Synergistic effect of counterregulatory hormones during insulin-induced hypoglycemia in rats: participation of lipolysis and gluconeogenesis to hyperglycemia

Aneurysmal bone cyst of the long bones in a purely intracortical or subperiosteal location is unusual. Three such cases are reported, and the radiographic and pathologic differential diagnoses are discussed. Those subperiosteal or intracortical aneurysmal bone cysts with radiographic features similar to the intramedullary variety should suggest the same diagnosis. However, the radiographic features may be less specific, so that a diagnosis of aneurysmal bone cyst must be entertained when considering a subperiosteal or intracortical lytic lesion.     

Electrocardiographic changes during insulin-induced hypoglycemia in healthy subjects

Hypoglycemia is associated with alterations of the ECG, a phenomenon which might be used for the development of a hypoglycemia detection device. We investigated the reproducibility and magnitude of ECG alterations during insulin-induced hypoglycemia in nine healthy volunteers. The subjects were studied twice with an identical study protocol on two different study days. During hypoglycemia frequent ECG recordings were done with a conventional 12 lead ECG. S.c. injection of 0.15 U/kg of regular insulin induced a fourfold increase in insulinemia on both study days as well as a mean decline in blood glucose by 1.6 mmol/l to a minimum of 2.8 mmol/l within 60 min after injection. Blood potassium levels declined by a mean of 0.25 mmol/l to minimal values of 3.69 mmol/l. On both study days, a progressive flattening of the T-waves was observed during the experiments. R-waves remained constant leading to an increase in RT ratios by at least 50% in comparison to baseline values. These changes were most pronounced in leads I, V3, V5 and V6. The magnitude and reproducibility of the observed ECG changes during hypoglycemia may allow the development of a hypoglycemia detection device.     

Counterregulation by epinephrine and glucagon during insulin-induced hypoglycemia in the conscious dog

We assessed the combined role of epinephrine and glucagon in regulating gluconeogenic precursor metabolism during insulin-induced hypoglycemia in the overnight-fasted, adrenalectomized, conscious dog. In paired studies (n = 5), insulin was infused intraportally at 5 mU.kg-1.min-1 for 3 h. Epinephrine was infused at a basal rate (B-EPI) or variable rate to simulate the normal epinephrine response to hypoglycemia (H-EPI), whereas in both groups the hypoglycemia-induced rise in cortisol was simulated by cortisol infusion. Plasma glucose fell to approximately 42 mg/dl in both groups. Glucagon failed to rise in B-EPI, but increased normally in H-EPI. Hepatic glucose release fell in B-EPI but increased in H-EPI. In B-EPI, the normal rise in lactate levels and net hepatic lactate uptake was prevented. Alanine and glycerol metabolism were similar in both groups. Since glucagon plays little role in regulating gluconeogenic precursor metabolism during 3 h of insulin-induced hypoglycemia, epinephrine must be responsible for increasing lactate release from muscle, but is minimally involved in the lipolytic response. In conclusion, a normal rise in epinephrine appears to be required to elicit an increase in glucagon during insulin-induced hypoglycemia in the dog. During insulin-induced hypoglycemia, epinephrine plays a major role in maintaining an elevated rate of glucose production, probably via muscle lactate release and hepatic lactate uptake.     

Circadian rhythm of insulin-induced hypoglycemia in man

Four healthy men were given an insulin tolerance test (0.1 IU/kg BW) six times in different days at the following clock hours: 0400 h, 0800h, 1200 h, 1600 h, 2000 h, and 2400 h, in random order. Four days separated two consecutive tests. The glucose disappearance rate (K value) was calculated for each test between 5 min and 25 min after iv injection of insulin. The statistical evaluation by Cosinor test showed a statistically significant circadian rhythm for the hypoglycemic action of exogenous insulin with a peak at 1030 h (95% condifence limits: 0830 to 1430 h).     

