Marginal zinc deficiency in older adults: responsiveness of zinc status indicators.

Approximately 12% of Americans do not consume the EAR for zinc and could be at risk for marginal zinc deficiency. There is accumulating evidence that zinc deficiency is associated with increased risk of cancer mortality and increased DNA damage in vitro. We hypothesize that zinc deficiency in vivo causes DNA damage through increases in oxidative stress and compromised oxidant defense. To test this hypothesis, SD rats were fed an adequate zinc diet (MZA 30ppm) or marginal zinc deficient diet (MZD 6ppm) for 6 weeks. Comet assay revealed a significant increase in DNA damage in peripheral blood cells of MZD rats. Oxidative stress was also increased as indicated by alterations in plasma F2‐isoprostanes. However, no changes in plasma total antioxidant capacity, ascorbic acid, α–tocopherol, and erythrocyte SOD activity were found with MZD. We also investigated the effects of severe zinc deficiency with repletion on DNA damage. Rats were fed an adequate zinc (30ppm), zinc deficient (<1ppm), or pair‐fed diet for 3 weeks prior to 1 week zinc repletion. DNA damage of peripheral blood cells was significantly increased after zinc depletion, but reversed back to normal levels after zinc repletion. These data suggest interactions among zinc deficiency, DNA integrity and oxidative stress and implicate the role of zinc deficiency in cancer susceptibility.

Zinc Deficiency Affects DNA Damage, Oxidative Stress, Antioxidant Defenses, and DNA Repair in Rats

Simple SummaryEnterotoxigenic Escherichia coli (ETEC) is one of the most common bacterial causes of diarrhea in children and farm animals. Zinc has received widespread attention for its roles in the prevention and treatment of diarrhea. However, zinc is also essential for the pathogenesis of ETEC. This study aimed to explore the accurate effect and mechanisms of marginal zinc deficiency on ETEC k88 infection and host intestinal health. Using the newly developed marginal zinc deficiency and ETEC k88 infection mouse model, we found that marginal zinc deficiency aggravated growth impairment, diarrhea, intestinal morphology, intestinal permeability, and inflammation induced by ETEC k88 infection. Consistently, intestinal ETEC k88 shedding was also higher in mice with marginal zinc deficiency. However, marginal zinc deficiency failed to affect host zinc levels and correspondingly the zinc-receptor GPR39 expression in the jejunum. In addition, marginal zinc deficiency upregulated the relative expression of virulence genes involved in heat-labile and heat-stable enterotoxins, motility, cellular adhesion, and biofilm formation in the cecum content of mice with ETEC infection. These findings provide a new explanation for zinc treatment of ETEC infection.Zinc is both essential and inhibitory for the pathogenesis of enterotoxigenic Escherichia coli (ETEC). However, the accurate effects and underlying mechanism of marginal zinc deficiency on ETEC infection are not fully understood. Here, a marginal zinc-deficient mouse model was established by feeding mice with a marginal zinc-deficient diet, and ETEC k88 was further administrated to mice after antibiotic disruption of the normal microbiota. Marginal zinc deficiency aggravated growth impairment, diarrhea, intestinal morphology, intestinal permeability, and inflammation induced by ETEC k88 infection. In line with the above observations, marginal zinc deficiency also increased the intestinal ETEC shedding, though the concentration of ETEC in the intestinal content was not different or even decreased in the stool. Moreover, marginal zinc deficiency failed to change the host’s zinc levels, as evidenced by the fact that the serum zinc levels and zinc-receptor GPR39 expression in jejunum were not significantly different in mice with ETEC challenge. Finally, marginal zinc deficiency upregulated the relative expression of virulence genes involved in heat-labile and heat-stable enterotoxins, motility, cellular adhesion, and biofilm formation in the cecum content of mice with ETEC infection. These findings demonstrated that marginal zinc deficiency likely regulates ETEC infection through the virulence factors, whereas it is not correlated with host zinc levels.

Zinc intake and status of South Koreans from rural, urban and metropolitan areas were investigated. The dietary habits of 760 healthy male and female adult subjects with a mean age of 54 were assessed using a food frequency questionnaire and were verified using 24 h dietary recall. Daily Zn intakes for men and women were 7.4±5.4 mg and 7.0±5.4 mg, respectively, which were 62% and 70% of the Korean RDA. The phytate : zinc and phytate×calcium : zinc molar ratios were 38 and 398, respectively. Both the low intake of zinc and the high extremely phytate and phytate×calcium ratios with zinc suggest that South Koreans may be at risk of zinc deficiency. Plasma zinc (86±61 μg/dL), urinary zinc (33±27 μg/dL) and plasma alkaline phosphatase (102±52 mU/mL) levels within the normal range did not however suggest marked zinc deficiency in these subjects. However, conventional zinc biomarkers are known to be unreliable for assessment of marginal zinc deficiency. Based on zinc intake alone, it is likely that at least a proportion of these subjects were marginally zinc deficient and the wider consumption of zinc rich, phytate deficient foods, particularly in rural areas, would be beneficial.

