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3D printed EBDB for juvenile scoliosis: experience with its design, materials and process. Stud Health Technol Inform 2021; 280:263-264. [PMID: 34190105 DOI: 10.3233/shti210489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
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2
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Effect of hole patterns on the biomechanical behavior of a brace. Stud Health Technol Inform 2021; 280:265. [PMID: 34190106 DOI: 10.3233/shti210490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
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Abstract
Background
Hyperglycemia leading to increased oxidative stress is implicated in the increased risk for the development of macrovascular and microvascular complications in patients with type 1 diabetes mellitus.
Methods and Results
A random subcohort of 349 participants was selected from the
DCCT
/
EDIC
(Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications) cohort. This included 320 controls and 29 cardiovascular disease cases that were augmented with 98 additional known cases to yield a case cohort of 447 participants (320 controls, 127 cases). Biosamples from
DCCT
baseline, year 1, and closeout of
DCCT
, and 1 to 2 years post‐
DCCT
(
EDIC
years 1 and 2) were measured for markers of oxidative stress, including plasma myeloperoxidase, paraoxonase activity, urinary F
2α
isoprostanes, and its metabolite, 2,3 dinor‐8
iso
prostaglandin F
2α
. Following adjustment for glycated hemoblobin and weighting the observations inversely proportional to the sampling selection probabilities, higher paraoxonase activity, reflective of antioxidant activity, and 2,3 dinor‐8
iso
prostaglandin F
2α
, an oxidative marker, were significantly associated with lower risk of cardiovascular disease (−4.5% risk for 10% higher paraoxonase,
P
<0.003; −5.3% risk for 10% higher 2,3 dinor‐8
iso
prostaglandin F
2α
,
P
=0.0092). In contrast, the oxidative markers myeloperoxidase and F
2α
isoprostanes were not significantly associated with cardiovascular disease after adjustment for glycated hemoblobin. There were no significant differences between
DCCT
intensive and conventional treatment groups in the change in all biomarkers across time segments.
Conclusions
Heightened antioxidant activity (rather than diminished oxidative stress markers) is associated with lower cardiovascular disease risk in type 1 diabetes mellitus, but these biomarkers did not change over time with intensification of glycemic control.
Clinical Trial Registration
URL
:
https://www.clinicaltrials.gov
. Unique identifiers:
NCT
00360815 and
NCT
00360893.
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Die postnatale Zunahme der B-Zell-Masse beim Menschen beruht primär auf der Replikation vorhandener B-Zellen. DIABETOL STOFFWECHS 2007. [DOI: 10.1055/s-2007-982443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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5
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Impact of lack of suppression of glucagon on glucose tolerance in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E283-90. [PMID: 10444424 DOI: 10.1152/ajpendo.1999.277.2.e283] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
People with type 2 diabetes have defects in both alpha- and beta-cell function. To determine whether lack of suppression of glucagon causes hyperglycemia when insulin secretion is impaired but not when insulin secretion is intact, twenty nondiabetic subjects were studied on two occasions. On both occasions, a "prandial" glucose infusion was given over 5 h while endogenous hormone secretion was inhibited. Insulin was infused so as to mimic either a nondiabetic (n = 10) or diabetic (n = 10) postprandial profile. Glucagon was infused at a rate of 1.25 ng. kg(-1). min(-1), beginning either at time zero to prevent a fall in glucagon (nonsuppressed study day) or at 2 h to create a transient fall in glucagon (suppressed study day). During the "diabetic" insulin profile, lack of glucagon suppression resulted in a marked increase (P < 0.002) in both the peak glucose concentration (11.9 +/- 0.4 vs. 8.9 +/- 0.4 mmol/l) and the area above basal of glucose (927 +/- 77 vs. 546 +/- 112 mmol. l(-1). 6 h) because of impaired (P < 0.001) suppression of glucose production. In contrast, during the "nondiabetic" insulin profile, lack of suppression of glucagon resulted in only a slight increase (P < 0.02) in the peak glucose concentration (9.1 +/- 0.4 vs. 8.4 +/- 0.3 mmol/l) and the area above basal of glucose (654 +/- 146 vs. 488 +/- 118 mmol. l(-1). 6 h). Of interest, when glucagon was suppressed, glucose concentrations differed only minimally during the nondiabetic and diabetic insulin profiles. These data indicate that lack of suppression of glucagon can cause substantial hyperglycemia when insulin availability is limited, therefore implying that inhibitors of glucagon secretion and/or glucagon action are likely to be useful therapeutic agents in such individuals.
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Effects of hepatic glycogen content on hepatic insulin action in humans: alteration in the relative contributions of glycogenolysis and gluconeogenesis to endogenous glucose production. J Clin Endocrinol Metab 1997; 82:1828-33. [PMID: 9177391 DOI: 10.1210/jcem.82.6.3971] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Hepatic glycogen content varies by almost 2-fold during the day, generally increasing from a nadir before breakfast to a peak 4-5 h after supper. To determine whether differences in hepatic glycogen content of this magnitude alter hepatic insulin action, nine subjects were studied on two occasions. On one occasion saline was infused, whereas on the other occasion an infusion of glucose [16.4 micromol/kg lean body mass (-lbm) x min] was started immediately after supper and continued throughout the night so as to spare hepatic glycogen. The nocturnal glucose infusion resulted in higher (P < 0.05) plasma glucose (6.0 +/- 0.1 vs. 5.1 +/- 0.1 mmol/L) and insulin (127 +/- 38 vs. 49 +/- 9 pmol/L) concentrations, and lower (P < 0.05) plasma glucagon concentrations (74 +/- 11 vs. 97 +/- 20 pg/mL) than did saline infusion. As anticipated, endogenous glucose production (EGP) was substantially lower (P < 0.001) during the glucose than during the saline infusion (7.0 +/- 0.9 vs. 19.4 +/- 1.3 micromol/kg-lbm x min). After discontinuation of the glucose infusion, glucose and insulin concentrations fell to levels that no longer differed from those observed during the saline infusion. In contrast, EGP increased to rates that were higher (P < 0.05) than those observed over the same interval after overnight saline infusion (19.2 +/- 1.2 vs. 16.5 +/- 0.7 micromol/kg-lbm x min). Despite higher EGP, the rate of incorporation of 14CO2 into glucose was lower (P < 0.001) after glucose than that after saline infusion (9.8 +/- 1.2% vs. 24.4 +/- 3.0%), implying a reciprocal relationship between hepatic glycogen content and gluconeogenesis. On the other hand, when differences in basal rates were taken into account, insulin-induced suppression of both EGP and incorporation of 14CO2 into glucose did not differ on the two occasions. Thus, whereas hepatic glycogen content influences both the absolute rate of EGP and the percent contribution of gluconeogenesis to EGP, it does not alter hepatic insulin action.
