Metformin Induces a Dietary Restriction–Like State and the Oxidative Stress Response to Extend C. elegans Healthspan via AMPK, LKB1, and SKN-1 (original) (raw)
Figure 2
Metformin does not further increase the median lifespan of DR-constitutive mutant eat-2, and metformin treatment triggers several DR phenotypes in wild-type C. elegans without impairing feeding.
A. Survival curves of eat-2(ad1116) mutants raised on 0 mM, 1 mM, 10 mM, and 50 mM metformin plates at 20°C. The median survival is 23, 25, 19, and 19 days for 0 mM, 1 mM, 10 mM, and 50 mM metformin, respectively. The survival curves of the animals raised on 0 mM and 1 mM metformin are not significantly different, but survival of the 10 mM and 50 mM groups are significantly reduced compared to controls (P = 0.0050 and 0.0033, respectively, by the Log-rank test). We performed this experiment a total of four times, with two of the trials showing significantly different survival curves for the 10 mM and 50 mM groups. Pooled data show approximately 9% declines in median lifespan for 10 mM and 50 mM metformin treatment and significant shifts in survival curves (P = 0.0037 and 0.0114 for 10 mM and 50 mM metformin treatment, respectively, by the Log-rank test), see Table S1D. B. Age pigment fluorescence measurements in wild-type animals raised on 0 mM, 1 mM, 10 mM, and 50 mM metformin plates. We found that age pigment fluorescence decreases with increasing metformin concentration with the levels in the 50 mM group significantly lower than the controls (P = 0.0270 by an unpaired t test). Scores are the average age pigment fluorescence intensity levels of three independent trials. We also observed shifts in the excitation wavelength corresponding to peak age pigment fluorescence intensity in animals treated with 100 mM metformin (see Fig. S1). C. Progeny profiles of wild-type animals raised on 0 mM, 1 mM, 10 mM, and 50 mM metformin. We recorded the number of progeny produced by 60 individuals for each group for each day of egg-laying. We found no significant differences between the progeny profiles of the 0 mM, 1 mM, and 10 mM metformin groups. The 50 mM metformin-treated animals, however, exhibit delays in egg-laying, with significantly higher percentages of total progeny produced on days 3 and 4 compared to the controls (P = 0.0431 and 0.0084 for days 3 and 4, respectively, by an unpaired t test). The 50 mM group also shows lower levels of progeny production on days 1 and 2 compared to controls, with the levels on day 2 being significantly different (P = 0.0361 by an unpaired t test). Data shown represent the average of three independent trials. D. Quantitation of Nile Red staining of lipid deposits in wild-type animals raised on 0 mM, 1 mM, 10 mM, and 50 mM metformin. Fluorescence levels decrease with increasing metformin concentration, with significantly lower levels in the 10 mM and 50 mM metformin groups (P = 0.0400 and 0.0205 for 10 mM and 50 mM metformin, respectively, by an unpaired t test). Data represent the average of three independent experiments. Animals not stained with the Nile Red dye produced no detectable levels of fluorescence in this wavelength range (data not shown). E. Pharyngeal pumping rates of wild-type animals raised on 0 mM, 1 mM, 10 mM, and 50 mM metformin. We recorded pumping rates of 30 individuals for 30 seconds on day 4 of life, and the averages of three separate experiments are shown. Pharyngeal pumping did not differ significantly for any of the groups (P = 0.9231, 0.1689, and 0.9142 for 1 mM, 10 mM, and 50 mM metformin, respectively, by unpaired t tests).