Effect of Conjugated Linoleic Acid on Insulin Sensitivity

Mice were fed a mixture of conjugated linoleic acid isomers (CLA) for nine weeks and then underwent an insulin tolerance test. CLA was then removed from the diet and a second insulin tolerance test was conducted following five weeks of recovery. CLA consumption impaired glucose response to insulin. When CLA was removed from the diet, insulin sensitivity of a low heat-loss genetic mouse line returned to normal. However, mice of a high heat-loss line remained insulin resistant for at least 32 days

Effect of Conjugated Linoleic Acid on Insulin Sensitivity

Mice were fed a mixture of conjugated linoleic acid isomers (CLA) for nine weeks and then underwent an insulin tolerance test. CLA was then removed from the diet and a second insulin tolerance test was conducted following five weeks of recovery. CLA consumption impaired glucose response to insulin. When CLA was removed from the diet, insulin sensitivity of a low heat-loss genetic mouse line returned to normal. However, mice of a high heat-loss line remained insulin resistant for at least 32 days

Short communication: Detection of yeast DNA in omasal digesta of dairy cows consuming dried distillers grains and solubles

Purine analysis is widely used to estimate microbial crude protein (MCP) flow, and the method assumes that all purines contained in feed are degraded in the rumen and that purines detected are of microbial origin. The objectives of our experiment were (1) to determine if DNA from yeast (Saccharomyces cerevisiae) contained in dried distillers grains and solubles (DDGS) escapes degradation in the rumen and (2) to estimate the proportion of yeast DNA compared with total bacterial DNA in omasal samples. Two ruminally fistulated Holstein dairy cows averaging 649 kg (SD = 42.0) and 126 d in milk (SD = 28.9) were fed in a crossover design during 2 periods of 21 d each. Treatments were (1) control, a total mixed ration (TMR) not containing DDGS and (2) a DDGS-based diet, a TMR in which DDGS were included at 30% of diet dry matter (DM). On d 20 and 21 at 0400 and 1600 h, omasal digesta samples were collected via a ruminal cannula, and DNA was extracted from each sample in duplicate. The DNA samples were subjected to a realtime PCR assay to detect the presence of DNA from yeast. Forward and reverse primers and a probe were designed to target a DNA segment contained on the second chromosome of Saccharomyces cerevisiae. Realtime PCR amplification curves indicated the presence of yeast DNA in samples from both treatments. Specifically, the estimate of relative abundance of yeast DNA from digesta samples collected from animals consuming the diet containing DDGS was 9.46 ± 0.67/g of DM and was significantly higher than that from animals consuming no DDGS, which was observed to be 0.091 ± 0.67/g of DM. Omasal samples were also analyzed for total bacterial DNA. Primers and a probe were designed from DNA encoding part of the 16S rRNA. When the DDGS-based diet was fed, the relative abundance of total bacterial DNA tended to increase from 610 to 626 ± 3.82/g of DM. Results suggest that yeast DNA is detected in the omasum and this is increased when cows consume DDGS but it does not represent a significant proportion of total microbial DNA in the omasal digesta samples

Short communication: Detection of yeast DNA in omasal digesta of dairy cows consuming dried distillers grains and solubles

Purine analysis is widely used to estimate microbial crude protein (MCP) flow, and the method assumes that all purines contained in feed are degraded in the rumen and that purines detected are of microbial origin. The objectives of our experiment were (1) to determine if DNA from yeast (Saccharomyces cerevisiae) contained in dried distillers grains and solubles (DDGS) escapes degradation in the rumen and (2) to estimate the proportion of yeast DNA compared with total bacterial DNA in omasal samples. Two ruminally fistulated Holstein dairy cows averaging 649 kg (SD = 42.0) and 126 d in milk (SD = 28.9) were fed in a crossover design during 2 periods of 21 d each. Treatments were (1) control, a total mixed ration (TMR) not containing DDGS and (2) a DDGS-based diet, a TMR in which DDGS were included at 30% of diet dry matter (DM). On d 20 and 21 at 0400 and 1600 h, omasal digesta samples were collected via a ruminal cannula, and DNA was extracted from each sample in duplicate. The DNA samples were subjected to a realtime PCR assay to detect the presence of DNA from yeast. Forward and reverse primers and a probe were designed to target a DNA segment contained on the second chromosome of Saccharomyces cerevisiae. Realtime PCR amplification curves indicated the presence of yeast DNA in samples from both treatments. Specifically, the estimate of relative abundance of yeast DNA from digesta samples collected from animals consuming the diet containing DDGS was 9.46 ± 0.67/g of DM and was significantly higher than that from animals consuming no DDGS, which was observed to be 0.091 ± 0.67/g of DM. Omasal samples were also analyzed for total bacterial DNA. Primers and a probe were designed from DNA encoding part of the 16S rRNA. When the DDGS-based diet was fed, the relative abundance of total bacterial DNA tended to increase from 610 to 626 ± 3.82/g of DM. Results suggest that yeast DNA is detected in the omasum and this is increased when cows consume DDGS but it does not represent a significant proportion of total microbial DNA in the omasal digesta samples

