O. S. Tkachenko¹*, H. V. Kosiakova¹, T. M. Horidko¹,
O. F. Mehed¹, A. H. Berdyshev¹, V. M. Klimashevsky¹,
S. A. Mykhalskiy², N. M. Hula¹

¹Palladin Institute of Biochemistry, National Academy
of Sciences of Ukraine, Kyiv;
²D.F.Chebotarev State Institute of Gerontology, National Academy
of Medical Sciences of Ukraine, Kyiv;
*e-mail: 888oksana.tkachenko@gmail.com

Received: 24 December 2025; Revised: 09 February 2026;
Accepted: 03 April 2026; Available on-line: April 2026

Obesity and related metabolic disorders remain one of the most pressing problems of modern biomedicine. Both obesity and aging cause functional and structural changes in the adipose organ, but the age-specificity of adipose tissue’s response to high-fat diet (HFD) remains poorly understood. The aim of the study was to analyze correlation between glucose, lipoproteins and adiponectin plasma levels, to determine Δ9-desaturase activity in adipocyte and to explore the morphological state of adipose tissue in rats of different ages. The experiment was carried out on male Wistar rats for 24 weeks, when young animals reached the age of 10 months, and older – 24 months. Animals of both age groups were divided into kept on a standard rodent diet or a diet with addition of pork visceral lard. The fatty acid composition was identified by gas-liquid chromatography with mass-detection, HDL and LDL cholesterol content – by commercial kits, adiponectin levels­ – using ELISA kit. The activity index of Δ9-desaturase was calculated as the ratio of oleic to stearic acid. It was shown that the saturated/ unsaturated fatty acids ratio in a standard pelleted feed was 1:4, whereas in the lard it was close to 1:1. No correlation between increased body weight and glucose level, and a positive correlation between adiponectin and HDL cholesterol levels were found in younger rats. In the older rats a positive correlation between body weight and glucose level, and a significant negative correlation between adiponectin and LDL cholesterol levels was observed. Activity of Δ9-desaturase in adipocytes was found to be increased with aging. When animals were kept on a HFD diet, Δ9-desaturase activity in younger group was increased to a large extent, while in older group it decreased significantly as compared with age-matched controls. Morphological analysis showed age-related differences in the morphology, cellular adaptation, and inflammation development in brown and white adipose tissue in response to a dietary fat overload. The results of our study facilitate the identification of potential biomarkers for the prevention and treatment of obesity and associated diseases across different age groups.