Metabolic control during total parenteral nutrition: use of an artificial endocrine pancreas

Novel Strategies to Prevent Total Parenteral Nutrition-Induced Gut and Liver Inflammation, and Adverse Metabolic Outcomes

Total parenteral nutrition (TPN) is a life-saving therapy administered to millions of patients. However, it is associated with significant adverse effects, namely liver injury, risk of infections, and metabolic derangements. In this review, the underlying causes of TPN-associated adverse effects, specifically gut atrophy, dysbiosis of the intestinal microbiome, leakage of the epithelial barrier with bacterial invasion, and inflammation are first described. The role of the bile acid receptors farnesoid X receptor and Takeda G protein-coupled receptor, of pleiotropic hormones, and growth factors is highlighted, and the mechanisms of insulin resistance, namely the lack of insulinotropic and insulinomimetic signaling of gut-originating incretins as well as the potentially toxicity of phytosterols and pro-inflammatory fatty acids mainly released from soybean oil-based lipid emulsions, are discussed. Finally, novel approaches in the design of next generation lipid delivery systems are proposed. Propositions include modifying the physicochemical properties of lipid emulsions, the use of lipid emulsions generated from sustainable oils with favorable ratios of anti-inflammatory n-3 to pro-inflammatory n-6 fatty acids, beneficial adjuncts to TPN, and concomitant pharmacotherapies to mitigate TPN-associated adverse effects.

Healthy twin birth after autologous islet transplantation in a pancreatectomized patient due to a benign tumor

OBJECTIVE

Autologous islet transplantation has been reported to show favorable outcomes on glucose metabolism. The objective of this study was to describe successful delivery of twins in an islet recipient who had undergone distal pancreatectomy.

PATIENT

A 35-year-old woman who underwent distal pancreatectomy owing to a solid pseudopapillary neoplasm received an autologous islet transplantation (140,000 islet equivalents). After 2.5 years, she unexpectedly became pregnant. Cesarean section was performed at 35 weeks delivering male twins without complications. Plasma glucose and insulin levels, insulinogenic index, and hemoglobin A1c were measured from the preoperative to the postpartum state as the main outcome.

RESULTS

The patient showed impaired glucose tolerance before pancreatectomy, but improved to a normal glucose tolerance after transplantation, maintaining euglycemia until pregnancy. Because her fasting glucose levels were within the normal range during pregnancy, fasting insulin represented insulin resistance. Her fasting insulin levels abruptly increased in the third trimester of pregnancy, but returned after delivery. Insulinogenic index increased over 1 year after transplantation, but gradually decreased thereafter. During pregnancy, it increased again, but could not compensate for the insulin resistance. Therefore, gestational diabetes mellitus developed: glucose homeostasis recovered to normal after delivery.

CONCLUSIONS

The current report suggested a successful pregnancy after autologous islet transplantation that did not itself permanently deteriorate graft function.

Expression of islet inducible nitric oxide synthase and inhibition of glucose-stimulated insulin release after long-term lipid infusion in the rat is counteracted by PACAP27

Chronic exposure of pancreatic islets to elevated plasma lipids (lipotoxicity) can lead to beta-cell dysfunction, with overtime becoming irreversible. We examined, by confocal microscopy and biochemistry, whether the expression of islet inducible nitric oxide synthase (iNOS) and the concomitant inhibition of glucose-stimulated insulin release seen after lipid infusion in rats was modulated by the islet neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP)27. Lipid infusion for 8 days induced a strong expression of islet iNOS, which was mainly confined to beta-cells and was still evident after incubating islets at 8.3 mmol/l glucose. This was accompanied by a high iNOS-derived NO generation, a decreased insulin release, and increased cyclic GMP accumulation. No iNOS expression was found in control islets. Addition of PACAP27 to incubated islets from lipid-infused rats resulted in loss of iNOS protein expression, increased cyclic AMP, decreased cyclic GMP, and suppression of the activities of neuronal constitutive (nc)NOS and iNOS and increased glucose-stimulated insulin response. These effects were reversed by the PKA inhibitor H-89. The suppression of islet iNOS expression induced by PACAP27 was not affected by the proteasome inhibitor MG-132, which by itself induced the loss of iNOS protein, making a direct proteasomal involvement less likely. Our results suggest that PACAP27 through its cyclic AMP- and PKA-stimulating capacity strongly suppresses not only ncNOS but, importantly, also the lipid-induced stimulation of iNOS expression, possibly by a nonproteasomal mechanism. Thus PACAP27 restores the impairment of glucose-stimulated insulin release and additionally might induce cytoprotection against deleterious actions of iNOS-derived NO in beta-cells.

