Effect of pravastatin on serum lipids, apolipoproteins and lipoprotein (a) in patients with non-insulin dependent diabetes mellitus

In 43 patients with non-insulin dependent diabetes mellitus (NIDDM) associated with hypercholesterolemia, the effect of pravastatin, a potent HMG CoA-reductase inhibitor, on serum lipids, apolipoproteins and lipoprotein (a) was examined. After 1 to 3 months administration of 10 mg per day of pravastatin, the serum levels of total cholesterol, triglycerides and low-density lipoprotein cholesterol (LDL-C) were significantly decreased, while the serum level of high density lipoprotein cholesterol (HDL-C) was significantly increased in patients with NIDDM. The levels of apolipoproteins B (apo B) and E were significantly decreased, while apolipoprotein AI (apo A-I) was not changed by the administration of pravastatin. The atherogenic indices (LDL-C/HDL-C and apo B/apo A-I) were significantly decreased by the administration of this drug. The serum lipoprotein (a), which was increased in the diabetic patients, was not affected by the pravastatin treatment. Plasma glucose and hemoglobin A1c levels were not affected by the treatment. We concluded that pravastatin is a potentially useful agent in the treatment of hypercholesterolemia in patients with NIDDM.

Effect of glucose on Na, K-ATPase activity in cultured bovine aortic endothelial cells

The effect of high concentrations of glucose on Na, K-ATPase activity and the polyol pathway was studied using cultured bovine aortic endothelial cells. Na, K-ATPase activity was expressed as ouabain-sensitive K+ uptake. A significant decrease in Na, K-ATPase activity with an intracellular accumulation of sorbitol was found in confluent endothelial cells incubated with 400 mg/dl glucose for 96 h. However, there was no significant change in the Na, K-ATPase activity or sorbitol content of the cells incubated with 100 mg/dl glucose plus 300 mg/dl mannitol. The decrease in Na, K-ATPase induced by the high glucose concentration was restored by the simultaneous addition of 10(-4) M ponalrestat (ICI 128,436; Statil), an aldose reductase inhibitor. The addition of this agent also significantly reduced the increase in sorbitol induced by high glucose levels. These results suggest that the decrease in Na, K-ATPase activity induced in cultured aortic endothelial cells by high concentrations of glucose may be caused in part by the accumulation of sorbitol.

[A case of the diabetic nephropathy without hyperglycemia]

We report a case of diabetic nephropathy with impaired glucose tolerance. A 52 year obese woman with nephrotic syndrome and hypertension showed severe and remarkable edema, as her legs were elephantiasis. To be clear the etiology of nephrotic syndrome, we performed renal biopsy. The histological findings of the specimen showed glomerulosclerosis. Additionally the examination of ocular fundus revealed microaneurysm and avascular area. We concluded that diagnosis of this case must be non-insulin-dependent diabetes mellitus.

Release of amylin from perfused rat pancreas in response to glucose and glucagon

The effects of glucose and glucagon on the release of amylin from the isolated perfused rat pancreas were studied. Amylin is a 37-amino acid peptide isolated from pancreatic islet amyloid of patients with non-insulin-dependent diabetes mellitus (NIDDM). Glucose dose-dependently stimulated a biphasic release of amylin from the pancreas in parallel with that of insulin. However, the release of amylin induced by high concentrations of glucose was partially dissociated from that of insulin. The amylin-insulin molar ratios induced by 22.2 mM and 33.3 mM glucose (1.11 +/- 0.05%, 1.05 +/- 0.04%, respectively) were significantly higher than that induced by 16.7 mM glucose (0.90 +/- 0.04%, P less than 0.01 vs 22.2 mM glucose, P less than 0.05 vs 33.3 mM glucose). In the presence of 5.6 mM glucose, glucagon also stimulated the release of amylin from the perfused pancreas in parallel with that of insulin. These findings suggest that amylin may be a secretory protein from the pancreas and that the concomitant secretion of amylin and insulin might contribute to glucose homeostasis.

Platelet stimulation for prostacyclin production in aortic endothelial cell cultures: alteration in diabetes mellitus

We evaluated the effect of platelets on prostacyclin (PGI2) production in bovine aortic endothelial cell cultures. Human platelet extract significantly stimulated PGI2 production by cultured aortic endothelial cells in a time- and dose-dependent manner, suggesting that platelets contain PGI2-stimulatory activity (PSA). Supernatant fluid separated from platelets activated by collagen also exhibited PSA. The factor(s) causing the PSA of platelets was non-dialysable and heat-stable (56 degrees C for 30 min or 100 degrees C for 3 min), was completely inhibited by trypsin pretreatment, and exhibited an affinity to heparin agarose. Furthermore, gel filtration chromatography showed that the factor(s) responsible for the platelet PSA was eluted at three different peaks with approximate molecular weights of 50,000, 25,000 and 11,000. The PSA of platelet extract from patients with non-insulin-dependent diabetes mellitus (NIDDM) (n = 10) was compared to that from age-matched control subjects (n = 10). Platelet extract from patients with NIDDM stimulated cultured aortic endothelial cells to produce greater amounts of PGI2 than did that from control subjects. These data suggest that the increased PSA of platelets isolated from diabetic patients may contribute to the abnormal interaction between platelets and the vascular wall in diabetic patients.

Increased inositol phosphate accumulation in platelets from patients with NIDDM

We evaluated thrombin-induced inositol phosphate accumulation in [3H]inositol-labeled platelets prepared from patients with non-insulin-dependent diabetes mellitus. There were no significant differences in [3H]inositol incorporation into and contents of phosphoinositides between the diabetic patients and their age-matched control subjects. Thrombin induced a dose- and time-dependent accumulation of inositol phosphate. The accumulation of [3H]inositol trisphosphate and [3H]inositol bisphosphate by thrombin stimulation were significantly enhanced in platelets from the diabetic patients, although the accumulation of [3H]inositol monophosphate did not differ between the diabetic patients and the control subjects. In addition, the platelet aggregation rate induced by thrombin was also significantly enhanced in the diabetic patients in correlation with the enhanced inositol phosphate accumulation. These results suggest that increased inositol phosphate accumulation may cause accelerated platelet functions in diabetes mellitus.

