The interplay between nutrients and the adipose tissue

Nutrition and exercise: Cornerstones of health with emphasis on obesity and type 2 diabetes management-A narrative review

While a broad consensus exists that integrated nutrition and regular exercise are foundational for health maintenance and serve as a robust non-pharmacological strategy against cardiometabolic diseases, the nuanced interplay between these elements remains incompletely understood. Through multifaceted interactions, these factors profoundly influence primary metabolic organs, notably the skeletal muscle and adipose tissue. Despite the critical nature of this interactivity, a holistic understanding of the combined effects of physical activity and dietary practices is still emerging. This narrative review aims to elucidate the intertwined roles of nutrition and exercise. It provides a comprehensive overview of their synergistic dynamics and emphasizes the importance of a dual-focus approach in mitigating and managing cardiometabolic disorders, predominantly obesity and type 2 diabetes.

White-to-Beige and Back: Adipocyte Conversion and Transcriptional Reprogramming

Obesity has become a pandemic, as currently more than half a billion people worldwide are obese. The etiology of obesity is multifactorial, and combines a contribution of hereditary and behavioral factors, such as nutritional inadequacy, along with the influences of environment and reduced physical activity. Two types of adipose tissue widely known are white and brown. While white adipose tissue functions predominantly as a key energy storage, brown adipose tissue has a greater mass of mitochondria and expresses the uncoupling protein 1 (UCP1) gene, which allows thermogenesis and rapid catabolism. Even though white and brown adipocytes are of different origin, activation of the brown adipocyte differentiation program in white adipose tissue cells forces them to transdifferentiate into "beige" adipocytes, characterized by thermogenesis and intensive lipolysis. Nowadays, researchers in the field of small molecule medicinal chemistry and gene therapy are making efforts to develop new drugs that effectively overcome insulin resistance and counteract obesity. Here, we discuss various aspects of white-to-beige conversion, adipose tissue catabolic re-activation, and non-shivering thermogenesis.

Relationship between overweight and obesity and insufficient micronutrient intake: a nationwide study in Taiwan

The aim of the present study is to examine whether overweight or obese people in Taiwan have an inadequate intake of selected micronutrients. A population-based study was conducted using data from the Nutrition and Health Survey in Taiwan (NAHSIT) 2013-2016. We evaluated fourteen nutrient intakes using the 24 h dietary recall method. The dietary reference intake (DRI) adherence was estimated by the prevalence of participants whose intake was lower than the recommended dietary allowance (RDA) or adequate intakes (AIs) for selected micronutrients. Body mass index (BMI) ≥ 27 kg/m² and waist circumference (WC), with men having WC ≥ 90 cm or women having WC ≥ 80 cm, were defined as obesity. A total of 3075 participants aged 19 years and above were included. After adjusting for confounders, we found that obese women have a lower DRI adherence of vitamin C (odds ratio (OR) 0⋅73, 95 % confidence interval (CI) 0⋅56, 0⋅95) and magnesium (OR 0⋅72, 95 % CI 0⋅54, 0⋅95), compared with normal-weight women. Obese men have a higher DRI adherence of vitamin B3 (OR 1⋅70, 95 % CI 1⋅29, 2⋅23), iron (OR 1⋅46, 95 % CI 1⋅06, 2⋅00) and zinc (OR 1⋅41, 95 % CI 1⋅07, 1⋅85), compared with normal-weight men. Similar findings were found using WC to define obesity. We conclude that obese women may have insufficient intakes of vitamin A, vitamin C and magnesium.

Comparative proteomics reveals that lipid droplet-anchored mitochondria are more sensitive to cold in brown adipocytes

Brown adipose tissue (BAT) is specialized for uncoupled heat production through mitochondrion fueled majorly from fatty acids (FAs) of lipid droplets (LDs). How the interaction between the two organelles contributes the generation of heat remains elusive. Here, we report that LD-anchored mitochondria (LDAM) were observed in the BAT of mice raised at three different temperatures, 30 °C, 23 °C, and 6 °C. The biochemical analyses including Western blotting of electron transport chain subunits showed that LDAM were functional. Comparative proteomics analysis was conducted, which revealed differential expressions of proteins between LDAM and cytoplasmic mitochondria (CM) at different temperatures. Higher expressions of proteins at low temperature were observed for i) FA β-oxidation in LDAM including FA synthesis and uncoupling, ii) pseudo-futile cycle in CM, and iii) two shuttle systems: glycerol 3-phosphate in both CM and LDAM and citrate malate in CM. Together, these results suggest that LDs and LDAM form a preorganized and functional organelle complex that permits the rapid response to cold.

