Densitometry-based equations for estimating body composition in Fischer rats

Male Fischer rats are widely used to evaluate the effects of nutritional repletion or deprivation on the rat's nutritional status. Practical methods are needed to evaluate changes in body composition. Chemical analysis is expensive, time consuming, and often not available; bioelectrical impedance analysis in laboratory animals lacks standardization. Postulating that the measurement of densitometry would allow reliable estimation of body composition in the male Fischer rat, we studied 27 male Fischer rats. Densitometric measurements of the carcasses and their chemical analysis were performed to obtain reference values. Initial estimation of the fraction of body fat based on densitometry was attempted with the Siri equation intended for use in humans. We found that this equation was not suitable for use in the male Fischer rat because it underestimated fat mass at high carcass weights and overestimated fat mass at low carcass weights. Therefore, the Siri equation was modified to more accurately predict carcass composition in the male Fischer rat. Three different predictive equations based on simple densitometric measurements were developed that allow separate estimation of carcass fat, carcass water, and carcass protein in the male Fischer rat. These equations were found to be accurate to within 2-5-3% of carcass weight.

Dynamics of central venous catheter-related sepsis in rats

To determine when catheter-related sepsis clears after removal of an infected central venous catheter (CVC) and when a new sterile CVC can be inserted without risk of recolonization, a catheter infected with 10(5) CFU of Staphylococcus epidermidis per ml was inserted into 40 Fischer 344 rats. Five control rats had sterile catheters. Insertion of an infected CVC was followed by a significant rise in leukocytes after 4 days and the presence of S. epidermidis in lungs, livers, spleens, kidneys, and the catheter tip, as examined by bacteriological assay. After the infected catheter was removed, the rat recovered from the induced catheter-related sepsis within 12 h. When a new sterile CVC was inserted into the femoral vein, the leukocyte count remained normal, and all catheter tips and tissue cultures were sterile 4 days later.

Current uses of total parenteral nutrition

Total parenteral nutrition has become a well-established intervention for the following indications: to sustain life in patients with short-bowel syndrome; for perioperative use in nutritionally deprived patients; to improve quality of life for patients with inflammatory bowel diseases; to assist the healing of enterocutaneous and pancreatic fistulas; for supportive care in patients with acute pancreatitis; as an adjunct to therapy in patients with acute renal or hepatic failure; for hypermetabolic states such as sepsis, trauma, burns and acquired immunodeficiency syndrome; in neonatal and pediatric patients; in transplantation recipients, including bone marrow, renal, cardiac and liver transplants; for precoronary artery bypass graft myocardial glycogen loading; in the field of obstetrics; to enhance survival in patients with closed head injuries; to treat life-threatening anorexia nervosa; in patients with cystic fibrosis and for nutritional support in home use.

Eating behavior and adherence to dietary prescriptions in obese adult subjects treated with 5-hydroxytryptophan

Previous observations have shown that oral administration of 5-hydroxytryptophan (5-HTP) without dietary prescriptions causes anorexia, decreased food intake, and weight loss in obese subjects. To confirm these data over a longer period of observation and to verify whether adherence to dietary restriction could be improved by 5-HTP, 20 obese patients were randomly assigned to receive either 5-HTP (900 mg/d) or a placebo. The study was double-blinded and was for two consecutive 6-wk periods. No diet was prescribed during the first period, a 5040-kJ/d diet was recommended for the second. Significant weight loss was observed in 5-HTP-treated patients during both periods. A reduction in carbohydrate intake and a consistent presence of early satiety were also found. These findings together with the good tolerance observed suggest that 5-HTP may be safely used to treat obesity.

