A Western-like fat diet is sufficient to induce a gradual enhancement in fat mass over generations

Dietary linoleic acid elevates the endocannabinoids 2-AG and anandamide and promotes weight gain in mice fed a low fat diet

Dietary intake of linoleic acid (LNA, 18:2n-6) has increased dramatically during the 20th century and is associated with greater prevalence of obesity. The endocannabinoid system is involved in regulation of energy balance and a sustained hyperactivity of the endocannabinoid system may contribute to obesity. Arachidonic acid (ARA, 20:4n-6) is the precursor for 2-AG and anandamide (AEA), and we sought to determine if low fat diets (LFD) could be made obesogenic by increasing the endocannabinoid precursor pool of ARA, causing excessive endocannabinoid signaling leading to weight gain and a metabolic profile associated with obesity. Mice (C57BL/6j, 6 weeks of age) were fed 1 en% LNA and 8 en% LNA in low fat (12.5 en%) and medium fat diets (MFD, 35 en%) for 16 weeks. We found that increasing dietary LNA from 1 to 8 en% in LFD and MFD significantly increased ARA in phospholipids (ARA–PL), elevated 2-AG and AEA in liver, elevated plasma leptin, and resulted in larger adipocytes and more macrophage infiltration in adipose tissue. In LFD, dietary LNA of 8 en% increased feed efficiency and caused greater weight gain than in an isocaloric reduction to 1 en% LNA. Increasing dietary LNA from 1 to 8 en% elevates liver endocannabinoid levels and increases the risk of developing obesity. Thus a high dietary content of LNA (8 en%) increases the adipogenic properties of a low fat diet.

Associations between plasma polyunsaturated fatty acids, plasma stearoyl-CoA desaturase indices and body fat

OBJECTIVE

Stearoyl-CoA desaturase (SCD)-1 deficient mice are resistant to obesity and plasma SCD indices are related to obesity in humans. Both n-3 and n-6 polyunsaturated fatty acids (PUFA) regulate expression of the SCD enzymes. Whether higher plasma PUFA were associated with lower SCD indices in humans was examined.

DESIGN AND METHODS

Population-based study of 2,021 elderly subjects from the Hordaland Health Study. Using multivariate linear regression, the cross-sectional associations among plasma PUFA, estimated SCD indices (from fatty acid profiles in plasma total lipids), and fat mass measured by dual-energy X-ray absorptiometry were explored. Two plasma SCD indices were used: SCD-16 (16:1n-7/16:0) and SCD-18 (18:1n-9/18:0).

RESULTS

Plasma total, n-6 and n-3 PUFA were inversely associated with both SCD indices (P < 0.001 for all). Among the individual PUFA, 18:2n-6 showed the strongest association with SCD-16 (partial r = -0.59, P < 0.001) followed by 20:5n-3 (partial r = -0.13; P < 0.001). Plasma total, n-6 and n-3 PUFA were inversely associated with body fat (P < 0.001 for all); the associations were markedly attenuated following adjustment for SCD-16.

CONCLUSIONS

The epidemiological data are in line with animal studies and suggest that PUFA may decrease SCD1 activity in humans, with possible reduction in body fat.

DNA hypomethylation of inflammation-associated genes in adipose tissue of female mice after multigenerational high fat diet feeding

OBJECTIVE

Maternal obesity significantly increases the susceptibility of offspring to develop obesity and chronic diseases in adulthood. The offspring of obese mothers are shown to prefer high fat diet (HFD) due to their altered neural circuitry, creating a 'feed-forward cycle' across generations. We hypothesized that the 'feed-forward cycle' caused by multigenerational HFD feeding would have exacerbated effects in adipose tissue of the offspring.

METHODS

Three generations (F0, F1 and F2) of HFD (60% Kcal fat)-fed and corresponding normal chow (NC)-fed C57BL/6 mice were generated. Body weight (BW) and food intake were monitored weekly. Parametrial adipose tissue (pAT) weight and endocrine parameters were measured in 9-month-old female offspring. Gene expression microarray, quantitative RT-PCR and bisulfite sequencing were performed using pAT.

