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.     

Changes in attention with hypo- and hyperglycaemia in children with insulin dependent diabetes mellitus

We compared the results of a computerized attention test (TOVA) in 38 children with insulin dependent diabetes mellitus in relation to various spontaneously occurring blood glucose levels. Testing was performed at the following blood glucose levels: <3.3 mmol/1 (hypoglycaemia), 3.3-8.3 mmol/1 (normoglycaemia) and >8.3 mmol/1 (hyperglycaemia). The attention (sum of errors and response time) varied significantly with the blood glucose level (P = 0.002). The highest number of errors of omission and the longest response time was observed during the test run with hypoglycaemia. Age, sex, age at manifestation of the disease, metabolic control and the results of the intelligence test had no significant influence on these results. We found that attention in children with diabetes was significantly reduced compared to TOVA norms especially during mild hypoglycaemia (P < 0.001). Irrespective of the blood glucose levels, reaction time and the variability of the reaction time differed significantly between TOVA norms and diabetic children (P < 0.01). CONCLUSION: In children with diabetes mellitus a significant reduction in attention was found at mild hypoglycaemia but as well at low normal blood glucose levels. Attention deficits due to transient lowering of blood glucose may therefore occur in diabetic children even before they are aware of hypoglycaemic symptoms.     

Hypoglycaemia in spinal muscular atrophy

Repeated episodes of hypoglycaemia were observed in two girls with spinal muscular atrophy. During a 12 h fast blood glucose fell to 3.4 and 2.7 mmol/L, respectively. One girl developed hypoglycaemia and ketonuria. Reduced gluconeogenesis was probably the cause of hypoglycaemia in these patients who had a muscle mass of about 10% of bodyweight (normal 30-40%). Hypoglycaemia must be suspected and treated when patients with severe muscle wasting due to chronic neuromuscular disorders are admitted comatose. In our experience this condition is often regarded as respiratory insufficiency.     

Oxygen consumption and biosynthetic function in perfused liver from rats at different stages of development

Changes in mitochondrial function were studied in perfused liver from rats aged 24-365 days. Oxygen consumption together with the rates of gluconeogenesis, urea synthesis and ketogenesis were determined. Basal mitochondrial respiration as well as the ability of the liver to synthesize glucose, urea and ketone bodies declined from 24- to 365-day-old rats. On the other hand, on transition from 24 to 60 days the liver oxidation rate of hexanoate, sorbitol and glycerol is enhanced, but not of ketone bodies or palmitate. Our results show that the transition from weaning to middle age is accompanied by defined changes in hepatic substrate oxidation. From the observed time course of the decrease in basal and substrate-stimulated oxygen consumption, it is concluded that in rat liver cells a decline in respiratory chain function, long-chain fatty acid and ketone body metabolism, gluconeogenesis and ureogenesis occurs at a relatively early life stage.     

Prognosis of infants of diabetic mothers in relation to neonatal hypoglycaemia

A prospective follow-up study was conducted to determine whether neonatal hypoglycaemia in infants of diabetic mothers affects subsequent neurological and intellectual performance. 37 such infants (25 hypoglycaemic and 12 non-hypoglycaemic) were examined for physical, neurological and developmental performance at an average age of 4 1/2 years. 11 children were abnormal, with generalised retardation and neurological abnormalities, or delays in particular areas of development; three children were possibly abnormal; and 23 children were normal. Abnormality at follow-up could not be related to neonatal blood glucose level, to the duration of hypoglycaemia or to any other measurement made in the neonatal period, nor to any factor relating to the maternal diabetes. Compared with the normal children, the abnormal group had slightly small head-circumferences at birth relative to their gestational age, but a follow-up there was no difference in head size. At follow-up the children of diabetic mothers tended to be shorter than average. The poor prognosis of the infants in this study was not due to brain damage caused by neonatal hypoglycaemia.     