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The role of splanchnic glucose appearance in determining carbohydrate tolerance. Diabet Med 1996; 13:S23-7. [PMID: 8894466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Postprandial hyperglycaemia in patients with Type 1 and Type 2 is now well-established. Studies of glucose turnover in these patients have shown that this results from a combination of excessive endogenous glucose production and a lack of appropriate stimulation of glucose uptake. In the case of patients with Type 2 diabetes, this may in part be due to a delay in the increase of plasma insulin concentrations. It may be concluded then that agents which delay the absorption of glucose in the postprandial period may help to improve glycaemic control in patients with diabetes by improving the match between meal-derived glucose appearance and the period of insulin availability.
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Glucose turnover in presence of changing glucose concentrations: error analysis for glucose disappearance. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:E557-67. [PMID: 7573434 DOI: 10.1152/ajpendo.1995.269.3.e557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The present studies were undertaken to determine whether 1) the cold- and hot-GINF techniques used with Steele's model provide equivalent estimates of the rates of glucose appearance (R(a)) and disappearance (R(d)) in the presence of physiological changes in glucose and insulin concentrations, 2) the conditions for the best estimation of R(a) are the same as those for R(d), 3) the magnitude of error (if present) differs in diabetic and nondiabetic subjects, and 4) situations exist in which the knowledge of R(d) allows inferences to be made on whole body glucose uptake. To do so we performed experiments in non-insulin-dependent diabetes mellitus and nondiabetic subjects using simultaneous infusions of [6-3H]glucose and [6-14C]glucose; glucose and insulin were infused to mimic normal postprandial glucose and insulin profiles; the infused glucose contained [6-14C]glucose but not [6-3H]glucose. Compared with the hot-GINF method, the traditional cold-GINF method underestimated (P < 0.05) R(a) and R(d) by 10-15% and hepatic glucose release by 25-50% during the 1st h of the study, with the magnitude of error being the same in both diabetic and nondiabetic subjects. Error analysis demonstrated that errors in R(a) and R(d) have different analytic expressions containing common structural but different volume errors. Both R(a) and R(d) can be accurately measured in diabetic and nondiabetic subjects if glucose specific activity is kept constant and the volume of the accessible pool is used to calculate glucose disappearance. The relationship between R(d) and whole body glucose uptake was also derived. Although R(d) can be determined by relying on measurements in the accessible pool only, the assessment of whole body glucose uptake requires a model of the nonaccessible portion of the glucose system. However, knowledge of R(d) can provide useful insights into the behavior of whole body glucose uptake.
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Effects of the normal nocturnal rise in cortisol on carbohydrate and fat metabolism in IDDM. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 268:E595-603. [PMID: 7733257 DOI: 10.1152/ajpendo.1995.268.4.e595] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Plasma cortisol concentrations increase approximately three- to five-fold during sleep in healthy humans. To determine the effects of the normal nocturnal rise in cortisol on carbohydrate and fat metabolism independent of changes in endogenous insulin secretion, we studied the disposition of a mixed meal in individuals with insulin-dependent diabetes mellitus (IDDM) in whom the normal nocturnal rise in cortisol had been either prevented or mimicked by using metyrapone and a constant or variable hydrocortisone infusion. Insulin was infused intravenously on both occasions in amounts sufficient to create relative postprandial insulin deficiency. The nocturnal rise in cortisol resulted in an approximately 30 mg/dl greater (P < 0.001) peak postprandial glycemic excursion due to greater (P < 0.01) systemic glucose appearance and inappropriately low (P < 0.05) tissue glucose uptake. The latter was most evident when postprandial glucose concentrations in the presence and absence of the nocturnal rise in cortisol were matched by means of an exogenous glucose infusion to avoid the confounding effects of differences in glycemia. The nocturnal rise in cortisol also resulted in increased (P < 0.01) incorporation of 14CO2 into glucose (an index of gluconeogenesis), decreased (P < 0.05) carbohydrate oxidation, and increased (P < 0.05) rates of palmitate appearance, lipid oxidation, and beta-hydroxybutyrate concentrations. Thus the normal nocturnal rise in cortisol, independent of changes in insulin secretion, is an important regulator of postabsorptive and postprandial carbohydrate, fat, and ketone body metabolism in humans.
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Abstract
Carbohydrate ingestion results in a fall in glucagon concentration in non-diabetic but not in diabetic individuals. To determine if, and the mechanism by which, lack of postprandial suppression of glucagon contributes to hyperglycaemia, nine subjects with insulin-dependent diabetes mellitus (IDDM) ingested 50 g of glucose containing both [2-3H] glucose and [6-3H] glucose on two occasions. [6-14C] glucose, insulin and low-dose somatostatin were infused intravenously at the same rates on both occasions. A basal glucagon infusion was started either at the same time ("constant glucagon") or 2 h following ("suppressed glucagon") glucose ingestion. This resulted in lower (p < 0.001) glucagon concentrations during the first 2 h of the suppressed than during the constant glucagon study days (63 +/- 1 vs 108 +/- 2 pg/ml). Lack of suppression of glucagon led to higher (p < 0.01) postprandial glucose concentrations (10.3 +/- 0.9 vs 8.1 +/- 0.7 mmol/l) and a greater (p < 0.02) integrated glycaemic response. The excessive rise in glucose was due to higher (p < 0.02) rates of postprandial hepatic glucose release during the constant than during the suppressed glucagon study days, whether measured using either [6-3H] glucose (2.6 +/- 0.2 vs 2.0 +/- 0.2 mmol.kg-1 per 6 h) or [2-3H] glucose (3.0 +/- 0.3 vs 2.4 +/- 0.2 mmol.kg-1 per 6 h) as the meal tracer. Glucose disappearance, initial splanchnic glucose clearance and hepatic glucose cycling did not differ on the two occasions. Thus, the present studies demonstrate that lack of postprandial suppression of glucagon, by increasing hepatic glucose release, contributes to hyperglycaemia in subjects with IDDM.
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The effects of non-insulin-dependent diabetes mellitus on the kinetics of onset of insulin action in hepatic and extrahepatic tissues. J Clin Invest 1995; 95:755-62. [PMID: 7860757 PMCID: PMC295544 DOI: 10.1172/jci117723] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The mechanism(s) of insulin resistance in non-insulin-dependent diabetes mellitus remains ill defined. The current studies sought to determine whether non-insulin-dependent diabetes mellitus is associated with (a) a delay in the rate of onset of insulin action, (b) impaired hepatic and extrahepatic kinetic responses to insulin, and (c) an alteration in the contribution of gluconeogenesis to hepatic glucose release. To answer these questions, glucose disappearance, glucose release, and the rate of incorporation of 14CO2 into glucose were measured during 0.5 and 1.0 mU/kg-1 per min-1 insulin infusions while glucose was clamped at approximately 95 mg/dl in diabetic and nondiabetic subjects. The absolute rate of disappearance was lower (P < 0.05) and the rate of increase slower (P < 0.05) in diabetic than nondiabetic subjects during both insulin infusions. In contrast, the rate of suppression of glucose release in response to a change in insulin did not differ in the diabetic and nondiabetic subjects during either the low (slope 30-240 min:0.02 +/- 0.01 vs 0.02 +/- 0.01) or high (0.02 +/- 0.00 vs 0.02 +/- 0.00) insulin infusions. However, the hepatic response to insulin was not entirely normal in the diabetic subjects. Both glucose release and the proportion of systemic glucose being derived from 14CO2 (an index of gluconeogenesis) was inappropriately high for the prevailing insulin concentration in the diabetic subjects. Thus non-insulin-dependent diabetes mellitus slows the rate-limiting step in insulin action in muscle but not liver and alters the relative contribution of gluconeogenesis and glycogenolysis to hepatic glucose release.