Effects of glucagon-like peptide 1 (7-36) amide and glucagon on amylin release from perfused rat pancreas

The effects of glucagon-like peptide 1 (7-36) amide [GLP-1 (7-36) amide] and glucagon on the release of islet amyloid polypeptide (IAPP), or amylin, from the isolated perfused rat pancreas were studied. In the presence of 5.6 mM glucose, GLP-1 (7-36) amide and glucagon stimulated the release of amylin from the perfused pancreas. The infusion of GLP-1 (7-36) amide at a concentration of 10(-9) M elicited a biphasic release of amylin similar to that of insulin. The cumulative output of amylin induced by 10(-9)M GLP-1 (7-36) amide was significantly higher than that by 10(-9)M glucagon (p less than 0.01). The amylin/insulin molar ratios induced by GLP-1 (7-36) amide and glucagon were about 1% and did not differ significantly. These findings suggest that GLP-1 (7-36) amide and glucagon stimulate the release of amylin from the pancreas and that the concomitant secretion of amylin and insulin might contribute to glucose homeostasis.

Haemostatic factors associated with vascular thrombosis in patients with systemic lupus erythematosus and the lupus anticoagulant

To elucidate the mechanism of vascular thrombosis in patients with systemic lupus erythematosus and the lupus anticoagulant changes in factors associated with haemostasis were investigated. The lupus anticoagulant was associated with an increased incidence of thrombosis, particularly cerebral thrombosis. Concentrations of fibrinopeptide A and fibrinopeptide B beta 15-42 were significantly raised in the plasma of patients with systemic lupus erythematosus and the anticoagulant compared with concentrations in patients without the lupus anticoagulant. The tendency towards formation of thrombosis was not found in all lupus patients with the anticoagulant, however. Concentrations of thromboxane B2 were remarkably raised in the plasma of the two patients with the lupus anticoagulant who had recently had thrombosis. Concentrations of 6-keto-prostaglandin F1 alpha, protein C, antithrombin III, and plasminogen were similar in both groups. No significant decrease in serum stimulatory activity on prostacyclin production by cultured aortic endothelial cells was noted in lupus patients with the anticoagulant, but inhibition was present in the two patients with recent thrombosis. These results indicate that although patients with the lupus anticoagulant are not always in a hypercoagulable state, haemostatic abnormalities found in some patients with the anticoagulant may be predictive of thrombotic events.

Release of amylin from perfused rat pancreas in response to glucose, arginine, beta-hydroxybutyrate, and gliclazide

Amylin is a 37-amino acid peptide isolated from the islet amyloid of patients with non-insulin-dependent diabetes mellitus. The isolated perfused normal rat pancreas was used to evaluate the effects of glucose and insulin secretagogues, such as arginine, beta-hydroxybutyrate, and gliclazide, on amylin secretion. Glucose and the other stimulants tested elicited a significant release of amylin from the rat pancreas in a biphasic pattern, similar to that of insulin. Dose-response studies of the glucose-induced release of amylin and insulin revealed that they possessed a similar dependency on glucose. However, the release of amylin induced by high concentrations of glucose was partially dissociated from that of insulin; that is, the amylin-insulin molar ratios induced by 22.2 and 33.3 mM glucose (1.11 +/- 0.05 and 1.05 +/- 0.04%, respectively) were significantly higher than those induced by 16.7 mM glucose (0.90 +/- 0.04%, P less than 0.01 vs. 22.2 mM glucose, P less than 0.05 vs. 33.3 mM glucose). Additionally, when the basal concentration of glucose in the perfusate was increased from 5.6 to 11.1 mM, the response of amylin was unchanged. These data suggest that amylin may be an islet hormone whose abundant response to high concentrations of glucose might contribute to the oversecretion of amylin in the hyperglycemia that accompanies diabetes mellitus.

Glucose reduces PDGF production and cell proliferation of cultured vascular endothelial cells

The effect of glucose on PDGF production and cell proliferation was studied on cultured bovine aortic endothelial cells. PDGF levels were measured using an enzyme-linked immunosorbent assay technique newly developed in our laboratory. The cell proliferation rate was determine on the basis of 3H-thymidine incorporation into cellular DNA. PDGF levels in culture medium were below the detection limit of the assay. However, PDGF levels were measurable in cultured endothelial cells at confluence. Both PDGF production and thymidine incorporation were significantly reduced in the endothelial cells cultured with high concentrations of glucose. These results suggest that reduced PDGF production and cell proliferation may be involved in altered vascular endothelial function in diabetics.

A case of insulin allergy: the crystalline human insulin may mask its antigenicity

We report an unusual case of insulin allergy. A 48-year-old man with non-insulin-dependent diabetes mellitus receiving biosynthetic isophane human insulin (Humulin N) developed itchy wheal-and-flare reactions at the sites of injection. When Humulin N was changed to a semi-synthetic crystalline human insulin zinc (Novolin U), the allergic reactions completely disappeared. Evaluation of his serum showed a high level of insulin-specific IgE. Skin testing with all commercially available insulins showed immediate local reactions to all agents tested except for Novolin U. In addition, decrystallized Novolin U prepared by lowering the pH with acetic acid also induced a positive reaction. These observations suggest that the crystallized structure of human insulin may mask its antigenicity for allergic reactions.

Increased intracellular calcium mobilization in platelets from patients with type 2 (non-insulin-dependent) diabetes mellitus

Enhanced platelet functions have been reported in patients with diabetes mellitus. Our recent study demonstrated that phosphoinositide turnover is increased in platelets from diabetic patients. In the present study, we evaluated the abnormality in platelet intracellular calcium mobilization in patients with Type 2 (non-insulin-dependent) diabetes mellitus using fura-2, a fluorescent calcium indicator. Washed platelets were prepared from six diabetic patients with increased platelet aggregation rates (DM-A group), seven diabetic patients with normal platelet aggregation rates (DM-B group), and eight age-matched healthy control subjects. The basal intracellular free calcium concentrations in platelets were similar among the three groups. Thrombin (0.025-0.1 U/ml) induced a dose-dependent increase in intracellular calcium in both the presence and the absence of extracellular calcium. This increase in the presence of extracellular calcium, which depends on calcium influx and release, was significantly higher in the DM-A group than in the DM-B and control groups. However, there was no significant difference between the control group and the DM-B group. In the absence of extracellular calcium, thrombin-induced calcium increase, which depends only on calcium release, was also significantly enhanced in the DM-A group. Furthermore, the calcium increase stimulated by platelet-activating factor (10 nmol/l) with and without extracellular calcium was significantly higher in the DM-A group than in the other groups. Additionally, calcium ionophore A23187 (100 nmol/l) caused a significantly higher calcium increase in the DM-A group with extracellular calcium, while the calcium increase without extracellular calcium showed no significant difference among the three groups. These observations suggest that enhanced intracellular calcium mobilization due to increased calcium influx and release may be closely related to platelet hyperfunctions in diabetes mellitus.

