Ingestion of Megalo‐type Isomaltoglucosaccharides Ameliorates Lipopolysaccharide‐induced Acute Liver Injury in Rats

Abstract

BackgroundNon‐digestible saccharides modulate various immune responses depending on their structures, which may contribute to maintenance of our health. Megalo‐type Isomaltoglucosaccharides (M‐IMs) are composed of 10 to 50 glucose units with α‐1,6‐glycoside linkages. M‐IMs display delayed absorption and may stay relatively long time in the gastrointestinal tract, which enables them to encounter innate immune cells. Our previous study demonstrated that M‐IMs modulated macrophage functions in terms of pro‐inflammatory cytokine productions in primary culture. It is possible that M‐IMs regulate not only innate immunity, but also adaptive immunity in vivo. To evaluate this possibility, we investigated the influence of M‐IMs on acute inflammation and antigen‐specific antibody production.MethodsMale F344/Jcl rats (5 weeks old) were fed diets supplemented with or without M‐IMs (30 g/kg diet) for 5 weeks. Keyhole limpet hemocyanin (KLH) was administered subcutaneously (1 mg/rat) at the second weeks. We measured KLH‐specific IgM and IgG in the serum on day 7 and 18 after the administration, respectively. At the end of the experimental period, the rats were administrated with 4 mg/kg of lipopolysaccharide (LPS) to induce acute liver injury. At 6 hours after the LPS administration, the aorta plasma was collected to measure plasma alanine transaminase (ALT) activity, aspartate transaminase (AST) activity and TNF‐α concentration. The liver was collected to analyze gene expressions associated with immune functions with PCR array and RT‐qPCR.ResultsThere was no significant differences between groups in productions of serum KLH‐specific antibodies (IgM and IgG) and plasma TNF‐α. In contrast, AST and ALT activities were significantly attenuated in aorta plasma of the rats fed the diet with M‐IM although there was no change on the expression of pro‐inflammatory cytokines in the liver. The results suggest that M‐IMs partially protect LPS‐induced liver injury.ConclusionThe ingestion of M‐IMs is considered to modulate innate immune responses such as regulation of macrophage polarization rather than adaptive immune responses in vivo, which may be involved in amelioration or prevention of acute inflammation.Support or Funding InformationThis work was supported by the science and technology research promotion program for agriculture, forestry, fisheries and food industry of the Ministry of Agriculture, Forestry and Fisheries (MAFF) of the Japanese government for financial support.