Determination of mitochondrial function and site-specific defects in electron transport in duodenal mitochondria in broilers with low and high feed efficiency

Abstract

Duodenal mitochondria were isolated from broiler breeder males with high (0.79+/-0.01, n = 9) and low (0.63+/-0.02, n = 9) feed efficiency (FE) to assess relationships of FE with duodenal mitochondrial function and site-specific defects in electron transport. Sequential additions of adenosine diphosphate (ADP) resulted in 1) higher respiratory control ratio (RCR; an index of respiratory chain coupling) in high FE mitochondria provided succinate, and 2) higher ADP to oxygen ratio (ADP:O; an index of oxidative phosphorylation) in low FE mitochondria provided NADH-linked substrates (malate, pyruvate, or both). Basal electron leak, measured as H2O2 production, was greater in low FE mitochondria provided succinate (P = 0.08) or NADH-linked substrates. As H2O2 levels were elevated in low FE compared with high FE mitochondria by complex I (P+/-0.07) and complex II inhibition, the higher basal electron leak in low FE mitochondria was apparently due to site-specific defects in electron transport at complexes I and II. Elevations in H2O2 above basal levels indicated that high FE mitochondria may also exhibit electron transport defects at complexes I and III. Despite an ability to produce adenosine triphosphate (ATP) that was equal or superior to that demonstrated in high FE duodenal mitochondria, low FE mitochondria exhibited a greater inherent degree of electron leak. The results provide insight into the role that duodenal mitochondria play in the phenotypic expression of FE in broilers.

Investigation of mitochondrial protein expression and oxidation in heart muscle in low and high feed efficient male broilers in a single genetic line

“…Higher weight gains on the same amount of feed consumed resulted in higher FE and lower FCR in broilers exhibiting the high FE phenotype. These results are similar to previous reports (Bottje et al, 2002;Ojano-Dirain et al, 2004;Iqbal et al, 2005).…”

“…Protein carbonyl levels, which represent oxidized proteins, were higher in low FE compared with high FE heart homogenate ( Figure 1) and concurs with previous studies in breast muscle, liver, duodenum, and lymphocytes Ojano-Dirain et al, 2004;Lassiter et al, 2006). Higher levels of oxidized proteins in low FE heart tissue would require considerable energy expenditure to repair or recycle damaged proteins in cell proteosomes (Mehlhase and Grune, 2002) and could make significant contributions to cellular inefficiencies (Bottje and Carstens, 2009).…”

“…Because COX II is instrumental in the terminal transfer of electrons to oxygen in the mitochondria, it is possible that decreased expression of COX II could be significant in regard to contributing to cellular inefficiency and the phenotypic expression of low FE. It was found that COX II expression was lower in intestines of low FE compared with high FE birds, however (Ojano-Dirain et al, 2004). Similarly, Cyt c1 expression in low FE birds was higher in breast muscle and intestines (Ojano-Dirain et al, 2004) but was lower in low FE lymphocytes (Lassiter et al, 2006); no difference in Cyt c1 expression was observed in liver.…”

“…It was found that COX II expression was lower in intestines of low FE compared with high FE birds, however (Ojano-Dirain et al, 2004). Similarly, Cyt c1 expression in low FE birds was higher in breast muscle and intestines (Ojano-Dirain et al, 2004) but was lower in low FE lymphocytes (Lassiter et al, 2006); no difference in Cyt c1 expression was observed in liver. Similar to observations in breast muscle , ANT1 protein expression was higher in low FE compared with high FE heart homogenate ( Table 2).…”

“…A hallmark of low FE appears to be higher oxidized proteins Ojano-Dirain et al, 2005;Lassiter et al, 2006) that could be from higher mitochondrial reactive oxygen species (ROS) production due to site-specific defects in electron transport (Bottje et al, 2002;Ojano-Dirain et al, 2004). Elevated mitochondrial ROS can affect protein expression and cause DNA mutations leading to mistranslated RNA and proteins (Crawford et al, 1997), as well as diminish mitochondrial respiratory capacity (Wallace, 1999).…”