Abstract
Objective
To investigate the effects of prebiotics combined with β-hydroxy-β-methylbutyrate (HMB) on muscle function, intestinal barrier integrity, and inflammation in elderly patients with sarcopenia.
Methods
A randomized controlled trial was conducted on 78 elderly sarcopenic patients recruited from Tongji University Affiliated Tenth People’s Hospital and Baoshan District Geriatric Care Hospital (Jan 2023 - Jan 2025). Participants were randomly assigned Group A (n = 32, standard diet + HMB-supplement), Group B (n = 31, standard diet + HMB + fructooligosaccharides), or Group C (n = 15, standard diet alone) for 30 days. Outcomes included muscle function (skeletal muscle mass index, grip strength, calf circumference), intestinal barrier markers (serum diamine oxidase, D-lactic acid, endotoxin), and inflammatory and nutritional markers (CRP, neutrophil/lymphocyte ratio, systemic immune inflammation index, albumin, prealbumin).
Results
Baseline indicators did not differ among groups (P > 0.05). After intervention, skeletal muscle mass index and grip strength improved significantly in Groups A and B (P < 0.05), with higher grip strengths to Group B than C (adj. P = 0.017). Calf circumference decreased in all groups (P < 0.05), most in Group C (t = 4.461, P = 0.001). Group B exhibited lower diamine oxidase, D-lactic acid, and endotoxin levels than Groups A and C (P < 0.05) and the greatest reductions in CRP, NLR, and SII (P < 0.001). Albumin or prealbumin showed no significant changes (P > 0.05).
Conclusion
HMB improves muscle function in sarcopenic elderly, prebiotics combined with HMB further enhance intestinal barrier repair and reduce inflammation, offering a promising gut-muscle-targeted nutritional strategy.
Keywords: Sarcopenia, Β-hydroxy-β-methylbutyric acid, HMB, Muscle function, Intestinal barrier
Introduction
Sarcopenia is a geriatric syndrome characterised by a progressive reduction in skeletal muscle mass and strength [1]. It has been demonstrated to be closely associated with adverse events such as falls, fractures, disability and mortality in the elderly, which significantly diminishes quality of life and increases the societal burden of healthcare [2]. As the global population ages, the prevalence of sarcopenia is increasing rapidly. According to the European Working Group on Sarcopenia in Older People (EWGSOP), the global prevalence of sarcopenia in older adults ranges from 10% to 27% [3, 4]. Within China, the prevalence of this condition among the elderly individuals is 20.7%, signifying its status as a pressing health concern that demands immediate consideration within the domain of geriatrics [5].
The pathogenesis of sarcopenia is complex and involves the synergistic effects of multiple factors, including nutritional imbalance, gut microbiota dysbiosis, chronic inflammation and endocrine disorders. Nutritional support and the regulation of the gut microbiome are two areas of research that have attracted considerable attention in recent times [6]. Among the various substances under investigation, β-hydroxy-β-methylbutyrate (HMB), a key metabolite of the branched-chain amino acid leucine, has been a particular focus in the field of muscle metabolism research. In the elderly population, the clinical value of HMB is particularly pronounced. It has been demonstrated that even in states of non-exercise, the ingestion of HMB supplementation has the capacity to enhance muscle strength, function and mass [7]. In accordance with the 2025 Position Statement of the International Society of Sports Nutrition (ISSN), HMB has been determined to exist in the human body in two distinct forms: namely, calcium salt (HMB-Ca) and free acid (HMB-FA) [8]. Both forms demonstrate excellent safety profiles. It is evident from the available literature that no deleterious effects on liver or kidney function, glucose tolerance, or insulin sensitivity have been observed with long-term oral administration at daily doses of up to 6 g [8–10]. Furthermore, the safety of both forms in elderly populations has been confirmed by multiple clinical studies [11].
Concurrently, the “gut-muscle axis” theory offers a novel perspective for the prevention and treatment of sarcopenia. As people age, there is an observed decline in diversity of gut microbiota, alongside a decrease in beneficial bacteria and an increase in harmful bacteria. This results in increased intestinal mucosal permeability, endotoxin entry into the bloodstream, and chronic inflammatory responses, which subsequently inhibit muscle protein synthesis and accelerate muscle breakdown [12]. As selective substrates for beneficial gut bacteria, prebiotics can indirectly improve muscle function by a number of mechanisms. These include the proliferation of beneficial bacteria, the enhancement of intestinal mucosal barrier integrity, and the reduction of inflammatory factor release. However, clinical studies on the synergistic regulation of muscle function and intestinal barrier in elderly sarcopenic patients by prebiotics combined with HMB remain scarce, and the specific mechanisms and clinical effects of their combined action remain unclear. The present study investigates the effects of prebiotics combined with HMB on muscle function, intestinal barrier function and inflammatory status in elderly patients with sarcopenia. The objective of this study is to establish new theoretical foundations and clinical protocols for nutritional interventions in sarcopenia.
