A vagal influence on schizophrenia? A nationwide retrospective cohort of vagotomized individuals

Background and Objectives

Emerging preclinical evidence suggests that vagal signals contribute to the development of schizophrenia-related abnormalities in brain and behavior. Whether vagal communication in general, and its impairment in particular, is a risk factor for schizophrenia in humans remains, however, unclear. Vagotomy, the surgical lesion of the vagus nerve, was routinely performed as a treatment for peptic ulcer before modern treatment options were available. Hence, the primary aim of this study was to investigate whether vagotomy modulates the subsequent risk of developing schizophrenia. Moreover, given the existence of diverse vagotomy techniques (i.e., "truncal" or "selective"), our secondary goal was to test whether the extent of denervation modulates the risk of schizophrenia.

Methods

Using a nationwide retrospective matched cohort design, we identified 8,315 vagotomized individuals from the Swedish National Patient Register during the period 1970-2020 and 40,855 non-vagotomized individuals matching for age, sex and type of peptic ulcer. The risk of being diagnosed with schizophrenia and associated psychoses (ICD10 codes F20-29) was analyzed using Cox proportional hazards regression models, including death as competing risk.

Results

When considering all types of vagotomy together, vagotomy was not significantly associated with schizophrenia (HR: 0.91 [0.72; 1.16]). However, truncal vagotomy (which denervates all subdiaphragmatic organs) significantly increased the risk of developing schizophrenia by 69% (HR: 1.69 [1.08; 2.64]), whereas selective vagotomy (which only denervates the stomach) showed no significant association (HR: 0.80 [0.61; 1.04]).

Discussion

Our results provide epidemiological support for the hypothesis that impairments in vagal functions could increase the risk of schizophrenia. Notably, the finding that truncal but not selective vagotomy is associated with an increased risk of schizophrenia raises the possibility that the activity of subdiaphragmatic non-gastric vagal branches may be of particular relevance for the development of schizophrenia.

Elevated circulating adiponectin levels do not prevent anxiety-like behavior in a PCOS-like mouse model

Polycystic ovary syndrome (PCOS) is associated with symptoms of moderate to severe anxiety and depression. Hyperandrogenism is a key feature together with lower levels of the adipocyte hormone adiponectin. Androgen exposure leads to anxiety-like behavior in female offspring while adiponectin is reported to be anxiolytic. Here we test the hypothesis that elevated adiponectin levels protect against the development of androgen-induced anxiety-like behavior. Pregnant mice overexpressing adiponectin (APNtg) and wildtypes were injected with vehicle or dihydrotestosterone to induce prenatal androgenization (PNA) in the offspring. Metabolic profiling and behavioral tests were performed in 4-month-old female offspring. PNA offspring spent more time in the closed arms of the elevated plus maze, indicating anxiety-like behavior. Intriguingly, neither maternal nor offspring adiponectin overexpression prevented an anxiety-like behavior in PNA-exposed offspring. However, adiponectin overexpression in dams had metabolic imprinting effects, shown as lower fat mass and glucose levels in their offspring. While serum adiponectin levels were elevated in APNtg mice, cerebrospinal fluid levels were similar between genotypes. Adiponectin overexpression improved metabolic functions but did not elicit anxiolytic effects in PNA-exposed offspring. These observations might be attributed to increased circulating but unchanged cerebrospinal fluid adiponectin levels in APNtg mice. Thus, increased adiponectin levels in the brain are likely needed to stimulate anxiolytic effects.

An appetite for aggressive behavior? Female rats, too, derive reward from winning aggressive interactions

While aggression is an adaptive behavior mostly triggered by competition for resources, it can also in and of itself be rewarding. Based on the common notion that female rats are not aggressive, much of aggression research has been centered around males, leading to a gap in the understanding of the female aggression neurobiology. Therefore, we asked whether intact virgin female rats experience reward from an aggressive interaction and assessed aggression seeking behavior in rats of both sexes. To validate the involvement of reward signaling, we measured mesolimbic dopamine turnover and determined the necessity of dopamine signaling for expression of aggression-seeking. Together our data indicate that female rats exhibit aggressive behavior outside of maternal context, experience winning aggressive behaviors as rewarding, and do so to a similar extent as male rats and in a dopamine-dependent manner.

Sex-divergent effects of hindbrain GLP-1-producing neuron activation in rats

Glucagon-like peptide-1 (GLP-1) analogs represent a new class of weight-loss medication, which has recently exponentially grown in popularity. GLP-1 is produced in the intestinal L cells in response to macronutrient intake, but it is also produced in the brain in a subset of neurons in the nucleus of the solitary tract (NTS). Exogenously-delivered GLP-1 analogs reduce food intake and food-motivated behavior in male and female rats, with some sex divergence of these effects in specific brain sites. These analogs potentially target GLP-1 receptors endogenously supplied by the gut and brain-produced GLP-1. The function of the NTS GLP-1-producing neurons [Gcg neurons] is still relatively unknown in rats. Moreover, even less is understood about the function of these neurons in females. We have recently developed a transgenic rat that expresses Cre under the Gcg promoter. Here, we interrogate this new animal model with optogenetics and chemogenetics to determine whether activation of the NTS GLP-1 neurons affects ingestive and motivated behavior in male and female rats. Optogenetic activation of the NTS Gcg neurons robustly reduced chow intake in both male and female rats. Interestingly, motivated behavior for a sucrose reward was reduced exclusively in females. To ensure that this unexpected sex difference was not activation method-specific, we next virally introduced excitatory DREADD receptors into the Gcg neurons and investigated the effect of chemogenetic activation of these neurons on ingestive and motivated behavior. Even upon chemogenetic activation, female rats reduced their motivation to obtain the sucrose reward, yet no effect on this behavior was observed in males. Our results show that activation of hindbrain Gcg neurons is sufficient to reduce food intake in both sexes. In females, but not males, Gcg neuron activation alone is also sufficient to reduce motivated behavior for sucrose. Thus, there is a sex difference in the ability of GLP-1-producing neuron activation to control motivated behavior for food.

Peripherally restricted oxytocin is sufficient to reduce food intake and motivation, while CNS entry is required for locomotor and taste avoidance effects

OBJECTIVES

Oxytocin (OT) has a well-established role in reproductive behaviours; however, it recently emerged as an important regulator of energy homeostasis. In addition to central nervous system (CNS), OT is found in the plasma and OT receptors (OT-R) are found in peripheral tissues relevant to energy balance regulation. Here, we aim to determine whether peripheral OT-R activation is sufficient to alter energy intake and expenditure.

