Cancer targeted gene therapy of BikDD inhibits orthotopic lung cancer growth and improves long-term survival.

Lung cancer is a leading cause of cancer death due to the high incidence of metastasis; therefore, novel and effective treatments are urgently needed. A current strategy is cancer-specific targeted gene therapy. Although many identified that cancer-specific promoters are highly specific, they tend to have low activity compared with the ubiquitous cytomegalovirus (CMV) promoter, limiting their application. We developed a targeted gene therapy expression system for lung cancer that is highly specific with strong activity. Our expression vector uses the survivin promoter, highly expressed in many cancers but not normal adult tissues. We enhanced the survivin promoter activity comparable to the CMV promoter in lung cancer cell lines using an established platform technology, whereas the survivin promoter remained weak in normal cells. In mouse models, the transgene was specifically expressed in the lung tumor tissue, compared with the CMV promoter that was expressed in both normal and tumor tissues. In addition, the therapeutic gene BikDD, a mutant form of pro-apoptotic Bcl2 interacting killer, induced cell killing in vitro, and inhibited cell growth and prolonged mouse survival in vivo. Importantly, there was virtually no toxicity when BikDD was expressed with our expression system. Thus, the current report provides a therapeutic efficacy and safe strategy worthy of development in clinical trials treating lung cancer.

Role of tumor suppressor PTEN in tumor necrosis factor alpha-induced inhibition of insulin signaling in murine skeletal muscle C2C12 cells.

In an attempt to clarify the role of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in muscle insulin resistance, we investigated the effect of PTEN on phosphoinositide 3 (PI3)-kinase/Akt related insulin signaling pathway in skeletal muscle-like C2C12 cells damaged by tumor necrosis factor-alpha (TNFalpha). C2C12 cells cultured with TNFalpha (10 ng/ml) for 1 h displayed a marked decrease of insulin-stimulated 2-[14C]-deoxy-D-glucose (2-DG) uptake in parallel with an elevation of PTEN mRNA and protein levels. However, pretreatment of PTEN antisense oligonucleotide (AS) (1 micromol/l for 3 days) for specific inhibition of PTEN expression in C2C12 cells abolished the TNFalpha-induced changes in 2-DG uptake. Similar pretreatment with PTEN AS, but not with sense oligonucleotide (1 micromol/l for 3 days), eliminated the ability of TNFalpha to impair insulin-stimulated signals including p85 regulatory subunit of PI3-kinase expression and the degree of Akt serine phosphorylation as well as protein expression in glucose transporter subtype 4. Data taken from cultured C2C12 cells emphasize the negative regulatory of muscle PI3-kinase/Akt signaling pathways as the major substrate of PTEN but also support the concept that PTEN contributes to the development of insulin resistance in skeletal muscle.

Mechanism for blockade of angiotensin subtype 1 receptors to lower plasma glucose in streptozotocin-induced diabetic rats.

AIMS: We investigated the mechanism(s) by which valsartan, a selective antagonist of angiotensin subtype 1 (AT(1)) receptor, decreased plasma glucose in streptozotocin (STZ)-induced diabetic rats. METHODS: The plasma glucose concentration was assessed by the glucose oxidase method. The concentration of beta-endorphin in plasma or medium incubating adrenal medulla was measured using an enzyme-linked immunosorbent assay. The mRNA levels of the subtype 4 form of glucose transporter (GLUT4) in soleus muscle and phosphoenolpyruvate carboxykinase (PEPCK) in the liver were detected by Northern blotting analysis, while the protein levels of GLUT4 in isolated soleus muscle and hepatic PEPCK were investigated using Western blotting analysis. RESULTS: A single intravenous injection of valsartan dose-dependently increased plasma beta-endorphin-like immunoreactivity (BER) in parallel with the lowering of plasma glucose concentration in STZ-induced diabetic rats. Naloxone and naloxonazine inhibited the plasma glucose-lowering action of valsartan at doses sufficient to block opioid micro-receptors. In contrast to its action in wild-type diabetic mice, valsartan failed to modify plasma glucose in opioid micro-receptor knockout diabetic mice. Bilateral adrenalectomy in STZ-induced diabetic rats eliminated both the plasma glucose-lowering action and the plasma BER-elevating action of valsartan. In the isolated adrenal medulla of STZ-induced diabetic rats, angiotensin II (Ang II) or valsartan did not affect spontaneous BER secretion. Activation of cholinergic receptors by 1.0 micromol/l acetylcholine (ACh) enhanced BER secretion from the isolated adrenal medulla of STZ-induced diabetic rats, but not in the presence of 1.0 nmol/l Ang II, while valsartan reversed this inhibition by Ang II in a concentration-dependent manner. Treatment of STZ-induced diabetic rats with valsartan (0.2 mg/kg) three times daily for 3 days resulted in an increase in gene expression of GLUT4 in soleus muscle and impeded the reduction of elevated mRNA or protein level of hepatic PEPCK. Both of these effects were blocked by opioid micro-receptor antagonist. CONCLUSIONS: The results suggest that blockade of AT(1) receptor by valsartan may enhance the adrenal beta-endorphin secretion induced by ACh, activating the opioid micro-receptors to increase glucose utilization and/or to decrease hepatic gluconeogenesis, resulting in the reduction of plasma glucose in STZ-induced diabetic rats.