Effects of lactate infusion on hepatic gluconeogenesis and glycogenolysis

Endogenous glucose production rate (EGPR) remains constant when lactate is infused in healthy humans. A decrease of glycogenolysis or of gluconeogenesis from endogenous precursors or a stimulation of glycogen synthesis, may all be involved; This autoregulation does not depend on changes in glucoregulatory hormones. It may be speculated that alterations in basal sympathetic tone may be involved. To gain insights into the mechanisms responsible for autoregulation of EGPR, glycogenolysis and gluconeogenesis were measured, with a novel method (based on the prelabelling of endogenous glycogen with 13C glucose, and determination of hepatic 13C glycogen enrichment from breath 13CO2 and respiratory gas exchanges) in healthy humans infused with lactate or saline. These measurements were performed with or without beta-adrenergic receptor blockade (propranolol). Infusion of lactate increased energy expenditure, but did not increase EGPR; the relative contributions of gluconeogenesis and glycogenolysis to EGPR were also unaltered. This indicates that autoregulation is attained, at least in part, by inhibition of gluconeogenesis from endogenous precursors. beta-adrenergic receptor blockade alone (with propranolol) did not alter EGPR, glycogenolysis or gluconeogenesis. During infusion of lactate, propranolol decreased the thermic effect of lactate but EGPR remained constant. This indicates that alterations of beta-adrenergic activity is not required for autoregulation of EGPR.     

Effect of nonselective beta-adrenergic blockade on blood plasma levels of glucagon in plasma during insulin-induced hypoglycemia

An effect of nonselective beta-adrenergic blockade with propranolol on the blood plasma level of glucagon during insulin-induced hypoglycemia was studies in 20 control dogs and 20 alloxan diabetic dogs. Increased sensitivity to exogenous insulin and prolonged hypoglycemia were noted during nonselective beta-adrenergic blockade. However, glucagon response to insulin-induced hypoglycemia following propranolol administration was increased.     

Carbon-14 tracer studies in the metabolism of isolated rat-liver parenchymal cells under conditions of gluconeogenesis from lactate and pyruvate

In rat liver perfusion experiments under conditions of gluconeogenesis from lactate and pyruvate 14C-labeling patterns of metabolites with (1-14C)-labeled and (2-14C)-labeled lactate or pyruvate, [14C]bicarbonate and [1-14C]octanoate as tracers, have been obtained, which do not agree with generally assumed reaction schemes. The experiments have been repeated with incubations of isolated rat-liver parenchymal cells. The results demonstrate that the discrepancies between expected and analysed 14C-labeling patterns of metabolites were still existent. From this observation it may be concluded, that 14C-labeling patterns of metabolites are indicative for the existence of still unknown metabolic relationships in liver parenchymal cells. Furthermore the results of our experiments prove that conclusions based on the exclusive analysis of metabolite levels are of limited value for studying intracellular events, because of uncharacterized compartmentations, which become evident in 14C-tracer studies. It cannot be answered by our studies, whether the apparent existence of differently labeled species of citrate, oxoglutarate or acetyl-CoA, represent intracellular compartmentation or whether it is the result of metabolic heterogeneity of liver parenchymal cells.     

Blockade of cerebral blood flow response to insulin-induced hypoglycemia by caffeine and glibenclamide in conscious rats

The possibility that adenosine and ATP-sensitive potassium channels (KATP) might be involved in the mechanisms of the increases in cerebral blood flow (CBF) that occur in insulin-induced hypoglycemia was examined. Cerebral blood flow was measured by the [14C]iodoantipyrine method in conscious rats during insulin-induced, moderate hypoglycemia (2 to 3 mmol/L glucose in arterial plasma) after intravenous injections of 10 to 20 mg/kg of caffeine, an adenosine receptor antagonist, or intracisternal infusion of 1 to 2 mumol/L glibenclamide, a KATP channel inhibitor. Cerebral blood flow was also measured in corresponding normoglycemic and drug-free control groups. Cerebral blood flow was 51% higher in untreated hypoglycemic than in untreated normoglycemic rats (P < 0.01). Caffeine had a small, statistically insignificant effect on CBF in normoglycemic rats, but reduced the CBF response to hypoglycemia in a dose-dependent manner, i.e., 27% increase with 10 mg/kg and complete elimination with 20 mg/kg. Chemical determinations by HPLC in extracts of freeze-blown brains showed significant increases in the levels of adenosine and its degradation products, inosine and hypoxanthine, during hypoglycemia (P < 0.05). Intracisternal glibenclamide had little effect on CBF in normoglycemia, but, like caffeine, produced dose-dependent reductions in the magnitude of the increases in CBF during hypoglycemia, i.e., +66% with glibenclamide-free artificial CSF administration, +25% with 1 mumol/L glibenclamide, and almost complete blockade (+5%) with 2 mumol/L glibenclamide. These results suggest that adenosine and KATP channels may play a role in the increases in CBF during hypoglycemia.     

