Fat Partitioning Research Articles

6420 Organokines and Liver Enzymes in Adolescent Girls with Polycystic Ovary Syndrome During Randomized Treatments

Abstract Disclosure: C. Garcia-Beltran: None. M. Peyrou: None. F.E. de Zegher: None. A. López-Bermejo: None. F. Villarroya: None. L. Ibanez: None. Introduction: Polycystic ovary syndrome (PCOS) is often related to metabolic associated fatty liver disease (MAFLD). MAFLD has been associated with altered hepatic function and systemic dysmetabolism and with abnormal circulating levels of signaling molecules, so-called organokines. Here, we assessed the effects of two randomized treatments on a set of organokines in adolescent girls with PCOS and without obesity, and report the associations with circulating biomarkers of liver damage which were assessed longitudinally in the aforementioned studies as safety markers. Materials and Methods: Liver enzymes [aspartate aminotransferase (AST), alanine amino transferase (ALT) and gamma-glutamyl transferase (GGT)] were assessed as safety markers in previous randomized pilot studies comparing the effects of an oral contraceptive (OC) to those of a low-dose combination of spironolactone-pioglitazone-metformin (spiomet) for 1 yr. As a post-hoc endpoint, the organokines fibroblast growth factor-21 (FGF21), diazepam-binding protein-1 (DBI) and meteorin-like protein (METRNL), were assessed by ELISA after 6 months on OC (N=26) or spiomet (N= 28). Auxological, endocrine-metabolic, body composition (by DXA) and abdominal fat partitioning (by MRI) were also evaluated. Healthy age-matched adolescent girls (N=17) served as controls. Results: Circulating ALT and GGT levels raised during OC treatment and returned to baseline concentrations in the post-treatment phase; in contrast, spiomet treatment elicited no detectable changes in ALT and GGT concentrations. In relation to organokines after 6 mo on treatment, (1) FGF21 levels were significantly higher in PCOS adolescents than in control girls; (2) DBI levels were lower in OC-treated girls as compared to controls and spiomet-treated girls; (3) no differences were observed in METRNL concentrations between PCOS girls and controls. Serum ALT and GGT levels directly correlated with circulating METRNL levels only in OC-treated girls (R=0.449; P=0.036 and R=0.552; P=0.004, respectively). Conclusion: The on-treatment increase in ALT and GGT levels occurring only in OC-treated girls associates with circulating METRNL levels suggesting an enhanced METRNL synthesis as a reaction to the hepatic changes elicited by OC treatment. Trial registration numbers: ISRCTN29234515 (https://doi.org/10.1186/ISRCTN29234515) and ISRCTN11062950 (https://doi.org/10.1186/ISRCTN11062950) Presentation: 6/2/2024

6420 Organokines and Liver Enzymes in Adolescent Girls with Polycystic Ovary Syndrome During Randomized Treatments

Abstract Disclosure: C. Garcia-Beltran: None. M. Peyrou: None. F.E. de Zegher: None. A. López-Bermejo: None. F. Villarroya: None. L. Ibanez: None. Introduction: Polycystic ovary syndrome (PCOS) is often related to metabolic associated fatty liver disease (MAFLD). MAFLD has been associated with altered hepatic function and systemic dysmetabolism and with abnormal circulating levels of signaling molecules, so-called organokines. Here, we assessed the effects of two randomized treatments on a set of organokines in adolescent girls with PCOS and without obesity, and report the associations with circulating biomarkers of liver damage which were assessed longitudinally in the aforementioned studies as safety markers. Materials and Methods: Liver enzymes [aspartate aminotransferase (AST), alanine amino transferase (ALT) and gamma-glutamyl transferase (GGT)] were assessed as safety markers in previous randomized pilot studies comparing the effects of an oral contraceptive (OC) to those of a low-dose combination of spironolactone-pioglitazone-metformin (spiomet) for 1 yr. As a post-hoc endpoint, the organokines fibroblast growth factor-21 (FGF21), diazepam-binding protein-1 (DBI) and meteorin-like protein (METRNL), were assessed by ELISA after 6 months on OC (N=26) or spiomet (N= 28). Auxological, endocrine-metabolic, body composition (by DXA) and abdominal fat partitioning (by MRI) were also evaluated. Healthy age-matched adolescent girls (N=17) served as controls. Results: Circulating ALT and GGT levels raised during OC treatment and returned to baseline concentrations in the post-treatment phase; in contrast, spiomet treatment elicited no detectable changes in ALT and GGT concentrations. In relation to organokines after 6 mo on treatment, (1) FGF21 levels were significantly higher in PCOS adolescents than in control girls; (2) DBI levels were lower in OC-treated girls as compared to controls and spiomet-treated girls; (3) no differences were observed in METRNL concentrations between PCOS girls and controls. Serum ALT and GGT levels directly correlated with circulating METRNL levels only in OC-treated girls (R=0.449; P=0.036 and R=0.552; P=0.004, respectively). Conclusion: The on-treatment increase in ALT and GGT levels occurring only in OC-treated girls associates with circulating METRNL levels suggesting an enhanced METRNL synthesis as a reaction to the hepatic changes elicited by OC treatment. Trial registration numbers: ISRCTN29234515 (https://doi.org/10.1186/ISRCTN29234515) and ISRCTN11062950 (https://doi.org/10.1186/ISRCTN11062950) Presentation: 6/2/2024

