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Biomedical subjects

M Mokan

Publications and source records attributed to M Mokan.

At least 19 recordsLinked to original sources
PubMed2006

Starting insulin therapy in type 2 diabetes: twice-daily biphasic insulin Aspart 30 plus metformin versus once-daily insulin glargine plus glimepiride.

AIM: To compare the efficacy and safety of two analog insulins as starting regimens in insulin-naïve Type 2 diabetes patients. METHODS: In this randomized, open-label parallel study, twice-daily biphasic insulin aspart 30 (30% soluble and 70% protaminated insulin aspart; BIAsp 30) plus metformin (met) was compared with once-daily insulin glargine (glarg) plus glimepiride (glim) in 255 insulin-naïve patients (131 male; mean+/-SD age, 61.2+/-9.1 years). Mean baseline HbA (1c) (+/-SD) was 9.2+/-1.4% and 8.9+/-1.3% for BIAsp 30 plus met ( N=128) and glarg plus glim ( N=127), respectively ( P=0.0747). Primary endpoint was the difference in absolute change in HbA (1c) between groups after 26 weeks of treatment. RESULTS: HbA (1c) change was significantly greater in the BIAsp 30 plus met group than the glarg plus glim group (between-group difference: -0.5% (95% CI: -0.8; -0.2); P=0.0002). Mean prandial plasma glucose increment was significantly lower for BIAsp 30 plus met compared with glarg plus glim: 1.4+/-1.4 mmol/l vs. 2.2+/-1.8 mmol/l; P=0.0002. During the maintenance phase (weeks 6-26), one major hypoglycemic episode occurred in each group; 20.3% and 9% of patients experienced minor hypoglycemic episodes in the BIAsp 30 plus met and glarg plus glim groups, respectively ( P=0.0124). At end-of-trial, mean daily insulin doses were 0.40 U/kg BIAsp 30 and 0.39 U/kg glarg. Glarg plus glim-treated patients experienced significant weight gain of 1.5 kg (95% CI: 0.84; 2.19; P<0.0001). Weight change with BIAsp 30 plus met of +0.7 kg was not statistically significant (95% CI: -0.07; 1.42; P=0.0762). CONCLUSIONS: Starting insulin in Type 2 diabetes patients with twice-daily BIAsp 30 plus met can reduce HbA (1c) and mean prandial plasma glucose increment to a greater extent than once-daily glarg plus glim.

Aged↗
PubMed1998

Reduced beta-adrenergic sensitivity in patients with type 1 diabetes and hypoglycemia unawareness.

OBJECTIVE: We tested the hypothesis that impaired tissue sensitivity to catecholamines contributes to hypoglycemia unawareness in subjects with type 1 diabetes. RESEARCH DESIGN AND METHODS: A total of 21 subjects with type 1 diabetes underwent a standardized insulin infusion protocol to produce a stepwise decrease in plasma glucose to 45-min plateaus of 4.3, 3.6, 3.0, and 2.3 mmol/l. Glycemic thresholds, maximum responses for adrenergic and neuroglycopenic symptoms, and counterregulatory hormones were determined. Patients were classified as hypoglycemia unaware if the initiation of adrenergic symptoms occurred at a plasma glucose level 2 SD below that of nondiabetic volunteers. beta-Adrenergic sensitivity was measured as the dose of isoproterenol required to produce an increment in heart rate of 25 beats per minute above baseline (I25) in resting subjects. RESULTS: Subjects with type 1 diabetes and hypoglycemia unawareness experienced the onset of adrenergic symptoms at a lower plasma glucose level than did those with awareness (2.5+/-0.1 vs. 3.7+/-0.1 mmol/l, P < 0.001), whereas neuroglycopenic symptoms occurred at similar glucose levels (2.7+/-0.2 vs. 2.8+/- 0.1 mmol/l). The plasma glucose levels for counterregulatory hormone secretion (epinephrine 2.9+/-0.2 vs. 4.1+/-0.2 mmol/l; norepinephrine 2.7+/-0.1 vs. 3.2+/-0.2 mmol/l; cortisol 2.5+/-0.2 vs. 3.3+/-0.2 mmol/l, P < 0.01) were also lower in subjects with unawareness. The maximal epinephrine (1,954+/-486 vs. 5,332+/- 1,059 pmol/l, P < 0.01), norepinephrine (0.73 +/- 0.14 vs. 1.47+/-0.21 nmol/l, P = 0.04), and cortisol (276+/-110 vs. 579+/-83 nmol/l, P < 0.01) responses were reduced in the unaware group. I25 was greater in unaware subjects than in subjects without unawareness (1.5+/-0.3 vs. 0.8+/-0.2 microg), where I25 was not different from that of controls (0.8 +/-0.2 microg). CONCLUSIONS: We conclude that subjects with type 1 diabetes and hypoglycemia unawareness have reduced beta-adrenergic sensitivity, which may contribute to their impaired adrenergic warning symptoms during hypoglycemia.

