Department of Entomology, Cornell University, Ithaca, New York, United States of America.
Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York, United States of America.
PLoS Pathog. 2024 Aug 12;20(8):e1012447. doi: 10.1371/journal.ppat.1012447. eCollection 2024 Aug.
Overnutrition with dietary sugar can worsen infection outcomes in diverse organisms including insects and humans, through generally unknown mechanisms. In the present study, we show that adult Drosophila melanogaster fed high-sugar diets became more susceptible to infection by the Gram-negative bacteria Providencia rettgeri and Serratia marcescens. We found that P. rettgeri and S. marcescens proliferate more rapidly in D. melanogaster fed a high-sugar diet, resulting in increased probability of host death. D. melanogaster become hyperglycemic on the high-sugar diet, and we find evidence that the extra carbon availability may promote S. marcescens growth within the host. However, we found no evidence that increased carbon availability directly supports greater P. rettgeri growth. D. melanogaster on both diets fully induce transcription of antimicrobial peptide (AMP) genes in response to infection, but D. melanogaster provided with high-sugar diets show reduced production of AMP protein. Thus, overnutrition with dietary sugar may impair host immunity at the level of AMP translation. Our results demonstrate that dietary sugar can shape infection dynamics by impacting both host and pathogen, depending on the nutritional requirements of the pathogen and by altering the physiological capacity of the host to sustain an immune response.
饮食中的糖份过剩会通过一般未知的机制，使包括昆虫和人类在内的各种生物的感染结果恶化。在本研究中，我们发现喂食高糖饮食的成年黑腹果蝇更容易受到革兰氏阴性菌普罗维登斯菌和粘质沙雷氏菌的感染。我们发现，在喂食高糖饮食的果蝇中，普罗维登斯菌和粘质沙雷氏菌的繁殖速度更快，导致宿主死亡的可能性增加。果蝇在高糖饮食中会出现高血糖，我们有证据表明，额外的碳源可用性可能会促进沙雷氏菌在宿主内的生长。然而，我们没有发现证据表明，增加的碳源可用性直接支持普罗维登斯菌的生长。两种饮食下的果蝇在感染后都能完全诱导抗菌肽（AMP）基因的转录，但提供高糖饮食的果蝇 AMP 蛋白的产量降低。因此，饮食中的糖份过剩可能会在 AMP 翻译水平上损害宿主免疫力。我们的研究结果表明，饮食中的糖份可以通过影响宿主和病原体来塑造感染动态，这取决于病原体的营养需求以及改变宿主维持免疫反应的生理能力。
