The effects on insulin action in adult hypopituitarism of recombinant human GH therapy individually titrated for six months.

There is controversy about the effect of replacement GH on insulin action in adult hypopituitary patients. GH replacement calculated from weight leads to unacceptable side effects in some patients. Recent studies suggest it should be individually titrated in adults using serum IGF-I levels. We have assessed the effect of titrated GH replacement on peripheral and hepatic insulin action in 13 adult-onset hypopituitary patients (8 males and 5 females; ages 47 +/- 10 yr, mean duration of hypopituitarism 6 yr) with confirmed GH deficiency (GHD; maximum GH <5 mU/liter during insulin induced hypoglycemia), ACTH deficiency, and normal glucose tolerance. All patients were on stable hydrocortisone replacement (15 mg with breakfast, 5 mg with evening meal) for at least 2 months before the trial. Insulin action was assessed by the euglycemic hyperinsulinemic glucose clamp technique (1 mU/kg x min) before and after 6 months of GH therapy. GH was started at 0.8 IU sc daily and titrated monthly until the serum IGF-I increased to within 1-2 SD of the mean of normal age-matched controls. Body mass index did not change significantly during the 6 months of GH therapy. Fasting plasma glucose and HbA1c increased significantly after 6 months (5.2 +/- 0.0 vs. 5.5 +/- 0.0 mmol/liter, P < 0.0001, and 4.5 +/- 0.1 vs. 4.7 +/- 0.1%, P < 0.0005, respectively). There was no increase in fasting serum insulin (51.6 +/- 10.2 vs. 60.0 +/- 10.2 pmol/liter, P = 0.12). Exogenous glucose infusion rates required to maintain euglycemia were similar after GH (23.0 +/- 0.4 vs. 21.1 +/- 0.3 micromol/kg x min, P = 0.6). Endogenous glucose production in the fasting state was also unchanged following GH (11.8 +/- 0.7 vs.12.3 +/- 0.9 micromol/kg x min, P = 0.5) and suppressed to a similar extent following insulin (4.4 +/- 0.8 vs. 5.5 +/- 0.8 micromol/kg x min, P = 0.3). In summary, GH therapy for 6 months, with serum IGF-I maintained in the upper physiological range, increased fasting plasma glucose and HbA1c. There was no effect on peripheral or hepatic insulin sensitivity. Patients receiving GH therapy require long-term monitoring of glucose tolerance.     

Effects of morning cortisol replacement on glucose and lipid metabolism in GH-treated subjects

OBJECTIVE: Insulin resistance is a frequent consequence of GH replacement therapy but patients on GH replacement therapy often also have replacement of other hormone deficiencies which theoretically could modify the metabolic effects of GH. In particular, cortisol replacement if given in supra physiologic doses immediately before the evaluation of insulin sensitivity could influence insulin sensitivity. The aim of this study was thus to evaluate the effect of morning cortisol replacement given prior to a euglycaemic clamp combined with infusion of [3-(3)H]glucose and indirect calorimetry on glucose and lipid metabolism. METHODS: Ten GH/ACTH-deficient adults received, in a double-blind manner, either cortisol (A) or placebo (B) before the clamp whereas five GH-deficient-ACTH-sufficient adults participated in a control (C) clamp experiment. All subjects received GH replacement therapy. RESULTS: Serum cortisol levels were significantly higher after cortisol than after placebo (324+/-156 vs 132+/-136 mmol/l; P=0.006) and similar to controls (177+/-104 mmol/l). As a measure of the biological effect of cortisol, eosinophil leukocyte counts in peripheral blood decreased (164+/-91 x 10(9)/l vs 216+/-94 x 10(9)/l; P=0.04). Cortisol replacement had no significant effect on insulin-stimulated glucose uptake (11.8+/-1.8 vs 13.2+/-3.9 micromol/kg min), either on glucose oxidation or on glucose storage. There was also no significant effect of cortisol on fasting endogenous glucose production and no effect was seen on serum free fatty acid concentrations. CONCLUSION: Administration of cortisol in the morning before a clamp cannot explain the insulin resistance seen with GH replacement therapy.     

Influence of growth hormone on glucose-induced glucose uptake in normal men as assessed by the hyperglycemic clamp technique

To determine whether physiological increments in circulating GH concentrations influence glucose-induced glucose uptake (GIGU), two-step sequential hyperglycemic clamp (plasma glucose, 6 and 14 mmol/L) studies were performed in six normal subjects with and without GH infusion (40 ng/kg.min). The latter resulted in serum GH levels of 15 +/- 1 (+/- SE) microgram/L. Infusion of somatostatin (250 micrograms/h during step 1 and 750 micrograms/h during step 2) together with a replacement dose of insulin (1.1 pmol/kg.min) resulted in serum insulin levels comparable to basal levels in both studies. The GIGU ([3-3H]glucose), assessed as the difference between steps 2 and 1 glucose utilization during the final 60 min of each step (150 min) was markedly impaired during GH infusion (with GH, 1.1 +/- 0.2 mg/kg.min; without GH, 3.1 +/- 0.3 mg/kg.min; P less than 0.001). Moreover, the percent increase in glucose uptake was considerably reduced during hypersomatotropinemia (with GH, 44 +/- 9%; without GH, 97 +/- 11%; P less than 0.01). In the GH infusion as well as control studies, endogenous glucose production (EGP) was similar at the two levels of glycemia, whereas GH infusion approximately doubled EGP [2.3 +/- 0.2 vs. 1.1 +/- 0.3 mg/kg.min and 2.0 +/- 0.4 vs. 1.1 +/- 0.4 mg/kg.min (step 1 and 2, respectively)]. We conclude that moderate hypersomatotropinemia for several hours is characterized by impaired GIGU as well as augmented EGP.     

