Is the association between dietary fat intake and insulin resistance modified by physical activity?

Prevention of Insulin Resistance by Dietary Intervention among Pregnant Mothers: A Randomized Controlled Trial

BACKGROUND

Chronic insulin resistance (IR) is a basic part of the pathophysiology of gestational diabetes mellitus. Nutrition significantly impacts IR and weight loss reduces insulin levels, whereas weight gain increases the concentrations. Therefore, we surveyed the effect of nutrition intervention on IR in pregnant women and whether this effect is irrespective of weight gaining in accordance with Institute of Medicine limits.

METHODS

This prospective, randomized clinical trial was carried out among 150 primiparous pregnant mothers in fifteen health centers, five hospitals, and 15 private obstetrical offices in Isfahan. The nutrition intervention included education of healthy diet with emphasize on 50%-55% of total energy intake from carbohydrate (especially complex carbohydrates), 25%-30% from fat (to increase mono unsaturated fatty acids and decrease saturated and trans-fatty acids), and 15%-20% from protein during pregnancy for experimental group. The controls received the usual prenatal care by their health-care providers.

RESULTS

This trial decreased pregnancy-induced insulin increases (P = 0.01) and IR marginally (P = 0.05). ANCOVA demonstrated that control of gestational weight gaining was more effective to decrease IR (P = 0.02) while insulin values decreased by nutrition intervention and irrespective of weight control (P = 0.06). Fasting plasma glucose (FPG) concentrations did not decrease by intervention (P = 0.56) or weight management (P = 0.15).

CONCLUSIONS

The current intervention was effective to decrease pregnancy-induced insulin increases and IR. Considering study results on FPG levels and incidence of GDM, we suggest repeat of study design in a larger sample.

The Association Between Physical Activity During Pregnancy and Gestational Diabetes Mellitus: A Case-Control Study

BACKGROUND

Gestational diabetes mellitus is one of the most common complications of pregnancy. Physical activity is associated with a lower risk of type 2 diabetes mellitus. A recent meta-analysis study suggested that more research is needed to investigate the type, duration and intensity of physical activity that can help to reduce the risk of gestational diabetes mellitus.

OBJECTIVES

The present study aimed to understand the association between physical activity and gestational diabetes mellitus through comparing the type and intensity of physical activity performed by pregnant females with gestational diabetes and healthy pregnant females in the first 20 weeks of their pregnancy.

PATIENTS AND METHODS

In the current case-control study, 100 pregnant females with gestational diabetes mellitus as the case group and 100 pregnant females as the non-diabetic control group were recruited. The age range of the participants was 18 - 40 years with the gestation of 20 - 28 weeks. To diagnose gestational diabetes mellitus using the criteria introduced by carpenter and coustan females with abnormal glucose challenge test (> 140 mg/dL) were asked to perform the three-hour 100 g oral glucose tolerance test. The details of physical activity were collected by a modified version of the pregnancy physical activity questionnaire. Anthropometric and relevant data were recorded for all of the participants. Data were analyzed by SPSS version 21. Risk estimates were obtained by logistic regression and adjusted for confounders.

RESULTS

Females who had low total physical activity according to the pregnancy physical activity questionnaire during early pregnancy were at a significantly higher risk of developing gestational diabetes mellitus (OR = 4.12, 95% CI (2.28 - 7.43), P = 0.001) compared to the ones who reported higher levels of physical activity. Moreover, after adjusting for age, body mass index (BMI), gravidity and a family history of diabetes, females with low physical activity in the domain of transportation activity during 20 weeks of pregnancy were at a significantly higher risk of developing gestational diabetes mellitus. The statistical findings indicate that females with the low intensity of sedentary, light and moderate physical activity are at a higher risk of developing gestational diabetes mellitus (OR 2.32; 95% CI 1.21-4.43, P = 0.010, OR 6.26; 95% CI 2.95 - 13.30, P = 0.001 and OR 6.73; 95% CI 3.15 - 14.38, P = 0.001) compared to females with a higher intensity of sedentary, light and moderate physical activity.

CONCLUSIONS

The amount and intensity of physical activity during pregnancy is associated with a lower risk of gestational diabetes mellitus. As a result, the pregnant Iranian females have to be encouraged to do regular daily physical activity during pregnancy, if there is no specific contraindication to it.

