Chronic high fructose intake reduces serum 1,25 (OH)2D3 levels in calcium-sufficient rodents

Intake and serum levels of micronutrients and chronic oral diseases burden

OBJECTIVE

To investigate pathways from micronutrient intake and serum levels to Chronic Oral Diseases Burden.

METHODS

We analyzed cross-sectional data from NHANES III (n = 7936) and NHANES 2011-2014 (n = 4929). The exposure was the intake and serum levels of vitamin D, calcium, and phosphorus. Considering the high correlation of those micronutrients in the diet, they were analyzed as a latent variable dubbed Micronutrient intake. The outcome was the Chronic Oral Diseases Burden, a latent variable formed by probing pocket depth, clinical attachment loss, furcation involvement, caries, and missing teeth. Pathways triggered by gender, age, socioeconomic status, obesity, smoking, and alcohol were also estimated using structural equation modeling.

RESULTS

In both NHANES cycles, micronutrient intake (p-value < 0.05) and vitamin D serum (p-value < 0.05) were associated with a lower Chronic Oral Diseases Burden. Micronutrient intake reduced the Chronic Oral Diseases Burden via vitamin D serum (p-value < 0.05). Obesity increased the Chronic Oral Diseases Burden by reducing vitamin D serum (p-value < 0.05).

CONCLUSION

Higher micronutrient intake and higher vitamin D serum levels seem to reduce Chronic Oral Diseases Burden. Healthy diet policies may jointly tackle caries, periodontitis, obesity, and other non-communicable diseases.

Vitamin D insufficiency is high in Malaysia: A systematic review and meta-analysis of studies on vitamin D status in Malaysia

PURPOSE

To estimate the vitamin D status of participants residing in Malaysia.

METHODS

PubMed, Scopus, Web of Science, and MyJurnal were searched up to June 2022 without language restrictions. Studies that reported the 25-hydroxyvitamin D [25(OH)D] concentrations and defined their cut-off for deficiency or insufficiency from healthy participants residing in Malaysia were included. The random effects model was used to pool vitamin D status using established cut-offs of <30, <50, and <75 nmol/L according to age group.

RESULTS

From 299 studies screened, 32 studies were included in the meta-analysis. The pooled proportion for <30 nmol/L was 21% (95% CI 9-36, n = 2,438 from 10 studies), while the pooled proportion <50 nmol/L was 64% (95% CI 56-72, n = 13,977 from 30 studies), and <75 nmol/L was 85% (95% CI 61-100, n = 1,376 from five studies). Heterogeneity was high (I2 ranged from 98-99%). Higher proportions of vitamin D insufficiency (defined as <50 nmol/L) were found in participants living in the urban areas (compared to rural areas), in females (compared to males), and in Malays and Malaysian Indians (compared to Malaysian Chinese) ethnicities.

CONCLUSION

More than half of Malaysians have insufficient vitamin D levels, despite being a country that is close to the equator. We strongly urge prompt public health measures to improve the vitamin D status in Malaysia.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021260259].

Excessive fructose intake inhibits skeletal development in adolescent rats via gut microbiota and energy metabolism

Excessive fructose intake from desserts and beverages may influence bone development among adolescents. The gut microbiota (GM) and energy metabolism play important roles in bone development. In this study, 40 female adolescent rats were randomly assigned to the control group, the fructose group with two concentrations, and the glucose group as the positive control group. After 10 weeks, serum glucose and lipids were detected by means of an automatic analyzer, and the bone microstructure was analyzed by Micro-CT. Then, the GM was determined via 16S rRNA sequencing analysis, and energy metabolism was detected by measuring serum carbohydrate metabolites. At last, bone metabolism markers were measured via ELISA kits. The results showed that excessive fructose intake could increase body weight and influence the glucolipid metabolism of female adolescent rats. Meanwhile, the bone microstructures were impaired with excessive fructose intake. Mechanistically, excessive fructose intake shifted the GM of rats with the decrease of Lachnospiraceae, Ruminococcaceae, and increase of Allobaculum, Lachnospiraceae. Energy metabolism analysis suggested that most metabolites of fructose did not enter the tricarboxylic acid cycle to provide energy for the body’s development. Furthermore, serum bone metabolism markers showed that excessive fructose intake could decrease both bone formation and resorption. Our results suggested that excessive fructose intake could inhibit skeletal development in adolescents. One potential mechanism might be that it affected the intestinal microbiota homeostasis in the juvenile body, thus changing the energy metabolism level, and ultimately affecting the bone metabolic balance.

