The distribution and expression of the nitric oxide system during renal ageing and the effect of sex steroid modulation

The protective effect of female sex in renal ageing and cardiovascular function is widely accepted, but poorly understood. Previous evidence has suggested a role for the nitric oxide and renin-angiotensin systems, though the precise mechanisms by which they elicit these effects remain elusive. Female animals and humans have increased nitric oxide bioavailability with age in comparison to males, and this effect can be negated by ovariectomy surgery, suggesting an interaction between ovarian steroids and nitric oxide. In addition, studies have shown an upregulation of the angiotensin II type 2 receptor (AT2R) in aged females in comparison with males. Whilst incompletely understood, the AT2R is known to mediate vasodilation, nitric oxide release, and can be modulated by oestrogen. Work in this laboratory has shown that the expression of AT2R, renal ageing, and blood pressure may all be sensitive to the nutritional environment encountered during foetal development. This thesis aimed to elucidate some of the mechanisms mediating this ‘protective effect’ of female gender in a rat model of developmentally programmed hypertension and accelerated renal ageing. It was hypothesised that ageing would result in decreased renal function and increased blood pressure. These effects would be significantly altered by sex steroid modulation, and negative effects exacerbated by exposure to a low protein diet during gestation. The mechanisms driving these effects would be, at least in part, linked in changes to renin angiotensin system-regulated nitric oxide release. The data obtained suggested that the nitric oxide system did not significantly change with sex steroid exposure, or in response to maternal diet. Unexpectedly, ovariectomy alone did not change physiological responses as has been described previously. Instead, a significant interaction was observed between exposure to a low protein diet during gestation and ovariectomy. Offspring from mothers fed a low protein diet had impaired responses to removal of ovarian steroids. In addition, low protein offspring had altered vascular reactivity in response to targeted agonism and antagonism of angiotensin II receptors. In conclusion, this work has shown that the protective effect of female gender is more complex than previously described. The data did not support the hypothesis that nitric oxide mediates the beneficial effects of female sex, and targeted stimulation of the AT2R is not an effective means of altering this. Moreover, these data suggest that foetal exposure to a low protein diet may permanently programme altered vascular function, and can significantly affect response to sex steroids

Exposure to maternal obesity during suckling outweighs in utero exposure in programming for post-weaning adiposity and insulin resistance in rats

Exposure to maternal obesity during early development programmes adverse metabolic health in rodent offspring. We assessed the relative contributions of obesity during pregnancy and suckling on metabolic health post-weaning. Wistar rat offspring exposed to control (C) or cafeteria diet (O) during pregnancy were cross-fostered to dams on the same (CC, OO) or alternate diet during suckling (CO, OC) and weaned onto standard chow. Measures of offspring metabolic health included growth, adipose tissue mass, and 12-week glucose and insulin concentrations during an intraperitoneal glucose tolerance test (ipGTT). Exposure to maternal obesity during lactation was a driver for reduced offspring weight post-weaning, higher fasting blood glucose concentrations and greater gonadal adiposity (in females). Males displayed insulin resistance, through slower glucose clearance despite normal circulating insulin and lower mRNA expression of PIK3R1 and PIK3CB in gonadal fat and liver respectively. In contrast, maternal obesity during pregnancy up-regulated the insulin signalling genes IRS2, PIK3CB and SREBP1-c in skeletal muscle and perirenal fat, favouring insulin sensitivity. In conclusion exposure to maternal obesity during lactation programmes offspring adiposity and insulin resistance, overriding exposure to an optimal nutritional environment in utero, which cannot be alleviated by a nutritionally balanced post-weaning diet

The impact of exposure to cafeteria diet during pregnancy or lactation on offspring growth and adiposity before weaning

Exposure to maternal obesity during early-life can have adverse consequences for offspring growth and adiposity. We aimed to assess the relative contributions of exposure to maternal obesity, induced by a highly varied cafeteria diet, during pregnancy and lactation on these measures in rat offspring prior to weaning. Female Wistar rats were fed either a control (C) or cafeteria diet (O) for 8 weeks before mating, throughout pregnancy and lactation. Offspring were cross-fostered at birth to a dam on the same (CC,OO) or alternate diet prior to birth (CO,OC). Feeding a cafeteria diet based on 40 different foods, was associated with a sustained period of elevated energy intake before birth and during lactation (up to 1.7-fold), through increased sugar, total fat and saturated fat intake, and lower protein consumption. Cafeteria fed dams sustained greater weight than animals fed a control chow diet and greater perirenal adiposity by the end of lactation. Exposure to obesity during pregnancy was associated with lower offspring birth weight and body weight in early-postnatal life. In contrast, exposure during lactation alone reduced offspring weight but increased adiposity in male CO offspring before weaning. This research highlights that exposure to maternal obesity during lactation alone can programme adiposity in a sex specific manner

Maternal protein-energy malnutrition during early pregnancy in sheep impacts the fetal ornithine cycle to reduce fetal kidney microvascular development

