Effects of fish oil on hypertension, plasma lipids, and tumor necrosis factor-α in rats with sucrose-induced metabolic syndrome

Dietary intervention in adult rats exposed to a high-sugar diet early in life permanently impairs sperm quality

Childhood obesity predicts the presence of adult obesity. Obesity is associated with poor sperm quality. We hypothesized that exposure to a high-sugar diet (HSD) in early life would cause permanent histomorphology damage to the testes, resulting in reduced sperm quality in adult life. Wistar rats (aged 21days) were divided into four groups (n=6). In the first experiment, the rats received tap water (control) and a 30% sucrose diet for two months (S30). In the second experiment, the control and 30% sucrose diets were fed for two months, followed by replacement with tap water for two months (IS30). Eating and drinking were monitored. Animals were then euthanized, visceral and gonadal fat tissue and testes were collected, and epididymal spermatozoa were excised. Testicular samples were used for morphological description by H&E staining and for quantifying triacylglycerol content, caspase activity, and oxidative stress. Serum testosterone concentration was evaluated. Spermatozoa were used to assess sperm quality. Our results show that sperm quality was impaired by consuming HSD and could not be restored by dietary intervention. HSD feeding induced hyperplasia of visceral adipose tissue, increased testicular weight, and serum testosterone levels. The dietary intervention increased visceral adipose tissue, serum, and testicular triacylglycerol levels and normalized serum testosterone levels. Overall, the HSD diet caused permanent changes in seminiferous tubule cross-sectional area, caspase activity, oxidative stress, and sperm quality. Therefore, a high-sugar diet in early life causes permanent damage to sperm quality in adulthood.

The mechanisms and applications of cryoprotectants in aquatic products: An overview

Frozen storage technology has been widely used for the preservation of Aquatic products. However, ice crystals formation, lipid oxidation and protein denaturation still easily causes aquatic products deterioration. Cryoprotectants are a series of food additives that could efficiently prolong the shelf life and guarantee the acceptability of frozen aquatic products. This review comprehensively illustrated the mechanism of protein denaturation caused by the ice crystal formation and lipid oxidation. The cryoprotective mechanism of various kinds of antifreeze agents (saccharides, phosphates, antifreeze proteins and peptides) and these cryoprotective structure-activity relationship, application efficiency on the quality of aquatic products were also discussed. Moreover, the advantages and disadvantages of each cryoprotectant are also prospected. Compared with others, antifreeze peptides show higher commercial and application values. While, lots of scientific research works are still required to develop novel antifreeze agent as a versatile ingredient with commercial value, applicable in the aquatic products preservation industry.

Non-Alcoholic Fatty Liver Disease and Bone Tissue Metabolism: Current Findings and Future Perspectives

Non-alcoholic fatty liver disease (NAFLD) is reaching epidemic proportions worldwide. Moreover, the prevalence of this liver disease is expected to increase rapidly in the near future, aligning with the rise in obesity and the aging of the population. The pathogenesis of NAFLD is considered to be complex and to include the interaction between genetic, metabolic, inflammatory, and environmental factors. It is now well documented that NAFLD is linked to the other conditions common to insulin resistance, such as abnormal lipid levels, metabolic syndrome, and type 2 diabetes mellitus. Additionally, it is considered that the insulin resistance may be one of the main mechanisms determining the disturbances in both bone tissue metabolism and skeletal muscles quality and functions in patients with NAFLD. To date, the association between NAFLD and osteoporosis has been described in several studies, though it worth noting that most of them included postmenopausal women or elderly patients and originated from Asia. However, taking into account the health and economic burdens of NAFLD, and the increasing prevalence of obesity in children and adolescents worldwide, further investigation of the relationship between osteopenia, osteoporosis and sarcopenia in NAFLD, including in young and middle-aged patients, is of great importance. In addition, this will help to justify active screening and surveillance of osteopenia and osteoporosis in patients with NAFLD. In this review, we will discuss various pathophysiological mechanisms and possible biologically active molecules that may interplay between NAFLD and bone tissue metabolism.

Metabolic Syndrome: Lessons from Rodent and Drosophila Models

Overweight and obesity are health conditions tightly related to a number of metabolic complications collectively called “metabolic syndrome” (MetS). Clinical diagnosis of MetS includes the presence of the increased waist circumference or so-called abdominal obesity, reduced high density lipoprotein level, elevated blood pressure, and increased blood glucose and triacylglyceride levels. Different approaches, including diet-induced and genetically induced animal models, have been developed to study MetS pathogenesis and underlying mechanisms. Studies of metabolic disturbances in the fruit fly Drosophila and mammalian models along with humans have demonstrated that fruit flies and small mammalian models like rats and mice have many similarities with humans in basic metabolic functions and share many molecular mechanisms which regulate these metabolic processes. In this paper, we describe diet-induced, chemically and genetically induced animal models of the MetS. The advantages and limitations of rodent and Drosophila models of MetS and obesity are also analyzed.

Biological Potential of Polyphenols in the Context of Metabolic Syndrome: An Analysis of Studies on Animal Models

Metabolic syndrome (MetS) is a disease that has a complex etiology. It is defined as the co-occurrence of several pathophysiological disorders, including obesity, hyperglycemia, hypertension, and dyslipidemia. MetS is currently a severe problem in the public health care system. As its prevalence increases every year, it is now considered a global problem among adults and young populations. The treatment of choice comprises lifestyle changes based mainly on diet and physical activity. Therefore, researchers have been attempting to discover new substances that could help reduce or even reverse the symptoms when added to food. These attempts have resulted in numerous studies. Many of them have investigated the bioactive potential of polyphenols as a "possible remedy", stemming from their antioxidative and anti-inflammatory effects and properties normalizing carbohydrate and lipid metabolism. Polyphenols may be supportive in preventing or delaying the onset of MetS or its complications. Additionally, the consumption of food rich in polyphenols should be considered as a supplement for antidiabetic drugs. To ensure the relevance of the studies on polyphenols' properties, mechanisms of action, and potential human health benefits, researchers have used laboratory animals displaying pathophysiological changes specific to MetS. Polyphenols or their plant extracts were chosen according to the most advantageous mitigation of pathological changes in animal models best reflecting the components of MetS. The present paper comprises an overview of animal models of MetS, and promising polyphenolic compounds whose bioactive potential, effect on metabolic pathways, and supplementation-related benefits were analyzed based on in vivo animal models.

Oils Rich in α-Linolenic Acid or Docosahexaenoic Acid Have Distinct Effects on Plasma Oxylipin and Adiponectin Concentrations and on Monocyte Bioenergetics in Women with Obesity

BACKGROUND

Omega-3 fatty acids, including DHA and α-linolenic acid (ALA), are proposed to improve metabolic health by reducing obesity-associated inflammation. Their effects are mediated in part by conversion to oxylipins. ALA is relatively understudied, and direct comparisons to other omega-3 fatty acids are limited.

OBJECTIVES

We compared the effects of equal doses of ALA and DHA on plasma oxylipins and markers of metabolic health in women with obesity.

METHODS

We carried out a randomized, double-blind, crossover clinical trial where women aged 20-51 with a BMI of 30-51 kg/m2 were supplemented with 4 g/day of ALA or DHA for 4 weeks in the form of ALA-rich flaxseed oil or DHA-rich fish oil. The primary outcome, the plasma oxylipin profile, was assessed at Days 0 and 28 of each phase by HPLC-MS/MS. Plasma fatty acids, inflammatory markers, and the monocyte glucose metabolism were key secondary outcomes. Data were analyzed using a mixed model.

