Long-term high fructose and saturated fat diet affects plasma fatty acid profile in rats

Potential role of fructose on human colon DNA methylation in racial disparities observed for colorectal cancer risk

Background and aims

An increasing body of observational studies has linked fructose intake to colorectal cancer (CRC). African Americans (AAs) are significantly more likely than European Americans to consume greater quantities of fructose and to develop right-side colon cancer. Yet, a mechanistic link between these two associations remains poorly defined. We aimed to identify differentially methylated regions (DMRs) associated with dietary fructose consumption measures obtained from food frequency questionnaires in a cohort of normal colon biopsies derived from AA men and women (n=79).

Methods

DNA methylation data from this study was obtained using the Illumina Infinium MethylationEPIC kit and is housed under accession GSE151732. DMR analysis was carried out using DMRcate in right and matched left colon, separately. Secondary analysis of CRC tumors was carried out using data derived from TCGA-COAD, GSE101764 and GSE193535. Differential expression analysis was carried out on CRC tumors from TCGA-COAD using DESeq2 .

Results

We identified 4,263 right-side fructose-DMRs. In contrast, only 24 DMRs survived multiple testing corrections (FDR<0.05) in matched, left colon. To identify targets by which dietary fructose drives CRC risk, we overlaid these findings with data from three CRC tumor datasets. Remarkably, almost 50% of right-side fructose-DMRs overlapped regions associated with CRC in at least one of three datasets. TNXB and CDX2 ranked among the most significant fructose risk DMRs in right and left colon respectively that also displayed altered gene expression in CRC tumors.

Conclusions

Our mechanistic data support the notion that fructose has a greater CRC-related effect in right than left AA colon, alluding to a potential role for fructose in contributing to racial disparities in CRC.

Appetite–regulating hormones in rats with fructose-induced metabolic changes

Objectives: The aim of this research is to examine the effects of fructose-drinking on the plasma levels of appetite-regulating hormones insulin, leptin and ghrelin in male and female rats.

Methods: Mature Wistar rats were divided as follows: two control groups - male (CM) and female (CF); two fructose-drinking groups - male (FDM) and female (FDF), received 15% fructose solution. The experiment lasted 11 weeks. At the end, insulin, leptin and ghrelin levels as well as lipid and glucose profile were assessed.

Results: Plasma concentrations of the examined hormones were elevated in fructose-drinking groups. However, in the FDM group only the leptin levels were significantly increased compared to the control. In the FDF group, all three appetite-regulating hormones showed the highest concentrations in comparison to the other groups.

Conclusion: Sex hormones may affect the appetite-regulation signals and could be a factor contributing to degree of metabolic changes caused by long-term fructose overconsumption.

Sugars and Gastrointestinal Health

Sugar overconsumption is linked to a rise in the incidence of noncommunicable diseases such as diabetes, cardiovascular diseases, and cancer. This increased incidence is becoming a real public health problem that is more severe than infectious diseases, contributing to 35 million deaths annually. Excessive intake of free sugars can cause many of the same health problems as excessive alcohol consumption. Many recent international recommendations have expressed concerns about sugar consumption in Westernized societies, as current consumption levels represent quantities with no precedent during hominin evolution. In both adults and children, the World Health Organization strongly recommends reducing free sugar intake to <10% of total energy intake and suggests a further reduction to below 5%. Most studies have focused on the deleterious effects of Western dietary patterns on global health and the intestine. Whereas excessive dietary fat consumption is well studied, the specific impact of sugar is poorly described, while refined sugars represent up to 40% of caloric intake within industrialized countries. However, high sugar intake is associated with multiple tissue and organ dysfunctions. Both hyperglycemia and excessive sugar intake disrupt the intestinal barrier, thus increasing gut permeability and causing profound gut microbiota dysbiosis, which results in a disturbance in mucosal immunity that enhances infection susceptibility. This review aims to highlight the roles of different types of dietary carbohydrates and the consequences of their excessive intake for intestinal homeostasis.