Activation of opioid mu-receptors by loperamide to improve interleukin-6-induced inhibition of insulin signals in myoblast C2C12 cells.

AIMS/HYPOTHESIS: This study investigated the role of opioid mu-receptor activation in the improvement of insulin resistance. METHODS: Myoblast C2C12 cells were cultured with IL-6 to induce insulin resistance. Radioactive 2-deoxyglucose (2-DG) uptake was used to evaluate the effect of loperamide on insulin-stimulated glucose utilisation. Protein expression and phosphorylation in insulin-signalling pathways were detected by immunoblotting. RESULTS: The insulin-stimulated 2-DG uptake was reduced by IL-6. Loperamide reversed this uptake, and the uptake was inhibited by blockade of opioid mu-receptors. Insulin resistance induced by IL-6 was associated with impaired expression of the insulin receptor (IR), IR tyrosine autophosphorylation, IRS-1 protein content and IRS-1 tyrosine phosphorylation. Also, an attenuated p85 regulatory subunit of phosphatidylinositol 3-kinase, Akt serine phosphorylation and the protein of glucose transporter subtype 4 were observed in insulin resistance. Loperamide reversed IL-6-induced decrement of these insulin signals. CONCLUSIONS/INTERPRETATION: Opioid mu-receptor activation may improve IL-6-induced insulin resistance through modulation of insulin signals to reverse the responsiveness of insulin. This provides a new target in the treatment of insulin resistance.

Activation of imidazoline receptors in adrenal gland to lower plasma glucose in streptozotocin-induced diabetic rats.

AIMS/HYPOTHESIS: The present study investigated the effect of agmatine, an endogenous ligand of imidazoline receptors, on plasma glucose in streptozotocin-induced diabetic rats (STZ-diabetic rats). METHODS: Plasma glucose was assessed by the glucose oxidase method. Plasma insulin and beta-endorphin-like immunoreactivity in plasma or adrenal medulla were measured by enzyme-linked immunosorbent assay. Systolic blood pressure was determined by the tail-cuff method. The mRNA levels of glucose transporter subtype 4 (GLUT4) in soleus muscle and phosphoenolpyruvate carboxykinase (PEPCK) in liver were detected by northern blotting. Protein levels of GLUT4 in soleus muscle and hepatic PEPCK were estimated using western blotting analysis. RESULTS: After intravenous injection into fasting STZ-diabetic rats for 30 min, agmatine decreased plasma glucose in a dose-dependent manner without changing systolic blood pressure. At the same time, plasma beta-endorphin-like immunoreactivity also increased in STZ-diabetic rats receiving the same treatment. Plasma glucose was significantly elevated in STZ-diabetic rats by an intravenous injection of clonidine at a dose sufficient to decrease systolic blood pressure. Involvement of I(1)-imidazoline receptors and/or alpha2-adrenoceptors in this effect of agmatine was thus unlikely. The lowering of plasma glucose and increase of plasma beta-endorphin-like immunoreactivity by agmatine were abolished by pretreating the rats with BU-224 at a dose sufficient to block I(2)-imidazoline receptors. Both effects of agmatine were also abolished in adrenalectomised STZ-diabetic rats. Moreover, agmatine enhanced beta-endorphin-like immunoreactivity release from the isolated adrenal medulla of STZ-diabetic rats, an effect also blocked by BU-224. Release of beta-endorphin from the adrenal glands by I(2)-imidazoline receptor activation seems responsible for the plasma glucose-lowering action of agmatine. This was supported by the fact that intravenous injection of naloxone or naloxonazine at doses sufficient to block opioid mu-receptors inhibited the action of agmatine. In addition to lowering plasma glucose, repeated intravenous injection of agmatine into STZ-diabetic rats for 4 days also increased mRNA and protein levels of GLUT4 in soleus muscle. The same treatment also reversed the higher mRNA and protein levels of PEPCK in liver of STZ-diabetic rats. CONCLUSIONS/INTERPRETATION: Our results suggest that agmatine may activate I(2)-imidazoline receptors in the adrenal gland. This enhances secretion of beta-endorphin, which can activate opioid mu-receptors to increase GLUT4 gene expression and/or suppress hepatic PEPCK gene expression, resulting in a lowering of plasma glucose in diabetic rats lacking insulin. The results provide a potential new target for intervention in type 1 diabetes.