Organokines and liver enzymes in adolescent girls with polycystic ovary syndrome during randomized treatments.

Polycystic ovary syndrome (PCOS) is often associated with metabolic-associated fatty liver disease (MAFLD). MAFLD has been associated with altered hepatic function, systemic dysmetabolism, and abnormal circulating levels of signaling molecules called organokines. Here, we assessed the effects of two randomized treatments on a set of organokines in adolescent girls with PCOS and without obesity, and report the associations with circulating biomarkers of liver damage, which were assessed longitudinally in the aforementioned studies as safety markers. Liver enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT)] were assessed as safety markers in previous randomized pilot studies comparing the effects of an oral contraceptive (OC) with those of a low-dose combination of spironolactone-pioglitazone-metformin (spiomet) for 1 year. As a post hoc endpoint, the organokines fibroblast growth factor-21 (FGF21), diazepam-binding protein-1 (DBI), and meteorin-like protein (METRNL) were assessed by ELISA after 6 months of OC (N = 26) or spiomet (N = 28). Auxological, endocrine-metabolic, body composition (using DXA), and abdominal fat partitioning (using MRI) were also evaluated. Healthy, age-matched adolescent girls (N = 17) served as controls. Circulating ALT and GGT levels increased during OC treatment and returned to baseline concentrations in the post-treatment phase; in contrast, spiomet treatment elicited no detectable changes in ALT and GGT concentrations. In relation to organokines after 6 months of treatment, (1) FGF21 levels were significantly higher in PCOS adolescents than in control girls; (2) DBI levels were lower in OC-treated girls than in controls and spiomet-treated girls; and (3) no differences were observed in METRNL concentrations between PCOS girls and controls. Serum ALT and GGT levels were directly correlated with circulating METRNL levels only in OC-treated girls (R = 0.449, P = 0.036 and R = 0.552, P = 0.004, respectively). The on-treatment increase in ALT and GGT levels occurring only in OC-treated girls is associated with circulating METRNL levels, suggesting enhanced METRNL synthesis as a reaction to the hepatic changes elicited by OC treatment. https://doi.org, identifiers 10.1186/ISRCTN29234515, 10.1186/ISRCTN11062950.

Isthmin-1 (ISM1), a novel adipokine that reflects abdominal adipose tissue distribution in individuals with obesity

BackgroundThe assessment of obesity-related health risks has traditionally relied on the Body Mass Index and waist circumference, but their limitations have propelled the need for a more comprehensive approach. The differentiation between visceral (VIS) and subcutaneous (SC) fat provides a finer-grained understanding of these risks, yet practical assessment methods are lacking. We hypothesized that combining the SC-VIS fat ratio with non-invasive biomarkers could create a valuable tool for obesity-related risk assessment.Methods and resultsA clinical study of 125 individuals with obesity revealed significant differences in abdominal fat distribution measured by CT-scan among genders and distinct models of obesity, including visceral, subcutaneous, and the SC/VIS ratio. Stratification based on these models highlighted various metabolic changes. The SC/VIS ratio emerged as an excellent metric to differentiate metabolic status. Gene expression analysis identified candidate biomarkers, with ISM1 showing promise. Subsequent validation demonstrated a correlation between ISM1 levels in SC and plasma, reinforcing its potential as a non-invasive biomarker for fat distribution. Serum adipokine levels also correlated with the SC/VIS ratio. The Receiver Operating Characteristic analysis revealed ISM1’s efficacy in discriminating individuals with favorable metabolic profiles based on adipose tissue distribution. Correlation analysis also suggested that ISM1 was involved in glucose regulation pathways.ConclusionThe study’s results support the hypothesis that the SC-VIS fat ratio and its derived non-invasive biomarkers can comprehensively assess obesity-related health risks. ISM1 could predict abdominal fat partitioning and be a potential biomarker for evaluating obesity-related health risks.

