Isocaloric intake of a high-fat diet modifies adiposity and lipid handling in a sex dependent manner in rats

Sex Differences in the Skeletal Muscle Response to a High Fat, High Sucrose Diet in Rats

Men are diagnosed with type 2 diabetes at lower body mass indexes than women; the role of skeletal muscle in this sex difference is poorly understood. Type 2 diabetes impacts skeletal muscle, particularly in females who demonstrate a lower oxidative capacity compared to males. To address mechanistic differences underlying this sex disparity, we investigated skeletal muscle mitochondrial respiration in female and male rats in response to chronic high-fat, high-sugar (HFHS) diet consumption. Four-week-old Wistar Rats were fed a standard chow or HFHS diet for 14 weeks to identify sex-specific adaptations in mitochondrial respirometry and characteristics, transcriptional patterns, and protein profiles. Fat mass was greater with the HFHS diet in both sexes when controlled for body mass (p < 0.0001). Blood glucose and insulin resistance were greater in males (p = 0.01) and HFHS-fed rats (p < 0.001). HFHS-fed males had higher mitochondrial respiration compared with females (p < 0.01 sex/diet interaction). No evidence of a difference by sex or diet was found for mitochondrial synthesis, dynamics, or quality to support the mitochondrial respiration sex/diet interaction. However, transcriptomic analyses indicate sex differences in nutrient handling. Sex-specific differences occurred in PI3K/AKT signaling, PPARα/RXRα, and triacylglycerol degradation. These findings may provide insight into the clinical sex differences in body mass index threshold for diabetes development and tissue-specific progression of insulin resistance.

The Effects of a Low Linoleic Acid/α-Linolenic Acid Ratio on Lipid Metabolism and Endogenous Fatty Acid Distribution in Obese Mice

A reduced risk of obesity and metabolic syndrome has been observed in individuals with a low intake ratio of linoleic acid/α-linolenic acid (LA/ALA). However, the influence of a low ratio of LA/ALA intake on lipid metabolism and endogenous fatty acid distribution in obese patients remains elusive. In this investigation, 8-week-old C57BL/6J mice were randomly assigned to four groups: low-fat diet (LFD) as a control, high-fat diet (HFD), high-fat diet with a low LA/ALA ratio (HFD+H3L6), and high-fat diet with a high LA/ALA ratio (HFD+L3H6) for 16 weeks. Our results show that the HFD+H3L6 diet significantly decreased the liver index of HFD mice by 3.51%, as well as the levels of triacylglycerols (TGs) and low-density lipoprotein cholesterol (LDL-C) by 15.67% and 10.02%, respectively. Moreover, the HFD+H3L6 diet reduced the pro-inflammatory cytokines interleukin-6 (IL-6) level and aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio and elevated the level of superoxide dismutase (SOD) in the liver. The HFD+H3L6 diet also resulted in the downregulation of fatty acid synthetase (FAS) and sterol regulatory element binding proteins-1c (SREBP-1c) expression and the upregulation of peroxisome proliferator-activated receptor-α (PPAR-α) and acyl-CoA oxidase 1 (ACOX1) gene expression in the liver. The low LA/ALA ratio diet led to a notable increase in the levels of ALA and its downstream derivative docosahexaenoic acid (DHA) in the erythrocyte, liver, perienteric fat, epididymal fat, perirenal fat, spleen, brain, heart, and gastrocnemius, with a strong positive correlation. Conversely, the accumulation of LA in abdominal fat was more prominent, and a high LA/ALA ratio diet exacerbated the deposition effect of LA. In conclusion, the low LA/ALA ratio not only regulated endogenous fatty acid levels but also upregulated PPAR-α and ACOX1 and downregulated SREBP-1c and FAS gene expression levels, thus maintaining lipid homeostasis. Optimizing dietary fat intake is important in studying lipid nutrition. These research findings emphasize the significance of understanding and optimizing dietary fat intake.

