Health In Focus
  • Kidney stones are one of the most common disorders of the urinary tract
  • Most kidney stones are calcium stones in the form of calcium oxalate.
  • Efficacy of hydroxycitrate (HCA) and citrate (CA) in inhibiting the growth of calcium oxalate crystals studied
  • HCA has the potential to cut the incidence rate of people with chronic kidney stone disease

Hydroxycitrate (HCA), a natural fruit extract was found to be capable of dissolving calcium oxalate crystals, the most common component of human kidney stones. This key finding could lead to the first advance in calcium oxalate treatment.

What are Kidney Stones?

Kidney stones are formed when the substances in the urine (calcium, oxalate and phosphorus) become highly concentrated. Common symptoms of kidney stones include severe pain in the side and the back, pain on urination and pink color urine. Hypertension, diabetes and overweight can increase the risk of kidney stones. Over the last three decades there is not much change in the preventive treatment.
New Effective Inhibitor of Kidney Stone Formation Identified
New Effective Inhibitor of Kidney Stone Formation Identified

In the United States more than 300,000 people go to emergency rooms for kidney stone problems.

Types of Kidney Stones

  • Calcium Stones - Most common type of kidney stone
  • Uric Acid Stones are formed when the urine is acidic
  • Struvite Stones usually result from kidney infections
  • Cystine Stones arise from a genetic disorder that causes cystine to leak through the kidneys and into the urine
Doctors often recommend citrate (CA) supplement in the form of potassium citrate to slow the oxalate crystal growth but some people are unable to tolerate the side effects of the drug.

The research study grew out of preliminary work done by collaborator John Asplin, a nephrologist at Litholink Corporation, who suggested HCA could be a possible treatment for treating kidney stones.

HCA or CA for Treating Kidney Stones

  • The chemical structure of HCA and CA is similar
  • HCA and CA are available in the form of dietary supplement
The studies compared the efficacy of CA and HCA in inhibiting the growth of calcium oxalate crystals and found that HCA was more potent and advantageous when compared to CA. Researchers used atomic force microscopy (AFM) technique to study the interactions between the crystals CA and HCA under realistic growth conditions.

Atomic Force Microscopy (AFM) Study Findings

Images generated by AFM recorded the shrinking of the crystal when exposed to specific HCA concentrations, reported Chung. Rimer suspected that Chung's initial finding was an abnormality, as it is a rare condition to see a crystal dissolve in a supersaturated growth solution. But later it was turned out that Chung's initial finding was correct. Scientists later carried out research work to figure out the reasons behind the shrinkage of the crystal in a supersaturated growth condition.

How HCA and CA Bind to the Calcium Oxalate Crystals?

Mpourmpakis and Taylor used density functional theory (DFT) a computational method to study the structure and the properties of the materials. HCA formed a stronger bond with the calcium oxalate crystal surfaces, inducing a strain that is relieved by the release two molecules - calcium and oxalate, which aid in the crystal dissolution.

HCA Testing on Humans

The efficacy of HCA was also tested in human subjects. Seven people took HCA in the form of dietary supplement for three days. HCA was excreted through urine, a requirement for a dietary supplement to work as a therapy.

While Rimer said the research established the groundwork to design an effective drug, questions remain. Long-term safety, dosage and additional human trials are needed. "But our initial findings are very promising," he said. "If it works in vivo, similar to our trials in the laboratory, HCA has the potential to reduce the incidence rate of people with chronic kidney stone disease."

Jeffrey Rimer, associate professor of chemical engineering at the University of Houston is the lead author of the study published in the online edition of Nature. In addition to Rimer and Asplin, authors on the paper include Giannis Mpourmpakis and his graduate student, Michael G. Taylor, of the University of Pittsburgh; Ignacio Granja of Litholink Corporation, and Jihae Chung, a UH graduate student working in Rimer's lab.

5 Simple Ways to Prevent Kidney Stones

  • Drink lots of water
  • Avoid foods rich in oxalate such as okra, spinach, almonds, rhubarb
  • Choose a low salt diet
  • Eat more dairy foods
  • Maintain a healthy weight
References :
  1. Kidney Stone Prevention - (
  2. Kidney Stones in Adults - (
Source: Medindia

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