Eero Helve

Hyperglycemia Decreases Glucose Uptake in Type I Diabetes

It has recently been postulated that hyperglycemia per se may contribute to insulin resistance in diabetes. To examine this possibility directly, we measured glucose uptake after 24 h of hyperglycemia (281 ±16 mg/dl) and normoglycemia (99 ± 6 mg/dl) in 10 type I (insulin-dependent) diabetic patients (age 33 ± 3 yr, relative body wt 102 ± 3%) treated with continuous subcutaneous insulin infusion. Hyperglycemia was induced by an intravenous glucose infusion, whereas saline was administered during the control day. During both studies the patient received a similar diet and insulin dose. After hyper- and normoglycemia, a primed continuous infusion of insulin (40 mU · m−2 · min−1) was started, and plasma glucose was adjusted to and maintained at 142 ± 2 and 140 ± 2 mg/dl, respectively, during 60–160 min of insulin infusion. The rate of glucose uptake after hyperglycemia averaged 8.3 ± 1.1 mg · kg−1 · min−1, which was lower than the rate after the normoglycemic period (10.1 ± 1.2 mg · kg−1 · min−1, P < .001). In conclusion, short-term hyperglycemia reduces glucose uptake in type I diabetic patients. Thus, part of the glucose or insulin resistance in these patients may be caused by hyperglycemia per se.

Insulin therapy induces antiatherogenic changes of serum lipoproteins in noninsulin-dependent diabetes.

To study the effect of rigorous inslulin on serum llpoproteins in patients with noninsulin-dependent diabetes not controlled with oral only, we measured serum llpoproteins, apoproteins, lipolytic enzymes, and glucose disposal using anf insulin clamp technique before and after 4 weeks of insulin therapy. Lipoproteins were isolated by ultracentrifugation and high density llpoprotein (HDL) subfractions, by rate-zonal density graddient ultracetrifugation. The group included 11 subfractions, by rate-zonal density gradient ultracentrifugation. The group included 11 women and eight men (age 58 ± 1 years adn RBW 125 ± 4%). Body weight, glycosylated hemoglobin, mean dlurnal glucose, plasma free insulin, and glucose uptake (M-value) were 75 vs. 76 kg; 11.9 vs. 8.9%; 234 vs. 124 mg/di; 123 vs. 27 μU/ml; and 5.0 ± 0.4 vs. 7.1 ± 0.6 mg/kg/min before and after insulin therapy, respectively. After Insulin therapy there was decrease of very low density lipoprotein (VLDL) triglyceride (−60%, p < 0.001) but an increase of HDL2 cholesterol (+21%, p < 0.001); HDL2 phosphollpids (+38%, p < 0.001); HDL2 proteins (+23% p < 0.01); and HDL2 mass (127 ± 11 vs. 158 ± 12 mg/dl, p < 0.001). There was a decrease of HDL3 cholesterol (−13%, p < 0.05); HDL3 phosphollpids (+38%, p < 0.001); HDL2 proteins (+23%, p < 0.01); and HDL2 mass (127 ± 11 vs. 158 ± 12 mg/dl, p < 0.001). There was a decrease of HDL3 cholesterol (−13%, p < 0.025<; HDL3 phospholipids (−16%, p < 0.05); HDL3 proteins (−18%, p < 0.001); and HDL3 mass (179 ± 6 vs. 146 ± 6, p < 0.01). Zonel profiles showed a redisttribution of particles from HDL3 to HDL2. Serum apo A-l increased (p < 0.05), apo A-ll remained constant, but apo B decreased (−29%, p < 0.001). The most marked change during insulin therapy was a 2.3-fold increase in adlpose tissue fllploprotein llpase (LPL) activity (p < 0.001). The changes of VLDL and HDL subfractions were not explained by respective changes of the blood glucose, free insulin, or M-value. The data indicate that intensive insulin therapy induces antiatherogenic changes in serum lipids and lipoproteins and suggest that the induction of LPL by insulin is the major factor responsible for redistribution of HDL particles from HDL3 to HDL2

Effect of apolipoprotein E polymorphism and Xbal polymorphism of apolipoprotein B on response to lovastatin treatment in familial and non‐familial hypercholesterolaemia