This paper identifies a common nutritional pathway relating maternal through to fetal protein-energy malnutrition (PEM) and compromised fetal kidney development. Thirty-one twin-bearing sheep were fed either a control (n=15) or low-protein diet (n=16, 17 vs. 8.7 g crude protein/MJ metabolizable energy) from d 0 to 65 gestation (term, ∼ 145 d). Effects on the maternal and fetal nutritional environment were characterized by sampling blood and amniotic fluid. Kidney development was characterized by histology, immunohistochemistry, vascular corrosion casts, and molecular biology. PEM had little measureable effect on maternal and fetal macronutrient balance (glucose, total protein, total amino acids, and lactate were unaffected) or on fetal growth. PEM decreased maternal and fetal urea concentration, which blunted fetal ornithine availability and affected fetal hepatic polyamine production. For the first time in a large animal model, we associated these nutritional effects with reduced micro- but not macrovascular development in the fetal kidney. Maternal PEM specifically impacts the fetal ornithine cycle, affecting cellular polyamine metabolism and microvascular development of the fetal kidney, effects that likely underpin programming of kidney development and function by a maternal low protein diet

Modelling maternal obesity: the effects of a chronic high-fat, high-cholesterol diet on uterine expression of contractile-associated proteins and ex vivo contractile activity during labour in the rat

Maternal obesity is associated with prolonged and dysfunctional labour and emergency caesarean section, but the mechanisms are unknown. The present study investigated the effects of an adiposity-inducing high fat, high-cholesterol (HFHC) diet on uterine contractile associated protein (CAP) expression and ex vivo uterine contractility in term non-labouring (TNL) and term labouring (TL) rats. Female rats were fed either control chow (CON n = 20) or HFHC (n = 20) diet 6 weeks before conception and during pregnancy. On gestational day 21(TNL) or day 22 (TL) CON and HFHC (n = 10) rats were killed to determine plasma cholesterol, triacylglycerol and progesterone concentrations and collection of myometrium for contractility studies and expression of CAPs caveolin-1 (Cav-1), connexin-43 (CX-43) and it’s phosphorylated form (pCX-43), oxytocin receptor (OXTR) and cyclooxygenase-2 (COX-2). HFHC feeding increased visceral fat (P 0.001), plasma cholesterol (P 0.001) and triacylglycerol (P = 0.039) concentrations. Stage of labour effected uterine expression of CAV-1 (P < 0.02), pCX43 and COX-2 (both P < 0.03). CAV-1 and pCX43 decreased but COX-2 increased with parturition. Significant diet- and labour-stage interactions were evident for CX-43 and pCX43 (P < 0.03 and P < 0.004 respectively). CX-43 decreased with TL in HFHC animals but was unaltered in CON. pCX-43 fell with labour in CON but remained high in HFHC. OXTR expression was significantly higher in HFHC compared with CON animals (P < 0.03). Progesterone was higher in HFHC rats at term (P < 0.014) but fell significantly with labour to similar concentrations as CON. Contractility studies identified synchronous contractions of stable amplitude in lean animals, but unstable asynchronous contractions with obesity. Uterine dose response to oxytocin was blunted during labour in HFHC rats with a log EC50 of −8.84 compared with −10.25 M in CON for integral activity (P < 0.05). In conclusion, our adiposity model exhibits adverse effects on contractile activity during labour that can be investigated further to unravel the mechanisms causing uterine dystocia in obese women

FXR activation protects against NAFLD via bile-acid-dependent reductions in lipid absorption

FXR agonists are used to treat non-alcoholic fatty liver disease (NAFLD), in part because they reduce hepatic lipids. Here, we show that FXR activation with the FXR agonist GSK2324 controls hepatic lipids via reduced absorption and selective decreases in fatty acid synthesis. Using comprehensive lipidomic analyses, we show that FXR activation in mice or humans specifically reduces hepatic levels of mono- and polyunsaturated fatty acids (MUFA and PUFA). Decreases in MUFA are due to FXR-dependent repression of Scd1, Dgat2, and Lpin1 expression, which is independent of SHP and SREBP1c. FXR-dependent decreases in PUFAs are mediated by decreases in lipid absorption. Replenishing bile acids in the diet prevented decreased lipid absorption in GSK2324-treated mice, suggesting that FXR reduces absorption via decreased bile acids. We used tissue-specific FXR KO mice to show that hepatic FXR controls lipogenic genes, whereas intestinal FXR controls lipid absorption. Together, our studies establish two distinct pathways by which FXR regulates hepatic lipids

PANC Study (Pancreatitis: A National Cohort Study): national cohort study examining the first 30 days from presentation of acute pancreatitis in the UK

