Activation of the Ras/mitogen-activated protein kinase signaling pathway alone is not sufficient to induce glucose uptake in 3T3-L1 adipocytes.

The signal transduction pathway by which insulin stimulates glucose transport is largely unknown, but a role for tyrosine and serine/threonine kinases has been proposed. Since mitogen-activated protein (MAP) kinase is activated by insulin through phosphorylation on both tyrosine and threonine residues, we investigated whether MAP kinase and its upstream regulator, p21ras, are involved in insulin-mediated glucose transport. We did this by examining the time- and dose-dependent stimulation of glucose uptake in relation to the activation of Ras-GTP formation and MAP kinase by thrombin, epidermal growth factor (EGF), and insulin in 3T3-L1 adipocytes. Ras-GTP formation was stimulated transiently by all three agonists, with a peak at 5 to 10 min. Thrombin induced a second peak at approximately 30 min. The activation of p21ras was paralleled by both the phosphorylation and the activation of MAP kinase: transient for insulin and EGF and biphasic for thrombin. However, despite the strong activation of Ras-GTP formation and MAP kinase by EGF and thrombin, glucose uptake was not stimulated by these agonists, in contrast to the eightfold stimulation of 2-deoxy-D-[14C]glucose uptake by insulin. In addition, insulin-mediated glucose transport was not potentiated by thrombin or EGF. Although these results cannot exclude the possibility that p21ras and/or MAP kinase is needed in conjunction with other signaling molecules that are activated by insulin and not by thrombin or EGF, they show that the Ras/MAP kinase signaling pathway alone is not sufficient to induce insulin-mediated glucose transport.

Reduced glucose transport and increased binding of insulin in adipocytes from diabetic and fasted rats.

1. Animals made diabetic by injection of streptozotocin or animals after 3 days of fasting show decreased insulin levels and a decrease in mean cell diameter of adipocytes from epidydymal fat pads in comparison with cells from normal animals. 2. 14CO2 production from D-[U-14C]glucose is impaired in diabetic and fasted animals both in presence or in absence of a concentration of insulin stimulating 14CO2 production maximally. 3. Insulin binding is increased in adipocytes from diabetic and fasted animals due to changes in affinity. 4. Transport studies show that basal and insulin stimulated 2-deoxy[1-14C]-glucose transport is decreased in absolute terms due to a decrease in V and an increase in Km. 5. The relative stimulatory effect of insulin is impaired in adipocytes of diabetic and fasted animals. 6. A shift of the maximal effect of insulin to lower insulin levels is seen in these cells.

The effect of insulin, serum and dexamethasone on mRNA levels for the insulin receptor in the human lymphoblastoic cell line IM-9.

The effect of insulin, serum and dexamethasone on mRNA levels in the insulin receptor in the human lymphoblastoic cell line IM-9 was examined. To this end, mRNA levels were quantitated by Northern blot analysis using a labeled cDNA probe for the insulin receptor. The presence of 0.1 microM dexamethasone in the medium had a strong stimulatory effect on mRNA levels in insulin receptor, suggesting the presence of a glucocorticoid inducible enhancer element near the insulin receptor gene. Also, the nature of the serum had an effect on insulin receptor mRNA levels, as cells maintained in 10% fetal calf serum had insulin receptor mRNA levels that were 40-50% of those found in IM-9 cells maintained in 1% newborn serum. Variations in insulin receptor mRNA levels led in each situation to concordant variations in insulin binding. Insulin levels of up to 1 microM had no effect on hybridizable insulin receptor mRNA levels making an insulin-induced feed-back mechanism on gene expression or mRNA stability unlikely.

Stimulatory and inhibitory effects of adrenaline and 8-bromo-cAMP on insulin-sensitive 2-deoxyglucose transport in rat adipocytes.

