Influence of low dietary lipid content on anorexia and [14C]glucose uptake in the intestine of zinc-deficient mice

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.

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.

Development of alimentary zinc deficiency in growing rats is retarded at low dietary protein levels

The aim of the present study was to determine whether the level of dietary protein would influence the onset of zinc deficiency in rats because zinc-deprived rats have problems metabolizing dietary protein. Young male Sprague-Dawley rats were fed isoenergetic Zn-deficient diets (0.8 mg Zn/kg diet) or control diets substituted with zinc sulfate (54 mg Zn/kg diet) and protein levels of 2, 5, 8, 10, 15, 20 or 25 g/100 g for 21 d to determine whether changing the protein level of Zn-deficient diets affects the Zn status of the rats. In rats fed low dietary protein levels of 2 and 5%, feed intake, growth and appearance did not differ between the Zn-deficient rats and the control rats because the low zinc requirement was met by mobilization of zinc from the skeleton. At higher dietary protein levels, the Zn-depleted rats developed marked signs of Zn deficiency and had reduced feed intake, growth, alkaline phosphatase activity in the serum and Zn concentrations in serum and femur compared with the control rats. The reduced feed intakes and decreased growth of Zn-depleted rats fed high dietary protein levels (20 and 25%) compared with control rats may be due to disturbed protein synthesis, as demonstrated by the increased activities of alanine aminotransferase, glutamate dehydrogenase and carbamoylphosphate synthetase in the liver. Zinc as an essential component of the diet is thus vital for the efficient utilization of dietary protein.

Neurobiology of zinc-influenced eating behavior

Zinc is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant function, growth and reproduction. Many aspects of zinc deficiency-induced anorexia have been well studied in experimental animals, most notably the laboratory rat. There is evidence that suggests zinc deficiency may be intimately involved with anorexia in humans: if not as an initiating cause, then as an accelerating or exacerbating factor that may deepen the pathology of the anorexia. The present review describes recent research investigating the relationship between zinc deficiency and the regulation of food intake, along with advances in the understanding of the food intake and body weight regulation systems. For more comprehensive reviews of zinc nutrition and zinc deficiency, readers are referred to the other reviews in this volume and the review text of Mills (1989). An excellent review focused solely on zinc status and food intake has been presented by O'Dell and Reeves (1989).

Excess bioavailability of zinc may cause obesity in humans

The body weight or body weight/height ratio exhibits a positive linear correlation to hair zinc (Zn) concentration which is more strongly positive in men than in women. The obese of both sexes possess higher Zn concentrations in their hair than those with normal body weight/height. The degree of obesity increases with the increase in the hair Zn concentration.

Lipid-zinc interaction: its effect on the testes of mice

Lipid-Zn interaction in the testes of mice was studied by feeding them low-fat (30 g maize oil/kg; group LFZD) and high-fat (90 g maize oil/kg; group HFZD) Zn-deficient diets for 6 weeks. The results were compared with those of corresponding Zn-supplemented-diet-fed controls (groups LFZS and HFZS). The integument-related Zn-deficiency symptoms appeared in group HFZD and not in group LFZD mice despite lack of Zn in their ration and an equal level of Zn in their blood serum. The feed intake, gain in body weight and testes weight of the LFZD group were comparable with those of the LFZS and HFZS groups (P > 0.05) but were higher than those of the group HFZD (P < 0.05). The testes of group HFZD displayed necrotic changes marked by the presence of giant cells, lower RNA, DNA and protein concentrations and higher phospholipid and cholesterol levels than those of mice in the LFZD group. The concentrations of these fractions were not significantly different between LFZD and HFZS. The results do not support the hypothesis that Zn is essential either for testicular function or for nucleic acid and protein synthesis in animals fed on a low-fat diet; however, it appears to be essential for animals fed on a high-fat diet. The changes observed in the testes of the HFZD animals suggest the excess intake of fat as their cause in Zn-deficient animals.