HMG-1 as a late mediator of endotoxin lethality in mice.

Endotoxin, a constituent of Gram-negative bacteria, stimulates macrophages to release large quantities of tumor necrosis factor (TNF) and interleukin-1 (IL-1), which can precipitate tissue injury and lethal shock (endotoxemia). Antagonists of TNF and IL-1 have shown limited efficacy in clinical trials, possibly because these cytokines are early mediators in pathogenesis. Here a potential late mediator of lethality is identified and characterized in a mouse model. High mobility group-1 (HMG-1) protein was found to be released by cultured macrophages more than 8 hours after stimulation with endotoxin, TNF, or IL-1. Mice showed increased serum levels of HMG-1 from 8 to 32 hours after endotoxin exposure. Delayed administration of antibodies to HMG-1 attenuated endotoxin lethality in mice, and administration of HMG-1 itself was lethal. Septic patients who succumbed to infection had increased serum HMG-1 levels, suggesting that this protein warrants investigation as a therapeutic target.

Leupeptin inhibits adrenocorticotropic hormone-induced protein breakdown in the conscious dog.

To elucidate the role of proteinase inhibitors in the regulation of protein breakdown in vivo, we measured the effect of leupeptin on the rate of appearance of leucine in the plasma compartment in overnight-fasted conscious dogs. Two groups of dogs were studied. The control group (I) received saline infusion, and the experimental group (II) was rendered hypercatabolic with daily administration of adrenocorticotropic hormone (ACTH) (500 U/d) for 4 d.ACTH treatment increased plasma cortisol from 2+/-0.4 to 17+/-2 mug/dl (P < 0.005). It raised plasma leucine levels (mumol/liter) from 123+/-6 in I to 206+/-5 in II (P < 0.01) and its rate of appearance into the plasma compartment (micromoles per kilogram per minute) from 3.1+/-0.1 in I to 4.6+/-0.3 in II (P < 0.01). Whole blood alanine concentration (micromoles per liter) increased by 50% (from 387+/-31 to 577+/-53, P < 0.01) and whole blood glutamine concentration (micromoles per liter) increased from 653+/-51 to 917+/-93 (P < 0.01). Leupeptin infusion in the ACTH-treated group significantly decreased both the concentration of plasma leucine and its rate of appearance. Blood glutamine declined by 30% (P < 0.05) after leupeptin, but no effect on blood alanine was observed. Leupeptin had no effect on the saline control group. These data indicate that leupeptin decreases the accelerated rate of protein breakdown induced by cortisol excess. The fact that it did not affect protein degradation in controls may indicate that control of protein breakdown in the postabsorptive state may differ from that during accelerated turnover. Thus, the antibiotic proteinase enzyme inhibitors may be potentially useful in treating conditions of inappropriate protein breakdown.

Beta-endorphin inhibits glucose production in the conscious dog.

The effect of human beta-endorphin (h beta E) infusion (0.2 mg/h) on glucose homeostasis was studied in 10 conscious overnight fasted dogs in which endocrine pancreatic function was fixed at basal levels with somatostatin plus intraportal replacement of basal insulin and glucagon. h beta E caused a fall in plasma glucose from 107 +/- 5 to 76 +/- 6 mg/dl by 3 h (P less than 0.01). This was due to a 25% fall in tracer-determined glucose production (Ra; P less than 0.01). A significantly larger fall in Ra was observed in four dogs in which hypoglycemia was prevented by use of an exogenous glucose infusion (45 vs. 25%, P less than 0.05). These changes occurred in the absence of changes in circulating levels of insulin, glucagon, epinephrine, norepinephrine, and cortisol. We conclude that the naturally occurring opioid peptide, beta-endorphin, inhibits glucose production by the liver in vivo. This appears to be a direct effect of the opioid on the liver, since the inhibition took place in the absence of changes in the other hormones measured. These results suggest that endorphins act on glucose homeostasis in a complex way, both by affecting other glucoregulatory hormones as demonstrated elsewhere, and by directly modulating hepatic glucose production as shown here.

Role of insulin in the regulation of leucine kinetics in the conscious dog.

