Showing papers on "Insulin published in 1988"
TL;DR: The possibility is raised that resistance to insulin-stimulated glucose uptake and hyperinsulinemia are involved in the etiology and clinical course of three major related diseases— NIDDM, hypertension, and CAD.
Abstract: Resistance to insulin-stimulated glucose uptake is present in the majority of patients with impaired glucose tolerance (IGT) or non-insulin-dependent diabetes mellitus (NIDDM) and in ∼25% of nonobese individuals with normal oral glucose tolerance. In these conditions, deterioration of glucose tolerance can only be prevented if the β-cell is able to increase its insulin secretory response and maintain a state of chronic hyperinsulinemia. When this goal cannot be achieved, gross decompensation of glucose homeostasis occurs. The relationship between insulin resistance, plasma insulin level, and glucose intolerance is mediated to a significant degree by changes in ambient plasma free-fatty acid (FFA) concentration. Patients with NIDDM are also resistant to insulin suppression of plasma FFA concentration, but plasma FFA concentrations can be reduced by relatively small increments in insulin concentration.Consequently, elevations of circulating plasma FFA concentration can be prevented if large amounts of insulin can be secreted. If hyperinsulinemia cannot be maintained, plasma FFA concentration will not be suppressed normally, and the resulting increase in plasma FFA concentration will lead to increased hepatic glucose production. Because these events take place in individuals who are quite resistant to insulinstimulated glucose uptake, it is apparent that even small increases in hepatic glucose production are likely to lead to significant fasting hyperglycemia under these conditions. Although hyperinsulinemia may prevent frank decompensation of glucose homeostasis in insulin-resistant individuals, this compensatory response of the endocrine pancreas is not without its price. Patients with hypertension, treated or untreated, are insulin resistant, hyperglycemic, and hyperinsulinemic. In addition, a direct relationship between plasma insulin concentration and blood pressure has been noted. Hypertension can also be produced in normal rats when they are fed a fructose-enriched diet, an intervention that also leads to the development of insulin resistance and hyperinsulinemia. The development of hypertension in normal rats by an experimental manipulation known to induce insulin resistance and hyperinsulinemia provides further support for the view that the relationship between the three variables may be a causal one. However, even if insulin resistance and hyperinsulinemia are not involved in the etiology of hypertension, it is likely that the increased risk of coronary artery disease (CAD) in patients with hypertension and the fact that this risk if not reduced with antihypertensive treatment are due to the clustering of risk factors for CAD, in addition to high blood pressure, associated with insulin resistance. These include hyperinsulinemia, IGT, increased plasma triglyceride concentration, and decreased high-density lipoprotein cholesterol concentration, all of which are associated with increased risk for CAD. It is likely that the same risk factors play a significant role in the genesis of CAD in the population as a whole. Based on these considerations the possibility is raised that resistance to insulin-stimulated glucose uptake and hyperinsulinemia are involved in the etiology and clinical course of three major related diseases— NIDDM, hypertension, and CAD.
12,460 citations
TL;DR: Not only are oxygen radicals involved in the cause of diabetes, they also appear to play a role in some of the complications seen in long-term treatment of diabetes.
1,136 citations
TL;DR: There are differences in substrate level between individuals with normal glucose tolerance and patients with NIDDM and differing degrees of glucose intolerance, unrelated to ambient insulin level, and these changes persist over 24 h.
Abstract: Fasting and postprandial plasma glucose, free fatty acid (FFA), lactate, and insulin concentrations were measured at hourly intervals for 24 h in 27 nonobese individuals-9 with normal glucose tolerance, 9 with mild non-insulin-dependent diabetes mellitus (NIDDM, fasting plasma glucose less than 175 mg/dl), and 9 with severe NIDDM (fasting plasma glucose greater than 250 mg/dl). In addition, hepatic glucose production (HGP) was measured from midnight to 0800 in normal individuals and patients with severe NIDDM. Plasma glucose concentration was highest in patients with severe NIDDM, lowest in those with normal glucose tolerance, and intermediate in those with mild NIDDM (two-way ANOVA, P less than .001). Variations in plasma FFA and lactate levels of the three groups were qualitatively similar, with lowest concentrations seen in normal individuals, intermediate levels in the group with mild NIDDM, and the highest concentration in those with severe NIDDM (two-way ANOVA, P less than .001). Of particular interest was the observation that plasma FFA concentrations were dramatically elevated from midnight to 0800 in patients with severe NIDDM. The 24-h insulin response was significantly increased in patients with mild NIDDM, with comparable values seen in the other two groups. Values for HGP fell progressively throughout the night in normal individuals and patients with severe NIDDM, despite a concomitant decline in plasma glucose and insulin levels. Although the magnitude of the fall in HGP was greater in NIDDM, the absolute value was significantly (P less than .001) greater than normal throughout the period of observation.(ABSTRACT TRUNCATED AT 250 WORDS)
761 citations
TL;DR: In obesity, although hypersecretion of insulin can be documented, the temporal pattern of secretion is largely unaltered, which suggests that the functioning beta cell mass is enhance, but normal regulatory mechanisms influencing secretion are still operative.
