the diabetic rats daily for 14 days. The anti-diabetic drug gliclazide (10 mg/kg, p.o.) was used as a positive control. Blood samples were collected from overnight fasted rats for the evaluation of the antihyperglycemic, antihyperlipidemic and antioxidant activities. The levels of glucose, triglycerides (TG), cholesterol (TC) and malondialdehyde (MDA) were increased significantly, whereas the levels of α-amylase, insulin and reduced glutathione (GSH) were decreased in the experimental diabetic rats. Pancreas and liver of the diabetic rats exhibited significant changes in the histopathology, morphology and DNA content. Administration of MEGC or SFGC led to a decrease in the levels of glucose, TG, TC and MDA. In addition, the levels of α-amylase, insulin and GSH were increased in MEGC and SFGC treated diabetic rats. Also, the histopathological and morphological changes, as well the changes in DNA were significantly reversed by the extracts. Thus, MEGC and SFGC exhibited potent hypoglycemic and hypolipidemic activities in STZ- induced diabetic rats.

Black garlic: A critical review of its production, bioactivity, and application

Black garlic is obtained from fresh garlic (Allium sativum L.) that has been fermented for a period of time at a controlled high temperature (60-90°C) under controlled high humidity (80-90%). When compared with fresh garlic, black garlic does not release a strong offensive flavor owing to the reduced content of allicin. Enhanced bioactivity of black garlic compared with that of fresh garlic is attributed to its changes in physicochemical properties. Studies concerning the fundamental findings of black garlic, such as its production, bioactivity, and applications, have thus been conducted. Several types of black garlic products are also available in the market with a fair selling volume. In this article, we summarize the current knowledge of changes in the components, bioactivity, production, and applications of black garlic, as well as the proposed future prospects on their possible applications as a functional food product.

Beneficial Effect of Aqueous Garlic Extract on Inflammation and Oxidative Stress Status in the Kidneys of Type 1 Diabetic Rats

One of the most important complications of diabetes is nephropathy. This study investigates the effects of aqueous garlic extract on inflammation and oxidative stress status in the kidneys of diabetic rats. Male rats were divided into four groups- control rats, diabetic rats, garlic extract-treated diabetic rats, garlic extract-treated normal rats. The glucose, urea, uric acid, and creatinine levels were measured in sera using colorimetric methods. To determine the oxidative stress condition in the kidney tissues, total antioxidant capacity (TAC), malondialdehyde (MDA), and total oxidant status (TOS) were measured using colorimetric methods. Inflammation status was evaluated by the determination of tumor necrosis factor-alpha (TNF-α) gene and protein expression using qRT-PCR and ELISA respectively, while nitric oxide (NO) level in these tissues was measured using the Griess method. Histological examination of Kidneys was carried out by H&E staining. The levels of glucose, urea, and uric acid were found to increase in the serum of diabetic rats and decrease in that of diabetic rats after treatment with garlic. Measurement of MDA, TOS, and TAC revealed oxidative stress in diabetic rats, which improved after receiving the extract. The NO and TNF-α protein levels in diabetic rats were higher than those in control rats. After treatment with garlic, the levels of TNF-α protein and NO became close to the normal levels. Histological results confirmed certain other data as well. Garlic has antioxidant properties; therefore, it can reduce oxidative stress, which plays an important role in the development of diabetic nephropathy. Reduction in oxidative stress has beneficial effects on inflammation because it leads to a decrease in the level of TNF-α.

Garlic Attenuates Plasma and Kidney ACE-1 and AngII Modulations in Early Streptozotocin-Induced Diabetic Rats: Renal Clearance and Blood Pressure Implications

