Decreased myoblast differentiation in chronic binge alcohol-administered simian immunodeficiency virus-infected male macaques: role of decreased miR-206.

Skeletal muscle stem cells play a critical role in regeneration of myofibers. We previously demonstrated that chronic binge alcohol (CBA) markedly attenuates myoblast differentiation potential and myogenic gene expression. Muscle-specific microRNAs (miRs) are implicated in regulation of myogenic genes. The aim of this study was to determine whether myoblasts isolated from asymptomatic CBA-administered simian immunodeficiency virus (SIV)-infected macaques treated with antiretroviral therapy (ART) showed similar impairments and, if so, to elucidate potential underlying mechanisms. Myoblasts were isolated from muscle at 11 mo after SIV infection from CBA/SIV macaques and from time-matched sucrose (SUC)-treated SIV-infected (SUC/SIV) animals and age-matched controls. Myoblast differentiation and myogenic gene expression were significantly decreased in myoblasts from SUC/SIV and CBA/SIV animals compared with controls. SIV and CBA decreased muscle-specific miR-206 in plasma and muscle and SIV decreased miR-206 expression in myoblasts, with no statistically significant changes in other muscle-specific miRs. These findings were associated with a significant increase in histone deacetylase 4 (HDAC4) and decrease in myogenic enhancer factor 2C (MEF2C) expression in CBA/SIV muscle. Transfection with miR-206 inhibitor decreased myotube differentiation, increased expression of HDAC4, and decreased MEF2C, suggesting a critical role of miR-206 in myogenesis. Moreover, HDAC4 was confirmed to be a direct miR-206 target. These results support a mechanistic role for decreased miR-206 in suppression of myoblast differentiation resulting from chronic alcohol and SIV infection. The parallel changes in skeletal muscle and circulating levels of miR-206 warrant studies to establish the possible use of plasma miR-206 as an indicator of impaired muscle function.

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.

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.

Advancing Behavioral HIV Prevention: Adapting an Evidence-Based Intervention for People Living with HIV and Alcohol Use Disorders.

Alcohol use disorders (AUDs) are highly prevalent among people living with HIV/AIDS (PLWHA) and are associated with increased HIV risk behaviors, suboptimal treatment adherence, and greater risk for disease progression. We used the ADAPT-ITT strategy to adapt an evidence-based intervention (EBI), the Holistic Health Recovery Program (HHRP+), that focuses on secondary HIV prevention and antiretroviral therapy (ART) adherence and apply it to PLWHA with problematic drinking. Focus groups (FGs) were conducted with PLWHA who consume alcohol and with treatment providers at the largest HIV primary care clinic in New Orleans, LA. Overall themes that emerged from the FGs included the following: (1) negative mood states contribute to heavy alcohol consumption in PLWHA; (2) high levels of psychosocial stress, paired with few adaptive coping strategies, perpetuate the use of harmful alcohol consumption in PLWHA; (3) local cultural norms are related to the permissiveness and pervasiveness of drinking and contribute to heavy alcohol use; (4) healthcare providers unanimously stated that outpatient options for AUD intervention are scarce, (5) misperceptions about the relationships between alcohol and HIV are common; (6) PLWHA are interested in learning about alcohol's impact on ART and HIV disease progression. These data were used to design the adapted EBI.

Differential tissue regulation of insulin-like growth factor-I content and binding proteins after endotoxin.