To study the effect of insulin on leucine kinetics, three groups of conscious dogs were studied after an overnight fast (16-18 h). One, saline-infused group (n = 5), served as control. The other two groups were infused with somatostatin and constant replacement amount of glucagon; one group (n = 6) received no insulin replacement, to produce acute insulin deficiency, and the other (n = 6) was constantly replaced with 600 muU/kg per min insulin, to produce twice basal hyperinsulinemia. Hepatic and extrahepatic splanchnic (gut) balance of leucine and alpha-ketoisocaproate (KIC) were calculated using the arteriovenous difference technique. l,4,5,[(3)H]Leucine was used to measure the rates (micromoles per kilogram per minute) of appearance (Ra) and disappearance (Rd), and clearance (Cl) of plasma leucine (milliliters per kilogram per minute). Saline infusion for 7 h resulted in isotopic steady state, where Ra and Rd were equal (3.2+/-0.2 mumol/kg per min). Acute insulin withdrawal of 4-h duration caused the plasma leucine to increase by 40% (P < 0.005). This change was caused by a decrease in the outflow of leucine (Cl) from the plasma, since Ra did not change. The net hepatic release of the amino acid (0.24+/-0.03 mumol/kg per min) did not change significantly; the arterio-deep femoral venous differences of leucine (-10+/-1 mumol/liter) and KIC (-12+/-2 mumol/liter) did not change significantly indicating net release of the amino and ketoacids across the hindlimb. Selective twice basal hyperinsulinemia resulted in a 36% drop in plasma leucine (from control levels of 128+/-8 to 82+/-7 mumol/liter, P < 0.005) within 4 h. This was accompanied by a 15% reduction in Ra and a 56% rise in clearance (P < 0.001, both). Net hepatic leucine production and net release of leucine and KIC across the hindlimb fell markedly. These studies indicate that physiologic changes in circulating insulin levels result in a differential dose-dependent effect on total body leucine metabolism in the intact animal. Acute insulin withdrawal exerts no effect on leucine rate of appearance, while at twice basal levels, insulin inhibited leucine rate of appearance and stimulated its rate of disappearance.

Effects of morphine on glucose homeostasis in the conscious dog.

This study was designed to assess the effects of morphine sulfate on glucose kinetics and on glucoregulatory hormones in conscious overnight fasted dogs. One group of experiments established a dose-response range. We studied the mechanisms of morphine-induced hyperglycemia in a second group. We also examined the effect of low dose morphine on glucose kinetics independent of changes in the endocrine pancreas by the use of somatostatin plus intraportal replacement of basal insulin and glucagon. In the dose-response group, morphine at 2 mg/h did not change plasma glucose, while morphine at 8 and 16 mg/h caused a hyperglycemic response. In the second group of experiments, morphine (16 mg/h) caused an increase in plasma glucose from a basal 99 +/- 3 to 154 +/- 13 mg/dl (P less than 0.05). Glucose production peaked at 3.9 +/- 0.7 vs. 2.5 +/- 0.2 mg/kg per min basally, while glucose clearance declined to 1.7 +/- 0.2 from 2.5 +/- 0.1 ml/kg per min (both P less than 0.05). Morphine increased epinephrine (1400 +/- 300 vs. 62 +/- 8 pg/ml), norepinephrine (335 +/- 66 vs. 113 +/- 10 pg/ml), glucagon (242 +/- 53 vs. 74 +/- 14 pg/ml), insulin (30 +/- 9 vs. 10 +/- 2 microU/ml), cortisol (11.1 +/- 3.3 vs. 0.9 +/- 0.2 micrograms/dl), and plasma beta-endorphin (88 +/- 27 vs. 23 +/- 6 pg/ml); all values P less than 0.05 compared with basal. These results show that morphine-induced hyperglycemia results from both stimulation of glucose production as well as inhibition of glucose clearance. These changes can be explained by rises in epinephrine, glucagon, and cortisol. These in turn are part of a widespread catabolic response initiated by high dose morphine that involves activation of the sympathetic nervous system, the endocrine pancreas, and the pituitary-adrenal axis. Also, we report the effect of a 2 mg/h infusion of morphine on glucose kinetics when the endocrine pancreas is clamped at basal levels. Under these conditions, morphine exerts a hypoglycemic effect (25% fall in plasma glucose, P less than 0.05) that is due to inhibition of glucose production (by 25-43%, P less than 0.05). The hypoglycemia was independent of detectable changes in insulin, glucagon, epinephrine and cortisol, and was not reversed by concurrent infusion of a slight molar excess of naloxone. Therefore, we postulate that the hypoglycemic effect of morphine results from the interaction of the opiate with non-mu receptors either in the liver or the central nervous system.