Adrenergic beta-Agonists↗
PubMed1997

Endogenous digoxin-like immunoactivity and diabetes mellitus: facts and hypotheses.

Substances with digoxin- and ouabain-like immunoactivity (DLIA) are specific inhibitors of Na(+)-K(+)-ATPase which increase the total amount of intracellular stored calcium (Ca2+i). In diabetic patients, DLIA levels have been reported to be increased. Although this increase is probably secondary to sodium retention and volume expansion (included in diabetic subjects by hyperinsulinemia and/or diabetic nephropathy), the question arises of whether it has pathophysiological consequences: namely, whether substances with DLIA, via their effect on Na(+)-K(+)-ATPase activity and Ca2+i stores, could in diabetic subjects facilitate development of hypertension and/or modulate insulin sensitivity or insulin secretion. Clinical findings of correlations of DLIA to blood pressure, insulin levels and to degree of insulin resistance, together with experimental findings of decreased Na(+)-K(+)-ATPase activity, increased Ca2+i and decreased Mg2+i in both diabetic and hypertensive subjects, support these hypotheses. However, the issue of whether or not these relations are causative and whether or not defects in intracellular milieu are primary or secondary to non-insulin-dependent diabetes mellitus has not been resolved yet. Moreover, pathogenesis of both diabetes mellitus and hypertension is multifactorial and includes many other factors. Therefore, further efforts should be made to elucidate the exact role of substances with DLIA in diabetes mellitus.

Diabetes Mellitus↗
PubMed1995

Metabolic effects of oral contraceptives in women with polycystic ovary syndrome.

Insulin resistance and dyslipidemia have been described in women with polycystic ovary syndrome (PCOS), a disorder characterized by hyperandrogenism and oligomenorrhea. Although oral contraceptives (OC) are often instituted to regulate menses and suppress HA in women with PCOS, their use has been postulated to cause a deterioration in insulin sensitivity and to adversely affect circulating lipids. To investigate these effects, 9 women with PCOS and 10 age- and weight-matched control women were studied before and during the third month of therapy with a low-dose norethindrone-containing triphasic combination OC using the hyperglycemic clamp technique. At baseline, the PCOS group had higher androgen, triglyceride, and glycosylated hemoglobin concentrations, with a greater insulin response to oral glucose and a lower insulin sensitivity index (ISI) than controls. During OC therapy, a reduction in ISI was observed in both groups, whereas an increase in triglycerides was observed only in controls, removing any observed difference between the two groups in ISI or lipids. In women with PCOS, an increase in insulin concentrations during hyperglycemia accounted for the decline in ISI (P = 0.026), whereas in control women the decrease in ISI was attributable to a decrease in glucose disposal (P = 0.004). In conclusion, PCOS is characterized by insulin resistance in the untreated state. Short-term therapy with a triphasic OC results in a further decline in ISI in women with PCOS, without inducing additional adverse effects on lipids. A more pronounced decline in ISI together with an elevation in triglyceride levels occurs in normal women with OCs. The mechanisms leading to this decrease in ISI are different for each group.

Adult↗
PubMed1994

Impaired postprandial glucose utilization in non-insulin-dependent diabetes mellitus.

