Although low-protein diets can improve the nitrogen utilization efficiency and alleviate economic pressures in ruminants, they may also negatively impact dairy performance. Rumen-protected lysine (RPL) supplementation can improve the health status and growth performance of ruminants without compromising nitrogen utilization efficiency and feed intake. In this study, a total of thirty-three multiparous dairy goats in the late-lactation period were randomly divided into three groups that were separately fed the control diet (namely the protein-adequacy group), the low-protein diet (namely the protein-deficient group), and the RPL-supplemented protein-deficient diet (namely RPL-supplementation group) for five weeks. Here, we investigated the molecular mechanisms regarding how low-protein diets with RPL supplementation compromise lactation phenotypes in dairy goats through cross-tissue transcriptomic analyses. Dietary protein deficiency caused an imbalance in amino acid (AA) intake, disrupted hepatic function, and impaired milk synthesis. Transcriptomic analyses further showed that RPL supplementation exhibited some beneficial effects, like mitigating abnormal lipid and energy metabolism in the liver, elevating hepatic resistance to oxidative stress, improving the mammary absorption of AAs, as well as activating mammary lipid and protein anabolism primarily through peroxisome proliferator-activated receptor (PPAR) and janus kinase-signal transducer (JAK)—signal transducer and activator of transcription (STAT) signaling, respectively. RPL supplementation of a low-protein diet contributes to maintaining late lactation in dairy goats primarily through mitigating hepatic energy disturbances and activating both lipid and protein metabolism in the mammary glands. Since RPL supplementation initiated a series of comprised events on mammary protein and lipid metabolism as well as the hepatic function and energy generation in dairy goats under protein deficiency during late lactation, these findings thus provide some insights into how RPL supplementation helps maintain milk production and health in dairy mammals especially at late lactation.

Background: Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder that poses management challenges due to the limited efficacy and adverse effects of current therapies. Saponins, a class of bioactive phytochemicals widely distributed in medicinal plants and other natural sources, exhibit antidiabetic activities through multi-target mechanisms, have emerged as promising therapeutic candidates for T2DM. This review systematically summarizes the pharmacological mechanisms and therapeutic potential of saponins in management of T2DM and its complications. Materials and methods: Studies involving molecular, cellular, animal, and clinical studies of saponins in T2DM and its complications were screened and analyzed to provide a systematic overview. All the literature information in this review was collected from relevant literature published up to 2025 from the scientific databases, including PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI). Results: The pathogenesis of T2DM is characterized by insulin resistance, β-cell dysfunction, genetic susceptibility, gut microbiota dysbiosis, and metabolic disturbances, leading to hyperglycemia and systemic complications. This review demonstrates that saponins exert multifaceted antidiabetic effects through modulating key signaling pathways, including Keap1/Nrf2, AMPK/PI3K/Akt, and NF-κB. Furthermore, saponins demonstrate significant organ-specific protection against major diabetic complications, such as nephropathy, cardiomyopathy, neuropathy, and retinopathy. Conclusion: Saponins represent a potent class of bioactive metabolites with multi-target therapeutic potential for T2DM and its complications. Their ability to simultaneously modulate metabolic, inflammatory, oxidative, mitochondrial, and gut microbiota-related pathways highlights clear advantages over single-target therapies. A growing body of research has underscored its potential clinical significance in T2DM, providing essential evidence for developing effective and safe therapeutic strategies.

Due to the substantial secretory burden, bovine mammary epithelial cells (BMECs) are highly susceptible to endoplasmic reticulum (ER) stress caused by the accumulation of misfolded proteins when protein-folding capacity is overwhelmed. However, how ATF3 regulates ER stress-induced impairment of milk synthesis and apoptosis in BMECs, particularly through its direct transcriptional targets, remains poorly understood. In this study, we investigated the protective role of activating transcription factor 3 (ATF3) against ER stress-induced impairment of milk synthesis in BMECs. Using a tunicamycin-induced ER stress model, we overexpressed ATF3 in BMECs and performed integrated RNA-seq and ChIP-seq analyses to elucidate the underlying molecular mechanisms. Our results indicated that ER stress disrupted milk protein and fat synthesis in BMECs by suppressing the expression of CSN2, FASN, FABP3 and promoting apoptosis via upregulation of BAX and CASP3. ATF3 overexpression effectively attenuated these effects, reducing apoptosis and restoring the expression of milk fat-related genes. Transcriptomics demonstrated that ATF3 activated MAPK and PI3K-Akt signaling and lipid metabolism pathways, significantly upregulating key genes involved in fatty acid uptake, transport, and metabolism (CD36, SLC27A1, ACSL1, PLIN1). Integrated RNA-seq and ChIP-seq analyses identified 81 overlapping genes, with RASGRP2, PRKACB, MAP3K5, and DUSP10 confirmed as direct transcriptional targets of ATF3, mediating its regulation of the MAPK pathway. Collectively, these findings elucidate the protective role of ATF3 against ER stress-induced lactation disruption and offer potential molecular targets for enhancing lactation resilience in dairy cattle under stress.