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Abstract
Both glucose and insulin are important regulators of glucose uptake and hepatic glucose release. Because insulin concentrations rarely if ever increase under daily living conditions, unless glucose concentrations also increase, we sought to determine whether hepatic and extrahepatic responses to changes in insulin and glucose concentration are impaired in patients with non-insulin-dependent diabetes mellitus (NIDDM). To address this question, glucose metabolism was measured in diabetic and nondiabetic subjects. A computer-driven infusion system was used to produce a nondiabetic postprandial insulin profile in both groups while sufficient exogenous glucose was infused to mimic nondiabetic postprandial glucose concentrations. Although NIDDM was associated with greater (P < 0.05) hepatic glucose release both before and during the prandial insulin infusion, suppression did not differ in the diabetic and nondiabetic subjects (-1.06 +/- 0.20 vs. -0.86 +/- 0.15 mmol/kg every 4 h). In contrast, stimulation of both glucose disappearance (0.77 +/- 0.27 vs. 1.68 +/- 0.27 mmol/kg every 4 h) and forearm glucose uptake (187 +/- 81 vs. 550 +/- 149 mumol/dl every 4 h) was lower (P < 0.05) in diabetic than in nondiabetic subjects. Thus, despite increased basal rates of glucose production, obese individuals with NIDDM had decreased stimulation of glucose disappearance but normal suppression of hepatic glucose release in response to nondiabetic prandial glucose and insulin concentrations. These data indicate that the increase in glucose that occurs with carbohydrate ingestion is likely to compensate for hepatic but not extrahepatic insulin resistance.
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The dual tracer time-varying volume method for measuring hepatic glucose release in nonsteady state: theoretical and simulation results. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 1994; 41:243-267. [PMID: 8187469 DOI: 10.1016/0169-2607(94)90058-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Measurement of hepatic glucose release in nonsteady state is difficult and experimental approaches have been developed in order to circumvent Steele's model inadequacy. Recently, a resurgence of interest in the time-varying volume method developed by Issekutz has taken place. Issekutz's approach assumes that the volume of Steele's model is not constant but time-varying and that its time course can be measured by infusing two tracers with different patterns. The time-varying volume is then substituted into Steele's equation and hepatic glucose release is estimated. The aim of this study was to analyze some basic aspects of Issekutz's method and to determine the accuracy of its estimate of hepatic glucose release. A theoretical analysis showed that the time-varying volume measured by Issekutz's approach is not unique but depends on the format of administration of the two tracers. In addition, such a volume allows an accurate estimate of hepatic glucose release if one of the two tracers is infused in such a way that its specific activity is maintained perfectly constant during the experiment. Since it is impossible to achieve a perfect clamp of specific activity, we also evaluated the performance of Issekutz's approach in more realistic experimental conditions which were reproduced by resorting to computer simulation. We simulated a euglycaemic clamp with insulin rising from basal to a plateau of approximately 40 microU/ml and then returning to basal. Nonsteady-state glucose kinetics were described by a previously validated two-compartment model while the time course of hepatic glucose release was derived from the literature. Both noise-free and noisy experimental conditions were simulated. We showed that the degree of accuracy of Issekutz's approach is very good and better than the one associated with the hot-ginf method. On the other hand, the major problem with Issekutz's approach is the sensitivity of the volume estimate to the measurement noise, which may limit its applicability in practice. In conclusion, we elucidated the theoretical grounds of Issekutz's approach and assessed its performance during nonsteady state in a realistic scenario using computer simulation.
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Metabolic effects of the nocturnal rise in cortisol on carbohydrate metabolism in normal humans. J Clin Invest 1993; 92:2283-90. [PMID: 8227343 PMCID: PMC288409 DOI: 10.1172/jci116832] [Citation(s) in RCA: 115] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Glucocorticoid concentrations vary throughout the day. To determine whether an increase in cortisol similar to that present during sleep is of physiologic significance in humans, we studied the disposition of a mixed meal when the nocturnal rise in cortisol was mimicked or prevented using metyrapone plus either a variable or constant hydrocortisone infusion. When glucose concentrations were matched with a glucose infusion, hepatic glucose release (2.6 +/- 0.2 vs. 1.5 +/- 0.4 nmol/kg per 6 h) was higher (P < 0.05) while glucose disappearance (5.9 +/- 0.3 vs. 7.3 +/- 0.9 mmol/kg per 6 h) and forearm arteriovenous glucose difference (64 +/- 24 vs. 231 +/- 62 mmol/dl per 6 h) were lower (P < 0.05) during the variable than basal infusion. The greater hepatic response during the variable cortisol infusion was mediated (at least in part) by inhibition of insulin and stimulation of glucagon secretion as reflected by lower (P < 0.05) C-peptide (0.29 +/- 0.01 vs. 0.38 +/- 0.04 mmol/liter per 6 h) and higher (P < 0.05) glucagon (42.7 +/- 2.0 vs. 39.3 +/- 1.8 ng/ml per 6 h) concentrations. In contrast, the decreased rates of glucose uptake appeared to result from a state of "physiologic" insulin resistance. The variable cortisol infusion also increased (P < 0.05) postprandial palmitate appearance as well as palmitate, beta-hydroxybutyrate, and alanine concentrations, suggesting stimulation of lipolysis, ketogenesis, and proteolysis. We conclude that the circadian variation in cortisol concentration is of physiologic significance in normal humans.
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Hepatic and extrahepatic insulin action in humans: measurement in the absence of non-steady-state error. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:E561-6. [PMID: 8476034 DOI: 10.1152/ajpendo.1993.264.4.e561] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The isotope dilution technique has been extensively used to assess insulin action in humans. To determine if nonsteady state (NSS) has led to erroneous estimates of hepatic and extrahepatic insulin sensitivity, we measured glucose turnover in healthy subjects during infusion of insulin at rates of 0.25, 0.6, and 2.0 mU.kg-1.min-1. Turnover was calculated using Steele's traditional NSS equations [fixed-effective volume (pV) method] as well as with methods [radioactive infused glucose (hot-GINF) or variable pV] designed to minimize NSS error. In contrast to the fixed-pV method, both the hot-GINF and variable-pV methods indicated that several hours were required for suppression of hepatic glucose release at all insulin concentrations and that small increases in plasma insulin (approximately 100 pmol/l) had comparable effects on glucose disappearance and hepatic glucose release. Nevertheless, despite these differences, when turnover during the final hour of the insulin infusions was plotted vs. the prevailing insulin concentration, all three methods yielded similar insulin dose-response curves for suppression of hepatic glucose release. Thus despite previous errors in measurement of glucose turnover, the widely accepted belief that the human liver is exquisitely sensitive to small changes in insulin is correct.
