Expression of lipogenic enzymes in chickens

Capillary Electrophoresis Assessment of Plasma Protein Changes in an African Penguin (Spheniscus demersus) With Aspergillosis

A decrease of avian biodiversity in the African continent has been the result of anthropogenic pressure in the region. This has resulted in the African penguin (Spheniscus demersus) being placed on the endangered species list and requires conservation efforts to maintain its free-ranging population and placement under managed care. In the latter environment, infection by Aspergillus fumigatus can be common. The diagnosis and treatment of this fungal disease in birds has presented with many difficulties, largely due to the diversity and limited knowledge that exists about this species. In this study, we implement a high-resolution capillary electrophoresis system for the fractionation of African penguin plasma, followed by mass spectrometry analysis for the identification of proteins associated with aspergillosis. Several protein differences were revealed, including changes in acute phase proteins and lipid metabolism. In addition, our results demonstrated that fibrinogen β chain is a protein largely present during the inflammatory process in an African penguin infected with A. fumigatus. These findings present a new avenue for the measurement of plasma proteins as a potential method for identifying important biomarkers to aid in monitoring African penguin health.

Turnover of muscle lipids and response to exercise differ between neutral and polar fractions in a model songbird, the zebra finch

The turnover rates of tissues and their constituent molecules give us insights into animals' physiological demands and their functional flexibility over time. Thus far, most studies of this kind have focused on protein turnover, and few have considered lipid turnover despite an increasing appreciation of the functional diversity of this class of molecules. We measured the turnover rates of neutral and polar lipids from the pectoralis muscles of a model songbird, the zebra finch (Taeniopygia guttata, N=65), in a 256 day C₃/C₄ diet shift experiment, with tissue samples taken at 10 time points. We also manipulated the physiological state of a subset of these birds with a 10 week flight training regimen to test the effect of exercise on lipid turnover. We measured lipid δ¹³C values via isotope ratio mass spectrometry (IRMS) and estimated turnover in different fractions and treatment groups with non-linear mixed-effect regression. We found a significant difference between the mean retention times (τ) of neutral and polar lipids (t₁₁₉=-2.22, P=0.028), with polar lipids (τ=11.80±1.28 days) having shorter retention times than neutral lipids (τ=19.47±3.22 days). When all birds were considered, we also found a significant decrease in the mean retention time of polar lipids in exercised birds relative to control birds (difference=-2.2±1.83 days, t₅₆=-2.37, P=0.021), but not neutral lipids (difference=4.2± 7.41 days, t₅₆=0.57, P=0.57). A larger, more variable neutral lipid pool and the exposure of polar lipids in mitochondrial membranes to oxidative damage and increased turnover provide mechanisms consistent with our results.

The effect of increasing feeding frequency on performance, plasma hormones and metabolites, and hepatic lipid metabolism of broiler breeder hens

An experiment was conducted to study the effects of feeding regimens on reproductive performance, plasma hormone and metabolite levels, and hepatic lipid metabolism of Cobb 500 broiler breeder hens from 26 to 38 wk of age. Seventy-two birds were used in a completely randomized design with 3 treatments, each replicated 4 times. Treatments were as follows: 1) once a day feeding, in which birds were fed once a day at 0615 h (control), 2) twice a day feeding, in which daily allocated feed was fed in 2 equal meals at 0615 and 1215 h, and 3) thrice a day feeding in which daily allocated feed was offered in 3 equal meals at 0615, 1215, and 1815 h. Through 38 wk of age, total hen-day egg production in the hens fed twice and thrice a day was greater (67.1 and 67.2 vs. 62.2 eggs/hen, P < 0.01). Similarly, egg weight was higher (P < 0.01) in birds fed more than once a day. Multi-meal-fed birds had significantly lower plasma triiodothyronine and glucose at 32 wk and also lower glucose and cholesterol, and higher 17β-estradiol levels at 38 wk than those fed once a day (P ≤ 0.05). Hepatic expression of malic enzyme, fatty acid synthase, acetyl-CoA carboxylase, and ATP citrate lyase relative to β-actin decreased (P < 0.05) in birds fed twice and thrice a day compared with birds fed once a day at peak egg production (32 wk). In contrast, feeding regimens did not affect the hepatic gene expression of lipogenic enzymes after peak egg production at 38 wk. Stearoyl-CoA desaturase 1 (SCD1) gene expression was constant over dietary regimens. There was no difference in malic enzyme activity in multi-meal-fed birds at 38 wk. In summary, feeding broiler breeder hens 2 or 3 meals per day improved the reproductive performance during the early lay cycle. Implementing twice or thrice a day feeding regimens altered hepatic lipogenic gene expression in broiler breeder hens only at peak egg production, which indicated a short-term effect of increasing feeding frequency on hepatic lipid metabolism.

Short term changes in the expression of lipogenic genes in broilers (Gallus gallus)

The purpose of these experiments were to determine possible relationships between certain indices of lipid metabolism and specific gene expression in chickens fed graded levels of dietary crude protein. Male, broiler chickens growing from 7 to 28 days of age were fed diets containing 12 or 30% protein ad libitum. Both groups were then switched on day 28 to the diets containing the opposite level of protein. Birds were killed on day 28 (basal values prior to the switch) and at 12, 18 and 24 h post switch. Measurements taken included in vitro lipogenesis, malic enzyme activity the expression of the genes for malic enzyme, fatty acid synthase and acetyl coenzyme carboxylase. In vitro lipogenesis and malic enzyme activity were inversely related to dietary protein levels (12 to 30%) and to acute changes from 12 to 30%. Malic enzyme, fatty acid synthase and acetyl coenzyme A carboxylase genes were constant over a dietary protein range of 12 to 21% as in previous experiments, but decreased by feeding a 30% protein diet in the present experiments (acute or chronic feeding). Results of the present study demonstrate a continued role for protein in the regulation of broiler metabolism. Metabolic regulation at the gene level only occurs when feeding very high levels of dietary protein.