The effects of adrenaline and 8-bromo-cAMP on 2-deoxyglucose uptake in isolated rat adipocytes were investigated under conditions of unidirectional flux, in which the transport process is rate limiting. Adrenaline showed a dualistic effect in the absence of insulin. At concentrations below 1 microM adrenaline stimulated 2-deoxyglucose uptake; at higher concentrations adrenaline inhibited the uptake. In the presence of insulin at the maximum effective concentration, addition of adrenaline further increased the 2-deoxyglucose uptake by about 50%. In the presence of insulin 8-bromo-cAMP had the same effect as adrenaline. In the absence of insulin, 8-bromo-cAMP only inhibited 2-deoxyglucose uptake.

The effects of 1-methyl-3-isobutylxanthine on insulin-sensitive 2-deoxyglucose transport.

The effect of 1-methyl-3-isobutylxanthine on insulin-sensitive 2-deoxyglucose uptake in rat adipocytes was studied. 1-Methyl-3-isobutylxanthine inhibited 2-deoxyglucose uptake rate substantially in both the absence and presence of insulin. The lag-time for the effect of insulin on 2-deoxyglucose uptake was prolonged. At the same time 1-methyl-3-isobutylxanthine caused a decrease in ATP levels. From experiments with isolated rat liver mitochondria it appeared that 1-methyl-3-isobutylxanthine inhibits glutamate plus malate oxidation in State 3.

Phloretin - an uncoupler and an inhibitor of mitochondrial oxidative phosphorylation.

The effect of phloretin on respiration by isolated mitochondria and submitochondrial particles was studied. In submitochondrial particles, both NADH- and succinate-dependent respiration was inhibited by phloretin. 50% maximum inhibition was reached at phloretin concentrations of 0.1 mM (NADH oxidation) and 0.7 mM (succinate oxidation). In isolated mitochondria, phloretin inhibited glutamate oxidation in both State 3 and State 4; 50% maximum inhibition occurred at about 30 microM. Succinate oxidation is inhibited in State 3 by phloretin, inhibition being half its maximum value at 0.5 mM, but in State 4 it is stimulated about 2-fold by phloretin at a concentration of 0.6 mM. Ascorbate oxidation is stimulated in both State 3 and State 4, maximum stimulation being equal to that obtained with an uncoupler of oxidative phosphorylation. Under all circumstances, phloretin lowered the transmembrane electrical potential difference in isolated mitochondria. These results are discussed in terms of mosaic non-equilibrium thermodynamics. We conclude that phloretin is both an uncoupler and an inhibitor of oxidative phosphorylation.

Transport-associated phosphorylation of 2-deoxyglucose in rat adipocytes.

The relationship between ATP levels and 2-deoxyglucose uptake was investigated. When the concentration in the medium lies between 1 and 10 mM 2-deoxyglucose uptake causes a marked decrease in ATP level. This could partly be explained by an inhibiting effect of 2-deoxyglucose and 2-deoxyglucose 6-phosphate on ATP synthesis in the mitochondria. A good correlation between the various ATP levels induced by 2,4-dinitrophenol and the rate of uptake of 5 microM and 0.5 mM (but not 5 mM) 2-deoxyglucose was observed. The addition of glucose and 2-deoxyglucose to cells incubated in the presence of trace amounts of 2-deoxy-[1-14C]glucose induced marked changes in the uptake of the tracer that were associated with a rapid decline in ATP level. It appeared that the phosphorylation of 2-deoxyglucose is an important step in the uptake of the sugar. It is hypothesized that the processes of transport and phosphorylation of 2-deoxyglucose are coupled in rat adipocytes.

In vivo insulin responsiveness for glucose uptake and production at eu- and hyperglycemic levels in normal and diabetic rats.