The early cancer anorexia paradigm: changes in plasma free tryptophan and feeding indexes

Tumor growth is accompanied by an anorexia mediated by humoral factors that appear to influence appetitive mechanisms in the brain. Because tumor resection is followed by resumption of normal food intake, the circulating anorexigenic substance(s) are produced either by the neoplastic tissue or by the host in response to the tumor. Increased levels of plasma free tryptophan and plasma ammonia have been proposed to mediate cancer anorexia. With animal models, it is often difficult to ascertain whether changes in food intake depend upon metabolic changes or the progressively increasing tumor mass per se. The feeding patterns and biochemical changes that occur during tumor growth were evaluated in 96 male Fischer rats that were inoculated with 10(6) methylcholanthrene sarcoma cells or saline (controls). Rats were placed into metabolic cages equipped with an Automated Computerized Rat Eater Meter to continuously determine meal size and meal number. Plasma free tryptophan and ammonia were evaluated 6, 10, 16, 18, 22, and 26 days after tumor inoculation. Anorexia developed by day 17-18, when food intake started to decrease via a decrease in meal size but not meal number and reached 60% of control by day 26. However, long before anorexia developed, free tryptophan was significantly higher 6 days after tumor inoculation, and the greatest increase occurred after 18 days. Ammonia did not differ from control at any time. Data confirm tumor-associated increases in plasma free tryptophan that occurred before the manifestation of anorexia and support a possible role of brain serotonin in cancer anorexia.

Muscle performance and adenine-nucleotides status in MCA-sarcoma tumor-bearing rats

The reduction in DNA, RNA, amino acid, and total protein in muscle tissue of tumor-bearing rats may influence muscle function. The effects of MCA-sarcoma tumor burden on muscle performance and adenine nucleotides was evaluated in three fiber types of skeletal muscle. Twenty-one days after MCA-sarcoma tumor inoculation, the gastrocnemius-soleus muscle group of Fischer 344 rats was stimulated using an in situ preparation; tetanic stimulation for 10 min at 7.5, 15, or 30 tetani per min (TPM) or 60 TPM for 5 min (n = 6 control and six tumor-bearing rats/group). ATP, ADP, AMP, IMP, phosphocreatine, and creatine content in white and red gastrocnemius muscle and soleus muscle was measured. There were no differences among controls and tumor-bearing rats in force output; however, ATP content in the soleus muscle of tumor-bearing rats was significantly reduced after 30 TPM for 10 min or 60 TPM for 5 min. The performance of skeletal muscle, over a wide range of stimulation frequency, in tumor-bearing rats does not appear to be influenced by changes in adenine nucleotide content.

Abnormal substrate metabolism and nutritional strategies in cancer management

Impairment of the nutritional state plays a major role in the morbidity and mortality of cancer patients. However, the opportunity of providing artificial nutritional support to these patients is still debated, because of the concern that energy substrates administered to replete the host may concomitantly stimulate tumor growth. A correct nutritional approach to cancer patients should thus be based on a thorough knowledge of both host and tumor metabolic needs and host-tumor metabolic interactions. Specific modifications of plasma levels of glucogenic, aromatic, sulfur-containing and branched-chain amino acids have been demonstrated in cancer patients, indicating a specific influence of the tumor on amino acid metabolism. Little is known about protein metabolism in neoplastic tissue. Interference with tumor growth has been attempted by deprivation of single amino acids with controversial results. Increased gluconeogenesis and insulin resistance are responsible for the two main abnormalities in carbohydrate metabolism in cancer patients, namely increased glucose turnover and impaired glucose tissue disposal. Lipid metabolism is also affected by the neoplasm: soluble factors such as "lipid-mobilizing factor" lead to increased fat mobilization from adipose tissue; plasma elimination of exogenous triglycerides has also been found to be reduced probably because of a tumor-related decrease in lipoprotein lipase activity. The differences in glucose and fat utilization between tumor and host should be considered in the nutritional approach to cancer patients. Data in this respect are controversial and have been obtained only in experimental animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of energy substrate manipulation on tumour cell proliferation in parenterally fed cancer patients

