Effects of estradiol in the heart of rats with fructose-rich diet-induced insulin resistance

Fruktoza je prirodni šećer, ĉiji se unos poslednjih decenija dramatiĉno povećao, najvećim delom zbog povećane upotrebe kukuruznog sirupa sa visokim sadrţajem fruktoze. Povećan unos fruktoze vodi ka razvoju metaboliĉkog sindroma kod ljudi i eksperimentalnih ţivotinja. Pored promena u jetri, adipoznom tkivu i skeletnim mišićima, ishrana bogata fruktozom je praćena i razvojem insulinske rezistencije u srcu. Poznato je da insulin ostvaruje svoje efekte na ćelije srca i da u stanju insulinske rezistencije u srcu dolazi do poremećaja u signalnom putu Akt/eNOS i balansu korišćenja energetskih supstrata. Posledice povećanog unosa fruktoze su polno zavisne, pri ĉemu je protektivni efekat pripisan estrogenim hormonima. Fiziološke koncentracije estrogena poboljšavaju osetljivost na insulin i deluju kardioprotektivno. TakoĊe, estradiol utiĉe na specifiĉno delovanje insulina u srcu. Cilj ove studije bio je analiza efekta estradiola na procese u srcu regulisane insulinom u stanju insulinske rezistencije izazvane ishranom bogatom fruktozom. Ţenke pacova su podvrgnute standardnoj ishrani ili ishrani obogaćenoj 10% rastvorom fruktoze tokom 9 nedelja i ovarijektomisane 2 nedelje pre ţrtvovanja, pri ĉemu je polovina ţivotinja na fruktoznoj ishrani dan nakon ovarijektomije podvrgnuta tretmanu estradiolom. U cilju izuĉavanja efekata ishrane bogate fruktozom i estradiola na insulinom regulisanu fosforilaciju i unutarćelijsku lokalizaciju ispitivanih molekula, polovina ţivotinja je tretirana insulinom 40 minuta pre ţrtvovanja. Analizirani su molekuli iz insulinskog signalnog puta (IRS-1, Akt i ERK1/2), kao i efektorni molekuli ĉiju funkciju reguliše insulin, kao što su eNOS, Na+/K+-ATP-aza i molekuli ukljuĉeni u transport i metabolizam energetskih supstrata u srcu (GLUT1, GLUT4, CD36, lipin 1 i CPTI) i lipidni profil srca. Ispitivana je ekspresija ovih molekula na nivou proteina, kao i njihova fosforilacija ili unutarćelijska lokalizacija. Ishrana bogata fruktozom je povećala unos teĉnosti i smanjila unos hrane, dok je povećala ukupan kalorijski unos i koncentraciju leptina u plazmi. Estradiol je većim delom poništio štetne efekte ishrane na regulaciju apetita, verovatno preko povećanja centralne osetljivosti na leptin. Ţivotinje na fruktoznoj ishrani su imale povišene koncentracije triglicerida i insulina u plazmi i povećan HOMA indeks, smanjenu koncentraciju slobodnih masnih kiselina, dok je koncentracija glukoze bila nepromenjena...Fructose is natural sugar whose intake has increased dramatically over the past decades, mostly due to increased consumption of high-fructose corn syrup. Increased intake of fructose initiates development of metabolic syndrome phenotype in humans and experimental animals. In addition to changes in liver, adippose tissue and skeletal muscle, fructose-rich diеt is accompanied by cardiac insulin resistance. Cardiac muscle is a target of insulin. Insulin resistance is accompanied by disturbances in Akt/eNOS signalling and altered cardiac usage of energetic substrates. Consequences of enhanced fructose intake are shown to be sex-dependent and the protective effect is attributed to estrogens. Physiological concentrations of estrogens improve insulin sensitivity and they are cardioprotective. Also, estrogens affect specific cardiac insulin action. The aim of the present study was to analyze effects of estradiol on insulin-regulated processes in the heart in insulin resistance state. Female rats were subjected to standard diet or diet containing 10% fructose in drinking water during 9 weeks. Two weeks before sacrifice, all animals were bilaterally ovariectomized and half of the fructose-fed animals were subjected to estradiol replacement treatment, day after ovariectomy. In order to study fructose-rich diet and estradiol effects on the insulin regulated phosphorylations and subcellular localization of analyzed molecules, half of the animals were treated with insulin, 40 min before killing. Insulin signaling molecules (IRS-1, Akt i ERK1/2) were analyzed, as well as insulin regulated effector molecules, such as eNOS, Na+/K+-ATPase and molecules involved in the transport and metabolism of energetic substrates in the heart (GLUT1, GLUT4, CD36, lipin 1 i CPTI), as well as profile of cardiac lipids. We examined the protein exppression of the molecules, as well as their phosphorylation or subcellular localization. Fructose-rich diet increased liquid intake and decreased food intake, while it increased total caloric intake and plasma leptin concentration. Estradiol abolished most of the detrimental effects of diet on appetite regulation, probably through increase in central leptin sensitivity. The fructose-fed rats had increased plasma triglycerides and insulin levels and increased HOMA index, decreased plasma free fatty acid level, while glucose concentration was unaltered..

