Effects of Dietary Cocoa on Cadmium-induced Nephrotoxicity in Mice

Cadmium (Cd) is a toxic pollutant derived from geogenic and anthropogenic sources. The movement of Cd from the soil into crops is a worldwide public health concern due to its long biological half-life and potential to bioaccumulate. The kidneys are the most vulnerable organ to Cd toxicity resulting from oxidative stress-induced protein misfolding and cell death. Theobroma cacao L. has a high propensity to uptake Cd from the soil. Cocoa, a dietary ingredient from T. cacao, also contains high levels of polyphenols, and previous studies have indicated that other polyphenol-rich foods can mitigate Cd-mediated toxicity. The objective of this study is to unravel the interactions between cocoa and Cd in the body. In the present study, we hypothesized that cocoa would reduce Cd-induced nephrotoxicity in a preclinical model. Male C57BL/6J mice were randomized to CdCl 2 (100 milligrams (mg) per liter (L))-containing drinking water alone or in combination with diets supplemented with cocoa power (20 or 80 milligrams (mg) per gram (g) of diet). After 8 weeks, mice were euthanized, and blood and tissues were collected. The absorption of Cd was evaluated by X-ray fluorescence. Renal markers of p62-dependent autophagy and the nuclear factor erythroid 2–related factor 2 (Nrf2) pathway were investigated by quantitative reverse transcriptase polymerase chain reaction and western blot. Mice co-treated with cocoa had a 64-88% lower absorption of Cd compared with the Cd control group. We found 22% lower blood urea nitrogen levels in the 80 mg/g cocoa-treated group indicating improved kidney function. In the kidneys, we observed a 37% reduction in ubiquitinated proteins in the cocoa-treated groups compared to the control. This was associated with a 41% reduction in the p62 autophagosome cargo protein and a 21-23% decrease in microtubule-associated protein light chain 3. Moreover, mice treated with 80 mg/g cocoa had 3.8-fold higher expression of transcription factor EB and higher expression of its downstream targets lysosomal-associated membrane protein-1 (2.7-fold higher mRNA) and mature cathepsin D (1.9-fold higher protein) compared to the Cd control. These changes indicate increased formation of lysosomes to complete autophagy. The reduction in p62-dependent autophagic flux was further associated with 77% lower p62-dependent Nrf2 protein levels in 80 mg/g cocoa-treated mice. Canonical variate analysis revealed a clear separation between the control and 80 mg/g cocoa-treatment groups. We conclude that dietary cocoa intake during Cd exposure offers a protective response to Cd-induced renal injury associated with oxidative stress. Additional investigations are needed to accurately assess the actual health risks arising from Cd toxicity in cacao-based products by taking into consideration the bioavailability of Cd. This work was funded by NIFA Hatch Grant PEN05008 Accession No. 7007470. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.