Bacterial polysaccharides inhibit sucrose-induced hyperglycemia in silkworms

Abstract

Diabetes and obesity result from sucrose-induced hyperglycemia. Prevention of hyperglycemia contributes to inhibit the onset of these life-related diseases. Here we show that polysaccharides obtained from soil bacteria inhibit sucrose-induced hyperglycemia in an in vivo silkworm evaluation system. Ethanol precipitates of extracellular polysaccharides were prepared from viscous bacterial colonies. Among 24 samples obtained from different bacterial species, oral administration of 6 samples from Rhizobium altiplani, Cupriavidus sp., Paenibacillus polymyxa, Pantoea eucalypti, Variovorax boronicumulans, and Xanthomonas cynarae suppressed sucrose-induced hyperglycemia in silkworm insect larvae. The R. altiplani fraction treated further with DNase I, RNase A, and proteinase K, followed by phenol extraction also exhibited suppressive activity. Our results suggest that silkworms provide an efficient screening system of bacterial polysaccharides that inhibit sucrose-induced hyperglycemia.

Polysaccharides of a fermented food, natto, suppress sucrose-induced hyperglycemia in an <i>in vivo</i> evaluation system and inhibit glucose uptake by human intestinal cells

“…Silkworms are useful for large-scale in vivo evaluation because they are inexpensive and can be reared in large groups (21)(22)(23)(24)(25)(26)(27). We reported the discovery of several active substances that suppress postprandial hyperglycemia using the silkworm evaluation system (4,11,28). The inhibitory effects of each of the four natto products we examined on sucrose-induced hyperglycemia in silkworms differed.…”

“…Two volumes of ethanol were added to the water extract fraction, and a filamentous precipitate was collected by centrifugation to obtain a water-soluble viscous fraction. Enzymatic treatment of the water-soluble viscous fraction was performed as described previously (11). The watersoluble viscous fraction was treated with DNase I (1,000 U/mL; Promega) and RNase A (10 μg/mL; NIPPON GENE CO., LTD.) for 24 h at 37°C, and then incubated overnight at 37°C with proteinase K (100 µg/mL).…”

“…Polysaccharides derived from bacteria have diverse structures and physiologic activities (8)(9)(10). Polysaccharides produced by soil bacteria, such as Rhizobium altiplani, Cupriavidus sp., Paenibacillus polymyxa, Pantoea eucalypti, Variovorax boronicumulans, and Xanthomonas cynarae, inhibit sucrose-induced hyperglycemia in silkworms (11). Therefore, we hypothesized that polysaccharides secreted by other types of bacteria could suppress postprandial hyperglycemia.…”

Additive effects of Kothala himbutu (<i>Salacia reticulata</i>) extract and a lactic acid bacterium (<i>Enterococcus faecalis</i> YM0831) for suppression of sucrose-induced hyperglycemia in an <i>in vivo </i>silkworm evaluation system

“…Evaluation methods using mammals, however, are not only expensive, but are also associated with ethical issues with respect to animal welfare. We previously reported that the silkworm, an insect larva, can be used to evaluate the effects of different hypoglycemic agents (3)(4)(5)(6)(7)(8)(9). Ingestion of sucrose rapidly increases the blood glucose level in silkworms, and acarbose and voglibose, α-glucosidase inhibitors used clinically for human patients, also suppress the increase in silkworms (3).…”

Suppressive effects of whey protein hydrolysate on sucrose-induced hyperglycemia in silkworms

“…We previously reported diabetic silkworm models for evaluating anti-diabetic agents such as human insulin, pioglitazone, and metformin (6)(7)(8)(9). Moreover, we established a silkworm model to search for substances that suppress sucrose-induced hyperglycemia (10)(11)(12)(13). Enterococcus faecalis YM0831, a lactic acid bacteria strain that was identified using an in vivo silkworm evaluation system, suppresses sucrose-induced hyperglycemia in humans (14).…”