Serum 1,5-anhydro-D-glucitol and glycemic control in patients with non-insulin-dependent diabetes mellitus

Serum 1,5-anhydro-D-glucitol (AG) levels, which have been reported to decrease specifically in diabetics, were measured in 102 patients with non-insulin-dependent diabetes mellitus (NIDDM). The mean of serum AG levels was 7.9 +/- 0.7 micrograms/ml (mean +/- S.E.). It was found a significant negative correlation between serum AG level and HbA1c or fasting blood sugar level. The decrease in serum AG levels inversely correlated with the extent of glycemic control in the patients with NIDDM. Additionally, the changes of serum AG levels negatively correlated with the changes of HbA1c levels during long-term (2 years) treatment. Furthermore, serum AG levels were compared between the patients with and without diabetic complication such as retinopathy, proteinuria or neuropathy. It was found that each group of the patients with complication had significantly decreased serum AG level compared with the complication free group. On the other hand, however, no differences were found in serum AG levels corrected by HbA1c levels using the linear regression formula between the group of the patients with and without diabetic complication.

Cultured bovine endothelial cells convert big endothelin isopeptides to mature endothelin isopeptides

The incubation of big endothelin-1 (big ET-1), big ET-2 or big ET-3 with cultured bovine endothelial cells (ECs) resulted in their conversions to mature endothelins (ETs). These conversions apparently exhibited Michaelis-Menten kinetics as a function of each big ET isopeptide. The conversions of big ETs were abolished by phosphoramidon. These results indicate that vascular endothelium can convert exogenous big ET-1 to mature ET-1 through a phosphoramidon-sensitive metalloprotease, and that this enzyme has also high affinities for big ET-2 and big ET-3.

Changes in phosphoinositide turnover, Ca2+ mobilization, and protein phosphorylation in platelets from NIDDM patients

Enhanced platelet functions have been demonstrated in patients with non-insulin-dependent diabetes mellitus (NIDDM). This study evaluated abnormalities in platelet signal transduction in diabetic patients, including turnover of phosphoinositides, mobilization of intracellular Ca2+, and phosphorylation of 20,000- and 47,000-Mr proteins (P20 and P47). Washed platelets were obtained from 6 patients with NIDDM whose platelet aggregation rates were abnormally elevated (DM-A group), 11 NIDDM patients with normal platelet aggregation rates (DM-B group), and 8 age-matched healthy control subjects. The mass and specific radioactivity of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), and phosphatidic acid (PA) in 32P-labeled platelets were not different among the three groups. Hydrolysis of PIP2, PIP, and PI; accumulation of PA; and phosphorylation of P20 in platelets stimulated by 0.05 U/ml thrombin were significantly increased in the DM-A group compared with the control or DM-B group. There was no difference in P47 phosphorylation among the three groups. On the contrary, P20 and P47 phosphorylation induced by 50 nM of 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, was significantly decreased in the DM-A group. Additionally, the intracellular free Ca2+ concentration [( Ca2+]i) was measured with the fluorescent Ca2+ indicator fura 2. Although the basal [Ca2+]i value was similar in the three groups, the rise in [Ca2+]i induced by 0.05 U/ml thrombin in the presence and the absence of extracellular Ca2+ was significantly higher in the DM-A group than the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of urinary albumin excretion by thromboxane synthetase inhibitor, OKY-046, through modulating renal prostaglandins in patients with diabetic nephropathy

We evaluated the effects of thromboxane synthetase inhibitor, OKY-046, on urinary albumin and prostaglandin (PG) excretion in 14 patients with non-insulin-dependent diabetes mellitus (NIDDM). Urinary excretion of 6-keto-PGF1 alpha (a stable metabolite of PGI2), TXB2 (a stable metabolite of TXA2) and PGE2 in NIDDM patients was comparable with that in control subjects. However, the urinary 6-keto-PGF1 alpha/TXB2 ratio in NIDDM patients with both micro- and macroalbuminuria was significantly (P less than 0.001) lower than that in the controls. By a single administration of OKY-046 (40 mg, i.v.) to the diabetic patients, urinary TXB2 excretion significantly (P less than 0.05) decreased from 169.7 +/- 23.9 to 140.2 +/- 17.9 ng/gCr, but urinary 6-keto-PGF1 alpha and PGE2 excretion did not change significantly. The urinary 6-keto-PGF1 alpha/TXB2 ratio thus significantly (P less than 0.01) increased from 1.02 +/- 0.13 to 1.73 +/- 0.41 as associated with significant increments in urine volume (P less than 0.05), urinary sodium excretion (P less than 0.01) and creatinine clearance (P less than 0.05). Of 14 diabetic patients, 7 with macroalbuminuria (albumin index exceeding 100 mg/gCr) were orally given OKY-046 (600 mg/day) for 8 weeks. After this period, the urinary albumin index significantly (P less than 0.05) decreased from 524.9 +/- 149.6 to 317.6 +/- 90.6 mg/gCr.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylin release from perfused rat pancreas in response to glucose and arginine

The effects of glucose and arginine on the release of amylin from the perfused rat pancreas were studied. Amylin, or islet amyloid polypeptide, is a 37-amino acid peptide isolated from pancreatic islet amyloid of patients with non-insulin-dependent diabetes mellitus (NIDDM). Glucose stimulated dose-dependently amylin release, showing a typical biphasic pattern. Additionally, 10 mM arginine in the presence of 5.5 mM glucose also stimulated amylin release. These findings suggest that amylin is a secretory protein and its release from the pancreas is regulated by glucose and other nutrients.

