Zarzio Ameliorates Non-alcoholic Fatty Liver Induced By a High Fat Diet in a Rat Experimental Model: A Histological and Immunohistochemical Study

SUMMARY: The therapeutic effect of a granulocyte-colony stimulating factor (G-CSF) biosimilar drug, zarzio, on non-alcoholic fatty liver disease (NAFLD) in a rat model was investigated in this study. Thirty-two rats were randomly divided into four groups. Groups I and II were fed a standard laboratory diet, whereas groups III and IV were fed a high fat diet (HFD) for 14 weeks. After 12 weeks of feeding, groups I and III were administered normal saline, and groups II and IV were intraperitoneally administered zarzio (200 mg/kg/day) for two consecutive weeks. Hematoxylin-eosin (H&E) staining was used to assess hepatic and pancreatic morphology in all groups, oil red O (ORO) staining for lipid accumulation, Masson's staining for fibrosis, and immunohistochemistry assay for hepatic protein expression of insulin receptor substrate 1 (IRS1), nuclear factor erythroid 2-related factor 2 (Nrf2), tumour necrosis factor alpha (TNF-α) and pancreatic caspase-3. The NAFLD rats (group III) developed hepatic steatosis with increased lipid accumulation, perisinusoidal fibrosis, upregulated IRS1, TNF-α (all P<0.05) without a significant increase in Nrf2 protein expression compared with normal control. In comparison, model rats treated with zarzio (group IV) showed significant rejuvenation of the hepatic architecture, reduction of fat accumulation, and fibrosis. This was accompanied by the upregulation of Nrf2, downregulation of IRS1 and TNF-α protein expression (all P<0.05). No correlation was detected between NAFLD and non-alcoholic fatty pancreas disease (NAFPD). However, the pancreatic β-cells in group III showed increased caspase-3 expression, which was decreased (P<0.05) in group IV. In conclusion, zarzio ameliorates NAFLD by improving the antioxidant capacity of liver cells, reducing hepatic IRS1, TNF-α protein expression and pancreatic β-cells apoptosis, suggesting that zarzio could be used as a potential therapy for NAFLD.

En este estudio se investigó el efecto terapéutico de un fármaco biosimilar del factor estimulante de colonias de granulocitos (G-CSF), zarzio, sobre la enfermedaddel hígado graso no alcohólico (NAFLD) en un modelo de rata. Treinta y dos ratas se dividieron aleatoriamente en cuatro grupos. Los grupos I y II fueron alimentados con una dieta estándar de laboratorio, mientras que los grupos III y IV fueron alimentados con una dieta alta en grasas (HFD) durante 14 semanas. Después de 12 semanas de alimentación, a los grupos I y III se les administró solución salina normal, y a los grupos II y IV se les administró zarzio por vía intraperitoneal (200 mg/kg/ día) durante dos semanas consecutivas. Se utilizó tinción de hematoxilina-eosina (H&E) para evaluar la morfología hepática y pancreática en todos los grupos, tinción con rojo aceite O (ORO) para la acumulación de lípidos, tinción de Masson para la fibrosis y ensayo de inmunohistoquímica para la expresión de la proteína hepática del sustrato 1 del receptor de insulina (IRS1), factor nuclear eritroide 2 relacionado con el factor 2 (Nrf2), factor de necrosis tumoral alfa (TNF-α) y caspasa-3 pancreática. Las ratas NAFLD (grupo III) desarrollaron esteatosis hepática con aumento de la acumulación de lípidos, fibrosis perisinusoidal, IRS1 y TNF-α regulados positivamente (todos P <0,05) sin un aumento significativo en la expresión de la proteína Nrf2 en comparación con el control normal. En comparación, las ratas modelo tratadas con zarzio (grupo IV) mostraron un rejuvenecimiento significativo de la arquitectura hepática, una reducción de la acumulación de grasa y fibrosis. Esto estuvo acompañado por la regulación positiva de Nrf2, la regulación negativa de la expresión de la proteína IRS1 y TNF-α (todas P <0,05). No se detectó correlación entre NAFLD y la enfermedad del páncreas graso no alcohólico (NAFPD). Sin embargo, las células β pancreáticas en el grupo III mostraron una mayor expresión de caspasa-3, que disminuyó (P <0,05) en el grupo IV. En conclusión, zarzio mejora la NAFLD al mejorar la capacidad antioxidante de las células hepáticas, reduciendo el IRS1 hepático, la expresión de la proteína TNF-α y la apoptosis de las células β pancreáticas, lo que sugiere que zarzio podría usarse como una terapia potencial para la NAFLD.