Circulating exosomes decrease in size and increase in number between birth and age 7: relations to fetal growth and liver fat.

Exosomes play a key role in cell-to-cell communication by transferring their cargo to target tissues. Little is known on the course of exosome size and number in infants and children. Longitudinally, we assessed the size and number of circulating exosomes at birth and at ages 2 and 7 yr in 75 infants/children born appropriate-for-gestational-age (AGA; n=40) or small-for-gestational-age (SGA; n=35 with spontaneous catch-up), and related those results to concomitantly assessed measures of endocrine-metabolic health (HOMA-IR; IGF-1), body composition (by DXA at ages 0 and 2) and abdominal fat partitioning (subcutaneous, visceral and hepatic fat by MRI at age 7). Circulating exosomes of AGAs decreased in size (on average by 4.2%) and increased in number (on average by 77%) between birth and age 7. Circulating exosomes of SGAs (as compared to those of AGAs) had a larger size at birth [146.8 vs 137.8 nm, respectively; p=0.02], and were in lower number at ages 2 [4.3x1011 vs 5.6x1011 particles/mL, respectively; p=0.01] and 7 [6.3x1011 vs 6.8x1011 particles/mL, respectively; p=0.006]. Longitudinal changes were thus more pronounced in SGAs for exosome size, and in AGAs for exosome number. At age 7, exosome size associated (P<0.0001) to liver fat in the whole study population. Early-life changes in circulating exosomes include a minor decrease in size and a major increase in number, and these changes may be influenced by fetal growth. Exosome size may become one of the first circulating markers of liver fat in childhood.

SPIOMET4HEALTH—efficacy, tolerability and safety of lifestyle intervention plus a fixed dose combination of spironolactone, pioglitazone and metformin (SPIOMET) for adolescent girls and young women with polycystic ovary syndrome: study protocol for a multicentre, randomised, double-blind, placebo-controlled, four-arm, parallel-group, phase II clinical trial

BackgroundPolycystic ovary syndrome (PCOS) is the most prevalent, chronic endocrine-metabolic disorder of adolescents and young women (AYAs), affecting 5–10% of AYAs worldwide. There is no approved pharmacological therapy for PCOS. Standard off-label treatment with oral contraceptives (OCs) reverts neither the underlying pathophysiology nor the associated co-morbidities. Pilot studies have generated new insights into the pathogenesis of PCOS, leading to the development of a new treatment consisting of a fixed, low-dose combination of two so-called insulin sensitisers [pioglitazone (PIO), metformin (MET)] and one mixed anti-androgen and anti-mineralocorticoid also acting as an activator of brown adipose tissue [spironolactone (SPI)], within a single tablet (SPIOMET). The present trial will evaluate the efficacy, tolerability and safety of SPIOMET, on top of lifestyle measures, for the treatment of PCOS in AYAs.MethodsIn this multicentre, randomised, double-blind, placebo-controlled, four-arm, parallel-group, phase II clinical trial, AYAs with PCOS will be recruited from 7 clinical centres across Europe. Intention is to randomise a total of 364 eligible patients into four arms (1:1:1:1): Placebo, PIO, SPI + PIO (SPIO) and SPI + PIO + MET (SPIOMET). Active treatment over 12 months will consist of lifestyle guidance plus the ingestion of one tablet daily (at dinner time); post-treatment follow-up will span 6 months. Primary endpoint is on- and post-treatment ovulation rate. Secondary endpoints are clinical features (hirsutism, menstrual regularity); endocrine-metabolic variables (androgens, lipids, insulin, inflammatory markers); epigenetic markers; imaging data (carotid intima-media thickness, body composition, abdominal fat partitioning, hepatic fat); safety profile; adherence, tolerability and acceptability of the medication; and quality of life in the study participants. Superiority (in this order) of SPIOMET, SPIO and PIO will be tested over placebo, and if present, subsequently the superiority of SPIOMET versus PIO, and if still present, finally versus SPIO.DiscussionThe present study will be the first to evaluate—in a randomised, double-blind, placebo-controlled way—the efficacy, tolerability and safety of SPIOMET treatment for early PCOS, on top of a lifestyle intervention.Trial registrationEudraCT 2021–003177-58. Registered on 22 December 2021.https://www.clinicaltrialsregister.eu/ctr-search/search?query=%092021-003177-58.

