Response to balanced and unbalanced plant diets

[Guest guest]

Hi All, Does the below just make your juices not flow?

The weights were lower from 1-3 weeks of amino acid deficiency, and were as

much lower after 4 weeks when the organs were harvested for analysis.

Note the CR-like changes in serum glucose and also protein of the amino

acid-deficient diet - see PMID: 11394882 [PubMed - indexed for MEDLINE] ).

Spleen = <anatomy> An organ that produces lymphocytes, filters the blood,

stores blood cells and destroys those that are aging. It is located on the

left side of the abdomen near the stomach.

Cecum --> caecum = <anatomy> A blind pouch-like commencement of the colon in

the right lower quadrant of the abdomen at the end of the small intestine.

The appendix is a diverticulum that extends off the caecum.

The PDF is available at: apapter@....

Cheers, Al.

Plant Foods for Human Nutrition 57: 245–255, 2002.

Pancreatic and intestinal enzyme activities in rats in

response to balanced and unbalanced plant diets

RAFAIL I. KUSHAK CHRISTIAN DRAPEAU ,and

HARLAND S. WINTER

Abstract. To simulate the effects of nutritionally adequate and inadequate

vegetarian diets,

rats were fed, for 28 days, an isonitrogenous, isocaloric, amino acid unbalanced

cereal diet

(CD) deficient in lysine and tryptophan or a balanced cereal-legume diet (CLD).

The impact of

these diets on enzymes responsible for digestion of proteins and carbohydrates

were measured.

Neither experimental diet significantly affected the animal’s final weight or

feed consumption

in comparison with controls fed a standard mixed diet from plant and animal

sources. How-ever,

during the first three weeks, the weight gain of rats fed the CD was

significantly lower

( 0.05), demonstrating increased feed consumption per unit of body weight. They

also had decreased pancreatic alpha-amylase activity ( 0.05) and serum protein

level ( 0.025; p<0.005)

than in the controls. It is hypothesized that decrease in a -amylase activity

was mostly related

to the tryptophan deficiency in the CD because this enzyme contains the highest

amount of

tryptophan units among all tested enzymes.

Key words: Adaptation, Digestive enzymes, Pancreas, Plant proteins, Serum, Small

intestine

Introduction

The effect of diets on nutrient absorption depends not only on their

com-position

but also on digestive enzyme adaptation. Following the work of

Pavlov [1], many investigators have shown that an increased quantity of

pro-tein,

carbohydrate or lipid in the diet is associated with elevated activities of

the corresponding pancreatic and intestinal enzymes [2–5]. Most likely, such

changes are related to increased biosynthetic rates [6, 7]. Studying adaptation

of digestive enzymes to animal and plant substrates, Ugolev [8] found that

canine gastric juice, obtained after feeding meat, hydrolyzed animal protein

(zoolytic effect) better than plant protein (phytolytic effect). Juice secreted

by

the same animal after feeding bread was more effective in hydrolyzing plant

protein than animal protein. Similar results were obtained with saliva. Saliva

taken from herbivores (rats, guinea pigs, monkeys) hydrolyzed starch more

actively than glycogen; whereas, carnivores’ (cats, foxes) saliva hydrolyzed

glycogen more actively than starch.

The effect of plant proteins on digestive enzyme adaptation is not well

characterized. When compared with animal proteins, some plant proteins

such as zein or wheat gluten in the diets of rats decrease the activity of

pancre-atic

enzymes [9]. However, other studies demonstrate [2] that the pancreatic

enzyme levels were not reduced significantly in rats fed isolated soy protein,

wheat gluten or peanut meal diets in comparison with a casein diet. Similar

data were obtained in baby pigs fed comparable levels of isolated soy protein

concentrate, fish protein concentrate or casein in short-term experiments [10].

The effect of plant proteins on intestinal enzyme activity is still unclear.

