Aging-US: Involvement of adiponectin in age-related increases in tear production09-08-2021
Aging-US published a Special Collection on Eye Disease which included "Involvement of adiponectin in age-related increases in tear production in mice" which reported that the infiltration of lymphocytes into the lacrimal glands occurs with age, and age-related increases in tear production have also been observed in mice.
The mechanisms underlying this increase remain unclear, but these authors show that it is not dependent on body weight gain or systemic conditions, such as insulin resistance, using aged mice and high-fat diet-fed mice. Senescence-associated T (SA-T) cells accumulated in the laceral glands of aged mice, particularly females, and they may represent potential targets for treating dry eyes in humans.
Dr. Yosuke Shikama from The National Center for Geriatrics and Gerontology said, "Epidemiological studies have shown that the prevalence of dry eye increases every five years after the age of 50 years, with a higher prevalence being reported in women than in men."
Age and female sex have been identified as the greatest risk factors for dry eye, and this is supported by clinical findings of decreased tear production in women through the 6th decade of life. Metabolic disorders, such as diabetes, affect tear production and are associated with dry eye. Adiponectin is a 30-kDa multimeric protein that is mainly secreted by white adipose tissue, and has insulin-sensitizing and anti-atherogenic properties.
Adiponectin and adipoR2 mRNA expression levels significantly increased in the lacrimal glands of aged mice, but not in those of high-fat diet-fed mice. These results indicate that these molecules are involved in age-related increases in tear production in mice.
Figure 5. Influence of aging or high-fat diet feeding on adiponectin, adipoR1, and adipoR2 expression in lacrimal glands. Adiponectin (A), adipoR1 (B), and adipoR2 (C) mRNA expression levels in lacrimal glands. Upper and lower graphs show results in young and aged mice (N=7-8), and in mice fed a normal diet (ND) or high-fat diet (HFD) for 8 weeks (N=4-5), respectively. (D) Detection of the AdipoR2 protein by Western blotting. Lysates prepared from the lacrimal glands of young and aged mice were immunoblotted with anti-AdipoR2 and anti-β-Actin antibodies. Left and right images show male (N=2) and female mice (N=2), respectively. The bar graph shows integrated signal intensities in AdipoR2 normalized to that of β-Actin (N=4). (E) AdipoR2 expression in the lacrimal glands of young and aged mice as detected by immunofluorescence. Nuclei were stained with DAPI. Bars = 40 μm. Values are presented as means ± SEM. NS, not significant. *p<0.05 and **p<0.01 (an unpaired Student’s t-test).
The Shikama Research Team concluded in their Aging-US Research Output, "the present results demonstrated the accumulation of SA-T cells in aged mice, which occurred to a greater extent in female than in male mice. Furthermore, increased tear secretion in aged mice appeared to be mediated by PPARγ and adiponectin-mediated signaling. These results may explain the discrepancy in the volume of tears secreted with age between humans and mice."
Full Text - https://www.aging-us.com/article/102322/text
Correspondence to: Yosuke Shikama email: email@example.com
Launched in 2009, Aging-US publishes papers of general interest and biological significance in all fields of aging research as well as topics beyond traditional gerontology, including, but not limited to, cellular and molecular biology, human age-related diseases, pathology in model organisms, cancer, signal transduction pathways (e.g., p53, sirtuins, and PI-3K/AKT/mTOR among others), and approaches to modulating these signaling pathways.