GC–MS Lipidomics Reveals Sublethal Deltamethrin Exposure Disrupts Honey Bee Brain Fatty Acid Homeostasis

Honey bees and other pollinators are increasingly at risk from chemicals in the environment, including common insecticides like deltamethrin. While low-level exposure is known to disrupt their thinking and ability to find food, scientists still do not fully understand how these chemicals affect their brain chemistry.Researchers at the University of Veterinary Medicine Budapest (Hungary) investigated whether acute oral exposure to sublethal doses of deltamethrin disrupts fatty acid homeostasis in the honey bee brain. Brain fatty acid composition was quantified by gas chromatography-mass spectrometry (GC-MS), and multivariate analyses were applied to characterize treatment-related metabolic shifts. A paper based on this research was published in Environmental Pollution.¹

Why Are Honey Bees Declining and How Are They Exposed to Pesticides?

Honey bees play a crucial role in pollinating plants, helping both wild ecosystems and crop production. But in recent years, their numbers have dropped significantly, raising widespread concern about their survival.² Although they were not intended to be targeted, bees can still encounter pesticides, either directly or through contaminated leaves, nectar, and pollen.^3,4

How Does Deltamethrin Affect Insects?

The neurotoxin deltamethrin affects insects’ nervous systems by keeping their nerve signals switched on for too long. This overstimulates their nerves, which at high doses can cause shaking, paralysis, and death. Even at lower, non-lethal levels, it can still disrupt how their nervous system works.^5,6

How Does Deltamethrin Affect Bee Brain Chemistry at Sublethal Doses?

The researchers exposed forager worker bees for 48 h to three field-realistic concentrations of deltamethrin corresponding to daily LD50/40, LD50/20 and LD50/10, while controls received solvent-matched sucrose solution. Deltamethrin induced pronounced, dose-dependent alterations in neural fatty acid metabolism, including significant elevations in total fatty acids, saturated fatty acids, and polyunsaturated fatty acids. Medium and high doses increased multiple individual fatty acids, notably palmitic, stearic, oleic, linoleic and α-linolenic acids, as well as several very-long-chain saturated species. The observed fatty acid accumulation is consistent with possible impaired mitochondrial β-oxidation and redox imbalance previously reported for deltamethrin-exposed organisms, which suggests the emergence of a lipotoxic neural environment that may compromise membrane integrity, myelination and synaptic function.¹

“Our findings,” write the authors of the paper,¹ “reveal fatty acid dysregulation as a sensitive mechanistic endpoint of pyrethroid neurotoxicity and highlight the importance of incorporating sublethal biochemical biomarkers into pesticide risk assessment frameworks aimed at protecting pollinator health.”

“While our findings highlight biochemical shifts that align with the timing of previously documented behavioral and cognitive impairments observed in deltamethrin-exposed bees,” the authors continue,¹ “future studies integrating lipid profiling with redox biomarkers and functional behavioral endpoints will be needed to explicitly clarify these relationships. These results underscore the need for more appropriate regulatory frameworks that account for sublethal neurochemical effects of pesticides on pollinator brain health.”

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References

1. 1.Mackei, M.; Kámán-Tóth, E.; Mátis, G. et al. Sublethal Deltamethrin Exposure Dysregulates Brain Fatty Acid Homeostasis in Honey Bee (Apis mellifera). Environ Pollut. 2026, 399, 128204. DOI: 10.1016/j.envpol.2026.128204
2. Rhodes C. J. Pollinator Decline - An Ecological Calamity in the Making? Sci Prog. 2018, 101 (2), 121-160. DOI: 10.3184/003685018X15202512854527
3. Kadala, A.; Kaabeche, M.; Charreton, M. et al. Unravelling Impacts of the Insecticide Deltamethrin on Neuronal Sodium Channels in Honey Bees: Molecular Insights and Behavioural Outcomes. Chemosphere 2024, 369, 143852. DOI: 10.1016/j.chemosphere.2024.143852
4. Dai, P. L.; Wang, Q.; Sun, J. H. et al. Effects of Sublethal Concentrations of Bifenthrin and Deltamethrin on Fecundity, Growth, and Development of the Honeybee Apis mellifera ligustica. Environ Toxicol Chem. 2010, 29 (3), 644-649. DOI: 10.1002/etc.67
5. Kadala, A.; Charreton, M.; Jakob, I. et al. Pyrethroids Differentially Alter Voltage-Gated Sodium Channels from the Honeybee Central Olfactory Neurons. PLoS One 2014, 9 (11), e112194. DOI: 10.1371/journal.pone.0112194
6. Zhou, T.; Zhou, W.; Wang, Q. et al. Effects of Pyrethroids on Neuronal Excitability of Adult Honeybees Apis mellifera. Pestic. Biochem. Physiol.2011, 100, 35-40. DOI: 10.1016/j.pestbp.2011.02.001