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.     

Lactate metabolism of subcutaneous adipose tissue studied by open flow microperfusion

Open flow microperfusion and a novel calibration technique (ionic reference technique) were evaluated for the frequent measurement of the absolute lactate concentration in sc adipose tissue. Furthermore, the influence of the plasma insulin concentration on the lactate concentration of sc adipose tissue was investigated during hyperglycemia. Sixteen lean healthy young men participated in the studies. In the postabsorbtive state the mean sc lactate concentrations were 1.29 and 1.36 mmol/L for the ionic reference technique and the no net flux protocol, respectively (not significant, P > 0.05). The simultaneously measured arterialized plasma lactate concentration was significantly lower at 0.77 mmol/L (P < 0.05). Both the sc lactate concentration (1.8+/-0.33 mmol/L) and the plasma lactate concentration (0.96+/-0.03 mmol/L) were significantly elevated during a hyperinsulinemic euglycemic clamp experiment. During a hyperglycemic clamp experiment the sc lactate concentration reached a significantly elevated plateau (2.15+/-0.27 mmol/L) that was not influenced by the increasing plasma insulin concentration. It is concluded that 1) open flow microperfusion combined with the ionic reference technique enables frequent measurement of the sc lactate concentration; 2) sc adipose tissue is a significant source of lactate release in the postabsorbtive state as well as during hyperinsulinemic clamp conditions; and 3) insulin concentrations greater than 180 pmol/L have no further influence on adipocyte stimulation of sc adipose tissue with respect to lactate release.     

Reproducibility of the first-phase insulin response to intravenous glucose is not improved by retrograde cannulation and arterialization or the use of a lower glucose dose

OBJECTIVE: To determine whether the reproducibility of the first-phase insulin response (FPIR) measured during an intravenous glucose tolerance test is improved by the use of a lower glucose dose or retrograde sampling from an arterialized hand vein. RESEARCH DESIGN AND METHODS: Previous studies have suggested that the high within-subject variation of FPIR measurement of up to 110% could be reduced by sampling from a retrograde cannulated and arterialized hand vein opposite to the cubital fossa vein through which the glucose was injected or by the use of a lower dose of glucose. Two low-dose (glucose, 5 g/m2 injected over 30 s) and two standard Islet Cell Antibody Registry Users Study (ICARUS) (glucose, 0.5 g/kg injected over 3 min) tests were performed on seven normal subjects at 2-week intervals. Samples were collected simultaneously from the cubital fossa vein, through which the glucose was injected, and from a retrograde cannulated, contralateral hand vein that was arterialized by heating. FPIR was expressed as the sum of the insulin measurements 1 and 3 min after the completion of the glucose injection and as the area under the insulin curve between 0 and 10 min. RESULTS: Responses to the mean sum of serum insulin concentrations at 1 and 3 min after intravenous glucose were significantly lower for the low-dose test (mean 94 mU/l) than for the high-dose test (mean 184 mU/l) for samples taken from the arm (P < 0.05); mean 0- to 10-min insulin areas were 367 and 596 mU/l for low- and high-dose tests, respectively (P < 0.05). Within-subject coefficients of variation for samples from the hand or the arm ranged from 0.33 to 17.5% and 1.3 to 38% for successive ICARUS and low-dose tests, respectively. Reproducibility, measured by the coefficient of variation between successive tests for each protocol, was not significantly different using samples taken from the arm or the contralateral hand. CONCLUSIONS: The intravenous glucose tolerance test is reproducible when performed by the same operator over a short time span. Reproducibility is not significantly improved by sampling from an arterialized, retrograde cannulated, contralateral hand vein. There is no case for changing the present ICARUS protocol to incorporate retrograde cannulation or low-dose (5 g/m2) glucose.     

