Metabolic Syndrome In Peritoneal Dialysis Is Associated With CVD And Its Possible Molecular Mechanism

Background and AimCardiovascular disease(CVD) has been one of the major complications and causes of death in end-stage renal disease(ESRD) patients. The increased morbidity of metabolic syndrome(Met S) in peritoneal dialysis(PD) patients has promoted the progress of CVD. Insulin resistance(IR) and hyperleptinemia play a key role in metabolic syndrome. The purposes of this study are as followed:1) Observe CVD morbidity in peritoneal dialysis patients and assess the risk factors of increased CVD morbidity.2) Investigate the morbidity of RI and hyperleptinemia in PD patients, assess the associated influence factors and their relationship with prognosis.3) Study the gene polymorphism of PD patients, elucidate the association of polymorphism with IR and hyperleptinemia.4) Investigate in uremic rats whether endoplasmic reticulum stress pathway PERK-e IF2α and molecular chaperone ORP150 play a key role in IR,whether intraperitoneal administration of recombinant leptin can improve IR by regulating endoplasmic reticulum stress pathway.Methods1. This study included all patients who started on PD between January 2003 and June 2009. They were followed up from the date of PD initiation until new onset CVD.2. PD patients with dialysis age more than three months and without diabetes before dialysis in our hospital were enrolled. We analyzed their leptin, lipids, glucose, dialysis adequacy, calculate insulin resistance index(HOMA-IR) and the numbers of conditions with metabolic syndrome each patient meets for prospective observation. We Assessed high HOMA-IR(H group), low HOMA-IR(L group) and diabetes group(DM group) for glucose and lipid metabolism, adipocytokines and the correlation between prognosis.3. In the second part of patients,we detected polymorphism of leptin gene promoter and exon, evaluated-2548 loci and 19 loci genotype polymorphism, leptin, insulin resistance index, Met S relevance and prognostic influence, assessed the difference of leptin gene polymorphism between high HOMA-IR, low HOMA-IR and DM group.4.The model of 5/6 nephrectomy rats was created and divided into five groups, including the saline control group, the rest groups received daily intraperitoneal injection of 4.25% glucose dialysis solution 20 ml, while HL and LL group were given leptin(4ug/100g/day and 2ug/100g/day), P group were given four phenyl butyric acid(PBA)for on month each. Western blot analysis was performed to detect PERK, e IF2α, ORP150 expression in the liver and intra-abdominal fat, peripheral fat and muscle tissues. Glucose tolerance and insulin analysis were performed. Adipocytokines expression was detected by ELISA. All the results were observed between groups.Results1. The median follow-up time was 44.13 months. In patients with preexisting CVD, both high triglyceride and the duration of dialysis were independent predictors of CVD progression, and the left atrial dimension(LAD), left ventricle septal thickness(LVST), left ventricle mass index(LVMI), Intima-media thickness(IMT) also had the difference. Serum albumin in CVD group was lower than in no CVD group. CCr and Kt/V in CVD group were lower than in no CVD group.2. A total of 157 patients were enrolled in the study. In the DM group, the incidence of metabolic syndrome in DM group is 73%, in H group the incidence is 64%,although there is no DM patient in this group, while in L group there were only 23% of patients had Met S. CVD was still the major causes of death in our PD patients. DM patients had poorer prognosis than other two groups, while the prognosis of patients in L group was better. This indicated the high morbidity of Met S in PD patients with high IR is similar with DM patients. Patients in L group were younger, they also had a lower level of BMI, cholesterol, triglyceride, glycated albumin and hs CRP and higher level of n PCR and HDL than patients in other two groups. Patients in DM group had a higher level of fasting blood-glucose and glycated albumin. Regression analysis indicated HOMA-IR was positively correlated with age, leptin level, triglyceride and negatively correlated with BMI. Logistic regression analysis of prognosis showed that dialysis age, Leptin, n PCR and hs CRP are associated with patients’ prognosis.3. The-2548 promoter region and exon 19 polymorphism correlates with serum leptin values and BMI in PD patients. PD patients with AA genotype of-2548 promoter were observed with lower level of BMI and leptin, while the increased gene frequency of A in exon 19 was related to a higher level of leptin and BMI. Patients with AA genotype of exon 19 were found with higher fasting blood-glucose and lower albumin. Statistical differences were found in Survivorship curve of three groups(GG,GA,AA)(p=0.037). PD patients of high IR and DM had an increased G allele polymorphism in-2548 and A allele polymorphism in exon 19.4. Compare with the control group, uremic rats with high glucose dialysis was found with significant reduced adiponectin, HDL-c, ISI and elevated resistin, leptin, blood glucose, insulin secretion, triglyceride, cholesterol and LDL-c, HOMA-IR, CRP. Western Blot showed a significant higher level of ORP150, p-PERK-p-e IF2α of liver tissue and ORP150, PERK-e IF2α, p-PERK-p-e IF2α of adipose tissue and muscle tissues in G group. Compared with the high glucose dialysis group, mice intraperitoneal injected with leptin 4ug/100g/d showed elevated adiponectin, HDL-c, ISI, reduced resistin, leptin, triglyceride, cholesterol and LDL-c, HOMA-IR, CRP and blood glucose, insulin secretion were almost normal. Western Blot protein detection showed a significant lower level of ORP150, p-PERK-p-e IF2α of liver tissue and ORP150, PERK-e IF2α, p-PERK-p-e IF2α of adipose tissue and muscle tissues in HL group. Compared with the high glucose dialysis group, mice intraperitoneal injected with leptin 2ug/100g/d or PBA 1mg/100g/d showed elevated adiponectin, HDL-c, ISI, reduced resistin, leptin, triglyceride, cholesterol and LDL-c, HOMA-IR, CRP and blood glucose, insulin secretion were almost normal. Western Blot protein detection showed a significant lower level of ORP150, p-PERK-p-e IF2α of liver tissue and ORP150, PERK-e IF2α, p-PERK-p-e IF2α of adipose tissue and muscle tissues in LL and P group, some indicators with statistical significance.ConclusionsIf the patients preexisting CVD, it is important to address traditional risk factors such as LVMI, IMT, lipid profile. If the patients without preexisting CVD, we should pay more attention to the nutritional status and PD prescription in order to lower the morbidity of CVD in these PD patients.HOMA-IR can be used to assess insulin resistance in peritoneal dialysis patients. A higher incidence of metabolic syndrome was found in diabetic group and high IR group together with elevated leptin, significantly blood glucose and lipid disorders, elevated hs CRP, increased all-cause mortality and poorer prognosis. Dialysis age, leptin, n PCR and hs CRP are associated with patients’ prognosis.Leptin gene polymorphism participates in insulin resistance, hyperleptinemia, glucose metabolism disorders in peritoneal dialysis patients. The-2548 promoter region and exon 19 polymorphism correlates with serum leptin values and BMI, Leptin A19 G polymorphism may be one of the risk factors for poor prognosis in patients with peritoneal dialysis.High glucose dialysis in uremic rats activates the endoplasmic reticulum stress in the liver, adipose tissue and muscle tissues, resulting in glucose tolerance disorder, dyslipidemia, insulin resistance, and abnormal expression of adipose tissue secretory factor Adiponectin, Leptin, Resistin, while IR leads to systemic micro-inflammatory state. Intraperitoneal injection of leptin 4ug/100g/day can down-regulate the endoplasmic reticulum stress in uremic rat liver, adipose tissue and muscle, and may be one of the ways to improve adipose tissue secretory factor metabolism disorder, insulin resistance and micro-inflammatory state. Leptin 2ug/100g/day or PBA effects worse than Leptin 4ug/100g/day.