PMC

Sequoyitol decreases hyperglycemia and glucose intolerance and increases plasma insulin in STZ-treated mice. C57BL/6 males (9 wk) were intraperitoneally injected with STZ (160 mg/kg body wt) and randomly divided into control and sequoyitol-treated groups. Con (n = 8) mice had free access to water; sequoyitol (n = 8) mice had free access to water supplemented with sequoyitol (7 mg/ml). A: growth curves. B: randomly fed blood glucose (10:00–11:00 AM). C: plasma insulin levels 14 days after sequoyitol treatments (Con: n = 7; sequoyitol: n = 7). D: GTT (glucose: 0.6 g/kg body wt) 29 days after sequoyitol treatments. Values are means ± SE. *P < 0.05.

Sequoyitol enhances insulin signaling and suppresses glucose production in hepatocytes. A: HepG2 cells were pretreated without or with sequoyitol (100 μM) for 12 h before insulin (10 nM) stimulation (5 min). Cell extracts were immunoprecipitated with α-IRS1 and immunoblotted with α-PY. The blots were reprobed with α-IRS1. Cell extracts were also immunoblotted with α-pSer473 or α-Akt. B: pIRS1 and Akt were quantified by densitometry and normalized to total IRS1 and Akt levels, respectively (Con: n = 3; sequoyitol: n = 3). C: HepG2 cells were treated with or without sequoyitol (100 μM) in the presence or absence of TNFα (10 ng/ml) for 12 h and then stimulated with insulin (10 nM for 5 min). Cell extracts were immunoprecipitated with α-IR and α-IRS1 and immunoblotted with α-PY. The same blots were reprobed with α-IR or α-IRS1, respectively. Cell extracts were also immunoblotted with α-pSer473 or α-Akt. IR, IRS1, and Akt phosphorylation was quantified and normalized to total IR, IRS1, and Akt protein levels, respectively (Con: n = 3; sequoyitol: n = 3). D: HepG2 cells were pretreated with myo-inositol (100 μM) in the presence or absence of TNFα (10 ng/ml) for 12 h and then stimulated with insulin (10 nM for 5 min). Cell extracts were immunoprecipitated with α-IR and α-IRS1, and immunoblotted with α-PY, α-IR, or α-IRS1, respectively. Cell extracts were also immunoblotted with α-pSer473 or α-Akt. E: primary hepatocytes were prepared from C57BL/6 males, treated without or with sequoyitol (100 μM) overnight, stimulated with a vehicle, N⁶,2′-O-dibutyryladenosine 3′,5′-cyclic monophosphate sodium salt (DB-cAMP; 10 μM), or DB-cAMP plus insulin (100 nM), and subjected to glucose production assays. Glucose production was normalized to total hepatocyte protein levels (Con: n = 4; sequoyitol: n = 4). Each experiment was performed three times. Values are means ± SE. *P < 0.05.

Sequoyitol enhances insulin signaling and increases glucose uptake in adipocytes. A: 3T3-L1 preadipocytes were fully differentiated into adipocytes (day 8). The adipocytes were pretreated without or with sequoyitol (100 μM) for 12 h and then stimulated with insulin (10 nM) for 5 min. Cell extracts were immunoprecipitated with α-IR or α-IRS1 and immunoblotted with α-PY. The same blots were reprobed with α-IR or α-IRS1. B: pIRS1 and Akt were quantified by densitometry and normalized to total IRS1 and Akt levels, respectively (Con: n = 3; sequoyitol: n = 3). C: 3T3-L1 adipocytes were treated with or without sequoyitol (100 μM) in the presence or absence of TNFα (10 ng/ml) for 12 h and then stimulated with insulin (10 nM) for 5 min. Cell extracts were immunoprecipitated with α-IR and α-IRS1 and immunoblotted with α-PY, α-IR, or α-IRS1, respectively. Cell extracts were also immunoblotted with α-pSer473 or α-Akt. IR, IRS1, and Akt phosphorylation was quantified and normalized to total IR, IRS1, and Akt protein levels, respectively (Con: n = 3; sequoyitol: n = 3). D: 3T3-L1 adipocytes were treated with or without myo-inositol (100 μM) in the presence or absence of TNFα (10 ng/ml) for 12 h and then stimulated with insulin (10 nM) for 5 min. Insulin signaling was examined as described in C. E: 3T3-L1 adipocytes were pretreated without or with sequoyitol (100 μM) for 6 or 12 h. The cells were subsequently stimulated with or without insulin (10 nM) and subjected to glucose uptake assays. F: primary adipocytes were isolated from C57BL/6 males fed a high-fat diet for 8 wk, treated without or with sequoyitol (100 μM) for 3 h, stimulated with or without insulin (5 nM), and subjected to glucose uptake assays. Each experiment was performed three times. Values are means ± SE. *P < 0.05.

Sequoyitol protects against streptozotocin (STZ)- and H₂O₂-induced INS-1 β-cell death. A: INS-1 β-cells were incubated with sequoyitol for 3 h and then with STZ or H₂O₂ in the presence of sequoyitol for an additional 12 h. Cell viability was measured using MTT assays (n = 4 for each group). B: INS-1 cells were deprived of serum overnight, pretreated with or without 10 mg/ml sequoyitol for 6 h, and then stimulated with 50 nM insulin for 15 min. Cell extracts were immunoblotted with α-PY, α-IR, α-pSer473, or α-Akt. Values are means ± SE. *P < 0.05.