RESULTS

BW and pAT weight increased in female mice across generations under continuous HFD stress, with the most severe phenotype found in the F2 generation. Genes involved in inflammatory response showed increased expression across generations in the pAT, accompanied by increased macrophage infiltration. The promoters of Toll-like receptor 1 (Tlr1), Tlr2 and linker for activation of T cells (Lat) were hypomethylated in the HF groups compared with the NC group, with additional hypomethylation on some specific CpG sites in the F2 generation.

CONCLUSIONS

A feed-forward cycle exists in female mice after continuous HFD stress as demonstrated by increased adiposity and progressive inflammation in adipose tissue across generations. DNA hypomethylation over generations lead to epigenetically altered expression of Tlr1, Tlr2 and Lat, which may contribute to the inflammation in adipose tissue. Our study provides a potential mechanism for enhanced inflammation in adipose tissue under multigenerational HFD-fed stress.

Hydrocarbons (jet fuel JP-8) induce epigenetic transgenerational inheritance of obesity, reproductive disease and sperm epimutations

Environmental compounds have been shown to promote epigenetic transgenerational inheritance of disease. The current study was designed to determine if a hydrocarbon mixture involving jet fuel (JP-8) promotes epigenetic transgenerational inheritance of disease. Gestating F0 generation female rats were transiently exposed during the fetal gonadal development period. The direct exposure F1 generation had an increased incidence of kidney abnormalities in both females and males, prostate and pubertal abnormalities in males, and primordial follicle loss and polycystic ovarian disease in females. The first transgenerational generation is the F3 generation, and the jet fuel lineage had an increased incidence of primordial follicle loss and polycystic ovarian disease in females, and obesity in both females and males. Analysis of the jet fuel lineage F3 generation sperm epigenome identified 33 differential DNA methylation regions, termed epimutations. Observations demonstrate hydrocarbons can promote epigenetic transgenerational inheritance of disease and sperm epimutations, potential biomarkers for ancestral exposures.

Different fatty acid pattern in breast milk of obese compared to normal-weight mothers

INTRODUCTION

The aim of this study was to investigate the fatty acid (FA) pattern in breast milk of obese mothers and their neonates' plasma compared to those of normal weight mothers.

PATIENTS AND METHODS

This was an observational study of 41 obese and 41 normal weight pregnant women. Twenty-nine obese women participating in a weight reduction program were investigated for comparison. FAs were analyzed in breast milk collected at 3 and 10 days and one and two months postnatally and in infant's plasma 3 days after birth.

RESULTS AND CONCLUSIONS

The concentration of long-chain n-3 FA were lower and the ratio n-6/n-3 FA higher in neonates and in consecutive samples of breast milk of obese mothers compared to normal weight mothers. The obese mothers that participated in an intervention program with general dietary advice had FA concentrations approaching that of the normal-weight mothers. The study indicates importance of dietary advice in pregnancy.

Omega-3 fatty acids and brain resistance to ageing and stress: body of evidence and possible mechanisms

The increasing life expectancy in the populations of rich countries raises the pressing question of how the elderly can maintain their cognitive function. Cognitive decline is characterised by the loss of short-term memory due to a progressive impairment of the underlying brain cell processes. Age-related brain damage has many causes, some of which may be influenced by diet. An optimal diet may therefore be a practical way of delaying the onset of age-related cognitive decline. Nutritional investigations indicate that the ω-3 poyunsaturated fatty acid (PUFA) content of western diets is too low to provide the brain with an optimal supply of docosahexaenoic acid (DHA), the main ω-3 PUFA in cell membranes. Insufficient brain DHA has been associated with memory impairment, emotional disturbances and altered brain processes in rodents. Human studies suggest that an adequate dietary intake of ω-3 PUFA can slow the age-related cognitive decline and may also protect against the risk of senile dementia. However, despite the many studies in this domain, the beneficial impact of ω-3 PUFA on brain function has only recently been linked to specific mechanisms. This review examines the hypothesis that an optimal brain DHA status, conferred by an adequate ω-3 PUFA intake, limits age-related brain damage by optimizing endogenous brain repair mechanisms. Our analysis of the abundant literature indicates that an adequate amount of DHA in the brain may limit the impact of stress, an important age-aggravating factor, and influences the neuronal and astroglial functions that govern and protect synaptic transmission. This transmission, particularly glutamatergic neurotransmission in the hippocampus, underlies memory formation. The brain DHA status also influences neurogenesis, nested in the hippocampus, which helps maintain cognitive function throughout life. Although there are still gaps in our knowledge of the way ω-3 PUFA act, the mechanistic studies reviewed here indicate that ω-3 PUFA may be a promising tool for preventing age-related brain deterioration.