Materials and methods
Study design and participants
The present research project has been reviewed and approved by the Ethics Committee of the Tenth People’s Hospital Affiliated to Tongji University (SHYS-IEC-5.0 / 23KY16 / P01) and registered with the China Clinical Trial Registry (Registration Number: ChiCTR2300072137).
Patients diagnosed with sarcopenia were recruited from the outpatient and inpatient departments of the Clinical Nutrition Department at the Tenth People’s Hospital Affiliated to Tongji University and the Baoshan Geriatric Nursing Hospital.
The inclusion criteria for the study are as follows: (1) Age ≥ 65 years; (2) Meeting the 2019 Asian Working Group for Sarcopenia (AWGS) revised diagnostic criteria [13], defined as skeletal muscle mass index (SMI) < 7.0 kg/m² for men and < 5.7 kg/m² for women, plus grip strength < 28 kg for men or < 18 kg for women, or walking speed < 0.8 m/s; (3) Nutritional Risk Screening Tool (NRS2002) score < 3; (4) Ability to understand and comply with informed consent.
Exclusion criteria included: (1) Participants who had enrolled in other drug clinical trials; (2) Patients diagnosed with GLIM-defined severe malnutrition; (3) Gastrointestinal diseases affecting gut microbiota, such as inflammatory bowel disease, irritable bowel syndrome, gastrointestinal bleeding, or major gastrointestinal surgery within the past five years; (4) Patients with other severe cardiovascular or cerebrovascular diseases, hepatic or renal insufficiency, immunodeficiency disorders, severe cognitive impairment, depression, or other psychiatric conditions; (5) Patients with pacemakers, arterial stents, or limb deficiencies that interfere with bioimpedance measurements; (6) Patients with muscular disorders or taking medications affecting muscle function; (7) Patients who underwent surgery or have tumors within the past month.
Randomization
Patients who met with the inclusion and exclusion criteria were required to sign informed forms. They were then randomly assigned to Group A, B, and C using the envelope method. A statistician not involved in clinical intervention or data collection prepared sequentially numbered. Eligible patients drew envelopes in the order of their clinic visits to complete randomization. Given the differences in nutritional supplement components (HMB alone, HMB + fructooligosaccharides, no supplement), double-blinding was not feasible for participants. However, single-blinding was implemented for data collectors (e.g., staff measuring grip strength, laboratory technicians analyzing serum markers) and statisticians (who were unaware of group assignments during data analysis) to minimize bias.
Interventions
All three groups received a dietary intervention in accordance with the guidelines [14, 15], with daily energy requirements calculated by dietitians at 25–30 kcal/(kg·d) and protein intake set at 1.2 g/(kg·d). Group A received the standard diet in addition to oral nutritional supplements (Abbott Nutrition, Inc., Ensure® Plus, 25 g/packet, containing 1.5 g HMB-Ca), administered as 25 g twice daily (morning and evening) for a total of 50 g daily, for 30 consecutive days. Intervention Group B received the standard diet in addition to oral nutritional supplement (Abbott Laboratories, Inc. Ensure®) containing an additional 5 g of fructooligosaccharides (FOS), administered once in the morning and once in the evening (60 g total daily) for a period of 30 days. Group C served as the control group, receiving only the standard diet with equivalent calories and protein for 30 days. During the period of hospitalization, all study supplements were dispensed at fixed times daily by ward nurses. Intake was directly documented daily by the nutritionist on a dedicated compliance log, ensuring 100% supervised administration. The outpatient follow-up process entailed the implementation of weekly telephone calls, with the objective of facilitating adherence to the stipulated intervention protocol. Participants or their caregivers were asked to mark intake on a simple log card, which was reviewed during subsequent calls.
Outcome measures
The following methods were employed to measure indicators prior to intervention and 30 days following intervention:
Muscle function indicators
Grip strength was measured using an electronic dynamometer, with three consecutive measurements being taken and the maximum value recorded. Calf circumference was measured using a soft tape measure positioned 10 centimeters below the tibial tuberosity, with the average of both sides being recorded. Skeletal muscle mass in the limbs at 50 kHz frequency was assessed using the Inbody S10 (Bio-space, Korea), calculating the height-adjusted SMI (skeletal muscle mass in limbs/height²(kg/m²)).
