The effect of dietary protein depletion and repletion on rat hepatic mixed function oxidase activities

Impact of protein deficient diet on the pharmacokinetics of glibenclamide in a model of malnutrition in rats

Purpose

The present investigation deals with the impact of protein energy malnourished condition on the pharmacokinetic profile of glibenclamide. Protein energy malnourished condition leads to malnutrition related diabetes mellitus (MRDM), Fibrocalculus pancreatic diabetes mellitus (FCPD) or Lean body mass diabetes mellitus (LBMDM).

Method

In the present study, malnutrition was developed in female wistar rats using a modified protein deficient diet (0.5%). The experiment was performed on 12 animals, each group containing 6 female wistar rats. The control group animals were fed with standard pellet diet (AIN 93 G diet) while group 2 received the low protein diet (0.5%) for 75 days. Glibenclamide (Gli) suspension (30 mg/kg) was administered orally to these rats on 75 days and kinetic parameters were evaluated by HPLC analysis.The pharmacokinetic interpretation done by pksolver software version 2.0, statistical comparison done by applying student T test.

Results

The results of body weight and hematological parameters indicated a significant decreased in the body weight in protein deficit rats to 124.1 ± 6.2 g compared to 235.5 ± 8.4 g (p < 0.01) control rats; whereas a decrease in the hemoglobin to 5.8 ± 0.6 g/dL, total blood protein level to 6.9 ± 0.6 g/dL and blood albumin levels to 2.7 ± 0.4 g/dL in protein deficit rats compared to 15 ± 0.7 g/dL(p < 0.05), 8.1 ± 0.4 g/dL(p < 0.05), and 4.5 ± 0.2 g/dL(p < 0.05), respectively in control rats. All these findings reflect the malnourished condition and weight loss due to a protein deficit diet in experimental animals. There was an increase in the fasting blood glucose levels up to 150 ± 17.4 mg/dL in the protein deficit diet group as compared to 98.7 ± 14.1 mg/dL(p < 0.05) in control rats reflect the prediabetes state in malnourished animals. The results of the pharmacokinetic study reflect a significant lowering of half-life (T½) of glibenclamide to 96.8 ± 0.8 min. in malnourished rats compared to 166.7 ± 0.74 min. (p < 0.001) in control rats. The maximum concentration (Cmax) of glibenclamide in the malnourished rats was significantly higher 20.74 ± 0.65 μg/mL and also took double time i.e. about 180 min. to reach maximum concentration (Tmax) compared to the control rats values 7.9 ± 0.84 μg/mL (p < 0.001) and 90.0 ± 0.24 min. (p < 0.001) respectively. The area under the plasma concentration-time curve [AUC(0-∞)] in malnourished rats increased 4439.1 ± 40.6 μg/ml*min as compared to 1235.9 ± 55.8 μg/ml*min (p < 0.001) in control rats. There was a lowering in the total body clearance (CL) to 0.4 ± 0.02 L/hr and volume of distribution (Vd) to 1.75 ± 0.07 L of glibenclamide in the protein deficit group compared to 1.4 ± 0.3 L/hr (p < 0.001) and 3.14 ± 0.8 L (p < 0.01), respectively in the control rats.

Conclusion

From this study it concludes that there is an increase in the T½, Cmax, Tmax and AUC(0-∞) of glibenclamide in malnourished rats while the total body clearance and volume of distribution is lowered. Therefore this study proposes to conduct an adequate pharmacokinetic study in malnourished patients to decide whether the standard glibenclamide dose should be adapted according to the nutritional status of the individual.

