A number of alterations have been identified in lipid metabolism within adipose tissue and liver in obesity. Less is known about the capacity of skeletal muscle for the metabolism of fatty acids in ...obesity-related insulin resistance, though it is evident that dry cow muscles may contain increased triglyceride content. The current study was therefore undertaken to evaluate the skeletal muscle expression of proteins of the fatty acid metabolism in dry cows with different body condition scores (BCS). Sixteen Holstein-Friesian close-up cows were divided into 2 equal groups based on their BCS as optimal (3.25 ≤ BCS ≤ 3.5) and high (4.0 ≤ BCS ≤ 4.25). Blood samples collection and skeletal muscle biopsies were carried out at day 10 before calving. Blood serum was assayed for concentration of resistin using a bovine specific ELISA. Protein expression of insulin receptor beta subunit (IRβ), glucose transporter 4 (GLUT4), fatty acid translocase (FAT/CD36), fatty acid transporter 1 (FATP1), carnitine palmitoyltransferase 1 (CPT1), AMP-acitvated protein kinase (AMPK) and lipin 1 were analyzed in semitendinosus muscle by immunoblot. Resistin differed non-significantly between high-BCS and optimal-BCS cows. Insulin-resistant lipid metabolism in obese cows was paralleled with increased skeletal muscle expression of lipin 1 and GLUT4, and decreased expression of IRβ and FATP1. These data suggest that in obesity-related insulin resistance, metabolic capacity in dry cow skeletal muscles appears to be organized towards the synthesis of signaling intermediates rather than fatty acids oxidation and that altered fatty acid uptake does not contribute to this disposition.
•Dairy cows exhibit insulin resistance related to lipid metabolism during obesity.•Lipin1 and FATP1 are involved in skeletal muscle insulin resistance prepartum.•Fatty acid metabolism is diverted towards the synthesis of signaling intermediates.•Fatty acid uptake does not contribute to this disposition in skeletal muscle.
Increased fructose consumption has been linked with chronic inflammation and metabolic syndrome (MetS). Activation of the renin-angiotensin system (RAS) and NF-κB have been detected in MetS. Walnuts ...are a rich source of polyunsaturated omega-3 fatty acids (n-3 PUFA) that were suggested to exert anti-inflammatory effects related to cardio-metabolic health. We hypothesized that walnut supplementation has the capacity to revert unfavorable fructose-rich diet (FRD)-induced activation of cardiac RAS and NF-κB in male rats. Due to the lack of similar studies, we investigated the effects of walnut supplementation (6 weeks) on the expression of four RAS molecules (ACE, ACE2, AT1R, and AT2R) and NF-κB in rat heart after FRD (10% w/v, 9 weeks). In addition, we followed the changes in the n-6/n-3 PUFA ratio in the total pool of heart lipids after both treatments to elucidate the walnut effects on fatty acids in the heart. 36 animals (9 per group) participated in the experiment. FRD significantly increased the ACE protein level in the heart (
p
< 0.001). Walnut supplementation significantly increased the ACE2 protein level in the heart of FRD (
p
< 0.001). In addition, walnut supplementation showed a significant main effect on the arachidonic acid/eicosapentaenoic acid ratio (
p
= 0.004). Walnut supplementation significantly reduced this ratio, in comparison with both, the control group (C vs. FW,
p
< 0.05) and the FRD group (F vs. FW,
p
< 0.05). However, walnut treatment failed to revert the significant effect of fructose (
p
< 0.001) on the elevation of NF-κB protein level. Our results suggest a beneficial effect of walnut supplementation on ACE2 protein level and n-6/n-3 PUFA level in the heart of the animal model of MetS. Such results highlight the approach of omega-3-rich walnut supplementation in the stimulation of endogenous production of favorable molecules in the heart which could be an affordable nutritional treatment formaintenance of cardio-metabolic health.