Abstract: The pattern of endogenous insulin secretion over a 24-h period, which included three mixed meals, was evaluated in 14 normal volunteers and 15 obese subjects. Insulin secretory rates were calculated from plasma C-peptide levels using individually derived C-peptide kinetic parameters and a validated open two-compartment model of peripheral C-peptide kinetics. Insulin secretion rates were consistently elevated in the obese subjects under basal conditions (11.6 +/- 1.2 vs. 5.4 +/- 0.5 nmol/h) and in the 4 h after breakfast (139 +/- 15 vs. 63 +/- 5 nmol/4 h, P less than 0.001), lunch (152 +/- 16 vs. 67 +/- 5 nmol/4 h, P less than 0.001), and dinner (145 +/- 18 vs. 65 +/- 6 nmol/4 h, P less than 0.001). In the normal subjects, basal insulin secretion represented 50 +/- 2.1% of total 24-h insulin production, insulin secretion returned to baseline between meals, and equal quantities of insulin were secreted in the 4 h after breakfast, lunch, and dinner, despite the fact that subjects consumed half the number of calories at breakfast compared to lunch and dinner. Overall glucose responses were also similar after the three meals. In contrast, the pattern of insulin secretion in obese subjects was largely normal, albeit set at a higher level. However, the insulin secretion rate after meals did not return to baseline, and the secretion rate immediately before lunch (350.5 +/- 81.9 pmol/min) and dinner (373.6 +/- 64.8 pmol/min) was considerably higher than the secretion rate immediately before breakfast (175.5 +/- 18.5 pmol/min). In these overweight subjects, the glucose response after lunch was lower than after dinner. Analysis of individual 24-h insulin secretory profiles in the normal subjects revealed that insulin secretion was pulsatile. On average 11.1 +/- 0.5 pulses were produced in each 24-h period. The most prevalent temporal distribution of postmeal secretory pulses was two pulses after breakfast and three pulses after both lunch and dinner. Insulin secretion was also pulsatile during the period without meal stimuli: 3.9 +/- 0.3 pulses occurred during the period of overnight sampling and in the 3-h period before ingestion of the breakfast meal. In the obese subjects, the number and timing of secretory pulses was similar to those of normal volunteers, although the amplitude of the pulses was significantly greater. In both groups of subjects, greater than 80% of insulin pulses were concomitant with a pulse in glucose concentration in the postmeal period. The concomitancy rate was significantly lower in the interval without the meal stimuli, averaging 47% in both groups. Thus in obesity, although hypersecretion of insulin can be documented, the temporal pattern of secretion i s largely unaltered, which suggests that the functioning beta cell mass is enhance, but normal regulatory mechanisms influencing secretion are still operative.
728 citations
TL;DR: It is concluded that insulin and PRL inhibit SHBG production and confirmed that T4, T, and E2 stimulate SH BG production in vitro, suggesting that insulin or PRL may be important factors in the regulation of SHBGProduction in vivo.
Abstract: Sex hormone-binding globulin (SHBG) production in humans has been thought to be stimulated by estrogens and thyroid hormone and inhibited by androgens. However, recent data indicate that SHBG production in vitro is stimulated by both androgens and estrogens. This study was designed to determine what other hormonal factors regulate SHBG production. Since hyperinsulinemia and hyperprolactinemia both occur in disease states in which low serum SHBG levels are found, the effects of insulin and PRL were compared to and/or studied in combination with estradiol (E2), T4, and testosterone (T) in a human hepatoma cell line (Hep G2). Hep G2 cells were grown to near confluence in medium including 10% fetal calf serum, and then 72-h experimental incubations were carried out which used only fetal calf serum-free medium. Compared to control incubations, both insulin (10(-8) mol/L) and PRL (10(-8) mol/L) decreased SHBG production from 65.0 +/- 0.6 (+/- SE) to 46.8 +/- 1.1 and 46.8 +/- 1.2 nmol/10(6) cells, respectively (P less than 0.01). Insulin also inhibited both E2 and T4-stimulated SHBG production. T stimulated SHBG production to the same degree as E2. Finally, both E2 and insulin significantly increased cell number, an important consideration when expressing the effect of a hormone on SHBG production in cultured cells. We conclude that insulin and PRL inhibit SHBG production and confirm that T4, T, and E2 stimulate SHBG production in vitro. These findings suggest that insulin and PRL may be important factors in the regulation of SHBG production in vivo.
693 citations
TL;DR: Data is presented based upon a monoclonal antibody against the fat cell glucose transporter that identifies a unique, insulin-regulatable glucose transport protein in muscle and adipose tissue that raises the question of whether hormonal regulation of glucose transport is conferred by virtue of a tissue-specific signalling mechanism or a tissue,specific glucose transporter.
Abstract: At least three different glucose transport systems exist in mammalian cells. These are: (1) the constitutively active, facilitative carrier characteristic of human erythrocytes, Hep G2 (ref. 2) cells and rat brain; (2) the Na-dependent active transporter of kidney and small intestine; and (3) the facilitative carrier of rat liver (B. Thorens and H. F. Lodish, personal communication). A fourth possible glucose transport system is the insulin-dependent carrier that may be specific to muscle and adipose tissue. This transporter resides primarily in an intracellular compartment in resting cells from where it translocates to the cell surface upon cellular insulin exposure. This raises the question of whether hormonal regulation of glucose transport is conferred by virtue of a tissue-specific signalling mechanism or a tissue-specific glucose transporter. Here we present data supporting the latter concept based upon a monoclonal antibody against the fat cell glucose transporter that identifies a unique, insulin-regulatable glucose transport protein in muscle and adipose tissue.
