Rat C peptide I and II stimulate glucose utilization in STZ-induced diabetic rats

Aims. To study the effects of physiological concentrations of rat proinsulin C peptide I and II, respectively, on whole body glucose utilization in streptozotocin diabetic and healthy rats. Methods. A sequential insulin clamp procedure was used (insulin infusion rates 3.0 and 30.0 mU · kg^–1· min^–1) in awake animals. C-peptide infusion rates were 0.05 and 0.5 nmol · kg^–1· min^–1. Blood glucose was clamped at 7.7 ± 0.3 mmol/l in the diabetic rats and at 3.9 ± 0.1 mmol/l in the healthy rats. Results. In diabetic rats infused at lower rates of C peptide and insulin, glucose utilization increased by 79–90 % (p < 0.001) compared with diabetic animals infused with saline and insulin. Increasing the rate of C-peptide infusion tenfold did not elicit a statistically significant further increase in glucose utilization. C peptide I and II exerted similar effects. The metabolic clearance rate for glucose in the diabetic animals infused with C peptide was not different from that of the healthy rats. During high-dose insulin infusion (30.0 mU · kg^–1· min^–1) glucose utilization increased considerably and no statistically significant C-peptide effects were observed. About 85 % of the increase in glucose utilization induced by C peptide could be blocked by treatment with N-monomethyl-l-arginine. Conclusions/interpretation. Physiological concentrations of homologous C peptide stimulate whole body glucose utilization in diabetic but not in healthy rats. C peptide I and II elicit similar effects. The influence of C peptide on glucose utilization may be mediated by nitric oxide. [Diabetologia (1999) 42: 958–964] Received: 8 January 1999 and in final revised form: 20 April 1999     

Cell-to-cell communication and expression of gap junctional proteins in human diabetic and nondiabetic skin fibroblasts

Wound healing involves the interactions of many cell types, and is controlled in part by growth factors. Intercellular communication mediated by gap junctions is considered to play an important role in the coordination of cellular metabolism during the growth and development of tissues and organs. Basic fibroblast growth factor (bFGF), known to be important in wound healing, has been found to increase Cx43 expression and intercellular communication in endothelial cells and cardiac fibroblasts. It has been proposed that an increased coupling is necessary for the coordination of these cells in wound healing and angiogenesis, and that one of the actions of bFGF is to modulate intercellular communication. The aim of our study was to evaluate the effects of bFGF on gap junctional intercellular communication (GJIC) in vitro, and the presence of gap junctional proteins connexin (Cx) 26, Cx32, and Cx43 in fibroblasts of diabetic and nondiabetic individuals. Fibroblast cell lines (n=10) were cultured for 3 d in serum-free media with or without bFGF (3 ng/mL). Cells were evaluated for the rate of GJIC by using laser cytometry, and for the presence of Cx26, Cx32, and Cx43 by immunohistochemical and Western analyses. All cell types communicated via contact-dependent mechanisms. The rate of GJIC was greater (p<0.01) for diabetic than for nondiabetic fibroblasts (4.1±0.01 vs 3.3±0.01 %/min). bFGF increased (p<0.01) the rate of GJIC for diabetic (4.9±0.01 vs 4.1±0.01%) and nondiabetic (4.1±0.01 vs 3.3±0.01%) fibroblasts. Immunohistochemistry identified Cx26 in the cytoplasm, Cx32 was not detected, and Cx43 was present on the cellular borders in all cultures. Image analysis of immunofluorescent staining demonstrated that bFGF increased (p<0.05) Cx43 expression in diabetic and nondiabetic fibroblasts. Western immunoblot analysis revealed bands at 43–46 kD that were similar in volume for diabetic and nondiabetic fibroblasts. Thus, gap junctions involving Cx43 and GJIC among fibroblasts appear to be targets for bFGF. Fibroblasts of diabetic individuals appear to have an increased rate of cell-cell coupling, correlating with a decreased rate of proliferation.     

Short-term treatment with ramipril normalizes renal haemodynamics and the natriuretic response to a sodium load in type 1 diabetic patients with early nephropathy

The objective of the present study was to determine whether acute inhibition of angiotensin converting enzyme (ACE) normalizes intrarenal sodium handling, renal haemodynamics and renal dopamine output in response to an i.v. NaCl infusion in type 1 diabetic patients with early nephropathy. Nine diabetic patients (aged 28±3 years) with elevated urinary albumin excretion (173±39 mg ⋅ min^–1) were studied. The effects of a 2-hour NaCl infusion (12.5 ml ⋅ kg^–1⋅ h^–1) on para-amino hippuric acid (PAH), inulin, lithium and sodium clearances as well as the urinary dopamine excretion were studied before and after 2 days of acute ACE inhibition. Fifteen healthy subjects (aged 34±1 years) served as controls. The results showed that 2 days of ACE inhibition improved the natriuretic response significantly (P<0.05) within the first 2 h following an i.v. NaCl load due to a normalization of the proximal tubular sodium handling. In control subjects urinary dopamine output increased by 14% (P<0.01) following i.v. NaCl infusion, whereas a blunted increase was seen in the diabetic patients, which tended to normalize following inhibition of ACE. In conclusion, this study demonstrates that patients with type 1 diabetes and early nephropathy display abnormalities in renal haemodynamics, natriuresis and urinary dopamine mobilization in response to a sodium load, which can be reversed by short-term inhibition of ACE. Received: 27 September 1996 / Accepted in revised form: 2 December 1996     