Partitioning of casein and fat in Cheddar cheese manufacturing as affected by cheese milk standardisation: A review

Cheesemaking offers the opportunity to exploit the unique nutritional, sensory, biological and other functionalities of both cheese and whey‐derived products. Milk standardisation is one of the essential cheesemaking operations designed to preserve the intrinsic cheese quality and may also improve whey composition because of its impact on partitioning of milk constituents between the two coproducts. The effectiveness of cheese milk standardisation in controlling constituent partitioning depends on the method and ingredients selected. This review explores how and why cheese milk standardisation affects the partitioning of casein and fat in Cheddar cheese and provides some perspective on a better approach.

Timing of introduction of complementary foods, breastfeeding, and child cardiometabolic risk: a prospective multiethnic Asian cohort study

BackgroundThe timing of introduction of complementary foods and the duration of breastfeeding (BF) have been independently associated with child overweight and obesity; however, their combined influence on body fat partitioning and cardiometabolic risk is unclear. ObjectiveWe investigated the associations of the timing of introduction of complementary foods, the duration of BF, and their interaction with child adiposity and cardiometabolic risk markers. MethodsWe analyzed data from 839 children in the prospective Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. Mothers reported the age at which infants were first fed complementary foods and BF duration, classified as early (≤4 mo) versus typical (>4 mo) complementary feeding (CF) and short (≤4 mo) versus long (>4 mo) duration of any BF, respectively. We measured adiposity and cardiometabolic risk markers at the age of 6 y and examined their associations with infant feeding patterns using multiple regression, adjusting for sociodemographics, parents’ body mass index (BMI), maternal factors, birth weight for gestational age, and infant weight gain. ResultsOf 839 children, 18% experienced early CF, whereas 54% experienced short BF. Short (vs. long) BF and early (vs. typical) CF were independently associated with higher z-scores of BMI [β (95% confidence interval), short BF, 0.18 standard deviation score (SDS) (−0.01, 0.38); early CF, 0.34 SDS (0.11, 0.57)] and sum of skinfolds [short BF, 1.83 mm (0.05, 3.61); early CF, 2.73 mm (0.55, 4.91)]. Children who experienced both early CF and short BF (vs. typical CF–long BF) had synergistically higher diastolic blood pressure [1.41 mmHg (−0.15, 2.97), P-interaction = 0.023] and metabolic syndrome score [0.81 (0.16, 1.47), P-interaction = 0.081]. Early CF–long BF (vs. early CF–short BF) was associated with a lower systolic blood pressure [−3.74 mmHg (−7.01, −0.48)], diastolic blood pressure [−2.29 mmHg (−4.47, −0.11)], and metabolic syndrome score [−0.90 (−1.80, 0.00)]. ConclusionsA combination of early CF and short BF was associated with elevated child adiposity and cardiometabolic markers. Longer BF duration may protect against cardiometabolic risk associated with early CF.This trial was registered at clinicaltrials.gov as NCT01174875.

Circulating GDF15 concentrations in girls with low birth weight: effects of prolonged metformin treatment.

Low birth weight (LBW) followed by a rapid postnatal catch-up in weight predisposes individuals to a central distribution of body fat, which is reverted by metformin. Growth-and-differentiation-factor-15 (GDF15) plays an important role in the regulation of energy homeostasis, reducing food intake and body weight. We assessed whether GDF15 concentrations are raised by long-term metformin treatment in LBW/catch-up girls with precocious pubarche (PP, pubic hair <8 years), and whether they relate to changes in endocrine-metabolic variables, body composition, and abdominal fat partitioning. Circulating GDF15 was determined in 30 LBW/catch-up girls with PP randomly assigned to receive metformin for 4 years (n = 15; 425 mg/d for 2 years, then 850 mg/d for 2 years) or to remain untreated (n = 15). Endocrine-metabolic variables, body composition (by absorptiometry), and abdominal fat partitioning (by MRI) were assessed at the start and yearly during follow-up. Circulating GDF15 concentrations increased significantly in LBW-PP girls only after 3 and 4 years on metformin. GDF15 levels associated negatively with insulin, HOMA-IR, androgens, body fat, and visceral fat. Prepubertal intervention with metformin reduces central adiposity and insulin resistance in girls with reduced prenatal growth. GDF15 could be among the mediators of such effects, especially over the long term. Low birth weight followed by a rapid postnatal catch-up in weight predisposes individuals to a central distribution of body fat, which is reverted by metformin. Growth-and-differentiation-factor-15 (GDF15) is a peptide hormone that reduces food intake and lowers body weight; metformin is an exogenous GDF15 secretagogue. Serum GDF15 concentrations increase after 3 and 4 years on metformin and associate negatively with insulin, androgens, body fat, and visceral fat. Prepubertal intervention with metformin reduces central adiposity and insulin resistance in girls with low birth weight. GDF15 could mediate these effects, especially over the long term.

