Monitoring of early and advanced glycation in relation to the occurrence of microvascular complications in children and adolescents with type 1 diabetes mellitus

The authors aimed to evaluate if the monitoring of serum advanced glycation end-products (s-AGEs) could help to predict a development of diabetic complications. Clinical and biochemical parameters including fructosamine (FAM), glycated hemoglobin (HbA1c) and serum AGEs were investigated in children and adolescents with 1 type diabetes with (+DC) and without (-DC) complications. FAM levels (in mmol/l) were significantly elevated in +DC diabetic group compared to -DC one (3.043+/-0.459 vs. 2.614+/-0.430; p<0.001) or to controls (3.043+/-0.459 vs. 1.620+/-0.340; p<0.001) as well as in -DC compared to controls (2.614+/-0.430 vs. 1.620+/-0.340; p<0.001). HbA1c (in %) were significantly elevated in +DC diabetic group compared to -DC one (10.48+/-1.83 vs. 8.41+/-1.19; p<0.001) or to controls (10.48+/-1.83 vs. 5.0+/-0.38, p<0.001) and also in -DC compared to controls (8.41+/-1.19 vs. 5.0+/-0.38; p<0.001). Serum AGEs levels (in A. U.) were significantly higher in +DC group than in -DC (73.0+/-14.09 vs. 65.8+/-9.05; p<0.05) and in group +DC than in controls (73.0+/-14.09 vs. 60.17+/-13.78; p<0.05), whereas there was no difference between -DC and controls. FAM correlated with HbA1c in both diabetic groups (+DC: r=0.374; p<0.05; -DC: r=0.719; p<0.001), but not in controls. Serum AGEs were correlated with HbA1c (r=0.478; p=0.003) in +DC, but not in -DC or controls. Enhanced serum AGEs levels show that they could be not only an attendant phenomenon of microangiopathies, but also a predictor of their development.     

Evidence for physiological coupling of insulin-mediated glucose metabolism and limb blood flow

We hypothesized that the vasodilation observed during insulin stimulation is closely coupled to the rate of glucose metabolism. Lean (L, n = 13), obese nondiabetic (OB, n = 13), and obese type 2 diabetic subjects (Type 2 DM, n = 16) were studied. Leg blood flow (LBF) was examined under conditions of euglycemic hyperinsulinemia (EH) and hyperglycemic hyperinsulinemia (HH), which produced a steady-state whole body glucose disposal rate (GDR) of approximately 2,000 micromol. m(-2). min(-1). At this GDR, under both conditions, subjects across the range of insulin sensitivity exhibited equivalent LBF (l/min EH: L, 0.42 +/- 0.03; OB, 0.43 +/- 0. 03; Type 2 DM, 0.38 +/- 0.07; P = 0.72 by ANOVA. HH: L, 0.44 +/- 0. 04; OB, 0.39 +/- 0.05; Type 2 DM, 0.41 +/- 0.04; P = 0.71). The continuous relationship between LBF and GDR did not differ across subject groups [slope x 10(-5) l/(micromol. m(-2). min(-1)) by ANOVA. EH: L, 8.6; OB, 9.2; Type 2 DM, 7.9; P = 0.91. HH: L, 4.2; OB, 2.5; Type 2 DM, 4.1; P = 0.77], although this relationship did differ between the EH and HH conditions (P = 0.001). These findings support a physiological coupling of LBF and insulin-mediated glucose metabolism. The mechanism(s) linking substrate delivery and metabolism appears to be intact in insulin-resistant states.     