PPARγ2 polymorphism and human health

The nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARγ) is an important transcription factor regulating adipocyte differentiation, lipid and glucose homeostasis, and insulin sensitivity. Numerous genetic mutations of PPARγ have been identified and these mutations positively or negatively regulate insulin sensitivity. Among these, a relatively common polymorphism of PPARγ, Pro12Ala of PPARγ2, the isoform expressed only in adipose tissue has been shown to be associated with lower body mass index, enhanced insulin sensitivity, and resistance to the risk of type 2 diabetes in human subjects carrying this mutation. Subsequent studies in different ethnic populations, however, have revealed conflicting results, suggesting a complex interaction between the PPARγ2 Pro12Ala polymorphism and environmental factors such as the ratio of dietary unsaturated fatty acids to saturated fatty acids and/or between the PPARγ2 Pro12Ala polymorphism and genetic factors such as polymorphic mutations in other genes. In addition, this polymorphic mutation in PPARγ2 is associated with other aspects of human diseases, including cancers, polycystic ovary syndrome, Alzheimer disease and aging. This review will highlight findings from recent studies.

Population-wide changes in reported lifestyle are associated with redistribution of adipose tissue

AIMS

The Northern Sweden MONICA project 1986-2004 demonstrated a marked increase in average body mass, an unchanged prevalence of diabetes, and a decrease in myocardial infarctions and lately also in stroke. This study estimates the relative importance of time-trends in lifestyle on average waist and hip circumference on a population level.

METHODS

From a series of independent cross-sectional surveys, a study population of 2,831 men and 2,976 women was formed. Associations between lifestyle factors and waist and hip circumference were estimated. Partial regression coefficients for every level of the lifestyle factors were multiplied by the differences in the proportion of the population reporting the corresponding levels of the respective lifestyle factors in 1986 and 2004. The sum of the product terms for each item represents the respective estimated impact of change in waist and hip circumference.

RESULTS

Lifestyle trends associated with changes in hip circumference were (women/men): higher education level (+4.0 mm/+2.4 mm), fewer smokers (+0.4 mm/+0.9 mm), a slight increase in alcohol consumption (+0.4 mm/+0.3 mm), and more saturated fat from meat in women (-0.9 mm) and more fibre from grains in men (+0.6 mm). Average waist circumference was influenced by increased levels of physical activity (-2.2 mm/-4.6 mm), fewer female smokers (-0.3 mm), and a higher intake of saturated fatty acids from meat among men (+1.8 mm).

CONCLUSIONS

We identified physical activity and the intake of meat and whole-grain products as prime candidates for lifestyle interventions in northern Sweden.

The association of intensity and overall level of physical activity energy expenditure with a marker of insulin resistance

AIMS/HYPOTHESIS

Physical activity is important in preventing insulin resistance, but it is unclear which dimension of activity confers this benefit. We examined the association of overall level and intensity of physical activity with fasting insulin level, a marker of insulin resistance.

METHODS

This was a cross-sectional analysis of the Medical Research Council Ely population-based cohort study (2000--2002). Physical activity energy expenditure (PAEE) in kJ kg(-1) min(-1) was measured by heart rate monitoring with individual calibration over a period of 4 days. The percentage of time spent above 1.5, 1.75 and 2 times resting heart rate (RHR) represented all light-to-vigorous, moderate-to-vigorous and vigorous activity, respectively.

RESULTS

Data from a total of 643 non-diabetic individuals (319 men, 324 women) aged 50 to 75 years were analysed. In multivariate linear regression analyses, adjusting for age, sex and body fat percentage, PAEE was significantly associated with fasting insulin (pmol/l) (beta = -0.875, p = 0.006). Time (% of total) spent above 1.75 x RHR and also time spent above 2 x RHR were both significantly associated with fasting insulin (beta = -0.0109, p = 0.007 and beta = -0.0365, p = 0.001 respectively), after adjusting for PAEE, age, sex and body fat percentage. Time spent above 1.5 x RHR was not significantly associated with fasting insulin in a similar model (beta = -0.0026, p = 0.137).

CONCLUSIONS/INTERPRETATION

The association between PAEE and fasting insulin level, a marker of insulin resistance, may be attributable to the time spent in moderate-to-vigorous and vigorous activity, but not to time spent in light-intensity physical activity.

Reported food intake and distribution of body fat: a repeated cross-sectional study

Background

Body mass, as well as distribution of body fat, are predictors of both diabetes and cardiovascular disease. In Northern Sweden, despite a marked increase in average body mass, prevalence of diabetes was stagnant and myocardial infarctions decreased. A more favourable distribution of body fat is a possible contributing factor.