The Regulation of Adipose Tissue Health by Estrogens.

Obesity and its’ associated metabolic diseases such as type 2 diabetes and cardiometabolic disorders are significant health problems confronting many countries. A major driver for developing obesity and metabolic dysfunction is the uncontrolled expansion of white adipose tissue (WAT). Specifically, the pathophysiological expansion of visceral WAT is often associated with metabolic dysfunction due to changes in adipokine secretion profiles, reduced vascularization, increased fibrosis, and enrichment of pro-inflammatory immune cells. A critical determinate of body fat distribution and WAT health is the sex steroid estrogen. The bioavailability of estrogen appears to favor metabolically healthy subcutaneous fat over visceral fat growth while protecting against changes in metabolic dysfunction. Our review will focus on the role of estrogen on body fat partitioning, WAT homeostasis, adipogenesis, adipocyte progenitor cell (APC) function, and thermogenesis to control WAT health and systemic metabolism.

A cross-sectional MR study of body fat volumes and distribution in chronic schizophrenia

People with schizophrenia show higher risk for abdominal obesity than the general population, which could contribute to excess mortality. However, it is unclear whether this is driven by alterations in abdominal fat partitioning. Here, we test the hypothesis that individuals with schizophrenia show a higher proportion of visceral to total body fat measured using magnetic resonance imaging (MRI). We recruited 38 participants with schizophrenia and 38 healthy controls matched on age, sex, ethnicity, and body mass index. We found no significant differences in body fat distribution between groups, suggesting that increased abdominal obesity in schizophrenia is not associated with altered fat distribution.

Breastfeeding may benefit cardiometabolic health of children exposed to increased gestational glycemia in utero.

There is altered breastmilk composition among mothers with gestational diabetes and conflicting evidence on whether breastfeeding is beneficial or detrimental to their offspring's cardiometabolic health. We aimed to investigate associations between breastfeeding and offspring's cardiometabolic health across the range of gestational glycemia. We included 827 naturally conceived, term singletons from a prospective mother-child cohort. We measured gestational (26-28weeks) fasting plasma glucose (FPG) and 2-h plasma glucose (2hPG) after an oral glucose tolerance test as continuous variables. Participants were classified into 2 breastfeeding categories (high/intermediate vs. low) according to their breastfeeding duration and exclusivity. Main outcome measures included magnetic resonance imaging (MRI)-measured abdominal fat, intramyocellular lipids (IMCL), and liver fat, quantitative magnetic resonance (QMR)-measured body fat mass, blood pressure, blood lipids, and insulin resistance at 6years old (all continuous variables). We evaluated if gestational glycemia (FPG and 2hPG) modified the association of breastfeeding with offspring outcomes after adjusting for confounders using a multiple linear regression model that included a 'gestational glycemia × breastfeeding' interaction term. With increasing gestational FPG, high/intermediate (vs. low) breastfeeding was associated with lower levels of IMCL (p-interaction = 0.047), liver fat (p-interaction = 0.033), and triglycerides (p-interaction = 0.007), after adjusting for confounders. Specifically, at 2 standard deviations above the mean gestational FPG level, high/intermediate (vs. low) breastfeeding was linked to lower adjusted mean IMCL [0.39% of water signal (0.29, 0.50) vs. 0.54% of water signal (0.46, 0.62)], liver fat [0.39% by weight (0.20, 0.58) vs. 0.72% by weight (0.59, 0.85)], and triglycerides [0.62mmol/L (0.51, 0.72) vs. 0.86mmol/L (0.75, 0.97)]. 2hPG did not significantly modify the association between breastfeeding and childhood cardiometabolic risk. Our findings suggest breastfeeding may confer protection against adverse fat partitioning and higher triglyceride concentration among children exposed to increased glycemia in utero.

