Spexin as an indicator of beneficial effects of exercise in human obesity and diabetes

Abstract

Spexin is a novel neuropeptide playing an emerging role in metabolic diseases such as obesity and diabetes via involvement in energy homeostasis and food intake. The present study investigated the effects of obesity and type 2 diabetes (T2D) on circulating levels of spexin and its modulation by physical exercise. Normal-weight (n = 50) and obese adults with and without T2D (n = 69 and n = 66, respectively) were enrolled in the study. A subgroup of obese participants (n = 47) underwent a supervised 3-month exercise programme. Plasma spexin levels were measured by ELISA and correlated with various markers. Plasma spexin levels decreased in obese participants with or without T2D compared with those of normal-weight participants (0.43 ± 0.11, 0.44 ± 0.12 and 0.61 ± 0.23 ng/ml, respectively; P < 0.001). Spexin levels negatively correlated with adiposity markers and blood pressure in the whole study population (P < 0.05). Multiple regression analysis revealed blood pressure was the greatest predictive determinant of plasma spexin levels, which significantly increased in response to physical exercise in obese participants without and with T2D (P < 0.05). Spexin levels significantly increased only in responders to exercise (those with increased oxygen consumption, VO₂ max) with a concomitant improvement in metabolic profile. In conclusion, plasma spexin levels may be an indicator of response to physical exercise.

Figure 1

Spexin levels in the plasma. (A) Circulating levels of spexin were measured by ELISA using plasma samples from normal-weight (n = 50) and obese people without (n = 66) and with diabetes (n = 69) at baseline. 2-way ANOVA test was used to determine significance of difference in means between the groups. (B) Obese participants without diabetes were segregated into 2 groups, metabolically healthy obese (MHO) and metabolically unhealthy obese (MUO) based on the Adult Treatment Panel-III (NCEP-ATPIII guideline) criteria for metabolic syndrome components including the following criteria: (1) TG ≥ 150 mg/dl; (2) HDL-C < 40 mg/dl for men and < 50 mg/dl for women; (3) BP ≥ 130/85 mm Hg and (4) FBG ≥ 100 mg/dl. Nonparametric Wilcoxon test was used to determine significance of difference in means between the two groups. (C) Good and poor glycaemic control participant classification are based on HbA1c levels. Nonparametric Wilcoxon test was used to determine significance of difference in means between the two groups.

Figure 2

Physical exercise increased the release of spexin in obese participants. Circulating levels of Spexin were measured by ELISA using plasma samples from (A) all obese participants, or obese participants without (B) and (C) with diabetes before and after a 3-month physical exercise intervention (n = 47, n = 20 and n = 27, respectively). The P value was determined using a paired t-test for intragroup comparisons before and after exercise.

Figure 3

Spexin levels are increased in obese participants displaying improvement of VO₂ max due to exercise. Circulating levels of Spexin were measured by ELISA using plasma samples from obese people and segregated according to increased (responders, n = 33) or not (non-responders, n = 14) VO₂ max levels after 3-month physical exercise. The P value was determined using a paired t-test for intragroup comparisons before and after exercise.