Citations

ABSTRACT The coexistence of obesity and insulin resistance is associated with elevated plasma amino acid concentrations. However, it remains unclear whether adiposity or insulin resistance is the stronger determinant of plasma amino acid dysregulation in this setting. Twenty-two adults (10 women, 12 men) spanning a broad range of body mass index (BMI) and insulin resistance underwent a 75-g oral glucose tolerance test (OGTT) after an overnight fast. Plasma glucose, insulin, and amino acid concentrations were measured serially, and insulin resistance/sensitivity was estimated from OGTT-derived glucose and insulin responses, using the homeostasis model assessment of insulin resistance (HOMA-IR) and the Matsuda insulin sensitivity index (Matsuda-ISI). Principal component analysis (PCA) of fasting plasma amino acid concentrations showed no clear separation by obesity or insulin resistance classifications. In contrast, PCA of OGTT-stimulated plasma amino acid concentrations revealed clearer clustering by BMI, fat mass, and waist circumference, whereas separation by HOMA-IR and Matsuda-ISI was less distinct. Importantly, regression analyses showed that BMI, fat mass, and waist circumference were significant predictors of OGTT-stimulated, but not fasting, amino acid responses, with waist circumference accounting for the greatest proportion of the variance in branched-chain amino acid responses during the OGTT (R 2 = 0.54). In conclusion, measures of adiposity, particularly total fat mass and waist circumference, accounted for a greater proportion of the variance in plasma amino acid responses under physiologically stimulated conditions than indices of insulin resistance. These findings support the view that plasma amino acid concentrations reflect adiposity-related metabolic alterations more strongly than insulin resistance.

ABSTRACT Background In healthy individuals, exercise and amino acid availability act synergistically to stimulate muscle anabolism. However, this interaction may be impaired in individuals with obesity. Objective We examined whether acute aerobic exercise alters amino acid-stimulated muscle protein synthesis during immediate postexercise recovery in adults with obesity. Methods Sixteen sedentary adults with a body mass index >30 kg/m 2 underwent a stable-isotope tracer infusion to measure mixed-muscle protein fractional synthesis rate (FSR) in the basal/fasted state and during an amino acid infusion, either with or without prior aerobic exercise. Participants were randomly assigned to receive either amino acid infusion alone (AA) or 45 min of cycling exercise at ∼65% heart rate reserve immediately before amino acid infusion (EX + AA). Results Amino acid infusion increased muscle protein FSR in the AA group ( P < 0.0001) but not in the EX + AA group ( P > 0.05), and the amino acid-stimulated increase in FSR was 78% lower in EX + AA than in AA ( P < 0.01). The amino acid infusion increased ( P < 0.05) plasma amino acid concentrations in both groups. However, during the amino acid infusion, plasma concentrations of essential and branched-chain amino acids, including leucine, were lower in EX + AA than in AA ( P < 0.05). Moreover, across participants, absolute changes in muscle protein FSR were positively associated with plasma leucine concentrations during the amino acid infusion ( P < 0.05). Conclusions These findings show that, in individuals with obesity, acute aerobic exercise markedly attenuates amino acid-stimulated muscle protein synthesis during early postexercise recovery. These findings have important implications for designing nutritional strategies to optimize muscle anabolism in this population.

Obesity is a persistent public health issue, often resulting in metabolic complications such as insulin resistance (IR). The secretion of pro-inflammatory cytokines from adipose tissue (AT) is increased during obesity, contributing to the impairment of systemic insulin sensitivity. While interventions in animal models have shown that reducing inflammation restores insulin sensitivity, human studies reducing systemic inflammation have produced inconsistent results. We recently demonstrated that three months of high-dose (4 g/daily) ω-3PUFA (fish oil, FO) supplementation improved insulin sensitivity, and decreased systemic and AT inflammation in individuals with obesity (BMI ≥ 30 kg/m2). Given recent studies highlighting the involvement of microRNA (miRNA) in inflammatory cytokine production, we investigated the effect of ω-3PUFA supplementation on AT miRNA expression in this cohort. AT biopsies were collected before and after ω-3PUFA supplementation. miRNA was processed on the Affymetrix miRNA 4.0 GeneChip and analyzed using existing inflammatory gene sets sourced from MSigDB. Unbiased, differentially expressed miRNA analysis identified miR-4498 and miR-5689 as significantly increased after three months of ω-3PUFA supplementation. Real-time PCR confirmed bioinformatic analysis findings. Our study reports the modulation of miRNA in AT, reductions in systemic and AT markers of inflammation, and the improvement of IR post ω-3PUFA supplementation. Further research is needed to elucidate the link between miR-4498, miR-5689, and whole-body insulin sensitivity.