Nutritional Renaissance and Public Health Policy

The science of nutrition has long been entrapped in reductionist interpretation of details, a source of great confusion. However, if nutrition is defined as the integration of countless nutrient factors, metabolic reactions and outcomes, biologically orchestrated as in symphony, its relevance for personal and public health would be less confusing and more productive. This more wholistic interpretation may be observed at the cellular and physiological levels and may be described, in part, by the concept of pleiotropy (multiple cell-based effects from one nutrient source), together with its more expansive cousin, epitropy (multiple cell-based effects from multiple nutrients). There are many consequences. First, wholistic interpretation helps to explain the profound but little-known health benefits of whole plant-based foods (not vegan or vegetarian) when compared with whole animal-based foods and/or with the nutritionally variable convenience foods (generally high in fat, salt, refined carbohydrates and low in complex carbohydrates). Second, wholistic interpretation explains why the U.S. Dietary Guidelines and related public policies, which are primarily conceived from reductionist reasoning, serve political agendas so effectively. If diet and health advisories were to acknowledge the biological complexity of nutrition, then make greater use of deductive (top down) instead of inductive (bottom up) reasoning, there would be less confusion. Third, wholistic nutrition, if acknowledged, could greatly help to resolve the highly-polarized, virtually intractable political debate on health care. And fourth, this definition tells why nutrition is rarely if ever offered in medical school training, is not one of the 130 or so medical specialties, and does not have a dedicated research institute at U.S. National Institutes of Health. Nutrition is a wholistic science whereas medical practice is reductionist, a serious mismatch that causes biased judgement of nutrition. But this dichotomy would not exist if the medical practice profession were to understand and adopt wholistic interpretation. Reductionist research, however, is crucially important because its findings provide the granular structure for wholistic interpretation-these two philosophies are inescapably interdependent. Evidence obtained in this manner lends strong support to the suggestion that nutrition is more efficacious and far more affordable in maintaining and restoring (treating) health than all the pills and procedures combined. Admittedly, this is a challenging paradigm for the domain of medical science itself.

The effect of dietary protein depletion on hepatic 5-fluorouracil metabolism

BACKGROUND

Protein calorie malnutrition, which is highly prevalent in tumor-bearing hosts, increases toxicity to 5-fluorouracil (5-FU), but the mechanisms are unclear. This study investigated the effects of protein depletion on 5-FU in vivo hepatic metabolism using F19-nuclear magnetic resonance spectroscopy (19F-NMRS).

METHODS

Rats received normal (21.5%) or low (2.5%) protein diet for 25 days. 5-FU was injected intraperitoneally, and hepatic fluorine spectra were obtained. Parallel experiments were conducted to determine serum 5-FU pharmacokinetics using high-performance liquid chromatography (HPLC) and to measure hepatic dihydropyrimidine dehydrogenase (DPD) activity.

RESULTS

The mean time of initial detection of fluoro-beta-alanine and the mean duration of the 5-FU signal in the liver were significantly prolonged in the low-protein group. 5-FU clearance and hepatic DPD activity were significantly lower in the low-protein group. Low-protein animals demonstrated increased toxicity, with diarrhea, weight loss, leukopenia (P < 0.001), and an 85% mortality, compared with regular diet animals, who had mild diarrhea and weight loss but no leukopenia and a 12% mortality.

CONCLUSION

Protein depletion results in increased toxicity to 5-FU, which is associated with a significantly decreased rate of hepatic metabolism and clearance of 5-FU and a significant decrease in hepatic DPD activity. 19F-NMRS can noninvasively identify these alterations of 5-FU metabolism in vivo and may serve as a useful guide to determining chemotherapy dosage adjustments to reduce toxicity.

The influence of dietary energy levels with and without PCB induction on the growth of tilapia, Oreochromis niloticos x O. aureus

The effects of three dietary energy levels, 323, 365 and 408 Kcal/100g diet, on the growth performance of hybrid tilapia, Oreochromis niloticus x O. aureus, were studied. The experiment was carried out for 3 months in a recirculating rearing system. Growth and feed conversion ratios were significantly reduced (p<0.05) in fish exposed to 100 ppm polychlorinated biphenyl (PCB), fed high energy diets (365 and 408 Kcal/100g diet). The hepatic cytochrome P-450 and NADPH-cytochrome c reductase activities were also significantly (p<0.05) lower in PCB-treated fish fed high energy diets (365 and 408 Kcal/100g diet) than fish fed lower energy diet (323 Kcal/100g diet). The malic enzyme activity and the body lipid content in fish generally increased as the dietary energy level increased.

