Agouti-related protein is a mediator of diabetic hyperphagia

To explore the role of agouti-related protein (AGRP) in diabetic hyperphagia changes in hypothalamic AGRP mRNA levels were examined in diabetic rats. Rats rendered diabetic by streptozotocin displayed marked hyperglycemia (blood glucose 456.0+/-8.4 mg/dl versus 71.8+/-1.9 mg/dl) and hyperphagia (36.9+/-1.0 g/day versus 22.0+/-0.4 g/day), that was associated with a 286.6+/-4.4% increase in hypothalamic AGRP mRNA and a 178.9+/-13.5% increase in hypothalamic NPY mRNA. Insulin treatment of diabetic rats partially corrected blood glucose (147.4+/-13.1 mg/dl) and ameliorated hyperphagia (26.6+/-2.0 g/day). Insulin replacement was also associated with a return of hypothalamic AGRP mRNA (111.7+/-8.3% of controls) and NPY mRNA (125.0+/-8.9% of controls) from the elevated levels that were observed in untreated diabetic rats. In contrast to insulin treated rats, sodium orthovanadate treated diabetic rats remained significantly hyperglycemic (361.5+/-12.5 mg/dl). However, despite their persistent hyperglycemia, orthovanadate treated diabetic rats were still observed to have a significant reduction of hypothalamic AGRP mRNA (138.7+/-11.4%) and NPY mRNA (129.9+/-9.8%). Simultaneous measurement of serum leptin revealed suppressed levels in both untreated diabetic (0.5+/-0.1 ng/ml) and sodium orthovanadate treated rats (0.5+/-0.1 ng/ml) compared to non-diabetic controls (2.1+/-0.1 ng/ml). These data indicate that AGRP is a mediator of diabetic hyperhpagia and suggest that insulin can directly influence hypothalamic AGRP and NPY mRNA expression.     

Changes in insulin response to glucose after exercise training in partially pancreatectomized rats

The effects of exercise training on glucose-stimulated insulin secretion (GSIS) were studied in male Sprague-Dawley rats made mildly to severely diabetic by partial pancreatectomy. Exercise trained (10 wk treadmill; T) and untrained (Unt) rats were grouped according to posttraining fed-state hyperglycemia as follows: T less than 200 and Unt less than 200 (glucose concn less than 200 mg/dl), T 200-300 and Unt 200-300 (glucose concn 200-300 mg/dl), and T greater than 300 and Unt greater than 300 (glucose concn greater than 300 mg/dl). After exercise training, hyperglycemic glucose clamps were performed in awake rats by elevation of arterial blood glucose concentration 126 mg/dl above fasting basal levels for 90 min. Exercise training significantly increased muscle citrate synthase activity. Prevailing hyperglycemia was reduced during the 10-wk exercise training period in all T rats with fed-state glucose concentrations less than 300, and only 53% of Unt rats in these groups had reduced glycemia. GSIS was significantly higher in T less than 200 [2.4 +/- 0.7 (SD) ng/ml at 90 min] than in Unt less than 200 (1.5 +/- 0.3). A similar response was found for T 200-300 (1.1 +/- 0.3 ng/dl) vs. Unt 200-300 (0.7 +/- 0.1) but not T greater than 300 (0.36 +/- 0.2) vs Unt greater than 300 (0.44 +/- 0.05). Sham-operated control rats had insulin concentrations of 6.6 +/- 1.6 ng/ml at the 90th min of the clamp. Acute exercise reduced fed-state glycemia in rats with mild-to-moderate (less than 300 mg/dl) diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth hormone and carbohydrate intolerance in cirrhosis

Patients with cirrhosis of the liver often have insulin resistance and elevated circulating growth hormone levels. This study was undertaken (a) to evaluate glucose intolerance, insulin resistance and abnormal growth hormone secretion and (b) to determine if GH suppression improves insulin resistance. Glucose tolerance tests (GTT), intravenous insulin tolerance tests (IVITT), arginine stimulation tests (AST) and glucose clamp studies before and during GH suppression with somatostatin were performed in a group of patients with alcohol-induced liver cirrhosis. During GTT cirrhotic subjects had a 2-hour plasma glucose of 200 +/- 9.8 ng/dl (N = 14) compared to 128 +/- 8.0 ng/dl in normal controls (N = 15), P less than 0.001. Basal GH was elevated in cirrhotic patients and in response to arginine stimulation reached a peak of 17.0 +/- 5.4 ng/ml (N = 7), compared to a peak of 11.3 +/- 1.8 ng/ml in 5 normal controls (P = NS). During IVITT patients with cirrhosis had a glucose nadir of 60.0 +/- 4.0 mg/dl (N = 9), compared to 29.0 +/- 7.0 mg/dl in controls (N = 5), P less than 0.001. Peak GH levels during IVITT were not significantly different in cirrhotics and controls. Glucose utilization rates in 4 patients with cirrhosis of the liver before somatostatin mediated GH suppression was 3.1 +/- 0.5 mg/kg/min and 6.5 +/- 1.5 mg/kg/min during somatostatin infusion, P less than 0.025. We conclude that patients with alcohol induced cirrhosis have sustained GH elevations resulting in insulin resistance which improves after GH suppression.     

