• Journal of Life Science
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• v.24 no.1
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• pp.86-91
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• 2014

Trichoplusia ni cells are used as a host permissive cell line in the baculovirus expression system, which is useful for large-scale production of human sugar transport proteins. However, the activity of endogenous sugar transport systems in insect cells is extremely high. Therefore, the transport activity resulting from the expression of exogenous transporters is difficult to detect. Furthermore, very little is known about the nature of endogenous insect transporters. To exploit the expression system further, the effect of D-fructose on 2-deoxy-D-glucose (2dGlc) transport by T. ni cells was investigated, and T. ni cell-expressed human transporters were photolabeled with [$^3H$] cytochalasin B to develop a convenient method for measuring the biological activity of insect cell-expressed transporters. The uptake of 1 mM 2dGlc by uninfected- and recombinant AcMPV-GTL infected cells was examined in the presence and absence of 300 mM of D-fructose, with and without $20{\mu}M$ of cytochalasin B. The sugar uptake in the uninfected cells was strongly inhibited by fructose but only poorly inhibited by cytochalasin B. Interestingly, the AcMPV-GTL-infected cells showed an essentially identical pattern of transport inhibition, and the rate of 2dGlc uptake was somewhat less than that seen in the non-infected cells. In addition, a sharply labeled peak was produced only in the AcMPV-GTL-infected membranes labeled with [$^3H$] cytochalasin B in the presence of L-glucose. No peak of labeling was seen in the membranes prepared from the uninfected cells. Furthermore, photolabeling of the expressed protein was completely inhibited by the presence of D-glucose, demonstrating the stereoselectivity of labeling.

• Journal of Life Science
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• v.27 no.3
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• pp.289-294
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• 2017

Diabetes mellitus is associated with insulin resistance, which leads to down-regulation of insulin signaling and the decreased glucose uptake. Adipocytes are sensitive to insulin, and closely implicated in insulin resistance and diabetes. Insulin stimulates differentiation of preadipocytes to adipocytes, and increases glucose transport. Allium species have been used as traditional medicine and health-promoting foods. Allium hookeri (A. hookeri) is reported to improve the pancreatic ${\beta}-cell$ damage and exhibit pancreatic anti-inflammatory activity in streptozotocin-induced diabetic rats. We investigated whether A. hookeri extract (AHE) may stimulate glucose uptake in adipocytes through increasing insulin sensitivity. AHE enhanced fat accumulation, a differentiation biomarker, under the partial induction of differentiation by insulin. $PPAR{\gamma}$, a transcription factor highly expressed in adipocytes, promotes adipocyte differentiation and insulin sensitivity. AHE increased the differentiation of preadipocytes through up-regulation of $PPAR{\gamma}$. The activation of $PPAR{\gamma}$ increases the GLUT4 expression during adipocyte differentiation. GLUT4 is responsible for glucose uptake into the adipocytes. AHE increased the expression of GLUT4 in adipocytes, and subsequently enhanced the insulin-stimulated glucose uptake. These results suggest that AHE promotes adipocyte differentiation through activation of $PPAR{\gamma}$, and leads to enhance glucose uptake in adipocytes along with GLUT4 up-regulation. Thus, AHE may be effective for the insulin-sensitizing and anti-diabetic activities.