RESULTS

Compared to the baseline visit, there were higher plasma levels of nearly all oxylipins derived from DHA (3.8-fold overall; P < 0.001) and EPA (2.7-fold overall; P < 0.05) after 28 days of fish-oil supplementation, while there were no changes to oxylipins after flaxseed-oil supplementation. Neither supplement altered plasma cytokines; however, adiponectin was increased (1.1-fold; P < 0.05) at the end of the fish-oil phase. Compared to the baseline visit, 28 days of flaxseed-oil supplementation reduced ATP-linked oxygen consumption (0.75-fold; P < 0.05) and increased spare respiratory capacity (1.4-fold; P < 0.05) in monocytes, and countered the shift in oxygen consumption induced by LPS.

CONCLUSIONS

Flaxseed oil and fish oil each had unique effects on metabolic parameters in women with obesity. The supplementation regimens were insufficient to reduce inflammatory markers but adequate to elicit increases in omega-3 oxylipins and adiponectin in response to fish oil and to alter monocyte bioenergetics in response to flaxseed oil. This trial was registered at clinicaltrials.gov as NCT03583281.

Motor learning impairment in rats under a high sucrose diet

Motor learning skills are reliable indicators of behavioral acquisition and cognitive disorders. The ease with which learning skills are measured disparities the complexity of the interpretation concerning neural plasticity. Conversely, a wealth of information regarding metabolic derangements has long been reported with direct connection to high sucrose diets. However, the impact of excessive sucrose consumption on undergoing cognitive processes has been only scarcely addressed up to now. Therefore, the goal of this work was to describe the associative relationship between high sucrose consumption and changes in motor learning skills acquisition. Motor learning impairments conditioned by central alterations are hypothesized. Rotarod, elevated plus-maze and open field trials, along with metabolic and pro-inflammatory biomarkers tests in Wistar rats under a high sucrose treatment, were performed. Motor learning impairment in high sucrose diet-treated rats was found while spontaneous locomotor activity remained unchanged. Even though, no anxiety-like behavior under high sucrose diet-treatment was observed. Consistently, the worst outcome in the glucose tolerance test was developed, the worst motor learning performance was observed. Furthermore, insulin resistance correlated positively with a pro-inflammatory state and a decreased latency to fall in the rotarod test. Indeed, C-reactive protein and tumor necrosis factor-α serum levels, along with the homeostasis model assessment of insulin resistance (HOMA-IR), significantly increased in motor learning impairment. Together, these results support behavioral, metabolic and pro-inflammatory changes associated with deleterious changes in central nervous system likely involving crucial motor learning structures. Underlying pro-inflammatory-triggered processes may explain cognitive disorders in advanced states of metabolic derangements.

Feeding pattern, biochemical, anthropometric and histological effects of prolonged ad libitum access to sucrose, honey and glucose-fructose solutions in Wistar rats

BACKGROUND/OBJECTIVES

The exposure to sucrose in rats has mimic abnormalities attributed to metabolic syndrome (MetS). The effects of honey bee and "free" glucose and fructose, have not been explored in this context. The aim was to expose Wistar rodents to sucrose solution (SS), honey solution (HS) and fructose/glucose solution (GFS) at 30% to assess their effects.

SUBJECTS/METHODS

HS (n = 10), SS (n = 10) and GFS (n = 10) groups were formed. Solutions were ad libitum along 14-weeks.

RESULTS

Between solutions consumptions, honey was significantly 42% higher (P = 0.000), while similar consumption was observed among GFS and SS. The feeding pattern of HS consumption was irregular along experiment; while the food intake pattern showed the similar trend among groups along time. Non statistical differences were obtained in any biochemical and anthropometric measure, however, a higher concentration of leptin (721 ± 507 pg/mL), lower concentration of total cholesterol (TC; 48.87 ± 2.41 mg/100 mL), very low density lipoprotein (VLDL; 16.47 ± 6.55 mg/100 mL) and triglycerides (82.37 ± 32.77 mg/100 mL) was obtained in SS group. For anthropometric values, HS showed less total adipose tissue (AT; average 26 vs. 31-33 g) and adiposity index (average 6.11 vs. 7.6). Due to sugar-sweetened beverages consumption increases the risk for the development of chronic diseases; correlations between fluid intake and anthropometric and biochemical parameters were assessed. A moderate correlation was obtained in groups with the weight of total AT and solution intake; for the weight gain in GFS group and for triglycerides in HS and GFS. The highest hepatic tissue damage was observed in SS group with multiple intracytoplasmic vacuoles, atypia changes, moderate pleomorphism and hepatocellular necrosis.

CONCLUSIONS

In spite of the significantly higher consumption of HS, biochemical, anthropometrical and histological effects were not remarkably different in comparision to other sweeteners.

Hypolipidemic and Hypoglycaemic Effect of Wholemeal Bread with Amaranth (Amaranthus dubius Mart. ex Thell.) on Sprague Dawley Rats

The effect of consuming breads made with wheat flour and Amaranth (Amaranthus dubius Mart. ex Thell.) wholemeal flour on Sprague Dawley rats with hyperlipidaemia and hyperglycaemia induced through feeding was studied. Four diets were provided: control (CD: Ratarina^®), commercial bread (CBD), bread with 100 g·kg⁻¹ (ABD10) and 200 g·kg⁻¹ (ABD20) amaranth flour. Zoometric and blood chemistry parameters were measured before and after consuming the diets. A completely random factorial design of 2 × 4 × 2 was used. The factors were blood lipids and glucose level (normal, N and elevated, E), diet (CD, CBD, ABD10 and ABD20) and sex (female, F and male, M). The rats consuming ABD10 and ABD20 diets presented the lowest glucose values, although with no differences (p > 0.05) between the groups of elevated blood lipids and glucose rats (E). Triglyceride concentrations decreased in ABD10 and ABD20 treatments in comparison with CD, elevated blood lipids and glucose (E) rats, while ABD10 rats showed lower total cholesterol level than normal (N) rats. The high-density lipoprotein cholesterol values increased in the ABD10 and ABD20 groups (p < 0.05), while it did lower for very low-density lipoprotein cholesterol and cardiac risk index (p < 0.05). In ABD10 and ABD20 treatments, the abdominal circumference decreased in both sexes (p < 0.05) between weeks 23 and 31. In conclusion, consumption of bread with amaranth improved lipid profiles of rats and could help to prevent metabolic and cardiovascular diseases.