Palmitic acid-induced lipotoxicity promotes a novel interplay between Akt-mTOR, IRS-1, and FFAR1 signaling in pancreatic ß-cells

BACKGROUND: Free fatty acid receptor 1 (FFAR1) is G-protein coupled receptor predominantly expressed in pancreatic ß-cells that is activated by a variety of free fatty acids (FFAs). Once activated, it promotes glucose-stimulated insulin secretion (GSIS). However, increased levels of FFAs lead to lipotoxicity, inducing loss of ß-cell function. FFAR1 plays a key role in the development of type 2 diabetes (T2D), and previous studies have indicated the importance of developing anti-diabetic therapies against FFAR1, although its role in the regulation of ß-cell function remains unclear. The present study investigated the role of FFAR1 under lipotoxic conditions using palmitic acid (PA). The rat insulinoma 1 clone 832/13 (INS-1 832/13) cell line was used as a model as it physiologically resembles native pancreatic ß-cells. Key players of the insulin signaling pathway, such as mTOR, Akt, IRS-1, and the insulin receptor (INSR1ß), were selected as candidates to be analyzed under lipotoxic conditions. RESULTS: We revealed that PA-induced lipotoxicity affected GSIS in INS-1 cells and negatively modulated the activity of both IRS-1 and Akt. Reduced phosphorylation of both IRS-1 S636/639 and Akt S473 was observed, in addition to decreased expression of both INSR1ß and FFAR1. Moreover, transient knockdown of FFAR1 led to a reduction in IRS-1 mRNA expression and an increase in INSR1ß; mRNA. Finally, PA affected localization of FFAR1 from the cytoplasm to the perinucleus. CONCLUSIONS: In conclusion, our study suggests a novel regulatory involvement of FFAR1 in crosstalk with mTOR-Akt and IRS-1 signaling in ß-cells under lipotoxic conditions.

Effect of wheatgrass on DNA damage, oxidative stress index and histological findings in diabetic rats / Efecto del pasto de trigo sobre el daño del ADN, el índice de estrés oxidativo y los hallazgos histológicos en ratas diabéticas

This study was aimed to search the effect of wheatgrass on the Total Antioxidan (TAS)-Oxidan Status (TOS) and DNA damage in rat with diabetes. The rats used in the study were randomly divided into 4 groups that each of has 10 rats: Control group; 1 ml single dose phosphate-citrate buffer injected i.p (pH: 4.5), Diabetes group; 45 mg/kg single dose streptozotocin injected i.p., Wheatgrass group; was given oral wheatgrass (10 ml/kg/day) for 6 weeks, Diabetes +Wheatgrass group; 45 mg/kg single dose streptozotocin injected i.p. and wheatgrass (10 ml/kg/day) was given by oral during 6 weeks. After the process of experiment during 6 weeks, blood sample and pancreas tissue were taken. The analysis were done of blood glucose levels, TAS, TOS levels by colorimetric kits; DNA damage by ELISA kits in serum. The pancreas tissues were examined histopathologically. In the group of Diabetes+Wheatgrass was determined that the levels of glucose levels (p<0.001), TOS (p<0.05) and OSI (p<0.01) statistically decreased and heal histopatolojical compared to diabetes group. In the group of Wheatgrass was determined that the levels of TAS p<0.05 statistically increased from other groups. The statistical significance were not found in the level of serum 8OHdG differences between the groups. The beta cells were seen to increase in the group receiving wheatgrass for therapeutic purposes.As a conclusion, it was determined that wheatgrass strengthened the anti-oxidant defense system and reduced the glucose level in diabetic rats.