Because of the role of plant based diets in the treatment of specific dis-eases,

the effect of plant proteins on digestive enzymes remains important

not only for animal but also for human nutrition. Individuals may prefer

specific foods such as strict plant based diets (vegans, macrobiotics) or plant

mixtures with milk and/or eggs (lacto-, ovo- or lacto-ovo-vegetarians) but

consequences of feeding such diets may be significant, especially in children

using poorly designed vegetarian diets [11]. Plant diets containing a single

source of protein (unbalanced plant diets) are thought to be less beneficial for

human health than mixed diets containing animal and plant proteins. How-ever,

balanced plant diets, containing a mixture of complementary proteins

and fortified with vitamins and minerals, do not have any disadvantage in

comparison with standard mixed diets [12–14]. Furthermore, plant diets rich

in fiber improve colonic function and facilitate lowering of blood cholesterol

[15].

The goal of this study was to evaluate the effect of different plant diets

on the growth, food consumption, nutrient metabolism and digestive enzyme

activity in the pancreas, small intestine and blood of rats. Plant proteins were

given in the form of cereal (unbalanced diet) or cereal and legume mixture

(balanced diet) to simulate nutritionally adequate and inadequate vegetarian

diets.

a Standard diet was represented by #5012 rat diet from Purina Test Diets

(Richmond, IN).

b Vitamins and minerals in all diets were according to ‘LabDiets. The

Richmond Standard. Animal Diet Reference Guide.’ PMI Feeds Inc.

c Calculated as a sum of the energy contained in protein, carbohydrate,

and fat fractions of the diet.

d Diet’s amino acid analyses were performed by PMI Feeds Inc.

Material and methods

Animals and diets

Male Sprague-Dawley rats ......Control rats continued for 28

days to receive the same standard diet, but the two other groups were fed the

experimental plant diets (Table 1). One group received mainly cereal protein

in the form of ground corn and gluten meal (cereal diet); the other group

was fed a mixture of cereal and legume proteins in the form of ground corn,

gluten meal and soybean meal (cereal-legume diet). All experimental diets

contained 2% brewer’s yeast.

[Corn and gluten were compensated by complementary oils

for the opposing diet. Lysine was 0.5311 deficient diet versus supplemented

1.3300% and Tryptophan 0.1497 versus 0.2876%.]

Analysis of the chemical composition of the diets demonstrated that they

were isonitrogenous and isocaloric (Table 1) and that the amount of

mac-ronutrients

and total digestible nutrient concentration in all three diets were

similar. Micronutrient levels in standard and experimental diets also were

similar. However, the cereal diet was deficient in some essential amino acids

such as lysine and tryptophan (correspondingly 38% and 51% of the level in

standard diet).

At the end of the experiment [four weeks], animals were fasted overnight and

......

Viscera (liver, kidney, small and large intestine, pan-creas,

cecum, spleen) were collected.........

Results

Dietary effects on growth and feed consumption

Initial average weights of control animals and rats fed cereal and cereal-legume

diets were similar. The final average weight of rats in different groups

also did not differ significantly. However, during the first three weeks of the

experiment, rats fed a cereal diet (but not cereal-legume diet) gained weight

more slowly (correspondingly p<0.01, p<0.01, and p<0.05 for the

first, second, and third weeks) than controls (Figure 1). Changes in food

consumption in different animal groups during the experimental period were

not appreciable and total food consumption also did not differ significantly.

The feed efficiency ratio, characterizing the feed consumption per unit

of weight gain in rats fed the cereal diet, was significantly higher (4.56

±0.12;

p<0.01) at the end of the experiment than in controls (4.09 ±0.12).

In the rats fed the cereal-legume diet, the ratio (4.37 ±0.10) did not differ

significantly from the control.

Figure 1. Initial weight (IW) and weight dynamics of rats fed standard diet

(SD), cereal diet

(CD) and cereal-legume diet (CLD). W1-W4 – weeks 1 to 4. Results are expressed

as mean

±SE, n = 8. During the first three weeks of the experiment rats fed a cereal

diet had lower body

weight than controls fed the standard mixed diet ( *p=0.01, **p=0.05).

