Intestistinal ecosystem remodeling during fasting

1. Publication date: 23rd March 2023
Journal: Trends in microbiology
Presented by,
Sunil Kumar Das
M.Sc. Biotechnology(Final)
The Maharaja Sayajirao University

2. Introduction
 Fasting is defined as the voluntary abstinence or strong limitation of caloric ingestion for a limited period of time,
triggering the G-to-K switch and major changes in the activity of signaling pathways.
Françoise Wilhelmi et al. (2020)
 Gut microorganisms rely largely on energy derived from the human diet to perform metabolic functions essential
for their survival, and the gut microbiome composition therefore rapidly responds to the food we eat.
David, L.A. et al.(2014)
 Caloric restriction (CR) up to 40% of nutritious diet intake reduces body weight and total fat amount,
delays the onset of multiple age-associated diseases, and improves metabolic health CR is a potent
physiological stimulus that promotes functional beige fat development which contributes to the inguinal
subcutaneous adipose tissue loss during CR.
De Guzman et al., (2013)
 The metabolic switch from utilizing glucose to stored energy (i.e., glycogen and fat) for energy generation is
associated with improvements in various clinical conditions, such as chronic inflammatory disorders and metabolic
syndrome.
de Toledo, F. et al. (2020)

3.  A decrease in the nutrient flow in the gastrointestinal tract, caused by caloric restriction or fasting, can thus have far-
reaching effects on gut microbes and our physiology.
David, L.A. et al.(2014)
 Fasting also has potent effects on the immune system, including in the gut, but the complexity of these effects is
evidenced by different forms and lengths of fasting having distinct and sometimes opposite effects on the immune
system.
Elisabeth et al., (2022)
 The intestinal epithelium is resorbed during long-term fasting . This profound remodeling of the intestinal epithelium
during fasting has long been thought to be the main contributor to changes in the gut microbiome.
Gacesa, R. et al., (2022 )

4. (Quinten R. et al., 2023)

5. List of further experiments
1. Intermittent fasting–provoked changes of bacterial taxa.
2. Fasting-mimicking diet (FMD) Cycles Ameliorate IBD-Associated Disease Phenotypes and
Increase Colon and Small Intestine Lengths
3. The fasting-mimicking diet (FMD) reduces blood glucose and growth factor levels in patients
with cancer.
4. Dietary restriction significantly protects the small intestine and ISCs from lethal doses of MTX
5. Mice in a fasted state are protected from S. Typhimurium-induced gastroenteritis

6. Intermittent fasting–provoked changes of bacterial taxa.
Taxa that show alternative abundance
before and after fasting (Junhong Su. et al., 2021)
A correlation matrix
between microbiota and
BMI before & after fasting
Multiple taxonomic differences were found, especially when the upregulation of phylum Firmicutes & class
Clostridia was evident and family Prevotellaceae & class Bacteroidia were reduced following intermittent fasting.
No significant correlation was found between gut microbiota composition and BMI before & after fasting.

7. Fasting-mimicking diet (FMD) Cycles Ameliorate IBD-Associated Disease Phenotypes and Increase Colon and Small
Intestine Lengths
Experimental scheme outlining the water schedule and duration of Dextran Sodium Sulfate (DSS), DSS+FMD,
and DSS+WF diets
(Rangan et al., 2019, Cell Reports 26, 2704–2719)

8. The modified disease activity index (DAI) score The body weight loss variable of the DAI scores
The stool consistency variable of the DAI scores The Hemoccult test variable of the DAI scores
(Rangan et al., 2019, Cell Reports 26, 2704–2719)

9. Visual representation of Hemoccult test result and colon length
Visual representation of small intestine and its length
(Rangan et al., 2019, Cell
Reports 26, 2704–2719)
Overall, these data suggest that FMD cycles reversed several symptoms and pathology in a mouse model for IBD.
In contrast, water-only fasting does not promote reversal of IBD-related pathology.

