Regulation of hepatic metabolism by enteral delivery of nutrients

Abstract

The liver plays a unique role in nutrient homeostasis. Its anatomical location makes it ideally suited to control the systemic supply of absorbed nutrients, and it is the primary organ that can both consume and produce substantial amounts of glucose. Moreover, it is the site of a substantial fraction (about 25 %) of the body's protein synthesis, and the liver and other organs of the splanchnic bed play an important role in sparing dietary N by storing ingested amino acids. This hepatic anabolism is under the control of hormonal and nutritional changes that occur during food intake. In particular, the route of nutrient delivery, i.e. oral (or intraportal) v. peripheral venous, appears to impact upon the disposition of the macronutrients and also to affect both hepatic and whole-body nutrient metabolism. Intraportal glucose delivery significantly enhances net hepatic glucose uptake, compared with glucose infusion via a peripheral vein. On the other hand, concomitant intraportal infusion of both glucose and gluconeogenic amino acids significantly decreases net hepatic glucose uptake, compared with infusion of the same mass of glucose by itself. Delivery of amino acids via the portal vein may enhance their hepatic uptake, however. Elevation of circulating lipids under postprandial conditions appears to impair both hepatic and whole-body glucose disposal. Thus, the liver's role in nutrient disposal and metabolism is highly responsive to the route of nutrient delivery, and this is an important consideration in planning nutrition support and optimising anabolism in vulnerable patients.

Evaluation of Intragastric Vs Intraperitoneal Glucose Tolerance Tests in the Evaluation of Insulin Resistance in a Rodent Model of Burn Injury and Glucagon-Like Polypeptide-1 Treatment

“…This implies that a substantial amount of intragastrically administered glucose is taken up by the splanchnic bed during its first pass through the organs. This has been proven by the studies by Dardevet et al 19 . An additional explanation is that intragastrically administered glucose may be more efficient in stimulating insulin release from pancreatic beta cells for lowering blood sugar levels (Figure 3).…”

“…Considering the significant first-pass uptake of glucose by the splanchnic region after oral glucose administration 19 , all animals received 2 g/kg of glucose via the indwelling gastric tube for IGGTT. After an overnight fast (from 5 pm to 8 am), the arterial catheter was connected to a Miniature Tubing Injection Port (SIP22/4, Instech Solomon, Plymouth Meeting, PA) for non-invasive blood sampling.…”

Metabolic response to high-carbohydrate and low-carbohydrate meals in a nonhuman primate model

“…The uptake and metabolism of glucose by the liver after food intake is affected by the rate of glucose and hormone delivery, which in turn depends on portal vein blood flow during a meal (11). Portal venous blood flow increases by 20 to 80% 30 min after a meal, depending on the type of meal (liquid vs. solid), and remains elevated for 2 h after meal consumption (10,12,16,44).…”

“…Accordingly, the ability to sample portal vein blood is important for understanding postprandial metabolic regulation. Several studies conducted in animal models have used portal vein catheterization to evaluate the effect of intraportal nutrient delivery on hepatic and whole body metabolism (11,43,49). However, we are not aware of any studies that have used portal vein catheterization to evaluate the effect of differences in dietary macronutrient composition on the metabolic response to a meal.…”

Proteomic profiling of liver from Elaphe taeniura, a common snake in eastern and southeastern Asia

“…This adaptability has been attributed to the development of a special metabolic system in snakes. The liver plays a major role in metabolism, including glycogen storage, red blood cell degradation, plasma protein synthesis, hormone production and detoxification (Dardevet et al , 2006; Reddy and Rao, 2006), and also contains disease-associated proteins (Zeindl-Eberhart et al , 2001; Yokoyama et al , 2004). Recent studies have shown that snake liver has a strong metabolic capacity (Ladyman et al , 2003; Starck et al , 2004) that may have an important role ensuring survival in nature.…”