Oral L-glutamine increases active GLP-1 (7-36) amide secretion and improves glycemic control in stretpozotocin-nicotinamide induced diabetic rats

In Silico Screening of Therapeutic Targets as a Tool to Optimize the Development of Drugs and Nutraceuticals in the Treatment of Diabetes mellitus: A Systematic Review

The Target-Based Virtual Screening approach is widely employed in drug development, with docking or molecular dynamics techniques commonly utilized for this purpose. This systematic review (SR) aimed to identify in silico therapeutic targets for treating Diabetes mellitus (DM) and answer the question: What therapeutic targets have been used in in silico analyses for the treatment of DM? The SR was developed following the guidelines of the Preferred Reporting Items Checklist for Systematic Review and Meta-Analysis, in accordance with the protocol registered in PROSPERO (CRD42022353808). Studies that met the PECo strategy (Problem, Exposure, Context) were included using the following databases: Medline (PubMed), Web of Science, Scopus, Embase, ScienceDirect, and Virtual Health Library. A total of 20 articles were included, which not only identified therapeutic targets in silico but also conducted in vivo analyses to validate the obtained results. The therapeutic targets most frequently indicated in in silico studies were GLUT4, DPP-IV, and PPARγ. In conclusion, a diversity of targets for the treatment of DM was verified through both in silico and in vivo reassessment. This contributes to the discovery of potential new allies for the treatment of DM.

GLP-1(7-36) protected against oxidative damage and neuronal apoptosis in the hippocampal CA region after traumatic brain injury by regulating ERK5/CREB

BACKGROUND

Glucagon-like peptide-1 (GLP-1) (7-36) amide, an endogenous active form of GLP-1, has been shown to modulate oxidative stress and neuronal cell survival in various neurological diseases.

OBJECTIVE

This study investigated the potential effects of GLP-1(7-36) on oxidative stress and apoptosis in neuronal cells following traumatic brain injury (TBI) and explored the underlying mechanisms.

METHODS

Traumatic brain injury (TBI) models were established in male SD rats for in vivo experiments. The extent of cerebral oedema was assessed using wet-to-dry weight ratios following GLP-1(7-36) intervention. Neurological dysfunction and cognitive impairment were evaluated through behavioural experiments. Histopathological changes in the brain were observed using haematoxylin and eosin staining. Oxidative stress levels in hippocampal tissues were measured. TUNEL staining and Western blotting were employed to examine cell apoptosis. In vitro experiments evaluated the extent of oxidative stress and neural apoptosis following ERK5 phosphorylation activation. Immunofluorescence colocalization of p-ERK5 and NeuN was analysed using immunofluorescence cytochemistry.

RESULTS

Rats with TBI exhibited neurological deterioration, increased oxidative stress, and enhanced apoptosis, which were ameliorated by GLP-1(7-36) treatment. Notably, GLP-1(7-36) induced ERK5 phosphorylation in TBI rats. However, upon ERK5 inhibition, oxidative stress and neuronal apoptosis levels were elevated, even in the presence of GLP-1(7-36).

CONCLUSION

In summary, this study suggested that GLP-1(7-36) suppressed oxidative damage and neuronal apoptosis after TBI by activating ERK5/CREB.

Exogenous glutamine ameliorates diabetic nephropathy in a rat model of type 2 diabetes mellitus through its antioxidant and anti-inflammatory activities

This study aimed to evaluate the effects of glutamine (Gln) on diabetic nephropathy and other complications in a rat model of type 2 diabetes mellitus. Streptozotocin/nicotinamide induced diabetic rats were enrolled as an animal model of type 2 diabetes mellitus. Animals were divided into control, diabetic, and Gln (1000 mg/l in drinking water, eight weeks) treated diabetic groups. Gln alleviated renal inflammatory and oxidative stress biomarkers (tumour necrosis factor-alpha, interleukin 6, glutathione peroxidase, total superoxide dismutase, and glutathione), decreased serum uric acid and creatinine, and restored renal histopathological changes (glomerular volume, sclerosis, and leukocyte infiltration). Additionally, Gln ameliorated other complications, including systemic oxidative stress (serum malondialdehyde and nitric oxide, serum and liver glutathione, glutathione peroxidase, and total superoxide dismutase, and liver catalase), insulin resistance, hyperglycaemia, and hyperlipidaemia. Collectively, Gln attenuates diabetic nephropathy and other complications in type 2 diabetes mellitus in rats through its antioxidant and anti-inflammatory activities.

