Transcapillary escape rate and relative metabolic clearance of glycated and non-glycated albumin in Type 1 (insulin-dependent) diabetes mellitus

Summary The transcapillary escape rate and relative plasma disappearance of glycated and non-glycated albumin were measured in 25 male Type 1 (insulin-dependent) diabetic patients using a double tracer technique. The patients were divided into three groups on the basis of their urinary albumin excretion: group 1, normal albumin excretion (<30 mg/24h) (n=8); group 2, microalbuminuria (30–300 mg/24 h) (n=9); and group 3, clinical nephropathy (>300 mg/24 h) (n=8). Six male age-matched non-diabetic persons served as control subjects. The transcapillary escape rate of glycated albumin was similar in group 1 and control subjects (4.7±2.1 versus 5.1±1.7%), but significantly increased in group2 (7.0±1.7%,p<0.05) and in group 3 (7.9±3.1%,p<0.05). The transcapillary escape rate of glycated albumin was slightly lower than that of non-glycated albumin in all groups, but significant only in normal control subjects. No difference in the catabolic rate of glycated and non-glycated albumin was found. We conclude that the in vivo effects of glycation on the clearance and transcapillary passage of albumin are small and not likely to play any significant role in the development of late diabetic microvascular complications.     

Inability of HDL from type 2 diabetic patients to counteract the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation

Aims/hypothesis In healthy normolipidaemic and normoglycaemic control subjects, HDL are able to reverse the inhibition of vasodilation that is induced by oxidised LDL. In type 2 diabetic patients, HDL are glycated and more triglyceride-rich than in control subjects. These alterations are likely to modify the capacity of HDL to reverse the inhibition of vasodilation induced by oxidised LDL.Subjects and methods Using rabbit aorta rings, we compared the ability of HDL from 16 type 2 diabetic patients and 13 control subjects to suppress the inhibition of vasodilation that is induced by oxidised LDL.Results Oxidised LDL inhibited endothelium-dependent vasodilation (maximal relaxation [Emax]=58.2±14.6 vs 99.3±5.2% for incubation without any lipoprotein, p<0.0001). HDL from control subjects significantly reduced the inhibitory effect of oxidised LDL on vasodilatation (Emax=77.6±12.9 vs 59.5±7.7%, p<0.001), whereas HDL from type 2 diabetic patients had no effect (Emax=52.4±20.4 vs 57.2±18.7%, NS). HDL triglyceride content was significantly higher in type 2 diabetic patients than in control subjects (5.3±2.2 vs 3.1±1.4%, p<0.01) and was highly inversely correlated to Emax for oxidised LDL+HDL in type 2 diabetic patients (r=−0.71, p<0.005).Conclusions/interpretation In type 2 diabetes mellitus, the ability of HDL to counteract the inhibition of endothelium-dependent vasorelaxation induced by oxidised LDL is impaired and is inversely correlated with HDL triglyceride content. These findings suggest that HDL are less atheroprotective in type 2 diabetic patients than in control subjects.     

Strict insulin therapy normalises organ nitrogen contents and the capacity of urea nitrogen synthesis in experimental diabetes in rats

Summary Rats with experimental diabetes due to streptozotocin (75 mg/kg body weight) and free access to food were divided into two groups. One group (n=9) was optimally treated with insulin (glucosuria <4.0 mmol/24 h), using heat treated very long-acting ultralente insulin. The other group (n=10) was poorly treated with insulin (glucosuria 20–30 mmol/24 h).The nitrogen balance and energy balance of optimally treated diabetic rats was positive and not different from the control group (n=6). In the poorly treated diabetic rats the nitrogen balance was reduced whereas the energy balance was not different from that of control rats. After 4 weeks the fasting glucagon was: 50±21 ng/l (mean±SEM) in control rats, 62±18 ng/l in optimally treated diabetic rats and 249±58 ng/l in poorly treated diabetic rats (p<0.01). The capacity of urea nitrogen synthesis determined during alanine loading was: 9.6±1.0 umol/(min 100 g body weight) in control rats, 10.6±1.7 umol/(min 100 g body weight) in optimally treated diabetic rats and 17.3±1.3 umol/(min 100 g body weight) in poorly treated diabetic rats (p<0.01).Nitrogen contents of carcass, heart, intestines, liver, and kidneys as determined by Kjeldahl analyses were identical in control rats and optimally treated diabetic rats. In the poorly treated diabetic rats carcass-nitrogen and heart-nitrogen contents were reduced to 89% of the control value (p<0.01), whereas the kidney-nitrogen content was increased to 112% of the control value (p<0.01).Strict insulin therapy in experimental diabetes leads to a normalisation of nitrogen metabolism and hyperglucagonaemia, whereas less than optimally insulin treated rats show marked abnormalities in nitrogen metabolism as well as hyperglucagonaemia.     