METHODS AND RESULTS

We first show that systemic OT potently reduced food intake and food-motivated behaviour for a high-fat reward in male and female rats. As it is plausible that peripherally, intraperitoneally (IP) injected OT crosses the blood-brain barrier (BBB) to produce some of the metabolic effects within the CNS, we screened, with a novel fluorescently labelled-OT (fAF546-OT, Roxy), for the presence of IP-injected Roxy in CNS tissue relevant to feeding control and compared such with BBB-impermeable fluorescent OT-B₁₂ (fCy5-OT-B_12; BRoxy). While Roxy did penetrate the CNS, BRoxy did not. To evaluate the behavioural and thermoregulatory impact of exclusive activation of peripheral OT-R, we generated a novel BBB-impermeable OT (OT-B₁₂ ), with equipotent binding at OT-R in vitro. In vivo, IP-injected OT and OT-B₁₂ were equipotent at food intake suppression in rats of both sexes, suggesting that peripheral OT acts on peripheral OT-R to reduce feeding behaviour. Importantly, OT induced a potent conditioned taste avoidance, indistinguishable from that induced by LiCl, when applied peripherally. Remarkably, and in contrast to OT, OT-B₁₂ did not induce any conditioned taste avoidance. Limiting the CNS entry of OT also resulted in a dose-dependent reduction of emesis in male shrews. While both OT and OT-B₁₂ proved to have similar effects on body temperature, only OT resulted in home-cage locomotor depression.

CONCLUSIONS

Together our data indicate that limiting systemic OT CNS penetrance preserves the anorexic effects of the peptide and reduces the clinically undesired side effects of OT: emesis, taste avoidance and locomotor depression. Thus, therapeutic targeting of peripheral OT-R may be a viable strategy to achieve appetite suppression with better patient outcomes.

Somatostatin Containing δ-Cell Number Is Reduced in Type-2 Diabetes

Recent developments suggest that increased glucagon and decreased somatostatin secretion from the pancreas contribute to hyperglycaemia in type-2 diabetes (T2D) patients. There is a huge need to understand changes in glucagon and somatostatin secretion to develop potential anti-diabetic drugs. To further describe the role of somatostatin in the pathogenesis of T2D, reliable means to detect islet δ-cells and somatostatin secretion are necessary. In this study, we first tested currently available anti-somatostatin antibodies against a mouse model that fluorescently labels δ-cells. We found that these antibodies only label 10-15% of the fluorescently labelled δ-cells in pancreatic islets. We further tested six antibodies (newly developed) that can label both somatostatin 14 (SST14) and 28 (SST28) and found that four of them were able to detect above 70% of the fluorescent cells in the transgenic islets. This is quite efficient compared to the commercially available antibodies. Using one of these antibodies (SST10G5), we compared the cytoarchitecture of mouse and human pancreatic islets and found fewer δ-cells in the periphery of human islets. Interestingly, the δ-cell number was also reduced in islets from T2D donors compared to non-diabetic donors. Finally, with the aim to measure SST secretion from pancreatic islets, one of the candidate antibodies was used to develop a direct-ELISA-based SST assay. Using this novel assay, we could detect SST secretion under low and high glucose conditions from the pancreatic islets, both in mice and humans. Overall, using antibody-based tools provided by Mercodia AB, our study indicates reduced δ-cell numbers and SST secretion in diabetic islets.

A low-carbohydrate diet induces hepatic insulin resistance and metabolic associated fatty liver disease in mice

OBJECTIVES

Metabolic-associated fatty liver disease (MAFLD) is the most common chronic liver disease that can range from hepatic steatosis to non-alcoholic steatohepatitis (NASH), which can lead to fibrosis and cirrhosis. Recently, ketogenic diet (KD), a low carbohydrate diet, gained popularity as a weight-loss approach, although it has been reported to induce hepatic insulin resistance and steatosis in animal model systems via an undefined mechanism. Herein, we investigated the KD metabolic benefits and its contribution to the pathogenesis of NASH.

METHODS

Using metabolic, biochemical and omics approaches, we identified the effects of a KD on NASH and investigated the mechanisms by which KD induces hepatic insulin resistance and steatosis.

RESULTS

We demonstrate that KD can induce fibrosis and NASH regardless of body weight loss compared to high-fat diet (HFD) fed mice at thermoneutrality. At ambient temperature (23 °C), KD-fed mice develop a severe hepatic injury, inflammation, and steatosis. In addition, KD increases liver cholesterol, IL-6, and p-JNK and aggravates diet induced-glucose intolerance and hepatic insulin resistance compared to HFD. Pharmacological inhibition of IL-6 and JNK reverses KD-induced glucose intolerance, and hepatic steatosis and restores insulin sensitivity.

CONCLUSIONS

Our studies uncover a new mechanism for KD-induced hepatic insulin resistance and NASH potentially via IL-6-JNK signaling and provide a new NASH mouse model.

Neural Pathway for Gut Feelings: Vagal Interoceptive Feedback From the Gastrointestinal Tract Is a Critical Modulator of Anxiety-like Behavior

BACKGROUND

Anxiety disorders are associated with an altered perception of the body's internal state. Therefore, understanding the neuronal basis of interoception can foster novel anxiety therapies. In rodents, the feeding status bidirectionally modulates anxiety-like behavior but how the sensing of gastrointestinal state affects anxiety remains unclear.

METHODS

We combined chemogenetics, neuropharmacology, and behavioral approaches in male and female rats to test whether vagal afferents terminating in the gastrointestinal tract mediate feeding-induced tuning of anxiety. Using saporin-based lesions and transcriptomics, we investigated the chronic impact of this gut-brain circuit on anxiety-like behavior.

RESULTS

Both feeding and selective chemogenetic activation of gut-innervating vagal afferents increased anxiety-like behavior. Conversely, chemogenetic inhibition blocked the increase in anxiety-like behavior induced by feeding. Using a selective saporin-based lesion, we demonstrate that the loss of gut-innervating vagal afferent signaling chronically reduces anxiety-like behavior in male rats but not in female rats. We next identify a vagal circuit that connects the gut to the central nucleus of the amygdala, using anterograde transsynaptic tracing from the nodose ganglia. Lesion of this gut-brain vagal circuit modulated the central amygdala transcriptome in both sexes but selectively affected a network of GABA (gamma-aminobutyric acid)-related genes only in males, suggesting a potentiation of inhibitory control. Blocking GABAergic signaling in the central amygdala re-established normal anxiety levels in male rats.

CONCLUSIONS

Vagal sensory signals from the gastrointestinal tract are critical for baseline and feeding-induced tuning of anxiety via the central amygdala in rats. Our results suggest vagal gut-brain signaling as a target to normalize interoception in anxiety disorders.

Commonly-used rodent tests of anxiety-like behavior lack predictive validity for human sex differences

Women are more likely to develop an anxiety disorder than men. Yet, preclinical models of anxiety were largely developed in male rodents, with poorly understood predictive validity for sex differences. Here, we investigate whether commonly-used anxiety-like behavior tests, elevated plus maze (EPM) and open field (OF), represent the human sex difference in adult Sprague-Dawley rats. When interpreted by EPM or OF, female rats displayed less anxiety-like behavior compared to males, as they spent twice as much time in the open arms of the EPM or the center of the OF compared to males. However, they also displayed vastly different levels of locomotor activity, possibly confounding interpretation of these locomotion-dependent tests. To exclude locomotion from the assessment, the acoustic startle response (ASR) test was used. When interpreted by the ASR test, females displayed more anxiety-like behavior compared to males, as indicated by a nearly two-fold higher startle amplitude. The observed sex differences were not driven by gonadal steroids. Overall, all but one of the tests fail to mirror the sex difference in anxiety reported in humans. Our findings suggest that the ASR might be a better fit in modelling female anxiety-like behavior.