AbstractWe investigated how obesity impacts the response of circulating insulin‐like growth factor‐1 (IGF‐1) to a single bout of endurance exercise in humans with and without obesity. Blood samples were collected before exercise, at 15 and 40 min during a 45‐min cycling session at 65% of heart rate reserve, and 15 min post‐exercise. Serum levels of total IGF‐1, free IGF‐1, IGF binding proteins 1 (IGFBP‐1) and 3 (IGFBP‐3), growth hormone, and insulin were measured. Both total IGF‐1 and IGFBP‐3 serum concentrations increased significantly (p < 0.05) during exercise in the study participants without obesity but not in those with obesity, returning to basal levels immediately after exercise. There was a statistically significant main effect on the growth hormone response, with circulating levels being higher in participants without obesity (p < 0.05). No significant effects were observed for either free IGF‐1 or IGFBP‐1 serum concentrations in response to exercise in either group (p > 0.05). We conclude that humans with obesity have blunted serum total IGF‐1 response during exercise. However, a concurrent attenuation in serum IGFBP‐3 response, which regulates free (i.e., biologically active) IGF‐1 in circulation, results in no change in circulating free IGF‐1 levels during endurance exercise in individuals with obesity.

Abstract The growing prevalence of obesity, a risk factor for disorders such as Alzheimer’s Disease (AD), raises concerns about the effects on cognitive health. AD currently impacts 6.9 million Americans aged 65 and older and is characterized by the presence of amyloid beta (Aβ) plaques, neurofibrillary tau tangles, and neuroinflammation, all of which contribute to cognitive impairment. Insulin resistance, common in both obesity and AD, disrupts brain glucose metabolism and accelerates neurodegeneration. Understanding the factors that link these conditions could lead to new strategies for combating disease. Notably, the B-like vitamin choline is necessary for fat metabolism and has been shown to help reduce obesity incidence. However, ∼90% of Americans are deficient, and decreases in this nutrient have been associated with cognitive decline. Here, we examined circulating choline levels, inflammation, and metabolic dysfunction in human participants with obesity (BMI > 30) compared to normal BMIs (18.5–24.9), as well as in 3xTg-AD mice, an AD model, fed a choline-deficient diet throughout adulthood. Our results revealed that obese participants exhibited significantly lower circulating choline levels compared to those with a healthy BMI. Lower choline levels correlated with higher %Body fat and increased markers of insulin resistance. Elevated inflammatory cytokines in obese participants were also seen in 3xTg-AD mice on a choline-deficient diet, which exhibited significant weight gain and metabolic dysfunction. AD-like pathology was also exacerbated in choline deficient 3xTg-AD mice. These findings underscore the relationship between low choline levels, obesity, insulin resistance, and cognitive decline risk. Adequate choline intake may mitigate the risk of obesity, potentially preventing cognitive decline and associated diseases. Highlights Obesity is linked to increased insulin resistance (IR) and systemic inflammation, both of which are recognized risk factors for Alzheimer’s disease (AD). Women exhibit lower circulating choline levels compared to men, and obese individuals display significantly lower choline levels than those with a healthy BMI. Lower circulating choline levels are linked to a higher body fat percentage, increased markers of IR and liver dysfunction, as well as heightened systemic inflammation. 3xTg-AD mice on a choline-deficient diet experience considerable weight gain, metabolic dysfunction, heightened systemic inflammation, and AD-like pathology, resembling the conditions observed in obese human participants.

Purpose The Sangre Por Salud (SPS) Biobank was established to facilitate biomedical research opportunities for the Latino community by creating an easily accessible prospective cohort for scientists interested in studying health conditions and health disparities in this population. Participants Individuals self-identifying as Latino, aged 18–85 years, were prospectively recruited from the primary care Internal Medicine clinic at Mountain Park Health Center in Phoenix, Arizona. After obtaining informed consent, detailed medical history questionnaires were captured, and blood samples were obtained for common laboratory tests. Participants authorised the research team to access their electronic health records for research purposes. In addition, participants had serum, plasma and DNA samples isolated and stored at the Mayo Clinic Arizona Biorepository Laboratory for long-term storage and future access. As part of the study, participants consented and agreed to be contacted for potential participation in future research studies. Findings to date 3756 participants provided informed consent, of whom 3733 completed all study questionnaires, an oral glucose tolerance test and had blood collected and stored. The SPS cohort is predominantly composed of females (72%), with a median age at time of consent of 42 years. All participants self-identified as Hispanic/Latino, 45% were married, 53% were employed for wages and 60% had less than a high school degree. Around 25% of participants met diagnostic criteria for overweight (BMI 25–29 kg/m 2 ), and 49% met for obesity (BMI≥30 kg/m 2 ). At time of recruitment, hypertension, hyperlipidaemia and depression affected 22%, 20% and 13% of the cohort, respectively. Future plans We plan to regularly update the participants’ electronic health records and self-reported health data to longitudinal research. Additionally, we plan to obtain a more comprehensive genomic analysis on the entire cohort, ensuring greater research interest and investigation into the underlying genetic factors that contribute to disease susceptibility in this cohort.