Inhibition of lipolysis during acute GH exposure increases insulin sensitivity in previously untreated GH-deficient adults

OBJECTIVE: Previous studies evaluating the lipolytic effect of GH have in general been performed in subjects on chronic GH therapy. In this study we assessed the lipolytic effect of GH in previously untreated patients and examined whether the negative effect of enhanced lipolysis on glucose metabolism could be counteracted by acute antilipolysis achieved with acipimox. METHODS: Ten GH-deficient (GHD) adults participated in four experiments each, during which they received in a double-blind manner: placebo (A); GH (0.88+/-0.13 mg) (B); GH+acipimox 250 mg b.i.d. (C); and acipimox b.i.d. (no GH) (D), where GH was given the night before a 2 h euglycemic, hyperinsulinemic clamp combined with infusion of [3-(3)H]glucose and indirect calorimetry. RESULTS: GH increased basal free fatty acid (FFA) levels by 74% (P=0.0051) and insulin levels by 93% (P=0.0051). This resulted in a non-significant decrease in insulin-stimulated glucose uptakes (16.61+/-8.03 vs 12.74+/-5.50 micromol/kg per min (s.d.), P=0.07 for A vs B). The rates of insulin-stimulated glucose uptake correlated negatively with the FFA concentrations (r=-0.638, P<0.0001). However, acipimox caused a significant improvement in insulin-stimulated glucose uptake in the GH-treated patients (17.35+/-5.65 vs 12.74+/-5.50 micromol/kg per min, P=0.012 for C vs B). The acipimox-induced enhancement of insulin-stimulated glucose uptake was mainly due to an enhanced rate of glucose oxidation (8.32+/-3.00 vs 5.88+/-2.39 micromol/kg per min, P=0.07 for C vs B). The enhanced rates of glucose oxidation induced by acipimox correlated negatively with the rate of lipid oxidation in GH-treated subjects both in basal (r=-0.867, P=0.0093) and during insulin-stimulated (r=-0.927, P=0.0054) conditions. GH did not significantly impair non-oxidative glucose metabolism (6.86+/-5.22 vs 8.67+/-6.65 micromol/kg per min, P=NS for B vs A). The fasting rate of endogenous glucose production was unaffected by GH and acipimox administration (10.99+/-1.98 vs 11.73+/-2.38 micromol/kg per min, P=NS for B vs A and 11.55+/-2.7 vs 10.99+/-1.98 micromol/kg per min, P=NS for C vs B). On the other hand, acipimox alone improved glucose uptake in the untreated GHD patients (24.14+/-8.74 vs 16.61+/-8.03 micromol/kg per min, P=0.0077 for D vs A) and this was again due to enhanced fasting (7.90+/-2.68 vs 5.16+/-2.28 micromol/kg per min, P=0.01 for D vs A) and insulin-stimulated (9.78+/-3.68 vs 7.95+/-2.64 micromol/kg per min, P=0.07 for D vs A) glucose oxidation. CONCLUSION: The study of acute administration of GH to previously untreated GHD patients provides compelling evidence that (i) GH-induced insulin resistance is mainly due to induction of lipolysis by GH; and (ii) inhibition of lipolysis can prevent the deterioration of insulin sensitivity. The question remains whether GH replacement therapy should, at least at the beginning of therapy, be combined with means to prevent an excessive stimulation of lipolysis by GH.     

The effect of manipulation of basal pulsatile insulin on insulin action in Type 2 diabetes.

AIM: Disordered insulin pulsatility is associated with insulin resistant states including Type 2 diabetes. However, whether abnormal basal insulin pulses play a role in the pathogenesis of insulin resistance or are simply an associated feature remains undetermined. We investigated this relationship further by studying the effect of overnight (10 h) pulsatile insulin infusion on subsequent insulin sensitivity. METHODS: We studied 17 Type 2 diabetic patients who underwent one of two protocols. In protocol A (10 patients) on two separate nights we infused insulin 0.1 mU/kg/min either in a constant infusion or in pulses every 13 min. Octreotide (0.43 microg/kg/h) was given to suppress endogenous insulin secretion and physiological replacement of glucagon (30 ng/kg/h) administered. Insulin sensitivity was measured using a hyperinsulinaemic euglycaemic clamp (2 mU/kg/min) next morning. In protocol B (seven patients), we employed the same experimental procedure but used a basal insulin infusion rate of 0.09 mU/kg/min in 7-min or 13-min pulses. RESULTS: Appropriate pulse patterns were confirmed in each protocol. In protocol A, after overnight infusions, glucose infusion rates required to maintain euglycaemia at steady state hyperinsulinaemia were similar (33.9 +/- 5.2 vs. 31.2 +/- 4.1 micromol/kg/min; P = NS). In protocol B, after overnight infusions the glucose infusion rates required during hyperinsulinaemia were significantly lower during 7-min pulses (39.9 +/- 5.7 vs. 44.7 +/- 5.6 micromol/kg/min; P < 0.05). CONCLUSION: There was no demonstrable priming effect derived from overnight pulsatile insulin compared with constant insulin infusion on subsequent insulin sensitivity in Type 2 diabetic subjects. The failure of 7-min pulses to exhibit an advantageous effect over 13-min pulses raises questions about the natural frequency of basal insulin pulses and their biological effect.     