Loperamide increases glucose ultilization in streptozotocin-induced diabetic rats.

1. Loperamide has an ability to lower the plasma glucose concentration in streptozotocin (STZ)-induced diabetic rats. In the present study, we investigated the molecular mechanisms by which loperamide regulates plasma glucose concentrations in the absence of insulin. 2. Loperamide, at a dose sufficient (17.6 microg/kg) to activate mu-opioid receptors, significantly decreased plasma glucose levels in STZ-diabetic rats. The mRNA and protein levels of glucose transporter 4 (GLUT-4) in soleus muscle, detected by northern and western blotting, respectively, were increased after repeated intravenous administration of loperamide (17.6 micro g/kg) to STZ-diabetic rats over 3 days. Moreover, similar treatment with loperamide (17.6 microg/kg) for 3 days reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase (PEPCK) in the liver of STZ-diabetic rats to near the levels seen in normal rats. 3. These results suggest that activation of mu-opioid receptors by loperamide can increase glucose utilization in peripheral tissues and/or reverse the higher gene expression of PEPCK to inhibit hepatic gluconeogenesis, thereby lower plasma glucose in diabetic rats lacking insulin.

Increase in adenosine A1 receptor gene expression in the liver of streptozotocin-induced diabetic rats.

BACKGROUND: Adenosine A1 receptor (A1-AR) activation can lower plasma glucose in diabetic rats lacking insulin. We investigated the change in A1-AR gene expression in diabetic rats. METHODS: The incorporation of [U-(14)C]-glucose into glycogen was carried out to evaluate the effect of N(6)-cyclopentyladenosine (CPA) on glucose utilization in vitro. The plasma glucose concentration was assessed by the glucose oxidase method. The mRNA and protein levels of A1-AR in isolated liver were detected by Western blotting analysis and Northern blotting analysis, respectively. RESULTS: The effect of CPA, an agonist of A1-AR, on glycogen incorporation in hepatocytes isolated from streptozotocin-induced diabetic rats (STZ-diabetic rats) was more marked than that from the normal rats. However, similar glycogen synthesis was not modified by 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, in the isolated hepatocytes from both the normal and the STZ-diabetic rats. A change in response at the receptor level can thus be considered. The mean level of liver mRNA transcripts encoding A1-AR was increased in STZ-diabetic rats to about 250% of that in normal rats. Exogenous insulin at a dose sufficient to normalize the plasma glucose of STZ-diabetic rats reversed the mRNA level of A1-AR in the liver after a four-day treatment. Similar results were also observed in STZ-diabetic rats that received treatment with phlorizin for four days. Moreover, the protein level of A1-AR was higher in the liver of STZ-diabetic rats than that in the normal rats. Similar treatment with exogenous insulin or phlorizin reversed the elevated protein level of A1-AR in the liver of STZ-diabetic rats to near the normal level. Therefore, correction of hyperglycemia in STZ-diabetic rats can reverse the higher gene expression of A1-AR in liver. CONCLUSIONS: The obtained results suggest that an increase in plasma glucose is responsible for the higher gene expression of A1-AR in the liver of STZ-diabetic rats.

Release of beta-endorphin by caffeic acid to lower plasma glucose in streptozotocin-induced diabetic rats.