Omega-6 polyunsaturated fatty acids and the early origins of obesity

PURPOSE OF REVIEW

The incidence of obesity and its related metabolic disorders has increased significantly over the past 3 decades, culminating in the current global epidemic of metabolic disease and leading to the search for contributing factors. Exposure of the developing foetus/neonate to a typical Western diet increases their risk of obesity and metabolic disorders throughout the life-course, creating an intergenerational cycle of metabolic disease. In Western countries, this epidemic of metabolic disease has coincided with a marked increase in the intake of omega-6 polyunsaturated fatty acids (omega-6 PUFA), leading to suggestions that the two may be causally related.

RECENT FINDINGS

Recent studies have emphasized the proadipogenic properties of the omega-6 PUFA, and provided evidence that rodents fed on diets with omega-6 PUFA contents similar to the typical US diet (6-8% energy) have an increased fat mass. Importantly, recent studies have shown that perinatal exposure to a high omega-6 PUFA diet results in a progressive accumulation of body fat across generations.

SUMMARY

This review highlights the recent evidence supporting the role of the omega-6 PUFA in the early life origins of obesity and metabolic disease, the need for more clinical studies and the potential need for health agencies to re-evaluate current recommendations to further increase omega-6 PUFA intakes.

Fatty Acid modulation of the endocannabinoid system and the effect on food intake and metabolism

Endocannabinoids and their G-protein coupled receptors (GPCR) are a current research focus in the area of obesity due to the system's role in food intake and glucose and lipid metabolism. Importantly, overweight and obese individuals often have higher circulating levels of the arachidonic acid-derived endocannabinoids anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) and an altered pattern of receptor expression. Consequently, this leads to an increase in orexigenic stimuli, changes in fatty acid synthesis, insulin sensitivity, and glucose utilisation, with preferential energy storage in adipose tissue. As endocannabinoids are products of dietary fats, modification of dietary intake may modulate their levels, with eicosapentaenoic and docosahexaenoic acid based endocannabinoids being able to displace arachidonic acid from cell membranes, reducing AEA and 2-AG production. Similarly, oleoyl ethanolamide, a product of oleic acid, induces satiety, decreases circulating fatty acid concentrations, increases the capacity for β -oxidation, and is capable of inhibiting the action of AEA and 2-AG in adipose tissue. Thus, understanding how dietary fats alter endocannabinoid system activity is a pertinent area of research due to public health messages promoting a shift towards plant-derived fats, which are rich sources of AEA and 2-AG precursor fatty acids, possibly encouraging excessive energy intake and weight gain.

Dietary fish oil supplementation inhibits formation of endometriosis-associated adhesions in a chimeric mouse model

OBJECTIVE

To examine whether dietary fish oil supplementation reduces development of spontaneous endometriosis-associated adhesions using an established model.

DESIGN

Laboratory-based study.

SETTING

Medical center research laboratory. PATIENT(S)/ANIMAL(S): Disease-free women of reproductive age and nude mice.

INTERVENTION(S)

Women were not provided any intervention. Mice were randomized to receive fish oil supplementation or control diet.

