Plasma levels and dietary intake of minerals in patients with type 2 diabetes and chronic kidney disease: A case-control study

BACKGROUND AND AIM

Diabetic kidney disease (DKD) is the primary cause of chronic kidney disease (CKD) worldwide. Altered mineral levels leading to adverse outcomes are widely reported in diabetes but limited in DKD, in the Indian scenario, hence this study was taken up to address this issue.

METHODS

A hospital-based case-control study was taken up with 54 healthy controls (C) and 140 subjects with type 2 diabetes wherein 74 subjects with diabetes and CKD formed the DKD group, and 66 subjects with diabetes but no CKD formed the diabetic no-chronic kidney disease (DNCKD) group. High-resolution inductively coupled plasma mass spectrometry was used to evaluate the blood levels of minerals (calcium (Ca), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), and selenium (Se)), and a raw food-based food frequency questionnaire for dietary intakes. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation (mL/min/1.73 m2) and albuminuria. Spearman's rank correlation was used to evaluate the relationship between the categorical variables.

RESULTS

The median values of plasma Ca in the DKD group were significantly lower compared with the DNCKD and C groups (10.5 mg/dL vs. 11.0 mg/dL and 11.7 mg/dL, p<0.001). Furthermore, plasma Ca levels lowered with declining kidney function, as evidenced by the eGFR and albuminuria segregation. Dietary intake of minerals did not correlate with the corresponding plasma levels. However, in the DKD group, eGFR correlated positively with the plasma levels of Ca (r= 0.422, p=0.001), Cr (r= 0.351, p=0.008), Mn (r= 0.338, p=0.011), Fe (r= 0.403, p=0.002), Cu (r= 0.274, p=0.041) and negatively with Se (r= -0.486, p<0.001).

CONCLUSION

Plasma Ca levels are lower in the DKD group with a strong positive association with eGFR, indicating its role in predicting the onset and progression of kidney function decline.

Development and Validation of an ICP-MS Method and Its Application to Determine Multiple Trace Elements in Small Volumes of Whole Blood and Plasma

Essential and nonessential element concentrations in human blood provide important information on the nutritional status of individuals and can assist in the screening or diagnosis of certain disorders and their association with other causative factors. A simple and sensitive method, suitable for use with small sample volumes, for quantification of multiple trace element concentrations in whole blood and plasma has been developed using inductively coupled plasma-mass spectrometry. Method validation was performed using standard reference materials of whole blood and serum using varying sample treatments with nitric acid, water and hydrogen peroxide. The method was applied to quantify the trace element concentrations in whole blood and plasma samples (0.1 mL) from 50 adult blood donors in Queensland. The whole blood sample (5 mL) was collected in Vacutainer tubes with K2EDTA as anticoagulant. The developed method was able to quantify, in blood and plasma samples over a wide range of concentrations, several essential elements: cobalt, copper, zinc, iron, manganese and selenium; the nutritionally probably essential elements vanadium and strontium; and nonessential elements including lead, cadmium, arsenic, caesium, barium, thallium and uranium. Significant differences (P < 0.0001) were observed between whole blood and plasma concentrations for 13 elements; 5 of the measured elements, cobalt (0.49 vs. 0.36 μg/L), copper (1.0 vs. 0.75 mg/L), strontium (28 vs. 16 μg/L), barium (1.5 vs. 0.64 μg/L) and thallium (0.06 vs. 0.03 μg/L), had higher mean concentrations in plasma than in blood. Whole blood concentrations of nine trace elements were significantly correlated (P < 0.0001) with plasma concentrations. The distribution of the trace elements between human blood and plasma varied considerably for the different elements. These results indicate that, using a small sample volume, this assay is suitable for the evaluation of nutritional status as well as in monitoring human toxic elemental exposures.

