Chronic High Fructose Intake Reduces Serum 1,25 (OH)2D-3 Levels in Calcium-Sufficient Rodents

Excessive fructose consumption inhibits adaptive increases in intestinal Ca2+ transport in lactating and weanling rats with increased Ca2+ requirements by preventing the increase in serum levels of 1,25(OH)(2)D-3. Here we tested the hypothesis that chronic fructose intake decreases 1,25(OH)(2)D-3 levels independent of increases in Ca2+ requirements. Adult mice fed for five wk a high glucose-low Ca2+ diet displayed expected compensatory increases in intestinal and renal Ca2+ transporter expression and activity, in renal CYP27B1 (coding for 1 alpha-hydroxylase) expression as well as in serum 1,25(OH)(2)D-3 levels, compared with mice fed isocaloric glucose- or fructose-normal Ca2+ diets. Replacing glucose with fructose prevented these increases in Ca2+ transporter, CYP27B1, and 1,25(OH)(2)D-3 levels induced by a low Ca2+ diet. In adult mice fed for three mo a normal Ca2+ diet, renal expression of CYP27B1 and of CYP24A1 (24-hydroxylase) decreased and increased, respectively, when the carbohydrate source was fructose instead of glucose or starch. Intestinal and renal Ca2+ transporter activity and expression did not vary with dietary carbohydrate. To determine the time course of fructose effects, a high fructose or glucose diet with normal Ca2+ levels was fed to adult rats for three mo. Serum levels of 1,25(OH)(2)D-3 decreased and of FGF23 increased significantly over time. Renal expression of CYP27B1 and serum levels of 1,25(OH)(2)D-3 still decreased in fructose-compared to those in glucose-fed rats after three mo. Serum parathyroid hormone, Ca2+ and phosphate levels were normal and independent of dietary sugar as well as time of feeding. Thus, chronically high fructose intakes can decrease serum levels of 1,25(OH)(2)D-3 in adult rodents experiencing no Ca2+ stress and fed sufficient levels of dietary Ca2+. This finding is highly significant because fructose constitutes a substantial portion of the average diet of Americans already deficient in vitamin D

Effect of chronic fructose feeding on renal expression of 1,25(OH)₂D₃ metabolizing enzymes and of Ca²⁺transporters.

<p>Rats were fed for three mo a normal Ca²⁺ diet containing either 43% glucose or fructose. (<b>A</b>) mRNA expression level of renal 1,25(OH)₂D₃ metabolic enzymes, CYP27B1 and CYP24A1 (<b>B</b>) The protein abundance of CYP27B1 and CYP24B1 using β-actin as a reference. (<b>C</b>) mRNA expression levels of renal TRPV6, CaBP28k, CaBP9k and PMCA1. All expression data were analyzed by real-time PCR using <i>EF1</i>α as a reference and normalized relative to levels seen in rat fed glucose diet. Data are means ± SEM (<i>n</i> = 6 per group). Differences (<i>P</i><0.05) between means are indicated by asterisks. Chronic consumption of high fructose diets reduces mRNA and protein expression of CYP27B1.</p

Fructose-fed mice demonstrate an inhibition of compensation for intestinal Ca²⁺transport rate and transporter expression induced by dietary Ca²⁺-deficiency.

<p>(A) Ca²⁺ transport was measured using everted duodenal sacs from mice fed diets containing either 43% glucose or fructose, in combination with either normal or low Ca²⁺. Active transepithelial Ca²⁺ transport from the luminal to the basolateral compartment was expressed as a ratio of the final quantity of ⁴⁵Ca²⁺ inside/outside of the everted gut sacs. (B) mRNA expression levels of intestinal Ca²⁺ (TRPV6, CaBP9k, PMCA1) transporters. All expression data were analyzed by real-time PCR using <i>EF1</i>α as a reference and then normalized to levels in mice fed a normal Ca²⁺-glucose diet (Nor Ca²⁺-G). Data are means ± SEM (<i>n</i> = 6 per group). Differences (<i>P</i><0.05) among means are indicated by differences in superscript letters, as analyzed by 1-way ANOVA LSD. Thus, within a gene of interest, bars with superscript “a” are > bars with “b” which in turn are > bars with “c”. Dietary fructose inhibits compensatory increases in Ca²⁺ transporter activity and expression induced by dietary Ca²⁺-deficiency.</p

Time course of the fructose-induced reduction in serum levels of 1,25-(OH)₂D₃ in adult rats fed for three mo a normal Ca²⁺ diet with either glucose or fructose.

<p>Glucose or Fructose = 43%. FGF  =  fibroblast growth factor, PTH  =  parathyroid hormone. <i>n</i> = 6 per group. Data are means ± SEM. Means with different superscript letters are significantly different from others in the same row (<i>P</i><0.05 by <i>posthoc</i> LSD test).</p

Fructose inhibits compensatory increases in renal expression of the 1,25(OH)₂D₃ metabolizing enzyme CYP27B1 induced by dietary Ca²⁺deficiency in mice.

<p>(A) mRNA expression levels of renal CYP27B1 (1α-hydroxylase) and CYP24A1 (24-hydroxylase). (B) The protein abundance of CYP27B1 and CYP24A1, using β-actin as a reference. (C) mRNA expression levels of renal TRPV6, CaBP28k, CaBP9k and PMCA1. Nor  =  normal; G  =  glucose; F  =  fructose. All mRNA expression level data were analyzed by real-time PCR using <i>EF1</i>α as a reference and normalized to levels in mice fed glucose and normal Ca²⁺ diet. Data are means ± SEM (<i>n</i> = 5–6 per group). Differences (<i>P</i><0.05) among means are indicated by differences in superscript letters, as analyzed by 1-way ANOVA LSD. Thus, within a gene of interest, bars with superscript “a” are > bars with “b” which in turn > bars with “c”. Dietary fructose inhibits compensatory increases in renal expression of Ca²⁺ transporters and 1,25(OH)₂D₃ metabolizing enzymes induced by dietary Ca²⁺-deficiency.</p

Effects of age on expression of intestinal Ca²⁺ transporters and of renal 1,25(OH)₂D₃ metabolic enzymes in mice.