The importance of impaired glucose utilization in the pathogenesis of postprandial hyperglycemia in non-insulin-dependent diabetes mellitus (NIDDM) is controversial. Three methods were used to assess glucose utilization following ingestion of a mixed meal in 18 NIDDM and 12 nondiabetic subjects. Dual glucose isotopes were used to determine first-pass splanchnic glucose uptake, suppression of endogenous glucose production, and systemic glucose utilization. Leg balance was used to evaluate skeletal muscle glucose metabolism, and systemic and limb indirect calorimetry were used to assess glucose and lipid oxidation. NIDDM subjects had marked postprandial hyperglycemia as compared with nondiabetics (15.35 +/- 0.72 v 5.83 +/- 0.28 mmol, P < .001), accompanied by lower postprandial insulin (179 +/- 25 v 253 +/- 46 pmol, P < .01) and elevated plasma free fatty acids ([FFA] 569 +/- 34 v 314 +/- 20 mumol/L, P < .001). Cumulative postprandial glucose appearance was nearly twofold greater in NIDDM (82.2 +/- 4.7 v 48.7 +/- 4.9 g.5h, P < .001) due to increased endogenous glucose production (56.4 +/- 4.8 v 24.5 +/- 1.9 g, P < .001), whereas first-pass splanchnic uptake of ingested glucose was normal in NIDDM. Cumulative postprandial glucose utilization in NIDDM, after correction for urinary glucose, was unchanged from postabsorptive rates, a pattern also found for postprandial glucose oxidation. Cumulative leg glucose uptake was somewhat less in NIDDM subjects (123 +/- 18 v 173 +/- 14 mumol/100 mL leg tissue.5 h, P = .06), whereas lactate and alanine net release across the leg were nevertheless twofold greater in NIDDM (P = .04) and accounted for nearly half of the leg glucose metabolism in NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Effect of hyperketonemia and hyperlacticacidemia on symptoms, cognitive dysfunction, and counterregulatory hormone responses during hypoglycemia in normal humans.

The brain usually depends almost exclusively on glucose for its energy requirements. During hypoglycemia associated with prolonged fasting or strenuous exercise, circulating ketone-body and lactate levels increase several-fold; in both situations, certain signs and symptoms of hypoglycemia are diminished. Therefore, to test the hypothesis that hyperketonemia or hyperlacticacidemia of the magnitude seen during certain clinical situations can substitute for glucose as an energy source for the brain and alter physiological responses to hypoglycemia, we assessed autonomic and neuroglycopenic symptoms, counterregulatory hormone responses, and cognitive function during standardized insulin-induced hypoglycemia in normal volunteers with and without infusion of beta-hydroxybutyrate (BOHB) or lactate designed to reproduce circulating levels of these substrates seen during prolonged fasting and strenuous exercise. Compared with paired control experiments, infusion of BOHB and lactate increased the glycemic threshold (required greater hypoglycemia for initiation) and reduced the magnitude of autonomic and neuroglycopenic symptoms, counterregulatory hormone responses, and cognitive dysfunction (all P < 0.05). The hypoglycemic threshold for autonomic symptoms increased from 3.8 +/- 0.1 to 3.1 +/- 0.2 mmol/l during BOHB infusion and from 3.7 +/- 0.1 to 2.8 +/- 0.1 mmol/l during lactate infusion, and the threshold for neuroglycopenic symptoms increased from 2.8 +/- 0.1 to 2.4 +/- 0.1 and 2.3 +/- 0.1 mmol/l, respectively. The magnitude for autonomic symptoms decreased from 12 +/- 2 and 11 +/- 1 to 6 +/- 2 and 4 +/- 1 during BOHB and lactate infusion, respectively. Neuroglycopenic synptoms decreased from 11 +/- 2 to 3 +/- 1 during both series of experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1994

Hypoglycemia unawareness in IDDM.

OBJECTIVE: To assess the characteristics of patients with hypoglycemia unawareness (development of neuroglycopenia without appropriate prior autonomic warning symptoms) and its predisposing factors. RESEARCH DESIGN AND METHODS: We studied 43 insulin-dependent diabetes mellitus patients who were objectively categorized as having or not having hypoglycemia using the stepped hypoglycemic clamp technique in which plasma glucose was clamped at plateaus of 4.3, 3.6, 3.0, and 2.3 mmol/l and a statistical criterion (onset of autonomic warning symptoms at a plasma glucose concentration 2 SD below normal) and examined their clinical characteristics and hormonal, symptomatic, and cognitive responses. RESULTS: Eleven (26%) of the patients were classified as having hypoglycemia unawareness. Compared with the other patients, unaware patients had a lower HbA1c level (P < 0.01), a longer duration of diabetes (P < 0.01), and a history of more severe hypoglycemia (P < 0.003). During experimental hypoglycemia, counterregulatory hormone responses, neuroglycopenic symptoms, and cognitive dysfunction all began at lower plasma glucose concentrations in unaware patients (P < 0.01, 0.03, and 0.01, respectively). Moreover, although the magnitudes of their plasma catecholamine responses and autonomic symptoms were reduced (both, P < 0.01), the plasma catecholamine levels at which autonomic symptoms began was not altered. Finally, as seen from glucose infusion rates necessary to maintain identical plasma glucose levels, patients with hypoglycemia unawareness had increased sensitivity to insulin (P < 0.001). CONCLUSIONS: Our results confirm an association between hypoglycemia unawareness and duration of diabetes, glycemic control, and occurrence of severe hypoglycemia, and in addition provide evidence that both autonomic and neuroglycopenic symptoms are affected and that insulin sensitivity is increased, but beta-adrenergic sensitivity is not diminished.