Effects of acetazolamide on kidney function in Type 1 (insulin-dependent) diabetic patients with diabetic nephropathy

Summary We investigated the effects of 3 days treatment with acetazolamide 250 mg three times daily on kidney function in 8 Type 1 (insulin-dependent) diabetic patients with nephropathy, and in 7 healthy subjects in a double-blind placebo controlled cross-over study. Glomerular filtration rate and extracellular fluid volume were measured with the single injection ⁵¹Cr-EDTA technique and fluid flow rate from the proximal tubules was determined by measurement of the renal lithium clearance. A 24% decline in glomerular filtration rate was observed in both groups during acetazolamide treatment (control subjects: 108±11 vs 82±9 ml/min, p<0.02, diabetic patients: 71±19 vs 54±14 ml/min, p<0.01). The renal lithium clearance (ml/min) remained about the same (control subjects: 22±6 vs 27±8, NS, diabetic patients: 14±5 vs 15±4, NS). Absolute proximal tubular reabsorption of water (ml/min) was reduced by about one-third (control subjects: 85±11 vs 56±7, p<0.02, diabetic patients: 55±17 vs 37±6, p<0.02), and fractional proximal reabsorption of water and sodium (%) declined (control subjects: 79±5 vs 67±8, p<0.02, diabetic patients: 79±5 vs 72±6, p<0.02). Renal sodium clearance and distal fractional reabsorption of sodium was unchanged. Extracellular fluid volume declined by 10% in both groups (p<0.02). Albuminuria and fractional albumin clearance decreased significantly in the nephropathic patients (p<0.02). Our study suggests that the effects of acetazolamide on kidney function are similar in healthy subjects and patients with diabetic nephropathy.     

Impaired intrarenal dopamine production following intravenous sodium chloride infusion in Type 1 (insulin-dependent) diabetes mellitus

Summary Type 1 (insulin-dependent) diabetes mellitus is characterized by impaired sodium excretion following NaCl infusion. To investigate the possible role of dopamine in the impaired natriuresis in diabetes, intrarenal sodium handling, sodium excretion and urinary dopamine output, reflecting intrarenal dopamine formation, were studied following a 2 h 0.9% NaCl infusion (25 ml/kg) in eight diabetic patients and nine control subjects. The increase in sodium excretion in response to NaCl infusion was significantly (p<0.01) reduced in diabetic patients (19±7%) as compared with control subjects (46±8%). Fractional proximal tubular sodium reabsorption (determined by lithium clearance) decreased in the control group (p<0.001) following NaCl infusion but not in the diabetic group. Fractional distal tubular reabsorption decreased similarly in both groups. In response to NaCl urinary dopamine excretion increased by approximately 15% (p<0.01) in the control group but did not change in the diabetic group. The mean urinary dopamine excretion above basal was significantly greater in the control group (8.4±2.1 nmol/h) than in the diabetic group (–2.2±2.1 nmol/h; p<0.01). The urinary sodium/dopamine excretion ratio did not differ significantly between the two groups in the basal state or following NaCl. Baseline plasma levels of atrial natriuretic peptide did not differ between control and diabetic patients. In the control group atrial natriuretic peptide levels increased significantly (p<0.01) in response to NaCl whereas atrial natriuretic peptide levels did not change in the diabetic group. The results of this study show that patients with Type 1 diabetes have a blunted natriuresis in response to isotonic NaCl. This abnormality seems mainly to be due to impaired inhibition of proximal tubular sodium reabsorption, which may be the result of defective intrarenal dopamine mobilisation.     

Presence of very low density lipoprotein compositional abnormalities in Type 1 (insulin-dependent) diabetic patients; effects of blood glucose optimisation