UNLABELLED: Whole body glucose uptake (BGU) and hepatic glucose production (HGP) at maximal plasma insulin concentrations (+/- 5000 microU/ml) were determined by eu- (EC) (6 mM) and hyperglycemic (HC) (20 mM) clamps (120 min), combined with [3-3H]glucose infusion, in normal and streptozotocin-treated (65 mg/kg) 3-day diabetic, conscious rats. In normal rats, during EC, BGU was 12.4 +/- 0.4 mg/min and during HC, when urinary glucose loss was 0.54 +/- 0.09 mg/min, BGU was 25.5 +/- 1.6 mg/min. However, throughout the final 60 min of HC, glucose infusion rate (GIR) was not constant but a linear decline in time (r = -0.99) of 17%, P less than 0.0001, was observed indicating a hyperglycemia-induced desensitization process. In diabetic rats, during EC, BGU was 7.7 +/- 0.3 mg/min and during HC, BGU was 15.5 +/- 1.4 mg/min. Throughout the final 60 min of HC, GIR was constant, suggesting that the hyperglycemia-induced desensitization process was already completed. In normal and diabetic rats, HGP was similar: during EC 0.2 +/- 0.5 mg/min and 0.1 +/- 0.5 mg/min, and during HC 0.4 +/- 0.4 mg/min and 0.5 +/- 0.6 mg/min, respectively. In vitro adipocyte and muscle insulin receptor studies showed normal to increased receptor number and increased receptor autophosphorylation in diabetic compared to normal rats. IN CONCLUSION: (i) 3-day diabetic rats show, at maximal plasma insulin concentrations, insulin resistance to BGU, but not to HGP. The resistance to BGU is equally present (reduction of 38%) at eu- and hyperglycemic levels as compared to normal rats. (ii) 3-day diabetic rats reveal no defect in adipocyte and muscle insulin receptor function. These data indicate that the diabetes induced insulin resistance for BGU is at the post-receptor level and due to a decreased maximal capacity (Vmax) for glucose uptake, with no change in affinity, or Km.

In vivo relationship between insulin clearance and action in healthy subjects and IDDM patients.

The relationship between plasma clearance rate of insulin (PCR) and insulin-stimulated glucose disposal was investigated in 15 healthy subjects and 30 insulin-dependent diabetes mellitus (IDDM) patients with the sequential euglycemic (5 mM) clamp technique (insulin infusion rates of 0.5, 1, 2, and 5 mU.kg-1.min-1 in 2-h steps). In IDDM patients, insulin-stimulated glucose disposal was decreased at low insulinemia (steps 1-3), whereas at maximal insulinemia (step 4), insulin action was normal. In the healthy subjects, strong positive correlations were found for PCR versus steady-state glucose infusion rate (SSGIR): r = 0.71 (P less than 0.005), 0.72 (P less than 0.005), 0.72 (P less than 0.005), and 0.78 (P less than 0.001) for steps 1-4, respectively. In contrast, in the IDDM patients, no relationship was observed: r = 0.01, -0.03, 0.06, and 0.01 (NS) for steps 1-4, respectively. In univariate analyses of PCR, no differences were found between patient subgroups with values for percentage of tracer binding below or above 5% or insulin-antibody-binding capacities and equilibrium constants below or above the median. In multiple regression models, adjusting for insulin antibodies, preceding glycemic control (HbA1 or fructosamine), and duration of IDDM, correlations for PCR versus SSGIR remained nonsignificant. In conclusion, insulin action is correlated to insulin clearance in healthy subjects, suggesting a functional relationship from an in vivo perspective. No such relationship was present in patients with IDDM, even after adjusting for insulin antibodies, preceding glycemic control, and duration of IDDM.

Low pH and ketoacids induce insulin receptor binding and postbinding alterations in cultured 3T3 adipocytes.

