The Small Intestine Converts Dietary Fructose into Glucose and Organic Acids

A fluorescent NBD "turn-on" probe for the rapid and on-site analysis of fructose in food

High fructose intake is an important cause of metabolic disease. Due to the increasing prevalence of metabolic diseases worldwide, the development of an accurate and efficient tool for monitoring fructose in food is urgently needed to control the intake of fructose. Herein, a new fluorescent probe NBD-PQ-B with 7-nitrobenz-2-oxa-1, 3-diazole (NBD) as the fluorophore, piperazine (PQ) as the bridging group and phenylboronic acid (B) as the recognition receptor, was synthesized to detect fructose. The fluorescence of NBD-PQ-B increased linearly at 550 nm at an excitation wavelength of 497 nm with increasing fructose concentration from 0.1 to 20 mM. The limit of detection (LOD) of fructose was 40 μM. The pKa values of NBD-PQ-B and its fructose complexes were 4.1 and 10.0, respectively. In addition, NBD-PQ-B bound to fructose in a few seconds. The present technique was applied to determine the fructose content in beverages, honey, and watermelon with satisfactory results. Finally, the system could not only be applied in an aqueous solution with a spectrophotometer, but also be fabricated as a NBD-PQ-B/polyvinyl oxide (PEO) film by electrospinning for on-site food analysis simply with the assistance of a smartphone.

Dietary supplementation with capsaicinoids alleviates obesity in mice fed a high-fat-high-fructose diet

Capsaicinoids are the pungent compounds in chili peppers. The present study investigated the effect of capsaicinoids on obesity in mice induced by a high-fat-high-fructose diet. Thirty-two male C57BL/6J mice were randomly divided into four groups (n = 8) and fed one of the following diets, namely, a low-fat diet (LFD), a high-fat-high-fructose diet (HFF), an HFF + 0.015% capsaicinoids (LCP), and an HFF + 0.045% capsaicinoids (HCP), for 12 weeks. Results showed that capsaicinoids significantly reversed HFF-induced obesity. Supplementation with capsaicinoids improved glucose tolerance, reduced plasma lipids, and attenuated inflammation. Capsaicinoids also reduced hepatic lipid accumulation by upregulating the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). In addition, capsaicinoids enhanced the production of fecal short-chain fatty acids (SCFAs) and increased the fecal excretion of lipids. Gut microbiota analysis revealed that capsaicinoids decreased the Firmicutes/Bacteroidetes ratio and beneficially reconstructed the microbial community. However, the effects of capsaicinoids on intestinal villus length and lipid tolerance were negligible. In conclusion, capsaicinoids effectively attenuated HFF-induced obesity and metabolic syndrome by favorably modulating lipid metabolism, improving SCFA production, and reshaping gut microbial structure.

HNF4α is required for Tkfc promoter activation by ChREBP

Triokinase/FMN cyclase (Tkfc) is involved in fructose metabolism and is responsible for the phosphorylation of glyceraldehyde to glyceraldehyde-3-phosphate. In this study, we showed that refeeding induced hepatic expression of Tkfc in mice. Luciferase reporter gene assays using the Tkfc promoter revealed the existence of 2 hepatocyte nuclear factor 4α (HNF4α)-responsive elements (HNF4RE1 and HNF4RE2) and 1 carbohydrate-responsive element-binding protein (ChREBP)-responsive element (ChoRE1). Deletion and mutation of HNF4RE1 and HNF4RE2 or ChoRE1 abolished HNF4α and ChREBP responsiveness, respectively. HNF4α and ChREBP synergistically stimulated Tkfc promoter activity. ChoRE1 mutation attenuated but maintained HNF4α responsiveness, whereas HNF4RE1 and HNF4RE2 mutations abolished ChREBP responsiveness. Moreover, Tkfc promoter activity stimulation by ChREBP was attenuated upon HNF4α knockdown. Furthermore, Tkfc expression was decreased in the livers of ChREBP-/- and liver-specific HNF4-/- (Hnf4αΔHep) mice. Altogether, our data indicate that Tkfc is a target gene of ChREBP and HNF4α, and Tkfc promoter activity stimulation by ChREBP requires HNF4α.

Gut Microbes, Diet, and Genetics as Drivers of Metabolic Liver Disease: A Narrative Review Outlining Implications for Precision Medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly increasing in prevalence, impacting over a third of the global population. The advanced form of MASLD, Metabolic dysfunction-associated steatohepatitis (MASH), is on track to become the number one indication for liver transplant. FDA-approved pharmacological agents are limited for MASH, despite over 400 ongoing clinical trials, with only a single drug (resmetirom) currently on the market. This is likely due to the heterogeneous nature of disease pathophysiology, which involves interactions between highly individualized genetic and environmental factors. To apply precision medicine approaches that overcome interpersonal variability, in-depth insights into interactions between genetics, nutrition, and the gut microbiome are needed, given that each have emerged as dynamic contributors to MASLD and MASH pathogenesis. Here, we discuss the associations and molecular underpinnings of several of these factors individually and outline their interactions in the context of both patient-based studies and preclinical animal model systems. Finally, we highlight gaps in knowledge that will require further investigation to aid in successfully implementing precision medicine to prevent and alleviate MASLD and MASH.

Pomegranate supplementation alleviates dyslipidemia and the onset of non-alcoholic fatty liver disease in Wistar rats by shifting microbiota and producing urolithin-like microbial metabolites

Non-alcoholic fatty liver disease (NAFLD), obesity and related chronic diseases are major non-communicable diseases with high mortality rates worldwide. While dietary sugars are known to be responsible for insulin resistance and metabolic syndrome (MetS), the underlying pathophysiological effects of sustained fructose consumption require further elucidation. We hypothesize that certain bioactive compounds (i.e. punicalagin and ellagic acid) from dietary pomegranate could counteract the harmful effects of sustained fructose consumption in terms of obesity and liver damage. The present study aimed to elucidate both the molecular mechanisms involved in the pathophysiology associated with fructose intake and the effect of a punicalagin-rich commercial pomegranate dietary supplement (P) used as a nutritional strategy to alleviate fructose-induced metabolic impairments. Thus, nineteen Wistar rats fed on a basal commercial feed were supplemented with either 30% (w/v) fructose in drinking water (F; n = 7) or 30% (w/v) fructose solution plus 0.2% (w/v) P (F + P; n = 6) for 10 weeks. The results were compared to those from a control group fed on the basal diet and provided with drinking water (C; n = 6). Body weight and energy intake were registered weekly. P supplementation decreased fat depots, counteracted the dyslipidemia caused by F and improved markers of liver injury including steatosis. The study of the microbiota by metagenomics and urine by untargeted MS-based metabolomics revealed microbial metabolites from P that may be responsible for these health benefits.

Regulation of Fructose Metabolism in Nonalcoholic Fatty Liver Disease

Elevations in fructose consumption have been reported to contribute significantly to an increased incidence of obesity and metabolic diseases in industrial countries. Mechanistically, a high fructose intake leads to the dysregulation of glucose, triglyceride, and cholesterol metabolism in the liver, and causes elevations in inflammation and drives the progression of nonalcoholic fatty liver disease (NAFLD). A high fructose consumption is considered to be toxic to the body, and there are ongoing measures to develop pharmaceutical therapies targeting fructose metabolism. Although a large amount of work has summarized the effects fructose exposure within the intestine, liver, and kidney, there remains a gap in our knowledge regarding how fructose both indirectly and directly influences immune cell recruitment, activation, and function in metabolic tissues, which are essential to tissue and systemic inflammation. The most recent literature demonstrates that direct fructose exposure regulates oxidative metabolism in macrophages, leading to inflammation. The present review highlights (1) the mechanisms by which fructose metabolism impacts crosstalk between tissues, nonparenchymal cells, microbes, and immune cells; (2) the direct impact of fructose on immune cell metabolism and function; and (3) therapeutic targets of fructose metabolism to treat NAFLD. In addition, the review highlights how fructose disrupts liver tissue homeostasis and identifies new therapeutic targets for treating NAFLD and obesity.

Mice Condition Cephalic-Phase Insulin Release to Flavors Associated with Postoral Actions of Concentrated Glucose

Rats can condition cephalic-phase insulin responses (CPIRs) to specific sounds or times of the day that predict food availability. The present study asked whether mice can condition a CPIR to the flavor of sapid solutions that produce postoral glucose stimulation. To this end, we subjected C57BL/6 mice to one of six experimental protocols. We varied both the duration of the five training sessions (i.e., 23 h or 1 h) and the nature of the training solution. In Experiment 1, consumption of a 0.61% saccharin solution was paired with IG co-infusion of a 16% glucose solution. In Experiments 2-6, the mice consumed a training solution containing a mixture of 0.61% saccharin + 16% glucose, 32% sucrose, 32% maltodextrin, flavored 32% maltodextrin, or 16% maltodextrin. We subsequently asked whether consumption of any of these fluids conditioned a CPIR to a test solution that produced a similar flavor, but which did not elicit a CPIR in naïve mice. The mice did condition a CPIR, but only to the solutions containing 32% maltodextrin. We attribute this conditioning to postoral actions of the concentrated maltodextrin solutions.