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Use of [3-3H]glucose and [6-14C]glucose to measure glucose turnover and glucose metabolism in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1992; 263:E17-22. [PMID: 1636695 DOI: 10.1152/ajpendo.1992.263.1.e17] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
[3-3H]glucose is frequently used to measure glucose turnover in humans. If fructose 6-phosphate-fructose 1,6-diphosphate cycling (Fpc) is negligible in both liver and muscle, then [3-3H]- and [6-14C]glucose (corrected for Cori cycle activity) should provide equivalent measures of glucose turnover. In addition, if glycogenolysis is fully suppressed, then [14C]lactate specific activity should equal that of [6-14C]glucose from which it was derived, and oxidation of [6-14C]glucose, as measured by rate of generation of 14CO2, should equal total glucose oxidation (i.e., that derived from intra- and extracellular pools) as measured by indirect calorimetry. To address these questions, glucose turnover was measured simultaneously with [3-3H]- and [6-14C]glucose in the basal state and in presence of low (approximately 200 pM) and high (approximately 750 pM) insulin concentrations. Glucose turnover rates measured with [3-3H]- and [6-14C]glucose were equivalent at all insulin concentrations, indicating that Fpc had no detectable effect on measurement of glucose appearance. [14C]lactate specific activity was lower (P less than 0.01) than that of [6-14C]glucose in the basal state but not during either low- or high-dose insulin infusion, implying that all lactate was derived from extracellular glucose. On the other hand, glucose oxidation as measured by rate of generation of 14CO2 was lower (P less than 0.05) than glucose oxidation as measured by indirect calorimetry during both insulin infusions, implying either that suppression of glycogenolysis was not complete in all tissues or that one or both of these techniques do not accurately measure glucose oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)
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Abstract
BACKGROUND Because a pancreas allograft is placed in the pelvis, pancreas transplantation abolishes the normal gradient between portal-vein and peripheral-vein insulin concentrations and causes systemic hyperinsulinemia. Whether pancreas transplantation restores carbohydrate metabolism to normal is not known. METHODS We studied seven patients with insulin-dependent diabetes mellitus after pancreas-kidney transplantation, seven nondiabetic patients after kidney transplantation (to control for immunosuppression), and eight normal subjects. Measurements were made after an overnight fast and after ingestion of a mixed meal. RESULTS Although plasma glucose concentrations did not differ in the two transplant groups, plasma insulin concentrations were significantly higher in the diabetic pancreas-kidney recipients than in the nondiabetic kidney recipients, both before the meal (mean +/- SE, 102 +/- 15 vs. 53 +/- 6 pmol per liter; P less than 0.05) and afterward (123 +/- 22 vs. 61 +/- 6 nmol per liter per six hours; P less than 0.05). Plasma C-peptide concentrations were the same in both groups, indicating that hyperinsulinemia was due to decreased insulin clearance rather than increased insulin secretion. Despite drainage of the venous effluent from the transplanted pancreas into the systemic circulation, the values for splanchnic clearance of ingested glucose, suppression of hepatic glucose release, incorporation of carbon dioxide into glucose, stimulation of glucose oxidation, glucose uptake, and forearm glucose clearance were all similar in the transplant groups and differed minimally from the values in the normal group. The similar rates of glucose uptake in the presence of higher systemic insulin concentrations indicated that the extrahepatic tissues of the diabetic pancreas-kidney recipients were insulin-resistant. CONCLUSIONS Despite systemic delivery of insulin, pancreas-kidney transplantation in patients with diabetes results in carbohydrate metabolism similar to that in nondiabetic subjects receiving the same immunosuppressive agents after kidney transplantation.
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Abstract
The metabolic consequences of the prolonged systemic insulin delivery associated with human pancreas transplantation have not been precisely defined. To determine if systemic insulin delivery in the absence of immunosuppressive agents results in alterations in hepatic or extrahepatic insulin action, three groups of dogs were studied 2 months after either a sham operation or after their pancreatic venous drainage was severed and anastomosed to the inferior vena cava or portal vein (sham, peripheral and portal groups, respectively). The pattern of venous drainage was documented by measuring vena cava and portal insulin concentrations before and after glucose injection. Systemic insulin concentrations were higher (p less than 0.05) in the peripheral group than in the portal group both following a 14-h fast and after intravenous glucose. During a hyperinsulinaemic euglycaemic clamp (1 mU.kg-1.min-1), glucose utilization (measured using [6(3)H]glucose) was slightly lower (p = 0.07) in the peripheral than in the portal group. Hepatic glucose release was equal in all groups. Carbon dioxide incorporation into glucose (an estimate of gluconeogenesis) was higher in the portal than peripheral group in the fasted state but not during insulin infusion. Plasma concentrations and flux rates of fatty acids and amino acids did not differ between groups. We conclude that chronic systemic insulin delivery results in a) systemic but not portal hyperinsulinaemia, b) a minimal impairment in insulin-stimulated glucose uptake, without altering insulin-induced suppression of hepatic glucose release, and c) no effect on fatty acid or amino acid turnover.(ABSTRACT TRUNCATED AT 250 WORDS)
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Mechanism of growth hormone-induced postprandial carbohydrate intolerance in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1991; 260:E513-20. [PMID: 2018116 DOI: 10.1152/ajpendo.1991.260.4.e513] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Growth hormone excess can cause postprandial carbohydrate intolerance. To determine the contribution of splanchnic and extrasplanchnic tissues to this process, subjects were fed an isotopically labeled mixed meal after either a 12-h infusion of saline or growth hormone (4 micrograms.kg-1.h-1 [corrected]). Growth hormone infusion resulted in higher glucose and insulin concentrations both before and after meal ingestion. Despite growth hormone-induced hyperglycemia and hyperinsulinemia, postprandial hepatic glucose release and carbon dioxide incorporation into glucose (a qualitative estimate of gluconeogenesis) were similar to those present during saline, suggesting altered hepatic regulation. This was confirmed when glucose was infused in the absence of growth hormone to achieve glucose (and insulin) concentrations comparable to those present during growth hormone infusion. Although growth hormone excess did not alter splanchnic uptake of ingested glucose, it resulted in a fivefold increase in postprandial hepatic glucose release (578 +/- 31 vs. 117 +/- 10 mg.kg-16 h-1, P less than 0.01), less suppression of carbon dioxide incorporation into glucose (-13 +/- 9 vs. -53 +/- 12 mg.kg-1. 6-h-1, P less than 0.01), and lower glucose uptake (1,130 +/- 59 vs. 1,850 +/- 150 mg.kg-1.6 h-1, P less than 0.01). The decrease in postprandial glucose uptake did not appear to be mediated by a change in substrate uptake since postprandial plasma concentrations and forearm balance of lactate, free fatty acids, and ketone bodies did not differ in the presence and absence of growth hormone excess.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparison of the pattern of postprandial carbohydrate metabolism after ingestion of a glucose drink or a mixed meal. J Clin Endocrinol Metab 1989; 68:647-53. [PMID: 2645312 DOI: 10.1210/jcem-68-3-647] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
To determine whether the postprandial pattern of carbohydrate metabolism differs after ingestion of an identical amount of glucose as either a drink or as a part of a mixed meal, normal subjects were studied on two occasions. On both occasions, hepatic and extrahepatic glucose metabolism were assessed using the dual isotope and forearm catheterization techniques as well as indirect calorimetry. Plasma glucose, insulin, and C-peptide concentrations and rate of systemic entry of ingested glucose all were lower (P less than 0.05) during the first 15 min after the mixed meal than after the glucose drink. The integrated C-peptide response was greater (P less than 0.05) after the mixed meal, whereas the integrated suppression of glucagon was greater (P less than 0.05) after the glucose drink. Despite these differences in circulating hormone concentrations, after the first 15 min, the rates of systemic entry of ingested glucose, endogenous glucose release, incorporation of carbon dioxide into glucose, and glucose and lipid oxidation as well as nonoxidative glucose storage were virtually the same after the mixed meal and the glucose drink. We conclude that the pattern of postprandial carbohydrate metabolism after ingestion of a glucose meal is remarkably similar to that after ingestion of a more traditional mixed meal. These data suggest that insights regarding the pattern of postprandial carbohydrate metabolism derived from previous studies employing only a glucose drink are likely to pertain to those observed when healthy individuals ingest a meal that contains protein and fat.
