Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

Abstract

Chronic kidney disease (CKD) is a multifactorial pathology that progressively leads to the deterioration of metabolic functions and results from deficient glomerular filtration and electrolyte imbalance. Its economic impact on public health is challenging. Mexico has a high prevalence of CKD that is strongly associated with some of the most common metabolic disorders like diabetes and hypertension. The gradual loss of kidney functions provokes an inflammatory state and endocrine alterations affecting several systems. High serum levels of prolactin have been associated with CKD progression, inflammation, and olfactory function. Also, the nutritional status is altered due to impaired renal function. The decrease in calorie and protein intake is often accompanied by malnutrition, which can be severe at advanced stages of the disease. Nutrition and olfactory functioning are closely interconnected, and CKD patients often complain of olfactory deficits, which ultimately can lead to deficient food intake. CKD patients present a wide range of deficits in olfaction like odor discrimination, identification, and detection threshold. The chronic inflammatory status in CKD damages the olfactory epithelium leading to deficiencies in the chemical detection of odor molecules. Additionally, the decline in cognitive functioning impairs the capacity of odor differentiation. It is not clear whether peritoneal dialysis and hemodialysis improve the olfactory deficits, but renal transplants have a strong positive effect. In the present review, we discuss whether the olfactory deficiencies caused by CKD are the result of the induced inflammatory state, the hyperprolactinemia, or a combination of both.

Comparison between olfactory training and curcumin therapy in improving olfactory dysfunction in patients with chronic kidney disease

“…A poor olfactory function could be due to several factors, including uremic toxicity, neuropathy, malnutrition, and inflammation-oxidative stress [ 8 , 21 ]. It could be due to the uremic toxic effects, which develop into uremic neuropathy characterized by olfactory peripheral epithelial neuron alterations and central processing dysfunctions [ [21] , [22] , [23] ]. Also, anorexia and malnutrition could limit the regeneration of olfactory epithelium cells [ 24 , 25 ].…”

“…But the biochemical imbalance in these patients could motivate systemic inflammation and oxidative stress, resulting in neurodegeneration and immune activation; therefore, odor detection could deteriorate by the olfactory epithelium changes [ 24 , 26 , 27 ]. The olfactory assessment and management of olfactory impairment could improve QOL in CKD patients [ 21 , 24 , 28 ].…”

Neuro-Vulnerability in Energy Metabolism Regulation: A Comprehensive Narrative Review

“…The significant incidence of both symptomatic and subclinical ischemic cerebrovascular lesions explains this risk [ 213 ]. It refers to the clinical, metabolic, and hormonal abnormalities that accompany progressive kidney failure [ 214 ]. Each patient with uremic syndrome of CKD develops cognitive decline, encephalopathy, seizures, asterixis, myoclonus, restless limb syndrome, central pontine myelinolysis, stroke, extrapyramidal movement disorders, neuropathies, and myopathy being among them ( Figure 1 ).…”

“…In fact, Corona et al specified that this decline in cognitive function impairs the ability to differentiate between odors in CDK patients. It is unclear whether peritoneal dialysis and hemodialysis enhance olfactory deficits, whereas renal transplants have a significant beneficial effect [ 214 ].…”