Inadequate copper intake and increased fructose consumption represent two important nutritional problems in the USA. Dietary copper-fructose interactions alter gut microbial activity and contribute to the development of nonalcoholic fatty liver disease (NAFLD). The aim of this study is to determine whether dietary copper-fructose interactions alter gut microbial activity in a sex-differential manner and whether sex differences in gut microbial activity are associated with sex differences in hepatic steatosis. Male and female weanling Sprague-Dawley (SD) rats were fed ad libitum with an AIN-93G purified rodent diet with defined copper content for 8 weeks. The copper content is 6 mg/kg and 1.5 mg/kg in adequate copper diet (CuA) and marginal copper diet (CuM), respectively. Animals had free access to either deionized water or deionized water containing 10% fructose (F) (w/v) as the only drink during the experiment. Body weight, calorie intake, plasma alanine aminotransferase, aspartate aminotransferase, and liver histology as well as liver triglyceride were evaluated. Fecal microbial contents were analyzed by 16S ribosomal RNA (16S rRNA) sequencing. Fecal and cecal short-chain fatty acids (SCFAs) were determined by gas chromatography-mass spectrometry (GC-MS). Male and female rats exhibit similar trends of changes in the body weight gain and calorie intake in response to dietary copper and fructose, with a generally higher level in male rats. Several female rats in the CuAF group developed mild steatosis, while no obvious steatosis was observed in male rats fed with CuAF or CuMF diets. Fecal 16S rRNA sequencing analysis revealed distinct alterations of the gut microbiome in male and female rats. Linear discriminant analysis (LDA) effect size (LEfSe) identified sex-specific abundant taxa in different groups. Further, total SCFAs, as well as, butyrate were decreased in a more pronounced manner in female CuMF rats than in male rats. Of note, the decreased SCFAs are concomitant with the reduced SCFA producers, but not correlated to hepatic steatosis. Our data demonstrated sex differences in the alterations of gut microbial abundance, activities, and hepatic steatosis in response to dietary copper-fructose interaction in rats. The correlation between sex differences in metabolic phenotypes and alterations of gut microbial activities remains elusive.

中文翻译：

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膳食铜-果糖相互作用引起的肠道微生物活性改变与肝脂肪变性的性别差异分析


铜摄入不足和果糖消耗增加是美国的两个重要营养问题。膳食铜-果糖相互作用会改变肠道微生物活性，并导致非酒精性脂肪肝（NAFLD）的发展。本研究的目的是确定膳食铜-果糖相互作用是否以性别差异的方式改变肠道微生物活性，以及​​肠道微生物活性的性别差异是否与肝脂肪变性的性别差异相关。雄性和雌性断奶 Sprague-Dawley (SD) 大鼠随意喂食具有规定铜含量的 AIN-93G 纯化啮齿动物饮食 8 周。足铜日粮（CuA）和边际铜日粮（CuM）中铜含量分别为6 mg/kg和1.5 mg/kg。实验期间动物可以自由饮用去离子水或含有10%果糖(F)(w/v)的去离子水作为唯一饮料。评估体重、热量摄入、血浆丙氨酸转氨酶、天冬氨酸转氨酶、肝脏组织学以及肝脏甘油三酯。通过 16S 核糖体 RNA (16S rRNA) 测序分析粪便微生物含量。通过气相色谱-质谱法 (GC-MS) 测定粪便和盲肠短链脂肪酸 (SCFA)。雄性和雌性大鼠对膳食铜和果糖的体重增加和热量摄入变化表现出相似的趋势，其中雄性大鼠的水平普遍较高。 CuAF组中的几只雌性大鼠出现轻度脂肪变性，而喂食CuAF或CuMF饮食的雄性大鼠则没有观察到明显的脂肪变性。粪便 16S rRNA 测序分析揭示了雄性和雌性大鼠肠道微生物组的明显变化。 线性判别分析（LDA）效应大小（LEfSe）确定了不同群体中性别特异性丰富的分类群。此外，雌性 CuMF 大鼠中总 SCFA 以及丁酸盐的降低程度比雄性大鼠更显着。值得注意的是，SCFA 的减少与 SCFA 产生量的减少同时发生，但与肝脂肪变性无关。我们的数据表明，大鼠肠道微生物丰度、活性和肝脏脂肪变性的变化因膳食铜-果糖相互作用而存在性别差异。代谢表型的性别差异与肠道微生物活性改变之间的相关性仍然难以捉摸。