Evaluation of intestinal barrier function and permeability
A volume of 3 ml of fasting venous blood must be collected, followed by centrifugation in order to separate the serum. The serum diamine oxidase (DAO), D-lactic acid, and endotoxin levels are then measured using the JY-DLT intestinal barrier function biochemical indicator analysis system.
Inflammation and nutritional markers
Venous blood was collected from patients in each group prior to and following the intervention in order to measure complete blood count, C-reactive protein, serum albumin, and prealbumin levels. The neutrophil-to-lymphocyte ratio (NLR) and systemic immune-inflammation index (SII) were calculated. The systemic immune-inflammation index is calculated by multiplying the platelet count by the neutrophil/lymphocyte ratio.
Statistical analyses
A complete case statistical analysis was conducted utilising the R software version 4.0.3. In the case of continuous variables, the Shapiro-Wilks normality test was employed to assess the distribution of the data. The data pertaining to normally distributed variables was expressed as the mean ± standard deviation, and then subjected to independent one-way ANOVA to ascertain differences between groups. Non-normally distributed variables were expressed as median (25th percentile, 75th percentile) and compared using the Kruskal-Wallis test. Categorical data were statistically described using frequency (percentage). The intergroup comparisons were conducted utilising the chi-square test or Fisher’s exact test, depending on the nature of the data. Statistically speaking, a P value of less than 0.05 was considered to be significant.
Results
Patient characteristics
As illustrated in Figs. 1 and 105 patients were screened from January 2023 to January 2025. This screening took place at the Clinical Nutrition Department outpatient clinic, inpatient ward of the Tenth People’s Hospital Affiliated to Tongji University, and Baoshan Geriatric Nursing Hospital. Of these patients, 85 were diagnosed with sarcopenia and met the inclusion criteria. During the intervention period, three patients requested withdrawal, two failed to adhere to nutritional supplement regimens, and two were excluded due to disease progression or gastrointestinal symptoms following assessment. The final sample comprised 78 patients: 32 in Group A, 31 in Group B, and 15 in Group C. A series of comparisons were made of gender, age, baseline muscle function indicators, body composition measurements, and inflammation/nutrition-related markers among the three groups showed no statistically significant differences (P > 0.05), indicating comparability. (Table 1)
Fig. 1.
Flowchart of the Study
Table 1.
Comparison of baseline data among the three groups
| Item | Group A (n = 32) | Group B (n = 31) | Group C (n = 15) | F/χ² | P |
|---|---|---|---|---|---|
| Gender (%) | 0.857 | 0.651 | |||
| F | 14 (43.75%) | 17 (54.84%) | 8 (53.33%) | ||
| M | 18 (56.25%) | 14 (45.16%) | 7 (46.67%) | ||
| Age (years) | 73.5 (67, 76.25) | 73 (69.5, 78.5) | 73 (72.5, 76) | 0.497 | 0.780 |
| Calf Circumference (cm) | 33.25 (31.6, 35) | 32.6 (30.8, 34.5) | 32.5 (32, 35.5) | 0.523 | 0.770 |
| Grip Strength (kg) | 21.5 (19.48, 24.52) | 21.8 (19.55, 24.75) | 20.5 (18.1, 24.35) | 0.215 | 0.898 |
| SMI (kg/m2) | 5.6 (5.4, 6.7) | 5.6 (5.5, 6.7) | 6.5 (5.5, 6.7) | 0.803 | 0.669 |