Enhanced secretion of endothelin-1 by elevated glucose levels from cultured bovine aortic endothelial cells

We have investigated the effect of glucose on the release of endothelin-1-like immunoreactivity (ET-1-LI) from cultured bovine aortic endothelial cells. Elevation of glucose concentrations in cultured media from 5.5 to 11.1 or 22.2 mM significantly stimulated ET-1-LI release from cultured endothelial cells. An aldose reductase inhibitor did not affect the high glucose-induced ET-1-LI release. These findings suggest the possibility that hyperglycemia in diabetic patients enhances ET-1-LI release at the local site of vascular endothelium, which might be involved in the developments of vascular complications and atherosclerosis.

Identification and characterization of endothelin converting activity in cultured bovine endothelial cells

Using a specific and sensitive radioimmunoassay (RIA) for the carboxyl terminal tail of endothelin (ET) (His16-Trp21), we have confirmed the presence of the converting activity from synthetic human big ET-1 to ET-1 in the homogenate of cultured bovine aortic endothelial cells. The optimal pHs for the converting activities were found at pH 3.0 and pH 7.0. The activity at pH 3.0 was completely inhibited by pepstatin A, whereas the activity at pH 7.0 was not affected by known various protease inhibitors except EDTA and EGTA. When the products from big ET-1 were analyzed on an ODS and a CN columns, only ET-1 was detected at pH 7.0, but various ET-like immunoreactivities other than ET-1 were detected at pH 3.0. These findings strongly suggest that mature ET-1 is formed from big ET-1 in the endothelial cells by a metal-dependent neutral protease.

Decreased VIP content in peripheral nerve from streptozocin-induced diabetic rats

After induction of diabetes with streptozocin (STZ-D) in rats, we measured vasoactive intestinal polypeptide (VIP) content in sciatic nerve and spinal cord obtained from nondiabetic, untreated STZ-D, and insulin-treated STZ-D rats. Eight weeks after the onset of diabetes, caudal nerve conduction velocity (NCV) in the untreated STZ-D rats (n = 13) was slower than in the controls (n = 11; mean +/- SE 30.9 +/- 0.6 vs. 41.4 +/- 1.8 m/s, P less than 0.001). The decrease in NCV was less marked in the insulin-treated STZ-D rats (n = 11; 36.3 +/- 0.9 m/s, P less than 0.05 vs. control). VIP content in sciatic nerve decreased in the untreated STZ-D rats (1.33 +/- 0.23 ng/g wet wt) compared with the other groups (control, 3.10 +/- 0.44, P less than 0.01; insulin-treated STZ-D, 2.44 +/- 0.55, P less than 0.05). However, in spinal cord, VIP content was not significantly different among the three groups. The VIP levels in sciatic nerve showed a positive correlation with NCV (r = 0.430, P less than 0.01). In addition, an inverse correlation between VIP levels and blood glucose levels was observed (r = -0.5624, P less than 0.001). NCV was also inversely correlated with blood glucose levels (r = -0.7662, P less than 0.001). Together with a previous morphological study, these findings suggest a possible causal relationship between reduced VIP content and diabetic neuropathy.

Effects of vitamin E administration on platelet function in diabetes mellitus

A decrease in the vitamin E content of human diabetic platelets is closely associated with the accelerated platelet aggregation and platelet prostaglandin metabolism seen in patients with diabetes mellitus. We investigated the effect of vitamin E supplementation on these abnormalities of physiological function and prostaglandin metabolism in 14 non-insulin dependent diabetics with proliferative retinopathy. ADP-induced platelet aggregation was inhibited in vitro by the addition of vitamin E in a dose-dependent manner. However, in lower concentrations considered to be physiological doses in vivo, significantly greater inhibition was observed in diabetic platelets than in the control platelets. Next, alpha-tocopheryl nicotinate was administered to diabetics at a daily dose of 600 mg. The platelet vitamin E content was restored to control levels in 13 of the 14 patients after 2-4 weeks of daily administration. The ADP-induced platelet aggregation rate, platelet thromboxane B2 (TXB2, a stable metabolite of TXA2, a vasoconstrictor production, and plasma TXB2 level were low in all 14 diabetics. In contrast, plasma 6-keto-PGF 1 alpha (a stable metabolite of PGI2, a vasodilator) was significantly increased and therefore the 6-keto-PGF 1 alpha/TXB2 ratio in plasma was restored to within normal limits. These results indicate that vitamin E may improve platelet function and prostaglandin metabolism in diabetes mellitus and may be able to provide further beneficial effects in relation to the development of diabetic vascular complications.

Effects of captopril on urinary excretion of albumin and prostaglandins in patients with diabetic nephropathy

Recently the beneficial effects of captopril (angiotensin-converting-enzyme inhibitor) on diabetic nephropathy, especially proteinuria, have been reported by some investigators. The mechanism whereby proteinuria is reduced, however, have not been clarified yet. The present study was undertaken to evaluate the effects of captopril on urinary albumin excretion in relation to urinary prostaglandins (PGs) excretion in patients with non-insulin-dependent diabetes mellitus (NIDDM). Captopril (37.5 mg/day) was orally administered to 13 diabetic patients for an eight-week period. A single administration of captopril (12.5 mg) was performed in the same patients. The spot urine samples were collected in the early morning and 2 hr after the single administration of captopril. The albumin index (mg/gram-creatinine) was markedly decreased in eight patients (Group A) within four weeks, but no decrease was found in five patients (Group B). Furthermore, in Group A, by the single administration of captopril urinary excretions of 6-keto-PCF1 alpha (a stable metabolite of PGI2) and PGE2 were significantly (p less than 0.05) increased while urinary TXB2 (a stable metabolite of TXA2) excretion did not change significantly. The urinary 6-keto-PGF1 alpha/TXB2 ratio, which is significantly (p less than 0.05) low in diabetic patients was significantly (p less than 0.01) increased up to the normal value in Group A. In Group B, however, there were no significant changes in urinary PGs excretion. These results suggest that captopril enhances the production of intrarenal vasodilatory PGs such as PGI2 and PGE2, which may be deeply involved in the reduction of intraglomerular capillary pressure and urinary protein excretion in diabetic patients.