Transport of glutamine in rat intestinal brush-border membrane vesicles.

Transport of glutamine across the brush-border membrane of the rat intestine was examined using brush-border membrane vesicle (BBMV) technique. Osmolarity and temperature studies indicated that the uptake of glutamine by BBMV is mostly the result of transport of the substrate into the intravesicular space. Transport of glutamine was Na+-gradient dependent (out greater than in) with a distinct 'overshoot' phenomenon. Initial rate of transport of glutamine as a function of concentration was saturable both in the presence and absence of a Na+ gradient (out greater than in). Apparent Km of 3.50 and 3.34 mM and Vmax of 707 and 282 pmol/mg protein per 7 s, were calculated for the Na+-dependent and the Na+-independent transport processes of glutamine. The transport of [3H]glutamine by the Na+-dependent and the Na+-independent processes was severely inhibited by the addition to the incubation medium of other amino acids and unlabelled glutamine. Inducing a relatively negative intravesicular compartment with the use of valinomycin and an outwardly directed K+ gradient stimulated glutamine transport. This indicates that transport of the substrate by the Na+-dependent process is electrogenic in nature. Transport of glutamine by the Na+-independent process, however, appeared to be electroneutral in nature. These results demonstrate the existence of two carrier-mediated transport processes for glutamine in the rat intestinal BBMV, one is Na+-dependent and the other is Na+-independent. Furthermore, the results suggest that glutamine transport by the Na+-dependent process probably occurs by a glutamine/Na+ cotransport mechanism.

Renal glucose production during insulin-induced hypoglycemia.

Recent in vivo studies have rekindled interest in the role of the kidney in glucose metabolism. We therefore undertook the present study to evaluate the contribution of the kidney to systemic glucose production and utilization rates during insulin-induced hypoglycemia using arteriovenous balance combined with a tracer technique. Ten days after the surgical placement of sampling catheters in the right and left renal veins and femoral artery and of an infusion catheter in the left renal artery of dogs, systemic and renal glucose kinetics were measured with the peripheral infusion of [6-3H]glucose. Renal blood flow was determined with a flowprobe. After baseline, six dogs received 2-h simultaneous infusions of peripheral insulin (4 mU x kg(-1) x min(-1)) and left intrarenal [6,6-2H]dextrose (14 micromol x kg(-1) x min(-1)) to achieve and maintain left renal normoglycemia during systemic hypoglycemia. Arterial glucose decreased from 5.3 +/- 0.1 to 2.2 +/- 0.1 mmol/l; insulin increased from 46 +/- 5 to 1,050 +/- 50 pmol/l; epinephrine increased from 130 +/- 8 to 1,825 +/- 50 pg/ml; norepinephrine increased from 129 +/- 6 to 387 +/- 15 pg/ml; and glucagon increased from 52 +/- 2 to 156 +/- 12 pg/ml (all P < 0.01). Systemic glucose appearance increased from 16.6 +/- 0.4 micromol x kg(-1) x min(-1) in the baseline to 24.2 +/- 0.6 micromol x kg(-1) x min(-1) during hypoglycemia when endogenous glucose production was 10.2 +/- 1.0 micromol x kg(-1) x min(-10 (P < 0.01). In the baseline, the liver accounted for 80% (13.3 +/- 0.8 micromol x kg(-1) x min(-1)) and each kidney contributed 10% (1.6 +/- 0.2 micromol x kg(-1) x min(-1)) to endogenous glucose production. During hypoglycemia, however, hepatic glucose production decreased to 4.0 +/- 0.4 micromol x kg(-1) x min(-1), whereas right renal glucose production doubled to 3.2 +/- 0.2 micromol x kg(-1) x min(-1) (P < 0.01). Left renal glucose production was 17 +/- 2 micromol x kg(-1) x min(-1), 14 of which were derived from the exogenous infusion. These results indicate that glucose production by the kidney is stimulated by counterregulatory hormones and represents an important component of the body's defense against insulin-induced hypoglycemia.