The role of alpha 1A -adrenoceptors in the regulation of opioid secretion from the adrenal glands of streptozotocin-induced diabetic rats (STZ-diabetic rats) was examined in an attempt to determine the mechanism of plasma glucose-lowering action of caffeic acid. In agreement with a previous report, we showed that caffeic acid produced a dose-dependent lowering of the plasma glucose concentration in STZ-diabetic rats along with an increase of plasma beta-endorphin-like immunoreactivity (BER). These actions of caffeic acid were abolished by pretreatment with WB 4101 or RS 17 056 at doses sufficient to block alpha 1A -adrenoceptors. In addition, naloxone and naloxonazine at doses effective for blocking opioid micro -receptors abolished the plasma glucose-lowering action of caffeic acid. Also, unlike that in wild-type diabetic mice, caffeic acid failed to produce a plasma glucose lowering effect in opioid micro -receptor knockout diabetic mice. We observed that caffeic acid could enhance BER release from isolated rat adrenal medulla in a concentration-dependent manner; inhibitors of alpha 1A -adrenoceptors such as WB 4101 and RS 1705 abolished this action. Investigations of the signal pathways further supported that activation of alpha 1A -adrenoceptor is responsible for the stimulatory effect of caffeic acid on BER secretion from the adrenal medulla. In the presence of U73312, a specific inhibitor of phospholipase C, the caffeic acid-induced increase of BER was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Chelerythrine and GF 109203X also diminished the action of caffeic acid at concentrations sufficient for inhibiting protein kinase C. Moreover, bilateral adrenalectomy in STZ-diabetic rats resulted in the loss of this plasma glucose-lowering effect of caffeic acid, and there was no increase in plasma BER with caffeic acid. Therefore, beta-endorphin release from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats induced by caffeic acid, through the activation of alpha 1A -adrenoceptors.

Plasma glucose-lowering effect of beta-endorphin in streptozotocin-induced diabetic rats.

The effect of beta-endorphin on plasma glucose levels was investigated in streptozotocin-induced diabetic rats (STZ-diabetic rats). A dose-dependent lowering of plasma glucose was observed in the fasting STZ-diabetic rat fifteen minutes after intravenous injection of beta-endorphin. The plasma glucose-lowering effect of beta-endorphin was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. Also, unlike wild-type diabetic mice, beta-endorphin failed to induce its plasma glucose-lowering effect in the opioid mu-receptor knock-out diabetic mice. In isolated soleus muscle, beta-endorphin enhanced the uptake of radioactive glucose in a concentration-dependent manner. Stimulatory effects of beta-endorphin on glycogen synthesis were also seen in hepatocytes isolated from STZ-diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. In the presence of U73312, the specific inhibitor of phospholipase C (PLC), the uptake of radioactive glucose into isolated soleus muscle induced by beta-endorphin was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the stimulatory action of beta-endorphin on the uptake of radioactive glucose at a concentration sufficient to inhibit protein kinase C (PKC). The data obtained suggest that activating opioid mu-receptors by beta-endorphin may increase glucose utilization in peripheral tissues via the PLC-PKC pathway to lower plasma glucose in diabetic rats lacking insulin.

Decrease in catechol-O-methyltransferase activity in the liver of streptozotocin-induced diabetic rats.

1. The present study compared the activity of catechol- O-methyltransferase (COMT) in the liver and plasma of streptozotocin (STZ)-induced diabetic rats with that in normal rats. The activity of COMT was estimated by the metabolism of noradrenaline to metanephrine (MN), both measured by high-performance liquid chromatography with electrochemical detection. 2. Formation of MN was decreased in the liver of STZ- diabetic rats compared with normal rats. The amount of MN was also decreased in plasma obtained from STZ-diabetic rats. A Michaelis-Menten plot showed a reduction in the maximum velocity and an increase in the Km for COMT in liver samples from STZ-diabetic rats. 3. The role of hyperglycaemia in the lowering of COMT activity was then investigated using phlorizin or insulin at doses sufficient to normalize plasma glucose from STZ-diabetic rats. Both insulin and phlorizin treatment of STZ-diabetic rats for 4 days restored the activity of COMT to that seen in normal rats. Thus, correction of hyperglycaemia in STZ-diabetic rats can reverse the decrease in COMT activity. The activity of COMT is lower in STZ-diabetic rats than in normal rats mainly due to the higher plasma glucose.

Plasma glucose-lowering effect of tramadol in streptozotocin-induced diabetic rats.

The effect of tramadol on the plasma glucose level of streptozotocin (STZ)-induced diabetic rats was investigated. A dose-dependent lowering of plasma glucose was seen in the fasting STZ-induced diabetic rats 30 min after intravenous injection of tramadol. This effect of tramadol was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. However, response to tramadol was not changed in STZ-induced diabetic rats receiving p-chlorophenylalanine at a dose sufficient to deplete endogenous 5-hydroxytrptamine (5-HT). Therefore, mediation of 5-HT in this action of tramadol is ruled out. In isolated soleus muscle, tramadol enhanced the uptake of radioactive glucose in a concentration-dependent manner. The stimulatory effects of tramadol on glycogen synthesis were also seen in hepatocytes isolated from STZ-induced diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. The mRNA and protein levels of the subtype 4 form of glucose transporter in soleus muscle were increased after repeated treatments for 4 days with tramadol in STZ-induced diabetic rats. Moreover, similar repeated treatments with tramadol reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase in the liver of STZ-induced diabetic rats. These results suggest that activation of opioid mu-receptors by tramadol can increase the utilization of glucose and/or decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin.

