| Parenteral nutrition(PN)is the primary nutritional treatment for patients with gastrointestinal dysfunction caused by various diseases or pathological factors,which has saved thousands of patients' lives.Long-term PN can lead to glucose metabolism disorder,the main manifestation of which is glycemic instability.PN-related hyper-or hypoglycemia is common,both of which affect patients' outcomes seriously.Traditionally,hyper-and hypoglycemia are caused by direct glucose infusion,and sudden cessation of PN or excess of insulin administration,respectively.However,there is a lack of further exploration on the mechanism of PN-related glucose metabolism disorder.Gut microbiota-drived tryptophan metabolites plays an important role in metabolic disorder syndrome and insulin resistance.Moreover,our previous data indicated gut microbiota disorder in PN.We hypothesized that impaired gut microbiota-derived tryptophan metabolism during PN may lead to glucose metabolism disorder by inducing insulin resistance.The present study contains two major parts: clinical research and mechanism research.Patients with chronic intestinal failure(CIF)who received long-term PN support were retrospectively analyzed to explore relationship between PN and insulin resistance,and the relationship between insulin resistance degree and clinical outcomes in the clinical research.For the mechanism study,we established total parenteral nutrition(TPN)mice model,and verified insulin resistance and liver glycogen deposition at animal and molecular level.Furthermore,the upstream mechanism of insulin resistance and glycogen synthesis disorder in TPN was determined by detecting gut microbiota,metabonomics and exogenous intervention in aryl hydrocarbon receptor(Ah R).The present study illustrated the causes and molecular mechanism of TPN related glucose metabolism disorder and provided a potential target for the prevention and treatment of TPN related glucose metabolism disorder.Part 1: Relationship between parenteral nutrition and insulin resistance in patients with chronic intestinal failureObjective: PN can induce glucose metabolism disorder.Insulin resistance,the most common mechanism of glucose metabolism disorder,was well documented in patients with critically illness and diabetes mellitus but not in patients with PN support.The purpose of this part is to investigate the correlation between PN and insulin resistance,as well as the relationship between insulin resistance degree and clinical prognosis,lean body mass rate in PN dependent patients.Methods: Adult patients diagnosed with CIF and received PN support in Department of General surgery and Clinical Nutrition Center,Jinling Hospital,Medical School of Nanjing University from August 2013 to August 2018 were included in this retrospective study.Patients were divided into two groups according nutritional strategy during hospitalization: the average energy from PN more than80% defined as TPN group;the average energy of PN from 10% to 80% defined as PEN group.Homeostatic model assessment for insulin resistance(HOMA-IR)was used to evaluate the degree of insulin resistance.The degree of insulin resistance,the incidence of in-hospital complications and lean body mass rate were compared between the two groups,and the correlation between HOMA-IR and PN calorie proportion,in-hospital complications,lean body mass rate was further analyzed.Results: A total of 256 patients with CIF were included in the final analysis.HOMA-IR was positively correlated with PN calorie proportion.Compared with patients in PEN group,TPN group showed significant higher mean fasting glucose and HOMA-IR value;higher incidence of in-hospital complications,including ICU transfer rate,liver injury,renal insufficiency,infection,fever and pneumonia;longer hospital stay and higher hospitalization costs as well.HOMA-IR was positively correlated with ICU transfer rate,liver injury,renal insufficiency,infection,pneumonia and fever,and negatively correlated with lean body mass rate.HOMA-IR together with body mass index(BMI),)sex,serum C-reactive protein(CRP)and blood cholesterol were independent risk factors for body protein mass rate,fat free mass rate and skeletal muscle mass rate.Conclusion: Insulin resistance is positively correlated with PN in a dose-dependent manner.It may be the potential mechanism of PN-related glucose metabolism disorder and is related to the poor prognosis of CIF patients.Part 2: Insulin resistance and impaired liver glycogen synthesis in total parenteral nutrition miceObjective: The clinical results proved the correlation between PN and insulin resistance,but failed to illustrate causal relationship.The aim of this part is(1)to explore whether TPN can induce insulin resistance;(2)to explore liver glycogen deposition in TPN.Methods: C57BL/6 male mice weighing 25-30 g at the same age of 12 weeks were randomly divided into two groups: TPN group(n = 8,drinking freely and fasting with TPN solution infusion)and Chow group(n = 8,Ad libitum and saline infusion).Intra-peritoneal glucose tolerance test(GTT)and insulin tolerance(ITT)test were performed after 7 days nutritional intervention.The fasting blood glucose,HOMA-IR,insulin signaling pathway and glycogen deposition in liver were compared between the two groups by using TPN mice model.Results: No significant difference was found in body weight between the two groups.Compared with Chow group,TPN group presented significantly higher fasting glucose level and HOMA-IR value;impaired glucose and insulin tolerance,higher serum AST and ALT level and the ratio of p-GSK3?