Renal lactate metabolism and gluconeogenesis during insulin-induced hypoglycemia.

The contribution of gluconeogenic precursors to renal glucose production (RGP) during insulin-induced hypoglycemia was assessed in conscious dogs. Ten days after surgical placement of sampling catheters in the right and left renal veins and femoral artery and an infusion catheter in the left renal artery, systemic and renal glucose and glycerol kinetics were measured with peripheral infusions of [6-3H]glucose and [2-13C]glycerol. Renal blood flow was determined with a flowprobe, and the renal balance of lactate, alanine, and glycerol was calculated by arteriovenous difference. After baseline, six dogs received 2-h simultaneous infusions of peripheral insulin (4 mU x kg(-1) x min(-1)) and left intrarenal [6,6-2H]dextrose (14 micromol x kg(-1) x min(-1)) to achieve and maintain left renal normoglycemia during systemic hypoglycemia. Arterial glucose decreased from 5.3 +/- 0.1 to 2.2 +/- 0.1 mmol/l; insulin increased from 46 +/- 5 to 1,050 +/- 50 pmol/l; epinephrine, from 130 +/- 8 to 1,825 +/- 50 pg/ml; norepinephrine, from 129 +/- 6 to 387 +/- 15 pg/ml; and glucagon, from 52 +/- 2 to 156 +/- 12 pg/ml (all P < 0.01). RGP increased from 1.7 +/- 0.4 to 3.0 +/- 0.5 (left) and from 0.6 +/- 0.2 to 3.2 +/- 0.2 (right) micromol x kg(-1) x min(-1) (P < 0.01). Whole-body glycerol appearance increased from 6.0 +/- 0.5 to 7.7 +/- 0.7 micromol x kg(-1) x min(-1)(P < 0.01); renal conversion of glycerol to glucose increased from 0.13 +/- 0.04 to 0.30 +/- 0.10 (left) and from 0.11 +/- 0.03 to 0.25 +/- 0.05 (right) micromol x kg(-1) x min(-1), (P < 0.05). Net renal gluconeogenic precursor uptake increased from 1.5 +/- 0.4 to 5.0 +/- 0.4 (left) and from 0.9 +/- 0.2 to 3.8 +/- 0.4 (right) micromol x kg(-1) x min(-1) (P < 0.01). Renal lactate uptake could account for approximately 40% of postabsorptive RGP and for 60% of RGP during hypoglycemia. These results indicate that gluconeogenic precursor extraction by the kidney, particularly lactate, is stimulated by counterregulatory hormones and accounts for a significant fraction of the enhanced gluconeogenesis induced by hypoglycemia.

Insulin's effect on Leucine turnover changes during early fasting in the conscious dog.

To study the effects of insulin on leucine turnover during fasting, acute insulin deficiency was induced by the simultaneous infusion of somatostatin and glucagon in conscious dogs fasted 18 h (N = 10) and 48 h (N = 11). Insulin levels during the basal period (before hormone perturbation) were similar in both groups of dogs (12 +/- 3 versus 10 +/- 3 microU/ml, respectively). Glucagon levels were similar in the two groups (94 +/- 9 versus 106 +/- 19 pg/ml). Leucine levels rose from 118 +/- 9 mumol/L to 155 +/- 12 mumol/L as fasting progressed (P less than 0.005). Its rate of appearance also increased by 30% (P less than 0.005) from 3.4 +/- 0.3 to 4.3 +/- 0.4 mumol/kg/min (P less than 0.005), while its clearance remained unchanged. Acute insulin deficiency caused an increase in leucine levels in both 18-h and 48-h-fasted dogs by 55% (to 181 +/- 10 mumol/L) and 45% (to 225 +/- 20 mumol/L), respectively (P less than 0.005). However, while the rate of appearance of leucine remained unchanged in dogs fasted overnight, it rose to 5.1 +/- 0.3 mumol/kg/min (P less than 0.01) in those fasted 48 h. The metabolic clearance rate fell in both groups, although this drop was twice as great in the 18-h group (from 28 +/- 3 to 17 +/- 3 ml/kg/min, P less than 0.005) as in the 48-h group (from 28 +/- 3 to 23 +/- 2 ml/kg/min, P less than 0.005). We conclude that insulin has disparate effects on protein turnover as fasting becomes more prolonged.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of an acute increase in epinephrine and cortisol on carbohydrate metabolism during insulin deficiency.

