Showing papers on "Insulin published in 1989"
TL;DR: PCO women have significant insulin resistance that is independent of obesity, changes in body composition, and impairment of glucose tolerance, and PCO is associated with a unique disorder of insulin action.
Abstract: Hyperinsulinemia secondary to a poorly characterized disorder of insulin action is a feature of the polycystic ovary syndrome (PCO). However, controversy exists as to whether insulin resistance results from PCO or the obesity that is frequently associated with it. Thus, we determined in vivo insulin action on peripheral glucose utilization (M) and hepatic glucose production (HGP) with the euglycemic glucose-clamp technique in obese ( n = 19) and nonobese ( n = 10) PCO women and age- and body-composition-matched normal ovulatory women ( n = 11 obese and n = 8 nonobese women). None had fasting hyperglycemia. Two obese PCO women had diabetes mellitus, established with an oral glucose tolerance test; no other women had impairment of glucose tolerance. However, the obese PCO women had significantly increased fasting and 2-h glucose levels after an oral glucose load and increased basal HGP compared with their body-composition-matched control group. There were statistically significant interactions between obesity and PCO in fasting glucose levels and basal HGP ( P < .05). Steady-state insulin levels of ∼100 μU/ml were achieved during the clamp. Insulin-stimulated glucose utilization was significantly decreased in both PCO groups whether expressed per kilogram total weight ( P < .001) or per kilogram fat free mass ( P < .001) or when divided by the steady-state plasma insulin (I) level (M/I, P < .001). There was residual HGP in 4 of 15 obese PCO, 0 of 11 obese normal, 2 of 10 nonobese PCO, and 0 of 8 nonobese normal women. The metabolic clearance rate of insulin did not differ in the four groups. We conclude that 1 ) PCO women have significant insulin resistance that is independent of obesity, changes in body composition, and impairment of glucose tolerance, 2 ) PCO and obesity have a synergistic deleterious effect on glucose tolerance, 3 ) hyperinsulinemia in PCO is not the result of decreased insulin clearance, and 4 ) PCO is associated with a unique disorder of insulin action.
1,916 citations
TL;DR: The proposed model of insulin/C-peptide kinetics, derived from the original conception of Eaton and Polonsky, suggests that in healthy individuals, there is a balance between secretion and insulin action such that insulin secretion × insulin sensitivity = constant, and supports the concept that, at physiological insulin levels, the time for insulin to cross the capillary endothelium is the process that determines the rate of insulin action in vivo.
Abstract: Glucose tolerance depends on a complex interaction among insulin secretion from the beta-cells, clearance of the hormone, and the actions of insulin to accelerate glucose disappearance and inhibit endogenous glucose production. An additional factor, less well recognized, is the ability of glucose per se, independent of changes in insulin, to increase glucose uptake and suppress endogenous output (glucose effectiveness). These factors can be measured in the intact organism with physiologically based minimal models of glucose utilization and insulin kinetics. With the glucose minimal model, insulin sensitivity (SI) and glucose effectiveness (SG) are measured by computer analysis of the frequently sampled intravenous glucose tolerance test. The test involves intravenous injection of glucose followed by tolbutamide or insulin and frequent blood sampling. SI varied from a high of 7.6 x 10(-4) min-1.microU-1.ml-1 in young Whites to 2.3 x 10(-4) min-1.microU-1.ml-1 in obese nondiabetic subjects; in all of the nondiabetic subjects, SG was normal. In subjects with non-insulin-dependent diabetes mellitus (NIDDM), not only was SI reduced 90% below normal (0.61 +/- 0.16 x 10(-4) min-1.microU-1.ml-1), but in this group alone, SG was reduced (from 0.026 +/- 0.008 to 0.014 +/- 0.002 min-1); thus, defects in SI and SG are synergistic in causing glucose intolerance in NIDDM. One assumption of the minimal model is that the time delay in insulin action on glucose utilization in vivo is due to sluggish insulin transport across the capillary endothelium. This was tested by comparing insulin concentrations in plasma with those in lymph (representing interstitial fluid) during euglycemic-hyperinsulinemic glucose clamps. Lymph insulin was lower than plasma insulin at basal (12 vs. 18 microU/ml) and at steady state, indicating significant loss of insulin from the interstitial space, presumably due to cellular uptake of the insulin-receptor complex. Additionally, during clamps, lymph insulin changed more slowly than plasma insulin, but the rate of glucose utilization followed a time course identical with that of lymph (r = .96) rather than plasma (r = .71). Thus, lymph insulin, which may be reflective of interstitial fluid, is the signal to which insulin-sensitive tissues are responding. These studies support the concept that, at physiological insulin levels, the time for insulin to cross the capillary endothelium is the process that determines the rate of insulin action in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)
1,043 citations
TL;DR: Cl cloning and sequencing of cDNAs isolated from both rat adipocyte and heart libraries that encode a protein recognized by mAb 1F8, and which has 65% sequence identity to the human HepG2 glucose transporter are described, indicating that this cDNA encodes a membrane protein with the characteristics of the translocatable glucose transporter expressed in insulin-responsive tissues.