Sex and Species Differences in the Development of Diet-Induced Obesity and Metabolic Disturbances in Rodents

Prevalence and health consequences of obesity differ between men and women. Yet, most preclinical studies investigating the etiology of obesity have, to date, been conducted in male rodents. Notably, diet is a major determinant of obesity, but sex differences in rodent models of diet-induced obesity, and the mechanisms that underlie such differences, are still understudied. Here, we aim to determine whether time course and characteristics of diet-induced obesity differ between sexes in rats and mice, and to investigate the potential causes of the observed divergence. To achieve this, we offered the most commonly tested rodents of both sexes, SD rats and C57BL/6 mice, a free choice of 60 % high-fat diet (HFD) and regular chow; body weight, food intake, fat mass, brown adipose responses, locomotor activity and glucose tolerance were assessed in a similar manner in both species. Our results indicate that overall diet-induced hyperphagia is greater in males but that females display a higher preference for the HFD, irrespective of species. Female rats, compared to males, showed a delay in diet-induced weight gain and less metabolic complications. Although male rats increased brown adipose tissue thermogenesis in response to the HFD challenge, this was not sufficient to counteract increased adiposity. In contrast to rats, female and male mice presented with a dramatic adiposity and impaired glucose tolerance, and a decreased energy expenditure. Female mice showed a 5-fold increase in visceral fat, compared to 2-fold increase seen in male mice. Overall, we found that male and female rodents responded very differently to HFD challenge, and engaged different compensatory energy expenditure mechanisms. In addition, these sex differences are divergent in rats and mice. We conclude that SD rats have a better face validity for the lower prevalence of overweight in women, while C57BL/6 mice may better model the increased prevalence of morbid obesity in women.

From an Empty Stomach to Anxiolysis: Molecular and Behavioral Assessment of Sex Differences in the Ghrelin Axis of Rats

Ghrelin, a stomach-produced hormone, is well-recognized for its role in promoting feeding, controlling energy homeostasis, and glucoregulation. Ghrelin's function to ensure survival extends beyond that: its release parallels that of corticosterone, and ghrelin administration and fasting have an anxiolytic and antidepressant effect. This clearly suggests a role in stress and anxiety. However, most studies of ghrelin's effects on anxiety have been conducted exclusively on male rodents. Here, we hypothesize that female rats are wired for higher ghrelin sensitivity compared to males. To test this, we systematically compared components of the ghrelin axis between male and female Sprague Dawley rats. Next, we evaluated whether anxiety-like behavior and feeding response to endogenous or exogenous ghrelin are sex divergent. In line with our hypothesis, we show that female rats have higher serum levels of ghrelin and lower levels of the endogenous antagonist LEAP-2, compared to males. Furthermore, circulating ghrelin levels were partly dependent on estradiol; ovariectomy drastically reduced circulating ghrelin levels, which were partly restored by estradiol replacement. In contrast, orchiectomy did not affect circulating plasma ghrelin. Additionally, females expressed higher levels of the endogenous ghrelin receptor GHSR_1A in brain areas involved in feeding and anxiety: the lateral hypothalamus, hippocampus, and amygdala. Moreover, overnight fasting increased GHSR_1A expression in the amygdala of females, but not males. To evaluate the behavioral consequences of these molecular differences, male and female rats were tested in the elevated plus maze (EPM), open field (OF), and acoustic startle response (ASR) after three complementary ghrelin manipulations: increased endogenous ghrelin levels through overnight fasting, systemic administration of ghrelin, or blockade of fasting-induced ghrelin signaling with a GHSR_1A antagonist. Here, females exhibited a stronger anxiolytic response to fasting and ghrelin in the ASR, in line with our findings of sex differences in the ghrelin axis. Most importantly, after GHSR_1A antagonist treatment, females but not males displayed an anxiogenic response in the ASR, and a more pronounced anxiogenesis in the EPM and OF compared to males. Collectively, female rats are wired for higher sensitivity to fasting-induced anxiolytic ghrelin signaling. Further, the sex differences in the ghrelin axis are modulated, at least partly, by gonadal steroids, specifically estradiol. Overall, ghrelin plays a more prominent role in the regulation of anxiety-like behavior of female rats.

Association between dietary patterns and prediabetes, undetected diabetes or clinically diagnosed diabetes: results from the KORA FF4 study

PURPOSE

Diet is one of the most important modifiable risk factors for the development of type 2 diabetes. Here, we aim to identify dietary patterns and to investigate their association with prediabetes, undetected diabetes and prevalent diabetes.

METHODS

The present study included 1305 participants of the cross-sectional population-based KORA FF4 study. Oral glucose tolerance test (OGTT) measurements together with a physician-confirmed diagnosis allowed for an accurate categorization of the participants according to their glucose tolerance status into normal glucose tolerance (n = 698), prediabetes (n = 459), undetected diabetes (n = 49), and prevalent diabetes (n = 99). Dietary patterns were identified through principal component analysis followed by hierarchical clustering. The association between dietary patterns and glucose tolerance status was investigated using multinomial logistic regression models.

RESULTS

A Prudent pattern, characterized by high consumption of vegetables, fruits, wholegrains and dairy products, and a Western pattern, characterized by high consumption of red and processed meat, alcoholic beverages, refined grains and sugar-sweetened beverages, were identified. Participants following the Western pattern had significantly higher chances of having prediabetes (odds ratio [OR] 1.92; 95% confidence interval [CI] 1.35, 2.73), undetected diabetes (OR 10.12; 95% CI 4.19, 24.43) or prevalent diabetes (OR 3.51; 95% CI 1.85, 6.67), compared to participants following the Prudent pattern.

CONCLUSION

To our knowledge, the present study is one of the few investigating the association between dietary patterns and prediabetes or undetected diabetes. The use of a reference group exclusively including participants with normal glucose tolerance might explain the strong associations observed in our study. These results suggest a very important role of dietary habits in the prevention of prediabetes and type 2 diabetes.

Demystifying functional role of cocaine- and amphetamine-related transcript (CART) peptide in control of energy homeostasis: A twenty-five year expedition

Cocaine- and amphetamine-related transcript (CART) is a neuropeptide first discovered in the striatum of the rat brain. Later, the genetic sequence and function of CART peptide (CARTp) was found to be conserved among multiple mammalian species. Over the 25 years, since its discovery, CART mRNA (Cartpt) expression has been reported widely throughout the central and peripheral nervous systems underscoring its role in diverse physiological functions. Here, we review the localization and function of CARTp as it relates to energy homeostasis. We summarize the expression changes of central and peripheral Cartpt in response to metabolic states and make use of available large data sets to gain additional insights into the anatomy of the Cartpt expressing vagal neurons and their expression patterns in the gut. Furthermore, we provide an overview of the role of CARTp as an anorexigenic signal and its effect on energy expenditure and body weight control with insights from both pharmacological and transgenic animal studies. Subsequently, we discuss the role of CARTp in the pathophysiology of obesity and review important new developments towards identifying a candidate receptor for CARTp signalling. Altogether, the field of CARTp research has made rapid and substantial progress recently, and we review the case for considering CARTp as a potential therapeutic target for stemming the obesity epidemic.

