Insulin dysregulation

Frank, Nicholas; Tadros, Elizabeth M.

doi:10.1111/evj.12169

Cited by 183 publications

(191 citation statements)

References 168 publications

(218 reference statements)

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“…Body condition score also was not available for PPID group animals, so determination of the impact of BCS on free cortisol measurements in this disease group was not conducted. It is also possible that some animals in the EMS group suffered from concurrent PPID, because both endocrine disorders can occur at the same time 4. It would have been ideal to measure plasma ACTH concentrations to screen horses in the EMS group for PPID, as performed in the control group, but archived samples were only available in limited amounts for EMS animals.…”

Section: Discussionmentioning

confidence: 99%

Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses

Hart

Wochele

Norton

et al. 2016

Veterinary Internal Medicne

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BackgroundIncreased free cortisol fraction is associated with insulin dysregulation (ID) in people with Metabolic Syndrome and Cushing's Disease. Free cortisol has not been investigated in equine endocrine disorders.Hypotheses(1) In healthy horses, sex, age, body condition score (BCS), and season impact free cortisol; (2) free cortisol is increased in horses with Pituitary Pars Intermedia Dysfunction (PPID) or Equine Metabolic Syndrome (EMS).AnimalsFifty‐seven healthy horses; 40 horses and ponies with PPID (n = 20) or EMS (n = 20).MethodsProspective study. Serum collected seasonally from healthy animals and archived serum from PPID and EMS animals was analyzed for insulin, total and free cortisol concentrations, and free cortisol fraction (FCF). Linear mixed models were used to determine effects of age, sex, season, and BCS on hormones in controls. Hormone measurements were compared between disease groups and age‐ and season‐matched controls with t‐tests. EMS and hyperinsulinemic PPID animals were combined in an ID (hyperinsulinemia) group.ResultsFree cortisol concentrations were increased in overweight/obese controls (0.3 ± 0.1 μg/dL) compared to lean controls (0.2 ± 0.1 μg/dL; P = .017). Mean FCF was significantly higher in animals with PPID (8.8 ± 5.8 μg/dL, P = .005) or ID (8.8 ± 10.2 μg/dL, P = .039) than controls (5.0 ± 0.9 μg/dL), but total cortisol concentrations were similar (P ≥ .350) (PPID: 4.2 ± 4.3 μg/dL; ID: 5.0 ± 4.5 μg/dL; controls: 4.6 ± 1.7 and 5.1 ± 2.1 μg/dL).Conclusions and Clinical ImportanceIncreased FCF is associated with obesity in healthy horses and with ID (hyperinsulinemia) in horses and ponies with endocrine disease. Decreased plasma cortisol‐binding capacity could be a component of these endocrine disorders in horses.

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Section: Discussionmentioning

confidence: 99%

Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses

Hart

Wochele

Norton

et al. 2016

Veterinary Internal Medicne

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“…In a recent survey, 35% of horses registered with UK veterinary practices were kept at pasture 24h/day [5], such animals may not have convenient access to stabling or bare paddocks. Moving animals to stabling for the purposes of ID testing could induce stress and may influence insulin sensitivity [6]. It is therefore unclear whether the OST can be applied to horses kept at pasture.…”

Section: Introductionmentioning

confidence: 99%

Use of the oral sugar test in ponies when performed with or without prior fasting