Abstract: A MAJOR mechanism by which insulin stimulates glucose transport in muscle and fat is the translocation of glucose transporters from an intracellular membrane pool to the cell surface1–5. The existence of a distinct insulin-regulatable glucose transporter was suggested by the poor cross-reactivity between antibodies specific for either the HepG2 or rat brain glucose transporters and the rat adipocyte glucose transporter6,7. More direct evidence was provided by the production of a monoclonal antibody (mAb 1F8) specific for the rat adipocyte glucose transporter that immunolabels a species of relative molecular mass 43,000 (43K) present only in tissues that exhibit insulin-dependent glucose transport8, suggesting that this protein may be encoded by a different gene from the previously described mammalian glucose transporters9–13. This antibody has been used to immunoprecipitate a 43K protein that was photoaffinity-labelled with cytochalasin B in a glucose displaceable way, and to immunolabel a protein in the plasma membrane of rat adipocytes, whose concentration was increased at least fivefold after cellular insulin exposure. Here we describe the cloning and sequencing of cDNAs isolated from both rat adipocyte and heart libraries that encode a protein recognized by mAb 1F8, and which has 65% sequence identity to the human HepG2 glucose transporter9. This cDNA hybridizes to an mRNA present only in skeletal muscle, heart and adipose tissue. Our data indicate that this cDNA encodes a membrane protein with the characteristics of the translocatable glucose transporter expressed in insulin-responsive tissues.
903 citations
TL;DR: It is concluded that impaired glucose metabolism is common in the first-degree relatives of patients with NIDDM, despite their normal results on oral glucose-tolerance tests.
Abstract: To identify early metabolic abnormalities in non-insulin-dependent diabetes mellitus (NIDDM), we measured sensitivity to insulin and insulin secretion in 26 first-degree relatives of patients with NIDDM and compared these subjects both with 14 healthy control subjects with no family history of NIDDM and with 19 patients with NIDDM. The euglycemic insulin-clamp technique, indirect calorimetry, and infusion of [3–3H]glucose were used to assess insulin sensitivity. Total-body glucose metabolism was impaired in the first-degree relatives as compared with the controls (P<0.01). The defect in glucose metabolism was almost completely accounted for by a defect in nonoxidative glucose metabolism (primarily the storage of glucose as glycogen). The relatives with normal rates of metabolism (mean±SEM, 1.81±0.27 mg per kilogram of body weight per minute) and impaired rates (1.40±0.22 mg per kilogram per minute) in oral glucose-tolerance tests had the same degree of impairment in glucose storage as compared wi...
886 citations
TL;DR: Hydchlorothiazide for the treatment of essential hypertension has adverse effects on glucose and lipid metabolism and it is possible, but not proved, that these changes may contribute to the risk for diabetes mellitus and coronary heart disease.
Abstract: It has been suggested that the metabolic side effects of antihypertensive drugs are responsible for their failure to reduce cardiovascular morbidity in patients with hypertension. Therefore, in 50 patients with essential hypertension, we performed a randomized, double-blind, crossover study comparing the effects of carbohydrate and lipid metabolism of captopril (mean [+/- SD] dose, 81 +/- 24 mg per day) and hydrochlorothiazide (40 +/- 12 mg per day) over two four-month treatment periods. Captopril increased the insulin-mediated disposal of glucose, as compared with placebo, from 5.7 +/- 2.4 to 6.3 +/- 2.5 mg per kilogram of body weight per minute (P less than 0.05), whereas hydrochlorothiazide caused a decrease from 6.4 +/- 2.0 to 5.7 +/- 1.9 (P less than 0.01). Captopril had no effect on the basal insulin concentration, but it decreased the late (30- to 90-minute) insulin response to glucose and increased the early (2- to 6-minute) insulin peak. Hydrochlorothiazide increased the basal insulin concentration and the late insulin response to glucose. These findings may be explained by an increase in insulin sensitivity with captopril and a decrease with hydrochlorothiazide. Little or no change was seen in serum lipid or lipoprotein levels during treatment with captopril, whereas hydrochlorothiazide caused significant increases in serum total (5 percent) and low-density lipoprotein (6 percent) cholesterol levels and total (15 percent) and very-low-density lipoprotein (25 percent) triglyceride levels, as compared with placebo (P less than 0.01 for all comparisons). We conclude that hydrochlorothiazide for the treatment of essential hypertension has adverse effects on glucose and lipid metabolism. It is possible, but not proved in this study, that these changes may contribute to the risk for diabetes mellitus and coronary heart disease. In contrast, captopril appears to have beneficial or no effects on glucose and lipid metabolism.