Light- and Manganese-Initiated Borylation of Aryl Diazonium Salts: Mechanistic Insight on the Ultrafast Time-Scale Revealed by Time-Resolved Spectroscopic Analysis

Manganese-mediated borylation of aryl/heteroaryl diazonium salts emerges as a general and versatile synthetic methodology for the synthesis of the corresponding boronate esters. The reaction proved an ideal testing ground for delineating the Mn species responsible for the photochemical reaction processes, that is, involving either Mn radical or Mn cationic species, which is dependent on the presence of a suitably strong oxidant. Our findings are important for a plethora of processes employing Mn-containing carbonyl species as initiators and/or catalysts, which have considerable potential in synthetic applications.

Intestinal glucagon-like peptide-1 effects on food intake: Physiological relevance and emerging mechanisms

The gut-brain hormone glucagon-like peptide-1 (GLP-1) has received immense attention over the last couple of decades for its widespread metabolic effects. Notably, intestinal GLP-1 has been recognized as an endogenous satiation signal. Yet, the underlying mechanisms and the pathophysiological relevance of intestinal GLP-1 in obesity remain unclear. This review first recapitulates early findings indicating that intestinal GLP-1 is an endogenous satiation signal, whose eating effects are primarily mediated by vagal afferents. Second, on the basis of recent findings challenging a paracrine action of intestinal GLP-1, a new model for the mediation of GLP-1 effects on eating by two discrete vagal afferent subsets will be proposed. The central mechanisms processing the vagal anorexigenic signals need however to be further delineated. Finally, the idea that intestinal GLP-1 secretion and/or effects on eating are altered in obesity and play a pathophysiological role in the development of obesity will be discussed. In summary, despite the successful therapeutic use of GLP-1 receptor agonists as anti-obesity drugs, the eating effects of intestinal GLP-1 still remain to be elucidated. Specifically, the findings presented here call for a further evaluation of the vago-central neuronal substrates activated by intestinal GLP-1 and for further investigation of its pathophysiological role in obesity.

Combining Recent Nutritional Data with Prospective Cohorts to Quantify the Impact of Modern Dietary Patterns on Disability-Adjusted Life Years: A Feasibility Study

Unhealthy diets are commonly associated with increased disability-adjusted life years (DALYs) from noncommunicable diseases. The association between DALYs and dietary patterns can be quantified with individual longitudinal data. This assessment, however, is often based on dietary data collected once at cohort entry, therefore reflecting the impact of “old” dietary habits on morbidity and mortality. To overcome this limitation, we tested the association of contemporary diets with DALYs. First, we defined contemporary dietary patterns consumed in Switzerland with the national nutrition survey menuCH (2014–2015). Second, we identified individuals who consumed similar diets in the NRP–MONICA census-linked cohort (1977–2015). In this cohort, individual data on disease and mortality were used to calculate the DALYs-dietary patterns association using a mixed regression model. A total of 58,771 DALYs from NCDs were recorded in a mean follow-up time of 25.5 years. After multivariable adjustments, the “Swiss traditional” pattern was not associated with an increase in DALYs compared to the “Prudent” pattern. However, individuals following a “Western” pattern had, on average 0.29 DALYs (95% CI 0.02, 0.56) more than those following a “Prudent” pattern, equating to a loss of healthy life of more than three months. These data highlight the feasibility of quantifying the impact of contemporary diets on DALYs without the establishment of new cohorts or the use of nationally aggregated data.

Blunted Vagal Cocaine- and Amphetamine-Regulated Transcript Promotes Hyperphagia and Weight Gain

The vagus nerve conveys gastrointestinal cues to the brain to control eating behavior. In obesity, vagally mediated gut-brain signaling is disrupted. Here, we show that the cocaine- and amphetamine-regulated transcript (CART) is a neuropeptide synthesized proportional to the food consumed in vagal afferent neurons (VANs) of chow-fed rats. CART injection into the nucleus tractus solitarii (NTS), the site of vagal afferent central termination, reduces food intake. Conversely, blocking endogenous CART action in the NTS increases food intake in chow-fed rats, and this requires intact VANs. Viral-mediated Cartpt knockdown in VANs increases weight gain and daily food intake via larger meals and faster ingestion rate. In obese rats fed a high-fat, high-sugar diet, meal-induced CART synthesis in VANs is blunted and CART antibody fails to increase food intake. However, CART injection into the NTS retains its anorexigenic effect in obese rats. Restoring disrupted VAN CART signaling in obesity could be a promising therapeutic approach.

Intake of Processed Meat and Association with Sociodemographic and Lifestyle Factors in a Representative Sample of the Swiss Population

Processed meat (PM) intake is associated with health risks, but data are lacking in Switzerland. Using national representative data from a recent menuCH Survey, we first aimed to quantify intake of PM and its subtypes, and second to investigate associations with sociodemographic and lifestyle factors by multivariable regression analysis. PM was consumed by 72% of the population, and mean daily intake was 42.7 g/day (standard error of the mean (SEM) 1.2 g/day), ranging considerably across PM subtypes: highest intake of sausages 18.1 g/day (SEM 0.7 g/day) and lowest of bacon 2.0 g/day (SEM 0.2 g/day). PM intake by women was 4.7 g/1000 kcal lower than men (95% confidence interval (CI): -6.7; -2.7) and 2.9 g/1000 kcal lower in the French- language region compared with the German region (95% CI: 2.4; 8.7). Among sociodemographic and lifestyle factors examined, BMI (obese vs. normal: 5.5 g/1000 kcal, 95% CI: 2.4; 8.7) and current smoking (vs. never smoked: 3.1 g/kcal, 95% CI: 0.6; 5.6) were independently associated with PM intake. The results are a first description of PM intake, separate from other meat types, and which identified associations with two unhealthy lifestyle factors in Switzerland. Such data will contribute to better nutritional recommendations and guidance for public health interventions.

Roux-en-Y gastric bypass surgery reprograms enterocyte triglyceride metabolism and postprandial secretion in rats

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) surgery produces rapid and persistent reductions in plasma triglyceride (TG) levels associated with fewer cardiovascular events. The mechanisms of the reduction in systemic TG levels remain unclear. We hypothesized that RYGB reduces intestinal TG secretion via altered enterocyte lipid handling.

METHODS

RYGB or Sham surgery was performed in diet-induced obese, insulin-resistant male Sprague-Dawley rats. First, we tested whether RYGB reduced test meal-induced TG levels in the intestinal lymph, a direct readout of enterocyte lipid secretion. Second, we examined whether RYGB modified TG enterocyte secretion at the single lipid level and in comparison to other lipid subclasses, applying mass spectrometry lipidomics to the intestinal lymph of RYGB and Sham rats (0-21 days after surgery). Third, we explored whether RYGB modulated the metabolic characteristics of primary enterocytes using transcriptional and functional assays relevant to TG absorption, reesterification, storage in lipid droplets, and oxidation.

RESULTS

RYGB reduced overall postprandial TG concentrations compared to Sham surgery in plasma and intestinal lymph similarly. RYGB reduced lymphatic TG concentrations more than other lipid subclasses, and shifted the remaining TG pool towards long-chain, unsaturated species. In enterocytes of fasted RYGB rats, lipid uptake was transcriptionally (Fatp4, Fabp2, Cd36) and functionally reduced compared to Sham, whereas TG reesterification genes were upregulated.

