No abstract

The fruit fly, Drosophila melanogaster is a broadly used model for gerontological research. Many studies are dedicated to understanding nutritional effects on ageing; however, the influence of dietary carbohydrate type and dosage is still poorly understood. We show that among three carbohydrates tested, fructose, glucose, and sucrose, the latter decreased life span by 13%-27%, being present in concentrations of 2%-20% in the diet. Life-span shortening by sucrose was accompanied by an increase in age-independent mortality. Sucrose also dramatically decreased the fecundity of the flies. The differences in life span and fecundity were determined to be unrelated to differential carbohydrate ingestion. The highest mitochondrial protein density was observed in flies fed sucrose-containing diet. However, this parameter was not affected by carbohydrate amount in the diet. Fly sensitivity to oxidative stress, induced by menadione, was increased in aged flies and was slightly affected by type and concentration of carbohydrate. In general, it has been demonstrated that sucrose, commonly used in recipes of Drosophila laboratory food, may shorten life span and lower egg-laying capability on the diets with very low protein content.

It has recently been demonstrated that as the ratio of protein to carbohydrate (P:C) in the diet declines, life span increases in Drosophila. Here we explored how extremely low dietary ratios of protein to carbohydrate affected longevity and a selection of variables associated with functional senescence. An increase in P:C ratio from 1:57 to 1:20 shortened life span by increasing age-dependent mortality; whereas a further decline in P:C from 1:57 to 1:95 caused a modest decrease in life span. Female flies consuming the 1:20 and 1:38 diets laid more eggs than those consuming the lower P:C diets. Flies fed diets with higher ratios were more resistant to heat stress. Flies consuming the diets with lowest P:C ratios needed more time to restore activity after paralysis. Our study has therefore extended to very low P:C ratios available data demonstrating that dietary P:C ratio affects life span, fecundity and heat stress resistance, with fecundity and heat stress responses showing the opposite trend to life span.

Fruit flies have eight identified Drosophila insulin-like peptides (DILPs) that are involved in the regulation of carbohydrate concentrations in hemolymph as well as in accumulation of storage metabolites. In the present study, we investigated diet-dependent roles of DILPs encoded by the genes dilp1–5, and dilp7 in the regulation of insect appetite, food choice, accumulation of triglycerides, glycogen, glucose, and trehalose in fruit fly bodies and carbohydrates in hemolymph. We have found that the wild type and the mutant lines demonstrate compensatory feeding for carbohydrates. However, mutants on dilp2,3, dilp3, dilp5, and dilp7 showed higher consumption of proteins on high yeast diets. To evaluate metabolic differences between studied lines on different diets we applied response surface methodology. High nutrient diets led to a moderate increase in concentration of glucose in hemolymph of the wild type flies. Mutations on dilp genes changed this pattern. We have revealed that the dilp2 mutation led to a drop in glycogen levels independently on diet, lack of dilp3 led to dramatic increase in circulating trehalose and glycogen levels, especially at low protein consumption. Lack of dilp5 led to decreased levels of glycogen and triglycerides on all diets, whereas knockout on dilp7 caused increase in glycogen levels and simultaneous decrease in triglyceride levels at low protein consumption. Fruit fly appetite was influenced by dilp3 and dilp7 genes. Our data contribute to the understanding of Drosophila as a model for further studies of metabolic diseases and may serve as a guide for uncovering the evolution of metabolic regulatory pathways.

BackgroundThis study was conducted to evaluate the effects of rhizome powder from the herb Rhodiola rosea, a traditional Western Ukraine medicinal adaptogen, on lifespan and age-related physiological functions of the fruit fly Drosophila melanogaster.ResultsFlies fed food supplemented with 5.0 mg/ml and 10.0 mg/ml of R. rosea rhizome powder had a 14% to 17% higher median lifespan, whereas at 30.0 mg/ml lifespan was decreased by 9% to 12%. The preparation did not decrease fly fecundity.The effect of R. rosea supplement on lifespan was dependent on diet composition. Lifespan extension by 15% to 21% was observed only for diets with protein-to-carbohydrate ratios less than 1. Lifespan extension was also dependent on total concentration of macronutrients. Thus, for the diet with 15% yeast and 15% sucrose there was no lifespan extension, while for the diet with protein-to-carbohydrate ratio 20:1 R. rosea decreased lifespan by about 10%.Flies fed Rhodiola preparation were physically more active, less sensitive to the redox-cycling compound menadione and had a longer time of heat coma onset compared with controls. Positive effects of Rhodiola rhizome on stress resistance and locomotor activity were highest at the ‘middle age’.ConclusionsThe present data show that long-term food supplementation with R. rosea rhizome not only increases D. melanogaster lifespan, but also delays age-related decline of physical activity and increases stress resistance, what depends on protein-to-carbohydrate ratio of the diet.