Different chrome sources influence on morpho-biochemical indicators and activity of digestive enzymes in Wistar rats

Abstract

Nowadays, issues of mineral nutrition of humans and animals are quite relevant. High-energy rations, multicomponent feed mixtures and additives in the diets require special attention when optimizing limited microelements. A priori, chromium, being an important trace element in animals, is used to correct carbohydrate, fat and lipid metabolism. Due to its low content in the components of diets, its role in the formation of the microecological status of the body is poorly understood. At the same time, its biological availability in the body depends on the source of chromium. In the present work, using a model object, the Wistar rats, we for the first time compared the biological effects of various chromium sources, i.e. picolinate (CrPic), nanoform (NP Cr2O3) and chloride (CrCl3) at doses of 300 and 500 μg/kg feed, according to a set of indicators (feed digestibility, hematological parameters, activity of digestive enzymes, composition of intestinal microflora) and established greater bioavailability and more pronounced positive effect of picolinate and chromium nanoparticles on body weight and hematological parameters and ambiguous influence of the studied forms on the activity of digestive enzymes and intestinal microflora. The purpose of this work was to study the biological effect of chromium in various forms and dosages on Wistar rats. The studies were carried out on 105 white male rats weighing 70-80 g under standard vivarium conditions (Federal Scientific Center for Biological Systems and Agrotechnologies of the Russian Academy of Sciences). Animals were divided into seven groups (n = 15 each). The control group was fed a common diet. The group I diet included Cr2O3 NPs at a dose of 300 µg/kg feed (NP 300), group II — CrCl3 at a dose of 300 mg/kg (CrCl3 300), group III — chromium picolinate (CrPic) at a dose of 300 mg/kg (CrPic 300), group IV — Cr2O3 NPs at a dose of 500 µg/kg of feed (NP 500), group V — CrCl3 at a dose of 500 mg/kg (CrCl3 500), and group VI — CrPic at a dose of 500 mg/kg (CrPic 500). Nanoparticles were introduced into the feed by mixing. The introduction of chromium in the form of CrPic and Cr2O3 NPs at a dose of 500 μg/kg, under the same feed consumption, was accompanied by an increase in the body weight of rats by 22.6 and 22.2 % (p ≤ 0.05). The effect of Cr2O3 NPs expressed as the absence of the reaction of lymphocytes, monocytes and granulocytes, in other cases their level exceeded control values by 14 to 45 %. Synthesis of hemoglobin was adequate to stimulation of erythropoiesis, but an increase in the number of platelets resulted in blood sludging, an increase in viscosity and difficulty in perfusion through vessels. This symptom was typical for NP Cr2O3 300, CrCl3 300 and CrCl3 500 (the difference with the control is from 70 to 90 %, p 0.05). High digestibility of CrPic and NPs Cr2O3 500 (from 20.2 to 34.0 %), accompanied by manifestation of hepato- and nephrotoxicity, with signs of oxidative stress, decreased activity of amylase and lipase in the blood plasma, indicating a depressant effect of high doses of chromium on enteropancreatic circulation of the digestive enzymes and metabolic disorders of Mg and Fe in the blood. Triglycerides, like true fats, decreased at maximum doses of chromium in the form of chloride and picolinate, confirming their participation in lipid metabolism, causing splitting of excess fat in the body, and reducing the ratio of fat to body weight ratio from 2 (control group) to 0.82 (NP Cr2O3 500). The indicators of bilirubin and creatinine clearly demonstrate the absence of toxicity at low doses, i.e. Cr2O3 NPs 300 and CrPic 300. Amylase activity in the pancreas is increased at a dose of 300 µg/kg of Cr2O3 NPs. Dietary CrPic in a similar dosage stimulated the activity of lipase and protease, whereas in the 12 duodenal ulcer it led to a decrease in the activity of amylase and lipase. CrCl3 and CrPic at a dosage of 500 µg/kg reduced the activity of lipase in the duodenum. The specific effect of Cr NPs 500 µg/kg on the microecological status of the organism was manifested in a decrease in the number of lactic acid bacteria by 55.9 %. The number of bifidobacteria was significantly higher, by 48.6 % (p 0.05), in the PicCr 500-fed group. The number of enterobacteria in the NP 300-fed group was 34.8 % lower than the control, while in the other groups their number increased 24.0-33.7 times (р 0.05). From the totality of the estimated parameters of the intestinal microflora, the use of nanoparticles in the composition of the diet is promising due to the lack of resistance. Thus, chromium of CrPic 500, NP Cr2O3 300 does not show a toxic effect on the body, and has a stimulating effect on growth, development, digestibility of chromium, the activity of the digestive enzymes and microecological status of the organism, which puts these forms in the category of promising sources of chromium for the correction of metabolism and the microbial composition of the gastrointestinal tract of animals.