Renal and hepatic nitrogen metabolism during NH4Cl ingestion in protein-deprived rats

PURPOSE: We assessed the morphodynamic features of cavernous arteries and helicine arterioles by power Doppler sonography in vasculogenic and nonvasculogenic impotent men. MATERIALS AND METHODS: A total of 40 impotent patients with and without definite vascular risk factors were studied by penile power Doppler sonography. The test was performed during penile flaccidity, after intracavernous injection of 20 mcg. alprostadil and after subsequent genital and audiovisual sexual stimulation. A second injection and stimulation were given if the erectile response observed after the initial injection was less than the maximum erection seen during sexual activity. Morphodynamic parameters evaluated by power Doppler imaging included vessel course, shape, wall thickness and pulsatility, peak systolic velocity, end diastolic velocity, acceleration time and resistance index. RESULTS: In the nonvasculogenic group all patients who achieved rigid erection showed normal cavernosal artery and helicine arteriole inflow. In these cases the arteriolar picture was characterized by the presence of 3 orders of distal ramifications originating from the cavernous arteries with an acute angle, systolic diastolic flow during penile tumescence and systolic flow alone at full rigidity. In the vasculogenic group patients with normal cavernous artery inflow showed an arteriolar tree that was pathological in 50% and was characterized by a reduced number of ramifications originating perpendicularly from the cavernous arteries and irregular caliber (arteriolar impotence). In the same group patients with reduced cavernous artery inflow also showed normal or pathological arteriolar components (pre-penile arterial impotence and diffused penile arterial impotence). CONCLUSIONS: Power Doppler sonography allows a precise study of the morphodynamics of the cavernous arteries and helicine arterioles. Our preliminary data suggest that the intracavernous arteriolar component may have a significant role in the genesis of some forms of vasculogenic impotence.     

Increased nonoxidative glucose metabolism in idiopathic reactive hypoglycemia

Idiopathic reactive hypoglycemia (IRH) is responsible for postprandial hypoglycemia. Normal insulin secretion and reduced response of glucagon to acute hypoglycemia, but mostly increased insulin sensitivity, represent the metabolic features of this syndrome- The present study has two aims: first, to investigate the fate of glucose utilization inside the cells to assess whether increased glucose disposal in IRH is due to the oxidative and/or nonoxidative pathway; and second, to evaluate glucagon response to prolonged insulin-induced hypoglycemia. In eight patients with IRH and eight normal (N) subjects, we performed two studies on different days: (1) 120-minute euglycemic-hyperinsulinemic (1.0 mU . kg-1 . min-1 regular human insulin) clamp associated with indirect calorimetry; and (2) 180-minute hypoglycemic (2.22 to 2.49 mmo/L achieved through 0.85 mU . kg-1 . min-1 intravenous [IV] regular human insulin) clamp. The results showed an increased insulin-mediated glucose uptake in IRH (9.10 +/- 0.19 v 6.78 +/- 0.18 mg kg-1 . min-1, P < .005). Glucose oxidation was similar in IRH subjects and controls both in basal conditions (1.39 +/- 0.16 v 1.42 +/- 0.15 mg . kg-1 . min-1 and during the clamp studies (2.57 +/- 0.21 v 2.78 +/- 0.26 mg . kg-1 . min-1. In contrast, nonoxidative glucose disposal was significantly higher in IRH than in N subjects (6.53 +/- 0.30 v 4.00 +/- 0.21 mg . kg-1 . min-1, P < .001). During insulinization, fat oxidation was reduced slightly more in IRH than in control subjects. During the hypoglycemic clamp, a significant (P < .01) increase in plasma glucagon concentrations was observed in normal subjects as compared with baseline, whereas no change occurred in IRH patients. In conclusion, in IRH: (1) increased insulin-mediated glucose disposal is due to the increase of nonoxidative glucose metabolism; and (2) glucagon secretion has been confirmed to be inadequate. The increase of insulin sensitivity associated with a deficiency in glucagon secretion can widely explain the occurrence of hypoglycemia in the late postprandial phase.     

Glucose and lactate metabolism in C6 glioma cells: evidence for the preferential utilization of lactate for cell oxidative metabolism

13C and 1H nuclear magnetic resonance spectroscopy (NMR) was used to investigate the metabolism of L-lactate and D-glucose in C6 glioma cells. The 13C enrichment of cell metabolites was examined after a 4-h incubation in media containing 5.5 mM glucose and 11 mM lactate, each metabolite being alternatively labelled with either [1-13C]D-glucose or [3-13C]L-lactate. The results indicated that exogenous lactate was the major substrate for oxidative metabolism. They were consistent with the concept of the existence of 2 pools of both lactate and pyruvate, of which 1 pool was closely connected with exogenous lactate and oxidative metabolism, and the other pool was closely related to glycolysis and disconnected from oxidative metabolism. The molecular basis of this behaviour could be related to different locations for the lactate dehydrogenase isoenzymes, as suggested by their immunohistochemical labelling.     