Erythrocytes from diabetics with neuropathy have fewer sodium pumps

Erythrocytes from diabetics with neuropathy had fewer binding sites for ouabain and, therefore, fewer sodium pumps than did erythrocytes from diabetics without neuropathy or from age-matched controls (P less than 0.001). Diabetics with neuropathy excreted in their urine significantly less C-peptide immunoreactivity (CPR) than those without neuropathy, which is a sign of lower endogenous insulin secretion levels. Significant positive correlations existed between the number of pumps and tibial motor nerve conduction velocity (MNCV) and urinary CPR in diabetics, and between urinary CPR and MNCV. This suggests that there is close correlation between the fall in the number of pumps in diabetics and diabetic neuropathy and insulin deficiency.

Effect of galanin on arginine-stimulated pancreatic hormone release from isolated perifused rat islets

The effect of galanin on pancreatic hormone release was studied using isolated perifused rat pancreatic islets. In the presence of 100 mg/dl glucose, 10(-8) mol/L galanin significantly inhibited the basal somatostatin release compared with the perifusion without galanin, whereas there was no significant change in the basal insulin and glucagon release. However, under stimulation of 20 mmol/L arginine, 10(-8) mol/L galanin significantly enhanced glucagon release and suppressed insulin and somatostatin release. These effects disappeared immediately after cessation of galanin infusion. Additionally, 10(-8) mol/L galanin significantly enhanced the first and second phase of glucagon release stimulated by arginine, whereas arginine-stimulated insulin and somatostatin releases were significantly inhibited in both phases. In the cysteamine-treated rat islets, neither enhancement of glucagon release nor suppression of insulin release by galanin was reproducible. These findings indicate two possible explanations. First, it is suggested that the effects of galanin on insulin and glucagon release may be direct and reversed by non-specific effect of cycteamine. Secondly, it seems likely that galanin-enhanced glucagon release may be indirect and in part due to the concomitant somatostatin suppression. Galanin may have an important regulatory function on endocrine pancreas.

Modification of prostacyclin-stimulatory activity in sera by glucose, insulin, low density lipoprotein, linoleic acid and linoleic acid hydroperoxide

Reduced prostacyclin (PGI2) production by the vascular wall has been proposed as one of the possible causes of diabetic vascular complications. We found an activity which stimulated PGI2 production by cultured endothelial cells (PGI2-stimulatory activity, PSA) in human plasma-derived serum (PDS). The PSA was less in patients with diabetes mellitus. The present study was undertaken to evaluate how metabolic factors relevant to diabetic angiopathy modify the PSA. Pooled PDS was prepared from 10 healthy volunteers. The 6-keto-PGF1 alpha (6KF, a stable metabolite of PGI2) production by cultured bovine aortic endothelial cells was maximally stimulated by Dulbecco's modified Eagle's medium (DMEM) containing 10% pooled PDS after incubation for 60 min. The production of 6KF was reduced in a dose-dependent manner by the addition of 10% pooled PDS with glucose and linoleic acid hydroperoxide (lipid peroxide). In contrast, human low density lipoprotein (LDL) and linoleic acid (unsaturated fatty acid) enhanced the production of 6KF by 10% pooled PDS in a dose-dependent manner. Insulin, however, showed no effect on the production of 6KF by 10% pooled PDS. These results suggest that the reduced PSA in diabetics may be the result, in part, of a modification of the PSA by diabetic metabolic factors such as glucose and lipid peroxide.

Serum fructosamine in assessment of diabetic control and relation to thyroid function

Measurement of serum fructosamine using a Roche kit is a simple and reliable method for the estimation of glycated serum proteins. The value of serum fructosamine can be affected by hyperglycemia in diabetics and an abnormal turnover rate of serum protein in patients with thyroid dysfunction. We measured the serum fructosamine level in 18 normal control subjects, 71 diabetics (8 IDDM, 63 NIDDM) and 46 non-diabetic untreated patients with thyroid dysfunction (28 hyperthyroidism, 18 hypothyroidism). The serum fructosamine level was significantly increased in the diabetics compared with the normal control subjects (3.84 +/- 0.15 mmol/l vs 2.58 +/- 0.08; mean +/- SE, P less than 0.01). The serum fructosamine level in the diabetics was positively correlated with the fasting plasma glucose and HbAlc level, showing the highest correlation with fasting plasma glucose at 2 weeks before and with the HbAlc level at 2 weeks after serum fructosamine measurement. In the patients with thyroid dysfunction, the serum fructosamine level in hyperthyroidism (2.08 +/- 0.03 mmol/l) and hypothyroidism (3.11 +/- 0.07 mmol/l) were significantly lower (P less than 0.001) and higher (P less than 0.001) than the normal control subjects (2.58 +/- 0.08 mmol/l), respectively. Furthermore, the serum fructosamine level in these patients was negatively correlated with the level of serum thyroid hormones such as T3 (P less than 0.001) and T4 (P less than 0.001). It is concluded that measurement of serum fructosamine is clinically useful for the evaluation of shorter-term glycemic control in diabetics, but its level for diabetic patients with thyroid dysfunction must be cautiously interpreted.

Modification of prostaglandin synthesis in washed human platelets and cultured bovine aortic endothelial cells by glycosylated low density lipoprotein

Glycosylation of low-density lipoprotein (LDL) is known to be increased in diabetic patients. Recent studies have demonstrated that glycosylated (glc-) LDL contributes to the acceleration of atherosclerosis in diabetes. In the present study, we evaluated the effect of glc-LDL prepared in vitro on platelet aggregation and thromboxane B2 (TxB2) production in washed human platelets and on 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) production by cultured bovine aortic endothelial cells. After preincubation of washed platelets with glc-LDL or control LDL, thrombin-induced platelet aggregation and TxB2 production were measured. Control LDL enhanced the platelet aggregation rate and TxB2 production in a time- and dose-dependent manner. Glc-LDL showed significantly greater enhancement of those platelet functions than control LDL. On the other hand, while 6-keto-PGF1 alpha production was stimulated by control LDL in a time- and dose-dependent manner, glc-LDL significantly reduced the stimulatory effect of control LDL on 6-keto-PGF1 alpha production. These results suggest that modification of prostaglandin synthesis in platelets and endothelial cells by glycosylated LDL may lead to platelet hyperaggregation and thrombus formation in diabetes.