Inhibitory effect of troglitazone on diabetic neuropathy in streptozotocin-induced diabetic rats

Summary Free-radical scavengers and inhibitors of tumour necrosis factor-α (TNF-α) such as N-acetylcysteine and pentoxifylline have been shown to inhibit the development of peripheral neuropathy in streptozotocin(STZ)-induced diabetic rats. In this study we examined the effect of troglitazone, an anti-diabetic thiazolidinedione, on diabetic neuropathy, since it also is a free-radical scavenger and a TNF-α inhibitor. Rats were fed powder chow mixed with troglitazone at 0.5 % and 0.125 % ad libitum. Although blood glucose concentrations were remarkably higher and body weight lower in diabetic than in nondiabetic rats, troglitazone had no effect on these throughout the 24-week experiment. Serum lipoperoxide concentrations, tibial nerve lipoperoxide content and serum TNF-α activity induced by lipopolysaccharide was increased in diabetic rats, but inhibited in troglitazone-treated rats. Motor nerve conduction velocity (MNCV) of the tibial nerve slowed in diabetic rats, compared with that in nondiabetic rats. On the other hand, the slowed MNCV was (p < 0.05–0.01) inhibited after weeks 12 and 16 of the experiment in diabetic rats treated with high and low doses of troglitazone, respectively. Morphometric analysis showed that troglitazone suppressed the decrease of the myelinated fibre area (p < 0.05), axon/myelin ratio (p < 0.01) and fascicular area (p < 0.05) and suppressed the increase of myelinated fibre density (p < 0.001) in diabetic rats. These results indicate that troglitazone has a beneficial effect on peripheral neuropathy in STZ-induced diabetic rats irrespective of blood glucose concentrations. [Diabetologia (1998) 41: 1321–1326] Received: 16 March 1998 and in revised form: 8 June 1998     

Plasma concentrations of glucagon during hyperglycemic clamp with or without somatostatin infusion in obese subjects

Summary The aim of the present study was to evaluate whether the inhibitory effect on pancreatic A-cell exerted by hyperglycemic hyperinsulinemia and/or by somatostatin administration is impaired in human obesity. For this purpose plasma glucagon concentrations were measured in 8 obese and 8 nonobese nondiabetic subjects during a 4-h hyperglycemic clamp. Synthetic cyclic somatostatin-14 was infused at the rate of 2.5 nmol/min during the third hour of the study. Fasting plasma glucagon was higher in obese than in nonobese subjects (242±32vs 163±15 pg/ml, p<0.05) (mean±SEM). In the last 20 min of the glucose infusion period preceding somatostatin administration (100–120 min of the study) plasma glucagon averaged 195±26 pg/ml in obese and 122±13 pg/ml in nonobese subjects (p<0.05), with a reduction of 19±3% in the former and 28±4% in the latter (p=n.s.). In both groups somatostatin infusion did not result in a further decrease in plasma glucagon, which averaged 192±27 pg/ml in obese and 123±16 pg/ml in nonobese subjects (p<0.05) in the 160–180 min period of the study. Also after discontinuing somatostatin infusion plasma glucagon levels did not change. These results suggest that in human obesity hyperglycemic hyperinsulinemia has a normal inhibitory effect on pancreatic A-cell and that somatostatin administration has no additive effect on hyperglycemia and hyperinsulinemia in either obese or nonobese nondiabetic subjects. Supported by grants n^o 83.02749.56, 84.03099.56, 85.00681.56, 86.01873.56, 83.02591.04, 85.00502.04 and 86.00102.04 fromConsiglio Nazionale delle Ricerche, Italy, and by grants fromMinistero della Pubblica Istruzione, Italy.     

