Whole Egg Consumption Exerts a Nephroprotective Effect in an Acute Rodent Model of Type 1 Diabetes

Whole egg consumption increases gene expression within the glutathione pathway in the liver of Zucker Diabetic Fatty rats

Nutrigenomic evidence supports the idea that Type 2 Diabetes Mellitus (T2DM) arises due to the interactions between the transcriptome, individual genetic profiles, lifestyle, and diet. Since eggs are a nutrient dense food containing bioactive ingredients that modify gene expression, our goal was to examine the role of whole egg consumption on the transcriptome during T2DM. We analyzed whether whole egg consumption in Zucker Diabetic Fatty (ZDF) rats alters microRNA and mRNA expression across the adipose, liver, kidney, and prefrontal cortex tissue. Male ZDF (fa/fa) rats (n = 12) and their lean controls (fa/+) (n = 12) were obtained at 6 wk of age. Rats had ad libitum access to water and were randomly assigned to a modified semi-purified AIN93G casein-based diet or a whole egg-based diet, both providing 20% protein (w/w). TotalRNA libraries were prepared using QuantSeq 3' mRNA-Seq and Lexogen smallRNA library prep kits and were further sequenced on an Illumina HighSeq3000. Differential gene expression was conducted using DESeq2 in R and Benjamini-Hochberg adjusted P-values controlling for false discovery rate at 5%. We identified 9 microRNAs and 583 genes that were differentially expressed in response to 8 wk of consuming whole egg-based diets. Kyto Encyclopedia of Genes and Genomes/Gene ontology pathway analyses demonstrated that 12 genes in the glutathione metabolism pathway were upregulated in the liver and kidney of ZDF rats fed whole egg. Whole egg consumption primarily altered glutathione pathways such as conjugation, methylation, glucuronidation, and detoxification of reactive oxygen species. These pathways are often negatively affected during T2DM, therefore this data provides unique insight into the nutrigenomic response of dietary whole egg consumption during the progression of T2DM.

Egg Intake in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are often instructed to adhere to a renal-specific diet depending on the severity and stage of their kidney disease. The prescribed diet may limit certain nutrients, such as phosphorus and potassium, or encourage the consumption of others, such as high biological value (HBV) proteins. Eggs are an inexpensive, easily available and high-quality source of protein, as well as a rich source of leucine, an essential amino acid that plays a role in muscle protein synthesis. However, egg yolk is a concentrated source of both phosphorus and the trimethylamine N-oxide precursor, choline, both of which may have potentially harmful effects in CKD. The yolk is also an abundant source of cholesterol which has been extensively studied for its effects on lipoprotein cholesterol and the risk of cardiovascular disease. Efforts to reduce dietary cholesterol to manage dyslipidemia in dialysis patients (already following a renal diet) have not been shown to offer additional benefit. There is a paucity of data regarding the impact of egg consumption on lipid profiles of CKD patients. Additionally, egg consumption has not been associated with the risk of developing CKD based on epidemiological studies. The egg yolk also contains bioactive compounds, including lutein, zeaxanthin, and vitamin D, which may confer health benefits in CKD patients. Here we review research on egg intake and CKD, discuss both potential contraindications and favorable effects of egg consumption, and describe the need for further research examining egg intake and outcomes in the CKD and end-stage renal disease population.