Prospective associations of dietary carbohydrate, fat, and protein intake with β-cell function in the CODAM study

Associations of Total Fat and Fatty Acid Intake With the Risk of Type 2 Diabetes Mellitus Among Japanese Adults: Analysis Based on the JACC Study

BACKGROUND

We prospectively examined the associations of total fat and fatty acid intake with type 2 diabetes (T2D) among Japanese adults.

METHODS

This study was conducted using data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC). A validated food frequency questionnaire evaluated the intake of total fat and fatty acids. Diabetes was assessed using self-reported data. Multivariable logistic regression analysis was performed to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of incident T2D across quintiles of total fat and fatty acid intake after adjusting for potential confounders.

RESULTS

A total of 19,088 non-diabetic participants (age range, 40-79 years) enrolled in the JACC between 1988 and 1990 were included in this study. During the 5-year study period, 494 the participants developed T2D. The OR of T2D for the highest versus lowest quintiles was 0.58 (95% CI, 0.37-0.90) for total fat, 0.78 (95% CI, 0.51-1.20) for saturated fatty acid (SFA), 0.55 (95% CI, 0.35-0.86) for monounsaturated fatty acids (MUFA), 0.61 (95% CI, 0.39-0.96) for polyunsaturated fatty acids (PUFA), 0.64 (95% CI, 0.42-0.99) for n-3 PUFA, and 0.70 (95% CI, 0.45-1.09) for n-6 PUFA. Total fat and fatty acid (except SFA and n-6 PUFA) intake were inversely associated with T2D in men. Total fat and fatty acid intake were not associated with T2D in women.

CONCLUSION

Higher intakes of total fats, MUFA, PUFA, and n-3 PUFA were inversely associated with T2D among Japanese men.

Changes in adiposity mediate the associations of diet quality with insulin sensitivity and beta-cell function

BACKGROUND AND AIMS

To examine the mediating role of adiposity on the associations of diet quality with longitudinal changes in insulin sensitivity and beta-cell function.

METHODS AND RESULTS

Adults at-risk for type 2 diabetes (T2D) in the PROMISE cohort had 4 assessments over 9 years (n = 442). Alternate Healthy Eating Index (AHEI) scores were used to assess diet quality. Generalized Estimating Equations (GEE) evaluated the associations between the AHEI and longitudinal changes in insulin sensitivity (HOMA2-%S and ISI) and beta-cell function (IGI/HOMA-IR and ISSI-2). The proportion of the mediating effect of waist circumference changes was estimated using the difference method. In the primary longitudinal analysis, AHEI was positively associated with insulin sensitivity and beta-cell function over time (% difference per standard deviation increase of AHEI for HOMA2-%S (β = 11.0, 95%CI 5.43-17.0), ISI (β = 10.4, 95%CI 4.35-16.8), IGI/HOMA-IR (β = 7.12, 95%CI 0.98-13.6) and ISSI-2 (β = 4.38, 95%CI 1.05-7.80), all p < 0.05). There was no significant association between AHEI and dysglycemia incidence (OR = 0.95, 95%CI 0.77-1.17). Adjustments for longitudinal changes in waist circumference substantially attenuated all associations of AHEI with insulin sensitivity and beta-cell function. Mediation analysis indicated that waist circumference mediated 73%, 70%, 83% and 81% of the association between AHEI and HOMA2-%S, ISI, IGI/HOMA-IR, and ISSI-2, respectively (all p < 0.01).

CONCLUSION

In a Canadian population at-risk for T2D, AHEI score was positively associated with changes in insulin sensitivity and beta-cell function. These associations were substantially mediated by waist circumference, suggesting that changes in adiposity may represent an important pathway linking diet quality with risk phenotypes for T2D.

Effects of Low-Carbohydrate versus Mediterranean Diets on Weight Loss, Glucose Metabolism, Insulin Kinetics and β-Cell Function in Morbidly Obese Individuals

Low-calorie Mediterranean-style or low-carbohydrate dietary regimens are widely used nutritional strategies against obesity and associated metabolic diseases, including type 2 diabetes. The aim of this study was to compare the effectiveness of a balanced Mediterranean diet with a low-carbohydrate diet on weight loss and glucose homeostasis in morbidly obese individuals at high risk to develop diabetes. Insulin secretion, insulin clearance, and different β-cell function components were estimated by modeling plasma glucose, insulin and C-peptide profiles during 75-g oral glucose tolerance tests (OGTTs) performed at baseline and after 4 weeks of each dietary intervention. The average weight loss was 5%, being 58% greater in the low-carbohydrate-group than Mediterranean-group. Fasting plasma glucose and glucose tolerance were not affected by the diets. The two dietary regimens proved similarly effective in improving insulin resistance and fasting hyperinsulinemia, while enhancing endogenous insulin clearance and β-cell glucose sensitivity. In summary, we demonstrated that a low-carbohydrate diet is a successful short-term approach for weight loss in morbidly obese patients and a feasible alternative to the Mediterranean diet for its glucometabolic benefits, including improvements in insulin resistance, insulin clearance and β-cell function. Further studies are needed to compare the long-term efficacy and safety of the two diets.