857 citations
TL;DR: It is concluded that healthy persons with hyperinsulinemia and normal glucose tolerance have an increase in risk factors for coronary artery disease, as compared with a well-matched group of healthy subjects with normal insulin levels.
Abstract: We studied the relation of serum insulin levels to plasma lipid levels and blood pressure in two groups drawn from among 247 healthy, normotensive nonobese subjects with normal glucose tolerance. One group of 32 subjects was defined as having hyperinsulinemia (serum insulin, greater than 2 SD above the mean) and then compared with 32 normoinsulinemic subjects (serum insulin within 1 SD of the mean) matched for age (mean, 39 years), sex (22 men and 10 women), and body-mass index (24.7). The two groups had similar patterns of smoking, drinking, and physical exercise. Plasma glucose levels after an oral glucose challenge were significantly higher (P less than 0.05) in the hyperinsulinemic group. In addition, the mean (+/- SEM) fasting plasma triglyceride levels in subjects with hyperinsulinemia were significantly higher (1.73 +/- 0.2 vs. 1.24 +/- 0.1 mmol per liter) and the plasma high-density lipoprotein cholesterol concentrations were lower (1.21 +/- 0.06 vs. 1.43 +/- 0.06 mmol per liter) than in subjects with normoinsulinemia. Both systolic (126 vs. 119 mm Hg; P less than 0.05) and diastolic (85 vs. 78 mm Hg; P less than 0.01) blood pressures were significantly elevated in the group with hyperinsulinemia. We conclude that healthy persons with hyperinsulinemia and normal glucose tolerance have an increase in risk factors for coronary artery disease, as compared with a well-matched group of healthy subjects with normal insulin levels.
803 citations
TL;DR: It is suggested that an increased rate of FFA/lipid oxidation may contribute to the impaired suppression of HGP and diminished stimulation of glucose oxidation by insulin in these patients.
Abstract: The effect of graded, physiologic hyperinsulinemia (+5, +15, +30, +70, +200 microU/ml) on oxidative and nonoxidative pathways of glucose and FFA metabolism was examined in nine lean non-insulin dependent diabetic patients (NIDDM) and in eight age- and weight-matched control subjects. Glucose and FFA metabolism were assessed using stepwise insulin clamp in combination with indirect calorimetry and infusion of [3H]3-glucose/[14C]palmitate. The basal rate of hepatic glucose production (HGP) was higher in NIDDM than in control subjects, and suppression of HGP by insulin was impaired at all but the highest insulin concentration. Glucose disposal was reduced in the NIDD patients at the three highest plasma insulin concentrations, and this was accounted for by defects in both glucose oxidation and nonoxidative glucose metabolism. In NIDDs, suppression of plasma FFA by insulin was impaired at all five insulin steps. This was associated with impaired suppression by insulin of plasma FFA turnover, FFA oxidation (measured by [14C]palmitate) and nonoxidative FFA disposal (an estimate of reesterification of FFA). FFA oxidation and net lipid oxidation (measured by indirect calorimetry) correlated positively with the rate of HGP in the basal state and during the insulin clamp. In conclusion, our findings demonstrate that insulin resistance is a general characteristic of glucose and FFA metabolism in NIDDM, and involves both oxidative and nonoxidative pathways. The data also demonstrate that FFA/lipid and glucose metabolism are interrelated in NIDDM, and suggest that an increased rate of FFA/lipid oxidation may contribute to the impaired suppression of HGP and diminished stimulation of glucose oxidation by insulin in these patients.
795 citations
TL;DR: This review outlines the purification and characterization of the binding proteins that have been identified to date, and describes the regulation of their production and of their levels in the circulation.
578 citations
TL;DR: A cDNA has been cloned from a skeletal muscle library that encodes a novel glucose transporter protein exhibiting the following properties of an insulin-regulated hexose carrier protein: it is expressed exclusively in adipose tissue, skeletal muscle and heart, the principal organs with insulin-responsive glucose transport.