Acute effects of ghrelin administration on glucose and lipid metabolism

CONTEXT: Ghrelin infusion increases plasma glucose and nonesterified fatty acids, but it is uncertain whether this is secondary to the concomitant release of GH. OBJECTIVE: Our objective was to study direct effects of ghrelin on substrate metabolism. DESIGN: This was a randomized, single-blind, placebo-controlled two-period crossover study. SETTING: The study was performed in a university clinical research laboratory. PARTICIPANTS: Eight healthy men aged 27.2 +/- 0.9 yr with a body mass index of 23.4 +/- 0.5 kg/m(2) were included in the study. INTERVENTION: Subjects received infusion of ghrelin (5 pmol x kg(-1) x min(-1)) or placebo for 5 h together with a pancreatic clamp (somatostatin 330 microg x h(-1), insulin 0.1 mU x kg(-1) x min(-1), GH 2 ng x kg(-1) x min(-1), and glucagon 0.5 ng.kg(-1) x min(-1)). A hyperinsulinemic (0.6 mU x kg(-1) x min(-1)) euglycemic clamp was performed during the final 2 h of each infusion. RESULTS: Basal and insulin-stimulated glucose disposal decreased with ghrelin [basal: 1.9 +/- 0.1 (ghrelin) vs. 2.3 +/- 0.1 mg x kg(-1) x min(-1), P = 0.03; clamp: 3.9 +/- 0.6 (ghrelin) vs. 6.1 +/- 0.5 mg x kg(-1) x min(-1), P = 0.02], whereas endogenous glucose production was similar. Glucose infusion rate during the clamp was reduced by ghrelin [4.0 +/- 0.7 (ghrelin) vs. 6.9 +/- 0.9 mg.kg(-1) x min(-1); P = 0.007], whereas nonesterified fatty acid flux increased [131 +/- 26 (ghrelin) vs. 69 +/- 5 micromol/min; P = 0.048] in the basal period. Regional lipolysis (skeletal muscle, sc fat) increased insignificantly with ghrelin infusion. Energy expenditure during the clamp decreased after ghrelin infusion [1539 +/- 28 (ghrelin) vs. 1608 +/- 32 kcal/24 h; P = 0.048], but the respiratory quotient did not differ. Minor but significant elevations in serum levels of GH and cortisol were observed after ghrelin infusion. CONCLUSIONS: Administration of exogenous ghrelin causes insulin resistance in muscle and stimulates lipolysis; these effects are likely to be direct, although a small contribution of GH and cortisol cannot be excluded.     

Prevalence of diabetes and impaired glucose tolerance in adult hypopituitarism on low dose oral hydrocortisone replacement therapy

OBJECTIVE: The conventional dosage of hydrocortisone, used for many years in the management of hypopituitarism (30 mg per day), has now been shown to be more than is physiologically necessary. On this conventional corticosteroid therapy studies have demonstrated an increased prevalence of diabetes and impaired glucose tolerance, which may contribute to the increased vascular morbidity and mortality reported in the condition. In these studies no information is available on oral glucose tolerance test (OGTT) timing in relation to administration of oral steroid and variable hydrocortisone doses were employed. PATIENTS: In order to assess glucose tolerance in patients treated with lower, more physiological doses, we performed a 75-g OGTT at least 1 month after hydrocortisone therapy was adjusted to 15 mg at 0800 h and 5 mg at 1700 h in 45 adult onset hypopituitary patients (30 M, 15 F). Mean (+/- SD) duration of hypopituitarism was 12 +/- 10 years, mean age 52 +/- 14 years and BMI 29.3 +/- 5.1 kg/m2. All were on hydrocortisone, 43 on thyroxine, 31 on sex steroids, 9 on desmopressin and 33 had documented growth hormone deficiency. Hydrocortisone 15 mg was taken at 0800 and the OGTT commenced at 0900. RESULTS: Using standard WHO criteria 36 patients (80%) had normal glucose tolerance, 1 (2%) had newly diagnosed diabetes and 8 (18%) had impaired glucose tolerance. Using the recently announced American Diabetes Association criteria for diagnosis 96% had normal glucose tolerance, 2% had diabetes and 2% impaired fasting glucose. CONCLUSION: The markedly reduced prevalence of diabetes and impaired glucose tolerance on lower hydrocortisone replacement doses in our series of patients with hypopituitarism, not previously known to be diabetic, is of great interest. This lower prevalence may eventually result in reduced vascular complication rates.     