Long-term sucrose solution consumption causes metabolic alterations and affects hepatic oxidative stress in Wistar rats

As the number of overweight and obese people has risen in recent years, there has been a parallel increase in the number of people with metabolic syndrome, diabetes and non-alcoholic fatty liver disease. The consumption of artificially sweetened beverages contributes to these epidemics. This study investigated the long-term effects of ingestion of a 40% sucrose solution on serum and hepatic parameters in male Wistar rats (Rattus norvegicus). After 180 days, the glycemic response, lipid profile and hepatic oxidative stress were compared to those of rats maintained on water. Sucrose ingestion led to higher body weight, increased fat deposits, reduced voluntary food intake and reduced feeding efficiency. Rats that received sucrose solution showed early signs of glucose intolerance and insulin resistance, such as hyperinsulinemia. Serum triacylglycerol (TG), very-low density lipoprotein (VLDL), cholesterol, ALT and AST levels increased after sucrose consumption. Elevated malondialdehyde and superoxide dismutase (SOD) levels and reduced glutathione levels characterize the hepatic oxidative stress due to sucrose ingestion. Liver sample histology showed vacuolar traces and increased fibrotic tissue. Our data showed the harmful effects of chronic consumption of sucrose solution, which can cause alterations that are found frequently in obesity, glucose intolerance and non-alcoholic hepatic disease, characteristics of metabolic syndrome.

Cd36 gene expression in adipose and hepatic tissue mediates the lipids accumulation in liver of obese rats with sucrose-induced hepatic steatosis

Obesity is considered a global epidemic and is mainly associated with the development of diabetes, cardiovascular diseases and Non-Alcoholic Fatty Liver (NAFLD). The pathogenesis between obesity and hepatic steatosis is partially known, but could involve differentiated or tissue-specific participation of the expression of Cd36 mRNA that codes for a receptor which is a transporter of free fatty acids (FFA) in different tissues, favoring the lipids storage. This relative expression was evaluated in adipose and liver tissue in rats with steatosis after consumption of sucrose for 30 and 40 weeks. Ten Wistar rats were divided into two experimental groups (St-30 and St-40), which received a standard diet plus 30 % sucrose in their water intake. These rats showed a significant increase in abdominal fat, serum biochemical determinations, HOMA-IR; as well as, changes in adipocytes size and mild portal hepatitis and grade 2 hepatic steatosis. The relative expression of Cd36 mRNA increased in liver tissue after 30 (4.5-fold) and 40 (8.5-fold) weeks of sucrose ingestión but no in adipose tissue; with respect to control group (P < 0.05). This expression was associated with a significant increase in the levles of sCD36 in serum, which is indicator of the presence of the FFA transporter in the hepatocyte membrane causing lipids accumulation. The above shows the link between the adipose and hepatic tissue for the accumulation of steatotic fat in the liver through time, mediated by the relative expression of cd36 mRNA that encodes for the FFA transporter.

Rodent models of obesity

Obese or overweight people exceed one-third of the global population and obesity along with diabetes mellitus consist basic components of metabolic syndrome, both of which are known cardio-cerebrovascular risk factors with detrimental consequences. These data signify the pandemic character of obesity and the necessity for effective treatments. Substantial advances have been accomplished in preclinical research of obesity by using animal models, which mimic the human disease. In particular, rodent models have been widely used for many decades with success for the elucidation of the pathophysiology of obesity, since they share physiological and genetic components with humans and appear advantageous in their husbandry. The most representative rodents include the laboratory mouse and rat. Within this review, we attempted to consolidate the most widely used mice and rat models of obesity and highlight their strengths as well as weaknesses in a critical way. Our aim was to bridge the gap between laboratory facilities and patient's bed and help the researcher find the appropriate animal model for his/her obesity research. This tactful selection of the appropriate model of obesity may offer more translational derived results. In this regard, we included, the main diet induced models, the chemical/mechanical ones, as well as a selection of monogenic or polygenic models.

Chronic exposure to liquid sucrose and dry sucrose diet have differential effects on peripheral taste responses in female rats

Sugar-sweetened beverages are the major source of added calories in the Western diet and their prevalence is associated with obesity and metabolic disruption. Despite the critical role of the taste system in determining food selection and consumption, the effects of chronic sucrose consumption on the peripheral taste system in mammals have received limited attention. We offered female Sprague Dawley rats free access to water and one of three diets for up to 40 days: (1) sucrose-free chow or "NS" diet; (2) a high-sucrose dry diet or "HS"; or (3) 30% sucrose solution and the NS diet, designated "LiqS" diet. Sucrose consumption by LiqS rats gradually increased and by day 14 was equal to that of HS rats. Food intake decreased in LiqS rats, but their energy intake remained higher than for NS or HS rats. There was no significant difference in weight gain of the groups during the study. Recordings from the chorda tympani nerve (CT), which innervates taste buds on the anterior tongue, revealed decreased responses to 1 M sucrose in both LiqS and HS rats and to acesulfame K and salt tastants in LiqS rats after 40 days on diet. Umami, bitter, and acid response magnitudes were unchanged in both groups. These results demonstrate that chronic sucrose exposure inhibits taste responses to higher concentrations of sweet stimuli. More surprisingly, CT responses to NaCl and 0.5M NaAc were significantly reduced in rats on the LiqS diet. Thus, the physical form of the diet influences taste responsiveness to salt and sweet taste function. These data suggest that taste buds are previously unappreciated targets of chronic sucrose consumption.

Supplementation of Non-Dairy Creamer-Enriched High-Fat Diet with D-Allulose Ameliorated Blood Glucose and Body Fat Accumulation in C57BL/6J Mice

D-allulose, which has 70% of the sweet taste of sucrose but nearly no calories, has been reported to inhibit the absorption of lipids and suppress body weight gain in obese mice. Fats in non-dairy creamer consist of highly saturated fatty acids, which can cause various lipid disorders when consumed over a long period. We investigated whether D-allulose supplementation alleviates the effects of a non-dairy creamer-enriched high-fat diet on lipid metabolism. High-fat diets enriched with non-dairy creamer were administered to C57BL/6J mice with or without D-allulose supplementation for eight weeks by the pair-feeding design. Lipid metabolic markers were compared between the non-dairy creamer control group (NDC) and non-dairy creamer allulose group (NDCA). Body, adipose tissue, and liver weights, and fasting blood glucose levels, were significantly lower in the NDCA group than in the NDC group. Fecal fatty acid and triglyceride levels were significantly higher in the NDCA group than in the NDC group. Supplementing a non-dairy creamer-enriched high-fat diet with D-allulose improved overall lipid metabolism, including the plasma and hepatic lipid profiles, hepatic and adipose tissue morphology, and plasma inflammatory adipokine levels in mice. These results suggest that D-allulose can be used as a functional food component for preventing body fat accumulation from a high-fat diet that includes hydrogenated plant fats.

Raman and infrared spectroscopy of carbohydrates: A review

Carbohydrates are widespread and naturally occurring compounds, and essential constituents for living organisms. They are quite often reported when biological systems are studied and their role is discussed. However surprisingly, up till now there is no database collecting vibrational spectra of carbohydrates and their assignment, as has been done already for other biomolecules. So, this paper serves as a comprehensive review, where for selected 14 carbohydrates in the solid state both FT-Raman and ATR FT-IR spectra were collected and assigned. Carbohydrates can be divided into four chemical groups and in the same way is organized this review. First, the smallest molecules are discussed, i.e. monosaccharides (d-(-)-ribose, 2-deoxy-d-ribose, l-(-)-arabinose, d-(+)-xylose, d-(+)-glucose, d-(+)-galactose and d-(-)-fructose) and disaccharides (d-(+)-sucrose, d-(+)-maltose and d-(+)-lactose), and then more complex ones, i.e. trisaccharides (d-(+)-raffinose) and polysaccharides (amylopectin, amylose, glycogen). Both Raman and IR spectra were collected in the whole spectral range and discussed looking at the specific regions, i.e. region V (3600-3050cm^-1), IV (3050-2800cm^-1) and II (1200-800cm^-1) assigned to the stretching vibrations of the OH, CH/CH₂ and C-O/C-C groups, respectively, and region III (1500-1200cm^-1) and I (800-100cm^-1) dominated by deformational modes of the CH/CH₂ and CCO groups, respectively. In spite of the fact that vibrational spectra of saccharides are significantly less specific than spectra of other biomolecules (e.g. lipids or proteins), marker bands of the studied molecules can be identified and correlated with their structure.