Sex-Dependent Role of Adipose Tissue HDAC9 in Diet-Induced Obesity and Metabolic Dysfunction

Obesity is a major risk factor for both metabolic and cardiovascular disease. We reported that, in obese male mice, histone deacetylase 9 (HDAC9) is upregulated in adipose tissues, and global deletion of HDAC9 protected against high fat diet (HFD)-induced obesity and metabolic disease. Here, we investigated the impact of adipocyte-specific HDAC9 gene deletion on diet-induced obesity in male and female mice. The HDAC9 gene expression was increased in adipose tissues of obese male and female mice and HDAC9 expression correlated positively with body mass index in humans. Interestingly, female, but not male, adipocyte-specific HDAC9 KO mice on HFD exhibited reduced body weight and visceral adipose tissue mass, adipocyte hypertrophy, and improved insulin sensitivity, glucose tolerance and adipogenic differentiation gene expression. Furthermore, adipocyte-specific HDAC9 gene deletion in female mice improved metabolic health as assessed by whole body energy expenditure, oxygen consumption, and adaptive thermogenesis. Mechanistically, compared to female mice, HFD-fed male mice exhibited preferential HDAC9 expression in the stromovascular fraction, which may have offset the impact of adipocyte-specific HDAC9 gene deletion in male mice. These results suggest that HDAC9 expressed in adipocytes is detrimental to obesity in female mice and provides novel evidence of sex-related differences in HDAC9 cellular expression and contribution to obesity-related metabolic disease.

Modulation of the Hypothalamic Nutrient Sensing Pathways by Sex and Early-Life Stress

There are sex differences in metabolic disease risk, and early-life stress (ES) increases the risk to develop such diseases, potentially in a sex-specific manner. It remains to be understood, however, how sex and ES affect such metabolic vulnerability. The hypothalamus regulates food intake and energy expenditure by sensing the organism's energy state via metabolic hormones (leptin, insulin, ghrelin) and nutrients (glucose, fatty acids). Here, we investigated if and how sex and ES alter hypothalamic nutrient sensing short and long-term. ES was induced in mice by limiting the bedding and nesting material from postnatal day (P)2-P9, and the expression of genes critical for hypothalamic nutrient sensing were studied in male and female offspring, both at P9 and in adulthood (P180). At P9, we observed a sex difference in both Ppargc1a and Lepr expression, while the latter was also increased in ES-exposed animals relative to controls. In adulthood, we found sex differences in Acacb, Agrp, and Npy expression, whereas ES did not affect the expression of genes involved in hypothalamic nutrient sensing. Thus, we observe a pervasive sex difference in nutrient sensing pathways and a targeted modulation of this pathway by ES early in life. Future research is needed to address if the modulation of these pathways by sex and ES is involved in the differential vulnerability to metabolic diseases.

Adult food choices depend on sex and exposure to early-life stress: Underlying brain circuitry, adipose tissue adaptations and metabolic responses

Exposure to early-life stress (ES) increases the risk to develop obesity later in life, and these effects may be sex-specific, but it is currently unknown what underlies the ES-induced metabolic vulnerability. We have previously shown that ES leads to a leaner phenotype under standard chow diet conditions, but to increased fat accumulation when exposed to an unhealthy obesogenic diet. However these diets were fed without a choice. An important, yet under investigated, element contributing to the development of obesity in humans is the choice of the food. There is initial evidence that ES leads to altered food choices but a thorough testing on how ES affects the choice of both the fat and sugar component, and if this is similar in males and females, is currently missing. We hypothesized that ES increases the choice for unhealthy foods, while it at the same time also affects the response to such a diet. In a mouse model for ES, in which mice are exposed to limited nesting and bedding material from postnatal day (P)2–P9, we investigated if ES exposure affected i) food choice with a free choice high-fat high-sugar diet (fcHFHS), ii) the response to such a diet, iii) the brain circuits that regulate food intake and food reward and iv) if such ES effects are sex-specific. We show that there are sex differences in food choice under basal circumstances, and that ES increases fat intake in females when exposed to a mild acute stressor. Moreover, ES impacts the physiologic response to the fcHFHS and the brain circuits regulating food intake in sex-specific manner. Our data highlight sex-specific effects of ES on metabolic functioning and food choice.

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Strong sex differences exist in food choice and metabolism in mice.

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Early-life stress (ES) increases fat intake in females after mild acute stress exposure.

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The physiological response to the diet is affected by ES in a sex-dependent manner.

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ES modulates the hedonic feeding circuitry.