Hormonal regulation of human leptin in vivo: effects of hydrocortisone and insulin

OBJECTIVE: To investigate the effects of continuous i.v. infusion of hydrocortisone or insulin on leptin secretion in humans. SUBJECTS: Six, nonfasting healthy adults (four women, two men), aged (mean +/- s.e.m.) 36.6 +/- 1.7 y; body mass index (BMI) 27.6 +/- 0.9 kg/m2. DESIGN: Randomized, placebo-controlled, cross-over study, with a 2-week 'wash-out' period. INTERVENTIONS: Intravenous infusion of hydrocortisone (3.3 microg/(kg min)), insulin (1 mU/(kg min)) or normal saline (placebo) for 24 h. MEASUREMENTS: Blood sampling every 1-2 h for measurement of glucose, insulin, cortisol and leptin; subcutaneous abdominal fat biopsy for determination of leptin mRNA expression. RESULTS: Plasma cortisol increased to 50.0 +/- 0.4 microg/dl during hydrocortisone infusion, but was unaltered during saline or insulin infusion. The plasma insulin levels were: 28.5 +/- 4.7 microU/ml (placebo), 40.8 +/- 9.2 microU/ml (hydrocortisone, P=0.214), and 243 +/- 23.0 microU/ml (insulin, P=0.0002). Peak hyperleptinemia occurred after 16h of insulin and 20h of hydrocortisone infusion; peak/baseline plasma leptin levels (ng/ml) were 18.2 +/- 4.2/15.1 +/- 3.3 (placebo, P=0.056), 42.1 +/- 7.0/16.0 +/- 3.8 (hydrocortisone, + 163%, P= 0.008) and 30.2 +/- 4.3/16.6 +/- 2.7 (insulin, +83%, P= 0.024). Adipocyte leptin mRNA increased by 350% after the hydrocortisone infusion. CONCLUSION: Hydrocortisone, a natural glucocorticoid, induces hyperleptinemia in vivo, with a potency greater than that of insulin. The interaction between glucocorticoids and leptin may be of metabolic significance in humans.     

Somatostatin does not alter insulin-mediated glucose disposal

We examined the effect of somatostatin (SRIH) infusion on insulin-mediated glucose disposal (Rd) in normal young subjects (n = 8) to determine the influence of SRIH on insulin action. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (25 mU/m2 X min) or insulin with SRIH (250 micrograms/h) and replacement of basal glucagon (0.4 ng/kg X min). Basal plasma glucose, insulin, glucagon (IRG), and GH concentrations, hepatic glucose production, and Rd were similar on each occasion. Steady state (10-180 min) plasma insulin insulin alone, 283 +/- 10 (+/- SEM); insulin, IRG, and SRIH, 284 +/- 10 pmol/L) and glucagon levels (insulin alone, 84 +/- 7; insulin, IRG, and SRIH, 82 +/- 7 ng/L) were similar. Hepatic glucose production (insulin alone, 0.66 +/- 0.12; insulin, IRG, and SRIH, 0.78 +/- 0.48 mg/kg X min) and Rd (insulin alone, 8.16 +/- 0.62; insulin, IRG, and SRIH, 8.17 +/- 0.61 mg/kg X min) were not different at steady state. We conclude that SRIH infusion with glucagon replacement does not augment insulin-mediated glucose disposal in normal young subjects at physiological insulin levels.     

Acute effect of glyburide on insulin sensitivity in type I diabetic patients

Possible extrapancreatic effects of glyburide on insulin action were studied in six patients with insulin-dependent diabetes mellitus. Each patient was studied on two separate occasions with continuous iv infusions of either glyburide (0.3 mg/h after a 1-mg iv bolus dose) or NaCl. During the studies blood glucose concentrations were controlled by a glucose-controlled infusion system (Biostator). The study included the 12-h period after the evening meal, followed by a 4-h period during which euglycemic hyperinsulinemic clamp studies were performed at two rates of insulin infusion: 1 and 10 mU/kg.min. During the glyburide infusion, the Biostator-determined insulin delivery rate was similar to that during the NaCl infusion for the first 6 h after the meal, but it decreased by 32% between the 6th and 12th hours after the meal. During the hyperinsulinemic clamp studies, glucose was delivered at a significantly higher rate when glyburide was infused; this was true for both rates of insulin infusion [5.6 +/- 1.9 (+/- SD) vs. 3.6 +/- 1.4 mg/kg.min and 12.1 +/- 2.4 vs. 9.1 +/- 2.1 mg/kg.min; P less than 0.05, glyburide vs. NaCl, respectively]. Plasma C-peptide was undetectable in all patients during both studies. These results indicate that 1) glyburide has an acute effect on insulin action in insulin-dependent diabetic patients; and 2) this effect occurs at physiological as well as pharmacological insulin concentrations.     