Selective targeting of angiopoietin-like 3 (ANGPTL3) with vupanorsen for the treatment of patients with familial partial lipodystrophy (FPLD): results of a proof-of-concept study

BackgroundFamilial partial lipodystrophy (FPLD) is a rare disease characterized by selective loss of peripheral subcutaneous fat, associated with dyslipidemia and diabetes mellitus. Reductions in circulating levels of ANGPTL3 are associated with lower triglyceride and other atherogenic lipids, making it an attractive target for treatment of FPLD patients. This proof-of-concept study was conducted to assess the efficacy and safety of targeting ANGPTL3 with vupanorsen in patients with FPLD.MethodsThis was an open-label study. Four patients with FPLD (two with pathogenic variants in LMNA gene, and two with no causative genetic variant), diabetes (HbA1c ≥ 7.0 % and ≤ 12 %), hypertriglyceridemia (≥ 500 mg/dL), and hepatic steatosis (hepatic fat fraction, HFF ≥ 6.4 %) were included. Patients received vupanorsen subcutaneously at a dose of 20 mg weekly for 26 weeks. The primary endpoint was the percent change from baseline in fasting triglycerides at Week 27. Other endpoints analyzed at the same time point included changes in ANGPTL3, fasting lipids and lipoproteins, insulin secretion/sensitivity, postprandial lipids, and glycemic changes in response to a mixed meal test, HFF measured by MRI, and body composition measured by dual-energy absorptiometry (DEXA).ResultsBaseline mean ± SD fasting triglyceride level was 9.24 ± 4.9 mmol/L (817.8 ± 431.9 mg/dL). Treatment resulted in reduction in fasting levels of triglycerides by 59.9 %, ANGPTL3 by 54.7 %, and in several other lipoproteins/lipids, including very low-density lipoprotein cholesterol by 53.5 %, non-high-density lipoprotein cholesterol by 20.9 %, and free fatty acids (FFA) by 41.7 %. The area under the curve for postprandial triglycerides, FFA, and glucose was reduced by 60 %, 32 %, and 14 %, respectively. Treatment with vupanorsen also resulted in 55 % reduction in adipose tissue insulin resistance index, while other insulin sensitivity indices and HbA1c levels were not changed. Additional investigations into HFF and DEXA parameters suggested dynamic changes in fat partitioning during treatment. Adverse events observed were related to common serious complications associated with diabetes and FPLD. Vupanorsen was well tolerated, and there was no effect on platelet count.ConclusionsAlthough limited, these results suggest that targeting ANGPTL3 with vupanorsen could address several metabolic abnormalities in patients with FPLD.

Regulation of lipoprotein metabolism by ANGPTL3, ANGPTL4, and ANGPTL8.

Triglyceride-rich lipoproteins deliver fatty acids to tissues for oxidation and for storage. Release of fatty acids from circulating lipoprotein triglycerides is carried out by lipoprotein lipase (LPL), thus LPL serves as a critical gatekeeper of fatty acid uptake into tissues. LPL activity is regulated by a number of extracellular proteins including three members of the angiopoietin-like family of proteins. In this review, we discuss our current understanding of how, where, and when ANGPTL3, ANGPTL4, and ANGPTL8 regulate lipoprotein lipase activity, with a particular emphasis on how these proteins interact with each other to coordinate triglyceride metabolism and fat partitioning.

A Muscle-Centric Perspective on Intermittent Fasting: A Suboptimal Dietary Strategy for Supporting Muscle Protein Remodeling and Muscle Mass?

Muscle protein is constantly “turning over” through the breakdown of old/damaged proteins and the resynthesis of new functional proteins, the algebraic difference determining net muscle gain, maintenance, or loss. This turnover, which is sensitive to the nutritional environment, ultimately determines the mass, quality, and health of skeletal muscle over time. Intermittent fasting has become a topic of interest in the health community as an avenue to improve health and body composition primarily via caloric deficiency as well as enhanced lipolysis and fat oxidation secondary to attenuated daily insulin response. However, this approach belies the established anti-catabolic effect of insulin on skeletal muscle. More importantly, muscle protein synthesis, which is the primary regulated turnover variable in healthy humans, is stimulated by the consumption of dietary amino acids, a process that is saturated at a moderate protein intake. While limited research has explored the effect of intermittent fasting on muscle-related outcomes, we propose that infrequent meal feeding and periods of prolonged fasting characteristic of models of intermittent fasting may be counter-productive to optimizing muscle protein turnover and net muscle protein balance. The present commentary will discuss the regulation of muscle protein turnover across fasted and fed cycles and contrast it with studies exploring how dietary manipulation alters the partitioning of fat and lean body mass. It is our position that intermittent fasting likely represents a suboptimal dietary approach to remodel skeletal muscle, which could impact the ability to maintain or enhance muscle mass and quality, especially during periods of reduced energy availability.