MAIN OUTCOME MEASURE(S)

Experimental endometriosis was established in mice via injection of human endometrial tissue within 16 hours of ovariectomy. Mice were provided standard or menhaden fish oil-supplemented diets for ≥ 2 weeks before initiation of experimental endometriosis and until killing them 1 week later. At necropsy, mice were examined for the presence and extent of adhesions and endometriotic-like lesions. Tissues were excised and morphologically characterized.

RESULT(S)

Adhesions/lesions were reduced in mice provided with dietary fish oil compared with control animals. Leukocytes were more numerous within the adhesions/lesions of the mice maintained on the standard diet compared with animals provided with fish oil. As indicated by staining intensity, collagen deposition was greater at adhesion sites within control mice compared with fish oil-supplemented animals.

CONCLUSION(S)

Wound-healing associated with surgery created an inflammatory peritoneal microenvironment that promoted the development of both experimental endometriosis and adhesions in a murine model. Targeting excessive inflammation with fish oil may be an effective adjuvant therapy to reduce the development of postsurgical adhesions related to endometriosis.

Maternal Prenatal Nutrition and Health in Grandchildren and Subsequent Generations

This review focuses on how maternal prenatal nutritional states may affect the health of grandchildren and later generations. We first summarize the limited current data in human populations relating to the potential transmission of phenotypes across multiple generations that result from the nutritional experience of a pregnant woman. We then discuss findings from other species, especially mammals, that provide important clues as to whether, and if so how, such transmission could occur in humans. Finally, we consider how studies of human populations could be best designed to detect transmission across multiple generations. We argue that just as epidemiologists embraced a life-course perspective to human health and disease in the twentieth century, we must now seek to better understand how health and disease could be shaped across multiple generations.

Dietary linoleic acid elevates endogenous 2-arachidonoylglycerol and anandamide in Atlantic salmon (Salmo salar L.) and mice, and induces weight gain and inflammation in mice

Dietary intake of linoleic acid (LA) has increased dramatically during the twentieth century and is associated with a greater prevalence of obesity. Vegetable oils are recognised as suitable alternatives to fish oil (FO) in feed for Atlantic salmon (Salmo salar L.) but introduce high amounts of LA in the salmon fillet. The effect on fish consumers of such a replacement remains to be elucidated. Here, we investigate the effect of excessive dietary LA from soyabean oil (SO) on endocannabinoid levels in Atlantic salmon and mice, and study the metabolic effects in mice when SO replaces FO in feed for Atlantic salmon. Atlantic salmon were fed FO and SO for 6 months, and the salmon fillet was used to produce feed for mice. Male C57BL/6J mice were fed diets of 35% of energy as fat based on FO- and SO-enriched salmon for 16 weeks. We found that replacing FO with SO in feed for Atlantic salmon increased LA, arachidonic acid (AA), decreased EPA and DHA, elevated the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (AEA), and increased TAG accumulation in the salmon liver. In mice, the SO salmon diet increased LA and AA and decreased EPA and DHA in the liver and erythrocyte phospholipids, and elevated 2-AG and AEA associated with increased feed efficiency, weight gain and adipose tissue inflammation compared with mice fed the FO salmon diet. In conclusion, excessive dietary LA elevates endocannabinoids in the liver of salmon and mice, and increases weight gain and counteracts the anti-inflammatory properties of EPA and DHA in mice.

Nocturnin: at the crossroads of clocks and metabolism

Many aspects of metabolism exhibit daily rhythmicity under the control of endogenous circadian clocks, and disruptions in circadian timing result in dysfunctions associated with the metabolic syndrome. Nocturnin (Noc) is a robustly rhythmic gene that encodes a deadenylase thought to be involved in the removal of polyA tails from mRNAs. Mice lacking the Noc gene display resistance to diet-induced obesity and hepatic steatosis, due in part to reduced lipid trafficking in the small intestine. In addition, Noc appears to play important roles in other tissues and has been implicated in lipid metabolism, adipogenesis, glucose homeostasis, inflammation and osteogenesis. Therefore, Noc is a potential key post-transcriptional mediator in the circadian control of many metabolic processes.

