Regulation of Biokinetics of 65 Zn by Curcumin and Zinc in Experimentally Induced Colon Carcinogenesis in Rats

Abstract

This study was conducted to investigate the role of curcumin and zinc on the biokinetics and biodistribution of ⁶⁵Zn during colon carcinogenesis. Male wistar rats were divided into five groups, namely normal control, 1,2-dimethylhydrazine (DMH) treated, DMH+curcumin treated, DMH+zinc treated, and DMH+curcumin+zinc treated. Weekly subcutaneous injections of DMH (30 mg/kg body weight) for 16 weeks initiated colon carcinogenesis. Curcumin (100 mg/kg body weight orally) and ZnSO₄ (227 mg/L in drinking water) were supplemented for 16 weeks. This study revealed a significant depression in the fast (Tb₁) and slow component (Tb₂) of biological half-life of ⁶⁵Zn in the whole body of DMH-treated rats, whereas liver showed a significant elevation in these components. Further, DMH treatment showed a significant increase in the uptake values of ⁶⁵Zn in colon, small intestine, and kidneys. Subcellular distribution depicted a significant increase in ⁶⁵Zn uptake values in mitochondrial, microsomal, and postmicrosomal fractions of colon. However, curcumin and zinc supplementation when given separately or in combination reversed the trends and restored the uptake values close to normal range. Our study concludes that curcumin and zinc supplementation during colon carcinogenesis shall prove to be efficacious in regulating the altered zinc metabolism.

Introduction

Cancer accounts for 8.2 million deaths annually and is a major factor resulting in morbidity and mortality worldwide.¹ The genesis of cancer involves the sequential accumulation of mutations that lead to the transformation of normal cell to the malignant ones.² The utilization and judicious intake of dietary nutrients has emerged out to be an important facet in combating the initiation of molecular events leading to mutagenesis and carcinogenesis.³ The basic approach behind cancer chemoprevention is to arrest or reverse the progression of premalignant cells toward full malignancy using physiological mechanisms without harming the healthy cells.^4

–7 Many dietary compounds, including curcumin and zinc, have been known to play a pivotal role in cancer chemoprevention. Curcumin has been studied for its potency in a wide variety of cancers and is known to ameliorate the process of carcinogenesis by counteracting the altered functionality of proliferative and apoptotic pathways.⁸ Several authors have reported the chemopreventive potential of curcumin in inhibiting colon cancer.^9,10

Zinc is an essential trace element that is required to regulate the activity of more than 300 enzymes and is quintessential in maintaining the structural integrity of more than 2000 transcription factors that work to regulate the gene expression.^11
–13 Interestingly, a number of evidences have suggested an intriguing link between the expression levels of Zn transporters in human tumors that correlate with malignancy. This further indicates that alteration in intracellular Zn homeostasis can contribute to the severity of cancer.^14,15 Stable isotope techniques have emerged as a prelude to evaluate the link between diet and zinc status and has paved the way for discerning the mechanisms responsible for homeostatic regulations of Zn.¹⁶ Sian et al. in their study observed that changes in the endogenous intestinal Zn excretion are pivotal for the maintenance of zinc homeostasis.¹⁷ It has also been revealed in a study that the tissue uptake of absorbed ⁶⁵Zn considerably varies and the maximum uptake was observed in liver.¹⁸ ⁶⁵Zn tracer study has been reported to follow two compartment kinetics after its administration in the body, which includes the initial faster component (Tb₁) and the delayed slower component (Tb₂).¹⁹ A number of pathophysiological processes can perturb the dynamic balance between the two pools that alters the systemic distribution, tissue deposition and mobilization of Zn. A recent study from our lab also demonstrated the altered biokinetics and biodistribution of ⁶⁵Zn in the aluminium-intoxicated rats.²⁰ Several authors have supported that 1,2-dimethylhydrazine alkylates DNA and O⁶-methylguanine (O⁶-MeG), a promutagenic lesion, is known to play a crucial role in the induction of cancer.^21,22 Highest levels of this promutagenic lesion were observed in the liver of rats administered with 1,2-dimethylhydrazine (DMH).²³

With a perspective to know the turnover of ⁶⁵Zn during colon carcinogenesis, this study was designed to study the effect of curcumin and zinc on biological half-lives of ⁶⁵Zn in whole body and liver and on distribution of ⁶⁵Zn in different organs of rats that were subjected to DMH treatment.