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Proceedings of the 12th Annual Meeting of the Irish Endocrine Society, Belfast, October 23rd and 24th 1987. Ir J Med Sci 1988. [DOI: 10.1007/bf02948350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Insulin action in insulin-dependent diabetes mellitus (type I): measurement during constant and changing insulin concentrations. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1988; 112:28-35. [PMID: 3292681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To test the hypothesis that insulin resistance in type I diabetes mellitus is characterized by a decrease in the rate as well as the amplitude of response to insulin, seven patients with diabetes mellitus and 12 subjects without diabetes were given an identical amount of insulin on two occasions: once as a primed constant and once as a variable eight-step infusion. On both occasions plasma glucose concentrations were maintained in the euglycemic range by means of an exogenous glucose infusion. The amplitude of stimulation of glucose utilization was decreased (p less than 0.05) in the type I patients compared with the subjects without diabetes during both a constant and a variable insulin infusion, whether measured as the peak (2.24 +/- 0.11 mg/kg/min vs 3.18; +/- 0.18 mg/kg/min constant and 2.80 +/- 0.30 mg/kg/min vs 3.54 +/- 0.23 mg/kg/min variable) or integrated response above basal (54 +/- 2 mg/kg vs 115 +/- 26 mg/kg constant and 60 +/- 26 mg/kg vs 147 +/- 21 mg/kg, variable). In addition, the rate of activation of glucose utilization (slope 0 to 90 minutes) was decreased (p less than 0.02) in the type I patients compared with subjects without diabetes during both the constant (0.003 +/- 0.001 mg/kg/min 2 vs 0.008 +/- 0.002 mg/kg/min 2) and variable (0.006 +/- 0.002 mg/kg/min 2 vs 0.015 +/- 0.002 mg/kg/min 2) insulin infusions. Insulin antibody binding did not correlate with the severity of insulin resistance. We conclude that insulin resistance in patients with insulin-dependent diabetes mellitus is attributable to a decrease in both the rate and amplitude of response to insulin.
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Insulin action in non-insulin-dependent diabetes mellitus: the relationship between hepatic and extrahepatic insulin resistance and obesity. Metabolism 1987; 36:1091-5. [PMID: 3312938 DOI: 10.1016/0026-0495(87)90031-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To determine the contribution of obesity to the insulin resistance of non-insulin-dependent diabetes mellitus, insulin dose response curves for suppression of glucose production and stimulation of glucose utilization were generated in lean and obese diabetic patients and compared to those observed in weight-matched nondiabetic subjects. Glucose utilization during 0.4, 1.0, and 10.0 mU/kg x min insulin infusions (producing insulin concentrations ranging from approximately 50 to 2,000 microU/mL) was lower (p less than .02 to .001) in lean and obese diabetic patients compared to weight-matched nondiabetic subjects indicating insulin resistance. Glucose utilization was not correlated with obesity in the diabetic subjects. Suppression of glucose production was impaired (P less than .03 and .001) in both the lean and obese diabetic subjects at physiologic but not supraphysiologic insulin concentrations. We conclude that patients with NIDDM have both hepatic and extrahepatic insulin resistance, the severity of which appears to be independent of the degree of obesity.
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Use of a variable insulin infusion to assess insulin action in obesity: defects in both the kinetics and amplitude of response. J Clin Endocrinol Metab 1987; 64:902-8. [PMID: 3549759 DOI: 10.1210/jcem-64-5-902] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
To determine whether the severity of insulin resistance in obesity, as assessed by the traditional hyperinsulinemic glucose clamp, reflects the severity of resistance present during changing insulin concentrations, such as occur after meal ingestion, 9 moderately obese and 12 lean subjects were studied on 2 occasions: once during a primed continuous insulin infusion and once during a variable 8-step insulin infusion. Identical amounts of insulin were given on each occasion, and euglycemia was maintained by a glucose infusion. Stimulation of isotopically determined glucose utilization above the basal value was lower in the obese than in the lean subjects during the variable [2.4 +/- 0.5 (+/- SEM) vs. 5.4 +/- 0.7 g/m2; P = 0.004] and the constant (2.9 +/- 0.7 vs 4.2 +/- 0.9 g/m2; P = 0.32) insulin infusions; however, the differences were only significant with the variable insulin infusion. The variable insulin infusion also was associated with lower rates of activation of glucose utilization (slope, 0-90 min, 0.27 +/- 0.05 vs. 0.55 +/- 0.09 mg/m2 X min 2; P = 0.01) in obese compared to lean subjects. In contrast, rates of activation during the low constant infusion (0.24 +/- 0.05 vs. 0.29 +/- 0.06 mg/m2 X min 2; P = 0.51) did not differ in the lean and obese subjects. Despite identical amounts of insulin, stimulation of glucose utilization was greater (P less than 0.03) during the variable than during the constant insulin infusion in the lean subjects. In contrast, stimulation during the variable and constant insulin infusions was equal in the obese subjects. These observations indicate that insulin resistance in obesity is due to a defect in the rate as well as absolute response achieved and suggest that under conditions of daily living the contribution of insulin resistance to impaired carbohydrate tolerance is greater than that previously estimated by a constant insulin infusion.