Maternal high-fat high-sucrose diet and gestational exercise modulate hepatic fat accumulation and liver mitochondrial respiratory capacity in mothers and male offspring

BACKGROUND

Maternal high-caloric nutrition and related gestational diabetes mellitus (GDM) are associated with a high-risk for developing metabolic complications later in life and in their offspring. In contrast, exercise is recognized as a non-pharmacological strategy against metabolic dysfunctions associated to lifestyle disorders. Therefore, we investigated whether gestational exercise delays the development of metabolic alterations in GDM mothers later in life, but also protects 6-week-old male offspring from adverse effects of maternal diet.

METHODS

Female Sprague-Dawley rats were fed with either control (C) or high-fat high-sucrose (HFHS) diet to induce GDM and submitted to gestational exercise during the 3 weeks of pregnancy. Male offspring were sedentary and fed with C-diet.

RESULTS

Sedentary HFHS-fed dams exhibited increased gestational body weight gain (p < 0.01) and glucose intolerance (p < 0.01), characteristic of GDM. Their offspring had normal glucose metabolism, but increased early-age body weight, which was reverted by gestational exercise. Gestational exercise also reduced offspring hepatic triglycerides accumulation (p < 0.05) and improved liver mitochondrial respiration capacity (p < 0.05), contributing to the recovery of liver bioenergetics compromised by maternal HFHS diet. Interestingly, liver mitochondrial respiration remained increased by gestational exercise in HFHS-fed dams despite prolonged HFHS consumption and exercise cessation.

CONCLUSIONS

Gestational exercise can result in liver mitochondrial adaptations in GDM animals, which can be preserved even after the exercise program cessation. Exposure to maternal GDM programs liver metabolic setting of male offspring, whereas gestational exercise appears as an important preventive tool against maternal diet-induced metabolic alterations.

Birth weight and body composition in 6-to-8 years old Maya children

OBJECTIVE

To test the hypothesis that fetal growth, indexed by birth weight (BW), induce metabolic adjustments in the fetus that will be reflected in differences in body composition in a sample of 6-to 8-years old urban Maya children from Yucatan, Mexico.

METHODS

We measured height (cm), weight (kg) and triceps skinfold (mm) in 260 children (boys: 132, girls: 128), and height (cm) and weight (kg) in their mothers. Body composition was estimated in children through bioelectrical impedance analysis. Outcome variables were fat free-mass index (FFMI = fat-free mass [kg]/height [m]² ) and fat mass index (FMI = fat mass [kg]/height [m]² ). The main independent variable was BW z-scores. Multiple linear regression models were used to analyze the association between BW z-scores and outcome variables measured during childhood. Separate analyses were done for boys and girls. Complementary models were run using outcomes as z-scores. Models were adjusted for location, children's and mothers' age, mother's body mass index and household overcrowding index.

RESULTS

BW in boys was positively associated with FFMI and FMI. FFMI increase 0.34 kg/m² per 1-SD increase in BW and FMI increase 0.40 kg/m² per 1-SD increase in BW. When outcomes were used as z-scores, FFMI increase 0.24 SD and FMI increase 0.18 SD per 1-SD increase in BW, respectively.

CONCLUSION

Our results are in contrast with previous findings that birth weight is more consistently associated with subsequent lean mass than with fat mass. Associations, detected only in boys, may be explained by sex differences in sensitivity to early life environments.

Dietary Fat and Cancer-Which Is Good, Which Is Bad, and the Body of Evidence

A high-fat diet (HFD) induces changes in gut microbiota leading to activation of pro-inflammatory pathways, and obesity, as a consequence of overnutrition, exacerbates inflammation, a known risk factor not only for cancer. However, experimental data showed that the composition of dietary fat has a greater impact on the pathogenesis of cancer than the total fat content in isocaloric diets. Similarly, human studies did not prove that a decrease in total fat intake is an effective strategy to combat cancer. Saturated fat has long been considered as harmful, but the current consensus is that moderate intake of saturated fatty acids (SFAs), including palmitic acid (PA), does not pose a health risk within a balanced diet. In regard to monounsaturated fat, plant sources are recommended. The consumption of plant monounsaturated fatty acids (MUFAs), particularly from olive oil, has been associated with lower cancer risk. Similarly, the replacement of animal MUFAs with plant MUFAs decreased cancer mortality. The impact of polyunsaturated fatty acids (PUFAs) on cancer risk depends on the ratio between ω-6 and ω-3 PUFAs. In vivo data showed stimulatory effects of ω-6 PUFAs on tumour growth while ω-3 PUFAs were protective, but the results of human studies were not as promising as indicated in preclinical reports. As for trans FAs (TFAs), experimental data mostly showed opposite effects of industrially produced and natural TFAs, with the latter being protective against cancer progression, but human data are mixed, and no clear conclusion can be made. Further studies are warranted to establish the role of FAs in the control of cell growth in order to find an effective strategy for cancer prevention/treatment.