Fructose-rich diet induces gender-specific changes in expression of the renin-angiotensin system in rat heart and upregulates the ACE/AT1R axis in the male rat aorta

Introduction: The cardiovascular renin-angiotensin system (RAS) could be affected by gender and dietary regime. We hypothesized that male rats will be more susceptible to activation of RAS in the heart and aorta, as a response to a fructose-rich diet (FRD). Materials and methods: Both male and female Wistar rats were given a 10% (w/v) fructose solution for 9 weeks. We measured the biochemical parameters, blood pressure (BP) and heart rate. We used Western blot and real-time polymerase chain reaction (PCR) to quantify protein and gene expression. Results: In the male rats, the FRD elevated BP and expression of cardiac angiotensin-converting enzyme (ACE), while the expression of angiotensin-converting enzyme 2 (ACE2) and angiotensin II Type 2 receptor (AT(2)R) were significantly decreased. In female rats, there were no changes in cardiac RAS expression due to FRD. Furthermore, the ACE/AT(1)R axis was overexpressed in the FRD male rats aortae, while only AT(1)R was upregulated in the FRD female rats aortae. ACE2 expression remained unchanged in the aortae of both genders receiving the FRD. Conclusions: The FRD induced gender-specific changes in the expression of the RAS in the heart and aortae of male rats. Further investigations are required in order to get a comprehensive understanding of the underlying mechanisms of gender-specific fructose-induced cardiovascular pathologies

Gender modulates development of the metabolic syndrome phenotype in fructose-fed rats

We analyzed the effects of a fructose-rich diet (FRD) to test the assumption that the expression of metabolic syndrome phenotype is different in male and female rats. Two-way ANOVA revealed a significant effect of FRD on feeding behavior and carbohydrate/lipid metabolism. The increased caloric intake in FRD rats of both sexes was followed by a cluster of gender-specific changes typical for the metabolic syndrome. Female rats were characterized by decreased glycemia, increased triglycerides, enlarged visceral adipose tissue and increased absolute mass of liver, without changes in systolic blood pressure and insulin sensitivity. In contrast, male rats developed less disturbances in physical and biochemical characteristics, but blood pressure and insulin sensitivity were impaired by FRD. The results emphasize the detrimental effects of fructose consumption on cardiovascular risk and insulin action in males, whereas females are affected by other metabolic disturbances. These results support the idea of gender-dependent differences in the expression of the metabolic syndrome phenotype.Projekat ministarstva br. 4100

Does oestradiol attenuate the damaging effects of a fructose-rich diet on cardiac Akt/endothelial nitric oxide synthase signalling?