Materials and Methods

Chemicals and radioisotope

1,2-dimethylhydrazine (DMH) and curcumin were purchased from Sigma-Aldrich (St. Louis, MO). ⁶⁵Zn was procured from Bhaba Atomic Research Centre (BRIT, Mumbai, India). All other chemicals and reagents used in this study were of analytical grade and procured from reputable Indian manufacturers.

Animal treatment

Male wistar rats (n=35) weighing 120–150 g in the age group of 75–90 days were procured from the Central Animal House Facility of Panjab University, Chandigarh. All animals were housed in polypropylene cages stacked with a hygienic bed of husk, placed in a well-ventilated animal room under optimum hygienic conditions with ambient light and temperature. They were provided with the standard pellet diet and drinking water ad libitum. Animal care procedures followed in this study were done in accordance with the ethical guidelines for care and use of laboratory animals that were approved by Institutional Animal Ethics Committee (IAEC), Panjab University, Chandigarh, India. The animals were acclimatized to the experimental conditions for 1 week before being subjected to various treatments.

Experimental design

Animals were segregated into five different treatment groups with six animals in each group. Group I animals served as normal controls and received 1 mM ethylene diammine tetraacetic acid (EDTA) saline subcutaneously every week, which was used as a vehicle in the DMH-treated group. Animals in group II were administered a weekly dose of DMH at a dose level of 30 mg/kg bodyweight dissolved in 1 mM EDTA-normal saline (pH-6.5), for a total duration of 16 weeks.²⁴ Group III animals were administered curcumin orally through intubation gavage at a dose level of 100 mg/kg body weight thrice a week in addition to the DMH treatment.²⁵ Animals in group IV, in addition to the DMH treatment, received zinc in the form of ZnSO₄·2H₂O in drinking water ad libitum at a dose level of 227 mg/L of drinking water for 16 weeks.²⁴ Group V animals received a combined treatment of DMH, curcumin, and zinc in a manner as was given to Group II, Group III, and Group IV animals respectively for a total duration of 16 weeks.

Whole body biological half-life of ⁶⁵Zn

Sixteen weeks after the commencement of various treatments, all the animals from the five different treatment groups were administered with 1.48 MBq activity of γ-emitting radionuclide ⁶⁵Zn intraperitoneally to evaluate its retention in the whole body as a function of time. A standard, with an equivalent amount of activity was used as a reference for calculating the physical decay of radionuclide. A well type γ-ray scintillation counter having NaI(Tl) crystal was utilized for recording the retained activity in the animals. The counter was first calibrated to attain the optimum energy peak of ⁶⁵Zn by adjusting extra high tension voltage of the counter along with the gain. The upper and lower level discriminators were set and the baseline was adjusted accordingly.²⁶ The retention and biological half-life of ⁶⁵Zn in whole body as a function of time were determined by placing the rats at a distance of 16 cm, from the top surface of the probe of the counter. The animals were placed in a Perspex (25-mm thick) cage (length 18 cm, width 8 cm, and height 6 cm) to restrict their movements during counting. The cage had several holes, thereby, serving the purpose of ventilation. Least variation in the count rate along the horizontal plane was observed at this distance. Further, the whole body counting was done 24 hours after the administration of radioactivity to each animal and the counting was continued daily for 7 days and then it was done on every alternate day, till the count rate was reduced appreciably. Counts of ⁶⁵Zn standard were recorded at the same distance from the probe and at the same time when the animals were counted, to account for physical decay of the radioisotope. Retention of ⁶⁵Zn in the whole body of each rat was recorded with respect to the standard counts. The uptake on the first day was taken as 100% and the percentage uptake value on subsequent days was calculated. The profile of the percentage retention versus time for each animal was plotted on a semi-log paper. The biological half-life of ⁶⁵Zn was calculated by taking the difference of any two points on x-axis scale where the percentage retention becomes half. The biological half-life of ⁶⁵Zn has been found to be governed by two components, that is, Tb₁ and Tb₂. These components represent the distribution and elimination of radioisotope (⁶⁵Zn) in various organs and from the whole body. Tb₁ represents the fast component, which illustrates the faster elimination of radioactivity from the biological system via urine and feces. This component primarily demonstrates the radioactivity that is not retained by different tissues. Whereas, Tb₂ is a slow component, which demonstrates the slower disappearance of the radionuclide, that is retained by various tissues and organs.

