Bone health in diabetes and prediabetes

Table 1 Bone turnover markers in prediabetes/insulin resistance and type 2 diabetes

BTM	Meaning	Pre-DM / IR	Ref.	T2D	Ref.
CTX	Bone resorption	↓ or ↔	[136,276,278-280]	↓	[129,132,134,137,281-286]
TRAP	Bone resorption	↑?	[287]	↓ or ↔	[132,281]
uNTX	Bone resorption			↓	[285]
Sclerostin	Inhibition of bone formation	↑	[65]	↑	[284,285,288,289]
OC	Bone formation	↓ or ↔	[128,276-278,280,290]	↓ or ↔	[129,132,134,281,283,285,286,291-294]
P1NP	Bone formation	↓ or ↔	[136,277,280]	↓ or ↔	[88,132,134,137,282,283,285,286]
BAP	Bone formation	Direct association with IR	[295]	↔ or ↓ or ↑	[132,281,284,286,292,294]
ALP	Bone formation	?	?	↔ or ↑	[292-294]
OPG	Inhibition of bone resorption	↑	[296]	↑	[293,296]

BTM: Bone turnover marker; pre-DM: Prediabetes; IR: Insulin resistance; T2D: Type 2 diabetes; CTX: Carboxy-terminal cross-linking telopeptide of type I collagen; OC: Osteocalcin; P1NP: Procollagen type 1 amino-terminal propeptide; TRAP: Tartrate-resistant acid phosphatase; uNTX: Urinary N-telopeptide of type I collagen; BAP: Bone-specific alkaline phosphatase; ALP: Alkaline phosphatase; OPG: Osteoprotegerin; ↑: Increased; ↓: Decreased; ↔: Similar to healthy controls; ?: Unknown.

Table 2 Effects of diabetes and prediabetes on bone health

	T1D	T2D	Prediabetes
Fracture risk	↑↑	↑	?
Bone mineral density	↓	↔ or ↑	↔ or ↑
Bone turnover	↓	↓↓	↓?
Bone marrow adiposity	↔	↑	↑?
Bone matrix - AGEs	↑	↑	?
Microarchitecture/geometry	↑ cortical porosity	↑ cortical porosity	↓ trabecular and cortical bone size

AGEs: Advanced glycation endproducts; T1D: Type 1 diabetes; T2D: Type 2 diabetes; ↑: Increased; ↓: Decreased; ↔: Similar to healthy controls; ?: Unknown.