Naringin Prevents Bone Damage in the Experimental Metabolic Syndrome Induced by a Fructose Rich Diet

We have analyzed the effect of naringin (NAR), a flavonoid from citric fruits, on bone quality and bone biomechanical properties as well as the redox state of bone marrow in rats fed a fructose rich diet (FRD), an experimental model to mimic human metabolic syndrome. NAR blocked the enhancement in the number of osteoclasts and adipocytes and the decrease in the number of osteocytes and osteocalcin (+) cells caused by FRD. The trabecular number was significantly higher in the FRD+NAR group. FRD induced a decrease in femoral trabecular and cortical bone mineral density, which was blocked by NAR. The fracture and ultimate loads were also decreased by the FRD and FRD+NAR groups. NAR increased the number of nodes to terminal trabecula, the number of nodes to node trabecula, the number of nodes, and the number of nodes with two terminals, and decreased the Dist (mean size of branches) value. Bone marrow catalase activity was decreased by the FRD, an effect prevented by NAR. In conclusion, FRD produces detrimental effects on long bones, which are associated with oxidative stress in bone marrow. Most of these changes are avoided by NAR through its antioxidant properties and promotion of bone formation. Novelty bullets: • Fructose rich diet produces detrimental effects on long bones, which are associated with oxidative stress in bone marrow. • Most of these changes are avoided by Naringin through its antioxidant properties and promotion of bone formation.

Expression of SARS-CoV-2 entry factors, electrolyte, and mineral transporters in different mouse intestinal epithelial cell types

Angiotensin-converting enzyme 2 (ACE2) and transmembrane proteases (TMPRSS) are multifunctional proteins required for SARS-CoV-2 infection or for amino acid (AA) transport, and are abundantly expressed in mammalian small intestine, but the identity of the intestinal cell type(s) and sites of expression are unclear. Here we determined expression of SARS-CoV-2 entry factors in different cell types and then compared it to that of representative AA, electrolyte, and mineral transporters. We tested the hypothesis that SARS-CoV-2, AA, electrolyte, and mineral transporters are expressed heterogeneously in different intestinal cell types by making mouse enteroids enriched in enterocytes (ENT), goblet (GOB), Paneth (PAN), or stem (ISC) cells. Interestingly, the expression of ACE2 was apical and modestly greater in ENT, the same pattern observed for its associated AA transporters B0 AT1 and SIT1. TMPRSS2 and TMPRSS4 were more highly expressed in crypt-residing ISC. Expression of electrolyte transporters was dramatically heterogeneous. DRA, NBCe1, and NHE3 were greatest in ENT, while those of CFTR and NKCC1 that play important roles in secretory diarrhea, were mainly expressed in ISC and PAN that also displayed immunohistochemically abundant basolateral NKCC1. Intestinal iron transporters were generally expressed higher in ENT and GOB, while calcium transporters were expressed mainly in PAN. Heterogeneous expression of its entry factors suggests that the ability of SARS-CoV-2 to infect the intestine may vary with cell type. Parallel cell-type expression patterns of ACE2 with B0 AT1 and SIT1 provides further evidence of ACE2's multifunctional properties and importance in AA absorption.

Bone Growth is Influenced by Fructose in Adolescent Male Mice Lacking Ketohexokinase (KHK)

Fructose is metabolized in the cytoplasm by the enzyme ketohexokinase (KHK), and excessive consumption may affect bone health. Previous work in calcium-restricted, growing mice demonstrated that fructose disrupted intestinal calcium transport. Thus, we hypothesized that the observed effects on bone were dependent on fructose metabolism and took advantage of a KHK knockout (KO) model to assess direct effects of high plasma fructose on the long bones of growing mice. Four groups (n = 12) of 4-week-old, male, C57Bl/6 background, congenic mice with intact KHK (wild-type, WT) or global knockout of both isoforms of KHK-A/C (KHK-KO), were fed 20% glucose (control diet) or fructose for 8 weeks. Dietary fructose increased by 40-fold plasma fructose in KHK-KO compared to the other three groups (p < 0.05). Obesity (no differences in epididymal fat or body weight) or altered insulin was not observed in either genotype. The femurs of KHK-KO mice with the highest levels of plasma fructose were shorter (2%). Surprisingly, despite the long-term blockade of KHK, fructose feeding resulted in greater bone mineral density, percent volume, and number of trabeculae as measured by µCT in the distal femur of KHK-KO. Moreover, higher plasma fructose concentrations correlated with greater trabecular bone volume, greater work-to-fracture in three-point bending of the femur mid-shaft, and greater plasma sclerostin. Since the metabolism of fructose is severely inhibited in the KHK-KO condition, our data suggest mechanism(s) that alter bone growth may be related to the plasma concentration of fructose.