Mitigation of the somnolence of insulin-induced hypoglycemia by a vasopressin V1 receptor antagonist in the rhesus monkey

In order to estimate the risk of tuberculosis infection among employees in the funeral service industry, we conducted a risk-assessment study of a convenience sample of funeral home employees. Study participants completed a risk-assessment questionnaire and underwent tuberculin skin testing. Of 864 employees tested, 101 (11.7%) had a reactive tuberculin skin test. Reactivity to the tuberculin skin test was significantly associated with job category; funeral home employees with a present or past history of embalming deceased-human remains were twice as likely to be reactive as were non-embalming personnel (14.9% versus 7.2%, P < 0.01). Reactivity was also associated with age, gender, race, past history of close contact with a person diagnosed with tuberculosis, and work history. After controlling for age and other factors, tuberculin reactivity was found to be associated in embalming personnel with the number of years spent performing embalmings (> or = 20), and, in non-embalming personnel, with a history of close contact with infected individuals. Based on these results, it is recommended that funeral home employees who routinely embalm cadavers undergo annual tuberculin skin testing, receive initial training on tuberculosis prevention, and wear respiratory protection when preparing known tuberculosis cases.     

Decreased epinephrine responses to hypoglycemia during sleep

BACKGROUND: In patients with type I diabetes mellitus, hypoglycemia occurs commonly during sleep and is frequently asymptomatic. This raises the question of whether sleep is associated with reduced counterregulatory-hormone responses to hypoglycemia. METHODS: We studied the counterregulatory-hormone responses to insulin-induced hypoglycemia in eight adolescent patients with type I diabetes and six age-matched normal subjects when they were awake during the day, asleep at night, and awake at night. In each study, the plasma glucose concentration was stabilized for 60 minutes at approximately 100 mg per deciliter (5.6 mmol per liter) and then reduced to 50 mg per deciliter (2.8 mmol per liter) and maintained at that concentration for 40 minutes. Plasma free insulin, epinephrine, norepinephrine, cortisol, and growth hormone were measured frequently during each study. Sleep was monitored by polysomnography. RESULTS: The plasma glucose and free insulin concentrations were similar in both groups during all studies. During the studies when the subjects were asleep, no one was awakened during the hypoglycemic phase, but during the final 30 minutes of the studies when the subjects were awake both the patients with diabetes and the normal subjects had symptoms of hypoglycemia. In the patients with diabetes, plasma epinephrine responses to hypoglycemia were blunted when they were asleep (mean [+/-SE] peak plasma epinephrine concentration, 70+/-14 pg per milliliter [382+/-76 pmol per liter]; P=0.3 for the comparison with base line), as compared with when they were awake during the day or night (238+/-39 pg per milliliter [1299+/-213 pmol per liter] P=0.004 for the comparison with base line, and 296+/-60 pg per milliliter [1616+/-327 pmol per liter], P=0.004, respectively). The patients' plasma norepinephrine responses were also reduced during sleep, whereas their plasma cortisol concentrations did not increase and their plasma growth hormone concentrations increased slightly. The patterns of counterregulatory-hormone responses in the normal subjects were similar. CONCLUSIONS: Sleep impairs counterregulatory-hormone responses to hypoglycemia in patients with diabetes and normal subjects.     

Effects of fatty acids and hormones on fatty acid metabolism and gluconeogenesis in bovine hepatocytes

Primary cultures of hepatocytes were used to study the effects of extracellular oleate concentration and hormones on fatty acid metabolism and gluconeogenesis. Rates of oleate uptake and oxidation to acid-soluble products varied linearly as oleate concentrations increased (0.1 to 2 mM), but rates of triglyceride accumulation varied quadratically. Insulin increased the proportion of oleate that was esterified by 22% without affecting the formation of acid-soluble products. Cells incubated with 2 mM [1-(14)C]oleate for 24 h eliminated 9.6% of the labeled intracellular lipid as acid-soluble products in the following 24 h when no oleate was present during depletion and eliminated 7.7% when 2 mM oleate was present. Insulin reduced labeled triglyceride depletion by 49%. Gluconeogenesis from [2-(14)C] propionate was depressed by 24%, and formation of acid-soluble products was increased by 46% in cells infiltrated with lipid because of previous exposure to 2 mM oleate for 45 h. Rates of gluconeogenesis from propionate were reduced 23% when 2 mM oleate was present during the 3-h period that gluconeogenesis was measured, and the effect was not modified by lipid infiltration. Lipid infiltration influenced hepatic function, and insulin regulated hepatic triglyceride concentration.     

