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Figure 1. The structure, molecular weight, and sulfation concentration of fucoidans from 5 sea cucumbers. 2,4DS-fucose was defined as fucose A, following with fucoses B, C, and D. Sulfation at fucose B and D (neighboring fucose A) was named sulfation at ortho-fucose position, while sulfation at fucose C (spacing fucose A) was named sulfation at meta-fucose position [19,20]. Acaudina molpadioides fucoidans, Am-FUC; Isostichopus badionotus fucoidans, Ib-LFUC; Thelenota ananas fucoidans, Ta-LFUC; Holothuria tubulosa fucoidans, Ht-LFUC; Pearsonothuria graeffei fucoidans, Pg-LFUC.
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Figure 2. Effects of Am-FUC with different molecular weights on alleviating insulin resistance in HFD-fed mice. Acaudina molpadioides fucoidans, Am-FUC. Am-FUC and the 4 depolymerized Am-LFUCs had the similar sulfate contents and different Mw. (A), Body weight gain; (B), Fasting blood glucose; (C), Serum insulin; (D), homeostasis model assessment of insulin resistance index (HOMA-IR) value; (E), quantitative insulin sensitivity check index (QUICKI) score; (F), oral glucose tolerance test (OGTT); (G), areas under the curve (AUC) in OGTT test; (H), intraperitoneal insulin tolerance test (IITT); (I), AUC in IITT test; (J), Hepatic glycogen; (K), GP activities; (L), PK activities; (M), HK activities; (N), G6Pase activities; (O), p-GS protein expression (p-GS and GS, 85 kDa); (P), m-Glut4 protein expression (m-Glut4 and Glut4, 43 kDa). Body weight gain was assessed using 12 mice. OGTT and IITT were assessed using 6 mice, respectively. p-GS protein was assessed using the 3 mice with 40 U/kg insulin stimulation while m-Glut4 protein was assessed with 0.5 U/kg insulin. The other parameters were assessed using the 6 mice treated with normal saline. Different lowercase letters represent significant difference (p < 0.05) compared between groups.
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Figure 3. Comparatively analyzing the effects of between Am-FUC and Ht-FUC (similar molecular weight but different sulfation concentration) on alleviating insulin resistance in HFD-fed mice. Acaudina molpadioides fucoidans, Am-FUC; Holothuria tubulosa fucoidans, Ht-LFUC. (A), Body weight gain; (B), Fasting blood glucose; (C), Serum insulin; (D), HOMIA-IR value; (E), QUICKI score; (F), OGTT test; (G), AUC in OGTT test; (H), IITT test; (I), AUC in IITT test; (J), Hepatic glycogen; (K), GP activities; (L), PK activities; (M), HK activities; (N), G6Pase activities; (O), p-GS protein expression (p-GS and GS, 85 kDa); (P), m-Glut4 protein expression (m-Glut4 and Glut4, 43 kDa). Body weight gain was assessed using 12 mice. OGTT and IITT were assessed using 6 mice, respectively. p-GS protein was assessed using the 3 mice with 40 U/kg insulin stimulation while m-Glut4 protein as 0.5 U/kg insulin. The other parameters were assessed using the 6 mice treated with normal saline. Different lowercase letters represent significant difference (p < 0.05) compared between groups.
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Figure 4. Comparatively analyzing the effects of between Ta-LFUC and Ib-FUC (a similar molecular weight but different sulfation concentration), Ta-LFUC with sulfation at ortho-fucose and Am-FUC with sulfation at meta-position (quite molecular weight and sulfation concentration) on hepatic p-GS protein expression and skeletal muscle m-Glut4 protein expression in HFD-fed mice. Acaudina molpadioides fucoidans, Am-FUC; Isostichopus badionotus fucoidans, Ib-LFUC; Thelenota ananas fucoidans, Ta-LFUC. (A), p-GS protein expression (Ta-LFUC vs. Ib-FUC; p-GS and GS, 85 kDa); (B), m-Glut4 protein expression (Ta-LFUC vs. Ib-FUC; m-Glut4 and Glut4, 43 kDa); (C), p-GS protein expression (Ta-FUC vs. Am-FUC); (D), m-Glut4 protein expression (Ta-FUC vs. Am-FUC). p-GS protein was assessed using the 3 mice with 40 U/kg insulin stimulation while m-Glut4 protein as 0.5 U/kg insulin. Different lowercase letters represent significant difference (p < 0.05) compared between groups.
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Figure 5. Comparatively analyzing the effects of between Am-LFUC3 with 2-O-sulfation and Pg-FUC with 4-O-sulfation (quite molecular weight and sulfation concentration) on alleviating insulin resistance in HFD-fed mice. Acaudina molpadioides fucoidans, Am-FUC; Pearsonothuria graeffei fucoidans, Pg-LFUC. (A), Body weight gain; (B), Fasting blood glucose; (C), Serum insulin; (D), HOMIA-IR value; (E), QUICKI score; (F), OGTT test; (G), AUC in OGTT test; (H), IITT test; (I), AUC in IITT test; (J), Hepatic glycogen; (K), GP activities; (L), PK activities; (M), HK activities; (N), G6Pase activities; (O), p-GS protein expression (p-GS and GS, 85 kDa); (P), m-Glut4 protein expression (m-Glut4 and Glut4, 43 kDa). Body weight gain was assessed using 12 mice. OGTT and IITT were assessed using 6 mice, respectively. p-GS protein was assessed using the 3 mice with 40 U/kg insulin stimulation while m-Glut4 protein as 0.5 U/kg insulin. The other parameters were assessed using the 6 mice treated with normal saline. Different lowercase letters represent significant difference (p < 0.05) compared between groups.
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Figure 6. The structure–activity relationship of fucoidans from sea cucumber on improvement of insulin resistance. Our data showed that low molecular, sulfate at meta-fucose, and 4-O-sulfation played a significant part in the insulin resistant alleviation of fucoidans in mice.
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