Effects of soy protein and isoflavones on glycemic control and insulin sensitivity: a 6-mo double-blind, randomized, placebo-controlled trial in postmenopausal Chinese women with prediabetes or untreated early diabetes

The association of serum C-reactive protein, uric acid and magnesium with insulin resistance in Chinese postmenopausal women with prediabetes or early untreated diabetes

OBJECTIVES

This study aimed to evaluate the association of serum inflammatory markers (C-reactive protein (CRP) and uric acid (UA)), magnesium and other CVD risk factors with insulin resistance (IR) among Chinese postmenopausal women with prediabetes. STUDY DESIGN AND MAIN OUTCOMES MEASURES: This is a cross-sectional analysis of baseline data among 180 postmenopausal women with prediabetes or early untreated diabetes. Major anthropometric and biochemical measures included body mass index (BMI), waist to hip ratio (WHR), fasting and postload glucose and insulin, serum CRP, UA, lipids profile, and magnesium. IR was estimated using fasting glucose and insulin by homeostasis model assessment (HOMA).

RESULTS

Multivariate linear regression analyses indicated that Lg CRP, WHR, serum triglycerides (TGs) and magnesium were the major predictors of HOMA-IR. A multivariate logistic analyses showed that a CRP level above 3.0 mg/l was significantly associated with a 2.8-fold risk of having higher HOMA-IR (>2.52). BMI plays a key role in mediating the relationship of CRP and IR. Elevated serum TG (>1.71 mmol/l), WHR (>0.88), UA (>357 mmol/l) and lower serum magnesium (<0.78 mg/l) were associated with 5.26 (95%CI: 2.52-10.98, P<0.05), 3.02 (95%CI: 1.64-5.55, P<0.05), 1.97 (95%CI: 1.02-3.83, P=0.05) and 0.51 (95%CI: 0.28-0.81) folds risk of higher HOMA-IR, respectively in the unadjusted model. Serum magnesium, but not UA was an independent risk factor of HOMA-IR.

CONCLUSION

The present study in prediabetic or early untreated diabetic Chinese postmenopausal women indicated that IR is significantly associated with increased inflammation (CRP and UA), serum TG, WHR and lower serum magnesium.

Randomized, double-blind, controlled, comparative trial of formula food containing soy protein vs. milk protein in visceral fat obesity. -FLAVO study-

BACKGROUND

The purpose of the present study was to clarify the efficacy of soy at reducing visceral fat. A randomized, double-blind, controlled, comparative trial was carried out to compare formula food containing soy protein (SP) to the same food in which soy was replaced with milk protein (MP).

METHODS AND RESULTS

Forty-eight participants were enrolled for the treatment of visceral fat obesity (visceral fat area >100 cm² on computed tomography). The SP formula contained 12 g of SP, 9 g of MP, and other nutrients, and was given for 20 weeks in the morning, while in the MP formula SP was replaced with MP. During the 20 weeks of the trial period, visceral fat area and subcutaneous fat area in the MP group were significantly reduced, while those in the SP group did not change as assessed on analysis of covariance. Although waist circumference was reduced in both the SP and MP groups, body weight and body mass index were significantly reduced only in the MP group. Based on a mixed-effects model, the difference in log-transformed visceral fat profiles between the 2 groups was statistically significant (P<0.05), while a negative relationship was observed between the changes in visceral fat and adiponectin in the MP group (P<0.001), but not in the SP group.

CONCLUSIONS

Formula food containing MP is superior to that containing SP for reducing visceral and subcutaneous fat.

The effect of Spirulina platensis versus soybean on insulin resistance in HIV-infected patients: a randomized pilot study