Free fatty acid-induced insulin resistance in the obese is not prevented by rosiglitazone treatment

OBJECTIVE: Elevation of free fatty acids (FFAs) by the infusion of triglyceride-heparin emulsion infusion (TG-Hep) causes insulin resistance (IR). We examined the effect of insulin sensitizer (rosiglitazone) on FFA-induced IR. DESIGN: Nine obese subjects underwent a 6-h infusion of TG-Hep before and after 6 wk of rosiglitazone (8 mg/d) treatment. Hyperinsulinemic euglycemic clamps were performed during 0-2 and 4-6 h of TG-Hep. RESULTS: After rosiglitazone for 6 wk, fasting FFA concentration fell, but not significantly (489 +/- 63 at 0 wk; 397 +/- 58 micromol/liter at 6 wk; P = 0.16), whereas C-reactive protein (4.26 +/- 0.95 at 0 wk; 2.03 +/- 0.45 microg/ml at 6 wk) and serum amyloid A (17.36 +/- 4.63 at 0 wk; 8.77 +/- 1.63 microg/ml at 6 wk) decreased significantly. At 0 wk, TG-Hep infusion caused a decrease in glucose infusion rate (GIR) from 4.49 +/- 0.95 mg/kg.min to 3.02 +/- 0.59 mg/kg.min (P = 0.018). Rosiglitazone treatment resulted in an increase in baseline GIR to 6.29 +/- 0.81 mg/kg.min (P = 0.03 vs. 0 wk), which decreased to 4.52 +/- 0.53 mg/kg.min (P = 0.001) after 6 h of TG-Hep infusion. The decrease in GIR induced by TG-Hep infusion was similar before and after rosiglitazone therapy [1.47 +/- 0.50 vs. 1.77 0.3 mg/kg.min (28.9 +/- 6.5 vs. 26.4 +/- 3.7%); P = 0.51]. The rise in FFAs and triglycerides after TG-Hep infusion was significantly lower at 6 wk (P = 0.006 for FFAs; P = 0.024 for triglycerides). CONCLUSIONS: We conclude that rosiglitazone: 1) causes a significant increase in GIR; 2) induces a decrease in inflammatory mediators, C-reactive protein, and serum amyloid A; 3) decreases the rise in FFAs and triglycerides after TG-Hep infusion; and 4) does not prevent FFA-induced IR.     

Acute cortisol excess results in unimpaired insulin action on lipolysis and branched chain amino acids, but not on glucose kinetics and C-peptide concentrations in man

To assess whether acute cortisol excess impairs insulin action on lipolysis, plasma amino acids, endogenous insulin secretion, and glucose kinetics, nine normal subjects were studied after acute cortisol excess (80 mg hydrocortisone by mouth) and after placebo. Insulin sensitivity was assessed 6 hours after hydrocortisone using the glucose clamp technique (insulin infusion of 20 mU/m2 X minute for 120 minutes, plasma insulin levels of approximately equal to 50 mU/L). Hyperinsulinemia suppressed plasma free fatty acids (FFA) similarly by 75 and 76%, respectively. Most plasma amino acid concentrations were increased after hydrocortisone; however, the insulin-induced decrease of branched chain amino acids, serine, threonine, and tyrosine was unimpaired after hydrocortisone. Plasma C-peptide concentrations were less suppressed during hyperinsulinemia after hydrocortisone than after placebo (by 0.15 +/- 0.03 v 0.25 +/- 0.02 nmol/L, P less than 0.01), suggesting diminished insulin-induced suppression of insulin secretion. The glucose infusion rates required to maintain euglycemia were 35% lower (P less than 0.01) after hydrocortisone due to decreased insulin effects on metabolic clearance rate of glucose and diminished suppression of hepatic glucose production (0.4 +/- 0.1 v -0.1 +/- 0.1 mg/kg X minute, p less than 0.05, 3-3H-glucose infusion method). The data demonstrate that acute elevation of plasma cortisol to levels near those observed in severe stress results in insulin resistance of peripheral and hepatic glucose metabolism but in unimpaired insulin effects on plasma FFA and branched chain amino acids, suggesting that cortisol's lipolytic and proteolytic effects are antagonized by elevated plasma insulin levels.     

Effect of hepatic glucose production on acute insulin resistance induced by lipid-infusion in awake rats