Activation of AMPD2 drives metabolic dysregulation and liver disease in mice with hereditary fructose intolerance

Hereditary fructose intolerance (HFI) is a painful and potentially lethal genetic disease caused by a mutation in aldolase B resulting in accumulation of fructose-1-phosphate (F1P). No cure exists for HFI and treatment is limited to avoid exposure to fructose and sugar. Using aldolase B deficient mice, here we identify a yet unrecognized metabolic event activated in HFI and associated with the progression of the disease. Besides the accumulation of F1P, here we show that the activation of the purine degradation pathway is a common feature in aldolase B deficient mice exposed to fructose. The purine degradation pathway is a metabolic route initiated by adenosine monophosphate deaminase 2 (AMPD2) that regulates overall energy balance. We demonstrate that very low amounts of fructose are sufficient to activate AMPD2 in these mice via a phosphate trap. While blocking AMPD2 do not impact F1P accumulation and the risk of hypoglycemia, its deletion in hepatocytes markedly improves the metabolic dysregulation induced by fructose and corrects fat and glycogen storage while significantly increasing the voluntary tolerance of these mice to fructose. In summary, we provide evidence for a critical pathway activated in HFI that could be targeted to improve the metabolic consequences associated with fructose consumption.

John Yudkin's hypothesis: sugar is a major dietary culprit in the development of cardiovascular disease

To date, the risk of developing atherosclerosis has extended beyond Western countries and now affecting individuals from various ethnic backgrounds and age groups. Traditional risk factors of atherosclerosis, such as hypercholesterolemia, has been better controlled than before due to highly effective and inexpensive therapies at lowering plasma cholesterol levels. However, the role of reducing dietary cholesterol intake, as a public healthy strategy, in preventing the occurrence of cardiovascular mortalities has been recently challenged. Indeed, despite our continuous decline of dietary cholesterol intake within the last 50 years, the incidence of cardiovascular mortalities has continued to rise, thus raising the possibility that other dietary factors, such as fructose-containing sugars, are the major culprit. In the 1970s, John Yudkin first proposed that sugar was the predominant dietary factor that underlies the majority of cardiovascular mortalities, yet his hypothesis was dismissed. However, over the last 25 years substantial scientific evidence has been accumulated to support Yudkin's hypothesis. The objectives of this review are to highlight Yudkin's significant contribution to nutritional science by reviewing his hypothesis and summarizing the recent advances in our understanding of fructose metabolism. The metabolic consequences of fructose metabolism, such as fructose-induced uricemia, insulin resistance, lipoprotein hyperproduction and chronic inflammation, and how they are linked to atherosclerosis as risk factors will be discussed. Finally, the review will explore areas that warrant future research and raise important considerations that we need to evaluate when designing future studies.

Mulberry and Hippophae-based solid beverage attenuate hyperlipidemia and hepatic steatosis via adipose tissue-liver axis

Dyslipidemia and hepatic steatosis are the characteristics of the initial stage of nonalcohol fatty liver disease (NAFLD), which can be reversed by lifestyle intervention, including dietary supplementation. However, such commercial dietary supplements with solid scientific evidence and in particular clear mechanistic elucidation are scarce. Here, the health benefits of MHP, a commercial mulberry and Hippophae-based solid beverage, were evaluated in NAFLD rat model and the underlying molecular mechanisms were investigated. Histopathologic examination of liver and white adipose tissue found that MHP supplementation reduced hepatic lipid accumulation and adipocyte hypertrophy. Serum biochemical results confirmed that MHP effectively ameliorated dyslipidemia and decreased circulation-free fatty acid level. RNA-Seq-based transcriptomic analysis showed that MHP-regulated genes are involved in the inhibition of lipolysis of adipose tissue and thus may contribute to the reduction of hepatic ectopic lipid deposition. Furthermore, MHP upregulated ACSL1-CPT1a-CPT2 pathway, a canonical pathway that regulated mitochondrial fatty acid metabolism, and promoted liver and adipose tissue fatty acid β-oxidation. These results suggest that adipose tissue-liver crosstalk may play a key role in maintaining glucose and lipid metabolic hemostasis. In addition, MHP can also ameliorate chronic inflammation through regulating the secretion of adipokines. Our study demonstrates that MHP is able to improve dyslipidemia and hepatic steatosis through crosstalk between adipose tissue and liver and also presents transcriptomic evidence to support the underlying mechanisms of action, providing solid evidence for its health claims.

High sucrose diet-induced abnormal lipid metabolism in mice is related to the dysbiosis of gut microbiota

BACKGROUND & AIMS

Excess sucrose intake induces metabolic syndrome. In human, abnormal lipids metabolism like obesity, hyperlipidemia and fatty liver are induced. However, excess sucrose causes different phenotypes in different species. Based on our previous study, excess sucrose induced fatty liver and hyperlipidemia in rats. The phenotypes and mechanism of abnormal lipid metabolism in mice is unclear. We investigated the different phenotypes in 5 strains of mice and the relationship between gut microbiome and abnormal lipid metabolism in C57BL/6N mice.

METHODS

We examined the effect of a high sucrose diet in 5 different strains of mice. Besides, to find out the relationship between gut microbiome and metabolic disorder induced by excess sucrose, C57BL/6N mice were fed with a high sucrose diet with or without antibiotics cocktail.

RESULTS

A high sucrose diet induced obesity and fatty liver in inbred mice, whereas did not induce hyperlipidemia in all strains of mice. Moreover, a high sucrose diet changed the composition of gut microbiota in C57BL/6N mice. Antibiotics treatment alleviated the abnormal lipid metabolism induced by high sucrose diet by changing the composition of gut short chain fatty acids.

CONCLUSIONS

These results indicates that the phenotypes of metabolic syndrome are influenced by genetic factors. Furthermore, the dysbiosis of gut microbiome caused by excess sucrose may contribute to the development of abnormal lipid metabolism via its metabolites.

Ileum Proteomics Identifies Distinct Pathways Associated with Different Dietary Doses of Copper-Fructose Interactions: Implications for the Gut-Liver Axis and MASLD

The interactions of different dietary doses of copper with fructose contribute to the development of metabolic dysfunction-associated steatotic liver disease (MASLD) via the gut-liver axis. The underlying mechanisms remain elusive. The aim of this study was to identify the specific pathways leading to gut barrier dysfunction in the ileum using a proteomics approach in a rat model. Male weanling Sprague Dawley rats were fed diets with adequate copper (CuA), marginal copper (CuM), or supplemented copper (CuS) in the absence or presence of fructose supplementation (CuAF, CuMF, and CuSF) for 4 weeks. Ileum protein was extracted and analyzed with an LC-MS. A total of 2847 differentially expressed proteins (DEPs) were identified and submitted to functional enrichment analysis. As a result, the ileum proteome and signaling pathways that were differentially altered were revealed. Of note, the CuAF is characterized by the enrichment of oxidative phosphorylation and ribosome as analyzed with the KEGG; the CuMF is characterized by an enriched arachidonic acid metabolism pathway; and focal adhesion, the regulation of the actin cytoskeleton, and tight junction were significantly enriched by the CuSF. In conclusion, our proteomics analysis identified the specific pathways in the ileum related to the different dietary doses of copper-fructose interactions, suggesting that distinct mechanisms in the gut are involved in the development of MASLD.

Clostridium sporogenes increases fat accumulation in mice by enhancing energy absorption and adipogenesis

Gut bacteria belonging to the Clostridium family play a pivotal role in regulating host energy balance and metabolic homeostasis. As a commensal bacterium, Clostridium sporogenes has been implicated in modulating host energy homeostasis, albeit the underlying mechanism remains elusive. Therefore, this study aimed to investigate the impact of C. sporogenes supplementation on various physiological parameters, intestinal morphology, particularly adipose tissue accumulation, and glucolipid metabolism in mice. The findings reveal that mice supplemented with C. sporogenes for 6 weeks exhibited a notable increase in body weight, fat mass, adipocyte size, and serum triglyceride (TG) levels. Notably, the increased fat accumulation is observed despite consistent feed intake in treated mice. Mechanistically, C. sporogenes supplementation significantly improved the structure integrity of intestinal villi and enhanced energy absorption efficiency while reducing excretion of carbohydrates and fatty acids in feces. This was accompanied by upregulation of glucose and fatty acid transporter expression. Furthermore, supplementation with C. sporogenes promoted adipogenesis in both liver and adipose tissues, as evidenced by increased levels of hepatic pyruvate, acetyl-CoA, and TG, along with elevated expression levels of genes associated with lipid synthesis. Regarding the microbiological aspect, C. sporogenes supplementation correlated with an increased abundance of Clostridium genus bacteria and enhanced carbohydrate enzyme activity. In summary, C. sporogenes supplementation significantly promotes fat accumulation in mice by augmenting energy absorption and adipogenesis, possibly mediated by the expansion of Clostridium bacteria population with robust glycolipid metabolic ability.

