Increased adipose tissue lipolysis in dairy cows with fatty liver is associated with enhanced autophagy activity

Abstract

Lipolysis is increased in adipose tissue of cows with fatty liver during the transition period. Autophagy, a major cellular degradation process, plays a critical role in adipose tissue homeostasis. The objective of this study was to explore the relationship between lipolysis and autophagy in adipose tissue of cows with fatty liver. Using a nested case-control design, we compared blood and adipose tissue samples from 10 control cows [parity: median = 3, range = 2-4; days in milk: median = 8 d, range = 5-10 d; hepatic triacylglycerol content: median = 0.55% liver wt, range = 0.48-0.61% liver wt] and 10 lactation stage-matched cows with fatty liver (parity: median = 3, range = 2-4; days in milk: median = 9 d, range = 5-11 d; hepatic triacylglycerol content: median = 6.28% liver wt, range = 2.86-7.75% liver wt). Data were analyzed using paired t-tests. Serum concentrations of free fatty acids and β-hydroxybutyrate were greater and glucose concentration was lower in cows with fatty liver, which we determined by using commercially-available kits. Furthermore, western blotting showed that increased protein abundance of ATGL (adipose triglyceride lipase), ATG5 (autophagyrelated gene 5), and ATG7; ratio of phosphorylated (p)-HSL (hormone-sensitive lipase) to HSL and MA-P1LC3 (microtubule-associated protein 1 light chain 3, also called LC3-II) to LC3-I along with decreased abundance of PLIN1 (perilipin 1), SQSTM1 (sequestosome-1, also called p62), and the ratio of p-mTOR (phosphorylated mechanistic target of rapamycin) to mTOR in cows with fatty liver. Quantitative reversetranscription PCR revealed an increase in abundance of MAP1LC3 mRNA and a decrease in SQSTM1 mRNA in cows with fatty liver. These findings were replicated using an adipocyte model. Primary cultures of calf adipocytes isolated from the adipose tissue of the peritoneal omentum and mesentery were treated with 10 mM 3-methyladenine (3-MA), 5 nM rapamycin, 1 µM isoproterenol (ISO), and 1 µM ISO + 10 mM 3-MA. Comparisons among groups were analyzed using one-way ANOVA. Compared with the control, the 1 µM ISO treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Compared with the 1 µM ISO treatment group, 1 µM ISO + 10 mM 3-MA downregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it upregulated the abundance of PLIN1 and p62. Compared with the control, the 5 nM rapamycin treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Overall, these data indicated that increased lipolysis in adipose tissue of cows with fatty liver was associated with enhanced autophagy. However, the specific molecular mechanisms that link lipolysis and autophagy need to be further investigated.

Dietary supplementation with calcium propionate could beneficially alter rectal microbial composition of early lactation dairy cows

“…The results of Chen et al ( 44 ) suggested that the specific species of Firmicutes may induce more hepatic steatosis by modulating fatty acid influx and lipogenesis compared to those of Bacteroidetes . The incidence of fatty liver is particularly high in the high-yielding dairy cows during the postpartum period for the excessive triglycerides deposit in the liver ( 45 ). The shifted relative abundances of Firmicutes and Bacteroidetes may explain the effect of calcium propionate in alleviating NEB.…”

An affinity tool for the isolation of endogenous active mTORC1 from various cellular sources

“…Anti-GST was purchased from Santa Cruz Biotechnology (#sc-138) and anti-Sin1 from Sigma-Aldrich (#07-2276-I). In bovine liver samples, rabbit monoclonal mTOR Cell Signaling Technology #2983 strongly detected mTORβ and for the detection of full-length mTORα in these samples, a polyclonal antibody against mTOR (ab2732, Abcam) was utilized in line with a previous study ( 35 ). In several of the experiments, proteins of similar sizes (such as Rictor and Raptor or Raptor and mTOR) had to be analyzed on separate gels due to the interference of secondary antibodies.…”

Dissecting loci that underpin the genetic correlations between production, fertility, and urea traits in Australian Holstein cattle

“…The liver, through enzymatic oxidation of cholesterol, generates numerous distinct bile acids that play two critical roles: (1) as detergents that facilitate digestion and absorption of dietary lipids, and (2) as steroid hormones that regulate lipid metabolism, energy homeostasis, detoxification, liver regeneration, inflammation, and hepatocarcinogenesis (de Aguiar Vallim et al, 2013). However, elevated levels of fatty acids due to increased lipolysis can damage the liver and potentially impair its functions (Dong et al, 2022;Du et al, 2018), thereby obstructing the biosynthesis bile acids and steroid hormones (i.e., progestogens, androgens, estrogens, etc.). Moreover, elevated fatty acid levels can also compromise oocyte quality, extend the interval from calving to first ovulation, and cause uterine bacterial infections (Ban et al, 2017;Leroy et al, 2008;Van Hoeck et al, 2011;Wathes et al, 2011Wathes et al, , 2012.…”