This study investigates the relative importance of individual food items for time trends in waist circumference (WC) and hip circumference (HC) on a population level.

Methods

Independent cross-sectional surveys conducted in 1986, 1990, 1994 and 1999 in the two northernmost counties of Sweden with a common population of 250000. Randomly selected age stratified samples, altogether 2982 men and 3087 women aged 25–64 years. Questionnaires were completed and anthropometric measurements taken. For each food item, associations between frequency of consumption and waist and hip circumferences were estimated. Partial regression coefficients for every level of reported intake were multiplied with differences in proportion of the population reporting the corresponding levels of intake in 1986 and 1999. The sum of these product terms for every food item was the respective estimated impact on mean circumference.

Results

Time trends in reported food consumption associated with the more favourable gynoid distribution of adipose tissue were increased use of vegetable oil, pasta and 1.5% fat milk. Trends associated with abdominal obesity were increased consumption of beer in men and higher intake of hamburgers and French fried potatoes in women.

Conclusion

Food trends as markers of time trends in body fat distribution have been identified. The method is a complement to conventional approaches to establish associations between food intake and disease risk on a population level.

Sex-specific differences in colon cancer associated with p53 mutations

INTRODUCTION

Sex-specific differences in observed incidence rates, tumor subsite, and diet and lifestyle associations with colon cancer have been observed. We evaluate sex-specific associations with p53 mutations in colon cancer to add to understanding of these differences. Data from a large population-based incident case-control study of colon cancer were used to evaluate age and gender associations with p53 mutations. To obtain a better understanding of gender-specific associations, we evaluated the role of estrogen as a mediator of risk. For these analyses, women were classified as estrogen positive or negative, based on menopausal status and use of hormone replacement therapy (HRT).

RESULTS

There was a significant interaction between age and sex and risk of an acquired p53 mutation compared with p53 Wt. Among men, there was an increase in p53 mutations with age, whereas among women the opposite was observed. Associations with parity, oral contraceptive use, and total ovulatory months were not associated with p53 mutations. However, recent use of HRT reduced risk of all tumors, as did being estrogen positive. Women who were estrogen positive (either premenopausal or recent users of HRT) were at a significantly increased risk of an acquired p53 mutation if they consumed a diet with a high sugar index (odds ratio = 2.94; 95% confidence interval = 1.47-5.89); similar increases in risk of p53 mutations were not observed for men or women who were estrogen negative.

CONCLUSIONS

Although sex-specific associations were detected for acquired p53 mutations, they do not indicate a unique role of estrogens in the mutation of p53. These data are consistent with a role for estrogen in altering susceptibility to diet and lifestyle factors possibly via an insulin-related mechanism.

Carbohydrate-restricted diets high in either monounsaturated fat or protein are equally effective at promoting fat loss and improving blood lipids

BACKGROUND

When substituted for carbohydrate in an energy-reduced diet, dietary protein enhances fat loss in women. It is unknown whether the effect is due to increased protein or reduced carbohydrate.

OBJECTIVE

We compared the effects of 2 isocaloric diets that differed in protein and fat content on weight loss, lipids, appetite regulation, and energy expenditure after test meals.

DESIGN

This was a parallel, randomized study in which subjects received either a low-fat, high-protein (LF-HP) diet (29 +/- 1% fat, 34 +/- 0.8% protein) or a high-fat, standard-protein (HF-SP) diet (45 +/- 0.6% fat, 18 +/- 0.3% protein) during 12 wk of energy restriction (6 +/- 0.1 MJ/d) and 4 wk of energy balance (7.4 +/- 0.3 MJ/d). Fifty-seven overweight and obese [mean body mass index (in kg/m(2)): 33.8 +/- 0.9] volunteers with insulin concentrations >12 mU/L completed the study.

RESULTS

Weight loss (LF-HP group, 9.7 +/- 1.1 kg; HF-SP group, 10.2 +/- 1.4 kg; P = 0.78) and fat loss were not significantly different between diet groups even though the subjects desired less to eat after the LF-HP meal (P = 0.02). The decrease in resting energy expenditure was not significantly different between diet groups (LF-HP, -342 +/- 185 kJ/d; HF-SP, -349 +/- 220 kJ/d). The decrease in the thermic effect of feeding with weight loss was smaller in the LF-HP group than in the HF-SP group (-0.3 +/- 1.0% compared with -3.6 +/- 0.7%; P = 0.014). Glucose and insulin responses to test meals improved after weight loss (P < 0.001) with no significant diet effect. Bone turnover, inflammation, and calcium excretion did not change significantly.