651 citations
TL;DR: The data show that impaired glucose tolerance in the study population is primarily due to impaired insulin action, and relative insulin deficiency first appears at the lower end of the second (diabetic) mode seen in population frequency distributions of plasma glucose concentrations.
Abstract: Impaired glucose tolerance often presages the development of non-insulin-dependent diabetes mellitus. We have studied insulin action and secretion in 24 Pima Indians before and after the development of impaired glucose tolerance and in 254 other subjects representing the whole spectrum of glucose tolerance, including subjects with overt non-insulin-dependent diabetes. The transition from normal to impaired glucose tolerance was associated with a decrease in glucose uptake during hyperinsulinemia, from 0.018 to 0.016 mmol per minute (from 3.3 to 2.8 mg per kilogram of fat-free body mass per minute) (P less than 0.0003). Mean plasma insulin concentrations increased during an oral glucose-tolerance test, from 1200 to 1770 pmol per liter (from 167 to 247 microU per milliliter). In 151 subjects with normal glucose tolerance, the insulin concentration measured during an oral glucose-tolerance test correlated with the plasma glucose concentration (r = 0.48, P less than or equal to 0.0001). This relation was used to predict an insulin concentration of 1550 pmol per liter (216 microU per milliliter) in subjects with impaired glucose tolerance (actual value, 1590 pmol per liter [222 microU per milliliter]; P not significant), suggesting that these subjects had normal secretion of insulin. In contrast, plasma insulin concentrations in the diabetics decreased as glucose concentrations increased (r = -0.75, P less than or equal to 0.0001), suggesting deficient secretion of insulin. This relative insulin deficiency first appears at the lower end of the second (diabetic) mode seen in population frequency distributions of plasma glucose concentrations. Our data show that impaired glucose tolerance in our study population is primarily due to impaired insulin action. In patients with non-insulin-dependent diabetes mellitus, by contrast, impaired insulin action and insulin secretory failure are both present.
630 citations
TL;DR: Data suggest that profound alterations in the amount and temporal organization of stimulated insulin secretion may be important in the pathophysiology of beta-cell dysfunction in diabetes.
Abstract: To determine whether non-insulin-dependent diabetes is associated with specific alterations in the pattern of insulin secretion, we studied 16 patients with untreated diabetes and 14 matched controls The rates of insulin secretion were calculated from measurements of peripheral C-peptide in blood samples taken at 15- to 20-minute intervals during a 24-hour period in which the subjects ate three mixed meals Incremental responses of insulin secretion to meals were significantly lower in the diabetic patients (P less than 0005), and the increases and decreases in insulin secretion after meals were more sluggish These disruptions in secretory response were more marked after dinner than after breakfast, and a clear secretory response to dinner often could not be identified Both the control and diabetic subjects secreted insulin in a series of discrete pulses In the controls, a total of seven to eight pulses were identified in the period from 9 am to 11 pm, including the three post-meal periods (an average frequency of one pulse per 105 to 120 minutes), and two to four pulses were identified in the remaining 10 hours The number of pulses in the patients and controls did not differ significantly However, in the patients, the pulses after meals had a smaller amplitude (P less than 003) and were less frequently concomitant with a glucose pulse (547 +/- 49 vs 822 +/- 50, P less than 0001) Pulses also appeared less regularly in the patients During glucose clamping to produce hyperglycemia (glucose level, 167 mmol per liter [300 mg per deciliter]), the diabetic subjects secreted, on the average, 70 percent less insulin than matched controls (P less than 0001) These data suggest that profound alterations in the amount and temporal organization of stimulated insulin secretion may be important in the pathophysiology of beta-cell dysfunction in diabetes
626 citations
TL;DR: It is concluded that abnormal oscillatory insulin secretion may be an early phenomenon in the development of non-insulin-dependent diabetes.
Abstract: In fasting nondiabetic subjects, insulin is secreted in regular pulses every 12 to 15 minutes, but patients with non-insulin-dependent diabetes lack regular oscillatory insulin secretion. To investigate whether abnormal insulin oscillations are an early feature of diabetes, we studied 10 minimally glucose-intolerant first-degree relatives of patients with non-insulin-dependent diabetes and 10 controls matched for age and obesity. We performed a time-series analysis of fasting plasma insulin levels in blood samples obtained at 1-minute intervals for 150 minutes. Fasting plasma glucose levels were higher in the relatives than in the controls (mean +/- SD, 5.4 +/- 0.7 vs. 4.4 +/- 0.3 mmol per liter). Autocorrelation of pooled data showed no regular oscillatory activity in the relatives but a 13-minute cycle in the controls (r = 0.23, P less than 0.001). Similarly, Fourier transform analysis showed no significant peak in the relatives but the expected significant peak at 13 to 14 minutes in the controls (P less than 0.05). First-phase (0 to 10 minutes) insulin secretory responses to glucose administered intravenously were not significantly impaired in the relatives (geometric mean, 188 pmol per liter [26.2 mU per liter]; range of SD, +103 to -67 pmol per liter [+14.4 to -9.3 mU per liter]), as compared with the controls (geometric mean, 231 pmol per liter [32.2 mU per liter]; range of SD, +131 to -83 pmol per liter [+18.2 to -11.6 mU per liter]). We conclude that abnormal oscillatory insulin secretion may be an early phenomenon in the development of non-insulin-dependent diabetes.