Long-term high-fructose high-fat diet feeding elicits insulin resistance, exacerbates dyslipidemia and induces gut microbiota dysbiosis in WHHL rabbits

The metabolic syndrome (MetS) has become a global public health burden due to its link to cardiovascular disease and diabetes mellitus. The present study was designed to characterize the metabolic and cardiovascular disturbances, as well as changes in gut microbiota associated with high-fructose high-fat diet (HFFD)-induced MetS in Watanabe heritable hyperlipidemic (WHHL) rabbits. Twenty-one Watanabe rabbits were assigned to a control (n = 9) and HFFD (n = 12) groups, receiving a chow diet and a HFFD, respectively. During a 12-weeks protocol, morphological parameters were monitored; plasma fasting levels of lipids, glucose and insulin were measured and a glucose tolerance test (GTT) was performed. HOMA-IR was calculated. Cardiac function and vascular reactivity were evaluated using the Langendorff isolated heart and isolated carotid arteries methods, respectively. 16S rRNA sequencing of stool samples was used to determine gut microbial composition and abundance. HFFD-fed Watanabe rabbits exhibited increased fasting insulin (p < 0.03, 12^th week vs. Baseline), HOMA-IR (p < 0.03 vs. Control), area under the curve of the GTT (p < 0.02 vs. Control), triglycerides (p < 0.05, 12^th week vs. Baseline), TC (p < 0.01 vs. Control), LDL-C (p < 0.001 vs. Control). The HFFD group also displayed a significant decrease in intestinal microbial richness, evenness and diversity (FDR < 0.001, FDR < 0.0001, FDR < 0.01, respectively vs. Control group) and an increase in its Firmicutes/Bacteroidetes ratio (R = 3.39 in control vs. R = 28.24 in the HFFD group) indicating a shift in intestinal microbial composition and diversity. Our results suggest that HFFD induces insulin resistance and gut microbiota dysbiosis and accentuates dyslipidemia; and that, when subjected to HFFD, Watanabe rabbits might become a potential diet-induced MetS animal models with two main features, dyslipidemia and insulin resistance.

Antihypertriglyceridemia activities of naturally fermented green tea, Heukcha, extract through modulation of lipid metabolism in rats fed a high-fructose diet

Hypertriglyceridemia, a symptom of elevated triglyceride level in the blood, is a potent risk factor for cardiovascular and metabolic disorders. Among the numerous treatments to regulate circulating triglyceride levels, fibrates are widely used to treat hypertriglyceridemia, although they also have side effects such as hepatotoxicity and gallstone formation. In the present study, we aimed to investigate the blood triglyceride-lowering effects of a naturally fermented green tea extract (NFGT) and the underlying mechanisms on hypertriglyceridemia in vitro and in vivo models. NFGT suppressed the expression of lipogenic genes, while augmented expression of fatty acid oxidation-related genes in cultured cells, leading to the significant decrease of intracellular triglyceride content. NFGT treated group in fructose-induced hypertriglyceridemic rat model significantly decreased plasma and hepatic triglyceride, which was accompanied by an increase in excretion of fecal fat. Taken together, we propose that NFGT could be potentially a novel functional ingredient to prevent or treat hypertriglyceridemia.

Beet (Beta vulgaris) Suppressed Gene Expression and Serum Fatty Acid Synthase in High Fat and Fructose-induced Rats

BACKGROUND: The expression and activity of fatty acid synthase (FAS) enzymes determine de novo fatty acid synthesis, which can be enhanced by a high-fat and high fructose diet or inhibited by some bioactive compound diets. Beets are a great source of therapeutic compounds that have the potential to improve health and prevent disease. AIM: This study examined the effects of beets on liver FAS gene expression and FAS levels. METHODS: A total of 25 male Wistar rats divided into five groups: (1) Standard diet (n); (2) high fat and fructose diet (HFFD); (3) HFFD have given beet 6%-contained standard diet (B1); (4) HFFD have given beet 9%-contained standard diet (B2), and (5) HFFD have given beet 12%-contained standard diet (B3). The HFFD was given to rats in the 2, 3, 4, and 5 group diets for 8 weeks? and then 3, 4, and 5 groups received beet-contained standard diet for 6 weeks. At the end of the intervention, FAS levels were measured (please specify where it was measured from) using the ELISA method, liver FAS gene expression was analyzed by quantitative polymerase chain reaction, and triglyceride (TG) levels were determined by the colorimetric method. RESULTS: The beet-substituted diet significantly suppressed the hepatic FAS gene expression and decreased the serum FAS levels in rats previously given HFFD (p < 0.05). The expression of the FAS gene showed a significant positive correlation with the levels of FAS serum (p < 0.05), and also with the hepatic TG levels but not significant (p > 0.05). Substitution of beet 9% in diet gives the best effect in hepatic FAS gene expression and the serum FAS levels. CONCLUSIONS: The diet contained beet 9% was seen as a necessary physiological dose to improve the effects of high-fat and diet fructose diet through suppressing FAS gene expression and a decreased serum FAS levels.

