The activation by glucose of liver membrane nitric oxide synthase in the synthesis and translocation of glucose transporter-4 in the production of insulin in the mice hepatocytes

Role of aspirin activated nitric oxide synthase in controlling DOCA-salt-induced hypertension in rats through the stimulation of renal r-cortexin in kidney cortex cells

OBJECTIVES

Because the damage of kidney tissue is associated with hypertension and impaired nitric oxide (NO) synthesis, and as aspirin is reported to stimulate the synthesis of renal r-cortexin, an anti-hypertensive protein, we investigated the role of aspirin as bolus dose on elevated blood pressure induced by deoxycorticosterone acetate (DOCA)-salt in animal model.

METHODS

The chronic antihypertensive effect of aspirin on DOCA treated with ASA group of rats (n = 6) was evaluated after ingestion of 0.35 μM aspirin as a bolus dose in every 24 h using tail cuff methods. The plasma aspirin, NO, and r-cortexin levels were determined by spectrophotometric, methemoglobin, and ELISA methods, respectively. Synthesis of r-cortexin mRNA was determined. Aspirin activated nitric oxide synthase (AANOS) was purified by chromatographic methods.

RESULTS

Our results showed after 3 h of administration of aspirin (0.35 μM) to the DOCA treated with ASA group of rats decreased the systolic blood pressure from 139.39 ± 7.36 mm of Hg to 116.57 ± 6.89 mm of Hg and diastolic blood pressure from 110.4 ± 7 mm of Hg to 86.4 ± 2.76 mm of Hg. The reduction of BPs was found to be related to the increased plasma aspirin from 0.00 μM to 0.042 μM, plasma NO from 0.4 ± 0.19 nM to 1.9 ± 0.5 nM, and cortexin levels from 64.36 ± 12.6 nM to 216.7 ± 21.3 nM. The molecular weight of purified AANOS is 18 kDa.

CONCLUSION

It can be concluded that aspirin possesses antihypertensive effect on blood pressure in chronic administration. Aspirin can stimulate NO synthesis through the activation of AANOS, which stimulated the production of r-cortexin in kidney cortex cells and thereby reducing elevated BP in hypertensive rats.

AKT ISOFORMS-AS160-GLUT4: The defining axis of insulin resistance

The Akt isoforms-AS160-GLUT4 axis is the primary axis that governs glucose homeostasis in the body. The first step on the path to insulin resistance is deregulated Akt isoforms. This could be Akt isoform expression, its phosphorylation, or improper isoform-specific redistribution to the plasma membrane in a specific tissue system. The second step is deregulated AS160 expression, its phosphorylation, improper dissociation from glucose transporter storage vesicles (GSVs), or its inability to bind to 14-3-3 proteins, thus not allowing it to execute its function. The final step is improper GLUT4 translocation and aberrant glucose uptake. These processes lead to insulin resistance in a tissue-specific way affecting the whole-body glucose homeostasis, eventually progressing to an overt diabetic phenotype. Thus, the relationship between these three key proteins and their proper regulation comes out as the defining axis of insulin signaling and -resistance. This review summarizes the role of this central axis in insulin resistance and disease in a new light.

Profiles of Two Glycaemia Modifying Drugs on the Expression of Rat and Human Sulfotransferases

AIMS

To study the effects of blood glucose regulating compounds on human and rat sulfotransferases (SULTs) expressions.

BACKGROUND

Phase-II enzymes, sulfotransferases catalyze the sulfuryl-group-transfer to endogenous/exogenous compounds. The alteration of expressions of SULTs may have influence on the sulfation of its substrate and other biomolecules.

OBJECTIVES

The influence of the altered biotransformation might alter different biochemical events, drug-drug interactions and bioaccumulation or excretion pattern of certain drug.

METHODS

In this brief study, diabetes-inducing drug streptozotocin (STZ; 10 or 50 mg/kg to male Sprague Dawley rat for 2 weeks) or hyperglycemia controlling drug tolbutamide (TLB 0.1 or 10μM to human hepato-carcinoma cells, HepG2 for 10 days) was applied and the SULTs expressions were verified. Extensive protein-protein (STa, SULT2A1/DHEAST) interactions were studied by the STRING (Search-Tool-for-the-Retrieval-of-Interacting Genes/Proteins) Bioinformatics-software.