<p>A comparison of the expression levels of Ca²⁺ transporters (<b>A</b>) and 1,25(OH)₂D₃ metabolic enzymes (<b>B</b>) in four mo old mice after three mo of feeding on normal Ca²⁺ diet containing 63% glucose (from study 2) and in two mo old mice fed a normal Ca²⁺ diet containing 43% glucose for five wk (from study 1). All expression data were analyzed by real-time PCR using <i>EF1</i>α as a reference and normalized relative to levels seen in four mo old mice. Data are means ± SEM (<i>n</i> = 5–6 per group). Differences (<i>P</i><0.05) between means are indicated by asterisks. Expression of intestinal Ca²⁺ transporters decreases with age.</p

Expression of 1,25(OH)₂D₃ metabolizing enzymes and of Ca²⁺transporters in the kidney of mice fed for three mo a high fructose, starch, or glucose diet containing normal Ca²⁺ levels.

<p>(A) Marked effects of excessive fructose intake on mRNA expression levels of renal 1,25(OH)₂D₃ metabolic enzymes, CYP27B1 and CYP24A1. (B) mRNA expression levels of renal TRPV6, CaBP28k, CaBP9k and PMCA1. All expression data were analyzed by real-time PCR using <i>EF1</i>α as a reference and normalized relative to levels seen in mice fed glucose diet. Data are means ± SEM (<i>n</i> = 5 per group). Differences (<i>P</i><0.05) among means are indicated by differences in superscript letters, as analyzed by 1-way ANOVA LSD. Thus, within a gene of interest, bars with superscript “a” are > bars with “b”. Chronic consumption of high fructose levels has dramatic effects on mRNA expression of renal 1,25(OH)₂D₃ metabolizing enzymes but not on Ca²⁺ transporter mRNA expression.</p

Chronic consumption of fructose has no significant effect on intestinal Ca²⁺ transport rate and transporter mRNA expression in mice fed for three mo a high fructose, starch, or glucose diet containing normal Ca²⁺ levels.

<p>(A) Active transduodenal Ca²⁺ transport from the luminal to the basolateral compartment was expressed as a ratio of the final quantity of (⁴⁵Ca²⁺ inside/⁴⁵Ca²⁺ outside) of the everted sacs of mice fed diets containing 63% fructose, glucose or starch. (B) mRNA expression levels of intestinal Ca²⁺ (TRPV6, CaBP9k, PMCA1) transporters. All expression data were analyzed by real-time PCR using <i>EF1</i>α as a reference and normalized relative to levels seen in mice fed glucose diet. Data are means ± SEM (<i>n</i> = 5 per group). Chronic consumption of high fructose levels has no significant effect on intestinal Ca²⁺ transport rate and transporter mRNA expression.</p

Blood chemistry of mice after consuming glucose- or fructose-based low and normal Ca^2<b>+</b> diets for five weeks.

<p>Normal Ca²⁺  = 0.5%; Low Ca²⁺  = 0.02%; Glucose or Fructose = 43%; FGF  =  fibroblast growth factor. <i>n</i> = 5–6 per group. Data are means ± SEM. Means with different superscript letters are significantly different from others in the same row (<i>P</i><0.05 by <i>posthoc</i> LSD test).</p

Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism

International audienceCurrent fructose consumption levels often overwhelm the intestinal capacity to absorb fructose. We investigated the impact of fructose malabsorption on intestinal endocrine function and addressed the role of the microbiota in this process. To answer this question, a mouse model of moderate fructose malabsorption [ketohexokinase mutant (KHK)-/-] and wild-type (WT) littermate mice were used and received a 20%-fructose (KHK-F and WT-F) or 20%-glucose diet. Cholecystokinin (Cck) mRNA and protein expression in the ileum and cecum, as well as preproglucagon (Gcg) and neurotensin (Nts) mRNA expression in the cecum, increased in KHK-F mice. In KHK-F mice, triple-label immunohistochemistry showed major up-regulation of CCK in enteroendocrine cells (EECs) that were glucagon-like peptide-1 (GLP-1)+/Peptide YY (PYY-) in the ileum and colon and GLP-1-/PYY- in the cecum. The cecal microbiota composition was drastically modified in the KHK-F in association with an increase in glucose, propionate, succinate, and lactate concentrations. Antibiotic treatment abolished fructose malabsorption-dependent induction of cecal Cck mRNA expression and, in mouse GLUTag and human NCI-H716 cells, Cck mRNA expression levels increased in response to propionate, both suggesting a microbiota-dependent process. Fructose reaching the lower intestine can modify the composition and metabolism of the microbiota, thereby stimulating the production of CCK from the EECs possibly in response to propionate.-Zhang, X., Grosfeld, A., Williams, E., Vasiliauskas, D., Barretto, S., Smith, L., Mariadassou, M., Philippe, C., Devime, F., Melchior, C., Gourcerol, G., Dourmap, N., Lapaque, N., Larraufie, P., Blottière, H. M., Herberden, C., Gerard, P., Rehfeld, J. F., Ferraris, R. P., Fritton, J. C., Ellero-Simatos, S., Douard, V. Fructose malabsorption induces cholecystokinin expression in the ileum and cecum by changing microbiota composition and metabolism