Abstract Background Acute pancreatitis is a common, yet complex, emergency surgical presentation. Multiple guidelines exist and management can vary significantly. The aim of this first UK, multicentre, prospective cohort study was to assess the variation in management of acute pancreatitis to guide resource planning and optimize treatment. Methods All patients aged greater than or equal to 18 years presenting with acute pancreatitis, as per the Atlanta criteria, from March to April 2021 were eligible for inclusion and followed up for 30 days. Anonymized data were uploaded to a secure electronic database in line with local governance approvals. Results A total of 113 hospitals contributed data on 2580 patients, with an equal sex distribution and a mean age of 57 years. The aetiology was gallstones in 50.6 per cent, with idiopathic the next most common (22.4 per cent). In addition to the 7.6 per cent with a diagnosis of chronic pancreatitis, 20.1 per cent of patients had a previous episode of acute pancreatitis. One in 20 patients were classed as having severe pancreatitis, as per the Atlanta criteria. The overall mortality rate was 2.3 per cent at 30 days, but rose to one in three in the severe group. Predictors of death included male sex, increased age, and frailty; previous acute pancreatitis and gallstones as aetiologies were protective. Smoking status and body mass index did not affect death. Conclusion Most patients presenting with acute pancreatitis have a mild, self-limiting disease. Rates of patients with idiopathic pancreatitis are high. Recurrent attacks of pancreatitis are common, but are likely to have reduced risk of death on subsequent admissions. </jats:sec

The distribution and expression of the nitric oxide system during renal ageing and the effect of sex steroid modulation

The protective effect of female sex in renal ageing and cardiovascular function is widely accepted, but poorly understood. Previous evidence has suggested a role for the nitric oxide and renin-angiotensin systems, though the precise mechanisms by which they elicit these effects remain elusive. Female animals and humans have increased nitric oxide bioavailability with age in comparison to males, and this effect can be negated by ovariectomy surgery, suggesting an interaction between ovarian steroids and nitric oxide. In addition, studies have shown an upregulation of the angiotensin II type 2 receptor (AT2R) in aged females in comparison with males. Whilst incompletely understood, the AT2R is known to mediate vasodilation, nitric oxide release, and can be modulated by oestrogen. Work in this laboratory has shown that the expression of AT2R, renal ageing, and blood pressure may all be sensitive to the nutritional environment encountered during foetal development. This thesis aimed to elucidate some of the mechanisms mediating this ‘protective effect’ of female gender in a rat model of developmentally programmed hypertension and accelerated renal ageing. It was hypothesised that ageing would result in decreased renal function and increased blood pressure. These effects would be significantly altered by sex steroid modulation, and negative effects exacerbated by exposure to a low protein diet during gestation. The mechanisms driving these effects would be, at least in part, linked in changes to renin angiotensin system-regulated nitric oxide release. The data obtained suggested that the nitric oxide system did not significantly change with sex steroid exposure, or in response to maternal diet. Unexpectedly, ovariectomy alone did not change physiological responses as has been described previously. Instead, a significant interaction was observed between exposure to a low protein diet during gestation and ovariectomy. Offspring from mothers fed a low protein diet had impaired responses to removal of ovarian steroids. In addition, low protein offspring had altered vascular reactivity in response to targeted agonism and antagonism of angiotensin II receptors. In conclusion, this work has shown that the protective effect of female gender is more complex than previously described. The data did not support the hypothesis that nitric oxide mediates the beneficial effects of female sex, and targeted stimulation of the AT2R is not an effective means of altering this. Moreover, these data suggest that foetal exposure to a low protein diet may permanently programme altered vascular function, and can significantly affect response to sex steroids

Impact of gonadectomy on sympatho-vagal balance in male and female normotensive rat

OBJECTIVE: It is well established that autonomic nervous system and sympatho-vagal balance plays an important role in maintaining arterial blood pressure (ABP) (Salman IM., 2016) and that autonomic regulation of ABP differs between males and females (Hart EC et al., 2014). We hypothesised that sex hormones affect blood pressure via the autonomic nervous system and that the late development of hypertension in females is due to protective effects of ovarian steroids in females rather than due to detrimental effects of testosterone in males. DESIGN AND METHOD: We used adult, 12 months old, Wistar female and male, intact and gonadectomised rats (n = 8, per each group). Resting ABP was recorded by radio-telemetry. Heart rate (HR) and ABP variability were calculated using Spike2 software. Effect of gender and gonadectomy were assessed by two-way Anova. RESULTS: Females had lower systolic (S)BP compared to males (121 ± 1 vs 128 ± 2 mmHg; P < 0.05). Intact (81 ± 2 mmHg) but not ovariectomised (89 ± 2 mmHg) females had lower diastolic (D)BP compared to males (91 ± 1 mmHg; P < 0.01). Moreover, intact (353 ± 6bpm) but not ovariectomised (307 ± 5 bpm) females had higher HR compared to males (353 ± 6bpm; P < 0.001). However, ovariectomy did not influence the higher respiratory rate in females vs males (91 ± 3 vs 78 ± 3 bpm; P < 0.001).Power spectra analysis of SBP shows that males (22.4 ± 3) and ovariectomised females (26.9 ± 3) had lower High Frequency percentage vs females (38 ± 3; P < 0.05) suggesting that female hormones affect ABP by modulating the parasympathetic activity. The Very Low Frequency percentage was higher in males vs females (40 ± 4 vs 28 ± 4; P < 0.05) suggesting that sympathetic vasomotor tone might play an important role in the differential regulation of SBP between males and females. CONCLUSIONS: Altogether, this results show that female hormones have a positive effect on ABP and that they affect ABP via modulating parasympathetic activity. Further analyses of BP and HR variability at different ages are needed to determine the interaction between age, BP and gender