Cardiovascular risk assessment in osteoporotic patients using osteoprotegerin as a reliable predictive biochemical marker

Osteoprotegerin (OPG), a member of the tumour necrosis factor receptor (TNFR) superfamily of proteins known to be involved in a large number of biological systems, plays a pivotal role in bone remodelling. In addition to the roles of OPG in bone metabolism, it has been reported to be associated with a high cardiovascular risk in patients with metabolic syndrome. In most cases, the exact functions of OPG remain to be established; however, the widespread expression of OPG suggests that this molecule may have multiple biological activities, mainly in the cardiometabolic environment. The aim of this study was to evaluate the value of OPG as a predictive marker for cardiovascular and metabolic risk in osteoporotic patients. The study group comprised patients with osteoporosis, in order to evaluate the association between OPG serum levels and cardiovascular pathology. Our results revealed significant correlations between classical biochemical bone and metabolic parameters, such as osteocalcin and parathyroid hormone with lipid and glucose biomarkers, sustaining the crosstalk between calcium and bone parameters and cardiovascular risk. The OPG serum level proved to have a significant and independent predictive value for metabolic syndrome (MetS) as a cardiovascular risk standard in osteoporotic patients. The OPG serum levels were increased in patients with MetS as a protective response against the atherosclerotic lesions. The serum levels of 25-hydroxy vitamin D had significant and independent predictive value for cardiovascular and metabolic risk in our subjects, sustaining the active role of vitamin D beyond the area of bone metabolism.

Fish oil diet may reduce inflammatory levels in the liver of middle-aged rats

The impact of dietary soybean oil, lard and fish oil on physiological responses in middle age is little studied. In this study, we investigated the changes of oxidative stress, inflammatory cytokines, telomere length, and age-related gene expression in the liver of middle-aged rats in response to the above three fat diets. Male Sprague Dawley rats (12 months old) were fed AIN-93M diets for 3 months, in which soybean oil was equivalently replaced by lard or fish oil. As compared to the lard diet, intake of fish oil diet significantly decreased body weight gain, white blood cell count, and levels of hepatic triacylglycerol, total cholesterol, fat accumulation, low-density lipoprotein, oxidative stress and inflammatory cytokines (P < 0.05), but increased telomere length (P < 0.05). On the other hand, lard diet and soybean oil diet showed great similarity in the above variables. PCR array analysis further indicated that fish oil diet significantly down-regulated gene expression related to inflammatory response, apoptosis, DNA binding, proteostasis and telomere attrition. Differentially expressed genes were enriched in the complement and coagulation cascades pathways. Such physiological and molecular responses could be due to different fatty acid composition in fish oil, lard and soybean oil.

Influence of omega-3 PUFAs on the metabolism of proanthocyanidins in rats

Studies of the bioavailability of proanthocyanidins usually consider them independently of other dietary constituents, while there is a tendency in the field of functional foods towards the combination of different bioactive compounds in a single product. This study examined the long-term effects of ω-3 polyunsaturated fatty acids of marine origin on the metabolic fate of grape proanthocyanidins. For this, female adult Wistar-Kyoto rats were fed (18weeks) with a standard diet supplemented or not with eicosapentaenoic acid/docosahexaenoic acid (1:1, 16.6g/kg feed), proanthocyanidin-rich grape seed extract (0.8g/kg feed) or both. A total of 39 microbial-derived metabolites and 16 conjugated metabolites were detected by HPLC-MS/MS either in urine or in the aqueous fraction of feces. An unexpected significant increase in many proanthocyanidin metabolites in urine and feces was observed in the group supplemented with ω-3 polyunsaturated fatty acids group as compared to the animals fed a standard diet, which contains a small amount of polyphenols. However, proanthocyanidin metabolites in rats given ω-3 polyunsaturated fatty acids and grape seed extract did not significantly differ from those in the group supplemented only with grape seed extract. It was concluded that ω-3 polyunsaturated fatty acids collaborate in the metabolism of polyphenols when present at low doses in the feed matrix, while the capacity of ω-3 polyunsaturated fatty acids to induce microbiota transformations when proanthocyanidins are present at high doses is not relevant compared to that of polyphenols themselves.

Effects of long-term intake of Antarctic krill oils on artery blood pressure in spontaneously hypertensive rats

BACKGROUND

In recent years, there has been a noticeable increase in research on krill oil (KO) for its health benefits. However, the action of KO in lowering blood pressure (BP) has not been studied yet. Therefore the aim of this study was to assess the ability of long-term KO supplementation to lower systolic BP (SBP) in spontaneously hypertensive rats (SHRs) and Sprague Dawley (SD) rats.

RESULTS

Compared with the blank control (BC) SHRs administered edible soybean oil, the high-dose (500 mg kg^-1 body weight (BW)) KO-supplemented SHRs in the 2nd, 3rd, 4th and 5th weeks following oral administration, the mid-dose (100 mg kg^-1 BW) KO-supplemented SHRs in the 4th and 5th weeks following oral administration and the low-dose (20 mg kg^-1 BW) KO-supplemented SHRs in the 5th week following oral administration showed significantly lower SBP (P < 0.05). However, supplementation of KO had no significant effect on the SBP of healthy SD rats. Meanwhile, 5 weeks of KO administration significantly increased the serum levels of nitric oxide (NO) and total NO synthase of SHRs (P < 0.05).

CONCLUSION

KO has an antihypertensive effect in SHRs that is associated with an NO-related mechanism. © 2016 Society of Chemical Industry.

Blue Maize Extract Improves Blood Pressure, Lipid Profiles, and Adipose Tissue in High-Sucrose Diet-Induced Metabolic Syndrome in Rats

The effect of blue maize extract in factors related to metabolic syndrome (MS) in Wistar rats was investigated. Total polyphenols, monomeric anthocyanins, and antioxidant activity were analyzed in blue maize. MS was induced in Wistar rats fed with high-sucrose (HS) diet for 12 weeks. During a period of 4 weeks, blue maize extract was administrated to HS groups fed with high-sucrose and high-cholesterol-high-sucrose (HS+C) diets. In the blue maize extract administered by orogastric cannulation, the levels of total polyphenols and anthocyanins were 9.97 and 2.92 mg/kg of weight, respectively. HS diet administered during a period of 12 weeks increased significantly systolic blood pressure, serum triglycerides, and decreased high-density lipoprotein cholesterol (HDL-C), alterations related to the MS. Abdominal adipose tissue was only increased in the HS + C group. Blue maize extract administration enhanced HDL-C and decreased systolic blood pressure, serum triglycerides, total cholesterol, and epididymal adipose tissue weight. The blue maize may represent a promising nutraceutical option for the treatment of MS.