Mechanisms of insulin resistance during acute endotoxemia

We characterized the mechanisms underlying acute endotoxin-induced alterations in glucose metabolism and determined the extent to which catecholamines mediate these changes. Acute endotoxemia was induced in chronically catheterized awake rats by a bolus injection of lipopolysaccharide (LPS; 1 mg/kg; LD10). Basal glucose turnover (Rt; infusion of [5-3H]glucose), in vivo insulin action on overall glucose utilization (euglycemic clamp), glycolysis, and glycogen synthesis were determined in four groups of rats. These groups received 1) LPS (LPS rats; n = 6), 2) saline (control rats; n = 6), 3) LPS and alpha beta-blockade (alpha beta-blockade and LPS rats; n = 9), or 4) saline and alpha beta-blockade (alpha beta-blockade control rats; n = 9). In the basal state, LPS induced hypotension and transient hyperglycemia. These changes were associated with glycogen depletion in both skeletal muscle and liver, and increased Rt. During hyperinsulinemia, whole body glucose disposal was 37% decreased (105 vs. 166 mumol/kg.min; P < 0.01). This whole body insulin resistance was characterized by decreased glycogen synthesis and glycogen synthase activity, but not by altered whole body glycolysis. alpha beta-Blockade abolished transient hyperglycemia, increased Rt, and accelerated basal liver glycogen depletion (45 vs. 105 mmol/kg dry, LPS and alpha beta-blockade rats vs. LPS rats; P < 0.05), but inhibited muscle glycogenolysis. alpha beta-Blockade did not reverse the insulin resistance induced by endotoxin. These data suggest that catecholamines counteract the LPS-induced increase in basal glucose turnover and stimulate muscle glycogenolysis during acute endotoxemia. These effects might explain the better preservation of hepatic glycogen in the absence than in the presence of alpha beta-blockade and serve as a defense mechanism against hypoglycemia. Catecholamines do not seem to be the immediate causes of insulin resistance during acute endotoxemia.     

The effect of dexamethasone treatment on the expression of the regulatory genes of ketogenesis in intestine and liver of suckling rats

The influence of the injection of dexamethasone on ketogenesis in 12 day old suckling rats was studied in intestine and liver by determining mRNA levels and enzyme activity of the two genes responsible for regulation of ketogenesis: carnitine palmitoyl transferase I (CPT I) and mitochondrial HMG-CoA synthase. Dexamethasone produced a 2 fold increase in mRNA and activity of CPT I in intestine, but led to a decrease in mit. HMG-CoA synthase. In liver the mRNA levels and activity of both CPT I and mit. HMG-CoA synthase decreased. Comparison of these values with the ketogenic rate of both tissues following dexamethasone treatment suggests that mit. HMG-CoA synthase could be the main gene responsible for the regulation of ketogenesis in suckling rats. The changes produced in serum ketone bodies by dexamethasone, with a profile that is more similar to the ketogenic rate in the liver than that in the intestine, indicate that liver contributes more to ketone body synthesis in suckling rats. Two day treatment with dexamethasone produced no change in mRNA or activity levels for CPT I in liver or intestine. While mRNA levels for mit. HMG-CoA synthase changed little, the enzyme activity is decreased in both tissues.     

Sulphide impairment of substrate oxidation in rat colonocytes: a biochemical basis for ulcerative colitis?

1. Isolated colonic epithelial cells of the rat were incubated for 40 min with [6-14C]glucose and n-[1-14C]butyrate in the presence of 0.1-2.0 mmol/l NaHS, a concentration range found in the human colon. Metabolic products, 14CO2, acetoacetate, beta-hydroxybutyrate and lactate, were measured and injury to cells was judged by diminished production of metabolites. 2. Oxidation of n-butyrate to CO2 and acetoacetate was reduced at 0.1 and 0.5 mmol/l NaHS, whereas glucose oxidation remained unimpaired. At 1.0-2.0 mmol/l NaHS, n-butyrate and glucose oxidation were dose-dependently reduced at the same rate. 3. To bypass short-chain acyl-CoA dehydrogenase activity necessary for butyrate oxidation, ketogenesis from crotonate was measured in the presence of 1.0 mmol/l NaHS. Suppression by sulphide of ketogenesis from crotonate (-10.5 +/- 6.1%) compared with control conditions was not significant, whereas suppression of ketogenesis from n-butyrate (-36.00 +/- 5.14%) was significant (P = < 0.01). Inhibition of FAD-linked oxidation was more affected by NaHS than was NAD-linked oxidation. 4. L-Methionine (5.0 mmol/l) significantly redressed the impaired beta-oxidation induced by NaHS. Methionine equally improved CO2 and ketone body production, suggesting a global reversal of the action of sulphide. 5. Sulphide-induced oxidative changes closely mirror the impairment of beta-oxidation observed in colonocytes of patients with ulcerative colitis. A hypothesis for the disease process of ulcerative colitis is that sulphides may form persulphides with butyryl-CoA, which would inhibit cellular short-chain acyl-CoA deHydrogenase and beta-oxidation to induce an energy-deficiency state in colonocytes and mucosal inflammation.     