Biological half-life of ⁶⁵Zn in liver

The clearance profile of ⁶⁵Zn from liver was also determined in the rats subjected to different treatments. A well-type scintillation counter was used to record the counts and was shielded by using a lead collimator in such a way that only the liver of the animal was exposed to the probe. A rectangular lead shield of length 13.5 cm and width 9 cm having thickness of 2 cm and a hole with diameter 1.5 cm in the center was used as a collimator to serve the purpose. The lead shield was placed over the probe and the hole was made to coincide with the detector probe.²⁷ Each rat was placed in such a way that only the liver was exposed to the counter by positioning the demarcated area above the hole while the rest of the body was shielded from the detector by the lead shield. Initially the counts of each rat were recorded daily for the first 7 days, then on alternate days for a total duration of 21 days. The activity in the reference standard was also counted to account for the physical decay of the radionuclide. Biological half-life of ⁶⁵Zn in liver was determined in a similar manner as was done in the case of whole body.

Biodistribution of ⁶⁵Zn

All the rats were injected with a tracer dose of 0.37 MBq of ⁶⁵Zn after 16 weeks of different treatments. Twenty-four hours after injection of radioactivity, the animals were sacrificed using light ether anesthesia. Various organs such as heart, liver, lungs, spleen, kidneys, small intestine, and colon were removed and the wet weights of all the organs were recorded. Each organ was placed in a test tube for digestion with 30% potassium hydroxide (KOH). On the following day, the activity of the digested fraction of different tissues were recorded using NaI(Tl) scintillation counter. The geometry was kept constant for each case. The percentage injected radioactivity per gram of the tissue weight was calculated with respect to the standard activity.

Subcellular distribution of ⁶⁵Zn in colon tissue

The colonic tissues from animals of different treated groups were removed, excised, and homogenized in Tris–Mannitol buffer (2 mM Tris+50 mM Mannitol, pH 7.2), by using a mechanically driven Teflon-fitted Potter Elvejhem homogenizer. The crude homogenates were subjected to different centrifugation speeds and times for the separation of nuclear (3000 g×15 minutes), mitochondrial (10,000 g×30 minutes), microsomal, and postmicrosomal fractions (100,000 g×45 minutes). The radioactivity in each fraction was recorded and the percentage uptake of that fraction was calculated with respect to the standard having the same amount of activity as injected to the treated animals.

Statistical analyses

Data were expressed in terms of mean±SD of six animals for each group. One-way analysis of variance was performed to compare the means between the different treatment groups using post hoc comparison by least significant difference method. The statistical software package SPSS v14 for windows was used for this purpose. A value of p≤0.05 was considered to be statistically significant in this study.

Results

Whole body biological half-life of ⁶⁵Zn

To study the effect of curcumin and zinc on the biokinetics of ⁶⁵Zn in the rats subjected to 16 weeks of DMH treatment, whole body biological half-life of ⁶⁵Zn was assessed as it is an indicator of zinc turnover. Our results revealed two compartment kinetics of ⁶⁵Zn as shown in Table 1. Tb₁ represented the initial fast component of the biological half-life of the radionuclide, whereas Tb₂ depicted the delayed slower component. DMH-treated rats showed a significant depression in both Tb₁ (p≤0.01) and Tb₂ (p≤0.001) components when compared with the normal control rats. However, curcumin and zinc treatment given separately and in combination significantly (p≤0.001) elevated both the components when compared to the DMH-afflicted group and brought back these components to within normal range.