This study was undertaken to investigate the effects of an acute increase in the plasma epinephrine level, with or without an accompanying increase in the plasma cortisol level, during selective insulin deficiency on glycogenolysis and gluconeogenesis in conscious overnight-fasted dogs. Experiments consisted of an 80-min tracer and dye equilibration period, a 40-min basal period, and a 180-min experimental period. In all protocols, selective insulin deficiency was created during the experimental period by infusing somatostatin peripherally (0.8 micrograms.kg-1.min-1) with basal replacement of glucagon intraportally (0.65 ng.kg-1.min-1). In EPI+SAL (n = 6), an additional infusion of epinephrine (0.04 micrograms.kg-1.min-1) was infused during the experimental period along with saline. In EPI+CORT (n = 6), hydrocortisone (3.0 microgram.kg-1.min-1) was infused in addition to epinephrine during the experimental period. In SAL+CORT (n = 5), hydrocortisone was infused during the experimental period. In SALINE (n = 5), neither epinephrine nor cortisol was infused. [3-3H]glucose, [U-14C]alanine, and indocyanine green dye were used to assess glucose production (rate of appearance [Ra]) and gluconeogenesis using tracer and arteriovenous difference techniques. During selective insulin deficiency in SALINE, the arterial plasma glucose level increased from 6.0 +/- 0.1 to 15.8 +/- 1.1 mmol/l; Ra increased from 14.7 +/- 0.7 to 24.9 +/- 1.7 mumol.kg-1.min-1. Gluconeogenic efficiency and the conversion of alanine and lactate to glucose increased to 300 +/- 55 and 355 +/- 67% of basal. In EPI+SAL and EPI+CORT, plasma glucose increased from 6.2 +/- 0.1 to 19.8 +/- 0.9 mmol/l and from 6.3 +/- 0.1 to 19.5 +/- 0.9 mmol/l. In EPI+SAL and EPI+CORT, Ra increased from 16.5 +/- 1.1 to 29.3 +/- 3.2 mumol.kg-1.min-1 and from 15.4 +/- 1.3 to 28.3 +/- 2.5 mumol.kg-1.min-1. The rise in gluconeogenic efficiency was similar to the rise that occurred in SALINE, but gluconeogenic conversion increased 17-fold in each of the two epinephrine groups. During the epinephrine infusion, gluconeogenesis accounted for a maximum of 55% of total glucose production as opposed to 31% during insulin deficiency alone. An increase in cortisol alone during insulin deficiency (SAL+CORT) had no effect on glucose level, glucose production, or gluconeogenesis. These results suggest that small increases in the plasma epinephrine level during insulin deficiency can significantly worsen the resulting hyperglycemia through stimulation of both glycogenolysis and gluconeogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Exercise in insulin-dependent diabetes mellitus: the effect of continuous insulin infusion using the subcutaneous, intravenous, and intraperitoneal sites.

The metabolic response to exercise in insulin-dependent diabetic (IDD) man was assessed during continuous insulin infusion using the subcutaneous (CSII), intravenous (CIVII), and intraperitoneal (CIPII) routes. During the basal period, plasma glucose levels were higher with CIPII (153 +/- 17 mg/dl) than with CSII (117 +/- 13 mg/dl) or CIVII (118 +/- 17 mg/dl). Basal free insulin concentrations were similar for CSII (12.3 +/- 10 microU/ml) and CIVII (12.4 +/- 1.4 MicroU/ml) but lower in CIPII (8.5 +/- 1.0 microU/ml, P less than 0.05). Exercise on a stationary bicycle at 75 W for 60 min produced a decline of plasma glucose in each protocol that was significantly only during CIVII (55 +/- 11 mg/dl, P less than 0.01). Insulin levels remained unchanged throughout the study period in all protocols. In normals, insulin values decreased during exercise and remained below basal levels through the recovery period (P less than 0.05), while plasma glucose remained unchanged. Plasma glucagon and epinephrine levels were similar in all protocols and remained unchanged with exercise, while plasma norepinephrine tended to be higher than normal in all diabetic subjects. Significant differences between normal and diabetic subjects (P less than 0.05) were observed for blood ketone bodies, while blood lactate, glycerol, and plasma FFA were similar. Normalization of intermediary metabolites occurred only with CIVII. Continuous insulin infusion provides near-normal glycemic and metabolic control before, during and following exercise in IDD man. However, to produce normal blood concentrations of intermediary metabolites during exercise, the insulin infusion rate may be excessive in terms of its hypoglycemic effect. CSII appears to be a safe, accessible, and adequate method for treating diabetic man during exercise.

