Insulin-Like Growth Factor 1 (IGF- 1) Levels And Left Ventricular Meridional End Systolic Stress (LVMESS) Interrelationship In Middle- Aged And Elderly Obese Subject With Type 2 Diabetes Mellitus

A Al-Dijaili, Amina; AMH Zwain, Akeel; Amber, Khalid

	Insulin-Like Growth Factor 1 (IGF- 1) Levels And Left Ventricular Meridional End Systolic Stress (LVMESS) Interrelationship In Middle- Aged And Elderly Obese Subject With Type 2 Diabetes Mellitus
kufa Journal for Nursing sciences
Article 1, Volume 4, Issue 3, 2014, Pages 46-55
Authors
Amina A Al-Dijaili; Akeel AMH Zwain; Khalid Amber
Abstract
Background: Left ventricular meridional end systolic stress (LVMESS) is a quantitative determinant index of LV afterload which is an essential determinant of LV performance. The key factors influencing LVMSS, notably ventricular wall thickness, chamber size and configuration are shown to be altered by both obesity and type2 diabetes mellitus (T2DM). There exist reports implicating high free insulin-like growth factor 1 (IGF-1) but not growth hormone (GH) levels, with increased left ventricular mass index (LVMI), abnormal LV geometric remodelling, and A1c levels. Objective: to explore whether a meaningful link exists between LVMESS and free IGF-1 plasma levels, in obese middle-aged and elderly individuals with or without T2DM. Subjects and methods: In this cross sectional study, a total of 145 participants Involved. Middle aged and elderly obese individuals with or without T2 DM were matched with healthy lean subjects of the same age group, with or without T2 DM. LVMESS and IGF-1 levels were compared between groups; group differences were analyzed using unpaired t test and linear correlation test. Data were expressed as the mean ± S.D, using SPSS version 18). Results: LVMESS values showed significant decrease in diabetic patients compared to control in both middle and old aged subjects. IGF-1, concentration levels were lower in the elderly obese diabetics compared to control, with significant (r=0.462; p= 0.04) negative correlation with LVMESS in healthy obese old aged, and a negative but non-significant correlation with LVMESS in lean old aged with or without diabetics. Conclusion:Nonlinear correlation of IGF-1 levels with LVMESS obtained. It could be hypothesized that because of its negative significant correlation with LVMESS in the elderly non diabetic obese, IGF-1 free level could be utilized to serve as a predictor of impaired LV systolic function in these subjects. In addition the results could shed some light on IGF-1- LVMESS relationship, when considering IGF-1 therapy in certain conditions. Recommendation: It is suggested that using IGF-1 plasma levels in the elderly with or without T2DM could aid as predictor for LV global systolic dysfunction .However, larger sample size are to be considered. Keywords: IGF- 1, left ventricular meridional end systolic stress, obesity, Type 2 Diabetes Mellitus. INTRODUCTION: Because of the biased validity of LV systolic function assessment by ejection fraction (EF) index, two other types of load independent estimates have been proposed for this purpose: the meridional LV wall stress which reflects the function of the longitudinal endocardial and epicardial fibers of the LV wall, has been used as an indirect measure of LV after load. The circumferential LV wall stress which is in line with the direction of the midwall circumferential fibers and has been used as a measure of myocardial contractility (1,2). The concept of after load literally means the stress encountered by LV myofibrils as they contract against the end-diastolic volume/ intra -ventricular pressure. obese individuals with or without diabetes tend to develop left ventricular (LV) structural changes in response to the operating overload: volume overload causing chamber dilation in proportion to mass (eccentric hypertrophy), and pressure overload producing increased LV mass out proportion to volume (concentric hypertrophy). These patterns of hypertrophy are independent of arterial pressure and age(3, 4).. Diabetic and hypertensive subjects have a higher likelihood to develop, impaired diastolic function, in addition to decreased afterload measured by meridional end-systolic stress, as compared with lean individual (5,6). Indeed, DM exclusively, can elicit changes in cardiac structure and function which are independent of associated ischemic heart disease or hypertension or increased BMI(7,8) Mounting evidence indicate growth hormone (GH)/ Insulin growth factor 1(IGF-1) axis also known to contribute to LV structural and functional modulations: Circulating IGF-1 is synthesized primarily by the liver under the control of growth hormone (GH) (9).However, IGF-1 can be synthesized by many other organs, including heart, and can act as an autocrine or a paracrine factor (10). IGF-1 circulates bound to protein carriers (IGFBPs), which serve not only to transport IGF-1 in the circulation but also to prolong its half-life, modulate its tissue specificity and strengthen or neutralize its biological actions (11) As growth factors, both GH andIGF-1 modulate myocyte growth and hypertrophy in the developing heart. IGF-1 has been demonstrated to induce nitric oxide (NO) production in vitro and has vasodilatory properties consistent with an NO-mediated effect in vivo that induces cellular proliferation and differentiation. In addition, it exerts both inotropic and growth effects that can influence LV geometry (12,13). However, until the time of preparation of this manuscript, studies on the impact of alteration of IGF-1 axis on meridional LV wall stress in obesity and obesity- related T2DM, are lacking. Objectives This study defined whether a relationship exsist between LVMESS and free LGF-1 plasma levels in obese middle age and elderly individuals with or without T2DM.

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