Flow-induced dilatation in isolated resistance arteries from control and streptozotocin-diabetic rats

Summary Acetylcholine-induced vasodilatation is impaired in animal models of insulin-dependent diabetes mellitus (IDDM), and may result from altered nitric oxide synthesis or release. The response to intraluminal flow, a more physiologically relevant stimulus for nitric oxide release, is unknown. This study examined flow-induced responses in isolated resistance arteries from male Sprague-Dawley control and streptozotocin-diabetic (45 mg/kg i.v, 4 week duration) rats. Mesenteric arteries (4–5th order) were dissected and cannulated on a pressure myograph (mean internal diameter ± SEM at 40 mmHg, control 223 ± 8, n = 9 vs diabetic 239 ± 12 μm, n = 8, NS). Arteries were preconstricted with noradrenaline (1 μmol/l) and intraluminal pressure raised and maintained at 80 mmHg. Luminal flow was raised in incremental steps (0–1.27 μl/s). Arteries from control animals dilated to flow while arteries from diabetic animals constricted (% change in internal diameter ± SEM at 0.79 μl/s: control 13.46 ± 6.52, n = 9 vs diabetic –7.44 ± 3.38 %, n = 8; p < 0.005). Incubation with Nω-nitro-l-arginine methyl ester (0.1 mmol/l) abolished flow responses in arteries from controls but not from diabetic rats. In conclusion, impaired flow-induced nitric oxide-mediated vasodilatation may contribute to vascular disease in IDDM. [Diabetologia (1998) 41: 34–39] Received: 18 June 1997 and in final revised form: 12 September 1997     

Oral treatment with an antioxidant (raxofelast) reduces oxidative stress and improves endothelial function in men with Type II diabetes

Aims/hypothesis. To determine whether raxofelast, a new water soluble antioxidant decreases oxidative stress and improves endothelial function in men with Type II (non-insulin dependent) diabetes mellitus. Methods. We treated ten normotensive, normocholesterolaemic men with Type II diabetes and as controls ten healthy men matched with them for age with raxofelast (600 mg twice daily) for 1 week. Plasma 8-epi-PGF₂α, a non-enzymic oxidation product of arachidonic acid was measured by gas chromatography/mass spectrometry as an index of oxidative stress. Forearm vasodilator responses to brachial artery infusion of acetylcholine (7.5, 15 and 30 μg min^–1) and of the nitric oxide donor nitroprusside (1, 3 and 10 μg min^–1) were measured by strain gauge plethysmography. Results. Plasma concentrations of 8-epi-PGF₂α were greater in diabetic than in control men (0.99 ± 0.20 vs 0.18 ± 0.01 nmol l^–1, means ± SEM, p < 0.001) and fell after raxofelast (from 0.99 ± 0.20 to 0.47 ± 0.07 nmol l^–1, p < 0.05) in diabetic men but not in control men. Blood flow responses to acetylcholine were lower (p < 0.05) in diabetic than in control men (7.4 ± 1.0 vs 12.9 ± 2.3 ml · min^–1· 100 ml^–1 for the highest dose). In diabetic men, but not in control men, raxofelast increased (p < 0.05) blood flow responses to acetylcholine (from 7.4 ± 1.0 ml · min^–1· 100 ml^–1 to 11.3 ± 2.3 ml · min^–1· 100 ml^–1 at highest dose). Blood flow responses to nitroprusside were similar in control and diabetic men and in both groups were similar before and after raxofelast. Conclusion/interpretation. Oral treatment with raxofelast for 1 week reduces oxidative stress and improves endothelial function in men with Type II diabetes. [Diabetologia (2000) 43: 974–977] Received: 14 October 1999 and in revised form: 28 May 2000     

Truncated and full-length glucagon-like peptide-1 (GLP-1) differentially stimulate intestinal somatostatin release

Glucagon-like peptide-1^7–36NH2 (GLP-1^7–36NH2) is a potent stimulator of insulin secretion, as well as of somatostatin-14 (SS-14) release from the pancreatic and gastric D-cells. To investigate the possible effects of this peptide on release of intestinal somatostatin (SS-28 and SS-14), rat intestinal cultures were treated with 10⁻¹²–10⁻⁶ M GLP-1^7–36NH2, as well as with the structurally related peptides, GLP-1^1–36NH2 and GLP-2. Both forms of GLP-1 stimulated dose-dependent increases in intestinal somatostatin; secretion reached 643±126% of controls (p<0.001) after treatment with 10⁻⁶ M GLP-1^7–36NH2, and 398±76% of controls (p<0.001) after 10⁻⁶ M GLP-1^1–36NH2. Thus, GLP-1^7–36NH2 was more effective than GLP-1^1–36NH2 in stimulating secretion of intestinal somatostatin-like immunoreactivity (SLI) (p<0.05). GLP-2 did not affect intestinal somatostatin release. Gel permeation analysis demonstrated that 10⁻⁶ M GLP-1^7–36NH2 stimulated SS-28 by 2.9±0.4-fold and SS-14 by 9.1±3.7-fold, whereas GLP-1^1–36NH2 exerted equivalent effects (2.8±0.9-fold) on both forms of somatostatin. These findings define a novel biological role for GLP-1^7–36NH2 in the regulation of intestinal somatostatin secretion, and demonstrate that GLP-1^1–36NH2 exerts unique biological activities in this system.     