The purpose of the present study was to investigate the regulation of plasma and tissue levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-1, -2, and -3 (IGFBP-1, -2, and -3) in rats injected with Escherichia coli lipopolysaccharide (LPS), a component of the outer cell wall of gram-negative bacteria. When injected iv into conscious overnight fasted rats, plasma IGF-I levels were initially decreased within 1 h, maximally depressed at 4 h, and still only 35-45% of control values at 24 h. GH levels were reduced as early as 30 min after LPS, averaged 80-90% of control values between 1-4 h, but had returned to basal levels by 24 h. The magnitude and duration of these changes were similar regardless of whether 100 or 10 micrograms/100 g BW (LD20 and LD0, respectively) LPS were injected. Plasma levels of IGFBP-1 and a 28K mol wt BP (BP-28K) were elevated 2- to 3-fold 4 h after LPS treatment, whereas IGFBP-3 and -2 levels were unchanged. The elevation in plasma IGFBP-1 and IGFBP-28K was observed as early as 1 h and was sustained for up to 24 h after LPS treatment. IGF-I levels were decreased 30-50% in liver, pituitary, and skeletal muscle, unchanged in brain, and elevated 5-fold in kidney in response to LPS. Of the tissues sampled, IGFBP-3 and -2 were selectively elevated in liver after LPS treatment. IGFBP-1 was increased in liver, muscle, and kidney in response to LPS. The level of the 28,000 mol wt BP was increased in liver (83%) and not changed in muscle or brain. These data indicate that LPS produces both rapid and sustained alterations in circulating levels of GH, IGF-I, and IGFBPs. Furthermore, there were marked tissue-specific changes in levels of IGF-I and IGFBPs. LPS-induced changes in plasma and tissue IGFBP-3 were not regulated by changes in GH, and changes in insulin could not explain the alterations in IGFBP-1 and -2. These results suggest that after the injection of LPS, changes in IGF-I and IGFBP levels are regulated by a mechanism(s) different from those previously described.

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.

Opiate modulation of hemodynamic, hormonal, and cytokine responses to hemorrhage.

The aim of the present study was to examine the role of opiate receptor activation in modulating the hemodynamic, neuroendocrine, and tissue (lung and spleen) cytokine responses to fixed pressure (40 mm Hg) hemorrhage. Chronically catheterized, conscious unrestrained non-heparinized male Sprague-Dawley rats were pretreated with either naltrexone (15 mg/kg intraperitoneally in 0.5 mL of saline) or saline (0.5 mL) 15 min prior to hemorrhage followed by fluid resuscitation with Ringer's lactate. Animals were sacrificed at completion of the 60-min resuscitation period. Blood loss required to achieve mean arterial blood pressure (MABP) of 40 mm Hg was higher in naltrexone-treated animals than in time-matched saline controls (4.4+/-0.2 versus 3.7+/-0.2 mL/100 g BW, P< 0.05). Hemorrhage increased plasma levels of corticosterone (30%) and ACTH (3-fold) within 15 min. Naltrexone prevented the hemorrhage-induced rise in corticosterone without affecting the rise in ACTH. Hemorrhage increased beta-endorphin levels (4-fold) and produced an immediate (5 min) and progressive increase in circulating epinephrine and norepinephrine levels reaching values that were 50- and 20-fold, respectively, higher than basal. Pre-treatment with naltrexone did not alter the time course or magnitude of the hemorrhage-induced increases in plasma beta-endorphin or catecholamines. Hemorrhage increased lung and spleen content of TNF (60%), IL-1alpha (300%), IL-6 (40%-60%), and IL-10 (80%) above values of time-matched sham control animals. Pre-treatment with naltrexone blunted the magnitude of the increases in tissue cytokine content in response to a given blood loss. These results indicate that endogenous opiates modulate the hemodynamic instability, neuroendocrine, and cytokine responses to hemorrhagic shock.

Hemorrhage alters neuroendocrine, hemodynamic, and compartment-specific TNF responses to LPS.

The aim of the present study was to determine the effects of fixed pressure (40 mmHg) hemorrhage (HEM) followed by fluid resuscitation with Ringer's lactate on the subsequent hemodynamic, neurohormonal, and TNF response elicited by systemic lipopolysaccharide (LPS) administration. Chronically catheterized, conscious, unrestrained male Sprague-Dawley rats were randomized to either HEM (n = 12) or sham (n = 12) groups. HEM and sham animals were randomized to receive either LPS (100 mg/100 g body weight) or an equal volume of intravenous saline 1.5 h after completion of the resuscitation period. LPS administration produced an immediate 20% decrease in mean arterial pressure in sham animals, which was accentuated in HEM animals (40%, P < 0.05 versus sham). Moreover, HEM blunted (75%, P < 0.05) the LPS-induced increase in plasma TNF concentrations. TNF was not detected in bronchoalveolar lavage fluid (BALF) obtained from sham LPS-treated animals. In contrast, TNF levels were significantly elevated (35 +/- 17 pg/mL) in HEM LPS-treated animals. A 400% increase in lung TNF content following LPS treatment was not affected by prior HEM. LPS administration produced a marked increase in plasma epinephrine, norepinephrine, and corticosterone levels in sham animals. HEM blunted the LPS-induced rise in circulating levels of epinephrine and corticosterone without altering that of norepinephrine. Our second set of studies showed that the increase in BALF TNF was associated with a 30% increase in wet-to-dry lung weight ratios, suggesting that this is most likely the result of leaky endothelium following hemorrhage and LPS. Furthermore, alterations in LPS-induced alveolar macrophage TNF production following HEM were not detected. These results indicate that HEM altered the hemodynamic, neurohormonal, and circulating TNF responses to systemic LPS administration. In addition, our results suggest that HEM impaired the compartmentalization of the inflammatory response to LPS, without affecting alveolar macrophage responses to LPS. The role of altered neuroendocrine responses to a second challenge in modulating proinflammatory responses remains to be elucidated.