Oestrogen replacement fails to fully revert ovariectomy-induced changes in adipose tissue monoglycerides, diglycerides and cholesteryl esters of rats fed a lard-enriched diet

Menopause may be accompanied by abdominal obesity and inflammation, conditions accentuated by high-fat intake, especially of saturated fat (SFA)-rich diets. We investigated the consequences of high-SFA intake on the fatty acid (FA) profile of monoglycerides, diglycerides and cholesteryl esters from retroperitoneal white adipose tissue (RET) of rats with ovariectomy-induced menopause, and the effect of oestradiol replacement. Wistar rats were either ovariectomized (Ovx) or sham operated (Sham) and fed either standard chow (C) or lard-enriched diet (L) for 12 weeks. Half of the Ovx rats received 17β-oestradiol replacement (Ovx + E2). Body weight and food intake were measured weekly. RET neutral lipids were chromatographically separated and FAs analysed by gas chromatography. Ovariectomy alone increased body weight, feed efficiency, RET mass, leptin and insulin levels, leptin/adiponectin ratio, HOMA-IR and HOMA-β indexes. OvxC + E2 showed attenuation in nearly all blood markers. HOMA-β index was restored in OvxL + E2. OvxC showed significantly disturbed SFA and polyunsaturated FA (PUFA) profile in RET cholesteryl esters (CE). OvxC also showed increased monounsaturated FA (MUFA) in the monoglyceride diglyceride (Mono-Di) fraction. Similar changes were not observed in OvxL, although increased SFA and decreased PUFA was observed in Mono-Di. Overall, HRT was only partially able to revert changes induced by ovariectomy. There appears to be increased mobilization of essential FA in Ovx via CE, which is a dynamic lipid species. The same results were not found in Mono-Di, which are more inert. HRT may be helpful to preserve FA profile in visceral fat, but possibly not wholly sufficient in reverting the metabolic effects induced by menopause.

Determination of Monounsaturated Fatty Acid Isomers in Biological Systems by Modeling MS3 Product Ion Patterns

Unsaturated free fatty acids are natively present in biological samples as isomers, where double bonds can be situated on different carbons in the acyl chain. While these isomers can have different actions and impacts on biological systems, they are inherently difficult to identify and differentiate by mass spectrometry alone. To address this challenge, several techniques for derivatization of the double bond or metal cationization at the carboxylic group have yielded diagnostic product ions for the respective isomer in tandem mass spectrometry. However, diagnostic product ions do not necessarily reflect quantitative isomeric ratios since fatty acid isomers have different ionization and fragmentation efficiencies. Here, we introduce a simple and rapid approach to predict the quantitative ratio of isomeric monounsaturated fatty acids. Specifically, empirically derived MS³ product ion patterns from fatty acid silver adducts are modeled using a stepwise linear model. This model is then applied to predict the proportion oleic and vaccenic acid in chemically complex samples at individual concentrations between 0.45 and 5.25 μM, with an average accuracy and precision below 2 and 5 mol %, respectively. We show that by simply including silver ions in the electrospray solvent, isomeric ratios are rapidly predicted in neat standards, rodent plasma, and tissue extract. Furthermore, we use the method to directly map isomeric ratios in tissue sections using nanospray desorption electrospray ionization MS³ imaging without any sample preparation or modification to the instrumental setup. Ultimately, this approach provides a simple and rapid solution to differentiate monounsaturated fatty acids using commonly available commercial mass spectrometers without any instrumental modifications.