Interaction of caerulein, glucose, and amino acids on insulin secretion from the perfused rat pancreas

The effect of caerulein on insulin response to graded amounts of glucose from the isolated perfused rat pancreas was investigated in the presence or absence of an amino acids mixture. Caerulein at a concentration of 0.1 ng/ml which is a submaximal concentration for an effect on exocrine pancreatic secretion potentiated insulin responses to glucose concentrations less than 200 mg/dl, but produced no further increase when added to a glucose stimulus over a 200 mg/dl. However, in the presence of amino acids the insulin response to 200 mg/dl glucose was significantly potentiated by the stimulation of 0.1 ng/ml caerulein. The effectiveness of caerulein as an insulinotropic agent depended on the glucose concentration only when amino acids were present. These results indicate that caerulein, at a concentration which stimulate pancreatic exocrine secretion, has a synergistic effect on insulin response to glucose and amino acids and therefore raises the possibility that endogenously released CCK may contribute to the entero-insular axis.     

Effect of a high protein diet on glucose tolerance in the rat model

The purpose of this study was to determine the effects of a high protein diet on glucose tolerance. Nine Sprague Dawley rats received a high protein (HP) diet (65% protein, 35% fat) and eight rats consumed a standard chow (SC) diet over eight weeks. Oral glucose tolerance tests (OGTT) were performed at the end of the third and the seventh week. The diet did not effect glucose tolerance in the first (SC=10357+/-294 mg/dl/120 min; HP=9846+/-300 mg/dl/120 min) or the second OGTT (SC=10134+/-395 mg/dl/120 min; HP=10721+/-438 mg/dl/120 min) as reflected by the area under the glucose concentration curve. Similarly, the area under the insulin concentration curve was not effected by the high protein diet during the first (SC=49.21+/-8.46 ng/ml/120 min; HP=41.75+/-10.54 ng/ml/120 min) or the second OGTT (SC=96.63+/-13.68 ng/ml/120 min; HP=92.77+/-17.44 ng/ml/120 min). The high protein diet group experienced a delayed glucose response for the first (SC=30 min at 112+/-7 mg/dl; HP=60 min at 101+/-5 mg/dl) and second OGTT (SC=15 min at 117+/-5 mg/dl; HP=60 min at 95+/-7 mg/dl). Body mass increased to the same extent in each diet group from the initial to final weighing (SC=159+/-2 g to 254+/-7 g; HP=157+/-2 g to 242+/-7 g). Despite a delay in peak glucose response, these findings suggest that glucose tolerance and body mass were neither adversely nor positively affected by a high protein diet.     

Increased insulin-insensitive glucose transport in polymorphonuclear leukocytes from non-insulin-dependent diabetic patients.

We studied the transport rate of a non-metabolizable hexose analogue, 3-O-methyl-D-glucose, in polymorphonuclear leukocytes (insulin-insensitive cells) from patients with untreated non-insulin-dependent diabetes mellitus. The mean glucose transport rate was significantly elevated in the diabetic patients compared with healthy controls (13.3 +/- 3.7 vs 10.4 +/- 2.5 fl/cell.sec, mean +/- SD, p less than 0.01). In the diabetic subjects, glucose transport rates were positively correlated with HbA1c levels (r = 0.563, p less than 0.01) but had no relations with ambient plasma glucose concentrations. Short-term incubation with 20 mM D-glucose had no effect on glucose transport in those cells. When glucose transport rates, HbA1c and fasting plasma glucose levels were simultaneously measured at weekly intervals over a four-week period in three diabetic subjects, the alterations in transport rates generally paralleled the changes observed in HbA1c levels rather than plasma glucose concentrations. It can be concluded that unlike insulin-sensitive cells such as adipocytes and muscle, glucose transport in human polymorphonuclear leukocytes, which are insulin insensitive cells, is increased in patients with non-insulin-dependent diabetes mellitus. Long-term, not short-term, derangement of glucose metabolism seems to be associated with increased glucose transport rate found in those patients.     

Growth hormone secretion, serum, and cerebral spinal fluid insulin and insulin-like growth factor-I concentrations in pigs with streptozotocin-induced diabetes mellitus.