576 citations
TL;DR: The results suggest that the 15-min ITT is suitable as a simple and rapid estimation of in vivo insulin action when glucose clamp studies are not feasible, as in large series of subjects or serial studies.
Abstract: We compared estimates of in vivo insulin action derived from insulin tolerance tests (ITT) and euglycemic and hyperglycemic glucose clamp studies in 17 normal subjects and 19 patients with various diseases characterized by insulin resistance. Fifteen subjects underwent an ITT and a euglycemic clamp study, 17 subjects underwent an ITT and a hyperglycemic clamp study, and 4 subjects underwent all 3 tests. The ITT consisted of a bolus iv injection of regular insulin (0.1 U/kg BW). The plasma glucose disappearance rate during the 3- to 15-min period following the insulin injection was taken as a measure of insulin action. In both euglycemic and hyperglycemic clamp studies, which were carried out with standard techniques, the ratio between the amount of glucose infused to maintain glycemia at the desired level and the mean plasma insulin concentration from 60-120 min (M) (euglycemic clamp studies) or 20-120 min (I) (hyperglycemic clamp studies) was used as a measure of insulin action. A close correlation was found between plasma glucose disappearance rate and the M/I ratio during either the euglycemic (r = 0.811; P less than 0.001) or the hyperglycemic (r = 0.826; P less than 0.001) clamp studies. These results suggest that the 15-min ITT is suitable as a simple and rapid estimation of in vivo insulin action when glucose clamp studies are not feasible, as in large series of subjects or serial studies.
545 citations
TL;DR: It is concluded from this pilot study that insulin treatment with an implanted, variable-rate, programmable pump is feasible for periods up to two years.
Abstract: We undertook a trial to determine whether an implanted insulin-delivery system, the programmable implantable medication system (PIMS), could be used to treat patients with insulin-dependent diabetes. PIMS is a pulsatile, programmable pump with a battery life expectancy of five years. The reservoir is refilled transcutaneously every two months with a surfactant-stabilized human insulin preparation containing 400 U of insulin per milliliter. Eighteen patients received PIMS-delivered insulin for 4 to 25 months (mean, 18). The total PIMS-implantation experience comprised 28 patient-years. Good glycemic control was established and sustained during treatment (mean plasma glucose level, 7.3 mmol per liter; mean glycohemoglobin level, 8 percent [upper limit of normal, 7.5 percent]), with significantly reduced glycemic fluctuations. The total mean daily insulin dose did not change. Insulin solutions withdrawn from the pump reservoirs contained 92 percent native insulin and preserved biologic activity. There were no surgical or skin complications, severe hypoglycemic episodes, or instances of diabetic ketoacidosis. One pump was replaced because of a manufacturing defect, and four patients had catheter blockages due to omental-tissue encapsulation; two withdrew from the study and two had devices that were repaired successfully. The actuarial rate of survival of catheter function was 78 percent at 1.5 years. We conclude from this pilot study that insulin treatment with an implanted, variable-rate, programmable pump is feasible for periods up to two years.
TL;DR: The high levels in adult skeletal Muscle and subcutaneous fat of mRNA encoding the adult skeletal muscle glucose transporter and its specific reactivity with monoclonal antibody 1F8 suggest that this protein is the major insulin-regulatable glucose transporter expressed in skeletal muscle and other insulin-responsive tissues.
TL;DR: In addition to the amount and type of food eaten, the frequency of meals may be an important determinant of fasting serum lipid levels, possibly in relation to changes in insulin secretion.
Abstract: We studied the effect of increasing the frequency of meals on serum lipid concentrations and carbohydrate tolerance in normal subjects. Seven men were assigned in random order to two metabolically identical diets. One diet consisted of 17 snacks per day (the nibbling diet), and the other of three meals per day (the three-meal diet); each diet was followed for two weeks. As compared with the three-meal diet, the nibbling diet reduced fasting serum concentrations of total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B by a mean (+/- SE) of 8.5 +/- 2.5 percent (P less than 0.02), 13.5 +/- 3.4 percent (P less than 0.01), and 15.1 +/- 5.7 percent (P less than 0.05), respectively. Although the mean blood glucose level and serum concentrations of free fatty acids, 3-hydroxybutyrate, and triglyceride were similar during both diets, during the nibbling diet the mean serum insulin level decreased by 27.9 +/- 6.3 percent (P less than 0.01) and the mean 24-hour urinary C-peptide output decreased by 20.2 +/- 5.6 percent (P less than 0.02). In addition, the mean 24-hour urinary cortisol excretion was lower by 17.3 +/- 5.9 percent (P less than 0.05) at the end of the nibbling diet than at the end of the three-meal diet. The blood glucose, serum insulin, and C-peptide responses to a standardized breakfast and the results of an intravenous glucose-tolerance test conducted at the end of each diet were similar. We conclude that in addition to the amount and type of food eaten, the frequency of meals may be an important determinant of fasting serum lipid levels, possibly in relation to changes in insulin secretion.
