The effect of omega-3 on cognition in hypothyroid adult male rats

Abstract

Thyroid hormones and omega-3 are essential for normal brain functions. Recent studies have suggested that omega-3 may protect against the risk of dementia. The aim of this study was to investigate the effect of hypothyroidism on spatial learning and memory in adult male rats, the underlying mechanisms and the possible therapeutic value of omega-3 supplementation. Thirty male rats were divided into three groups; control, hypothyroid and omega-3 treated. Hypothyroidism induced significant deficits in working and reference memories in radial arm maze, retention deficits in passive avoidance test and impaired intermediate and long-term memories in novel object recognition test. Serum total antioxidant capacity (TAC) and hippocampal serotonin and γ-aminobutyric acid (GABA) levels were decreased in the hypothyroid group as compared to the control group. Moreover, the hippocampus of hypothyroid rats showed marked structural changes as diffuse vacuolar degeneration and distortion of the pyramidal cells. Immunohistochemistry showed that the expression of Cav1.2 (the voltage dependent LTCC alpha 1c subunit) protein was increased in the hypothyroid group as compared to the control group. Omega-3 supplementation ameliorated memory deficits, increased TAC, decreased the structural changes and decreased the expression of Cav1.2 protein. In conclusion omega-3 could be useful as a neuroprotective agent against hypothyroidism-induced cognitive impairment.Keywords: hypothyroidism, cognition, omega-3, Cav1.2, GABA and serotonin Thyroid hormones play an important role in the development and the normal function of CNS by different mechanisms. They regulate synaptic transmission (15), modulate the synthesis and turnover of neurotransmitters and modify the sensitivity of their receptors (42, 51). They modulate signal transduction pathways in the CNS through Ca 2+ channels. L-type voltagesensitive Ca 2+ (Cav) channel (L-VSCC) mediates long lasting Ca 2+ currents (55) that play important roles in neurotransmitters release, second messenger cascades and gene regulation (28). L-VSCCs localize prominently on neuronal cell bodies and proximal dendrites (24). They consist of five subunits: α1, α2, β, γ and δ (40); α1 subunit is the ion-conducting pore and contains the binding sites for dihydropyridine (9). There are two different L-VSCC α1 subunits: α1C (Cav1.2) and α1D (Cav1.3) (47). Growing evidence has suggested that excessive Ca 2+ influx through L-VSCCs may be detrimental to memory (55). Moreover, L-VSCC currents were reported to be increased in the hippocampus of aged rats and rabbits and thus, had been implicated in aged-related memory deficits (50). Omega-3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are major components of neuronal membranes and have a wide range of functions including neural growth (18), neuroprotection and modulation of

Effect of Different Types of Omega-3 Fish Oil on the Physiological, Biochemical and Immunological Parameters in Male Rabbits

“…Also, the Serotonin level in the other experimental groups remained unchanged with the control group. These observations are in support of the study carried out by Abd Allah, 29 who reported a similar effect in his study on omega-3 fatty acids. Glutathione level was significantly high in the Group 2 and 3 animals (26.32 ± 7.09 and 26.04 ± 7.22 µmol/L, respectively) in comparison with the control group (10.01 ± 2.12 µmol/L).…”

Nutrients, Microglia Aging, and Brain Aging

“…The potential role of DHA and EPA in the prevention of cognitive decline, including the decline associated with AD, has attracted major interest over the past 20 years. Recent research showed that n-3 fatty acids supplementation ameliorated memory deficits, which increased the serum total antioxidant capacity [ 118 ]. On the other hand, EPA and DHA supplementation for 2 years was not found to affect the cognitive decline in healthy elderly individuals [ 119 ].…”

Nutraceuticals in Thyroidology: A Review of in Vitro, and in Vivo Animal Studies

“…ω-3 FAs supplementation improved memory deficits, increased serum total antioxidant capacity, and also a diminished expression of Cav1.2 protein (the voltage dependent LTCC alpha 1c subunit), together with reduced structural changes, were observed. The data showed that ω-3 FAs could be a useful neuroprotective agent against the cognitive damage that hypothyroidism can induce [43].…”

“…Another study investigated in adult male rats the effect of hypothyroidism on spatial learning and memory, the underlying mechanisms and the potential therapeutic role of ω-3 supplementation [43]. A subdivision into 3 groups was done starting from 30 male rats: Control, hypothyroid and ω-3 treated.…”