Alterations in glucose metabolism in the elderly patient with diabetes

OBJECTIVE: To determine the alterations in glucose metabolism in elderly patients with NIDDM. RESEARCH DESIGN AND METHODS: We studied 9 healthy elderly control subjects (73 +/- 1 yr of age; body mass index 25.7 +/- 0.4 kg/m2) and 9 untreated elderly NIDDM patients (72 +/- 2 yr of age; BMI 25.9 +/- 0.5 kg/m2). Each subject underwent a 3-h oral glucose tolerance test (40 g/m2); a 2-h hyperglycemic glucose clamp study (glucose 5.4 mM above basal); and a 4-h euglycemic insulin clamp (40 mM.m2.min-1). Tritiated glucose methodology was used to measure glucose production and disposal rates during the euglycemic clamp. RESULTS: Patients with NIDDM had a higher fasting glucose (9.3 +/- 0.3 vs. 5.1 +/- 0.1 mM in control subjects vs. NIDDM patients, respectively, P < 0.001) and a greater area under the curve for glucose during the OGTT (16.0 +/- 0.6 vs. 6.7 +/- 0.3 mM in control subjects vs. NIDDM patients, respectively, P < 0.01) than the healthy control subjects. During the hyperglycemic clamp, patients with NIDDM had an absent first-phase insulin response (112 +/- 6 vs. 250 +/- 31 pM in control subjects vs. NIDDM patients, respectively, P < 0.01), and a blunted second-phase insulin response (159 +/- 11 vs. 337 +/- 46 pM in control subjects vs. NIDDM patients, respectively, P < 0.01). Before the euglycemic clamp, fasting insulin (99 +/- 5 vs. 111 +/- 10 pM in control subjects vs. NIDDM patients, respectively) and hepatic glucose production (11.8 +/- 0.7 vs. 11.5 +/- 0.5 mumol.kg-1-min-1 in control subjects vs. NIDDM patients, respectively) were similar. Steady-state (180-240 min) glucose disposal rates during the euglycemic clamp were slightly, but not significantly, higher in the normal control subjects (36.5 +/- 1.1 vs. 33.1 +/- 1.9 mumol.kg-1-min-1 in control subjects vs. NIDDM patients, respectively, NS). CONCLUSIONS: We conclude that NIDDM in nonobese elderly subjects is characterized by a marked impairment in insulin release. This may be attributable to the toxic effects of chronic hyperglycemia on the beta-cell. When compared with age-matched control subjects, the NIDDM patients showed no increase in fasting insulin or hepatic glucose production, and insulin resistance was mild.     

Effects of methyltestosterone on insulin secretion and sensitivity in women

The frequent coexistence of hyperandrogenism and insulin resistance is well established; however, whether a cause and effect relationship exists remains to be established. In this study we tested the hypothesis that short-term androgen administered to women would induce insulin resistance. To test this hypothesis, regularly menstruating, nonobese women were studied before and during methyltestosterone administration (5 mg tid for 10-12 days) by the hyperglycemic (n=8) and euglycemic, hyperinsulinemic (n=7) clamp techniques. Short-term methyltestosterone administration had no significant effects on the fasting levels of glucose, insulin, c-peptide, glucagon, or glucose turnover. During the hyperglycemic clamp studies, the mean glucose level during the final hour was 203+/-2 and 201+/-1 mg/dL in the methyltestosterone and control studies, respectively. The insulin response to this hyperglycemic challenge was slightly but not significantly greater during methyltestosterone treatment (first phase 59+/-8 vs. 50+/-8 microU/mL in controls; second phase 74+/-9 vs. 67+/-9 microU/mL in controls; total insulin response 133+/-16 vs. 117+/-15 microU/mL in controls). In spite of this, glucose uptake was reduced from the control study value of 10.96+/-1.11 to 7.3+/-0.70 mg/kg/min by methyltestosterone (P < 0.05). The ratio of glucose uptake per unit of insulin was also significantly reduced from a control study value of 14.3+/-1.4 to 9.4+/-1.3 mg/kg/min per microU/mL x 100 during methyltestosterone administration. In the euglycemic hyperinsulinemic clamp studies, insulin was infused at rates of 0.25 and 1.0 mU/kg/min to achieve insulin levels of approximately 25 and 68 microU/mL, respectively. During low-dose insulin infusion, rates of endogenous hepatic glucose production were equivalently suppressed from basal values of 2.37+/-0.29 and 2.40+/-0.27 mg/kg/min to 0.88+/-0.25 and 0.77+/-0.26 mg/kg/min in the methyltestesterone and control studies respectively. Whole body glucose uptake during low-dose insulin infusion was minimally affected. During the high-dose insulin infusion, endogenous hepatic glucose production was nearly totally suppressed in both groups. However, whole body glucose uptake was reduced from the control value of 6.11+/-0.49 mg/kg/min to 4.93+/-0.44 mg/kg/min during methyltestosterone administration (P < 0.05). Our data demonstrate that androgen excess leads to the development of insulin resistance during both hyperglycemic and euglycemic hyperinsulinemia. These findings provide direct evidence for a relationship between hyperandrogenemia and insulin resistance, and its associated risk factors for cardiovascular disease.     