The etiology of insulin resistance during diabetic ketoacidosis is still poorly understood. Changes in insulin receptor binding and the existence of postreceptor alterations have been proposed. In an attempt to clarify the role of low pH and ketone bodies in the insulin resistance, we examined the effectiveness of insulin during and after 48 h of exposure of cultured 3T3-L1 adipocytes to low pH and ketoacids. In the "acute" stage, lowering of physiologic pH (pH 7.4) to pH 6.9 induced a decrease in insulin binding (50%), which was due to a decrease in the rate of association. Concomitantly, the insulin sensitivity was decreased (ninefold). The basal hexose uptake and insulin responsiveness were only slightly decreased at low pH. Beta-hydroxybutyrate partially counteracted the effect of low pH on insulin binding and sensitivity in a dose-dependent fashion (ED50: 10 mM). The binding-enhancing effect of ketoacids was more pronounced at low pH than at physiologic pH and absent at optimum pH (pH 8.0). After 48 h of exposure of the cells to pH 6.9, insulin binding and insulin sensitivity (measured at physiologic pH) were similar as in cells cultured at pH 7.4. The insulin response, however, was substantially impaired (40%), due to an increase in basal hexose uptake as well as a decrease in maximal insulin-stimulated uptake. These postbinding alterations induced by low pH could be reversed by culturing the cells at physiologic pH for another 48 h. Prolonged exposure to ketoacids did not affect the insulin effectiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased insulin action and clearance in hyperthyroid newly diagnosed IDDM patient. Restoration to normal with antithyroid treatment.

In a patient with hyperthyroidism and newly diagnosed insulin-dependent diabetes mellitus (IDDM), insulin action and clearance were studied before the initiation of antithyroid treatment and at 3-mo intervals for 1 yr thereafter. The sequential euglycemic clamp technique (5 mM) was used with insulin infusion rates of 0.5, 1.0, 2.0, and 5.0 mU.kg-1.min-1 in four steps of 2 h. The data were compared with nine control subjects and nine newly diagnosed euthyroid IDDM patients treated with insulin for 0.5 mo. Insulin sensitivity was increased in the patients (ED50 40 vs. 52 mU/L, range 43-70, in controls and 70 mU/L, range 59-120, in IDDM subjects). Insulin responsiveness was markedly elevated; the steady-state glucose infusion rate (SSGIR) of step 4 was 104 vs. 64 mumol.kg-1.min-1 (range 50-79) in controls and 61 mumol.kg-1.min-1 (range 47-69) in IDDM subjects. Insulin clearance was elevated in all steps (1-3, 20-23 vs. 9-15 ml.kg-1.min-1; 4, 18 vs. 6-12 ml.kg-1.min-1 in control and IDDM subjects). Parallel to the normalization of thyroid metabolism, insulin action (ED50 60 mU/L, SSGIR in step 4, 51 mumol.kg-1.min-1) and insulin clearance (steps 1-3, 11-14 ml.kg-1.min-1; step 4, 7 ml.kg-1.min-1) returned to the normal range in 6 mo. Both remained within the normal range until 12 mo. In the patient with newly diagnosed IDDM, the initial marked increases of insulin action and clearance were due to coexistent hyperthyroidism. With the amelioration of the hyperthyroid state, both processes became normal. The parallelism between insulin action and clearance suggests a functional relationship.

Receptor binding and effect of biosynthetic human insulin on 2-deoxyglucose transport.

Biosynthetic human insulin (BHI) and purified pork insulin (PPI) were compared for binding properties and stimulatory effect on 2-deoxyglucose transport in isolated rat fat cells. No difference between these types of insulin could be demonstrated.

Antilipolytic action of insulin in adipocytes from starved and diabetic rats during adenosine-controlled incubations.