Diabetes mellitus was induced using streptozotocin in five gilts between 8 and 12 weeks of age. Gilts were maintained with exogenous insulin (INS) except during experimental periods. Four litter-mate gilts served as controls. At 9 months of age, all gilts were ovariectomized, and 30 days after ovariectomy, Experiment (Exp) 1 was conducted. Jugular vein catheters were inserted and blood samples were collected every 10 min for 8 hr. Experiment 2 was conducted when gilts were 11 months of age. Venous blood and cerebrospinal fluid (CSF) samples were collected in the absence (Phase I) or presence (Phase II) of INS therapy. In Experiment 1, plasma glucose concentrations were greater (P < 0.05) in diabetic (465 +/- 17 mg/100 ml) than in control (82 mg +/- 17 mg/100 ml) gilts, whereas serum INS was lower (P < 0.0001) in diabetic gilts (0.3 +/- 0.02 vs 0.9 +/- 0.05 ng/ml) and insulin-like growth factor-I was similar in diabetic and control gilts (32 +/- 3 vs 43 +/- 4 ng/ml, respectively). Mean serum GH concentration was 2-fold greater (P < 0.02) in diabetics (2.8 +/- 0.4 ng/ml) than in control gilts (1.2 +/- 0.2 ng/ml). Diabetic gilts exhibited a greater (P < 0.05) number of GH pulses than control gilts (3.2 +/- 0.4 vs 1.5 +/- 0.3/8 hr, respectively). In addition, GH pulse magnitude was markedly elevated (P < 0.02) in diabetic (5.8 +/- 0.4 ng/ml) compared with control gilts (3.3 +/- 0.6 ng/ml). Mean basal serum GH concentrations were greater (P < 0.07) in diabetic (2.2 +/- 0.5 ng/ml) compared with control gilts (1.0 +/- .1 ng/ml). In Experiment 2, CSF concentrations of insulin-like growth factor-I, INS, GH, and protein were similar for diabetic and control gilts in both phases. Serum GH levels were similar for diabetics and controls in Phase I, but were greater (P < 0.05) in diabetics than in controls in Phase II. CSF glucose levels were greater in diabetic than in control gilts in both the presence (P < 0.003) and absence (P < 0.0002) of INS therapy, whereas plasma glucose was greater (P < 0.003) in diabetic than in control gilts in the absence of INS, but returned to control concentrations in the presence of INS. However, serum GH levels were unchanged after INS therapy in the diabetic gilts. In conclusion, altered GH secretion in the diabetic gilt may, in part, be due to elevated CSF glucose concentrations, which may alter GH-releasing hormone and/or somatostatin secretion from the hypothalamus.     

Oxidative DNA damage and plasma antioxidant capacity in type 2 diabetic patients with good and poor glycaemic control

Diabetes mellitus is a complex metabolic disorder characterized by a disturbance in glucose metabolism. Recent evidence suggests that increased oxidative damage as well as reduction in antioxidant capacity could be related to the complications in patients with type 2 diabetes. The aim of this study was to measure plasma antioxidant status in type 2 diabetic patients with good and poor glycaemic control and its relationship with oxidative DNA damage. Thirty-nine type 2 diabetic patients and eighteen healthy subjects were recruited for this study. We found that diabetic patients had slightly, but not significantly lower antioxidant capacity, measured with the "ferric reducing ability of plasma" (FRAP) assay, than healthy subjects. On the contrary, oxidative DNA damage (measured by the Comet assay) in leukocytes obtained from diabetic patients was significantly higher compared to healthy subjects. Taking into account glucose control, we found that the FRAP level was significantly (p<0.05) lower in diabetic subjects with poor glycaemic control than healthy subjects, while patients with good glycaemic control had FRAP values similar to controls. We also observed an unexpected positive correlation between FRAP values and oxidative DNA damage in diabetic patients; moreover, a positive correlation was found between FRAP and glucose level or HbA(1c) in patients with poor glycaemic control. In conclusion, our results confirm that patients with type 2 diabetes have a higher oxidative DNA damage than healthy subjects and that plasma antioxidant capacity is significantly lower only in patients with poor glycaemic control, moreover, in these patients FRAP values are positively correlated with glycaemic levels and HbA(1c). These observations indicate that a compensatory increase of the antioxidant status is induced as a response to free radical overproduction in type 2 diabetes. Therefore, the addition of antioxidant supplements to the current pharmacological treatment could have potentially beneficial effects in diabetic patients with poor glycaemic control.     

