Metformin modulates the gut microbiome in broiler breeder hens

Broiler breeder hens, the parent stock of commercial broiler chickens, are genetically selected for rapid growth. Due to a longer production period and the focus of genetic selection on superior carcass traits in their progeny, these hens have the propensity to gain excess adipose tissue and exhibit severe ovarian dysfunction, a phenotype that is similar to human polycystic ovary syndrome (PCOS). Metformin is an antihyperglycemic drug approved for type 2 diabetes that is prescribed off-label for PCOS with benefits on metabolic and reproductive health. An additional effect of metformin treatments in humans is modulation of gut microbiome composition, hypothesized to benefit glucose sensitivity and systemic inflammation. The effects of dietary metformin supplementation in broiler breeder hens have not been investigated, thus we hypothesized that dietary metformin supplementation would alter the gut microbiome of broiler breeder hens. Broiler breeder hens were supplemented with metformin at four different levels (0, 25, 50, and 75 mg/kg body weight) from 25-65 weeks of age, and a subset of hens (n=8-10 per treatment group) was randomly selected to undergo longitudinal microbiome profiling with 16S rRNA sequencing. Metformin impacted the microbial community composition in 75 mg/kg metformin compared to controls (adjusted PERMANOVA P = 0.0006) and an additional dose-dependent difference was observed between 25 mg/kg and 75 mg/kg (adjusted PERMANOVA P = 0.001) and between 50 mg/kg and 75 mg/kg (adjusted PERMANOVA P = 0.001) but not between 25 mg/kg and 50 mg/kg (adjusted PERMANOVA P = 0.863). There were few differences in the microbiome attributed to hen age, and metformin supplementation did not alter alpha diversity. Bacteria that were identified as differentially relatively abundant between 75 mg/kg metformin treatment and the control, and between metformin doses, included Ruminococcus and members of the Clostridia family that have been previously identified in human trials of PCOS. These results demonstrate that metformin impacts the microbiome of broiler breeder hens in a dose-dependent manner and several findings were consistent with PCOS in humans and with metformin treatment in type 2 diabetes. Metformin supplementation is a potentially promising option to improve gut health and reproductive efficiency in broiler breeder hens.

肉种母鸡（broiler breeder hens）作为商品肉鸡的父母代种鸡群，经遗传选育以获得快速生长性能。由于生产周期更长，且遗传选育聚焦于后代优异的胴体性状，这类种母鸡易过量积累脂肪组织，并表现出严重的卵巢功能障碍，其表型与人类多囊卵巢综合征（polycystic ovary syndrome, PCOS）相似。二甲双胍（Metformin）是获批用于治疗2型糖尿病的抗高血糖药物，目前被超适应症用于多囊卵巢综合征的治疗，可改善患者的代谢与生殖健康状况。人类使用二甲双胍治疗的额外效应是调节肠道菌群组成，该效应被推测可改善葡萄糖敏感性与全身炎症状态。目前尚无关于日粮添加二甲双胍对肉种母鸡影响的相关研究，因此本研究假设日粮添加二甲双胍可改变肉种母鸡的肠道菌群组成。本研究将肉种母鸡分为四组，日粮分别添加0、25、50、75 mg/kg体重剂量的二甲双胍，干预周期为25至65周龄；随后从每个处理组中随机选取8-10只个体，采用16S rRNA测序技术开展纵向肠道菌群谱分析。与对照组相比，75 mg/kg二甲双胍组的微生物群落组成发生了显著改变（校正后置换多元方差分析（permutational multivariate analysis of variance, PERMANOVA）P=0.0006）；此外，25 mg/kg与75 mg/kg组（校正后PERMANOVA P=0.001）、50 mg/kg与75 mg/kg组（校正后PERMANOVA P=0.001）之间均存在剂量依赖性的显著差异，但25 mg/kg与50 mg/kg组之间无显著差异（校正后PERMANOVA P=0.863）。母鸡日龄对肠道菌群的影响极小，且日粮添加二甲双胍未改变菌群的α多样性（alpha diversity）。本研究鉴定出在75 mg/kg二甲双胍组与对照组之间、以及不同二甲双胍剂量组之间相对丰度存在显著差异的细菌，包括瘤胃球菌属（Ruminococcus）及梭菌科（Clostridia family）成员，这类菌群此前在人类多囊卵巢综合征临床试验中已被报道。本研究结果表明，二甲双胍可通过剂量依赖性方式改变肉种母鸡的肠道菌群，且多项发现与人类多囊卵巢综合征及2型糖尿病患者的二甲双胍治疗效应相符。日粮添加二甲双胍或可成为改善肉种母鸡肠道健康与繁殖性能的潜在有效手段。