Short-term very low calorie diet reduces oxidative stress in obese type 2 diabetic patients

Oxidative stress is higher in obese diabetic than in non-diabetic subjects. This pilot study evaluates oxidative stress during short-term administration of a very low calorie diet in obese persons. Nine obese Type 2 diabetic patients (age 55+/-5 years, BMI 35.9+/-1.9 kg/m2) and nine obese non-diabetic control subjects (age 52+/-6 years, BMI 37.3+/-2.1 kg/m2) were treated by a very low calorie diet (600 kcal daily) during 8 days stay in the hospital. Serum cholesterol, triglycerides, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (B-HB), ascorbic acid (AA), alpha-tocopherol (AT), plasma malondialdehyde (MDA) and superoxide dismutase (SOD) activity in erythrocytes were measured before and on day 3 and 8 of very low calorie diet administration. A decrease of serum cholesterol and triglyceride concentrations on day 8 was associated with a significant increase of NEFA (0.30+/-0.13 vs. 0.47+/-0.11 micromol/l, p<0.001) and B-HB (0.36+/-.13 vs. 2.23+/-1.00 mmol/l, p<0.001) in controls but only of B-HB (1.11+/-0.72 vs. 3.02+/-1.95 mmol/l, p<0.001) in diabetic patients. A significant decrease of plasma MDA and serum AT together with an increase of SOD activity and AA concentration (p<0.01) was observed in control persons, whereas an increase of SOD activity (p<0.01) was only found in diabetic patients after one week of the very low calorie diet. There was a significant correlation between NEFA or B-HB and SOD activity (p<0.01). We conclude that one week of a very low calorie diet administration decreases oxidative stress in obese non-diabetic but only partly in diabetic persons. Diabetes mellitus causes a greater resistance to the effects of a low calorie diet on oxidative stress.     

Insulin action on protein metabolism in acromegalic patients

Insulin resistance in acromegaly causes glucose intolerance and diabetes, but it is unknown whether it involves protein metabolism, since both insulin and growth hormone promote protein accretion. The effects of acromegaly and of its surgical cure on the insulin sensitivity of glucose and amino acid/protein metabolism were evaluated by infusing [6,6-(2)H(2)]glucose, [1-(13)C]leucine, and [2-(15)N]glutamine during a euglycemic insulin (1 mU x kg(-1) x min(-1)) clamp in 12 acromegalic patients, six studied again 6 mo after successful adenomectomy, and eight healthy controls. Acromegalic patients, compared with postsurgical and control subjects, had higher postabsorptive glucose concentration (5.5 +/- 0.3 vs. 4.9 +/- 0.2 micromol/l, P < 0.05, and 5.1 +/- 0.1 micromol/l) and flux (2.7 +/- 0.1 vs. 2.0 +/- 0.2 micromol x kg(-1) x min(-1), P < 0.01, and 2.2 +/- 0.1 micromol x kg(-1) x min(-1), P < 0.05) and reduced insulin-stimulated glucose disposal (+15 +/- 9 vs. +151 +/- 18%, P < 0.01, and 219 +/- 58%, P < 0.001 from basal). Postabsorptive leucine metabolism was similar among groups. In acromegalic and postsurgical subjects, insulin suppressed less than in controls the endogenous leucine flux (-9 +/- 1 and -12 +/- 2 vs. -18 +/- 2%, P < 0.001 and P < 0.05), the nonoxidative leucine disposal (-4 +/- 3 and -1 +/- 3 vs. -18 +/- 2%, P < 0.01 and P < 0.05), respectively, indexes of proteolysis and protein synthesis, and leucine oxidation (-17 +/- 6% in postsurgical patients vs. -26 +/- 6% in controls, P < 0.05). Within 6 mo, surgery reverses insulin resistance for glucose but not for protein metabolism. After adenomectomy, more leucine is oxidized during hyperinsulinemia.     