Abstract. Despite the well‐documented efficacy of lovastatin, a wide inter‐individual variation in treatment responses has been observed. The aim of the present study was to investigate the possible roles of apolipoprotein E (apo E) phenotype and apolipoprotein B (apo B) Xbal genotype on this variation. The apo E phenotype was determined in 232 subjects (78 cases of familial hypercholesterolaemia [FH] and 154 cases of non‐familial hypercholesterolaemia [non‐FH]) and the apo B Xbal genotype was determined in 211 subjects (67 cases of FH, 144 cases of non‐FH). Depending on their baseline total serum cholesterol levels, these patients used a starting dose of lovastatin of either 20 or 40 mg nightly. After 6 weeks of therapy, slightly but significantly smaller reductions in LDL‐cholesterol were observed in patients with the E4/3 phenotype compared with those with the E3/3 phenotype in non‐FH with lovastatin 20 mg (–20 vs. –28%; P = 0.043) and in total cholesterol in FH with lovastatin 40 mg (–23 vs. –27%; P = 0.023). No significant differences were found in non‐FH patients starting with lovastatin, 40 mg. After doubling of the lovastatin doses, all treatment responses became similar among apo E phenotypes. Moreover, when all patients using lovastatin 40 mg either at 6 or 12 weeks were pooled (n = 224), no differences in treatment responses were observed between the E3/2, E3/3, E4/3 and E4/4 phenotypes. The apo B Xbal genotype did not affect the hypocholesterolaemic efficacy of lovastatin in any of the patient groups. Thus our results indicate that inter‐individual variation in the treatment response to lovastatin in both familial and non‐familial hypercholesterolaemia is mainly due to factors other than the apo E phenotype or apo B Xbal genotype.

Pathogenesis and Prevention of the Dawn Phenomenon in Diabetic Patients Treated with CSII

The mechanism of the dawn phenomenon was studied in 12 C-peptide-negative type I diabetic patients (age 30 ± 2 yr) treated with continuous subcutaneous insulin infusion. During constant basal infusion, nocturnal glycemia remained constant until 4 a.m., but began to rise thereafter in 10/12 patients, with the mean rise from 4.6 ± 0.4 mmol/L to 6.1 ± 0.7 mmol/L (P < 0.01) by 8 a.m. In these patients the rate of glucose production (Ra, 2.14 ± 0.04 mg/kg/min, 3-H3-glucose infusion) exceeded the rate of utilization (Rd, 1.89 ± 0.03 mg/kg/ min, P < 0.02). When the patients were restudied after the infusion rate was increased by 49 ± 7%, Ra fell to 1.75 ± 0.03 mg/kg/min (P < 0.01) and the dawn phenomenon was abolished. However, both Ra and Rd remained higher in the diabetic subjects (P / 0.05) than in eight healthy control subjects, in whom Ra (1.66 ± 0.02 mg/kg/min) was equal to Rd with glycemia remaining unchanged. Peripheral free insulin levels in the diabetic patients were similar during constant (12.3 ± 0.5 mU/L) and increased infusion rate (11.3 ± 0.4 mU/L), and higher than those of the control subjects (5.2 ± 0.2 mU/L, P < 0.05). A diurnal rise in serum cortisol levels occurred 1 h earlier in the diabetic than in the control subjects, and Ra was directly proportional to serum cortisol concentration (r = 0.61; P < 0.01). Serum growth hormone levels were also slightly higher in the diabetic than the control subjects. In conclusion: (1) A dawn phenomenon is associated with an excessive rate of glucose production, rather than impaired utilization; (2) this may be explained, at least in part, by elevated counterregulatory hormone levels; and (3) a step-up in the overnight insulin delivery reduces hepatic glucose production and so prevents the dawn phenomenon.