The effects of age and dietary protein restriction on the pharmacokinetics of theophylline in the rat

The influence of dietary protein levels on theophylline kinetics was examined in male Fischer 344 virgin rats of 2, 14 and 20 months of age fed for four weeks on a 23% (control) or 5% (low) protein diet ad libitum. Protein deficiency led to a significant decrease in body weight gain for the 2 month old rats (10.9% versus 26.5%). In addition, decreases in total body weight of 7.5% and 15.3% were seen for the 14 and 20 month old rats, respectively, on a low protein diet. Total proteins and albumin levels in plasma were not significantly affected by age or dietary protein levels. After intravenous administration of 10 mg/kg aminophylline, the average mean residence time (MRT) was significantly longer in 20 month old rats as compared to the younger rats, while 14 month old rats had a greater elimination rate constant than the 2 and 20 month old rats. There were significant reductions in the mean steady-state apparent volume of distribution (Vss) in the 2 and 14 month old rats on a low protein diet of 31% and 18%, respectively, while there was no difference between the diets in 20 month old rats. In addition, the Vss decreased from 0.71 L/kg to 0.57 L/kg in the 2 and 20 month old rats, respectively, on a normal protein diet. Dietary protein deficiency led to a significant reduction of total body clearance from approximately 73 to 45 ml/hr/kg in the 2 and 14 month old rats.2+p

Absorption and disposition kinetics of chlorothiazide in protein-calorie malnutrition

The influence of dietary protein deficiency on the absorption and disposition kinetics of chlorothiazide was investigated in male Sprague-Dawley rats fed for 4 weeks on a 23 per cent (control) or a 5 per cent (low) protein diet ad libitum. Chlorothiazide in plasma and urine was determined by a sensitive and specific HPLC assay. Following an intravenous dose of 10 mg kg-1 chlorothiazide, there was a significant decrease in the total plasma clearance (Cl) per kg of body weight from 1.80 +/- 0.15 to 1.29 +/- 0.15 l h-1 kg-1 and apparent steady-state volume of distribution from 0.65 +/- 0.13 to 0.38 +/- 0.07 l kg-1 in the protein-deficient rats. However, no significant difference was found in the two groups of animals with respect to mean residence time (MRT) and free fraction of drug in plasma. The mean harmonic half-life was increased from 72 to 91 min in the protein-deficient rats. The urinary recovery of unchanged chlorothiazide in 48 h was essentially complete in both groups of animals. The absorption of chlorothiazide, as assessed by the mean urinary recovery of unchanged drug after oral administration, was 66 per cent and 68 per cent in normal and protein-deficient rats, respectively.

The effect of medroxyprogesterone acetate on the hepatic drug-metabolizing enzymes in normal and protein-deficient female rats

Effect of depot medroxyprogesterone acetate on the hepatic drug-metabolizing enzymes was studied in female protein-deficient and normal pair-fed rats. Treatment with this drug did not cause any change in organ weight, microsomal protein, and soluble protein yield per gram of tissue in both groups. MPA administration resulted in significant increases in the content of cytochrome P-450 and b5, and activities of benzo[a]pyrene hydroxylase, UDP-glucuronosyltransferase, and NADPH-Cyt c reductase in both pair-fed control and protein-deficient rats. However, the content of glutathione and activity of glutathione-S-transferase were not affected appreciably. The present study suggests that MPA treatment induces drug-metabolizing enzymes in liver to almost the same extent in both protein-deficient and normal pair-fed rats.