Reduced incretin effect in Type 2 (non-insulin-dependent) diabetes

Summary Integrated incremental immunoreactive insulin and connecting peptide responses to an oral glucose load of 50 g and an “isoglycaemic” intravenous glucose infusion, respectively, were measured in 14 Type 2 (non-insulin-dependent) diabetic patients and 8 age- and weight-matched metabolically healthy control subjects. Differences between responses to oral and intravenous glucose administration are attributed to factors other than glucose itself (incretin effect). Despite higher glucose increases, immunoreactive insulin and connecting peptide responses after oral glucose were delayed in diabetic patients. Integrated responses were not significantly different between both groups. However, during “isoglycaemic” intravenous infusion, insulin and connecting peptide responses were greater in diabetic patients than in control subjects as a consequence of the higher glycaemic stimulus. The contribution of incretin factors to total insulin responses was 72.8 ± 6.9% (100% = response to oral load) in control subjects and 36.0 ± 8.8% in diabetic patients (p ≦ 0.05). The contribution to connecting peptide responses was 58.4 ± 7.6% in control subjects and 7.6 ± 14.5% (p ≦ 5 0.05) in diabetic patients. Ratios of integrated insulin to connecting peptide responses suggest a reduced (hepatic) insulin extraction in control subjects after oral as compared to intravenous glucose. This was not the case in diabetic patients. Immunoreactive gastric inhibitory polypeptide responses were not different between control subjects and diabetic patients. A reduced or lost incretin effect in the face of normal gastric inhibitory polypeptide response in Type 2 diabetic patients may be explained by decreased sensitivity of the B cells towards the insulinotropic effect of gastric inhibitory polypeptide or to hyposecretion or reduced effectiveness of as yet unidentified humoral or nervous gut factors with incretin activity.     

Involvement of non-esterified fatty acid oxidation in glucocorticoid-induced peripheral insulin resistance in vivo in rats

Summary The mechanism by which glucocorticoids induce insulin resistance was studied in normal rats administered for 2 days with corticosterone then tested by euglycaemic hyperinsulinaemic clamps. Corticosterone administration induced a slight hyperglycaemia, hyperinsulinaemia and increased non-esterified fatty acid levels. It impaired insulin-stimulated total glucose utilization (corticosterone 15.7±0.7; controls 24.6±0.8 mg·kg⁻¹·min⁻¹), as well as residual hepatic glucose production (corticosterone 4.9±1.0; controls 2.0±0.7 mg·kg⁻¹·min⁻¹). During the clamps, insulin did not decrease the elevated non-esterified fatty acid levels in corticosterone-administered rats (corticosterone 1.38±0.15, controls 0.22±0.04 mmol/l). Corticosterone administration decreased the in vivo insulin-stimulated glucose utilization index by individual muscles by 62±6%, and the de novo glycogen synthesis by 78±2% (n=8–9 muscles). GLUT4 protein and mRNA levels were either unchanged or slightly increased by corticosterone administration. Inhibition of lipid oxidation by etomoxir prevented corticosterone-induced muscle but not hepatic insulin resistance. In conclusion, glucocorticoid-induced muscle insulin resistance is due to excessive nonesterified fatty acid oxidation, possibly via increased glucose fatty-acid cycle ultimately inhibiting glucose transport, or via decreased glycogen synthesis, or by a direct effect on glucose transporter translocation or activity or both.     

Prevalence of left ventricular hypertrophy in Type I diabetic patients with diabetic nephropathy

Summary The increased mortality of patients with diabetic nephropathy is mainly due to cardiovascular disease and end stage renal failure. Left ventricular hypertrophy is an independent risk factor for myocardial ischaemia and sudden death. The aim of our cross-sectional study was to evaluate left ventricular structure and function in Type I (insulin-dependent) diabetic patients with diabetic nephropathy. M-mode and Doppler echocardiography were done on 105 Type I diabetic patients with diabetic nephropathy [61 men, age (means ± SD) 44 ± 9 years, and albuminuria [median(range)] 567(10–8188) mg/24 h, serum creatinine 109 (53–558) μmol/l], and 140 Type I diabetic patients with persistent normoalbuminuria [79 men, 47 ± 10 years, urinary albumin excretion rate 8 (0–30) mg/24 h, and serum creatinine 81 (55–121) μmol/l]. Patients with and without nephropathy were comparable with respect to sex, body mass index, and duration of diabetes. Arterial blood pressure was slightly higher in patients with nephropathy: 140/79 ± 17/9 mm Hg vs 134/78 ± 15/8 mm Hg, p < 0.01, and the majority of proteinuric patients received antihypertensive drugs, 84 vs 17 %, respectively, p < 0.001. Left ventricular mass index was increased in the nephropathic group (means ± SD) 100.6 ± 23.9 g/m² compared with the normoalbuminuric group 91.4 ± 21.9 g/m², p = 0.002. Left ventricular hypertrophy was found more often in patients with nephropathy 23 (14–31)% compared with patients with normoalbuminuria 9 (5–14)%, p < 0.005. Diastolic function, assessed by the ratio between the peak diastolic velocity and the peak atrial systolic velocity (E/A ratio) and isovolumic relaxation time, was reduced in patients with vs without nephropathy: 1.17 ± 0.29 vs 1.34 ± 0.32, and 81.7 ± 16.5 vs 74.6 ± 14.5, p < 0.001 and p = 0.002, respectively. Systolic function was about the same and normal in both groups. Our study suggests that an increase in left ventricular mass index and a decrease in diastolic function occurs early in the course of diabetic nephropathy. [Diabetologia (1999) 42: 76–80] Received: 16 April 1998 and in final revised form: 5 August 1998     