Hormonal Influence on Fat Synthesis in Cattle

The ability of adenosine, insulin and human acylation-stimulating protein to modify fat synthesis was determined using cultures of fat tissue from steers. Adenosine did not influence fat synthesis. However, acylation stimulating protein and insulin promoted fat synthesis. These observations, coupled with knowledge of how fat synthesis is regulated in other species, justify investigation of whether cattle synthesize acylation-stimulating protein, and how this synthesis is regulated. An understanding of how acylation-stimulating protein production and action is regulated should expose potential places for intervention to manipulate fat synthesis in cattle

Acylation Stimulating Protein: A Potential Regulator of Fat Synthesis

The long term goal of this project is to understand the molecular mechanisms controlling fat synthesis. These experiments indicate that acylation stimulating protein (ASP) can stimulate the incorporation of fatty acids into lipid in cultured adipose tissue. This finding justifies a future effort to determine if manipulation of ASP can modify fat deposition

Conjugated Linoleic Acid Metabolism and Body Fat Loss in Mice

Mice were fed conjugated linoleic acid (CLA) with or without fish oil or aspirin, which deplete tissue arachidonic acid and block arachidonic acid metabolism, respectively. Mice fed fish oil did not lose body fat when supplemented with CLA but mice fed soy oil did. Aspirin did not alter CLA-induced body fat loss. CLA may be metabolized to an isomer of arachidonic acid to induce a loss of body fat. However, this body fat loss is apparently not mediated via alteration of prostaglandin synthesis. Understanding the regulation of body fat by CLA may offer insight into the mechanisms of body fat regulation in cattle

Uncoupling proteins and energy expenditure in mice divergently selected for heat loss

The objective of this study was to determine whether variation in energy expenditure created by selection on heat loss is mediated by uncoupling protein-1 (UCP1) in brown adipose tissue. Divergent selection for heat loss developed lines of mice with high (MH) and low (ML) maintenance energy expenditure. Concentration of UCP1 mRNA in brown adipose tissue (BAT) was 93% greater in ML than in MH mice (P \u3c 0.02). Two new lines of mice, KH and KL, were bred by backcrossing a UCP1 knockout gene into the MH and ML lines, respectively; KH and KL with both knockout (−/−) and wild type (+/+) UCP1 genotypes were generated. At 13 wk of age, KH mice exhibited greater heat loss (166 kcal∙kg0.75∙d−1) than KL mice (126.4 kcal∙ kg0.75∙d−1) regardless of the UCP1 knockout (P \u3c 0.0001). Concentration of UCP2 mRNA in BAT was 74% greater in UCP1 knockout mice (−/−) than in wild type (+/+; P = 0.0001). We conclude that response to selection for increased energy expenditure was not mediated by increased expression or function of UCP1

Cross Regulation of Sirtuin 1, AMPK, and PPARy in Conjugated Linoleic Acid Treated Adipocytes

Trans-10, cis-12 conjugated linoleic acid (t10c12 CLA) reduces triglyceride (TG) levels in adipocytes through multiple pathways, with AMP-activated protein kinase (AMPK) generally facilitating, and peroxisome proliferator-activated receptor γ (PPARγ) generally opposing these reductions. Sirtuin 1 (SIRT1), a histone/protein deacetylase that affects energy homeostasis, often functions coordinately with AMPK, and is capable of binding to PPARγ, thereby inhibiting its activity. This study investigated the role of SIRT1 in the response of 3T3-L1 adipocytes to t10c12 CLA by testing the following hypotheses: 1) SIRT1 is functionally required for robust TG reduction; and 2) SIRT1, AMPK, and PPARγ cross regulate each other. These experiments were performed by using activators, inhibitors, or siRNA knockdowns that affected these pathways in t10c12 CLA-treated 3T3-L1 adipocytes. Inhibition of SIRT1 amounts or activity using siRNA, sirtinol, nicotinamide, or etomoxir attenuated the amount of TG loss, while SIRT1 activator SRT1720 increased the TG loss. SRT1720 increased AMPK activity while sirtuin-specific inhibitors decreased AMPK activity. Reciprocally, an AMPK inhibitor reduced SIRT1 activity. Treatment with t10c12 CLA increased PPARγ phosphorylation in an AMPK-dependent manner and increased the amount of PPARγ bound to SIRT1. Reciprocally, a PPARγ agonist attenuated AMPK and SIRT1 activity levels. These results indicated SIRT1 increased TG loss and that cross regulation between SIRT1, AMPK, and PPARγ occurred in 3T3-L1 adipocytes treated with t10c12 CLA

Effect of Conjugated Linoleic Acid on Cell Death in Adipose Tissue

Mice fed conjugated linoleic acid (CLA) lose body fat. This loss of body fat is accompanied by an increases in DNA fragmentation, indicative of apoptosis or programmed cell death. Adipose apoptosis was observed in mice fed the trans-10, cis-12 isomer or a mixture of isomers but not the cis-9,trans-11 isomer. The trans-10,cis-12 isomer also induced DNA fragmentation in preadipocytes in vitro, but not mature adipocytes. The cis-9,trans-11 CLA isomer, the predominant isomer in ruminant-derived products, was reported to induce apoptosis of cancer cells. Determining the mechanism of action of CLA will improve our understanding of body fat regulation