Fructose-rich diets (FRD) cause cardiac insulin resistance manifested by impairment of Akt/endothelial NO synthase (eNOS) signalling. In contrast, oestradiol (E2) activates this signalling pathway in the heart. To study the ability of E2 to revert the detrimental effect of fructose on cardiac Akt/eNOS, female rats were subjected to a FRD and ovariectomy followed with or without E2 replacement. We also analysed the effects of the FRD and E2 on cardiac extracellular signal-regulated kinase (Erk 1/2) signalling related to their role in cardiac hypertrophy development. Expression of Akt, eNOS and Erk 1/2, as well as regulatory phosphorylations of these molecules were determined. The protein expression of cardiac Akt and eNOS was not affected by the diet or E2 treatment. However, the FRD was accompanied by a decrease in Akt phosphorylation at Ser(473) and Thr(308), and eNOS at Ser(1177), while the phosphorylation of eNOS at Thr(495) was increased. E2 replacement in ovariectomised fructose-fed rats caused a reversion of the diet effect on Akt and eNOS serine phosphorylation, but mostly had no effect on threonine phosphorylation of the molecules. The FRD and E2 treatment did not influence Erk 1/2 expression and phosphorylation and heart mass as well. The data show that E2 selectively suppress the negative effects of a FRD on Akt/eNOS signalling and probably point to the different effects of E2 on kinase/phosphatase pathways responsible for phosphorylation/dephosphorylation of Akt and eNOS. Furthermore, the results suggest that the heart of females in the reproductive period is partially protected against the damaging effects of increased fructose intake

Improvement of lipid metabolism regulation by low-intensity exercise in fructose-fed rats

Excessive dietary fructose consumption in parallel with limited physical activity contributes to the global increase in prevalence of metabolic disorders. Metabolic syndrome represents a collection of cardiometabolic risk factors that includes obesity, insulin resistance, hypertension, and dyslipidemia, and it is undoubtedly linked to increased risk for two global maladies, type 2 diabetes, and cardiovascular diseases. Fructose-rich diet is accompanied by the development of insulin resistance in the heart, and it could change the use of cardiac energy substrates towards increased fatty acid (FA) uptake, and catabolism. Exercise may be beneficial in prevention and treatment of the metabolic syndrome. The aim of this study was to analyse the impact of low-intensity exercise on protein expression of nuclear transcription factors involved in regulating FA β- oxidation in a heart of fructose fed rats. Male Wistar rats were divided into control group, and two groups that received 10% fructose for 9 weeks, one which was sedentary and one which was additionally exposed to low intensity exercise. The protein expression of important transcriptional regulators of fatty acid β-oxidation PPARα, and FOXO1, and coregulators Lipin1, PGC-1, and SIRT1 are analyzed in cardiac lysate and/or nuclear fraction by Western blot. Gene expression of ACADL, the enzyme that catalyzes the initial step of mitochondrial β-oxidation, was quantified by real-time PCR. Fructose-rich diet decreased nuclear PPARα compared to control. Exercise increased nuclear PPARα, nuclear FOXO1, lysate PGC1, and nuclear Lipin1 in fructose-fed rats compared to sedentary fructose-fed rats. Exercise increased lysate PPARα, lysate and nuclear FOXO1, lysate PGC1, lysate and nuclear SIRT1, and nuclear Lipin1 in fructose-fed rats compared to control. In conclusion, running at low intensity is accompanied by increased expression of key regulators of fatty acid oxidation. The results indicate that exercise achieves its effect by increasing the nuclear content of PPARα, Lipin1, and FOXO1

Gender modulates development of the metabolic syndrome phenotype in fructose-fed rats