Genetic background and diet affect brown adipose gene coexpression networks associated with metabolic phenotypes

Adipose is a dynamic endocrine organ that is critical for regulating metabolism and is highly responsive to nutritional environment. Brown adipose tissue is an exciting potential therapeutic target; however, there are no systematic studies of gene-by-environment interactions affecting function of this organ. We leveraged a weighted gene coexpression network analysis to identify transcriptional networks in brown adipose tissue from LG/J and SM/J inbred mice fed high- or low-fat diets and correlate these networks with metabolic phenotypes. We identified eight primary gene network modules associated with variation in obesity and diabetes-related traits. Four modules were enriched for metabolically relevant processes such as immune and cytokine response, cell division, peroxisome functions, and organic molecule metabolic processes. The relative expression of genes in these modules is highly dependent on both genetic background and dietary environment. Genes in the immune/cytokine response and cell division modules are particularly highly expressed in high fat-fed SM/J mice, which show unique brown adipose-dependent remission of diabetes. The interconnectivity of genes in these modules is also heavily dependent on diet and strain, with most genes showing both higher expression and coexpression under the same context. We highlight several genes of interest, Col28a1, Cyp26b1, Bmp8b, and Ngef, that have distinct expression patterns among strain-by-diet contexts and fall under metabolic quantitative trait loci previously mapped in an F16 generation of an advanced intercross between LG/J and SM/J. Each of these genes have some connection to obesity and diabetes-related traits, but have not been studied in brown adipose tissue. Our results provide important insights into the relationship between brown adipose and systemic metabolism by being the first gene-by-environment study of brown adipose transcriptional networks.

Metabolic Cytokines at Fasting and During Macronutrient Challenges: Influence of Obesity, Female Androgen Excess and Sex

Scope: Cytokines have pleiotropic functions within the organism and their levels may be influenced by obesity, visceral adiposity and sex hormones. Diet composition may also affect their systemic concentrations during fasting and in the postprandial period. Hence, we studied the influence of sex steroids and obesity on the circulating levels of a panel of metabolic cytokines in the fasting state and after single macronutrient challenges. Methods: On alternate days we submitted 17 women with polycystic ovary syndrome (PCOS) (9 non-obese, 8 obese), 17 non-hyperandrogenic control women (9 non-obese, 8 obese) and 19 control men (10 non-obese, 9 obese) to isocaloric oral glucose, lipid and protein loads. Serum levels of omentin-1, vaspin, lipocalin-2, adipsin, PAI-1, chemerin, FGF-21 and FGF-23 were determined by Luminex multiplex technology. Results: During fasting, obese patients presented higher levels of PAI-1, chemerin and adipsin but decreased FGF-23 and omentin-1 compared with non-obese subjects. Vaspin showed sexual dimorphism with lower levels in men than women with PCOS and female controls. Following macronutrient ingestion, most metabolic cytokines presented a similar physiological response consisting of a decrease in circulating concentrations, which was inversely associated with the fasting levels of these molecules. Protein intake caused the major postprandial decrease whereas glucose did not significantly reduce PAI-1, FGF-23 and vaspin, and even increased FGF-21. Regardless of the macronutrient administered, vaspin levels showed a larger reduction in non-obese individuals while the decrease in PAI-1 was particularly noticeable in the obese subgroup. The postprandial reductions of omentin-1 and FGF-23 after glucose and protein loads were influenced by obesity. No major differences were found between patients with PCOS and male and female controls. Conclusions: Obesity, but not PCOS or sex, markedly influences metabolic cytokine levels at fasting and after macronutrient ingestion. The observed postprandial decrease in their circulating concentrations might represent a physiological compensatory mechanism against food-induced inflammation and oxidative stress. This mechanism is altered by obesity and is differently modulated by macronutrients, suggesting a larger contribution of glucose to stressful postprandial responses.