Auditory information processing during acute insulin-induced hypoglycaemia in non-diabetic human subjects

Acute insulin-induced hypoglycaemia impairs performance on tests of general mental ability in humans. It is recognized that different brain functions vary in their sensitivity to neuroglycopenia, but little is known about the effects of neuroglycopenia on specific brain processes. The effect of controlled hypoglycaemia on two aspects of auditory information processing (auditory temporal processing and simple auditory processing) was examined in a homogeneous group of 20 healthy non-diabetic human subjects. Auditory temporal processing (temporal order discrimination) and simple auditory processing (pitch discrimination, single-tone duration and single-tone loudness discrimination) tests were part of the Test of Basic Auditory Capabilities (TBAC). Two tests of general cognitive performance (Digit Symbol Substitution and Trail Making B) were included to provide a measure of general brain functioning during hypoglycaemia. Hypoglycaemia lead to a significant deterioration in auditory temporal processing (P < 0.01), and a deterioration in one of three tasks of simple auditory processing (discrimination of single-tone loudness, P < 0.05). Significant disruptions also occurred in both tests of general brain functioning. These results are congruent with other studies in human subjects, showing a disruptive effect of hypoglycaemia on visual information processing when examined under conditions of limited perceptual time, and they provide further evidence of the importance of sensory processing speed in basic perceptual and cognitive functions. The disruptive effect of moderate insulin-induced hypoglycaemia on auditory perception may have implications for insulin-treated diabetic humans exposed to this metabolic stress, because of the importance of hearing in everyday life.     

The reliability of lactate measurements during exercise

The study of the epidemiology of dementia, specifically Alzheimer's disease, in developing countries requires specialized instruments and personnel. Cultural and sub-cultural differences among populations are highly relevant to the design of such instruments. Over and above the cultural issues, it is widely recognized that low education and illiteracy pose considerable challenges to reliable and valid cognitive screening. The overall objectives of the Indo-US Cross-National Dementia Epidemiology Study were: a) to determine the prevalence and incidence of, and risk factors for, Alzheimer's and other dementias in a defined Indian community; and b) to compare these results with those found in a defined American community. To achieve these epidemiological objectives, our first task was to develop, systematically and empirically, suitable cognitive and activities assessment screening instruments for use in India, which would 1) be culturally fair, psychometrically sound, and valid for a population with little or no education; 2) be optimally sensitive and specific for dementia; and 3) allow not only the identification but also the more detailed characterization of dementia, and of normal and abnormal cognitive aging. In this paper we address the practical issues involved in the development and administration of the modified cognitive screening battery in our rural Indian context.     

Continuous measurement of subcutaneous lactate concentration during exercise by combining open-flow microperfusion and thin-film lactate sensors

The present study was carried out to investigate in vivo in healthy humans the method of open-flow microperfusion for monitoring of the subcutaneous (s.c.) lactate concentration during rest and cycle ergometer exercise. Using open-flow microperfusion, a perforated double lumen catheter with an inflow and an outflow connection is inserted into the s.c. adipose tissue and perfused with a sterile, isotonic, ionfree fluid. Due to the low flow rate, the fluid partially equilibrates with the surrounding tissue. The equilibrated perfusate passes a sensor flow chamber where the substance of interest and the rate of recovery (i.e. the ratio of sampled concentration to interstitial concentration) are continuously monitored. Within this study, the method was evaluated in four healthy volunteers during cycle ergometer exercise. The relative increase of the lactate concentration was approximately a third in the s.c. tissue compared to the capillary blood and the peak time was delayed on average by 10 min. The correlation coefficient between blood and s.c. tissue lactate concentration ranged from r = 0.41 to r = 0.90 (n = 29) in the individual experiments. The combination of open-flow microperfusion and lactate and conductivity sensors enables on-line monitoring of the s.c. lactate concentration without in vivo calibration during steady-state and cycle ergometer exercise.