Western diet consumption through early life induces microvesicular hepatic steatosis in association with an altered metabolome in low birth weight Guinea pigs

Uteroplacental insufficiency-induced low birth weight (LBW) and postnatal high saturated fat/high sucrose-fructose diet (Western Diet, WD) consumption have been independently associated with the development of hepatic steatosis, while their additive effect on fatty acid, acylcarnitine and amino acid profiles in early adulthood have not been widely reported. We employed LBW, generated via uterine artery ablation, and normal birth weight (NBW) male guinea pigs fed either a WD or control diet (CD) from weaning to postnatal day 150 (early adulthood). Hepatic steatosis was absent in CD-fed offspring, while NBW/WD offspring displayed macrovesicular steatosis and LBW/WD offspring exhibited microvesicular steatosis, both occurring in a lean phenotype. Life-long consumption of the WD, irrespective of birth weight, was associated with an increase in hepatic medium- and long-chain saturated fatty acids, monounsaturated fatty acids, acylcarnitines, reduced oxidative phosphorylation complex III activity and polyunsaturated fatty acids, and molecular evidence of disrupted hepatic insulin signaling. In NBW/WD, hepatic C15:1 and C16:1n-6 fatty acids in phospholipids, C16, C18 and C18:1 acylcarnitines, concentrations of aspartate, phenylalanine, tyrosine and tryptophan and expression of carnitine palmitoyltransferase 1 alpha (CPT1α) and uncoupling protein 2 (UCP2) genes were elevated compared to LBW/WD livers. Our results suggest that LBW and life-long WD combined are influential in promoting hepatic microvesicular steatosis in conjunction with a specific mitochondrial gene expression and metabolomic profile in early adulthood.

Hepatic metabolic effects of Curcuma longa extract supplement in high-fructose and saturated fat fed rats

The metabolic effects of an oral supplementation with a Curcuma longa extract, at a dose nutritionally relevant with common human use, on hepatic metabolism in rats fed a high fructose and saturated fatty acid (HFS) diet was evaluated. High-resolution magic-angle spinning NMR and GC/MS in combination with multivariate analysis have been employed to characterize the NMR metabolite profiles and fatty acid composition of liver tissue respectively. The results showed a clear discrimination between HFS groups and controls involving metabolites such as glucose, glycogen, amino acids, acetate, choline, lysophosphatidylcholine, phosphatidylethanolamine, and β-hydroxybutyrate as well as an increase of MUFAs and a decrease of n-6 and n-3 PUFAs. Although the administration of CL did not counteract deleterious effects of the HFS diet, some metabolites, namely some n-6 PUFA and n-3 PUFA, and betaine were found to increase significantly in liver samples from rats having received extract of curcuma compared to those fed the HFS diet alone. This result suggests that curcuminoids may affect the transmethylation pathway and/or osmotic regulation. CL extract supplementation in rats appears to increase some of the natural defences preventing the development of fatty liver by acting on the choline metabolism to increase fat export from the liver.

Review of a causal role of fructose-containing sugars in myocardial susceptibility to ischemia/reperfusion injury

In 2012, the World Health Organization Global Status Report on noncommunicable diseases showed that 7.4 million deaths were due to ischemic heart disease. Consequently, cardiovascular disease is a significant health burden, especially when partnered with comorbidities such as obesity, metabolic syndrome, and type 2 diabetes mellitus. Of note, these diseases can all be induced or exacerbated by diet. Carbohydrates, in particular, fructose and glucose, generally form the largest part of the human diet. Accumulating evidence from animal studies suggests that if large amounts of fructose are consumed either in isolation or in combination with glucose (fructose-containing sugars), myocardial susceptibility to ischemia/reperfusion (I/R) injury increases. However, the underlying mechanisms that predisposes the myocardium to I/R injury in the fructose model are not elucidated, and no single mechanistic pathway has been described. Based on all available data on this topic, this review describes previously investigated mechanisms and highlights 3 main mechanistic pathways whereby fructose has shown to increase myocardial susceptibility to I/R injury. These pathways include (1) increased reactive oxygen species, resulting in reduced nitric oxide synthase and coronary flow; (2) elevated plasma fatty acids and insulin, leading to increased cardiac triglyceride content and lipotoxicity; and (3) disrupted myocardial calcium handling/homeostasis. Moreover, we highlight various factors that should be taken into account when the fructose animal model is used, such as rat strain, treatment periods, and doses. We argue that failure to do so would result in erratic inferences drawn from the existing body of evidence on fructose animal models.

