Postprandial insulin response and mitochondrial oxidation in obese men nutritionally treated to lose weight

Effects of dietary soy content on cerebral artery function and behavior in ovariectomized female mice

As females age, they transition through menopause, experiencing a decrease in estrogen and an increase in cardiovascular and neurodegenerative disease risk. Most standard rodent chows contain phytoestrogen-rich soybean meal, which can mimic the effects of estrogen. Understanding the impact of this soybean meal on vascular outcomes is crucial to proper experimental design. Thus, this study aimed to compare the effects of standard and soy-free chows on cerebral artery endothelial function and cognitive function in ovariectomized mice. Young female C57Bl/6J mice (n = 43; ∼6 mo) were randomly assigned to three groups: sham, ovariectomy (OVX), or ovariectomy on a diet containing soy (OVX + Soy). In posterior cerebral arteries, the OVX mice had a 27% lower maximal response to insulin compared with the sham mice. The OVX + Soy mice had a 27% greater maximal vasodilation to insulin compared with the OVX mice and there were no differences in vasodilation between the OVX + Soy and sham groups. The group differences in vasodilation were mediated by differences in nitric oxide bioavailability. The OVX + Soy mice also had greater insulin receptor gene expression in cerebral arteries compared with the OVX mice. However, no differences in aortic or cerebral artery stiffness were observed between groups. Interestingly, the OVX + Soy group scored better on nesting behavior compared with both sham and OVX groups. In summary, we found that ovariectomy impairs insulin-mediated vasodilation in cerebral arteries, but a diet containing soy mitigates these effects. These findings highlight the importance of considering dietary soy when performing vascular and behavioral tests in mice, particularly in females.NEW & NOTEWORTHY To properly design experiments, we must consider how variables like diet impact our outcomes, particularly the effects of soy on females. We found that cerebral artery vasodilation in response to insulin was impaired in ovariectomized female mice compared with intact shams. However, ovariectomized mice fed a soy diet had a preserved cerebral artery insulin-mediated vasodilation. These results highlight that the effects of diet on vascular function may explain inconsistencies found between studies.

The role of dietary strategies in the modulation of hallmarks of aging

The hallmarks of aging constitute an interconnected network of basic mechanisms that modulate aging and can be modulated by lifestyle factors, including dietary strategies. This narrative review aimed to summarize the evidence on promoting dietary restriction or adherence to specific dietary patterns on hallmarks of aging. Studies with preclinical models or humans were considered. Dietary restriction (DR), usually operationalized as a reduction in caloric intake, is the main strategy applied to study the axis diet-hallmarks of aging. DR has been shown to modulate mainly genomic instability, loss of proteostasis, deregulating nutrient sensing, cellular senescence, and altered intercellular communication. Much less evidence exists on the role of dietary patterns, with most of the studies evaluating the Mediterranean Diet and other similar plant-based diets, and the ketogenic diet. Potential benefits are described in genomic instability, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, and altered intercellular communication. Given the predominant place of food in human life, it is imperative to determine the impact of nutritional strategies on the modulation of lifespan and healthspan, considering applicability, long-term adherence, and side effects.

The Influence of Oxidative Stress on Thyroid Diseases

Thyroid diseases, including neoplasms, autoimmune diseases and thyroid dysfunctions, are becoming a serious social problem with rapidly increasing prevalence. The latter is increasingly linked to oxidative stress. There are many methods for determining the biomarkers of oxidative stress, making it possible to evaluate the oxidative profile in patients with thyroid diseases compared to the healthy population. This opens up a new perspective for investigating the role of elevated parameters of oxidative stress and damage in people with thyroid diseases, especially of neoplastic nature. An imbalance between oxidants and antioxidants is observed at different stages and in different types of thyroid diseases. The organ, which is part of the endocrine system, uses free radicals (reactive oxygen species, ROS) to produce hormones. Thyroid cells release enzymes that catalyse ROS generation; therefore, a key role is played by the internal defence system and non-enzymatic antioxidants that counteract excess ROS not utilised to produce thyroid hormones, acting as a buffer to neutralise free radicals and ensure whole-body homeostasis. An excess of free radicals causes structural cell damage, undermining genomic stability. Looking at the negative effects of ROS accumulation, oxidative stress appears to be implicated in both the initiation and progression of carcinogenesis. The aim of this review is to investigate the oxidation background of thyroid diseases and to summarise the links between redox imbalance and thyroid dysfunction and disease.

