Hepatic Lipid Accumulation and Dysregulation Associate with Enhanced Reactive Oxygen Species and Pro-Inflammatory Cytokine in Low-Birth-Weight Goats

Abstract

Occurrence of low birth weight (LBW) is a major concern in livestock production, resulting in poor postnatal growth, lowered efficiency of feed utilization, and impaired metabolic health in adult life. In the southwest region of China, birth weight of indigenous strains of goats varies seasonally with lower weights in summer and winter, but the metabolic regulation of the LBW offspring is still unknown. In this study, by comparing LBW goats to normal birth weight group, we examined hepatic lipid content in association with regulatory mechanisms. Histological studies showed higher microvesicular morphology in the liver of LBW goats in accompany with a significantly higher level of hepatic free fatty acids, total triglycerides, and cholesterols. Lipid metabolism impairment, increased oxidative stress, and inflammation were observed by transcriptome analysis. Meanwhile, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation further demonstrated lipid peroxidation, antioxidant pathway, and pro-inflammatory response involved in the hepatic lipid dysregulation from LBW group. Therefore, dysregulations of hepatic lipid metabolism, including fatty acid biosynthesis and degradation, lipid transportation, and oxidative stress, played important roles to contribute the lipid accumulation in LBW goats. Moreover, due to impaired antioxidant capacity, the oxidative damage could interact with persisting pro-inflammatory responses, leading to a higher risk of liver injury and metabolic syndromes in their adult life.

Keywords: antioxidant capacity; goat; lipid accumulation; liver; low birth weight.

Figure 1

Histological analysis of the liver tissue in control (A,C) and LBW (B,D) goat kids. H with arrowheads indicate hepatocyte; M with arrowheads indicate microvesicular steatosis.

Figure 2

Metabolic features of free fatty acids (A), total triglycerides (B), total cholesterol (C), MDA (D), GPx (E), glycogen (F), and ATP content (G) were determined in liver from control and LBW kids. **, p < 0.01; *, p < 0.05; †, p = 0.057. MDA, malondialdehyde; GPx, glutathione peroxidase; LBW, low birth weight.

Figure 3

The distribution of commonly expressed genes (CEGs) and differently expressed genes (DEGs). There were 13,620 annotated transcripts identified in liver from the control and LBW kids, with 204 DEGs and 13,416 CEGs.

Figure 4

Volcano plot of global genes expression. The statistically significant genes with ≥ 1.5-fold change and false discovery rate of less than 0.05 are plotted in red (up-regulated genes) and blue (down-regulated genes). FDR, false discovery rate; FC, fold change.

Figure 5

KEGG pathway enrichment analysis of DEGs.

Figure 6

Gene expression determined by RNAseq reflects qPCR. The log₂ transformed fold changes are plotted for RNAseq results (abscissa) and qPCR results (ordinate). Fold change of eight genes determined by qPCR correlated significantly (p < 0.0043) with the fold change determined by RNAseq. The slope of best fit after Pearson correlation was 0.88, with a 95% confidence interval of 0.45 to 0.98.

Figure 7

mRNA expression levels in livers of control and LBW kids. (A), relative fold changes for nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (HO-1), superoxide dismutase 2 (SOD2), and glutathione peroxidase (GPx). *, p < 0.05; †, p = 0.064. (B), quantifications of mtDNA/nDNA.

Figure 8

Relative protein expression of Nrf2 and TNFα in liver. (A,B), representative immunoblots for Nrf2 and TNFα between control and LBW kids. Original Western Blot could be found as Figures S1–S4. (C,D), relative protein concentration of Nrf2 and TNFα normalized by abundance of β-actin. Nrf2: nuclear factor erythroid 2-related factor 2; TNFα: tumor necrosis factor alpha. **, p < 0.01. Original Western Blot figures can be found at Supplementary Material.

Figure 9

Relative protein expression level of oxidative phosphorylation complexes in livers. (A) representative immunoblots for the complexes I (CI, NDUFB8), II (CII, SDHB), IV (CIV, MTCO1) and V (CV, ATP5A) in livers of control and LBW kids. (B) relative protein concentration of oxidative phosphorylation complexes normalized by abundance of β-actin. Original Western Blot could be found as Figures S5 and S6.

Figure 10

Hepatic lipid accumulation was associated with impairment of lipid metabolism and oxidative regulation in LBW goats. Overproduction of ROS and lower antioxidant capacity could contribute oxidative stress, which interacts with pro-inflammation cytokine, resulting in persistent lipid dysregulation and hepatosteatosis in the LBW goat’s adult life. FFA, free fatty acid; TC, total cholesterol; TNFα, tumor necrosis factor alpha; MDA, malondialdehyde.