However, the production of H2O2 and phenolic compounds, and higher PPO activity in the translucent tissue were detected specifically in the VB tissues, not in other living non-VB cells after chilling . These data indicated that IB did not randomly occur in any living parenchyma cell but is specific to the phloem. Therefore, if the phloem is the site of IB initiation in PCI of pineapple fruit, then future studies should focus on how different traits ofthephloem, e.g.,membrane properties, antioxidant system, etc., vary among cultivars differing in IB response.In all IB-occurring cultivars studied, the VBs found at the F/C boundary contained fewer sclerenchyma fiber cells than did the VBs found at the C region, except in the PTV cultivar . The sclerenchyma fibers are composed of lignified cells, which offer protection to the VBs . When these anatomical features of the pineapple are considered, the link between VB number and the appearance of IB at the F/C is clear. This occurrence may be explained by the morphological structure of the pineapple fruit. The fruit is a composite of multiple individual fruitlets, fused to each other and to the C.
At maturity, hydroponic nft system the fruitlets become the ediblefleshly part ofthe fruit composed predominantly of parenchyma cells and some VBs containing lignified cell walls . The C of the fruit consists mainly of VBs with connections to the stem. The C region constitutes a stele of VB, one connected to the other vertically. From the C region,theVBs are distributed to the F/C of the fruit . The VBs in the F/C region form the denser network that grows both vertically and horizontally toward the F regions . These data suggested that the higher number of VBs at the F/C regions might explain why IB symptoms are easily detectable to the naked eye. However, as mentioned previously, the properties of phloem, e.g., their membrane properties and antioxidant system, at the F/C region might play a role in IB development.Consistent with published data,the IB-resistant MD2 showed no IB and TS after being stored at 10 ◦C for three weeks . It is possible to hypothesize that differences invascular structure may play a role in the observed lack of IB in resistant cultivars. Among all four cultivars studied here,the number and size of the xylem elements and phloem per VB did not correlate with varietal IB resistance . It is noteworthy,however,thatthe IB-resistantMD2hadfewerVBs but more sclerenchyma fiber cells surrounding the phloemand xylem, resulting in a larger size of VBs compared with other cultivars. In addition, the number and size of VBs and the number of sclerenchyma cells in all regions of the MD2 fruit were similar . In MD2, there were the multiple layers of the sclerenchyma cells on the lateral sides of VB. In contrast, in PTV and SV, there were no more than two layers of the sclerenchyma cells on the lateral sides ofVB, and only a single one in TST.
These special anatomical features may serve a protective purpose, preventing separation of the VBs themselves and limiting further damage to the tissue from chilling injury . Interestingly, MD2 stored at 10 ◦C for six weeks exhibited chilling injury at the exocarp . These data suggested that there are potentially different physiological and biochemical processes occurring in the fruit of the IB-resistant MD2 including: different physiological and biochemical properties of phloem cell ,fewer metabolically active phloem cells due to the lower number of VBs compared to the susceptible lines , and very low levels of PPO activity or phenolics so that any browning compounds produced were not visibly detectable .A plant-based diet is defined as the consumption of plants such as fruits, vegetables, nuts, seeds, oils, whole grains, legumes, and beans. It may or may not include small amounts of animal products such as meat, fish, sea-food, eggs, and dairy, but these foods tend to be avoided. Plant foods are rich in phytochemicals, antioxidants, vitamins, and minerals which prove beneficial to health on a micronutrition level, especially when plants are consumed in their whole, unprocessed form. When brought to the forefront of a patient’s dietary pattern, these naturally nutritious foods may translate into clinically significant improvements to patients’ quality of life and disease prognosis, and mitigate disease complications.
Historically, these foods have been avoided in patients on dialysis due to concerns of hyperkalemia and protein deficiency. However, the recent recognition of their potential benefits and improved understanding of potential pitfalls have favored the reintroduction of these foods into the diet of patients on dialysis.Traditional dietary interventions in patients with kidney disease encourage the restriction of phosphorus, potassium, sodium, and fluid as well as tailoring protein intake to the patient’s CKD stage and whether they require kidney replacement therapy. These guidelines tend to result in a diet devoid of fruits and vegetables, lacking in variety and resulting in limited satisfaction. Broadening the diet of patients with kidney disease to include these otherwise healthy foods may not only improve satisfaction and increase variety but may also carry additional benefits. A recent multinational cohort study found that higher consumption of fruits and vegetables in patients on dialysis was associated with lower all-cause and non-cardiovascular death. In this study, patients receiving long-term hemodialysis completed a food frequency questionnaire for a median follow-up of 2.7 years . Only 4% of the patients consumed at least 4 servings of fruit and vegetables per day as recommended in the general population. Plant-based diets, a fiber- and polyphenol-rich intervention, may attenuate cardiovascular disease risk markers in patients on hemodialysis. Polyphenols are a diverse group of micronutrients only consumed through plants. A systematic review and meta-analysis of 12 studies found that polyphenol-rich interventions in patients on hemodialysis improved diastolic blood pressure , triglycerides , and myeloperoxidase. Fiber supplementation was found to significantly lower total cholesterol, LDL cholesterol, and inflammatory markers – all of which are known cardiovascular risk factors. Plant fats, which are rich in unsaturated fatty acids, have shown to be beneficial in the diets of patients on hemodialysis by improving inflammatory markers. Vegetable oils are rich in polyunsaturated fatty acids, such as linoleic acid, nft channel which are known to have cardioprotective and anti-inflammatory properties. In one study, linoleic acid levels, as a proportion of plasma fatty acids, were shown to be inversely associated with IL-6 and all-cause mortality in a cross-sectional study of hemodialysis patients.Dietary fiber is a nondigestible, nonabsorbable carbohydrate polymer that may be used to treat chronic kidney disease by exploiting its ability to reduce uremic toxin production and, perhaps, postpone dialysis. Since dietary fiber is exclusively found in plants, there may be a unique advantage associated with the use of plant-based diets . Fermentable fibers are metabolized into short-chain fatty acids, especially acetate, propionate, and butyrate. Short-chain fatty acids may play a role in kidney health by modulating systemic inflammation and maintaining the integrity of the gut mucosal barrier. Today, plant-derived complex carbohydrates are recognized as prebiotics for their role in promoting the growth and metabolic activity of beneficial saccharolytic organisms like Bifidobacteria and Lactobacillus.