AIM: To explore the influence of hepatic glucose production on acute insulin resistance induced by a lipid infusion in awake rats. METHODS: A hyperinsulinaemic-euglycaemic clamp was established in awake chronically catheterized rats. Two groups of rats were studied either with a 4-h intraarterial infusion of lipid/heparin or saline. Insulin-mediated peripheral and hepatic glucose metabolism was assessed by hyperinsulinaemic-euglycaemic clamp combined with [3-^3H]-glucose infusion. RESULTS: During hyperinsulinaemic-euglycaemic clamp,there was a significant increase in plasma free fatty acid (FFA, from 741.9&#177;50.6 to 2346.44&#177;238.5μmol/L, P&lt;0.01) in lipid-infused group. The glucose infusion rates (GIR) in the lipid infusion rats, compared to control rats, were significantly reduced (200-240 min average: lipid infusion; 12.64&#177;1.5 vs control; 34.04&#177;1.6 mg/kg.min, P&lt;0.01), declining to - 35% of the corresponding control values during the last time of the clamp (240min: lipid infusion; 12.04&#177;1.9 vs control; 34.74&#177;1.7 mg/kg&#183;min, P&lt;0.0001). At the end of clamp study,the hepatic glucose production (HGP) in control rats was significantly suppressed (88%) from 19.04&#177;4.5 (basal) to 2.34&#177;0.9 mg/kg.min (P&lt;0.01). The suppressive effect of insulin on HGP was significantly blunted in the lipid-infused rats (200-240 min: from 18.74&#177;3.0 to 23.24&#177;3.1 mg/kg.min (P&lt;0.05). The rate of glucose disappearance (GRd) was a slight decrease in the lipid-infused rats compared with controls during the clamp.CONCLUSION: These data suggest that lipid infusion could induces suppression of hepatic glucose production, impairs the abilities of insulin to suppress lipolysis and mediate glucose utilization in peripheral tissue. Therefore, we conclude that lipid-infusion induces an acute insulin resistance in vivo.     

Circadian hydrocortisone infusions in patients with adrenal insufficiency and congenital adrenal hyperplasia

OBJECTIVE: Conventional hydrocortisone therapy in adrenal insufficiency cannot provide physiological replacement. We have explored the potential of circadian delivery of hydrocortisone as proof of concept for such therapy delivered in modified-release tablet formulation. METHODS: We investigated whether the circadian intravenous infusion of hydrocortisone could improve control of ACTH and androgen levels. Two healthy subjects, two patients with Addison's disease and two patients with congenital adrenal hyperplasia (CAH) were studied. RESULTS: In patients on thrice daily oral hydrocortisone, peak serum cortisol levels were higher than in normal subjects and overnight levels were very low. Patients had very high plasma ACTH levels before their morning dose of hydrocortisone, both at the beginning and at the end of their conventional oral therapy: mean +/- SEM 311.8 +/- 123.2 and 311.2 +/- 85.4 ng/l, respectively. In the patients with CAH, serum 17-hydroxyprogesterone levels were also elevated: 550 and 642 nmol/l at the beginning and 550 and 777 nmol/l at the end of conventional treatment, respectively. The overall 24-h mean cortisol levels were similar for conventional oral hydrocortisone and the circadian infusion. At 0700 h, ACTH levels were much higher on conventional treatment than after circadian infusion: mean +/- SEM 311.2 +/- 85.4 vs. 70.5 +/- 45.0 ng/l, respectively (P < 0.05). The same pattern was observed in 17-hydroxyprogesterone levels, which were 550 and 777 nmol/l after conventional treatment and 3 and 64 nmol/l after circadian infusion. CONCLUSIONS: In patients with poor biochemical control of Addison's disease and CAH, a 24-h circadian infusion of hydrocortisone can decrease morning ACTH and 17-hydroxyprogesterone levels to near normal.     

Adipose tissue, hepatic, and skeletal muscle insulin sensitivity in extremely obese subjects with acanthosis nigricans

We evaluated insulin action in skeletal muscle (glucose disposal), liver (glucose production), and adipose tissue (lipolysis) in 5 extremely obese women with acanthosis nigricans (AN), who had normal oral glucose tolerance, and 5 healthy lean subjects, by using a 5-stage pancreatic clamp and stable isotopically labeled tracer infusion. Basal plasma insulin concentration was much greater in obese subjects with AN than lean subjects (54.8 +/- 4.5 vs 8.0 +/- 1.3 microU/mL, P < .001), but basal glucose and free fatty acid concentrations were similar in both groups. During stage 1 of the clamp, glucose rate of appearance (R(a)) (2.6 +/- 0.3 vs 3.7 +/- 0.3 micromol x kg FFM(-1) x min(-1), P = .02) and palmitate R(a) (2.4 +/- 0.6 vs 7.0 +/- 1.5 micromol x kg FFM(-1) x min(-1), P < .05) were greater in obese subjects with AN than lean subjects despite slightly greater plasma insulin concentration in subjects with AN (3.0 +/- 0.7 vs 1.1 +/- 0.4 microU/mL, P < .05). The area under the curve for palmitate R(a) (1867 +/- 501 vs 663 +/- 75 micromol x kg FFM(-1) x 600 min(-1), P = .03) and glucose R(a) (1920 +/- 374 vs 1032 +/- 88 micromol x kg FFM(-1) x 600 min(-1), P = .02) during the entire clamp procedure was greater in subjects with AN than lean subjects. During intermediate insulin conditions (plasma insulin, approximately 35 microU/mL), palmitate R(a) was 5-fold greater in subjects with AN than in lean subjects (2.6 +/- 1.1 vs 0.5 +/- 0.2 micromol x kg FFM(-1) x min(-1), P = .05). Maximal glucose disposal was markedly lower in obese subjects with AN than in lean subjects (13.0 +/- 0.8 vs 23.4 +/- 1.8 mg x kg FFM(-1) x min(-1), P = .01) despite greater peak plasma insulin concentration (1842 +/- 254 vs 598 +/- 38 microU/mL, P < .05). These data demonstrate obese young adults with AN have marked insulin resistance in multiple tissues. However, marked insulin hypersecretion can compensate for impaired insulin action, resulting in normal glucose and fatty acid metabolism during basal conditions.     