Effects of oral clonidine premedication on plasma glucose and lipid homeostasis associated with exogenous glucose infusion in children

BACKGROUND: Oral clonidine may influence plasma glucose and lipid homeostasis by modulating endocrinologic responses to surgical stress. The effect of oral clonidine premedication on plasma glucose and lipid homeostasis associated with exogenous glucose infusion were investigated in children undergoing minor surgery. METHODS: Otherwise healthy children (n, 120; aged 3-13 yr) were assigned randomly to six groups according to the glucose concentration of the intravenous solution (0%, 2%, or 5%, at a rate of 6 ml kg(-1) x h(-1)) and the preoperative medications (4 microg/kg clonidine or placebo given 100 min before anesthesia) they were to receive. The plasma concentrations of glucose, nonesterified fatty acid, ketone bodies, epinephrine, norepinephrine, and cortisol were determined. RESULTS: Infusion of 5% glucose caused hyperglycemia (mean glucose concentration >200 mg/dl) in six children receiving placebo and two receiving clonidine. Although the mean plasma glucose concentration increased in three placebo groups, it was unchanged and the plasma concentrations of total ketone bodies and nonesterified fatty acid were increased in children receiving clonidine and glucose-free solution. The plasma epinephrine, norepinephrine, and cortisol levels in children receiving placebo increased in response to surgery. Clonidine attenuated the increase in catecholamines and cortisol. CONCLUSIONS: Oral clonidine premedication attenuated the hyperglycemic response, probably by inhibiting the surgical stress-induced release of catecholamines and cortisol. Infusion of 2% of glucose maintained plasma glucose concentrations within physiologic ranges in children receiving clonidine.     

The relationship between glucose production and plasma glucose concentration in children with falciparum malaria

The pathophysiology of hypoglycaemia in children with acute falciparum malaria, a frequent and serious complication, is unknown due to absence of data on glucose kinetics. We investigated the correlation between basal glucose production and plasma glucose concentration in 20 children (8 girls) with acute, uncomplicated falciparum malaria by infusion of [6,6-2H2]glucose. Median plasma glucose concentration was 4.5 (range 2.1-6.5) mmol/L and the median glucose production 5.0 (range 4.1-8.4) mg/kg/min. There was a positive correlation between basal glucose production and plasma glucose concentration (r = 0.53, P = 0.016). There was no correlation between the rate of glucose production and the plasma concentrations of alanine, lactate, counter-regulatory hormones or cytokines. It was concluded that, in children with acute uncomplicated falciparum malaria, endogenous glucose production is an important determinant of plasma glucose concentration, contrary to previous findings in adults with malaria, in whom peripheral uptake seems to be more important than glucose production in determining plasma glucose concentration.     

Endotoxin modulates arachidonic acid-induced glycogenolysis in the perfused rat liver

Effects of endotoxin on arachidonic acid (AA)-induced hepatic glycogenolysis were examined in perfused rat liver. In normal rat liver, infusion of AA increased oxygen consumption and glucose production concurrently. In rats injected with lipopolysaccharide (LPS) 6 h before, AA increased glucose production but suppressed oxygen consumption. The changes in LPS-injected rat were abolished by a thromboxane (Tx) A2 receptor antagonist. The release of Tx B2 by AA increased after LPS-injection. These results suggest that priming of hepatic macrophage by endotoxin in vivo enhances Tx synthesis, resulting in modulating hepatic glycogenolysis.     