/GSK3? in liver.The insulin-derived glycogen synthesis signaling pathway in liver was significantly inhibited,and liver glycogen storage was significantly decreased.Conclusion: TPN can induce systemic and liver insulin resistance,thereafter impair liver glycogen synthesis.Part 3: Impaired gut microbiota and tryptophan metabolism in total parenteral nutrition mice modelObjective: The altered gut microbiota and its metabolites may be the source of metabolic disorder syndrome in TPN.The aim of this part is to explore the changes of gut microbiota and bacterial metabolites in gut contents during TPN,and to analyze the correlation between differential metabolites and specific gut bacteria.Methods: C57BL/6male mice weighing 25-30 g from the same batch of 12 weeks old were randomly divided into two groups: TPN group(n = 5,drinking freely and fasting with TPN solution infusion)and Chow group(n = 5,Ad libitum and saline infusion).Seven days later,the mice were killed for quick freezing of fresh cecum contents by liquid nitrogen.The abundance,diversity and structure of gut microbiota were compared by 16 s high throughput DNA sequencing.The non-targeted metabonomics analysis was used to identify the different metabolites and metabolic pathways between two groups.The corregulation of different metabolites and microbiota was analyzed.Results: Both gut microbiota and bacterial metabolites spectrum in TPN group was significantly altered compared to Chow group.No significant difference was found in total abundance of microbiota between the two groups at the level of phylum,class,order and genus.The OTU diversity number in TPN group was lower than Chow group,but failed to achieve statistical difference.Compared with Chow group,f?Lactobacillaceae,f?Muribaculaceae,g?Lactobacillus and g?Muribaculum were significantly decreased,and f?Ruminococcaceae,f?Lachnospiraceae were significantly increased in TPN group.Tryptophan metabolites were significantly decreased in TPN group,including indole,hydroxyindole,indole carbaldehyde,indole-3-acetic acid,indole acetate,indole-3-lactic acid,5-methoxyindole,kynurenic acid etc.KEGG pathway analysis suggested that tryptophan metabolic pathway was one of the main differential metabolic pathways between the two groups.Correlation analysis showed that g?Lactobacillus was positively correlated with trypotophan metabolites,including 5-methoxyindole,indole-3-lactic acid,indole-3-lactic acid and indole acetate.Conclusion: g?Lactobacillus reduction leads to tryptophan metabolism disorder,which results in indole metabolites decreased during TPN.Part 4: Effect of exogenous intervention on aryl hydrocarbon receptor on parenteral nutrition related insulin resistanceObjective: Altered gut microbiota during TPN leads to tryptophan metabolites reduction.Tryptophan metabolites are important endogenous ligands of Ah R.Impaired Ah R activation can lead to insulin resistance by down-regulate GLP-1production.The objective of this part is to explore the role of Ah R pathway in TPN related insulin resistance by exogenous intervention in Ah R.Methods: C57BL/6 male mice weighing 25-30 g from the same batch of 12 weeks old were randomly divided into four groups: Chow+DMSO group(n = 8,intra-peritoneal injection of DMSO),Chow+CH223191 group(n = 8,intra-peritoneal injection of DMSO with CH223191),TPN+DMSO group(n = 8,intra-peritoneal injection of DMSO),TPN+Ficz group(n = 8,intra-peritoneal injection of DMSO with Ficz).After 7 days nutritional intervention,intra-peritoneal glucose tolerance test and insulin tolerance test were performed.The insulin signaling pathway and liver glycogen deposition were compared among 4 groups in TPN mice model.Results: Compared with Chow+DMSO group,serum GLP-1 was significantly decreased,glucose and insulin tolerance were impaired,and liver glycogen deposition was significantly decreased in TPN+DMSO group.In mice of TPN,exogenous stimulation of Ah R by Ficz significantly improved the impaired GLP-1 level,insulin sensitivity and liver glycogen depositon during TPN.In mice with enteral feeding,inhibition of Ah R by CH223191 could induce phenotypes similar to TPN,including insulin resistance and liver glycogen.Moreover,exogenous stimulation or inhibition of Ah R had no significant effect on liver injury.Conclusion: Exogenous intervention on Ah R can regulate insulin resistance in TPN through GLP-1.Ah R may be the key therapeutic target for TPN related glucose metabolism disorder. |
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