Amelioration of nerve conduction velocity following simultaneous kidney/pancreas transplantation is due to the glycaemic control provided by the pancreas

Summary Diabetic polyneuropathy is a common, disabling chronic complication of diabetes mellitus. Previous studies have suggested that combined pancreas-kidney transplantation can ameliorate nerve conduction. The relative contribution of the correction of hyperglycaemia and uraemia on nerve function is still a matter of debate. Nerve conduction velocity (NCV) was assessed before and after simultaneous pancreas and kidney transplantation, and before and after pancreas graft failure in five insulin-dependent diabetic (IDDM) patients affected by severe diabetic polyneuropathy. Sensory and motor NCV were recorded in five nerves and expressed as a cumulative index for each patient. Metabolic control was evaluated by fasting blood glucose and glycosylated haemoglobin levels. NCV index was below normal values before transplant: –3.8 ± 0.7 (normal value: 0.89), improved 1 and 2 years after transplant: –3.1 ± 1.3 and –2.6 ± 0.9 (p = 0.0019), stabilised until pancreas failure and deteriorated to pre-transplant values 2 years after pancreas graft failure: –3.6 ± 1.0 (p = 0.034). Fasting blood glucose levels worsened after pancreas graft failure. HbA_{1 c} levels, in the normal range during functioning pancreas graft (6.6 ± 0.6 %), deteriorated after its failure (8.0 ± 0.6 %, p = 0.04). Kidney function was preserved. These data support a positive effect of pancreas transplantation per se on NCV in IDDM subjects with diabetic polyneuropathy, thus demonstrating that metabolic control provided by a self-regulated source of insulin not only halts but also ameliorates nerve function, even if polyneuropathy is advanced. [Diabetologia (1997) 40: 1110–1112] Received: 14 May 1997 and in revised form: 12 June 1997     

Immunoradiometric assay of insulin,intact proinsulin and 32–33 split proinsulin and radioimmunoassay of insulin in diet-treated Type 2 (non-insulin-dependent) diabetic subjects

Summary Plasma insulin, intact proinsulin and 32–33 split proinsulin measured by specific immunoradiometric assays and insulin and C-peptide measured by radioimmunoassay were measured during a constant infusion of glucose test in ten diet-treated subjects with a history of Type 2 (non-insulin-dependent) diabetes (termed diabetic subjects), mean fasting plasma glucose 6.0 ± 1.0 mmol/l (mean ± SD), and 12 non-diabetic control subjects. Immunoreactive insulin concentrations measured by radioimmunoassay were 33 higher than insulin and 16 % higher than the sum of insulin and its precursors by immunoradiometric assay. The diabetic and non-diabetic subjects had similar fasting concentrations of insulin, intact proinsulin and 32–33 split proinsulin. The ratio of fasting intact proinsulin to total insulin was greater in the diabetic than the non-diabetic group 12.0 % (6.8–21.0 %, 1 SD range) and 6.3 % (4.0–9.8 %), respectively,p < 0.01), though the groups overlapped substantially. After glucose infusion, diabetic and non-diabetic subjects had similar intact proinsulin concentrations (geometric mean 4.9 and 5.2 pmol/l, respectively), but the diabetic group had impaired insulin secretion by immunoradiometric assay (geometric means 55 and 101 pmol/1,p < 0.05) or by radioimmunoassay C-peptide (geometric means 935 and 1410 pmol/1,p < 0.05), though not by radioimmunoassay insulin (87 and 144 pmol/1,p = 0.12), respectively. Individual immunoradiometric assay insulin responses to glucose expressed in terms of obesity were subnormal in nine of ten diabetic subjects. Radioimmunoassay insulin and C-peptide gave less complete discrimination ( subnormal responses in six of ten and eight of ten, respectively). Thus, raised proinsulin and proinsulin:total insulin ratio are not necessarily a feature of mild diet-treated Type 2 diabetic patients with subnormal insulin responses to glucose.     

