Physicochemical Properties, Structural Characterization, Immunoenhancing and Hypoglycemic Activities of Fucoidan Extracts from Two Sargassums Species

In this study, the chemical compositions, structures, immunomodulatory and hypoglycemic activities of fucoidans from Sargassum zhangii (SZ-Fuc) and Sargassum hemiphylla (SH-Fuc) were analyzed and compared. The results showed that the sulfate group content and molecular mass of SZ-Fuc were (29.74 ± 0.01)% and 111.28 kDa, respectively, and SZ-Fuc had a relatively loose surface structure. The main chain of SZ-Fuc was composed of (→1) linked fucose, xylose, glucose, mannose and galactose, (1→3)- and (1→4)- linked xylose, (1→2)-linked mannose, (1→3)-, (1→4)- and (1→6)-linked galactose, and (1→4)- and (1→6)-linked glucose. Meanwhile, the sulfate group content and molecular mass of SH-Fuc were (44.11 ± 0.01)% and 1 166.48 kDa, respectively, SH-Fuc had a compact surface structure, and its main chain contained (→1), (1→3)- and (1→4)-linked fucose, (→1), (1→4)- and (1→6)-linked glucose, (→1) and (1→2)-linked mannose, and (1→4)-linked galactose. Besides, both SZ-Fuc and SH-Fuc had branched structures. They significantly increased NO release from RAW264.7 cells and improved the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), indicating good immunomodulatory activity. The immunomodulatory activity of SZ-Fuc was better than that of SH-Fuc, while the inhibitory effect of SH-Fuc on α-glucosidase was better than that of SZ-Fuc, suggesting that SH-Fuc had better hypoglycemic potential. This study can provide a theoretical basis for polysaccharides from S. zhangii and S. hemiphylla in the development of functional and nutritional foods with immunomodulatory and blood glucose-reducing activity

Associations between trajectories of cardiovascular risk factor change and cognitive impairment in Chinese elderly: A nationwide cohort study

Objectives: This study aimed to investigate the relationship between long-term trajectories of changes in cardiovascular risk factors (CVRFs) and the risk of cognitive impairment among Chinese adults over 60 years old. Methods: Data were obtained from the Chinese Longitudinal Healthy Longevity Survey 2005–2018. Cognitive function was evaluated longitudinally through the Chinese version of the Mini-Mental State Examination (C-MMSE), and cognitive impairment (C-MMSE ≤23) was used as the main outcome variable. The cardiovascular risk factors, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), and body mass index (BMI), were continuously measured in the follow-up duration. The patterns of trajectories of changes in CVRFs were derived from the latent growth mixture model (LGMM). The Cox regression model was used to evaluate the cognitive impairment hazard ratio (HR) across different CVRF trajectories. Results: A total of 5,164 participants aged ≥60 years with normal cognitive function at baseline were included in the study. After a median follow-up of 8 years, 2,071 participants (40.1%) developed cognitive impairment (C-MMSE ≤ 23). The four-class trajectories of SBP and BMI were obtained by means of LGMM, and the trajectories of DBP, MAP, and PP were grouped into a three-class subgroup. In the final adjusted Cox model, the lowered SBP [adjusted HR (aHR): 1.59; 95% CI: 1.17–2.16], lowered PP (aHR: 2.64; 95% CI: 1.66–4.19), and progressively obese (aHR: 1.28; 95% CI: 1.02–1.62) and stable slim (aHR: 1.13; 95% CI: 1.02–1.25) were associated with the higher risk of cognitive impairment. Low stable DBP (aHR: 0.80; 95% CI: 0.66–0.96) and elevated PP (aHR: 0.76; 95% CI: 0.63–0.92) decreased the risk for cognitive impairment among participants. Conclusion: Lowered SBP, lowered PP, progressive obesity, and stable slim increased the risk for cognitive impairment in the Chinese elderly. Low stable DBP and elevated PP were protective against cognitive impairment, but more DBP lowering and ≥25 mmHg growth in PP contributed to a higher risk of cognitive impairment. The findings have important implications for preventing cognitive impairment in elder adults based on the long-term trajectories of changes in CVRFs

Soil diazotrophic abundance, diversity, and community assembly mechanisms significantly differ between glacier riparian wetlands and their adjacent alpine meadows

Global warming can trigger dramatic glacier area shrinkage and change the flux of glacial runoff, leading to the expansion and subsequent retreat of riparian wetlands. This elicits the interconversion of riparian wetlands and their adjacent ecosystems (e.g., alpine meadows), probably significantly impacting ecosystem nitrogen input by changing soil diazotrophic communities. However, the soil diazotrophic community differences between glacial riparian wetlands and their adjacent ecosystems remain largely unexplored. Here, soils were collected from riparian wetlands and their adjacent alpine meadows at six locations from glacier foreland to lake mouth along a typical Tibetan glacial river in the Namtso watershed. The abundance and diversity of soil diazotrophs were determined by real-time PCR and amplicon sequencing based on nifH gene. The soil diazotrophic community assembly mechanisms were analyzed via iCAMP, a recently developed null model-based method. The results showed that compared with the riparian wetlands, the abundance and diversity of the diazotrophs in the alpine meadow soils significantly decreased. The soil diazotrophic community profiles also significantly differed between the riparian wetlands and alpine meadows. For example, compared with the alpine meadows, the relative abundance of chemoheterotrophic and sulfate-respiration diazotrophs was significantly higher in the riparian wetland soils. In contrast, the diazotrophs related to ureolysis, photoautotrophy, and denitrification were significantly enriched in the alpine meadow soils. The iCAMP analysis showed that the assembly of soil diazotrophic community was mainly controlled by drift and dispersal limitation. Compared with the riparian wetlands, the assembly of the alpine meadow soil diazotrophic community was more affected by dispersal limitation and homogeneous selection. These findings suggest that the conversion of riparian wetlands and alpine meadows can significantly alter soil diazotrophic community and probably the ecosystem nitrogen input mechanisms, highlighting the enormous effects of climate change on alpine ecosystems

Structural and biochemical studies of human lysine methyltransferase Smyd3 reveal the important functional roles of its post-SET and TPR domains and the regulation of its activity by DNA binding

The SET- and MYND-domain containing (Smyd) proteins constitute a special subfamily of the SET-containing lysine methyltransferases. Here we present the structure of full-length human Smyd3 in complex with S-adenosyl-l-homocysteine at 2.8 Å resolution. Smyd3 affords the first example that other region(s) besides the SET domain and its flanking regions participate in the formation of the active site. Structural analysis shows that the previously uncharacterized C-terminal domain of Smyd3 contains a tetratrico-peptide repeat (TPR) domain which together with the SET and post-SET domains forms a deep, narrow substrate binding pocket. Our data demonstrate the important roles of both TPR and post-SET domains in the histone lysine methyltransferase (HKMT) activity of Smyd3, and show that the hydroxyl group of Tyr239 is critical for the enzymatic activity. The characteristic MYND domain is located nearby to the substrate binding pocket and exhibits a largely positively charged surface. Further biochemical assays show that DNA binding of Smyd3 can stimulate its HKMT activity and the process may be mediated via the MYND domain through direct DNA binding