The effects of superphysiologic hyperinsulinemia on glucose and lipid metabolism in glucose-tolerant offspring of patients with non-insulin-dependent diabetes mellitus (NIDDM).

First-degree relatives of patients with NIDDM manifest severe insulin resistance despite normal glucose tolerance test. To examine the mechanisms underlying the normal glucose tolerance, we evaluated the serum glucose/C-peptide/insulin dynamics and free fatty acid (FFA) as well as substrate oxidation rates and energy expenditure (EE) (indirect calorimetry) in nine young offspring of NIDDM patients (mean +/- SEM age 30 +/- 2.3 years, body mass index 24.2 +/- 1.2 kg/m2). Nine age-, sex- and weight-matched, normal subjects with no family history of diabetes served as the controls. Metabolic parameters were measured before, during and after a two-step glucose infusion (2 and 4 mg/kg.min) for 120 min. Mean basal serum glucose, insulin and C-peptide levels were similar in both groups. During 2 mg/kg.min glucose infusion, mean serum insulin and C-peptide rose to significantly (P less than 0.05-0.02) greater levels in the offspring vs. controls, while serum glucose levels were similar. With the 4 mg/kg.min glucose infusion, mean serum glucose, insulin and C-peptide levels were significantly (P less than 0.02-0.001) greater in the offspring at 100-120 min. Isotopically-derived (D[3-3H]glucose), basal hepatic glucose output (HGO) was not significantly different between the offspring vs. controls (1.86 +/- 0.30 vs. 1.78 +/- 0.06 mg/kg.min). During glucose infusion, basal HGO was partially suppressed by 66% at 60 min and by 100% at 120 min in the offspring. In contrast, HGO was completely (100%) suppressed at both times in the controls. Following cessation of glucose infusion, HGO rose to 1.64 +/- 0.12 mg/kg.min in the offspring and 1.46 +/- 0.05 mg/kg.min in the controls (P less than 0.05) between 200 and 240 min. These were 88% and 82% of the respective basal HGO values. At low glucose infusion (t = 0-60 min), the mean absolute, non-oxidative glucose disposal remained 1.5-fold greater in the offspring while at higher glucose infusion, nonoxidative glucose metabolism was not different in both groups. Throughout the study period, oxidative glucose disposal rate was not significantly different in both groups. The mean basal FFA was significantly greater in the offspring vs. controls (865 +/- 57 vs. 642 +/- 45 microEq/l). It was appropriately suppressed during glucose infusion to a similar nadir in both groups (395 +/- 24 vs. 375 +/- 33 microEq/l). The mean basal lipid oxidation was also significantly greater in the offspring than controls (1.06 +/- 0.05 vs. 0.75 +/- 0.04 mg/kg.min, P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)     

Impact of acute epinephrine removal on hepatic glucose metabolism during stress hormone infusion.

We examined the effect of acute discontinuation of an epinephrine (EPI) infusion on hepatic glucose metabolism during stress hormone infusion (SHI). Glucose metabolism was assessed in 11 conscious, 20-hour fasted dogs using tracer and arteriovenous techniques after a 3-day exposure to SHI. SHI increased EPI, norepinephrine, cortisol, and glucagon levels (approximately sixfold to 10-fold), which led to marked hyperglycemia, hyperinsulinemia, and accelerated glucose metabolism. On day 3, EPI infusion was acutely discontinued for 180 minutes in five dogs while infusion of the other hormones was continued (SHI - EPI). In the remaining six dogs, all hormones were continued for the duration of the study (SHI + EPI). In SHI - EPI, EPI levels decreased from 1,678+/-191 to 161+/-47 pg/mL. Isoglycemia (183+/-10 to 185+/-15 mg/dL) was maintained with an exogenous glucose infusion. Arterial insulin levels increased from 41+/-8 to 64+/-8 microU/mL. Whole-body glucose utilization increased from 3.5+/-0.5 to 9.4+/-1.9 mg/kg/min. Nonesterified fatty acids ([NEFAs] 763+/-292 to 147+/-32 micromol/L) decreased. Net hepatic glucose output decreased (2.6+/-0.6 to 0.1+/-0.3 mg/kg/min). In SHI + EPI, hepatic glucose metabolism remained unaltered. In summary, EPI plays a pivotal role during SHI by stimulating glucose production and inhibiting glucose utilization. In part, these effects are mediated by restraining pancreatic insulin secretion.     

Pharmacokinetics and pharmacodynamics of subcutaneously administered U40 and U100 formulations of regular human insulin.