10. The fasting-mimicking diet (FMD) reduces blood glucose and growth factor levels in patients with cancer.
Schematics of the FMD regimen, with the
calorie content of each day of FMD (d1–d5)
Concentration of plasma glucose, serum insulin and serum IGF-1 before and after FMD
(Claudio Vernieri et al., 2021)
The FMD favorably modulates key blood metabolic parameters

11. Dietary restriction significantly protects the small intestine and ISCs from lethal doses of MTX
(Duozhuang Tang et al., 2019)
Representative images of H&E staining of sections on day 3 after MTX administration
Villi height in μm

12. Crypt number per millimeter
Cell number per crypt
Representative images of
immunofluorescent staining of PCNA of
jejunum on day 3 after MTX treatment
(scale bar: 20μm)
Basal crypt PCNA-positive cell number per crypt
counted from the whole small intestine at
indicated timepoints after MTX administration
Representative images of cultured crypts on day 6 in culture
derived from mice on day 3 after indicated treatment
Seeding efficiency of cultured crypts on day 3
and number of viable organoids from cultured
crypts on day 6
Together, these data indicated that DR pre-treatment protected basal crypt PCNA-positive cells from depletion
and preserved the functioning of ISCs after MTX administration, which could contribute to improved regeneration
under dietary restricted conditions.
(Duozhuang Tang et al., 2019)

13. Mice in a fasted state are protected from S. Typhimurium-induced gastroenteritis
Experimental timeline of infection and fasting
regimen and concurrent body weight loss
Blood glucose and β-hydroxybutyrate
levels in mouse serum
Representative
macroscopic images of
mouse cecal and colonic
pathology
(Graef FA et al., 2021)

14. Representative hematoxylin-and-
eosin (H&E)-stained cecal sections of
mice
Representative immunofluorescence
staining of S. Typhimurium and IEC from
cecal sections
S. Typhimurium CFU per g cecal tissue
and stool (combined)
IL-1β protein levels measured by ELISA in
whole cecum lysates of mice infected
with S. Typhimurium
qPCR analysis of inflammatory genes in
mouse cecum expressed as fold change
over fed ctrl
Invasion score quantifying S.
Typhimurium presence in IEC by
analyzing immunofluorescently stained
cecal sections
Representative immunofluorescence
staining of macrophages and neutrophils on
cecal sections
(Graef FA et al., 2021)
Pathogenicity of S. Typhimurium was reduced in fasted mice and fasting abrogates the host pro-inflammatory
response to S. Typhimurium infection

15. Summary
 The overall response to fasting in the gut microbiome is conserved in humans and animals, with an increased
reliance on host-derived substrates when dietary substrates are lacking.
 The profound remodelling of intestinal tissues during fasting – leading to a renewal of the mucosa, changes in
immune function, and a decreased inflammatory state – are thus probably key in determining the effects of
fasting on the gut ecosystem.
 Intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk for cardiometabolic
diseases.
 Periodic fasting (PF) and fasting-mimicking diets (FMDs) have been effective in increasing healthy lifespan or as
therapies in mouse models for a variety of diseases.
 FMD cycles reduced intestinal inflammation, increased stem cell number, stimulated protective gut microbiota,
and reversed intestinal pathology caused by DSS in mouse model.
 Fasting increases the colonization resistance to pathogens.
 FMD can be used in cancer treatment as it favorably modulates the key metabolic parameters.

16. References
1. David, L.A. et al. (2014) Diet rapidly and reproducibly alters the human gut microbiome. Nature 505, 559–563.
2. Buono, R. and Longo, V.D. (2019) When fasting gets tough, the tough immune cells get going-or die. Cell 178, 1038–
1040.
3. Tang, D. et al. (2020) Dietary restriction increases protective gut bacteria to rescue lethal methotrexate-induced
intestinal toxicity. Gut Microbes 12, 1714401.
4. 67. Mao, Y.-Q. et al. (2023) The anti-tumour effects of caloric restriction are mediated by the gut microbiome. Nat.
Metab. 5, 96–110.
5. Mousavi, S.N. et al. (2022) Effects of Ramadan and non-ramadan intermittent fasting on gut microbiome. Front. Nutr. 9,
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6. Su, Junhong et al. “Remodeling of the gut microbiome during Ramadan-associated intermittent fasting.” The
American journal of clinical nutrition vol. 113,5 (2021): 1332-1342. doi:10.1093/ajcn/nqaa388
7. Rangan, Priya et al. “Fasting-Mimicking Diet Modulates Microbiota and Promotes Intestinal Regeneration to
Reduce Inflammatory Bowel Disease Pathology.” Cell reports vol. 26,10 (2019): 2704-2719.e6.
doi:10.1016/j.celrep.2019.02.019