Date Published: October 11, 2007
Publisher: BioMed Central
Author(s): Paul Holtenius, Kjell Holtenius.
Impairment of the insulin regulation of energy metabolism is considered to be an etiologic key component for metabolic disturbances. Methods for studies of insulin sensitivity thus are highly topical. There are clear indications that reduced insulin sensitivity contributes to the metabolic disturbances that occurs especially among obese lactating cows. Direct measurements of insulin sensitivity are laborious and not suitable for epidemiological studies. We have therefore adopted an indirect method originally developed for humans to estimate insulin sensitivity in dairy cows. The method, “Revised Quantitative Insulin Sensitivity Check Index” (RQUICKI) is based on plasma concentrations of glucose, insulin and free fatty acids (FFA) and it generates good and linear correlations with different estimates of insulin sensitivity in human populations. We hypothesized that the RQUICKI method could be used as an index of insulin function in lactating dairy cows. We calculated RQUICKI in 237 apparently healthy dairy cows from 20 commercial herds. All cows included were in their first 15 weeks of lactation. RQUICKI was not affected by the homeorhetic adaptations in energy metabolism that occurred during the first 15 weeks of lactation. In a cohort of 24 experimental cows fed in order to obtain different body condition at parturition RQUICKI was lower in early lactation in cows with a high body condition score suggesting disturbed insulin function in obese cows. The results indicate that RQUICKI might be used to identify lactating cows with disturbed insulin function.
In humans the prevalence of obesity, overweight and other food related problems are increasing in many areas in the world with a number of metabolic diseases as a consequence . There is general agreement that the etiologic key component in the pathogenesis of these metabolic diseases is insulin resistance (IR). Insulin resistance is defined as a condition when higher than normal insulin concentrations are needed to achieve normal metabolic responses . One general effect of disturbed insulin function in man is infiltration of fat in the liver which in turn may give rise to a number of pathological changes [3,4]. Also in dairy cows obesity and fatty liver occur frequently and the fat cow syndrome is a well-known problem .
We have demonstrated that RQUICKI was not affected by the adaptations that normally occur in apparently healthy cows during the first months of lactation. However, RQUICKI was lower, reflecting disturbed insulin function, in obese cows. The results indicate that RQUICKI might be used to identify cows with disturbed insulin function. However evidence of a relationship between RQUICKI and metabolic diseases in dairy cows is yet lacking.
The author(s) declare that they have no competing interests.
PH came up with the idea. The manuscript was drafted in co-operation. Both authors approved the final manuscript