IMPORTANCE

The Clostridia clusters have been implicated in energy metabolism, the specific species and underlying mechanisms remain unclear. This present study is the first to report Clostridium sporogenes is able to affect fat accumulation and glycolipid metabolism. We indicated that gavage of C. sporogenes promoted the adipogenesis and fat accumulation in mice by not only increasing the abundance of Clostridium bacteria but by also enhancing the metabolic absorption of carbohydrates and fatty acids significantly. Obviously, changes of gut microbiota caused by the C. sporogenes, especially the significant increase of Clostridium bacteria, contributed to the fat accumulation of mice. In addition, the enhancement of Clostridium genus bacteria remarkably improved the synthesis of hepatic pyruvate, acetyl-CoA, and triglyceride levels, as well as reduced the excretion of fecal carbohydrates, short-chain fatty acids, and free fatty acids remarkably. These findings will help us to understand the relationship of specific bacteria and host energy homeostasis.

Sucrose Solution Ingestion Exacerbates Dinitrofluorobenzene-Induced Allergic Contact Dermatitis in Rats

Allergic dermatitis is a skin disease with growing prevalence worldwide that has been associated with diets high in fats and sugars. Regular consumption of sucrose-containing beverages may increase the risk for several health problems, including allergic diseases and particularly asthma, but the association between sucrose consumption and allergic dermatitis is understudied. We investigated the effects of sucrose solution intake on allergic contact dermatitis in rats and found early exacerbation of 2,4-dinitrofluorobenzene (DNFB)-induced disease symptoms and altered composition of the gut microbiota after 14 d of intake. The levels of short-chain fatty acids-produced by fermentation by the intestinal microbiota-were not affected in the cecal contents and feces but decreased in the blood; this effect was especially notable for acetate. To restore blood acetate concentrations, triacetin was mixed with a 10% sucrose solution and fed to the rat model. This strategy prevented the early exacerbation of DNFB-induced symptoms. The decreased absorption of short-chain fatty acids from the intestinal lumen was not linked to the decreased expression of short-chain fatty acid transporters in the small intestine; instead, the mechanism involves a reduction in the sodium concentration in the intestinal lumen due to increased expression of sodium-glucose transporter 1 (SGLT1).

Diet predisposes to pancreatic cancer through cellular nutrient sensing pathways

Pancreatic cancer is a lethal disease with limited effective treatments. A deeper understanding of its molecular mechanisms is crucial to reduce incidence and mortality. Epidemiological evidence suggests a link between diet and disease risk, though dietary recommendations for at-risk individuals remain debated. Here, we propose that cell-intrinsic nutrient sensing pathways respond to specific diet-derived cues to facilitate oncogenic transformation of pancreatic epithelial cells. This review explores how diet influences pancreatic cancer predisposition through nutrient sensing and downstream consequences for (pre-)cancer cell biology. We also examine experimental evidence connecting specific food intake to pancreatic cancer progression, highlighting nutrient sensing as a promising target for therapeutic development to mitigate disease risk.

Transcriptomic insights into the lipotoxicity of high-fat high-fructose diet in rat and mouse

Along with the increasing prevalence of obesity worldwide, the deleterious effects of high-calorie diet are gradually recognized through more and more epidemiological studies. However, the concealed and chronic causality whitewashes its unhealthy character. Given an ingenious mechanism orchestrates the metabolic adaptation to high-fat high-fructose (HFF) diet and connive its lipotoxicity, in this study, an experimental rat/mouse model of obesity was induced and a comparative transcriptomic analysis was performed to probe the mystery. Our results demonstrated that HFF diet consumption altered the transcriptomic pattern as well as different high-calorie diet fed rat/mouse manifested distinct hepatic transcriptome. Validation with RT-qPCR and Western blotting confirmed that SREBP1-FASN involved in de novo lipogenesis partly mediated metabolic self-adaption. Moreover, hepatic ACSL1-CPT1A-CPT2 pathway involved in fatty acids β-oxidation, played a key role in the metabolic adaption to HFF. Collectively, our findings enrich the knowledge of the chronic adaptation mechanisms and also shed light on future investigations. Meanwhile, our results also suggest that efforts to restore the fatty acids metabolic fate could be a promising avenue to fight against obesity and associated steatosis and insulin resistance challenged by HFF diet.

Approaches to nutritional research using organoids; fructose treatment induces epigenetic changes in liver organoids

Nutritional researches have successfully used animal models to gain new insights into nutrient action. However, comprehensive descriptions of their molecular mechanisms of action remain elusive as appropriate in vitro evaluation systems are lacking. Organoid models can mimic physiological structures and reproduce in vivo functions, making them increasingly utilized in biomedical research for a better understand physiological and pathological phenomena. Therefore, organoid modeling can be a powerful approach for to understand the molecular mechanisms of nutrient action. The present study aims to demonstrate the utility of organoids in nutritional research by further investigating the molecular mechanisms responsible for the negative effects of fructose intake using liver organoids. Here, we treated liver organoids with fructose and analyzed their gene expression profiles and DNA methylation levels. Microarray analysis demonstrated that fructose-treated organoids exhibited increased selenoprotein p (Sepp1) gene expression, whereas pyrosequencing assays revealed reduced DNA methylation levels in the Sepp1 region. These results were consistent with observations using hepatic tissues from fructose-fed rats. Conversely, no differences in Sepp1 mRNA and DNA methylation levels were observed in two-dimensional cells. These results suggest that organoids serve as an ideal in vitro model to recapitulate in vivo tissue responses and help to validate the molecular mechanisms of nutrient action compared to conventional cellular models.

Effect of short-term moderate intake of ice wine on hepatic glycolipid metabolism in C57BL/6J mice

As the correlation between high fructose intake and metabolism-related diseases (e.g., obesity, fatty liver, and type 2 diabetes) has been increasingly reported, the health benefits of consuming ice wine high in fructose have been called into question. In this study, 6-week-old male C57BL/6J mice were divided into control (pure water), fructose (130 g L-1 fructose solution), alcohol (11% alcohol solution), low-dose (50% diluted ice wine) and high-dose ice wine (100% ice wine) groups to investigate the effects and mechanisms of short-term (4 weeks) ice wine intake on hepatic glycolipid metabolism in mice. The results showed that short-term consumption of ice wine suppressed the elevation of low-density lipoprotein cholesterol content and did not cause hepatic lipid accumulation compared with those of the fructose group. Meanwhile, ice wine had no significant effect on lipogenesis although it inhibited fatty acid oxidation via the PPARα/CPT-1α pathway. Compared with the control group, ice wine interfered with the elevation of fasting glucose and the insulin resistance index in a dose-dependent manner, and led to an increase in plasma uric acid levels, which may further contribute to the disruption of glucolipid metabolism. Overall, short-term moderate intake of ice wine over a 4-week period may not significantly affect hepatic glycolipid metabolism in C57BL/6J mice for the time being.

Inhibition of α-glucosidase activity and intestinal glucose transport to assess the in vivo anti-hyperglycemic potential of dodecyl-acylated phlorizin and polydatin derivatives

A diet containing natural active compounds that can inhibit the hydrolytic activity of α-glucosidase on carbohydrates and intestinal glucose absorption is an effective means of controlling postprandial hyperglycemia. Phlorizin and polydatin as phenolic glycosides have a high affinity for the catalytic site of α-glucosidase, but exhibited unsatisfactory competitive inhibitory capacity, with an IC50 of 0.97 and >2 mM, respectively. However, dodecyl-acylated derivatives of phlorizin and polydatin exerted α-glucosidase inhibitory capacity, with an IC50 of 55.10 and 70.95 μM, respectively, which were greatly enhanced and much stronger than that of acarbose with an IC50 of 2.46 mM. The SPR assay suggested the high affinity of dodecyl phlorizin and dodecyl polydatin to α-glucosidase with equilibrium dissociation constant (KD) values of 12.0 and 7.9 μM, respectively. Both dodecyl phlorizin and dodecyl polydatin reduced the catalytic ability of α-glucosidase by reversible noncompetitive and uncompetitive mixed inhibition, which bind noncovalently to the allosteric site 2 through hydrogen bonds and hydrophobic interactions, thereby inducing the secondary structure unfolding and intrinsic fluorescence quenching of α-glucosidase. Confocal microscopy detection visually showed significant inhibitory effects on FITC-labeled glucose uptake in intestinal Caco-2 cells by phlorizin, polydatin, dodecyl phlorizin and dodecyl polydatin. In addition, based on the differentiated Caco-2 cell monolayer model, dodecyl phlorizin and dodecyl polydatin suppressed intestinal glucose transport more effectively than phlorizin and polydatin, suggesting that they were promising in vivo hypoglycemic active compounds.