The effects of isocaloric carbohydrate-based vs. fat-based total parenteral nutrition (TPN) regimens on cancer cell proliferation and host nutritional status were evaluated in 27 patients with tumours of the gastro intestinal tract consecutively assigned to receive for 14 days: a glucose-based (A) or a lipid-based (B) TPN formula, or an oral diet (C) isocaloric and isonitrogenous to A and B. Cancer cell replication rate was evaluated by thymidine labelling index (LI) on tumour samples before and at the end of each nutritional regimen. The number of replicating cells increased by 32.2% in patients receiving regimen A. LI decreased by 24.3% in patients given regimen B. LI values were slightly increased (+15%) in patients maintained on regimen C. Nutritional status remained within normal limits. None of the LI changes observed between and within the three arms of the trial were found to be statistically significant. Thus we failed to prove that glucose consistently stimulates or lipids inhibit tumour proliferation despite a trend in this sense.

Increased plasma free tryptophan levels in human cancer: a tumor related effect?

High free tryptophan (F-TRP) plasma levels are found in cancer patients (CP). F-TRP plasma concentrations are affected by the levels of its carrier, albumin (ALB), and free fatty acids (FFA) competing with TRP for ALB binding sites. The lack of correlation between F-TRP, ALB and FFA in CP suggests a tumor-dependent effect on the rise in F-TRP. To verify this hypothesis, F-TRP, ALB and FFA levels were assayed in 12 lung and 16 breast CP susceptible to radical surgery, before and 15 days after surgical removal of the tumor. F-TRP levels significantly decreased after tumor ablation. Since no correlation was found between F-TRP, ALB and FFA variations, it is conceivable that the tumor itself may be responsible for the high F-TRP levels in CP.

Plasma and CSF tryptophan in cancer anorexia

Eighteen untreated cancer patients and ten sex- and age-matched healthy volunteers were studied. In all patients eating behavior was investigated by means of a specific questionnaire from which the presence of anorexia and anorexia-related symptoms was assessed. To investigate the role of tryptophan in cancer anorexia, fasting plasma and CSF levels of tryptophan and other neutral amino acids were assayed in patients and controls. Cancer patients showed abnormally high plasma free tryptophan levels. In case of patients with cancer anorexia a significant rise of the ratio in plasma between free and tryptophan/large neutral amino acids, competing with tryptophan for its brain entry, was observed. This increase was correlated to a consistent rise of CSF tryptophan levels suggesting a specific role of the serotoninergic system in the pathogenesis of cancer anorexia.

Plasma clearance of exogenous lipids in patients with malignant disease

Abnormalities in lipid metabolism have been widely described in cancer-bearing patients and animals. In particular, the presence of the tumor seems to profoundly affect triglyceride (TG) utilization by interfering with lipoprotein lipase (LPL) activity. Exogenous TG plasma clearance was evaluated in 10 nonmalnourished patients with cancers of various origin and 10 normolipidemic volunteers by means of a three-stage intravenous lipid clearance test. This technique allows precise determination of both the fractional removal rate (K2) and the maximal clearing capacity (K1) for exogenous lipids. Mean K2 values (min-1) were found to be significantly reduced in cancer patients compared with control subjects (0.07 +/- 0.006 vs 0.13 +/- 0.013 SEM, p less than 0.005). K1 values (mumol/L/min) were also found to be significantly lower in cancer patients than in the control group (109.43 +/- 6.3 vs 143 +/- 6.3 SEM, p less than 0.01). The data obtained indicate that the capacity to eliminate exogenous lipids from the bloodstream is reduced in cancer-bearing patients. This may be the consequence of a tumor-related impairment of LPL system activity.