The protective effects of gut microbiota have been widely studied in chronic kidney disease, but there is a paucity in data regarding the bidirectional gut-kidney axis in hemodialysis patients. Compared to healthy individuals, a cross-sectional study found end-stage kidney disease patients on hemodialysis to have an increased relative abundance of Proteobacteria , Actinobacteria, and Firmicutes by phylogenic microarrays. Of note, these taxa are not usually associated with uremic toxin production. Indoxyl sulfate and p-cresol are uremic toxins generated by colonic bacteria in response to food that is not absorbed in the small bowel. Uremic toxins accumulatein patients with chronic kidney disease and may contribute to the progressive loss of glomerular filtration rate by increasing the expression of transforming growth factor beta which increases fibrogenesis. A cross-sectional study of patients undergoing hemodiafiltration found that vegetarian patients had 47% lower levels of indoxyl sulfate and 67% lower levels of p-cresyl sulfate than the nonvegetarian patients. In another study of patients on hemodialysis, an increase in fiber intake was shown to significantly reduce plasma levels of indoxyl sulfate by 17% and non-significantly reduce plasma levels of p-cresol by 8% in a randomized control trial . Another cross-sectional study found that increased levels of p-cresol were associated with an increased risk of death in patients on maintenance hemodialysis. Outside of decreasing uremic toxins, fiber supplementation in patients on hemodialysis also improved lipid profiles and oxidative status and decreased systemic inflammation when compared to a placebo in a 6-week randomized control trial. The results of the trial revealed a significant decrease in total cholesterol level, high-density lipoprotein level, and TC:LCL ratio; a significant decrease in total antioxidant capacity and malondialdehyde; and a significant decrease in tumor necrosis factor-α, interleukin-6, interleukin-8, and C-reactive protein in the 10 and 20 g per day fiber supplement groups. A long term prospective cohort study of patients on peritoneal dialysis showed an independent association between fiber intake and all-cause mortality wherein each gram per day increase in fiber intake correlated with a 13% reduction in all-cause mortality. Contrarily, low dietary fiber intake has been shown to negatively impact patients on hemodialysis on multiple occasions. In a prospective cohort study of patients on dialysis , lower fiber intake was associated with an increased risk for major adverse cardiovascular events when compared to patients with higher fiber intake. Another study on maintenance hemodialysis patients found that dietary fiber level was independently correlated with advanced glycation end products and C-reactive protein levels.In hemodialysis patients, the incidence of constipation varied according to the definition of constipation, but it was noted to be 71.7% in a 2013 cross-sectional study using the Roma III criteria. As a chronic or frequently recurrent symptom, constipation impairs patients’ health-related quality of life and may result in a substantial emotional and social burden. The issue may be easily treated by emphasizing the consumption of high-fiber foods, like plants. It may be possible that the historically low consumption of fiber-rich foods of patients on hemodialysis may be to blame for the high rate of constipation in this population. In the general population, patients with constipation had 12% higher all-cause mortality, 11% higher incidence of coronary heart disease, and 19% higher incidence of ischemic stroke compared to patients without constipation. US Veterans using one or >2 types of laxatives experienced a similarly higher risk of all-cause mortality and cardiovascular and cerebrovascular burden when compared to US veterans not taking any laxatives. A recent multi-center study evaluated the prevalence and correlates of constipation in hemodialysis patients from 4 dialysis centers using a questionnaire based on the Roma IV criteria to assess constipation status and lifestyle habits along with a food frequency questionnaire focused on the main sources of dietary fiber and found that >30% of patients had constipation at a given point in time. In this study, the independent predictors of constipation symptoms included diabetes and lower frequency of fruit intake. Moreover, constipation can worsen hyperkalemia, while having soft bowel movement may be associated with a lower likelihood of hyperkalemia.Although phosphorus is an essential nutrient, it is difficult for patients to avoid states of phosphate excess in advanced CKD. Consequently, patients must be placed on phosphorus-restricted diets to reduce the risk of hyperphosphatemia, which has been associated with an increased risk of death and cardiovascular disease. Given the varying bio-availability of phosphorus from foods, dietary changes may be made to take advantage of low phosphate-containing foods. In the gut, 40–60% of phosphate in animal protein is absorbed by the intestinal tract compared to only 10–30% of phosphorus in plant protein. This is partly because the bulk of phosphorus in plants is bound to phytate, which is difficult for humans to digest due to lack of phytase to release the phosphorus. In a cross-over trial in patients with CKD, the effects of vegetarian and meat diets on phosphorus balance showed that 1 week of a vegetarian diet led to significantly lower serum phosphorus and significantly lower fibroblast growth factor-23 levels than being on a meat diet . This finding has also been seen in a small observational study by Wu et al. wherein serum phosphate levels were significantly lower in vegetarian patients than in non-vegetarian patients on hemodialysis.When diagnosed with end-stage kidney disease, traditional dietary interventions may place patients at risk for vitamin deficiencies.