Effects of branched-chain volatile fatty acids on lactation performance and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows

Branched-chain volatile fatty acids (BCVFA) supplements could promote lactation performance and milk quality by improving ruminal fermentation and milk fatty acid synthesis. This study was conducted to evaluate the effects of BCVFA supplementation on milk performance, ruminal fermentation, nutrient digestibility and mRNA expression of genes related to fatty acid synthesis in mammary gland of dairy cows. A total of 36 multiparous Chinese Holstein cows averaging 606±4.7 kg of BW, 65±5.2 day in milk (DIM) with daily milk production of 30.6±0.72 kg were assigned to one of four groups blocked by lactation number, milk yield and DIM. The treatments were control, low-BCVFA (LBCVFA), medium-BCVFA (MBCVFA) and high-BCVFA (HBCVFA) with 0, 30, 60 and 90 g BCVFA per cow per day, respectively. Experimental periods were 105 days with 15 days of adaptation and 90 days of data collection. Dry matter (DM) intake tended to increase, but BW changes were similar among treatments. Yields of actual milk, 4% fat corrected milk, milk fat and true protein linearly increased, but feed conversion ratio (FCR) linearly decreased with increasing BCVFA supplementation. Milk fat content linearly increased, but true protein content tended to increase. Contents of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0 and C15:0 fatty acids in milk fat linearly increased, whereas other fatty acids were not affected with increasing BCVFA supplementation. Ruminal pH, ammonia N concentration and propionate molar proportion linearly decreased, but total VFA production and molar proportions of acetate and butyrate linearly increased with increasing BCVFA supplementation. Consequently, acetate to propionate ratios linearly increased. Digestibilities of DM, organic matter, CP, NDF and ADF also linearly increased. In addition, mRNA expressions of peroxisome proliferator-activated receptor γ, sterol regulatory element-binding factor 1 and fatty acid-binding protein 3 linearly increased, mRNA expressions of acetyl-coenzyme A carboxylase-α, fatty acid synthase and stearoyl-CoA desaturase quadratically increased. However, lipoprotein lipase mRNA expression was not affected by treatments. The results indicated that lactation performance and milk fat synthesis increased with BCVFA supplementation by improving ruminal fermentation, nutrient digestibility and mRNA expressions of genes related to milk fat synthesis.     

Novel multialveolar epithelial structures from rabbit mammary gland that synthesize milk specific fatty acids in response to prolactin

Summary Multialveolar mammary epithelial structures have been prepared from rabbit mammary gland by treating the tissue with collagenase plus hyaluronidase. These structures synthesize milk specific fatty acids when cultured with physiological concentrations (0.05 μg/ml) of prolactin in the presence of insulin and corticosterone. They have many of the advantages but few of the disadvantages of either mammary explains or primary cells in culture. For example, they are easily prepared in large numbers and respond to prolactin in culture even in the absence or other tissue extracts. Because their level of organization is intermediate between that of explants and single cells, they provide a complementary system for studies on mammary differentiation. This work was supported by grants from the Agricultural Research Council of Great Britain and the Royal Society to R. R. Dils, by U.S. Public Health Service Grant CA-16392, and an American Cancer Society-Eleanor Roosevelt International Cancer Fellowship to H. L. Hosick. Prolactin was a gift from the Endocrinology Study Section, National Institutes of Health, Bethesda, MD.     