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.

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.

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.

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.

CNI-1493 attenuates hemodynamic and pro-inflammatory responses to LPS.

The increased production of pro-inflammatory cytokines and nitric oxide have been postulated to contribute to the deleterious sequella of LPS administration. To date, clinical strategies to control these responses using individual specific inhibitors have been disappointing. The aim of the present study was to determine whether a tetravalent guanylhydrazone compound (CNI-1493) attenuates LPS-induced stress responses by suppressing multiple inflammatory mediators. Rats were injected intravenously with either CNI-1493 (10 mg/kg) or vehicle (1 mL NaCl) 60 min prior to the injection of LPS (100 microg/100 g body weight). LPS produced a 20% decrease in mean arterial blood pressure and a significant increase in circulating TNF-alpha levels as well as in tissue content of TNF-alpha, IL-1beta, and IL-6. This was associated with a marked increase in lung and gut apoptosis and myeloperoxidase (MPO) activities as well as with an increase in lung and spleen nitric oxide end products (NOx). Pretreatment with CNI-1493 attenuated the LPS-induced drop in mean arterial blood pressure (MABP) and blunted (40%) the rise in circulating TNF-alpha levels. CNI-1493 attenuated the LPS-induced increase in tissue cytokine (TNF-alpha, IL-1beta, and IL-6) content in lung and spleen but did not alter that of liver or gut. CNI-1493 pretreatment protected both lung and gut from LPS-induced apoptosis and in addition attenuated the rise in MPO activity in the gut. These results suggest diverse effects of CNI-1493 that are tissue specific and that confer protection against the hemodynamic and inflammatory responses to LPS.

Contribution of excitatory amino acids to hypoglycemic counter-regulation.

We determined the contribution of central N-methyl-D-aspartate (NMDA) receptor activation to the neuro-endocrine counter-regulatory response to insulin-induced hypoglycemia. Glucose kinetics, gluconeogenic substrate balance and counter-regulatory hormonal responses were determined in two groups of conscious dogs fitted with chronic vascular catheters and intracerebroventricular (i.c.v.) cannula. Peripheral insulin infusion (5 mU/kg per min for 3 h) decreased plasma glucose levels 40% and increased the rate of glucose appearance (R(a)) 2-fold. This was associated with significant increases in net hepatic uptake of glycerol and lactate, without any change in the net hepatic uptake of alanine. i.c.v. pretreatment with MK-801, an NMDA receptor antagonist, blunted (50%) the rise in glucose R(a) as well as the increase in the net hepatic uptake of glycerol and lactate. Hypoglycemia increased plasma cortisol (3-fold to 14.3+/-1 mg/dl) and epinephrine levels (14-fold to 3811+/-172 pg/ml), and this stress response was attenuated (30% and 60%, respectively) by MK-801 pretreatment. In controls, MK-801 did not alter the increase in norepinephrine or glucagon elicited by hypoglycemia. These results indicate that during hypoglycemia, central excitatory amino acids contribute to the modulation of the glucoregulatory response through activation of NMDA receptors, resulting in stimulation of the sympathoadrenal and hypothalamic-pituitary adrenal axis. This mechanism appears to play an important role in the sustained elevation in hepatic glucose production during hypoglycemia.

Morphine-3-glucuronide: hyperglycemic and neuroendocrine potentiating effects.