Intense sympathetic nerve activity in adults with hypopituitarism and untreated growth hormone deficiency

Perturbations in the sympathetic nervous system may be anticipated in adults with hypopituitarism and untreated GH deficiency, because the syndrome is associated with both peripheral and central factors known to modulate sympathetic traffic. The higher prevalence of hypertension and increased cardiovascular morbidity/mortality reported in GH-deficient patients may suggest increased activity of the sympathetic nervous system. We recorded muscle sympathetic nerve activity (MSNA) in 10 hypopituitary adults with adequate hormonal replacement therapy except GH and in 10 healthy controls matched for age, gender, and body mass index to test whether hormonal aberrations in hypopituitarism and untreated GH deficiency are associated with an increase in sympathetic nerve traffic. Blood samples for insulin-like growth factor I, free T4, and TSH were taken after an overnight fast, followed by an oral glucose tolerance test. Direct intraneural recordings of MSNA were performed with a tungsten microelectrode from the peroneal nerve. The hypopituitary subjects had markedly increased MSNA (54 +/- 4 bursts/min vs. 34 +/- 4 in controls; P < 0.002), which was not related to abdominal obesity or altered glucose metabolism. When assessed for the whole study group, MSNA was inversely correlated to serum insulin-like growth factor I (r = -0.59; P < 0.006) and TSH (r = -0.46; P < 0.04). MSNA was positively correlated to diastolic blood pressure (r = 0.80; P < 0.0005) in patients, but not in controls. The intense sympathetic discharge is suggested to be of central origin and may be an important underlying mechanism for the secondary hypertension and increased cardiovascular morbidity/mortality in this patient group.     

Renal glycosuria treated as diabetes mellitus: case report

A case of renal glycosuria is reported. A 55 year old female was diagnosed and treated in an upcountry hospital for diabetes mellitus. She developed symptoms of hypoglycaemia while on an oral hypoglycaemic agent, leading to her admission in Mulago Hospital. Persistent glycosuria was noted despite treatment and normal serum glucose. Oral glucose tolerance test and timed urine glucose showed a normal curve but high urine sugar. A diagnosis of renal glycosuria was made, oral hypoglycaemic therapy was stopped, patient improved and was discharged. Though renal glycosuria is a benign condition, mistaken diagnosis for diabetes mellitus puts patients at risk of hypoglycaemia due to treatment. Diagnosis of the condition requires physicians' awareness of its existence in our community and the use of Marbles' criteria obviates confusion with diabetes mellitus though it does not absolutely exclude Fanconi syndrome.     

Propranolol and exercise as a screening test for growth hormone deficiency

There is a need for a safe, inexpensive, and reliable screening test for growth hormone (GH) reserve. Exercise has been utilized for this purpose but false-negative responses (inadequate GH release in non-GH-deficient patients) has limited the effectiveness of this stimulus as a screening test. Beta-adrenergic blockade (propranolol) was used to enhance the effect of exercise on GH release. Thirty-two non-GH-deficient children and five GH-deficient children were evaluated. All of the non-GH-deficient children responded to propranolol and exercise with serum GH levels exceeding 7 ng/ml. The peak serum GH levels in the five GH-deficient patients did not exceed 4 ng/ml. Propranolol and exercise appears to be an effective screening test for GH function.     