CONCLUSION

Our results show that RYGB substantially reduces intestinal TG secretion and modifies enterocyte lipid absorption and handling in rats. These changes likely contribute to the improvements in the plasma TG profile observed after RYGB in humans.

Oleoylethanolamide-induced anorexia in rats is associated with locomotor impairment

The endogenous peroxisome proliferator‐activated receptor alpha (PPAR‐α) agonist Oleoylethanolamide (OEA) inhibits eating in rodents, mainly by delaying the onset of meals. The underlying mechanisms of OEA‐induced anorexia, however, remain unclear. Animals treated with high OEA doses were shown to display signs of discomfort and impaired locomotion. Therefore, we first examined whether the impaired locomotion may contribute to OEA's anorectic effect. Second, it is controversial whether abdominal vagal afferents are necessary for OEA's anorectic effect. Thus, we explored alternative peripheral neural pathways mediating IP OEA's anorectic effect by performing a celiac‐superior mesenteric ganglionectomy (CGX) or a subdiaphragmatic vagal deafferentation (SDA) alone or in combination. Exogenously administered OEA at a commonly used dose (10 mg/kg BW, IP) concurrently reduced food intake and compromised locomotor activity. Attempts to dissociate both phenomena using the dopamine D2/D3 receptor agonist Quinpirole (1 mg/kg BW, SC) failed because Quinpirole antagonized both, OEA‐induced locomotor impairment and delay in eating onset. CGX attenuated the prolongation of the latency to eat by IP OEA, but neither SDA nor CGX prevented IP OEA‐induced locomotor impairment. Our results indicate that IP OEA's anorectic effect may be secondary to impaired locomotion rather than due to physiological satiety. They further confirm that vagal afferents do not mediate exogenous OEA's anorectic effects, but suggest a role for spinal afferents in addition to an alternative, nonneuronal signaling route.

Cultural Differences in Diet and Determinants of Diet Quality in Switzerland: Results from the National Nutrition Survey menuCH

Sociodemographic differences in dietary consumption were observed in different populations. The current study aimed to identify sociodemographic and lifestyle determinants of diet quality and to investigate the differences in diet quality between the three main language regions of Switzerland. Using data of the Swiss National Nutrition Survey menuCH (n = 2057), two diet quality scores—Alternate Healthy Eating Index and Mediterranean Diet Score—were computed. Linear regression models were used to investigate the determinants of diet quality and chi-square tests were used to test for differences in single score components between language regions. Significantly higher diet quality scores were observed for individuals who were female, older, normal weight, non-Swiss, with tertiary education or moderate-to-high physical activity level. Additionally, residents of the French- and Italian-speaking parts of Switzerland scored higher than residents of the German-speaking region. More specifically, the higher diet quality observed in the French- and Italian-speaking regions was mediated by higher scores in the components of alcohol, dairy products, fat, fish, sugar-sweetened beverages and whole grains. The present results may help to better characterize population groups requiring specific dietary recommendations, enabling public health authorities to develop targeted interventions.

Vitamin D status and its determinants in healthy pregnant women living in Switzerland in the first trimester of pregnancy

OBJECTIVES

Our study aimed at assessing the prevalence and determinants of vitamin D deficiency (25-hydroxy-vitamin D [25(OH)D] < 20 ng/mL) in pregnant women in the first trimester living in Switzerland.

METHODS

From September 2014 through December 2015, 204 pregnant women were conveniently recruited during their first clinical appointment at the Clinic of Obstetrics of the University Hospital Zurich (between week 6 and 12 of pregnancy). Blood samples were collected and a questionnaire focusing on lifestyle and skin colour was completed face-to-face with the responsible physician. Logistic regression analyses were performed with vitamin D status as dependent variable.

RESULTS

63.2% of the participating women were vitamin D deficient, and the median vitamin D concentration in the overall sample was 17.1 ng/mL [Q1, Q3: 9.78, 22.3]. The highest proportions of vitamin D deficiency were detected in women originating from Africa and Middle East (91.4% deficient, median vitamin D concentration of 10.7 ng/mL [Q1, Q3: 6.55, 14.45]) and from South-East Asia/Pacific (88.5% deficient, median vitamin D concentration of 8.4 ng/mL [Q1, Q3: 6.10, 14.88]). Multivariable logistic regression showed that significant risk factors of vitamin D deficiency were country of origin (women born in Switzerland and Germany had a lower risk than women born in other countries), smoking status (lower risk for former smokers) and intake of vitamin D supplements.

CONCLUSIONS

Our results confirm a high prevalence of vitamin D deficiency in this Swiss cohort, in particular in women coming from Asian and African countries, and underline the importance of appropriate counseling and vitamin D supplementation in early pregnancy.

Dietary Patterns and Their Sociodemographic and Lifestyle Determinants in Switzerland: Results from the National Nutrition Survey menuCH

From a public health perspective, determinants of diets are crucial to identify, but they remain unclear in Switzerland. Hence, we sought to define current dietary patterns and their sociodemographic and lifestyle determinants using the national nutrition survey menuCH (2014⁻2015, n = 2057). First, we applied multiple factorial analysis and hierarchical clustering on the energy-standardised daily consumption of 17 food categories. Four dietary patterns were identified ("Swiss traditional": high intakes of dairy products and chocolate, n = 744; "Western 1": soft drinks and meat, n = 383; "Western 2": alcohol, meat and starchy, n = 444; and "Prudent": n = 486). Second, we used multinomial logistic regression to examine the determinants of the four dietary patterns: ten sociodemographic or lifestyle factors (sex, age, body mass index, language region, nationality, marital status, income, physical activity, smoking status, and being on a weight-loss diet) were significantly associated with the dietary patterns. Notably, belonging to the French- and Italian-speaking regions of Switzerland increased the odds of following a "Prudent" diet (Odds ratio [95% confidence interval]: 1.92 [1.45⁻2.53] and 1.68 [0.98⁻2.90], respectively) compared to the German-speaking regions. Our findings highlight the influence of sociodemographic and lifestyle parameters on diet and the particularities of the language regions of Switzerland. These results provide the basis for public health interventions targeted for population subgroups.

Glucagon-like peptide-1 regulates brown adipose tissue thermogenesis via the gut-brain axis in rats

Endogenous intestinal glucagon-like peptide-1 (GLP-1) controls satiation and glucose metabolism via vagal afferent neurons (VANs). Recently, VANs have received increasing attention for their role in brown adipose tissue (BAT) thermogenesis. It is, however, unclear whether VAN GLP-1 receptor (GLP-1R) signaling affects BAT thermogenesis and energy expenditure (EE) and whether this VAN mechanism contributes to energy balance. First, we tested the effect of the GLP-1R agonist exendin-4 (Ex4, 0.3 μg/kg ip) on EE and BAT thermogenesis and whether these effects require VAN GLP-1R signaling using a rat model with a selective Glp1r knockdown (kd) in VANs. Second, we examined the role of VAN GLP-1R in energy balance during chronic high-fat diet (HFD) feeding in VAN Glp1r kd rats. Finally, we used viral transsynaptic tracers to identify the possible neuronal substrates of such a gut-BAT interaction. VAN Glp1r kd attenuated the acute suppressive effects of Ex4 on EE and BAT thermogenesis. Consistent with this finding, the VAN Glp1r kd increased EE and BAT activity, diminished body weight gain, and improved insulin sensitivity compared with HFD-fed controls. Anterograde transsynaptic viral tracing of VANs infected major hypothalamic and hindbrain areas involved in BAT sympathetic regulation. Moreover, retrograde tracing from BAT combined with laser capture microdissection revealed that a population of VANs expressing Glp1r is synaptically connected to the BAT. Our findings reveal a novel role of VAN GLP-1R signaling in the regulation of EE and BAT thermogenesis and imply that through this gut-brain-BAT connection, intestinal GLP-1 plays a role in HFD-induced metabolic syndrome.

