Table 1 Characteristics of included studies

Shi et al. [25]

C57Bl/6 J male mice

27w

n = 6 per group

The nesting behavior; temporal order memory tests

Mice fed with a diet rich in microbiota-accessible carbohydrates (MACs) based on the high fat: mixed with 316 g/kg from fat (soybean oil 56 g and lard 260 g) and LabDiet 5010 powder 634 g/kg

Mice fed with a diet with high fat (315 g/kg from fat: soybean oil 55 g and lard 260 g) and fiber-deficient (50 g/kg cellulose)

MACs improve cognitive impairments via the gut microbiota–brain axis induced by the consumption of a high fat diet

Yang et al. [26]

Sprague Dawley (SD) male rats

35w

n = 5 per group

Novel object recognition test

Mice with abdominal surgery and administered with Prebiotic Bimuno^® galactooligosaccharide (B-GOS) solution

Mice with abdominal surgery and administered with normal drinking water

Administration of B-GOS has a beneficial effect on regulating cognitive impairment through the manipulation of gut microbiota in a rat model of abdominal surgery

Shi et al. [27]

C57BL/6 J male mice

27w

n = 5 per group

Object location; novel object recognition; Nesting behavioral tests

Mice fed with oat β-glucan derived from OatWell™ oat bran (CreaNutrition, Switzerland) added into the high fat diet

Mice fed with a diet with high fat (55% by energy) and fiber-deficient (50 g/kg from cellulose, 5% fiber by weigh)

β-glucan improves indices of cognition and brain function through manipulation of gut microbiota

Jena et al. [19]

C57BL/6 male mice

32w

n = 7 CBE group; n = 4 for non-CBE group

Open field behavior study

Mice fed with fructose, palmitate, and cholesterol (FPC) enriched diet constituting 29% fat, 34% sucrose, and 1.25% cholesterol (Envigo, Indianapolis, IN, USA) plus inulin (6%, Montclair, CA, USA) supplementation

Mice fed with FPC enriched diet plus 42 g/L glucose and fructose (55%/45%)

Inulin supplementation prevented cognitive deficit caused by FPC intake via microbiota and metabolites alteration

Wang et al. [28]

C57BL/6 J male mice

20w

n = 30 per group

Nest building test; novel object recognition test; Morris-water maze test; Shuttle-box test

Mice fed a standard chow diet

Mice fed a chow diet supplemented with 1% choline

Excessive choline intake is associated with poorer brain health and cognitive function by remodeling the intestinal microbiota

Lee et al. [33]

C57BL/6 male mice

8w

n = 5 per group

Y-maze; novel object recognition; Barnes maze

(a) Sham-operated mice

(a) Mice with tIsc administered with ampicillin, 1–2 g/60 kg/day

Oral administration of antibiotics can deteriorate cognitive impairment with gut dysbiosis in ischemic brain

(b) Mice with transient global forebrain ischemia (tIsc)

(b) Mice with tIsc administered with vancomycin, 0.5–2 g/60 kg/day

Hsieh et al. [29]

Sprague Dawley (SD) male rats

16w

n = 5 for CBE group; n = 4 for non-CBE group

Morris-water maze test

(a) Offspring of mothers receiving the control diet

Offspring from mothers continuously receiving the low-iron diet

Maternal iron deficiency leads to an offspring spatial memory deficit and is associated with alternations in gastrointestinal microbiota and metabolite

(b) Offspring of mothers receiving the low-iron diet but the control diet through the pregnancy

© Offspring of mothers receiving the low-iron diet during pregnancy but the control diet during lactation

Yang et al. [30]

C57BL/6 J male mice

11w–12w

n = 5 per group

Temporal order memory: novel object recognition; Y-maze tests

Mice fed with high fat diet supplemented with curdlan from Alcaligenes faecailis (500 mg/kg food, Sigma-Aldrich, St. Louis, MO, United States)

Mice receiving the high fat diet (30% fat by weight)

Curdlan mitigated synaptic impairments induced by a high fat diet. Thus, curdlan, as a food additive and prebiotic, can prevent cognitive deficits induced by high fat diet via the colon–brain axis

Liu et al. [31]

C57BL/6 J male mice

14w

n = 15 per group

Novel object recognition test; Morris-water maze test;

Cerebral ischemia–reperfusion injury model mice were treated with the intragastric administration of 100 mg/kg baicalin

Cerebral ischemia–reperfusion injury model mice administered with physiological saline (0.1 ml/100 g)

Baicalin showed neuroprotective effects in cerebral ischemia–reperfusion injury model thorough modulation of the gut microbiota

Wang et al. [20]

C57BL/6 J male mice

15w

n = 15 per group

Morris-water maze test; novel object recognition test

Mice with age-matched healthy sham-operated

Mice with global cerebral ischemia induced by bilateral common carotid arteries

The gut microbiota components from mice with cerebral ischemia–reperfusion injury can alter animal behavior and brain functional connectivity

Xin et al. [32]

ICR male mice

18w

n = 6 per group

T maze; novel object recognition test

(a) Mice administered with phosphate-buffered saline (PBS)

Mice were provided fluoridated drinking water (100 ppm NaF) from 28 to 98 days

Lactobacillus johnsonii BS15 against fluoride-induced memory dysfunction in mice by modulating the gut–brain axis

(b) Mice administered with probiotic Lactobacillus johnsonii BS15 (0.2 mL/day) for 28 days prior to and throughout a 70-day exposure to sodium fluoride (NaF)