Nephroprotective Effect of Coenzyme Q10 alone and in Combination with N-acetylcysteine in Diabetic Nephropathy

Aim

Oxidative stress due to chronic hyperglycaemia is a key factor in the development and progression of various microvascular complications including diabetic nephropathy (DN) and associated renal injury. Treatment with antioxidants is one of the strategies to protect the kidney from oxidative tissue damage to improve renal physiology during DN. The investigation, therefore, was designed to assess the nephroprotective effect of coenzyme Q10 (CoQ10) and N-acetylcysteine (NAC), either alone or in combination in streptozotocin (STZ)-nicotinamide (NAD) induced diabetic nephropathy (DN) in rats.

Methods

T2DM induced by STZ (55 mg/kg, i.p.)-NAD (110 mg/kg, i.p.) in Sprague-Dawley rats (220–250 g) was confirmed by the elevated blood glucose level and glycated haemoglobin. DN was assessed by renal function tests. The diabetic rats were treated with CoQ10 (10 mg/kg, p.o.) and/or NAC (300 mg/kg, p.o.) for 8 weeks after confirmation of DN. Oxidative tissue damage due to STZ-NAD was estimated by malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT), reduced glutathione (GSH), myeloperoxidase (MPO) and nitric oxide (NO) in the renal homogenate.

Results

Data showed significant alteration in serum and urinary creatinine, total protein, albumin, serum urea, blood urea nitrogen (BUN) and uric acid in diabetic animals as compared to the control rats. CoQ10 and/or NAC effectively alleviated the disturbances in renal function. Diabetic rats showed increased MDA, decreased SOD and CAT activities and decreased GSH along with a significant increase in MPO activity and nitrite content. Treatment with the aforementioned antioxidants and their combination ameliorated the kidney damage as indicated by the reduced OS with improved renal function.

Conclusion

The investigation suggests that the chronic hyperglycaemia-induced OS leads to the development and progression of DN. The combined treatment with CoQ10 and NAC has shown a remarkable nephroprotective effect suggesting that combined antioxidant therapy with CoQ10 and NAC may be useful in the attenuation of DN.

Postprandial glycemia and insulin secretion following glutamine administration: A randomized controlled trial

Objective: The objective of the present study is to investigate the effects of glutamine administration on postprandial glycemia, insulin, and C-peptide concentration in patients with type 2 diabetes. Methods: A randomized, double-blind, placebo-controlled trial was conducted on patients with type 2 diabetes so that 33 subjects were recruited in each group. The patients were randomly allocated to receive either 30 g/d glutamine or placebo (with instructions to take in half glass of ice-cold water 5 to 10 min before each main meal) for 6 weeks. Postprandial C-peptide, insulin, and glucose were measured at the baseline and at the end of the study at 30 and 90 min after consuming a meal comprising wheat-cake and reduced fat milk. Results: The repeated measures ANOVA revealed no significant difference between the groups for glucose and insulin after 6 weeks of intervention (p > 0.05). However, C-peptide was reduced in both intervention groups at all measurement points. Between-group differences remained significant by the end of the study (p = 0.02). Conclusions: Glutamine supplementation before each main meal does not represent an effective nutritional strategy to improve postprandial glycemic control or postprandial insulin secretion in type 2 diabetes patients.