544 citations
TL;DR: It is drawn that prolonged moderate exercise increases insulin action on glucose uptake in humans by reducing apparent Km and increasing Vmax, and may be related to an exercise-induced increase in glycogen synthase activity.
Abstract: The effect of acute physical exercise on insulin sensitivity and responsiveness of glucose uptake and hepatic glucose production was studied. Seven untrained men were subjected to four sequential euglycemic hyperinsulinemic clamps after rest (R), immediately after exercise (E), as well as 48 h after 60 min of 150 W ergometer exercise (ER). Insulin-mediated glucose uptake was higher on E and ER days compared with R days. Apparent Km decreased after exercise (52 +/- 3 R vs. 43 +/- 4 E and 40 +/- 3 ER microU/ml, means +/- SE) and Vmax increased (9.5 +/- 0.8 R vs. 10.9 +/- 0.7 E and 10.7 +/- 0.8 ER mg.min-1.kg-1). Glucose oxidation increased with the increasing insulin infusion rate, and maximal glucose oxidation rate was lower on E days compared with R days. The maximal conversion rate of glucose to glycogen was higher on E and ER days (8.0 +/- 0.3 and 7.2 +/- 0.2, respectively) than on R days (5.7 +/- 0.6 mg.min-1 kg-1). Muscle glycogen synthase I activity was higher immediately after exercise and remained higher for the next 48 h. No change in any glucoregulatory hormone or metabolite could explain the increased insulin action seen after exercise. In additional experiments (n = 3), no remaining effect existed 5 days after exercise. Both insulin and exercise suppressed the pancreatic secretion of insulin and proinsulin. The conclusions drawn are that prolonged moderate exercise increases insulin action on glucose uptake in humans by reducing apparent Km and increasing Vmax. This effect lasts 48 h but not 5 days. The increased insulin action may be related to an exercise-induced increase in glycogen synthase activity.
520 citations
TL;DR: It is suggested that CS-045 increases not only insulin sensitivity but also insulin responsiveness, and may reduce abnormalities of glucose and lipid metabolism in obese and non-insulin-dependent diabetes mellitus patients with insulin resistance.
Abstract: CS-045 is a new oral antidiabetic agent that was effective in insulin-resistant diabetic animal models, including the KK mouse, the ob/ob mouse, and the Zucker fatty rat. CS-045 was not effective in the streptozocin-treated mouse, an insulin-deficient diabetic animal model. In fed KK mice, CS-045 lowered the plasma glucose levels in a dose-dependent manner after a single oral administration, and the hypoglycemic effect lasted for at least 18 h. In normal rats, however, plasma glucose levels were not changed after administration of CS-045. CS-045 when given chronically (2 wk) to diabetic KK and ob/ob mice as a 0.2% food admixture dramatically improved hyperglycemia, hyperinsulinemia, and hypertriglyceridemia to near-normal values and decreased plasma lactate, free fatty acid, and ketone body levels without reducing food intake or body weight. In the obese Zucker fatty rat, oral administration of CS-045 had a similar effect in lowering plasma glucose, insulin, triglyceride, free fatty acid, lactate, and ketone body levels. The CS-045-treated Zucker fatty rats showed increased glucose tolerance and decreased insulin secretion in response to oral glucose. After 9 days of treatment, insulin binding to adipocyte plasma membranes from both CS-045-treated Zucker fatty rats and KK mice was increased. Furthermore, 2-deoxyglucose uptake in CS-045-treated adipocytes was increased and the insulin dose-response curve was shifted to the left. These findings suggest that CS-045 increases not only insulin sensitivity but also insulin responsiveness. Based on its pharmacological profile, CS-045 is a new orally effective antidiabetic agent that may reduce abnormalities of glucose and lipid metabolism in obese and non-insulin-dependent diabetes mellitus patients with insulin resistance.
TL;DR: It is reported that human pancreatic amylin and rat CGRP-1 are potent inhibitors of both basal and insulin-stimulated rates of glycogen synthesis in stripped rat soleus muscle in vitro, which may provide a basis for a new understanding of the molecular mechanisms that cause insulin resistance in skeletal muscle.
Abstract: Insulin resistance occurs in a variety of conditions, including diabetes, obesity and essential hypertension, but its underlying molecular mechanisms are unclear. In type 2 (non-insulin-dependent) diabetes mellitus, it is insulin-resistance in skeletal muscle, the chief site of insulin-mediated glucose disposal in humans, that predominantly accounts for the low rates of glucose clearance from the blood, and hence for impaired glucose tolerance. Human type 2 diabetes is characterized by a decrease in non-oxidative glucose storage (muscle glycogen synthesis), and by the deposition of amyloid in the islets of Langerhans. Amylin is a 37-amino-acid peptide which is a major component of islet amyloid and has structural similarity to human calcitonin gene-related peptide-2 (CGRP-2; ref. 8). CGRP is a neuropeptide which may be involved in motor activity in skeletal muscle. We now report that human pancreatic amylin and rat CGRP-1 are potent inhibitors of both basal and insulin-stimulated rates of glycogen synthesis in stripped rat soleus muscle in vitro. These results may provide a basis for a new understanding of the molecular mechanisms that cause insulin resistance in skeletal muscle.
TL;DR: It is reported that it is possible, by single amino-acid substitutions, to make insulins which are essentially monomeric at pharmaceutical concentrations and which have largely preserved their biological activity, capable of giving diabetic patients a more physiological plasma insulin profile at the time of meal consumption.
