Excess bioavailability of zinc may cause obesity in humans

Prediction of cardiovascular disease risk by serum zinc and copper concentrations and anthropometric measurements

INTRODUCTION

We aimed to investigate the association between cardiovascular disease (CVD) and various anthropometric indices, as well as the serum levels of copper (Cu) and zinc (Zn), copper-zinc ratio (Cu/Zn ratio) and zinc-copper ratio (Zn/Cu ratio), in a large population sample from northeastern Iranian.

METHOD

9704 individuals aged 35 to 65 were enrolled in the first phase of the study. After a 10-year follow-up, 7560 participants were enrolled into the second phase. The variables used in this study included demographic characteristics, such as gender and age; biochemical parameters including: serum Zn, Cu, Cu/Zn ratio, and Zn/Cu ratio; anthropometric parameters including: waist circumference (WC), body mass index (BMI), and waist-to-hip ratio (WHR). The relationship between the aforementioned indices and CVD was examined using decision tree (DT) and logistic regression (LR) models.

RESULTS

A total of 837 individuals were diagnosed with CVD among the 7560 participants. LR analysis showed that BMI, age, WH zinc-copper ratio (Zn/Cu ratio), and serum Zn/Cu ratio were significantly associated the development of CVD in men, and WHR, age, BMI, serum Cu, and Cu/Zn ratio in women. DT analysis showed that, age was the most important predictor of CVD in both genders. 71% of women, older than 49 years, with a WHR≥ 0.89, serum Cu< 75 (µg/dl), BMI≥ 22.93 (kg/m2), and serum Cu≥ 14 (µg/dl), had the highest risk of CVD. In men, among those who were ≥ 53 years, with a WHR≥ 0.98, serum Zn/Cu ratio< 1.69, and BMI≥ 22.30, had the highest risk of CVD.

CONCLUSION

Among Iranian adult population, BMI, age, and WHR were one of the predictors of CVD for both genders. The Zn/Cu ratio was CVD predictor for men while Cu/Zn ratio was CVD predictor for women.

Heavy metals controlling cardiovascular diseases risk factors in myocardial infarction patients in critically environmentally heavy metal-polluted steel industrial town Mandi-Gobindgarh (India)

Heavy metals (HMs) have a very significant clinical role in the pathogenesis, progression and management of cardiovascular diseases (CVDs). The prevalence of CVDs was reported to be higher in critically environmentally HM-polluted (EHMP) steel industrial town Mandi-Gobindgarh (India) for the last more than a decade. To ascertain the role of HMs in the onset of CVDs, the present study was chosen to investigate HMs content in myocardial infarction (MI) patients from EHMP steel industrial town Mandi-Gobindgarh. Total of 110 MI patients along with number- and age-matched healthy volunteers were recruited in the present investigation. The CVDs risk factors estimated in MI patients were overweight (higher body mass index), hypertension (higher systolic and diastolic blood pressures), dyslipidaemia (higher serum cholesterol, triglycerides and lower HDL cholesterol), inflammation (higher-serum C reactive protein and aldosterone) and elevated oxidative stress (higher urinary 8-hydroxydeoxyguanosine). An imbalance of serum electrolyte concentrations including Na (hypernatremia), Ca (hypercalcaemia) and K (hypokalaemia) was also observed in MI patients in which CVDs risk factors were found to correlate positively with serum Na and Ca and negatively with serum K, respectively. Hair HM analysis was used as a bio-indicator for monitoring body HM status from past environmental HM exposure in which CVDs risk factors were observed to correlate positively with higher hair concentrations of Zn, Fe, Mo, Pb, As, Ca and Na and negatively with lower hair concentrations of Cu, Mg, Mn and K in MI patients, respectively. Thus, higher hair concentrations of Zn and Pb indicate their higher environmental exposure and possible cause of higher CVDs risk factors in MI patients from Mandi-Gobindgarh.

Gender differences in the relationship between serum zinc concentration and metabolic syndrome

BACKGROUND

Zinc, a co-factor of antioxidant enzymes, may be involved in the pathophysiology of metabolic syndrome (MetS).

