Modulation of fatty acid metabolism by glucagon in man. IV. Effects of a physiologic hormone infusion in normal man

This study was done to explore the role of physiologic elevations of glucagon concentration in plasma ketone body concentration in normal man. During the period of hormone elevation, plasma free fatty acids were pharmacologically elevated to ensure adequate free fatty acid substrate delivery to the liver to support hepatic ketogenesis. Eighty-minute infusions of glucagon resulted in a plasma hormone concentration of approximately 300 pg./ml. During the infusion, ketone bodies declined from their basal concentration and remained below basal for the duration of the infusion. An acute heparin-induced pharmacologic elevation of plasma free fatty acid concentration resulted in a transient rise in plasma ketone body concentration, but at no time did it attain the concentration observed during the control saline infusion. Plasma glucose concentration was not altered by glucagon infusion, but plasma insulin concentration rose by approximately 2.5 muU./ml. These results suggest that glucagon is not ketogenic in normal man as has been previously reported in insulin-deficient diabetics. The glucagon-induced rise in plasma insulin concentration may participate in the observed reduction in plasma ketone body concentration.     

Increased splanchnic blood flow after hypoglycaemia in diabetic and normal man: evidence against glucagon as a mediator

Analysis of non-Hodgkin lymphoma (NHL) involvement of bone marrow trephine biopsy specimens by morphologic features and immunohistochemistry is often difficult, and the criteria for involvement are ill defined. We compared the morphologic and immunohistochemical analysis of B-cell NHL involvement with immunoglobulin heavy chain gene (IgH) rearrangement analysis by polymerase chain reaction (PCR) amplification of the complementarity determining region 3 (CDR3) in bone marrow biopsy specimens from patients with mantle cell lymphoma (n = 53) or hairy cell leukemia (n = 71). By combing morphologic features and phenotype, 54 specimens were considered positive, 62 negative, and 8 inconclusive. PCR analysis showed clonal IgH rearrangements in 46 positive and 6 inconclusive specimens. No clonal IgH rearrangements were present in 61 negative specimens. The 1 false-positive and most false-negative PCR results were likely due to sampling error or DNA degradation of the fixed tissues. In most cases, bone marrow involvement by NHL can be identified by histologic and immunohistochemical examination. Furthermore, clonality of the B-cell population can be detected by amplification of the IgH CDR3 on DNA extracted from bone marrow trephine biopsy sections, which can be helpful in cases diagnosed as inconclusive.     

Effect of glibenclamide on insulin release at moderate and high blood glucose levels in normal man

Insulin release occurs in two phases; sulphonylurea derivatives may have different potencies in stimulating first- and second-phase insulin release. We studied the effect of glibenclamide on insulin secretion at submaximally and maximally stimulating blood glucose levels with a primed hyperglycaemic glucose clamp. Twelve healthy male subjects, age (mean +/- SEM) 22.5 +/- 0.5 years, body mass index (BMI) 21.7 +/- 0.6 kgm-2, were studied in a randomized, double-blind study design. Glibenclamide 10 mg or placebo was taken before a 4-h hyperglycaemic clamp (blood glucose 8 mmol L-1 during the first 2 h and 32 mmol L-1 during the next 2 h). During hyperglycaemic clamp at 8 mmol L-1, the areas under the delta insulin curve (AUC delta insulin, mean +/- SEM) from 0 to 10 min (first phase) were not different: 1007 +/- 235 vs. 1059 +/- 261 pmol L-1 x 10 min (with and without glibenclamide, P = 0.81). However, glibenclamide led to a significantly larger increase in AUC delta insulin from 30 to 120 min (second phase): 16087 +/- 4489 vs. 7107 +/- 1533 pmol L-1 x 90 min (with and without glibenclamide respectively, P < 0.03). The same was true for AUC delta C-peptide no difference from 0 to 10 min but a significantly higher AUC delta C-peptide from 30 to 120 min on the glibenclamide day (P < 0.01). The M/I ratio (mean glucose infusion rate divided by mean plasma insulin concentration) from 60 to 120 min, a measure of insulin sensitivity, did not change: 0.26 +/- 0.05 vs. 0.22 +/- 0.03 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.64). During hyperglycaemic clamp at 32 mmol L-1, the AUC delta insulin from 120 to 130 min (first phase) was not different on both study days: 2411 +/- 640 vs. 3193 +/- 866 pmol L-1 x 10 min (with and without glibenclamide, P = 0.29). AUC delta insulin from 150 to 240 min (second phase) also showed no difference: 59623 +/- 8735 vs. 77389 +/- 15161 pmol L-1 x 90 min (with and without glibenclamide, P = 0.24). AUC delta C-peptide from 120 to 130 min and from 150 to 240 min were slightly lower on the glibenclamide study day (both P < 0.04). The M/I ratio from 180 to 240 min did not change: 0.24 +/- 0.04 vs. 0.30 +/- 0.07 mumol kg-1 min-1 pmol L-1 (with and without glibenclamide, P = 0.25). In conclusion, glibenclamide increases second-phase insulin secretion only at a submaximally stimulating blood glucose level without enhancement of first-phase insulin release and has no additive effect on insulin secretion at maximally stimulating blood glucose levels. Glibenclamide did not change insulin sensitivity in this acute experiment.     