Glucomannan and glucomannan plus spirulina added to pork significantly block dietary cholesterol effects on lipoproteinemia, arylesterase activity, and CYP7A1 expression in Zucker fa/fa rats

Zucker fa/fa rats easily develop dyslipidemia and obesity. Restructured pork (RP) is a suitable matrix for including functional ingredients. The effects of glucomannan- RP or glucomannan plus spirulina-enriched RP on plasma lipid/lipoprotein levels, cytochrome P450 7A1 (CYP7A1) expression, and arylesterase activity in growing fa/fa rats fed high-energy, high-fat cholesterol-enriched diets were tested. Groups of six rats each received diet containing 15% control-RP (C), 15% glucomannan-RP diet (G), 15% glucomannan + spirulina-RP diet (GS), and same diets enriched with 2.4% cholesterol and 0.49% cholic acid (cholesterol-enriched control (HC), cholesterol-enriched glucomannan (HG), and cholesterol-enriched glucomannan + spirulina (HGS) diets) over a 7-week period. C diet induced obesity, severe hyperglycemia, moderate hypercholesterolemia, and hypertriglyceridemia. Those facts were not significantly modified by G or GS diets. G diet increased CYP7A1 expression but decreased the total cholesterol/high density lipoproteins (HDL)-cholesterol ratio (p < 0.05) vs. C diet. GS vs. G diet increased (p < 0.05) CYP7A1 expression. HC vs. C diet reduced food intake, body weight gain, and plasma glucose (p < 0.01) but increased cholesterolemia (p < 0.01), lipidemia (plasma cholesterol plus triglycerides) (p < 0.001), cholesterol/triglyceride ratio in very low density lipoproteins (VLDL), and HDL (p < 0.05), cholesterol transported by VLDL and intermediate density lipoproteins (IDL) + low density lipoproteins (LDL), total cholesterol/HDL-cholesterol ratio and CYP7A1 expression (at least p < 0.05). HG and HGS diets vs. HC noticeably reduced lipidemia (p < 0.001), normalized VLDL and IDL + LDL lipid composition, and increased CYP7A1 expression (p < 0.01) but did not modify the cholesterol/HDL-cholesterol ratio. HGS vs. HG decreased triglyceridemia, the triglyceride-glucose (TyG) index and increased arylesterase/HDL-cholesterol activity (p < 0.05). In conclusion, G- and GS-RP act as functional foods and notably blocked the dietary cholesterol effects. In addition, HGS-RP improved the glucomannan hypolipidemic effects, increased arylesterase/HDL-cholesterol activity, and decreased insulin resistance.

Metabolomic and Lipidomic Analysis of Serum Samples following Curcuma longa Extract Supplementation in High-Fructose and Saturated Fat Fed Rats

We explored, using nuclear magnetic resonance (NMR) metabolomics and fatty acids profiling, the effects of a common nutritional complement, Curcuma longa, at a nutritionally relevant dose with human use, administered in conjunction with an unbalanced diet. Indeed, traditional food supplements have been long used to counter metabolic impairments induced by unbalanced diets. Here, rats were fed either a standard diet, a high level of fructose and saturated fatty acid (HFS) diet, a diet common to western countries and that certainly contributes to the epidemic of insulin resistance (IR) syndrome, or a HFS diet with a Curcuma longa extract (1% of curcuminoids in the extract) for ten weeks. Orthogonal projections to latent structures discriminant analysis (OPLS-DA) on the serum NMR profiles and fatty acid composition (determined by GC/MS) showed a clear discrimination between HFS groups and controls. This discrimination involved metabolites such as glucose, amino acids, pyruvate, creatine, phosphocholine/glycerophosphocholine, ketone bodies and glycoproteins as well as an increase of monounsaturated fatty acids (MUFAs) and a decrease of n-6 and n-3 polyunsaturated fatty acids (PUFAs). Although the administration of Curcuma longa did not prevent the observed increase of glucose, triglycerides, cholesterol and insulin levels, discriminating metabolites were observed between groups fed HFS alone or with addition of a Curcuma longa extract, namely some MUFA and n-3 PUFA, glycoproteins, glutamine, and methanol, suggesting that curcuminoids may act respectively on the fatty acid metabolism, the hexosamine biosynthesis pathway and alcohol oxidation. Curcuma longa extract supplementation appears to be beneficial in these metabolic pathways in rats. This metabolomic approach highlights important serum metabolites that could help in understanding further the metabolic mechanisms leading to IR.