Simultaneous analysis of 25 trace elements in micro volume of human serum by inductively coupled plasma mass spectrometry (ICP-MS)

INTRODUCTION

In recent years, trace elements have gained importance as biomarkers in many chronic diseases. Unfortunately, the requirement for sample volume increases with the extent of investigation either for diagnosis or elucidating the mechanism of the disease. Here, we describe the method development and validation for simultaneous determination of 25 trace elements (lithium [Li], beryllium [Be], magnesium [Mg], aluminium [Al], vanadium [V], chromium [Cr], manganese [Mn], iron [Fe], cobalt [Co], nickel [Ni], copper [Cu], zinc [Zn], gallium [Ga], arsenic [As], selenium [Se], rubidium [Rb], strontium [Sr], silver [Ag], cadmium [Cd], caesium [Cs], barium [Ba], mercury [Hg], thallium [Tl], lead [Pb], uranium [U]) using only 20 μL of human serum.

METHODS

Serum samples were digested with nitric acid and hydrochloric acid (ratio 1:1, v/v) and analysed by inductively coupled plasma-mass spectrometry (ICP-MS). Seronorm®, a human-derived serum control material was used as quality control samples.

RESULTS

The coefficient of variations for both intra- and inter-day precisions were consistently <15% for all elements. The validated method was later tested on 30 human serum samples to evaluate its applicability.

CONCLUSION

We have successfully developed and validated a precise and accurate analytical method for determining 25 trace elements requiring very low volume of human serum.

Discrete sampling based-flow injection as an introduction system in ICP-MS for the direct analysis of low volume human serum samples

Discrete sampling based on the flow injection options offered by advanced autosamplers has been tested and applied for the direct analysis of low volume samples (human serum) for multi-elemental purposes (simultaneous Al, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Ni, Pb, Rb, Se, V, and Zn assessment). Serum samples (200 µL aliquots) were directly diluted to 2.0 mL with 1% (v/v) HNO₃, and discrete sampling operating conditions were optimized to allow cleaning, loading (300 µL injection loop), and measuring steps by using a volume lower than 2.0 mL (diluted serum sample). Matrix effect has been overcome by using the standard addition technique, and accurate results implied the use of kinetic energy discrimination (KED) mode (He as a collision gas) for measurements. The proposed method has been found to be reliable for serum samples analysis because of the low sample volume requirements, the minimal sample preparation required, and high sampling rate (each replicate analysis takes 2.50 min). In addition, validation results show good precision and accuracy (both analytical recovery and analysis of certified reference materials), and acceptable sensitivity. Applicability of the proposed method has been finally demonstrated by analysing several serum samples from healthy adults.

Determination of Zn, Cu and Fe in human patients' serum using micro-sampling ICP-MS and sample dilution

A high-throughput, sensitive and rapid method was developed for the determination of Zn, Cu and Fe in small volumes (30 μL) of human serum using inductively coupled plasma mass spectrometry (ICP-MS). The sample preparation procedure employed simple 100-fold dilution of the serum samples with 1.0% butanol, 0.5% v/v ammonia, 0.02% v/v Triton X-100 and 0.01% v/v HNO₃. The reliability of the method was evaluated using serum UTAK certified reference material, and the results matched well with the certified values. The method was applied to determine Zn, Cu and Fe in 81 human serum samples from participants in Alzheimer disease (AD) and age-related macular degeneration (AMD) studies. No significant differences were found in Zn and Cu levels between age matched controls, AD and AMD patients. Whilst iron levels appeared marginally higher in the AMD group, compared with the AD group, iron showed larger overall variability than the other two elements.