TL;DR: The importance of deep abdominal fat as an independent correlate of glucose tolerance in obese women is emphasized, as no association was observed between total adiposity and glucose tolerance after control for accumulation ofDeep abdominal fat.
Abstract: Computed tomography (CT) was used to study the association between adipose tissue localization and glucose tolerance in a sample of 52 premenopausal obese women aged 35.7 +/- 5.5 yr (mean +/- SD) and with a body fat of 45.9 +/- 5.5%. Body-fat mass and the body mass index (BMI) were significantly correlated with plasma glucose, insulin, and connecting peptide (C-peptide) areas after glucose (75 g) ingestion (.40 less than or equal to r less than or equal to .51, P less than .01). Trunk-fat accumulation and the size of fat cells in the abdomen displayed highly significant correlations with postglucose insulin levels. The C-peptide area was also positively correlated with abdominal fat cell size (r = .76, P less than .01) and was more closely associated with the sum of trunk skin folds (r = .59, P less than .001) than with the extremity skin folds (r = .29, P less than .05). Subcutaneous and deep-abdominal-fat areas measured by CT displayed comparable associations with the plasma insulin area (r = .44 and .49, respectively; P less than .001) but marked differences in the associations with glucose tolerance. Indeed, subcutaneous abdominal fat was not significantly correlated with the glucose area, whereas deep abdominal fat showed a significant correlation (r = .57, P less than .001) with the glucose area. Midthigh fat deposition measured by CT was not, however, correlated with plasma glucose, insulin, or C-peptide areas.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: A mechanism whereby GABA, co-secreted with insulin from β cells, may mediate part of the inhibitory action of glucose on glucagon secretion by activating GABAA-receptor Cl− channels in α2 cells is described.
Abstract: The endocrine part of the pancreas plays a central role in blood-glucose regulation. It is well established that an elevation of glucose concentration reduces secretion of the hyperglycaemia-associated hormone glucagon from pancreatic alpha 2 cells. The mechanisms involved, however, remain unknown. Electrophysiological studies have demonstrated that alpha 2 cells generate Ca2+-dependent action potentials. The frequency of these action potentials, which increases under conditions that stimulate glucagon release, is not affected by glucose or insulin. The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is present in the endocrine part of the pancreas at concentrations comparable to those encountered in the central nervous system, and co-localizes with insulin in pancreatic beta cells. We now describe a mechanism whereby GABA, co-secreted with insulin from beta cells, may mediate part of the inhibitory action of glucose on glucagon secretion by activating GABAA-receptor Cl- channels in alpha 2 cells. These observations provide a model for feedback regulation of glucagon release, which may be of significance for the understanding of the hypersecretion of glucagon frequently associated with diabetes.
TL;DR: Two structurally related polypeptides, insulin-like growth factors (IGFs) I and II, can substitute for insulin in this role in virtually all cell types.
TL;DR: The persistent increase in insulin sensitivity after exercise in carbohydrate-deprived rats was unrelated to caloric intake, as muscles of fasted and fat-fed rats behaved similarly.
Abstract: Exercise can induce short-term increases in the sensitivity and responsiveness of skeletal muscle glucose transport to insulin. The purpose of this study was to determine the effect of carbohydrate deprivation on the persistence of increased insulin sensitivity and responsiveness after a bout of exercise. Three hours after a bout of exercise, epitrochlearis muscles from carbohydrate-deprived (fat fed) rats showed a 25% greater increase in 3-O-methylglucose (3-MG) transport in response to a maximal insulin stimulus compared with muscles of nonexercised rats; this increase in insulin responsiveness had reversed 18 h postexercise. Muscles of rats fed carbohydrate showed no increase in insulin responsiveness 3 h after exercise. The effect of 60 microU/ml of insulin on 3-MG transport was approximately twofold greater in muscles studied 3 h after exercise than in nonexercised controls regardless of dietary carbohydrate intake. This increase in insulin sensitivity was lost within 18 h in carbohydrate-fed rats but persisted for at least 48 h in carbohydrate-deprived rats. Muscle glycogen increased approximately 41 mumol/g in the rats fed carbohydrate for 18 h, and only approximately 14.5 mumol/g in the rats fed fat for 48 h, after exercise. The persistent increase in insulin sensitivity after exercise in carbohydrate-deprived rats was unrelated to caloric intake, as muscles of fasted and fat-fed rats behaved similarly.