[Metabolico-nutritional changes in the cancer patient]

The severe impairment of the nutritional state, which usually accompanies malignant diseases, heavily contributes to the high morbidity and mortality rates observed in cancer patients. Nevertheless, the utility of an artificial energy supply to these patients is still controversial because the nutrients given to replete the host may also stimulate tumor growth. Consequently, a correct nutritional approach for cancer patients should be based upon a well-defined understanding of tumor as well as host-metabolic needs. In this regard, the most typical metabolic abnormalities observed in cancer patients and experimental animals are examined. Specific modifications of the plasma levels of different groups of amino acids--including glucogenic, aromatic, sulphur-containing and branched-chain amino acids--have been observed in cancer patients independently of the their degree of malnutrition, glucose tolerance and tumor diffusion. This may reflect a series of specific modifications induced by the neoplastic tissue on host's protein turnover. Little information is available regarding the protein metabolism in the neoplastic tissue. A number of attempts have been made to reduce tumor growth by withholding single amino acids considered essential to the tumor; nevertheless, the results obtained are still controversial. The two major abnormalities of carbohydrate metabolism observed in cancer patients are an increased glucose turnover and an impaired glucose tissue disposal. The former seems to be due to an increased glucogenesis, whereas the latter may be attributed to an insulin resistance in contrast to the high anaerobic glucose utilization observed in the neoplastic tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of oral 5-hydroxytryptophan administration on feeding behavior in obese adult female subjects

Nineteen obese female subjects with body mass index ranging between 30 and 40 were included in a double-blind crossover study aimed at evaluating the effects of oral 5-hydroxytryptophan administration on feeding behavior, mood state and weight loss. Either 5-hydroxytryptophan (8 mg/kg/day) or placebo was administered for five weeks during which patients were not prescribed any dietary restrictions. Feeding behavior was investigated by means of a questionnaire designed to establish the onset of anorexia and related symptoms. Food intake was evaluated using a three-day diet diary. BDI, SI, STAI-T, and STAI-S were used to assess mood state. The administration of 5-hydroxytryptophan resulted in no changes in mood state but promoted typical anorexia-related symptoms, decreased food intake and weight loss during the period of observation.

Uptake of amino acids by brain microvessels isolated from rats with experimental chronic renal failure

The neurological disorders seen in patients with chronic renal failure and liver cirrhosis are analogous. Previous in vivo studies have shown that the impaired blood-brain amino acid transport seen in rats with chronic renal failure is similar to that of rats with portocaval anastomosis. To elucidate whether a comparable underlying pathogenic mechanism plays a role in both pathological conditions, blood and brain amino acid levels together with amino acid transport by isolated brain microvessels have been studied in rats with chronic renal failure and in sham-operated rats. Brain microvessels isolated from rats with experimental chronic renal failure showed that the uptake of labeled large neutral amino acid, i.e., leucine or phenylalanine, but not of lysine or alpha-methylaminoisobutyric acid, was significantly increased with respect to sham-operated rats; conversely, the uptake of glutamic acid in rats with chronic renal failure was significantly lower compared with values in controls. Kinetic analysis indicated that this was mainly due to increased exchange transport activity (Vmax) of the L-system, rather than to changes in the affinity (Km) of the carrier system for the relative substrate. These data, together with the significant rise of brain glutamine levels and an increased brain-to-plasma ratio of the sum of large neutral amino acids, are analogous to what was previously observed in rats with portocaval anastomosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acids and hepatic encephalopathy

The consideration of HE and its etiology has undergone a radical turn within the past decade. At present HE is seen in the context of severe metabolic derangements, which failure of the liver, the central biochemical powerhouse of the body, must bring with it. The increased awarenesses on the biochemical mechanisms involved in the pathogenesis of HE have found, step by step, their own place in a complex but consequential mosaic of events, in which amino acid and HE are tightly linked. Clinical and experimental studies are needed to further improve the knowledge in this field, nontheless a certain number of corner-stones can be identified: A profound alteration of the central nervous system neurotransmission is responsible for most, if not all, of the symptoms characterizing HE. The plasma amino acid imbalance observed in cirrhotic patients represents a 'condicio sine qua non' HE may develop. A functional impairment of the amino acid transport systems at the level of the blood-brain barrier seems to play a crucial role in causing deleterious modifications of the synaptic neurotransmission in the central nervous system. The reduction of the brain entry of the "toxic" aromatic amino acids usually obtained by parenteral administration of especially tailored amino acid mixtures is most frequently followed by awakening from HE. In conclusion, most of the results obtained have demonstrated that HE represents a research field in which progresses in the knowledge of some of the pathogenic mechanisms have brought the investigators to new therapeutic approaches which have clearly improved the prognosis of patients suffering from this severe neuropsychiatric syndrome.

