Josef E. Fischer

Lactate is an unreliable indicator of tissue hypoxia in injury or sepsis

High blood lactate concentration (hyperlactacidaemia) in trauma or sepsis is thought to indicate tissue hypoxia and anaerobic glycolysis even when blood pressure, cardiac output, and urine output are within clinically acceptable ranges. However, mechanisms of lactate generation by well-oxygenated tissues have received little attention. Within cells, oxidative and glycolytic energy production can proceed in separate, independent compartments. In skeletal muscle and other tissues, aerobic glycolysis is linked to ATP provision for the Na+-K+ pump, the activity of which is stimulated by epinephrine. In injured patients, hypokalaemia may reflect increased Na+,K+-ATPase activity. We propose that increased blood lactate often reflects increased aerobic glycolysis in skeletal muscle secondary to epinephrine-stimulated Na+,K+-ATPase activity and not anaerobic glycolysis due to hypoperfusion. The hypothesis explains why hyperlactacidaemia often neither correlates with traditional indicators of perfusion nor diminishes with increased oxygen delivery. When other variables have returned to normal, continued attempts at resuscitation based on elevated blood lactate may lead to unnecessary use of blood transfusion and inotropic agents in an effort to increase oxygen delivery and lactate clearance.

Sepsis is associated with increased mRNAs of the ubiquitin-proteasome proteolytic pathway in human skeletal muscle.

Previous studies provided evidence that sepsis-induced muscle proteolysis in experimental animals is caused by increased ubiquitin-proteasome-dependent protein breakdown. It is not known if a similar mechanism accounts for muscle proteolysis in patients with sepsis. We determined mRNA levels for ubiquitin and the 20 S proteasome subunit HC3 by Northern blot analysis in muscle tissue from septic (n = 7) and non-septic (n = 11) patients. Plasma and muscle amino acid concentrations and concentrations in urine of 3-methylhistidine (3-MH), creatinine, and cortisol were measured at the time of surgery to assess the catabolic state of the patients. A three- to fourfold increase in mRNA levels for ubiquitin and HC3 was noted in muscle tissue from the septic patients concomitant with increased muscle levels of phenylalanine and 3-MH and reduced levels of glutamine. Total plasma amino acids were decreased by approximately 30% in the septic patients. The 3-MH/creatinine ratio in urine was almost doubled in septic patients. The cortisol levels in urine were higher in septic than in control patients but this difference did not reach statistical significance. The results suggest that sepsis is associated with increased mRNAs of the ubiquitin-proteasome pathway in human skeletal muscle.

Review of 404 patients with gastrointestinal fistulas. Impact of parenteral nutrition.

This paper represents an extensive review, spanning 30 years of experience with 404 patients with gastrointestinal fistulas. It includes the first period (1945–1960) during the introduction of antibiotics, the second period (1960–1970) which saw rapid improvements in parasurgical care including, respiratory support, perfection of antibiotics, some introduction of nutritional support and improved monitoring, and the third period which saw the introduction of parenteral nutrition specifically central venous hyperalimentation using hypertonic glucose and amino acids (1970–1975) in the treatment of patients with fistulas. The principal causes for mortality in the historical sense were malnutrition, sepsis and electrolyte imbalance. Mortality among patients with gastrointestinal cutaneous fistulas decreased between the first and second periods from approximately 48 to 15%. Surprisingly, mortality did not decrease further in the “hyperalimentation period” although spontaneous closure of gastrointestinal fistulas increased. The results suggest that the improvement in mortality in patients with gastrointestinal cutaneous fistulas is mostly due to the introduction of improved parasurgical care. It is acknowledged that nutritional support was practiced in the 1960s although this was generally not in the form of hyperalimentation. The addition of hyperalimentation in large scale to the treatment of gastrointestinal cutaneous fistulas has improved spontaneous closure and is a valuable part of the armamentarium. The decrease in mortality however, cannot be attributed to parenteral nutrition.

The expression of genes in the ubiquitin-proteasome proteolytic pathway is increased in skeletal muscle from patients with cancer

BACKGROUND The intracellular mechanisms of muscle cachexia in patients with cancer are not known. To assess the role of the ubiquitin-proteasome proteolytic pathway in cancer-induced muscle breakdown, we determined messenger RNA levels for ubiquitin and several 20S proteasome subunits in muscle from patients undergoing surgery for cancer METHODS A biopsy specimen was obtained from the rectus abdominis muscle in patients undergoing laparotomy for cancer (n = 6) or noncancer disease (n = 6). Tissue levels of mRNA for ubiquitin and the 20S proteasome subunits HC3, HC5, HC7, and HC9 were determined by dot blot analysis. RESULTS The mRNA levels for ubiquitin and the 20S proteasome subunits were 2 to 4 times higher in muscle from patients with cancer than in muscle from control patients. CONCLUSION This is the first report of increased expression of genes in the ubiquitin-proteasome proteolytic pathway in muscle tissue from patients with cancer. Cancer-induced muscle catabolism may at least in part reflect ubiquitin-proteasome-dependent protein breakdown.

ANOREXIA FOLLOWING THE INTRAHYPOTHALAMIC ADMINISTRATION OF AMYLIN

The intrahypothalamic injection of rat amylin reduced feeding in schedule-fed rats for eight hours. Specificity of this anorectic response was indicated by an appropriate dose-response relationship and the absence of effect of human amylin. Amylin-induced anorexia was accompanied by alterations in neurotransmitter metabolism similar to those observed in anorectic tumor-bearing rats. These results indicate that amylin may inhibit feeding by acting directly on hypothalamic neurons to alter metabolism of neurotransmitter systems known to affect feeding behavior.

