The Effect of 12-month Prune (Dried Plum) Supplementation on Inflammatory Responses and Cardiometabolic Health in Postmenopausal Women
Restricted (Penn State Only)
- Author:
- Damani, Janhavi
- Graduate Program:
- Integrative and Biomedical Physiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 12, 2023
- Committee Members:
- Donna Korzick, Program Head/Chair
Penny Kris-Etherton, Outside Field Member
Joshua Lambert, Outside Unit Member
Connie Rogers, Co-Chair & Dissertation Advisor
Mary Jane De Souza, Co-Chair & Dissertation Advisor - Keywords:
- prunes (dried plums)
osteoporosis
bone mineral density
immunity
inflammation
pro-inflammatory cytokines
oxidative stress
menopause
cardiometabolic health
nutritional intervention
randomized controlled trial - Abstract:
- Osteoporosis is a chronic bone disease characterized by significant loss in bone mineral density (BMD) and reduced bone strength, predisposing individuals to increased risk for fractures. Worldwide, over 200 million women have osteoporosis, and one in three women over 50 years of age will experience an osteoporotic fracture. In the United States, of the estimated 13.4 million adults aged over 50 years with osteoporosis, over 11 million are postmenopausal women, and this is projected to rise to 13.6 million by 2030, thus underscoring osteoporosis as a significant health concern in postmenopausal women. Estrogen deficiency and subsequent deterioration in bone mass and strength are important hallmarks of osteoporosis. During the menopause transition, estrogen withdrawal accelerates the effect of aging on bone by upregulating chronic inflammation and oxidative stress, both of which favor bone resorption, resulting in net bone loss. Current osteoporosis drugs encompassing hormone therapy, antiresorptive, and anabolic agents are effective but associated with high cost and adverse effects, which contribute to their poor compliance. Therefore, there is increasing interest in the use of phenolic-rich fruits as alternative dietary interventions to mitigate postmenopausal bone loss, partly through their potent antioxidant and anti-inflammatory activities. Prunes, i.e., dried plums (Prunus domestica L.), represent an emerging functional food for bone health and are rich in phenolic compounds, fiber, vitamins, and minerals. Findings from rodent models of ovarian hormone deficiency and clinical studies in postmenopausal women suggest that prune consumption confers positive effects on bone through improvement in biomarkers of bone turnover, BMD, and bone microarchitectural strength. However, our understanding of the mechanisms underlying these osteoprotective effects of prunes through inflammatory pathways in postmenopausal women is limited. The Prune Study (NCT02822378) was a single-center, multi-arm, parallel-design 12-month randomized controlled trial (RCT) conducted in a free-living study cohort of postmenopausal women (aged 55–75 years, BMD T-score between 0.0 and –3.0 at the lumbar spine, total hip, or femoral neck) and designed to investigate the effects of prune intake (at two doses, 50g/day and 100g/day) as a whole-food nutritional intervention supplemented with the recommended dose of calcium and vitamin D3 for 1 year on bone density, geometry, and estimated bone strength compared to a “no-prune” control group supplemented with calcium and vitamin D3 alone. In total, 235 postmenopausal women (aged 62.1±5.0 years) were enrolled in the RCT [control (n=78), 50g/day prune (n=79), and 100g/day prune (n=78)], of which 183 participants completed the entire 12-month intervention (22% dropout): control (n=70), 50g/day prune (n=67), and 100g/day prune (n=46). The prune effects on primary BMD outcomes are presented elsewhere. The current dissertation comprises secondary-outcome investigations of the Prune Study with an overarching objective to evaluate whether circulating markers of inflammation are linked to low BMD and bone strength in postmenopausal women from the parent RCT prior to intervention and whether prune supplementation at two doses, 50g/day and 100g/day, attenuates inflammatory mediators after 12 months in comparison to the no-prune control group. Furthermore, postmenopausal women are at increased risk for cardiovascular disease as estrogen withdrawal during menopause is linked to adverse changes in the cardiometabolic profile and body composition. Thus, a corollary objective of this dissertation was to investigate whether prune supplementation improves cardiometabolic risk factors in postmenopausal women after 12 months in comparison to the no-prune control group. Study 1 was a cross-sectional, secondary analysis of baseline data from postmenopausal women who completed the 12-month RCT (n=183, 55–75 years old) with bone mineral density (BMD) T-score between 0.0 and –3.0 at any site. BMD was measured using dual-energy X-ray absorptiometry, and