Changes in hepatic glycogen cycling during a glucose load in healthy humans

Aims/hypothesis Glycogen cycling, i.e. simultaneous glycogen synthesis and glycogenolysis, affects estimates of glucose fluxes using tracer techniques and may contribute to hyperglycaemia in diabetic conditions. This study presents a new method for quantifying hepatic glycogen cycling in the fed state. Glycogen is synthesised from glucose by the direct and indirect (gluconeogenic) pathways. Since glycogen is also synthesised from glycogen, i.e. glycogen→glucose 1-phosphate→glycogen, that synthesised through the direct and indirect pathways does not account for 100% of glycogen synthesis. The percentage contribution of glycogen cycling to glycogen synthesis then equals the difference between the sum of the percentage contributions of the direct and indirect pathways and 100. Materials and methods The indirect and direct pathways were measured independently in nine healthy volunteers who had fasted overnight. They ingested ²H₂O (5 ml/kg body water) and were infused with [5-³H]glucose and acetaminophen (paracetamol; 1 g) during hyperglycaemic clamps (7.8 mmol/l) lasting 8 h. The percentage contribution of the indirect pathway was calculated from the ratio of ²H enrichments at carbon 5 to that at carbon 2, and the contribution of the direct pathway was determined from the ³H-specific activity, relative to plasma glucose, of the urinary glucuronide excreted between 2 and 4, 4 and 6, and 6 and 8 h. Results Glucose infusion rates increased (p<0.01) to ∼50 μmol kg⁻¹ min⁻¹. Plasma insulin and the insulin : glucagon ratio rose ∼3.6- and ∼8.3-fold (p<0.001), respectively. From the difference between 100% and the sum of the direct (2–4 h, 54±6%; 4–6 h, 59±5%; 6–8 h, 63±4%) and indirect (32±3, 38±4, 36±3%) pathways, glycogen cycling was seen to be decreased (p<0.05) from 14±4% (2–4 h) to 4±3% (4–6 h) and 1±3% (6–8 h). Conclusions/interpretation This method allows measurement of hepatic glycogen cycling in the fed state and demonstrates that glycogen cycling occurs most in the early hours after glucose loading subsequent to a fast.     

Glomerular size-and charge selectivity in Type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy

Summary In an attempt to evaluate the mechanisms of proteinuria in diabetic kidney disease, we measured the renal clearances of albumin, total IgG, and IgG4 in 20 male Type 2 (non-insulin-dependent) diabetic patients with diabetic glomerulosclerosis (biopsy proven), in 10 male Type 2 diabetic patients without nephropathy (urinary albumin excretion rate ≤ 30 mg/24 h), and in 10 healthy male subjects. The fractional clearance of albumin was increased in patients with nephropathy: 659 (42–4355) · 10^–6 (median (range)), compared to 2.6 (0.2–14.2) · 10^–6 in patients without nephropathy, and 2.3 (0.4–4.2) · 10^–6 in healthy subjects. The fractional clearance of total IgG (neutral) and of IgG4 (anionic) was 40–50 times higher in patients with nephropathy compared to the two other groups. The IgG/IgG4 selectivity index was not significantly different in the three groups, being: 1.12 (0.06–5.65), 1.16 (0.45–3.72) and 1.35 (0.65–3.34) in patients with nephropathy, patients without nephropathy, and healthy subjects, respectively. The IgG/albumin selectivity index was decreased in patients with nephropathy: 0.27 (0.01–1.26) compared to 1.29 (0.07–2.67) (p<0.05) and 1.23 (0.76–7.84) (p<0.001) in patients without nephropathy and healthy subjects, respectively. No significant change in IgG/albumin selectivity index was observed between patients without nephropathy and healthy subjects. The systolic blood pressure was elevated in the patients with nephropathy: 164±21 mm Hg (mean ± SD) compared to patients without nephropathy: 145±20 mm Hg (p<0.05) and to healthy subjects: 133±19 mm Hg (p<0.005). The diastolic blood pressure was higher in patients with and without nephropathy: 92±7 vs 90±10 mm Hg compared to 79±8 mm Hg (p<0.005) in healthy subjects. Our cross-sectional study suggests that impaired barrier size selectivity, probably due to an increase in large pore area (“shunt pathway”) in the glomerular capillary wall and systemic hypertension are the major pathogenic mechanisms of proteinuria in Type 2 diabetic patients with diabetic nephropathy. [Diabetologia (1994) 37: 195–201] Received: 7 June 1993 and in revised form: 25 August 1993     

Remission from insulin dependence induced by continuous subcutaneous insulin infusion (CSII) in type I,newly diagnosed diabetics: Role of some hormonal and immunologic factors

