The adenine nucleotide content of rat liver during infusions of carbohydrates and polyols

Serum enzyme, bilirubin, uric acid, and cholesterol concentration changes during 7 days of total parenteral nutrition

Lactic dehydrogenase, glutamic oxalacetic transaminase, and alkaline phosphatase remained within normal limits during 7 days of total parenteral nutrition. Five patients showed a rise of total bilirubin up to 1.1 mg/100 ml on the fifth postoperative day, with no change in serum enzymes. Uric acid concentration fell continuously up to the third postoperative day (but within normal limits) and remained decreased until the end of infusion. During the preoperative nutrition period and after surgical intervention, cholesterol concentration showed a steep fall. Very low cholesterol concentrations can cause an alteration of erythrocyte membrane synthesis and should, therefore, be avoided.

[Comparison of metabolic effects of infusions of glucose and glucose substitutes]

The side effects of high dosed infusions of glucose and glucose substitutes (fructose, sorbitol, xylitol) in metabolically healthy volunteers have been studied. Infusions of glucose or fructose in high dose cause an increase in blood lactate levels. This effect, to a lesser degree, is observed with sorbitol. No effect, however, was seen with xylitol. Following the termination of the glucose infusions the lactate levels remain elevated, whereas after termination of the fructose infusions the lactate concentration is normalized within a short time. A decrease in the serum phosphate levels was observed for all the substances used. The most active were glucose and xylitol, followed by fructose and sorbitol, respectively. Similarly, all these substances cause an elevation of the serum bilirubin levels, though enzyme activities in serum remain unaffected. Xylitol had the greatest effect on bilirubin levels, however, glucose was also effective. The only side effect caused by the glucose substitutes was the stimulation of uric acid synthesis. In this respect xylitol was most effective. Some of metabolic effects of glucose and glucose substitutes are not yet clearly understood. However, even at very high doses these effects are not to be regarded as true "side-effects".

[Changes in several important metabolic parameters and insulin level during a 7-day total parenteral nutrition under pre- and postoperative conditions]

After the 24 hours preoperative infusion period 0.37% glucose, 0.05% fructose and 1.28% xylitol of the infused amount were excreted in the urine. Postoperatively fructose was the best metabolized energy donator before xylitol and glucose. As a sign of an undisturbed hepatic synthesis of lipoproteins the triglycerides rose up to the 5th postoperative day. During the parenteral nutrition and the additional surgical intervention the cholesterol fell from 192.3 to 128.5 mg/100 ml on the first postoperative day. The infusion solutions caused a rise of the insulin concentration from 23.2 to 46.3 U/l on the operation day. There is a positive nitrogen balance of 3.5 g/24 h on the operation day. The slight negative balance of - 1.15 g/24 h on the first postoperative day is reduced to - 0.61 g/24 h on the postoperative day. The changes of the enzymes LDH, GOT and AP were at normal range. The postoperative changes were due to the surgical intervention. Without a simultaneous change of enzymes, 5 patients had a rise of bilirubin up to 1.1 mg/100 ml. To avoid a too great loose of phosphate during a long-term parenteral nutrition period, it is important to put up a balance.

[Biokinetic behavior and metabolic effect of fructose in high dose continuous infusion in the rat]

The steady-state blood level of fructose during 24 hours intravenous infusion in response to different doses follows saturation kinetics. Even after toxic doses of 1.5 g/kg/h no depletion of liver adenine nucleotides can be observed after 24 hours. In the kidneys, however, ATP, ADP and total adenine nucleotides were decreased after a dose of 1.5 g/kg/h of fructose. The blood glucose increased continuously at infusion rates of 1.5 g/kg/h. Inorganic phosphate in the blood increased at doses of 1.0 and 1.5 g/kg/h. The weight of the kidneys increased, presumably through water uptake. Urinary secretion was drastically reduced at doses above 1.0 g/kg/h. An appreciable activity of ketohexokinase can be demonstrated in the kidneys.

[Oxygen, carbohydrate and fat metabolism of the splanchnic region under the influence of equimolecular parenteral doses of glucose and fructose]

Hepatic metabolic balances derived from arterio-hepatic venous substrate differences and hepatic blood flow exhibited similar results during fructose and glucose infusion (10 g/5 min, 0.5 g/kg X h) as compared to those from the isolated perfused organ. Accordingly, in account of hepatic utilization of fructose glucose homeostasis and secretion maintained during fructose infusion. However, the smaller insulin response during fructose infusion did not reduce hepatic free fatty acid utilization to such an extend as to increase pyruvate oxydation. Thus, splanchnic production of lactate and pyruvate descending from fructose was enhanced leading to a 7-fold increase of arterial lactate concentration. Since hepatic venous lactate to pyruvate substrate ratios did not change, the rise of the arterial redox couple could not be due to hepatic fructose metabolism. According to the findings from the isolated perfused organ, fructose seemed to be phosphorylated at a rate which was found to be 2-3-fold that of glucose as calculated from splanchnic utilization rates. The rapid ATP-breakdown was followed by an increment in splanchnic oxygen consumption. The larger energy demand during fructose infusion seemed to be satisfied by an enhanced endoxydation of free fatty acids.