An internal standard method for the unattended high-performance liquid chromatographic analysis of ascorbic acid in blood components

A paired-ion, reversed-phase, high-performance liquid chromatography procedure using electrochemical detection and internal standard quantitation based on isoascorbic acid (IA) is described for the determination of ascorbic acid (AA) in blood cells and plasma. By correcting for vial-to-vial variations in the AA oxidation rate, use of IA as an internal standard overcomes a major problem associated with AA instability and eliminates the necessity of assaying samples immediately after they are prepared for analysis. The ion-pairing agent, dodecyltriethylammonium phosphate, gives improved AA-IA resolution over agents with shorter carbon chains and also eliminates the interference of an unidentified substance extracted with platelet AA. Five percent metaphosphoric acid extracts of mononuclear leukocytes (MN), polymorphonuclear leukocytes (PMN), platelets, or plasma were mixed with the IA internal standard and diluted with an EDTA-cysteine solution. The samples were placed in a refrigerated autosampler at 4 degrees C prior to chromatography on a 5-microns octadecylsilyl column. AA concentrations (mean +/- SD) in platelets, MN, and PMN from six healthy volunteers were 0.25 +/- 0.05, 15.2 +/- 6.28, and 2.43 +/- 1.63 micrograms/10(8) cells, respectively; the mean plasma AA concentration was 0.97 +/- 0.34 mg/dl. All are in good agreement with published values. Refrigerated sample extracts containing the internal standard can be reassayed up to 3 weeks later with negligible change in calculated AA concentration. Up to 70 samples can be assayed per day with a detection limit (3 X SD) and minimum quantifiable level (less than 5% coefficient of variation) of 0.02 and 0.2 ng/injection, respectively.     

Semen traits and metabolic and gonadotropic hormone profiles in ram lambs treated with glucose

Two experiments were conducted to examine reproductive and endocrine responses of ram lambs to exogenous glucose. In Experiment 1, three ram lambs (6 mo of age) received 100 ml ip of saline (0.9%) daily and three animals received 50 g glucose (100 ml 50% dextrose) daily for 18 d. In Experiment 2, ten lambs (5 per group) were treated similarly for 10 d. Serum samples were collected intensively before and after GnRH treatment on the last day of both experiments. After 15 d of glucose treatment in Experiment 1, treated rams weighed 58 kg compared with 68 kg for the controls (P = 0.08). A similar numerical trend was observed in Experiment 2, suggesting that intraperitoneal glucose decreases feed intake. In both experiments, 50 g of glucose induced a rapid elevation in serum glucose to greater than 120 mg/dl compared with 70 to 80 mg/dl for the controls (P < 0.05). Serum insulin rose to over 6 ng/ml in both trials in lambs receiving glucose compared with values of about 2 ng/ml for the controls (P < 0.01). Serum growth hormone was not altered (P > 0.10) by glucose in either experiment and IGF-1 was similar (P > 0.20) between groups in Experiment 2. Although serum concentrations of prolactin tended (P = 0.14) to be reduced by glucose treatment (64 +/- 21 ng/ml) compared with that of the controls (120 +/- 21 ng/ml) in Experiment 1, the opposite trend (P = 0.20) was observed in Experiment 2. Serum thyroxine was elevated (P = 0.08) in glucose-treated rams compared with that in controls in Experiment 2 but triiodothyronine concentrations were similar (P > 0.80) between groups. In Experiment 1, area under the curve (AUC) for LH after a GnRH challenge tended (P = 0.14) to be greater in glucose-treated (1,351 units) than in control (999 +/- 139 units) animals. The AUC for FSH (Experiment 1) did not differ (P = 0.30) between groups. The LH AUC in Experiment 2 was about 2,500 units for both groups (P = 0.80). The AUC for testosterone in Experiment 1, was 5,452 and 2,597 (+/- 1051) units for rams treated with 0 and 50 g glucose/d (P = 0.13), but testosterone AUC in Experiment 2 was similar between groups (P > 0.70). No effect of exogenous glucose was evident in either experiment for semen traits. Results suggest that 50 g ip glucose daily for 10 or 18 d induced large increases in serum insulin but other metabolic and reproductive hormones were not greatly influenced.     

Urinary platelet-activating factor excretion is elevated in non-insulin dependent diabetes mellitus.

