Inflammatory bowel disease is characterized by extensive intestinal inflammation, and therapies against the disease target suppression of the inflammatory cascade. Nutrition has been closely linked to the development and suppression of inflammatory bowel disease, which to a large extent is attributed to the complex immunomodulatory properties of nutrients. Diets containing fish have been suggested to promote health and suppress inflammatory diseases. Even though most of the health-promoting properties of fish-derived nutrients are attributed to fish oil, the potential health-promoting properties of fish protein have not been investigated. Fish sidestreams contain large amounts of proteins, currently unexploited, with potential anti-inflammatory properties, and may possess additional benefits through bioactive peptides and free amino acids. In this project, we utilized fish protein hydrolysates, based on mackerel and salmon heads and backbones, as well as flounder skin collagen. Mice fed with a diet supplemented with different fish sidestream-derived protein hydrolysates (5% w/w) were exposed to the model of DSS-induced colitis. The results show that dietary supplements containing protein hydrolysates from salmon heads suppressed chemically-induced colitis development as determined by colon length and pro-inflammatory cytokine production. To evaluate colitis severity, we measured the expression of different pro-inflammatory cytokines and chemokines and found that the same supplement suppressed the pro-inflammatory cytokines IL-6 and TNFα and the chemokines Cxcl1 and Ccl3. We also assessed the levels of the anti-inflammatory cytokines IL-10 and Tgfb and found that selected protein hydrolysates induced their expression. Our findings demonstrate that protein hydrolysates derived from fish sidestreams possess anti-inflammatory properties in the model of DSS-induced colitis, providing a novel underexplored source of health-promoting dietary supplements.

Obesity and type 2 diabetes are characterized by low-grade systemic inflammation and glucose intolerance, which can be partially controlled with nutritional interventions. Protein-containing nutritional supplements possess health-promoting benefits. Herein, we examined the effect of dietary supplementation with protein hydrolysates derived from fish sidestreams on obesity and diabetes, utilizing a mouse model of High-Fat Diet-induced obesity and type 2 diabetes. We examined the effect of protein hydrolysates from salmon and mackerel backbone (HSB and HMB, respectively), salmon and mackerel heads (HSH and HMH, respectively), and fish collagen. The results showed that none of the dietary supplements affected weight gain, but HSH partially suppressed glucose intolerance, while HMB and HMH suppressed leptin increase in the adipose tissue. We further analyzed the gut microbiome, which contributes to the metabolic disease implicated in the development of type 2 diabetes, and found that supplementation with selected protein hydrolysates resulted in distinct changes in gut microbiome composition. The most prominent changes occurred when the diet was supplemented with fish collagen since it increased the abundance of beneficial bacteria and restricted the presence of harmful ones. Overall, the results suggest that protein hydrolysates derived from fish sidestreams can be utilized as dietary supplements with significant health benefits in the context of type 2 diabetes and diet-induced changes in the gut microbiome.

Borrelia burgdorferi (Bb), a vector-borne bacterial pathogen and the causative agent of Lyme disease, can spread to distant tissues in the human host by traveling in and through monolayers of endothelial cells (ECs) lining the vasculature. To examine whether Bb alters the physical forces of ECs to promote its dissemination, we exposed ECs to Bb and observed a sharp and transient increase in EC traction and intercellular forces, followed by a prolonged decrease in EC motility and physical forces. All variables returned to baseline at 24 h after exposure. RNA sequencing analysis revealed an upregulation of innate immune signaling pathways during early but not late Bb exposure. Exposure of ECs to heat-inactivated Bb recapitulated only the early weakening of EC mechanotransduction. The differential responses to live versus heat-inactivated Bb indicate a tight interplay between innate immune signaling and physical forces in host ECs and suggest their active modulation by Bb.

Cancer cells that seed in the lung require lipids often produced by alveolar type II (AT2) cells. However, whether overt metastases depend on AT2 cell–derived lipids and whether AT2 cells can be targeted to reduce metastasis growth remains unknown. We discovered that breast cancer–derived lung metastases stimulate the proliferation of AT2 cells in their vicinity and reprogram them into lipid feeder cells in mice and patients using spatial analysis. Mechanistically, the metastasis secretome activates the transcription factor sterol regulatory element–binding transcription factor 1 (SREBP-1) in AT2 cells, enhancing the expression of key de novo lipid synthesis genes, including fatty acid synthase (FASN) and glycerol-3-phosphate acyltransferase 1 (GPAM). Deleting Fasn selectively in AT2 cells or targeting FASN and GPAM systemically significantly impairs lung metastasis growth in mice. In summary, we discovered that overt metastases reprogram AT2 cells and that targeting the lipid metabolism of AT2 cells impairs metastasis growth. Significance: Current therapies in oncology targeting the cancer or immune cell compartment of tumors show limited efficacy against breast cancer–derived metastases. We discovered that decreasing the lipid metabolism of lung resident AT2 cells is sufficient to impair lung metastasis growth in mice without apparent adverse effects.

Supplementary Figure 1 Surfactant lipids are enriched in the vicinity of lung metastases from patients with breast cancer; Supplementary Figure 2 AT2 cells and surfactant lipids co-localize in the vicinity of metastases from mice; Supplementary Figure 3 Metastases progression increases the enrichment of AT2 cells; Supplementary Figure 4 The metastasis secretome reprograms AT2 cell lipid metabolism by activating SREBP-1; Supplementary Figure 5 Gpam knockdown in cancer cells does not affect 3D spheroid growth in vitro; Supplementary Figure 6 GPAM and FASN inhibition in cancer cells does not affect metastasis formation in vitro and in vivo