No net splanchnic release of glutathione in man during N-acetylcysteine infusion

Glutathione and amino acid concentrations were measured in arterial and hepatic vein plasma in four healthy volunteers and two patients with cirrhosis. There was no significant splanchnic efflux of glutathione (95% confidence limits, -0.501 to 0.405 mumol/min). After infusion of N-acetylcysteine (NAC) in a high dose (150 mg/kg body weight primer plus 15 mg/(h x kg BW), corresponding to treatment of acetaminophen overdose, there was no change in the splanchnic glutathione efflux (95% confidence limits, -0.531 to 0.375 mumol/min). NAC increased hepatic plasma flow rate from 0.90 +/- 0.531 min-1 to 0.97 +/- 0.11 (mean +/- SEM; p < 0.05). The effects of NAC treatment on plasma amino acids corresponded to an increased load on hepatic metabolic N conversion and transamination among nonessential amino acids. Splanchnic uptake of serine, alanine, cystine, isoleucine, and phenylalanine increased after NAC compatible with stimulated hepatic glutathione synthesis. In contrast to the rat, plasma glutathione in man probably originates mainly from extrahepatic tissues.     

Influence of glucagon replacement on the hyperglycemic and hyperketonemic response to prolonged somatostatin infusion in normal man

Somatostatin was infused for 6 h into seven normal subjects with and without a replacement dose of glucagon. The addition of glucagon to somatostatin resulted in a 30-40% rise in plasma glucagon, whereas plasma insulin declined by 40-50% in both treatment groups. Plasma glucose and glucose production initially increased 2-fold with glucagon replacement, and subsequently declined by 2-3 h to levels comparable to those observed with somatostatin alone. After 6 h plasma glucose and glucose kinetics were no different whether or not glucagon was present. The rise in blood ketones after somatostatin was not exaggerated by glucagon replacement. We conclude that glucagon lack is not a modifying factor in the late hyperglycemic and hyperketonemic response to prolonged infusions of somatostatin.     

Effect of chlorpromazine on blood glucose and plasma insulin in man

In three groups of normal subjects and in one group of patients with latent diabetes mellitus a study has been made of the effects of chlorpromazine (CPZ) on blood glucose and plasma insulin. CPZ 75 mg/day for 7 days did not alter the plasma insulin response after oral glucose; nor did CPZ 50 mg/day for 7 days affect the glucose assimilation rate or insulin response to glucose injection. Infusion of CPZ 50 mg in 60 min slightly increased the basal blood glucose level but had no significant effect on basal plasma insulin. The insulin/glucose ratio after the end of the infusion was significantly higher than during the period of infusion of the drug. In latent diabetic patients CPZ infusion significantly diminished the insulin/glucose ratio during an intravenous glucose tolerance test. These results suggest that, whereas prolonged treatment with low doses of CPZ did not modify glucose tolerance and glucose-stimulated pancreatic response, higher acute doses of the drug may induce hyperglycaemia and can inhibit insulin secretion both in normal man and in patients with latent diabetes mellitus.     

Urea, glucose and alanine kinetics in man: effects of glucose infusion

1. The simultaneous effects of an intravenous glucose infusion on plasma urea, glucose and alanine kinetics were investigated in normal post-absorptive man. 2. The primed constant intravenous infusion of compounds labelled with stable isotopes, [15N2]urea, [6-2H]glucose and [3-13C]alanine, was used. 3. The rate of appearance of glucose and urea in the plasma was rapidly reduced by the 17.7 mumol min-1 kg-1 glucose infusion. 4. In contrast, during the glucose infusion there was an increased rate of appearance of alanine in the plasma, and an increased percentage of glucose carbon atoms derived from alanine. 5. Reduced production of glucose and urea during the glucose infusion was not due to decreased gluconeogenesis from alanine.     