The effect of thyroid hormones on gluconeogenesis and forearm metabolism in man.

The present study was designed to examine the effects of excess T3 on total body glucose production and forearm exchange of glucose, amino acids, and other metabolites. Five healthy male volunteers were studied after an overnight fast, before and 7 days after the administration of 150 micrograms/day T3. Glucose production (milligrams per kg/min) was measured using a primed continuous infusion of [3-3H]glucose and gluconeogenic index (micromoles per kg/min) was measured by following the conversion of infused [14C]alanine to [14C]glucose. Blood flow across the forearm was measured using capacitance plethysmography and forearm release of substrates was determined by the Fick principle. After T3 administration, there was a 3.7-fold rise in T3 from 150 +/- 15 to 530 +/- 12 ng/dl (P less than 0.001), with no change in insulin (12 +/- 1 microU/ml pre-T3 vs. 13 +/- 2 microU/ml post-T3) and glucagon (79 +/- 5 pre-T3 vs. 84 +/- 7 pg/ml post-T3). T3 administration resulted in an increase in plasma glucose (from 83 +/- 5 to 98 +/- 5 mg/dl; P less than 0.05), net glucose uptake by the forearm (from 250 +/- 90 to 712 +/- 60 nmol/100 ml forearm tissue X min; P less than 0.005) and glucose production (1.7 +/- 0.09 to 2.2 +/- 0.08 mg/kg X min; P less than 0.005), without a change in glucose clearance (2.1 +/- 0.02 vs. 2.0 +/- 0.02 ml/kg X min); the rate of conversion of [14C]alanine to [14C]glucose increased by 30% (0.56 +/- 0.03 to 0.74 +/- 0.03 mumol/ kg X min P less than 0.005). These values were associated with a 25% increase in blood lactate to 712 +/- 69 mumol/liter (P less than 0.05) and a 131% increase in lactate release across the forearm to 434 +/- 90 (P less than 0.005). Forearm release of alanine (96 +/- 29 nmol/100 ml forearm tissue X min) and glutamine (151 +/- 41 nmol/100 ml forearm tissue X min) increased by 90% (P less than 0.005 and P = 0.04, respectively), with no change in their concentrations. Forearm release of branched chain amino acids did not change, while those of their ketoacids, alpha-ketoisocaproate (KIC) and alpha-ketoisovalerate (KIV), doubled (to 64 +/- 9 mumol/liter for KIC and 39 +/- 6 mumol/liter for KIV; P less than 0.05). These were associated with a 45% increase in the branched chain amino acid levels and a 46% rise in both KIC and KIV levels to 41 +/- 9 and 28 +/- 7 mumol/liter, respectively (P less than 0.05). There was a concurrent significant (P less than 0.05) change in the arterial levels of phenylalanine (-32%), tyrosine (-29%), threonine (-20%), glycine (-20%), and serine (-15%), without any change in their efflux across the forearm. The data indicate that a pharmacologically induced rise in T3, to levels comparable to those seen in hyperthyroidism, results in enhanced glucose production, with an increase in glucose uptake by the forearm. The former can be partially accounted for by an increase in hepatic gluconeogenesis, glycogenolysis, or possibly increased renal glucose production...

Short-term effects of dietary-fat ingestion on energy expenditure and nutrient balance.

