Somatotropic Axis and Obesity: Is There Any Role for the Mediterranean Diet?

Giovanna Muscogiuri,Silvia Savastano,Luigi Barrea,Annamaria Colao,Ciro Salzano,Carolina Di Somma,Daniela Laudisio,Gabriella Pugliese

doi:10.3390/nu11092228

Abstract

Obesity is associated with reduced spontaneous and stimulated growth hormone (GH) secretion and basal insulin-like growth factor I (IGF-1) levels—which in turn is associated with increased prevalence of cardiovascular risk factors. The aim of this study was to investigate: (1) the association of somatotropic axis with cardiometabolic status; (2) the association of somatotropic axis with the Mediterranean diet and nutritional pattern in people with obesity. Cross-sectional observational study was carried out in 200 adult women, aged 36.98 ± 11.10 years with severe obesity (body mass index—BMI of 45.19 ± 6.30 kg/m2). The adherence to the Mediterranean diet and the total calorie intake was assessed. Anthropometric measurements, body composition and biochemical profile were determined along with Growth Hormone (GH)/Insulin like Growth Factor 1 (IGF-1) axis and insulin resistance (homeostatic model assessment for insulin resistance—HoMA-IR). The enrolled subjects were compared after being divided according to GH peak response and according to IGF-1 standard deviation scores (SDS). Derangements of GH peak were detected in 61.5% of studied patients while IGF-1 deficiency was detected in 71% of the population. Both blunted GH peak response and IGF-1 SDS were indicators of derangements of somatotropic axis and were associated with comparable results in terms of cardiometabolic sequelae. Both GH peak and IGF-1 levels were inversely associated with anthropometric and metabolic parameters. The adherence to the Mediterranean diet predicts GH peak response. Fatty liver index (FLI), fat mass (FM) and phase angle (PhA) were predictive factors of GH peak response as well. In conclusion derangements of somatotropic axis is associated with a worse cardiometabolic profile in people with obesity. A high adherence to the Mediterranean diet—and in particular protein intake—was associated with a better GH status.

Highlights

The Growth hormone (GH)/Insulin like Growth Factor 1 (IGF-1) axis is finely regulated at multiple steps by neuroendocrine mediators, tissue and soluble receptors and carrier proteins
Based on GH peak response and IGF-1 standard deviation scores (SDS), an altered GH peak and IGF-1 deficiency was found in 123 individuals (61.5%) and 142 individuals (71%), respectively
In view of the existing association between visceral fat mass, insulin resistance and non-alcoholic fatty liver disease (NAFLD), we found that derangements of somatotropic axis were associated with increased visceral fat and fat liver in obesity, as demonstrated by higher visceral adiposity index (VAI) and fatty liver index (FLI)

Summary

Introduction

The GH/IGF-1 axis is finely regulated at multiple steps by neuroendocrine mediators, tissue and soluble receptors and carrier proteins. The alterations of GH/IGF-1 axis in obesity are characterized by the decrease in the half-life of GH along with a reduction in both frequency and amplitude of GH secretory bursts. These phenomena are associated with an increased GH metabolic clearance rate which at the end results in low plasma GH levels [3]. The alterations of GH/IGF-1 axis could encourage the onset of sarcopenic obesity which in turn could represent a further obstacle for physical activity, worsening cardiovascular risk and mineral metabolism [8,9]. The low GH status in obesity is considered to be an acquired functional defect; it has been demonstrated to be reversed after weight loss process

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