Impact of occupational cadmium exposure on bone in sewage workers

Cadmium (Cd) is one of the environmental risk factors for bone loss. The present study included 40 sewage workers occupationally exposed to Cd. Forty nonexposed men were included as a control group. Current smokers represented 65% and 47.5% of the exposed and control groups, respectively. The study aimed to investigate the hazard of occupational Cd exposure on bone health. This was achieved through measuring serum and urinary Cd, and calcium (Ca), in addition to serum osteoprotegerin (OPG) and estrogen receptor-α gene. Results showed significant elevation in serum Cd, OPG, and urinary Ca levels in the exposed compared to the controls. Bony aches and joint pain were more prevalent among the exposed workers. Serum and urinary Cd increased in exposed smokers relative to control smokers. Also, serum OPG levels showed significant rise among exposed smoker and nonsmoker compared to control smoker and nonsmoker groups. Serum Cd level increased significantly in PP and pp genotypes in exposed workers compared to controls, while elevated levels of serum OPG was observed in PP and Pp genotypes in exposed workers relative to controls. Urinary Cd exhibited significant rise in both PP and pp genotypes in exposed workers, while Ca excretion was elevated in pp genotype only. The study reflected an association of genetic predisposition and Cd exposure in progression of osteoporosis. Further research is needed to explain the mechanisms of Cd impact on bone. The role of smoking is important and hence smoking cessation programs are essential for sewage workers.

Melted Paraffin Wax as an Innovative Liquid and Solid Extractant for Elemental Analysis by Laser-Induced Breakdown Spectroscopy

This work proposes a new development in the use of melted paraffin wax as a new extractant in a procedure designed to aggregate the advantages of liquid phase extraction (extract homogeneity, fast, and efficient transfer, low cost and simplicity) to solid phase extraction. As proof of concept, copper(II) in aqueous samples was converted into a hydrophobic complex of copper(II) diethyldithiocarbamate and subsequently extracted into paraffin wax. Parameters which affect the complexation and extraction (pH, DDTC, and Triton X-100 concentration, vortex agitation time and complexation time) were optimized in a univariate way. The combination of the extraction proposed procedure with laser-induced breakdown spectroscopy allowed the precise copper determination (coefficient of variation = 3.1%, n = 10) and enhanced detectability because of the concentration factor of 18 times. A calibration curve was obtained with a linear range of 0.50-10.00 mg L^-1 (R² = 0.9990, n = 7), LOD = 0.12 mg L^-1, and LOQ = 0.38 mg L^-1 under optimized conditions. An extraction procedure efficiency of 94% was obtained. The accuracy of the method was confirmed through the analysis of a reference material of human blood serum, by the spike and recovery trials with seawater, tap water, mineral water, and alcoholic beverages and by comparing with those results obtained by graphite furnace atomic absorption spectrometry.

Copper brain protein protection against free radical-induced neuronal death: Survival ratio in SH-SY5Y neuroblastoma cell cultures

In Creutzfeldt Jakob, Alzheimer and Parkinson diseases, copper metalloproteins such as prion, amyloid protein precursor and α-synuclein are able to protect against free radicals by reduction from cupric Cu⁺² to cupreous Cu⁺. In these pathologies, a regional copper (Cu) brain decrease correlated with an iron, zinc or manganese (Mn) increase has previously been observed, leading to local neuronal death and abnormal deposition of these metalloproteins in β-sheet structures. In this study we demonstrate the protective effect of Cu metalloproteins against deleterious free-radical effects. With neuroblastoma SH-SY5Y cell cultures, we show that bovine brain prion protein in Cu but not Mn form prevents free radical-induced neuronal death. The survival ratio of SH-SY5Y cells has been measured after UV irradiation (free radical production), when the incubating medium is supplemented with bovine brain homogenate in native, Cu or Mn forms. This ratio, about 28% without any addition or with bovine brain protein added in Mn form, increases by as much as 54.73% with addition to the culture medium of native bovine brain protein and by as much as 95.95% if the addition is carried out in cupric form. This protective effect of brain copper protein against free radical-induced neuronal death has been confirmed with Inductively Coupled Plasma Mass Spectrometry Mn and Cu measurement in bovine brain homogenates: respectively lower than detection limit and 9.01μg/g dry weight for native form; lower than detection limit and 825.85μg/g dry weight for Cu-supplemented form and 1.75 and 68.1μg/g dry weight in Mn-supplemented brain homogenate.