Preoperative cardiac evaluation is unnecessary in most patients undergoing vascular operations

OBJECTIVES AND METHODS: Our goal was to describe nutritional homeostasis in healthy exclusively breastfed infants (n = 175) during their first 5 d, by cross-sectional measurements of body weight, blood glucose, plasma insulin, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding-protein-1 (IGFBP-1), free fatty acids (FFA), glycerol, ketone (3-OH-butyric acid) and lactate. We also investigated whether nutrition affected feeding behaviour by timing the interval between feedings. RESULTS: A progressive loss of body weight, as percentage of birthweight, occurred up to 2 d of age, with a maximal decrease of 5.8 +/- 2.1% (mean +/- SD); this was accompanied by inhibition of anabolic hormone and metabolic pathways and an increased mobilization of stored fat and ketogenesis. The interval between feedings decreased between d 1 and 2. Weight gain occurred at 3 d and the following re-feeding phase returned fuel stores to their previous levels and established an anabolic hormonal and metabolic situation. Infants with weight loss exceeding 10% had a further accentuation in their peripheral picture of starvation and a further 7% shortening of the interval between feedings. CONCLUSIONS: breastfeeding on demand is accompanied by a balanced nutritional situation and an increased drive to eat when weight reduction is <6%. However, a weight loss of > or = 10%, probably elicits hunger sensations in response to decreased fuel availability.     

Shape-dependent effects in a series of aromatic nitro compounds acting as mutagenic agents on S. typhimurium TA98

Freshly isolated hepatocytes of the clawed toad, Xenopus laevis, were cultured for at least 3 days. The viability of the cells was characterized using staining and biochemical methods. In particular, the glucose and glycogen balance was tested. After culture for 16-20 hrs, the cells were subjected to hormonal treatment. Both adrenaline and arginine vasotocin stimulated the release of glucose in a dose dependent manner. 10(-6) M concentrations were strongly effective. The determination of the glycogen balance made it clear that the glucose release is mainly due to glycogenolysis. Using receptor antagonists and agonists, it has been shown that the effect of adrenaline is clearly mediated by beta-type receptors. Arginine vasotocin stimulated glycogenolysis via a type of receptor which is similar to the V2-receptor of mammals. This means that cAMP is involved in the response to both types of hormones which is in contrast to that which is known about the effect of nonapeptides on the liver of mammals.     

A novel assay for evaluating glycogenolysis in rat adipocytes and the inability of insulin to antagonize glycogenolysis in this cell type

We report here on a novel procedure for measuring glycogenolysis in rat adipocytes. In this procedure, cells are incubated for 30 min at 37 degrees C with insulin or vanadate, and with [U-14C]glucose to label the glycogen pool with radioactive glucose. The cells are washed and preincubated for an additional 1 h, before being assayed. The extent of glycogenolysis is determined by the decrease in radioactivity in precipitated glycogen, which was quite substantial under experimental conditions facilitating glycogenolysis. From the assay, we determined the following. (a) Glycogenolysis is activated in rat adipocytes in response to lipolytic hormones (i.e. catecholamines and adrenocorticotropic hormone). (b) Other agents and conditions elevating intracellular adenosine 3',5'-monophosphate levels (i.e. cholera toxin, dibutyryladenosine 3',5'-monophosphate, and isobutylmethylxanthine) also activate glycogenolysis. (c) Glycogenolysis (as opposed to lipolysis) is activated at concentrations of adrenocorticotropic hormone or isoproterenol 7-11-fold lower and at adenosine 3',5'-monophosphate concentrations 7-fold lower. (d) Calyculin A, a specific inhibitor of protein phosphatase 1, activates glycogenolysis as well. Calyculin A also activates lipolysis at an equimolar potency. (e) Insulin does not antagonize glycogenolysis in rat adipocytes. In conclusion, the assay allowed us to compare glycogenolysis to lipolysis within the same cell, and to find that the sensitivity to hormones and adenosine 3',5'-monophosphate was about 1 order of magnitude higher for glycogenolysis than for lipolysis. A more striking finding was the inability of insulin to antagonize glycogenolysis in the rat adipose cell, an effect which occurs readily in liver and muscle cells via protein phosphatase 1-activating machinery. This rules out a role for adipose protein phosphatase 1 activation in the mechanism by which insulin antagonizes lipolysis and supports the contention that the insulin effect in lowering adenosine 3',5'-monophosphate levels is the central mechanism by which insulin antagonizes lipolysis.     