Insulin action on adipocytes induces two major metabolic effects: stimulation of glucose transport and inhibition of lipolysis. Previously, we have shown that incubated isolated adipocytes from starved (S), and streptozotocin-treated diabetic (D) rats show insulin resistance on glucose transport. It is not known whether insulin resistance is also present on antilipolysis. In this study the antilipolytic action of insulin was investigated. Since basal lipolysis was low, lipolysis was first stimulated by isoproterenol (ISO). This showed that differences existed in sensitivity for ISO among control (C), S, and D adipocytes. We investigated whether changes in adenosine accumulation could attribute to the differences in ISO action and thereby influence insulin action. When endogenous accumulating adenosine was removed by adenosine deaminase and replaced by a fixed concentration (200 nM) of the nonhydrolyzable adenosine analog phenylisopropyladenosine, the differences in ISO action disappeared. This indicates that the sensitivity of C, S, and D adipocytes for ISO is strongly influenced by endogenous adenosine release. The dose-response relationship between insulin and inhibition of ISO-stimulated lipolysis showed that insulin sensitivity was increased and responsiveness unaltered in S and D compared to C adipocytes for incubations with both uncontrolled and controlled adenosine concentrations. This indicates that during S and D states, endogenous adenosine release has no major effect on insulin action. The increased sensitivity for insulin of S and D adipocytes was paralleled by an increased binding of [125I]iodoinsulin. The unaltered responsiveness for insulin indicates that there is no insulin resistance at the postbinding level for antilipolysis, i.e. intracellular processes for antilipolysis are intact. This is in contrast to glucose transport, where insulin resistance exists at the postbinding level during S and D. Thus, insulin resistance is no general phenomenon, but is confined to specific effector systems.

Characterization of the sulfonylurea-induced potentiation of the insulin response in cultured 3T3 adipocytes.

Studies were carried out to determine the role of sulfonylureas in the regulation of insulin-sensitive hexose uptake in cultured 3T3 adipocytes. Exposure (0-72 hr) of cells to the sulfonylurea-derivative tolbutamide (0.05-0.3 mg/ml) induced a time- and concentration-dependent potentiation of the stimulatory effect of insulin on hexose uptake (500 vs 340%). The effect was maximal within 24 hr and completely reversible. It was strictly limited to the presence of insulin. Basal hexose uptake and insulin binding were not affected by the drug. High concentrations of the agent (greater than 0.3 mg/ml) induced a decrease in insulin response, suggesting a concentration optimum. Lineweaver-Burk analysis of uptake data revealed that the potentiating effect of tolbutamide was due to enhancement of the insulin-induced increase in apparent Vmax, i.e. in the number or activity of hexose transporters. This enhancement was inhibited by cycloheximide (1 microgram/ml), indicating involvement of protein synthesis in the induction of the effect. It is concluded that sulfonylureas act by influencing synthesis of protein(s) which potentiate the effect of insulin on hexose uptake.

Insulin action is normalized in newly diagnosed type I diabetic patients after three months of insulin treatment.

We studied insulin action at submaximal and maximal insulin levels in seven newly diagnosed type I (insulin-dependent) diabetic patients after 2 weeks (t1/2) and after 3 months (t3) of insulin treatment, and in seven control subjects. Insulin action was determined with a sequential euglycemic (5.0 mmol/L) glucose clamp technique using insulin infusion rates of 0.5, 1.0, 2.0, and 5.0 mU.kg-1.min-1 in four periods of two hours each. The final 30 minutes of each infusion period (referred to as steady-state) were taken for the assessment of insulin action. Steady-state insulin levels were similar in the diabetic patients at t1/2 and t3, and in control subjects. During the first and second infusion periods, steady-state glucose infusion rates (SSGIR) were lower at t1/2 than at t3 (12.2 +/- 1.7 v 18.8 +/- 2.4, P less than .05, and 34.3 +/- 3.8 v 47.6 +/- 2.5 mumol.kg-1.min-1, P less than .02, respectively), and were lower at t1/2 compared to controls (12.2 +/- 1.7 v 22.4 +/- 2.3, P less than .01, and 34.3 +/- 3.8 v 47.3 +/- 2.8 mumol.kg-1.min-1, P less than .02). No differences were found during the third and fourth infusion periods between t1/2 and t3, or t1/2 and controls. When these data were used to construct dose-response curves, insulin action was decreased in the diabetic patients at t1/2 at submaximal insulin levels (shift to the right), while insulin responsiveness was unchanged. This finding may be regarded as a still-present manifestation of the metabolic derangement at the onset of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue-related changes in insulin receptor number and autophosphorylation induced by starvation and diabetes in rats.

