Scholnick DA and Winslow AE (2020), The role of fasting on spine regeneration and b...

ECB-ART-48590

PLoS One 2020 Jan 01;152:e0228711. doi: 10.1371/journal.pone.0228711.

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The role of fasting on spine regeneration and bacteremia in the purple sea urchin Strongylocentrotus purpuratus.

Scholnick DA , Winslow AE .

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Fasting has been shown to increase longevity and alter immune function in a variety of animals, but little is understood about how reduced caloric intake may impact regeneration and infections in animals that must regularly repair and regenerate tissue in marine environments that contain high levels of bacteria. We examined the possibility that fasting could enhance spine regeneration and reduce bacteremia in the purple sea urchin Strongylocentrotus purpuratus. A small number of spines were removed from urchins and rates of spine regrowth and levels of culturable bacteria from the coelomic fluid were measured for 21 days in fed and fasted urchins. Fasted urchins had higher rates of spine regrowth and lower levels of colony-forming units (CFU) per milliliter of coeolomic fluid. The predominant bacteria in the coelomic fluid was isolated and identified by DNA sequence-based methods as Vibrio cyclitrophicus. After 21 days, fasted and fed urchins were injected with V. cyclitrophicus. Two hours after injection, fed urchins had about 25% more culturable bacteria remaining in their coelomic fluid compared to fasted urchins. We found no evidence that fasting altered coelomic fluid cell number or righting response, indicators of physiologic and behavioral stress in urchins. Our results demonstrate that V. cyclitrophicus is present in purple urchin coelomic fluid, that fasting can increase spine regeneration and that fasted urchins have much lower levels of culturable bacteria in their coelomic fluid than fed urchins. Overall, our data suggests that fasting may ultimately reduce bacteremia and infection in injured or damaged urchins.

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Genes referenced: impact LOC100887844 LOC115919910

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	Fig 1. Spine regeneration rate.Rate of spine regeneration (Î¼m day-1) for spines cut at the base (entire) or at half the spine length (half) after 21 days of feeding ad libitum (white bars) or fasted (black bars). Mean values Â± standard error are shown (n = 9 for each treatment group). Fed animals had significantly lower spine regeneration rates for whole and half spine removal (P = 0.0421, t = 2.772; P = 0.00752, t = 3.0871 respectively).
	Fig 2. Fasting decreases colony forming units.Coelomic fluid bacteria measured as the total number of colony-forming units (CFU) per milliliter of coelomic fluid. Bacteremia was assessed initially and 21 days after spine amputation in animals that were either fed (white bars) or fasted (black bars). Following fasting, urchins were injected with Vibrio and total bacterial CFU per milliliter of coelomic fluid were counted 2 hours post injection. Mean values Â± standard error are shown (n = 9 for each treatment group). Significant differences between groups and over time are indicated by letters above bars (two-way ANOVA, P < 0.05). Following bacterial injection, the net increase in culturable bacteria in coelomic fluid was significantly higher in urchins that had been fed for 21 days compared to fasted urchins 2 h post injection (P = 0.032, t = 2.3594, unpaired t-test).
	Fig 3. Change in coelomocytes.Total number of coelomocytes (A) and red spherules (B) per milliliter of urchin coelomic fluid in fed (white bars) and fasted (black bars) urchins. Cells were counted initially and 21 days after spine amputation. Following fasting, urchins were injected with Vibrio and coelomic cells counted 2 hours post injection. Mean values Â± standard error are shown (n = 9 for each treatment group). Fasting had no significant impact on coelomocyte number compared to animals that were fed (P > 0.05, RMANOVA). Decreases in coelomic cell numbers following injection of bacteria did not differ between fed and fasted urchins (P > 0.05, unpaired t-test).
	Fig 4. Righting response.Righting time, the time taken to return to upright position following inversion, in fed (white bars) and fasted (black bars) urchins. Righting time was measured initially and 21 days after spine amputation. Following fasting, urchins were injected with Vibrio and righting time measured 2 hours post injection. Mean values Â± standard error are shown (n = 9 for each treatment group). Fasting had no significant impact on righting time compared to fed animals (P > 0.05, ANOVA). There was no difference in righting response time following injection of bacteria between fed and fasted urchins (P > 0.05, unpaired t-test).

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