HIV-infected patients develop abnormalities of glucose metabolism due to the virus and antiretroviral drugs. Spirulina and soybean are nutritional supplements that are cheap, accessible in our community and affect glucose metabolism. We carried out a randomized study to assess the effect of Spirulina platensis versus soybean as a food supplement on HIV/HAART-associated insulin resistance (IR) in 33 insulin-resistant HIV-infected patients. The study lasted for two months at the National Obesity Centre of Cameroon. Insulin resistance was measured using the short insulin tolerance test. Physical activity and diet did not change over the study duration. On-treatment analysis was used to analyze data. The Mann-Whitney U test, the Students T test and the Chi square test were used as appropriate. Curve gradients were analyzed using ANCOVA. Seventeen subjects were randomized to spirulina and 16 to soybean. Each received 19 g of supplement daily. The follow up rate was 65% vs. 100% for spirulina and soybean groups, respectively, and both groups were comparable at baseline. After eight weeks, insulin sensitivity (IS) increased by 224.7% vs. 60% in the spirulina and soybean groups respectively (p < 0.001). One hundred per cent vs. 69% of subjects on spirulina versus soybean, respectively, improved their IS (p = 0.049) with a 1.45 (1.05-2.02) chance of improving insulin sensitivity on spirulina. This pilot study suggests that insulin sensitivity in HIV patients improves more when spirulina rather than soybean is used as a nutritional supplement.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT01141777.

Lupin and soya reduce glycaemia acutely in type 2 diabetes

Addition of fibre or protein to carbohydrate-rich foods can reduce the glycaemic response to those foods. This may assist with glycaemic management in individuals with type 2 diabetes. Lupin is a legume rich in fibre and protein. We assessed the acute effects of lupin- and soya-based beverages on glucose and insulin responses in type 2 diabetic individuals. We hypothesised that the lupin and soya beverages would lower the acute glycaemic response compared with a control beverage containing no protein or fibre, and that lupin would reduce the postprandial glucose more than soya. In a randomised, controlled, cross-over trial, twenty-four diabetic adults (nineteen men and five women) attended three testing sessions, each 1 week apart. At each session, participants consumed a beverage containing 50 g glucose (control), 50 g glucose plus lupin kernel flour with 12·5 g fibre and 22 g protein (lupin), or 50 g glucose plus 12·5 g fibre and 22 g protein from soya isolates (soya). Serum glucose, insulin and C-peptide were measured periodically for 4 h following beverage consumption. Compared with the control beverage, the 4 h post-beverage glucose response was lower (P < 0·001), and the 4 h post-beverage insulin and C-peptide responses were higher (P < 0·001) for lupin and soya. Glucose (P = 0·25) and C-peptide (P = 0·07) responses did not differ significantly between lupin and soya, but lupin resulted in a lower insulin response compared with soya (P = 0·013). Adding lupin or soya to a carbohydrate-rich beverage reduces glycaemia acutely in type 2 diabetic individuals. This may have a beneficial role in glycaemic management.

Effects of soy intake on glycemic control: a meta-analysis of randomized controlled trials

BACKGROUND

Evidence from animal and observational studies has supported the beneficial effects of soy intake on glycemic control, but intervention studies in humans have generated mixed results and have not been systematically examined.

OBJECTIVE

We aimed to quantitatively evaluate the effects of soy intake on measures of glycemic control.

DESIGN

We conducted a structured electronic search of PubMed, EMBASE, the Cochrane Library, and the China National Knowledge Infrastructure (updated to March 2010) databases for randomized controlled trials that described the effectiveness of different soy regimes on measures of glycemic control [homeostatic model assessment of insulin resistance (HOMA-IR) and fasting glucose and insulin, glycated hemoglobin (Hb A(1c)), and 2-h glucose and insulin concentrations]. Data on participants, interventions, outcomes, and potential effect modifiers were extracted independently. Weighted mean effect sizes were calculated for net changes by using fixed-effects or random-effects models. We performed prespecified subgroup analyses to explore the influence of covariates on net changes of fasting glucose and insulin concentrations.

RESULTS

Twenty-four trials with a total of 1518 subjects were included in the meta-analysis. Soy consumption did not significantly affect measures of glycemic control. The mean (95% CI) difference was -0.69 mg/dL (-1.65, 0.27 mg/dL) for fasting glucose concentrations in the fixed-effects model (P = 0.16) and -0.18 mg/dL (-0.70, 0.34 mg/dL) for fasting insulin concentrations in the random-effects model (P = 0.50). Significant heterogeneity was noted in the results of fasting insulin concentrations and HOMA-IR.

CONCLUSIONS

There was not a significant overall effect of soy intake on improvements of fasting glucose and insulin concentrations; however, a favorable change in fasting glucose concentrations was observed in studies that used whole soy foods or a soy diet in the subgroup analysis. Evidence for other glycemic variables such as Hb A(1c) and 2-h postchallenge glucose and insulin concentrations was limited because of the small number of trials.