Distinct genetic subtypes of adiposity and glycemic changes in response to weight-loss diet intervention: the POUNDS Lost trial

PURPOSE

Obesity is a heterogeneous condition and distinct adiposity subtypes may differentially affect type 2 diabetes risk. We assessed relations between genetically determined subtypes of adiposity and changes in glycemic traits in a dietary intervention trial.

METHODS

The four genetic subtypes of adiposity including waist-hip ratio-increase only (WHRonly+), body mass index-increase only (BMIonly+), WHR-increase and BMI-increase (BMI+WHR+), and WHR-decrease and BMI-increase (BMI+WHR-) were assessed by polygenetic scores (PGSs), calculated based on 159 single nucleotide polymorphisms related to BMI and/or WHR. We examined the associations between the four PGSs and changes in fasting glucose, insulin, β-cell function (HOMA-B) and insulin resistance (HOMA-IR) in 692 overweight participants (84% white Americans) who were randomly assigned to one of four weight-loss diets in a 2-year intervention trial.

RESULTS

Higher BMI+WHR-PGS was associated with a greater decrease in 2-year changes in waist circumference in white participants (P = 0.002). We also found significant interactions between WHRonly+PGS and dietary protein in 2-year changes in fasting glucose and HOMA-B (P = 0.0007 and < 0.0001, respectively). When consuming an average-protein diet, participants with higher WHRonly+PGS showed less increased fasting glucose (β = - 0.46, P = 0.006) and less reduction in HOMA-B (β = 0.02, P = 0.005) compared with lower WHRonly+PGS. Conversely, eating high-protein diet was associated with less decreased HOMA-B among individuals with lower than higher WHRonly+PGS (β = - 0.02, P = 0.006).

CONCLUSIONS

Distinct genetically determined adiposity subtypes may differentially modify the effects of weight-loss diets on improving glucose metabolism in white Americans. This trial was registered at clinicaltrials.gov as NCT00072995.

Effect of Sechium edule var. nigrum spinosum (Chayote) on Telomerase Levels and Antioxidant Capacity in Older Adults with Metabolic Syndrome

Patients with metabolic syndrome (MetS) have a redox imbalance, due to a decay in antioxidant capacity. Oxidative stress (OxS) is considered an important modulator of telomere shortening and telomerase activity. One of the fruits that has been associated with an antioxidant effect is Sechium edule and although its properties are well established, there is only one exploratory study evaluating its effectiveness in patients with MetS. The present investigation is a much more robust and controlled study, including a placebo group. Hence, we determined the effect of consumption of the dried fruit powder (500 mg, three times per day) for three months. We measured effects on telomerase levels, antioxidant capacity, and markers for OxS. The study was performed in a sample of 75 older adults: placebo group (n = 30) and experimental group (n = 45) with the diagnosis of MetS according to the National Adult Treatment Panel of the National Cholesterol Program III (NCEP/ATP III) criteria. All markers were measured before and after three months of treatment. There was a statistically significant decrease in lipoperoxides and protein carbonylation with an increased superoxide dismutase (SOD), as well as sustained levels of telomerase in patients who consumed Sechium edule. Our findings suggest that consumption of this fruit has a hypoglycemic, hypotensive, and antioxidant effect, without altering telomerase levels, which could suggest better protection against telomere shortening.

Whole Fruits and Fruit Fiber Emerging Health Effects

Less than 10% of most Western populations consume adequate levels of whole fruits and dietary fiber with typical intake being about half of the recommended levels. Evidence of the beneficial health effects of consuming adequate levels of whole fruits has been steadily growing, especially regarding their bioactive fiber prebiotic effects and role in improved weight control, wellness and healthy aging. The primary aim of this narrative review article is to examine the increasing number of health benefits which are associated with the adequate intake of whole fruits, especially fruit fiber, throughout the human lifecycle. These potential health benefits include: protecting colonic gastrointestinal health (e.g., constipation, irritable bowel syndrome, inflammatory bowel diseases, and diverticular disease); promoting long-term weight management; reducing risk of cardiovascular disease, type 2 diabetes and metabolic syndrome; defending against colorectal and lung cancers; improving odds of successful aging; reducing the severity of asthma and chronic obstructive pulmonary disease; enhancing psychological well-being and lowering the risk of depression; contributing to higher bone mineral density in children and adults; reducing risk of seborrheic dermatitis; and helping to attenuate autism spectrum disorder severity. Low whole fruit intake represents a potentially more serious global population health threat than previously recognized, especially in light of the emerging research on whole fruit and fruit fiber health benefits.