Proteinuria is currently considered a very sensitive predictor of diabetic nephropathy, but 20-25% of all diabetic patients with negative Albustix reaction excrete higher than normal (< 20 mg/24 h) amounts of albumin in their urine. It is our hypothesis that platelet-activating factor (PAF), a potent glycerophospholipid that acts as a chemical mediator for a wide spectrum of biological activities, including increased vascular permeability, may be produced in significant amounts during periods preceding microalbuminuria. In this study, we compared urinary PAF excretion in Mexican-American subjects who were diagnosed with non-insulin dependent diabetes mellitus (NIDDM) with their healthy control counterparts. The age of the NIDDM subjects (45.9 +/- 2.1 years) was not significantly different from the healthy control group, which was 39.4 +/- 2.7 years (P < 0.0672). The NIDDM subjects (body mass index, 29.9 +/- 1.1 compared to 26.1 +/- 0.9 kg/m2 in healthy controls) were characterized by significantly increased (P < 0.05) fasting plasma glucose (192 +/- 11 vs. 97 +/- 4 mg/dl in healthy controls), fasting insulin (20.9 +/- 2.4 vs. 12.3 +/- 1.6 microU/ml), fasting C-peptide (2.93 +/- 1.26 vs. 1.48 +/- 0.51 ng/ml), and hemoglobin A1c (10.3 +/- 0.7 vs. 5.6 +/- 0.3%), respectively. The urine output for the NIDDM and control subjects were 1942 +/- 191 ml/24 h and 1032 +/- 94 ml/24 h, respectively, and urinary albumin excretion (UAE) rates were estimated to be 38 +/- 7 micrograms/min and 11 +/- 1 micrograms/min, respectively. The NIDDM subjects produced significantly increased levels of urinary PAF (2606.3 +/- 513.1 ng/24 h compared with 77.9 +/- 14.1 ng/24 h in controls (or 1706.3 +/- 420.8 ng/ml compared with 85.4 +/- 17.8 pg/ml of urine, in NIDDM and control subjects, respectively). We found that urinary PAF excretion was significantly correlated with microalbumin excretion (r = 0.7) especially at UAE rates greater than 30 mg/day and more importantly, some NIDDM patients with negative Albustix reaction (i.e. normal UAE) produced significantly more PAF, suggesting that PAF excretion may precede microalbuminuria and that subtle injury to the kidneys are present in NIDDM long before overt albuminuria ensues, urinary PAF measurements could potentially therefore serve as a sensitive indicator of renal injury in diabetes mellitus. These results lend further credence to our hypothesis that PAF may be the biochemical compound linking the various members of the insulin resistance syndrome.     

Serum Magnesium and Atherogenic Lipid Fractions in Type II Diabetic Patients of Lahore, Pakistan

This study was conducted to determine the prevalence of hypomagnesemia and its effect on the lipid profile of local type II diabetic patients. For this purpose, 219 diabetic patients and 100 age-matched control subjects were enrolled. Blood samples of the subjects were analyzed for fasting glucose, Mg, triglyceride, total cholesterol, HDL-cholesterol, and LDL-cholesterol. Results showed that mean serum values of these parameters were differing in diabetic patients as compared to control subjects. The reference range of serum magnesium in healthy controls was 1.2-4.4 mg/dl. Mean serum magnesium in diabetic patients was significantly lower as compared to healthy subjects (1.6 ± 0.23 mg/dl vs. 2.8 ± 0.8 mg/dl). Among diabetic patients, 143 (65.3%) had serum magnesium level below 1.7 mg/dl (hypomagnesemia). The corresponding figure for control subjects was 11 (11%). The difference was significant (p < 0.01). Diabetes mellitus patients with current hyperglycemic status had significantly lower serum Mg as compared to euglycemic patients (p = 0.05). Serum Mg in diabetic patients was correlated with all lipid parameters. Among them, HDL-cholesterol was significantly (p < 0.05) positively correlated (r = 0.34), while total cholesterol and LDL-cholesterol was negatively correlated, albeit non-significantly, with serum Mg. These results demonstrate that hypomagnesemia is accompanied by atherogenic alterations in the lipid profiles of type II diabetic patients of Lahore, Pakistan.     

Retinal photocoagulation does not influence intraocular levels of IGF-I, IGF-II and IGF-BP3 in proliferative diabetic retinopathy-evidence for combined treatment of PDR with somatostatin analogues and retinal photocoagulation?

Retinal photocoagulation reduces the incidence of severe visual loss in proliferative diabetic retinopathy (PDR). Reduced levels of VEGF/VPF might result in an improved function of the blood-retina barrier and cause a decrease of blood derived intraocular growth factors such as IGF-I. This study investigates whether retinal photocoagulation is able to normalize the concentrations of IGF-I, IGF-II and IGF-BP3 in the vitreous humor of patients undergoing vitrectomy. Levels of IGFs and the permeability marker, albumin, were measured in serum and vitreous of 52 patients. Three groups were compared: controls without proliferating eye disease (n = 19) and patients with PDR with (PDR+; n = 25) and without (PDR-; n = 8) previous retinal photocoagulation. IGF-I, IGF-II, IGF-BP3 and albumin were determined by immunological methods and were confirmed to be increased in patients with PDR compared to controls. Retinal photocoagulation influenced neither the intraocular concentration of the permeability marker albumin (PDR+: 253.2 +/- 46 mg/dl; PDR-: 256.4 +/- 66.5 mg/dl) nor the levels of IGFs (PDR+: IGF-I: 1.2 +/- 0.1 ng/ml; p = 0.38; IGF-II: 34.8 +/- 2.2 ng/ml; p = 0.1; IGF-BP3: 75.7 +/- 9.7 ng/ml; p = 0.27; PDR-: IGF-I: 1.1 +/- 0.2ng/ml; IGF-II: 29.3 +/- 5.2 ng/ml; IGF-BP3: 61.5 +/- 18.3 ng/ml). Systemic levels of albumin and IGFs were not changed significantly by retinal photocoagulation. These results demonstrate that previous retinal photocoagulation in patients undergoing vitrectomy does not functionally reestablish the blood-retina barrier despite decreases in VEGF/VPF. The lack of influence on intraocular concentrations of the serum-derived growth factors, IGF-I, IGF-II and IGF-BP3, might in part explain the failure of previous photocoagulation in the investigated patients. These results suggest that a combined treatment with retinal photocoagulation and growth hormone-lowering drugs, such as somatostatin analogues, could be a useful treatment, which may prevent further loss of visual acuity in patients with PDR.     