Glutamine deprivation induces metabolic adaptations associated with beta cell dysfunction and exacerbate lipotoxicity

Studies have reported that plasma glutamine is reduced in type 2 diabetes (T2D) patients. Glutamine supplementation improves glycaemic control, however the mechanisms are unclear. Here, we evaluated in vitro the pancreatic beta cell bioenergetic and insulin secretory responses to various levels of glutamine availability, or treatment in the presence of an inhibitor of intracellular glutamine metabolism. The impact of glutamine deprivation to the pathological events induced by the saturated fatty acid palmitate was also investigated. Glutamine deprivation induced a reduction in mitochondrial respiration and increase in glucose uptake and utilization. This phenotype was accompanied by impairment in beta cell function, as demonstrated by diminished insulin production and secretion, and activation of the unfolded protein response pathway. Palmitate led to insulin secretory dysfunction, loss of viability and apoptosis. Importantly, glutamine deprivation significantly exacerbated these phenotypes, suggesting that low glutamine levels could participate in the process of beta cell dysfunction in T2D.

GLP-1 mediates the modulating effect of thymoquinone on feeding behaviors in diabetic rats

Background: Thymoquinone (TQ) is a safe nutrient isolated from the seeds or volatile oil extract of Nigella sativa. In addition to its benefits in glucose regulation, TQ improves feeding disorders in diabetic animals. Glucagon-like peptide-1 (GLP-1) analogs improve glycemic control and ameliorate obesity or hyperphagia. Therefore, the present study aimed to investigate the role of GLP-1 in TQ-induced anorexia. Method: Type 2 diabetes was induced in rats by nicotinamide and streptozotocin injection. TQ was orally administered to diabetic rats at different doses for 45 days. Following TQ treatment, changes in serum glucose levels, GLP-1 concentration, body weight, food intake, and water intake were determined. To further explore the interaction between GLP-1 and TQ, the inhibitor of dipeptidyl peptidase 4, sitagliptin and the GLP-1 receptor antagonist exendin 9-39 (Ex 9-39) were separately administered to TQ- or vehicle-treated diabetic rats. Results: TQ treatment attenuated hyperglycemia and reduced hyperphagy and water intake in streptozotocin-induced diabetic rats in a dose-dependent manner. Moreover, TQ treatment elevated plasma GLP-1 levels compared to those in control rats. The effects of TQ were enhanced by treatment with sitagliptin and reduced by the injection of Ex 9-39 into the brain. In contrast, similar treatment with another antioxidant (either ascorbic acid or N-acetylcysteine) produced the same anorexic effect as TQ without changing the plasma GLP-1 levels in diabetic rats. Therefore, TQ attenuated hyperphagy while increasing plasma GLP-1 levels and had antioxidant-like effects. Conclusion: TQ increased endogenous GLP-1 levels to reduce hyperphagy in diabetic rats.

Oleoyl-lysophosphatidylinositol enhances glucagon-like peptide-1 secretion from enteroendocrine L-cells through GPR119

The gastrointestinal tract is increasingly viewed as critical in controlling glucose metabolism, because of its role in secreting multiple glucoregulatory hormones, such as glucagon like peptide-1 (GLP-1). Here we investigate the molecular pathways behind the GLP-1- and insulin-secreting capabilities of a novel GPR119 agonist, Oleoyl-lysophosphatidylinositol (Oleoyl-LPI). Oleoyl-LPI is the only LPI species able to potently stimulate the release of GLP-1 in vitro, from murine and human L-cells, and ex-vivo from murine colonic primary cell preparations. Here we show that Oleoyl-LPI mediates GLP-1 secretion through GPR119 as this activity is ablated in cells lacking GPR119 and in colonic primary cell preparation from GPR119^-/- mice. Similarly, Oleoyl-LPI-mediated insulin secretion is impaired in islets isolated from GPR119^-/- mice. On the other hand, GLP-1 secretion is not impaired in cells lacking GPR55 in vitro or in colonic primary cell preparation from GPR55^-/- mice. We therefore conclude that GPR119 is the Oleoyl-LPI receptor, upstream of ERK1/2 and cAMP/PKA/CREB pathways, where primarily ERK1/2 is required for GLP-1 secretion, while CREB activation appears dispensable.