El objetivo de este estudio fue buscar el efecto del pasto de trigo sobre el estado total de antioxidantes (TAS) -Oxidan Status (TOS) y el daño del ADN en ratas con diabetes. Las ratas analizadas en el estudio se dividieron aleatoriamente en 4 grupos de 10 ejemplares cada uno: grupo control; 1 ml de tampón fosfato-citrato de dosis única inyectado i.p. (pH: 4,5)., Grupo diabetes; 45 mg / kg de estreptozotocina en dosis única inyectada i.p., grupo pasto de trigo; se administró pasto de trigo oral (10 ml / kg / día) durante 6 semanas, grupo diabetes + pasto de trigo; 45 mg / kg de estreptozotocina en dosis única inyectada i.p. y pasto de trigo (10 ml / kg / día) por vía oral durante 6 semanas. Después del proceso experimental durante 6 semanas, se tomaron muestras de sangre y tejido de páncreas. Se midieron los niveles de glucosa en sangre, TAS, y TOS mediante kits colorimétricos; El daño al ADN fue realizado por kits de ELISA en suero. Los tejidos del páncreas se examinaron histopatológicamente. En el grupo de diabetes + pasto de trigo se determinó que los niveles de glucosa (p <0,001), TOS (p <0,05) y OSI (p <0,01) disminuyeron estadísticamente y curaron histopatológicamente en comparación con el grupo de diabetes. En el grupo de pasto de trigo se determinó que los niveles de TAS p <0,05 se incrementaron estadísticamente con respecto a otros grupos. No fue estadísticamente significativo el nivel de las diferencias séricas de 8OHdG entre los grupos. Se observó que las células beta aumentaron en el grupo que recibió pasto de trigo con fines terapéuticos. Como conclusión, se determinó que el pasto de trigo fortaleció el sistema de defensa antioxidante y redujo el nivel de glucosa en las ratas diabéticas.

Antidiabetic activity of a triterpenoid saponin isolated from Momordica cymbalaria Fenzl.

Glucose uptake by isolated diaphragms of both diabetic, following streptozotocin administration, and non-diabetic animals increased in presence of an oleanane-type triterpenoid saponin isolated from the roots of M. cymbalaria. Insulin release was augmented by the presence of the saponin of M. cymbalaria (1 mg/mL) in rat insulinoma cell line (RIN-5F) pre-exposed to adrenaline (5 µM) and nifedipine (50 µM). Pancreatic histology also indicated considerable quantitative increase in β-cells (75%) when treated with the saponin. The results suggest that the saponin of M. cymbalaria possesses potential antidiabetic activity with respect to insulin secretion, which may be attributed to modulation of calcium channel, and β-cell rejuvenation.

Signaling mechanisms of glucose-induced F-actin remodeling in pancreatic islet beta cells

The maintenance of whole-body glucose homeostasis is critical for survival, and is controlled by the coordination of multiple organs and endocrine systems. Pancreatic islet beta cells secrete insulin in response to nutrient stimuli, and insulin then travels through the circulation promoting glucose uptake into insulin-responsive tissues such as liver, skeletal muscle and adipose. Many of the genes identified in human genome-wide association studies of diabetic individuals are directly associated with beta cell survival and function, giving credence to the idea that beta-cell dysfunction is central to the development of type 2 diabetes. As such, investigations into the mechanisms by which beta cells sense glucose and secrete insulin in a regulated manner are a major focus of current diabetes research. In particular, recent discoveries of the detailed role and requirements for reorganization/remodeling of filamentous actin (F-actin) in the regulation of insulin release from the beta cell have appeared at the forefront of islet function research, having lapsed in prior years due to technical limitations. Recent advances in live-cell imaging and specialized reagents have revealed localized F-actin remodeling to be a requisite for the normal biphasic pattern of nutrient-stimulated insulin secretion. This review will provide an historical look at the emergent focus on the role of the actin cytoskeleton and its regulation of insulin secretion, leading up to the cutting-edge research in progress in the field today.