AIM

To determine the association between serum zinc concentration and MetS in a population-based study.

SUBJECTS AND METHODS

In the Tehran Lipid and Glucose Study, serum zinc concentration was measured by flame atomic absorption spectrometry in 2626 adult participants. After removal of outliers, usable data was available for 2401 participants. Dietary zinc was assessed by a validated semi-quantitative food frequency questionnaire.

RESULTS

Compared to those without the MetS, serum zinc concentration was significantly higher in men with syndrome (17.1 ± 4.9 vs 16.5 ± 4.6 μmol/L, p = 0.035); however, values were comparable in females (16.1 ± 4.8 vs 15.8 ± 4.4, p = 0.460). Men in tertile 3 of serum zinc had significantly higher chances of having MetS, even after multivariate adjustment (OR = 1.48, 95% confidence interval (CI) = 1.07-2.06, p = 0.020). Women in tertile 2 of serum zinc had significantly lower chances of having MetS, which remained significant after multivariate adjustment (OR = 0.68, 95% CI = 0.47-0.99, p = 0.046).

CONCLUSION

This study observed a gender difference between serum zinc and MetS, with higher levels being positively associated with MetS in men and having a protective effect in women. Further studies are needed to elucidate the role of zinc status in the development of MetS.

Excessive zinc in diet induces leptin resistance in Wistar rat through increased uptake of nutrients at intestinal level

PROJECT

The ob gene has either been found to be mutant defective resulting in a deficiency of its product leptin or leptin has been found to be resistant to its receptors in obese human and rodents. The factors inducing leptin resistance have not been identified. Since excessive bioavailability of Zn has been implicated in obesity, we investigated if its excess in diet induces leptin resistance.

PROCEDURE

For the investigations, three groups of Wistar rats were included in this study and they were fed on equicalories semi synthetic basal diet containing 20 mg, 40 mg or 80 mg Zn/kg diet for 120 days. There after they were sacrificed for hormonal status and intestinal investigations.

RESULTS

The data of this study revealed that the food intake, gain in body weight, serum leptin, glucose, insulin, cortisol increased with increased Zn concentration in diet. TEM study showed a positive correlation between Zn concentration in diet and number of microvilli/unit surface area of the mucosal epithelial cells of the intestine.

CONCLUSION

The results of this study suggest that excessive bioavailability of Zn induces leptin resistance through increased uptake of nutrients at intestinal level, leading to the growth of the fat cells which aggravated the leptin synthesis and its release in the blood stream. In spite of its higher circulating level, it was unable to reduce the food intake and gain in body weight in Zn treated rats equivalent to the control group.

Body weight reduction in rats by oral treatment with zinc plus cyclo-(His-Pro)

BACKGROUND AND PURPOSE

We have previously shown that treatment with zinc plus cyclo-(His-Pro) (CHP) significantly stimulated synthesis of the insulin degrading enzyme and lowered plasma insulin and blood glucose levels, alongside improving oral glucose tolerance in genetically type 2 diabetic Goto-Kakizaki (G-K) rats and in aged obese Sprague-Dawley (S-D) rats. Thus, we postulated that zinc plus CHP (ZC) treatment might also improve body weight control in these rats. We therefore determined the effects of ZC treatment on body weights in both genetically diabetic, mature G-K rats and non-diabetic, obese S-D rats.

EXPERIMENTAL APPROACH

G-K rats aged 1.5-10 months and non-diabetic overweight or obese S-D rats aged 6-18 months were treated with 0-6 mg CHP plus 0-10 mg zinc L(-1) drinking water for 2-4 weeks, and changes in weight, serum leptin and adiponectin levels, food and water intakes were measured.

KEY RESULTS

The optimal dose of CHP (in combination with zinc) to reduce weight and plasma leptin levels and to increase plasma adiponectin levels was close to 0.1 mg kg(-1) day(-1), in either mature G-K rats and aged overweight or obese S-D rats. Food and water intake significantly decreased in ZC treated rats in both aged S-D rats and mature G-K rats, but not in young S-D and G-K rats.