The greater potency of morphine-6-glucuronide (M6G) as well as the inactivity of morphine-3-glucuronide (M3G) with respect to the antinociceptive effects of the parent molecule, morphine (MOR), have been well established. It has been suggested that M3G is an antagonist of MOR's antinociceptive and respiratory depressive effects. The present study addressed the central nervous system (CNS) interaction of these opiate metabolites on their metabolic and hormonal effects. Whole body glucose kinetics were assessed on conscious, chronically catheterized, unrestrained rats. M3G (5 microg) or H2O (5 microl) was injected intracerebroventricularly (i.c.v.) 15 min prior to the bolus administration of H2O (5 microl), M6G (1 microg), or MOR (80 microg). i.c.v. M3G (5 microg) resulted in behavioral excitation, hyperglycemia (+50%), stimulation of glucose rate of appearance (Ra; +100%), glucose rate of disappearance (Rd; +70%), and metabolic clearance rate (MCR; +33%) within 30 min after injection with no alterations in hormone concentrations. i.c.v. M6G and MOR produced progressive hyperglycemia with significantly high catecholamine and corticosterone levels. M3G pretreatment resulted in enhanced elevations in plasma glucose levels (+52% and + 18%), plasma lactate (+138% and +108%), norepinephrine (+96% and +30%), and epinephrine (+62% and +67%) in response to both i.c.v. MOR and M6G administration. These findings suggest a non-opiate and non-hormonal mechanism for M3G-induced hyperglycemia. In contrast, the metabolic and hormonal responses to i.c.v. M6G and MOR are associated with elevations in catecholamine and corticosterone levels. which are remarkably enhanced by M3G pretreatment, most likely through accelerated catecholamine release. Our findings suggest a modulatory role for MOR glucuronidation, not only by rendering it inactive, as in the case of M3G, but by an interplay of the metabolic effects of the parent molecule and its metabolite.

Role of IL-1 alpha in central nervous system immunomodulation of glucoregulation.

Hyperglycemia is a hallmark of the stress response, and has been largely attributed to elevated plasma levels of catabolic hormones. Recently, various cytokines have been shown to be endogenously produced within the brain and may represent an important component of the central regulation of this metabolic response. Therefore, the aim of the present study was to determine whether the intracerebroventricular (i.c.v.) injection of one such peptide, interleukin (IL)-1, can produce hormonal and metabolic alterations comparable to those observed under stress conditions. An i.c.v. cannula and vascular catheters were placed in rats prior to the experiment. Whole body glucose flux was assessed in overnight fasted conscious unrestrained rats using [3-3H]glucose. A mild hyperglycemia was elicited 20 min after the i.c.v. injection of IL-1 alpha (human recombinant, 100 ng) that was not detected in control rats. Glucose levels gradually increased and were 26% higher than control values during the last hour of the 3 h experimental period. The hyperglycemia resulted from a 44% increase in the rate of hepatic glucose output (HGO), which preceded a proportional rise in peripheral glucose utilization. No increase in metabolic clearance rate was observed, suggesting that the increased glucose uptake was the result of mass action. The increased glucose flux was associated with a transient hyperinsulinemia (+95%), and sustained elevations in the arterial concentrations of glucagon (56%) and corticosterone (175%). In contrast, glucose flux was not altered by intravenous administration of the same dose of IL-1 alpha, or i.c.v. injection of IL-1 beta, or heat-inactivated IL-1 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential hemodynamic, metabolic and hormonal effects of morphine and morphine-6-glucuronide.

Although the hyperglycemic effect of morphine has been previously described, it is not clear whether this is the result of increased glucose production and/or decreased glucose utilization and if this metabolic effect is lost with glucuronidation. This study assessed the hemodynamic (heart rate; HR and mean arterial blood pressure; MABP), hormonal and whole body glucose metabolic effects of morphine (MOR) and its metabolite morphine 6-glucuronide (MOR-6G) in conscious unrestrained chronically catheterized rats. Whole body glucose kinetics were assessed with a primed constant intravenous infusion of [3-3H]glucose in rats infused i.c.v. with H2O (Con; 5 microliters/h), MOR (80 micrograms/h) or MOR-6G (1 microgram/h) for a total of 4 h. MOR administration resulted in a significant 20% elevation in HR and no change in MABP. MOR-6G produced a 14% increase in HR and no change in MABP. A significant rise in plasma glucose (+23%), hepatic glucose production (Ra; +27-61%) and whole body glucose utilization (Rd; +31-61%) was also observed within 60 min of MOR administration. I.c.v. MOR-6G resulted in hyperglycemia (+60%), stimulation of glucose Ra (+60%) and glucose Rd (+50%). No significant alterations were noted in hemodynamic, metabolic and hormonal parameters of H2O infused rats. I.c.v. MOR resulted in a significant increases in epinephrine (2-fold), norepinephrine (50%), corticosterone (97%) with no alterations in plasma insulin and glucagon. I.c.v. MOR-6G resulted in more marked elevations in norepinephrine (5-fold), epinephrine (7-fold) and similar elevation in corticosterone (99%) and modest elevation of glucagon (40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of excitatory amino acids to morphine-induced metabolic alterations.