Influence of central command and ergoreceptors on the splanchnic circulation during isometric exercise

The splanchnic circulation can make a major contribution to blood flow changes. However, the role of the splanchnic circulation in the reflex adjustments to the blood pressure increased during isometric exercise is not well documented. The central command and the muscle chemoreflex are the two major mechanisms involved in the blood pressure response to isometric exercise. This study aimed to examine the behaviour of the superior mesenteric artery during isometric handgrip (IHG) at 30% maximal voluntary contraction (MVC). The pulsatility index (PI) of the blood velocity waveform of the superior mesenteric artery was taken as the study parameter. A total of ten healthy subjects [mean age, 21.1 (SEM 0.3) years] performed an IHG at 30% MVC for 90 s. At 5 s prior to the end of the exercise, muscle circulation was arrested for 90 s to study the effect of the muscle chemoreflex (post exercise arterial occlusion, PEAO). The IHG at 30% MVC caused a decrease in superior mesenteric artery PI, from 4.84 (SEM 1.57) at control level to 3.90 (SEM 1.07) (P = 0.015). The PI further decreased to 3.17 (SEM 0.70) (P = 0.01) during PEAO. Our results indicated that ergoreceptors may be involved in the superior mesenteric artery vasodilatation during isometric exercise.     

Effect of parasympathetic denervation of liver and pancreas on glucose kinetics in man

The study aim was to investigate the role of the parasympathetic nervous system in the control of glucose tolerance in man. Glucose kinetics were determined during an oral glucose tolerance test (OGTT) in six subjects with truncal vagotomies and six control subjects. Basal plasma glucose levels in the two groups were equal; however, 20 to 40 minutes after the OGTT, glucose was higher in vagotomized compared with control subjects (P < .02). There were no differences in insulin levels between the subjects. Glucagon decreased after the OGTT in the controls, whereas in the vagotomized subjects it increased transiently and did not decrease beyond basal levels. There was no difference in basal hepatic glucose production, but suppression was greater in controls in the first 10 minutes (P < .01). Gut-derived glucose appearance increased faster and to a higher level (56.0 +/- 8 v 29.7 +/- 2.9 mumol/kg/min, P < .02) in vagotomized subjects. There were no differences in the metabolic clearance rate of glucose between the two groups. It is concluded that parasympathetic innervation of the pancreas is essential for suppression of glucagon secretion during hyperglycemia. However, abnormal glucose tolerance in vagotomized subjects is primarily due to rapid gut glucose absorption, with the denervated parasympathetic system playing only a minor role.     

Measurement and estimation system for monitoring physiologic parameters of man and biological feedback training

A flexible instrumental programmed system realizing the biological feedback (BFB) method and permitting an easy tuning of the channels and parameters for treatment and reflection of physiological information is designed. A measurement and estimation real-time medical system for monitoring and BFB training is described, based on visual programming. An example of practical clinical application of the system to BFB training for the EEG rhythms is offered.     

Pathogenesis and characterization of hyperglucagonemia in the uremic rat

The pathogenesis of hyperglucagonemia and of the alterations in the pattern of circulating immunoreactive glucagon (IRG) associated with renal insufficiency was studied in rats in which a comparable degree of uremia was induced by three different methods, i.e., bilateral nephrectomy, bilateral ureteral ligation, and urine autoinfusion. Nephrectomized and ureteral-ligated rats were markedly hyperglucagonemic (575 +/- 95 pg/ml and 492 +/- 54 pg/ml, respectively), while IRG levels of urine autoinfused animals (208 +/- 35 pg/ml) were similar to those of control rats (180 +/- 26 pg/ml), indicating that uremia per se does not account for the hyperglucagonemia observed in renal failure. Similarly, plasma IRG composition in this group of animals was indistinguishable from that of controls, in which 88.2 +/- 5.9% of total IRG consisted of the 3,500-mol wt fraction. The same component was almost entirely responsible (82.6 +/- 4.1%) for the hyperglucagonemia observed in ligated rats, while it accounted for only 57.6 +/- 5.0% of the circulating IRG in nephrectomized animals. In the latter group, 36.8 +/- 6.6% of total IRG had a mol wt of approximately 9,000, consistent with a glucagon precursor. This peak was present in samples obtained as early as 2 h after renal ablation and its concentration continued to increase with time reaching maximal levels at 24 h. These results confirm that the kidney is a major site of glucagon metabolism and provide evidence that the renal handling of the various circulating IRG components may involve different mechanisms. Thus, the metabolism of the 3,500-mol wt fraction is dependent upon glomerular filtration, while the uptake of the 9,000-mol wt material can proceed in its absence, as long as renal tissue remains adequately perfused. This finding suggests that the 9,000-mol wt component may be handled by peritubular uptake.     