Selective induction of inducible nitric oxide synthase in pancreatic islet of rat after an intravenous glucose or intralipid challenge

OBJECTIVE

Constant exposure of pancreatic islets to high levels of glucose or free fatty acids can lead to irreversible beta-cell dysfunction, a process referred to as glucotoxicity or lipotoxicity, respectively. In this context a role for nitric oxide generated by pancreatic islet has been suggested. The present investigation examined whether the route of glucose administration, i.e., given orally (OG) or infused intravenously (IVG), could have any effect on the expression and activity of inducible nitric oxide synthase (iNOS) in pancreatic islets.

METHODS

Rats were infused with glucose (50%) or Intralipid intravenously for 24 h or given glucose orally. A freely fed control group (FF) was also included. At 24 h rats were killed and blood samples were drawn for analysis of plasma insulin, glucagon, and glucose. Pancreatic islets were harvested from each animal and investigated for the occurrence of iNOS by the use of confocal microscopy, western blot, and high-performance liquid chromatographic analysis. The effect of intravenously infused glucose was then compared with the effect of an intravenous infusion of Intralipid (IL).

RESULTS

Plasma insulin levels were markedly decreased after 24 h of infusion of glucose (IVG group) or Intralipid (IL group) compared with the FF or OG group. Plasma glucagon and glucose levels were markedly increased in the IVG group, whereas both parameters were decreased in the IL group. No significant differences in plasma insulin, glucagon, or glucose were found between the OG and FF groups. Immunocytochemical (confocal microscopy), western blot, and biochemical (high-performance liquid chromatographic) analyses showed that a sustained increase in plasma level of glucose or free fatty acids by an intravenous infusion of either nutrient for 24 h resulted in a marked expression and activity of iNOS in pancreatic islets. No sign of iNOS expression could, however, be detected in the islets of FF control or OG rats.

CONCLUSION

The data suggest that impaired beta-cell function found after 24 h of an intravenous infusion of glucose or Intralipid might be mediated, at least in part, by the induction of iNOS in pancreatic islets. This may subsequently result in an exclusive production of nitric oxide, which is deleterious for beta-cells.

Endothelial function and mechanical properties of the common carotid artery in children on parenteral nutrition

Intravenous administration of nutrition mixtures induces endothelial damage and arterial wall remodeling in animal models. To study endothelial function and common carotid artery mechanical properties in children receiving parenteral nutrition, we used noninvasive ultrasonic measurements in 18 children on parenteral nutrition and 18 controls. No difference appeared in the geometry of the common carotid artery (intima media thickness, systolic and diastolic diameters) between the patients on parenteral nutrition and the controls. The incremental elastic modulus was significantly higher in the patients on parenteral nutrition (1.8 +/- 0.4 versus 1.4 +/- 0.5 4 mm Hg x 10(3), p < 0.05) reflecting alteration of the elastic properties of the arterial wall independent of the vessel geometry. The flow-mediated dilatation of the brachial artery was significantly lower in the patients on parenteral nutrition (6 +/- 3 versus 8 +/- 3%, p < 0.05), whereas the dilatation after glyceryl trinitrate administration was similar (22 +/- 9 versus 25 +/- 9%). Children on parenteral nutrition exhibit endothelial dysfunction and altered stiffness of the common carotid artery. The noninvasive methods used in this study may prove useful for objectively determining the effects of various preventive methods.

Total parenteral nutrition modulates hormone release by stimulating expression and activity of inducible nitric oxide synthase in rat pancreatic islets

The expression and activities of constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) in relation to insulin and glucagon secretory mechanisms were investigated in islets isolated from rats subjected to total parenteral nutrition (TPN) for 10 d. TPN is known to result in significantly increased levels of plasma lipids during the infusion time. In comparison with islets from freely fed control rats, islets taken from TPN rats at d 10 displayed a marked decrease in glucose-stimulated insulin release (4.65 +/- 0.45 ng/[islet x h] vs 10.25 +/- 0.65 for controls) (p < 0.001) accompanied by a strong iNOS activity (18.3 +/- 1.1 pmol of NO/[min x mg of protein]) and a modestly reduced cNOS activity (11.3 +/- 3.2 pmol of NO/[min x mg of protein] vs 17.7 +/- 1.7 for controls) (p < 0.01). Similarly, Western blots showed the expression of iNOS protein as well as a significant reduction in cNOS protein in islets from TPN-treated rats. The enhanced NO production, which is known to inhibit glucose-stimulated insulin release, was manifested as a strong increase in the cyclic guanosine 5'-monophosphate content in the islets of TPN-treated rats (1586 +/- 40 amol/islet vs 695 +/- 64 [p < 0.001] for controls). Moreover, the content of cyclic adenosine monophosphate (cAMP) was greatly increased in the TPN islets (80.4 +/- 2.1 fmol/islet vs 42.6 +/- 2.6 [p < 0.001] for controls). The decrease in glucose-stimulated insulin release was associated with an increase in the activity of the secretory pathway regulated by the cAMP system in the islets of TPN-treated rats, since the release of insulin stimulated by the phosphodiesterase inhibitor isobutylmethylxanthine was greatly increased both in vivo after iv injection and after in vitro incubation of isolated islets. By contrast, the release of glucagon was clearly reduced in islets taken from TPN-treated rats (33.5 +/- 1.5 pg/[islet x h] vs 45.5 +/- 2.2 for controls) (p < 0.01) when islets were incubated at low glucose (1.0 mmol/L). The data show that long-term TPN treatment in rats brings about impairment of glucose-stimulated insulin release, that might be explained by iNOS expression and a marked iNOS-derived NO production in the beta-cells. The release of glucagon, on the other hand, is probably decreased by a direct "nutrient effect" of the enhanced plasma lipids. The results also suggest that the islets of TPN-treated rats have developed compensatory insulin secretory mechanisms by increasing the activity of their beta-cell cAMP system.