Effects of Excessive High-fructose Corn Syrup Drink Intake in Middle-aged Mice

BACKGROUND/AIM

The global prevalence of type 2 diabetes (T2D) continues to increase, necessitating the need for understanding the causes of its development. The widespread use of high-fructose corn syrup (HFCS) in drinks and diets is suspected to play a role in metabolic disorders. Although many studies have reported on the effects of excessive HFCS and excessive energy intakes in middle-aged individuals, few have focused on energy restriction. This study aimed to investigate the effects of excessive HFCS drink intake under energy restriction on developing T2D in early middle-aged mice.

MATERIALS AND METHODS

Early middle-aged mice were divided in HFCS and control groups; they were provided either 10% HFCS water or deionized water ad libitum for 12 weeks, respectively. Total energy intake was controlled using a standard rodent diet. Oral glucose tolerance test (OGTT), insulin tolerance test (ITT), tissue weight measurements, serum parameter analyses, and mRNA expression assessments were performed.

RESULTS

No increase in body and adipose tissue weight was observed with excessive HFCS intake under energy restriction. Moreover, serum lipid parameters did not differ from those of controls. However, in the OGTT and ITT, the HFCS group showed higher blood glucose levels than the control group. Moreover, the pancreatic weight and insulin II mRNA expression were reduced.

CONCLUSION

The excessive HFCS drink intake under energy restriction did not induce obesity; however, it induced impaired glucose tolerance, indicating its negative effects on the pancreas in early middle-aged mice. When translated in human physiology, our results show that even if one does not become obese, excessive HFCS may affect the overall metabolic mechanism; these effects may vary depending on age.

Fructose-induced metabolic reprogramming of cancer cells

Excess dietary fructose consumption has been long proposed as a culprit for the world-wide increase of incidence in metabolic disorders and cancer within the past decades. Understanding that cancer cells can gradually accumulate metabolic mutations in the tumor microenvironment, where glucose is often depleted, this raises the possibility that fructose can be utilized by cancer cells as an alternative source of carbon. Indeed, recent research has increasingly identified various mechanisms that show how cancer cells can metabolize fructose to support their proliferating and migrating needs. In light of this growing interest, this review will summarize the recent advances in understanding how fructose can metabolically reprogram different types of cancer cells, as well as how these metabolic adaptations can positively support cancer cells development and malignancy.

Dual intervention on the gut and skin microbiota attenuates facial cutaneous aging

The gut and skin microbiota are microbial barriers, resisting harmful foreign microorganisms and maintaining internal homeostasis. Dysbiosis of the gut and skin microbiota is involved in aging progression. However, interventions targeting facial skin wellness taking into account the gut-skin axis are scarce. In this study, the impact of an eight-week intervention with oral (O), topical (T), and both oral and topical (OT) xylo-oligosaccharides (XOS) by regulating gut and skin microbiota on facial cutaneous aging was investigated in a double-blind placebo-controlled trial in females. An increase in the proportion of participants with skin rejuvenation was observed, along with a significant reduction in facial pores after OT intervention. The reduction of cutaneous Cutibacterium by OT intervention was greater than that in the O and T groups. These interventions can change the skin microbial structure. Intestinal Bifidobacterium was enriched only by dual treatment with oral and topical XOS. Function prediction analysis revealed a decrease in K02770 encoding fructose-1-phosphate kinase involved in de novo lipid synthesis from fructose with dual intervention, suggesting that inhibition of lipophilic Cutibacterium may contribute to reducing facial pores. Overall, the dual XOS intervention approach is most effective for improving both gut and skin microbiota, as well as facial skin aging.

Fructose dose-dependently influences colon barrier function by regulation of some main physical, immune, and biological factors in rats

Little is known about the effects of fructose on colonic function. Here, forty-eight 7-week-old male SD rats were randomly divided into four groups and given 0, 7.5%, 12.75%, and 35% fructose in diet for 8 weeks respectively to investigate the regulatory influence of fructose on colonic barrier function. The exact amount of fructose intake was tracked and recorded. We showed that fructose affects colonic barrier function in a dose-dependent manner. High-fructose at a dose of 1.69±0.23 g/kg/day could damage the physical barrier function of the colon by down-regulating expression of tight junction proteins (ZO-1 and occludin) and mucus layer biomarkers (MUC2 and TFF3). High fructose reduced sIgA and the anti-inflammatory cytokine (IL-10), induced abdominal fat accumulation and pro-inflammatory cytokines (IL-6 and IL-8), leading to colon inflammation and immune barrier dysfunction. In addition, high-fructose altered the biological barrier of the colon by decreasing the abundance of Blautia, Ruminococcus, and Lactobacillius, and increasing the abundance of Allobaculum at the genus level, leading to a reduction in short-chain fatty acids (SCFAs), amino acids, and carbohydrates, etc. Low fructose at a dose of 0.31±0.05 g/kg/day showed no adverse effects on the colonic barrier. The ability of fructose to affect the colonic barrier through physical, immune, and biological pathways provides additional insight into the intestinal disorders caused by high-fructose diets.

Fructose overconsumption-induced reprogramming of microglia metabolism and function

The overconsumption of dietary fructose has been proposed as a major culprit for the rise of many metabolic diseases in recent years, yet the relationship between a high fructose diet and neurological dysfunction remains to be explored. Although fructose metabolism mainly takes place in the liver and intestine, recent studies have shown that a hyperglycemic condition could induce fructose metabolism in the brain. Notably, microglia, which are tissue-resident macrophages (Mφs) that confer innate immunity in the brain, also express fructose transporters (GLUT5) and are capable of utilizing fructose as a carbon fuel. Together, these studies suggest the possibility that a high fructose diet can regulate the activation and inflammatory response of microglia by metabolic reprogramming, thereby altering the susceptibility of developing neurological dysfunction. In this review, the recent advances in the understanding of microglia metabolism and how it supports its functions will be summarized. The results from both in vivo and in vitro studies that have investigated the mechanistic link between fructose-induced metabolic reprogramming of microglia and its function will then be reviewed. Finally, areas of controversies and their associated implications, as well as directions that warrant future research will be highlighted.

The Impact of Excessive Fructose Intake on Adipose Tissue and the Development of Childhood Obesity

Worldwide, childhood obesity cases continue to rise, and its prevalence is known to increase the risk of non-communicable diseases typically found in adults, such as cardiovascular disease and type 2 diabetes mellitus. Thus, comprehending its multiple causes to build healthier approaches and revert this scenario is urgent. Obesity development is strongly associated with high fructose intake since the excessive consumption of this highly lipogenic sugar leads to white fat accumulation and causes white adipose tissue (WAT) inflammation, oxidative stress, and dysregulated adipokine release. Unfortunately, the global consumption of fructose has increased dramatically in recent years, which is associated with the fact that fructose is not always evident to consumers, as it is commonly added as a sweetener in food and sugar-sweetened beverages (SSB). Therefore, here, we discuss the impact of excessive fructose intake on adipose tissue biology, its contribution to childhood obesity, and current strategies for reducing high fructose and/or free sugar intake. To achieve such reductions, we conclude that it is important that the population has access to reliable information about food ingredients via food labels. Consumers also need scientific education to understand potential health risks to themselves and their children.

Fructose-induced hyperuricaemia - protection factor or oxidative stress promoter?

Accumulating evidence suggests that dietary fructose may play a role in the hyperuricaemia development, but the precise mechanism remains unclear. Hyperuricaemia is characterised by excessive production and deposition of urate crystals, and the metabolism of fructose has been implicated in the elevation of serum urate levels. The association between fructose intake and the risk of hyperuricaemia is explained by the metabolism of fructose in the liver, small intestine, and kidney. Many studies have confirmed the correlation between fructose consumption and an increased risk of developing hyperuricaemia, but more prospective studies to fully elucidate the role of fructose intake in the pathogenesis of hyperuricaemia are needed. It is important to note that maintaining a balanced diet, and lifestyle is crucial when considering fructose intake. Limiting the consumption of products high in added sugars and maintaining a healthy weight can contribute to reducing the risk of hyperuricaemia and associated health complications.