Insulin action is subject to regulation at the level of the insulin receptor and at postreceptor levels. Starvation and diabetes are often associated with insulin resistance for glucose metabolism in various tissues. In muscle, fat, and liver, we examined whether changes in the functionality of the insulin receptor correlated with changes in insulin action in the starved and diabetic state. Insulin-stimulated receptor autophosphorylation reflects an early physiologic step in transmission of the insulin signal, and for that reason, changes in autophosphorylation activity of the insulin receptor were used as a marker to determine the functionality of the insulin receptor. Glycoprotein fractions prepared from skeletal muscle, diaphragm, epididymal fat, and liver of control, 3-day starved, short-term 3-day (S) diabetic (streptozotocin, 70 mg/kg intravenously), and long-term 6-month (L) diabetic (neonatal streptozotocin 100 micrograms/g intraperitoneally) rats were used in this study. Receptor activity was monitored by measuring insulin-stimulated [gamma-32P]adenosine triphosphate (ATP) receptor autophosphorylation. In addition, to obtain information about whether changes in receptor autophosphorylation are related to changes in receptor number, relative numbers of high-affinity insulin receptors were determined by affinity cross-linking of [125I]insulin to the receptor alpha-chain and quantitation of the yield of labeled receptor alpha-chain. Control, starved, S diabetic, and L diabetic rats had plasma insulin and glucose levels of 294 +/- 42, 90 +/- 24, 48 +/- 12, and 216 +/- 30 pmol/L and 6.7 +/- 0.2, 4.1 +/- 0.2, 23.3 +/- 0.7, and 21.6 +/- 2.9 mmol/L, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose disposal and intermediary metabolism during one year of continuous subcutaneous insulin infusion (CSII).

To study the effects of CSII on insulin action and intermediary metabolism, seven type 1 diabetic patients (duration 17 +/- 4 (SEM) years), underwent sequential euglycemic clamps 1/4, 6 and 12 months after changing from conventional insulin treatment to continuous subcutaneous insulin infusion (CSII); seven healthy subjects served as controls. For at least 14 h before the study, blood glucose was maintained between 4-10 mmol/l in the patients by intravenous insulin infusion, to avoid negatively biased clamp measures. A metabolite profile was taken in the basal state and during euglycemic hyperinsulinemia. At 1/4 month insulin sensitivity was decreased in the patients (ED50 82 +/- 14 vs 52 +/- 4 mU/l in controls, P less than 0.02), whereas insulin responsiveness was normal. During the course of one year, no change towards control values was found for insulin-stimulated glucose disposal. Concomitantly, HbA1 did not change either, and remained elevated (1/4 month 11.1 +/- 0.7%, 12 months 10.0 +/- 0.9% vs 6.5 +/- 0.3% in controls, P less than 0.01). Regarding basal intermediary metabolism, triglycerides became significantly improved (1/4 month 1.32 +/- 0.13 mmol/l, 12 months 0.70 +/- 0.05 mmol/l, P less than 0.05, vs 0.70 +/- 0.08 mmol/l in controls). The acetoacetate/3-OH-butyric acid ratio increased from 0.10 at 3 to 0.26 at 12 months, which was similar to controls. The absolute levels of acetoacetate and 3-OH-butyric acid remained elevated 2-3 fold. For other basal metabolite levels no systematic trend for improvement was found for 1/4 to 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes monitoring system in The Netherlands.

Under the aegis of the European Regional Offices of the World Health Organization (WHO) and the International Diabetes Federation (IDF) a joint action programme to contest the growing burden of diabetes has been drawn up. The St. Vincent Declaration (1980) specifies targets for diabetes care, the reduction of complications, the integration into society and the education of the diabetic individual. The WHO/IDF have drawn up a data set to monitor progress in reaching the targets of the St. Vincent Declaration. The objective of the project Diabetes Monitoring System is to examine the possibilities for implementing a longitudinal-based and standardised diabetes monitoring system in the Netherlands. Although computerised recording systems for diabetes are seldom used and the agreement with the WHO/IDF data set varies substantially, the willingness of physicians to participate is clearly sufficient. This principally explorative project will hopefully lead to the implementation of a monitoring system in which a widely accepted data set is recorded to establish improvements in quality of care and to perform epidemiological research.

