Maternal heat stress regulates the early fat deposition partly through modification of m6A RNA methylation in neonatal piglets

Abstract

It is known that heat stress induces various physiological challenges in livestock production including changes in lipid metabolism. However, the molecular mechanism of how heat stress regulates lipid metabolism at the mRNA level is still largely unknown. N 6 -methyl-adenosine (m 6 A) is the most common and abundant modification on RNA molecules present in eukaryotes, which affects almost all aspects of RNA metabolism and thus gives us the hint that it may participate in changes of gene expression of lipid metabolism during heat stress. Therefore, the purpose of the present study was to investigate the effect of heat stress on fat metabolism in 21-day Large White × Landrace piglets from sows challenged by heat stress from day 85 of gestation until day 21 of lactation. We measured the expression of heat shock proteins (HSPs), genes associated with lipid metabolism, m 6 A-related enzymes, and m 6 A levels in abdominal fat and liver of offspring piglets. Our results showed that high ambient temperature significantly increased the expression of HSP70 (P < 0.01) in both liver and abdominal fat and upregulated HSP27 in the liver (P < 0.05). Additionally, genes involved in fat metabolism such as ACACA, FASN, DGAT1, PPAR-γ, SREBP-1c, and FABP4 were upregulated in abdominal fat in the experimental group challenged by high ambient temperature. In the liver, heat stress increased the mRNA expression of DGAT1, SREBP-1c, and CD36 and decreased ATGL and CPT1A expression (P < 0.05). The m 6 A level was higher in the heat stress group compared with the control group in the liver and abdominal fat of offspring piglets (P < 0.01). Notably, heat stress also increased gene expression of METTL14, WTAP, FTO, and YTHDF2 (P < 0.05) in both abdominal fat and liver. The protein abundances of METTL3, METTL14, and FTO were upregulated after heat stress in abdominal fat (P < 0.05) but not in the liver. Although there was no difference in the protein abundance of YTHDF2 in abdominal fat, its level was increased in the liver (P < 0.05). In conclusion, our findings showed that heat stress increased expression of genes involved in lipogenesis, which provided scientific evidence to the observation of increased fatness in pigs under heat stress. We also demonstrated a possible mechanism that m 6 A RNA modification may be associated with these changes in lipid metabolism upon heat stress.

Early-Life m6A RNA Demethylation by Fat Mass and Obesity-Associated Protein (FTO) Influences Resilience or Vulnerability to Heat Stress Later in Life

“…Moreover, heat exposure at the critical period of thermal-control establishment has a long-term effect on RNA methylation: one week after the treatment, m 6 A global levels in both harsh-and mild-temperature-conditioned chicks were significantly lower than those in non-conditioned counterparts. Although two other studies have shown an increase in m 6 A RNA methylation in sheep liver (Shi et al, 2018) and abdominal fat and liver of piglets (Heng et al, 2019) under exposure to high environmental temperature, the differential effect of heat stress on m 6 A modification may be reasoned by different experimental models (animals, organs, and tissues) as well as heat stress stringency. Regulation of m 6 A RNA levels in the brain has been shown to be highly specific in a contextand experience-dependent manner (Widagdo et al, Figure 5.…”

Function and evolution of RNA N6-methyladenosine modification

“…m 6 A methylation expedites adipogenesis of intramuscular preadipocyte through enhancing MTCH2 expression in a YTHDF1-dependent mRNA translation [69]. Besides, m 6 A participates in heat stress-associated lipid metabolism, and its regulators including METTL14, WTAP, FTO, and YTHDF2 and m 6 A levels are increased in the liver and abdominal fat of neonatal piglets following heat stress exposure [70]. In summary, m 6 A modification and its modulators, especially FTO, functionally regulate adipogenesis (Figure 3), which provides a new understanding for pathogenesis and treatment of obesity-associated diseases from the RNA epitranscriptome modification.…”

Role of N6-Methyladenosine RNA Modification in Cardiovascular Disease

“…Many risk factors of CVD such as hyperlipidaemia, diabetes, and inflammation have been identified, but their molecular mechanisms in regulating CVD are still investigated (47)(48)(49). Recently, it has been found that m 6 A RNA methylations are dysregulated in risk conditions, and involved in the pathology of CVD (50,51). These findings may provide insight into the molecular mechanisms underlying CVD development.…”

“…Hyperlipidaemia and obesity are risk factors for CVD development, and m 6 A functional enzymes are dysregulated and involved in lipid metabolism (47,50). Oscillations in mRNA m 6 A methylation in the murine liver depend on a functional circadian clock, which is essential for lipid metabolic homeostasis (52).…”