Page 195 - Petelin, Ana. 2021. Ed. Zdravje starostnikov / Health of the Elderly. Proceedings. Koper: University of Primorska Press.
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e«. We limited the search to the last 10 years. The literature review was fo- the gut microbiota in the elderly 193
cused on the change of gut microbiota during aging, the effect of nutrition on
gut microbiota and various nutritional and other interventions for microbiota
manipulation and its link to neurodegenerative diseases and pathologies.
Results and Discussion
Gut microbiota shows wide inter-individual variation, but its within-individ-
ual variation is relatively stable over time (Kim and Jazwinski, 2018). Taxo-
nomically, bacteria are classified according to phyla, classes, orders, families,
genera and species (Rinninella et al., 2019). The dominant bacterial phyla are
Bacteroidetes and Firmicutes, which constitute 90% of the total gut microbio-
ta (Kim & Jazwinski, 2018), with Actinobacteria, Proteobacteria, Fusobacteria,
and Verrucomicrobia also frequently present. Microbiota diversity increases
from birth and at about the age of three years, a child’s gut microbiota com-
position is mostly adult-like (Rinninella et al., 2019). The composition of the
intestinal microbiota in older people is variable between individuals and dif-
fers from the microbiota and diversity levels of younger adults (Claesson et al.,
2012). In the elderly, changes in dietary habits, digestion, nutrient absorption
and weaker immune activity can affect gut microbiota composition (Rinninel-
la et al., 2019). Changes in diet could be attributed to the loss of taste and smell
and difficulties with chewing food. This frequently leads to the increased in-
take of foods high in fat and sugar and decreased intake of plant foods (Mangi-
ola et al., 2018). The loss of diversity in the common microbiota groups is asso-
ciated with increased frailty and reduced cognitive performance (O’Toole and
Jeffery, 2015).
The microbiota-gut-brain axis is a bidirectional communication system
that is connected through neural, immune, endocrine and metabolic path-
ways. The gut microbiota plays a vital role in the modulation of brain functions
(Jiang et al., 2017). Gut bacteria have been found to affect the maturation of the
nervous, endocrine and immune systems in mice (Pluta et al., 2020). Research
supports a possible link between the gut microbiota and Alzheimer’s disease
(AD), which is characterized by the deposition of amyloid-β (Aβ) and tau in
the brain, leading to degeneration of cognitive function (Mangiola et al., 2018).
Theories for the role of gut microbiota in AD pathophysiology include direct
microbial action (microbial infection in AD), indirect action (hygene hypoth-
esis) and processes related to aging of the immune system (Angelucci et al.,
2019). The increased gut and blood-brain barrier permeability induced by mi-
crobiota dysbiosis may modulate AD pathogenesis and other neurodegenera-
tive disorders, especially aging-related (Jiang et al., 2017). The inflammatory re-
sponse from the gut along with aging and poor diet in the elderly have been
found to contribute to the pathogenesis of AD (Pluta et al., 2020). Gut microbi-
ota products, such as SCFA (butyrate, acetate, propionate), have specific func-
tions in the gut and the brain where butyrate has been found to have protec-
tive properties in the brain. Gut microbiota also produces more than 90% of
cused on the change of gut microbiota during aging, the effect of nutrition on
gut microbiota and various nutritional and other interventions for microbiota
manipulation and its link to neurodegenerative diseases and pathologies.
Results and Discussion
Gut microbiota shows wide inter-individual variation, but its within-individ-
ual variation is relatively stable over time (Kim and Jazwinski, 2018). Taxo-
nomically, bacteria are classified according to phyla, classes, orders, families,
genera and species (Rinninella et al., 2019). The dominant bacterial phyla are
Bacteroidetes and Firmicutes, which constitute 90% of the total gut microbio-
ta (Kim & Jazwinski, 2018), with Actinobacteria, Proteobacteria, Fusobacteria,
and Verrucomicrobia also frequently present. Microbiota diversity increases
from birth and at about the age of three years, a child’s gut microbiota com-
position is mostly adult-like (Rinninella et al., 2019). The composition of the
intestinal microbiota in older people is variable between individuals and dif-
fers from the microbiota and diversity levels of younger adults (Claesson et al.,
2012). In the elderly, changes in dietary habits, digestion, nutrient absorption
and weaker immune activity can affect gut microbiota composition (Rinninel-
la et al., 2019). Changes in diet could be attributed to the loss of taste and smell
and difficulties with chewing food. This frequently leads to the increased in-
take of foods high in fat and sugar and decreased intake of plant foods (Mangi-
ola et al., 2018). The loss of diversity in the common microbiota groups is asso-
ciated with increased frailty and reduced cognitive performance (O’Toole and
Jeffery, 2015).
The microbiota-gut-brain axis is a bidirectional communication system
that is connected through neural, immune, endocrine and metabolic path-
ways. The gut microbiota plays a vital role in the modulation of brain functions
(Jiang et al., 2017). Gut bacteria have been found to affect the maturation of the
nervous, endocrine and immune systems in mice (Pluta et al., 2020). Research
supports a possible link between the gut microbiota and Alzheimer’s disease
(AD), which is characterized by the deposition of amyloid-β (Aβ) and tau in
the brain, leading to degeneration of cognitive function (Mangiola et al., 2018).
Theories for the role of gut microbiota in AD pathophysiology include direct
microbial action (microbial infection in AD), indirect action (hygene hypoth-
esis) and processes related to aging of the immune system (Angelucci et al.,
2019). The increased gut and blood-brain barrier permeability induced by mi-
crobiota dysbiosis may modulate AD pathogenesis and other neurodegenera-
tive disorders, especially aging-related (Jiang et al., 2017). The inflammatory re-
sponse from the gut along with aging and poor diet in the elderly have been
found to contribute to the pathogenesis of AD (Pluta et al., 2020). Gut microbi-
ota products, such as SCFA (butyrate, acetate, propionate), have specific func-
tions in the gut and the brain where butyrate has been found to have protec-
tive properties in the brain. Gut microbiota also produces more than 90% of
