VOLUMETRIC ANALYSIS OF LYMPHOCYTE LIPID DROPLETS IN TYPE 2 DIABETES MELLITUS PATIENTS WITH HYPERLIPIDEMIA

  • Aleksa Živković Univerzitet u Beogradu, Medicinski fakultet, Beograd, Srbija
Keywords: type 2 diabetes mellitus, hyperlipidemia, lipid droplets, autophagic vesicles containing lipid droplets, lipolysosomes

Abstract


Introduction: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by inadequate glucose homeostasis. A common occurrence in T2DM is diabetic dyslipidemia. Given lipid droplets’ role in intracellular lipid storage, these structures lie at the center of lipid and energy homeostasis. Lipolysosomes are cell organelles that have the structure of lipid droplets surrounded by a membrane. Lipophagy is a selective form of autophagy which enables lipid droplet degradation, thus representing an important mechanism in the regulation of lipid droplet homeostasis.

The Aim: The aim of our research was fractional volume analysis of lipid droplets, autophagic vesicles containing lipid droplets and lipolysosomes in the lymphocytes of patients with T2DM and hyperlipidemia.

Material and Methods: Mononuclear cells were isolated from the peripheral blood of T2DM patients with hyperlipidemia and from healthy individuals. Cells were fixed in glutaraldehyde and postfixed in 1% osmium tetroxide. After contrasting with 4.7% uranyl acetate, the samples were embedded in epoxy resins and cut by an ultramicrotome. The ultrathin sections were then contrasted with uranyl acetate and lead citrate and analyzed using transmission electron microscopy. The fractional volume of lipid droplets, autophagic vesicles containing lipid droplets and lipolysosomes was determined using the double “coherent point“ grid with dots distributed at two different densities.

Results: While there was no difference in the fractional volumes of lipid droplets and autophagic vesicles containing lipid droplets, the fractional volume of lipolysosomes was significantly higher in the lymphocytes of T2DM patients with hyperlipidemia compared to healthy individuals (p < 0.05).

Conclusion: A higher fractional volume of lipolysosomes revealed in the lymphocytes of T2DM patients with hyperlipidemia can be due to an increase in the activity of these organelles, as well as an overall increase in cellular lipid metabolism in these patients.

References

1. Tomic D, Shaw JE, Magliano DJ. The burden and risks of emerging complications of diabetes mellitus. Nat Rev Endocrinol. 2022; 18(9):525-39.


2. Galicia-Garcia U, Benito-Vicente A, Jebari S, Larrea-Sebal A, Siddiqi H, Uribe KB, et al. Pathophysiology of type 2 diabetes mellitus. Int J Mol Sci. 2020; 21(17):6275.


3. DeDronzo RA, Ferrannini E, Groop L, Henry RR, Herman WH, Holst JJ, et al. Type 2 diabetes mellitus. Nat Rev Dis Primers. 2015; 1:15019.


4. Olzmann JA, Carvalho P. Dynamics and functions of lipid droplets. Nat Rev Mol Cell Biol. 2019; 20(3):137-55.


5. Iancu TC, Manov I, Shaoul R, Haimi M, Lerner A. What's in a name?-"Lipolysosome": ultrastructural features of a lipid-containing organelle. Ultrastruct Pathol. 2013; 37(5):293-303.


6. Haimi M, Iancu TC, Shaffer LG, Lerner A. Severe lysosomal storage disease of liver in del(1)(p36): a new presentation. Eur J Med Genet. 2011; 54(3):209-13.


7. Hayashi H, Sameshima Y, Lee M, Hotta Y, Kosaka T. Lipolysosomes in human hepatocytes: their increase in number associated with serum level of cholesterol in chronic liver diseases. Hepatology. 1983; 3(2):221-5.


8. Parzych KR, Klionsky DJ. An overview of autophagy: morphology, mechanism, and regulation. Antioxid Redox Signal. 2014; 20(3):460-73.