In Vivo Investigation of High-Fat Diet-Induced Hepatic Lipid Dysfunctions

Fat distribution, on top of general obesity, contributes to the severity of histologic features in patients with nonalcoholic fatty liver diseases (NAFLD); and visceral obesity has been correlated to fatty liver diseases. Therefore, investigation of fat distribution in vivo could be a good predictor of fatty liver risks in obesity. Fatty acids composition is a key player in hepatic dysfunctions and cardiovascular risk in obesity. Because fatty acids can damage biological membranes, fatty acid accumulation in the liver may be partially responsible for the functional and morphological changes that are observed in NAFLD. Fatty acids stored into triglycerides are lipid species that act as signaling molecules and therefore are key regulators of posttranslational regulation of biological functions such as lipid homeostasis and lipotoxicity. Here, we describe magnetic resonance methods to investigate in vivo whole-body fat distribution and hepatic liver fatty acid composition in order to directly assess the liver metabolic status and may allow to anticipate liver diseases.

Sex differences in the peripubertal response to a short-term, high-fat diet intake

Obesity is one of the most important health problems facing developed countries because being overweight is associated with a higher incidence of type 2 diabetes, cardiovascular disease and cancer, as well as other comorbidities. Although increased weight gain results from a combination of poor dietary habits and decreased energy expenditure, not all individuals have equal propensities to gain weight or to develop secondary complications of obesity. This is partially a result not only of genetics, including sex, but also the time during which an individual is exposed to an obesogenic environment. In the present study, we have compared the response of male and female mice to short-term exposure to a high-fat diet (HFD) or a low-fat diet during the peripubertal period (starting at 42 days of age) because this is a stage of dramatic hormonal and metabolic modifications. After 1 week on a HFD, there was no significant increase in body weight, although females significantly increased their energy intake. Serum leptin levels increased in both sexes, even though no change in fat mass was detected. Glyceamia and homeostasis model assessment increased in males, suggesting a rapid change in glucose metabolism. Hypothalamic pro-opiomelanocortin mRNA levels were significantly higher in females on a HFD compared to all other groups, which may be an attempt to reduce their increased energy intake. Hypothalamic inflammation and gliosis have been implicated in the development of secondary complications of obesity; however, no indication of activation of inflammatory processes or gliosis was found in response to 1 week of HFD in the hypothalamus, hippocampus or cerebellum of these young mice. These results indicate that there are both sex and age effects in the response to poor dietary intake because peripubertal male and female mice respond differently to short-term dietary changes and this response is different from that reported in adult rodents.

Anti-inflammatory effects of oestrogen mediate the sexual dimorphic response to lipid-induced insulin resistance

KEY POINTS

Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Insulin sensitivity is greater in premenopausal women compared with age-matched men, and metabolism-related cardiovascular diseases and type 2 diabetes are less frequent in these same women. Both female and male mice treated with oestradiol are protected against obesity-induced insulin resistance. The protection against obesity-induced insulin resistance is associated with reduced ectopic lipid content in liver and skeletal muscle. These results were associated with increased insulin-stimulated suppression of white adipose tissue lipolysis and reduced inflammation.

ABSTRACT

Oestrogen has been shown to play an important role in the regulation of metabolic homeostasis and insulin sensitivity in both human and rodent studies. Overall, females are protected against obesity-induced insulin resistance; yet, the mechanisms responsible for this protection are not well understood. Therefore, the aim of the present work was to evaluate the underlying mechanism(s) by which female mice are protected against obesity-induced insulin resistance compared with male mice. We studied male and female mice in age-matched or body weight-matched conditions. They were fed a high-fat diet (HFD) or regular chow for 4 weeks. We also studied HFD male mice treated with oestradiol or vehicle. Both HFD female and HFD male mice treated with oestradiol displayed increased whole-body insulin sensitivity, associated with reduction in ectopic hepatic and muscle lipid content compared to HFD male mice. Reductions in ectopic lipid content in these mice were associated with increased insulin-stimulated suppression of white adipose tissue (WAT) lipolysis. Both HFD female and HFD male mice treated with oestradiol also displayed striking reductions in WAT inflammation, represented by reductions in plasma and adipose tissue tumour necrosis factor α and interleukin 6 concentrations. Taken together these data support the hypothesis that HFD female mice are protected from obesity-induced insulin resistance due to oestradiol-mediated reductions in WAT inflammation, leading to improved insulin-mediated suppression of WAT lipolysis and reduced ectopic lipid content in liver and skeletal muscle.