CONCLUSIONS AND IMPLICATIONS

ZC treatment improved weight control and may be a possible treatment for overweight and obesity.

The relationship between established coronary risk factors and serum copper and zinc concentrations in a large Persian cohort

INTRODUCTION

The relationship between demographic and biochemical characteristics, including several established coronary risk factors, and serum copper and zinc was assessed in a large Iranian population sample.

MATERIALS AND METHODS

A group of 2233 individuals, 15-65 years of age [1106 (49.5%) males and 1127 (50.5%) females] was recruited from residents of the Greater Khorasan province in northeast of Iran. Demographic data were collected using questionnaires. Coronary risk factors were determined using standard protocols, and trace elements were measured in serum using atomic absorption spectroscopy.

RESULTS

Degree of glucose tolerance and smoking habit were not associated with serum zinc and copper levels. Serum copper levels were significantly higher in obese and hypertensive than in normal subjects (p<0.001). In the whole group and for the female subgroup, serum zinc (p<0.01) and copper (p<0.001) were both significantly lower in individuals with normal versus high levels of low-density lipoprotein cholesterol. A strong positive correlation was found between serum copper and body mass index (BMI) (r=0.85, p<0.001). Weaker positive associations were found between serum copper and calculated 10 years' coronary risk (r=0.11, p<0.001). Serum zinc/copper ratio was strongly inversely associated with calculated 10 years' coronary risk (r=-0.10, p<0.001). The partial Eta squared (PES) values for factors determining serum zinc were hypertension (0.007, p=0.01) and BMI (0.004, p=0.01); and for serum copper, they were gender (0.02, p=0.001), hypertension (0.004, p=0.009), and 10 years' coronary risk for men (0.003, p=0.03) and women (0.002, p=0.07).

CONCLUSION

Significant associations between serum trace element concentrations and several coronary risk factors, including calculated 10 years' coronary risk scores, were found.

Normolipidemic effect of antioxidants in low cholesterol-modified poultry eggPsi on Zn-induced dyslipidemia and liver pathology in Wistar rats

A low cholesterol (CH)-modified poultry egg (ME Psi) containing more vitamin E, lenolenic acid, and minerals Cu and Mg but low total lipid (TL) and Zn contents than the conventional egg evaluated to reduce the severity of dyslipidemia induced by excessive Zn in the diet. The experimental data was recorded on male rats fed on normolipidemic (NL) semi-synthetic basal diet containing 20 mg Zn/kg diet in control group I, Zn supplemented dyslipidemic diet-A (Zn-DL-A) and B (Zn-DL-B) containing 40 and 80 mg Zn/kg diet in groups II and III, and ME Psi-mixed Test diet-A (Zn-DL-A + 4 ME Psi) and Test diet-B (Zn-DL-B + 4 ME Psi) in groups IIEM and IIIEM, respectively, for 180 and 90 days. Data recorded on liver and blood lipid profiles showed reduction in the concentration of TL, CH, triglycerides, and glycogen (GG) in liver consequently leading to their rise in blood serum including rise in VLDL-c and LDL-c but fall in HDL-c in groups II and III rats that reversed after ME Psi treatment resulting in rise of their levels in the liver and fall in the blood of groups IIEM and IIIEM rats, respectively. Mineral status in the liver showed a rise in Zn but fall in Cu and Mg levels in groups II and III that was reversed after ME Psi treatment resulting in fall in Zn and rise in Cu and Mg concentration in the liver of groups IIEM and IIIEM rats. Hepatopathogical studies showed reduction in the dilatation of long citernal profile of endoplasmic reticulum and increase in GG and TL granules in the cytoplasm of hepatocytes of groups IIEM and IIIEM after ME Psi treatment than those of groups II and III rats. It was concluded that the inclusion of ME Psi would be helpful in reducing dyslipidemia by correcting the ionic imbalance generated by excessive Zn intake in rats or by drugs, even in chronic diseased conditions without aggravating risk factors for heart diseases in humans that need further studies.