Effectiveness of vitamin D supplementation in Swedish children may be negatively impacted by BMI and serum fructose

In regions where sunlight exposure is limited, dietary vitamin D intake becomes important for maintaining status. However, Swedish children have been shown to have deficient or marginal status during the winter months even if the recommended dietary intake is met. Since low vitamin D status has been associated with several disease states, this study investigated the metabolic changes associated with improved vitamin D status due to supplementation. During the 3 winter months, 5-7-year-old children (n=170) in northern (Umeå, 63° N) and southern (Malmö, 55° N) Sweden were supplemented daily with 2 (placebo), 10 or 25 μg of vitamin D. BMI-for-age z-scores (BAZ), S-25(OH)D concentrations, insulin concentrations and the serum metabolome were assessed at baseline and follow-up. S-25(OH)D concentrations increased significantly in both supplementation groups (P<.001). Only arginine and isopropanol concentrations exhibited significant associations with improvements in S-25(OH)D. Furthermore, the extent to which S-25(OH)D increased was correlated with a combination of baseline BAZ and the change in serum fructose concentrations from baseline to follow up (P=.012). In particular, the change in S-25(OH)D concentrations was negatively correlated (P=.030) with the change in fructose concentrations for subjects with BAZ ≥0 and consuming at least 20 μg vitamin D daily. These results suggest that although the metabolic changes associated with improved vitamin D status are small, the effectiveness of dietary supplementation may be influenced by serum fructose concentrations.

The deficiency and the supplementation of vitamin D and liver: Lessons of chronic fructose-rich diet in mice

The fructose added to soft drinks and processed food, as well as frequent detection of vitamin D deficiency in the body, are two insults increasingly considered to cause lesions in target organs. We studied the liver after a chronic high-fructose diet deficient and supplemented with vitamin D. Sixty C57BL/6 mature male mice were allocated into six groups (n = 10) for ten weeks: control (C), control deficient in vitamin D (CDD), control supplemented with vitamin D (CDS), fructose (F), fructose deficient in vitamin D (FDD), and fructose supplemented with vitamin D (FDS). The gene expressions of vitamin D receptor and CYP27B1 and 25 hydroxyvitamin D plasma level ensured that the diets caused vitamin D deficiency or supplementation. Body mass did not change, but blood pressure (BP) increased in CDD, F, and FDD, whereas BP was controlled in FDS. Insulinemia, insulin tolerance and resistance were seen in both vitamin D deficiency and fructose groups but improved with vitamin D supplementation. The steatosis and fibrosis were observed in the CDD, F and FDD groups. Also, F and FDD showed activation of stellate cells (HSC). Lipogenesis and inflammation gene expressions were enhanced in the CDD, F and FDD groups, but diminished with vitamin D supplementation. In conclusion, we demonstrated the adverse effects of vitamin D deficiency on metabolism, liver steatosis and, combined with fructose intake, liver interstitial fibrosis with hepatic stellate cell activation, and alteration of the lipogenesis, beta-oxidation, and liver inflammation. All these data improved when vitamin D was supplemented in the animals.

Glutathione depleting drugs, antioxidants and intestinal calcium absorption

Glutathione (GSH) is a tripeptide that constitutes one of the main intracellular reducing compounds. The normal content of GSH in the intestine is essential to optimize the intestinal Ca²⁺ absorption. The use of GSH depleting drugs such as DL-buthionine-S,R-sulfoximine, menadione or vitamin K₃, sodium deoxycholate or diets enriched in fructose, which induce several features of the metabolic syndrome, produce inhibition of the intestinal Ca²⁺ absorption. The GSH depleting drugs switch the redox state towards an oxidant condition provoking oxidative/nitrosative stress and inflammation, which lead to apoptosis and/or autophagy of the enterocytes. Either the transcellular Ca²⁺ transport or the paracellular Ca²⁺ route are altered by GSH depleting drugs. The gene and/or protein expression of transporters involved in the transcellular Ca²⁺ pathway are decreased. The flavonoids quercetin and naringin highly abrogate the inhibition of intestinal Ca²⁺ absorption, not only by restoration of the GSH levels in the intestine but also by their anti-apoptotic properties. Ursodeoxycholic acid, melatonin and glutamine also block the inhibition of Ca²⁺ transport caused by GSH depleting drugs. The use of any of these antioxidants to ameliorate the intestinal Ca²⁺ absorption under oxidant conditions associated with different pathologies in humans requires more investigation with regards to the safety, pharmacokinetics and pharmacodynamics of them.