Table 2. Weight of viscera (g/100 g body weight) from animals consuming cereal

and

cereal-legume diets

Diet

SD Spleen 0.17 ±0.01 Cecum1.16 ±0.06

CD Spleen 0.20 ±0.09a Cecum 0.91 ±0.01a

CLD Spleen 0.21 ±0.01b Cecum 1.45 ±0.12b

Value are mean ±SE, n = 8. SD – standard diet, CD – cereal diet, CLD –

cereal-legume

diet.

a = p<0.05 and b = p<0.025 versus the standard diet.

Table 3. Effect of plant diets on rat’s pancreatic and intestinal enzyme

activities

Enzymes Cereal-legume diet

alpha-Amylase Standard diet 220.65 ±42.05 Cereal diet 127.72 ±19.65*,

p<0.05

versus the standard diet. Cereal -legume diet 143.29 ±27.71

Table 4. Standard Cereal

Cerial-legume

Glucose 106.62 ±7.41 108.63 ±11.02 138.12 ±12.82b

Protein 13.30 ±0.66 11.61 ±0.44a 15.68 ±0.29c

Values are mean ±SE, n=8. Glucose concentration in mg/100 ml; pro-tein

concentration in mg/ml.

a = p<0.05, b p= <0.025, and c = p<0.005 versus the standard diet.

Compared with controls, weight of viscera (g/100 g body weight) showed

a slight but statistically significant decrease ( 0.05) for the spleen in rats

fed the cereal diet, and an increase

for spleen and cecum ( 0.05) (Table 3). Rats

fed the cereal-legume diet also had lower a -amylase activity than the controls,

but this difference was not statistically significant. The protein source in the

diet did not affect trypsin activity in the rat’s pancreas. The same was true

for maltase, sucrase and aminopeptidase N activities in the small intestinal

mucosa.

Diets and blood serum characteristics

Blood serum analysis in rats fed the cereal diet showed significant inhibition

of protein concentration (Table 4). Rats fed the cereal-legume diet

demonstrated elevated levels of serum protein (0.025).

In all animal groups, starch hydrolysis by serum a -amylase (phytolytic

activity) was two times higher than glycogen hydrolysis (zoolytic activity)

(Table 5). The difference between the hydrolysis of these two substrates was

highly significant (0.05) lower than in controls.

Table 5. Blood serum phyto- and zoolytic a -amylase activity

Phytolytic 421.00 ±27.18 a 344.51 ±29.59 a b 456.60

±46.84 a

Zoolytic 206.82 ±7.61 176.47 ±13.10 b 179.54

±13.58

Value are mean ±SE, n = 8. a -Amylase activity in U/mg protein.

a p<0.0005 versus zoolytic activity.

b p<0.05 versus the standard diet.

In all animal groups, starch hydrolysis by serum a -amylase (phytolytic

activity) was two times higher than glycogen hydrolysis (zoolytic activity)

(Table 5). The difference between the hydrolysis of these two substrates was

highly significant ( 0.05) lower than in controls.

Discussion

Lack of metabolic energy, vitamins and/or minerals as well as low protein

quality are considered the principal reasons for insufficiency of vegetarian

diets [12]. However, in the present experiment with custom modified

isonitro-genous,

isocaloric diets, containing similar amounts of vitamins and minerals,

the main reason for changes in animal growth or feed consumption may

be the quality of the plant proteins. The cereal diet was deficient in lysine

and tryptophan, and as a result, the animals fed this diet may have grown

more slowly than the controls or the rats fed a balanced plant diet. However,

such growth retardation was observed only during the first three weeks of

the experiment. After the fourth week, the weights of animals in all groups

were similar; however, the animals in the cereal diet group still consumed

more feed per unit of weight gain than the controls. By that time the sus-pected

essential amino acid deficiency may have been corrected by proteins

from endogenous sources (digestive gland secretion, mucous, desquamated

cells) which represent a significant amount of the proteins absorbed from the

gastrointestinal tract [22]. However, the efficiency of such a compensatory

mechanism is limited.253

The activity of pancreatic a -amylase, the only enzyme sensitive to dietetic

changes, was decreased in animals fed an unbalanced plant diet compared

with those animals fed a standard mixed diet. Plant diets altered neither

tryp-sin

activity in the pancreas nor sucrase, maltase and aminopeptidase N activ-ity

in the small intestine in controls and animals fed balanced or unbalanced

plant diets. Researchers speculate that pancreatic a -amylase, the key enzyme

in the metabolic chain of polysaccharide digestion, is more sensitive to the

protein quality in the diet than the other digestive enzymes.