Adult↗
PubMed1993

Interaction between glucose and free fatty acid metabolism in human skeletal muscle.

The mechanism by which FFA metabolism inhibits intracellular insulin-mediated muscle glucose metabolism in normal humans is unknown. We used the leg balance technique with muscle biopsies to determine how experimental maintenance of FFA during hyperinsulinemia alters muscle glucose uptake, oxidation, glycolysis, storage, pyruvate dehydrogenase (PDH), or glycogen synthase (GS). 10 healthy volunteers had two euglycemic insulin clamp experiments. On one occasion, FFA were maintained by lipid emulsion infusion; on the other, FFA were allowed to fall. Leg FFA uptake was monitored with [9,10-3H]-palmitate. Maintenance of FFA during hyperinsulinemia decreased muscle glucose uptake (1.57 +/- 0.31 vs 2.44 +/- 0.39 mumol/min per 100 ml tissue, P < 0.01), leg respiratory quotient (0.86 +/- 0.02 vs 0.93 +/- 0.02, P < 0.05), contribution of glucose to leg oxygen consumption (53 +/- 6 vs 76 +/- 8%, P < 0.05), and PDH activity (0.328 +/- 0.053 vs 0.662 +/- 0.176 nmol/min per mg, P < 0.05). Leg lactate balance was increased. The greatest effect of FFA replacement was reduced muscle glucose storage (0.36 +/- 0.20 vs 1.24 +/- 0.25 mumol/min per 100 ml, P < 0.01), accompanied by decreased GS fractional velocity (0.129 +/- 0.26 vs 0.169 +/- 0.033, P < 0.01). These results confirm in human skeletal muscle the existence of competition between glucose and FFA as oxidative fuels, mediated by suppression of PDH. Maintenance of FFA levels during hyperinsulinemia most strikingly inhibited leg muscle glucose storage, accompanied by decreased GS activity.

Adult↗
PubMed1993

Influence of plasma glucose rate of decrease on hierarchy of responses to hypoglycemia.

To test the hypothesis that the rate of decrease in plasma glucose concentration may affect the hierarchy of responses to hypoglycemia, we compared plasma couterregulatory hormone concentrations, autonomic and neuroglycopenic symptom scores, and cognitive function test performance in 10 normal volunteers whose plasma glucose concentration was either rapidly (over 30 min) decreased to 3.7 mmol (66 mg/dL) or was slowly decreased in a stepwise manner to plateaus of 4.3 mmol (78 mg/dL), 3.7 mmol (66 mg/dL), 3.0 mmol (54 mg/dL), and 2.3 mmol (42 mg/dL). Comparable plasma counterregulatory hormone concentrations and autonomic symptom scores were observed in both sets of experiments during the 3.7 mmol (66 mg/dL) plateaus. In the stepwise decrement experiments, significant increases in neuroglycopenic symptom scores and deterioration in cognitive performance occurred only during the last glycemic plateau (2.3 mmol, 42 mg/dL). In the rapid decrement experiments, no increase in neuroglycopenic symptom score or deterioration in cognitive performance was observed during the 3.7 mmol (66 mg/dL) plateau. We, therefore, conclude that in normal volunteers the rate of decrease in plasma glucose concentration does not affect the hierarchy of responses to hypoglycemia.

Adult↗
PubMed1993

Induction of hypoglycemia unawareness by asymptomatic nocturnal hypoglycemia.