Animal models of metabolic syndrome: a review

Metabolic syndrome (MetS) consists of several medical conditions that collectively predict the risk for cardiovascular disease better than the sum of individual conditions. The risk of developing MetS in human depends on synergy of both genetic and environmental factors. Being a multifactorial condition with alarming rate of prevalence nowadays, establishment of appropriate experimental animal models mimicking the disease state in humans is crucial in order to solve the difficulties in evaluating the pathophysiology of MetS in human. This review aims to summarize the underlying mechanisms involved in the pathophysiology of dietary, genetic, and pharmacological models of MetS. Furthermore, we will discuss the usefulness, suitability, pros and cons of these animal models. Even though numerous animal models of MetS have been established, further investigations on the invention of new animal model and clarification of plausible mechanisms are still necessary to confer a better understanding to researchers on the selection of animal models for their studies.

Electrophysiological basis of metabolic-syndrome-induced cardiac dysfunction

Myocardial contractility is controlled by intracellular Ca2+ cycling with the contribution of sarcoplasmic reticulum (SR). In this study, we aimed to investigate the role of altered SR function in defective regulation of intracellular Ca2+ levels in rats with metabolic syndrome (MetS) induced by a 16-week high-sucrose drinking-water diet. Electric-field stimulated transient intracellular Ca2+ changes in MetS cardiomyocytes exhibited significantly reduced amplitude (∼30%) and prolonged time courses (2-fold), as well as depressed SR Ca2+ loading (∼55%) with increased basal Ca2+ level. Consistent with these data, altered ryanodine receptor (RyR2) function and SERCA2a activity were found in MetS cardiomyocytes through Ca2+ spark measurements and caffeine application assay in a state in which sodium calcium exchanger was inhibited. Furthermore, tetracaine application assay results and hyperphosphorylated level of RyR2 also support the “leaky RyR2” hypothesis. Moreover, altered phosphorylation levels of phospholamban (PLN) support the depressed SERCA2a-activity thesis and these alterations in the phosphorylation of Ca2+-handling proteins are correlated with altered protein kinase and phosphatase activity in MetS cardiomyocytes. In conclusion, MetS-rat heart exhibits altered Ca2+ signaling largely due to altered SR function via changes in RyR2 and SERCA2a activity. These results point to RyR2 and SERCA2a as potential pharmacological targets for restoring intracellular Ca2+ homeostasis and, thereby, combatting dysfunction in MetS-rat heart.

Dose-related antihyperglycemic and hypolipidemic effects of two novel thiazolidin-4-ones in a rodent model of metabolic syndrome

BACKGROUND

The replacement of the thiazolidinedione moiety with a thiazolidinone may yield antidiabetic compounds with similar pleiotropic effects. Hence, the aim of the present study was to explore the dose-related antihyperglycemic and hypolipidemic effects of two synthesized novel thiazolidin-4-one derivatives, one with a nicotinamide and the other with a p-chlorophenoxyacetamide substitution at the N3 position of the thiazolidinone ring (NAT1 and PAT1, respectively), in a rodent model of metabolic syndrome (MetS).

METHODS

Metabolic syndrome was induced in Wistar rats by neonatal administration of monosodium glutamate (i.p.) on 4 consecutive days followed by high-sucrose diet feeding for 6 months. The effects of NAT1 (33 and 66 mg/kg) and molar equivalent doses of PAT1 (40 and 80 mg/kg) on relevant biochemical parameters were evaluated. Because MetS is a state of chronic low-grade inflammation, we also evaluated the effects of these compounds on proinflammatory markers, namely interleukin (IL)-6, tumor necrosis factor (TNF)-α, reactive oxygen species (ROS), and nitric oxide (NO).

RESULTS

Both NAT1 and PAT1 attenuated hyperglycemia, hypertriglyceridemia, hypoalphalipoproteinemia, and glucose intolerance. PAT1 exhibited superior antihyperglycemic and antihypoalphalipoproteinemic effects than NAT1. However, NAT1 had a better triglyceride-lowering effect. At the lower dose tested, both compounds significantly reduced elevated malondialdehyde levels. In addition, PAT1 (80 mg/kg) restored hepatic superoxide dismutase enzyme levels. There was a tendency for NAT1 and PAT1 to inhibit elevated hepatic IL-6 and TNF-α levels, but the differences did not reach statistical significance. In addition, PAT1 exhibited in vitro anti-inflammatory activity by reducing proinflammatory ROS and NO levels in RAW264.7 macrophages.

CONCLUSIONS

The novel thiazolidin-4-ones NAT1 and PAT1 could be potential pleiotropic drug candidates targeting MetS.

The combined action of omega-3 polyunsaturated fatty acids and grape proanthocyanidins on a rat model of diet-induced metabolic alterations

It has been suggested that food components such as ω-3 polyunsaturated fatty acids (ω-3 PUFAs) and (poly)phenols counteract diet-induced metabolic alterations by common or complementary mechanisms. To examine the effects of a combination of ω-3 PUFAs and (poly)phenols on such alterations, adult Wistar-Kyoto rats were fed an obesogenic high-fat high-sucrose diet supplemented, or not, for 24 weeks with: eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) 1 : 1 (16.6 g kg(-1) feed); proanthocyanidin-rich grape seed extract (GSE, 0.8 g kg(-1) feed); or EPA/DHA 1 : 1 + GSE. Body weight, feed intake, and plasma glucose were evaluated every 6 weeks, while adipose tissue weight, insulin, glucagon, ghrelin, leptin, adiponectin, cholesterol, and triglycerides were evaluated at the end of the experiment. ω-3 PUFAs reduced plasma leptin and cholesterol levels, but did not modify diet-induced perigonadal fat or plasma insulin levels; while GSE increased plasma triglyceride levels. The combined action of ω-3 PUFAs and the proanthocyanidins reduced plasma insulin and leptin, as well as partially prevented perigonadal fat accumulation. While separate supplementation with ω-3 PUFAs or grape proanthocyanidins may not counteract all the key metabolic changes induced by a high-energy-dense diet, the combination of both supplements reverts altered insulin, leptin and triglyceride levels to normal.

Role of chrysin on expression of insulin signaling molecules

Background:

Currently available drugs are unsuccessful for the treatment of tye-2 diabetes due to their adverseside-effects. Hence, a search for novel drugs, especially ofplant origin, continues. Chrysin (5,7-dihydroxyflavone) is a flavonoid, natural component of traditional medicinal herbs, present in honey, propolis and many plant extracts that hasbeen used in traditional medicine around the world to treat numerous ailments.

Objective:

The present study was aimed to identify the protective role of chrysin on the expression of insulin-signaling molecules in the skeletal muscle of high fat and sucrose-induced type-2 diabetic adult male rats.

Materials and Methods:

The oral effective dose of chrysin (100 mg/kg body weight) was given once a day until the end of the study (30 days post-induction of diabetes) to high fat diet-induced diabetic rats. At the end of the experimental period, fasting blood glucose, oral glucose tolerance, serum lipid profile, lipid peroxidation (LPO) and free radical generation, as well as the levels of insulin signaling molecules and tissue glycogen in the gastrocnemius muscle were assessed.

Results:

Diabetic rats showed impaired glucose tolerance and impairment in insulin signaling molecules (IR, IRS-1, p-IRS-1Tyr⁶³², p- Akt^Thr308), glucose transporter subtype 4 [GLUT4] proteins and glycogen concentration. Serum insulin, lipid profile, LPO and free radical generation were found to be increased in diabetic control rats. The treatment with chrysin normalized the altered levels of blood glucose, serum insulin, lipid profile, LPO and insulin signaling molecules as well as GLUT4 proteins.