Abstract: The use of insulin as an injected therapeutic agent for the treatment of diabetes has been one of the outstanding successes of modern medicine. The therapy has, however, had its associated problems, not least because injection of insulin does not lead to normal diurnal concentrations of insulin in the blood. This is especially true at meal times when absorption from subcutaneous tissue is too slow to mimic the normal rapid increments of insulin in the blood. In the neutral solutions used for therapy, insulin is mostly assembled as zinc-containing hexamers and this self-association, which under normal physiological circumstances functions to facilitate proinsulin transport, conversion and intracellular storage, may limit the rate of absorption. We now report that it is possible, by single amino-acid substitutions, to make insulins which are essentially monomeric at pharmaceutical concentrations (0.6 mM) and which have largely preserved their biological activity. These monomeric insulins are absorbed two to three times faster after subcutaneous injection than the present rapid-acting insulins. They are therefore capable of giving diabetic patients a more physiological plasma insulin profile at the time of meal consumption.
TL;DR: Serum 34K IGF-binding protein levels are elevated in type 1 and 2 diabetic patients and decreased in patients with insulinoma; the serum binding protein, but not IGF-I concentration is decreased by acute hyperinsulinemia; and these data suggest that the serum insulin concentration plays a role in regulation of the serum IGF- binding protein concentration.
Abstract: The serum levels of 34K insulin-like growth factor (IGF)-binding protein were measured by RIA in 88 type 1 diabetic patients, 9 patients with type 2 diabetes, 7 patients with insulinoma, 19 normal subjects (all after an overnight fast), and 82 normal subjects after a breakfast meal. In addition, the effect of 2- to 3-h euglycemic steady state hyperinsulinemia on serum IGF-binding protein and IGF-1 levels was studied in some subjects in each of the fasted groups. Compared with normal subjects, the mean serum IGF-binding protein levels were 4-fold (P less than 0.001) higher in type I diabetic patients treated with conventional insulin injections, 2.5-fold (P less than 0.001) higher in those treated with continuous sc insulin infusion, and 2-fold (P less than 0.05) higher in patients with type 2 diabetes. In the patients with insulinoma, the mean IGF-binding protein level was 63% below normal (P less than 0.001), and it normalized after removal of the tumor. There was a slight negative correlation between the IGF-binding protein level and insulin dose in the diabetic patients (r = -0.22; P less than 0.05). In normal subjects, serum insulin concentrations were 2-fold higher (P less than 0.001) and the IGF-binding protein level was 29% lower after a meal (P less than 0.05) than in the fasting state. Serum IGF-I concentrations were virtually identical in the type 1 and 2 diabetic patients, insulinoma patients, and normal subjects. During steady state euglycemic hyperinsulinemia, the IGF-binding protein level fell by 40-70% in each group (P less than 0.001), whereas the IGF-I level declined (P less than 0.05) in the type 2 diabetic patients only. The decline of binding protein was closely related to the baseline level (r = 0.94; P less than 0.001). No correlation was found between serum IGF-I and binding protein levels in any group. In conclusion, 1) serum 34K IGF-binding protein levels are elevated in type 1 and 2 diabetic patients and decreased in patients with insulinoma; 2) the serum binding protein, but not IGF-I concentration is decreased by acute hyperinsulinemia; and 3) these data suggest that the serum insulin concentration plays a role in regulation of the serum 34K IGF-binding protein concentration.
TL;DR: Preadipocytes have the potential for a maximal response to IGF-I, whereas the accumulation of more than 95% of adipocyte insulin receptors and the appearance of responsiveness to insulin are consequences of differentiation.
TL;DR: Under basal, fasting conditions and during ingestion of a mixed diet, the hyperinsulinemia of obesity results predominantly from increased insulin secretion, and a reduction in insulin clearance may contribute to the greater increase in peripheral insulin concentrations that are characteristic of the obese state.
Abstract: The secretion and hepatic extraction of insulin were compared in 14 normal volunteers and 15 obese subjects using a previously validated mathematical model of insulin secretion and rate constants for C-peptide derived from analysis of individual decay curves after intravenous bolus injections of biosynthetic human C-peptide. Insulin secretion rates were substantially higher than normal in the obese subjects after an overnight fast (86.7 +/- 7.1 vs. 50.9 +/- 4.8 pmol/m2 per min, P less than 0.001, mean +/- SEM), over a 24-h period on a mixed diet (279.6 +/- 24.2 vs. 145.8 +/- 8.8 nmol/m2 per 24 h, P less than 0.001), and during a hyperglycemic intravenous glucose infusion (102.2 +/- 10.8 vs. 57.2 +/- 2.8 nmol/m2 per 180 min, P less than 0.001). Linear regression analysis revealed a highly significant relationship between insulin secretion and body mass index. Basal hepatic insulin extraction was not significantly different in the normal and obese subjects (53.1 +/- 3.8 vs. 51.6 +/- 4.0%). In the normal subjects, fasting insulin did not correlate with basal hepatic insulin extraction, but a significant negative correlation between fasting insulin and hepatic insulin extraction was seen in obesity (r = -0.63, P less than 0.02). This finding reflected a higher extraction in the six obese subjects with fasting insulin levels within the range of the normal subjects than in the nine subjects with elevated fasting insulin concentrations (61 +/- 3 vs. 45 +/- 6%, P less than 0.05). During the hyperglycemic clamp, the insulin secretion rate increased to an average maximum of 6.2-fold over baseline in the normal subjects and 5.8-fold in the obese subjects. Over the same time, the peripheral insulin concentration increased 14.1-fold over baseline in the normals and 16.6-fold over baseline in the obese, indicating a reduction in the clearance of endogenously secreted insulin. Although the fall in insulin clearance tended to be greater in the obese subjects, the differences between the two groups were not statistically significant. Thus, under basal, fasting conditions and during ingestion of a mixed diet, the hyperinsulinemia of obesity results predominantly from increased insulin secretion. In patients with more marked basal hyperinsulinemia and during intense stimulation of insulin secretion, a reduction in insulin clearance may contribute to the greater increase in peripheral insulin concentrations that are characteristic of the obese state.+
TL;DR: Differences in the resultant SSPG concentrations allowed direct comparison of insulin’s ability to stimulate disposal of an glucose challenge and insulin-stimulated glucose uptake in Chinese men to be compared.