Action profiles of 12 U of regular human insulin (Actrapid HM) administered subcutaneously as a U40 or U100 formulation were studied. Euglycaemic glucose clamps were performed on two separate days in 8 healthy subjects (basal i.v. insulin infusion 0.1 mU/kg/min, plasma glucose 5.0 mmol/l, mean +/- SD age 25 +/- 2 years, BMI 22.7 +/- 1.4 kg/m2). Serum insulin concentrations increased after injection of U40 or U100 from similar baseline values to maximal individual concentrations of 305 +/- 79 vs. 285 +/- 62 pmol/l (NS) after 90 +/- 33 vs. 114 +/- 58 min (NS). Ten, 15, and 20 min post injection insulin concentrations were significantly higher by an average of 30 pmol/l after U40 insulin vs. U100 insulin (p less than 0.05). Glucose infusion rates increased from comparable baseline rates to maximal individual glucose infusion rates of 10.7 +/- 2.4 vs. 10.9 +/- 3.0 mg/kg/min (NS) after 172 +/- 51 vs. 169 +/- (39) min (NS). At the three time points when significantly different serum insulin concentrations occurred soon after insulin injection, glucose infusion rates were not significantly different between U40 and U100. Although small differences in insulin pharmacokinetics were detected early after s.c. insulin injection (U40 was absorbed faster than U100 insulin) the pharmacodynamics of the U40 and U100 formulation of regular human insulin appear to be comparable in healthy subjects.     

Impact of type 2 diabetes on myocardial insulin sensitivity to glucose uptake and perfusion in patients with coronary artery disease

BACKGROUND AND HYPOTHESIS: Myocardial insulin resistance (IR) is a feature of coronary artery disease (CAD) with reduced left ventricular ejection fraction (LVEF). Whether type 2 diabetes mellitus (T2DM) with CAD and preserved LVEF induces myocardial IR and whether insulin in these patients acts as a myocardial vasodilator is debated. METHODS: We studied 27 CAD patients (LVEF > 50%): 12 with T2DM (CAD+DM), 15 without T2DM (CAD-NoDM). Regional myocardial and skeletal glucose uptake, myocardial and skeletal muscle perfusion were measured with positron emission tomography. Myocardial muscle perfusion was measured at rest and during hyperemia in nonstenotic and stenotic regions with and without acute hyperinsulinemia. RESULTS: Myocardial glucose uptake was similar in CAD+DM and CAD-NoDM in both nonstenotic and stenotic regions [0.38 +/- 0.08 and 0.36 +/- 0.11 micromol/g.min; P value nonsignificant (NS)] and (0.35 +/- 0.09 and 0.37 +/- 0.13 micromol/g.min; P = NS). Skeletal glucose uptake was reduced in CAD+DM (0.05 +/- 0.04 vs. 0.10 +/- 0.05 micromol/g.min; P = 0.02), and likewise, whole-body glucose uptake was reduced in CAD+DM (4.0 +/- 2.8 vs. 7.0 +/- 2.4 mg/kg.min; P = 0.01). Insulin did not alter myocardial muscle perfusion at rest or during hyperemia. Insulin increased skeletal muscle perfusion in CAD-NoDM (0.11 +/- 0.03 vs. 0.06 +/- 0.03 ml/g.min; P = 0.02), but not in CAD+DM (0.08 +/- 0.04 and 0.09 +/- 0.05 ml/g.min; P = NS). CONCLUSION: Myocardial IR to glucose uptake is not an inherent feature in T2DM patients with preserved LVEF. Acute physiological insulin exposure exerts no coronary vasodilation in CAD patients irrespective of T2DM.     

Effect of overnight restoration of euglycemia on glucose effectiveness in type 2 diabetes mellitus.

The ability of glucose to stimulate its own uptake and suppress its own release is impaired in type 2 diabetes. To determine whether glucose effectiveness is improved by short term euglycemia, 10 type 2 diabetic subjects were studied on 2 occasions. Insulin was infused throughout the night to maintain euglycemia (approximately 5 mmol/L), or glucose was permitted to remain at ambient hyperglycemic levels (approximately 10 mmol/L) until the following morning when euglycemia was achieved with a variable insulin infusion. A prandial glucose infusion (containing 35 g glucose) was started at 1000 h, and the variable insulin infusion was replaced by a constant infusion of insulin (0.25 mU/ kg x min), somatostatin (60 ng/kg x min), glucagon (0.65 ng/kg x min), and GH (3 ng/kg x min) to maintain hormone concentrations at constant basal levels. Although nocturnal glucose concentrations were (by design) higher (P<0.01) on the hyperglycemic than on the euglycemic study day (10.1+/-0.2 vs. 5.4+/-0.1 mmol/L), glucose concentrations did not differ either before (4.9+/-0.1 vs. 4.9+/-0.1 mmol/L) or during the prandial glucose infusion (peak, 11.1+/-0.5 vs. 11.3+/-0.5 mmol/L; incremental area, 1390+/-254 vs. 1409+/-196 mmol/L x 6 h). Furthermore, glucose-induced stimulation of glucose disappearance (2068+/-218 vs. 1957+/-244 micromol/kg x 6 h) and suppression of glucose production (-2253+/-378 vs. -2124+/-257 micromol/kg x 6 h) did not differ. Thus, restoration of euglycemia by means of an overnight insulin infusion does not alter glucose effectiveness in people with type 2 diabetes.