Nutritional effectors of hepatic steatosis induced by parenteral nutrition in the rat

The relative importance of three nutritional variables, nonprotein energy level, glucose-lipid calorie distribution and amino acid nitrogen level, in contributing to the steatosis that develops during a short course of parenteral nutrition was studied in intravenously fed rats. Eight infusates were tested that contained various combinations of glucose, lipid emulsion and amino acids. The infusate nonprotein energy level was the predominant effector of liver lipid content. The excessive energy level was associated with significant increments in steatosis, ranging from a 26% increase for high-fat, adequate-nitrogen infusates to a 95% increase for low-fat, adequate-nitrogen infusates. An interaction of amino nitrogen level and glucose-lipid calorie distribution also affected the severity of steatosis. The steatosis observed with inadequate-nitrogen infusates was accentuated in combination with the high-fat calorie distribution and was attenuated with the low-fat calorie distribution. The most striking effect of nitrogen inadequacy was a 3-fold increase in liver lipid content with the excessive calorie, high-fat infusates. The infusate that minimized steatosis provided energy and nitrogen at adequate levels and was low in fat content. This infusate also led to liver lipid composition and plasma lipid levels that most closely resembled those of rats fed stock diet.

Dietary evaluation of outpatients with chronic obstructive pulmonary disease

Protein-calorie malnutrition is prevalent among individuals with chronic obstructive pulmonary disease (COPD), and suboptimal body weight has been associated with increased morbidity and mortality. Pulmonary function, anthropometric measurements, and dietary intake were evaluated in 64 outpatients with stable COPD to assess interrelationships of those parameters. Those individuals with body weights less than 75% of standard for height, age, and sex had the greatest degree of airway obstruction, poorest lung diffusing capacity, and greatest loss of body fat and muscle mass. Contrary to what had been anticipated, calorie and protein intake levels were highest in the less than 75% of standard body weight group, decreased as relative body weight increased, and were lowest in the greater than 105% of standard body weight group. Those results indicate that caloric needs increase as COPD progresses. Intake levels of calcium, phosphorus, iron, vitamin A, thiamin, riboflavin, niacin, and vitamin C were adequate in terms of the RDAs and were not related to relative body weight.

The prevalence and determinants of nutritional changes in chronic obstructive pulmonary disease

Sixty outpatients with chronic obstructive pulmonary disease underwent nutritional, physiologic, and psychologic evaluation to determine the prevalence of nutritional depletion and the relationship to physiologic and psychologic factors. Weight loss was reported in 27 percent. Triceps skinfolds (TSF) were less than 60 percent of standard in 33 percent, none had mid-arm muscle circumference (MAMC) less than 60 percent of standard, and 5 percent had body weight (BW) less than 60 percent of ideal. Values for BW-percent of ideal, TSF-percent of standard, and MAMC-percent of standard were inversely correlated with the percent of estimated caloric expenditure ingested. Also, BW percent was correlated with FEV1 percent predicted, diffusion capacity percent predicted, and oxygen consumption/kg at rest (VO2 percent/kg). There were five variables that explained 62.6 percent of the variation in BW percent: VO2/kg at rest explained 22.2 percent; ventilatory equivalent 13.5 percent; PaCO2 9.8 percent; log vital capacity percent predicted 9.2 percent; and depression 7.8 percent. It is concluded that increased caloric utilization without adequate compensation in dietary intake is the reason for nutritional depletion.

Development of hepatic steatosis and essential fatty acid deficiency in rats with hypercaloric, fat-free parenteral nutrition

