Nutrition and metabolism最新文献

6 patients in end-stage renal failure of varying aetiologies have been studied on low protein dietary regiments according to a P 6 formulation. All patients had part of their daily protein allowance substituted by an essential amino acid capsule also containing histidine and glutamic acid. All patients were maintained in nutritional balance as a result of the regiments prescribed. No toxic effects were noted and patient compliance was good. Our studies suggest the amino acid formulation given is safe and did not cause any fluctuations in patient plasma amino acid profiles. Our studies suggest an improved method of low protein dietary management for chronic renal failure patients together with a greater flexibility and wider range of prescribing possibilities. It is recommended that amino acid supplements according to the formula produced here constitute an improvement on currently prescribed Giovannetti regimens.

Monolayer cultures of normal human fibroblasts were used to study the effects of the main subclasses of high-density lipoproteins, HDL2 and HDL3, on 3-hydroxy-3-methylglutaryl CoA reductase (EC 1.1.1.34) activity. In this system, HDL3 (d = 1.125-1.210 g/cm3) specifically induced HMG-CoA reductase activity. Evaluation of culture dynamics revealed that enzyme induction was restricted to the stationary phase of growth. When the cells were incubated with HDL2 (d = 1.063-1.125 g/cm3), suppression of reductase activity was observed. Mixtures of HDL2 and HDL3 suppressed reductase activity when HDL2 was greater than 35% of the total HDL. The suppressive effects of HDL2 were abolished by treatment with cyclohexanedione and restored by regeneration of the arginyl residues, suggesting an apoprotein-mediated suppressive mechanism. These observations show that the cellular effects of HDL depend upon the stage of cell growth and the ratio of HDL subclasses in HDL as usually isolated.

Among the cholesterol-carrying lipoproteins, low-density lipoproteins (LDL) have been associated with coronary heart disease as a risk factor while high-density lipoproteins (HDL) appear to protect against coronary heart disease. According to studies with cells in tissue culture, control mechanisms of receptor-mediated LDL uptake are important in maintaining the cholesterol balance within the arterial cells. HDL may be a vehicle for transporting cholesterol from peripheral cells to the liver. Recent results, derived from studies of patients affected with Tangier disease (absence of HDL in plasma), favor the hypothesis that HDL precursors (e.g. surface remnants of chylomicrons) may be more potent in cholesterol uptake than mature HDL.

Two groups of rats were fed diets containing large amounts (45-50% of the total digestible energy) of sunflower seed oil or hydrogenated coconut oil for 4-5 days. The left ventricular working capacity, the coronary flow rate, the oxygen consumption, the glucose uptake and the lactate release were determined in the isolated perfused heart. The fatty acid composition of the heart phospholipids was also determined. The left ventricular working capacity and the coronary flow rate of hearts of rats fed sunflower seed oil are higher (10-20%) than those of rats fed hydrogenated coconut oil. Feeding the two fats for 3-4 weeks instead of 4-5 days does not alter the results. There are no or only minor differences between the two dietary groups as to the other quantities mentioned. It is concluded that dietary fats affect the properties of the heart already after a short feeding time.

The effect of undernutrition on the fatty acid profiles of cerebrosides and phospholipids in the developing rat brain has been investigated. Undernutrition was imposed post-natally in pups by the method of large litter size and feeding a protein-deficient diet during the post-weaning period. The results showed that lignoceric (24:0) and nervonic (24:1) acids of cerebrosides, which are marker fatty acids of myelin, were significantly lower in 50-day-old undernourished rats than in well-nourished controls. Among the polyunsaturated fatty acids of phospholipids the contribution of arachidonic acid (20:4) to the total fatty acids was lower in 10- and 21-day-old as well as 50-day-old rats. Altered fatty acid pattern of lipid classes might be the result of impaired myelination of brain due to nutritional stress.

L-[U-14C]-sorbose was administered orally as single doses to 5 normal rats. The recovery of radioactivity was 5.3% in the urine, 46% in the faeces exclusively as L-sorbose 16% as carbon dioxide. Caloric utilization was approximately 25%. A second group of 3 rats that had previously received L-sorbose in their diet showed 14C recoveries of 8.9% in the urine, 6.6% in the faeces and 59% as carbon dioxide. The time course of expired carbon dioxide suggests that a portion of L-sorbose was rapidly absorbed and partially metabolized while the principal pathway involved fermentation by the intestinal microflora to volatile fatty acids which were subsequently absorbed and metabolized. The total caloric utilization of L-sorbose was estimated to be 70%. It was observed that a human intestinal microflora also required an adaptation period in order to ferment this sugar. The efficiency of the fermentation was estimated to be 70%.

Serum calcium, inorganic phosphate and alkaline phosphatase, tubular reabsorption of phosphate (TRP) estimation and radiological examination of the skeleton were conducted in 40 cases (18-50 years of age) on anticonvulsant therapy and 20 controls. The epileptic group showed a statistically significant rise in serum alkaline phosphatase and a fall in TRP. In none of the cases, however, was there clinical or radiological evidence of osteomalacia. Biochemical abnormalities were seen mainly in the youngest individuals. It seems that the critical factor for the development of anticonvulsant osteomalacia is the lack of dietary vitamin D/solar exposure or increased body requirement of the vitamin.

The bioabailability of zinc in three cereals was determined by a rat assay, using total femur zinc as the indicator. The basal diet contained 25% egg white solids and 0.6 microgram zinc per gram. The infant cereals were included in the diets at three graded levels to supply 3--12 microgram zinc per gram. Zinc sulphate was used as a standard source, with and without supplemental iron (185, 370, 555 microgram/g, respectively) at 3, 6 and 9 microgram zinc per gram with a view to determine the effect of excess iron on zinc availability. Added iron from sodium iron pyrophosphate was not found to have any effect on the bioavailability of zinc from zinc sulphate. The responses for the three cereals were linear but the regression lines representing them and the standard source did not have a common intercept. However, the ratio of the slope of the regression line for the test source to that of the standard indicated that the cereal containing soy protein was a better source of zinc (ratio = 0.49) than the barley cereal (9.10) or the rice cereal (0.32). These ratios did not show any correlation with the actual iron-precipitable phytate phosphorus content or the reported crude fibre content.

According to most existing theories, the regulation of energy balance is achieved by control of energy intake. This study was undertaken to find out whether there was control of energy output as well. Food intake, energy balance and the feed efficiency of weanling female mice made obese with injections of gold-thioglucose and monosodium glutamate indicate that the obesity is primarly due to an increased energetic efficiency, and suggest that the hypothalamus plays a role in controlling energy output. In the case of treatment with MSG, a relative obesity was observed, i.e. an increase in body fat without any change in body weight. This indicates that the CNS centres for the regulation of body weight and body fat are probably not the same. It is suggested that MSG obesity will be a suitable model for comparative studies of body weight and the regulation of fat content. It is concluded that chemically induced obesity is due more to a lower metabolic rate than to an elevated food intake.