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First published online October 5, 2006
Journal of Experimental Biology 209, 4129-4139 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02492
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Delayed development and lifespan extension as features of metabolic lifestyle alteration in C. elegans under dietary restriction

Nathaniel J. Szewczyk1,2,*, Ingrid A. Udranszky3, Elena Kozak1, June Sunga1, Stuart K. Kim4, Lewis A. Jacobson2 and Catharine A. Conley1

1 NASA Ames Research Center, M/S 239-11, Moffett Field, CA 94035-1000, USA
2 Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
3 Wyle Laboratories, M/S 239-11, Moffett Field, CA 94035-1000, USA
4 Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA


Figure 1
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  		Fig. 1. Development is temperature and diet dependent. Animals grown on NGM (filled symbols) develop faster than animals grown in CeMM (open symbols) at the same temperature. Animals also grow faster as temperature is increased from 15°C (blue) to 20°C (black) or 25°C (red) regardless of diet. Each point represents the mean ± s.d. of three trials of ten animals each.

 

Figure 2
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  		Fig. 2. Moulting profile in CeMM. Animals grown in CeMM appear to moult at approximately the same length regardless of temperature. 200 moulted sheaths were measured following random selection from 3-week-old cultures grown at 15°C (blue), 20°C (black), or 25°C (red). Each of the four peaks represents one of the four larval stage transitions (L1–L2, L2–L3, L3–L4, L4–adult).

 

Figure 3
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  		Fig. 3. Life history alteration in response to diet. Animals grown on NGM have larger broodsizes whereas animals grown in CeMM live longer. Each point represents a single animal. Growth at 25°C is represented by diamonds, 20°C by squares and 15°C by triangles. Growth on NGM is represented by filled symbols and growth on CeMM by open symbols. Data on these same cohorts (N=100 each) also appear in Fig. 4 and Tables 1, 2, 3.

 

Figure 4
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  		Fig. 4. Effects of diet and temperature on survival. Lifespan of C. elegans at 25°C (diamonds), 20°C (squares) and 15°C (triangles) on NGM (filled symbols) or in CeMM (open symbols). (A) A typical death curve. Inset is a table of median, mean ± s.d. and maximum life span. (B) Data expressed as percentage of median lifespan. (C) Data expressed as a percentage of maximum lifespan. This format is also known as a survival curve.

 

Figure 5
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  		Fig. 5. CeMM culture results in decreased lipid and protein stores. (A) Nile Red staining of lipid deposits in the intestinal cells reveals decreased lipid stores. Almost all animals display strong staining when fed on NGM and decreased staining when starved for 24 h or fed CeMM. All images had the same exposure time. The percentage of 100 animals per condition displaying similar fluorescence intensity is shown on the right of each image. Images of animals fed CeMM are only of the gut immediately posterior to the pharynx. This is the most fluorescent portion of the gut as seen in the image of the NGM fed animal. The CeMM fed group fall into three categories: normal fluorescence (top), weak fluorescence (middle) and very weak fluorescence (bottom). Assignment to these three groups reflects the relative exposure time (RE) needed to produce an image with normal fluorescence top (RE=1), middle (RE=2) bottom (RE=4). Starved NGM have an RE=2 whereas starved CeMM have an RE=4. Note the fed NGM image is saturated at RE=1. (B) Staining for ß-galactosidase activity in unc-54::lacZ transgenic animals reveals decreased protein stores. The percentage of 100 animals per condition displaying the staining pattern is shown on the right of each image. Almost all animals display full body wall muscle staining when fed on NGM and no staining when starved for 48 h (stain near the vulva is embryo staining). Most animals in CeMM display no body wall muscle staining but head and vulval muscle staining, as associated with 24 h starvation (Zdinak et al., 1997Go). A smaller percentage of animals display body wall muscle staining when fed CeMM and an even smaller percentage no staining. In contrast to the degradation of this reporter seen in starved animals, microarray analysis suggests the decreased staining is due to decreased synthesis alone.

 

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© The Company of Biologists Ltd 2006