In vivo and in vitro regulation of hepatic glucagon receptor mRNA concentration by glucose metabolism

We have recently cloned the murine glucagon receptor (GR) gene and shown that it is expressed mainly in liver. In this organ, the glucagon-GR system is involved in the control of glucose metabolism as it initiates a cascade of events leading to release of glucose into the blood stream, which is a main feature in several physiological and pathological conditions. To better define the metabolic regulators of GR expression in liver we analyzed GR mRNA concentration in physiological conditions associating various glucose metabolic pathways in vivo and in vitro in the rat and in the mouse. First, we report that the concentration of the GR mRNA progressively increased from the first day of life to the adult stage. This effect was abolished when newborn rodents were fasted. Second, under conditions where intrahepatic glucose metabolism was active such as during fasting, diabetes, and hyperglycemic clamp, the concentration of GR mRNA increased independent of the origin of the pathway that generated the glucose flux. These effects were blunted when hyperglycemia was corrected by phlorizin treatment of diabetic rats or not sustained during euglycemic clamp. In accordance with these observations, we demonstrated that the glycolytic substrates glucose, mannose, and fructose, as well as the gluconeognic substrates glycerol and dihydroxyacetone, increased the concentration of GR mRNA in primary cultures of hepatocytes from fed rats. Glucagon blunted the effect of glucose without being dominant. The stimulatory effect of those substrates was not mimicked by the nonmetabolizable carbohydrate L-glucose or the glucokinase inhibitor glucosamine or when hepatocytes were isolated from starved rats. In addition, inhibitors of gluconeogenesis and lipolysis could decrease the concentration of GR mRNA from hepatocytes of starved rats. Combined, these data strongly suggest that glucose flux in the glycolytic and gluconeogenic pathways at the level of triose intermediates could control expression of GR mRNA and participate in controlling its own metabolism.     

Acute and chronic effects of insulin on leptin production in humans: Studies in vivo and in vitro

This study was undertaken to investigate the changes in obesity (OB) gene expression and production of leptin in response to insulin in vitro and in vivo under euglycemic and hyperglycemic conditions in humans. Three protocols were used: 1) euglycemic clamp with insulin infusion rates at 40, 120, 300, and 1,200 mU / m / min carried out for up to 5 h performed in 16 normal lean individuals, 30 obese individuals, and 31 patients with NIDDM; 2) 64-to 72-h hyperglycemic (glucose 12.6 mmol/l) clamp performed on 5 lean individuals; 3) long-term (96-h) primary culture of isolated abdominal adipocytes in the presence and absence of 100 nmol/l insulin. Short-term hyperinsulinemia in the range of 80 to > 10,000 microU/ml had no effect on circulating levels of leptin. During the prolonged hyperglycemic clamp, a rise in leptin was observed during the last 24 h of the study (P < 0.001). In the presence of insulin in vitro, OB gene expression increased at 72 h (P < 0.01), followed by an increase in leptin released to the medium (P < 0.001). In summary, insulin does not stimulate leptin production acutely; however, a long-term effect of insulin on leptin production could be demonstrated both in vivo and in vitro. These data suggest that insulin regulates OB gene expression and leptin production indirectly, probably through its trophic effect on adipocytes.     