We analyzed the effects of a fructose-rich diet (FRD) to test the assumption that the expression of metabolic syndrome phenotype is different in male and female rats. Two-way ANOVA revealed a significant effect of FRD on feeding behavior and carbohydrate/lipid metabolism. The increased caloric intake in FRD rats of both sexes was followed by a cluster of gender-specific changes typical for the metabolic syndrome. Female rats were characterized by decreased glycemia, increased triglycerides, enlarged visceral adipose tissue and increased absolute mass of liver, without changes in systolic blood pressure and insulin sensitivity. In contrast, male rats developed less disturbances in physical and biochemical characteristics, but blood pressure and insulin sensitivity were impaired by FRD. The results emphasize the detrimental effects of fructose consumption on cardiovascular risk and insulin action in males, whereas females are affected by other metabolic disturbances. These results support the idea of gender-dependent differences in the expression of the metabolic syndrome phenotype.Projekat ministarstva br. 4100

Effects of estradiol in the heart of rats with fructose-rich diet-induced insulin resistance

Fruktoza je prirodni šećer, ĉiji se unos poslednjih decenija dramatiĉno povećao, najvećim delom zbog povećane upotrebe kukuruznog sirupa sa visokim sadrţajem fruktoze. Povećan unos fruktoze vodi ka razvoju metaboliĉkog sindroma kod ljudi i eksperimentalnih ţivotinja. Pored promena u jetri, adipoznom tkivu i skeletnim mišićima, ishrana bogata fruktozom je praćena i razvojem insulinske rezistencije u srcu. Poznato je da insulin ostvaruje svoje efekte na ćelije srca i da u stanju insulinske rezistencije u srcu dolazi do poremećaja u signalnom putu Akt/eNOS i balansu korišćenja energetskih supstrata. Posledice povećanog unosa fruktoze su polno zavisne, pri ĉemu je protektivni efekat pripisan estrogenim hormonima. Fiziološke koncentracije estrogena poboljšavaju osetljivost na insulin i deluju kardioprotektivno. TakoĊe, estradiol utiĉe na specifiĉno delovanje insulina u srcu. Cilj ove studije bio je analiza efekta estradiola na procese u srcu regulisane insulinom u stanju insulinske rezistencije izazvane ishranom bogatom fruktozom. Ţenke pacova su podvrgnute standardnoj ishrani ili ishrani obogaćenoj 10% rastvorom fruktoze tokom 9 nedelja i ovarijektomisane 2 nedelje pre ţrtvovanja, pri ĉemu je polovina ţivotinja na fruktoznoj ishrani dan nakon ovarijektomije podvrgnuta tretmanu estradiolom. U cilju izuĉavanja efekata ishrane bogate fruktozom i estradiola na insulinom regulisanu fosforilaciju i unutarćelijsku lokalizaciju ispitivanih molekula, polovina ţivotinja je tretirana insulinom 40 minuta pre ţrtvovanja. Analizirani su molekuli iz insulinskog signalnog puta (IRS-1, Akt i ERK1/2), kao i efektorni molekuli ĉiju funkciju reguliše insulin, kao što su eNOS, Na+/K+-ATP-aza i molekuli ukljuĉeni u transport i metabolizam energetskih supstrata u srcu (GLUT1, GLUT4, CD36, lipin 1 i CPTI) i lipidni profil srca. Ispitivana je ekspresija ovih molekula na nivou proteina, kao i njihova fosforilacija ili unutarćelijska lokalizacija. Ishrana bogata fruktozom je povećala unos teĉnosti i smanjila unos hrane, dok je povećala ukupan kalorijski unos i koncentraciju leptina u plazmi. Estradiol je većim delom poništio štetne efekte ishrane na regulaciju apetita, verovatno preko povećanja centralne osetljivosti na leptin. Ţivotinje na fruktoznoj ishrani su imale povišene koncentracije triglicerida i insulina u plazmi i povećan HOMA indeks, smanjenu koncentraciju slobodnih masnih kiselina, dok je koncentracija glukoze bila nepromenjena...Fructose is natural sugar whose intake has increased dramatically over the past decades, mostly due to increased consumption of high-fructose corn syrup. Increased intake of fructose initiates development of metabolic syndrome phenotype in humans and experimental animals. In addition to changes in liver, adippose tissue and skeletal muscle, fructose-rich diеt is accompanied by cardiac insulin resistance. Cardiac muscle is a target of insulin. Insulin resistance is accompanied by disturbances in Akt/eNOS signalling and altered cardiac usage of energetic substrates. Consequences of enhanced fructose intake are shown to be sex-dependent and the protective effect is attributed to estrogens. Physiological concentrations of estrogens improve insulin sensitivity and they are cardioprotective. Also, estrogens affect specific cardiac insulin action. The aim of the present study was to analyze effects of estradiol on insulin-regulated processes in the heart in insulin resistance state. Female rats were subjected to standard diet or diet containing 10% fructose in drinking water during 9 weeks. Two weeks before sacrifice, all animals were bilaterally ovariectomized and half of the fructose-fed animals were subjected to estradiol replacement treatment, day after ovariectomy. In order to study fructose-rich diet and estradiol effects on the insulin regulated phosphorylations and subcellular localization of analyzed molecules, half of the animals were treated with insulin, 40 min before killing. Insulin signaling molecules (IRS-1, Akt i ERK1/2) were analyzed, as well as insulin regulated effector molecules, such as eNOS, Na+/K+-ATPase and molecules involved in the transport and metabolism of energetic substrates in the heart (GLUT1, GLUT4, CD36, lipin 1 i CPTI), as well as profile of cardiac lipids. We examined the protein exppression of the molecules, as well as their phosphorylation or subcellular localization. Fructose-rich diet increased liquid intake and decreased food intake, while it increased total caloric intake and plasma leptin concentration. Estradiol abolished most of the detrimental effects of diet on appetite regulation, probably through increase in central leptin sensitivity. The fructose-fed rats had increased plasma triglycerides and insulin levels and increased HOMA index, decreased plasma free fatty acid level, while glucose concentration was unaltered..

