Effect of metabolic status on response to SIV infection and antiretroviral therapy in nonhuman primates.

Current antiretroviral therapy (ART) regimens efficiently limit HIV replication, thereby improving life expectancy of people living with HIV, but also cause metabolic side effects. The ongoing obesity epidemic has resulted in more people with metabolic comorbidities at the time of HIV infection, yet the impact of pre-existing metabolic dysregulation on infection sequelae and response to ART is unclear. Here, to investigate the impact of preexisting obesity and insulin resistance on acute infection and subsequent long-term ART, we infected a cohort of lean and obese adult male macaques with SIV and administered ART. The responses of lean and obese macaques to SIV and ART were similar with respect to plasma and cell-associated viral loads, ART drug levels in plasma and tissues, SIV-specific immune responses, adipose tissue and islet morphology, and colon inflammation, with baseline differences between lean and obese groups largely maintained. Both groups exhibited a striking depletion of CD4+ T cells from adipose tissue that did not recover with ART. However, differential responses to SIV and ART were observed for body weight, omental adipocyte size, and the adiponectin/leptin ratio, a marker of cardiometabolic risk. Thus, obesity and insulin resistance had limited effects on multiple responses to acute SIV infection and ART, while several factors that underlie long-term metabolic comorbidities were influenced by prior obesity and insulin resistance. These studies provide the foundation for future investigations into the efficacy of adjunct therapies such as metformin and glucagon-like peptide-1 receptor agonists in the prevention of metabolic comorbidities in people living with HIV.

Bedding as an Enrichment Strategy in Group-housed Mauritian Cynomolgus Macaques (Macaca fascicularis).

The research community is committed to improving the well-being of nonhuman primates by providing opportunities to express species-specific behaviors such as foraging. In the wild, macaques spend a large part of their day foraging; this behavior is greatly limited in captivity. Bedding (wood shavings substrate) has been shown to promote foraging in rhesus macaques. However, the amount of bedding needed to affect these changes is unknown. Further, few studies have examined other benefits of bedding, including its potential to reduce noise levels, which can negatively impact welfare. We examined the use of bedding substrate in male Mauritius cynomolgus macaques (2-3-y-old) living in one of 2 social groups with either a full bale of bedding (that is, approximately 6 in of substrate) or a half bale (approximately 3 in) added to the pens for 10 d, followed by 4 d without bedding. We performed focal observations on 8 monkeys biweekly for 8 wk and used a dosimeter to measure sound in the room for 42 d. As expected, monkeys spent significantly more time foraging and less time self-grooming when bedding was present than when it was not. The amount of bedding did not make a difference. The presence of bedding did not affect social grooming or aggression, although it did help to dampen sound. Both peak and mean sound levels were lower with a full bale of bedding than with no bedding. Taken together, these results suggest that bedding is an effective enrichment strategy that can improve welfare of group-housed macaques.

Arterial Platelet Adhesion in Atherosclerosis-Prone Arteries of Obese, Insulin-Resistant Nonhuman Primates.

Background Platelet-endothelial interactions are thought to contribute to early atherogenesis. These interactions are potentiated by oxidative stress. We used in vivo molecular imaging to test the hypothesis that platelet-endothelial interactions occur at early stages of plaque development in obese, insulin-resistant nonhuman primates, and are suppressed by NADPH-oxidase-2 inhibition. Methods and Results Six adult rhesus macaques fed a Western-style diet for a median of 4.0 years were studied at baseline and after 8 weeks of therapy with the NADPH-oxidase-2-inhibitor apocynin (50 mg/kg per day). Six lean control animals were also studied. Measurements included intravenous glucose tolerance test, body composition by dual-energy X-ray absorptiometry, carotid intimal medial thickness, carotid artery contrast ultrasound molecular imaging for platelet GPIbα (glycoprotein- Ibα) and vascular cell adhesion molecule-1, and blood oxidative markers on mass spectrometry. Compared with lean controls, animals on a Western-style diet were obese (median body mass: 16.0 versus 8.7 kg, P=0.003; median truncal fat: 49% versus 20%, P=0.002), were insulin resistant (4-fold higher insulin-glucose area under the curve on intravenous glucose tolerance test, P=0.002), had 40% larger carotid intimal medial thickness (P=0.004), and exhibited oxidative signatures on proteomics. In obese but not lean animals, signal enhancement on molecular imaging was significantly elevated for GPIbα and vascular cell adhesion molecule-1. The signal correlated modestly with intimal medial thickness but not with the degree of insulin resistance. Apocynin significantly (P<0.01) reduced median signal for GPIbα by >80% and vascular cell adhesion molecule-1 signal by 75%, but did not affect intimal medial thickness, body mass, or intravenous glucose tolerance test results. Conclusion In nonhuman primates, diet-induced obesity and insulin resistance leads to platelet-endothelial adhesion at early atherosclerotic lesion sites, which is associated with the expression of pro-inflammatory adhesion molecules. These responses appear to be mediated, in part, through oxidative pathways.

Effects of pre- and postnatal protein restriction on maternal and offspring metabolism in the nonhuman primate.

Women in low- and middle-income countries frequently consume a protein-deficient diet during pregnancy and breastfeeding. The effects of gestational malnutrition on fetal and early postnatal development can have lasting adverse effects on offspring metabolism. Expanding on previous studies in rodent models, we utilized a nonhuman primate model of gestational and early-life protein restriction (PR) to evaluate effects on the organ development and glucose metabolism of juvenile offspring. Offspring were born to dams that had consumed a control diet containing 26% protein or a PR diet containing 13% protein. Offspring were maintained on the PR diet and studied [body and serum measurements, intravenous glucose tolerance tests (ivGTTs), and dual-energy X-ray absorptiometry scans] up to 7 mo of age, at which time tissues were collected for analysis. PR offspring had age-appropriate body weight and were euglycemic but exhibited elevated fasting insulin and reduced initial, but increased total, insulin secretion during an ivGTT at 6 mo of age. No changes were detected in pancreatic islets of PR juveniles; however, PR did induce changes, including reduced kidney size, and changes in liver, adipose tissue, and muscle gene expression in other peripheral organs. Serum osteocalcin was elevated and bone mineral content and density were reduced in PR juveniles, indicating a significant impact of PR on early postnatal bone development.

