Dietary fructose inhibits intestinal calcium absorption and induces vitamin D insufficiency in CKD

J Am Soc Nephrol. 2010 Feb;21(2):261-71. doi: 10.1681/ASN.2009080795. Epub 2009 Dec 3.

Abstract

Renal disease leads to perturbations in calcium and phosphate homeostasis and vitamin D metabolism. Dietary fructose aggravates chronic kidney disease (CKD), but whether it also worsens CKD-induced derangements in calcium and phosphate homeostasis is unknown. Here, we fed rats diets containing 60% glucose or fructose for 1 mo beginning 6 wk after 5/6 nephrectomy or sham operation. Nephrectomized rats had markedly greater kidney weight, blood urea nitrogen, and serum levels of creatinine, phosphate, and calcium-phosphate product; dietary fructose significantly exacerbated all of these outcomes. Expression and activity of intestinal phosphate transporter, which did not change after nephrectomy or dietary fructose, did not correlate with hyperphosphatemia in 5/6-nephrectomized rats. Intestinal transport of calcium, however, decreased with dietary fructose, probably because of fructose-mediated downregulation of calbindin 9k. Serum calcium levels, however, were unaffected by nephrectomy and diet. Finally, only 5/6-nephrectomized rats that received dietary fructose demonstrated marked reductions in 25-hydroxyvitamin D(3) and 1,25-dihydroxyvitamin D(3) levels, despite upregulation of 1alpha-hydroxylase. In summary, excess dietary fructose inhibits intestinal calcium absorption, induces marked vitamin D insufficiency in CKD, and exacerbates other classical symptoms of the disease. Future studies should evaluate the relevance of monitoring fructose consumption in patients with CKD.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase / metabolism
  • Animals
  • Bone Density
  • Calcifediol / metabolism
  • Calcitriol / metabolism
  • Calcium / metabolism*
  • Chronic Disease
  • Dietary Carbohydrates / adverse effects
  • Dietary Carbohydrates / pharmacology*
  • Disease Models, Animal
  • Fructose / adverse effects
  • Fructose / pharmacology*
  • Glucose / pharmacology
  • Intestinal Absorption / drug effects*
  • Kidney / metabolism
  • Kidney / surgery
  • Kidney Diseases / complications
  • Kidney Diseases / metabolism*
  • Male
  • Nephrectomy
  • Phosphates / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Vitamin D Deficiency / etiology
  • Vitamin D Deficiency / metabolism*

Substances

  • Dietary Carbohydrates
  • Phosphates
  • Fructose
  • 25-Hydroxyvitamin D3 1-alpha-Hydroxylase
  • Calcitriol
  • Glucose
  • Calcifediol
  • Calcium