The relationship between Nigerian Bonny Light crude oil (NBLCO) induced hypoglycaemia and endogenous serum insulin concentration; the role of antioxidant vitamin C or E supplementation was the focus of this study. Forty adult male Wistar rats were randomly divided into group I, which served as the control, group II, which was oral gavaged 6 ml/kg of NBLCO, groups III and IV, which were in addition to 6 ml/kg of NBLCO supplemented with 9 ml/kg and 1 mg/kg of vitamin E or C, respectively for 28 days. Results showed that NBLCO significantly (p < 0.05) lower body weight and food intake compared with control. These effects exerted by NBLCO were however significantly (p < 0.05) reversed by vitamin E or C supplementation. The NBLCO significantly (p < 0.05) reduced fasting blood glucose (FBG) when compared with control, the antioxidant vitamins supplementation significantly (p < 0.05) reversed the crude oil effect. The mean serum insulin level in NBLCO, vitamin E or C supplemented groups is not significantly different from the control. There was no significant correlation between FBG and fasting serum insulin concentrations in all the groups on day 28. It has been demonstrated in this study that direct oral ingestion of crude oil (NBLCO) could reduce food intake, body weight and cause hypoglycemia; the hypoglycemia may not be a function of serum insulin concentration. Interestingly, the hazardous effects of NBLCO could be ameliorated with antioxidant vitamin C or E supplementation.
The prevalence of crude oil spillages and the attendant contamination is increasing rapidly in the Niger Delta region of Nigeria with a resultant unrestricted exposure of animals including humans [
Most reports on the toxicological effects of crude oil in relation to its refined products on health of organisms have centered much on the inhalation of petroleum fumes with little or no attention on oral ingestion. It is therefore pertinent to note that most of the rural dwellers that indulge in the unorthodox folklore medicine actually consume crude oil by oral ingestion. Apart from this sub-lethal effect from direct crude oil ingestion, crude oil can also be indirectly incorporated into the food chain [
The Crude petroleum was obtained from the EXXON/MOBIL laboratory Eket, Nigeria. The chemical used was chloroform from BDH Chemicals Ltd, (Poole, England).
Mature male Wistar albino rats weighing between 130 - 135 g were obtained from the animal house of the Faculty of Pharmacy, University of Uyo, Nigeria and were kept in a well-ventilated experimental section in the animal house for fourteen (14) days to acclimatize. The animals were allowed food and water ad libitum. After the acclimatization period, the animals were weighed, their fasting blood glucose levels (FBG) taken, before the commencement of experimental treatment.
A total of forty (40) adult male Wistar albino rats were randomly divided into four groups, group I served as control. It was experimentally designed thus; group II, the crude oil group (CO) was oral gavaged 6 ml/kg of Nigerian Bonny Light Crude Oil (NBLCO) according to the dose described by Eyong et al. [
The rats in all treated groups were repeatedly exposed by oral gavaged to NBLCO (CO), NBLCO + vitamin E (CO + Vit. E) and NBLCO + vitamin C (CO + Vit. C) as earlier stated for 28 days. Rats in the control group were similarly oral gavaged with 10ml/kg of normal saline as control vehicle for the same 28 days. The weight of animals and glucose levels were taken on day 1, 7, 14, 21 and 28, before the animals were sacrificed.
After twenty eight (28) days of administration, the rats were again weighed and anaesthetised with chloroform soaked in swap of cotton wool in a desiccator. A (5 ml) sterile syringe with needle was used for collection of blood from the heart, by cardiac puncture. The blood sample was transferred into properly labeled sterile sample bottles.
The blood samples were spun with table top centrifuge (RM-12 Micro centrifuge, REMI, England) at 3000 rpm for 10 minutes. Then the serum was separated gently with the help of micropipette and stored in labeled eppendrof tubes at −20˚C until assayed for serum chemistry.
These animals were kept singly in clean plastic cages. They were given rat chow (Vital feeds, Grand Cereals Ltd, Jos). The food intake was determined by measuring the initial amount of food (in gramme) presented to the rats and amount by weight of left-over after 24 hours. The amount of left-over was subtracted from the initial weight to obtain the amount presumably consumed by the rats.