Exogenous lipid clearance in compensated liver cirrhosis

The tolerance to exogenous fats has been evaluated in patients with liver cirrhosis. A three-stage lipid clearance test with continuous infusion (3 hr) of a triglyceride emulsion, Intralipid, was performed on 10 patients with well compensated liver cirrhosis and 10 normolipidemic volunteers. During the infusion, blood samples were collected for the measurement of particulate triglycerides (TG) by nephelometry; samples were also collected for total TG, free fatty acids (FFA) and free tryptophan (TRP) determinations. Plasma endogenous triglycerides were calculated as the total minus exogenous, particulate, TG. The fractional removal rate (K2) and the maximal clearing capacity (K1) for exogenous TG were lower in patients than in controls, though a significant difference (p less than 0.05) was found only for K1. Endogenous TG and FFA showed a comparable rise in patients and controls during Intralipid infusion. A significant increase in free TRP was noted in cirrhotics upon maximal infusion rate. It is concluded that: in patients with well compensated liver cirrhosis the maximal clearing capacity (K1) for exogenous TG is impaired. Nonetheless, moderate amounts of fat may be removed at a normal rate from the bloodstream; a normal synthesis rate of exogenous TG may be maintained even in a severely damaged liver; considering the possible role of free TRP in the pathogenesis of hepatic encephalopathy (HE), the use of large amounts of lipids should be discouraged in patients with decompensated liver cirrhosis, or even avoided in those with impending or overt HE.

Use of branched chain amino acids for treating hepatic encephalopathy: clinical experiences

The efficacy of branched chain amino acids in two consecutive clinical studies in patients with severe hepatic encephalopathy was tested. In the preliminary uncontrolled study 19 patients with grade 3-4 hepatic encephalopathy were given an intravenous solution containing leucine 11 g/l, isoleucine 9 g/l, and valine 8.4 g/l in 20% dextrose. A complete recovery of mental state was obtained in all patients in a mean time of 20.5 hours. In a subsequent controlled study 40 patients with grade 3-4 hepatic encephalopathy were randomly assigned to receive intravenous branched chain amino acid in 20% dextrose (group A) or oral lactulose (group B). Twelve patients (70.6%) in group A and eight (47%) in group B regained consciousness in a mean time of 27.6 and 31.5 hours, respectively. The difference in the recovery rate between the two groups, although evident, was not significant. Intravenous branched chain amino acids are thus at least as effective as lactulose in reversing hepatic coma. These data argue strongly in favour of a therapeutic effect of branched chain amino acids in the treatment of hepatic encephalopathy in patients with chronic liver failure.

Plasma tryptophan and anorexia in human cancer

A correlation between anorexia and brain levels of serotonin and tryptophan (TRP) has been reported in tumor-bearing animals. In the present investigation 45 patients with various types of cancer and 13 control subjects were studied. Prior to the study the patients had received no antineoplastic therapy and were unaware of the malignancy of their disease. Feeding behavior was investigated by means of a questionnaire in which the presence of anorexia (A), aversion to meat (MA), taste (TA) or smell (SA) alterations, nausea and/or vomiting (NV) and early satiety (ES) was assessed. Plasma levels of free TRP, the other neutral amino acids (NAA), albumin and non-esterified fatty acids (NEFA) were assayed. Plasma-free TRP was significantly increased in anorectic cancer patients. The free TRP/competing NAA ratio, which might better predict brain TRP levels, was significantly higher in patients with A, MA, TA, SA, NV and ES than in controls or in non-anorectic (NA) cancer patients. These findings seem to confirm that free TRP may play an important role in human cancer anorexia.