Table 1.

Effect of Curcumin and Zinc on Biological Half-Life of ⁶⁵ Zn in the Whole Body of Rats Subjected to 16 Weeks of DMH Treatment

Groups	Tb₁ (days)	Tb₂ (days)
Control	6.45±0.30	18.15±0.68
DMH	4.75±0.58^a	15.15±1.22^b
DMH+Curcumin	6.65±0.90^c	19.80±0.49^a,c
DMH+Zinc	7.35±0.47^c	17.90±0.74^c
DMH+Curcumin+Zinc	6.85±0.81^c	17.70±0.60^c

Tb₁ represents the faster elimination and Tb₂ represents the delayed component of the biological half-life.

Data are expressed as mean±SD.

p≤0.01 and ^b p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with normal control group.

p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with DMH-treated group.

DMH, 1,2-dimethylhydrazine.

Biological half-life of ⁶⁵Zn in liver

Liver plays a crucial role in the metabolism of DMH. Therefore, it was meaningful to evaluate the biological half-life of the radionuclide in the liver as well. In contrast to whole body biological half-life of ⁶⁵Zn, this study depicted a significant elevation in both the Tb₁ (p≤0.001) and Tb₂ (p≤0.01) components of ⁶⁵Zn in the liver of the DMH-treated group when compared to the normal control group as shown in Table 2. Interestingly, it was observed that curcumin and zinc treatment when given separately and in combination to the DMH-treated rats reversed the trend as evidenced by a significant decrease in the Tb₁ (p≤0.001) and Tb₂ (p≤0.01) components of the radionuclide.

Table 2.

Effect of Curcumin and Zinc on Biological Half-Life of ⁶⁵ Zn in Liver of Normal Control and Treated Rats

Groups	Tb₁ (days)	Tb₂ (days)
Control	4.80±0.36	9.13±1.05
DMH	7.00±0.31^a	11.48±1.46^b
DMH+Curcumin	5.30±0.35^c	10.36±1.15
DMH+Zinc	5.40±0.34^c,d	9.20±0.97^e
DMH+Curcumin+Zinc	5.00±0.70^c	9.52±0.77^e

Tb₁ represents the faster elimination and Tb₂ represents the delayed component of the biological half-life.

Data are expressed as mean±SD.

p≤0.05, ^b p≤0.01 and ^a p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with normal control group.

p≤0.01 and ^c p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with DMH-treated group.

Uptake and biodistribution of ⁶⁵Zn

To evaluate the physiological and protective role of curcumin and zinc against DMH-induced colon carcinogenesis, it was necessary to decipher the changes occurring in various other organs along with the colon. The differential uptake of the activity by various organs of the rats subjected to different treatments could help in addressing this issue. Therefore, we determined the uptake and biodistribution pattern of ⁶⁵Zn in the normal and treated rats as shown in Table 3. Our results revealed that there was a significant increase (p≤0.001) in the percent uptake values of ⁶⁵Zn in the colon, small intestine, and kidneys of the rats subjected to 16 weeks of DMH treatment in comparison to the normal control group. On the contrary, uptake of the radionuclide in the liver of DMH-treated rats showed a significant decrease (p≤0.05) when compared with the normal control rats. However, treatment with curcumin and zinc restored the uptake values of ⁶⁵Zn in the colon, small intestine, and kidneys to within normal range, whereas a significant increase (p≤0.05) in the liver uptake was observed following curcumin and zinc treatment.

Table 3.

