Omega-3 polyunsaturated fatty acids favourably modulate cardiometabolic biomarkers in type 2 diabetes: a meta-analysis and meta-regression of randomized controlled trials

BACKGROUND: Randomized controlled trials (RCTs) suggest that supplementation with omega-3 polyunsaturated fatty acids (n-3PUFAs) may favourably modify cardiometabolic biomarkers in type 2 diabetes (T2DM). Previous meta-analyses are limited by insufficient sample sizes and omission of meta-regression techniques, and a large number of RCTs have subsequently been published since the last comprehensive meta-analysis. Updated information regarding the impact of dosage, duration or an interaction between these two factors is therefore warranted. The objective was to comprehensively assess the effect of n-3PUFAs supplementation on cardiometabolic biomarkers including lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control, in people with T2DM, and identify whether treatment dosage, duration or an interaction thereof modify these effects. METHODS: Databases including PubMed and MEDLINE were searched until 13th July 2017 for RCTs investigating the effect of n-3PUFAs supplementation on lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control. Data were pooled using random-effects meta-analysis and presented as standardised mean difference (Hedges g) with 95% confidence intervals (95% CI). Meta-regression analysis was performed to investigate the effects of duration of supplementation and total dosage of n-3PUFAs as moderator variables where appropriate. RESULTS: A total of 45 RCTs were identified, involving 2674 people with T2DM. n-3PUFAs supplementation was associated with significant reductions in LDL [ES: - 0.10, (95% CI - 0.17, - 0.03); p = 0.007], VLDL (ES: - 0.26 (- 0.51, - 0.01); p = 0.044], triglycerides (ES: - 0.39 (- 0.55, - 0.24; p ≤ 0.001] and HbA1c (ES: - 0.27 (- 0.48, - 0.06); p = 0.010]. Moreover, n-3PUFAs supplementation was associated with reduction in plasma levels of TNF-α [ES: - 0.59 (- 1.17, - 0.01); p = 0.045] and IL-6 (ES: - 1.67 (- 3.14, - 0.20); p = 0.026]. All other lipid markers, indices of glycaemic control, inflammatory parameters, and blood pressure remained unchanged (p > 0.05). CONCLUSIONS: n-3PUFAs supplementation produces favourable hypolipidemic effects, a reduction in pro-inflammatory cytokine levels and improvement in glycaemia. Neither duration nor dosage appear to explain the observed heterogeneity in response to n-3PUFAs. Trial registration This trial was registered at http://www.crd.york.ac.uk as CRD42016050802

Body mass index and the all-cause mortality rate in patients with type 2 diabetes mellitus

Aims - The relationship between obesity and mortality rate among diabetic patients is a controversial topic. The aim of this study was to investigate the association between obesity and all-cause mortality risk in patients with type 2 diabetes. Methods - In this retrospective database study, 2383 patients with type 2 diabetes, who had been registered in the Isfahan Endocrine and Metabolism Research Center, Iran, were enrolled between 1992 and 2010. The mean (SD) of diabetes duration and follow-up period was 15.5 (8.0) and 7.8 (3.9) years. The main outcome was all-cause mortality. All-cause mortality rates were calculated for the body mass index (BMI) categories of underweight, normal, overweight and class I, II and III obese. Cox proportional hazard models were used to estimate the adjusted hazard ratio for BMI as categorical variable using BMI of 18.5–24.9 kg/m2 as the reference group. Results - The mortality rate in patients with normal weight was higher than overweight patients (59.11 vs. 33.17 per 1000 person-years). The adjusted hazard ratios of all-cause mortality were 0.82 [95%CI 0.68–0.99; P = 0.037], 0.79 [95%CI 0.61–1.02; P = 0.069], 0.71 [95%CI 0.42–1.19; P = 0.191] and 1.36 [95%CI 0.55–3.33; P = 0.507] for overweight, class I, II and III obesity, respectively. When BMI was included in the Cox model as a time-dependent variable, the U-shaped relationship between BMI and all-cause mortality did not change. Conclusions - The results show a U-shaped association of BMI with all-cause mortality in patients with type 2 diabetes with the lowest risk observed among the overweight patients