Summary Plasma lipoprotein compositional abnormalities were investigated in eight normolipidaemic (plasma cholesterol <5.70 mmol/l; triglyceride <2.03 mmol/l) young male Type 1 (insulin-dependent) diabetic patients (before and after a short period of optimised blood glucose control) and in nine healthy control subjects, matched for sex, age and body mass index. Free and esterified cholesterol, triglyceride, phospholipids were assayed in all lipoprotein classes (VLDL, IDL, LDL) and in HDL subclasses (HDL2 and HDL3); apoB was measured only in very low density lipoproteins (VLDL). All VLDL constituents were increased in the diabetic group, the differences being more striking for apoB (6.0±1.1 mg/dl vs 2.0±0.1 mg/dl, p<0.02), free cholesterol (0.27±0.04 mmol/l vs 0.13±0.02 mmol/l, p<0.02) and esterified cholesterol (0.32±0.08 mmol/l vs 0.13±0.01 mmol/l, p<0.05). Also HDL subfractions showed differences between the two groups: all HDL2 constituents were increased, while in HDL3 only triglyceride was significantly increased (0.11±0.01 mmol/l vs 0.08±0.004 mmol/l, p<0.02). After two weeks of optimised blood glucose control all VLDL constituents were reduced and particularly: esterified cholesterol (–39%, p<0.02), free cholesterol (–37%, p<0.05), apoB (– 35%, p<0.05). Expressing each VLDL constituent as percent of the total lipoprotein mass, it was evident that the diabetic VLDL was rich in cholesterol both esterified (8.4±1.0% vs 5.4±0.5%, p<0.02) and free (8.5±0.7% vs 5.5±0.3%, p<0.001), apo B (5.1±0.6% vs 2.6±0.3%, p<0.001) and depleted in triglyceride (57.0±1.7% vs 64.1±1.7%, p<0.001). Two weeks of optimised blood glucose control were not able to correct the abnormal composition of VLDL. In conclusion, Type 1 (insulin-dependent) diabetic patients, although normolipidaemic, show an abnormal VLDL composition suggesting an increased prevalence of smaller and, possibly, more atherogenic VLDL particles. This abnormality is not corrected by a short period of blood glucose optimisation.     

Renal insulin-like growth factor I and growth hormone receptor binding in experimental diabetes and after unilateral nephrectomy in the rat

Summary We have measured specific binding of insulin-like growth factor I and growth hormone to renal plasma membranes from control, streptozotocin-diabetic, insulin-treated diabetic, uninephrectomised and combined diabetic-uninephrectomised male Wistar rats. Control, insulin-treated and uninephrectomised rats had similar body weights after 7 days (243±2 g), whereas diabetic and diabetic-uninephrectomised animals were significantly lighter (219±4 and 203±4 g, p<0.05). Blood glucose concentrations were similar in the diabetic and diabetic-uninephrectomised animals (around 26 mmol/l) but significantly lower in the insulin-treated group. Right kidney weight increased by 14% in the control, insulin-treated and sham-nephrectomised animals, by 33% in the diabetic group, 38% in the nephrectomised animals and 60% in the diabetic-nephrectomised group. The renal content of insulin-like growth factor I was similar and stable in the control, insulin-treated and sham-nephrectomised animals (208±14 ng/g wet weight) but rose to a peak of 669±35 ng/g in the diabetic group (p<0.001), 871±34 ng/g in the nephrectomised animals (p<0.001) and 1012±43 ng/g in the diabetic-uninephrectomised group (p<0.001). Maximum binding of insulin-like growth factor I fell on day 1 in the diabetic group (8.3±1.4 vs 5.2±0.71× 10^– mol/l; p<0.01) but thereafter was identical to control animals. In the insulin-treated animals, maximum binding rose to 11.0±1.1×10^–11 mol/l, significantly different from control and diabetic animals (p<0.01). Growth hormone binding fell acutely in both the diabetic and diabetic-nephrectomised animals (3.13±0.58 and 2.83±0.21 vs 7.77±0.68×10^–12 mol/l; p<0.001 for both). Following uninephrectomy, maximum binding of insulin-like growth factor I and growth hormone was unchanged from control values. We conclude that the rise in renal content of insulin-like growth factor I which precedes the compensatory growth seen after induction of diabetes and uninephrectomy is not due to alterations in insulin-like growth factor I receptor binding and is independent of growth hormone binding.     

The Maillard protein cross-link pentosidine in urine from diabetic patients

Summary The Maillard protein cross-link pentosidine is a fluorescent condensation product of lysine, arginine and ribose. It accumulates in human tissues with age, and the accumulation process is accelerated in the tissues of diabetic patients. Using SP-Sephadex C-25 in the pretreatment for HPLC, we examined levels of pentosidine in urine without hydrolysis (free form) and levels of pentosidine in urine after hydrolysis (total forms), from 23 diabetic patients and 21 control subjects. The mean percentages of the values of free form per total forms (±SD) were 89±15% in diabetic patients, 88±16% in control subjects and 89±15% in total populations of diabetic patients and control subjects. There was a significant correlation between the values of free form and total forms in diabetic patients (r=0.938, p=0.0001), in control subjects (r=0.820, p<0.02) and in total populations of diabetic patients and control subjects (r=0.951, p=0.0001). The mean level of pentosidine per mol creatinine (±SD) was significantly elevated in urine from diabetic patients as compared to the level in control subjects (8.8±4.3 mol/mol creatinine vs 4.2±1.4 mol/mol creatinine, p=0.0001 in free form; 10.1±5.3 mol/mol creatinine vs 4.7±1.4 mol/mol creatinine, p=0.0001 in total forms). These results demonstrate that urinary pentosidine, especially in free form, could be a useful marker for the assessment of diabetes and diabetic complications.     