Fatty acid composition in the mature milk of Bolivian forager-horticulturalists: controlled comparisons with a US sample

Breast milk fatty acid (FA) composition varies greatly among individual women, including in percentages of the long-chain polyunsaturated FAs (LCPUFA) 20:4n-6 (arachidonic acid, AA) and 22:6n-3 (docosahexaenoic acid, DHA), which are important for infant neurological development. It has been suggested that owing to wide variation in milk LCPUFA and low DHA in Western diets, standards of milk FA composition should be derived from populations consuming traditional diets. We collected breast milk samples from Tsimane women at varying lactational stages (6-82 weeks). The Tsimane are an indigenous, natural fertility, subsistence-level population living in Amazonia Bolivia. Tsimane samples were matched by lactational stage to samples from a US milk bank, and analysed concurrently for FA composition by gas-liquid chromatography. We compared milk FA composition between Tsimane (n = 35) and US (n = 35) mothers, focusing on differences in LCPUFA percentages that may be due to population-typical dietary patterns. Per total FAs, the percentages of AA, DHA, total n-3 and total n-6 LCPUFA were significantly higher among Tsimane mothers. Mean percentages of 18:2n-6 (linoleic acid) and trans FAs were significantly higher among US mothers. Tsimane mothers' higher milk n-3 and n-6 LCPUFA percentages may be due to their regular consumption of wild game and freshwater fish, as well as comparatively lower intakes of processed foods and oils that may interfere with LCPUFA synthesis.

Accumulation of endoplasmic reticulum stress and lipogenesis in the liver through generational effects of high fat diets

BACKGROUND & AIMS

The dramatic rise of nonalcoholic fatty liver disease (NAFLD) among children in the past decade cannot be solely explained by the increased high fat diet (HFD) intake in kids. Recent studies suggest that the offspring of HFD-fed mothers develop a worse form of NAFLD when weaned on the HFD than when weaned on the normal chow (NC), indicating that a feed-forward circle may exacerbate the syndromes throughout multiple generations. In the present study, the aforementioned feed-forward circle was investigated in mice by employing continuous HFD feeding for three generations.

METHODS

C57BL/6 mice were fed with either a HFD or NC for three consecutive generations (F0, F1, and F2). Body weight, food intake, hepatic histology; levels of insulin, leptin, and triglycerides; expression of factors involved in lipogenesis and endoplasmic reticulum (ER) stress pathways; and histone methylation status were investigated in male offspring.

RESULTS

Obesity occurred earlier, became more severe through generations (F2>F1>F0), and was accompanied by a gradual increase of histological scoring of steatosis in male mice with transgenerational HFD feeding. The highest degree of steatosis occurred in HFD-treated F2 mice and was associated with the highest levels of insulin and leptin. The latter mice were characterized by enhanced lipogenesis and ER stress with a trend of transgenerational changes was detected for LXRα, ERO1-α, histone methylations, and H3K9 histone methyltransferase. Furthermore, chromatin immunoprecipitation (CHIP) assay demonstrated a significantly reduced accumulation of methylated histones in LXRα and ERO1-α gene promoters.

CONCLUSIONS

Under HFD feeding stress, the male offspring of the F2 generation (derived from both grand-maternal and maternal obesity) are extremely susceptible to developing obesity and hepatic steatosis. This is presumably a consequence of transgenerational accumulation of epigenetic modifications leading to up-regulation of lipogenesis and ER stress pathways in the liver.

Epigenetics: a tool to understand diet-related cardiovascular risk?