Effect of the combination of metformin and fenofibrate on glucose homeostasis in diabetic Goto-Kakizaki rats

Metformin has been reported to increase the expression of the glucagon-like peptide-1 (GLP-1) receptor in pancreatic beta cells in a peroxisome proliferator-activated receptor (PPAR)-alpha-dependent manner. We investigated whether a PPARalpha agonist, fenofibrate, exhibits an additive or synergistic effect on glucose metabolism, independent of its lipid-lowering effect, when added to metformin. Non-obese diabetic Goto-Kakizaki (GK) rats were divided into four groups and treated for 28 days with metformin, fenofibrate, metformin plus fenofibrate or vehicle. The random blood glucose levels, body weights, food intake and serum lipid profiles were not significantly different among the groups. After 4 weeks, metformin, but not fenofibrate, markedly reduced the blood glucose levels during oral glucose tolerance tests, and this effect was attenuated by adding fenofibrate. Metformin increased the expression of the GLP-1 receptor in pancreatic islets, whereas fenofibrate did not. During the intraperitoneal glucose tolerance tests with the injection of a GLP-1 analog, metformin and/or fenofibrate did not alter the insulin secretory responses. In conclusion, fenofibrate did not confer any beneficial effect on glucose homeostasis but reduced metformin's glucose-lowering activity in GK rats, thus discouraging the addition of fenofibrate to metformin to improve glycemic control.

The efficacy of SPA0355 in protecting beta cells in isolated pancreatic islets and in a murine experimental model of type 1 diabetes

Cytokines activate several inflammatory signals that mediate beta-cell destruction. We recently determined that SPA0355 is a strong anti-inflammatory compound, thus reporting its efficacy in protecting beta cells from various insults. The effects of SPA0355 on beta-cell survival were studied in RINm5F cells and primary islets. The protective effects of this compound on the development of type 1 diabetes were evaluated in non-obese diabetic (NOD) mice. SPA0355 completely prevented cytokine-induced nitric oxide synthase (iNOS) expression and cytotoxicity in RINm5F cells and isolated islets. The molecular mechanism of SPA0355 inhibition of iNOS expression involves the inhibition of nuclear factor kappaB and Janus kinase signal transducer and activator of transcription pathways. The protective effects of SPA0355 against cytokine toxicity were further demonstrated by normal insulin secretion and absence of apoptosis of cytokine-treated islets. In experiments with NOD mice, the occurrence of diabetes was efficiently reduced when the mice were treated with SPA0355. Therefore, SPA0355 might be a valuable treatment option that delays the destruction of pancreatic beta cells in type 1 diabetes.

Reduced Food Intake is the Major Contributor to the Protective Effect of Rimonabant on Islet in Established Obesity-Associated Type 2 Diabetes

PURPOSE: Although the presence of cannabinoid type 1 (CB1) receptor in islets has been reported, the major contributor to the protective effect of rimonabant on islet morphology is unknown. We determined whether the protective effect of rimonabant on pancreatic islet morphology is valid in established diabetes and also whether any effect was independent of decreased food intake. MATERIALS AND METHODS: After diabetes was confirmed, Otsuka Long-Evans Tokushima Fatty rats, aged 32 weeks, were treated with rimonabant (30 mg/kg/d, rimonabant group) for 6 weeks. Metabolic profiles and islet morphology of rats treated with rimonabant were compared with those of controls without treatment (control group), a pair-fed control group, and rats treated with rosiglitazone (4 mg/kg/d, rosiglitazone group). RESULTS: Compared to the control group, rats treated with rimonabant exhibited reduced glycated albumin levels (p<0.001), islet fibrosis (p<0.01), and improved glucose tolerance (p<0.05), with no differences from the pair-fed control group. The retroperitoneal adipose tissue mass was lower in the rimonabant group than those of the pair-fed control and rosiglitazone groups (p<0.05). Rimonabant, pair-fed control, and rosiglitazone groups showed decreased insulin resistance and increased adiponectin, with no differences between the rimonabant and pair-fed control groups. CONCLUSION: Rimonabant had a protective effect on islet morphology in vivo even in established diabetes. However, the protective effect was also reproduced by pair-feeding. Thus, the results of this study did not support the significance of islet CB1 receptors in islet protection with rimonabant in established obesity-associated type 2 diabetes.