Metabolism of oral glucose in pancreas transplant recipients with normal and impaired glucose tolerance

To gain insight into the pathophysiology of impaired glucose tolerance in pancreas transplantation, glucose kinetics and insulin secretion were assessed after an oral glucose load in four combined pancreas-kidney recipients with impaired glucose tolerance (IPx), in five combined pancreas-kidney recipients with normal glucose tolerance, in six nondiabetic kidney transplant recipients, and in eight normal subjects employing a dual isotope technique, beta-Cell function was evaluated by calculating prehepatic insulin secretion rates, which subsequently were correlated to the ambient glucose concentrations to obtain an index of beta-cell responsiveness. Oxidative and nonoxidative glucose metabolism were assessed by indirect calorimetry. Basal insulin secretion rates, the glucose-stimulated early insulin secretion rates, as well as beta-cell responsiveness were markedly reduced in IPx than in the glucose-tolerant transplant subjects. Total systemic glucose appearance was similar in the groups with apparently comparable inhibition of systemic glucose release and increase in exogenous glucose appearance. The hyperglycemic response in IPx was due to a significant reduction in the glucose disappearance rates during the first 2 h after glucose ingestion. Nonoxidative glucose metabolism increased significantly less in IPx than in glucose-tolerant groups. Glucagon secretion was less suppressed in the early part of the study in IPx, which may have contributed to the excessive hyperglycemia. In conclusion, IPx after pancreas transplantation was characterized by 1) impaired early insulin secretion, 2) reduced beta-cell responsiveness, 3) reduced glucose uptake, 4) impaired nonoxidative glucose metabolism, and 5) impaired early inhibition of glucagon secretion.     

Effects of arterial versus venous sampling on analysis of glucose kinetics in man

A compartmental model is presented to account for transient and steady-state changes in blood glucose concentration which result from transit through the forearm and hand in man. This model permits the inter-conversion of arterial and venous data and the derivation of arterial equivalent total body glucose models from venous data. Data were obtained from subjects in the basal state following a pulse injection of [1-14C]glucose tracer. An artery, an antecubital vein, and a dorsal vein of a heated hand (68 degrees C environment) were sampled. Blood transit time is shorter 0.3 vs. 1.0 min) and irreversible glucose loss is reduced (1.9 vs. 2.9%) in the heated hand preparation when compared to the antecubital vein preparation. Because of the smaller correction required and the smaller variation among individuals when heated hand rather than antecubital vein data are obtained, we suggest that for analysis of whole-body kinetics such data should be used along with the compartmental model correction when arterial data cannot be obtained.     

Influence of probenecid and spironolactone on furosemide kinetics and dynamics in man

The pharmacokinetics and pharmacodynamics following administration of furosemide (40 mg intravenously) have been studied before and after treatment with probenecid (0.5 gm orally every 6 hr for 3 days) and spironolactone (200-mg initial oral dose followed by 50 mg every 6 hr for 3 days) in 6 normal male subjects. Urine losses during each study period were replaced with saline-dextrose-KCl intravenously. The study was performed with the use of a Latin-square design. Probenecid pretreatment induced significant reductions in renal clearance of furosemide by 78%, the extrarenal clearance by 56%, and the volume of distribution by 52%. As a consequence, furosemide half-life was increased by 54%. Probenecid significantly reduced the rate of sodium excretion at all plasma concentrations of furosemide, but the ratio between urinary furosemide concentration and urinary sodium concentration was not altered. Since the proportion of furosemide excreted unchanged in the urine was not markedly changed, total diuretic response was not influenced by probenecid. There was no evidence of any pharmacokinetic interaction between spironolactone and furosemide. The relationship of furosemide kinetics to dynamics observed in these studies confirms that, in man, the diuretic response is determined by drug that reaches the renal tubule rather than the drug level in plasma.     

Mechanisms of whole-body glycogen deposition after oral glucose in normal subjects. Influence of the nutritional status