No difference between high-fructose and high-glucose diets on liver triacylglycerol or biochemistry in healthy overweight men

BACKGROUND & AIMS

Diets high in fructose have been proposed to contribute to nonalcoholic fatty liver disease. We compared the effects of high-fructose and matched glucose intake on hepatic triacylglycerol (TAG) concentration and other liver parameters.

DESIGN

In a double-blind study, we randomly assigned 32 healthy but centrally overweight men to groups that received either a high-fructose or high-glucose diet (25% energy). These diets were provided during an initial isocaloric period of 2 weeks, followed by a 6-week washout period, and then again during a hypercaloric 2-week period. The primary outcome measure was hepatic level of TAG, with additional assessments of TAG levels in serum and soleus muscle, hepatic levels of adenosine triphosphate, and systemic and hepatic insulin resistance.

RESULTS

During the isocaloric period of the study, both groups had stable body weights and concentrations of TAG in liver, serum, and soleus muscle. The high-fructose diet produced an increase of 22 ± 52 μmol/L in the serum level of uric acid, whereas the high-glucose diet led to a reduction of 23 ± 25 μmol/L (P < .01). The high-fructose diet also produced an increase of 0.8 ± 0.9 in the homeostasis model assessment of insulin resistance, whereas the high-glucose diet produced an increase of only 0.1 ± 0.7 (P = .03). During the hypercaloric period, participants in the high-fructose and high-glucose groups had similar increases in weight (1.0 ± 1.4 vs 0.6 ± 1.0 kg; P = .29) and absolute concentration of TAG in liver (1.70% ± 2.6% vs 2.05% ± 2.9%; P = .73) and serum (0.36 ± 0.75 vs 0.33 ± 0.38 mmol/L; P = .91), and similar results in biochemical assays of liver function. Body weight changes were associated with changes in liver biochemistry and concentration of TAGs.

CONCLUSIONS

In the isocaloric period, overweight men who were on a high-fructose or a high-glucose diet did not develop any significant changes in hepatic concentration of TAGs or serum levels of liver enzymes. However, in the hypercaloric period, both high-fructose and high-glucose diets produced significant increases in these parameters without any significant difference between the 2 groups. This indicates an energy-mediated, rather than a specific macronutrient-mediated, effect. Clinical trials.gov no: NCT01050140.

Mitochondrial DNA mutations and breast tumorigenesis

Breast cancer is a heterogeneous disease and genetic factors play an important role in its genesis. Although mutations in tumor suppressors and oncogenes encoded by the nuclear genome are known to play a critical role in breast tumorigenesis, the contribution of the mitochondrial genome to this process is unclear. Like the nuclear genome, the mitochondrial genome also encodes proteins critical for mitochondrion functions such as oxidative phosphorylation (OXPHOS), which is known to be defective in cancer including breast cancer. Mitochondrial DNA (mtDNA) is more susceptible to mutations due to limited repair mechanisms compared to nuclear DNA (nDNA). Thus changes in mitochondrial genes could also contribute to the development of breast cancer. In this review we discuss mtDNA mutations that affect OXPHOS. Continuous acquisition of mtDNA mutations and selection of advantageous mutations ultimately leads to generation of cells that propagate uncontrollably to form tumors. Since irreversible damage to OXPHOS leads to a shift in energy metabolism towards enhanced aerobic glycolysis in most cancers, mutations in mtDNA represent an early event during breast tumorigenesis, and thus may serve as potential biomarkers for early detection and prognosis of breast cancer. Because mtDNA mutations lead to defective OXPHOS, development of agents that target OXPHOS will provide specificity for preventative and therapeutic agents against breast cancer with minimal toxicity.

Lymphocytes mitochondrial physiology as biomarker of energy metabolism during fasted and fed conditions

Mitochondria are central coordinators of energy metabolism, and changes of their physiology have long been associated with metabolic disorders. Thus, observations of energy dynamics in different cell types are of utmost importance. Therefore, tools with quick and easy handling are needed for consistent evaluations of such interventions. In this paper, our main hypothesis is that during different nutritional situations lymphocytes mitochondrial physiology could be associated with the metabolism of other cell types, such as cardiomyocytes, and consequently be used as metabolic biomarker. Blood lymphocytes and heart muscle fibers were obtained from both fed and 24 h-fasted mice, and mitochondrial analysis was assessed by high-resolution respirometry and western blotting. Carbohydrate-linked oxidation and fatty acid oxidation were significantly higher after fasting. Carnitine palmitoil transferase 1 and uncouple protein 2 contents were increased in the fasted group, while the glucose transporters 1 and 4 and the ratio phosphorylated AMP-activated protein kinase/AMPK did not change between groups. In summary, under a nutritional status modification, mitochondria demonstrated earlier adaptive capacity than other metabolic sensors such as glucose transporters and AMPK, suggesting the accuracy of mitochondria physiology of lymphocytes as biomarker for metabolic changes.