B-cell translocation gene 2 positively regulates GLP-1-stimulated insulin secretion via induction of PDX-1 in pancreatic beta-cells

Glucagon-like peptide-1 (GLP-1) is a potent glucoincretin hormone and an important agent for the treatment of type 2 diabetes. Here we demonstrate that B-cell translocation gene 2 (BTG2) is a crucial regulator in GLP-1-induced insulin gene expression and insulin secretion via upregulation of pancreatic duodenal homeobox-1 (PDX-1) in pancreatic beta-cells. GLP-1 treatment significantly increased BTG2, PDX-1 and insulin gene expression in pancreatic beta-cells. Notably, adenovirus-mediated overexpression of BTG2 significantly elevated insulin secretion, as well as insulin and PDX-1 gene expression. Physical interaction studies showed that BTG2 is associated with increased PDX-1 occupancy on the insulin gene promoter via a direct interaction with PDX-1. Exendin-4 (Ex-4), a GLP-1 agonist, and GLP-1 in pancreatic beta-cells increased insulin secretion through the BTG2-PDX-1-insulin pathway, which was blocked by endogenous BTG2 knockdown using a BTG2 small interfering RNA knockdown system. Finally, we revealed that Ex-4 and GLP-1 significantly elevated insulin secretion via upregulation of the BTG2-PDX-1 axis in pancreatic islets, and this phenomenon was abolished by endogenous BTG2 knockdown. Collectively, our current study provides a novel molecular mechanism by which GLP-1 positively regulates insulin gene expression via BTG2, suggesting that BTG2 has a key function in insulin secretion in pancreatic beta-cells.

[Metformin effect on the mouse pancreatic langerhans islets volume]

Metformin is a widely used medicine for treatment of type 2 diabetes. In this study, the effect of various doses of metformin on the mouse islets of langerhans volume was investigated. Twenty four C57BL/6 adult male mice weighting 30 +/- 5 gr were randomly divided into 4 groups. Normal saline was given to the control group [group 4] and the experimental groups [groups 1-3] received 75, 150 and 300 mg/kg metformin daily by intraperitoneal injection for seven days. One day after the last injection the mice were sacrificed by cervical dislocation and their pancreases were fixed in 10% formalin for histological studies. The volume of the islets of langerhans was estimated by using Cavalieri method. Volume of the islets of langerhans in doses of 75 and 150 mg/kg Metformin showed a nonsignificant difference in comparison to control group [P>0.05]. 300 mg/kg metformin treated mice showed a significant increase in islets of langerhans volume compared to the control group [P<0.05]. Metformin increases in the islets of langerhans volume in a dose-dependent manner. Increasing effects of Metformin on the islets of langerhans volume may be due to proliferation or hypertrophy of beta cells

[Effect of metformin on the Pdx-1 gene expression during development of mouse pancreas]

Metformin, an oral medicine used to treat type 2 diabetes, is a Glucagon-Like Peptide-1 [GLP-1] analogue, which has been demonstrated to stimulate the expression of Pancreatic duodenal homeobox-1 [Pdx-1], Insulin and Glucose transporter 2 [Glut-2] genes. In this study, the regulatory effect of metformin on beta cells function through the expression of Pdx-1, Insulin and Glut-2 genes was investigated. Pregnant C57BL/6 mice were randomly divided into 2 groups. Normal saline was given to the control group and the experimental group received 75, 150 and 250 mg/kg metformin daily by intraperitoneal injection from day 8.5 of pregnancy. Half the pregnant animals were then sacrificed by cervical dislocation or day 19.5 of pregnancy and the pancreases of embryos were dissected. The other half of pregnant animals were allowed to deliver their pups and the pancreases of one day old mice were dissected. The dissected pancreases were then used for assessment of Pdx-1, Insulin and Glut-2 genes expression by semi-quantitative RT-PCR method. Results showed that the administration of various doses of metformin caused no changes in the expression of Pdx-1, Insulin and Glut-2 genes compared to the control group [P>0.05]. The regulatory effect of metformin on beta cells function might not be related to the expression of Pdx-1, Insulin and Glut-2 genes and may be related to the expression of gloconeogenesis pathway genes

