A low alpha-linolenic intake during early life increases adiposity in the adult guinea pig

Regulation of Adipose Tissue Biology by Long-Chain Fatty Acids: Metabolic Effects and Molecular Mechanisms

Long-chain fatty acids (LCFA) modulate metabolic, oxidative, and inflammatory responses, and the physiological effects of LCFA are determined by chain length and the degree of saturation. Adipose tissues comprise multiple cell types, and play a significant role in energy storage and expenditure. Fatty acid uptake and oxidation are the pathways through which fatty acids participate in the regulation of energy homeostasis, and their dysregulation can lead to the development of obesity and chronic obesity-related disorders, including type 2 diabetes, cardiovascular diseases, and certain types of cancer. Numerous studies have reported that many aspects of adipose tissue biology are influenced by the number and position of double bonds in LCFA, and these effects are mediated by various signaling pathways, including those regulating adipocyte differentiation (adipogenesis), thermogenesis, and inflammation in adipose tissue. This review aims to describe the underlying molecular mechanisms by which different types of LCFA influence adipose tissue metabolism, and to further clarify their relevance to metabolic dysregulation associated with obesity. A better understanding of the effects of LCFA on adipose tissue metabolism may lead to improved nutraceutical strategies to address obesity and obesity-associated diseases.

The effects of dietary fatty acids in the physiological outcomes of maternal high-fat diet on offspring energy homeostasis in mice

The early-life origins of disease hypothesis has been applied to obesity research and modeled through overnutrition, usually with a high-fat diet (HFD). Since the obesity epidemic coincided with societal change in dietary fat consumption, rather than amount, manipulation of fatty acid (FA) profile is an under-investigated area of study. Additionally, the binding of FAs to nuclear receptors may have persistent intergenerational, extranutritive endocrinological effects that interact with the actions of reproductive steroids causing sex-dependent effects. To determine the role of FA type in the effects underlying maternal HFD, we fed wild-type C57BL6/J mating pairs, from preconception through lactation, a HFD with high saturated fat levels from coconut oil or high linoleic acid (LA) levels from vegetable oil. Male and female offspring body weight and food intake were measured weekly for 25 weeks. Assays for glucose metabolism, body composition, and calorimetry were performed at 25 weeks. Plasma metabolic peptides and liver mRNA were measured terminally. Obesity was primarily affected by adult rather than maternal diet in males, yet in females, maternal HFD potentiated the effects of adult HFD. Maternal HFD high in LA impaired glucose disposal in males weaned onto HFD and insulin sensitivity of females. Plasma leptin correlated with adiposity, but insulin and insulin receptor expression in the liver were altered by maternal LA in males. Our results suggest that maternal FA profile is most influential on offspring glucose metabolism and that adult diet is more important than maternal diet for obesity and other parameters of metabolic syndrome.

Fats & fatty acids in Indian diets: Time for serious introspection

Recommended dietary allowances for fat and fatty acid (FA) intakes are set on global standards aimed at prevention of lifestyle diseases. Yet, the fat composition of a diet is both ethnic/region specific as well as income dependent. Indian diets are predominantly vegetarian and relatively low in fat. Furthermore, the main sources of fat are of plant origin rather than animal origin. This results in a diet that is relatively low in saturated FA, high in n-6 polyunsaturated fatty acids (PUFA), and very low in n-3 PUFA. Though this appears as a good dietary composition as per global standards, the undeniable increase in the incidence of obesity, diabetes and cardiovascular diseases in India begs for an explanation. In this context, the current article is aimed at reopening the debate on fat intakes in Indian diets, with a focus on a balance between fats, carbohydrates and proteins, rather than an emphasis on individual macronutrients.

Early Low-Fat Diet Enriched With Linolenic Acid Reduces Liver Endocannabinoid Tone and Improves Late Glycemic Control After a High-Fat Diet Challenge in Mice

Evidence suggests that alterations of glucose and lipid homeostasis induced by obesity are associated with the elevation of endocannabinoid tone. The biosynthesis of the two main endocannabinoids, N-arachidonoylethanolamine and 2-arachidonoyl-glycerol, which derive from arachidonic acid, is influenced by dietary fatty acids (FAs). We investigated whether exposure to n-3 FA at a young age may decrease tissue endocannabinoid levels and prevent metabolic disorders induced by a later high-fat diet (HFD) challenge. Three-week-old mice received a 5% lipid diet containing lard, lard plus safflower oil, or lard plus linseed oil for 10 weeks. Then, mice were challenged with a 30% lard diet for 10 additional weeks. A low n-6/n-3 FA ratio in the early diet induces a marked decrease in liver endocannabinoid levels. A similar reduction was observed in transgenic Fat-1 mice, which exhibit high tissue levels of n-3 FA compared with wild-type mice. Hepatic expression of key enzymes involved in carbohydrate and lipid metabolism was concomitantly changed. Interestingly, some gene modifications persisted after HFD challenge and were associated with improved glycemic control. These findings indicate that early dietary interventions based on n-3 FA may represent an alternative strategy to drugs for reducing endocannabinoid tone and improving metabolic parameters in the metabolic syndrome.