Some implications for quantitative risk assessment if hormesis exists

Insulin resistance is associated with hyperleptinemia, whilst exposure of hepatoma cells and isolated adipocytes to high concentrations of leptin has been demonstrated to result in attenuated insulin response and a reduced suppression of gluconeogenesis. To determine the acute metabolic effects of hyperleptinemia, we measured whole body glucose uptake (WBU) and hepatic glucose production rate (HGP) in rats using the euglycemic hyperinsulinemic clamping technique. Anesthetised male rats received recombinant murine leptin (1 microg/min) or vehicle into the jugular vein for 90 min. After 30 min of leptin infusion, insulin was infused to a level of 70 microU/ml and a variable-rate glucose infusion was adjusted to maintain blood glucose levels to 4-4.5 mmol/l. Glucose infusion rates during clamping were not different between leptin-infused and control rats, and there were no significant effects on the HPR or WBU measured using [6-(3)H]glucose under basal or clamped conditions. In summary, our data demonstrate that acute hyperleptinemia in normal weight Wistar rats does not appear to reduce insulin sensitivity, in vivo, or to affect HPR under clamp conditions.     

The effect of systemic venous drainage of the pancreas on insulin sensitivity in dogs

To assess the metabolic consequences of the diversion of the pancreatic venous drainage to the systemic circulation, the pancreaticoduodenal and gastrosplenic veins were anastomosed to the inferior vena cava in nine normal dogs. This procedure maintained the integrity of the entire pancreas while shunting the hormonal output of the pancreas to the periphery. The metabolic effects were assessed from the sensitivity to insulin during a euglycemic hyperinsulinemic glucose clamp using an insulin infusion of 800 microU/kg per min. The studies were controlled by their duplication in seven dogs identically treated but with the pancreatic veins reanastomosed to the portal vein. No differences in systemic insulin levels or insulin sensitivity before and after surgery were seen under these circumstances. After diversion, however, basal insulin levels rose from 4.5 +/- 1.0 to 11.5 +/- 2.5 microU/ml. Basal glucose metabolic clearance rate (MCR) rose to 3.0 +/- 0.4 from 2.0 +/- 0.3 ml/kg per min. On insulin infusion, maximal stimulation of MCR within the 2-h infusion period was to 15.2 +/- 2.5 ml/kg per min preoperatively and to 7.2 +/- 0.8 ml/kg per min after diversion. Using ratios of MCR-to-insulin concentration as an index of insulin sensitivity, it was demonstrated that this index decreased by at least 50% after diversion. These data imply that portal venous drainage of the pancreas is an important factor in the determination of peripheral insulin sensitivity.     

Circadian rhythmicity of heart rates in centenarians]

Insulin and branched-chain amino acid (BCAA) metabolism was studied in 14 adolescents with uremia on hemodialysis. Glucose tolerance was measured by intravenous glucose tolerance tests. Insulin sensitivity was measured by the euglycemia clamp technique. Insulin secretion during constant hyperglycemia was measured by the hyperglycemic clamp technique. Fasting plasma BCAA concentrations were compared with data from 8 adolescent controls, whereas insulin indices were compared with 8 young adults controls and with published normal data in adolescents. The patients could be further sub-divided into two groups with respect to their growth velocity standard deviation score (GVSDS). Group 1 consisted of 7 patients with GVSDS less than -2. This group demonstrated insulin resistance, glucose intolerance, and low insulin secretion. This group also had low plasma valine, leucine, and isoleucine concentrations compared with control values. Group 2 consisted of 7 patients with GVSDS more than -2. This group demonstrated insulin resistance, but normal glucose tolerance and normal insulin secretion. Plasma valine, leucine, and isoleucine concentrations in group 2 were not different from control values. Total plasma BCAA correlated with glucose tolerance index and with insulin secretion, but not with insulin sensitivity. Growth failure in uremia is associated with glucose intolerance, hypoinsulinemia, and low plasma BCAA concentrations. Impaired utilization of conventional energy sources leading to preferential oxidation of BCAA may contribute to reduced anabolism and growth failure in uremia.     