9. Klionsky DJ, Petroni G, Amaravadi RK, Baehrecke EH, Ballabio A, Boya P, et al. Autophagy in major human diseases. EMBO J. 2021; 40(19):e108863.


10. Lorincz P, Juhasz G. Autophagosome-lysosome fusion. J Mol Biol. 2020; 432(8):2462-82.


11. Hu Y, Reggiori F. Molecular regulation of autophagosome formation. Biochem Soc Trans. 2022; 50(1):55-69.


12. Shin DW. Lipophagy: Molecular mechanisms and implications in metabolic disorders. Mol Cells. 2020; 43(8):686-93.


13. Lucocq JM, Hacker C. Cutting a fine figure: On the use of thin sections in electron microscopy to quantify autophagy. Autophagy. 2013; 9(9):1443-8.


14. Krahmer N, Farese Jr RV, Walther TC. Balancing the fat: lipid droplets and human disease. EMBO Mol Med. 2013; 5(7):905-15.


15. Greenberg AS, Coleman RA, Kraemer FB, McManaman JL, Obin MS, Puri V, et al. The role of lipid droplets in metabolic disease in rodents and humans. J Clin Invest. 2011; 121(6):2102-10.


16. Zhou K, Yao P, He J, Zhao H. Lipophagy in nonliver tissues and some related diseases: Pathogenic and therapeutic implications. J Cell Physiol. 2019; 234(6):7938-47.


17. Jung HS, Chung KW, Kim JW, Kim J, Komatsu M, Tanaka K, et al. Loss of autophagy diminishes pancreatic beta cell mass and function with resultant hyperglycemia. Cell Metab. 2008; 8(4):318-24.


18. Yang L, Li P, Fu S, Calay ES, Hotamisligil GS. Defective hepatic autophagy in obesity promotes ER stress and causes insulin resistance. Cell Metab. 2010; 11(6):467-78.


19. Cai J, Pires KM, Ferhat M, Chaurasia B, Buffolo MA, Smalling R, et al. Autophagy ablation in adipocytes induces insulin resistance and reveals roles for lipid peroxide and Nrf2 signaling in adipose-liver crosstalk. Cell Rep. 2018; 25(7):1708-17.


20. Rovira-Llopis S, Diaz-Morales N, Banuls C, Blas-Garcia A, Polo M, Lopez-Domenech S, et al. Is autophagy altered in the leukocytes of type 2 diabetic patients?. Antioxid Redox Signal. 2015; 23(13):1050-6.


21. Alizadeh S, Mazloom H, Sadeghi A, Emamgholipour S, Golestani A, Noorbakhsh F, et al. Evidence for the link between defective autophagy and inflammation in peripheral blood mononuclear cells of type 2 diabetic patients. J Physiol Biochem. 2018; 74(3):369-79.


22. Hayashi H, Sternlieb I. Lipolysosomes in human hepatocytes. Ultrastructural and cytochemical studies of patients with Wilson's disease. Lab Invest. 1975; 33(1):1-7.


23. Carroti S, Aquilano K, Zalfa F, Ruggiero S, Valentini F, Zingariello M, et al. Lipophagy impairment is associated with disease progression in NAFLD. Front Physiol. 2020; 11:850.


24. Nehemiah JL, Novikoff AB. Unusual lysosomes in hamster hepatocytes. Exp Mol Pathol. 1974; 21(3):398-423.


25. Drevon CA, Hovig T. The effects of cholesterol/fat feeding on lipid levels and morphological structures in liver, kidney and spleen in guinea pigs. Acta Pathol Microbiol Scand A. 1977; 85A(1):1-18.


26. Hayashi H, Hotta Y, Sakamoto N. Electron microscopic study on the floating lipids of human liver. Lysosomal involvement in the fatty liver associated with diabetes mellitus. Acta Pathol Jpn. 1983; 33(5):923-8.

Published
2023/08/23
Section
Original Scientific Paper