In mammals, peripheral serotonin is involved in regulating energy balance. Herein, we characterized the transcriptomic profile and microstructure of adipose and muscle in pre-weaned calves with increased circulating serotonin. Holstein bull calves (21 ± 2 days old) were fed milk replacer supplemented with saline (CON, 8 mL/day n = 4) or 5-hydroxytryptophan (5-HTP, 90 mg/day, n = 4) for 10 consecutive days. Calves were euthanized on d10 to harvest adipose and muscle for RNA-Sequencing and histological analyses. Twenty-two genes were differentially expressed in adipose, and 33 in muscle. Notably, Interferon gamma inducible protein-47 was highly expressed and upregulated in muscle and adipose (avg. log FC = 6.5). Enriched pathways in adipose tissue revealed serotonin’s participation in lipid metabolism and PPAR signaling. In muscle, enriched pathways were related to histone acetyltransferase binding, Jak-STAT signaling, PI3K-Akt signaling and cell proliferation. Supplementation of 5-HTP increased cell proliferation and total cell number in adipose and muscle. Adipocyte surface area was smaller and muscle fiber area was not different in the 5-HTP group. Manipulating the serotonin pathway, through oral supplementation of 5-HTP, influences signaling pathways and cellular processes in adipose and muscle related to endocrine and metabolic functions which might translate into improvements in calf growth and development.

在哺乳动物中，外周血清素参与调节能量平衡。在此，我们表征了具有增加的循环血清素的断奶前犊牛脂肪和肌肉的转录组学特征和微观结构。荷斯坦公牛犊（21 ± 2 天）连续 10 天喂食补充有生理盐水（CON，8 毫升/天，n  = 4）或 5-羟色氨酸（5-HTP，90 毫克/天，n  = 4）的代乳品. 小牛在第 10 天被安乐死以收获脂肪和肌肉用于 RNA 测序和组织学分析。22 个基因在脂肪中差异表达，33 个在肌肉中差异表达。值得注意的是，干扰素γ诱导蛋白47在肌肉和脂肪中高度表达和上调（平均 log FC = 6.5）。脂肪组织中的丰富通路揭示了血清素参与脂质代谢和PPAR 信号传导。在肌肉中，丰富的通路与组蛋白乙酰转移酶结合、Jak-STAT 信号、PI3K-Akt 信号和细胞增殖有关. 补充 5-HTP 可增加脂肪和肌肉中的细胞增殖和总细胞数。5-HTP 组的脂肪细胞表面积较小，肌肉纤维面积没有差异。通过口服补充 5-HTP 来控制血清素通路，影响脂肪和肌肉中与内分泌和代谢功能相关的信号通路和细胞过程，这可能转化为小牛生长发育的改善。