A postbiotic from Aspergillus oryzae attenuates the impact of heat stress in ectothermic and endothermic organisms

Abstract

Heat stress is detrimental to food-producing animals and animal productivity remains suboptimal despite the use of heat abatement strategies during summer. Global warming and the increase of frequency and intensity of heatwaves are likely to continue and, thus, exacerbate the problem of heat stress. Heat stress leads to the impairment of physiological and cellular functions of ectothermic and endothermic animals. Therefore, it is critical to conceive ways of protecting animals against the pathological effects of heat stress. In experiments with endothermic animals highly sensitive to heat (Bos taurus), we have previously reported that heat-induced systemic inflammation can be ameliorated in part by nutritional interventions. The experiments conducted in this report described molecular and physiological adaptations to heat stress using Drosophila melanogaster and dairy cow models. In this report, we expand previous work by first demonstrating that the addition of a postbiotic from Aspergillus oryzae (AO) into the culture medium of ectothermic animals (Drosophila melanogaster) improved survival to heat stress from 30 to 58%. This response was associated with downregulation of genes involved in the modulation of oxidative stress and immunity, most notably metallothionein B, C, and D. In line with these results, we subsequently showed that the supplementation with the AO postbiotic to lactating dairy cows experiencing heat stress decreased plasma concentrations of serum amyloid A and lipopolysaccharide-binding protein, and the expression of interleukin-6 in white blood cells. These alterations were paralleled by increased synthesis of energy-corrected milk and milk components, suggesting enhanced nutrient partitioning to lactogenesis and increased metabolic efficiency. In summary, this work provides evidence that a postbiotic from AO enhances thermal tolerance likely through a mechanism that entails reduced inflammation.

Figure 1

Cumulative egg production by D. melanogaster flies fed control or control medium supplemented with 5% of an Aspergillus oryzae postbiotic (AO). Mated, age-matched w¹¹¹⁸ females were maintained at a constant ambient temperature of either (A) 25 °C (standard culture conditions) or (B) 29 °C for 14 days. Data are least squares means ± SEM from 5 independent experiments (n = 5/experiment). Treatment × day interaction was not significant at 25 °C (P = 0.732) and 29 °C (P = 0.867). The effect of AO was significant at 25 °C (P = 0.021) and 29 °C (P = 0.004).

Figure 2

Survival (A) and differential gene expression profiles (B,C) of heat-stressed D. melanogaster flies maintained according to the feeding protocols C and AO. (A) Data are least square means ± SEM of flies survived the challenge of 39 °C heat exposure for 75 min after a subsequent recovery period of 24 h (*effect of AO, P < 0.0001). Results are from 9 independent experiments performed in two-to forth-fold determination with 18–22 flies per vial (N = 500 per condition). (B,C) Female, age-matched 10-day old D. melanogaster flies were placed in groups of 18–22 per vial containing control or AO medium and subsequently exposed to sub-lethal heat stress at 39 °C for 60 min. Data are log2 fold change of differentially expressed genes after (B) 60 min of heat stress (t₆₀) or (C) subsequent 180 min of recovery (t₂₄₀) from the challenge (n = 5/time point). Labeled, gray colored genes were affected by AO (adjusted P < 0.05).