TL;DR: In this paper, the hyperinsulinemic (approximately 800 pmol/L) euglycemic clamp in rats fed equal amounts of glucose or fructose (35% of calories) for 4 wk was assessed by using the syringes.
TL;DR: It is now possible and necessary to designate most NIDDM patients as insulin deficient, as these substances cross-react as insulin in most, if not all, insulin radioimmunoassays but have very little biological insulin-like activity.
TL;DR: A role for hyperglycemia per se in the enhanced state of activation of protein kinase C seen in glomeruli from diabetic rats is supported.
Abstract: Glomerular inositol content and the turnover of polyphosphoinositides was reduced by 58% in 1-2 wk streptozotocin diabetic rats. Addition of inositol to the incubation medium increased polyphosphoinositide turnover in glomeruli from diabetic rats to control values. Despite the reduction in inositol content and polyphosphoinositide turnover, protein kinase C was activated in glomeruli from diabetic rats, as assessed by an increase in the percentage of enzyme activity associated with the particulate cell fraction. Total protein kinase C activity was not different between glomeruli from control and diabetic rats. Treatment of diabetic rats with insulin to achieve near euglycemia prevented the increase in particulate protein kinase C. Moreover, incubation of glomeruli from control rats with glucose (100-1,000 mg/dl) resulted in a progressive increase in labeled diacylglycerol production and in the percentage of protein kinase C activity which was associated with the particulate fraction. These results support a role for hyperglycemia per se in the enhanced state of activation of protein kinase C seen in glomeruli from diabetic rats. Glucose did not appear to increase diacylglycerol by stimulating inositol phospholipid hydrolysis in glomeruli. Other pathways for diacylglycerol production, including de novo synthesis and phospholipase C mediated hydrolysis of phosphatidylcholine or phosphatidyl-inositol-glycan are notmore » excluded.« less
TL;DR: Long term use of metoprolol and atenolol causes metabolic abnormalities that may be related to the increased incidence of diabetes in patients with hypertension who are treated pharmacologically, and may help to explain why the two drugs have failed consistently to reduce the incidence of coronary heart disease.
Abstract: OBJECTIVE--To compare the effects of metoprolol and atenolol on carbohydrate and lipid metabolism and on insulin response to an intravenous glucose load. DESIGN--Randomised, double blind, double dummy, controlled crossover trial. SETTING--University Hospital, Uppsala, Sweden. PATIENTS--60 Patients with primary hypertension (diastolic blood pressure when resting supine 95-119 mm Hg on at least two occasions during four to six weeks of treatment with placebo) randomised to receive either metoprolol (n = 30) or atenolol (n = 30) during the first treatment period. INTERVENTIONS--Placebo was given for a run in period of four to six weeks. Metoprolol 100 mg twice daily or atenolol 25 mg twice daily was then given for 16 weeks. The two drugs were then exchanged and treatment continued for a further 16 weeks. END POINT--Evaluation of effects of treatment with metoprolol and atenolol on glucose, insulin, and lipid metabolism and glucose disposal mediated by insulin. MEASUREMENTS AND MAIN RESULTS--Reduction of blood pressure was similar and satisfactory during treatment with both drugs. Glucose uptake mediated by insulin was measured during a euglycaemic hyperinsulinaemic clamp to evaluate patients9 sensitivity to insulin. Glucose uptake decreased from 5.6 to 4.5 mg/kg/min when patients were taking metoprolol and from 5.6 to 4.9 mg/kg/min when they were taking atenolol. Both drugs caused a small increase in fasting plasma insulin and blood glucose concentrations and glycated haemoglobin concentration. Despite decreased sensitivity to insulin the increase in insulin concentration in response to an intravenous glucose tolerance test was small, suggesting inhibition of release of insulin. Very low density lipoprotein and low density lipoprotein triglyceride concentrations were increased with both drugs and high density lipoprotein cholesterol concentration was decreased. Low density lipoprotein cholesterol concentration was not affected. CONCLUSIONS--Long term use of metoprolol and atenolol causes metabolic abnormalities that may be related to the increased incidence of diabetes in patients with hypertension who are treated pharmacologically. These results may help to explain why the two drugs have failed consistently to reduce the incidence of coronary heart disease in several large scale studies.
TL;DR: Local contraction-induced increases in insulin sensitivity and responsiveness play an important role in postexercise recovery of human skeletal muscle.