小反刍兽疫病毒Ｍ基因的截短表达及多抗血清的制备

目的 截短表达小反刍兽疫病毒M蛋白基因并将其用于多抗血清的制备。方法 之前有研究未能表达完整的M蛋白,而若在抗原性较弱的区域将其一分为二,以截短的形式进行表达,却能达到较理想的水平。因此根据GenBank上公布的PPRV M基因的序列,设计1对特异性引物,扩增出480 bp的目的基因,将其克隆至原核表达载体pET-32a(+)中,得到重组表达质粒pET-32a-PPRV-M1,后转化至Rosetta感受态细胞中,IPTG诱导表达后,通过SDS-PAGE和Western blot试验对重组蛋白进行鉴定,将纯化后的重组蛋白免疫6周龄BALB/c雌鼠,制备多克隆抗体血清。结果 经SDS-PAGE及Western blot鉴定,证明截短的M基因的蛋白主要以包涵体形式高效表达并具有良好的反应原性。结论 成功克隆表达了截短的小反刍兽疫病毒M基因的蛋白并制备了多抗血清,为建立血清学相关的检测方法及临床治疗奠定了基础。     

Role of a new mammalian gene family in the biosynthesis of very long chain fatty acids and sphingolipids

Whereas the physiological significance of microsomal fatty acid elongation is generally appreciated, its molecular nature is poorly understood. Here, we describe tissue-specific regulation of a novel mouse gene family encoding components implicated in the synthesis of very long chain fatty acids. The Ssc1 gene appears to be ubiquitously expressed, whereas Ssc2 and Cig30 show a restricted expression pattern. Their translation products are all integral membrane proteins with five putative transmembrane domains. By complementing the homologous yeast mutants, we found that Ssc1 could rescue normal sphingolipid synthesis in the sur4/elo3 mutant lacking the ability to synthesize cerotic acid (C(26:0)). Similarly, Cig30 reverted the phenotype of the fen1/elo2 mutant that has reduced levels of fatty acids in the C(20)-C(24) range. Further, we show that Ssc1 mRNA levels were markedly decreased in the brains of myelin-deficient mouse mutants known to have very low fatty acid chain elongation activity. Conversely, the dramatic induction of Cig30 expression during brown fat recruitment coincided with elevated elongation activity. Our results strongly implicate this new mammalian gene family in tissue-specific synthesis of very long chain fatty acids and sphingolipids.     

Desaturase-defective fungal mutants: useful tools for the regulation and overproduction of polyunsaturated fatty acids

Increasing demand for biologically important polyunsaturated fatty acids has led to the search for alternative sources, especially fungi. Although successes in this area have induced interest in developing fungal fermentation processes, manipulation of their lipid composition requires new biotechnological strategies to achieve high yields of the desired polyunsaturated fatty acids. Fungal desaturase mutants with unique enzyme systems are useful not only for the regulation and overproduction of valuable polyunsaturated fatty acids but also because they are excellent models for the elucidation of fungal lipogenesis.     

Effect of a linseed diet on lipogenesis, fatty acid composition and stearoyl-CoA-desaturase in rabbits

The aim of the study was to examine the effect of a linseed diet on meat quality and on lipogenesis in rabbits. Twelve rabbits were fed a control or a linseed diet. There was no diet effect on growth, food consumption, carcass characteristics and meat ultimate pH and colour. Feeding the linseed diet increased the n-3 polyunsaturated fatty acids (PUFA) levels in perirenal and interscapular fats, in the Longissimus dorsi muscle and in the liver. The linseed diet produced lower linoleic acid/α-linolenic acid ratios in adipose tissues and in the Longissimus dorsi muscle, but not in the liver. Diet did not affect lipogenic enzyme activities in the Longissimus dorsi muscle, whereas the linseed diet decreased the lipogenic potential in perirenal and interscapular fats, and in the liver. Feeding rabbits with a high n-3 PUFA diet led to a decrease in the oxidative stability of perirenal fat and the Longissimus dorsi muscle, and to an inhibition of stearoyl-CoA-desaturase activity in liver and in adipose tissues, but not in muscle.     

Role of glucocorticoids in the regulation of lipogenesis

Traditionally, the glucocorticoids have been viewed as catabolic hormones. However, with the present knowledge about how the glucocorticoid receptor protein functions in the stimulation of mRNA synthesis, a new view must be accepted: These steroids also have an anabolic function. They are anabolic because they stimulate the de novo synthesis of enzymes of anabolic pathways. In the liver, stimulation of lipogenic enzymes has been shown. These findings suggest that glucocorticoids can increase feed efficiency and thereby play a role in the etiology of obesity.     