| Weight (kg) | 56.22 ± 7.2 | 55.29 ± 6.05 | 56.99 ± 8.39 | 0.321 | 0.726 |
| Height (cm) | 162.93 ± 7.49 | 161.5 ± 7.7 | 160.4 ± 10.35 | 0.541 | 0.584 |
| BMI (kg/m2) | 21.85 (21, 22.63) | 21.1 (20.1, 22.1) | 20.3 (19.55, 21.7) | 5.289 | 0.071 |
| Skeletal muscle mass (kg) | 19.4 (18.17, 23.4) | 19.7 (17.5, 23.35) | 22.7 (18.05, 24.65) | 1.501 | 0.472 |
| Body Fat Percentage (%) | 32.05 ± 4.94 | 30.46 ± 5.46 | 28.05 ± 8.45 | 2.329 | 0.104 |
| Basal metabolic rate (kcal) | 1161 (1118.5, 1309.75) | 1173 (1099, 1299) | 1281 (1127, 1360) | 1.795 | 0.408 |
| Visceral fat area (cm²) | 86.35 (75.88, 103.92) | 81.9 (68.9, 95.25) | 83.7 (60.95, 89.15) | 3.553 | 0.169 |
| Upper arm muscle circumference (cm) | 22.5 (21.7, 23.5) | 22.5 (21.5, 23.2) | 22.9 (21.5, 23.4) | 0.523 | 0.770 |
| White blood cell count (×109/L) | 5.46 ± 1.43 | 5.85 ± 1.46 | 5.5 ± 1.84 | 0.57 | 0.568 |
| Lymphocyte count | 1.31 ± 0.57 | 1.58 ± 0.64 | 1.64 ± 0.52 | 2.393 | 0.098 |
| Neutrophil count | 3.53 ± 1.22 | 3.66 ± 1.1 | 3.29 ± 1.43 | 0.461 | 0.633 |
| Red blood cells (×1012/L) | 3.92 (3.49, 4.43) | 4.25 (3.92, 4.6) | 4.19 (3.86, 4.61) | 4.047 | 0.132 |
| Hemoglobin (g/L) | 120.31 ± 16.6 | 128.55 ± 16.97 | 130.53 ± 15.71 | 2.778 | 0.069 |
| Fasting blood glucose (mmol/L) | 5.04 (4.63, 6.02) | 5.83 (4.88, 7.73) | 5.67 (5.11, 6.44) | 4.104 | 0.129 |
| Total Protein (g/L) | 65.24 ± 7.07 | 66.62 ± 7.15 | 65.43 ± 5.49 | 0.352 | 0.704 |
| Albumin (g/L) | 38 (36.08, 42.25) | 38.7 (36.55, 42) | 39 (36.15, 41.4) | 0.159 | 0.924 |
| Prealbumin (mg/L) | 245.93 ± 61.51 | 232.9 ± 55.26 | 213.89 ± 57.78 | 1.559 | 0.217 |
| C-reactive protein (mg/L) | 3.1 (1, 10.77) | 1.6 (0.95, 4.9) | 1.3 (0.8, 3.9) | 1.824 | 0.402 |
| NLR | 2.79 (2.12, 4.05) | 2.42 (1.89, 3.15) | 2.59 (1.33, 2.72) | 3.79 | 0.15 |
| SII | 614.39 (431.97, 791.29) | 520.67 (324.77, 867.39) | 354.06 (288.97, 506.83) | 2.966 | 0.227 |
BMI, Body Mass Index; SMI, Skeletal Muscle Mass Index; NLR, Neutrophil-to-Lymphocyte Ratio; SII, Systemic Inflammatory Index
Comparison of muscle function indicators before and after intervention
The results in Table 2 and Fig. 2 demonstrate that no statistically significant differences were observed in pre-intervention muscle function indicators (i.e. grip strength, calf circumference, and SMI) among the three groups (P > 0.05). Subsequent to the intervention, the distributions of SMI and calf circumference across the three groups demonstrated no statistically significant disparities (P > 0.05). The Kruskal-Wallis test was utilised for the purpose of conducting intergroup comparisons of grip strength post-intervention, a process which yielded statistically significant differences in distribution. Pairwise comparisons employed the Bonferroni-corrected FSA package’s Dunn test function to adjust P-values for significance. The results indicated a statistically significant difference between Group B and Group C (adj. P = 0.017), as demonstrated in Table 3. A comparison of the outcomes before and after the intervention across the three groups revealed significant improvements in SMI and grip strength in Groups A and B (P < 0.05). However, a significant trend toward reduced calf circumference was exhibited by all three groups, with the greatest mean decrease observed in Group C (t = 4.461, P = 0.001).
Table 2.