RESULTS

Present result suggests that while STZ increased the STa (in rat) (dehydroepiandrosterone catalyzing SULT; DHEAST in human HepG2), tolbutamide decreased PPST (phenol catalyzing SULT) and DHEAST activity in human HepG2 cells. Moderate decreases of MPST (monoamine catalyzing SULT) and EST (estrogen catalyzing) activities are noticed in this case. STa/DHEAST was found to be highly interactive to SHBG/- sex-hormone-binding-globulin; PPARα/lipid-metabolism-regulator; FABP1/fatty-acid-binding-protein.

CONCLUSION

Streptozotocin and tolbutamide, these two glycaemia-modifying drugs demonstrated regulation of rat and human SULTs activities. The reciprocal nature of these two drugs on SULTs expression may be associated with their contrasting abilities in influencing glucose-homeostasis. Possible association of certain SULT-isoform with hepatic fat-regulations may indicate an unfocused link between calorie-metabolism and the glycemic-state of an individual. Explorations of this work may uncover the role of sulfation metabolism of specific biomolecule on cellular glycemic regulation.

Xiaokeyinshui extract combination, a berberine-containing agent, exerts anti-diabetic and renal protective effects on rats in multi-target mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaokeyinshui (XKYS) formula, an anti-diabetic formula, was recorded in many ancient Chinese medical books. Xiaokeyinshui extract combination (XEC) originated from this ancient formula, consisting extracts of four herbal drugs, namely, Coptidis Rhizoma, Liriopes Radix, bitter melon, and Cassiae Semen.

OBJECTIVE

Therapeutic effects of Xiaokeyinshui extract combination (XEC) were assessed on diabetic rats.

MATERIALS AND METHODS

Herb extracts were prepared and mixed, yielding XEC. XEC were intragastrically given at doses of 260, 380 and 500 mg/kg/d to diabetic rats for 60 days. Anti-diabetic effects of XEC were studied, with measurement of body weight, and assessment of both glycemic control and lipid management. Measurement of oxidative stress and inflammatory cytokines were conducted in accordance to protocols of commercial kits. Parameters related to renal functions were also measured. Western blot (WB) analysis was performed to explore the anti-diabetic and renal protective mechanisms of XEC.

RESULTS

Compared to diabetic control, XEC exhibited significant effects in both glucose-lowering and lipid management (p < 0.01). Both oxidative stress and inflammatory cytokines were reduced after treatment of XEC for two months. In addition, XEC exhibited renal protective effects. WB analysis of liver tissue demonstrated that XEC achieved anti-diabetic effects through up-regulation of InsRα/IRS-1/PI3K/Akt/GLUT4 signaling pathway and phosphorylation of AMPK. In addition, renal protective effects were also achieved with down-regulation of RAGE and VEGF expressions in kidney.

CONCLUSIONS

XEC exerts promising anti-diabetic and renal protective effects on diabetic rats in multi-target mechanisms. XEC could be a satisfying alternative treating T2DM and preventing diabetic nephropathy.

Role of Nitric Oxide in Insulin Secretion and Glucose Metabolism

Nitric oxide (NO) contributes to carbohydrate metabolism and decreased NO bioavailability is involved in the development of type 2 diabetes mellitus (T2DM). NO donors may improve insulin signaling and glucose homeostasis in T2DM and insulin resistance (IR), suggesting the potential clinical importance of NO-based interventions. In this review, site-specific roles of the NO synthase (NOS)-NO pathway in carbohydrate metabolism are discussed. In addition, the metabolic effects of physiological low levels of NO produced by constitutive NOS (cNOS) versus pathological high levels of NO produced by inducible NOS (iNOS) in pancreatic β-cells, adipocytes, hepatocytes, and skeletal muscle cells are summarized. A better understanding of the NOS-NO system in the regulation of glucose homeostasis can hopefully facilitate the development of new treatments for T2DM.

Telmisartan increases hepatic glucose production via protein kinase C ζ-dependent insulin receptor substrate-1 phosphorylation in HepG2 cells and mouse liver

Background

Dysregulation of hepatic glucose production (HGP) contributes to the development of type 2 diabetes mellitus. Telmisartan, an angiotensin II type 1 receptor blocker (ARB), has various ancillary effects in addition to common blood pressure-lowering effects. The effects and mechanism of telmisartan on HGP have not been fully elucidated and, therefore, we investigated these phenomena in hyperglycemic HepG2 cells and high-fat diet (HFD)-fed mice.