Animal Models for the Study of the Relationships between Diet and Obesity: A Focus on Dietary Protein and Estrogen Deficiency

Obesity is an increasing major public health concern asking for dietary strategies to limit weight gain and associated comorbidities. In this review, we present animal models, particularly rats and mice, which have been extensively used by scientists to understand the consequences of diet quality on weight gain and health. Notably, modulation of dietary protein quantity and/or quality has been shown to exert huge effects on body composition homeostasis through the modulation of food intake, energy expenditure, and metabolic pathways. Interestingly, the perinatal window appears to represent a critical period during which the protein intake of the dam can impact the offspring’s weight gain and feeding behavior. Animal models are also widely used to understand the processes and mechanisms that contribute to obesity at different physiological and pathophysiological stages. An interesting example of such aspect is the situation of decreased estrogen level occurring at menopause, which is linked to weight gain and decreased energy expenditure. To study metabolic disorders associated with such situation, estrogen withdrawal in ovariectomized animal models to mimic menopause are frequently used. According to many studies, clear species-specific differences exist between rats and mice that need to be taken into account when results are extrapolated to humans.

Mangiferin attenuates DSS colitis in mice: Molecular docking and in vivo approach

Inflammation, oxidative stress and altered mucosal barrier permeability are potential etiopathological or triggering factors for inflammatory bowel disease (IBD). In this study, the therapeutic potential of Mangiferin was investigated in vivo in mouse model of colitis and also attempts were made to understand mechanistic insights of Mangiferin in IBD. In present study, colitis was induced by administration of 5% DSS for 11 days, followed by 3 days of DSS free period. On day 14, animals were sacrificed and colon tissues were taken for biochemical and histological analysis. Therapeutic treatment with Mangiferin after colitis induction (i.e. day 5) ameliorated symptoms of colitis (presence of blood in stools, body weight loss and diarrhea) as evidenced by reduced DAI score, attenuated the levels of catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO). It also decreased the colonic pro-inflammatory mediators tumor necrosis factor (TNF-α), interleukin 1β (IL-1β) levels, matrix metalloproteinase-9 (MMP-9) activity and histopathological score. Molecular docking of Mangiferin against TNF-α and MMP-9 was evaluated using GLIDE software. Mangiferin demonstrated the glide score of -8.04 kcal/mol for TNF-α and -9.97 kcal/mol for MMP-9, which indicated its binding potential with TNF-α and MMP-9. In conclusion, Mangiferin reduces colonic damage in a murine model of colitis, alleviates the oxidative and inflammatory events partly through directly influencing the activity of TNF-α and MMP-9 and therefore might have therapeutic usefulness in the management of inflammatory bowel disease.

Mechanisms for the cardiovascular effects of glucagon-like peptide-1

Over the past three decades, at least 10 hormones secreted by the enteroendocrine cells have been discovered, which directly affect the cardiovascular system through their innate receptors expressed in the heart and blood vessels or through a neural mechanism. Glucagon-like peptide-1 (GLP-1), an important incretin, is perhaps best studied of these gut-derived hormones with important cardiovascular effects. In this review, I have discussed the mechanism of GLP-1 release from the enteroendocrine L-cells and its physiological effects on the cardiovascular system. Current evidence suggests that GLP-1 has positive inotropic and chronotropic effects on the heart and may be important in preserving left ventricular structure and function by direct and indirect mechanisms. The direct effects of GLP-1 in the heart may be mediated through GLP-1R expressed in atria as well as arteries and arterioles in the left ventricle and mainly involve in the activation of multiple pro-survival kinases and enhanced energy utilization. There is also good evidence to support the involvement of a second, yet to be identified, GLP-1 receptor. Further, GLP-1(9-36)amide, which was previously thought to be the inactive metabolite of the active GLP-1(7-36)amide, may also have direct cardioprotective effects. GLP-1's action on GLP-1R expressed in the central nervous system, kidney, vasculature and the pancreas may indirectly contribute to its cardioprotective effects.