Knowles

Harris²,

Elliott

et al. 2016

Equine Veterinary Journal

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Summary Background It is recommended that the oral sugar test (OST) for insulin dysregulation (ID) be performed after an overnight fast, but fasting is impractical in ponies kept solely at pasture. There are few data on OST repeatability and reliability in ponies. Objectives To report 1) whether OST results obtained in the morning after an overnight fast or without fasting in the afternoon (FASTING/FED) can be used interchangeably, 2) time of highest insulin concentration Tmax[insulin], repeatability and reliability of insulin response to the OST when FASTING or FED and 3) dichotomous agreement (ID/normal) within a small sample when FASTING or FED. Study design Method comparison study. Methods Oral sugar tests were performed on four occasions in 10 adult native British ponies, twice FASTING and twice FED. Insulin concentrations were measured by radioimmunoassay at 0–120 min (T0,30,60,75,90,120). Differences between FASTING and FED results were assessed using mixed effects models. Indices of repeatability and reliability were calculated; dichotomous agreement was reported using kappa statistics. Results Serum [insulin] was significantly (P≤0.05) higher at T60–T90 with prior fasting (estimated differences [95% confidence intervals]): T60: 23.5 μiu/ml (8.7–38.4 μiu/ml), T75: 27.1 μiu/ml (12.3–41.8 μiu/ml), T90: 15.1 (0.36–29.9 μiu/ml). Most frequently, Tmax[ins] occurred at T30. At any single time point, within‐subject coefficients of variation were: FASTING: 40% and FED: 31%. The 95% limits for repeatability were FASTING: 29–340%, FED: 41–240%. Test reliabilities were FASTING: 0.70 and FED: 0.67. For dichotomous interpretation similar results (kappa = 0.7) were obtained using cut‐offs of [Insulin] >60 μiu/ml at T60 or T90 for FASTING and [Insulin] >51 μiu/ml at T30 or T60 for FED samples. Main limitations Oral sugar tests were performed on a small number of animals on one pasture during one season (spring). Conclusions Clinicians should beware of interpreting changes in absolute OST results owing to poor repeatability. When stabling is unavailable, OSTs of ponies at pasture may yield similar dichotomous results without prior fasting.

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“…Insulin resistance (IR) is defined as a state of reduced responsiveness of tissues to insulin, despite its normal or elevated concentration in blood; the disorder mainly occurs in adipose tissue, skeletal muscle cells, and liver (Bhattacharya et al 2007;Frank & Tadros 2014). The consequences of IR include impaired glucose uptake by the tissues, increased efficiency of gluconeogenesis, and increased lipolysis (Treiber et al 2006).…”

Section: Mechanisms Of Insulin Resistancementioning

confidence: 99%

“…Evolutionarily adapted to living in a food-poor environment, horses and ponies are more predisposed to obesity and IR where food is available throughout the year (Johnson et al 2009;Frank & Tadros 2014).…”

Section: Mechanisms Of Insulin Resistancementioning

confidence: 99%

“…The augmented flow of FFA to the liver causes an increase in the secretion of very low-density lipoproteins (VLDL), a decrease in hepatic insulin degradation, and an extended production and release of glucose from hepatocytes, which result in the development of hyperinsulinemia, hyperglycaemia, as well as dyslipidaemia. The latest research on animals indicate a considerable role of interleukin-6 (IL-6) in the development of hepatic IR (Konstantynowicz et al 2011;Frank & Tadros, 2014;De Graaf-Roelfsema 2014) In horses and ponies, liver IR has been shown to induce hypertriglyceridemia. Although plasma triglycerides and VLDL are only slightly elevated in obese horses and ponies with hyperinsulinemia, they are potential indicator factors of IR in the liver.…”

Section: Mechanisms Of Insulin Resistancementioning

confidence: 99%

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Insulin resistance in the horse: a review

Kaczmarek

Janicki

Głowska

2015

Journal of Applied Animal Research

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Insulin resistance (IR) is a state in which the tissues show a reduced sensitivity to insulin despite its normal or even increased concentration in blood. IR causes inability of peripheral tissues to respond to the hormone and to increase the glucose uptake from blood nor to raise the metabolism rate. The tissues resistance to insulin may refer to the prereceptor malfunctions, which reduce the concentration of insulin or decrease the number of insulin receptors; however, in most cases changes in signal transduction after insulin binding to the receptor are observed. The development of IR is determined by a number of genetic and environmental factors. One of the most relevant causes is obesity, which develops into a growing problem among the horse population all over the world. The accumulation of lipids in the tissues (lipotoxicity) and a mild inflammation caused by the release of proinflammatory adipokines and cytokines from the fat tissue are a common denominator that links obesity with IR. Both IR and obesity seem to cause metabolism malfunctions in horses and are the key components of equine metabolic syndrome; moreover, both may be the reason for endocrinological laminitis. The methods of prevention and treatment of IR include feeding the animals with low glycemic index food and increasing physical activity as well as pharmacological treatment, where levothyroxine sodium and metformin are of the highest importance. ARTICLE HISTORY

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Insulin dysregulation

Cited by 183 publications

References 168 publications

Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses

Effect of Age, Season, Body Condition, and Endocrine Status on Serum Free Cortisol Fraction and Insulin Concentration in Horses

Use of the oral sugar test in ponies when performed with or without prior fasting

Insulin resistance in the horse: a review

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