In addition to pancreatic a -amylase activity, a -amylase activity in serum,

which is a mixture of predominantly pancreatic and salivary enzymes, was

also studied. There are at least eight pancreatic isozymes and six salivary

isozymes that split starch and glycogen [23, 24]. Salivary isoamylases have

higher affinity for starch while pancreatic isoamylases have a higher affinity

for glycogen [25]. a -Amylase activity, using both substrates, was studied;

findings indicate that, in rats, starch hydrolysis by serum a -amylase

(phyto-lytic

activity) was significantly higher than glycogen hydrolysis (zoolytic

activity). The same observations were made by Ugolev [8] many years ago in

salivary a -amylase of rats and other herbivores. The balanced cereal-legume

diet did not affect the activity of either form of serum a -amylase; however,

the unbalanced cereal diet significantly inhibited both phytolytic and zoolytic

a -amylase activity in comparison to the controls.

The role that protein quality plays in animal growth and development was

supported by the observations in rats fed a cereal-legume diet. This diet,

con-taining

a mixture of plant proteins complementing each other with essential

amino acids, especially lysine and S-containing amino acids [13], resulted in

growth patterns and a feed efficiency ratio similar to animals on a standard

diet. Increased weight of spleen and cecum in animals fed cereal-legume

diet may be related to higher microflora activity needed for specific soybean

sugars (raffinose, stachyose) and fiber fermentation [15]. These experimental

data also support a number of earlier observations showing that plant proteins,

if fed as the sole source of protein, are of relatively low value for promoting

growth. However, a balanced mixture of plant proteins supports human and

animal growth similar to high quality animal proteins [12, 14].

The decreased activity of a -amylase, in contrast to other digestive en-zymes,

in animals consuming the unbalanced protein diet may be related to a

specific deficiency of tryptophan. The Gene Bank cDNA analysis of enzymes

showed (Table 6) that the amount of tryptophan (but not lysine) in a -amylase

is much higher than in other tested protein. Trypsin, sucrase, maltase, and

aminopeptidase N contain 45%, 68%, 69%, and 70%, respectively, of the

amount of tryptophan found in a -amylase.

In conclusion, the results of this study demonstrate that a balanced plant

diet containing cereal and legume proteins does not affect animal growth,

food consumption and digestion. However, an unbalanced vegetable diet has

a negative effect on these functions. One can hypothesize that a decrease in

a -amylase activity may eventually affect the organism’s energy production.

The effect of an unbalanced plant diet on digestive enzyme activity should

be taken into consideration when choosing a strict vegetarian diet for human

nutrition.

References

1. Pavlov IP (1897) Lectures on the Functioning of the Main Digestive Glands.

The com-plete

works. vol. 2, book 2, Moscow-Leningrad: Publishers USSR Acad. Sci., 1951. (in

Russian).

2. Snook JT (1973) Protein digestion. Nutritional and metabolic considerations.

World Rew

Nutr Diet 18: 121–176.

3. Corring T (1980) The adaptation of digestive enzymes to the diet: its

physiological

significance. Repr Nutr Devel 20: 1217–1235.

4. Puigserver A, Wicker C, Gaucher C (1986) Adaptation of pancreatic and

intestinal

hydrolases to dietary changes. In Desnuelle P, Sjöström H, Noren O (eds),

Molecu-lar

and Cellular Basis of Digestion, Amsterdam, New York, London: Elsevier Science

Publishers B.V., pp 113–124.

