Trophocytes and oenocytes of honeybees are used in studies of cellular senescence, but their cellular energy metabolism with age is poorly understood. In this study, the molecules involved in cellular energy metabolism were evaluated in the trophocytes and oenocytes of young and old worker bees. The results revealed that (i) β-oxidation and protein synthesis decreased with age, (ii) fat and glycogen accumulation increased with age, and (iii) glycolysis did not change with age. These results indicate that the trophocytes and oenocytes of young bees have higher activity of cellular energy metabolism compared with old worker bees and that aging results in a decline in the cellular energy metabolism of worker bees.

-The lifespans of queen honeybees (Apis mellifera ) are much longer than those of worker bees. Mitochondrial energy utilization in the trophocytes and oenocytes of worker bees during aging has been determined, but it remains unknown in queen bees. In this study, mitochondrial energy utilization was assayed in the trophocytes and oenocytes of young and old queen bees. The mitochondrial density and mitochondrial membrane potential (Δψm); nicotinamide adenine dinucleotide (NAD + ), nicotinamide adenine dinucleotide reduced form (NADH), and adenosine triphosphate (ATP) levels; NAD + /NADH ratio; and relative expression of NADH dehydrogenase 1 (ND1) and ATP synthase normalized against mitochondrial density were not significantly different between young and old queen bees. These results indicate that mitochondrial energy utilization maintains a young status in the trophocytes and oenocytes of old queen bees and that trophocytes and oenocytes have longevity-promoting mechanisms that can be investigated to clarify the secret of longevity in queen bees.

Trophocytes and oenocytes in the abdomen of honey bees do not divide after eclosion; however, trophocytes and oenocytes of queen bees have a longer lifespan and maintain better cellular function than those of worker bees. To explore this phenomenon, we assayed the molecules involved in the cholesterol-hydroxyecdysonevitellogenin (Vg) pathway in the trophocytes and oenocytes of young and old worker and queen bees. The results showed that Vg and cholesterol levels in hemolymph and cholesterol levels, 20-hydroxyecdysone (20E) levels, and the messenger RNA levels of cytochrome P450 314A1 20-hydroxylase (Cyp314A1), ecdysone receptor isoform A (EcR-A), ecdysone receptor isoform B1 (EcR-B1), ultraspiracle (USP), ecdysone-induced protein 74 (E74), ecdysone-induced protein 75 (E75), broad-complex (BR-C), Vg , and Vg receptor (VgR) in trophocytes and oenocytes were increased in queen bees compared with worker bees. These findings indicated that queen bees have higher expression of molecules in the cholesterol-hydroxyecdysone-Vg pathway than worker bees.

Ambient temperature reduction (ATR) can extend the lifespan of organisms, but the underlying mechanism is poorly understood. In this study, cellular degradation activity was evaluated in the muscle of an annual fish (Nothobranchius rachovii) reared under high (30 °C), moderate (25 °C), and low (20 °C) ambient temperatures. The results showed the following: (i) the activity of the 20S proteasome and the expression of polyubiquitin aggregates increased with ATR, whereas 20S proteasome expression did not change; (ii) the expression of microtubule-associated protein 1 light chain 3-II (LC3-II) increased with ATR; (iii) the expression of lysosome-associated membrane protein type 2a (Lamp 2a) increased with ATR, whereas the expression of the 70-kD heat shock cognate protein (Hsc 70) decreased with ATR; (iv) lysosome activity increased with ATR, whereas the expression of lysosome-associated membrane protein type 1 (Lamp 1) did not change with ATR; and (v) the expression of molecular target of rapamycin (mTOR) and phosphorylated mTOR (p-mTOR) as well as the p-mTOR/mTOR ratio did not change with ATR. These findings indicate that ATR activates cellular degradation activity, constituting part of the mechanism underlying the longevity-promoting effects of ATR in N. rachovii.

Despite the identical genomic context, trophocytes and oenocytes in worker bees exhibit aging-related phenotypes, in contrast to the longevity phenotypes in queen bees. To explore this phenomenon at the molecular level, we evaluated the age-associated transcriptomes of trophocytes and oenocytes in worker bees and queen bees using high-throughput RNA-sequencing technology (RNA-seq). The results showed that (i) while gene expression profiles were different between worker and queen bees, they remained similar between young and old counterparts; (ii) worker bees express a high proportion of low-abundance genes, whereas queen bee transcriptomes display a high proportion of moderate-expression genes; (iii) genes were upregulated to a greater extent in queen bees vs. worker bees; and (iv) distinct aging-related and longevity-related candidate genes were found in worker and queen bees. These results provide new insights into the cellular aging and longevity of trophocytes and oenocytes in honey bees. Identification of aging-associated biomarker genes also constitutes a basis for translational research of aging in higher organisms.