Comparison of muscle function indicators before and after intervention in three patient groups
| Item | Group A (n = 32) | Group B (n = 31) | Group C (n = 15) | Total (n = 78) | Chi-square | P | |
|---|---|---|---|---|---|---|---|
|
SMI (kg/m2) |
Pre-intervention | 5.6 (5.4, 6.7) | 5.6 (5.5, 6.7) | 6.5 (5.5, 6.7) | 5.7 (5.43, 6.7) | 0.803 | 0.669 |
| After intervention | 6.85 (5.88, 7.32) | 6.5 (5.8, 7.35) | 5.9 (5.75, 6.4) | 6.45 (5.8, 7.3) | 3.108 | 0.211 | |
| t | − 3.495 | − 3.834 | − 0.063 | − 4.436 | |||
| P | 0.001 # | 0.001 # | 0.951 | < 0.001 # | |||
| Grip Strength (kg) | Before intervention | 21.5 (19.48, 24.52) | 21.8 (19.55, 24.75) | 20.5 (18.1, 24.35) | 21.35 (19.4, 24.58) | 0.215 | 0.898 |
| Post-intervention | 23.85 (20.23, 30.05) | 25.5 (23.3, 31.3) | 21.5 (18.85, 23.85) | 23.85 (20.7, 28.62) | 7.669 | 0.022* | |
| t | − 2.154 | − 3.342 | 0.142 | − 3.534 | |||
| P | 0.039 # | 0.002 # | 0.889 | 0.001 # | |||
|
Calf Circumference (cm) |
Before intervention | 33.25 (31.6, 35) | 32.6 (30.8, 34.5) | 32.5 (32, 35.5) | 33 (31, 35) | 0.523 | 0.770 |
| Post-intervention | 29.75 (27.5, 33.12) | 30 (28, 32) | 29 (28, 30.95) | 29.5 (28, 32.08) | 0.872 | 0.647 | |
| t | 3.802 | 3.951 | 4.461 | 6.768 | |||
| P | 0.001 # | < 0.001 # | 0.001 # | < 0.001 # |
*Differences in distribution between groups are statistically significant, P < 0.05; # Differences in muscle function indicators before and after intervention are statistically significant, P < 0.05
Fig. 2.
Box plots of muscle function changes in the three groups before and after the intervention
Table 3.
Pairwise comparisons of grip strength values between groups
| Comparison | Z | P.unadj | P.adj |
|---|---|---|---|
| Group A - Group B | − 1.354338 | 0.17563 | 0.52689 |
| Group A - Group C | 1.681139 | 0.09274 | 0.27821 |
| Group B - Group C | 2.757700 | 0.00582 | 0.01746 |
Comparison of intestinal barrier function indicators before and after intervention
Prior to the implementation of the intervention, serum DAO, D-lactic acid, and endotoxin levels exhibited no statistically significant disparities among the three groups (P > 0.05). Following the intervention, serum DAO, D-lactic acid, and endotoxin levels in both Group A and Group B patients were found to be significantly lower than their respective pre-intervention levels (P < 0.05), with the most pronounced difference observed in Group B (P < 0.05) (Table 4) and Fig. 3.
Table 4.
Comparison of intestinal barrier function indicators before and after intervention in the three patient groups
| Group | Time | DAO (U/L) | D-lactic acid (mmol/L) | Endotoxin (EU/ml) |
|---|---|---|---|---|
| Group A | Pre-intervention | 10.3 ± 1.9 | 2.53 ± 0.32 | 0.43 ± 0.07 |
| Post-intervention | 8.3 ± 1.6*# | 2.20 ± 0.28*# | 0.37 ± 0.06*# | |
| Group B | Before intervention | 10.2 ± 1.8 | 2.51 ± 0.31 | 0.42 ± 0.06 |
| Post-intervention | 6.2 ± 1.2*#△ | 1.83 ± 0.23*#△ | 0.29 ± 0.04*#△ | |
| Group C | Before intervention | 10.4 ± 2.0 | 2.54 ± 0.33 | 0.44 ± 0.08 |
| After Intervention | 10.1 ± 1.8 | 2.50 ± 0.30 | 0.42 ± 0.07 |
* Compared with pre-intervention in the same group, P < 0.05; # Compared with post-intervention in Group C, P < 0.05; △ Compared with post-intervention in Group A, P < 0.05
Fig. 3.
Line graphs of intestinal barrier function indicators before and after intervention
Comparison of inflammatory and nutritional markers before and after intervention among the three groups
Statistically significant differences were not observed in serum inflammatory markers and nutritional indicators among the three groups (P > 0.05). Following the intervention, Group B demonstrated the most significant decrease in C-reactive protein, NLR, and SII levels, with substantial intra-group variations (P < 0.001). Group A demonstrated only slight decreases in these indicators, while Group C exhibited no significant changes (P > 0.05). Statistically significant differences were not observed in the nutritional indicators albumin and prealbumin between the groups, or before and after the intervention (P > 0.05), as demonstrated in Table 5.
Table 5.