Abstract Context Humans with obesity and insulin resistance exhibit lipid accumulation in skeletal muscle, but the underlying biological mechanisms responsible for the accumulation of lipid in the muscle of these individuals remain unknown. Objective We investigated how plasma insulin modulates the extraction of circulating triglycerides (TGs) and nonesterified fatty acids (NEFAs) from ingested and endogenous origin in the muscle of lean, insulin-sensitive humans (Lean-IS) and contrasted these responses to those in humans with obesity and insulin resistance (Obese-IR). Methods The studies were performed in a postprandial state associated with steady-state plasma TG concentrations. The arterio-venous blood sampling technique was employed to determine the extraction of circulating lipids across the forearm muscle before and after insulin infusion. We distinguished the kinetics of TGs and NEFAs from ingested origin from those from endogenous origin across muscle by incorporating stable isotope-labeled triolein in the ingested fat. Results Insulin infusion rapidly suppressed the extraction of plasma TGs from endogenous but not ingested origin in the muscle of the Lean-IS, but this response was absent in the muscle of the Obese-IR. Furthermore, in the muscle of the Lean-IS, insulin infusion decreased the extraction of circulating NEFAs from both ingested and endogenous origin; however, this response was absent for NEFAs from ingested origin in the muscle of the Obese-IR subjects. Conclusion Partitioning of circulating lipids away from the skeletal muscle when plasma insulin increases during the postprandial period is impaired in humans with obesity and insulin resistance.

Abstract Patients with newly diagnosed Graves disease often elect for treatment with the drug methimazole (MMI) over alternative therapies. However, MMI can commonly result in skin allergy that in severe cases can lead to discontinuation of therapy. We present a case of Graves thyrotoxicosis with a delayed hypersensitivity reaction while on MMI. The patient was successfully treated with a novel, individualized, 27-day desensitization protocol that resulted in tolerance of MMI with subsequent improvement in thyroid indices. Previous literature has offered various rapid desensitization protocols to MMI for immediate type hypersensitivity reactions. However, in nonimmediate, delayed hypersensitivity reactions, a slower desensitization protocol can be considered. As demonstrated in this case, desensitization to MMI is a reasonable alternative in patients who wish to avoid definitive therapy who develop an initial adverse reaction to MMI, as this can occur in up to 13% of treated cases.

Background: The prevalence of type 2 diabetes (T2D) is increasing in Hispanic or Latino adults. The American Diabetes Association (ADA) score to identify current risk of T2D was developed with limited Hispanic or Latino representation. Therefore, we sought to validate the ADA score in a cohort of Hispanic or Latino adults. Methods: At enrollment in the Sangre Por Salud Biobank, 3,625 Hispanic or Latino adults from Phoenix, Arizona completed a baseline questionnaire. Current risk of undiagnosed T2D was based on non-laboratory risk factors and ADA score ≥5 (Table). Participants also completed T2D screening (ie, fasting glucose, 2-hour oral glucose tolerance test, and/or hemoglobin A1c). Undiagnosed T2D was based on 'no self-reported T2D but meeting T2D diagnostic’ criteria. Multivariable logistic regression analyzed associations of ADA risk factors and undiagnosed T2D, and model performance was based on sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Results: At enrollment, 7.3% of participants had undiagnosed T2D (n=265/3,625). In multivariable analysis, most risk factors described for the ADA score were significantly associated with T2D, except for sex, which showed no association. ADA score ≥5 had sensitivity 50%, specificity 79%, PPV 18%, and NPV 95%. However, ADA score ≥4 had sensitivity 72%, specificity 61%, PPV 14%, and NPV 96%. ADA score ≥4 vs ≥5 identified 22% (n=59) additional cases of undiagnosed T2D. Furthermore, using the revised definition for elevated blood pressure (>120/80 mmHg) vs ≥140/90 mmHg (current ADA score) further improved the ADA score ≥4 (sensitivity 81%; specificity 52%). Other scores had lower performance using both hypertension definitions. Conclusion: In Hispanic or Latino adults, a lower ADA score than currently recommended identified additional cases of undiagnosed T2D. The ADA score requires validation and recalibration, including for the updated hypertension guidelines.