Hypoglycemia has been incriminated as a possible factor responsible for development of the hypoglycemia unawareness phenomenon in patients with type I diabetes. Many patients with this condition, however, do not have a history of recent hypoglycemia. Because asymptomatic nocturnal hypoglycemia commonly occurs in type I diabetes, we tested the hypothesis that such episodes might be capable of inducing this phenomenon. Accordingly, autonomic and neuroglycopenic symptoms, counterregulatory hormone responses, and cognitive function were assessed during standardized insulin-induced hypoglycemia in 10 normal volunteer subjects on two occasions--once after induction of asymptomatic nocturnal hypoglycemia and once after control studies in which saline rather than insulin was infused overnight. Compared with control experiments, asymptomatic nocturnal hypoglycemia increased the threshold (required greater hypoglycemia for initiation) and reduced the magnitude of autonomic and neuroglycopenic symptoms, counterregulatory hormone responses, and cognitive dysfunction during subsequent hypoglycemia (all, P < 0.05). These results indicate that asymptomatic hypoglycemia may induce hypoglycemia unawareness and, thus, may explain why not every patient with this condition has a history of prior hypoglycemia. Our results therefore support the concept that in type I diabetes this phenomenon may be largely attributable to antecedent hypoglycemia.

Adult↗
PubMed1993

Metabolic pathways of glucose in skeletal muscle of lean NIDDM patients.

OBJECTIVE: To characterize the ability of insulin to activate the skeletal muscle metabolic pathways of glucose storage, oxidation, and glycolysis in normal weight patients with NIDDM and nondiabetic volunteer subjects closely matched for age, sex, relative weight, and body composition. RESEARCH DESIGN AND METHODS: Ten patients with NIDDM (body mass index 23.9 +/- 0.74 kg/m2) and 8 nondiabetic volunteer subjects (body mass index 23.4 +/- 0.41 kg/m2) were studied. Leg muscle glucose uptake, non-oxidized glycolysis, glucose oxidation, and glucose storage were determined during euglycemic-hyperinsulinemic clamp experiments using the leg balance technique combined with leg indirect calorimetry. Percutaneous muscle biopsies were obtained to assay insulin stimulation of muscle glycogen synthase activity as a biochemical marker of insulin action. RESULTS: During hyperinsulinemic clamp experiments, leg glucose uptake was equivalent in NIDDM patients and nondiabetic subjects (6.38 +/- 1.14 vs. 6.41 +/- 0.73 mumol.min-1 x 100 ml tissue-1), as were rates of leg glucose oxidation (1.63 +/- 0.25 vs. 2.14 +/- 0.17 mumol.min-1 x 100 ml tissue-1) and leg glucose storage (4.35 +/- 1.10 vs. 3.48 +/- 0.65 mumol.min-1 x 100 ml tissue-1). The combined net balance of lactate and Ala (non-oxidized glycolysis) was lower in NIDDM patients (-0.39 +/- 0.06 vs. -0.79 +/- 0.11 mumol.min-1 x 100 ml tissue-1, P = 0.01). Muscle glycogen synthase was activated to a similar extent during the hyperinsulinemic clamp in NIDDM patients and nondiabetic volunteer subjects, through basal glycogen synthase activity was lower in NIDDM patients. Nondiabetic subjects and NIDDM patients who were withdrawn from sulfonylurea therapy had impaired insulin secretion during a 75-g oral glucose tolerance test, with similar basal levels as nondiabetic subjects (54 +/- 12 vs. 42 +/- 6 pM), but reduced peak insulin levels (126 +/- 30 vs. 468 +/- 102 pM, P < 0.01). CONCLUSIONS: Detailed in vivo and in vitro assessment of insulin regulation of skeletal muscle glucose metabolism in lean NIDDM patients indicates that insulin action is intact in the muscle tissue of these patients.

Alanine↗
PubMed1992

Role of reduced suppression of glucose production and diminished early insulin release in impaired glucose tolerance.