Novel role of GLP-1 receptor signaling in energy expenditure during chronic high fat diet feeding in rats

OBJECTIVE

Glucagon-like peptide-1 (GLP-1) secreted from intestinal L-cells plays a major role in meal termination and glucose-dependent insulin secretion. Several lines of evidence indicate, however, that the acute satiating and incretin effects of GLP-1 are attenuated with high fat diet (HFD) exposure. Here we tested the hypothesis that endogenous GLP-1 differentially affects energy balance and glucose homeostasis dependent on whether rats are fed chow or HFD (60% energy from fat).

METHODS

We blocked GLP-1 receptor (GLP-1R) signaling by daily intraperitoneal (IP) injection of the GLP-1R antagonist exendin (9-39) (Ex9, 10 μg/kg) or vehicle for 5 weeks in male Sprague-Dawley rats fed either chow or HFD, recorded body weight (BW) and food intake throughout, and assessed energy expenditure (3rd week) and glucose tolerance (4th week).

RESULTS

Five week daily Ex9 injections reduced BW gain in HFD-fed rats, but did not affect BW in chow-fed rats. On the other hand, chronic Ex9 treatment did not affect daily food intake in either chow or HFD-fed rats during the entire study. The reduced BW gain in HFD-fed rats was associated with an increase in energy expenditure. Interestingly, chronic Ex9 treatment induced glucose intolerance in chow-fed rats, but not in HFD-fed rats, suggesting a differential role of GLP-1R signaling in glucose metabolism during chow and HFD feeding.

CONCLUSIONS

Our findings reveal a novel role of GLP-1R signaling, modulating energy expenditure rather than eating behavior during HFD feeding. Furthermore, these results suggest a previously unrecognized contribution of GLP-1R signaling to the pathophysiology of obesity.

Loss of dorsomedial hypothalamic GLP-1 signaling reduces BAT thermogenesis and increases adiposity

Objective

Glucagon-like peptide-1 (GLP-1) neurons in the hindbrain densely innervate the dorsomedial hypothalamus (DMH), a nucleus strongly implicated in body weight regulation and the sympathetic control of brown adipose tissue (BAT) thermogenesis. Therefore, DMH GLP-1 receptors (GLP-1R) are well placed to regulate energy balance by controlling sympathetic outflow and BAT function.

Methods

We investigate this possibility in adult male rats by using direct administration of GLP-1 (0.5 ug) into the DMH, knocking down DMH GLP-1R mRNA with viral-mediated RNA interference, and by examining the neurochemical phenotype of GLP-1R expressing cells in the DMH using in situ hybridization.

Results

GLP-1 administered into the DMH increased BAT thermogenesis and hepatic triglyceride (TG) mobilization. On the other hand, Glp1r knockdown (KD) in the DMH increased body weight gain and adiposity, with a concomitant reduction in energy expenditure (EE), BAT temperature, and uncoupling protein 1 (UCP1) expression. Moreover, DMH Glp1r KD induced hepatic steatosis, increased plasma TG, and elevated liver specific de-novo lipogenesis, effects that collectively contributed to insulin resistance. Interestingly, DMH Glp1r KD increased neuropeptide Y (NPY) mRNA expression in the DMH. GLP-1R mRNA in the DMH, however, was found in GABAergic not NPY neurons, consistent with a GLP-1R-dependent inhibition of NPY neurons that is mediated by local GABAergic neurons. Finally, DMH Glp1r KD attenuated the anorexigenic effects of the GLP-1R agonist exendin-4, highlighting an important role of DMH GLP-1R signaling in GLP-1-based therapies.

Conclusions

Collectively, our data show that DMH GLP-1R signaling plays a key role for BAT thermogenesis and adiposity.

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DMH GLP-1R stimulation acutely increases BAT thermogenesis.

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DMH GLP-1R mRNA knockdown decreases EE and BAT thermogenesis.

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DMH GLP-1R mRNA knockdown impairs lipid and glucose metabolism.

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Reduced DMH GLP-1R signaling blunts the anorexigenic responses to Ex-4.

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DMH GLP-1R signaling indirectly regulates NPY gene expression.

Intestinal lymph as a readout of meal-induced GLP-1 release in an unrestrained rat model

Intestinal lymph supposedly provides a readout for the secretion of intestinal peptides. We here assessed how mesenteric lymph duct (MLD) lymph levels of glucagon-like peptide (GLP-1), insulin, and metabolites [glucose and triglycerides (TG)] evolve after isocaloric high- and low-fat diet (HFD and LFD) meals and how they compare with hepatic portal vein (HPV) plasma levels. Moreover, we examined the effects of intraperitoneally administered GLP-1 (1 or 10 nmol/kg) on these parameters. At 20 min after the HFD meal onset, GLP-1 levels were higher in MLD lymph than in HPV plasma. No such difference occurred with the LFD meal. Intraperitoneal injections of 10 nmol/kg GLP-1 before meals enhanced the meal-induced increases in MLD lymph and HPV plasma GLP-1 levels except for the MLD lymph levels after the HFD meal. Intraperitoneal injection of 1 nmol/kg GLP-1 only increased HPV plasma GLP-1 levels at 60 min after the HFD meal. GLP-1 injections did not increase the MLD lymph or HPV plasma GLP-1 concentrations beyond the physiological range, suggesting that intraperitoneal GLP-1 injections can recapitulate the short-term effects of endogenous GLP-1. Dipeptidyl peptidase IV (DPP-IV) activity in MLD lymph was lower than in HPV plasma, which presumably contributed to the higher levels of GLP-1 in lymph than in plasma. Insulin and glucose showed similar profiles in MLD lymph and HPV plasma, whereas TG levels were higher in lymph than in plasma. These results indicate that intestinal lymph provides a sensitive readout of intestinal peptide release and potential action, in particular when fat-rich diets are consumed.

Rhodium(III)-Catalyzed C-H Activation/Heterocyclization as a Macrocyclization Strategy. Synthesis of Macrocyclic Pyridones

Structurally diverse macrocyclic pyridones can be efficiently synthesized by a rhodium(III)-catalyzed C-H activation/heterocyclization of ω-alkynyl α-substituted acrylic hydroxamates. The use of a O-pivaloyl hydroxamate as directing group was crucial to achieve efficient catalyst turnover in a redox-neutral process.

