Implications of impaired zinc homeostasis in diabetic cardiomyopathy and nephropathy

Diabetic cardiomyopathy - Zinc preventive and therapeutic potentials by its anti-oxidative stress and sensitizing insulin signaling pathways

Oxidative stress and insulin resistance are two key mechanisms for the development of diabetic cardiomyopathy (DCM, cardiac remodeling and dysfunction). In this review, we discussed how zinc and metallothionein (MT) protect the heart from type 1 or type 2 diabetes (T1D or T2D) through its anti-oxidative function and insulin-mediated PI3K/Akt signaling activation. Both T1D and T2D-induced DCM, shown by cardiac structural remodeling and dysfunction, in wild-type mice, but not in cardiomyocyte-specific overexpressing MT mice. In contrast, mice with global MT gene deletion were more susceptible to the development of DCM. When we used zinc to treat mice with either T1D or T2D, cardiac remodeling and dysfunction were significantly prevented along with increased cardiac MT expression. To support the role of zinc homeostasis in insulin signaling pathways, treatment of diabetic mice with zinc showed the preservation of phosphorylation levels of insulin-mediated glucose metabolism-related Akt2 and GSK-3β and even rescued cardiac pathogenesis induced by global deletion of Akt2 gene in a MT-dependent manner. These results suggest the protection by zinc from DCM is through both the induction of MT and sensitization of insulin signaling. Combined our own and other works, this review comprehensively summarized the roles of zinc homeostasis in the development and progression of DCM and its therapeutic implications. At the end, we provided pre-clinical and clinical evidence for the preventive and therapeutic potential of zinc supplementation through its anti-oxidative stress and sensitizing insulin signaling actions. Understanding the intricate connections between zinc and DCM provides insights for the future interventional approaches.

Associations of multiple plasma metals with chronic kidney disease in patients with diabetes

As common contaminants, metals are non-negligible risk factors for diabetes and chronic kidney disease. However, whether there is an association between multiple metals exposure and incident chronic kidney disease (CKD) risk in patients with diabetes is unclear. We conducted a prospective study to evaluate these associations. In total, 3071 diabetics with baseline estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² from the Dongfeng-Tongji cohort were included. We measured baseline plasma concentrations of 23 metals and investigated the associations between plasma metal concentrations and CKD in diabetics using logistic regression, the least absolute shrinkage and selection operator (LASSO), and the Bayesian Kernel Machine Regression (BKMR) models. During average 4.6 years of follow-up, 457 diabetics developed CKD (14.9 %). The three models consistently found plasma levels of zinc, arsenic, and rubidium had a positive association with incident CKD risk in patients with diabetes, while titanium, cadmium, and lead had an inverse correlation. The results of BKMR showed a significant and positive overall effect of 23 metals on the risk of CKD, when all of the metals were above the 50th percentile as compared to the median value. In addition, potential interactions of zinc and arsenic, zinc and cadmium, zinc and lead, titanium and arsenic, and cadmium and lead on CKD risk were observed. In summary, we found significant associations of plasma titanium, zinc, arsenic, rubidium, cadmium, and lead with CKD in diabetes and interactions between these metals except for rubidium. Co-exposure to multiple metals was associated with increased CKD risk in diabetics.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Influence of zinc levels and Nrf2 expression in the clinical and pathological changes in patients with diabetic nephropathy

Objective

We investigated the correlation between zinc levels and Nrf2 expression and potential effects on the clinicopathology of patients with diabetic nephropathy (DN).

Methods

We selected 30 patients with DN, diagnosed via renal biopsy at our hospital from March 2018 to November 2019, and enrolled 30 healthy individuals from a medical examination center as the control group. Patients with DN were divided into normal-zinc and low-zinc groups. We detected the levels of zinc, copper, and Nrf2 mRNA in their serum, and collected the clinical and pathological data of DN patients.

Results

Serum zinc level and Nrf2 mRNA expression were significantly decreased in patients with DN compared to those of healthy people (P < 0.05). Of the 30 patients, 16 had low zinc (53.3%) and 14 had normal zinc levels (46.7%). There was no significant difference in the blood Nrf2 mRNA expression between the two groups (P > 0.05). However, the expression of Nrf2 in the kidney tissue of the low-zinc group was significantly lower compared to the normal-zinc group (P < 0.05). Diastolic blood pressure and copper levels were significantly higher in the low-zinc group (P < 0.05). In contrast, body mass index, red blood cell count, Hb level, and the ratio of zinc to copper were significantly lower in the low-zinc group (P < 0.05). The pathological classifications of the low-zinc group were more severe (P < 0.05).