Cardiovascular disease (CVD) is a leading cause of mortality and is projected to hold its grim record as developing countries increase their wealth. Since specific nutritional habits are important risk factors for CVD, it is imperative to understand how ingredients of risk-associated diets convert a healthy cellular transcriptional program into a pathological one. Epigenetics has enriched our view of the genome by showing that DNA-associated regulatory proteins and RNAs, together with chemical modifications of the DNA itself, determine which parts of the DNA chain are transcribed or silent in a given phase of a cell's life. This complex biological entity--the epigenome--accounts for the enormous phenotypic diversity within a multicellular organism despite its unicellular origin. Crucially, the epigenome can be modified by diet and other exogenous factors, thus suggesting that epigenetic mechanisms might underlie pathological responses to CVD risk factors. Here, we will review the current knowledge of epigenetic mechanisms in diet-gene interactions and propose ways in which epigenetics might clarify the impact of genetic variants on CVD risk.

Influence of pre- and peri-natal nutrition on skeletal acquisition and maintenance

Early life nutrition has substantial influences on postnatal health, with both under- and overnutrition linked with permanent metabolic changes that alter reproductive and immune function and significantly increase metabolic disease risk in offspring. Since perinatal nutrition depends in part on maternal metabolic condition, maternal diet during gestation and lactation is a risk factor for adult metabolic disease. Such developmental responses may be adaptive, but might also result from constraints on, or pathological changes to, normal physiology. The rising prevalence of both obesity and osteoporosis, and the identification of links among bone, fat, brain, and gut, suggest that obesity and osteoporosis may be related, and moreover that their roots may lie in early life. Here we focus on evidence for how maternal diet during gestation and lactation affects metabolism and skeletal acquisition in humans and in animal models. We consider the effects of overall caloric restriction, and macronutrient imbalances including high fat, high sucrose, and low protein, compared to normal diet. We then discuss potential mechanisms underlying the skeletal responses, including perinatal developmental programming via disruption of the perinatal leptin surge and/or epigenetic changes, to highlight unanswered questions and identify the most critical areas for future research.

Systematic review of diet in the pathogenesis of acute pancreatitis: a tale of too much or too little?

BACKGROUND/AIM

The role of diet as the cause of acute pancreatitis (AP) has been suggested. The aim of the current review was to determine if there exists sufficient evidence linking nutrition, or the lack of it, to the pathogenesis of AP.

PATIENTS AND METHODS

A systematic search of the scientific literature was carried out using Embase, PubMed, MEDLINE, and the Cochrane Central Register of Controlled Trials for the years 1965 - 2011 to obtain access to studies involving dietary factors and the pathogenesis of AP.

RESULTS

A total of 17 studies were identified describing diet and AP. These included 12 human and 5 animal studies. 8 reports were found to link malnutrition and/or refeeding to the pathogenesis of AP. Two studies found an increased consumption of fats and proteins in patients with alcohol-related AP while 1 study noted a lesser intake of carbohydrate in patients. However, none of these differences attained statistical significance. A recent prospective case-control study found a significantly higher risk for AP amongst patients eating par-boiled rice and fresh water fish.

CONCLUSIONS

Evidence from literature does not appear to support the role of diet as a single bolus meal as a cause for AP. Prolonged consumption of diets rich in proteins and fats may work synergistically with gallstones / alcohol to trigger an attack of AP indicating a possible role of diet as a cofactor in the development of AP possibly by lowering the threshold needed by these other agents to lead to the attack of AP.

[N-6 fatty acids and cardiovascular health: dietary intake recommendations]

Omega-6 polyunsaturated fatty acids (n-6 PUFA) are well known for their critical role in many physiological functions and reduce risks of cardiovascular disease (CVD). However, some argue that excessive consumption of n-6 PUFA may lead to adverse effects on health and therefore recommend reducing dietary n-6 PUFA intake or fixing an upper limit. Epidemiological studies show that n-6 PUFA dietary intake significantly lowers blood LDL-cholesterol levels. In addition, n-6 PUFA intake lower several cardiovascular risk factors such as blood pressure, inflammatory markers, haemostatic parameters and obesity. Data from prospective cohort and interventional studies converge towards a specific protective role of dietary n-6 PUFA intake, in particular linoleic acid, against CVD. In regards to studies examined in this narrative review, recommendation for n-6 PUFA intake above 5%, and ideally about 10% of total energy appears justified for the prevention of ischemic heart disease.