Comparison of inflammatory and Nutrition-Related markers before and after intervention in three patient groups
| Indicator | Group | Pre-intervention | After Intervention | Intragroup Comparison Before and After Intervention (Z/t value) |
P | Intergroup comparison after intervention (H/F value) |
P |
|---|---|---|---|---|---|---|---|
|
White blood cell count (×10⁹/L) |
Group A | 5.46 ± 1.43 | 5.38 ± 1.35 | 0.312 | 0.756 | 0.289 | 0.75 |
| Group B | 5.85 ± 1.46 | 5.72 ± 1.38 | 0.455 | 0.652 | |||
| Group C | 5.50 ± 1.84 | 5.42 ± 1.76 | 0.201 | 0.842 | |||
|
C-reactive protein (mg/L) |
Group A | 3.1 (1.0, 10.77) | 2.0 (1.2, 5.3) | − 2.103 | 0.035# | 8.621 | 0.013* |
| Group B | 1.6(0.95,4.9) | 1.0(0.8,2.5) | − 3.215 | 0.001# | |||
| Group C | 1.3 (0.8, 3.9) | 1.2 (0.9, 3.7) | − 0.382 | 0.702 | |||
| NLR | Group A | 2.79 (2.12, 4.05) | 2.40 (1.95, 3.22) | − 1.987 | 0.047# | 9.052 | 0.011* |
| Group B | 2.42(1.89,3.15) | 1.85(1.52,2.31) | − 3.562 | < 0.001# | |||
| Group C | 2.59 (1.33, 2.72) | 2.50 (1.41, 2.68) | − 0.516 | 0.606 | |||
| SII | Group A | 614.39 (431.97, 791.29) | 520.41 (400.33, 680.55) | − 2.054 | 0.040# | 10.238 | 0.006* |
| Group B | 520.67(324.77,867.39) | 380.25(290.12,550.78) | − 3.891 | < 0.001# | |||
| Group C | 354.06 (288.97, 506.83) | 345.12 (280.66, 490.33) | − 0.428 | 0.669 | |||
|
Albumin (g/L) |
Group A | 38.0 (36.08, 42.25) | 38.5 (36.22, 42.50) | − 1.126 | 0.26 | 0.358 | 0.836 |
| Group B | 38.7 (36.55, 42.00) | 39.0 (36.80, 42.30) | − 0.985 | 0.324 | |||
| Group C | 39.0 (36.15, 41.40) | 38.8 (36.05, 41.60) | − 0.217 | 0.828 | |||
|
Prealbumin (mg/L) |
Group A | 245.93 ± 61.51 | 252.17 ± 58.33 | − 0.689 | 0.495 | 0.521 | 0.595 |
| Group B | 232.90 ± 55.26 | 238.65 ± 52.71 | − 0.573 | 0.57 | |||
| Group C | 213.89 ± 57.78 | 218.42 ± 55.19 | − 0.396 | 0.696 |
NLR, neutrophil-to-lymphocyte ratio; SII, systemic immune inflammation index; * Significant intergroup difference before and after intervention, P < 0.05; # Significant intragroup difference before and after intervention, P < 0.05
Discussion
Sarcopenia has been shown to have a significant impact on the quality of life of elderly individuals, with a complex pathogenesis involving multiple factors. The present study concentrated on the nutritional intervention of elderly sarcopenia patients. By comparing the effects of HMB alone, HMB combined with prebiotics, and conventional diet, it revealed the synergistic characteristics of HMB in muscle protection and prebiotics in optimizing the intestinal environment.
Effects of HMB and prebiotics on muscle function
The findings of this study demonstrate that both Group A and Group B exhibited significant improvements in SMI and grip strength post-intervention in comparison to their respective baselines. Conversely, Group C demonstrated no significant changes. This finding is consistent with the established dual-action muscle metabolism mechanism of HMB. The Position Statement of the International Society of Sports Nutrition (ISSN) asserts that HMB exerts a direct effect on the process of muscle protein synthesis by activating the mTORC1 signalling pathway, operating independently of the leucine-sensing pathway. Concurrently, HMB inhibits the ubiquitin-proteasome pathway and mitochondrial apoptosis, thereby reducing muscle protein breakdown [7, 16]. A subsequent meta-analysis by Lin et al., involving 896 elderly subjects, further confirmed that HMB’s muscle strength-enhancing effects are independent of exercise intervention, providing evidence-based support for the finding in this study that HMB alone can improve SMI and grip strength [17, 18].
