Effects of zinc supplementation and deficiency on bone metabolism and related gene expression in rat.

One hundred male rats were randomly divided into four groups (n = 25) and fed a Zn-adequate diet (ZA, 46.39 mg/kg), Zn-deficient diet (ZD, 3.20 mg/kg), Zn-overdose diet (ZO, 234.39 mg/kg), or were pair-fed a Zn-adequate diet (PF) for 5 weeks, respectively. The body weight, femur weight, and activity of alkaline phosphatase (ALP) were reduced in the ZD group but were increased in the ZO group. Zn concentrations in both liver and femur were elevated in the ZO group, whereas femur Zn was decreased in the ZD group. The concentrations of calcium and phosphorus were lower in the ZD than those in other groups. Serum calcium concentration was decreased in the ZD. The relative expression level of ALP was decreased in both ZD and PF, and no significant differences were observed between ZO and ZA. Insulin-like growth factor-I (IGF-I) mRNA level was reduced in the ZD but unchanged in the ZO and PF group. Zn deficiency also decreased ALP mRNA level as compared with that of PF group. Carbonic anhydrase II mRNA level was not affected by Zn. Nevertheless, dietary Zn influenced the growth, bone metabolism, and expression of IGF-I and ALP in male growing rats.

The effect of peripheral administration of zinc on food intake in rats fed Zn-adequate or Zn-deficient diets.

Zinc deficiency induces a striking reduction of food intake in animals. To elucidate the mechanisms for this effect, two studies were connectedly conducted to determine the effects of peripheral administration of zinc on food intake in rats fed the zinc-adequate or zinc-deficient diets for a 3-week period. In study 1, two groups of male Sprague-Dawley rats were provided diets made either adequate (ZA; 38.89 mg/kg) or deficient (ZD; 3.30 mg/kg) in zinc. In study 2, after feeding for 3 weeks, both ZA and ZD groups received intraperitoneal (IP) injection of zinc solution with three levels (0.5, 1.0, and 2.0 microg zinc/g body weight, respectively) and cumulative food intake at 0.5, 1, 2, 4, and 24 h, and plasma hormones concentrations were measured. The results in study 1 showed rats fed the ZD diets revealed symptoms of zinc deficiency, such as sparse and coarse hair, poor appetite, susceptibility to surroundings, lethargy, and small movements. Zinc concentrations in serum, femur, and skeletal muscle of rats fed the ZD diets declined by 26.58% (P < 0.01), 27.32% (P < 0.01), and 24.22% (P < 0.05), respectively, as compared with ZA control group. These findings demonstrated that rat models with zinc deficiency and zinc adequacy had been fully established. The results in study 2 showed that IP administration of zinc in both ZA and ZD rats did not influence food intake at each time points (P > 0.05), although zinc deficiency suppressed food intake. Plasma neuropeptide Y (NPY) was higher, but insulin and glucagon were lower in response to zinc deficiency or zinc administration by contrast with their respective controls (P < 0.05). Leptin, T3, and T4 concentrations were uniformly decreased (P < 0.05) in rats fed the ZD diets in contrast to ZA diets; however, no differences (P > 0.05) were observed during zinc injection. Calcitonin gene-related peptide was unaffected (P > 0.05) by either zinc deficiency or zinc administration. The present studies suggested that zinc administration did not affect short-term food intake in rats even in the zinc-deficient ones; the reduced food intake induced by zinc deficiency was probably associated with the depression in thyroid hormones. The results also indicated that NPY and insulin varied conversely during the control of food intake.

Effects of zinc on hepatic antioxidant systems and the mRNA expression levels assayed by cDNA microarrays in rats.

BACKGROUND: This study evaluated effects of zinc on the hepatic lipid peroxidation, antioxidant components and mRNA expression levels in rats. METHODS: Three diets with different Zn levels including Zn adequacy (ZA; 34.50 mg/kg, control), Zn deficiency (ZD; 3.30 mg/kg), and Zn overdose (ZO; 345.45 mg/kg) were fed to rats for 6 weeks. The mRNA expression levels were analyzed by cDNA microarrays. RESULTS: The body weight of rats fed the ZD diet was less (p < 0.01) than that of rats fed the ZA diet. Zn overdose elevated body weight, but the increase was not detected (p > 0.05) at week 6. Although copper and iron status in serum were declined (p < 0.01), those in liver were not affected (p > 0.05) by the high intake of zinc. The glutathione peroxidase (GPx) and glutathione (GSH) remained unchanged (p > 0.05) by zinc treatment. Rats fed the ZD diet showed reductions(p < 0.01) in the Cu-Zn superoxide dismutase (Cu-Zn SOD) and catalase (CAT) activity, and increases (p < 0.01) in the malondialdehyde and hydrogen peroxide (H(2)O(2)) contents. Rats fed the ZO diet particularly had higher Cu-Zn SOD (p < 0.01) activity. The mRNA expression levels of SOD were upregulated in the ZO group, and CAT was downregulated in the ZD group, while no changes in GPx mRNA levels were found after zinc treatment. CONCLUSION: The study suggested that zinc deficiency largely decreased body weight; zinc overdose, however, moderately stimulated growth in the early growing phase of rats. High dietary zinc did not compete with liver copper and iron status. Although Zn deficiency impaired antioxidant functions, zinc overdose hardly enhanced the antioxidant systems of animals.