Effect of Curcumin and Zinc on the Biodistribution Pattern of ⁶⁵ Zn in Various Organs of the Normal Control and Treated Rats

Groups	Liver	Spleen	Kidneys	Small intestine	Colon
Control	0.846±0.178	0.562±0.018	0.488±0.066	0.792±0.052	0.422±0.086
DMH	0.654±0.067^a	0.621±0.055	0.723±0.095^b	1.088±0.209^b	0.572±0.057^b
DMH+Curcumin	0.702±0.115^b	0.590±0.074	0.573±0.047^c	0.742±0.042^c	0.479±0.099
DMH+Zinc	0.957±0.137^c	0.568±0.054	0.530±0.102^c	0.870±0.125^d	0.413±0.060^c
DMH+Curcumin+Zinc	0.821±0.103^e	0.577±0.017	0.528±0.050^c	0.763±0.086^c	0.432±0.042^c

Data are expressed as mean±SD. Result is expressed in the form of % injected dose per gram of the tissue weight.

p≤0.05 and ^b p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with normal control group.

p≤0.05, ^d p≤0.01 and ^c p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with DMH-treated group.

Subcellular distribution of ⁶⁵Zn in colon tissue

Table 4 demonstrates the localization and uptake of ⁶⁵Zn in various subcellular fractions of the colon of the rats subjected to different treatments. A significant increase in the ⁶⁵Zn uptake in the mitochondrial (p≤0.001), microsomal (p≤0.001), and postmicrosomal (p≤0.01) fractions was observed in the rats subjected to 16 weeks of DMH treatment in comparison with the normal control group. Supplementation of curcumin and zinc, however, caused a significant depression in the uptake values. Administration of curcumin and zinc to the DMH-treated rats also led to an increased uptake value in the nuclear fraction, which was significantly decreased in the DMH-afflicted group.

Table 4.

Effect of Curcumin and Zinc on the Subcellular Distribution Pattern of ⁶⁵ Zn in the Colon of the Normal Control and Treated Rats

Groups	Nuclear	Mitochondrial	Microsomal	Postmicrosomal
Control	0.869±0.091	0.450±0.015	0.392±0.004	0.402±0.020
DMH	0.585±0.061^a	0.517±0.017^a	0.435±0.014^a	0.465±0.008^b
DMH+Curcumin	0.688±0.091^b	0.465±0.008^c	0.419±0.013^b	0.420±0.005^d
DMH+Zinc	0.724±0.099^d,e	0.434±0.007^c	0.420±0.014^b	0.405±0.003^d

Data are expressed as mean±SD. Result is expressed in the form of percentage uptake of the activity.

p≤0.05, ^b p≤0.01 and ^a p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with normal control group.

p≤0.01 and ^c p≤0.001 by one-way analysis of variance followed by post-hoc test when values are compared with DMH-treated group.

Discussion

Cancer has emerged as one of the major causes of mortality worldwide. Inadequate dietary intake of nutrients along with lifestyle changes has posed a high risk for human colon cancer and mandates the investigation to explore the chemopreventive role of several micronutrients and natural compounds in combating the disease.^28,29 Regulation of Zn levels in the body has been reported to be of prime importance in maintaining human growth,³⁰ immune system,³¹ skin repair,³² numerous enzymes,¹⁰ and activities required for normal functioning of various organ systems.³³ Several authors have demonstrated that any disruption in the zinc pools in the body (vesicular, free ionic, and protein bound) can disrupt the metabolic processes, which may further result into a diseased condition.^34,35 Lower levels of zinc have been reported in prostate cancers and several neoplastic diseases, which make it a potential prognostic marker for cancer detection.^36,37 Preclinical studies on different cancer cell lines have explored the potential of curcumin as a chemopreventive agent and the outcomes have well signified its role as a phenomenal anticancer drug.^38

–41 Curcumin possesses the remarkable ability to sequester the mutagenic/carcinogenic reactive species induced in the body during oxidative stress.⁴² Dietary deficiencies of Zn have been known to significantly contribute to the single- and double-stranded DNA breaks and oxidative modifications to DNA that increases the risk for cancer development.⁴³ Zn has also been proved to be vital for the regulation of proteins, transcription factors, and replicative enzymes involved in DNA damage, signaling, and repair.^44,45

Therefore, we designed this study to investigate the role of curcumin and zinc on the biokinetics and biodistribution of ⁶⁵Zn in the DMH-afflicted rats. Our earlier findings revealed that 16 weeks of DMH treatment induced colon carcinogenesis in experimental rat models.⁴⁶ In this study, the altered ⁶⁵Zn uptake in the whole body, colon, and liver of the rats indicated the disrupted Zn metabolism. Our results also demonstrate the uptake of ⁶⁵Zn as a function of time in both whole body and liver, which represents the Zn turnover in the body.