Impact of physical exercise on visceral adipose tissue fatty acid profile and inflammation in response to a high-fat diet regimen

PURPOSE

Studies associate specific fatty-acids (FA) with the pathophysiology of inflammation. We aimed to analyze the impact of exercise on adipose tissue FA profile in response to a high-fat diet (HFD) and to ascertain whether these exercise-induced changes in specific FA have repercussions on obesity-related inflammation.

METHODS

Sprague-Dawley rats were assigned into sedentary, voluntary physical-activity (VPA) and endurance training (ET) groups fed a standard (S, 35kcal% fat) or high-fat (71kcal% fat) diets. VPA-animals had unrestricted access to wheel-running. After 9-wks, ET-animals engaged a running protocol for 8-wks, while maintained dietary treatments. The FA content in epididymal white-adipose tissue (eWAT) triglycerides was analyzed by gas-chromatography and the expression of inflammatory markers was determined using RT-qPCR, Western and slot blotting.

RESULTS

Eight-wks of ET reversed obesity-related anatomical features. HFD increased plasma tumor necrosis factor (TNF)-α content and eWAT monocyte chemoattractant protein (MCP)-1 protein expression. HFD decreased eWAT content of saturated FA and monounsaturated FA, while increased linoleic acid and prostaglandin E2 (PGE2) levels in eWAT. VPA decreased visceral adiposity, adipocyte size and MCP-1 in HFD-fed animals. The VPA and ET interventions diminished palmitoleic acid and increased linoleic acid in HFD-fed groups. Moreover, both interventions increased PGE2 levels in standard diet-fed groups and decreased in HFD. ET increased eWAT fatty acid desaturase 1 (FADS1) and elongase 5 (ELOVL5) protein content in both diet types. ET reduced eWAT inflammatory markers (TNF-α, IL-6), macrophage recruitment (MCP-1 and F4/80) and increased IL-10/TNF-α ratio in plasma and in eWAT in both diet types.

CONCLUSIONS

Exercise induced FA-specific changes independently of dietary FA composition, but only ET attenuated the inflammatory response in VAT of HFD-fed rats. Moreover, the exercise-induced FA changes did not correlate with the inflammatory response in VAT of rats submitted to HFD.

Male mice are susceptible to high fat diet-induced hyperglycaemia and display increased circulatory retinol binding protein 4 (RBP4) levels and its expression in visceral adipose depots

Vitamin A and its metabolites are known to modulate adipose tissue development and its associated complications. Here, we assessed the vitamin A status and its metabolic pathway gene expression in relation to sexual dimorphism by employing 35 days old C57BL/6J male and female mice, which were fed either stock or high fat (HF) diet for 26 weeks. HF diet feeding increased body weight/weight gain and white adipose tissue (WAT) of visceral and subcutaneous regions, however, increase in vitamin A levels observed only in subcutaneous WAT. Further, the expression of most of the vitamin A metabolic pathway genes showed no sexual dimorphism. The observed HF diet-induced hyperglycaemia in male corroborates with increased retinol binding protein 4 (RBP4) levels in plasma and its expression in visceral adipose depots. In conclusion, the male mice are susceptible to high fat diet-induced hyperglycaemia and display higher plasma RBP4 levels, possibly due to its over-expression in visceral adipose depots.