Individual differences in cephalic-phase insulin response are stable over time and predict glucose tolerance in mice

Oral stimulation by glucose triggers a rapid insulin response, which enhances glucose tolerance. This so-called cephalic-phase insulin response (CPIR) has been documented in many mammal species, but its functional properties are poorly characterized. Here, we studied CPIR in lean C57BL/6 mice. Experiment 1 asked whether the large individual differences in CPIR magnitude were real or reflected experimental noise. We measured CPIR magnitude four times across a period of 30 days in the same mice. The individual differences in CPIR magnitude were remarkably stable across the repeated trials, indicating that they were real. Experiment 2 examined the functional consequences of individual differences in CPIR magnitude. We found that higher CPIR magnitudes contributed to larger postprandial insulin responses and greater glucose tolerance. Experiment 3 examined the observation that the CPIRs in Experiments 1 and 2 were associated with a rapid rise in blood glucose. To determine whether the rapid rise in blood glucose caused the CPIRs, we asked whether mice would generate a CPIR if we prevented cephalic-phase stimulation of beta cells by either delivering the glucose intragastrically or blocking parasympathetic input to the pancreatic beta cells with atropine. The mice subjected to these treatments experienced a rapid rise in blood glucose, but they did not exhibit a CPIR. This indicates that it was the oral glucose stimulation, and not the rise in blood glucose, that triggered the CPIRs in Experiments 1 and 2. We conclude that (i) individual differences in CPIR magnitude are stable over time; (ii) CPIR magnitudes predicted postprandial insulin responses and glucose tolerance; and (iii) a rapid rise in blood glucose is not sufficient to trigger a CPIR in mice.

Liver fibrosis pathologies and potentials of RNA based therapeutics modalities

Liver fibrosis (LF) occurs when the liver tissue responds to injury or inflammation by producing excessive amounts of scar tissue, known as the extracellular matrix. This buildup stiffens the liver tissue, hinders blood flow, and ultimately impairs liver function. Various factors can trigger this process, including bloodborne pathogens, genetic predisposition, alcohol abuse, non-steroidal anti-inflammatory drugs, non-alcoholic steatohepatitis, and non-alcoholic fatty liver disease. While some existing small-molecule therapies offer limited benefits, there is a pressing need for more effective treatments that can truly cure LF. RNA therapeutics have emerged as a promising approach, as they can potentially downregulate cytokine levels in cells responsible for liver fibrosis. Researchers are actively exploring various RNA-based therapeutics, such as mRNA, siRNA, miRNA, lncRNA, and oligonucleotides, to assess their efficacy in animal models. Furthermore, targeted drug delivery systems hold immense potential in this field. By utilizing lipid nanoparticles, exosomes, nanocomplexes, micelles, and polymeric nanoparticles, researchers aim to deliver therapeutic agents directly to specific biomarkers or cytokines within the fibrotic liver, increasing their effectiveness and reducing side effects. In conclusion, this review highlights the complex nature of liver fibrosis, its underlying causes, and the promising potential of RNA-based therapeutics and targeted delivery systems. Continued research in these areas could lead to the development of more effective and personalized treatment options for LF patients.

Dietary approaches for exploiting metabolic vulnerabilities in cancer

Renewed interest in tumor metabolism sparked an enthusiasm for dietary interventions to prevent and treat cancer. Changes in diet impact circulating nutrient levels in the plasma and the tumor microenvironment, and preclinical studies suggest that dietary approaches, including caloric and nutrient restrictions, can modulate tumor initiation, progression, and metastasis. Cancers are heterogeneous in their metabolic dependencies and preferred energy sources and can be addicted to glucose, fructose, amino acids, or lipids for survival and growth. This dependence is influenced by tumor type, anatomical location, tissue of origin, aberrant signaling, and the microenvironment. This review summarizes nutrient dependencies and the related signaling pathway activations that provide targets for nutritional interventions. We examine popular dietary approaches used as adjuvants to anticancer therapies, encompassing caloric restrictions, including time-restricted feeding, intermittent fasting, fasting-mimicking diets (FMDs), and nutrient restrictions, notably the ketogenic diet. Despite promising results, much of the knowledge on dietary restrictions comes from in vitro and animal studies, which may not accurately reflect real-life situations. Further research is needed to determine the optimal duration, timing, safety, and efficacy of dietary restrictions for different cancers and treatments. In addition, well-designed human trials are necessary to establish the link between specific metabolic vulnerabilities and targeted dietary interventions. However, low patient compliance in clinical trials remains a significant challenge.

Steady Laminar Flow Decreases Endothelial Glycolytic Flux While Enhancing Proteoglycan Synthesis and Antioxidant Pathways

Endothelial cells in steady laminar flow assume a healthy, quiescent phenotype, while endothelial cells in oscillating disturbed flow become dysfunctional. Since endothelial dysfunction leads to atherosclerosis and cardiovascular disease, it is important to understand the mechanisms by which endothelial cells change their function in varied flow environments. Endothelial metabolism has recently been proven a powerful tool to regulate vascular function. Endothelial cells generate most of their energy from glycolysis, and steady laminar flow may reduce endothelial glycolytic flux. We hypothesized that steady laminar but not oscillating disturbed flow would reduce glycolytic flux and alter glycolytic side branch pathways. In this study, we exposed human umbilical vein endothelial cells to static culture, steady laminar flow (20 dynes/cm2 shear stress), or oscillating disturbed flow (4 ± 6 dynes/cm2 shear stress) for 24 h using a cone-and-plate device. We then measured glucose and lactate uptake and secretion, respectively, and glycolytic metabolites. Finally, we explored changes in the expression and protein levels of endothelial glycolytic enzymes. Our data show that endothelial cells in steady laminar flow had decreased glucose uptake and 13C labeling of glycolytic metabolites while cells in oscillating disturbed flow did not. Steady laminar flow did not significantly change glycolytic enzyme gene or protein expression, suggesting that glycolysis may be altered through enzyme activity. Flow also modulated glycolytic side branch pathways involved in proteoglycan and glycosaminoglycan synthesis, as well as oxidative stress. These flow-induced changes in endothelial glucose metabolism may impact the atheroprone endothelial phenotype in oscillating disturbed flow.

Fructose regulates the pentose phosphate pathway and induces an inflammatory and resolution phenotype in Kupffer cells

Over-consumption of fructose in adults and children has been linked to increased risk of non-alcoholic fatty liver disease (NAFLD). Recent studies have highlighted the effect of fructose on liver inflammation, fibrosis, and immune cell activation. However, little work summarizes the direct impact of fructose on macrophage infiltration, phenotype, and function within the liver. We demonstrate that chronic fructose diet decreased Kupffer cell populations while increasing transitioning monocytes. In addition, fructose increased fibrotic gene expression of collagen 1 alpha 1 (Col1a1) and tissue metallopeptidase inhibitor 1 (Timp1) as well as inflammatory gene expression of tumor necrosis factor alpha (Tnfa) and expression of transmembrane glycoprotein NMB (Gpnmb) in liver tissue compared to glucose and control diets. Single cell RNA sequencing (scRNAseq) revealed fructose elevated expression of matrix metallopeptidase 12 (Mmp12), interleukin 1 receptor antagonist (Il1rn), and radical S-adenosyl methionine domain (Rsad2) in liver and hepatic macrophages. In vitro studies using IMKC and J774.1 cells demonstrated decreased viability when exposed to fructose. Additionally, fructose increased Gpnmb, Tnfa, Mmp12, Il1rn, and Rsad2 in unpolarized IMKC. By mass spectrometry, C13 fructose tracing detected fructose metabolites in glycolysis and the pentose phosphate pathway (PPP). Inhibition of the PPP further increased fructose induced Il6, Gpnmb, Mmp12, Il1rn, and Rsad2 in nonpolarized IMKC. Taken together, fructose decreases cell viability while upregulating resolution and anti-inflammatory associated genes in Kupffer cells.