Route of nutrient delivery affects insulin sensitivity and liver glucose transporter expression in rat

To optimize artificial nutrition (AN) techniques for patients suffering from malnutrition or reduced intestinal absorption, utilization of energy fuels, especially glucose, requires better understanding. Because the liver plays a key role in glucose homeostasis, the aim of this study was to assess the effects of continuous intragastric and intravenous nutrition on insulin secretion and several markers of liver glucose metabolism, especially glucose transporter GLUT-2. Wistar male rats underwent catheterization of either stomach (intragastric) or vena cava (intravenous) and received 24 h/day the same all-in-one formula over 7 to 14 days. The metabolic parameters from intragastrically fed rats did not differ significantly from those from orally fed control rats. Intravenous nutrition induced insulin resistance (marked hyperinsulinemia and/or mild hyperglycemia) and reduced liver GLUT-2 protein and mRNA levels. The decrease in liver GLUT-2 gene expression might be mediated either by an inhibitory role of hyperinsulinemia or by the decrease in gut or portal factors. These results suggest that the route of nutrient delivery influences their utilization by the liver.

Liver and biliary tract changes and injury associated with total parenteral nutrition: pathogenesis and prevention

Total parenteral nutrition (TPN), now widely used, is successful in preventing and reversing malnutrition in individuals with various diseases and conditions. However, hepatic and biliary complications of TPN are encountered in both adult and pediatric patients. Certain complications, such as sepsis and TPN-associated cholestasis, occur more frequently in very young infants. Continuing problems commonly seen in adults are steatosis and steatonecrosis. Reasons for the development of these complications are multifactorial. Etiologies of hepatic complications, especially the role of deficiency/excess of nutrients in the pathogenesis of hepatobiliary disorders, are summarized. Complications caused by the duration of TPN are discussed with emphasis on prevention and management. Evidence now suggests that prompt enteral feeding, even in minimal amounts, may prevent many of the metabolic complications associated with TPN. TPN should be used only in amounts meeting needs and for a duration essential to survival.

Insulin regulation of glucose and lipid metabolism in massive obesity

Eight obese patients and 12 normal individuals underwent a euglycaemic insulin clamp (20 and 40 mU m2-1.min-1) along with continuous infusion of 3-3H-glucose and 1-14C-palmitate and indirect calorimetry. Basal plasma glucose concentration (4.7 +/- 0.3 vs 4.4 +/- 0.2 mmol/l) was similar in the two groups, whereas hepatic glucose production was slightly higher in obese individuals (1.11 +/- 0.06 vs 0.84 +/- 0.05 mmol/min) in spite of higher plasma insulin levels (17 +/- 2 vs 6 +/- 1 mU/l; p less than 0.01). Insulin inhibition of hepatic glucose production was impaired in obese subjects. Glucose disposal by lean body mass was markedly reduced both at baseline (11.7 +/- 1.1 vs 15.6 +/- 0.6 mumol.kg-1.min-1; p less than 0.05) and during clamp (15.0 +/- 1.1 vs 34.4 +/- 2.8 and 26.7 +/- 3.9 vs 62.2 +/- 2.8 mumol.kg-1.min-1; p less than 0.01) Oxidative (12.2 +/- 1.1 vs 17.8 +/- 1 and 16.1 +/- 1.1 vs 51.1 +/- 1.7 mumol.kg-1.min-1; p less than 0.05-0.002) and non-oxidative glucose metabolism (3.9 +/- 1.1 vs 15.0 +/- 2.8 and 12.8 +/- 3.3 vs 38.2 +/- 2.2 mumol.kg-1.min-1; p less than 0.01-0.001) were impaired. Basal plasma concentrations of non-esterified fatty acids (635 +/- 75 vs 510 +/- 71 mumol/l) and blood glycerol (129 +/- 17 vs 56 +/- 5 mumol/l; p less than 0.01) were increased in obese patients.(ABSTRACT TRUNCATED AT 250 WORDS)