Coleoptera cholesterol

Coleoptera. The confused flour beetle, Tribollum confusum, was the first phytophagous insect we found that produces an appreciable amount of a sterol other than cholesterol from radiolabeled dietary C28 and C29 phytosterols. We found this insect produced large quantities of 7-dehydrocholesterol, equivalent to as much as 70% of the total tissue sterols isolated (12). It was further determined that cholesterol and 7-dehydrocTfolesterol were in equilibrium in this flour beetle. Another new intermediate, 5,7,24-cholestatrien-3B-ol was identified as an intermediate between desmosterol and 7-dehydrocholesterol (Figure 3). We found very similar pathways of sterol metabolism to exist in the closely related flour beetle, Tribolium castaneum (13). However, another flour beetle, Tenebrio moHtor, nad only about one-third or less of the levels of 7-dehydrocholesterol as the two Tribolium species, but still much higher levels of this sterol than has been found in most species. Fucosterol 24,28-epoxide was also implicated as an intermediate in the synthesis of cholesterol from sitosterol in T. mol i tor (14). 

Coleoptera. Sterol metabolism studies with another important stored products pest, the khapra beetle, Trogoderma granarium, revealed another phytophagous Insect that is unable to dealkylate and convert C28 and C29 phytosterols to cholesterol (23). Similar results were obtained whether a diet consisting of cracked wheat and brewer s yeast or an artificial diet coated with radiolabeled sterols was used (24). There was some selective uptake of cholesterol from tFe dietary sterols, as indicated by an enrichment of cholesterol in the pupal sterols 1.2% of total), compared to the dietary sterols (0.5% of total). Unlike the previously discussed stored product coleopteran pests, T. confusum and T. castaneum, both of which had high levels of 7-dehycTrochoiesterol, Tfo 7-dehydrocholesterol could be identified in the sterols from the khapra beetle. 

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