Effect of improved metabolic control on loss of kidney function in Type 1 (insulin-dependent) diabetic patients: an update of the Steno studies

Summary We re-examined 69 of the 70 patients entering the two independent Steno Studies of effects of improved metabolic control on progression of late diabetic complications. They were analysed according to an intent to treat after follow-up for 8 years (Steno Study 1) and 5 years (Steno Study 2). The glycaemic control had improved in the insulin infusion group compared with the conventional treatment group (mean HbA_1c) by 2.0±0.6% vs 0.7±1.2 in Steno Study 1 and by 1.8±1.2% vs 0.4±1.3 (p<0.01) in Steno Study 2. In the insulin infusion groups three patients had died during episodes of ketoacidosis. These were not caused by malfunction of the insulin infusion pumps. In the conventional treatment groups, three patients suffered five cardiovascular events causing two deaths. From the sixth month of Steno Study 1 the annual change of the glomerular filtration rate was –3.7 (–5.4 to –2.0) ml·min^–1·1.73 m^–2 vs –1.0 (–2.1 to –0.1) (conventional vs insulin infusion group, mean (95% confidence interval, p<0.01)). The change in urinary albumin excretion was associated with the glycaemic control (n=69, r=0.49, p<0.0002). No progression was observed among 32 patients with low range microalbuminuria (30 to 99 mg/24 h). Among the 19 patients with an initial albumin excretion between 100 and 300 mg/24 h, progression of complications was more frequent during conventional treatment (n=10) vs insulin infusion (n=9): Clinical nephropathy (10 of 10 vs 2 of 9, p<0.01) and arterial hypertension (7 of 10 vs 1 of 9, p<0.01). The glomerular filtration rate declined during conventional treatment by –23 (–42 to –4) ml·mm^–1·1.73 m^–2 (p<0.05) but not during insulin infusion (–13 (–31 to 5) NS). These results suggest that patients at risk of nephropathy should be offered near normal glycaemic control in order to preserve their kidney function.     

Disproportionate elevation of immunoreactive proinsulin in Type 2 (non-insulin-dependent) diabetes mellitus and in experimental insulin resistance

Summary In this study, we found that the ratio of proinsulin to total immunoreactive insulin was much higher in 22 patients with Type 2 (non-insulin-dependent) diabetes mellitus than in 28 non-diabetic control subjects of similar age and adiposity (32±3 vs 15±1%, p<0.001). In addition, the arginine-induced acute proinsulin response to total immunoreactive insulin response ratio was greater in diabetic patients (n=10) than in control subjects (n=9) (8±2 vs 2±0.5%, p=0.009), suggesting that increased islet secretion per se accounted for the increased ratio of proinsulin to immunoreactive insulin. One explanation for these findings is that increased demand for insulin in the presence of islet dysfunction leads to a greater proportion of proinsulin secreted from the B cell. We tested this hypothesis by comparing proinsulin secretion before and during dexamethasone-induced insulin resistance in diabetic patients and control subjects. Dexamethasone treatment (6 mg/day for 3 days) raised the proinsulin to immunoreactive insulin ratio in control subjects from 13±2 to 21±2% (p<0.0001) and in diabetic patients from 29±5 to 52±7% (p<0.001). Dexamethasone also raised the ratio of the acute proinsulin response to the acute immunoreactive insulin response in control subjects from 2±0.5 to 5±2% (p=0.01) and in diabetic patients from 8±2 to 14±4% (p=NS), suggesting that the dexamethasone-induced increment in the basal ratio of proinsulin to immunoreactive insulin was also due to increased secretion. We conclude that: (1) The basal proinsulin to immunoreactive insulin ratio is increased in obese Type 2 diabetic patients. (2) An increase in tissue demand for insulin leads to a rise in the proinsulin to immunoreactive insulin ratio, which is exaggerated in Type 2 diabetic patients. (3) The increased proinsulin to immunoreactive insulin ratio in these diabetic patients in the basal state and in diabetic patients and control subjects during experimental insulin resistance is probably due to increased B-cell secretion of proinsulin.     

