Sterol and lipid metabolism in bees

Abstract

Background Bees provide essential pollination services for many food crops and are critical in supporting wild plant diversity. However, the dietary landscape of pollen food sources for social and solitary bees has changed because of agricultural intensification and habitat loss. For this reason, understanding the basic nutrient metabolism and meeting the nutritional needs of bees is becoming an urgent requirement for agriculture and conservation. We know that pollen is the principal source of dietary fat and sterols for pollinators, but a precise understanding of what the essential nutrients are and how much is needed is not yet clear. Sterols are key for producing the hormones that control development and may be present in cell membranes, where fatty-acid-containing species are important structural and signalling molecules (phospholipids) or to supply, store and distribute energy (glycerides). Aim of the review In this critical review, we examine the current general understanding of sterol and lipid metabolism of social and solitary bees from a variety of literature sources and discuss implications for bee health. Key scientific concepts of review We found that while eusocial bees are resilient to some dietary variation in sterol supply the scope for this is limited. The evidence of both de novo lipogenesis and a dietary need for particular fatty acids (FAs) shows that FA metabolism in insects is analogous to mammals but with distinct features. Bees rely on their dietary intake for essential sterols and lipids in a way that is dependent upon pollen availability.

The effect of pollen monodiets on fat body morphology parameters and energy substrate levels in the fat body and hemolymph of Apis mellifera L. workers

“…The nutritional value of pollen lies not only in the proteins but also the fats. Pollen is also the principal dietary source of sterols, triglycerides and phospholipids 67 . Fatty acids are stored in the form of triglycerides as energy reserves for use in the fat body.…”

Expression of honey bee (Apis mellifera) sterol homeostasis genes in food jelly producing glands of workers

“…Sterols are essential nutrients ensuring cell and organelle membrane integrity and are precursors for the synthesis of hormones (Hartmann, 1998;Jing & Behmer, 2020). Honey bees as with most insects, are unable to synthesize sterols de novo (Ritter & Wientjens, 1967) and thus have to acquire sterols from their pollen diet (Furse et al, 2023;Svoboda, Herbert, Lusby, et al, 1983;Wright et al, 2018). Plants synthesize a variety of phytosterols, such as campesterol, sitosterol, and 24-methylenecholesterol (24MC).…”

“…In contrast to many other insects, honey bees are not able to convert C 28 and C 29 phytosterols into C 27 cholesterol for further use , which means that they have to integrate them directly into their membranes. As C 28 and C 29 phytosterols are always the main sterols of different honey bee life stages and organs (Buttstedt et al, 2023b;Svoboda et al, 1980;Svoboda, Herbert, Lusby, et al, 1983;Svoboda, Herbert, Thompson, & Feldlaufer, 1986), direct membrane integration is strongly indicated even though this has never been shown specifically (Furse et al, 2023). Further, phytosterols are used for synthesis of the molting hormone makisterone A .…”

Quantifying the production of plant pollen at the farm scale

“…If either of these essential nutrients are in low supply during development, this can lead to negative effects on adult bee physiology and offspring performance (K€ a mper et al, 2016;Bukovinszky et al, 2017;Rotheray et al, 2017;Woodard & Jha, 2017). Proteins and lipids comprise a large proportion of pollen mass, but their relative concentration differs considerably amongst plant species (Buchman, 1986;Roulston & Cane, 2000;Donkersley et al, 2014;Vaudo et al, 2020;Furse et al, 2023b). This variation in the protein: lipid ratio of pollen is thought to be a major driver of foraging behaviour in bees (Vaudo et al, 2020(Vaudo et al, , 2024.…”