Limiting glucocorticoid secretion increases the anorexigenic property of Exendin-4

Objective

Glucagon-like peptide-1 (GLP-1) analogs are attractive options for the treatment of type II diabetes and obesity because of their incretin and anorexigenic effects. Peripheral administration of the GLP-1R agonist Exendin-4 (Ex-4) also increases glucocorticoid secretion in rodents and humans, but whether the released glucocorticoids interact with Ex-4's anorexigenic effect remains unclear.

Methods

To test this, we used two experimental approaches that suppress corticosterone secretion and then assessed Ex-4 effects on eating in adult male rats. First, we combined acute and chronic low dose dexamethasone treatment with Ex-4. Second, we ablated hindbrain catecholamine neurons projecting to the hypothalamus with anti-dopamine-β-hydroxylase-saporin (DSAP) to block Ex-4-induced corticosterone secretion.

Results

Combining dexamethasone and Ex-4 produced a larger acute anorexigenic effect than Ex-4 alone. Likewise, chronic dexamethasone and Ex-4 co-treatment produced a synergistic effect on eating and greater body weight loss in diet-induced obese rats than Ex-4 alone. DSAP lesions not only blunted Ex-4's ability to increase corticosterone secretion, but potentiated the anorexigenic effect of Ex-4, indicating that Ex-4-dependent corticosterone secretion opposes Ex-4's actions. Consistent with the enhancement of Ex-4's anorexigenic effect, DSAP lesion altered Ex-4-dependent changes in neuropeptide Y, preproglucagon, and corticotropin releasing hormone gene expression involved in glucocorticoid feedback.

Conclusions

Our findings demonstrate that limiting glucocorticoid secretion and actions with low dose dexamethasone or DSAP lesion increases Ex-4's ability to reduce food intake and body weight. Novel glucocorticoid receptor based mechanisms, therefore, may help enhance GLP-1-based obesity therapies.

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Blocking HPA axis by low dose dexamethasone increased the anorexigenic property of Ex-4.

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Dexamethasone/Ex-4 co-treatment reduced food intake and body weight in diet-induced obese rats more than Ex-4 alone.

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A brain lesion model identified a potential central interaction between glucocorticoids and GLP-1 in food intake control.

Knockdown of GLP-1 Receptors in Vagal Afferents Affects Normal Food Intake and Glycemia

Nutrient stimulation of enteroendocrine L cells induces the release of the incretin and satiating peptide glucagon-like peptide 1 (GLP-1). The vagus nerve innervates visceral organs and may contribute to the mediation of gut-derived GLP-1's effects on food intake, energy homeostasis, and glycemic control. To test the hypothesis that vagal afferent neuron (VAN) GLP-1 receptors (GLP-1Rs) are necessary for these effects of endogenous GLP-1, we established a novel bilateral nodose ganglia injection technique to deliver a lentiviral vector and to knock down VAN GLP-1Rs in male Sprague Dawley rats. We found that a full expression of VAN GLP-1Rs is not necessary for the maintenance of long-term energy balance in normal eating conditions. VAN GLP-1R knockdown (kd) did, however, increase meal size and accelerated gastric emptying. Moreover, postmeal glycemia was elevated and insulin release was blunted in GLP-1R kd rats, suggesting that VAN GLP-1Rs are physiological contributors to the neuroincretin effect after a meal. Collectively, our results highlight a crucial role for the VANs in mediating the effects of endogenous GLP-1 on food intake and glycemia and may promote the further development of GLP-1-based therapies.

Mild acute renal failure potentiates metformin accumulation in the diabetic rat kidney without further impairment of renal function

OBJECTIVES

To analyze, in acute renal failure (ARF) in diabetic rats, how moderate functional ARF would modify metformin (MET) pharmacokinetics and if plasma and renal tissue MET accumulation could aggravate renal insufficiency and/or elicit plasma lactate accumulation.

METHODS

Streptozotocin-induced diabetic rats were allocated to four groups: control, MET, ARF, ARF-MET (6-7 rats per group). MET (100 mg/kg/day) was given per os for two weeks before ARF was induced by drinking restriction and enalapril treatment. The effects of MET and/or ARF were examined in vivo on renal function in conscious rats (metabolic cages) and ex vivo on renal vascular reactivity (isolated kidney).

RESULTS

MET treatment (plasma level: 5.3 +/- 1.4 microg/ml, mean+/-SEM), resulted in biguanide accumulation in cortex and medulla (53 +/- 17 and 80 +/- 40 microg/g respectively). MET was devoid of any effect on creatinine clearance, mean blood pressure or renal vascular resistance, but moderately increased plasma lactate (3.8 +/- 0.5 vs 3.2 +/- 0.2 mM, P<0.05) and decreased angiotensin II-induced renal vasoconstriction. ARF, although mild, decreased renal MET clearance (0.29 +/- 0.05 vs 1.01 +/- 0.31 ml/min/100 g, P<0.05) and increased plasma and renal tissue MET levels (x 2-4). MET however did not worsen the fall in glomerular filtration rate, nor modify renal vascular reactivity. ARF did not change the MET-elicited moderate increase in plasma lactate.

CONCLUSION

Despite the increase in MET plasma and renal tissue levels subsequent to moderate ARF, no harmful metabolic effect on plasma lactate and no further impairment of renal function was observed in MET-treated diabetic rats subjected to ARF.

High concentrations of oxytocin cause vasoconstriction by activating vasopressin V1A receptors in the isolated perfused rat kidney

The aim of this study was to evaluate the renal vascular effects of oxytocin in Sprague-Dawley rats and in Brattleboro heterozygous or homozygous rats, the latter being genetically deficient in vasopressin synthesis. Studies were performed in vitro, in the isolated kidney perfused in an open circuit with a Tyrode's solution. Oxytocin induced a concentration-dependent renal vasoconstriction in Sprague-Dawley rats, at rather high concentrations (EC50=170+/-39 nM, mean +/- SEM, n=6) with a maximum response amounting to 44% of that elicited by vasopressin (increase in renal vascular resistance: 11.5+/-0.9 mmHg min ml(-1) vs. 26.2+/-2.2 mmHg min ml(-1)). Oxytocin-evoked renal vasoconstriction was abolished by SR 49059, a selective vasopressin V1A receptor antagonist (10 nM), but not by d(CH2)5[Tyr(Me)2,Thr4,Orn8,Tyr-(NH2)9] vasotocin, an oxytocin receptor antagonist (10 nM). In the presence of SR 49059, oxytocin did not induce renal vasorelaxation. Oxytocin induced renal vasoconstriction in Brattleboro homozygotes and heterozygotes (EC50=59+/-12 nM and 262+/-110 nM; Emax=7.8+/-1.1 mmHg min ml(-1) and 6.9+/-0.4 mmHg min ml(-1), n=5 respectively) with characteristics similar as observed in Sprague-Dawley rats concerning partial agonist activity, low potency and antagonism by SR 49059. Responsiveness to vasopressin did not differ in Brattleboro homozygotes and heterozygotes (EC50 approximately 0.25 nM) and was similar as we reported in Sprague-Dawley rats. These findings indicate that high concentrations of oxytocin induce renal vasoconstriction in the rat by activating vasopressin V1A receptors. The low agonist activity makes it unlikely that oxytocin can substitute functionally for vasopressin at the renal vascular V1A receptor in Brattleboro homozygous rats which are deficient in endogenous vasopressin.