Facile fingerstick insulin analysis: Application to monitoring postprandial insulin responses to snack foods

BACKGROUND

Energy intake from snacks has been increasing in the American diet, but insulin and glucose responses to foods are generally reported for meal-sized portions (800-1200 kJ). Established methods for insulin determination routinely use indwelling catheters and radioimmunoassay (RIA). The aim of the present study was to develop a more facile method, collecting fingerstick blood samples and measuring insulin with precise ELISA, and then applying this method to determine responses to snack-sized food portions.

METHODS

Six healthy, fasting adult volunteers consumed seven different snack foods on separate days, containing approximately 400 kJ/portion. Insulin was measured by ELISA and glucose was measured with the hexokinase procedure in samples collected by fingerstick at 0, 30, and 60 min after consumption of the snack food.

RESULTS

A portion of doughnut (half a glazed doughnut) led to marked changes in insulin and glucose; skim milk, an apple, and oatmeal changed insulin significantly; wrinkled peas resulted in a lower glucose response than smooth peas; and walnuts led to non-significant changes in both insulin and glucose over a 60-min period.

CONCLUSIONS

The fingerstick sampling and insulin measurement procedure is simple, economical, and more precise than established RIA. The method can be applied to children and adults to monitor insulin responses following food consumption, as well as during therapeutic assessments or intervention trials. Public health advisories regarding snacks that minimize increases in insulin are desirable for individuals trying to reduce or maintain their weight, because elevated insulin stimulates carbohydrate conversion to fat and suppresses the mobilization of stored triglycerides for energy generation.

Effects of two energy-restricted diets differing in the carbohydrate/protein ratio on weight loss and oxidative changes of obese men

INTRODUCTION

Low-carbohydrate, high-protein diets are a current challenge in the nutritional treatment of obesity.

OBJECTIVE

To compare the effect of a low-carbohydrate high-protein diet with a traditional hypocaloric diet on weight loss and mitochondrial oxidative metabolism.

SUBJECTS AND METHODS

Nineteen obese men (age 36+/-6 years; body mass index 34+/-2 kg/m2) were randomized to follow one of the two diets-control diet (15% protein; 30% lipids; 55% carbohydrates) or high-protein diet (30% protein; 30% lipids; 40% carbohydrates)-over an 8-week period. Anthropometry, biochemical variables, resting energy expenditure and mitochondrial oxidation were measured at the start and at the end of the intervention.

RESULTS

The high-protein diet produced a greater weight loss (-8.3+/-1.2% versus -5.5+/-2.5%, P = 0.012) than the control diet. Interestingly, an activation in the mitochondrial oxidation was found in the high-protein-fed group. This stimulation was positively correlated with the final resting energy expenditure and negatively associated with the final fat mass content.

CONCLUSION

Low-carbohydrate high-protein diets could involve specific changes in mitochondrial oxidation that could be related to a higher weight loss.

Enhanced short-term improvement of insulin response to a low-caloric diet in obese carriers the Gly482Ser variant of the PGC-1alpha gene

AIM

The Gly482Ser missense mutation of the transcriptional coactivator, peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) has been involved in insulin function impairments, with conflicting results. The current study investigated the relationships of carrying this polymorphism with insulin resistance (IR) during a short-term weight-loss and the subsequent weight follow-up.

METHODS

The Gly482Ser was genotyped in 180 Spanish volunteers [body mass index: 31.4+/-3.2kg/m(2); age: 35+/-5 years]. Specific phenotypical measurements were determined at baseline, following an 8-week low-calorie diet (LCD) as well as after 6-month and 1-year of follow-up.

RESULTS

At baseline the Ser482Ser genotype was associated with higher HOMA-IR and insulin concentrations than the other genotypes (p<0.05), which was accompanied by an increased higher risk of IR (OR: 2.97; 95% CI: 1.24-7.15). After following the LCD, such increased risk of insulin insensitivity in Ser482Ser carriers was toned down (p>0.05). This outcome was sustained after 6-month and 1-year of follow-up (p>0.05).