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Abstract
Pathological, morphometric, and teased fiber studies of sural nerve from 36 diabetic patients with (n = 32) and without (n = 4) neuropathy and from 47 healthy subjects provide evidence that in diabetic polyneuropathy: (1) fiber loss is primary; (2) demyelination and remyelination with or without onion bulb formation are secondary; (3) remaining fibers, on average, have the same ratio of small to large fibers as in healthy individuals, but with a greatly increased variability; and (4) the spatial distribution of fiber loss is both diffuse and multifocal. Criteria developed during the study of experimental models of ischemic neuropathy were employed to assess whether ischemic nerve damage had occurred in diabetic polyneuropathy. We conclude that there is increasing evidence that microvascular pathological abnormality and ischemia may be involved in the pathogenesis of human diabetic polyneuropathy. Cases with selective loss of small or large afferent fibers are probably extremes of a normal distribution and not different disorders.
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Insulin resistance in acromegaly: defects in both hepatic and extrahepatic insulin action. THE AMERICAN JOURNAL OF PHYSIOLOGY 1986; 250:E269-73. [PMID: 3513613 DOI: 10.1152/ajpendo.1986.250.3.e269] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Short-term growth hormone excess is associated with impaired hepatic and extrahepatic responses to insulin in the absence of a change in insulin binding. To determine whether similar defects occur after chronic growth hormone excess, insulin dose-response curves for stimulation of glucose utilization and suppression of glucose production and monocyte and erythrocyte insulin binding were determined in five acromegalic patients and six healthy volunteers of comparable age, sex, and obesity. During infusion of insulin, glucose infusion rates required to maintain euglycemia were significantly lower (P less than 0.02 all) in the acromegalic patients than in the control subjects. Suppression of glucose production was impaired in the acromegalic subjects at insulin concentrations in the physiological range but not at insulin concentrations in the supraphysiological range. In contrast stimulation of glucose utilization was decreased in the acromegalic subjects at both physiological and supraphysiological insulin concentrations. Neither monocyte nor erythrocyte insulin binding differed significantly in the acromegalic and control subjects. These data indicate that chronic growth hormone excess is associated with a defect in both hepatic and extrahepatic insulin action. The decrease in glucose utilization at supraphysiological insulin concentrations in the acromegalic subjects and the normal monocyte and erythrocyte insulin binding suggest a postbinding alteration in insulin action.
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The role of autoregulation of the hepatic glucose production in man. Response to a physiologic decrement in plasma glucose. Diabetes 1986; 35:186-91. [PMID: 2867944 DOI: 10.2337/diab.35.2.186] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In man, a decrease in plasma glucose concentration results in a compensatory increase in hepatic glucose release. Studies in vitro have suggested that a low glucose concentration per se may directly stimulate hepatic glucose release, an effect often referred to as autoregulation. Whether autoregulation occurs in man in response to a physiologic decrement in blood glucose is not known. Therefore, seven healthy, nonobese subjects were studied on two occasions to determine the role of autoregulation in mediating the increase in glucose production that accompanies a physiologic decrement in plasma glucose concentration. On both occasions, plasma glucose concentrations were clamped successively at 95, 65, and 95 mg/dl for 2 h each. Insulin (approximately 14 microU/ml) and glucagon (approximately 70 pg/ml) were maintained constant on both occasions by an infusion of somatostatin and insulin. Phentolamine and propranolol also were infused on one occasion to produce combined alpha- and beta-adrenergic blockade. In the absence of adrenergic blockade, glucose production increased by approximately 1.3 mg/kg X min when the plasma glucose concentration was decreased from 95 to 65 mg/dl and decreased by approximately 1.5 mg/kg X min when glucose was increased from 65 to 95 mg/dl. In the presence of adrenergic blockade, the increase and decrease in glucose production averaged 0 and 0.5 mg/kg X min, respectively, representing 70-100% inhibition. We conclude that, in the presence of low physiologic insulin concentrations, autoregulation is not a major contributor to the hepatic response to a physiologic decrement in plasma glucose concentration in man.
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Effect of thyroid hormone excess on action, secretion, and metabolism of insulin in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1985; 248:E593-601. [PMID: 3887944 DOI: 10.1152/ajpendo.1985.248.5.e593] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To determine the effect of thyroid hormone excess on insulin secretion, metabolism and action in humans, we examined intravenous glucose tolerance, glucose-induced insulin secretion, insulin clearance, monocyte insulin receptor binding, and the dose-response characteristics for the effects of insulin on glucose production, uptake, oxidation, and nonoxidative disposal in 10 normal volunteers for 14 days before and after oral administration of triiodothyronine (T3) in doses that increased plasma T3 to levels observed in spontaneous thyrotoxicosis (P less than 0.001). After T3 postabsorptive plasma glucose (P less than 0.05) and insulin (P less than 0.05) both increased; intravenous glucose tolerance was unaffected, but plasma insulin responses were increased (P less than 0.01); basal glucose production, uptake, and oxidation all increased (all P less than 0.05), whereas nonoxidative glucose disposal was unaffected (P = NS); monocyte insulin receptor binding increased (P less than 0.01) due to increased receptor affinity (P less than 0.05); and receptor number was not significantly altered (P = NS). Insulin clearance was increased. Insulin-induced suppression of glucose production was impaired (Km 22 +/- 3 vs. 37 +/- 7 microU/ml, P less than 0.02); maximal insulin-induced glucose uptake (10.7 +/- 0.6 vs. 13.0 +/- 0.9 mg X kg-1 X min-1, P less than 0.001) and oxidation (3.41 +/- 0.30 vs. 5.34 +/- 0.59 mg X kg-1 X min-1, P less than 0.001) were increased without a significant change in Km. However, submaximal rates of nonoxidative glucose disposal and glucose uptake were inappropriately low for the increased insulin receptor binding.(ABSTRACT TRUNCATED AT 250 WORDS)
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Abstract
The incidence and prevalence of diabetic neuropathies in Insulin Dependent (IDDM) and Non-Insulin Dependent (NIDDM) Diabetes Mellitus is not known because in previous studies the heterogeneity of diabetes and of the neuropathies was not taken into account, criteria for diagnosis and surveillance for neuropathy were variable, and studies were not prospective or population based. We have begun such prospective epidemiologic studies using a uniform algorithm for the classification of the diabetic disorders and uniform and validated approaches for the assessment of symptoms, neurologic deficits and various quantitative end-points of neural dysfunction. As regards cause, a key question which we are trying to answer is whether hyperglycemia and associated metabolic alterations affect neural tissue directly or whether there is an intervening tissue alteration between metabolic derangement and tissue change. Improved control of hyperglycemia does not appear to be associated with rapid neurologic improvement, possibly arguing for an intervening tissue alteration. The recently observed decrease in nerve oxygen tension and blood flow in streptozotocin diabetes suggests that an alteration of the nerve microenvironment may relate importantly to the cause of diabetic neuropathy.