Conclusion

Patients with DN were more likely to have zinc deficiency and lower expression of Nrf2. Additionally, DN patients with zinc deficiency were prone to have more severe clinical and pathological manifestations.

Preparation and hypoglycemic effects of chromium- and zinc-rich Acetobacter aceti

BACKGROUND

At present, there is no ideal method to cure diabetes, and there are few reports on the treatment of diabetes with probiotics.

AIM

To propose a method for preparing a new type of chromium- and zinc-rich Acetobacter aceti (A. aceti) and explore its ability to enhance the hypoglycemic effects of probiotics in the treatment of diabetes.

METHODS

A. aceti was cultured in a liquid medium that contained chromium trichloride and zinc chloride, both at a concentration of 64 mg/mL, with the initial concentration of the bacterial solution 1 × 10⁴ CFU/mL. After the bacterial solution had been inducted for 48 h, the culture media was changed and the induction was repeated once. The levels of chromium and zinc in the bacteria were detected by inductively coupled plasma mass spectrometry, and the contents of NADH and glucose dehydrogenase were determined using an NAD/NADH kit and glucose dehydrogenase kit, respectively. Streptozotocin was used to establish a mouse model to evaluate the hypoglycemic effects of the proposed chromium- and zinc-rich A. aceti. Ten-times the therapeutic dose was administered to evaluate its biological safety. The effect on MIN6 islet cells was also assessed in vitro.

RESULTS

The levels of chromium metal, metallic zinc, NADH coenzyme, and glucose dehydrogenase in A. aceti prepared by this method were 28.58-34.34 mg/kg, 5.35-7.52 mg/kg, 5.13-7.26 μM, and 446.812-567.138 U/g, respectively. The use of these bacteria resulted in a better hypoglycemic effect than metformin, promoting the repair of tissues and cells of pancreatic islets in vivo and facilitating the growth of MIN6 pancreatic islet cells and increasing insulin secretion in vitro. Ten-times the therapeutic dose of treatment was non-toxic to mice.

CONCLUSION

Chromium trichloride and zinc chloride can be employed to induce the preparation of chromium- and zinc-rich A. aceti, which can then promote the hypoglycemic effect found in normal A. aceti. The bacteria biotransforms the chromium and zinc in a way that could increase their safety as a treatment for diabetes.

Zinc status, insulin resistance and glycoxidative stress in elderly subjects with type 2 diabetes mellitus

Zinc deficiencies have been reported in numerous pathologies, such as diabetes mellitus, but also in the physiological process of ageing. Similarly, the end products of glycoxidation processes, advanced glycation end products (AGEs), are damaging compounds, a myriad of reports linking them to the development and progression of several age-associated chronic diseases. The aim of the present study was to analyze the relationships between zinc status, glycoxidative stress and insulin resistance (IR) in elderly subjects with type 2 diabetes mellitus (T2DM). A group of 52 non-smoking subjects (9 men and 43 women, aged 65-83 years) were enrolled in this cross-sectional study: 27 patients with T2DM, and 25 apparently healthy control subjects. Serum zinc (Zn) levels were assessed using a commercial kit based on an end-point colorimetric method, and serum AGEs were evaluated with a fluorimetric analytic procedure. The calculated glucose-to-zinc ratio (Gly/Zn), insulin-to-zinc ratio (Ins/Zn) and insulin-zinc resistance index (HOMA-IR/Zn) were further used to study the associations between serum Zn levels, secretory function of β-pancreatic cells and AGEs. T2DM patients presented significantly higher serum insulin and Zn levels, as compared to the controls. We found a significant inverse correlation between Zn and AGEs, and a strong positive correlation between AGEs and the Gly/Zn ratio, suggesting that both Zn and AGEs are biomarkers that could reflect the persistence of hyperglycemia. We identified new surrogate biomarkers useful for the assessment of glycemic control with great potential for the development of preventive and therapeutic strategies for elderly diabetics, based on the evaluation of serum Zn levels.