Effect of insulin on renal sodium handling in hyperinsulinaemic Type 2 (non-insulin-dependent) diabetic patients with peripheral insulin resistance

Summary The sodium retaining effect of insulin was studied in ten Type 2 (non-insulin-dependent) diabetic patients (mean age 56 (43–73) years, mean body mass index 29.5 (24.2–33.7) kg/m²) and eight age-matched control subjects (mean age 57 (43–68) years, mean body mass index 23.4 (20.8–26.6) kg/m²). The renal clearances of ^99mTc-DTPA, lithium, sodium and potassium were measured over a basal period of 90 min. Then insulin was infused at a rate of 40 mU·mirr^–1·m^–2. After an equilibration period of 90 min, the clearance measurements were repeated during a new 90 min period. Blood glucose was clamped at the basal level (diabetic patients: 9.9±3.5, control subjects: 5.3±0.5 mmol/l) by a variable glucose infusion. Basal plasma insulin concentration was elevated in the diabetic patients (0.12±0.05 vs 0.05±0.02 pmol/ml, p<0.01). Insulin infusion resulted in comparable absolute increments in plasma insulin concentrations in the diabetic group and in the control group (0.44±0.13 vs 0.36±0.07 pmol/ml, NS). The metabolic clearance rate of glucose during the last 30 min of insulin infusion was lower in the diabetic patients (155±62 vs 320±69 ml·min^–1·m², p<0.01), reflecting peripheral insulin resistance. The decline in sodium clearance during insulin infusion was similar in diabetic subjects (1.8±1.1 vs 0.7±0.4 ml·min^–1·1.73 m^–2, p< 0.01) and in control subjects (1.7±0.3 vs 0.8±0.3 ml · min^–1 · 1.73 m^–2, p<0.01). The glomerular filtration rate and lithium clearance was unchanged, consequently calculated distal tubular fractional sodium reabsorption increased (diabetic patients: 92.9±4.1 vs 97.1±1.5, p<0.01, control subjects: 93.1±1.1 vs 96.5±0.6%, p< 0.01). Estimated extracellular fluid volume was 10% higher in the diabetic subjects (16.3±2.1 vs 14.8±2.01·1.73 m^–2, NS). In conclusion, the sodium retaining effect of insulin is preserved in Type 2 diabetic patients with peripheral insulin resistance. Insulin may contribute to sodium and fluid retention and thus to the increased frequency of hypertension in hyperinsulinaemic Type 2 diabetic patients.     

Association between plasma activities of semicarbazide-sensitive amine oxidase and angiotensin-converting enzyme in patients with type 1 diabetes mellitus

Aims/hypothesis Plasma semicarbazide-sensitive amine oxidase (SSAO) is elevated in patients with type 1 and type 2 diabetes and has been implicated in the pathophysiology of diabetic late complications. The regulation of SSAO production remains unknown. We studied correlations between plasma SSAO activity and parameters associated with diabetic late complications.Methods Plasma SSAO was measured in a well-characterised group of 287 patients with type 1 diabetes. Standard statistical methods were used to investigate correlations with clinical parameters and components of the renin–angiotensin system.Results Overall, plasma SSAO was elevated, at 693±196 mU/l (mean±SD; normal controls 352±102 mU/l). Plasma SSAO was higher in the group with late complications or hypertension, and in patients treated with ACE-inhibitors. In univariate analysis a significant positive correlation (p<0.001, r=0.27) was found between plasma SSAO and serum ACE activity in patients untreated with ACE inhibitors or angiotensin II receptor antagonists (n=221), but plasma SSAO did not differ by ACE I/D genotype. Plasma SSAO correlated positively with duration of diabetes, HbA₁c and plasma renin, and negatively with plasma angiotensinogen and body mass index. A multiple regression analysis including these variables resulted in serum ACE activity (p<0.001), ACE genotype (negatively, p<0.001) and HbA₁c (p=0.023) as explaining variables.Conclusions/interpretation Results suggest that a common factor is involved in the regulation of both plasma SSAO and serum ACE, which is different from the genetic determination of ACE activity.     