Transcellular Barriers to Glucose Delivery in the Body

Glucose is the universal fuel of most mammalian cells, and it is largely replenished through dietary intake. Glucose availability to tissues is paramount for the maintenance of homeostatic energetics and, hence, supply should match demand by the consuming organs. In its journey through the body, glucose encounters cellular barriers for transit at the levels of the absorbing intestinal epithelial wall, the renal epithelium mediating glucose reabsorption, and the tight capillary endothelia (especially in the brain). Glucose transiting through these cellular barriers must escape degradation to ensure optimal glucose delivery to the bloodstream or tissues. The liver, which stores glycogen and generates glucose de novo, must similarly be able to release it intact to the circulation. We present the most up-to-date knowledge on glucose handling by the gut, liver, brain endothelium, and kidney, and discuss underlying molecular mechanisms and open questions. Diseases associated with defects in glucose delivery and homeostasis are also briefly addressed. We propose that the universal problem of sparing glucose from catabolism in favor of translocation across the barriers posed by epithelia and endothelia is resolved through common mechanisms involving glucose transfer to the endoplasmic reticulum, from where glucose exits the cells via unconventional cellular mechanisms.

Association between higher duodenal levels of the fructose carrier glucose transporter-5 and nonalcoholic fatty liver disease and liver fibrosis

BACKGROUND

An increased dietary fructose intake has been shown to exert several detrimental metabolic effects and contribute to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). An augmented intestinal abundance of the fructose carriers glucose transporter-5 (GLUT-5) and glucose transporter-2 (GLUT-2) has been found in subjects with obesity and type 2 diabetes. Herein, we investigated whether elevated intestinal levels of GLUT-5 and GLUT-2, resulting in a higher dietary fructose uptake, are associated with NAFLD and its severity.

METHODS

GLUT-5 and GLUT-2 protein levels were assessed on duodenal mucosa biopsies of 31 subjects divided into 2 groups based on ultrasound-defined NAFLD presence who underwent an upper gastrointestinal endoscopy.

RESULTS

Individuals with NAFLD exhibited increased duodenal GLUT-5 protein levels in comparison to those without NAFLD, independently of demographic and anthropometric confounders. Conversely, no difference in duodenal GLUT-2 abundance was observed amongst the two groups. Univariate correlation analyses showed that GLUT-5 protein levels were positively related with body mass index, waist circumference, fasting and 2 h post-load insulin concentrations, and insulin resistance (IR) degree estimated by homeostatic model assessment of IR (r = 0.44; p = 0.02) and liver IR (r = 0.46; p = 0.03) indexes. Furthermore, a positive relationship was observed between duodenal GLUT-5 abundance and serum uric acid concentrations (r = 0.40; p = 0.05), a product of fructose metabolism implicated in NAFLD progression. Importantly, duodenal levels of GLUT-5 were positively associated with liver fibrosis risk estimated by NAFLD fibrosis score.

CONCLUSION

Increased duodenal GLUT-5 levels are associated with NAFLD and liver fibrosis. Inhibition of intestinal GLUT-5-mediated fructose uptake may represent a strategy for prevention and treatment of NAFLD.

Ingestion of Bean Leaves Reduces Metabolic Complications and Restores Intestinal Integrity in C57BL/6 Mice with Obesity Induced by a High-Fat and High-Fructose Diet

Consumption of foods with fiber and compounds can promote gastrointestinal health and reduce obesity complications. Therefore, treatment with common bean leaves (BL) against obesity was evaluated in mice with a high-fat and high-fructose diet (HFFD) for 14 weeks. The bromatological and phytochemical characterization of BL were determined. Afterwards, the animals were supplemented with BL (10%) or a standard diet (SD) as a strategy to encourage a healthy diet for 12 additional weeks. Changes in body composition, lipid profile, and intestinal integrity were analyzed. The characterization of BL stood out for its content of 27.2% dietary fiber, total phenolics (475.04 mg/100 g), and saponins (2.2 mg/100 g). The visceral adipose tissue (VAT) decreased in the BL group by 52% compared to the HFFD group. Additionally, triglyceride levels were 23% lower in the BL consumption group compared to the HFFD group. The improvement in lipid profile was attributed to the 1.77-fold higher fecal lipid excretion in the BL consumption group compared to the HFFD group and the inhibition of pancreatic lipase by 29%. Furthermore, BL supplementation reduced the serum levels of IL-6 (4.4-fold) and FITC-dextran by 50% compared with those in the HFFD group. Metabolic endotoxemia was inhibited after BL supplementation (-33%) compared to the HFFD group. BL consumption as a treatment in obese mice reduces adipose tissue accumulation and improves the lipid profile. Furthermore, we report for the first time that BL consumption improves intestinal integrity.

Intestinal Morphology and Glucose Transporter Gene Expression under a Chronic Intake of High Sucrose

Sucrose is a disaccharide that is degraded into fructose and glucose in the small intestine. High-sucrose and high-fructose diets have been reported, using two-dimensional imaging, to alter the intestinal morphology and the expression of genes associated with sugar transport, such as sodium glucose co-transporter 1 (SGLT1), glucose transporter 2 (GLUT2), and glucose transporter 5 (GLUT5). However, it remains unclear how high-fructose and high-sucrose diets affect the expression of sugar transporters and the intestinal morphology in the whole intestine. We investigate the influence of a chronic high-sucrose diet on the expression of the genes associated with sugar transport as well as its effects on the intestinal morphology using 3D imaging. High sucrose was found to increase GLUT2 and GLUT5 mRNA levels without significant changes in the intestinal morphology using 3D imaging. On the other hand, the delay in sucrose absorption by an α-glucosidase inhibitor significantly improved the intestinal morphology and the expression levels of SGLT1, GLUT2, and GLUT5 mRNA in the distal small intestine to levels similar to those in the proximal small intestine, thereby improving glycemic control after both glucose and sucrose loading. These results reveal the effects of chronic high-sugar exposure on glucose absorption and changes in the intestinal morphology.

Effects of aging on glucose and lipid metabolism in mice

Aging is accompanied by multiple molecular changes that contribute to aging-associated pathologies, such as accumulation of cellular damage and mitochondrial dysfunction. Tissue metabolism can also change with age, in part because mitochondria are central to cellular metabolism. Moreover, the co-factor NAD+, which is reported to decline across multiple tissue types during aging, plays a central role in metabolic pathways such as glycolysis, the tricarboxylic acid cycle, and the oxidative synthesis of nucleotides, amino acids, and lipids. To further characterize how tissue metabolism changes with age, we intravenously infused [U-13C]-glucose into young and old C57BL/6J, WSB/EiJ, and Diversity Outbred mice to trace glucose fate into downstream metabolites within plasma, liver, gastrocnemius muscle, and brain tissues. We found that glucose incorporation into central carbon and amino acid metabolism was robust during healthy aging across these different strains of mice. We also observed that levels of NAD+, NADH, and the NAD+/NADH ratio were unchanged in these tissues with healthy aging. However, aging tissues, particularly brain, exhibited evidence of up-regulated fatty acid and sphingolipid metabolism reactions that regenerate NAD+ from NADH. Because mitochondrial respiration, a major source of NAD+ regeneration, is reported to decline with age, our data supports a model where NAD+-generating lipid metabolism reactions may buffer against changes in NAD+/NADH during healthy aging.

Fructose: a modulator of intestinal barrier function and hepatic health?

PURPOSE

Consumption of fructose has repeatedly been discussed to be a key factor in the development of health disturbances such as hypertension, diabetes type 2, and non-alcoholic fatty liver disease. Despite intense research efforts, the question if and how high dietary fructose intake interferes with human health has not yet been fully answered.

RESULTS

Studies suggest that besides its insulin-independent metabolism dietary fructose may also impact intestinal homeostasis and barrier function. Indeed, it has been suggested by the results of human and animal as well as in vitro studies that fructose enriched diets may alter intestinal microbiota composition. Furthermore, studies have also shown that both acute and chronic intake of fructose may lead to an increased formation of nitric oxide and a loss of tight junction proteins in small intestinal tissue. These alterations have been related to an increased translocation of pathogen-associated molecular patterns (PAMPs) like bacterial endotoxin and an induction of dependent signaling cascades in the liver but also other tissues.

CONCLUSION

In the present narrative review, results of studies assessing the effects of fructose on intestinal barrier function and their impact on the development of health disturbances with a particular focus on the liver are summarized and discussed.

Metabolomic and Transcriptomic Analysis of Effects of Three MUFA-Rich Oils on Hepatic Glucose and Lipid Metabolism in Mice

SCOPE

Olive oil, rapeseed oil, and lard are dietary fats rich in monounsaturated fatty acids, but the effects of dietary oils enriched in monounsaturated fatty acids on hepatic lipid deposition have seldom been compared.