Dietary zinc restriction and repletion affects DNA integrity in healthy men

Zinc Supplementation Prevents Alcoholic Liver Injury in Mice through Attenuation of Oxidative Stress

Secondary Zinc Deficiency via Exposure to the Environmental Toxicant Di-2-ethylhexyl phthalate Affects Neurogenesis at Embryonic Day 19

Zinc: An Essential Trace Element for Parenteral Nutrition

Disruption of steroid hormone signaling has been implicated independently in the developmental abnormalities resulting from maternal phthalate plasticizer exposure and developmental zinc deficiency. This study investigated if secondary zinc deficiency may result from dietary exposure to a low level of di-2-ethylhexyl phthalate (DEHP) through gestation and if this could be associated with altered steroid metabolism. The interaction between marginal zinc nutrition and DEHP exposure to affect pregnancy outcome, zinc status, and steroid metabolism was also assessed. For this purpose, rats were fed a diet containing an adequate (25 mg/kg) or marginal (10 mg/kg) level of zinc without or with DEHP (300 mg/kg) from gestation day (GD) 0 until GD 19. Steroid profiles were measured in dam liver, plasma, adrenal glands, and in fetal liver by UPLC/MS-MS. In dams fed the adequate zinc diet, DEHP exposure decreased maternal weight gain and led to hepatic acute-phase response and zinc accumulation. The latter could compromise zinc availability to the fetus. DEHP and marginal zinc deficiency caused several adverse effects on the maternal and fetal steroid profiles. Interactions between DEHP exposure and marginal zinc deficient nutrition affected 17OH pregnenolone and corticosterone, while pregnenolone levels were specifically affected by DEHP exposure. Maternal marginal zinc deficiency specifically affected maternal progesterone and aldosterone, and presented evidence of increased androgen aromatization activity in maternal and fetal tissues. Results stress the potential major impact of mild DEHP exposure on maternal/fetal steroid metabolism that can be potentiated by nutritional and chronic disease states leading to zinc deficiency.

Zinc Status Elicits Age-Dependent Effects in the Gut Microbiome

Pseudogout, or calcium pyrophosphate deposition disease (CPPD), is a common form of inflammatory arthritis in older adults. Although metabolic/endocrine factors such as magnesium deficiency and hyperparathyroidism are established risk factors, the role of zinc remains unclear. Since zinc deficiency is prevalent among older adults and zinc influences inflammation control and cartilage metabolism, its potential contribution to CPPD warrants investigation. This study aimed to explore the potential association between zinc deficiency and CPPD in older adults undergoing rehabilitation. We report a case series of five women aged 82-92 years undergoing rehabilitation who developed CPPD. Affected joints included the knees, ankles, wrists, and metatarsophalangeal joints. All patients had serum zinc levels below the reference range (49-67 µg/dL), while other minerals were generally within normal limits. In our study, zinc deficiency was independent of the general malnutrition status. Recurrent CPPD occurred in two patients, particularly those with lower functional status during rehabilitation. This exploratory, hypothesis-generating case series could suggest a potential link between hypozincemia and CPPD in older adults. Lower functional status may also be related to CPPD attacks. While limited by sample size, these findings highlight a clinically relevant hypothesis that warrants further investigation in larger prospective studies.

Metallothionein (MT) and zinc are both reported to be protective against oxidative and inflammatory stress and may also influence energy metabolism. The role of MT in regulating intracellular labile zinc, thus influencing zinc (Zn)-modulated protein activity, may be a key factor in the response to stress and other metabolic challenges. The objective of this study was to investigate the influence of dietary zinc intake and MT on hepatic responses to a pro-oxidant stress and energy challenge in the form of a high dietary intake of linoleic acid, an omega-6 polyunsaturated fatty acid. Male MT-null (KO) and wild-type (WT) mice, aged 16 weeks, were given semisynthetic diets containing 16% fat and either 5 (marginally zinc-deficient [ZD]) or 35 (zinc-adequate [ZA]) mg Zn/kg. For comparison, separate groups of KO and WT mice were given a rodent chow diet containing 3.36% fat and 86.6 mg Zn/kg. After 4 months on these diets, the body weights of all mice were equal, but liver size, weight, and lipid content were much greater in the animals that consumed semisynthetic diets compared to the chow diet. The increase in liver size was significantly lower in ZA but not ZD KO mice, compared with WT mice. Principally, MT appears to affect the diet-induced increase in liver tissue but it also influences the concentration of hepatic lipid. Plasma levels of C-reactive protein (CRP), a marker of inflammation, were increased by zinc deficiency in WT mice, suggesting that marginal zinc deficiency is proinflammatory. CRP was unaffected by zinc deficiency in KO mice, indicating a role for MT in modulating the influence of zinc. Neither zinc nor MT deficiency affects the level of soluble liver proteins, as determined using two-dimensional (2D) gel proteomics. This study highlights the close association between zinc and MT in the manifestation of stress responses.