Hyperlipoproteinemia impairs endothelium-dependent vasodilation

Atherogenic lipoproteins can cause endothelial dysfunction in the initial stage of atherogenesis. In our study we examined 134 patients with defined hyperlipoproteinemia (non-HDL cholesterol>4.1 mmol/l or triglycerides>2.5 mmol/l or taking any of lipid lowering drugs)--94 men and 40 women. The subgroup of controls of comparable age contained 54 normolipidemic individuals--30 men and 24 women. Patients with hyperlipoproteinemia revealed significantly lower ability of endothelium-dependent flow-mediated vasodilation (EDV) measured on brachial artery (4.13+/-3.07 vs. 5.41+/-3.82 %; p=0.032) and higher carotid intima media thickness than normolipidemic controls (0.68+/-0.22 vs. 0.58+/-0.15 mm; p=0.005). In regression analysis, EDV correlated significantly with plasma concentrations of oxLDL (p<0.05) HDL-cholesterol (p<0.05), Apo A1 (p<0.05), ATI (p<0.01) and non-HDL cholesterol (p<0.05). Patients with hyperlipoproteinemia showed higher plasma levels of oxLDL (65.77+/-9.54 vs. 56.49+/-7.80 U/l; p=0.015), malondialdehyde (0.89+/-0.09 vs. 0.73+/-0.08 micromol/l; p=0.010) and nitrites/nitrates (20.42+/-4.88 vs. 16.37+/-4.44 micromol/l; p=0.018) indicating possible higher long-term oxidative stress in these patients.     

Contribution of nitric oxide to cutaneous microvascular dilation in individuals with type 2 diabetes mellitus

Microvascular pathophysiology associated with type 2 diabetes mellitus (T2DM) contributes to several aspects of the morbidity associated with the disease. We quantified the contribution of nitric oxide (NO) to the cutaneous vasodilator response to nonpainful local warming in subjects with T2DM (average duration of diabetes mellitus 7 +/- 1 yr) and in age-matched control subjects. We measured skin blood flow in conjunction with intradermal microdialysis of N(G)-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or vehicle during 35 min of local warming to 42 degrees C. Microdialysis of sodium nitroprusside (SNP) was used for assessment of maximum cutaneous vascular conductance (CVC). Resting CVC was higher in T2DM subjects at vehicle sites (T2DM: 19 +/- 2 vs. control: 11 +/- 3%maxCVC; P < 0.05); this difference was abolished by l-NAME (T2DM: 10 +/- 1 vs. control: 8 +/- 1%maxCVC; P > 0.05). The relative contribution of NO to the vasodilator response to local warming was not different between groups (T2DM: 46 +/- 4 vs. control: 44 +/- 6%maxCVC; P > 0.05). However, absolute CVC during local warming was approximately 25% lower in T2DM subjects (T2DM: 1.79 +/- 0.15 AU/mmHg; controls: 2.42 +/- 0.20 AU/mmHg; P < 0.01), and absolute CVC during SNP was approximately 20% lower (T2DM: 1.91 +/- 0.12 vs. control: 2.38 +/- 0.13 AU/mmHg; P < 0.01). We conclude that the relative contribution of NO to vasodilation during local warming is similar between subjects with T2DM and control subjects, although T2DM was associated with a lower absolute maximum vasodilation.     

Paraoxonase 1 gene polymorphisms and enzyme activities in diabetes mellitus

Paraoxonase 1 (PON1), an antioxidant enzyme closely associated with HDL (high-density lipoproteins), preserves LDL (low-density lipoproteins) against oxidation. Less protection may be therefore supposed by decreased PON1 activity. This study was undertaken to investigate the association of PON1 gene polymorphisms with diabetic angiopathy and to evaluate the relationship of these polymorphisms with PON1 activity. Total of 86 Type 1 (T1DM) and 246 Type 2 (T2DM) diabetic patients together with 110 healthy subjects were examined. DNA isolated from leukocytes was amplified with polymerase chain reaction (PCR) followed by restriction enzyme digestion. The products were analyzed for L55M and Q192R polymorphisms in coding region and for -107 C/T and -907 G/C in promotor sequence of PON1. Serum enzyme activity was measured spectrophotometrically. Significant differences were found between T1DM or T2DM and control persons in L55M polymorphism (allele M more frequent in T1DM and T2DM vs. controls, p<0.05) and Q192R polymorphism (R allele less frequent in T1DM and T2DM vs. controls, p<0.01) of the PON1 gene. Serum PON1 activity was significantly decreased in T1DM (110+/-68 nmol/ml/min) and T2DM patients (118+/-69 nmol/ml/min) compared to the control persons (203+/-58 nmol/ml/min), both p<0.01. The presence of MM and QQ genotypes was accompanied by lower PON1 activity than of LL and RR genotypes (p<0.05), respectively. Better diabetes control was found in patients with LL than with MM genotypes and similarly in RR genotype than QQ genotype with p<0.05. Significantly different allele frequencies were found in diabetic patients with macroangiopathy than in those without it (M: 0.59 vs. 0.44. R: 0.12 vs. 0.19, p<0.01). The association of PON1 polymorphisms, lower PON1 activity and poorer diabetes control found in patients with macroangiopathy further support the idea of genetic factors contributing to the development of vascular disorders in diabetes.     