Conclusion:

Our present findings indicate that chrysin improves glycemic control through activation of insulin signal transduction in the gastrocnemius muscle of high fat and sucrose-induced type-2 diabetic male rats.

High Sucrose Intake Ameliorates the Accumulation of Hepatic Triacylglycerol Promoted by Restraint Stress in Young Rats

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder. Stress promotes the onset of the NAFLD with a concomitant increment in the activity of the hepatic 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1). However, the interaction between the stress and a carbohydrate-enriched diet for the development of NAFLD in young animals is unknown. In the present study, we evaluated the impact of chronic stress on the hepatic triacylglycerol level of young rats fed or not with a high sucrose-diet. For doing this, 21-day old male Wistar rats were allocated into 4 groups: control (C), chronic restraint stress (St), high-sucrose diet (S30), and chronic restraint stress plus a 30 % sucrose diet (St + S30). Chronic restraint stress consisted of 1-hour daily session, 5 days per week and for 4 weeks. Rats were fed with a standard chow and tap water (C group) or 30 % sucrose diluted in water (S30 group). The St + S30 groups consumed less solid food but had an elevated visceral fat accumulation in comparison with the St group. The St group showed a high level of serum corticosterone and a high activity of the hepatic 11β-HSD-1 concomitantly to the augmentation of hepatic steatosis signs, a high hepatic triacylglycerol content, and hepatic oxidative stress. Conversely, the high-sucrose intake in stressed rats (St + S30 group) reduced the hepatic 11β-HSD-1 activity, the level of serum corticosterone, and the hepatic triacylglycerol content. Present findings show that a high-sucrose diet ameliorates the triacylglycerol accumulation in liver promoted by the restraint stress in young male rats.

Healthy effect of different proportions of marine ω-3 PUFAs EPA and DHA supplementation in Wistar rats: Lipidomic biomarkers of oxidative stress and inflammation

Dietary intervention with ω-3 marine fatty acids may potentially modulate inflammation and oxidative stress markers related with CVD, metabolic syndrome and cancer. The aim of this study was to evaluate whether different proportions of ω-3 EPA and DHA intake provoke a modulation of the production of lipid mediators and then, an influence on different indexes of inflammation and oxidative stress in a controlled dietary animal experiment using Wistar rats. For such scope, a lipidomic SPE-LC-ESI-MS/MS approach previously developed was applied to determine lipid mediators profile in plasma samples. The effect of ω-3 fatty acids associated to different ratios EPA:DHA was compared with the effect exerted by ω-3 ALA supplementation from linseed oil and ω-6 LA from soybean oil. CRP showed a tendency to greater inflammatory status in all ω-3-fed animals. Interestingly, ratios 1:1 and 2:1 EPA:DHA evidenced a noteworthy healthy effect generating a less oxidative environment and modulating LOX and COX activities toward a decrease in the production of proinflammatory ARA eicosanoids and oxidative stress biomarkers from EPA and DHA. In addition, the ability of 1:1 and 2:1 fish oil diets to reduce lipid mediator levels was in concurrence with the protective effect exerted by decreasing inflammatory markers as ω-6/ω-3 ratio in plasma and membranes. It was also highlighted the effect of a higher DHA amount in the diet reducing the healthy benefits described in terms of inflammation and oxidative stress. Results support the antiinflammatory and antioxidative role of fish oils and, particularly, the effect of adequate proportions EPA:DHA.

Overproduction of altered VLDL in an insulin-resistance rat model: Influence of SREBP-1c and PPAR-α

BACKGROUND

In insulin-resistance, VLDL presents alterations that increase its atherogenic potential. The mechanism by which insulin-resistance promotes the production of altered VLDL is still not completely understood. The aim of this study was to evaluate the relationship between the expression of sterol regulatory element binding protein 1c (SREBP-1c) and of peroxisome proliferator-activated receptor-α (PPAR-α), with the features of composition and size of VLDL in an insulin-resistance rat model induced by a sucrose rich diet (SRD).

METHODS

The study was conducted on 12 male Wistar rats (180g) receiving SRD (12 weeks) and 12 controls. Lipid profile, free fatty acids, glucose, and insulin were measured. Lipid content in liver and visceral fat were assessed. Isolated VLDL (d<1.006g/ml) was characterized by its chemical composition and size by HPLC. The respective hepatic expression of SREBP-1c and PPAR-α was determined (Western blot).

RESULTS

As expected, SRD had elevated triglycerides (TG), free fatty acids and insulin levels, and decreased HDL-cholesterol (p<0.05), together with augmented hepatic and visceral fat (p<0.05). SRD showed higher VLDL total mass - with increased TG content - and predominance of large VLDL (p<0.05). SRD showed an increase in SREBP-1c (precursor and mature forms) and decreased PPAR-α expression (p<0.045). SREBP-1c forms were positively associated with VLDL total mass (p<0.04), VLDL-TG% (p<0.019), and large VLDL% (p<0.002). On the other hand, PPAR-α correlated negatively with VLDL total mass (p=0.05), VLDL-TG% (p=0.005), and large VLDL% (p=0.002).

CONCLUSIONS

Insulin-resistance, by coordinated activation of SREBP-1c and reduction of PPAR-α, could promote the secretion of larger and TG over-enriched VLDL particles, with greater atherogenic capacity.

Effect of n-3 PUFA supplementation at different EPA:DHA ratios on the spontaneously hypertensive obese rat model of the metabolic syndrome

The increasing incidence of the metabolic syndrome (MetS), a combination of risk factors before the onset of CVD and type 2 diabetes, encourages studies on the role of functional food components such as long-chain n-3 PUFA as preventive agents. In the present study, we explore the effect of EPA and DHA supplementation in different proportions on spontaneously hypertensive obese (SHROB) rats, a model for the MetS in a prediabetic state with mild oxidative stress. SHROB rats were randomised into four groups (n 7), each supplemented with EPA/DHA at ratios of 1:1, 2:1 and 1:2, or soyabean oil as the control for 13 weeks. The results showed that in all the proportions tested, EPA/DHA supplementation significantly lowered total and LDL-cholesterol concentrations, compared with those of the control group. EPA/DHA supplementation at the ratios of 1:1 and 2:1 significantly decreased inflammation (C-reactive protein levels) and lowered oxidative stress (decreased excretion of urinary isoprostanes), mainly at the ratio of 1:2. The activity of antioxidant enzymes increased in erythrocytes, abdominal fat and kidneys, with magnitudes depending on the EPA:DHA ratio. PUFA mixtures from fish affected different MetS markers of CVD risk factors in SHROB rats, depending on the ratios of EPA/DHA supplementation. The activation of endogenous defence systems may be related to the reduction of inflammation and oxidative stress.

Time course of adipose tissue dysfunction associated with antioxidant defense, inflammatory cytokines and oxidative stress in dyslipemic insulin resistant rats

Time course of adipose tissue dysfunction in dyslipemic insulin resistant rats.

Atorvastatin combined with poly-unsaturated fatty acid confers better improvement of dyslipidemia and endothelium function

Background

Atorvastatin and poly-unsaturated fatty acid (PUFA) are beneficial for lipid-modification, whether atorvastatin plus PUFA could confer better improvement on dyslipidemia and endothelium function is unknown.