Abstract: The effect of 1 h of dynamic one-legged exercise on insulin action in human muscle was studied in 6 healthy young men. Four hours after one-legged knee extensions, a three-step sequential euglycemic hyperinsulinemic clamp combined with arterial and bilateral femoral vein catheterization was performed. Increased insulin action on glucose uptake was found in the exercised compared with the rested thigh at mean plasma insulin concentrations of 23, 40, and 410 microU/ml. Furthermore, prior contractions directed glucose uptake toward glycogen synthesis and increased insulin effects on thigh O2 consumption and at some insulin concentrations on potassium exchange. In contrast, no change in insulin effects on limb exchange of free fatty acids, glycerol, alanine or tyrosine were found after exercise. Glycogen concentration in rested vastus lateralis muscle did not increase measurably during the clamp even though indirect estimates indicated net glycogen synthesis. In contrast, in exercised muscle estimated and biopsy-verified increases in muscle glycogen concentration agreed. Local contraction-induced increases in insulin sensitivity and responsiveness play an important role in postexercise recovery of human skeletal muscle.
TL;DR: The results suggest that hyperinsulinemia in obese women with polycystic ovary syndrome may directly increase serum testosterone levels.
Abstract: To test the hypothesis that insulin plays a role in the hyperandrogenism of obese women with polycystic ovary syndrome, we conducted a prospective study in which the androgen status of five obese women with polycystic ovary syndrome was assessed on two occasions: before and after 10 days of oral diazoxide (100 mg, three times daily) administration. Fasting serum insulin levels decreased from 177 +/- 45 (+/- SE) to 123 +/- 43 pmol/L (P less than 0.01) and insulin release in response to 100 g oral glucose administration decreased from 223.0 +/- 29.2 to 55.6 +/- 7.9 nmol.min/L (P less than 0.002) after diazoxide administration. At the same time, serum total testosterone fell from 2.5 +/- 0.4 to 2.1 +/- 0.3 nmol/L (P less than 0.007), serum testosterone not bound to sex hormone-binding globulin fell from 1.9 +/- 0.3 to 1.4 +/- 0.2 nmol/L (P less than 0.01), and the molar ratio of serum androstenedione to serum estrone fell from 25.7 +/- 7.7 to 16.6 +/- 5.5 (P less than 0.04). Serum sex hormone-binding globulin levels increased slightly but not significantly from 13.2 +/- 1.0 to 21.7 +/- 4.1 nmol/L. Serum androstenedione, dehydroepiandrosterone sulfate, estradiol, estrone, and progesterone concentrations did not change, nor did basal or GnRH-stimulated serum LH and FSH concentrations. These results suggest that hyperinsulinemia in obese women with polycystic ovary syndrome may directly increase serum testosterone levels.
TL;DR: It is concluded that IGF-I influences kidney function and, in contrast to GH, exerts an insulin-sparing effect and may be speculated that the therapeutic spectrum of IGF-i is quite different from that of GH.
Abstract: Insulin-like growth factor I (IGF-I) is an important mediator of growth hormone (GH) action and it appeared tempting to evaluate possible clinical applications. Recombinant IGF-I was infused s.c. at a dose of 20 micrograms/kg of body weight per hour during 6 days in two healthy adult subjects. Blood glucose and fasting insulin levels remained within normal limits and IGF-II levels were suppressed. In contrast to insulin, fasting C peptide levels were decreased. GH secretion was also suppressed by IGF-I. Our preliminary data allow us to distinguish between the effects of GH per se and those of IGF-I: GH causes hyperinsulinism, whereas IGF-I leads to decreased insulin secretion. Glomerular filtration rate, as estimated by creatinine clearance, increased to 130% of preinfusion values during the IGF-I infusion. Total creatinine and urea excretion remained unchanged. We conclude that IGF-I influences kidney function and, in contrast to GH, exerts an insulin-sparing effect. It may be speculated that the therapeutic spectrum of IGF-I is quite different from that of GH.
TL;DR: The results confirm earlier observations that untreated patients with hypertension are insulin resistant, hyperglycemic, and hyperinsulinemic compared to a well-matched normotensive control group, and suggest that conventional treatment programs for lowering blood pressure many exaggerated these metabolic defects.
01 Jan 1989
TL;DR: Long-term intake of dietary amylose may be valuable in decreasing insulin response while maintaining proper control of glucose tolerance and low levels of blood lipids.