Dietary regulation of mammary lipogenesis in lactating rats.

The proportion of medium-chain fatty acids (C8:0, C10:0 and C12:0) in rat milk increased significantly between day 4 and day 8 of lactation and for the remainder of lactation these acids comprised 40-50mol% of the total fatty acids. The milk fatty acid composition from day 8 was markedly dependent on the presence of dietary fat and altered to include the major fatty acids of the fats (peanut oil, coconut oil and linseed oil). The distribution of fatty acids made within the gland, however, was independent of dietary lipid and C8:0, C10:0 and C12:0 acids accounted for over 70% of the fatty acids made. The rates of lipogenesis in both the mammary gland and liver determined in vivo after the administration of 3H2O were affected by the presence of dietary lipid. In the mammary gland the rate for rats fed a diet containing peanut oil for 7 days was only one fifth that for rats fed a fat-free diet. Coconut oil also suppressed lipogenesis. Both dietary fats also suppressed lipogenesis in the liver.     

Transcriptional regulation of acetyl-CoA carboxylase α isoforms in dairy ewes during conjugated linoleic acid induced milk fat depression

Feeding trans-10, cis-12 CLA to lactating ewes reduces milk fat by down-regulating expression of enzymes involved in lipid synthesis in the mammary gland and increases adipose tissue lipogenesis. Acetyl-CoA carboxylase α (ACC-α) is a key regulated enzyme in de novo fatty acid synthesis and is decreased by CLA. In the ovine, the ACC-α gene is expressed from three tissue-specific promoters (PI, PII and PIII). This study evaluated promoter-specific ACC-α expression in mammary and adipose tissue of lactating cross-bred Lacaune/Texel ewes during milk fat depression induced by rumen-unprotected trans-10, cis-12 CLA supplement. In all, 12 ewes arranged in a completely randomized design were fed during early, mid and late lactation one of the following treatments for 14 days: Control (forage+0.9 kg of concentrate on a dry matter basis) and CLA (forage+0.9 kg of concentrate+27 g/day of CLA (29.9% trans-10, cis-12)). Mammary gland and adipose tissue biopsies were taken on day 14 for gene expression analysis by real-time PCR. Milk fat yield and concentration were reduced with CLA supplementation by 27%, 21% and 35% and 28%, 26% and 42% during early, mid and late lactation, respectively. Overall, our results suggest that trans-10, cis-12 CLA down-regulates mammary ACC-α gene expression by decreasing expression from PII and PIII in mammary gland and up-regulates adipose ACC-α gene expression by increasing expression from PI.     

Gelsolin expression in sheep milk somatic cells during lactation

The identification of genes involved in phenotypes related to milk quality is important for both economic and health aspects in livestock production. The aim of this study was to assess the level of gelsolin gene expression in two breeds of dairy sheep – Sarda and Gentile – with pronounced differences in quantitative and qualitative milk traits. Gelsolin, a type of actin-modulating proteins is involved in the processes of actin remodeling during cell growth and apoptosis; therefore a role of this protein in mammary changes during lactation was here hypothesized. Individual milk samples were collected three times during lactation from 26 ewes of the two breeds. The differential gene expression of gelsolin in the two breeds and the three lactation times was estimated by quantitative PCR on RNA extracted from milk somatic cells. Correlations of gelsolin gene expression with milk yield and quality and days of lactation were also estimated. The results showed that gelsolin gene expression was significantly higher in the Sarda compared to the Gentile at each lactation stage, in agreement with the longer lactation duration and the higher daily milk yield of the first breed. Significant correlations of gelsolin gene expression were found with milk fat content in Sarda breed (−0.46, P<0.05). Gelsolin expression analysis confirmed the link between gelsolin gene function and milk fat content of sheep.