Abstract: Plasma glucose and insulin responses to a glucose challenge and insulin-stimulated glucose uptake were measured in 24 age-, weight-, and sex-matched Chinese men (8 with normal blood pressure, 8 with untreated hypertension, and 8 patients with hypertension treated with thiazide and β-adrenergic antagonist drugs). Plasma glucose and insulin responses were determined by measuring plasma glucose and insulin concentrations before and at 30-min intervals for 2 h after a 75-g oral glucose dose. Insulin-stimulated glucose uptake was estimated by measuring the steady state plasma glucose (SSPG) and insulin (SSPI) concentrations achieved during the last 60 min of a 180-min continuous infusion of somatostatin, insulin, and glucose (insulin suppression test). Under these conditions endogenous insulin secretion was suppressed, and similar SSPI concentrations were achieved in all men; thus, the differences in the resultant SSPG concentrations allowed direct comparison of insulin’s ability to stimulate disposal of an id...
TL;DR: It is concluded that strict glycemie control of IDDM lowers the plasma glucose level required to generate epinephrine release during hypoglycemia, which may diminish patient recognition of moderate hypoglyCEmia and increase the risk of severe hypoglycesmia in intensively treated IDDM.
Abstract: To evaluate the effect of strict glycemie control of insulin-dependent diabetes mellitus (IDDM) on the plasma glucose threshold initiating counterregulatory hormone responses to hypoglycemia, we used the glucose clamp technique to produce a standardized gradual glucose decline from 90 to 40 mg/dl in seven young IDDM patients before and after 2–6 mo of intensified insulin therapy. Before intensive therapy [hemoglobin A 1 (HbA 1 ) 9.6 ± 1.1%], epinephrine responses were triggered at a higher plasma glucose level (67 ± 4 mg/dl) than in normal control subjects (56 ± 1 mg/dl, P P
TL;DR: It is concluded that polyalkylcyanoacrylate nanocapsules preserve the therapeutic effect of insulin when administered orally and prolong this effect when administered subcutaneously and orally.
Abstract: Polyalkylcyanoacrylate nanocapsules (mean size 220 nm), composed of spheric polymeric structures, have been used as a drug carrier for insulin. The rate of encapsulation of insulin is 54.9%, and we studied the therapeutic efficiency of the nanocapsules in diabetic and normal rats. When administered subcutaneously, insulin-loaded nanocapsules prolonged the hypoglycemic effect of insulin; the duration of this effect increased with the doses. When administered orally by force-feeding to diabetic rats, insulin nanocapsules (12.5, 25, and 50 U/kg) decreased fasted glycemia 50-60% by day 2. This effect was maintained for 6 or 20 days with 12.5 or 50 U/kg, respectively. Only the dose of 100 U/kg decreased fed glycemia by 25% in diabetic rats. In normal rats, hyperglycemia induced by an oral glucose load was reduced by 50% with the same dose of oral insulin nanocapsules. We concluded that polyalkylcyanoacrylate nanocapsules preserve the therapeutic effect of insulin when administered orally and prolong this effect when administered subcutaneously and orally.
TL;DR: Amylin may be a factor in the etiology of the insulin resistance in type 2 diabetes mellitus, as both deposition of the peptide in islet amyloid and decreased rates of glucose uptake and glycogen synthesis in skeletal muscle are characteristic of this condition.
Abstract: Diabetes-associated peptide has recently been isolated and characterized from the amyloid of the islets of Langerhans in type 2 (non-insulin-dependent) diabetics, and immunoreactivity with antibodies to the peptide has been demonstrated in islet B cells of both normal and type 2 diabetic subjects. In view of the evidence presented in this paper that this 37-amino acid peptide may be a hormone present in normal individuals, we now propose the name "amylin" to replace "diabetes-associated peptide." Because increased amylin, deposited as amyloid within the islets of Langerhans, is characteristic of type 2 diabetes, the study below was performed to examine the possible effects of amylin on peripheral glucose metabolism. Whole amylin was synthesized by using solid-phase techniques, with formation of the disulfide linkage by oxidation in dilute aqueous solution and recovery of the peptide by lyophilization. The effects of amylin on glucose metabolism were studied in two preparations in vitro, isolated rat soleus muscle strips and isolated rat adipocytes. In skeletal muscle exposed to 120 nM amylin for 1 hr, there was a marked decrease in both basal and submaximally insulin-stimulated rates of glycogen synthesis, which resulted in significant reduction in the rates of insulin-stimulated glucose uptake. In muscles treated with amylin there was no response at the concentration of insulin required to stimulate glucose uptake half-maximally in untreated (control) muscles. In marked contrast, amylin had no effect on either basal or insulin-stimulated rates of glucose incorporation into either CO2 or triacylglycerol in isolated adipocytes. Therefore, amylin may be a factor in the etiology of the insulin resistance in type 2 diabetes mellitus, as both deposition of the peptide in islet amyloid and decreased rates of glucose uptake and glycogen synthesis in skeletal muscle are characteristic of this condition.