Fasting blood glucose was determined from drops of blood from cut tip of rat tail using one-touch life-scan blood glucose meter (USA). This was done on the first day of experiment, thereafter was done on weekly basis and on the day of sacrifice blood sample collected directly from the heart was used for glucose determination.
The DRG insulin enzyme immunoassay kit (Germany) was used for the determination of insulin in serum.
Values of the biochemical assays were expressed as mean (±) standard error (SE) and were statistically analysed with SPSS 15.0 version using one way analysis of variance and results were further subjected to post hoc test using Least Square Deviation (LSD). p < 0.05 was considered to be significant.
The initial body weight, final body weight and weight change in the control, CO, COE and COC rats are as presented in Table1 The results showed that Nigerian Bonny Light crude oil significantly reduced body weight compared with control (p < 0.05). However, the body weight reduction exerted by NBLCO was significantly (p < 0.05) reverse by vitamin E or C supplementation.
The weekly food intakes in the control and treatment groups are presented in
The Nigerian Bonny Light crude oil (CO) significantly (p < 0.05) reduced fasting blood glucose (FBG) when compared with control. Vitamin E or C supplementation significantly (p < 0.05) reversed this effect compared with CO group, this effect was not significantly different from control, as presented in
Legend: ap < 0.05 vs Control; bp < 0.05 vs CO; cp < 0.05 vs COE; CO = crude oil; COE = crude oil plus vitamin E; COC = crude oil plus vitamin C.
glucose (FBG) compared with control on day 28, but vitamin E or C supplementation significantly (p < 0.05) increased FBG when compared with CO and control groups.
The correlation between fasting blood glucose (FBG) and fasting serum insulin levels on day 28 of treatment was determined for the control and various treatment groups as presented in
There was no significant correlation between FBG and fasting serum insulin concentrations in all the groups on day 28.
Ingestion of crude oil causes a wide spectrum of toxicological effects, as well as biochemical and physiological dysfunctions that may constitute serious health hazards and threat to humanity; such is evidenced in this study.
Nigerian Bonny Light crude oil significantly reduced food consumption and body weight in the treatment rats throughout the experimentation. Crude petroleum contamination can have severe consequences on the health of organisms including humans. Stress, fright, hypothermia and exhaustion are some physical manifestations that may be associated with oil spills [
The concentration of oxidants in the body can be elevated by xenobiotic insults such as crude oil [
Antioxidants are potentially protective agents that may help guard against oxidation as evidenced in this study by the significant reversal of the hazardous effects of NBLCO with antioxidant vitamin E or C supplementation. This corroborate previous findings that potentially damaging oxidative stress is kept in check by endogenous cellular antioxidant defense mechanisms, which include antioxidant enzymes (Superoxide dismutase, catalase
and glutathione peroxidase), antioxidant micro-elements, and nutrient-derived antioxidant small molecules (Vitamins A, C, E, carotenes, flavonoids, glutathione) [
This study confirmed the hypoglycemic effect of crude oil ingestion reported in experimental animals [
Similar alterations in oxygen consumption, tissue glycogen and glucose levels following exposure of fish to crude oil fractions have been reported [
The results of this study showed significant decrease in blood glucose level, which is corroborated by earlier work of Alonso-Alvarez, et al. [
The non-elevated fasting insulin levels recorded in NBLCO-treated group may suggest inadequate secretion due to beta cell dysfunction or beta cell damage [
The direct administration of NBLCO through oral gavage to rats reduces food consumption and consequently resulted in weight loss in comparison with control throughout the period of administration. It appeared that the hypoglycemia recorded was a direct function of NBLCO as serum insulin did not show any significant increase. This might also suggest possible injury to the glucogenic organs like the liver and kidney. Interestingly, vitamin C or E supplementation ameliorated the aforementioned effects.
It has been demonstrated in this study that direct oral ingestion of crude oil (NBLCO) could reduce food intake, body weight and cause hypoglycemia, and that the hypoglycemia is not a function of plasma insulin concentration. And the hazardous consequences of ingestion of NBLCO could be ameliorated with antioxidant vitamin C or E supplementation.