Regulation of fat partitioning by ANGPTL4

Altered triglyceride metabolism and changes in fatty acid partitioning are major contributors to metabolic diseases including metabolic syndrome, diabetes, and atherosclerosis. The triglycerides in plasma lipoproteins are hydrolyzed by lipoprotein lipase (LPL), and the levels of LPL activity in the capillary beds of peripheral tissues such as heart, skeletal muscle, and adipose serve as the primary determinant dietary fat delivery to those tissues. LPL activity is regulated by a variety of extracellular proteins including angiopoietin-like 4 (ANGPTL4). ANGPTL4 regulates plasma triglyceride metabolism by inactivating LPL. ANGPTL4 is most highly expressed in adipose tissue and liver, but it is also expressed at lower levels in muscle, heart, kidney, and intestine. It also circulates in plasma. Using whole-body and tissue-specific ANGPTL4 knockout mice we sought to determine where and when ANGPTL4 acts on LPL, and how the action of ANGPTL4 alters lipid partitioning. We found that ANGPTL4-deficiency specifically increases the uptake of triglyceride-derived fatty acids into adipose tissue, and that is effect is observed most prominently in the fasted state. Adipose-specific knockout of ANGPTL4 could wholly recapitulate the plasma triglyceride and fat partitioning phenotypes of whole-body ANGPTL4 knockouts, supporting the idea that adipose-derived ANGPTL4 is the primary driver of ANGPTL4’s effect on plasma triglycerides. Our data also suggest that ANGPTL4 expressed in adipose primarily acts locally to suppress LPL activity in the fasted state. Consistent with other reports, we also found that adipose-specific deletion of ANGPTL4 leads to short-term improvement in glucose tolerance in mice fed a high fat diet. However, we found that this improvement disappears with age. Moreover, we found that in wild-type mice LPL activity, ANGPTL4 expression, and lipid portioning are all altered with age. As age is also an important risk factor for metabolic disease, these finding suggest that age-induced changes in triglyceride metabolism may contribute to the increased risk of metabolic disease associated with aging.

Mismatch between poor fetal growth and rapid postnatal weight gain in the first 2 years of life is associated with higher blood pressure and insulin resistance without increased adiposity in childhood: the GUSTO cohort study.

Using longitudinal ultrasounds as an improved fetal growth marker, we aimed to investigate if fetal growth deceleration followed by rapid postnatal weight gain is associated with childhood cardiometabolic risk biomarkers in a contemporary well-nourished population. We defined fetal growth deceleration (FGD) as ultrasound-measured 2nd-3rd-trimester abdominal circumference decrease by ≥0.67 standard deviation score (SDS) and rapid postnatal weight gain (RPWG) as 0-2-year-old weight increase by ≥0.67 SDS. In the GUSTO mother-offspring cohort, we grouped 797 children into four groups of FGD-only (14.2%), RPWG-only (23.3%), both (mismatch, 10.7%) or neither (reference, 51.8%). Adjusting for confounders and comparing with the reference group, we tested associations of these growth groups with childhood cardiometabolic biomarkers: magnetic resonance imaging (MRI)-measured abdominal fat (n = 262), liver fat (n = 216), intramyocellular lipids (n = 227), quantitative magnetic resonance-measured overall body fat % (BF%) (n = 310), homeostasis model assessment of insulin resistance (HOMA-IR) (n = 323), arterial wall thickness (n = 422) and stiffness (n = 443), and blood pressure trajectories (ages 3-6 years). Mean±SD birthweights were: FGD-only (3.11 ± 0.38 kg), RPWG-only (3.03 ± 0.37 kg), mismatch (2.87 ± 0.31 kg), reference (3.30 ± 0.36 kg). FGD-only children had elevated blood pressure trajectories without correspondingly increased BF%. RPWG-only children had altered body fat partitioning, higher BF% [BF = 4.26%, 95% confidence interval (CI) (2.34, 6.19)], HOMA-IR 0.28 units (0.11, 0.45)] and elevated blood pressure trajectories. Mismatch children did not have increased adiposity, but had elevated ectopic fat, elevated HOMA-IR [0.29 units (0.04,0.55)] and the highest blood pressure trajectories. Associations remained even after excluding small-for-gestational-age infants from analyses. Fetal growth deceleration coupled with rapid postnatal weight gain was associated with elevated childhood cardiometabolic risk biomarkers without correspondingly increased BF%.