BACKGROUND: Insulin resistance and impaired insulin secretion both occur in non-insulin-dependent diabetes (NIDDM), but their relative importance is unclear. Hyperglycemia itself has adverse effects on tissue insulin sensitivity and insulin secretion that make it difficult to distinguish between primary and secondary abnormalities. To avoid this problem we studied subjects with postprandial glucose intolerance but not sustained hyperglycemia. METHODS: We compared the rate of systemic appearance and disappearance of glucose, the output of endogenous hepatic glucose, splanchnic and muscle uptake of glucose, and plasma insulin and glucagon responses after the ingestion of 1 g of glucose per kilogram of body weight in 15 subjects with impaired glucose tolerance (8 of them nonobese and 7 obese) and in 16 normal subjects (9 nonobese and 7 obese) who were matched for age and weight. RESULTS: After glucose ingestion the mean (+/- SE) rate of total systemic appearance of glucose was significantly higher in both the nonobese subjects (455 +/- 12 mmol per five hours) and the obese subjects (486 +/- 17 mmol per five hours) with impaired glucose tolerance than in the respective normal subjects (411 +/- 11 and 436 +/- 7 mmol per five hours). This difference was fully accounted for by the reduced suppression of endogenous hepatic glucose in the subjects with impaired glucose tolerance (a reduction of about 28 percent, vs. 48 percent in the normal subjects; P less than 0.01). Despite late hyperinsulinemia, at 30 minutes the subjects with impaired glucose tolerance had smaller increases in plasma insulin and smaller reductions in plasma glucagon (both P less than 0.01). Molar ratios of plasma insulin to plasma glucagon levels correlated inversely (r = -0.62, P less than 0.001) with the rates of systemic glucose appearance; the latter correlated positively (r = 0.72, P less than 0.0001) with peak plasma glucose concentrations. CONCLUSIONS: Impaired glucose tolerance, the precursor of NIDDM, results primarily from reduced suppression of hepatic glucose output due to abnormal pancreatic islet-cell function. The late hyperinsulinemia may be the consequence of an inadequate early beta-cell response rather than of insulin resistance.

Blood Glucose↗
PubMed1992

Evidence against the hypothesis that hyperinsulinemia increases sympathetic nervous system activity in man.

To test the hypothesis that physiologic hyperinsulinemia activates the sympathetic nervous system in humans, we measured changes in plasma norepinephrine as well as epinephrine concentrations during euglycemic hyperinsulinemic clamp experiments in which normal volunteers were infused with insulin for up to 12 hours, at rates chosen to simulate the basal and postprandial hyperinsulinemia seen in insulin-resistant states. Infusions of insulin increased plasma insulin threefold (to approximately 200 pmol/L) and 15-fold (to approximately 1,000 pmol/L) in simulations of fasting and postprandial hyperinsulinemia. In neither experiment did plasma norepinephrine or epinephrine change significantly. In control experiments in which saline was infused for 12 hours, plasma epinephrine increased twofold (P less than .05), but plasma norepinephrine did not change. Therefore, we conclude that hyperinsulinemia of the magnitude seen in the insulin-resistant humans does not increase sympathetic nervous system activity.

Adult↗
PubMed1992

A simple insulin infusion algorithm for establishing and maintaining overnight near-normoglycemia in type I and type II diabetes.

The purpose of this study was to evaluate the safety and efficacy of an insulin infusion algorithm for establishing and maintaining overnight near-normoglycemia in patients with either type I or type II diabetes. Twenty-nine patients (20 with type I diabetes and 9 with type II diabetes) were infused iv with insulin via an Imed pump from 2100-0730 h; plasma glucose was sampled every 30 min, and adjustments in insulin infusion rates were made every 30 min according to the algorithm. The insulin concentration of the infusate was varied dependent on the patient's weight. Initial (2100 h) plasma glucose concentrations of approximately 15 mmol/L were made near-normoglycemic (plasma glucose, less than 8 mmol/L) in 2-4 h. From 0230-0730 h, plasma glucose averaged approximately 6.3 mmol/L, with a coefficient of variation of 10%. Three patients were given 2-cc injections of 50% glucose for plasma glucose levels less than 4.4 mmol/L. The lowest plasma glucose observed was 3.5 mmol/L. The insulin infusion algorithm described in the present study provides a safe and effective means to establish and maintain near-normoglycemia in adult patients with either type I and type II diabetes.

Adult↗
PubMed1992

Simultaneous assessment of insulin secretion and insulin sensitivity using a hyperglycemia clamp.