bone geometry and strength were measured using peripheral quantitative computed tomography. Blood was collected at baseline to measure (1) bone turnover markers, including procollagen type 1 N-terminal propeptide (P1NP) and C-terminal telopeptide and (2) circulating inflammatory markers, including high-sensitivity C-reactive protein (hs-CRP) and plasma pro-inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, and monocyte chemoattractant protein (MCP)-1, using enzyme-linked immunosorbent assay. Serum hs-CRP negatively correlated with P1NP (r=–0.197, p=0.042). Plasma IL-1β, IL-6, IL-8, and TNF-α negatively correlated with trabecular bone score at the lumbar spine (all p<0.05). Plasma IL-6 negatively predicted BMD at the total body (β=–0.131, p=0.027) and lumbar spine (β=–0.151, p=0.036), whereas plasma TNF-α negatively predicted total hip BMD (β=–0.114, p=0.028). Study 1 demonstrated that at baseline, circulating markers of inflammation were inversely associated with various estimates of bone density, geometry, and strength in postmenopausal women, suggesting that inflammatory markers may be an important mediator for postmenopausal bone loss. Study 2 was a longitudinal analysis of immune, inflammatory, and oxidative stress markers, all collected at baseline and 12 months as secondary outcomes of the RCT. At baseline and after 12 months of intervention, fasting blood samples were collected to measure serum hs-CRP, serum total antioxidant capacity (TAC), plasma 8-isoprostane, pro-inflammatory cytokines [IL-1β, IL-6, IL-8, MCP-1, and TNF-α] in plasma and lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs) culture supernatants, and the percentage and activation of circulating monocytes, all quantified as secondary outcomes. Prune supplementation did not modulate hs-CRP, TAC, 8-isoprostane, and plasma cytokine concentrations. However, percent change in circulating activated monocytes from baseline was lower in the 100g/day prune group (mean ± SEM: −1.76±1.04%; p<0.01) compared to control. Furthermore, in LPS-stimulated PBMC supernatants, the percent change in TNF-α secretion from baseline was lower in the 50g/day prune group (−4.39±7.17%; p<0.01) compared to control, and the percent change in IL-1β, IL-6, and IL-8 secretion from baseline was lower in the 100g/day prune group (−8.87±13.46, −4.27±16.45, and −14.28±13.27% respectively, for IL-1β, IL-6, and IL-8; all p<0.05) compared to the control group. Study 2 demonstrated that 50g–100g prune supplementation for 12 months reduced pro-inflammatory cytokine secretion from PBMCs and suppressed the percentage of activated monocytes in postmenopausal women, thus attenuating markers of chronic inflammation associated with postmenopausal bone loss. Study 3 was an ancillary analysis of cardiometabolic health markers collected at baseline, 6 months, and 12 months as exploratory outcomes of the RCT. Blood was collected at baseline, 6 months, and 12 months/post to measure markers of glycemic control, blood lipids, and liver function. Body composition was assessed at baseline, 6 months, and 12 months/post using dual-energy X-ray absorptiometry to estimate regional fat distribution. Prune supplementation at 50g or 100g/day did not alter markers of glycemic control, blood lipids, and liver enzymes after 12 months compared to the no-prune control group (all p>0.05). Furthermore, gynoid percent fat and visceral adipose tissue indices did not significantly differ in women consuming 50g or 100g/day prunes compared to the control group after 12 months of intervention. However, android total mass increased by 3.19% from baseline in the control group, while the 100g/day prune group experienced 0.02% decrease in android total mass from baseline (p<0.01). Prune supplementation at 50g/day or 100g/day into the daily diet for 12 months did not adversely affect blood biomarkers of cardiometabolic risk factors and central adiposity in postmenopausal women. Observational research from study 1 demonstrates that pro-inflammatory cytokines were associated with decreased bone density in our study population of postmenopausal women at baseline, prior to the prune intervention. Findings from both study 2 and 3 suggest that prunes may represent a plausible non-pharmacological treatment approach to preserve bone health by attenuating chronic, low-grade inflammation associated with postmenopausal bone loss concurrently without any adverse effects on cardiometabolic risk factors. As current dietary guidelines shift to a whole-food, healthy dietary pattern approach as opposed to a single dietary component or an isolated nutrient, future work is warranted to translate these findings from the clinical setting to determine whether prunes incorporated into a particular dietary pattern exert differential health benefits on bone and cardiometabolic risk markers in postmenopausal women.