Bedtime Insulin for Suppression of Overnight Free–Fatty Acid, Blood Glucose, and Glucose Production in NIDDM

We studied the clinical effectiveness and mechanism underlying the glucose-lowering effect of evening insulin therapy. Nocturnal profiles of blood glucose, plasma free fatty acid (FFA), glycerol, and lactate and overnight glucose kinetics ([3-3H] glucose infusion) were measured in 15 non-insulin-dependent diabetic (NIDDM) patients with a relative body weight of 128 ± 4% who were poorly controlled with oral therapy alone. The patients were studied before and 2 wk and 3 mo after bedtime insulin (23 ± 3 IU) was given in addition to oral therapy. An early-morning rise in blood glucose (>31 mg/dl = 1.5 mM) was present in two-thirds of the patients and was associated with an overnight rise in plasma FFA and an increase in glucose production (Ra) during the early-morning hours (change 0.42 ± 0.10 mg · kg−1 · min−1 P < .05, between 0300 and 0800). The overnight mean levels of blood glucose, plasma FFA, and serum insulin averaged 212 ± 9 vs. 137 ± 11 vs. 133 ± 11 mg/dl (P < .001), 674 ± 61 vs. 491 ± 57 vs. 484 ± 36 μM (P < 0.01) and 12.7 ± 1.6 vs. 18.1 ± 2.2 vs. 20.7 ± 2.4 μU/ (P < .01) before and 2 wk and 3 mo after the combination therapy. The decrements in overnight glucose and FFA levels after 2 wk of bedtime insulin therapy were closely correlated (r = .86, P < .001). The nocturnal profile of plasma lactate was similar before and during bedtime insulin therapy. The overnight mean glucose Ra fell significantly after insulin administration (2.31 ± 0.13 vs. 1.83 ± 0.09 vs. 1.83 ± 0.10 mg · kg−1 min−1 P < .01, respectively). There was a positive correlation between the overnight mean values of Ra and the plasma FFA concentration (r = .58, P < .001). These data raise the possibility the improvement in overall glycemic control by the administration of evening insulin is related to the suppression of overnight plasma FFA concentrations and to a consequent reduction in overnight glucose production.

Genetic polymorphism of the apolipoprotein B gene locus influences serum LDL cholesterol level in familial hypercholesterolemia

SummaryAn XbaI restriction fragment length polymorphism (RFLP) within the coding region of the apolipoprotein B (apoB) gene has been found to be associated with serum cholesterol and triglyceride levels in several populations. Mutations in another genetic locus, the low density lipoprotein (LDL) receptor gene, give rise to familial hypercholesterolemia (FH), a disease characterized by hypercholesterolemia, tendon xanthmas and atherosclerosis. We determined the XbaI genotypes and serum lipoprotein levels of 120 unrelated patients with the heterozygous form of FH. A non-parametric analysis of variance showed a significant association between elevated serum total cholesterol concentration (P<0.05), serum LDL-choleterol concentration (P<0.025) and the presence of the XbaI restriction site (X2 allele). Thus, patients homozygous for the presence of the XbaI restriction site (genotype X2X2, n=28) had on average a 14% higher serum total cholesterol level and a 21% higher serum LDL-cholesterol level than those homozygous for the absence of this site (genotype X1X1, n=29); patients heterozygous for the XbaI restriction site (genotype X1X2, n=63) had intermediate serum total and LDL-cholesterol levels. No significant differences were seen in serum triglyceride or high-density lipoprotein (HDL)-cholesterol values between these patient groups. These data demonstrate that genetic polymorphism of the principal ligand for the LDL receptor, apoB, may contribute to serum cholesterol regulation, even in patients with grossly distorted cholesterol homeostasis.

The adjustment of diet and insulin dose during long-term endurance exercise in type 1 (insulin-dependent) diabetic men.

SummaryWe examined in 2 consecutive years the effect of a 75-km (>7 h) cross country skiing on dietary and insulin requirements and glycaemic control in 9 Type 1 (insulin-dependent) diabetic patients. In the first year, the patients were hyperglycaemic (20.9±1.8 mmol/l) before the race due to excessive carbohydrate loading (65 g) and reduction (by 58%) of short-acting insulin for breakfast. In the second year, breakfast included less carbohydrate (40 g) and more protein, and the morning short-acting insulin was reduced by 35%. With this adjustment of therapy the pre-exercise hyperglycaemia was less (p<0.05). The morning intermediate-acting insulin was reduced by 28 and 38% in consecutive years. During both races carbohydrate intake approximated 40 g/h, and blood glucose was maintained at near normal levels after 33 km of skiing. Hypoglycaemia did not occur during exercise, but one patient had symptomatic hypoglycaemia after finishing the second race. The day after exercise insulin sensitivity was increased in all four patients studied. Insulin treated patients can perform strenuous long-term exercise and maintain near normoglycaemia with a proper adjustment of therapy. Augmented insulin sensitivity may contribute to post-exercise hypoglycaemia.