Lipoprotein composition in NIDDM: effects of dietary oleic acid on the composition,oxidisability and function of low and high density lipoproteins

Summary Oxidation of low density lipoprotein (LDL) plays an important role in the pathogenesis of atherosclerosis and is related to the fatty acid composition which is altered in diabetes mellitus. This study examines the relationship between the fatty acid composition of LDL and high density lipoprotein (HDL) and lipoprotein oxidation. A group of nine non-insulin-dependent diabetic (NIDDM) patients were compared to seven healthy control subjects before and after a high monounsaturated diet. Lipoproteins were isolated and oxidisability was measured by conjugated diene formation and lipid peroxide analysis. Serum HDL cholesterol was significantly lower in the diabetic patients. LDL cholesteryl ester linoleic acid in the diabetic patients was significantly higher at baseline and decreased after diet (p<0.05) while oleic acid increased in both diabetic and non-diabetic subjects (p<0.05). HDL cholesteryl ester oleic acid was lower in the diabetic patients compared with control subjects (p<0.05) before diet and it increased significantly after diet (p<0.05). LDL lipid peroxides and conjugated diene formation were related to LDL glycation (r=0.46, p<0.05 and r=0.49, p<0.05, respectively). Both decreased following diet (lipid peroxides for diabetic patients from 476±30 to 390±20 nmol/mg protein p<0.05 and for control subjects from 350±36 to 198±30 nmol/mg protein p<0.05). HDL conjugated diene formation decreased in both groups after diet but only significantly in the control group (55.4±7.5 to 53.2±6.7 nmol/mg protein for diabetic patients and 45.8±6.4 to 31.6±4.8 nmol/mg protein p<0.05 for control subjects). There was a positive correlation between LDL lipid peroxide formation and percentage of cholesteryl ester linoleic acid in LDL from diabetic patients (r=0.61, p<0.05) and control subjects (r=0.91, p<0.01). Fatty acid composition of LDL was reflected in the composition of HDL. In the presence of HDL lipoprotein peroxidation decreased. This decrease in lipoprotein peroxidation was positively related to the percentage of linoleic acid in LDL (r=0.71, p<0.05). This study confirms the close relationship between the fatty acid composition of LDL and HDL and demonstrates the importance of the fatty acid composition of the cholesteryl ester fraction in relation to LDL oxidation in diabetes. Linoleic acid in HDL appears to be a protecting factor against oxidation.Abbreviations BHT Butylated hydroxytoluene - EDTA ethyl-enediaminetetraacetic acid - TBARS thiobarbituric reacting substances - HPLC high performance liquid chromatography - MDA malondialdehyde - HbA_1c glycated haemoglobin     

Erythrocyte sodium-lithium countertransport activity is related to membrane fluidity in IDDM patients

Summary Sodium-lithium countertransport (SLC) activity at a standard physiological sodium concentration is raised in uncomplicated IDDM, for which the kinetic mechanism is a raised maximum velocity (V_max). Diabetic patients with nephropathy do not have raised values for V_max but a low Michaelis constant (k_m). Transporter activity could be influenced by its membrane lipid environment. This was assessed in 21 control subjects, 32 uncomplicated diabetic patients, 17 patients with diabetic nephropathy and 11 patients with nondiabetic nephropathy by measuring the fluorescence anisotropy of DPH and TMA-DPH to assess different membrane regions. Standard SLC was higher in all the patient groups compared to the control subjects: 0.307±0.020 mmol Li/h x 1 cells in uncomplicated IDDM; 0.300±0.032 in diabetic nephropathy patients and 0.276±0.019 in non-diabetic nephropathy patients vs 0.216±0.011 mmol Li/h x 1 cells in control subjects (p<0.001, p<0.05, p<0.05, respectively). This was due to raised V_max values in the uncomplicated group: 0.528±0.035 vs 0.385±0.022 mmol Li/h x 1 cells in control subjects (p=0.001) and low values for k_m in the diabetic nephropathy group: 58 (27–170) vs 106 (81–161) mmol/l in control subjects (p<0.001). Raised SLC in the non-diabetic nephropathy group was largely due to raised V_max: 0.460±0.030 mmol Li/h x 1 cells; p=0.053, with no difference in k_m: 99.5 (74–137). DPH anisotropy was lower in the uncomplicated diabetic patients (0.210±0.0009) compared to the control subjects (0.214±0.0007: p=0.006) and was related to both standard SLC (rs=-0.68, p<0.001) and V_max (rs= –0.77, p<0.001). Though DPH anisotropy in the diabetic nephropathy group was not different from normal control subjects, it also correlated with SLC (rs=-0.72, p<0.001) due to the same relationship with V_max (rs=-0.73, p<0.001) as in uncomplicated diabetes. TMA-DPH anisotropy showed no difference between the four groups and was not related to either standard SLC, V_max or k_m. Therefore, changes in membrane fluidity in the hydrophobic regions of the erythrocyte membrane may be responsible for some of the differences in SLC in IDDM.Abbreviations SLC sodium-lithium countertransport - DPH 1,6-diphenyl-1,3,5-hexatriene - TMA-DPH 1,4-trimethylammonium-3,5-hexatriene - IDDM insulin-dependent diabetes mellitus - NIDDM non-insulin-dependent diabetes mellitus     