Lower omega-3 index is a marker of increased propensity of hypertensive rat heart to malignant arrhythmias

Polyunsaturated omega-3 fatty acids (omega-3 PUFA) are important components of cell membrane affecting its function and their deficiency is deleterious to health. We have previously shown that spontaneously hypertensive rats (SHR) are prone to life-threatening arrhythmias that are reduced by omega-3 PUFA intake. Purpose of this study was to explore plasma and red blood cells (RBC) profile of omega-3 and omega-6 PUFA as well as to determine omega-3 index, a risk factor for sudden cardiac death, in aged SHR and the effect of omega-3 PUFA intake. Male and female 12-month-old SHR and age-matched Wistar rats fed with omega-3 PUFA (200 mg/kg BW/day/2 month) were compared with untreated rats. Composition of omega-3 PUFA: alpha linolenic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as omega-6 PUFA: linoleic acid and arachidonic acid was analyzed by gas chromatography. Results showed sex- and strain-related differences of basal omega-3 and omega-6 PUFA levels in plasma and RBC as well as in response to omega-3 PUFA intake. Comparing to Wistar rats omega-3 index, expressed as a percentage of EPA+DHA of total fatty acids, was lower in SHR and it increased due to consumption of omega-3 PUFA. Findings support our hypothesis that lower omega-3 index may be also a marker of increased propensity of the hypertensive rat heart to malignant arrhythmias.

Glucose-stimulated insulin secretion: Effects of high-fat diet and acute stress

BACKGROUND

One of the major topics in modern societies is the study of relationships between diet, stress and incidence of metabolic disorders.

AIM

This study aimed to investigate possible impairment in glucose-stimulated insulin secretion induced by a high-fat (cow intra-abdominal fat) diet in response to acute stress.

MATERIALS AND METHODS

Male Wistar rats were divided into high-fat and normal diet groups and each group was further divided into stress and control subgroups. Stress was induced by a communication box. Plasma levels of glucose, insulin and corticosterone were measured in both diet groups. Glucose tolerance, homeostasis model assessment of insulin resistance (HOMA-IR) index, glucose-stimulated insulin secretion from isolated islets, food and energy intake as well as body weight were also evaluated.

RESULTS

In the normal diet group, physical stress increased plasma glucose concentrations. In both diet groups, plasma corticosterone levels increased after stress. HOMA-IR index decreased in high-fat fed rats. Food intake decreased while energy intake increased in the high-fat diet rats. Body weight in both diet groups increased in a similar manner. The high-fat diet did not affect insulin secretion; however, stress decreased insulin secretion from isolated islets of both diet groups. Only in the high fat diet group did physical stress increase insulin secretion at 16.7 mM glucose.

CONCLUSIONS

The cow intra-abdominal fat, did not affect either plasma glucose and insulin concentrations or glucose-induced insulin secretion. Interestingly, it seems that the high-fat diet enabled the islets of the physically stressed rats to secrete more insulin in response to high glucose concentrations.

Intake of n-3 Polyunsaturated Fatty Acids Increases Omega-3 Index in Aged Male and Female Spontaneously Hypertensive Rats

The purpose of this study was to examine whether n-3 PUFA intake affects n-3 and n-6 FA levels in plasma and red blood cells as well as omega-3 index in old male and female spontaneously hypertensive (SHR) and healthy rats. Plasma linoleic acid and eicosapentaenoic acid increased due to n-3 PUFA intake in SHR and healthy rats. Comparing to healthy rats the levels of PUFA in red blood cells of SHR were lower in males and higher in females with exception of arachidonic acid, which was high in males and low in females. Feeding of rats with n-3 PUFA resulted in increase of red blood cells levels of eicosapentaenoic acid and/or docosahexaenoic acid in a sex- and strain-dependent manner. Moreover, n-3 PUFA intake decreased arachidonic acid in healthy female rats but increased it in SHR and did not affect it in males. Omega-3 index was lower in SHR comparing to healthy rats and it increased due to the consumption of n-3 PUFA. Results point out sex- and strain-related differences in red blood cells levels of n-3 and n-6 PUFA in basal conditions as well as in response to n-3 PUFA intake.