It is known that prior fasting enhances whole-body glycogen retention after glucose ingestion. To identify the involved mechanisms, 33 normal volunteers underwent a total fast, varying between 14 h and 4 days, and ingested thereafter 75 g glucose labeled with [14C]glucose. Measurements of oral glucose oxidation (expired 14CO2, corrected for incomplete recovery) and total carbohydrate (CHO) oxidation (indirect calorimetry) were performed over the following 5 h. These data allowed us to calculate oral glucose storage (uptake oxidation), glycogen oxidation (CHO oxidation - oral glucose oxidation), and net CHO balance (oral glucose uptake - CHO oxidation). As compared with an overnight fast, prolonged fasting (4 days) inhibited the uptake (64.8 vs. 70.3 g/5 h; P < 0.01) and the oxidation (10.9 vs. 20.0 g/5 h; P < 0.001) of oral glucose and stimulated slightly its conversion to glycogen (53.9 vs. 50.3 g/5 h; P < 0.05). The latter effect played only a minor role in the marked increase in net CHO balance (52.3 vs. 25.2 g/5 h; P < 0.001), which was almost entirely related to a decrease in glycogen oxidation (1.6 vs. 25.1 g/5 h; P < 0.001). Considering the whole series of data, including intermediate durations of fast, it was observed that the modifications in postprandial CHO metabolism, induced by fasting, correlated strongly with basal CHO oxidation, suggesting that the degree of initial glycogen depletion is a major determinant of glycogen oxidation and net CHO storage. Thus, prior fasting stimulates postprandial glycogen retention, mainly through an inhibition of the glycogen turnover that exists in overnight-fasted subjects, during the absorptive period.     

Effects of intravenous histamine on static lung compliance and airway resistance in normal man

Static lung compliance and airway resistance were measured in 30 experiments on 6 healthy subjects after intravenous injection of a bolus of histamine (4 mug per kg of body weight). Analysis of the pooled results showed a significant decrease in static lung compliance (maximal mean decrease,--16 per cent occurring 20 sec after injection). There was no significant change in functional residual capacity or vital capacity after injection of the histamine. Administration of propranolol (a beta-adrenergic blocking agent) did not significantly enhance the responses to histamine. The results suggested that humans, like other species, can constrict peripheral airways sufficiently to produce alterations in the static elastic properties of the lungs.     

Influence of dietary protein and carbohydrate on antipyrine and theophylline metabolism in man

This study was undertaken to examine the influence of changes in dietary carbohydrate and protein content on the oxidation of antipyrine and theophylline in man. When the diets of 6 normal volunteers were changed from their usual home diets to low carbohydrate-high protein diets, the plasma half-life of antipyrine decreased from 16.2 hr to 9.5 hr, and the half-life of theophylline decreased from 8.1 hr to 5.2 hr. When the subjects' diets were changed from low carbohydrate-high protein diets to a high carbohydrate-low protein diets, the mean antipyrine half-life increased from 9.5 hr to 15.6 hr and the mean theophylline half-life increased from 5.2 hr to 7.6 hr. These changes in half-lives were accompanied by changes in metabolic clearance rates but not in the apparent volumes of distribution of the drugs tested. Qualitatively similar results were obtained when the subjects were placed on standard diets followed by the standard diets supplemented with carbohydrate or protein. Supplementing the standard diets with carbohydrate caused an increase in drug half-lives, whereas a protein supplement caused a decrease in the drug half-lives. These data demonstrate marked influences of nutritional factors on oxidative biotransformation of drugs in man.     

Age-related reduction in glucose elimination is accompanied by reduced glucose effectiveness and increased hepatic insulin extraction in man

This study examined whether insulin secretion, insulin sensitivity, glucose effectiveness (SG), and hepatic extraction (HE) of insulin are altered by age when glucose tolerance is normal. A frequently sampled i.v. glucose tolerance test was performed in 20 elderly (E, 10/10 male/female, all 63 yr old) and in 20 young subjects (Y, 10/10 male/female, all 27 yr old), who were similar in body mass index and 2-h blood glucose during oral glucose tolerance test. E exhibited impaired glucose elimination (i.v. tolerance index, 1.31 +/- 0.10 vs. 1.70 +/- 0.12% min-1; P = 0.019). First-phase insulin secretion and SI did not differ between the groups, whereas E had lower glucose sensitivity of second-phase insulin secretion (0.40 +/- 0.07 vs. 0.70 +/- 0.08 (pmol/L)min-2/(mmol/L), P = 0.026), lower SG, 0.017 +/- 0.002 vs. 0.025 +/- 0.002 min-1, P = 0.004), and higher HE (81.3 +/- 2.4 vs. 73.2 +/- 2.1%, P = 0.013). Across both groups, SG correlated positively with glucose tolerance index (r = 0.58, P < 0.001) and negatively with HE (r = -0.54, P < 0.001). Plasma leptin and glucagon did not change by age, whereas plasma pancreatic polypeptide (PP) was higher in E (122 +/- 18 vs. 66 +/- 6 pg/mL, P = 0.004). PP did not, however, correlate to any other parameter. We conclude that E subjects with normal oral glucose tolerance have reduced SG, impaired second-phase insulin secretion, and increased HE, whereas SI and first-phase insulin secretion seem normal. SG seems most related to age-dependent impairment of glucose elimination, whereas leptin, glucagon, and PP do not seem to contribute.