Summary Optimal and early control of recent onset, type I diabetes by intensive insulin therapy has been reported to allow insulin withdrawal in about two thirds of subjects treated. We used continuous s.c. insulin infusion (CSII) in the attempt to induce a temporary remission of insulin dependence in 18 newly diagnosed young adult diabetics. After 10 days of optimized glycometabolic control, insulin infusion was stopped and patients were switched to glibenclamide (15 mg/die) plus metformin (1 g/die). Diabetics were considered in remission of insulin dependence when their metabolic control fulfilled the following criteria for at least 3 months: absence of glycosuria, pre- and post-prandial blood glucose ≤ 120 and 180 mg/dl, respectively, HbA_lc ≤ 7%. Insulin therapy could be discontinued for periods of over three months in 11 subjects (61%) and for as long as 18 months in one case. Insulin requirement during CSII was slightly higher in non-remitters (NR) than in remitters (R): 0.36–0.64vs 0.26–0.41 U/kg/die. After 24 months from CSII, R still showed lower insulin requirement (0.35–0.42 U/kg/die) than NR (0.55–0.75 U/kg/die). Further, the role of some hormonal and immunologic factors was investigated. Plasma C-peptide and glucagon were measured, fasting and 2h after each meal, both on admission and immediately after CSII, when patients were switched to oral therapy. No difference in hormone levels could be detected on admission, whereas, after CSII, mean post-prandial increase of C-peptide over basal was significantly higher in R than in NR (1.18 ± 0.37vs 0.22 ± 0.16 ng/ml, p<0.001). Finally, blood distribution of T, B, T4 and T8 lymphocyte subsets was measured in all patients, both before and after CSII. The T4/T8 ratio was found to be significantly increased in NR group patients (3.19 ± 0.45vs 2.41 ± 0.23, p<0.005). The immunologic pattern did not show any significant modification after ten days of optimized control by CSII. In conclusion, immunologic background and residual B-cell function may be associated with a different susceptibility to remission from insulin therapy in newly diagnosed young adult diabetics.     

Serum glucose level at hospital admission correlates with left ventricular systolic dysfunction in nondiabetic, acute coronary patients: the Hellenic Heart Failure Study

The purpose of this work was to evaluate the relation between serum glucose levels at hospital admission and left ventricular systolic function in nondiabetic patients with an acute coronary syndrome (ACS). Of the 1000 ACS patients who were consecutively enrolled during 2007–2008, 583 (63 ± 13 years, 20% females) nondiabetic patients were studied in this work. Of these, 254 presented left ventricular systolic dysfunction (ejection fraction <40%). Biochemical measurements and detailed medical information were recorded in all participants. Patients having glucose levels at hospital admission in the highest tertile (>155 mg/dl) had lower left ventricular ejection fraction (40% vs 45%, P = 0.003), were older (66 ± 11 vs 61 ± 13, P = 0.004) and less physically active (49% vs 63%, P = 0.02), had higher troponin (14.7 ± 39.7 vs 5.6 ± 13.5, P = 0.03), higher brain natriuretic peptide (510.39 ± 932.33 vs 213.4 ± 301.14, P = 0.008), higher C-RP (42.26 ± 55.26 vs 26.46 ± 38.18, P = 0.04), lower creatinine clearance levels (68 ± 33 vs.81 ± 31, P = 0.009), higher white blood cell count (13 416 ± 16 420 vs 9310 ± 3020, P = 0.001), and lower body mass index (26.8 ± 4 vs 27.2 ± 4.4, P = 0.07), compared to those in the lowest tertile (<114 mg/dl). The multiadjusted logistic regression analysis revealed that a 10 mg/dl difference in glucose levels was independently associated with 8% (95% confidence interval 2%–14%) higher likelihood of left ventricular systolic dysfunction. Low glucose concentrations at hospital admission in nondiabetic post-ACS patients is a predictor for the appearance of left ventricular dysfunction, and could be a target marker for risk stratification.     

Glomerular hyperfiltration in microalbuminuric NIDDM patients

Summary Glomerular hyperfiltration and microalbuminuria are both regarded as risk factors for the development of diabetic nephropathy in insulin-dependent diabetic patients. Information on glomerular hyperfiltration is scarse in microalbuminuric non-insulin-dependent diabetic (NIDDM) patients. Therefore, we performed a cross-sectional study of glomerular filtration rate (single i. v. bolus injection of ⁵¹Cr-EDTA, plasma clearance for 4 h) in 158 microalbuminuric NIDDM patients compared to 39 normoalbuminuric NIDDM patients and 20 non-diabetic control subjects. The groups were well-matched with regard to sex, age and body mass index. The uncorrected (ml/min) and the adjusted (ml · min^–1· 1.73 m^–2) glomerular filtration rate were both clearly elevated in the microalbuminuric patients: 139 ± 29 and 117 ± 24 as compared to 115 ± 19 and 99 ± 15; 111 ± 23 and 98 ± 21 in normoalbuminuric NIDDM patients and control subjects, respectively (p < 0.001). The glomerular filtration rate (ml · min^–1· 1.73 m^–2) in NIDDM patients who had never received antihypertensive treatment was also clearly elevated in the microalbuminuric patients (n = 96): 119 ± 22 as compared to 100 ± 14 and 98 ± 21 in normoalbuminuric NIDDM patients (n = 27) and control subjects (n = 20), respectively (p < 0.001). Glomerular hyperfiltration (elevation above mean glomerular filtration rate plus 2 SD in normoalbuminuric NIDDM patients) was demonstrated in 37 (95 % confidence interval 30–45)% of the microalbuminuric patients. Multiple regression analysis revealed that HbA_{1 c}, 24-h urinary sodium excretion, age and known duration of diabetes were correlated with glomerular filtration rate in microalbuminuric NIDDM patients (r ² = 0.21, p < 0.01). Our cross-sectional study indicates that NIDDM patients at high risk of developing diabetic nephropathy are also characterized by an additional putative risk factor for progression, glomerular hyperfiltration. [Diabetologia (1996) 39: 1584–1589]     