Intravenous (i.v.) infusion of excessive energy has been associated with hepatic steatosis. The time course of liver lipid accumulation was examined during 6 days of i.v. hyperalimentation with fat-free infusate. Adult male rats with indwelling superior vena cava cannulas received a dextrose-amino acid infusate for 0, 1/2, 1, 2, 4 or 6 days to provide 146% of nonprotein energy requirement [congruent to 350 non-protein kcal/(kg . day)] and 335% of nitrogen requirement [congruent to 2.7 g amino nitrogen/(kg . day)]. Significant hepatomegaly was apparent by day 1/2. Initially, glycogen deposition accounted for the liver enlargement, but after day 2, liver glycogen was declining and liver lipid was increasing. By day 4, liver lipid had increased fourfold and was the major contributor to hepatomegaly. Concurrent with fatty liver metamorphosis, hepatic essential fatty acid deficiency (EFAD) developed by day 4; liver linoleic acid levels had dropped from 20 to 1% of total fatty acids, and liver triene:tetraene ratio was 0.68. Similar changes in hepatic phospholipid fatty acids were observed. Enhanced lipogenesis and impaired lipid transport is known to accompany EFAD and may underlie the observed steatosis. A doubling of plasma cholesterol levels was also associated with steatosis. The mechanism leading to this increase in plasma cholesterol warrants further investigation.

Decreases in serum high-density-lipoprotein cholesterol and total cholesterol resulting from naturally produced and recombinant DNA-derived leukocyte interferons

A three-phase study was conducted to examine the effect of leukocyte interferon administration on serum high-density-lipoprotein (HDL) cholesterol and total cholesterol levels. In the initial phase, human leukocyte interferon decreased HDL cholesterol (P less than 0.05) and total cholesterol (P less than 0.05) levels in patients with breast carcinoma. Decreases began with initiation of the interferon administration, were sustained throughout the period of treatment, and increased toward pretreatment values with discontinuation of interferon. In the second phase of the study, in neither of two comparison groups of women receiving cytotoxic chemotherapy, excluding interferon, did any similar decrease in HDL cholesterol occur. In a third comparison group of women being treated for metastatic breast carcinoma, a predicted and significant (P less than 0.01) drop in HDL cholesterol level without a concomitant lowering of total cholesterol level occurred immediately following the initiation of androgen therapy. To confirm that the observed cholesterol level decreases were associated with interferon rather than a contaminant thereof, analyses were also carried out on samples from a study utilizing interferon rather than a contaminant thereof, analyses were also carried out on samples from a study utilizing interferon produced by recombinant DNA techniques and purified to homogeneity. A similar decrease in HDL cholesterol (P less than 0.05) and total cholesterol (P less than 0.01) was observed. A definite relationship therefore appears to exist between the administration of human leukocyte interferon and decreased plasma levels of HDL cholesterol and total cholesterol.

Predictive clinical value of nutritional assessment factors in COPD

Thirty-nine stable outpatients with moderate-to-severe chronic obstructive pulmonary disease (COPD) were studied prospectively to determine the predictive value of several nutritional factors on the clinical outcome. Physiologic evaluation including FEV1, diffusing capacity, PaO2, as well as nutritional evaluation including triceps skin fold (TSF), midarm muscle circumference, body weight percentage of standard, history of 5 percent weight loss in the year prior to clinic visit, and average daily caloric intake based on a three-day diet record were all done at the clinic visit. Hospitalization or death during the six months to one year following the initial evaluation were the clinical outcome factors evaluated. Five of the 16 patients (31 percent) needing hospitalization during that time had weight loss during the year prior to the initial evaluation, while eight out of the 23 (35 percent) not requiring hospitalization had weight loss. There was a significantly lower TSF percent standard (TSF%) in the subgroup who subsequently required hospitalization (p less than 0.05). Nonhospitalized patients with severe depletion of body fat (TSF% less than 60) at initial evaluation ingested significantly more calories per kilogram than the severely depleted patients requiring hospitalization in the next six to 12 months (p less than 0.05) suggesting a protective effect of increased caloric intake. Increased caloric intake did not improve mortality statistics.

Comparison of rat hepatic cholesterol biosynthesis during skim milk versus whey permeate ingestion

Whey permeate is an ultrafiltrate of whey that is devoid of protein but contains lactose, salts, and other soluble low molecular weight compounds. These experiments compared cholesterol concentrations of blood plasma, hepatic lipids, and hepatic cholesterol biosynthesis of rats ingesting skim milk powder versus whey permeate powder. Groups of young male rats weighing 90 to 92 g were fed a casein-based diet into which skim milk powder or whey permeate powder was incorporated isocalorically. No effects of skim milk or whey permeate on plasma cholesterol concentrations were observed at any time during 5-wk of feeding. However, 3-hydroxy-3-methylglutaryl co-enzyme A reductase activity was increased by either skim milk or whey permeate feeding. Hepatic cholesterol, triglyceride, and phospholipid concentrations at wk 5 were unchanged. Plasma and hepatic cholesterol responses of rats to whey permeate ingestion are similar to those that occur with skim milk consumption, and plasma and hepatic cholesterol concentrations do not reflect necessarily an increase in hepatic cholesterol biosynthesis.