Increased plasma adiponectin concentrations are associated with microangiopathy in type 1 diabetic subjects

Aims/hypothesis Insulin resistance is related to an increased risk of diabetic retinopathy and nephropathy in type 1 diabetes. Patients with insulin resistance and/or macrovascular disease have abnormally low levels of adiponectin. The aim of this study was to investigate the relationships between adiponectin and renal and retinal diabetic complications in type 1 diabetic patients.Methods In this 6-year prospective follow-up observational study, we evaluated the severity of retinopathy at baseline and determined the incident risk of microalbuminuria in 126 normoalbuminuric patients with type 1 diabetes. Each patient was age- and sex-matched to two non-diabetic control subjects.Results Plasma adiponectin concentrations were significantly higher in diabetic subjects than in control subjects (p<0.0001). The adiponectin concentration was significantly higher in patients with severe diabetic retinopathy than in those without (39.1±14.0 vs 29.0±13.0 g/ml, p=0.0005). The 18 patients who developed persistent microalbuminuria had higher adiponectin concentrations than the other patients (35.8±14.5 vs 30.6±13.7 g/ml). Increased adiponectin concentrations were independently associated with the occurrence of microalbuminuria (p=0.0158) after adjustment for baseline urinary albumin concentration (p=0.004), sex (p=0.0054), blood pressure (NS) and metabolic control (NS).Conclusions/interpretation The elevated adiponectin concentrations observed in subjects with microvascular disease may indicate an altered regulation of this adipocytokine in patients with complications associated with type 1 diabetes.     

Abnormal radiofurosemide binding by Tamm Horsfall glycoprotein of diabetic patients

Summary In the present study, 8 Type 1 diabetic patients with normal creatinine clearance and 8 matched controls were examined. Tamm Horsfall glycoprotein was isolated with the NaCl precipitation procedure. Its purity was checked by gelelectrophoresis, immunodiffusion and isoelectric focussing. Tamm Horsfall glycoprotein of diabetic patients had higher glucose (p<0.05) and lower N-acetylneuraminic acid content (p<0.01) than controls. ¹⁴C-furosemide binding by Tamm Horsfall glycoprotein was examined using an Amicon ultrafiltration system at 0 °C. In nominally sodium-free medium, furosemide binding by Tamm Horsfall glycoprotein was significantly (p<0.01) higher in diabetic patients than in matched controls. The increment of binding capacity with sodium was similar in controls and diabetic patients so that maximal binding capacity in a NaCl system was 1.7±0.3 in controls and 3.64±0.5 in diabetic patients (p<0.025). Half maximal furosemide binding by Tamm Horsfall glycoprotein occured at 1.4±0.2mmol Na/l in controls and 0.52±0.12 in diabetic patients (p<0.01). Abnormal radiofurosemide binding of Tamm Horsfall glycoprotein of diabetic patients may be the consequence of abnormal postribosomal modification of the glycoprotein which is synthesized in an insulin- and glucose-sensitive nephron segment.     

Social Consequences of Insulin-dependent Diabetes Mellitus are Limited: A Population-based Comparison of Young Adult Patients vs Healthy Controls

In a population-based study, the social situation of 91 young adult patients with Type 1 diabetes mellitus (IDDM) since childhood was compared to that of an age- and sex-matched group of 189 healthy persons. Their mean age was 37.2 years, duration of diabetes 28.7 years and severe complications were present in 13 of the 91 patients. A nearly 10-fold increased mortality rate was found in diabetic patients, mainly due to diabetic nephropathy and trauma, including suicide. The employment rate was lower in diabetic patients (71 % vs 85 %, p < 0.05); the need for welfare benefits was greater (15 % vs 3 %, p < 0.01). These differences were mainly the consequence of diabetic late complications. Education, housing conditions, life style, civil state, alcohol and smoking habits were similar in both groups. Confidence in the future was slightly less in diabetic patients (p < 0.05). In conclusion, besides an increased mortality rate, the present study has shown no serious social consequences in adult Type 1 diabetic patients without severe late complications, as compared to matched controls. Our results indicate that IDDM affects social life only to a limited extent, in the absence of severe vascular complications.     

