Effect of Xylooligosaccharide Enriched Yogurt on Serum Profile in Albino Rats

INTRODUCTION

Non Digestible Oligosaccharides (NDO) like Xylooligosaccharides (XOs) have a number of health benefits associated with them like improving gastrointestinal health, preventing of certain diseases such as dental caries, colon cancer and stimulating mineral absorption. Most of the NDOs including XOs are known to have prebiotic characteristics. A prebiotic is defined as a substrate or food ingredient that is non-digestible for the host but is fermented selectively by some of the intestinal microflora (Scholz-Ahrens et al., 2001). In this way, it enhances the growth and activity of bacteria with beneficial effects for the host’s health. Many of the scientific substantiation for the functional properties of NDOs is supported by animal experiments in which NDOs increased the availability of calcium, magnesium, zinc and iron. This stimulatory effect of some NDOs is assumed to be primarily because of their prebiotic character.

Xylooligosaccharides (XOs) are functional oligosaccharide composed of 2-10 xylose molecules linked together by β (1-4) linkage and are used as food ingredients owing to their technological properties and health effects. XOs are stable over a wide range of pH and temperature enabling them to be used in acidic juices and dairy products like yogurt (Vázquez et al., 2000). The main property of the physiological functions results from the indigestibility of XOs, which leads to fermentation in the large intestine, consequently increase Bifidobacteria and Short-chain Fatty Acid (SCFA) production. This property results in many types of physiological functions, among which the promotion of mineral absorption, including an increase of bone density and relief of anemia is of particular interest (Hirayama, 2002).

The XOs behave as dietary fibre and since the dietary fibre has the properties mandatory for its consideration as an important ingredient in the preparation of functional foods, due to its beneficial effects such as increasing the volume of faecal bulk, decreasing the time of intestinal transit, cholesterol and glycaemia levels, trapping substances that can be dangerous for the human organism, stimulating the growth of the intestinal flora, etc.

It has also been reported that XOs exhibit some other advantageous consequences on health. Xylooligosaccharides were given in experimental diet to diabetic rats and certain metabolic parameters like blood glucose, serum and liver lipids were examined. The experiment showed that XOs can improve growth retardation, hyperphagia, polydipsia and elevated levels of serum glucose. This is also stated that lowered liver triglycerides and reduction in desaturation index fatty acid composition of liver phosphatidylcholine are outcome of XOs diet. Concluding from above stated observation, it can be recommended that XOs have got properties to be used as sweetener for improving diabetic conditions (Imaizumi et al., 1991).

Considering the above stated findings, the present study was conducted to determine the effect of XOs enriched yogurt on the serum biochemical profile in male Albino rats. Since the other XOs are already known to have positive impact on serum biochemical profile, synergistic effect of XOs enriched yogurt was investigated to verify the hypothesis whether synbiotic products have the same impact.

MATERIALS AND METHODS
Study design, animals and diets: Male Albino rats weighing 150±10 g were purchased from the National Institute of Health, Islamabad, Pakistan. The rats were individually housed in stainless steel wire bottom cages in an environmentally controlled room at 25±2^oC and 60±5% relative humidity with 12 h light-dark cycle. The rats were fed on the freshly prepared basal diets for a week and then randomly assigned to 5 dietary treatments for 21 days. Composition of experimental diet is given in Table 1.

Table 1:	Ingredient composition of dietary treatments fed to rats
1Mineral (mg/kg): Ca, 5000; P, 1561; K, 3600; Na, 1019; Cl, 1571; S, 300; I, 0.2; Fe, 35; Mg, 507; Zn, 30; Cu, 6; Mn, 10; Mo, 0.15; Se, 0.15; Cr, 1; Si, 5; F, 1; Ni, 0.5; B, 0.5; Li, 0.1 and V, 0.1 2Vitamin (mg/kg): thiamin, 5; riboflavin, 6; pyridoxine, 6; nicotinic acid, 30; pantothenate, 15; folic acid, 2; phylloquinone, 0.75; biotin, 0.2; cyanocobalamin, 0.025; all-trans-retinyl palmitate (500,000 IU/g), 8; all-rac-atocopheryl acetate (500 IU/g), 150 and cholecalciferol (400,000 IU/g), 2.5

The detail of the groups on five dietary treatments is given below:

XOs were produced in another experiment from corncobs through alkali and enzymatic hydrolysis. Experimental yogurt were prepared according to method described by Mumtaz et al. (2008).

All rats were given free access to experimental diets and deionized water. The diet consumed by each rat was determined by deducting the leftover and spilled diet from the total amount supplied per day. Net feed intake of individual rat was measured on daily basis by excluding leftover and collecting spilled diet during the entire period to observe the impact of individual experimental diet. Deionized water was provided with the help of graduated drinking bottles. Gain in body weight of individual rats in each group was determined on weekly basis throughout the experimental period to find out the effect of individual diet on body weight.

Sampling procedures: At the end of the experiment after 21 days, the blood samples were collected from the cecal vein of overnight fasted rats. The serum was separated by centrifugation at 3000 rpm for 15 min after allowing the blood to stand for at least 30 min at room temperature as explained by Uchida et al. (2001). After blood sampling, cecum with contents were also removed and weighed. Cecal contents were divided into two halves; one was kept for pH measurement and other one was frozen at -20^oC.

Statistical analysis: The data obtained was analyzed using Minitab version 14.1. All the experimental groups were compared using analysis of variance (ANOVA). Values in tables and graphs are expressed as mean± SEM. A P value of less than 0.05 was considered to be significant.