Our observations for the biological half-life of ⁶⁵Zn exemplified dual compartmental kinetics. The faster component Tb₁ indicates the rapid elimination of the radiotracer, presumably through urine and feces, whereas, the slower component represented by Tb₂ characterizes the turnover of the radionuclide, which is incorporated into various tissues potentially by binding to metallothionein or other enzymes.

The results observed in the present study depict a significant decrease both in the faster (Tb₁) and the slower component (Tb₂) of the biological half-life of ⁶⁵Zn in the whole body of rats afflicted with DMH. This may be due to the decreased capacity of the whole body to retain ⁶⁵Zn in the biological system. This further corresponds to the faster elimination of zinc from the body during carcinogenesis as a consequence of the displacement of Zn from Zn-binding ligands, which is also substantiated by decreased levels of Zn in the serum and colon of the DMH-treated rats in an earlier study from our lab.⁴⁷ Metallothioneins (MT) are known to constitute a thermodynamic sink for zinc and their binding affinity to zinc is much higher in comparison to most other Zn proteins.⁴⁸ The role of MT in Zn metabolism and protection against certain metal toxicities has also been demonstrated by Davis and Cousins.⁴⁹ They play a major role in counteracting the oxidative stress induced in the body. Augmented expression of MT has been found in tumor cells,^50,51 which induce antiapoptotic effects and can further be linked to their increased resistance to cytotoxic agents.⁵² Therefore, the decrease in both the components can be attributed to the increased mobilization of MT in the systemic circulation to counteract the oxidative stress induced by the metabolites of DMH. However, co-supplementation of curcumin and zinc to the DMH-inflicted rats mitigated the oxidative stress and resulted in significantly increased turnover of ⁶⁵Zn, as evidenced by enhanced Tb₁ and Tb₂ components, so as to harmonize the depreciated concentrations of zinc in the carcinogenic processes. The increase in both the components can thus be attributed to decreased mobilization of MT following curcumin and Zn supplementation.

Conversely, the biokinetics of ⁶⁵Zn in the liver of DMH-treated rats revealed a significant increase in both the fast and slow components. The observed result depicts the slow turnover and over all increased retention of ⁶⁵Zn in the liver of rats following 16 weeks of DMH treatment. Metabolic activation and conversion of DMH by series of reactions, involving azoxymethane (AOM) and methylazoxymethanol (MAM), to the ultimate carcinogenic metabolite, highly reactive methyldiazonium ion is known to take place in the liver.⁵³ The carcinogenic metabolite further augments the requirement of Zn in the liver to combat its toxic effects, which can be correlated with the increased retention of ⁶⁵Zn in the liver. Further, a significant decrease in both the components was observed in the rats following administration of curcumin and zinc to the DMH-afflicted rats. This may be attributed to the increased availability of Zn, which further leads to the nonavailability of binding sites for ⁶⁵Zn. Therefore, curcumin and Zn supplementation normalized the fast and slow components as a consequence of normal excretion of unbound ⁶⁵Zn.

Previous studies from our lab have well advocated the inhibitory effects of Zn on the ultrastructural modifications and antioxidant status in the colon of rats during experimentally induced colon carcinogenesis.^47,54 Another study from our lab documents the role of curcumin and resveratrol in maintaining the adequate Zn levels, which further stimulates p21 and regulates p53 during lung carcinogenesis in mice.⁵⁵ In this study also, coadministration of curcumin and Zn to the DMH-afflicted rats normalized both the Zn kinetics in the whole body and liver of rats, which is suggestive of the regulation of Zn levels, thereby, implicating their chemopreventive role against colon carcinogenesis.