Suitability of non-glucose-carbohydrates for parenteral nutrition

Postoperative parenteral nutrition can only be optimally effective if the characteristics of post-traumatic metabolism are taken into account. Two main possibilities are discussed for the carbohydrate component of parenteral nutrition during this phase: glucose with high doses of insulin or non-glucose carbohydrates (sugar substitutes) possibly in a suitable combination with glucose. The risks as well as the technical and organisational problems involved in the use of them are discussed and the authors prefer the second of the two alternatives. Possible side effects of non-glucose carbohydrates are pointed out and it is shown how these can be avoided by observing dose guidelines. So far a combination of frucose : glucose : xylitol in a ratio of 2 : 1 :1 with a total dose of 0.50 g/kg/hour has been studied most thoroughly. This combination normalises the fat metabolism and improves glucose tolerance without requiring exogenous insulin. Experiences with this combination as well as individual non-glucose carbohydrates on operated patients have been given continuously for up to 7 days and in some cases even for several weeks. No side effects, no deviations from a steady state and no abnormal changes of the laboratory values occurred. The authors are of the opinion that non glucose carbohydrates are necessary if the facilities for frequent blood sugar controls are not available.

[Metabolic effect of a carbohydrate combination during simultaneous amino acid infusion]

During a period of 12 hours, eight normal subjects were infused with an electrolyte containing combined 24% carbohydrate solution of fructose, glucose, and xylitol at a ratio of 2:1:1 (Triofusin E 1000 Pfrimmer) with a rate of supply of 0.6 gm/kg/h. Lamino acids (Aminofusin L 10% carbohydrate-free Pfrimmer) were simultaneously administered at a rate of 0.1 gm/kg/h. The serum substrate concentrations of fructose, glucose and xylitol and their excretion were measured. The utilization of fructose was 99%, of glucose practically 100% and of xylitol 88%. In accordance with the slight glucose increase, the concentration of insulin also showed an only slight increase. An increased serum concentration of oxalate was not observed. Despite the infusion of a glycine containing amino acid mixture, the excretion of oxalic acid even decreased during the infusion. The dilution effect measured by means of hematocrit, hemoglobin, erythrocyte count, total protein, and albumin was between 2 and 5%. The lactate concentration did not change significantly whereas hydroxy butyrate decreased significantly by the end of the infusion indicating the antiketogenic effect. A disturbance of fat metabolism was not observed as was indicated by the concentrations of neutral fat and cholesterol. The decrease of free glycerol cannot be clearly explained. A highly significant reduction of the serum uric acid concentration resulted from an increased renal elimination. The electrolyte concentrations of potassium, sodium, calcium and phosphate showed only slight modifications. The concentration of potassium initially rose significantly within normal ranges. Sodium and chloride remained constant whereas calcium decreased slightly but not significantly and phosphate decreased significantly until the 12th hour. The serum transaminase and bilirubin concentrations did not show any change. During the permanent infusion, a respiratory alkalosis developed. The average urinary excretion was 134 ml per hour, the excretion of potassium was 6 mEq/h, of sodium 15 mEq/h, and of phosphate 27 mg/h. The utilazation of a combined carbohydrate solution was in the same range with or without the simultaneous application of amino acids. The reduction of the uric acid concentration and the absent increase of lactate, bilirubin and oxalate may be considered as an additional desirable effect of the simultaneous application of amino acids.

[Studies on the pharmacokinetics of carbohydrates as a basis for their use in parenteral feeding]

Metabolic effects of glucose, fructose, sorbitol, xylitol and their combinations during intravenous application in men were investigated. The totale and metabolic clearance, the renal and metabolic elimination, the half-time and the turnover rate were measured. For all sugars intravenous long-term infusions from six to twelve hours were performed. Up to a dosage of 0.75 g/kg/h for glucose 0.5 g/kg/h for sorbitol and 0.25 g/kg/h for fructose and xylitol a steady state of substrates and metabolites has been found. If these dosage-limits are exceeded during glucose application a hyperglucosemia, after sorbitol a continous rise in sorbitol blood level, during fructose a rise in lactate and during xylitol infusion clinical side effects occurred. It could be shown that during simultaneous application of glucose, fructose and xylitol the utilization of glucose rises whereas the utilization of fructose and xylitol remain on such levels as if these sugar were infused alone.