Abstract: Twelve men consumed a diet containing 34% ofcalories as 70% arnylose or amylopectin starch to determine if the structure of starch could influence metabolic factors associated with abnormal states. Each starch was fed to subjects for 5 wk in a crossover design. No significant differences were observed in glucose or insulin levels when a glucose tolerance was given after 4 wk on each starch. However, glucose and insulin responses were significantly lower when a meal containing amylose compared with arnylopectin was consumed after 5 wk on each starch. Summation of 0.5 through 2-h levels of insulin but not glucose were signifi- cantly lower after amybose compared with levels after arnylopectin. Mean fasting triglyceride and cholesterol levels were significantly bower during the period when amybose was consumed. Long-term intake of dietary arnylose may be valuable in decreasing insulin response while maintaining proper control ofglucose tolerance and bow levels ofbbood lipids. Am J Clin Nutr 1989;49:337-44.
TL;DR: The intimate relationship between lymph insulin and Rd suggests that the transcapillary insulin transport is primarily responsible for the delay in Rd, and if altered, it could be an important component of insulin resistance in obesity and diabetes mellitus.
Abstract: This study examined the relationship between transcapillary insulin transport and insulin action in vivo. During euglycemic clamps (n = 7) in normal conscious dogs we simultaneously measured plasma and thoracic duct lymph insulin and glucose utilization (Rd). Clamps consisted of an activation phase with constant insulin infusion (0.6 mU/kg per min) and a deactivation phase. [14C]Inulin was infused as a passively transported control substance. While [14C]inulin reached an equilibrium between plasma and lymph, steady-state (ss) plasma insulin was higher than lymph (P less than 0.05) and the ratio of 3:2 was maintained during basal, activation, and deactivation phases: 18 +/- 2 vs. 12 +/- 1, 51 +/- 2 vs. 32 +/- 1, and 18 +/- 3 vs. 13 +/- 1 microU/ml. In addition, it took longer for lymph insulin to reach ss than plasma insulin during activation and deactivation: 11 +/- 2 vs. 31 +/- 5 and 8 +/- 2 vs. 32 +/- 6 min (P less than 0.02). Rd increased from 2.6 +/- 0.1 to a ss of 6.6 +/- 0.4 mg/kg per min within 50 +/- 8 min. There was a remarkable similarity in the dynamics of insulin in lymph and Rd: the time to reach ss for Rd was not different from lymph insulin (P greater than 0.1), and the relative increases of the two measurements were similar, 164 +/- 45% and 189 +/- 29% (P greater than 0.05). While there was only a modest correlation (r = 0.78, P less than 0.01) between Rd and plasma insulin, the dynamic changes of lymph insulin and Rd showed a strong correlation (r = 0.95, P less than 0.01). The intimate relationship between lymph insulin and Rd suggests that the transcapillary insulin transport is primarily responsible for the delay in Rd. Thus, transcapillary transport may be rate limiting for insulin action, and if altered, it could be an important component of insulin resistance in obesity and diabetes mellitus.
TL;DR: It is concluded that suppression of endogenous insulin by intensive, continuous insulin treatment during the first two weeks after the diagnosis of IDDM may improve beta-cell function during the subsequent year.
Abstract: A period of early, intensive insulin treatment is thought to improve subsequent beta-cell function in insulin-dependent diabetes mellitus (IDDM). To study this hypothesis, we randomly assigned adolescents with newly diagnosed IDDM to receive either conventional treatment (n = 14) (NPH insulin, 1 U per kilogram of body weight per day, in two divided doses) or an experimental treatment (n = 12) (a two-week hospitalization with maintenance of blood glucose levels between 3.3 and 4.4 mmol per liter by continuous insulin infusion delivered by an external artificial pancreas [Biostator]). During the two-week intervention, the experimental-therapy group received four times more insulin than the conventionally treated group, and their endogenous insulin secretion was more completely suppressed, as evidenced by a urinary C-peptide excretion rate one seventh that of the conventionally treated group. After the first two weeks, both groups were treated similarly and received similar amounts of insulin. At one year, the mean (+/- SEM) plasma level of C peptide was significantly higher after mixed-meal stimulation in the experimental-therapy group than in the conventionally treated group (0.51 +/- 0.07 vs. 0.27 +/- 0.06; P less than 0.01). The experimental-therapy group also had better metabolic control, as evidenced by lower glycohemoglobin values (7.2 +/- 0.7 vs. 10.8 +/- 1.2 percent; P less than 0.01). We conclude that suppression of endogenous insulin by intensive, continuous insulin treatment during the first two weeks after the diagnosis of IDDM may improve beta-cell function during the subsequent year.
TL;DR: Results confirm the clinical observation that antihypertensive therapy slows diabetic glomerulopathy, but also suggest that CAP affords superior long-term protection as compared to the other anti Hypertensive drug regimen studied.