Antioxidants attenuate early up regulation of retinal vascular endothelial growth factor in streptozotocin-diabetic rats

Aims/hypothesis: A strong positive correlation has been found between lipid peroxidation product and vascular endothelial growth factor concentrations in the vitreous of patients with proliferative diabetic retinopathy. To establish a causal relation between diabetes-associated enhanced oxidative stress and vascular endothelial growth factor production, we evaluated two antioxidants, dl-α-lipoic acid and taurine, on retinal vascular endothelial growth factor protein and mRNA expression and on parameters of oxidative stress in streptozotocin-diabetic rats. Methods: Our experiments were on control rats and streptozotocin-diabetic rats with a 6-week duration of diabetes, treated with or without dl-α-lipoic acid (100 mg · kg^–1· d^–1, i. p.) or taurine (1 % in the diet) starting from induction of diabetes. Vascular endothelial growth factor protein in retinal homogenates was assessed by sandwich ELISA with an affinity-purified polyclonal antibody and vascular endothelial growth factor mRNA by ribonuclease protection assay. Retinal lipid peroxidation products i. e. malondialdehyde plus 4-hydroxyalkenals were quantified with n-methyl-2-phenylindole. Retinal reduced and oxidized glutathione, ascorbate, dehydroascorbate, and sorbitol pathway intermediates were measured spectrofluorometrically, and taurine by reverse-phase HPLC. Results: Vascular endothelial growth factor protein concentration (means ± SD) was increased in diabetic rats compared with control rats (33 ± 7 vs 19 ± 5 pg/mg total protein, p < 0.01) This increase was attenuated by taurine (26 ± 8, p < 0.05) and prevented by dl-α-lipoic acid (21 ± 4, p < 0.01). Vascular endothelial growth factor mRNA abundance was reduced by 1.4-fold in diabetic rats compared with control rats and this decrease was attenuated but not completely prevented by both antioxidants. Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats compared with control rats, and both antioxidants arrested accumulation of lipid peroxidation products. Taurine, reduced glutathione, oxidized glutathione, ascorbate, dehydroascorbate and sorbitol pathway intermediate concentrations as well as oxidized glutathione/reduced glutathione and dehydroascorbate/ascorbate ratios were similar in control and diabetic rats treated with or without taurine. Conclusion/interpretation: Oxidative stress is directly involved in up regulation of vascular endothelial growth factor protein in the retina during early diabetes. [Diabetologia (2001) 44: 1102–1110] Received: 29 December 2001 and in revised form: 21 May 2001     

Experimental diabetes treated with ficus carica extract: effect on oxidative stress parameters

Parameters related to oxidative stress were studied in rats divided into 4 groups: streptozotocin-induced diabetic rats (n=10), diabetic rats who received a single dose of a basic fraction of Ficus carica extract (n=14), diabetic rats who received a single dose of a chloroform fraction of the extract (n=10), and normal rats (n=10). Compared to normal animals, the diabetic animals presented significantly higher values for erythrocyte catalase normalized to haemoglobin levels (1.5±0.15 vs. 0.96±0.18 μg/mg) and for plasma vitamin E (73.4±43.9 vs. 12.0±1.6 mg/l), monounsaturated fatty acids (0.219±0.118 vs. 0.067±0.014 mg/ml), polyunsaturated fatty acids (PUFA, 0.567±0.293 vs. 0.175±0.040 mg/ml), saturated fatty acids (0.779±0.262 vs. 0.401±0.055 mg/ml), and linoleic acid (0.202±0.086 vs. 0.106 ±0.014 mg/ml). Both Ficus carica fractions tended to normalize the values of the diabetic animals' fatty acids and plasma vitamin E values. On studying the ratios of vitamins E and A to PUFA (129.4±77.5 diabetic and 68.8±9.1 μg/mg normal; 37.5±20.8 vs. 108.0±43.6 μg/mg) and to C18:2 (259.9±65.8 vs. 161.0±21.3 μg/mg; 68.3±37.9 vs. 252.7±102.1 μg/mg), we found statistically significant differences as a function of diabetes, with the vitamin E/C18:2 ratio being normalized by the administration of the chloroform fraction (to 152.1±80.3 μg/mg) and the vitamin A/C18:2 ratio being raised relative to the untreated diabetic rats by the administration of the basic fraction (91.9±14.5 μg/mg). Our work confirms that antioxidant status is affected in the diabetes syndrome, and that Ficus carica extracts tend to normalize it. Received: September 2000 / Accepted in revised form: September 2002 Correspondence to M.D. Torres