Raw garlic aqueous extract (GE) has ameliorative actions on the renin-angiotensin system in type-1 diabetes mellitus (DM); however its effects on plasma and kidney angiotensin I converting enzyme type-1 (ACE-1) and angiotensin II (AngII) require further elucidation. This study investigated the effect of GE on plasma and kidney ACE-1 and AngII concentrations and in relation to systemic and renal clearance indicators significant to blood pressure (BP) homeostasis in early streptozotocin- (STZ-) induced type-1 DM. Normal rats (n = 10) received 0.5 mL normal saline (NR/NS), diabetic rats (n = 10) received 0.5 mL NS (DR/NS), and treated diabetic rats (n = 10) received 50 mg/0.1 mL/100 g body weight GE (DR/GE) as daily intraperitoneal injections for 8 weeks. Compared to NR/NS, DR/NS showed a significant increase in plasma ACE-1 and AngII and conversely a decrease in kidney ACE-1 and AngII. These changes were associated with an increase in BP and clearance functions. Alternatively and compared to DR/NS, DR/GE showed normalization or attenuation in plasma and kidney ACE-1 and AngII. These GE induced rectifications were associated with moderation in BP elevation and renal clearance functions. Garlic attenuates modulations in plasma and kidney ACE-1 and AngII, in addition to BP and renal clearance function in type-1 DM.

Garlic decreases liver and kidney receptor for advanced glycation end products expression in experimental diabetes

The up-regulation of the receptor for advanced glycation end products (RAGE) has been implicated as a major mediator in the development and progression of diabetic nephropathy and hepatic fibrogenesis. The present study was designed to investigate the potential of garlic (Allium sativum L.) to modulate the level of expression of RAGE in renal and hepatic tissues of diabetic rats. Three groups of rats were studied after 8 weeks following diabetes induction: normal, streptozotocin-induced diabetic (control diabetic), and garlic-treated diabetic rats. A polyclonal antibody of proven specificity to RAGE indicated in immunohistochemical assays that RAGE labeling was significantly increased in renal and hepatic tissues of control diabetic rats compared to the normal group. The increased RAGE labeling involved mesangial cells in glomeruli exhibiting signs of mesangial expansion, mesangial nodule formation and glomerulosclerosis. In the liver, a significant up-regulation of RAGE was observed in hepatocytes and bile ducts and vessels in portal tracts. In 2-dimensional Western blots, RAGE expression in both tissues was dominated by heterogeneous charge variants, represented by 46-50kDa isoforms with more basic pIs compared to their counterparts in normal rats. Compared to control diabetic rats, RAGE labeling in the garlic-treated diabetic group was significantly reduced throughout renal and hepatic regions and was marked by the expression of 43-50kDa acidic charge variants comparable to those observed in normal rats. The capacity of garlic to modulate diabetes-induced up-regulation of selective RAGE polymorphic variants may be implicated in attenuating the detrimental consequences of excessive RAGE signaling manifested by diabetes-associated disorders.

Attenuation of erythrocyte membrane oxidative stress by Sesbania grandiflora in streptozotocin-induced diabetic rats

The aim of the present study was to investigate the protective effects of Sesbania grandiflora flower (SGF) extract on erythrocyte membrane in Streptozotocin (STZ)-induced diabetic rats. Adult male albino rats of Wistar strain, weighing 190-220 g, were made diabetic by an intraperitonial administration of STZ (45 mg/kg). Normal and diabetic rats were treated with SGF, and diabetic rats were also treated with glibenclamide as drug control, for 45 days. In this study plasma insulin and haemoglobin levels were decreased and blood glucose, glycosylated haemoglobin, protein oxidation, lipid peroxidation markers, and osmotic fragility levels were increased in diabetic rats. Moreover, erythrocytes antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxide, glutathione reductase, glutathione-S-transferase, and glucose-6-phosphate dehydrogenase activities and non-enzymatic antioxidants such as vitamin C, vitamin E, reduced glutathione (GSH), and oxidized glutathione (GSSG) levels were altered. Similarly, the activities of total ATPases, Na(+)/K(+)-ATPase, Ca(2+)-ATPase, and Mg(2+)-ATPase were also decreased in the erythrocytes of diabetic rats. Administration of SGF to STZ-induced diabetic rats reduced blood glucose and glycosylated haemoglobin levels with increased levels of insulin and haemoglobin. Moreover, SGF reversed the protein and lipid peroxidation markers, osmotic fragility, membrane-bound ATPases activities, and antioxidant status in STZ-induced diabetic rats. These results suggest that SGF could provide a protective effect on diabetes by decreasing oxidative stress-associated diabetic complications.