Enalapril in subantihypertensive dosage attenuates kidney proliferation and functional recovery in normotensive ablation nephropathy of the rat

Most studies on the antiproliferative action of angiotensin converting enzyme inhibitors (ACEI) were performed in a rat hypertensive remnant kidney model with 5/6 kidney ablation which raised objections about the antihypertensive effect of ACEI and the influence of other antihypertensive drugs administered to remnant kidney control rats. To prevent these objections, a normotensive 4/6 remnant kidney model was elaborated and a subantihypertensive dosage of enalapril was used to evaluate its antiproliferative action. Subtotally nephrectomized rats (Nx) markedly increased the remnant kidney weight during a 4-week period and this rise was prevented by the treatment with enalapril (NxE) (Nx +297+/-35 mg vs. sham-operated +145+/-32 mg, p<0.001; NxE +154+/-35 mg vs. Nx p<0.001). While collagen concentration in the kidney cortex was not increased in sham-operated rats (Sham) in comparison with the control group (Ctrl) at the beginning of the study, the subsequent increase was significant in the Nx group and enalapril did not attenuate this increase (Sham 148+/-5 mg/100 g w.w. vs. Nx 164+/-2 mg/100 g w.w., p<0.01; NxE 161+/-4 mg/100 g w.w. vs. Sham p<0.05). The tubular protein/DNA ratio increase, which was significant in the Nx group, was inhibited by enalapril (Nx 26.2+/-10.5 vs. NxE 15.3+/-2.6, p<0.05). The protein/DNA ratio was much lower in glomeruli, with no significant changes in either the Nx or NxE groups. Serum urea concentrations were slightly higher in the Nx group than in the sham-operated group, but markedly elevated in the NxE group (Nx 10.71+/-0.76 mmol/l vs. Sham 6.10+/-0.33 mmol/l, p<0.001; NxE 28.9+/-2.6 mmol/l vs. Sham p<0.001). Creatinine concentrations in the Nx group were increased in comparison with the sham-operated group and markedly increased in the NxE group (Nx 63.7+/-3.56 micromol/l vs. Sham 37.2+/-2.84 micromol/l, p<0.001; NxE 107.0+/-5.2 micromol/l vs. Sham p<0.001). The clearance of creatinine was lower in the Nx group than in the sham-operated group and was markedly reduced in the NxE group (Nx 0.89+/-0.06 ml/min.g kidney wt. vs. Sham 1.05+/-0.16 ml/min x g kidney wt., p<0.01; NxE 0.58+/-0.029 ml/min x g kidney wt. vs. Sham, p<0.001). Enalapril improved proteinuria in comparison with the Nx group (NxE 5.6+/-0.6 mg/24 h vs. Nx 16.1+/-3.4 mg/24 h, p<0.05). Thus remnant kidney proliferation is substantial even in normotensive rats. It includes both proliferation and collagen accumulation with partial recovery of kidney weight and function, but is accompanied by enhanced proteinuria. Enalapril attenuates the proliferation and decreases proteinuria but prolongs kidney function recovery.     