The Effect of Early Insulin Therapy on Pancreatic beta-Cell Function and Long-Term Glycemic Control in Newly Diagnosed Type 2 Diabetic Patients

BACKGROUND/AIMS: Based on the results of well designed clinical studies, intensive insulin therapy has been established to improve glycemic control in newly diagnosed diabetes. However, discrepancies exist between the findings of clinical trials and experiences in general practice. Furthermore, the efficacy of an early insulin therapy (EIT) - commonly used in general practice - on long-term glycemic control has not been established. Therefore, we evaluated the effects of EIT on pancreatic beta-cell function and glycemic control using insulin-based methods widely employed in general practice. METHODS: We performed a retrospective cohort study that initially involved reviewing patients' medical records. Following a thorough review, 61 patients who received either biphasic or prandial EIT at the time of diagnosis were enrolled. We then evaluated changes in beta-cell function and glycemic control during a 48-month follow-up period. RESULTS: Mean HbA1c decreased significantly as a result of EIT from 10.7 +/- 1.8% to 6.2 +/- 1.1% (p < 0.001). On average, 2.6 months was required to achieve an HbA1c value < 7%. EIT significantly improved the insulinogenic index. Glycemic control was well maintained for 48 months. More than 70% of patients were able to maintain glycemic control following lifestyle modifications or treatment with oral antidiabetic drugs. No significant differences were identified between patients receiving biphasic EIT and prandial EIT in terms of glycemic control or pancreatic beta-cell function. CONCLUSIONS: Our results suggest that regardless of the method of delivery, EIT significantly improves beta-cell function and facilitates long-term glycemic control in patients with newly diagnosed type 2 diabetes mellitus.

Sulfuretin protects against cytokine-induced beta-cell damage and prevents streptozotocin-induced diabetes

NF-kappaB activation has been implicated as a key signaling mechanism for pancreatic beta-cell damage. Sulfuretin is one of the main flavonoids produced by Rhus verniciflua, which is reported to inhibit the inflammatory response by suppressing the NF-kappaB pathway. Therefore, we isolated sulfuretin from Rhus verniciflua and evaluated if sulfuretin could inhibit cytokine- or streptozotocin-induced beta-cell damage. Rat insulinoma RINm5F cells and isolated rat islets were treated with IL-1beta and IFN-gamma to induce cytotoxicity. Incubation of cells and islets with sulfuretin resulted in a significant reduction of cytokine-induced NF-kappaB activation and its downstream events, iNOS expression, and nitric oxide production. The cytotoxic effects of cytokines were completely abolished when cells or islets were pretreated with sulfuretin. The protective effect of sulfuretin was further demonstrated by normal insulin secretion of cytokine-treated islets in response to glucose. Treatment of mice with streptozotocin resulted in hyperglycemia and hypoinsulinemia, which was further evidenced by immunohistochemical staining of islets. However, the diabetogenic effects of streptozotocin were completely prevented when mice were pretreated with sulfuretin. The anti-diabetogenic effects of sulfuretin were also mediated by suppression of NF-kappaB activation. Collectively, these results indicate that sulfuretin may have therapeutic value in preventing beta-cell damage.

