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Urinary C-peptide of insulin as a non-invasive marker of nutritional status: some practicalities.

Higham JP, Girard-Buttoz C, Engelhardt A, Heistermann M - PLoS ONE (2011)

Bottom Line: We show that contamination of urine samples by faeces led to a decrease in UCP levels by >90%, but that contamination with dirt did not have substantial effects.Short-term storage (up to 12 hours) of samples on ice did not affect UCP levels significantly, but medium-term storage (up to 78 hours) did.Freezing and lyophilization for long-term storage did not affect UCP levels, but blotting onto filter paper did.

View Article: PubMed Central - PubMed

Affiliation: Junior Research Group Primate Sexual Selection, Reproductive Biology Unit, German Primate Centre, Göttingen, Lower Saxony, Germany. jhigham@dpz.eu

ABSTRACT
Nutritional status is a critical element of many aspects of animal ecology, but has proven difficult to measure non-invasively in studies of free-ranging animals. Urinary C-peptide of insulin (UCP), a small polypeptide cleaved in an equimolar ratio from proinsulin when the body converts it to insulin, offers great promise in this regard, and recent studies of several non-human primate species have utilized it with encouraging results. Despite this, there are a number of unresolved issues related to the collection, processing, storage and transport of samples. These include: contamination of samples on collection (most commonly by dirt or faeces), short-term storage before returning to a field station, differences in processing and long-term storage methods (blotting onto filter paper, freezing, lyophilizing), and for frozen samples, transportation while keeping samples frozen. Such issues have been investigated for urine samples in particular with respect to their effects on steroid hormone metabolites, but there has been little investigation of their effects on UCP measurement. We collected samples from captive macaques, and undertook a series of experiments where we systematically manipulated samples and tested the effects on subsequent UCP measurements. We show that contamination of urine samples by faeces led to a decrease in UCP levels by >90%, but that contamination with dirt did not have substantial effects. Short-term storage (up to 12 hours) of samples on ice did not affect UCP levels significantly, but medium-term storage (up to 78 hours) did. Freezing and lyophilization for long-term storage did not affect UCP levels, but blotting onto filter paper did. A transportation simulation showed that transporting frozen samples packed in ice and insulated should be acceptable, but only if it can be completed within a period of a few days and if freeze-thaw can be avoided. We use our data to make practical recommendations for fieldworkers.

Show MeSH
UCP levels in samples blotted onto filter paper and: a) reconstituted the next day; b) stored for 8 months.
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pone-0022398-g003: UCP levels in samples blotted onto filter paper and: a) reconstituted the next day; b) stored for 8 months.

Mentions: Samples blotted onto filter paper and reconstituted the next day had significantly lower UCP values when compared to controls (50±9.7%; T+ = 43, n = 9, p = 0.012; Figure 3a). However, UCP values were nonetheless strongly and significantly correlated with controls (r = 0.946, n = 9, p<0.001), but did change in their relative rank order (Figure 3a). Samples blotted onto filter paper and stored for 8 months before being reconstituted showed a substantial and variable decline compared to controls (62±14.2%), which was statistically significant (T+ = 40, n = 9, p = 0.039; Figure 3b). However, values were still nonetheless strongly correlated with controls (r = 0.867, n = 9, p = 0.005), but again did change in their relative rank order (Figure 3b).


Urinary C-peptide of insulin as a non-invasive marker of nutritional status: some practicalities.

Higham JP, Girard-Buttoz C, Engelhardt A, Heistermann M - PLoS ONE (2011)

UCP levels in samples blotted onto filter paper and: a) reconstituted the next day; b) stored for 8 months.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3142156&req=5

pone-0022398-g003: UCP levels in samples blotted onto filter paper and: a) reconstituted the next day; b) stored for 8 months.
Mentions: Samples blotted onto filter paper and reconstituted the next day had significantly lower UCP values when compared to controls (50±9.7%; T+ = 43, n = 9, p = 0.012; Figure 3a). However, UCP values were nonetheless strongly and significantly correlated with controls (r = 0.946, n = 9, p<0.001), but did change in their relative rank order (Figure 3a). Samples blotted onto filter paper and stored for 8 months before being reconstituted showed a substantial and variable decline compared to controls (62±14.2%), which was statistically significant (T+ = 40, n = 9, p = 0.039; Figure 3b). However, values were still nonetheless strongly correlated with controls (r = 0.867, n = 9, p = 0.005), but again did change in their relative rank order (Figure 3b).

Bottom Line: We show that contamination of urine samples by faeces led to a decrease in UCP levels by >90%, but that contamination with dirt did not have substantial effects.Short-term storage (up to 12 hours) of samples on ice did not affect UCP levels significantly, but medium-term storage (up to 78 hours) did.Freezing and lyophilization for long-term storage did not affect UCP levels, but blotting onto filter paper did.

View Article: PubMed Central - PubMed

Affiliation: Junior Research Group Primate Sexual Selection, Reproductive Biology Unit, German Primate Centre, Göttingen, Lower Saxony, Germany. jhigham@dpz.eu

ABSTRACT
Nutritional status is a critical element of many aspects of animal ecology, but has proven difficult to measure non-invasively in studies of free-ranging animals. Urinary C-peptide of insulin (UCP), a small polypeptide cleaved in an equimolar ratio from proinsulin when the body converts it to insulin, offers great promise in this regard, and recent studies of several non-human primate species have utilized it with encouraging results. Despite this, there are a number of unresolved issues related to the collection, processing, storage and transport of samples. These include: contamination of samples on collection (most commonly by dirt or faeces), short-term storage before returning to a field station, differences in processing and long-term storage methods (blotting onto filter paper, freezing, lyophilizing), and for frozen samples, transportation while keeping samples frozen. Such issues have been investigated for urine samples in particular with respect to their effects on steroid hormone metabolites, but there has been little investigation of their effects on UCP measurement. We collected samples from captive macaques, and undertook a series of experiments where we systematically manipulated samples and tested the effects on subsequent UCP measurements. We show that contamination of urine samples by faeces led to a decrease in UCP levels by >90%, but that contamination with dirt did not have substantial effects. Short-term storage (up to 12 hours) of samples on ice did not affect UCP levels significantly, but medium-term storage (up to 78 hours) did. Freezing and lyophilization for long-term storage did not affect UCP levels, but blotting onto filter paper did. A transportation simulation showed that transporting frozen samples packed in ice and insulated should be acceptable, but only if it can be completed within a period of a few days and if freeze-thaw can be avoided. We use our data to make practical recommendations for fieldworkers.

Show MeSH