Insulin resistance,intramyocellular lipid content,and plasma adiponectin in patients with type 1 diabetes

Insulin resistance is a key pathogenic factor of type 2 diabetes (T2DM); in contrast, in type 1 diabetes (T1DM) it is considered a secondary alteration. Increased intramyocellular lipid (IMCL) content accumulation and reduced plasma adiponectin were suggested to be pathogenic events of insulin resistance in T2DM. This study was designed to assess whether IMCL content and plasma adiponectin were also associated with the severity of insulin resistance in T1DM. We studied 18 patients with T1DM, 7 older and overweight/obese patients with T2DM, and 15 nondiabetic, insulin-resistant offspring of T2DM parents (OFF) and 15 healthy individuals (NOR) as appropriate control groups matched for anthropometric features with T1DM patients by means of the euglycemic hyperinsulinemic clamp combined with the infusion of [6,6-2H2]glucose and 1H magnetic resonance spectroscopy of the calf muscles. T1DM and T2DM patients showed reduced insulin-stimulated glucose metabolic clearance rate (MCR: 5.1 +/- 0.6 and 3.2 +/- 0.8 ml x kg(-1) min(-1)) similar to OFF (5.3 +/- 0.4 ml x kg(-1) x min(-1)) compared with NOR (8.5 +/- 0.5 ml x kg(-1) min(-1), P < 0.001). Soleus IMCL content was increased in T1DM (112 +/- 15 AU), T2DM (108 +/- 10 AU) and OFF (82 +/- 13 AU) compared with NOR (52 +/- 7 AU, P < 0.05) and the result was inversely proportional to the MCR (R2 = 0.27, P < 0.001); an association between IMCL content and Hb A1c was found only in T1DM (R2 = 0.57, P < 0.001). Fasting plasma adiponectin was reduced in T2DM (7 +/- 1 microg/ml, P = 0.01) and OFF (11 +/- 1 microg/ml, P = 0.03) but not in T1DM (25 +/- 6 microg/ml), whose plasma level was increased with respect to both OFF (P = 0.03) and NOR (16 +/- 2 microg/ml, P = 0.05). In conclusion, in T1DM, T2DM, and OFF, IMCL content was associated with insulin resistance, demonstrating that IMCL accretion is a marker of insulin resistance common to both primary genetically determined and secondary metabolic (chronic hyperglycemia) alterations. The increased adiponectin levels in insulin-resistant patients with T1DM, in contrast to the reduced levels found in patients with T2DM and in OFF, demonstrated that the relationship of adiponectin to insulin resistance in humans is still unclear.     

Effects of glutamine supplementation, GH, and IGF-I on glutamine metabolism in critically ill patients

During critical illness glutamine deficiency may develop. Glutamine supplementation can restore plasma concentration to normal, but the effect on glutamine metabolism is unknown. The use of growth hormone (GH) and insulin-like growth factor I (IGF-I) to prevent protein catabolism in these patients may exacerbate the glutamine deficiency. We have investigated, in critically ill patients, the effects of 72 h of treatment with standard parenteral nutrition (TPN; n = 6), TPN supplemented with glutamine (TPNGLN; 0.4 g x kg(-1) x day(-1), n = 6), or TPNGLN with combined GH (0.2 IU. kg(-1). day(-1)) and IGF-I (160 microg x kg (-1) x day(-1)) (TPNGLN+GH/IGF-I; n = 5) on glutamine metabolism using [2-(15)N]glutamine. In patients receiving TPNGLN and TPNGLN+GH/IGF-I, plasma glutamine concentration was increased (338 +/- 22 vs. 461 +/- 24 micromol/l, P < 0.001, and 307 +/- 65 vs. 524 +/- 71 micromol/l, P < 0.05, respectively) and glutamine uptake was increased (5.2 +/- 0.5 vs. 7.4 +/- 0.7 micromol x kg(-1) x min(-1), P < 0.05 and 5.2 +/- 1.1 vs. 7.6 +/- 0.8 micromol x kg(-1) x min(-1), P < 0.05). Glutamine production and metabolic clearance rates were not altered by the three treatments. These results suggest that there is an increased requirement for glutamine in critically ill patients. Combined GH/IGF-I treatment with TPNGLN did not have adverse effects on glutamine metabolism.