255

5. Brannon PM (1990) Adaptation of exocrine pancreas to diet. An Rev Nutr 10:

85–105.

6. Dagorn JC, Lahaie RG (1981) Dietary regulation of pancreatic protein

synthesis. I.

Rapid and specific modulation of enzyme synthesis by changes in dietary

composition.

Biochim Biophys Acta 654: 111–118.

7. on IRS (1997) Diet and gene expression in the intestine. Balliere’s

Clin

Gastroenterol 11: 441–463.

8. Ugolev AM (1961) Digestion and its Adaptational Evolution. Moscow: Publishers

Vischaja Schkola, (in Russian).

9. Magee DF, EG (1955) Changes in pancreatic enzymes brought about by

alteration in the nature of the dietary protein. Amer J Physiol 181: 79–82.

10. Pond WW, Snyder W, Snook JT, EF, McNeil DA, Stillings BR (1971)

Relative

utilization of casein, fish protein concentrate and isolated soybean protein for

growth

and pancreatic enzyme regeneration of the protein-calorie malnourished baby pig.

J Nutr

101: 1193–1200.

11. Committee on Nutrition American Academy of Pediatrics (1998). Nutritional

aspects of

vegetarian diets. In RE Kleinman (ed), Pediatric Nutrition Handbook. 4th ed. Elk

Grove

Village, IL: American Academy of Pediatrics, pp 573–586.

12. Gong EJ, Heald FP (1988) Diet, nutrition and adolescence. In Shils ME, Young

VR (eds),

Modern Nutrition in Health and Disease, Philadelphia: Lea & Febiger, pp 969–981.

13. Young VR, Pellett PL (1994) Plant proteins in relation to human protein and

amino acid

nutrition. Am J Clin Nutr 59 (suppl): 1203S–1212S.

14. Havala S, Dwyer J (1993) Position of the American Dietetic Association:

vegetarian

diets. J Amer Diet Assoc 93: 1317–1319.

15. Slavin J (1993) Nutritional benefits of soy protein and soy fibers. J Amer

Diet Assoc 91:

816–819.

16. Pierre KJJ, Tung KK, Nadj H (1976) A new enzymatic kinetic method for

determination

of amylase. Clin Chem 22: 1219.

17. Rick W (1974) Trypsin. Measurment with N -p-toluensulfonyl-L-arginine methyl

ester

as substrate. In Bergmayer HU (ed), Methods of Enzymatic Hydrolysis, New York,

London: Academic Press 2: 1021–024.

18. Dahlqvist A (1968) Assay of intestinal disaccharidases. Anal Biochem 22:

99–107.

19. Fujita M, Parsons DS, Wojnarowska F (1972) Oligopeptidases of brush-border

mem-branes

of rat small intestinal mucosal cells. J Physiol 227: 377–394.

20. Bradford MM (1976) A refined and sensitive method for the quantitation of

microgram

quantities of protein utilizing the principle of protein-dye binding. Anal

Biochem 72:

248–254.

21. Rick W, Stegbauer HP (1974) a -Amylase. Measurement of reducing groups. In

Bergmeyer NH (ed), Methods of enzymatic analysis. New York, London: Academic

Press 2: 885–890.

22. Van Dyke RW(1989) Mechanism of digestion and absorption of food. In

Slesenger MH,

Fordtran JS (eds) Gastrointestinal Disease, Pathophysiology, diagnosis,

management.

Saunders Company, pp 1062–1088.

23. Levitt MD, Ellis C, Engel RR (1977) Isoelectric focusing studies of human

serum and

tissue isoamylases. J Lab Clin Med 90: 141–152.

24. Lebenthal E, Lerner A (1995) Salivary secretion. In Yamada T (ed), Textbook

of

Gastroenterology v.1. Philadelphia: Pippincott Company, pp 279–295.

25. Kazmarek MJ, Rosenmund H (1977) The action of human pancreatic and salivary

isoamylases on starch and glycogen. Clin Chim Acta 79: 69–73.