Association of nephropathy and retinopathy, blood pressure, age in newly diagnosed type 2 diabetes mellitus.

In this study, we investigated the prevalence of chronic complications, including nephropathy and retinopathy, in patients newly diagnosed as type 2 diabetes mellitus. All hyperglycemic subjects were recruited into our study when they visited the outpatient department at Kaohsiung Medical University Hospital over a one-year period. These subjects had fasting plasma glucose higher than 140 mg/dl, or plasma glucose higher than 200 mg/dl in the 2nd hour during an oral glucose tolerance test. Among 148 patients registered as newly diagnosed type 2 diabetes mellitus, 18.2% of the patients had nephropathy, noted by measuring their urine albumin excretion rate and daily protein loss, and 25.5% had retinopathy, noted by fundoscope and fluorescent angiography. The age of overt proteinuric patients (41.5 +/- 3.4 yrs) was significantly younger than those without nephropathy (51.8 +/- 1.0 yrs). Systolic and diastolic blood pressure was significantly higher in patients with microalbuminuria (142.4 +/- 6.0/88.8 +/- 2.6 mmHg) and overt proteinuria (153.8 +/- 13.6/96.8 +/- 9.5 mmHg) than normoalbuminuric patients (128.3 +/- 2.3/81.9 +/- 1.1 mmHg). There was no significant difference in cholesterol, triglyceride, HbA1C, sex or body mass index among normoalbuminric, microalbuminuric, or overt proteinuric patients. The severity of retinopathy was parallel with the severity of nephropathy. Based on our results, chronic diabetic complications, including nephropathy and retinopathy, may occur even when diabetes is newly diagnosed. It is necessary to look for complications, especially in newly documented diabetic patients who are young and hypertensive.

Increase of opioid mu-receptor gene expression in streptozotocin-induced diabetic rats.

Opioids play an important role in the regulation of glucose homeostasis. In the previous report, we showed that activation of opioid mu-receptors produced a plasma glucose lowering effect in diabetic rats lacking insulin. In the present study, we found that the response of opioid mu-receptor is more sensitive in streptozotocin-induced diabetic rats (STZ-diabetic rats) than in normal rats. Intravenous injection of loperamide, an agonist of opioid mu-receptors, induced a dose-dependent decrease of plasma glucose from 3 microg/kg to 60 microg/kg in fasting STZ-diabetic rats. However, loperamide decreased the plasma glucose of normal fasting rats at the doses of 0.3 mg/kg to 1.5 mg/kg, which were much higher than those needed to produce the same effect in diabetic rats. The plasma glucose-lowering action of loperamide at the dose effective in normal rats disappeared in opioid mu-receptor knockout mice, while the plasma glucose-lowering response to loperamide was still observed in wild-type mice. This opens the possibility of mediation through opioid mu-receptor in the plasma glucose-lowering action of loperamide. Moreover, the mRNA level of opioid mu-receptor in the liver markedly increased in STZ-diabetic rats compared to normal rats. Normalization of plasma glucose concentrations in STZ-diabetic rats with exogenous insulin or phlorizin reversed mRNA and protein levels of opioid mu-receptor in the liver after 4 days of treatment. This shows that correction of hyperglycemia in STZ-diabetic rats may reverse the higher gene expression of opioid mu-receptor. These results suggest that hyperglycemia is responsible for increase of opioid mu-receptor in STZ-diabetic rats.

Release of beta-endorphin by prostaglandin E2 to lower plasma glucose in streptozotocin-induced diabetic rats.

