Effects of glucose or fat calories in total parenteral nutrition on fat metabolism and systemic inflammation in rats

This study compared the effects of total parenteral nutrition (TPN) by central vein with or without fat provided at maintenance energy requirement on fatty acid metabolism, de novo lipogenesis, and the risk of hepatic and systemic inflammation in rats. Study 1 was conducted in 2 groups: high glucose (HG), where fat-free TPN was given at maintenance levels of 180 kcal/(kg d), and low glucose (LG), where fat-free TPN containing 30% fewer calories at 126 kcal/(kg d) was provided by reducing 54 kcal/(kg d) from parenteral glucose. Study 2 contained 3 TPN groups: 1 LG group at 126 kcal/(kg d) and 2 groups at 180 kcal/(kg d) with 30% of total calories (54 kcal/[kg d]) either from soybean or fish oil emulsion. In both studies, animals fed a chow diet ad libitum were included. Plasma and hepatic triglyceride and phospholipid fatty acid profiles, enzymes indicating hepatic injury, and C-reactive protein levels (CRP) reflecting systemic injury were measured. In study 1, evidence of de novo lipogenesis was noted in LG and was more prominent in HG with elevation of CRP in HG. In study 2, de novo lipogenesis was reduced by adding either fat to LG to achieve maintenance energy levels. Moreover, adding fat as soybean oil but not fish oil significantly increased plasma and hepatic triglyceride and also elevated aspartate aminotransferase and CRP levels, reflecting inflammation. Thus, in rats, either hypocaloric feeding as glucose-based TPN or TPN provided at maintenance energy levels with the addition of fish oil limits hepatic lipid accumulation and prevents the evidence of hepatic and systemic injury found with maintenance level TPN as glucose only or glucose plus soybean oil.