Insights on zinc regulation of food intake and macronutrient selection.

Zinc (Zn) is an essential trace element required for human beings and animals. This divalent cation is involved in many physiological functions, including immune and antioxidant function, growth, and reproduction. Deficiency of Zn produces several pathological disorders and abnormalities in its metabolism, such as anorexia, weight loss, poor efficiency, and growth retardation. Although it has been known for more than 50 yr that Zn deficiency regularly and consistently causes anorexia in many animal species, the mechanism that causes this phenomenon still remains an enigma. The present review describes recent research investigating the relationship between Zn deficiency and the regulation of food intake, as well as macronutrient selection.

Distribution and characteristics of endogenous digestive enzymes in the red-eared slider turtle, Trachemys scripta elegans.

Distribution and properties of the main digestive enzymes including protease and amylase, from stomach, pancreas and the anterior, middle and posterior intestine of the adult red-eared slider turtle Trachemys scripta elegans were studied at various pHs and temperatures. The optimum temperature and pH for protease in stomach, pancreas and the anterior, middle and posterior intestine were 40 degrees C, 2.5; 50 degrees C, 8.0; 50 degrees C, 7.0; 50 degrees C, 8.0; and 50 degrees C, 8.5; respectively. The optimum temperature and pH for amylase in stomach, pancreas and anterior, middle and posterior intestine were 40 degrees C, 8.0; 30 degrees C, 7.5; 40 degrees C, 7.0; 50 degrees C, 8.0; and 50 degrees C, 8.0; respectively. Under the optimum conditions, the order of protease activity from high to low was of pancreas, stomach and the anterior, posterior and middle intestine; the activity of amylase in descending order was of anterior intestine, pancreas, posterior intestine, middle intestine and stomach.

Effect of zinc on biochemical parameters and changes in related gene expression assessed by cDNA microarrays in pituitary of growing rats.

OBJECTIVE: The present study simultaneously investigated the effects of different zinc (Zn) levels on the growth performance and relative biochemical parameters in growing rats and analyzed the molecular mechanism of zinc influencing food intake. METHODS: Three diets with different Zn levels--Zn adequate (ZA; 35.94 mg/kg, control), Zn deficient (ZD; 3.15 mg/kg), and Zn overdose (ZO; 347.50 mg/kg)--were fed to rats for 6 wk. Dietary Zn was supplemented with ZnSO4. The relation between zinc and food intake was studied by pituitary cDNA microarrays. RESULTS: Compared with ZA group, rats fed the ZD diet showed decreases in body weight (P < 0.01), food intake (P < 0.05), tissue zinc concentrations (P < 0.01), and specific activities of alkaline phosphatase (P < 0.01) and copper/Zn superoxide dismutase (P < 0.05), whereas the ZO diet had positive effects on body weight (P < 0.05), zinc concentrations (P < 0.01), and alkaline phosphatase activity (P < 0.05). The villi of the jejunum became shorter (P < 0.01), shriveled, and flattened. This change in morphology decreased absorption surface area, and there was a substantial decrease (P < 0.01) in villi number per unit area in ZD rats. Metallothionein concentration was increased in livers of rats fed ZD (P < 0.01) and ZO (P < 0.05) diets. Moreover, ZD and ZO influenced normal growth and development of organs. The results from pituitary cDNA arrays indicated that different Zn levels affect gene expression of appetite-related peptides, including neuropeptide-Y, melanin-concentrating hormone, ghrelin, calcitonin gene-related product, and serotonin. CONCLUSION: The present results showed that zinc deficiency has a negative effect on the growth performance and biochemical parameters of rats. The ZO diet increased body weight (P < 0.05) but had no effect (P > 0.05) on food intake, copper/Zn superoxide dismutase activity, and intestinal morphology. The ZD diet decreased rat food intake by regulating appetite-related gene expression in the pituitary gland.