Supplementing diet with blackberry extract causes a catabolic response with increments in insulin sensitivity in rats

Blackberry (Rubus sp.) fruit has a high content of anthocyanins, but its health benefits have not been sufficiently explored in healthy individuals. Thus, the aim of the study was to determine the effects of blackberry extract on lipid and glucose variables in female and male rats. Sprague Dawley rats were given a standard pellet (SD) or cafeteria (CD) diet supplemented (SD+R and CD+R) or not with Rubus extract for 80 days. Female rats given SD+R had lower body and liver weights than SD females; both sexes given SD+R showed lower plasma glucose and insulin, higher plasma NEFA, glycerol and 3-hydroxybutyrate, and higher liver concentration of triacylglycerols than SD rats. The homeostasis model of insulin resistance (HOMA) was lower in SD+R rats than in SD rats, but higher in CD rats. No effects of Rubus extract were observed in CD rats. In conclusion, Rubus extract, in rats given SD, decreased glycemia and increased insulin sensitivity. It also increased lipid breakdown in adipose tissue. The effects were greater in females than in males. No effect was seen in rats given CD, probably as a result of their high insulin resistance.

Perinatal maternal feeding with an energy dense diet and/or micronutrient mixture drives offspring fat distribution depending on the sex and growth stage

Maternal nutrition during pregnancy and lactation influences offspring development and health. Novel studies have described the effects on next generation obesity-related features depending on maternal macro- and micro-nutrient perinatal feeding. We hypothesized that the maternal obesogenic diet during pregnancy and lactation programs an obese phenotype, while maternal micronutrient supplementation at these stages could partially prevent these features. Thus, the aim was to assess the influence of a perinatal maternal feeding with an obesogenic diet enriched in fat and sucrose and a micronutrient supplementation during pregnancy and lactation on offspring growth and obese phenotypical features during life course. Female Wistar rats were assigned to four dietary groups during pregnancy and lactation: control, control supplemented with micronutrients (choline, betaine, folic acid and vitamin B12 ), high-fat sucrose (HFS) and HFS supplemented. At weaning, the offspring were transferred to a chow diet, and weight and fat mass were measured at weeks 3, 12 and 20. At birth, both male and female offspring from mothers fed the obesogenic diet showed lower body weight (-5 and -6%, respectively), while only female offspring weight decreased by maternal micronutrient supplementation (-5%). During lactation, maternal HFS diet was associated with increased body weight, while micronutrient supplementation protected against body weight gain. Whole body fat mass content increased at weeks 3, 12 and 20 (from 16 to 65%) due to maternal HFS diet. Maternal micronutrient supplementation decreased offspring fat mass content at week 3 (-8%). Male offspring showed higher adiposity than females at weeks 12 and 20. In conclusion, maternal HFS feeding during pregnancy and lactation was associated with a low offspring weight at birth and obese phenotypical features during adult life in a sex- and time-dependent manner. Furthermore, maternal methyl donor supplementation protected against body weight gain in male offspring during lactation and in female offspring also during juvenile period.

Physical exercise antagonizes clinical and anatomical features characterizing Lieber-DeCarli diet-induced obesity and related metabolic disorders

BACKGROUND & AIMS

Lieber-DeCarli diet has been used to induce obesity and non-alcoholic steatohepatitis (NASH). As scarce anatomical and clinical-related information on this diet model exists and being exercise an advised strategy to counteract metabolic diseases, we aimed to analyze the preventive (voluntary physical activity - VPA) and therapeutic (endurance training - ET) effect of exercise on clinical/anatomical features of rats fed with Lieber-DeCarli diet.

METHODS

In the beginning of the protocol, Sprague-Dawley rats were divided into standard-diet sedentary (SS, n = 20), standard-diet VPA (SVPA, n = 10), high-fat diet sedentary (HS, n = 20) and high-fat diet VPA (HVPA, n = 10) groups. After 9-weeks, half (n = 10) of SS and HS groups were engaged in an ET program (8 wks/5 d/wk/60 min/day). At this time, a blood sample was collected for biochemical analysis. At the end of protocol (17-weeks) anatomic measures were assessed. Heart, liver, femur and visceral fat were weighted and blood was collected again. Liver section was used for histopathological examination.

RESULTS

At 17-weeks, high-fat diet increased visceral adiposity (HS vs. SS), which was counteracted by both exercises. However, ET was the only intervention able to diminished obesity-related measures and the histological features of NASH. Moreover, blood analysis at 9 weeks showed that high-fat diet increased ALT, AST, cholesterol and HDL while VLDL and TG levels were decreased (HS vs. SS). Notably, although these parameters were counteracted after 9-weeks of VPA, they were transitory and not observed after 17-weeks.