Equally rapid activation of lipogenesis in nibbling and gorging mice

Minimal average rates of exogenous glucose-C-conversion to whole body, total lipid fatty acids were measured in nibbling and gorging mice. Gorgers trained to eat 1 meal/day (8-10 am) were fasted 22-24 hr and given [14C]glucose with pure glucose, 30% glucose in water, or a 58% glucose, fat-free diet. Conversion of glucose-C to total lipid fatty acids increased from 0.6 (fasted) to approximately 20 mug/min/20 g body weight during 40 min after glucose feeding using each test meal. Dietary amino acids were not required for activation of lipogenesis in gorgers. Exogenous glucose-C was incorporated into fatty acids as fast in nibbling mice as in gorgers. This was true after varying all of the following conditions: training period, number of meals gorged, previous fasting time, and diet composition. The total rate of fatty acid synthesis from body glucose-C during absorption of a glucose load was also estimated in absorption of a glucose load was also estimated in previously fasted nibbling and gorging mice. These estimates were based on composite, serial measurement of both plasma glucose specific activities and 14C-labeled fatty acids. The total rate of fatty acid synthesis from both exogenous and endogenous glucose-C was only 15% higher than the rate from exogenous glucose-C between 10 and 40 min. No significant differences between nibblers and gorgers were found.     

Myocardial glucose uptake in patients with NIDDM and stable coronary artery disease

Whole body insulin resistance characterizes patients with NIDDM, but it is not known whether insulin also has impaired ability to stimulate myocardial glucose uptake (MGU) in these patients. This study was designed to evaluate MGU as measured by 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in patients with NIDDM and stable coronary artery disease (CAD) under standardized metabolic conditions. Eight patients with NIDDM, 11 nondiabetic patients with CAD, and 9 healthy control subjects were enrolled in the study. MGU was quantitated in the normal myocardial regions with [18F]FDG and PET and the whole body glucose disposal by glucose-insulin clamp technique (serum insulin, -430 pmol/l). Plasma glucose and serum insulin concentrations were comparable in all groups during PET studies. The whole body glucose uptake was 45% lower in NIDDM patients (22 +/- 9 micromol x min(-1) X kg(-1) body wt [mean +/- SD]), compared with healthy control subjects (40 +/- 17 micromol x min(-1) x kg(-1) body wt, P < 0.05). In CAD patients, whole body glucose uptake was 30 +/- 9 micromol x min(-1) x kg(-1) body wt (NS between the other groups). MGU was similar in the normal segments in all three groups (69 +/- 28 micromol x min(-1) x 100 g(-1) in NIDDM patients, 72 +/- 17 micromol x min(-1) x 100 g(-1) in CAD patients, and 76 +/- 10 micromol x min(-1) x 100 g(-1) in healthy control subjects, NS). No correlation was found between whole body glucose uptake and MGU. As studied by [18F]FDG PET under stable normoglycemic hyperinsulinemic conditions, MGU is not reduced in patients with NIDDM and CAD in spite of peripheral insulin resistance. These findings suggest that there is no significant defect in MGU in patients with NIDDM.     

The value of beta-2 transferrin analysis and MR cisternography for the diagnosis of cerebrospinal fluid fistulas

Blood chemical values, including ketone bodies, were measured in 25 cows with abomasal displacement (displacement group), 16 cows with primary ketosis (ketosis group), and nine normal controls to investigate the pathophysiology of abomasal displacement. Increases in aspartate aminotransferase, gamma-glutamyl transpeptidase, non-esterified fatty acid (NEFA), and ketone bodies (3-hydroxybutyric acid and acetoacetic acid) were observed in the displacement and ketosis groups. Total cholesterol increased significantly in the ketosis group but decreased in the displacement group. Glucose was significantly low and reversely correlated to ketone bodies in the ketosis group but was not low and was not correlated with ketone bodies in the displacement group. While NEFA was correlated to ketone bodies in the ketosis group, it was not in the displacement group. A correlation between the values of acetoacetic acid and 3-hydroxybutyric acid was seen in both the ketosis and displacement groups. The fact that blood chemical values in ketosis cows were clearly different from those in displacement cows suggest that the biochemical mechanism of ketogenesis is different between these two groups.