A hyperglycemic clamp is an established method to assess insulin secretion and is generally used only for this purpose. To determine whether it could also be used to assess insulin sensitivity, we compared insulin sensitivity indices (ISI) obtained during euglycemic and hyperglycemic clamp experiments in 22 nonobese volunteers (body mass index, 23.9 +/- 0.6 kg/m2) and in 20 obese individuals (body mass index, 30.8 +/- 1.3 kg/m2) matched for age and gender. The ISI values (micromoles per kg.min/pmol) of the obese group assessed during hyperglycemic (0.088 +/- 0.011) and euglycemic (0.050 +/- 0.005) clamp experiments were both significantly lower than the ISI of the nonobese group assessed in hyperglycemic and euglycemic clamp experiments (0.179 +/- 0.024 and 0.096 +/- 0.009, respectively; both P less than 0.01). Although the ISI values obtained with hyperglycemic clamps were consistently greater than those obtained with euglycemic clamp (0.137 +/- 0.016 vs. 0.075 +/- 0.007; P less than 0.001), they were highly correlated (r = 0.84; P less than 0.0001). Moreover, when these indices were converted to clearance rates, thereby correcting for the mass action effects of glucose on glucose disposal, the values obtained with the hyperglycemic clamp (0.0137 +/- 0.0016 mL/kg.min/pmol) were statistically identical to those obtained with the euglycemic clamp (0.0142 +/- 0.0013 mL/kg.min/pmol), as indicated by a regression equation having an intercept of 0 and a slope (1.03) not different from 1. We, therefore, conclude that the hyperglycemic clamp and the euglycemic clamp yield comparable estimates of insulin sensitivity and that, under appropriate conditions, the hyperglycemic clamp technique may be used to assess both insulin sensitivity and insulin secretion in the same individual in a single experiment.

Blood Glucose↗
PubMed1992

Intracellular defects in glucose metabolism in obese patients with NIDDM.

Skeletal muscle insulin resistance in obese patients with non-insulin-dependent diabetes mellitus (NIDDM) is characterized by decreased glucose uptake. Although reduced glycogen synthesis is thought to be the predominant cause for this deficit, studies supporting this notion often have been conducted at supraphysiological insulin concentrations in which glucose storage is the overwhelming pathway of glucose disposal. However, at lower, more physiological insulin concentrations, decreased muscle glucose oxidation could play a significant role. This study was undertaken to determine whether, under euglycemic conditions, insulin resistance for leg muscle glucose uptake in NIDDM patients is due primarily to decreased glucose storage or to oxidation. The leg balance technique and leg indirect calorimetry were used under steady-state euglycemic conditions to estimate muscle glucose uptake, storage, and oxidation in eight moderately obese NIDDM patients and eight matched-control subjects. Leg muscle biopsies also were performed to determine whether alterations in muscle pyruvate dehydrogenase or glycogen synthase activities could explain defects in glucose oxidation or storage. At insulin concentrations of approximately 500-600 pM, leg glucose uptake, oxidation, and storage in the NIDDM group (2.03 +/- 0.42, 1.00 +/- 0.13, 0.66 +/- 0.36 mumol.min-1.100 ml-1) were significantly lower (P less than 0.05) than rates in control subjects (5.14 +/- 0.64, 1.92 +/- 0.17, 2.80 +/- 0.54). Pyruvate dehydrogenase and glycogen synthase activities were also decreased, consistent with the in vivo metabolic defects. The average deficit in leg glucose uptake in NIDDM was 3.11 +/- 0.42 mumol.min-1.100 ml-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1991

Hierarchy of glycemic thresholds for counterregulatory hormone secretion, symptoms, and cerebral dysfunction.

To define glycemic thresholds for activation of counterregulatory hormone secretion, initiation of symptoms (autonomic and neuroglycopenic), and onset of deterioration of cognitive function, we measured indexes of these responses during glycemic plateaus of 90, 78, 66, 54, and 42 mg/dl in 10 normal volunteers, with the use of the hyperinsulinemic glucose clamp technique. Activation of glucagon, epinephrine, norepinephrine, and growth hormone secretion began at arterialized venous plasma glucose concentrations of 68 +/- 1, 68 +/- 1, 65 +/- 1, and 67 +/- 2 (SE) mg/dl, respectively. Autonomic symptoms (anxiety, palpitations, sweating, irritability, and tremor) began at 58 +/- 2 mg/dl, which was significantly (P = 0.0001) lower. Neuroglycopenic symptoms (hunger, dizziness, tingling, blurred vision, difficulty thinking, and faintness) and deterioration in cognitive function tests began at 51 +/- 3 and 49 +/- 2 mg/dl, respectively, values that were both significantly (P = 0.018 and 0.004, respectively) lower than that for initiation of autonomic symptoms. We therefore conclude that there is a distinct hierarchy of responses to decrements in plasma glucose, such that the threshold for activation of counterregulatory hormone secretion occurs at higher plasma glucose levels than that for initiation of autonomic warning symptoms, which in turn occurs at higher plasma glucose levels than that for onset of neuroglycopenic symptoms and deterioration in cerebral function. Such a hierarchy would maximize the opportunity to avoid incapacitating hypoglycemia.

Adult↗