Joule for joule, dietary fat may promote obesity more than protein or carbohydrate. In this study we determined whether the addition of 50 g dietary fat to a standard breakfast would increase energy expenditure or fat oxidation during the immediate 6-h postprandial period or over the ensuing 18 h. We also determined whether subjects with a high level of aerobic physical fitness would show a greater increase in fat oxidation after the ingestion of the extra fat than would less fit subjects. Adding fat did not increase fat oxidation or energy expenditure either during the immediate 6-h postprandial period or over the following 18 h. This was true regardless of the subject's fitness level. Acutely, dietary fat ingested in excess of its usual rate of oxidation appears to be stored in the body. Being physically fit does not appear to provide an advantage in avoiding short-term storage of excess dietary fat.

Nutrient balance and energy expenditure during ad libitum feeding of high-fat and high-carbohydrate diets in humans.

To study the influence of diet composition on regulation of body weight, we fed 21 weight-stable subjects (11 lean, 10 obese) high-carbohydrate (HC) and high-fat (HF) diets for 1 wk each. Although diet composition was fixed, total energy intake was unrestricted. Subjects had a higher energy intake on the HF (11,039 +/- 2700 kJ/d) than on the HC (10,672 +/- 2617 kJ/d) diet (P less than 0.05), but energy expenditure was not different between diets. On day 7 of the HC diet, carbohydrate (CHO) oxidation was significantly related to CHO intake with the slope of the regression line 0.99, suggesting that overall CHO balance was near zero. However, the slope of the regression line was greater for obese than for lean subjects. On day 7 of the HF diet, fat oxidation was significantly related to fat intake but the slope of the line was 0.50, suggesting that overall fat balance was positive. However, this relationship was due entirely to lean subjects, with obese subjects showing no relationship between fat intake and oxidation.

Thiamin deficiency impairs endotoxin-induced increases in hepatic glucose output.

We addressed the role of thiamin, a cofactor for several enzymes involved in glucose metabolism, in the glucose metabolic response to endotoxin. Characterized by hyperglycemia, increased hepatic glucose production exceeding elevated rates of whole-body glucose utilization, this response is mediated by hormones and cytokines and is dependent on the immune and nutritional status of the host. We hypothesized that a thiamin-deficient state would impair the metabolic response to endotoxin. Rats were fed a thiamin-deficient or control diet for 6 wk before in vivo assessment of glucose kinetics. In control rats, Escherichia coli endotoxin increased the rate of glucose appearance (+76%), disappearance (+70%), and metabolic clearance (+50%). Thiamin deficiency resulted in increased plasma glucose (18%) and lactate (3- to 4-fold) as well as in a 30% decrease in insulin and an increase in glucagon (2.6-fold) and corticosterone (3.6-fold). Thiamin deficiency inhibited the endotoxin-induced hyperglycemia and the rise in hepatic glucose production, glucose utilization, and metabolic clearance rate.

Dopamine D2 receptor availability in opiate-dependent subjects before and after naloxone-precipitated withdrawal.

Dopamine may play a role in opiate withdrawal and dependence. We measured dopamine D2 receptor availability in 11 opiate-dependent subjects using PFT and [11C]raclopride at baseline and during naloxone-precipitated withdrawal. Because [11C]raclopride is sensitive to endogenous dopamine, this strategy enabled us to test whether we could document in humans the DA reductions reported in animal models of opiate withdrawal. Results were compared with values from 11 controls, two of which also received naloxone. The ratio of the distribution volume in striatum to that in cerebellum (Bmax/Kd + 1) was used as model parameter for D2 receptor availability. Baseline measures for Bmax/Kd were lower in opiate-dependent subjects (2.44 +/- 0.4) than in controls (2.97 +/- 0.45 P < or = .009). Naloxone precipitated an intense withdrawal in the abusers but did not change the Bmax/Kd ratio. This study documents decreases in D2 receptors in opiate-dependent subjects but does not document significant changes in striatal DA concentration during acute withdrawal.

Energy metabolism and fuel mobilization: from the perioperative period to recovery.