TL;DR: It is concluded that the insulin resistance of pregnancy is associated with a postbinding defect in insulin action, probably related to increasing amounts of progesterone, cortisol, PRL, and placental lactogen.
Abstract: Pregnancy is associated with insulin resistance. We studied insulin binding and postbinding function in isolated adipocytes from pregnant and nonpregnant rats. We also used a primary culture system for female virgin rat adipocytes to assess the effects of gestational hormones in vitro on insulin binding and postbinding function. Insulin binding to adipocytes was normal during pregnancy, but [14C]3-O-methylglucose transport was reduced. When hCG or estradiol was added to the culture medium, no change in maximum [14C]3-O-methylglucose transport was found; however, maximum insulin binding was increased with estradiol. Progesterone and cortisol both decreased maximum insulin binding and [14C]3-O-methylglucose transport. PRL and placental lactogen decreased maximum [14C]3-O-methylglucose transport, but did not change insulin binding. When these hormones were added concurrently no change in insulin binding was found, but maximum [14C]3-O-methylglucose transport was reduced. We conclude that the insulin resistance of pregnancy is associated with a postbinding defect in insulin action. Estradiol increased insulin receptor binding, but during pregnancy this effect may be offset by the reduction in insulin binding induced by progesterone and cortisol. The postbinding defect in insulin action during pregnancy is probably related to increasing amounts of progesterone, cortisol, PRL, and placental lactogen.
TL;DR: It is concluded that early treatment with cyclosporine in children with recent-onset Type I diabetes can induce remission from insulin dependence, with half the patients not requiring insulin after a full year.
Abstract: To improve criteria for entry into future trials of immunosuppression, we enrolled 40 children with recent-onset Type I insulin-dependent diabetes in a pilot trial of cyclosporine. Twenty-seven patients were able to discontinue insulin therapy 48 +/- 5 days after the start of immunosuppression. At four months, their fasting and postprandial blood glucose concentrations averaged 110 and 160 mg per deciliter (6.1 and 8.9 mmol per liter) with a mean hemoglobin A1c level of 6.15 percent. Seventy-five percent of these patients with early remission still did not need insulin at 12 months, and their glycemic control was similar to that at 4 months. The major differences between the 27 patients with remission and the 13 without remission were the duration of symptoms before diagnosis (26.8 vs. 48.0 days, P less than 0.01), the degree of weight loss (3.2 vs. 10 percent of body weight, P less than 0.001), the initial hemoglobin A1c level (10.7 vs. 13.2 percent, P less than 0.001), and the frequency of ketoacidosis (11 vs. 61.5 percent, P less than 0.001). The lesser degree of weight loss was the strongest independent predictor of remission. The response of C-peptide to intravenous glucagon (0.50 vs. 0.17 pmol per milliliter, P less than 0.05) was also an independent predictor. No differences were observed between the two groups of patients in age, sex, HLA phenotype, autoantibodies to insulin or islet-cell antigens, or doses or trough levels of cyclosporine. Only minimal manifestations of toxicity were detected over the period of observation. We conclude that early treatment with cyclosporine in children with recent-onset Type I diabetes can induce remission from insulin dependence, with half the patients not requiring insulin after a full year.
TL;DR: This study shows that treatment of moderately obese hypertensive patients with prazosin is associated with an increase of the insulin-mediated glucose disposal and a decrease of theulin response to an intravenous glucose load.
Abstract: The aim of this study was to determine whether insulin sensitivity measured by the euglycaemic insulin clamp technique is lower in patients with primary hypertension than in matched healthy control subjects, and whether this sensitivity was affected after 12 weeks of antihypertensive treatment with the alpha 1-adrenoceptor blocking drug prazosin. Twelve moderately obese normoglycaemic patients (four men), with hypertension not previously treated with pharmacological agents and diastolic blood pressure above 100 mm Hg, and 12 healthy matched control subjects participated. Supine blood pressure decreased 12/5 mmHg (p<0.01) and standing blood pressure 14/9 mmHg (p=0.001) during prazosin treatment (mean dosage 5.3±1.6 mg/day (SD)). During euglycaemic insulin clamp studies the control subjects showed a higher mean glucose uptake than the untreated hypertensive patients (7.5±1.0 and 5.8±1.9 mg·kg b.w.−1·min−1, respectively, p<0.01). During prazosin treatment there was no significant difference between the hypertensive patients and the control subjects in this respect (6.6±2.8 and 7.5±1.0, respectively, p=0.21). During prazosin treatment, however, the disappearance rate of glucose decreased during the intravenous glucose tolerance test (from 1.7±0.9 to 1.3±0.6, p<0.02) and the area under the glucose concentration-time curve decreased by 38% (from 473±119 to 294±99, p<0.001). The peak insulin concentration decreased from 55±35 to 46±32 mU/l (p<0.006) and the area under the insulin concentration-time curve was suppressed by 38% (from 2368±1597 to 1479±940, p<0.01). This study shows that treatment of moderately obese hypertensive patients with prazosin is associated with an increase of the insulin-mediated glucose disposal and a decrease of the insulin response to an intravenous glucose load.