Methods

Glucose production and glucose uptake were measured in HepG2 cells. Expression levels of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase α (G6Pase-α), and phosphorylation levels of insulin receptor substrate-1 (IRS-1) and protein kinase C ζ (PKCζ) were assessed by western blot analysis. Animal studies were performed using HFD-fed mice.

Results

Telmisartan dose-dependently increased HGP, and PEPCK expression was minimally increased at a 40 μM concentration without a change in G6Pase-α expression. In contrast, telmisartan increased phosphorylation of IRS-1 at Ser302 (p-IRS-1-Ser³⁰²) and decreased p-IRS-1-Tyr⁶³² dose-dependently. Telmisartan dose-dependently increased p-PKCζ-Thr⁴¹⁰ which is known to reduce insulin action by inducing IRS-1 serine phosphorylation. Ectopic expression of dominant-negative PKCζ significantly attenuated telmisartan-induced HGP and p-IRS-1-Ser³⁰² and -inhibited p-IRS-1-Tyr⁶³². Among ARBs, including losartan and fimasartan, only telmisartan changed IRS-1 phosphorylation and pretreatment with GW9662, a specific and irreversible peroxisome proliferator-activated receptor γ (PPARγ) antagonist, did not alter this effect. Finally, in the livers from HFD-fed mice, telmisartan increased p-IRS-1-Ser³⁰² and decreased p-IRS-1-Tyr⁶³², which was accompanied by an increase in p-PKCζ-Thr⁴¹⁰.

Conclusion

These results suggest that telmisartan increases HGP by inducing p-PKCζ-Thr⁴¹⁰ that increases p-IRS-1-Ser³⁰² and decreases p-IRS-1-Tyr⁶³² in a PPARγ-independent manner.

A Mitochondrial VDAC1-Based Peptide Greatly Suppresses Steatosis and NASH-Associated Pathologies in a Mouse Model

Non-alcoholic steatosis and non-alcoholic steatohepatitis (NASH) are liver pathologies characterized by severe metabolic alterations due to fat accumulation that lead to liver damage, inflammation, and fibrosis. We demonstrate that the voltage-dependent anion channel 1 (VDAC1)-based peptide R-Tf-D-LP4 arrested steatosis and NASH progression, as produced by a high-fat diet (HFD-32) in a mouse model, and reversed liver pathology to a normal-like state. VDAC1, a multi-functional mitochondrial protein, regulates cellular metabolic and energetic functions and apoptosis and interacts with many proteins. R-Tf-D-LP4 treatment eliminated hepatocyte ballooning degeneration, inflammation, and liver fibrosis associated with steatosis, NASH, and hepatocarcinoma, and it restored liver pathology-associated enzyme and glucose levels. Peptide treatment affected carbohydrate and lipid metabolism, increasing the expression of enzymes and factors associated with fatty acid transport to mitochondria, enhancing β-oxidation and thermogenic processes, yet decreasing the expression of enzymes and regulators of fatty acid synthesis. The VDAC1-based peptide thus offers a promising therapeutic approach for steatosis and NASH.

Huangqi (astragalus) decoction ameliorates diabetic nephropathy via IRS1-PI3K-GLUT signaling pathway