Fatty acid status in early life in low-income countries--overview of the situation, policy and research priorities

Fat intake may be low in low-income countries and little information is available on its composition in terms of (n-3) and (n-6) fatty acids (FA). As a result, long chain poly-unsaturated fatty acid (LCPUFA) status is a concern, especially in settings where fish intake is low and/or common sources of fat have a low alpha-linolenic acid (ALA) and high linoleic acid (LA) content. High LA levels, as found for instance in sunflower, safflower, corn, peanut and soy oils, may inhibit the conversion of ALA into its LC-PUFA derivatives. Other factors that affect LA and ALA conversion into LC-PUFA, including genetic factors, are little known and should also be investigated in different populations. Different interventions that could feasibly improve LC-PUFA status in low-income countries should be tested and their effects on functional outcomes assessed, preferably starting from pregnancy. Identifying affordable sources of ALA or LC-PUFA that could be made locally available and easily introduced in the diet early in life is also a priority.

Conversion of linoleic acid and alpha-linolenic acid to long-chain polyunsaturated fatty acids (LCPUFAs), with a focus on pregnancy, lactation and the first 2 years of life

Over the past two decades, there has been a marked shift in the fatty acid composition of the diets of industrialized nations towards increased intake of the n-6 fatty acid linoleic acid (LA, 18:2n-6), largely as a result of the replacement of saturated fats with plant-based polyunsaturated fatty acid (PUFA). While health agencies internationally continue to advocate for high n-6 PUFA intake combined with increased intakes of preformed n-3 long-chain PUFAs (LCPUFA) docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) to reduce the incidence of cardiovascular disease (CVD), there are questions as to whether this is the best approach. LA competes with alpha-linolenic acid (18:3n-3) for endogenous conversion to the LC derivatives EPA and DHA, and LA also inhibits incorporation of DHA and EPA into tissues. Thus, high-LA levels in the diet generally result in low n-3 LCPUFA status. Pregnancy and infancy are developmental periods during which the fatty acid supply is particularly critical. The importance of an adequate supply of n-3 LCPUFA for ensuring optimal development of infant brain and visual systems is well established, and there is now evidence that the supply of n-3 LCPUFA also influences a range of growth, metabolic and immune outcomes in childhood. This review will re-evaluate the health benefits of modern Western diets and pose the question of whether the introduction of similar diets to nations with emerging economies is the most prudent public health strategy for improving health in these populations.

Metabolic programming of long-term outcomes due to fatty acid nutrition in early life

Understanding of the importance of dietary fatty acids has grown beyond a simple source of energy to complex roles in regulating gene expression and cell and intracellular communication. This is important because the metabolic and neuroendocrine environment of the fetus and infant plays a key role in guiding the set point of neural receptors that regulate energy homeostasis and expression of genes that control energy storage and oxidation. Early deviations in these pathways have the potential to lead to lasting adaptations, termed metabolic programming, which may combine to increase the risk of metabolic syndrome in later life. The quality of fatty acids in human diets has undergone major changes in the last 50 years, characterized by an increase in ω-6 and decrease in ω-3 fatty acids. Evidence is accumulating to support the concept that the maternal intake of ω-6 and ω-3 fatty acids in gestation and lactation, possibly involving both excess ω-6 and inadequate ω-3 fatty acids, can impact the developing infant tissue lipids and neuroendocrine and metabolic pathways relevant to metabolic programming. Further work is needed to understand the needs for different ω-6 and ω-3 fatty acids during fetal and infant life, and their roles with respect to development of energy homeostasis and metabolism.

Omega-3 index, obesity and insulin resistance in children

OBJECTIVES

Recent studies in adults have suggested that the plasma level of omega-3 fatty acids may be associated with weight status and abdominal adiposity, limited studies exist in paediatric populations. The present study examined the relationship between the omega-3 index, weight status and insulin resistance in children.