Effect of aldose reductase inhibitor (Ponalrestat) on erythrocyte Na,K-ATPase activity in non-insulin-dependent diabetic patients with polyneuropathy

The binding capacity of ouabain to erythrocyte Na,K-ATPase was determined to analyze alterations in this enzyme activity in non-insulin-dependent diabetic patients. A significant (p less than 0.001) reduction of the binding capacity of ouabain was found in erythrocytes obtained from the diabetic patients with polyneuropathy (0.51 +/- 0.02 pmol/10(9) erythrocytes, m +/- SE, n = 14) as compared with the patients without neuropathy (0.67 +/- 0.02, n = 14) or age-matched control subjects (0.71 +/- 0.04, n = 11). Accordingly, the effect of an aldose reductase inhibitor (ARI; Ponalrestat) on erythrocyte Na,K-ATPase activity was studied following two or three months oral administration in seven of the diabetic patients with polyneuropathy. After treatment with Ponalrestat the mean binding capacity of ouabain was significantly increased from 0.53 +/- 0.04 to 0.57 +/- 0.03 (p less than 0.05 by paired t-test). Furthermore, enzyme kinetics showed that in normal subjects the apparent Km and Vmax of erythrocyte membrane Na,K-ATPase were 0.51 +/- 0.07 mM (n = 5, m +/- SE) and 7.19 +/- 0.27 nmol Pi/mg protein/min (n = 5, m +/- SE), respectively. The Vmax with 3 mM ATP was significantly (p less than 0.05) decreased in the diabetic patients with polyneuropathy as compared with age-matched control subjects. However, the apparent Km did not change. Finally, the in vitro effect of Ponalrestat was examined in erythrocyte membrane fractions from the diabetic patients with polyneuropathy. The activity of erythrocyte membrane Na,K-ATPase was found to be directly stimulated about 1.2 fold by the addition of pharmacological doses of Ponalrestat (10(-10), 10(-8), 10(-6) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Albumin index in spot urine from outpatients with noninsulin-dependent diabetes mellitus

The albumin index (mg/g . creatinine) was determined in untimed spot urine collected in the early morning from 92 randomly selected outpatients with noninsulin-dependent diabetes mellitus (NIDDM). The patients were divided into three groups: 49 patients with normo-albuminuria (albumin index less than 9.1), 24 with micro-albuminuria (albumin index between 9.1 and 100), and 19 with overt-albuminuria (albumin index over than 100). With diabetic duration, the frequency of the patients with overt-albuminuria was increased, but that with normo-albuminuria was decreased. The patients treated with only a diet almost showed normo-albuminuria. In contrast, micro-and overt-albuminuria were found more frequently in the patients treated with oral hypoglycemic agents or insulin. Micro- and overt-albuminuria were found more frequently in the patients with poor glycemic control than in those with good glycemic control. The urinary albumin index was significantly high in the micro-albuminuric patients with poor glycemic control. Similarly, micro- and overt-albuminuria were found more frequently in the patients associated with diabetic retinopathy or neuropathy than in those without diabetic complications. In addition, overt-albuminuria was found more frequently in the patients with hypertension. The urinary albumin index was significantly high in the overt-albuminuric patients with hypertension. In conclusion, the determination of the albumin index in spot urine may be outpatients with NIDDM.

Antithrombin III stimulates prostacyclin production by cultured aortic endothelial cells

Prostacyclin (PGI2) is a potent vasodilator and an inhibitor of platelet aggregation. We found that antithrombin III (AT III), an anticoagulant present in circulating blood, stimulated PGI2 production by cultured bovine aortic endothelial cells in a dose- and time-dependent manner. The stimulation of PGI2 production by AT III was observed at physiological concentrations and was inhibited by the addition of anti-AT III antiserum and heparin. These results suggest that AT III may stimulate PGI2 production by binding to heparin-like molecules on the endothelial cell membrane.

Abnormality in prostacyclin-stimulatory activity in sera from diabetics

A reduction in prostacyclin (PGI2) production by vascular wall may cause platelet hyperaggregability in diabetics, which is considered to be a possible pathogenesis of diabetic vascular complications. In the present study, the presence of PGI2-stimulatory activity (PSA) in rat and human plasma-derived serum (PDS) was confirmed by cultured bovine aortic endothelial cells. PSA in PDS was significantly decreased in streptozotocin-induced diabetic rats and in patients with non-insulin-dependent diabetes mellitus (NIDDM). PDS from patients with NIDDM showed less PSA prior to the clinical onset of diabetic vascular complications, such as retinopathy and proteinuria. The reduction in PSA was still observed in dialyzed PDS from the patients with NIDDM. The nondialyzable PSA was heat-stable at 56 degrees C for 30 minutes and partially stable at 100 degrees C for five minutes. This activity was not extractable with diethylether and was precipitable with trichloroacetic acid. The study of Sephadex G-50 column chromatography showed that a major part of PSA in dialyzed PDS was found in the area of the molecular weight of 12,000 to 17,000 daltons. In conclusion, the reduction in PSA from diabetics may cause a reduction of PGI2 production by vascular wall, subsequently contributing to the development of diabetic vascular complications.

A new case of familial hyperproinsulinemia

We reported a case with increased serum immunoreactive insulin (IRI) and C-peptide immunoreactivity (CPR). The molar ratio of IRI to CPR was also increased. The propositus was diabetic with background retinopathy and neuropathy. No antibody to insulin or insulin receptor was detected in his serum and his insulin resistance was not so remarkable. When the serum was fractionated by gel filtration, about 90% of total IRI was recovered in the fraction where biosynthetic human proinsulin was eluted. The major part of the CPR was also recovered in the same fraction as proinsulin-like material. His daughter, 28 years old, a non-obese female, also had high IRI, CPR and a high molar ratio of IRI to CPR. A gel filtration study demonstrated the same elution profile as the propositus. Tryptic digestion failed to convert the proinsulin-like material from the propositus to insulin in a sufficient quantity to convert human proinsulin to insulin. These data strongly suggest that this family is a new case of familial hyperproinsulinemia, and the defect resides in the proinsulin molecule, not in the converting enzymes.