Leptin in type 2 diabetic or myotonic dystrophic women.

BACKGROUND: Insulin resistance is an important determinant of circulating leptin concentrations in humans, but its independent contribution on plasma leptin levels are controversial. In the present study, we characterized plasma leptin levels and their regulation in women with 2 different insulin resistance states: type 2 diabetes and myotonic dystrophy disease, and in controls. MATERIAL AND METHODS: We studied 3 groups of women: 21 type 2 diabetic patients, 20 myotonic dystrophic patients and a control group of 20 normoglycemic subjects, matched in age and body mass index. Body composition, fasting glucose and insulin, IGF-I, IGF-binding protein-3 and leptin were studied. Body composition was measured using a bioelectrical impedance analyser. Insulin sensitivity (in percentage) was modeled according to a computer-based homeostasis model assessment model. Data are expressed in mean +/- SEM. RESULTS: In both groups of patients, glucose concentrations were higher in type 2 diabetic patients than in myotonic dystrophic patients, and insulin concentrations and insulin sensitivity were similar in the 2 groups of patients (82.4 +/- 18.6% in type 2 diabetic patients vs. 69.7 +/- 9.7% in myotonic dystrophic patients, p = 0.2) and lower than in controls. Serum leptin and leptin/fat mass ratio were higher in myotonic dystrophic patients than in type 2 diabetic patients (30 +/- 4.9 ng/ml vs. 17.7 +/- 2.6 ng/ml, p = 0.03 and 2.32 +/- 0.69 ng/ml/kg vs. 1.07 +/- 0.2 ng/ml/kg, p = 0.02, respectively) or those found in controls. In type 2 diabetic patients, leptin concentrations were correlated with body mass index and body fat, and in myotonic dystrophic patients leptin concentrations were correlated with age, body mass index, fasting insulin and lower insulin sensitivity, whereas leptin concentrations were not correlated with body fat. CONCLUSIONS: These findings suggest that leptin concentrations and regulation in myotonic dystrophic patients are different from type 2 diabetes.     

Plasma soluble intercellular adhesion molecule 1 levels are increased in type 2 diabetic patients with nephropathy

BACKGROUND/AIM: Intercellular adhesion molecule 1 (ICAM-1) is a mediator in the recruitment of leukocytes in the glomerular cells. The role of ICAM-1 in diabetic complications is still a matter of debate. This study was performed to investigate the relation of plasma soluble ICAM-1 (sICAM-1) to nephropathy in patients with type 2 diabetes mellitus. METHODS: Ninety-three patients (24 males and 69 females) with type 2 diabetes mellitus were included into the study. Fifty patients had nephropathy, and 43 were free from nephropathy. Fifty healthy subjects (14 males and 36 females) served as the control group (group 1). Twenty-five of the diabetic patients had microalbuminuria (group 2), 25 had macroalbuminuria (group 3), and 43 had neither micro- nor macroalbuminuria (group 4). The plasma sICAM-1 levels were measured in blood samples drawn after fasting. RESULTS: The mean plasma sICAM-1 levels were not different in the 93 diabetic patients as compared with the healthy controls (392.7 +/- 119.5 vs. 350.1 +/- 90.2 ng/ml, p > 0.05). The mean sICAM-1 level was significantly higher in the diabetic patients with nephropathy than in those without nephropathy (430.3 +/- 78.2 vs. 368.2 +/- 122.5 ng/ml, p = 0.03) and in the controls (430.3 +/- 78.2 vs. 350.1 +/- 90.2 ng/ml, p = 0.016). The difference in sICAM-1 levels between groups 2 and 3 was not significant (p > 0.05). The plasma sICAM-1 levels were significantly higher in both groups 2 and 3 than in both groups 1 and 4 (434.5 +/- 129.2 vs. 427.2 +/- 113.7 ng/ml and 368.2 +/- 122.5 vs. 350.1 +/- 90.2 ng/ml, respectively). CONCLUSIONS: The plasma sICAM-1 levels in patients with type 2 diabetes mellitus are not significantly different from those in nondiabetic subjects. High levels of sICAM-1 suggest that sICAM-1 may play a role in the development of nephropathy in patients with type 2 diabetes mellitus.     