Notably, pairwise comparisons showed that grip strength in Group B was significantly higher than in Group C (adj. P = 0.017), but no significant difference was observed between Group A and Group B. A randomised controlled trial conducted on nursing home residents demonstrated substantial enhancements in skeletal muscle function, including muscle fatigue resistance and grip strength, following a 13-week intervention with a prebiotic blend of inulin and fructooligosaccharides [19]. A daily dose of 3 g HMB-Ca has been reported as optimal for improving muscle function. In this study, both Groups A and B utilised the specified dosage, with the result that HMB predominantly influenced the balance between muscle protein synthesis and breakdown. However, no statistically significant differences were observed between the groups. This may be attributed to the short intervention duration (30 days) and modest sample size, which may have precluded the full manifestation of the indirect muscle support effects of prebiotics through their regulatory effect on the microbiota. A preliminary investigation conducted on a small sample size (n = 17) revealed that the prolonged administration of synbiotics (fructooligosaccharides, Lactobacillus strains, and Bifidobacterium lactis) did not yield significant enhancements in lean body mass or muscle strength in elderly subjects [20]. Concurrently, Song et al.‘s meta-analysis of 17 studies involving 4,307 participants revealed that the remodelling of gut microbiota in sarcopenic patients requires a minimum of 12 weeks to stabilise, while muscle function exhibits a time-lag effect in responding to microbiota changes [21] .
It is noteworthy that all three groups demonstrated substantial decreases in calf circumference following the intervention, with Group C exhibiting the most pronounced reduction. This outcome does not necessarily indicate muscle loss, but rather, it may be indicative of an improvement in sarcopenia’s pathological feature of “muscle-fat substitution.” Sarcopenia in the elderly is frequently characterised by intramuscular fat infiltration, and the reduction in calf circumference is likely indicative of decreased body fat content rather than muscle mass loss [22]. However, the present study did not incorporate the muscle-to-fat ratio as a metric to analyse the pre- and post-intervention changes. It is concluded, based on the findings that are currently available, that the two intervention groups achieved muscle preservation and fat reduction through HMB-induced muscle protection and prebiotic-mediated metabolic regulation. Conversely, the untreated C group exhibited persistent muscle loss in conjunction with impaired fat metabolism, resulting in a more pronounced decrease in calf circumference. This finding is further corroborated by the absence of any discernible improvement in SMI in the C group, despite a documented reduction in calf circumference.
Synergistic effects of HMB and prebiotics on the gut-muscle axis
The most significant intervention difference in this study was observed in intestinal barrier function. Following intervention, Group B exhibited significantly lower serum DAO, D-lactic acid, and endotoxin levels compared to Groups A and C. This finding is in alignment with the “gut-muscle axis” theory. There is a close interaction between the gut microbiota and the host, and impaired intestinal barrier function coupled with microbiota dysbiosis may play a crucial role in the onset and progression of sarcopenia [23, 24]. Impaired intestinal barrier function has been demonstrated to result in increased intestinal permeability, thus allowing bacteria and their metabolites, including endotoxins, to enter the bloodstream. This process has been shown to activate the immune system, trigger chronic inflammatory responses, and promote muscle protein degradation, which can ultimately result in a reduction in muscle mass and strength.
The prebiotic employed in this study has been shown to modulate the composition of gut microbiota, significantly increasing the levels of beneficial bacteria, such as Bifidobacterium, and concomitantly reducing the levels of potentially harmful bacteria. The presence of these beneficial bacteria correlates positively with intestinal barrier integrity and muscle function in sarcopenia patients [21, 25, 26]. Furthermore, FOS promote the synthesis of short-chain fatty acid, especially butyrate, which serve as the primary energy source for intestinal epithelial cells. Butyrate upregulates the expression of tight junction protein expression (occludin, ZO-1), thereby reducing intestinal permeability, as evidenced by a decrease in DAO and D-lactic acid levels in Group B [25]. Simultaneously, enhanced intestinal barrier function reduces endotoxin entry into the bloodstream, thereby mitigating systemic chronic inflammation. Liu et al.‘s systematic review indicates that the endotoxin-activated NF-κB pathway is a key inflammatory pathway leading to muscle protein breakdown [12], providing indirect evidence for improved inflammatory markers and muscle function protection in Group B. Comparing intestinal differences between Groups A and B reveals that HMB alone improves function by inhibiting muscle breakdown but fails to regulate the intestinal microenvironment. The incorporation of prebiotics establishes a synergistic chain, thereby rendering Group B the optimal group for intestinal barrier repair.
Effects on inflammatory and nutritional markers
After intervention, Group B showed the most significant reductions in CRP, NLR, and SII (P < 0.001), while Group A had only modest decreases and Group C showed no changes. In the event of an impairment to the intestinal barrier, the resultant entry of endotoxins into the bloodstream is known to activate the immune system and to trigger a state of chronic inflammation. Inflammatory factors (e.g. TNF-α) have been shown to accelerate muscle protein breakdown by activating the ubiquitin-proteasome pathway while simultaneously inhibiting the mTORC1 pathway, thereby reducing muscle protein synthesis [13]. The present study firstly made a comparison between blood routine indicators and inflammatory indices (NLR and SII) in sarcopenic patients. Although there is evidence that NLR and SII correlate with multiple diseases, the absence of a healthy elderly control group means that their association with sarcopenia cannot be verified. A comparison of the results obtained before and after the intervention revealed that Group B, which demonstrated the optimal intestinal barrier, exhibited the lowest levels of endotoxin and the mildest inflammatory response. This resulted in the creation of a more stable internal environment for muscle metabolism.