Anti-inflammatory activity of Punica granatum L. (Pomegranate) rind extracts applied topically to ex vivo skin

Coadministered pomegranate rind extract (PRE) and zinc (II) produces a potent virucidal activity against Herpes simplex virus (HSV); however, HSV infections are also associated with localised inflammation and pain. Here, the objective was to determine the anti-inflammatory activity and relative depth penetration of PRE, total pomegranate tannins (TPT) and zinc (II) in skin, ex vivo. PRE, TPT and ZnSO₄ were dosed onto freshly excised ex vivo porcine skin mounted in Franz diffusion cells and analysed for COX-2, as a marker for modulation of the arachidonic acid inflammation pathway, by Western blotting and immunohistochemistry. Tape stripping was carried out to construct relative depth profiles. Topical application of PRE to ex vivo skin downregulated expression of COX-2, which was significant after just 6h, and maintained for up to 24h. This was achieved with intact stratum corneum, proving that punicalagin penetrated skin, further supported by the depth profiling data. When PRE and ZnSO₄ were applied together, statistically equal downregulation of COX-2 was observed when compared to the application of PRE alone; no effect followed the application of ZnSO₄ alone. TPT downregulated COX-2 less than PRE, indicating that tannins alone may not be entirely responsible for the anti-inflammatory activity of PRE. Punicalagin was found throughout the skin, in particular the lower regions, indicating appendageal delivery as a significant route to the viable epidermis. Topical application of TPT and PRE had significant anti-inflammatory effects in ex vivo skin, confirming that PRE penetrates the skin and modulates COX-2 regulation in the viable epidermis. Pomegranates have potential as a novel approach in ameliorating the inflammation and pain associated with a range of skin conditions, including cold sores and herpetic stromal keratitis.

In vitro permeation and biological activity of punicalagin and zinc (II) across skin and mucous membranes prone to Herpes simplex virus infection

Coadministration of pomegranate rind extract (PRE) and zinc (II) ions has recently been reported as a potential new topical treatment for Herpes simplex virus (HSV) infections. In the current work we examined the in vitro topical delivery of punicalagin (major phytochemical of PRE) and zinc from hydrogels across epithelial membranes that can become infected with HSV. Porcine epidermal, buccal and vaginal mucous membranes were excised and mounted in Franz diffusion cells and dosed with a simple hydrogel containing PRE and zinc sulphate (ZnSO₄). The permeation of punicalagin and zinc were determined by HPLC and ICPMS respectively; punicalagin was also determined in the basal layers by reverse tape stripping. Receptor phases from the epidermal membrane experiment were also used to challenge HSV-1 in Vero host cells, and ex vivo porcine skin was used to probe COX-2 modulation. Punicalagin and zinc permeated each of the three test membranes, with significantly greater amounts of both delivered across the epidermal membrane. The amounts of punicalagin permeating the buccal and vaginal membranes were similar, although the amount of zinc permeating the vaginal membrane was comparatively very large - it is known that zinc interacts with vaginal mucosa. The punicalagin recovered by reverse tape stripping of the epidermal, buccal and vaginal membranes gave 0.47±0.016, 0.45±0.052 and 0.51±0.048nMcm^-2 respectively, and were statistically the same (p<0.05). A 2.5 log reduction was achieved against HSV-1 using diffusion cell receptor phase, and COX-2 expression was reduced by 64% in ex vivo skin after 6h. Overall, a hydrogel containing 1.25mgmL^-1 PRE and 0.25M ZnSO₄ was able to topically deliver both the major bioactive compound within PRE and Zn (II) across all membranes and into the site specific region of Herpes simplex vesicular clusters, while maintaining potentiated virucidal and anti-inflammatory properties. This novel therapeutic system therefore has potential for the topical treatment of HSV infections.