Prolactin Levels Are Associated to Glucose Metabolism in Patients with Overweight and Obesity. an Adaptive Hormonal Pathway to Affect Insulin Secretion Capacity?

Presentation Number: MON 593
Date of Presentation: April 3rd, 2017

Abraham Stijn Meijnikman*1, Theodorus B Twickler2, Christophe E De Block3 and Luc F Van Gaal4
1Antwerp University hospital, Edegem, Belgium, 2Antwerp University Hospital, Edegem, Belgium, 3Antwerp University Hospital, Edegem (Antwerp), Belgium, 4Faculty of Medicine, Antwerp University Hospital, Edegem, Belgium

Abstract

Prolactin (PRL) is a pituitary hormone that exerts various physiological functions in humans. Recent rodent studies found PRL playing a role in glucose homeostasis, especially in pregnancy. Human studies included mostly pregnancy related metabolism. The aim of this study was to analyze whether PRL could be related to insulin secretion and insulin resistance in male middle-aged subjects with overweight or obesity.

PRL was measured in 343 overweight and obese male subjects (BMI 38.5±6.4 kg/m², age 47±12 y). All subjects were tested for glucose metabolism, including an OGTT and HbA1c. Fat distribution was measured and HOMA-IR and HOMA-B were calculated. In addition, first and second phase insulin secretion was determined using OGTT results.

In our total study population, PRL was positively associated with HOMA-IR (r2=0.19, p<0.001), HOMA-B (r2=0.23, p=0.22), and fasting c-peptide levels (r2= 0.15, p=0.006). Furthermore, a positive association exist between PRL levels and SAT (r2= 0.36, p<0.001) and an inverse association with VAT (r2= -0.16, p=0.007) and VAT/SAT ratio (r2=-.0.15, p=0.006). After stratification for PRL in tertiles, both HOMA-B and HOMA-IR increased along PRL tertiles. In line with these observations, FPG and 2-h post OGTT glucose levels did not differ significantly between distinctive PRL tertiles. Of interest, both first and second phase insulin secretion increased significantly along PRL tertiles.

In order to define whether PRL was a principal factor in presence of a disturbed glucose metabolism, the total study population was divided into three groups, 113 subjects with a normal glucose tolerance (NGT), 170 subjects with a prediabetic status (preDM) and 60 patients with a diabetic status (DM). In NGT and preDM, PRL was significantly associated with HOMA-B (r2=0.20, p=0.04 vs. r2= 0.34, p<0.001, respectively). HOMA-IR, fasting insulin and c-peptides were only significantly associated with PRL in preDM. Furthermore, an inverse association exists between PRL and FPG was in preDM (r2= -0.15, p=0.048). Interestingly, in both NTG and preDM, a positive associations between PRL and SAT was observed, and a negative association between PRL and VAT. In DM, all prior presented associations with PRL and glucose metabolism were no longer significant.

In conclusion, along BMI range, prolactin appeared being closely related to different components in glucose metabolism, especially in those subjects with overweight or obesity and in a prediabetic condition. Interestingly, PRL was positively associated with SAT. Our observations contribute to the hypothesis that PRL, partly released from SAT, may be an important hormone in the adaptive modulation of glucose metabolism in male subjects with a high BMI.

 

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