A controlled trial of a high fibre,low fat and low sodium diet for mild hypertension in type 2 (non-insulin-dependent) diabetic patients

Summary Fifty hypertensive Type 2 (non-insulin-dependent) diabetic patients were allocated, in a controlled trial, to a treatment diet of high fibre, low fat and low sodium composition, or to a control diet by the hospital dietitian. After 3 months treatment, the modified diet-treated group showed a highly significant reduction in mean systolic (180.5±19.0 to 165.0±20.7 mmHg) and diastolic blood pressure (96.6±9.3 to 88.0±10.5 mmHg), accompanied by significant reductions in urinary sodium excretion (183.0±62.1 to 121.7+ 65.8 mmol/day) glycosylated haemoglobin (12.4±3.1 to 10.5±2.9%), weight (74.6s±13.5 to 71.7±12.1 kg) and serum triglyceride levels (p<0.05). The mean values of diastolic pressure (p<0.01), urinary sodium/potassium ratio (p< 0.001), urinary potassium (p<0.01) was significantly reduced at 3 months compared to control. No changes in serum HDL-cholesterol levels were observed. The number of patients with normal blood pressure at 3 months was greater in the modified diet-treated group (ten versus five). Treatment of mild hypertension in diabetic subjects with this form of dietary regimen has a hypotensive response, with improvement in glycaemic control and no side effects. This modified diet may be an attractive alternative to anti-hypertensive drug therapy as a first line treatment.     

Very low density lipoprotein subfraction abnormalities in IDDM patients: any effect of blood glucose control?

Summary Normolipidaemic insulin-dependent diabetic (IDDM) patients are characterized by an increase in the smaller VLDL particles, considered to be the most atherogenic. Since blood glucose control is one of the main regulators of lipid metabolism in diabetic patients, it could influence the shift in the distribution of VLDL subfractions towards smaller particles. To evaluate this possibility, VLDL subfractions, post-heparin lipoprotein lipase and hepatic lipase activities have been evaluated in male IDDM patients with either unsatisfactory blood glucose control (group 1, HbA_1c>8%, n=18) or good blood glucose control (group 2, HbA_1c<8%, n=16) and in 16 normoglycaemic individuals. The three groups were comparable for sex, age, body mass index, and plasma lipid levels. Three VLDL subfractions (large, Svedberg flotation unit (Sf) 175–400; intermediate, Sf 100–175; small, Sf 20–100) were separated by density gradient ultracentrifugation and analysed for cholesterol, triglyceride, and phospholipid levels. When compared to control subjects both groups of IDDM patients showed a clear shift in VLDL subfraction distribution with a significant increase in the proportion of small VLDL (group 1; 49±2%; p<0.005; group 2: 51±3%, p<0.01; control subjects 40±2%) (mean ± SEM) in relation to total VLDL. By contrast, the absolute lipid concentration of small VLDL was higher only in group 1, compared to control subjects (35±4 vs 27±3 mg/dl, p=0.05). Post-heparin hepatic lipase activity was significantly reduced in both IDDM groups (group 1: 254±19 mU/ ml, p<0.05; group 2: 202±19 mU/ml, p<0.005; control subjects 317±31 mU/ml). In conclusion, normolipidaemic IDDM patients show an increase in the smallest VLDL, whatever their degree of blood glucose control. However, this abnormality may be clinically relevant only in patients with unsatisfactory blood glucose control, since absolute lipid concentration of these potentially atherogenic particles is only increased in this group.Abbreviations IDDM Insulin-dependent diabetes mellitus - VLDL very low density lipoprotein - LPL lipoprotein lipase - HL hepatic lipase     

Ketone bodies increase glomerular filtration rate in normal man and in patients with Type 1 (insulin-dependent) diabetes mellitus

Summary The purpose of this study was to investigate whether the administration of acetoacetic and hydrochloric acids in a group of control and Type 1 (insulin-dependent) diabetic patients influenced renal haemodynamics. Renal plasma flow increased from 657±88 to 762±81 ml·min^–1. 1.73 m^–2 in diabetic patients (p<0.01) and from 590±71 to 691±135 in control subjects (p<0.01). Glomerular filtration rate increased from 135±9 to 180±8 ml·min^–1·1.73 m^–2 in diabetic patients (p< 0.001) and from 117±8 to 145±7 in control subjects (p<0.01). Similar effects on renal haemodynamics, even if less pronounced, were observed with low dose acetoacetic but not with hydrochloric acid infusion. Total protein, 2-microglobulin but not albumin excretion rates were increased by acetoacetic acid. We conclude that an acute increase in blood concentration of ketone bodies within the range found in diabetic patients with poor metabolic control (1) increases renal plasma flow and glomerular filtration rate both in control subjects and diabetic patients and (2) causes a tubular proteinuria.