Glucagon-like peptides 1 and 2: intestinal hormones implicated in the pathophysiology of mucositis

PURPOSE OF REVIEW

Chemotherapy often causes adverse effects, including pain, bloating, diarrhea, and inflammation and ulceration of the mucous membranes lining the digestive tract, which are collectively referred to as mucositis. Unfortunately, no remedy has been found yet to manage these side-effects.

RECENT FINDINGS

The intestinal glucagon-like peptide-2 (GLP-2) is secreted from the intestinal endocrine L cells after nutrient intake, but recent findings show that the peptide concentration in the plasma also rises after intestinal injury and that GLP-2 receptor activation is crucial for intestinal healing. The antidiabetic hormone GLP-1, cosecreted with GLP-2, diminished mucositis in an animal model of the condition. Therefore, both peptides could be involved in the pathophysiology of mucositis.

SUMMARY

The intestinal GLPs have shown beneficial effects in experimental trials and have potential for therapeutic use. In type 2 diabetic and obese patients, GLP secretion is impaired. Elucidating the role of these endogenous hormones could lead to the identification of mucositis risk factors and an alternative preventive therapy for these patients.

Supplementation with L-Glutamine and L-Alanyl-L-Glutamine Changes Biochemical Parameters and Jejunum Morphophysiology in Type 1 Diabetic Wistar Rats

We evaluated the effects of the supplementation with L-glutamine and glutamine dipeptide (GDP) on biochemical and morphophysiological parameters in streptozotocin-diabetic rats. For this purpose, thirty animals were distributed into six groups treated orally (gavage) during thirty days: non diabetic rats (Control) + saline, diabetic + saline; Control + L-glutamine (248 mg/kg), Diabetic + L-glutamine (248 mg/kg), Control + GDP (400 mg/kg), Diabetic + GDP (400 mg/kg). Diabetes was induced by an intravenous injection of streptozotocin (60 mg/kg) and confirmed by fasting glucose ≥ 200 mg/dL. Physiological parameters, i.e., body mass, food intake, blood glucose, water intake, urine and faeces were evaluated during supplementation. After the period of supplementation, the animals were euthanized. The blood was collected for biochemical assays (fructosamine, transaminases, lipid profile, total protein, urea, ammonia). Moreover, the jejunum was excised and stored for morphophysiological assays (intestinal enzyme activity, intestinal wall morphology, crypt proliferative index, number of serotoninergic cells from the mucosa, and vipergic neurons from the submucosal tunica). The physiological parameters, protein metabolism and intestinal enzyme activity did not change with the supplementation with L-glutamine or GDP. In diabetic animals, transaminases and fructosamine improved with L-glutamine and GDP supplementations, while the lipid profile improved with L-glutamine. Furthermore, both forms of supplementation promoted changes in jejunal tunicas and wall morphometry of control and diabetic groups, but only L-glutamine promoted maintenance of serotoninergic cells and vipergic neurons populations. On the other hand, control animals showed changes that may indicate negative effects of L-glutamine. Thus, the supplementation with L-glutamine was more efficient for maintaining intestinal morphophysiology and the supplementation with GDP was more efficient to the organism as a whole. Thus, we can conclude that local differences in absorption and metabolism could explain the differences between the supplementation with L-glutamine or GDP.

Thymoquinone modulates nitric oxide production and improves organ dysfunction of sepsis

AIMS

The present investigation was designed to evaluate the effect of thymoquinone in a septic animal model and to explore the role of nitric oxide (NO) in the process.

MAIN METHODS

To achieve this, mice (n=12 per group) were treated in parallel with thymoquinone (0.75mg/kg/day) and/or NG-nitro-l-arginine methyl ester (L-NAME; 400μg/g/day) prior to sepsis induction with live Escherichia coli.

