In vivo monitoring of hepatic glycolipid distribution of n-6 ∕ n-3 in jugular-vein-cannulated rats as a nutritional research model for monogastric animal

Abstract

The metabolic distribution via blood from liver of glycerolipids by omega-6 to omega-3 fatty acid ( $n$ -6 $/$ $n$ -3) ratio in monogastric animal nutrition is very important. In vivo monitoring technique using jugular-vein-cannulated rats as a nutritional model for monogastric animal can yield important insights into animal nutrition. This study was conducted to determine the effect of different $n$ -6 $/$ $n$ -3 ratios ( $71:1$ , $4:1$ , $15:1$ , $30:1$ ) on metabolic distribution of glycerolipids newly synthesized and secreted in the liver of the rats and explore the mechanism involved. Regarding ${}^{14}{\mathrm{CO}}_2$ released from oxidation of glycerolipid metabolism, it was the highest (22.5 %) in groups with a $n$ -6 $/$ $n$ -3 ratio of $4:1$ ( $P<0.05$ ). The control group showed the highest total glycerolipid level, followed by the $30:1$ , $15:1$ , and $4:1$ groups in order ( $P<0.05$ ). When secreted triacylglycerol level of each group was compared with that of the control group, the $4:1$ , $15:1$ , and $30:1$ groups were decreased by 36.3 %, 20.9 %, and 13.3 %, respectively ( $P<0.05$ ). Regarding the distribution of phospholipid against total glycerolipid compared to the control group, the $4:1$ , $15:1$ , and $30:1$ groups were 1.38, 1.29, and 1.17 times higher, respectively ( $P<0.05$ ). In the comparison of ${}^{14}{\mathrm{CO}}_2$ emission against total glycerolipid compared with the control group, the $4:1$ , $15:1$ , and $30:1$ groups were 1.61, 1.52, and 1.29 times higher, respectively ( $P<0.05$ ). These results demonstrate that a dietary $n$ -6 $/$ $n$ -3 fatty acid ratio of $4:1$ could significantly decrease harmful lipid levels in the blood by controlling the mechanism of metabolic distribution via blood from triglyceride and phospholipid newly synthesized in the liver of cannulated rat.

Figure 1

Distribution of acyl moiety fluxes for oxidation and glycerolipid synthesis in the liver of jugular-vein-cannulated rats ($n=\mathrm{6}$). DG, diacylglycerol; TG, triglyceride; PC, phosphatidylcholine; PE, phosphatidylethanolamine.