Fertility testing: profiling with NMR

Seminal traditions

Traditional clinical tests on seminal fluid for infertility and sub-fertility prediction do not provide many insights into the underlying biological problems. Metabolic NMR tests could offer a less time-consuming and less labour-intensive alternative to address this shortcoming.

Infertility affects between one in six and one in eight couples worldwide and is defined as the inability to conceive within a year of regular unprotected sexual intercourse. It is rarely acknowledged that in half of all cases it is male infertility that is to blame, male infertility is the most difficult to find an underlying cause and the hardest to treat. According to Ashish Gupta, Abbas Ali Mahdi, Mohammad Kaleem Ahmad, Kamla Kant Shukla, Shyam Pyari Jaiswerb and Satya Narain Shankhwar of the Department of Biochemistry, Chhatrapati Shahuji Maharaj Medical University, Lucknow, India, traditional measures of fertility are based on sperm count, morphology and motility, which are not necessarily the best indicators of fecundity, indeed this is a popular misconception as many other factors are at play. The researchers have now used spectroscopy and chemometrics to investigate putative biomarkers that correlate with different fertility levels in men.

The team points out that seminal fluid is highly complex, contains inorganic ions, low molecular weight organic compounds, peptides and hormones. This mixture is generated by various endocrine glands but while the various constituents are well established few have proven clinical relevance.

Complex fertility rights

The team has now used high-resolution proton nuclear magnetic resonance spectroscopy to identify and classify specific biomarkers in semen samples collected from 60 healthy, fertile men and from 125 infertile (normozoospermic and oligozoospermic) patients. They looked at lactate,alanine, choline, citrate, glycerophosphocholine (GPC), glutamine, tyrosine, histidine, phenylalanine and uridine and then used linear multivariate discriminant function analysis (DFA) to determine the signature descriptors of the compounds. Clinical laboratory data were also analysed using standard techniques to obtain measures of sperm concentration, motility, lipid peroxidation and total protein. This information was also analysed statistically but independently of the NMR data.

Amino acid solution

Their DFA results show that alanine, citrate, GPC, tyrosine, and phenylalanine correlate directly with infertility with 92.4% accuracy based on the NMR data. Conventional clinical measures were accurate to a marginally higher level at 94.1%. Essentially, both approaches were accurate nine times out of ten in differentiating healthy controls from infertile patients. "The advantage of measuring the amino acids - alanine, histidine, phenylalanine and tyrosine by NMR spectroscopy is that they can be quantified specifically and separately with well-resolved spectra, " the team points out. The same statistical procedures could also differentiate between normozoospermic and oligozoospermic samples (92.9% by NMR and 92.6% by the clinical laboratory method). "NMR-based metabolic screening appears to be a promising, rapid, and non-invasive approach to probing infertility that has similar sensitivity and specificity to the tedious laboratory method," the team asserts.

"Adaption of this technique may open new windows for the differential diagnosis of infertility that can be used for making decisions before the recommendation of an assisted reproductive technology as well as for the new drug development because it is clear that NMR spectroscopy has the requisite sensitivity and specificity to detect subtle changes at clinically relevant means of measuring concentrations of the endogenous metabolites," the team reports. "Use of this technique may contribute toward better understanding of the vital biological causes of infertility, an essential step for improving its clinical management," they conclude.

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