Esophageal squamous cell carcinoma (ESCC) is a deadly disease with a 5-year survival of only 10% [1]. Because of the absence of early symptoms, ESCC is commonly diagnosed at an advanced stage. Thus, the development of new prevention and therapeutic approaches are urgently needed. Dietary zinc (Zn) deficiency (ZD), a significant public health issue affecting 31% of the global population [2], is associated with an increased risk of ESCC development [3]. Since marginal Zn deficiency is prevalent in humans [4], it was important to learn the effect of mild to moderate Zn deficiency on ESCC etiology. Our previous work, using rat model systems, has advanced understanding of the role of Zn in ESCC carcinogenesis. Zn deficiency promotes ESCC by inducing an inflammatory gene signature with up-regulation of cancer-associated inflammation genes & an oncogenic microRNA (miRNA) signature featuring up-regulation of oncogenic miR-31 [5]. Our recent dose-response study [6] showed that miRNA dysregulation and esophageal cancer development depended on the extent of dietary Zn deficiency. This tumorigenesis study used low doses of the environmental carcinogen N-nitrosomethyl-benzylamine (NMBA) in rats fed diets containing different amounts of Zn (3, 6, 12, or 60 mg Zn/kg) to represent marked-ZD, moderate-ZD, mild-ZD, and Zn-sufficiency in human Zn nutrition. miRNA expression profiling of human tumors has identified signatures associated with staging, progression, prognosis, and response to treatment [7]. We correlated miRNA expression changes with the above noted ZD doses and ZD-associated esophageal tumor outcome by performing miRNA profiling of esophageal mucosa from carcinogen-treated and untreated rats at study endpoint. Marked zinc deficiency (3 mg Zn/kg diet) alone induced a highly proliferative/inflammatory esophagus accompanied by an oncogenic 5-microRNA signature (miR-31, -223, -21, -146b, -146a). Moderate & mild zinc deficiency (6 & 12 mg Zn/kg diet) also induced sustained hyperplasia and inflammation, albeit less pronounced than marked deficiency, with a 2-microRNA signature (miR-31, -146a). The oncomiR miR-21 that was prominently overexpressed (up 4.2 fold) in the highly hyperplastic marked zinc deficient esophagus, however, was not differentially expressed in the less hyperplastic moderate/mild zinc deficient esophagus, providing evidence that miRNA signatures distinguish the highly hyperplastic esophageal phenotype induced by marked deficiency from the less hyperplastic esophageal phenotype induced by moderate and mild zinc deficiency. With exposure to NMBA, ∼16% of moderate/mild-ZD rats developed ESCC, an incidence greater than for Zn-sufficient rats (0%) (P≤0.05) but lower than for marked-ZD rats (68%) (P<0.001) (n=27 rats/cohort). These data show a dose-response relationship between the extent of zinc deficiency and ESCC development and provide the first evidence that moderate to mild zinc deficiency, combined with low doses of the environmental carcinogen NMBA, produces ESCC. Importantly, the high ESCC-burden, marked zinc deficient esophagus had a 15-miRNA signature, with strong to modest up-regulation of oncogenic miR-223, -21, -31, -146a, -146b, -27a, -221, -27b, -194, -24, -203, -183, -130b, -106b, -22 (up 3.6 to 1.4 fold), that resembled the human ESCC miRNAome. By contrast, low ESCC-burden, moderate & mild-ZD esophagus displayed, respectively, a 3-miRNA signature (miR-223, -31, -27b) and a 2-miRNA signature (miR-223, -31) with modest up-regulation. Thus, miRNA-signatures can distinguish the divergent ESCC progression in marked zinc deficiency versus moderate/mild zinc deficiency rat cohorts, as well as discriminate the hyperplastic marked deficiency esophageal phenotype from the less hyperplastic moderate/mild deficiency phenotype. Together, the data showed that these miRNA signatures not only differentiate stages of ESCC initiation and progression but they also highlight the molecular impact of dietary zinc deficiency on miRNA dysregulation in the pathogenesis of ESCC. In addition, Fbxw7, Pdcd4, and Stk40 (tumor-suppressor targets of miR-223, miR-21 and miR-31, respectively) were down-regulated in the markedly deficient cohort at the mRNA and protein level and they were predicted to interact to alter network of target proteins in cancer pathways. The data are in accord with the finding that miR-223, miR-21 and miR-31 expression levels play important roles in ESCC and may be useful prognostic biomarkers and therapeutic targets for ESCC. Using ChIP-seq and an antibody for histone mark H3K4me3, we previously showed that in Zn-deficient esophagus, the miR-31 promoter region and NF-κB binding site were activated [5]. However, the mechanism(s) by which miR-223 and miR-21 are upregulated by zinc deficiency remains to be elucidated. In summary, our recent work [6] showed for the first time that ESCC development and the underlying miRNA dysregulation are dependent on the extent of dietary deficiency of the nutrient Zn. The data have identified Zn deficiency-associated miRNA signatures that may underlie the molecular pathogenesis of ESCC in Zn-deficient populations. These findings suggest that dietary Zn may have preventive and therapeutic properties for ESCC.

Gestational marginal zinc deficiency impaired fetal neural progenitor cell proliferation by disrupting the ERK1/2 signaling pathway

The role of zinc and vitamin A in persistent diarrhea among infants and young children.