CONCLUSIONS

ET used as a therapeutic tool mitigated the clinical/anatomical-related features induced by Liber-DeCarli diet, thus possibly contributing to control obesity and metabolic disorders.

Rats fed diets with different energy contribution from fat do not differ in adiposity

OBJECTIVE

To determine whether rats reaching the same body mass, having been fed either a low-fat (LFD) or a high-fat diet (HFD), differ in white adipose tissue (WAT) deposition.

METHODS

In experiment 1, 22 Sprague-Dawley rats of the same age were divided into 11 rats with body mass below the batch median and fed a HFD, and 11 above the median and fed a LFD. In experiment 2, 20 Sprague-Dawley rats of the same age and starting body mass were randomised to either a HFD or LFD. When all groups reached similar final body mass, WAT was quantified using magnetic resonance imaging (MRI), dissection, and plasma leptin.

RESULTS

In experiment 1, both groups reached similar final body mass at the same age; in experiment 2 the HFD group reached similar final body mass earlier than the LFD group. There were no significant differences in WAT as assessed by MRI or leptin between the HFD and LFD groups in both experiments. Dissection revealed a trend for higher retroperitoneal and epididymal adiposity in the HFD groups in both experiments.

CONCLUSIONS

We conclude that at similar body mass, adiposity is independent of the macronutrient composition of the feeding regimen used to achieve it.

The impact of high fat diets on physiological changes in euthyroid and thyroid altered rats

The association of adverse health with high fat intake has long been recognized. However, the lack of research focusing on the interrelationship of thyroid and liver function, and the pathogenesis of a high fat diet leaves these topics poorly understood. The objective of this study was to evaluate and compare the physiological changes in euthyroid and thyroid altered animal model fed saturated and unsaturated high fat diets. To achieve this objective adult male Sprague Dawley rats (n = 100) were fed one of five diets; a control or one of four test diets containing 25% saturated or unsaturated, and 37% saturated or unsaturated fats for a period of eight weeks. Each experimental group consisted of ten euthyroid and ten thyroid altered animals. An altered thyroid state was chemically induced with the addition of 0.05% propylthiouracil (PTU) in the drinking water. Euthyroid animals fed high fat diets increased in body weights and body lengths, compared to thyroid altered animals (P < 0.05). Alanine aminotransferase (ALT) and asparte aminotransferase (AST) levels increased across all experimental groups. HbA1C values and urinary glucose values were within normal range for all animals. Liver morphology showed increased hepatic stellate (ito) and vacuole cells in thyroid altered animals. These findings suggest that altered thyroid status negatively impacts growth and weight gain, and simultaneously affected lipid metabolism, resulting in abnormal liver morphology.

Sex differences in adipose tissue: It is not only a question of quantity and distribution

Obesity and its associated secondary complications are active areas of investigation in search of effective treatments. As a result of this intensified research numerous differences between males and females at all levels of metabolic control have come to the forefront. These differences include not only the amount and distribution of adipose tissue, but also differences in its metabolic capacity and functions between the sexes. Here, we review some of the recent advances in our understanding of these dimorphisms and emphasize the fact that these differences between males and females must be taken into consideration in hopes of obtaining successful treatments for both sexes.

Adipose tissue stearoyl-CoA desaturase 1 index is increased and linoleic acid is decreased in obesity-prone rats fed a high-fat diet

Background

Fatty acid (FA) composition and desaturase indices are associated with obesity and related metabolic conditions. However, it is unclear to what extent desaturase activity in different lipid fractions contribute to obesity susceptibility. Our aim was to test whether desaturase activity and FA composition are linked to an obese phenotype in rats that are either obesity prone (OP) or resistant (OR) on a high-fat diet (HFD).

Methods

Two groups of Sprague–Dawley rats were given ad libitum (AL-HFD) or calorically restricted (HFD-paired; pair fed to calories consumed by chow-fed rats) access to a HFD. The AL-HFD group was categorized into OP and OR sub-groups based on weight gain over 5 weeks. Five different lipid fractions were examined in OP and OR rats with regard to proportions of essential and very long-chain polyunsaturated FAs: linoleic acid (LA), alpha-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid and the stearoyl-CoA desaturase 1 (SCD-1) product 16:1n-7. FA ratios were used to estimate activities of the delta-5-desaturase (20:4n-6/20:3n-6), delta-6-desaturase (18:3n-6/18:2n-6), stearoyl-CoA desaturase 1 (SCD-1; 16:1n-7/16:0, SCD-16 and 18:1n-9/18:0, SCD-18), de novo lipogenesis (16:0/18:2n-6) and FA elongation (18:0/16:0). Fasting insulin, glucose, adiponectin and leptin concentrations were measured in plasma.