Effects of hyperchloremia on blood oxygen binding in healthy calves

Three different levels of hyperchloremia were induced in healthy Friesian calves to study the effects of chloride on blood oxygen transport. By infusion, the calves received either 5 ml/kg of 0.9% NaCl (low-level hyperchloremia; group A), 5 ml/kg of 7.5% NaCl (moderate hyperchloremia; group B), or 7.5 ml/kg of 7.5% NaCl (high-level hyperchloremia; group C). Blood was sampled from the jugular vein and the brachial artery. Chloride concentration, hemoglobin content, arterial and venous pH, PCO2, and PO2 were determined. At each time point (0, 15, 30, 60, and 120 min), the whole blood oxygen equilibrium curve (OEC) was measured under standard conditions. In groups B and C, hyperchloremia was accompanied by a sustained rightward shift of the OEC, as indicated by the significant increase in the standard PO2 at 50% hemoglobin saturation. Infusion of hypertonic saline also induced relative acidosis. The arterial and venous OEC were calculated, with body temperature, pH, and PCO2 values in arterial and venous blood taken into account. The degree of blood desaturation between the arterial and the venous compartments [O2 exchange fraction (OEF%)] and the amount of oxygen released at tissue level by 100 ml of bovine blood (OEF vol%) were calculated from the arterial and venous OEC combined with the PO2 and hemoglobin concentration. The chloride-induced rightward shift of the OEC was reinforced by the relative acidosis, but the altered PO2 values combined with the lower hemoglobin concentration explained the absence of any significant difference in OEF (% and vol%). We conclude that infusion of hypertonic saline induces hyperchloremia and acidemia, which can explain the OEC rightward shift observed in arterial and peripheral venous blood.     

Two-stage arterialized flow-through venous flap transfer for third-degree burn defects on the dorsum of the hand

A modified, two-stage arteriovenous flow-through venous flap was designed to repair skin defects due to third-degree burns on the dorsum of the hand in four patients. Two weeks after plasty of an arteriovenous (A-V) shunt between the greater saphenous vein and dorsalis pedis artery, the arterialized flow-through venous flap was transferred using the greater saphenous vein as the pedicle. The size of the flaps utilized ranged from 7 x 13 cm to 9 x 13 cm. In three patients the entire flap survived without complication. In one patient whose flap had only one drainage vein, the flap survived with superficial necrosis of about 10 percent of the flap at the borders. During the 2 weeks after A-V shunt creation, the authors believe that microcirculation around the arterialized vein probably develops, contributing to better irrigation and thereby to flap survival. Using this two-stage procedure, it might be feasible to obtain larger grafts and to attain a higher flap survival rate.     

Lactate release and uptake in hepatoma 7288CTC perfused in situ with L-[(U)-14C]lactate or D-[(U)-14C]glucose

