Eating behavior and food purchases during the COVID-19 lockdown: A cross-sectional study among adults in the Netherlands.

Skeletal muscle and bone are connected anatomically and physiologically, and play a crucial role in human locomotion and metabolism. Historically, the coupling between muscle and bone has been viewed in light of mechanotransduction, which dictates that the mechanical forces applied to muscle are transmitted to the skeleton to initiate bone formation. However, these organs also communicate through the endocrine system, orchestrated by a family of cytokines namely myokines (derived from myocytes) and osteokines (derived from bone cells). A third player in this biochemical crosstalk is adipose tissue and the secretion of adipokines (derived from adipocytes). In this review, we discuss the bidirectional effects of myokines and osteokines on muscle and bone metabolism, and the impact of adipokines on both of these secretory organs. Several myokines, notably, IL6, irisin, IGF-1, BDNF, myostatin, and FGF2 exert anabolic/catabolic effects on bone, while the osteokines osteocalcin and sclerostin have shown to induce muscle anabolism and catabolism, respectively. Adipokines, such as leptin, resistin, adiponectin, and TNFα (released from adipose tissue), can also modulate muscle and bone metabolism. Contrarily, exercise-mediated release of lipolytic myokines (IL6, irisin, and LIF) stimulates thermogenesis by promoting the browning of adipocytes. Myokines, osteokines, and adipokines exert autocrine/paracrine effects locally as well as through the endocrine system, to regulate muscle, bone, and fat metabolism. Reductions in physical activity and increases in energy intake, both linked with aging, leads to adipocyte hypertrophy and the recruitment of immunological cells (macrophages). In turn, this releases pro-inflammatory adipokines which induces chronic low-grade inflammation (LGI), a key player in the pathology of several diseases. However, exercise-induced stimulation of bioactive cytokines, through muscle-bone-fat crosstalk, increases muscle anabolism, bone formation, mitochondrial biogenesis, glucose utilization, and fatty acid oxidation, and attenuates chronic LGI.

Muscle, Bone, and Fat Crosstalk: the Biological Role of Myokines, Osteokines, and Adipokines

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

As the global COVID‐19 pandemic unfolds, over 90% of U.S. adult residents are confined to their homes, with restaurants, shops, schools, and workplaces shut down to prevent disease spread. While it is a priority to mitigate the immediate impact, one area of great concern is the long‐term effects of this pandemic on weight management in adults. As evident from previous research, small changes in body weight in relatively short time periods can become permanent and lead to substantial weight gain over time(1). Considering that the current situation could last a total of several months, this extended home confinement could exacerbate the problem of obesity in adults by substantially contributing to or exceeding annual weight gain.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/oby.22904

COVID-19-Related Home Confinement in Adults: Weight Gain Risks and Opportunities.

Osteoblasts are specialized mesenchymal cells that synthesize bone matrix and coordinate the mineralization of the skeleton. These cells work in harmony with osteoclasts, which resorb bone, in a continuous cycle that occurs throughout life. The unique function of osteoblasts requires substantial amounts of energy production, particularly during states of new bone formation and remodelling. Over the last 15 years, studies have shown that osteoblasts secrete endocrine factors that integrate the metabolic requirements of bone formation with global energy balance through the regulation of insulin production, feeding behaviour and adipose tissue metabolism. In this article, we summarize the current understanding of three osteoblast-derived metabolic hormones (osteocalcin, lipocalin and sclerostin) and the clinical evidence that suggests the relevance of these pathways in humans, while also discussing the necessity of specific energy substrates (glucose, fatty acids and amino acids) to fuel bone formation and promote osteoblast differentiation. Osteoblasts synthesize bone matrix and work in harmony with bone-resorbing osteoclasts in a continuous bone remodelling cycle. This Review discusses three known osteoblast-secreted endocrine factors (osteocalcin, lipocalin and sclerostin) and highlights how these hormones integrate the metabolic requirements of bone formation with respect to whole-body metabolism.

/pdf/the-role-of-osteoblasts-in-energy-homeostasis-5ucb2yuke9.pdf

The role of osteoblasts in energy homeostasis

Effects of exercise during the holiday season on changes in body weight, body composition and blood pressure

Objective

Determine subjective and physiological appetite responses and ad libitum intake to high-fat (HF) meals rich in either monounsaturated (MUFAs), polyunsaturated (PUFAs), or saturated fatty acids (SFAs) in women with obesity.



Methods

In this single-blind crossover study, three HF meals (70% of energy) rich in MUFAs, PUFAs, or SFAs in 16 women with obesity were tested. At each visit, anthropometrics and a fasting blood sample were collected. Participants then consumed one of the HF meals, and postprandial blood draws and visual analog scale (VAS) measures were collected over 5 h. An ad libitum buffet lunch was provided 5 h after the HF meal.



Results

Decrease in ghrelin was significantly greater for PUFA (P < 0.05) and MUFA (P < 0.01) vs. SFA while the increase in peptide YY was significantly greater for PUFA vs. both SFA and MUFA (P < 0.05). Change in glucagon-like peptide-1, VAS measurements, or total energy consumed at the buffet showed no differences between HF meals (ns).



Conclusions

Fatty acid composition differentially affected physiological markers of hunger and satiety. However, it was unable to show changes in subjective appetite ratings or changes in energy intake when alterations were made to fatty acid composition from an acute HF meal.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/oby.21202

Hunger and satiety responses to high-fat meals of varying fatty acid composition in women with obesity

Objective

The role of lipocalin-2 (Lcn2) was determined in regulating metabolism in cell, animal, and human models.



Design and Methods

Adipocytes were treated with recombinant lipocalin-2 (rLcn2) to determine the effect on lipid metabolism. rLcn2 was injected into mice to determine the effect on metabolism in vivo. To assess the relationship between Lcn2 and fat oxidation (FatOx) in humans, normal weight (NW) and obese (OB) women were given three separate high fat (HF) meals followed by indirect calorimetry. The relationship between postprandial Lcn2 with macronutrient metabolism and total energy expenditure (TEE) using Pearson correlations was determined.



Results

Lcn2 increased expression of genes involved in β-oxidation including peroxisome proliferator-activated receptor-δ in adipocytes, as well as 3H labeled oleate β-oxidation. Lcn2 injected into chow-fed mice directly increased TEE by 18% after the first dark cycle (232 ± 1.4 cal vs. 341 ± 1.4 cal; PBS vs. Lcn2) and remained significantly elevated by 10% after the second dark cycle (296 ± 1.4 cal vs. 326 ± 1.4 cal; PBS vs. Lcn2). Lcn2 was correlated with TEE in all three HF meal challenges in NW but not OB females.



Conclusions

Lipocalin-2 is a novel adipokine that promotes FatOx and TEE and its function may be impaired in obesity.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/oby.20507

Jada L. Stevenson

Papers

Effects of exercise during the holiday season on changes in body weight, body composition and blood pressure

Hunger and satiety responses to high-fat meals of varying fatty acid composition in women with obesity

Lipocalin-2 increases fat oxidation in vitro and is correlated with energy expenditure in normal weight but not obese women.

Parents' Underestimations of Child Weight: Implications for Obesity Prevention.

Metabolic responses to dietary fatty acids in obese women