Exendin-4 Protects Oxidative Stress-Induced beta-Cell Apoptosis through Reduced JNK and GSK3beta Activity

Oxidative stress induced by chronic hyperglycemia in type 2 diabetes plays a crucial role in progressive loss of beta-cell mass through beta-cell apoptosis. Glucagon like peptide-1 (GLP-1) has effects on preservation of beta-cell mass and its insulin secretory function. GLP-1 possibly increases islet cell mass through stimulated proliferation from beta-cell and differentiation to beta-cell from progenitor cells. Also, it probably has an antiapoptotic effect on beta-cell, but detailed mechanisms are not proven. Therefore, we examined the protective mechanism of GLP-1 in beta-cell after induction of oxidative stress. The cell apoptosis decreased to ~50% when cells were treated with 100 microM H2O2 for up to 2 hr. After pretreatment of Ex-4, GLP-1 receptor agonist, flow cytometric analysis shows 41.7% reduction of beta-cell apoptosis. This data suggested that pretreatment of Ex-4 protect from oxidative stress-induced apoptosis. Also, Ex-4 treatment decreased GSK3beta activation, JNK phosphorylation and caspase-9, -3 activation and recovered the expression of insulin2 mRNA in beta-cell lines and secretion of insulin in human islet. These results suggest that Ex-4 may protect beta-cell apoptosis by blocking the JNK and GSK3beta mediated apoptotic pathway.

Role of phospholipase D1 in glucose-induced insulin secretion in pancreatic beta cells

As glucose is known to induce insulin secretion in pancreatic beta cells, this study investigated the role of a phospholipase D (PLD)-related signaling pathway in insulin secretion caused by high glucose in the pancreatic beta-cell line MIN6N8. It was found that the PLD activity and PLD1 expression were both increased by high glucose (33.3 mM) treatment. The dominant negative PLD1 inhibited glucose-induced Beta2 expression, and glucose-induced insulin secretion was blocked by treatment with 1-butanol or PLD1-siRNA. These results suggest that high glucose increased insulin secretion through a PLD1-related pathway. High glucose induced the binding of Arf6 to PLD1. Pretreatment with brefeldin A (BFA), an Arf inhibitor, decreased the PLD activity as well as the insulin secretion. Furthermore, BFA blocked the glucose-induced mTOR and p70S6K activation, while mTOR inhibition with rapamycin attenuated the glucose induced Beta2 expression and insulin secretion. Thus, when taken together, PLD1 would appear to be an important regulator of glucose-induced insulin secretion through an Arf6/PLD1/mTOR/p70S6K/Beta2 pathway in MIN6N8 cells.

[Effects of conjugated linoleic acid on insulin sensitivity and diabetes markers in type 2 diabetic patients]

Some cell culture and animal studies have reported that Conjugated Linoleic Acids [CLAs] have several health related benefits. CLAs have been shown to have antiadipogenic, antiatherogenic, antidiabetogenic and anti-inflammatory properties. While increase in insulin resistance with 10-trans, 12-cis isomer of CLA was reported in some animal studies, there are controversial results about a 50:50 isomer mixture. The object of the present study was to determine the effect of CLAs supplementation [providing equal proportions of c9, t11 and t10, c12 - CLA] on plasma glucose, insulin, proinsulin, C-peptide, insulin sensitivity, insulin resistance, beta cell function and HbA1c in patients with type 2 diabetes mellitus. The study was performed as an 8-week randomized double-blind, placebo-controlled parallel intervention. Participants were 39 [19 men and 20 women] type 2 diabetic subjects [35 to 50 Y, BMI >25 and <30], stratified according to sex, age and BMI into two groups. Group one were given 3.0 g CLA/d [3x1 g capsules, a 50:50 isomer blend of c9, t11 and t10, c12 CLA] and, group 2 took CLA placebos [soy bean oil] for 8 weeks. Blood sample collection after fasting and 2 hours after a standard breakfast, was done before and after the intervention in order to determine insulin, glucose, pre insulin, c-peptide and HbA1c levels. No significant differences were seen in fasting and postprandial glucose, insulin, proinsulin, C- peptide and HbA1c levels between groups or in insulin resistance, insulin sensitivity, beta cell function and beta cell responsiveness. CLA supplementation has no effects on diabetes glucose level and insulin function and its prescription is not recommended

The traditional plant, Andrographis paniculata (Sambiloto), exhibits insulin-releasing actions in vitro.