Assessment of minerals in obesity-related diseases in the Chandigarh (India) population

Excessive Zn but normal Cu and Mg in the staple food consumed by the people of Chandigarh (Union territory and capital of Punjab and Haryana States of India) has been considered to be the major risk factor for the prevalence of obesity (33.15%) and obesity-related diseases in this region. Therefore, in the present investigations, in obesity-related diseases, the status of these minerals was estimated in their tissues, including hair, nails, and blood serum and urine, and compared with those of normal subjects. They were grouped as: normal subjects in control Group A, middle-aged diabetics in Group D(M), older diabetics in Group D(O), and diabetics with osteoarthritis in Group D+ OA, osteoarthritis in Group OA and rheumatoid arthritis in Group RA, respectively. The results evaluated in the order as: hair Zn, group D+OA>D(M)>OA>A (control)>RA>D(O) (p < 0.001); hair Cu, group A (control)>D(M)>OA>D+OA>D(O)>RA (p < 0.001); hair Mg, group A (control)>D(M)>OA>D+OA>RA>D(O) (p < 0.001, 0.01); hair Mn, group A (control)>RA>OA>D-OA>D(M)>D(O) (p < 0.001); nail Zn, group D(M)>D+OA>OA>A (control)>RA>D(O) (p < 0.001, 0.05); nail Cu, group A (control)>OA>D(M)>D+OA>RA>D(O) (p < 0.001); nail Mg, group A (control)>OA>D(M)>D(O)>D+OA >RA (p < 0.001); nail Mn, group A (control) >RA>OA>D+OA>D(M)>D(O) (p < 0.01); urine Zn, group D(O)>D(M)>D+OA>A (control)>RA>OA (p < 0.01); urine Cu, group RA>D+OA>D(O)>OA> D(M)>A (control) (p<0.001); urine Mg, group RA>OA>D+OA>D(O)>D(M)>A (control; p < 0.001); urine Mn, group D(O)>D(M)>OA>D+OA>RA>A (control; p < 0.001), respectively. The analysis of the mineral status in serum of diabetics further showed their highly significant rise from lower mean age subgroup to higher mean age subgroup than their control counter parts (p < 0.001, 0.01, and 0.05) with coincident deficiencies of Cu, Mg, and Mn in their tissues. This study would be helpful considering the status of minerals in these obesity-related diseases depending on the choice of the food consumed to improve the quality of life and prognosis for the diseases.

Relationship between hair elements and severity of atrioventricular block in horses

The aim of this study was to investigate the relationships between the mean concentrations of trace elements and the severity of the second-degree atrioventricular (AV) block in the mane hair of horses. Electrocardiographs of horses were continually recorded for 6 h using a holter cardiac monitor to determine dropped ventricular beats (DVBs) which can be used as an indicator of the severity of the AV block. Mane hair Ca, Cu, Mg, and Zn concentrations were measured by the particle-induced X-ray emission method. The Zn/Cu ratio and Ca concentration in mane hair were significantly and positively correlated with the hourly DVBs in horse with a second-degree AV block (p<0.01, r2=0.485; p<0.05, r2=0.351, respectively). Proposed diagnostic cutoff points for hair Ca concentration and Zn/Cu ratio based on receiver operating characteristics curves analysis in detecting second-degree AV block were set at 1536 microg/g and 26.0, respectively. Those results with horse hair suggest that the evaluation of the Ca, Cu, Mg, and Zn status in mane hair by this method is strongly related to the severity of second-degree AV block and might predict the susceptibility of an individual much before the development of the symptom.