Sepsis and endotoxemia stimulate intestinal interleukin-6 production

BACKGROUND Endotoxemia stimulates tumor necrosis factor (TNF) and interleukin-1 (IL-1) production in mucosa of the small intestine, but the effect on IL-6 production is not known. Intestinal IL-6 may be especially important, considering its role in the acute phase response. We tested the influence of endotoxemia and sepsis in mice on intestinal IL-6 and IL-6 messenger RNA (mRNA) levels. METHODS Mice were injected with lipopolysaccharide (LPS 10 mg/kg) or saline solution. In some experiments animals were pretreated with indomethacin (5 mg/kg) or N-nitro-L-arginine (NNA, 100 mg/kg) before LPS injection. In other experiments, sepsis was induced by cecal ligation and puncture (CLP); controls were sham operated. Serum and jejunal mucosa were harvested at intervals during 16 hours, and IL-6 levels were determined by enzyme-linked immunosorbent assay. IL-6 mRNA was detected by polymerase chain reaction. RESULTS Endotoxemia and sepsis increased serum and mucosal IL-6 and IL-6 mRNA, with maximum levels noted at 1 and 4 hours after LPS and at 8 hours after CLP. Pretreatment of endotoxemic mice with indomethacin or NNA blunted the increase in mucosal IL-6. CONCLUSIONS Results suggest that sepsis and endotoxemia stimulate IL-6 production in small intestinal mucosa and that this response may be transcriptionally regulated. The effect of endotoxemia may be partly mediated by prostaglandins and nitric oxide. The results also suggest that the intestinal mucosa may be a participant in the cytokine response, rather than just a passive bystander.

Characterization of neuropeptide Y binding sites in rat cardiac ventricular membranes

Neuropeptide Y (NPY) binding sites in rat cardiac ventricular membranes have been characterized in detail. 125I-NPY bound to the membranes with high affinity. Binding was saturable, reversible and specific, and depended on time, pH and temperature. Analysis of the binding data obtained under optimal conditions, 2 hr, 18 degrees C and at pH 7.5, revealed the presence of low and high affinity binding sites. The high affinity binding sites had an apparent dissociation constant (Kd) of 0.38 nM and a binding capacity (Bmax) of 7.13 fmol/mg protein. The apparent Kd and Bmax for low affinity binding sites were 22.34 nM and 261.25 fmol/mg protein, respectively. Peptides unrelated to NPY did not compete with 125I-NPY for the binding sites even at 1 microM concentrations, whereas homologous peptides, peptide YY (PYY) and pancreatic polypeptide (PP), and NPY(13-36) inhibited 125I-NPY binding but with lower potency compared to NPY. 125I-NPY binding was sensitive to the nonhydrolyzable GTP analog, Gpp(NH)p, suggesting that the NPY receptor is coupled to the adenylate cyclase system. The ventricular membrane receptor characterized in this study may play an important role in mediating the physiological effects of NPY in the heart.

Hypothalamic concentration and release of neuropeptide Y into microdialysates is reduced in anorectic tumor-bearing rats.

Hypothalamic concentration of neuropeptide Y was decreased significantly in anorectic tumor-bearing rats, while NPY level was increased significantly in matched carcass weight control rats as compared with freely-feeding controls. In vivo microdialysis of the perifornical hypothalamic area of tumor-bearing rats prior to the development of anorexia revealed no alteration in NPY in dialysates. Following the development of anorexia, however, tumor-bearing rats exhibited significant reduction in NPY concentration in dialysates as compared with either matched carcass weight or freely-feeding control group. These results suggest that hypothalamic NPY concentration and release are decreased selectively in anorectic tumor-bearing rats. Since NPY also elicits less feeding in tumor-bearing rats, dysfunction of hypothalamic NPY feeding mechanisms may be of primary importance in cancer anorexia.

Anorexia following the systemic injection of amylin

The intravenous injection of 100 micrograms/kg of rat amylin reduced food intake in schedule-fed rats for 1 h of an 8 h measurement period. Associated with this brief anorexia was a hyperglycemic response, observed 30 min after a subsequent amylin administration. Determination of neurochemical alterations revealed increased concentration of serotonin in the hypothalamus and decreased level of the dopamine metabolite, 3-methoxytyramine, in the corpus striatum. Since similar neurochemical alterations were observed following the systemic injection of glucose, both the neurochemical changes and anorexia following intravenous amylin treatment may be secondary to hyperglycemia.

Decreased myofibrillar protein breakdown following treatment with clenbuterol

Daily treatment of Fischer-344 rats for 14 days with the beta 2-adrenergic agonist, clenbuterol, increased gastrocnemius muscle mass and protein content. Coadministration with the beta-adrenergic antagonist, nadolol, significantly reduced these anabolic effects of clenbuterol. Although clenbuterol treatment reduced food intake during the first 4 days, clenbuterol-treated rats were hyperphagic during the second week of drug administration. Nadolol treatment also blocked these effects of clenbuterol on feeding. In a second experiment, in vitro incubation of extensor digitorum longus muscles taken from post weaning food-deprived rats demonstrated decreased release of 3-methylhistidine by clenbuterol-treated rats, suggesting decreased breakdown of myofibrillar protein. Protein synthesis was not increased in vitro in the soleus muscles taken from these rats. These experiments demonstrate that the anabolic effect of clenbuterol is due in part to beta-adrenergic activity and may involve reduced myofibrillar protein degradation. These results appear to have direct application to nutrition and protein repletion in various catabolic diseases.