AIM: to examine the effect of A.paniculata on pancreatic b-cells. METHODS: sixty minutes incubation of BRIN-BD11 in Modified Kreb-Ringer Solution containing 16.7 mM glucose (KRB-3) + 0.625 - 2.5 mg/mL A.paniculata evoked 1.7 - 3.73 fold of insulin secretion compared to 16.7 mM glucose only (p = 0.003 - p < 0.001). RESULTS: compared to the effect of 100 mM glibenclamide, 60 minutes incubation of BRIN-BD11 in KRB-3 containing 1.25 and 2.5 mg/mL A. paniculata evoked 1.5 fold (p=0.034) and 2.3 fold (p=0.001) insulin secretion. Twenty minutes incubation of BRIN-BD11 in KRB-3 + 0.625-5 mg/mL A.paniculata, evoked 1.4 - 4.7 fold (p = 0.002 - p < 0.001) of insulin secretion compared to 16.7 mM glucose only. Twenty minutes incubation of BRIN-BD11 in KRB-1 containing 1.11 mM glucose + 0.625 - 10 mg/mL A.paniculata, evoked 1.3 - 3.7 fold (p = 0.019 - p < 0.001) of insulin secretion compared to 16.7 mM glucose only. CONCLUSION: this study conclude that A.paniculata was a very strong, dose dependent insulinotropic agent, glucose dependent and independent insulin secreting agent. This study also conclude that A.paniculata affected one of the membrane receptors, mostly ATP-dependent potassium channels (K+ATP).

[Effect of GABA on plasma cytokine concentration and beta and alpha cell mass in CD1 diabetic mice]

Type I diabetes is an autoimmune disease associated with T lymphocytes function in beta cells. This process can increase cytokine secretion, which can cause beta cell inflammation and death. Since GABA, [y-aminobutyric acid] is a major inhibitory neurotransmitter, and low concentration of GABA can increase cytokine secretion, the aim of this study was demonstrate to the inhibitory effect of GABA administration on cytokine secretion and decrease in beta cell death and also to show the ability of beta cells in insulin secretion. Seven week old CD1 mice were used. To induce diabetes, animals received 40 mg/kg of STZ five days continuously. Two months later, animals were divided into two groups, one receiving 200 micromole of GABA and the other [controls] the same volume of PBS for 10 weeks. Serum glucagon levels, and alpha cells significantly decreased in the [IL12 IL1beta, TNF alpha] mass and some cytokine levels in the GABA group. Plasma insulin level and beta cell mass significantly increased in comparison to the control group. From the results of this study we conclude that GABA administration causes inhibition in cytokine secretion, improves beta cell mass and increases insulin secretion. May be, in the future, if GABA shows no side effects we can use GABA for type one diabetes

Regeneration of beta cells in islets of Langerhans of pancreas of alloxan diabetic rats by acetone extract of Momordica charantia (Linn.) (bitter gourd) fruits.

Acetone extract of whole fruit powder of M. charantia (bitter gourd) in doses 25, 50 and 75 mg/100 g body weight lowered the blood glucose from 13.30 to 50% after 8 to 30 days treatment in alloxan diabetic albino rats, confirming antihyperglycemic effect of this plant in diabetic animals and humans. Histological observations with acetone extract showed different phases of recovery of beta cells of the islets of Langerhans of pancreas, which in the untreated diabetic rats were less in number and showed varied degree of atrophy. The most important finding of the present study was observation of the presence of small scattered islets among the acinar tissue in some experimental animals, which may reflect neoformation of islets from pre-existing islet cells. The liver of alloxan diabetic rats showed hydropic degeneration, fatty change and necrosis at some places but liver of extract treated animals was normal. Glycogen localization in liver of diabetic rats was faint but after 30 days treatment with different doses of extract, normal to heavy glycogen localization was observed.