Mineral factors controlling essential hypertension--a study in the Chandigarh, India population

Essential hypertension (EH) is a major public health problem world over and in India. Recent data on EH in the population of Chandigarh (Union Territory and capital of Punjab and Haryana States of India) revealed that the prevalence of EH has become double in the last 30 years in the residents of Chandigarh (26.9 to 45.80% in the year 1968 and 2002). Zinc (Zn), copper (Cu), magnesium (Mg), and manganese (Mn) in the serum are considered important in maintaining the human hypertension. The high Zn intake was considered to increase the blood pressure (BP) and to affect the other mineral status in the body. Recent survey on the trace metal status of different vegetables in the State of Punjab around Chandigarh (India) revealed that Zn level is significantly higher (40 mg/kg or more in above ground vegetables and 120 mg/kg or above in underground vegetables) in underground water-irrigated vegetables, but the levels of Cu and Mg are within prescribed limit. The present study was conducted on Chandigarh population to evaluate the levels of Zn, Cu, Mg, and Mn in the blood and urine of normotensive (NT) control and hypertensive (HT) subjects matched with number, age and sex. Atomic absorption spectrophotometer studies reevaluated that the levels of serum Zn, Mg, and Mn were significantly higher (p < 0.001), but the level of Cu was low in the HT subjects (BP = 160/93) compared to NT control (BP = 140/83). Higher levels of urinary Zn, Cu, Mg, and Mn were observed in the HT subject vs NT control (p < 0.001). Positive correlations were evaluated between the levels of serum Zn, Mg, and Mn vs systolic and diastolic pressures (DP and SP), respectively (r = 0.928, 0.863, 0.876, 0.808, 0.404, 0.326, p < 0.01), but negative and positive nonsignificant correlations between the serum Cu with SP and DP were recorded (r = -0.032, r = 0.024). Positive correlations were also evaluated between urinary levels of Zn, Cu, Mg, and Mn vs SP and DP (r = 0.718, 0.657, 0.750, 0.681, 0.630, 0.578, 0.516, 0.461, p < 0.01). Prevalence of essential hypertension may be due to higher Zn level in the food chain that makes the individuals vulnerable to other diseases over the time related to essential hypertension.

Zinc supplementation on serum levels and hepatic conversion of thyroid hormones in obese (ob/ob) mice

The supplemental effects of zinc on thyroid status in obese (ob/ob) mice were studied. Four-week-old obese mice and their lean controls were fed either a basal diet or a zinc-supplemented diet (200 mg/kg diet) for 8 wk. Following the 8-wk basal diet, obese mice had lower serum T4 values, as well as hepatic T4 and T3 values, than lean mice (p < 0.05). A significant decrease in hepatic 5'-deiodinase activity was also observed in obese mice. Dietary zinc supplementation significantly reduced serum T4 levels in both the obese and lean mice. However, the zinc-supplemented effects on diminishing hepatic T4 and T3 values, as well as on 5'-deiodinase activities, were found only in obese mice (p < 0.05). Furthermore, the 5'-deiodinase activities in hepatic microsomal pellets after incubation with various zinc concentrations (0.5, 1.0, and 2.5 mM) were also examined. The 5'-deiodinase activities, in hepatic samples from all mice, were significantly attenuated by zinc treatments. However, this effect was more predominant in obese mice following the addition of 0.5 mM zinc. This study suggests that a lower hepatic 5'-deiodinase activity, resulting from a higher zinc level, might be related to abnormal energy metabolism in the ob/ob mice.

Zinc status in plasma of obese individuals during glucose administration

To know whether plasma zinc status is altered under acute hyperglycemic state, the interrelationships among plasma glucose, insulin, and zinc concentrations during oral glucose tolerance test (OGTT) in obese individuals and their lean controls were studied. Plasma glucose and insulin concentrations under fasting as well as those values in response to OGTT were significantly higher in obese individuals than those in lean controls. On the other hand, the obese had lower fasting plasma zinc concentrations compared to lean controls (13.5 vs 18.1 mumol/L, p < 0.005). Under fasting, plasma zinc concentrations in overall individuals inversely correlated to their body mass index (BMI) (r = -0.516), plasma glucose (r = -0.620), and plasma insulin (r = -0.510). However, there were no significant changes in plasma zinc and copper values during OGTT in both obese individuals and lean controls. This study showed that plasma zinc values had no changes during OGTT in obese individuals. The results also indicated that lower fasting plasma zinc concentrations in obese individuals were not the short-term metabolic result.