Decrease in insulin binding to aortic endothelial cells cultured with high glucose concentration

We studied the effects of glucose on specific insulin binding to cultured endothelial cells from the bovine aorta. We cultured the cells in Dulbecco's modified Eagle's medium, containing 100 or 300 mg/dl glucose or 100 mg/dl glucose plus 200 mg/dl mannitol. We added 125I-insulin to monolayers of these cells and counted the radioactivity resulting. Specific insulin binding increased with time and dosage. Maximal binding resulted from 0.17 nM 125I-insulin being incubated for 30 min at 37 degrees C, and amounted to 0.35% per 10(5) cells being bound in cultures of 100 mg/dl glucose. The higher concentration of glucose led to significantly less binding (P less than 0.05) (0.24 +/- 0.03% vs. 0.38 +/- 0.02%, n = 6). The addition of mannitol, on the other hand, did not affect binding. All three incubation conditions produced curvilinear competition curves. Scatchard analysis showed that insulin bound significantly less (P less than 0.05) to endothelial cells in 300 mg/dl glucose than to those in 100 mg/dl glucose (4.0 +/- 1.2 nmol/l vs. 12.8 +/- 3.1, n = 6, mean +/- SEM). Insulin binding capacity, however, did not change. We conclude that glucose can reduce insulin binding to endothelial cells and that it may reduce receptor-related insulin transport into and out of the cells.

Reduced stimulatory activity on prostacyclin production by cultured endothelial cells in serum from aged and diabetic patients

Reduced prostacyclin (PGI2) generation by the vascular wall shows a close relationship with the development of atherosclerosis. The present study found plasma-derived serum (PDS) to contain an activity which stimulated PGI2 production by cultured bovine aortic endothelial cells. Diabetic and aged patients with atherosclerotic disease were examined for abnormalities in that stimulatory activity in PDS. PDS obtained from both diabetics (NIDDM) and aged patients showed a significant reduction in the stimulation of PGI2 production by cultured bovine aortic endothelial cells compared with age-matched controls and young healthy volunteers, respectively. It was suggested that the reduced PGI2 stimulatory activity in PDS may be one of the pathogenic mechanisms of vascular lesions such as atherosclerosis in diabetics and aged humans.

Glucose inhibits prostacyclin production by cultured aortic endothelial cells

A reduction in production of prostacyclin (PGI2) by the cells in the vascular wall may play a role in the pathogenesis of atherosclerosis in diabetic patients. The present study was undertaken to evaluate the effect of glucose on PGI2 production by endothelial cells in vitro. It was shown that PGI2 production by cultured bovine aortic endothelial cells was significantly reduced in the presence of a high concentration of glucose (300 mg/dl) compared with physiological concentrations of glucose (100 mg/dl). In contrast, no reduction in PGI2 production was observed in cells cultured with equimolar mannitol, suggesting that glucose itself, rather than the effect of osmolality, inhibited PGI2 production by cultured endothelial cells. In addition, a high concentration of glucose also inhibited the proliferation of cultured endothelial cells.

Defective processing of insulin-receptor precursor in cultured lymphocytes from a patient with extreme insulin resistance

We have studied a patient with extreme insulin resistance, acanthosis nigricans, and decreased erythrocyte insulin binding. EBV-transformed lymphocytes from this patient exhibited markedly reduced binding of 125I-insulin. Radioiodination of cell surface receptors followed by immunoprecipitation with anti-receptor antibodies revealed the presence of increased amounts of a 210-kD protein but no detectable alpha or beta subunits. Continuous labeling with 2-[3H]mannose revealed the synthesis of a 190-kD precursor and a 210-kD protein. The 210-kD protein was phosphorylated in an insulin-dependent manner at high insulin concentrations. These results suggest that in this patient the biosynthesis of 190-kD receptor precursor, its terminal glycosylation, and intracellular transport to the cell surface proceed normally, while proteolytic maturation to alpha and beta subunits does not occur. We postulate that this defect either results from mutation(s) within the insulin-receptor gene, which render the precursor resistant to cleavage, or from a defect in the receptor processing enzyme.

Stimulatory activity on prostacyclin production decreases in sera from streptozotocin-induced diabetic rats

We recently reported that serum stimulatory activity on prostacyclin (PGI2) production by cultured bovine aortic endothelial cells decreased in noninsulin-dependent diabetic patients. In the present study, this activity was compared in streptozotocin-induced (STZ) diabetic rats and controls. Platelet-poor plasma-derived serum (PDS) from Wistar male rats stimulated 6-keto-PGF1 alpha production (a stable metabolite of PGI2) by cultured bovine aortic endothelial cells, rat lung fibroblasts, and rat aortic rings in a time- and dose-dependent manner. Namely, PDS from rats has a stimulatory activity on PGI2 production (PGI2 stimulatory activity; PSA). Furthermore, PSA in PDS from STZ diabetic rats (n = 12) significantly decreased as compared with that from control rats (n = 10) using three types of in vitro systems. The reduction in PDS-stimulated PGI2 production by the vascular wall may lead to platelet hyperaggregation and thrombus formation in diabetics, which is considered to be involved in the pathogenesis of diabetic macro- or microangiopathy.

Effect of glibenclamide on pancreatic hormone release from isolated perifused islets of normal and cysteamine-treated rats

The effect of glibenclamide, a sulfonylurea agent, on islet hormone secretion, particularly on glucagon was studied using isolated perifused pancreatic islets of normal and cysteamine-treated rats. In normal rat islets, glibenclamide enhanced both insulin and somatostatin release in normoglycemic (50 mg/dL) and glucopenic (0 mg/dL) states, as well as under the condition of arginine stimulation. In contrast, glibenclamide stimulated glucagon release only transiently, then suppressed it in a sustaining manner in each state. In the cysteamine-treated islets, as expected, somatostatin concentrations in the perifusate remained unchanged during the infusion of arginine and/or glibenclamide. Under this condition, glibenclamide enhanced insulin release to the same extent as seen in normal islets, and again markedly inhibited glucagon release. These observations indicate that in isolated perifused rat pancreatic islets, glibenclamide suppresses glucagon secretion independently of D cell stimulation. It is concluded that glibenclamide may exert its inhibitory effect directly on A cell rather than through paracrine action of concomitant somatostatin release, and that the suppression of glucagon secretion by glibenclamide may, in part, contribute to the antidiabetogenic effect of this compound.