Associations of fat and cholesterol intake with serum lipid levels and cardiovascular disease: the EURODIAB IDDM Complications Study.

The EURODIAB IDDM Complications Study, a cross-sectional, clinic-based study examined the fat and cholesterol intakes of European individuals with type 1 diabetes for possible relations to serum lipid levels (total cholesterol, HDL- and LDL-cholesterol, fasting triglycerides) and to the prevalence of cardiovascular disease (past history or electrocardiogram abnormalities). Fat intake (total fat, saturated fat, cholesterol) from 2,868 subjects with type 1 diabetes (mean age 32.9 +/- 10.2 years (range: 14-61 years), mean diabetes duration 14.7 +/- 9.4 years (range: 1-56 years)) was assessed by a standardized 3-day dietary record at the Nutrition Co-Ordinating Centre (Düsseldorf). Serum lipid levels were determined in the central laboratory (London) by standard enzymatic methods. Energy-adjusted total and LDL-cholesterol levels increased significantly with higher intakes of total fat, saturated fat and cholesterol. However, these relations were largely explained by concomitant decreases in dietary fibre intake. For levels of HDL-cholesterol and triglycerides no independent associations were observed with fat or cholesterol intake. Increased intakes of total fat, saturated fat and cholesterol were also related to higher prevalences of cardiovascular disease. These associations were, however, no longer significant after adjustment for dietary fibre intake for which we previously demonstrated independent associations with the serum cholesterol pattern and CVD. Since higher fat intakes are commonly accompanied by lower carbohydrate and fibre intakes we conclude that restricted intakes of cholesterol, saturated fat and total fat combined with higher fibre intakes beneficially affect both the levels of total and LDL-cholesterol and the risk for cardiovascular disease in European individuals with type 1 diabetes.

Counterregulatory hormone responses during graded hyperinsulinemic euglycemia in conscious rats.

It has been suggested that hyperinsulinemia per se may affect the levels of some counterregulatory hormones in the absence of hypoglycemia. We studied the effect of graded hyperinsulinemia and concomitant increased glucose metabolism on the levels of counterregulatory hormones by means of the 5-step sequential hyperinsulinemic euglycemic clamp technique, combined with [3-3H]-glucose infusion, in conscious rats. Insulin infusion rates (IIR) of 0, 0.5, 1, 3, and 16 mU/min, resulted in steady-state plasma insulin levels (mean +/- SEM) of 24 +/- 4, 44 +/- 3, 98 +/- 8, 418 +/- 48, and 6626 +/- 361 microU/ml, peripheral glucose uptake (PGU) of 3.1 +/- 0.2, 3.6 +/- 0.3, 5.4 +/- 0.3, 9.2 +/- 0.4, and 12.4 +/- 0.2 mg/min and hepatic glucose production (HGP) of 3.1 +/- 0.2, 2.4 +/- 0.4, 0.8 +/- 0.3, -0.1 +/- 0.2, and -0.5 +/- 0.3 mg/min, respectively. Plasma glucagon levels were half maximally suppressed between IIRs of 0.5 and 1 mU/min and maximally suppressed at 3 mU/min. The suppression exactly paralleled the inhibition of HGP (r = 0.87 +/- 0.04, p < 0.02) but not the stimulation of PGU (r = -0.66 +/- 0.12, p = NS). This suggests that the inhibition of HGP by insulin is at least partially mediated by a simultaneous suppression of plasma glucagon levels. The adrenal hormones corticosterone and epinephrine were not influenced during the clamp.(ABSTRACT TRUNCATED AT 250 WORDS)