Musculoskeletal health in response to the combined effect of age and an obesogenic diet in male C57BL/6J mice
Bibliographic record
Abstract
Aging and obesity are two major aspects that can negatively impact musculoskeletal structure and function; however, their combined effects have not been well investigated. Thus, the study objective was to investigate the combined effects of aging and diet‐induced obesity, via high‐fat sucrose (HFS) diet, on bone and muscle structure and function in mice. Bone to muscle ratios were calculated since these tissues are inter‐dependent with an established mechanical relationship. Male C57BL/6J mice were randomized to control (AGE, AIN93M, 10.3% kcal fat, 100 g/kg sucrose) or HFS (HFS‐AGE, 45.3% kcal fat 200 g/kg sucrose) diet for 13 weeks from 20 weeks of age. Proximal tibia trabecular bone structure, volumetric bone mineral density (vBMD), and body composition were measured longitudinally at 20, 24, 28, and 32 weeks of age. In vitro contractile measures were performed on isolated soleus and extensor digitorum longus (EDL) muscles at baseline (BSL, 21 weeks of age, n= 11) and at the end of the 13‐week intervention when AGE (n=12) and HFS‐AGE (n=12) mice were 33 weeks of age. Following the 13‐week intervention, HFS‐AGE weighed +30% more than AGE (p<0.0001), had a greater decrease in lean mass (AGE −13%; HFS‐AGE −46%, p<0.0001), greater increase in fat mass (AGE +51%, HFS‐AGE +79%, p<0.0001), and an increase in bone mass for AGE (+15%), but a decrease for HFS‐AGE (−27%, p<0.0001). Both AGE and HFS‐AGE had similar declines in trabecular bone with age: percent bone volume (BV/TV, AGE −34%, p<0.0001; HFS‐AGE −45%, p<0.0001), trabecular thickness (Tb.Th, AGE −9%, p<0.05; HFS‐AGE −8%, p<0.05), trabecular number (Tb.N, AGE −29%, p<0.05; HFS‐AGE −41%, p<0.05), vBMD (AGE −17%, p<0.001; HFS‐AGE −23%, p<0.001). There was also an increase in trabecular separation (Tb.Sp) for HFS‐AGE only (+19%, p<0.05) with age. For muscle contractile function, HFS‐AGE resulted in larger soleus cross‐sectional area (CSA) compared AGE (p>0.001), but this did not translate to greater twitch or tetanus peak force. The ratio of outcomes of bone to muscle declined in both groups due to a greater decline in key measures of bone structure (BV/TV) than muscle function (soleus and EDL peak tetanus and CSA) and was not altered by HFS. For the soleus, there were decreases in the following ratios compared to BSL: BV/TV to soleus peak tetanus (AGE −48%, p<0.01), BV/TV to soleus CSA (AGE −36%, p<0.01; HFS‐AGE −48%, p<0.001), vBMD to soleus peak tetanus (AGE −23%, p<0.05), and vBMD to soleus CSA (HFS‐AGE −30%, p<0.001). In addition, the vBMD to peak tetanus was lower for AGE compared to HFS‐AGE (−23%, p<0.05) and vBMD to soleus CSA was lower for the HFS‐AGE compared to AGE (−21%, p<0.05). While for the EDL, the following ratios decreased compared to BSL: BV/TV to EDL peak tetanus (AGE −41%, p<0.05), BV/TV to EDL CSA (AGE −46%, p<0.0001; HFS‐AGE −61%, p<0.01), and vBMD to EDL CSA (AGE −23%, p<0.01; HFS‐AGE −24%, p<0.01). In conclusion, consumption of a HFS diet during middle age did not exacerbate age‐related declines in bone or alter muscle function, but these tissues do not decline in a coordinate manner. During aging, bone structure declined at a greater rate than muscle function. Support or Funding Information Natural Sciences and Engineering Research Council of Canada, Canadian Foundation for Innovation, K.N.B. is funded through an Ontario Graduate Scholarship
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".