The biodistribution pattern in the normal control rats revealed the maximum uptake of the radiotracer in liver over the various organs under study, followed by small intestine, spleen, kidneys, and colon. High concentration of ⁶⁵Zn in liver has also been evidenced in an earlier study.²⁶ The uptake of ⁶⁵Zn was found to be significantly reduced in the liver but significantly increased uptake was observed in the kidneys, small intestine, and colon of the rats following 16 weeks of DMH treatment, when compared with the respective normal control group. The enhanced uptake may be due to the decreased levels of Zn under cancerous conditions,⁴⁷ which can be correlated with the depression in the whole body biological half-lives (Tb₁ and Tb₂). This is also indicative of the increased requirement of zinc to suppress the adverse effects induced by DMH in these organs, especially, colon. On the contrary, the reduced uptake in liver may be due to the saturation of Zn-binding sites as indicated by the slow turnover of ⁶⁵Zn and increase in Tb₁ and Tb₂ components in the liver. The conversion of DMH to its carcinogenic metabolites in liver might have upsurged the demand of Zn leading to its retention for a longer period. This may also be apparently due to the increased requirement of Zn by other organs containing increased reserves of MT. Therefore, decreased uptake of radioactive tracer was observed in the liver of rats administered with DMH. However, the uptake values were found to be regulated to normal limits following curcumin and zinc treatment to the DMH-affected rats.

To support this contention, we also analyzed the distribution of ⁶⁵Zn in the subcellular fractions within colonic cells, which is reflective of the modifications and binding sites of Zn in the cellular compartments. A notable decline in the uptake in the nuclear fraction was observed in the rats subjected to DMH treatment, which illustrates the decreased availability of zinc-binding sites. However, observations from the mitochondrial, microsomal, and postmicrosomal fractions depicted the increased uptake of ⁶⁵Zn. However, the uptake values of ⁶⁵Zn in different cellular fractions were found to be normalized following curcumin and Zn treatment, which could be due to the regulation of zinc homeostasis within the cell that might have revived the activities of various proteins in the cell.

This study therefore concludes that curcumin and zinc play a pivotal role in maintaining zinc homeostasis by regulating ⁶⁵Zn biokinetics in the DMH-afflicted rats. The promising results of the combined supplementation of both the nutraceuticals have indicated their increased potency in chemoprevention of cancer and paves the way for further exploration to be used in combination as chemopreventive agents.

Footnotes

Acknowledgments

The financial assistance for carrying out this work has been provided by the Department of Science and Technology (INSPIRE Program) and is gratefully acknowledged. We are also thankful to the Department of Biophysics, Panjab University, Chandigarh for providing the necessary facilities.

Disclosure Statement

The authors declare no conflict of interest.

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Regulation of Biokinetics of 65 Zn by Curcumin and Zinc in Experimentally Induced Colon Carcinogenesis in Rats

Abstract

Introduction

Materials and Methods

Chemicals and radioisotope

Animal treatment

Experimental design

Whole body biological half-life of 65Zn

Biological half-life of 65Zn in liver

Biodistribution of 65Zn

Subcellular distribution of 65Zn in colon tissue

Statistical analyses

Results

Whole body biological half-life of 65Zn

Biological half-life of 65Zn in liver

Uptake and biodistribution of 65Zn

Subcellular distribution of 65Zn in colon tissue

Discussion

Footnotes

Acknowledgments

Disclosure Statement

References

Whole body biological half-life of ⁶⁵Zn

Biological half-life of ⁶⁵Zn in liver

Biodistribution of ⁶⁵Zn

Subcellular distribution of ⁶⁵Zn in colon tissue

Whole body biological half-life of ⁶⁵Zn

Biological half-life of ⁶⁵Zn in liver

Uptake and biodistribution of ⁶⁵Zn

Subcellular distribution of ⁶⁵Zn in colon tissue