The metabolic basis of the increase of the increase in energy expenditure in severely burned patients

Attenuation of posttraumatic muscle catabolism and osteopenia by long-term growth hormone therapy

OBJECTIVE

To determine whether the beneficial effects of growth hormone persist throughout the prolonged hypermetabolic and hypercatabolic response to severe burn.

SUMMARY BACKGROUND DATA

The hypermetabolic response to severe burn is associated with increased energy expenditure, insulin resistance, immunodeficiency, and whole body catabolism that persists for months after injury. Growth hormone is a potent anabolic agent and salutary modulator of posttraumatic metabolic responses.

METHODS

Seventy-two severely burned children were enrolled in a placebo-controlled double-blind trial investigating the effects of growth hormone (0.05 mg/kg per day) on muscle accretion and bone growth. Drug or placebo treatment began on discharge from the intensive care unit and continued for 1 year after burn. Total body weight, height, dual-energy x-ray absorptiometry, indirect calorimetry, and hormone values were measured at discharge, then at 6 months, 9 months, and 12 months after burn. Results were compared between groups.

RESULTS

Growth hormone subjects gained more weight than placebo subjects at the 9-month study point; this disparity in weight gain continued to expand throughout the remainder of the study. Height also increased in the growth hormone group compared with controls at 12 months. Change in lean body mass was greater in those treated with growth hormone at 6, 9, and 12 months. Bone mineral content was increased at 9 and 12 months; this was associated with higher parathormone levels.

CONCLUSIONS

Low-dose recombinant human growth hormone successfully abates muscle catabolism and osteopenia induced by severe burn.

A comparison of renal phosphorus regulation in thermally injured and multiple trauma patients receiving specialized nutrition support

To compare phosphorus intake and renal phosphorus regulation between thermally injured patients and multiple trauma patients, 40 consecutive critically ill patients, 20 with thermal injury and 20 with multiple trauma, who required enteral tube feeding were evaluated. Phosphorus intakes were recorded for 14 days from the initiation of tube feeding which was started 1 to 3 days postinjury. Serum for determination of phosphorus concentrations was collected at days 1, 3, 7, and 14 of the study period. A 24-hour urine collection was obtained during the first and second weeks of nutrition support for urinary phosphorus excretion, fractional excretion of phosphorus, renal threshold phosphate concentration, and phosphorus clearance. Average total daily phosphorus intake during the 14-day study for thermally injured patients and multiple trauma patients was 0.99+/-0.26 mmol/kg/d vs 0.58+/-0.21 mmol/kg/d, respectively, p < .001. Serum phosphorus concentration on the third day of observation was significantly lower in the thermally injured group than those with multiple trauma (1.9+/-0.8 mg/dL vs 3.0+/-0.8 mg/dL, p < or = .01). A trend toward hypophosphatemia in the thermally injured group persisted by the seventh day of feeding (2.7+/-1.2 mg/dL vs 3.3+/-0.6 mg/dL, p < or = .04). Differences in urinary phosphorus excretion was not statistically significant between the thermally injured and multiple trauma groups (271+/-213 mg/d vs 171+/-181 mg/d for week 1, and 320+/-289 mg/d vs 258+/-184 mg/d for week 2, respectively). Urinary phosphorus clearance, fractional excretion of phosphorus, or renal threshold phosphate concentrations were also not significantly different between thermally injured and multiple trauma patients. During nutrition support, serum phosphorus concentrations are lower in thermally injured patients compared with multiple trauma patients despite receiving a significantly greater intake of phosphorus. Renal phosphorus regulation does not significantly contribute to the profound hypophosphatemia observed in thermally injured patients when compared with multiple trauma patients during nutrition support.

Metabolism 2000: the emperor needs new clothes

Metabolism is one of the corner stones of nutritional science. As biology enters the post-genomic era and with functional genomics beginning to takeoff, we anticipate that the study of metabolism will play an increasingly important role in helping to link advances made via the reductionist paradigm, that has been so successful in molecular and cellular biology, with those emerging from observational studies in animals and human subjects. A reconstructive metabolically-focused approach offers a timely paradigm for enhancing the elegance of nutritional science. Here we give particular attention to the use of tracers as phenotyping tools and discuss the application of our metaprobe concepts with respect to some novel features of metabolism, including 'underground metabolism', 'metabolic hijacking', 'catalytic promiscuity' and 'moonlighting proteins'. The opportunities for enhancing the study of metabolism by new and emerging technologies, and the importance of the interdisciplinary research enterprise are also touched upon. We conclude that: (1) the metaprobe concepts and approach, discussed herein, potentially yield a quantitative physiological (metabolic) phenotype against which to elaborate partial or focused genotypes; (2) physiological (metabolic) phenotypes which have a whole-body or kinetically-discernible inter-organ tissue-directed metabolic signature are an ideal target for this directed tracer-based definition of the 'functional' genotype; (3) metabolism, probed with tracer tool kits suitable for measuring rates of turnover, change and conversion, becomes in the current sociology of the 'Net', like AOL, Yahoo. Alta Vista, Lycos or Ask Jeeves, the portal for an exploration of the metabolic characteristics of the 'Genomics Internet'.

Splanchnic metabolism of fuel substrates in acute liver failure

BACKGROUND/AIMS

This study aimed to characterize the exchange of fuel substrates in the splanchnic circulation in acute liver failure.

METHODS

Liver vein catheterization was used in 22 patients with acute liver failure after development of hepatic encephalopathy grade III-IV Healthy controls, patients with cirrhosis and patients with acute on chronic liver disease were also studied.

RESULTS

In acute liver failure there was splanchnic removal of glucose (0.21+/-0.44 mmol/min), release of lactate (0.34+/-0.37 mmol/min), pyruvate (0.08+/-0.06 mmol/min) and ketone bodies (0.04+/-0.02 mmol/min), while extraction of amino acids and free fatty acids was insignificant. In the acute liver failure group, a normal hepatic venous oxygen saturation (0.69+/-0.12) and normal pyruvate/lactate ratio suggested absence of hypoxia even though the acetoacetate/beta-hydroxybutyrate ratio was decreased. Only in the acute liver failure group did the measured splanchnic oxygen content difference exceed what could be accounted for even by hypothesizing complete oxidation of all extracted blood-borne fuel substrates; oxidation of endogenous substrates may be quantitatively important in this condition.

CONCLUSION

Acute liver failure was associated with a state of accelerated glycolysis in the splanchnic region, leading to release of lactate in the absence of splanchnic hypoxia.