Huangqi decoction (HD) is a prescription for the treatment of diabetes in traditional Chinese medicine. The study was aimed to investigate the effect of HD on diabetic nephropathy. Male diabetic db/db mice which develop diabetic nephropathy spontanously and non-diabetic db/m control mice were used in the current study, and received the treatment of HD for 14 consecutive weeks. HD treatment dose-dependently decreased the body weight, urine volume, water intake and food intake, improved glucose tolerance and insulin resistance, and lowered blood glucose, serum glycosylated hemoglobin, insulin and insulin resistance index in db/db mice. The db/db mice also showed low levels of serum creatinine, blood urea nitrogen and urine albumin, and improved renal functions such as glomerular filtration rate after HD treatment. Histological examination showed that HD treatment prevented the deterioration of basement membrane of glomerular capillary, mesangial matrix and renal tubular lumen in the db/db mice. Through examining the cell signaling pathways which might be involved in the pathology of diabetic nephropathy, we found that HD treatment activated phospho-IR^Y1361, phospho-IRS1^Y896, phospho-PI3K, and inhibited phospho-IRS1^S636/639, phospho-AKT^T308 and phospho-AKT^S473. HD treatment abolished the change in the expression of glucose transporters in the diabetic kidney with an increase in GLUT4 but decrease in GLUT1 expression in the kidney in a dose-dependent manner. Our study suggests that HD prevents the development of diabetes and improves renal function in the db/db mice and HD regulation of the IRS1-PI3K-GLUT signaling pathway significantly improves diabetic nephropathy.

The role of Dermcidin isoform-2 in the occurrence and severity of Diabetes

Diabetes is now epidemic worldwide. Several hundred-million peoples are presently suffering from this disease with other secondary-disorders. Stress, hypertension, sedentary life-style, carbohydrate/lipid metabolic-disorders due to genetic or environmental factors attributes to type-1 and/or type-2 diabetes. Present investigation demonstrates that stress-induced protein dermcidin isoform-2 (DCN-2) which appears in the serum of diabetic-patients play a key-role in this disease pathogenesis/severity. DCN-2 suppresses insulin production-release from liver/pancreas. It also increases the insulin-resistance. Stress-induction at the onset/progression of this disease is noticed as the high-level of lipid peroxides/low-level of free-thiols in association with increase of inflammatory-markers c-reactive protein and TNF-α. DCN-2 induced decrease in the synthesis of glucose-activated nitric oxide synthase (GANOS) and lower production of NO in liver has been shown here where NO is demonstrated to lower the expression of glucose trabsporter-4 (GLUT-4) and its translocation on liver membrane surface. This finally impairs glucose transport to organs from the extracellular fluid. Low level of glucose uptake further decreases glucose-induced insulin synthesis. The central role of DCN-2 has been demonstrated in type-1/type-2 diabetic individuals, in rodent hepatocytes and pancreatic-cell, tissue-slices, in-vitro and in-vivo experimental model. It can be concluded that stress-induced decrease in insulin synthesis/function, glucose transport is an interactive consequence of oxidative threats and inflammatory events.

HMGB1 facilitates hypoxia-induced vWF upregulation through TLR2-MYD88-SP1 pathway

Increased plasma level of von Willebrand Factor (vWF) is associated with major cardiovascular diseases. We previously reported that multimeric vWF binds to NO synthase and inhibits insulin-induced production of NO, thus promoting insulin resistance during acute hypoxia (AH). However, the transcriptional regulation of vWF during AH is not clearly understood. Here, we investigated the mechanisms underlying the upregulation of vwf in mice. AH significantly upregulates the tlr2, tlr3, myd88, and vwf expression and phosphorylation of specificity protein 1 (SP1). Furthermore, AH significantly upregulates high mobility group box-1 (HMGB1) in a time-dependent manner. Moreover, a TLR2 agonist upregulates vWF but a TLR3 agonist does not. Pretreatment with an HMGB1 inhibitor, TLR2-immunoneutralizing antibody, or SP1 inhibitor significantly inhibits vWF expression. Furthermore, Tlr2 silencing completely inhibited MYD88, vWF expression, and SP1 phosphorylation. However, pretreatment with glycyrrhizic acid or silencing of Tlr2 completely blocks binding of Sp1 to the Vwf promoter, thus inhibiting its expression, and enhances insulin resistance during AH. Patients with type 2 diabetes mellitus also showed significantly elevated levels of HMGB1, TLR2, SP1, and vWF, thereby supporting the results of the murine model of AH. Taken together, HMGB1 upregulates vWF in vivo through the TLR2-MYD88-SP1 pathway in mice.