METHODS AND RESULTS

Ninety 8-week-old C57BL/6J male mice are randomly divided into six groups and fed diets containing lard, rapeseed oil, or olive oil with a 10% or 45% fat energy supply for 16 weeks. Under high-fat conditions, serum total cholesterol levels in the lard and olive oil groups are significantly higher than those in the rapeseed oil group. Hepatic lipid content in the olive oil group is higher than that in the other two groups. Compared with rapeseed oil, lard increases the liver levels of arachidonic, palmitic, and myristic acids and decreases the levels of eicosapentaenoic linolenic acid and linoleic acid. Olive oil increases the liver levels of docosatrienoic, arachidonic, oleic, and myristic acids; maltose; and fructose and decreases the levels of eicosapentaenoic, linolenic, and linoleic acids.

CONCLUSION

Olive oil probably causes hepatic lipid deposition in mice, which may enhance hepatic lipid synthesis by activating the starch and sucrose metabolic pathways. By contrast, rapeseed oil shows a significant anti-lipid deposition effect on the liver.

Unmasking the enigma of lipid metabolism in metabolic dysfunction-associated steatotic liver disease: from mechanism to the clinic

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly defined as non-alcoholic fatty liver disease (NAFLD), is a disorder marked by the excessive deposition of lipids in the liver, giving rise to a spectrum of liver pathologies encompassing steatohepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma. Despite the alarming increase in its prevalence, the US Food and Drug Administration has yet to approve effective pharmacological therapeutics for clinical use. MASLD is characterized by the accretion of lipids within the hepatic system, arising from a disarray in lipid provision (whether through the absorption of circulating lipids or de novo lipogenesis) and lipid elimination (via free fatty acid oxidation or the secretion of triglyceride-rich lipoproteins). This disarray leads to the accumulation of lipotoxic substances, cellular pressure, damage, and fibrosis. Indeed, the regulation of the lipid metabolism pathway is intricate and multifaceted, involving a myriad of factors, such as membrane transport proteins, metabolic enzymes, and transcription factors. Here, we will review the existing literature on the key process of lipid metabolism in MASLD to understand the latest progress in this molecular mechanism. Notably, de novo lipogenesis and the roles of its two main transcription factors and other key metabolic enzymes are highlighted. Furthermore, we will delve into the realm of drug research, examining the recent progress made in understanding lipid metabolism in MASLD. Additionally, we will outline prospective avenues for future drug research on MASLD based on our unique perspectives.

Inflammation-induced TRIM21 represses hepatic steatosis by promoting the ubiquitination of lipogenic regulators

Nonalcoholic steatohepatitis (NASH) is a leading cause for chronic liver diseases. Current therapeutic options are limited due to an incomplete mechanistic understanding of how steatosis transitions to NASH. Here we show that the TRIM21 E3 ubiquitin ligase is induced by the synergistic actions of proinflammatory TNF-α and fatty acids in livers of humans and mice with NASH. TRIM21 ubiquitinates and degrades ChREBP, SREBP1, ACC1, and FASN, key regulators of de novo lipogenesis, and A1CF, an alternative splicing regulator of the high-activity ketohexokinase-C (KHK-C) isoform and rate-limiting enzyme of fructose metabolism. TRIM21-mediated degradation of these lipogenic activators improved steatosis and hyperglycemia as well as fructose and glucose tolerance. Our study identifies TRIM21 as a negative regulator of liver steatosis in NASH and provides mechanistic insights into an immunometabolic crosstalk that limits fatty acid synthesis and fructose metabolism during metabolic stress. Thus, enhancing this natural counteracting force of steatosis through inhibition of key lipogenic activators via TRIM21-mediated ubiquitination may provide a therapeutic opportunity to treat NASH.

High dietary fructose promotes hepatocellular carcinoma progression by enhancing O-GlcNAcylation via microbiota-derived acetate

Emerging studies have addressed the tumor-promoting role of fructose in different cancers. The effects and pathological mechanisms of high dietary fructose on hepatocellular carcinoma (HCC) remain unclear. Here, we examined the effects of fructose supplementation on HCC progression in wild-type C57BL/6 mice using a spontaneous and chemically induced HCC mouse model. We show that elevated uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) and O-GlcNAcylation levels induced by high dietary fructose contribute to HCC progression. Non-targeted metabolomics and stable isotope tracing revealed that under fructose treatment, microbiota-derived acetate upregulates glutamine and UDP-GlcNAc levels and enhances protein O-GlcNAcylation in HCC. Global profiling of O-GlcNAcylation revealed that hyper-O-GlcNAcylation of eukaryotic elongation factor 1A1 promotes cell proliferation and tumor growth. Targeting glutamate-ammonia ligase or O-linked N-acetylglucosamine transferase (OGT) remarkably impeded HCC progression in mice with high fructose intake. We propose that high dietary fructose promotes HCC progression through microbial acetate-induced hyper-O-GlcNAcylation.

Impact of Sustained Fructose Consumption on Gastrointestinal Function and Health in Wistar Rats: Glycoxidative Stress, Impaired Protein Digestion, and Shifted Fecal Microbiota

The gastrointestinal tract (GIT) is the target of assorted pathological conditions, and dietary components are known to affect its functionality and health. In previous in vitro studies, we observed that reducing sugars induced protein glycoxidation and impaired protein digestibility. To gain further insights into the pathophysiological effects of dietary sugars, Wistar rats were provided with a 30% (w/v) fructose water solution for 10 weeks. Upon slaughter, in vivo protein digestibility was assessed, and the entire GIT (digests and tissues) was analyzed for markers of oxidative stress and untargeted metabolomics. Additionally, the impact of sustained fructose intake on colonic microbiota was also evaluated. High fructose intake for 10 weeks decreased protein digestibility and promoted changes in the physiological digestion of proteins, enhancing intestinal digestion rather than stomach digestion. Moreover, at colonic stages, the oxidative stress was harmfully increased, and both the microbiota and the intraluminal colonic metabolome were modified.

The chronic consumption of dietary fructose promotes the gut Clostridium species imbalance and bile acid alterations in developing nonalcoholic fatty liver disease

Excessive fructose intake is associated with the rising prevalence of nonalcoholic fatty liver disease (NAFLD). The gut microbiome (GM) and bile acids (BAs) are involved in the pathogenesis of NAFLD, but the impact of fructose on their cross-talk is unclear. In this study, adult male C57BL/6J mice were fed a normal diet with tap water (ND) or with 4% fructose in the drinking water (Fru), 60% high-fat diet with tap water (HF) or with 4% fructose solution (HFF) for 12 weeks. Targeted BA analysis was performed in five anatomical sites including the liver, ileum contents, portal serum, cecum contents, and feces. Metagenomic sequencing was performed to explore gut dysbiosis. Within 12 weeks, the 4% fructose diet could initially stimulate gut dysbiosis and BA upregulation in the ileum, portal serum, and cecum when the intestinal and hepatic transport system remained stable without hepatic lipid accumulation. However, the chronic consumption of fructose promoted HF-induced NAFLD, with significantly increased body weight, impaired glucose tolerance, and advanced liver steatosis. BA transporters were inhibited in HFF, causing the block of internal BA circulation and increased BA secretion via cecum contents and feces. Notably, lithocholic acid (LCA) and its taurine conjugates were elevated within the enterohepatic circulation. Meanwhile, the Clostridium species were significantly altered in both Fru and HFF groups and were closely associated with fructose and BA metabolism. In summary, excessive fructose caused gut dysbiosis and BA alterations, promoting HF-induced NAFLD. The crosstalk between Clostridium sp. and LCA species were potential targets in fructose-mediated NAFLD.

The Impact and Burden of Dietary Sugars on the Liver

NAFLD, or metabolic dysfunction-associated steatotic liver disease, has increased in prevalence hand in hand with the rise in obesity and increased free sugars in the food supply. The causes of NAFLD are genetic in origin combined with environmental drivers of the disease phenotype. Dietary intake of added sugars has been shown to have a major role in the phenotypic onset and progression of the disease. Simple sugars are key drivers of steatosis, likely through fueling de novo lipogenesis, the conversion of excess carbohydrates into fatty acids, but also appear to upregulate lipogenic metabolism and trigger hyperinsulinemia, another driver. NAFLD carries a clinical burden as it is associated with obesity, type 2 diabetes, metabolic syndrome, and cardiovascular disease. Patient quality of life is also impacted, and there is an enormous economic burden due to healthcare use, which is likely to increase in the coming years. This review aims to discuss the role of dietary sugar in NAFLD pathogenesis, the health and economic burden, and the promising potential of sugar reduction to improve health outcomes for patients with this chronic liver disease.