Previous studies have indicated that excitatory amino acids are involved in the analgesic and addictive properties of morphine. However, their role in the morphine-induced alterations in glucose metabolism is not known. This study assessed the contribution of NMDA receptor activation to the morphine-induced hormonal and metabolic alterations in conscious unrestrained chronically catheterized rats. Whole body glucose flux was assessed with a primed constant intravenous infusion of [3-3H]glucose in rats pretreated with the NMDA-receptor antagonist MK-801 (0.25 mg/kg, intraarterial) or an equal volume (1.5 ml) of sterile saline (0.9%) administered 15 min prior to i.c.v. injection of H2O (Con; 5 microliters) or morphine sulfate (80 micrograms). No significant alterations were noted in metabolic and hormonal parameters of H2O injected rats. i.c.v. morphine increased the plasma glucose concentration (60%), hepatic glucose production (Ra; 60%) and whole body glucose utilization (Rd; 53%), but did not alter the glucose metabolic clearance rate (MCR). MK-801 alone resulted in transient hyperglycemia (25%), stimulation of glucose Ra (60%) and glucose Rd (53%), and a significant (30%) increase in MCR. MK-801 pretreatment blunted the morphine-induced hyperglycemia and the increased glucose Ra and Rd. Morphine increased the plasma concentration of epinephrine (4-fold), norepinephrine (2-fold) and corticosterone (67%); however, no alterations in plasma insulin and glucagon were detected. MK-801 pretreatment, blunted the morphine-induced increase in corticosterone and norepinephrine, and elicited a significant rise in insulin concentrations. These results indicate that activation of the NMDA receptors contributes to the morphine-induced hyperglycemia and hormonal alterations. Furthermore, this response appears partially mediated by activation of sympathetic outflow and suppression of insulin release, which is blunted by inhibition of NMDA receptors.

Differential control of glucoregulatory hormone response and glucose metabolism by NMDA and kainate.

The aim of the present study was to elucidate the effect of kainate and N-methyl-D-aspartate (NMDA), two different excitatory amino acid (EAA) agonists, on glucoregulatory hormone production and whole body glucose metabolism. Rates of hepatic glucose production (HGP) and peripheral glucose utilization (GU) were assessed in overnight fasted, catheterized, conscious rats using [3-3H]glucose. At the highest dose of kainate examined (16 mg/kg), glucose levels increased 97% after 1 h; thereafter, glucose fell towards basal values but was still elevated 25% at the end of the 3 h experiment. This hyperglycemia resulted from a rapid increase in HGP that exceeded an increased rate of GU. Both HGP and GU were elevated 86% throughout the final 2 h of the experiment. NMDA induced changes in glucose flux that were qualitatively similar, yet of smaller magnitude and of shorter duration, than those produced by kainate. Kainate-induced increases in glucose metabolism were associated with an early transient hyperinsulinemia followed by a period of insulinopenia, and sustained increases in the plasma concentrations of glucagon, corticosterone, epinephrine and norepinephrine. In contrast, sustained increases in glucagon and catecholamines, as well as the late hypoinsulinemia were not detected in NMDA-treated rats. Adrenergic blockade attenuated the kainate- but not the NMDA-induced increase in glucose metabolism. These results indicate that EAA agonists that bind preferentially to different receptor subtypes produce qualitatively similar changes in glucose metabolism. Whereas the increased HGP in kainate-injected rats was associated with sustained elevations in glucagon, catecholamines and corticosterone, NMDA only transiently elevated circulating glucocorticoid levels, suggesting a different mechanism of action. These data, support the involvement of EAA in various aspects of glucoregulation.