No significant differences in albumin or prealbumin were observed between groups, though Group A and B showed slight upward trends compared to Group C. This may be attributed to the nutritional support role of HMB, as HMB has been shown to enhance muscle protein synthesis efficiency, reduce the body’s breakdown and utilisation of plasma proteins, and thereby maintain serum protein levels [14]. The investigation revealed that prebiotics did not demonstrate substantial additional benefits on nutritional indicators, thereby suggesting that their primary mechanism of action occurs indirectly through the gut rather than directly enhancing nutrient absorption efficiency.
Beyond nutritional intervention, exercise (especially resistance training) is another key strategy for sarcopenia management. For example, resistance training can regulate myokines and inflammatory factors to improve muscle metabolism [27], even in populations with chronic conditions, physical activity can enhance muscle health and overall status [28]. These findings suggest that combining HMB-prebiotic nutrition with appropriate exercise may further enhance muscle function in sarcopenic older adults—an area worthy of future exploration.
Study limitations and future directions
This study has certain limitations. Firstly, the small sample size (especially 15 participants in Group C) reduced statistical power for intergroup comparisons. Future studies should expand the sample size (especially for control groups) to improve result reliability. Secondly, the 30-day intervention cycle is relatively short and insufficient to observe the long-term efficacy (such as the impact on falls or disability) or the comprehensive effects of the gut microbiota-muscle interaction. In the future, longer cycles (≥ 12 weeks) of intervention will be needed to verify the sustained benefits of the HMB and prebiotic combination regimen. In addition, potential confounding factors such as baseline dietary patterns, physical activity levels, and the severity of comorbidities were not fully controlled. Subsequent studies can monitor these variables through 24-hour dietary retrospectives and triaxial accelerometers, and make corrections in the analysis. Finally, the present study exclusively examined the effects of prebiotics combined with HMB on muscle function and intestinal barrier function in elderly patients with sarcopenia. The precise mechanisms through which these effects occur require further investigation. As metabolites such as short-chain fatty acids were not measured, it is difficult to elucidate the synergistic mechanism of the “prebiotic-HMB-gut microbiota” interaction. It is possible to consider using animal models, such as SAMP8 senescent mice, and cell co-culture systems to deeply verify the relevant mechanism pathways. Futher research should address these limitations by designing large-sample, long-term randomized controlled trials and integrating multi-omics approaches to clarify the synergistic mechanisms of HMB and prebiotics. This would provide a more robust theoretical foundation for clinical treatment.
Conclusion
This study confirms that HMB s a key intervention for improving muscle function in elderly patients with sarcopenia, as evidenced by significant enhancements in SMI and grip strength. While prebiotics did not further improve muscle function in the short term, they remodeled the gut microbiota, strengthened the intestinal mucosal barrier, and reduced systemic inflammation—making the HMB-prebiotic combination the optimal strategy for intestinal barrier repair. In clinical practice, this combination should be considered for elderly sarcopenia patients with impaired intestinal barriers to improve their quality of life and reduce societal and family burdens. However, large-scale, long-term follow-up research is needed to validate the safety and efficacy of this regimen and clarify its specific mechanisms.
Acknowledgements
We are grateful to all patients and their families, as well as all members of the study group.
Author contributions
Conceptualized and designed the study: Ting Han.Data curation: Ning Yang and Zhihua Qu.Formal analysis: Fangjing Hong.Investigation: Jialu Zhuo and Ning Yang.Methodology: Zixiang Li.Writing - original draft: Jialu ZhuoWriting- review and editing: Ting HanAll authors approved the final version of the manuscript.
Funding
This study was funded by the Research Fund Project of the Chinese Society for Parenteral and Enteral Nutrition (Project No.: Z-2017-24-2211).
Data availability
No datasets were generated or analysed during the current study.
Declarations
Competing interests
The authors declare no competing interests.
Ethics approval and consent to participate
This study was approved by the Ethics Committee of Shanghai Tenth People’s Hospital (approval number: SHYS-IEC-5.0 / 23KY16 / P01). Written informed consent was obtained from all individual participants included in the study.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Jialu Zhuo and Ting Han are Co-first authors.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
No datasets were generated or analysed during the current study.