Vitamin A and its metabolic pathway play a determinant role in high-fructose-induced triglyceride accumulation of the visceral adipose depot of male Wistar rats

Here, we tested a hypothesis that vitamin A and/or its metabolic pathways are involved in the high-fructose-mediated alteration in adipose tissue biology. For this purpose, weanling male Wistar rats were provided with one of the following diets: control (C), control with vitamin A deficiency (C-VAD), high fructose (HFr), and HFr with VAD (HFr-VAD) for 16 weeks, except that half of the C-VAD diet-fed rats were shifted to HFr diet (C-VAD(s)HFr), after 8-week period. Compared with control, feeding of HFr diet significantly increased the triglyceride content (P ≤ .01) and thus adipocyte size (hypertrophy) (P ≤ .001) in visceral adipose depot; retroperitoneal white adipose tissue (RPWAT) and these changes were corroborated with de novo lipogenesis, as evidenced by the increased glycerol-3-phosphate dehydrogenase activity (P ≤ .01) and up-regulation of lipogenic pathway transcripts, fructose transporter, and aldehyde dehydrogenase 1 A1. On the contrary, the absence of vitamin A in the HFr diet (HFr-VAD) failed to exert these changes; however, it induced adipocyte hyperplasia. Further, vitamin A deficiency-mediated changes were reversed by replenishment, as evident from the group that was shifted from C-VAD to HFr diet. In conclusion, vitamin A and its metabolic pathway play a key determinant role in the high-fructose-induced triglyceride accumulation and adipocyte hypertrophy of visceral white adipose depot. SIGNIFICANCE OF THE STUDY: Here, we report the metabolic impact of high-fructose feeding under vitamin A-sufficient and vitamin A-deficient conditions. Feeding of high-fructose diet induced triglyceride accumulation and adipocyte hypertrophy of the visceral white adipose depots. These changes corroborated with augmented expression of vitamin A and lipid metabolic pathway genes. Contrarily, absence of vitamin A in the high-fructose diet did not elicit such responses, while vitamin A replenishment reversed the changes exerted by vitamin A deficiency. To our knowledge, this is the first study to report the role of vitamin A and its metabolic pathway in the high-fructose-induced triglyceride synthesis and its accumulation in visceral adipose depot and thus provide a new insight and scope to understand these nutrients interaction in clinical conditions.

Combining traditional dietary assessment methods with novel metabolomics techniques: present efforts by the Food Biomarker Alliance

FFQ, food diaries and 24 h recall methods represent the most commonly used dietary assessment tools in human studies on nutrition and health, but food intake biomarkers are assumed to provide a more objective reflection of intake. Unfortunately, very few of these biomarkers are sufficiently validated. This review provides an overview of food intake biomarker research and highlights present research efforts of the Joint Programming Initiative 'A Healthy Diet for a Healthy Life' (JPI-HDHL) Food Biomarkers Alliance (FoodBAll). In order to identify novel food intake biomarkers, the focus is on new food metabolomics techniques that allow the quantification of up to thousands of metabolites simultaneously, which may be applied in intervention and observational studies. As biomarkers are often influenced by various other factors than the food under investigation, FoodBAll developed a food intake biomarker quality and validity score aiming to assist the systematic evaluation of novel biomarkers. Moreover, to evaluate the applicability of nutritional biomarkers, studies are presently also focusing on associations between food intake biomarkers and diet-related disease risk. In order to be successful in these metabolomics studies, knowledge about available electronic metabolomics resources is necessary and further developments of these resources are essential. Ultimately, present efforts in this research area aim to advance quality control of traditional dietary assessment methods, advance compliance evaluation in nutritional intervention studies, and increase the significance of observational studies by investigating associations between nutrition and health.

Enhanced nutrition improves growth and increases blood adiponectin concentrations in very low birth weight infants

Background

Adequate nutrient supply is essential for optimal postnatal growth in very low birth weight (VLBW, birth weight<1,500 g) infants. Early growth may influence the risk of metabolic syndrome later in life.

Objective

To evaluate growth and blood metabolic markers (adiponectin, leptin, and insulin-like growth factor-1 (IGF-1)) in VLBW infants participating in a randomized nutritional intervention study.