Zinc Supplementation Prevented Type 2 Diabetes-Induced Liver Injury Mediated by the Nrf2-MT Antioxidative Pathway

Zinc is an essential trace element that is often reduced under the type 1 diabetic condition. Previous studies demonstrated that zinc deficiency enhanced type 1 diabetes-induced liver injury and that zinc supplementation significantly helped to prevent this. Due to the differences in pathogenesis between type 1 and type 2 diabetes, it is unknown whether zinc supplementation can induce a beneficial effect on type 2 diabetes-induced liver injury. This possible protective mechanism was investigated in the present study. A high-fat diet, along with a one-time dose of streptozotocin, was applied to metallothionein (MT) knockout mice, nuclear factor-erythroid 2-related factor (Nrf) 2 knockout mice, and age-matched wild-type (WT) control mice, in order to induce type 2 diabetes. This was followed by zinc treatment at 5 mg/kg body weight given every other day for 3 months. Global metabolic disorders of both glucose and lipids were unaffected by zinc supplementation. This induced preventive effects on conditions caused by type 2 diabetes like oxidative stress, apoptosis, the subsequent hepatic inflammatory response, fibrosis, hypertrophy, and hepatic dysfunction. Additionally, we also observed that type 2 diabetes reduced hepatic MT expression, while zinc supplementation induced hepatic MT expression. This is a crucial antioxidant. A mechanistic study showed that MT deficiency blocked zinc supplementation-induced hepatic protection under the condition of type 2 diabetes. This suggested that endogenous MT is involved in the hepatic protection of zinc supplementation in type 2 diabetic mice. Furthermore, zinc supplementation-induced hepatic MT increase was unobserved once Nrf2 was deficient, indicating that Nrf2 mediated the upregulation of hepatic MT in response to zinc supplementation. Results of this study indicated that zinc supplementation prevented type 2 diabetes-induced liver injury through the activation of the Nrf2-MT-mediated antioxidative pathway.

Pengaruh Konsumsi Buah jeruk (Citrus reticulata) dan Suplementasi Zinc terhadap Kadar Glukosa Darah Puasa pada Wanita Diabetes Melitus Tipe 2

 Background: Patients with Diabetes Mellitus (DM) Type 2 are at risk of micronutrient loss related to metabolic diseases, one of them is zinc. It plays an important role since it affects the function of pancreatic cell β, insulin activities, glucose homeostasis and pathogenesis of DM. Low zinc levels are associated with higher complications of DM. One of the nutrients that helps absorbing zinc is organic acids such as citric acid and ascorbic acid contained in citrus fruits.Objective: to analyze the effect of citrus fruits (Citrus reticulata) and zinc supplements consumption on fasting blood glucose in women with DM Type 2.Method: This study was an experimental study using pretest and posttest method with control group. The subjects were 30 people with DM Type 2 in Prolanis club in three Puskesmas in Surabaya who had been selected using consecutive sampling, and divided into 2 groups, namely the treatment group that consumed 200 g of orange and 20 mg of zinc supplement per day and the control group that consumed only 20 mg zinc per day. Citrus fruits and zinc supplements were consumed daily for four weeks. Fasting blood glucose was analyzed using automatic chemistry analyzer. Data analysis included univariate analysis with Shapiro-Wilk and bivariate analysis with Independent t-test, Mann-Whitney and Paired t-testResults: Fasting blood glucose in the subjects consuming citrus fruits and zinc supplements was decreased by 16.67 mg/dl (from 155.87 mg/dl to 139.20 mg/dl) (p = 0.121), while the group with zinc consumption was decreased by 9.85 mg/dl (from 140.93 mg/dl to 131.13 mg/dl) (p = 0.095). The decrease in fasting blood glucose in both groups was not statistically significant.Conclusion: Consumption of citrus fruits and zinc supplements did not significantly reduce fasting blood glucose in women with DM Type 2. Further research is needed with a longer period of intervention to better reflect the changes in zinc metabolism related to blood glucose control.ABSTRAKLatar Belakang : Pasien Diabetes Mellitus (DM) Tipe 2 beresiko kehilangan zat gizi mikro terkait metabolik penyakitnya, salah satunya adalah zinc. Zinc berperan penting karena mempengaruhi fungsi sel β pankreas, aktifitas insulin, homeostasis glukosa dan patogenesis DM. Kadar zinc yang rendah terkait dengan komplikasi DM yang lebih tinggi. Salah satu zat gizi yang membantu penyerapan zinc adalah asam organik seperti asam sitrat dan asam askorbat yang terkandung dalam buah jeruk.Tujuan : Menganalisa pengaruh konsumsi buah jeruk (Citrus reticulata) dan suplementasi zinc terhadap kadar gula darah puasa wanita DM tipe 2.Metode : Rancangan berupa quasi eksperimental dengan metode pretest and posttest with control group. Jumlah subjek 30 orang wanita DM tipe 2 anggota klub Prolanis di 3 Puskesmas di Kota Surabaya yang dipilih secara consecutive sampling, terbagi dalam 2 kelompok yaitu kelompok perlakuan yang mengkonsumsi 200 gram jeruk dan suplementasi zinc 20 mg/hari serta kelompok kontrol hanya mengkonsumsi zinc 20 mg/hari. Intervensi dilakukan 4 minggu. Gula darah puasa dianalisa menggunakan automatic chemistry analizer. Analisis data meliputi univariat dengan Shapiro-Wilk, analisa bivariat meliputi Independent t-test dan Mann-Whitney.Hasil : Meskipun rata-rata penurunan gula darah puasa sebesar 16,67 mg/dl pada subjek yang mengkonsumsi jeruk dan suplementasi zinc (p=0,121), namun tidak signifikan secara statistik.Kesimpulan : Konsumsi buah jeruk dan suplementasi zinc tidak signifikan menurunkan gula darah puasa wanita DM Tipe 2. Diperlukan penelitian lanjutan dengan jangka waktu intervensi yang lebih lama.