Arteriovenous differences (AVD) for glucose and lactic acid measured across tissue-isolated rat tumors in vivo have shown that individual tumors with similar rates of glucose consumption may either release or utilize lactic acid. The experiments described here investigated the relationships among arterial blood lactate concentrations and tumor lactate and glucose balances. AVDs for lactate, pyruvate, glucose, 14CO2, PO2, PCO2, pH, and lactate specific activities were measured across 17 tissue-isolated 7288CTC hepatomas perfused in situ with arterial blood containing 2.5 to 14.4 mmol/L lactate and either L-[(U)-14C]lactic acid or D-[(U)-14C]glucose. Measurements were made over a range of blood flow rates from 60% to 200% of the mean in vivo rate, 0.11 mL/min. Data collected during steady states were compared by regression analysis. Tumor lactate balance and the arterial blood lactate concentration were directly related (r = .895, n = 22, P < .01). Net negative and positive balances occurred below and above approximately 6.5 mmol/L arterial blood lactate, respectively. The mean intratumor lactate concentration for all tumors was 6.9 +/- 1.0 mmol/L (mean +/- SD, n = 13). Rates of 14C-lactate oxidation to 14CO2 (r = .716, n = 18, P < .01) and tumor venous/arterial blood 14C-lactate specific activity ratios (r = .845, n = 19, P < .01) were low during lactate release and were increased during lactate uptake. Total arterial blood lactate removal estimated from chemical and isotopic analyses was 23.1% +/- 11% and 43.0% +/- 16% (P < .05), respectively, for six lactate-utilizing tumors. Perfusions performed with 14C-glucose showed that approximately 50% of the glucose consumed during net negative lactate balance was released as 14C-lactate to the tumor venous blood, whereas only 5% was released as 14C-lactate during net positive lactate balance. The data support the following conclusions: Arterial blood lactate controls net lactate balance in solid tumors; high concentrations increase uptake. Lactate uptake inhibits lactate formation from glucose without changing the glucose balance. Lactate is release during net lactate uptake. Since lactate uptake may exceed glucose uptake, arterial blood lactate can be a substrate for tumor energy metabolism and growth.     

Effect of metabolic acidosis on insulin action and secretion in uremia

BACKGROUND: Metabolic acidosis affects both vitamin D and insulin metabolism. Vitamin D is important in modulation of both insulin secretion and insulin sensitivity in uremia. The present study examines the effect of correction of metabolic acidosis on insulin action and secretion as well as 1,25 vitamin D3 concentrations in uremic patients. METHODS: Eight patients (age 18 +/- 1 year) on maintenance hemodialysis with metabolic acidosis were studied before and after two weeks of oral sodium bicarbonate (NaHCO3) treatment to correct the acidosis. To control for the effect of additional sodium, they were also studied after two weeks of an equivalent amount of oral sodium chloride (NaCl). Controls consisted of 7 healthy controls (age 19 +/- 1 year). Insulin sensitivity was measured by the hyperinsulinemic euglycemic clamp technique. Insulin secretion was measured by the hyperglycemic clamp technique. RESULTS: Oral NaHCO3 treatment led to significant increases in venous pH and serum bicarbonate concentrations but no significant change in intact parathyroid hormone (PTH) concentrations. Circulating 1,25 dihydroxyvitamin [(OH)2] D3 were significantly lower than control values initially and increased significantly after treatment. Oral NaCl did not change any of the biochemical parameters. Before treatment of acidosis, uremic patients had lower insulin sensitivity (insulin resistance) during constant hyperinsulinemia and lower insulin secretion during constant hyperglycemia compared with controls. Following two weeks of NaHCO3 treatment there were significant increases in insulin sensitivity and insulin secretion, although the values did not normalize. There were no changes in insulin sensitivity or insulin secretion following two weeks of NaCl. CONCLUSION: Treatment of metabolic acidosis increased both insulin sensitivity and insulin secretion in patients with uremia. This was accompanied by an increase in the circulating levels of 1,25(OH)2D3 but no change in those of parathyroid hormone.     

Comparative pharmacokinetics and glucodynamics of two human insulin mixtures. 70/30 and 50/50 insulin mixtures