Binding of high density lipoprotein (HDL) and discoidal reconstituted HDL to the HDL receptor scavenger receptor class B type I. Effect of lipid association and APOA-I mutations on receptor binding

The binding of apoA-I-containing ligands to the HDL receptor scavenger receptor class B type I (SR-BI) was characterized using two different assays. The first employed conventional binding or competition assays with (125)I-labeled ligands. The second is a new nonradioactive ligand binding assay, in which the receptor-associated ligand is detected by quantitative immunoblotting ("immunoreceptor assay"). Using both methods, we observed that the K(d) value for spherical HDL (density = 1.1-1.13 g/ml) was approximately 16 microgram of protein/ml, while the values for discoidal reconstituted HDL (rHDL) containing proapoA-I or plasma apoA-I were substantially lower (approximately 0.4-5 microgram of protein/ml). We also observed reduced affinity and/or competition for spherical (125)I-HDL cell association by higher relative to lower density HDL and very poor competition by lipid-free apoA-I and pre-beta-1 HDL. Deletion of either 58 carboxyl-terminal or 59 amino-terminal residues from apoA-I, relative to full-length control apoA-I, resulted in little or no change in the affinity of corresponding rHDL particles. However, rHDL particles containing a double mutant lacking both terminal domains competed poorly with spherical (125)I-HDL for binding to SR-BI. These findings suggest an important role for apoA-I and its conformation/organization within particles in mediating HDL binding to SR-BI and indicate that the NH(2) and COOH termini of apoA-I directly or indirectly contribute independently to binding to SR-BI.

Vascular effects of [Arg8]vasopressin in the isolated perfused rat kidney

The renal vascular effects of [Arg8]vasopressin (vasopressin) were investigated in the isolated perfused rat kidney. Vasopressin (0.01-3 nM) elicited a dose-dependent vasoconstriction in kidneys from Sprague Dawley rats, with a EC50 value of 0.206 +/- 0.044 nM. Inhibition of nitric oxide synthase by N omega-nitro-L-arginine (100 microM) shifted the vasopressin-induced vasoconstrictor response curve to the left. Inhibition of cyclooxygenase by indomethacin (10 or 30 microM) blunted the constriction induced by low concentrations of the peptide. Vasopressin, like angiotensin II but not noradrenaline, induced tachyphylaxis, SR 49059 ((2S)1-[(2R,3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene- sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2- carboxamide) (1-30 nM), a new potent and selective non-peptide vasopressin V1A receptor antagonist, shifted the concentration-response curve for vasopressin to the right without decreasing the maximum contraction. Antagonism became competitive with a pA2 value (+/- S.D.) of 9.72 +/- 0.20 during inhibition of nitric oxide release. [Mpa1,D-Arg8]Vasopressin (desmopressin; 0.1-100 nM), or vasopressin (0.01-1 nM) after blockade of the vasopressin V1A receptor by SR 49059, induced no vasopressin V2 receptor-related renal relaxation in kidneys with vascular tone previously restored by noradrenaline or prostaglandin F2 alpha. These findings indicate that in the isolated perfused rat kidney vasopressin is a potent renal vasoconstrictor. The constriction depends on activation of smooth muscle vasopressin V1A receptors and is modulated by endothelial nitric oxide but not by prostacyclin or vasopressin V2 receptor-related vasodilation.

Endothelium-dependent relaxation in the isolated rat kidney: impairment by cyclosporine A

The therapeutical use of cyclosporine A (CsA) is hampered by the development of nephrotoxicity characterized by a marked increase in renal vascular resistance (RVR). We investigated vascular functions in kidneys of rats treated with CsA. The ex vivo vascular reactivity of kidneys from control rats and animals treated subacutely with CsA [50 mg/kg/day subcutaneously (s.c.) for 16-21 days] or an olive oil vehicle (1 ml/kg) was analyzed in male Wistar rats. The right kidney was isolated and perfused with Tyrode's or Krebs solution in an open circuit. The effects of acetylcholine (Ach), fenoldopam (FEN), and sodium nitroprusside (SNP) on norepinephrine (NE) preconstricted kidneys were studied. In control kidneys (untreated or vehicle-treated), Ach induced a relaxation (EC50 = 0.56 +/- 0.05 x 10(-9)M; Emax = 88.2 +/- 2.1% decrease in the vascular tone restored by NE) which was endothelium-dependent [near-complete abolition after treatment with a detergent, 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propane-sulfonate (CHAPS) treatment] but only partially inhibited by indomethacin (EC50 = 1.71 +/- 0.39 x 10(-9)M, p < 0.05; Emax = 87.1 +/- 4.9%, NS) or indomethacin with NG-nitro-L-arginine methyl ester (L-NAME: EC50 = 1.04 +/- 0.38 x 10(-9)M, NS; Emax = 63.8 +/- 2.5%, p < 0.01). CsA treatment induced a marked decrease in creatinine clearance and natriuresis measured in vivo but had no effect on systolic blood pressure (SBP). In CsA-treated rats, Ach-induced renal relaxation was partially blunted (EC50 = 1.88 +/- 0.34 x 10(-9)M, p < 0.01; Emax = 82.8 +/- 4.6, NS), with both a defect in prostaglandin (PG) and nitric oxide (NO)-related responses. CsA treatment had no effect on endothelium-independent relaxations induced by FEN and SNP. These results show that subacute CsA treatment selectively impairs renal endothelium-dependent relaxation related to PGs and NO release.

Stereoselective renal effects of the loop diuretic ozolinone in the anesthetized dog

The renal effects of i.v. injections of (+/-)-ozolinone, its enantiomers (-)-ozolinone and (+)-ozolinone and its prodrug (+/-)-etozoline, were compared with those of furosemide, in pentobarbital anesthetized dogs. Renal blood flow (electromagnetic flow-meter) and glomerular filtration rate (polyfructosan clearance) were assessed on the left denervated kidney together with renin secretion and urinary electrolyte excretion. (-)-Ozolinone (15.5 mg/kg i.v.) behaves as a stereoselective loop diuretic equipotent to 20 mg/kg of furosemide and 45 mg/kg of (+/-)-ozolinone; (+)-ozolinone induced only minor salidiuretic effects. Both ozolinone enantiomers markedly increased the renal blood flow and decreased the filtration fraction, suggesting that the vosodilating effect predominates on the efferent glomerular arterioles. (-)-Ozolinone also induced an acute rise in renin secretion. The inhibition of prostaglandin synthesis (indomethacin or meclofenamate) prevented renin hypersecretion in response to (-)-ozolinone and modified its salidiuretic effects but had no effect on the vascular response. The inhibition of the kallikrein-kinin system by aprotinin had no effect on the overall renal response to (-)-ozolinone. The inhibition of the renin-angiotensin system by captopril decreased blood pressure, prolonged the (-)-ozolinone-induced decrease in renal vascular resistance and increased renin secretion. Our results demonstrate that the loop diuretic, ozolinone, induces stereoselective and prostaglandin-dependent renin secretion, which is involved in the regulation of intra-renal hemodynamics.