GLUT5: structure, functions, diseases and potential applications

Glucose transporter 5 (GLUT5) is a membrane transporter that specifically transports fructose and plays a key role in dietary fructose uptake and metabolism. In recent years, a high fructose diet has occupied an important position in the daily intake of human beings, resulting in a significant increase in the incidence of obesity and metabolic diseases worldwide. Over the past few decades, GLUT5 has been well understood to play a significant role in the pathogenesis of human digestive diseases. Recently, the role of GLUT5 in human cancer has received widespread attention, and a large number of studies have focused on exploring the effects of changes in GLUT5 expression levels on cancer cell survival, metabolism and metastasis. However, due to various difficulties and shortcomings, the molecular structure and mechanism of GLUT5 have not been fully elucidated, which to some extent prevents us from revealing the relationship between GLUT5 expression and cell carcinogenesis at the protein molecular level. In this review, we summarize the current understanding of the structure and function of mammalian GLUT5 and its relationship to intestinal diseases and cancer and suggest that GLUT5 may be an important target for cancer therapy.

Association of sugar-sweetened beverages with the risk of colorectal cancer: a systematic review and meta-analysis

The association between sugar-sweetened beverages intake and colorectal cancer (CRC) remains controversial. A metaanalysis was performed to clarify the correlation between sugar-sweetened beverages and CRC risk/mortality. A systematic literature search was conducted in PubMed, Web of Science, Embase, China National Knowledge Infrastructure (CNKI), Sinomed (CBM), Wanfang Data Knowledge Service Platform, and China Science and Technology Journal VIP database. Articles were restricted to be available in any language until March 31, 2022. The highest exposed categories were used to calculate the pooled relative risks (RR) values. Pooled relative risks (RR) and 95% confidence intervals (CI) were used to estimate the association of sugar-sweetened beverages with CRC risk and mortality. Heterogeneity was assessed with the Cochran Q statistic and quantified with the I2 statistic. A total of 17 studies (6 case-control and 11 cohort) involving 557,391 subjects were included in this meta-analysis. The pooled RRs for CRC incidence and mortality among people taking sugar-sweetened beverages were 1.17 (95% CI: 1.07-1.28) and 1.13 (95% CI: 0.99-1.29), respectively. In subgroup analysis, a correlation was found in the distal colon with a pooled RR of 1.41 (95% CI: 1.10-1.80). There was no correlation in the proximal colon with a pooled RR of 1.58 (95% CI: 0.79-3.17). We found statistically significant associations between CRC incidence and sugar-sweetened beverages intake in North America and Oceania, with pooled RRs of 1.16 (95% CI: 1.00-1.33) and 1.32 (95% CI: 1.13-1.55), respectively. In sensitivity analysis, after excluding each study and calculating heterogeneity and effect sizes, there was still a correlation between sugar-sweetened beverages intake and CRC risk. This meta-analysis suggests that sugar-sweetened beverages intake may increase CRC risk, independent of CRC mortality. Whether CRC risk increases with increased sugar-sweetened beverage intake needs further investigation in the future. This meta-analysis aimed to indicate the relationship between sugar-sweetened beverages intake and the risk and mortality of colorectal cancer. A total of 17 studies involving 557,391 subjects were included. The results showed that sugar-sweetened beverages may increase the risk of colorectal cancer but may not be associated with colorectal cancer mortality.

Fructose aggravates copper-deficiency-induced non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), is the most common cause of chronic liver disease, affecting 24% of the global population. Accumulating evidence demonstrates that copper deficiency (CuD) is implicated in the development of NAFLD, besides, high fructose consumption by promoting inflammation contributes to NAFLD. However, how CuD and/or fructose (Fru) causes NAFLD is not clearly delineated. The present study aims to investigate the role of CuD and/or fructose supplement on hepatic steatosis and hepatic injury. We established a CuD rat model by feeding weaning male Sprague-Dawley rats for 4 weeks with CuD diet. Fructose was supplemented in drinking water. We found the promoting role of CuD or Fructose (Fru) in the progress of NAFLD, which was aggravated by combination of the two. Furthermore, we presented the alteration of hepatic lipid profiles (including content, composition, and saturation), especially ceramide (Cer), cardiolipin (CL), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was closely associated with CuD and/or Fru fed induced-NAFLD in rat models. In conclusion, insufficient copper intake or excessive fructose supplement resulted in adverse effects on the hepatic lipid profile, and fructose supplement causes a further hepatic injury in CuD-induced NAFLD, which illuminated a better understanding of NAFLD.

Genetic ablation of ketohexokinase C isoform impairs pancreatic cancer development

Although dietary fructose is associated with an elevated risk for pancreatic cancer, the underlying mechanisms remain elusive. Here, we report that ketohexokinase (KHK), the rate-limiting enzyme of fructose metabolism, is a driver of PDAC development. We demonstrate that fructose triggers KHK and induces fructolytic gene expression in mouse and human PDAC. Genetic inactivation of KhkC enhances the survival of KPC-driven PDAC even in the absence of high fructose diet. Furthermore, it decreases the viability, migratory capability, and growth of KPC cells in a cell autonomous manner. Mechanistically, we demonstrate that genetic ablation of KHKC strongly impairs the activation of KRAS-MAPK pathway and of rpS6, a downstream target of mTORC signaling. Moreover, overexpression of KHKC in KPC cells enhances the downstream KRAS pathway and cell viability. Our data provide new insights into the role of KHK in PDAC progression and imply that inhibiting KHK could have profound implications for pancreatic cancer therapy.

Early life high fructose exposure disrupts microglia function and impedes neurodevelopment

Despite the success of fructose as a low-cost food additive, recent epidemiological evidence suggests that high fructose consumption by pregnant mothers or during adolescence is associated with disrupted neurodevelopment 1-7 . An essential step in appropriate mammalian neurodevelopment is the synaptic pruning and elimination of newly-formed neurons by microglia, the central nervous system's (CNS) resident professional phagocyte 8-10 . Whether early life high fructose consumption affects microglia function and if this directly impacts neurodevelopment remains unknown. Here, we show that both offspring born to dams fed a high fructose diet and neonates exposed to high fructose exhibit decreased microglial density, increased uncleared apoptotic cells, and decreased synaptic pruning in vivo . Importantly, deletion of the high affinity fructose transporter SLC2A5 (GLUT5) in neonates completely reversed microglia dysfunction, suggesting that high fructose directly affects neonatal development. Mechanistically, we found that high fructose treatment of both mouse and human microglia suppresses synaptic pruning and phagocytosis capacity which is fully reversed in GLUT5-deficient microglia. Using a combination of in vivo and in vitro nuclear magnetic resonance- and mass spectrometry-based fructose tracing, we found that high fructose drives significant GLUT5-dependent fructose uptake and catabolism, rewiring microglia metabolism towards a hypo-phagocytic state. Importantly, mice exposed to high fructose as neonates exhibited cognitive defects and developed anxiety-like behavior which were rescued in GLUT5-deficient animals. Our findings provide a mechanistic explanation for the epidemiological observation that early life high fructose exposure is associated with increased prevalence of adolescent anxiety disorders.

Microbiota dysbiosis caused by dietetic patterns as a promoter of Alzheimer's disease through metabolic syndrome mechanisms

Microbiota dysbiosis and metabolic syndrome, consequences of a non-adequate diet, generate a feedback pathogenic state implicated in Alzheimer's disease development. The lower production of short chain fatty acids (SCFAs) under dysbiosis status leads to lipid homeostasis deregulation and decreases Angptl4 release and AMPK activation in the adipose tissue, promoting higher lipid storage (adipocyte hypertrophy) and cholesterol levels. Also, low SCFA generation reduces GPR41 and GPR43 receptor activation at the adipose tissue (increasing leptin release and leptin receptor resistance) and intestinal levels, reducing the release of GLP-1 and YPP. Therefore, lower satiety sensation and energy expenditure occur, promoting a weight gaining environment mediated by higher food intake and lipid storage, developing dyslipemia. In this context, higher glucose levels, together with higher free fatty acids in the bloodstream, promote glycolipotoxicity, provoking a reduction in insulin released, insulin receptor resistance, advanced glycation products (AGEs) and type 2 diabetes. Intestinal dysbiosis and low SCFAs reduce bacterial biodiversity, increasing lipopolysaccharide (LPS)-producing bacteria and intestinal barrier permeability. Higher amounts of LPS pass to the bloodstream (endotoxemia), causing a low-grade chronic inflammatory state characterized by higher levels of leptin, IL-1β, IL-6 and TNF-α, together with a reduced release of adiponectin and IL-10. At the brain and neuronal levels, the generated insulin resistance, low-grade chronic inflammation, leptin resistance, AGE production and LPS increase directly impact the secretase enzymes and tau hyperphosphorylation, creating an enabling environment for β-amyloid senile plaque and tau tangled formations and, as a consequence, Alzheimer's initiation, development and maintenance.