OBJECTIVE: To compare and contrast the pharmacokinetics and glucodynamics of two insulin mixtures, one of 50% NPH human insulin and 50% Regular human insulin (50/50) and one of 70% NPH human insulin and 30% Regular human insulin (70/30), in healthy male volunteers after subcutaneous administrations of 0.3 U/kg. RESEARCH DESIGN AND METHODS: We administered single doses of 50/50 and 70/30 insulins to 18 volunteers in a randomized crossover fashion. All subjects received 0.3 U/kg of each mixture separated by at least 7 days. Each dose was given after an overnight fast and during a glucose clamp to maintain a euglycemic state. We measured serum insulin and C-peptide concentrations through frequent blood sampling after each treatment. Pharmacokinetic measurements were calculated from insulin data corrected for C-peptide, including maximum insulin concentration (Cmax), time to maximum insulin concentration (tmax), terminal rate constant (beta), area under the curve from 0 to infinity (AUCinfinity0), and mean residence time (MRT). Pharmacodynamic measurements were summarized from C-peptide concentrations (minimum C-peptide concentration [Cmin], time to minimum C-peptide concentration [tmin], area between the C-peptide baseline and the C-peptide suppression curve [AOCc], absolute maximal difference from baseline [Sdiff] and glucose clamp measurements. The glucose clamp measurements included maximum infusion rates (Rmax) and time to Rmax (TRmax) from glucose infusion rate (GIR) documentation, as well as cumulative glucose infused during the first 4 h ((0)4Gtot) and total glucose infused (Gtot) during the study. RESULTS: For the pharmacokinetic assessment, statistically greater values of insulin Cmax and beta were found for the 50/50 mixture, whereas the 70/30 mixture had a greater MRT. Statistical differences were also detected in glucodynamics, with greater values of Rmax and (0)4Gtot found with the 50/50 mixture. Notably, differences were not detected for insulin AUCinfinity0 and Gtot values. CONCLUSIONS: Higher insulin concentrations and a greater initial response were present with the 50/50 mixture, but the two mixtures had equivalent bioavailability and cumulative effects. These results support use of the 50/50 mixture in situations where greater initial glucose control is required.     

Relation of the white blood cell count to obesity and insulin resistance: effect of race and gender

Recent reports suggest that the white blood cell (WBC) count is related to plasma insulin concentrations and insulin resistance in healthy individuals. The present study examines whether these relations are independent of obesity and the pattern of body fat distribution and tests whether race and gender affect these relations. WBC counts, insulin responses to a 75 gram oral glucose tolerance test (OGTT) and glucose disposal during a two-step hyperinsulinemic euglycemic clamp were measured in 300 men and women (149 Pima Indians, 100 whites, and 51 blacks) with a wide range of obesity. WBC counts were lower in blacks than Pima Indians or whites and tended to be higher in women than men. The subgroups were comparable in age and body weight, but percent body fat and plasma insulin concentrations were higher and glucose disposal during the glucose clamp was lower in Pima Indians than in blacks or whites. In the group as a whole, the WBC count correlated with obesity (body mass index and percent body fat), the waist to thigh ratio (an index of the pattern of body fat distribution), and plasma insulin concentrations and was negatively related to age and glucose disposal during the clamp. In multiple regression analyses, only age, race and obesity were significantly associated with the WBC count. When the analyses were restricted to Pima men, in whom correlations between the WBC count and the metabolic variables appeared the strongest, the WBC count remained significantly associated with plasma insulin concentrations, but not glucose disposal, after controlling for age and obesity. The results of this study indicate that age, race, and obesity are significantly associated with the WBC count in healthy individuals. Plasma insulin concentrations, but not insulin resistance per se, may also be weakly associated with the WBC count, but this may be population specific.     

Heritable disorder resembling neuronal storage disease in mice expressing prion protein with deletion of an alpha-helix

Ethanol abuse is frequently associated with protein malnutrition. To assess the acute effects of ethanol on whole-body protein metabolism, [1-13C]leucine kinetics were measured in eight postabsorptive normal male subjects three times, ie, during administration of two doses of ethanol (dose 1, 0.52 g/kg during 2 hours and 0.3 g/kg during 3 hours; dose 2, 0.69 g/kg during 2 hours and 0.3 g/kg during 3 hours) and during saline (controls). During the last 2 hours of the studies, glucose, insulin, and amino acids were infused to assess the effects of ethanol on protein kinetics under anabolic conditions (euglycemic clamp). The decreases in leucine flux (reflecting whole-body protein breakdown) and nonoxidative leucine disappearance (a parameter of protein synthesis) during saline infusion were abolished in both ethanol protocols (P < .05 or less v saline). The rate of leucine oxidation decreased during the higher dose of ethanol compared with saline (P < .005), indicating an anticatabolic effect. During anabolic conditions (clamp), leucine flux and nonoxidative leucine disappearance were significantly higher in both ethanol studies compared with saline (P < .05). Resting energy expenditure (REE) and oxygen consumption (VO2) during the euglycemic clamp increased to a greater degree during both ethanol studies than during saline (P < .05 or less). Thus, an elevation of blood ethanol concentrations to the levels observed in social drinking results in a net anticatabolic effect (diminished leucine oxidation) when ethanol is administered alone. However, during administration of other nutritional substrates, the anticatabolic effect was not detectable, possibly because ethanol enhanced nutrient-induced thermogenesis.     