KEY FINDINGS

Thymoquinone significantly improved renal and hepatic functions alone and in combination with L-NAME. This was associated with less NO production and lower oxidative stress in treated animals. Tumor necrosis factor-α concentration with thymoquinone and L-NAME were 36.27±3.41pg/ml and 56.55±5.85pg/ml, respectively, as opposed to 141.11±6.46pg/ml in septic controls. Similarly, Interleukin-1α, 2, 6 and 10 levels decreased significantly upon treatment with thymoquinone and L-NAME as compared with untreated septic animals. NF-κB and NF-κB-DNA binding activity in nuclear proteins were also significantly down-regulated. Vascular responsiveness studies in isolated mouse aortae demonstrated a reduced relaxation to acetylcholine exposure in septic mice treated with thymoquinone.

SIGNIFICANCE

These findings suggest that thymoquinone prevents sequels of the multiple organ failure syndrome of sepsis by modulating the production of NO and its inflammatory sequela, and adjusting vascular responsiveness.

Cardioprotective Activity of Pongamia pinnata in Streptozotocin-Nicotinamide Induced Diabetic Rats

Pongamia pinnata (L.) Pierre has been used in traditional medicine for the treatment for diabetes and metabolic disorder. The aim of this study was to investigate the effect of petroleum ether extract of the stem bark of P. pinnata (known as PPSB-PEE) on cardiomyopathy in diabetic rats. Diabetes was induced in overnight fasted Sprague-Dawley rats by using injection of streptozotocin (55 mg/kg, i.p.). Nicotinamide (100 mg/kg, i.p.) was administered 20 min before administration of streptozotocin. Rats were divided into group I: nondiabetic, group II: diabetic control (tween 80, 2%; 10 mL/kg, p.o.) as vehicle, and group III: PPSB-PEE (100 mg/kg, p.o.). The blood glucose level, ECG, hemodynamic parameters, cardiotoxic and antioxidant biomarkers, and histology of heart were carried out after 4 months after STZ with nicotinamide injection. PPSB-PEE treatment improved the electrocardiographic, hemodynamic changes; LV contractile function; biological markers; oxidative stress parameters; and histological changes in STZ induced diabetic rats. PPSB-PEE (100 mg/kg, p.o.) decreased blood glucose level, improved electrocardiographic parameters (QRS, QT, and QTc intervals) and hemodynamic parameters (SBP, DBP, EDP, max dP/dt, contractility index, and heart rate), controlled levels of cardiac biomarkers (CK-MB, LDH, and AST), and improved oxidative stress (SOD, MDA, and GSH) in diabetic rats. PPSB-PEE is a promising remedy against cardiomyopathy in diabetic rats.

L-glutamine supplementation prevents the development of experimental diabetic cardiomyopathy in streptozotocin-nicotinamide induced diabetic rats

The objective of the present investigation was to evaluate the effect of L-glutamine on cardiac myopathy in streptozotocin-nicotinamide induced diabetic rats. Diabetes was induced in overnight fasted Sprague Dawely rats by using intraperitonial injection of streptozotocin (55 mg/kg). Nicotinamide (100 mg/kg, i.p.) was administered 20 min before administration of streptozotocin. Experimental rats were divided into Group I: non-diabetic control (distilled water; 10 ml/kg, p.o.), II: diabetic control (distilled water, 10 ml/kg, p.o.), III: L-glutamine (500 mg/kg, p.o.) and IV: L-glutamine (1000 mg/kg, p.o.). All groups were diabetic except group I. The plasma glucose level, body weight, electrocardiographic abnormalities, hemodynamic changes and left ventricular contractile function, biological markers of cardiotoxicity, antioxidant markers were determined after 4 months after STZ with nicotinamide injection. Histopathological changes of heart tissue were carried out by using H and E stain. L-glutamine treatment improved the electrocardiographic, hemodynamic changes; LV contractile function; biological markers; oxidative stress parameters and histological changes in STZ induced diabetic rats. Results from the present investigation demonstrated that L-glutamine has seemed a cardioprotective activity.

