Glucagon-mediated impairments in hepatic and peripheral tissue nutrient disposal are not aggravated by increased lipid availability

Nutritional regulation of glucokinase: a cross-species story

The glucokinase (GK) enzyme (EC 2.7.1.1.) is essential for the use of dietary glucose because it is the first enzyme to phosphorylate glucose in excess in different key tissues such as the pancreas and liver. The objective of the present review is not to fully describe the biochemical characteristics and the genetics of this enzyme but to detail its nutritional regulation in different vertebrates from fish to human. Indeed, the present review will describe the existence of the GK enzyme in different animal species that have naturally different levels of carbohydrate in their diets. Thus, some studies have been performed to analyse the nutritional regulation of the GK enzyme in humans and rodents (having high levels of dietary carbohydrates in their diets), in the chicken (moderate level of carbohydrates in its diet) and rainbow trout (no carbohydrate intake in its diet). All these data illustrate the nutritional importance of the GK enzyme irrespective of feeding habits, even in animals known to poorly use dietary carbohydrates (carnivorous species).

Combined therapy for acute hepatic failure

Acute hepatic failure (AHF) is a devastating clinical syndrome characterized by rapid impairment of liver functions and development of encephalopathy, multiple organ failure, and in most cases cerebral edema. AHF has a high mortality rate. Although advances in drug treatment, artificial liver and liver transplantation have significantly improved the prognosis of AHF, there is still a lack of effective treatment for AHF because of its complicated etiopathogenesis, rapid progression and less clinical knowledge about managing the disease. There is an urgent need to develop effective treatments for AHF. This article aims to review recent advances in the treatment of AHF.

Nutritional and metabolic abnormalities and nutrition support therapy in patients with liver failure

Nutritional and metabolic damage is an important manifestation of severe liver disease and is significantly associated with prognosis. In this paper, we review nutritional and metabolic abnormalities and nutritional support therapy in patients with liver failure by summarizing the indicators for evaluating the nutritional and metabolic status and the features of nutrients and energy metabolism. We point out that resting energy expenditure can be measured using CCM-D nutrition metabolism test system in liver failure patients. Energy supply is primarily contributed by fat oxidation in patients with chronic liver failure, and their respiratory quotient is significantly lower than the predicted values. In addition, we discuss nutritional support intervention methods and intake for different stages of liver failure. Our aim is to raise the awareness of clinicians for malnutrition in patients with liver failure to formulate individualized nutrition support therapy.

Physiologic action of glucagon on liver glucose metabolism

Glucagon is a primary regulator of hepatic glucose production (HGP) in vivo during fasting, exercise and hypoglycaemia. Glucagon also plays a role in limiting hepatic glucose uptake and producing the hyperglycaemic phenotype associated with insulin deficiency and insulin resistance. In response to a physiological rise in glucagon, HGP is rapidly stimulated. This increase in HGP is entirely attributable to an enhancement of glycogenolysis, with little to no acute effect on gluconeogenesis. This dramatic rise in glycogenolysis in response to hyperglucagonemia wanes with time. A component of this waning effect is known to be independent of hyperglycemia, though the molecular basis for this tachyphylaxis is not fully understood. In the overnight fasted state, the presence of basal glucagon secretion is essential in countering the suppressive effects of basal insulin, resulting in the maintenance of appropriate levels of glycogenolysis, fasting HGP and blood glucose. The enhancement of glycogenolysis in response to elevated glucagon is critical in the life-preserving counterregulatory response to hypoglycaemia, as well as a key factor in providing adequate circulating glucose for working muscle during exercise. Finally, glucagon has a key role in promoting the catabolic consequences associated with states of deficient insulin action, which supports the therapeutic potential in developing glucagon receptor antagonists or inhibitors of glucagon secretion.

Continuous low-dose fructose infusion does not reverse glucagon-mediated decrease in hepatic glucose utilization

An adaptation to continuous total parenteral nutrition (TPN; 75% of nonprotein calories as glucose) is the liver becomes a major consumer of glucose with lactate release as a by-product. The liver is able to further increase liver glucose uptake when a small dose of fructose is acutely infused via the portal system. Glucagon, commonly elevated during inflammatory stress, is a potent inhibitor of glucose uptake by the liver during TPN. The aim was to determine if continuous fructose infusion could overcome the glucagon-mediated decrease in hepatic glucose uptake. Studies were performed in conscious, insulin-treated, chronically catheterized, pancreatectomized dogs that adapted to TPN for 33 hours. They were then assigned to 1 of 4 groups: TPN (C), TPN + fructose (4.4 μmol kg(-1) min(-1); F), TPN + glucagon (0.2 pmol kg(-1) min(-1); GGN), or TPN + fructose and glucagon (F + GGN) for an additional 63 hours (33-96 hours). Insulin, fructose, and glucagon were infused into the portal vein. During that period, all animals received a fixed insulin infusion of 0.4 mU·kg(-1)·min(-1) (33-96 hours); and the glucose infusion rates were adjusted to maintain euglycemia (6.6 mmol/L). Continuous fructose infusion was unable to further enhance net hepatic glucose uptake (in micromoles per kilogram per minute) (31.1 ± 2.8 vs 36.1 ± 5.0; C vs F), nor was it able to overcome glucagon-mediated decrease in net hepatic glucose uptake (10.0 ± 4.4 vs 12.2 ± 3.9; GGN vs F + GGN). In summary, continuous fructose infusion cannot augment liver glucose uptake during TPN; nor can it overcome the inhibitory effects of glucagon.

Treatment with growth hormone, somatostatin, and insulin in combination with hypocaloric parenteral nutrition in gastrointestinal cancer patients after surgery

OBJECTIVE

The metabolic response to gastrointestinal cancer in patients undergoing surgery is associated with hypermetabolism and insulin resistance. The potential use of synergetic anabolic hormones in conjunction with hypocaloric parenteral nutrition (HPN) has become a significant area of investigation. The presented study was performed to determine the clinical efficiency and safety of hormone therapy combined with HPN in patients with gastrointestinal cancer.

METHODS

One hundred patients with a Nutrition Risk Screening score of 3 or 4 undergoing surgery for gastrointestinal cancer were randomized into two groups. The patients in the control group received standard total parenteral nutrition and systemic insulin. The patients in the study group received HPN and systemic insulin in addition to pretreatment with recombinant human growth hormone and octreotide. Clinical efficiency and safety were evaluated by the measurement of hormones and protein metabolites, immune function, clinical outcome, and adverse events. Follow-ups were performed to determine the influence on prognosis.

RESULTS

Treatment with recombinant human growth hormone, octreotide, and insulin in combination with HPN significantly increased protein synthesis, immune function, and metabolic tolerance, decreased infectious complications, and shortened postoperative hospital stays, but did not increase the risk of tumor development and recurrence in the study group compared with the control group.

CONCLUSION

The proper short-term perioperative administration of growth hormone, somatostatin, and insulin in combination with HPN can overcome the postoperative stress response through the increase of protein synthesis to improve immune function in patients with gastrointestinal cancer after surgery.