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Mechanism of hyperglycemia and response to treatment with an inhibitor of fatty acid oxidation in a patient with insulin resistance due to antiinsulin receptor antibodies. J Clin Endocrinol Metab 1984; 59:658-64. [PMID: 6480801 DOI: 10.1210/jcem-59-4-658] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Severe hyperglycemia and insulin resistance due to antiinsulin receptor antibodies developed over a period of 3 months in a 50-yr-old insulin-requiring diabetic patient. The hyperglycemia resulted from overproduction of glucose due to excessive rates of glycogenolysis and gluconeogenesis rather than decreased glucose utilization. Treatment with methyl-2-tetradecylglycidate, an inhibitor of fatty acid oxidation, resulted in a decrease in plasma glucose concentration. This was associated with a decrease in the rate of glucose production due to decreases in both gluconeogenesis and glycogenolysis rates, as well as an increase in the respiratory quotient. Plasma glucose concentrations continued to respond to the drug for the next 2 months until the sudden development of terminal hypoglycemia. The hypoglycemic action of the drug is consistent with the existence of an insulin-independent effect of fatty acid oxidation on glucose metabolism in man.
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Infusion of insulin impairs human adipocyte glucose metabolism in vitro without decreasing adipocyte insulin receptor binding. Diabetologia 1984; 27:358-63. [PMID: 6389241 DOI: 10.1007/bf00304850] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
To determine whether hyperinsulinaemia can cause insulin resistance in man and, if so, whether this occurs at a receptor or post-receptor site, nine normal volunteers were infused with insulin for 6 h at a rate (2 mU X kg-1 X min-1) which resulted in steady-state plasma insulin concentrations of 140 +/- 13 mU/l and four subjects were infused with saline (0.45%). Isolated adipocytes and monocytes were used as models for studying insulin binding, while adipocytes were also used to study insulin action in vitro. Adipocyte insulin binding did not decrease following infusion of insulin (4.6 +/- 0.5 versus 4.4 +/- 0.4% per 2 X 10(5) cells, before and after, respectively), whereas monocyte insulin binding did (7.2 +/- 0.6 versus 6.2 +/- 0.6% per 10(7) cells, p less than 0.05). Initial rates of adipocyte 3-0-methyl glucose transport were decreased in the absence of insulin (basal) and at submaximally effective (33.3 pmol/l) but not at maximally effective insulin concentrations. At all insulin concentrations and in the absence of insulin, rates of glucose conversion to lipids were decreased more than 50% (p less than 0.05), whereas rates of glucose oxidation were unaffected. This decrease in the rates of conversion of glucose to lipids could not be accounted for by the decrease in rates of glucose transport. These results suggest that hyperinsulinaemia can cause insulin resistance in man and that, at least initially, this occurs at a post-receptor site. Furthermore, the discordant effect of hyperinsulinaemia on monocyte and adipocyte insulin binding indicates that monocyte insulin binding may not always reflect insulin binding in insulin-sensitive tissues.
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Comparison of porcine and semisynthetic human insulins using euglycemic clamp-derived glucose-insulin dose-response curves in insulin-dependent diabetes. Metabolism 1984; 33:132-5. [PMID: 6363874 DOI: 10.1016/0026-0495(84)90125-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In order to compare the biologic effectiveness of porcine and semisynthetic human insulins, a euglycemic clamp method was used in eight insulin-dependent diabetic subjects. Each subject was tested for each insulin on separate days. In order to derive glucose-insulin dose-response curves for both insulins, sequential but constant infusion rates of 0.2, 0.5, 1.0, and 2.0 mU/kg/min were performed. Plasma glucose levels attained during the euglycemic clamp were 96 +/- 3 mg/dL. At each insulin infusion rate, the steady-state glucose infusion rate required to maintain euglycemia was measured. At each increment of insulin infused, steady-state glucose infusion rates for porcine insulin were 1.12 +/- 0.22, 1.90 +/- 0.59, 4.28 +/- 0.61, and 9.37 +/- 0.66 mg/kg/min compared with 1.27 +/- 0.42, 2.38 +/- 0.20, 4.25 +/- 0.43, and 8.87 +/- 0.67 mg/kg/min for semisynthetic human insulin. By ANOVA, no significant difference was noted between the two insulins. Because insulin infusion rates may not result in predictable circulating free insulin levels in subjects who have circulating insulin antibodies, free insulin levels were determined. When steady-state glucose infusion rates were compared with free insulin levels achieved at the four insulin infusion rates, dose-response curves for both porcine and semisynthetic human insulins were virtually identical. These data suggest that semisynthetic human insulin has equivalent biologic effects on overall glucose metabolism compared with porcine insulin in insulin-dependent diabetes.
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Influence of changes in insulin receptor binding during insulin infusions on the shape of the insulin dose-response curve for glucose disposal in man. J Clin Endocrinol Metab 1984; 58:392-6. [PMID: 6363438 DOI: 10.1210/jcem-58-2-392] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
To determine the influence of insulin infusions used in dose-response studies on monocyte insulin binding, monocyte insulin binding and glucose disposal were measured in six normal subjects before and at the end of each of four sequential 2-h insulin infusions (0.4, 1.0, 2.0, and 10 mU kg-1 min-1). Monocyte insulin binding was unaltered at the end of the first three infusions (plasma insulin, 31 +/- 2 (SEM), 77 +/- 3, and 184 +/- 10 microU/ml) but was decreased after the last infusion (plasma insulin, 1730 +/- 125 microU/ml) at 0.2 through 10.2 ng/ml insulin concentrations in the binding assay (P less than 0.01). Using a one-site model, this could be ascribed to a decrease in insulin receptor affinity (1.54 +/- 0.26 vs. 2.27 +/- 0.48 X 10(8) M-1, P less than 0.05), whereas in a two-site model this appeared to be due to a decrease in high affinity binding sites (1,868 +/- 228 vs. 2,387 +/- 207, P less than 0.02). Nevertheless, insulin receptor occupancies estimated to occur during the insulin infusions were virtually identical whether preinsulin infusion binding data (745 +/- 72, 1,383 +/- 117, 2,572 +/- 302, and 10,092 +/- 1,708) or binding data at the end of each infusion (702 +/- 56, 1,367 +/- 150, 2,383 +/- 318, and 9,158 +/- 2,023) were used to calculate occupancy. These results indicate that although monocyte insulin binding decreased during dose-response experiments using sequential infusions of insulin, due to the concentrations of insulin at which this occurs this decrease did not alter the shape of the dose-response curve relating glucose disposal to monocyte insulin receptor occupancy.
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Stimulation of human pancreatic polypeptide secretion by hypoglycemia is independent of adrenergic mechanisms. J Clin Endocrinol Metab 1982; 55:1234-6. [PMID: 6752172 DOI: 10.1210/jcem-55-6-1234] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Human pancreatic polypeptide (HPP) increases after insulin-induced hypoglycemia. To determine whether adrenergic mechanisms contribute to this increase in normal man, six subjects were studied on two occasions: once after insulin alone and once after insulin plus simultaneous alpha (phentolamine)- and beta (propranolol)-adrenergic blockade. Despite comparable hypoglycemia (51 +/- 4 vs. 49 +/- 4 mg/dl), the increase in HPP did not differ in the presence or absence of adrenergic blockade (721 +/- 215 vs. 736 +/- 193 pg/ml, respectively). These findings suggest that HPP secretion during hypoglycemia is not dependent on adrenergic mechanisms.