In the present study, Wistar rats, which received a streptozotocin injection to induce diabetes (STZ-diabetic rats), a model similar to insulin-dependent diabetes mellitus (IDDM) or type 1 diabetes mellitus, were used to investigate the effect of prostaglandin (PG) E2 on plasma glucose. Intravenous injection of PGE2 produced a dose-dependent lowering of plasma glucose level in fasting STZ-diabetic rats after 60 min. In addition to the blockade of this hypoglycemic effect by guanethidine (a noradrenergic nerve terminal-blocking agent), prazosin at a dose effective to block alpha1-adrenoceptors abolished the action of PGE2. An increase of plasma norepinephrine (NE) was also observed in STZ-diabetic rats receiving PGE2 injections. Participation of sympathetic stimulation by PGE2 may thus be speculated. Also, the plasma glucose-lowering effect of PGE2 was also blocked by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptor. Injection of PGE2 increased plasma beta-endorphin-like immunoreactivity (BER) in STZ-diabetic rats, and this action was abolished by prazosin. Bilateral adrenalectomy resulted in the loss of this PGE2 effect, and no increase was seen in plasma BER with PGE2 in STZ-diabetic rats. Therefore, beta-endorphin from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats by PGE2 through an increase of NE release to activate alpha1-adrenoceptors.

Insulin action and insulin secretion in newly diagnosed type 2 diabetic patients.

To clarify the insulin action and insulin secretion in newly diagnosed type 2 diabetic subjects, we investigated insulin and C-peptide response to an oral glucose tolerance test (OGTT) in 15 newly diagnosed type 2 diabetic patients and 17 healthy subjects. For insulin action, we found fasting hyperinsulinemia (8.4 +/- 0.8 vs. 6.0 +/- 0.5 microIU/ml, p = 0.014), higher insulin resistance by homeostasis model assessment (HOMA) (4.33 +/- 0.2 vs. 1.34 +/- 0.1 microIU/ml.mmol/l, p < 0.001), and lower insulin sensitivity index (ISI) (51.0 +/- 0.7 vs. 104.0 +/- 0.8, p < 0.001) in newly diagnosed diabetic patients compared to normal subjects. For insulin secretion, the increments of AUCI (area under curve of insulin) and AUCC-P (area under curve of C-peptide) (increment of AUCI: 26.1 +/- 1.4 vs. 82.8 +/- 4.5 microIU/ml.hour, p < 0.001; increment of AUCC-P: 3.9 +/- 0.2 vs. 11.4 +/- 0.6 ng/ml.hour, p < 0.001), insulin secretion by HOMA model (20.7 +/- 1.2 vs. 79.1 +/- 3.8 IU/mol, p < 0.001), and ratio of 30 min increment of fasting insulin to glucose during OGTT (1.14 +/- 0.1 vs. 13.1 +/- 0.5 IU/mol, p < 0.001) were significantly lower in the newly diagnosed diabetic patients than normal subjects. In addition, body mass index (BMI) in our type 2 diabetes is relatively lower (24 +/- 0.65 kg/m2) than those in western countries. These findings revealed poor insulin action and decreased insulin secretion in relatively less obese Taiwanese with newly diagnosed type 2 diabetes.

Neuronal and endothelial nitric oxide synthase expression in outer medulla of streptozotocin-induced diabetic rat kidney.

AIMS/HYPOTHESIS: Several investigations have shown that the renal medulla has a greater capacity to generate nitric oxide than the renal cortex. To further evaluate the changes of nitric oxide synthesis in the kidney, particularly in the outer medulla, in disorders involving fluid and electrolyte imbalances, we sought to determine renal nitric oxide synthase expression in the diabetic rats. METHODS: We determined renal nitric oxide synthase mRNA and urinary nitrite/nitrate excretion in 12 normal and 12 streptozotocin-induced diabetic rats by reverse transcription-polymerase chain reaction with Southern blot hybridization and with Griess reaction, respectively. Nitric oxide synthase immunoreactivity was detected by immunohistochemistry in four normal and four diabetic rats. RESULTS: Neuronal and endothelial nitric oxide synthase mRNA were 3.5-fold and 1.8-fold increased in the outer medulla of 12 diabetic rats with no difference found in the cortex and inner medulla when compared with 12 normal rats. Urinary nitrite/nitrate excretion was significantly increased from the first week after diabetic induction. In normal rats, immunohistochemical studies showed positive neuronal and endothelial nitric oxide synthase immunostaining in almost all segments of renal tubules. Diabetic rats had the greatest enhancement of immunostaining for neuronal and endothelial nitric oxide synthase in the proximal straight tubule and medullary thick ascending limb. CONCLUSION/INTERPRETATION: Our results indicate that increases in neuronal and endothelial nitric oxide synthase synthesis in the kidney, particularly in the outer medulla, possibly play an important part in the adaptation of renal function to hyperglycaemia and hyperosmolality in diabetes.