Results

After AL-HFD access, OP rats had a significantly higher SCD-16 index and 16:1n-7 proportion, but a significantly lower LA proportion, in subcutaneous adipose tissue (SAT) triacylglycerols, as well as significantly higher insulin and leptin concentrations, compared with OR rats. No differences were found between the two phenotypes in liver (phospholipids; triacylglycerols) or plasma (cholesterol esters; phospholipids) lipid fractions or for plasma glucose or adiponectin concentrations. For the desaturase indices of the HFD-paired rats, the only significant differences compared with the OP or OR rats were higher SCD-16 and SCD-18 indices in SAT triacylglycerols in OP compared with HFD-paired rats.

Conclusion

The higher SCD-16 may reflect higher SCD-1 activity in SAT, which in combination with lower LA proportions may reflect higher insulin resistance and changes in SAT independent of other lipid fractions. Whether a lower SCD-16 index protects against diet-induced obesity is an interesting possibility that warrants further investigation.

High-fat diet consumption during pregnancy and the early post-natal period leads to decreased α cell plasticity in the nonhuman primate

We investigated the impact of poor maternal nutrition and metabolic health on the development of islets of the nonhuman primate (NHP). Interestingly, fetal offspring of high fat diet (HFD) fed animals had normal total islet and β cell mass; however, there was a significant reduction in α cell mass, and decreased expression of transcription factors involved in α cell differentiation. In juvenile animals all offspring maintained on a HFD during the postweaning period demonstrated increases in total islet mass, however, the control offspring displaying increased islet number, and HFD offspring displayed increased islet size. Finally, while control offspring had increases in α and β cells, the HFD offspring had increases only in β cell number. These studies indicate that consumption of a HFD diet during pregnancy in the NHP, independent of maternal metabolic health, causes long-term abnormalities in α cell plasticity that may contribute to chronic disease susceptibility.

Impact of an obesogenic diet program on bone densitometry, micro architecture and metabolism in male rat

BACKGROUND

The relationships between fat mass and bone tissue are complex and not fully elucidated. A high-fat/high-sucrose diet has been shown to induce harmful effects on bone micro architecture and bone biomechanics of rat. When such diet leads to obesity, it may induce an improvement of biomechanical bone parameters in rodent.Here, we examined the impact of a high-fat/high-sucrose diet on the body composition and its resulting effects on bone density and structure in male rats. Forty three Wistar rats aged 7 months were split into 3 groups: 1 sacrificed before diet (BD, n = 14); 1 subjected to 16 weeks of high-fat/high-sucrose diet (HF/HS, n = 14); 1 subjected to standard diet (Control, n = 15). Abdominal circumference and insulin sensitivity were measured and visceral fat mass was weighed. The bone mineral density (BMD) was analyzed at the whole body and tibia by densitometry. Microcomputed tomography and histomorphometric analysis were performed at L2 vertebrae and tibia to study the trabecular and cortical bone structures and the bone cell activities. Osteocalcin and CTX levels were performed to assess the relative balance of the bone formation and resorption. Differences between groups have been tested with an ANOVA with subsequent Scheffe post-hoc test. An ANCOVA with global mass and global fat as covariates was used to determine the potential implication of the resulting mechanical loading on bone.

RESULTS

The HF/HS group had higher body mass, fat masses and abdominal circumference and developed an impaired glucose tolerance (p < 0.001). Whole body bone mass (p < 0.001) and BMD (p < 0.05) were higher in HF/HS group vs. Control group. The trabecular thickness at vertebrae and the cortical porosity of tibia were improved (p < 0.05) in HF/HS group. Bone formation was predominant in HF/HS group while an unbalance bone favoring bone resorption was observed in the controls. The HF/HS and Control groups had higher total and abdominal fat masses and altered bone parameters vs. BD group.

CONCLUSIONS

The HF/HS diet had induced obesity and impaired glucose tolerance. These changes resulted in an improvement of quantitative, qualitative and metabolic bone parameters. The fat mass increase partly explained these observations.