Intestinal Absorption of Fructose

Increased understanding of fructose metabolism, which begins with uptake via the intestine, is important because fructose now constitutes a physiologically significant portion of human diets and is associated with increased incidence of certain cancers and metabolic diseases. New insights in our knowledge of intestinal fructose absorption mediated by the facilitative glucose transporter GLUT5 in the apical membrane and by GLUT2 in the basolateral membrane are reviewed. We begin with studies related to structure as well as ligand binding, then revisit the controversial proposition that apical GLUT2 is the main mediator of intestinal fructose absorption. The review then describes how dietary fructose may be sensed by intestinal cells to affect the expression and activity of transporters and fructolytic enzymes, to interact with the transport of certain minerals and electrolytes, and to regulate portal and peripheral fructosemia and glycemia. Finally, it discusses the potential contributions of dietary fructose to gastrointestinal diseases and to the gut microbiome.

Two Cases of Mistaken Polyuria and Nephrocalcinosis in Infants with Glucose-Galactose Malabsorption: A Possible Role of 1,25(OH)2D3

BACKGROUND/AIMS

Glucose-galactose malabsorption (GGM) is a rare and potentially fatal disorder. The autosomal recessive mutation of the SGLT1 gene interferes with the active glucose transport in the gut resulting in osmotic diarrhea and failure to thrive (FTT). Two nonrelated infants with GGM are presented as well as a novel mutation in SGLT1.

CASE PRESENTATION

The first case consulted for FTT and presented with hypercalcemia and hypercalciuria. His mother had self-medicated with high doses of vitamin D. The second case consulted for macroscopic hematuria, and presented with dehydration and secondary acute kidney injury. In both cases, the profuse diarrhea, initially mistaken for polyuria, promptly resolved after the introduction of glucose-galactose-free milk. Investigations showed bilateral nephrocalcinosis and high levels of 1,25(OH)2D3 in both patients. We hypothesize that the upregulation of epithelial calcium channels (TRPV6) and 1,25(OH)2D3 are possible factors involved in the pathophysiology of nephrocalcinosis sometimes seen in GGM. Furthermore, a novel intronic SGLT1 mutation (c.207+2dup) is described.

CONCLUSION

These 2 cases demonstrate that a malabsorption disorder such as GGM can present with nephrocalcinosis and/or hypercalcemia, with increased 1,25(OH)2D3 levels in infants. Prompt recognition of GGM is sometimes difficult but crucial.
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Naringin prevents the inhibition of intestinal Ca2+ absorption induced by a fructose rich diet

This study tries to elucidate the mechanisms by which fructose rich diets (FRD) inhibit the rat intestinal Ca²⁺ absorption, and determine if any or all underlying alterations are prevented by naringin (NAR). Male rats were divided into: 1) controls, 2) treated with FRD, 3) treated with FRD and NAR. The intestinal Ca²⁺ absorption and proteins of the transcellular and paracellular Ca²⁺ pathways were measured. Oxidative/nitrosative stress and inflammation parameters were evaluated. FRD rats showed inhibition of the intestinal Ca²⁺ absorption and decrease in the protein expression of molecules of both Ca²⁺ pathways, which were blocked by NAR. FRD rats showed an increase in the superoxide anion, a decrease in the glutathione and in the enzymatic activities of the antioxidant system, as well as an increase in the NO content and in the nitrotyrosine content of proteins. They also exhibited an increase in both IL-6 and nuclear NF-κB. All these changes were prevented by NAR. In conclusion, FRD inhibit both pathways of the intestinal Ca²⁺ absorption due to the oxidative/nitrosative stress and inflammation. Since NAR prevents the oxidative/nitrosative stress and inflammation, it might be a drug to avoid alteration in the intestinal Ca²⁺ absorption caused by FRD.

Effect of dietary fructose on portal and systemic serum fructose levels in rats and in KHK-/- and GLUT5-/- mice