Design

Fifty VLBW infants were randomized to an enhanced nutrient supply or a standard nutrient supply. Thirty-seven infants were evaluated with growth measurements until 2 years corrected age (CA). Metabolic markers were measured at birth and 5 months CA.

Results

Weight gain and head growth were different in the two groups from birth to 2 years CA (weight gain: p_interaction=0.006; head growth: p_interaction=0.002). The intervention group improved their growth z-scores after birth, whereas the control group had a pronounced decline, followed by an increase and caught up with the intervention group after discharge. At 5 months CA, adiponectin concentrations were higher in the intervention group and correlated with weight gain before term (r=0.35) and nutrient supply (0.35≤r≤0.45). Leptin concentrations correlated with weight gain after term and IGF-1 concentrations with length growth before and after term and head growth after term (0.36≤r≤0.53).

Conclusion

Enhanced nutrient supply improved early postnatal growth and may have prevented rapid catch-up growth later in infancy. Adiponectin concentration at 5 months CA was higher in the intervention group and correlated positively with early weight gain and nutrient supply. Early nutrition and growth may affect metabolic markers in infancy.

Clinical Trial Registration (ClinicalTrials.gov) no.: NCT01103219

New concepts in white adipose tissue physiology

Numerous studies address the physiology of adipose tissue (AT). The interest surrounding the physiology of AT is primarily the result of the epidemic outburst of obesity in various contemporary societies. Briefly, the two primary metabolic activities of white AT include lipogenesis and lipolysis. Throughout the last two decades, a new model of AT physiology has emerged. Although AT was considered to be primarily an abundant energy source, it is currently considered to be a prolific producer of biologically active substances, and, consequently, is now recognized as an endocrine organ. In addition to leptin, other biologically active substances secreted by AT, generally classified as cytokines, include adiponectin, interleukin-6, tumor necrosis factor-alpha, resistin, vaspin, visfatin, and many others now collectively referred to as adipokines. The secretion of such biologically active substances by AT indicates its importance as a metabolic regulator. Cell turnover of AT has also recently been investigated in terms of its biological role in adipogenesis. Consequently, the objective of this review is to provide a comprehensive critical review of the current literature concerning the metabolic (lipolysis, lipogenesis) and endocrine actions of AT.

Activation of Liver X receptors in the heart leads to accumulation of intracellular lipids and attenuation of ischemia-reperfusion injury

Liver X receptor (LXR)-α and -β play a major role in lipid and glucose homeostasis. Their expression and function in the heart is not well characterized. Our aim was to describe the expression of LXRs in the murine heart, and to determine effects of cardiac LXR activation on target gene expression, lipid homeostasis and ischemia. Both LXRα and -β were expressed in heart tissues, HL-1 cells and isolated cardiomyocytes as determined by qRT-PCR. Elevated cardiac expression of LXR target genes and LXRβ was observed 24 h after in vivo permanent coronary artery ligation. The synthetic LXR agonist GW3965 induced mRNA expression of the LXR target genes in HL-1 cells and isolated cardiomyocytes. This was associated with a buildup of intracellular triglycerides and expanding lipid droplets as quantified by confocal microscopy. Mice injected with GW3965 had cardiac LXR activation as judged by increased target gene expression and lipid droplet accumulation. GW3965 in vivo and in vitro increased expression of genes inducing triglyceride synthesis, and altered expression of lipid droplet-binding protein genes. GW3965 protected HL-1 cells against hypoxia-reoxygenation induced apoptosis. LXR activation by GW3965 in vivo prior to heart isolation and perfusion with induced global ischemia and reperfusion improved left ventricular contractile function and decreased infarct size. In conclusion, LXRs are expressed in the murine heart in the basal state, and are activated by myocardial infarction. Activation of LXR by the synthetic agonist GW3965 is associated with intracardiac accumulation of lipid droplets and protection against myocardial ischemia-reperfusion injury.