Oral L-arginine stimulates GLP-1 secretion to improve glucose tolerance in male mice

Pharmacological and surgical interventions that increase glucagon-like peptide 1 (GLP-1) action are effective to improve glucose homeostasis in type 2 diabetes mellitus. In light of this, nutritional strategies to enhance postprandial GLP-1 secretion, particularly in the context of diet-induced obesity, may provide an alternative therapeutic approach. Importantly, recent evidence suggests the amino acid L-arginine, a well-known insulin secretagogue, can also stimulate release of GLP-1 from isolated rat intestine. Here we tested the hypothesis that oral L-arginine acts as a GLP-1 secretagogue in vivo, to augment postprandial insulin secretion and improve glucose tolerance. To test this, we administered L-arginine or vehicle by oral gavage, immediately prior to an oral glucose tolerance test in lean and diet-induced obese mice. In both lean and obese mice oral L-arginine increased plasma GLP-1 and insulin and substantially improved glucose clearance. To directly assess the contribution of GLP-1 receptor (GLP-1R)-signaling to these improvements, L-arginine was given to Glp1r knockout mice and their wild-type littermates. In this experiment oral l-arginine significantly augmented insulin secretion and improved glucose clearance in WT mice, but not in Glp1r knockout littermates. Taken together these findings identify L-arginine as a GLP-1 secretagogue in vivo and demonstrate that improvement of glucose tolerance by oral L-arginine depends on GLP-1R-signaling. These findings raise the intriguing possibility that L-arginine-based nutritional and/or pharmaceutical therapies may benefit glucose tolerance by improving the postprandial GLP-1 response in obese individuals.

Effect of concomitant administration of L-glutamine and cycloart-23-ene-3β, 25-diol (B2) with sitagliptin in GLP-1 (7-36) amide secretion, biochemical and oxidative stress in streptozotocin - nicotinamide induced diabetic Sprague Dawley rats

Previously we have reported that, cycloart-23-ene-3β, 25-diol (called as B2) and L-glutamine stimulated glucagon like peptide-1 (GLP-1) (7–36) amide secretion diabetic rats. The objective of present investigation was to investigate the concomitant administration of cycloart-23-ene-3β, 25-diol+sitagliptin and L-glutamine+sitagliptin in streptozotocin - nicotinamide induced diabetic Sprague Dawley. Type 2 diabetes was induced in overnight fasted male Sprague Dawley rats pre-treated with nicotinamide (100 mg/kg, i.p.) followed by administration of streptozotocin (55 mg/kg, i.p.) 20 min after. The rats were divided into; I- non-diabetic, II- diabetic control, III- Sitagliptin (5 mg/kg, p.o.)+cycloart-23-ene-3β, 25-diol (1 mg/kg, p.o.), IV- Sitagliptin (5 mg/kg, p.o.)+L-glutamine (1000 mg/kg, p.o.). The concomitant treatment of cycloart-23-ene-3β, 25-diol and L-glutamine with sitagliptin was 8 weeks. Plasma glucose, body weight, food and water intake were determined every week. Glycosylated haemoglobin, lipid profile, plasma and colonic active (GLP-1) (7–36) amide, plasma and pancreatic insulin, histology of pancreata and biomarkers of oxidative stress were measured after 8^th week treatment. Concomitant administration of cycloart-23-ene-3β, 25-diol and L-glutamine with sitagliptin significantly (p<0.001) reduced plasma glucose, glyoxylated haemoglobin, lipid profile and oxidative stress parameters compared to diabetic control groups. Both concomitant treatment increased plasma and pancreatic insulin as well as plasma and colonic active (GLP-1) (7–36) amide secretion. Histological analysis by Gomori staining observed less destruction of pancreatic β cells. The result obtained from this study; it is concluded that concomitant administration of cycloart-23-ene-3β, 25-diol+sitagliptin and L-glutamine+sitagliptin showed additive antihyperglycaemic effect in diabetic rats.