The adaptive immune role of metallothioneins in the pathogenesis of diabetic cardiomyopathy: good or bad

Diabetes is a metabolic disorder characterized by hyperglycemia, resulting in low-grade systemic inflammation. Diabetic cardiomyopathy (DCM) is a common complication among diabetic patients, and the mechanism underlying its induction of cardiac remodeling and dysfunction remains unclear. Numerous experimental and clinical studies have suggested that adaptive immunity, especially T lymphocyte-mediated immunity, plays a potentially important role in the pathogenesis of diabetes and DCM. Metallothioneins (MTs), cysteine-rich, metal-binding proteins, have antioxidant properties. Some potential mechanisms underlying the cardioprotective effects of MTs include the role of MTs in calcium regulation, zinc homeostasis, insulin sensitization, and antioxidant activity. Moreover, metal homeostasis, especially MT-regulated zinc homeostasis, is essential for immune function. This review discusses aberrant immune regulation in diabetic heart disease with respect to endothelial insulin resistance and the effects of hyperglycemia and hyperlipidemia on tissues and the different effects of intracellular and extracellular MTs on adaptive immunity. This review shows that intracellular MTs are involved in naïve T-cell activation and reduce regulatory T-cell (Treg) polarization, whereas extracellular MTs promote proliferation and survival in naïve T cells and Treg polarization but inhibit their activation, thus revealing potential therapeutic strategies targeting the regulation of immune cell function by MTs.

Serum Zinc Levels in Hidradenitis Suppurativa: A Case-Control Study

BACKGROUND

Serum zinc levels in patients with hidradenitis suppurativa (HS) have not been previously studied.

OBJECTIVE

The aim was to investigate the association between HS and serum zinc levels.

METHODS

A multicenter, prospective clinical and analytical case-control study was designed to assess the possible association between HS and serum zinc levels. Consecutive patients with moderate or severe HS (Hurley II or III exclusively) were enrolled. A control population was recruited from primary care clinics. Fasting blood samples were extracted from each patient and serum zinc levels determined. Candidate predictors for low serum zinc levels were determined using logistic regression models.

RESULTS

In total, 122 patients with HS and 122 control subjects were studied. Of the 122 HS patients, 79 (64.8%) were Hurley II and 43 (35.2%) were Hurley III. Low serum zinc levels (≤ 83.3 µg/dL) were more prevalent in HS (adjusted odds ratio [ORa] 6.7, P < 0.001). After logistic regression analysis, low serum zinc levels were associated with Hurley III (ORa 4.4, P < 0.001), Dermatology Life Quality Index ≥ 9 (ORa 3.1, P = 0.005), number of affected sites ≥ 3 (ORa 2.4, P = 0.042), genital location (ORa 2.9, P = 0.009), and perineal location (ORa 2.5, P = 0.025).

CONCLUSION

Low serum zinc levels are more prevalent in HS than in a healthy population, an indicator that may also be associated with disease severity.