High-dose oral vitamin C partially replenishes vitamin C levels in patients with Type 2 diabetes and low vitamin C levels but does not improve endothelial dysfunction or insulin resistance

Endothelial dysfunction is a hallmark of Type 2 diabetes related to hyperglycemia and oxidative stress. Nitric oxide-dependent vasodilator actions of insulin may augment glucose disposal. Thus endothelial dysfunction may worsen insulin resistance. Intra-arterial administration of vitamin C improves endothelial dysfunction in diabetes. In the present study, we investigated effects of high-dose oral vitamin C to alter endothelial dysfunction and insulin resistance in Type 2 diabetes. Plasma vitamin C levels in 109 diabetic subjects were lower than healthy (36 +/- 2 microM) levels. Thirty-two diabetic subjects with low plasma vitamin C (<40 microM) were subsequently enrolled in a randomized, double-blind, placebo-controlled study of vitamin C (800 mg/day for 4 wk). Insulin sensitivity (determined by glucose clamp) and forearm blood flow in response to ACh, sodium nitroprusside (SNP), or insulin (determined by plethysmography) were assessed before and after 4 wk of treatment. In the placebo group (n = 17 subjects), plasma vitamin C (22 +/- 3 microM), fasting glucose (159 +/- 12 mg/dl), insulin (19 +/- 7 microU/ml), and SI(Clamp) [2.06 +/- 0.29 x 10(-4) dl x kg(-1) x min(-1)/(microU/ml)] did not change significantly after placebo treatment. In the vitamin C group (n = 15 subjects), basal plasma vitamin C (23 +/- 2 microM) increased to 48 +/- 6 microM (P < 0.01) after treatment, but this was significantly less than that expected for healthy subjects (>80 microM). No significant changes in fasting glucose (156 +/- 11 mg/dl), insulin (14 +/- 2 microU/ml), SI(Clamp) [2.71 +/- 0.46 x 10(-4) dl x kg(-1) x min(-1)/(microU/ml)], or forearm blood flow in response to ACh, SNP, or insulin were observed after vitamin C treatment. We conclude that high-dose oral vitamin C therapy, resulting in incomplete replenishment of vitamin C levels, is ineffective at improving endothelial dysfunction and insulin resistance in Type 2 diabetes.     

Vitamin D receptor activation in a diabetic-like environment: potential role in the activity of the endothelial pro-inflammatory and thioredoxin pathways

High blood and tissue concentrations of glucose and advanced glycation end products (AGEs) are thought to play an important role in the development of diabetic vascular complications. Thioredoxin interacting protein (TXNIP) is up-regulated in response to high levels of glucose and is an endogenous inhibitor of thioredoxin (TRX), and may play a contributory role in the occurrence of diabetic-related vascular diseases. Vitamin D inhibits endothelial proliferation and is a cardiovascular protective agent. The present study evaluated the impact of paricalcitol and calcitriol on the endothelial inflammatory and TXNIP pathways in cultured endothelial cells exposed to a diabetic-like environment. Fresh human umbilical vein cord endothelial cells (HUVEC) were treated for 24h with 200 μg/ml AGE-HSA and 250 mg/dl glucose concentrations, with paricalcitol or calcitriol. IL6, IL8, NFκB (p50/p65), receptor of AGE (RAGE), TXNIP, and TRX expressions were evaluated at the levels of mRNA, protein, and TRX activity. Calcitriol and paricalcitol significantly down-regulated the markers involved in the inflammatory responses. Only paricalcitol induced a significant decrease in TXNIP mRNA and protein expressions. Neither paricalcitol nor calcitriol affected TRX reductase activity or TRX mRNA and protein expressions. Our findings indicate that in an endothelial diabetic-like environment, paricalcitol and calcitriol significantly decreased the expression of genes involved in the inflammatory pathway. In this in vitro study, it seems that the TRX antioxidant system was not involved. The different effects found between paricalcitol and calcitriol might reflect the selectivity of vitamin D receptor (VDR) activation.     

Systemic levels contribute significantly to increased intraocular IGF-I, IGF-II and IGF-BP3 [correction of IFG-BP3] in proliferative diabetic retinopathy.