A Long-Acting PYY3-36 Analog Mediates Robust Anorectic Efficacy with Minimal Emesis in Nonhuman Primates.

The gut hormone PYY3-36 reduces food intake in humans and exhibits at least additive efficacy in combination with GLP-1. However, the utility of PYY analogs as anti-obesity agents has been severely limited by emesis and rapid proteolysis, a profile similarly observed with native PYY3-36 in obese rhesus macaques. Here, we found that antibody conjugation of a cyclized PYY3-36 analog achieved high NPY2R selectivity, unprecedented in vivo stability, and gradual infusion-like exposure. These properties permitted profound reduction of food intake when administered to macaques for 23 days without a single emetic event in any animal. Co-administration with the GLP-1 receptor agonist liraglutide for an additional 5 days further reduced food intake with only one animal experiencing a single bout of emesis. This antibody-conjugated PYY analog therefore may enable the long-sought potential of GLP-1/PYY-based combination treatment to achieve robust, well-tolerated weight reduction in obese patients.

Temporal Changes in Skeletal Muscle Capillary Responses and Endothelial-Derived Vasodilators in Obesity-Related Insulin Resistance.

The inability of insulin to increase skeletal muscle capillary blood volume (CBV) reduces glucose uptake in insulin resistance (IR). We hypothesized that abnormalities in endothelial-derived vasodilator pathways are temporally associated with the development of IR and an impaired ability to increase skeletal muscle CBV. A comprehensive metabolic and vascular screening assessment was performed on 10 adult rhesus macaques at baseline and every 4-6 months for 2 years after starting a high-fat diet supplemented with fructose. Diet changes resulted in an 80% increase in truncal fat by 4 months. Hyperinsulinemia and decreased glucose utilization were observed from 4 to 18 months. At 24 months, pancreatic secretory function and the glucose utilization rate declined. CBV at rest and during an intravenous glucose tolerance test demonstrated a sustained increase from 4 to 18 months and then abruptly fell at 24 months. Nitric oxide bioavailability progressively decreased over 2 years. Conversely, endothelial-derived vasodilators progressively increased over 18 months and then abruptly decreased at 24 months in concert with the CBV. The increase in basal and glucose-mediated CBV early in IR may represent a compensatory response through endothelial-derived vasodilator pathways. The inability to sustain a vascular compensatory response limits glucose-mediated increases in CBV, which correlates with the severity of IR.

Proinflammatory endothelial activation detected by molecular imaging in obese nonhuman primates coincides with onset of insulin resistance and progressively increases with duration of insulin resistance.

BACKGROUND: Inflammation and insulin resistance (IR) are associated processes that potentiate risk for cardiovascular disease in obesity. The temporal relation between IR and inflammation is not completely characterized. We hypothesized that endothelial cell adhesion molecule expression in large arteries is an early event that coincides with diet-induced obesity and IR in primates. METHODS AND RESULTS: Ten adult male rhesus macaques were studied at baseline and every 4 to 6 months on a high-fat diet for 2 years. Truncal fat, carotid intima-media thickness, plasma inflammatory biomarkers, and carotid P-selectin and vascular cell adhesion molecule-1 expression by contrast-enhanced ultrasound molecular imaging were assessed. Intravenous glucose tolerance test was performed at baseline and at 4 and 18 months. A high-fat diet produced a rapid increase (P<0.01) in weight, truncal fat, and degree of IR indicated by the insulin area under the curve and glucose disappearance rate on intravenous glucose tolerance test, all of which worsened minimally thereafter. Molecular imaging detected a progressive increase in endothelial cell adhesion molecule expression over time (5- to 7-fold greater than control agent signal at 2 years; P<0.01). Changes in intima-media thickness were not detected until 2 years and, although there was a trend toward an increase in plasma markers of inflammation (monocyte chemotactic protein-1, C-reactive protein), the pattern of increase varied considerably over time. CONCLUSIONS: In primates with diet-induced obesity, endothelial inflammatory activation is an early event that occurs coincident with the development of IR and long before any measurable change in carotid intima-media thickness. Endothelial activation is related more to the duration rather than to the severity of IR and is not mirrored by changes in plasma biomarkers.

Targeting oxidized LDL improves insulin sensitivity and immune cell function in obese Rhesus macaques.

Oxidation of LDL (oxLDL) is a crucial step in the development of cardiovascular disease. Treatment with antibodies directed against oxLDL can reduce atherosclerosis in rodent models through unknown mechanisms. We demonstrate that through a novel mechanism of immune complex formation and Fc-γ receptor (FcγR) engagement, antibodies targeting oxLDL (MLDL1278a) are anti-inflammatory on innate immune cells via modulation of Syk, p38 MAPK phosphorylation and NFκB activity. Subsequent administration of MLDL1278a in diet-induced obese (DIO) nonhuman primates (NHP) resulted in a significant decrease in pro-inflammatory cytokines and improved overall immune cell function. Importantly, MLDL1278a treatment improved insulin sensitivity independent of body weight change. This study demonstrates a novel mechanism by which an anti-oxLDL antibody improves immune function and insulin sensitivity independent of internalization of oxLDL. This identifies MLDL1278a as a potential therapy for reducing vascular inflammation in diabetic conditions.