Exercise is important nonpharmacological treatment for improvement of insulin sensitivity in menopause. However, its effect on menopausal cardiac insulin resistance is needing further research. We ...investigated protective effects of low-intensity exercise on cardiac insulin signaling, inflammation, regulation of nitric oxide synthase (NOS) and matrix metalloproteinase 9 (MMP-9) in ovariectomized (OVX) Wistar rats, submitted to 10% fructose solution for 9 weeks. OVX rats were divided into control, sedentary fructose, and exercise fructose groups. Measurements of physical and biochemical characteristics were carried out to evaluate metabolic syndrome development. Messenger RNA and protein levels and phosphorylation of cardiac insulin signaling molecules, endothelial and inducible NOS (eNOS and iNOS), p65 subunit of nuclear factor κB (NFκB), tumor necrosis factor α (TNF-α), suppressor of cytokine signaling 3 (SOCS3), and MMP-9 were analyzed. Fructose increased insulin level, homeostasis model assessment (HOMA) index, and visceral adipose tissue weight, while low-intensity exercise prevented insulin level and HOMA index increase. Fructose also decreased cardiac pAkt (Ser473), peNOS (Ser1177) and increased insulin receptor substrate 1 (IRS1) phosphorylation at Ser307, pNFκB (Ser276) and NFκB and MMP-9 content, without any effect on iNOS, protein-tyrosine phosphatase 1B, TNF-α, and SOCS3. Exercise prevented changes in pIRS1 (Ser307), pAkt (Ser473), peNOS (Ser1177), pNFκB (Ser276), and NFκB expression. In addition, exercise increased pIRS1 (Tyr632), pAkt (Thr308), and eNOS expression. Low-intensity exercise prevented cardiac insulin signaling disarrangement in fructose-fed OVX rats and therefore eNOS dysfunction, as well as pro-inflammatory signaling activation, without effect on tissue remodeling, suggesting physical training as a way to reduce cardiovascular risk.
We investigated the hypothesis that obesity in dairy cows enhanced expression of proteins involved in hepatic fatty acid uptake and metabolism. Sixteen Holstein-Friesian close-up cows were divided ...into 2 equal groups based on their body condition score (BCS) as optimal (3.25≤BCS≤3.5) and high (4.0≤BCS≤4.25). Intravenous glucose tolerance test (GTT) and liver biopsies were carried out at day 10 before calving. Blood samples were collected before (basal) and after glucose infusion, and glucose, insulin and non-esterified fatty acid (NEFA) levels were determined at each sample point. In addition, β-hydroxybutyrate and triglycerides levels were measured in the basal samples. The liver biopsies were analyzed for total lipid content and protein expression of insulin receptor beta (IRβ), fatty acid translocase (FAT/CD36) and sterol regulatory element-binding protein-1 (SREBP-1). Basal glucose and insulin were higher in high-BCS cows, which coincided with higher circulating triglycerides and hepatic lipid content. Clearance rate and AUC for NEFA during GTT were higher in optimal-BCS cows. The development of insulin resistance and fatty liver in obese cows was paralleled by increased hepatic expression of the IRβ, CD36 and SREBP-1. These results suggest that increased expression of hepatic CD36 and SREBP-1 is relevant in the obesity-driven lipid accumulation in the liver of dairy cows during late gestation.
•Dairy cows are challenged by hepatic lipid accumulation during obesity.•CD36 and SREBP-1 are involved in the development of fatty liver prepartum.•These processes are presumably mediated through insulin signaling pathways.
Increased intake of fructose in humans and laboratory animals is demonstrated to be a risk factor for development of metabolic disorders (insulin resistance, metabolic syndrome, type 2 diabetes) and ...cardiovascular diseases. On the other hand, estradiol is emphasized as a cardioprotective agent. The main goal of this review is to summarize recent findings on damaging cardiac effects of fructose-rich diet in females, mostly experimental animals, and to evaluate protective capacity of estradiol. Published results of our and other research groups indicate mostly detrimental effects of fructose-rich diet on cardiac insulin signaling molecules, glucose and fatty acid metabolism, nitric oxide production and ion transport, as well as renin-angiotensin system and inflammation. Some of these processes are involved in cardiac insulin signal transmission, others are regulated by insulin or have an influence on insulin action. Administration of estradiol to ovariectomized female rats, exposed to increased intake of fructose, was mostly beneficial to the heart, but sometimes it was ineffective or even detrimental, depending on the particular processes. We believe that these data, carefully translated to human population, could be useful for clinicians dealing with postmenopausal women susceptible to metabolic diseases and hormone replacement therapy.
