# Comparative Analysis of Fatty Acids Concentration in Liver and Muscle Tissues of Rats and Mice
## 4 Discussion  
In our study, the overall quantity of muscle total FAs derived from PL is greater in mice compared to rats. This distinction is also evident when examining other categories of fatty acids, including SFAs and UFAs. Particularly within the UFAs derived from PL, only the skeletal muscles of mice exhibit higher levels of MUFAs in comparison to rats, while both species exhibit similar levels of PUFAs. Differences between species in the content of fatty acids derived from PL are also visible at the level of the liver. The total amount of UFAs was higher in mice; however, statistically significant differences were only observed for MUFAs. Polar lipids play a critical role in biological membranes and are essential for various cellular processes, including maintenance of cell integrity, control of the molecules passage  
Figure 4: The comparison of selected fatty acids concentrations from mice and rat liver. **(A,B)**: All of the values expressed as median \(\pm\) quartile range; **\(p\)**\(<\) 0.05, **\(p\)**\(<\) 0.01. Multiple Mann–Whitney test; n = 6 per animal group. **(C)**: Heat map. Fatty acid level expressed as median interquartile range. Caproic Acid **(C6:0)**; Caprylic Acid **(C8:0)**; Myristic Acid **(C14:0)**; Pentadecenoic Acid **(C15:0)**; Palmitic Acid **(C16:0)**; Palmitic Acid **(C16:1)**; Heptadecenoic Acid **(C17:0)**; cis-10-Stearic Acid **(C18:0)**; Oleic Acid **(C18:1n9c)**; Linoleic Acid **(C18:2n6c)**; Arachid Acid **(C20:0)**; cis-11-Eicosanoic Acid **(C20:1)**; Linolenic Acid **(C18:3n3)**; cis-8,11,14-Eicosatrienoic Acid **(C20:3n6)**; Tricosanoic Acid **(C23:0)**; cis-4,7,10,13,16,19-Docosahexaneonic Acid **(C22:6n3)**. \begin{table}
\begin{tabular}{c c c c c} \hline
**Liver FA** & \multicolumn{2}{c}{**Mice**} & \multicolumn{2}{c}{**Rat**} \\ \hline  & **nmol/mg** & **Q25–Q75** & **nmol/mg** & **Q25–Q75** \\ \hline NL/PL & 1.45 & 0.10–1.29 & 3.16 & 0.74–0.29 \\ \hline UFA/TFA & 0.37 & 0.06–0.03 & 0.31 & 0.07–0.04 \\ \hline PUFA/UFA & 0.51 * & 0.07–0.05 & 0.72 * & 0.06–0.02 \\ \hline \end{tabular} Abbreviations: TFA—total fatty acids; PL—total fatty acids derived from polar lipids; NFL—total fatty acids derived from non-polar lipids; SFA—saturated fatty acids; UFA—unsaturated fatty acids; MUFA—monounsaturated fatty acids; PUFA—polyunsaturated fatty acids; NL/PL—proportion of fatty acids derived from non-polar and polar lipids; UFA/TFA—ratio of unsaturated fatty acids in the total volume of fatty acids; PUFA/UFA—polyunsaturated fatty acids in the total volume of unsaturated fatty acids; PUFA/TFA—polyunsaturated fatty acids in the total number of identified ones; MUFA/UFA—monousaturated fatty acids in the total volume of unsaturated fatty acids; all of the values expressed as median \(\pm\) quartile range; Multiple Mann–Whitney test; n = 6 per animal group; \(p<\) 0.05 —-significant differences.  
\end{table} 
Table 3: _Cont._in and out of cells, and facilitation of the cell communication [19; 20]. Despite the lack of differences between species in the total PUFAs content in muscle and liver derived from PL, significant inter-species differences were noted in the concentration of FAs derived from NPL. One of the primary functions of NPL is to serve as an efficient long-term energy storage molecule. Lipid droplets serve to prevent the harmful effects of unesterified fatty acids and offer a lipid reserve that can be readily tapped into to meet cellular demands in various metabolic and physiological conditions. Precise regulation of lipid droplet formation and the release of neutral lipids in terms of timing and location is crucial for directing lipid intermediates to their respective cellular destinations and ensuring cellular balance is upheld. Recent study suggests that non-polar lipids, particularly certain lipid species such as ceramides, may play a role in metabolic signaling and regulation [21].