Effect of 2,4-thiazolidinedione on limousin cattle growth and on muscle and adipose tissue metabolism

The main adipogenic transcription factor PPARγ possesses high affinity to 2,4-TZD, a member of the Thiazolidinedione family of insulin-sensitizing compounds used as adipogenic agents. We evaluated 2,4-TZD's effect on bovine growth and PPAR tissue expression. Seventeen Limousin bulls (18 month-old; 350 kg body weight (BW)) were assigned into 2 treatments: control and 2,4-TZD (8 mg/70 kg BW) and were fed until bulls reached 500 kg BW. They were weighed and their blood was sampled. DNA, RNA, and protein were determined in liver; skeletal muscle; subcutaneous (SC), omental, perirenal adipose tissues (AT) to determine protein synthesis rate and cellular size. Expression of PPAR mRNA was measured in liver and muscle (PPARα, -δ, and -γ) and SC adipose tissue (γ) by real-time PCR. No significant differences were found (P > 0.1) in weight gain, days on feed, and carcass quality. Muscle synthesis was greater in controls (P < 0.05); cell size was larger with 2,4-TZD (P < 0.05). PPARα, -δ, and -γ expressions with 2,4-TZD in liver were lower (P < 0.01) than in muscle. No differences were found for PPARγ mRNA expression in SCAT. The results suggest the potential use of 2,4-TZD in beef cattle diets, because it improves AT differentiation, liver, and muscle fatty acid oxidation that, therefore, might improve energy efficiency.

Calcium and vitamin D in obesity

New and more effective nutritional measures are urgently needed for the prevention of obesity. The role of Ca and vitamin D in obesity has been recently implicated. Low Ca intake and low vitamin D status have been linked with an increased risk of obesity in epidemiological studies; however, clinical intervention trials designed to test this association have produced controversial results. The suggested anti-obesity mechanisms of Ca and vitamin D include the regulation of adipocyte death (apoptosis), adipogenesis and lipid metabolism. Dietary Ca has been also shown to increase faecal fat excretion. The potential role of Ca and vitamin D in shifting energy balance towards a more negative state is an area of considerable interest. Ultimately, a review of recent research findings does not allow the reaching of a definitive conclusion that increasing Ca intake and rising vitamin D status will influence fat mass and body weight or decrease the risk of obesity and overweight.

Altered adipose tissue metabolism in offspring of dietary obese rat dams

To investigate further the mechanisms of developmental programming, we analysed the effects of maternal overnutrition and of postnatal high-fat feeding on adipose tissue metabolism in the offspring. Postnatal changes in serum adiponectin, leptin and TAG [triacylglycerol (triglyceride)] levels, adipose tissue TAGs, fatty acids and enzyme activities were determined in offspring of cafeteria-diet-fed dams during gestation and lactation, weaned on to standard chow or on to cafeteria diet. Obese rats showed higher adiposity (+35% to 85%) as well as a significant increase in serum glucose, insulin, leptin, adiponectin and TAG levels (P<0.01) and adipose tissue LPL (lipoprotein lipase) and GPDH (glycerol-3-phosphate dehydrogenase) activities (P<0.01), compared with control pups at weaning (day 21) and at adulthood (day 90). Adipose HSL (hormone-sensitive lipase) activity was increased only at day 90 (P<0.05), and FAS (fatty acid synthase) activity remained unchanged. The proportions of SFAs (saturated fatty acids) and MUFAs (mono-unsaturated fatty acids) and the Δ9-desaturation index were significantly increased (P<0.05), whereas PUFAs (polyunsaturated fatty acids) were decreased (P<0.01) in serum and adipose TAGs of obese pups compared with controls. The cafeteria diet at weaning induced more severe abnormalities in obese rats. In conclusion, maternal overnutrition induced permanent changes in adipose tissue metabolism of the offspring. These pre-existing alterations in offspring were worsened under a high-fat diet from weaning to adulthood. Consequently, adipose adipokines and enzymes could provide a potential therapeutic target, and new investigations in this field could constitute strategies to improve the impact of early-life overnutrition.

Disruption of inducible 6-phosphofructo-2-kinase ameliorates diet-induced adiposity but exacerbates systemic insulin resistance and adipose tissue inflammatory response