Variability in Cholesterolemic Response of Rats Consuming Skim Milk

The hypocholesterolemic property of skim milk powder (SMP) was investigated using rats in a series of six separate experiments. SMP was incorporated at a level of 25% by weight into stock diets or semipurified diets with casein or soy as the protein source. Ingestion of SMP with casein-based diets for periods of 5 to 12 weeks produced a transient hypocholesterolemia only when diets were introduced within 1 week of weaning. In two different experiments, when weanling rats were fed stock diets with or without SMP for periods of 8 and 16 weeks, SMP ingestion led to a transient decrease in plasma cholesterol (CH) levels in only one experiment. Finally, SMP was not hypocholesterolemic when fed to weanling rats with a soy-based diet for 8 weeks. Together, these results reveal that consumption of SMP does not consistently elicit hypocholesterolemia in rats. We found that to observe significant differences in plasma CH levels between the control and SMP groups, semipurified diets containing SMP had to be fed to rats within the first week of weaning; in addition, the diets had to be free of, or reduced in other components with cholesterol-lowering properties. Finally, the SMP-induced hypocholesterolemia that we observed appeared to facilitate the normal rate of decline in plasma CH levels during the post-weaning period, producing only a transient difference between control and SMP groups.

Plasma and hepatic cholesterol and hepatic HMG CoA reductase levels in rats fed fluid or powdered skim milk

The effects of skim milk powder (SMP) and fluid skim milk (FSM) on plasma cholesterol (CH) and hepatic liquid concentrations, and 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG CoA) reductase activity of rats of different ages were compared. Groups of young (23 days old) and older (45 days old) rats were fed a casein -based diet and provided tap water; the casein-based diet and FSM as fluid source; or tap water and the casein diet into which SMP (25% by wt.) had been isocalorically incorporated. Plasma CH concentrations were determined at 0, 1.5, 3 and 5 wk, hepatic total lipid, triglyceride and CH at 5 wk. Half of each group were killed at wk 3 and the other half at wk 5 for determinations of HMG CoA reductase activity. Both FSM and SMP decreased plasma CH levels at 1.5 and 3 wk of feeding in the young rats; plasma CH concentrations of the older rats were not altered by either FSM or SMP. Both milk derivatives increased HMG CoA reductase activity at wk 3 and wk 5 in both ages of rat, whereas hepatic lipid levels were unchanged. In these experiments the effects of feeding FSM of SMP along with a casein-based diet were comparable and included an increase in HMB CoA reductase activity, no change in hepatic lipid levels, and a decrease in plasma CH; the latter response depended on the initial age of the rat.

Intestinal secretion of lipids and lipoproteins during carbohydrate absorption in the rat

To assess the effects of carbohydrate ingestion on the characteristics and quantities of triglyceride-rich lipoproteins produced by the intestine, mesenteric lymph was collected from rats receiving intraduodenal infusions of saline, sucrose or starch. Lymph total lipid (mg/hour) was greatest during saline infusion, decreased during sucrose and became significantly less (P less than 0.05) during starch infusion. Lipoproteins were isolated from lymph by ultracentrifugation followed by gel filtration chromatography. During saline infusion total lipid in very low density lipoproteins (VLDL) was 2-fold higher than total lipid in chylomicrons; with both carbohydrate infusions this ratio increased to seven. Both carbohydrates significantly lowered the rate of secretion of total lipid as chylomicrons. The VLDL lipid secretion rates during sucrose infusion were equivalent to those during saline, whereas starch infusion tended to decrease VLDL lipid secretion rates. These results suggest that during the process of carbohydrate absorption, carbohydrate does not enhance the flow of intestinal VLDL into the circulation; digestion and absorption of complex carbohydrates in fact may retard the intestinal contribution of triglyceride-rich lipoproteins.