Objective Fasting hypometabolism regulation technology has broad application potential in long-term space flight and survival in extreme extraterrestrial environments.In-depth research on the substrate conversion of energy metabolism and the formation of new steady states under fasting hypometabolism will provide theoretical basis and experimental data support for formulating effective prolonged fasting application mode.Methods 30 SD rats were randomly divided into control group and fasting group(fasting for 1,2,3,and 5 days).Blood biochemical examination,qRT-PCR,and western blotting were performed to analyze the body weight,blood biochemistry,and expression changes of genes and proteins related to glucose and lipid metabolism during different fasting periods.Results Prolonged fasting significantly reduced the body weight,blood glucose,and triglyceride levels of rats;increased the blood ketone level,and replaced glucose as the main energy substance in the body.There are temporal and tissue-specific changes as a whole.Hepatic and renal gluconeogenesis play major roles respectively during different fasting periods.As the fasting time prolongs,the level of hepatic gluconeogenesis gradually decreases,the content of FFA in the blood increases,the expression level of genes related to fat synthesis decreases,fatty acid oxidation is enhanced,and the expression level of the key gene HMGCS2 for ketone body generation increases.Conclusion During prolonged fasting,there is a significant conversion of glucose-ketone energy supply substrates,and a new steady state of energy metabolism mainly supplied by ketone bodies is formed within 2-5 days of fasting.The body maintains a low metabolic state by regulating changes in key genes in pathways such as glucose and lipid metabolism.

Two strains of porcine reproductive and respiratory syndrome virus (PRRSV) were isolated in 2006 and 2016 and designated as FZ06A and FZ16A, respectively. Inoculation experiments showed that FZ06A caused 100% morbidity and 60% mortality, while FZ16A caused 100% morbidity without death. By using genomic sequence and phylogenetic analyses, close relationships between a Chinese highly pathogenic PRRSV strain and the FZ06A and FZ16A strains were observed. Based on the achieved results, multiple genomic variations in Nsp2, a unique N-glycosylation site (N³³→K³³), and a K151 amino acid (AA) substitution for virulence in the GP5 of FZ16A were detected; except the 30 AA deletion in the Nsp2-coding region. Inoculation experiments were conducted and weaker virulence of FZ16A than FZ06A was observed. Based on our results, a 30 AA deletion in the Nsp2-coding region is an unreliable genomic indicator of a high virulence PRRSV strain. The Nsp2 and GP5 differences, in addition to the virulence difference between these two highly pathogenic PRRSV strains, have the potential to be used to establish a basis for further study of PRRSV virulence determinants and to provide data useful in the development of vaccines against this economically devastating disease.
Asian Continental Ancestry Group ; China ; Genomics ; Humans ; Mortality ; Phylogeny ; Porcine Reproductive and Respiratory Syndrome ; Porcine respiratory and reproductive syndrome virus ; Vaccines ; Virulence