METHODS

School-age children between 5-12 years, classified as non-obese or obese on the basis of body mass index (BMI) z-scores, were examined. Fat intake was assessed using a parent reported 135-item semi-quantitative food frequency questionnaire. Erythrocyte fatty acid composition was determined using gas chromatography. The Omega-3 index (O3I) was calculated by adding eicosapentaenoic and docosahexaenoic acid % (weight/weight) values.

RESULTS

Obese children had altered erythrocyte fatty acid composition unrelated to reported dietary intake. A greater proportion of obese (BMI z-score > 2.25) children (33%) had an omega-3 index of < 4.0 (high risk) compared with non-obese children (BMI z-score < 2.25) (17%). Simultaneously, the number of children with a higher omega-3 index (6.0-8.0 lower risk) was lower in the obese (13%) versus non-obese children (25%, respectively). A moderate, but statistically significant correlation was found between O3I and fasting insulin level (r = -0.3, P = 0.03) and with homeostatic model assessment (HOMA) scores (r = -0.3, P = 0.04). CONCLUSION; The observed association between the omega-3 index, weight status and insulin resistance in children highlights the importance of omega-3 fatty acids in the prevention of obesity-related chronic diseases in later life. The results presented merits confirmation in a larger sample of obese children.

Rodent models for metabolic syndrome research

Rodents are widely used to mimic human diseases to improve understanding of the causes and progression of disease symptoms and to test potential therapeutic interventions. Chronic diseases such as obesity, diabetes and hypertension, together known as the metabolic syndrome, are causing increasing morbidity and mortality. To control these diseases, research in rodent models that closely mimic the changes in humans is essential. This review will examine the adequacy of the many rodent models of metabolic syndrome to mimic the causes and progression of the disease in humans. The primary criterion will be whether a rodent model initiates all of the signs, especially obesity, diabetes, hypertension and dysfunction of the heart, blood vessels, liver and kidney, primarily by diet since these are the diet-induced signs in humans with metabolic syndrome. We conclude that the model that comes closest to fulfilling this criterion is the high carbohydrate, high fat-fed male rodent.

PPARγ: a circadian transcription factor in adipogenesis and osteogenesis

Peroxisome proliferator-activated receptor γ (PPARγ) is a critical factor for adipogenesis and glucose metabolism, but accumulating evidence demonstrates the involvement of PPARγ in skeletal metabolism as well. PPARγ agonists, the thiazolidinediones, have been widely used for the treatment of type 2 diabetes mellitus owing to their effectiveness in lowering blood glucose levels. However, the use of thiazolidinediones has been associated with bone loss and fractures. Thiazolidinedione-induced alterations in the bone marrow milieu-that is, increased bone marrow adiposity with suppression of osteogenesis-could partially explain the pathogenesis of drug-induced bone loss. Furthermore, several lines of evidence place PPARγ at the center of a regulatory loop between circadian networks and metabolic output. PPARγ exhibits a circadian expression pattern that is magnified by consumption of a high-fat diet. One gene with circadian regulation in peripheral tissues, nocturnin, has been shown to enhance PPARγ activity. Importantly, mice deficient in nocturnin are protected from diet-induced obesity, exhibit impaired circadian expression of PPARγ and have increased bone mass. This Review focuses on new findings regarding the role of PPARγ in adipose tissue and skeletal metabolism and summarizes the emerging role of PPARγ as an integral part of a complex circadian regulatory system that modulates food storage, energy consumption and skeletal metabolism.

Skeletal aging and the adipocyte program: New insights from an "old" molecule

Aging is associated with profound changes in bone mass and body composition. Emerging evidence supports the hypothesis that alterations in mesenchymal stromal cell fate are a critical etiologic factor. In addition, time-keeping at the cellular level is affected as aging progresses, particularly in the adipocyte. In this Extra View we discuss the interactive role of three molecules, PPARγ, nocturnin and IGF-I in regulating stem cell fate in the marrow and the potential implications of this network for understanding cellular aging.