Increased intraocular levels of angiogenic growth factors such as insulin-like growth factor I (IGF-I) have been demonstrated in proliferative diabetic retinopathy (PDR). It is unclear whether increased leakage of the blood retina barrier or local synthesis primarily determine intraocular levels of IGFs in man, which is of special interest regarding possible therapeutic options with somatostatin analogues in PDR. This is the first study investigating parallelly serum and vitreous levels of IGF-I/II, IGF-BP3 and the liver-derived permeability marker albumin to determine in vivo the amount of circulation-derived intraocular IGFs. A control group without retinal proliferation and patients with PDR were compared. Levels of IGF-I/II, IGF-BP3 and albumin were determined by immunological methods. Vitreous levels of albumin were 2.2-fold elevated in patients with PDR (254.1 +/- 37.2mg/dl; n = 27; p = 0.0027) compared to controls (115.7 +/- 36.2mg/dl; n =10), whereas serum levels were slightly decreased in diabetes patients (5049 +/- 196 mg/dl vs. 4330 +/- 186 mg/dl; p = 0.0283). This was comparable to an increase of IGF-I/11 and IGF-BP3 in vitreous from PDR patients (IGF-I: 2.3 +/- 1.1 ng/ml p = 0.005. IGF-II: 37.9 +/- 4.9 ng/ml; p = 0.0003. IGF-BP3: 97.9 +/- 26.9 ng/ml; p = 0.0001; n = 34) compared to controls (IGF-I: 0.7 +/- 0.1 ng/ml. IGF-II: 21.3 +/- 4.2 ng/ml. IGF-BP3: 31.3 +/- 4.9 ng/ml: n = 19). Serum levels did not differ significantly among the groups regarding IGF-I, II and IGF-BP3. Intraocular albumin and IGF-I levels calculated as percentage of the respective serum levels correlated significantly (r = 0.42; p = 0.012). This study demonstrates that influx of IGF-I, II and IGF-BP3 in PDR quantitatively parallels influx of the liver derived serum protein albumin suggesting that leakage of the blood retina barrier and serum levels of IGF primarily determine intravitreal IGF levels rather than local synthesis. Suppression of systemic IGF levels by new, highly effective somatostatin-analogues therefore provides a promising approach to prevent PDR.     

Fetal rat islet insulin deficiency following maternal administration of streptozotocin

Pancreatic islets were isolated from the fetuses of normal rats and rats made diabetic by the iv administration of streptozotocin (STZ) on either Day 3 or 5 of pregnancy. Of the rats made diabetic on Day 3, one group also received insulin injections at the appearance of glucosuria. Maternal blood glucose on Day 20 of gestation was significantly different in the diabetic rats (405 +/- 27 mg/dl) from the normal (97 +/- 1 mg/dl) and insulin-treated diabetic rats (69 +/- 9 mg/dl). While fetal weight was significantly decreased in the STZ-treated rats (2.64 +/- 0.13 g vs 3.52 +/- 0.05 g for the control group, P less than 0.005), fetal glucose was significantly higher in the STZ-treated than in normal pups (342 +/- 11 vs 35 +/- 1 mg/dl, P less than 0.005). Both fetal weight and glucose were normalized by insulin treatment: 3.16 +/- 0.18 g and 31 +/- 7 mg/dl, respectively. Insulin release from fetal islets of diabetic dams was blunted after a week in culture both in basal and stimulated conditions. After 2 weeks in culture, there was partial recovery in the insulin response to glucose but it did not equal to that measured in fetal islets from the normal and insulin-treated diabetic rats. These data suggest maternal hyperglycemia severely impairs fetal weight and insulin release from fetal rat islets in vitro, and correction of the hyperglycemia by insulin treatment not only improves fetal weight and glucose concentrations, but it also normalizes insulin release from fetal rat islets in vitro.     

Beneficial effects of Trigonella foenum graecum and sodium orthovanadate on metabolic parameters in experimental diabetes

Oxidative stress in diabetic tissues is accompanied by high-level of free radicals with simultaneously declined antioxidant enzymes status leading to cell membrane damage. The present study was carried out to observe the effect of sodium orthovanadate (SOV) and Trigonella foenum graecum seed powder (TSP) administration on blood glucose and insulin levels, antioxidant enzymes, lipid peroxidation, pyruvate kinase, lactate dehydrogenase and protein kinase C in heart, muscle and brain of the alloxan-induced diabetic rats to see whether the treatment with SOV and TSP was capable of reversing the diabetic effects. Diabetes was induced by administration of alloxan monohydrate (15?mg/100?g body weight), and rats were treated with 2?IU insulin, 0.6?mg/ml SOV, 5% TSP in the diet and a combination of 0.2?mg/ml SOV and 5% TSP separately for 21?days. Blood glucose levels increased markedly in diabetic rats, animals treated with a combined dose of SOV and TSP had glucose levels almost comparable with controls, similar results were obtained in the activities of pyruvate kinase, lactate dehydrogenase, antioxidant enzymes and protein kinase C in diabetic animals. Our results showed that lower doses of SOV (0.2?mg/ml) could be used in combination with TSP to effectively reverse diabetic alterations in experimental diabetes. Copyright ? 2012 John Wiley & Sons, Ltd.