Orexin-A stimulates the expression of GLUT4 in a glucose dependent manner in the liver of orange-spotted grouper (Epinephelus coioides)

Orexins are hypothalamic neuropeptides involved in the central regulation of feeding behavior, sleep-wake cycle and other physiological functions. Orexin-A can regulate energy metabolism and increase glucose uptake, suggesting a role in glucose metabolism. In this study, we investigated the effects of orexin-A on GLUT4 mRNA and protein levels and the intracellular signaling mechanisms mediating orexin-A activity in the hepatocytes of grouper. Our results demonstrate that intraperitoneal injection of orexin-A increased the expression of GLUT4 in the liver, and this effect was significantly enhanced by co-injection of glucose. Treatment of primary cultured hepatocytes with either orexin-A or glucose alone had no effect on the expression of GLUT4, while co-treatment with orexin-A and glucose significantly increased the expression of GLUT4. This stimulatory effect was partially blocked by inhibitors to ERK1/2, JNK or p38 MAPK and was further blocked by an orexin receptor antagonist, which indicates that orexin-A could stimulate the expression of GLUT4 in a glucose dependent manner in primary hepatocytes via ERK1/2, JNK and p38 signaling. Our results suggest that orexin-A could play a pivotal role in stimulating glucose utilization in grouper, for a long-term goal, which might be useful in reducing costs in the aquaculture industry.

The impaired synthesis of insulin and its inability to inhibit platelet aggregation in cerebrovascular accident

Both ischemic stroke (IS) and hemorrhagic stroke (HS) are reported to occur due to thrombosis on the arteries of the brain. As diabetes mellitus is a risk factor for strokes and insulin is reported to prevent thrombosis, the role of insulin in IS and HS was investigated. Forty eight stroke victims (IS = 22, HS = 26) and equal number of aged and sex matched normal volunteers participated in the study. Nitric oxide was determined by methemoglobin method. Insulin and Dermcidin isoform-2 (DCN2) level was determined by ELISA by using insulin and dermcidin antibody. Insulin binding to the platelet membrane was analyzed by scat chard plot. Treatment of normal platelet rich plasma (10(8)platelets/ml) with 15μUnits insulin/ml produced 1.41 nmol NO. The PRP from the IS and HS victims produced 0.38 nmol NO and 0.08 nmol NO respectively. Pretreatment of PRP from IS or HS subjects with 15 μM aspirin followed by 15μUnits of insulin/ml resensitized the platelets to the inhibitory effect of insulin. Mice hepatocytes treated with 0.14 μM DCN2 abolished the glucose induced insulin synthesis by NO that can be reversed by using 15 μM aspirin. It can be concluded that presence of DCN2 in stroke causes a condition similar to type I diabetes and nullified the effect of insulin in the inhibition of platelet aggregation in both IS and HS. The effect was reversed by 15 μM aspirin.

Diabetes in rural individuals of different nutritional status and the alarming situation demands focus more on its under-nutrition association

OBJECTIVE

To study the relationship of nutritional-status with diabetes.

DESIGN

The socioeconomics/anthropometrics, blood-glucose/systemic-hypertension are evaluated in consecutively-selected diabetic-patients.

SETTING

Semi-urban/rural India.

SUBJECTS

Hyperglycaemic patients (total 90/male 37).

RESULTS

Blood-glucose (PP-mean ± SE) in individuals is overweight - 38.89% (226.94 ± 9.59), normal-weight - 50% (217.58 ± 1.34), underweight - 11.11% (305.50 ± 21.35) indicating most hyperglycaemia in undernourished-group (F = 6.357, p < 0.003). This group occupies higher glucose-groups in ≤140, 141-270, and ≥270 mg/dL. The blood-glucose negatively correlates with waist(r = -0.282; p < 0.01) and hip (r = -0.254; p < 0.05) circumference indicating the under-nutrition association with glucose-homeostasis (F = 7.6-8.2, p < 0.001). The higher glucose is noticed in more number of individuals in lower (<40 years) age-group (χ(2 )= 12.86; p < 0.002/ρ = -0.355; p < 0.001). The prevalence of hypertension is 28% (underweight = 20%, overweight = 27%, normal = 30%). The group of 141-270 mg/dL glucose has 45% and rest groups together have 23% hypertensive individuals relating directly, hypertension and diabetic-onset.

CONCLUSIONS

Diabetes, explored in <40 years group and even more in female should be extensively studied accounting WHO categorization (1985/TRS/727) of malnutrition related diabetes (MRDM). Further, different interactive risk-factors should be properly addressed and the global-malnutrition/gender-based inequities be eradicated.