The benefits of walnut (Juglans regia) consumption for metabolic health are known, but the molecular background underlying their putative antioxidant and anti-inflammatory/immunomodulatory effects is ...underexplored. We assessed that walnut supplementation (6 weeks) reverted unfavorable changes of the SIRT1/FoxO3a/MnSOD/catalase axis in the heart induced by fructose-rich diet (FRD). Intriguingly, Nox4 was increased by both FRD and walnut supplementation. FRD increased the cytosolic fraction and decreased the nuclear fraction of the uniquely elucidated ChREBP in the heart. The ChREBP nuclear fraction was decreased in control rats subjected to walnuts. In addition, walnut consumption was associated with a reduction in systolic BP in FRD and a decrease in fatty acid AA/EPA and AA/DHA ratios in plasma. In summary, the protective effect of walnut supplementation was detected in male rats following the fructose-induced decrease in antioxidative/anti-inflammatory capacity of cardiac tissue and increase in plasma predictors of low-grade inflammation. The current results provide a novel insight into the relationship between nutrients, cellular energy homeostasis, and the modulators of inflammatory/immune response in metabolic syndrome, emphasizing the heart and highlighting a track for translation into nutrition and dietary therapeutic approaches against metabolic disease.
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•10% fructose diet increased AMPK and decreased FoxO3a activity.•10% fructose diet decreased SIRT1, MnSOD and Nox4 protein expression.•Estradiol decreased phosphorylation of cardiac ...AMPK and FoxO3a in fructose fed rats.•Estradiol enhanced antioxidative capacity in the heart of FRD rats.
Harmful effects of fructose-rich diet (FRD) were predominantly observed in males, suggesting protective effects of estrogens. Little is known about AMPK/sirtuin-1 (SIRT1)/forkhead box O3 (FoxO3a)/manganese superoxide dismutase (MnSOD)/catalase signaling in the heart in state of metabolic syndrome and oxidative stress induced by fructose over-consumption. We investigated the effect of 10% FRD on expression of AMPK-SIRT1-FoxO3a-MnSOD/catalase axis in myocardium and potentially beneficial effect of 17β-estradiol replacement. The expression of NADPH oxidase 4 (Nox4) and miRNA-155, unfavorable regulators of this axis, were also investigated. FRD significantly increased AMPK and decreased FoxO3a activity, decreased SIRT1, MnSOD and Nox4 protein expression while E2 reverted these changes, except for Nox4, and increased catalase protein level. E2 diminished Nox4 and MnSOD mRNA level in FRD ovariectomized rats. These results suggest independent response of AMPK and SIRT to FRD treatment. The proposed signaling in the heart should be further investigated in the prooxidative and antioxidative milieu.
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 (AT2R) were significantly decreased. In female rats, there were no changes in cardiac RAS expression due to FRD. Furthermore, the ACE/AT1R axis was overexpressed in the FRD male rats’ aortae, while only AT1R 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.
Excessive fructose consumption causes ectopic lipid storage leading to metabolic disorders and cardiovascular diseases associated with defective substrate utilisation in the heart.
Examining the ...preventive impact of low-intensity exercise on alterations related to fructose-rich diet (FRD) on cardiac fatty acid (FA) transport and metabolism.
Male Wistar rats were divided into control and two groups that received 10% fructose for 9 weeks, one of which was additionally exposed to exercise.
FRD elevated plasma and cardiac TAG, FATP1 in plasma membrane, Lipin 1 in microsomes and HSL mRNA, while mitochondrial CPT1 was decreased. Exercise decreased plasma free FA level, raised CD36 in plasma membrane and FATP1 in lysate, mitochondrial CPT1 and decreased microsomal Lipin 1 in fructose-fed rats.
FRD changed plasma lipids and augmented partitioning of FA to TAG storage in the heart, whereas exercise in FRD rats switched metabolism of FA towards β-oxidation.
Walnut consumption mostly has a positive implication for cardiovascular health. Walnut diet effects on the cardiac fatty acid (FA) metabolism of healthy rats and those with fructose diet-induced ...metabolic burden were analysed. Both walnuts and fructose increased CD36 transporter level and the nuclear content of some/all of Lipin 1/PPARα/PGC-1 complex partners, as well as cytosolic and nuclear FOXO1. However, fructose, independently of walnuts, increased the content of palmitic (PA), oleic, and vaccenic acid (VA), while in walnut-fed rats failed to increase palmitoleic acid (POA) level and the POA/PA ratio, as well as total MUFA content. In opposite, walnuts reduced the level of PA and VA and increased alpha-linolenic, eicosapentaenoic and docosapentaenoic acid level, regardless of fructose. In conclusion, both fructose and walnuts stimulated the uptake and oxidation of FA in the heart, but the walnuts, opposite to fructose, favourably altered cardiac FA profile in healthy and metabolically compromised rats.
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