Obesity and diet affect glucose dynamics and insulin sensitivity in Thoroughbred geldings

AKA-Glucose: a program for kinetic and epidemiological analysis of frequently sampled intravenous glucose tolerance test data using database technology

BACKGROUND

The Bergman Minimal Model enables estimation of two key indices of glucose/ insulin dynamics: glucose effectiveness and insulin sensitivity.

METHODS AND RESULTS

In this paper we describe AKA-Glucose, a program that combines MINMOD Millennium (minimal model analysis software) with relational database technologies. AKA-Glucose enables the fitting of individual frequently sampled intravenous glucose tolerance test (FSIGT) data sets to the Minimal Model and the secure storage in a dedicated database (and retrieval from) of thousands of individual subjects' demographic data, their individual FSIGT data, and each subject's parameters and indices derived from minimal model analysis. AKA-Glucose also enables the population analysis of various strata or subpopulations within the database. AKA-Glucose has all of the capabilities of MINMOD Millennium, provides Minimal Model parameter estimates that are concordant with estimates from previous MINMOD software, and allows importation of data files from earlier versions of the MINMOD software.

CONCLUSIONS

By combining FSIGT data fitting, population analysis, and relational database technologies, AKA-Glucose is the first minimal model software designed specifically for researchers confronted with minimal model and epidemiological analysis of large numbers of either human or animal FSIGT data sets.

Correlation between plasma -melanocyte-stimulating hormone concentration and body mass index in healthy horses

OBJECTIVE

To evaluate the correlation between plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentration and body mass index (BMI) in healthy horses.

ANIMALS

82 healthy horses.

PROCEDURE

Plasma alpha-MSH concentration was determined by radioimmunoassay. At the time blood samples were collected, body condition scores (BCS) were determined and measurements of girth circumference, body length, and height were obtained. Weight was estimated by use of the following formula: estimated weight (kg) = [girth (cm)2 x length (cm)]/11,877. Body mass index was calculated as estimated weight (kg)/height (m)2.

RESULTS

A correlation was found between BMI and BCS (rs = 0.60 [95% confidence interval (CI), 0.44 to 0.731). A weak correlation was found between plasma alpha-MSH concentration and BMI (rs = 0.25 [95% CI, 0.03 to 0.45]) and BCS (rs = 0.26 [95% CI, 0.04 to 0.46]). A correlation was found between plasma alpha-MSH concentration and BMI in horses > or = 10 years old (rs = 0.49 [95% CI, 0.20 to 0.69]) but not in horses < 10 years old (rs = -0.04). Horses in the upper quartile of BMI had significantly greater plasma alpha-MSH concentration (median, 9.1 pmol/L; range, 2.0 to 95.3 pmol/L) than horses in the lowest quartile of BMI (median, 70 pmol/L; range, 3.6 to 15.7 pmol/L).

CONCLUSIONS AND CLINICAL RELEVANCE

A correlation exists between plasma alpha-MSH concentration and BMI in horses. Further study is required to determine whether melanocortin receptor defects underlie this correlation or, alternately, whether plasma alpha-MSH concentration is simply a correlate of adiposity.

Glycemic index of cracked corn, oat groats and rolled barley in horses1

Muscle glycogen synthesis depends on glucose availability. This study was undertaken to determine the glycemic and insulinemic response of horses to equal amounts of hydrolyzable carbohydrates (starch and sugar) in the form of one of three grain meals or intragastric administration of a glucose solution. In a randomized crossover design, seven horses were fed each of three grain meals (cracked corn, steamed oat groats, or rolled barley) or were infused intragastrically with glucose solution at 2 g of hydrolyzable carbohydrate (starch plus sugar) per kilogram of BW. The quantity of hydrolyzable carbohydrate ingested was not different among all treatments (P = 0.70). Plasma glucose concentration peaked in all four treatments by 1.5 to 2 h after feeding. Plasma glucose concentration remained higher than baseline in oat groats or barley-fed horses throughout 8 h, whereas plasma glucose returned to baseline by 5 to 6 h in corn-fed horses or after glucose administration. Meal consumption was slower in oat groats-fed horses than in corn-fed ones, which may confound the glycemic and insulinemic responses observed after grain feeding. Plasma glucose area under the curve (AUC) was 63% both in corn and oat groats and 57% in barley-fed horses compared with that of horses administered glucose (P = 0.13). Serum immunoreactive insulin concentration peaked between 2 and 3 h after feeding or glucose administration, and barley-fed horses had lower serum immunoreactive insulin concentration by 3 to 4 h than corn-fed horses or after glucose administration (P < 0.05). We conclude, in horses, ingestion of oat groats, corn, and barley result in similar plasma glucose AUC and, compared with the glycemic index of 100 as the glucose reference, corn, oat groats, and barley had a glycemic index of approximately 60.