Pharmacokinetics of theophylline in protein-calorie malnutrition

The influence of protein-calorie malnutrition (PCM) on the disposition of theophylline was investigated in male Sprague-Dawley rats fed for four weeks on a 23 per cent (control) or 5 per cent (low) protein diet ad lib. Dietary protein deficiency led to a decrease in body weight gain, plasma proteins, albumin, microsomal proteins, and cytochrome P-450. After intravenous administration of aminophylline equivalent to 10 mg kg-1 theophylline, the average mean residence time (MRT) was 58 per cent higher in the protein-deficient rats, while the total plasma clearance (Cl) per kilogram of body weight and elimination rate constant (k) were decreased by 39 per cent and 45 per cent, respectively, when compared to rats on a normal protein diet. No significant difference was found in the two groups of animals with respect to the apparent steady-state volume of distribution (Vss). The present results suggest that the mechanism responsible for the observed pharmacokinetic changes in the protein-deficient rats is related to the reduced amount and/or activity of the hepatic mixed function oxidases.

Effect of dietary composition and estradiol implants on hepatic microsomal mixed function oxidase and lipid deposition in growing chicks

Three experiments were conducted to investigate the effect of diet and estradiol (E2) administration on hepatic microsomal mixed function oxidase (MFO) activity, E2 metabolism, and liver lipid content in male broiler chicks. Broiler chicks (3 weeks of age) were fed either a corn-soybean (CS) diet or a diet containing fish meal, alfalfa meal, and torula yeast (FAY) for 19 days in Experiments 1 and 3 and for 14 days in Experiment 2, respectively. Half of the chicks were implanted with tubes containing E2. In all experiments when the chicks were estrogenized, feeding FAY significantly lowered liver lipid content and plasma E2 concentration. Activity of hepatic microsomal aniline hydroxylase and content of cytochrome P-450 were significantly increased by feeding FAY with or without E2 administration. The chicks fed the CS diet had a significantly lower content of cytochrome P-450 when E2 was administered. Activities of aminopyrine demethylase and nicotinamide adenine dinucleotide phosphate, reduced (NADPH)-cytochrome C reductase did not differ significantly between the diets. In in vitro studies, conversion of 14C-E2 into the water soluble fraction was significantly increased in microsomes from chicks fed the FAY diet as compared to ones from chicks fed the CS diet. The results suggest that some of the hepatic microsomal functions on the CS diet are modified by the change in diet composition and that these modifications are probably associated with E2 metabolism and occurrence of fatty liver.

The effects of gum arabic, wheat offal and various of its fractions on the metabolism of 14C-labelled aflatoxin B1 in the male weanling rat

1. Male weanling rats were given for extended periods diets containing gum arabic or wheat offal or various offal fractions. The fractions included two lipid fractions, a water-soluble extract and a modified-acid-detergent (MAD)-fibre extract. The diets contained either low concentrations of aflatoxin B1 (induced rats) or were free from this source of aflatoxin (non-induced rats). The distribution of 14C was then studied after the rats received 14C-labelled aflatoxin B1 in their feed. Blood plasma concentrations of triglycerides, and total cholesterol were also measured. 2. Gum arabic and wheat offal accelerated the rate of passage of 14C through the small intestine and wheat offal very considerably decreased retention time in the large intestine. Both fibre sources increased faecal bulk. However, only wheat offal decreased liver and urinary accumulation of 14C and the effect could be explained entirely by the MAD-fibre fraction of wheat offal. 3. The possible induction of either microsomal enzymes unrelated to the production of mutagenic aflatoxin metabolites, or of extramicrosomal enzymes is discussed; but it is concluded that the main effect brought about by wheat offal on the toxicity and carcinogenicity of aflatoxin can be attributed to a direct influence of the MAD fibre fraction of wheat offal on the intestinal absorption of aflatoxin B1. 4. The relevance of these conclusions to drug safety studies is discussed, because comparable studies may yield differing results, despite a use of diets having the same nutrient composition but differing ingredient composition.