Sugar-sweetened beverage consumption is associated with visceral fat in children.

Sugar-sweetened beverage (SSB) consumption has been associated with visceral fat partitioning in adults; however, the underlying mechanisms in childhood remain unclear and warrant exploration. This cross-sectional study aimed to investigate the association between SSB consumption and body fat in children aged 9-13 years and the potential modifying effect of children's sex and serum cortisol levels. A sample of 2665 Greek schoolchildren participated in the 'Healthy Growth Study', and anthropometric, body composition, dietary intake and serum cortisol data were assessed. SSB consumption was defined as low (<1 serving/d), medium (1-2 servings/d) or high (>2 servings/d). We used linear regression models to assess the association between SSB consumption and measures of adiposity and to assess effect modification; models were stratified by sex and tertiles of morning serum cortisol. A significant positive association was observed between high SSB consumption and visceral adipose tissue (VAT) (β = 1·4, 95 % CI 0·4, 2·3, P = 0·01) but not BMI or BMI z-score. When stratified by sex, the association was observed in boys (β = 1·8, 95 % CI 0·3, 3·4, P = 0·02) but not in girls. When stratified by cortisol levels, SSB consumption was associated with VAT in children with cortisol levels in the lowest tertile (β = 2·8, 95 % CI 1·0, 4·6, P < 0·01). These results indicate that increased SSB consumption is associated with visceral adiposity in schoolchildren and this association may be modified by sex and morning serum cortisol. To prevent VAT accumulation and concomitant disease risk, dietary interventions should target SSB consumption during childhood.

Obesity and Weight Gain in Persons with HIV.

The proportion of overweight and obese persons with HIV (PWH) has increased since the introduction of antiretroviral therapy (ART). We aim to summarize recent literature on risks of weight gain, discuss adipose tissue changes in HIV and obesity, and synthesize current understanding of how excess adiposity and HIV contribute to metabolic complications. Recent studies have implicated contemporary ART regimens, including use of integrase strand transfer inhibitors and tenofovir alafenamide, as a contributor to weight gain, though the mechanisms are unclear. Metabolic dysregulation is linked to ectopic fat and alterations in adipose immune cell populations that accompany HIV and obesity. These factors contribute to an increasing burden of metabolic diseases in the aging HIV population. Obesity compounds an increasing burden of metabolic disease among PWH, and understanding the role of fat partitioning and HIV- and ART-related adipose tissue dysfunction may guide prevention and treatment strategies.

Role of Complement and Complement-Related Adipokines in Regulation of Energy Metabolism and Fat Storage.

Adipose tissue releases many cytokines and inflammatory factors described as adipokines. In obesity, adipokines released from expanding adipose tissue are implicated in disease progression and metabolic dysfunction. However, mechanisms controlling the progression of adiposity and metabolic complications are not fully understood. It has been suggested that expanding fat mass and sustained release of inflammatory adipokines in adipose tissue lead to hypoxia, oxidative stress, apoptosis, and cellular damage. These changes trigger an immune response involving infiltration of adipose tissue with immune cells, complement activation and generation of factors involved in opsonization and clearance of damaged cells. Abundant evidence now indicates that adipose tissue is an active secretory source of complement and complement-related adipokines that, in addition to their inflammatory role, contribute to the regulation of metabolic function. This article highlights advances in knowledge regarding the role of these adipokines in energy regulation of adipose tissue through modulating lipogenic and lipolytic pathways. Several adipokines will be discussed including adipsin, Factor H, properdin, C3a, Acylation-Stimulating Protein, C1q/TNF-related proteins, and response gene to complement-32 (RGC-32). Interactions between these factors will be described considering their immune-metabolic roles in the adipose tissue microenvironment and their potential contribution to progression of adiposity and metabolic dysfunction. The differential expression and the role of complement factors in gender-related fat partitioning will also be addressed. Identifying lipogenic adipokines and their specific autocrine/paracrine roles may provide means for adipose-tissue-targeted therapeutic interventions that may disrupt the vicious circle of adiposity and disease progression. © 2019 American Physiological Society. Compr Physiol 9:1411-1429, 2019.