Conjugal transfer of hydrogen-oxidizing ability of Alcaligenes hydrogenophilus to Pseudomonas oxalaticus

Conjugal transfer of hydrogen-oxidizing ability (Hox) of the hydrogen bacterium Alcaligenes hydrogenophilus was examined. Intraspecific cross of plasmid pHG21-a that encodes hydrogenases that mediate hydrogen oxidation was most frequent at 25 C; the optimal temperature for growth was 30 C. The plasmid could be transferred from A. hydrogenophilus to Pseudomonas oxalaticus OX1 and OX4, and the resulting strains gained the capacity for autotrophic growth with H2 and CO2. Plasmid pHG21-a was maintained in P. oxalaticus OX1 and OX4 as stably as in A. hydrogenophilus.

Isolation of hydrogen-oxidation gene from Alcaligenes hydrogenophilus and its expression in Pseudomonas oxalaticus

A gene bank of a megaplasmid encoding the hydrogen-oxidizing enzyme system (Hox) in Alcaligenes hydrogenophilus was constructed using a broad host range cosmid vector pVK102, and established in Escherichia coli. Hybrid cosmids containing hox genes were identified by transferring the bank into Pseudomonas oxalaticus OX1 and screening colonies for the ability of H2-dependent autotrophic growth. About 800 colonies were formed under autotrophic conditions. One of the Hox+ transconjugants was isolated and its hydrogenases activities were measured. Although soluble hydrogenase was not detected, the Hox+ transconjugant had four times the membrane-bound hydrogenase activity of A. hydrogenophilus.

Plasma fibronectin and platelet aggregation in diabetes mellitus

Plasma fibronectin (FN) is a high-molecular weight glycoprotein produced by endothelial cells, fibroblasts, and other mesenchymal cells. Plasma FN levels were measured in non-insulin-dependent diabetics (NIDDM) (n = 42) and compared with age-matched control subjects (n = 20). Plasma FN levels were significantly higher in the NIDDM patients (44.2 +/- 2.2 mg/dl, mean +/- SE) than in the control subjects (31.2 +/- 2.2 mg/dl). In addition, the rate of platelet aggregation was studied in 23 of the 42 NIDDM patients. Interestingly, the plasma FN levels were significantly elevated, particularly in diabetic patients with enhanced platelet aggregation. It is suggested that elevated plasma FN may be closely related to the abnormality of platelet function in diabetics, which leads to diabetic vascular lesions.

Reduced serum-stimulatory activity on prostacyclin production by cultured aortic endothelial cells in diabetes mellitus

Reduced prostacyclin (PGI2) production by the vascular wall has been proposed as a possible cause of macro- or microangiopathy in diabetes mellitus. In the present study, we confirmed the stimulatory activity on PGI2 (PSA) production in plasma-derived serum (PDS) by cultured aortic endothelial cells. Furthermore, the abnormality of PSA was examined in diabetic PDS. PSA in PDS from non-insulin-dependent diabetics significantly decreased as compared with that in PDS from age-matched control subjects. There was no difference in PSA in PDS between diabetic patients with and without vascular complications such as retinopathy and nephropathy. In addition, after treatment with dialysis, PSA in diabetic PDS was still not restored to that in normal PDS. These findings suggest that relatively heat-stable (56 degrees C, 30 min) and nondialyzable PGI2 stimulatory substance(s) may decrease in diabetic PDS. It is concluded that a reduction in PDS-stimulated PGI2 production by the vascular wall can play an important role in the pathogenesis of vascular lesions in diabetes mellitus.

Abnormalities of platelet-derived growth factors in insulin-dependent diabetes

Platelets are involved in homeostasis of the vascular wall at various levels. An important feature of this involvement is the potential for platelet proliferation. Platelets from normal subjects contain platelet-derived growth factor (PDGF), epithelial growth factor (EGF), and transforming growth factor. We have detected the presence of an excessive growth-promoting activity in the heated supernatant fraction derived from the platelets of young, insulin-dependent diabetics. This activity is most pronounced when measured in cultures of smooth muscle cells and fibroblasts. This activity may be further separated into cationic and anionic fractions by ion exchange chromatography of the platelet-rich supernatant. The cationic factor corresponds to PDGF, whereas the anionic factor appears to be identical to EGF. Chronic, intensive insulin therapy normalizes the excessive growth-promoting activity of platelets from diabetics. Further studies are needed to evaluate the differential release of those growth-promoting factors found in platelets of normal subjects and in patients with vascular disease.

Effect of prostaglandin synthetase inhibitors on platelet aggregation and thromboxane production in diabetes mellitus

Platelet aggregation is known to be increased in diabetes mellitus, and the enhanced thromboxane production has been shown to be one of the causes of such abnormal platelet function. To investigate which step is activated in diabetic prostaglandin metabolism, three specific inhibitors of prostaglandin synthetases were used in this study, which were mepacrine, indomethacin and imidazole. Platelet aggregation induced by collagen was significantly increased accompanying enhanced thromboxane production in diabetics with proliferative retinopathy compared with age matched controls. Platelet aggregation in diabetics with proliferative retinopathy was less inhibited by the addition of each inhibitor compared with controls. However, there was no difference in inhibitory pattern of platelet aggregation among the three inhibitors. In addition, thromboxane production during aggregation in diabetics with proliferative retinopathy was significantly greater than that in controls by the addition of each inhibitor. Inhibitory patterns of thromboxane production did not differ among the addition of three inhibitors. It is concluded that enhanced thromboxane production resulting in enhanced platelet aggregation would be related to diabetic vascular complications. This abnormal prostaglandin production can be due to the activation of general steps in prostaglandin metabolism in diabetic platelets, not of a specific enzyme.

Effect of vitamin E on platelet aggregation in diabetes mellitus

Vitamin E is known to be an inhibitor of platelet prostaglandin production and aggregation. The rate of platelet aggregation induced by adenosine diphosphate was significantly increased in diabetics with proliferative retinopathy and the enhanced production of thromboxane B2, a stable metabolite of thromboxane A2, was demonstrated in those patients. On the other hand, vitamin E in platelets was significantly reduced in diabetics compared with age matched controls. In addition, it was shown that vitamin E content in platelets examined in diabetic and control subjects inversely correlated with both the rate of platelet aggregation and thromboxane B2 production during aggregation. It is suggested that the reduced vitamin E levels in diabetic platelets can contribute to the mechanisms of the enhanced platelet thromboxane production and aggregation which relate to the development of vascular complications.