CONCLUSIONS

These data show an increased risk of IR in obese carrying the rs8192673 Ser482Ser genotype. This risk was markedly reduced by an energy-restricted diet, which was sustained 6 months and 1 year after the diet therapy. This observation allows identifying obese subjects who might personally profit most from an energy-restrictive treatment concerning insulin response and lead to more individualized prognostic and therapeutic decisions.

Sirtuin gene expression in human mononuclear cells is modulated by caloric restriction

BACKGROUND

Sirtuins may provide novel targets for treating some diseases associated with oxidative stress, such as obesity and its comorbidities. However, there are a few in vivo studies in humans about the potential role of sirtuins as therapeutic targets among obese patients undergoing caloric restriction. Therefore, the aim of this study was to assess if the gene expression of sirtuins is modulated in peripheral blood mononuclear cells (PBMC) by a hypocaloric diet devised to lose weight in humans.

MATERIALS AND METHODS

Gene expression of two sirtuins (SIRT1 and SIRT2) in the PBMC of obese subjects (32.3 +/- 5.5 kg m(-2)) before and following an 8-week hypocaloric diet was investigated. NADH-coenzyme Q reductase (NDUFS2) and cytochrome c oxidase assembly protein (COX15) gene expression was selected together with plasma antioxidant power and nitric oxide as markers of antioxidant status. A quantitative real-time polymerase chain reaction approach was performed to assess the nutrigenomics outcome. Moreover, 2-keto[1-(13)C]isocaproate breath test (KICA-BT) parameters were evaluated to study mitochondrial oxidation in vivo.

RESULTS

The intervention up-regulated the expression of both sirtuins, being inversely associated with total antioxidant capacity and directly related to nitric oxide, mitochondrial oxidation assessed by the KICA-BT and the expression of the mitochondrial proteins COX15 and NDUFS2.

CONCLUSION

SIRT1 and SIRT2 may serve as key regulators for some obesity comorbidities related to antioxidant status, while PBMC could be a model to study the effect of the sirtuin response in obesity therapy.

Impact of interleukin 6 -174G>C polymorphism on obesity-related metabolic disorders in people with excess in body weight

Low-grade inflammation has been related to obesity, insulin resistance, and related metabolic disorders. In this context, the -174G>C gene polymorphism of the proinflammatory interleukin 6 (IL-6) cytokine has also been associated with these diseases. Based on this, the aim of the current study was to evaluate the role of IL-6 -174G>C polymorphism in the risk of developing metabolic alterations in people with excessive body weight. One hundred six Caucasian volunteers (body mass index, 33.2 +/- 5.3 kg/m(2)) were recruited to assess the potential relationship between carrying the -174G>C polymorphism and the risk of developing obesity-related metabolic disorders, such as hypertension, atherogenic dyslipidemia, and insulin resistance evaluated by the homeostasis model assessment of insulin resistance index. Subjects carrying the C allele showed higher plasma insulin concentrations and systolic blood pressure than homozygotes for the G allele. A multiple regression analysis showed that the presence of the C allele induced an increase in the homeostasis model assessment of insulin resistance index as compared with GG subjects (adjusted R(2) = .26, P < .001). Analyzing the mentioned obesity-related diseases, an enhanced prevalence of presenting high risk of developing these complications was found for the GC and CC genotypes relative to GG, with an adjusted odds ratio of 5.2 (P = .003). This association remained significant after controlling for multiple comparisons by the 10,000-permutation test (P = .004838). These data demonstrate that the occurrence of C allele of IL-6 -174 G>C gene polymorphism in people with excessive body weight is accompanying a higher risk of developing obesity-related metabolic disorders, especially insulin resistance.

Impact of fish intake on oxidative stress when included into a moderate energy-restricted program to treat obesity

BACKGROUND

The role of some nutritional factors and hypocaloric diets on oxidative balance is a matter of debate, especially related to the prevention and treatment of obesity and co-morbidities.

AIM OF THE STUDY

The aim was to investigate the antioxidant capacity of different energy restricted diets in the treatment of obesity, paying emphasis to the effect of incorporating omega-3 fatty acids with or without other seafood components.