Methods

Dyslipidemia model of 40 rabbits were produced with atherogenic diet, and thereafter saline, atorvastatin, PUFA, or atorvastatin plus PUFA were prescribed for 1 week. Ten rabbits given normal diet served as the sham group. Parameters of interest including lipid profiles, endothelium function (nitric oxide, NO) and activation (solution vascular-cellular adhesion molecule, (sVCAM) and intracellular adhesion molecule, (sICAM)), markers of inflammation (C-reactive protein, CRP) and oxidation (malondialdehyde, MDA) were compared among groups.

Results

There was no significant difference of parameters among groups at the initial. With 1 week of atherogenic diet administration, serum levels of lipid profiles, sVCAM and sICAM, CRP and MDA were significantly increased, accompanying with profound NO reduction, as compared to the sham group. After 1 week of medical intervention, as compared to the control group (saline administration), dyslipidemia and endothelium function were modestly improved with either atorvastatin or PUFA therapy. Nevertheless, these efficacies were further and significantly enhanced with combined therapy when compared to the control group (p < 0.005), suggesting that there was synergistic effects of atorvastatin and PUFA co-therapy in rabbits with dyslipidemia.

Conclusion

Atorvastatin plus PUFA therapy could immediately contribute to better improvement of lipid-modification and endothelium function in rabbits with dyslipidemia.

Effect of troxerutin on insulin signaling molecules in the gastrocnemius muscle of high fat and sucrose-induced type-2 diabetic adult male rat

Troxerutin is a trihydroxyethylated derivative of the flavonoid, rutin. It has been reported to possess the hepatoprotective, nephroprotective, antioxidant, anti-inflammatory, and antihyperlipidemic activities. Troxerutin treatment reduced the blood glucose and glycosylated hemoglobin levels in high-cholesterol-induced insulin-resistant mice and in type-2 diabetic patients. However, the mechanism by which it exhibits antidiabetic property was unknown. Therefore, the present study was designed to evaluate the effect of troxerutin on insulin signaling molecules in gastrocnemius muscle of high fat and sucrose-induced type-2 diabetic rats. Wistar male albino rats were selected and divided into five groups. Group I: Control. Group II: High fat and sucrose-induced type-2 diabetic rats. Group III: Type-2 diabetic rats treated with troxerutin (150 mg/kg body weight/day orally). Group IV: Type-2 diabetic rats treated with metformin (50 mg/kg body weight/day orally). Group V: Normal rats treated with troxerutin (150 mg/kg body weight/day orally). After 30 days of treatment, fasting blood glucose, oral glucose tolerance, serum lipid profile, and the levels of insulin signaling molecules, glycogen, glucose uptake, and oxidation in gastrocnemius muscle were assessed. Diabetic rats showed impairment in insulin signaling molecules (IR, p-IRS-1(Tyr632), p-Akt(Ser473), β-arrestin-2, c-Src, p-AS160(Thr642), and GLUT4 proteins), glycogen concentration, glucose uptake, and oxidation. Oral administration of troxerutin showed near normal levels of blood glucose, serum insulin, lipid profile, and insulin signaling molecules as well as GLUT4 proteins in type-2 diabetic rats. It is concluded from the present study that troxerutin may play a significant role in the management of type-2 diabetes mellitus, by improving the insulin signaling molecules and glucose utilization in the skeletal muscle.

Sugared water consumption by adult offspring of mothers fed a protein-restricted diet during pregnancy results in increased offspring adiposity: the second hit effect

Poor maternal nutrition predisposes offspring to metabolic disease. This predisposition is modified by various postnatal factors. We hypothesised that coupled to the initial effects of developmental programming due to a maternal low-protein diet, a second hit resulting from increased offspring postnatal sugar consumption would lead to additional changes in metabolism and adipose tissue function. The objective of the present study was to determine the effects of sugared water consumption (5% sucrose in the drinking-water) on adult offspring adiposity as a 'second hit' following exposure to maternal protein restriction during pregnancy. We studied four offspring groups: (1) offspring of mothers fed the control diet (C); (2) offspring of mothers fed the restricted protein diet (R); (3) offspring of control mothers that drank sugared water (C-S); (4) offspring of restricted mothers that drank sugared water (R-S). Maternal diet in pregnancy was considered the first factor and sugared water consumption as the second factor - the second hit. Body weight and total energy consumption, before and after sugared water consumption, were similar in all the groups. Sugared water consumption increased TAG, insulin and cholesterol concentrations in both the sexes of the C-S and R-S offspring. Sugared water consumption increased leptin concentrations in the R-S females and males but not in the R offspring. There was also an interaction between sugared water and maternal diet in males. Sugared water consumption increased adipocyte size and adiposity index in both females and males, but the interaction with maternal diet was observed only in females. Adiposity index and plasma leptin concentrations were positively correlated in both the sexes. The present study shows that a second hit during adulthood can amplify the effects of higher adiposity arising due to poor maternal pregnancy diet in an offspring sex dependent fashion.

Protective effect of the omega-3 polyunsaturated fatty acids: Eicosapentaenoic acid/Docosahexaenoic acid 1:1 ratio on cardiovascular disease risk markers in rats

Background

High consumption of fish carries a lower risk of cardiovascular disease as a consequence of dietary omega-3 long chain polyunsaturated fatty acid (n-3 PUFA; especially EPA and DHA) content. A controversy exists about the component/s responsible of these beneficial effects and, in consequence, which is the best proportion between both fatty acids. We sought to determine, in healthy Wistar rats, the proportions of EPA and DHA that would induce beneficial effects on biomarkers of oxidative stress, and cardiovascular disease risk.

Methods

Female Wistar rats were fed for 13 weeks with 5 different dietary supplements of oils; 3 derived from fish (EPA/DHA ratios of 1:1, 2:1, 1:2) plus soybean and linseed as controls. The activities of major antioxidant enzymes (SOD, CAT, GPX, and GR) were determined in erythrocytes and liver, and the ORAC test was used to determine the antioxidant capacity in plasma. Also measured were: C reactive protein (CRP), endothelial dysfunction (sVCAM and sICAM), prothrombotic activity (PAI-1), lipid profile (triglycerides, cholesterol, HDLc, LDLc, Apo-A1, and Apo-B100), glycated haemoglobin and lipid peroxidation (LDL-ox and MDA values).

Results

After three months of nutritional intervention, we observed statistically significant differences in the ApoB100/ApoA1 ratio, glycated haemoglobin, VCAM-1, SOD and GPx in erythrocytes, ORAC values and LDL-ox. Supplementation with fish oil derived omega-3 PUFA increased VCAM-1, LDL-ox and plasma antioxidant capacity (ORAC). Conversely, the ApoB100/ApoA1 ratio and percentage glycated haemoglobin decreased.

Conclusions

Our results showed that a diet of a 1:1 ratio of EPA/DHA improved many of the oxidative stress parameters (SOD and GPx in erythrocytes), plasma antioxidant capacity (ORAC) and cardiovascular risk factors (glycated haemoglobin) relative to the other diets.

Enhanced peroxisomal β-oxidation is associated with prevention of obesity and glucose intolerance by fish oil-enriched diets

OBJECTIVE

The effects of different amounts of omega 3-polyunsaturated fatty acids in diets with normal or high content of fat on lipid and carbohydrate metabolism were investigated.