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Insulin increases the maximum velocity for glucose uptake without altering the Michaelis constant in man. Evidence that insulin increases glucose uptake merely by providing additional transport sites. J Clin Invest 1982; 70:1310-4. [PMID: 6757268 PMCID: PMC370349 DOI: 10.1172/jci110731] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The present studies were undertaken to assess the mechanism by which insulin increases glucose uptake in man. Because glucose uptake in most mammalian tissues occurs predominantly by a facilitated transport system that follows Michaelis-Menten kinetics, glucose uptake was measured isotopically in normal volunteers over the physiologic range of plasma glucose and insulin concentrations and was subjected to Lineweaver-Burk and Eadie-Hofstee analysis. With both methods, increases in plasma insulin from 18 microunits/ml to 80 and 150 microunits/ml were found to increase the maximum velocity (Vmax) for glucose uptake nearly three- and fivefold, respectively, (P less than 0.025 and P less than 0.001) without significantly altering the Michaelis constant (Km). Because an increase in the affinity or molecular activity of transport sites or provision of additional transport sites that differed from those present basally should have altered the Km, whereas a mere increase in the number of transport sites would have only increased the Vmax, our results indicate that in man, insulin may increase glucose uptake merely by providing additional transport sites.
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Abstract
The ability of glucagon to impair glucose tolerance has been questioned by studies involving infusion of exogenous glucagon during a glucose load. Since such hormone administration may not reflect the physiologic pattern of glucagon secretion and may result in hepatic downregulation to glucagon, the present experiments have examined the effects of intermittent endogenous hyperglucagonemia (induced by episodic infusion or arginine) on plasma glucose profiles of normal man following ingestion of mixed meals. In control studies following meal ingestion, plasma glucose, insulin and glucagon increased respectively 15-30 mg/dl, 30-60 uU/ml and 25-50 pg/ml. When meals were accompanied by arginine infusions, plasma glucagon responses were augmented three to fourfold (p less than 0.05). Amplitudes of glycemic excursions during infusion of arginine (345 +/- 40 mg/dl) were significantly augmented compared to those observed in control studies (286 +/- 34 mg/dl, p less than 0.02). These results indicate that intermittent increases in plasma glucagon within the physiologic range can adversely affect postprandial glucose profiles in normal man despite concomitant hyperinsulinemia and suggest that such hyperglucagonemia may contribute to impaired postprandial glucose tolerance in diabetic individuals in whom insulin secretion is deficient.
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Hormonal mechanisms in acute glucose counterregulation: the relative roles of glucagon, epinephrine, norepinephrine, growth hormone, and cortisol. Metabolism 1980; 29:1164-75. [PMID: 7432175 DOI: 10.1016/0026-0495(80)90026-8] [Citation(s) in RCA: 108] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Differential effects of epinephrine on glucose production and disposal in man. THE AMERICAN JOURNAL OF PHYSIOLOGY 1979; 237:E356-62. [PMID: 495714 DOI: 10.1152/ajpendo.1979.237.4.e356] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Normal subjects were infused 1) with epinephrine (50 ng/(kg.min)) for 180 min followed by epinephrine plus glucagon (3 ng/(kg.min)) for 60 min after which the epinephrine infusion rate was increased (125 ng/(kg.min)) or 2) with epinephrine plus somatostatin (500 microgram/h) for 180 min. Epinephrine increased glucose production and plasma glucagon transiently but caused persistent suppression of glucose clearance and sustained hyperglycemia (despite increased plasma insulin and gluconeogenic substrates); glucose production increased again on addition of glucagon and on increasing the epinephrine infusion rate. During epinephrine plus somatostatin, glucose production still increased transiently, but further suppression of glucose clearance caused more marked hyperglycemia. In conclusion, 1) in man hyperepinephrinemia within the physiological range caused sustained suppression of glucose clearance but only a transient increase in glucose production; 2) this transient hepatic response a) was not due to glycogen or substrate depletion, b) occurred without changes in plasma glucagon or insulin, c) was specific for epinephrine but permitted subsequent responses to changes in plasma epinephrine; 3) epinephrine can serve as a physiological regulator of glucose homeostasis in man both by increasing glucose production and by decreasing glucose clearance.
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Effect of intermittent endogenous hyperglucagonemia on glucose homeostasis in normal and diabetic man. J Clin Invest 1979; 63:1119-23. [PMID: 447838 PMCID: PMC372058 DOI: 10.1172/jci109404] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED Infusion of glucagon causes only a transient increase in glucose production in normal and diabetic man. To assess the effect of intermittent endogenous hyperglucagonemia that might more closely reflect physiologic conditions, arginine (10 g over 30 min) was infused four times to 8 normal subjects and 13 insulin-dependent diabetic subjects (4 of whom were infused concomitantly with somatostatin to examine effects of arginine during prevention of hyperglucagonemia). Each arginine infusion was separated by 60 min. Diabetic subjects were infused throughout the experiments with insulin at rates (0.07-0.48 mU/kg per min) that had normalized base-line plasma glucose and rates of glucose appearance (Ra) and disappearance (Rd). Basal plasma glucagon and arginine-induced hyperglucagonemia were similar in both groups; basal serum insulin in the diabetics (16+/-1 muU/ml, P < 0.05) exceeded those of the normal subjects (10+/-1 muU/ml, P < 0.05) but did not increase with arginine. Serum insulin in normal subjects increased 15-20 muU/ml with each arginine infusion. In both groups each arginine infusion increased plasma glucose and Ra. Increments of Ra in the diabetics exceeded those of normal subjects, (P < 0.02); Rd was similar in both groups. In normal subjects, plasma glucose returned to basal levels after each arginine infusion, whereas in the diabetics hyperglycemia persisted reaching 151+/-15 mg/dl after the last arginine infusion. When glucagon responses were prevented by somatostatin, arginine infusions did not alter plasma glucose or Ra. CONCLUSIONS Infusion of arginine acutely increases plasma glucose and glucose production in man solely by stimulating glucagon secretion; physiologic increments in plasma glucagon (100-150 pg/ml) can result in sustained hyperglycemia when pancreatic beta cell function is limited.
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Radioimmunoassay of somatostatin and its application in the study of pancreatic somatostatin secretion in vitro. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1979; 93:1009-17. [PMID: 438602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A sensitive and specific radioimmunoassay for somatostatin is described. With the use of this system, somatostatin release from incubated rat pancreatic islets and perfused rat pancreases has been studied in vitro. Both arginine and glucose, known modulators of insulin and glucagon secretion, were found to stimulate somatostatin release. These results provide additional support for the concept that somatostatin may act as a local regulator of pancreatic A cell function.
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Hormonal mechanisms of recovery from insulin-induced hypoglycemia in man. THE AMERICAN JOURNAL OF PHYSIOLOGY 1979; 236:E380-5. [PMID: 434200 DOI: 10.1152/ajpendo.1979.236.4.e380] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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