CONCLUSION

The magnitude of weight loss and the improvements in insulin resistance and cardiovascular disease risk factors did not differ significantly between the 2 diets, and neither diet had any detrimental effects on bone turnover or renal function.

A case-control study of maternal recreational physical activity and risk of gestational diabetes mellitus

Despite the maternal and infant morbidity associated with gestational diabetes mellitus (GDM), few modifiable risk factors have been identified. We explored the relation between recreational physical activity performed during the year before and during the first 20 weeks of pregnancy and the risk of GDM. 155 GDM cases and 386 normotensive, non-diabetic pregnant controls provided information about the type, intensity, frequency, and duration of physical activity performed during these time periods. Women who participated in any recreational physical activity during the first 20 weeks of pregnancy, as compared with inactive women, experienced a 48% reduction in risk of GDM (odds ratio [OR] = 0.52; 95% confidence interval [CI] 0.33-0.80). The number of hours spent performing recreational activities and the energy expended were related to a decrease in GDM risk. No clear patterns related to distance walked and pace of walking emerged. Daily stair climbing, when compared with no stair climbing, was associated with a 49-78% reduction in GDM risk (P for trend <0.011). Recreational physical activity performed during the year before the index pregnancy was also associated with statistically significant reductions in GDM risk, but women who engaged in physical activity during both time periods experienced the greatest reduction in risk (OR = 0.40; 95% CI 0.23-0.68). These data suggest that recreational physical activity performed before and/or during pregnancy is associated with a reduced risk of GDM.

Does peroxisome proliferator-activated receptor gamma genotype (Pro12ala) modify the association of physical activity and dietary fat with fasting insulin level?

Peroxisome proliferator-activated receptor gamma (PPARgamma) has a role in controlling adipogenesis and insulin sensitivity. Previous studies have suggested that a common polymorphism (Pro12Ala) in the PPARgamma-2 isoform of this gene may be associated with markers of insulin resistance. We have previously shown that in combination, the relationships with fasting insulin of dietary polyunsaturated to saturated fatty acid ratio (P:S ratio) and physical activity are additive. We have also demonstrated that the association between P:S ratio and fasting insulin level is modified by the Pro12Ala genotype. The purpose of the present study was to investigate whether the Pro12Ala genotype modified the combined relationships of P:S ratio and physical activity level (PAL) on fasting insulin concentration. A population-based cohort of 506 Caucasian men and women aged 31 to 71 years was genotyped for the Pro12Ala polymorphism. P:S ratio was assessed by food-frequency questionnaire (FFQ) and PAL was estimated from 4 days of free-living heart rate monitoring following individual calibration of heart rate against energy expenditure during an exercise stress test. The combined associations of PAL and P:S ratio on fasting insulin level were examined stratified by Pro12Ala genotypes in a dominant model for the Ala allele. Among Pro allele homozygotes, there was no interaction between PAL and P:S ratio on fasting insulin (P =.929). However, in carriers of the Ala allele the association of P:S ratio with fasting insulin was modified by activity level (interaction P = 0.038). In those who were inactive and carried the Ala allele, the age-, sex-, and body mass-adjusted relationship between P:S ratio and log insulin was not significant (beta = -0.03, P =.93). In contrast, in physically active Ala carriers, the association of P:S ratio with log fasting insulin was highly significant (beta = -0.93, P =.004). In conclusion, this study examined the modification by PPARgamma genotype of the association between energy expenditure, P:S ratio, and fasting insulin level, a measure of insulin resistance. These data show that in Pro allele homozygotes the combined associations of P:S ratio and PAL are additive. In contrast, in Ala allele carriers, PAL modifies the association between P:S ratio and fasting insulin level in a multiplicative manner.

Nutrition and prevention of type 2 diabetes

In recent years, the prevalence of type 2 diabetes has increased alarmingly worldwide, giving diabetes the dimension of an epidemic. Striking parallel increases in the prevalence of obesity reflect the importance of body fatness as a contributing factor to diabetes incidence. Moreover, it has been estimated that up to 75% of the risk of type 2 diabetes is attributable to obesity. Recent clinical trials and observational epidemiologic studies demonstrate the efficacy of lifestyle changes, including decreased energy intake, decreased fat intake, and weight loss, as well as regular participation in physical activity, in improving insulin sensitivity (SI) and reducing the risk of diabetes. This review evaluates evidence of the effect of diet on insulin resistance, insulin secretion, and glucose tolerance, and reflects on directions for future work toward primary prevention of type 2 diabetes.