Elevated blood fructose concentrations constitute the basis for organ dysfunction in fructose-induced metabolic syndrome. We hypothesized that diet-induced changes in blood fructose concentrations are regulated by ketohexokinase (KHK) and the fructose transporter GLUT5. Portal and systemic fructose concentrations determined by HPLC in wild-type mice fed for 7 days 0% free fructose were <0.07 mM, were independent of time after feeding, were similar to those of GLUT5(-/-), and did not lead to hyperglycemia. Postprandial fructose levels, however, increased markedly in those fed isocaloric 20% fructose, causing significant hyperglycemia. Deletion of KHK prevented fructose-induced hyperglycemia, but caused dramatic hyperfructosemia (>1 mM) with reversed portal to systemic gradients. Systemic fructose in wild-type and KHK(-/-) mice changed by 0.34 and 1.8 mM, respectively, for every millimolar increase in portal fructose concentration. Systemic glucose varied strongly with systemic, but not portal, fructose levels in wild-type, and was independent of systemic and portal fructose in KHK(-/-), mice. With ad libitum feeding for 12 wk, fructose-induced hyperglycemia in wild-type, but not hyperfructosemia in KHK(-/-) mice, increased HbA1c concentrations. Increasing dietary fructose to 40% intensified the hyperfructosemia of KHK(-/-) and the fructose-induced hyperglycemia of wild-type mice. Fructose perfusion or feeding in rats also caused duration- and dose-dependent hyperfructosemia and hyperglycemia. Significant levels of blood fructose are maintained independent of dietary fructose, KHK, and GLUT5, probably by endogenous synthesis of fructose. KHK prevents hyperfructosemia and fructose-induced hyperglycemia that would markedly increase HbA1c levels. These findings explain the hyperfructosemia of human hereditary fructosuria as well as the hyperglycemia of fructose-induced metabolic syndrome.

An assessment of molecular pathways of obesity susceptible to nutrient, toxicant and genetically induced epigenetic perturbation

In recent years, the etiology of human disease has greatly improved with the inclusion of epigenetic mechanisms, in particular as a common link between environment and disease. However, for most diseases we lack a detailed interpretation of the epigenetic regulatory pathways perturbed by environment and causal mechanisms. Here, we focus on recent findings elucidating nutrient-related epigenetic changes linked to obesity. We highlight studies demonstrating that obesity is a complex disease linked to disruption of epigenetically regulated metabolic pathways in the brain, adipose tissue and liver. These pathways regulate (1) homeostatic and hedonic eating behaviors, (2) adipocyte differentiation and fat accumulation, and (3) energy expenditure. By compiling these data, we illustrate that obesity-related phenotypes are repeatedly linked to disruption of critical epigenetic mechanisms that regulate key metabolic genes. These data are supported by genetic mutation of key epigenetic regulators, and many of the diet-induced epigenetic mechanisms of obesity are also perturbed by exposure to environmental toxicants. Identifying similarly perturbed epigenetic mechanisms in multiple experimental models of obesity strengthens the translational applications of these findings. We also discuss many of the ongoing challenges to understanding the role of environmentally induced epigenetic pathways in obesity and suggest future studies to elucidate these roles. This assessment illustrates our current understanding of molecular pathways of obesity that are susceptible to environmental perturbation via epigenetic mechanisms. Thus, it lays the groundwork for dissecting the complex interactions between diet, genes and toxicants that contribute to obesity and obesity-related phenotypes.

Lifestyle and Dietary Factors Associated with Serum 25-Hydroxyvitamin D Levels in Korean Young Adults

Inadequate vitamin D status is highly prevalent in the Korean population, especially among young adults. Nonetheless, correlates of suboptimal vitamin D levels in young adults are not well defined. This study aimed to investigate potentially modifiable determinants of vitamin D levels in young adults in Korea. This cross-sectional study was based on health check-up data from 3,450 healthy male and female university students aged 18-29 yr in Seoul between April and May 2013. Serum 25-hydroxyvitamin D [25(OH)D] levels were determined using chemiluminescent immunoassay. Anthropometric data were measured, and lifestyle, dietary, and sociodemographic factors were obtained through self-administered questionnaires. General linear regression was used to assess correlates of serum 25(OH)D levels. The mean serum 25(OH)D level was 11.1 ng/mL, and the prevalence of 25(OH)D levels less than 10 ng/mL was 44.7% (39.5% in men, 50.2% in women). In a final multivariable model, significant positive correlates of serum 25(OH)D were older age, male sex, increased physical activity, sunlight exposure ≥ 30 min/day, eating breakfast regularly, consumption of dairy and fatty fish, and use of vitamin D-containing supplements. In contrast, significant inverse correlates were obesity (body mass index, BMI ≥ 25 kg/m(2)) or underweight (BMI < 18.5 kg/m(2)), abdominal obesity, increased sedentary time, and frequent consumption of instant noodles and sugar-sweetened beverages. In conclusion, many modifiable lifestyle and dietary factors were associated with low serum 25(OH)D levels in Korean young adults. Further studies on potential mechanisms of the correlates and optimal strategies to improve vitamin D status in this vulnerable subpopulation are warranted.