METHODS

The study was a randomized 8-weeks parallel intervention trial prescribed to lose weight, which was implemented in 276 subjects aged 31.4 +/- 5.4 y.o. following four different balanced hypocaloric diets (TEE-30%): fish-restricted (control), cod and salmon based diets and DHA+EPA supplemented administration. At baseline (day 0) and at the end of the trial (day 56), anthropometry, dietary intake, erythrocyte membrane fatty acid content, circulating malondialdehyde (MDA) and plasma antioxidant status (AOP) were determined.

RESULTS

Overall, percent weight loss was -5.8 +/- 3.2% (P < 0.001) and the AOP statistically increased after the energy restriction period (P = 0.015), basically due to the seafood-based diets. In contrast, MDA statistically only decreased (P = 0.026) after the cod-based diet intake with no changes after the other nutritional treatments. In fact, the cod-based intervention statistically decreased oxidative stress when expressed as the MDA/AOP ratio (P = 0.006).

CONCLUSIONS

A moderate calorie-restricted cod-based diet was found as a useful strategy to lose weight, which was accompanied by a specific improvement on oxidative stress markers. The low saturated fat content and the seafood protein source of this diet may be important factors involved in these findings.

Weight regain after slimming induced by an energy-restricted diet depends on interleukin-6 and peroxisome-proliferator-activated-receptor-γ2 gene polymorphisms

Weight-loss maintenance after following an energy-restricted diet is a major problem that a number of studies are trying to characterise. The aim of the present study was to investigate the role of IL-6 -174G > C and PPAR-γ2 Pro12Ala variants on weight regulation in obese subjects receiving a low-energy diet and at 1 year after the acute slimming period. Sixty-seven volunteers (age 34·7 (sd 7·0) years; BMI 35·8 (sd 4·8) kg/m2) were enrolled in a 10-week dietary intervention and were contacted again 1 year after the end of this period. Body composition was measured at three times during the study. Also, PPAR-γ2 Pro12Ala and IL-6 -174G > C polymorphisms were analysed in the participants. No statistical differences were observed depending on the genetic variants at baseline for anthropometric variables, or after the intervention. However, the C allele of the -174G > C IL-6 gene polymorphism was more frequently observed (P=0·032) in subjects with successful weight maintenance (<10 % weight regain). In fact, the C allele partially protected against weight regain (odds ratio 0·24;P=0·049), while the conjoint presence of both gene variants (C+ and Ala+) further improved the ability for weight maintenance (odds ratio 0·19;P=0·043). The present study demonstrates that the C allele of the -174G > C polymorphism gives protection against regain of weight lost. Moreover, the presence of the Ala allele of the PPARγ-2 together with the C allele strengthens this protection. These findings support a role for these polymorphisms on weight regulation and suggest a synergetic effect of both variants on weight maintenance after following a diet to lose weight.

A role for fruit content in energy-restricted diets in improving antioxidant status in obese women during weight loss

OBJECTIVE

The aim of the present work was to estimate the ability of two hypocaloric diets with different fruit contents to improve antioxidant biomarkers related to lipid peroxidation in obese women.

METHODS

Fifteen obese women (age 32 +/- 6 y, body mass index 34.9 +/- 2.9 kg/m2) were assigned to two different dietary treatments for 8 wk. The subjects received a hypocaloric diet (600 kcal/d restriction from the measured individual energy expenditure) containing 5% (n = 8) or 15% (n = 7) energy supplied by fructose from fruits. Anthropometric measurements, blood lipid profile, plasma oxidative markers, total antioxidant capacity, and malondialdehyde (MDA) were evaluated before and after the nutritional intervention in addition to some relations among them.

RESULTS

No differences in weight loss were observed between diets (5% energy from fructose in the low fruit diet -6.9 +/- 2% versus 15% energy from fructose in the high fruit diet -6.6 +/- 2%; P = 0.781). Low-density lipoprotein cholesterol levels significantly decreased (P = 0.048) in obese women who followed the high fruit diet, which was accompanied by a statistical (P = 0.046) diet-related decrease (-30%) in the ratio of MDA to antioxidant capacity. There was a positive association between MDA diet-related change and low-density lipoprotein cholesterol (r = 0.665, P = 0.003), with antioxidant capacity directly proportional to the fiber plus fructose content associated with fruit consumption (r = 0.697, P = 0.025).

CONCLUSION

A fruit-enriched hypocaloric diet appears to be more effective against oxidative stress. Consumption of antioxidant substances contained in fruit could be a useful strategy in the design of hypocaloric diets that, with the weight reduction, could increase the improvement of cardiovascular risk factors related to obesity.