Adiposity is commonly associated with adipose tissue dysfunction and many overnutrition-related metabolic diseases including type 2 diabetes. Much attention has been paid to reducing adiposity as a way to improve adipose tissue function and systemic insulin sensitivity. PFKFB3/iPFK2 is a master regulator of adipocyte nutrient metabolism. Using PFKFB3(+/-) mice, the present study investigated the role of PFKFB3/iPFK2 in regulating diet-induced adiposity and systemic insulin resistance. On a high-fat diet (HFD), PFKFB3(+/-) mice gained much less body weight than did wild-type littermates. This was attributed to a smaller increase in adiposity in PFKFB3(+/-) mice than in wild-type controls. However, HFD-induced systemic insulin resistance was more severe in PFKFB3(+/-) mice than in wild-type littermates. Compared with wild-type littermates, PFKFB3(+/-) mice exhibited increased severity of HFD-induced adipose tissue dysfunction, as evidenced by increased adipose tissue lipolysis, inappropriate adipokine expression, and decreased insulin signaling, as well as increased levels of proinflammatory cytokines in both isolated adipose tissue macrophages and adipocytes. In an in vitro system, knockdown of PFKFB3/iPFK2 in 3T3-L1 adipocytes caused a decrease in the rate of glucose incorporation into lipid but an increase in the production of reactive oxygen species. Furthermore, knockdown of PFKFB3/iPFK2 in 3T3-L1 adipocytes inappropriately altered the expression of adipokines, decreased insulin signaling, increased the phosphorylation states of JNK and NFkappaB p65, and enhanced the production of proinflammatory cytokines. Together, these data suggest that PFKFB3/iPFK2, although contributing to adiposity, protects against diet-induced insulin resistance and adipose tissue inflammatory response.

Impact of micronutrient deficiencies on obesity

Micronutrient deficiencies have been found in obese individuals across age groups worldwide. While the effects of micronutrient deficiencies on human functions have been studied widely in different populations, there is limited information on how these micronutrient deficiencies affect obese populations. An examination of the available literature suggests associations exist between micronutrient deficiencies and obesity in different populations. These associations and possible mechanisms of the deficiencies' metabolic effects, such as their influence on leptin and insulin metabolism, are discussed here. Further studies are needed to clarify the roles of the different micronutrient deficiencies with respect to obesity and its comorbid conditions.

Diet-induced obesity increases NF-kappaB signaling in reporter mice

The nuclear factor (NF)-kappaB is a primary regulator of inflammatory responses and may be linked to pathology associated with obesity. We investigated the progression of NF-kappaB activity during a 12-week feeding period on a high-fat diet (HFD) or a low-fat diet (LFD) using NF-kappaB luciferase reporter mice. In vivo imaging of luciferase activity showed that NF-kappaB activity was higher in the HFD mice compared with LFD-fed mice. Thorax region of HFD females displayed fourfold higher activity compared with LFD females, while no such increase was evident in males. In male HFD mice, abdominal NF-kappaB activity was increased twofold compared with the LFD males, while females had unchanged NF-kappaB activity in the abdomen by HFD. HFD males, but not females, exhibited evident glucose intolerance during the study. In conclusion, HFD increased NF-kappaB activity in both female and male mice. However, HFD differentially increased activity in males and females. The moderate increase in abdomen of male mice may be linked to glucose intolerance.

mTOR complex 2 in adipose tissue negatively controls whole-body growth

Mammalian target of rapamycin (mTOR), a highly conserved protein kinase that controls cell growth and metabolism in response to nutrients and growth factors, is found in 2 structurally and functionally distinct multiprotein complexes termed mTOR complex 1 (mTORC1) and mTORC2. mTORC2, which consists of rictor, mSIN1, mLST8, and mTOR, is activated by insulin/IGF1 and phosphorylates Ser-473 in the hydrophobic motif of Akt/PKB. Though the role of mTOR in single cells is relatively well characterized, the role of mTOR signaling in specific tissues and how this may contribute to overall body growth is poorly understood. To examine the role of mTORC2 in an individual tissue, we generated adipose-specific rictor knockout mice (rictor(ad-/-)). Rictor(ad-/-) mice are increased in body size due to an increase in size of nonadipose organs, including heart, kidney, spleen, and bone. Furthermore, rictor(ad-/-) mice have a disproportionately enlarged pancreas and are hyperinsulinemic, but glucose tolerant, and display elevated levels of insulin-like growth factor 1 (IGF1) and IGF1 binding protein 3 (IGFBP3). These effects are observed in mice on either a high-fat or a normal diet, but are generally more pronounced in mice on a high-fat diet. Our findings suggest that adipose tissue, in particular mTORC2 in adipose tissue, plays an unexpectedly central role in controlling whole-body growth.