Impact Of Chronic Prenatal Hypoxia And Postnatal High Fat Diet On Blood Pressure Of Male Offspring Rat And Its Vascular Ion Channel Mechanism

Background:Cardiovascular disease(CVD)is the leading cause of global mortality.A large number of clinical and experimental studies have confirmed that low birth weight is closely related to the occurrence of cardiovascular disease in adult offspring.Intrauterine hypoxia can result in fetal intrauterine growth restriction,which significantly increases the risk of cardiovascular disease such as hypertensionlater in life.High fat diet acting as a bad factor has always been a focus in the field of nutrition.A large number of studies have confirmed that high fat diet can cause obesity and hyperlipidemia,which leads to cardiovaseular diseases such as hypertension and coronary heart disease.Although reeent studies have suggested that prenatal hypoxia made offspring more susceptible to high-fat-induced cardiovascular disease,but its specific mechanism is still unknown.Therefore,from the molecular and cellular levels,this study intends to explore the effect of chronic prenatal hypoxia and postnatal high fat diet on blood pressure of male offspring rat and its vascular ion channel mechanism,using the methods of rat femoral artery cannulation,micro vascular function detection,patch clamp technique and molecular biology.Part 1 The effects of prenatal hypoxia and postnatal high fat diet on fatal development and body weight and lipid profiles in adult male offspringObjective:To study the effects of hypoxia and high salt diet during pregnancy on body weight and blood lipids in offspring rats.Methods:Female SD rats were divided into control group and hypoxia group after pregnancy.On the 5th to 21st day of pregnancyGestation Day,GD5-21),the pregnant rats in the hypoxic group were placed in the hypoxia chamber with 10.5%of 02.the pregnant rats of control group were placed in a correspondingly sized normal oxygen chamber with 21%of O2.Newborn rats were removed within 3 to 8 hours after natural delivery for recording the weight.At the 4-16th week after birth,the two groups of offsprings were randomly divided into the normal diet group and the high fat diet(45%fat)group.Then,four groups were created:normoxia control offspring with the LF diet(CLF),normoxia control offspring with the HF diet(CHF),Prenatal hypoxia offspring with the LF diet(HLF),and prenatal hypoxia offspring with the HF diet(HHF).During this period,the body weight and food intake of offspring in each group were recorded every two weeks.The basal blood pressure and resting heart rate were measured by femoral artery cannulation technique.Results:The birth weight of offspring with prenatal hypoxia was significantly lower than that of normal offspring.However,at 4 weeks of age,there was no difference in body weight between PH and control pups.After 12 weeks of feeding,the body weight of rats with high fat diet was significantly higher than that of normal diet rats.Compared with the offspring with normal diet,the levels of plasma triglycerides,cholesterol,low-density lipoprotein and free fatty acids increased significantly in the high fat diet offspring,while the high-density lipoprotein levels significantly decreased.Prenatal hypoxia further exacerbates the effects of high fat diets on triglycerides,low-density lipoproteins,and free fatty acids.Conclusion:Hypoxia during pregnancy causes intrauterine growth restriction in the fetus and aggravates the effect of high fat diet on blood lipids after birth.Part 2 The effects of prenatal hypoxia and postnatal high fat diet on blood pressure and vessel contractions in male offspring ratsObjective:To study the effects of prenatal hypoxia and postnatal high fat diet on blood pressure and vessel contractions in male offspring rats.Methods:Pregnant Sprague-Dawley rats were randomly assigned to hypoxia(10.5%oxygen)or normoxia(21%02)groups from gestation day 5 to 21.A subset of male offspring was placed on a high fat diet(HF,45%fat)from 4 to 16 weeks of age.The blood pressure was measured in male offspring by femoral artery cannulation.The systolic function of the mesenteric artery of the offspring was detected by a microvascular function test platform.Results:The the systolic blood pressure,heart rate and the mesenchymal arteries to PE were significantly decreased in high fat diet offspring compared with the offspring normal diet.The hypoxia during pregnancy further aggravated the effects of High fat diet on systolic blood pressure and mesenteric artery systolic function.It was found that prenatal hypoxia and high fat diet during pregnancy can increase the diastolic blood pressure of the offspring.High fat diet but not hypoxia during pregnancy can reduce the sensitivity to the Ach relaxation response in the mesenchymal artery.Conclusion:High fat diet can increase the systolic blood pressure of the offspring and the contractile response of mesenteric artery to PE.Hypoxia during pregnancy can further aggravate the effect of high fat diet on systolic blood pressure and mesenteric artery tone.Part 3 The effects of prenatal hypoxia and postnatal high fat diet on on the BK channel of mesenchymal arterial smooth muscle cells in offspringObjective:To study the effects of prenatal hypoxia and postnatal high fat diet on BK channels in mesenteric artery smooth muscle cells in male offspring and its molecular mechanism.Methods:The patch-clamp single-channel technique was used to detect the biophysical properties of BK channels in the mesenchymal arterial smooth muscle cells.The whole-cell current of the BK channel was recorded using a traditional patch-clamp whole cell model.The mRNA and protein expression of a subunit and β1 subunit were detected by qRT-PCR and Western blot.Results:Compared with the offspring with normal diet,the activity of BK channel was significantly enhanced in mesenteric artery of offspring with high fat diet,which is independent of prenatal hypoxia factor.High fat diet significantly increased whole-cell potassium current and BK channel current density in mesenteric artery smooth muscle cells.The Ca2+ sensitivity,open probability,open time and β1 subunit mRNA and protein expression of BK channel in the high fat diet group were significantly increased,which is independent of prenatal hypoxia.Both high fat diet and prenatal hypoxia did not afifect mRNA and protein expression of BK channel a subunit.Conclusion:High fat diet can significantly increase the activity of BK channel and the expression of β1 subunit in the mesenteric artery of offspring.The hypoxia during pregnane cannot further aggravate the effects of high fat on that.Part 4 The effects of Prenatal hypoxia and postnatal high fat diet on blood pressure and vessel contractions in male offspring ratsObjective:To study the effects of prenatal hypoxia and postnatal high fat diet on L-type calcium channels in mesenteric smooth muscle cells in male offspring.Methods:The contractile function of mesenteric artery in offspring rats was detected by microvascular function detection platform.Whole-cell calcium channel currents were reeorded using a traditional whole-cell model.The mRNA and protein expression of L-type calcium channel α1C subunit were detected by qRT-PCR and Western blot.Results:After incubation of nifedipine(a specific Cavl.2 channel blocker),the A phenylephrine-induced vasoconstrictions was significantly increased in HF-fed offspring.Importantly,a further significant increase of A phenylephrine-induced vasoconstrictions was observed in HHF compared with CHF.Compared with the normal diet group,the maximum peak current density of whole-cell L-type calcium channels was significantly increased in mesenteric smooth muscle cells in offspring exposed to high fat diet with or without the addition of BayK 8644(a specific Cavl.2 channel agonist,5 μmol/L).The nifedipine(1μmol/L)insensitive current densities were similar among the four groups.Prenatal hypoxia can further aggravate the effect of high fat diet on L-type calcium channel currents.High fat diet can reduce the inactivation of L-type calcium channels in smooth muscle cells.The mRNA and protein expression of the pore-forming α1C-subunit of Cavl.2 channels was significantly increased in HF-fed offspring,which was exacerbated by prenatal hypoxia.Conclusion:High fat diet can significantly increase the activity of calcium channel of mesenteric artery smooth muscle cells and the expression of alC subunit.The prenatal hypoxia further aggravates the effect of high fat diet on ealcium channel.