TL;DR: The status of insulin and IGFs as regulatory peptides in the CNS is summarized, with a focus on recent reports, controversial issues, and unsolved problems.
TL;DR: The evidence that supports the hypothesis that insulin and LH both regulate ovarian androgen production was presented and in vitro evidence suggests that hyperinsulinemia may play a central role in the development of ovarian hyperandrogenism.
TL;DR: Endogenous glucose production was promptly inhibited in diabetic and normal subjects alike, but the mean residual hepatic glucose production after glucose ingestion was significantly greater in the diabetic group.
Abstract: Following glucose ingestion, tissue glucose uptake is enhanced and endogenous glucose production is inhibited, thus contributing to the maintenance of normal glucose tolerance. To examine whether these responses are disturbed in diabetes, glucose kinetics after oral glucose administration were studied in 12 non-insulin-dependent diabetic and 10 age- and weight-matched control subjects. A double tracer approach was used, whereby the endogenous glucose pool was labeled with 3-3H-glucose and the oral load with 1-14C-glucose. The two glucose tracers were separated in plasma by a two-step chromatographic procedure, and the two sets of isotopic data were analyzed according to a two-compartment model for the glucose system. Basally, glucose production was slightly higher in diabetics than in controls (2.51 +/- 0.24 v 2.28 +/- 0.11 mg/kg.min, NS) even though the former had higher plasma glucose (189 +/- 19 v 93 +/- 2 mg/dL, P less than .001) and insulin (23 +/- 4 v 12 +/- 1 microU/mL, P less than .05) concentrations. Following the ingestion of 1 g/kg of glucose, oral glucose appeared in the peripheral circulation in similar time-course and amount in the two groups (75 +/- 2% of the load over 3.5 hours in the diabetics v 76 +/- 3% in controls). Endogenous glucose production was promptly inhibited in diabetic and normal subjects alike, but the mean residual hepatic glucose production after glucose ingestion was significantly greater in the diabetic group (17 +/- 2 v 10 +/- 3 g/3.5 h, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The hypothesis that insulin-like growth factor I (IGF-I) and insulin play a role in androgen production by rat ovarian thecal-interstitial cells is tested and proteins with characteristics of type I IGF receptors are revealed.
Abstract: We tested the hypothesis that insulin-like growth factor I (IGF-I) and insulin play a role in androgen production by rat ovarian thecal-interstitial cells. Collagenase/ DNase-dispersed rat ovarian thecal-interstitial cells obtained from immature hypophysectomized Sprague-Dawley rats were cultured at a concentration of 106 cells/ml in serum-free medium in the presence of increasing concentrations of LH, IGF-I, or insulin. The medium was replaced every 48 h, and the androsterone concentration in the culture supernatants was used as an index of androgen production. In the absence of added hormones (control) androsterone levels were consistently less than 0.1 ng/ ml. Increasing concentrations of LH stimulated androsterone synthesis in a dose-dependent manner. IGF-I, in the absence of LH, did not significantly increase androsterone levels above control values. However, when combined with 10 ng/ml LH, IGF-I increased androsterone synthesis above levels seen with LH alone in a dose-related fashion: for example, ...
TL;DR: An in vitro muscle preparation suitable for metabolic studies with human muscle tissue is developed and the effects of obesity and non-insulin-dependent diabetes mellitus (NIDDM) on glucose transport is investigated.
Abstract: We have developed an in vitro muscle preparation suitable for metabolic studies with human muscle tissue and have investigated the effects of obesity and non-insulin-dependent diabetes mellitus (NIDDM) on glucose transport. Transport of 3-O-methylglucose and 2-deoxyglucose was stimulated approximately twofold by insulin in muscle from normal nonobese subjects and stimulation occurred in the normal physiological range of insulin concentrations. In contrast to insulin stimulation of 3-O-methylglucose and 2-deoxyglucose transport in muscle from normal, nonobese subjects, tissue from morbidly obese subjects, with or without NIDDM, were not responsive to insulin. Maximal 3-O-methylglucose transport was lower in muscle of obese than nonobese subjects. Morbidly obese patients, with or without NIDDM, have a severe state of insulin resistance in glucose transport. The novel in vitro human skeletal muscle preparation herein described should be useful in investigating the mechanism of this insulin resistance.
TL;DR: The possibility that mutations in the insulin receptor gene may account for the insulin resistance in some patients with non-insulin-dependent diabetes mellitus is raised.
Abstract: Insulin receptor complementary DNA has been cloned from an insulin-resistant patient with leprechaunism whose receptors exhibited multiple abnormalities in insulin binding. The patient is a compound heterozygote, having inherited two different mutant alleles of the insulin receptor gene. One allele contains a missense mutation encoding the substitution of glutamic acid for lysine at position 460 in the alpha subunit of the receptor. The second allele has a nonsense mutation causing premature chain termination after amino acid 671 in the alpha subunit, thereby deleting both the transmembrane and tyrosine kinase domains of the receptor. Interestingly, the father is heterozygous for this nonsense mutation and exhibits a moderate degree of insulin resistance. This raises the possibility that mutations in the insulin receptor gene may account for the insulin resistance in some patients with non-insulin-dependent diabetes mellitus.