Comparison of lovastatin and probucol in treatment of familial and non-familial hypercholesterolemia: different effects on lipoprotein profiles

In order to compare the effects of lovastatin and probucol on lipoprotein profiles, we treated 32 familial hypercholesterolemia (FH) heterozygotes and 26 patients with non-familial hypercholesterolemia for 14 weeks with either probucol (1 g/d) or lovastatin (40-80 mg/d) in a randomized double-blind study. Lovastatin at 80 mg/d reduced low density lipoprotein (LDL)-cholesterol and apo B by more than 40% in both familial and non-familial hypercholesterolemia (non-FH). Probucol reduced LDL-cholesterol by 10-17% while LDL-apo B levels were not influenced at all (FH) or fell by 13% (non-FH). Analysis of LDL composition demonstrated that the LDL-cholesterol lowering effect of probucol in FH was entirely due to reduction in the proportion of cholesterol in LDL with no reduction in LDL mass. Serum high density lipoprotein2 (HDL2)-cholesterol levels fell by 27-33% during probucol, whereas HDL2-cholesterol increased by 10-18% with lovastatin 80 mg/d. These changes in HDL2 were not mediated by lipoprotein lipase or hepatic lipase, both of which are known to participate in regulation of this lipoprotein.

Smoking and insulin sensitivity in type I diabetic patients

Smoking increases counterregulatory hormone secretion and reduces capillary flow, both of which could reduce insulin mediated glucose disposal. To evaluate whether smoking has any effect on body sensitivity to insulin, we measured insulin-mediated glucose disposal (1 mU euglycemic insulin clamp) during acute smoking in seven male type I diabetic patients. In addition, we performed a cross-sectional study to compare insulin sensitivity in 12 habitually smoking and 22 nonsmoking diabetic patients matched for age, relative body weight, sex, diabetes duration, HbA1, C-peptide, and insulin dose. In the acute study, baseline counterregulatory hormone levels were comparable in the smoking and control experiment. During smoking (9 to 12 cigarettes), carboxyhemoglobin level rose by 57% (P less than 0.01). Circulating adrenaline, cortisol, growth hormone, and glucagon levels were 40% to 100% higher during smoking than during the control clamp study (P less than 0.05-0.01). During acute smoking the rate of insulin-mediated glucose uptake (7.3 +/- 1.0 mg/kg/min) was not significantly different from that without cigarettes (6.8 +/- 0.7 mg/kg/min). In the cross-sectional study, the rate of glucose uptake was comparable in habitually smoking (5.0 +/- 0.5 mg/kg/min) and nonsmoking patients (4.8 +/- 0.3 mg/kg/min). Thus, inspite of a significant rise in counterregulatory hormones, neither acute nor habitual smoking causes substantial changes in insulin sensitivity in type I diabetics.

Inhibition of Dietary Cholesterol Absorption During Lovastatin (Mevinolin) Treatment

SummaryDietary butter was replaced by egg yolks in hypercholesterolaemic subjects treated with lovastatin (mevinolin) in order to record the effect of dietary cholesterol loading on serum cholesterol levels and cholesterol metabolism. The increase in cholesterol intake by 530 mg/day caused no change in total serum cholesterol, lipoprotein cholesterol or cholesterol precursor levels. Outputs of faecal bile acids were unchanged and those of neutral sterols were increased to the extent of the increase in dietary cholesterol intake, indicating that cholesterol synthesis was unchanged. Serum non-cholesterol sterol levels and sterol balance data did not suggest changes in cholesterol absorption or synthesis during the high cholesterol diet. In contrast to that in butter-fed control subjects, cholesterol absorption efficiency was significantly decreased by 25% in the cholesterol-fed patients. Calculations revealed that, owing to the decreased absorption efficiency, the increase in the intestinal cholesterol pool by dietary cholesterol was associated with increased dietary, decreased biliary and unchanged total amounts of absorbed cholesterol. Thus, impairment of cholesterol absorption by lovastatin may render a strict limitation in dietary cholesterol intake unnecessary during long term treatment.