Lipid deposition in intestine as a possible cause of malabsorption of nutrients in zinc-deficient common carp (Cyprinus carpio).
An experiment was performed to examine the interaction between Zn deficiency and lipid intake in carp. The carp were given a high-lipid diet that was either Zn-deficient (ZD) or Zn-supplemented (ZS), or were pair-fed (PF) the ZS diet to the intake of the ZD group. After 8 weeks the carp were killed and measurements were made of intestinal glucose uptake, levels of DNA, RNA and triacylglycerol, and alkaline phosphatase (EC 3.1.3.1) activity in liver and intestine samples. A further group of similar carp were given the same diets but at week 8 were transferred to low-lipid diets, with the exception of half the ZD group. After a further 8 weeks of treatment, carps were killed for biochemical studies. Intestinal [14C]glucose uptake, levels of DNA, RNA and alkaline phosphatase activity in intestine and liver were significantly (P < 0.05) lower in the high-lipid ZD group than in the high-lipid ZS and PF diet groups. The triacylglycerol concentration in the intestine was higher in the high-lipid ZD group than in the other two groups. When the carp were given the corresponding low-lipid diets, the variables measured in intestine and liver of the ZD group were close to those of the other groups. The results of this study demonstrate that lipid, when present in excess in the diet, accumulates in the intestine under Zn-deficient conditions and may reduce the absorption of glucose in carp. The reduced RNA and DNA levels and alkaline phosphatase activity in liver and intestine of ZD fish compared with those of ZS fish given high-lipid diets is proposed to be due to the malabsorption of nutrients linked with lipid deposition in the intestine, rather than their dependence on the level of Zn in the diet.