Surgical creation of portacaval shunts during temporary intestinal arterial and venous occlusion in dogs

OBJECTIVE: To surgically create complete portacaval shunts in dogs during temporary arrest of intestinal arterial and portal venous blood flow. DESIGN: Complete portacaval anastomoses were surgically created, and liver function was evaluated for 14 to 18 weeks after surgery. ANIMALS: 32 adult mixed-breed dogs of either sex. PROCEDURE: Administration of deferoxamine and temporary intestinal arterial occlusion were used to minimize the intestinal cellular damage resulting from the complete, temporary arrest of portal venous blood flow during creation of the portacaval anastomosis. Side-to-side, appositional anastomoses ( > 2 cm diameter) were formed between the portal vein and caudal vena cava. Dogs were observed daily for signs of hepatic encephalopathy, and food intake was recorded. Body weight was recorded weekly. Preprandial plasma ammonia, serum urea nitrogen, and glucose concentrations and sulfobromophthalein retention were measured monthly. The dogs were euthanatized, and necropsy was performed 14 to 18 weeks after surgery. RESULTS: 30 of 32 dogs recovered without complications. Complete portosystemic shunting was documented by increased plasma ammonia concentration, decreased serum urea nitrogen and glucose concentrations, prolonged sulfobromophthalein retention (P < 0.01), and inspection at necropsy. CONCLUSION: This method of providing temporary, complete arrest of portal venous blood flow was helpful in allowing accurate, appositional portacaval anastomoses to be created that remained patent for 14 to 18 weeks. CLINICAL RELEVANCE: This method of providing temporary, complete arrest of portal venous blood flow may prove useful in clinical surgery when temporary arrest of portal blood flow is desired.     

Abnormalities in oxygenation, coagulation, and fibrinolysis in colonic blood of horses with experimentally induced strangulation obstruction

OBJECTIVE: To measure arterial and venous blood gas, coagulation, and fibrinolysis variables in blood from isolated segments of control and ischemic large colons for the purpose of identifying variables for rapid, indirect assessment of colonic mucosal injury. DESIGN: Variables were determined at specific intervals during the 4-hour study (3 hours of ischemia and 1 hour of reperfusion). ANIMALS: Seven clinically normal horses between 2 and 15 years old. PROCEDURES: Horses underwent laparotomy and occlusion of the lumen and vasculature of the mid-portion of the pelvic flexure of the large colon. During ischemia of 1 randomly-chosen colonic segment, variables were measured to determine colonic mucosal damage and were compared with histologic scores of colonic biopsy specimens. RESULTS: Significant (P < 0.05) differences from control values were observed over time for venous pH, PCO2, PO2, oxygen saturation, oxygen content, arteriovenous oxygen difference, and lactate and glucose concentrations. Mean histologic scores of biopsy specimens obtained from ischemic colons were significantly (P < 0.05) greater (indicating greater damage) than those from control colons, and increased significantly (P < 0.05) with duration of ischemia. CONCLUSIONS: Venous lactate, oxygen saturation, and PO2 values were the most significant predictors of the severity of histologic damage within the ischemic colons (R2 = 0.661). CLINICAL RELEVANCE: Venous blood gas and lactate values in the large colon are good predictors of the amount of intestinal damage incurred during 3 hours of ischemia, and may be clinically useful for the rapid determination of colonic viability.