Iatrogenic lipodystrophy in HIV patients – the need for very-low-fat diets

In HIV patients, chronic treatment with protease inhibitors often precipitates a peripheral lipodystrophy associated with insulin resistance syndrome and premature coronary disease. In vitro studies demonstrate that these drugs can compromise the ability of adipocytes to store triglycerides; in vivo, peripheral subcutaneous adipocytes appear to be most affected, such that body fat often redistributes to visceral or truncal adipose stores. Dysfunction of peripheral subcutaneous adipocytes - ordinarily quite efficient for storing fat - can be expected to give rise to an excessive flux of free fatty acids (FFAs) following fatty meals; chronic overexposure of tissues to FFAs is a likely explanation for the insulin resistance syndrome associated with lipodystrophy. These considerations suggest that a very-low-fat diet - less than 15% fat calories - may ameliorate the cardiovascular risk associated with lipodystrophy; such diets are known to have a favorable effect on the insulin sensitivity of healthy subjects. Very-low-fat whole-food vegan diets are particularly recommendable in this context, as they may help to shrink visceral fat depots while markedly reducing LDL cholesterol. Appropriate adjunctive measures may include aerobic exercise training - beneficial both for insulin sensitivity and weight control - as well as administration of statins or policosanol, and of fibrates or fish oil, to decrease LDL and triglycerides, respectively. Despite perceptions to the contrary, very-low-fat diets can meet with good compliance in well-motivated subjects given appropriate instruction.

Benefit and risk of exercise on myocardial function in diabetes

Regular physical activity promotes cardiorespiratory fitness and has been considered a cornerstone for non-pharmacological treatment of more than 17 million Americans with diabetes mellitus. Physical exercise has been shown to positively affect certain cardiovascular risk factors such as insulin resistance, glucose metabolism, blood pressure and body fat composition, which are closely associated with diabetes and heart disease. With the increasingly sedentary life style in our society, routine daily exercise of moderate intensity is highly recommended to reduce cardiovascular risk, the leading cause of death in diabetic patients. Exercise produces many beneficial effects to the heart function such as reduced incidence of coronary heart disease, attenuated severity of diabetic cardiomyopathy, improved cardiac performance, cardiac reserve and autonomic regulation. Nevertheless, many diabetic patients do not appear to gain much benefit from exercise or may even be at risk of performing physical exercise. This review summarizes the benefit and risk of exercise on diabetic heart function, with a special emphasis on myocardial and autonomic function.

Establishing the role of gene-environment interactions in the etiology of type 2 diabetes

The descriptive epidemiology of type 2 diabetes and findings from cohort studies suggest that this disorder originates in large part from a complex interaction between genetic and environmental factors. Determining the details of these interactions using the nested case-control design may be optimal, but is a long-term and expensive strategy. Quicker and cheaper results may be obtained by studying interaction on the quantitative traits that underlie diabetes; however, the power of such studies to detect interaction is highly dependent on the precision with which non-genetic exposures are measured. Unraveling these interactions will undoubtedly shed light on the etiology of diabetes and will, we hope, lead to opportunities for targeted prevention. Recent studies in high-risk groups such as people with impaired glucose tolerance suggest that the incidence of diabetes can be reduced by more than 50% by interventions aimed at changing dietary and physical activity behavior [39,40]; however, it may be that individuals with a particular genotype are particularly susceptible to the negative metabolic consequences of sedentary living, and that they conversely, therefore, would have most to gain from a targeted preventive intervention program. Understanding how to detect these individuals and which environmental factors a program should attempt to manipulate is a major goal of studies that attempt to unravel gene-environment interaction.

[Prognosis of diabetic patients with ischemic cardiopathy]

The prevalence of diabetes in Spain is about 6% and increases with age and obesity. Diabetes is present in approximately 25% of patients with coronary heart disease (CHD). Pre-diabetic and diabetic patients have a higher incidence of CHD and poorer prognosis, with high short- and long-term mortality. The protective effect of pre-menopause status is suppressed by diabetes. Diabetes has a synergic effect with other cardiovascular risk factors. Primary prevention in diabetic patients should be approached as in non-diabetic post-infarction patients. In diabetes, a healthy life-style and strict control of blood sugar and the other cardiovascular risk factors, particularly hypertension, is mandatory.