Blood and liver telomere length, mitochondrial DNA copy number, and hepatic gene expression of mitochondrial dynamics in mid-lactation cows supplemented with l-carnitine under systemic inflammation.

The current study was conducted to examine the effect of l-carnitine (LC) supplementation on telomere length and mitochondrial DNA copy number (mtDNAcn) per cell in mid-lactation cows challenged by lipopolysaccharide (LPS) in blood and liver. The mRNA abundance of 31 genes related to inflammation, oxidative stress, and the corresponding stress response mechanisms, the mitochondrial quality control and the protein import system, as well as the phosphatidylinositol 3-kinase/protein kinase B pathway, were assessed using microfluidics integrated fluidic circuit chips (96.96 dynamic arrays). In addition to comparing the responses in cows with or without LC, our objectives were to characterize the oxidative and inflammatory status by assessing the circulating concentration of lactoferrin (Lf), haptoglobin (Hp), fibrinogen, derivates of reactive oxygen metabolites (dROM), and arylesterase activity (AEA), and to extend the measurement of Lf and Hp to milk. Pluriparous Holstein cows were assigned to either a control group (CON, n = 26) or an LC-supplemented group (CAR; 25 g LC/cow per day; d 42 ante partum to d 126 postpartum (PP), n = 27). On d 111 PP, each cow was injected intravenously with LPS (Escherichia coli O111:B4, 0.5 µg/kg). The mRNA abundance was examined in liver biopsies of d -11 and +1 relative to LPS administration. Plasma and milk samples were frequently collected before and after the challenge. After LPS administration, circulating plasma fibrinogen and serum dROM concentrations increased, whereas AEA decreased. Moreover, serum P4 initially increased by 3 h after LPS administration and declined thereafter irrespective of grouping. The Lf concentrations increased in both groups after LPS administration, with the CAR group showing greater concentrations in serum and milk than the CON group. After LPS administration, telomere length in blood increased, whereas mtDNAcn per cell decreased; however, both remained unaffected in liver. For mitochondrial protein import genes, the hepatic mRNA abundance of the translocase of the mitochondrial inner membrane (TIM)-17B was increased in CAR cows. Moreover, TIM23 increased in both groups after LPS administration. Regarding the mRNA abundance of genes related to stress response mechanisms, 7 out of 14 genes showed group × time interactions, indicating a (local) protective effect due to the dietary LC supplementation against oxidative stress in mid-lactating dairy cows. For mtDNAcn and telomere length, the effects of the LPS-induced inflammation were more pronounced than the dietary supplementation of LC. Dietary LC supplementation affected the response to LPS primarily by altering mitochondrial dynamics. Regarding mRNA abundance of genes related to the mitochondrial protein import system, the inner mitochondrial membrane translocase (TIM complex) seemed to be more sensitive to dietary LC than the outer mitochondrial membrane translocase (TOM complex).

Effects of dietary l-carnitine supplementation on the response to an inflammatory challenge in mid-lactating dairy cows: Hepatic mRNA abundance of genes involved in fatty acid metabolism.

This study aimed at characterizing the effects of dietary l-carnitine supplementation on hepatic fatty acid (FA) metabolism during inflammation in mid-lactating cows. Fifty-three pluriparous Holstein dairy cows were randomly assigned to either a control (CON, n = 26) or an l-carnitine supplemented (CAR; n = 27) group. The CAR cows received 125 g of a rumen-protected l-carnitine product per cow per day (corresponding to 25 g of l-carnitine/cow per day) from d 42 antepartum (AP) until the end of the trial on d 126 postpartum (PP). Aside from the supplementation, the same basal diets were fed in the dry period and during lactation to all cows. In mid lactation, each cow was immune-challenged by a single intravenous injection of 0.5 µg of LPS/kg of BW at d 111 PP. Blood samples were collected before and after LPS administration. The mRNA abundance of in total 39 genes related to FA metabolism was assessed in liver biopsies taken at d -11, 1, and 14 relative to LPS (d 111 PP) and also on d 42 AP as an individual covariate using microfluidics integrated fluidic circuit chips (96.96 dynamic arrays). In addition to the concentrations of 3 selected proteins related to FA metabolism, acetyl-CoA carboxylase α (ACACA), 5' AMP-activated protein kinase (AMPK), and solute carrier family 25 member 20 (SLC25A20) were assessed by a capillary Western blot method in liver biopsies from d -11 and 1 relative to LPS from 11 cows each of CAR and CON. On d -11 relative to LPS, differences between the mRNA abundance in CON and CAR were limited to acyl-CoA dehydrogenase (ACAD) very-long-chain (ACADVL) with greater mRNA abundance in the CAR than in the CON group. The liver fat content decreased from d -11 to d 1 relative to the LPS injection and remained at the lower level until d 14 in both groups. One day after the LPS challenge, lower mRNA abundance of carnitine palmitoyltransferase 1 (CPT1), CPT2, ACADVL, ACAD short-chain (ACADS), and solute carrier family 22 member 5 (SLC22A5) were observed in the CAR group as compared with the CON group. However, the mRNA abundance of protein kinase AMP-activated noncatalytic subunit gamma 1 (PRKAG1), ACAD medium-chain (ACADM), ACACA, and FA binding protein 1 (FABP1) were greater in the CAR group than in the CON group on d 1 relative to LPS. Two weeks after the LPS challenge, differences between the groups were no longer detectable. The altered mRNA abundance before and 1 d after LPS pointed to increased transport of FA into hepatic mitochondria during systemic inflammation in both groups. The protein abundance of AMPK was lower in CAR than in CON before the LPS administration. The protein abundance of SLC25A20 was neither changing with time nor treatment and the ACACA protein abundance was only affected by time. In conclusion, l-carnitine supplementation temporally altered the hepatic mRNA abundance of some genes related to mitochondrial biogenesis and very-low-density lipoprotein export in response to an inflammatory challenge, but with largely lacking effects before and 2 wk after LPS.