To determine the metabolic responses to surgical trauma, we assessed the rates of whole body (WB) proteolysis and glucose turnover using established isotopic techniques in combination with interorgan amino acid and substrate balances (using arteriovenous differences times flow) after laparotomy. Circulating levels of hormones and mediators known to affect these parameters were also examined. Mongrel dogs (n = 5-8 per group) were studied postoperatively under general anesthesia (immediate postoperative period) and at 3 days postoperatively (3 dPO) and 2 weeks later. Our results show that the immediate postoperative period is characterized by significant hyperglycemia, secondary to decreased glucose clearance (without any alterations in the rates of hepatic glucose production) and significant increase in gut proteolysis, with a mild increase in WB proteolysis. The gut proteolysis accounted for nearly 40% of WB proteolysis. At 3 dPO, blood glucose levels returned to normal, whereas the rate of WB proteolysis was maximally increased. Gut proteolysis was mildly elevated and accounted for nearly 8% of WB proteolysis. All metabolic parameters were back to near basal at 2 weeks postoperatively. These metabolic changes were accompanied by significant elevations in the plasma levels of endogenous morphine and cortisol and lower glucagon and insulin growth factor-I levels in the immediate postoperative period and at 3 dPO. These studies underscore the importance of the gut as a reservoir of amino acids during the immediate postoperative period, accounting for more than one-third of WB proteolysis. At 3 dPO, when maximal stimulation of WB proteolysis and amino acid oxidation are observed, the contribution from the gut is negligible and is most likely replaced by breakdown from skeletal muscle.

Mammalian opiate alkaloid synthesis: lessons derived from plant biochemistry.

The presence of opiate receptors in mammalian tissues has stimulated the search for endogenous ligands to these receptors and has led to the discovery and characterization of endogenous opioid peptides. However, recent studies have provided evidence for the presence of opiate alkaloids in mammalian tissues and for their endogenous synthesis. The study of their origin and synthetic pathway has been significantly influenced by the early classical biochemical studies performed in plants. This review is a historical account of the use and abuse of opiates, the elucidation of morphine's synthetic pathway in the poppy plant, and the subsequent characterization of its presence in mammalian tissues. Clearly, our understanding of its synthetic pathway and regulation is a reflection of observations originally made in plant biochemistry.

Endogenous opiates do not modulate LPS-induced alterations in carbohydrate metabolism.

This study aimed to determine the contribution of endogenous opiates to the hormonal and glucose metabolic response to lipopolysaccharide (LPS). Rats were infused with naloxone (NAL) (32 micrograms/h) for 2 h prior to the injection of LPS (100 micrograms/100 g body weight) and hemodynamic, hormonal, and metabolic parameters were determined. NAL produced no detectable alterations in any of the parameters assessed. LPS transiently decreases (26%) mean arterial blood pressure (MABP) and increased plasma glucose concentration (100-130%), glucose rate of appearance (50-100%), and glucose rate of disappearance (50-100%). NAL did not alter the LPS-induced drop in mean arterial blood pressure or the glucose response to LPS. LPS reduced plasma insulin (54%), and increased glucagon (270%), corticosterone (180%), and tumor necrosis factor concentrations in plasma (peak 3200-4600 pg/mL at 90 min), with no modification by NAL pretreatment. These results suggest a lack of involvement of endogenous opiate pathways in the glucose metabolic and hormonal responses to LPS.

Resuscitation with lactated Ringer's solution after hemorrhage: lack of cardiac toxicity.

The toxicity of D-lactate has been recognized for almost 30 years. This compound is found in the racemic mixture of lactated Ringer's solutions routinely used for peritoneal dialysis and the resuscitation of trauma victims. The current study was designed to investigate whether toxicity occurred at the D-lactate concentrations achieved during hemorrhage resuscitation with racemic lactated Ringer's solution. Conscious unrestrained male Sprague-Dawley rats (n = 24) were monitored for electrocardiographic abnormalities while undergoing hemorrhage and subsequent resuscitation with either L-lactated, D-lactated, or racemic lactated Ringer's solution. The rats infused with D-lactate showed significant toxicity as evidenced by bradycardia, premature ventricular contractions, and ventricular fibrillation. No such alterations were observed in the animals resuscitated with L-lactate or racemic solutions. Resuscitation with the racemic lactate mixture increased the D-lactate concentrations in the blood, but was not associated with overt changes in cardiac rhythm. The infusion of the different resuscitation fluids produced few significant differences in acid-base status of hemorrhaged rats. These findings indicate that although toxicity may be achieved with a Ringer's solution containing only D-lactate, resuscitation using the racemic mixture does not achieve D-lactate concentrations high enough to be detrimental to the animal.