Quercetin decreases fructose drinking in model of fructose-induced insulin resistance. Antioxidant effects of fructose - methyl cellulose combination

The excessive fructose consumption is linked with metabolic changes and serious health problems. Overconsumption of fructose-sweetened food products mainly sugar-sweetened beverages is associated with body-weight gain, obesity, inflammation and cardiometabolic disturbances. The majority of fructose is metabolized in liver and an excess of fructose is converted to fat. The triglycerides are taken up by the adipose tissue for storage– consequently the fructose fed rats display enhancement of the adipose tissue mass and elevated blood uric acid. High fructose intake increases oxidation stress. Quercetin is one of the most commonly occurring bioactive flavonoids in human foods. It is present in tea, apples, broccoli, onion berries and red grapes. The quercetin is known for its beneficial health effects including mainly anti-inflammatory and antioxidant properties. In the presented study we adopted rats with fully developed fructose induced insulin resistance (9 weeks of 10% fructose treatment) which were then continuously treated with combination of fructose and 20 mg/kg/day quercetin for additional 6 weeks. Quercetin was delivered by gavage as solubilized in 1% methyl cellulose. Our results showed that quercetin treatment lead to the normalization of the fructose solution drinking to the level of drinking water intake as well as the decrease of plasma glucose in rats consuming fructose. Moreover, a significant decrease of plasma uric acid, oxidative stress biomarkers (TBARS, nitrotyrosine), AGEs fluorescence and hemoglobin leakage was induced by combination of fructose with methyl cellulose. Thus, methyl cellulose with fructose had positive impacts like antioxidant, anti-glycation and erythrocyteprotective effects. We might speculate that methyl cellulose possibly shifts the fructose metabolism in favour of utilization of antioxidant features of fructose. Moreover, in vitro experiments showed that fructose and methyl cellulose had a moderate antioxidant activity with additive effect showed in the ferric reducing antioxidant power assay.Redox Biology Congress 2023 : Abstracts : 6-9 June 2023, Vienna, Austri