Linoleic acid and the pathogenesis of obesity

The modern Western diet has been consumed in developed English speaking countries for the last 50 years, and is now gradually being adopted in Eastern and developing countries. These nutrition transitions are typified by an increased intake of high linoleic acid (LA) plant oils, due to their abundance and low price, resulting in an increase in the PUFA n-6:n-3 ratio. This increase in LA above what is estimated to be required is hypothesised to be implicated in the increased rates of obesity and other associated non-communicable diseases which occur following a transition to a modern Westernised diet. LA can be converted to the metabolically active arachidonic acid, which has roles in inducing inflammation and adipogenesis, and endocannabinoid system regulation. This review aims to address the possible implications of excessive LA and its metabolites in the pathogenesis of obesity.

Synergism of α-linolenic acid, conjugated linoleic acid and calcium in decreasing adipocyte and increasing osteoblast cell growth

Whole fat milk and dairy products (although providing more energy compared to low- or non-fat products), are good sources of α-linolenic acid (ALA), conjugated linoleic acid (CLA) and calcium, which may be favorable in modulating bone and adipose tissue metabolism. We examined individual and/or synergistic effects of ALA, CLA and calcium (at levels similar to those in whole milk/dairy products) in regulating bone and adipose cell growth. ST2 stromal, MC3T3-L1 adipocyte-like and MC3T3-E1 osteoblast-like cells were treated with: (a) linoleic acid (LNA):ALA ratios = 1-5:1; (b) individual/combined 80-90 % c9, t11 (9,11) and 5-10 % t10, c12 (10,12) CLA isomers; (c) 0.5-3.0 mM calcium; (d) combinations of (a), (b), (c); and (e) control. Local mediators, including eicosanoids and growth factors, were measured. (a) The optimal effect was found at the 4:1 LNA:ALA ratio where insulin-like growth factor-1 (IGF-1) and IGF binding protein-3 (IGFBP-3) production was the lowest in MC3T3-L1 cells. (b) All CLA isomer blends decreased MC3T3-L1 and increased MC3T3-E1 cell differentiation. (c) 1.5-2.5 mM calcium increased ST2 and MC3T3-E1, and decreased MC3T3-L1 cell proliferation. (d) Combination of 4:1 LNA:ALA + 90:10 % CLA + 2.0 mM calcium lowered MC3T3-L1 and increased MC3T3-E1 cell differentiation. Overall, the optimal LNA:ALA ratio to enhance osteoblastogenesis and inhibit adipogenesis was 4:1. This effect was enhanced by 90:10 % CLA + 2.0 mM calcium, indicating possible synergism of these dietary factors in promoting osteoblast and inhibiting adipocyte differentiation in cell cultures.

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.

The guinea pig as a model for metabolic programming of adiposity

BACKGROUND

The human infant accumulates body fat during intrauterine life. The guinea pig shares this characteristic and is born with similar adiposity; thus, it may be a relevant model to study obesity programming.

OBJECTIVE

The objective of this study was to evaluate guinea pig adipose tissue (AT) development and the effect of a maternal high-fat diet on the offspring's body composition.

DESIGN

In experiment 1, adipogenesis dynamics were evaluated at 3, 10, 21, and 136 d in epididymal and retroperitoneal AT with the use of (2)H(2)O labeling. In experiment 2, dams received a control or high-fat diet from mating to 21 d after delivery. The offspring received a high-fat diet from 22 to 105 d; adiposity was measured at 2, 21, 54, and 97 d.

RESULTS

The fractional proliferation rate (FPR) of cells in epididymal AT was 25.2% of cells synthesized in 5 d at 3 d of age and decreased over time (P < 0.001). Age had no effect on retroperitoneal FPR (P = 0.179). In both depots, the fractional synthesis rate (FSR) of palmitate decreased extensively from day 3 to day 10, increasing by day 21 and declining by day 136 (P < 0.001). The FSR of triglycerides decreased with age (P < 0.001). A maternal high-fat diet increased the offspring's adiposity at 2 d and 21 d (P < 0.05) but had no effect on body composition later in life.

CONCLUSIONS

Adipogenesis in the guinea pig is very active during early life and was altered by a maternal high-fat diet; thus, it is an adequate model for intrauterine fat deposition. However, there were no effects of maternal diet later in life.