DESIGN AND METHODS

Mice were fed for 8 weeks on diets enriched with fish oil or lard at 10% or 60% of energy. Energy balance and energy expenditure were analyzed. Fatty acid (FA) oxidative capacity of the liver and the activity of enzymes involved in this pathway were assessed.

RESULTS

Fish oil-fed mice had lower body weight and adiposity compared with lard-fed animals, despite having lower rates of oxygen consumption. Mice fed diets containing fish oil also displayed lower glycemia, reduced fat content in the liver, and improved glucose tolerance compared with lard-fed animals. The fish oil-containing diets increased markers of hepatic peroxisomal content and increased the generation of metabolites derived from FA β-oxidation in liver homogenates. In contrast, no changes were observed in the content of mitochondrial electron transport chain proteins or carnitine palmitoyl transferase-1 in the liver, indicating little direct effect of fish oil on mitochondrial metabolism.

CONCLUSION

Collectively, our findings suggest that the energy inefficient oxidation of FAs in peroxisomes may be an important mechanism underlying the protection against obesity and glucose intolerance of fish oil administration.

Metabolic syndrome induces changes in KATP-channels and calcium currents in pancreatic β-cells

Metabolic syndrome (MS) can be defined as a group of signs that increases the risk of developing type 2 diabetes mellitus (DM2). These signs include obesity, hyperinsulinemia and insulin resistance. We are interested in the mechanisms that trigger hyperinsulinemia as a step to understand how β cells fail in DM2. Pancreatic β cells secrete insulin in response to glucose variations in the extracellular medium. When they are chronically over-stimulated, hyperinsulinemia is observed; but then, with time, they become incapable of maintaining normal glucose levels, giving rise to DM2. A chronic high sucrose diet for two months induces MS in adult male Wistar rats. In the present article, we analyzed the effect of the internal environment of rats with MS, on the activity of ATP-sensitive potassium channels (KATP) and calcium currents of pancreatic β cells. After 24 weeks of treatment with 20% sucrose in their drinking water, rats showed central obesity, hyperinsulinemia and insulin resistance, and their systolic blood pressure and triglycerides plasma levels increased. These signs indicate the onset of MS. KATP channels in isolated patches of β cells from MS rats, had an increased sensitivity to ATP with respect to controls. Moreover, the macroscopic calcium currents, show increased variability compared with cells from control individuals. These results demonstrate that regardless of genetic background, a high sucrose diet leads to the development of MS. The observed changes in ionic channels can partially explain the increase in insulin secretion in MS rats. However, some β cells showed smaller calcium currents. These cells may represent a β cell subpopulation as it becomes exhausted by the long-term high sucrose diet.

Omega-3 improves glucose tolerance but increases lipid peroxidation and DNA damage in hepatocytes of fructose-fed rats

The high consumption of fructose is linked to the increase in various characteristics of the metabolic syndrome. Fish oil is beneficial for the treatment of these comorbidities, such as insulin resistance, dyslipidemia, and hepatic steatosis. The objective of this study was to evaluate the consequences of the administration of fish oil concomitant to fructose ingestion during the experiment (45 days) and during the final 15 days in high-fructose-fed rats. Male Wistar rats were divided into 5 groups: control; those receiving 10% fish oil (FO); those receiving 60% fructose (Fr); those receiving 60% fructose and 10% fish oil for 45 days (FrFO); and those receiving fructose plus soybean oil for 30 days and fish oil for the final 15 days of the study (FrFO15). There was an increase in triacylglycerol, serum total cholesterol, and hepatic volume in the Fr group. The FO and FrFO groups experienced an increase in lipid peroxidation and a decrease in serum reduced glutathione. The FrFO group suffered greater hepatic injury, with increased alanine aminotransferase levels and DNA damage. Marked n-3 incorporation occurred in the groups receiving fish oil, favoring a better response to the oral glucose tolerance test. Fructose induced comorbidities of the metabolic syndrome, and the use of fish oil promoted a better glucose tolerance, although it was accompanied by more hepatocyte damage.

Hepatic and biochemical repercussions of a polyunsaturated fat-rich hypercaloric and hyperlipidic diet in Wistar rats

CONTEXT

Non-alcoholic fatty liver disease is characterized by lipid deposits in the hepatocytes and has been associated with obesity, dyslipidemia and type-2 diabetes. It is considered a hepatic manifestation of the metabolic syndrome, of which the main component is insulin resistance leading to hyperinsulinemia and increased production of inflammatory cytokines. Saturated fat promotes hypertriglyceridemia and hyperinsulinemia, reduces levels of high-density cholesterol and increases levels of low-density cholesterol, while polyunsaturated fat is associated with hypolipidemic, antiinflammatory and imunoregulating action.

OBJECTIVE

To evaluate the hepatic and biochemical repercussions of a polyunsaturated fat-rich diet in Wistar rats.

METHODS

Twenty-two rats were distributed equally in two groups: GI - standard diet (Biobase Bio-tec Ratos e Camundongos®) providing 3.000 kcal/kg and GII - hypercaloric and hyperlipidic diet providing 4.250 kcal/kg (ω-6:ω-3 = 3:1). The animals were euthanized after 23 weeks of experiment. The weight, biochemical parameters and hepatohistological changes were registered.

RESULTS

Findings were submitted to variance analysis with the level of statistical significance at 5%. The average weight did not differ significantly between the groups at baseline (P = 0.711), but was greater in Group II by the end of the experiment (P = 0.000). The levels of triglycerides (P = 0.039), total cholesterol (P = 0.015) and HDL (P = 0.005) were higher in Group I than in Group II. Macrovesicular steatosis was significantly more common in Group II than in Group I (P = 0.03).

CONCLUSION

Hypercaloric and hyperlipidic diet rich in polyunsaturated fat promotes weight gain and favors the development of hepatic steatosis while reducing serum levels of triglycerides, total cholesterol and HDL.

Early endocrine and molecular changes in metabolic syndrome models

The twenty-first century arrived in the middle of a global epidemic of metabolic syndrome (MS) and type 2 diabetes mellitus (DM2). It is generally accepted that an excess of nutrients linked to a low physical activity triggers the problem. However, the molecular features that interact to develop the MS are not clear. In an effort to understand and control them, they have been extensively studied, but this goal has not been achieved yet. Nonhuman animal models have been used to explore diet and genetic factors in which experimental conditions are controlled. For example, only one factor in the diet, such as fats or carbohydrates can be modified to better understand a single change that would be impossible in humans. Most of the studies have been done in rodents. However, it is difficult to directly compare them, because experiments are different in more than one variable; genetic strains, amount, and the type of fat used in the diet and sex. Thus, the only possible criteria of comparison are the relevance of the observed changes. We review different animal models and add some original observations on short-term changes in metabolism and beta cells in our own model of adult Wistar rats that are not especially prone to get fat or develop DM2, treated with 20% sucrose in drinking water. One early change observed in pancreatic beta cells is the increase in GLUT2 expression that is located to the membrane of the cells. This change could partially explain the presence of insulin hypersecretion and hyperinsulinemia in these rats. Understanding early changes that lead to MS and in time to pancreatic islet exhaustion is an important biomedical problem that may contribute to learn how to prevent or even reverse MS, before developing DM2.