Background Watermelon intake has demonstrated effects on blood pressure regulation along with other health benefits. Objective We hypothesized that intake of whole watermelon and products made from watermelon rind (WR) and watermelon skin (WS) would remediate metabolic complications in C57BL/6 J male mice fed a diet modeling a Western-style diet. Methods Ten-week-old male C57BL/6 J mice were provided either a low-fat (LF) diet [10% fat (by energy), 8% sucrose (by energy) and no added cholesterol], a high-fat (HF) diet [45% fat (by energy), 20% kcal sucrose (by energy), and 1% (w/w) cholesterol], or an HF diet plus WS, WR, or watermelon flesh (WF) for 10 wk. Dried WF was provided at 8% of total energy (equivalent to 2 servings/d) and watermelon skin and rind were added at 2.25% (w/w, dry weight of additives) of diet. Animals were provided experimental diets ad libitum. Body weights, food intake, and glucose tolerance were determined. Serum insulin, inflammatory markers, microbiome, and the relative hepatic concentrations of 709 biochemicals were measured postmortem. Results The final body weight of the LF control group was significantly lower than that of the HF-fed control group (32.8 ± 0.9 g compared with 43.0 ± 1.7 g, P ≤ 0.05). Mice in treatment groups fed HF supplemented with watermelon products had final body weights similar to those of the HF-fed control mice. Serum insulin concentrations were reduced by ∼40% in mice fed an HF diet with WR supplementation compared with mice fed an HF diet alone (P ≤ 0.05). Depending on the individual species or group, microbiome populations changed significantly. Supplementation with WF resulted in a return to the basal hepatic concentrations of monohydroxy fatty acids and eicosanoids observed in LF-fed mice (P ≤ 0.05). Conclusions In obese male mice, supplementation with each of the watermelon products to an HF diet improved fasting blood glucose, circulating serum insulin concentrations, and changes in hepatic metabolite accumulation. At a modest level of supplementation to an HF diet, fiber-rich additives made from WR and WS further improved glucose metabolism and energy efficiency and shifted the microbiome composition.

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Background Sea vegetables are rich sources of nutrients as well as bioactive components that are linked to metabolic health improvement. Algal polysaccharides improve satiety and modulate gut microbiota while proteins, peptides, and phenolic fractions exert anti-inflammatory, antioxidant, and antidiabetic effects. Objective We tested the hypothesis that dietary supplementation with either Pacific dulse (Palmaria mollis, red algae) or wakame (Undaria pinnatifida, brown algae) could remediate metabolic complications in high-fat diet-induced obesity. Methods Individually caged C57BL/6J mice (n = 8) were fed ad libitum with either a low-fat diet (LFD), 10% kcal fat; high-fat diet (HFD), 60% kcal fat; HFD + 5% (wt:wt) dulse (HFD + D); or HFD + 5% (wt:wt) wakame (HFD + W) for 8 weeks. Food intake and weight gain were monitored weekly. Glucose tolerance, hepatic lipids, fecal lipids, and plasma markers were evaluated, and the gut microbiome composition was assessed. Results Despite the tendency of higher food and caloric intake than the HFD (P = 0.04) group, the HFD + D group mice did not exhibit higher body weight, indicating lower food and caloric efficiency (P < 0.001). Sea vegetable supplementation reduced plasma monocyte chemotactic protein (MCP-1) (P < 0.001) and increased fecal lipid excretion (P < 0.001). Gut microbiome analysis showed that the HFD + D group had higher alpha-diversity than the HFD or LFD group, whereas beta-diversity analyses indicated that sea vegetable–supplemented HFD-fed mice (HFD + D and HFD + W groups) developed microbiome compositions more similar to those of the LFD-fed mice than those of the HFD-fed mice. Conclusion Sea vegetable supplementation showed protective effects against obesity-associated metabolic complications in C57BL/6J male mice by increasing lipid excretion, reducing systemic inflammatory marker, and mitigating gut microbiome alteration. While the obese phenotype development was not prevented, metabolic issues related to lipid absorption, inflammation, and gut microbial balance were improved, showing therapeutic promise and warranting eventual mechanistic elucidations.

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Tuna backbone peptide (TBP) has been reported to exert potent inhibitory activity against lipid peroxidation in vitro. Since this bears relevant physiological implications, this study was undertaken to assess the impact of peptide modifications on its bioactivity and other therapeutic potential using in vitro and in silico approach. Some TBP analogs, despite lower purity than the parent peptide, exerted promising antioxidant activities in vitro demonstrated by ABTS radical scavenging assay and cellular antioxidant activity assay. In silico digestion of the peptides resulted in the generation of antioxidant, angiotensin-converting enzyme (ACE), and dipeptidyl peptidase-IV (DPPIV) inhibitory dipeptides. Using bioinformatics platforms, we found five stable TBP analogs that hold therapeutic potential with their predicted multifunctionality, stability, non-toxicity, and low bitterness intensity. This work shows how screening and prospecting for bioactive peptides can be improved with the use of in vitro and in silico approaches.